Substrate processing apparatus and substrate processing method

Abstract

A substrate processing apparatus that forms a friction reduction film on a back surface of a substrate, wherein the substrate processing apparatus includes: a processing container that houses the substrate and forms a sealed processing space; a heating section that heats the back surface of the substrate inside the processing container; a supply section that supplies a material that forms the friction reduction film toward the back surface of the substrate inside the processing container; a first gas supply section that supplies a non-active gas from above the substrate inside the processing container toward a peripheral portion of the substrate; a second gas supply section that supplies a non-active gas from above the substrate inside the processing container toward a center side of the substrate compared to a supply position of the substrate by the first gas supply section; and an exhaust section that exhausts an atmosphere of the processing space from around or below the substrate inside the processing container.

Description

Technical Field

[0001] This disclosure relates to a substrate processing apparatus and a substrate processing method. Background Technology

[0002] Patent Document 1 describes a substrate processing apparatus for applying a coating liquid to the surface of a substrate and developing an exposed coating film on the surface of the substrate. The substrate processing apparatus includes a film forming section that forms a friction-reducing film on the back side of the substrate before exposure processing. The friction-reducing film reduces friction between the back side of the substrate and a holding surface that holds the back side of the substrate during exposure processing.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-121683 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The technology disclosed herein suppresses detours to the substrate surface when a friction-reducing film is formed relative to the back side of the substrate.

[0008] Solution for solving the problem

[0009] One technical solution disclosed herein is a substrate processing apparatus that forms a friction-reducing film on the back side of a substrate. The substrate processing apparatus comprises: a processing container that houses the substrate, forming a closed processing space; a heating unit that heats the back side of the substrate within the processing container; a supply unit that supplies material for forming the friction-reducing film toward the back side of the substrate within the processing container; a first gas supply unit that supplies an inactive gas from above the substrate within the processing container toward the periphery of the substrate; a second gas supply unit that supplies an inactive gas from above the substrate within the processing container toward the center of the substrate relative to the supply position of the first gas supply unit; and an exhaust unit that exhausts the atmosphere of the processing space from around or below the substrate within the processing container.

[0010] The effects of the invention

[0011] According to this disclosure, the technology disclosed herein can suppress detours to the substrate surface when a friction-reducing film is formed relative to the back side of the substrate. Attached Figure Description

[0012] Figure 1 This is a schematic side cross-sectional view illustrating the structure of the substrate processing apparatus of this embodiment.

[0013] Figure 2 Viewed from the lower surface side Figure 1 An explanatory diagram obtained from the top of the substrate processing apparatus.

[0014] Figure 3 It indicates that it was formed in Figure 2 The situation of the first ejection hole at the top Figure 2 A magnified illustration of a portion of the image.

[0015] Figure 4 It means in Figure 1 An explanatory diagram showing the process of supporting a wafer on a gap pin and processing the wafer in a substrate processing apparatus.

[0016] Figure 5 This is an explanatory diagram illustrating the processing of a wafer using a substrate processing apparatus with a first ejection hole formed at an angle.

[0017] Figure 6 This is an explanatory diagram showing the process of processing a wafer using a substrate processing apparatus having a third ejection hole.

[0018] Figure 7 This is an illustrative diagram obtained by viewing the top of the first ejection hole, which is a ring-shaped slit hole, from the lower surface side.

[0019] Figure 8 This is an explanatory diagram obtained by viewing the top of the first ejection hole, which is an arc-shaped slit hole, from the lower surface side.

[0020] Figure 9 This is an explanatory diagram obtained by viewing the second ejector hole formed at the top from the lower surface side, with the top being set off-center relative to the center. Detailed Implementation

[0021] For example, in the manufacturing process of semiconductor devices with multilayer wiring structures, multiple photolithography processes are performed to form resist patterns on a substrate, such as a semiconductor wafer (hereinafter sometimes simply referred to as "wafer"). In the photolithography process, a predetermined resist pattern is formed on the wafer by performing a resist coating process to form a resist film by coating a resist on the wafer, an exposure process to expose a predetermined pattern on the resist film, and a development process to develop the exposed resist film.

