Silicon Carbide Wafer Cleaning via Low-Speed Brush Scrubbing

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Solution Overview

Problem

Chemical Mechanical Polishing (CMP) processes for silicon carbide wafers leave behind significant impurities, including cohered particles and metal impurities, which can cause scratches and defects on the wafer surface, affecting the quality of semiconductor devices.

Innovation Solution

A method involving a scrubbing operation using a brush at a rotation rate of 200 rpm or less, followed by sequential cleaning operations with specific solutions, including ammonia, hydrogen peroxide, and hydrochloric acid, to effectively remove impurities from the wafer surface, along with ultrasonic waves and inert gas cleaning processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If CMP process is used to polish wafer surface, then surface flatness is improved, but impurity particles and metal impurities are generated and remain on the wafer

Engineering Contradiction:

Improvewafer surface flatnessVSAvoidimpurity particles and metal impurities

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The cleaning process is divided into multiple sequential stages: first cleaning operation with first cleaning solution, second cleaning operation with second cleaning solution, and third cleaning operation with third cleaning solution. Each stage targets different types of impurities generated during CMP, systematically removing particles and metal contaminants without compromising the polished surface flatness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different cleaning solutions with specific chemical compositions are used in sequence to address different impurity types. The chemical parameters of the cleaning solutions are optimized to effectively remove impurities while maintaining the wafer surface quality achieved during CMP polishing.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If slurry is supplied during CMP process, then polishing effectiveness is improved, but cohered particles are generated that cause scratches and defects

Engineering Contradiction:

Improvepolishing effectivenessVSAvoidcohered particles causing scratches and defects

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The cleaning operations are performed immediately after the CMP process while the wafer is still in the processing sequence. This preliminary cleaning action removes cohered particles before they can cause scratches or defects in subsequent processing steps, maintaining both polishing effectiveness and wafer quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Multiple cleaning solutions act as intermediaries between the CMP process and subsequent device fabrication steps. These solutions chemically interact with and remove cohered particles and metal impurities, preventing them from causing harm to the wafer surface in later processing.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If conventional cleaning process is used after CMP, then some particles are removed, but metal impurities remain that affect device characteristics

Engineering Contradiction:

Improveparticle removalVSAvoiddevice characteristics affected by metal impurities

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The cleaning process uses multiple cleaning solutions with different chemical compositions and parameters. The first cleaning solution addresses organic contaminants, while subsequent cleaning solutions with different chemical properties target metal impurities, achieving comprehensive purification that conventional single-solution cleaning cannot accomplish.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The cleaning process is segmented into multiple operations, each targeting specific impurity types. This segmented approach ensures that both particles and metal impurities are removed, preventing device characteristic degradation that would occur with conventional single-stage cleaning.

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

The method significantly reduces impurity concentrations on the wafer, enhancing the quality of the semiconductor device and reducing defective rates during manufacturing by effectively removing metal impurities and improving device performance.

Implementation Method 1

a scrubbing operation including treating a target wafer to be cleaned with a brush at a rotation rate of 200 rpm or less

Methodology Applied

Scientific EffectMechanical scrubbing: Friction

Implementation Method 2

cleaning the brush cleaned wafer with a cleaning solution

Methodology Applied

Scientific EffectUltrasonic cleaning: Ultrasonic Vibration

Implementation Method 3

the first cleaning operation includes cleaning the brush cleaned wafer with a first cleaning solution including ammonia and hydrogen peroxide

Methodology Applied

Scientific EffectChemical cleaning: Chemical Bonding

Data Source

PatentUS11646209B2Method of cleaning wafer and wafer with reduced impurities

Publication Date: 2023.05.09 EIN CRYSTAL CO LTD

AI summary

A method of cleaning a wafer comprises: a scrubbing operation comprising treating a target wafer to be cleaned with a brush at a rotation rate of 200 rpm or less to prepare a brush cleaned wafer; and a cleaning operation comprising cleaning the brush cleaned wafer with a cleaning solution to prepare a cleaned bare wafer, wherein the cleaning operation comprises a first cleaning operation and a second cleaning operation sequentially.