ScAlN thin films for 5G RF-MEMS
- Unmatched stress uniformity and flexibility
- No abnormal outgrows
- Scandium concentrations up to 40%
- At a fraction of the cost
Because of its very high electro-mechanical coupling, scandium-doped aluminum nitride (ScAlN) is of great interest in high frequency MEMS applications. As the 5G market keeps growing, the request for higher frequency band-filters are imposing challenges to current high-volume production technologies. Solmates offers customers a technology advance in terms of film uniformity (yield) and cost per wafer.
Solmates-PLD enables mass production of > 30% ScAlN films, matching the high-quality performance the industry demands. The fully cluster compatible Solmates PLD platform combines all necessities for ScAlN thin film processing with full automation, easy maintenance, high wafer throughput and stable and clean performance.
Highly doped ScAlN
- Sc-doping values from 20% to 40%
- Smooth and dense thin films on (patterned) electrode materials
- Demonstrated for film thicknesses ranging from 250 to 1000 nm
Solmates PLD offers a deposition technology to deposit high quality ScAlN up to very high Scandium concentrations. Benefiting from several intrinsic advantages of PLD over conventional PVD, we have demonstrated high quality films of 40% ScAlN with our own affordable Scanramics deposition targets. The combination of high quality ceramic deposition targets that are very small compared to the wafer size, creates an opportunity to deposit high Scandium concentrations in a cost-efficient manner.
Excellent grain control
Solmates has developed custom ScAlN process recipes for different device layouts and interfaces that allow customers to have defect-free films without any unwanted abnormal outgrows. The tuneability of our process arises from the dynamic nature of our PLD plasma.
Solmates has demonstrated this for:
- Any Scandium concentration
- Any stress value
- A variety of bottom electrode materials
- A variety of device geometries
- With conservation of crystal properties
Dynamic local stress control
- Best-in-class WiW stress control: < 50 MPa full range
- Fexibility to tune the average stress from compressive to tensile
- No change in e31,f
Today stress control is becoming increasingly important in BAW device manufacturing. The relation between coupling factor and film stress imposes a strong demand for very high within wafer stress uniformity, to avoid the use of any reworking steps. Since Solmates PLD is a local
deposition technology that uses substrate scanning to achieve large area coverage, Solmates has a unique opportunity to modulate PLD settings to achieve best-of-class WiW-uniformity values. PLD even enables the application of an intentional stress non-uniformity on your wafer to compensate for other layers.
Other ScAlN applications
Besides RF resconators, our unique Scanramics ScAlN process supports a wide-range of other MEMS applications that benifit from high Scandium concentrations and stress flexibility.
- Low noise PiezoMEMS microphones
- Ultra-sound transducers (pMUTs)
- Ferroelectric ScAlN thin film applications
- SAW device layouts
Typical performance specifications for Solmates ScAlN thin films
| Parameter | Unit | 30% ScAlN | 40% ScAlN |
|---|---|---|---|
| Piezo -e31,f | C/m2 | 2.6 | 3.5 |
| Piezo d33 | pN/C | 15 | 23 |
| Dielectric constant | - | 19 | 26 |
| Dielectric loss tangent | - | < 0.001 | 0.001 |
| Breakdown voltage | V/um | > 160 | TBD |
| Tunable stress range | MPa | - 600 < x < 600 | - 600 < x < 600 |
| Stress WiW-uniformity | MPa [max-min] | < 50 | < 50 |
| Thickness WiW-uniformity | 1 sigma | < 0.5% | < 0.5% |
| FWHM of rocking curve | Degree | < 2 | 2.1 |
| Surface roughness | nm RMS | < 2 | < 2 |
| Abnormal outgrows | Yes / no | No | No |
