US20050109460A1 - Adjustable gas distribution system - Google Patents

Abstract

The present invention provides a gas distribution apparatus comprising a plurality of outlets and at least one replaceable insert placed in at least one of the outlets. The insert is provided with a passageway adapted to alter the size of the at least one of the outlets and/or the direction of gases exiting the at least one of the outlets. The insert is provided with passageway that may be substantial straight and cylindrical. The passageway may have a first portion with a smaller diameter and a second portion with a larger diameter to selectively alter the size of the outlet passage in the gas distribution apparatus. Alternatively, the insert is provided with a main passageway and plurality of secondary passageways branched and angled from the main passageway. The angle between the main and branch passageways is in the range from about 10 to about 90 degrees. In one embodiment, the angle between the main and branch passageways is about 90 degrees.

Description

CROSS REFERENCES TO RELATED APPLICATIONS
• This application claims the benefit of and priority to U.S. Provisional Application No. 60/475,079 filed May 30, 2003, the disclosure of which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
• The present invention relates generally to the field of semiconductor equipment and processing. More specifically, the present invention relates to an adjustable gas distribution apparatus useful in semiconductor fabrication.
BACKGROUND OF THE INVENTION
• Wafer processing reactor systems and methods are widely used in the manufacture of semiconductors and integrated circuits. One particular type of wafer processing system utilizes chemical vapor deposition (CVD) to deposit films or layers on the surface of a substrate as a step in the manufacture of semiconductors and integrated circuits. As described in the prior art, in chemical vapor deposition in semiconductor device fabrication (or other chemical reactors in which reaction products are desired to deposit or form in certain geometric manifestations), it is often required to modify a gas dispersion device from a simple basic design that imparts changes necessary to achieve a desired end result. Examples of such systems are shown for instance in U.S. Pat. Nos. 6,415,736, 6,410,089, 6,284,673, 6,050,506, 6,184,986 and 6,126,753, among others.
• Atomic layer deposition (ALD) is an alternative to CVD processes to deposit very thin films. ALD can be performed at comparatively lower temperatures which is compatible with the industry's trend toward lower temperatures, has high precursor utilization efficiency, and can produce conformal thin film layers. More advantageously, ALD can control film thickness on an atomic scale, and can be used to “nano-engineer” complex thin films. In an ALD process cycle, each reactant gas is introduced independently into a reaction chamber through, for example a showerhead, so that no gas phase intermixing occurs. A monolayer of a first reactant is physi- or chemisorbed onto a substrate surface. Excess first reactant is evacuated from the reaction chamber preferably with the aid of an inert purge gas. A second reactant is then introduced to the reaction chamber and reacted with the first reactant to form a monolayer of the desired thin film via a self-limiting surface reaction. The self-limiting reaction stops once the initially adsorbed first reactant fully reacts with the second reactant. Excess second reactant is evacuated, preferably with the aid of an inert purge gas. A desired film thickness is obtained by repeating the deposition cycle as necessary. The film thickness can be controlled to atomic layer accuracy by simply counting the number of deposition cycles.
• In many CVD or ALD applications, a simple basic geometry of outlet holes in a gas distribution apparatus does not achieve the required deposition thickness specifications. It has been demonstrated that a constant array of outlet holes or “pitch” does not necessarily create a uniform deposition on a wafer. It is therefore desirable to alter the outlet hole pattern or size to create the desired end effect. One prior art approach is to alter the location and/or size of the outlets to achieve the desired deposition pattern. This approach has had limited success however, as it does not allow for adjustment if further changes are necessary, such as in utilizing the same apparatus for more than one particular process or recipe which may be effected by the outlet configuration. Therefore, further development in gas distribution apparatus useful in CVD and ALD are needed.
SUMMARY OF THE INVENTION
• An adjustable gas distribution apparatus useful in semiconductor fabrication is provided. The adjustable gas distribution apparatus of the present invention allows one to alter the size and/or direction of gases exiting the gas distribution apparatus and thus selectively tailor the configuration of the apparatus to achieve a desired end response.
• In one aspect, the present invention provides a gas distribution apparatus comprising a plurality of outlets and at least one replaceable insert placed in at least one of the outlets. The insert is provided with a passageway adapted to alter the size of and/or the direction of gases exiting the at least one of the outlets. The insert can be placed in the outlet by threading. Alternatively, the insert can be placed in the outlet by press fit.
