US 6,477,672 B1Granted

Memory testing apparatus

AssigneeAdvantest Corporation

InventorKazuhiko Satoh

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Abstract

A memory testing apparatus is provided, which can test in short time a memory having a block function like a flash memory. In addition to a failure analysis memory AFM capable of storing failures of all bits of a memory under test MUT, are provided a first bad block memory BBM and a second bad block memory CFM each having its storage capacity corresponding to the number of blocks that the memory under test has. The results of an initial test are stored in the first bad block memory. Utilizing the results of the initial test as mask data, bad blocks which have been determined to be failure in the initial test are masked by the mask data, respectively, so that a functional test for the bad blocks are omitted and the functional test for only pass blocks is performed. The results of the functional test are stored in the second bad block memory, and only the blocks having their bad block data stored in the second bad block memory are determined as to whether they are repairable or not.

Claims28

Dependent claims

A memory testing apparatus for testing a non-volatile memory that includes a plurality of memory blocks each including a plurality of memory cells in which stored data can be electrically erased in one or more of the blocks and rewritten, said memory testing apparatus comprising:

a pattern generator;
a failure analysis memory;
and
a first bad block memory having its storage areas the number of which corresponds to the number of blocks that a memory under test has;and
wherein the memory-testing apparatus operates in an initial test mode in which
a constant logical value is written in memory cells of each of all the blocks of the memory under test,
the written logical value is read out,
a decision is rendered whether a memory cell is defective according to whether the read-out logical value is in disaccord with the written logical value,
failure data is written into the failure analysis memory for memory cells that are decided to be defective,
each block having even one memory cell the read-out logical value from which is in disaccord with the written logical value is detected as a failure block, and
bad block data representing said failure blocks are stored in a storage area of said first bad block memory corresponding to said failure blocks.

8 more elements

Dependencies are inferred from the claim text.