WO2002069365A2

WO2002069365A2 - Vessel for processing microelectronic workpieces

Info

Publication number: WO2002069365A2
Application number: PCT/US2002/005158
Authority: WO
Inventors: Dana R. Scranton
Original assignee: Semitool, Inc.
Priority date: 2001-02-27
Filing date: 2002-02-21
Publication date: 2002-09-06
Also published as: WO2002069365A3; AU2002244101A1

Abstract

A processor (2) for processing microelectronic workpieces within a vapor-phase environment includes a process vessel (4) adapted to hold one or more microelectronic workpieces (6) within a rotatable fixture. A drive motor (20) is coupled to the rotatable fixture to spin the rotatable fixture during processing. A gas introduction system (30, 33) introduces a gas into the process vessel for processing of the microelectronic workpieces. The processor can be used to clean, etch, or strip microelectronic workpieces.

Description

PROCESS VESSEL WITH ROTATION OF MICROELECTRONIC WORKPIECES

Field of the Invention [0001] The field of the invention is cleaning, stripping, and etching of microelectronic workpieces. More specifically, the field of the invention relates to methods and devices that use vapor or gas phase processes to clean, strip, etch, or otherwise process the surface of a microelectronic workpiece. A microelectronic workpiece is defined here to include a workpiece formed from a substrate on which microelectronic circuits or components, data storage elements or layers, or micro-mechanical or optical elements are formed.

Background of the Invention [0002] During the processing of microelectronic workpieces into e.g., electronic devices such as integrated circuits, it is often necessary to etch the surface of the workpiece, or to chemically process the surface of the workpiece. In addition, it is often necessary to clean the surface of the workpiece by stripping photoresist or contaminants that remain on the surface of the workpiece. In some etching and cleaning processes, a vapor-phase is used to bathe the workpiece with various chemically reactive substances.

[0003] Cleaning processes are intended to remove photoresist, particulate matter, organic species and other contaminants from the surface of the workpiece. Contaminants that are not removed during cleaning tend to reduce the overall yield of the manufacturing process. This reduces the number of usable electronic components, such as integrated circuits, microprocessors, memory devices, etc. that can be obtained from a workpiece. [0004] In cleaning, stripping, and etching processes, it is important to achieve a high level of process uniformity on each microelectronic workpiece. Process uniformity refers to uniform processing across the surface of an individual microelectronic workpiece as well as to uniform processing of separate microelectronic workpieces contained within a given batch. Maintaining a high level of process uniformity across the surface of an individual microelectronic workpiece can present engineering challenges. Even relatively minor variations in processing parameters can severely degrade the processed microelectronic workpiece. [0005] Processing microelectronic workpieces in batches

(in contrast to single workpiece processing) further complicates achieving a high level of process uniformity.

Batch processes have the inherent advantage of faster and more efficient production, when conducting the same processing step. Unfortunately, batch processing has the disadvantage that the workpieces are typically held within a process vessel and are closely spaced together and parallel in an array configuration. This configuration limits the access of processing fluids to the surfaces of the workpieces.

[0006] Thus, there are increased challenges to achieving process uniformity across the front and back surfaces of the workpieces, because the edges of the microelectronic workpieces are more accessible to the processing fluids than the interior areas. Batch processing accordingly tends to work against process uniformity across a single microelectronic workpiece. Moreover, batch processing can also create non-uniform process conditions with respect to separate microelectronic workpieces in a given batch. For example, the processing fluid more easily accesses the microelectronic workpieces nearest to the ends of the parallel processing array since these microelectronic workpieces are not confined within the interior portion of the processing array. [0007] Obtaining a high level of process uniformity in batch processes can also be difficult to achieve for vapor- phase chemical processing. Initially, the chemical vapor used must be homogenous within the process vessel. Still more challenging is the difficulty in achieving homogenous vapor concentrations when there are multiple chemical constituents in addition to air, nitrogen, or other carrier gases with which the vapors are mixed. For example, the relative amounts of constituent chemicals in a liquid state mixture often change when the mixture is transformed to a vapor-phase. These variations work against process uniformity. Additional difficulties arise when the temperature of the vapor-phase chemicals must be controlled.

Temperature gradients can develop within the process vessel, thereby impacting the reaction rates of the liquid or vapor-phase chemical on the microelectronic workpieces. [0008] Accordingly, there remains a need for improved methods and apparatus for vapor-phase processing, such as cleaning, etching, and stripping in a reliable, repeatable, and uniform manner.

