WO2012166618A2

WO2012166618A2 - Capping layer for reduced outgassing

Info

Publication number: WO2012166618A2
Application number: PCT/US2012/039629
Authority: WO
Inventors: Linlin Wang; Abhijit Basu Mallick; Nitin K. Ingle
Original assignee: Applied Materials, Inc.
Priority date: 2011-06-03
Filing date: 2012-05-25
Publication date: 2012-12-06
Also published as: WO2012166618A3; US20120309205A1; US8466073B2; TW201308432A

Abstract

A method of forming a silicon oxide layer is described. The method first deposits a silicon-nitrogen-and-hydrogen-containing (polysilazane) film by radical-component chemical vapor deposition (CVD). The silicon-nitrogen-and-hydrogen-containing film is formed by combining a radical precursor (excited in a remote plasma) with an unexcited carbon-free silicon precursor. A capping layer is formed over the silicon-nitrogen-and-hydrogen-containing film to avoid time-evolution of underlying film properties prior to conversion into silicon oxide. The capping layer is formed by combining a radical oxygen precursor (excited in a remote plasma) with an unexcited silicon-and-carbon-containing-precursor. The films are converted to silicon oxide by exposure to oxygen-containing environments. The two films may be deposited within the same substrate processing chamber and may be deposited without breaking vacuum.

Description

CAPPING LAYER FOR REDUCED OUTGASSING

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a PCT application of U.S. Patent Application No. 13/448,624, entitled "CAPPING LAYER FOR REDUCED OUTGASSING," filed April 17, 2012, and is related to and claims the benefit of U.S. Provisional Patent Application No. 61/492,914, entitled "CAPPING LAYER FOR REDUCED OUTGASSING," filed June 3, 201 1, both of which are incorporated herein by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

Semiconductor device geometries have dramatically decreased in size since their introduction several decades ago. Modern semiconductor fabrication equipment routinely produce devices with 45 nm, 32 nm, and 28 nm feature sizes, and new equipment is being developed and implemented to make devices with even smaller geometries. The decreasing feature sizes result in structural features on the device having decreased spatial dimensions. The widths of gaps and trenches on the device narrow to a point where the aspect ratio of gap depth to its width becomes high enough to make it challenging to fill the gap with dielectric material. The depositing dielectric material is prone to clog at the top before the gap completely fills, producing a void or seam in the middle of the gap.

Over the years, many techniques have been developed to avoid having dielectric material clog the top of a gap, or to "heal" the void or seam that has been formed. One approach has been to start with highly flowable precursor materials that may be applied in a liquid phase to a spinning substrate surface (e.g., SOG deposition techniques). These flowable precursors can flow into and fill very small substrate gaps without forming voids or weak seams.

However, once these highly flowable materials are deposited, they have to be hardened into a solid dielectric material.

In many instances, the hardening includes a heat treatment to remove carbon and hydroxyl groups from the deposited material to leave behind a solid dielectric such as silicon oxide. Unfortunately, the departing carbon and hydroxyl species often leave behind pores in the hardened dielectic that reduce the quality of the final material. In addition, the hardening dielectric also tends to shrink in volume, which can leave cracks and spaces at the interface of the dielectric and the surrounding substrate. In some instances, the volume of the hardened dielectric can decrease by 40% or more.

Spin-on dielectrics (SOD) have also been used to flow into features on a patterned substrate. The material is generally converted to silicon oxide from a silazane-type film which contains silicon, nitrogen and hydrogen. Silicon, nitrogen and hydrogen containing films are typically converted to silicon oxide at high temperature in an oxygen containing environment. Oxygen from the environment displaces nitrogen and hydrogen to create the silicon oxide film. High temperature exposure to oxygen environments can ruin underlying films for some circuit architectures. This consideration results in the need to stay within a "thermal budget" during a manufacturing process flow. Thermal budget considerations have largely limited SOD to process flows incorporating an underlying silicon nitride layer which can protect underlying features from oxidation (e.g. DRAM applications).

Alternative methods have been developed which deposit silazane containing layers by radical-component CVD. Radical-component CVD can create a flowable film by exciting one precursor and combining it with an unexcited silicon-containing precursor in the plasma- free substrate processing region. Film properties, including density, may change slightly in time until the silazane containing film is converted to silicon oxide. Controlling the evolution of the film properties improves the manufacturability of devices using these films. Thus, there is a need for new deposition processes and materials to form dielectric materials which do not evolve over time. This and other needs are addressed in the present application.

BRIEF SUMMARY OF THE INVENTION

A method of forming a silicon oxide layer is described. The method first deposits a silicon- nitrogen-and-hydrogen-containing (polysilazane) film by radical-component chemical vapor deposition (CVD). The silicon-nitrogen-and-hydrogen-containing film is formed by combining a radical precursor (excited in a remote plasma) with an unexcited carbon-free silicon precursor. A capping layer is formed over the silicon-nitrogen-and-hydrogen- containing film to avoid time-evolution of underlying film properties prior to conversion into silicon oxide. The capping layer is formed by combining a radical oxygen precursor (excited in a remote plasma) with an unexcited silicon-and-carbon-containing-precursor. The films are converted to silicon oxide by exposure to oxygen-containing environments. The two films may be deposited within the same substrate processing chamber and may be deposited without breaking vacuum. Embodiments of the invention include methods of forming a silicon oxide layer on a substrate. The methods include forming a first layer comprising silicon, nitrogen and hydrogen by flowing an unexcited precursor into a remote plasma region to produce a radical-precursor, combining a carbon-free silicon-containing precursor with the radical- precursor in the plasma-free substrate processing region, and depositing a carbon-free silicon- nitrogen-and-hydrogen-containing layer over the substrate. The methods further include forming a second layer comprising silicon and carbon by flowing an unexcited oxygen- containing precursor into a remote plasma region to produce a radical-oxygen precursor, combining a silicon-and-carbon-containing precursor with the radical-oxygen precursor in the plasma- free substrate processing region, and depositing a silicon-oxygen-and-carbon- containing capping layer over the silicon-nitrogen-and-hydrogen-containing layer.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the invention. The features and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference numerals are used throughout the several drawings to refer to similar components. In some instances, a sublabel is associated with a reference numeral and follows a hyphen to denote one of multiple similar components. When reference is made to a reference numeral without specification to an existing sublabel, it is intended to refer to all such multiple similar components. FIG. 1 is a flowchart illustrating selected steps for making a silicon oxide film according to embodiments of the invention.

