Plasma Etching Method for SiON Film Line Uniformity
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Solution Overview
Problem
Conventional plasma etching methods result in roughness and non-uniformity of lines formed on SiON films due to the transfer of resist mask roughness during the etching process.
Innovation Solution
A plasma etching method involving a plasma process using a hydrogen-containing gas to preprocess the photoresist pattern on the target object, followed by an etching process with CF-based and CHF-based gases, where the plasma process and etching process are repeated multiple times, with the plasma process performed at lower pressure and higher temperature than the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional etching process is performed directly on the SiON film using a resist mask, then the etching can be completed in a single step, but the roughness of the resist mask is transcribed to the SiON film resulting in non-uniform line width and edge roughness
Solution Approach 1:
The etching process is divided into multiple alternating plasma and etching cycles. The plasma process steps (using H2, N2, or O2) are performed separately from the etching steps (using CF4/CHF3), creating a segmented multi-cycle process that prevents direct transcription of resist roughness while maintaining etching efficiency
Solution Approach 2:
The plasma process is performed as a preliminary action before the actual etching. This preliminary plasma treatment modifies the resist mask surface and the SiON film surface, creating a smoother interface that prevents roughness transcription during subsequent etching operations
2Manufacturing precision
If multiple plasma and etching cycles are performed, then the line uniformity and roughness are significantly improved, but the total processing time increases
Solution Approach 1:
The plasma and etching processes are performed at different pressure and temperature parameters. The plasma process uses lower pressure (1-10 mTorr) and higher temperature (20-50°C), while the etching process uses higher pressure (10-50 mTorr) and lower temperature (15-30°C). These parameter optimizations enable faster cycle times while maintaining improved line uniformity
Solution Approach 2:
The process uses periodic alternating cycles of plasma treatment and etching. This periodic action allows the system to achieve the smoothing effect through repeated cycles while maintaining a controlled rhythm that optimizes total processing time through efficient parameter switching between cycles
3Manufacturing precision
If different gases are used for plasma and etching processes, then the chemical reactions are optimized for each step, but the process complexity increases
Solution Approach 1:
Different gas compositions are used for different process steps (H2, N2, or O2 for plasma; CF4/CHF3 for etching), optimizing the chemical reactions locally for each specific operation. This local quality approach ensures optimal performance for plasma generation and optimal etching chemistry separately
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 significantly reduces the roughness and non-uniformity of the lines formed, leading to improved etching quality and uniformity of the SiON film.
Implementation Method 1
a plasma process of plasma-processing a surface of a photoresist with plasma generated from a hydrogen-containing gas
Implementation Method 2
an etching process of etching a silicon-containing film with plasma generated from a CF-based gas and a gas containing a CHF-based gas
Data Source
AI summary
A plasma etching method includes a plasma process of plasma-processing a surface of a photoresist, which has a predetermined pattern with plasma generated from a hydrogen-containing gas. Further, the plasma etching method includes an etching process of etching a silicon-containing film with plasma generated from a CF-based gas and a gas containing a CHF-based gas by using the plasma-processed photoresist as a mask. Furthermore, in the plasma etching method, the plasma process and the etching process are repeated at least two or more times.