Browse Prior Art Database

Forming Thick Metal Silicide for Contact Barrier

IP.com Disclosure Number: IPCOM000087529D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Tsang, PJ: AUTHOR

Abstract

Metal silicides are used as ohmic contact barriers to alleviate the so-called aluminum-spiking problem. Thicker silicide is favored for its greater stopping power for silicon and aluminum migration. However, the thickness of the silicide is limited by the shallowness of the NP junction by the conventional method where silicide-forming metal is put directly on the substrate. In the present method, the thickness of the metal silicide formed in the device contact area is not limited by the NP junction depth.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 64% of the total text.

Page 1 of 2

Forming Thick Metal Silicide for Contact Barrier

Metal silicides are used as ohmic contact barriers to alleviate the so-called aluminum-spiking problem. Thicker silicide is favored for its greater stopping power for silicon and aluminum migration. However, the thickness of the silicide is limited by the shallowness of the NP junction by the conventional method where silicide-forming metal is put directly on the substrate. In the present method, the thickness of the metal silicide formed in the device contact area is not limited by the NP junction depth.

The method includes the following steps:

1. After the contact holes are open in the layer of silicon dioxide 3, a layer of polycrystalline silicon (poly-Si) 4 of appropriate thickness is deposited. The poly- Si thickness sets the thickness of the silicide to be formed, as shown in Fig. 1A.

2. A blocking mask is applied and the poly-Si outside the contact hole area is etched away leaving a poly-Si cap 5 in the contact hole, as shown in Fig. 1B.

3. Silicide-forming metal 6 (e.g., Pt, Pd or Rh) is then vacuum-deposited to form the Fig. 1C structure.

4. Heat treatment is applied to the structure to form metal silicide 7. The unreacted metal can then be removed by selective chemical etch, leaving the silicide contact barrier in the device contact hole area, as seen in Fig. 1D.

The thickness of the silicide-forming metal should be so chosen that it is slightly more than is required to completely consume the poly-Si laye...