Temperature Sensitive Micro-electro-mechanical Systems (Part II ) Amy Kumpel Richard Lathrop John Slanina Haruna Tada featuring MACIS 16 July 1999 Tufts University TAMPL REU

Overview Brief review and progress report Basic theory and setup –Imaging system, beam curvature System Analysis –Incident light angle –High temperature exposure E(T) and  (T) values Conclusion and Future work

Measurement and characterization –mechanical properties of micro-scale devices –thermal properties of device materials under high temperatures Tri-layered Poly-Si and SiO 2 cantilever beams Brief Review of T-MEMS Determine Young’s Modulus, E(T), and the coefficient of thermal expansion,  (T), of thin films (poly-Si, SiN x ) at high temperatures

Recent Progress More data (and more data) with current setup Error Analysis Modified the LabVIEW program for piecewise  (T) analysis Obtained additional values for  (T) and E(T) Assisted Haruna with her thesis

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

Theory: Imaging System reflection from curved beam substrate beam I. image of beam on camera II. Apparent Beam Length, L beam

Theory: Beam Curvature Nomenclature –radius of curvature, R –apparent length, * L beam –tip deflection, h –half cone angle,  –arc angle of beam,    R L beam   C A B h *changes with focusing

Analysis: Tilt Angle (  Asymmetric data hints that the system is tilted –Angle  effects negative curvature values, but not positive Adjust numerical program to compensate for  –Find  from experiments Values: 0.5°~1.0° C   R L beam   h 

Analysis: High Temperature Exposure Assumption: beams experience fatigue when exposed to high temperatures TMEMS heated to ~850°C for various amounts of time Measured deflection after each run Trend: as time at 850°C increased, deflection becomes more negative

High Temperature Exposure  time (min)total time (min)deflection (  m)curvature (1/  m)

Determining  (T) Two material properties approximate beam curvature for both Poly-Si and SiO 2 –Young’s Modulus (E) –Coefficient of Thermal Expansion (  ) Estimate E(T) from previous publications Find a best fit  (T) using a numerical model

Linear Approximation of  Si (T)  300  50 Analyzed 5 different ranges of data Averaged the  Si value for each range Extrapolated to 50°C and 300°C temperature (°C)

  Values SiO 2 Poly-Si

Conclusions The coefficient  was found for 50°C to 1000°C for both Poly-Si and SiO 2 The experimental error in curvature was found –Angle  gives ~3% for negative values –Variance in focusing gives ~2% for all values

Future Work Modify setup for Nitride beam analysis Create x-y-z stage for easy movement of sample Get more values for E(T) and  (T) through more runs Prepare for final presentation

Any Questions For Us?