Cr/Au films are nowadays receiving considerable attention for many MEMS devices which operate in high temperature conditions as for example micromachined chemoresistive sensors for gas detection. For this kind of application a microhotplate to maintain the sensing layer to a high temperature working condition (nearly 400�C) is required. In this research work we evaporated Cr as adhesion layer and Au as contact layer on Silicon wafers. These metal layers show good adhesion and also good Au wire bondability at room temperature, but for temperature higher than 250�C the metal is not reliable due to the inter-diffusion. To overcome this problem we introduced nickel as barrier layer between Cr and Au films. Different Ni thicknesses were evaporated to test the properties of the metal multilayer before and after annealing. The resulting Cr/Ni/Au sandwich structures were annealed at temperature in the range of 200-550�C to evaluate the effectiveness of the barrier in preventing Cr/Au interaction. The interaction was studied by the use of optical and electron microscopy, Auger electron spectroscopy and sheet resistance measurements.
Cr/Ni/Au multilayer films for high temperature MEMS applications
Guarnieri, Vittorio;Bagolini, Alvise;Micheli, Victor;Filippi, Massimiliano;Decarli, Massimiliano;Moscon, Franco;Giacomozzi, Flavio;Margesin, Benno;Soncini, Giovanni;Zen, Mario
2002-01-01
Abstract
Cr/Au films are nowadays receiving considerable attention for many MEMS devices which operate in high temperature conditions as for example micromachined chemoresistive sensors for gas detection. For this kind of application a microhotplate to maintain the sensing layer to a high temperature working condition (nearly 400�C) is required. In this research work we evaporated Cr as adhesion layer and Au as contact layer on Silicon wafers. These metal layers show good adhesion and also good Au wire bondability at room temperature, but for temperature higher than 250�C the metal is not reliable due to the inter-diffusion. To overcome this problem we introduced nickel as barrier layer between Cr and Au films. Different Ni thicknesses were evaporated to test the properties of the metal multilayer before and after annealing. The resulting Cr/Ni/Au sandwich structures were annealed at temperature in the range of 200-550�C to evaluate the effectiveness of the barrier in preventing Cr/Au interaction. The interaction was studied by the use of optical and electron microscopy, Auger electron spectroscopy and sheet resistance measurements.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
