A Novel System for High- Temperature Curvature Measurements of T-MEMS Amy Kumpel Richard Lathrop John Slanina Haruna Tada Introducing MACS 30 July 1999 Tufts University TAMPL REU FINAL PRESENTATION

Overview T-MEMS Background The MACS system Experimental Procedure Theory Imaging Results –Curvature and Deflection Material Properties –Analytical Model and Results Conclusion and Future Work

Background: Composition Tri-layered cantilever beams 1.03  m SiO 2, 0.54  m poly-Si 0.19  m SiO 2 (thin, protective coat) 0.19  m SiO  m SiO  m poly-Si Si substrate SiO 2 poly-Si

Imaging System image of beam on camera II. Apparent Beam Length, l beam reflection from curved beam substrate beam I. well

CCD camera collimated light source beam splitter Al reflector quartz plate W-halogen lamp and housing sample thermocouple Si wafer quartz rod Experimental Setup

Experimental Procedure Center sample to CCD camera Heat to ~850°C using tungsten-halogen lamp then gradually cool to room temperature –LabVIEW program records temperature vs. time data Save grayscale images every 20 to 30 seconds during the trial –LabVIEW program determines l beam from grayscale values of each image Calculate beam curvature, K, at each temperature

Theory: Beam Curvature  CC R l beam CC C A B h  C Strategy Find room-temperature R from initial h and L arc Find  C from room- temperature R and l beam Solve for R at all other temperatures from  C and values of l beam

Theory: Beam Curvature  CC R l beam CC C A B h (1) h = R - R cos   = R ( 1 - cos  ) (2) h = R ( 1 - cos  ) R L arc (3) L arc R =  (4) l beam = R sin  C  = sin  C K  C

Mismatched curvature data –due to incident light angle,  Experimental Correction –Perform two trials, using different sample orientation –Adjust numerical program to compensate for  –Find  so that curvature data matches for the two trials Theory: The Angle   c  l beam  T  T

Imaging Results: Beam Curvature (K) and Deflection (h) at High Temperatures

Analytical Model ()   f T i dT T T 0  thermal i  thermal strain:    n i t i E t  i1 2 2 i    i1 i E i t neutral plane ( ):  n                                         n i ii i ii n i n j jj n j thermal jjj i i ii ttt tt tE tE tE t E K       Townsend (1987)

Material Properties: Determining  (T) K = f(,,, ) Low temperature (50°C to 300°C) –Find through linear extrapolation –Assume constant, exhibiting glass- like behavior High temperature (300°C to 1000°C) –Assume –Find through linear extrapolation

Material Properties: Linear Approximation of  (T)  300  50 Analyze different ranges of data Average the  value for each range Extrapolate through temperature range Temp (°C)

Material Properties:  (T) Values from 50°C to 1000°C Poly-Si SiO 2

Conclusion and Future Work Modified MACS for increased accuracy Found values for  (T) of thin films Created a website Wrote and submitted paper to: Measurement and Science Technology Modify MACS for nitride beam analysis Verify values of  (T) for SiO 2 at high temperatures Obtain  (T) values for SiN x

Group T-MEMS Thank You