ドントケア抽出を用いた縮退故障テストの遷移故障検出率向上手法

摘要

In recent year, transition fault testing and/or bridging fault testing for VLSIs are increasingly required in addition to stuck-at fault testing because the number of gates on VLSIs is rapidly increasing and their complexity is growing with advances in semiconductor technology. However, additional test patterns to detect fault models other than stuck-at fault cause the increase of testing cost. In this paper, we propose a method to generate a modified test set that not only guarantees to detect stuck-at faults but also detects as many as possible transition faults by applying don't care identification techniques to a given stuck-at test set. Therefore, there are no negative impacts on testing cost. Experimental results for ITC'99 benchmark circuits show that the modified test sets obtained by the proposed method detect more transition faults from 27% than the test sets initially generated for stuck-at faults.%近年VLSIの大規模化，複雑化に伴い，縮退故障テスト以外に遷移故障やブリッジ故障に対するテストの要求が高まってきている．しかしながら，縮退故障以外の故障モデルを検出するために新たにテストパターンを追加すると，テストパターン数に比例してテストコストが増大する．本論文では，ドントケア抽出技術を用いて与えられた縮退故障テストパターンに対して，ドントケアを抽出し，できるだけ多数の遷移故障を検出するようにドントケアに対する値の再割り当て方法を提案する．ITC'99ベンチマーク回路に対して本提案手法を適用した結果，テストパターン数を増加させることなく，遷移故障検出率を最大27％向上させることができた．