Method and system for testing memory programming devices

• US 5,682,472 A
• Filed: 03/17/1995
• Issued: 10/28/1997
• Est. Priority Date: 03/17/1995
• Status: Expired due to Term

• Current Assignee: AEHR Test Systems
• Original Assignee: AEHR Test Systems
• Inventors: Shepherd, Patrick M., Brehm, Jeffrey A.
• Primary Examiner(s): Beausoliel, Jr., Robert W.
• Assistant Examiner(s): Wright, Norman M.
• Application Number:
  US08/407,103
• Time in Patent Office: 956 Days
• Field of Search: 395/183.01, 395/183.03, 395/183.06, 395/184.01, 395/183.18, 395/183.21, 395/185.07, 395/185.01, 395/183.22
• US Class Current: 714/25
• CPC Class Codes: G01R 31/3191 Calibration
• CPC Class Codes: G11C 29/10 Test algorithms, e.g. memory scan [MScan] algorithms; Test patterns, e.g. checkerboard patterns
• CPC Class Codes: G11C 29/56 External testing equipment for static stores, e.g. automatic test equipment [ATE]; Interfaces therefor

Abstract

A novel system and method for testing semiconductor devices has a pattern generator implementing a test signal algorithm uniquely coupled with a recording system which is an individual hardware system for each device under test. The improved pattern generator and recording system functions in conjunction with a system designed to perform parallel test and burn-in of semiconductor devices, such as the Aehr Test MTX System. The MTX can functionally test large quantities of semiconductor devices in parallel. It can also compensate for the appropriate round trip delay value for each chip select state for each device under test. This system of testing provides an effective and practical method for reducing overall test cost without sacrificing quality.

Claims

1. A method of testing a plurality of semiconductor devices which comprises the steps of:

coupling a passflag to a recording system for each individual semiconductor device of said plurality of semiconductor devices;

sending write commands and data to a first address of said plurality of semiconductor devices in parallel;

verifying said data on the first address for each individual semiconductor device in parallel;

if said data were not successfully written into the first address for all of said plurality of semiconductor devices, repeating the steps of sending and verifying said write commands and data to the first address only for those of said plurality of semiconductor devices for which said data were not successfully written into the first address;

counting the number of repeated attempts to successfully program the first address;

if said count of repeated attempts reaches a given maximum, then rejecting any of said plurality of semiconductor devices for which said data were not successfully written into the first address as defective;

if said data are successfully written into the first address of all of said plurality of semiconductor devices, then terminating any further write attempts to the first address;

if said data are successfully written into the first address of a particular one of said plurality of semiconductor devices, setting said passflag for that particular one of said semiconductor devices to true;

if said passflag for that particular one of said semiconductor devices is set to true, terminating the sending of write commands to the first address for that particular one of said semiconductor devices; and

repeating all the preceding steps for successive addresses until a last address is reached.

2. The method of claim 1 in which said steps more specifically comprise, separately for each of said semiconductor devices:

setting a loop count to 0;

setting n to 0;

setting address to n;

setting pass flag to false;

sending commands to address=n;

sending dam to address=n;

verifying said data at address=n;

if address=n has not been successfully programmed, then checking to see if the loop count has reached the maximum number;

if the loop count is less than maximum number allowed, then adding one to the loop count;

then re-sending said command and data to address=n and repeating the step of verifying said data;

if the loop count has reached maximum, then checking a state of said passflag;

if the passflag is still set to false, then rejecting that particular one of said plurality of semiconductor devices as defective;

if address=n has been successfully programmed, then setting the passflag for that particular one of said plurality of semiconductor devices to true;

if the passflag is set to true, then terminating the sending of write commands by sending no-operation commands to the first address for that particular one of said plurality of semiconductor devices and adding 1 to n; and

repeating the preceding steps beginning at sending commands to address=n.

3. The method of claim 1 in which said recording system coupled with said passflag is an individual hardware system for each device under test.

4. The method of claim 1 in which said recording system coupled with said passflag keeps track of the state of said passflag.

5. The method of claim 4 in which the state of said passflag is either true or false.

6. The method of claim 1 in which said recording system comprises:

a first set of latches for keeping track of the state of said passflag for each data bit of a device; and

a second latch for keeping track of the first set of latches.

7. The method of claim 6 in which the device under test is coupled to both the first set of latches and the second latch.

8. A system of testing semiconductor devices using the memory programming algorithm of claim 1 in which a testing apparatus is coupled with said algorithm for performing parallel tests of devices.

9. The system of testing semiconductor devices of claim 8 in which said testing apparatus includes:

a pattern generator for generating information to be inputted into devices under test; and

a device test board connected to said pattern generator for facilitating said semiconductor devices to be tested.

