Cyclic Plasma Etching of Silicon Films for Uniformity and Selectivity
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Solution Overview
Problem
Existing substrate processing methods for etching silicon-based films on substrates do not achieve optimal etching characteristics, particularly in terms of uniformity and selectivity.
Innovation Solution
A substrate processing method involving repeated cycles of etchant gas supply, plasma excitation of a reaction gas, and purging, which includes using hydrogen fluoride (HF) as an etchant and a mixture of ammonia (NH3) and nitrogen (N2) gases to generate hydrogen radicals and active species for nitration, followed by controlled etching and purging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used, then the etching process can be completed, but the etching uniformity and selectivity are insufficient
Solution Approach 1:
The patent applies periodic action by implementing a cyclic etching process that alternates between introducing etchant gas (SF6) and introducing a termination gas (NH3/N2 mixture). This periodic switching allows the etching reaction to proceed during the SF6 phase and then terminates or modifies the reaction during the NH3/N2 phase, enabling precise control over etching uniformity and selectivity for different film types
Solution Approach 2:
The patent employs parameter changes by varying the gas composition, flow rates, and introduction timing throughout the etching cycle. Specifically, the ratio of NH3 to N2 in the termination gas, the duration of each gas introduction phase, and the pressure conditions are adjusted to optimize etching characteristics for different silicon-based films, achieving both uniformity and selectivity
2Length of moving object
If etching is performed on high aspect ratio features, then the etching depth can be achieved, but the etching uniformity across different regions becomes difficult to control
Solution Approach 1:
The periodic introduction of etchant gas followed by termination gas allows the etching process to proceed in controlled bursts, enabling deep etching of high aspect ratio features while maintaining uniformity. The cyclical nature ensures that reactive species are continuously supplied and then terminated, preventing excessive side-wall etching and ensuring uniform depth across different regions
Solution Approach 2:
The patent maintains continuous useful action by ensuring that the etching process operates continuously through repeated cycles rather than intermittently. The cyclic introduction of SF6 followed by NH3/N2 creates a continuous etching front that progresses uniformly through high aspect ratio features, maintaining consistent etching rates across different regions
3Productivity
If different film types are etched simultaneously, then the processing efficiency is high, but the selectivity between film types decreases
Solution Approach 1:
The periodic switching between etchant gas (SF6) and termination gas (NH3/N2) enables selective etching of different film types within the same process. Different film types respond differently to the gas cycles, allowing simultaneous processing with maintained selectivity through the rhythmic application and termination of etching conditions
Solution Approach 2:
The patent achieves selectivity through parameter changes in the gas composition and timing. By adjusting the NH3/N2 ratio, flow rates, and cycle timing, the etching process can be tuned to etch different film types at different rates or at different stages of the cycle, enabling simultaneous processing of multiple film types while maintaining their relative 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
This method enables uniform and selective etching of silicon-based films, including high aspect ratio features, with controlled etching of recesses and selective etching of different film types such as amorphous silicon, SiN, and SiO2, achieving improved etching characteristics across a wide temperature range.
Implementation Method 1
plasma-exciting a reaction gas to expose the substrate
Implementation Method 2
generate hydrogen radicals and active species for nitration
Implementation Method 3
etching a silicon-based film formed on a substrate
Implementation Method 4
using hydrogen fluoride (HF) as an etchant
Implementation Method 5
active species for nitration
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.