Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Patent
1999-05-28
2000-11-28
Young, Christopher G.
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
430 30, 430296, 430942, G03F 900
Patent
active
061533408
ABSTRACT:
Methods and reticles are provided for performing charged-particle-beam microlithography in which degradations in transfer accuracy arising from the space-charge effect and/or resist heating are reduced. A reticle is divided into multiple exposure units (e.g., subfields) each having at least one pattern feature, and each exposure unit is divided into multiple subunits. Certain features include non-exposed regions having dimensions larger than the resolution limit of the projection-optical system used to project the reticle pattern onto the substrate. Also, the non-exposed regions are desirably smaller than the dimensional limit at which resolution is impossible due to the proximity effect. With stencil reticles, the non-exposed regions are preferably provided at boundaries between complimentary pairs of large-dimension features inside exposure units having different feature densities. The non-exposed regions absorb backscattered electrons from the exposure doses received by surrounding portions of the feature. The dose represented by the backscattered electrons is typically above a threshold value for developing the resist. Such features reduce the feature-density variation of the pattern as defined on the reticle.
REFERENCES:
Kratschmer et al., "Resist Heating Effects in 25 and 50 kV e-beam Lithography on Glass Masks," J. Vac. Sci. Technol. 8:1898-1902 (1990).
Liddle et al., "Proximity Effect Correction in Projection Electron Beam Lithography (Scattering with Angular Limitation Projection Electron-Beam Lithography)," Jpn. J. Appl. Phys. 34:6672-6678 (1995).
Nakajima et al., "Calculation of a Proximity Resist Heating in Variably Shaped Electron Beam Lithography," J. Vac. Sci. Technol. 10:2784-2788 (1992).
Nakajima et al., "New Compensation Method for Avoiding Proximity Resist Heating in Variably Shaped Electron Beam Lithography," J. Vac. Sci. Technol 8:1437-1440 (1990).
Nikon Corporation
Young Christopher G.
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