KR20050054950A - Electrostatic chuck having a low level of particle generation and method of fabricating same - Google Patents

Abstract

An electrostatic chuck having either a conformal or non-conformal coating upon a surface for supporting a substrate. The coating reduces a number of particles generated by the electrostatic chuck.

Description

ELECTROSTATIC CHUCK HAVING A LOW LEVEL OF PARTICLE GENERATION AND METHOD OF FABRICATING SAME

The present invention relates generally to a substrate support chuck for supporting a product such as a semiconductor wafer in a semiconductor wafer processing system. In particular, the present invention relates to an electrostatic chuck for electrostatically clamping a semiconductor wafer to the chuck surface while processing the wafer.

The electrostatic chuck is used to hold the semiconductor wafer, or other product, in a fixed position during processing in the semiconductor wafer processing system. The electrostatic chuck can operate in a vacuum chamber in which a vacuum chuck can be used, providing more uniform clamping and better usability of the wafer surface than a mechanical chuck. The electrostatic chuck includes a chuck body having one or more electrodes in the body. The chuck body is typically formed of aluminum nitride, alumina doped with a metal oxide such as titanium oxide (Ti0 ₂ ), or other ceramic material having similar mechanical and resistive properties. In use, the wafer is clamped to the support surface of the electrostatic chuck as a chucking voltage is applied to the electrodes. The support surface can have grooves, mesas, openings, recessed regions and similar features that can be coated with polyimide, alumina, aluminum-nitride, and similar dielectric materials.

The clamped wafer backside has a physical contact with the support surface of the electrostatic chuck. Contact between the wafer and the support surface of the electrostatic chuck results in particulate generation that contaminates the processing chamber of the semiconductor wafer processing system. In addition, the movement of the wafer relative to the support surface of the chuck causes the generation of particulates. This movement always occurs during the chucking or dechucking process of the wafer, the heating or cooling cycle, and similar processes (eg, due to differences in the coefficients of thermal expansion of the wafer and the chuck body material).

Another source of particulate generation is in the support surface defects of the electrostatic chuck. In the prior art, either the support surface or one of the dielectric coating (s) on the support surface generally includes defects such as micro cracks, pinholes and pores. These defects accumulate particulates that are buried on the support surface during the manufacturing process (eg lapping, grinding, polishing, etc.) or during maintenance of the electrostatic chuck. In use, during wafer processing, these particulates are released into the semiconductor wafer processing system.

Particulates generated or released from the electrostatic chuck contaminate the wafer and damage the device on the wafer. During production of semiconductor devices, reduced yields from particulates of either of these causes are major limitations in achieving high productivity.

Therefore, there is a need for a technique for an electrostatic chuck with low particle generation.

1 is a vertical sectional view of a first embodiment of an electrostatic chuck of the present invention;

1A is a detailed cross-sectional view of region 1A of FIG. 1;

FIG. 1B is a detailed cross-sectional view of region 1B of FIG. 1; FIG.

2 is a top plan view showing a mesa pattern of the second embodiment of the electrostatic chuck of the present invention;

3 is a vertical sectional view of a second embodiment of the electrostatic chuck of FIG. 2;

3A is a detailed cross-sectional view of region 3A of FIG. 3;

3B is a cross-sectional view of another optional embodiment of the present invention;

3C is a cross-sectional view of an alternative embodiment of the present invention; And

4 illustrates an exemplary application for the electrostatic chuck of the present invention in an ion implanter semiconductor wafer processing system.

For the sake of understanding, the same reference numerals have been used where possible to refer to the same members in common in the drawings.

It is to be understood, however, that the appended drawings illustrate only typical embodiments of this invention and are not intended to limit the scope thereof, and that the present invention may permit other equivalent effective embodiments.

Generally, the present invention is applied to a wafer support surface of a non-conformal coating of poly-para-xylylene or a chuck applied to a wafer support surface of an electrostatic chuck and a chuck with low particle generation. A method of making a chuck using a conformal coating of diamondoid carbon material. The coating conceals the fine particles embedded in the support surface of the chuck to reduce the number of particulates generated during the physical contact between the wafer and the chuck. The surface of the non-conformal coating has a roughness lower than the roughness of the lower wafer support surface. In optional embodiments, the edges of the support surface, mesa, and other features with physical contacts with the wafer are rounded or planarized prior to coating.

The description of the present invention will be readily understood with reference to the following detailed description in conjunction with the accompanying drawings.

