Abrading – Machine – Rotary tool
Reexamination Certificate
1999-10-26
2001-06-26
Banks, Derris H. (Department: 3723)
Abrading
Machine
Rotary tool
C451S268000, C451S269000
Reexamination Certificate
active
06250997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a processing machine, such as grinding machine, lapping machine or polishing machine, useful for the processing of a surface of a plate type work-piece, e.g. silicon wafer, to which very precise flatness; parallelism and surface roughness are required. In move in detail, the present invention relates to the driving mechanism which drives the platen of the processing machine.
2. Description of the Prior Art
Lapping or polishing to obtain excellent surface precision and surface roughness on the plate type of work piece to which precise flatness and parallelism are required, has been accomplished using the following method. That is, a work piece is pressed to a rotatable platen of lapping or polishing machine, then lapped or polished by a rotating action of the work piece and platen under the constant supply of compound for lapping or polishing containing abrasives, and the surface roughness of the work piece is improved.
Recently, the requirements to improve the machining accuracy and the dimensional stability to a silicon wafer and a compound semiconductor wafer, which are the starting materials of integrated circuit (IC) or large-scale integration (LSI), and a magnetic disk substrate made of aluminium alloy or glass, are becoming more important. Accordingly, the requirements for the processing machine to improve the thermal stability against temperature changes, and to reduce the vibration of machine, which greatly affect the processing results, are also becoming more important, further, regarding other incidental conditions, more severe control is becoming necessary.
In general, these machines such as lapping machine, or polishing machine, have a platen of considerable thickness made of metal e.g., cast iron, copper, tin or low steel, or non metallic materials, e.g., ceramics or glass, and the platen and a work piece are rotated severally. The processing is carried out on the surface of the platen. The mechanism of these type machines is to process the surface of work piece by friction caused by rotating action of fine particles of abrasive which exist between the platen and work piece. Therefore, the rotating speed must not be effected by the change of friction force and must not cause vibration. In the case of these machines the platen is rotated by the driving motor arranged at the lower position of the housing, while, the work piece is rotated by the driving motor arranged in one or more carrier heads which are placed at the upper position of the machine. The rotating speed of each driving motor is reduced to the necessary rotating ratio by a decelerator, and conveyed to the platen by a belt or a chain.
The above mentioned method converts high speed rotation of an electric motor to low speed high torque rotation by a reduction gear, and, since the size of the decelerator is relatively big, the total size of driving mechanism containing conveying parts becomes big. Therefore, the size of machine becomes bigger and also the weight of machine becomes heavier. The place where the machine can be set up is limited, and the machine can not be considered as a handy type machine.
The above mentioned conventional machine has following problems. That is, the reduction gear will generate heat which is unique to the reduction gear, and especially in a case of high precision processing, it is necessary to prepare a shelter board made of adiabator to prevent the transmittance of generated heat to the platen, or to prepare a quenching ventilator, and these additional apparatuses encourage the tendency of large size and heavy weight of machine. Further, the effective diameter of platen is becoming bigger to meet the bigger size work piece and to satisfy the requirement to improve the productivity, and this tendency is becoming more remarkable. Furthermore, since the supplying line of lapping or polishing compound is placed on the upper position of the machine, the size of machine becomes bigger and more complicated.
Further, reduction gear type decelerator has a tendency to cause the vibration accompanied with the rotation, and by the influence of the vibration, not only surface roughness or TTV (total thickness variation) of processed surface of work piece is deteriorated, but also the problem that the accuracy of an end point detection, which detects the stock removal of work piece, is put out of order further, the trouble of causing noise is also mentioned. And, in a case of the decelerator based on mechanical mechanism, the periodical supply of lubricating oil by periodical maintenance is necessary, further the stains of machine and environment by leaked oil is mentioned as another big problem.
In a driving system which is furnished with a conventional motor, a reduction gear type decelerator and a power transmitting mean, since electric current intensity and putout, that is, load and power, are not in proportion to, each other, the positioning accuracy of a work piece on a platen before and after processing is not good, and it is pointed out as one of the big obstacles for the development of an automatic and continuous type machine. Therefore, in a conventional type machine, it is necessary to equip an additional position sensor and position corrector, which are one of the factors which make the machine complicated.
OBJECT OF THE INVENTION
The inventors of this invention have carried out an intensive study to solve above mentioned problems which characterize conventional lapping and polishing machine, and have found that the use of direct motor driving system gives good results and can solve above mentioned problems, and have accomplished the present invention. That is, the object of this invention is to provide a lapping and a polishing machine which does not generate excess heat, is small and light, has good machining accuracy and does not generate noise and stains.
BRIEF SUMMARY OF THE INVENTION
The above mentioned object can be accomplished by a lapping or polishing machine which processes the surface of a work piece stuck to a carrier head of said lapping or polishing machine by frictional force caused between the surface of a rotating platen of said lapping or polishing machine and the surface of the work piece stuck to the carrier head which is pressed to said rotating platen with supply of lapping or polishing compound, wherein said platen is connected directly to a direct drive motor and driven by said direct drive motor, and the point i.e., positioning to point control of said platen is carried out by a rotary encoder. In said lapping or polishing machine, the carrier head can be directly driven by a direct drive motor. Further, a supplying tube of lapping or polishing compound can be passed through the hollow passage duct in the center of rotating shaft of direct driving motor which drives directly the platen, and lapping or polishing compound can be supplied through a supplying nozzle connected to said supplying tube during the lapping or polishing operation.
The direct driving motor of this invention is a motor which transmits the rotation of motor directly to a rotating part of machine without use of a decelerator or a power transmitting means such as belt or chain, and mainly composed by a stator and a rotor. The rotor is directly connected to the driving shaft of the machine and the rotation of rotor is directly transmitted. The direct driving motor does not have it's own frame or housing and is directly built in the machine. Further, since the direct driving motor has a function of rotary encoder, the positioning to control of the platen or carrier head is very easy and accurate.
REFERENCES:
patent: 5197230 (1993-03-01), Simpfendorfer et al.
patent: 5554064 (1996-09-01), Breivogel et al.
patent: 5593344 (1997-01-01), Weldon et al.
patent: 5791976 (1998-08-01), Honda
patent: 6004187 (1999-12-01), Nyui et al.
patent: 6093081 (2000-07-01), Nyui et al.
patent: 23845 (1899-12-01), None
Hatano Kazutomo
Maruya Mitsuru
Banks Derris H.
Speedfam-Ipec Co LTD
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