FREQUENCY COMPENSATED OSCILLATOR DESIGN FOR PROCESS TOLERANCES

• US 20180248532A1
• Filed: 04/30/2018
• Published: 08/30/2018
• Est. Priority Date: 10/03/2003
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Lutz, Markus, Partridge, Aaron
• Granted Patent: US 10,439,579 B2
• Time in Patent Office: Days
• CPC Class Codes: H03H 2009/02299 Comb-like, i.e. the beam comprising a plurality of fingers or protrusions along its length
• CPC Class Codes: H03H 2009/0233 comprising perforations
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 3/0072 of microelectro-mechanical resonators or networks micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C
• CPC Class Codes: H03H 3/0076 for obtaining desired frequency or temperature coefficients
• CPC Class Codes: H03H 3/0077 by tuning of resonance frequency
• CPC Class Codes: H03H 9/2447 Beam resonators H03H9/2468 takes precedence
• CPC Class Codes: H03H 9/2457 Clamped-free beam resonators
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

A continuous or distributed resonator geometry is defined such that the fabrication process used to form a spring mechanism also forms an effective mass of the resonator structure. Proportional design of the spring mechanism and/or mass element geometries in relation to the fabrication process allows for compensation of process-tolerance-induced fabrication variances. As a result, a resonator having increased frequency accuracy is achieved.

Claims

1-26. -26. (canceled)

27. A resonator comprising:

a substrate;

an anchor;

a mass element having an effective mass m; and

a spring beam;

wherein;

the spring beam is movably suspended over the substrate;

a first end of the spring beam is attached to the anchor, which anchors the spring beam, at the first end, to the substrate;

a second end of the spring beam is attached to the mass element;

the spring beam has an actual width that is defined by a process used to form the spring beam from a constituent material and to form the mass element;

an effective mechanical stiffness k_y that defines a limitation on the movability of the spring beam is defined as

28. The resonator of claim 27, wherein the actual width results from a design width and a total deviation from the design width due to imperfections in the process.

29. The resonator of claim 28, wherein:

the total deviation is defined by a nominal undercut and a tolerance of undercut; and

the nominal undercut is accounted for in a design procedure defining the design width.

30. The resonator of claim 29, wherein the net effect of the tolerance of undercut associated with the process, as applied proportionally to the actual width of the spring beam and the effective mass of the mass element, results in little change to the ratio defined by a change in the effective mechanical stiffness and a change in the effective mass.

31. The resonator of claim 27, wherein the spring beam and the mass element are formed from the same constituent material.

32. The resonator of claim 27, wherein the process includes at least one etch step selected from a group of etch steps including wet etch, plasma etch, and vapor etch.

33. The resonator of claim 27, wherein a first side of the mass element is attached to the spring beam, which is anchored to the substrate via the anchor, and a second side of the mass element, opposite the first side, is not attached to the spring beam and is not separately anchored to the substrate.

34. The resonator of claim 27, wherein the plurality of beams of the mass element are uniformly formed with widths that are ⅓

of the actual with of the spring beam.

35. A resonator comprising:

a substrate;

a spring mechanism of predetermined length l having an actual width W_real defining an effective mechanical stiffness k_y, a height h, a defined geometry including a plurality of bores within and extending through the spring mechanism, and an effective mass m; and

anchors to which respective ends of the spring mechanism are attached and anchoring the respective ends to the substrate so that the spring mechanism is movably suspended over the substrate;

wherein;

k_y is

36. The resonator of claim 35, wherein the spring mechanism includes a beam and one or more additional mass structures formed integral to the beam.

37. The resonator of claim 36, wherein the bores are formed in the one or more additional mass structures.