• In one embodiment, the insert is provided with a passageway that is substantially straight and cylindrical. The passageway may have a first portion with a smaller diameter and a second portion with a larger diameter to selectively alter the size of the outlet passage in the gas distribution apparatus.
• In another embodiment, the insert is provided with a main passageway and plurality of secondary passageways branched and angled from the main passageway. The angle between the main and branch passageways is in the range from about 10 to about 90 degrees. In one embodiment, the angle between the main and branch passageways is about 90 degrees.
• In another aspect, the present invention provides a gas distribution apparatus comprising a unitary body having a surface facing a processing region and a plurality of outlet passages formed within the unitary body and extending through the surface for providing gases into the processing region. At least one replaceable insert is placed in at least one of the outlet passages to allow altering the size of at least one of the outlet passages and/or the direction of gases exiting the at least one of the outlet passages into the processing region.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other objects and advantages of the present invention become apparent upon reading of the detailed description of the invention provided below and upon reference to the drawings in which:
• FIG. 1 is external view of a showerhead showing a plurality of through outlet holes in which one or more replaceable inserts of the present invention can be installed.
• FIG. 2 shows an internal gas distribution network within the showerhead as illustrated inFIG. 1.
• FIG. 3 is a front view of a screw type insert according to one embodiment of the present invention.
• FIG. 4 is a top view of the screw type insert illustrated inFIG. 3 according to one embodiment of the present invention.
• FIG. 5 is a cross-sectional view along line A-A of the screw type insert illustrated inFIG. 4 according to one embodiment of the present invention.
• FIG. 6 is a partial cross-sectional view of a showerhead installed with the insert illustrated inFIGS. 3-5 according to one embodiment of the present invention.
• FIG. 7 is a front view of a press-fit type insert having multiple branch passageways angled from a main passageway according to one embodiment of the present invention.
• FIG. 8 is a top view of the press-fit type insert illustrated inFIG. 7 according to one embodiment of the present invention.
• FIG. 9 is a cross-sectional view along line B-B of the press-fit type insert illustrated inFIG. 8 according to one embodiment of the present invention.
• FIG. 10 is a partial cross-sectional view of a showerhead installed with the press-fit type insert illustrated inFIGS. 7-9 according to one embodiment of the present invention.
• FIG. 11 is a front view of a press-fit type of insert having multiple branch passageways perpendicular to a main passageway according to one embodiment of the present invention.
• FIG. 12 is a top view of the press-fit type insert illustrated inFIG. 11 according to one embodiment of the present invention.
• FIG. 13 is a cross-sectional view along line C-C of the press-fit type insert illustrated inFIG. 12 according to one embodiment of the present invention.
• FIG. 14 is a partial cross-sectional view of a showerhead installed with the press-fit type insert illustrated inFIGS. 11-13 according to one embodiment of the present invention.
• FIG. 15 is a front view of a press-fit type insert showing details of press fit engagement region according to one embodiment of the present invention.
• FIG. 16 is a top view of the press-fit type insert illustrated inFIG. 15 according to one embodiment of the present invention.
• FIG. 17 is a cross-sectional view along line D-D of the press-fit type insert illustrated inFIG. 16 according to one embodiment of the present invention.
• FIG. 18 is a partial cross-sectional view of a showerhead showing engagement details between the press-fit type insert illustrated inFIGS. 15-17 and the outlet in the showerhead according to one embodiment of the present invention.
• FIG. 19 is a front view of a press-fit type insert showing details of press fit engagement region according to one embodiment of the present invention.
• FIG. 20 is a top view of the press-fit type insert illustrated inFIG. 19 according to one embodiment of the present invention.
• FIG. 21 is a front view of a screw type insert showing multiple passageways according to one embodiment of the present invention.
• FIG. 22 is a top view of the screw type insert illustrated inFIG. 21 according to one embodiment of the present invention.
• FIG. 23 is a cross-sectional view along line F-F of the screw type insert illustrated inFIG. 22 according to one embodiment of the present invention.
• FIG. 24 is a partial cross-sectional view of a showerhead installed with the screw type insert illustrated inFIGS. 21-23 according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• An adjustable gas distribution apparatus useful in semiconductor fabrication is provided. In general, the adjustable gas distribution apparatus of the present invention comprises a plurality of gas outlets and one or more inserts installed in one or more of the outlets which allow altering of the size of the outlets and/or the direction of gases exiting the gas distribution apparatus and thus selectively tailoring the gas flow velocity and pattern to specific process requirements.
