US 5,055,838 AGranted

Silicon tactile imaging array and method of making same

AssigneeThe Regents of the University of Michigan

InventorsKensall D. Wise, Kenichiro Suzuki

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Abstract

A high-performance single-crystal silicon tactile imaging array organized in a X-Y matrix of capacitor elements. Metallic column lines are formed on a glass support substrate, while the row lines are formed from a contiguous chain of doubly-supported bridge structures, with one such structure for each sensing element. All of the bridge structures are simultaneously fabricated from a single-crystal silicon semiconductor wafer using a two-step boron diffusion process, followed by a silicon-to-glass electrostatic bonding step and subsequent unmasked wafer dissolution. Each bridge structure has a thick center plate for the sense capacitor supported by thinner beams connected to adjacent row single-crystal silicon support rails bonded to the glass substrate. The force sensitivity and maximum operating range of the tactile imager can be selected over a very wide range by appropriately setting the dimensions of these thinner support beams. The resulting imager is rugged, of high resolution and high density, and is inherently stable over time and temperature.

Claims14

Dependent claims

A miniature tactile imaging array having a plurality of adjustable parallel plate capacitors each of which is responsive to force applied to one plate thereof, the array comprising:

a support substrate having an insulating surface;
at least first and second electrically conductive stripes spaced from one another and disposed on the insulating surface and constituting a set of address lines;
a first plurality of electrically conductive plates spaced from one another and electrically connected to the first stripe, each such plate forming one plate of a distinct one of the adjustable capacitors;
a second plurality of electrically conductive plates spaced from one another and electrically connected to the second stripe, each such plate forming one plate of a distinct one of the adjustable capacitors;
and
first and second pluralities of force-sensitive bridge structures made from a common wafer of single-crystal semiconductor material, with the first and second pluralities of bridge structures being electrically isolated from one another and with the bridge structures within each such plurality of bridge structures being electrically interconnected to one another and constituting at least part of one line of a set of output lines, said output lines being formed so as to cross the set of first address lines at an angle,
each such bridge structure including a central plate portion, a pair of flexible beam portions thinner than the central plate portion and connected to, supporting and extending outwardly from opposite sides of the central plate portion, and a pair of side support portions each permanently attached to the support substrate and connected to and supporting a distinct one of the beam support portions on a side thereof opposite the central plate portion, the central plate portion and beam portions being positioned and patterned such that the central plate portion is nominally suspended and directly supported a predetermined distance above the insulating surface of the support substrate only by the pair of flexible beam portions, and
each such bridge structure being positioned with its central plate portion located above a distinct one of the electrically conductive plates, whereby each such central portion constitutes a second plate of a distinct one of the adjustable capacitors.

5 more elements

A miniature tactile sensor structure made at least in part from single-crystal semiconductor material and including therein a parallel plate capacitor whose capacitance varies generally in accordance with the magnitude of a mechanical force applied thereto, comprising:

a support substrate having at least one generally flat surface upon which an electrically conductive pad is formed, the pad constituting one plate of the capacitor;
and
a force-sensing bridge structure made from a unitary piece of patterned single-crystal semiconductor material and having a pair of generally elongated support rails spaced apart from one another permanently mounted to the support substrate, having a predetermined first height, a relatively thick plate centrally located between the pair of support rails, and a pair of flexible relatively thin beams located on opposite sides of and mechanically interconnecting the thick plate to the support rails, thereby allowing the thick plate to move in response to a sufficient mechanical force applied thereto in a direction normal to the surface of the support substrate;
the thick plate being spaced apart from the surface of the support substrate, supported by the thin beams and having a second height above the surface of the support substrate greater than the first height, whereby mechanical contact between the bridge structure and a larger object moving generally perpendicular towards the bridge structure occurs first at the thick plate;
and
the thick plate being unsupported on two sides thereof intermediate the thin support beams and forming the second plate of the capacitor.

3 more elements

Dependencies are inferred from the claim text.