Raith Maintenance and Testing Hours -- LONG BUT PLEASE READ ME

James Conway jwc at snf.stanford.edu
Wed Nov 24 17:03:51 PST 2004


Greetings Ali Javey and the entire Raith Community:

Ali Javey and Others whom have commented:
 Thank you for your emails. This is my sincere attempt to address all 
your questions within this email and to continue this thread for 
discussion on the Raith discussion list.  It is well overdue and we 
should hold our next  Ebeam Town Hall Meeting in the coming weeks. Next 
Tuesday afternoon I will post an announcement for the next two meetings. 
One to be held in December ( December 15? 2- 4 PM) and another 2005 
Kickoff meeting in mid January.  The primary purpose is to get everyone 
together to discuss the issues that are most important to users and find 
amiable solutions that meet with everyones satisfaction. We have created 
a community, and as a community member your participation and inputs are 
valuable to SNF and myself in order to help us develop a World Class 
E-beam Lab User facility within Stanford and the NNIN.

Background:
Over the course of the last three months we have been all burdened with 
several performance issues on the system as we extended our Preventative 
Maintenance interval beyond the time we normally would have sought to 
perform this routine.
At the level of usage that this system has experienced over the course 
of the last year, we simply will need to perform these routines more 
often. IMHO: PM's should be performed twice a year versus the annual 
schedule we had been maintaining thus far.

These are the specific issues of concern that have been leading me to 
the decision to do the PM:

    * Aperture charging effects observed when blanking and unblanking
      the beam resulting in Image drift during the write field
      acquisition.  This adds to the challenge of properly aligning the
      write fields making it difficult to  complete the alignment
      routine accurately. This problem negatively impacts users working
      in high resolution materials on features below 100 nm, and all
      whom need accurate write field to write field stitching to
      specifications. (60 nm)
    * Problems with the Raith Beam Blanker leakage level has plagued
      users working with sensitive resist (UVN-30 and ZEP-520-12) as
      well as those whom are exposing a single write field for long
      enough periods that the blanker leakage dosage summed reaches the
      'dose to clear' for the resist.  While we have come up with some
      work-around methods to reduce this effect; some users are still
      unable to get exposures completed. Not all users have been able to
      get the results they demand and expect from the system.
    * A number of users and myself have observed an emerging problem
      with  non circularity of both single shot dot exposures and for
      exposures made using the RAITH circles mode.  This may be simply
      the challenge mentioned above of completing the align write field
      properly and obtaining the correct ZOOM U, ZOOM V parameter. 
      However charging effects in the aperture plate and column can also
      greatly influence this, but with the caveat that I would expect
      the exposure results to be more variable and random in the
      magnitude of its effect and its severity.  These features in fact
      are consistent in their non circularity.  In the past, based on
      performance test we made last year, circularity has never been
      observed to be an issue of concern.  This problem is steadily
      growing more severe and apparent to anyone examining their fine
      high resolution features by SEM closely.
    * Beam Current has been steadily falling through the period since
      the last PM, and for some users we are moving below acceptable
      values for beam current for the 30 and the 10 um apertures. This
      results in longer exposure time  reducing the amount of time
      available on the system for all users.
    * Multiple beam spots are being observed by users working within a
      reduced raster scan field, these shots are appearing outside the
      area of the reduced raster scanning. I have also witness myself
      single pixel line running across structures I have written
      presumably from charging effects in the apertures upon unblanking
      the E-beam.
    * Finally in the last month only, I have had several user reports of
      the diameter of a short shot contamination dot to be increasing
      from the 15 - 20 nm dot diameter that all users have become
      accustomed to obtaining.  I checked this myself and also can
      verify this with my best shots previously  12 - 15 nm AFTER
      careful focusing and stigmation now being measured at 23 - ~32
      nm.  I also have not seen Single Pixels Lines below 37 nm in the
      exposures I made with the RAITH Group XI class in October.
      Additional recent exposures are in the SEM inspection queue, but I
      myself have been unable to get on the system to finish this work
      in the last two weeks due to my working with users on the above
      mentioned issues during my PCM testing time slots.

I firmly believe that all of the above mentioned issues and phenomenon 
will be corrected once we complete the Preventative Maintenance routine 
on the LEO column. This is a standard approach and practice for any SEM.


 >>What exactly will be done during this maintenance of the Raith system?
Great Question and one whose answer changes from PM to PM as we address 
specific issues on the system.
[Click here] 
<http://snf.stanford.edu/cgi-bin/ezmlm-cgi?2160:mss:994:200411:lpdogknifecakapmdebf> 
to link to a summary of the task we hope to complete in the next PM 
which we have now scheduled for December 13, 2004 - January 4, 2005.

