Method and system for statistical comparison of a plurality of testers
AssigneeTexas Instruments Incorporated
InventorJoel L. Dobson
Life of this patent
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Abstract
The invention provides methods and systems for statistically comparing yields among two or more testers in a testing environment where a lot of manufactured articles such as semiconductor wafers are randomly divided among and independently tested by the testers. Generally, in real-time, tests are performed on the lot and yield statistics are determined for each of the two or more testers as a function of test yields and the number of tests performed by each tester. Using the yield statistics, a univariate T-statistic for each tester is determined and serves as the basis for comparing each tester with a predetermined threshold statistical range.
Claims26
In a wafer testing environment, a method of statistically comparing yields among two or more testers comprising the steps of:
- for a plurality of wafers comprising a lot, randomly dividing the lot among the two or more testers;
- for each of the two or more testers, determining yield statistics as a function of real-time wafer test yields and the number of wafer tests performed on the lot by each tester;
- and
- using the yield statistics, determining a univariate T-statistic for each tester for comparing the univariate T-statistic for each tester with a predetermined threshold statistical range.
A system for statistically comparing two or more testers testing a randomly divided lot of manufactured articles, comprising:
- a plurality of testers for independently performing tests on articles selected from a manufactured lot and generating test data;
- one or more computer coupled to the plurality of testers;
- software executable by the one or more computer, the software further comprising;
- means for determining yield statistics as a function of real-time test data and a count of the tests performed on the lot by each tester;
- means for determining a univariate T-statistic for each tester;
- and
- means for comparing the univariate T-statistic of each tester with a predetermined threshold statistical range.
Machine readable instructions executable by a computer for use in making real-time statistical comparisons of two or more testers testing a randomly divided lot of manufactured articles, comprising:
- means for maintaining a count of tests performed by each of the two or more testers;
- means for monitoring test data generated by each of the two or more testers;
- means for determining yield statistics as a function of test count and test data for each tester;
- means for calculating a univariate T-statistic for each tester;
- and
- means for comparing each univariate T-statistic with a predetermined threshold statistical range.
Dependencies are inferred from the claim text.