Overlay Mark Measurement for Wafer Distortion Correction
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Solution Overview
Problem
Existing lithography processes face challenges in maintaining overlay accuracy due to wafer distortion caused by processing steps like resist coating, development, etching, and CMP, which conventional grid control methods struggle to address effectively, especially when using limited reference wafers and exclusive reticles.
Innovation Solution
A measurement device with a movable stage, drive system, absolute position measurement, and mark detection system to accurately measure and control the position of multiple marks on a substrate, enabling precise alignment and exposure using an exposure apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grid control methods are used with limited reference wafers and exclusive reticles, then device complexity is reduced, but manufacturing precision deteriorates due to wafer distortion from processing steps
Solution Approach 1:
The patent divides the wafer surface into multiple measurement regions, each with its own set of marks, allowing independent measurement and correction of local distortions. The grid is segmented into multiple zones that can be corrected separately, addressing the limitation of conventional single-grid approaches.
Solution Approach 2:
The patent performs preliminary measurement of mark positions before exposure using the measurement device, calculates correction values for grid distortion in advance, and applies these corrections to the exposure parameters. This preliminary correction action compensates for anticipated wafer distortion from processing steps.
2Measurement precision
If the number of measurement marks is increased to cover more shot areas, then measurement precision improves, but measurement time increases
Solution Approach 1:
The patent segments the measurement process into multiple independent regions, allowing parallel measurement of different mark sets simultaneously. This reduces total measurement time while maintaining high precision through multiple measurement points across the wafer surface.
Solution Approach 2:
The measurement device continuously scans and measures mark positions across multiple shot areas without interruption, maintaining continuous useful action throughout the measurement process. This eliminates idle time between measurements while capturing comprehensive position information.
3Manufacturing precision
If wafer grid distortion is corrected for each shot map, then manufacturing precision improves, but device complexity and resource requirements increase significantly
Solution Approach 1:
The patent creates a universal correction approach where the measurement device and control system can handle multiple shot maps and wafer types using the same fundamental measurement and correction methodology. The system measures mark positions, calculates corrections, and applies them across different exposure scenarios without requiring separate dedicated systems for each case.
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
Enhances overlay accuracy by providing precise position information and alignment, allowing for improved device manufacturing through accurate control of substrate arrangement and overlay measurement.
Implementation Method 1
an absolute position measurement system that has one of a measurement surface having a grating section and a head section which irradiates a beam on the measurement surface and can acquire position information of the stage by irradiating the beam from the head section on the measurement surface and receiving a return beam of the beam from the measurement surface
Data Source
AI summary
A measurement device has: a slider which holds a substrate and is movable parallel to the XY plane; a drive system that drives the slider; a position measurement system which emits beams from a head section to a measurement surface in which grating section are provided on the slider, which receives respective return beams of the beams from the measurement surface, and which is capable of measuring position information in at least directions of three degrees of freedom including the absolute position coordinates of the slider; a mark detection system that detects a mark on the substrate; and a controller which detects the marks on the substrate using the mark detection system while controlling the drive of the slider, and which obtains the absolute position coordinates of each mark based on the detection result of each mark and measurement information by the position measurement system at the time of detection.