Etching Liquid Selectivity for Titanium and Silicon Layers
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Solution Overview
Problem
Current etching processes for semiconductor production face challenges in achieving high selectivity and controlling surface roughness when removing titanium-containing and silicon-containing layers, particularly in adjusting the etching rate ratio between these layers without compromising the overall etching rate.
Innovation Solution
An etching liquid comprising nitric acid, a fluorine-containing compound, and specific nitrogen-containing or phosphorus-containing organic compounds is used, allowing for the adjustment of the etching rate ratio between silicon-containing and titanium-containing layers by varying the molecular weight and concentration of these additives, thereby enhancing selectivity and minimizing surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching liquids are used to remove titanium-containing and silicon-containing layers, then the etching process can be completed, but the selectivity between layers is insufficient and surface roughness increases
Solution Approach 1:
The patent applies parameter changes by systematically adjusting the concentrations of nitric acid (5-50%), fluorine-containing compounds (0.1-10%), and nitrogen-containing organic compounds (0.01-5%) in the etching liquid formulation. This multi-parameter optimization enables simultaneous improvement of etching selectivity (achieving 10:1 or higher between titanium and silicon layers) and surface finish quality, directly resolving the technical contradiction between manufacturing precision and surface roughness.
Solution Approach 2:
The etching liquid employs a composite formulation combining multiple chemical components: nitric acid as the primary etchant, fluorine-containing compounds (such as HF, NH4F, or organic fluorides) for enhanced silicon etching, and nitrogen-containing organic compounds (such as PVA, PEG, or amines) as buffering agents and surface protectors. This composite material approach allows the liquid to simultaneously achieve high selectivity for titanium removal while protecting silicon layers and minimizing surface roughness.
2Productivity
If the etching rate of silicon-containing layer is increased to improve productivity, then the overall etching speed improves, but the selectivity ratio between silicon and titanium layers decreases
Solution Approach 1:
The patent applies local quality by creating chemically selective environments for different materials. The etching liquid is formulated to exhibit fundamentally different etching mechanisms: fluorine-containing compounds aggressively etch silicon through Si-F bond formation, while nitric acid selectively attacks titanium through oxidation. The nitrogen-containing organic compounds provide localized protection to silicon surfaces. This local chemical specificity enables high silicon etching rates while maintaining 10:1 or higher selectivity against titanium layers.
Solution Approach 2:
The patent resolves the productivity-selectivity contradiction through parameter changes in the chemical formulation. By optimizing the fluorine-to-nitrogen compound ratio and adjusting acid concentrations, the process achieves rapid silicon removal (high productivity) while the nitrogen-containing organic compounds buffer the etching action to preserve selectivity. Experimental data in the patent demonstrates that with proper parameter selection, both high etching rates and high selectivity ratios can be achieved simultaneously.
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 etching liquid effectively removes titanium-containing and silicon-containing layers with high selectivity while maintaining a controlled etching rate ratio, reducing surface roughness and ensuring efficient semiconductor substrate production.
Implementation Method 1
nitric acid
Implementation Method 2
a fluorine-containing compound
Data Source
AI summary
There is provided an etching liquid including nitric acid; a fluorine-containing compound; and a nitrogen-containing organic compound A containing a nitrogen atom, or a phosphorus-containing compound B.