Metal-Containing Etch Mask for Uniform High-Aspect-Ratio Profiles
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Solution Overview
Problem
High aspect ratio etching processes in semiconductor manufacturing face challenges such as increased device failure, limited device density, and performance issues due to tapered features, non-uniform passivation leading to defects like notching and profile twisting, especially when using tungsten passivation on silicon oxide.
Innovation Solution
A metal or metalloid containing mask is used to etch semiconductor stacks, where the sputtered metal or metalloid redeposits on sidewalls as a passivation layer, combining chemical and physical deposition processes to provide uniform protection and control lateral etch rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten passivation is used during high aspect ratio etching, then passivation and etching can occur simultaneously, but non-uniform deposition on silicon oxide leads to increased defects such as CD increase, notching, and profile twisting
Solution Approach 1:
The patent changes the deposition mechanism parameter from chemical vapor deposition to physical sputtering. By using a metal-containing mask that sputters metal atoms during the etch process, the patent achieves uniform physical deposition on sidewalls without the selective deposition issues of chemical processes. This parameter change resolves the contradiction by providing consistent passivation thickness regardless of the underlying material composition.
Solution Approach 2:
The patent replaces the chemical deposition mechanism with a physical sputtering mechanism. Instead of relying on chemical reactions that cause selective deposition on different materials, the patent uses physical ejection of metal atoms from the mask during plasma etching. This mechanical/physical substitution eliminates the chemical selectivity problem that causes non-uniform passivation and associated defects.
2Productivity
If high aspect ratio etching is performed to increase device density, then device capacity increases, but tapered features result in increased device failure and limited device depth
Solution Approach 1:
The patent converts the harmful effect of plasma bombardment (which causes sputtering) into a beneficial effect. By incorporating metal into the mask, the patent causes metal atoms to be sputtered from the mask and physically redeposit on the sidewalls as protective passivation. This transforms the potentially harmful sputtering that could damage features into a useful protective mechanism that enables deeper, more uniform high aspect ratio etching with reduced device failure.
3Manufacturing precision
If amorphous carbon mask is used for high aspect ratio etching, then mask selectivity is achieved, but sidewall etching increases and straight profiles are difficult to maintain
Solution Approach 1:
The patent transitions from a pure amorphous carbon mask to a composite metal-containing mask. This composite structure combines the etch selectivity properties of carbon with the sputtering properties of metal atoms. The metal component physically deposits on sidewalls during etching, providing protective passivation that maintains straight profiles, while the carbon component continues to provide mask selectivity. This composite approach resolves the contradiction between selectivity and profile control.
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 enables precise control of feature profiles, reduces defects, and enhances etch depth, allowing for deeper and more uniform high aspect ratio features, improving device performance and reducing manufacturing costs.
Implementation Method 1
the etching sputters metal or metalloid in the metal or metalloid containing mask and the sputtered metal or metalloid physically redeposits on sidewalls of features etched in the stack as a sputtered metal or metalloid containing passivation layer
Data Source
AI summary
A method for etching features in a stack is provided. A metal or metalloid containing mask is formed over the stack. The stack is etched through the metal or metalloid containing mask, wherein the etching sputters metal or metalloid in the metal or metalloid containing mask and the sputtered metal or metalloid physically redeposits on sidewalls of features etched in the stack as a sputtered metal or metalloid containing passivation layer.