Folding Mirror Optical Path for Large Wafer Measurement
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Solution Overview
Problem
Existing semiconductor wafer measuring tools become excessively large and costly when scaled up to accommodate larger wafers, such as from 300 mm to 450 mm, making them physically unsuitable for existing facilities and prone to vibrational distortion.
Innovation Solution
A compact optical arrangement using mirrors to redirect the interferometric image along axes parallel to the wafer surface, allowing the optical path to be extended along the length of the tool, enabling the use of larger optics while maintaining a compact and stable measuring tool design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the measuring tool is scaled up to accommodate larger wafers (from 300 mm to 450 mm), then the measurement capability for larger wafers is improved, but the size of the measuring tool increases significantly (fifty percent larger in every direction) and the cost increases
Solution Approach 1:
The patent introduces a folding mirror system that redirects the optical path along an axis parallel to the wafer surface, effectively extending the optical path length without increasing the physical footprint of the tool in the vertical dimension. This allows the tool to accommodate larger 450 mm wafers while maintaining a compact size suitable for existing facilities.
2Adaptability or versatility
If the measuring tool is scaled up to accommodate larger wafers, then the measurement capability for larger wafers is improved, but the cost of the measuring tool increases significantly
Solution Approach 1:
By utilizing the horizontal dimension through folding mirrors, the patent avoids the need to scale up all dimensions of the tool, thereby reducing the cost of optical components, mechanical structures, and overall system complexity while maintaining the capability to measure larger wafers.
3Adaptability or versatility
If the size of the measuring tool is increased to accommodate larger wafers, then the measurement capability is improved, but the tool becomes more prone to vibrational distortion
Solution Approach 1:
The folding mirror configuration extends the optical path horizontally rather than vertically, creating a more compact tool that is less susceptible to vibrational distortion. The shorter vertical dimension reduces the leverage effect of vibrations, improving measurement reliability while maintaining the capability to measure larger wafers.
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
Enables measurement of larger semiconductor wafers within the constraints of existing facilities, reducing the size and cost of the measuring tool while minimizing vibrational distortion and allowing for improved stability and efficiency.
Implementation Method 1
mirrors for reflecting an interferometric image from a first axis normal to a surface of the semiconductor wafer to a second axis parallel to the first axis
Implementation Method 2
two channels of interferometers are employed to measure both surfaces of the wafer
Data Source
AI summary
A semiconductor measuring tool has a folding mirror configuration that directs a light beam to pass the same space multiple times to reduce the size and footprint. Furthermore, the folding mirrors may reflect the light beam at less than forty-five degrees; thereby allowing for smaller folding mirrors as compared to the prior art.