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.

Model-based proximity effect correction for electron-beam direct-write lithography

Abstract: A model-based proximity effect correction methodology is proposed and tested for electron-beam-direct-write lithography. It iteratively modulates layout geometry by feedback compensation until the correction error converges. The energy intensity distribution is efficiently calculated by fast convolving the modulated layout with a point-spread function which models electron beam shape and proximity effects primarily due to electron scattering in resist. The effectiveness of this methodology is measured by iteration numbers required for meeting the patterning fidelity specifications. It is examined versus process parameters including acceleration voltage and resist thickness with several regular mask geometries and practical design layouts.

Proximity effect correcting method in electron beam lithography technique

Abstract: PROBLEM TO BE SOLVED: To provide a proximity effect correcting method which can optimize the correction exposufe amount at the center of an unit division in a boundary region where the pattern area density sharply changes. SOLUTION: Firstly, (A) each unit division is subjected to bit map expansion, and the pattern area density in each of the unit divisions is calculated. (B) The pattern area density in each of the unit divisions is subjected to averaging process, and the pattern area density is calculated. (C) Stored energy caused by backward scattering is calculated on the basis of an EID(energy intensity distribution) function and the pattern area density. Secondly, (D) when the sum of square of the difference between the stored energy calculated in the above (C) and the stored energy caluculated on the basis of the pattern area density after the averaging process which is obtained in the above (B) is greater than or equal to a specified value, the pattern area density is corrected. The electron beam exposure amount in the unit division is corrected on the basis of the obtained pattern area density after correction.

Proximity effect correction data processing system for electron beam lithography

Abstract: A proximity effect correction system has been developed by utilizing an efficient dose modulation technique based on a double Gaussian proximity function. A shaped electron beam system is assumed to be used. Two improvements are made. First, an optimal exposure dose on each pattern is determined by a new fast iterative method. The optimal dose makes the development isocontour conform to the pattern specification fairly well. Second, a ‘‘simple cell unit algorithm’’ that one of identical cells is proximity‐corrected, and the result is used to the other remaining cells is introduced. This offers to both decrease the processing time and save the memory/disk space. The present system is applied to the data processing of scaled‐down version of an aluminum wiring layer pattern of 16 Mbit dynamic random access memory with its minimum dimension of 0.4 μm. The calculation is successfully completed within 1 h of CPU time on a 10 MIPS general‐purpose computer. The dimensional accuracy of 10% is confirmed experimenta...

Low-proximity contact hole formation by using double-exposure technology (DET)

Abstract: As semiconductor technologies move toward 0.18um and below, it is difficult to get high pattern fidelity by 248-nm wavelength exposure. To reduce proximity effect, a lot of resolution enhancement technologies (RET) such as OPC, assistant feature, and double exposure technologies (DET) have been introduced. In this paper, random contact holes with low proximity effect were delivered by using 248-nm exposure tool in conjunction with double exposure technology. A low proximity resist patterns were formed by a well-designed Pack-mask. Then ion implantation treatment produced a solvent proof skin on the developed resist. The second lithography process was performed over the post-implanted resist layer. Resist coating as well as exposure perfectly transfer the patterns from Cover-mask. After etch, random holes with low proximity effect were easily achieved. In addition, higher energy association with higher dosages is able to maintain good critical dimension even if wafers went through three rework processes.

30 nm resolution zero proximity lithography on high‐Z substrates

Abstract: In order to fabricate masks for x‐ray lithography, there is growing interest in subtractive patterning of high atomic mass (high‐Z) materials such as tungsten or gold. Favorable writing speeds and sub‐50 nm resolution without proximity effects combine to make heavy ion focused ion beam lithography an ideal candidate for this area of nanofabrication. Using a 50 keV Ga+ beam with an 8 nm spot diameter, we have exposed a variety of proximity effect test patterns in 60 nm thick PMMA on 0.5 μm thick tungsten films. The results indicate that 30‐nm resolution or better is possible at line/space pitches as small as 80 nm. The test patterns show no apparent proximity effects at these dimensions. An anomalous ‘‘inverse proximity effect’’ was observed, and was determined to be an artifact of the scanning electron microscope technique used to observe the PMMA resist.