WO2010014626A2

WO2010014626A2 - Novel silicon precursors to make ultra low-k films with high mechanical properties by plasma enhanced chemical vapor deposition

Info

Publication number: WO2010014626A2
Application number: PCT/US2009/051983
Authority: WO
Inventors: Kang Sub Yim; Alexandros T. Demos
Original assignee: Applied Materials, Inc.
Priority date: 2008-07-31
Filing date: 2009-07-28
Publication date: 2010-02-04
Also published as: US20090017231A1; CN102113099B; US7989033B2; WO2010014626A3; CN102113099A; JP2011530174A; KR20110052674A; KR101139593B1; TWI388685B; TW201012962A; JP5312588B2

Abstract

A method for depositing a low dielectric constant film on a substrate is provided. The low dielectric constant film is deposited by a process comprising reacting one or more organosilicon compounds and a porogen and then post-treating the film to create pores in the film. The one or more organosilicon compounds include compounds that have the general structure Si-C_X-Si or -Si-O-(CH₂)_n-O-Si-. Low dielectric constant films provided herein include films that include Si-C_X-Si bonds both before and after the post-treatment of the films. The low dielectric constant films have good mechanical and adhesion properties, and a desirable dielectric constant.

Description

NOVEL SILICON PRECURSORS TO MAKE ULTRA LOW-K FILMS WITH HIGH MECHANICAL PROPERTIES BY PLASMA ENHANCED CHEMICAL VAPOR

DEPOSITION

BACKGROUND OF THE INVENTION Field of the Invention

[0001] Embodiments of the present invention generally relate to the fabrication of integrated circuits. More particularly, embodiments of the present invention relate to a process for depositing low dielectric constant films for integrated circuits.

Description of the Related Art

[0002] Integrated circuit geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore's Law), which means that the number of devices on a chip doubles every two years. Today's fabrication facilities are routinely producing devices having 90 nm and even 65 nm feature sizes, and tomorrow's facilities soon will be producing devices having even smaller feature sizes.

[0003] The continued reduction in device geometries has generated a demand for films having lower dielectric constant (k) values because the capacitive coupling between adjacent metal lines must be reduced to further reduce the size of devices on integrated circuits. In particular, insulators having low dielectric constants, less than about 4.0, are desirable. Examples of insulators having low dielectric constants include spin-on glass, fluorine-doped silicon glass (FSG), carbon-doped oxide, and polytetrafluoroethylene (PTFE), which are all commercially available.

[0004] More recently, low dielectric constant organosilicon films having k values less than about 3.0 and even less than about 2.5 have been developed. One method that has been used to develop low dielectric constant organosilicon films has been to deposit the films from a gas mixture comprising an organosilicon compound and a compound comprising thermally labile species or volatile groups and then post-treat the deposited films to remove the thermally labile species or volatile groups, such as organic groups, from the deposited films. The removal of the thermally labile species or volatile groups from the deposited films creates nanometer-sized voids in the films, which lowers the dielectric constant of the films, as air has a dielectric constant of approximately 1.

[0005] While low dielectric constant organosilicon films that have desirable low dielectric constants have been developed as described above, some of these low dielectric constant films have exhibited less than desirable mechanical properties, such as poor mechanical strength, which renders the films susceptible to damage during subsequent semiconductor processing steps. Semiconductor processing steps which can damage the low dielectric constant films include plasma-based etching processes that are used to pattern the low dielectric constant films. Ashing processes to remove photoresists or bottom anti-reflective coatings (BARC) from the dielectric films and wet etch processes can also damage the films.

[0006] Thus, there remains a need for a process for making low dielectric constant films that have improved mechanical properties and resistance to damage from subsequent substrate processing steps.