In general, the present invention relates to an electrostatic chuck with low particle generation and a method of manufacturing the chuck. The electrostatic chuck of the present invention includes a non-conformal coating of dielectric material provided on the wafer support surface of the chuck. Non-conformal coatings are in particular polymer manufacturers such as poly-para-xylene (e.g. Parylene C), which are readily available from Union Carbide Corporation of Danbury, Connecticut and Advanced Coatings of Rancho Cucamonga, CA. It is formed of a substance. Such materials have very low permeability to moisture and other corrosive gases. Generally, non-conformal coated surfaces have no microcracks, pinholes, pores, or the like. In general terms, the non-conformal coating is attached to a relatively rough lower surface (eg, the support surface of the electrostatic chuck) and has a surface that is considerably flatter than the lower surface. In addition, the non-conformal coating prevents the particulates from being released into the semiconductor wafer processing system while using the chuck to effectively "buries" the particulates embedded in the defects of the support surface. Non-conformal coatings can be provided using conventional methods such as vacuum deposition.

In a second embodiment of the invention, a conformal coating of dielectric material is provided on the wafer support surface of the chuck. The conformal coating is formed of diamond-like carbon available from Diamonex Coating, Allentown, Pennsylvania. Diamond-like carbon-materials have a low coefficient of friction and are durable. As such, this coating minimizes particulate generation and mitigates the possibility of scratches on the wafer backside.

1 is a vertical cross-sectional view of the first embodiment of the electrostatic chuck 100 of the present invention, and FIGS. 1A and 1B are detailed cross-sectional views of FIGS. To better understand this embodiment, reference should be made to FIGS. 1 and 1A and 1B simultaneously. The cross section shown in FIG. 1 is obtained along the center line. The chuck 100 includes a chuck body 102 with an electrode 104 embedded therein, a support surface 106, a peripheral edge 118, and an optional conduit 114. Body 102 includes a plurality of conduits 114 formed in chuck body 102, lift pins, and openings for similar purposes on the backside of wafer 112 to provide access to backside gas. To prevent backside gas leakage, the support surface 106 has a continuous rise (not shown) near the edge 118 to seal the space between the wafer 112 and the support surface 106. The support surface 106 may include other features such as grooves, openings, recessed or raised areas, and the like (not shown). The use of such features for chucking, dechucking, backside heating and cooling improvement of wafer 112 is known.

Generally, however, the support surface 106 is a planar surface, which can be convex or concave to substantially fit the wafer 112. 1 and 1A, 1B, coating 110 is optionally shown as extending over peripheral edge 118 toward sidewall surface 116. In this optional embodiment, the coating 110 "burys" a defect in the chuck body 102, which may be embedded with particulates. In one embodiment, layer 110 is formed of poly-para-xylene (available from Union Carbide Corporation under the name PARYLENE C). The non-conformal layer 110 has an inner surface 120 and an outer surface 122. The inner surface 120 is attached to the lower support surface 106 and has the same roughness as the surface 106. However, the outer surface 122 is considerably flatter than the support surface 106 (ie, has a low roughness, such as about 0.2-0.01 RA m). As such, the dielectric coating is considered “non-conformal” because the outer surface of the coating supporting the wafer does not follow the roughness of the lower support surface of the chuck. In turn, when used, the contact between the wafer 112 and the outer surface 122 generates less particulates than the contact between the wafer 112 and the support surface 106 generates. To further reduce particulate generation during use of the electrostatic chuck 100, the area along the entire coating 110 or the peripheral edge 118, the edge (s) of the conduit (s) 114 and the wafer 112. Other features having physical contacts with the back side may be rounded or planarized using a process such as chemical etching, mechanical polishing or CMP, laser melting or the like (not shown).

2 is a top view of an exemplary pattern for the support surface 106 of the second embodiment of the present invention. In this embodiment, the support surface 106 of the electrostatic chuck 200 includes a plurality of mesas 202 supporting the wafer 112 or other product in spaced relation relative to the support surface 106. The spacing between the back surface of the wafer 112 and the support surface 106 is defined by the thickness of the mesa. The mesa may be properly positioned on the support surface 106 to improve the performance of the electrostatic chuck, such as chucking, dechucking, wafer temperature control, and the like. In FIG. 2, mesa 202 is shown to be located along concentric circles 204, 206. In general, the mesa 202 is formed as individual pads having a thickness between 5 and 350 m and dimensions between 0.5 and 5 mn in plan view. However, in the prior art, mesas are known which have a shape other than circular pads and have vertical or inclined walls. In general, the mesa is formed of the same material as, for example, the chuck body of AlN. Optionally, the mesa may be formed of other materials such as Si ₃ N ₄ , SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , SiC, polyimide, and the like. The method for producing the mesa is commonly assigned US Patent No. 1, issued May 11, 199. 5,903,428.

