US 4,735,911 AGranted

Process for the simultaneous production of bipolar and complementary MOS transistors on a common silicon substrate

AssigneeSiemens Aktiengesellschaft

InventorHans-Christian Schaber

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Abstract

A process for the simultaneous production of bipolar transistors and complementary MOS transistors on a common silicon substrate wherein to accommodate the p-channel transistors, n-doped zones are produced in a p-doped substrate and npn bipolar transistors are provided in the n-doped zones where the n-zones form the collector of the transistor and the n-zones are superimposed over n.sup.+ -doped zones. The latter are connected in the bipolar transistor zone by deeply extending collector terminals. The use of sidewall insulation on the p.sup.+ - and n.sup.+ -conducting structures composed of polysilicon or a silicide which are used for diffusing-out source/drain zones and base-emitter zones permit the formation of shorter channel lengths. The process is used to produce VLSI circuits which have high switching speeds.

A process for the simultaneous production of bipolar and complementary MOS transistors on a common p-doped silicon substrate which comprises the following steps in sequence:

(a) implanting n-doping ions in said p-doped substrate to form buried n.sup.+ -doped zones in the regions where bipolar or p-channel MOS transistors are to be formed,
(b) applying a doped epitaxial layer to the entire surface,
(c) applying and patterning a double layer of silicon oxide and silicon nitride over said epitaxial layer whereby the silicon nitride layer overlies the silicon oxide layer,
(d) locally oxidizing the resulting surface using said silicon nitride as an oxidation mask to produce field oxide zones,
(e) implanting and diffusing-in n-zones and p-zones as well as n.sup.+ -zones for deep collector terminals in said substrate,
(f) removing said double layer of silicon oxide and silicon nitride,
(g) depositing a boron-doped layer of a material selected from the group consisting of polysilicon, refractory metal silicide and a double layer of polysilicon and metal silicide over the entire surface,
(h) depositing a first insulating layer over the entire surface,
(i) structuring said boron-doped layer and said first insulating layer by dry etching to form vertical sidewalls therein while exposing the substrate to define the base zone of bipolar transistors and source/drain zones of p-channel transistors,
(j) implanting boron ions to produce an active base in said substrate,
(k) depositing a second insulating layer over the entire surface,
(l) etching the surface anisotropically to produce lateral insulating strips from said second insulating layer at the sidewalls of the p.sup.+ -conducting layer structures,
(m) depositing an n.sup.+ -conducting layer of a material selected from the group consisting of polysilicon, refractory metal silicide and a double layer of polysilicon and refractory metal silicide over the entire surface,
(n) structuring the n.sup.+ -conducting layer to form source/drain terminals of n-channel transistors and the emitter and collector terminals of bipolar transistors on the substrate,
(o) oxidizing the free silicon or silicide surfaces to provide an oxide layer, while diffusing source/drain zones of the MOS transistors and the base and emitter zones of the bipolar transistors from the p.sup.+ - and n.sup.+ -conducting zones,
(p) etching away the gate zones of the MOS transistors while providing a thickness of oxide strips at the sidewalls of the p.sup.+ - and n.sup.+ -conducting structures in accordance with the desired gate lengths of the MOS transistors,
(q) growing a gate oxide between said sidewalls,
(r) implanting boron ions over the entire surface,
(s) depositing, doping and structuring gate electrodes at the gate zones and
(t) applying electrodes to the active transistor zones thus produces.

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Abstract

Claims7