Abstract:
The present invention is directed to a top surface of a workpiece surface influencing device and a method of using the same. The top surface of the workpiece surface influencing device is adapted for use in an electrochemical mechanical processing apparatus in which a solution becomes disposed onto a conductive surface of a workpiece and electrochemical mechanical processing of the conductive surface is performed while relative movement and physical contact exists between the top surface and the conductive surface. The top surface comprises a ceramic material that presents a substantially planar contact area to the conductive surface, the ceramic material having a hardness greater than that of the conductive surface. A plurality of channels are formed through the top surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/302,755, filed Nov. 21, 2002, now U.S. Pat. No. 7,204,917, which claims priority to U.S. Provisional Application No. 60/331,783 filed Nov. 21, 2001. U.S. patent application Ser. No. 10/302,755 is a continuation-in-part of U.S. patent application Ser. No. 10/165,673 filed Jun. 6, 2002, now U.S. Pat. No. 6,837,979, which is a divisional of U.S. patent application Ser. No. 09/373,681, filed Aug. 13, 1999, now U.S. Pat. No. 6,409,904, which is a continuation-in-part application of U.S. patent application Ser. No. 09/201,929, filed Dec. 1, 1998, now U.S. Pat. No. 6,176,992, and U.S. patent application Ser. No. 09/285,621, filed Apr. 3, 1999, now U.S. Pat. No. 6,328,872. The disclosures of the foregoing applications and patents are hereby incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to manufacture of semiconductor integrated circuits and, more particularly to a method for planar deposition or etching of conductive layers. 
     BACKGROUND OF THE INVENTION 
     Conventional semiconductor devices generally include a semiconductor substrate, usually a silicon substrate, and a plurality of sequentially formed dielectric interlayers such as silicon dioxide and conductive paths or interconnects made of conductive materials. Copper and copper alloys have recently received considerable attention as interconnect materials because of their superior electromigration and low resistivity characteristics. The interconnects are usually formed by filling copper in features or cavities etched into the dielectric interlayers by a metallization process. The preferred method of copper metallization process is electroplating. In an integrated circuit, multiple levels of interconnect networks laterally extend with respect to the substrate surface. Interconnects formed in sequential interlayers can be electrically connected using vias or contacts. 
     In a typical process, first an insulating interlayer is formed on the semiconductor substrate. Patterning and etching processes are performed to form features such as trenches and vias in the insulating layer. Then, copper is electroplated to fill all the features. However, the plating process results in a thick copper layer on the substrate some of which need to be removed before the subsequent step. Conventionally, after the copper plating, CMP process is employed to globally planarize or reduce the thickness of the copper layer down to the level of the surface of the insulation layer. However, CMP process is a costly and time consuming process that reduces production efficiency. 
     The adverse effects of conventional material removal technologies may be minimized or overcome by employing an Electrochemical Mechanical Processing (ECMPR) approach that has the ability to provide thin layers of planar conductive material on the workpiece surface, or even provide a workpiece surface with no or little excess conductive material. The term of Electrochemical Mechanical Processing (ECMPR) is used to include both Electrochemical Mechanical Deposition (ECMD) processes as well as Electrochemical Mechanical Etching (ECME), which is also called Electrochemical Mechanical Polishing. It should be noted that in general both ECMD and ECME processes are referred to as electrochemical mechanical processing (ECMPR) since both involve electrochemical processes and mechanical action. 