FIG. 3 shows a vertical cross sectional view of the electrostatic chuck 200 of FIG. 2 and FIG. 3A provides a detailed cross sectional view of FIG. 3 region 3A. To better understand this embodiment of the present invention, reference should be made to FIGS. 3 and 3A simultaneously. 3 is a cross-sectional view taken along the centerline 3-3 of FIG. 2. In this embodiment, the non-conformal layer 110 is formed over a mesa 202 having a wafer 112, a wall surface 304, and an upper surface 302 having an edge 308. 3 and 3A, the mesa 202 is shown having a generally flat upper surface 302 and vertical sidewalls 304. Other shaped sidewalls or surfaces may be used. The inner surface 120 of the non-conformal layer 110 adheres along the lower surfaces 106, 302, 304 and has the same roughness as those surfaces. To enhance the adhesion of the non-conformal layer 110 to the bottom surfaces 106, 302, 304, the surfaces 106, 302, 304 may be plasma cleaned prior to providing a coating. The outer surface 122 of the non-conformal layer 110 is considerably flatter than the surfaces 106, 302, 304. In particular, the portion of the non-conformal layer 110 located on the top surface 302 of the mesa 202 has a lower roughness than the underlying top surface 302. In turn, in use, the contact between the wafer 112 and the mesa 202 with the coating 110 generates less particulates than would occur with the contact between the wafer 112 and the top surface 302. To further reduce particulate generation during use of the electrostatic chuck 200, the area along the entire coating 110 or the peripheral edge 118, the edge 308, the edge (s) of the conduit (s) 114, and Other features having physical contacts with the backside of the wafer 112 may be rounded or planarized (as shown by dashed line 350) using processes such as chemical etching, laser melting, mechanical polishing or CMP, and the like.

3B shows a cross section of an alternative embodiment of the present invention. In the present invention, one or more mesa 322 edges 308 are intentionally rounded or planarized prior to providing the non-conformal layer 110. In another embodiment, the entire top surface of mesa 322 is rounded or planarized (not shown). Edge 308 of mesa 322 may be shaped using a process such as a computer-controlled router with a diamond-coated head, chemical etching, grinding, grit blasting, or the like. Similarly, the roughness of the outer surface 122 can be further reduced using a process such as chemical etching, mechanical polishing or CMP. In use, the electrostatic chuck of this embodiment of the present invention provides a greater reduction in the number of particulates generated during contact between wafer 112 and top surface 122 than a chuck including mesas having sharp edges.

In certain exemplary embodiments, a non-conformal coating is formed from poly-para-xylene and provided to a support surface of an electrostatic chuck suitable for holding 12 mm (300 mm) wafers. The chuck body is made of ceramic material such as aluminum nitride. The support surface has a roughness of about 0.2-0.01 RAm. The coating is provided to a thickness between 5 and 10 m using a vacuum deposition process.

Generally free of defects such as microcracks, pinholes, pores, poly-para-xylylene coatings may be used in the defects of the support surface during the manufacture of the electrostatic chuck or prior to the provision of the non-conformal coatings of the present invention. It hides the particles that are stuck in it. Thus, these "buried" particulates are blocked from penetrating into the processing chamber of the semiconductor wafer processing system. In addition, defects in the support surface of the electrostatic chuck can accumulate particulates during normal maintenance of the chuck (eg, chemical and / or mechanical cleaning of sub-byproducts of deposition and wafer processing). However, the poly-para-xylene coating surface has a low roughness that does not retain loose particulates that can result in maintenance procedures. Thus, poly-para-xylene coatings reduce the number of particulates generated by the electrostatic chuck during physical contact and during chuck maintenance during use in relative motion between the support surface and the wafer.

