Charged Particle Beam Focus Adjustment via Retarding Voltage
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Solution Overview
Problem
The existing charged particle beam apparatuses face challenges in setting appropriate optical conditions for focus adjustment due to varying contact resistance between the contact pin and the sample, leading to poor responsiveness and potential image blur, especially when the insulation film thickness is unknown or excessively applied, affecting measurement accuracy and throughput.
Innovation Solution
A charged particle beam apparatus that includes a control device to measure the surface potential of the sample after applying a retarding voltage, allowing for focus adjustment based on the time constant of the potential change, ensuring reliable measurement and inspection regardless of the insulation film thickness or contact state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact pin is used to break the insulation film for focus adjustment, then focus adjustment can be performed, but the contact resistance varies with insulation film thickness and contact state, leading to poor response speed
Solution Approach 1:
The patent replaces the mechanical contact pin system with an electrostatic field-based system. Instead of using a physical contact pin that mechanically breaks the insulation film, the invention applies a retarding voltage to the sample stage, creating an electrostatic field that penetrates the insulation film non-contactly. This eliminates mechanical wear and contact resistance variability while maintaining the ability to adjust focus and measure surface potential.
Solution Approach 2:
The patent introduces the retarding voltage as an intermediary between the control system and the sample. The retarding voltage serves as a mediator that can penetrate the insulation film without direct contact, enabling focus adjustment and surface potential measurement while avoiding the contact resistance issues inherent in direct pin-to-sample contact.
2Reliability
If the insulation film is thick or improperly removed, then the contact resistance increases, but this leads to decreased response speed and inappropriate focus adjustment conditions
Solution Approach 1:
The patent changes the operational parameters from direct contact (pin-to-sample) to non-contact electrostatic field interaction (retarding voltage to sample). By applying a retarding voltage that can penetrate varying thicknesses of insulation film, the system maintains consistent performance regardless of film thickness, eliminating the need for precise insulation film removal and enabling reliable measurements across different sample conditions.
Solution Approach 2:
The patent performs preliminary assessment of the insulation film condition by measuring the surface potential response to retarding voltage before proceeding with measurements. This preliminary action allows the system to determine whether the insulation film thickness is appropriate for the measurement, preventing wasted time on unsuitable samples and improving overall throughput by identifying viable measurements early.
3Measurement precision
If the contact resistance is great, then the response speed decreases, but this also causes focus blur and reduced measurement accuracy
Solution Approach 1:
The patent replaces the mechanical contact system with an electrostatic field system that does not suffer from contact resistance. By using retarding voltage applied to the sample stage rather than direct pin contact, the invention eliminates the source of contact resistance variability, ensuring consistent and rapid response regardless of insulation film conditions, thereby maintaining both speed and precision.
Solution Approach 2:
The patent implements feedback by measuring the surface potential of the sample in response to applied retarding voltage. This feedback mechanism allows the system to assess the insulation film condition and adjust measurement parameters accordingly, ensuring that focus accuracy is maintained while avoiding the pitfalls of high contact resistance that would otherwise slow down the response.
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 configuration enables high accuracy and high throughput measurements by ensuring appropriate apparatus conditions are set, preventing focus blur and maintaining reliable image quality across different insulation film situations.
Implementation Method 1
an electrostatic chuck mechanism holding a sample by electrostatic adsorption
Implementation Method 2
an objective lens for focusing a charged particle beam emitted from a charged particle source
Implementation Method 3
there is also a focusing ion beam apparatus for processing and observing the semiconductor device by using an ion beam
Data Source
AI summary
In a charged particle beam apparatus that applies a retarding voltage to a sample through a contact terminal and executes measurement or inspection of a surface of the sample, potential variation of the sample when changing the retarding voltage applied to the contact terminal is measured by a surface potential meter, a time constant of the potential variation of the sample is obtained, and it is determined whether execution of measurement or inspection by a charged particle beam continues or stops based on the time constant, or a conduction ensuring process between the sample and the contact terminal is executed.