10. The system of testing semiconductor devices of claim 9 in which one pattern generator generates information to be inputted into a multiplicity of devices.

11. The system of testing semiconductor devices of claim 9 in which said system utilizes reprogrammable pass/fail logic for accommodation of different configurations of devices.

12. The system of testing semiconductor devices of claim 9 in which said device test board is divided into a multiplicity of sections where each section has its own set of signals.

13. The system of testing semiconductor devices of claim 9 in which said pattern generator comprises:

a chip selector for enabling semiconductor devices to be tested; and

a timing generator with a multiplicity of timing sets.

14. The system of testing semiconductor devices of claim 13 where said timing generator variably compensates for appropriate round trip delay value for each group of semiconductor devices selected by said chip selector.

15. The system of testing semiconductor devices of claim 13 in which said chip selector enables a multiplicity of said semiconductor devices simultaneously.

16. The system of claim 13 in which said pattern generator further comprises:

a micro-sequencer to control said pattern generator functions;

an address generator to select or create address patterns; and

a data generator to select or create unique data patterns.

17. The system of testing semiconductor devices of claim 13 in which said testing apparatus further includes a driver board to assemble information from the pattern generator and provide signals to the devices.

18. The system of testing semiconductor devices of claim 9 in which said testing apparatus further includes an unsealed hot chamber with a temperature range of approximately +45°

C. to +250°

C.

19. The system of testing semiconductor devices of claim 18 in which said hot chamber draws cool air as necessary and heats air as necessary.

20. The system of testing semiconductor devices of claim 9 in which said testing apparatus further includes a sealed hot/cold chamber with a low temperature range of below +45°

C.

21. The system of testing semiconductor devices of claim 9 in which said testing apparatus further includes an ambient station which does not require a temperature control.

22. The method of claim 1 in which the sending of write commands to the first address for that particular one of said semiconductor devices is terminated by sending a no-operation command to the first address for that particular one of said semiconductor devices.

26. The system of testing semiconductor devices of claim 22 further comprising a testing apparatus coupled with said algorithm.

27. The system of testing semiconductor devices of claim 26 in which said testing apparatus includes:

a pattern generator for generating information to be inputted into devices under test; and

a device test board connected to said pattern generator for facilitating said semiconductor devices to be tested.

28. The system of testing semiconductor devices of claim 27 in which one pattern generator generates information to be inputted into a multiplicity of devices.

29. The system of testing semiconductor devices of claim 27 in which said system utilizes reprogrammable pass/fail logic for accommodation of different configurations of devices.

30. The system of testing semiconductor devices of claim 27 in which said device test board is divided into a multiplicity of sections where each section has its own set of signals.

31. The system of testing semiconductor devices of claim 27 in which said pattern generator comprises:

a chip selector for enabling semiconductor devices to be tested; and

a timing generator with a multiplicity of timing sets.

32. The system of testing semiconductor devices of claim 31 in which said timing generator compensates for appropriate round trip delay value for each semiconductor device in each stab selected by said chip selector.

33. The system of claim 31 in which said pattern generator further comprises:

an address generator to select or create address patterns;

a data generator for selecting or creating unique data patterns; and

a micro-sequencer to control said pattern generator functions.

34. The system of testing semiconductor devices of claim 31 in which said chip selector enables a multiplicity of said semiconductor devices simultaneously.

35. The system of testing semiconductor devices of claim 31 in which said testing apparatus further includes a driver board to assemble the information from the pattern generator and provide signals to the devices.

36. The system of testing semiconductor devices of claim 27 in which said testing apparatus further comprises an unsealed hot chamber with a temperature range of approximately +45°

C. to +250°

C.

37. The system of testing semiconductor devices of claim 36 in which said hot chamber draws cool air as necessary and heats air as necessary.

38. The system of testing semiconductor devices of claim 27 in which said testing apparatus comprises a sealed hot/cold chamber with a low temperature range of below +45°

C.

39. The system of testing semiconductor devices of claim 27 in which said testing apparatus comprises an ambient station which does not require a temperature control.

23. A system of testing semiconductor devices comprising:

a passflag signal generator coupled to a memory programing algorithm for performing parallel tests Of devices indicating whether the semiconductor devices are defective;

a first set of latches coupled to said passflag signal generator for keeping track of a state of a passflag signal generated by the passflag signal generator for each data bit of each semiconductor device; and

a second latch for keeping track of a collective set of the first set of latches for each device;

said algorithm comprising the steps of, for each of the semiconductor devices;

sending commands and data to a first address;

verifying said data at the first address;

if said data were not successfully programmed onto the first address, repeating the steps of sending and verifying said commands and data onto the first address;

counting the number of repeated attempts to successfully program the first address;

if said count of repeated attempts reaches a given maximum, then rejecting that particular one of the semiconductor devices as defective;

if said data are successfully programmed onto the first address, setting said passflag signal to true for that particular one of the semiconductor devices;

if said passflag is set to true, terminating the sending of write commands to the first address for that particular one of the semiconductor devices; and

repeating all the preceding steps for successive addresses until a last address is reached.

