High-Temperature Etching of Silicon Nitride Using Composite Solution
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Solution Overview
Problem
Current etching methods for silicon nitride (SiN) films in semiconductor manufacturing lack sufficient selectivity and high etching rates compared to silicon oxide (SiO2) films, necessitating improved techniques to enhance processing efficiency.
Innovation Solution
A liquid processing method involving an etching solution composed of a fluorine ion source material, water, and a boiling point adjusting agent, heated to and maintained at a temperature of at least 140°C to achieve an etching rate of silicon nitride exceeding 100 Å/min and a selectivity ratio of 75 or higher compared to silicon oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the etching solution temperature is increased to improve the etching rate of silicon nitride, then the etching rate increases, but the selectivity ratio between silicon nitride and silicon oxide decreases
Solution Approach 1:
The patent changes multiple parameters of the etching solution simultaneously: temperature (100-200°C), composition (HF, H2SO4, H2O in specific ratios), and additives (ammonium fluoride, dimethyl sulfoxide). This multi-parameter optimization resolves the contradiction by finding a combination where high temperature (improving etching rate) coexists with appropriate chemical composition (maintaining selectivity), achieving both >100 Å/min etching rate and >75 selectivity ratio.
Solution Approach 2:
The patent uses a composite etching solution containing multiple chemical components (hydrogen fluoride, sulfuric acid, water, ammonium fluoride, and dimethyl sulfoxide) rather than a single substance. This composite formulation allows the solution to simultaneously provide high etching rate through thermal activation and high selectivity through chemical specificity, resolving the contradiction between productivity and manufacturing precision.
2Loss of time
If a higher etching rate is achieved by adjusting the etching solution composition, then the processing time is reduced, but the selectivity against silicon oxide is not sufficiently high
Solution Approach 1:
The patent optimizes the chemical composition parameters including HF concentration (0.01-10%), H2SO4 concentration (1-80%), and the addition of ammonium fluoride (0.01-5%) and dimethyl sulfoxide (0.1-20%). These parameter adjustments create an etching solution that achieves both high etching rate (>100 Å/min) and high selectivity (>75), simultaneously reducing processing time while maintaining manufacturing precision.
3Productivity
If the temperature is increased to accelerate the etching process, then the etching rate improves, but the damage to the semiconductor wafer increases
Solution Approach 1:
The patent optimizes the temperature parameter within a specific range (100-200°C, preferably 120-180°C) and combines it with controlled chemical composition parameters. This parameter optimization achieves high etching rates while minimizing wafer damage by avoiding excessive temperature that would cause thermal stress, and by using chemical composition that provides selective etching rather than aggressive mechanical removal.
Solution Approach 2:
The patent replaces mechanical/physical etching methods with a chemically-driven liquid etching process. By using a chemically active etching solution with specific composition (HF, H2SO4, ammonium fluoride, dimethyl sulfoxide) rather than physical sputtering or mechanical abrasion, the process achieves high etching rates through chemical reactions that are inherently more selective and cause less physical damage to the wafer structure.
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 effectively increases the etching rate and selectivity of silicon nitride while minimizing damage to the semiconductor wafer, providing a more efficient and selective etching process compared to existing techniques.
Implementation Method 1
producing an etching solution by mixing a fluorine ion source material, water and a boiling point adjusting agent
Implementation Method 2
controlling the temperature of the etching solution to be equal to or higher than about 140° C.
Data Source
AI summary
There are provided a liquid processing method and a liquid processing apparatus capable of providing a high etching rate and a high etching selectivity for silicon nitride against silicon oxide, and a storage medium storing the method thereon. In the method for etching, by an etching solution, a substrate on which silicon nitride and silicon oxide are exposed, the etching solution is produced by mixing a fluorine ion source material, water and a boiling point adjusting agent; the produced etching solution is heated to a substrate processing temperature equal to or higher than 140° C.; after a temperature of the etching solution reaches the substrate processing temperature, the temperature of the etching solution is maintained at the substrate processing temperature for a first preset time; and after a lapse of the first preset time, the substrate is etched by the etching solution maintained at the substrate processing temperature.