Infrared detecting element

A thermal-type infrared detecting element is provided which includes an infrared detecting member, a support member supporting the infrared detecting member, a substrate holding the support member, and a low thermal conduction part intervening between the substrate and a central portion of the support member, the support member having a link portion in at least a peripheral portion thereof which links the support member to the substrate and slits and/or grooves defined at a location adjacent the link portion. This infrared detecting element exhibits excellent sensitivity and responsiveness while requiring no cooling, and a one- or two-dimensional array of the element assures clear imaging with less crosstalk.

BACKGROUND OF THE INVENTION 
The present invention relates to infrared detecting elements adapted to 
detect infrared rays utilizing a change in physical properties thereof due 
to heat such as pyroelectricity, change in resistance with varying 
temperature or thermoelectromotive force. More particularly, it relates to 
an infrared detecting element which assures a substantial rise in 
temperature in response to incident infrared rays of a very small thermal 
responsiveness with less crosstalk, and which is suitable quantity and 
offers excellent sensitivity and for high integration and is used solely 
or in an array arrangement. 
Conventional infrared detecting elements include quantum detectors and 
thermal detectors. The quantum detectors include one utilizing 
photoconduction, one utilizing photovoltaic effect and the like, and 
generally offer excellent responsiveness and sensitivity. However, they 
must be cooled to temperatures lower than the temperature of liquid 
nitrogen (77 K.) for use and, hence, the major disadvantages thereof 
include difficulties in downscaling and handling and their high price. By 
contrast, the thermal detectors include one utilizing pyroelectricity, one 
utilizing a change in resistance with varying temperature, one utilizing 
thermoelectromotive force, and the like, and generally offer less 
sensitivity and responsiveness than the quantum detectors. Nevertheless, 
they offer great advantages in that they need no cooling, allow 
downscaling and lightening and offer a low price. 
Objectives common to these thermal detectors in enhancing the sensitivity 
thereof include: 
(1) to make the detection part exhibit a large rise in temperature in 
response to incident infrared rays of a very small thermal quantity, i.e., 
to reduce the thermal capacity of the detection part; 
(2) to reduce thermal leakage due to thermal conduction from the detection 
part to its peripheral portions; 
(3) to reduce heat conduction from the element in operation to elements 
adjacent thereto if the thermal detector is in an array arrangement; 
(4) to form the detection part integrally with a signal processing system 
and; 
(5) to make the array of elements have a sufficient strength. 
Of the thermal detectors, the pyroelectric-type element is considered to 
offer the highest sensitivity and has been put into practical use in some 
forms of two-dimensional array detector. A pyroelectric-type, 
two-dimensional array detector described in, for example, "Bulletin of 
Ceramic Process", Vol. 41, 1989, pp. 205 to 217, is fabricated by 
mechanically polishing a pyroelectric ceramic wafer to a thickness of 
several tens .mu.m and forming grooves into the wafer by ion milling for 
thermal isolation of individual detection parts. Top electrodes of the 
detection parts of this detector is connected to a signal processing 
circuit by means of a metallic bump to achieve electrical connection 
therebetween. 
On the other hand, a pyroelectric-type, two-dimensional array detector 
described in, for example, "ITEJ Technical is Report", Vol. 13, 1989, p. 
7, is fabricated by forming a thin film on an MgO substrate to form 
detection parts, forming a protective film of polyimide over the resulting 
surface and completely removing the portion of the MgO substrate lying 
under the detection parts by etching so as to retain the MgO substrate in 
the form of a frame lying on the outermost detection part side as 
supporting the overall array of elements in a bridged fashion. In this 
detector the elements in each column of the array are connected in series 
and further electrically connected to an external signal processing 
circuit at an end portion of the column. 
The former detector, however, involves problems in that: (1) there is a 
limitation in making the ceramic wafer thin, namely, in reducing the 
thermal capacity of each detection part or the size thereof since the 
ceramic wafer is machined; (2) high fabrication precision is needed for 
obtaining stable sensitivity; (3) the use of bump connection causes the 
productivity to decrease and the mechanical strength of the detector to be 
lowered; and the like. Similarly, the latter detector suffers problems in 
that: (1) the complete removal of the substrate under the 
two-dimensionally arrayed detection parts by etching results in a 
structure with low strength; only one signal processing circuit is 
provided to each column of elements, resulting in a disadvantageous 
signal-to-noise ratio; (3) in association with the low mechanical 
strength, the detection parts are likely to vibrate, so that the noise 
based on the piezoelectric property of the pyroelectric material is likely 
to occur; and the like. 
It is, therefore, an object of the present invention to overcome the 
foregoing problems and to provide a thermal-type infrared detecting 
element having a thin film detecting part with less thermal capacity and 
less thermal conduction to peripheral portions and a method for 
fabricating the same. 
