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SPIE Professional: Letters to the Editor

Some letters may be edited for clarity, spelling, etc.

20 October, 2008
Dear Editor,

image from NIST test on silicon waferThe piece "Sensitive Photoresists" in the October issue of the SPIE Professional reported that the "photoresists used in EUV lithography processes are twice as sensitive as previously believed." As it turns out, however, subsequent measurements by NIST have shown that the factor of two difference between the assumed sensitivity and the value obtained in an absolute sensitivity measurement is not true for all EUV Lithography (EUVL) photoresists.

The factor of two discrepancy applies to the two EUVL photoresists that have been used to calibrate the SEMATECH Berkeley MET tool and several of the other MET tools in use that were either calibrated against the Berkeley tool or calibrated using the same photoresists as dose calibration "standards."

NIST has recently measured the EUV resist used in the dose calibration of the ASML Alpha Demonstration Tools (ADT) at the College of Nanoscale Science and Engineering in Albany, NY and at IMEC in Leuven, Belgium. This dose calibration resist XP4502-J was measured at NIST to have a sensitivity value that is within 15% of what has been in use for several years to calibration the dose system on the ASML tools, and this is well within the uncertainty introduced by conditions associated with processing environments. These results were presented at the IEUVI Resist Technical Working Group meeting in Lake Tahoe in September.3

We would recommend that the next issue of the SPIE Professional report on the new measurements showing that the previously reported discrepancy was not found in the resists used to calibrate the ASML Alpha Demonstration Tools, and thus there is no uncertainty in dose calibration or 2X factor in productivity of these EUVL systems.

Further, the additional testing by NIST validates that resist screening can be done on both METs and ADTs without worry of calibration differences.


  1. "Absolute sensitivity calibration of extreme ultraviolet photoresists," Patrick P. Naulleau, Eric M. Gullikson, Andy Aquila, Simi George, and Dimitra Niakoula. Optics Express, Vol. 16, Issue 15, pp. 11519-11524.
  2. "Absolute EUV resist E0 measurement at NIST", S. Grantham, C. Tarrio, R. E. Vest, T. B. Lucatorto, A. Novembre, M. Cangemi, and V. Prabhu, K.W. Choi, M. Chandhok, T. Younkin, and J. S Clarke. Presented at the SEMATECH source workshop May, 2008.
  3. "Resist-based dose calibrations update", Noreen Harned, presented at the IEUVI Resist Technical Working Group, Lake Tahoe, CA, October, 2008.

Charles Tarrio, NIST

6 November, 2008

I just printed the article Find an Adviser for some housemates of mine. It really summarizes and enhances what we were speaking about two days ago after dinner. They are looking for a PhD position and they did not know where and how to start. I think this article will really help them.

I also read the article, Getting the Most Out of Conferences (in the SPIE Student Newsletter), yesterday and I found it very encouraging, too. It does not make you anxious, but it motivates you to be active.

Thank you for finding the right people to write sensibly about important subjects.

Hugo de las Heras, Helmholtz-DAAD PhD student

6 November, 2008

Hi SPIE Professional Magazine,

I recently received a complimentary issue of SPIE Professional Magazine.

As both the Engineering Librarian and the Graduate Services coordinator here in the library, I found the article entitled, Find an Adviser in your October 2008 issue informative and wanted to make a link to it in our Dissertation Calculator. Certainly, help with choosing an adviser is a significant part of Step 1 of the 18 steps included in the calculator and something that I know graduate students struggle with, especially BS/MS students who are less savvy about interacting with faculty.

Upon future investigation, I see that SPIE Professional is a member magazine in every sense of word. Nothing is freely available from your Web site, it's not included in the SPIE Digital Library (to which we subscribe), and it's not indexed or carried by other aggregator databases.

While I'm sure you want to want to include the magazine as a benefit of membership, there are other organizations that do include their member magazine as part of their own database and/or do give away some content freely on their own Web sites.

It might benefit the organization to share some of this content in some limited format beyond membership. It might expose people who would never have known about SPIE to your organization.

Thank you for considering opening up your magazine to a wider audience.


Linette Koren, Librarian/Liaison for KGCOE/CIMS and CAST/ET and Graduate Services Coordinator, Wallace Library, Rochester Institute of Technology

EDITOR'S NOTE: While SPIE Professional magazine designates for open access only one article per issue, the SPIE.org Web site has much information that is freely available, including free technical articles in the SPIE Newsroom, free educational posters, a photonics clusters database, public policy updates and more.

DOI: 10.1117/2.4200810.48

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