Acoustic Wave Damping for Multilayer Structure Quality Control
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Solution Overview
Problem
Conventional methods for measuring the quality of multilayer structures in semiconductor devices are either time-consuming, costly, or unable to detect small-scale irregularities and non-uniformities, limiting their effectiveness in quality assurance.
Innovation Solution
A method and apparatus that utilize an excitation light beam to generate an acoustic wave in a periodic structure, with a probe light beam detecting the damping rate of this wave to assess the structure's quality, allowing for the detection of small-scale irregularities and non-uniformities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If imaging techniques such as SEM are used to measure multilayer structure dimensions, then measurement contrast is improved, but measurement time increases and device complexity increases due to vacuum chamber requirements
Solution Approach 1:
The patent replaces mechanical imaging systems (SEM) with an optical-acoustic measurement system. A laser generates acoustic waves in the multilayer structure, and optical detection methods measure the acoustic signal. This substitution eliminates the need for vacuum chambers and complex mechanical imaging while providing rapid, non-contact measurement of layer dimensions and uniformity.
Solution Approach 2:
The patent changes the measurement parameter from direct optical imaging to acoustic wave frequency analysis. By measuring the frequency of acoustic waves generated in the structure, the system indirectly determines layer dimensions and uniformity. This parameter transformation enables rapid measurement without the time-consuming processes of conventional imaging.
2Productivity
If conventional acoustic wave frequency measurement is used to determine multilayer structure period, then measurement speed is improved, but detection capability for irregularities deteriorates
Solution Approach 1:
The patent introduces optical detection as an intermediary between the acoustic wave generation and measurement. The optical system detects acoustic wave characteristics (frequency, damping rate, amplitude) in the multilayer structure. This intermediary enables simultaneous measurement of average period through frequency analysis and detection of local irregularities through damping rate analysis, overcoming the limitations of conventional acoustic-only methods.
3Productivity
If faster measurement methods are used to improve productivity, then measurement time is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent utilizes the periodic nature of acoustic waves generated in the multilayer structure. By analyzing the temporal evolution of these periodic acoustic oscillations, the system extracts multiple quality parameters (frequency for average period, damping rate for uniformity, amplitude for interface quality). This periodic action enables comprehensive quality assessment in a single rapid measurement cycle, maintaining high precision while improving productivity.
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 provides a more accurate and efficient means to monitor the quality of multilayer structures by detecting damping rates, enabling the identification of irregularities and non-uniformities, thereby improving the quality control of semiconductor devices.
Implementation Method 1
The method includes illuminating the periodic structure through a first layer in the stack of layers with at least one excitation light beam. The excitation light beam excites an acoustic wave in the periodic structure.
Implementation Method 2
The method also includes illuminating the periodic structure with at least one probe light beam and detecting the at least one probe light beam, using a photodetector, after interaction with the periodic structure, as to generate a signal representing a damping rate of the acoustic wave.
Data Source
AI summary
Quality control of a periodic structure is performed using the damping rate of acoustic waves generated in the periodic structure. In this technique, an excitation light beam illuminates the first layer in the periodic structure to excite an acoustic wave. Possible irregularities in the periodic structure can scatter the acoustic wave, thereby increasing the damping rate of the acoustic wave. A sequence of probe light beams illuminates the periodic structure to measure the acoustic wave as a function of time to generated a temporal signal representing the damping rate of the acoustic signal. The acquired damping rate is employed to evaluate the quality of the periodic structure.