Wafer-Chuck Alignment Using Pressure-Sensitive Test Wafer Marks
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Solution Overview
Problem
There is a need for a system and method to achieve proper wafer-chuck alignment in semiconductor process tools without a pre-aligner, as existing methods are inadequate for ensuring accurate centering and angular orientation of wafers.
Innovation Solution
A system utilizing a test wafer with pressure-sensitive features that are marked by pins of the chuck, combined with a measurement device and cameras to determine a misalignment vector by comparing the marked features to nominal features, allowing for precise adjustment of subsequent wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pre-aligner is incorporated into a wafer metrology tool, then wafer centering and angular orientation are improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the alignment measurement function from complex pre-aligner hardware and relocates it to a separate, simpler measurement device. The test wafer with pressure-sensitive features is removed from the process tool and measured independently, separating the measurement function from the processing function.
Solution Approach 2:
The invention uses a test wafer as a copy or surrogate to measure chuck alignment characteristics. Instead of measuring the actual production wafer on the complex pre-aligner, a dedicated test wafer with pressure-sensitive features is used to capture pin locations and transfer this alignment information back to the process tool.
2Device complexity
If no pre-aligner is used in a process tool, then device complexity is reduced, but wafer-chuck alignment precision deteriorates
Solution Approach 1:
The invention introduces an intermediary measurement device and test wafer system that mediates between the simple process tool and the alignment requirement. The measurement device acts as an intermediary that captures alignment data using pressure-sensitive features and provides correction information, enabling precise alignment without complex pre-aligner hardware.
Solution Approach 2:
The invention performs preliminary alignment measurement using a dedicated test wafer before actual production wafer processing. The test wafer with pressure-sensitive features is placed on the chuck to pre-measure pin locations and determine misalignment vectors, allowing correction data to be established in advance.
3Measurement precision
If pressure-sensitive features are used to mark pin locations, then alignment measurement capability is improved, but test wafer complexity increases
Solution Approach 1:
The invention uses pressure-sensitive features that exhibit visual changes (such as color changes or deformations) when contacted by chuck pins. This allows the pin contact locations to be captured and measured through optical means, transforming mechanical contact information into visually detectable signals without complex sensors.
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 accurate alignment of wafers on the chuck by determining and correcting misalignment vectors, ensuring proper positioning and orientation, even in the absence of a pre-aligner.
Implementation Method 1
a test wafer including a plurality of pressure-sensitive features distributed across the test wafer, wherein a respective pressure-sensitive features is markable by a respective pin of a plurality of pins of the chuck
Implementation Method 2
the controller is configured to direct the plurality of cameras of the measurement device to acquire a plurality of calibration images of the plurality of nominal measurement features of the plate of the measurement device
Data Source
AI summary
A wafer-chuck alignment system includes a measurement device including a set of cameras and a feature plate including nominal measurement features. The nominal measurement features correspond to the nominal locations of the pins of a chuck of a process tool to be characterized. A robot is configured to transfer a test wafer between the chuck of a process tool and the measurement device. The test wafer includes pressure-sensitive features distributed across the test wafer which are markable by the pins of the chuck. Once the test wafer is marked by the chuck pins and imaged by the cameras of the measurement device, a controller is configured to determine a misalignment vector between the test wafer and the chuck by comparing measurement images of markings formed on the pressure-sensitive features of the test wafer to calibration images of the nominal measurement features of the feature plate of the measurement device.