BACKGROUND OF THE INVENTION

Field of the Invention

[0001] Embodiments of the present invention generally relate to a substrate support for use in a substrate processing chamber.

Description of the Related Art

[0002] Plasma enhanced chemical vapor deposition (PECVD) is generally employed to deposit thin films on a substrate such as a flat panel or semiconductor wafer. PECVD is generally accomplished by introducing a precursor gas into a vacuum chamber that contains a substrate. The precursor gas is typically directed through a distribution plate situated near the top of the chamber. The precursor gas in the chamber is energized {e.g., excited) into a plasma by applying RF power to the chamber from one or more RF sources coupled to the chamber. The excited gas reacts to form a layer of material on a surface of the substrate that is positioned on a temperature controlled substrate support.

[0003] During processing, small local variations in film thickness, often manifesting as spots of thinner film thickness, have been observed which may be detrimental to the device produced. It is believed that variation is glass thickness and flatness, along with a smooth substrate support surface, creates a local capacitance variation in certain locations across the substrate, thereby creating local plasma non-uniformities that leads in deposition variations, e.g., thin spots.

[0004] Therefore, there is a need for an improved substrate support. SUMMARY OF THE INVENTION

[0005] The present invention generally relates to a substrate support for use in a substrate processing chamber. A roughened substrate support reduces arcing within the chamber and also contributes to uniform deposition on the substrate. The roughening can occur in two steps. In a first step, the substrate support is bead blasted to initially roughen the surfaces. Then, the roughened surface is bead blasted with a finer grit to produce a substrate support with a surface roughness of between about 707 micro-inches and about 837 micro-inches. Following the surface roughening, the substrate support is anodized.

[0006] In one embodiment, a method of forming a roughened substrate support comprises bead blasting a surface of a substrate support in a first process where the beads have a first grit size and bead blasting the surface of the substrate support in a second process where the beads have a second grit size that is smaller than the first grit size.

[0007] In another embodiment, a method of forming a roughened substrate support comprises bead blasting a surface of a substrate support in a first process. The first process comprises scanning the nozzle across the surface of the substrate support in a first direction, shifting the nozzle along the surface of the substrate support in a second direction perpendicular to the first direction and scanning the nozzle across the surface of the substrate support in a third direction opposite the first direction. The method further comprises bead blasting the surface of the substrate support in a second process. The second process comprises first scanning the nozzle across the surface of the substrate support in the first direction, shifting the nozzle along the surface of the substrate support in the second direction, second scanning the nozzle across the surface of the substrate support in the third direction, rotating the substrate support about 90 degrees counterclockwise and repeating the first scanning, shifting, second scanning and rotating.

[0008] In another embodiment, a substrate support comprises a substrate support body having a surface roughness of between about 707 micro-inches and about 834 micro-inches and an anodized coating on the substrate support. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0010] Figure 1 is a cross sectional view of a PECVD apparatus according to one embodiment of the invention.

[0011] Figure 2 is a partial sectional view of a substrate support according to one embodiment.

[0012] Figure 3A is a schematic cross-sectional view of substrate support after a first step of roughening according to one embodiment.

[0013] Figure 3B is a schematic cross-sectional view of the substrate support of Figure 3A after a second step of roughening according to one embodiment.

[0014] Figure 4 is a schematic illustration of a roughing instrument relative to a substrate support according to one embodiment.

[0015] Figure 5A is a schematic illustration of a substrate support being roughened in first step according to one embodiment.

[0016] Figure 5B-5E are schematic illustrations of the substrate support of Figure 5A being roughened in a second step according to one embodiment.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION

[0018] The present invention generally relates to a substrate support for use in a substrate processing chamber. A roughened substrate support reduces arcing within the chamber and also contributes to uniform deposition on the substrate. The roughening can occur in two steps. In a first step, the substrate support is bead blasted to initially roughen the surfaces. Then, the roughened surface is bead blasted with a finer grit to produce a substrate support with a surface roughness of between about 707 micro-inches and about 837 micro-inches. Following the surface roughening, the substrate support is anodized.

[0019] The description herein will be made with reference to a PECVD chamber available from AKT America, Inc., a subsidiary of Applied Materials, Inc., Santa Clara, CA. It is to be understood that the embodiments herein are equally applicable to other processing chambers as well, including processing chamber sold by other manufacturers.

