A Study of Material Removal Characteristics by Friction Monitoring System of Sapphire Wafer in Single Side DMP
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-04-30 |
| Journal | Journal of the Korean Society of Tribologists and Lubrication Engineers |
| Authors | Wonseok Jo, Sangjik Lee, Hyoungjae Kim, Taekyung Lee, Seongbeom Lee |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Diamond Mechanical Polishing (DMP) of Sapphire Wafers
Section titled âTechnical Documentation and Analysis: Diamond Mechanical Polishing (DMP) of Sapphire WafersâExecutive Summary
Section titled âExecutive SummaryâThis research investigates the complex material removal characteristics of sapphire wafers during Diamond Mechanical Polishing (DMP), validating fundamental tribological principles and deriving a new empirical model based on monitored friction data. This analysis underscores the crucial role of diamond material, tool geometry, and precise process monitoringâareas where 6CCVD provides market-leading solutions.
- Model Validation: The study successfully validated the widely used Preston equation ($q=K \cdot P \cdot V$) for sapphire DMP, demonstrating a linear correlation between Material Removal Rate (MRR) and the product of pressure (P) and velocity (V).
- Novel Methodology: A real-time friction monitoring system was employed to analyze process phenomena, enabling the derivation of a highly correlative, friction-energy-based MRR model ($q=Kâ Fs$).
- Key Achievement: The friction-energy model (R2 = 0.97) proved more accurate than the traditional Preston model (R2 = 0.944) in correlating MRR across various processing conditions.
- Tool Geometry Impact: Experimental results showed that the polishing platen groove geometry, specifically decreasing the pitch size, significantly increased both friction force and the MRR.
- Material Utilization: The experiments utilized 3 ”m Polycrystalline Diamond (PCD) slurry, highlighting the indispensable role of highly specialized diamond material in achieving high-precision surface finishing.
- 6CCVD Relevance: The requirement for ultra-high precision, controllable diamond materials, and advanced tribological understanding directly aligns with 6CCVDâs expertise in MPCVD diamond growth and high-accuracy polishing services (Ra < 1 nm).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data was extracted from the experimental conditions and results related to the Diamond Mechanical Polishing (DMP) process:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Wafer Substrate | 4 inch Sapphire | N/A | Material being Polished |
| Abrasive Type | Polycrystal Diamond | N/A | Slurry Material |
| Diamond Particle Diameter | 3 | ”m | Abrasive Grain Size |
| Slurry Flow Rate | 4 | ml/min | Process Input |
| Platen Material | Copper-Resin Plate (KEMET) | N/A | Polishing Tool |
| Standard Pressure Range (P) | 200 - 400 | g/cm2 | Primary Test Variable |
| Standard Velocity Range (V) | 60 - 105 | rpm | Primary Test Variable |
| Platen Groove Pitch Test Range | 4, 5, 6.7, 10, 20 | mm | Geometry Variable |
| Polishing Time | 10 (4 repetitions) | minutes | Test Duration |
| Preston Equation R2 | 0.944 | N/A | Fit Quality (MRR vs. P·V) |
| Friction Energy Rate Model R2 | 0.97 | N/A | Fit Quality (MRR vs. Friction Energy) |
| Derived Friction MRR Model | q = Kâ Fs | N/A | Friction-based Material Removal Equation |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on a controlled Diamond Mechanical Polishing setup integrated with advanced real-time monitoring for tribological analysis.
- Equipment Setup: A single-head rotary polisher was used, specifically integrated with a friction monitoring system. This system included a Piezoelectric quartz sensor (9134B, Kistler) and a charge amplifier (5039A, Kistler) for real-time measurement of friction force ($F_{f}$).
- Substrate and Slurry: 4 inch sapphire wafers were processed using an oil-based slurry containing 3 ”m Polycrystalline Diamond (PCD) particles. The slurry was supplied at a constant rate of 4 ml/min.
- Platen Configuration: The polishing platen was a Copper-Resin Plate featuring specific spiral grooves (1 mm depth, 2 mm land width).
- Process Variable Testing (Preston Validation): Initial experiments varied pressure (P) from 200 to 400 g/cm2 and platen velocity (V) from 60 to 105 rpm to analyze the relationship between P, V, and MRR.
- Geometry Variable Testing (Pitch Impact): Subsequent experiments maintained fixed conditions (P=400 g/cm2, V=90 rpm) while varying the platen groove pitch from 4 mm up to 20 mm to determine the geometrical influence on MRR and friction characteristics.
