Optical Grade Quartz Single Crystal Wafers
Single Crystal Quartz Wafers for SAW, Optical and Frequency-Control Applications
Single crystal quartz wafers, also known as synthetic quartz crystal wafers, are precision substrates used for SAW filters, frequency-control devices, resonators, optical low-pass filters, polarizing optics, sensors, semiconductor processes, and photonics components.
Unlike fused quartz or fused silica, single crystal quartz is a crystalline SiO2 material with piezoelectric and birefringent properties. Wafer performance depends on crystal handedness, cut orientation, orientation tolerance, inclusion grade, Q value, etch channel density, thickness, TTV, LTV, bow, warp, surface roughness, and wafer edge condition.
ATR Crystal supplies quartz wafers from 1 inch to 4 inch, with X-cut, Y-cut, Z-cut, AT-cut, ST-cut, 42.75 degree Y-X cut, and custom orientations available for review. Quartz blanks, left-handed quartz, optical-grade quartz, SAW-grade quartz, and drawing-defined quartz components can also be discussed according to application and inspection requirements.
Applications of Quartz Single Crystal Wafers
SAW filters, RF components, and acoustic wave substrates
Frequency-control devices, resonators, and piezoelectric elements
Optical low-pass filters and precision optical plates
Waveplates, polarizers, optical isolators, and fiber-optic components
Sensors, semiconductor processing, and microelectronics substrates
Quartz blanks, custom optics, and research-grade substrates
Advantages of Synthetic Quartz Crystal Wafers
- Piezoelectric performanceSingle crystal quartz is widely used for frequency control and SAW applications where cut angle and crystal quality are critical.
- Stable optical behaviorQuartz crystal provides useful optical transmission and birefringence for optical plates, waveplates, and polarizing components.
- High insulation and chemical stabilitySynthetic quartz crystal is highly insulating, chemically stable, and insoluble in water under normal conditions.
- High-temperature resistanceQuartz crystal has useful thermal stability for precision optical and electronic substrate applications.
- Custom cut orientationX-cut, Y-cut, Z-cut, AT-cut, ST-cut, 42.75 degree Y-X cut, and other rotated cuts can be reviewed.
- Wafer-grade inspectionTTV, LTV, bow, warp, Ra, scratch-dig, particles, inclusions, ECD, Q value, edge defects, and packaging can be specified.
Available Quartz Wafer and Blank Options
Common supply options for synthetic quartz crystal wafers and blanks.
| Item | Available Option | Design Notes |
|---|---|---|
| Orientation | X-cut, Y-cut, Z-cut, AT-cut, ST-cut, 42.75 degree Y-X cut, and custom cuts | SAW and frequency-control devices require exact cut angle and orientation tolerance. |
| Diameter | 1 inch, 2 inch, 3 inch, 4 inch | Availability depends on cut, thickness, grade, and quantity. |
| Thickness | 0.05 mm and above; common values include 0.2 mm, 0.5 mm, and 1.0 mm | Thickness tolerance and TTV should be confirmed with wafer diameter. |
| Surface type | SSP or DSP | Single-side polished or double-side polished processing. |
| Material grade | SAW grade, optical grade, laser grade, left-handed quartz, custom blanks | Grade should be selected according to piezoelectric, optical, or laser requirements. |
| Product form | Wafers, blanks, custom optics, and drawing-defined substrates | Custom processing can be reviewed case by case. |
Quality Evaluation of Synthetic Quartz Crystal
The amount of crystal defect and impurity in synthetic quartz crystal depends on growth rate, mineralizer, raw material, and post-growth processing. Growth conditions influence infrared absorption coefficient, Q value, inclusion behavior, and frequency-temperature performance. For SAW and frequency-control applications, crystal quality should be specified using the relevant grade system and inspection method.
