BACKSIDE DEPOSITION PREVENTION ON SUBSTRATES

Various systems and methods are provided to prevent backside deposition on a substrate by using a combination of approaches. The approaches include clamping the substrate to a pedestal and/or supplying purge gases to an area where deposition is not desired. The clamping methods include electrostatic or vacuum clamping. In addition, various pedestal and edge ring designs are provided for supplying purge gases to the area where deposition is not desired. The use of clamping in conjunction with purging can further enhance the performance without affecting deposition of materials on front side of the substrate. The clamping along the edge of the substrate can be made more effective by machining an upper surface of the pedestal to have a slight dish or dome like shape (i.e., concave or convex, respectively).

FIELD

The present disclosure relates generally to substrate processing systems and more particularly to systems and methods for preventing backside deposition on substrates.

BACKGROUND

Atomic Layer Deposition (ALD) is a thin-film deposition method that sequentially performs a gaseous chemical process to deposit a thin film on a surface of a material (e.g., a surface of a substrate such as a semiconductor wafer). Most ALD reactions use at least two chemicals called precursors (reactants) that react with the surface of the material one precursor at a time in a sequential, self-limiting manner. Through repeated exposure to separate precursors, a thin film is gradually deposited on the surface of the material. ALD is typically performed in a heated processing chamber. The processing chamber is maintained at a sub-atmospheric pressure using a vacuum pump and a controlled flow of an inert gas. The substrate to be coated with a film is placed in the processing chamber and is allowed to equilibrate with the temperature of the processing chamber before starting the ALD process.

SUMMARY

A system comprises a pedestal arranged below a showerhead. The pedestal includes a base portion and a stem portion. The base portion supports a substrate. The base portion is disc shaped and has an annular recess on an upper surface of the base portion along an outer diameter of the base portion. The stem portion is connected to the base portion. The system comprises a heat shield arranged below a lower surface of the base portion. The heat shield and the lower surface define a manifold that is in fluid communication with a gas inlet. The system comprises an edge ring including a cylindrical portion and an annular portion. The cylindrical portion surrounds the base portion. The cylindrical portion has a first end resting on an outer edge of the heat shield and has a second end. An inner surface of the cylindrical portion and an outer surface of the base portion define a first gap in fluid communication with the manifold. The annular portion extends radially inwards over the annular recess from the second end of the cylindrical portion. The annular portion and the annular recess define a second gap in fluid communication with the first gap. A purge gas supplied to the gas inlet flows through the manifold, the first and second gaps, and radially outwards over the annular portion.

In other features, the purge gas is supplied to the gas inlet while a material is deposited from the showerhead on a showerhead-facing surface of the substrate, and the purge gas prevents the material from depositing on a pedestal-facing surface of the substrate.

In another feature, the pedestal includes an electrostatic clamping system to clamp the substrate to the upper surface of the base portion.

In another feature, the pedestal includes a vacuum clamping system to clamp the substrate to the upper surface of the base portion.

In another feature, the upper surface of the base portion lies in a higher plane at an outer diameter of the base portion than at a center of the base portion.

In another feature, the upper surface of the base portion lies in a lower plane at an outer diameter of the base portion than at a center of the base portion.

In another feature, the system further comprises an annular sealing band arranged on the upper surface of the base portion. An outer diameter of the annular sealing band is equal to an inner diameter of the annular recess and an outer diameter of the substrate.

In another feature, the system further comprises an actuator configured to move the pedestal vertically relative to the showerhead to adjust a gap between the substrate and the showerhead during processing.

In another feature, an upper surface of the annular portion lies in a higher plane than a showerhead-facing surface of the substrate.

In other features, each of upper and lower surfaces of the annular portion includes a radially outer portion and a radially inner portion. The radially outer portions extend parallel to the annular recess from the cylindrical portion, and the radially inner portions slope towards an inner diameter of the annular portion.

In other features, the cylindrical portion is parallel to the outer surface of the base portion, and the annular portion is parallel to the annular recess.

In another feature, outer diameters of the cylindrical and annular portions are equal.

In another feature, an inner diameter of the annular recess is greater than or equal to an outer diameter of the substrate.

In another feature, an inner diameter of the annular portion is greater than an inner diameter of the annular recess and an outer diameter of the substrate.

In other features, an upper surface of the annular portion is level with a showerhead-facing surface of the substrate. A lower surface of the annular portion extends parallel to the annular recess from the cylindrical portion and slopes upwards towards an inner diameter of the annular portion.

In other features, the system further comprises a second ring arranged at a distance above the upper surface of the annular portion. Inner and outer diameters of the second ring are equal to respective diameters of the annular portion. Upper and lower surfaces of the second ring are parallel to the upper surface of the annular portion.

In another feature, the annular portion includes a plurality of holes extending radially outwards from an inner diameter of the annular portion.

In other features, a lower surface of the annular portion extends parallel to the annular recess from the cylindrical portion and slopes upwards towards an inner diameter of the annular portion. An upper surface of the annular portion includes a first portion that slopes upwards from the inner diameter of the annular portion for a first distance and a second portion that slopes downwards towards from the first distance to an outer diameter of the annular portion. The upper surface of the annular portion includes a plurality of holes extending radially through the first portion and partially through second portion.

In another feature, the system further comprises a controller to control flow of the purge gas through the gas inlet.

In another feature, the gas inlet is located at a bottom of the stem portion.

In still other features, a pedestal to support a substrate arranged below a showerhead comprises a base portion having a disc shape and a stem portion extending from the base portion. The base portion includes an annular ridge on an upper surface, an annular protrusion on a lower surface, and a plurality of holes extending outwardly from the lower surface to the upper surface. The annular ridge has an outer diameter less than an outer diameter of the base portion and has an inner diameter greater than or equal to an outer diameter of the substrate. The annular protrusion has a diameter less than the inner diameter of the annular ridge and the outer diameter of the substrate. The holes are arranged along a first circle on the upper surface and along a second circle on the lower surface. The first circle has a first diameter that is less than the inner diameter of the annular ridge and the outer diameter of the substrate and greater than the diameter of the annular protrusion. The second circle has a second diameter that is less than the diameter of the annular protrusion.

In other features, a system comprises the pedestal, a heat shield arranged parallel to and below the lower surface of the base portion, and a gas source. The heat shield is connected to the annular protrusion. The heat shield, the lower surface, and the annular protrusion define a manifold that is in fluid communication with a gas inlet. The gas source supplies a purge gas to the gas inlet while a material is deposited from the showerhead on a showerhead-facing surface of the substrate. The purge gas flows through the manifold and the holes, flows radially outwards over the annular ridge, and prevents the material from depositing on a pedestal-facing surface of the substrate.

In another feature, the pedestal further comprises an electrostatic clamping system or a vacuum clamping system to clamp the substrate to the upper surface of the base portion.

In another feature, the annular ridge ascends vertically from the upper surface of the base portion at the inner diameter of the annular ridge, extends outwards at an angle relative to a vertical axis of the stem portion, extends radially outwards, and descends vertically to the upper surface of the base portion at the outer diameter of the annular ridge.

In another feature, the holes extend from the lower surface to the upper surface at an acute angle relative to a vertical axis of the stem portion.

In another feature, the pedestal further comprises an annular sealing band arranged on the upper surface of the base portion. An outer diameter of the annular sealing band is less than the first diameter of the first circle.

In another feature, the pedestal further comprises an actuator configured to move the pedestal vertically relative to the showerhead to adjust a gap between the substrate and the showerhead during processing.

In another feature, the system further comprises a controller to control flow of the purge gas through the gas inlet.

In another feature, the gas inlet is located at a bottom of the stem portion.

In other features, the system further comprises a ring arranged around the pedestal. The ring includes a cylindrical portion surrounding the base portion and having a first end aligned with an outer edge of the heat shield and a second end. The ring includes an annular portion extending radially inwards from the second end over the upper surface of the base portion to the outer diameter of the annular ridge. Upper surfaces of the annular ridge and the annular portion of the ring are coplanar.

In still other features, a pedestal assembly comprises a pedestal including a base plate having a first surface and a second surface opposite the first surface, and including a stem extending from the second surface of the base plate. A plurality of through holes extend from the first surface through the second surface of the base plate at a location radially outside of the stem. The pedestal includes a collar arranged around the stem and the plurality of through holes. The collar defines a first annular volume between an inner surface of the collar and an outer surface of the stem. An upper surface of the collar forms a surface-to-surface seal with the second surface of the base plate. The pedestal assembly comprises an annular heat shield having a first portion arranged below the second surface of the base plate and having a second portion extending from a radially inner end of the first portion. The second portion surrounds the collar and defines a second annular volume between an inner surface of the second portion of the annular heat shield and an outer surface of the collar.

In another feature, the first annular volume is separate from the second annular volume.

In another feature, one or more gases are suctioned out from under a substrate placed on the base plate via the plurality of through holes and the first annular volume to clamp the substrate to the base plate.

In another feature, a purge gas is injected into the second annular volume to egress around edges of a substrate placed on the base plate during processing.

In another feature, the purge gas prevents deposition on a pedestal-facing surface of the substrate.

In other features, the pedestal assembly further comprises an edge ring surrounding the base plate. A bottom surface of the edge ring forms a surface-to-surface seal with an upper surface of the first portion of the annular heat shield. The upper surface of the first portion of the annular heat shield, an inner side surface of the edge ring, and the second surface of the base plate define a manifold that is in fluid communication with the second annular volume. A purge gas is injected into the second annular volume to egress through a gap between the edge ring and the base plate.

