Selective Etching Composition for W and TiN Without Substrate Damage
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Solution Overview
Problem
The semiconductor industry faces challenges in selectively etching aluminum oxide (AlOx), tungsten (W), and titanium nitride (TiN) without damaging adjacent materials during the etching process, as existing methods often result in damage to gate insulating layers and semiconductor substrates, and lack sufficient selectivity over other semiconductor materials.
Innovation Solution
A composition comprising phosphoric acid, acetic acid, nitric acid, and water is used to selectively etch AlOx, W, and TiN, with specific weight percentages of each acid and water, along with optional metal elements and corrosion inhibitors, to enhance etch selectivity and control etching rates, thereby minimizing damage to other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching process is used on AlOx, W and TiN layers, then etching capability is improved, but damage to gate insulating layer and semiconductor substrate occurs
Solution Approach 1:
A wet etching composition is introduced as an intermediary solution between plasma etching and the materials to be etched. This liquid etchant provides the necessary etching capability while being controllable to prevent damage to underlying gate insulating layers and substrates, thus mediating between the need for effective etching and the need to protect sensitive structures.
Solution Approach 2:
The patent replaces the plasma etching process (a physical/chemical field-based method) with a wet etching process using a specifically formulated liquid composition. This substitution allows for better control over etching selectivity and damage prevention while maintaining effective etching of AlOx, W, and TiN layers.
2Manufacturing precision
If wet etching methods are used for AlOx, W and TiN, then selectivity over other materials is improved, but etch rate is insufficient and other exposed metals undergo corrosion
Solution Approach 1:
The patent modifies the chemical parameters of the etching composition by incorporating specific acids (nitric acid, acetic acid, phosphoric acid) in controlled concentrations. These parameter changes enable simultaneous achievement of high etch rates for AlOx, W, and TiN while maintaining selectivity and preventing corrosion of other metals through the balanced chemical formulation.
Solution Approach 2:
The etching composition is formulated as a composite chemical system containing multiple acids working synergistically. This composite approach allows the solution to exhibit multiple functions: high etching power for target materials, selectivity control, and corrosion inhibition for non-target metals, which cannot be achieved with single-component etchants.
3Reliability
If additional protective device manufacturing steps are employed to avoid etching damage, then device reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the protective function from separate manufacturing steps and integrates it directly into the etching composition itself. By incorporating corrosion inhibitors and selective etching agents into the etchant, the composition inherently protects sensitive structures during etching, eliminating the need for additional protective steps while maintaining device reliability.
Solution Approach 2:
The etching composition is designed to perform multiple functions simultaneously: etching AlOx, W, and TiN with high rates, providing selectivity against other materials, preventing corrosion of exposed metals, and protecting underlying structures. This multi-functionality consolidates what would otherwise require multiple separate process steps into a single operation.
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 solution achieves high etch rates for AlOx, W, and TiN while maintaining low etch and corrosion rates for other semiconductor materials, improving device yield and reducing the need for additional protective manufacturing steps.
Implementation Method 1
nitric acid in an amount of from about 0.01 wt % to about 5 wt % of the composition
Implementation Method 2
phosphoric acid in an amount of from about 65 wt % to about 90 wt % of the composition; acetic acid in an amount of from about 0.01 wt % to about 4 wt % of the composition
Data Source
AI summary
The present disclosure is directed to etching compositions that are useful, e.g., for selectively removing tungsten (W) and/or titanium nitride (TiN) from a semiconductor substrate as an intermediate step in a multistep semiconductor manufacturing process.