4-présentation de cécile genevoisaudace-reliability.crihan.fr/ateliers_files/2-failure analysis...
TRANSCRIPT
WorkShop Audace
INSA ROUEN8 juin 2012
Groupe de Physique des Matériaux
Failure analysis of the HEMT GaN
Cécile Genevois
8 juin 2012
AGENDA
� Context
� GPM presentation
� GPM: High Technology instruments
� Power amplifier HEMT – GaN reliability: HPA application
� Conclusion
Context
� Control of the reliability
• Economic and Scientific issues
� Challenge of failure analysis
• Identification and highlighting of the physical mechanisms
responsible to electrical damage
� High Technology instruments
• Multiscale investigations
From macroscopic to atomic scale
GPM presentation
140 persons
8 teams
� Physic of materials
• Various materials
• Material environments
• Microstructures and properties
evolutions
• Physical mechanism studies
• APT instrumentation
� Electronic
• Electronic reliability and failure
� Electric caracterisation of the componants – lifemode ageing
� Chemical or laser depackaging
GPM: High Technology instruments
Pulsed IV measurment unitAgeing bench in L and S band
Laser Sésame 1000 Laser ablation
Jet Etch II Chemical opening
� Default localisation : Photon Emission Microscopy
� Reactive ion etching plasma
Si-CCD- high sensibility camera:OBIRCH laser diode option 1300nm 90mW; Prober SussMicroteK PM8DSP
PHEMOS 1000-Hamamatsu Photonics France
Plasma Lab 80 Plus-RIE/PE
Source RF 300W 13.56MHzPlasma ConcentratorGaz: SF6, CF4, CHF3, O2, Ar
� Microstructurale analyse
• SEM / FIB
• HR TEM
SEM-FIB NVISION 40 zeiss LDMOS cross section
JEM ARM200F JEOLFEG gun - Probe Cs corr
HRTEM micrograph
• APT (atom probe tomography)
LAWATAPAPT analyse of a bipolar transistor(acknowledgements for S.Duguay; E. Cadel
STMicroelectronics collaboration)
Power amplificator HEMT-GaN : HPA applications
� Technology choice
• HEMT GaN transistor in AB/B class
• Band S
• POUT 50W (≈ P3dB datasheet)
• Power added efficiency greater than 60% to P3dB
� Electric caracterisation
• Ageing conditions
Pulsed-RF saturated runningVDS0 : ≈ VDSBR/2IDS0 : 0mA (Classe B) Operating frequency : Band SFlange temperature : 20°CStress test duration : 700 H
Compared deep class-AB and class-B ageing on AlGaN/GaN HEMT in S-Band
Pulsed-RF Operating Life
See « Accelerating ageing tests in pulsed-RF mode: Application to power AlGaN/GaN HEMTs reliabilitystudy » by J.B. Fonder
∆ Output power (Pout): ↓10%∆ Average drain current (Ids): ↓ 4%∆ Power Added Efficiency (PAE): ↓6%∆ Average gate current (Igs): ↑150%∆ RdsOn: ↑ 8%
- Vp <0 - Schottky barrier height ↓0.1eV
=> 2 mechanisms- One reversible induced by trapped charges- One irreversible induced by physical degradations
• Loss of electrical performances
� Default localisation: Photon Emission Microscopy(PEM)
Fresh
Aged
TEM-3 TEM-2
TEM-1
Superimposed PEM images. Bias point isVDS=20V and ID=100mA for both devices.White squares localize TEM samples.Scale bar = 100µm
- Unstressed device = quite uniform distribution of Photon emission along the 80fingers
- Stressed device = ↑ light intensity at the centre= almost no photon emission at the periphery
→Non uniform degradation → non uniform drain current distribution
→ Vp more negative at the centre than the edge + ≠ temperatures → moredegradation at the centre than the edge
- 3 TEM samples
� TEM Caracterisation
• Gate structure
TEM micrograph of the gate region on TEM-3 sample. Drain=left side
Elemental composition of the TEM-1 schottky contact (EDS line scan)
Elemental composition of the TEM-3 schottky contact (EDS line scan)
HRTEM micrograph of the Ni/AlGaN interfaceof the stressed sample gate contact (TEM-3)
GaN
AlGaN
Ni
Au
EDX overlay mapsAu (blue) /Ni (green) /Al (red)
TEM-3
Drain side
Au
Ni
GaNAlGaN
Si3N4
TEM-2
Drain side
Au
Ni
GaNAlGaN
Si3N4
TEM-1
Drain side
Au
Ni
GaNAlGaN
Si3N4
STEM-HAADF gate contact micrographsScale bar = 100nm
• Schottky contact- Ni layer not uniform on the drain side = process
- ↑ stress => ↑ Ni layer alteration
- Ni layer alteration = Ni/Au interface corrugated+ Ni dissolution in several areas
- Temperature gradient effect
HRTEM micrograph of the Si 3N4/AlGaN passivation interface at drain side (TEM-3)
Elemental composition of the TEM-3 schottky contact (EDS line scan)
- Ni / nickel oxyde / AlGaN → Au / nickeloxyde / AlGaN
- Phenomenon linked to Vp shift and Schottkybarrier drop
- No degradation of the passivation layer
- No delamination of the Si3N4 / AlGaNinterface
Conclusion
• Pulsed RF-life tests → non-uniform Schottky contactdegradation
• PEM analysis = non uniform signature along the die
• TEM analysis = Schottky contact modification = consistentwith electrical measurements
• Edge damage < centre damage = consistent with atemperature gradient. Temperature measurments areoccuring.
• As part of the AUDACE project, new instruments(Depackaging, PEM, RIE) are used to study the reliability ofnew technologies. These new instruments, associated to theGPM equipments (SEM/FIB, TEM, ATP), strengthen GPMexpertise in the field of reliability.
THANK FOR YOUR ATTENTION