In another feature, the purge gas prevents deposition on a pedestal-facing surface of a substrate arranged on the base plate.

In other features, a bottom end of the stem of the pedestal includes a flange extending radially outwardly. The pedestal assembly further comprises a pedestal support structure attached to the flange with an O-ring disposed between the flange and the pedestal support structure.

In another feature, the pedestal support structure includes a cylindrical body with a side wall, a vertical bore in the side wall defines a gas channel, and the gas channel fluidly communicates with the first annular volume and the plurality of through holes.

In another feature, the pedestal support structure includes a cylindrical body with a side wall, a bore in the side wall defines a gas channel, and the gas channel fluidly communicates with the second annular volume.

In other features, the pedestal support structure includes a cylindrical body defining an inner cavity and includes a second flange extending radially outwardly from an upper surface of the cylindrical body. The pedestal assembly further comprises one or more clamps connecting the flange at the bottom end of the stem to the second flange of the pedestal support structure.

In other features, the pedestal support structure includes a cylindrical body defining an inner cavity and includes a second flange extending radially outwardly from an upper surface of the cylindrical body. The pedestal assembly further comprises a clamp having an L-shaped cross-section. The second flange rests on a horizontal portion of the clamp forming a surface-to-surface seal therewith.

In another feature, an upper end of a vertical portion of the clamp includes a third flange extending radially outwardly and includes first and second vertical portions respectively extending from radially outer and inner ends on an upper surface of the third flange.

In other features, a bottom end of the collar forms a first surface-to-surface seal with the second vertical portion, and a bottom end of the second portion of the annular heat shield forms a second surface-to-surface seal with the first vertical portion.

In another feature, the first and second surface-to-surface seals prevent fluid communication between the first and second annular volumes.

In other features, the cylindrical body includes a vertical portion extending upwards from the second flange. A radially inner portion of the upper end of the vertical portion of the clamp forms a surface-to-surface seal with a radially outer surface of an upper end of the vertical portion of the cylindrical body.

In other features, the cylindrical body has a side wall having a first bore therein. The vertical portion of the clamp is spaced from the vertical portion of the cylindrical body extending upwards from the second flange defining a cavity that is in fluid communication with the first bore. The upper end of the vertical portion of the clamp includes a second bore that is in fluid communication with the cavity and the second annular volume.

In other features, the pedestal assembly further comprises a valve and a controller. The valve is configured to selectively connect the gas channel, the first annular volume, and the plurality of through holes to a vacuum pump. The controller is configured to selectively control the valve to remove one or more gases from under a substrate arranged on the base plate via the gas channel, the first annular volume, and the plurality of through holes to clamp the substrate to the base plate during processing of the substrate.

In other features, the pedestal assembly further comprises a valve and a controller. The valve is configured to selectively connect the gas channel and the second annular volume to a source of a purge gas. The controller is configured to selectively control the valve to supply the purge gas through the gas channel and the second annular volume during processing of a substrate arranged on the base plate to prevent deposition on a pedestal facing side of the substrate.

In other features, the pedestal assembly further comprises an annular seal band disposed on the first surface of the base plate along an outer diameter of the first surface. The pedestal assembly further comprises a plurality of projections extending upwards from the first surface of the base plate. The projections are distributed from a center of the first surface to an inner diameter of the annular seal band.

In another feature, a height of the projections decreases from the inner diameter of the annular seal band to the center of the first surface of the base plate.

In another feature, a height of the projections increases from the inner diameter of the annular seal band to the center of the first surface of the base plate.

In still other features, a pedestal assembly comprises a pedestal including a base plate and a stem extending from the base plate. The base plate is disc shaped and has an upper surface. The pedestal assembly comprises a plurality of projections extending upwards from the upper surface of the base plate and distributed from a center of the upper surface of the base plate to an outer diameter of the pedestal. The projections have a height tailored to tune a conductive heat transfer proximate to the projections.

In another feature, the projections have a profile defined by upper ends of the projections.

In another feature, the projections have equal height.

In another feature, a first set of the projections has a different height than a second set of the projections.

In another feature, a height of the projections decreases from the inner diameter of the annular seal band to the center of the upper surface of the base plate.

In another feature, a height of the projections increases from the inner diameter of the annular seal band to the center of the upper surface of the base plate.

In another feature, the projections are cylindrical.

In another feature, the pedestal assembly further comprises an electrostatic clamping system disposed in the pedestal to clamp a substrate to the upper surface of the base plate.

In another feature, the pedestal assembly further comprises a vacuum clamping system disposed in the pedestal to clamp a substrate to the upper surface of the base plate.

In another feature, a substrate is not clamped to the upper surface of the base plate.

In another feature, a height of the projections changes linearly from one radial edge to an opposite radial edge of the upper surface of the base plate.

In another feature, the upper surface of the base plate including the projections is concave.

In another feature, the upper surface of the base plate including the projections is convex.

In still other features, a pedestal assembly comprises a pedestal including a base plate and a stem extending from the base plate. The base plate is disc shaped and has an upper surface that is concave. The pedestal assembly comprises a plurality of projections extending upwards from the upper surface of the base plate and distributed from a center of the upper surface of the base plate to an outer diameter of the pedestal.

The projections have top ends that are concave.

In another feature, radii of curvature of the upper surface of the pedestal and the top ends of the projections are equal.

In another feature, radii of curvature of the upper surface of the pedestal and the top ends of the projections are different.

In another feature, a first radius of curvature of the upper surface of the pedestal is greater than a second radius of curvature of the top ends of the projections.

In another feature, a first radius of curvature of the upper surface of the pedestal is less than a second radius of curvature of the top ends of the projections.

In still other features, a pedestal assembly comprises a pedestal including a base plate and a stem extending from the base plate. The base plate is disc shaped and has an upper surface that is convex. The pedestal assembly comprises a plurality of projections extending upwards from the upper surface of the base plate and distributed from a center of the upper surface of the base plate to an outer diameter of the pedestal. The projections have top ends that are convex.

In another feature, radii of curvature of the upper surface of the pedestal and the top ends of the projections are equal.

In another feature, radii of curvature of the upper surface of the pedestal and the top ends of the projections are different.

In another feature, a first radius of curvature of the upper surface of the pedestal is greater than a second radius of curvature of the top ends of the projections.

In another feature, a first radius of curvature of the upper surface of the pedestal is less than a second radius of curvature of the top ends of the projections.

DETAILED DESCRIPTION

Backside deposition prevention while depositing materials (e.g., metal films) on substrates (e.g., semiconductor wafers) can be a critical performance metric. Modern deposition techniques such as atomic layer deposition (ALD) and plasma enhanced chemical vapor deposition (PECVD) have a relatively higher conformal performance. Therefore, it has become increasingly challenging to prevent deposition where it is not desired (e.g., on the backside of a substrate) while depositing materials on the front side of the substrate.

The present disclosure provides systems and methods to prevent backside deposition by using a combination of approaches. The approaches include clamping the substrate to a pedestal and/or supplying purge gases to an area where deposition is not desired. The clamping methods include electrostatic or vacuum clamping. In addition, various pedestal and edge ring designs are provided for supplying purge gases to the area where deposition is not desired. The use of clamping in conjunction with purging can further enhance the performance without affecting deposition of materials on the front side of the substrate.

Specifically, viscous flow of deposition chemistries to the backside of the substrate can be readily prevented by placing the substrate on a highly polished (i.e., smooth) surface on a pedestal (e.g., a sealing band). Placing the substrate on a highly polished surface allows only molecular flow to the backside of the substrate. Allowing only molecular flow to the backside of the substrate can be adequate in some applications to prevent the backside deposition to a desired level. By purging a bevel area of the substrate or the backside of the substrate, with gaps between the substrate and an edge ring that can sustain viscous flow, a reduction in concentration of deposition chemistries in the bevel area can be achieved. With enough viscous flow in a gap having a predetermined size, the concentration of these chemistries can be reduced in the bevel area to a level that does not sustain deposition on the backside of the substrate. Other approaches include using a deposition inhibitor, or using either inert chemistries or reactive chemistries that react with precursors before the precursors can adhere to the substrate surface.

The above approaches are most effective when the substrate is clamped to the pedestal surface with a substantial force (e.g., 50× the weight of the substrate). Clamping methods can include using a pressure differential (i.e., vacuum clamping) or electrostatic clamping (e.g., an electrostatic chuck or ESC). The clamping along the edge of the substrate can be made more effective by machining an upper surface of the pedestal to have a slight dish or dome like shape. That is, the upper surface of the pedestal can be machined to be slightly concave or convex. Due to the curved shaping, the edge portion of the pedestal is either slightly higher (in case of dish shape) or lower (in case of dome shape) than the center portion of the pedestal. The curved shaping significantly improves clamping along the edge of the substrate. The improved clamping along the edge of the substrate further prevents backside deposition on substrates.

The present disclosure is organized as follows. Initially, a substrate processing system comprising a processing chamber that can utilize a pedestal and an edge ring designed to prevent backside deposition is shown and described with reference toFIGS.1A and1B.FIG.1Ashows use of electrostatic clamping.FIG.1Bshows use of vacuum clamping. Subsequently, various designs of the pedestal and the edge rings are shown and described in detail with reference toFIGS.2-7C. A method for preventing backside deposition is shown and described with reference toFIG.8. Vacuum clamping is shown and described in detail with reference toFIGS.9A and9B. The curved shaping of the upper surface of a pedestal is shown and described with reference toFIGS.10A-10C. Various configurations in which projections (mesas) can be arranged on the upper surface of the pedestal are shown and described with reference toFIGS.11A-12E.

