Pedestal including seal

Abstract

A pedestal assembly for a substrate processing system includes a pedestal plate having a plurality of gas through-holes and a rod extending downwardly from the pedestal plate. The plurality of gas through-holes extend from a first surface of the pedestal plate to a second surface of the pedestal plate at radially outward locations on the rod. A collar is disposed around the rod of the pedestal, and openings of the plurality of gas through-holes are located on the second surface of the pedestal. The collar defines a ring-shaped volume between the collar and the rod of the pedestal. An upward-facing surface of the collar forms a surface seal with the second surface of the pedestal.

Description

[Technical Field]

[0001] This disclosure relates to substrate processing systems, and more particularly to pedestals containing seals. [Previous Technology]

[0002] The prior art description provided herein is intended to provide a general overview of the context of this disclosure. The scope of the achievements of the inventors currently listed in this prior art section, together with any descriptions that may not otherwise be considered prior art at the time of the application, are not explicitly or implicitly included as prior art relative to this disclosure.

[0003] Several types of atomic layer deposition (ALD) can be used to deposit thin films onto a substrate. Examples of ALD include plasma-enhanced ALD (PEALD) and thermal ALD (T-ALD). Substrate processing systems used to perform T-ALD typically include a heated stage on which the substrate is placed during processing. [Summary of the Invention]

[0004] A pedestal assembly for a substrate processing system includes a pedestal plate having a plurality of gas through-holes and a rod extending from the pedestal plate. The plurality of gas through-holes extend from a first surface of the pedestal plate to a second surface of the pedestal plate at locations radially outward of the rod. A collar is disposed around the rod of the pedestal, and openings of the plurality of gas through-holes are located on the second surface of the pedestal. The collar defines a ring volume between the collar and the rod of the pedestal. An upward-facing surface of the collar forms a surface seal with the second surface of the pedestal.

[0005] Among other features, a pedestal support structure is attached to the distal end of the rod. An O-ring is located between the distal end of the rod and the pedestal support structure. The rod of the pedestal includes a flange extending radially outward at its bottom edge, and a pedestal support structure attached to the flange of the rod. A collar is attached to the pedestal support structure. An O-ring is located between the distal end of the collar and the pedestal support structure.

[0006] Among other features, the seal between surfaces includes the seal between planes.

[0007] Among other features, the pedestal support structure includes a cylindrical body with sidewalls. Vertical holes in the sidewalls define gas passages. The gas passages are in fluid communication with an annular volume and a plurality of gas through-holes. The pedestal support structure includes a cylindrical body defining an inner cavity and a flange extending radially outward from the upper surface of the cylindrical body. One or more clamps connect the flange located at the distal end of the rod to the flange extending radially outward from the cylindrical body of the pedestal support structure.

[0008] Among other features, the collar includes a first flange and a second flange located on its upper and lower surfaces, respectively. A fixture is positioned around the flange of the pedestal support structure and the second flange of the collar. An O-ring is located between the second surface of the second flange and the upper surface of the fixture.

[0009] Among other features, the first valve is configured to selectively connect the gas passage, the annular volume, and the gas via to a vacuum source. The controller is configured to selectively control the first valve to supply vacuum to the gas passage, the annular volume, and the gas via during substrate processing.

[0010] Among other features, the second valve is configured to selectively connect a gas passage, annular volume, and gas orifice to a purge gas source. Furthermore, the controller is configured to selectively control the second valve to purge the gas passage, annular volume, and gas orifice.

[0011] Among other features, the valve is configured to selectively connect a gas passage, annular volume, and gas orifice to a purge gas source. The controller is configured to selectively control the valve to purge the gas passage, annular volume, and gas orifice. The base is made of ceramic. The base is made of aluminum nitride. The collar is made of ceramic. The collar is made of alumina.