FIG. 2 shows a substrate processing system according to embodiments of the invention. FIG. 3 A shows a substrate processing chamber according to embodiments of the invention. FIG. 3B shows a gas distribution showerhead according to embodiments of the invention. DETAILED DESCRIPTION OF THE INVENTION A method of forming a silicon oxide layer is described. The method first deposits a silicon- nitrogen-and-hydrogen-containing (polysilazane) film by radical-component chemical vapor deposition (CVD). The silicon-nitrogen-and-hydrogen-containing film is formed by combining a radical precursor (excited in a remote plasma) with an unexcited carbon-free silicon precursor. A capping layer is formed over the silicon-nitrogen-and-hydrogen- containing film to avoid time-evolution of underlying film properties prior to conversion into silicon oxide. The capping layer is formed by combining a radical oxygen precursor (excited in a remote plasma) with an unexcited silicon-and-carbon-containing-precursor. The films are converted to silicon oxide by exposure to oxygen-containing environments. The two films may be deposited within the same substrate processing chamber and may be deposited without breaking vacuum.

Capping a radical-component CVD silicon-nitrogen-and-hydrogen-containing film with a radical-component CVD silicon-oxygen-and-carbon-containing film has been found to reduce and/or eliminate outgassing and concomitant evolution of film properties over time upon exposing the substrate to air. Without the silicon-oxygen-and-carbon-containing capping layer, the properties and stoichiometry of the film may change over time. The films evolve in time due to the outgassing of silicon-containing species, ammonia and the like. The properties may also evolve due to the absorption of water or other components present in the surrounding atmosphere (air) within a typical fabrication facility. Changing film properties can complicate the manufacturing process by requiring rigid control over the delay between film formation and processing within another substrate processing system or chamber. These complications and requirements are undesirable. The silicon-oxygen-and-carbon-containing capping layers described herein have been found to suppress outgassing but still allow conversion of the underlying silicon-nitrogen-and-hydrogen-containing film to a silicon-and- oxygen-containing film and to silicon oxide.

Radical-component CVD films capped with silicon-oxygen-and-carbon-containing films according to the methods contained herein have been found to exhibit properties which do not evolve when the substrate is exposed to typical cleanroom atmospheres. Additional details about the methods and systems of forming the silicon oxide layer will now be described.

Exemplary Silicon Oxide Formation Process

FIG. 1 is a flowchart showing selected steps in a method 100 of making silicon oxide films according to embodiments of the invention. The method 100 includes providing a carbon- free silicon-containing precursor to a substrate processing region 102. The carbon-free silicon-containing precursor does not pass through a plasma excitation, in embodiments, so the precursor travels into the substrate processing region intact. Excitation is then provided only by the radical precursor to be described shortly. The carbon-free silicon-containing precursor may be, for example, a silicon-and-nitrogen-containing precursor, a silicon-and- hydrogen-containing precursor, or a silicon-nitrogen-and-hydrogen-containing precursor, among other classes of silicon precursors. The absence of carbon reduces the shrinkage of the deposited film. The silicon-containing precursor may be oxygen-free in addition to carbon- free. The lack of oxygen results in a lower concentration of silanol (Si-OH) groups in the silicon-and-nitrogen-containing layer formed from the precursors. Excess silanol moieties in the deposited film can cause increased porosity and shrinkage during post deposition steps that remove the hydroxyl (-OH) moieties from the deposited layer.

Specific examples of carbon-free silicon precursors may include silyl-amines such as H₂N(SiH₃), HN(SiH₃)₂, and N(SiH₃)₃, among other silyl-amines. The flow rates of a silyl- amine may be greater than or about 200 seem, greater than or about 300 seem or greater than or about 500 seem in different embodiments. All flow rates given herein refer to a dual chamber substrate processing system. Single wafer systems would require half these flow rates and other wafer shapes/sizes would require flow rates scaled by the processed area. These silyl-amines may be mixed with additional gases that may act as carrier gases, reactive gases, or both. Additional gases may include H₂, N₂, NH₃, He, Ne and/or Ar, among other gases. Examples of carbon- free silicon-containing precursors may also include silane (SiH₄) either alone or mixed with other silicon (e.g., N(SiH₃)₃), hydrogen (e.g., H₂), and/or nitrogen (e.g., N₂, NH₃) containing gases. Carbon-free silicon-containing precursors may also include disilane, trisilane, even higher-order silanes, and chlorinated silanes, alone or in combination with one another or the previously mentioned carbon-free silicon-containing precursors.

A radical precursor is also provided to the substrate processing region 104. A radical precursor describes plasma effluents produced in the plasma excitation outside the substrate processing region from any stable species (inert or reactive). The radical precursor may be a nitrogen-containing radical precursor which will be referred to herein as a radical-nitrogen precursor. The radical-nitrogen precursor is a nitrogen-radical-containing precursor that was generated outside the substrate processing region from a more stable nitrogen precursor. A stable precursor may be referred to herein as an unexcited precursor to indicate that the precursor has not yet passed through a plasma. A stable nitrogen precursor compound containing NH₃, hydrazine (N₂H₄) and/or N₂ may be activated in a chamber plasma region or another remote plasma system (RPS) outside the processing chamber to form the radical- nitrogen precursor, which is then transported into the substrate processing region to excite the carbon- free silicon-containing precursor. The activation of the stable nitrogen precursor into the radical-nitrogen precursor involves dissociation which may be accomplished thermal dissociation, ultraviolet light dissociation, and/or plasma dissociation, among other methods. Plasma dissociation may involve striking a plasma from helium, argon, hydrogen (H₂), xenon, ammonia (NH₃), etc., in a remote plasma generating chamber and introducing the stable nitrogen precursor to the plasma region to generate the radical-nitrogen precursor.

