Multi-Wavelength Interferometry for Shallow Depth Profiling

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Solution Overview

Problem

Existing methods for determining the depth profile of surface structures, such as semiconductor layers, using interferometric effects face limitations in precision and accuracy, especially for shallow depths, due to the reliance on single wavelengths and the inability to effectively control etching processes with high precision.

Innovation Solution

The method involves irradiating the surface structure with light components of different wavelengths to generate trend curves, using light component weighting factors determined through principal component analysis to optimize the occurrence of extreme values and turning points, thereby enhancing precision and compensating noise and drift components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If single wavelength light is used for interferometric measurement, then the measurement system is simple, but the measurement precision for shallow depths is insufficient

Engineering Contradiction:

Improvedepth profile determination precisionVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the measurement process by using multiple discrete wavelength components instead of a continuous spectrum. Each wavelength provides independent interferometric measurements that are combined to achieve high precision depth profiling, particularly for shallow depths where single wavelength methods fail.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from single-wavelength (one-dimensional) interferometry to multi-wavelength (multi-dimensional) interferometry. By adding the wavelength dimension to the measurement space, the system achieves enhanced sensitivity and precision for shallow depth measurements without proportionally increasing system complexity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If multiple wavelengths are used to improve precision, then the measurement accuracy increases, but the signal-noise ratio deteriorates

Engineering Contradiction:

Improvedepth profile determination precisionVSAvoidnoise and drift components

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements feedback through iterative optimization of wavelength combinations. The system analyzes interferometric signals from multiple wavelengths, identifies noise and drift patterns, and adjusts the weighting of different wavelength components to maximize signal quality and minimize noise impact in the final depth profile.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent creates a composite measurement signal by combining interferometric data from multiple wavelength components. Each wavelength contributes specific information, and their weighted combination produces a composite signal that enhances precision while allowing noise filtering through the complementary nature of different wavelength responses.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If traditional interferometric methods are used, then the system is easy to operate, but the control precision of surface structure formation is insufficient

Engineering Contradiction:

Improvesurface structure formation control precisionVSAvoidmeasurement and control operation simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent enables self-service operation through automated multi-wavelength interferometric analysis. The system automatically processes signals from multiple wavelengths, performs depth profile calculations, and provides real-time feedback for surface structure formation control without requiring complex manual intervention, maintaining ease of operation while achieving high manufacturing precision.

Inventive Principle:

Principle #25Self-service

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 allows for high-precision depth profile determination with improved signal-noise ratio, enabling better control of surface structure formation and reducing the distance to target depth, even for shallow profiles, without the need for expensive hardware modifications.

Implementation Method 1

determining a depth profile of a surface structure using interferometric effects

Methodology Applied

Scientific EffectInterferometric effects: Interference

Implementation Method 2

The irradiation light is reflected at the surface structure, thereby (at least partially) being converted into reflection light

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7812966B2Method of determining the depth profile of a surface structure and system for determining the depth profile of a surface structure

Publication Date: 2010.10.12 INFINEON TECHNOLOGIES AG

AI summary

According to one embodiment of the present invention, a method of determining the depth profile of a surface structure includes: irradiating the surface structure with irradiation light including light components of different wavelengths; and determining the depth profile of the surface structure in dependence on interferometric effects caused by the reflection of the irradiation light at the surface structure.