Specimen Potential Measurement in Charged Particle Beam Devices
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Solution Overview
Problem
Current methods for measuring and focusing in charged particle beam devices, such as scanning electron microscopes, are inefficient in handling mixed presence of fixed and induced charges on semiconductor wafers, leading to prolonged measurement times and reduced throughput.
Innovation Solution
Implementing a specimen potential measuring method that selectively uses multiple devices to measure and adjust specimen potential, both inside and outside the specimen chamber, to accurately account for fixed and induced charges, ensuring precise and rapid charge measurement and focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If retarding focus method is used to measure specimen potential by changing voltage applied to specimen, then measurement precision is improved, but measurement time increases considerably
Solution Approach 1:
The patent applies preliminary action by measuring the fixed charge component of the specimen potential before introducing the specimen into the specimen chamber using an electrometer. This preliminary measurement allows the system to pre-calculate the required voltage adjustment range, so that when the specimen is later measured in the chamber, the voltage only needs to be adjusted within a limited range rather than sweeping through a wide range, thereby significantly reducing the measurement time while maintaining precision.
Solution Approach 2:
The patent segments the specimen potential measurement into two distinct parts: (1) measurement of the fixed charge component outside the specimen chamber using an electrometer, and (2) measurement of the total potential inside the specimen chamber. By separating these measurements, the system can optimize each for its specific purpose - the first for speed and the second for precision - thereby resolving the contradiction between measurement time and precision.
2Reliability
If wide voltage range is set for each radiation point to account for maximum charge quantity, then measurement completeness is improved, but throughput decreases
Solution Approach 1:
The patent uses preliminary action to measure the fixed charge component before specimen introduction, which allows the system to establish a baseline charge value. This preliminary information enables the system to limit the voltage adjustment range during actual measurement to only what is necessary beyond the fixed charge, rather than sweeping through a wide range to account for maximum possible charge, thereby improving throughput while maintaining measurement completeness.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the voltage range based on the measured fixed charge value. Instead of using a fixed wide voltage range for all measurements, the system modifies the voltage parameters to start from the measured fixed charge level and only sweep through the necessary additional range, optimizing both completeness and throughput.
3Speed
If electrometer is arranged outside specimen chamber to measure fixed charge, then measurement speed is improved, but induced charge cannot be detected
Solution Approach 1:
The patent segments the charge measurement into two parts: fixed charge measured outside the chamber by electrometer, and induced charge measured inside the chamber by detector. This segmentation allows each measurement to be optimized for its specific type - speed for fixed charge and accuracy for induced charge - while the results are combined to provide complete specimen potential information.
Solution Approach 2:
The patent merges the results from two different measurement approaches: the fixed charge measurement from the electrometer outside the chamber and the total potential measurement from the detector inside the chamber. By combining these measurements and calculating the difference, the system recovers both the fixed charge and induced charge components, thereby detecting all charge types while maintaining high measurement speed.
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
Enables high-speed and high-precision measurement of specimen potential, allowing for accurate charge quantification and focus adjustment, thereby improving measurement throughput and precision in semiconductor device evaluation.
Implementation Method 1
a charged particle beam device represented by a scanning electron microscope is a device which radiates a charged particle beam such as an electron beam onto a specimen to detect secondary electrons or the like emitted from the radiated position
Implementation Method 2
specimen potential measurement is conducted by a first specimen potential measuring device which measures specimen potential on the basis of energy distribution of electrons
Data Source
AI summary
The present invention has an object to perform specimen charge measurement or focusing at a high speed and with high precision also for a specimen in which fixed charge and induced charge may be mixedly present.As one mode to achieve the object, there are proposed a specimen potential measuring method and a device to implement the method characterized in that when specimen potential information obtained by a first specimen potential measuring device disposed outside a specimen chamber or specimen potential information beforehand obtained is equal to or more than a predetermined threshold value or is more than the threshold value, measurement of specimen potential is selectively conducted by use of a second specimen potential measuring device in the specimen chamber.