       FIG. 1  shows an exemplary conventional ECMPR system  2 , which system  2  includes a workpiece-surface-influencing device (WSID)  3  such as a mask, pad or a sweeper, a carrier head  4  holding a workpiece  5  and an electrode  6 . The workpiece-surface-influencing-device (WSID) is used during at least a portion of the electrotreatment process when there is physical contact or close proximity and relative motion between the workpiece surface and the WSID. Surface of the WSID  3  sweeps the surface of the workpiece  5  while an electrical potential is established between the electrode  6  and the surface of the workpiece. Channels  7  of the WSID  3  allow a process solution  8  such as an electrolyte to flow to the surface of the workpiece  5 . If the ECMD process is carried out, the surface of the workpiece  5  is wetted by a deposition electrolyte which is also in fluid contact with the electrode (anode) and a potential is applied between the surface of the workpiece and the electrode rendering the workpiece surface cathodic. If the ECME process is carried out, the surface of the workpiece  5  is wetted by the deposition electrolyte or a special etching electrolyte, which is also in fluid contact with an electrode (cathode) and a potential is applied between the surface of the workpiece and the electrode rendering the workpiece surface anodic. Thus etching takes place on the workpiece surface. Very thin planar deposits can be obtained by first depositing a planar layer using an ECMD technique and then using an ECME technique on the planar film in the same electrolyte by reversing the applied voltage. Alternately, the ECME step can be carried out in a separate machine and a different etching electrolyte. The thickness of the deposit may be reduced in a planar manner. 
     Descriptions of various planar deposition and planar etching methods i.e. ECMPR approaches and apparatus can be found in the following patents and pending applications, all commonly owned by the assignee of the present invention. U.S. Pat. No. 6,126,992 entitled “Method and Apparatus for Electrochemical Mechanical Deposition.” U.S. application Ser. No. 09/740,701 entitled “Plating Method and Apparatus that Creates a Differential Between Additive Disposed on a Top Surface and a Cavity Surface of a Workpiece Using an External Influence,” filed on Dec. 18, 2001, and application Ser. No. 09/169,913 filed on Sep. 20, 2001, entitled “Plating Method and Apparatus for Controlling Deposition on Predetermined Portions of a Workpiece”. These methods can deposit metals in and over cavity sections on a workpiece in a planar manner. They also have the capability of yielding novel structures with excess amount of metals selectively over the features irrespective of their size, if desired. 
     The surface of the WSID preferably contains hard-abrasive material for efficient sweeping. U.S. application Ser. No. 09/960,236 filed on Sep. 20, 2001, entitled “Mask Plate Design,”,U.S. Provisional Application Ser. No. 60/326,087 filed on Sep. 28, 2001, entitled “Low Force Electrochemical Mechanical Processing Method and Apparatus,” and U.S. application Ser. No. 10/155,828 filed May 23, 2002, all of which are assigned to the same assignee as the present invention, disclose various workpiece-surface-influencing device embodiments. 
     Fixed abrasive sheets or pads, which are supplied by companies such as 3M and which are commonly used in CMP applications, work efficiently on WSID surfaces. Such abrasive sheets are generally comprised of abrasive composites that have a discernible precise shape such as pyramidal or cylindrical. The abrasive composite shapes include a plurality of abrasive grains dispersed in a binder that also bonds abrasive composite shapes to a backing. During a CMP process, as the abrasive sheet is being used to abrade a surface, the abrasive composite shapes break down and expose unused abrasive grains embedded in the binder. As the sheet is used for an extended time period, the composite shapes further break down and expose more abrasive grains. For an ECMPR process, due to the constant breaking down of the abrasive layer, such abrasive sheets have relatively short life time and need to be replaced often. This in turn lowers throughput and also adversely affect product consistency. 
     Therefore, it will be desirable to provide a longer life abrasive and hard surface for the WSID used in an ECMPR technique. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a top surface of a workpiece surface influencing device and a method of using the same. The top surface of the workpiece surface influencing device is adapted for use in an electrochemical mechanical processing apparatus in which a solution becomes disposed onto a conductive surface of a workpiece and electrochemical mechanical processing of the conductive surface is performed while relative movement and physical contact exists between the top surface and the conductive surface. The top surface comprises a ceramic material that presents a substantially planar contact area to the conductive surface, the ceramic material having a hardness greater than that of the conductive surface. A plurality of channels are formed through the top surface. 
     In one aspect, the substantially planar contact area includes a plurality of contact regions, each of the contact regions including a region top surface that is substantially planar with other region top surfaces. These plurality of contact regions may each be raised above a layer disposed below, which layer may be another ceramic material, or a metal that can be used as an anode or a cathode. Each of the plurality of contact regions will have an associated region top surface, which may be flat, rounded, triangular or some other shape, such that the top portion of each of the region top surfaces together form a substantially planar contact area. 
