Vacuum Microscope Objective Assembly Design
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Solution Overview
Problem
Existing methods for inspecting semiconductor wafers in evacuated or low-pressure chambers face challenges due to space constraints and contamination risks from electronic components within the vacuum environment.
Innovation Solution
A microscope design where the optical objective assembly is located partially or fully within the evacuated volume, with an image sensor outside the chamber, using a transparent window or relay lens train to convey radiation, allowing for improved positioning and image quality without degrading the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electronic parts are included inside the vacuum chamber for wafer inspection, then inspection capability is achieved, but space is consumed and contamination risk increases
Solution Approach 1:
The patent extracts the image sensor from the vacuum chamber environment and places it outside, while keeping the optical objective assembly inside. This separation removes the problematic electronic components from the vacuum space, freeing up chamber volume while preserving inspection functionality through optical coupling via a transparent window.
2Adaptability or versatility
If electronic parts are included inside the vacuum chamber for wafer inspection, then inspection capability is achieved, but contamination risk increases
Solution Approach 1:
The image sensor, which is susceptible to vacuum damage and potential contamination source, is extracted from the vacuum chamber and positioned externally. The optical coupling through a transparent window allows the sensor to remain outside the vacuum environment, eliminating contamination risks while maintaining full inspection capability.
3Object-affected harmful factors
If the optical objective assembly is located completely outside the evacuated volume, then contamination risk is reduced, but positioning freedom and image quality deteriorate
Solution Approach 1:
The optical system is segmented into two parts: the optical objective assembly which requires vacuum proximity for optimal positioning and image quality, and the image sensor which remains outside the vacuum. A transparent window separates these segments, allowing the objective to operate in the evacuated volume while the sensor operates in ambient conditions.
4Ease of operation
If a window is placed after the objective to transfer radiation, then the sensor can be located outside the chamber, but image degradation may occur
Solution Approach 1:
A transparent window serves as an intermediary element between the vacuum chamber interior and exterior optical paths. It allows radiation to pass through while separating the vacuum and ambient environments. The window is positioned and designed to minimize optical degradation while enabling the sensor to be located outside the chamber for easier operation and protection.
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 enhances image quality, allows for easier manipulation of the objective, and supports the use of objectives with different magnifications and resolutions, while minimizing contamination risks and image distortion.
Implementation Method 1
The optical objective assembly collects radiation from a region on the surface and, typically, focuses the radiation to a primary image
Implementation Method 2
The sensor optics focus the primary image to a secondary image on the image sensor
Data Source
AI summary
A microscope for inspecting a surface in an evacuated volume, including an optical objective assembly which is located in the evacuated volume in proximity to the surface. The assembly is arranged to collect and convey radiation from the surface while focusing the radiation so as to form an image of the surface. The microscope further includes a sensor, located in a space outside the evacuated volume, which is arranged to receive the radiation conveyed from the optical objective assembly so as to generate a signal corresponding to the image.