Double-Exposure Mask Auxiliary Structures for Photolithography Depth of Focus
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Solution Overview
Problem
The critical dimension of holes at the margin region in semiconductor fabrication is insufficient for subsequent processes due to light diffraction issues in photolithography, particularly in double-exposure techniques where marginal auxiliary masks fail to provide adequate depth of focus.
Innovation Solution
A double-exposure mask structure and method that includes parallel and spaced first and second masks, a margin connecting section, and auxiliary masks arranged in a straight line parallel to the first masks, which are not in contact with each other, to assist overlapping regions with sufficient depth of focus and enhance exposure and focusing margins during photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If marginal auxiliary masks are used to assist photolithography at margin regions, then depth of focus is improved, but critical dimension of holes remains too small for subsequent processes
Solution Approach 1:
The mask structure is segmented into multiple functional zones: central region with first and second masks, margin region with marginal auxiliary masks, and transition region with third masks. This segmentation allows each zone to be optimized independently - the third masks in the transition region provide additional support to achieve sufficient critical dimension while the marginal auxiliary masks maintain depth of focus.
Solution Approach 2:
Different mask configurations are applied to different regions of the substrate. The central region uses a standard cross-pattern of first and second masks, while the margin region incorporates marginal auxiliary masks parallel to the first masks, and the transition region uses third masks connecting these elements. This local differentiation ensures optimal photolithography performance in each specific region.
2Productivity
If double-exposure technique is used to reduce line width and transistor size, then productivity is improved, but light diffraction causes incorrect exposure position
Solution Approach 1:
The mask structure is designed in advance with predetermined positions for first masks, second masks, marginal auxiliary masks, and third masks. This preliminary configuration ensures that during the double-exposure process, the light diffraction effects are pre-compensated for, maintaining correct exposure positions while achieving high transistor density.
3Manufacturing precision
If auxiliary masks are added to assist photolithography at overlapping regions, then device complexity increases, but manufacturing precision is improved
Solution Approach 1:
The third masks serve multiple functions: they connect the central region masks to the margin region masks, provide additional support for critical dimension control in the transition region, and maintain the overall structural integrity of the mask system. This multi-functionality reduces the need for separate specialized components.
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 auxiliary masks ensure sufficient depth of focus and increased exposure margin, effectively addressing the insufficient critical dimension issue by enhancing the photolithography process, particularly in semiconductor fabrication with decreasing linewidths.
Implementation Method 1
severe complications caused by effect of light diffraction have gradually emerged
Implementation Method 2
the manufacture of a semiconductor is performed by photolithography
Data Source
AI summary
Double-exposure mask structure and photolithography method for performing a photolithography process on a substrate are provided. The substrate has a central region and a margin region. A double-exposure mask structure includes a plurality of parallel and spaced first masks corresponding to the central region, a plurality of parallel and spaced second masks corresponding to the central region, and a plurality of auxiliary masks. The second masks intersect with the first masks to form a plurality of overlapping regions. The auxiliary masks are not in contact with one another, and correspond to the Second masks to assist the overlapping regions neighboring to the auxiliary masks to have sufficient depth of focus for photolithography. With the auxiliary masks, the overlapping regions in the central region and neighboring to the margin region can have preferred photolithography and etching effect.