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PROCESS FOR LOW RESISTIVITY CoSi2 CONTACT TO VERY SHALLOW N-P JUNCTION

IP.com Disclosure Number: IPCOM000036212D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 85K

Publishing Venue

IBM

Related People

Aboelfotoh, MO: AUTHOR [+4]

Abstract

In this disclosure a process for making very low resistivity CoSi2 contact to shallow p-n junction as well as low resistivity CoSi2 FET gate is discussed. Referring to Figs. 1a through 1d, a layer of Co is deposited on n-type substrate through a window defined by an SiO2 layer as shown in Fig. 1a. The structure is then heated at sufficiently high temperature to form CoSi2 . Following the heat treatment process, excess CoS is chemically removed, resulting in the structure shown in Fig. 1b. Boron (B) is implanted into the CoSi2 layer. Energy of the implanted ions is such that the width of the implanted region is 10 to 20% of the total thickness of CoSi2 layer, as shown in Fig. 1c. (Image Omitted)

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PROCESS FOR LOW RESISTIVITY CoSi2 CONTACT TO VERY SHALLOW N- P JUNCTION

In this disclosure a process for making very low resistivity CoSi2 contact to shallow p-n junction as well as low resistivity CoSi2 FET gate is discussed. Referring to Figs. 1a through 1d, a layer of Co is deposited on n-type substrate through a window defined by an SiO2 layer as shown in Fig. 1a. The structure is then heated at sufficiently high temperature to form CoSi2 . Following the heat treatment process, excess CoS is chemically removed, resulting in the structure shown in Fig. 1b. Boron (B) is implanted into the CoSi2 layer. Energy of the implanted ions is such that the width of the implanted region is 10 to 20% of the total thickness of CoSi2 layer, as shown in Fig. 1c.

(Image Omitted)

It has been found that such boron implantation process results in a remarkable reduction in the resistivity of CoSi2 layer as compared to that of the unimplanted layer. The structure of Fig. 1c is then heated at sufficiently high temperature (600oC) for drive in of B into the p-Si substrate, thus forming a shallow p+-n junction, as shown in Fig. 1d. It has also been found that such annealing process which is required to driving in boron, has essentially no effect on the resistivity of the CoSi2 layer. Furthermore, the same results have been found for arsenic (As) implantation, thus allowing the fabrication of n+-p junction. Resistivity results obtained with As implantation are shown in Fig. 2. On the other hand, this effect, i.e., ion implantation induced reduction in resistivity of CoSi2 is not observed to the same extent when antimony (Sb) or phosphorus (P) are used. Because of the temperature required to activate As, the use of As in the contact structures as described above is less advantageous than that of B. However, it is useful in lowering the resistivity of polysilicon gate where both...