Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2001-01-30
2002-09-10
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S330000, C250S332000, C250S338400, C250S339020, C250S338100
Reexamination Certificate
active
06448557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates both to a thermal infrared detector having a high fill factor and a construction in which a photosensitive area that receives infrared light is held above the substrate with a space interposed by beams, i.e., having a thermal isolation structure, and to a method of fabricating the detector.
2. Description of the Related Art
Various configurations have been proposed for improving the fill factor of a thermal infrared detector having a thermal isolation structure, including the configuration of the infrared ray solid-state imaging device disclosed in Japanese Patent Laid-open Publication No. 209418/98 by Kimata et al. and the configuration of the thermal infrared detector array disclosed in the paper by Ishikawa et al. (“Low-cost 320×240 uncooled IRFPA (Infrared Focal Plane Array) using a conventional silicon IC process”; SPIE Vol. 3698, 1999, pp. 556-564). Referring to
FIG. 1
, the two-dimensional infrared solid-state imaging device described in Japanese Patent Laid-open Publication No. 209418/98 is shown as an example of a prior-art thermal infrared detector having a thermal isolation structure.
FIG. 1
shows a sectional view taken along the current path in one picture element of the two-dimensional infrared solid-state imaging device.
First, regarding the thermal infrared detector shown in FIGS. and
2
, a concavity that is to become cavity
104
is formed on the surface of silicon substrate
100
as shown in FIG.
1
. Beams
102
and
103
composed of dielectric films
108
and
109
laminated on the surface of silicon substrate
100
overlay cavity
104
. Each of dielectric films
108
and
109
is several hundred nanometers thick, and beams
102
and
103
are approximately 1 &mgr;m thick, i.e., the sum of the thicknesses of the dielectric films on silicon substrate
100
. The width of each of beams
102
and
103
is on the order of 1-3 &mgr;m.
Each of beams
102
and
103
supports thermal detector
105
, which includes thermistor bolometer thin-film
101
, and holds thermal detector
105
above cavity
104
. Each of these dielectric films
108
and
109
is composed of a material such as a silicon nitride film or a silicon oxide film having high thermal resistance, and each dielectric film controls the flow of heat from thermal detector
105
to silicon substrate
100
. These two dielectric films
108
and
109
constitute the mechanical structure of beams
102
and
103
and thermal detector
105
and support thermal detector
105
.
Metal wiring
106
and
107
is formed between dielectric films
108
and
109
. One end of each of metal wiring
106
and
107
is connected to thermistor-bolometer thin-film
101
. The other end of metal wiring
106
is electrically connected to signal line
202
, which is provided on silicon substrate
100
as shown in
FIG. 2
, by way of contact
110
that is formed on dielectric film
109
. Signal line
202
provided on silicon substrate
100
has been omitted in FIG.
1
. The other end of metal wiring
107
is electrically connected to signal read-out circuit
201
by way of contact
111
formed on dielectric film
109
. In other words, thermistor-bolometer thin-film
101
is electrically connected to signal read-out circuit
201
by way of metal wiring
106
and
107
and contacts
110
and
111
. Signal read-out circuit
201
, which is provided in silicon substrate
100
, is omitted in FIG.
1
.
Infrared ray absorbing part
112
is joined to the surface of thermal detector
105
that is directed away from cavity
104
by way of junction pillar
113
. Infrared ray absorbing part
112
is a component for absorbing infrared rays and converting these rays to heat, and is constituted by a silicon nitride film or a silicon oxide film, or by a lamination of these films. Junction pillar
113
both keeps infrared ray absorbing part
112
separated from thermal detector
105
and thermally links infrared ray absorbing part
112
and thermal detector
105
. Similar to infrared ray absorbing part
112
, junction pillar
113
is constituted by a silicon nitride film or a silicon oxide film, or by a lamination of these films. The dimensions of junction pillar
113
are preferably, for example, several &mgr;m thick and 1-2 &mgr;m long, and junction pillar
113
may be of any shape.
Upon irradiation of infrared rays onto the infrared ray absorbing part in a thermal infrared detector, the infrared rays are absorbed into the infrared ray absorbing part, causing the temperature of the infrared ray absorbing part to rise. The infrared rays that have been irradiated upon the infrared ray absorbing part are then detected by sensing the temperature change of the infrared ray absorbing part. The thermal infrared detector of the prior art shown in
FIGS. 1 and 2
is thus mainly constituted by, infrared ray absorbing part
112
and thermal detector
105
. In this thermal infrared detector, the temperature change brought about in infrared ray absorbing part
112
by the infrared rays that are incident to infrared ray absorbing part
112
are conveyed to thermal detector
105
by way of junction pillar
113
. The change in temperature of infrared ray absorbing part
112
is then detected by detecting change in the characteristics of thermal detector
105
that is caused by the temperature change, which in concrete terms is the change in electrical resistance of thermistor-bolometer thin-film
101
shown in
FIGS. 1 and
,
2
.
FIG. 2
shows one entire picture element
200
and one portion of signal read-out circuit
201
. Signal read-out circuit
201
that is established in picture element
200
is constituted by a MOS transistor or a diode. Contact
205
is formed in this signal read-out circuit
201
. This contact
205
is connected by way of metal wiring
204
to contact
206
, which is formed in control clock bus line
203
. Control clock bus line
203
is provided for controlling signal read-out circuit
201
. Metal wiring
106
, on the other hand, is connected to signal line
202
by way of contact
110
.( signal line
202
is provided for reading out signals from thermal detector
105
.
FIG. 3
shows another example of a thermal infrared detector described in Japanese Patent Laid-open Publication No. 209418 in which thermal detector
301
is arranged above, and separated by the distance of cavity
302
from, silicon substrate
300
. Thermistor-bolometer thin-film
303
is provided in thermal detector
301
, thermistor-bolometer thin-film
303
being surrounded by dielectric protective films
304
and
305
. Thermal detector
301
is supported above silicon substrate
300
by beams
306
and
307
.
Thermistor-bolometer thin-film
303
is connected to a signal read-out circuit (not shown in the figure) in silicon substrate
300
by metal wiring
308
and
309
, each of which is formed for carrying current, and contacts
311
and
312
formed on dielectric protective film
305
and dielectric film
310
. Metal wiring
308
and
309
is enclosed by dielectric protective films
304
and
305
.
A photosensitive area, which is composed by sandwiching infrared ray absorbing part
315
between metal reflecting film
313
and infrared ray absorbing film
316
, also made of metal, is link e d by way of junction pillar
314
to the surface of thermal detector
301
that is directed away from silicon substrate
300
. Junction pillar
314
is formed as a single unit with metal reflecting film
313
. Infrared ray absorbing part
315
and metal infrared ray absorbing film
316
are laminated in that order on the surface of metal reflecting film
313
that is directed away from junction pillar
314
. A three-layer optical resonation structure is thus constituted by metal reflecting film
313
, infrared ray absorbing part
315
, and metal infrared ray absorbing film
316
.
If &lgr; is the wavelength of the infrared light that is to be detected by the thermal infrared detector and n is the refractive index of infrared ray absorbing part
315
, the thickness of infrared ray absorbin
Hannaher Constantine
Moran Timothy
NEC Corporation
LandOfFree
Thermal infrared detector provided with shield for high fill... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal infrared detector provided with shield for high fill..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal infrared detector provided with shield for high fill... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2865103