Heater pedestal with improved uniformity

Abstract

To improve temperature uniformity, a method is provided for improving temperature uniformity across the wafer on the heater pedestal. [Solution] A heater pedestal (100) that reduces temperature drop in the chucking channel, wherein the chucking channel (220) that is fluidly connected to at least one outlet (225) from the vacuum channel is concave and has a depth in the range of 10 mils to 20 mils, providing a negative backside pressure to the substrate to ensure that the substrate does not move on the heater pedestal.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to methods for improving temperature uniformity across a wafer on a heater pedestal, and more particularly, to methods for modifying the physical dimensions and placement of elements to improve temperature uniformity. [Background technology]

[0002] Semiconductor processing chambers typically include a pedestal suspended within the chamber to support a wafer or substrate being processed. In many embodiments, the pedestal also includes a heater to maintain the substrate at an elevated temperature during processing.

[0003] The pedestal also includes several gas channels to aid in processing the substrate. For example, in some cases, the pedestal includes vacuum channels that are used to provide a vacuum to secure the substrate to the pedestal. Another example is an edge purge channel that provides a flow of purge gas to a region near the peripheral edge of the substrate to avoid unwanted deposition.

[0004] Unfortunately, both of these gas channels can reduce the substrate temperature immediately surrounding the channel. This temperature variation or "non-uniformity" (N / U) can affect the kinetics of processes occurring at the substrate surface during processing, resulting in thickness variations across the substrate surface (i.e., thickness non-uniformity).

[0005] Therefore, there is a need for an improved heater pedestal that provides better temperature uniformity, and there is also a need to modify existing heater pedestals to provide better temperature uniformity. Summary of the Invention

[0006] One or more embodiments of the present disclosure are directed to methods of modifying a heater pedestal to reduce temperature non-uniformity across a substrate supported on the heater pedestal, including modifying the height of mesas in one or more concentric regions of the heater pedestal, modifying the number of mesas on the heater pedestal, modifying the depth of a chucking channel that secures the substrate to the heater pedestal, modifying the composition of an edge ring surrounding the substrate, or modifying the height of the edge ring.

[0007] Additional embodiments of the present disclosure are directed to methods of modifying a heater pedestal to reduce temperature non-uniformity across a substrate supported on the heater pedestal, including moving a heater plate containing one or more heater coils above a lower top plate containing edge purge channels and vacuum chucking channels, modifying the flow direction of edge purge gas relative to the edge of the heater plate, or modifying the thickness of the heater pedestal to increase the flow path distance of the edge purge gas flow proximate to the heater plate.

[0008] A further embodiment of the present disclosure is directed to a heater pedestal for supporting a substrate during processing. The pedestal includes a base plate with an edge purge channel extending from near the center of the pedestal toward the peripheral edge of the pedestal and a vacuum channel extending from near the center of the pedestal toward multiple outlets. A heater plate is located on the base plate. The heater plate includes two concentric heaters: a first heater extending from the center of the pedestal to a radius of approximately 135 mm and a second heater extending from a radius of approximately 135 mm to the peripheral edge of the pedestal. A top plate is located on the heater plate. The top plate includes multiple upper outlets and multiple substrate support mesas on an upper surface of the top plate. The upper outlets provide fluid connection to an outlet through the heater plate and the top plate. An edge ring surrounds the base plate, heater plate, top plate, and, if present, the substrate.

[0009] So that the features of the present disclosure can be understood in detail, a more particular description of the present disclosure, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present disclosure and therefore should not be considered as limiting its scope, since the present disclosure may admit of other equally effective embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view of a heater pedestal according to one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a top view of a heater pedestal according to one or more embodiments of the present disclosure. [Figure 3] FIG. 1 is an enlarged perspective view of a top portion of a heater pedestal according to one or more embodiments of the present disclosure. [Figure 4] FIG. 1 is a top view of an internal channel within a heater pedestal in accordance with one or more embodiments of the present disclosure. [Figure 5A] Simulated temperature profiles before and after modification according to one or more embodiments of the present disclosure [Figure 5B] Simulated deposition thickness profile before and after modification according to one or more embodiments of the present disclosure [Figure 6] FIG. 1 is an enlarged side view of a peripheral edge of a heater pedestal according to one or more embodiments of the present disclosure. [Figure 7] Simulated deposition thickness profile before and after modification according to one or more embodiments of the present disclosure DETAILED DESCRIPTION OF THE INVENTION

