Micromechanical capacitive acceleration sensor

• US 20060156818A1
• Filed: 03/07/2002
• Published: 07/20/2006
• Est. Priority Date: 03/08/2001
• Status: Active Grant

• Current Assignee: Conti Temic Microelectronic GmbH (Continental AG)
• Original Assignee: Conti Temic Microelectronic GmbH (Continental AG)
• Inventors: Weinacht, Manfried, Seidel, Helmut, Knittl, Peter, Prechtel, Ulrich, Kapser, Konrad, Toelg, Sebastian
• Granted Patent: US 7,343,801 B2
• Time in Patent Office: Days
• US Class Current: 73/514.320
• CPC Class Codes: F16N 11/08 with mechanical drive, other than directly by springs or weights lubricating-pumps F16N13/00
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration
• CPC Class Codes: G01P 2015/0834 the mass constituting a pendulum having the pivot axis disposed symmetrically between the longitudinal ends, the center of mass being shifted away from the plane of the pendulum which includes the pivot axis
• CPC Class Codes: G01P 2015/0845 using a plurality of spring-mass systems being arranged on one common planar substrate, the systems not being mechanically coupled and the sensitive direction of each system being different
• CPC Class Codes: G01P 2015/0857 using a particular shape of the suspension spring
• CPC Class Codes: G01P 2015/086 using a torsional suspension spring

Abstract

A micromechanical capacitive acceleration sensor is described for picking up the acceleration of an object in at least one direction. The sensor includes a frame structure (110), a sensor inertia mass (101) made of a wafer and movably mounted relative to the frame structure (110) about a rotation axis, and a capacitive pick-up unit (120) for producing at least one capacitive output signal representing the position of the sensor mass (101) relative to the frame structure (110). The sensor inertia mass (101) has a center of gravity which offset relative to the rotation axis in a direction perpendicularly to a wafer plane for measuring accelerations laterally to the wafer plane. The sensor mass (101) and the frame structure (110) are made monolithically of one single crystal silicon wafer. A cover section (112) forms a common connector plane (150) for the connection of capacitor electrodes (125,126). Torqueable elements (105) form an electrically conducting bearing device for the sensor mass (101).

Claims

1. A micromechanical capacitive acceleration sensor for picking up the acceleration of an object in at least one direction, said sensor comprising a frame structure, a sensor inertia mass made of a wafer movably supported about a rotation axis (A_x, A_y) relative to said frame structure, and a capacitive pick-up unit for producing at least one capacitive output signal representing the position of said sensor inertia mass relative to said frame structure, wherein said sensor inertia mass comprises a center of gravity (M_x, M_y) which is offset relative to said rotation axis (A_x, A_y) in a direction extending perpendicularly to a plane of said wafer.

2. The acceleration sensor of claim 1, wherein said sensor inertia mass and/or said frame structure are made monolithically of a single crystal silicon wafer.

49. The acceleration sensor of claim 1, further comprising a bearing device including torqueable elements made of silicon for supporting said sensor inertia mass.

50. The acceleration sensor of claim 1, further comprising an electrical contacting on said frame structure and a bearing device for supporting said sensor inertia mass, said bearing device forming an electrically conducting connection between said sensor inertia mass and said electrical contacting on said frame structure.

51. The acceleration sensor of claim 1, further comprising a bearing device arranged on said sensor inertia mass close to a surface of said wafer.

52. The acceleration sensor of claim 1, wherein said sensor inertia mass has a shape selected from any one of the following shapes:

a cubic shape, a parallelepiped, a frustum and a truncated pyramid.

53. The acceleration sensor of claim 1, comprising a plurality of sensor inertia masses movably mounted relative to a respective rotation axis (A_X, A_Y, A_Z) for measuring accelerations in a plurality of directions (x, y, z) extending perpendicularly to one another, wherein one or more sensor inertia masses respectively have a center of gravity (M_Z, M_Y) which is offset relative to its respective rotation axis (A_X, A_Y) in a direction extending perpendicularly to a plane of said wafer.

54. The acceleration sensor of claim 1, wherein said center of gravity of said sensor inertia mass is arranged relative to the respective rotation axis (A_X, A_Y) and laterally displaced in a direction of said wafer plane.

55. The acceleration sensor of claim 1, wherein said capacitive pick-up unit comprises first capacitor electrodes provided on said sensor inertia mass and second capacitor electrodes provided on said frame structure opposite said first capacitor electrodes, said pick-up unit further comprising first connector elements for electrically connecting said first capacitor electrodes and/or second connector elements electrically connecting said second capacitor electrodes, said first and second connector elements being arranged in a common connector plane.

56. The acceleration sensor of claim 55, wherein said first connector elements and/or said second connector elements are contacted on a single side.

57. The acceleration sensor of claim 1, wherein said capacitive pick-up unit is contacted electrically on a single side.

58. The acceleration sensor of claim 55, wherein said second capacitor electrodes on said frame structure and said first and second connector elements are arranged on or in said common connector plane.

