Electron Beam Irradiation Area Control for Precharging
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Solution Overview
Problem
Conventional electron beam apparatuses for semiconductor wafer inspection require a separate precharging unit, which complicates replacement and control of precharging, and fail to efficiently remove detected foreign matter from the wafer surface.
Innovation Solution
An electron beam apparatus with an integrated precharging function that adjusts the irradiation area relative to the viewing area, allowing for precise control of precharging and electrostatic adsorption of foreign matter using a charged adsorption electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate precharging unit is provided adjacent to the electron beam source, then precharging function is achieved, but device complexity increases and replacement becomes complicated
Solution Approach 1:
The patent combines the precharging function with the primary optical system by using the electron beam source to perform both observation and precharging operations. The electron beam source is configured to irradiate a first area for observation and a second area for precharging, merging two functions into one system component, thereby reducing device complexity while maintaining precharging capability
Solution Approach 2:
The electron beam source is designed to serve multiple purposes: it acts as both the observation beam source and the precharging unit. By controlling the irradiation area to include both the first area (for observation) and the second area (for precharging), the system achieves multi-functionality, eliminating the need for a separate precharging unit
2Stability of the object's composition
If the irradiation area of precharging is set wider than the field of view, then uniform charging is achieved, but area outside the observed portion is also charged up and repeating precharging may destroy elements on the wafer
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different areas: the first area receives electron beam irradiation for observation, while the second area receives charged particle irradiation for precharging. This localized approach ensures that precharging is applied uniformly to the required area without excessive charging of areas outside the observed portion, preventing element destruction
Solution Approach 2:
The patent uses partial action by configuring the irradiation area to extend beyond the field of view only to the necessary extent for uniform precharging. The second area for precharging is deliberately designed to be wider than the first area for observation, but this extension is controlled and limited to avoid excessive charging that would damage wafer elements
3Reliability
If a separate precharging unit is provided, then precharging is achieved, but vacuuming of the additional space is required
Solution Approach 1:
The patent merges the precharging function into the existing vacuum chamber that houses the electron beam source. By using the same vacuum space for both observation and precharging operations, there is no need for additional vacuuming systems, thereby reducing device complexity while maintaining the precharging function
4Stability of the object's composition
If the amount of dosing of charged particles is increased to achieve uniform precharging, then charging uniformity improves, but control precision decreases
Solution Approach 1:
The patent changes the parameter of irradiation area configuration to achieve uniform precharging. By configuring the irradiation area to include both the first area and the second area, and by controlling the relative positioning of these areas, the system achieves uniform charging without relying solely on increasing dosing amount, thereby maintaining control precision
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 solution enables uniform precharging without additional units and effectively removes foreign matter from the wafer surface, improving inspection accuracy and efficiency.
Implementation Method 1
a secondary optical system for detecting electrons which have been generated through irradiation of the electron beam onto the sample
Implementation Method 2
a primary optical system for generating an electron beam having an irradiation area and irradiating the electron beam onto the sample
Implementation Method 3
charging an adsorption electrode facing and close to the sample surface with a polarity different from a charge polarity of the foreign matter and thereby electrostatically adsorbing the foreign matter which approaches the adsorption electrode
Data Source
AI summary
The electron beam apparatus is provided with a stage for mounting a sample thereon, a primary optical system for generating an electron beam having an irradiation area and irradiating the electron beam onto the sample, a secondary optical system for detecting electrons which have been generated through the irradiation of the electron beam onto the sample and have acquired structural information of the sample and acquiring an image of the sample about a viewing area and an irradiation area changing section for changing the position of the irradiation area with respect to the viewing area.