SUMMARY OF THE INVENTION

[0007] The present invention generally provides methods for depositing a low dielectric constant film. In one embodiment, the method includes introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprise a compound having the general structure:

R¹ R¹

I I

R¹ R¹ wherein each R¹ has the general formula C_nH_2n+I, OC_nH_2n+I or C_nH_2n-I. In some embodiments, each R¹ is independently selected from the group consisting of CH₃, CH=CH₂, H, and OH, and R² is selected from the group consisting of (CH₂)_a, C=C, C≡C, C₆H₄, C=O, (CF₂)_b, and combinations thereof, with a and b being independently 1 to 4. In some embodiments, at most one silicon atom will be bonded to an oxygen atom. In some embodiments, the one or more organosilicon compounds comprise a compound having the general structure:

^Si *^** ^«-<. Si "^

wherein each R³ has the general formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-I. In some embodiments, each R³ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and c and d are independently 1 to 4. The method also includes introducing a porogen into the chamber and reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber. The low dielectric constant film is then post-treated to substantially remove the porogen from the low dielectric constant film. The post-treating may comprise a UV, e-beam, or thermal annealing treatment. The post-treated low dielectric constant film comprises Si-C_x-Si bonds.

[0008] In another embodiment, a method for depositing a low dielectric constant film comprises introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprises a compound having the general structure:

wherein each R⁵ has the general formula C_nH_2n+1, OC_nH_2n+1, or C_nH_2n-1. In some embodiments, each R⁵ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and e is 1 to 3. In other embodiments, the one or more organosilicon compounds comprises a compound having the general structure R⁶ R ,6

I i

R^e — Si-O — (CH₂)r — O — Si— R^β

R^B R⁶

wherein each R⁶ has the general formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-I. In some embodiments, each R⁶ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and f is 1 to 4. The method also includes introducing a porogen into the chamber and reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber. The low dielectric constant film is then post-treated to substantially remove the porogen from the low dielectric constant film. The post-treating may comprise a UV, e-beam, or thermal annealing treatment.

[0009] In an additional embodiment, a method for depositing a low dielectric constant film comprises introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprises bis(triethoxysilyl)methane, introducing a porogen into the chamber, reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber, and then post- treating the low dielectric constant film to substantially remove the porogen from the low dielectric constant film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0011] Figure 1 is a flow diagram illustrating an embodiment of the invention. [0012] Figure 2 is a flow diagram illustrating another embodiment of the invention.

[0013] Figure 3 is a graph of the flow rates of the one or more organosilicon compounds and the porogen according to an embodiment of the invention.

[0014] Figure 4 is a FTIR of a post-treated low dielectric constant film provided according to embodiments of the invention.

DETAILED DESCRIPTION

[0015] The present invention provides a method of depositing a low dielectric constant film. The low dielectric constant film comprises silicon, oxygen, and carbon. The film also comprises nanometer-sized pores. The low dielectric constant film has a dielectric constant of about 3.0 or less, preferably about 2.5 or less, such as between about 2.0 and 2.2. The low dielectric constant film may have an elastic modulus of at least about 6 GPa. The low dielectric constant film may be used as an intermetal dielectric layer, for example. A method of depositing a low dielectric constant film according to an embodiment of the invention will be described briefly with respect to Figure 1 and then further described below.

[0016] Figure 1 is a process flow diagram summarizing an embodiment of the invention. In step 102, one or more organosilicon compounds are introduced into a chamber. The one or more organosilicon compounds comprise a compound having the general structure -Si-C_x-Si-, wherein x is between 1 and 4 or the general structure -Si-O-(CH₂)_n-O-Si-, wherein n is between 1 and 4. In step 104, a porogen is introduced into the chamber. In step 106, the one or more organosilicon compounds and the porogen are reacted in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber. In step 108, the low dielectric constant film is post-treated to substantially remove the porogen from the low dielectric constant film.

[0017] The chamber into which the one or more organosilicon compounds and the porogen are introduced may be a plasma enhanced chemical vapor deposition (PECVD) chamber. The plasma for the deposition process may be generated using constant radio frequency (RF) power, pulsed RF power, high frequency RF power, dual frequency RF power, or combinations thereof. An example of a PECVD chamber that may used is a PRODUCER^® chamber, available from Applied Materials, Inc. of Santa Clara, CA. However, other chambers may be used to deposit the low dielectric constant film.