FIG.1Ashows an example of a substrate processing system100comprising a processing chamber102configured to process a substrate (e.g., using ALD). The processing chamber102comprises a substrate support (e.g., a pedestal)104. The pedestal104is made of a ceramic material to withstand relatively high process temperatures. For example, the process temperatures can be greater than 600 degrees Celsius. Examples of the pedestal104are shown in further detail inFIGS.2and7A-7C.

During processing, a substrate106is arranged on an upper surface of the pedestal104. The substrate106may be clamped to the upper surface of the pedestal104using electrostatic clamping employed by the pedestal104. For example, one or more clamping electrodes112-1,112-2(collectively the clamping electrodes112) may be disposed in the pedestal104. The clamping electrodes112clamp the substrate106to the upper surface of the pedestal104using an electrostatic force.

An edge ring108is arranged around the upper surface of the pedestal104and the substrate106. The edge ring108may include any of the edge rings shown inFIGS.3-6. The edge ring108is also made of a ceramic material that can withstand relatively high process temperatures, which can be greater than 600 degrees Celsius.

One or more heaters110(e.g., a heater array, zone heaters, etc.) are disposed in the pedestal104to heat the substrate106during processing. Additionally, while not shown, a cooling system comprising cooling channels through which a coolant can flow to cool the pedestal104may be disposed in the pedestal104. Additionally, while not shown, one or more temperature sensors are disposed in the pedestal104to sense the temperature of the pedestal104. While the clamping electrodes112are shown as being arranged above the heaters110, the clamping electrodes112and the heaters110may be arranged in the pedestal104in other ways.

Additionally, a fluid delivery system128supplies a coolant to a cooling system (e.g., comprising a plurality of cooling channels, not shown) in the pedestal104. The fluid system128generally will not flow the coolant through the pedestal104for relatively high temperature processes (e.g., process temperatures greater than 600 degrees Celsius). For some relatively low temperature processes (e.g., process temperatures less than 300 degrees Celsius) the pedestal104may use a liquid inside the pedestal104as a ballast to make up for lower thermal energy losses.

The processing chamber102further comprises a gas distribution device114such as a showerhead to introduce and distribute process gases into the processing chamber102. The gas distribution device (hereinafter showerhead)114may include a stem portion116including one end connected to a top surface of the processing chamber102. A base portion118of the showerhead114is generally cylindrical and extends radially outwardly from an opposite end of the stem portion116at a location that is spaced from the top surface of the processing chamber102.

A substrate-facing surface of the base portion118of the showerhead114comprises a ceramic faceplate120. The ceramic faceplate120comprises a plurality of outlets or features (e.g., slots or through holes) through which process gases flow into the processing chamber102. While not shown, the showerhead114also comprises heating and cooling plates that respectively include one or more heaters and cooling channels. Further, while not shown, one or more temperature sensors may be disposed in the showerhead114to sense the temperature of the showerhead114. The fluid delivery system128supplies a coolant to the cooling channels in the showerhead114.

An actuator122moves the pedestal104vertically relative to the showerhead114, which is stationary. By vertically moving the pedestal104relative to the showerhead114using the actuator122, a gap between the showerhead114and the pedestal104(and therefore a gap between the substrate106and the ceramic faceplate120of the showerhead114) can be varied. The gap can be varied dynamically during a process or between processes performed on the substrate106. During processing, the ceramic faceplate120of the showerhead114is closer to the pedestal104than shown.

A gas delivery system130comprises one or more gas sources132-1,132-2, . . . , and132-N (collectively gas sources132), where N is an integer greater than 1. The gas sources132are connected by valves134-1,134-2, . . . , and134-N (collectively valves134) and mass flow controllers136-1,136-2, . . . , and136-N (collectively mass flow controllers136) to a manifold139. An output of the manifold139is fed to the processing chamber102.

The gas sources132may supply process gases, cleaning gases, purge gases, inert gases, and so on to the processing chamber102. One of the gas sources132supplies a purge gas through a gas inlet (hereinafter the inlet)124at the bottom of the pedestal104. As shown and described below in detail with reference toFIGS.2-7C, the purge gas from the inlet124flows through a stem portion105of the pedestal104. In one example, the purge gas flows through a manifold under the pedestal104and a gap between the edge of the pedestal104and the edge ring108as shown and described below in detail with reference toFIGS.2-6. Alternatively, the purge gas flows via through holes in the pedestal104as shown and described below in detail with reference toFIGS.7A-7C. In either example, the purge gas prevents deposition on the backside of the substrate106.

A temperature controller150is connected to the heaters110and temperature sensors in the pedestal104, to the heaters and temperature sensors in the showerhead114, and to the fluid delivery system128. The temperature controller150controls power supplied to the heaters110and coolant flow through the cooling system in the pedestal104to control the temperature of the pedestal104and the substrate106. The temperature controller150also controls power supplied to the heaters in the showerhead114and coolant flow through the cooling channel in the showerhead114to control the temperature of the showerhead114.

A valve156is connected to an exhaust port of the processing chamber102and to the vacuum pump158. A vacuum pump158maintains sub-atmospheric pressure inside the processing chamber102during substrate processing. The valve156and the vacuum pump158are used to control pressure in the processing chamber102and to evacuate exhaust gases and reactants from the processing chamber102. A system controller160controls the components of the substrate processing system100.

FIG.1Bshows a substrate processing system101where a pedestal103employs vacuum clamping instead of electrostatic clamping. The substrate processing system101shown inFIG.1Bis identical to the substrate processing system100shown inFIG.1Aexcept for the following. In the substrate processing system101, the pedestal103uses vacuum clamping instead of electrostatic clamping. Accordingly, the clamping electrodes112are not used in the pedestal103. The pedestal103is shown and described in detail with reference toFIGS.9A-9B.

Briefly, the pedestal103includes an annular volume125in the stem portion105. The annular volume125is in fluid communication with a plurality of gas through holes in the upper surface of the pedestal103, which are shown and described in detail with reference toFIGS.9A-9B. The annular volume125is in fluid communication with the vacuum pump158through a valve162. The system controller160controls the valve162.

During processing, the vacuum pump158creates a vacuum under the substrate106by suctioning gases from under the substrate106through the plurality of through holes in the upper surface of the pedestal103. The vacuum pump158removes the gases from under the substrate106through the annular volume125and the valve162. The vacuum created by the vacuum pump158clamps the substrate106to the upper surface of the pedestal103.

The inlet124through which the purge gas is supplied to the pedestal103is shown and described in further detail with reference toFIGS.9A-9B. Briefly, the inlet124is also annular in shape and surrounds the annular volume125. The inlet124is not in fluid communication with the annular volume125. The inlet124is connected to the manifold139through a valve164. The system controller160controls the valve164. The purge gas flows through a gap between the edge of the pedestal103and the edge ring108. Alternatively, the purge gas flows via through holes in the pedestal103. The purge gas prevents deposition on the backside of the substrate106as described above with reference toFIG.1Aand as described in further detail below with reference toFIGS.3-6. These and other features of the vacuum clamping used in the pedestal103are described below in greater detail with reference toFIGS.9A-9B.

Below are various designs of the pedestal and the edge rings that can be arranged around the pedestal and the substrate in a processing chamber (e.g., the processing chamber102shown inFIGS.1A and1B). For illustrative purposes, only partial views of the pedestals are shown inFIGS.2,7A-7C, and9A. However, it is understood that the top surface of the pedestals on which the substrate is arranged during processing is generally circular in shape. Further, it is understood that the top surface of the pedestals additionally has other structural and geometric details as shown and described below. Also, for illustrative purposes, only partial views of the edge rings are shown inFIGS.3-6. However, it is understood that the edge rings are generally annular in shape. Further, it is understood that the edge rings additionally have other structural and geometric details as shown and described below.

FIG.2shows an example of a pedestal200according to the present disclosure. Any of the edge rings shown inFIGS.3-6can be used with the pedestal200to prevent backside deposition as described below. The pedestal200includes a base portion202and a stem portion204. In some examples, the base portion202is disc shaped, and the stem portion204is cylindrical. The stem portion204extends vertically downwards from a center of the base portion202. The stem portion204supports the base portion202. The pedestal200includes one or more features of the pedestal104(e.g., the inlet124, one or more heaters, the cooling system, one or more temperature sensors, etc.). The pedestal200can be used instead of the pedestal104in the subsystem processing system100.

The base portion202includes an annular recess206along an outer edge207of the base portion202. The annular recess206extends radially inwards from the outer edge207of the base portion202. An inner diameter (ID) of the annular recess206defines an outer diameter (OD) of an upper surface208of the base portion202. An OD of the annular recess206is equal to an OD of the base portion202.

A highly polished (i.e., smooth) annular seal band210is arranged on the upper surface208of the base portion202. For example, a surface roughness, which is expressed as roughness average (Ra), for the seal band210may be 2-8 micro-inches but with a specification limit of 16 micro-inches. An OD of the seal band210is equal to the OD of the upper surface208of the base portion202. The OD of the seal band210is equal to the ID of the annular recess206. A substrate212(shown inFIGS.3-6) is arranged on the upper surface208of the base portion202during processing. The substrate212rests on the seal band210and on multiple mesas or minute projections (shown and described below in detail with reference toFIGS.10A-10C). The mesas are distributed throughout the upper surface208of the base portion202. The mesas are surrounded by the seal band210. An OD of the substrate212is approximately equal to the OD of the seal band210. The substrate212covers the seal band210(as shown inFIGS.3-6).

