Silicon Nitride Etching Composition for Polysilicon Selectivity
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Solution Overview
Problem
Current methods for selectively etching silicon nitride in the presence of silicon oxide and polysilicon are inadequate, as they often damage polysilicon surfaces and lack sufficient selectivity, particularly when using aqueous phosphoric acid solutions.
Innovation Solution
A composition comprising concentrated phosphoric acid, polysilicon corrosion inhibitors such as C8-C16 alkylbenzenesulfonic acids and C6-C12 alkyldiphenyl oxide disulfonic acids, and specific silane compounds like phenyl trimethoxysilane, which enhances the selectivity of silicon nitride etching while preventing polysilicon corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aqueous phosphoric acid is used to etch silicon nitride, then silicon nitride removal is achieved, but polysilicon surfaces are damaged
Solution Approach 1:
The patent introduces polysilicon corrosion inhibitors as intermediary substances that mediate between the phosphoric acid etching agent and the polysilicon surfaces. These inhibitors form protective layers on polysilicon surfaces, preventing direct contact and damage from the phosphoric acid while allowing silicon nitride etching to proceed selectively.
Solution Approach 2:
The patent modifies the chemical composition parameters of the etching solution by adding specific corrosion inhibitors and adjusting the ratio of phosphoric acid to water. This parameter change transforms the solution from one that damages polysilicon to one that selectively etches silicon nitride while protecting polysilicon surfaces.
2Productivity
If conventional wet etching is used to remove silicon nitride, then etching is performed, but selectivity relative to polysilicon is insufficient
Solution Approach 1:
The patent creates a composite etching solution that combines phosphoric acid with specific corrosion inhibitors and other additives. This composite formulation achieves both high etching efficiency for silicon nitride and high selectivity by protecting polysilicon surfaces through the synergistic effects of multiple components.
Solution Approach 2:
The patent optimizes multiple parameters including the concentration of phosphoric acid, the amount of corrosion inhibitors, temperature, and processing time to achieve both high productivity and high selectivity. The modified solution composition and process parameters enable simultaneous achievement of fast etching and high selectivity.
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 significantly improves the selectivity of silicon nitride etching relative to polysilicon, reducing damage to polysilicon surfaces and maintaining high etch rates, thereby addressing the limitations of existing methods.
Implementation Method 1
a step of removing silicon nitride is common... silicon nitride is removed from a microelectronic device surface by a wet etching process that involves exposing the substrate surface to concentrated phosphoric acid
Implementation Method 2
aqueous phosphoric acid methods tend to cause corrosion of polysilicon surfaces... the combination of the two inhibitor types was found to greatly improve the selectivity of the silicon nitride etching operation in the presence of polysilicon
Data Source
AI summary
The invention relates to compositions and methods for the selective wet etching of a surface of a microelectronic device that contains both silicon nitride (SiN) and polysilicon. An etching composition as described comprises phosphoric acid, certain polysilicon corrosion inhibitors, along with certain silanes. The combination of the two components was found to greatly improve the selectivity of the silicon nitride etching composition in the presence of polysilicon.