Semiconductor Substrate Metal Contamination Detection

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Solution Overview

Problem

Metal ions from mirror polishing slurries contaminate semiconductor substrates during the manufacturing process, leading to crystal defects and surface roughness that are not detectable by conventional inspection methods, resulting in potentially defective products.

Innovation Solution

Using a slurry with Cu, Ni, and Fe contents of approximately equal to or less than 10 ppb, 10 ppb, and 1,000 ppb respectively, and employing SC-1 cleaning or HF etching to detect metal contaminants as bright points on the substrate surface for quality evaluation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mirror polishing is conducted using conventional slurry, then the surface of the silicon wafer achieves mirror finish, but metal ions (Cu, Ni, Fe) diffuse into the wafer causing bulk contamination and crystal defects

Engineering Contradiction:

Improvesurface finish qualityVSAvoidmetal contamination in bulk

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the slurry by strictly controlling metal ion concentrations (Cu ≤10 ppb, Ni ≤10 ppb, Fe ≤1,000 ppb). This parameter modification allows the slurry to maintain its mirror polishing function while eliminating the harmful metal contamination that diffuses into the wafer bulk during polishing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a disposable slurry system where the slurry is replaced after a single use or limited uses. This prevents metal ion accumulation in the slurry that would otherwise continue to contaminate subsequent wafers, ensuring each wafer is polished with fresh, low-contamination slurry.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Measurement precision

If conventional inspection methods are used to detect defects, then particles and surface pits are detected as bright points, but metal contamination-induced crystal defects and surface roughness are not detected

Engineering Contradiction:

Improvedetection of surface defectsVSAvoidquality assessment accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The invention performs preliminary etching of the wafer surface before inspection. This preliminary action removes the metal contamination layer and exposes the underlying crystal defects and surface roughness that were caused by metal diffusion, making them visible as bright points in subsequent optical inspection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention uses an etching solution as an intermediary substance that selectively removes metal contaminants from the wafer surface. This intermediary action transforms invisible bulk contamination into visible surface features that can be detected by conventional optical inspection equipment.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 metal contamination in semiconductor substrates, enabling the detection and elimination of defective products and ensuring the supply of high-quality substrates with reduced metal impurities.

Implementation Method 1

metal ions contained in the slurry used in mirror polishing diffuse into the wafer during mirror polishing

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

conducting SC-1 cleaning (Standard Clean 1—typically a mixture of NH4OH, H2O2, and deionized water) and/or Fluoric acid (HF) cleaning to selectively etch the substrate surface

Methodology Applied

Scientific EffectEtching: Ablation

Data Source

PatentUS7479204B2Method of manufacturing semiconductor substrate and method of evaluating quality of semiconductor substrate

Publication Date: 2009.01.20 SUMCO CORP

AI summary

A method of evaluating the presence or absence and/or degree of metal contamination of a semiconductor substrate including etching the surface of the semiconductor substrate by SC-1 cleaning and/or a HF cleaning, detecting bright points on the surface of the etched substrate with a foreign matter inspection device, and evaluating the presence or absence and/or degree of metal contamination of the semiconductor substrate based on the distribution pattern of bright points detected on the surface of the substrate. Also disclosed is a method of manufacturing a semiconductor substrate comprising mirror polishing a silicon wafer surface, wherein the mirror polishing is conducted using a slurry having a Cu content of approximately equal to or less than 10 ppb, a Ni content of approximately equal to or less than 10 ppb, and an Fe content of approximately equal to or less than 1,000 ppb, and evaluating the semiconductor substrate as above.