Selective Titanium Nitride Etching Composition
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Solution Overview
Problem
The semiconductor industry faces challenges in selectively etching titanium nitride (TiN) without damaging adjacent materials, such as metal conductors and low-k dielectric layers, due to the limitations of current etching processes which often result in corrosion or insufficient etch rates.
Innovation Solution
A composition and process involving an oxidizing agent, chelating agent, metal corrosion inhibitor, organic solvent, amidine base, and water are used to selectively etch TiN, with specific weight percentages and pH adjustments to optimize etch rates while minimizing damage to other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching process is used on TiN layer, then etching capability is achieved, but damage occurs to gate insulating layer and semiconductor substrate
Solution Approach 1:
The patent uses a carefully formulated wet etching composition as an intermediary medium to etch TiN selectively. The composition includes hydrogen peroxide as oxidizing agent, chelating agents like EDTA or DTPA, corrosion inhibitors such as benzotriazole derivatives, and pH buffers to maintain selective etching. This liquid intermediary enables TiN removal without the harsh physical bombardment of plasma, thereby protecting underlying insulating layers and substrates from damage while achieving effective etching of the titanium nitride layer.
Solution Approach 2:
The patent employs precise control of chemical parameters in the etching composition to achieve selective etching. By adjusting pH to specific ranges (maintained by amidine buffers), controlling oxidizing agent concentration (hydrogen peroxide), and optimizing chelating agent ratios, the process achieves high etch rates for TiN while maintaining low etch rates for other materials. This parameter optimization allows selective removal of TiN without damaging adjacent structures.
2Productivity
If wet etching with hydrofluoric acid is used, then TiN etching is achieved, but selectivity is insufficient and other metals undergo corrosion
Solution Approach 1:
The patent fundamentally changes the chemical parameters of the etching system by replacing hydrofluoric acid with a hydrogen peroxide-based oxidizing environment. This parameter change shifts the etching mechanism from fluoride-ion attack to oxidation-based removal. The composition maintains pH between specific ranges using amidine buffers and includes corrosion inhibitors like benzotriazole derivatives that specifically protect copper and other metals. This parameter transformation achieves both high TiN etch rates and excellent selectivity, preventing corrosion of underlying metal interconnects and other sensitive materials.
Solution Approach 2:
The patent converts the potential harm of aggressive etching into a benefit by using hydrogen peroxide oxidation. The strong oxidizing power of hydrogen peroxide, when controlled at specific concentrations and pH levels, selectively attacks TiN through oxidation to form soluble titanium oxides and hydroxides that are then complexed by chelating agents. This converted mechanism provides both the etching power needed for TiN removal and the selectivity required to protect other materials, transforming what would be uncontrolled corrosion into controlled selective etching.
3Reliability
If hydrogen peroxide/ammonia/EDTA mixtures are used, then acidic HF etchants are overcome, but etch rates are insufficient
Solution Approach 1:
The patent optimizes the parameters of hydrogen peroxide-based etching by adjusting concentrations, pH, and additive ratios. By maintaining hydrogen peroxide at specific concentrations (optimized balance between etch rate and selectivity), controlling pH within narrow ranges using amidine buffers, and incorporating corrosion inhibitors at precise levels, the process achieves both high etch rates for TiN and excellent selectivity. This parameter optimization overcomes the insufficient etch rate problem while maintaining the safety and selectivity benefits of non-HF chemistry.
Solution Approach 2:
The patent creates a composite etching chemistry by combining multiple functional components: hydrogen peroxide (oxidizing agent), chelating agents like EDTA or DTPA (for complexing dissolved Ti), corrosion inhibitors such as benzotriazole derivatives (for metal protection), and amidine buffers (for pH control). This composite composition works synergistically to achieve high etch rates while maintaining selectivity and preventing corrosion, overcoming the limitations of simpler hydrogen peroxide/ammonia/EDTA mixtures.
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 TiN etch rates with low etch and corrosion rates for other semiconductor materials, maintaining compatibility and extending the shelf life of the etching composition.
Implementation Method 1
at least one oxidizing agent
Implementation Method 2
at least one chelating agent
Implementation Method 3
at least one metal corrosion inhibitor
Data Source
AI summary
This disclosure relates to etching compositions containing 1) at least one oxidizing agent; 2) at least one chelating agent; 3) at least one metal corrosion inhibitor; 4) at least one organic solvent; 5) at least one amidine base; and 6) water.