• Referring to the drawings where like components are designated by like reference numerals, the present adjustable gas distribution apparatus is described in more detail.
• FIG. 1 shows ashowerhead10 in which one or more inserts of the present invention can be used. It should be noted that theshowerhead10 shown inFIG. 1 is for illustrative purpose only and not intended to limit the scope of the invention in any way. The inserts described below can be used in any other gas distribution apparatus where adjustment of flow velocity and/or direction of gases exiting the apparatus is desired. Generally, in a showerhead, a plurality of channels, passages or holes are created to form an internal gas distribution network in a member. The member can be a single unitary block within which an internal gas distribution network is formed. The member can also be comprised of several individual blocks, within each of which a plurality of channels, passages or holes are formed. These individual blocks are then connected and assembled as a unit, for example by a plurality of bolts. The channels, passages or holes can be formed by any suitable machining methods such as drillings, reaming and electrical discharge machining, etc.
• In particular,FIG. 1 shows an external view of ashowerhead10.FIG. 2 shows an internalgas distribution network12 formed within theshowerhead10. A plurality ofhorizontal channels14 are formed in a unitarycylindrical member16. Theunitary member16 can be comprised of an aluminum, steel, or nickel-based alloy block, or any other suitable materials. Thesehorizontal channels14 converge at a convergingpoint18 and extend radially and outwardly to theperiphery surface20 of thecylindrical member16. Theperiphery surface20 is closed. Thehorizontal channels14 can be formed by drilling from theperiphery surface20. The unnecessary openings on the periphery surface are closed, for example by sealing plugs after thechannels14 are formed. Avertical inlet passage22 is formed and connected with the convergingpoint18. Theinlet passage18 extends upwardly and through theupper surface24 of theunitary member16 and connected to a gas source (not shown). Gases are introduced through theinlet passage22 and distributed into thehorizontal channels14 via the convergingpoint18.
• A plurality of outlet passages orholes26 are formed along the path of thehorizontal channels14. These outlet holes26 extend downwardly and through thebottom surface28 of theunitary member16. For clarity and simplicity, only some outlet holes are shown inFIGS. 1 and 2. It should be noted that numerous horizontal channels and outlet passages or holes along the horizontal channels can be formed. Various patterns and configurations of outlet holes can be designed according to process specifications. The diameter of the outlet holes can be uniform throughout the bottom surface of the showerhead. Alternatively, the diameters of the outlet holes may differ. For example, the diameter of the outlet holes can be larger in the inner region and smaller in the outer region of the showerhead bottom surface to provide uniform back pressure. Any or all of the through outlet holes in the showerhead may include an insert described below to allow modification of the outlet size or diameter and/or the directions of gases exiting the showerhead.
• The insert is designed to be installed onto, for example, a showerhead as illustrated inFIGS. 1 and 2, to provide a known diameter passageway leading from the internal gas distribution network within the showerhead to the process chamber or region. The insert may be a small precision machined part. The insert can be made of the same material as the showerhead body. Alternatively, the insert is made of a different material to capitalize on differences in physical properties that is desirable, such as different coefficients of thermal expansion to improve sealing between the insert and the showerhead body when used at elevated temperatures. The insert is provided with passageways by any suitable machining method such as drilling, reaming, electrical discharge machining, and the like.
• FIGS.3 to6 show ascrew type insert30 according to one embodiment of the invention. Theinsert30 is provided withthreads32 for engaging theinsert30 with anoutlet passage26 which, in this embodiment, is also provided with threads for receiving theinsert30. The installation is accomplished by screwing theinsert30 into theshowerhead outlet26 until the insert is sufficiently seated to ensure that the gases from the upstream side, i.e., outlet passages, find no route except that through the precision passageway in theinsert30. Acylindrical passageway34 is formed in theinsert30 and extends through thebottom surface36 of theinsert30. When installed, theinsert passageway34 is coaxial and in fluid communication with theoutlet passage26. Gases from theinternal distribution network12 exit theshowerhead10 via theinsert30 in a direction perpendicular to thebottom surface28 of theshowerhead10. The diameter of theinsert passageway34 can be varied to tailor gas flow velocity to specific process requirements. For example, the insert passageway may have afirst portion38 with a smaller diameter proximate to thegas distribution channel14 and asecond portion39 with a larger diameter distal to thedistribution channel14. The smaller diameter in thefirst portion38 provides a metering function to create uniform back pressure. The larger diameter in thesecond portion39 allows the reduction of a “jetting” effect of the gas stream and facilitate installation and removal of theinsert30.
