[Fwd: Re: Lampoly recipe for silicon-rich nitride]

Mary Tang mtang at snf.stanford.edu
Tue Sep 30 16:29:49 PDT 2008


Hi again --

Aaron would like to be able to etch polysilicon with <1% Erbium in 
amtetcher.  It was approved for lampoly -- how about amtetcher?  Can we 
give him an answer in the next day or two?  Masks are arriving and he'd 
like to get his etch processes characterized....

Thanks,

Mary

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
(650)723-9980
mtang at stanford.edu
http://snf.stanford.edu



Mary Tang wrote:
> Hi all --
>
> This material was approved for etch on the lampoly ("trace" Er.)  OK 
> for amtetcher as well?
>
> Mary
>
> -------- Original Message --------
> Subject:     Re: Lampoly recipe for silicon-rich nitride
> Date:     Thu, 25 Sep 2008 10:06:08 -0700
> From:     Aaron Hryciw <ahryciw at gmail.com>
> To:     Mary Tang <mtang at stanford.edu>
> References: 
> <4d36fb940809241236h456c4846r6385a3de53e53196 at mail.gmail.com> 
> <Pine.LNX.4.44.0809242150030.25336-100000 at cis.Stanford.EDU>
>
>
>
> Hi Mary –
>
> So, Jim is suggesting that AMT would be best for this (NF3 via etch).  
> My SRN etch-test wafers will be "clean," but since the actual device 
> film I'll want to etch will contain a little less than 1% erbium 
> (which is a non-standard metal), does this mean that AMT is completely 
> out of the picture?  Is there some sort of decontamination procedure I 
> could do after my etch, which would allow me to use this tool for the 
> Er-doped films?
>
> Cheers!
>
> – Aaron
>
>
>
> On Wed, Sep 24, 2008 at 10:00 PM, Jim McVittie 
> <mcvittie at cis.stanford.edu <mailto:mcvittie at cis.stanford.edu>> wrote:
>
>    Aaron,
>
>    Ok, since you do not care about how much Si you etch, the Lam is not
>    automatically off the table. But I still would not go with the Lam 
> since
>    really do not have a nitride etch process in the Lam. If I was you, I
>    would go with the P5000 since it is quick and uniform. The std oxide
>    etch
>    process process will work fine or you can use a nitride process. If 
> you
>    already know the AMT but not the P5000, then go with the AMT. THe
>    via etch
>    shouls work fine. I would timed etch since you have non-critical
>    needs. If
>    really want to use endpoint, I can probably it up for you,
>
>           Jim
>
>    On Wed, 24 Sep 2008, Aaron Hryciw wrote:
>
>     > Hi Mary, Jim –
>     >
>     > The purpose of this etch will be to define silicon-rich nitride 
> (SRN)
>     > microdisks, the pillars of which will afterwards be defined by a
>    TMAH etch.
>     > As such, my tolerance for etching into the underlying Si is not too
>     > critical, just so long as I punch through the SRN.  To answer your
>     > questions:
>     >
>     > 1. What kind of film are you etching exactly? (Target 
> composition and
>     > > thickness.)
>     > >
>     >
>     > The final process wafers will be:  1) SRN, ~49% Si, 51% N, and 2)
>    SRN doped
>     > with up to 1% Er.  In both cases, the film will be ~50 nm thick.
>     >
>     > 2. What feature size and what is your masking material (thickness
>    and type
>     > > of resist, whether there's a sacrificial mask.)
>     > >
>     >
>     > For the first experiments, the features will be widely-spaced
>    circles,
>     > ranging from ~1 to 100 um in diameter.  The intended masking
>    material is
>     > Shipley 3612, patterned using the ASML (1 um thick? 1.6 um?
>     with/without UV
>     > cure? --> will test).  If necessary, however, a sacrificial mask
>    (Cr?) could
>     > certainly be used.
>     >
>     >
>     > > 3. What are you stopping on and what is your tolerance for
>    etching into
>     > > this?
>     > >
>     >
>     > I will be stopping on Si.  As mentioned above, so long as I
>    manage to punch
>     > through the SRN, the tolerance for etching into the underlying Si
>    substrate
>     > is quite large; for instance, I imagine I could etch a micron
>    into the Si
>     > without any problem.  Presumably, since the etch rate of Si
>    should be much
>     > larger than SRN, it should be detectable as a spike in Si-related
>    byproducts
>     > in the endpoint detection plots, correct?
>     >
>     > 4. What are your uniformity (and selectivity) requirements?
>     > >
>     >
>     > I will have several dies on the wafer, each with the 1 to 100 um
>    diameter
>     > (roughly equally on a logarithmic scale) disks on them, and for the
>     > experiments, I will be looking at single disks, so uniformity
>    across the
>     > wafer will also not be too much of an issue.  Even 10% or so
>    should be
>     > fine.  Since there is only a single masking/etching step, the
>    only material
>     > being etched is the SRN, so selectivity isn't really a problem,
>    except
>     > insofar as I can tell when I've reached the Si.  If endpoint
