Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2003-04-11
2004-06-15
Mulpuri, Savitri (Department: 2812)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S338400
Reexamination Certificate
active
06750452
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal type-infrared detection device used for non-contact measurement of temperature and prevention of crimes and disasters, a method for manufacturing such the detection device, and an array composed of such the thermal type-infrared detection.
2. Description of the Prior Art
Heretofore, an infrared detection device of thermopile type, pyroelectric type or a bolometer type has been used as the thermal type-infrared detection device as mentioned above, however, an infrared detection section is formed on a diaphragm composed so as to be thermally isolated from a semiconductor substrate for improving the sensitivity in any type of the devices.
Thus, in a case of the thermal type-infrared detection device of thermopile type as an example of the conventional thermal type-infrared detection device, the thermal type infrared detection device
101
has thermal isoplated structure formed through silicon micro-machining technique as shown in FIG.
7
.
That is, the thermal type-infrared detection device
101
is provided with a silicon substrate
102
as a semiconductor substrate, a diaphragm
103
made of an insulating material, and an infrared detection section
104
positioned on the diaphragm
103
. The silicon substrate
102
is formed with a concave
106
removed by etching the lower part of the diaphragm
103
with silicon etchant infiltrated through an etching aperture
105
, accordingly the diaphragm
103
is thermally isolated from the silicon substrate
102
through this concave
106
.
The infrared detection section
104
on the diaphragm
103
is provided with a thermopile
110
having a plurality of thermocouples
109
arranged in parallel and electrically connected in series which are composed of n-type semiconductor
107
(e.g. n-type polysilicon) and p-type semiconductor
108
(e.g. p-type polysilicon), and a heat absorption layer
112
stacked on the thermopile
110
through an insulation layer
111
. The detection section
104
is so structured as to read an electric signal through lead wires
113
connected with both ends of the thermocouples
109
and made of aluminum or so, and high thermal resisting beam structure is used in order to try to improve the sensitivity of said device
101
in the example shown in the FIG.
7
.
In this case, it is possible to apply the method based of surface micro-machining technique using a sacrifice layer, however in any method, the diaphragm
103
has a configuration that the lower part of a cold junction
109
C of the thermocouples
109
is formed directly or through a frame-shaped layer on the silicon substrate
102
.
Such the infrared detection device
101
forms an array
120
of thermal type-infrared detection device by arranging a plurality of them as shown in FIG.
8
. In the thermal type infrared detection device array
120
, wires
121
and a device-selection switching mechanism
122
are disposed on the great majority of the substrate area excepting the cold junctions
109
C of the thermocouples
109
.
However, in the conventional thermal infrared-type detection device as mentioned above, the lower part of the cold junction
109
C of the thermocouples
109
is formed directly on the silicon substrate
102
, or formed indirectly on the silicon substrate
102
through the frame-shaped layer. Accordingly, the lead wires
113
, which are indispensable in the device
101
, are distributed in the area of the cold junction
109
C of the thermocouple
109
in the case of forming the diaphragm
103
directly on the silicon substrate
102
(the device-selection switching mechanism
122
is disposed in the thermal type infrared detection device array
120
), thus, the lead wires
113
and the circuit zone are positioned on the outer peripheral portion of the device, and occupy the greater part of the area assigned for the device.
On the other side, although the wires
113
and the device-selection switching mechanism
122
are disposed at the lower part of the frame-shaped layer in the case of forming the diaphragm
103
on the silicon substrate
102
through the frame-shaped layer, an area out of contact with the cold junction
109
C in the area of the frame-shaped layer becomes wider, therefore an area of the heat absorption layer
112
, which exert influence directly on the signal of the infrared detection, becomes narrow relatively against the area assigned for the infrared detection device
101
. Namely, there is a problem in that an opening rate (hereinafter referred to as “fill factor”) of the detection device becomes lower, consequently it may become hard to detect feeble infrared lays, and it is the subject to solve the above-mentioned problem of the conventional infrared detection device.
SUMMARY OF THE INVENTION
The present invention is made in view of the above-mentioned problem in the prior art, and it is an object to provide a thermal type-infrared detection device which is possible to enlarge the occupied area of the heat absorption layer by raising the fill factor and possible to improve the sensitivity and the output signal without lowering the strength of the diaphragm, and a production method of the device of this kind, in addition to an array of thermal type-infrared detection device.
The thermal type-infrared detection device according to this invention is characterized by comprising a semiconductor substrate having a concave, a diaphragm made of an insulating material and substantially covering the concave of the semiconductor substrate, and an infrared detecting section positioned on the diaphragm, the semiconductor substrate is provided with a projection made of a thermal conductor for supporting the diaphragm away from the semiconductor substrate. Such the configurations of the thermal type-infrared detection device serve as a means for solving the aforementioned problem of the prior art.
The thermal type-infrared detection device according to respective embodiments of this invention is characterized in that the thermal conductor is made of a silicon-polycrystalline material or a metallic material, or the device is any one of a thermopile type, a bolometer type, and a pyroelectric type.
Moreover, the production method according to this invention is characterized by comprising the steps of preparing a semiconductor substrate formed with a first insulation layer on the surface thereof, removing a part of the first insulation layer of the semiconductor substrate to form an aperture for anisotropic etching of the semiconductor substrate, stacking an etching sacrifice layer on a whole surface including the first insulation layer on the semiconductor substrate and the aperture of the first insulation layer, stacking a diaphragm and a second insulation layer on the etching sacrifice layer in order, infiltrating etchant into the etching sacrifice layer after taking a measure for making the etching sacrifice layer withstand the etchant at a position to be formed with the projection, etching and removing the etching sacrifice layer excepting the position corresponding to the projection, and removing a part of the semiconductor substrate to form the concave through anisotropic etching by infiltrating anisotropic etchant through the aperture of the first insulation layer on the semiconductor substrate at the time of producing the thermal type-infrared detection device according to this invention. Such the configurations of the production method of the infrared detection device serve as a means for solving the aforementioned problem of the prior art.
Furthermore, the array of thermal type-infrared detection device according to this invention is composed of a plurality of the thermal type-infrared detection devices according to this invention arranged with each other, and the array according to an embodiment of this invention is characterized in that projections adjacent to each other of the respective devices are formed in continuous one body.
In the thermal type-infrared detection device according to this invention, the lead wires
IHI Aerospace Co., Ltd.
Mulpuri Savitri
Sughrue & Mion, PLLC
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