Narrow Band Interference Filter for High Transmittance Lithography
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Solution Overview
Problem
Current lithography systems for semiconductor manufacturing are inadequate in achieving high transmittance and selective wavelength filtering, as they fail to efficiently pass a narrow band of wavelengths while rejecting others, leading to suboptimal performance in feature size reduction and complexity in semiconductor circuits.
Innovation Solution
The development of a narrow band high transmittance interference filter using a transparent substrate with alternating layers of materials with different refractive indices, deposited using ion beam assisted deposition, to form a bandpass filter and anti-reflective structure, allowing a specific wavelength to pass while blocking others, enhancing transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional lithography systems use broad spectrum light sources, then the system can illuminate the entire wavelength range, but the transmittance at specific wavelengths is insufficient and selective filtering is poor
Solution Approach 1:
The filter is divided into multiple alternating layers of materials with different refractive indices (e.g., TiO2 and SiO2). Each layer has a specific thickness (quarter-wavelength at the target wavelength) that contributes to the overall interference effect. This segmentation allows precise control over wavelength selection while maintaining high transmittance at the target wavelength.
Solution Approach 2:
The patent uses composite material structures with alternating high and low refractive index materials. This composite approach creates constructive interference for the target wavelength (enhancing transmittance) and destructive interference for other wavelengths (blocking them). The combination of materials like TiO2 (high index) and SiO2 (low index) in specific thickness ratios achieves the desired optical filtering performance.
2Measurement precision
If the filter uses multiple alternating layers to achieve narrow band filtering, then wavelength selectivity improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the thickness parameters of each layer to be exactly one-quarter of the target wavelength in the respective material. By carefully controlling these thickness parameters during deposition, the filter achieves narrow bandwidth (high wavelength precision) while the standardized quarter-wavelength design simplifies the manufacturing process compared to arbitrary thickness combinations.
3Illumination intensity
If conventional filters are used to block unwanted wavelengths, then some wavelength selection is achieved, but the transmission rate at the desired wavelength remains below 95%
Solution Approach 1:
The patent converts the harmful effect of multiple wavelength interference into a beneficial narrow-band filtering effect. By using multiple alternating layers with specific thicknesses, the filter creates destructive interference for unwanted wavelengths (blocking them) and constructive interference for the target wavelength (enhancing transmittance to >95%). The very structure that could cause complex interference patterns is designed to produce the desired selective transmission.
Solution Approach 2:
The patent transitions from single-layer or simple multi-layer filters to a sophisticated alternating layer structure that operates in the dimensional space of refractive index contrast. By alternating between high and low index materials, the filter creates additional degrees of freedom for controlling the interference pattern, enabling both high peak transmittance and sharp wavelength discrimination.
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 interference filter achieves a peak transmission rate of up to 95% for a narrow range of wavelengths, significantly improving the lithography system's ability to selectively expose semiconductor wafers, thereby supporting the production of smaller and more complex semiconductor circuits.
Implementation Method 1
A plurality of alternating material layers are deposited over a first surface of the transparent substrate... allowing a specific wavelength to pass while blocking others
Implementation Method 2
deposited using ion beam assisted deposition
Data Source
AI summary
The present disclosure provides an interference filter, a lithography system incorporating an interference filter, and a method of fabricating an interference filter. The interference filter includes a transparent substrate having a front surface and a back surface, a plurality of alternating material layers formed over the front surface of the transparent substrate that form a bandpass filter, and an anti-reflective structure formed over the back surface of the transparent substrate. The alternating material layers alternate between a relatively high refractive index material and a relatively low refractive index material.