Nitride Semiconductor Buffer Layer Oxygen Flow Control

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Solution Overview

Problem

Conventional methods for manufacturing nitride semiconductor elements result in buffer layers with polycrystalline or amorphous states, leading to suboptimal crystallinity of the nitride semiconductor layers.

Innovation Solution

A method involving the sequential lamination of a first nitride semiconductor layer of single crystals AlxGa1-xN on a sapphire substrate using metal organic chemical vapor deposition, where oxygen is supplied initially to stabilize the layer, and then reduced or stopped to improve crystallinity, followed by the growth of a second nitride semiconductor layer with a flat crystal surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oxygen is supplied at high flow rate to stably grow the buffer layer, then the buffer layer can be stably grown with proper polarity, but the crystallinity of the nitride semiconductor layer deteriorates due to polycrystalline or amorphous state formation

Engineering Contradiction:

Improvestability of buffer layer growthVSAvoidcrystallinity of nitride semiconductor layer

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The buffer layer growth process is divided into two distinct stages: a first stage with high oxygen flow rate to establish stable growth and proper polarity, and a second stage with reduced or zero oxygen flow rate to improve crystallinity. This segmentation allows each stage to optimize for its specific purpose without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first stage of buffer layer growth with high oxygen supply performs a preliminary action to establish stable growth conditions and correct polarity orientation. This preliminary stabilization enables the second stage to focus on improving crystallinity without risking growth instability.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If low temperature growth is used for the buffer layer, then the growth process is simpler and energy consumption is lower, but the buffer layer forms in a polycrystalline or amorphous state rather than single crystal

Engineering Contradiction:

Improvesimplicity of growth processVSAvoidcrystalline state of buffer layer

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The oxygen flow rate parameter is dynamically changed during the growth process. By adjusting this parameter from high to low (or zero) between the two stages, the process achieves both stable growth and high crystallinity without requiring complex temperature changes or additional process steps.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If high temperature is used to grow the nitride semiconductor layer for better crystallinity, then the crystallinity improves, but the buffer layer stability and polarity control become more difficult

Engineering Contradiction:

Improvecrystallinity of nitride semiconductor layerVSAvoidstability of buffer layer growth

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The growth process is segmented into two stages with different oxygen supply conditions. The first stage ensures buffer layer stability at manageable temperatures, while the second stage optimizes for crystallinity by reducing oxygen supply, allowing the nitride semiconductor layer to form with high crystallinity without compromising buffer layer stability.

Inventive Principle:

Principle #1Segmentation

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 enhances the crystallinity of the nitride semiconductor layers, reducing dislocations and improving the overall quality of the semiconductor element.

Implementation Method 1

a first step of coating an entire upper surface of the sapphire substrate with an under nitride semiconductor layer while supplying oxygen

Methodology Applied

Scientific EffectMetal organic chemical vapor deposition: Chemical Vapour Deposition

Implementation Method 2

the step of laminating the first nitride semiconductor layer includes a first step of coating an entire upper surface of the sapphire substrate with an under nitride semiconductor layer while supplying oxygen

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 3

a second step of growing an upper nitride semiconductor layer while supplying oxygen at a smaller flow rate than that of oxygen supplied in the first step, or without supplying oxygen

Methodology Applied

Scientific EffectMetal organic chemical vapor deposition: Chemical Vapour Deposition

Data Source

PatentUS9252323B2Method for manufacturing nitride semiconductor element

Publication Date: 2016.02.02 NICHIA CORP

AI summary

A first nitride semiconductor layer laminating step includes a first step and a second step. In the first step, an entire upper surface of the sapphire substrate is coated with a first nitride semiconductor layer, while supplying oxygen. In the second step, crystals of the first nitride semiconductor layer are grown by supplying oxygen at a smaller flow rate than that of oxygen supplied in the first step, or without supplying the oxygen.