[0012] Among other features, the second surface of the pedestal plate and the upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 20 microinches. The second surface of the pedestal plate and the upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 16 microinches. The second surface of the pedestal plate and the upper surface of the rod are polished to a surface roughness (Ra) in the range of 3 to 8 microinches.

[0013] A pedestal assembly includes a pedestal having a pedestal plate including a plurality of gas through-holes and a rod extending from the pedestal plate. The plurality of gas through-holes extend from a first surface of the pedestal plate to a second surface of the pedestal plate. A collar is disposed around the rod of the pedestal. The pedestal plate has a first diameter, the rod has a second diameter smaller than the first diameter, and the collar has a third diameter smaller than the first diameter and larger than the second diameter. The plurality of gas through-holes are arranged in a first region of the pedestal plate defined between the second diameter and the third diameter. The gas through-holes are not located in a second region outside the first region or in a third region within the first region. The collar defines a toroidal volume between the collar and the rod of the pedestal.

[0014] Among other features, the first surface of the collar and the second surface of the base form a surface seal. A base support structure is attached to the distal end of the rod. An O-ring is located between the distal end of the rod and the base support structure. The second surface of the base plate and the upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 20 microinches. The second surface of the base plate and the upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 16 microinches. The second surface of the base plate and the upper surface of the rod are polished to a surface roughness (Ra) in the range of 3 to 8 microinches.

[0015] Among other features, the surface seal includes the plane seal. A plurality of gas passages are arranged in a circle in the first region.

[0016] The applicability of this disclosure to other areas will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure.

Implementation Method

[0024] Several types of atomic layer deposition (ALD) are available for depositing thin films. Examples of ALD include plasma-enhanced ALD (PEALD) and thermal ALD (T-ALD). Each PEALD cycle includes a preparation step that exposes the substrate to a precursor during its duration, a purging step, an RF plasma step, and a purging step. In T-ALD, the substrate is placed on a heated stage during the process and no plasma is used. Each T-ALD cycle typically includes the following steps: a first preparation step that exposes the substrate to a first precursor during its duration, a purging step, a second preparation step that exposes the substrate to a second precursor during its duration, and a purging step. A single layer is typically deposited during each ALD cycle. Multiple ALD cycles are performed to deposit a layer with a desired thickness.

[0025] Although the foregoing description describes a sealing system for a stage assembly used in T-ALD processing, the sealing system and stage assembly can be used in other substrate processing applications. Delivering gas to the high-temperature stage used in T-ALD is challenging. In some examples, the stage and substrate temperatures can range from 200°C to 1000°C, but other processing temperatures may also be used.

[0026] The pedestal assembly includes a pedestal having a pedestal plate and a rod. In some examples, the rod includes a hollow cylindrical portion extending from the pedestal plate. The pedestal plate includes gas through-holes that extend through the pedestal plate to fluidly communicate an annular space or annular volume surrounding the rod. As used herein, fluid communication means that gas flows from one volume to another via a gas passage. The sealing system includes a collar abutting a second surface of the pedestal plate and surrounding the rod to create the annular volume.

[0027] The collar provides an inter-surface seal to the second surface of the pedestal plate. In other words, one surface of the collar is pressed against the other surface of the pedestal to form a seal without welding or otherwise connecting the two surfaces or using O-rings at the surface-to-surface contact. In some examples, the inter-surface seal is located in a single plane and is an inter-plane seal. To maintain a sufficient seal, the second surface of the pedestal and the first surface of the collar are polished to a surface roughness sufficient to maintain the desired amount of seal. In some examples, the inter-plane seal comprises a ceramic-to-ceramic seal between the collar and the second surface of the pedestal plate. The inter-plane seal does not provide a suitable rate of leakage to the atmosphere. However, the seal does provide adequate isolation of gas species and pressure differentials for the transmission of purge gases or vacuum in the processing chamber, as will be further explained below.

[0028] The collar forms a sealed annular volume around the base rod. In some examples, an O-ring located at the distal end of the collar provides spring force. In other words, the collar is biased against a second surface of the base plate to create a seal that isolates the vacuum clamping from the chamber pressure.

