Showerhead for substrate processing tools

Abstract

One example provides a showerhead for a substrate processing tool, the showerhead comprising: a faceplate with a plurality of outlet holes, a backplate coupled to the faceplate, a plenum between the faceplate and the backplate, and a plurality of posts connecting the faceplate and the backplate, wherein an outermost set of posts of the plurality of posts are positioned between 45% and 65% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 65% and 100% of the distance from the center of the plenum to the outer periphery of the plenum.

Description

[Background technology]

[0001] Semiconductor processing tools may include components designed to distribute process gases relatively uniformly across a substrate. Such components are commonly referred to in the industry as "showerheads." Showerheads typically include a faceplate that faces a plenum. The faceplate includes a plurality of exit holes that allow process gases in the plenum to flow through the faceplate and across the surface of the substrate. The through-holes are positioned such that gas distribution across the wafer allows for substantially uniform processing of the substrate. Summary of the Invention

[0002] This Summary is provided to introduce a selection of concepts in a simplified form, further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Moreover, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] One example provides a showerhead for a substrate processing tool, the showerhead comprising: a faceplate with a plurality of outlet holes; a backplate coupled to the faceplate; a plenum between the faceplate and the backplate; and a plurality of posts connecting the faceplate and the backplate, wherein an outermost set of posts of the plurality of posts are positioned between 45% and 65% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 65% and 100% of the distance from the center of the plenum to the outer periphery of the plenum.

[0004] In some such examples, alternatively or additionally, the outermost set of posts of the plurality of posts is positioned between 50 and 65% of the distance from the center of the plenum to the periphery of the plenum.

[0005] In some such examples, alternatively or additionally, the outermost set of posts of the plurality of posts are positioned between 52 and 58% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 58% and 100% of the distance from the center of the plenum to the outer periphery of the plenum.

[0006] In some such examples, alternatively or additionally, the posts are arranged such that any radial line extending from the center of the plenum to the periphery of the plenum intersects at most one post.

[0007] In some such examples, alternatively or additionally, the posts are arranged such that any radial line extending from the center of the plenum to the periphery of the plenum intersects at most one post.

[0008] In some such examples, alternatively or additionally, the plurality of posts comprises 20 or more posts.

[0009] In some such examples, alternatively or additionally, the faceplate has a thickness greater than 0.35 inches and less than or equal to 1 inch.

[0010] In some such examples, alternatively or additionally, the faceplate has a thickness within the range of 0.45 inches to 0.65 inches.

[0011] In some such examples, alternatively or additionally, the backplate includes a post access hole for each post, each post access hole including an arcuate edge at the opening of the post access hole on the outer surface of the backplate.

[0012] In some such examples, alternatively or additionally, each post is integral with the faceplate and welded to the backplate, and each post comprises a radial structure where the post abuts a flat surface of the inner surface of the faceplate.

[0013] In some such examples, alternatively or additionally, the outermost set of posts are arranged in a circular pattern with at least three posts for each quadrant of the circular pattern, a first post being spaced a first angular distance along the circular pattern from a second post of the three posts, and the second post being spaced a second angular distance along the circular pattern from a third post, the first distance being less than the second distance.

[0014] Another example provides a showerhead for a substrate processing tool, the showerhead including: a faceplate including a plurality of outlet holes, a backplate coupled to the faceplate, a plenum between the faceplate and the backplate, a plurality of posts connecting the faceplate and the backplate, and a plurality of post access holes formed in the backplate, each post access hole including an arcuate edge at an opening of the post access hole in an outer surface of the backplate.

[0015] In some such examples, alternatively or additionally, the radius of curvature of the arcuate edge is in the range of 0.05 inches to 0.25 inches.

[0016] In some such examples, alternatively or additionally, the outermost set of posts of the plurality of posts are positioned between 52 and 58% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 58% and 100% of the distance from the center of the plenum to the outer periphery of the plenum.

[0017] In some such examples, alternatively or additionally, the posts are arranged such that any radial line extending from the center of the plenum to the periphery of the plenum intersects at most one post.

[0018] In some such examples, alternatively or additionally, the plurality of posts comprises 20 or more posts.

[0019] In some such examples, alternatively or additionally, the faceplate has a thickness greater than 0.45 inches and less than or equal to 0.55 inches.

[0020] Another example provides a showerhead for a substrate processing tool, the showerhead comprising: a faceplate with a plurality of outlet holes, a backplate coupled to the faceplate, a plenum between the faceplate and the backplate, and a plurality of posts connecting the faceplate and the backplate, an outermost set of posts of the plurality of posts arranged in a circular pattern with at least three posts for each quadrant of the circular pattern, a first post spaced a first angular distance along the circular pattern from a second post of the three posts, the second post spaced a second angular distance along the circular pattern from a third post, the first distance being less than the second distance.

[0021] In some such examples, alternatively or additionally, the outermost set of posts of the plurality of posts are positioned between 52 and 58% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 58% and 100% of the distance from the center of the plenum to the outer periphery of the plenum.

[0022] In some such examples, alternatively or additionally, the backplate includes a post access hole for each post, each post access hole including an arcuate edge at the opening of the post access hole on the outer surface of the backplate. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 shows a schematic diagram of an exemplary processing tool including a showerhead.

