Electrostatic chuck with laser machined mesa - Patents.com

Abstract

An electrostatic chuck (ESC) for a reactor or plasma processing chamber, and a method of manufacturing the ESC are described. For example, a method of manufacturing a substrate support assembly includes providing a ceramic top plate having an upper surface with a processing region. A plurality of mesas are formed in the processing region and on the upper surface of the ceramic plate. Laser machining of one or more of the plurality of mesas is performed to reduce or increase a surface roughness of one or more of the plurality of mesas.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 17 / 700,203, filed March 21, 2022, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to the field of reactors or plasma processing chambers, and more particularly to electrostatic chucks having laser machined mesas. [Background technology]

[0003] Processing systems such as reactors or plasma reactors are used to form devices on substrates such as semiconductor wafers or transparent substrates. Often, the substrate is held on a support for processing. The substrate may be held on the support by vacuum, gravity, electrostatic force, or other suitable techniques. During processing, a precursor gas or gas mixture in the chamber is activated (e.g., excited) into a plasma by applying power (e.g., radio frequency (RF) power) to an electrode in the chamber from one or more power sources coupled to the electrode. The excited gas or gas mixture reacts to form a layer of material on the surface of the substrate. The layer may be, for example, a passivation layer, a gate insulator, a buffer layer, and / or an etch stop layer.

[0004] In the semiconductor and other industries, electrostatic chucks (ESCs) are used to hold a workpiece, such as a substrate, on a support during processing of the substrate. A typical ESC may include a base, an electrically insulating layer disposed on the base, and one or more electrodes embedded in the electrically insulating layer. The ESC may be provided with an embedded electric heater as well as be fluidly connected to a source of heat transfer gas for controlling the substrate temperature during processing. In use, the ESC is fixed to a support within a processing chamber. The electrodes within the ESC are electrically biased by a voltage source with respect to a substrate disposed on the ESC. Opposing electrostatic charges build up in the electrodes of the ESC and on the surface of the substrate, and an insulating layer prevents the flow of charge therebetween. Electrostatic forces resulting from the buildup of electrostatic charges hold the substrate against the ESC during processing of the substrate. Summary of the Invention

[0005] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure include an electrostatic chuck (ESC) for a reactor or plasma processing chamber, and a method of manufacturing the ESC.

[0006] In one embodiment, a method of manufacturing a substrate support assembly includes providing a ceramic top plate having a top surface with a processing region. A plurality of mesas are formed in the processing region and on the top surface of the ceramic plate. Laser machining of one or more of the plurality of mesas is performed to reduce surface roughness of one or more of the plurality of mesas.

[0007] In one embodiment, a method of manufacturing a substrate support assembly includes providing a ceramic top plate having a top surface with a processing region. A plurality of mesas are formed in the processing region and on the top surface of the ceramic plate. Laser machining of one or more of the plurality of mesas is performed to increase a surface roughness of one or more of the plurality of mesas.

[0008] In one embodiment, the substrate support assembly includes a ceramic top plate having a top surface with a processing region. One or more DC brazed connections are in the ceramic top plate. One or more electrodes are in the ceramic top plate. A plurality of mesas are in the processing region and on the top surface of the ceramic plate. The one or more mesas are laser machined mesas. [Brief description of the drawings]

[0009] [Figure 1A] 1 illustrates a plan view of a top surface of an electrostatic chuck (ESC) and a corresponding close-up view, according to an embodiment of the present disclosure. [Figure 1B] 1A-1D illustrate cross-sectional views of a method for reducing mesa surface roughness by laser machining according to an embodiment of the present disclosure. [Figure 1C] 1A-1D show cross-sectional views of a method for increasing surface roughness of a mesa by laser machining according to an embodiment of the present disclosure. [Figure 2A] 1A-1D illustrate cross-sectional views of an electrostatic chuck (ESC) including mesas in various positions according to an embodiment of the present disclosure. [Figure 2B] 1A-1C show cross-sectional views of another electrostatic chuck (ESC) including mesas at various positions in accordance with another embodiment of the present disclosure. [Figure 2C] 1A-1C show cross-sectional views of another electrostatic chuck (ESC) including mesas at various positions in accordance with another embodiment of the present disclosure. [Diagram 3] FIG. 1 illustrates a cross-sectional view of an electrostatic chuck (ESC) according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic cross-sectional view of a processing chamber including a substrate support assembly according to an embodiment of the present disclosure. [Diagram 5] 1 is a schematic partial cross-sectional view of a processing chamber including a substrate support assembly according to an embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates a block diagram of an exemplary computer system according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An electrostatic chuck (ESC) for a plasma processing chamber and a method for manufacturing the ESC are described. In the following description, numerous specific details are set forth, such as electrostatic chuck components and material forms, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one of ordinary skill in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known aspects, such as plasma enhanced chemical vapor deposition (PECVD) or plasma enhanced atomic layer deposition (PEALD) processing, have not been described in detail so as not to unnecessarily obscure embodiments of the present disclosure. Additionally, it should be understood that the various embodiments illustrated in the figures are illustrative representations and are not necessarily drawn to scale.

