Epi-Isolated Substrate Contact to Polycrystalline Silicon Trench
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
In polycrystalline silicon (poly-Si)-filled trench isolation for substrate application, the trench poly-Si frequently tends to be overplanarized. This is caused by excessive poly-Si etch back and insufficient poly-Si. The active N-epi region 1 adjacent to the trench could be exposed and shorted to poly-Si by substrate contact (Fig. 1). The transistor collector in this N-epi region would then be shorted to the substrate. The active N-epi region can still be isolated from the substrate even if the back-fill poly-Si is overplanarized. In this method, two floating N-epi islands 2 and 3 (Fig. 2) are provided for the substrate contact area 4, one at each adjacent side of the poly-Si trench.