[0024] [Figure 2] FIG. 2 shows a perspective view of an exemplary showerhead.

[0025] [Figure 3] FIG. 3 shows a cross-sectional view of the showerhead of FIG.

[0026] [Figure 4] FIG. 4 shows a top view of the showerhead of FIG.

[0027] [Figure 5] FIG. 5 shows a schematic diagram of an exemplary arrangement of posts on a faceplate of a showerhead.

[0028] [Figure 6] FIG. 6 illustrates a cross-sectional view of a post access hole in the backplate of the showerhead of FIG.

[0029] [Figure 7] FIG. 7 shows a perspective view of the arcuate junction where the post meets the planar interior surface of the faceplate of an exemplary showerhead.

[0030] [Figure 8] FIG. 8 shows a cross-sectional view of the gas flow baffle and support post of an exemplary showerhead. DETAILED DESCRIPTION OF THE INVENTION

[0031] The term "atomic layer deposition (ALD)" generally refers to a process of forming a film in one or more discrete layers on a substrate by sequentially adsorbing precursors onto the substrate and then chemically converting the adsorbed precursors to form the film layers.

[0032] The term "backplate" generally refers to a component of a showerhead. The backplate, together with the faceplate, defines the plenum of the showerhead. The backplate faces away from the substrate holder of a processing tool.

[0033] The term "chemical vapor deposition" (CVD) generally refers to a process for forming films on a substrate by exposing the substrate to a stream of reactive gas-phase precursors.

[0034] The term "etching" generally refers to the removal of material from a substrate. Wet etching uses liquid-phase solutions to remove material from a substrate. Dry etching uses gas-phase chemicals to remove material from a substrate.

[0035] The term "faceplate" generally refers to the portion of a showerhead that faces the substrate holder of a processing tool. The faceplate contains exit holes for emitting processing chemicals from a plenum located behind the faceplate toward the substrate.

[0036] The term "exit holes" generally refers to openings in a showerhead that emit processing chemicals from the plenum toward a substrate during substrate processing.

[0037] The term "plenum" generally refers to the volume of space between the faceplate and the backplate. Process gases enter the plenum through a process gas inlet and exit the plenum toward the substrate through a number of exit holes that extend into the faceplate and fluidly connect the plenum with the environment outside the plenum.

[0038] The term "post" generally refers to the structural support that extends across the plenum of the showerhead between the faceplate and backplate of the showerhead. The posts are integrally formed with the faceplate and can be welded to the backplate.

[0039] The term "processing chamber" generally refers to an enclosure in which chemical and / or physical processes are performed on a substrate. Components of a processing tool, such as a showerhead and pedestal, are located within the processing chamber.

[0040] The term "quadrant" generally refers to a wedge-shaped portion of the showerhead that corresponds to one-quarter of the angular distance around the showerhead.

[0041] The term "rounded edge" generally refers to a corner of a structure where two surfaces meet, where the corner is rounded rather than sharp.

[0042] The term "showerhead" generally refers to a structure for distributing process gases across the surface of a substrate. A showerhead may include a plenum between a faceplate and a backplate and a plurality of exit holes formed in the faceplate.

[0043] The term "substrate" generally refers to any structure onto which a film can be deposited.

[0044] As described above, showerheads are used in many semiconductor processing tools to distribute process gases relatively uniformly across a substrate. The showerhead may include a faceplate bonded to a backplate to define a plenum. Process gases are introduced into the plenum through an inlet in the backplate. The process gases flow from the plenum toward the substrate through a plurality of outlet holes distributed across the faceplate.

[0045] The faceplate can be joined to the backplate at multiple attachment points. For example, the perimeter region of the backplate can be joined to the perimeter region of the faceplate by welded joints. Additionally, multiple posts can join the faceplate and backplate at multiple locations within the plenum. The posts can be integrally formed with the faceplate and welded to the backplate.

[0046] During a substrate processing cycle, a substrate on a pedestal within the processing chamber can be heated to a relatively high temperature. The faceplate, which directly faces the substrate, is radiatively heated during substrate processing. The backplate can be cooled by a fluid cooling system during use. Such a fluid cooling system can be attached to the stem of the backplate. Thus, a temperature gradient exists along the showerhead from the faceplate to the backplate during substrate processing.

[0047] A thermal gradient can cause the faceplate to thermally expand radially (across the plane of the faceplate) at a faster rate than the backplate. This faster rate of thermal expansion of the faceplate compared to the backplate can have various mechanical effects. For example, a thermal gradient can cause the backplate to expand radially and the faceplate to compress radially. This can cause the faceplate to bow away from the backplate.

[0048] The posts connecting the faceplate and backplate act to resist this bending effect. However, the faster rate of thermal expansion of the faceplate compared to the backplate can place stress on the posts. This is because the location where the posts interface with the faceplate experiences greater radial displacement due to thermal expansion than the location where the posts interface with the backplate. Furthermore, because the magnitude of thermal expansion is higher at the periphery of the showerhead plenum than near the center of the plenum, posts closer to the periphery of the showerhead plenum can experience greater stress than posts near the center of the showerhead plenum. The stresses experienced by the posts can pose a risk of post fracture after multiple heating cycles.

