Optical Flatness Critical Glass Disc Substrates for Thin-Film Deposition

Material

• High-Purity Glass: Typically made from fused silica (JGS1/JGS2), borosilicate, or quartz, selected for ultra-low thermal expansion and chemical inertness.

  • Fused Silica: Preferred for its exceptional homogeneity, low OH content, and resistance to thermal shock.

  • Borosilicate: Cost-effective alternative with moderate thermal stability and good surface polishability.

• Surface Quality: Engineered with λ/10 to λ/20 flatness to ensure minimal deviation for precision coatings.

Key Properties

1. Optical Flatness: Surface flatness ≤ λ/10 (at 632.8 nm), critical for uniform thin-film deposition and minimizing wavefront distortion.

2. Thermal Stability: Low coefficient of thermal expansion (e.g., 0.55 x 10⁻⁶/°C for fused silica) prevents deformation during high-temperature processes like CVD or sputtering.

3. Chemical Resistance: Inert to acids, plasmas, and solvents, ensuring durability in aggressive deposition environments.

4. Surface Homogeneity: Refractive index uniformity (±5 x 10⁻⁶) avoids optical distortions in coated films.

5. Mechanical Durability: High hardness (Mohs 5–7) resists scratching during handling and processing.

Function

• Thin-Film Substrate: Provides an ultra-flat, stable base for depositing coatings (anti-reflective, dielectric, metallic).

• Process Compatibility: Compatible with PVD, CVD, ALD, and sputtering techniques, ensuring uniform film adhesion and thickness.

• Metrology Reference: Serves as a calibration standard for interferometers and surface profilers due to precise flatness.

Applications

• Semiconductor Manufacturing: Photomasks, EUV lithography mirrors, and optical MEMS devices.

• Optics Industry: Coated filters, beam splitters, and laser optics requiring nanometer-level precision.

• Research & Development: Nanotechnology, photonics, and quantum computing experiments.

• Aerospace & Defense: Precision sensors, satellite optics, and laser guidance systems.

• Medical Devices: Optical coatings for imaging systems, endoscopes, and diagnostic equipment.