Microstructures for Temperature Uniformity Mapping during PECVD SFR Workshop May 24, 2001 Dwight Howard, Eunice Lee, Scott Collins and Rosemary Smith MicroInstruments and Systems Laboratory Davis, CA 2001 GOAL: to demonstrate a thermal mapping array for PECVD, using thin film microstructures and/or MEMS thermal actuators by 9/30/2001. 5/24/2001

Motivation Small feature reproducibility requires film thickness uniformity Uniformity of PECVD films depends on spatial control of process parameters: plasma composition (gas flow rates and pressure) plasma energy (power) substrate surface Temperature Substrate surface temperature relies on thermal conductivity of substrate and contact of substrate to platen, and is not controlled or monitored. A simple, tool independent, low cost, temperature mapping method for PECVD processes would provide useful data for process and tool development. 5/24/2001

Thin Film Temperature Sensor Metal, thin film, bilayer resistors 500Å Cr SiO2 Silicon Al/Cr or Al/PolySi Resistor Effect: permanent change in R with T Mechanism: interdiffusion, alloying, or annealing 5/24/2001

Al/Cr Resistors R/R0 R/R0 Temperature (C) 10 8 6 4 2 1 130 150 170 190 1.3 8 1.25 2nd Phase Formation 1.2 6 1.15 4 1.1 2 1.05 1.0 1 130 150 170 190 210 230 250 270 290 310 330 350 Temperature (C) 5/24/2001

Temperature Mapping Demonstration Al/Cr Resistors, 120 nm PECVD Si3N4 platen set T= 330 C time = 10 min SiH4 + NH3 Al/Cr 312 < TS < 330 5/24/2001

Al/PolySi Resistors An alternative resistor structure employing VLSI materials Highly reproducible effect, independent of Al thickness and underlying film, but mechanism is as yet undetermined. 5 min 10 min 20 min Al, 600 Å PolySi, 6000 Å SiO2 Si 5/24/2001

Al/PolySi Temp Mapping Demonstration 100 nm PECVD Si3N4 Degrees, C 400 350 300 250 Platen T=300C 300 < T < 380 C 5/24/2001

MEMS Thermal Actuator (remaining task for 2001) Aluminum, 1 mm Cantilever Beam Silicon, 2 mm aAl=23(10-6) C-1 aSi=2.6(10-6) C-1 Silicon Thermal expansion coefficient mismatch strain displacement T= T0 T1 >T0 TC>T1 TC depends on geometry of cantilever. Array of microstructures with varying TC. Readout can be an optical imager.. in situ or post processing. 5/24/2001

Thermal Actuator as Temperature Sensor Al/polySi Bimetal Actuator T Bending Cantilever Beam Buckling Microbridge 5/24/2001