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.

X‐ray mask fogging by electrons backscattered beneath the membrane*

Abstract: Proximity effects can be reduced when exposing x‐ray mask membranes by increasing the electron‐beam accelerating voltage. Forward scattering in the resist is reduced and exposure due to backscattered electrons is also reduced since the more energetic electrons are able to pass through the electroplating base and thin mask membrane. However, electrons that pass through the mask can strike an object down stream from the mask, backscatter, and produce a broad background exposure or ‘‘fogging’’ in the resist. Under some conditions, fogging can cause >40% dose variations over the mask, degrading the line width control severely. We investigated this fogging effect for different electron trap materials at various electron energies. Our results indicate that dose variation from fogging can be reduced to <3% by placing a carbon mat downstream from the membrane. The effect of fogging has been further attenuated to <1% by using a textured, low Z material (Aluminium Honeycomb) to trap (absorb) the electrons that are ...

Single Level Dry Developable Resist Systems, Based On Gas Phase Silylation

Abstract: In this paper various single level resist systems are presented that combine gas phase silylation with dry development. For novolak-diazoquinone type resists it is shown that the photoselectivity of the silylation process is determined, to a large extent, by the presence of hydrogen bonds between the resin and the un-exposed sensitizer. Upon irradiation these physical crosslinks are replaced by weaker hydrogen bonds between the resin and the indene-carboxylic acid. The effect of the presilylation bake temperature and decarboxylation are discussed. Also the influence of decomposition of the photoactive compound on the selectivity is shown. Other systems presented in this paper are based on chemical crosslinking of the resist. SUPER (SUbmicron Positive dry Etch Resist) is based on the combination of acid-catalyzed crosslinking and gas phase silylation. Because of the chemistry that is used, SUPER can be an interesting candidate for DUV-lithography. Crosslinking of, novolak-diazoquinone type photoresists is another possibility to create a selectivity for the silylation process. A system based on electron beam lithography is presented. Sub-half-micron features, without problems with the proximity effect, are shown.

A Three-Dimensional Study of the Absorbed Energy Density in Electron-Resist Films on Substrates

Abstract: A computer program has been developed for the three-dimensional calculation of the absorbed energy density in polymer films on substrates in electron beam lithography. In this calculation the Monte Carlo results have been used for the radial energy intensity distribution for a point source electron beam. The program is based on the reciprocity principle proposed by Chang. Some exposure experiments have been conducted with an electron resist of PMMA (polymethyl methacrylate) for isolated patterns in the from of a line of finite length (8.1 µm) as well as of a rectangle (3.1×8.1 µm2) in order to check the reliability of the calculations. Operating beam voltages used for the investigation are 14 and 20 keV. The electron resist thickness is 8000 A. Relatively good agreement has been obtained between the calculated and the experimental results. This program is applicable to an arbitraty pattern, and therefore it will be useful for investigations of the proximity effect in electron beam lithography.

Etch proximity correction by integrated model-based retargeting and OPC flow

Abstract: Model-based Optical Proximity Correction (OPC) usually takes into consideration optical and resist process proximity effects. However, the etch bias proximity effect usually can not be completely eliminated by etch process optimization only and needs to be compensated for in OPC flow for several critical layers. Since the understanding of the etch process effect is getting better and accurate etch bias modeling is available now, lithographers start to migrate from rule-based correction to model-based correction. Conventionally when etch bias is considered in model-based correction, optical/resist/etch effect is corrected in one step by using the input layout as the final etch target. In this paper, we proposed a new flow in which etch and optical/resist process effect are separated in both model calibration and layout correction. This double separation allows easier control over etch and resist target, resulting in drastic reduction of OPC runtime. In addition it enables post-OPC verification at both resist and etch level. Advantages of the new integrated model-based retarget/OPC flow in RET implementation are also discussed.

Proximity effect correction in electron-beam lithography based on computation of critical-development time with swarm intelligence

Abstract: Electron-beam lithography (EBL) is an important technique in manufacturing high-resolution nanopatterns for broad applications. However, the proximity effect in EBL can degrade the pattern quality and, thus, impact the performance of the applications greatly. The conventional proximity effect correction (PEC) methods, which employ computationally intensive cell or path removal method for development simulation, are very computational lengthy, especially for complex and large-area patterns. Here, the authors propose a novel short-range PEC method by transforming the evaluation of pattern feasibility into the shortest path problem based on the concept of critical-development time. The authors combine this evaluation algorithm with the swarm intelligence which mimics the natural collective behavior of animals to optimize the design of electron dose distribution in EBL. The PEC algorithm is applied for pattern fabrication for U-shaped split-ring resonator and produces optimized exposure pattern that shows exc...