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.

Fast computation method for exposure intensity and pattern correction in electron‐beam lithography

Abstract: A fast computation method to correct for the proximity effect in electron‐beam lithography is studied for practical uses. Formerly, to compute the proximity effect a double integral of two Gaussian distribution functions was applied. To save computation time and memory size, a simplified computation using the error function is discussed. In this solution the proximity effect correction is determined by two real multiplications, four subtractions and one addition. Not only beam intensity but also a pattern element size is considered in every pattern. A large pattern is divided into small sections. In this method, the computation time is proportional to the number of elements. It takes 105 minutes to compute 10 000 test pattern elements with a minicomputer. The experiment proves that the corrected pattern can be exposed as designed. This procedure has proven effective to design VLSI by using a minicomputer.

Solution for 100nm - EBM-4000

Abstract: Optical lithography will be extended down to 65nm to 50 nm. However, a mask with high accurate CD uniformity and resolution enhancement technology (RET) such as optical proximity effect correction (OPC) and phase shifting mask (PSM) are required to achieve resolution by exposure wave length. The mask technology is the key of the optical lithography extension. We developed the electron beam mask writer EBM-3000 for 180-150nm design rule 1),2) , and EBM-3500 for 150-130nm design rule 3) , to achieve high accuracy CD uniformity mask and small OPC pattern writing. They were variable shaped electron beam mask writing system with continuous moving stage, at 50kV acceleration voltage, and had the functions of multi-pass field shift writing, real-time proximity effect correction, grid matching correction, and automatic adjustment for election optical column. The LSI road map calls for 90nm feature size as that so close to optical resolution limitation where increasingly complex optical proximity corrections (OPC) as well as extremely good mask CD uniformity and image placement accuracy are required. It requires larger data sizes of LSI designs. Thus the newly developed electron beam mask lithography system EBM-4000 is designed to overcome all these difficult problems associated with 90nm as well as 65nm node masks based on prior EBM-3500 model. Major improvements of BM-4000 are electron optical column, writing circuits, vacuum system, and mechanical control system, to achieve the writing accuracy, throughput, handling of large data volume, and maintainability of the tool. To realize 90nm technology node, EBM-4000 is the essential tool.

Fabrication of the 70-nm line patterns with ArF chromeless phase-shift masks

Abstract: The problems of chromeless phase shift masks (CL-PSMs), which cannot fabricate large patterns, can be overcome by using CL-PSMs that have opaque chrome (Cr). This paper presents evaluation results for these enhanced CL-PSMs. We exposed with an ArF scanner of 0.60 numerical aperture with annular illumination and we used a positive chemically amplified ArF resist 0.21 μm thick. We did not use assist bars. For it was difficult to make assist bars which were smaller than sub-70-nm main patterns. We obtained good critical dimension controlled patterns with bias optical proximity correction. The mask error enhancement factors were about 1 for >300-nm pitch patterns. The resist pattern profiles were good. The depth of focus of isolated line patterns was about 0.3 μm. We could fabricate random logic patterns that had various pattern widths from 70 nm to more than 100 nm.

Electron beam lithography system

Abstract: PURPOSE:To properly correct proximity effect even when performing a self- projection type drawing. CONSTITUTION:On a stencil mask, a pattern 20-2 of Lc in width for reduction copying and a shielding area 22 of Lc/2 in width between patterns 20-1 and 20-3 adjoining thereto are formed. An image 23G drawn by electron beam in preceding step is horizontally slid to the area 22 in order to irradiate only a part of the pattern 20-2 and a part of the pattern image is drawn on a target while changing dosage.

Checkerboard pattern for PSF parameter determination in electron beam lithography

Abstract: In electron beam lithography, the electron scattering and the corresponding proximity effect highly influence the feature resolution. Especially for sub-100 nm features a compensation for this effect is needed. There are several methods of determination of the proximity parameters, which mostly are time-consuming and complex due to a need of an initial proximity effect correction and immense measurement effort. In this paper the checkerboard pattern is proposed to provide the opportunity for proximity parameter determination in a fast and easy manner without using a sophisticated CD-SEM metrology. The concept is illustrated by simulation and first experimental results are shown.