Improving AlN & ScAlN Thin Film Technology for Next Generation PiezoMEMS SEMICON Taiwan MEMS FORUM

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1 Improving AlN & ScAlN Thin Film Technology for Next Generation PiezoMEMS SEMICON Taiwan MEMS FORUM Nick Knight PVD Product Manager, SPTS Technologies

2 SPTS Technologies A leading manufacturer of etch and deposition process solutions and equipment for the semiconductor manufacturing industry Global presence Headquartered in the UK Manufacturing sites in UK and US Deep domain expertise Established and long standing partnerships with major industry players Etch PVD CVD Release Etch *Thermal *Sold under agreement with SPP Technologies

3 Volume AlN Adoption in MEMS / RF AlN key resonator component in BAW filters Precise control of film properties required Front end equipment used for volume MEMS AlN resonator layer Deposited by PVD Courtesy of Qorvo

4 BAW Filter Market Trends Source: Qorvo Website 41 separate RF bands supported by a smartphone Different countries, different carriers, GSM to 4G There are 20 BAW filters in an iphone 6S Duplexers for 9 bands. Bandpass & rejection filters We estimate 8B BAW filters were shipped in 2015 Although phone growth slowing, BAW content increasing Source: Qorvo Website

5 MEMS Microphone Content Increasing Up to 4 MEMS mics in a modern smartphone Large arrays give stronger signal, better pick-up To support large arrays need: High signal to noise ratio (SNR) Tight tolerance, mic to mic

6 PiezoMEMS Microphones Capacitive PiezoMEMS Capacitive mic read signal across two near surfaces Surfaces can stick together. Sensitive to dust & moisture Acoustic resistance (air in gap), has noise In a piezo mic, sound deflects AlN plates Creates strain, converts into electrical signal Insensitive to particles, moisture hydrophone potential No acoustic resistance, high Signal to Noise Ratio (SNR), 68 db(a) vs 65 for Cap

7 pmut Fingerprint Sensors Capacitive sensors rely on pushing surfaces together A ridge closes the gap, valley does not. Can be fooled by dirt, moisture, oils A pmut sensor uses ultrasonic reflections Finger valleys contain air strong echo Ridges give weak echo AlN Generate a 3D image, with some depth information Impervious to moisture, grime. More fool-proof AlN used for the ultrasonic resonator material Rapidly growing market 17% CAGR to $14B by 2020 Sigma fxp is used for development/pilot production

8 Market Leader for Piezo AlN Working with AlN since 1998 Example applications: BAW filters/duplexers Sensors, actuators Gyroscopes, Energy Harvesters Microphones/speakers Si oscillators Largest AlN install base ~50% market share More AlN shipments and more production accounts than any other vendor

9 200mm PVD System Options Sigma c2l Sigma fxp R&D Production Loadlocks 1 1 or 2 Degas/Pre-clean 1 1 PVD Modules Up to 2 Up to 5

10 Typical PiezoMEMS Process Flow SPTS has expertise in all deposition & etch steps Sigma PVD Omega Synapse plasma etch Top Electrode Deposition AlN Deposition Electrode Deposition Underlayer Preparation Electrodes AlN Cavity Substrate AlN etch HF or XeF 2 vapor etch Release etch

11 Process Module Hardware Process Gas MHz Coil RF Platen MHz Platen RF RHSE Module Combined degas/pre-clean ICP Ar sputter etch High density plasma above wafer Wafer separately biased Low energy, high flux at wafer Patented smoothing etch Smoothing Etch AlN Texture FWHM Rough oxide underlayer No >2.5 Rough oxide underlayer Yes 1.4 Planar rotating magnetron Adjustable magnet position Adjustable motor speed AlN Sputter in Ar/N 2 environment Reactive deposition by Pulsed DC Electrode uses same hardware >90% uptime in AlN production fab Magnetron Target Platen PVD Module

