Role of Test Chips in process development, definition,

Role of Test Chips

Hi there,

As i know that a test chip is used to analyze the specifications of the new technology during the process development phases and at the same time to prepare the future Back-end-of-line(BEOL) failure analysis of a defected chip in the manufacturing process.

However can anyone explain to me the following questions:
1.The defination of test chip.
1.what are the roles of test chips in process development and yield enhancement in a more specific way.
2.I would also like to know its defference of roles for current generation process and past generation processes.

Thank you.

Role of Test Chips

Test chips usually goes before real product to collect the following data:
1. Characterization of key devices, for choosing the right circuit structure.
2. failure density, for redundancy and architecture design reference.
3. to test new ideas of circuit implementation for certain function.
4. to understand device performance distribution, whihc is especially important for memory circuit design.
5. to understand the reliability of cells, see how they degrade with cycling, high temperature and etc.

to design a new test chip, we normally use interpolated model parameters learned from past few generations ( say gm reduced 20% for every generation, and etc). and leave a lot of options to adjust reference voltages, current sources and decide the right value through silicon, not simulation.

Role of Test Chips

Hi mdcui,

It is very insightful.
Thank you.

Re: Role of Test Chips

mdcui answer is correct.
However, some test chips are also designed fitting the scribe lines between product chips.
In this way you can monitor during the in-line production any tool shifting from the specs and you can also predict the right time to stop the chain and start a maintenance cycle.