Prediction of Subsurface Microcrack Damage Depth Based on Surface Roughness in Diamond Wire Sawing of Monocrystalline Silicon

At a Glance

Metadata	Details
Publication Date	2024-01-24
Journal	Materials
Authors	Keying Wang, Yufei Gao, Chunfeng Yang
Institutions	Shandong University
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Subsurface Damage Prediction in Brittle Material Processing

This document analyzes the research paper “Prediction of Subsurface Microcrack Damage Depth Based on Surface Roughness in Diamond Wire Sawing of Monocrystalline Silicon” to provide technical specifications and highlight how 6CCVD’s advanced MPCVD diamond materials and services can support and extend this critical research area.

Executive Summary

The research establishes a fast, non-destructive method for predicting Subsurface Microcrack Damage Depth (SSD) in monocrystalline silicon (mono-Si) wafers, a critical factor in subsequent processing yield and mechanical integrity.

Core Achievement: Developed an improved theoretical model linking SSD directly to measurable surface roughness ($R_a$) using indentation fracture mechanics.
Key Relationship: The non-linear relationship was refined and validated experimentally as $\text{SSD} = 21.179 \text{ Ra}^{4/3}$.
Accuracy: The optimized prediction model achieved excellent agreement with experimental measurements, reducing the relative error to within 5%.
Process Dependency: SSD and Surface Roughness ($R_a$) increase when wire speed ($V_s$) decreases or feed speed ($V_w$) increases, providing clear guidance for process optimization.
Material Science Insight: The model incorporates factors like tangential force, elastic stress fields, and material ductile regime removal, confirming the complex role of diamond abrasive quality and processing parameters in brittle material removal.
Industrial Relevance: This non-destructive prediction method is highly suitable for industrial applications, allowing for rapid quality control and optimization of diamond wire saw cutting processes.

Technical Specifications

The following table summarizes the key material properties, processing parameters, and resulting damage metrics extracted from the research.

Parameter	Value	Unit	Context
Workpiece Material	Mono-Si (111)	N/A	Sawn crystal plane
Elastic Modulus (E)	187	GPa	Material characteristic
Hardness (H)	9	GPa	Mohs hardness
Static Fracture Toughness (K_IC)	0.82	MPa·m^1/2	Material characteristic
Abrasive Tip Half Angle ($\phi$)	65	°	Assumed for calculation
Median Crack Deflection Angle ($\beta$)	24.785	°	Calculated based on $\phi$
Tangential Load Correction Factor ($\epsilon$)	1.072	N/A	Based on K ratio
Wire Speed ($V_s$) Range	48 to 78	m/min	Experimental range
Feed Speed ($V_w$) Range	0.18 to 0.54	mm/min	Experimental range
Measured Surface Roughness ($R_a$) Range	0.53 to 0.82	µm	Experimental results
Measured SSD Range	9.7 to 15.9	µm	Experimental results
Improved SSD Prediction Formula	SSD = 21.179 Ra^4/3	µm	Final optimized model
Relative Error (Optimized Model)	< 5	%	Accuracy of prediction

Key Methodologies

The experimental validation relied on precise control of diamond wire sawing parameters and rigorous measurement techniques for both surface roughness and subsurface damage.

Sawing Setup: Reciprocating single-wire diamond wire saw cutting machine used for all experiments.
Workpiece Preparation: Mono-Si ingots (10 mm x 10 mm x 40 mm) were cut along the (111) crystal plane, yielding 0.5 mm thick wafers.
Diamond Wire Specifications: Diameter of 120 µm, diamond abrasive particle size of 15-20 µm, and effective cutting length of 20 m.
Surface Roughness ($R_a$) Measurement: A contact surface roughness measuring instrument was used to measure five points perpendicular to the wire mark, with the average taken as the final $R_a$ value.
Subsurface Damage (SSD) Measurement (Destructive): Wafers were embedded, ground, and polished perpendicular to the wire movement direction. Specimens were then corroded in hydrofluoric acid solution for 15 s to reveal microcracks.
SSD Observation: An OLYMPUS optical microscope was used to observe and measure the median crack propagation depth at five locations, averaged for the final SSD value.
Model Refinement: The theoretical SSD prediction model, based on indentation fracture mechanics, was refined by adding a coefficient ($\eta$) to account for the influence of material ductile regime removal on $R_a$ values.

6CCVD Solutions & Capabilities

The research underscores the critical need for precise control over material removal mechanisms and subsequent surface finishing to manage SSD. 6CCVD provides the high-performance MPCVD diamond materials and precision services necessary to replicate, extend, and industrialize this type of research.

Applicable Materials

The principles governing SSD in mono-Si sawing are directly relevant to other hard, brittle materials like SiC and Sapphire. 6CCVD offers materials optimized for extreme mechanical and thermal environments:

Optical Grade Single Crystal Diamond (SCD): Ideal for applications requiring the highest purity, hardness, and thermal conductivity. SCD is essential for components (e.g., anvils, windows) where minimal intrinsic defect density is paramount.
High-Purity Polycrystalline Diamond (PCD): Available in large formats (up to 125 mm wafers), PCD offers exceptional wear resistance and is suitable for large-scale abrasive applications or substrates where high mechanical strength is required.
Boron-Doped Diamond (BDD): For electrochemical or sensor applications where the mechanical properties of diamond must be combined with controlled electrical conductivity.