>    detection is
>     > not possible, and I have to go with a timed etch (after
>    characterising the
>     > process with test wafers), so be it!
>     >
>     > 5. I'm presuming that your substrates are 100 mm silicon rounds
>    of standard
>     > > thickness?
>     > >
>     >
>     > Correct.
>     >
>     > Thanks again to both of you for all your help.
>     >
>     > Cheers!
>     >
>     >  – Aaron
>     >
>     >
>     > On Wed, Sep 24, 2008 at 10:55 AM, Mary Tang <mtang at stanford.edu
>    <mailto:mtang at stanford.edu>> wrote:
>     >
>     > > Hi Aaron --
>     > >
>     > > Jim is absolutely right -- my apologies, I think I confused
>    yours with
>     > > another project and didn't realize you were stopping on
>    silicon. I don't
>     > > know about this machine specifically, but silicon etches about
>    an order of
>     > > magnitude faster with SF6 than silicon nitride (stoichiometric).
>     > >
>     > > As I neglected to perform due diligence before by asking you a
>    bunch of
>     > > questions, I'm going to ask right now (and no doubt, Jim will
>    have more.)
>     > >
>     > > 1. What kind of film are you etching exactly? (Target
>    composition and
>     > > thickness.)
>     > > 2. What feature size and what is your masking material
>    (thickness and type
>     > > of resist, whether there's a sacrificial mask.)
>     > > 3. What are you stopping on and what is your tolerance for
>    etching into
>     > > this?
>     > > 4. What are your uniformity (and selectivity) requirements?
>     > > 5. I'm presuming that your substrates are 100 mm silicon rounds
>    of standard
>     > > thickness?
>     > >
>     > > Again, sorry about that --
>     > >
>     > > Mary
>     > >
>     > >
>     > > Jim McVittie wrote:
>     > >
>     > >> Hi,
>     > >>
>     > >> I just sent you a copy of a note I sent Mary. We never got
>    great Nitride
>     > >> results in our Lam. The other tools gave better results so we
>    never push
>     > >> the Lam to get a good niride process. I would NOT use the Lam
>    to stop on
>     > >> Si.  It is a Si etcher and not optimized to stop on Si. You
>    need to use an
>     > >> oxide etcher which has the polymer deposition which will slow
>    down the
>     > >> etch rate when you hit Si. SF6 is not a good chice since it
>    loves to etch
>     > >> etch Si. I can help you if you want to use the AMT or P5000.
>     > >>
>     > >>        Jim
>     > >>
>     > >>
>     > >> On Wed, 24 Sep 2008, Aaron Hryciw wrote:
>     > >>
>     > >>
>     > >>
>     > >>> Hi Jim –
>     > >>>
>     > >>> I need an anisotropic etch recipe for silicon-rich nitride 
> (SRN);
>     > >>> ultimately, I'll need to etch through a 350-nm-thick SRN
>    film, stopping
>     > >>> on
>     > >>> Si.  Mary suggested using the lampoly tool with a SF6-based
>    chemistry,
>     > >>> and
>     > >>> said that you would likely be able to offer some advice as
>    how best to
>     > >>> proceed.  She said that recipe 99 (a "clean" recipe with SF6
>    and Cl with
>     > >>> no
>     > >>> bias, for general chamber cleaning) might be a good place to
>    start, and
>     > >>> she
>     > >>> also sent me a link to the standard nitride recipe (SF6 and
>    He) for
>     > >>> etching
>     > >>> on the Lam1 tool in Berkeley's Microlab (although this is 
> quite a
>     > >>> different
>     > >>> tool compared to SNF's).
>     > >>>
>     > >>> I'm going to ask Maurice for some dummy low-stress nitride
>    (which are
>     > >>> apparently quite Si-rich) to use as etch-test wafers, and I
>    was hoping
>     > >>> you
>     > >>> could give me a few lampoly "rules of thumb" (pressures, RF
>    power, bias,
>     > >>> etc.) for anisotropic SF6-based etching which I could use as
>    a starting
>     > >>> point.  Many thanks!
>     > >>>
>     > >>> Cheers!
>     > >>>
>     > >>>  – Aaron
>     > >>>
>     > >>>
>     > >>>
>     > >>>
>     > >>>
>     > >>
>     > >>
>     > >>
>     > >
>     > >
>     > > --
>     > > Mary X. Tang, Ph.D.
>     > > Stanford Nanofabrication Facility
>     > > CIS Room 136, Mail Code 4070
>     > > Stanford, CA  94305
>     > > (650)723-9980
>     > > mtang at stanford.edu <mailto:mtang at stanford.edu>
>     > > http://snf.stanford.edu
>     > >
>     > >
>     >
>     >
>     >
>
>    --
>    --------------------------------------------------------------
>    Jim McVittie, Ph.D.                     Senior Research Scientist
>    Allen Center for Integrated Systems     Electrical Engineering
>    Stanford University                     jmcvittie at stanford.edu
>    <mailto:jmcvittie at stanford.edu>
>    Rm. 336, 330 Serra Mall                 Fax: (650) 723-4659
>    Stanford, CA 94305-4075                 Tel: (650) 725-3640
>
>
>
>
>



More information about the specmat mailing list