Method for testing characteristics of a semiconductor memory device in a series of steps

• US 5,550,838 A
• Filed: 11/22/1993
• Issued: 08/27/1996
• Est. Priority Date: 08/07/1991
• Status: Expired due to Term

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Okajima, Susumu
• Primary Examiner(s): Nguyen, Hoa T.
• Application Number:
  US08/156,392
• Time in Patent Office: 1,009 Days
• Field of Search: 371/21.1, 371/21.4, 371/28, 371/21.2, 324/73.1, 324/158 R, 324/158 T
• US Class Current: 714/719
• CPC Class Codes: G11C 29/10 Test algorithms, e.g. memory scan [MScan] algorithms; Test patterns, e.g. checkerboard patterns
• CPC Class Codes: G11C 29/44 Indication or identification of errors, e.g. for repair

Abstract

Transfer data indicating a measurement status of a characteristics test of a semiconductor memory device is written into the semiconductor memory device itself in any one of a series of measurement steps. In the immediately following measurement step, the transfer data is read out, before performance of a characteristics test of this step, to judge the measurement status of the preceding measurement step. For example, the transfer data is data indicating that the characteristics test has been performed in the preceding step. Alternatively, it is classification data indicating a rank of the semiconductor memory device.

Claims

1. A method of testing a semiconductor memory device classifiable into one of a plurality of classifications and having an erasable memory comprising the steps of:

performing a first measurement on the semiconductor memory device, including;

conducting a first test on the semiconductor device;

recording in the erasable memory of the semiconductor device being tested transfer data relating to the result of the first test;

performing immediately after the first measurement a second measurement on the semiconductor memory device, including;

reading the transfer data recorded in the erasable memory to determine if the first measurement has been performed by determining whether the read-out transfer data is of a predetermined kind;

if the read-out transfer data is of the predetermined kind, conducting a second test on the semiconductor memory device;

classifying the semiconductor memory device into one of a plurality of classifications based on the transfer data read-out in the reading step and based on the result of the second test; and

erasing the data recorded in the erasable memory.

2. A method according to claim 1, wherein the transfer data includes data for determining whether the first measurement has been performed.

3. A method according to claim 1, wherein the transfer data includes data for determining a classification status of the semiconductor memory device.