Low Dose Rate Acceptance Testing
Intersil Introduces Wafer by Wafer Low Dose Rate Acceptance Testing
The low dose rate ionizing dose response of semiconductors has become a key issue in space applications. Routine 60Co qualification testing at high dose rates in the 50 – 300 rad(Si)/s range has been demonstrated to be nonconservative for some technologies, and may be regarded as an accelerated test that has transitioned into a nonlinear range. Intersil is addressing this changed market by introducing wafer by wafer low dose rate acceptance testing as a complement to current high dose rate acceptance testing.
Intersil's Low Dose Rate 60Co Irradiator
Fig. 1: External view of the low dose rate 60Co irradiator.
Fig. 2: View of ‘pop-up’ source (center) and surrounding test racks. Several vertical test board supports and their PbAl spectrum hardening filter boxes are shown. The holders can be moved towards the centrally located source as it loses activity. The system supports 64 simultaneous tests.
Low dose rate acceptance testing procedures
- The Intersil low dose rate acceptance testing procedure is similar to the current high dose rate flow
- Low dose rate acceptance testing is performed on a wafer by wafer basis, providing hardness assurance at the most basic level of the IC fabrication process
- All hardened products will be acceptance tested at low dose rate, including not only bipolar and BiCMOS products but CMOS parts as well
- This reflects increased emphasis on low dose rate performance within our customer base
- Four sample die are drawn from each probed wafer and are processed through the entire high-reliability Class V screening sequence
- The samples (2 biased, 2 grounded) are then irradiated to 50 krad(Si) at 0.01 rad(Si)/s.
- A second round of room temperature ATE testing is performed, and any rejects fail the wafer
- The existing high dose rate acceptance testing procedure will continue
- An enhanced data package will accompany each shipment of QML class V low dose rate qualified product
- The data package includes Certificates of Compliance (C of C) for high and low dose rate testing
- The data package also provides high and low dose rate room temperature variables data for pre and post irradiation tests
The Intersil Palm Bay low dose irradiation facility
- 50 Curie air actuated ‘pop-up’ panoramic 60Co source
- Design dose rate of 0.01 rad(Si)/s
- Predicted total dose uncertainty is ±3% or better, and all irradiations are overtested by 3% to compensate
- The test fixturing accommodates 64 DUT boards
- All boards are enclosed in a PbAl spectrum hardening box
- The DUT board fixturing approximates an isodose sphere
- All DUT boards are bar code identified
- Dedicated control computer for scheduling, accumulated dose and source depletion
- Dedicated power supply computer sequences and ramps supplies
- All systems are on an uninterruptible power source
