Mask assisted off-axis illumination technique for random logic

Garofalo, Joseph G.; Biddick, C.; Kostelak, R. L.; Vaidya, S.

doi:10.1116/1.586579

Cited by 33 publications

(16 citation statements)

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“…4. Using annular illumination with mask assist features [35] more than doubles the depth-of-focus to 1.98 m but decreases the exposure latitude slightly to 13.4%. The better lithography approach may be discounted if the techniques are evaluated based on the maximum exposure latitude.…”

Section: A the "Total Window" Metricmentioning

confidence: 95%

Level-specific lithography optimization for 1-Gb DRAM

Wong

Ferguson

Mansfield

et al. 2000

IEEE Trans. Semicond. Manufact.

103

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A general level-specific lithography optimization methodology is applied to the critical levels of a 1-Gb DRAM design at 175-and 150-nm ground rules. This three-step methodology-ruling out inapplicable approaches by physical principles, selecting promising techniques by simulation, and determining actual process window by experimentation-is based on process latitude quantification using the total window metric. The optimal lithography strategy is pattern specific, depending on the illumination configuration, pattern shape and size, mask technology, mask tone, and photoresist characteristics. These large numbers of lithography possibilities are efficiently evaluated by an accurate photoresist development bias model. Resolution enhancement techniques such as phase-shifting masks, annular illumination and optical proximity correction are essential in enlarging the inadequate process latitude of conventional lithography.

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Section: A the "Total Window" Metricmentioning

confidence: 95%

Level-specific lithography optimization for 1-Gb DRAM

Wong

Ferguson

Mansfield

et al. 2000

IEEE Trans. Semicond. Manufact.

103

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show abstract

“…the cd proximity effect. Therefore a method has been proven to get these exposure windows closer to each other which is called "feature assisted lithography" [8]. The principle is demonstrated in Figure 13a Figure 13b for Al -is remarkable.…”

Section: Feature Assisted Lithographymentioning

confidence: 98%

<title>Improvement of the focus exposure latitude using optimized illumination and mask design</title>

et al. 1994

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AB STRACTThe performance of off-axis illumination techniques in comparison to conventional illumination has been investigated for features in the O.5*(/NA) range. Conventional masks, chrome masks with assistant features, and halftone phase-shifting masks have been used in combination with these techniques. The analysis includes dense and isolated test features as well as real design features of a random logic IC. Advanced positive tone i-line resists and a O.48NA wafer stepper have been applied. Focus and exposure latitudes, linearity, cd proximity effects, and feature deformations caused by the applied techniques are considered. The analysis is done experimentally and theoretically based on cd calculations of developed resist features using Depict-3. The advantages and drawbacks of these techniques are discussed.Generally, off-axis illumination techniques improve the latitudes of dense features of high periodicity, but show stronger proximity effect, worse linearity, and stronger feature deformations. Quadrupole illumination improves the depth-of-focus of dense periodic lines best, but shows the strongest proximity effect -specifically for isolated spaces -, worst linearity and has a non-symmetric imaging quality regarding feature orientation. Annular illumination shows a moderate improvement of dense features, but less proximity effect, better linearity and smaller feature deformations compared to that. Combining weak phase-shifting masks with off-axis illumination improves the exposure latitude of isolated features and the overlapping latitudes. A very effective method to increase the overlapping latitudes in the interesting size range is to apply assistant features to the isolated features. Significant improvements of the overlapping latitudes have been achieved using this techniques. Furthermore the impact of the resist performance is demonstrated. The better the performance the smaller the relative latitude improvements of the off-axis illumination technique. An ultimate resolution of dense IC features down to O.3Om for a O.48NA i-line wafer stepper is achieved using annular illumination with halftone phase-shifting masks. For O.5*(AJNA) features, usable latitudes are demonstrated.

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“…By selecting an operating point for exposure, E0 , and defocus, F0 , Equation 1 becomes S=8(G1) (2) where ö(G1)=S(E0,F0,G). Equation 2 is the "rule" for correcting the placement of edge i.…”

Section: The Rules-based Approachmentioning

confidence: 99%

<title>Automated optical proximity correction: a rules-based approach</title>

Otto

Garofalo

Low³

et al. 1994

SPIE Proceedings

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In this work we demonstrate the power, speed and effectiveness of an automated rules-based approach for performing optical proximity correction. The approach applies to both conventional and phase-shifting mask layouts for optical lithography. Complex imaging, substrate and process phenomena can be folded into comparatively few rules parameters. Using simple arithmetic, these parameters pre-compensate the layout for the combined proximity effects. The rules consist of edge rules and corner rules for biasing feature edges and for adding sub-resolution assist features. This paper describes an integrated solution which includes rules parameter generation and fast, hierarchical rules application. Experimental results demonstrate improved edge placements and wider process latitude than for non-corrected layouts.

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Mask assisted off-axis illumination technique for random logic

Cited by 33 publications

References 0 publications

Level-specific lithography optimization for 1-Gb DRAM

Level-specific lithography optimization for 1-Gb DRAM

<title>Improvement of the focus exposure latitude using optimized illumination and mask design</title>

<title>Automated optical proximity correction: a rules-based approach</title>

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