Silicon Nitride Etching Selectivity via Phosphoric Acid Composition
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Solution Overview
Problem
Current etchant compositions for silicon nitride films in semiconductor manufacturing fail to achieve high selectivity over silicon oxide films, leading to issues like particle adsorption, undesired removal of silicon nitride films, and re-growth of silicon oxide films, especially when using hydrofluoric acid or other additives that compromise etching selectivity.
Innovation Solution
An etchant composition containing an inorganic acid, a silicon-based compound represented by specific chemical formulas, and water, without fluorine, which selectively etches silicon nitride films while inhibiting silicon oxide film etching, with an etching rate of the silicon nitride film at least 200 times faster than the silicon oxide film at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydrofluoric acid is included in the etchant to increase etching rate, then the etching rate of silicon nitride film is improved, but the etching selectivity to silicon oxide film deteriorates causing unwanted removal of oxide film
Solution Approach 1:
The patent removes hydrofluoric acid from the etchant composition entirely, extracting the harmful component that causes non-selective etching of silicon oxide film while maintaining the etching capability for silicon nitride film through alternative chemical mechanisms
Solution Approach 2:
The patent changes the chemical parameters of the etchant by using phosphoric acid as the primary component instead of hydrofluoric acid, and by controlling the concentration of phosphoric acid at 70-90 wt% to achieve both high etching rate and high selectivity for silicon nitride film
2Stability of the object's composition
If deionized water is added to the phosphoric acid mixture to maintain etching rate, then the etching rate stability is improved, but the etching selectivity to oxide film changes causing process defects
Solution Approach 1:
The patent optimizes the concentration parameter of phosphoric acid to 70-90 wt%, which provides both stable etching rate and high selectivity to silicon nitride film without the need for deionized water, thereby maintaining etching selectivity to oxide film
3Manufacturing precision
If additives such as silicate or fluorosilicic acid are used to suppress silicon oxide film etching, then the etching selectivity is improved, but the silicon concentration in the composition increases causing oxide film re-growth
Solution Approach 1:
The patent removes harmful additives such as silicate and fluorosilicic acid from the etchant composition, extracting the components that cause silicon oxide film re-growth while maintaining high etching selectivity through the optimized phosphoric acid-based formulation
Solution Approach 2:
The patent changes the compositional parameters by using a simplified system of phosphoric acid (70-90 wt%) and water (10-30 wt%), eliminating the need for additives that increase silicon concentration and cause oxide film re-growth
4Speed
If oxime silane is added to the phosphoric acid composition to enhance silicon nitride film etching, then the etching rate is improved, but particle adsorption and generation on semiconductor substrate increases
Solution Approach 1:
The patent removes oxime silane from the etchant composition, extracting the component that causes particle adsorption and generation on the semiconductor substrate while maintaining effective etching of silicon nitride film through the phosphoric acid-based 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
The composition provides high etching selectivity and controlled etching rates, preventing silicon oxide film etching and reducing particle adsorption, allowing for improved semiconductor manufacturing processes with enhanced pattern formation and reduced defects.
Implementation Method 1
a first etchant composition comprising phosphoric acid and a silicon-based compound
Implementation Method 2
a silicon nitride film etching enhancer
Implementation Method 3
a silicon oxide film etching inhibitor such as silicate, fluorosilicic acid, fluorosilicate
Data Source
AI summary
A silicon nitride etching composition effective to selectively etch a silicon nitride film contains an inorganic acid; a silicon-based compound; from 0.01 to 1 wt%, based on total weight of the etching composition, of an ammonium-based compound composed of ammonium acetic acid; and water. The silicon-based compound may be represented by Chemical Formula 1 below or Chemical Formula 2 below,(R1)3-Si-R2-Si-(R1)3 Chemical Formula 1,(R3)3-Si-R4-Si-(R3)3 Chemicl Formula 2.A method of etching a silicon nitride film includes providing the etching composition; and wet etching the silicon nitride film in the etching composition at an etching rate that is at least 200 times faster than a corresponding silicon oxide film.