Wafer Surface Height Sensing in Laser Dicing Optics
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Solution Overview
Problem
Existing laser processing apparatuses face challenges in accurately measuring the upper surface height of wafers due to insufficient reflection of detection light, particularly when the kind and surface state of the wafer vary, affecting the precision of wafer division into individual device chips.
Innovation Solution
The apparatus incorporates a wide wavelength band detection light source with a selector that chooses a specific wavelength for detection light, using band-pass filters to optimize reflection, and a dual optical path system with light receiving elements to compare the intensity of reflected light, ensuring accurate measurement of the wafer's upper surface position regardless of its type or surface state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength detection light source is used, then the measurement system is simple, but the measurement precision deteriorates when wafer surface state varies
Solution Approach 1:
The detection light source is designed to emit multiple wavelengths simultaneously, enabling the system to adapt to different wafer types and surface states without changing the light source itself. This multi-wavelength capability allows the same detection system to universally handle various measurement conditions.
Solution Approach 2:
The system changes the wavelength parameter of the detection light based on the measured object characteristics. By selecting appropriate wavelengths from the multi-wavelength light source according to wafer surface state, the measurement precision is optimized for different conditions.
2Adaptability or versatility
If detection light with fixed wavelength is used, then the device structure is simple, but the adaptability to different wafer kinds deteriorates
Solution Approach 1:
The detection light source具备 multi-functionality by emitting multiple wavelengths, allowing the system to adapt to different wafer kinds and surface states without requiring multiple separate light sources or complex switching mechanisms.
Solution Approach 2:
The system dynamically selects and utilizes appropriate wavelengths from the multi-wavelength light source based on the specific wafer characteristics being measured, enabling flexible adaptation to varying measurement conditions.
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 solution enables precise measurement of the wafer's upper surface height, allowing for proper positioning of the laser beam and effective division into device chips, irrespective of the wafer's kind and surface state, thereby enhancing the accuracy and reliability of the laser processing.
Implementation Method 1
calculates the upper surface position of the wafer by reflected light arising from reflection at the upper surface of the wafer
Implementation Method 2
a beam condenser that condenses the laser beam emitted by the laser oscillator and positions a condensed point to the wafer held by the chuck table
Data Source
AI summary
A laser processing apparatus includes a laser oscillator that emits a laser beam, a beam condenser that condenses the laser beam emitted by the laser oscillator and positions the condensed point to a wafer, a condensed point position adjuster that is disposed between the laser oscillator and the beam condenser and adjusts the position of the condensed point, and an upper surface position detector that detects the upper surface position of the wafer. The upper surface position detector includes a detection light source that emits detection light of a wide wavelength band and a selector that selects detection light with a specific wavelength from the detection light emitted by the detection light source.