[0049] Some recipes require cycling between substrate processing conditions using very high temperatures of 570° C. or higher. In some instances, the showerhead could be exposed to a plasma cleaning process using pedestal temperatures up to 485° C. It has been found that exposing the showerhead to recipes that include these types of processes (e.g., recipes that cycle between very high and low temperatures) poses a particular risk of post fracture.

[0050] Therefore, an example of a showerhead that can prevent excessive load from being applied to the posts between the backplate and the faceplate is disclosed. For example, the exemplary showerhead of the present disclosure can utilize a thicker faceplate than a conventional showerhead. In some examples, the faceplate thickness is greater than 0.35 inches and less than or equal to 1.00 inches. In contrast, conventional showerheads typically have faceplates that are 0.35 inches thick or less. Heat transfer between the faceplate and backplate of a showerhead occurs primarily at the periphery of the showerhead, where the faceplate and backplate are welded together. By using a thick faceplate (greater than 0.35 inches thick), the heat transfer per unit time from the faceplate to the backplate at the periphery of the showerhead may be greater than that using a conventional faceplate (less than or equal to 0.35 inches thick). This may result in a lower temperature difference between the faceplate and backplate of a showerhead with a thick faceplate compared to a showerhead with a faceplate that is 0.35 inches thick or less. The lower temperature differential can reduce the differential thermal expansion between the faceplate and the backplate, which can reduce the load on the posts compared to showerheads that experience a larger temperature differential between the faceplate and the backplate.

[0051] Alternatively or additionally, in some examples, the outermost set of posts connecting the faceplate and backplate of the showerhead is located within a range of 45% to 65% of the distance from the center of the plenum to the periphery of the plenum. No posts are located between the outermost set of posts and the periphery of the plenum. In some such examples, the outermost set of posts is located within a range of 52% to 58% of the distance from the center of the plenum to the periphery of the plenum. Again, no posts are located between the outermost set of posts and the periphery of the plenum. This post placement, which does not include posts between the periphery of the plenum and the higher end of these ranges, avoids the possibility of post fracture due to repeated loads during substrate processing. Furthermore, by not including posts between the periphery of the plenum and 58% of the distance from the center of the plenum to the periphery of the plenum, the outermost posts are subjected to less load than posts located 65% of the distance from the center of the plenum to the periphery of the plenum. This may further help prevent post fracture due to repeated thermal cycling.

[0052] In some examples, showerheads according to the present disclosure may have 20 or more posts, whereas other showerheads may have fewer posts. Using more posts can provide greater resistance to bending of the faceplate compared to using fewer posts. Using more posts can also provide more paths for heat transfer from the faceplate to the backplate, which can help reduce the temperature difference between the faceplate and the backplate.

[0053] Some conventional showerheads may include post access holes that are plugged during manufacturing. A post access hole is a hole in a backplate through which a post extending from the faceplate to the backplate can be welded to the backplate during manufacturing. Current showerheads may include plugs welded into the post access holes during manufacturing. Using plugs welded into the post access holes can help prevent the formation of hollow cathode discharges in unplugged post access holes when using the showerhead as an electrode to form a plasma. However, welding plugs into post access holes also increases manufacturing costs for the showerhead. In contrast, examples of the present disclosure may include arcuate top edges at the openings of the post access holes in the backplate of the showerhead. The arcuate top edges can help prevent the formation of hollow cathode discharges without the use of plugs. Eliminating plugs in the post access holes reduces manufacturing costs.

[0054] Referring now to FIG. 1 , an exemplary processing tool 100 for processing a substrate is shown. The processing tool 100 may be configured for thermal or plasma-enhanced chemical vapor deposition (CVD), thermal or plasma-enhanced atomic layer deposition (ALD), or other substrate processes. The processing tool 100 includes a processing chamber 102 including a showerhead 104. The showerhead 104 includes a stem 106 connected to the processing chamber. The showerhead 104 also includes a lower portion 110 extending radially outward from the bottom of the stem 106. As described in more detail below, the showerhead 104 includes a faceplate with a plurality of outlet holes, a backplate, and a plenum between the faceplate and the backplate.

[0055] The processing tool 100 further includes a pedestal 114. The illustrated pedestal 114 is configured as an electrostatic chuck pedestal. During operation, a substrate 116 is placed on the pedestal 114. An electrode 118 electrostatically attracts and securely holds the substrate 116 during processing. In other examples, other types of pedestals can be used.

[0056] The processing tool 100 is configured to perform plasma-enhanced substrate processing, such as plasma-enhanced atomic layer deposition (PEALD) and plasma-enhanced chemical vapor deposition (PECVD). Accordingly, the processing tool 100 includes an RF generation system 120 that generates and outputs RF power. In this example, the pedestal 114 is configured as a powered electrode, and the showerhead 104 is grounded. In another example, the showerhead 104 can be powered by the RF generation system 120, and the pedestal 114 can be grounded. The RF generation system 120 includes an RF generator 122 that generates the RF power. The RF generation system 120 further includes a matching and distribution network 124. The substate processing tool further includes an actuator 126 and a lift pin assembly 128. The lift pin assembly includes P lift pins 128, where P is an integer greater than 2. The actuator 126 and the lift pin assembly 128 are used during loading and unloading of the substrate 116 from the chamber.