The stable nitrogen precursor may also be a mixture comprising NH₃ & N₂, NH₃ & H₂, NH3 & 2 & H₂ and 2 & H₂, in different embodiments. Hydrazine may also be used in place of or in combination with NH₃ and in the mixtures involving 2 and H₂. The flow rate of the stable nitrogen precursor may be greater than or about 300 seem, greater than or about 500 seem or greater than or about 700 seem in different embodiments. The radical-nitrogen precursor produced in the chamber plasma region may be one or more of -N, -NH, -NH₂, etc., and may also be accompanied by ionized species formed in the plasma. Sources of oxygen may also be combined with the more stable nitrogen precursor in the remote plasma in embodiments of the invention. The addition of a source of oxygen pre-loads the film with oxygen while decreasing flowability. Sources of oxygen may include one or more of 0₂, H₂0, 0₃, H₂0₂, N₂0, NO or N0₂.

In embodiments employing a chamber plasma region, the radical-nitrogen precursor is generated in a section of the substrate processing region partitioned from a deposition region where the precursors mix and react to deposit the silicon-and-nitrogen-containing layer on a deposition substrate (e.g., a semiconductor wafer). The radical-nitrogen precursor may also be accompanied by a carrier gas such as hydrogen (H₂), nitrogen (N₂), helium, neon, argon etc. The substrate processing region may be described herein as "plasma-free" during the growth of the silicon-nitrogen-and-hydrogen-containing layer and during subsequent processes. "Plasma- free" does not necessarily mean the region is devoid of plasma. The borders of the plasma in the chamber plasma region are hard to define and may encroach upon the substrate processing region through the apertures in the showerhead. In the case of an inductively-coupled plasma, e.g., a small amount of ionization may be initiated within the substrate processing region directly. Furthermore, a low intensity plasma may be created in the substrate processing region without compromising the flowable nature of the forming film. All causes for a plasma having much lower ion density than the chamber plasma region during the creation of the radical nitrogen precursor do not deviate from the scope of "plasma-free" as used herein.

In the substrate processing region, the carbon-free silicon precursor and the radical-nitrogen precursor mix and react to deposit a silicon-nitrogen-and-hydrogen-containing film on the deposition substrate 106. The deposited silicon-nitrogen-and-hydrogen-containing film may deposit conformally with some recipe combinations in embodiments. In other embodiments, the deposited silicon-nitrogen-and-hydrogen-containing film has flowable characteristics unlike conventional silicon nitride (S1₃N₄) film deposition techniques. The flowable nature during formation allows the film to flow into narrow features before solidifying. The substrate temperature may be between about 0°C and about 225°C, between about room temperature (25°C) and about 125°C or between about 40°C and about 95°C in embodiments of the invention. These temperature ranges also apply to the capping layer described shortly in embodiments.

Nitrogen in the silicon-nitrogen-and-hydrogen-containing film may originate from either (or both) of the radical precursor or the unexcited precursor. The carbon- free silicon-containing precursor may be essentially nitrogen-free, in some embodiments. However, in other embodiments, both the carbon-free silicon-containing precursor and the radical-nitrogen precursor contain nitrogen. In a third suite of embodiments, the radical precursor may be essentially nitrogen-free and the nitrogen for the silicon-nitrogen-and-hydrogen-containing layer may be supplied by the carbon-free silicon-containing precursor. As a result, the radical precursor may be referred to herein as a "radical-nitrogen-and/or-hydrogen precursor," which means that the precursor contains nitrogen and/or hydrogen. Analogously, the precursor flowed into the plasma region to form the radical-nitrogen-and/or-hydrogen precursor may be referred to as a nitrogen-and/or-hydrogen-containing precursor. This nomenclature may be applied to each of the embodiments disclosed herein. In embodiments, the nitrogen-and/or- hydrogen-containing precursor comprises hydrogen (¾) while the radical-nitrogen-and/or- hydrogen precursor comprises Ή, etc.

Returning to the specific example shown in FIG. 1, the flowability of a silicon-nitrogen-and- hydrogen-containing film may be due to a variety of properties which result from mixing a radical-nitrogen precursors with a carbon-free silicon-containing precursor. These properties may include a significant hydrogen component in the deposited film and/or the presence of short chained polysilazane polymers. These short chains grow and network to form more dense dielectric material during and after the formation of the film. For example the deposited film may have a silazane-type, Si-NH-Si backbone (i.e., a carbon-free Si-N-H film). When both the silicon-containing precursor and the radical precursor are carbon-free, the deposited silicon-nitrogen-and-hydrogen-containing film is also substantially carbon-free. Of course, "carbon- free" does not necessarily mean the film lacks even trace amounts of carbon. Carbon contaminants may be present in the precursor materials that find their way into the deposited silicon-and-nitrogen-containing precursor. The amount of these carbon impurities however are much less than would be found in a silicon precursor having a carbon moiety (e.g., tetraethylorthosilicate, tetramethyldisiloxane, etc.).

At this point in the process, the process effluents may be removed from the substrate processing region in embodiments of the invention. Process effluents may include any unreacted carbon- free silicon-containing precursor, unreacted radical-nitrogen precursor, inert carrier gases and reaction by-products from the film growth. The process effluents may be displaced by flowing inert species into the substrate processing region and/or by exhaustion through an exhaust port in disclosed embodiments. Prior to the deposition of the capping layer, the substrate may not be exposed to air in order to further minimize any evolution of film properties.

