Chromeless Phase-Shifting Mask for Dense Line Patterns
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Solution Overview
Problem
Existing chromeless phase-shifting masks fail to effectively transfer dense line patterns due to transmission imbalance and phase errors, particularly at sub-100 nm line widths, leading to inadequate pattern resolution and uniformity in semiconductor manufacturing.
Innovation Solution
A chromeless phase-shifting mask design featuring a transparent substrate with alternating first and second phase-shifting line patterns of equal width, where the first phase has 5%-10% light-blocking regions and the second phase is 100% light transmittable, creating a 180-degree phase difference to enhance image contrast and pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a chromeless phase-shifting mask with transparent regions of different thickness is used to create phase shifting, then image contrast is improved, but transmission imbalance occurs in phase shifted and non-phase-shifted regions
Solution Approach 1:
The patent applies local quality by creating different thickness regions within the transparent substrate - specifically, a first transparent region with a first thickness and a second transparent region with a second thickness that is different from the first. This local variation in thickness produces the desired phase shifting effect in specific areas while maintaining uniformity in other areas, thereby improving image contrast without causing transmission imbalance across the entire mask.
2Reliability
If alternating phase-shifting mask with chrome material is used, then phase shifting can be achieved, but double-exposure process is required increasing process complexity
Solution Approach 1:
The patent extracts and eliminates the chrome material from the mask structure, replacing it with a chromeless design that uses thickness variations in the transparent substrate to achieve phase shifting. This extraction of the chrome component simplifies the mask structure and eliminates the need for complex double-exposure processes, while still maintaining the phase shifting capability through the remaining transparent regions of different thickness.
3Reliability
If transparent regions of different thickness are used for phase shifting, then 180-degree phase shift is achieved, but dense line patterns with pitch equal to twice the line width cannot be transferred
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness values of the transparent regions. Specifically, the first transparent region has a first thickness and the second transparent region has a second thickness that is different from the first, creating the desired 180-degree phase shift. By optimizing these thickness parameters, the patent enables successful transfer of dense line patterns with pitch equal to twice the line width, resolving the limitation of prior art chromeless masks.
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 design improves the critical dimension uniformity and pattern resolution of dense line patterns, enabling successful transfer of equal line/space patterns with reduced wavelike profiles and enhanced CD uniformity, suitable for sub-100 nm features in semiconductor devices.
Implementation Method 1
The transparent region 22 is thicker than both the transparent regions 24, 26, which causes a 180 degree phase-shifting in light passing through the transparent regions 24, 26
Implementation Method 2
Because of this 180-degree phase difference, there is destructive interference at the phase boundaries of the phase-shifting regions 24, 26 and the non-phase-shifting region 22
Data Source
AI summary
A phase-shifting mask suited for equal line/space, small pitched, dense line pattern is disclosed. The phase-shifting mask includes a transparent substrate, a partially shielded mesa line pattern of first phase formed on the substrate, and a clear recessed line pattern of second phase etched into the substrate and is disposed right next to the partially shielded mesa line pattern. The partially shielded mesa line pattern has a plurality of alternating 5%-10% transmittance light-shielding regions and clear regions of the first phase. The partially shielded mesa line pattern and the clear recessed line pattern have the same line width. The light that passes through the clear regions of the first phase and the light that passes through the clear recessed line pattern of second phase have a phase difference of 180 degree.