Study on the Motion Trajectory of Abrasives and Surface Improvement Mechanism in Ultrasonic-Assisted Diamond Wire Sawing Monocrystalline Silicon

At a Glance

Metadata	Details
Publication Date	2025-06-13
Journal	Micromachines
Authors	Honghao Li, Yufei Gao, Shaoming Hu, Zhipu Huo
Institutions	Shandong University
Analysis	Full AI Review Included

Executive Summary

This study investigates the mechanism by which Ultrasonic-Assisted Diamond Wire Sawing (UADWS) improves the surface quality of monocrystalline silicon (mono-Si) wafers compared to conventional Diamond Wire Sawing (DWS).

Mechanism Elucidation: UADWS applies high-frequency vibration parallel to the feed direction, transforming the abrasive trajectory from approximately linear (DWS) to sinusoidal.
Kinematic Advantage: The sinusoidal trajectory increases the abrasive cutting arc length while simultaneously reducing the cutting depth. This promotes ductile material removal and minimizes brittle fracture damage.
Surface Quality Improvement: UADWS achieved a significant reduction in surface roughness (Ra reduced from 0.31 µm to 0.27 µm) and drastically lowered the Peak-Valley (PV) height of wire marks.
Wire Mark Mitigation: The ultrasonic vibration induces a micro-grinding effect on the peaks and valleys of the wire marks, effectively trimming them and reducing the PV height by over 50% (from 3.34 µm to 1.65 µm).
Micro-Grinding Effect: Trajectory modeling confirms that cross-interference between adjacent abrasive trajectories acts as a polishing mechanism, removing residual material and improving surface flatness.
Process Optimization: Lower wire speeds are found to be more conducive to exploiting the benefits of ultrasonic vibration, as abrasives remain in the processing area longer, increasing the number of vibration cycles.

Technical Specifications

Parameter	Value	Unit	Context
Workpiece Material	Monocrystalline Silicon (mono-Si)	N/A	Slicing experiment
Specimen Size	10 x 10	mm	Experimental sample
Diamond Wire Length	70	m	Electroplated wire saw
Diamond Wire Diameter	220	µm	Electroplated wire saw
Workpiece Feed Speed (v_w)	0.4	mm/min	DWS and UADWS experiments
Wire Speed (v_s)	1200	m/min	DWS and UADWS experiments
Ultrasonic Frequency (f)	20	kHz	Simulation and experimental system
Ultrasonic Amplitude (A)	18	µm	UADWS experimental condition
DWS Surface Roughness (Ra)	0.31	µm	Measured result
UADWS Surface Roughness (Ra)	0.27	µm	Measured result (12.9% reduction)
DWS Wire Mark PV Value	3.34	µm	Measured result
UADWS Wire Mark PV Value	1.65	µm	Measured result (50.6% reduction)

Key Methodologies

Abrasive Motion Trajectory Modeling:
- Established an O-xyz coordinate system centered on the wire cross-section.
- Derived the motion equation for a single abrasive in UADWS, incorporating workpiece feed speed (v_w), wire speed (v_s), ultrasonic amplitude (A), and frequency (f).
- Simulated the abrasive trajectory, confirming the change from a straight line (DWS) to an approximately sinusoidal curve (UADWS).
Kinematic Parameter Calculation:
- Calculated the abrasive cutting arc length (l) and cutting depth (h) for both DWS and UADWS by integrating the abrasive velocity equations.
- Analysis showed that UADWS increases l and decreases h, supporting the shift toward ductile material removal.
Multi-Abrasive Interference Analysis:
- Analyzed the mutual interference of trajectories between adjacent abrasives based on their spacing (Delta L) relative to the trajectory wavelength (Lambda).
- Demonstrated that high interference (when Delta L is not equal to Lambda) enhances the material removal rate and contributes to surface polishing.
Experimental Setup:
- Utilized a diamond single-wire reciprocating cutting machine (SH300) integrated with a 20 kHz ultrasonic vibration system (transducer, horn, and generator).
- Cut 10 mm x 10 mm mono-Si specimens using both DWS (A = 0 µm) and UADWS (A = 18 µm) under identical v_w and v_s conditions.
Surface Characterization:
- Measured the surface morphology, roughness (Ra), and wire mark Peak-Valley (PV) values using a laser confocal microscope (Keyence VK-X200K).
- Measurements were taken at 1000x magnification for roughness and 200x magnification for wire marks, with five points averaged to ensure accuracy.

