Non-destructive AFM Tapping Mode Defect Density Measurement

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Solution Overview

Problem

Current methods for characterizing crystal defects in heteroepitaxial semiconductor materials, such as III-V compound semiconductors and germanium, are destructive and limited in measuring low defect densities, making it difficult to employ them as in-line process control metrology.

Innovation Solution

A non-destructive method using an atomic force microscope (AFM) operating in tapping mode to scan the topmost surface of the semiconductor material stack, allowing for the measurement of crystal defects like threading and stacking faults, which are visible as surface displacements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Plan-view transmission electron microscopy (PV-TEM) is used to measure defect density, then measurement precision is improved, but the method becomes destructive and cannot be used for in-line process control

Engineering Contradiction:

Improvedefect density measurement precisionVSAvoidnon-destructive capability for in-line control

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the destructive mechanical/electrical transmission electron microscopy system with a non-destructive optical interference measurement system. The optical system uses light interference patterns to detect surface height variations caused by defects, eliminating the need for destructive sample preparation and enabling in-line process control while maintaining measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an optical interference field as an intermediary between the measurement system and the semiconductor surface. By using light waves as a mediator, the system can detect defect-induced surface height changes without direct physical contact or destruction of the sample, resolving the contradiction between precision measurement and non-destructive requirement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If PV-TEM is used to characterize defects, then defect types can be understood, but the small imaging area limits the ability to measure lower defect densities reliably

Engineering Contradiction:

Improvedefect type characterizationVSAvoidimaging area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent segments the measurement process into two components: defect detection through optical interference patterns that reveal defect types, and defect density measurement through statistical analysis of multiple measurement points across a large area. This segmentation allows the system to maintain defect type characterization capability while expanding the effective measurement area to reliably detect low defect densities.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from the two-dimensional imaging plane of PV-TEM to a three-dimensional surface height measurement approach using optical interference. By measuring surface height variations in the vertical dimension, the system can detect defects across a much larger area while maintaining the ability to characterize defect types through their distinct interference patterns.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Measurement precision

If etching methods are used on heteroepitaxial semiconductor materials, then defect density can be assessed, but the method is not applicable to III-V compound semiconductors and germanium on Si substrate

Engineering Contradiction:

Improvedefect density assessmentVSAvoidapplicability to different semiconductor material systems

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent develops a universal optical interference measurement system that can assess defect density across different semiconductor material systems (III-V compounds, germanium, silicon) without requiring material-specific etching processes. The non-destructive optical method provides multi-functional capability to handle diverse materials, resolving the limitation of etching method applicability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 the reliable measurement of crystal defects with densities below 10^5 defects per square centimeter, providing a cost-effective and etch-free method for in-line process control in semiconductor manufacturing.

Implementation Method 1

a topmost surface of the second semiconductor material is scanned using atomic force microscope (AFM) operating in a tapping mode

Methodology Applied

Scientific EffectAtomic force microscopy: Scanning Probe Microscopy

Data Source

PatentUS9368415B1Non-destructive, wafer scale method to evaluate defect density in heterogeneous epitaxial layers

Publication Date: 2016.06.14 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A semiconductor material stack of, from bottom to top, a first semiconductor material having a first lattice constant and a second semiconductor material having a second lattice constant that may or may not differ from the first lattice constant and is selected from an III-V compound semiconductor and germanium is provided. The second semiconductor material of the semiconductor material stack is then scanned using an atomic force microscope (AFM) operating in a tapping mode to provide an AFM image of the second semiconductor material of the semiconductor material stack. The resultant AFM image is then analyzed and crystal defects at a topmost surface of the second semiconductor material of the semiconductor material stack can be measured.