Tunable TiOxNy Hardmask for Sub-40 nm Lithography
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Solution Overview
Problem
Conventional trilayer lithography processes face challenges in achieving sub-40 nm ground rules due to the aspect ratio problem during wet development of 193-nm single-layer resists, and existing hardmask materials like titanium nitride suffer from high absorbance in the UV range and difficulty in removal without collateral damage.
Innovation Solution
A multilayer lithographic structure employing a titanium oxynitride (TiOxNy) hardmask layer with a composition of x from 2.5 to 3.5 and y from 0.75 to 1.25, which provides low extinction coefficient and high etch rate, allowing for effective patterning and easy removal while maintaining antireflective properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium nitride is used as hardmask material, then etch resistance is improved, but UV absorbance increases causing resist poisoning and footing
Solution Approach 1:
The patent changes the compositional parameters of the hardmask material from pure titanium nitride (TiN) to titanium oxynitride (TiOxNy) with controlled oxygen content. By adjusting the oxygen concentration during deposition, the material's optical properties are modified to reduce UV absorbance while maintaining etch resistance, thereby eliminating resist poisoning and footing issues
Solution Approach 2:
The patent employs a composite material approach by creating titanium oxynitride that combines titanium, oxygen, and nitrogen in specific ratios. This composite structure integrates the beneficial properties of titanium dioxide (low UV absorbance) and titanium nitride (high etch resistance), achieving a material that simultaneously solves both the optical and mechanical requirements
2Manufacturing precision
If conventional trilayer lithography is used, then sub-40 nm patterning is achieved, but aspect ratio problems occur during wet development
Solution Approach 1:
The patent modifies the material composition parameter of the hardmask layer to titanium oxynitride with controlled oxygen content, which fundamentally changes the etching behavior. This enables the use of dry etching processes that can achieve sub-40 nm patterning without the aspect ratio problems associated with wet development, as dry etching provides better anisotropy and control over vertical profile formation
3Productivity
If hardmask removal is performed, then pattern transfer is completed, but collateral damage occurs to surrounding structures
Solution Approach 1:
The patent changes the chemical composition of the hardmask to titanium oxynitride with specific oxygen content (x=2.5-3.5, y=0.75-1.25), which fundamentally alters the material's reactivity profile. This enables selective removal using targeted chemistries (such as phosphoric acid or specific plasma treatments) that dissolve the titanium oxynitride hardmask while leaving the patterned features and surrounding structures intact, thereby eliminating collateral damage
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 titanium oxynitride hardmask layer enables superior overlay performance and pattern transfer with reduced resist poisoning and footing, achieving efficient etching and dry etching rates comparable to titanium nitride and dioxide, respectively.
Implementation Method 1
The titanium oxynitride is of the formula TiOxNy, wherein x is from 2.5 to 3.5 and y is from 0.75 to 1.25... has an extinction coefficient less than 1.0 over a wavelength range from 400 nm to 800 nm
Implementation Method 2
The exposed portion of the titanium oxynitride layer is etched to expose a portion of the organic planarizing layer... has an etch rate greater than 2 nm per minute in a wet etch solution comprising ammonium hydroxide, hydrogen peroxide and water at a temperature of 20° C.
Implementation Method 3
The exposed portion of the organic planarizing layer is dry etched to the substrate to expose at a least a portion of the conformal metal layer
Data Source
AI summary
Lithographic multilayer structures are disclosed that generally include an organic planarizing layer and a tunable titanium oxynitride layer on the organic planarizing layer, wherein the titanium oxynitride includes TiOxNy, and wherein x is from 2.5 to 3.5 and y is from 0.75 to 1.25. The lithographic multilayer structure further includes a photosensitive resist layer on the titanium oxynitride layer. The tunable titanium oxynitride is configured to function as a hard mask and as an antireflective coating. Also disclosed are methods for patterning the lithographic multilayer structures.