[0029] Referring now to FIG1, an example of a substrate processing system 100 includes a processing chamber 102 configured to process a substrate. In some examples, the processing includes thermal atomic layer deposition (T-ALD). The processing chamber 102 includes sidewalls, a first surface, and a second surface. The processing chamber 102 surrounds other elements of the substrate processing system 100. During processing, a substrate 106 is placed on a stage 104. One or more heaters 108 (e.g., an array of heaters) may be disposed in the stage 104 to heat the stage 104 and the substrate 106 during processing. In some examples, the stage 104 is made of ceramic, such as aluminum nitride (AlN), alumina, or other suitable oxide or non-oxide ceramic materials. In other examples, metallic materials such as aluminum may be used.

[0030] The processing chamber 102 includes a gas distribution device 110, such as a spray head, for introducing and distributing processing gas into the processing chamber 102. The gas distribution device (hereinafter referred to as the spray head) 110 may include a rod 112, the rod 112 including one end connected to a first surface of the processing chamber 102. The base 113 of the spray head 110 is generally cylindrical and extends radially outward from the opposite end of the rod 112 at a location spaced apart from the first surface of the processing chamber 102. The substrate-facing surface of the base 113 of the spray head 110 includes a panel 114. Gases, such as carrier gases, inert gases, and precursor gases, flow through the rod 112, onto a dispersion plate 116, and into an inflation chamber 117. The gas then flows through a plurality of gas through-holes (indicated at 115 in FIG. 3) in the panel 114 into the processing chamber 102.

[0031] The gas delivery system 130 includes one or more gas sources 132-1, 132-2, ..., and 132-N (collectively referred to as gas sources 132), where N is an integer greater than zero. Gas sources 132 are connected to manifold 139 by valves 134-1, 134-2, ..., and 134-N (collectively referred to as valves 134) and mass flow controllers 136-1, 136-2, ..., and 136-N (collectively referred to as mass flow controllers 136). The output of manifold 139 is fed to processing chamber 102. Gas sources 132 can supply processing gas, cleaning gas, purge gas, inert gas, precursors, etc., to processing chamber 102.

[0032] Controller 160 controls the components of substrate processing system 100. Controller 160 may be connected to heater 108 in pedestal 104 and one or more temperature sensors 150. Controller 160 may control the power supplied to heater 108 based on the sensed temperature to control the temperature of pedestal 104 and substrate 106. Heater 108 may be placed in one or more areas.

[0033] The vacuum pump 158 maintains a pressure below atmospheric pressure within the processing chamber 102 during substrate processing. In some examples, the pressure in the processing chamber is maintained in a pressure range from 10 mTorr to 100 Torr. In some examples, the pressure in the processing chamber is maintained in a pressure range from 20 Torr to 40 Torr (e.g., 30 Torr).

[0034] Valve 156 is connected to the exhaust port of processing chamber 102. Valve 156 and vacuum pump 158 are used to control the pressure in processing chamber 102 and to discharge reactants from processing chamber 102 via valve 156.

[0035] During processing, the substrate 106 is supported on the first surface of the stage 104 by vacuum. The stage 104 includes a plurality of gas through holes (marked at 224 in FIG2) that allow gas to pass from the first surface of the stage 104 to the second surface.

[0036] The sealing system 162 maintains a sufficiently tight seal around the openings of the plurality of holes 224 located on the second surface of the stage 104. The sealing system 162 allows a vacuum to be maintained during processing to hold the substrate against the stage 104, or allows gas to be delivered through the plurality of holes 224 during purging. The sealing system 162 includes a collar 164 disposed around the stage rod 165. In some examples, the collar 164 is made of a material having a similar coefficient of thermal expansion (CTE) to the stage 104. In some examples, the collar 164 is made of ceramic, for example, alumina.

