Abrading – Accessory – Dressing
Reexamination Certificate
1999-07-09
2001-04-17
Banks, Derris H. (Department: 3723)
Abrading
Accessory
Dressing
C451S056000
Reexamination Certificate
active
06217429
ABSTRACT:
BACKGROUND
This invention relates generally to the planarization of semiconductor substrates and, more particularly to the conditioning of polishing pads.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface.
Chemical mechanical polishing is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically-reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate.
Important factors in the chemical mechanical polishing process are: substrate surface planarity and uniformity, and the polishing rate. Inadequate planarity and uniformity can produce substrate defects. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus.
It is important to take appropriate steps to counteract any deteriorative factors which either present the possibility of damaging the substrate (such as by scratches resulting from accumulated debris in the pad) or reduce polishing speed and efficiency (such as results from glazing of the pad surface after extensive use). The problems associated with scratching the substrate surface are self-evident. The more general pad deterioration problems both decrease polishing efficiency, which increases cost, and create difficulties in maintaining consistent operation from substrate to substrate as the pad decays.
The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad's roughness and its ability to apply fresh slurry to the substrate.
It is, therefore, desirable to continually condition the pad by removing trapped slurry, and unmatting or re-expanding the pad material.
A conventional conditioning apparatus places an abrasive material in contact with the moving polishing pad. For example, a diamond coated screen or disk may be used to scrape and abrade the pad surface, and to expand and re-roughen the pad. The diamond coated disk can be attached to a rotatable backing element.
Two manufacturers of diamond coated disks are Abrasive Technology, Inc., of Westerville, Ohio, and TBW Industries, Inc. of Furlong, Penn. The disks from Abrasive Technology are thicker than those of TBW. Also, mechanical means are used to secure the Abrasive Technology disks to the backing element, whereas magnetic means are used to secure the TBW disks to the backing element. Different disk holders are needed to hold these different types of disks.
SUMMARY
In one aspect, the invention is directed to a conditioner head to condition the polishing surface of a polishing pad. The conditioner head has a disk having an abrasive surface to contact a polishing pad, a disk holder to carry the disk and to hold it in contact with the polishing pad, and a drive element to rotate the disk about an axis. The disk holder has a generally flat mounting surface.
Implementations of the invention may include one or more of the following features. A mechanical fastener may secure the disk to the disk holder. The mechanical fastener may include a plurality of holes provided around a periphery of the disk holder. The holes may extend through the disk holder. A plurality of first cavities may be provided around a periphery of the disk corresponding to the plurality of holes of the disk holder. A plurality of screws may be inserted into the plurality of holes and the plurality of first cavities to secure the disk to the disk holder. The disk holder may include an upwardly protruding rim. A ring may be positioned on the rim of the disk holder, and the ring may have a plurality of holes at its edges. A membrane cover may be secured between the ring and the rim to prevent contaminants from falling into an interior of the disk holder. Each of the plurality of holes on the ring may include an upper cavity and a lower cavity, with the lower cavity extending radially further into the ring than the upper cavity. The disk holder may include a generally convex spherical portion protruding upward on an opposing side of the mounting surface. The disk holder may be secured to the disk by a plurality screws. A plurality of drive pins on the disk receiving surface of the disk holder may transfer torque to the disk, and a plurality of drive bores on the disk may receive the drive pins. A generally annular, flat adapter may be positioned between the disk and the disk holder. A plurality of second cavities may be provided around a periphery of the adapter to correspond to the plurality of holes of the disk holder, and a plurality of screws may be inserted into the plurality of holes and the plurality of second cavities to secure the adapter to the disk holder. The adapter may include a plurality of drive bores to receive the drive pins of the disk holder. The disk holder may include a generally convex spherical portion protruding upward on an opposing side of the mounting surface. A generally flat lower surface of the disk may be secured to the adapter and the disk holder defines a disk plane, and the disk, the adapter and the disk holder may be configured such that the center of the spherical portion is located substantially at the disk plane. A magnetic plate may be positioned between the adapter and the disk to magnetically couple the disk to the adapter.
In another aspect, the invention is directed to a disk holder of a conditioner head to carry and hold an abrasive disk against a polishing surface of a polishing pad. The disk holder has a generally convex spherical portion protruding upward from an upper surface of the disk holder, a generally flat mounting surface provided on a lower surface of the disk holder, and a plurality of holes around a periphery of the disk holder. The holes are configured to receive a plurality of screws which are used to secure the disk or an adapter to the mounting surface of the disk holder.
In another aspect, the invention is directed to a conditioner head to condition the polishing surface of a polishing pad. The conditioner head has a disk having an abrasive surface to contact a polishing pad, a disk holder to carry the disk and to hold it in contact with the polishing pad, and a drive element to rotate the disk about a longitudinal axis. The disk holder has a generally flat mounting surface on one side and a generally convex spherical portion protruding upward on an opposing side of the mounting surface. A generally flat adapter is secured to the disk on one side and mounted to the mounting surface of the disk holder on an opposing side thereof. A generally flat lower
Applied Materials Inc.
Banks Derris H.
Fish & Richardson
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