[0057] The processing tool 100 further comprises a gas supply system 130. The gas supply system 130 includes one or more gas sources 132-1, 132-2, ..., and 132-N (collectively, gas sources 132), where N is an integer greater than 0. The gas sources 132 supply one or more process gases, such as deposition precursors, purge gases, and etching gases. In some examples, vaporized precursors may also be used (not shown). The gas sources 132 are connected to a manifold 140 by valves 134-1, 134-2, ..., and 134-N (collectively, valves 134), mass flow controllers 136-1, 136-2, ..., and 136-N (collectively, mass flow controllers 136), and valves 138-1, 138-2, ..., and 138-N (collectively, valves 138). The output of the manifold 140 is supplied to the processing chamber 102 by the gas supply system 130. For example, the output of the manifold 140 is fed to the showerhead 104 .

[0058] A heater controller 142 ("HC") is connected to a resistive heater disposed within the pedestal 114. The heater controller 142 can be used to control the temperature of the pedestal 114. Additionally, the pedestal 114 can include internal channels (not shown) for flowing fluid from a fluid source (not shown) to provide further control of the temperature of the pedestal and substrate.

[0059] Valves 150 and pump system 152 can be used to evacuate reactants and products from the process chamber 102 and / or control the pressure within the process chamber. A controller 160 can be used to control various components of the processing tool 100 described herein. For example, the controller 160 can cause the robot arm 170 to load and unload the substrate 116 onto and from the pedestal 114. The controller 160 communicates with the gas supply system 130 to control the supply of process gases, purge gases, and / or inert gases. The controller communicates with the valves 150 and pump 152 to control the pressure within the process chamber and / or control the evacuation of reactants. The controller 160 also causes a voltage source 172 to output a voltage to the electrode 118 to clamp and unclamp the substrate.

[0060] FIG. 2 shows a perspective view of an exemplary showerhead 200. FIG. 3 shows a cross-sectional view of the showerhead 200. The showerhead 200 is an example of the showerhead 104 of FIG. 1. The showerhead 200 includes a faceplate 202 and a backplate 204. Referring to the cross-sectional view of FIG. 3, a plenum 206 is located between the faceplate 202 and the backplate 204. The faceplate 202 includes multiple exit holes 208 that lead from the plenum 206 to the outside of the showerhead 200. In some examples, the showerhead may have approximately hundreds to thousands of exit holes. The exit holes 208 in FIG. 2 are shown schematically and not to scale.

[0061] The plenum 206 receives process gas through a process gas inlet 210. A baffle 212 is located within the plenum 206 below the process gas inlet 210. The baffle 212 is attached to the faceplate 202 within the plenum by a number of mounts 213. In some examples, the baffle 212 can be attached by three mounts 213. In other examples, the baffle 212 can be attached by any other suitable number of mounts 213. The process gas enters the plenum 206, impinges on the baffle 212, and is distributed throughout the plenum 206. The baffle 212 prevents the exit hole 208 directly below the process gas inlet 210 from emitting a higher flow rate of process gas than the other exit holes.

[0062] As described above, the faceplate 202 of the showerhead 200 may have a greater thickness than faceplates of conventional showerheads. Heat transfer between the faceplate 202 and backplate 204 of the showerhead 200 occurs primarily at the periphery of the showerhead 200, where the faceplate 202 and backplate 204 are welded together. In some examples, the faceplate 202 may have a thickness greater than 0.35 inches and less than or equal to 1.00 inches. Using a faceplate with a thickness within this range may allow for greater heat transfer per unit time from the faceplate to the backplate at the periphery of the showerhead than using a faceplate with a thickness of 0.35 inches or less. This may result in a lower temperature difference between the faceplate and the backplate compared to showerheads having faceplates with thicknesses of 0.35 inches or less. The lower temperature difference between the faceplate 202 and the backplate 204 may reduce the thermal expansion difference between the faceplate and the backplate. This may reduce the load on posts 220 (described below) connecting faceplate 202 and backplate 204 compared to showerheads, which experience a larger temperature difference between the faceplate and backplate.

[0063] In some examples, the faceplate 202 may have a thickness ranging from 0.45 inches to 0.65 inches. Depending on operating conditions, the faceplate 202 may have a thickness of, for example, 0.45, 0.50, 0.55, 0.60, or 0.65 inches. Faceplates within this thickness range may be easier to manufacture than faceplates thicker than 0.65 inches, while still providing sufficient thermal conductivity to avoid excessive stress on the posts. For example, the outlet holes 208 are formed by drilling holes in the faceplate 202. The outlet holes 208 may have a uniform, narrow diameter, which presents challenges when drilling holes in thicker materials. Furthermore, as discussed above, the showerhead 200 may have hundreds or even thousands of outlet holes 208. Therefore, drilling a large number of outlet holes 208 in a faceplate thicker than 0.65 inches may be more time-consuming and expensive than drilling outlet holes 208 in a faceplate within the 0.25 to 0.65 inch range. Therefore, a faceplate having a thickness between 0.45 inches and 0.65 inches may provide a suitable balance of manufacturability and heat transfer performance.

