6.777J/2.751J Material Property Database

 

Material: Amorphous Silicon (a-Si)

Please note the most texts switch between a-Si and a-Si:H (10% hydrogenated amorphous silicon) at random. According to Madou (2001), page 298, “Unfortunately very little is known about the mechanical properties of amorphous Si.” This seems to be due to the optoelectronic application of the material. In most cases the mechanical properties were not available and where I deemed suitable, I included Si properties. I tried to indicate exactly which properties were included.

 

Property

Value

Reference

Image/URL (optional)

Mass density

For Silicon: 2.33 g/cm3

McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988

 

Young's modulus

80±20 GPa

Freund, L.B. and Suresh, S., “Thin film materials”, Cambridge University Press, 2003, page 96

 

Poisson ratio

0.22

Freund, L.B. and Suresh, S., “Thin film materials”, Cambridge University Press, 2003, page 96

 

Stiffness Constants

(1) For Si [dynes/cm2]: C11 = 1.67x1012

C12 = 0.65x1012

C44 = 0.79x1012

(2) For Si [GPa]:

E11 = 164.8

E12 = 63.5

E44 = 79.0

(1) McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988

(2) Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 198.

 

Tensile or fracture strength

 

 

 

Residual stress on silicon

For Poly-Si deposited with LPCVD (560-670 degrees C):

-0.1 to -0.3 GPa

Ohring, M. “Material science of thin films”, Academic Press, 2002, page 743.

 

Specific heat

 

 

 

Thermal conductivity

For a-SI:H:

4x10-6 [1/K]

Street, R.A., “Technology and application of amorphous silicon”, Springer, 2000, p242

 

Dielectric constant

For Si: 11.8

McGuire, G.E., “Semiconductor Materials and Process Technology Handbook” William Andrew Publishing/Noyes, 1988

 

Index of refraction

4.5 @ 600nm wavelength

Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 298.

 

Electrical conductivity

σ = 3x10-5 (ε=0.33 eV at T=310 K)

σ = 270 (ε=0.77 eV at T=400 K)

Values -1cm-1] given for a-Si, prepared with glow discharge technique and has strong dependence on activation energy [eV] and temperature [K].

Le Comber, P.G. and Mort, J., “Electronic and structural properties of amorphous semiconductors”, Academic Press, New York, 1973, page 377.

 

Magnetic permeability

 

 

 

Piezoresistivity

 

Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 200 gives an overview for Si, but does not mention anything for a-Si. He does state that the coefficient do depend on the crystal orientation of the material, so it is unclear whether or not a-Si will exhibit Piezoresistivity.

 

Piezoelectricity

 

 

 

Wet etching method

KOH (1)

a-Si is etched by HF, but poly-Si is not (2)

(1) Perry, R.H. and Green, D.W., “Perry's Chemical Engineers' Handbook (7th Edition)”, McGraw-Hill, 1997

(2) O'Mara, W.C., Herring, R.B. and Hunt, L.P., “Handbook of Semiconductor Silicon Technology”, William Andrew Publishing, 1990

 

Plasma etching method

For Si: CF4 or SF6

Senturia, S.D., “Microsystem design”, Kluwer Academic Publishers, 2001, page 69.

 

Adhesion to silicon dioxide

 

 

 

Biocompatibility

For Si: yes, but cell- and protein adhesion remains problematic and there is considerable room for improvement.

Madou, M.J., “Fundamentals of Microfabrication”, CRC Press, 2001, page 511.

 

Hydrophobicity