Titanium Nitride Etchant Composition for Selective Recess Formation
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Solution Overview
Problem
In semiconductor manufacturing, there is a challenge in achieving selective etching of titanium nitride films without affecting underlying metal conductor layers such as molybdenum, aluminum oxide, and silicon dioxide, particularly in the dual damascene process where precise control of via and trench dimensions is crucial as device sizes decrease.
Innovation Solution
A composition comprising water, an oxidizing agent, a fluoride-containing etchant, a metal corrosion inhibitor, and optionally a pH adjustor and water-miscible solvent is used for selective etching of titanium nitride, achieving high selectivity over molybdenum and other materials, with etch rates exceeding 3.5 Å/minute and stability for over 24 hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wet etching process is used to remove titanium nitride hard masks, then the metal hard mask can be effectively removed, but the underlying metal conductor layer and low-k dielectric material may be affected
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by incorporating specific inhibitors (benzotriazole for copper protection, hydroquinone for low-k dielectric protection) alongside oxidizing agents and fluoride sources. This parameter adjustment enables selective etching of titanium nitride while protecting underlying sensitive layers through chemical inhibition mechanisms
Solution Approach 2:
The patent introduces protective chemical intermediaries (inhibitors) that act as mediators between the etching environment and sensitive underlying layers. These inhibitors selectively adsorb onto metal surfaces or react with etchant species to prevent unwanted etching of copper and low-k dielectric materials while allowing titanium nitride etching to proceed
2Manufacturing precision
If the etching process is made more selective for titanium nitride, then the underlying metal conductor layer is protected, but the etching rate may decrease
Solution Approach 1:
The patent optimizes the concentration parameters of multiple components simultaneously: oxidizing agents (0.01-5% H2O2, 0.001-1% periodic acid), fluoride sources (0.01-5% HF, 0.001-1% ammonium fluoride), and inhibitors (0.001-5% benzotriazole, 0.001-1% hydroquinone). This multi-parameter optimization achieves both high selectivity (5-25:1 over molybdenum) and acceptable etching rates (3.5-100 Å/min)
Solution Approach 2:
The etching solution functions as a composite chemical system combining multiple active ingredients with complementary roles: oxidizing agents activate the etching process, fluoride sources provide selective titanium nitride dissolution, and inhibitors offer protective effects. This composite approach enables simultaneous achievement of high selectivity and maintained etching rate
3Manufacturing precision
If a dual damascene process is used with metal hard masks, then better profile control of vias and trenches is achieved, but the process complexity increases
Solution Approach 1:
The patent extracts and addresses the critical challenge of metal hard mask removal by providing a specialized etching solution that selectively removes titanium nitride and photoresist residues while protecting underlying layers. This targeted approach simplifies the overall dual damascene process by providing a single-step solution for hard mask removal that doesn't require additional protective layer deposition or complex process sequences
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 enables uniform recess formation in microelectronic devices, such as 3D NAND flash memory devices, with high selectivity and stability, ensuring effective removal of titanium nitride without damaging other materials, thus improving the precision and efficiency of the etching process.
Implementation Method 1
a. water; b. at least one oxidizing agent
Implementation Method 2
c. at least one fluoride containing etchant
Data Source
AI summary
Provided are compositions and methods for selectively etching titanium nitride, generally leaving molybdenum present unaffected by the process, as well as any aluminum oxide, silicon dioxide, and polysilicon which may be present on the device. In general, the compositions of the invention were able to achieve titanium nitride etch rates exceeding 3.5 Å/minute, thereby providing uniform recess top and bottom layers in patterns.