ScAlN thin films for 5G RF-MEMS

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

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:

Dynamic local stress control

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.

Stress Level_graph

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.

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