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| siliconOnSapphireSub.compParam | siliconOnSapphireSub.compSOS | siliconOnSapphireSub.compSOI |
|---|---|---|
| Buried Insulator | Sapphire (Al₂O₃, single crystal) | SiO₂ (amorphous) |
| Insulator εᵣ | 9.4–11.5 | 3.9 |
| Thermal Conductivity | 40 W/m·K (sapphire) | 1.4 W/m·K (SiO₂) |
| Radiation Hardness | > 100 krad(Si), no latchup | Up to 100 krad(Si), BOX trapping |
| Max Operating Temp | 300°C | 250°C |
| Substrate Loss (RF) | Extremely low (insulating sapphire) | Low, but HR-Si handle needed |
| Si Film Quality | Heteroepitaxial (defects at interface) | Single-crystal (smart-cut or BESOI) |
| Wafer Diameter | 2″–8″ | 100mm–300mm |
| Cost | $$$ | $$ |
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| siliconOnSapphireSub.specParam | siliconOnSapphireSub.specValues |
|---|---|
| Base Substrate | R-plane (1-102) sapphire, 2″–8″ diameters, 330–650μm thick |
| Silicon Film Thickness | 100nm, 150nm, 200nm, 300nm, 500nm, 1000nm, ±10% tolerance |
| Deposition Method | CVD heteroepitaxial growth, solid-phase epitaxy |
| Silicon Crystal Quality | Single-crystal (100) Si on R-plane sapphire, FWHM < 0.5° XRD |
| Resistivity | Intrinsic: > 100 Ω·cm; N-type or P-type doped per specification |
| Mobility | Electron μₑ: 400–700 cm²/V·s; Hole μₕ: 150–250 cm²/V·s |
| Defect Density | Microtwin density reduced via SPE, < 10⁶/cm² |
| Surface Roughness | RMS < 0.5nm |
| TTV/Bow | TTV < 5μm, Bow < 15μm for 150mm |
| Buried Interface Quality | Si/Sapphire interface: abrupt, contamination < 5×10¹¹/cm² |
| Dielectric Isolation | Sapphire insulator: εᵣ = 9.4–11.5 |
| Thermal Conductivity | Sapphire: 40 W/m·K |
| Operating Temperature | -55°C to +300°C with appropriate metallization |
| Radiation Tolerance | > 100 krad(Si) total dose, no latchup |
| Packaging | Vacuum-sealed single-wafer cassette, Class 100 |
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Radiation-Hardened CMOS
SOS is the premium substrate for radiation-hardened integrated circuits in space, defense, and nuclear applications. The insulating sapphire substrate completely eliminates latchup — the parasitic thyristor effect that destroys bulk CMOS ICs under heavy-ion or proton irradiation. SOS CMOS circuits withstand total ionizing dose (TID) exceeding 100 krad(Si) and single-event latchup (SEL) immunity to LET > 120 MeV·cm²/mg.
RF Switches & Front-Ends
The insulating sapphire substrate eliminates the conductive silicon handle wafer present in conventional SOI, dramatically reducing RF substrate losses. SOS RF switches achieve insertion loss < 0.3 dB and isolation > 30 dB at 2 GHz, with harmonic distortion (HD2/HD3) significantly lower than bulk CMOS or GaAs pHEMT alternatives. Essential for antenna tuning and band selection in multi-mode 4G/5G smartphones.
High-Temperature Electronics
SOS CMOS circuits operate reliably from -55°C to +300°C due to the full dielectric isolation eliminating junction leakage — the primary failure mechanism in bulk silicon at elevated temperatures. Applications include downhole oil and gas instrumentation, automotive engine compartment electronics, and jet engine sensor interfaces where conventional silicon fails above 200°C.
Integrated Photonics
SOS substrates combine a high-index silicon device layer (n = 3.47) on a moderate-index sapphire substrate (n = 1.77), providing sufficient index contrast for sub-micron optical waveguides while enabling evanescent coupling to the sapphire for mid-IR sensing. SOS photonic platforms operating at 1.55μm and in the mid-IR (3–5μm) are used for on-chip spectroscopy and chemical sensing.
X-Ray & Particle Detectors
SOS pixel detectors for high-energy physics experiments and synchrotron X-ray imaging benefit from the fully depleted, low-capacitance silicon film on an insulating substrate. The absence of a conductive bulk eliminates cross-talk between adjacent pixels, while radiation hardness ensures stable operation over years of high-flux exposure at facilities like CERN and synchrotron beamlines.
Aerospace & Satellite Systems
SOS technology has been deployed in over 200 satellite programs, including GPS Block III, Iridium NEXT, and Mars rover missions. The combination of radiation hardness, wide temperature range, and proven flight heritage (> 500 million device-hours in orbit) makes SOS the trusted substrate for mission-critical spacecraft avionics, star trackers, and communication payloads.
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