[0022] Exposure processing is performed between each photolithography step by photographing the same area of ​​the wafer. Moreover, due to the miniaturization of resist patterns resulting from the further high integration of semiconductor devices in recent years, it is necessary to improve the positional alignment accuracy, i.e., the coverage (overlap) accuracy, between the areas photographed in the preceding photolithography step and the areas photographed in the subsequent photolithography step.

[0023] Therefore, as disclosed in Patent Document 1, it is proposed to improve coverage by applying a friction-reducing film to the back of the wafer, thereby mitigating adsorption deformation when the wafer is held on the stage of the exposure machine.

[0024] When applying a friction-reducing film to the back side of the wafer, while venting the processing container from the periphery of the wafer housed within the processing container, raw material gas and vapor are supplied to the center of the back side of the wafer.

[0025] In this situation, the raw material gas or vapor supplied to the back side of the wafer sometimes detours from the wafer's periphery towards the surface. This detour tends to occur, especially when the distance between the back side of the wafer and the raw material gas or vapor is narrowed to improve coating efficiency. If the raw material of this friction-reducing film, such as a fluoropolymer film, detours from the wafer's periphery towards the surface, it may affect the wettability of the coating film (e.g., SOC, resist film) on the wafer surface, and may also affect the EBR process.

[0026] Here, using the technology disclosed herein, even when venting is performed on the processing container from the periphery and below of the wafer housed within the processing container, and vapors or gases that form a friction-reducing film are supplied to the back side of the wafer, the vapors or gases will be prevented from meandering from the periphery of the wafer to the surface.

[0027] Hereinafter, the structure of the substrate processing device of this embodiment will be described with reference to the accompanying drawings. Furthermore, in this specification, elements having substantially the same functional structure are labeled with the same reference numerals, thereby omitting repeated descriptions.

[0028] Figure 1 This is a schematic side view showing the structure of the substrate processing apparatus 1 according to this embodiment. The substrate processing apparatus 1 has a lower member 2 and an upper member 3 constituting a processing container C. The lower member 2 includes: a circular hot plate 20 having a radius larger than the radius of the wafer W that serves as the substrate; and a flat cylindrical outer casing 21 that surrounds the portion other than the upper surface of the hot plate 20.

[0029] A heater 22, consisting of a resistance heating element, is provided within the hot plate 20 as a heating section. The heater 22 is configured, for example, to be divided into multiple concentric circles centered on the center of the hot plate 20, thereby enabling highly uniform heating of the surface of the hot plate 20. Furthermore, in Figure 1 For ease of illustration, heater 22 is depicted as being divided into two parts.

[0030] On the surface of the hot plate 20, a plurality of, for example, eight, gap pins 23 are provided along a circle with a radius shorter than the radius of the wafer W, centered on the center of the hot plate 20. The height of each gap pin 23 is set to, for example, 1 mm away from the surface of the hot plate 20. Furthermore, for ease of illustration, in... Figure 1 Only two clearance pins 23 are shown in the image.

[0031] Three lifting pins 24 are provided circumferentially along a circle centered on the center of the hot plate 20 near the central portion of the gap pin 23. These three lifting pins 24 pass through the hot plate 20. The three lifting pins 24 are connected to a lifting mechanism 26, for example, composed of a cylinder, by means of a lifting member 25. Furthermore, for ease of illustration, in... Figure 1 Only two lifting pins 24 are shown in the image.

[0032] A flow path 31 for the material to flow for vapor deposition (described later) is formed through the center of the hot plate 20. The front end of the flow path 31 forms an outlet 32 ​​that opens at the center of the hot plate 20. That is, the outlet of the flow path 31 becomes the outlet 32, constituting a supply section. Furthermore, the base end of the flow path 31 extends through the center of the outer casing 21 and is connected to a raw material supply pipe 33. The raw material supply pipe 33 is connected to a raw material supply source 35 via valve V1, flow regulator 34, and valve V2. For example, HMDS vapor or mist is prepared in the raw material supply source 35. This HMDS vapor or mist circulates within the raw material supply pipe 33 using a carrier gas, such as nitrogen. Furthermore, the HMDS vapor or mist is generated by vaporizing liquid HMDS using a vaporizer or by using known techniques such as bubbling; therefore, detailed description is omitted. In addition to this, fluoropolymer resins, such as PTFE, can also be used as the material for the friction-reducing film of this disclosure.