FIG.3shows an edge ring300according to the present disclosure. The edge ring300is arranged around the base portion202of the pedestal200. The edge ring300includes a cylindrical portion302and an annular portion304. The cylindrical portion302extends vertically downwards from an OD of the annular portion304and surrounds the base portion202of the pedestal200. The annular portion304extends radially inwards perpendicularly from a top end303of the cylindrical portion302. The annular portion304extends horizontally over the annular recess206in the base portion202of the pedestal200. The annular portion304is parallel to the annular recess206.

A heat shield310is arranged below a bottom surface220of the base portion202of the pedestal200. The heat shield310extends from the stem portion204of the pedestal200radially outwards and parallel to the bottom surface220of the base portion202of the pedestal200. A bottom end305of the cylindrical portion302of the edge ring300rests on an upper surface312of the heat shield310at a distal end311of the heat shield310. A surface-to-surface seal is created at an interface between the upper surface312of the heat shield310and a bottom surface of the cylindrical portion302of the edge ring300.

In some examples, the surface-to-surface seal includes a flat-to-flat seal that is created when two flat surfaces are arranged in direct contact without joining the two surfaces using welding or using a separate seal such as an O-ring between the two surfaces. In other examples, the surface-to-surface seal includes complementary, non-planar surfaces. In other words, the abutment of the two surfaces forms the seal. In some examples, the upper surface312of the heat shield310and the bottom surface of the cylindrical portion302of the edge ring300are polished to a surface roughness (Ra) in a range from 3 to 20 micro-inches. In other examples, the surface roughness is in a range from 3 to 16 micro-inches. In other examples, the surface roughness is in a range from 3 to 8 micro-inches.

A manifold222is defined by the bottom surface220of the base portion202of the pedestal200and the upper surface312of the heat shield310. A gap320is defined by an inner vertical surface (or inner wall)322of the cylindrical portion302of the edge ring300and the outer edge207of the base portion202of the pedestal200. A gap330is defined by an inner (i.e., lower) horizontal surface332of the annular portion304of the edge ring300and the annular recess206in the base portion202of the pedestal200. The manifold222is in fluid communication with the inlet124(shown inFIGS.1Aand1B). For example, the inlet124may be connected to the manifold222by suitable piping within the stem portion204. Alternatively, the inlet124may be directly connected to the manifold222instead of being connected to the bottom of the stem portion204. The manifold222is in fluid communication with the gaps320and330.

A distal end307of the annular portion304of the edge ring300(i.e., an ID of the annular portion304of the edge ring300), which is opposite to the top end303of the cylindrical portion302of the edge ring300, is spaced apart from the OD of the upper surface208of the base portion202(i.e., from a top end211of the annular recess206) and from the OD of the substrate212. A gap308is defined between the distal end307of the annular portion304(i.e., the ID of the annular portion304) of the edge ring300and the OD of the upper surface208of the base portion202(i.e., the top end211of the annular recess206) and the OD of the substrate212. The gap308is in fluid communication with the gaps320,330and the manifold222.

A first portion of the inner (i.e., lower) horizontal surface332of the annular portion304of the edge ring300extends radially inwards from near the top end303of the cylindrical portion302and parallel to the annular recess206. Thereafter, the remainder of the inner (i.e., lower) horizontal surface332of the annular portion304slopes upwards towards the distal end307of the annular portion304of the edge ring300. That is, the remainder of the inner (i.e., lower) horizontal surface332of the annular portion304slopes upwards towards the ID of the annular portion304of the edge ring300at an obtuse angle.

A first portion of an outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300extends radially inwards from the top end303of the cylindrical portion302and parallel to the annular recess206. Thereafter, the remainder of the outer horizontal surface334of the annular portion304slopes downwards towards the distal end307of the annular portion304of the edge ring300. That is, the remainder of the outer horizontal surface334of the annular portion304slopes towards the ID of the annular portion304of the edge ring300at an obtuse angle.

Accordingly, the inner (i.e., lower) horizontal surface332and the outer (i.e., top) horizontal surface334of the annular portion304extend radially inwards from the top end303of the cylindrical portion302and parallel to the annular recess206for a distance. Thereafter, the remainder portions of the inner (i.e., lower) horizontal surface332and the outer (i.e., top) horizontal surface334of the annular portion304taper towards and converge at the distal end307(i.e., at the ID) of the annular portion304at an obtuse angle. The distal end307(i.e., the ID) of the annular portion304is rounded.

The outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300is not aligned with (i.e., is not in the same plane as) a top surface213of the substrate212. Rather, the outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300is parallel to the top surface213of the substrate212and lies in a plane that is slightly higher than a plane in which lies the top surface213of the substrate212.

During processing, the pedestal200, with the substrate212arranged on the upper surface208of the base portion202of the pedestal200, is moved closer to a showerhead (not shown). The showerhead is fixed above the substrate212and the pedestal200in a processing chamber (e.g., see the showerhead114in the processing chamber102shown inFIGS.1A and1B). A small gap exists between the showerhead and the outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300. For example, the gap between the edge ring300and the showerhead may be about 0.050″, and the gap between the top surface213of the substrate212and the faceplate of the showerhead may be about 0.150″. The showerhead deposits material (e.g., using ALD) on the top surface (i.e., the front side)213of the substrate212.

During deposition, a purge gas flows from the inlet124(shown inFIGS.1A and1B) through the manifold222and the gaps320,330,308. The purge gas flows over the outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300. The purge gas exits by flowing through a gap between the showerhead and the outer (i.e., top) horizontal surface334of the annular portion304of the edge ring300. The flow of the purge gas is shown by arrows336-1,336-2,336-3,336-4, and336-5(collectively the arrows336). The flow of the purge gas is controlled (e.g., by the system controller160shown inFIGS.1A and1B). The flow of the purge gas prevents deposition on a bottom surface (i.e., a backside)214of the substrate212.

Throughout the present disclosure, for the purposes of preventing backside deposition on substrates, the backside214of the substrate212is defined as an area of the substrate212beginning at a bottom edge of the bevel of the substrate212and extending to the center of the backside214of the substrate212. The process gases delivered to the top surface (i.e., the front side)213of the substrate212by the showerhead during deposition flow in the direction indicated by arrows338-1,338-2(collectively the arrows338). During deposition, the process gases flowing in the direction shown by the arrows338help push the purge gas to flow in the direction shown by the arrows336. The flow of the purge gas during deposition does not affect the deposition on the top surface (i.e., the front side)213of the substrate212.

To further prevent deposition from occurring on the backside214of the substrate212, the substrate212is clamped to the upper surface208of the pedestal200using electrostatic clamping as described with reference toFIG.1A. Alternatively, the substrate212is clamped to the upper surface208of the pedestal200using vacuum clamping shown and described below in detail with reference toFIGS.9A-9B. In either approach, the amount of clamping force exerted on the substrate212is controlled by the system controller160shown inFIGS.1A and1B.

To further enhance the clamping force on the substrate212, the upper surface208of the pedestal200may be machined to have either a slight dish or dome like shape. Accordingly, the OD of the upper surface208of the pedestal200may be slightly higher (if the upper surface208is dish shaped) or lower (if the upper surface208is dome shaped) than the center of the upper surface208of the pedestal200. The OD of the substrate212rests on the seal band210. The curved shaping of the upper surface208of the pedestal200enhances the clamping force with which the substrate212is clamped to the seal band210on the upper surface208of the pedestal200. The enhanced clamping force further prevents deposition from occurring on the backside214of the substrate212. The curved shaping of the upper surface208of the pedestal200is shown and described below in further detail with reference toFIGS.10A-10C.

FIG.4shows an edge ring350according to the present disclosure. The edge ring350differs from the edge ring300in only one respect. An outer (i.e., top) horizontal surface352of an annular portion354of the edge ring350extends radially inwards from the top end303of the cylindrical portion302and parallel to the annular recess206but does not slope downwards towards the distal end307of the annular portion354of the edge ring350(i.e., the ID of the annular portion354of the edge ring350) at an obtuse angle. Instead, the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350is flat and extends radially inwards along a straight line from the top end303of the cylindrical portion302and parallel to the annular recess206all the way to the distal end307of the annular portion354of the edge ring350(i.e., the ID of the annular portion354of the edge ring350). The outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350is aligned with (i.e., lies in the same plane as) the top surface213of the substrate212. Accordingly, the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350is not only parallel to the top surface213of the substrate212but is also level with the top surface213of the substrate212.

The flatness of the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350and the alignment of the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350with the top surface213of the substrate212help the purge gas to flow out of the gap between the showerhead and the edge ring350faster than in the edge ring300, which further prevents the deposition on the backside214of the substrate212and does not affect the deposition on the top surface (i.e., the front side)213of the substrate212. All other description of the edge ring300applies to the edge ring350and is therefore not repeated for brevity.

FIGS.5A-5Cshows an edge ring400according to the present disclosure. InFIG.5A, the edge ring400differs from the edge ring300in two respects. First, the edge ring400includes a plurality of radially extending holes402-1,402-2,403-3, and so on (collectively holes402) in an annular portion404of the edge ring400; and second, an outer (i.e., top) surface403of the annular portion404of the edge ring400extends radially inwards from the top end303of the cylindrical portion302sloping upwards for a distance and then slopes downwards towards the distal end307of the annular portion404of the edge ring400(i.e., towards the ID of the annular portion404of the edge ring400).