Poly-para-xylene coatings are stable in a non-plasma environment that can be exposed to a wide range of temperatures and most plasma and semiconductor wafer processing systems. Similarly, the coating is compatible with back heaters or means used to control the temperature of the chucked wafer, such as gases, infrared (IR) or ultraviolet (UV) radiation, and the like. The coating forms strong bonds with ceramic materials (eg, aluminum nitride, alumina doped with metal oxides such as titanium oxide (TiO ₂ ), etc.) used to form the body of the electrostatic chuck. This coupling force forms one of the features having a flat, convex or concave surface and sharp edges (eg, mesas, grooves, openings, etc.). The poly-para-xylene coating has a bulk resistivity of about (6-8) × 10 ¹⁶ ohms, which is about 10 ² -10 ⁶ times greater than that of other materials forming an electrostatic chuck. As such, the coating does not increase the current induced by the electrodes of the chuck.

Optionally, as shown in FIG. 3C, mesa 202 (or flat chuck surface of FIG. 1) is coated with conformal coating 380. An example of a conformal coating that is durable and has a low coefficient of friction is diamond-like carbon. Diamond-like carbon is available from Allentown Diamonex Coatings, Pennsylvania. Durability and low coefficient of friction reduce the likelihood that contact between the wafer and mesa will generate particulates.

As shown in FIG. 3C, the conformal coating 380 has an interior surface 384 associated therewith along the rough surface 304 of the chuck 102. The outer surface 382 of the conformal coating 380 closely matches the roughness of the chuck surface. As such, prior to coating, mesa 202 is removed using, for example, plasma etching. Those skilled in the art will recognize various techniques that can be used for the removal or planarization of the mesa surface.

4 particularly discloses the electrostatic chuck of the present invention for securing a wafer in an ion implanter semiconductor wafer processing system 400. System 400 includes a vacuum chamber 460, ion generator 462, electrostatic chuck 164, backside gas source 466, and control electronics 402. Although the present invention has been disclosed by way of example for an ion implantation system, the present invention can be conventionally applied to other semiconductor wafer processing systems in which an electrostatic chuck is used to hold the wafer in the processing chamber.

The wafer 112 is positioned vertically so that all positions on the wafer 112 can be exposed to the ion beam while the other source of ions for ion implantation generated by the ion beam or ion generator 462 is scanned horizontally. . Electrostatic chuck 464 is disposed in chamber 460. The electrostatic chuck 464 includes a pair of coplanar electrodes 410 embedded in the chuck body 412 forming a support surface 434 on the electrostatic chuck 464 holding the wafer 112. . The electrostatic chuck 464 forms a sufficient suction force for the chuck to rotate from the horizontal position to the vertical position without moving the wafer 112 relative to the support surface 434.

The chuck body 412 collects heat transfer gas or gases, such as helium, which is supplied to the interstitial space between the support surface 434 and the wafer 112 to facilitate heat transfer from the backside gas source 466. Permit passage 468 is included. The mesa may be located on the support surface 434, for example, to promote a uniform temperature across the wafer or to produce a specific temperature change across the wafer.

Exemplary chuck 464 for use with an ion implanter is hereby incorporated by reference in its entirety herein, on March 28, 2001, at Coliing Gasd Delivery System for a Rotatable Semiconductor Substrate. It is shown and disclosed in US Patent Application No. 09 / 820,497, filed under "Support Assembly." The patent application discloses a rotary wafer support assembly (eg, a chuck) having a rotary shaft coupled to the chuck and a housing disposed on the shaft. The shaft, housing and multiple seals form part of a gas delivery system for providing cooling gas (eg, helium) to the wafer.

As another example, a chuck 464 for use with an ion implanter is shown in US Pat. No. 6,207,959, entitled “Ion Implanter”, which is incorporated herein by reference in its entirety, and is commonly assigned to Applied Materials, Inc. of Santa Clara, California. Is disclosed. The patent discloses an injector having a scanning arm assembly that allows rotation of a wafer holder (eg, an electrostatic chuck) near the wafer axis. It is noted here that a vacuum robot is provided in the chamber for removing the processed wafer from the wafer holder (eg, the chuck) and delivering a new wafer to the wafer holder. As such, in this example of an ion implanter processing system, their respective lift pin passages and lift pin actuators 428 (exemplarily shown in FIG. 4) through lift pins and chucks are such that the ion implanter semiconductor wafer processing system 400 is provided. Not required).

