Reducing Plasma Etching of Silicon-Containing Block Copolymers
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Solution Overview
Problem
Current optical lithography techniques are unable to fabricate structures with pitches less than 80 nm, and silicon-containing block copolymers (BCPs) are susceptible to bowing and sidewall attack when using oxidizing plasmas for selective etching, leading to feature collapse and line wiggling.
Innovation Solution
A method involving a block copolymer thin film with microphase-separated domains of a silicon-containing and a non-silicon-containing block, where the non-silicon-containing block is selectively removed using a reducing plasma, potentially preceded by an oxidizing plasma to form an etch barrier, with the reducing plasma being nitrogen-containing and/or hydrogen-containing, and operated at higher chamber pressures to maintain straight sidewalls and prevent profile bowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxidizing plasma is used for selective etching of non-silicon-containing blocks, then etching selectivity is improved, but sidewall bowing and feature collapse occur
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma by using reducing plasmas (nitrogen-containing and/or hydrogen-containing) instead of oxidizing plasmas. This parameter change in plasma chemistry selectively removes non-silicon-containing blocks while maintaining straight sidewalls and preventing bowing, thus resolving the contradiction between etching selectivity and sidewall profile integrity
Solution Approach 2:
The patent employs an inert or reducing atmosphere (nitrogen-containing and/or hydrogen-containing plasma) to protect the silicon-containing blocks from oxidation and sidewall attack. This inert environment prevents the harmful oxidative reactions that cause bowing and collapse, while still allowing selective etching of non-silicon blocks through the reducing plasma chemistry
2Shape
If reducing plasma is used to selectively remove non-silicon-containing blocks, then sidewall integrity is improved, but etching selectivity may be reduced
Solution Approach 1:
The patent optimizes parameters of the reducing plasma including chamber pressure (higher than oxidizing plasma), gas composition (nitrogen-containing and/or hydrogen-containing), and plasma power to achieve both high sidewall integrity and sufficient etching selectivity. By tuning these parameters, the reducing plasma selectively etches non-silicon blocks while maintaining straight sidewalls
3Productivity
If oxidizing plasma is used for etching, then processing speed is improved, but feature collapse and line wiggling occur
Solution Approach 1:
The patent changes the plasma chemistry from oxidizing to reducing (nitrogen-containing and/or hydrogen-containing) and operates at higher chamber pressures. This parameter change modifies the etching mechanism to be less aggressive but more selective and sidewall-friendly, achieving acceptable processing speed while preventing feature collapse and line wiggling through the protective reducing environment
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
This approach enables selective etching of silicon-containing BCPs with high selectivity and straight sidewalls, reducing the risk of feature collapse and line wiggling, while maintaining the integrity of the etched patterns, allowing for the fabrication of structures with smaller domain sizes and pitches.
Implementation Method 1
exposing the BCP thin film to a reducing plasma to selectively remove the non-silicon-containing block
Implementation Method 2
The reducing plasma may be a nitrogen-containing and/or hydrogen-containing plasma
Implementation Method 3
exposing the BCP thin film to an oxidizing plasma prior to exposing the BCP thin film to a reducing plasma
Data Source
AI summary
Provided herein are methods of selectively etching silicon-containing block copolymer (BCP) materials. The methods involve exposing a BCP material that includes at least one silicon-containing block and at least one non-silicon-containing block to a plasma that has a reducing chemistry. The reducing plasma selectively removes the non-silicon-containing block, the silicon-containing block to be used in further processing. In some embodiments, the silicon-containing block is used as an etch mask. The reducing plasma reduces or eliminates profile bowing and undercut of the silicon-containing domains, allowing processing of high aspect ratio features. Examples of reducing chemistries include nitrogen (N2), hydrogen (H2), ammonia (NH3), hydrazine (N2H4), and mixtures thereof. Also provided are apparatuses to perform the methods.