Proximity effect (electron beam lithography)

About: Proximity effect (electron beam lithography) is a research topic. Over the lifetime, 940 publications have been published within this topic receiving 8508 citations.

ELECTRON BEAM LITHOGRAPHY FROM 20 TO 120 kev WITH A HIGH QUALITY BEAM.

Abstract: We have performed electron beam lithography studies on thick substrates using beam energies of 20–120 keV and a nominal beam diameter of 2 nm in a Philips 400 electron microscope with scanning capability. Metal lines as narrow as 10 nm were fabricated on Si and GaAs substrates using liftoff of a single thin layer of resist. High resolution (approximately 10 nm) patterns could be written at all beam energies with an exposure latitude that remained approximately constant up to energies for which the range of the backscattered electrons became significantly larger than the pattern area. For large area patterns written with the small beam, the proximity effect is greatly reduced, even at 20 keV, because of the sharp edge of the exposure profile. At high beam energies, the range of backscattered electrons is large enough that they contribute only a slowly varying background dose, leading to a relatively simple proximity correction even for complex patterns.

Methods for forming microlithographic masks that compensate for proximity effects

Abstract: Methods are disclosed for forming microlithography (photolithography or charged-particle-beam projection lithography) masks exhibiting reduced proximity effects. A first exposure is made, using an electron beam at a first exposure intensity level, on a mask substrate. The first exposure is made on region(s) of the mask substrate corresponding to the desired basic feature(s) of the mask pattern. A second exposure is made, using, the electron beam at a second exposure intensity level, at "secondary exposure regions" that at least partially reside within the basic feature(s). Thus, portions of the basic features receive a cumulative electron exposure that is greater than other portions of the basic features. Such increased cumulative exposure causes an alteration of the profile of the subject basic feature sufficient to cause the resulting modified basic feature to exhibit a reduced proximity effect. The secondary exposure areas are preferably square and/or rectangular, extending along one or more edges of the subject basic feature, and can overlap or not overlap the corresponding edge(s) of the basic feature. The width and exposure intensity levels for the secondary exposure areas are controlled to produce a mask pattern area with widened and outgrown areas of the basic features that compensate for the proximity effect.

Phase holograms in polymethyl methacrylate

Abstract: Complex computer generated phase holograms (CGPHs) have been fabricated in polymethyl methacrylate (PMMA) by partial exposure and subsequent partial development. The CGPH was encoded as a sequence of phase delay pixels and written by e‐beam (JEOL JBX‐5DII), a different dose being assigned to each value of phase delay. Following carefully controlled, partial development, the pattern appears, rendered in relief, in the PMMA which then acts as the phase‐delay medium. The exposure dose was in the range 20–200 μC/cm2, and very aggressive development in pure acetone led to low contrast. This enabled etch depth control to better than ±20 nm corresponding to an optical phase shift in transmission, relative to air, of ±λvis/60. That result was obtained by exposing isolated 50 μm square patches and measuring resist removal over the central area where the proximity effect dose was uniform and related only to the local exposure. For complex CGPHs with pixel size of the order of the proximity radius, the patterns must be corrected for proximity effects. In addition, the isotropic nature of the development process will produce sidewall etching effects. The devices fabricated were designed with 16 equal phase steps per retardation cycle, were up to 3 mm square, and consisted of up to 10 million 0.3–2.0 μm square pixels. Data files were up to 60 Mb long and exposure times ranged to several hours. No sidewall etch corrections were applied to the pattern and proximity effects were only treated approximately. A Fresnel phase lens was fabricated that had diffraction limited optical performance with 83% efficiency.

Correcting method for proximity effect

Abstract: PURPOSE: To shorten processing time by calculating proximity effect correction for each hierarchical layer and each cell while maintaining the hierarchical layer structure for design data having a hierarchical layer structure of cells. CONSTITUTION: If resist coated on a board is exposed, when proximity effect is supplemented for a design pattern having a hierarchical layer structure of cells, a first frame region having a predetermined width is provided inside the boundary of the cells, and a second frame region having a predetermined width is provided inside the first region. When pattern data in each cell is corrected for the proximity effect, the pattern in the second region and the pattern inside the second region are to be corrected, and the pattern in the first region is used as a reference pattern. When the pattern of a hierarchical layer cell directly above each cell is corrected for the proximity effect, the pattern in the first region in each cell is added as to be corrected, the pattern in the second region in each cell is used as a reference pattern, and proximity effect corrective operation is carried out. COPYRIGHT: (C)1991,JPO&Japio