59. The acceleration sensor of claim 1, further comprising a coupling arrangement for coupling of first capacitor electrodes provided on said sensor inertia mass to first connector elements provided on said frame structure, said coupling arrangement comprising a galvanic or capacitive connection for bridging an elevational difference between said first capacitor electrodes and a common connector plane.

60. The acceleration sensor of claim 1, wherein said frame structure comprises a central frame section laterally enclosing said sensor inertia mass and a first cover section elevationally displaced relative to said sensor inertia mass and arranged on said central frame section and second capacitor electrodes provided on a facing side of said first cover section which faces said sensor inertia mass.

61. The acceleration sensor of claim 60, wherein said facing side of said first cover section facing said sensor inertia mass forms a common connector plane for an electrical connection of said capacitive pick-up unit.

62. The acceleration sensor of claim 55, wherein said second capacitor electrodes are formed either by a metallizing layer on said sensor inertia mass or by said sensor inertia mass that is made of an electrically conducting material.

86. The acceleration sensor of claim 1, comprising a plurality of sensor inertia masses and wherein each sensor inertia mass is equipped with a respective capacitive pick-up unit for picking up the acceleration of an object in a plurality of directions (x, y, z), a plurality of bearing devices, each of said plurality of sensor inertia masses being supported by a respective bearing device in said frame structure independently of one another, each sensor inertia mass comprising a respective capacitive pick-up unit for producing an output signal representing the position of the respective sensor inertia mass relative to the frame structure.

87. The acceleration sensor of claim 86, wherein said sensor inertia masses are mounted in a common plane in said frame structure, and wherein first and second connector elements of all sensor inertia masses are provided in a common connector plane.

94. A method for producing an acceleration sensor as defined in claim 86, said method comprising the following steps:

a) first producing each of said plurality of sensor inertia masses as a single sensor with its own frame structure and

b) assembling said single sensors to a complete sensor.

3-48. -48. (canceled)

63. A micromechanical capacitive acceleration sensor, for picking up acceleration of an object in at least one direction (x, y, z), comprising a frame structure which is stationary relative to said object, a sensor inertia mass which is movable relative to said frame structure, a bearing device elastically supporting said sensor inertia mass relative to said frame structure for movement about a starting position, said capacitive acceleration sensor further comprising a capacitive pick-up unit for producing at least one capacitive output signal representing a position of said sensor inertia mass relative to said frame structure, said capacitive pick-up unit comprising first capacitor electrodes provided on said sensor inertia mass and second capacitor electrodes provided on said frame structure opposite said first capacitor electrodes, and a coupling arrangement including first connector elements coupled to said first capacitor electrodes, said first connector elements being provided on said frame structure, and second connector elements coupled to said second capacitor electrodes, and wherein said first connector elements and/or said second connector elements are arranged in a common connector plane which is elevationally displaced relative to said first capacitor electrodes provided on said sensor mass and/or relative to said second capacitor electrodes provided on said frame structure.

64. The acceleration sensor of claim 63, wherein said coupling arrangement comprises means for bridging an elevational difference between said first capacitor electrodes and/or said second capacitor electrodes and said common connector plane.

65. The acceleration sensor of claim 63, wherein said second capacitor electrodes provided on said frame structure and said first and second connector elements are arranged in or on said common connector plane, and wherein said coupling arrangement comprises means for bridging an elevational difference to said common connector plane.

66. The acceleration sensor of claim 63, wherein said coupling arrangement forms a galvanic or capacitive connection which bridges said elevational difference to said common connector plane.

67. The acceleration sensor of claim 63, wherein said frame structure comprises a central section laterally surrounding said sensor inertia mass and a first cover section elevationally displaced relative to said sensor inertia mass and arranged on said central section, wherein said second capacitor electrodes are provided on that side of said first cover section which faces said sensor inertia mass, and wherein said first capacitor electrodes are provided on said sensor inertia mass opposite said second capacitor electrodes.

68. The acceleration sensor of claim 67, wherein said common connector plane in which said first connector elements and said second connector elements are arranged, is formed by that side of said first cover section which faces said sensor inertia mass and wherein said second capacitor electrodes are also provided in or on said side of said first cover section facing said sensor inertia mass.

69. The acceleration sensor of claim 68, wherein said first connector elements, said second connector elements and said second capacitor electrodes which are connected to the second connector elements, are made of a single conductive layer formed on the side of the first cover section which faces said sensor inertia mass.

70. The acceleration sensor of claim 69, further comprising a second coupling electrode formed on that side of said first cover section which faces said sensor inertia mass, wherein a first coupling electrode is provided on said sensor inertia mass opposite said second coupling electrode, whereby said first and second coupling electrodes form a capacitive connection of the coupling arrangement for coupling the first capacitor electrodes provided on the sensor inertia mass with a first connector element provided on said frame structure.

71. The acceleration sensor of claim 70, wherein said second coupling electrode and said first connector element are provided in said common connector plane which is formed by that side of said first cover section which faces the sensor inertia mass.

