MEMS
2020 7. 10
MEMS Acoustic, MEMS Microphone time-varying pressure sensor
Size Electro Characteristics


• Engineering Process Review
-
- 1 , Q.C.D
- Back-End =
. EOL ,


- Engineering

RD ( ) TS (R&D), PI () V&V ()
Terminology (CMMI)

Product Requirements Product Components, Work products, V&V, Verification and validation reports
Customer needs
ProductsProduct Components
Alternative Solutions
2) TS(Technical Solution), ,
3) PI (Product Integration),
4) VER(Verification), 5) VAL(Validation),
Introduction


Acoustical Energy Electrical EnergyTransducer, Sensor
Microphone → Time varying Pressure Sensor
Microphone is a transducer which convert from acoustical energy to electrical energy
MEMS microphone is a microphone using MEMS and CMOS design and fabrication
Sensor, Actuator (Microphone, Speaker) - Acoustic
Sensor →

MEMS die
Vb, Voltage Generation
Vdd
Introduction

Brief Target Electro-Acoustic Characteristic
Min.Typ. Max.
Foreign Material Protection & Water proof IEC-529 Standard N/A
MIC Package Information Packaged (Bottom) View Dimension - mm Dimension (refer to Package View) 3.50x2.65x0.98T
Supply Voltage Vdd V 1.5 1.8 3.6
Supply Current Idd Vsupply 3.3 V 500 -
Sensitivity S dBV/Pa 94dB SPL @ 1kHz -35 -38 -41
Signal to Noise Ratio SNR dB(A) 94dB SPL @ 1kHz, 20~20kHz A-weighted 62 65
Total Harmonic Distortion THD % 125 dB SPL 1.0
THD1 % 135 dB SPL 10
Output Impedance Zout @ 1kHz 500
MEMS Die Information MEMS Acoustic Plain View
MEMS Size mm 1.4×1.4×0.45 T
Effective/Membrane Size m 500, 800 ~ 1000
Membrane or BP material - PolySi, TiN
Zero Capacitance, C0 (pF) 3.4
Vbias Voltage Vbia (V) 5, 7, 10V
ROIC Die Information ASIC Plain View
ROIC Size m 600×800
Current Consumption Idd A 130 ~ 150A
Gain (dB) dB 1.3 ~ 6
PSRR dB Vdd=2V, 100mVpp square wave@217Hz 78
Noise Floor dBV -101 3
3. 50 ±
0. 1

Acoustical Energy Electrical EnergyTransducer

Vb = 13, 7, 5V
electrically short between two electrodes
End
(MEMS Plain View)
Vb, Voltage Generation
Performance of Capacitive Microphone: the open-circuit 1) Sensitivity is defined by
(the diaphragm mechanical sensitivity) x (the electrical field strength exerting across the capacitor gap)
=
27 0
for Circular Diaphragm
e0 (dielectric constant of air), (Mechanical sensitivity of the diaphragm)
for Homogeneous Diaphragm, piston-like movement
= × =
27 0


•
(Mechanical sensitivity of the flat diaphragm) Lower stress → corrugation to reduce stress → increase the
mechanical stiffness
For Good Mechanical Sensitivity, Good MEMS Design and Fabrication Capabilities are required
(Mechanical sensitivity of the flat diaphragm) the changes in air gap and pressure for central deflection P (applied pressure), 0 (central deflection of the diaphragm- circular)
=
(Plate theory )
where R is the radius of the diaphragm (for circular shape), and and are the stress and the thickness of the diaphragm
R&D (design) MEMS Capacitive Acoustic Sensor Design
3) Bandwidth of the microphone
Bandwidth< (resonance frequency)


where - E (Young’s Modulus) - (Poisson’s ratio) - (density of material) - k (compressibility of air) - g (air gap between the plates) - (thickness) - a (thickness and length of diaphragm)
for circular diaphragm, 2 = 2


σ (MPa) residual stress 20~60
d (μm) Air gap 5~20
deff (μm) Effective air gap 8.9
V (V) Polarization voltage 2~155
Xo (μm) unit cell 43
rh (μm) 13
h (μm) 30
Nh 85

υ Poisson’s ratio 0.3
(kg/m3) 3200
μ (μPas) 17.8
() ()
R&D (design) MEMS Capacitive Acoustic Sensor Design
=

+
+
=

E0 = polarization h = unpolarized air gap β = a = b =
Cto = Ci = preamplifier input Cs = stray
=


MEMS Process Runsheet Product Control PlanCore Work Products:
Production (, )