24. The system of testing semiconductor devices of claim 23 in which the state of said passflag is either true or false.

25. The system of testing semiconductor devices of claim 24 in which said algorithm more specifically comprises, separately for each of the semiconductor devices:

setting a loop count to 0;

setting n to 0;

setting address to n;

setting said passflag signal to false;

sending commands to address=n;

sending data to address=n;

verifying said data on address=n;

if said data are successfully written into the first address of all of said plurality of semiconductor devices, then terminating any further write attempts to address=n;

if address=n has not been successfully programmed, then checking to see if the loop count has reached the maximum number;

if the loop count is less than maximum number allowed, then adding one to the loop count;

then re-sending said command and data to address=n and repeating the step of verifying said data;

if the loop count has reached maximum, then checking to see a state of said passflag signal, wherein said passflag signal is coupled to a recording system;

if said passflag signal is still set to false, then rejecting that particular one of the semiconductor devices as defective;

if address=n has been successfully programmed, then setting said passflag signal to true for that particular one of the semiconductor devices;

if said passflag signal is set to true, then terminating the sending of write commands by sending no-operation commands to the first address for that particular one of the semiconductor devices and adding 1 to n; and

repeating the preceding steps beginning at sending commands to address=n.

40. A method of testing a plurality of semiconductor devices which comprises the steps of:

generating a plurality of test signals for the semiconductor devices;

coupling a plurality of semiconductor devices in parallel to receive the plurality of test signals;

coupling a plurality of test result readers to each of said plurality of semiconductor devices;

variably compensating for appropriate round trip delay value for different groups of the semiconductor devices;

generating the plurality of test signals comprising the steps of, for each of the plurality of semiconductor devices;

sending commands and data to a first address;

verifying said data at the first address;

if said data were not successfully programmed onto the first address, repeating the steps of sending and verifying said commands and data onto the first address;

counting the number of repeated attempts to successfully program the first address;

if said count of repeated attempts reaches a given maximum, then rejecting that particular one of the plurality of semiconductor devices as defective;

if said data are successfully programmed onto the first address, setting said passflag signal to true for that particular one of the plurality of semiconductor devices;

if said passflag is set to true, terminating the sending of write commands to the first address for that particular one of the plurality, of semiconductor devices; and

repeating all the preceding steps for successive addresses until a last address is reached.

41. A semiconductor device testing apparatus, which comprises:

a pattern generator for generating a plurality of test signals for the semiconductor devices;

an interface for coupling a plurality of semiconductor devices in parallel to said pattern generator, and

a plurality of test result readers connected to said interface so that one of said plurality of test result readers can be coupled to each of said plurality of semiconductor devices;

where said pattern generator variably compensates for appropriate round trip delay value for different groups of the semiconductor devices.

42. The semiconductor device testing apparatus of claim 41 in which said interface for coupling is a chip selector which enables a multiplicity of said semiconductor devices simultaneously.

43. The semiconductor device testing apparatus of claim 41 in which said pattern generator includes a timing generator with a multiplicity of timing sets.

44. The semiconductor device testing apparatus of claim 43 in which the timing generator variably compensates for appropriate round trip delay value for different groups of the semiconductor devices.

45. The semiconductor device testing apparatus of claim 41 in which said pattern generator further comprises:

a micro-sequencer to control said pattern generator functions;

an address generator to select or create address patterns; and

a data generator for selecting or creating unique data patterns.

46. The semiconductor device testing apparatus of claim 41 in which said testing apparatus further comprises a driver board to assemble information from the pattern generator and provide signals to the devices.

47. The semiconductor device testing apparatus of claim 41 further comprises an unsealed hot chamber with a temperature range of approximately +45°

C. to +250°

C.

48. The semiconductor device testing apparatus of claim 47 in which said hot chamber draws cool air as necessary and heats air as necessary.

49. The semiconductor device testing apparatus of claim 41 in which said testing apparatus comprises a sealed hot/cold chamber with a low temperature range of below +45°

C.

50. The semiconductor device testing apparatus of claim 41 in which the semiconductor devices are mounted in a device test board and said device test board is divided into a multiplicity of sections where each section has its own set of signals, including a chip select sisal to enable a group of devices in that section for testing.