[0020] Figure 1 is a cross sectional view of a PECVD apparatus that may utilize the substrate support described herein. The apparatus includes a chamber 100 in which one or more films may be deposited onto a substrate 120. The chamber 100 generally includes walls 102, a bottom 104 and a showerhead 106 which define a process volume. A substrate support 1 18 is disposed within the process volume. The process volume is accessed through a slit valve opening 108 such that the substrate 120 may be transferred in and out of the chamber 100. The substrate support 1 18 may be coupled to an actuator 1 16 to raise and lower the substrate support 1 18. Lift pins 122 are moveably disposed through the substrate support 1 18 to move a substrate to and from the substrate receiving surface. The substrate support 1 18 may also include heating and/or cooling elements 124 to maintain the substrate support 1 18 at a desired temperature. The substrate support 1 18 may also include RF return straps 126 to provide an RF return path at the periphery of the substrate support 1 18. [0021] The showerhead 106 is coupled to a backing plate 1 12 by a fastening mechanism 150. The showerhead 106 may be coupled to the backing plate 1 12 by one or more fastening mechanisms 150 to help prevent sag and/or control the straightness/curvature of the showerhead 106.

[0022] A gas source 132 is coupled to the backing plate 1 12 to provide gas through gas passages in the showerhead 106 to a processing area between the showerhead 106 and the substrate 120. A vacuum pump 1 10 is coupled to the chamber 100 to control the process volume at a desired pressure. An RF source 128 is coupled through a match network 190 to the backing plate 1 12 and/or to the showerhead 106 to provide an RF current to the showerhead 106. The RF current creates an electric field between the showerhead 106 and the substrate support 1 18 so that a plasma may be generated from the gases between the showerhead 106 and the substrate support 1 18.

[0023] A remote plasma source 130, such as an inductively coupled remote plasma source 130, may also be coupled between the gas source 132 and the backing plate 1 12. Between processing substrates, a cleaning gas may be provided to the remote plasma source 130 so that a remote plasma is generated. The radicals from the remote plasma may be provided to chamber 100 to clean chamber 100 components. The cleaning gas may be further excited by the RF source 128 provided to the showerhead 106.

[0024] The showerhead 106 may additionally be coupled to the backing plate 1 12 by showerhead suspension 134. In one embodiment, the showerhead suspension 134 is a flexible metal skirt. The showerhead suspension 134 may have a lip 136 upon which the showerhead 106 may rest. The backing plate 1 12 may rest on an upper surface of a ledge 1 14 coupled with the chamber walls 102 to seal the chamber 100.

[0025] Figure 2 is a partial sectional view of the substrate support 1 18. The substrate support 1 18 includes a body 202 substantially covered with an anodized coating 210. The body 202 may be comprised of one or more coupled members or a unitary casted body having the heating and/or cooling elements 124 embedded therein. In one embodiment, the body 202 may comprise aluminum.

[0026] The body 202 generally includes a substrate support surface 204 and an opposing mounting surface 206. The anodized coating 210 covers at least the support surface 204 of the body 202 and provides a separating layer between the substrate 120 and the support surface 204.

[0027] The coating 210 includes an outer surface 212 and an inner surface 214. The inner surface 214 is generally disposed directly on the body 202. In one embodiment, the anodized coating has a thickness of between about 23 μιτι to about 27 μιτι, such as about 25 μιτι. The inner surface 214 has a surface roughness that translates to the anodized coating 210. A portion 218 of the outer surface 212 positioned above the substrate support surface 204 has a geometry configured to support the substrate 120 thereon. The portion 218 of the outer surface 212 has a surface finish 216 of a predefined roughness that promotes uniform thickness of films deposited on the substrate 140. The surface finish 216 has a roughness of about 707 micro- inches to about 847 micro-inches, such as about 777 micro-inches. The surface finish 216 advantageously results in improved film thickness uniformity.

