As we are a materials company the expertise is not in EE, so I am asking a very simple question. I tried to search online for this, but could not find an answer. We are making transistors with our special materials and need to put many on a test chip. Hooking each one of them up with their own pads we quickly run out of pads and are limited to fewer devices.
What strategies exist to "chain" the structures together to share pads? What risks are there in doing this?
See the example of the four transistors that use 12 pads to test. Can the source and/or drain be one common pad and only need to change the tester for the gate?
Any references that would be helpful would be greatly appreciated.
Thanks.
Best Answer
Any time you add probe pads, you're sacrificing the density of test devices. The density you end up with depends on how accurately you can probe, how small a probe pad you can make, and how many terminals on your transistor you can share.
A word of caution, make sure you know what the minimum pitch and pad size you can probe effectively is using your equipment. It does you no good to have twice as many structures to test if it takes you much longer to land probes.
From a typical 4 terminal device perspective, the main question is how many pads can you save by tying them together, and what can go wrong.
My preference would be to have as few shorted terminals as possible. Shorting the source is relatively low risk, but higher current measurements will suffer. Shorting all gates and shorting all sources is something I wouldn't do for anything more than a process monitoring structure, preferably not for device characterization.
Keysight has a pretty good book on transistor characterization from the measurement perspective: The Parametric Measurement Handbook. There's a lot of good general information, and there's a decent amount of up-selling a $100-500k semiconductor parameter measurement tool.