Modulated Optical Reflectance Depth Profiling for Semiconductor Metrology
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Solution Overview
Problem
Current methods for depth profiling of semiconductor wafers, particularly for continuously inhomogeneous electronic properties, are inadequate as they are either destructive, non-destructive but inaccurate, or fail to provide reliable and sensitive enough techniques for modern semiconductor manufacturing needs.
Innovation Solution
The development of a modulated optical reflectivity (MOR) method that uses varying experimental parameters such as lateral beam offsets, modulation frequencies, and wavelengths to reconstruct depth profiles, combining parameter-based and full forward and inverse problem approaches for accurate characterization of thermal and electronic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional depth profiling methods are used, then some measurement capability is achieved, but the methods are either destructive, non-destructive but inaccurate, or fail to provide reliable and sensitive enough techniques
Solution Approach 1:
The patent applies parameter changes by systematically varying multiple experimental parameters including pump beam modulation frequency, probe beam wavelength, and lateral beam offset distances. This multi-parameter approach enables the extraction of depth profile information with high accuracy and reliability, resolving the contradiction between measurement precision and reliability that plagues conventional single-parameter methods
Solution Approach 2:
The patent introduces additional measurement dimensions by combining multiple MOR measurements taken at different lateral beam offsets, modulation frequencies, and wavelengths. This multi-dimensional data acquisition approach transforms insufficient one-dimensional measurements into comprehensive depth profile information, achieving both high precision and reliability
2Measurement precision
If single-parameter MOR measurements are used, then measurement simplicity is maintained, but depth profile reconstruction accuracy is insufficient
Solution Approach 1:
The patent systematically varies experimental parameters (modulation frequency, wavelength, lateral offset) to extract multiple independent measurements. This parameter-based approach enables accurate depth profile reconstruction while maintaining a relatively simple optical setup, resolving the contradiction between measurement precision and device complexity
3Measurement precision
If destructive methods are used for depth profiling, then accurate depth information can be obtained, but the sample is damaged and cannot be used for further analysis
Solution Approach 1:
The patent replaces destructive mechanical or chemical analysis methods with non-destructive optical MOR measurements. By using photothermal and plasma wave detection, the system obtains accurate depth profile information without physically altering or damaging the semiconductor sample, eliminating the contradiction between measurement accuracy and sample integrity
4Measurement precision
If conventional MOR measurements are used, then measurement speed is maintained, but sensitivity and precision for modern semiconductor manufacturing needs are insufficient
Solution Approach 1:
The patent uses periodic modulation of the pump beam at optimized frequencies to generate detectable plasma and thermal waves. This periodic action enhances the sensitivity of the MOR signal, enabling high-precision measurements that meet modern semiconductor manufacturing requirements while maintaining efficient measurement throughput through optimized modulation parameters
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 fast, reliable, and non-destructive depth profiling of semiconductor wafers, providing accurate information on parameters like carrier concentration, damage, and thermal diffusivity, overcoming the limitations of existing techniques by enhancing sensitivity and precision in semiconductor metrology.
Implementation Method 1
an intensity modulated pump laser beam is focused on the sample surface for periodically exciting the sample. In the case of a semiconductor, thermal and plasma waves are generated in the sample that spread out from the pump beam spot
Implementation Method 2
a second laser is provided for generating a probe beam of radiation. This probe beam is focused collinearly with the pump beam and reflects off the sample. A photodetector is provided for monitoring the power of reflected probe beam
Data Source
AI summary
Methods of obtaining dopant and damage depth profile information are disclosed using modulated optical reflectivity (MOR) measurements. In one aspect, the depth profile is constructed using information obtained from various measurements such as the junction depth, junction abruptness and dopant concentration. In another aspect, a full theoretical model is developed. Actual measurements are fed to the model. Using an iterative approach, the actual measurements are compared to theoretical measurements calculated from the model to determine the actual depth profile.