[0028] The surface finish 216 of the anodized coating 210 may be achieved by treating at least a portion 220 of the outer substrate support surface 204 underlying the substrate 140 as will be discussed below. The surface finish 208 of the substrate support surface 204 may be formed in a number of manners, including bead blasting, abrasive blasting, grinding, embossing, sanding, texturing, etching or other method for providing a predefined surface roughness. In one embodiment, the surface finish 208 of the support surface 204 of the body 202 is about 707 micro-inches to about 847 micro-inches, such as about 777 micro-inches. [0029] Optionally, a strip 224 of the support surface 204 bounding the portion 220 positioned out from under the substrate 120 may be left untreated to minimize the fabrication costs. This results in a strip 222 of the anodized coating 210 above the untreated strip 224 that may have a finish different than the finish 216, but as the strip 222 is beyond the substrate 120, the surface finish of the strip 222 has no effect on film deposition uniformity. In one embodiment, the strip 222 of the anodized coating 210 has a smoother surface finish than the portion 218 of the coating 210 it bounds.

[0030] In order to roughen the substrate support 1 18, a two step process may occur. Figure 3A is a schematic cross-sectional view of substrate support 1 18 after a first step of roughening according to one embodiment. In the first step of the process, the substrate support is exposed to a first bead blasting process to form valleys 302 within the substrate support 1 18 separated by plateaus 304. The bead blasting may occur by exposing the substrate support 1 18 to beads ejected from a nozzle 402.

[0031] Figure 4 is a schematic illustration of a roughing instrument {e.g., nozzle 402) relative to a substrate support 1 18 according to one embodiment. The nozzle 402 may be disposed at an angle a relative to the surface of the substrate support 1 18 that is being bead blasted. The angle a may be between about 85 degrees and about 95 degrees, for example, 90 degrees. The nozzle 402 may be spaced from the substrate support 1 18 by a distance "A" of between about 400 mm and about 600 mm. The beads for the bead blasting may have a first grit size of between about 23 grit and about 25 grit, for example 24 grit. The beads used are spherical beads.

[0032] In operation, the nozzle 402 scans over the substrate support 1 18, however, it is contemplated that the substrate support 1 18 can move relative to the nozzle 402 or both the nozzle 402 and substrate support 1 18 may move. Figure 5A is a schematic illustration of the substrate support 1 18 being roughened in first step according to one embodiment. As shown, the substrate support 1 18 has is has a generally rectangular shape such that four sides 501 -504 are present. [0033] The nozzle 402 moves laterally as shown by arrows "E" and scans across the surface 505 of the substrate support 1 18 in a first direction from a first side 501 to a second side 502 as shown by arrow "B". Thereafter, the nozzle 402 shifts in a second direction that is perpendicular to the first direction as shown by arrow "C". The nozzle 402 then ejects the beads towards the surface 505 as the nozzle 402 moves in a third direction opposite the first direction from second side 502 to first side 501 as shown by arrow "D". The nozzle 402 then shifts again in the second direction as shown by arrow "C". When the nozzle 402 shifts, the nozzle shifts a distance of between about 20 mm and about 40 mm. Thus, the nozzle 402 follows a serpentine pattern to expose the entire surface 505 to bead blasting.

[0034] Following the first bead blasting process, the substrate support 1 18 is roughened as shown in Figure 3A, but the surface 505 is not sufficiently rough. Additionally, during substrate 120 placement onto the substrate support 1 18 and during processing, gas may be trapped within the valleys 302 and be unable to escape because the plateaus 304 contact the substrate 120 and prevent gas from escaping the valleys 302. Therefore, the substrate support 1 18 is bead blasted in a second process to roughen the plateaus 304 and further roughen the valleys 302. Figure 3B is a schematic cross-sectional view of the substrate support 1 18 of Figure 3A after a second step of roughening according to one embodiment. As shown in Figure 3B, the plateaus 304 are no longer present, but rather, a roughened surface 306 is present. Following the second bead blasting process, the surface roughness of the substrate support 1 18 may be between about 707 micro-inches and about 837 micro-inches, for example 777 micro-inches. Because a grit size of between about 58 grit and about 61 grit, such as 60 grit, is utilized, rough peaks/edges on the substrate support 1 18 are few and far between. Peaks/edges are sharp points where the substrate 120 will contact the substrate support 1 18 and can lead to arcing between the substrate 120 and substrate support 1 18, as well as scratching of the substrate 120. Additionally, due to the uneven surface and lack of plateaus, gas that may otherwise be trapped between the substrate support 1 18 and substrate 120 may freely be evacuated from between the substrate support 1 18 and substrate 120. The beads used are spherical beads.

