Wafer Chuck Edge-Light Alignment for Precise Positioning
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Solution Overview
Problem
Current wafer alignment methods in semiconductor processing are limited by the precision of pre-aligners and wafer transport mechanisms, which can result in inaccuracies in determining the rotational and translational position of wafers, especially in modern photolithography where die locations need to be precise to within a few thousandths of an inch.
Innovation Solution
A method and apparatus that utilize a light-sensitive element to detect light passing through the edge of a wafer, allowing for precise determination of the wafer's position and orientation by generating detection signals, which are then used to control the alignment of the wafer on a receptacle, potentially eliminating the need for pre-alignment tools and improving alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-aligners and wafer transport mechanisms are used for wafer alignment, then wafer alignment can be achieved, but alignment precision is limited to within a degree of rotation and a few thousandths of an inch
Solution Approach 1:
The patent replaces mechanical alignment systems (pre-aligners and transport mechanisms) with an optical detection system. A light source illuminates the wafer edge, and a sensor detects the light pattern to determine wafer position and orientation. This substitution eliminates mechanical complexity while achieving superior alignment precision beyond what mechanical systems can provide.
Solution Approach 2:
The patent introduces light as an intermediary between the wafer and the detection system. The light passes through or reflects off the wafer edge, carrying information about the wafer's position and orientation. This optical intermediary enables non-contact, high-precision measurement without the limitations of mechanical systems.
2Measurement precision
If pre-alignment tools are used, then wafer alignment is achieved, but time and space are consumed in clean room environments
Solution Approach 1:
The patent extracts the alignment function from separate pre-alignment tools and integrates it directly into the processing system. The light source and sensor are positioned to work in-line with the wafer processing, eliminating the need for separate pre-alignment equipment and the time it would consume.
Solution Approach 2:
The patent combines the alignment detection function with the wafer processing system. The same optical path used for processing also performs alignment measurement, merging two functions into one system and eliminating redundant time and equipment.
3Loss of information
If radial measurements are taken to determine wafer position, then alignment information is obtained, but measurement precision is limited by transport mechanism precision
Solution Approach 1:
The patent replaces mechanical radial measurement systems with optical detection. Instead of using the transport mechanism's precision to determine position, the system uses light patterns at the wafer edge to directly measure position and orientation with higher precision, independent of mechanical transport accuracy.
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 approach enhances the precision of wafer alignment, reducing the need for pre-alignment tools and saving time and space in clean room environments, while enabling more accurate positioning for subsequent processing steps such as cutting or edge processing.
Implementation Method 1
shining a light on an edge of the wafer... based on light that passed the edge of the wafer
Data Source
AI summary
In an embodiment a method includes placing a wafer on a receptacle comprising a chuck base, wherein a light port for emitting light from a source of light is an opening located in a surface of the chuck base, and wherein the light port is located underneath the wafer, shining the light from the light port at an edge of the wafer so that light passes by the edge of the wafer and processing the wafer on the receptacle based on the light that passed by the edge of the wafer and that is received by a light sensitive element.