Advanced mask technique to improve bit line CD uniformity of 90 nm node flash memory in low-k1 lithography

Jong-doo Kim; Jae-young Choi; Jea-hee Kim; Jae-won Han

doi:10.1117/12.801557

17 October 2008 Advanced mask technique to improve bit line CD uniformity of 90 nm node flash memory in low-k1 lithography

Jong-doo Kim, Jae-young Choi, Jea-hee Kim, Jae-won Han

Author Affiliations +

Proceedings Volume 7122, Photomask Technology 2008; 71220X (2008) https://doi.org/10.1117/12.801557
Event: SPIE Photomask Technology, 2008, Monterey, California, United States

Abstract

As devices size move toward 90nm technology node or below, defining uniform bit line CD of flash devices is one of the most challenging features to print in KrF lithography. There are two principal difficulties in defining bit line on wafer. One is insufficient process margin besides poor resolution compared with ArF lithography. The other is that asymmetric bit line should be made for OPC(Optical Proximity Correction) modeling. Therefore advanced ArF lithography scanner should be used for define bit line with RETs (Resolution Enhancement Techniques) such as immersion lithography, OPC, PSM(Phase Shift Mask), high NA(Numerical Aperture), OAI(Off-Axis Illumination), SRAF(Sub-resolution Assistant Feature), and mask biasing.. Like this, ArF lithography propose the method of enhancing resolution, however, we must spend an enormous amount of CoC(cost of ownership) to utilize ArF photolithography process than KrF. In this paper, we suggest method to improve of bit line CD uniformity, patterned by KrF lithographic process in 90nm sFlash(stand alone Flash) devices. We applied new scheme of mask manufacturing, which is able to realize 2 different types of mask, binary and phase-shift, into one plate. Finally, we could get the more uniform bit lines and we expect to get more stable properties then before applying this technique.

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Jong-doo Kim, Jae-young Choi, Jea-hee Kim, and Jae-won Han "Advanced mask technique to improve bit line CD uniformity of 90 nm node flash memory in low-k1 lithography", Proc. SPIE 7122, Photomask Technology 2008, 71220X (17 October 2008); https://doi.org/10.1117/12.801557

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KEYWORDS

Photomasks

Lithography

Semiconducting wafers

Chromium

Optical proximity correction

Optical simulations

Binary data

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