 >>Can you please clarify the maintenance and testing policies of the Raith?
There are no current policies for maintenance or testing other than I 
have to ensure the system is working within specifications we would 
expect for a factory qualified RAITH 150 system.  If I am not obtaining 
perfect quality results in my testing work and/or Users are reporting 
problems on the system my specific mission is to determine the source of 
the problems and with alacrity correct these issues promptly to the best 
of my ability and using the support of RAITH Companies and Zeiss SMT 
Field Service groups.

To determine that the system has been repaired and the outstanding 
issues have been address, and to establish baselines of performance to 
aid in monitoring the system performance, we must then qualify the 
system using qualified reference resist  material.   Initially we call 
this the RAITH Qualification procedure and is it normally the first set 
of exposures performed on the system.  For nearly the past year I have 
been working off a template that I initially established in March of 
2004 after the last period of downtime after the FEB. 14th PM routine 
was completed.  I have now developed this into a document and have 
attached this to the RAITH Notebook No 2. in the Ebeam Lab and also 
attached to this email: [Template_Qualification_RAITH 150.doc]

Once we have qualified the RAITH system it is important to perform 
periodic System Performance and  Process Control Monitoring (PCM) to 
establish and track system  and resist performance issues.  This in fact 
has been mandated by Paul Rissman to be performed Daily on the system 
and this project was added to my review goals for the next year.

Process Control Monitors:
 Last year we started developing Process Control Monitors patterns 
(PCM's)  for both the Hitachi HL-700 E-beam and  the RAITH both to 
qualify the system and monitor process capability both at exposure and 
after pattern transfer.  These were designed to be of use to anyone 
working on the systems with the hopes that Users would step forward and 
more readily report their results obtained on the systems.

This year past it became apparent that daily performance monitoring 
while greatly needed was impractical from a system utilization and 
measurement task standpoint.  The Performance testing for May/June 
report that I published to the bulletin board outside the Ebeam lab 
displayed some of the best results ever obtained on the system here at 
SNF, and confirmed nearly exactly similar work I obtained at the end of 
the year in 2003.  Hard Copies of this report are available upon request.
This work took me nearly 100 hours of my time and 45 hours of Beam time 
to complete to my satisfaction.  But it did establish a baseline we wish 
to strive for and a direction to pursue towards meeting with Paul 
Rissman and my shared goal for system performance monitoring.

In the last five months I have been diligently working on establishing a 
core set of PCM test patterns and measurement methods that will:

    * Write on the Raith system in a reasonable amount of time targeting
      less than an hour of write time.
    * Perform semiautomatic and automated measurements of the exposed
      pattern using the RAITH metrology package.
    * Render quality statistics on system performance for minimum
      features resolved, typical SPL CD dimension, dot shot and
      circularity size, and accurate measurement and plots of pattern
      stitching and overlay results.
    * Allow the data gathered is to be plotted and presented as
      Statistical Process Control (SPC) reports of system performance as
      well as providing example images for our presentations and public
      displays here at SNF.
    * Establish default exposure and measurement files that can be
      included with any RAITH user's exposure adding to our  knowledge
      database enhancing the process development task that are being
      continuously improved in my other project development of the 
      Ebeam Resist Processes Suite on our web site.
      <http://snf.stanford.edu/Process/Lithography/ebeamres.html>

To say the least this has been a significant focus of my work on the 
system adding to the many task and the number of hours of my time I work 
here at SNF.

 >> I was able to write 20 nm features using Raith across a 10x10 mm chip.
Great! Fantastic.  Show me the data and a SEM measurement!  Post it to 
the Board outside the Lab!
How come no one has ever posted their results or even an image to the 
list or onto the Bulletin Board?
 >>>To the best of my knowledge that is below the spec.
There is no minimum specification but SPL's are specified to be at 20 nm 
on 100 nm PMMA.  Smallest shot dot I have measured is 7 - 10 nm  (gage 
of measurement is +- 3 nm) Smallest feature last month I have found 
after pattern transfer is a 23 nm dot shot, but smaller features have 
been generated.  They are very hard to find and even more difficult to 
image.
 >>> Talking to some of the other experienced users, it seems that they 
are also getting nice results. 
But not all of the people all of the time.  There are several users 
struggling to get the results they desperately need.  One group in fact 
requested a refund of the moneys they have been charged by SNF because 
they claim they did not get the results they expected in their use of 
the system over the last year.  Would that group care to comment on this 
list?
 >>> Also by looking at the log book, I noticed that the experienced 
users have not reported any problems recently.
Only one user, Joshua Ratchford, has reported to the RAITH logbook any 
pattern results on the system whatsoever other than myself! Clearly not 
acceptable, in conflict with all SNF requirements for reporting , and 
you are not participating fully in the community if you do not report 
your project results.  Please think about starting to contribute a 
periodic report your results as this give me quality data to establish 
baselines of performance. This will then  allow me more time to address 
specific user problems and take up less of my time to evaluate normal 
system performance characteristics.