[0033] The upper member 3 has a flat, cylindrical cover 41 that covers the space above the lower member 2. The lower surface of the peripheral wall portion 42 of the cover 41 is formed to overlap with the upper surface of the outer mounting portion 21. The cover 41 is configured to move up and down between a position overlapping with the lower member 2 and a position where the wafer W is transferred between the external substrate transport mechanism (not shown) and the lifting pin 24 using a lifting mechanism 4. Furthermore, the upper surface of the outer mounting portion 21 is in close contact with the outer lower surface of the peripheral wall portion 42 of the cover 41, that is, the outer lower surface of the outer side of the vent passage 5 described later, thereby forming a processing space S between the cover 41 and the outer mounting portion 21. The upper surface inside the cover 41 forms a top 41a.

[0034] A gas flow path 43 is formed through the center of the top 41a of the cover 41, and the gas flow path 43 opens into the processing space S formed between the cover 41 and the outer part 21. The upper end of the gas flow path 43 is connected to the purge gas supply pipe 44, and a valve V3, a flow adjustment unit 45, and a purge gas supply source 46 are sequentially connected to the purge gas supply pipe 44 from the downstream side. In this example, an inert gas, such as nitrogen, is used as the purge gas. The gas flow path 43 constitutes a second gas supply unit, and the lower end opening of the gas flow path 43 constitutes a second ejection port 43a.

[0035] A plurality of gas flow paths 51 are provided around the top 41a of the cover portion 41. These gas flow paths 51 are used to supply purge gas toward the periphery of the wafer W housed in the processing container C. The gas flow paths 51 constitute a first gas supply section. The gas flow paths 51 open into the processing space S, and their lower openings constitute a first ejection port 51a.

[0036] like Figure 2 As shown, the first ejection port 51a is provided in a circular shape on the periphery of the top 41a. That is, in this embodiment, 360 first ejection ports 51a are provided along the circumference of the wafer W, which is placed on the gap pin 23 and housed in the processing container C. Furthermore, the diameter of the first ejection port 51a is, for example, set to 3 mm. Additionally, as... Figure 3 As shown, the interval d between adjacent first ejection holes 51a is set to, for example, 3 mm.

[0037] The upper end of each gas flow path 51 is connected to the manifold 52. A purge gas supply pipe 53 is connected to the manifold 52. The purge gas supply pipe 53 is equipped with a valve V4 and a flow adjustment section 54, and the purge gas supply pipe 53 is connected to the purge gas supply source 46. The manifold 52 may also be located inside the cover 41.

[0038] like Figure 1 As shown, multiple exhaust passages 5, each extending vertically, are arranged along the circumference of the cover 41 inside the peripheral wall portion 42. As previously explained, the lower surface of the peripheral wall portion 42, which is outermost than the exhaust passages 5, is in close contact with the upper surface of the outer casing 21, while the lower surface of the peripheral wall portion 42, which is innermost than the exhaust passages 5, is not in close contact with the upper surface of the outer casing 21. That is, the height of the lower surface of the peripheral wall portion 42, which is innermost than the exhaust passages 5, is higher than the height of the lower surface of the peripheral wall portion 42, which is outermost than the exhaust passages 5. Therefore, an annular exhaust port 6 leading to the exhaust passages 5 is formed between the lower surface of the peripheral wall portion 42, which is innermost than the exhaust passages 5, and the upper surface of the outer casing 21. The exhaust port 6 constitutes the exhaust portion.

[0039] Furthermore, an exhaust chamber 7, which is formed in a ring shape along the circumferential direction, is provided on the periphery of the upper surface of the cover 41, and the exhaust passage 5 communicates with the exhaust chamber 7. A plurality of exhaust pipes 8 are connected to the exhaust chamber 7 along the circumferential direction, and the downstream end of the exhaust pipes 8 is connected to an exhaust pipe (not shown) that is commonly connected to the exhaust passages of various areas within the factory.

[0040] The substrate processing apparatus 1 with the above structure is controlled by a control unit 100. The control unit 100 is, for example, a computer equipped with a CPU, memory, etc., and has a program storage unit (not shown). The program storage unit stores programs for controlling various processes in the substrate processing apparatus 1. For example, based on this program, the control unit 100 controls the opening and closing of valves V1 to V4, lifting mechanisms 4 and 26, and flow adjustment units 45 and 54. Alternatively, the program can be stored on a computer-readable storage medium H and loaded into the control unit 100 from that storage medium H. Furthermore, the program can also be a program loaded via a network. The storage medium H can be temporary or non-temporary.