The method 100 also includes the remote generation of a radical-oxygen precursor in a remote plasma system (RPS) outside the deposition region 108. The radical-oxygen precursor includes the plasma effluents created in the RPS and may contain atomic oxygen. The same RPS may be used to create the radical-oxygen precursor of operation 108 as was used to create the radical-nitrogen precursor in operation 104 in embodiments. The radical- oxygen precursor may be generated by the dissociation of an oxygen containing precursor such as molecular oxygen (⁽¾), ozone (O3), an nitrogen-oxygen compound (e.g., NO, NO2, N2O, etc.), a hydrogen-oxygen compound (e.g., H₂0, H2O2, etc.), a carbon-oxygen compound (e.g., CO, CO2, etc.), as well as other oxygen containing precursors and combinations of precursors. The dissociation of the oxygen containing precursor to generate the radical- oxygen precursor may be done by the same means used to create the radical-nitrogen precursor in operation 104.

The radical-oxygen precursor is then introduced to the deposition chamber 108 where it may mix for the first time with a silicon-and-carbon-containing precursor, which is also introduced to the chamber 1 10. The radical-oxygen precursor reacts with the silicon precursor (and other deposition precursors that may be present in the reaction chamber) at moderate temperatures (e.g., reaction temperatures less than 100°C in embodiments) and pressures (e.g., about 0.1 Torr to about 10 Torr; 0.5 to 6 Torr total chamber pressure, etc.) to form a silicon-oxygen-and-carbon-containing film 112. Generally speaking, the silicon- oxygen-and-carbon-containing film may be a silicon-and-oxygen-containing layer. During the deposition, the wafer may be adjusted (i.e., heated or cooled) by a wafer pedestal that supports the wafer to a temperature of about 0°C to about 150°C. Process parameters described for the carbon-free silicon-nitrogen-and-hydrogen-containing layer formation process or the silicon-oxygen-and-carbon-containing layer formation process also apply to the other layer in embodiments. The thickness of the silicon-oxygen-and-carbon-containing capping layer (or a silicon-and-oxygen-containing capping layer) is greater than about 100 A, 150A or 200A in disclosed embodiments.

The silicon-and-carbon-containing precursor may include a organosilane compound with direct Si-C bonding and/or compounds with Si-O-C bonding. Examples of organosilane silicon precursors may include dimethylsilane, trimethylsilane, tetramethylsilane, tetramethyldisiloxane, diethylsilane, tetramethylorthosilicate, tetraethylorthosilicate, octamethyltrisiloxane, octamethylcyclotetrasiloxane, tetramethyldimethyldimethoxydisilane, tetramethylcyclotetrasiloxane, dimethyldimethoxysilane, diethylmethylsilane,

methyltriethoxysilane, phenyldimethylsilane, and phenylsilane, among others. The silicon- and-carbon-containing precursor may be mixed with a carrier gas before or during its introduction to the deposition chamber. A carrier gas may be an inactive gas that does not unduly interfere with the formation of the oxide film on the substrate. Examples of carrier gases include helium, neon, argon, nitrogen (N₂), and hydrogen (H₂), among other gases. No curing operation is required following formation of the second layer (the capping layer) to prevent evolution of film properties over time upon exposure to air, in embodiments. Curing may still be carried out to convert the film stack to a silicon-and-oxygen-containing layer. The film stack may be cured after method 100 is complete. The curing stage involves exposing the silicon-nitrogen-and-hydrogen-containing layer to an ozone-containing atmosphere. Ozone is generated outside the substrate processing region, in embodiments, and flowed into the substrate processing region. Plasma power may or may not be applied to the substrate processing region to further excite the ozone atmosphere in different embodiments of the invention. Absence of plasma, in embodiments, avoids generation of atomic oxygen which could modify the near surface network and thwart subsurface oxidation. The reduction of nitrogen and increase in oxygen occurs not only near the surface, but also in the subsurface region due to the ability of relatively stable ozone to penetrate the network of the silicon-nitrogen-and-hydrogen layer. A plasma may subsequently be applied to the substrate processing region to excite the ozone atmosphere in another stage of ozone curing in embodiments. Next, assorted parameters are described which apply to the curing operation. The deposition substrate may remain in the substrate processing region for curing, or the substrate may be transferred to a different chamber where the ozone-containing atmosphere is introduced. The curing temperature of the substrate during either/both stages may be less than or about 300°C, less than or about 250°C, less than or about 225°C, or less than or about 200°C in different embodiments. The temperature of the substrate may be greater than or about room temperature (25°C), greater than or about 50°C, greater than or about 100°C, greater than or about 125°C or greater than or about 150°C in different embodiments. Any of the upper bounds may be combined with any of the lower bounds to form additional ranges for the substrate temperature according to additional disclosed embodiments. The flow rate of the ozone (just the ozone contribution) into the substrate processing region during the curing operation may be greater than 500 seem, greater than 1 slm or greater than 2 slm in disclosed embodiments. The partial pressure of ozone during the curing operation may be greater than or about 20 Torr, greater than or about 30 Torr, greater than or about 50 Torr or greater than or about 100 Torr in disclosed embodiments.

The curing operation modified the silicon-nitrogen-and-hydrogen-containing layer into a silicon-and-oxygen-containing layer. The silicon-and-oxygen-containing layer may be converted into a silicon oxide layer by annealing the substrate at relatively high temperature in an oxygen-containing environment or by exposing the substrate to water at much lower temperatures. The deposition substrate may remain in the same substrate processing region used for curing when the oxygen-containing atmosphere is introduced, or the substrate may be transferred to a different chamber where the oxygen-containing atmosphere is introduced. The oxygen-containing atmosphere may include one or more oxygen-containing gases such as molecular oxygen (⁽¾), ozone (O3), water vapor (H2O), hydrogen peroxide (H2O2) and nitrogen-oxides (NO, NO₂, etc.), among other oxygen-containing gases. The oxygen- containing atmosphere may also include radical oxygen and hydroxyl species such as atomic oxygen (O), hydroxides (OH), etc., that may be generated remotely and transported into the substrate chamber. Ions of oxygen-containing species may also be present. The oxygen anneal temperature of the substrate may be less than or about 1 100°C, less than or about 1000°C, less than or about 900°C or less than or about 800°C in different embodiments. The temperature of the substrate may be greater than or about 500°C, greater than or about 600°C, greater than or about 700°C or greater than or about 800°C in different embodiments. Once again, any of the upper bounds may be combined with any of the lower bounds to form additional ranges for the substrate temperature according to additional disclosed

embodiments.

