Dilute TMAH Etching Oxygen Control
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Solution Overview
Problem
Current semiconductor processing techniques face challenges in achieving selective and uniform etching of silicon films due to low etch selectivity between polysilicon and oxide, especially as device features decrease in size and density, leading to insufficient removal efficiency and uniformity.
Innovation Solution
The method involves controlling the oxygen content in the treatment solution and process chamber environment, using a dilution solution and TMAH with controlled oxygen concentrations, and exposing the substrate to a nitrogen-rich gas to minimize oxygen exposure, thereby enhancing etch selectivity and uniformity across the microelectronic substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching techniques are used, then etching process is simple, but etch selectivity between polysilicon and oxide is low
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using dilute TMAH (tetramethylammonium hydroxide) with controlled oxygen content, specifically maintaining oxygen concentration below 1% in the treatment solution and exposing to nitrogen-rich gas with oxygen concentration below 20%. This parameter change achieves high etch selectivity between polysilicon and oxide while managing process complexity through controlled environmental conditions.
Solution Approach 2:
The patent applies an inert atmosphere principle by using nitrogen-rich gas to create an oxygen-controlled environment during the etching process. The nitrogen gas suppresses oxide formation on the polysilicon surface, thereby enhancing etch selectivity. The process chamber is maintained with nitrogen gas having oxygen concentration less than 20%, creating an inert environment that prevents unwanted oxidation during etching.
2Manufacturing precision
If conventional etching techniques are used, then process is easier to implement, but etch uniformity across the substrate is insufficient
Solution Approach 1:
The patent achieves improved etch uniformity by precisely controlling the oxygen content parameter in the treatment solution and chamber environment. The dilute TMAH solution with oxygen content below 1% combined with nitrogen-rich gas atmosphere (oxygen below 20%) ensures consistent etching conditions across the entire substrate surface, preventing non-uniform oxide growth that would cause etch uniformity issues.
Solution Approach 2:
The nitrogen-rich gas acts as an intermediary medium between the etching solution and the substrate environment. It mediates the chemical environment by suppressing oxidative reactions that would otherwise occur during etching, thereby ensuring uniform etching conditions across the substrate while maintaining operational feasibility through gas flow control.
3Manufacturing precision
If oxygen content is not controlled, then process is simpler, but oxide growth occurs reducing etch selectivity
Solution Approach 1:
The patent implements an inert atmosphere by using nitrogen-rich gas to displace oxygen from the process environment. The nitrogen gas with oxygen concentration less than 20% creates an oxygen-depleted environment that prevents oxide growth on the polysilicon surface during etching, thereby maintaining high etch selectivity. This approach manages oxygen concentration control through atmospheric composition rather than direct chemical control.
Solution Approach 2:
The patent changes the oxygen concentration parameter from conventional levels (typically 21% in air) to controlled low levels (below 20% in chamber gas and below 1% in treatment solution). This parameter change directly prevents oxide formation that would reduce etch selectivity, achieving the desired manufacturing precision through quantitative control of oxygen content.
4Productivity
If feature sizes decrease, then device density increases, but etch selectivity and uniformity become insufficient
Solution Approach 1:
The patent uses parameter changes in the form of dilute TMAH solution with controlled oxygen content to achieve high etch selectivity for smaller features. The dilute solution combined with oxygen control (below 1% in solution, below 20% in chamber) provides precise etching capability that maintains selectivity even as feature dimensions decrease, thereby supporting increased device density without sacrificing precision.
Solution Approach 2:
The nitrogen-rich inert atmosphere provides a controlled environment that enhances etch selectivity for small-scale features. By suppressing oxide formation through the nitrogen environment (oxygen < 20%), the process maintains consistent etching performance across reduced feature sizes, enabling higher device density while preserving 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 approach significantly improves etch selectivity and uniformity by reducing oxide growth and optimizing etch rates and profiles, ensuring efficient removal of polysilicon without affecting surrounding materials, even at smaller feature sizes.
Implementation Method 1
A treatment solution is applied to the microelectronic substrate to etch the silicon
Implementation Method 2
exposing the treatment solution or an environment in the process chamber to a nitrogen-containing gas
Data Source
AI summary
Embodiments of the invention provide a method for treating a microelectronic substrate with dilute TMAH. In the method, a microelectronic substrate is received into a process chamber, the microelectronic substrate having a layer, feature or structure of silicon. A treatment solution is applied to the microelectronic substrate to etch the silicon, where the treatment solution includes a dilution solution and TMAH. A controlled oxygen content is provided in the treatment solution or in an environment in the process chamber to achieve a target etch selectivity of the silicon, or a target etch uniformity across the layer, feature or structure of silicon, or both by the treatment solution.