MONOCRYSTALLINE SEMICONDUCTOR BODY HAVING DIELECTRICALLY ISOLATED REGIONS AND METHOD OF FORMING

1,274,726. Semi-conductor devices. INTERNATIONAL BUSINESS MACHINES CORP. 17 Dec., 1970 [6 Jan., 1970], No. 59908/70. Heading H1K. A method of forming a dielectrically isolated region in a semi-conductor body comprises bombarding the region with ions of at least one element, and subsequently heating the body to react the implanted ions with ions within the body to produce an isolation area surrounding the region. The body 10, which may be of silicon, is bombarded with ions of oxygen, nitrogen, carbon, or a combination thereof through a mask 12 having apertures 14 with bevelled edges 15 (Step 1). The energies of the ions, e.g. 1 to 3 Mev., produces a region 21 and a surrounding region 22 containing ions to a concentration of 1018 to 1022/c.c., the region 22 being formed by a reduction in the penetration of the body caused by the bevelled mask edge 15 (Step 2). The body is heated, e.g. to 1100‹ C. for 30 mins, in order that the ions react with the body to form an isolating region 23 of silicon dioxide, silicon nitride, or silicon carbide (Step 3). Within the isolated region 26 may be formed transistors (Step 4) to produce an integrated circuit. The body may alternatively be of GaAs or Ge in which case silicon ions are included in the bombardment. The mask edge 15 may be formed from a mask having four layers, each of 500 to 1000 Š thickness, each layer being bombarded with inert ions following deposition, the radiation dose increasing with each layer to produce a mask with a controlled, variable, etch rate. A control mask may determine the position of the apertures 14 during etching. The mask may be of gold, silver, molybdenum, tungsten, silicon dioxide or silicon nitride. Alternatively the mask may be pyrolitically deposited silicon oxide having a controlled, variable, etching rate provided by doping with boron or phosphorus. Alternatively the energy of the ions could be varied to produce the region 22 without the need of a bevelled edge mask.