Nitride Semiconductor Wafer Crystallinity Control

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Solution Overview

Problem

Nitride semiconductor devices exhibit significant variation in electric characteristics due to dispersion in substrate surface crystallinity, leading to inconsistent performance across multiple devices produced from a single epitaxial wafer.

Innovation Solution

A nitride semiconductor epitaxial wafer with a substrate diameter of at least 50 mm and a nitride semiconductor layer thickness of at least 100 μm, where the in-plane dispersion of the full width half maximum (FWHM) of the X-ray rocking curve is controlled to be no more than 30% or 25%, ensuring uniform crystallinity and reduced n-type impurity incorporation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a nitride semiconductor epitaxial wafer is produced without controlling in-plane dispersion of FWHM, then manufacturing process is simpler, but electric characteristics vary significantly between devices

Engineering Contradiction:

Improveelectric characteristics consistencyVSAvoidin-plane dispersion of FWHM

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention controls the in-plane dispersion of FWHM within a specific range (not more than 30%) as a critical parameter to ensure uniform crystallinity across the substrate surface. This parameter control during epitaxial growth directly resolves the contradiction by maintaining reliable electric characteristics while managing manufacturing precision requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces subjective quality assessment with objective measurement systems. By using X-ray diffraction to measure FWHM values and quantifying in-plane dispersion numerically, the patent establishes an objective criterion (≤30% dispersion) that can be systematically controlled and measured, transitioning from mechanical/subjective quality control to precise instrumental measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If substrate diameter is increased to improve device yield, then more devices can be produced per wafer, but dispersion in crystallinity across the substrate surface increases

Engineering Contradiction:

Improvedevice yield per waferVSAvoidcrystallinity uniformity

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The invention establishes a quantitative threshold for in-plane FWHM dispersion (not more than 30%) that can be maintained even on large-diameter substrates (2 inches or more). This parameter control enables production of high-yield wafers with 50 mm or more diameter while preserving crystallinity uniformity across the entire substrate surface.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention divides the large-diameter substrate into multiple measurement regions to assess in-plane dispersion systematically. By measuring FWHM at multiple points across the substrate surface and calculating the dispersion percentage, the patent can verify that crystallinity uniformity is maintained across the entire large-area wafer, enabling higher device yield.

Inventive Principle:

Principle #1Segmentation

3Reliability

If epitaxial layer thickness is increased to improve device performance, then more n-type impurities are incorporated, but electric characteristics become less consistent

Engineering Contradiction:

Improvethreshold voltage stabilityVSAvoidn-type impurity amount

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention controls the in-plane dispersion of FWHM to not more than 30%, which ensures uniform crystallinity and consequently uniform n-type impurity incorporation throughout the epitaxial layer. This parameter control maintains consistent electric characteristics even when producing large-diameter wafers with substantial epitaxial layer thickness for high device yield.

Inventive Principle:

Principle #35Parameter changes

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 results in nitride semiconductor devices with decreased dispersion in electric characteristics, enhancing yield by stabilizing the threshold voltage and deep level amount of high electron mobility transistors, thereby improving the overall performance and consistency of nitride semiconductor devices.

Implementation Method 1

a full width half maximum of X-ray rocking curve in a predetermined plane is used

Methodology Applied

Scientific EffectX-ray diffraction: X-Ray

Implementation Method 2

full width half maximum (FWHM) of an X-ray rocking curve in the (002) plane or a (100) plane

Methodology Applied

Scientific EffectX-ray reflection: X-Ray

Data Source

PatentUS9293539B2Nitride semiconductor epitaxial wafer and nitride semiconductor device

Publication Date: 2016.03.22 SUMITOMO CHEM CO LTD

AI summary

A nitride semiconductor epitaxial wafer includes a substrate, and a nitride semiconductor layer formed on the substrate, the nitride semiconductor layer including a (002) plane in an upper surface thereof. An in-plane dispersion of a full width half maximum (FWHM) of an X-ray rocking curve in the (002) plane or a (100) plane of the nitride semiconductor layer is not more than 30%. The wafer is not less than 100 μm in thickness and not less than 50 mm in diameter.