Wet SiO2 Atomic Layer Etching with Self-Limiting Passivation
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Solution Overview
Problem
Existing etching methods for silicon dioxide (SiO2) in semiconductor manufacturing cause surface damage and roughening, and lack selectivity over other silicon-containing materials.
Innovation Solution
A wet atomic layer etching (ALE) process using anhydrous basic solutions with non-aqueous solvents to form a self-limiting silicate passivation layer on SiO2, followed by a dissolution step that selectively removes the passivation layer without affecting the underlying SiO2, allowing for controlled and smooth etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional plasma or wet etching methods are used to etch SiO2, then etching speed is improved, but surface damage and roughening occur
Solution Approach 1:
The etching process is divided into multiple sequential cycles, each consisting of a surface modification step followed by a dissolution step. This segmentation allows the process to remove material in controlled increments while maintaining surface quality, resolving the contradiction between etching speed and surface smoothness.
Solution Approach 2:
The patent employs periodic cycling between surface modification and dissolution steps. Each cycle modifies the surface temporarily and then dissolves the modified layer, creating a repeating pattern that enables continuous etching while maintaining surface integrity throughout the process.
2Productivity
If traditional wet etching with HF solutions is used, then etching rate is improved, but selectivity over other silicon-containing materials is lost
Solution Approach 1:
The surface modification step creates a locally altered surface layer with different chemical properties than the bulk material. This local quality change enables selective dissolution of the modified layer while leaving unmodified SiO2 and other silicon-containing materials unaffected, achieving both high etching rate and selectivity.
Solution Approach 2:
The patent changes the chemical state of the SiO2 surface through modification (e.g., forming silane layers or altering surface chemistry), which fundamentally changes how the surface interacts with etchants. This parameter change enables selective etching by making the modified surface chemically distinct from unmodified surfaces and other materials.
3Productivity
If continuous wet etching is used, then etching efficiency is improved, but lack of selectivity to other silicon-containing materials occurs
Solution Approach 1:
The continuous etching process is segmented into discrete modification and dissolution steps. This segmentation introduces temporal separation between chemical reactions, allowing selective removal of modified material while preserving selectivity to other silicon-containing materials that are not modified.
Solution Approach 2:
The surface modification step is performed as a preliminary action before dissolution. This preliminary modification creates a temporary, chemically distinct surface layer that can be selectively removed in the subsequent dissolution step, enabling both efficient etching and material selectivity.
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 process provides a self-limiting and selective etch of SiO2, improving etch uniformity and control, while maintaining a smooth surface and avoiding metal contamination.
Implementation Method 1
exposing the surface of the substrate to a surface modification solution comprising a base dissolved in a non-aqueous solvent. When exposed to the surface modification solution, the base reacts with the surface of the silicon dioxide (SiO2) layer to form a silicate passivation layer
Implementation Method 2
exposing the surface of the substrate to a dissolution solution that selectively dissolves the silicate passivation layer
Data Source
AI summary
The present disclosure provides a new wet atomic layer etch (ALE) process for etching silicon dioxide (SiO2) materials. More specifically, the present disclosure provides various embodiments of methods that utilize new etch chemistries for etching a SiO2 layer in a cyclic wet ALE process. The new etch chemistries disclosed herein use an anhydrous basic surface modification solution to create self-limiting reactions on exposed surfaces of the SiO2 layer and form a silicate passivation layer, which is insoluble in the surface modification solution, but readily soluble in a dissolution solution.