Multi-Wavelength Pump-Probe Profiling for 3D Wafer Depth Analysis
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Solution Overview
Problem
Existing pump-probe techniques for depth profiling of nanostructures are limited by the inherent coupling between optical and acoustic properties, hindering effective 3D profiling of nanostructures.
Innovation Solution
An optical system using multiple probe pulses with different wavelengths, combined with a lock-in amplifier and optical setup, to decouple optical and acoustic properties, allowing for the extraction of structural information from regions deep below the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard pump-probe technique is used, then depth information with high resolution can be obtained, but effective 3D profiling of nanostructures is limited due to coupling between optical and acoustic properties
Solution Approach 1:
The invention segments the measurement process by using multiple probe pulses with different wavelengths. Each wavelength provides independent information about either optical or acoustic properties, allowing the system to separate and independently measure these coupled properties. This segmentation enables effective 3D profiling by decoupling the previously intertwined measurements.
Solution Approach 2:
The invention changes the parameter of probe pulse wavelength to achieve decoupling. By varying the wavelength of probe pulses, the system can selectively probe different properties (optical vs acoustic) at different depths, thereby resolving the coupling limitation and enabling comprehensive 3D nanostructure profiling.
2Adaptability or versatility
If multiple probe pulses with different wavelengths are used, then optical and acoustic properties can be decoupled, but system complexity increases
Solution Approach 1:
The invention merges multiple probe pulses with different wavelengths into a single optical path that targets the same sample region. This combining approach allows simultaneous acquisition of multiple wavelengths' data without requiring separate measurement setups, thereby reducing overall system complexity while maintaining the decoupling capability.
Solution Approach 2:
The optical system is designed with multi-functionality to handle multiple wavelengths through a single integrated path. The same optical components and detection system process all wavelengths, making the system universal rather than requiring wavelength-specific setups for each measurement, thus reducing complexity.
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 in-depth 3D profiling of nanostructures by effectively separating optical and acoustic properties, providing improved structural information and overcoming limitations of standard methods like SEM.
Implementation Method 1
an ultrashort light pulse (usually referred to as a 'pump pulse') may be projected and partially absorbed on an external or internal surface of a structure. A thin tranche of the structure, adjacent to and including the absorbing surface, is heated by absorbing the light pulse
Implementation Method 2
Due to the heating thereof, the tranche expands, leading to the formation of an acoustic pulse
Implementation Method 3
the formation of an acoustic pulse (also referred to as an 'elastic strain pulse' or 'strain pulse'), which travels into the depth of the structure and away from the external surface. On reaching a boundary surface, such as the opposite side of a thin film or a second layer of a multi-layered structure, at least part of the acoustic pulse is reflected
Implementation Method 4
A probe signal is projected on the structure such as to be incident thereon when the acoustic pulse arrives thereat. The probe signal reflected off the structure and the intensity of the reflected component of the probe signal is monitored
Data Source
AI summary
A systems for in-depth profiling of patterned wafer samples including a pump pulse and plurality of probe pulses each having a different wavelength (λ1-λn), and an optical setup configured to combine the plurality of probe pulses, such that they simultaneously reach the same target region of the sample and to separate the plurality of probe pulses upon their reflection from the sample, such that each of the plurality of probe pulses is detected by a separate detector.