Patent Application
20240141492
This application claims priority to India application for patent numbered 202241061142, dated Oct. 27, 2022, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of the disclosure relate to substrate supports for process chambers. In particular, embodiments of the disclosure are directed to susceptors with wafer pockets configured to prevent wafer breakage.
In some CVD and ALD processing chambers, the substrates, also referred to herein as wafers, move relative to the precursor injector and heater assembly. If the motion creates acceleration forces larger than that of the frictional force, the wafer can become displaced causing damage or related issues. The wafers placed off-axis can slip at high acceleration/deceleration on a moving/rotating susceptor. Friction from the weight of the wafer itself is insufficient to hold the wafer on tools where higher throughput is desired.
To prevent the rotation forces from dislodging the wafer during process, additional hardware to clamp or chuck the wafer in place may be needed. The additional hardware can be expensive, difficult to install, difficult to use and/or cause damage to the wafers during use.
In many batch processing chambers, multiple substrates are supported on large platen susceptors for processing. The susceptors typically rotate around a central shaft at constant or varying speeds. Without support, the substrates on the susceptor would move outward toward the edge of the susceptor as a result of centrifugal force. One method of preventing substrates from moving on the susceptor includes a pocket formed in the top of the susceptor sized for hold the substrate.
Current pocket design can cause stress on the coating on the pocket edge resulting in edge cracking. Higher stress causes cracking or other defects of the pocket edge which leads to particle issues on the edge of the wafer and on-wafer performance.
Accordingly, there is a need in the art for improved apparatus to prevent pocket edge cracking due to high stress with film accumulation.
One or more embodiments of the disclosure are directed to susceptor assemblies comprising a susceptor base having a plurality of pockets formed in a surface thereof. Each of the pockets has a pocket edge angle in the range of 30 to 75° and a pocket edge radius in the range of 0.40 mm to 1.20 mm±0.05 mm.
A susceptor assembly comprising a susceptor base having a plurality of pockets formed in a surface thereof. Each of the pockets comprises a raised central region defining a wafer placement surface and an outer portion that is deeper than the raised central region, relative to the surface of the susceptor base. The wafer placement surface is in the range of 0.1 mm to 0.4 mm higher than a surface of the outer portion of the pocket. Each of the pockets has a pocket edge angle in the range of 30 to 75° and a pocket edge radius in the range of 0.40±0.05 mm to 1.20 mm±0.05 mm.
A susceptor assembly comprising a susceptor base having a plurality of pockets formed in a surface thereof. Each of the pockets comprises a raised central region defining a wafer placement surface and an outer portion that is deeper than the raised central region, relative to the surface of the susceptor base. The raised central region has a plurality of raised mesas with gas channels allowing a flow of backside gas from a center portion of the raised central region to the outer portion of the pocket. The wafer placement surface is in the range of 0.1 mm to 0.4 mm higher than a surface of the outer portion of the pocket. Each of the pockets has a pocket edge angle in the range of 30 to 75° and a pocket edge radius in the range of 0.40±0.05 mm to 1.20 mm±0.05 mm.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways.
A “substrate” as used herein, refers to any substrate, or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, 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, without limitation, semiconductor wafers. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal and/or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed may also be performed on an under-layer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such under-layer as the context indicates. Thus for example, where a film/layer or partial film/layer has been deposited onto a substrate surface, the exposed surface of the newly deposited film/layer becomes the substrate surface. The terms “wafer”, “workpiece”, and the like, are used interchangeably with substrate.
As used in this specification and the appended claims, the terms “precursor”, “reactant”, “reactive gas” and the like are used interchangeably to refer to any gaseous species that can react with the substrate surface.
In some spatial ALD chambers, the precursors used for deposition are injected in close proximity to the wafer surface. To develop the desired gas dynamics, the injector channels are independently controlled at a higher pressure than the surrounding chamber. By creating a pressure differential between the front side of the wafer and the back side of the wafer, a positive pressure force adequate to hold the wafer against relativity larger acceleration force can be generated.
Embodiments of the disclosure are directed to the use of differential pressure to hold substrates (wafers) on a susceptor under large acceleration forces. The large acceleration forces occur as a result of high rotation speeds, which may be experienced in carousel-type processing chambers, from larger batch sizes and processing speeds or higher reciprocating motion for higher wafer throughput.
In some embodiments, the wafers sit in shallow pockets on a susceptor below the injector assemblies. The susceptor can provide heat transfer, improved gas dynamics and act as a carrier vehicle for the substrates.
