Patent Application
20070262488
1. Field of the Invention
Embodiments of the invention generally relate to a method for joining two dissimilar materials together. Embodiments of the invention specifically relate to a retaining ring for retaining a substrate and a method of making the retaining ring.
2. Description of the Related Art
Sub-micron multi-level metallization is one of the key technologies for the next generation of ultra large-scale integration (ULSI). The multilevel interconnects that lie at the heart of this technology require planarization of interconnect features formed in high aspect ratio apertures, including contacts, vias, trenches and other features. Reliable formation of these interconnect features is very important to the success of ULSI and to the continued effort to increase circuit density and quality on individual substrates and die.
Planarization is generally performed using Chemical Mechanical Polishing (CMP) and/or Electro-Chemical Mechanical Deposition (ECMP). A planarization method typically requires that a substrate be mounted in a carrier head, with the surface of the substrate to be polished exposed. The substrate supported by the carrier head is then placed against a rotating polishing pad. The carrier head holding the substrate may also rotate, to provide additional motion between the substrate and the polishing pad surface. A polishing solution is generally provided to the polishing pad and the substrate to promote chemical and/or mechanical polishing.
During planarization, a substrate is typically mounted on the carrier head within a retaining ring. The retaining ring is configured to keep the substrate from slipping away during mounting or polishing and keep the polishing pad flat near the edge of the substrate so that the substrate is polished evenly. This requires the retaining ring to have a generally rigid structure. Since the retaining ring also in contact with the polishing pad and the polishing solution, it is necessary for at least part of the retaining ring to be resistive to wear from the polishing pad and the chemicals in the polishing solution.
To meet these requirements, a retaining ring generally comprises two sections made of two dissimilar materials: a polymer section for wear and chemical resistance and a metal section for rigidity. An epoxy bond is generally used to join the plastic section and the metal section in the state of the art retaining ring. However, there are several disadvantages for the epoxy bond. The epoxy bond is very sensitive to temperature and may become delaminated during certain processes when temperature elevates. The epoxy bond also fatigues with cyclic load, thus, limiting the lifetime of the retaining ring. The chemical compatibility of the epoxy bond with the polishing solution is unknown because the formation of epoxy bond is a trade secret for the supplier. If the polishing solution attacks the epoxy bond, the epoxy bond may be weakened and contamination may also be generated. The curing of the epoxy bond usually takes 5 days resulting in high manufacturing cost. Also, mixing and application of the epoxy bond requires skilled labor and leaves room for human error.
Therefore, there is a need for methods to improve the bonding between two dissimilar materials in a retaining ring and other applications.
Embodiments of the invention generally relate to using friction weld to join two dissimilar materials together. Embodiments of the invention specifically relate to a retaining ring comprising a mechanical bond and a method of making the retaining ring.
One embodiment provides a method for joining two materials. The method comprises generating a relative motion between a first material and a second material while pressing the first material against the second material, wherein the first material is non metallic and the second material is metal, and holding the first material against the second material without relative motion to form a mechanical joint between the first and second materials.
Another embodiment provides a method for making a retaining ring. The method comprises providing a first annular portion comprising a first material, providing a second annular portion comprising a second material, wherein the first material is non metallic and the second material is metal, generating a relative motion between the first and second annular portion while pressing the first annular portion against the second annular portion, and holding the first annular portion against the second annular portion without relative motions to form a mechanical joint between the first and second annular portions.
Yet another embodiment provides a retaining ring. The retaining ring comprises a first annular portion made from a first material, and a second annular portion made from a second material, wherein the first annular portion and the second annular portion are bond together with a mechanical joint, the first material and the second material is vastly dissimilar.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention provides embodiments of retaining ring manufactured from two dissimilar materials frictional welded together and method of frictional welding of two vastly different materials. The two materials are pressed together while relative motions between the two materials generate frictional heat to locally melt one material. When the relative motion stops, a mechanical joint is formed between the two materials.
In one embodiment, the rigid ring 102 is rotated about the common axis 103 at an angular rate w and at least one of the rigid ring 102 or the non reactive ring 101 is moved along the common axis 103 so that the joint surface 111 of the non reactive ring 101 is in solid contact with the joint surface 121 of the rigid ring 102, as shown in
It should be noted that the relative motion in
It should be noted that the relative motion may also be a linear motion or vibration. The method for joining two vastly dissimilar materials may be used to join any structure that may be formed by two vastly different materials.
Further machining may be performed to the joined non reactive ring 101 and rigid ring 102 to reach final dimension and designed structure for a retaining ring. Detailed description of a retaining ring may be found in U.S. Pat. No. 6,974,371, and U.S. patent application Ser. No. 10/659,047, which are incorporated herein as references.
In one embodiment, the circular grooves 212 and 213 may have a thickness of about 0.1 inch. In another embodiment, more or less circular grooves may be formed on the top surface 211. In case of more than two concentric circular grooves formed on the top surface 211, inner radial openings may be formed between the inner circular groove and a neighboring groove, which is eventually connected to the outer surface 218 or the inner surface 217.
Mechanical joints formed using the method of the present invention, such as the mechanical joints 130 of
It should be noted that the method of the present invention may be used to join any structures formed by two dissimilar materials. Parameters of the relative motion, amplitude and duration of the pressing force, and surface features may be chosen according to the structure and material involved.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