STEP System
Process Runsheet
Wafer MAP
Wafer MAP
Global: GF, TMSC
Supply Chain No RnD (1) RnD (2) Foundry Vendor(IT) Customer
1
MEMS
ASIC
3 Infineon Infineon GoerTek CHN,SEC
4 Infineon Infineon, Dongb BSE SEC, LG
5 ADI TSMC STM, ADI → Invensense
7 VESPER (BCI) -Piezoelectric Michigan, Towerjazz GF AAC
MEMS Microphone Production Process and Supply ChainProduction (, )
MEMS MEMS


IC Processes
• Bulk Micromachining • Surface Micromachining • Wafer Boding • Deep Silicon RIE • LIGA • Micromolding • etc
Micro Machining Processes
PCB Process

Wafer wafer in
ti o n
MEMS wafer ( ) initial Runsheet = design or benchmarked for i = n, Engineering Sample (i) = es-Runsheet (i), end; % n < 10 for j = m, Pilot Sample ( j) = pp-Runsheet ( j), end; % m < 3
End ( ) → In-House Process Runsheet (i)
Production (, )

SiO2
Wafer wafer in

Temperature (°C)
Wafer wafer in
SiO2

MEMS Process - Lithography
• Lithography comes from two Greek words : “lithos" means stone, and "graphein" means write.
"writing a pattern in stone"
Tooling spec

Gas Flow (SCCM) Pressure (mTorr)
Power(W) Etch Rate (A/min)CF4 O2
36 4 40 230 -
Plasma based Dry Etching
CF4(g) gives F(g)
O2 combines with CF3, CF2 reducing
their recombination with F.
Etching gas

IC Processes
(MEMS Plain View)
Vb, Voltage Generation
Vdd





• : (Ar/N2) () ,
• :
•:
•:
- Ar ()
ASM Series ASM Series
PLASMA CLEANING


Encapsulation I


• :


* :
: 4gf
EPOXY 0.45 ±0.3
EPOXY 0.12 ±0.05

& Array Sawing Measurement Tape & Reel Label & Pack


•: •:
Singulation - -
PLASMA CLEANING


•
- MEMS Microphone : 1 Pa MEMS
MEMS Microphone Production (, )
-


Acoustic & Electrical
Directivity Omnidirectional
Sensitivity S dBV/Pa 94dB SPL @ 1kHz -37 -38 -39
Signal to Noise Ratio High SNR
dB(A) 94dB SPL @ 1kHz,
20~20kHz A-weighted 65
Total Harmonic Distortion THD % 125 dB SPL 1.0
Output Impedance Zout @ 1kHz 500
MEMS Die Information
ASIC Size m 500×500×250T
Current Consumption Idd A 130 ~ 150A
PSRR dB Vdd=2V,
100mVpp square wave@217Hz 78
Noise Floor dBV -103
Production (, ) MEMS Microphone
MEMS Microphone Sensitivity Bandwidth
Wide Band




TEMPERATURE CYCLE TEST After exposure at 70±2 for 1 hour, at 20±2 for 30 minutes, at 25±2 for 1 hour. 5
cycles, sensitivity to be within ±3 from initial sensitivity.
LOW TEMPERATURE TEST After exposure at -25±2 for 200 hours, sensitivity to be within ±3 from initial sensitivi
ty.
HIGH TEMPERATURE TEST After exposure at 70±2 for 200 hours, sensitivity to be within ±3 from initial sensitivit
y.
TEMPERATURE SHOCK Temperature change from 80±2 to -40±2 each 5 minutes for 1 hour.
After 32 cycles, sensitivity to be within ±3 from initial sensitivity.


HUMIDITY TEST After exposure at 70±2 to 95% relative humidity for 200 hours, sensitivity to be withi
n ±3 from initial senstivity.
DURABILITY LIFE TEST After exposure at 85 to 85% relative humidity for 24 hours, sensitivity to be within ±
3dB from initial sensitivity.
HIGH HUMIDITY TEST
After exposure at 85 to 85% relative humidity for 120 hours, sensitivity to be within ±
3dB from initial sensitivity.
DROP TEST
To be no interference in operation after dropped to steel floor 12 times from 1.5 meter
height in state of packing.

VIBRATION TEST
To be no interference in operation after vibrations. 10Hz to 55Hz for 1 minute full ampl
itude 1.52mm, for 2 hours at three axes. After vibration test. Sensitivity must be within
±3dB from initial sensitivity.
ESD TEST
(Electrostatic Discharge )
The microphone under test must be discharged between each ESD exposure without gr
ound. ( HBM : ±2kV , MM : ±200V )

REFLOW SENSITIVITY TEST
Max 249, during 1 hour, 2 passes of reflow. After reflow test 2 times, Sensitivity must
be within ±3.0dB from initial sensitivity
Production (, )

IoT
• • •
/
• • •
• • •

• • •
• ( ) • •