[0011] One or more embodiments are directed to laser machining the mesa to achieve surface smoothness or to achieve surface roughness. Embodiments may include a dry and wash approach to fabricate the mesa on a ceramic or metal pedestal. In one embodiment, the approach described herein provides a rapid and accurate approach that is programmable for repeatability. In one or more embodiments, the mesa profile is laser machined.

[0012] By way of background, it may be advantageous to provide a mesa above a pedestal with a consistent surface roughness and profile. This may involve ceramic or metal edge profiling and surface roughness (Ra) control. Traditional approaches involve polishing, but such approaches may not be clean.

[0013] Advantages of implementing and / or properties of the embodiments described herein may include one or more of the following: (1) application for minimal contact area polishing or roughening, (2) ability to process only specific mesas, (3) very fast process, such as on the order of a few seconds per mesa, (4) very clean process compared to slurry processing, (5) ability to contour edges to remove sharp corners and reduce particles on the wafer, (6) adjustable laser spot, and / or (7) applicability to ceramics such as alumina or AlN.

[0014] In one embodiment, the mesas are first fabricated to have a surface roughness (Ra) defined by the mesa fabrication process (e.g., using bead blasting). A laser is used to trim the ends of the mesas to achieve a target profile and Ra value. In one embodiment, the surfaces of approximately 1 mm diameter ESCs initially fabricated with an Ra value of 8-12 or an Ra value of 6-8 are laser machined to produce an Ra value of 1-4. In another embodiment, the surfaces of approximately 1 mm diameter ESCs initially fabricated with an Ra value of 1-4 are laser machined to produce an Ra value of 6-8 or an Ra value of 8-12.

[0015] By way of background, a mesa on the surface of the ESC can be used to support a workpiece, raising it slightly above the entire global top surface of the top plate of the ESC. In an exemplary embodiment, the extent of the mesa can be about 65% of the entire surface area of ​​the processing surface, but can be larger or smaller. The mesa can be about 15 microns high, but can be higher or lower. The mesa can be about 1 mm in diameter, but can be larger or smaller.

[0016] For example, mesas may be fabricated on the top surface of the ESC surface, either by grinding or bead blasting. Such mesas may be described as continuous with the top surface of the ceramic top plate. The mesas may be particles, such as diamond particles, formed in or applied to the surface of the ceramic. FIG. 1A illustrates a top view and corresponding close-up 150 of an electrostatic chuck (ECS) top surface according to one embodiment of the present disclosure.

[0017] 1A, the top surface 102 of the ESC 100 includes an exterior region 104 surrounding an interior region 106. The top surface 102 can be a ceramic surface, such as aluminum nitride on an aluminum oxide surface. The interior region 106 can include a processing region 107 having electrical wiring 108 therein, e.g., slightly below the surface of the ceramic. The electrical wiring 108 can be present, e.g., for electrostatic electrodes of the ESC 100. The processing region 107 can further include a DC braze joint location 110, e.g., slightly below the surface of the ceramic. A plurality of mesas 112 are fabricated on the surface of the processing region 107. In an embodiment, one or more of the mesas 112 are laser machined mesas, as described below.

[0018] FIG. 1B illustrates a cross-sectional view of a method for reducing the surface roughness of a mesa by laser machining according to an embodiment of the present disclosure.

[0019] 1B, a method of manufacturing a substrate support assembly includes providing a ceramic top plate having a top surface with a processing region. A plurality of mesas, such as mesa 160, are formed in the processing region and on the top surface of the ceramic plate. Laser machining of one or more of the plurality of mesas is performed to reduce a surface roughness of one or more of the plurality of mesas, for example, to form mesa 170. In an embodiment, reducing the surface roughness includes reducing the surface roughness from an Ra value of 8-12 microns to an Ra value of 1-4 microns. In an embodiment, as shown in FIG. 1B, reducing the surface roughness of one or more of the plurality of mesas includes forming rounded corners on one or more of the plurality of mesas.

[0020] It should be appreciated that depending on the needs or behavior of the chuck, it may not be optimal to reduce the roughness of the mesa surface by laser machining all of the mesas of the ESC, in some embodiments, one or more of the plurality of mesas (of type 170) are fewer than all of the plurality of mesas (of type 160), leaving both types 160 and 170 on the surface of the ESC.

[0021] In some embodiments, the plurality of mesas are contiguous with an upper surface of the ceramic top plate. In some embodiments, the ceramic top plate comprises aluminum nitride. In some embodiments, the ceramic top plate comprises aluminum oxide. In some embodiments, the method further comprises forming one or more electrodes in the ceramic top plate.

[0022] FIG. 1C illustrates a cross-sectional view of a method for increasing the surface roughness of a mesa by laser machining according to an embodiment of the present disclosure.

[0023] 1C, a method of manufacturing a substrate support assembly includes providing a ceramic top plate having a top surface with a processing region. A plurality of mesas, such as mesa 180, are formed in the processing region and on the top surface of the ceramic plate. Laser machining of one or more of the plurality of mesas is performed to increase a surface roughness of one or more of the plurality of mesas, for example, to form mesa 190. In an embodiment, increasing the surface roughness includes increasing the surface roughness from an Ra value of 1-4 microns to an Ra value of 8-12 microns. In an embodiment, as shown in FIG. 1C, increasing the surface roughness of one or more of the plurality of mesas includes forming sharp corners on one or more of the plurality of mesas.