• FIGS.7 to10 show a pressfit type insert40 according to another embodiment of the invention. Press fit installation alleviates the need for threaded joining. Amain passageway42 is formed in theinsert40 and branched into a plurality ofsecondary passageways44. In this embodiment, fourbranch passageways44 are formed. The branch passageways44 extend through theside surface46 of theinsert40. Each of thebranch passageways44 are angled from themain passageway42 in the range from about 10 to 89 degrees. After theinsert40 is installed, the insertmain passageway42 is coaxial with theoutlet passage26. Theinsert40 extends out of thebottom surface28 of theshowerhead10 so that the openings of the branch passageways42 on theside surface46 of theinsert40 are positioned outside of the plane of thebottom surface28 of theshowerhead10 to direct gases into a processing region. In this embodiment, gases exit the branch passageways44 in a direction non-perpendicular to thebottom surface28 of theshowerhead10 or non-perpendicular to a substrate in a process region, for example, in an angle from about 10 to about 89 degrees with respect to thebottom surface28. This flow pattern minimizes prior art problems of “spotting,” or varying deposition thickness that matches the outlet spacing. By modifying the flow directions, the downward momentum of the gas stream entering the process region is reduced, and as a result gases are more evenly distributed in the process region. Accordingly, the gas flow direction or flow pattern can be altered by selectively choosing the angle between thebranch passageways44 and themain passageway42.
• FIGS. 11-14 show another press-fit type insert50 according to one embodiment of the present invention. As compared to theinsert40 illustrated inFIGS. 7-10, theinsert50 shown inFIGS. 11-14 has amain passageway52 and fourbranch passageways54 intersecting with themain passageway52 in 90 degrees. When theinsert50 is installed, gases fromdistribution channels14 exit the openings of the branch passageways54 in a direction parallel to thebottom surface28 of theshowerhead10.
• FIGS.15 to20 show in detail the engagement of a press-fit type insert60 of the present invention with theoutlet26 in theshowerhead10. In theengagement region62, the outer diameter (D2) of theinsert60 is slightly larger than the outer diameter (D1) in thenon-engagement region64. In a testing or trial stage, a preliminary insert can be sized so that the section in the engagement region is substantially shorter than the section in the non-engagement region (L2<L1) to ease installation and removal of the insert. Threading70 can be provided in the preliminary insert to facilitate installation and removal of theinsert60. Once the desired insert passageway size is determined, the preliminary insert may be removed and replaced with afinal insert72 that has a larger engagement section as illustrated inFIGS. 19 and 20. In thefinal insert72, the engagement section is substantially longer than the non-engagement section (L2>L1). A large engagement region between an insert and an outlet minimizes internal gaps or pocket volume and ensure enhanced sealing between the insert and the showerhead.
• FIGS.21 to24 show anotherscrew type insert80 according to one embodiment of the invention. Theinsert80 has ahexagonal section82 andcylindrical section84. Thecylindrical section84 is provided withthreads86 for engaging theinsert80 with theoutlet26 in theshowerhead10, which is also provided with threads for receiving theinsert80. Amain passageway88 is formed within thecylindrical section84 and extends into thehexagonal section82. Themain passageway88 is branched in thehexagonal section82 into multiplehorizontal passageways90 which extend radially and outwardly. Thehorizontal passageways90 extend through the side surfaces92 of thehexagonal section82 to direct gases into a processing region. The hexagonal configuration also provides a tool engagement means for installation and removal of theinsert80. Once theinsert80 is installed, thehexagonal section82 of the insert extends out of thebottom surface28 of theshowerhead10. Theinsert80main passageway88 is coaxial with theoutlet passage26 in theshowerhead10. Gases flow through themain passageway88 and change flow directions from vertical to horizontal with respect to thebottom surface28 of theshowerhead10 as indicated by the arrows inFIG. 24.
• Advantageously, the inserts of the invention can be placed in any selected outlets to alter the size and/or direction of the gases exiting the apparatus. Process results can be used as feedback to change the corresponding inserts to achieve the desired end response. The resulting configuration can then be used as is, or used to provide the design criteria to replicate the showerhead in a fixed, non-adjustable version that may be preferred in a production environment in which a minimum of process variables is desired.
• As described above, an adjustable gas distribution apparatus has been provided by the present invention. The foregoing description of specific embodiments of the invention have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications, embodiments, and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (23)

