METHOD FOR PREPARING A NARROW ANGLE DEFINED TRENCH IN A SUBSTRATE

집적 밀도 향상이 트렌치 측벽 사이 거리를 감소시킴으로서 증가된다. 거리는 감소시키면서 단락을 방지하기 위해 각진 반응성 이온 에치가 사용되어 각각의 트렌치의 한 측벽으로부터 접촉용 폴리실리콘을 제거해 준다. Polysilicon in a trench is etched at an angle to produce a conductor within the trench that has shape characteristics which approximate the shadow of the side wall of the trench closest the beam source. Specifically, when the first side wall is closest to the beam source and the second side wall is furthest from the beam source, the polysilicon on the first side wall is almost as high as the first side wall, while the polysilicon on the more exposed side wall is considerably lower than the first side wall and approximates the shadow of the first side wall on the second side wall relative to the beam. The polysilicon in the trench may be in the shape of a solid angled block approximating the shadow line from the top of side wall to the shadow line on side wall however, it is preferred that the polysilicon take the form of a conformal layer in trench prior to etching such that the polysilicon ultimately has an angled "U" shape which approximates the shadow line. Contact is made to the polysilicon using strap that electrically connects the side wall with the polysilicon. Strap is sized such that it does not extend to the opposite side wall of trench, thereby avoiding short circuits. Having the polysilicon approximate the shadow line of the etch permits narrowing the distance between adjacent straps and in an array without the risk of creating a short.