Vibrating beam accelerometer two-wafer fabrication process

A method for fabrication of microelectromechanical systems (MEMS) integrated micro devices, the method comprising:

• forming an array of first three-dimensional micromechanical device features in each of a plurality of first silicon wafers each having top and bottom substantially parallel surfaces spaced apart by a thickness of the first silicon wafer material, including forming an array of first three-dimensional proof masses suspended for motion relative to first frames by one or more flexures;
• applying a first alignment mark to a face of each of the first wafers relative to the array of first device features;
• in each of a plurality of second silicon wafers each having top and bottom substantially parallel surfaces spaced apart by a thickness of the second silicon wafer material, forming an array of second three-dimensional micromechanical device features that includes one or more device features that are different from one or more of the first device features formed in the first wafers and are configured to cooperate with different ones of the first device features formed in the first wafers, including forming an array of second three-dimensional proof masses suspended for motion relative to second frames by one or more vibratory beams;
• applying a second alignment mark to a face of each of the second wafers relative to the array of second device features;
• preparing one of each of the first and second wafers for wafer bonding;
• mutually aligning the first and second wafers as a function of aligning the respective first and second alignment marks;
• and
• permanently bonding the first and second wafers into a single composite wafer having the first device features formed in the first wafer permanently bonded to the second device features in the second wafer configured to cooperate therewith including permanently bonding respective first and second three-dimensional frames into single composite three-dimensional frames, and permanently bonding respective first and second three-dimensional proof masses into single composite three-dimensional proof masses suspended from respective composite frames by respective flexures and coupled thereto by respective vibratory beams.

A method for fabrication of microelectromechanical systems (MEMS) integrated micro devices, the method comprising:

• micromachining an array of first three-dimensional micromechanical device features in a first silicon wafer, the first three-dimensional micromechanical device features including at least one partial three-dimensional micromechanical device feature;
• micromachining an array of second three-dimensional micromechanical device features in a second silicon wafer, the second three-dimensional micromechanical device features being configured to cooperate with the first three-dimensional micromechanical device features and including at least one partial three-dimensional micromechanical device feature that is configured to be joined with the partial device feature in the first silicon wafer;
• mutually aligning the first and second arrays of device features;
• permanently joining the first and second arrays of device features into an array of integrated micro devices as a function of permanently joining the first and second silicon wafers into a single composite wafer;
• and
• subsequently separating the array of integrated devices into individual devices each having a set of the first and second device features.

A method for fabrication of microelectromechanical systems (MEMS) integrated micro devices, the method comprising:

• forming an array of first three-dimensional micromechanical device features in each of a plurality of first silicon wafers, the first device features including first proof mass and frame features with each of the first proof mass features being suspended for motion relative to one of the first frame features by one or more flexure features;
• applying a first alignment mark to a face of each of the first wafers relative to the array of first device features;
• forming an array of second three-dimensional micromechanical device features in each of a plurality of second silicon wafers, the second device features including second proof mass and frame features that are configured to cooperate with the first proof mass and frame features;
• applying a second alignment mark to a face of each of the second wafers relative to the array of second device features;
• preparing one of each of the first and second wafers for wafer bonding;
• mutually aligning the first and second wafers as a function of aligning the respective first and second alignment marks;
• and
• permanently bonding the first proof mass and frame features to the second proof mass and frame features.