Embodiments of the disclosure are directed to susceptors with an angled hole for vacuum from inner diameter of susceptor-bottom up to the wafer pocket. The susceptor can get a vacuum source through the rotation shaft and rotation motor below the shaft. If the susceptor is made of Silicon Carbide Coated (SiC) Graphite, then additional holes which are spaced, for example, every three times hole diameter, are needed from top or bottom of the susceptor for better penetration of the SiC coating. The redundant holes are plugged for vacuum. Graphite plugs can be press-fit before SiC Coating and then the susceptor is SiC coated. In some embodiments, threaded SiC Coated plugs on SiC Coated susceptor and a second SiC coat can be applied for better sealing of graphite with SiC for more corrosive applications.
The specific type of gas distribution assembly 120 used can vary depending on the particular process being used. Embodiments of the disclosure can be used with any type of processing system where the gap between the susceptor and the gas distribution assembly is controlled. While various types of gas distribution assemblies can be employed (e.g., showerheads), embodiments of the disclosure may be particularly useful with spatial gas distribution assemblies which have a plurality of substantially parallel gas channels. As used in this specification and the appended claims, the term “substantially parallel” means that the elongate axis of the gas channels extend in the same general direction. There can be slight imperfections in the parallelism of the gas channels. In a binary reaction, the plurality of substantially parallel gas channels can include at least one first reactive gas A channel, at least one second reactive gas B channel, at least one purge gas P channel and/or at least one vacuum V channel. The gases flowing from the first reactive gas A channel(s), the second reactive gas B channel(s) and the purge gas P channel(s) are directed toward the top surface of the wafer. Some of the gas flow moves horizontally across the surface of the wafer and out of the process region through the purge gas P channel(s). A substrate moving from one end of the gas distribution assembly to the other end will be exposed to each of the process gases in turn, forming a layer on the substrate surface.
In some embodiments, the gas distribution assembly 120 is a rigid stationary body made of a single injector unit. In one or more embodiments, the gas distribution assembly 120 is made up of a plurality of individual sectors (e.g., injector units 122), as shown in
A susceptor assembly 140 is positioned beneath the gas distribution assembly 120. A susceptor assembly 140, as used herein, refers to a combination of components including a susceptor 130 and a support post 160. Other components can be included in a susceptor assembly 140 without deviating from the scope of the disclosure.
The susceptor assembly 140 includes a susceptor 130 with a top surface 141 and at least one pocket 142 in the top surface 141. The susceptor 130 also has a bottom surface 143 and an edge 144. As used herein, the top surface 141, the pocket 142, bottom surface 143 and edge 144 refer to both the susceptor 130 and the susceptor assembly 140, unless otherwise indicated.
The pocket 142 can be any suitable shape and size depending on the shape and size of the wafers 110 being processed. In the embodiment shown in
In some embodiments, as shown in
The susceptor assembly 140 of
In some embodiments, the gap 170 distance is in the range of about 0.1 mm to about 5.0 mm, or in the range of about 0.1 mm to about 3.0 mm, or in the range of about 0.1 mm to about 2.0 mm, or in the range of about 0.2 mm to about 1.8 mm, or in the range of about 0.3 mm to about 1.7 mm, or in the range of about 0.4 mm to about 1.6 mm, or in the range of about 0.5 mm to about 1.5 mm, or in the range of about 0.6 mm to about 1.4 mm, or in the range of about 0.7 mm to about 1.3 mm, or in the range of about 0.8 mm to about 1.2 mm, or in the range of about 0.9 mm to about 1.1 mm, or about 1 mm.
The processing chamber 100 shown in the Figures is a carousel-type chamber in which the susceptor assembly 140 can hold a plurality of wafers 110. As shown in
Processing chambers having multiple gas injectors can be used to process multiple wafers simultaneously so that the wafers experience the same process flow. For example, as shown in
The processing chamber 100 shown in
The embodiment shown in
Rotation of the carousel (e.g., the susceptor assembly 140) can be continuous or intermittent (discontinuous). In continuous processing, the wafers are constantly rotating so that they are exposed to each of the injectors in turn. In discontinuous processing, the wafers can be moved to the injector region and stopped, and then to the region 128 between the injectors and stopped. For example, the carousel can rotate so that the wafers move from an inter-injector region across the injector (or stop adjacent the injector) and on to the next inter-injector region where the carousel can pause again. Pausing between the injectors may provide time for additional processing steps between each layer deposition (e.g., exposure to plasma).
Referring to both
With reference to the embodiments shown in
Referring to
The injector unit 122 of
Referring to
During processing a substrate may be exposed to more than one process region 250 at any given time. However, the portions that are exposed to the different process regions will have a gas curtain separating the two. For example, if the leading edge of a substrate enters a process region including the second gas port 135, a middle portion of the substrate will be under a gas curtain 150 and the trailing edge of the substrate will be in a process region including the first reactive gas port 125.