Alternatively or in combination, the silicon-and-oxygen-containing layer may be converted to silicon oxide by exposing the silicon-and-oxygen-containing layer to a humid environment. The humid environment may be provided in the same region used for curing or the substrate may be moved to a separate processing station in disclosed embodiments. The humid environment may have a relative humidity greater than 50%, greater than 60%, greater than 70%, greater than 75%, greater than 80% or greater than 85% in embodiments of the invention. The substrate temperature may be between room temperature (25°C) and about 100°C, between about 40°C and about 95°C, between about 50°C and about 90°C, 60°C and about 90°C or between about 70°C and about 90°C in embodiments. The duration of the humidity treatment may be less than 2 minutes, less than 5 minutes, less than 10 minutes, less than 30 minutes or less than an hour in embodiments of the invention.

The ozone curing operation typically takes place at higher substrate temperature than the humidity treatment. The curing operation and the humidity treatment may be carried out in separate chambers/stations, in embodiments, since these low temperatures are somewhat hard to precisely adjust within the same region. The inclusion of the low temperature humidity treatment described herein makes a high temperature oxygen atmosphere anneal (e.g. around 400°C or higher) unnecessary. The curing operation in combination with the humidity treatment completes the silicon oxide conversion process in embodiments of the invention. In other embodiments, only the humidity treatment is used to perform the conversion process. In either case, the removal of a high temperature oxygen treatment allows the conversion process to occur without oxidizing underlying layers. The absence of a high temperature anneal in an oxygen atmosphere enables integrated circuit manufacturers to stay within oxidation budgets. Removing these higher temperature oxygen anneals improves yield and performance of integrated circuit devices. Though an oxidizing anneal has been obviated by the invention described herein, a high temperature inert anneal may still be included, in embodiments, to densify the silicon oxide film. A high temperature anneal in an inert environment counts toward a thermal budget but not towards the more specific oxidation budget, each of which are determined for and associated with a particular process flow.

The ozone-containing atmospheres of the curing, annealing and the humidity treatment provides oxygen to convert the silicon-nitrogen-and-hydrogen-containing film into the silicon oxide (S1O₂) film. Alternative humidity treatments will be described shortly. The substrate used for depositing the silicon-nitrogen-and-hydrogen-containing layer and the capping layer may be a patterned substrate and may have a plurality of gaps for the spacing and structure of device components (e.g., transistors) formed on the substrate. The gaps may have a height and width that define an aspect ratio (AR) of the height to the width (i.e., H/W) that is significantly greater than 1 : 1 (e.g., 5: 1 or more, 6: 1 or more, 7: 1 or more, 8: 1 or more, 9: 1 or more, 10: 1 or more, 1 1 : 1 or more, 12: 1 or more, etc.). In many instances the high AR is due to small gap widths of that range from about 90 nm to about 22 nm or less (e.g., less than 90 nm, 65 nm, 50 nm, 45 nm, 32 nm, 22 nm, 16 nm, etc.). Because the silicon-nitrogen- and-hydrogen-containing layer is flowable, it can fill gaps with high aspect ratios without creating voids or weak seams around the center of the filling material. For example, a depositing flowable material is less likely to prematurely clog the top of a gap before it is completely filled to leave a void in the middle of the gap.

The substrate is then transferred out of the ozone-containing atmosphere and the silicon-and- oxygen-containing layer is dipped into a liquid solution comprising both oxygen and hydrogen to complete the conversion to a silicon oxide layer. Further anneals may not be necessary, in embodiments of the invention, due to the presence of the liquid solution step. Ozone curing and dipping the resulting film in the liquid bath, as described herein, produces a silicon oxide layer on the substrate, including the substrate gap. As noted above, the silicon oxide layer has fewer pores and less volume reduction than similar layers formed with carbon-containing precursors that have significant quantities of carbon present in the layer before the heat treatment step. In many cases, the volume reduction is slight enough (e.g., about 15 vol.% or less) to avoid post heat treatment steps to fill, heal, or otherwise eliminate spaces that form in the gap as a result of the shrinking silicon oxide. In some embodiments, the silicon oxide layer in the trench is substantially void- free. The liquid bath, substrate and cured film may be held at the same temperature during the operation of dipping the cured film in the liquid bath. The liquid bath may be between room temperature (25°C) and about 100°C, between about 40°C and about 95°C, between about 50°C and about 90°C, 60°C and about 90°C or between about 70°C and about 90°C in embodiments. The duration of the liquid bath immerson may be less than 2 minutes, less than 5 minutes, less than 10 minutes, less than 30 minutes or less than an hour in

embodiments of the invention. Subsequent high temperature oxygen anneals have been found to be unnecessary, in embodiments of the invention, once a silicon-nitrogen-and- hydrogen layer has been sequentially treated with an ozone cure and then a liquid bath as described herein. The inventors have further found that the liquid baths may be sufficient to transition a silicon-and-oxygen-containing layer to silicon oxide in some cases. Neither a preceding ozone cure nor a subsequent high temperature oxygen anneal was necessary to achieve silicon oxide.

The liquid bath or solution comprises oxygen and hydrogen and may include one or more of water, hydrogen peroxide or ammonium hydroxide. The silicon-and-oxygen film is dipped in the liquid solution and, in some embodiments, the substrate may be submerged in the liquid solution during dipping operation. The liquid solution may be SCI or SC2 baths in embodiments. The liquid solutions may comprise deionized water, at least 10% ammonium hydroxide and at least 10% hydrogen peroxide. All percentages are given herein by volume. The liquid solution may comprise deionized water, at least 10% hydrochloric acid and at least 10% hydrogen peroxide. Other liquid baths may be created which contain both oxygen and hydrogen. The inventors have also discovered that the rate of conversion to silicon oxide is increased when the pH is lowered into the acidic range or raised into the basic range.