[0035] Figure 5B-5E are schematic illustrations of the substrate support 1 18 of Figure 5A being roughened in the second process according to one embodiment. The second process spaces the nozzle 402 from the substrate support 1 18 by the same distance and at the same angle as in the first process. The second process has four separate steps in the case of a rectangular shaped substrate support 1 18.

[0036] In the first step of the second process, shown in Figure 5B, the nozzle 402 scans across the substrate support 1 18 in a manner similar to the first process. Namely, the nozzle 402 scans in the first direction from the first side 501 to the second side 502 as shown by arrow "B". Then, the nozzle shifts as shown by arrows "C" in the second direction towards the third side 503. Thereafter, the nozzle scans in the third direction from the second side

502 to the first side 501 as shown by arrows "D". The nozzle 402 then shifts again in the second direction as shown by arrows "C". When the nozzle 402 shifts, the nozzle shifts a distance of between about 20 mm and about 40 mm. Thus, the nozzle 402 follows a serpentine pattern to expose the entire surface 505 to bead blasting.

[0037] In the second step, shown in Figure 5C, the substrate support 1 18 is rotated counterclockwise about 90 degrees. It is to be understood that rather than counterclockwise, the substrate support 1 18 may be rotated clockwise. Following the rotation, the nozzle 402 scans in the first direction from a fourth side 504 to the third side 503 as shown by arrow "B". Then, the nozzle shifts as shown by arrows "C" in the second direction towards the first side 501 . Thereafter, the nozzle scans in the third direction from the third side

503 to the fourth side 504 as shown by arrows "D". The nozzle 402 then shifts again in the second direction as shown by arrows "C". When the nozzle 402 shifts, the nozzle shifts a distance of between about 20 mm and about 40 mm. Thus, the nozzle 402 follows a serpentine pattern to expose the entire surface 505 to bead blasting. [0038] In the third step, shown in Figure 5D, the substrate support 1 18 is rotated counterclockwise about 90 degrees. It is to be understood that rather than counterclockwise, the substrate support 1 18 may be rotated clockwise so long as the rotation for the third step is in the same direction as in the second step. Following the rotation, the nozzle 402 scans in the first direction from the second side 502 to the first side 501 as shown by arrow "B". Then, the nozzle shifts as shown by arrows "C" in the second direction towards the fourth side 504. Thereafter, the nozzle scans in the third direction from the first side 501 to the second side 502 as shown by arrows "D". The nozzle 402 then shifts again in the second direction as shown by arrows "C". When the nozzle 402 shifts, the nozzle shifts a distance of between about 20 mm and about 40 mm. Thus, the nozzle 402 follows a serpentine pattern to expose the entire surface 505 to bead blasting.

[0039] In the fourth step, shown in Figure 5E, the substrate support 1 18 is rotated counterclockwise about 90 degrees. It is to be understood that rather than counterclockwise, the substrate support 1 18 may be rotated clockwise so long as the rotation for the third step is in the same direction as in the second step. Following the rotation, the nozzle 402 scans in the first direction from the third side 503 to the fourth side 504 as shown by arrow "B". Then, the nozzle shifts as shown by arrows "C" in the second direction towards the second side 502. Thereafter, the nozzle scans in the third direction from the fourth side 504 to the third side 503 as shown by arrows "D". The nozzle 402 then shifts again in the second direction as shown by arrows "C". When the nozzle 402 shifts, the nozzle shifts a distance of between about 20 mm and about 40 mm. Thus, the nozzle 402 follows a serpentine pattern to expose the entire surface 505 to bead blasting.

[0040] Now that the second bead blasting process is complete, the substrate support 1 18 has a surface 505 with a roughness of between about 707 micro-inches to about 837 micro-inches, for example 777 micro-inches. Following the bead blasting process, the substrate support 1 18 is anodized to form an anodized coating 210 thereover to a thickness of between about 23 μιτι to about 27 μιτι, for example, 25 μιτι.

[0041] The roughened substrate support 1 18 reduces or eliminates arcing between the substrate support 1 18 and the substrate 120. Additionally, the roughened substrate support 1 18 reduces or eliminates thin spots during the deposition onto the substrate 120 such that a substantially uniformly thick layer may be deposited onto the substrate 120. Even though the substrate support 1 18 is roughened, the substrate support 1 18 does not substantially scratch the substrate.

[0042] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.