Low pressure diffusion furnace for doping semiconductors

摘要

A low pressure diffusion furnace is used for the doping of small plates of semiconducting material utilising a source of doping liquid. The furnace incorporates a heated tube (1) in which the small plates are arranged, with an intake for the gaseous doping flux at one end of the tube and an outlet blowpipe (5) emerging towards the other end of the tube. The blowpipe (5) is connected to a pump (7). A pressure regulation system (14) is provided to control the pressure in the tube to a consigned pressure (K-p-1) by a restricting vane (15) placed at the inlet to the pump. The restricting vane (15) is surrounded by a heating system (17) to eliminate condensation. A nitrogen purging system is also provided to eliminate all gas when the diffusion operation is stopped together with a pressure regulation system to maintain the doping gas at a consigned pressure (K-p-2) during the stoppage.