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DIFFUSION BARRIER FOR PtSi/Si STRUCTURES

IP.com Disclosure Number: IPCOM000044309D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Eizenberg, M: AUTHOR [+3]

Abstract

Platinum silicide forms a high barrier height Schottky barrier diode to silicon, and aluminum is used as a low resistance metallization. During conventional heat treatment (sintering) of the Al/PtSi/Si structure at temperatures around 450ŒC, penetration of Al into PtSi occurs and, after a longer time, Al can penetrate into the interface between PtSi and Si. This reduces the barrier height. In order to overcome this problem, diffusion barriers, such as TiW, CrOx, or TiNx, are deposited between the PtSi layer and the Al layer.

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DIFFUSION BARRIER FOR PtSi/Si STRUCTURES

Platinum silicide forms a high barrier height Schottky barrier diode to silicon, and aluminum is used as a low resistance metallization. During conventional heat treatment (sintering) of the Al/PtSi/Si structure at temperatures around 450OEC, penetration of Al into PtSi occurs and, after a longer time, Al can penetrate into the interface between PtSi and Si. This reduces the barrier height. In order to overcome this problem, diffusion barriers, such as TiW, CrOx, or TiNx, are deposited between the PtSi layer and the Al layer.

An improved diffusion barrier is one which can be formed in two stages. A thin layer of Al is deposited which reacts with a diffusion barrier layer of Ti or V at high temperatures to form a stable Al-rich compound. After this, a thick layer of Al is deposited which is used for interconnections. This thick layer can be processed at lower temperatures without consuming the unreacted Ti or V. The unreacted layer of Ti or V prevents reactions between the Al-rich compounds and the underlying silicon, in order to prevent degradation of the barrier height. The method is shown in Figs. 1 and 2. In Fig. 1, a silicon substrate 10 has a layer 12 of PtSi thereon.

A metal layer 14 of Ti or V is deposited on the PtSi layer. Layer 14 will have a negligible reaction with Si or PtSi at temperatures around 450OEC, but will react strongly with the overlying Al layer 16 to form a layer 18 of Al3Ti or Al3V at 450OEC. In t...