[0011] Before describing several example embodiments of the present disclosure, it is to be understood that the present disclosure is not limited to the details of construction or process steps set forth in the following description. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0012] As used herein and in the appended claims, the term "substrate" is used to refer to a surface or portion of a surface on which processing occurs. Those skilled in the art will also understand that a reference to a substrate may refer to only a portion of a substrate, unless the context clearly indicates otherwise. Furthermore, a reference to deposition on a substrate may refer to both a bare substrate and a substrate having one or more films or features deposited or formed thereon.

[0013] As used herein, "substrate" refers to any substrate or material surface formed on a substrate on which film processing is performed during a manufacturing process. For example, substrate surfaces that can be processed include materials such as silicon, silicon oxide, strained silicon, silicon-on-insulator (SOI), carbon-doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, but are not limited to, semiconductor wafers. Substrates may be subjected to pretreatment processes to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, electron beam cure, and / or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in this disclosure, any disclosed film processing steps can also be performed on underlying layers formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include such underlying layers as the context indicates.

[0014] One or more embodiments of the present disclosure are directed to a pedestal heater. Some embodiments of the present disclosure advantageously provide lower temperature non-uniformity across a supported wafer during processing. Some embodiments of the present disclosure advantageously provide lower thickness non-uniformity of a deposited film across a supported wafer during processing. Some embodiments of the present disclosure advantageously reduce temperature characteristics of a chucking channel on a supported wafer during processing.

[0015] For purposes of this disclosure, we refer to variation plots and values ​​derived therefrom. The variation plots measure the substrate across the entire substrate surface. In some embodiments, the variation plots measure 49 or 73 points on the substrate surface. In some embodiments, the variation plots measure the temperature of the substrate. In some embodiments, the variation plots measure the thickness of the deposited film.

[0016] In some embodiments, the deposited film is a TiAl film deposited by atomic layer deposition at a substrate temperature of about 350°C.

[0017] Throughout this disclosure, we refer to a measure of non-uniformity called 3 sigma. The 3 sigma value refers to the percentage of measurement points that fall outside three standard deviations from the mean. Thus, lower 3 sigma values ​​correspond to higher uniformity and lower non-uniformity.

[0018] 1-4, one or more embodiments are directed to a heater pedestal 100. In some embodiments, the heater pedestal 100 includes a shaft 105 connected to a base plate 110. A heater plate 120 is positioned on the base plate 110. A top plate 130 is positioned on the heater plate 130. Although the shaft 105, base plate 110, heater plate 120, and top plate 130 are each shown separately in FIG. 1, one skilled in the art will understand that these elements may be formed from the same material, or one or more of these elements may be integrally formed together.

[0019] Shaft 105 provides conduits for gas flow (eg, purge, vacuum), electrical connections (eg, heater power, measurement sensors, etc.), and mechanical connections (eg, motor connections, structural support).

[0020] The base plate 110 is connected to the shaft 105 and provides structural support to the heater plate 120 and the top plate 130. The heater plate 120 contains one or more heaters for maintaining a supported substrate at a fixed temperature during processing. A number of factors can cause the temperature across the substrate surface to vary or to have some degree of non-uniformity.

[0021] In some embodiments, heater plate 120 includes multiple heating elements. In some embodiments, the multiple heating elements are arranged concentrically such that one or more heaters operate primarily in the inner region of the substrate, while one or more additional heaters operate in the outer or peripheral region of the substrate. In some embodiments, heater plate 120 includes two heating elements. In some embodiments, a first heating zone is heated by heater 630 and covers an area up to a radius of 135 mm, while a second heating zone is heated by heater 640 and covers a radius from 135 mm to the outer peripheral edge of the heater pedestal. In some embodiments, the heater pedestal has a radius of 152 mm.

