Plasma Etching with Tungsten Protection for SiO2/SiN Selectivity
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Solution Overview
Problem
Existing etching methods struggle to achieve a high etching selection ratio between silicon nitride and silicon oxide regions, particularly in forming contact holes, leading to issues like shoulder inclination and carbon film clogging.
Innovation Solution
An etching method involving a plasma process using a gas mixture of carbon, fluorine, and tungsten, with a tungsten-containing protective layer formed on the silicon nitride region, enhancing the etching selection ratio and preventing carbon film clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used on silicon nitride and silicon oxide regions, then etching can be performed, but the etching selection ratio between the two regions is insufficient
Solution Approach 1:
A tungsten-containing protective layer is formed on the silicon nitride region before the etching process begins. This preliminary protective layer prevents excessive etching of the silicon nitride region and prevents carbon film clogging during etching, thereby improving the etching selection ratio and preventing shoulder inclination
Solution Approach 2:
The tungsten-containing protective layer acts as an intermediary substance between the plasma etching process and the silicon nitride region. It selectively protects the silicon nitride region while allowing the silicon oxide region to be etched, thereby achieving high etching selection ratio without shoulder inclination or carbon film clogging
2Productivity
If fluorocarbon-based plasma is used for etching silicon oxide, then etching can proceed, but carbon film deposition occurs and can clog contact holes
Solution Approach 1:
The tungsten-containing protective layer converts the harmful carbon film deposition into a beneficial protective mechanism. The protective layer provides a barrier that prevents carbon film from reaching and clogging the contact holes, while still allowing the fluorocarbon-based plasma to effectively etch the silicon oxide region at high rates
3Productivity
If high etching rate is achieved on silicon oxide, then productivity improves, but the silicon nitride region may be over-etched due to insufficient selectivity
Solution Approach 1:
The tungsten-containing protective layer is formed in advance on the silicon nitride region to establish selective protection before high-rate etching begins. This allows the silicon oxide region to be etched at high rates while the protected silicon nitride region remains intact, achieving both high productivity and high etching 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 method improves the etching selection ratio between silicon nitride and silicon oxide regions, maintaining a flat surface area and reducing carbon film deposition, thereby optimizing contact hole formation.
Implementation Method 1
etching the second region while forming a tungsten-containing protective layer on the first region, by exposing the first and second regions to plasma generated from a processing gas containing carbon, fluorine, and tungsten
Implementation Method 2
forming a tungsten-containing protective layer on the first region, by exposing the first and second regions to plasma generated from a processing gas containing carbon, fluorine, and tungsten
Data Source
AI summary
An etching method includes: preparing a substrate including a first region containing silicon and nitrogen, and a second region containing silicon and oxygen; and etching the second region while firming a tungsten-containing protective layer on the first region, by exposing the first and second regions to plasma generated from a processing gas containing carbon, fluorine, and tungsten.