Surface Finish & SSD Mitigation

The paper demonstrates that the as-sawn SSD layer (9.7-15.9 µm) must be removed in subsequent steps. 6CCVD’s advanced polishing capabilities ensure rapid and efficient removal of this damage layer, leading to superior final product quality:

Material	Polishing Capability	Resulting Roughness	Application Relevance
SCD Wafers	Ultra-Precision Polishing	$R_a < 1 \text{ nm}$	Achieving atomic-level flatness for quantum computing or high-power optics.
PCD Wafers	Precision Polishing (Inch-size)	$R_a < 5 \text{ nm}$	Preparing large substrates for semiconductor or high-frequency electronics integration.

Customization Potential

6CCVD’s core strength is providing custom specifications tailored to research and industrial needs, far exceeding standard catalog offerings:

Custom Dimensions: We offer plates and wafers up to 125 mm (PCD) and custom substrates up to 10 mm thick, supporting scaling from lab experiments to production runs.
Thickness Control: SCD and PCD layers can be grown from 0.1 µm up to 500 µm, allowing precise control over material volume and cost.
Advanced Metalization: We offer in-house deposition of standard and custom metal stacks (Au, Pt, Pd, Ti, W, Cu) for electrical contact or bonding layers, essential for integrating diamond into complex devices.

Engineering Support

6CCVD’s in-house PhD team specializes in the growth and characterization of MPCVD diamond. We offer authoritative professional consultation to assist engineers and scientists in:

Material Selection: Determining the optimal diamond grade (SCD, PCD, BDD) based on required hardness, thermal properties, and surface finish targets for brittle material processing projects.
Process Optimization: Applying fracture mechanics principles to minimize SSD and maximize material removal efficiency in grinding, lapping, or sawing applications.
Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for time-sensitive research and production schedules.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

In diamond wire saw cutting monocrystalline silicon (mono-Si), the material brittleness removal can cause microcrack damage in the subsurface of the as-sawn silicon wafer, which has a significant impact on the mechanical properties and subsequent processing steps of the wafers. In order to quickly and non-destructively obtain the subsurface microcrack damage depth (SSD) of as-sawn silicon wafers, this paper conducted research on the SSD prediction model for diamond wire saw cutting of mono-Si, and established the relationship between the SSD and the as-sawn surface roughness value (SR) by comprehensively considering the effect of tangential force and the influence of the elastic stress field and residual stress field below the abrasive on the propagation of median cracks. Furthermore, the theoretical relationship model between SR and SSD has been improved by adding a coefficient considering the influence of material ductile regime removal on SR values based on experiments sawing mono-Si along the (111) crystal plane, making the theoretical prediction value of SSD more accurate. The research results indicate that a decrease in wire speed and an increase in feed speed result in an increase in SR and SSD in silicon wafers. There is a non-linear increasing relationship between silicon wafer SSD and SR, with SSD = 21.179 Ra4/3. The larger the SR, the deeper the SSD, and the smaller the relative error of SSD between the theoretical predicted and experimental measurements. The research results provide a theoretical and experimental basis for predicting silicon wafer SSD in diamond wire sawing and optimizing the process.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17030553

References

2023 - Multi-Objective Optimization of Energy Consumption, Surface Roughness, and Material Removal Rate in Diamond Wire Sawing for Monocrystalline Silicon Wafer [Crossref]
2018 - The impact of subsurface damage on the fracture strength of diamond-wire-sawn monocrystalline silicon wafers [Crossref]
2018 - Study on the Subsurface Microcrack Damage Depth in Electroplated Diamond Wire Saw Slicing Sic Crystal [Crossref]
2023 - Study on Subsurface Microcrack Damage Depth of Diamond Wire As-Sawn Sapphire Crystal Wafers [Crossref]
2015 - Effect of Initial Deflection of Diamond Wire on Thickness Variation of Sapphire Wafer in Multi-Wire Saw [Crossref]
2023 - Investigation of Cutting Rate of Diamond Wire Saw Machine Using Numerical Modeling [Crossref]
2014 - Distribution of Diamond Grains in Fixed Abrasive Wire Sawing Process [Crossref]
2022 - Image-processing-based Model for the Characterization of Surface Roughness and Subsurface Damage of Silicon Wafer in Diamond Wire Sawing [Crossref]
2022 - Experiment and Theoretical Prediction for Subsurface Microcracks and Damage Depth of Multi-Crystalline Silicon Wafer in Diamond Wire Sawing [Crossref]
2017 - Experimentally Validated Finite Element Analysis for Evaluating Subsurface Damage Depth in Glass Grinding Using Johnson-Holmquist Model [Crossref]