Patent GB-1336845-A (GB)
Title: Methods of manufacturing a semiconductor device
IPC: H01J29/45
Filed: 1969-11-19
Abstract: 1336845 Semi-conductor devices MULLARD Ltd 4 Nov 1970 [19 Nov 1969] 56574/69 Heading H1K A semi-conductor body 1 is doped by providing a layer 5 consisting of or including the dopant on the body surface and bombarding it with ions e.g. of an inert gas such as Ar, Kr or Xe, so that dopant atoms in the layer 5 are knocked-on and implanted in the body 1, most of the bombarding ions being absorbed in the layer 5 and/or other materials, such as silica layer 3, on the body surface. As shown Al atoms from the layer 5 are implanted in an N type Si body 1 to form a simple PN junction diode. The bombardment is followed by a relatively low temperature anneal, and the Al layer 5 is retained as an anode electrode. Manufacture of a Schottky barrier diode is described, in which Au from a layer (15), Fig. 4 (not shown), on a Si body is knocked-on by ion bombardment to penetrate a surface-contaminating film on the Si and to form an intimate rectifying contact with the Si. A Si IGFET is provided with relatively shallow peripheral portions around the B-diffused source and drain regions (29, 30), Fig. 10 (not shown), by knockon implantation of Al atoms from a deposited layer. Relatively thick portions of a passivating layer (23) and thick Ni source, drain and gate electrodes (27, 27<SP>1</SP>) act as masks to define the lateral extent of the implanted portions. This method may be used for a discrete device or a number of such devices in an integrated circuit, and in the latter case part of the Al layer is retained as an interconnection pattern. In the manufacture of an air-isolated integrated circuit containing a bipolar transistor, a diode and a resistor various regions of differing conductivity types are defined by scanning an ion beam of modulated energy across a semi-conductor body (71), Figs. 11-13 (not shown), over an entire surface of which are provided superposed deposited layers of Sb (73) and Al (74). For relatively high ion energies both Sb and Al are implanted, the heavier Sb atoms entering the body to a relatively shallow level to provide, for example, the emitter region (78) of the transistor, while the Al atoms penetrate more deeply, for example to provide the base region (75). In areas over which the ion beam has a lower energy only the lighter Al atoms are implanted, for example to provide a diode region (76). After provision of a glass support (82) over the implanted and  electrode-carrying surface the back surface of the semi-conductor is ground and selectively etched with an anisotropic etchant to separate the air-isolated islands. A GaAs photocathode is formed by knock-on implanting Zn atoms into a surface of a weakly P type body (91), Figs. 14, 15 (not shown), to provide a P + surface layer (84). After dip etching and heat-cleaning in vacuum to remove excess Zn, caesium and oxygen are alternately deposited while the photo-emission of electrons from the surface is monitored, deposition continuing until the photo-emission passes through a maximum. A PN junction radiation detector may also be manufactured in accordance with the invention. In integrated circuit manufacture in accordance with the invention device isolation in an N(P) type epitaxial layer on a P(N) type substrate may be achieved by channels of dielectric material or by P(N) type isolation zones either extending fully through the epitaxial layer or extending only partly therethrough. In the latter case isolation is completed by the downwardly extending depletion region associated with the isolation zone. It is possible, in accordance with the invention, to use different ion species at different energies or to vary the ion energy during bombardment to produce a desired implantation concentration profile. As well as the materials referred to above the semi-conductor body may be of Ge or a II-VI compound. The bombarded layer may, for example, also be of B-doped silica. Reference has been directed by the Comptroller to Specification 1,239,044.