High-Transmittance Attenuating PSM with Central Opaque Pattern
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Solution Overview
Problem
High-transmittance attenuating phase shift masks (PSMs) face challenges in effectively transferring specific patterns, particularly isolated patterns with larger surface areas and line patterns with large widths and spaces, due to issues like central collapse and collapsed apertures in photoresist patterns.
Innovation Solution
An improved attenuating PSM design featuring a transparent substrate with a first dummy pad pattern and a smaller, concentric opaque pattern at its center, both made of phase shifter material, to enhance pattern transfer without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-transmittance attenuating PSM (T>15%) is used to improve light transmission and reduce exposure dose, then productivity and cost efficiency are improved, but central collapse and aperture defects occur in photoresist patterns for isolated and semi-isolated patterns
Solution Approach 1:
The patent applies local quality by introducing an opaque pattern specifically at the center of isolated and semi-isolated dummy pad patterns, while leaving other areas with high transmittance. This localized modification creates different optical properties in different regions: the center receives reduced light intensity (preventing overexposure and collapse) while the surrounding areas maintain high transmission (preserving productivity benefits). The opaque pattern acts as a local countermeasure tailored to the specific problem of isolated pattern collapse.
2Manufacturing precision
If high-transmittance attenuating PSM is used to enhance resolution and depth of focus, then manufacturing precision is improved, but pattern transfer fails for specific patterns with large surface area and wide lines
Solution Approach 1:
The invention applies local quality by selectively placing opaque patterns only at the centers of isolated and semi-isolated dummy pad patterns, rather than uniformly across the entire mask. This localized approach preserves the high transmittance benefits for resolution and depth of focus in most areas, while locally correcting the overexposure problem in specific isolated patterns. The solution tailors the optical properties to the specific geometric characteristics of problematic patterns.
Solution Approach 2:
The patent segments the dummy pad pattern into two functional zones: a central opaque region and a surrounding high-transmittance phase shifter region. This segmentation allows independent optimization of each zone - the center is protected from overexposure while the periphery maintains high transmission for enhanced resolution. The segmentation strategy enables the mask to simultaneously achieve both high manufacturing precision and reliable pattern transfer.
3Reliability
If opaque pattern is added at the center of dummy pad pattern to prevent collapse, then pattern transfer reliability is improved, but device complexity increases
Solution Approach 1:
The invention minimizes device complexity by applying the opaque pattern modification only where necessary - specifically at the centers of isolated and semi-isolated dummy pad patterns - rather than modifying the entire mask structure. This localized approach adds minimal complexity (simple circular opaque regions) while achieving the reliability improvement. The solution avoids complex multi-layer structures or complicated geometries, using a simple yet effective local modification.
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 prevents central collapse and aperture defects in photoresist patterns, enabling reliable transfer of isolated and semi-isolated patterns with larger surface areas and line patterns, even at high transmittance levels.
Implementation Method 1
When the light passes through the phase shifter material layer of the phase shift masks, the phase of the electric field of the light is shifted exactly 180°
Implementation Method 2
the phase difference between the incident light and the shifted light is exactly half-wavelength and destructive interference is therefore formed on the wafer
Implementation Method 3
the transmittance of the attenuating PSM increases, problems arise when using these high-transmittance attenuating PSMs
Data Source
AI summary
An attenuating PSM includes a quartz substrate, a first dummy pad pattern disposed on the quartz substrate, wherein the first dummy pad pattern is composed of a first phase shifter material layer with a transmission rate of greater than or equal to 15%, and a first opaque pattern disposed at a center area of the first dummy pad pattern. The first opaque pattern has a shape that is analogous to the first dummy pad pattern and surface area of the first opaque pattern is smaller than that of the first dummy pad pattern.