hi,
 if you  look at the
changes you have made in the flow of DCS gas, it has gone almost double.

I feel there is some problem with DCS flow. and more importantly the flow
of the gas inside the tube. Since the thickness on all wafers
excepting the first one is as excepted now, i feel you are not supplying
enough DCS.... and so the initial problem has already been overruled. But
now there must be some other problem which is causing the first wafer to
show vague results.
In case of horizontal furnaces, since the gases enter from the back
side of the tube the first wafer
will see the majority of that gas which is striking at the door and then
returning back. So many factors come into picture now- like the turbulence
created because of striking, slight leakage at the door, door temperature
(least responsible, but cannot be overruled).

May be you  should try at a slightly different amount of gas flow, may be
>600sccm.
 Regds,
Ravi Shankar

        THE MAN WHO DOES NOT READ GOOD BOOKS HAS NO ADVANTAGE
                        OVER THE MAN WHO CANNOT READ.........
 ****************************************************************************
        Ravi Shankar
        Engineer VLSI-FAB,                    Phone: 91-172-254401
        Semiconductor Complex Ltd.,                  Ext: 576,552.
        Phase-VIII, S.A.S Nagar,                Fax:91-172-253378
        Punjab. Pin:160059.                E-mail: shankar@sclchd.ernet.in

 ****************************************************************************