- Data Analysis: Material removal was measured, and the results were correlated against the calculated P·V product and the calculated Friction Energy Rate ($F_{f} \cdot s$), confirming the validity of both the Preston equation and the newly derived friction-energy model.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical importance of diamond abrasives, material purity, and controlled polishing environmentsâall foundational competencies of 6CCVD. By supplying superior MPCVD diamond and offering precision engineering services, 6CCVD can facilitate both the replication and advancement of this high-precision finishing technology.
Applicable Materials
Section titled âApplicable MaterialsâThe study relies on Polycrystalline Diamond (PCD) abrasives. 6CCVD specializes in producing the highest quality MPCVD diamond materials necessary for both advanced tooling and substrate applications:
| 6CCVD Material | Application Relevance | Customization Potential |
|---|---|---|
| Polycrystalline Diamond (PCD) | Ideal for producing superior, long-lifetime polishing platens or high-purity, large-format diamond substrates for research up to 125mm. | Available in wafers up to 500 ”m thick and in custom shapes/dimensions for platen inserts. |
| Single Crystal Diamond (SCD) | Critical for final-stage polishing applications requiring the lowest possible defects. Our Optical Grade SCD achieves unparalleled smoothness (Ra < 1 nm). | Available in high-purity wafers (Type IIa) up to 500 ”m thickness, enabling highly controlled tribological experiments. |
| Boron-Doped Diamond (BDD) | For experiments requiring conductive platens or substrates for electrochemical polishing variants, 6CCVD provides highly stable, heavy Boron-Doped PCD. | Customizable doping levels and thickness up to 500 ”m. |
Customization Potential
Section titled âCustomization PotentialâThe precision control over geometry (platen pitch) and surface finish discussed in the paper requires advanced manufacturing capabilities. 6CCVD offers the necessary services to tailor materials for rigorous tribological research:
- Ultra-Precision Polishing: We offer guaranteed surface roughness of Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring research starts with the highest quality base substrates.
- Custom Dimensions and Shapes: Replication or extension of this work often requires specific diamond tool inserts or substrates. 6CCVD provides custom laser cutting and shaping for diamond plates up to 125mm.
- Integrated Metalization Services: For experiments requiring integrated sensors (like the Kistler load cells used) or thermal management layers, 6CCVD provides in-house metalization services, including common layers like Ti/Pt/Au, W, Cu, and Pd, applied directly to the diamond substrate.
Engineering Support
Section titled âEngineering SupportâThe successful development of a friction-energy model requires a deep understanding of diamond material properties, processing mechanics, and tribology.
- In-House Expertise: 6CCVDâs team of PhD-level material scientists and engineers possesses extensive knowledge of the MPCVD growth process and downstream precision processing (lapping, polishing, metalization).
- Project Consultation: Our engineers can assist researchers in selecting the optimal MPCVD diamond material (SCD or PCD) based on application requirements (e.g., optical windows, semiconductor substrates, or advanced tool development) for similar high-precision tribology and DMP projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Sapphire has a high hardness and strength and chemical stability as a superior material. It is used mainly as a material for a semiconductor as well as LED. Recently, the cover glass industry used by a sapphire is getting a lot of attention. The sapphire substrate is manufactured through ingot sawing, lapping, diamond mechanical polishing (DMP) and chemical mechanical polishing (CMP) process. DMP is an important process to ensure the surface quality of several nm for CMP process as well as to determine the final form accuracy of the substrate. In DMP process, the material removal is achieved by using the mechanical energy of the relative motion to each other in the state that the diamond slurry is disposed between the sapphire substrate and the polishing platen. The polishing platen is one of the most important factors that determine the material removal characteristics in DMP. Especially, it is known that the geometric characteristics of the polishing platen affects the material removal amount and its distribution. This paper investigated the material removal characteristics and the effects of the polishing platen groove in sapphire DMP. The experiments were preliminarily carried out to evaluate the sapphire material removal characteristics according to process parameters such as pressure, relative velocity and so on. In the experiment, the monitoring apparatus was applied to analyze process phenomena in accordance with the processing conditions. From the experimental results, the correlation was analyzed among process parameters, polishing phenomena and the material removal characteristics. The material removal equation based on phenomenological factors could be derived. And the experiment was followed to investigate the effects of platen groove on material removal characteristics.