     In another embodiment each of a plurality of contact regions is formed as a separable sweep element, thereby resulting in a plurality of separable sweep elements. The separable sweep elements can have a region top surface that is flat, rounded, triangular, or some other shape. Further, the sweep elements may include drain channels, particularly on the leading edge of the sweep element. 
     The method according to the present invention provides for electrochemical mechanical processing of a conductive surface of a workpiece using a workpiece surface influencing device as described above and hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts an ECMPR system; 
         FIG. 2  schematically depicts a portion of an ECMPR system using an embodiment of a WSID of the present invention; 
         FIG. 3  schematically depicts a planar view of an embodiment of a WSID of the present invention; 
         FIG. 4  schematically depicts a side cross section of an embodiment of a WSID of the present invention; 
         FIG. 5A  schematically shows sweep elements in conjunction with the WSID according to the present invention; 
         FIGS. 5B-5H  schematically shows cross-sectional views of various embodiments of the sweep elements and drain channels according to the present invention; 
         FIG. 5I  schematically shows a perspective view of a sweep element and drain channel according to the present invention; 
         FIGS. 6A to 6D  schematically show a method of making an embodiment of a WSID of the present invention; 
         FIG. 6E  schematically shows an alternative step in method of making a WSID of the present invention; and 
         FIG. 7  schematically depicts a planar copper layer formed on a surface of a workpiece using the WSID of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In one embodiment, a workpiece surface influencing device (WSID) of the present invention includes a pattern of raised regions that provides a longer life cycle when compared to a conventional WSID. As used herein, the terms “workpiece surface,” “wafer surface” and the like include, but are not limited to, the surface of the work piece or wafer prior to processing and the surface of any layer formed thereon, including oxidized metals, oxides, spun-on glass, ceramics, etc. 
     Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIG. 2  schematically depicts one embodiment of a WSID of the present invention, which WSID is placed in close proximity of a workpiece  11 , such as a wafer, having a surface  12  to be plated. 
     The WSID may include a body  13  having a plurality of raised regions  14  and recessed regions  18  distributed on an upper surface of the WSID body  13 . Recessed regions  18  are surface channels extending along the surface  15  of the WSID body  13 . A top surface  19  of the raised regions  14  sweeps the wafer surface  12  during the process. The WSID body  13  may be constructed of more than one layer. Preferably, the body  13  is comprised of materials that are non-reactive with the deposited or etched metal layer and the process solution that is used. Thus, the body  13  may be one of a reinforced or pure polymeric material, a metallic material, a ceramic material, a glass material, and mixtures thereof. Useful polymeric materials include polypropylene and polyvinyl chloride (PVC). Metallic materials can include titanium, tantalum, or their platinum coated versions. The WSID body  13  can also be an electrode for example an anode for the above described ECMD processes and a cathode for the above described ECME processes. In such case, parts of the WSID body that may contact the workpiece can be coated with an insulator layer, or the raised regions can be made of insulating materials. Irrespective of whether the body  13  is an electrode or just a support element for the raised regions, the WSID body  13  preferably includes a plurality of openings or channels  17 . Channels  17  communicate electrolyte between an electrode (not shown) and the wafer surface  12  on which a metal layer, preferably copper layer, may be deposited (See also  FIG. 1 ). Channels  17  are connected to the recessed regions  18  and may have the same width and length as the recessed regions  18 . The plurality of raised regions  14  may be an integral part of or non-separable from the body  13 . Thus, the raised regions  14  may comprise the same material as the body  13 . Additionally, the plurality of raised regions  14  is preferably disposed in a pattern, and the recessed regions  18  continue among them. While each of the raised regions  14  is illustrated as being of the same size and configuration, the present invention contemplates that the raised regions  14  may be constructed with differing sizes and configurations. In general, the raised regions  14  and in particular the top surface  19  of the raised regions, may serve to sweep the electrolyte across the wafer surface  12  as well as polish the wafer surface  12 . As with the raised regions  14 , the recessed regions  18  among the raised regions may be constructed with the same or differing sizes and configurations. 
