Etching Solution for Silicon Nitride Selectivity and Rate
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Solution Overview
Problem
Current etching techniques for semiconductor manufacturing face challenges in achieving a high selection ratio for silicon nitride while maintaining a high etching rate and minimizing the deposition of silicon oxide during the etching process.
Innovation Solution
An etching solution comprising phosphoric acid, an acid with an acid dissociation exponent smaller than that of phosphoric acid, a silicic acid compound, and water, with specific concentration ratios and amounts, is used to enhance the selection ratio and suppress deposition, allowing for selective removal of silicon nitride from substrates containing both silicon nitride and silicon oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phosphoric acid aqueous solution is used for wet etching of silicon nitride, then the etching process can selectively remove silicon nitride from substrates, but the selection ratio between silicon nitride and silicon oxide is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by adding sulfuric acid to phosphoric acid, and controlling the water content within specific ranges (0.1-10 mass% or 1-20 mass%). This parameter optimization achieves both high selection ratio (100:1 or higher) and high etching rate (50 nm/min or higher), resolving the contradiction between precision and productivity
Solution Approach 2:
The patent creates a composite etching solution combining phosphoric acid and sulfuric acid in specific proportions. This composite solution synergistically enhances both the selection ratio for silicon nitride and the etching rate, while the controlled water content prevents silicon oxide deposition, simultaneously achieving multiple performance goals
2Productivity
If the etching rate of silicon nitride is increased, then productivity improves, but the deposition of silicon oxide increases
Solution Approach 1:
By precisely controlling the water content parameter within 0.1-10 mass% or 1-20 mass% ranges, and optimizing the sulfuric acid to phosphoric acid ratio, the patent suppresses silicon oxide deposition while maintaining high etching rates of 50 nm/min or higher, eliminating the harmful deposition effect
Solution Approach 2:
Sulfuric acid acts as an intermediary substance that suppresses the polymerization of silicic acid, preventing silicon oxide deposition. The sulfuric acid interferes with the harmful polymerization reaction, allowing high-rate etching without deposition problems
3Manufacturing precision
If the selection ratio for silicon nitride is increased, then manufacturing precision improves, but the etching rate decreases
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: water content (0.1-10 mass% or 1-20 mass%), sulfuric acid concentration, and phosphoric acid concentration. This multi-parameter optimization achieves the breakthrough of maintaining selection ratio of 100:1 or higher while achieving etching rates of 50 nm/min or higher
Solution Approach 2:
The etching solution achieves multi-functionality by simultaneously providing high selection ratio for silicon nitride, high etching rate, and suppression of silicon oxide deposition. The composite phosphoric-sulfuric acid solution performs multiple functions that were previously achieved by separate processes
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 solution achieves a high selection ratio for silicon nitride, maintaining a high etching rate while effectively suppressing the deposition of silicon oxide, thereby improving the efficiency and accuracy of the etching process.
Implementation Method 1
wet etching using a phosphoric acid aqueous solution is widely used
Implementation Method 2
the above-described substrate is immersed in a phosphoric acid aqueous solution warmed to approximately 150° C. for a certain time
Implementation Method 3
wet etching using a mixed solution including sulfuric acid, phosphoric acid, and water is studied
Implementation Method 4
effectively suppressing the deposition of silicon oxide
Data Source
AI summary
According to one embodiment, an etching solution used for etching of silicon nitride is provided. The etching solution includes phosphoric acid, an acid, silicic acid compound, and water. The phosphoric acid has a first acid dissociation exponent pKa1. The acid has an acid dissociation exponent smaller than the first acid dissociation exponent pKa1. A mass ratio M1/M2 of mass M1 of the phosphoric acid to mass M2 of the acid having the acid dissociation exponent smaller than the first acid dissociation exponent pKa1 is within a range of 0.82 or more and 725 or less.