Another object of the present invention is to provide a thermal-type 
infrared detector apparatus with less crosstalk wherein detecting elements 
of the same type as above are arranged in an array. 
A further object of the present invention is to provide a thermal-type 
infrared detector apparatus wherein the detection part and a signal 
processing circuit are integrally formed. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention, there is provided an 
infrared detecting element comprising an infrared detecting member, a 
support member supporting the infrared detecting member, a substrate 
holding the support member, and a low thermal conduction part intervening 
between the substrate and a central portion of the support member, the 
support member having a link portion in at least a peripheral portion 
thereof which links the support member to the substrate and slits and/or 
grooves formed at a location adjacent the link portion. 
Preferably, the low thermal conduction part comprises a cavity portion 
provided between the support member and the substrate. 
Alternatively, the low thermal conduction part comprises a porous member 
provided between the support member and the substrate. 
In the infrared detecting element of the present invention, preferably, the 
slits or the grooves each have a difference in width between one end and 
the other end thereof, whereby each slit or groove extends in an increased 
area and hence can also serve as an opening for etching. 
Preferably, the slits or grooves are discretely defined along the 
peripheral edge of the support member for preventing thermal conduction to 
the surrounding substrate. 
Further preferably, the slits or grooves define at least two circuits along 
the peripheral edge of the support member, the slits or grooves in the 
inner circuit are located as covering portions intervening between the 
slits or grooves in the outer circuit. 
In addition, the slits or grooves may overlap mutually. 
According to another aspect of the inventin, there is provided an infrared 
detecting present element comprising a substrate, a porous member having a 
low thermal conductance and disposed on the substrate, a support member 
formed of a thin insulator film and disposed on the porous member, and an 
infrared detecting member disposed on a surface of the support member. 
According to yet another aspect of the present invention, there is provided 
a method for fabricating an infrared detecting element including a 
substrate, a low thermal conduction part disposed on a surface of the 
substrate, a support member disposed on the low thermal conduction part 
and an infrared detecting member disposed on a surface of the support 
member, the method comprising the steps of: 
defining a concave portion into the substrate at a location where the 
infrared detecting member is to be formed; 
filling the concave portion with an easy-to-etch material made of a 
material to be easily etched or a material to be easily etched while 
retaining a porous skeleton having a low thermal conductivity; 
sequentially stacking the support member and the infrared detecting member 
on the easy-to-etch material, followed by patterning; and 
etching the easy-to-etch material to define a cavity portion or to form a 
porous member. 
According to yet another aspect of the present invention, there is provided 
a method for fabricating an infrared detecting element including a 
substrate, a low thermal conduction part disposed on a surface of the 
substrate, a support member disposed on the low thermal conduction part 
and an infrared detecting member disposed on a surface of the support 
member, the method comprising the steps of: 
forming a convex portion on a surface of the substrate at a location where 
the infrared detecting member is to be formed, the convex portion being 
formed of an easy-to-etch material made of a material to be easily etched 
or a material to be easily etched while retaining a porous skeleton having 
a low thermal conductance; 
sequentially stacking the support member and the infrared detecting member 
on the substrate including the convex portion, followed by patterning; and 
etching the convex portion to define a cavity portion or to form a porous 
member. 
According to still yet another aspect of the present invention, there is 
provided a method for fabricating an infrared detecting element including 
a substrate, a low thermal conduction part disposed on a surface of the 
substrate, a support member disposed on the low thermal conduction part 
and an infrared detecting member disposed on a surface of the support 
member, the method comprising the steps of: 
forming a spacer on a surface of the substrate at a location where the 
infrared detecting member is to be formed, the spacer being formed of an 
easy-to-etch material made of a material to be easily etched or a material 
to be easily etched while retaining a porous skeleton having a low thermal 
conductance; 
forming an intermediate layer made of a material hard to etch having a high 
thermal conductance on a surface of the substrate at a location where the 
infrared detecting element is not to be formed; 
sequentially stacking the support member and the infrared detecting member 
on the spacer, followed by patterning; and 
etching the spacer to define a cavity portion or to form a porous member. 
According to a further aspect of the present invention, there is provided a 
method for fabricating an infrared detecting element comprising the steps 
of: 
stacking on a substrate a support member and an infrared detecting member, 
followed by patterning; 
etching a spacer provided between the substrate and the support member or a 
surface of the substrate lying under the support member to define a cavity 
portion between the support member and the substrate; and 
filling the cavity portion with a porous member forming material, followed 
by a post-treatment to form a porous member. 
