Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1998-07-20
2001-03-13
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S338400, C250S332000
Reexamination Certificate
active
06201243
ABSTRACT:
FIELD OF THE INVENTION
The present invention is concerned with a microbridge structure and a method for forming this microbridge structure. The invention relates to various types of micro sensors for environmental sensing including radiation, temperature, flow, and chemical sensors. More particularly, the invention relates to uncooled IR bolometric detectors.
BACKGROUND OF THE INVENTION
Known in the art, there is the U.S. Pat. No. 5,399,897 of B. T. Cunningham and P. V. Richard, describing a microstructure comprising a surface member and at least one leg, a proximate end of the leg being connected to a substrate and the distant end thereof being connected to the surface member. The leg is a multi layer leg comprising at least one dielectric layer and one electrically conductive layer.
Also known in the art, there are the U.S. Pat. No. 5,021,663 of L. J. Hornbeck and the U.S. Pat. No. 5,288,649 of W. F. Keenan. The supports described in these two patents are made entirely of metal or metal alloy films.
The following US patents also describe microstructures:
U.S. Pat. No.
Issue Date
Inventor (s)
5,010,251
Apr. 23, 1991
Grinberg et al
5,286,976
Feb. 15, 1994
Cole
5,300,915
Apr. 5, 1994
Higashi et al
5,602,393
Feb. 11, 1997
Gerard
5,672,903
Sept. 30, 1997
Butler et al
5,688,699
Nov. 18, 1997
Cunningham et al
Referring now to
FIG. 1
, there is shown a perspective schematic view of a typical microbridge structure of the prior art. The microbridge structure shown in
FIG. 1
consists of a microstructure
40
suspended over a substrate layer
41
, and two inclined legs
42
. The microstructure
40
provides a support for a sensing layer
43
. The microstructure
40
is equipped with slots
44
cut through its entire thickness in order to elongate the path of heat conduction from the microstructure
40
to the substrate layer
41
, and thus improving thermal isolation of this microstructure. The microstructure
40
is also equipped with a reticulated metal layer
45
. The metal layer
45
partially overlapping the sensing layer
43
provides an electrically conductive path between the sensing layer
43
and the legs
42
.
The legs
42
provide a support for the microstructure
40
. The proximate ends of each leg are connected to the substrate layer
41
via electrical contact pads
46
. The distant ends of the legs are connected to the microstructure
40
. Each leg
42
is a multi layer leg consisting of a reticulated dielectric layer
47
and a reticulated electrically conductive layer
48
providing an electrically conductive path between the substrate layer
41
via contact pads
46
and the electrically conductive layer
45
of the microstructure
40
via contacts
49
.
A drawback with the microbridge structures of the prior art is that when several microbridge structures are mounted side by side over a given area of the substrate layer
41
to form the sensitive surface, a portion of the area is needed to accommodate the legs of the microbridge structures. Such portion of the area that is needed to accommodate the legs is useless for sensing purposes and therefor limit the detecting capabilities of the microbridge structures.
An object of the present invention is to provide a microstructure bridge that can be used in a detector array made of several microstructure bridges mounted side by side within a given area to obtain a detector array with improved detecting capability.
Another object of the present invention is also to provided a method for making a microstructure bridge that can be used in a detector array made of several microstructure bridges mounted side by side within a given area to obtain a detector array with improved detecting capability.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a microbridge structure comprising:
a substrate layer provided with two first electrical contacts;
a microstructure including a sensing area provided with two second electrical contacts; and
a micro support for suspending the microstructure over and at a predetermined distance from the substrate layer, the micro support having two electrically conductive paths made of electrically conductive layers, the two electrically conductive paths connecting respectively the two first electrical contacts of the substrate layer to the two second electrical contacts of the microstructure, the micro support extending generally underneath the microstructure, between the microstructure and the substrate layer.
According to the present invention, there is also provided a method for forming a microbridge structure comprising microstructure suspended from a substrate layer by a micro support, the method comprising steps of:
(a) providing the substrate layer with two first electrical contacts;
(b) covering the substrate layer with a first temporary layer, and patterning and etching first cavities in the first temporary layer to provide accesses to the two first electrical contacts of the substrate layer;
(c) covering the layers of the previous steps (a) to (b) with a first electrically conductive layer, and patterning and etching the first electrically conductive layer to provide two first electrically conductive paths extending respectively from the two first electrical contacts, the two first electrically conductive paths being parts of the micro support;
(d) covering the layers of the previous steps (a) to (c) with a second temporary layer, and patterning and etching second cavities in the second temporary layer to provide accesses to the two second electrical contacts;
(e) covering the layers of the previous steps (a) to (d) with a sensing layer, and patterning and etching the sensing layer to define a sensing area located generally over the first electrically conductive paths;
(f) covering the layers of the previous steps (a) to (e) with a second electrically conductive layer, and patterning and etching the second electrically conductive layer to provide two second electrically conductive paths extending respectively from the two first electrically conductive paths to two electrical contacts of the sensing area, the second electrically conductive paths being parts of the micro support; and
(g) removing the first and second temporary layers to reveal the micro support which extends generally underneath the microstructure, between the microstructure and the substrate layer.
REFERENCES:
patent: 5010251 (1991-04-01), Grinberg et al.
patent: 5021663 (1991-06-01), Hornbeck
patent: 5286976 (1994-02-01), Cole
patent: 5288649 (1994-02-01), Keenan
patent: 5300915 (1994-04-01), Higashi et al.
patent: 5399897 (1995-03-01), Cunningham et al.
patent: 5455421 (1995-10-01), Spears
patent: 5602393 (1997-02-01), Gerard
patent: 5672903 (1997-09-01), Butler et al.
patent: 5688699 (1997-11-01), Cunningham et al.
patent: 5777328 (1998-07-01), Gooch
patent: 5831266 (1998-11-01), Jerominek et al.
Hannaher Constantine
Institut National d'Optique
Israel Andrew
Merchant & Gould P.C.
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