[0024] It should be appreciated that depending on the needs or behavior of the chuck, it may not be optimal to increase the roughness of the mesa surface by laser machining all of the mesas of the ESC, in one embodiment, one or more of the plurality of mesas (of type 190) are fewer than all of the plurality of mesas (of type 180), leaving both types 180 and 190 on the surface of the ESC.

[0025] In some embodiments, the plurality of mesas are contiguous with a top surface of the ceramic top plate. In some embodiments, the ceramic top plate comprises aluminum nitride. In some embodiments, the ceramic top plate comprises aluminum oxide. In some embodiments, the method further comprises forming one or more electrodes in the ceramic top plate.

[0026] It should be appreciated that any suitable laser processing process may be used to laser process the mesa according to the embodiments described herein, for example, a nanosecond based laser processing process, a picosecond based laser processing process, or a femtosecond based laser processing process may be used.

[0027] In one embodiment, the mesa is laser machined with a Gaussian laser beam, although non-Gaussian beams may also be used. Additionally, the beam may be stationary or rotating. In one embodiment, a femtosecond-based laser is used as the laser source for the laser machining process. For example, in one embodiment, a femtosecond-based laser, i.e., femtosecond (10 GHz) laser, is used with a laser having wavelengths in the visible spectrum plus ultraviolet (UV) and infrared (IR) ranges (together resulting in a broadband optical spectrum). -15 A laser having a pulse width on the order of 100 Hz is provided.

[0028] When the laser beam is a femtosecond-based laser beam, in one embodiment, the femtosecond laser source has a pulse width in the range of about 10 femtoseconds to 500 femtoseconds, but preferably in the range of 100 femtoseconds to 400 femtoseconds. In an embodiment, the femtosecond laser source has a wavelength in the range of about 1570 nanometers to 200 nanometers, but preferably in the range of 540 nanometers to 250 nanometers. In an embodiment, the laser and corresponding optical system provide a focal spot at the work surface in the range of about 3 microns to 15 microns, but preferably in the range of about 5 microns to 10 microns, or 10 to 15 microns.

[0029] In one embodiment, the laser source has a pulse repetition rate in the range of about 200 kHz to 10 MHz, but preferably in the range of about 500 kHz to 5 MHz. In one embodiment, the laser source delivers pulse energy to the work surface in the range of about 0.5 μJ to 100 μJ, but preferably in the range of about 1 μJ to 5 μJ. In one embodiment, the laser scribing process travels along the surface of the workpiece at a speed in the range of about 500 mm / sec to 5 m / sec, but preferably in the range of about 600 mm / sec to 2 m / sec.

[0030] The mesa laser machining process may be performed in only one pass or in multiple passes, but in one embodiment, preferably in one to two passes. In one embodiment, the depth of the laser machining in the workpiece is within a range of about 5 microns to 50 microns, preferably within a range of about 10 microns to 20 microns. In one embodiment, the kerf width of the generated laser beam is within a range of about 2 microns to 15 microns.

[0031] In another aspect, one or more embodiments are directed to reducing surface stress in an electrostatic chuck (ESC) through mesa engineering, profile, and ESC material design. The embodiments may include ESC mesa engineering and top material structure design. In one embodiment, the one or more mesas are laser machined mesas.

[0032] By way of background, in past and prior art implementations, mesas are typically placed in a number of locations, including locations based on high stress regions on the surface of the ESC, which may be accompanied by the initiation of cracks on the top surface of the ESC due to high stress and / or thermal stresses in the defect regions.

[0033] Mesa engineering and profile structure of the top ESC material and design according to one or more embodiments of the present disclosure are implemented for surface stress reduction. Benefits of implementing one or more embodiments described herein may include targeted location of the mesa, improved profile of the top surface of the ESC. The embodiments described herein may be implemented to enable use of the ESC without cracking due to thermal shock at temperatures above 500° C. on the top surface. The embodiments described herein may be implemented to eliminate or mitigate cracking due to ESC thermal shock stresses. In one embodiment, the one or more mesas are laser machined mesas as described herein.

[0034] 1A, and in particular the close-up view 150, the plurality of mesas 112 includes mesas at multiple locations including gentle regions, as well as mesas 112A in an area above the area of ​​the DC braze bond location 110. It has been found that the presence of mesas 112A in an area above the area of ​​the DC braze bond location 110 may place mesas 112A in a high stress area.

[0035] FIG. 2A illustrates a cross-sectional view of an electrostatic chuck (ESC) including mesas in various positions according to one embodiment of the present disclosure.