According to a yet further aspect of the present invention, there is 
provided an infrared detecting element comprising a signal processing 
circuit part formed in a superficial portion of a semiconductor substrate, 
a support member formed of a thin insulator film and disposed above the 
signal processing circuit part with intervention of a cavity portion 
between the support member and the signal processing circuit part, and an 
infrared detecting member disposed on a surface of the support member. 
According to a still further aspect of the present invention, there is 
provided an infrared detector apparatus comprising infrared detecting 
elements of the type same as any one of the foregoing infrared detecting 
elements which are arranged one- or two-dimensionally. 
According to a yet still further aspect of the present invention, there is 
provided an infrared detector apparatus comprising an infrared detecting 
element section having the aforesaid infrared detecting elements, and a 
sealing container accommodating the infrared detecting element section and 
provided, at its inside, with a vacuum, a reduced pressure atmosphere or a 
low thermal conduction gas atmosphere. 
The infrared detecting element of the present invention includes the low 
thermal conduction part which comprises a cavity defined by, for example, 
any one of various etching techniques and provided with a vacuum therein 
or filled with any gas such as air, or which comprises a porous material 
having a multiplicity of pores instead of the cavity. With this 
construction, thermal of a very small thermal quantity generated at the 
detection part due to incident infrared rays is prevented from escaping 
from the support member to the underlying substrate through the link 
portion lying therebetween due to thermal conduction. 
Further, the infrared detecting element of the present invention includes 
at least one link portion linking the detection part to the surrounding 
portion and the grooves and/or slits for thermal isolation extending as 
crossing the straight line defined between the junction point of the link 
portion and the center of the detection part. Such construction assures a 
lengthened thermal conduction path or a virtually lengthened heat 
conduction path and hence an increased thermal conduction resistance, 
thereby impeding the thermal conduction. Accordingly, only the thermal 
conduction resistance of the infrared detecting element can be increased 
without reducing the effective area of the detection part. 
In the infrared detecting element of the present invention, where the 
cavity portion underlying the detection part is filled with a porous 
member having a good thermal insulating characteristic, the porous member 
serves to suppress the thermal conduction to the substrate while 
supporting the detection part, thereby improving the mechanical strength 
of the link portion between the support member and the surrounding 
portion. 
In the infrared detector apparatus of the present invention, a signal 
processing circuit part is formed adjacent each infrared detecting element 
on the same substrate so as to be integrated therewith. This leads to an 
infrared detector apparatus with lessened noise and improved sensitivity. 
In the method for fabricating an infrared detecting element according to 
the present invention, the infrared detecting member is stacked on the 
easy-to-etch material and then the easy-to-etch material is etched to 
define a cavity portion or to form a porous member, thereby forming the 
low thermal conduction part which provides a desired space between the 
substrate and the detecting member and is formed of a material different 
from the substrate.

DETAILED DESCRIPTION 
A thermal-type, infrared detecting element according to the present 
invention is designed to include an infrared detection part having a 
reduced thermal capacity, so that the heat received will efficiently 
contribute to a temperature rise at an infrared detecting member. In 
addition the element is designed to have an increased thermal conduction 
resistance of the portion between the infrared detecting member and the 
substrate so as not to permit the received heat to escape. 
Specifically, as the means for reducing the thermal capacity of the 
detection part a low thermal conduction part is provided intermediate 
between the support member supporting the infrared detecting member and 
the substrate, and further, to increase the thermal conduction resistance 
of the portion intermediate between the infrared detecting member and the 
substrate, slits or grooves are provided in the periphery of the support 
member, particularly in a portion adjacent the link portion linking the 
support member to the substrate. 
The slits or grooves in the periphery of the support member serve to 
inhibit the heat absorbed by the infrared detection part from escaping 
toward the substrate through the support member. It is particularly 
preferable to provide the slits or grooves in a link portion 11 linking 
the support member 2 to the substrate as shown in, for example, FIG. 1(a) 
since the thermal conduction path defined from the central portion of the 
support member 2 to the link portion 11 is cut off thereby, so that the 
heat conducts while making a detour around the slits or grooves 9. 
Since the support member 2 is formed of a thin insulator film such as made 
of SiO.sub.2 or SiN.sub.4 having a thickness of about 1000 to about 2000 
.ANG., the slits extending vertically through the support member 2 are 
more preferable than the groove for the sake of easy fabrication and for 
the formation of an opening for etching against the substrate, as will be 
described later. Nevertheless, the grooves not extending vertically 
through the support member serve the purpose since the retained portion in 
each groove is very thin, which contributes to the cutting-off of the 
thermal conduction path. In addition to these slits or grooves, it is 
preferable to provide an etching hole 10 for etching the substrate and an 
easy-to-etch material to be described later. 
