Wafer Bevel Strip Plasma for Silicon Nitride Sidewall Protection
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Solution Overview
Problem
Current methods for stripping polymer films from semiconductor wafers with silicon nitride layers during etching processes often result in sidewall damage and defects due to exposure to atmosphere, leading to contact profile erosion and contamination, and existing stripping gases like O2 can damage silicon nitride layers causing oxidation and roughness.
Innovation Solution
A method involving a plasma formed from a stripping gas comprising hydrogen and gases like CO2, CO, N2O, or NO2, which creates radicals to remove polymer films from both sidewalls and the backside of the wafer without breaking vacuum, minimizing exposure to humidity and oxidation of silicon nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional stripping methods are used to remove polymer films, then polymer removal is achieved, but sidewall damage and defects occur due to atmosphere exposure
Solution Approach 1:
The patent performs the stripping process in a vacuum environment without breaking vacuum, using a plasma formed from stripping gas (hydrogen containing gas and CO2, CO, N2O, NO, or NO2) to remove polymer films. This inert vacuum atmosphere prevents oxidation and damage to silicon nitride layers and sidewalls that would otherwise occur during atmosphere exposure, while still achieving effective polymer removal through plasma chemistry.
2Productivity
If oxygen-based stripping gases are used, then polymer films are removed, but silicon nitride layers are damaged through oxidation
Solution Approach 1:
The patent changes the chemical composition parameters of the stripping gas from conventional oxygen-based gases to a hydrogen-containing gas combined with CO2, CO, N2O, NO, or NO2. This parameter change in gas composition enables effective polymer removal through plasma chemistry while preventing oxidation of silicon nitride layers, as the hydrogen-based plasma chemistry does not cause the same oxidative damage as oxygen-based stripping.
3Ease of operation
If vacuum is broken during wafer transfer, then wafer can be moved between chambers, but polymer films cause contamination and defects
Solution Approach 1:
The patent maintains continuous vacuum conditions throughout the wafer transfer process from the etch chamber to the stripping chamber, breaking vacuum only at the very end after stripping is complete. This continuous vacuum action prevents polymer film contamination and defects during transfer, while still enabling wafer movement between chambers through a vacuum-compatible transfer mechanism.
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 effectively strips polymer films with reduced damage to silicon nitride layers, minimizing oxidation and defects, and allows for high polymer removal rates while maintaining the integrity of the wafer surfaces, thereby improving the manufacturing process for 3D NAND devices.
Implementation Method 1
A plasma is formed from a stripping gas, the stripping gas comprising a hydrogen (H2) containing gas and at least one of CO2, CO, N2O, NO, or NO2, wherein the plasma creates radicals from the stripping gas
Implementation Method 2
the plasma creates radicals from the stripping gas. The wafer is exposed to the radicals, wherein the radicals remove the polymer containing sidewall film and the polymer containing deposition layer
Data Source
AI summary
A method for stripping a polymer containing sidewall film from etch features and a polymer containing deposition layer from a backside of a bevel of a wafer with a stack with at least one silicon nitride containing layer is provided. A plasma is formed from a stripping gas, the stripping gas comprising a hydrogen (H2) containing gas and at least one of CO2, CO, N2O, NO, or NO2, wherein the plasma creates radicals from the stripping gas. The wafer is exposed to the radicals, wherein the radicals remove the polymer containing sidewall film and the polymer containing deposition layer.