Accordingly, the outer (i.e., top) surface403of the annular portion404of the edge ring400is not parallel to the annular recess206. Instead, the outer (i.e., top) surface403of the annular portion404of the edge ring400includes two sloping portions that respectively slope downwards towards the ID and OD of the annular portion404of the edge ring400(i.e., towards both the distal end307of the annular portion404and the top end303of the cylindrical portion302). Accordingly, the outer (i.e., top) surface403of the annular portion404of the edge ring400is not only not aligned with (i.e., is not in the same plane as) the top surface213of the substrate212but is also not parallel to the top surface213of the substrate212.

The dual sloping feature of the outer (i.e., top) surface403of the annular portion404of the edge ring400and the holes402help the purge gas to flow out of the gap between the showerhead and the edge ring400faster than in the edge ring300, which further prevents the deposition on the backside214of the substrate212and does not affect the deposition on the top surface (i.e., the front side)213of the substrate212. All other description of the edge ring300applies to the edge ring400and is therefore not repeated for brevity.

Additional views of the holes402are shown inFIGS.5B and5C. InFIGS.5B and5C, each of the holes402begins at the distal end307of the annular portion404of the edge ring400(i.e., at the ID of the annular portion404of the edge ring400) and extends radially outwards towards the OD of the annular portion404of the edge ring400(i.e., towards the top end303of the cylindrical portion302of the edge ring400). Accordingly, the purge gas not only flows and exits by flowing over the outer (i.e., top) surface403of the annular portion404of the edge ring400, but additionally flows out through the holes402. The additional flow of purge gas through the holes402further prevents the deposition on the backside214of the substrate212and does not affect the deposition on the top surface (i.e., the front side)213of the substrate212. The volume and flow rate of the purge gas can be controlled (e.g., by the system controller160shown inFIGS.1A and1B) based on the dimensions and density of the holes402.

FIG.6shows the edge ring350and an additional second ring450arranged above and parallel to the annular portion354of the edge ring350. The second ring450is a flat and thin annular (i.e., disc shaped) structure arranged above and parallel to the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350. A width of the second ring450(i.e., a distance between an ID and OD of the second ring450) is about the same as a width of the annular portion354of the edge ring350(i.e., a distance between the ID of the annular portion354and the OD of the cylindrical portion302of the edge ring350). A thickness of the second ring450may be about the same as a thickness of the substrate212. The second ring450is arranged along a plane parallel to and slightly above the plane of the substrate212. The second ring450is also parallel to the annular recess206.

The second ring450is connected to (i.e., mounted on) the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350using posts454arranged at three or more locations on the outer (i.e., top) horizontal surface352of the annular portion354. The posts454may be located anywhere on the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350. The posts454may be preferably arranged closer to the OD of the annular portion354of the edge ring350so as to not obstruct an exhaust path of the purge gas. The purge gas exits through a gap452between a bottom of the second ring450and the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350.

During processing, the showerhead may be proximate to or may rest on top of the second ring450. The flatness of the second ring450and the outer (i.e., top) horizontal surface352of the annular portion354of the edge ring350helps the purge gas to flow out of the gap452between the second ring450and the edge ring350faster than in the edge ring300, which further prevents the deposition on the backside214of the substrate212and does not affect the deposition on the top surface (i.e., the front side)213of the substrate212. All other description of the edge ring300applies to the edge ring350and is therefore not repeated for brevity.

FIGS.7A-7Cshow a pedestal500that supplies a purge gas through a plurality of holes502-1,502-2,502-3, and so on (collectively holes502) in the pedestal500to prevent backside deposition on a substrate510according to the present disclosure. The pedestal500includes a base portion501and a stem portion503. The base portion501is disc shaped. The stem portion503is cylindrical. The stem portion503extends vertically downwards from a center of the base portion501. The stem portion503supports the base portion501. The pedestal500includes one or more features of the pedestal104(e.g., the inlet124, one or more heaters, the cooling system, one or more temperature sensors, etc.). The pedestal500can be used instead of the pedestal104in the subsystem processing system100.FIGS.7A and7Cshow a substrate510arranged on the pedestal500.FIG.7Bshows the pedestal500without the substrate510to illustrate additional features of the pedestal500.

The base portion501of the pedestal500includes an annular ridge504on a top surface506of the base portion501. The annular ridge504is located closer to an OD of the base portion501of the pedestal500. The annular ridge504surrounds the substrate510arranged on the top surface506of the base portion501of the pedestal500. An ID of the annular ridge504is about the same as (i.e., greater than or equal to) an OD of the substrate510. An OD of the annular ridge504is less than the OD of the base portion501of the pedestal500.

The annular ridge504ascends vertically from the top surface506of the base portion501at the ID of the annular ridge504, extends outwards (i.e., away from the center of the base portion501) at an angle relative to a vertical axis of the stem portion503, then extends radially outwards parallel to the top surface506of the base portion501, and then descends vertically to the top surface506of the base portion501at the OD of the annular ridge504.

The annular ridge504may be machined as an integral portion of the top surface506of the base portion501. Alternatively, the annular ridge504may be separate from the pedestal500, may be in the form a ring having the geometry described above, and may be attached to the top surface506of the base portion501.

The holes502are arranged along a first circle on the top surface506of the base portion501. The first circle has a smaller diameter than the ID of the annular ridge504. Accordingly, the annular ridge504surrounds the holes502. The holes502extend downwards through the base portion501of the pedestal500and through a bottom surface514of the base portion501. The holes502descend inwardly (i.e., towards the center of the pedestal500) from the top surface506to the bottom surface514of the base portion501at an angle relative to a vertical axis of the stem portion503of the pedestal500. For example, the angle may be 45 degrees. For example, the angle may be between 30 and 60 degrees. The holes502in the bottom surface514of the base portion501lie along a second circle having a smaller diameter than the first circle.

A highly polished (i.e., smooth) annular seal band512is arranged on the top surface506of the base portion501. An OD of the seal band512is less than the diameter of the first circle along which the holes502are arranged on the top surface506of the base portion501. Accordingly, the holes502surround the seal band512. An OD the substrate510is greater than the OD of the seal band512and the diameter of the first circle along which the holes502lie on the top surface506of the base portion501. A substantial portion of the substrate510radially extends beyond the seal band512and the holes502up to the ID of the annular ridge504.

An annular L-shaped ring520surrounds the OD of the annular ridge504and the OD of the base portion501of the pedestal. The ring520acts as a heat shield. The horizontal portion522of the ring520rests on the top surface506of the base portion501between the OD of the annular ridge504and the OD of the base portion501. A top surface523of the horizontal portion522of the ring520is level with (i.e., is in the same plane as) a top surface505of the annular ridge504.

A heat shield530is arranged below the bottom surface514of the base portion501of the pedestal500. The heat shield530extends from the stem portion503of the pedestal500radially outwards and parallel to the bottom surface514of the base portion501of the pedestal500. A distal end531of the heat shield530extends up to the OD of the base portion501of the pedestal500and aligns with a bottom end526of a vertical portion524of the ring520.

An annular protrusion536on the bottom surface514of the base portion501is connected to a top surface534of the heat shield530. The annular protrusion536surrounds the holes502in the bottom surface514of the base portion501. The annular protrusion536is adjacent to the holes502in the bottom surface514of the base portion501. The annular protrusion536has a greater diameter than the second circle along which the holes502lie in the bottom surface514of the base portion501. The diameter of the annular protrusion536is less than the diameter of the first circle along which the holes502lie in the top surface506of the base portion501.

A manifold532is defined by the bottom surface514of the base portion501of the pedestal500, the top surface534of the heat shield530, and the annular protrusion536. The manifold532is in fluid communication with the holes502and the inlet124(shown inFIGS.1A and1B). For example, the inlet124may be connected to the manifold532by suitable piping within the stem portion503. Alternatively, the inlet124may be directly connected to the manifold532instead of being connected to the bottom of the stem portion503.

During processing, the pedestal500, with the substrate510arranged on the top surface506of the base portion501of the pedestal500, is moved closer to a showerhead540, which is fixed above the substrate510and the pedestal500in a processing chamber (e.g., the processing chamber102shown inFIGS.1A and1B). A small gap exists between the showerhead540and the top surface505of the annular ridge504. For example, the gap between top surface505of the annular ridge504and the showerhead540may be about 0.050″, and the gap between the top surface513of the substrate510and the faceplate of the showerhead540may be about 0.150″. The showerhead deposits material (e.g., using ALD) on a top surface (i.e., the front side)513of the substrate510.

During deposition, a purge gas flows from the inlet124(shown inFIGS.1A and1B) through the manifold532and the holes502onto a portion of a bottom surface (i.e., a backside)515of the substrate510that is between the OD of the substrate510and the first circle along which lie the holes502in the top surface506of the base portion501. The purge gas exits by flowing over the annular ridge504(i.e., through a gap between the showerhead540and the top surface534of the annular ridge504) and over the top surface523of the horizontal portion522of the ring520. The process gases from the showerhead540also exit by flowing over the annular ridge504(i.e., through a gap between the showerhead540and the top surface534of the annular ridge504) and over the top surface523of the horizontal portion522of the ring520. The flow of the purge gas through the holes502onto the backside515of the substrate510towards the OD of the substrate510prevents deposition on the bottom surface (i.e., a backside)515of the substrate510. Again, for the purposes of preventing backside deposition on substrates, the backside515of the substrate510is defined as an area of the substrate510beginning at a bottom edge of the bevel of the substrate510and extending to the center of the backside515of the substrate510.

