Local Gas Flow Layout for Low-Scatter Semiconductor Inspection
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Solution Overview
Problem
Current semiconductor inspection systems face challenges in creating a vacuum environment for semiconductor inspection, as they struggle with non-specimen induced light scatter and foreign material contamination, which are exacerbated by the need for vacuum configurations that are difficult to maintain cleanliness and costly.
Innovation Solution
A system and method using two gas flow subsystems to create a local vacuum and purging air, respectively, to reduce light scatter and maintain cleanliness, employing helium or vacuum as the first medium and clean dry air or helium as the second medium to minimize light scatter and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large vacuum chamber is used to reduce air scattering, then light scattering is reduced, but tool size and cost increase
Solution Approach 1:
The patent divides the vacuum environment into segments: a small local vacuum volume between the objective and specimen, and a larger atmospheric volume elsewhere. This segmentation allows light scattering reduction only where needed while avoiding the cost and size of a complete vacuum chamber.
Solution Approach 2:
The patent applies vacuum conditions locally only in the critical inspection region between the objective and specimen, rather than throughout the entire tool. This local application of vacuum reduces air scattering where it affects measurement while minimizing overall system complexity.
2Object-affected harmful factors
If a vacuum chamber is used to reduce air scattering, then light scattering is reduced, but throughput decreases due to vacuum drawing time
Solution Approach 1:
The vacuum is applied only to the small local volume between objective and specimen rather than the entire tool, allowing for much faster vacuum establishment and wafer exchange times, thereby maintaining high throughput.
Solution Approach 2:
The patent applies vacuum only to the extent necessary for the inspection region, using partial vacuum action in a localized area rather than excessive vacuum throughout the entire system, reducing the time and energy required.
3Object-affected harmful factors
If a vacuum environment is used, then light scattering is reduced, but maintaining cleanliness becomes difficult
Solution Approach 1:
The patent introduces a gas flow subsystem that acts as an intermediary, introducing purging gas around the specimen to prevent particle contamination while the local vacuum reduces light scattering in the inspection region.
Solution Approach 2:
The patent uses an inert or clean gas atmosphere introduced around the specimen through the gas flow subsystem, creating a protective environment that prevents particle contamination while allowing vacuum to be applied in the inspection region.
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 system effectively reduces light scatter and maintains cleanliness, enhancing inspection sensitivity and throughput by minimizing the need for large vacuum chambers and reducing overhead time, while keeping the specimen clean.
Implementation Method 1
a first gas flow subsystem configured for replacing a gas in a first local volume surrounding the area on the specimen with a first medium that scatters less of the light than the gas
Implementation Method 2
a second gas flow subsystem configured for replacing the gas in a second local volume proximate the first local volume with a second medium different than the first medium
Data Source
AI summary
Methods and systems for inspecting a specimen are provided. One system includes an inspection subsystem configured for directing light to an area on the specimen and for generating output responsive to light from the area on the specimen. The system also includes a first gas flow subsystem configured for replacing a gas in a first local volume surrounding the area on the specimen with a first medium that scatters less of the light than the gas. In addition, the system includes a second gas flow subsystem configured for replacing the gas in a second local volume proximate the first local volume with a second medium different than the first medium. The system further includes a computer subsystem configured for detecting abnormalities on the specimen based on the output.