[0041] Next, the process of forming a friction-reducing film on the back side of the wafer W using the substrate processing apparatus 1 with the above structure will be described. First, the cover 41 is raised, opening the processing container C. The wafer W, on which a semiconductor device is formed on the surface side, is transported to the area above the hot plate 20 using a substrate transport mechanism (not shown), and then transferred from the substrate transport mechanism to the lifting pin 24. After the substrate transport mechanism retracts beyond the processing container C, the cover 41 is lowered, closing the processing container C. Figure 1 (The state shown).

[0042] The wafer W is supported on the lifting pin 24 with the distance between the back side of the wafer W and the surface of the hot plate 20 set, for example, to 2 mm. At this time, the wafer W is supported on the lifting pin 24 such that the center of the wafer W is aligned with the center of the hot plate 20, i.e., the center of the second ejection hole 43a, within a predetermined allowable range.

[0043] Then, valves V3 and V4 are opened, and nitrogen gas, used as a purge gas, is supplied into the processing container C from the purge gas supply source 46. Purge gas is then supplied to the periphery of the wafer W from the plurality of first ejector holes 51a located on the top 41a of the cover portion 41 opposite to the wafer W, and to the center of the wafer W from the second ejector hole 43a located closer to the center than the first ejector holes 51a. Meanwhile, the atmosphere of the processing space S is discharged from the periphery of the wafer W from the exhaust port 6.

[0044] In this state, the lifting pin 24 is lowered, as shown in the image. Figure 4When wafer W is supported on gap pin 23 as shown, HMDS is deposited on the back side of wafer W. The height of gap pin 23 is set to 1 mm from the surface of hot plate 20, as explained, so that the space between the back side of wafer W and hot plate 20 is small, and HMDS is deposited on the back side of wafer W efficiently.

[0045] However, if the space between the back side of the wafer W and the hot plate 20 is small, HMDS vapor will meander from the periphery of the wafer W to the surface of the wafer W. However, in this embodiment, purge gas is supplied to the periphery of the wafer W from a plurality of first ejector holes 51a, and purge gas is supplied to the center of the wafer W from a second ejector hole 43a located closer to the center than the first ejector holes 51a. Therefore, such meandering of HMDS vapor can be suppressed.

[0046] That is, in this embodiment, purge gas is supplied not only to the periphery of the wafer W from the first ejection hole 51a, but also to the center of the wafer W from the second ejection hole 43a. Therefore, such detours can be effectively suppressed. In detail, even if detours from the periphery are suppressed by supplying purge gas from the first ejection hole 51a, the possibility of some amount of detours towards the surface occurring depending on the supply flow rate cannot be ruled out. However, since purge gas is also supplied to the center of the wafer W, an airflow of purge gas from the center to the periphery can be formed on the surface of the wafer W. Therefore, this airflow can be used to push back HMDS vapor that is about to invade the center towards the periphery.

[0047] Regarding the supply flow rates from the first ejector hole 51a and the second ejector hole 43a, for example, in the case where the interval d between the plurality of first ejector holes is 3 mm, as in this embodiment, it is preferable that the supply flow rate from the second ejector hole 43a is less than the supply flow rate from the first ejector hole 51a. The reason is as follows: When the interval d between the first ejector holes 51a is "close" (less than 3 mm), the flow of purge gas from each first ejector hole 51a can form an air curtain at the periphery of the wafer W, strongly suppressing detours towards the surface. Therefore, even if HMDS vapor detours and attempts to penetrate towards the center of the wafer W, the amount is extremely small.

[0048] On the other hand, in cases where the spacing d between the first ejector holes 51a exceeds 3 mm, for example, 4 mm, or is considered "sparse", it can be assumed that the amount of HMDS vapor detours from the gap of the purge gas supplied from the first ejector hole 51a to the center of the wafer W surface increases. Therefore, if the supply flow rate from the second ejector hole 43a is greater than the supply flow rate from the first ejector hole 51a, it can be properly addressed.