Brief Statement of the Invention [0009] in a first aspect of the invention, a processor for processing microelectronic workpieces within a vapor- phase environment includes a process vessel adapted to hold one or more microelectronic workpieces. The microelectronic workpieces are preferably held within a rotatable fixture. A motor rotates the fixture. A gas or vapor system supplies gas or vapor into the process vessel for processing microelectronic workpieces. The rotation of the workpieces and fixture provides more uniform processing. As an alternative, if the workpieces are fixed in position, the vapor can be made to circulate around them via a spinning vane or rotor element, pumping or spraying. [0010] In a second aspect of the invention, the processor according to first aspect uses a gas or vapor selected from the group consisting of H₂0, 0₃, HF, HC1, and NH₄OH. [0011] In a third aspect of the invention, independent of any apparatus aspects or elements, a method of processing microelectronic workpieces includes the step of rotating the microelectronic workpieces in the presence of the gas or vapor. [0012] In a fourth aspect of the invention, in practicing the method of the third aspect above, the workpieces are placed into a rotatable fixture within a chamber. [0013] It is an object of the invention to provide improved methods and apparatus for cleaning, etching, and stripping of a microelectronic workpiece. [0014] The invention resides as well in subcombinations of the features and steps described. The use of any particular vapor-phase chemistry is not essential to the invention. Rather, the invention more broadly contemplates performing a batch vapor-phase process within a process vessel and with rotation of the microelectronic workpieces within the vapor-phase environment.

Brief Description of the Drawings [0015] FIG. 1 is a cut away perspective view of the process vessel.

[0016] FIG. 2 is a cut away perspective view of the process vessel according to a second, separate aspect of the invention.

[0017] FIG. 3 is side view of two microelectronic workpieces contained within the rotatable fixture.

[0018] FIG. 4 is a perspective view of a rotatable fixture according to one aspect of the invention. [0019] FIG. 5 is a side view of the a process vessel according to yet another aspect of the invention. Detailed Description [0020] In a method for processing microelectronic workpieces, a chemical vapor or gas environment is provided around the workpieces, with the workpieces rotating within that environment. No other steps or apparatus is essential. The workpieces are preferably, but not necessarily, already rotating, before the chemical vapor or gas is introduced to form the vapor or gas environment around the workpieces. The vapor or gas, or the workpieces themselves, may optionally be heated before and/or during processing. [0021] Various apparatus may be used to perform these methods, and the drawings show some preferred examples. [0022] Referring now to Figure 1, a processor 2 includes a process vessel or tank 4. The term "process vessel" here means walls forming a confined space for at least partially containing a gas or vapor. A process vessel may have one or more open sides or ends, such as a channel or duct. The processor 2 is used to house microelectronic workpieces 6 during processing. The microelectronic workpieces 6 can include, for example, semiconductor wafers, memory media, optical media, etc. The processor 2 is adapted for use in cleaning, etching, or stripping of microelectronic workpieces 6. [0023] A rotatable fixture 8 is supported within the interior of the process vessel 4. The term "rotatable fixture" here means any structure capable of holding workpieces during rotation of the workpieces. The rotatable fixture 8 preferably includes two opposing end plates 10 that are connected by retainers 12. While Figure 1 shows three workpiece retainers 12 that connect the end plates 10 of the rotatable fixture 8, additional workpiece retainers 12 can also be used. Preferably, as best shown in Figure 3, each workpiece retainer 12 contains a plurality of grooves 14 along a portion of its length. The grooves 14 have slots or are shaped to receive the edges 7 of microelectronic workpieces 6. The rotatable fixture, however, need not be an essential element, as other techniques are available to achieve relative movement between the workpieces and the vapor.

[0024] With respect to the embodiments shown in Figures 1 and 2, the fixture 8 is rotatably supported at one or both ends of the process vessel 4. A shaft 16 is connected to one of the end plates 10 of the rotatable fixture 8 and projects through the wall 18 of the process vessel 4. The shaft 16 is coupled to a motor 20 via a belt, drive chain 22, gears, or any equivalent connection. Rotation of the motor 20 causes rotation of the fixture 8 and micro- electronic workpieces 6 within the process vessel 4.

[0025] The processor 2 preferably includes a lid 24 that is located atop the process vessel 4. The lid 24 closes off the top of the vessel 4 and optionally forms a substantially air-tight seal with the process vessel 4 when in place. The lid 24 thus reduces or prevents the escape of gas or vapor during processing of the microelectronic workpieces 6. The lid 24 is preferably removable from the process vessel 4, or movable into an open position (by e.g., pivoting, sliding, etc.) such that the workpieces 6 can be removed from the process vessel 4 after processing. For some applications, a lid is not necessary and may be omitted.