[0037] The volume between collar 164 and base rod 165 is selectively connected to vacuum pump 158 or another vacuum source via valve 170. In some examples, the volume between collar 164 and base rod 165 may be selectively connected to purge gas source 178 via valve 174. A first cylinder 166 is radially spaced from and surrounds collar 164 and extends from a second surface of the processing chamber. A second cylinder 168 is radially spaced from and surrounds first cylinder 166 and extends from a second surface of base 104. The first cylinder 166 and the second cylinder 168 are configured to allow relative axial movement between them to allow limited gas flow between them and to guide gas out of the interior of the second cylinder 168 in a downward direction.

[0038] During operation, substrate 106 is placed on pedestal 104 and valve 170 is opened to vacuum pump 158. Vacuum holds substrate 106 against pedestal 104. Processing is performed on substrate 106, then valve 170 is closed, vacuum is turned off, and substrate 106 is removed. A purging step can be performed between certain substrate processing cycles and / or during maintenance by opening valve 174 (with valve 170 closed) to allow purge gas to flow through the volume between collar 164 and pedestal rod 165, and through a plurality of gas through-holes 224 in pedestal 104. The plurality of gas through-holes 224 extend from a first surface of pedestal 104 to a second surface of pedestal 104.

[0039] Referring now to FIG2, the pedestal 200 shows a first surface 204 having an outer sealing strip 208, a lifting pin hole 210, a plurality of protrusions or flat-topped protrusions 220, and a plurality of gas passages 224. The plurality of protrusions or flat-topped protrusions 220 may be spaced out and positioned within the first surface 204 to support the substrate in a flat, convex, inclined (from one radial edge to the opposite radial edge), or concave position. In some examples, the outer sealing strip 208 and the plurality of protrusions or flat-topped protrusions 220 extend upward to a predetermined height above the first surface 204. In some examples, the predetermined height of the protrusions or flat-topped protrusions 220 may be varied. In some examples, the substrate is kept flat during processing, and the height of the protrusions may be uniform or varied in many patterns to provide a desired cooling mode.

[0040] Referring now to FIG3, a pedestal 310 including a sealing system 162 is shown. The pedestal 310 includes a pedestal plate 320 on which a substrate is supported during processing, and a rod 322 extending downward from the pedestal plate 320. In some examples, the pedestal 310 is made of ceramic. In some examples, the pedestal plate 320 has a flat cylindrical shape. In some examples, the pedestal plate 320 has a first diameter (d1). In some examples, the rod 322 includes a sidewall 323 having a second diameter (d2). In some examples, the sidewall 323 extends a predetermined distance. In some examples, the second diameter is smaller than the first diameter. In some examples, the second diameter is less than or equal to 60%, 50%, 40%, or 30% of the first diameter. A flange 326 is located at the lower end of the sidewall 323. In some examples, the flange 326 extends radially outward from the sidewall 323. Sidewall 323 defines the inner cavity 324.

[0041] The collar 330 is spaced from and surrounds the sidewall 323 of the rod portion 322 of the pedestal 310. The collar 330 has a third diameter (d3) and defines the annular volume between the inner surface 332 of the collar 330 and the outer surface of the sidewall 323 of the rod portion 322 of the pedestal 310. The collar 330 includes flanges 334 and 336 extending radially outward from its lower and upper ends, respectively. The lower radially inner surface of the collar 330 abuts the upper radially outer surface of the pedestal support structure 350.

[0042] In some examples, the gas through-holes 224 are arranged in a region of the base plate 320, which is located between the sidewall 323 of the rod 322 and the inner surface 332 of the collar 330. In some examples, the gas through-holes 224 are not located in a first region of the base plate 320, either inside the sidewall 323 of the rod or outside the inner surface 332 of the collar 330.

