The yield of an oxide isolated bipolar technology was substantially enhanced by changing the photolithography processing at the isolation layer. Changing the exposure bias improved the Cpk by 25% and the yield by 6%. Changing to a different develop chemistry eliminated corner defects and substantially reduced fallout for leakage. Corner defects are correlated to microgrooves and protuberances in the photoresist profile. In this paper, the mechanism for the yield improvement is explained.