In this paper we investigate fundamental resist properties to enhance resolution and focus margin for immersion
contact hole patterning. Basic chemistry factors have been used to manipulate the iso-focal region (the region of
smallest critical dimension variation through focus) of the photoresist and study the impact on resolution and focus
margin for small isolated contact holes. Acid diffusion length is one of the key factors investigated, which can be
controlled by polymer, PAG, quencher, bake temperature and bake time. The various criteria investigated for this study
were: focus and exposure latitude for dense L/S, dense C/H and semi-dense C/H. The effect of manipulating the acid diffusion of the photoresist on imaging small contact holes was verified using ultra-high NA immersion imaging at 1.35
Reflectivity comparison study of bottom anti reflectivity coating (BARC) was investigated at 30nm node devices with same gate width at different pitch sizes. The goal of this study is to elucidate the practical target of reflectivity for high NA immersion lithography especially focusing on the changes in the CD variation. Using double patterning technology (DPT) and single patterning technology (SPT) patterns in high NA systems, we studied the impact of reflectivity to the lithography performance for various ARC thicknesses.
A strong dependence of n, k values (of BARC and substrate) on reflectivity was confirmed by simulation. Standing wave effects were investigated by vertical profiles inspection and changes in lithographic performances. Finally, we investigated the critical dimension uniformity (CDU), and line width roughness (LWR) variations for various reflectivities using hard mask substrates. Our experimental and simulation results clearly show that a 0.1% reflectivity target is highly recommendable for the sub-30 nm device process using high NA immersion lithography.
Immersion barrier coats were formulated and evaluated on ArF photoresist in view of interaction between photoresist and top coats. Acrylate polymers having an acid-labile protecting group, an acid group, and a polar group were synthesized to realize water barrier property and developability. To compensate the insufficient developability, thermal acid generator was included as an additive that can enhance the developability of the acrylate top coats by post exposure bake. In the course of the material evaluation, it became evident that carboxyl acid group in the top coat base polymers has great influence on photoresist profiles, and this result was fedback to a new acid group, deuterated carboxyl acid, that is suitable for both ArF wavelength and EUV wavelength. When top coat materials having deuterated carboxyl acid were applied on ArF photoresist, fine pattern profiles were confirmed. Further, an extension of barrier coating concept to EUV lithography as outgas barrier coats was examined on an EUV photoresists test sample. These outgas barrier coat materials do not include fluorine atoms, therefore, achieves good transparency at EUV wavelength.
Line edge and line width roughness (LER/LWR) is commonly estimated by standard deviation sigma. Since the
standard deviation is a function of sample line length L, the behavior of sigma(L) curve is characterized by the
correlation length and roughness exponent. In this paper, an efficient and practical macro LER/LWR analysis is
implemented by characterizing an arbitrary array of similar features within a single CD-SEM image. A large amount of
statistical data is saved from a single scan image. As a result, it reports full LER/LWR information including correlation
length, roughness exponent, sigma at infinite line length, and power spectrum. Off-line, in-house software is developed
for automated investigation, and it is successfully evaluated against various patterns. Starting with the detailed
description of the algorithm, experimental results are discussed.
Proc. SPIE. 5376, Advances in Resist Technology and Processing XXI
KEYWORDS: Lithography, Optical lithography, Calibration, Interfaces, Electron microscopes, 3D modeling, Scanning electron microscopy, Thermal modeling, Resolution enhancement technologies, Temperature metrology
The PR(Photoresist) flow process after the development step has been used for patterning of sub-200nm contact holes as the design rule decreases rapidly. To optimize the layout design and process parameters, we develop the new viscous PR flow model which is verified for various PRs by experimental results. Using the model and simulation, we demonstrate the close agreement with VSEM(vertical scanning electron microscope) of the top corner rounding profile of PR and investigate the effect of the dominant variables such as the contact size, surrounding bulk density, and temperature. This model is also integrated with lithography simulator. The layout design and process condition of patterns with various contact sizes are optimized by using our new methodology. The viscous flow model linked to the lithography simulator can be effectively used in predicting the contact patterning process and optimizing the layout as well as analyzing defects.
As the required contact holes dimension (CD) reaches to the physical limit of the conventional lithography, the image quality formed in a photoresist film is degraded seriously. To overcome this obstacle, several process-based techniques for ArF lithography have been suggested and some of them are reported to show excellent feasibilities. In this article, three primary techniques for sub-80nm contact holes patterning are examined. They are ArF thermal flow, ArF SAFIER (Shrink Assist Film for Enhanced Resolution) and ArF RELACS (Resolution Enhancement Lithography Assisted by Chemical Shrink). These techniques are originated from different reaction mechanisms and result in distinguished shrink behaviors. Contact holes CDs of different patterns diverge one another depending on the adapted shrink process even though the initial CDs are identical. This is so called a bulk effect and is compensated by the optical proximity correction (OPC) procedure. The relationship of pattern CDs between mask and wafer is used to extract the correction factor. For the shrink process, it is divided to an optical factor and a process factor, that is, the shrink behavior is analyzed in terms of mask error factor (MEF) and process error factor (PEF). The PEF is calculated from the proportionality of post-shrink CD to initial CD of photoresist patterns. Using the PEF, it is possible to characterize each shrink process in the view of CD controllability. Consequently, we classify the shrink processes for the production of 65nm node devices considering the shrink properties and the cost of ownership.