Microelectromechanical system pressure sensor and method for making and using

#A pressure sensor may convert an amount of pressure into an electrical value. For example, a pressure sensor may use a sensor diaphragm or membrane positioned parallel to a plane of a wafer to convert an amount of pressure into a capacitance value. Note that the overall size of the pressure sensor may be important. For example, the amount of space on a wafer that is occupied by a pressure sensor (referred to as the sensor's “footprint”) might make a device expensive to produce and/or make the sensor impractical for some applications. Thus, it may be important that a pressure sensor does not occupy too large of an area on a wafer.

#In addition, increasing the sensitivity of a pressure sensor might require an increase in the sensor's footprint. Moreover, such a change could require that some parts of the sensor are completely re-designed (which can be a difficult and time-consuming process).

#According to some embodiments, an apparatus includes a substrate that defines a plane. The apparatus also includes a first conducting plate that is substantially normal to the substrate and a second conducting plate that is (i) substantially normal to the substrate and (ii) deformable in response to a pressure.

#FIG. 1 is a perspective view of a known pressure sensor.

#FIG. 2 is a side view of the pressure sensor of FIG. 1.

#FIG. 3 is a perspective view of an apparatus constructed in accordance with an exemplary embodiment of the invention.

#FIG. 1 illustrates a capacitive pressure sensor 100. The sensor 100 includes a pair of conducting plates 110, 120 that are positioned substantially parallel to a horizontal plane that is defined by a non-conducting substrate 130 (e.g., a wafer). Note that in some cases, the plate 110 could formed as an integral part of the substrate 130. One of these plates 120 is deformable in response to pressure (P). In particular, as shown in the side view of the sensor 100 illustrated in FIG. 2, the plate 120 might be a thin film diaphragm that flexes such that the distance between the two plates 110, 120 will decrease when a pressure P acting on the conducting plates 110, 120 is increased.

#Note that the capacitance C between the plates 110, 120 depends in part on the distance between them. In particular, when the two plates 110, 120 are electrically isolated from each other, it can be detected that the amount of capacitance C increases as the plates 110, 120 move together. An increase in the pressure P, therefore, can be measured based on the increased capacitance C, since the increased pressure will push one plate 120 closer to the other plate 110. Instead of capacitance, a resistance associated with a single deformable plate or diaphragm might be used to measure pressure. For example, one or more piezoreistors could be embedded in a diaphragm. In this case, the diaphragm itself might be formed of a non-conducting material.

#The plates 110, 120 used for the pressure sensor 100 sensor might be, for example, several hundred microns wide. Moreover, improving the sensitivity of the sensor 100 may require even larger plates 110, 120. The relatively large footprint associated with the sensor 100 might make the device expensive to produce and/or make the sensor 100 impractical for some applications. In addition, the large plates 110, 120 could be damaged if too much pressure is applied (e.g., the flexible plate 120 could detach from a supporting structure).