Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2001-04-06
2004-04-27
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S398000
Reexamination Certificate
active
06726538
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sample polishing apparatus and a sample polishing method for polishing a sample formed of a flat plate such as a semiconductor substrate, in particular, to configurations of fixed parts of a sample suck pad and a chuck base which hold the above sample.
As for a uniform flattening polishing method of an Si wafer, a semiconductor device wafer, or the like, a CMP (Chemical Mechanical Polishing) method is known which utilizes a precision polishing apparatus, a polishing slurry, a polishing pad, and the like and which is used for the flattening of an insulating film, for a capacitor formation, for an STI (Shallow Trench Isolation) and for the formation of a plug or a metal wire of Al, Cu, W, or the like.
A sample polishing apparatus (CMP apparatus) utilized in the CMP method comprises a platen of a large diameter where a polishing pad is stuck to the entirety of the upper surface thereof and a chuck base of a small diameter of which the lower surface faces the platen and which holds a sample as the polishing object such as a semiconductor substrate on that lower surface. The chuck base and the platen both have a thick disk form which are supported by respective supporting axes perpendicular to the respective faces opposite to each other in a coaxial manner so as to rotate around these supporting axes for the operation. In addition, a diamond electrodeposition ring is arranged on the same side of the platen as the chuck base so that the lower surface thereof faces the platen. A nozzle is arranged so as to face platen between the chuck base and the electrodeposition ring so that polishing slurry is supplied to the surface of the platen from the nozzle.
The chuck base is linked to a head which carries out the positioning in the horizontal direction and in the vertical direction on the platen. A chuck (sample suck pad) is stuck to the entirety of the lower surface of the chuck base, which faces the platen, via an adhesive layer so that a sample is fixed on the chuck. In addition, a retainer for preventing the sample from flying out and for preventing excessive polishing of the edges of the sample is provided on the lower surface of the chuck. The retainer is formed of a ceramic or of a specific resin such as Teflon (registered trademark) since chemical resistance and swelling resistance to the polishing slurry as well as resistance to abrasion from the polishing pad and from the polishing grains are required.
In the case that polishing is carried out by using such an apparatus, first, a sample is fixed on the chuck and the chuck base is positioned above a predetermined circle on top of the platen by means of the head so that both are rotated while being approached each other and then the surface to be polished(lower surface) of the sample is pressed on the polishing pad with a predetermined pressure so as to make contact with each other while grinding via the polishing slurry supplied from the nozzle. In addition, in order to stabilize the polishing rate, an in-situ dress of the polishing pad is carried out by the diamond electrodeposition ring for every predetermined number of samples being polished.
As described above, at the time of polishing process of an Si wafer and a semiconductor device wafer, polishing slurry is used. As for the polishing liquid of the polishing slurry, silica sol (pH≈10.5), ceria sol (pH≈6.5) or the like are used in the case of the flattening of an insulating film. Silica sol in general has a buffer solution as a base and pH thereof is fixed to alkaline by using potassium hydroxide, ammonia, or the like. The merits of this are cited as follows: the polishing rate is stabilized through the enhancement of dispersibility of the polishing grains and the polishing rate is increased through the hydration of the silicon oxide film. In addition, in the metal polishing using Al, Cu, W, or the like, alumina is generally used as the polishing grains and a method is used where the metal surface is mechanically peeled with the polishing grains while oxidizing with an oxidant such as hydrogen peroxide. The pH of the polishing slurry of this case is, in many cases, fixed in the range from 3.5 to the neutrality.
Since the alkaline or acid polishing slurry is, in many cases, utilized in this manner, the chemical resistance of the parts used in the CMP apparatus is important in enhancing the stability of the polishing apparatus. Particularly in the polishing process of a semiconductor wafer, the chuck structure for holding a sample is cited as a part which greatly influences the uniformity and the flattening of the wafer.
As for the chuck structure, a system of bonding a sample to a high precision flat plate by means of wax, a system of sucking and fixing a sample onto a high precision flat plate by means of vacuum suck and a template system wherein a sample is bonded onto a backing film which is a non woven fabric formed of a soft artificial leather are known. The bonding system by means of wax has a problem that lack of uniformity of the wax application greatly influences the polishing uniformity of the sample and the setting and releasing step through heating and cooling is necessary. And the template system by means of the backing film has a problem that aggregation grains are mixed in between the backing film and the wafer or a bubble is mixed in at the time of wafer suck so as to generate dimples and thereby the uniformity is deteriorated. In regard to these points, a vacuum suck system is adopted in many cases and the vacuum suck system has advantages that the number of polishing steps is smaller and the step management is simpler in comparison with other systems and the dimples on the wafer surface can be reduced.
In the case that the above described CMP apparatus is formed in accordance with the vacuum suck system, a chuck base made of ceramic where the lower surface is formed as a highly precise plane is utilized and pin holes of which the diameter is approximately 0.1 mm are provided at a few mm intervals over the entire surface of this chuck base. In addition, the chuck made of synthetic resin has been processed so as to have trenches on the suck surface toward a wafer so that the vacuum suck area is increased. In particular, for a sample which has a macroscopic waviness such as a semiconductor wafer, the vacuum suck and the surface standard polishing can be made effective by combining a chuck base which has the air permeability in the above manner and a chuck formed of a non woven fabric, rubber, resin, artificial leather, or the like which has the air permeability and the elasticity. Such a chuck structure is proposed by the present applicant in Japanese Patent Application Laid-Open No.8-181092(1996).
As described above, the chuck is stuck and fixed to the chuck base via an adhesive layer and the adhesive layer is formed of a commercially available acryl adhesive double coated tape or a resin based adhesive such as an epoxy resin or a light curing agent. In the case that the chuck is fixed to the chuck base by using an acryl adhesive double coated tape, however, the adhesive double coated tape is exposed to the acid and alkaline polishing slurry and the problem arises that the quality of the acryl resin on the outer periphery of the adhesive double coated tape is changed and this outer periphery becomes swollen due to moisture absorption so as to peel off from the chuck base. This is because the acryl acid ester (R
1
—COO—R
2
), which is the skeleton of the acryl adhesive double coated tape, undergoes hydrolysis in the acid or alkaline polishing slurry so that the adhesiveness is deteriorated.
In addition, in the case that the chuck is fixed to the chuck base by using a resin-based adhesive, there are problems that the elasticity is inferior to that of the adhesive double coated tape and therefore a pressure shock at the time of polishing movement cannot be buffered and in addition, the resin-based adhesive is swollen through the erosion by the polishing slurry and thereby the edge parts of the
Saguchi Akihiko
Takahashi Wataru
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hail III Joseph J.
Ojini Anthony
Tokyo Electron Limited
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