Segmented Lithography Mask Enhances Focus Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithographic processing techniques face challenges in maintaining focus sensitivity near the best scanner focus position, leading to low sensitivity and difficulty in distinguishing focus changes, which complicates focus control in production.
Innovation Solution
A lithography mask and method that include segmented cell structures with unresolvable segmentation pitches, allowing for the generation of printed patterns that shift the best focus position and enhance focus sensitivity, utilizing alignment errors between asymmetric cells to determine focus changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If isolated lines or nominal test target structures are used for focus measurement, then the measurement method is simple and easy to implement, but the sensitivity to focus changes is low near the best scanner focus position
Solution Approach 1:
The mask structure is divided into multiple segments with different pitches along the first direction, creating asymmetric cell structures. This segmentation enables the generation of printed patterns with shifted best focus positions, thereby increasing sensitivity to focus changes while maintaining a manageable target structure design
Solution Approach 2:
Asymmetric cell structures are created by combining mask segments with different pitches in a non-symmetric arrangement. This asymmetry causes the printed patterns to exhibit different focus offsets, converting focus changes into measurable alignment errors between asymmetric cells, thus improving focus sensitivity without requiring complex measurement systems
2Measurement precision
If phase shift masks are used to achieve high sensitivity to scanner focus changes, then focus sensitivity is improved, but manufacturing cost increases significantly
Solution Approach 1:
The invention uses standard opaque material mask structures with segmented patterns instead of expensive phase shift masks. These mask structures can be fabricated using conventional lithography processes, significantly reducing manufacturing costs while achieving the desired focus sensitivity through the asymmetric cell design and focus offset mechanism
Solution Approach 2:
The invention changes the pitch parameters of mask segments to create different focus offsets in printed patterns. By varying the pitch values along the first direction and arranging them asymmetrically, the system achieves high focus sensitivity using conventional mask materials and fabrication processes, avoiding the need for costly phase shift mask technology
3Measurement precision
If standard test targets are used for focus measurement, then the measurement process is straightforward, but the ability to distinguish focus changes near best focus position is difficult
Solution Approach 1:
The mask structure is pre-designed with segments of different pitches arranged asymmetrically to create printed patterns with predetermined focus offsets. This preliminary structuring ensures that when the wafer is printed, the patterns automatically exhibit different focus positions, allowing focus changes to be detected as alignment errors between the asymmetric cells without requiring complex real-time adjustments or operations
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 significantly improves focus sensitivity and accuracy, enabling precise focus control by shifting the best focus position and using alignment errors to measure focus changes, thereby addressing the limitations of existing methods.
Implementation Method 1
each cell structure includes a set of features having an unresolvable segmentation pitch along a first direction... wherein the unresolvable segmentation pitch is suitable for generating a printed pattern for shifting the best focus position of the lithography tool
Data Source
AI summary
A segmented mask includes a set of cell structures, wherein each cell structure includes a set of features having an unresolvable segmentation pitch along a first direction, wherein the unresolvable segmentation pitch along the first direction is smaller than the illumination of the lithography printing tool, wherein the plurality of cell structures have a pitch along a second direction perpendicular to the first direction, wherein the unresolvable segmentation pitch is suitable for generating a printed pattern for shifting the best focus position of the lithography tool by a selected amount to achieve a selected level of focus sensitivity.