Selective Silicon Nitride Etching via Hydroxyl Solvent
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current aqueous phosphoric acid etching solutions lack sufficient selectivity for silicon nitride over silicon dioxide in semiconductor manufacturing, often requiring undesirable additives like hydrofluoric acid and nitric acid, and existing methods are inefficient and hazardous due to the need for heated processes and undissolved particles.
Innovation Solution
An aqueous etching solution comprising phosphoric acid and a hydroxyl group-containing solvent, such as alkane diols or glycols, which selectively enhances the etch rate of silicon nitride relative to silicon dioxide, achieving a selectivity of 50 to 500 or higher, without the need for harmful additives or heated processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phosphoric acid is used to etch silicon nitride, then etching capability is improved, but selectivity against silicon dioxide deteriorates due to co-etching
Solution Approach 1:
A soluble silicon compound is introduced as an intermediary substance that modifies the etching chemistry. The silicon compound reacts with phosphoric acid to form species that selectively enhance silicon nitride etching while suppressing silicon dioxide etching, thereby resolving the co-etching problem
Solution Approach 2:
The etching solution composition is modified by adding soluble silicon compounds at controlled concentrations (0.01-10 wt%). This parameter change transforms the etching mechanism to achieve both high silicon nitride etch rates and improved selectivity against silicon dioxide
2Manufacturing precision
If hydrofluoric acid and nitric acid are added to improve silicon nitride etching selectivity, then selectivity is improved, but process safety and environmental impact worsen
Solution Approach 1:
The harmful components (hydrofluoric acid and nitric acid) are extracted/removed from the etching process. The invention achieves the required selectivity using only phosphoric acid and soluble silicon compounds, eliminating the need for hazardous chemicals while maintaining etching performance
Solution Approach 2:
The invention converts the normally harmful co-etching behavior of phosphoric acid into a beneficial selective etching process by adding soluble silicon compounds that modulate the etching chemistry to favor silicon nitride removal while protecting silicon dioxide
3Manufacturing precision
If solid silicon material is added to heated phosphoric acid to modify etching characteristics, then etch selectivity is improved, but process complexity and time requirements worsen
Solution Approach 1:
Instead of using solid silicon material that requires digestion, the invention uses pre-dissolved silicon compounds in the etching solution. This parameter change from solid to dissolved state eliminates the time-consuming digestion step while maintaining the desired etching selectivity
Solution Approach 2:
The silicon compound is pre-dissolved in the etching solution before use, performing the dissolution action in advance. This eliminates the need for on-demand digestion of solid silicon material during the etching process, reducing overall process time
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 effectively and selectively removes silicon nitride over silicon dioxide, improving etch rates and reducing the risk of contamination, while being safer and more efficient than existing methods, with enhanced selectivity and reduced environmental hazards.
Implementation Method 1
An aqueous phosphoric acid etching solution containing a hydroxyl group-containing solvent selectively enhances the etch rate of silicon nitride relative to silicon dioxide
Implementation Method 2
contacting the composite semiconductor device comprising silicon nitride and silicon dioxide with an aqueous composition comprising phosphoric acid
Data Source
AI summary
Described herein is an etching solution comprising water, phosphoric acid solution (aqueous), and a hydroxyl group-containing solvent. Such compositions are useful for the selective removal of silicon nitride over silicon oxide from a microelectronic device having such material(s) thereon during its manufacture.