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.

Three‐dimensional electron‐beam resist profile simulator

Abstract: A three‐dimensional (3D) electron‐beam (EB) lithography simulator SEED‐3D (system for evaluating electron‐beam writing and developing 3D) has been developed for resist profile simulation and analysis of proximity effects. SEED calculates an exposure intensity distribution (EID), a 3D accumulated energy distribution after pattern exposure, and a 3D profile of the developed resist. SEED can take into account proximity effects in a wider region, because SEED takes a short time to calculate the 3D accumulated energy distribution. The concept of the 3D accumulated energy calculation is that the proximity effects in the forward scattering region are estimated precisely, and the proximity effects in the backscattering region are evalulated roughly. This 3D EB lithography simulator allows us to examine resist‐pattern profiles of 0.3‐μm line and space patterns. This simulator also gives an acceptable value for η which can be used for dose correction.

Exposure method, method of adjusting pattern dimension, and method of obtaining defocusing amount

Abstract: PROBLEM TO BE SOLVED: To carry out exposure so that a desired pattern can be obtained without changing a mask even if the mask is bias-corrected with an improper amount of correction to a proximity effect. SOLUTION: The exposure method comprises a first exposure process (S106) wherein a first wafer is exposed to a focused electron beam using a mask wherein a bias is applied to a prescribed region thereof; and an n-th exposure process (S118) wherein, in the case that the pattern width of a pattern transferred from the mask starting from the bias-applied region and formed on a substrate is not consistent with a desired pattern since an amount of the bias is too large, an n-th wafer is exposed to an electron beam which is defocused to obtain a defocusing amount where the pattern width becomes consistent with the desired one. Wafers exposed after obtaining the defocusing amount are exposed to an electron beam defocused by the obtained defocusing amount to adjust the dimension of a pattern formed on the wafer to be exposed after the defocusing amount is obtained. COPYRIGHT: (C)2006,JPO&NCIPI

Region‐wise proximity effect correction for heterogeneous substrates in electron‐beam lithography: Shape modification

Abstract: PYRAMID, a hierarchical rule‐based scheme for proximity effect correction in electron‐beam lithography, has been demonstrated to enable rapid correction of circuit patterns exposed on homogeneous substrates with minimum feature size of 0.1 μm. The current version of PYRAMID modifies the shape of circuit primitives. So far, it has been limited to homogeneous substrates only. This article describes an extension of our pattern shape modification scheme for heterogeneous substrates. The space‐varying nature of a heterogeneous substrate makes exposure estimation and proximity correction more involved than in case of a homogeneous substrate. As a result, the schemes developed for homogeneous substrates cannot be used directly used to deal with heterogeneous substrates. A simple but effective approach has been implemented in an effort to allow our shape modification scheme to correct patterns on heterogeneous substrates. The principal idea is to correct a circuit region‐wise where each region is homogeneous. A transition zone is defined between two adjacent regions of a substrate and additional adjustment is done on primitives within transition zones to get smooth transition between regions. A fuzzy factor, adjustment factor, is introduced to make the convergence of correction faster. This article describes the region‐wise proximity effect correction scheme proposed for heterogeneous substrates and presents preliminary simulation results indicating successful correction.

Recent Progress in Electron-Beam Cell Projection Technology

Abstract: NEC's recent progress in the development of electron-beam (EB) cell projection technology is reviewed. To make it practical, not only the development of a high-performance EB direct writing system but also the establishment of its peripheral technologies in the micro-fabrication process are pursued. In order to obtain high lithographic performance in the EB cell projection lithography system HL-800D (Hitachi), the fundamental effects in EB lithography such as the Coulomb interaction effects, the proximity effect and electron scattering by cell projection aperture (EB mask), have been studied. In addition, high-resolution and high-sensitivity resists have been developed. The Coulomb interaction effects are found to be the most critical issue in cell projection lithography because it affects resolution, linewidth accuracy and throughput. For high resolution, the beam current was reduced to suppress the Coulomb interaction. As a result, a resolution of 0.15 µ m, which is sufficient for fabricating a 1G DRAM, was obtained using the high-resolution resist. To achieve high-linewidth accuracy of less than ±5% for 0.2 µ m lines-and-lines (L/S), optimization of the EB mask structure and the development of a proximity effect correction method which includes the Coulomb interaction effect correction were carried out. Inspection technology for devices of 0.2 µ m or less was also investigated in order to accurately measure linewidth, and to detect defects, particularly those caused by shot stitching error. Finally, the cell projection technology has been applied to the device fabrication of a 1G DRAM, and was demonstrated to be feasible for the development of futuristic advanced devices.