| Quality Item | Evaluation Note |
|---|---|
| Twinning | No electrical or optical twinning should be present in the usable region. |
| Strain | No harmful strain should be present in the seed crystal or grown quartz crystal according to agreed inspection criteria. |
| Cracks and fractures | No cracks, fractures, or unacceptable chipping should be present in the usable region. |
| Inclusion density | Inclusion grading can be specified according to IEC 60758 or agreed customer standard. |
| SAW wafer criteria | Wafer edge, roughness, warp, TV5/LTV, and TTV can be specified with reference to IEC 62276 or customer drawing. |
Product Parameters of Quartz Single Crystal Wafers
The following values summarize typical quartz wafer parameters. Final limits depend on cut orientation, wafer diameter, thickness, grade, and inspection standard.
| Parameter | Typical Value / Option |
|---|---|
| Material | Synthetic quartz single crystal / SiO2 |
| Cutting angle | X-cut, Y-cut, Z-cut, AT-cut, ST-cut, 42.75 degree Y-X cut, and custom cuts |
| Diameter | 1 inch / 25.4 mm to 4 inch / 100 mm |
| Diameter tolerance | <= +/-0.20 mm |
| Thickness | 0.05 mm or more; custom thickness available |
| LTV / TV5 | <1 um within 5 mm x 5 mm area, if specified and feasible for wafer size/grade |
| TTV | Typically <3 um for selected grades; other limits can be reviewed by wafer size and thickness |
| Bow | Typically within +/-30 um, depending on wafer size and thickness |
| Warp | <40 um, depending on wafer size and grade |
| Surface type | Single-side polished, SSP; double-side polished, DSP |
| Polished side Ra | <0.5 nm for selected optical or SAW-grade surfaces |
| Backside criteria | Typically 0.2-0.5 um Ra, or customized |
| Scratch / dig | Better than 40/20, or custom specification |
| Edge criteria | Compliant with SEMI M1.2 or IEC 62276 reference, depending on order requirement |
| Etch channel density / ECD | Better than grade 4, if specified by material grade system |
| Inclusion | Better than grade I, or according to IEC 60758 / customer standard |
| Q value | Better than grade C, or according to agreed frequency-control grade |
| Particles | Particles larger than 0.3 um: <= 30, if specified in the order |
| Scratch and chipping | None by agreed visual inspection criteria |
| Defects | No edge cracks, scratches, saw marks, or stains by agreed inspection criteria |
| Packaging | Typically 25 pcs per wafer box, or custom packing on request |
Product Parameters of Quartz Single Crystal Blanks
Quartz blanks can be supplied for optical, frequency-control, or laser-related processing. Final dimensions depend on orientation, handedness, grade, and drawing.
| Material | Grade | Typical Dimension | Inclusion | Q Value | Optical Homogeneity |
|---|---|---|---|---|---|
| Quartz | Optical | Z: 135 mm; X: 150 mm; Y: 240-280 mm | IEC Class I | >2.40 million | 1 x 10^-5 |
| Quartz | Laser | Z <40 mm; X <110 mm; Y <200 mm | Better than IEC Class IA | >2.40 million | 5 x 10^-6 |
Properties of Optical Grade Quartz Single Crystal Wafers
Typical physical, thermal, dielectric, and elastic properties of synthetic quartz crystal. Values vary by orientation and measurement condition.
| Property | Typical Value |
|---|---|
| Density | 2.65 g/cm3 |
| Melting point | Approx. 1467 C |
| Thermal conductivity at 25 C | 10.7 W/(m K) parallel to Z-axis; 6.2 W/(m K) perpendicular to Z-axis |
| Thermal expansion coefficient, 0-25 C | 7.1 x 10^-6/C parallel to Z-axis; 13.2 x 10^-6/C perpendicular to Z-axis |
| Mohs hardness | 7 |
| Specific heat capacity at 25 C | 710 J/(kg K) |
| Dielectric constant at 30 MHz | 4.34 parallel to Z-axis; 4.27 perpendicular to Z-axis |
| Young’s modulus | 97.2 GPa parallel to Z-axis; 76.5 GPa perpendicular to Z-axis |
| Shear modulus | 31.14 GPa |
| Bulk modulus | 36.4 GPa |
| Chemical stability | Insoluble in water |
| Elastic coefficients | C11 = 87, C12 = 7, C44 = 58, C13 = 13, C14 = 18, C33 = 106 |
Synthetic Quartz Crystal Refractive Index vs. Wavelength
Typical ordinary and extraordinary refractive indices for synthetic crystal quartz. Wavelength is listed in micrometers.