FIGS. 11 to 13 each illustrate another example of the shape of the slits or 
grooves though only partially. The slits or grooves 9 shown in FIG. 11 
each have end portions different in width. For example, each slit or 
groove is shaped into a large triangle so as to serve also as the opening 
for etching. 
The slits or grooves 9 shown in FIG. 12 define two circuits along the 
peripheral edge of the support member 2 in such a manner that the slits or 
grooves in the inner circuit cover the portions intervening between the 
discrete slits or grooves in the outer circuit. Thus, the thermal 
conduction is cut off more efficiently. 
Further, the slits or grooves 9 shown in FIG. 13 are not aligned in the 
same line and alternately overlap each other at end portions thereof. In 
this way the thermal is efficiently prevented from escaping from the end 
portions of the slits or grooves. 
As shown in, for example, FIG. 1(b) or FIG. 5(b), low thermal conduction 
part 8 is formed by defining a cavity portion in the substrate 1 at a 
location under the support member 2 or forming the support member 2 above 
the substrate 1 with an intervening cavity portion or, as shown in FIG. 9, 
interposing a porous member made of a material having a low thermal 
conductance between the support member 2 and the substrate 1. Note that 
FIG. 1(b) is a sectional view taken along with a line I--I of FIG. 1(a), 
and FIG. 5(b) is a sectional view taken along with a line IV--IV of FIG. 
5(a). 
The provision of the cavity portion between the support member and the 
substrate makes it possible to efficiently inhibit thermal conduction 
since air in the cavity portion has a very low thermal conductance and 
hence allows poor thermal conduction. 
Alternatively, the provision of the porous member made of a low thermal 
conduction material such as glass or an oxide between the support member 
and the substrate makes it possible to inhibit heat from escaping by 
virtue of air existing in the pores while supporting the support member on 
the substrate to assure a high mechanical strength. 
The embodiments having the cavity portion or the porous member will be 
specifically described later. The cavity portion or porous member is 
formed by, for example etching the substrate at a location under the 
support member after the formation of the infrared detection part, or 
filling a concave portion previously provided into the substrate with an 
easy-to-etch material or forming a convex portion of the easy-to-etch 
material on the substrate; stacking the support member and the infrared 
detecting member, followed by patterning; and removing the easy-to-etch 
material by etching. Any material having a high selective etching ratio to 
the substrate is herein usable as the easy-to-etch material. For instance, 
where the support member is made of SiO.sub.2 or Si.sub.3 N.sub.4 film and 
the substrate is of silicon, the easy-to-etch material is formed of glass, 
polycrystalline silicon or the like, otherwise where the substrate is made 
of GaAs, the easy-to-etch material is made of Al.sub.x Ga.sub.1-x As or 
the like. 
Alternatively, the material capable of being porously etched is used to 
form the porous member instead of complete removal thereof. Such porous 
member is formed by heat treating the material formed of, for example, 
Na.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 glass at about 500.degree. C. to 
separate into Na.sub.2 O--B.sub.2 O.sub.3 phase and SiO.sub.2 phase and 
etching the glass with diluted hydrochloric acid to afford a porous 
material with only the Na.sub.2 O--B.sub.2 O.sub.3 phase removed. As a 
substitute for the Na.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 glass can be 
used NR.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 --Al.sub.2 O.sub.3 glass, 
Na.sub.2 O--B.sub.2 O.sub.3 --SiO--NiO glass, Na.sub.2 O--B.sub.2 O.sub.3 
--SiO.sub.2 --Al.sub.2 O.sub.3 --Fe.sub.2 O.sub.3 --As.sub.2 O.sub.3 glass 
or the like. In this case the skeleton retained after the etching is 
preferably made of a material having a low thermal conductance. 
Where the easy-to-etch material is filled into the concave portion 
previously defined into the substrate as described above, there is not 
there is not necessarily conducted anisotropic etching against the 
substrate, and the substrate may be formed of Si other than Si in a 
specific crystal plane, GaAs, MgO, SrTiO.sub.3 or the like. 
The porous member may also be formed by forming the cavity portion, filling 
the cavity portion with a porous member forming material and then 
rendering the material porous by post-treatment. In this case, examples of 
the porous member forming material include those affording porous material 
by heat treatment such as SiO.sub.2, Al.sub.2 O.sub.3, B.sub.2 O.sub.3 and 
the like which are formed by sol-gel process, those utilizing hydration 
such as 3CaO.multidot.SiO.sub.2, and those utilizing sintering such as 
alumina silicate ceramics, alumina ceramics, diatomaceous earth ceramics 
and zeolite ceramics. 