[0064] In some examples, the faceplate 202 and the backplate 204 can be joined at the weld joint 214 around the perimeter of the plenum 206 by friction stir welding. Friction stir welding is a non-fusion joining process and does not have a heat-affected zone, which can weaken material in fusion joining methods. Furthermore, the penetration depth of friction stir welding can be more precisely controlled than fusion joining methods, at least because the penetration depth of friction stir welding is controlled by the weld bit. Friction stir welding can also achieve deeper penetration than fusion joining processes while reducing faceplate deformation due to residual stresses compared to fusion joining methods. Friction stir welding can extend the operational life of the perimeter joint between the faceplate and backplate compared to fusion joining methods.

[0065] Continuing with FIG. 3, the showerhead 200 includes a plurality of posts 220 connecting the faceplate 202 and the backplate 204. Two posts 220 are shown in cross section in FIG. 3. The posts 220 are integrally formed with the faceplate 202 and are weldable to the backplate 204. The backplate 204 includes a post access hole 222 for each post 220. Referring to FIG. 2, as described in more detail below, the backplate 204 has a total of 24 post access holes 222, and the faceplate 202 has a corresponding 24 posts 220. The post access holes 222 allow the posts 222 to be welded to the backplate 204 during showerhead fabrication. For example, electron beam welding can be used to weld the posts 222 by placing each post 220 into a corresponding post access hole 222 and irradiating an electron beam into the post access hole 222 to weld the post to the backplate. In some examples, the showerhead 200 may have a total of 25 to 30 posts. Additional posts would be placed within the radial range of the outermost set of posts. In certain operations, too many posts may reduce gas flow, so having too many posts is undesirable. As the number of posts increases, the number of exit holes may decrease because exit holes cannot be placed below the posts.

[0066] As noted above, posts within a showerhead may be subjected to cyclic loads due to temperature and thermal expansion differences between the faceplate and backplate. Posts closer to the periphery of the showerhead plenum may experience greater loads than posts closer to the center of the showerhead plenum because the thermal expansion mismatch at the periphery is greater than near the center of the plenum.

[0067] Thus, the showerhead 200 positions the outermost set of posts 240 between 45% and 65% of the distance (indicated by the dashed boundary around the corresponding post holes 222) from the radial center of the plenum 206 (hereafter referred to as the center 242 of the plenum 206), as indicated by the dashed line 242, to the outer periphery 244 of the plenum 206. The term "outermost set of posts" refers to the set of posts 220 closest to the outer periphery 244 of the plenum 206. The showerhead 200 does not have posts 220 positioned between 65% and 100% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206. Positioning the outermost set of posts 240 within the range of 45% to 65% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206 avoids placing excessive stress on the posts 220 while providing sufficient resistance to thermal bending of the faceplate 202. Using a relatively thick faceplate 202 (e.g., greater than 0.35 inches and less than 1.0 inch thick) may further help avoid excessive loads on the posts 220 because such a faceplate 202 can transfer more heat per unit from the faceplate 202 to the backplate 204 than a backplate 204 having a thickness of 0.35 inches or less. This may help reduce temperature and thermal expansion differences between the faceplate 202 and the backplate 204 compared to using a thinner faceplate 202.

[0068] In some examples, the outermost set of posts 240 are positioned between 50% and 65% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206. Positioning the outermost posts at 50% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206 can provide greater resistance to thermal deformation of the faceplate 202 than an outermost set of posts positioned less than 50% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206. In a further example, the outermost set of posts 240 are positioned between 52 and 58% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206. In such examples, no posts are positioned between 58% and 100% of the distance from the center 242 of the plenum 206 to the outer periphery 244 of the plenum 206. Posts 220 positioned within this range can, in some instances, provide an optimal balance between avoiding harmful loads on posts 220 and supporting faceplate 202 against thermal bending.

[0069] 2 and 3, the backplate includes a showerhead stem 230. The showerhead stem 230 includes a plurality of mounting holes 232 for mounting the showerhead 200 within a processing tool. The showerhead stem 230 also includes one or more holes 234 for accommodating an electric heater or heaters (not shown) and one or more holes 236 for accommodating one or more corresponding temperature probes. In other examples, the showerhead stem may have any other suitable configuration.

[0070] The posts 220 are positioned so as not to obstruct the flow of process gas within the plenum 206. In some examples, the posts may be positioned such that any radial line extending from the center of the plenum to the periphery 244 of the plenum intersects at most one post. FIG. 4 illustrates a top view of the showerhead 200, showing an example arrangement of the post access holes 222 on the backplate 204. FIG. 5 schematically illustrates an example arrangement of the posts 220 on the faceplate 202. As can be seen in FIG. 5, any radial line drawn from the center 242 of the plenum to the periphery 244 of the plenum intersects at most one post 220. Because the gas inlet 210 is located at the center of the plenum, gas impinges on the baffle 212 and then diffuses through the plenum 206. In addition to the advantages disclosed above, the illustrated arrangement of the posts 220 helps ensure uniform distribution of gas within the plenum 206 before it exits the plenum 206 through the outlet holes 208.