[0018] Returning to step 102, the compound having the general structure -Si-C_x- Si- includes compounds that have the general structure:

R¹ R^%

R ¹ Si — R² S i R¹

I I

R¹ R*

wherein each R¹ has the general formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-I- In some embodiments, at least one R¹ comprises carbon. In other embodiments, at most one of the R¹ groups is a methylsilano group. In some embodiments, R¹ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and R² is selected from the group consisting of (CH₂)_a, C=C, C≡C, CeH₄, C=O, (CF₂)_b, and combinations thereof, with a and b being 1 to 4. In some embodiments, at most one silicon atom is bonded to an oxygen atom. In some embodiments, the compound having the general structure -Si-C_x-Si- includes compounds that have the general structure:

R³/ \ (CH₂), s" ^R₃

wherein each R³ has the general formula C_nH_2n+1, OC_nH_2n+1, or C_nH_2n-1. In some embodiments, each R³ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and c and d are independently 1 to 4. As defined herein, values for R groups and other groups that are independently selected may be the same or different than the other groups. In some embodiments, the compound having the general structure -Si-C_x-Si- is a poly- silanoalkane.

[0019] An example of a compound having the general structure:

I I

R¹ R¹

is bis(triethoxysilano)methane (Ci₃H₃₂O₆Si₂).

[0020] An example of a compound having the general structure:

is tetramethyl-1 ,3-disilacyclobutane (C₆Hi₆Si₂).

[0021] Other compounds that have the general structure -Si-C_x-Si- include compounds that have the general structure:

wherein each R⁵ has the general formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-I. In some embodiments, each R⁵ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and e is 1 to 3. An example of such a compound is tetramethyl-2,5-disila-1-oxacyclopentane tetramethyldisilafuran (C₆H₁₆OSi₂).

[0022] The one or more organosilicon compounds having the general structure -Si-O-(CH₂)_n-O-Si- may comprise compounds having the structure

R⁶ R⁶

I

R© C ^■O i ϊ f K\J ... Y \f ¹W¹M * >^ t}f . f y-fv.... . Q O ,f_ o rx6

R⁵ R⁶ wherein each R⁶ has the general formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-1. In some embodiments, each R⁶ is independently selected from the group consisting of CH₃, OCH₃, OC₂H₅, CH=CH₂, H, and OH, and f is 1 to 4. An example of such a compound is bis(trimethylsiloxy)ethane (C₈H₂₂O₂Si₂).

[0023] By using organosilicon compounds that comprise Si-C_x-Si bonds and the processing conditions described herein, low dielectric constant films that comprise Si-C_x-Si bonds (with x being between 1 and 4) both before and after post-treatment may be obtained. Depending on the organosilicon compounds used, the films may also comprise Si-O-Si bonds. Films comprising Si-C_x-Si bonds are desirable, as it has been observed that films with high Si-C_x-Si/Si-CH₃ ratios have improved ashing resistance, adhesion, and thermal conductivity properties compared to films having more Si-CH₃ bonds.

[0024] The one or more organosilicon compounds may also comprise organosilicon compounds that do not include the general structures described above. For example, the one or more organosilicon compounds may include methyldiethoxysilane (MDEOS), tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), trimethylsilane (TMS), pentamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, dimethyldisiloxane, tetramethyldisiloxane, hexamethyldisiloxane (HMDS), 1 ,3- bis(silanomethylene)disiloxane, bis(1 -methyldisiloxanyl)methane, bis(1 - methyldisiloxanyl)propane, hexamethoxydisiloxane (HMDOS), dimethyldimethoxysilane (DMDMOS), or dimethoxymethylvinylsilane (DMMVS).

[0025] Returning to step 104, the porogen is a compound that comprises thermally labile groups. The thermally labile groups may be cyclic groups, such as unsaturated cyclic organic groups. The term "cyclic group" as used herein is intended to refer to a ring structure. The ring structure may contain as few as three atoms. The atoms may include carbon, nitrogen, oxygen, fluorine, and combinations thereof, for example. The cyclic group may include one or more single bonds, double bonds, triple bonds, and any combination thereof. For example, a cyclic group may include one or more aromatics, aryls, phenyls, cyclohexanes, cyclohexadienes, cycloheptadienes, and combinations thereof. The cyclic group may also be bi-cyclic or tri-cyclic. In one embodiment, the cyclic group is bonded to a linear or branched functional group. The linear or branched functional group preferably contains an alkyl or vinyl alkyl group and has between one and twenty carbon atoms. The linear or branched functional group may also include oxygen atoms, such as in a ketone, ether, and ester. The porogen may comprise a cyclic hydrocarbon compound. Some exemplary porogens that may be used include norbornadiene (BCHD, bicycle(2.2.1)hepta-2,5-diene), alpha-terpinene (ATP), vinylcyclohexane (VCH), phenylacetate, butadiene, isoprene, cyclohexadiene, 1- methyl-4-(1-methylethyl)-benzene (cymene), 3-carene, fenchone, limonene, cyclopentene oxide, vinyl-1 ,4-dioxinyl ether, vinyl furyl ether, vinyl-1 ,4-dioxin, vinyl furan, methyl furoate, furyl formate, furyl acetate, furaldehyde, difuryl ketone, difuryl ether, difurfuryl ether, furan, and 1 ,4-dioxin.