       FIG. 3  schematically shows a top view of an exemplary embodiment of a WSID  40  with a pattern of raised regions  42  together with recessed regions  44  and channels  46  or holes. While  FIG. 3  shows the patterns of raised regions  42  and recessed regions  44  in a regular sequence, the scope of the present invention also includes a pattern of an irregular sequence. In  FIG. 3 , the raised regions  42  may be in the shape of ribs or blades. The raised regions  42  may also have a triangular cross section (not shown). Between the raised regions  42  may be a plurality of recessed regions  44  connected to the channels  46 . 
     As shown in  FIG. 4 , in another embodiment, which schematically depicts a side cross sectional view of a portion of a WSID  30 . The WSID  30  may include a top surface  29 . In this embodiment, an outer layer  31  is formed on and conformally coats and the top surface  29  and hence the raised and recessed regions  14 ,  18 . As will be described below, the outer layer may  31  be made of an insulating material. As seen in  FIG. 4 , the outer layer  31  may have openings  32  to enable the electrolyte to flow between the channels  17  and the recessed regions  18 . 
     Optionally, and as shown in  FIG. 5A , top of the WSID  30  may further include a plurality of surface features  34  or sweep elements integrated and/or separable from the WSID  30 . The sweep elements  34  can help sweep the electrolyte from the work piece surface  12  (see  FIG. 2 ). The sweep elements  34  may also be integrated into and/or separable from the raised regions  14 . In other words, the plurality of sweep elements  34  may be removable, replaceable, and/or re-buildable as needed. For example, the sweep elements  34  may be placed into or held in place by grooves  35  formed in the WSID body  13  or in the raised regions  14 . When the sweep elements  34  are worn, they can be replaced by a new set of sweep elements  34  (such as with a cartridge of sweep elements). Replacement of them can be performed by sliding the sweep elements  34  into the grooves  35 . Accordingly, the sweep elements  34  may be made of titanium, titanium oxide, aluminum oxide, polyamides, epoxies, reinforced structural polymers or ceramics or various combinations. The sweep elements may be of various configurations, such as that shown in  FIG. 5B , to cooperate with the raised regions  14  in sweeping process solution across and from the wafer surface  12 . A useful dimension for the sweep element  34  is between about 0.1 micron to 20 mm. 
     The sweep elements  34  may also contain channels  34   a  for draining electrolyte off the surface  12  of the work piece  11  ( FIG. 2 ). Also, the channels  34   a  can enhance fluid mixing or transfer within the fluid boundary layer regions between the sweep elements  34  and work piece  11  ( FIG. 2 ). Concurrently, the affected electrolyte is prevented from accumulating in front of the sweep elements  34  by draining through the channels  34   a . Thus, the channels  34   a  enhances mass transfer at the work piece interface and help reduce the accumulation of electrolyte in the work piece interface during the sweeping action. The channels  34   a  in the sweep elements may be of various configurations, such as circular, rectangular, and triangular. Regardless of the shape of the channels  34   a , the channels may be spread from one another by around 2 to 5 mm. The drain channels  34   a  of the sweep elements  34  may be parallel or inclined to the leading edge of the sweep elements  34 . The relative position of the channels  34   a  and their orientation is such that they can maximize the preferential deposition of high quality metal in the various features or cavities (see  FIG. 7 ) in the work piece  11 . 
     In making the WSID  30 ,  FIGS. 6A to 6D  schematically depict one preferred method. In  FIG. 6A , the WSID body  13  may initially be patterned by one of a photolithographic method and/or a masking method. While the foregoing methods are preferred due to manufacturing ease, conventional machining, laser ablation, or water jet material fabrication methods may also be used. Either of the foregoing preferred methods can employ conventional techniques to produce a patterned mask  22  on the top surface  29  of the WSID body  13 . The patterned mask  22  preferably provides a pattern that matches the pattern of raised regions  14  that will eventually be produced on the top surface  29 . 