[0071] As mentioned above, in some examples, a showerhead according to the present disclosure can have more than 20 posts. Continuing with FIGS. 4 and 5, showerhead 200 includes 24 posts. The inner 12 posts are arranged in a generally hexagonal configuration. FIG. 5 shows posts 220 as solid circles. FIGS. 4 and 5 show lines 400, 402 that define the quadrants of the showerhead: first quadrant 410, second quadrant 412, third quadrant 414, and fourth quadrant 416, respectively. Referring to FIG. 5, posts 220 are shown as solid circles. It can be seen that the inner 12 posts are arranged along an inner circle 500 and a middle circle 502. The outermost set of posts 240, indicated at 240 by a pair of dashed lines in FIG. 2, is shown arranged along an outer circle 504 in FIG. 5.

[0072] For the inner 12 posts, proceeding clockwise from the vertical quadrant, the first quadrant 410 includes a post on the middle circle 502 at 0 degrees, then a post on the inner circle 500 at 30 degrees, then a post on the middle circle 502 at 60 degrees. The second quadrant 412 includes a post on the inner circle 500 at 90 degrees, then a post on the middle circle 502 at 120 degrees, then a post on the inner circle 500 at 150 degrees. The third quadrant 414 includes a post on the middle circle 502 at 180 degrees, then a post on the inner circle 500 at 210 degrees, then a post on the middle circle 502 at 240 degrees. The fourth quadrant 416 includes a post on the inner circle 500 at 270 degrees, then a post on the middle circle 502 at 300 degrees, then a post on the inner circle 500 at 330 degrees. In other examples, any suitable number and arrangement of medial posts can be used.

[0073] Some conventional showerheads may include several posts arranged within the plenum. However, conventional showerheads do not include posts arranged within the range described by this disclosure. In FIG. 5 , the outermost set of posts 240 is shown as a black circle arranged along the outer circle 504. The outermost set of posts along the outer circle 504 includes 12 posts. The first quadrant 410, the second quadrant 412, the third quadrant 414, and the fourth quadrant 416 each include three posts in their outermost set of posts. Furthermore, in each quadrant, the first post of the outermost set of posts within the quadrant is separated from the second post of the outermost set of posts within the quadrant by a first angular distance along the outer circle 504. Furthermore, the second post of the outermost set of posts within the quadrant is separated from the third post of the outermost set of posts within the quadrant by a second angular distance. The first angular distance is less than the second angular distance. For example, referring to the first quadrant 410, the first post 220A of the outermost post set 240 along the circle 504 is spaced 21.8 degrees from the second post 220B. The second post 220B is separated from the third post 220C by an angular distance of 38.2 degrees. Thus, the first post 220A is separated from the third post 220C by 60 degrees. This spatial pattern is repeated every 60 degrees around the outer circle 504. More specifically, the relative separation between the first post 220A, the second post 220B, and the third post 220C is the same as the relative separation between the third post 220C, the fourth post 220D, and the fifth post 220E. The relative separation is the same between the fifth post 220E, the sixth post 220F, and the seventh post 220G. The pattern continues to repeat in this manner around the outer circle 504.

[0074] The illustrated post arrangements also form other patterns. For example, continuing with FIG. 5 , the second quadrant 412 has a pattern of posts 220 along outer circle 504 that is a mirror image across line 402 of the pattern of posts along outer circle 504 in the first quadrant 410. The third quadrant has a pattern of posts along outer circle 504 that is a mirror image across line 400 of the pattern of posts along outer circle 504 in the second quadrant. The fourth quadrant has a pattern of posts along outer circle 504 that is a mirror image of the first quadrant 410 across line 400 and the third quadrant 414 across line 402.

[0075] In the illustrated post arrangement, each post of the outermost set of posts (along outer circle 504) is relatively close to one adjacent post and relatively far from another adjacent post. For example, second post 220B on outer circle 504 is closer to first post 220A than third post 220C. Similarly, first post 220A is closer to second post 220B than post 220H in the opposite direction along outer circle 504. In this manner, the outer posts form a pattern in which pairs of posts are distributed along outer circle 504. Example pairs of posts are shown as pair 520A, pair 520B, and pair 520C.

[0076] FIG. 5 also shows that the outermost set of posts along the outer circle 504 is spaced between 52% and 58% of the distance from the center of the plenum 510 to the outer periphery of the plenum 512. As noted above, outermost posts located within this radial distance may help resist thermally induced bending of the faceplate while avoiding excessive loads that could lead to the risk of fracture due to thermal cycling over the lifetime of the showerhead. In another example, the outermost set of posts may be located within 50% to 65% of the distance from the center of the plenum to the outer periphery of the plenum. A set of outermost posts located within 58% to 65% of the distance from the center of the plenum to the outer periphery of the plenum may provide additional support against bending compared to a set of outermost posts located less than 58% of this distance. In a further example, the set of outermost posts may be located within 45% to 65% of the distance from the center of the plenum to the outer periphery of the plenum. By positioning the outermost set of posts at the lower end of this range (e.g., less than 50% of the distance from the center of the plenum to the outer periphery of the plenum), the load on the outermost posts due to differential thermal expansion between the faceplate and backplate may be reduced compared to when they are positioned at the higher end of this range.

