Repairable/bypassable Scan chains for Product/Technology development phase
Publication Date: 2011-Oct-12
The IP.com Prior Art Database
Disclosed is a method to render scan chains repairable through the use of a redundancy latch and data-shifting scheme.
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Repairable/bypassable Scan chains for Product /Technology development phase
In a typical technology development phase, encountering scan chains with a failing latch results in a failing scan chain. A failure on a critical scan chain results in failure of the chiplet. Both the scan chain and the chiplet are rendered unusable. Current scan chains are not repairable
There is a solution which requires multiple copies of scan chains and uses a comparison of the failing chain to the known passing chain to "fix" the failing scan chain. The drawbacks to this solution are that it is a complex operation, requires area overhead, and performance is limited.
The disclosed solution is to create repairable scan chain to increase the resiliency of scan chains and overall number of usable chiplets. The method uses a redundancy latch and a data-shifting scheme to place a scan chain in a repairable state. The main idea is to:
• Implement wrapper circuitry around the latch to enable bypassing
• Implement a decoder circuitry to select the failing latch to bypass
If a failure occurs, a decoder can be used to address the failing latch (bypass_enable signal). All data from the failing latch through the end of the scan chain is then shifted by 1 latch, thus enabling the use of the redundancy latch.
Repairing the scan chain increases the resiliency of the chiplet to defects and allows recovery of the chiplet, even with a scan chain defect.
This solution is applicable to:
• Early te...