[0026] As shown in step 106, the one or more organosilicon compounds and the porogen are reacted in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber. One or more porogens may be reacted with the one or more organosilicon compounds. The porogen reacts with the one or more organosilicon compounds to deposit a film that retains the thermally labile groups therein. Post-treating the film, as described in step 108, results in the decomposition and evolution of the porogens and/or the thermally labile groups from the film, resulting in the formation of voids or nanometer-sized pores in the film.

[0027] The one or more organosilicon compounds may be introduced into the chamber at a flow rate between about 10 mgm and about 5000 mgm. The porogen may be introduced into the chamber at a flow rate between about 10 mgm and about 5000 mgm. Optionally, an oxidizing gas, such as O₂, N₂O, CO₂, or combinations thereof, may be introduced into the chamber at a flow rate between about 0 seem and about 10000 seem and reacted with the one or more organosilicon compounds and the porogen. A dilution or carrier gas, such as helium, argon, or nitrogen, may also be introduced into the chamber at a flow rate between about 10 seem and about 10000 seem. [0028] The flow rates described above and throughout the instant application are provided with respect to a 300 mm chamber having two isolated processing regions, such as a PRODUCER^® chamber, available from Applied Materials, Inc. of Santa Clara, CA. Thus, the flow rates experienced per each substrate processing region are half of the flow rates into the chamber.

[0029] Although the introduction of the one or more organosilicon compounds and the introduction of the porogen into the chamber are shown sequentially as steps 102 and 104, the introduction of the one or more organosilicon compounds and the introduction of the porogen may be performed simultaneously. However, in a preferred embodiment, the one or more organosilicon compounds are introduced into the chamber before the porogen. In this embodiment, the one or more organosilicon compounds are introduced into the chamber at a first flow rate and then ramped up to a second flow rate. The porogen is introduced into the chamber at a third flow rate and then ramped up to a fourth flow rate. The one or more organosilicon compounds are ramped up to the second flow rate before the porogen is ramped up to the fourth flow rate.

[0030] Figure 2 is a process flow diagram illustrating a method of depositing a low dielectric constant film according to an embodiment in which the one or more organosilicon compounds are introduced into the chamber before the porogen. In step 201 , a substrate is positioned on a substrate support in a processing chamber capable of performing PECVD. In step 203, a gas mixture having a composition including one or more organosilicon compounds and optionally one or more oxidizing gases is introduced into the chamber through a gas distribution plate of the chamber, such as a showerhead. A radio-frequency (RF) power is applied to an electrode, such as the showerhead, in order to provide plasma processing conditions in the chamber. The gas mixture is reacted in the chamber in the presence of RF power to deposit an initiation layer comprising a silicon oxide layer that adheres strongly to the underlying substrate.

[0031] In step 205, the flow rate of the one or more organosilicon compounds is increased at a ramp-up rate between about 100 mg/min/sec and about 5000 mg/min/sec, preferably, between about 1000 mg/min/sec and about 2000 mg/min/sec, in the presence of the RF power, to deposit a first transition layer until reaching a predetermined organosilicon compound gas mixture. The ramp-up of the flow rate conditions is performed such that variation in DC bias of the gas distribution plate is less than 60 volts, preferably less than 30 volts, to avoid plasma induced damage (PID).

[0032] In step 207, while keeping the predetermined organosilicon compound gas mixture constant, a gas mixture having a composition including a porogen is introduced into the chamber through the gas distribution plate. In step 209, the flow rate of the porogen is increased at a ramp-up rate between about 100 mg/min/sec and about 5000 mg/min/sec, preferably, between about 200 mg/min/sec and about 1000 mg/min/sec, to deposit a second transition layer until reaching a predetermined final gas mixture.