| Wavelength | no | ne | Wavelength | no | ne | Wavelength | no | ne |
|---|---|---|---|---|---|---|---|---|
| 0.185 | 1.676 | 1.690 | 0.243 | 1.605 | 1.617 | 0.589 | 1.544 | 1.553 |
| 0.194 | 1.660 | 1.673 | 0.263 | 1.593 | 1.604 | 1.083 | 1.534 | 1.543 |
| 0.204 | 1.643 | 1.656 | 0.291 | 1.581 | 1.591 | 1.800 | 1.524 | 1.532 |
| 0.219 | 1.625 | 1.637 | 0.340 | 1.567 | 1.577 | 2.500 | 1.512 | 1.520 |
| 0.231 | 1.614 | 1.626 | 0.405 | 1.557 | 1.567 | 3.000 | 1.500 | 1.507 |
Quartz vs. Related Crystal Wafer Materials
Single crystal quartz is often selected when piezoelectric stability, SAW/frequency-control behavior, optical birefringence, and thermal stability are important. LiTaO3 and LiNbO3 may be preferred for other acoustic, electro-optic, pyroelectric, or nonlinear optical requirements.
| Material | Common Use | Main Advantage | Design Notes |
|---|---|---|---|
| Single crystal quartz | SAW filters, resonators, frequency control, optical plates, waveplates, sensors | Stable piezoelectric and optical material with mature wafer processing | Cut angle, handedness, ECD, inclusion grade, Q value, TTV, LTV, and flat orientation are critical. |
| LiTaO3 | SAW devices, pyroelectric sensors, optical and nonlinear components | Good piezoelectric, pyroelectric, and chemical stability characteristics | Often selected for SAW and pyroelectric applications. |
| LiNbO3 | Electro-optic modulators, PPLN, photonics, nonlinear optics, SAW devices | Strong electro-optic and nonlinear optical properties | Often selected for modulation, photonics, and frequency-conversion projects. |
| Fused quartz / fused silica | Optical windows, UV optics, high-temperature glass components | Excellent optical transmission and thermal shock resistance | Not the same as single crystal quartz; it does not provide the same crystalline piezoelectric behavior. |
How to Specify Quartz Wafers
For quartz wafer orders, the most important specifications are cut orientation, orientation tolerance, handedness, diameter, thickness, thickness tolerance, LTV/TV5, TTV, bow, warp, surface type, polished-side Ra, backside roughness, scratch-dig, edge criteria, particles, inclusion grade, ECD grade, Q value, and packing method. For SAW filters, 42.75 degree Y-X cut, ST-cut, flat orientation, and seedless or seeded requirement may also be important.
If the wafer will be used for optical components, confirm transmission range, birefringence requirement, refractive-index basis, surface quality, coating, wedge, parallelism, and optical homogeneity. If the wafer will be used for frequency-control or acoustic devices, provide the full cut angle, IEC reference, and process drawing whenever possible.
Quartz Wafer RFQ Checklist
Providing the following information helps ATR Crystal review feasibility and quote more accurately.
| RFQ Item | Information to Provide |
|---|---|
| Application | SAW filter, resonator, frequency-control device, optical plate, waveplate, sensor, or custom substrate. |
| Crystal requirement | Optical grade, SAW grade, left-handed or right-handed quartz, seeded or seedless requirement, inclusion grade, ECD grade, and Q value. |
| Orientation | X-cut, Y-cut, Z-cut, AT-cut, ST-cut, 42.75 degree Y-X cut, orientation tolerance, primary flat direction, and flat length. |
| Wafer geometry | Diameter, thickness, thickness tolerance, LTV/TV5, TTV, bow, warp, bevel, and edge criteria. |
| Surface requirement | SSP or DSP, polished-side Ra, backside roughness, scratch-dig, particle limit, and visual defect criteria. |
| Order information | Quantity, wafer box requirement, inspection report requirement, packaging, delivery schedule, and drawing. |
