Handling: hand and hoist-line implements – Utilizing fluid pressure – Venturi effect
Reexamination Certificate
1999-04-09
2001-09-18
Cherry, Johnny D (Department: 3652)
Handling: hand and hoist-line implements
Utilizing fluid pressure
Venturi effect
C269S021000, C294S907000
Reexamination Certificate
active
06290274
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a system that may be used in conjunction with chucks, and, more particularly, to a system and method for securing a semiconductor wafer substantially flat on a chuck and a system and method for cooling a heated chuck.
2. Disclosure of Related Art
Chucks have long been used to fixedly hold semiconductor wafers during testing. Each semiconductor wafer may contain several thousand integrated circuits on a wafer surface that must be tested. Probers having a chuck and a probe card are utilized to make electrical contact with the integrated circuits. Electrical test signals can be transmitted from testers via the probe card to the integrated circuits. The probe cards contain conductive probe needles that make contact with force on conductive test pads disposed on each integrated circuit. The needles contacting the test pads are commonly referred to as “probing.”
In at least one known wafer holding system, a vacuum source is connected to a chuck having a plurality of holes to create a vacuum force for holding a wafer against the chuck. However, the known systems have several problems. First, the known systems do not allow for a relatively soft engagement between the chuck and a wafer when the vacuum force is initially induced. The known systems induce a vacuum force that may slam the wafer against the chuck. Slamming the wafer against the chuck may create surface cracks on the wafer resulting in scrapped integrated circuits. Second, the known systems will not pull down a warped wafer resting on the chuck so that it is substantially flat against the chuck. It is essential during wafer testing that the wafer be held flat against the chuck. Holding the wafer flat allows the probe needles to make adequate electrical contact with the integrated circuit test pads. Otherwise, erroneous integrated circuit test failures will occur during testing. Third, the known systems will not quickly cool down a heated chuck used for “hot chuck testing” the wafers. Utilizing known systems, after hot chuck testing the wafers, the chuck must sit idle until it cools to an ambient temperature. Thereafter, the chuck can be used to test wafers at an ambient temperature. Cooling a heated chuck using the ambient atmosphere may take several hours resulting in manufacturing downtime and associated manufacturing costs.
The present invention addresses the need for providing greater control over the wafer flattening process such that the surface of the semiconductor wafer is rendered essentially flat without damaging the wafer. The present invention also addresses the need for cooling a heated chuck relatively quickly as compared with known methods.
SUMMARY OF THE INVENTION
The present invention provides a system and method for securing a semiconductor wafer substantially flat on a chuck and a system and method for cooling a chuck.
One object of the present invention is to provide a system and a method for pulling down a semiconductor wafer against a chuck while providing a relatively soft initial engagement between the chuck and a wafer as compared with known systems.
Another object of the present invention is to provide a system and a method for cooling a chuck to an ambient temperature that is faster than known methods.
A system for securing a wafer on a chuck in accordance with the present invention includes first and second conduits, first and second valves, and a first sensor means. The first and second conduits each fluidly connect a first plurality of holes in the chuck to a vacuum source. The first and second valves are disposed within the first and second conduits respectively. The first sensor means is in fluid communication with one of the first and second valves. The first sensor means measures a first vacuum level applied to one of the first and second valves. One of the first and second valves opens to induce a first vacuum force at the first plurality of holes. When the first vacuum level reaches a predetermined vacuum level, the other of said first and second valves opens to increase the first vacuum force. It should be understood that the two stage increase in vacuum force between the chuck and the wafer allows for a softer initial engagement between the chuck and the wafer as compared with conventional systems.
A system for cooling a chuck in accordance the present invention includes a cooling gas source, a first conduit, and a first valve. The first conduit fluidly connects a first plurality of holes in the chuck to the cooling gas source. The first valve is disposed within the first conduit. When the first valve is open, the cooling gas source urges gas to flow through the first plurality of holes to cool the chuck.
A method of securing a wafer disposed on a chuck in accordance with the present invention involves providing first and second conduits each fluidly connecting a first plurality of holes in the chuck to a vacuum source. The method includes providing first and second valves being disposed within the first and second conduits respectively. The method includes applying a vacuum from the vacuum source to the first and second valves. The method includes opening one of the first and second valves to induce a first vacuum force between the chuck and the wafer. The method includes measuring a first vacuum level applied to one of the first and second valves. Finally, the method includes opening the other of the first and second valves to increase the first vacuum force when the first vacuum level is greater than a predetermined vacuum level.
A method for cooling a chuck in accordance with the present invention involves providing a cooling gas source. The method includes providing a first conduit fluidly connecting a first plurality of holes in the chuck to the cooling gas source. The method includes providing a first valve disposed within the first conduit. The method includes opening the first valve to allow gas from the cooling gas source to flow through the first plurality of holes to cool the chuck.
These and other features and objects of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.
REFERENCES:
patent: 3716147 (1973-02-01), Pipes
patent: 4561688 (1985-12-01), Tsutsui
patent: 4707012 (1987-11-01), Takagi
patent: 4721462 (1988-01-01), Collins
patent: 5191218 (1993-03-01), Mori et al.
patent: 5470117 (1995-11-01), Schmidt
patent: 5564682 (1996-10-01), Tsuji
patent: 5857667 (1999-01-01), Lee
patent: 6012509 (2000-01-01), Nonaka
Cherry Johnny D
Dykema Gossett PLL
TSK America, Inc.
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