Silicon chip for use in a force-detection sensor

• US 5,600,074 A
• Filed: 05/10/1994
• Issued: 02/04/1997
• Est. Priority Date: 11/15/1991
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Bantien, Frank, Schmidt, Steffen, Herden, Werner, Weiblen, Kurt, Marek, Jiri, Kuesell, Matthias
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Dougherty, Elizabeth L.
• Application Number:
  US08/240,740
• Time in Patent Office: 1,001 Days
• Field of Search: 73/DIG. 4, 73/862.625, 73/862.637, 73/862.68, 73/721, 257/418, 257/419, 338/4
• US Class Current: 73/862.625
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 23/18 by resistance strain gauges
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

A force sensor employing a silicon chip having a force application area on a top surface and attached to a support at a bottom surface. Piezoresistive elements are arranged on the silicon chip in areas of high mechanical tension and produce signals. Circuits, which receive the signals produced by the piezoresistive elements, are arranged on the silicon chip in areas of low mechanical tension. The areas of mechanical tension may be influenced by providing grooves and/or recesses in the bottom surface of the silicon chip and by providing grooves in the top surface of the silicon chip.

Claims

1. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a) a piezoresistive element, said piezoresistive element

i) arranged in an area of high mechanical tension, and

ii) used to produce signals; and

b) circuits, said circuits

i) arranged in an area of low mechanical tension, and

ii) used to evaluate the signals produced by said piezoresistive element,

wherein the force application area is located on a top surface of the silicon chip, the top surface including a groove located between said force application area and said circuits, and

wherein the groove extends to a depth below the top surface which depth is less than a thickness of the silicon chip.

2. The silicon chip of claim 1, wherein:

the piezoresistive element is arranged in the force application area, and

the silicon chip has a bottom surface which is arranged on a support.

3. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a) a first piezoresistive element, said first piezoresistive element

i) arranged in an area of high mechanical tension, and

ii) used to produce signals;

b) circuits, said circuits

i) arranged in an area of low mechanical tension, and

ii) used to evaluate the signals produced by said first piezoresistive element; and

c) a support which contacts a bottom side of the silicon chip only in an area opposite the force application area wherein said circuits lie outside said area.

4. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a) a piezoresistive element, said piezoresistive element

i) arranged in an area of high mechanical tension, and

ii) used to produce signals; and

b) circuits, said circuits

i) arranged in an area of low mechanical tension, and

ii) used to evaluate the signals produced by said piezoresistive element,

wherein the silicon chip has a bottom surface including a groove, said groove completely surrounding an area of the bottom surface opposite the force application area, and said groove being arranged between the force application area and said circuits,

wherein the bottom surface of the silicon chip is arranged on a support and wherein at least a portion of the area of the bottom surface completely surrounded by the groove is in contact with the support.

5. The silicon chip of claim 4 wherein the surrounded area has a recess emanating from the center of the bottom surface.

6. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a) a first, a second, a third and a fourth piezoresistive element, each of said piezoresistive elements

i) arranged in an area of high mechanical tension,

ii) having a longitudinal direction, and

iii) used to produce signals;

b) circuits, said circuits

i) arranged in an area of low mechanical tension, and

ii) used to evaluate the signals produced by said piezoresistive elements; and

c) a support joining only an edge of a bottom surface of the silicon chip thereby defining a joined area and an unjoined area separated by a boundary,

wherein said piezoresistive elements are arranged on a first line, said first and second piezoresistive elements being oriented such that their-longitudinal direction is along the first line, and said third and fourth piezoresistive elements being oriented such that their longitudinal direction is perpendicular to the first line, and

wherein the unjoined area of the silicon chip is thinner than the joined area of the silicon chip, the boundary is a straight line, the first line is located along the boundary, and said circuits are arranged on the unjoined area.

7. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a) a first, a second, a third and a fourth piezoresistive element, each of said piezoresistive elements

i) arranged in an area of high mechanical tension,

ii) having a longitudinal direction, and

iii) used to produce signals;

b) circuits, said circuits

i) arranged in an area of low mechanical tension, and

ii) used to evaluate the signals produced by said piezoresistive elements,

wherein said piezoresistive elements are arranged on a first line, said first and second piezoresistive elements being oriented such that their longitudinal direction is along the first line, and said third and fourth piezoresistive elements being oriented such that their longitudinal direction is perpendicular to the first line, and

wherein the silicon chip has a bottom surface including a groove, said groove surrounding approximately 270°

of an area of the bottom surface opposite the force application area, the area of the silicon chip having a reduced thickness at a recess on the bottom surface, the first line arranged along a section of the force application area not surrounded by the groove and the groove being arranged between said circuits and the force application area.

8. A silicon chip having a force application area on which a stamp presses, for use in a force sensor, comprising:

a first piezoresistive element, said first piezoresistive element arranged in an area of high mechanical tension, and used to produce signals;

circuits, said circuits arranged in an area of low mechanical tension, and used to evaluate the signals produced by said piezoresistive element; and

a bottom surface having two parallel grooves, wherein the force application area is arranged between the two grooves, the two grooves are arranged between the force application area and said circuits, an area of the bottom surface of the silicon chip between the two grooves has a recess which defines an area of reduced thickness thereby defining two boundaries between the area of reduced thickness and the remaining area of the silicon chip; and

a second, a third, and a fourth piezoresistive element, each of said piezoresistive elements having a longitudinal direction, said first and second piezoresistive elements lying on a first of said two boundaries, said first piezoelectric element oriented such that its longitudinal direction is parallel to the first boundary and said second piezoelectric element oriented such that its longitudinal direction is perpendicular to the first boundary, said third and fourth piezoresistive elements lying on a second of said two boundaries, said third piezoresistive element oriented such that its longitudinal direction is parallel to the second boundary and said fourth piezoresistive element oriented such that its longitudinal direction is perpendicular to the second boundary.