摘要:
This invention provides a miniaturized silicon thermal flow sensor with improved characteristics, based on the use of two series of integrated thermocouples (6, 7) on each side of a heater (4), all integrated on a porous silicon membrane (2) on top of a cavity (3). Porous silicon (2) with the cavity (3) underneath provides very good thermal isolation for the sensor elements, so as the power needed to maintain the heater (4) at a given temperature is very low. The formation process of the porous silicon membrane (2) with the cavity (3) underneath is a two-step single electrochemical process. It is based on the fact that when the anodic current is relatively low, we are in a regime of porous silicon formation, while if this current exceeds a certain value we turn into a regime of electropolishing. The process starts at low current to form porous silicon (2) and it is then turned into electropolishing conditions to form the cavity (3) underneath.Various types of thermal sensor devices, such as flow sensors, gas sensors, IR detectors, humidity sensors and thermoelectric power generators are described using the proposed methodology. Furthermore the present invention provides a method for the formation of microfluidic channels (16) using the same technique of porous silicon (17) and cavity (16) formation.
摘要:
This invention provides a front-side silicon micromachining process for the fabrication of suspended Porous Silicon membranes in the form of bridges or cantilevers and of thermal sensor devices employing these membranes. The fabrication of the suspended Porous Silicon membranes comprises the following steps: (a) formation of a Porous Silicon layer (2) in, at least one, predefined area of a Silicon substrate (1), (b) definition of etch windows (5) around or inside said Porous Silicon layer (2) using standard photolithography and (c) selective etching of the Silicon substrate (1), underneath the Porous Silicon layer (2), by using dry etching techniques to provide release of the Porous Silicon membrane and to form a cavity (6) under the said Porous Silicon layer. Furthermore, the present invention provides a method for the fabrication of thermal sensors based on Porous Silicon membranes with minimal thermal losses, since the proposed methodology combines the advantages that result from the low thermal conductivity of Porous Silicon and the use of suspended membranes. Moreover, the front-side micromachining process proposed in the present invention simplifies the fabrication process. Various types of thermal sensor devices, such as calorimetric-type gas sensors, conductometric-type gas sensors and thermal conductivity sensors are described utilizing the proposed methodology.
摘要:
This invention provides a front-side silicon micromachining process for the fabrication of suspended Porous Silicon membranes in the form of bridges or cantilevers and of thermal sensor devices employing these membranes. The fabrication of the suspended Porous Silicon membranes comprises the following steps: (a) formation of a Porous Silicon layer (2) in, at least one, predefined area of a Silicon substrate (1), (b) definition of etch windows (5) around or inside said Porous Silicon layer (2) using standard photolithography and (c) selective etching of the Silicon substrate (1), underneath the Porous Silicon layer (2), by using dry etching techniques to provide release of the Porous Silicon membrane and to form a cavity (6) under the said Porous Silicon layer. Furthermore, the present invention provides a method for the fabrication of thermal sensors based on Porous Silicon membranes with minimal thermal losses, since the proposed methodology combines the advantages that result from the low thermal conductivity of Porous Silicon and the use of suspended membranes. Moreover, the front-side micromachining process proposed in the present invention simplifies the fabrication process. Various types of thermal sensor devices, such as calorimetric-type gas sensors, conductometric-type gas sensors and thermal conductivity sensors are described utilizing the proposed methodology.
摘要:
There is disclosed a current generating arrangement having a plurality of thermocouples characterised in that the device comprises: a thick porous silicon layer; 'hot' thermocouple contacts on said thick porous silicon layer; a bulk crystalline silicon member; and 'cold' thermocouple contacts on said bulk, crystalline silicon layer.