Abrading – Machine – Rotary tool
Reexamination Certificate
2000-01-06
2001-08-21
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S388000
Reexamination Certificate
active
06277009
ABSTRACT:
BACKGROUND
The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to a carrier head for a chemical mechanical polishing apparatus.
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 increasingly non-planar. This non-planar surface presents problems in the photolithographic steps of the integrated circuit fabrication process. Therefore, there is a need to periodically planarize the substrate surface.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed against a rotating polishing pad. The polishing pad may be either a “standard” pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles, if a standard pad is used, is supplied to the surface of the polishing pad. The polishing slurry tends to be abrasive and corrosive, and can damage the mechanical parts inside the carrier head.
The substrate is typically vacuum-chucked to the underside of the carrier head at certain times during the polishing process, such as when the substrate is to be moved between polishing stations. However, the stress applied to the substrate during the vacuum-chucking procedure, particularly as the substrate is lifted off the polishing pad, may damage the substrate, e.g., the substrate may fracture. Also, it is possible for the substrate to become detached from the carrier head, e.g., when the carrier head is being moved between polishing stations, if the substrate is not properly chucked. If the substrate drops, it may be damaged when it falls.
Accordingly, it would be useful to provide a carrier head capable of reliably lifting the substrate off the polishing pad. It would also be useful if the interior of the carrier head was not exposed to contamination by slurry.
SUMMARY
In one aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus. The carrier head comprises a base, a flexible membrane coupled to the base to define an evacuable chamber and provide a substrate receiving surface, and a compliant backing member having a plurality of indentations. The backing member is positioned relative to the flexible membrane such that when the chamber is evacuated, the flexible membrane contacts the backing member.
In another aspect, the carrier head comprises a base, a flexible membrane coupled to the base to define an evacuable chamber, a first surface of the flexible membrane providing a substrate receiving surface, and a backing member having a plurality of indentations formed in a compliant surface thereof. The backing member is positioned between the base and the flexible membrane such that when the chamber is evacuated, a second surface of the flexible membrane contacts the compliant surface of the backing member.
In another aspect, the carrier head comprises a base, a flexible membrane coupled to the base to define an evacuable chamber and provide a substrate receiving surface, and a compliant backing member including an upper sheet and a lower sheet. A peripheral portion of the upper and lower sheets is joined so that the backing member encloses a cavity, and the upper and lower sheets are further joined in a plurality of regions located interior to the peripheral portion to define an array of indentations in the backing member. The backing member is positioned between the base and the flexible membrane such that when the chamber is evacuated, the flexible membrane contacts the backing member.
In another aspect, the carrier comprises a base, a flexible membrane coupled to the base to define an evacuable chamber and provide a substrate receiving surface, and a compliant backing member including an upper sheet and a lower sheet. A peripheral portion and a plurality of interior portions of the upper and lower sheets are joined together to define an array of interconnected cells. The backing member is positioned between the base and the flexible membrane such that when the chamber is evacuated, the flexible membrane contacts the backing member.
Implementations of the invention may include the following. The backing member may enclose a pressurizable cavity. The backing member may include a flexible upper member and a flexible lower member (e.g., bonded silicone rubber sheets), with the upper member joined to the lower member in a plurality of joined regions. The joined regions may define the indentations and the non-joined regions may define the cavity. Apertures may extend through the joined regions. The cells may be substantially annular, and each may surround a joined central region. An aperture may extend through the backing member in the central region of each annular cell. The cells and/or the indentations may be arranged in a hexagonal array. The cells may be air pockets formed between the upper and lower member. The base may include a passage to provide fluid communication to the cavity. A mesh may be positioned in the cavity to prevent the upper and lower members from adhering in the non-joined regions. The cells may be connected by channels between the upper and lower sheets. In another aspect, the invention is directed to an assembly for a chemical mechanical polishing system. The assembly comprises a carrier head, a vacuum source, and a sensor. The carrier head includes a base, a flexible membrane coupled to the base to define a chamber and provide a substrate receiving surface, and a compliant backing member having a plurality of indentations and enclosing a cavity. The vacuum source fluidly connected to the chamber to evacuate the chamber. The sensor measures the pressure in the cavity and generates an output signal indicative of whether the substrate is attached to the substrate receiving surface. The flexible membrane and backing member are configured such that if the chamber is evacuated and a substrate is attached to the substrate receiving surface, the substrate presses against the backing member so that a pressure in the cavity increases to a first pressure which is greater than a second pressure that would result if the substrate were not attached to the substrate receiving surface.
Implementations may include the following. The assembly may further comprise a processor configured to indicate that the substrate is attached to the substrate receiving surface if the pressure in the cavity is greater than a threshold pressure.
In another aspect, the invention is directed to a method of chucking a substrate to a carrier head. The substrate is positioned against a lower surface of a flexible membrane of the carrier head. A compliant backing member which includes a plurality of indentations and which is located adjacent to the flexible membrane of the carrier head is inflated. A chamber defined by the flexible membrane is evacuated to draw the flexible membrane into contact with the backing member.
Implementations may include the following. The substrate may be lifted off a polishing pad.
Advantages of the invention include the following. The carrier head reliably chucks the substrate. In addition, the compliant backing member reduces stress on the substrate and thus reduces the danger of damaging the substrate.
Other advantages and features of the invention will become apparent from the following description, including the drawings and claims.
REFERENCES:
patent: 4
Chen Hung
Zuniga Steven M.
Applied Materials Inc.
Fish & Richardson
Rose Robert A.
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