[0043] The pedestal support structure 350 has a cylindrical body attached below the flange 326 of the pedestal 310 and defining an inner cavity 352. The sidewall 354 of the pedestal support structure 350 includes a hole 355 defining a gas passage 356. The gas passage 356 can be connected to a vacuum source to hold the substrate against the pedestal 310, or to a purge gas source to purge the pedestal 310 when the substrate is removed as described above. A sac seal 359 provides a flexible seal around the pedestal support structure 350 above the lower support 364.

[0044] The bottom of the rod portion 322 of the pedestal 310 is connected to the pedestal support structure 350 using one or more clamps. In some examples, one or more clamps include clamping rings having annular or split annular shapes. The first clamp 340 is connected to a first surface of the pedestal support structure 350 via a second clamp 344 by one or more fasteners 342. As used herein, the term "clamp" refers to an annular or arcuate portion that is secured to another element to hold one or more elements together. In some examples, the second clamp 344 has a "C-shaped" cross-section (90 degrees clockwise).

[0045] A third clamp 370 is attached to the bottom-facing surface of the flange (410 in FIG. 4) of the pedestal support structure 350. In some examples, the third clamp 370 has an "L-shaped" cross-section and includes an upwardly projecting portion 376 and a radially inwardly projecting portion 375. An "O-ring" 378 provides a seal between the second surface of the flange 334 and the upward-facing surface of the radially inwardly projecting portion 375. Similarly, an "O-ring" 390 is located between the second surface of the flange 326 and the upward-facing surface of the pedestal support structure 350. An annular heat-insulating baffle 380 is positioned at a predetermined distance below the pedestal 310 and includes a central opening wide enough to accommodate the collar 330 and the rod portion 322 of the pedestal 310.

[0046] Referring now to FIG4, the pedestal support structure 350 includes a body 404 and a flange 410 extending radially outward from the upper portion of the body 404. The sidewall 354 of the pedestal support structure 350 includes a hole 355 defining a vertical portion of a gas passage 356 to allow purge gas flow or to provide a vacuum. An annular opening 428 formed on a first surface of the flange 410 defines a vertical surface 432 and a horizontal surface 430 extending radially inward therefrom. A groove 434 is formed on the horizontal surface 430. An O-ring 390 may be disposed in the groove 434. A radial hole 440 passes through the flange portion (or another portion of the pedestal support structure 350) and is in fluid communication with the gas passage 356. An annular protrusion 461 extends upward from the radially outer surface and the upper surface of the flange 410.

[0047] Referring now to FIG5, the third clamp 370 is secured to the downward-facing surface 512 of the flange 410 of the pedestal support structure 350 by one or more fasteners 520. The first clamp 340 is secured to the upper surface 524 of the flange 410 by the fastener 342 via the second clamp 344.

[0048] As can be understood, an inter-surface seal is created at the interface between the upper surface of the flange 336 of the collar 330 and the second surface of the base 310. In some examples, the inter-surface seal includes an inter-planar seal, which is created when two flat surfaces are arranged in direct contact without welding to join the two materials or using a separate seal such as an O-ring. In other examples, the inter-surface seal includes complementary non-planar surfaces. In other words, the abutment of the two surfaces forms a seal. In some examples, the upper surface of the flange 336 of the collar 330 and the second surface of the base 310 are polished to a surface roughness (Ra) ranging from 3 to 20 microinches. In other examples, the surface roughness ranges from 3 to 16 microinches. In other examples, the surface roughness ranges from 3 to 8 microinches.

[0049] The collar 330 is adjacent to the O-ring 378, which biases the upper surface of the flange 336 of the collar 330 against the second surface of the base 310. Similarly, the O-ring 390 provides a seal between the second surface of the flange 326 and the upper surface of the base support structure 350.

[0050] The foregoing description is illustrative in nature and is in no way intended to limit the scope of this disclosure, its application, or use. The broad teachings of this disclosure can be implemented in many forms. Therefore, while this disclosure includes specific examples, its true scope should not be so limited, as other modifications will become apparent upon reading the drawings, specification, and accompanying claims. It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of this disclosure. Furthermore, although the embodiments are described above as having specific features, any one or more of those features described with respect to any embodiment of this disclosure may be implemented in and / or combined with features of any other embodiment, even if such combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitution of one or more embodiments for each other remains within the scope of this disclosure.

