Failure File Formats

The Mentor Graphics YieldAssist™ advanced failure diagnosis tool provides a comprehensive set of functionality to quickly analyze devices that fail manufacturing test. It leverages production scan patterns, either compressed (generated by TestKompress) or uncompressed (generated by FastScan™), to rapidly and accurately identify and isolate yield-limiting defects.

One of the inputs to YieldAssist is failure file which contains test fail information from testers. Traditionally, failure file is pattern-based, requiring fail information on test pattern ID, scan cell ID and scan chain ID; and the user has to map tester fail log to it. It’s very difficult to develop and error prone due to the complexity of test patterns and the fact that tester fail log is normally cycle-based. YieldAssist reads in cycle-based failure file where the user only needs to provide failing cycle, design pin and expect/actual value. This has greatly simplified the failure file development process and reduced errors to a minimum. The following is an example of cycle-based failure file:

// cycle-based failure file example
format cycle

                   et_expected_z_handling H  //optional
tracking_info_begin        //optional
lot_id 12345                 //optional
wafer_id 98765             //optional
design_id 54820            //optional
tracking_info_end          //optional
failures_begin
13450 pin100 H L
15345 pin140 L H
15900 pin130 H L
15900 pin140 L H
17120 pin130 H L
19201 pin130 L H
19320 pin130 H L
failures_end
total_cycles 60150         //optional

The syntax of cycle-based failure file format is documented in the YieldAssist User’s Guide. The YieldAssist cycle-based failure file format is supported directly by Verigy 93K tester. Please see the appnote >>

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