AC-Characteristics and the Pass/Fail Performance of a Memory Chip

Abstract

The continuing rapid development in memory device technology results in more dense and more complex storage structures. At the time Dynamic Random Access Memories (DRAM) are able to store about 1.000.000 bits. Speed quantities like access, hold and setup times are AC-parameters (alternating current). They depend on internal processes and indicate the efficiency of a chip. The measured values of these parameters show the timing conditions of a chip which is working correctly. If all AC-parameters of a chip meet the specification, the chip passes the test and can be classified into a group which indicates its speed. With each chip generation the number of AC-parameters may increase, e.g. the timing conditions of the Siemens 1 M DRAM are characterized by 48 AC-parameters. Analysing the timing conditions becomes more and more difficult since vast amount of data is the result of testing. By the selection of more suitable parameters, the analysis of data is simplified and the costs of testing are reduced. Our results are shown by the example of the read cycle.