Lithography Vertical Control via Field Segmentation
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Solution Overview
Problem
Conventional vertical control methods for lithography machines struggle to accurately manage surface profile irregularities, especially for larger workpieces with complex surface profiles, as they rely on static adjustments that do not account for real-time local surface profile variations during scanning exposure.
Innovation Solution
A method for vertical control of lithography machines that involves real-time measurement and adjustment of the workpiece's surface profile using vertical measurement sensors, allowing for dynamic compensation of local surface profile irregularities by controlling the mask stage, workpiece stage, and projection objective during scanning exposure, using Z-directional, Rx-directional, and Ry-directional movements to ensure the workpiece surface aligns with a reference focal plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional three-point global leveling method is used, then the control method is simple and easy to implement, but it cannot accurately compensate for local surface profile irregularities of large workpieces during scanning exposure
Solution Approach 1:
The patent divides the workpiece surface into multiple exposure fields, each with its own local coordinate system. Instead of treating the entire large workpiece as a single entity, the method segments the surface profile measurement and compensation into field-by-field operations. This allows accurate local compensation for each exposure field while maintaining overall global leveling, resolving the contradiction between simple implementation and high precision for large workpieces.
Solution Approach 2:
The patent implements local quality by performing field-by-field global leveling where each exposure field receives customized vertical compensation based on its specific local surface profile characteristics. The system calculates separate Z, Rx, and Ry compensation values for each field's local coordinate system, enabling precise local adaptation to surface irregularities while maintaining overall system simplicity through modular processing.
2Productivity
If static adjustment based on three-point measurement is used, then the control process is fast and efficient, but it cannot adapt to real-time local surface profile variations during scanning exposure
Solution Approach 1:
The patent transforms the static three-point global leveling into a dynamic field-by-field global leveling system. By establishing local coordinate systems for each exposure field and calculating real-time compensation values based on measured surface profiles, the system adapts dynamically to local variations while maintaining high control speed through efficient coordinate transformations and modular computation.
Solution Approach 2:
The patent performs preliminary measurement of the entire workpiece surface profile before scanning exposure using vertical measurement sensors. This advance measurement allows the system to pre-calculate compensation values for each exposure field's local coordinate system, enabling real-time adaptation during exposure without slowing down the production process.
3Manufacturing precision
If field-by-field global leveling is implemented, then local surface profile compensation accuracy is improved, but the control system complexity increases
Solution Approach 1:
The patent manages system complexity by implementing dynamic coordinate transformations between global and local coordinate systems. The field-by-field global leveling uses systematic mathematical transformations that automatically adapt to each exposure field's position and orientation, providing high compensation accuracy through structured algorithms rather than complex hardware modifications.
4Reliability
If conventional vertical control is used for large workpieces, then the overall global leveling can be achieved, but local surface profile irregularities within exposure fields cannot be compensated
Solution Approach 1:
The patent segments the vertical control into two hierarchical levels: global leveling for the entire workpiece and field-by-field local compensation for each exposure field. This segmentation allows the system to maintain reliable overall global leveling while simultaneously achieving precise local compensation within each field through separate compensation calculations in local coordinate systems.
Data Source
AI summary
A method for vertical control of a lithography machine includes step 1, prior to a scanning exposure, controlling vertical measurement sensors to measure workpiece to obtain overall surface profile data of the workpiece; step 2, performing a global leveling based on the overall surface profile data of the workpiece; and step 3, during the scanning exposure of each exposure field, measuring a local surface profile of the workpiece in real time by the vertical measurement sensors and controlling at least one of a mask stage, a workpiece stage and a projection objective to move vertically according to a Z-directional height value, an Rx-directional tilt value and an Ry-directional tilt value corresponding to the local surface profile of the workpiece, to compensate for the local surface profile of the workpiece in real time, so that an upper surface of each exposure field coincides with a reference focal plane for the exposure field. This method enables flexible vertical control with high accuracy by providing multiple control options.