Hypohalite Alkaline Silicon Etching for Higher Wet Etch Rate
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Solution Overview
Problem
The productivity of wet etching in silicon processing is limited by the variability in etching solutions required for different semiconductor chip structures, necessitating a high etching rate solution that can adapt to diverse materials and conditions.
Innovation Solution
An aqueous alkaline silicon etching solution containing hypohalite ions within a specific concentration range (0.05 mmol/L to 5 mmol/L) and a pH of 12.5 or greater, with quaternary ammonium ions as counter cations, and minimal metal content, is developed to enhance etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional wet etching solutions are used, then processing can be performed on large areas simultaneously with high productivity, but the etching rate is insufficient compared to dry etching and varies depending on semiconductor chip structure
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by introducing hypohalite ions (ClO⁻, BrO⁻, or IO⁻) at specific concentrations (0.01-10 mmol/L, preferably 0.05-5 mmol/L) and controlling pH to 12.5 or greater. This parameter modification enables the solution to achieve high etching rates comparable to dry etching while maintaining the bulk processing capability of wet etching, thus resolving the contradiction between productivity and etching rate.
Solution Approach 2:
The patent creates a composite etching solution system combining quaternary ammonium hydroxide (providing alkaline environment and quaternary ammonium ions) with hypohalite compounds (providing oxidizing capability). This composite chemical system synergistically enhances the etching rate while maintaining solution stability and adaptability to different semiconductor structures, addressing both productivity and speed requirements.
2Manufacturing precision
If different etching solutions are used for different semiconductor chip structures, then optimal etching performance can be achieved for each structure, but the complexity of solution selection and process management increases
Solution Approach 1:
The patent develops a universal etching solution formulation based on quaternary ammonium hydroxide combined with hypohalite that can be applied to various semiconductor chip structures (different materials, patterns, and configurations) while maintaining optimal etching performance. The hypohalite ions provide broad-spectrum oxidizing capability that works effectively across different semiconductor materials, eliminating the need for multiple specialized solutions and simplifying process management.
Solution Approach 2:
By establishing specific parameter ranges (hypohalite concentration: 0.01-10 mmol/L, pH: 12.5 or greater, temperature: 20-80°C), the patent creates a flexible yet standardized solution system that can adapt to different semiconductor structures within these parameters, reducing process complexity while maintaining manufacturing precision.
3Speed
If strong oxidizing agents are used to increase etching rate, then silicon can be etched rapidly, but the solution becomes more hazardous and costly
Solution Approach 1:
The patent uses hypohalite ions (ClO⁻, BrO⁻, IO⁻) at controlled concentrations (0.01-10 mmol/L, preferably 0.05-5 mmol/L) as oxidizing agents. These provide sufficient oxidizing power to achieve high etching rates while being less hazardous than traditional strong oxidizers like concentrated nitric acid or permanganate. The low concentration range further reduces safety hazards and costs while maintaining effective etching performance.
Solution Approach 2:
The patent employs hypohalite compounds that can be prepared in situ or added as stable precursors (like calcium hypochlorite or sodium hypochlorite) that decompose to release active oxidizing species during etching. This approach uses cheaper, safer materials that provide the necessary oxidizing function temporarily during the etching process, reducing both safety hazards and material costs compared to persistent strong oxidizers.
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 solution significantly increases the etching rate of silicon, enabling high productivity even in challenging conditions, while maintaining safety and cost-effectiveness by using non-metallic quaternary ammonium ions and hypohalite ions as oxidizing agents.
Implementation Method 1
the etching rate of silicon is increased remarkably when an aqueous alkaline solution contains hypohalite ions
Implementation Method 2
containing a quaternary ammonium ion
Data Source
AI summary
A silicon etching solution including an aqueous alkaline solution containing a hypohalite ion in a range of 0.05 mmol/L or greater and 5 mmol/L or less and having a pH of 12.5 or greater at 24° C.