[0049] In this embodiment, the supply flow rate from the first ejector hole 51a and the supply flow rate from the second ejector hole 43a can be controlled separately by independent supply systems. Moreover, this allows for further intentional control of the HMDS's detour from the periphery of the wafer W towards the center.

[0050] That is, by controlling the supply flow rate from the first ejection hole 51a and the supply flow rate from the second ejection hole 43a, for example, by actively directing HMDS toward the periphery of the wafer W, and depositing HMDS within a desired range from the periphery, a friction-reducing film corresponding to the subsequent processing of the wafer W can be formed on the periphery of the surface of the wafer W.

[0051] The results obtained by the inventors in verifying the substrate processing apparatus 1 of the embodiment will be described. During the verification, since the area where HMDS is deposited is hydrophobic, the water-repellent width of the periphery was measured by supplying water, and this water-repellent width was set as the HMDS deposition width. Then, the supply flow rate from the first ejection hole 51a was changed sequentially in increments of 1 [L / min] within the range of 6 to 10 [L / min], and the supply flow rate from the second ejection hole 43a was also changed sequentially in increments of 1 [L / min] within the range of 1 to 5 [L / min].

[0052] As a result, it was confirmed that the deposition width is maximized when both the supply flow rate from the first nozzle 51a and the supply flow rate from the second nozzle 43a are minimized. If the supply flow rate from the first nozzle 51a is gradually increased while keeping the supply flow rate from the second nozzle 43a at its minimum, the deposition width gradually decreases. Furthermore, it was confirmed that if the supply flow rate from the second nozzle 43a is gradually increased while keeping the supply flow rate from the first nozzle 51a at its minimum, the deposition width gradually decreases. Additionally, it was confirmed that the deposition width varies slightly depending on the combination of different flow rates. Based on these findings, it is clear that by controlling the supply flow rates from the first nozzle 51a and the second nozzle 43a, the radial length of the HMDS (deposition width) of the wafer W, circumferentially extending from the periphery of the wafer W, can be adjusted.

[0053] By utilizing this, it is possible not only to improve the coverage accuracy during exposure by forming a friction-reducing film before exposure, but also to control the evaporation width and form a friction-reducing film before resist coating, thereby achieving appropriate substrate treatment that takes into account EBR and other factors for subsequent resist film formation.

[0054] In the described embodiment, the first ejection orifice 51a ejects the purging gas in a vertical direction to supply purging gas to the periphery of the wafer W, but if Figure 5 As shown, the flow path can also be tilted so that the purging gas supplied from the first ejection hole 51a is ejected from the center toward the obliquely outward relative to the periphery of the wafer W.

[0055] Furthermore, in the described embodiment, a second ejector hole 43a is provided at a position near the center of the first ejector hole 51a that supplies purge gas to the periphery of the wafer W, but if... Figure 6 As shown, a third ejector hole 61 may also be provided between the first ejector hole 51a and the second ejector hole 43a to supply purge gas to the region between the periphery and the center of the wafer W. In this case, it is preferable that the supply flow rate from the third ejector hole 61 is less than the supply flow rate from the first ejector hole 51a and the supply flow rate from the second ejector hole 43a.

[0056] In the described embodiment, the first ejection hole 51a is a circular hole, and a structure in which a plurality of such holes are arranged in a ring. However, from the viewpoint of suppressing detours toward the surface by forming an air curtain, it could also be, for example, as... Figure 7 As shown, the first ejector hole 51b is designed to be annular. In this case, its function as an air curtain is superior to that of the embodiment described above. Therefore, it is preferable that the supply flow rate from the second ejector hole 43a is less than the supply flow rate from the first ejector hole 51b.

[0057] Alternatively, it could be like this: Figure 8 As shown, the first ejector hole 51c is designed as an arc-shaped slit. In this case, since the spacing between the first ejector holes 51c is narrowed, its function as an air curtain is also superior to that of the embodiment described above. Therefore, it is preferable that the supply flow rate from the second ejector hole 43a is less than the supply flow rate from the first ejector hole 51c.