[0077] 5 illustrates specific example radial and angular positions of the posts 220. The illustrated radial and angular positions are examples of angular positions that may facilitate achieving a suitably uniform gas flow within the plenum 220 of the showerhead 200. However, the specific angular positions illustrated are provided for illustrative purposes and are not intended to be limiting. In other examples, one or more posts 220 may have different radial and / or angular positions than those illustrated. Furthermore, in other examples, a showerhead may have fewer or more than 24 posts. Furthermore, in other examples, a quadrant may have fewer or more than three posts in the outermost set of posts.

[0078] As mentioned above, in some showerheads, the post access holes are plugged during fabrication after the posts of the showerhead faceplate are welded to the backplate through the post access holes. Plugging the post access holes can help prevent the formation of hollow cathode discharge in the post access holes during plasma generation using the showerhead as an electrode. Such parasitic plasma formation reduces the plasma power used for substrate processing. However, plugging the post access holes typically involves welding a plug into each post access hole, which increases the fabrication time and cost of the showerhead. However, it has been discovered that plugging the post access holes can be avoided by forming arcuate edged post access hole openings on the showerhead backplate. FIG. 6 shows a cross-sectional view of a portion of the showerhead 200, illustrating the arcuate edge 600 at the opening of the post access hole 222 on the outer surface of the backplate. The arcuate edge can have any suitable radius of curvature. Examples include radii of curvature in the range of 0.05 inches to 0.25 inches. The ranges described herein are inclusive.

[0079] Referring now to FIG. 7, in some such examples, each post of the showerhead may include a radial structure where the post meets the flat surface of the inner surface of the faceplate. FIG. 7 shows a portion of a view of an example showerhead 700 including a post 702 and a radial structure 704 where the post meets the flat surface of the inner surface of a faceplate 706. The radial structure 704 may help the post 702 distribute loads experienced by the post 702 over a wider area than if the post did not have the radial structure 704. FIG. 7 also shows multiple outlet holes 708 arranged around the periphery of the post 702. The post 702 and radial structure 704 are positioned such that the regular pattern of outlet holes 708 across the showerhead's faceplate 706 is not obstructed by the post 702 and radial structure 704.

[0080] As described above, the showerhead may include a baffle positioned within the showerhead plenum. Process gases entering the showerhead through the gas inlets impinge on the baffle and diffuse into other portions of the plenum. The use of such a baffle may help prevent the amount of process gas flowing out of the outlet holes directly below the gas inlets from exceeding the amount flowing out of the outlet holes located on the outer periphery of the plenum. Referring briefly back to FIG. 3 , the baffles 212 are attached to a plurality of mounts 213. The mounts 213 may be integrated with or attachable to the faceplate 202.

[0081] In some examples, the baffle can be welded to the fixture that supports it. In other examples, the baffle can be swage-connected to the fixture. The term "swage connection" refers to the mechanical connection of two parts by forcing a mounting post on one part into an opening on the other part. The mounting post is held in place by compression / friction within the opening. Additionally, in some examples, the distal end of the post can be flared after the post is forced into the opening.

[0082] 8 shows an example of a baffle 800 attached to a baffle mount 802 via a swage connection. The baffle 800 is pressed into the baffle mount 802 such that the baffle mount 802 is a compression fit into the hole in the baffle 800. Additionally, pressure can be applied to the distal end 804 of the baffle mount 802 to form a flared shape at the distal end 804, which may help maintain the baffle 800 attached to the baffle mount 802 during repeated thermal cycling.

[0083] Exemplary showerheads disclosed herein include structural features, including, for example, a unique post placement, an optimized faceplate thickness, and a novel post access hole configuration that addresses long-standing challenges in the semiconductor processing industry. To function, a showerhead must be able to withstand the required processing conditions. Currently, with advances in wafer fabrication technology, recipes requiring extreme operating conditions are on the rise. For example, as described above, certain recipes may require processing conditions that pose a particularly high risk of post fracture. Some recipes require cycling between substrate processing conditions using extremely high temperatures, even at or above 570°C. In some instances, showerheads may be exposed to plasma cleaning processes using pedestal temperatures up to 485°C. If the posts crack, the showerhead will be destroyed. There is a need to develop a showerhead that can withstand more extreme operating conditions for a longer period of time.

[0084] Adding an outermost set of posts farther from the center of the plenum than the outermost set of posts in a conventional showerhead would create a higher risk of fracture. However, the post placement and faceplate thickness of the present disclosure unexpectedly reduce the risk of post fracture. The post placement and faceplate thickness of the present disclosure facilitate improved heat transfer between the faceplate and backplate compared to heat transfer in conventional showerheads. This reduces the thermal expansion differential between the faceplate and backplate, reducing stress on the posts, especially in recipes requiring extreme operating conditions. However, simply adding more posts to extend the showerhead's lifespan may not be effective. In fact, random or improper post placement may result in a shorter showerhead lifespan. Furthermore, the placement of some additional posts can adversely affect the uniformity of process gas flow within the showerhead's plenum. Non-uniform process gas flow within the plenum can result in non-uniform substrate processing because different device regions on the substrate receive different process gas flows.

[0085] The post arrangement and faceplate thickness of the present disclosure represent a careful balance of performance and manufacturability considerations, offering the unexpected benefit of a lower risk of post fracture, even though the outermost set of posts is located farther from the center of the plenum than in conventional showerheads. Compared to conventional showerheads, the post arrangement of the present disclosure is carefully positioned so as not to affect the uniformity of process gas flow within the showerhead plenum. Furthermore, the use of rounded corners at the openings of the post access holes avoids the formation of parasitic plasma without the need to plug the post access holes. This helps avoid plasma power reduction due to parasitic plasma.