Commercial Applications

The UADWS technology, by significantly improving the surface quality of sliced wafers, holds critical implications for industries requiring high-precision cutting of brittle materials.

Photovoltaic Manufacturing:
- Directly applicable to the slicing of mono-Si and polycrystalline silicon ingots for solar cell substrates.
- Improved surface quality (lower Ra and PV) reduces the need for extensive subsequent lapping and polishing steps, lowering manufacturing costs and increasing yield.
Semiconductor Industry:
- Used for precision slicing of silicon wafers, where surface integrity and minimal subsurface damage are paramount for device performance.
Advanced Materials Processing:
- Applicable to sawing other hard and brittle materials, such as single-crystal SiC (Silicon Carbide) and ceramics (e.g., Si₃N₄, ZTA), where ultrasonic assistance minimizes brittle fracture and micro-cracking.
Precision Machining:
- The micro-grinding effect induced by UADWS can be leveraged in general precision machining of difficult-to-machine materials to achieve superior surface finishes.

View Original Abstract

The surface quality of diamond wire sawing (DWS) wafers directly affects the efficiency and yield of subsequent processing steps. This paper investigates the motion trajectory of abrasives in ultrasonic-assisted diamond wire sawing (UADWS) and its mechanism for improving surface quality. The influence of ultrasonic vibration on the cutting arc length, cutting depth, and interference of multi-abrasive trajectories was analyzed through the establishment of an abrasive motion trajectory model. The ultrasonic vibration transforms the abrasive trajectory from linear to sinusoidal, thereby increasing the cutting arc length while reducing the cutting depth. A lower wire speed was found to be more conducive to exploiting the advantages of ultrasonic vibration. Furthermore, the intersecting interference of multi-abrasive trajectories contributes to enhanced surface quality. Experimental studies were conducted on monocrystalline silicon (mono-Si) to verify the effectiveness of ultrasonic vibration in improving surface morphology and reducing wire marks during the sawing process. The experimental results demonstrate that, compared with DWS, UADWS achieves a significantly lower surface roughness Ra and generates micro-pits. The ultrasonic vibration induces a micro-grinding effect on both peaks and valleys of wire marks, effectively reducing their peak-valley (PV) height. This study provides a theoretical basis for optimizing UADWS process parameters and holds significant implications for improving surface quality in mono-Si wafer slicing.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi16060708

References

2025 - Bridging efficiency and scalability: A systematic evaluation of diamond wire sawn silicon wafer texturing technologies for high-performance photovoltaics [Crossref]
2022 - Direct solar-driven reduction of greenhouse gases into hydrocarbon fuels incorporating thermochemical energy storage via modified calcium looping [Crossref]
2024 - Effect of nano-scratch speed on removal behavior of single crystal silicon
2021 - Science and art of ductile grinding of brittle solids [Crossref]
2024 - Fractal analysis on the surface topography of Monocrystalline silicon wafers sawn by diamond wire [Crossref]
2019 - Surface characteristics and wire wear of electroplated diamond wire saw slicing photovoltaic polycrystalline silicon
2013 - Study on ultrasonic vibration cutting of monocrystal silicon material with electroplated diamond wire saw
2022 - Prediction and verification of wafer surface morphology in ultrasonic vibration assisted wire saw (UAWS) slicing single crystal silicon based on mixed material removal mode [Crossref]
2023 - Theoretical and experimental investigations of surface generation induced by ultrasonic assisted grinding [Crossref]