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Growth of a Self Aligned Gate FET Structure by Selective Refractory Metal Deposition

IP.com Disclosure Number: IPCOM000075531D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 87K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+2]

Abstract

In Fig. 1 there is shown a series of steps whereby a self-aligned Si(3)N(4) gate FET structure may be fabricated by employing selective chemical vapor deposition (CVD) techniques.

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Growth of a Self Aligned Gate FET Structure by Selective Refractory Metal Deposition

In Fig. 1 there is shown a series of steps whereby a self-aligned Si(3)N(4) gate FET structure may be fabricated by employing selective chemical vapor deposition (CVD) techniques.

In step A, layer 1 of SiO(2), for example, is first formed on a silicon substrate
3. The SiO(2) layer may typically be 3500 Angstroms. In step B, SiO(2) layer is etched down to the silicon substrate, leaving adjacent SiO(2) regions 5 and 7. Thereafter, a 200 Angstrom, SiO(2) layer 9, for example, is formed on the silicon substrate between regions 5 and 7. Then, a 300 Angstrom layer of Si(3)N(4) may typically be deposited upon the various regions of SiO(2). The layer of Si(3)N(4) is shown at 11 in step B. After etching the silicon nitride so as to remove all of the silicon nitride except for that required for the gate, step C, the silicon nitride is used as a mask to etch SiO(2) region 9 so as to form the structure shown in step D.

After the Si(3)N(4) and SiO(2) insulator gate regions are formed, step D, the various remaining insulator regions may be used as a diffusion barrier or mask for forming source and drain regions 13 and 15, step E. It should be noted that in order to achieve selective CVD of tungsten, for example, on the Si(3)N(4) layer so as to obtain a self-aligned gate, surfaces surrounding the Si(3)N(4) must be oblative to the tungsten. In this regard, boro-silicate or phospho silicate glass is known to be oblative to tungsten when deposited by the H(2) reduction of WF(6). Accordingly, an advantage is derived in using SiO(2) as the surrounding diffusion barrier, at 5 and 7, since a boro-silicate or phospho silicate glass may thereby readily be obtained during the source and drain forming diffusion step, where diffusion involves B(2)O(3) or P(2)O(5). Thus, where, for example, B(2)O(3) is diffused into silicon substrate 3 to form source and drain regions 13 and 15, simultaneous therewith the top portion of SiO(2) regions 5 and 7, and the top portion of the exposed por...