The volume and flow rate of the purge gas can be controlled (e.g., by the system controller160shown inFIGS.1A and1B) based on the dimensions and density of the holes502. The flow of the purge gas through the holes502during deposition does not affect the deposition of material from the showerhead540on the top surface (i.e., the front side)513of the substrate510. To further prevent deposition from occurring on the backside515of the substrate510, the substrate510is clamped to the top surface506of the pedestal500using either electrostatic clamping or vacuum clamping as described with reference toFIGS.1A and1B.

FIG.8shows a method600for preventing backside deposition on substrates according to the present disclosure. A controller of a substrate processing system (e.g., element160shown inFIGS.1A and1B) may perform some of the steps of the method600. In the method600, at602, a substrate is placed on a pedestal (e.g., element200shown inFIG.2or element500shown inFIG.7A). At604, the pedestal is moved closer to a showerhead. At606, the method600determines whether to being the processing (e.g., deposition) of the substrate.

At608, the method600begins processing the substrate by depositing material (e.g., using ALD) on the front side of the substrate from the showerhead. At610, while the processing (e.g., deposition) is ongoing, the method600supplies a purge gas around the edge of the substrate (e.g., using the pedestal200ofFIG.2and any of the edge rings shown inFIGS.3-6). Alternatively, the method600supplies a purge gas from under the substrate towards the edge of the substrate (e.g., using the pedestal shown inFIGS.7A-7C). The purge gas prevents deposition on the backside of the substrate (i.e., throughout the area of the substrate from a bottom edge of the bevel to the center of the bottom surface of the substrate).

FIGS.9A and9Bshow an example of a pedestal700employing vacuum clamping according to the present disclosure. Any of the edge rings shown inFIGS.3-6can be used with the pedestal700to prevent backside deposition as described above. InFIG.9A, the pedestal700includes a base portion702and a stem portion704. In some examples, the base portion702is disc shaped, and the stem portion704is cylindrical. The stem portion704extends vertically downwards from a center of the base portion702. The stem portion704supports the base portion702. The stem portion704provides vacuum clamping and purge gas flow as described below in detail with reference toFIG.9B. The pedestal700includes one or more features of the pedestal103ofFIG.1B(e.g., the inlet124, one or more heaters, the cooling system, one or more temperature sensors, etc.). The pedestal700can be used instead of the pedestal103in the subsystem processing system101inFIG.1B.

The base portion702includes an annular recess706along an outer edge707of the base portion702. The annular recess706extends radially inwards from the outer edge707of the base portion702. An inner diameter (ID) of the annular recess706defines an outer diameter (OD) of an upper surface708of the base portion702. An OD of the annular recess706is equal to an OD of the base portion702.

A highly polished (i.e., smooth) annular seal band710(seeFIG.9A) is arranged on the upper surface708of the base portion702. The seal band710is similar to the seal band210shown inFIG.2. For example, a surface roughness, which is expressed as roughness average (Ra), for the seal band710may be 2-8 micro-inches but with a specification limit of 16 micro-inches. An OD of the seal band710is equal to the OD of the upper surface708of the base portion702. The OD of the seal band710is equal to the ID of the annular recess706.

A substrate212(shown inFIGS.3-6) is arranged on the upper surface708of the base portion702during processing. The substrate212rests on the seal band710and on multiple mesas or minute projections (shown and described below in detail with reference toFIGS.10A-10C). The mesas are distributed throughout the upper surface708of the base portion702. The mesas are surrounded by the seal band710. An OD of the substrate212is approximately equal to the OD of the seal band710. The substrate212covers the seal band710(as shown with the seal band210inFIGS.3-6).

For example only, the edge ring300is arranged around the base portion702of the pedestal700. The edge ring300is already described above in detail with reference toFIG.3. The description of the edge ring300is therefore omitted for brevity. Alternatively, any of the edge rings shown inFIGS.4-6can be used with the pedestal700instead of the edge ring300. The vacuum clamping is now described in detail.

FIG.9Bshows the stem portion704in further detail. The stem portion704provides vacuum clamping and purge gas flow as follows. The following description includes various instances of forming a surface-to-surface seal. The method of forming a surface-to-surface seal is already described above in detail with reference toFIG.3and is therefore omitted for brevity.

The stem portion704includes a support structure750of the pedestal700. The support structure750includes a first cylindrical portion752and a second cylindrical portion744. An upper and radially outer end of the first cylindrical portion752includes a flange742. The flange742extends radially outwards from the upper and radially outer end of the first cylindrical portion752. An upper and radially inner end of the first cylindrical portion752includes a slot740. The second cylindrical portion744extends vertically upwards from an upper and radially outer end of the flange742. The second cylindrical portion744has a greater diameter than the first cylindrical portion752.

The bottom of the stem portion704of the pedestal710is connected to the support structure750using one or more clamps. In some examples, the one or more clamps include clamping rings with an annular or split annular shape. A first clamp850is connected by one or more fasteners852-1,852-2, and so on (collectively the fasteners852) through a second clamp854to an inner surface of the support structure750. As used herein, the term clamp refers to an annular or arcuate portion that is fastened to another component to hold one or more components together.

The first clamp850is spaced from a side wall720(described below in detail) of the stem portion704. An inner surface of the first clamp850and an outer surface of the side wall720of the stem portion704define a cavity853. The second clamp854includes a plurality of through holes855-1,855-2, and so on (collectively the through holes855). The cavity853and the through holes855are in fluid communication with each other. As described below in detail, the cavity853and the through holes855provide a passage for gases suctioned by the vacuum pump158from under a substrate mounted on the upper surface708of the pedestal700.

A third clamp770is attached to a bottom facing surface of the flange742of the first cylindrical portion752of the support structure750. In some examples, the third clamp770has an “L”-shaped cross-section and includes an upwardly projecting portion774and a radially inwardly projecting portion772. The third clamp770surrounds an upper portion of the support structure750.

A first end of the radially inwardly projecting portion772extends radially inwards from a lower end of the upwardly projecting portion774. A second end of the radially inwardly projecting portion772forms a surface-to-surface seal with an outer wall775of the first cylindrical portion752of the support structure750. A lower end of the flange742rests on and forms a surface-to-surface seal with an upper surface776of the radially inwardly projecting portion772.

The upwardly projecting portion774extends vertically upwards from a radially outer end (i.e., the first end) of the radially inwardly projecting portion772. An inner surface of the upwardly projecting portion774is spaced from an outer surface of the second cylindrical portion744of the support structure750. The inner surface of the upwardly projecting portion774and the outer surface of the second cylindrical portion744define a cavity780.

An upper end of the upwardly projecting portion774includes a flange779. The flange779extends radially outwards from the upper end of the upwardly projecting portion774. A first vertical portion778extends vertically upwards from a radially outer end of the flange776. A second vertical portion782extends vertically upwards from near a radially inner end of the flange776. The first and second vertical portions778and782are spaced apart from each other and define a cavity784. The first and second vertical portions778are of approximately equal height. The flange779and the first and second vertical portions778and782form a U-shaped (or a fork-shaped) structure781.

A radially inner portion790of the upper end of the upwardly projecting portion774projects radially inwards and forms a surface-to-surface seal with the outer surface of the second cylindrical portion744of the support structure750. The radially inner portion790is located radially opposite to the flange779. Specifically, the radially inner portion790also extends radially inwards from a lower and radially inner portion of the second vertical portion782.

A bore788extends at an angle from a radially inner and upper end of the upwardly projecting portion774to an upper surface of the flange779. The bore788is in fluid communication with the cavity784defined by the first and second vertical portions778and782. The bore788is also in fluid communication with the cavity780defined by the inner surface of the upwardly projecting portion774and the outer surface of the second cylindrical portion744. The bore788and the cavities784,780provide a passage for the purge gas as described below.

The stem portion704includes the side wall720. The side wall720extends vertically downwards from a center region715of a bottom surface716of the base portion702as shown inFIG.9A. A flange726is located at a lower end of the side wall720. The flange726extends radially outwardly from the side wall720. A lower end of the flange726is arranged in the slot740in the support structure750. An O-ring748arranged in the slot740under the lower end of the flange726to form a seal. The side wall720defines an inner cavity724of the stem portion704. Connections (not shown) to electrical components (e.g., heaters, heat sensors, etc.) located in the base portion702are provided through the inner cavity724.

A collar730is spaced from and surrounds the side wall720of the stem portion704of the pedestal700. The collar730and the side wall720define an annular volume725between an inner surface of the collar730and an outer surface of the side wall720of the stem portion704of the pedestal700. The collar730includes flanges734and736extending radially outwardly from the lower and upper ends thereof, respectively. A radially outer surface of the flange734forms a surface-to-surface seal with a radially inner surface of the second vertical portion782of the U-shaped structure781. An upper surface of the flange736forms a surface-to-surface seal with the bottom surface716of the base portion702. The annular volume725is fluid communication with the cavity853between the first clamp850and the side wall720and with the through holes855in the second clamp854.

The upper surface708of the base portion702of the pedestal includes a plurality of through holes712-1,712-2,712-3, and so on (collectively the through holes712). The through holes712extend vertically downwards from the upper surface708through the bottom surface716of the base portion702. The through holes712are arranged along a circle. The diameter of the circle is greater than an OD of the side wall720of the stem portion704. The diameter of the circle is less than an ID of the collar730. The through holes712are in fluid communication with the annular volume725between the side wall720and the collar730. The through holes712are also in fluid communication with the cavity853between the first clamp850and the side wall720and with the through holes855in the second clamp854. As explained below, the through holes712, the annular volume725, the cavity853, and the through holes855provide a passage for gases to be suctioned out and to form vacuum under a substrate placed on the base portion702of the pedestal700.

