Investigation of chemically vapour deposited tungsten and tungsten silicide as contacts to n+ and p+ silicon areas

• Tungsten and WSi2 have been examined as contact barriers between aluminium and n+ - or p+ -Si. The specific contact resistivity and diode leakage current were evaluated after heat treatment at different temperatures. Rutherford backscattering spectrometry measurements, X-ray diffraction analysis, scanning electron microscopy and sheet resistance measurements were performed to study the thermal stabilities of the Al/W/Si and Al/WSi2/Si systems. The contact resistivities of chemically vapour deposited tungsten and WSi2 to n+ -Si with a surface concentration of 7.5 × 1019 cm-3 were 8 × 10-7 Ωcm2 and 9 × 10-7 Ωcm2 respectively. To p+ -Si with a surface concentration of 2.6 × 1019 cm-3, they were 5 × 10-6 and 1 × 10-6 Ωcm2. Diffusion of aluminium was revealed to occur above 475°C in the case of tungsten and at 475°C in the case of WSi2. The void formation in silicon substrates was observed after heat treatment at 500°C for the Al/WSi2/Si system. The increase in leakage current for the Al/W/Si and Al/WSi2/Si structures is related to the onset of Si-Al interpenetration. Alloy formation was observed at 500°C for tungsten contacts whereas W-Al or other alloys were not detected up to 600°C for the WSi2 contact.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

Aluminum and Alloys--Diffusion

Integrated Circuits

VLSI

Semiconducting Silicon--Contacts

X-rays--Diffraction

Rutherford Backscattering Spectrometry

Tungsten Silicide

Tungsten and Alloys

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