SiC Film Etching Selectivity for EUV Resist Underlayers
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Solution Overview
Problem
Conventional etching chemistries fail to provide adequate etch selectivity for silicon carbide (SiC) films in extreme ultraviolet (EUV) lithography, leading to defects such as toppling over of EUV resist features and incomplete pattern transfer.
Innovation Solution
A substrate processing method involving a pulsed plasma etching process using a gas mixture of C4F8, O2, and Ar, which selectively transfers patterns from EUV resist layers to SiC films while preserving the resist layer, achieving greater than 2.5:1 etch selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching chemistries are used on SiC films, then etching process can be performed, but etch selectivity between SiC film and EUV resist is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the etching chemistry composition (using C4F8 and O2 in specific ratios), adjusting process parameters (RF power, pressure, gas flow rates), and controlling plasma conditions to achieve selective etching of SiC while preserving EUV resist integrity. This resolves the contradiction by tuning process parameters to differentiate between SiC and resist etching rates.
Solution Approach 2:
The patent uses a composite etching gas mixture of C4F8 and O2 that creates a plasma environment with specific chemical reactivity. This composite chemistry provides both the necessary etching capability for SiC and the selectivity to protect EUV resist, resolving the contradiction between achieving etching and maintaining resist integrity.
2Manufacturing precision
If conventional etching chemistries are used on SiC films, then etching can proceed, but pattern transfer completeness is insufficient
Solution Approach 1:
The patent optimizes process parameters including RF power (100-500W), pressure (10-100 mTorr), and gas flow rates to achieve complete and defect-free pattern transfer. By carefully controlling these parameters, the process ensures full pattern transfer from EUV resist to SiC without creating defects, resolving the contradiction between transfer completeness and defect reduction.
3Reliability
If SiC films are used as underlayers for EUV lithography, then resist toppling is reduced, but adequate etch selectivity is not achieved
Solution Approach 1:
The patent achieves etch selectivity by modifying etching chemistry parameters (C4F8/O2 ratios, gas pressures) and plasma conditions. This enables the manufacturing process to work effectively with SiC underlayers, resolving the contradiction between resist stability benefits and etching difficulty.
4Manufacturing precision
If photoresist layer is used for pattern definition, then pattern transfer can be performed, but complete removal of photoresist is required which complicates the process
Solution Approach 1:
The patent extracts or removes the need for a separate photoresist stripping step by designing an etching process that achieves complete pattern transfer while leaving minimal or no photoresist residue. The optimized C4F8/O2 plasma etching selectively removes the SiC pattern while the photoresist can be easily removed or is already sufficiently removed during etching, simplifying the overall process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively transfers patterns from EUV resist layers to SiC films with high selectivity, preventing toppling and reducing defects, and allows for the use of SiC films as reliable underlayers in EUV lithography.
Implementation Method 1
plasma-exciting an etching gas containing a fluorocarbon-containing gas and an oxygen-containing gas, and exposing the substrate to the plasma-excited etching gas to transfer the pattern to the silicon carbide film
Implementation Method 2
exposing the substrate to the plasma-excited etching gas to transfer the pattern to the silicon carbide film
Data Source
AI summary
A substrate processing method is described for etching silicon carbide films for resist underlayer applications. The method includes providing a substrate containing a silicon carbide film thereon, and a photoresist layer defining a pattern over the silicon carbide film, plasma-exciting an etching gas containing a fluorocarbon-containing gas and an oxygen-containing gas, and exposing the substrate to the plasma-excited etching gas to transfer the pattern to the silicon carbide film, where at least a portion of a thickness of the photoresist layer survives the exposing. For example, the photoresist layer includes an EUV resist layer and the etching gas includes C4F8 gas, O2 gas, and Ar gas. In another example, the exposing includes exposing the substrate to a) a plasma-excited etching gas containing C4F8 gas, O2 gas, and Ar gas, and b) exposing the substrate to a plasma-excited Ar gas, where steps a) and b) are sequentially performed at least once.