TEA Systems                        Corporate News                      FijiFilm Interface 2006

TEA Systems presents paper

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"Full sub-65 nm data-modeling for Photomask Manufacturing

& the benefits derived in device fabrication"


FujiFilm Interface 2006 conference - 29-Oct-2006

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Reticle data removed from wafers to view wafer-bias process response;

a new, improved method to full-field Process Windows for OPC control!

  • Have you ever tried to use process window calculations for OPC qualification?

  • Frustrated with trying to make sense of multi-site and multi-feature process windows?

  • Who says you can't see all the sources of the Mask Error Function?

  • Direct measurement of reticles using Optical Digital Scatterometry! How does this compare with CD-SEM?


If the precision and relative accuracy of the Photomask Facility’s toolset contains sufficient process margin then production yields can be efficiently controlled using statistical methods. It’s simply a matter of gathering the data and confirming the proper operation of each metrology and patterning tool using maintenance procedures.  However these simpler times are gone when device designs enter the realm of the sub-65 nm design rule reticle set. To meet these new challenges the industry needs to tune the Photomask Facility’s Optical Proximity Correction (OPC) simulation tools and fabrication processes to the anticipated interactions of the reticle image as it is perturbed during imaging on the wafer.

Recent introductions of commercial, hardware-enhanced simulators are used to optimize the full-field image in order to reduce costly feature-enhancement mistakes during design. These simulations have taken the first few steps to apply real-world boundary conditions to their calculations by incorporating a calibration to the process excursions measured across the customer’s process using focus-exposure matrices and the classic “process window” analysis. Yet these methods do not consider the additional significant process and toolset specific signatures of the end-customer.

Recently awareness has risen for the need to verify both overly and etch-depth during Phase Shift Mask (PSM) manufacture. Here we see a need to bias phase shift etch-depth parameters away from their theoretical design targets to compensate for “unknown” biases that are in fact systematic process and tool errors. The considerations studied in these papers neglect the full final response in the customer wafer fab. The studies also neglect to link the wafer processes true feature-profile response to the individual site-signatures of the mask by relying solely on arbitrary width measurement of profiles. 

If a precise analysis were available that could carefully model the spatial distributions of the feature profiles, it could then also extract process signatures and a detailed mask response to them. The coefficients of the modeled process signature could be used to stabilize and tune production in both photomask and end-customer device manufacturing and therefore optimize final device yields and minimize the time required to achieve optimum yield for new processes.

What is lacking is the proper analytical toolset to perform this link between the simulation optimized OPC photomask and the process signatures of the wafer and photomask process. Process window comparative evaluations assume a response model first presented 3 decades ago. A comparison of individual OPC structure responses using classic process window techniques does not have the resolution to determine the performance and response of the process to small changes in design.  The linkage must be capable of providing a direct and clear comparison of reticle-structure design option performance as well as accurate calibration metrics for the structure’s design simulator.

The resolution of this problem lies in the ability of new metrology technology to quantitatively and accurately measures the full profile of the actinic film stack of a wafer exposure. New analysis techniques are needed to take advantage of this full-profile characterization.

We present here a direct and conceptually simple approach to improve the evaluation of OPC designs using multi-layer empirical data modeling of the imaging process. The method is illustrated by an analysis of the variance of reticle-to-wafer bias based on metrology gathered from both reticle and wafer profiles.  While the wafer bias variable is used as a demonstration vehicle for the method, any profile variable could be used with equal precision.


TEA Systems

TEA Systems offers products to model films, photomasks, wafers, feature profiles, process and lens data for characterization and setup of semiconductor design, simulators, tools and the process.


TEA Systems, a privately held corporation since 1988, specializes in advanced, intelligent modeling of the semiconductor process and toolset. Products from TEA allow the user to decouple process, tool and random perturbations for enhanced process setup & control.

TEA Systems products include:

Weir PSFM: Full-wafer/field/scan analysis tool for FOCUS derived from proprietary defocus sensitive features.

Weir PW:    Reticle/Full-wafer/field/scan analysis for any metrology with advanced process window capabilities for both wafer and photomask control.

LithoWorks PEB: A tool to link and correlate profile, film and critical element control to thermal reactions such as PEB and ChillPlate

Weir DMA:   Macro Automation interface for Weir PSFM and Weir PW for external program calling, automated data gathering or one-button analysis of commonly used sequences. Includes data trending and web interface.


Copyright 2006 TEA Systems Corporation, All rights reserved. Legal


TEA Systems Corp. | Tel: +1 610 682 4146
65 Schlossburg St., Alburtis, PA USA


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