Lithography Mask Alignment Using Coordinate Transformation
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Solution Overview
Problem
Current methods for measuring and aligning lithography masks and mask blanks lack the precision required for sub-nanometer accuracy, particularly in the DUV and EUV ranges, leading to errors in structure positioning and overlay, which are critical for producing smaller semiconductor features.
Innovation Solution
A multistage method involving the alignment of a substrate coordinate system relative to a position measurement system, using multiple marker structures and transformations to minimize positional deviations, allowing for precise measurement and alignment with sub-nanometer accuracy, and the use of optical methods with varying wavelengths for enhanced resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used for lithography masks, then the measurement process is simple, but the measurement precision cannot achieve sub-nanometer accuracy
Solution Approach 1:
The measurement process is divided into multiple stages: first aligning the substrate coordinate system using marker structures, then performing high-precision position measurements. This segmentation allows each stage to be optimized independently, achieving sub-nanometer precision without overwhelming complexity
Solution Approach 2:
The substrate coordinate system is aligned using marker structures before the actual position measurements are taken. This preliminary alignment action establishes a precise reference framework that enables subsequent sub-nanometer measurement accuracy
2Manufacturing precision
If the resolution is increased to measure smaller structures, then the positioning accuracy improves, but the measurement requirements become more stringent
Solution Approach 1:
Marker structures are introduced as intermediary reference elements on the substrate. These markers serve as mediators between the measurement system and the actual structures, simplifying the measurement process while maintaining sub-nanometer positioning accuracy through coordinate system transformation
3Manufacturing precision
If multiple exposure and multiple patterning are used to increase resolution, then smaller features can be produced, but the overlay accuracy requirements increase
Solution Approach 1:
The position measurement system is designed to measure both marker structures and actual structure elements using the same coordinate system. This multi-functionality ensures consistent measurement capabilities for both alignment markers and pattern structures, enabling precise overlay measurement across multiple exposures
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
This approach significantly improves the precision and reproducibility of position data, reducing positional deviations by a factor of up to 10 and achieving measurement accuracy better than 0.5 nm, enabling more accurate lithography mask production and overlay establishment.
Implementation Method 1
an optical method is provided for measuring the at least one first marker structure and/or for determining the actual position data of the second marker structure. In particular, an optical method, in which illumination radiation with a wavelength in the UV, VUV, DUV or EUV range is used
Data Source
AI summary
A method for measuring a substrate in the form of a lithography mask or a mask blank for producing a lithography mask comprises the alignment of a substrate coordinate system (SKS), predetermined by a first marker structure, relative to a position measurement system, a measurement of actual position data (IST) of a second marker structure with predetermined intended position data (POS) in the substrate coordinate system (SKS), and an establishment of a transformation (T) of the substrate coordinate system (SKS) into a transformed substrate coordinate system (tSKS), wherein the transformation (T) is established in such a way that deviations between the actual position data (IST) and the intended position data (POS) of the second marker structure are reduced.