New techniques for elimination of the bird´s head and bird´s beak

This paper introduces new techniques for the elimination of the infamous bird\´s head and bird\´s beak which result from the recessed Isoplanar technology. The first technique to be described is intended only for "scalping" the bird\´s head. The process utilizes a phosphogermanosilicate glass as a planarizing medium and a novel wet etching process for transferring the planarized surface into the protruding bird\´s head. The second technique to be described precludes the formation of a bird\´s beak in addition to removing the birds head structure. In this method, a polysilicon spacer is formed along the sidewall of the silicon island by LPCVD of poly and plasma etchback. The sidewall poly layer prevents oxygen penetration to the pad oxide during field oxidation, thereby eliminating the formation of a bird\´s beak.