Enhanced Parametric Test Insights Through Dynamic Data-Driven Test Flow Execution

Parametric test is used to evaluate how well the semiconductor process was executed, usually through the application of statistics to the measurement of device parameters such as threshold voltages, breakdown voltages, current leakages, sheet resistances, and capacitances, etc.
Statistics are ideal for detecting distribution trends and for finding outliers. Historically the statistics from parametric test have been analyzed post-test time through a variety of tools, many times unique to the fabricating company's manufacturing operations. The response to unexpected results is often a secondary test flow execution that focuses on the found data anomalies and drills-down to search for the causes to the observed effects. This secondary testing requires significant human involvement and valuable test cell operating time to collect the additional data. What has been a human-centric exercise in parametric test evaluation was an opportunity for automation and building a learning environment to capture and formalize best-known-methods of wafer parametric evaluation.
A parametric test DA (data analytics) system has been developed to provide instantaneous evaluation of electrical device test results and test cell system health, dynamically driving real-time test-flow with improved efficiency and enhanced insights into wafer process monitoring and characterization results. Upon "a data result of interest", the DA system instantly reprograms the test flow to apply additional test methodologies to the suspect devices and surrounding wafer topology to better understand the potential causes of the anomalous data within milliseconds. This provides the device test engineer with the information they would need to execute an automatic disposition or to perform deeper evaluation and correlation through the post-test analysis tools integrated with the DA system.
In this paper we will share some of the results and experiences we have gained in using the Dynamic Parametric Test solution developed in a collaboration between Advantest and PDF Solutions. These same DA techniques have been extended to functional wafer sort to quickly assess the health of the test cell, for optimum utilization. Data feed-forward between parametric test and functional wafer sort becomes an obvious next step in the application of DA to higher quality testing results and greater test cell efficiency.