1. A gas distribution apparatus, comprising:

a body having a surface facing a processing region,

a plurality of outlet passages formed within the body and extending through the surface for providing gases into the processing region; and

at least one replaceable insert placed in at least one of the outlet passages, said insert is provided with a passageway adapted to alter the size of the at least one of the outlet passages and/or the direction of gases exiting the at least one of the outlet passages into the processing region.

2. The apparatus ofclaim 1 wherein said insert passageway is substantially cylindrical.

3. The apparatus ofclaim 1 wherein the insert passageway comprises a first portion having a smaller diameter and a second portion having a greater diameter.

4. The apparatus ofclaim 1 wherein said insert passageway is coaxial with the passage of the outlet placed with the insert.

5. The apparatus ofclaim 1 wherein the insert passageway comprises a first portion coaxial with the passage of the outlet placed with the insert and a plurality of second portions branched and angled from the first portion for directing the gases into the processing region.

6. The apparatus ofclaim 5 wherein said second portions of the insert passageway are angled from the first portion in the range from about 10 to about 90 degrees.

7. The apparatus ofclaim 5 wherein said second portions of the insert passageway are perpendicular to the first portion.

8. The apparatus ofclaim 5 wherein said second portions of the insert passageway are in parallel to the surface of the unitary body.

9. The apparatus ofclaim 1 wherein said outlet passages are substantially cylindrical.

10. The apparatus ofclaim 9 wherein said outlet passages comprises a first portion having a smaller diameter and a second portion having a greater diameter.

11. The apparatus ofclaim 1 wherein the insert is placed in the outlet passage by press fit.

12. The apparatus ofclaim 1 wherein the outlet passage and insert are provided with threads and the insert is placed in the outlet passage by threading.

13. The apparatus ofclaim 12, wherein the insert comprises means for engaging installment tools.

14. A gas distribution apparatus, comprising a plurality of outlets and at least one replaceable insert placed in at least one of the outlets, said insert is provided with a passageway adapted to alter the size of and/or the direction of gases exiting the at least one of the outlets.

15. The apparatus ofclaim 14 wherein the insert passageway is substantially cylindrical.

16. The apparatus ofclaim 14 wherein the insert passageway is coaxial with the outlet placed with the insert.

17. The apparatus ofclaim 15 wherein the insert passageway comprises a first portion having a smaller diameter and a second portion having a greater diameter.

18. The apparatus ofclaim 14 wherein the insert passageway comprises a first portion coaxial with the outlet placed with the insert and a plurality of second portions branched and angled from the first portion.

19. The apparatus ofclaim 18 wherein said second portions of the insert passageway are angled from the first portion in the range from about 10 to about 90 degree.

20. The apparatus ofclaim 18 wherein said second portions of the insert passageway are perpendicular to the first portion.

21. The apparatus ofclaim 14 wherein the insert is placed in the outlet by press fit.

22. The apparatus ofclaim 14 wherein the outlet and insert are provided with threads and the insert is placed in the outlet by screwing.

23. The apparatus ofclaim 22, wherein the insert is provided with means for engaging installation tools.

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