New SEMI Standards Proposal for Standards Test Data Format (STDF) Memory Fail Datalog

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New SEMI Standards Proposal for Standards Test Data Format (STDF) Memory Fail Datalog – Call for Vote

Yield learning in modern technologies requires fail data logging from the scan and memory structural tests to gain insight into the failing location inside a chip. Currently there is no standard format to store the fail data in an efficient way. The lack of standard for storing structural test fail datalog leads to many proprietary formats to be used. Furthermore, the use of proprietary formats leads to unnecessary investments in readers and writers for such formats. A standard format would thus remove this unnecessary investment on the part of customers as well as vendors.

Discussions for a Standard Test Data Format (STDF) Memory Fail Datalog started within the Collaborative Alliance for Semiconductor Test (CAST), a SEMI special interest group. CAST formed a STDF working group in 2008 as a successor to a previously independent standards group, then in July 2009 at SEMICON West, the SEMI Standards STDF Task Force was formed.

Comprised of more than 20 companies from ATE, EDA, semiconductor and yield management companies, the STDF Task Force, chartered under the North America Automated Test Equipment (ATE) Standards Committee, has recently completed its development of a standard proposal that would address this problem.

The task force developed SEMI Draft Document 4782A – New Standard: Specification for Standard Test Data Format (STDF) Memory Fail Datalog – and submitted the document for the Cycle 1, 2011 voting period which starts January 17 and ends February 16.

As part of the Standard, Teradyne, Inc. has granted a world-wide royalty-free license of STDF, and any intellectual property rights, to SEMI to use, distribute, modify and support STDF. Under the supervision of SEMI International Standards, the license of STDF will ensure standards development and new products using STDF and future extensions will be unencumbered by IP ownership conflicts.

Ballot 4782A proposes a common format for memory fail datalog specification along with necessary synchronization information enabling an efficient dataflow for volume diagnostics applications for memories.

The scope of 4782 includes:

  • Direct Access
  • BISTed


  • Single Die
  • Stacked Dice

The proposed Datalog format provides:

  • Definition of records and their use for storing failure information
  • Data format for storing Memory design information in the datalog
  • Definition of format for enabling data integrity and consistency checking
  • Reduction in data volume for storing a given amount of failure information

Draft Document 4782A is the latest attempt by the STDF Task Force toward an approved SEMI Standard in this area. The first ballot, 4782, failed to receive sufficient return of votes during the Cycle 6, 2010 voting period. SEMI ATE Technical Committee members are strongly encouraged to vote on ballot 4782A (accept, reject or abstain if this topic is not in their field of expertise)while new participants and voters are invited to register as SEMI Standards members.

Multiple datalog formats and the lack of industry standards prevent the efficient use of test data across multiple test platforms and IC designs. An approved SEMI Standard in this area would represent an important milestone in the semiconductor test industry by enabling the industry-wide application of the Standard Test Data Format (STDF) and future STDF extensions in the maintenance and development of test programs. The demand for comprehensive datalog standards is greater than ever as IDMs, foundries, and outsourced test and assembly firms are looking to lower costs, improve test quality and speed implementation of test strategies across multiple test platforms and EDA vendors.

The NA ATE Standards Committee and the SEMI CAST Working Group on STDF are currently evaluating continued development and enhancements of STDF. For more information and to participate, please contact Paul Trio at SEMI.

SEMI Standards Watch – January 2011