[0022] A top plate 130 is positioned above the heater plate 120 and provides support to the substrate during processing. In some embodiments, the top plate 130 has a radius of about 150 mm.

[0023] 2 and 3, the substrate is supported by a plurality of mesas 210. In some embodiments, the top plate includes between about 500 and about 650 mesas. In some embodiments, the mesas are circular in shape with a radius of about 30 mils. In some embodiments, the mesas have a height between about 2 mils and about 4 mils.

[0024] For purposes of this disclosure, mesa 210 can be identified as lying within concentric zones 215a-215d. Zone 215a is the area enclosed by line A. Zone 215b is the area between lines A and B. Zone 215c is the area between lines B and C. Zone 215d is the area between line C and the perimeter of top plate 130.

[0025] 2 and 3 show four zones, the present disclosure may allow for a greater or lesser number of zones. In some embodiments, line A is positioned at a radius of about 25 mm. In some embodiments, line B is positioned at a radius of about 50 mm. In some embodiments, line C is positioned at a radius of about 100 mm.

[0026] Also shown in Figures 2 and 3 is a chucking channel 220. The chucking channel 220 is fluidly connected to at least one outlet 225 from a vacuum channel 430 (shown in Figure 4). As shown in Figure 3, the chucking channel 220 is recessed and has a depth ranging from 10 mils to 20 mils. The chucking channel 220 provides a negative backside pressure to the substrate to ensure that the substrate does not move on the heater pedestal 100.

[0027] Referring to Figure 4, the top plate 130 also includes a vacuum channel 430 and an edge purge channel 440 therein. Both the vacuum channel 430 and the edge purge channel 440 begin near the center of the top plate 130. As shown in Figure 4, the vacuum channel 430 begins at 432 and leads to four outlets 225. The edge purge channel 440 begins at 442 and leads to sixteen outlets 445. Although four outlets 225 and sixteen outlets 445 are shown in Figure 4, any suitable number of outlets is contemplated as part of this disclosure.

[0028] Without being bound by theory, it is believed that gas flows through the vacuum channels 430 and edge purge channels 440, reducing the local temperature of a substrate positioned above these channels by reducing the thermal conductance of the pedestal. In the heater pedestal design shown in Figures 1-4, the outer radius of the vacuum channels 430 exhibits the most significant temperature non-uniformity at a radius of approximately 75 mm (see Figures 5A and 5B). Therefore, when these channels are used, the temperature non-uniformity increases.

[0029] As a result of this temperature non-uniformity, the inventors have discovered several ways to modify the heater pedestal 100 to reduce the temperature non-uniformity across a substrate supported on the heater pedestal 100.

[0030] In some embodiments, the method includes increasing the relative thermal conductance of the pedestal above the vacuum channel 430 to counteract the resulting conductance loss of the channel. In some embodiments, the method includes decreasing the thermal conductance of the pedestal not above the vacuum channel 430 to provide a more uniform thermal conductance throughout the pedestal.

[0031] In some embodiments, the method includes modifying the height of the mesa in one or more regions. In some embodiments, the height of the mesa is increased in one or more regions. In some embodiments, the height of the mesa is increased by up to 200%. In some embodiments, the height of the mesa 210 in zone 215a may be increased by 100%, the height of the mesa 210 in zone 215b may be increased by 50%, the height of the mesa 210 in zone 215c may be increased by 0%, and the height of the mesa 210 in zone 215d may be increased by 50%. In some embodiments, the height of the mesa 210 in zone 215a may be increased by 2 mils, the height of the mesa 210 in zone 215b may be increased by 1 mil, the height of the mesa 210 in zone 215c may be increased by 0 mils, and the height of the mesa 210 in zone 215d may be increased by 1 mil.

[0032] In some embodiments, the method includes reducing the number of mesas 210 on the heater pedestal 100. In some embodiments, the outermost ring of mesas 210 is removed. In some embodiments, the number of mesas is reduced by 15% or more. In some embodiments, the number of mesas is reduced from 622 to 528.