Additional process parameters may be introduced during the description of an exemplary silicon oxide deposition system.

Exemplary Silicon Oxide Deposition System

Deposition chambers that may implement embodiments of the present invention may include high-density plasma chemical vapor deposition (HDP-CVD) chambers, plasma enhanced chemical vapor deposition (PECVD) chambers, sub-atmospheric chemical vapor deposition (SACVD) chambers, and thermal chemical vapor deposition chambers, among other types of chambers. Specific examples of CVD systems that may implement embodiments of the invention include the CENTURA ULTIMA® HDP-CVD chambers/systems, and

PRODUCER® PECVD chambers/systems, available from Applied Materials, Inc. of Santa Clara, Calif. Examples of substrate processing chambers that can be used with exemplary methods of the invention may include those shown and described in co-assigned U.S. Provisional Patent App. No. 60/803,499 to Lubomirsky et al, filed May 30, 2006, and titled "PROCESS CHAMBER FOR DIELECTRIC GAPFILL," the entire contents of which is herein incorporated by reference for all purposes. Additional exemplary systems may include those shown and described in U.S. Pat. Nos. 6,387,207 and 6,830,624, which are also incorporated herein by reference for all purposes.

Embodiments of the deposition systems may be incorporated into larger fabrication systems for producing integrated circuit chips. FIG. 2 shows one such system 200 of deposition, baking and curing chambers according to disclosed embodiments. In the figure, a pair of FOUPs (front opening unified pods) 202 supply substrate substrates (e.g., 300 mm diameter wafers) that are received by robotic arms 204 and placed into a low pressure holding area 206 before being placed into one of the wafer processing chambers 208a- f. A second robotic arm 210 may be used to transport the substrate wafers from the holding area 206 to the processing chambers 208a-f and back.

The processing chambers 208a-f may include one or more system components for depositing, annealing, curing and/or etching a flowable dielectric film on the substrate wafer. In one configuration, two pairs of the processing chamber (e.g., 208c-d and 208e-f) may be used to deposit the flowable dielectric material on the substrate, and the third pair of processing chambers (e.g., 208a-b) may be used to anneal the deposited dielectic. In another configuration, the same two pairs of processing chambers (e.g., 208c-d and 208e-f) may be configured to both deposit and anneal a flowable dielectric film on the substrate, while the third pair of chambers (e.g., 208a-b) may be used for UV or E-beam curing of the deposited film. In still another configuration, all three pairs of chambers (e.g., 208a-f) may be configured to deposit and cure a flowable dielectric film on the substrate. In yet another configuration, two pairs of processing chambers (e.g., 208c-d and 208e-f) may be used for both deposition and UV or E-beam curing of the flowable dielectric, while a third pair of processing chambers (e.g. 208a-b) may be used for annealing the dielectric film. Any one or more of the processes described may be carried out on chamber(s) separated from the fabrication system shown in different embodiments.

In addition, one or more of the process chambers 208a-f may be configured as a wet treatment chamber. These process chambers include heating the flowable dielectric film in an atmosphere that includes moisture. Thus, embodiments of system 200 may include wet treatment chambers 208a-b and anneal processing chambers 208c-d to perform both wet and dry anneals on the deposited dielectric film.

FIG. 3A is a substrate processing chamber 300 according to disclosed embodiments. A remote plasma system (RPS) 310 may process a gas which then travels through a gas inlet assembly 31 1. Two distinct gas supply channels are visible within the gas inlet assembly 31 1. A first channel 312 carries a gas that passes through the remote plasma system (RPS) 310, while a second channel 313 bypasses the RPS 310. The first channel 312 may be used for the process gas and the second channel 313 may be used for a treatment gas in disclosed embodiments. The lid (or conductive top portion) 321 and a perforated partition 353 are shown with an insulating ring 324 in between, which allows an AC potential to be applied to the lid 321 relative to perforated partition 353. The process gas travels through first channel 312 into chamber plasma region 320 and may be excited by a plasma in chamber plasma region 320 alone or in combination with RPS 310. The combination of chamber plasma region 320 and/or RPS 310 may be referred to as a remote plasma system herein. The perforated partition (also referred to as a showerhead) 353 separates chamber plasma region 320 from a substrate processing region 370 beneath showerhead 353. Showerhead 353 allows a plasma present in chamber plasma region 320 to avoid directly exciting gases in substrate processing region 370, while still allowing excited species to travel from chamber plasma region 320 into substrate processing region 370. Showerhead 353 is positioned between chamber plasma region 320 and substrate processing region 370 and allows plasma effluents (excited derivatives of precursors or other gases) created within chamber plasma region 320 to pass through a plurality of through holes 356 that traverse the thickness of the plate. The showerhead 353 also has one or more hollow volumes 351 which can be filled with a precursor in the form of a vapor or gas (such as a silicon-containing precursor) and pass through small holes 355 into substrate processing region 370 but not directly into chamber plasma region 320. Showerhead 353 is thicker than the length of the smallest diameter 350 of the through-holes 356 in this disclosed

embodiment. In order to maintain a significant concentration of excited species penetrating from chamber plasma region 320 to substrate processing region 370, the length 326 of the smallest diameter 350 of the through-holes may be restricted by forming larger diameter portions of through-holes 356 part way through the showerhead 353. The length of the smallest diameter 350 of the through-holes 356 may be the same order of magnitude as the smallest diameter of the through-holes 356 or less in disclosed embodiments.

