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Doping of Sputtered Amorphous Semiconductors

IP.com Disclosure Number: IPCOM000088334D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Brodsky, MH: AUTHOR [+2]

Abstract

It has been reported that amorphous silicon (a-Si) deposited out of a plasma glow discharge of silane (SiH(4)) can be doped n- or p-type by the addition of small amounts of phosphine (PH(3)) or diborane (B(2)H(6)) to the silane in the glow discharge [1]. In subsequent reports [e.g., 2], they have pointed out the apparent unique suitability of glow discharge produced a-Si for doping because the glow discharge method yields a-Si films with a low density of gap states compared to films produced by other means such as evaporation, sputtering or ion bombardment.

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Doping of Sputtered Amorphous Semiconductors

It has been reported that amorphous silicon (a-Si) deposited out of a plasma glow discharge of silane (SiH(4)) can be doped n- or p-type by the addition of small amounts of phosphine (PH(3)) or diborane (B(2)H(6)) to the silane in the glow discharge [1]. In subsequent reports [e.g., 2], they have pointed out the apparent unique suitability of glow discharge produced a-Si for doping because the glow discharge method yields a-Si films with a low density of gap states compared to films produced by other means such as evaporation, sputtering or ion bombardment.

The lower density of states may result from incorporation of hydro gen into a-Si when silane is used as the source gas in a glow discharge. The importance and necessity of hydrogen is controversial.

The Dundee group of Spear, LeComber, et al tend to minimize the role of hydrogen (see, for example, LeComber, Loveland, Spear and Vaughan, Amorphous and Liquid Semiconductors, Taylor and Francis, London, 1974, p. 245). However, it has been pointed out that hydrogen added to the argon sputtering gas during sputter-deposition of amorphous Ge (a-Ge) or a-Si seems to give materials similar in many respects to glow discharge produced a-Ge from (GeH(4)) or a-Si from (SiH(4)) [3].

We have found that a-Si and other related materials can be doped during sputtering by using hydrogen plus one or more sources of dopants. To make low resistivity n-type a-Si, we have used a mixture of 98% argon, 1.9% hydrogen and
0.1% phosphine as a sputtering gas. In one case, the hydrogen and phosphine were introduced from a single source with a 95% to 5% composition ratio. The sane mixture without the phosphine gives undoped high resistivity a-Si films. Other gases added to the hydrogen should also work; for example, arsine (AsH(3)) should also give n-type a-Si, while B(2)H(6) gives p-type a-Si. An alternate approach is to use a hydrogen/argon mixture without an...