Abrading – Accessory – Dressing
Reexamination Certificate
2000-12-22
2002-03-26
Banks, Derris H. (Department: 3723)
Abrading
Accessory
Dressing
C451S444000, C451S056000
Reexamination Certificate
active
06361423
ABSTRACT:
BACKGROUND
1. Technical Field
This invention relates generally to the planarization of semiconductor substrates and, more particularly to the conditioning of polishing pads in slurry-type polishers.
2. Background Information
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 number of conditioning procedures and apparatus have been developed. Common are mechanical methods wherein an abrasive material is placed in contact with the moving polishing pad. For example, a diamond coated screen or bar may be used which scrapes and abrades the pad surface, and both removes the contaminated slurry trapped in the pad pores and expands and re-roughens the pad.
SUMMARY
In one aspect, the invention is directed to a conditioner head for conditioning the polishing surface of a polishing pad. The head includes a drive element carried for rotation about a longitudinal axis. The head further includes a disk backing element for carrying an abrasive disk and holding the lower surface of the disk in engagement with the polishing pad. A driven element couples the disk backing element to the drive element and transmits torque and rotation therebetween. The driven element is longitudinally movable between retracted and extended positions. An annular diaphragm spans a gap between the drive element and the driven element and is coupled to the drive element and the driven element so as to rotate therewith as a unit.
Implementations of the invention may include one or more of the following. The diaphragm may in part bound a pressure chamber which may be pressurized to shift the driven element from the retracted position to the extended position and depressurized to shift the driven element from the extended position to the retracted position. During transition between the retracted and extended positions a first surface of the diaphragm, exterior to the pressure chamber, rolls of a generally annular outer surface portion of the driven element traverses the gap and rolls onto a generally annular inner surface portion of the drive element.
The drive element may include a drive shaft and a collar substantially fixed to the drive shaft and having a generally annular inner surface portion. The driven element may include a drive sleeve encircling at least a length of the drive shaft and having a generally annular outer surface portion. The annular diaphragm may extend between an outer periphery and an inner aperture and may be sealingly secured along the outer periphery to the collar and along the inner aperture to the drive sleeve. The generally annular outer surface portion of the drive sleeve may be a circular cylinder and the generally annular inner surface portion of the collar may be a circular cylinder. The diaphragm may in part bound a pressure chamber. The pressure chamber may be pressurized to shift the drive sleeve from the retracted position to the extended position and depressurized to shift the drive sleeve from the extended position to the retracted position. During transition between the retracted and extended positions, a first surface of the diaphragm, exterior to the pressure chamber, may roll off the generally annular outer surface portion of the drive sleeve. The first surface of the diaphragm may then traverse a gap between the generally annular outer surface portion of the drive sleeve and the generally annular inner surface portion of the collar and roll onto the generally annular inner surface portion of the collar. A fluid for inflating the pressure chamber may be introduced to the pressure chamber through a channel in the drive shaft. The head may include a housing substantially rigidly coupled to a conditioner arm for moving the head at least transverse to the longitudinal axis. The housing may include a first portion encircling at least the length of the collar, which first portion is coupled to the collar by a bearing system for permitting the collar to rotate relative to the first portion about the longitudinal axis. A web may be formed at the upper end of the drive shaft, the collar depending from the web. A pulley may be substantially fixed to the web for transmitting torque to the drive shaft. The collar may comprise a first piece depending from and fixed to the web and a second piece, separately formed from the first piece. The second piece may engage the bearing system and the diaphragm may be secured along the outer periphery to the collar between the first and second pieces. The diaphragm may be partially sandwiched between an outer cylindrical surface of an annular lip depending from the first piece and a generally annular inner surface of the second piece which forms the generally annular inner surface portion of the collar.
In another aspect, the invention is directed to a disk holder for holding a conditioning disk for conditioning a polishing pad. The disk holding element has a lower face for engaging an upper surface of the conditioning disk. The disk holding element defines a plurality of generally radially outward extending channels along the upper surface of t
Gurusamy Jayakumar
Rosenberg Lawrence M.
Applied Materials Inc.
Banks Derris H.
Fish & Richardson
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