Sub-10 nm resolution Electron Beam Lithography in ultrathin HSQ resist layers

Sub-10 nm resolution Electron Beam Lithography in ultrathin HSQ resist layers

Grigorescu, A.E.

Kruit, P. (promotor)
Hagen, C.W. (promotor)

Applied Sciences

Charged Particle Optics Group

2009-11-04

The continuous shrinking of the feature size forces scientists and engineers to develop new lithographic techniques and suitable materials which can meet the requirements of the market. Despite its low throughput, EBL remains the number one candidate when writing very small structures. Achieving ultimate resolution with EBL requires not only a very good lithographic tool (with small probe size) but also a highly sensitive electron beam resist which is able to undergo the lithographic process and at the same time yields a very high resolution. Most of the exposures are performed with a SEM and the use of smaller probe sizes (eg, in STEM) is quite limited due to the delicate handling of the thin samples which have to be used in this case. Nowadays, in EBL, as will be demonstrated in this thesis, sub-10 nm features can be obtained using different types of organic and inorganic resists. In order to test the ultimate resolution of this lithographic technique, dense features should be written for which the distance between two adjacent features is equal to the feature size measured after the development process. We might say that fabricating ultrahigh resolution structures using resist based EBL is like a chain reaction which starts with the spin coating of the resists and ends with the development process and inspection session. The goal of this thesis is to understand and explain the phenomena that take place in ultrathin resist layers to be able to optimize the process for generating dense sub 20-nm features. The understanding of the electron scattering that takes place, both in the resist and in the substrate, is a crucial factor when choosing the material for nanolithography. Because the interaction of the beam with the sample is a very complex process, a Monte Carlo simulation has been developed to calculate the bond breaking distributions for different resist materials. By varying one parameter at a time (e.g. resist thickness, resist material, acceleration voltage), the resolution can be predicted from the bond breaking distributions. Ultra-high resolution has been obtained with ultrathin Hydrogen silsesquioxane (HSQ) resist layers. For this specific resist, the most important factors which limit the resolution are being discussed throughout the chapters of this thesis.

ultra high resolution
Electron Beam Lithography
HSQ

http://resolver.tudelft.nl/uuid:f3693531-eda3-43e6-8373-3a6d3966dd8f

9789090247915

Institutional Repository

doctoral thesis

(c) 2009 Grigorescu, A.E.