[0033] In step 211 , the predetermined final gas mixture, i.e., the final gas mixture having a composition including the one or more organosilicon compounds and the porogen, is reacted in the chamber in the presence of RF power to deposit a final layer that is a low dielectric constant film. Upon completion of the deposition, the RF power is terminated. The chamber pressure is maintained during the RF power termination, such as by not opening the chamber throttle valve. Not wishing to be bound by theory, it is believed that by separating the ramp-up rates of the organosilicon compounds and the porogen compound, a more stable and manufacturable process can be obtained, yielding dielectric films with less defect issues, such as particle adders.

[0034] In step 213, the low dielectric constant film is post-treated to substantially remove the porogen from the low dielectric constant film.

[0035] Figure 3 is a graph illustrating the flow rates of the one or more organosilicon compounds and the porogen versus time according to an embodiment of the invention. The gas mixture having a composition including one or more organosilicon compounds and optionally one or more oxidizing gases is introduced into the chamber to deposit an initiation layer, as described above with respect to step 203 of Figure 2. The initiation layer deposition may have a time range of between about 1 second and about 10 seconds.

[0036] The flow rate of the one or more organosilicon compounds is then increased at the ramp-up rate to deposit a first transition layer until reaching a predetermined organosilicon compound gas mixture, as described above with respect to step 205 of Figure 2. The first transition layer deposition may have a time range of between about 1 second and about 10 seconds.

[0037] While keeping the predetermined organosilicon compound gas mixture constant, a gas mixture having a composition including one or more porogen compounds is introduced into the chamber, and the flow rate of the one or more porogen compounds is increased at a ramp-up rate to deposit a second transition layer until reaching a predetermined final gas mixture, as described above with respect to step 209 of Figure 2. The second transition layer deposition may have a time range of between about 1 second and about 180 seconds.

[0038] The predetermined final gas mixture having a composition including the one or more organosilicon compounds and the porogen is reacted in the chamber in the presence of RF power to deposit a final layer that is a low dielectric constant film, as described above with respect to step 211 of Figure 2. The final layer deposition may have a time range of between about 15 seconds and about 180 seconds.

[0039] It is believed that the initiation sequence for the deposition of the low dielectric constant film described above with respect to Figures 2 and 3 improves the adhesion of the low dielectric constant film to the underlying layer on the substrate on which it is deposited by providing improved control of the porosity and carbon content of the low dielectric constant film at the interface between the low dielectric constant film and the underlying layer.

[0040] Returning to step 106 of Figure 1 , during the reaction of the one or more organosilicon compounds and the porogen to deposit the low dielectric constant film on the substrate in the chamber, the substrate is typically maintained at a temperature between about 100⁰C and about 400°C. The chamber pressure may be between about 1 Torr and about 20 Torr, and the spacing between a substrate support and the chamber showerhead may be between about 200 mils and about 1500 mils. A power density ranging between about 0.14 W/cm² and about 2.8 W/cm², which is a RF power level of between about 100 W and about 2000 W for a 300 mm substrate, may be used. The RF power is provided at a frequency between about 0.01 MHz and 300 MHz, such as about 13.56 MHz. The RF power may be provided at a mixed frequency, such as at a high frequency of about 13.56 MHz and a low frequency of about 350 kHz. The RF power may be cycled or pulsed to reduce heating of the substrate and promote greater porosity in the deposited film. The RF power may also be continuous or discontinuous.

[0041] After the low dielectric constant film is deposited, the film is post-treated, as described in step 108. Post-treatments that may be used include electron beam (e-beam) treatments, ultraviolet (UV) treatments, thermal annealing treatments (in the absence of an electron beam and/or UV treatment), and combinations thereof.

[0042] Exemplary UV post-treatment conditions that may be used include a chamber pressure of between about 1 Torr and about 10 Torr and a substrate support temperature of between about 350⁰C and about 500⁰C. The UV radiation may be provided by any UV source, such as mercury microwave arc lamps, pulsed xenon flash lamps, or high-efficiency UV light emitting diode arrays. The UV radiation may have a wavelength of between about 170 nm and about 400 nm, for example. Further details of UV chambers and treatment conditions that may be used are described in commonly assigned U.S. Patent Application Serial No. 11/124,908, filed on May 9, 2005, which is incorporated by reference herein. The NanoCure™ chamber from Applied Materials, Inc., is an example of a commercially available chamber that may be used for UV post-treatments.

