Microelectronic Repair Techniques for Wafer-Level Integration

Wafer-level integration was employed to mount the microshutter array for the James Webb Space Telescope (JWST) and the detector-read-out hybrid for TIRS (Thermal Infrared Sensor). In the case of the JWST substrate, two conductors (polysilicon and aluminum) separated by a silicon oxide insulating layer were fabricated on a roughly 85-mm-square silicon wafer. The size of the substrate, the density and length of the conductive traces, and the requirement of zero shorts and zero opens on the finished device necessitated nearly impossible cleanroom requirements. Techniques were developed to repair the inevitable shorts and opens created during the wafer fabrication process. The wafers were repaired to zero shorts and zero opens without degradation of device performance.