FREQUENCY COMPENSATED OSCILLATOR DESIGN FOR PROCESS TOLERANCES

• US 20150263699A1
• Filed: 06/02/2015
• Published: 09/17/2015
• 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 9,800,222 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 spring mechanism having an actual width defining an effective mechanical stiffness;

a mass element having an effective mass;

wherein;

the actual width is defined by a fabrication process used to form the spring mechanism from a constituent material; and

the mass element comprises a plurality of beams structures having a geometry defined such that formation of the actual width by the fabrication process results in little change to a ratio defined by a change in the effective mechanical stiffness and a change in the effective mass.

28. The resonator of claim 27, wherein the actual width is defined in relation to a design width and a total undercut associated with the fabrication process.

29. The resonator of claim 28, wherein:

the total undercut 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 fabrication process, as applied proportionally to the actual width of the spring mechanism 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 mechanism and the mass element are formed from the same constituent material.

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

33. A resonator comprising:

a spring mechanism of predetermined length having an actual width defining an effective mechanical stiffness, a defined geometry, and an effective mass;

wherein the actual width and the effective mass of the spring mechanism are simultaneously defined by application of a fabrication process to a constituent material; and

,

wherein the geometry is defined such that application of the fabrication process to the constituent material results in little change to a ratio defined by a change in the effective mechanical stiffness and a change in the effective mass.

34. The resonator of claim 33, wherein the geometry comprises one or more voids formed in the length of the spring mechanism.

35. The resonator of claim 33, wherein the geometry comprises an outer edge having a plurality of indentations, the plurality of indentations having the effect of increasing a surface area of the outer edge exposed to the fabrication process.

36. The resonator of claim 33, further comprising one or more additional mass structures formed integral to the spring mechanism.

37. The resonator of claim 36, wherein the one or more additional mass structures comprises one or more voids formed respectively in a body of the one or more additional mass structures.

38. The resonator of claim 36, wherein the one or more additional mass structures comprises an outer edge having a plurality of indentations, the plurality of indentations having the effect of increasing a surface area of the outer edge exposed to the fabrication process.

39. The resonator of claim 38, wherein the one or more additional mass structures further comprises one or more voids formed respectively in a body of the one or more additional mass structures.

40. A resonator comprising:

a spring-mass mechanism having an effective mechanical stiffness, an effective mechanical mass, and a geometry that defines the effective mechanical stiffness and mass;

wherein;

the geometry includes at least one of a void and a plurality of indentations in a first portion of the spring-mass mechanism, the at least one of the void and plurality of indentations being dimensioned so that, when the spring-mass mechanism, after it is formed, is subjected to a process that removes material from the spring-mass mechanism, a greater surface area of first portion is exposed to the process than a remaining portion of the spring-mass mechanism, the difference in exposure resulting in a change in at least one of the effective mechanical stiffness and the effective mechanical mass produced in the first portion by the removal of the material that offsets a change in at least one of the effective mechanical stiffness and the effective mechanical mass produced in the remaining portion by the removal of the material, thereby providing a predetermined ratio between the effective mechanical stiffness and the effective mechanical mass upon completion of the process;

the spring-mass mechanism includes a spring beam and a mass formed by a plurality of stacked beams;

a width of the spring is greater than a width of each of the stacked beams; and

the void is formed by an interconnection of at least two of the stacked beams.