Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
1999-04-30
2002-02-19
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S072000, C451S443000, C125S003000, C125S008000
Reexamination Certificate
active
06347981
ABSTRACT:
FILED OF THE INVENTION
The present invention generally relates to methods and apparatus for polishing or planarizing workpieces such as semiconductor wafers. More particularly, the present invention relates to methods and apparatus for conditioning polishing pads used for the planarization of workpieces. The present invention is also directed to methods and apparatus for the planarization of workpieces which utilizes diamond brazed conditioning rings having a titanium nitride based coating or a coating comprising a thin film diamond deposition.
BACKGROUND OF THE INVENTION
The production of integrated circuits began with the creation of high-quality semiconductor wafers. During the wafer fabrication process, the wafers may undergo multiple masking, etching and dielectric and conductor deposition processes. Because of the high-precision required in the production of these integrated circuits, an extremely flat surface is generally needed on at least one side of the semiconductor wafer to ensure proper accuracy and performance of the microelectronic structures being created on the wafer surface. As the size of the integrated circuits continues to decrease and the density of the microstructures per integrated circuit increases, the need for precise wafer surfaces becomes more important. Therefore, between each processing step, it is usually necessary to polish or planarize the surface of the wafer to obtain the flattest surface possible.
For a discussion of chemical mechanical planarization (CMP) processes and apparatus, see, for example, Arai, et al., U.S. Pat. No. 4,805,348, issued February, 1989; Arai, et al., U.S. Pat. No. 5,099,614, issued March, 1992; Karlsrud et al.,U.S. Pat. No. 5,329,732, issued July, 1994; Karlsrud, U.S. Pat. No. 5,498,196, issued March, 1996; and Karlsrud et al., U.S. Pat. No. 5,498,199, issued March, 1996.
Such polishing is well known in the art and generally includes attaching one side of the wafer to a flat surface of a wafer carrier or chuck and pressing the other side of the wafer against a flat polishing surface. In general, the polishing surface comprises a horizontal polishing pad that has an exposed abrasive surface of, for example, cerium oxide, aluminum oxide, fumed/precipitated silica or other particulate abrasives. Polishing pads can be formed of various materials, as is known in the art, and which are available commercially. Typically, the polishing pad may be a blown polyurethane, such as the IC and GS series of polishing pads available from Rodel Products Corporation in Scottsdale, Ariz. The hardness and density of the polishing pad depends on the material that is to be polished.
During the polishing or planarization process, the workpiece (e.g. wafer) is typically pressed against the polishing pad surface while the pad rotates about its vertical axis. In addition, to improve the polishing effectiveness, the wafer may also be rotated about its vertical axis and oscillated back and forth over the surface of the polishing pad. It is well known that polishing pads tend to wear unevenly during the polishing operation, causing surface irregularities to develop on the pad. To ensure consistent and accurate planarization and polishing of all workpieces, these irregularities should either be removed or accounted for.
One method of removing the surface irregularities which develop in the polishing pad is to condition or dress the pad with some sort of roughing or cutting means. Generally this truing or dressing of the polishing pad can occur either while the wafers are being polished (in-situ conditioning), or between polishing steps (ex-situ conditioning). An example of ex-situ conditioning is disclosed in Cesna, et al., U.S. Pat. No. 5,486,131, issued on Jan. 23, 1996, and entitled Device for Conditioning Polishing Pads. An example of in-situ conditioning is disclosed in Karlsrud, U.S. patent application Ser. No. 08/487,530, filed on Jul. 3, 1995, and entitled Polishing Pad Conditioning. Both the Cesna, et al. patent and the Karlsrud application are herein incorporated by reference.
Generally, in the semiconductor wafer polishing and planarization context small roughing or cutting elements, such as diamond particles, are used to condition the polishing pads. As shown in both the Cesna, et al, patent and the Karlsrud application, both in-situ and ex-situ conditioning apparatus utilize circular ring conditioners which have these cutting elements secured to a bottom flange of the ring. Generally, these cutting elements are secured to the bottom surface of the flange of the carrier ring by an electroplating process or brazing process. Electroplating produces a simple mechanical entrapment of the cutting elements on the carrier ring by depositing metal, for example in a layer-by-layer fashion around the cutting elements until they are entrapped. However, one problem with the electroplating process is that the electroplating bond holding the cutting elements to the ring surface is relatively weak and the cutting elements occasionally become dislodged from the conditioning ring and embedded in the polishing pad. Further, because the electroplating bond is susceptible to shearing forces, a substantial amount of bonding material is needed to hold the cutting elements in place. As a result, the bonding material actually covers most, if not all, of the many cutting elements, thereby, comprising the conditioning capacity of the conditioning ring. Thus, the previously mentioned brazing process is preferred. A detailed discussion of the brazing process is discussed herein as well as in Holzapfel, et al., U.S. patent application Ser. No. 08/683,571, filed Jul. 15, 1996, which is herein incorporated by reference.
The cutting elements which are secured to the bottom surface of the flange of the carrier rings may comprise diamonds, polycrystalline chips/slivers, silicon carbide particles, and the like. However, regardless of whether the conditioning rings are braze plated or electroplated in order to retain the cutting elements, such as diamonds, these processes are not ideal in that they exhibit a very short lifetime which results in diamond loss, diamond fracture, or plating wear. As previously indicated, these lost or fractured diamonds can cause severe scratches in the wafers that are being polished. Wafers that are scratched are considered to be scrap and this can result in increased costs to the consumer. Further, the short lifetime of the conditioning rings due to plating wear is significant in that the conditioning rings are typically the most expensive consumable component part on the CMP apparatus.
Although the brazing of the cutting elements to secure them to the carrier ring is preferable over the electroplating process, there are still some problems associated with the brazing process. The problems associated with the unreliability of the bond created using brazed diamond technology in various applications has been addressed in the prior art. For example, in Kapoor et al., U.S. Pat. No. 5,567,525, the reliability of a braze joint formed between a diamond film and a tungsten carbide object is increased by covering the diamond film with a braze comprising vanadium. Further, a method for utilizing high temperature and high pressure to form a polycrystalline composite compact having reduced abrasive layer stresses is disclosed in U.S. Pat. No. 5,560,754 issued to Johnson et al. Also, U.S. Pat. No. 4,899,922, issued to Slutz et al., describes a brazed implement having a thermally stable polycrystalline diamond with shear strengths exceeding about 50 kpsi even while furnace cycling the brazed implements. This is achieved by brazing the compact to another compact or to a cemented carbide support using a brazing alloy containing an effective amount of chromium and having a liquidus above about 700 degrees C. Still, each of these methods for creating a more reliable brazed bond requires substantial mechanical and/or chemical manipulation including a temperature application. Further, none of these prior art patents suggests the use of their respective method
Eley Timothy V.
Snell & Wilmer L.L.P.
SpeedFam-Ipec Corporation
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