In the embodiment shown, showerhead 353 may distribute (via through holes 356) process gases which contain oxygen, hydrogen and/or nitrogen and/or plasma effluents of such process gases upon excitation by a plasma in chamber plasma region 320. In embodiments, the process gas introduced into the RPS 310 and/or chamber plasma region 320 through first channel 312 may contain one or more of oxygen ((¾), ozone (O₃), 2O, NO, NO2, NH₃, N_xH_y including N2H4, silane, disilane, TSA and DSA. The process gas may also include a carrier gas such as helium, argon, nitrogen (N₂), etc. The second channel 313 may also deliver a process gas and/or a carrier gas, and/or a film-curing gas (e.g. O₃) used to remove an unwanted component from the growing or as-deposited film. Plasma effluents may include ionized or neutral derivatives of the process gas and may also be referred to herein as a radical-oxygen precursor and/or a radical-nitrogen precursor referring to the atomic constituents of the process gas introduced.

In embodiments, the number of through-holes 356 may be between about 60 and about 2000. Through-holes 356 may have a variety of shapes but are most easily made round. The smallest diameter 350 of through holes 356 may be between about 0.5 mm and about 20 mm or between about 1 mm and about 6 mm in disclosed embodiments. There is also latitude in choosing the cross-sectional shape of through-holes, which may be made conical, cylindrical or a combination of the two shapes. The number of small holes 355 used to introduce a gas into substrate processing region 370 may be between about 100 and about 5000 or between about 500 and about 2000 in different embodiments. The diameter of the small holes 355 may be between about 0.1 mm and about 2 mm.

FIG. 3B is a bottom view of a showerhead 353 for use with a processing chamber according to disclosed embodiments. Showerhead 353 corresponds with the showerhead shown in FIG. 3 A. Through-holes 356 are depicted with a larger inner-diameter (ID) on the bottom of showerhead 353 and a smaller ID at the top. Small holes 355 are distributed substantially evenly over the surface of the showerhead, even amongst the through-holes 356 which helps to provide more even mixing than other embodiments described herein.

An exemplary film is created on a substrate supported by a pedestal (not shown) within substrate processing region 370 when plasma effluents arriving through through-holes 356 in showerhead 353 combine with a silicon-containing precursor arriving through the small holes 355 originating from hollow volumes 351. Though substrate processing region 370 may be equipped to support a plasma for other processes such as curing, no plasma is present during the growth of the exemplary film.

A plasma may be ignited either in chamber plasma region 320 above showerhead 353 or substrate processing region 370 below showerhead 353. A plasma is present in chamber plasma region 320 to produce the radical nitrogen precursor from an inflow of a nitrogen- and-hydrogen-containing gas. An AC voltage typically in the radio frequency (RF) range is applied between the conductive top portion 321 of the processing chamber and showerhead 353 to ignite a plasma in chamber plasma region 320 during deposition. An RF power supply generates a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.

The top plasma may be left at low or no power when the bottom plasma in the substrate processing region 370 is turned on during the second curing stage or clean the interior surfaces bordering substrate processing region 370. A plasma in substrate processing region 370 is ignited by applying an AC voltage between showerhead 353 and the pedestal or bottom of the chamber. A cleaning gas may be introduced into substrate processing region 370 while the plasma is present. The pedestal may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate. This configuration allows the substrate temperature to be cooled or heated to maintain relatively low temperatures (from room temperature through about 120°C). The heat exchange fluid may comprise ethylene glycol and water. The wafer support platter of the pedestal (preferably aluminum, ceramic, or a combination thereof) may also be resistively heated in order to achieve relatively high temperatures (from about 120°C through about 1100°C) using an embedded single-loop embedded heater element configured to make two full turns in the form of parallel concentric circles. An outer portion of the heater element may run adjacent to a perimeter of the support platter, while an inner portion runs on the path of a concentric circle having a smaller radius. The wiring to the heater element passes through the stem of the pedestal.

The substrate processing system is controlled by a system controller. In an exemplary embodiment, the system controller includes a hard disk drive, a floppy disk drive and a processor. The processor contains a single-board computer (SBC), analog and digital input/output boards, interface boards and stepper motor controller boards. Various parts of CVD system conform to the Versa Modular European (VME) standard which defines board, card cage, and connector dimensions and types. The VME standard also defines the bus structure as having a 16-bit data bus and a 24-bit address bus.

The system controller controls all of the activities of the deposition system. The system controller executes system control software, which is a computer program stored in a computer-readable medium. Preferably, the medium is a hard disk drive, but the medium may also be other kinds of memory. The computer program includes sets of instructions that dictate the timing, mixture of gases, chamber pressure, chamber temperature, RF power levels, susceptor position, and other parameters of a particular process. Other computer programs stored on other memory devices including, for example, a floppy disk or other another appropriate drive, may also be used to instruct the system controller.

A process for depositing a film stack (e.g. sequential deposition of a silicon-nitrogen-and- hydrogen-containing layer and then a silicon-oxygen-and-carbon-containing layer) on a substrate, converting a film to silicon oxide or a process for cleaning a chamber can be implemented using a computer program product that is executed by the system controller. The computer program code can be written in any conventional computer readable programming language: for example, 68000 assembly language, C, C++, Pascal, Fortran or others. Suitable program code is entered into a single file, or multiple files, using a conventional text editor, and stored or embodied in a computer usable medium, such as a memory system of the computer. If the entered code text is in a high level language, the code is compiled, and the resultant compiler code is then linked with an object code of precompiled Microsoft Windows® library routines. To execute the linked, compiled object code the system user invokes the object code, causing the computer system to load the code in memory. The CPU then reads and executes the code to perform the tasks identified in the program.

The interface between a user and the controller is via a flat-panel touch-sensitive monitor. In the preferred embodiment two monitors are used, one mounted in the clean room wall for the operators and the other behind the wall for the service technicians. The two monitors may simultaneously display the same information, in which case only one accepts input at a time. To select a particular screen or function, the operator touches a designated area of the touch- sensitive monitor. The touched area changes its highlighted color, or a new menu or screen is displayed, confirming communication between the operator and the touch-sensitive monitor. Other devices, such as a keyboard, mouse, or other pointing or communication device, may be used instead of or in addition to the touch-sensitive monitor to allow the user to communicate with the system controller.

