Etching Liquid Control for Silicon Nitride Selectivity
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Solution Overview
Problem
Conventional substrate liquid processing apparatuses etch both silicon nitride and silicon oxide films when using phosphoric acid aqueous solutions, leading to unintended thinning of the silicon oxide underlayer, which can disrupt the formation of circuit patterns and reduce yield.
Innovation Solution
A substrate liquid processing apparatus with a controller that adjusts the etching liquid's temperature and concentration to supply a low etching rate initially to minimize silicon oxide film etching, followed by a high etching rate to efficiently etch the silicon nitride film, ensuring the silicon oxide film thickness is preserved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphoric acid aqueous solution is used to etch the silicon nitride film, then the etching efficiency is improved, but the silicon oxide underlayer is also etched leading to unintended thinning
Solution Approach 1:
The etching process is divided into two sequential stages: first using phosphoric acid aqueous solution to etch the silicon nitride film efficiently, then using a different etching liquid to remove phosphoric acid residues without attacking the silicon oxide underlayer. This segmentation allows each etching liquid to perform its specific function without causing harmful side effects.
Solution Approach 2:
A third liquid (different etching liquid) is introduced as an intermediary substance to remove phosphoric acid residues from the silicon nitride film surface. This intermediary liquid acts as a mediator that cleans the surface without damaging the underlying silicon oxide structure, thus preventing unintended thinning.
2Speed
If high concentration phosphoric acid is used for etching, then the etching rate increases, but the selectivity between silicon nitride and silicon oxide decreases
Solution Approach 1:
The etching process is segmented into two distinct phases with different chemical agents: the first phase uses phosphoric acid for high-speed silicon nitride etching, while the second phase uses a different etching liquid that provides selective removal of phosphoric acid residues without affecting silicon oxide. This segmentation maintains both high etching rate and high selectivity.
Solution Approach 2:
The chemical composition parameter of the etching liquid is changed between two steps. The first liquid contains phosphoric acid optimized for silicon nitride etching rate, while the second liquid has different compositional parameters that provide selectivity for removing phosphoric acid residues while being inert to silicon oxide. This parameter change enables both high speed and high reliability.
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
This approach effectively etches the silicon nitride film while minimizing the etching of the silicon oxide underlayer, maintaining the integrity of the underlayer and improving the yield of subsequent circuit pattern formation.
Implementation Method 1
a substrate liquid processing apparatus that performs a liquid processing on a film formed on a surface of a substrate (e.g., a semiconductor wafer or a liquid crystal substrate) with an etching liquid (processing liquid)
Data Source
AI summary
Disclosed is a substrate liquid processing apparatus that includes: a liquid processing unit that performs a liquid processing on a film formed on a surface of a substrate with an etching liquid; an etching liquid supply unit that supplies an etching liquid to the liquid processing unit; and a controller that controls the etching liquid supply unit. The controller is configured to perform a control such that an etching liquid in a state of having a relatively low etching rate for the film is supplied from the etching liquid supply unit to the liquid processing unit so that the substrate is etched in the liquid processing unit, and then, an etching liquid in a state of having a relatively high etching rate for the film is supplied from the etching liquid supply unit to the liquid processing unit so that the substrate is etched in the liquid processing unit.