Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-01-21
2001-10-09
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S041000, C451S443000, C451S444000, C451S285000
Reexamination Certificate
active
06299511
ABSTRACT:
BACKGROUND
This invention relates generally to the planarization of semiconductor substrates and, more particularly, to a chemical mechanical polishing conditioner.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. Specific structures and devices are formed by preferential etching of the layers aided by photolithography. High resolution and accurate focusing of the photolithography apparatus allows the formation of well defined micro- or nano-structures. Accurate focusing of the photolithography apparatus is difficult for non-planar surfaces. 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 provides a controllable load, i.e., pressure, on the substrate to push it against the 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.
The effectiveness of a CMP process may be measured by its polishing rate, and by the resulting finish (absence of small-scale roughness) and flatness (absence of large-scale topography) of the substrate surface. Inadequate flatness and finish can produce substrate defects. The polishing rate, finish and flatness are determined by the pad and slurry combination, the relative speed between the substrate and pad, and the force pressing the substrate against the pad. 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 may either damage 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 efficiently polish 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. A conventional conditioner has an arm holding a conditioner head with an abrasive disk against the polishing pad. A bearing system rotatably supports the abrasive disk at the end of the arm. The abrasive disk rotates against the polishing pad to physically abrade the polishing pad and remove the glazing layer from the polishing pad.
During the conditioning operation, slurry or fragments of the polishing pad glazing layer may enter openings in the conditioner head and interfere with its rotational motion. In particular, if slurry is deposited on the bearing system, it may cause bearing reliability problems and may reduce the life of the conditioning head.
SUMMARY
In general, in one aspect, the present invention features a conditioner head for conditioning the polishing surface of a polishing pad. The conditioner head has an abrasive element engageable with the polishing pad, and a drive assembly coupled to the abrasive element and transmitting rotation to the abrasive head. A housing surrounds the drive assembly and a bearing couples the drive assembly to the housing. The bearing enables rotation of the drive assembly within the housing. A fluid purge system is provided to direct fluid into the housing past the bearing to prevent particles from reaching the bearing.
Implementations of the invention may include one or more of the following features. The conditioner head may include a backing element carrying the abrasive element, and the abrasive element may be an abrasive disk. The drive assembly may have a drive element carried for rotation about a longitudinal axis and a rotatable element coupling the abrasive element to the drive element. The drive element may include a drive shaft and a collar, the collar being substantially fixed to the drive shaft. The rotatable element may include a drive sleeve surrounding at least a length of the drive shaft. The bearing may couple the collar to the housing for permitting the collar to rotate within the housing.
The housing may have a bottom opening and may include a shield attached to the bottom opening to prevent particles from entering the conditioner head and a labyrinth opening may be formed between the shield and the collar. Fluid may be supplied to the labyrinth opening.
The fluid purge system may include a source providing a fluid, and a fluid line that carries fluid from the source to the housing past the bearing and into the labyrinth opening. The fluid may be a gas selected from the group consisting of nitrogen, argon, helium and air. The fluid may also be a liquid selected from the group consisting of water and reactive solvents.
The housing may be coupled to a conditioner arm for moving the head at least transverse to the longitudinal axis and the fluid may be directed to the bearing and labyrinth opening through a fluid line in the conditioner arm and the housing.
In general, in another aspect, the invention features a conditioner head for conditioning the polishing surface of a polishing pad. The conditioner head has an abrasive element engageable with the polishing surface of the polishing pad, a drive assembly coupled to the abrasive element and transmitting rotation to the abrasive element, and a housing surrounding the drive assembly. A fluid purge system directs fluid into the housing to prevent particles from contaminating the drive assembly.
In general, in another aspect, the invention features a method for conditioning a polishing pad having a polishing surface. The method includes: providing an abrasive conditioning element carried by a carrier head and having a lower surface engageable with the polishing surface of the polishing pad, rotating the conditioning element and bringing the lower surface of the conditioning element into engagement with the polishing surface of the polishing pad, and directing a fluid past a bearing system in the carrier head, said bearing system enabling the rotation motion of the conditioning element, and said fluid preventing particles from reaching the bearing system.
Among the advantages of the invention may be one or more of the following. The flow of fluid in the labyrinth past the bearing prevents the accumulation of debris in the labyrinth. It also prevents deterioration of the bearing and other moving components in the conditioner head. This improves the reliability of the conditioner head.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments, and from the claims.
REFERENCES:
patent: 357547
Gurusamy Jayakumar
Medvinsky Alexander
Rosenberg Lawrence M.
Applied Materials Inc.
Fish & Richardson
Hail III Joseph J.
Nguyen George
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