Upper and lower electrode films and a pyroelectric film are formed by known 
process such as physical or chemical vapor phase synthesis, sol-gel 
process or electrophoresis. These processes enable a precise formation of 
a thin film having a thickness of 10 .mu.m or less with ease. Hence, the 
thermal capacity of the detection part can be reduced to promote the 
sensitivity to infrared rays, and even an infrared detecting element 
formed of a film having a large area can be formed with ease. Further, the 
lift off method is preferably used in such film formation since it allows 
a hard-to-etch material to be patterned and prevents wet or dry etching 
from damaging non-etch portions. 
Infrared detecting elements of the type described above are arranged one- 
or two-dimensionally to form an infrared detector apparatus exhibiting 
good sensitivity. In this case, if the substrate uses a silicon substrate 
and a signal processing circuit part is formed in the substrate at a 
location under the infrared detection part, the connection between the 
infrared detecting element and the signal processing circuit part can 
easily be achieved, and the resulting detector apparatus can perform a 
compactly integrated form. 
If the infrared detecting element section is held within a sealing 
container, there can be provided a vacuum, reduced pressure or low thermal 
conduction gas within the container. This is advantageous in that the 
thermal radiation from the detection section is alleviated and that 
frosting is prevented when the detector apparatus is used in a low 
temperature environment. 
Further, where the signal processing circuit part is formed in a separate 
substrate, it is preferable to connect the signal processing circuit part 
to respective electrodes of the detecting elements using a bump of a 
low-melting-point metal since the signal processing circuit part will not 
be adversely affected even by elevated temperatures needed for the 
formation of the detection section. In this case, the respective 
electrodes of the detecting elements is led out onto the reverse side of 
the substrate and connected to the signal processing circuit part through 
the bump. 
Hereinafter, the present invention will be described in more detail by way 
of specific examples thereof. 
EXAMPLE 1 
FIGS. 2(a) to 2(c), FIG. 3 and FIG. 4 are explanatory views for 
illustrating in sequence the process for fabricating one embodiment of the 
infrared detecting element according to the present invention. FIGS. 2(b) 
and 2(c) are sectional views taken along with lines III--III and II--II, 
respectively, of FIG. 2(a). 
As shown in FIGS. 2(a) to 2(c), on a surface of an Si (100) substrate 1 was 
formed an Si.sub.3 N.sub.4 film having about 2000 .ANG. thickness to serve 
as a support member 2 by CVD process. Hatched portions of the Si.sub.3 
N.sub.4 film shown in FIG. 2(a) were removed by dry etching according a 
pattern having triangular etching holes 10 at four corners thereof and 
hook-like-shaped thermal isolation slits 9 at locations adjacent 
respective link portions 11 for increasing the thermal conduction 
resistance. In this case, the length of side A of the central detection 
part was about 50 .mu.m, the length of side E of each triangular etching 
hole which was perpendicular to the counterpart side of the hole was about 
34 .mu.m, width B of each slit was about 1 .mu.m, the length of side C of 
each slit 9 was about 10 .mu.m, and the width of thermal conduction path D 
defined outside each slit 9 was about 2 .mu.m. 
In turn, as shown in FIG. 3, portions other than the portion intended for 
the formation of a lower electrode 4 were covered with a resist (not 
shown), and then a Pt film of about 500 .ANG. thickness to serve as the 
lower electrode 4 was formed over the resulting surface by sputtering. 
Thereafter, the resist was solved by a solvent such as acetone and 
ultrasonic application to remove unnecessary Pt film. Thus, the lower 
electrode 4 as shown in FIG. 3 was formed. 
In turn, as shown in FIG. 4, like in the preceding step, portions other 
than the hatched portion were covered with phosphosilicate glass of about 
3 .mu.m thickness. In this case, the phosphosilicate glass functioned like 
the aforesaid resist. On the resulting surface was formed a pyroelectric 
film of PZT (Pb--Zr--Ti--O) to about 2 .mu.m thickness by sputtering in a 
gas (Ar:O.sub.2 =9:1) at 10 mTorr with the substrate temperature set at 
about 500.degree. C. or higher. Thereafter, the phosphosilicate glass was 
removed using hydrofluoric acid to provide a pyroelectric film 5 only in 
the hatched portion. 
Finally, as shown in FIG. 1(a), the resulting surface except for the 
portion intended for the formation of an upper electrode was covered with 
a resist (not shown), and then an Ni--Cr film (not shown) serving as both 
the upper electrode and an infrared absorption layer was deposited to 
about 1000 .ANG. thickness on the resulting surface by sputtering. 
