High critical electric field of thin silicon film and its realization in SOI high voltage devices

Taking threshold energy epsiv
_T
into accounting for electron multiplying, the formula of silicon critical electric field E
_S,C
is given as a function of silicon film thickness t
_s
from an effective ionization rate alpha
_eff
. E
_S,C
is increasing with the decreasing of t
_s
especially at thinner t
_s
. 2-D simulative and some experimental results as well as the comparing with several other familiar expressions of electric field proved the proposed E
_S,C
is valid for both thick and thin silicon film. Thin silicon film with high E
_S,C
can be used to enhance dielectric field E
_I
and increase vertical breakdown voltage V
_B,V
of SOI high voltage devices. A high voltage SOI device with 80 nm silicon layer and 0.4mum dielectric layer is designed. A high E
_S,C
of 134V/mum is obtained, which makes E
_I
and V
_B,V
reach to 416 V/mum and 178 V, respectively.