Performing on-chip partial good die identification
In one embodiment, a multiple input signature register (MISR) shadow works with a MISR to compress test responses of a layout partition in a functional region of an integrated circuit. In operation, for each test pattern in a test pattern split, the MISR generates a MISR signature based on the responses of the layout partition. As the test patterns in the test pattern split execute, the MISR shadow accumulates the MISR signatures and stores the result as MISR shadow data. After the final test pattern included in the test pattern split executes, the MISR shadow combines the bits in the MISR shadow data to form a single bit MISR shadow status that indicates whether the layout partition, and therefore the functional region, responds properly to the test pattern split. By efficiently summarizing the test responses, the MISR shadow optimizes the resources required to identify defective functional regions.
1. A computer-implemented method for identifying defective functional regions within a die, the method comprising:
computing a first signature based on a first test pattern that is applied to a first layout partition within the die;
combining the first signature and first shadow data to generate second shadow data;
reducing a number of bits included in the second shadow data to generate a first status indicator;
tagging a scan-out pin with a first tag to associate a functional region within the die with a first clock cycle, wherein the first status indicator is scanned out via the scan-out pin during the first clock cycle; and
determining whether the functional region is defective based on the first status indicator and the first tag.
2. The computer-implemented method of claim 1 , further comprising storing a complement signature in one or more storage elements, wherein the complement signature reflects an expected response of the first layout partition to the first test pattern.
3. The computer-implemented method of claim 1 , wherein combining the first signature and the first shadow data comprises performing one or more bitwise exclusive OR operations between the first signature and the first shadow data.
4. The computer-implemented method of claim 1 , wherein reducing the number of bits included in the second shadow data comprises performing one or more OR operations between bits included in the second shadow data.
5. The computer-implemented method of claim 1 , further comprising:
generating a second status indicator based on applying a second test pattern to a second layout partition within the die; and
sequentially scanning out the first status indicator and the second status indicator via a first pin.
6. The computer-implemented method of claim 1 , further comprising, prior to when the first test pattern is applied to the first layout partition:
applying a second test pattern to the first layout partition to compute a second signature;
combining the second signature with a third shadow data to generate the first shadow data; and
storing the first shadow data in one or more storage elements.
7. The computer-implemented method of claim 1 , wherein determining that the functional region is defective comprises comparing the first status indicator to a Boolean value of one.
8. A system, comprising:
an accumulation logic circuit that is configured to combine a first signature and a first shadow data to generate second shadow data, wherein the first signature is associated with a first test pattern that is applied to a first layout partition within a die during a first cycle of a first clock;
a status logic circuit that is configured to reduce a number of bits included in the second shadow data to generate a first status indicator during a second cycle of a second clock, wherein a period of the second clock is longer than a period of the first clock;
a test pattern generator that is configured to tag a scan-out pin with a first tag to associate a functional region within the die with the first clock cycle, wherein the first status indicator is scanned out via the scan-out pin during the first clock cycle; and
a test response analyzer that is configured to determine whether the functional region is defective based on the first status indicator and the first tag.
9. The system of claim 8 , wherein the first layout partition is included in a first functional region within the die.
10. The system of claim 8 , wherein the accumulation logic circuit is further configured to store a complement signature in one or more storage elements, wherein the complement signature reflects an expected response of the first layout partition to the first test pattern.
11. The system of claim 8 , wherein the accumulation logic circuit is configured to combine the first signature and the first shadow data by performing one or more bitwise exclusive OR operations between the first signature and the first shadow data.
12. The system of claim 8 , wherein that status logic circuit is configured to reduce the number of bits included in the second shadow data by performing one or more OR operations between bits included in the second shadow data.
13. The system of claim 8 , wherein a previous cycle of the first clock occurs prior to the first cycle, and the accumulation logic circuit is further configured to:
combine a second signature with a third shadow data to generate the first shadow data, wherein the second signature is associated with a second test pattern that is applied to the first layout partition during the previous cycle; and
store the first shadow data in one or more storage elements.
14. The system of claim 8 , wherein a number of bits included in the first status indicator equals one.
15. A system configured to identify defective functional regions within a die, the system comprising:
a signature register that is configured to compute a first signature based on a first test pattern that is applied to a first layout partition within the die;
a signature accumulation logic circuit that is configured to:
for each signature bit included in the first signature, generate a bit included in shadow data based on the signature bit, and
reduce included in the shadow data to generate a first status indicator;
a test pattern generator that is configured to tag a scan-out pin with a first tag to associate a functional region within the die with a first clock cycle, wherein the first status indicator is scanned out via the scan-out pin during the first clock cycle; and
a test response analyzer that is configured to determine whether the functional region is defective based on the first status indicator and the first tag.
16. The system of claim 15 , wherein the signature accumulation logic circuit is configured to generate a first bit included in the shadow data by performing an exclusive OR operation between a first signature bit included in the first signature and the first bit.
17. The system of claim 15 , wherein the signature accumulation logic circuit is configured to reduce the bits included in the shadow data by performing one or more OR operations between the bits included in the shadow data.
18. The system of claim 15 , wherein a number of bits included in the first status indicator equals one.
19. The system of claim 15 , wherein the first layout partition is included in a first functional region within the die.