Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1999-02-09
2001-09-04
Ostrager, Allen (Department: 3725)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S287000, C451S288000
Reexamination Certificate
active
06283827
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is in the field of semiconductor manufacturing and more specifically relates to improvements in apparatus for handling semiconductor wafers as they are carried through a planarizing machine.
As supplied to the planarizing machine, the surface of a wafer may exhibit departures from flatness. Typically, 25 wafers are loaded into a cassette which is hand carried to a complex machine called a planarizer. The purpose of the planarizer is to render the front surface of the wafer flat to within a fraction of a micron. After each wafer has been rendered flat, the planarizer inserts it into a cassette. When the cassette is full, it may be removed from the planarizer and transported to any of a number of other processing machines.
The present invention cannot be fully appreciated without an understanding of the operation of the planarizer. Once the cassette containing typically 25 pre-processed wafers has been inserted into the planarizer, the operation of the planarizer in processing the wafers is completely autonomous. The operations are carried out under control of a computer that controls the application of power to various actuators in response to sensed inputs in a time-coordinated manner. In order for its lengthy program of operations to be carried out without mishap, it is important that means be provided to interrupt the accumulation of positional errors. It can also be appreciated that the wafers must be handled carefully to avoid scratching the processed surfaces which are so fragile that they are never again touched by human hands.
The present invention can best be understood by following a typical wafer as it is moved through the planarizer. The wafer is extracted from the cassette by a portion of the planarizer called a robot. The robot carries the wafer to a fixed location known as the load station. After the robot has deposited the wafer at the load station and has moved out of the way, a different part (called a spindle carrier) moves into position above the wafer and acquires it. The spindle carrier transports the wafer to a rotating polishing platen and rotates the wafer while holding it in contact with the rotating polishing platen until the wafer has been rendered flat. Thereafter, the spindle lifts the wafer from the polishing platen and transports it back to the load station where the wafer is rinsed. After the spindle carrier has deposited the wafer at the load station and has moved out of the way, the robot picks up the polished wafer and carries it to a cassette and deposits the wafer in the cassette. Throughout these operations, the wafer is maintained in a horizontal position with the side that is to be polished facing downward. That downward facing side of the wafer is also referred to as the front side of the wafer. The path of an individual wafer through the planarizer will be depicted in greater detail below.
Upon reflection it will be seen that the main purpose of the load station is to accurately center the wafer into the carrier notwithstanding the errors in their relative positions as they enter the load station.
In addition to centering the wafer with respect to the carrier, the load station performs a number of useful ancillary functions. The load station includes provision for sensing the presence of the wafer at the load station, for rinsing the wafer, for lifting the wafer into the carrier, and for supporting the processed wafer on cushions of water to avoid direct contact. Thus, the load station serves several other functions in addition to centering the wafer with respect to the carrier.
SUMMARY OF THE INVENTION
As indicated in
FIGS. 1-10
, the wafer is maintained with its fragile processed side facing downward as the wafer is passed from the robot to the load station and from the load station to the spindle carrier, and then returned from the spindle carrier to the load station to the robot. It is an objective of the present invention to accomplish these transfers without anything solid contacting the downwardly facing side of the wafer.
In accordance with the present invention this is accomplished by supporting the wafer while it is on the load station on cushions of purified water. The cushions are formed at three spaced areas on the lower side of the wafer by upwardly-directed nozzles located below the wafer. The purified water is discharged with sufficient force to prevent the wafer from contacting the nozzles.
The use of three separate cushions insures stability of the wafer.
The novel features which are believed to be characteristic of the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.
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patent: 4508161 (1985-04-01), Holden
patent: 4521995 (1985-06-01), Sekiya
patent: 4625463 (1986-12-01), Sekiya
patent: 4903717 (1990-02-01), Sumnitsch
patent: 5267418 (1993-12-01), Curie et al.
patent: 5423716 (1995-06-01), Strasbaugh
patent: 5449316 (1995-09-01), Strasbaugh
patent: 5800248 (1998-09-01), Pant et al.
patent: 6062959 (2000-05-01), Weldon et al.
patent: 0 493 117 A2 (1992-07-01), None
Lentz Terry L.
Vogtmann Michael R.
Hong William
Lam Research Corporation
Martine & Penilla LLP
Ostrager Allen
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