Nace Layadi, Leonidas Ocola, Fred Klemens, Reginald Farrow, Myrtle Blakey, Paul Orphanos, Avi Kornblit, Masis Mkrtchyan, Joseph Kraus, Isik Kizilyalli, Sailesh Merchant, Gregg Gallatin, Joseph Felker, Christopher Biddick, James Liddle, Warren Waskiewicz
KEYWORDS: Charged-particle lithography, Semiconducting wafers, Optical alignment, Signal detection, Lithography, Photomasks, Signal to noise ratio, Electron beam lithography, CMOS sensors, Scanning electron microscopy
A manufacturable process for fabricating alignment marks that are compatible the SCALPEL lithography system is described. The marks were fabricated in a SiO2/WSi2 structure using SCALPEL lithography and plasma processing. The positions of the marks were detected through e-beam resist in the SCALPEL proof of lithography (SPOL) tool by scanning the image of the corresponding mask mark over the wafer mark and detecting the backscattered electron (BSE) signal. Scans of 1 micrometers line-space patterns yielded mark positions that were repeatable within 20 nm 3(sigma) with a dose of 4 (mu) C/cm2 and signal-to-noise of 32 dB. An analysis shows that the measured repeatability is consistent with a random noise limited response combined with SPOL machine factors. By using a digitally sequenced mark pattern, the capture range of the mark detection was increased to 13 micrometers while maintaining 35 nm 3(sigma) precision. Further improvements in mark detection repeatability are expected when the SCALPEL electron optics is fully optimized.
Successful deployment of SCALPEL for several post-optical production lithography generations requires a unique optimum writing-strategy. Since the electron optics sub-field and the strutted mask patten segment are both smaller than the final device image area, SCALPEL utilizes a stitching approach to image-formation. A dynamic sub-field placement scheme, or 'writing strategy', must provide precise 2D stitching at high speed, and eliminate mask strut images on the wafer. It should also provide the extended dynamic lens field necessary for good throughput, while minimizing all non-exposure times per wafer and maintaining the time- averaged current near the instantaneous space-charge limit. The preferred writing-strategy replaces mechanical stage acceleration events with beam deflection wherever possible. The unique writing-strategy presented here also generates the required 2D seam-blending dose-profiles, which are vital to robust CD control with stitching.
Myrtle Blakey, Harry Wade, Warren Waskiewicz, James Liddle, J. Custy, David Windt, Pat Watson, A. Crorken, Chester Knurek, Stephen Bowler, R. DeMarco, Richard Kasica, Leslie Hopkins, Lloyd Harriott, Joseph Felker, Anthony Novembre, Christopher Biddick, Reginald Farrow, Milton Peabody, Linus Fetter, Ron Camarda, Kevin Brady, Regine Tarascon-Auriol, Harold Huggins, Kurt Werder, Richard Freeman, Joseph Kraus, Steven Berger, Len Rutberg, Masis Mkrtchyan, Wayne Connelly
We have designed, constructed, and are now performing experiments with a proof-of-concept projection electron-beam lithography system based upon the SCALPELR (scattering with angular limitation projection electron-beam lithography) principle. This initial design has enabled us to demonstrate the feasibility of not only the electron optics, but also the scattering mask and resist platform. In this paper we report on some preliminary results which indicate the lithographic potential and benefits of this technology for the production of sub-0.18 micrometer features.
Harry Wade, Myrtle Blakey, Lloyd Harriott, Kevin Brady, Steven Berger, Harold Huggins, Wayne Simpson, James Liddle, Milton Peabody, Anthony Novembre, Stephen Bowler, Wayne Connelly, Joseph Felker, Reginald Farrow, Masis Mkrtchyan, Christopher Biddick, Thomas Russell, Warren Waskiewicz, Ron Camarda, Kevin Bolan, Linus Fetter, Pat Watson, Regine Tarascon-Auriol, Joseph Kraus
We have proposed an approach to projection electron beam lithography, termed the SCALPEL system, which we believe offers solutions to previous problems associated with projection electron beam lithography.
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