Optimization of Diamond Polishing Process for Sub-Nanometer Roughness Using Ar/O2/SF6 Plasma
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-03 |
| Journal | Materials |
| Authors | Lei Zhao, Xiangbing Wang, Minxing Jiang, Chao Zhao, Nan Jiang |
| Institutions | Chinese Academy of Sciences, Guilin University of Electronic Technology |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Ultra-Precision Diamond Polishing via ICP Etching
Section titled âTechnical Analysis & Documentation: Ultra-Precision Diamond Polishing via ICP EtchingâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the optimization of Inductively Coupled Plasma (ICP) etching using an Ar/O2/SF6 plasma mixture to achieve sub-nanometer surface roughness on Single Crystal Diamond (SCD). This advancement is critical for high-performance optical, semiconductor, and quantum applications.
- Core Achievement: Surface roughness (Ra) of SCD was reduced by 74.7%, from an initial 2.22 nm (merchant polished) to an optimized 0.562 nm.
- Methodology: A systematic five-part experiment optimized ICP power, RF bias power, gas flow ratio (Ar/O2/SF6), chamber pressure, and etching time.
- Optimal Recipe: The lowest roughness was achieved using 200 W ICP power, 40 W RF bias power, 40/50/10 sccm gas flow, 20 mTorr pressure, and 10 minutes etching time.
- Mechanism: The process balances chemical etching (O2/SF6) and physical sputtering (Ar) to uniformly remove carbon and minimize the formation of nanopillar protrusions caused by initial mechanical polishing.
- Application Impact: The resulting ultra-smooth surface enhances the diamondâs suitability for high-precision optical components and next-generation wide-bandgap semiconductor electronics.
- 6CCVD Relevance: This research validates the need for high-quality, low-defect SCD starting material and confirms the feasibility of achieving Ra < 1 nm surfaces, a standard capability offered by 6CCVD.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key quantitative results and optimized parameters derived from the ICP etching experiments on single-crystal diamond.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Initial Surface Roughness (Ra) | 2.22 | nm | Before optimized ICP etching |
| Final Surface Roughness (Ra) | 0.562 | nm | After optimized ICP etching (20 x 20 ”m2 area) |
| Roughness Improvement | 74.7 | % | Decrease from initial Ra |
| Optimal ICP Power | 200 | W | Regulates plasma density |
| Optimal RF Bias Power | 40 | W | Controls ion kinetic energy |
| Optimal Gas Flow Ratio (Ar/O2/SF6) | 40/50/10 | sccm | Balances physical sputtering and chemical reaction |
| Optimal Chamber Pressure | 20 | mTorr | Achieves optimal balance of etching and ion bombardment |
| Optimal Etching Time | 10 | min | Prevents surface deterioration and nanostructure growth |
| Substrate Material | (100) Type IIa | SCD | Laboratory-synthesized single-crystal diamond |
| Plasma Frequency | 13.56 | MHz | High-frequency power supply |
| Temperature Range | 30 - 35 | °C | Controlled experimental temperature |
Key Methodologies
Section titled âKey MethodologiesâThe study employed a systematic, multi-stage optimization process using an Inductively Coupled Plasma (ICP) device to polish single-crystal diamond.
- Material Selection: Laboratory-synthesized (100) type IIa Single Crystal Diamond (SCD) samples (3 x 3 x 0.5 mm3) were used.
- Pre-Cleaning: Samples were immersed in boiling piranha solution (H2SO4:H2O2 = 7:3) for 8 hours, followed by rinsing in acetone and ethanol, and nitrogen gas purging.
- Etching Equipment: Experiments were conducted using an ICP system operating at 13.56 MHz.