[0043] Exemplary electron beam conditions that may be used include a chamber temperature of between about 200⁰C and about 600⁰C, e.g. about 350⁰C to about 400⁰C. The electron beam energy may be from about 0.5 keV to about 30 keV. The exposure dose may be between about 1 μC/cm² and about 400 μC/cm². The chamber pressure may be between about 1 mTorr and about 100 mTorr. The gas ambient in the chamber may be any of the following gases: nitrogen, oxygen, hydrogen, argon, a blend of hydrogen and nitrogen, ammonia, xenon, or any combination of these gases. The electron beam current may be between about 0.15 mA and about 50 mA. The electron beam treatment may be performed for between about 1 minute and about 15 minutes. Although any electron beam device may be used, an exemplary electron beam chamber that may be used is an EBk™ electron beam chamber available from Applied Materials, Inc. of Santa Clara, CA.

[0044] An exemplary thermal annealing post-treatment includes annealing the film at a substrate temperature between about 200°C and about 500°C for about 2 seconds to about 3 hours, preferably about 0.5 to about 2 hours, in a chamber. A non-reactive gas such as helium, hydrogen, nitrogen, or a mixture thereof may be introduced into the chamber at a rate of about 100 to about 10,000 seem. The chamber pressure is maintained between about 1 mTorr and about 10 Torr. The preferred substrate spacing is between about 300 mils and about 800 mils.

[0045] The following examples illustrate embodiments of the invention. The substrates in the examples were 300 mm substrates. The low dielectric constant films were deposited on the substrates in a PRODUCER^® chamber available from Applied Materials, Inc. of Santa Clara, CA and UV treated in a NanoCure™ chamber available from Applied Materials, Inc. of Santa Clara, CA.

[0046] Example 1

[0047] A low dielectric constant film was deposited on a substrate at about 7.5 Torr and a temperature of about 300⁰C. The spacing was 300 mils, and the RF power was provided at 300 W at 13.56 MHz. The following processing gases and flow rates were used: bis(triethoxysilyl)methane at 2000 mgm, norbomadiene at 300 mgm, helium at 1500 seem. The film was the post-treated with a UV treatment. After the post-treatment, the film had a refractive index of 1.3702, a dielectric constant of 2.44, an elastic modulus of 9.1 GPa, a hardness of 1.2 GPa, and a shrinkage of 9.8%.

[0048] Example 2

[0049] A low dielectric constant film was deposited on a substrate at about 7.5 Torr and a temperature of about 225°C. The spacing was 400 mils, and the RF power was provided at 450 W at 13.56 MHz. The following processing gases and flow rates were used: bis(triethoxysilyl)methane at 500 mgm, alpha-terpinene at 2000 mgm, methyldiethoxysilane at 500 mgm, oxygen at 50 seem, and helium at 3500 seem. The film was the post-treated with a UV treatment. After the post- treatment, the film had a refractive index of 1.3443, a dielectric constant of 2.51 , an elastic modulus of 11.1 GPa, a hardness of 1.6 GPa, and a shrinkage of 15.70%.

[0050] Figure 4 shows the results of FTIR analysis performed on the low dielectric constant film of Example 1 after the UV treatment. The FTIR analysis shows that the Si-C-Si bonding (Si-C-Si peak at 1630 cm^'1) provided by the organosilicon compound bis(triethoxysilyl)methane is preserved in the post-treated film, and thus, the post-treated film has a desirable Si-C-Si network structure.

[0051] It was also found that using precursors with Si-C-Si bonds to obtain films with higher Si-C-Si/SiCH₃ ratios also resulted in films having smaller pore sizes after post-treatment than other films have similar dielectric constants and lower Si-C- Si/SiCH₃ ratios. Films with smaller pore sizes are desirable as they are stronger and less likely to be damaged during further processing than films with larger pore sizes.