So I put out this challenge to the RAITH community:
You would help me and SNF greatly by promptly and accurately reporting 
your results on the RAITH logbook for each and every exposure made on 
the system. It would help me even more if you posted your results in 
monthly summaries to the discussion list 
<http://snf.stanford.edu/cgi-bin/ezmlm-cgi/2160>, or onto the RAITH 
SWIKI <http://elrey.stanford.edu:8080/Raith>, or your SWIKI or web page.
Finally PLEASE post your best results and feature images on the Bulletin 
Board outside the Lab for all to see.

I will be posting my report 'Performance Testing of the RAITH 150 system 
for November 2004' once I measure my last samples. I hope to have this 
completed by the end of next week. I will also post to the Bulletin 
Board images obtained in the last two months highlighting some of the 
problems we have been attempting to resolve that I outlined above.

 >>My second concern is regarding the total number of hours that is 
reserved by yourself.
 >> Can you please explain how the other hours are used?

Another great question I will attempt to answer herein:

In October and November nearly half my time on the system has been spent 
with troubleshooting the system, responding to users reports of problems 
in their writes, many test and measurements requested by RAITH Field 
service, and in maintenance and repair issues all related to the 
problems reported.  The end results is we determined we must complete 
the PM routine ASAP to resolve the issues on the system, or at least to 
get to the next level of items to troubleshoot seeking resolution of all 
issues.

Completed last month was the mechanical adjustment to and measurements 
of levelness the Electrostatic Chuck allowing it to level using the 
within 13 - 18 microns of flatness at 5 mm. This work continues with 
characterizing the Std. Sample holder and determining a figure of merit 
for leveling using piezo's on the STD. Sample Holder.   This was 
prompted by Users, all of whom are using focus correction by adjusting 
working distance, whom reported Write field  rotations leading to Y 
stitching breaks.

During many of my "PCM Testing and Measurement" sessions I have been 
barraged by users requesting additional help on the system for specific 
training points and troubleshooting their processes and exposure results.
 More than a few of you have requested all, or part of, my reservation 
times for urgent rework and to meet your conference deadlines.  Then let 
me point out the 100's of times and many hours of opportunity lost when 
I am interrupted during my work to help you and answer your questions,  
when I am actually attempting to get work performed on the system.
 This has become very acute in recent weeks and my tolerance for this 
behavior is growing very thin.
 I have recently started charging your projects for the time and impact 
of these interruptions take up including the time it takes to return to 
task.   I have recently given verbal warnings to two users to stop this 
behavior in the last two weeks.
I have an office hour every day from 8:30 - 9:30 AM when I am available 
to meet with you -- make use of it.
Several days in November were also lost to crashes, downtime and 
repairs, and a full day and night lost at the Power Failure several 
weeks ago. 

This month I have  been working with users from Octobers RAITH Basic 
Users class assisting them to quickly come up to speed on the system.  
This work directly benefits everyone as it pushed these new users well 
up the learning curve promptly. They are all working on very challenging 
projects and I feel that this time has been very well spent.
Users KQYOUN, LEVI, HANSJ, MAKAROVA, GOETZINGER, WINGCAT, DWSHIN, 
KHANSOLO, YKYOON would you care to comment on the usefulness of these 
sessions for your research?

Currently I also have been teaching a small group users the RAITH Basic 
Users course over several sessions spread over the last month.. Mainly 
users MAKAROVA, GOETZINGER, Kenneth Chen and some walk ins whom wished 
to joined us to get first views and demo of the system  This has the 
same impact as the 4 day intensive short course I teach every two months 
on the system. This effort was made to get several users through the 
class in November so it would open 2 or 3 slots for the next Raith 
class.  I have many more persons whom wish to be on using the system 
than I can train in one class (4 persons Max. per class. with 12 more 
and growing on my wait listed to be trained after the next class.)
 In effect all users will feel the reduced total time to access the system.

Finally I am doing my own process development work while working on a 
number of projects on the system.  In October and November I completed 
work for both Lawrence Livermore Nat'l Labs (LLNL) and for Georgia Tech 
(GIT)/ Devry's University.  The LLNL work was 4 wafer writes of a NIL 
pattern to 23 nm, the GaTech group project is waveguides and photonics 
crystals. this work is ongoing and will require overnight writes.  These 
members are industrial and academic users of our lab, they are helping 
to fund out lab.
  I have striven to minimized the impact of these efforts to your system 
access and often utilize times that the system has remained open.  
Rarely do I make these reservation outside your 10 day reservation view 
window.  Both of these projects have suffered many significant delays 
while I wait for system access time, due to cancellations to give you 
access, and due to unscheduled down time. Generally it seems to me that 
my reservations become less valuable than yours when we have system 
problems or you express an urgent deadline or need for access. Does 
anyone at all disagree?