[0036] 2A, ESC 200 includes a central zone 202, a main zone 204, a DC rod 206, and an ESC mesh 208. DC rod 206 may reside in a central location 210 as shown. ESC 200 also includes mesas, such as mesas 212A, 212B, 212C, and 212D. Mesa 212A is on top of a high voltage connection region 210, such as on top of DC rod 206. Mesa 212B is on top of an electrode end. Mesa 212C is in a non-electrode region. Mesa 212D is completely on top of the electrode. Mesas 212A, 212B, 212C, and 212D are at relatively shallow spacings above ESC mesh 208. In one embodiment, one or more mesas are laser machined mesas, as described herein.

[0037] Referring again to FIG. 2A, the surface of the ESC may include a stress distribution including high and low stress regions on the top surface based on its manufacturing characteristics. Some high stress regions are caused by high voltage electrodes present approximately 1 mm below the top surface. For example, high stress may be present (A) at the boundary of the positive or negative polarity electrode ends, (B) at the top of the brazed connection, and / or at the end of the ESC. According to an embodiment of the present disclosure, a mesa structure is included on top of the low stress region, but not on top of the high stress region. For example, mesas 212A and 212B are in high stress locations, while mesas 212C and 212D are in low stress regions. In one embodiment, a mesa is included at location 212C and / or 212D, but not at location 212A or 212B. In one embodiment, one or more mesas are laser machined mesas as described herein.

[0038] In another aspect, the surface of the prior art ESC may have a profile after machining and / or polishing the top surface. The profile may have a ridge in the center of the ESC. The size of such ridge in the center may be about 10-20 microns with a 15 micron mesa along the contour, as described below and illustrated in FIG. 2B. When the wafer is placed on the ESC, it may have various contact points. The ridge in the center may cause the wafer not to contact the mesa immediately adjacent to the center. According to one or more embodiments of the present disclosure, a value of the vertical length (topographical feature) of the surface for the horizontal distance of a given mesa height is determined. Heat transfer between the wafer and the ESC, and from the plasma to the wafer via gas coupling to the ESC, may control the wafer temperature in the region. When only the center ridge is polished, the wafer may develop a concave contact region with all mesas and heat transfer uniform. In an embodiment, before the mesas are generated, a flatness profile is measured on the surface of the ESC, and mesas are not formed at locations where the vertical slope (e.g., 15 microns / 10 mm) criteria is not met. In one embodiment, at the locations where mesas are formed, one or more mesas are laser machined mesas, as described herein.

[0039] FIG. 2B illustrates a cross-sectional view of another electrostatic chuck (ESC) including mesas in various positions according to another embodiment of the present disclosure.

[0040] 2B, the support surface topography 250 may include a mesa profile 254 on top of a ceramic top surface profile 252. The ceramic top surface profile 252 may have a central apex 252A and end locations 252B. The mesa profile 254 shows grinding locations 256A and 256B with a high central point. A mesa 262 is on top of the ceramic top surface profile 252. In one embodiment, after it is determined that the central point is the apex, the mesa 262A is not formed at the central location. As a result, the wafer profile (dotted line 258) is not formed at the high point of the mesa profile 254 where the mesa 262A would have been included. In one embodiment, where a mesa is formed, one or more mesas are laser machined mesas as described herein.

[0041] In one embodiment, the top layer on the high voltage electrode is made with a thickness of more than 1 mm and less than 3 mm to strengthen the top surface and reduce surface stresses of the AIN ESC. In one embodiment, the brazed high voltage connection is 2-4 mm from the top surface to reduce stresses. In one embodiment, the top layer on the electrode is made with high resistivity and high thermal shock resistance. In one embodiment, the microstructure design provides thermal shock resistance of 400 degrees or more.

[0042] Referring again to Figures 1A, 1B, 1C, 2A, and / or 2B, according to an embodiment of the present disclosure, a substrate support assembly includes a ceramic top plate having an upper surface with a processing region. One or more DC brazed connections are within 1-2 mm of a surface of the ceramic top plate. A plurality of mesas are within the processing region and on the upper surface of the ceramic plate. None of the plurality of mesas are vertically above the one or more DC brazed connections. In one embodiment, the one or more mesas are laser machined mesas, as described herein.

[0043] Referring again to Figures 1A, 1B, 1C, 2A, and / or 2B, according to another embodiment of the present disclosure, a substrate support assembly includes a ceramic top plate having an upper surface with a processing region. The upper surface has one or more high topography regions. A plurality of mesas are in the processing region and on the upper surface of the ceramic plate. None of the plurality of mesas is above the one or more high topography regions of the upper surface of the processing region or the high voltage electrode end. In one embodiment, the one or more mesas are laser machined mesas as described herein.

[0044] 1A, 1B, 1C, 2A, and / or 2B, according to another embodiment of the present disclosure, a substrate support assembly includes a ceramic top plate having a top surface with a processing region. The top surface has one or more high stress regions. A plurality of mesas are in the processing region and on the top surface of the ceramic plate. None of the plurality of mesas are in the one or more high stress regions of the top surface of the processing region. In one embodiment, the one or more mesas are laser machined mesas, as described herein.

[0045] FIG. 2C illustrates a cross-sectional view of an electrostatic chuck (ESC) including mesas in various positions according to another embodiment of the present disclosure.

