Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-05-22
2001-02-20
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
Reexamination Certificate
active
06191596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for detecting a contact position where probe pins are first brought into contact with a wafer at the time of an IC test.
2. Description of the Related Art
For the purpose of inspecting an IC at its wafer stage, there has been used an EB (electron beam) test system which inspects a wafer by the use of an electron beam. In this EB test system, probe pins connected to a semiconductor test device (IC tester) are first moved to detect a first touch position where the probe pins are first brought into contact with the wafer. Thereafter, the probe pins are pushed against the wafer by a constant distance from the first touch position so that the probe pins may come into certain contact with the wafer.
According to a prior art method for detecting a contact position in such an EB test system, the first touch position is detected by manually moving the wafer little by little while checking the state of contact between the wafer and probe pins with the semiconductor test device.
Such a prior art method for detecting a contact position will be explained below with reference to a flowchart of FIG.
1
.
The operator first uses a semiconductor test device to conduct a contact test to find out whether or not the wafer is in contact with the probe pins (step
31
). When the operator determines that the wafer is not in contact with the probe pins in step
31
, the operator manually raises the stage upon which the wafer is carried by one pitch (step
32
) and again conducts the contact test (step
31
). When the contact between the wafer and probe pints is detected, the test processing is terminated (step
32
).
However, the aforementioned prior art method is a disadvantageous in that a time necessary for the position detection is long because detection of the first touch position is carried out manually.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method, which is capable of detecting a first touch position in a short time.
To achieve the above object, there is provided in accordance with the present invention a method for detecting a contact position, which comprises the steps of moving the stage on which an object under measurement is carried up in units of a first predetermined distance and lowering the stage in units of the first predetermined distance when the number of measuring pins in contact with the object becomes equal to or greater than a predetermined constant value. And, when the number of contacted pins becomes smaller than the constant value, the stage is again raised in units of a second predetermined distance smaller than the first predetermined distance. When the number of contacted pins is equal to or greater than the constant value, the then position of the stage at that time is the first touch position.
Therefore, the present method can detect the first touch position more accurately than when the movement of the stage is carried out entirely in units of the first predetermined distance, and can detect the contact position in a shorter time than when the movement of the stage is carried out entirely in units of the smaller second predetermined distance. For this reason, the method of the present invention can automatically detect the first touch position of the object under measurement and measuring pins and also can shorten a position detection time when compared with that of the manual position detection of the prior art.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.
REFERENCES:
patent: 4201939 (1980-05-01), Lee et al.
patent: 4780836 (1988-10-01), Miyazaki et al.
patent: 4864227 (1989-09-01), Sato
patent: 5315237 (1994-05-01), Iwakura et al.
patent: 5436571 (1995-07-01), Karasawa
patent: 5777485 (1998-07-01), Tanaka et al.
Advantest Corporation
Nguyen Vinh P.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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