Etching Solution Polysilicon Selectivity Oxide Corrosion
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Solution Overview
Problem
Conventional polysilicon wet etching chemistry struggles with high etch rates for polysilicon while minimizing oxide loss, particularly in advanced technology nodes, where the thin gate oxide layer is prone to corrosion and prolonged etching times due to low etch rates and increased risk of oxide damage.
Innovation Solution
An alkaline wet chemical etching composition comprising quaternary ammonium hydroxide, alkanolamine, and nitrogen-containing compounds is developed, which selectively enhances the etch rate of polysilicon over silicon oxide, ensuring minimal oxide etching and corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etchants like NH4OH or TMAH are used to remove polysilicon, then the etch rate of polysilicon is sufficient, but the etch rate of silicon oxide becomes unacceptably high causing oxide layer corrosion
Solution Approach 1:
The patent introduces an intermediary substance (oxide corrosion inhibitor) that mediates between the etchant and the oxide layer. The inhibitor selectively binds to the oxide surface, preventing the etchant from attacking it, while allowing polysilicon etching to proceed. This resolves the contradiction by adding a protective intermediary that differentially protects materials based on their etching requirements.
Solution Approach 2:
The patent applies local quality by making the etching solution's effect location-dependent. The oxide corrosion inhibitor provides selective protection only where oxide layers are present, while allowing full etching action on polysilicon regions. This creates spatially differentiated etching behavior within the same solution, enabling high polysilicon etch rates without oxide damage.
2Object-affected harmful factors
If the etch rate of polysilicon is reduced to minimize oxide loss, then oxide layer protection is improved, but the time required for dummy gate removal is prolonged
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by adding oxide corrosion inhibitors and adjusting composition ratios. This parameter modification enables the solution to exhibit dual characteristics: high etching power for polysilicon and low etching power for oxide layers. The parameter change resolves the time-loss contradiction by decoupling the etching rates of different materials through chemical formulation optimization.
3Object-generated harmful factors
If a high dielectric material and metal gate are used instead of silicon oxide and polysilicon, then leakage current and power consumption are reduced, but the dummy gate removal process becomes more complex and risky
Solution Approach 1:
The patent extracts the problematic element (oxide corrosion risk) from the dummy gate removal process by selectively removing only the polysilicon dummy gate while leaving the oxide layer intact. The oxide corrosion inhibitor enables this selective extraction, separating the removal of unwanted material from the risk of damaging adjacent structures, thereby simplifying the overall process despite the advanced device architecture.
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 composition achieves a high etch rate selectivity of polysilicon over silicon oxide, greater than 1,000, effectively reducing oxide loss and corrosion, thereby improving the efficiency and reliability of the dummy gate removal process in semiconductor manufacturing.
Implementation Method 1
certain surfactants and nitrogen-containing compounds can significantly suppress oxide etch rate in an alkaline wet chemical etching formulation
Implementation Method 2
conventional polysilicon wet etching chemistry typically employs etchants like NH4OH or TMAH that exhibit decent polysilicon removal power
Data Source
Figure 1
Figure 2~3
AI summary
Described herein is an etching solution suitable for the selective removal of polysilicon over silicon oxide from a microelectronic device, which comprises: water; at least one of a quaternary ammonium hydroxide compound; optionally at least one alkanolamine compound; a water-miscible solvent; at least one nitrogen containing compound selected from the group consisting of a C4-12 alkylamine, a polyalkylenimine, a polyamine, a nitrogen-containing heterocyclic compound, a nitrogen-containing aromatic compound, or a nitrogen-containing heterocyclic and aromatic compound ; and optionally, a surfactant.