[0046] 2C, ESC 270 includes central zone 272, main zone 274, DC rod 276, and ESC mesh 278. DC rod 276 may be in central location 280 as shown. ESC 270 further includes mesas such as mesas 282A, 282B, 282C, and 282D. Mesa 282A is on top of high voltage connection region 280, such as on top of DC rod 276. Mesa 282B is on top of the electrode end. Mesa 282C is in a non-electrode region. Mesa 282D is completely on top of the electrode. Mesas 282A, 282B, 282C, and 282D are at relatively shallow spacings above ESC mesh 278. Compared to FIG. 2A, in one embodiment, ESC 270 of FIG. 2C includes a molybdenum high voltage electrode mesh 278. Molybdenum high voltage electrode mesh 278 is joined to brazed nickel rod 276 a few mm (e.g., 1-4 mm) inside the ceramic by metal paste 290 through approximately 0.5 mm vias 292. In one such embodiment, this arrangement reduces stress at the top while maintaining electrical connection from the nickel rod to the molybdenum mesh through a fine layer of vertical paste at the horizontal mesh plane. In one embodiment, mesa 282D is at a relatively lower stress location than mesa 212D of FIG. 2A. In one embodiment, one or more mesas are laser machined mesas as described herein.

[0047] More generally, as an exemplary fabricated ESC, FIG. 3 illustrates a cross-sectional view of an electrostatic chuck (ESC) according to an embodiment of the present disclosure.

[0048] 3, the ESC 300 includes a ceramic bottom plate 302 having a heater coil 304. The heater coil 304 may be coupled to a heater connection 305. (It should be understood that in another embodiment, for tape cast AAIN or AAIN plate materials used for ESC fabrication, the heater electrodes are screen printed.) A shaft 306 is coupled to the bottom surface of the ceramic bottom plate 302. The ESC 300 also includes a ceramic top plate 308. The ceramic top plate 308 has an ESC (clamping) electrode 310 or electrode assembly. A layer 312, such as a metal layer or a diffusion bond layer, may be used to bond the ceramic top plate 308 to the top surface of the ceramic bottom plate 302. A thermocouple 314 extends through an opening 315 in the ceramic bottom plate 302 and the metal layer 312. A high voltage insulator 316 extends through an opening 315 in the ceramic bottom plate 302 and the metal layer 312 to house the ESC high voltage connection 318. Mesa-covered surface 399 may be a mesa surface manufactured according to the embodiments described above. In one embodiment, one or more mesas are laser machined mesas, as described herein.

[0049] 3 , in accordance with an embodiment of the present disclosure, the substrate support assembly 300 includes a ceramic bottom plate 302 having a heating element 304. The substrate support assembly 300 further includes a ceramic top plate 308 having an electrode 310. A metal layer 312 is between the ceramic top plate 308 and the ceramic bottom plate 302. The ceramic top plate 308 is in direct contact with the metal layer 312, which is in direct contact with the ceramic bottom plate 302.

[0050] The standard method of making an ESC is to hot press the plates together by bonding them together, followed by diffusion bonding the plates to the shaft. In an embodiment without diffusion bonding, the metal layer 312 provides the incorporation of a metal bond in place of a ceramic-to-ceramic diffusion bond that can otherwise change the resistivity of the top ceramic during diffusion bond formation. In an embodiment, the metal layer 312 is a metal foil, such as an aluminum foil. In one such embodiment, the metal layer 312 is an aluminum foil impregnated with about 2% to 20% silicon (e.g., as an atomic % of the foil composition), with the remainder being aluminum or substantially all aluminum (i.e., the aluminum foil includes silicon having an atomic concentration in the range of 2% to 20% of the aluminum foil). In an embodiment, the metal layer 312 is pre-patterned to include openings 315 and / or additional openings, for example to accommodate lift pins, etc. In an embodiment, the metal layer 312 is an aluminum foil having a thickness in the range of 50 to 500 microns, which may be about 250 microns. In one embodiment, the metal layer 312 is an aluminum foil and is cleaned prior to inclusion in the ESC manufacturing process, e.g., to remove a passivation layer prior to bonding. In one embodiment, the metal layer 312 is an aluminum foil and can survive a corrosion process, such as a chlorine-based process, without etching or degradation of the metal layer 312 when the ESC is in use. However, if used in a non-chlorine-based process, the metal layer 312 may be comprised of a silver-copper alloy, e.g., with or without the addition of titanium. In one embodiment, the metal layer 312 is bonded to the top plate 308 and bottom plate 302 at a temperature below 600° C., more preferably below 300° C. It should be appreciated that higher ESC operating temperatures, such as 650° C., can be used if the metal bond is performed with a high temperature metal bond, such as silver-copper or gold-nickel, that has a temperature much lower than 1400° C., but much higher than the operating temperature of 650° C.

[0051] Referring to the ceramic top plate 308 with ESC (clamping) electrode 310, in one embodiment, the body of the top plate may be formed by sintering a ceramic material, such as aluminum nitride (AlN), aluminum oxide powder, or other suitable material. An RF mesh may be embedded in the body. The RF mesh may have electrical connections that extend through the bottom surface of the body. The RF mesh may include a molybdenum or another suitable metallic material mesh around it. In one embodiment, the mesh is about 125 microns in diameter. The material may be sintered to form a monolithic structure. In one embodiment, the electrode 310 is fabricated from a metallic material, such as molybdenum, that may have a similar thermal expansion factor as the body. In one embodiment, the ceramic top plate 308 may include dopants to optimize the process for such a target temperature range, with a goal of maintaining a temperature below 350° C., for example between 150-300° C.

