Design and Thermal-Electrical Modeling of Low Power Micro-Heater with High Uniform Thermal Gradient

In this paper, the design and evaluation of micro-heaters on borosilicate glass are presented for development of MEMS atomic clocks based on CPT spectroscopy. For CPT based MEMS atomic clocks, the pressured alkali cell is heated for vaporization of alkali metal from liquid or solid state because of sufficient absorption of the laser light over a path. In order to control and maintain operating temperature for the alkali cell in the physics, heaters and RTDs are formed on glass lid of micro-fabricated alkali vapor cell. They were patterned meander shape to reduce the net magnetic fields by the current through the heater and RTD. The proposed device is fabricated by typical lift-off process on the borosilicate glass substrate and annealed by self-heating of micro-heater under the atmosphere environment. The fabricated device has volume of 2x3x0.7 mm(3) and the resistance of micro-heater was 1.2 k Omega. The thermal resistance was significantly increased to 3800 K/W by reduction of the air pressure of 10 mTorr. The simulation and evaluation of micro-heaters for alkali cell in vacuum environment presented the possibility of further reduction of the size of physics for atomic clocks with high thermal resistance.