The control circuit 402 includes a DC power supply 404, a metric measuring device 470, and a computer device 406. DC power supply 404 provides a voltage to electrode 410 to retain (ie, “chuck”) wafer 112 on surface 434 of the chuck. The chucking voltage provided by the power supply 404 is controlled by the computer 406. Computer 406 is a general-purpose programmable computer system including a conventional support circuit 416 and a central processing unit (CPU) 414 coupled to memory circuits 418 such as ROM and RAM. The computer 406 is also coupled to the metric measurement device 470, which is coupled to the flow sensor 472 of the gas supplied by the backside gas source 466. Computer 406 monitors and regulates gas flow to the chuck in response to measurement readings from flow sensor 472.

As described above, in one embodiment chuck 464 includes a non-conformal coating of poly-para-xylene. In another embodiment, chuck 464 is coated with a conformal coating of diamondoid carbon. Thus, the coated chuck 464 according to either embodiment not only promotes improved wafer processing but also provides low particulate generation without worrying about the backside structure shape of the wafer 112. Briefly, the present invention provides the various advantages mentioned above for semiconductor processing systems, in particular ion implanter systems.

While various embodiments have been shown and described in the Detailed Description of the Invention, those skilled in the art will recognize that various other modifications may be made in addition to the above description.

Claims (38)

An electrostatic chuck that electrostatically supports the product, A chuck body having a support surface for supporting the product; And And a poly-para-xylene coating disposed on the support surface. The method of claim 1, And said coating has a thickness between 5 and 100 microns. The method of claim 1, Wherein said coating has a roughness of about 0.2-0.01 RA microns. The method of claim 1, The surface roughness of the coating is lower than the roughness of the support surface. The method of claim 1, And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 5, And the mesa edge is rounded. The method of claim 5, And the roughness of the coating on the upper surface of the mesa is about 0.2-0.01 RA microns. The method of claim 1, And the coating is a non-conformal coating. An electrostatic chuck manufacturing method for electrostatically supporting a product, Providing an electrostatic chuck having a support surface and Depositing a poly-para-xylene coating on the support surface. The method of claim 9, Wherein said coating has a thickness between 5 and 100 microns. The method of claim 9, Wherein the coating has a roughness of about 0.2-0.01 RA microns. The method of claim 9, The surface roughness of the coating is lower than the roughness of the support surface. The method of claim 9, And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 13, And said mesa edge is rounded. The method of claim 13, And roughness of the coating on the upper surface of the mesa is about 0.2-0.01 RA microns. A semiconductor wafer processing system, Process chambers; A substrate support pedestal positioned in the process chamber to support a substrate for processing in the process chamber, the substrate support pedestal having a support surface and an electrostatic chuck having a poly-para-xylene coating on the support surface. Semiconductor wafer processing system. The method of claim 16, The process chamber further comprises an ion beam source of ions and performing an ion implantation process on the substrate. The method of claim 16, And the coating has a thickness between 5 and 100 microns. The method of claim 16, And the coating has a roughness of about 0.2-0.01 RA microns. The method of claim 16, And the surface roughness of the coating is less than the roughness of the support surface. The method of claim 16, And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 21, And the edge of the mesa is rounded. The method of claim 21, And roughness of the coating on the top surface of the mesa is about 0.2-0.01 RA microns. An electrostatic chuck that electrostatically supports the product, A chuck body having a support surface for supporting the product; And And a diamond-like carbon coating disposed on said support surface. The method of claim 24, And said coating has a thickness between 5 and 100 microns. The method of claim 24, And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 26, And the edges of the mesa are rounded. The method of claim 24, And said coating is a conformal coating. An electrostatic chuck manufacturing method for electrostatically supporting a product, Providing an electrostatic chuck having a support surface; And Depositing a diamond-like carbon coating on the support surface. The method of claim 29, Wherein the coating has a thickness between 5 and 10 microns. The method of claim 29, And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 31, wherein And said mesa edge is rounded. A semiconductor wafer processing system, Process chambers; A semiconductor support pedestal disposed in the process chamber to support a substrate for processing in the process chamber, the substrate support pedestal having a support surface and an electrostatic chuck having a diamond shaped carbon coating on the support surface; Wafer processing system. The method of claim 33, wherein The process chamber further comprises an ion beam source of ions and performing an ion implantation process on the substrate. The method of claim 33, wherein And the coating has a thickness between 5 and 100 microns. The method of claim 33, wherein And the surface roughness of the coating is lower than that of the support surface. The method of claim 33, wherein And said support surface comprises a plurality of mesas having an upper surface and an edge and protruding from said support surface. The method of claim 37, And the mesa edge is rounded.