Cyclic Plasma Etching of Silicon Films for High-Aspect Uniformity
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Solution Overview
Problem
Existing substrate processing methods for etching silicon-based films face challenges in achieving good etching characteristics, particularly in uniformly etching films with high aspect ratios and selectively etching different types of silicon-based materials.
Innovation Solution
A substrate processing method involving repeated cycles of supplying an etchant gas and plasma-exciting a reaction gas to expose the substrate to plasma, which includes alternating steps of etchant gas supply, purging, reaction gas application, and further purging, to etch silicon-based films effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-step plasma etching is used, then the etching process is simple and fast, but uniform isotropic etching of high aspect ratio films cannot be achieved
Solution Approach 1:
The etching process is divided into multiple distinct steps: first etchant gas supply for initial etching, then purging to remove byproducts, followed by reaction gas plasma treatment for isotropic etching. This segmentation allows each step to optimize specific etching characteristics, achieving uniform isotropic etching of high aspect ratio films that cannot be achieved in a single step.
Solution Approach 2:
The patent employs periodic alternation between different gas supplies and plasma treatments. The cycle of etchant gas supply → purging → reaction gas application → further purging creates periodic action that maintains etching uniformity while preventing byproduct accumulation, enabling precise control over etching characteristics for complex structures.
2Manufacturing precision
If conventional plasma etching is used, then the process is straightforward, but selective etching of different silicon-based materials cannot be achieved
Solution Approach 1:
The patent applies different gas compositions and plasma conditions at different stages of the etching process. The first etchant gas targets specific silicon-based materials while the reaction gas provides isotropic etching, creating local quality variations in the etching action that enable selective removal of different materials based on their chemical and physical properties.
Solution Approach 2:
The process utilizes parameter changes by alternating between different gas types (etchant gas vs. reaction gas), different plasma powers, and different pressure conditions. These parameter variations enable selective etching of different silicon-based materials by optimizing the etching chemistry and kinetics for each material type throughout the multi-step cycle.
3Productivity
If high plasma power is used for fast etching, then productivity increases, but etching uniformity and selectivity deteriorate
Solution Approach 1:
The periodic alternation between high-power plasma etching steps and lower-power or non-plasma purging steps allows the system to achieve high overall etching rates while maintaining uniformity. During plasma phases, higher power can be applied for faster etching, while purging phases remove byproducts that would otherwise cause non-uniformity, thus decoupling productivity from uniformity constraints.
Solution Approach 2:
By segmenting the etching process into multiple steps with different power levels and gas compositions, the patent achieves high productivity through cumulative etching while maintaining uniformity through intermediate purging and conditioning steps. Each segment contributes to the overall etching rate without sacrificing uniformity, as the process resets conditions between segments.
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 method enables uniform isotropic etching of silicon-based films with high aspect ratios and allows selective etching of various silicon-based materials, including amorphous silicon, polysilicon, and germanium-based films, with controlled etching rates and selectivity.
Implementation Method 1
supplying an etchant gas, and plasma-exciting a reaction gas
Implementation Method 2
plasma-exciting a reaction gas to expose the substrate to plasma of the reaction gas
Data Source
AI summary
A substrate processing method of etching an etching target film formed on a substrate includes: preparing the substrate having the etching target film; and etching the etching target film, wherein the etching the etching target film includes repeating, a plurality of times, supplying an etchant gas, and plasma-exciting a reaction gas to expose the substrate to plasma of the reaction gas.