Hello All,

    Was wondering if anyone on this forum happens to know if the mechanical
properties of heavily-doped p-type silicon (B doped) wafers are any different
than those of standard p-type silicon wafers.  The reason I ask is because we
are in the midst of developing a MEMS design in which we plan to use the
silicon substrate as not only  the material from which the structure is etched
but also as the electrical conductor for our electrostatic actuation scheme.
Consequently, we will be trying to use p++ Si wafers as the substrate in which
we deep etch our structures.  We've based our designs on the assumption that
the mechanical properties (youngs modulus, shear modulus, fracture strength,
etc) are the same as standard single-crystal silicon, but it was recently
brought to our attention that this may not necessarily be true. It would be
greatly appreciated if someone could verify this for me and/or point me in the
direction of where I could find more quantitative information about the
degredation (i.e mechanical properties of the heavily doped wafers).  I've
been looking through various text books, going on-line, searching the
literature, etc but have yet to find a definitive answer.

    Keep in mind here that I am asking about the properties of a bulk
heavily-doped WAFER, not a thin film or layer produced implantation or
diffusion.  If the heavily-doped wafers are made by adding the dopants to the
Si melt from which the ingot is pulled, as I assume they are, I would think
that they would be free of the defects that are seen in post-solidifcation
implantation and diffusion. Is this correct?  Again, any and all info would be
greatly appreciated.

Thanks for help!

Masa