Test apparatus, pattern generator, test method and pattern generating method

1. A test apparatus testing a specimen by using a test pattern and an expected value pattern, the test apparatus comprising:

a control unit to output the test pattern to the specimen;

a pattern converting unit to convert the expected value pattern based on an output pattern, the output pattern output from the specimen upon an input of the test pattern; and

a determination unit to determine the specimen as one of a non-defective product and a defective product by using the converted expected value pattern.

2. The test apparatus according to claim 1 , wherein the pattern converting unit converts the expected value pattern based on the output pattern output from the specimen selected as the non-defective product based on results of tests other than a delay test.

3. The test apparatus according to claim 1 , wherein the pattern converting unit comprises:

an error log generating unit to generate an error log in which a difference between the output pattern and the expected value pattern is stored; and

a pattern conversion executing unit to convert the expected value pattern based on the error log.

4. The test apparatus according to claim 3 , wherein the pattern conversion executing unit inverts a logical value of the expected value pattern based on the error log.

5. The test apparatus according to claim 1 , wherein the control unit further outputs a clock having a predetermined frequency set based on a comparison between the output pattern and the expected value pattern.

6. The test apparatus according to claim 5 , further comprising a test frequency setting unit setting the frequency of the clock output from the control unit,

wherein the test frequency setting unit comprises:

an error list generating unit to generate an error list to associate a number of errors each indicating a difference between the output pattern and the expected value pattern, with the predetermined frequency of the clock;

a histogram generating unit to generate an error histogram indicating a change in the number of errors with respect to a change in the frequency of the clock, based on the error list; and

a test frequency selecting unit selecting the frequency of the clock to be output from the control unit, based on the error histogram.

7. The test apparatus according to claim 6 , wherein the frequency of the clock is set by the test frequency setting unit so that the output pattern obtained at the frequency is different from the expected value.

8. The test apparatus according to claim 6 , wherein the number of errors each indicating the difference between the output pattern and the expected value pattern is determined based on one of the number of the expected value patterns that are each different from the output pattern, and the number of error logical values included in the expected value patterns that are each different from the output pattern.

9. The test apparatus according to claim 6 , wherein:

the error list generating unit generates a plurality of error lists at a plurality of predetermined frequencies at least as high as a normal operating frequency of the specimen; and

the test frequency selecting unit selects the plurality of predetermined frequencies at least as high as the normal operating frequency of the specimen.

10. The test apparatus according to claim 1 , wherein the specimen includes a semiconductor integrated circuit.

11. The test apparatus according to claim 1 , further comprising:

a test pattern storing unit to store the test pattern; and

an expected value pattern storing unit to store the expected value pattern.

12. A pattern generator generating a pattern for determination to be used for a delay test of a specimen, the pattern generator comprising:

a control unit to output a test pattern to the specimen; and

a pattern converting unit to:

convert an expected value pattern based on an output pattern, the output pattern output from the specimen upon an input of the test pattern, and

to output the converted expected value pattern.

13. The pattern generator according to claim 12 , wherein the pattern converting unit converts the expected value pattern based on the output pattern output from the specimen selected as a non-defective product based on results of tests other than a delay test.

14. The pattern generator according to claim 12 , wherein the pattern converting unit comprises:

an error log generating unit to generate an error log in which a difference between the output pattern and the expected value pattern is stored; and

a pattern conversion executing unit to convert the expected value pattern based on the error log.

15. The pattern generator according to claim 12 , wherein the control unit further outputs a clock having a predetermined frequency set based on a comparison between the output pattern and the expected value pattern.

16. The test pattern generator according to claim 15 , further comprising a test frequency setting unit setting the frequency of the clock output from the control unit,

wherein the test frequency setting unit comprises:

an error list generating unit to generate an error list to associate a number of errors each indicating a difference between the output pattern and the expected value pattern, with the predetermined frequency of the clock;

a histogram generating unit to generate an error histogram indicating a change in the number of errors with respect to a change in the frequency of the clock, based on the error list; and

a test frequency selecting unit to select the frequency of the clock to be output from the control unit, based on the error histogram.

17. The pattern generator according to claim 16 , wherein the frequency of the clock set by the test frequency setting unit matches a frequency at which the output pattern and the expected value pattern are different from each other.

18. A test method of testing a specimen by using a test pattern and an expected value pattern, the test method comprising:

inputting the test pattern to the specimen;

converting the expected value based on an output pattern, the output pattern output from the specimen upon an input of the test pattern; and

determining the specimen as one of a non-defective product and a defective product by using the converted expected value pattern.

19. The test method according to claim 18 , wherein the expected value pattern is converted based on the output pattern output from the specimen selected as the non-defective product based on results of tests other than a delay test.

20. A pattern generating method of generating a pattern for determination to be used for a delay test of a specimen, the pattern generation method comprising:

inputting a test pattern to the specimen; and

converting an expected value pattern based on an output pattern, the output pattern output from the specimen upon an input of the test pattern.