[0052] It is recognized that the organosilicon compounds provided herein can be used in gas mixtures that do not contain a porogen to chemically vapor deposit low dielectric constant films. However, while films deposited from gas mixtures that comprise the organosilicon compounds described herein and lack a porogen are expected to have improved mechanical properties compared to films deposited from porogen-free mixtures comprising other organosilicon compounds, typically, a porogen is included to provide the desired, lower dielectric constants of about 2.4 or less. [0053] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1. A method of depositing a low dielectric constant film, comprising: introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprises a compound having the general structure:

R¹ R¹

wherein each R¹ has the formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-1, at least one R¹ comprises carbon, and at most one R¹ group is a methylsilano group, and R² is selected from the group consisting of (CH₂)_a, C=C, C≡C, C₆H₄, C=O, (CF₂)_b, and combinations thereof, with a and b being independently 1 to 4, and at most one silicon atom having a bond with an oxygen atom, or the general structure:

R³/ \ {CH₂)_d ^ ^R₃

wherein each R³ has the formula C_nH_2n+-_I, OC_nH_2n+1, or C_nH_2n-1; introducing a porogen into the chamber; reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber; and then post-treating the low dielectric constant film to substantially remove the porogen from the low dielectric constant film, wherein the post-treated low dielectric constant film comprises Si-Cx-Si bonds.

2. The method of claim 1 , wherein each R¹ and R³ is independently selected from the group consisting of CH₃, CH=CH₂, OCH₃, OC₂H₅, H, and OH.

3. The method of claim 1 , wherein the one or more organosilicon compounds comprises tetramethyl-1 ,3-disilacyclobutane.

4. The method of claim 1 , wherein introducing the one or more organosilicon compounds into the chamber comprises introducing the one or more organosilicon compounds at a first flow rate and ramping up to a second flow rate, introducing the porogen into the chamber comprises introducing the porogen at a third flow rate and ramping up to a fourth flow rate, and the one or more organosilicon compounds are ramped up to the second flow rate before the porogen is ramped up to the fourth flow rate.

5. The method of claim 4, wherein the low dielectric constant film has a dielectric constant of about 2.0 to about 2.5 and an elastic modulus of at least about 6 GPa.

6. The method of claim 4, further comprising introducing an oxidizing gas into the chamber and reacting the oxidizing gas with the one or more organosilicon compounds and the porogen.

7. A method of depositing a low dielectric constant film, comprising: introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprises a compound having the general structure:

or the general structure:

wherein each R⁵ and R⁶ has the formula C_nH_2n+I, OC_nH_2n+I, or C_nH_2n-I ; introducing a porogen into the chamber; reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber; and then post-treating the low dielectric constant film to substantially remove the porogen from the low dielectric constant film.

8. The method of claim 7, wherein each R⁵ and R⁶ is independently selected from the group consisting of CH₃, CH=CH₂, OCH₃, OC₂H₅, H, and OH.

9. The method of claim 7, wherein the post-treated low dielectric constant film comprises Si-Cx-Si bonds.

10. The method of claim 7, wherein the one or more organosilicon compounds comprises tetramethyl-2,5-disila-1-oxacyclopentane, tetramethyldisilafuran, or bis(trimethylsiloxy)ethane.

11. The method of claim 6, wherein introducing the one or more organosilicon compounds into the chamber comprises introducing the one or more organosilicon compounds at a first flow rate and ramping up to a second flow rate, introducing the porogen into the chamber comprises introducing the porogen at a third flow rate and ramping up to a fourth flow rate, and the one or more organosilicon compounds are ramped up to the second flow rate before the porogen is ramped up to the fourth flow rate.

12. A method of depositing a low dielectric constant film, comprising: introducing one or more organosilicon compounds into a chamber, wherein the one or more organosilicon compounds comprises a poly-silanoalkane having at most one silicon atom bonded to an oxygen atom, having at most one methytsilano group, and having at least one silicon atom bonded to more than one carbon atom; introducing a porogen into the chamber; reacting the one or more organosilicon compounds and the porogen in the presence of RF power to deposit a low dielectric constant film on a substrate in the chamber; and then post-treating the low dielectric constant film to substantially remove the porogen from the low dielectric constant film.

13. The method of claim 12, wherein the porogen comprises norbomadiene.

14. The method of claim 12, wherein the porogen comprises alpha-terpinene.

15. The method of claim 14, wherein the one or more organosilicon compounds further comprises methyldiethoxysilane.