Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2000-08-03
2003-04-22
Epps, Georgia (Department: 2873)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S338400
Reexamination Certificate
active
06552344
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an infrared detector and, in particular, relates to a thermal infrared detector having a heat insulation structure section.
2. Background Art
FIG. 10
is a sectional view of an infrared detector disclosed in Japanese Patent Laid-Open No. 10-209418. In the infrared detector of
FIG. 10
, an insulating film
2
, such as SiO
2
is formed on a silicon substrate
1
. In the insulating film
2
, there are a heat detection section
3
, such as bolometer; and a metal wiring
4
connected to the heat detection section
3
.
Further, the silicon substrate
1
below the heat detection section
3
is provided with a hollow section
6
, thereby making a vicinity of the heat detection section
3
into a heat insulating structure section
7
.
Above the heat detection section
3
, there is provided a plate-like infrared absorption section
9
supported by a support section
5
such as SiO
2
. The infrared absorption section
9
comprises an insulating layer
10
, an infrared absorption film
11
on a surface of the insulating layer
10
, and an infrared reflection film
12
on a rear surface of the insulation layer
10
. Infrared light incident on the infrared detector is absorbed by the infrared absorption section
9
and thereby converted into heat, and is transmitted to the heat detection section
3
through the support section
5
. In the heat detection section
3
, a thermal change due to such a heat is detected. Thus, the incident of infrared light on the infrared absorption section
9
is detected. In the structure shown in
FIG. 10
, infrared absorption efficiency is increased by providing the infrared reflection film
12
on the rear surface of the insulation layer
10
to thereby reflect the infrared ray transmitted through the infrared absorption film
11
and causing it to come into the infrared absorption film
11
again.
However, in order to manufacture the infrared detector with high sensitivity, it is further necessary to increase the infrared absorption efficiency in the infrared absorption section
9
. Contrary to this, it is known that the infrared absorption efficiency is increased by adopting an optical cavity structure in which an optical distance between the infrared absorption film
11
and the infrared reflection film
12
is set to one quarter of the center wavelength of the infrared light absorbed.
However, in order to make the infrared detector of
FIG. 10
into an optical cavity structure, the thickness of the insulating layer
10
sandwiched between the infrared absorption film
11
and the infrared reflection film
12
must be on the order of 1 &mgr;m, so that the heat capacity of the infrared absorption section
9
becomes large. Therefore, the thermal time constant in heat detection section becomes large, so that there has been a problem that infrared detection following a rapid temperature change becomes impossible.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the invention is to provide a high sensitivity infrared detector with no increase in heat capacity of the infrared absorption section, and to provide, in particular, a detector having an optical cavity structure.
This object and advantages of the invention are achieved by providing a novel and improved infrared detector, and the infrared detector is an infrared detector for detecting an absorbed infrared ray by converting it into heat, comprising: a semiconductor substrate having a heat insulation section; a heat detection section provided in the heat insulation section; an infrared absorption film disposed substantially parallel to a surface of the semiconductor substrate with a predetermined spacing being kept from the surface; and an infrared reflection film provided on the semiconductor substrate; wherein an infrared ray having transmitted through the infrared absorption film is reflected by the infrared reflection film and comes into the infrared absorption film again.
Further, according to one aspect of the invention, there is provided a method of producing an infrared detector for detecting an absorbed infrared ray by converting it into a heat, comprising the steps of forming, on a semiconductor substrate, a wiring layer and a heat detection section connected to the wiring layer, and covering them with an insulation film; forming an infrared reflection film on the insulation film; forming a sacrifice film on the infrared reflection film, and forming an opening portion in the sacrifice film above the heat detection section, thereby exposing the infrared reflection film; forming, on the sacrifice film, an infrared absorption section including an infrared absorption film; removing the sacrifice film; and forming, below the heat detection section, a hollow section by etching the semiconductor substrate.
Furthermore, according to another aspect of the invention, there is provided a method of producing an infrared detector for detecting an absorbed infrared ray by converting it into a heat, comprising the steps of forming a metal layer on a semiconductor substrate, and forming a wiring layer and an infrared reflection film separated from the wiring layer by patterning the metal layer; forming a heat detection section connected to the wiring layer, and covering it with an insulation film; forming a sacrifice film on the insulation film, and forming an opening portion in the sacrifice film above the insulation film, thereby exposing the insulation film; forming, on the sacrifice film, an infrared absorption section including an infrared absorption film; removing the sacrifice film; and forming, below the heat detection section, a hollow section by etching the semiconductor substrate.
The above object and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly appear, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.
Thus, as a result of intensive study, the inventors has found the fact that the infrared absorption efficiency can be increased without increasing the thermal time constant by means of forming an optical cavity structure by providing an infrared reflection film on a semiconductor substrate and using such an infrared reflection film and an infrared absorption film provided in an infrared detection section, and thereby the invention has been completed.
REFERENCES:
patent: 5021663 (1991-06-01), Hornbeck
patent: 5286976 (1994-02-01), Cole
patent: 6031231 (2000-02-01), Kimata et al.
patent: 6201243 (2001-03-01), Jerominek
patent: 10-209418 (1998-08-01), None
Ishikawa Tomohiro
Nakaki Yoshiyuki
Sone Takanori
Epps Georgia
Hanig Richard
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
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