Antireflective Coating Composition for High NA Photolithography
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Solution Overview
Problem
Current antireflective coatings (ARCs) used in photolithography for semiconductor fabrication are inadequate in preventing exposure light reflection, especially at higher numerical apertures, leading to reduced resolution and pattern deformation due to insufficient etching rates and intermixing with resist films.
Innovation Solution
A composition comprising polymers with specific extinction coefficients and refractive indices, applied as a bi-layer or graded absorption coating, which segregates into distinct layers to enhance antireflection and etching rates, preventing reflection and deformation of resist patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer organic ARC is used, then the process is simple and no special equipment is needed, but the antireflection effect is insufficient at high NA
Solution Approach 1:
The invention divides the single-layer ARC into a bi-layer structure with a lower layer (higher extinction coefficient) adjacent to the substrate and an upper layer (lower extinction coefficient) adjacent to the resist film. This segmentation allows each layer to perform its specific function optimally, achieving superior antireflection effect at high NA while maintaining process simplicity through single-coat application.
Solution Approach 2:
The invention applies local quality by assigning different extinction coefficients to different regions of the ARC. The lower layer has a higher extinction coefficient (0.5-1.5) to strongly absorb reflected light at the substrate interface, while the upper layer has a lower extinction coefficient (0.1-0.5) to provide gradual optical transition toward the resist film, optimizing the overall antireflection performance.
2Reliability
If the extinction coefficient of the ARC is increased to improve antireflection, then reflection is reduced, but etching rate decreases and resist pattern deforms
Solution Approach 1:
The invention applies local quality by assigning different extinction coefficients to different regions of the ARC. The lower layer has a higher extinction coefficient (0.5-1.5) to strongly absorb reflected light at the substrate interface, while the upper layer has a lower extinction coefficient (0.1-0.5) to provide gradual optical transition toward the resist film, optimizing the overall antireflection performance.
Solution Approach 2:
The invention divides the single-layer ARC into a bi-layer structure with a lower layer (higher extinction coefficient) adjacent to the substrate and an upper layer (lower extinction coefficient) adjacent to the resist film. This segmentation allows each layer to perform its specific function optimally, achieving superior antireflection effect at high NA while maintaining process simplicity through single-coat application.
3Reliability
If a bi-layer ARC with optimal antireflection is used, then reflection is minimized, but the process complexity increases
Solution Approach 1:
The invention merges the application of two layers into a single coating process. Both the lower layer resin and upper layer resin are mixed in a single coating solution, allowing simultaneous deposition and automatic phase separation into the desired bi-layer structure during drying, thus achieving complex functionality through a simple process.
Solution Approach 2:
The coating solution contains both resins that automatically self-organize into a bi-layer structure during the drying process based on their different solubility parameters. The lower layer resin (higher extinction coefficient) naturally segregates toward the substrate interface while the upper layer resin (lower extinction coefficient) remains near the surface, eliminating the need for separate deposition steps.
4Manufacturing precision
If immersion lithography with high NA is used, then pattern resolution is improved, but light reflection from substrate increases
Solution Approach 1:
The invention divides the single-layer ARC into a bi-layer structure with a lower layer (higher extinction coefficient) adjacent to the substrate and an upper layer (lower extinction coefficient) adjacent to the resist film. This segmentation allows each layer to perform its specific function optimally, achieving superior antireflection effect at high NA while maintaining process simplicity through single-coat application.
Solution Approach 2:
The invention changes the optical parameters of the ARC by using resins with specifically controlled extinction coefficients. The lower layer uses resin with extinction coefficient 0.5-1.5 while the upper layer uses resin with extinction coefficient 0.1-0.5, creating an optimized optical gradient that maximizes antireflection effect for immersion lithography at high NA.
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 effectively reduces substrate reflectance and enhances etching rates, enabling the formation of fine feature patterns with improved resolution and stability in photolithography processes.
Implementation Method 1
polymer (A) having an extinction coefficient k in the range of 0.01 to 0.4 and a refractive index n in the range of 1.4 to 2.1
Implementation Method 2
refractive index n in the range of 1.4 to 2.1 at a preselected imaging radiation wavelength
Implementation Method 3
the composition...segregates into distinct layers to enhance antireflection and etching rates
Data Source
AI summary
A composition comprising (A) a fluorinated polymer having k=0.01-0.4 and n=1.4-2.1 and (B) an aromatic ring-bearing polymer having k=0.3-1.2 is used to form an antireflective coating. The ARC-forming composition can be deposited by the same process as prior art ARCs. The resulting ARC is effective in preventing reflection of exposure light in photolithography and has an acceptable dry etching rate.