Patent ID: 7647688

Claim:
A method for fabricating a low frequency quartz resonator, the method comprising: forming a first cavity in a silicon handle; metalizing a top-side of a quartz wafer with a metal etch stop; depositing a first metal layer over the top-side of the quartz wafer and over the metal etch stop; patterning the first metal layer to form a top electrode for the low frequency quartz resonator; aligning and bonding the quartz wafer to the silicon handle so that the top electrode and the metal etch stop are within the first cavity in the silicon handle; thinning the quartz wafer to a desired thickness; depositing and patterning a second metal layer over a bottom-side of the quartz wafer to form a hard etch mask for masking the etching of the quartz wafer; etching the quartz wafer to form a first quartz area for the resonator and to form a via through the quartz wafer for contacting the top electrode; removing the hard etch mask without removing the metal etch stop; depositing a third metal layer on the bottom side of the quartz wafer; applying and patterning photoresist over the third metal layer to form a soft mask; etching areas left unmasked by the soft mask of the third metal layer to form a bottom electrode for the low frequency quartz resonator; removing the photoresist to form a quartz resonator on the silicon handle; depositing a fourth metal layer for a substrate bond pad onto a host substrate wafer; aligning and bonding the quartz resonator on the silicon handle to the substrate bond pad; and removing the silicon handle.