Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1998-12-22
2001-06-05
Ham, Seungsook (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
Reexamination Certificate
active
06242738
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an infrared bolometer; and, more particularly, to a structurally stable infrared bolometer.
BACKGROUND OF THE INVENTION
Bolometers are energy detectors based upon a change in the resistance of materials (called bolometer elements) when exposed to a radiation flux. The bolometer elements have been made from metals or semiconductors. In metals, the resistance change is essentially due to variations in the carrier mobility, which typically decreases with temperature. Greater sensitivity can be obtained in high-resistivity semiconductor bolometer elements in which the free-carrier density is an exponential function of temperature, but thin film fabrication of semiconductor for bolometers is a difficult problem.
FIG. 1
provides a perspective view illustrating a three-level bolometer
1
, disclosed in a copending commonly own application, U.S. Ser. Application No. 09/207,054, entitled “INFRARED BOLOMETER WITH AN ENHANCED STRUCTURAL STABILITY AND INTEGRITY” and
FIG. 2
presents a schematic cross sectional view depicting the three-level bolometer
1
taken along A—A in FIG.
1
. The bolometer
1
comprises an active matrix level
10
, a support level
20
, a pair of posts
40
and an absorption level
30
.
The active matrix level
10
has a substrate
12
including an integrated circuit (not shown), a pair of connecting terminals
14
and a protective layer
16
. Each of the connecting terminals
14
is electrically connected to the integrated circuit and the protective layer
16
covers the substrate
12
.
The support level
20
includes a bridge
22
made of an insulating material and a pair of conduction lines
24
made of an electrically conducting material. The bridge
22
is provided with a pair of anchor portions
22
a
, a pair of leg portions
22
b
and an elevated portion
22
c
. Each of the anchor portions
22
a
is fixed to the active matrix level
10
and includes a via hole
26
through which one end of each of the conduction lines
24
is electrically connected to each of the connecting terminals
14
in the active matrix level
10
, each of the leg portions
22
b
supports the elevated portion
22
c
on which the other end of each of the conduction lines
24
is electrically disconnected from each other. Additionally, the elevated portion
22
c
is formed to have a serpentine shape to minimize the thermal exchange between the active matrix level
10
and the absorption level
30
.
The absorption level
30
is provided with a bolometer element
36
surrounded by an absorber
32
, a reflective layer
34
formed at bottom of the absorber
32
and an infrared absorber coating
38
(hereinafter, “IR absorber coating”) positioned on top of the absorber
32
. The reflective layer
34
is made of a metal is used for returning the transmitted IR back to the square absorber
32
. The IR absorber coating
38
is used for enhancing an absorption efficiency.
Each of the posts
40
is placed between the absorption level
30
and the support level
20
, wherein a top portion of each of the posts
40
is attached to the center portion of the absorber
32
and a bottom portion thereof is attached on the elevated portion
22
c
of the bridge
22
. Each of the posts
40
includes an electrical conduit
42
made of a metal and surrounded by an insulating material
44
. Top end of the electrical conduit
42
is electrically connected to one end of the bolometer element
36
and bottom end thereof is electrically connected to the respective conduction line
24
of the supporting level
20
, in such a way that both ends of the bolometer element
36
in the absorption level
30
are electrically connected to the integrated circuit of the active matrix level
10
through the electrical conduits
42
, the conduction lines
24
and the connecting terminals
14
.
When exposed to infrared radiation, the resistivity of the bolometer element changes, causing a current and a voltage to vary, accordingly. The varied current or voltage is amplified by the integrated circuit, in such a way that the amplified current or voltage is read out by detective circuit (not shown).
One of the major shortcomings of the above-described bolometer is a structural instability caused by the ways in which the stresses accumulated therein during the forming thereof are released. For example, as shown in
FIG. 3
, since the absorber
32
having a square shape is, at its center, supported by the posts
40
, the stresses therein tend to be relieved at its respective corner portion in the direction indicated by arrows, resulting in deforming an entire configuration of the absorber
32
, detrimentally affecting to the structural integrity of the infrared bolometer
1
.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a structurally stable infrared bolometer.
In accordance with one aspect of the present invention, there is provided an infrared bolometer, which comprises: an active matrix level including a substrate and a pair of connecting terminals; a support level provided with a bridge and a pair of conduction lines, ends of the bridge being fixed to the active matrix level; an absorption level including an absorber and a bolometer element surrounded by the absorber, and formed with a groove along and near its side edges for preventing the absorption level from deforming; and a pair of posts being positioned between the absorption level and the support level, each of the posts including an electrical conduit, wherein top end of each of the posts is attached to a bottom center portion of the absorber and bottom end thereof is attached to the bridge in such a way that both ends of the bolometer element are electrically connected to the respective connecting terminal through the respective conduit and the respective conduction line.
REFERENCES:
patent: 5399897 (1995-03-01), Cunningham et al.
patent: 5841137 (1998-11-01), Whitney
patent: 6165587 (2000-12-01), Nonaka
patent: 03115583 (1991-05-01), None
patent: 07128139 (1995-05-01), None
patent: 10122950 (1998-05-01), None
Daewoo Electronics Co. Ltd.
Ham Seungsook
Lee Shun
Pennie & Edmonds LLP
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