The first cylindrical portion752of the support structure750includes a bore800. The bore800is in fluid communication with the annular volume725between the side wall720and the collar730. The bore800is in fluid communication with the valve162(seeFIG.1B). During processing, a substrate (e.g., the substrate212shown inFIG.3) is placed on the upper surface708of the pedestal700. The system controller160activates the valve162. The vacuum pump158creates vacuum under the substrate212by removing gases from under the substrate212via the through holes712, the annular volume725, the cavity853, the through holes855, the bore800, and the valve162. For example, the flow of gases is indicated by downward pointing arrows802-1,802-2, and802-3(collectively the arrows802). Due to the vacuum, the substrate212is clamped to the upper surface708of the pedestal700.

A heat shield810shown inFIG.9Ais similar to the heat shield310shown inFIGS.3-6. The heat shield810is arranged a predetermined distance below the bottom surface716of the base portion702of the pedestal700. The heat shield810is annular. The heat shield810includes a central opening wide enough to receive the collar730and the stem portion704of the pedestal700. The heat shield810extends from an upper end of the stem portion704of the pedestal700radially outwards and parallel to the bottom surface716of the base portion702of the pedestal700. The bottom end305of the cylindrical portion302of the edge ring300rests on an upper surface812of the heat shield810at a distal end811of the heat shield810. A surface-to-surface seal is created (as explained above in detail with reference toFIG.3) at an interface between the upper surface812of the heat shield810and a bottom surface of the cylindrical portion302of the edge ring300.

A manifold822is defined by the bottom surface716of the base portion702of the pedestal700and the upper surface812of the heat shield810. A gap820is defined by an inner vertical surface (or inner wall)322of the cylindrical portion302of the edge ring300and the outer edge707of the base portion702of the pedestal700. A gap830is defined by an inner (i.e., lower) horizontal surface332of the annular portion304of the edge ring300and the annular recess706in the base portion702of the pedestal700. The gaps820and830are in fluid communication with the manifold822. Additional details of the edge ring300are described above with reference toFIG.3and are therefore omitted for brevity.

The heat shield810includes a vertical portion880. The vertical portion880extends vertically downwards from a center region of the heat shield810. The vertical portion880is spaced from and surrounds the collar730. A distal end of the vertical portion880includes a flange882. The flange882extends radially outwards from the distal end of the vertical portion880. The radially outer surface of the flange882forms a surface-to-surface seal with a radially inner surface of the first vertical portion778of the U-shaped structure781. An inner surface of the vertical portion880and an outer surface of the collar730define a second annular volume884. The second annular volume884is separate from the annular volume725. The second annular volume884is not fluidly connected to the annular volume725. The second annular volume is in fluid communication with the cavity784, the bore788, and the cavity780. The manifold822is in fluid communication with the second annular volume884.

The first cylindrical portion752of the support structure750includes a second bore886. The bore886extends vertically upwards through the first cylindrical portion752and then radially through the flange742. The bore886is in fluid communication with the cavity780, the bore788, the cavity784, the second annular volume884, and the manifold722. The bore886is in fluid communication with the inlet124and valve164(seeFIG.1B).

During processing, a substrate (e.g., the substrate212shown inFIG.3) is arranged on the upper surface708of the pedestal700. The system controller160activates the valve164. The purge gas flows though the valve164, the inlet124, the bore886, the cavity780, the bore788, the cavity784, the second annular volume884, the manifold722, and the gaps820and830between the edge ring300and the base portion702of the pedestal700. For example, the flow of the purge gas is indicated by upward pointing arrows890-1,890-2, and890-3(collectively the arrows890). The purge gas prevents deposition on the backside of the substrate212.

As described above, the design of the stem portion704of the pedestal700provides separate (i.e., independent) passages for the vacuum clamping and the purge gas. The passages are not in fluid communication with each other. Gases flow though the passages in opposite directions as described above. The passages for the vacuum clamping and the purge gas provided by the stem portion704can also be used with the pedestal500shown inFIGS.7A-7C.

FIGS.10A-10Cshow an example of the mesas provided on the upper portion708of the pedestal700.FIG.10Ashows a plan view of the base portion702of the pedestal700.FIG.10Bshows a cross-section of the base portion702.FIG.10Cshows the mesas in detail. To focus on the mesas, all other features of the base portion702(e.g., the through holes712) are omitted. The mesas can also be similarly employed in the pedestals200and500shown and described above with reference toFIGS.2-7C.

FIG.10Ashows mesas900-1,900-2, and so on (collectively the mesas900). The mesas900are minute projections (seeFIG.10C). For example only, the mesas900can be cylindrical in shape. The mesas900can have any other shape. The mesas900are surrounded by the seal band710disposed along the OD of the upper surface708of the base portion702of the pedestal700. The mesas900populate the upper surface708of the base portion702of the pedestal700. The mesas900are distributed from the center of upper surface708of the base portion702to the ID of the seal band710. Alternatively, the mesas900are distributed from the center of upper surface708of the base portion702to the OD of the upper surface708of the base portion702of the pedestal700.

The mesas900can be machined to have varying heights. For example, the mesas900can be machined to provide a convex or a concave shape to the upper portion708of the pedestal700. For example only, for a pedestal designed to process a13″ substrate, the mesas900can be machined to provide a curvature of a sphere having a diameter of 50 feet.FIG.10Bshows an example of a concave shape provided by the mesas900to the upper portion708of the pedestal700. The example shown is not to scale. The example shown in exaggerated for illustrative purposes. The example shows that a peripheral region904of the upper portion708of the pedestal700lies in a higher plane than a center region902of the upper portion708of the pedestal700. In the example shown, the height of the mesas900decreases from the peripheral region904of the upper portion708of the pedestal700to the center region902of the upper portion708of the pedestal700.

Conversely, the mesas900can provide a convex shape to the upper portion708of the pedestal700. In this example, the peripheral region904of the upper portion708of the pedestal700will lie in a lower plane than the center region902of the upper portion708of the pedestal700. In this example, the height of the mesas900will increase from the peripheral region904of the upper portion708of the pedestal700to the center region902of the upper portion708of the pedestal700.

In another example, the mesas900can also be machined to provide a flat surface on which a substrate can be placed during processing. In this example, all of the mesas900will be of equal (uniform) height. Alternatively, the mesas900can be machined to provide a tilted surface (from one radial edge to an opposite radial edge of the upper surface708of the base portion702) on which a substrate can be placed during processing. In this example, the height of the mesas900will taper (i.e., increase or decrease linearly) from one radial edge to an opposite radial edge of the upper surface708of the base portion702.

In other examples, the mesas900can be machined to have a height tailored to tune a conductive heat transfer proximate to the mesas900. The conductive heat transfer occurs between the upper surface708of the pedestal700and the substrate212through the mesas900. For example, the mesas900of equal height can ensure consistent conductive heat transfer in the vicinity of the mesas900. Alternatively, the mesas900can have a predetermined profile defined by the upper ends of the mesas900. In some examples, thermal non-uniformities (e.g., caused by nonlinearities of the heater110shown inFIG.1A) can be corrected by varying the height of the mesas900.

A substrate212(shown inFIGS.3-6) is arranged on the upper surface708of the base portion702of the pedestal700during processing. The substrate212rests on the seal band710and on the mesas900. The OD of the substrate212is approximately equal to the OD of the seal band710. The substrate212covers the seal band710(e.g., as shown inFIGS.3-6). The curved shape provided by the mesas900to the upper portion708of the pedestal700improves the clamping force with which the substrate212is clamped to the pedestal700during processing. The mesas900improve both electrostatic and vacuum clamping of the substrate212to the upper surface708of the pedestal700. In some examples, the substrate212may not be clamped to the upper portion708of the pedestal700.

FIGS.11A-12Eshow various configurations in which the mesas900can be arranged on the upper surface708of the pedestal700. Specifically, the configurations include various combinations of concave (cup shaped) and convex (dome shaped) surfaces formed by the mesas900and the upper surface708of the pedestal700on which a substrate is arranged during processing. Briefly,FIG.11Ashows an arrangement of the mesas900on the upper surface708of the pedestal700that provide a flat surface on which the substrate is arranged during processing.FIGS.11B-11Fshow various arrangements of the mesas900and the upper surface708of the pedestal700that include a concave upper surface708and/or a concave surface formed by the mesas900on which the substrate is arranged during processing.FIGS.12A-12Eshow various arrangements of the mesas900and the upper surface708of the pedestal700that include a convex upper surface708and/or a convex surface formed by the mesas900on which the substrate is arranged during processing. These configurations are now described in detail.

InFIG.11A, the upper surface708of the pedestal700is flat. That is, the upper surface708of the pedestal700is parallel to a plane of a substrate (e.g., the substrate212shown inFIGS.3-6) that is arranged on the pedestal700during processing. For example, the upper surface708of the pedestal700has a roughness in the range of about 1 Ra to 64 Ra (Micro-inch). The mesas900are arranged on the upper surface708of the pedestal700such that the mesas900extend vertically upwards from the upper surface708of the pedestal700. The mesas900are of equal height (or length). The top ends of the mesas900are flat and lie in a plane parallel to the plane of the upper surface708of the pedestal700, which is parallel to the plane in which the substrate lies when arranged on the mesas900during processing.

