Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-01-11
2001-08-28
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S060000, C451S446000, C451S287000
Reexamination Certificate
active
06280297
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to chemical mechanical polishing of substrates, and more particularly to an apparatus and method for distributing slurry to the surface of a polishing pad.
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 more non-planar. This occurs because the distance between the outer surface and the underlying substrate is greatest in regions of the substrate where the least etching has occurred, and least in regions where the greatest etching has occurred. With a single patterned underlying layer, this non-planar surface comprises a series of peaks and valleys wherein the distance between the highest peak and the lowest valley may be the order of 7000 to 10,000 Angstroms. With multiple patterned underlying layers, the height difference between the peaks and valleys becomes even more severe, and can reach several microns.
This non-planar outer surface presents a problem for the integrated circuit manufacturer. If the outer surface is non-planar, then photolithographic techniques used to pattern photoresist layers might not be suitable, as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize this substrate surface to provide a planar layer surface. Planarization, in effect, polishes away a non-planar, outer surface, whether conductive, semiconductive, or insulative, to form a relatively flat, smooth surface. Following planarization, additional layers may be deposited on the outer surface to form interconnect lines between features, or the outer surface may be etched to form vias to lower features.
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. In addition, the carrier head may rotate 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: the finish (roughness) and flatness (lack of large scale topography) of the substrate surface, and the polishing rate. Inadequate flatness and finish 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.
Each polishing pad provides a surface which, in combination with the specific slurry mixture, can provide specific polishing characteristics. Thus, for any material being polished, the pad and slurry combination is theoretically capable of providing a specified finish and flatness on the polished surface. The pad and slurry combination can provide this finish and flatness in a specified polishing time. Additional factors, such as the relative speed between the substrate and pad, and the force pressing the substrate against the pad, affect the polishing rate, finish and flatness.
Because inadequate flatness and finish can create defective substrates, the selection of a polishing pad and slurry combination is usually dictated by the required finish and flatness. Given these constraints, the polishing time needed to achieve the required finish and flatness sets the maximum throughput of the polishing apparatus.
An additional limitation on polishing throughput is “glazing” of the polishing pad. Glazing occurs when the polishing pad becomes packed with the byproducts of polishing and as the pad is compressed in regions where the substrate is pressed against it. The peaks of the polishing pad are pressed down and the pits of the polishing pad are filled up, so the surface of the polishing pad becomes smoother and less abrasive. As a result, the time required to polish a substrate increases. Therefore, the polishing pad surface must be periodically returned to an abrasive condition, or “conditioned”, to maintain a high throughput.
An additional consideration in the production of integrated circuits is process and product stability. To achieve a low defect rate, each successive substrate should be polished under similar conditions. Each substrate should be polished by approximately the same amount so that each integrated circuit is substantially identical.
In view of the foregoing, there is a need for a chemical mechanical polishing apparatus which optimizes polishing throughput, flatness, and finish, while minimizing the risk of contamination or destruction of any substrate.
Specifically, there is a need for an apparatus and method to distribute slurry to the surface of the polishing pad. The apparatus slurry distribution system should provide slurry in an even, uniform layer across the entire polishing pad. In addition, the system should reduce slurry consumption in the polishing process.
Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the claims.
SUMMARY OF THE INVENTION
In one embodiment, the present invention is a method of polishing a substrate in a chemical mechanical polishing apparatus. The method comprises rotating the substrate and the polishing pad, bringing the substrate into contact with the polishing pad, and dispensing a slurry solution through a central port.
The slurry may be dispensed at a first flow rate if the substrate is not positioned over the central port, and at a second, higher, flow rate if the substrate is positioned over the central port. Slurry may be pumped through the central port in intermittent pulses. The flow rate during the pulses may be sufficiently high to overcome pressure from the carrier head.
In another embodiment, the present invention is a chemical mechanical polishing apparatus. The apparatus comprises a rotating polishing pad, a slurry dispenser, and a flexible member disposed to sweep slurry across the surface of the polishing pad.
The flexible member may extend linearly from the edge to near the center of the polishing pad. A gap may separate the flexible member from the polishing pad, or the flexible member may contact the surface of the polishing pad. Multiple flexible members can be used. The flexible member may be mounted to a rigid arm. The arm may be connected to a rotary motor to move the arm over the polishing pad. The apparatus may also include a control system to control the motion of the carrier head and the arm to prevent collisions therebetween.
REFERENCES:
patent: 3028711 (1962-04-01), Campbell et al.
patent: 3261510 (1966-07-01), Day et al.
patent: 3848366 (1974-11-01), David
patent: 4260396 (1981-04-01), Glemza
patent: 4435247 (1984-03-01), Basi et al.
patent: 4513894 (1985-04-01), Doyle et al.
patent: 4600469 (1986-07-01), Fusco et al.
patent: 4850157 (1989-07-01), Holmstrand et al.
patent: 4910155 (1990-03-01), Cote et al.
patent: 5109931 (1992-05-01), Biebesheimer et al.
patent: 5234867 (1993-08-01), Schultz et al.
patent: 5245796 (1993-09-01), Miller et al.
patent: 5246525 (1993-09-01), Sato
patent: 5291693 (1994-03-01), Nguyen
patent: 5433650 (1995-07-01), Winebarger
patent: 5562530 (1996-10-01), Runnels et al.
patent: 5650039 (1997-07-01), Talieh
patent: 5709593 (1998-01-01), Guthrie et al.
patent: 6051499 (2000-04-01), Tolles et al.
patent: 837807 (1981-06-01), None
Cheng Tsungnan
Guthrie William L.
Marks Jeffrey
Tolles Robert D.
Applied Materials Inc.
Fish & Richardson
Hail III Joseph J.
Nguyen George
LandOfFree
Apparatus and method for distribution of slurry in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for distribution of slurry in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for distribution of slurry in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498877