Moisture Resistive, U. V. Transmissive Passivation for Plastic Encapsulated EPROM Devices

A unique U. V. transmissive passivation process for One Time Programmable EPROMS has been developed which provides moisture resistance for the plastic encapsulated devices and allows erasure of hermetic devices. This passivation, which consists of a two layer film of plasma enhanced CVD oxynitride and phosphorus doped oxide, requires no change in current interlayer dielectric, metal composition or circuit layout. This approach is novel in that it continues to utilize 9% to 10% phosphorus doped CVD oxide as an interlayer dielectric, while most plastic compatable processes require control of phosphorus concentration to approximately 7%. Observed moisture related failure mechanisms, which include single bit charge loss, metal line corrosion and input/output leakage, were investigated and related to specific processing parameters. Processing limits were then determined to eliminate these failure modes.