Graded Spin-On BARC for High NA Lithography
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Solution Overview
Problem
High numerical aperture (NA) optical lithography systems face challenges with substrate reflectivity and reflective notching, leading to non-uniform photoresist linewidth and image quality issues due to light scattering and interference, which are exacerbated by the use of monochromatic light and complex substrate topography.
Innovation Solution
A single-layer spin-on graded antireflective coating (ARC) with varying optical properties throughout its thickness, composed of two or more polymer components with chromophore and transparent moieties, segregating to the ARC-photoresist and ARC-substrate interfaces to minimize reflectivity and enhance optical control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a homogeneous single-layer BARC is used, then the manufacturing process is simple, but the reflectivity control over a wide range of angles is insufficient
Solution Approach 1:
The patent applies local quality by creating a graded BARC where the composition varies through the thickness of the layer. The BARC contains a first polymer component with different optical properties than the second polymer component, with the concentration of each component varying continuously from the substrate interface to the photoresist interface. This gradient structure provides different local optical properties at different depths, enabling effective reflectivity control across a wide range of incident angles while maintaining a single-layer spin-on fabrication process.
2Manufacturing precision
If high NA optical systems are used, then the resolution is improved, but the reflectance at interfaces increases causing standing waves and CD swing
Solution Approach 1:
The patent applies parameter changes by systematically varying the optical parameters (refractive index and absorption coefficient) through the thickness of the BARC layer. The graded composition creates a continuous change in these parameters from the substrate interface to the photoresist interface, which effectively manages the reflection and interference effects caused by high NA imaging systems, thereby reducing standing waves and CD swing while maintaining high resolution capability.
3Manufacturing precision
If monochromatic light is used, then chromatic aberration is eliminated, but constructive and destructive interference is exacerbated
Solution Approach 1:
The graded BARC structure with varying composition through its thickness creates different local optical properties that work together to mitigate interference effects. The first polymer component concentration varies from 10-90% at the substrate interface to 90-10% at the photoresist interface, creating a gradient that manages the phase and amplitude of reflected light, thereby reducing the impact of constructive and destructive interference when monochromatic light is used for exposure.
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 graded ARC effectively reduces substrate reflectivity and reflective notching, enabling improved control of feature sizes below 65 nm and maintaining image quality by minimizing radiation reflection and scattering, thus enhancing the resolution and uniformity of lithographic patterns.
Implementation Method 1
surface energy differences between optically contrasting polymer components of a spin-on BARC composition are used as a driving force for the preferential segregation of such components towards the ARC-air and ARC-substrate interfaces
Implementation Method 2
the light that penetrates the ARC layer is absorbed, thus minimizing the radiation reflected from the underlying substrate
Implementation Method 3
Light can scatter from the interface into regions of the resist where exposure was not intended, resulting in linewidth variations
Data Source
AI summary
An antireflective coating that contains at least two polymer components and comprises chromophore moieties and transparent moieties is provided. The antireflective coating is useful for providing a single-layer composite graded antireflective coating formed beneath a photoresist layer.