[0051] Various terms are used to describe spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.), including "connection," "joint," "coupled," "adjacent," "beside," "on," "above," "below," and "set." When describing a relationship between first and second elements in the foregoing disclosure, unless explicitly described as "direct," the relationship can be a direct relationship in which no other intermediate elements exist between the first and second elements, or an indirect relationship in which one or more intermediate elements (spatial or functional) exist between the first and second elements. As used herein, the terms A, B, and C, at least one of which should be interpreted as meaning a logic using a non-mutually exclusive "OR" (A or B or C), and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C."

[0052] In some embodiments, the controller is part of a system, which may be part of the above-described examples. Such a system may include semiconductor processing equipment, including one or more processing devices, one or more chambers, one or more platforms for processing, and / or specific processing elements (wafer pedestals, airflow systems, etc.). These systems may be integrated with electronic equipment for controlling their operation before, during, and after processing semiconductor wafers or substrates. This electronic equipment may be referred to as a "controller," which controls many elements or sub-parts of one or more systems. Depending on the processing requirements and / or system type, the controller may be programmed to control any of the processes disclosed herein, including the delivery of working 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, position and operation settings, wafer in and out, devices connected to or interfaced with a particular system, and other transmission devices and / or load locks.

[0053] Broadly speaking, a controller can be defined as an electronic device having numerous integrated circuits, logic, memory, and / or software for receiving instructions, issuing instructions, controlling operations, initiating cleaning operations, initiating endpoint measurements, etc. Integrated circuits may include chips in the form of firmware storing 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 transmitted to the controller in the form of numerous individual settings (or program files) to define operating parameters for performing specific processes on or for a semiconductor wafer or system. In some embodiments, operating parameters may be a portion of a recipe defined by a process engineer to complete one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0054] In some embodiments, the controller may be part of a computer or coupled to a computer integrated with, coupled to, or otherwise networked to the system. For example, the controller may be in the "cloud" or in all or part of the host system manufacturing plant, allowing remote access to wafer processing. The computer may enable remote access to the system to monitor the current progress of manufacturing operations, examine the history of past manufacturing operations, examine trends or performance indicators from multiple manufacturing operations, change parameters of the current processing, set processing steps to follow the current processing, or start a new processing. In some examples, the remote computer (e.g., a server) may provide processing recipes to the system via a network, which may include a local area network or the Internet. The remote computer may include input or programming parameters and / or a user interface for setting, and then transmit them from the remote computer to the system. In some examples, the controller receives instructions in the form of data, specifying parameters for each processing step to be executed during one or more operations. It should be understood that these parameters may be specific to the type of processing to be performed and the type of device to which the controller is configured to interface with or control. Therefore, as explained above, the controller can be distributed, for example by comprising one or more individual controllers networked together and working toward a common goal (such as the processing and control described herein). An example of a distributed controller for such a purpose would be one or more integrated circuits on a chamber connected to one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer), which together control the processing on the chamber.

[0055] Without limitation, exemplary systems may include plasma etching chambers or modules, deposition chambers or modules, rotary rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, bevel etching chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etching (ALE) chambers or modules, ion implantation chambers or modules, orbital chambers or modules, and any other semiconductor processing systems that may be associated with or used in the manufacture and / or manufacturing of semiconductor wafers.