InFIG.11B, the upper surface708of the pedestal700is concave. The mesas900are arranged on the upper surface708of the pedestal700such that the mesas900extend vertically upwards from the upper surface708of the pedestal700. The top ends of the mesas900are flat. A substrate is placed on the top ends of the mesas900during processing. The mesas900are of different height (or length). However, the top ends of the mesas900are aligned with each other and lie in a plane parallel to the plane in which the substrate lies when arranged on the mesas900during processing. Thus, while the upper surface708of the pedestal700is concave, the top ends of the mesas900provide a flat surface on which the substrate lies during processing. Due to the concave shape of the upper surface708of the pedestal700and since the top ends of the mesas900lie in a single plane, the height of the mesas900and consequently the distance between the substrate and the concave upper surface708of the pedestal700varies (decreases) from the center to the periphery of the concave upper surface708of the pedestal700.

InFIG.11C, the upper surface708of the pedestal700is flat as inFIG.11A. The mesas900are arranged on the upper surface708of the pedestal700such that the mesas900extend vertically upwards from the upper surface708of the pedestal700. The mesas900are of different lengths (i.e., height). The top ends of the mesas900are not aligned with each other and do not lie in a single plane parallel to the plane of the upper surface708of the pedestal700. Instead, the top ends of the mesas900are concave and form a concave surface on which a cupped substrate can be placed during processing. Since the top ends of the mesas900form a concave surface, the distance between the substrate and the upper surface708of the pedestal700varies (increases) from the center to the periphery of the upper surface708of the pedestal700.

FIGS.11D-11Fshow different configurations of a concave upper surface708of the pedestal700and a concave surface formed by the top ends of the mesas900. InFIGS.11D-11F, R1denotes a radius of the concave upper surface708of the pedestal700, and R2denotes a radius of the concave surface formed by the concave top ends of the mesas900.

InFIG.11D, R1=R2. The mesas900are of equal length (i.e., height). The top ends of the mesas900are concave. A cupped substrate is placed on the concave top ends of the mesas900during processing. Since the mesas900are of equal length and R1=R2, the distance between the concave upper surface708of the pedestal700and the cupped substrate is fixed (constant) from the center to the periphery of the concave upper surface708of the pedestal700. That is, the gap between the cupped substrate and the concave upper surface708of the pedestal700is fixed (constant) from the center to the periphery of the concave upper surface708of the pedestal700.

InFIG.11E, R2<R1. The height (i.e., length) of the mesas900varies (increases) from the center to the periphery of the concave upper surface708of the pedestal700. The top ends of the mesas900are concave. A cupped substrate is placed on the concave top ends of the mesas900during processing. Since the height of the mesas900increases from the center to the periphery of the concave upper surface708of the pedestal700and R2<R1, the distance between the concave upper surface708of the pedestal700and the cupped substrate varies (increases) from the center to the periphery of the concave upper surface708of the pedestal700. That is, the gap between the cupped substrate and the concave upper surface708of the pedestal700varies (increases) from the center to the periphery of the concave upper surface708of the pedestal700.

InFIG.11F, R2>R1. The height (i.e., length) of the mesas900varies (decreases) from the center to the periphery of the concave upper surface708of the pedestal700. The top ends of the mesas900are concave. A cupped substrate is placed on the concave top ends of the mesas900during processing. Since the height of the mesas900decreases from the center to the periphery of the concave upper surface708of the pedestal700and R2>R1, the distance between the concave upper surface708of the pedestal700and the cupped substrate varies (decreases) from the center to the periphery of the concave upper surface708of the pedestal700. That is, the gap between the cupped substrate and the concave upper surface708of the pedestal700varies (decreases) from the center to the periphery of the concave upper surface708of the pedestal700.

These configurations provide various advantages. Below are some non-limiting examples of the advantages. For example, some of these configurations improve the clamping of the substrate to the pedestal700. Cupping the top surfaces of the mesas900(i.e., by making the top surfaces of the mesas900concave) allows a cupped substrate to sit lower (i.e., be closer to the upper surface708of the pedestal700). In some of the configurations (e.g., inFIGS.11D and11F), cupping the top surfaces of the mesas900can result in a relatively small gap between the cupped substrate and the upper surface708of the pedestal700at the edge of the pedestal700, which allows creating an improved pressure gradient in the vacuum clamping system used to clamp the cupped substrate to the pedestal700. Clamping can be most effective when R1=R2(FIG.11D).

Additionally, the configuration with R1=R2also provides uniform heat transfer from the pedestal700to the substrate as a function of radius. The configuration with R2<R1(FIG.11E) can help improve clamping, and any issues with thermal uniformity (i.e., uniform heat transfer from the pedestal700to the substrate as a function of radius) can be corrected or improved by the varying the gap between the substrate and the upper surface708of the pedestal700. The top to bottom height of a mesa900defines the localized gap. The gap between the substrate and the upper surface708of the pedestal700can be varied by varying the height of the mesas900while maintaining R2<R1. The configuration shown inFIG.11Bmay not help with clamping but can be useful in correcting/improving thermal uniformity. Many other advantages are contemplated.

FIGS.12A-12Dshow additional configurations in which the mesas900can be arranged on the upper surface708of the pedestal700. InFIG.12A, the upper surface708of the pedestal700is convex. The mesas900are arranged on the upper surface708of the pedestal700such that the mesas900extend vertically upwards from the upper surface708of the pedestal700. The top ends of the mesas900are flat. A substrate is placed on the top ends of the mesas900during processing. The mesas900are of different lengths. However, the top ends of the mesas900are aligned with each other and lie in a plane parallel to the plane of the upper surface708of the pedestal700, which is also parallel to the plane in which the substrate lies on the mesas900. Thus, while the upper surface708of the pedestal700is convex, the top ends of the mesas900provide a flat surface on which the substrate lies. Due to the convex shape of the upper surface708of the pedestal700and since the top ends of the mesas900lie in a single plane, the height of the mesas900and consequently the distance between the substrate and the convex upper surface708of the pedestal700varies (increases) from the center to the periphery of the convex upper surface708of the pedestal700.

InFIG.12B, the upper surface708of the pedestal700is flat as inFIG.11A. The mesas900are arranged on the upper surface708of the pedestal700such that the mesas900extend vertically upwards from the upper surface708of the pedestal700. The mesas900are of different lengths (i.e., height). The top ends of the mesas900are not aligned with each other and do not lie in a single plane parallel to the plane of the upper surface708of the pedestal700. Instead, the top ends of the mesas900form a convex surface or a dome shape on which a domed substrate can be placed during processing. The bottom ends of the mesas900are flat. Since the top ends of the mesas900form a convex surface, the distance between the substrate and the upper surface708of the pedestal700varies (decreases) from the center to the periphery of the upper surface708of the pedestal700.

FIGS.12C-12Eshow different configurations of a convex shape of the upper surface708of the pedestal700and a convex surface formed by the top ends of the mesas900. InFIGS.12C-12E, R1denotes a radius of the convex upper surface708of the pedestal700, and R2denotes a radius of the convex surface formed by the convex top ends of the mesas900.

InFIG.12C, R1=R2. The mesas900are of equal length (i.e., height). The top ends of the mesas900are convex. A domed substrate is placed on the convex top ends of the mesas900during processing. Since the mesas900are of equal length and R1=R2, the distance between the convex upper surface708of the pedestal700and the domed substrate is fixed (constant) from the center to the periphery of the convex upper surface708of the pedestal700. That is, the gap between the domed substrate and the convex upper surface708of the pedestal700is fixed (constant) from the center to the periphery of the convex upper surface708of the pedestal700.

InFIG.12D, R2<R1. The height (length) of the mesas900varies (decreases) from the center to the periphery of the convex upper surface708of the pedestal700. The top ends of the mesas900are convex. A domed substrate is placed on the convex top ends of the mesas900during processing. Since the height of the mesas900decreases from the center to the periphery of the convex upper surface708of the pedestal700and R2<R1, the distance between the convex upper surface708of the pedestal700and the domed substrate varies (decreases) from the center to the periphery of the convex upper surface708of the pedestal700. That is, the gap between the domed substrate and the convex upper surface708of the pedestal700varies (decreases) from the center to the periphery of the convex upper surface708of the pedestal700.

InFIG.12E, R2>R1. The height (length) of the mesas900varies (increases) from the center to the periphery of the convex upper surface708of the pedestal700. The top ends of the mesas900are convex. A domed substrate is placed on the convex top ends of the mesas900during processing. Since the height of the mesas900increases from the center to the periphery of the convex upper surface708of the pedestal700and R2>R1, the distance between the convex upper surface708of the pedestal700and the domed substrate varies (increases) from the center to the periphery of the convex upper surface708of the pedestal700. That is, the gap between the domed substrate and the convex upper surface708of the pedestal700varies (increases) from the center to the periphery of the convex upper surface708of the pedestal700.

These convex configurations provide advantages similar to those mentioned above for the concave configurations except that the thermal uniformity is reversed (i.e., there is an inversion in thermal uniformity in the convex configurations relative to the concave configurations). The domed wafers are inherently easy to clamp because they naturally make a good edge seal. However, the convex configurations can impact the thermal uniformity as follows. In general, areas of a substrate with smaller gaps between the substrate and the upper surface708of the pedestal700can be hotter than areas of the substrate with larger gaps between the substrate and the upper surface708of the pedestal700. In configurations with a varying gap between the substrate and the upper surface708of the pedestal700, the thermal uniformity can correspondingly vary proportional to the varying gap. Many additional advantages are contemplated.

It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems.

The controller, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system.

Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software).

Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, dielectric, insulator, surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process.

In some examples, a remote computer (e.g., a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control.

Thus as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.