72. The acceleration sensor of claim 71, wherein said second coupling electrode and said first connector element connected to said first coupling electrode, said second capacitor electrodes and said second connector elements connected with the second capacitor electrodes are made of a single conducting layer formed on that side of said first cover section which faces said sensor inertia mass.

73. The acceleration sensor of claim 67, further comprising a second cover section provided elevationally displaced relative to said sensor inertia mass, said second cover section being positioned at said central section opposite said first cover section, said second cover section forming together with said central section and with said first cover section a hermetically sealed housing enclosing said sensor inertia mass, said first capacitor electrodes and said second capacitor electrodes.

74. The acceleration sensor of claim 63, wherein said bearing device comprises torsion elements to which said sensor inertia mass is mounted to the frame structure in a torsion elastic manner for motion relative to and about said starting position.

75. The acceleration sensor of claim 74, wherein said two torsion elements forming said bearing device are positioned relative to a common rotation axis, said two torsion elements being effective on opposite sides of said sensor inertia mass, whereby said sensor inertia mass is movable only relative to a single direction (x, y, z) relative to the frame structure.

76. The acceleration sensor of claim 74, wherein said torsion elements are rigidly secured, on the one hand, to said sensor inertia mass and, on the other hand, to said central section of said frame structure.

77. The acceleration sensor of claim 74, wherein said coupling arrangement is formed by a galvanic connection which includes said torsion elements.

78. The acceleration sensor of claim 63, wherein said bearing device comprises one or more bending elements on which said sensor inertia mass is supported in a bending elastic manner around said starting position and relative to said frame structure.

79. The acceleration sensor of claim 78, wherein two bending elements are provided in a common plane spaced from each other and rigidly connected to said sensor inertia mass, whereby said sensor inertia mass is movable only in a single direction (x) relative to said frame structure.

80. The acceleration sensor of claim 78, wherein two bending elements are rigidly connected, on the one hand, to the sensor inertia mass and, on the other hand, to said first cover section of said frame structure.

81. The acceleration sensor of claim 78, wherein said coupling arrangement is formed by a galvanic connection which includes said bending elements.

82. The acceleration sensor of claim 78, comprising a single bending element which is centrally and rigidly connected to said sensor inertia mass, whereby said sensor inertia mass is movable with respect to two different directions (x, y) relative to said frame structure, and wherein said pick-up unit is adapted for producing two capacitive output signals which represent the position of said sensor inertia mass relative to said frame structure.

83. The acceleration sensor of claim 82, wherein said pick-up unit comprises four first capacitor electrodes secured to said sensor inertia mass in pairs positioned opposite each other and on opposite sides of said bending element, and four second capacitor electrodes secured to said first cover section of said frame structure, said second capacitor electrodes being arranged in pairs positioned opposite each other on opposite sides of said bending element and opposite said first capacitor electrodes.

84. The acceleration sensor of claim 82, wherein said coupling arrangement comprises a first coupling electrode provided on said sensor inertia mass and surrounding said bending element, and a second coupling electrode provided on said first cover section of said frame structure, and wherein said second coupling electrode is positioned opposite said first coupling electrode and surrounding said bending element.

85. The acceleration sensor of claim 82, wherein said coupling arrangement comprises a galvanic connection including said bending element.

88. The acceleration sensor of claim 63, wherein said sensor inertia mass is adapted for picking-up an acceleration of said object in a horizontal direction (x, y) and wherein said bearing device of said sensor inertia mass is elevationally displaced upwardly relative to the mass center of gravity (M_Z, M_Y), whereby the sensor inertia mass performs, in response to an acceleration of said object, a rotational motion about a rotation axis (A_X, A_Y) defined by said bearing device.

89. The acceleration sensor of claim 63, wherein said sensor inertia mass is adapted for picking-up an acceleration of said object in a vertical direction (z), and wherein said bearing device of said sensor inertia mass is laterally offset relative to the mass center of gravity (M_Z) whereby the sensor mass performs, in response to an acceleration of the object, a rotational motion about a rotation axis (A_Z) defined by the bearing device.

90. The acceleration sensor of claim 63, wherein said first capacitor electrodes are provided on said sensor inertia mass in pairs and respectively on opposite sides of a rotation axis (A_X, A_Y, A_Z) defined by said bearing device wherein said second capacitor electrodes are provided on said frame structure also in pairs and respectively positioned opposite said first capacitor electrodes, and wherein a differential capacity of said capacitor electrodes forming pairs is used for producing a capacitive output signal of said pick-up unit.

91. The acceleration sensor of claim 63, wherein said first capacitor electrodes provided on the sensor inertia mass are formed of a conducting material of which the sensor mass is made.

92. The acceleration sensor of claim 67, wherein said first cover section of said frame structure is made of a glass containing an alkali metal.

93. The acceleration sensor of claim 73, wherein said second cover section of said frame structure is made of a glass containing an alkali metal.