C. Hibert, EPFL- CMI CMI-Comlab revue, june 4t h, 2002 Dry etching in Dry etching in MEMS fabrication MEMS fabrication by Cyrille Hibert by Cyrille Hibert in charge of etching in charge of etching activities in CMI activities in CMI clean room clean room É CO LE PO L Y T E C H N IQ U E F ÉDÉRA LE D E LA U SAN N E
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C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Dry etching in MEMS Dry etching in MEMS fabricationfabrication
by Cyrille Hibertby Cyrille Hibert
in charge of etching activities in charge of etching activities in CMI clean roomin CMI clean room
É C O L E P O L Y T E C H N I Q U EF É D É R A L E D E L A U S A N N E
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
CMI etchersCMI etchers
Alcatel 601E STS Multiplex ICP
Other etcher manufacturers for MEMS processing: Oxford, Unaxis, AKT (Applied Material).
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
ICP reactorsICP reactors
Basic of ICP reactors Plasma density and ions energy are decoupled
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Complementarity of the two ICP etchers Complementarity of the two ICP etchers in CMIin CMI
Alcatel 601E STS Multiplex
chuck Mechanical clamping Electrostatic clamping
Chemistry and material to be etched
Fluorine: Si (anisotropic, isotropic), Si3N4,
CxFy: SiO2(thin film).
Cl: metal (Al, Ti, Pt) and others Si, Saphir, AlN,
O2: Polymer,
CxFy: SiO2 (deep).
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Si etchingSi etching
1) Deep anisotropic etching:• Bosch process,• Room T continuous process,• Cryogenic process.
2) Thin film etching.
3) Isotropic etching. Interdigit structure etching on SOI wafer using A601E.
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Basic on Bosch processBasic on Bosch process
SF6 plasma
C4F8 plasma
SF6 plasma
SiF4F+ions
thin fluoro-carbon polymer film (passivation)
Si
Si
Simasque
ions
Si etching using Bosch process - scalloping effect (on
A601E)
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Bosch process on A601EBosch process on A601E
State of the art at CMI:
• Anisotropy at 90° (vertical sidewall),• Etching uniformity (2 % to 5 %),• Selectivity Si:SiO2 (1:200 to 400) et Si:RP (1:100 to 200),• Etching rate: 6 to 12 um/min (loading effect + ARDE),• Sidewall roughness (actual process developpment),• Notching (hardware modification + process developpment).
Under control
In developpment
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Sidewall roughness at the top of a deep anisotropic etching of Si (Bosch process on A601E) as a function of pulse duration:
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Deep polymer etchingDeep polymer etchingO2
plasma COx
O + ions
Passivation layerformed by the
redeposition of sputtered material
20 °C thick polymer layer mask
hold substrate
6 um polyimide etching on STS Multiplex ICP
- Mask (PR, SiO2, Al, Pt),- ER: 1 um/min.
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
Metal etchingMetal etching
AlSi etching using Cl2/BCl3 chemistry (on STS Multiplex ICP)
• selectivity Al:RP 2:1,• ER: 0.2 to 0.5 um/min.
Pt etching using Cl2/Ar chemistry (on STS Multiplex ICP)
• selectivity Pt:RP 1:8,• ER: 30 nm/min.
C. Hibert, EPFL-CMI CMI-Comlab revue, june 4th, 2002
ConclusionConclusionCMI etching process evolution:• Maintaining existing processes (Si, SiO2, Si3N4, Polymer, Al, Pt, Ti, AlN, Saphir),• Deep Si etching : sidewall roughness.
Equipements evolution:• A601E Upgrade for notching control (Si etching),• Etcher dedicated to silice:
- At the present time done on the 2 ICP not dedicated for this,- Increased ask for deep silica etching (microchannel, waveguide, holes),- Exclusive equipement (new internal/external pojects).