[0086] It will be understood that the configurations and / or approaches described herein are exemplary in nature and that numerous variations are possible, and therefore these specific examples are not to be construed in a limiting sense. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, acts, and / or properties disclosed herein, and any and all equivalents thereof.

[0087] The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, operations, and / or properties disclosed herein, and any and all equivalents thereof.

Claims

1. 1. A showerhead for a substrate processing tool, comprising: a faceplate having a plurality of exit holes; a backplate coupled to the faceplate; a plenum between the faceplate and the backplate; a plurality of posts connecting the faceplate and the backplate, wherein an outermost set of posts of the plurality of posts are positioned between 45% and 65% of the distance from the center of the plenum to the outer periphery of the plenum, and no posts are positioned between 65% and 100% of the distance from the center of the plenum to the outer periphery of the plenum; Equipped with a shower head.

2. 10. The showerhead of claim 1, the outermost set of posts of the plurality of posts are positioned between 50% and 65% of the distance from the center of the plenum to the outer periphery of the plenum.

3. 10. The showerhead of claim 1, the outermost set of posts of the plurality of posts is positioned between 52% and 58% of the distance from the center of the plenum to the periphery of the plenum; The showerhead, wherein no posts are positioned between 58% and 100% of the distance from the center of the plenum to the periphery of the plenum.

4. 4. The showerhead of claim 3, The showerhead, wherein the plurality of posts are arranged such that any radial line extending from the center of the plenum to the outer periphery of the plenum intersects at most one post.

5. 10. The showerhead of claim 1, The showerhead, wherein the plurality of posts are arranged such that any radial line extending from the center of the plenum to the outer periphery of the plenum intersects at most one post.

6. 10. The showerhead of claim 1, The showerhead, wherein the plurality of posts comprises 20 or more posts.

7. 10. The showerhead of claim 1, The showerhead, wherein the faceplate has a thickness greater than 0.35 inches and less than or equal to 1 inch.

8. 8. The showerhead of claim 7, The showerhead, wherein the faceplate has a thickness in the range of 0.45 to 0.65 inches.

9. 10. The showerhead of claim 1, the backplate has a post access hole for each post, and each post access hole has an arcuate edge at the opening of the post access hole on the outer surface of the backplate.

10. 10. The showerhead of claim 1, each post integral with said faceplate and welded to said backplate; The showerhead, wherein each post has a radial structure where the post abuts a planar surface of the inner surface of the faceplate.

11. 10. The showerhead of claim 1, the outermost set of posts are arranged in a circular pattern with at least three posts for each quadrant of the circular pattern, a first post being spaced a first angular distance along the circular pattern from a second post of the three posts, the second post being spaced a second angular distance along the circular pattern from a third post, the first distance being less than the second distance.

12. 1. A showerhead for a substrate processing tool, comprising: a faceplate with a plurality of exit holes; a backplate coupled to the faceplate; a plenum between the faceplate and the backplate; a plurality of posts connecting the face plate and the back plate; a plurality of post access holes formed in the backplate, each post access hole having an arcuate edge at an opening of the post access hole on an outer surface of the backplate; Equipped with a shower head.

13. 13. The showerhead of claim 12, The radius of curvature of the arcuate edge is in the range of 0.05 inches to 0.25 inches.

14. 13. The showerhead of claim 12, an outermost set of posts of the plurality of posts is positioned between 52% and 58% of the distance from the center of the plenum to the outer periphery of the plenum; The showerhead, wherein no posts are positioned between 58% and 100% of the distance from the center of the plenum to the periphery of the plenum.

15. 13. The showerhead of claim 12, The showerhead, wherein the plurality of posts are arranged such that any radial line extending from the center of the plenum to the outer periphery of the plenum intersects at most one post.

16. 13. The showerhead of claim 12, The showerhead, wherein the plurality of posts comprises 20 or more posts.

17. 13. The showerhead of claim 12, The showerhead, wherein the faceplate has a thickness greater than 0.45 inches and less than or equal to 0.55 inches.

18. 1. A showerhead for a substrate processing tool, comprising: a faceplate having a plurality of exit holes; a backplate coupled to the faceplate; a plenum between the faceplate and the backplate; a plurality of posts connecting the faceplate and the backplate, an outermost set of posts of the plurality of posts arranged in a circular pattern with at least three posts for each quadrant of the circular pattern, a first post being spaced a first angular distance along the circular pattern from a second post of the three posts, and the second post being spaced a second angular distance along the circular pattern from a third post, the first distance being less than the second distance; Equipped with a shower head.

19. 20. The showerhead of claim 18, the outermost set of posts of the plurality of posts is positioned between 52% and 58% of the distance from the center of the plenum to the periphery of the plenum; The showerhead, wherein no posts are positioned between 58% and 100% of the distance from the center of the plenum to the periphery of the plenum.

20. 20. The showerhead of claim 18, the backplate has a post access hole for each post, and each post access hole has an arcuate edge at the opening of the post access hole on the outer surface of the backplate.

Images