> ---------- Forwarded message ----------
> From: jpt sharma 
> To: [email protected]
> Date: Thu, 21 Sep 2006 14:14:13 -0700 (PDT)
> Subject: [mems-talk] Ohmic contact on Si
> Hi guys
>   i am trying to make the ohmic contact on Si. I am thinking to deposit Al by
thermal evaporator. Do you guys have any idea if it works.
>   Also I am wondering about the oxidation of Si. I want to deposit Al on si
not on Silicon oxide. Do you have any best idea to remove SiO2 (I used BOE). And
How long does it takes to oxidised again.
>   Thanks and hope to hear from you.
>
>   Jpt
>

Hi Chen,

 Did you find the I-V characteristics for Cr/Au on P-type (Boron
implanted) silicon was linear? We experienced similar kind of
problem.. Our doping concentration is about 10^17 atoms/cc and we
tried with Cr/Au since it acts as a mask against KOH and TMAH. But,
when we examined I-V characteristics it showed non-linear behaviour.
(in forward and reverse direction). As you said, we didnt do
annealing, since it may result in diffusion of Cr into Au.

   Also while using Cr/Au for contact metallization, one should be
carefull while going for TMAH etching, since Au may form galvanic cell
with Si and etching charaeteristics may be affected. ( But, if
Au/Exposed silicon is less than 5, then it will not be a problem). Al
is the best choice.

If native oxide is the only problem, then it can be overcome by
applying sufficiently large bias voltage so that native oxide
permanently breaks down. also avoid using DI water with  the si wafers
before you load into evaporator m/c.jpt,  if you have any problem, you
can contact me by mail.

A. Ravi Shankar,
Research Scholar,
E&ECE Department,
Advanced Technology Centre,
IIT Kharagpur.