A factory interface 280, which can be, for example, a load lock chamber, is shown connected to the processing chamber 100. A wafer 110 is shown superimposed over the gas distribution assembly 120 to provide a frame of reference. The wafer 110 may often sit on a susceptor assembly to be held near the front surface 121 of the gas distribution assembly 120. The wafer 110 is loaded via the factory interface 280 into the processing chamber 100 onto a substrate support or susceptor assembly (see
Embodiments of the disclosure are directed to processing methods comprising a processing chamber 100 with a plurality of process regions 250a-250h with each process region separated from an adjacent region by a gas curtain 150. For example, the processing chamber shown in
A plurality of wafers 110 are positioned on a substrate support, for example, the susceptor assembly 140 shown
One or more embodiments of the disclosure provide susceptor pockets with modified/enhanced susceptor pocket edge design using pocket edge radius and edge angles to improve pocket edge performance. Embodiments of the disclosure address the issue of pocket edge cracking due to stress with accumulation on the susceptor.
A passage 240 extends between the drive shaft (support post 160) of the susceptor assembly 140, or from a hollow area 161 (see
The passage 240 illustrated has a plurality of holes 247 connecting the top surface 141 of the susceptor 130 with the passage 240. In some embodiments, there is at least one hole extending from one of the top surface 141 of the susceptor 130 or the bottom surface 143 of the susceptor 130 to the passage 240.
The holes 247 can be created (e.g., drilled) during the manufacture of the susceptor 130 to allow the inside of the passage 240, or portions of the inside of the passage 240, to be coated and/or sealed. For example, in some embodiments, the susceptor 130 has a silicon carbide coating. The susceptor 130 of some embodiments is a silicon carbide coated graphite. The holes 247 allow the silicon carbide to be coated on the passage 240 and are then sealed with plugs 248. The plugs 248 can be made of any suitable material including, but not limited to, silicon carbide, silicon carbide coated graphite, a material with a silicon carbide coating and/or graphite. After the plugs 248 have been inserted into the holes 247, the susceptor 130 can be coated with silicon carbide again to provide an additional sealing of the holes 247. The plugs 248 can be press-fit (e.g., friction fit), connected to the holes 247 by complementary screw threads or connected by some other mechanical connection (e.g., epoxy or brazing).
During the preparation of a silicon carbide coated susceptor 130, the holes 247 provide a useful passageway for the silicon carbide to coat the passage 240. The size and spacing of the holes 247 may have an impact on the efficiency of the coating. In some embodiments, the holes 247 are spaced in increments of the hole diameter. For example, if the holes are 5 mm in diameter, the spacing might be 5x mm, with x being any suitable value. For example, the spacing may be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 times the hole diameter. The holes 247 can be positioned at any suitable points along the length of the passage 240, and do not need to be evenly distributed across the passage 240 length. As shown in
The passages 240 can be used to supply a vacuum to the pocket 142 to chuck the wafer 110. However, when the wafer 110 is processed, the vacuum may be too strong to easily remove the processed wafer from the recess. To ease removal of the wafer, the passages 240 can also be used to provide a flow of gas toward the back surface 113 of the wafer 110. Thus providing a positive pressure to the back side of the wafer 110 to allow the wafer 110 to be easily removed from the susceptor 130.
Referring back to
The valve 171 can be set to a closed position, isolating the passage 240, or to a position where a connection is formed between the passage 240 to a dechucking gas plenum 173 through connector 242. The dechucking gas plenum 173 is shown in fluid communication with a dechucking gas source 175. The dechucking gas source 175 can comprise any suitable gas including, but not limited to, nitrogen, argon, helium or an inert gas.
The vacuum source 165 can be connected to the hollow area 161 through valve 166. The valve 166 can be used to isolate the hollow area 161 from the vacuum source 165 in the event that there is a loss of vacuum from the vacuum source 165. This allows the hollow area 161 to act as a vacuum plenum so that the wafers on the susceptor assembly remain chucked while the vacuum source is being reconnected or repaired.
Each of the individual pocket 142 in the susceptor 130 can include a separate passage 240 and valve 171. This allows each individual pocket 142 to be isolated from the vacuum in the hollow area 161. For example, a processed wafer 110 can be moved to the loading/unloading area of the processing chamber. The valve 171 can be closed or switched to the dechucking gas plenum 173 to cause a positive pressure on the back side of the wafer 110, allowing a robot to pick up the wafer. After picking up the wafer, the valve 171 can close so that the pressure in the pocket 142 will be equal to the pressure of the chamber. A new wafer 110 can be placed in the pocket 142 and the valve 171 switched back to allow fluid connection with the hollow area 161 to chuck the new wafer 110.