[0052] The clamping electrode 310 may include at least a first and a second electrode. During the process, a negative charge is applied to the first electrode and a positive charge is applied to the second electrode, or vice versa. This may generate an electrostatic force. During chucking, the electrostatic force generated from the electrodes holds the substrate in a fixed position. Because the power supplied from the power supply is cut off, the charge present at the interface between the electrodes may be maintained for a long period of time. To release the substrate held by the electrostatic chuck, a short power pulse of opposite polarity may be supplied to the electrodes, which removes the charge present at the interface.

[0053] The electrode assembly may be formed by a metal bar, sheet, stick, foil, or may be pre-poured, pre-cast, pre-fabricated, and placed on the surface of the insulating base during the manufacture of the electrostatic chuck. Alternatively, a metal deposition process may be performed to deposit and form the electrode assembly directly on the top surface of the insulating base. Suitable deposition processes may include PVD, CVD, plating, inkjet printing, rubber stamping, screen printing, or aerosol printing processes. In addition, a metal paste / metal line may be formed on the top surface of the insulating base. The metal paste / metal line may be initially a liquid, paste, or metal gel. These may be patterned on the target surface in a certain pattern to form electrode fingers with various configurations or dimensions on the top surface of the insulating base.

[0054] The ceramic top plate 308 or the ceramic bottom plate 302 may include, but are not limited to, aluminum nitride, glass, silicon carbide, aluminum oxide, yttrium-containing materials, yttrium oxide (YO), yttrium aluminum garnet (YAG), titanium oxide (TiO), or titanium nitride (TiN). With reference to the ceramic bottom plate 302, in one embodiment, the ceramic bottom plate 308 targets a temperature up to 650° C. and may include dopants to optimize the process for such target temperature range. In an embodiment, the ceramic bottom plate 302 has an aluminum nitride composition that is different from the aluminum nitride composition of the ceramic top plate 308. The heating element 304 included in the ceramic bottom plate 302 may utilize any suitable heating technique, such as resistive heating or inductive heating. The heating element 304 may be comprised of a resistive metal, a resistive metal alloy, or a combination of the two. Suitable materials for the heating element may include materials with high thermal resistance, such as tungsten, molybdenum, titanium, etc. In one embodiment, the heating element 304 is constructed of molybdenum wire. The heating element 304 may be fabricated using a material having thermal properties, such as, for example, a thermal expansion factor, that are substantially compatible with at least one or both of the aluminum nitride bodies, thereby reducing stresses caused by mismatched thermal expansion.

[0055] In one embodiment, the ceramic top plate 308 is fabricated and then bonded to the ceramic bottom plate with the metal layer 312 (which may already include one or more patterned openings). In one embodiment, the metal layer 312 is bonded to the ceramic top plate 308 at the same time that it is bonded to the ceramic bottom plate 302. In another embodiment, the metal layer 312 is first bonded to the ceramic top plate 308, and then the ceramic top plate / metal layer 312 combination is bonded to the ceramic bottom plate 302. In another embodiment, the metal layer 312 is first bonded to the ceramic bottom plate 302, and then the ceramic bottom plate / metal layer 312 combination is bonded to the ceramic top plate 308. In either case, in one particular embodiment, the ceramic top plate is formed from aluminum nitride (AlN) or aluminum oxide (Al2O3) powder and a sintered metal mesh.

[0056] In one embodiment, bonding the ceramic top plate 308 to the ceramic bottom plate 302 having the metal layer 312 includes heating the ceramic bottom plate 302, the metal layer 312, and the ceramic top plate 308 to a temperature less than 600° C. In one embodiment, the metal layer 312 is aluminum foil, and the method includes cleaning a surface of the aluminum foil to remove a passivation layer of the aluminum foil prior to bonding the ceramic top plate 308 to the ceramic bottom plate 302 having the metal layer 312.

[0057] In another aspect, FIG. 4 is a schematic cross-sectional view of a processing chamber 400 including a substrate support assembly 428, according to an embodiment of the present disclosure. In the example of FIG. 4, the processing chamber 400 is a plasma enhanced chemical vapor deposition (PECVD) chamber. As shown in FIG. 4, the processing chamber 400 includes one or more sidewalls 402, a bottom 404, a gas distribution plate 410, and a cover plate 412. The sidewalls 402, the bottom 404, and the cover plate 412 collectively define a processing space 406. The gas distribution plate 410 and the substrate support assembly 428 are distributed within the processing space 406. The processing space 406 is accessed through a sealable slit valve opening 408 formed through the sidewall 402, by which a substrate 405 can be transferred into and out of the processing chamber 400. A vacuum pump 409 is coupled to the chamber 400 to control the pressure within the processing space 406.

