March tests for word-oriented memories

Abstract

Most memory test algorithms are optimized tests for a particular memory technology and a particular set of fault models, under the assumption that the memory is bit-oriented; i.e., read and write operations affect only a single bit in the memory. Traditionally, word-oriented memories have been tested by repeated application of a test for bit-oriented memories whereby a different data background (which depends on the used intra-word fault model) is used during each iteration. This results in time inefficiencies and limited fault coverage. A new approach for testing word-oriented memories is presented, distinguishing between inter-word and intra-word faults and allowing for a systematic way of converting tests for bit-oriented memories to tests for word-oriented memories. The conversion consists of concatenating the bit-oriented test for inter-word faultswith a test for intra-word faults. This approach results in more efficient tests with complete coverage of the targeted faults. Because most memories have an external data path which is wider than one bit, word-oriented memory tests are very important.

A systematic method for modifying march tests for bit-oriented memories into tests for word-oriented memories

“…Using the uCFid fault type for intraword faults, the intraword test has to use a set of DBs which have to be applied to the memory in a particular sequence, i.e., a sequence of DBs, also called the data background sequence (DBS), is required [5]. This sequence is derived below.…”

“…Eight uCFdsts subtypes exist [4], [5]: < r0; "> c a ;c v , < r0; #> c a ;c v , < r1; "> c a ;c v , < r1; #> c a ;c v , < w0; "> c a ;c v , < w0; #> c a ;c v , < w1; "> c a ;c v , and < w1; #> c a ;c v , where a; v 2 f0; 1; . .…”

“…Subsets of this problem have been addressed in [5], [6]. The conversion consists of concatenating to the march test for single-cell faults, and possible interword faults (i.e., faults between words), a march test designed for intraword faults (i.e., faults within words).…”

New data-background sequences and their industrial evaluation for word-oriented random-access memories

“…Traditionally, WOMs have been tested by repeated application of BOM tests, where different data backgrounds (DBs) are used during each iteration [5], [15]- [17], [19]. The disadvantages of this methodology are test time inefficiency and limited fault coverage of coupling faults (CFs) between cells within the same word, which are called intraword CFs.…”

“…In addition, it does not guarantee the detection of all intraword CFs. In [17] and [19], DB sequences (DBSs) for intraword idempotent and disturb CFs have been presented. In addition, a systematic way for converting BOM tests into WOM tests has been introduced, based on concatenating the BOM test (which detects faults between words) and the WOM test (which detects the faults within a word).…”