PROTECTION OF FIELD OXIDE IN TRENCH ISOLATION AGAINST CONTACT HOLE ETCHING TO IMPROVE ALIGNMENT TOLERANCE

We demonstrate that field oxide in trench isolation is successfully pr otected against contact hole etching by inserting a thin etch-stopping Si3N4 film into the SiO2 interlayer. Results suggest that alignment t olerance of the contact hole can be drastically improved. The breakdow n voltage (Vb) of trench isolation was maintained at 15 V, even with o verlap of the contact hole and trench isolation as long as 0.26 mu m, though the Vb value for a conventional structure was considerably degr aded by overlapping.