Charge Control Apparatus for Uniform Electron Illumination
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Solution Overview
Problem
Current semiconductor measurement technologies face challenges in maintaining high precision and speed due to surface electrification during charge control, particularly when using electron beam inspection instruments, as existing methods lack efficient means for real-time charge monitoring and control, leading to suboptimal detection of electric characteristics in semiconductor devices.
Innovation Solution
A charge control apparatus that uses relative movement between electrons and the specimen, combined with monitoring of absorption currents and secondary electrons, allows for uniform charge distribution and high-speed charge control, enabling improved measurement precision and repeatability by integrating a CNT cathode electron source for efficient charge processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If electron beam inspection is used to detect electric characteristics, then detection capability is improved, but surface electrification occurs causing measurement precision deterioration
Solution Approach 1:
The charge control apparatus applies preliminary electron beam irradiation to the specimen surface before actual inspection to create a controlled charge state. This preliminary action prevents unwanted surface electrification during inspection by establishing a stable charge distribution in advance, thereby maintaining measurement precision while preserving detection capability.
Solution Approach 2:
The system changes the parameters of electron beam irradiation by controlling the ratio between primary electrons and secondary electrons. By adjusting the electron beam conditions to make secondary electron emission exceed primary electron incidence, the system achieves net charge removal from the surface, preventing electrification effects that would degrade measurement precision.
2Measurement precision
If charge control processing is performed to maintain measurement precision, then measurement precision is improved, but processing time increases
Solution Approach 1:
The charge control apparatus performs charge control processing continuously during the inspection process rather than as a separate preliminary step. The electron beam used for inspection simultaneously performs charge control function by controlling the primary-to-secondary electron ratio, eliminating the need for separate charge control steps and reducing total processing time while maintaining measurement precision.
Solution Approach 2:
The inspection electron beam serves dual purposes: it both inspects the specimen and performs charge control. By making the inspection beam itself capable of charge control through parameter adjustment, the system eliminates the need for separate charge control equipment and processing steps, thereby reducing processing time while maintaining measurement precision.
3Productivity
If high current electron source is used to increase processing speed, then productivity is improved, but vacuum environment stability deteriorates
Solution Approach 1:
The system uses dynamic control of the electron beam parameters, specifically adjusting the acceleration voltage and beam current during the inspection process. This dynamic adjustment allows the system to optimize the primary-to-secondary electron ratio in real-time, achieving effective charge control at lower currents that maintain vacuum stability while still providing sufficient processing speed through optimized beam conditions.
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
The solution enables high-sensitivity detection of electric characteristics in semiconductor devices by ensuring uniform charge distribution, enhancing measurement precision and repeatability while maintaining a stable vacuum environment to prevent damage to the electron source.
Implementation Method 1
energy of a primary electron is adjusted so that the number of secondary electrons emitted from a specimen may become larger than the number of the primary electrons incident on the specimen
Implementation Method 2
using the charge control electrode disposed right above the illumination area, a potential difference between the specimen and the electrode is maintained at a desired potential, whereby charge control is conducted
Implementation Method 3
As one of electron sources satisfying such requirements, there is a Carbon NanoTube electron source (hereinafter, abbreviated as CNT cathode)
Data Source
AI summary
The invention solves charge nonuniformity of a specimen surface resulting from emission variation of a carbon nanotube electron source and individual difference of emission characteristics. During charge control processing, charge of the specimen surface is measured in real time. As means for solving charge nonuniformity resulting from nonuniformity of electron illumination density, electrons illuminating the specimen and the specimen are moved relatively to average electron illumination density. Moreover, an absorption current flowing into the specimen and the numbers of secondary electrons emitted from the specimen and of backscattered electrons are measured as means for monitoring charge of the specimen surface in real time.