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Proceedings ArticleDOI

Practical application of full-feature alternating phase-shifting technology for a phase-aware standard-cell design flow

22 Jun 2001-pp 93-96

TL;DR: This paper presents a methodology targeted for standard-cell or structured-custom design styles that start from standard-cells created in a manner in which all issues regarding generation of AltPSM are effectively considered, and are then used in a typical cell-based (synthesis-automatic place and route) flow to produce design layouts that are ready for cost-effective silicon manufacturing.

AbstractAs the semiconductor industry enters the subwavelength era where silicon features are much smaller that the wavelength of the light used to create them, a number of “subwavelength” technologies such as Optical Proximity Correction (OPC) and Phase-Shifting Masks (PSM) have been introduced to produce integrated circuits (ICs) with acceptable yields. An effective approach to subwavelength IC production includes a combination of these techniques, including OPC and PSM. Nevertheless, as we approach silicon features of 0.10&mgr and below, Alternating PSM (AltPSM) becomes a critical part of the technology portfolio needed to achieve IC requirements. An effective EDA methodology that generates AltPSM ICs must guarantee correct generation of AltPSM layouts, maintain or improve today's design productivity, and leverage existing tools and flows. The implementation of such a methodology becomes more complex as phase shifting is applied to all critical features, including those outside of transistor gates. In this paper, we present a methodology targeted for standard-cell or structured-custom design styles. We also present examples of designs that start from standard-cells created in a manner in which all issues regarding generation of AltPSM are effectively considered, and are used in a typical cell-based (synthesis-Automatic Place & Route) flow to produce design layouts that are ready for cost-effective silicon manufacturing.

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Citations
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Journal Article
Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

700 citations


Patent
06 Feb 2002
Abstract: Techniques are provided for extending the use of phase shift techniques to implementation of masks used for complex layouts in the layers of integrated circuits, beyond selected critical dimension features. The method includes identifying features for which phase shifting can be applied, automatically mapping the phase shifting regions for implementation of such features, resolving phase conflicts which might occur according to a given design rule, and application of assist features and proximity correction features. The method includes applying an adjustment to a phase shift mask pattern including a first and a second phase shift window, and a control chrome with a control width, and/or to a trim mask pattern having a trim shape with a trim width based upon one or both of a rule based correction and a model based correction to improve a match between a resulting exposure pattern and a target feature.

241 citations


Patent
23 Sep 2002
Abstract: Performing optical proximity correction (OPC) is typically done during a critical time, wherein even small delays in finishing OPC can have significant adverse effects on product introduction and/or market exposure. In accordance with one feature of the invention, sets of repeating structures in library elements and/or layout data can be identified during a noncritical time, e.g. early in cell library development, possibly years prior to the direct application of OPC to a final layout. OPC can be performed on repeating structures during this noncritical time. Later, during the critical time (e.g. during tape out), an OPC tool can use the pre-processed structures in conjunction with a chip layout to more quickly generate a modified layout, thereby saving valuable time as a chip moves from design to production.

170 citations


Patent
31 Aug 2001
Abstract: A method and apparatus for providing correction for microloading effects is described. Hybrid proximity correction techniques are used to make the problem computationally more feasible. More specifically, feature edges in a layout can be grouped into those edges, or edge segments, with a large edge separation (group B), e.g. greater than n, and those having less than that separation (group A). The group B features can then be corrected for microloading effects rapidly using rules based correction. Then both groups of edges can be corrected using model based optical proximity correction using the output of the rule based correction as the ideal, or reference, layout.

140 citations


Patent
10 Sep 2004
Abstract: A method for defining a full phase layout for defining a layer of material in an integrated circuit is described. The method can be used to define, arrange, and refine phase shifters to substantially define the layer using phase shifting. Through the process, computer readable definitions of an alternating aperture, dark field phase shift mask and of a complimentary mask are generated. Masks can be made from the definitions and then used to fabricate a layer of material in an integrated circuit. The separations between phase shifters, or cuts, are designed for easy mask manufacturability while also maximizing the amount of each feature defined by the phase shifting mask. Cost functions are used to describe the relative quality of phase assignments and to select higher quality phase assignments and reduce phase conflicts.

140 citations


References
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Journal Article
Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

700 citations


"Practical application of full-featu..." refers methods in this paper

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Journal ArticleDOI
Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10X tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

659 citations


Proceedings ArticleDOI
01 Jun 1999
TL;DR: This tutorial paper surveys the potential implications of subwavelength optical lithography for new tools and flows in the interface between layout design and manufacturability and addresses the necessary changes in the design-to-manufacturing flow.
Abstract: This tutorial paper surveys the potential implications of subwavelength optical lithography for new tools and flows in the interface between layout design and manufacturability. We review control of optical process effects by optical proximity correction (OPC) and phase-shifting masks (PSM), then focus on the implications of OPC and PSM for layout synthesis and verification methodologies. Our discussion addresses the necessary changes in the design-to-manufacturing flow, including infrastructure development in the mask and process communities, evolution of design methodology, and opportunities for research and development in the physical layout and verification areas of EDA.

70 citations


Proceedings ArticleDOI
29 Jun 1998
Abstract: In this paper we present the results of experimental patterning 140 nm poly gates withdouble-exposure alternating phase-shifting masks (PSM) using a Nikon EX- 1 (KrF,0.42NA) stepper. We show that: systematic intrafield line width variations can becontrolled within 10 nm (3), interfield variations across the wafer to within 6 nm (3),and total variation across the wafer held to within 15 nm (3), with a target k1 factor of k1=0.237 (140 nm target gate lengths). We also present the results of studies addressingseveral issues related to the production application of alternating PSM' s, including mask manufacturing tolerances and full chip PSM design capabilities. We show that, incomparison to conventional binary masks, alternating PSM's reduce the criticality of mask line width control and reduce the sensitivity to mask defects. Furthermore tolerance to PSM phase errors can be significantly improved by placing a chrome regulator between phase-shifters. Automatic, high-speed full chip design of alternating strong PSMis now possible.Keywords: Optical lithography, Phase-shifting masks, line width variations, CD control

62 citations


Proceedings ArticleDOI
12 Feb 1997
Abstract: In this paper we show that the problem of intrafield line width variations can be effectively solved through a novel application of alternating phase-shifting mask (PSM) technology. To illustrate its advantages, we applied this approach to produce 140 nm transistor gates using DUV (248 nm wavelength, KrF) lithography. We show that: systematic intrafield line width variations can be controlled to within 10 nm (3 (sigma) ), and variations across the wafer held to within 15 nm (3 (sigma) ), with a target k1 factor of K1 equals 0.237 (140 nm target gate lengths).

45 citations