     Next, as shown in  FIG. 6B , exposed portions  29   a  of the top surface  29  can be etched so as to produce relief structures  23  that may become the eventual recessed regions  18 . Thereafter, the patterned mask  22  may be removed by conventional methods; thereby leaving the raised regions  14  and the recessed regions  18  integrated onto the top surface  29 , as shown in  FIG. 6C . 
     In  FIG. 6D , the outer layer  31  or an insulating layer, which is also shown in  FIG. 4 , may be formed on the exposed surfaces of the raised and recessed regions using methods such as anodization, sputtering, spin coating, and baking. The insulating layer  31  is a hard material and serves to polish the workpiece surface  12  (see  FIG. 2 ) as it is plated. The layer  31  protects the WSID  30  and provides electrical insulation for it when contact is made with the workpiece surface  12 . Accordingly, the insulating layer  31  may be made of A1.sub.2O.sub.3, SiN, TiO.sub.2, or other ceramics, and particulate reinforced chemical resistant polymers and mixtures thereof, and produced by well-known methods such as dipping, spin coating, spraying and sputtering. In a specific example, the insulating layer  31  may be fabricated by anodizing the exposed surfaces of raised and recessed regions  14 ,  18 . For example the WSID maybe made of Ti or Ta and the surface may be anodized to obtain a protective hard layer of Ti-oxide or Ta-oxide. Referring to  FIG. 6D , in another specific example, if the WSID body  13  is made of a hard polymeric material such as a polycarbonate or high density polyethylene, the layer  31  can be formed as a hard coating or an abrasive surface. In this case abrasiveness of the layer  31  can be controlled by selecting materials from different friction coefficients. For example, if the coating include alumina it will be hard and abrasive. If it includes diamond like carbon coating, it will be hard but less abrasive because such coatings are more slippery. Best abrasive coating can be selected by selecting the coating without changing the shape of the surface of the WSID. 
     Following the formation of the insulating layer  31 , the channels  17  may be formed by machining the channels through the WSID  30 . The channels may be formed by various methods such as drilling, electro etching, wet etching, laser ablation, water jet cutting, etc. 
     Alternatively, the insulating layer  31  may be formed after the openings  32  are formed, thereby producing an insulating layer  31  not only over the raised and recessed regions  14 ,  18  but also over the walls of the channels  17 , as shown in  FIG. 6E . In another embodiment, the initial topography of the WSID structure, including the raised regions  14 , the channels  17  and recessed regions  18 , may be fabricated by mechanically machining the WSID. Thereafter, the structure&#39;s surface can be selectively anodized or spin coated with a suitable insulating, abrasive or electrolyte sweeping elements or devices. 
     In view of the above, it can be seen that the present invention can provide a way of rebuilding of a plurality of newer raised regions and recessed regions after the raised regions in use are worn. In other words, a second plurality of raised regions and recessed regions are produced by reprocessing the used WSID. Such rebuilding can be accomplished by removing the worn raised regions or surface, such as by wet etch methods, oxygen plasma, or machine resurfacing. Thereafter, new or second raised regions are reformed, such as by anodizing the prepared surface or spin coating on the prepared surface. Although not necessary, a reformed or second mask may correlate to the prior pattern of raised regions and recessed regions. The exposed areas of the second mask may then be insulated or anodized with another insulating or anodized layer. The entire WSID may be then annealed to toughen the WSID  30 , and improve its chemical resistance to various electrolytes. 
     Whichever particular embodiment of the WSID  10 , WSID  30  or method of the present invention is employed,  FIG. 7  schematically depicts a portion  50  of the workpiece  11 , shown in  FIG. 2 , on which a planar metal layer  28 , a copper layer, produced using the ECMPR. The planar metal layer  28  is formed on the workpiece by filling features or cavities such as vias  51  and trenches  52  formed through an insulating layer  33 . Conventionally, a barrier layer  26 , preferably a Ta or TaN layer and a seed layer  27 , preferably a thin copper layer are coated over the insulating layer  33  having the features  51 ,  52  before the copper plating of the workpiece. The WSID of the present invention may be used to remove, i.e., etch or electro-etch or electro-polish as in the CMP of copper on a wafer or a substrate. 
     It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention.