SiC Substrate Modified Layer Removal via Si Vapor Pressure

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Solution Overview

Problem

Conventional methods for manufacturing semiconductor elements using SiC substrates face inefficiencies due to the formation of modified layers from mechanical polishing, which cause latent scratches and macro-step bunching, leading to prolonged processing times and reduced production efficiency.

Innovation Solution

A method involving a high-temperature vacuum furnace for removing modified layers and macro-step bunching under controlled Si vapor pressure conditions, including specific temperature and pressure ranges, to facilitate rapid etching and improve substrate flatness, combined with epitaxial layer formation and ion activation steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mechanical polishing is used to planarize the substrate surface, then the surface flatness is improved, but a modified layer is generated causing latent scratches that reduce manufacturing quality

Engineering Contradiction:

Improvesurface flatnessVSAvoidsubstrate quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent extracts and removes the harmful modified layer generated by mechanical polishing through chemical-mechanical polishing. This secondary polishing process specifically targets and eliminates the latent scratches and modified layer while preserving the overall surface flatness achieved by the first mechanical polishing step.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces purely mechanical polishing with a chemical-mechanical polishing process that combines chemical etching with mechanical removal. This substitution allows for more selective removal of the modified layer while minimizing damage to the underlying substrate, thereby improving both surface quality and reducing latent scratches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If chemical-mechanical polishing is used to remove the modified layer, then the substrate quality is improved, but the processing time is significantly increased to 80 hours or more

Engineering Contradiction:

Improvesubstrate qualityVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent changes the chemical composition and physical parameters of the polishing slurry to optimize the removal rate of the modified layer. By adjusting parameters such as slurry composition, polishing pressure, and temperature, the process achieves faster removal rates while maintaining substrate quality, thereby reducing the overall processing time from 80 hours to a more practical duration.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies chemical-mechanical polishing with controlled excessive action, where the polishing process is designed to remove slightly more material than the minimum required. This approach ensures complete elimination of the modified layer and latent scratches while maintaining a buffer that prevents under-polishing, achieving a balance between quality and efficiency.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If ion activation is performed by heating at high temperature after ion implantation, then the ion activation is achieved, but latent scratches are exposed on the surface making the substrate unusable

Engineering Contradiction:

Improveion activation effectivenessVSAvoidsurface quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent performs chemical-mechanical polishing as a preliminary action before ion implantation and activation steps. By removing the modified layer and potential latent scratches beforehand, the substrate surface is prepared in a state that can withstand subsequent high-temperature ion activation without exposing harmful defects, ensuring both activation effectiveness and surface quality.

Inventive Principle:

Principle #10Preliminary action

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 significantly reduces processing time, enhances substrate flatness, and improves the yield of semiconductor elements by effectively removing modified layers and macro-step bunching, thereby increasing production efficiency.

Implementation Method 1

removing a modified layer produced by subjecting the substrate to mechanical polishing by heating the substrate under Si vapor pressure

Methodology Applied

Scientific EffectVapor pressure: Vapour Pressure

Implementation Method 2

heating the substrate under Si vapor pressure... facilitates rapid etching and improve substrate flatness

Methodology Applied

Scientific EffectThermal etching:

Implementation Method 3

ions are activated by heating the substrate

Methodology Applied

Scientific EffectThermal activation:

Data Source

PatentUS11081347B2Method for manufacturing silicon-carbide semiconductor element

Publication Date: 2021.08.03 KWANSEI GAKUIN EDUCTIONAL FOUND

AI summary

In this method for manufacturing a semiconductor element, a modified layer produced by subjecting a substrate (70) to mechanical polishing is removed by heating the substrate (70) under Si vapor pressure. An epitaxial layer formation step, an ion implantation step, an ion activation step, and a second removal step are then performed. In the second removal step, macro-step bunching and insufficient ion-implanted portions of the surface of the substrate (70) performed the ion activation step are removed by heating the substrate (70) under Si vapor pressure. After that, an electrode formation step in which electrodes are formed on the substrate (70) is performed.