A New Process for Defect-free Definition of Active Areas in Deep Trench Isolated Bipolar Devices

In the bipolar application of DTI it is essential to eliminate any possibility of generating dislocations because they will produce Collector-Emitter short circuits. Most DTI processes produce a vertical bird's beak which may produce networks of loop dislocations. A modified process sequence is presented where there is no possibility of forming a vertical bird's beak. Electrical assessment of transistor arrays employing the modified DTI process indicates failure rates in the region of 20 defects per million transistors, sufficently low to yield circuits with hundreds of thousands of devices.