[0033] In some embodiments, the method includes modifying the depth of the chucking channel 220. In some embodiments, the depth of the chucking channel is reduced. In some embodiments, the depth of the chucking channel is reduced by 25% or more. In some embodiments, the depth of the chucking channel is reduced from about 15 mils to about 11 mils.

[0034] The inventors have surprisingly found that by implementing one or more of the methods of the present disclosure, temperature non-uniformity (3 sigma) can be reduced by 40% or more. For example, an unmodified heater pedestal provides a 3 sigma value of about 3%, while a heater pedestal modified by the methods of the present disclosure provides a 3 sigma value of about 1.8% for temperature non-uniformity.

[0035] Similarly, the inventors have surprisingly found that by implementing one or more of the methods of the present disclosure, the thickness non-uniformity (3 sigma) of a film deposited on a substrate can be reduced by 50% or more. For example, an unmodified heater pedestal provides a 3 sigma value of approximately 3%, while a heater pedestal modified by the methods of the present disclosure provides a 3 sigma value of thickness non-uniformity of approximately 1.5%. Figures 5A and 5B show simulated temperature and deposition thickness profiles before and after modification.

[0036] In some embodiments, the disclosed methods reduce temperature non-uniformity by 40% or more. In some embodiments, the disclosed methods reduce thickness non-uniformity of deposited films by 50% or more. In some embodiments, the temperature drop in the chuck channels is reduced.

[0037] Referring to FIG. 6 , one or more embodiments are directed to a modified heater pedestal 600. For the avoidance of doubt, the dimensions in FIG. 6 are not drawn to scale. In some embodiments, the top plate 130 is split to accommodate the heater plate 120. The lower top plate 130a includes vacuum channels (not shown) and the edge purge channels 440 described above with respect to FIG. 4 . The upper top plate 130b includes the mesas and chucking channels (both not shown) described above with respect to FIGS. 2 and 3 . A substrate 610 is supported on the upper top plate 130b. In some embodiments, an outlet (not shown) traverses the heater plate 120 from the lower top plate 130a, which includes the vacuum channels, to the upper top plate 130b, which includes the chucking channels.

[0038] In some embodiments, the modified heater pedestal 600 includes an edge ring 620. In some embodiments, the edge ring 620 consists essentially of Al2O3. In some embodiments, the edge ring 620 consists essentially of AlN.

[0039] Without being bound by theory, it is believed that if the edge ring composition has a higher thermal conductivity (AlN is higher than Al2O3), a higher amount of energy is imparted to the purge gas, resulting in a higher purge gas temperature and less effective edge cooling.

[0040] In some embodiments, as described above, when the top plate 130 is split to accommodate the heater plate 120, the heater pedestal 600 and edge ring 620 increase in thickness to accommodate the increased distance between the lower top plate 130a and the upper top plate 130b.

[0041] In some embodiments, the outlets 445 of the edge purge channels 440 are vertically oriented. In some embodiments, the vertical orientation of the outlets 445 increases the residence time of the purge gas near the heater plate 120.

[0042] Without being bound by theory, it is believed that the improved temperature non-uniformity is due to one or more of the following factors: First, the heater plate is closer to the substrate than the vacuum channels 430 and edge purge channels 440. Therefore, the temperature drop typically observed as a result of these channels is smaller. Furthermore, the temperature effects of the channels are more easily counteracted by the heater(s) before they affect the substrate.

[0043] Second, increasing the thickness between the edge purge channel and the substrate increases the flow distance of the purge gas when approaching the heater, and the resulting increased temperature of the purge gas is believed to reduce the cooling effect on the edge of the substrate.

[0044] The inventors have surprisingly found that by implementing one or more of these methods, the thickness non-uniformity (3 sigma) of a film deposited on a substrate can be reduced by 60% or more. For example, an unmodified heater pedestal provides a 3 sigma value of approximately 3%, while a heater pedestal modified by the disclosed method provides a 3 sigma value of thickness non-uniformity of approximately 1.2%. Figure 7 shows simulated deposition thickness profiles before and after modification.

[0045] In some embodiments, the disclosed methods reduce thickness non-uniformity of deposited films by 60% or more, and in some embodiments, reduce or eliminate temperature drops in the chucking channel.

