With huge growth in automotive electronics it is not surprising that more semiconductor companies than ever before are starting to use part average testing or PAT. I was recently asked by a fabless company who should have control of their part average testing.
We can start answering this question by explaining how part average testing at wafer sort (probe) works in this modern age.
Wafer sort PAT flow
- Data from tester and wafer maps from prober sent automatically to a server
- The server processes the data calculating Dynamic PAT limits per site per wafer
- Good Die in Bad Neighbourhood (GDBN) is also calculated
- The wafer map is updated
- Lot level or wafer level reports are presented to engineers for sign off
- After sign off updated wafer maps are sent automatically to the assembly house
Who needs to control this?
In the past it was necessary for the test house to have control as the action of calculating and applying different limit sets needed to be close to the testers. With a modern system there is no need to change test limits and as this is done on a private cloud server so the server can be anywhere in the world.
Rather than being required to hand over control to a test house, PAT is now firmly in the control of the product engineers who oversee the manufacturing and product quality. Using private cloud technology means that an engineer can control the system from anywhere in the world. Manufacturing and test can be in Taiwan and the product engineer can be in the USA. Management can also see exactly where the process is up to.
Another key element of putting the fabless company in control is that all data, the original data and the additional data created during PAT and GDBN processing, is stored in the database on the cloud server. So full traceability, every limit for every test site on every wafer with a record of every die through that limit, is stored under the control of the fabless company.
Product quality in the hands of the product owner
With the fabless company, or product group in an IDM, owning the PAT process then it can be setup exactly as needed to give the highest quality for the smallest yield loss. Choose which tests to include in PAT processing and choose which bins to include in GDBN. “Who should control your Part Average Testing?” You should control it, efficiently and from your location.
By Kevin Robinson