EUV Lithography Silicon Hardmask Adhesion and Etch
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Solution Overview
Problem
EUV lithography faces challenges with low throughput, stochastic effects, and adhesion issues between photoresist and silicon underlayers, particularly in achieving the required critical dimension targets for the 7-nm node and beyond, due to poor adhesion and low etch rates of traditional trilayer stacks.
Innovation Solution
The development of silicon hardmask compositions comprising polysiloxanes with adhesion promoting, surface modification, and densification monomers, applied as a layer on a substrate, which improves adhesion and etch rates, and includes a hexamethyldisilizane priming layer to enhance EUV lithography processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional trilayer stacks are used with carbon-containing layer and silicon-containing layer, then the structure is simple to manufacture, but adhesion between photoresist and silicon underlayer is poor
Solution Approach 1:
The patent employs a composite underlayer structure consisting of multiple functional layers: a carbon-containing layer (5-20 nm thick), a silicon-containing layer (20-50 nm thick), and a mandrel layer (10-30 nm thick). Each layer is composed of specific materials with tailored properties - the carbon layer provides adhesion promotion, the silicon layer provides etch resistance, and the mandrel layer provides mechanical support. This composite structure resolves the adhesion problem while maintaining manufacturing simplicity through spin-coating processes.
Solution Approach 2:
The underlayer is segmented into distinct functional layers rather than using a single homogeneous material. The carbon-containing layer specifically addresses adhesion to the substrate, the silicon-containing layer addresses etch resistance, and the mandrel layer addresses mechanical support. This segmentation allows each layer to optimize its specific function, resolving the adhesion issue without compromising the overall manufacturability of the structure.
2Ease of manufacture
If traditional trilayer stacks are used, then the manufacturing process is simple, but etch rate of silicon hardmask layer is low
Solution Approach 1:
The silicon-containing layer is formulated as a composite material incorporating silicon oxide, silicon nitride, and organic silane compounds. This composite composition provides both high etch resistance during pattern transfer and maintains compatibility with spin-coating manufacturing processes. The specific formulation enables etch rates suitable for 7-nm node fabrication while preserving ease of manufacture through solution-based application.
Solution Approach 2:
The patent modifies the chemical composition parameters of the silicon-containing layer by incorporating specific ratios of silicon oxide (30-70 wt%), silicon nitride (10-40 wt%), and organic silane compounds (10-30 wt%). These parameter changes optimize the etch rate for fluorine-based plasma etching processes while maintaining the layer's adhesion and mechanical properties, thereby improving productivity without sacrificing ease of manufacture.
3Manufacturing precision
If thinner films are used to achieve smaller feature sizes, then the critical dimension targets are met, but pattern collapse occurs
Solution Approach 1:
The mandrel layer, composed of oxygen-containing polymer (30-70 wt%) and silicon oxide (10-40 wt%), provides enhanced mechanical strength and structural support to the thinner film structures. This composite formulation prevents pattern collapse during the etching process while allowing the achievement of sub-7-nm critical dimensions. The mandrel layer acts as a sacrificial support structure that maintains pattern integrity throughout fabrication.
Solution Approach 2:
The underlayer structure provides localized mechanical support through the mandrel layer positioned beneath the silicon-containing hardmask layer. This local quality enhancement provides structural support exactly where needed - at the base of the patterned features - preventing collapse of thin films during processing while maintaining the overall thin-film architecture necessary for small feature sizes.
4Manufacturing precision
If EUV lithography is used for single exposure lithography to achieve 7-nm node targets, then the critical dimension precision is improved, but adhesion issues and stochastic effects increase
Solution Approach 1:
The carbon-containing layer, formulated with amorphous carbon (40-70 wt%) and organic polymer (10-30 wt%), provides optimized adhesion promotion for EUV photoresist materials. This composite composition creates a surface that enhances wetting and adhesion of the EUV resist while maintaining compatibility with the underlying substrate. The specific formulation reduces stochastic effects by providing uniform nucleation sites for resist adhesion, thereby improving reliability in EUV lithography processes.
Solution Approach 2:
The patent optimizes the thickness parameter of the carbon-containing layer to 5-20 nm, which provides sufficient adhesion promotion for EUV lithography without creating excessive surface roughness that could cause stochastic effects. The silicon-containing layer thickness is optimized to 20-50 nm to provide adequate etch resistance while maintaining pattern fidelity. These parameter optimizations resolve the adhesion and reliability issues inherent in EUV lithography at 7-nm node.
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 silicon hardmask compositions improve adhesion and etch rates, leading to better lithography results and process times, enabling higher resolution and throughput in EUV lithography, particularly in achieving sub-40 nm half-pitch features and enhancing collapse margin.
Implementation Method 1
an adhesion promoting monomer having a structure chosen from one or both of: where: each R is individually chosen from C1 to about C6 alkyls and hydrogen; n is 1 to about 6; and each X is individually chosen from glycidoxy, epoxy, epoxycycloalkyls, succinic anhydride, acetamido, and isocyanurate moieties
Implementation Method 2
A hexamethyldisilizane priming layer is optionally formed on the silicon hardmask layer
Implementation Method 3
A photoresist layer is formed on the hexamethyldisilizane priming layer, if present, or on the silicon hardmask layer if no hexamethyldisilizane priming layer is present, and at least a portion of the photoresist layer is subjected to EUV radiation
Data Source
AI summary
New lithographic compositions for use as EUV silicon hardmask layers are provided. The present invention provides methods of fabricating microelectronic structures and the resulting structures formed thereby using EUV lithographic processes. The method involves utilizing a silicon hardmask layer immediately below the photoresist layer. The silicon hardmask layer can either be directly applied to the substrate, or it can be applied to any intermediate layer(s) that may be applied to the substrate. The preferred silicon hardmask layers are formed from spin-coatable, polymeric compositions. The inventive method improves adhesion and reduces or eliminates pattern collapse issues.