[0058] Furthermore, in all the examples described, the second ejection port 43a is positioned at the center of the top 41a opposite to the wafer W, i.e., it is positioned to supply purge gas toward the center of the wafer W, but as... Figure 9 As shown, the second ejector hole 43a can also be provided at a position offset from the center of the top 41a, and purge gas can be supplied to the position offset from the center of the wafer W. In this case, since the purge gas is supplied to a position closer to the center than the first ejector hole 51a, the vapor of HMDS that has invaded the center can also be pushed back to the outer periphery.

[0059] Thus, depending on the purpose of supplying purge gas to a position closer to the center of the first ejection port 51a, the number of second ejection ports 43a need not be limited to one, and more than two can be provided.

[0060] It should be considered that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The above embodiments can be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0061] Explanation of reference numerals in the attached figures

[0062] 1. Substrate processing apparatus; 2. Lower component; 3. Upper component; 5. Exhaust passage; 6. Exhaust port; 20. Hot plate; 22. Heater; 41. Cover; 41a. Top; 43a. Second ejection port; 44. 53. Purge gas supply pipe; 45. 54. Flow adjustment unit; 46. Purge gas supply source; 51a. First ejection port; 100. Control unit; C. Processing container; S. Processing space; V1 to V4. Valves; W. Wafer.

Claims

1. A substrate processing apparatus, wherein a friction-reducing film is formed on the back side of a substrate, wherein, The substrate processing apparatus includes: A processing container that houses the substrate, forming a closed processing space; A heating unit that heats the back side of the substrate inside the processing container; A supply unit that supplies the material for forming the friction-reducing film toward the back side of the substrate within the processing container; The first gas supply unit supplies inactive gas from the top of the substrate inside the processing container to the periphery of the substrate. A second gas supply unit supplies an inactive gas from above the substrate within the processing container, closer to the center of the substrate than the supply position of the first gas supply unit to the substrate; and An exhaust section that discharges the atmosphere of the processing space from around or below the substrate within the processing container.

2. The substrate processing apparatus according to claim 1, wherein, The first gas supply unit has a plurality of first ejection holes. The plurality of first ejection holes are disposed at the top of the processing container along the circumference of the substrate.

3. The substrate processing apparatus according to claim 1, wherein, The first gas supply unit has one or more slit holes. The slit hole is located at the top of the processing container along the circumference of the substrate.

4. The substrate processing apparatus according to claim 2, wherein, The spacing between the plurality of first ejection holes of the first gas supply unit is less than 3 mm, and the supply flow rate from the second gas supply unit is less than the supply flow rate from the first gas supply unit.

5. The substrate processing apparatus according to claim 2, wherein, The spacing between the plurality of first ejection holes of the first gas supply unit exceeds 3 mm, and the supply flow rate from the second gas supply unit is greater than the supply flow rate from the first gas supply unit.

6. The substrate processing apparatus according to claim 3, wherein, The supply flow rate from the second gas supply unit is less than the supply flow rate from the first gas supply unit.

7. The substrate processing apparatus according to any one of claims 1 to 6, wherein, The second gas supply unit has one or more second ejection holes at the top of the processing container, facing the center of the substrate.

8. The substrate processing apparatus according to any one of claims 1 to 6, wherein, The supply flow rate from the first gas supply unit and the supply flow rate from the second gas supply unit are controlled separately.

9. The substrate processing apparatus according to any one of claims 1 to 6, wherein, No other gas supply unit is provided between the first gas supply unit and the second gas supply unit.

10. The substrate processing apparatus according to any one of claims 1 to 6, wherein, A third gas supply unit is provided between the first gas supply unit and the second gas supply unit to supply inactive gas to the substrate.

11. The substrate processing apparatus according to claim 10, wherein, The supply flow rate from the third gas supply unit is less than the supply flow rate from the first gas supply unit and the supply flow rate from the second gas supply unit.

12. The substrate processing apparatus according to any one of claims 1 to 6, wherein, The inactive gas supplied from the first gas supply unit is ejected at an angle from the center to the outside relative to the periphery of the substrate.

13. A substrate processing method comprising forming a friction-reducing film on the back side of a substrate within a processing container, wherein, In this substrate processing method, While heating the back side of the substrate inside the processing container, material for forming the friction-reducing film is supplied toward the back side, and exhaust is vented from the periphery of the substrate. Inactive gases are supplied from above the substrate toward the periphery and center of the substrate, respectively. The supply of inactive gases to the periphery and center can be controlled independently.

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