Compensation for the proximity effect in electron lithography can be achieved by equalization of the backscattered dose received by all pattern points. This is accomplished by exposing the reverse tone of the required pattern with a beam diameter dc=2σb ×(1+ηe)−1/4 and dose Qc=Qe ×[ηe/(1+ηe)], where σb is the radius of the Gaussian spatial distribution function of backscattered electrons at normally exposed pixels, ηe is the ratio of backscattered to forwardscattered energy, and Qe is the dose delivered to normally exposed pixels. This correction method has been confirmed to work for 500-nm features by computer simulation of electron beam exposure and development and by experiment on a raster scan electron beam lithography system.
A convenient and unambiguous way of characterizing the proximity effect is by use of the modulation transfer function. Six types of correction scheme are compared in this way, these being the use of high beam energies (>20 keV), of low beam energies (<20 keV), the use of multilayer resists, exact dose correction, ‘‘self-consistent’’ dose correction, and the application of correction exposures. The main conclusions drawn are that the use of high beam energies reduces the proximity effect significantly; that exact dose correction, in addition to performing better than the ‘‘self-consistent’’ technique, is computationally superior; and that correction exposures are effective, particularly in combination with other correction techniques.
Electron lithography is a technique which is in widespread use for making masks and reticles for the manufacture of integrated circuits. It is also commonly used in research laboratories for exposing micron or sub-micron patterns directly on wafers. In addition, direct exposure is used, to a limited extent, in manufacturing plants, although generally at coarser resolutions. The reasons for using electron lithography in these applications are explained, and a history of the technique's evolution is given. The two major types of instrument-the scanning instrument and the projection instrument-are described and their limitations are pointed out. Interactions between electrons with energies of tens of keV (the energies typically used in electron lithography), the substrate (wafer or mask plate) and the resist material (in which a latent image is formed) are discussed. It is shown how these interactions affect the quality of the resist image before and after development.
Geraint OwenHewlett Packard Laboratory, Fremont, CA 94538 A two-dimensional self-calibration experiment obtains Cartesian traceability for high-precision tools. The cdibration procedure incorporates group theory principks to solve our indust,y's two-dimensional calibration problem.With group theory, a Cartesian system is obtainable through mathematics; thus, eliminating the need for any certifIed standards. The calibration algorithm was developed by Jun Ye at Stanford University and funded by the Semiconductor Research Corporation (SRC) with collaboration from Hewlett Packard (HP) and IBM1. The data was collected from Leica's LMS2000 and LMS2O2O systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.