Finally realize that just because it says 'JWC' on the Coral system 
often it is for reservations and scheduling adjustments I have made to 
smooth out the flow of things and improving the throughput on the system 
<http://snf.stanford.edu/cgi-bin/ezmlm-cgi?2160:mss:997:200411:ajaoobjcpeplmhnfceii>.  
Most of these adjustments have been requested and driven by your needs 
and not mine. I often include the task as planned in the comments 
section of the reservation so you can determine what is going on with 
the system by clicking on my reservation in CORAL.

There are  no limits to the time I can reserve the system during normal 
business hours. I do work days and not nights/weekends. The '8 hour 
rule' does not apply to the task I am completing on the system as all of 
you will benefit from my work.  As always, I normally plan to make use 
of the open time on the system but some writes will require me to block 
out significant amounts of continuous time to write on the RAITH.  As we 
move into more NIL pattern work these needs will likely increase in the 
near future.

Questions for the RAITH Community: 
Should we limit or eliminate access to the system for new Stanford 
University users wishing to work on the system?
Should we eliminate all outside academic and industrial users access 
working on the system?
Should we penalize those users whom do not honor, nor make timely notice 
of their cancellations on the system?
Should  we charge more for access to the RAITH system, or consider 
elimination of the time cap on the usage charges of this system?
Would users be supportive of  justifying the purchase of a second RAITH 
system either another RAITH 150 or a RAITH 100 suitable for chip writes?
Your comments, opinions, and critique of these ideas are requested. Post 
your replies to this RAITH discussion list.

I do sincerely hope you will appreciate and consider the comments I have 
made in reply to the very thoughtful note that Ali Javey presented last 
week. I gave this response much thought and consideration over the past 
week with the aim of accurately and succinctly answer all your questions. 

You are the RAITH community and your work and goal of obtaining perfect 
results on the RAITH 150 are important to me. I would expect that any 
user will come to me immediately upon running into problems on the 
system, especially if it be performance or scheduling issues.
Working closely together I know we can achieve truly World Class status 
for our Ebeam Lab. Participation in this goal is up to you and you alone.

Thank you for your support! Your comments are invited.

James Conway
650-725-7075

Ali Javey wrote:

>Hi James,
>
>Can you please clarify the maintenance and testing policies of the Raith?
>I have noticed that Raith will be shut down again at the end of next week
>for "maintenance".  What exactly will be done during this maintenance?
>The reason that I am asking is because at the moment Raith seems to be
>working well.  Over the weekend, I was able to write 20 nm features using
>Raith across a 10x10 mm chip.  To the best of my knowledge that is below
>the spec.  Talking to some of the other experienced users, it seems that
>they are also getting nice results.  Also by looking at the log book, I
>noticed that the experienced users have not reported any problems
>recently. May be users can reply to this message and report whether they
>have observed any problems/errors in their recent writes. My concern with
>the maintenance is that from the past, it seems that whenever the column
>is brought down for aperture or tip replacements, the system typically
>becomes unstable for few weeks with constant down time. So the question is
>when are the repairs and maintenance absolutely necessary to achieve the
>highest possible efficiency and performance for the equipment.
>
>My second concern is regarding the total number of hours that is reserved
>by yourself.  By looking at Coral, it seems that for example, you have
>signed up for 11 hours both on Tuesday and Wednesday of this week.  There
>is also a 5-hrs reservation block on Thursday and 3-hrs block on Friday.
>This adds up to a total of 30 hrs of reservation to your name just for
>this week, mainly during the prime hours.  This is for the week before the
>shutdown and at the time when Raith is heavily used. It seems that only 3
>hrs (Friday) of these reservations are for user training.  Can you please
>explain how the other hours are used?  From Coral, it seems that 22 hrs
>are used for GI and PCM (testing?).  Should there be a limit to such
>reservations?  Should the 8 hrs rule also apply to yourself. Is testing
>really necessary or can we rely on users' inputs for system qualification?
>>From talking to various users from various groups, it seems that such long
>reservation hrs are an issue of concern to many users.
>
>I will appreciate your comments regarding the above issues and I really
>hope that all users can also provide their inputs through e-mails to this
>list in order for us to make the system more efficient and available to
>all.
>
>Best,
>Ali
>  
>
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