Further, the resist layer was removed using a solvent to form the 
structure of an infrared detecting member wherein the pyroelectric film 5 
was sandwiched between the upper and lower electrodes 4 and 6 as shown in 
FIG. 1(b). In turn, the Si substrate 1 was etched in a portion thereof 
underlying the thus constructed structure mainly through the triangular 
etching holes 10 using 30% KOH at 70.degree. C. Because of Si (100) plane 
very easy to etch compared with Si (111) plane, the substrate was etched 
through the triangular etching holes 10 defined in the support member 2 to 
form cavities in reversed pyramid form. This etching progressed at a 
location under the Si.sub.3 N.sub.4 support member 2 having the structure 
of infrared detecting member 7 thereon to form four cavities in reversed 
pyramid form which were arranged in a matrix fashion in the substrate 1. 
By allowing the etching to further progress, a low thermal conduction part 
8 was formed under the infrared detecting member 7 as comprising a cavity 
in which an Si ridge shaped like cross with slopes was retained centrally, 
resulting in the support member 2 lifted as if floating (refer to FIG. 
1(b)). The procedure thus described afforded an infrared detecting element 
of the structure comprising the support member 2 of Si.sub.3 N.sub.4, 
lower electrode 4, pyroelectric film 5 and upper electrode 6 as shown in 
FIGS. 1(a) and 1(b). 
The infrared detecting element thus fabricated was electrically connected 
to an external signal processing circuit through upper and lower leads 
extending from the infrared detecting element to form an infrared detector 
apparatus. By employing such arrangement, heat derived from infrared rays 
incident on the detection part efficiently caused the temperature of the 
detection part to rise thereby assuring improved detection sensitivity, 
since the thermal conduction from the peripheral portion or lower portion 
of the detection part was suppressed to a very large extent. 
EXAMPLE 2 
FIGS. 6(a) to 6(b), FIG. 7 and FIG. 8 are explanatory views for 
illustrating the process for fabricating another embodiment of the 
infrared detecting element according to the present invention. FIG. 6(b) 
is sectional view taken along line V--V of FIG. 6(a). 
As shown in FIGS. 6(a) and 6(b), on a surface of an Si substrate 1 was 
formed an easy-to-etch material layer made of phosphosilicate glass, which 
was then patterned to form a spacer 15. On the resulting surface was 
deposited an Si.sub.3 N.sub.4 film having about 2000 .ANG. thickness to 
serve as a support member 2 by CVD process. On a surface of the thus 
formed Si.sub.3 N.sub.4 film for the formation of a detection part was 
formed a phosphosilicate glass layer to about 2 .mu.m thickness, followed 
by patterning. Further, on the resulting surface was formed an Si.sub.3 
N.sub.4 film to about 1000 .ANG. thickness by CVD process. Hatched 
portions of the Si.sub.3 N.sub.4 film shown in FIG. 6 were removed by dry 
etching according a pattern having etching holes 10 and hook-like-shaped 
thermal isolation slits 9 at locations adjacent respective link portions 
11 for increasing this the thermal conduction resistance. In case, the 
length of side A of the central detection part was about 50 .mu.m, width B 
of each slit was about 1 .mu.m, length C of one side of each slit 9 was 
about 10 to about 15 .mu.m, and width D of thermal conduction path defined 
outside each slit 9 was about 2 .mu.m. 
In turn, as shown in FIG. 7, portions other than the portion intended for 
the formation of a lower electrode 4 were covered with a resist (not 
shown), and then a Pt film of about 1000 .ANG. thickness to serve as the 
lower electrode 4 was formed over the resulting surface by sputtering. 
Thereafter, the resist was solved by a solvent such as acetone and 
ultrasonic application to remove unnecessary Pt film. Thus, the lower 
electrode 4 as shown in FIG. 7 was formed. 
In turn, as shown in FIG. 8, like in the preceding step, portions other 
than the hatched portion were covered with phosphosilicate glass of about 
3 .mu.m thickness. On the resulting surface was formed a pyroelectric film 
of PZT (Pb--Zr--Ti--O) to about 2 .mu.m thickness by sputtering in a gas 
(Ar:O.sub.2 =9:1) at 10 mTorr with the substrate temperature set at about 
500.degree. C. or higher. Thereafter, the upper phosphosilicate glass 
layer was removed using hydrofluoric acid to provide a pyroelectric film 5 
only in the hatched portion. 
Further, as shown in FIG. 5(a), the resulting surface except for the 
portion intended for the formation of an upper electrode was covered with 
a resist, and then an Ni--Cr film (not shown) to serve as both the upper 
electrode 6 and an infrared absorption layer was deposited to about 1000 
.ANG. thickness on the resulting surface by sputtering. The resist layer 
was then removed using a solvent to form the structure of an infrared 
detecting member wherein the pyroelectric film 5 was interposed between 
the upper and lower electrodes 4 and 6 as shown in FIGS. 5(a) and 5(b). In 
turn, the spacer of phosphosilicate glass underlying the thus constructed 
structure was removed mainly through the rectangular etching holes 10 by 
etching using hydrofluoric acid. The procedure thus described afforded an 
infrared detecting element of the structure comprising the support member 
2 of Si.sub.3 N.sub.4, lower electrode 4, pyroelectric film 5 and upper 
electrode 6 as shown in FIGS. 5(a) and 5(b). 
