Alpha Quartz Wafers & Single-Crystal Quartz Substrates

Alpha Quartz Wafers for Chemical Vapor Deposition

Answer:

The single Alpha Quartz crystal will have phase transition @ 572° C ( change to Beta Quartz).

What is the temperature unit below °C or ° F?

Reference #162264 for specs and pricing.

How Quartz Photomask Substrates Are Made

Quartz-based photomasks are produced through precision polishing, opaque-film deposition, photoresist coating, lithographic patterning and inspection. High-purity fused silica is commonly used for photomask blanks, while crystalline alpha quartz may be selected for specialized optical and research applications. The correct material depends on wavelength, birefringence, flatness and thermal requirements.

1. Blank Material and Preparation

• Material: High-purity fused silica or specialty crystalline quartz is selected according to wavelength, birefringence and tool requirements.

• Blank preparation: The substrate is formed, annealed or grown using a process appropriate to the selected quartz material.

• Cutting: The blank is sliced or diced to the required mask dimensions and thickness.

• Orientation: When crystalline quartz is used, its cut and optical axis must match the application.

2. Lapping and Polishing

• Lapping: The rough wafer surface is mechanically ground to achieve uniform thickness.

• Polishing: Surfaces are polished to the flatness, parallelism and scratch-dig specification required by the lithography process.

• Cleaning: Ultrasonic and chemical cleaning remove any residues or particles.

3. Chrome Layer Deposition

• Sputtering or Evaporation: A thin layer (~100 nm) of chrome (Cr) is deposited onto one side of the quartz wafer. Chrome provides the opaque layer necessary for photomask patterning.

• Adhesion Layer (optional): A very thin layer of chromium oxide or another adhesive is sometimes applied to improve chrome adhesion to quartz.

4. Photoresist Coating

• A layer of photoresist is spin-coated over the chrome surface.

• This layer is sensitive to UV light and will define the circuit pattern.

5. Photolithographic Patterning

• Exposure: The photoresist-coated substrate is exposed to UV light through a master pattern (reticle).

• Development: The exposed or unexposed regions (depending on resist type) are dissolved away, revealing parts of the chrome layer underneath.

6. Chrome Etching

• Wet or Dry Etch: The exposed chrome areas are chemically etched away, leaving behind the chrome pattern corresponding to the desired circuit design.

7. Resist Stripping

• The remaining photoresist is stripped, leaving behind a clean chrome-on-quartz circuit pattern.

8. Inspection and Quality Control

• Flatness, line width accuracy, and optical transmission (>90% UV-Vis) are rigorously tested.

• Defect inspection ensures no particles, pits, or pattern errors are present.

9. Final Cleaning and Packaging

• The photomask is cleaned again and then sealed in a cleanroom-safe container for delivery or integration into lithographic tools.

Need a quartz substrate for a photomask or lithography experiment? Specify the wavelength, blank size, thickness, flatness, surface quality and coating requirements when requesting a quote.

What Is Alpha Quartz?

Alpha quartz (α-quartz) is the stable, low-temperature crystalline form of silicon dioxide (SiO₂). Its ordered crystal structure gives it direction-dependent optical, elastic and piezoelectric behavior. Above approximately 573°C at atmospheric pressure, alpha quartz undergoes a reversible transition to beta quartz.

Alpha quartz is crystalline and piezoelectric; fused silica is amorphous and is selected for many UV, optical and photomask applications. Choosing between them depends on the required crystal response, transmission range, thermal behavior and fabrication process.

Common Alpha Quartz Wafer Cuts

• AT-cut quartz wafers for resonators, oscillators and frequency-control research.
• ST-cut quartz wafers for selected surface acoustic wave and sensor applications.
• X-cut and Y-cut quartz wafers for piezoelectric, acoustic and electrical characterization.
• Z-cut quartz wafers for optical-axis and specialty materials research.

Key Properties of Alpha Quartz

• Chemical formula: SiO₂

• Crystal Structure: Trigonal/hexagonal lattice

• Thermal Stability: Stable below 573°C, above which it transitions to β-quartz

• Piezoelectric Effect: Exhibits piezoelectric properties (generates electric charges under mechanical stress)

Alpha Quartz in Semiconductor Research

Alpha quartz is an electrical insulator rather than a semiconductor. Its combination of optical transparency, piezoelectric response, chemical stability and low dielectric loss makes it useful in selected semiconductor, RF, acoustic and materials-research workflows.

1. Substrate and Dielectric Material:

• Quartz substrates (often fused silica or crystalline α-quartz) are widely used in semiconductor processing, especially for photolithography masks, optical elements, and high-frequency RF/Microwave devices due to low dielectric loss, high optical transparency, and dimensional stability.

2. Quartz Crystal Oscillators:

• Alpha quartz is essential for quartz crystal resonators used as oscillators in semiconductor-based electronics. Due to its piezoelectric nature, it precisely controls frequency generation in clocks, microprocessors, radio transmitters, and other timing-critical semiconductor circuits.

3. Thermal and Chemical Stability:

• Alpha quartz is chemically inert and has minimal thermal expansion, making it ideal for semiconductor processing tools, masks, and equipment components exposed to harsh fabrication conditions (such as plasma etching, deposition, and high-temperature treatments).

4. Deposition Substrate for Thin Films:

• Alpha quartz substrates can support thin-film deposition and materials growth experiments involving graphene, carbon nanotubes, III-V semiconductors and metal-oxide materials. The correct surface finish, orientation and thermal budget depend on the deposition process.

Alpha Quartz Applications

Alpha quartz wafers are used in frequency-control components, QCM, SAW devices, piezoelectric sensors, optical experiments, thin-film deposition and specialized photolithography research. Review our single-crystal quartz wafer guide to compare AT-, ST-, X-, Y- and Z-cut material.

Related Quartz Wafer Resources

• Single-Crystal Quartz Wafers
• AT-Cut Quartz Wafers
• ST-Cut Quartz Wafers
• X-Cut Quartz Wafers
• Y-Cut Quartz Wafers
• Z-Cut Quartz Wafers
• Fused Silica Wafers
• Piezoelectric Materials
• Quartz Photomasks