Metal Gate Etching with Carbon Nitride Sidewall Protection
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Solution Overview
Problem
The formation of high aspect ratio trenches during semiconductor fabrication results in excessive tilt angles due to by-product accumulation, leading to incomplete etching and increased device shorts at wafer edges.
Innovation Solution
A method involving plasma etching with controlled deposition and etching cycles is employed to form vertical trenches by maintaining a protective film on the sidewalls, minimizing by-product accumulation and reducing tilt angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is performed on high aspect ratio trenches at wafer edges, then trench formation is achieved, but excessive tilt angles occur due to by-product accumulation
Solution Approach 1:
A protective film is deposited on the trench sidewalls before the etching process begins. This preliminary protective layer prevents by-products from accumulating on the sidewalls during etching, thereby maintaining trench verticality and reducing tilt angles at wafer edges
Solution Approach 2:
The protective film acts as an intermediary layer between the etchant and the trench sidewalls. It mediates the etching process by preventing direct contact between by-products and the sidewall surface, eliminating the harmful accumulation effect while allowing the etching to proceed
2Length of stationary object
If conventional plasma etching is used for high aspect ratio trenches, then etching is completed, but reduced vertical depth occurs due to tilt angles
Solution Approach 1:
The protective film is deposited in advance on the sidewalls before etching, creating a barrier that maintains trench verticality throughout the etching process. This preliminary protection ensures that the trench achieves its full vertical depth without the tilt angle reduction that would otherwise occur
3Manufacturing precision
If high aspect ratio trenches are etched at wafer edges, then trench formation is achieved, but device shorts occur due to excessive tilt angles
Solution Approach 1:
The protective film is applied before etching to prevent sidewall damage and maintain proper trench geometry. This preliminary protection ensures that trenches at wafer edges maintain adequate depth and verticality, preventing device shorts that would result from tilted profiles
Solution Approach 2:
The protective film provides beforehand cushioning to the sidewalls against the harmful effects of by-product accumulation. This prior protection cushioning prevents the tilt angle development that would lead to insufficient trench depth and potential device shorts
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 achieves vertical trenches with reduced tilt angles, ensuring complete etching through metal gate lines and minimizing device shorts, thereby improving semiconductor device integrity.
Implementation Method 1
performing a plasma etching process including cycles of depositing a carbon nitride film on the sidewall and etching the metal
Implementation Method 2
cycles of depositing a carbon nitride film on the sidewall
Implementation Method 3
performing a plasma etching process including cycles of depositing a carbon nitride film on the sidewall
Data Source
AI summary
Methods for etching metal, such as for processing a metal gate, are provided. A method includes forming a hard mask over the metal, wherein the hard mask includes a sidewall defining an opening; and performing a plasma etching process including cycles of depositing a carbon nitride film on the sidewall and etching the metal.