[0046] In some embodiments, the height H of the edge ring 620 is modified. In some embodiments, the height H of the edge ring 620 is reduced so that the top of the edge ring 620 is substantially coplanar with the top surface 615 of the substrate 610. As used in this context, "substantially coplanar" means that the top of the edge ring 620 and the top surface 615 of the substrate 610 are within ±5 mils.

[0047] References throughout this specification to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "one or more embodiments," "a particular embodiment," "one embodiment," or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0048] Although the disclosure herein has been described with reference to particular embodiments, it is to be understood that the described embodiments are merely illustrative of the principles and applications of the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed method and apparatus without departing from the spirit and scope of the disclosure. Accordingly, the present disclosure may include modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. 1. A method of modifying a heater pedestal to reduce temperature non-uniformity across a substrate supported on said heater pedestal, comprising: modifying the height of the mesas within one or more concentric regions of the heater pedestal; modifying the number of mesas on the heater pedestal; modifying the depth of a chucking channel that secures the substrate to the heater pedestal; modifying the composition of an edge ring surrounding the substrate; or Modifying the height of the edge ring A method comprising:

2. 10. The method of claim 1, wherein the method reduces the temperature range by 40% or more.

3. 10. The method of claim 1, wherein the method reduces thickness non-uniformity of the deposited film by 50% or more.

4. The method of claim 1 , wherein the temperature of the chucking channel increases by 1° C. or more.

5. The method of claim 1 , wherein the height of the mesa increases.

6. The method of claim 5 , wherein the mesa height is increased by up to 100%.

7. The method of claim 1 , wherein the heater pedestal comprises four concentric mesa regions.

8. 8. The method of claim 7, wherein the outer radii of the mesa regions are approximately 25 mm, 50 mm, 100 mm, and 150 mm, respectively.

9. The method of claim 8 , wherein the mesa height increases by 100%, 50%, 0%, and 50%, respectively.

10. The method of claim 8 , wherein the mesa heights increase by 2 mils, 1 mil, 0 mil, and 1 mil, respectively.

11. The method of claim 1 , wherein the number of mesas is reduced by 15% or more.

12. The method of claim 11 , wherein the number of mesas is reduced from 622 to 528.

13. The method of claim 1 , wherein the depth of the chucking channel is reduced by 25% or more.

14. 14. The method of claim 13, wherein the depth decreases from a depth of 15 mils to a depth of 11 mils.

15. 10. The method of claim 1, wherein the edge ring consisting essentially of Al2O3 is replaced with an edge ring consisting essentially of AlN.

16. The method of claim 1 , wherein the height of the edge ring is reduced to be substantially coplanar with the height of the substrate.

17. 1. A method of modifying a heater pedestal to reduce temperature non-uniformity across a substrate supported on said heater pedestal, comprising: moving a heater plate including one or more heater coils over a lower top plate including an edge purge channel and a vacuum chucking channel; modifying the direction of edge purge gas flow relative to the edge of the heater plate; or Modifying the heater pedestal thickness to increase the flow path distance of the edge purge gas flow adjacent to the heater plate. A method comprising:

18. 20. The method of claim 17, wherein the method reduces thickness non-uniformity of the deposited film by 60% or more.

19. a heater pedestal for supporting a substrate during processing, a base plate including an edge purge channel extending from near the center of the pedestal toward a peripheral edge of the pedestal, and a vacuum channel extending from near the center of the pedestal toward a plurality of outlets; a heater plate on the base plate including two concentric heaters, a first heater covering an area from the center of the pedestal to a radius of about 135 mm and a second heater covering an area from a radius of about 135 mm to the peripheral edge of the pedestal; a top plate on the heater plate, the top plate including a plurality of upper outlets and a plurality of substrate support mesas on an upper surface of the top plate, the upper outlets providing fluid connections to the outlets through the heater plate and the top plate; and the base plate, the heater plate, the top plate, and, if present, an edge ring surrounding the periphery of the substrate; heater pedestal.

20. 20. The heater pedestal of claim 19, wherein the thickness non-uniformity of the TiAl film deposited on the substrate has a 3 sigma value of 1.5% or less.

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