Process reliability screening in situ

• Effects of environmental stresses (Unbiased HAST and HTS) on GaAs wafers are shown.
• Different test structures were used to evaluate and interpret the results of the stresses.
• This method allows a faster method for evaluating effects of process changes on device reliability.
• Results of a process DOE evaluated by environment al stresses are presented.

A critical element of process technology development is reliability and consequently reliability testing. Environmental stress tests such as Unbiased Highly Accelerated Stress Test (UHAST), Temperature Humidity Bias (THB), Thermal Cycling and High Temperature Storage (HTS) are traditionally performed on sample products or standard product-like qualification vehicles when introducing a new process technology. Because of the long cycle time for assembly and reliability stressing, these tests are not typically performed as part of the development cycle. This paper describes the use of HTS and UHAST at the wafer level to evaluate a new backend process currently in development.