HIGH FLOW RATE PERMEATION MEMBRANE ON POROUS SILICON FOR HYDROGEN FILTERING DEVICES

A porous silicon based hydrogen filter has been designed in STMicroelectronics RD so a working temperature ranging between 200 and 500 O C is requested to obtain proper flow rates. Moreover, the cost of Pd alloy membranes as purifiers is quite high, due to the thickness of the Pd alloy foil able to withstand at high permeation pressure gradients. In order to improve the performance of a device like that described above, in the STMicroelectronics it has been proposed a new design in which a very thin Pd layer (500 nm) on a porous silicon substrate (200 pm thick) allows to obtain high flow rates using a very small amount of the precious metal (Pd), with no mechanical filter robustness degradation. The thickness of the porous substrate, as well as the design of the polymer sustain, will be evaluated.