Material or article handling – Apparatus for moving material between zones having different...
Reexamination Certificate
1996-04-30
2001-01-23
Bratlie, Steven A. (Department: 3652)
Material or article handling
Apparatus for moving material between zones having different...
C414S226010, C414S937000, C414S939000, C414S941000
Reexamination Certificate
active
06176667
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to equipment for processing semiconductor wafers, and in particular to a method and apparatus for processing two or more wafers at the same time in two or more vertically arranged processing chambers.
Numerous techniques and apparatus are well known for use in the processing of semiconductor wafers to make integrated circuits. The state of the art fabrication facilities (known as “fabs”) for carrying out such processes are typically large buildings within which “clean rooms” of thousands of square feet of floor area are provided. The clean rooms contain the equipment within which the various semiconductor fabrication processes are carried out, for example, chemical vapor deposition equipment for deposition of conductive or insulative materials on the wafers, ion implantation equipment for introduction of impurities into the wafers, furnaces for heating the wafers, plasma etchers for removing material from the wafers, etc.
Compared even to their recent predecessors, clean rooms today are extraordinarily clean, often having particle densities of less than class
1
. Such low particle densities require expensive equipment to purify the air in the clean room, as well as unusual care in all other respects. The result of these measures is that floor space in such clean rooms is expensive. The per-square-foot construction cost, as well as maintenance cost, is high.
Another trend in the manufacture of integrated circuits is the use of single wafer processing equipment. In single wafer equipment, processing is carried out on the wafers one wafer at a time. That is, one wafer is introduced from a cassette holding many wafers into the processing chamber. The necessary process on the wafer is carried out in the chamber, then the wafer is removed from the chamber and the next wafer introduced. Typically, such single wafer processing chambers are clustered around a central robot which can load the chambers with individual wafers. The use of single wafer processing provides higher yields by making the process more controllable across the entire wafer, typically 8 inches in diameter, with 12 inches in the near future. The higher yields produced by single wafer systems have resulted in their use in many of the advanced fabrication facilities used today in the semiconductor industry.
SUMMARY OF THE INVENTION
This invention enables the use of single or multiple wafer process chambers, yet increases the throughput of such systems per unit area of clean room space consumed by the equipment, and at a lower capital cost per wafer processed. This is achieved by stacking the process chambers one above another vertically. By transferring two (or more) wafers at a time from a wafer storing cassette or other means, the vertically arranged process chambers can be operated simultaneously, thereby increasing the number of wafers processed per unit time per unit area of clean room space. This lowers the capital cost per wafer processed, while increasing the utilization of clean room space.
In a preferred embodiment the system of this invention includes a wafer storage mechanism for storing a group of wafers, at least one set of processing chambers having at least two chambers stacked one above the other, and a wafer transfer chamber for moving wafers from the wafer storage mechanism to the at least two chambers.
In another embodiment of the invention, a method for processing more than one wafer simultaneously consists of the steps of providing at least two wafer processing chambers, one disposed above the other, storing a plurality of wafers in a wafer storage mechanism, removing at least two wafers from the wafer storage mechanism, placing each of the at least two wafers in a corresponding process chamber, performing a process on the wafers to change their condition, removing at least one of the at least two wafers from its corresponding process chamber, and returning the wafers removed in the preceding step to the wafer storage mechanism. In either embodiment the wafer storage mechanism itself can be supplied with wafers from a wafer cassette using a second robot, if desired.
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Fairbairn Kevin
Sinha Ashok
Applied Materials Inc.
Bratlie Steven A.
Townsend & Townsend & Crew
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