The passage 240 is formed in the susceptor 130 by drilling from the edge 144 of the susceptor 130 toward the center 131 of the susceptor 130. The channel 246 is formed to connect the bottom 147 of the pocket 142 to the passage 240. In the illustrated embodiment, the channel 246 is formed in approximately the center of the pocket 142. However, the skilled artisan will recognize that this is merely one possible configuration and should not be taken as limiting the scope of the disclosure.
To prevent leakage, the passage 240 is sealed using plug 248 which is inserted into the end of the passage 240 adjacent the edge 144 of the susceptor 130. The plug 248 of some embodiments is screwed into position in passage 240, allowing the plug 248 to be removed for replacement of cleaning of the passage 240. In some embodiments, the plug 248 is permanently affixed into position in the passage 240. In the embodiment illustrated, the plug 248 does not extend completely to the channel 246 leaving a dead leg 249 in the passage 240. As the passage 240 is primarily used for vacuum chucking, the presence of the dead leg 249 does not interfere with use of the susceptor 130.
The susceptor 130 illustrated in
However, it has been surprisingly found that incorporating an edge radius and an edge angle into the pocket 142 substantially reduces the likelihood of chipping, or forming a defect 136 in the coating 133 on the susceptor body 132. The inventors have surprisingly found that the increased corner radius and decreased angle results in a reduction in the stress on the edge of the pocket 142 compared to a pocket 142 with a sharp corner 138. The stress on the edge of the pocket 142 results in formation of the defects 136 in the coating 133 on the susceptor body 132. The defect 136 can be, for example, a chip in the coating 133, peeling of the coating 133 or a crack in the coating 133. The defect 136 can be any surface artifact that results in the exposure or potential exposure of the susceptor base 132 through the coating 133.
The illustrated pocket 142 includes a raised central region 185 upon which the wafer 110 sits. The outer portion 187 of the pocket 142 is deeper than the raised central region 185 so that the outer peripheral edge 119 of the wafer 110 is elevated above the surface 188 of the outer portion 187 of the pocket 142.
The raised central region 185 can be a continuous surface of material or can include a plurality of raised mesas 191, as shown in
The diameter DW of the substrate is greater than the diameter DC of the raised central region 185, or the outermost ring of mesas supporting the wafer 110. In some embodiments, the difference between the diameter DW of the wafer 110 and the diameter DC of the raised central region 185 is in the range of 0.5 mm to 5 mm, or in the range of 1 mm to 3 mm.
The wall 194 transitioning between the raised central region 185 and the outer portion 187 is illustrated sloping downward to the surface 188 of the outer portion 187 and outward to the outer peripheral edge of the pocket 142. In some embodiments, the wall 194 is perpendicular to the wafer placement surface 186 connecting the wafer placement surface 186 with the surface 188 of the outer portion 187 with 90° angles. In some embodiments, the wall 194 has a smooth transition between the wafer placement surface 186 and the surface 188 with a curved shape (e.g., an ogee).
In some embodiments, the edge radius 183 has a radius r in the range of 0.40 mm±0.05 mm to 1.20 mm±0.05 mm. In some embodiments, the edge radius 183 is in the range of 0.50±0.05 mm to 1.00±0.05 mm.
According to one or more embodiments of the disclosure, the pocket edge angle θ is in the range of 30 to 75°. The pocket edge angle θ is measured relative to an imaginary line perpendicular PL to the surface of the outer portion 187 of the pocket 142, as shown. A pocket edge angle θ of 0° would be perpendicular to the surface 188 of the outer portion 187 of the pocket 142. In some embodiments, the pocket edge angle θ is about 30°. In some embodiments, the pocket edge angle θ is about 45°. In some embodiments, the pocket edge angle θ is about 75°.
The raised central region 185, also referred to as the wafer placement surface 186, of some embodiments is in the range of 0.1 to 0.4 mm higher than the surface 188 of the outer portion 187 of the pocket 142. In some embodiments, the outer portion 187 of the pocket 142 is in the range of 0.9 mm to 1.1 mm lower than the top surface 141 of the susceptor 130. In some embodiments, the surface 188 of the outer portion 187 of the pocket 142 is 1 mm lower than the top surface 141 of the susceptor base 148.
Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.
Although the disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure include modifications and variations that are within the scope of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202241061142 | Oct 2022 | IN | national |
