METHOD TO MAKE A SILICON LAYER BEING PARTLY POLYCRYSTALLINE AND PARTLY MONOCRYSTALLINE

摘要

The method starts from a monocrystalline semiconductor substrate (2) having a highly doped region (1), and being covered by an oxide mask (3) which is apertured above region (1). A layer (6) of polysilicon is deposited over oxide mask (3). The structure is exposed to laser radiation (14) to convert layer (6) into monocrystalline silicon within and above the oxide apertures.
The method is useful in making filamentary pedestal transistors without extrinsic base-collector junctions. In this present case, region (1) serves as a subcollector, two polycrystalline areas are made monocrystalline, with the one area(4) and the polycrystalline area (7) surrounding it being doped with a base dopant, and the other area (5) being made the collector reach-through region. The upper portion (10) of area (4) is made the emitter.