[0026] The process vessel 4 also preferably includes at least one vapor or gas intake port 30. The intake port 30 delivers vapor or gas phase chemicals into the process vessel 4. While the intake port 30 is shown in one of the walls 18 of the process vessel 4, it can be located in other locations such as within the lid 24. The process vessel 4 also preferably includes a vent 32 to vent or exhaust vapor from the process vessel 4. While the vent 32 is shown in Figures 1 and 2 as being located in the lid 24, the vent 32, if used, can be located in other locations of the process vessel 4.

[0027] ^' The vapor intake port 30 is connected to a source of gas or vapor 33 such as H₂0, 0₃, HF, HC1, and NH₄OH (gas and vapor are used here interchangeably) . The intake port 30 and the source of vapor 33 form a vapor or gas introduction system. While H₂0, 0₃, HF, HC1, and NH₄OH are preferred process chemicals, other gases or vapors used for etching, cleaning, or stripping of microelectronic workpieces 6 can also be used with the processor 2. [0028] Figure 1 also shows heaters 34 on the wall 18 of the process vessel 4. The heaters 34 are used to heat the gases or vapors contained within the process vessel 4. The heaters 34 can instead be located at or around the gas intake port 30 so that heat is more easily transferred to the incoming gas. The heaters 34 can also be located upstream of the gas intake port 30 to pre-heat the vapor before it enters the process vessel 4. [0029] Figure 2 illustrates an alternative embodiment of the processor 2. In this embodiment, the motor 20 is directly coupled with the rotatable fixture 8. Preferably, the motor 20 is external to the process vessel 2 as is shown in Figure 2. The motor 20 can include a servo-motor that allows for precise control of the rotational characteristics of the rotatable fixture 8.

[0030] Figure 3 schematically illustrates one of the advantages of the present processor 2. Rotation of the microelectronic workpieces 6 causes the boundary layer near the front and back surfaces of the microelectronic workpieces 6 to eject flow radially outward as illustrated by arrows A. This boundary layer is replaced with the inflow of homogenous vapor from the environment within the process vessel 4 as shown by arrow B. The rotational movement of the fixture 8 facilitates a uniform flow of vapor over the front and back surfaces of the microelectronic workpieces 6.

[0031] Figure 4 shows a rotatable fixture 8 with the workpiece retainers 12 having projections or vanes 36 extending radially outwardly. The projections or vanes 36 assist in mixing the vapor environment within the process vessel 4. The projections 36 also assist in creating flow of homogenous vapor over the front and back surfaces of the microelectronic workpieces 6.

[0032] Figure 5 shows still another embodiment of the processor 2 with the fixture 8 is rotatable along a vertical axis as opposed to a horizontal axis of rotation shown in Figures 1 and 2. In addition, in the process vessel 4 shown in Figure 5, the fixture 8 is mounted only to one end of the process vessel 4. The motor 20 and rotatable fixture 8 can be vertically lifted out of the process vessel 4 in the direction of arrow C when processing is complete. [0033] The retainers 12, grooves 14, shaft 16, plates 10, motor 20, chain 22, lid 24, intake port 30, vent 32, heaters 34, and vanes 36, described above are not essential, and may be omitted or replaced with equivalents or manual steps. [0034] In operation of the processor 2, the microelectronic workpieces 6 are loaded into the rotatable fixture 8. The microelectronic workpieces 6 are preferably loaded using a robot arm 40 having an end effector 42, as shown in Fig. 1. The microelectronic workpieces 6 are lowered into position within the process vessel 4 wherein the microelectronic workpieces 6 are secured into the corresponding grooves 14 of the workpiece retainers 12.

Alternatively, the entire rotatable fixture 8 can first be removed from the process vessel 4 wherein the loading of the individual microelectronic workpieces 6 occurs outside of the process vessel 4. In this case, the loaded fixture 8 is then placed back into the process vessel 4.

[0035] With the microelectronic workpieces 6 secured in the rotatable fixture 8, the lid 24 is closed, and optionally sealed on top of the process vessel 4. The motor 20 is then turned on to spin the fixture 8 within the process vessel 4. Preferably, the rotation of the motor 20 is controlled via a controller 21. [0036] Depending on the particular process, the fixture 8 is rotated at from 1-3000 rpm, or more preferably from about 5 or 8 to 800 or 900 rpm, or from 200 or 300 to 500, 600, or 700 rpm. The rotation speed depends on the makeup of the gases or vapors, the temperature of the vapors, the concentration of the vapors, and the amount of mixing created by the rotation of the fixture 8.

