Parallel parameter testing moves to asynchronous mode

Parallel testing is a time-honored method for increasing yields, and asynchronous parallel testing has long been recognized as an effective way to significantly improve throughput while maximizing the use of existing test hardware (Reference 1). What is new is the application of parallel technology to semiconductor parametric testing.

Keithley Instruments pioneered the concept of synchronous parallel test capability and published a book (with comments on this issue on page 22) that discusses the advantages of parallel parametric testing, provides tips on how to apply this technology to legacy devices, and shows how to design new test structures to take full advantage of parallel test capabilities.

Keithley released version 5.2 of its KTE interactive test environment software last December for the company's S600 series parametric test systems. KTE V5.2 comes with a routine called PT_Execute that allows for quick evaluation of parallel and sequential tests. The company also added a feature called FMI (Forced Measurement Interlock), which uses firmware and software to reduce crosstalk, noise, and measurement variability in parallel test applications.

Now, Agilent Technologies has also made a high-profile entry, introducing asynchronous parallel parametric testing capabilities on its 4080 series parametric test platform, which was launched in April of this year. The new system uses a test shell that Agilent calls SPECS (Semiconductor Process Evaluation Core Software) to

Supports both synchronous and asynchronous parallel testing.

According to Alan Wadsworth, marketing manager for Agilent's Hachioji Semiconductor Test Division, the 4080 parametric test platform is designed for foundries using advanced processes, including those extending below 45nm, where engineers need large amounts of data to address issues such as line width variations. In addition to the system's parallel testing capabilities, Wadsworth noted that the 4080 series has a much more powerful CPU than its predecessor, the 4070 series , and he said that the new CPU alone can increase the workload of traditional sequential test programs by 10% to 20%.

However, the real advantage comes from developing programs that fully use the 4080 series' asynchronous parallel testing capabilities. Wadsworth said that asynchronous parallel testing time can be reduced by 50% over traditional sequential test methods. He added that the goal of asynchronous mode is to squeeze out some of the useless measurement time left in synchronous parallel test schemes (see figure).

The 4080 is available in three models: the 4082A performs general purpose parametric testing; the 4082F targets flash memory cell parametric testing of NAND/NOR devices; and the 4083A features a 20GHz 8x10 RF array that can measure up to five RF structures at a time.

References
Mazza, Ed, “Asynchronous Testing Increases Throughput,” Test & Measurement World, December 2000.