Wafer & Die Testing
Our high throughput testers are utilized around the world for front end testing from wafer level probe tests to testing and sorting singulated known good die (KGD).
The key features and benefits of our system are:
Productivity gains
- Multiple probers from one test system
- Lowest cost of test
- Reduced floor space
- Automated set-up with network capability
- Off line Binning
Capability
- Multiple die test capability
- Avalanche testing on wafer
- Low RDS(ON) test capability
- Dynamic switching at wafer level
- Wafer map / yield analysis
- Known Good Die solutions
Production testing at wafer level is performed on an automatic wafer prober. Each die on the wafer is only contacted once to prevent surface damage due to the scrubbing action of the probe needles. The test resources therefore need to be integrated to a single test site and the tests are performed sequentially. Cosmic provides a range of serial test heads for up to 2000 V and 200 A for wafer testing. The test groups may be summarised as follows:
The High voltage test generator performs high voltage breakdown and leakage current measurements. The Low voltage test generator performs the high current on-state and active region tests.
All power discrete devices need verification that the bonding processes have been successful during assembly. These tests are performed on the FB test generator.
Clamped inductive load dynamic switching tests and short circuit tests are primarily performed on IGBT devices and their associated fast rectifier diodes. The dynamic switching test generator performs all these tests and also provides a dynamic gate charge test capability.
MOSFETs especially, need a functional test to verify the ruggedness necessary for inductive load applications. These may be performed on the unclamped inductive switching test generator (UIS). Cosmic has the capability of testing up to 4 die in a single prober touchdown.
If a precise measurement accuracy of 0.02% on voltage regulation is required the Voltage Regulator test generator is the solution.
Cosmic has worked with customers to measure the latest trench designed MOSFET wafers with an RDS(ON) of less than 2 mOhms, and experimented with 600 uOhm die.
Known Good Die (KGD) testing
If die are assembled in automotive multi-chip modules containing 36 die, and the module yield needs to be at least 85% to be economically viable, the average die yield must be at least 99.55% assuming a zero defect rate for assembly.
Normal parametric screening of the die at wafer level may not be sufficient to eliminate the failure rate to below 0.45% it may become necessary to screen out defects after dicing into individual die.
Cosmic has provided solutions for known-good die testing both for conventional IGBT and MOSFET die, and for Flip-chip devices. We have delivered customer satisfaction in the USA, Europe and Japan.
Wafer Test
For vertical power discrete wafers, the single back contact at high currents and cross-coupling between die during high voltage breakdown can cause difficulties in obtaining consistently accurate test results on parallel die. Cosmic developed a sequential test head to enable multiple die to be tested at a single prober touchdown. The same test program may be used for multiple die or single die, and the die present signal is obtained from the wafer prober.