[0037] Next, gas or vapor is introduced into the process vessel 4 via the intake port 30. The gas or vapor that is admitted to the interior of the process vessel 4 may include a mixture of multiple process gases or a single process gas. In addition, the gas or vapor may also be mixed with a carrier gas such as air, N₂, or the like. The gas or vapor introduced to the process vessel 4 may be pre-heated prior to entry or heated within the process vessel 4 via heaters 34. [0038] The gas or vapor within the process vessel 4 then reacts with surfaces of the microelectronic workpieces 6. For example, if the processor 2 is used for etching silicon, a vapor containing HF might be used. Once the processing is complete, the motor 20 reduces the speed of rotation of the rotatable fixture 8 until the fixture comes to a complete stop. The lid 24 is then opened up or removed from the process vessel 4 and the microelectronic workpieces 6 are lifted out of the process vessel 4. Preferably, the microelectronic workpieces 6 are lifted out of the process vessel 4 using the robot arm 40 and end effector 42. [0039] The apparatus and methods described are effective for processing with gases or vapors, rather than liquids. [0040] During processing, the vessel is preferably substantially free or empty of any liquid or if any liquid is present, such liquid is below the level of the rotatable fixture, so that the rotatable fixture does not move through or mix any liquid. The vessel may have a closed bottom with no drain, other than for the vent 32, which vents gas or vapor.

Claims

What is Claimed:

[0041] 1. A processor for processing microelectronic workpieces comprising: a process vessel; a rotatable fixture within the process vessel, adapted to hold one or more microelectronic workpieces; a motor for rotating the rotatable fixture; and a gas introduction system for supplying a gas into the process vessel, for processing the microelectronic workpieces.

[0042] 2. The processor according to claim 1, with the process vessel further including one or more heating elements.

[0043] 3. The processor according to claim 1, wherein the rotatable fixture is horizontally oriented.

[0044] 4. The processor according to claim 1, wherein the rotatable fixture is vertically oriented.

[0045] 5. The processor according to claim 1, with the rotatable fixture including vanes for mixing the gas phase environment within the process vessel.

[0046] 6. The processor according to claim 1, wherein the motor is external to the process vessel.

[0047] 7. The processor according to claim 1, wherein the gas introduction system includes a source of gas selected from the group consisting of H₂0, 0₃, HF, HCl, and NH₄0H. [0048] 8. The processor of claim 1 wherein the rotatable fixture is removable from the process vessel, for loading and unloading workpieces.

[0049] 9. The processor according to claim 1, wherein the motor rotates the rotatable fixture at from about 5-900 rpm.

[0050] 10. A processor for processing microelectronic workpieces within a vapor-phase environment comprising: a workpiece holder within the process vessel; a process vessel adapted to hold one or more microelectronic workpieces; a motor for rotating the workpiece holder at over 200 rpm; and a gas system for supplying a gas or vapor into the process vessel for processing the microelectronic workpieces.

[0051] 11. The processor of claim 10 where the gas is selected from the group consisting of H₂0, 0₃, HF, HCl, and NH₄0H.

[0052] 12. A method of processing microelectronic workpieces, comprising the steps of: placing the microelectronic workpieces into a process vessel; introducing a gas into the process vessel; and rotating the microelectronic workpieces relative to the gas, within the process vessel.

[0053] 13. The method of claim 12 further including the step of loading the workpieces into a rotatable fixture. [0054] 14. The method of claim 12, further comprising the step of heating the gas.

[0055] 15. The method of claim 12, wherein the gas is selected from the group consisting of H₂0, 0₃, HF, HCl, and NH₄0H.

[0056] 16. The method of claim 13, wherein the microelectronic workpieces are loaded into the rotatable fixture while the fixture is outside of the process vessel.

[0057] 17. The method of claim 2, wherein the rotatable fixture is rotated between 200 and 900 rpm.

[0058] 18. The method of claim 17, wherein the rotatable fixture is rotated between 300 and 800 rpm.

[0059] 19. The method of claim 12 wherein the process chamber is substantially free of liquid, so that the workpieces do not contact any liquid while they are rotating.

[0060] 20. A processor for processing microelectronic workpieces, comprising:

a process vessel; a gas system for supplying a gas into the process vessel, for processing the microelectronic workpieces; and means for creating relative rotational movement between the workpieces and the gas.