Silicon Dioxide Wet Etch Composition Selectivity
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Solution Overview
Problem
Conventional wet etchants for silicon dioxide, such as BOE, face issues with Solid Phase Segregation of ammonium fluoride, leading to stability and contamination problems, limiting the etch selectivity to silicon nitride films, and reducing productivity in semiconductor processing.
Innovation Solution
A composition comprising 1 to 40 wt % hydrogen fluoride, 5 to 40 wt % ammonium hydrogen fluoride, water, and optional anionic surfactants and silicon dioxide etching accelerators, which achieves an etch selectivity of 150 or higher for silicon dioxide to silicon nitride films and an etch rate of 10000 Å/min or higher, addressing the limitations of conventional etchants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the concentration of hydrogen fluoride and ammonium fluoride is increased to improve etch rate, then the etch rate of silicon dioxide increases, but Solid Phase Segregation of ammonium fluoride occurs causing stability and contamination problems
Solution Approach 1:
The patent changes the chemical composition parameters by replacing conventional ammonium fluoride with ammonium hydrogen fluoride and adjusting the HF concentration range (5-40 wt%), achieving both high etch rate and stability without Solid Phase Segregation
Solution Approach 2:
The patent creates a composite etchant system combining hydrogen fluoride (5-40 wt%) and ammonium hydrogen fluoride (40-80 wt%) with specific concentration ratios, achieving synergistic effects that resolve the contradiction between etch rate and stability
2Speed
If the concentration of hydrogen fluoride and ammonium fluoride is increased to improve etch rate, then the etch rate of silicon dioxide increases, but the etch selectivity to silicon nitride film decreases
Solution Approach 1:
The patent optimizes the concentration parameters of HF (5-40 wt%) and NH4HF2 (40-80 wt%) to achieve the optimal balance point where etch rate is maximized while etch selectivity is maintained at 150 or higher
Solution Approach 2:
The patent introduces ammonium hydrogen fluoride as an intermediary substance that mediates between the etching action of HF and the protection of silicon nitride, enabling high etch rate with maintained selectivity
3Manufacturing precision
If conventional BOE is used to achieve high etch selectivity, then selectivity to silicon nitride film is maintained, but productivity is reduced due to long process time required
Solution Approach 1:
The patent changes the etchant composition parameters to achieve both high etch rate (10000 Å/min or higher) and high etch selectivity (150 or higher), resolving the contradiction between processing speed and selectivity maintenance
Solution Approach 2:
The patent enables continuous high-rate etching throughout the process by preventing Solid Phase Segregation and maintaining chemical stability, maximizing productivity without sacrificing selectivity
4Ease of manufacture
If ammonium fluoride is used in conventional BOE, then etching capability is achieved, but contamination occurs due to sublimation property of ammonium fluoride in spray nozzle
Solution Approach 1:
The patent extracts ammonium fluoride from the etchant composition and replaces it with ammonium hydrogen fluoride, eliminating the sublimation-related contamination problem while preserving etching capability
Solution Approach 2:
The patent uses a composition that avoids materials with sublimation properties, preventing contamination of equipment and particles without requiring complex contamination control measures
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 significantly increases etch selectivity and rate, reducing process time and improving productivity in single-type semiconductor processing by maintaining high etch rates and selectivity, while avoiding the stability and contamination issues of conventional etchants.
Implementation Method 1
a composition for wet etching of silicon dioxide includes 1 to 40 wt % of hydrogen fluoride (HF), 5 to 40 wt % of ammonium hydrogen fluoride (NH4HF2)
Data Source
AI summary
Provided is an etching composition for electively removing silicon dioxide at a high etch rate, more particularly, a composition for wet etching of silicon dioxide, including 1 to 40 wt % of hydrogen fluoride (HF); 5 to 40 wt % of ammonium hydrogen fluoride (NH4HF2); and water, and further including a surfactant to improve selectivity of the silicon dioxide and a silicon nitride film. Since the composition for wet etching of silicon dioxide has the high etch selectivity of the silicon dioxide to the silicon nitride film, it is useful for selectively removing silicon dioxide.