Patent ID: 8516906

Claim:
A force sensor having a sensor substrate joined to a base substrate, wherein the sensor substrate comprises: a pressure receiving unit formed on a first surface of the sensor substrate; a displacement portion configured to be displaced by an external load applied thereto through the pressure receiving unit; a plurality of piezoresistance elements provided on a second surface of the sensor substrate opposite to the first surface, each of the plurality of piezoresistance elements having an electrical resistance that changes in accordance with an amount of displacement of the displacement portion; a sensor-side support provided on the second surface of the sensor substrate, configured to displaceably support the displacement portion, the sensor-side support being formed in a shape having an inner peripheral edge enclosing an entire periphery of the displacement portion in plan view, at least part of the sensor-side support overlapping the plurality of piezoresistance elements in plan view; and a plurality of sensor-side electrically connecting portions provided on the second surface along a periphery of the sensor substrate so as to surround an outer periphery of the sensor-side support, each of the plurality of sensor-side electrically connecting portions being electrically connected to a corresponding one of the plurality of piezoresistance elements, and located at a separated position that does not cross a virtual line passing through a center of the pressure receiving unit and a center of each of the plurality of piezoresistance elements, wherein the base substrate includes: a base-side support provided on a surface facing the sensor substrate, the base-side support being joined to the sensor-side support; a plurality of base-side electrically connecting portions provided on the surface along a periphery of the base substrate so as to surround an outer periphery of the base-side support, the plurality of base-side electrically connecting portions being connected to the plurality of sensor-side electrically connecting portions; and a plurality of electrode pads formed at ends of electrical wiring extending from the base-side electrically connecting portions, the plurality of electrode pads providing electrical connections to external circuitry, and wherein the sensor-side support is joined to the base-side support with a metal joint layer disposed therebetween, and each of the plurality of sensor-side electrically connecting portions is joined to a corresponding one of the plurality of base-side electrically connecting portions with a metal joint layer disposed therebetween, each of the metal joint lavers having a thickness of 300 nm or smaller and being formed of an alloy including one or more of materials selected from the group consisting of Al, Ti, Cr, Ni, Cu, Ru, Rh, Ir, Pt, Ta, Fe, and Au, or a multilayer film composed of two or more lavers each including a material selected from the group consisting of Al, Ti, Cr, Ni, Cu, Ru, Rh, Ir, Pt, Ta, Fe, and Au.