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Method for analyzing wafer test parameters

  • US 6,968,280 B2
  • Filed: 03/24/2003
  • Issued: 11/22/2005
  • Est. Priority Date: 03/24/2003
  • Status: Active Grant
First Claim
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1. A method for analyzing wafer test parameters of a plurality of lots of wafers, each lot of the wafers comprising a lot number, each wafer of each lot comprising at least one wafer test parameter generated by performing at least one wafer test item stored in a database, parameters related to at least one sample test item, one in-line quality control (QC) item and one process step item related to the wafer test item being stored in the database, the method comprising:

  • dividing the lots of wafers into at least a high yield group and a low yield group based on yield of the lots;

    obtaining a first standard value within a first range by analyzing the wafer test parameters of the wafers in the high yield group;

    performing a first comparison step to compare each wafer test parameter of each lot in the low yield group with the first standard value and delete lot numbers of lots with wafer test parameters within the first range;

    determining a first amount of residual lots in the low yield group after the first comparison step;

    while the first amount of residual lots in the low yield group is not equal to zero, performing the following steps;

    performing a first searching step to determine which item of sample test items, in-line QC items and process step items is related to the wafer test item of each residual lot in the low yield group from the database;

    when the sample test item is determined to be related to the wafer test item in the first searching step, obtaining a second standard value within a second range by analyzing the parameters related to the sample test item of the wafers in the high yield group;

    performing a second comparison step to compare the parameters of sample test item of each residual lot in the low yield group with the second standard value and delete lot numbers of residual lots with parameters related to the sample test item within the second range;

    determining a second amount of residual lots in the low yield group after the second comparison step;

    while the second amount of residual lots in the low yield group is not equal to zero, performing the following steps;

    a second searching step to determine which item of the in-line QC items and the manufacturing machine items is related to the sample test item of each residual lot from the low yield group in the database;

    when the in-line QC item is determined to be related to the sample test item in the second searching step, obtaining a third standard value within a third range by analyzing the parameters related to the in-line QC item of the wafers in the high yield group;

    performing a third comparison step to compare the parameters of in-line QC item of each residual lot in the low yield group with the third standard value and delete lot numbers of residual lots with the parameters related to the in-line QC item within the third range;

    determining a third amount of residual lots in the low yield group after the third comparison step;

    while the third amount of residual lots in the low yield group is not equal to zero, performing the following steps;

    performing a third searching step to determine the process step item related to the in-line QC item of each residual lot in the low yield group in the database;

    when the process step item is determined to be related to the in-line QC item in the third searching step, searching for manufacturing machines utilized for the production of the wafers in the high yield group at the process step;

    searching for manufacturing machines utilized for the production of the residual lots of wafers in the low yield group at the process step; and

    performing a determining process to determine manufacturing machines utilized for producing more wafers included in the residual lots in the low yield group than wafers in the high yield group; and

    while the third amount of residual lots in the low yield group is equal to zero, stopping performing the third searching step; and

    while the second amount of residual lots in the low yield group is equal to zero, stopping performing the second searching step; and

    while the first amount of residual lots in the low yield group is equal to zero, stopping performing the first searching step.

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