Substrate Level Mapping for Multi-Height Focused Measurement
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Solution Overview
Problem
Existing lithographic systems face challenges in accurately measuring and compensating for the varying topography of substrates, particularly in 3D NAND memory arrays, leading to measurement faults and inaccuracies due to the trade-off between measurement range, resolution, and noise, which affects the precision of substrate exposure.
Innovation Solution
A system utilizing a combination of coarse and fine sensors to define regions of interest based on pre-scanning, generating measurement control maps, and applying servo control signals to maintain critical areas within the focal plane, while ignoring non-critical regions to enhance measurement accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sensor is used to measure the entire substrate surface, then the measurement range is sufficient to cover large height variations, but the measurement precision and resolution deteriorate due to the trade-off between range and resolution
Solution Approach 1:
The substrate surface is divided into multiple regions with different height levels (first region with first surface level, second region with second surface level). Different sensors are assigned to measure different regions: a first sensor measures the first region while a second sensor measures the second region. This segmentation allows each sensor to operate at its optimal resolution without being compromised by the need to cover the entire height range of the substrate.
Solution Approach 2:
Different measurement qualities are applied to different regions of the substrate. The first sensor provides high-resolution measurements for the first region, while the second sensor provides measurements for the second region with different height characteristics. This local quality approach ensures that each region is measured with the appropriate precision level needed for its specific topography.
2Measurement precision
If all regions of the substrate are measured with high resolution, then the measurement precision is improved, but the measurement time and productivity decrease
Solution Approach 1:
A preliminary measurement is performed to generate first level data that identifies regions of interest and non-critical areas. Based on this preliminary information, a measurement control map is created that directs the second sensor to focus only on critical regions. This preliminary action allows the system to prioritize measurement resources on areas that require high precision while reducing or skipping measurements in non-critical areas, thereby improving overall measurement speed without sacrificing precision where needed.
3Area of stationary object
If the measurement system attempts to follow the entire substrate topography, then complete coverage is achieved, but measurement accuracy decreases due to focusing limitations
Solution Approach 1:
The substrate measurement area is segmented into multiple focal planes corresponding to different height levels. The first sensor is dedicated to measuring the first region at the first surface level, while the second sensor measures the second region at the second surface level. This segmentation of the measurement space into discrete focal planes allows each sensor to maintain optimal focus for its assigned region, eliminating the focusing compromises that would occur if a single sensor attempted to cover the entire height range.
Data Source
AI summary
Systems, apparatuses, and methods are provided for generating level data. An example method can include receiving first level data for a first region of a substrate. The first region can include a first subregion having a first surface level, and a second subregion having a second surface level. The example method can further include generating, based on the first level data, measurement control map data. The example method can further include generating, based on the measurement control map data, second level data for a second region of the substrate. The second region can include a plurality of third subregions each having a third surface level equal to about the first surface level, and, optionally, no region having a surface level equal to about the second surface level.