[0058] The gas distribution plate 410 is coupled around its periphery to a cover plate 412. A gas source 420 is coupled to the cover plate 412 and supplies one or more gases through the cover plate 412 to a number of gas passages 411 formed in the cover plate 412. The gases flow through the gas passages 411 into the process space 406 toward the substrate receiving surface 432.

[0059] An RF power source 422 is coupled to the cover plate 412 and / or directly to the gas distribution plate 410 by an RF power feed 424 to provide RF power to the gas distribution plate 410. Various RF frequencies can be used. For example, the frequency can be between about 0.3 MHz and about 200 MHz, such as about 13.56 MHz. An RF return path 425 couples the substrate support assembly 428 to the RF power source 422 through the sidewall 402. The RF power source 422 generates an electric field between the gas distribution plate 410 and the substrate support assembly 428. The electric field forms a plasma from the gas present between the gas distribution plate 410 and the substrate support assembly 428. The RF return path 425 completes the electrical circuit for the RF energy and prevents stray plasma from causing RF arcing due to voltage differences between the substrate support assembly 428 and the sidewall 402. Thus, the RF return path 425 mitigates arcing that can cause process drift, particle contamination, and damage to chamber components.

[0060] The substrate support assembly 428 includes a substrate support 430 and a stem 434. The stem 434 is coupled to a lift system 436 adapted to raise and lower the substrate support assembly 428. The substrate support 430 includes a substrate receiving surface 432 for supporting the substrate 405 during processing. Lift pins 438 are movably disposed through the substrate support 430 to move the substrate 405 toward and away from the substrate receiving surface 432 to facilitate substrate transfer. The actuator 414 is used to extend and retract the lift pins 438. The ring assembly 433 may be disposed around the periphery of the substrate 405 during processing. The ring assembly 433 is configured to prevent or reduce undesired deposition on surfaces of the substrate support 430 that are not covered by the substrate 405 during processing.

[0061] The substrate support 430 may further include heating and / or cooling elements 439 to maintain the substrate support 430 and substrate 405 disposed thereon at a desired temperature. In one embodiment, the heating and / or cooling elements 439 may be used to maintain the temperature of the substrate support 430 and substrate 405 disposed thereon at about 800° C. or less during processing. In an embodiment, the heating and / or cooling elements 439 may be used to control the temperature of the substrate to less than 650° C., such as between 300° C. and about 400° C. In one embodiment, the substrate support 430 / substrate support assembly 428 is as described above.

[0062] In another aspect, FIG. 5 is a schematic partial cross-sectional view of a processing chamber 500 including a substrate support assembly 300, according to an embodiment of the present disclosure. The processing chamber 500 has a body 501. The body has a sidewall 502, a bottom 504, and a showerhead 512. The sidewall 502, the bottom 504, and the showerhead 512 define an interior space 506. In one embodiment, the substrate support assembly 300 is disposed within the interior space 506, as described above. An RF generator 580 may be coupled to an electrode 582 within the showerhead 512. The RF generator 580 may have an associated RF return path 588 for completing an RF circuit when a plasma is present. Advantageously, an RF ground path for sustaining the plasma may be maintained to provide a long life for the substrate support assembly 300.

[0063] In one embodiment, the semiconductor wafer or substrate supported by the substrate support assembly 300 is composed of a material suitable for withstanding manufacturing processes and on which semiconductor processing layers may be appropriately disposed. For example, in one embodiment, the semiconductor wafer or substrate is composed of a Group IV based material, such as, but not limited to, crystalline silicon, germanium, or silicon / germanium. In a specific embodiment, the semiconductor wafer comprises a single crystal silicon substrate. In one particular embodiment, the single crystal silicon substrate is doped with impurity atoms. In another embodiment, the semiconductor wafer or substrate is composed of a III-V material.

[0064] An embodiment of the present invention may be provided as a computer program product or software that may include a machine-readable medium having instructions stored thereon that may be used to program a computer system (or other electronic device) to perform processes according to embodiments of the present invention. In an embodiment, the computer system is coupled to the process chamber 400 and the substrate support assembly 428 as described above in connection with FIG. 4, or to the process chamber 500 and the substrate support assembly 300 as described in connection with FIG. 5. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., computer) readable storage medium (e.g., read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.), a machine (e.g., computer) readable transmission medium (in electrical, optical, acoustic, or other form of propagated signal (e.g., infrared signal, digital signal, etc.)), etc.

[0065] FIG. 6 illustrates a schematic diagram of an exemplary form of a machine, a computer system 600, within which a set of instructions may be executed to cause the machine to perform any one or more of the methods described herein. In alternative embodiments, the machine may be connected (e.g., networked) to other machines in a local area network (LAN), an intranet, an extranet, or the Internet. The machine may operate in the capacity of a server or a client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile phone, a web appliance, a server, a network router, a switch, or a bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify operations to be performed by the machine. Additionally, although only a single machine is shown, the term "machine" may be interpreted to include any collection of machines (e.g., a computer) that individually or together execute a set (or sets) of instructions to perform any one or more of the methods described herein.