The infrared detecting element thus fabricated was electrically connected 
to an external signal processing circuit through upper and lower leads 
extending from the infrared detecting element to form an infrared detector 
apparatus. By employing such arrangement, heat derived from infrared rays 
incident on the detection part allowed the temperature of the detection 
part to rise efficiently, thereby assuring improved detection sensitivity, 
since the thermal conduction from the peripheral portion or lower portion 
of the detection part was suppressed to a very large extent. 
EXAMPLE 3 
On a surface of an Si substrate was deposited an Si.sub.3 N.sub.4 film 
having about 2000 .ANG. thickness to serve as a support member 2 by CVD 
process. On a surface of the thus formed Si.sub.3 N.sub.4 film for the 
formation of a detection part was formed a borosilicate glass layer 
containing 2% or more by weight of Na.sub.2 O to about 2 .mu.m thickness, 
followed by patterning. Further, on the resulting surface was formed an 
Si.sub.3 N.sub.4 film to about 1000 .ANG. thickness by CVD process. 
Hatched portions of the Si.sub.3 N.sub.4 film as shown in FIGS. 6(a) and 
6(b) were removed by dry etching according a pattern defining a central 
detection part, etching holes 10 and hooked thermal isolation slits 9 
located adjacent respective link portions 11 for increasing the thermal 
conduction resistance. In this case, the length of side A of the central 
detection part was about 50 .mu.m, width B of each slit was about 1 .mu.m, 
length C of one side of each slit 9 was about 10 to about 15 .mu.m, and 
width D of thermal conduction path defined outside each slit 9 was about 2 
.mu.m. 
In turn, as shown in FIG. 7, portions other than the portion intended for 
the formation of a lower electrode 4 were covered with a resist, and then 
a Pt film of about 1000 .mu.m thickness to serve as the lower electrode 4 
was formed over the resulting surface by sputtering. Thereafter, the 
resist was solved by a solvent such as acetone and ultrasonic application 
to remove unnecessary Pt film. Thus, the lower electrode 4 was formed. 
In turn, like in the preceding step, portions other than the hatched 
portion as shown in FIG. 8 were covered with phosphosilicate glass of 
about 3 .mu.m thickness. On the resulting surface was formed a 
pyroelectric film of PZT (Pb--Zr--Ti--O) to about 2 .mu.m thickness by 
sputtering in a gas (Ar:O.sub.2 =9:1) at 10 mTorr with the substrate 
temperature set at about 500.degree. C. or higher. Thereafter, the 
phosphosilicate glass layer was removed using hydrofluoric acid to provide 
a pyroelectric film 5 only in the hatched portion of FIG. 8. 
Further, the resulting surface except for the portion intended for the 
formation of an upper electrode was covered with a resist, and then an 
Ni--Cr film (not shown) to serve as both the upper electrode 6 and an 
infrared absorption layer was deposited to about 1000 .ANG. thickness on 
the resulting surface by sputtering. The resist layer was then removed 
using a solvent to form a structure wherein the pyroelectric film 5 was 
sandwiched between the upper and lower electrodes 4 and 6 (refer to FIG. 
9. In turn, the structure thus constructed was subjected to a heat 
treatment to phase separate the spacer of borosilicate glass into Na.sub.2 
O--B.sub.2 O.sub.3 phase and SiO.sub.2 phase. The phase separated 
borosilicate glass was etched using diluted hydrochloric acid heated to 
90.degree. C. to remove the Na.sub.2 O--B.sub.2 O.sub.3 phase through 
mainly the rectangular etching holes 10, whereby the borosilicate glass 
was rendered porous. The procedure thus described afforded an infrared 
detecting element of the structure comprising the support member 2 of 
Si.sub.3 N.sub.4, lower electrode 4, pyroelectric film 5, upper electrode 
6 and porous, low thermal conduction part 8 which also served to support 
the detection part, as shown in FIG. 9. 
The infrared detecting element thus fabricated was electrically connected 
to an external signal processing circuit part through upper and lower 
leads extending from the infrared detecting element to form an infrared 
detector apparatus. By employing such an arrangement, heat derived from 
infrared rays incident on the detection part allowed the temperature of 
the detection part to rise efficiently, thereby assuring improved 
detection sensitivity, since the thermal conduction from the peripheral 
portion or lower portion of the detection part was suppressed to a very 
large extent. In addition, since the porous glass part mechanically 
supported the bridging detection part, the infrared detector apparatus 
comprised a detecting element of bridge structure having an improved 
mechanical strength and hence was capable of performing an improved 
strength against a very large stress such as an impact. 
