Hi Aslam, everyone.
Deep reactive ion etching is normally done using an ICP reactor, where the
plasma is generated inductively in a region away from the wafer.  The wafer
sits on an RF powered stage (as in RIE) downstream from the plasma
generation region.
The most widely used DRIE process is known as the "Bosch" process, after the
company that holds the patent (and issues licenses) for this process.  It
uses short etch steps flowing SF6 to etch the silicon, alternating with
deposition of passivation using C4F8.  The combination allows very high
aspect ratio, deep holes to be patterned.  Typical etch rates are around 5
microns/minute, but for certain conditions, rates over 10 microns/minute
have been achieved.  In order to run this process, you need to have a
machine with a Bosch license, capable of gas chopping.  These systems are
available from us (Oxford Instruments Plasma Technology), Surface Technology
Systems, Unaxis and Alcatel.  I have heard that Applied Materials now has
licensed this process too.
An alternative is to use a combination of SF6 and O2, with the wafer clamped
onto a cooled electrode which operates at around -100 degrees C (cooled with
liquid nitrogen).  This can achieve similar etch rates of around 5
microns/minute, with better selectivity to the mask and smoother sidewalls,
but with the drawback that it consumes liquid nitrogen and must have good
thermal contact on the bottom of the wafer to achieve good profile
uniformity.
Other processes are available (see papers from Meint de Boer, University of
Twente, Netherlands, or from Richard Syms, Imperial College, London, UK) but
generally run at lower etch rates, which make through wafer etching
impractical.
For more comparison of Bosch and cryo processes, see my paper on this link.
http://www.oxford-instruments.com/pdf/spie2.pdf
Martin Walker
>aslam muhammad wrote on Thu, 16 May 2002 09:49:33 -0700 (PDT)
>Hi all
>
>how can I etch silicon wafer (500 micron thick) using
>reactive ion etching (DRIE).  can any body tell the
>recipe of DRIE etching at constant etch rate. Please
>
>
>Thankx
>
>M. Aslam
>LAUNCH - Your Yahoo! Music Experience
>


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