The directed self-assembly (DSA) of block copolymers offers a promising route for scaling feature sizes below 20 nm. At these small dimensions, plasmas are often used to define the initial patterns. It is imperative to understand how plasmas interact with each block in order to design processes with sufficient etch contrast and pattern fidelity. Symmetric lamella forming block copolymers including, polystyrene-b-poly(methyl methacrylate) and several high-χ silicon-containing and tin-containing block copolymers were synthesized, along with homopolymers of each block, and exposed to various oxidizing, reducing, and fluorine-based plasma processes. Etch rate kinetics were measured, and plasma modifications of the materials were characterized using XPS, AES, and FTIR. Mechanisms for achieving etch contrast were elucidated and were highly dependent on the block copolymer architecture. For several of the polymers, plasma photoemissions were observed to play an important role in modifying the materials and forming etch-resistant protective layers. Furthermore, it was observed for the silicon- and tin-containing polymers that an initial transient state exists, where the polymers exhibit an enhanced etch rate, prior to the formation of the etch-resistant protective layer. Plasma developed patterns were demonstrated for the differing block copolymer materials with feature sizes ranging from 20 nm down to approximately 5 nm.
The major issue related to line width roughness (LWR) is the significant LWR of the photoresist patterns printed by 193-nm lithography that is partially transferred into the gate stack during the subsequent plasma etching steps. The strategy used today to overcome this issue is to apply postlithography treatments to reduce photoresist pattern LWR before transfer. In this article, we investigate the impact of various plasma treatments (HBr, H 2 , He, Ar) on the minimization of the LWR of dense and isolated photoresist patterns and its transfer during gate patterning. To do so, we use critical dimension scanning electron microscopy measurements combined with power spectrum density fitting method to extract unbiased LWR values and provide a spectral analysis of the LWR. We show that plasma treatments that lead to carbon redeposition from the gas phase on the resist pattern sidewalls are less efficient to reduce LWR than plasma treatments where the redeposition is limited. Among all plasma chemistries, H 2 plasmas seem very promising to decrease resist LWR in the whole spectral range, while maintaining square resist profiles. In addition, we show that all frequency roughness components are not equally transferred during gate patterning, and more particularly that the high frequency roughness components are lost.
With the decrease of semiconductor device dimensions, line width roughness (LWR) becomes a challenging parameter
that needs to be controlled below 2nm in order to ensure good electrical performances of CMOS devices of the future
technological nodes. One issue is the significant LWR of the photoresist patterns printed by 193nm lithography that is
known to be partially transferred into the gate stack during the subsequent plasma etching steps. This issue could be
partially resolved by applying plasma pre treatment on photoresist before plasma transfer. Another issue is linked to the
noise level of the metrology tool, that causes a non negligible bias from true LWR values. Recently we proposed an
experimental protocol combining CD-SEM measurements and Power Spectral Density (PSD) fitting method for an
accurate estimation of the CDSEM noise level and extraction of unbiased LWR.
In this article, we use the developed CDSEM protocol to extract roughness parameters (true LWR, correlation length,
fractal exponent) of dense and isolated photoresist patterns exposed to various plasma treatments (HBr, H2, He, Ar), and
also to follow the evolution of the LWR during the subsequent plasma etching steps involved in gate patterning. We
show that the resist LWR is less improved in isolated than in dense lines with HBr plasma treatment because of carbon
species redeposition more important on isolated resist pattern sidewalls. Plasmas such as H2 that limit carbon
redeposition are more efficient to decrease significantly resist LWR in both dense and isolated lines. In addition we show
that all frequency roughness components are not equally transferred during gate patterning, and more particularly that the
high frequency roughness components are lost.
Since more than 30 years, CW plasmas have been used in the microelectronics industry to pattern complex
stacks of materials involved in Integrated Circuit technologies. Even if miniaturization challenges have been successfully
addressed thanks to plasma patterning technologies, several fundamental limitations of the plasmas remain and are
limiting our ability to shrink further the device dimensions. In this work, we analyze the capabilities of synchronized
pulsed ICP technologies and their potential benefits for front end etch process performance.
The impact of duty cycle and frequency on the ion energy distribution function and plasma chemistry is
analyzed. Our results show that decreasing the duty cycle in ICP plasmas generates less fragmentation of the feed gas
stock molecules compared to CW plasmas, leading in final to a decrease of the radical density in the plasma. On a process point of view, we have studied the etching of ultra-thin layers (SiO2, HfO2,SiN spacer) involved in front end processes and investigated what synchronized pulsed plasmas could bring to substrate damage and selectivity issues.
In this paper, we propose to bring new insights of the resist chemical modifications induced by HBr plasma treatment by
using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) measurements and thermal analysis.
In order to isolate effect of plasma ions and radicals of resist chemical modification induced by VUV plasma light,
samples coated with a model 193nm resist (polymer only and full formulation) and exposed to a HBr plasma (directly or
via a LiF window) are analysed. Our approach, based on TD-GC/MS technique, is an indirect method to monitor the
outgassed by-products during different treatments. Thus the outgassing rate associated with sample exposed directly to
HBr cure plasma is significantly lower that outgassing rate of the samples exposed under LiF window, suggesting plasma
induced surface hardening. Moreover a short O2 plasma treatment seems enough to remove the surface layer.
Quantitative and qualitative TD-GCMS analysis correlated with Thermo-Gravimetric Analysis (TGA) allow us to show
that plasma H+ ions induce resist deprotection .
In conclusion, using such methodology we propose a fine analysis of fundamental mechanisms involved in 193nm resist
modification under HBr cure plasma treatment.
193nm photoresist pattern printed by optical lithography are known to present significant sidewalls roughness, also
called linewidth roughness (LWR) after the lithographic step, that is partially transferred into the underlayers during
plasma etching processes. This study is aimed to identify the factors that impact the photoresist pattern sidewalls
roughness during plasma exposure. Among them, plasma VUV light (110-210nm) is identified as being the main
contributor to LWR decrease during plasma etching processes. Moreover, it was found that the LWR obtained after
plasma exposure is strongly dependent on the surface roughening mechanisms taking place at the top of the resist pattern.
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