Complex Sensing Device for Simultaneous Wafer Thickness and Shape Measurement
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Solution Overview
Problem
Current thickness and surface shape sensing technologies face challenges in simultaneously measuring the thickness and surface shape of a wafer from its surface to an interface with high precision, particularly in laser pump-probe systems, where accurate reflectance changes and time-of-flight differences are crucial but difficult to accurately capture.
Innovation Solution
A complex sensing device is developed, incorporating a pulse generator to produce probe and pump pulses, optical splitters to split and direct these pulses, and detectors to process signals for thickness and surface shape measurements. The device utilizes phase differences between split pulses to determine surface shape and reflectance changes to calculate thickness, enabling simultaneous acquisition of surface information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser pump-probe system is used to measure thickness and surface shape, then non-contact sensing is achieved, but simultaneous high-precision measurement of both thickness and surface shape is difficult
Solution Approach 1:
The sensing device is divided into two independent but coordinated subsystems: a thickness sensing device that measures thickness using reflectance changes, and a surface shape sensing device that measures surface shape using phase detection. Each subsystem is optimized for its specific measurement task, allowing both measurements to be performed simultaneously with high precision without requiring a single complex system to handle both functions
Solution Approach 2:
The system uses a single laser source that generates both pump pulses and probe pulses, which are then split into multiple paths to serve different sensing functions. The optical splitters and beam combiners enable the same light source to simultaneously perform thickness measurement (via reflectance detection) and surface shape measurement (via phase detection), achieving multi-functionality from a single laser system
2Productivity
If separate measurement systems are used for thickness and surface shape, then measurement accuracy is maintained, but measurement efficiency decreases
Solution Approach 1:
The thickness sensing device and surface shape sensing device are merged into a single integrated sensing system that shares common components including the laser source, optical splitters, and detector. The system simultaneously processes both thickness measurement (based on reflectance changes) and surface shape measurement (based on phase differences) through coordinated signal processing, achieving both high efficiency and high accuracy in a single measurement operation
3Measurement precision
If phase detection is used for surface shape measurement, then surface shape accuracy is improved, but the complexity of signal processing increases
Solution Approach 1:
The system uses optical splitters and beam combiners as intermediary components to separate and recombine light paths for different measurement functions. The phase detection process is facilitated by introducing reference beams through the optical splitters, which serve as intermediaries to enable accurate phase difference measurement without requiring complex direct measurement techniques
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 allows for precise and simultaneous measurement of thickness and surface shape, improving the accuracy and efficiency of sensing by leveraging phase detection and reflectance changes, thereby overcoming previous limitations in laser pump-probe systems.
Implementation Method 1
The pump pulse generates ultrasonic waves in an object such as a wafer. The probe pulse is affected by the ultrasonic waves, and a reflectance change occurs on the wafer surface.
Implementation Method 2
measure a surface shape of the sample based on a phase difference between the split probe pulse and the split reflection probe pulse
Data Source
AI summary
Provided is a complex sensing device including a thickness sensing device including pulse generating device configured to generate a probe pulse and a pump pulse, a first optical splitter configured to split the probe pulse and direct the pump pulse to a surface of a sample and generate an acoustic signal in the sample, a detector configured to receive a reflection probe pulse generated by the probe pulse being reflected from the sample, a first processor configured to receive and process a first signal from the detector, and a second optical splitter on a path of the reflection probe pulse from the sample to the detector, the second optical splitter being configured to split the reflection probe pulse, and a surface shape sensing device configured to receive a split probe pulse split from the first optical splitter and a split reflection probe pulse split from the second optical splitter, and measure a surface shape of the sample based on a phase difference between the split probe pulse and the split reflection probe pulse.