[0066] The exemplary computer system 600 includes a processor 602, a main memory 604 (e.g., read only memory (ROM), flash memory, dynamic random access memory (DRAM) (Synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM)), etc.), a static memory 606 (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory 618 (e.g., a data storage device), which communicate with each other via a bus 630.

[0067] Processor 602 represents one or more general-purpose processing devices, such as a microprocessor, a central processing unit, or the like. More specifically, processor 602 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or a processor implementing a combination of instruction sets. Processor 602 may also be one or more special-purpose processing devices, such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, or the like. Processor 602 is configured to execute processing logic 626 to perform the operations described herein.

[0068] Computer system 600 may further include a network interface device 608. Computer system 600 may also include a video display unit 610 (e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 612 (e.g., a keyboard), a cursor control device 614 (e.g., a mouse), and a signal generating device 616 (e.g., a speaker).

[0069] The secondary memory 618 may include a machine-accessible storage medium (or, more specifically, a computer-readable storage medium) 632 on which one or more sets of instructions (e.g., software 622) are stored that embody any one or more of the methods or functions described herein. The software 622 may reside, completely or at least partially, within the main memory 604 and / or the processor 602 during execution by the computer system 600. The main memory 604 and the processor 602 also constitute machine-readable storage media. The software 622 may further be transmitted or received over the network 620 via the network interface device 608.

[0070] While in the exemplary embodiment, the machine-accessible storage medium 632 is shown as a single medium, the term "machine-readable storage medium" should be interpreted to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store one or more sets of instructions. The term "machine-readable storage medium" should be interpreted to include any medium capable of storing or encoding a set of instructions that are executed by a machine and that cause the machine to perform any one or more of the methods of the present disclosure. Thus, the term "machine-readable storage medium" should be interpreted to include, but is not limited to, solid-state memories, optical media, and magnetic media.

[0071] Thus, an electrostatic chuck (ESC) for a reactor or plasma processing chamber and a method for manufacturing the ESC have been disclosed.

Claims

1. 1. A method of manufacturing a substrate support assembly, comprising: providing a ceramic top plate having an upper surface with a processing region; forming a plurality of mesas within the processing region and on the top surface of the ceramic plate; laser machining one or more of the plurality of mesas to reduce a surface roughness of the one or more of the plurality of mesas; A method comprising:

2. The method of claim 1 , wherein reducing the surface roughness comprises reducing the surface roughness from an Ra value of 8-12 microns to an Ra value of 1-4 microns.

3. 2. The method of claim 1 , wherein reducing the roughness of the surface of the one or more of the plurality of mesas comprises forming rounded corners on the one or more of the plurality of mesas.

4. The method of claim 1 , wherein the plurality of mesas are contiguous with the upper surface of the ceramic top plate.

5. The method of claim 1 , wherein the one or more of the plurality of mesas is less than all of the plurality of mesas.

6. The method of claim 1 , wherein the ceramic top plate comprises aluminum nitride.

7. The method of claim 1 , wherein the ceramic top plate comprises aluminum oxide.

8. The method of claim 1 , further comprising forming one or more electrodes in the ceramic top plate.

9. 1. A method of manufacturing a substrate support assembly, comprising: providing a ceramic top plate having an upper surface with a processing region; forming a plurality of mesas within the processing region and on the top surface of the ceramic plate; laser machining one or more of the plurality of mesas to increase a surface roughness of the one or more of the plurality of mesas; A method comprising:

10. 10. The method of claim 9, wherein increasing the surface roughness comprises increasing the surface roughness from an Ra value of 1-4 microns to an Ra value of 8-12 microns.

11. 10. The method of claim 9, wherein reducing the surface roughness of the one or more of the plurality of mesas comprises forming sharp corners on the one or more of the plurality of mesas.

12. The method of claim 9 , wherein the plurality of mesas are contiguous with the upper surface of the ceramic top plate.

13. The method of claim 9 , wherein the one or more of the plurality of mesas is less than all of the plurality of mesas.

14. The method of claim 9 , wherein the ceramic top plate comprises aluminum nitride.

15. The method of claim 9 , wherein the ceramic top plate comprises aluminum oxide.

16. The method of claim 9 , further comprising forming one or more electrodes in the ceramic top plate.

17. 1. A substrate support assembly comprising: a ceramic top plate having an upper surface with a processing area; one or more DC brazed connections in the ceramic top plate; one or more electrodes in the ceramic top plate; and A plurality of mesas within the processing region and on the top surface of the ceramic plate. Equipped with A substrate support assembly, wherein one or more of the mesas are laser machined mesas.

18. 20. The substrate support assembly of claim 17, wherein none of the plurality of mesas is vertically above the one or more DC brazed connections or vertically above an edge of one of the one or more electrodes.

19. The method of claim 17 , wherein the plurality of mesas are contiguous with the upper surface of the ceramic top plate.

20. The substrate support assembly of claim 17 , wherein the ceramic top plate comprises aluminum nitride.

21. The substrate support assembly of claim 17 , wherein the ceramic top plate comprises aluminum oxide.

22. The substrate support assembly of claim 17 , wherein the one or more electrodes comprise molybdenum.

Images