The proposed standard is a 'die-centric' standard; it applies to a die that is intended to be part of a multi-die stack. The proposed standard defines die-level features, that, when compliant dies are brought together in a stack, comprise a stack-level architecture that enables transportation of control and data signals for the test of (1) intra-die circuitry and (2) inter-die interconnects in both (a) pre-stacking and (b) post-stacking situations, the latter for both partial and complete stacks in both pre-packaging, post-packaging, and board-level situations. The primary focus of inter-die interconnect technology addressed by this standard is Through-Silicon Vias (TSVs); however, this does not preclude its use with other interconnect technologies such as wire-bonding.
The standard will consist of two related items.
1. 3D Test Wrapper Hardware
On-die hardware features that enable transportation of test (control and data) signals in the following configurations.
* Pre-stacking: From on-die I/Os to die-internal DfT/test features, and vice versa. These on-die I/Os might be functional I/Os; however, if they are not present or not accessible, it might be necessary to add additional test I/Os.
o 'Turn' mode: From on-die I/Os to die-internal DfT/test features, and vice versa. These on-die I/Os might be external I/Os on the die itself, and/or inter-die interconnections coming from (or going to) an adjacent die in the stack.
o 'Elevator' mode: From on-die I/Os, through THIS DIE, to the inter-die interconnections to an adjacent die, and vice versa. These on-die I/Os might be external I/Os on the die itself and/or inter-die interconnections coming from (or going to) another adjacent die in the stack.
2. Description + Description Language
A description of the Test Wrapper features in a standardized human- and computer-readable language. This description should allow the usage of the die within a multi-die stack for test and test access purposes.
The proposed standard does not mandate specific defect or fault models, test generation methods, nor die-internal design-for-test, but instead focuses on generic test access to and between dies in a multi-die stack. The proposed standard is based on and works with digital scan-based test access and should leverage existing test access ports (such as based on IEEE Std 1149.x) and on-chip design-for-test (such as IEEE Std 1500) and design-for-debug (IEEE P1687) infrastructure wherever applicable and appropriate.
The proposed standard is 'die-centric', and hence does not aim at 'stack/product-centric' challenges, solutions, and standards, such as the inclusion of Boundary Scan features for board-level interconnect testing. However, the proposed standard should not prohibit the application of such solutions.