12 Doped AlN AlN is the CMOS friendly choice Able to integrate into monolithic devices CMOS MEMS Mature, understood, cost-effective Sc-doped AlN Higher coupling coefficient Kt2 6.5% 8.5% Improved signal strength Improved battery life Other materials considered MgX-AlN (X = Hf, Zr) Taiyo Yuden Y-AlN TU Wien Ti-AlN Univ Linkoping, Univ Madrid Cr-AlN Univ Penn Source: Internet ScAlN AlN Film stress, MPa

13 Sc Adoption BAW Working in 5-15 Wt% Sc range Several BAW manufacturers now working with ScAlN MEMS Ideally looking for up to 43 Wt% Sc for sensors Improved sensitivity vs PZT BUT costs need to be considered Sigma fxp used for ScAlN programs at major BAW and MEMS manufacturers BKM recipes available

14 AlSc PVD Target Manufacturing Melt Casting Target Challenging alloy system prone to macro segregation Currently limited to < 15 at% Sc Exhibits low oxygen content < 200ppm Higher Sc% extremely brittle & can fracture during processing >15 At% Sc development continues Casting Powder Processing Powder Processed Target Currently required for Sc >15 at% due to the presence of brittle intermetallic Highest Sc content of interest 43 at% Powder based products exhibit high oxygen content >>1000ppm

15 Super Uniformity ScAlN WIW thickness uniformity critical to yield Thickness determines resonant frequency Super Uniformity hardware developed Radial NU changed by adjusting magnet offset Fine tuning through magnet rotation speed adjustment Non-radial NU adjusted by rotating the wafer N S Increasing offset gives more deposition at centre of wafer S N 1.3 µm ScAlN < 0.3% 1σ, 3 mm EE 200 mm wafer Wafer Rotating Platen

16 B-MAX - Improving AlN Yield Steep reduction in AlN thickness at wafer edge on 200 mm wafers High density ions near major erosion zone re-sputtering AlN film below Films create surfaces too steep/thin for trim correction B-MAX solution steers ions away from wafer edge Previous B-MAX 200 mm WIW NU Spec based on 10 mm EE B-MAX extends mm EE for spec to 3 mm EE Qualified and in production

17 ScAlN Stress Control RF Bias used to control stress of AlN film More ion bombardment -> more compressive film Control Options Forward Power DC Bias Film Thickness Increasing thickness requires higher bias for set stress level Sc doped films require enhanced stress control e - Ar + e - Ar + e- Matching Unit MHz Generator 200 Stress (MPa) Wafer Count

18 Don t Trust 2D Linescans! New hardware optimizes WIW stress range Resolves any non-radial stress component Often hidden with 2D Line Scans Region of non-radial compressive AlN. Tests suggest plasma related. Stress Range < ± 50 MPa

19 ScAlN Grain Morphology ScAlN films have tendency to form high density single crystal defects Reduces Q, etch issues, affects top electrode growth Highest density in wafer centre centre centre centre edge edge

20 Controlling Crystal Defects Defect density strongly dependant on stress Density increases with high tensile stress Defect density highest in wafer centre matching max tensile stress Defects Density with Stress -1200nm ScAlN Defects/100um W,288 MPa center mid edge 100W,210 MPa 120W,-265 MPa Increasing tensile stress 140W,-621 MPa Stress (MPa) Centre Tensile stress Wafer Diameter(mm) Edge compressive

21 Stress Control Techniques Applied 1300 nm (< 10At%) ScAlN on Si Mean stress ~360 MPa Patent application in progress Centre Edge <1 defects per 100um 2 <1 defects per 100um 2

22 AlScN WIW Thickness & Stress 1µm AlSc 8.2%at N Film NU < 0.3%1σ 200mm wafer 3 mm EE Symmetrical stress profile

23 Summary RF BAW continues to grow New devices increases AlN adoption ScAlN needed for both BAW and MEMs devices Increased Kt2 Improved SNR, low power efficiency Thickness and Stress are key requirements We provide high performance, highly productivity solutions 20+ years experience Excellent thickness uniformity and stress control features Reliable systems

24 If you would like to.. find out more about SPTS & ScAlN deposition or any of our other served markets. Please come and visit us at Booth #324