[0056] As described above, depending on one or more processing steps performed by the device, the controller may be connected to one or more of the following: other device circuits or modules, other device components, clustered devices, other device interfaces, adjacent devices, adjacent devices, devices located at various locations in the plant, a host computer, another controller, or devices used in the semiconductor manufacturing industry for transporting wafer containers to and from device locations and / or loading ports. [Simplified Explanation of the Diagram]

[0017] This disclosure will be more fully understood from the detailed description and accompanying drawings, wherein:

[0018] Figure 1 is a functional block diagram of an example of a substrate processing system including a platform with a seal, according to the present disclosure;

[0019] Figure 2 is a top view of the first surface of an example of a pedestal according to the present disclosure.

[0020] Figure 3 is a cross-sectional side view of an example of a gas distribution device and a base including a seal according to the present disclosure.

[0021] Figure 4 is a cross-sectional side view of an example of a pedestal support structure including sidewalls with gas channels; and

[0022] Figure 5 is a cross-sectional side view of an example of a pedestal including a seal according to the present disclosure.

[0023] In the diagram, reference numbers may be used repeatedly to identify similar and / or identical elements.

Claims

1. A pedestal assembly comprising: a pedestal including a pedestal plate and a rod extending from the pedestal plate; a collar surrounding the rod of the pedestal, wherein the collar defines an annular volume between an inner surface of the collar and an outer surface of the rod of the pedestal; and a plurality of gas through-holes extending from a first surface of the pedestal plate to a second surface of the pedestal plate at a location radially outward of the rod, wherein the plurality of gas through-holes are located within the annular volume between the inner surface of the collar and the outer surface of the rod of the pedestal, and wherein the first surface of the collar and the second surface of the pedestal form an inter-surface seal.

2. The pedestal assembly of claim 1 further includes a pedestal support structure attached to a distal end of one of the rods.

3. The pedestal assembly of claim 2 further includes an "O-ring" located between the distal end of the rod and the pedestal support structure.

4. The pedestal assembly of claim 1, wherein the rod of the pedestal includes a flange extending radially outward at a bottom edge thereon, and further includes a pedestal support structure attached to the flange of the rod.

5. The pedestal assembly as claimed in claim 2, wherein the collar is attached to the pedestal support structure.

6. The pedestal assembly of claim 5 further includes an "O-ring" located between a distal end of the collar and the pedestal support structure.

7. The pedestal assembly of claim 2, wherein the pedestal support structure includes a cylindrical body having a sidewall, a vertical hole in the sidewall defining a gas passage, and the gas passage being in fluid communication with the annular volume and the plurality of gas through holes.

8. The pedestal assembly of claim 2, wherein the pedestal support structure includes a cylindrical body defining an inner cavity and a flange extending radially outward from an upper surface of the cylindrical body.

9. The pedestal assembly of claim 8 further includes one or more clamps that connect a flange located at a distal end of the rod to a flange extending radially outward from the cylindrical body of the pedestal support structure.

10. The pedestal assembly of claim 8, wherein the collar includes first and second flanges located on its upper and lower surfaces, respectively, and further includes a clamp disposed around the flange of the pedestal support structure and the second flange of the collar.

11. The pedestal assembly of claim 10 further includes an "O-ring" located between a second surface of the second flange and an upper surface of the clamp.

12. The pedestal assembly of claim 7 further comprises: a first valve configured to selectively connect the gas passage, the annular volume, and the gas vias to a vacuum source; and a controller configured to selectively control the first valve to supply vacuum to the gas passage, the annular volume, and the gas vias during processing of a substrate.

13. The pedestal assembly of claim 12 further includes a second valve configured to selectively connect the gas passage, the annular volume, and the gas through-holes to a purge gas source, wherein the controller is further configured to selectively control the second valve to purge the gas passage, the annular volume, and the gas through-holes.

14. The pedestal assembly of claim 7 further comprises: a valve configured to selectively connect the gas passage, the annular volume, and the gas orifices to a purge gas source; and a controller configured to selectively control the valve to purge the gas passage, the annular volume, and the gas orifices.