- Parameter Optimization (Sequential Experiments I-V): The process was optimized sequentially, determining the optimal setting for each variable while holding others constant:
- Experiment I: Etching Time (Optimal: 10 min)
- Experiment II: Gas Flow Ratio (Optimal Ar/O2/SF6: 40/50/10 sccm)
- Experiment III: ICP Power (Optimal: 200 W)
- Experiment IV: RF Bias Power (Optimal: 40 W)
- Experiment V: Chamber Pressure (Optimal: 20 mTorr)
- Surface Analysis: Surface roughness (Ra) was measured before and after etching using Atomic Force Microscopy (AFM, Bruker Dimension Icon) in tapping mode over a 20 x 20 ”m2 area.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and scaling of this ultra-precision plasma polishing technique rely fundamentally on the quality and consistency of the starting diamond material. 6CCVD is uniquely positioned to supply the necessary high-specification SCD and PCD materials, along with critical customization services.
| Research Requirement | 6CCVD Applicable Materials | 6CCVD Customization Potential |
|---|---|---|
| High-Purity SCD Substrates | Optical Grade Single Crystal Diamond (SCD): We supply high-quality, low-defect (100) and (111) oriented SCD, essential for achieving uniform etching and minimizing plasma-induced defects. | Thickness Control: SCD wafers available from 0.1 ”m up to 500 ”m, allowing researchers to select the optimal thickness for thermal management or specific optical path lengths. |
| Sub-Nanometer Surface Quality | Precision Polished SCD: Our standard polishing service guarantees Ra < 1 nm on SCD, providing a superior starting surface compared to the 2.22 nm initial roughness used in the study. | Pre-Etch Polishing: Supplying material pre-polished to Ra < 1 nm significantly reduces the required ICP etching time, mitigating the risk of nanopillar formation and improving throughput. |
| Scaling to Production | Polycrystalline Diamond (PCD) Wafers: For applications requiring larger areas (e.g., optics or wide-bandgap electronics), we offer PCD plates up to 125 mm in diameter. | Custom Dimensions: We provide custom laser cutting and shaping services to match any required geometry, from small 3 x 3 mm samples to inch-size wafers. |
| Integration into Devices | Boron-Doped Diamond (BDD): For electrochemical or semiconductor applications, we supply BDD films with controlled doping levels. | Metalization Services: We offer internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for creating electrodes or contact pads, crucial for integrating polished diamond into microelectronic devices. |
Engineering Support
Section titled âEngineering SupportâThe optimization of ICP etching parameters (power, pressure, gas ratio) is highly dependent on the intrinsic properties of the diamond substrate. 6CCVDâs in-house PhD team specializes in material science and can assist clients with material selection for similar High-Precision Optical and Semiconductor projects. We ensure that the crystal orientation, nitrogen content, and initial surface finish are perfectly matched to the clientâs specific plasma chemistry requirements (e.g., Ar/O2/SF6 or H2/O2).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).
View Original Abstract
Diamond, known for its exceptional physical and chemical properties, shows great potential in advanced fields such as medicine, semiconductors, and optics. However, reducing surface roughness is critical for enhancing its performance. This study employs inductively coupled plasma (ICP) polishing to etch single-crystal diamond and analyzes the impact of different etching parameters on surface roughness using atomic force microscopy (AFM). Using the change in surface roughness before and after etching as the main evaluation metric, the optimal etching parameters were determined: Ar/O2/SF6 gas flow ratio of 40/50/10 sccm, ICP power of 200 W, RF bias power of 40 W, chamber pressure of 20 mTorr, and etching time of 10 min. Results show that increased etching time and SF6 flow rate raise surface roughness; although higher ICP and RF power reduce roughness, they also cause nanostructure formation, affecting surface quality. Lower chamber pressure results in smaller roughness increases, while higher pressure significantly worsens it. Based on the optimized process parameters, the pristine single-crystal diamond was further etched in this study, resulting in a significant reduction of the surface roughness from 2.22 nm to 0.562 nm, representing a 74.7% decrease. These improvements in surface roughness demonstrate the effectiveness of the optimized process, enhancing the diamondâs suitability for high-precision optical applications.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2025 - A review: CNT/diamond composites prepared via CVD and its potential applications [Crossref]
- 2008 - Nanoscale magnetic sensing with an individual electronic spin in diamond [Crossref]
- 2024 - Coherent Microwave, Optical, and Mechanical Quantum Control of Spin Qubits in Diamond
- 2025 - Evolution of mechanical and thermal properties of diamond under external stress [Crossref]
- 2014 - Nanotwinned diamond with unprecedented hardness and stability [Crossref]
- 2025 - Study on mechanism and characteristics of laser repair of surface damage after ultra-precision grinding of monocrystalline silicon [Crossref]
- 2013 - Diamond polishing [Crossref]