Method for the manufacturing of a capacitive pressure sensor, and a capacitive pressure sensor

#The invention relates to measuring devices used in the measuring of pressure, and more specifically to capacitive pressure sensors. The object of the invention is to provide an improved method for the manufacturing of a capacitive pressure sensor and a capacitive pressure sensor suitable, in particular, for use in small capacitive pressure sensor solutions.

#The principle of measuring based on a capacitive pressure sensor has proved to be a simple and reliable way of measuring pressure. Capacitance measuring is based on a change in the gap between two surfaces of a pair of electrodes in the sensor. The capacitance between the surfaces, i.e. the storage capacity of electric charge, is a function of the area of the surfaces and the distance between the surfaces. Capacitance measuring can be used even at fairly low ranges of pressure.

#The basis for the structure of small capacitive pressure sensors is a thin-film structure manufactured on silicon. The thin membrane forming one of the electrodes bends under influence of pressure and thus changes the capacitance to be measured.

#The present invention and its preferred embodiments are described below in detail, with exemplifying reference to the attached figures, in which:

#FIG. 1 shows the progress with time of wet etching according to prior art, using two different etching masks,

#FIG. 2 shows an ideal membrane structure of a pressure sensor,

#The FIGS. 1-4 are presented above.

#The invention and the preferred embodiments thereof are described with reference to the FIGS. 5 to 7.

#FIG. 5 shows a silicon wafer of type (100) according to the present invention, in which wafer pressure sensor membrane structures have been produced by anisotropic wet etching. Sixteen diamond shaped etched areas are depicted in the silicon wafer 15 according to the present invention. In the figure, circles indicate the area 17 of the flexible membrane portion of the pressure sensor, which area is patterned on the back surface of the membrane. The cutting lines for the pressure sensor elements are drawn with heavy black lines. In the solution according to the present invention, the orientation of the cutting is turned by 45 degrees in relation to the direction <110>.