Cobalt Wet Etch Using pH-Controlled Water
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Solution Overview
Problem
Conventional methods for etching cobalt in semiconductor fabrication, such as wet etching with corrosive materials or dry etching with plasma, suffer from poor selectivity and undesirable byproducts, and lack effective etch rates.
Innovation Solution
A method involving the use of water at a pH of 4 to 10, free of added buffers or bases, and temperatures between 25 to 100°C, for selectively etching cobalt layers, which is effective in removing cobalt while being selective to other materials commonly found in semiconductor structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional wet etching with corrosive and toxic materials is used to etch cobalt, then etching capability is achieved, but environmental harm and safety issues arise
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using water with controlled pH (4-10) and temperature (25-100°C) instead of conventional corrosive chemicals. This parameter change enables effective cobalt etching while eliminating environmental harm associated with toxic materials.
Solution Approach 2:
The patent uses water as the etching medium, which is inexpensive, environmentally benign, and can be easily disposed of or recycled. This replaces expensive and hazardous chemical etchants while maintaining effective etching performance.
2Productivity
If dry etching using plasma is used to etch cobalt, then etching capability is achieved, but poor selectivity to other films and materials results
Solution Approach 1:
The patent achieves high selectivity by controlling the pH and temperature parameters of the water-based etching solution. The selective removal of cobalt over other materials is accomplished through optimized chemical parameters rather than plasma physics parameters.
3Productivity
If conventional wet etching methods are used to etch cobalt, then etching capability is achieved, but poor selectivity and undesirable byproducts result
Solution Approach 1:
The patent uses water as the etching medium, which produces no harmful byproducts. The simple molecular structure of water ensures that etching reactions produce only benign products that can be easily managed, eliminating the byproduct management issues of conventional etching.
Solution Approach 2:
The patent converts the typically harmful role of water (which is generally ineffective for etching metals) into a beneficial etching agent by controlling pH and temperature parameters, thereby eliminating harmful byproducts while maintaining etching effectiveness.
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 achieves high etch rates greater than 10 Angstroms per minute, is environmentally friendly, and selectively removes cobalt without damaging adjacent materials, overcoming the limitations of prior etching methods.
Implementation Method 1
applying water to selectively remove at least a portion of the cobalt from the cobalt layer, wherein the water is at a pH of 4 to 10 and is free of added buffer, acid, and/or base
Data Source
AI summary
An environmentally green wet etch process for selective removal of cobalt metal generally includes applying water that is free of added buffers, acids, and/or bases to a substrate including exposed cobalt metal. The process can be utilized to form recesses where desired such as may be implemented for metal contact fill, metal gate fill, interconnect fill, or the like.