Silicon Nitride Etching Composition Balancing Rate, Selectivity, and Stability
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Solution Overview
Problem
Existing etching compositions for silicon nitride layers suffer from reduced selectivity and stability issues due to gelation and increased etching rates at high temperatures, leading to undesired changes in composition and decreased performance.
Innovation Solution
A composition comprising hydrofluoric acid, a boron-containing or phosphite compound, water, and a protic solvent is used to etch silicon nitride layers, which maintains stability and enhances selectivity by minimizing the etching rate of silicon oxide layers while increasing the etching rate of silicon nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of phosphoric acid is increased to increase the etching rate, then the etching rate of silicon nitride layer is improved, but the etching rate of silicon oxide layer is also increased, reducing selectivity
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a silane compound to phosphoric acid, creating a new etching composition that enables high etching rate at lower temperatures while maintaining high selectivity. The specific parameter change is the addition of silane compound at controlled concentrations (0.1-10 wt%) to modify the etching chemistry.
Solution Approach 2:
The patent creates a composite etching composition by combining phosphoric acid with silane compound, where the two materials work synergistically. The phosphoric acid provides the primary etching action while the silane compound enhances selectivity and prevents gelation, creating a composite system that outperforms either component alone.
2Manufacturing precision
If a silane compound is added to control the etching rate of silicon oxide layer, then etching selectivity is improved, but gelation occurs due to silanol group formation
Solution Approach 1:
The patent optimizes the concentration parameters of both phosphoric acid and silane compound to prevent gelation while maintaining selectivity. By controlling the silane compound concentration within 0.1-10 wt% and adjusting the phosphoric acid concentration, the patent finds the optimal parameter range that prevents excessive silanol formation and subsequent gelation.
Solution Approach 2:
The patent modifies the local chemical environment by introducing silane compound that selectively interacts with silicon oxide. The silane compound creates a localized protective effect on silicon oxide surfaces through silanol group formation, while the overall composition remains stable due to controlled concentrations and the presence of phosphoric acid.
3Productivity
If etching is performed at high temperature, then etching rate is improved, but boiling occurs causing composition changes and gelation
Solution Approach 1:
The patent changes the temperature parameter from high temperature processing to low temperature processing (room temperature or slightly elevated). This parameter change, combined with the compositional modification, enables the etching process to proceed at lower temperatures where boiling does not occur, maintaining composition stability while achieving high etching rates through the enhanced chemistry.
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 achieves a high etching rate for silicon nitride layers with improved selectivity and stability, allowing for precise etching processes at lower temperatures without gelation or composition changes.
Implementation Method 1
hydrofluoric acid; a boron-containing compound or a phosphite compound
Implementation Method 2
a boron-containing compound or a phosphite compound
Implementation Method 3
water; and a protic solvent
Data Source
AI summary
A composition for etching a silicon nitride layer according to an embodiment includes hydrofluoric acid, a boron-containing compound or a phosphite compound, water and a protic solvent. The composition for etching a silicon nitride layer may etch the silicon nitride layer at a high speed while etching the silicon oxide layer less.