EXAMPLE 4 
A signal processing circuit part such as an FET was formed in a region of 
an Si substrate, on which region an infrared detection structure was to be 
formed. In turn, on a surface of the Si substrate was deposited an 
Si.sub.3 N.sub.4 film having about 2000 .ANG. thickness to serve as a 
support member 2 by CVI) process. On the surface of the thus formed 
Si.sub.3 N.sub.4 film for the formation of a detection part was formed a 
phosphosilicate glass layer to about 2 .mu.m thickness, followed by 
patterning. Further, on the resulting surface was formed an Si.sub.3 
N.sub.4 film to about 1000 .ANG. thickness by CVD process. The upper 
Si.sub.3 N.sub.4 film was partially removed at hatched portions defined 
according to a pattern similar to that shown in FIGS. 6(a) and 6(b) which 
defined a central detection part, etching holes, hook-like-shaped thermal 
isolation slits located adjacent respective link portions for increasing 
the thermal conduction resistance and a through-hole for the connection 
between the signal processing circuit part in the underlying Si substrate 
and the detection part. In this case, the length of one side of the 
central detection part was about 50 .mu.m, the width of each slit was 
about 1 .mu.m, the length of one side of each slit was about 10 .mu.m, and 
the width of thermal conduction path defined outside each slit was about 2 
.mu.m. 
In turn, portions other than the portion intended for the formation of a 
lower electrode 4 were covered with a resist, and then a Pt film of about 
1000 .ANG. thickness to serve as the lower electrode 4 was formed over the 
resulting surface by sputtering, whereupon the connection between the Pt 
film and the underlying signal processing circuit part was made. 
Thereafter, the resist was solved by a solvent such as acetone and 
ultrasonic application to remove unnecessary Pt film. Thus, the lower 
electrode 4 was formed as shown in FIG. 7. 
In turn, like in the preceding step, portions other than the hatched 
portion as shown in FIG. 8 were covered with phosphosilicate glass of 
about 3 .mu.m thickness. On the resulting surface was formed a 
pyroelectric film of PZT (Pb--Zr--Ti--O) to about 2 .mu.m thickness by 
sputtering in a gas (Ar:O.sub.2 =9:1) at 10 mTorr with the substrate 
temperature set at about 500.degree. C. or higher. Thereafter, the upper 
glass layer was removed using hydrofluoric acid to provide a pyroelectric 
film 5 only in the hatched portion of FIG. 8. 
Further, the resulting surface except for the portion intended for the 
formation of an upper electrode shown in FIG. 5(b) was covered with a 
resist, and then an Ni--Cr film to serve as both the upper electrode and 
an infrared absorption layer was deposited to about 1000 .ANG. thickness 
on the resulting surface by sputtering. The resist layer was then removed 
using a solvent to form a structure wherein the pyroelectric film was 
interposed between the upper and lower electrodes. Further, the 
phosphosilicate glass layer underlying this structure was removed by 
etching using hydrofluoric acid through mainly the rectangular etching 
holes. The procedure thus described afforded an infrared detecting element 
of the integral structure comprising the signal processing circuit 16, 
support member 2 of Si.sub.3 N.sub.4, lower electrode 4, pyroelectric film 
5 and upper electrode 6 as illustrated in FIG. 10. By employing such 
arrangement, heat derived from infrared rays incident on the detection 
part allowed the temperature of the detection part to rise efficiently, 
thereby assuring improved detection sensitivity, since the thermal 
conduction from the peripheral portion or lower portion of the detection 
part was suppressed to a very large extent. 
As has been described, with the infrared detecting element structure 
according to the present invention there can be obtained a sufficient 
resistance against the thermal conduction from the detecting element to 
its surrounding portions without largely decreasing the areal ratio of the 
detection part to a pixel. Further, the provision of the low thermal 
conduction structure under the detection part allows incident infrared 
rays to raise the temperature of the detection part efficiently, thereby 
assuring a high sensitivity. In addition, it is possible to make the 
infrared detecting element structure have an excellent mechanical strength 
if the porous material or the like is used. 
When a plurality of infrared detecting elements according to the present 
invention are arranged in array, each detecting element offers, as well as 
high sensitivity, less crosstalk with the elements adjacent thereto and 
hence assures a dear image. Further, the detection part is able to be 
formed integrally with a signal processsing circuit part. In this case the 
detecting element exhibits a more excellent sensitivity. 
While only certain presently preferred embodiments have been described in 
detail, as will be apparent with those familiar with the art, certain 
changes and modifications can be made without departing from the spirit 
and scope of the invention as defined the following claims.