Fully Isolated High Side and Low Side LIGBTs in Junction Isolation Technology

It is well known that the operating conditions of adjacent LIGBTs is greatly restricted in JI technology due to severe cross-talk limitations. Extensive investigations reveal that grounded guard rings are ineffective to prevent such cross-talk. To overcome this problem, a new isolation technique is proposed herein. It is shown that cross-talk suppression can be achieved through using a combination of deep oxide filled trenches made through the back of the wafer and a single grounded guard ring. It is shown that the width and depth of the oxide trenches are quite tolerant to dimensional fluctuations. Furthermore, the solution is shown to be easily extendable to realise compact, monolithic integration of both low-side and high-side LIGBTs in junction isolation technology.