Work holders – With catch pan
Reexamination Certificate
1999-09-03
2001-06-05
Hail, III, Joseph J. (Department: 3723)
Work holders
With catch pan
C451S388000, C269S021000
Reexamination Certificate
active
06241226
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a vacuum system coupled to a wafer chuck for holding an effluent covered wafer. The vacuum system is capable of detecting excessive effluent in the vacuum system, removing vapor and liquid effluents that have entered the vacuum system and detecting if a wafer has become dislodged from the wafer chuck.
BACKGROUND OF THE INVENTION
A flat disk or “wafer” of single crystal silicon is the basic substrate material in the semiconductor industry for the manufacture of integrated circuits. Semiconductor wafers are typically created by growing an elongated cylinder or boule of single crystal silicon and then slicing individual wafers from the cylinder. During the process of building and connecting the integrated circuits on the wafer, the wafer must be transported from processing station to processing station as well as transported within the same processing station many times. The devices that hold the wafers are generally referred to as wafer chucks. Common examples are wafer carriers (shown in
FIG. 2
) and robotic end effectors (shown in
FIG. 3
) that are commonly used in chemical-mechanical polishing machines as shown in U.S. Pat. No. 5,498,199.
Vacuum systems that are coupled to wafer chucks are well known in the art to assist in the transportation of the wafers. Common pressures within these vacuum systems are between −22 and −27 inHg. As long as the wafer is dry, vacuum systems experience very few failures in assisting a wafer chuck to hold and retain a wafer. However, during chemical-mechanical polishing, cleaning and other semiconductor processing steps, the wafer may be exposed to deionized (DI) water, slurry or other effluents used during the processing of the wafer.
A common problem for vacuum systems used to hold effluent covered wafers is that effluent may be sucked into the vacuum system and plug the valves or foul the vacuum pump. This problem is especially troublesome since the effluent sometimes enters a vapor stage under vacuum conditions making it difficult to effectively remove the effluent from the vacuum system.
Another common problem is that it is difficult to know when a wafer has accidentally been dislodged from the wafer chuck, known as a “lost wafer condition”. If the wafer chuck continues to operate as if the wafer were still firmly held, a valuable wafer might be broken and other wafers and the processing station may also be damaged.
Yet another problem is that effluents can build up in the vacuum system and plug the vacuum lines, valves and vacuum pump. If this “excessive effluent condition” is not detected, it will cause the vacuum system to lose its vacuum thereby making it easier for the wafer to become dislodged from the wafer chuck.
What is needed is a vacuum system in fluid communication with a wafer chuck for reliably holding effluent covered wafers. The vacuum system must be able to remove vapor and liquid effluents that have entered the vacuum system and signal the system computer to take corrective action if a “lost wafer condition” or an “excessive effluent condition” is detected.
SUMMARY OF THE INVENTION
Thus it is an object of the present invention to provide an apparatus for reliably holding effluent covered wafers, which addresses and resolves the shortcomings of the prior art described above.
Another object of the present invention is to provide a vacuum system in fluid communication with a wafer chuck that is tolerant of effluents. The vacuum system must be able to remove the vapor and liquid effluents sucked into the vacuum system and store the effluents until they can be effectively removed.
Yet another object of the present invention is to provide a vacuum system in fluid communication with a wafer chuck that is able to detect a “lost wafer condition” or an “excessive effluent condition” and notify the processing station's computer so that the necessary actions may occur to correct for the detected condition and minimize the damage done to the wafer and the processing station.
In accordance with these and other objects of the present invention, a vacuum system in fluid communication with a wafer chuck has been invented for reliably holding a wafer during or between processing steps. The invention has a vacuum pump for generating a vacuum used by a wafer chuck to retain and hold a wafer. A tank is connected between the vacuum pump and the wafer chuck so as to be part of the vacuum system and in fluid communication with the wafer chuck and the vacuum pump. The tank is capable of knocking vapor effluent out of the air (returning the vapor effluent to a liquid state) sucked into the vacuum system and storing the liquid effluent until it can be conveniently discharged.
These and other aspects of the present invention are described in full detail in the following description, claims and appended drawings.
REFERENCES:
patent: 5655956 (1997-08-01), Ferreira et al.
patent: 5797789 (1998-08-01), Tanaka et al.
patent: 5800251 (1998-09-01), Nakazato et al.
patent: 5897425 (1999-04-01), Fisher et al.
patent: 6067977 (2000-05-01), Wark et al.
patent: 6083083 (2000-07-01), Nishimura
Lichner Christopher J.
Olsen Gregory A.
Rayer, II Phillip
Voelkers Chad J.
Hail III Joseph J.
Shanley Daniel
Snell & Wilmer L.L.P.
SpeedFam-IPEC Corporation
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