15. The pedestal assembly of claim 1, wherein the pedestal is made of ceramic.

16. The platform assembly of claim 1, wherein the platform is made of aluminum nitride.

17. The pedestal assembly of claim 1, wherein the collar is made of ceramic.

18. The pedestal assembly of claim 1, wherein the collar is made of aluminum oxide.

19. The pedestal assembly of claim 1, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 20 microinches.

20. The pedestal assembly of claim 1, wherein the seal between the surfaces comprises a seal between the planes.

21. The pedestal assembly of claim 1, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 16 microinches.

22. The pedestal assembly of claim 1, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) ranging from 3 to 8 microinches.

23. The pedestal assembly of claim 1, wherein the plurality of gas through-holes are in fluid communication with the annular volume.

24. The pedestal assembly of claim 1 further comprises: a first cylinder radially spaced from and surrounding the collar and extending upward from a lower surface of a processing chamber receiving the pedestal assembly; and a second cylinder spaced from and surrounding the first cylinder and extending downward from the second surface of the pedestal plate, wherein the first and second cylinders are configured to overlap and allow relative axial movement therebetween.

25. The pedestal assembly of claim 1 further comprises: a support structure supporting a bottom end of the pedestal assembly; and a clamp attached to the support structure, wherein, The collar is attached to the clamp in a sealing manner.

26. The pedestal assembly of claim 1 further includes an annular heat-insulating baffle disposed at a predetermined distance below the pedestal plate, and includes a central opening for receiving the collar and the rod.

27. A pedestal assembly comprising: a pedestal including a pedestal plate and a rod extending from the pedestal plate; a collar surrounding the rod of the pedestal, wherein the pedestal plate has a first diameter, the rod has a second diameter smaller than the first diameter, and the collar has a third diameter smaller than the first diameter and larger than the second diameter; and a plurality of gas through-holes extending from a first surface of the pedestal plate to a second surface of the pedestal plate, wherein the plurality of gas through-holes are arranged in a first region of the pedestal plate defined between the second diameter and the third diameter, and wherein the plurality of gas through-holes are not located in a second region outside the first region and in a third region within the first region.

28. The pedestal assembly of claim 27, wherein a first surface of the collar and a second surface of the pedestal form a surface seal.

29. The pedestal assembly of claim 27 further includes a pedestal support structure attached to a distal end of one of the rods.

30. The pedestal assembly of claim 29 further includes an "O-ring" located between the distal end of the rod and the pedestal support structure.

31. The pedestal assembly of claim 27, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 20 microinches.

32. The pedestal assembly of claim 27, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) of less than or equal to 16 microinches.

33. The pedestal assembly of claim 27, wherein the second surface of the pedestal plate and an upper surface of the rod are polished to a surface roughness (Ra) ranging from 3 to 8 microinches.

34. The pedestal assembly of claim 28, wherein the seal between the surfaces comprises a seal between the planes.

35. The pedestal assembly of claim 27, wherein the plurality of gas through-holes are arranged in a circle in the first region of the pedestal plate.

36. The pedestal assembly of claim 27, wherein the second and third diameters define an annular volume between the collar and the rod of the pedestal, and wherein the plurality of gas through-holes are located within the annular volume.

37. The pedestal assembly of claim 36, wherein the plurality of gas through-holes are in fluid communication with the annular volume.

38. The pedestal assembly of claim 27 further comprises: a first cylinder radially spaced from and surrounding the collar and extending upward from a lower surface of a processing chamber receiving the pedestal assembly; and a second cylinder spaced from and surrounding the first cylinder and extending downward from the pedestal plate, wherein the first and second cylindrical systems are configured to overlap and allow relative axial movement therebetween.

39. The pedestal assembly of claim 27 further comprises: a support structure supporting a bottom end of the pedestal assembly; and a clamp attached to the support structure, wherein, The collar is attached to the clamp in a sealing manner.

40. The pedestal assembly of claim 27 further includes an annular heat-insulating baffle disposed at a predetermined distance below the pedestal plate, and includes a central opening for receiving the collar and the rod.

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