As used herein "substrate" may be a support substrate with or without layers formed thereon. The support substrate may be an insulator or a semiconductor of a variety of doping concentrations and profiles and may, for example, be a semiconductor substrate of the type used in the manufacture of integrated circuits. A layer of "silicon oxide" may include minority concentrations of other elemental constituents such as nitrogen, hydrogen, carbon and the like. In some embodiments, silicon oxide consists essentially of silicon and oxygen. The term "precursor" is used to refer to any process gas which takes part in a reaction to either remove material from or deposit material onto a surface. A gas in an "excited state" describes a gas wherein at least some of the gas molecules are in vibrationally-excited, dissociated and/or ionized states. A gas (or precursor) may be a combination of two or more gases (or precursors). A "radical precursor" is used to describe plasma effluents (a gas in an excited state which is exiting a plasma) which participate in a reaction to either remove material from or deposit material on a surface. A "radical-nitrogen precursor" is a radical precursor which contains nitrogen and a "radical-hydrogen precursor" is a radical precursor which contains hydrogen. The phrase "inert gas" refers to any gas which does not form chemical bonds when etching or being incorporated into a film. Exemplary inert gases include noble gases but may include other gases so long as no chemical bonds are formed when (typically) trace amounts are trapped in a film.

The term "trench" is used throughout with no implication that the etched geometry has a large horizontal aspect ratio. Viewed from above the surface, trenches may appear circular, oval, polygonal, rectangular, or a variety of other shapes. The term "via" is used to refer to a low aspect ratio trench which may or may not be filled with metal to form a vertical electrical connection. As used herein, a conformal layer refers to a generally uniform layer of material on a surface in the same shape as the surface, i.e., the surface of the layer and the surface being covered are generally parallel. A person having ordinary skill in the art will recognize that the deposited material likely cannot be 100% conformal and thus the term "generally" allows for acceptable tolerances. Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a process" includes a plurality of such processes and reference to "the precursor" includes reference to one or more precursor and equivalents thereof known to those skilled in the art, and so forth.

Also, the words "comprise," "comprising," "include," "including," and "includes" when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

Claims

WHAT IS CLAIMED IS:

1. A method of forming a silicon oxide layer on a substrate, the method comprising:

forming a first layer comprising silicon, nitrogen and hydrogen by:

flowing an unexcited precursor into a first remote plasma region to produce a radical-precursor,

combining a carbon-free silicon-containing precursor with the radical- precursor in a first plasma-free substrate processing region, and depositing a carbon-free silicon-nitrogen-and-hydrogen-containing layer over the substrate; and

forming a second layer comprising silicon and oxygen by:

flowing an unexcited oxygen-containing precursor into a second remote plasma region to produce a radical-oxygen precursor,

combining a silicon-and-carbon-containing precursor with the radical- oxygen precursor in a second plasma- free substrate processing region, and depositing a silicon-oxygen-and-carbon-containing capping layer over the carbon-free silicon-nitrogen-and-hydrogen-containing layer.

2. The method of claim 1 wherein the substrate is not exposed to air between forming the first layer and forming the second layer.

3. The method of claim 1 wherein unreacted precursors and reaction byproducts are removed from the first plasma- free substrate processing region after forming the first layer and before forming the second layer.

4. The method of claim 1 wherein the first remote plasma region is the same as the second remote plasma region and the first plasma-free substrate processing region is the same as the second plasma-free substrate processing region.

5. The method of claim 1 wherein a temperature of the substrate is greater than or about 0°C and less than or about 225°C during forming of the first layer and the second layer.

6. The method of claim 1 wherein no curing operation is required after forming the second layer to prevent evolution of film properties over time upon exposing the substrate to air.

7. The method of claim 1 wherein the silicon-and-carbon-containing precursor comprises one of dimethylsilane, trimethylsilane, tetramethylsilane, diethylsilane, tetramethylorthosilicate, tetramethyldisiloxane, tetraethylorthosilicate, octamethyltrisiloxane, octamethylcyclotetrasiloxane, tetramethyldimethyldimethoxydisilane,

tetramethylcyclotetrasiloxane, dimethyldimethoxysilane, diethylmethylsilane,

methyltriethoxysilane, phenyldimethylsilane, and phenylsilane.

8. The method of claim 1 further comprising curing the first and second layers in an ozone-containing atmosphere to convert the first and second layers to a silicon- and-oxygen-containing layer.

9. The method of claim 8 wherein a temperature of the substrate is greater than or about 75°C and less than or about 225°C during the curing operation.

10. The method of claim 8 further comprising exposing the silicon-and- oxygen-containing layer to a humid environment having at least 50% relative humidity to convert the silicon-and-oxygen-containing layer to a silicon oxide layer.

11. The method of claim 10 wherein a temperature of the substrate is greater than or about 25°C and less than 100°C during the exposing operation.

12. The method of claim 10 wherein the silicon oxide layer consists essentially of silicon and oxygen.

13. The method of claim 1 wherein a thickness of the second layer is between about ΙΟθΑ and about 300A.

14. The method of claim 1 wherein the carbon-free silicon-nitrogen-and- hydrogen-containing layer is flowable during deposition.

15. The method of claim 1 wherein the substrate is patterned and has a trench having a width of about 50 nm or less.

16. The method of claim 1 wherein the unexcited precursor comprises nitrogen and the radical-precursor is a radical-nitrogen precursor.

17. The method of claim 1 wherein the unexcited precursor comprises at least one of N₂H₂, NH₃, N₂ and H₂.

18. The method of claim 1 wherein the carbon-free silicon-containing precursor comprises one of N(SiH₃)H₂, N(SiH₃)₂H or N(SiH₃)₃.

19. The method of claim 1 further comprising removing process effluents from the first plasma-free substrate processing region between the operations of forming the first and second layers.