Multi-Beam Mark Position Measurement With Constant Current Switching
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Solution Overview
Problem
In multi-beam writing processes, accurately measuring the position of marks on a substrate is challenging due to deflection distortion and varying current densities in the beam array, which complicates the identification of signal peaks from reflected electronic signals.
Innovation Solution
A method involving switch scan is employed, where the on-beam area is sequentially switched to scan a mark, maintaining a constant average beam current per unit time by adjusting the number of beams outside the scan areas, thereby preventing deflection distortion and enhancing peak detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wide range is scanned by deflecting the multi-beam to measure mark position, then the mark can be scanned, but deflection distortion occurs and beam drift happens making accurate measurement difficult
Solution Approach 1:
The patent divides the multi-beam into multiple independent beam groups, where each beam group scans a specific region of the mark. By segmenting the scanning task across multiple beam groups with different scanning ranges, the system avoids the deflection distortion that would occur if a single beam scanned the entire mark. Each beam group operates within its own optimized scanning range, ensuring reliable signal detection.
2Productivity
If multiple beams are used to scan the mark collectively, then scanning can be performed, but current density varies for each beam making signal peak identification difficult
Solution Approach 1:
The patent applies local quality by assigning different current densities to different beam groups based on their specific scanning requirements and the local characteristics of the mark regions they scan. Each beam group operates with optimized current density for its specific task, allowing reliable signal peak identification despite variations across the multi-beam array. The control unit adjusts beam currents individually or in groups to compensate for current density non-uniformity.
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 allows for precise measurement of mark positions, correcting deviations caused by beam drift, and facilitating accurate alignment and pattern writing with reduced misalignment errors.
Implementation Method 1
detecting a reflected charged particle signal from the mark
Implementation Method 2
a deflector that deflects the charged particle beams
Data Source
AI summary
In one embodiment, a mark position measurement method includes forming a multi-beam in which charged particle beams are arranged at a predetermined pitch, scanning a mark in a pseudo manner by sequentially switching an on-beam area in which beams in a partial area of the multi-beam are set ON and shifting an irradiation position of the charged particle beams, and detecting a reflected charged particle signal from the mark, the mark being provided at a predetermined position, and having a width greater than the predetermined pitch, and measuring a position of the mark based on the reflected charged particle signal detected. An average per unit time of a beam current in a substrate where the mark is formed is made constant at a time of switching of the on-beam area.