Inorganic Sidewall Passivation for High Aspect Ratio Silicon Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Bosch process for etching through-silicon vias and deep trenches faces challenges with sidewall protection, leading to a trade-off between bow and tapered profiles, especially when etching high aspect ratio features, as the organic polymer protection does not hold with increased etch factors, and excessive O2 oxidation limits etch rate and profile control.
Innovation Solution
A gas modulated cyclical etching method involving alternating phases of sidewall deposition with silicon-containing gases like SiF4 and oxygen/nitrogen, followed by etching with halogen components like SF6, forming a more etch-resistant silicon oxide or nitride passivation layer, allowing for improved profile control and increased etch aggressiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If organic polymer protection is used in Bosch process for sidewall protection, then etching can proceed, but the protection does not hold with increased etch factors leading to poor profile control
Solution Approach 1:
The patent changes the material parameter of the sidewall protection layer from organic polymer to inorganic material (silicon oxide or silicon nitride), which fundamentally alters the protection mechanism to be more stable and reliable under high etch factors, thereby maintaining profile control
Solution Approach 2:
The patent creates a composite etching process that deposits inorganic passivation layers (silicon oxide or silicon nitride) over the organic polymer mask, combining the benefits of both materials to achieve superior sidewall protection and profile control
2Manufacturing precision
If excessive O2 is used for oxidation protection, then sidewalls are protected, but etch rate is limited and profile control is reduced
Solution Approach 1:
The patent changes the oxidation mechanism from gas-phase O2 oxidation to in-situ oxidation during the etching process itself, allowing oxidation protection without the need for excessive O2 that would limit etch rate, thereby maintaining both profile control and productivity
Solution Approach 2:
The patent introduces inorganic passivation layers (silicon oxide or silicon nitride) as intermediary protective layers that provide sidewall protection without requiring excessive oxygen, enabling faster etching while maintaining profile control
3Productivity
If aggressive etching is used to increase productivity, then etch rate increases, but undercutting and bowing increase reducing manufacturing precision
Solution Approach 1:
The patent performs preliminary deposition of inorganic passivation layers on the sidewalls before the aggressive etching process begins, creating a protective barrier that enables aggressive etching without undercutting or bowing, thus maintaining profile control while increasing etch rate
Solution Approach 2:
The patent changes the nature of the protective layer from organic polymer to inorganic material that can withstand aggressive etching conditions, enabling higher productivity without sacrificing manufacturing precision
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 method enhances profile control by reducing undercutting and bowing, enabling more aggressive and faster etching with improved passivation layer strength compared to traditional Bosch processes, particularly effective for high aspect ratio features.
Implementation Method 1
forming a plasma from the sidewall deposition phase gas in the plasma processing chamber
Implementation Method 2
providing a flow of sidewall deposition phase gas comprising a silicon containing compound gas and at least one of oxygen, nitrogen or NOx into the plasma processing chamber, forming a plasma from the sidewall deposition phase gas
Implementation Method 3
forming a plasma from the etching gas in the plasma processing chamber
Implementation Method 4
providing a flow of an etching gas comprising a halogen component into the plasma processing chamber, forming a plasma from the etching gas
Data Source
AI summary
A method for etching features into a silicon substrate disposed below a mask in a plasma processing chamber is provided. The silicon substrate is etched through the mask comprising a plurality of cycles, wherein each cycle comprises a sidewall deposition phase and an etch phase. The sidewall deposition phase comprises providing a flow of sidewall inorganic deposition phase gas comprising a silicon containing compound gas and at least one of oxygen, nitrogen or NOx, into the plasma processing chamber, forming a plasma from the sidewall deposition phase gas in the plasma processing chamber, and stopping the flow of the sidewall deposition gas into the plasma processing chamber. The etch phase comprises, providing a flow of an etching gas comprising a halogen component, forming a plasma from the etching gas in the plasma processing chamber, and stopping the flow of the etching gas.