Surface Inspection Device Vertical Adjustment
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Solution Overview
Problem
In surface inspection devices for semiconductor manufacturing, the challenge is to maintain high inspection sensitivity and throughput while ensuring accurate positional control of the sample surface during high-speed rotation, especially when using image detection optical systems with shallow focal depth.
Innovation Solution
The solution involves a surface inspection device equipped with a sample-driving unit that includes a vertical driving stage and a sample-driving unit capable of precise vertical adjustments. During rotation, the controller calculates and applies adjustment amounts in the vertical direction based on detected in-plane positions and vertical positions, ensuring the sample surface remains within the focal depth of the detection optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wavelength of laser light is shortened to improve inspection sensitivity, then detection performance improves, but the focal depth becomes shallow making it difficult to maintain focus during sample rotation
Solution Approach 1:
The patent implements dynamic focal adjustment by varying the focal position during sample rotation. The focal position is adjusted based on the rotation angle to compensate for centrifugal force effects, allowing the system to maintain focus throughout the rotation cycle despite the shallow focal depth inherent to short-wavelength imaging systems.
Solution Approach 2:
The system uses feedback from rotation angle sensors and position detection to continuously adjust the focal position. The controller receives information about the current rotation state and modifies the focal position accordingly, creating a closed-loop control system that maintains optimal focus during high-speed rotation.
2Productivity
If the sample rotation speed is increased to improve throughput, then inspection speed improves, but centrifugal force causes deformation of the sample-holding unit affecting focal position
Solution Approach 1:
The system performs preliminary adjustment of the focal position based on the detected rotation angle before the actual inspection at that position. By pre-compensating for the expected centrifugal deformation at each rotation angle, the system ensures the sample surface remains within the focal depth range throughout the inspection process.
Solution Approach 2:
The patent changes the focal position parameter dynamically during rotation based on the rotation angle. The focal position is adjusted as a function of rotation angle to compensate for centrifugal force effects, allowing high rotation speeds to be maintained while preserving focus accuracy.
3Productivity
If the sample is held at high rotation speed to improve throughput, then inspection speed improves, but vibration and warpage affect positional accuracy
Solution Approach 1:
The system dynamically adjusts the focal position in real-time during high-speed rotation to track and compensate for vibrations and warpage. By continuously varying the focal position based on rotation angle and detected position, the system maintains focus despite the dynamic disturbances caused by high-speed rotation.
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 enables stable sample holding and high-accuracy positional control during high-speed rotation, effectively maintaining inspection sensitivity and throughput by ensuring the sample surface remains focused within the detection optical system.
Implementation Method 1
a displacement sensor configured to detect a height of the sample
Implementation Method 2
When a foreign substance or a defect on the sample surface is irradiated with laser light, the laser light scatters
Implementation Method 3
the centrifugal force acts on the sample-holding unit, resulting in deformation of the sample-holding unit in a direction in which the height of the center of gravity coincides with the height of the position where the sample-holding unit is fixed
Data Source
AI summary
Provided is a surface inspection device 1 comprising a sample-driving unit 4 that stably holds a sample 2 irrespective of a rotation angle and that can precisely control the position of the sample 2 relative to vertical-direction driving. The sample-driving unit 4 has a support member 4a that holds the sample 2 and that can displace a sample-holding unit 3 in the vertical direction, and a sample drive source 4b that generates drive force for driving the sample 2. Based on the in-plane position and vertical-direction position of the sample 2 as sensed by a displacement sensor 10 while a spindle shaft 5 is rotating, a controller 13 calculates a different vertical-direction adjustment amount for each in-plane position of the sample 2 and drives the sample 2 by a first adjustment amount in the vertical direction by using a vertical driving stage 6. The sample-driving unit 4 drives the sample 2 in the vertical direction by a second adjustment amount smaller than the first adjustment amount.