JPH06283766A - Infrared ray sensor and its manufacture - Google Patents

Abstract

PURPOSE:To provide an infrared ray sensor which can detect both the infrared rays from a body moving as a single element and the infrared rays from a body standing still. CONSTITUTION:A pyroelectric element 15 and thermopile parts 19 and 20 are formed integrally in noncontact on the same topside insulating film 11 made on the surface of a semiconductor substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor for detecting infrared rays emitted from an object, and more particularly to an infrared sensor capable of accurately detecting whether the object is stationary or moving with a single element. It is about.

[0002]

2. Description of the Related Art A typical example of an element that receives infrared rays emitted from an object to generate heat and converts the heat into an electric signal to detect infrared rays is a thermopile or a pyroelectric using a thermocouple. There is a pyroelectric element that uses the body. These are used in a wide variety of applications such as home appliances that detect heat sources by utilizing their characteristics, medical equipment, control units of various furnaces, crime prevention equipment, fire alarms, automatic personnel counting, etc.

FIG. 8 shows the basic structure of a thermopile. The insulating thin film 2 is formed on the surface of the semiconductor substrate 1, and dissimilar metals or semiconductors 3 and 4 are bonded and disposed on the insulating thin film 2 to form a thermocouple. The semiconductor substrate layer below the region is removed. In the thermopile, when infrared rays enter and the joint is heated, an electromotive force is generated between the dissimilar metals or semiconductors 3 and 4 by the Seebeck effect, and the infrared rays are detected by the electromotive force.
Usually, the thermopile used is configured such that a plurality of thermocouples having the above structure are connected in series to obtain a sufficient voltage. The advantage of the thermopile is that the temperature can be measured in a non-contact state by providing a separate processing circuit, and it can be detected with high sensitivity in the steady state where the incident infrared ray does not change with time. . However, a drawback is that it is relatively insensitive to infrared rays that change with time.

FIG. 9 shows the basic structure of a pyroelectric element. The insulating thin film 6 is formed on the surface of the semiconductor substrate 5, and the lower electrode 7, the pyroelectric thin film 8 and the upper electrode 9 are arranged on the insulating thin film 6 in a laminated structure. The semiconductor substrate layer under the central region is removed. In the pyroelectric element,
When infrared rays enter and the pyroelectric thin film 8 is heated, electric charges are induced in the upper electrode 9 and the lower electrode 7 by the pyroelectric effect,
Electromotive force is generated. Infrared rays are detected by this electromotive force. The advantage of the pyroelectric element is that it can detect incident infrared rays with high sensitivity when it changes with time, and by arranging multiple pyroelectric elements on it, it can detect the moving direction of the object. . On the other hand, a drawback is that due to the characteristics of the pyroelectric effect, a highly sensitive output can be obtained when the incident infrared ray changes with time, but the output becomes zero when the incident infrared ray is in a steady state. Therefore, when the stationary infrared ray from the stopped object is detected by the pyroelectric element, a special operation such as chopping the infrared ray is required. Since the thermopile and the pyroelectric element each have the above-mentioned drawbacks, when detecting infrared rays from a moving object and infrared rays from a stationary object without fail, conventionally, the thermopile and the pyroelectric element are A method of using both elements together has been adopted.

[0005]

Conventionally, the thermopile and the pyroelectric element are separate elements, and when the thermopile and the pyroelectric element are used together, it is naturally necessary to separately incorporate them into a handling device, etc. There is a problem in that a space is required for each of the physical and electric circuits, a large space is required, and the cost is high. The present invention has been made to solve the above problems,
It is an object of the present invention to provide an infrared sensor in which a single element has both thermopile and pyroelectric element functions.

[0006]

In the infrared sensor of the present invention, a pyroelectric element part and a thermopile part are integrally formed in a non-contact structure on the same upper surface insulating thin film formed on the surface of a semiconductor substrate, and the thermopile and the pyropile are integrated. It has both the functions of an electric element.

[0007]

With the above construction, the infrared rays emitted from the stationary object are detected by the thermopile section, and the infrared rays emitted from the moving object are detected by the pyroelectric element section, and the single element is detected. It is possible to accurately detect both the moving object and the stationary object.

[0008]

1 (a) and 1 (b) show an embodiment of the present invention. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A, 10 is a semiconductor substrate of n-type Si crystal pieces, 11 is a top insulating thin film made of SiO ₂ , 12
Is a contact area between the semiconductor substrate 10 and the upper insulating thin film 11, 13
Is a cavity region, 14 is a lower electrode formed of Pt, and 15 is Pb.
TiO ₃ , Pb (Zr, Ti) O ₃ , (Pb, La) (Z
A pyroelectric thin film made of r, Ti) O ₃ or the like, 16 is an upper electrode formed of Au, and a lower electrode 14 and a pyroelectric thin film 15 are provided.
The upper electrode 16 constitutes a pyroelectric element portion. Reference numeral 19 is a thermoelectric material having a positive thermoelectric power composed of (BiSb) ₂ Te ₃ , PbTe, ZnSb, etc., and 20 is Bi ₂ (TeS
e) A thermoelectric material B having a negative thermoelectric power composed of ₃ , InSb, InAsP, etc., and these different kinds of thermoelectric materials A19 and B20 are alternately connected in series and arranged to form a plurality of thermocouples. This thermocouple constitutes a thermopile section. The hot contacts 17 of the plurality of thermocouples are formed between the upper electrode 16 of the pyroelectric element portion and the contact region 12, and the cold contacts 18 are formed on the contact region 13 of the upper insulating thin film 11. 22 and 23 are thermoelectric material shells of the thermopile part, electrode pads 2 connected to ends 19 and 20, 2
4 and 25 are electrode pads electrically connected to the electrodes 14 and 16 of the pyroelectric element portion, 26 is a metal frame for holding the semiconductor substrate 10, 27 is an absorber for absorbing infrared rays, and the SiO ₂ film is made of Au black. Alternatively, it is covered with Bi black. In the figure, the absorber 27 is formed only on the upper electrode 16 of the pyroelectric element portion, but it is not particularly limited to that location, and the hot contact 17 of the thermopile portion may be covered. Reference numeral 28 denotes a lower surface insulating thin film.

FIG. 2 shows a manufacturing method of the embodiment shown in FIG. First, a SiO ₂ film is formed on both upper and lower surfaces of a single semiconductor substrate 10 made of n-type Si crystal pieces by thermal oxidation, and an upper insulating thin film 11 and a lower insulating thin film 28 are provided on the upper and lower surfaces, respectively (FIG. 2A). Then, the central region of the lower insulating film 28 is removed by etching [FIG. 2 (b)]. Next, Pt is deposited on the upper surface insulating thin film 11 by the sputtering method to form the lower electrode 14, and PbTiO ₃ , Pb (Zr, Ti) O ₃ (Pb,
La) (Zr, Ti) O ₃ or the like is deposited to form a pyroelectric thin film 15
Is formed, and Au is deposited thereon by an evaporation method to form the upper electrode 16. As described above, the lower electrode 14, the pyroelectric thin film 15, and the upper electrode 16 formed in the laminated structure constitute the pyroelectric element portion, but the shape of each is particularly limited to the circular shape shown in FIG. It is not necessary to have a rectangular shape or a polygonal shape as will be shown later in the embodiment, and it is not necessary that each shape has the same shape. The lower electrode 14 on which Pt is deposited
The reverse sputtering method is used for the selective etching of PbTiO ₃ ,
Pb (Zr, Ti) O ₃ , (Pb, La) (Zr, T
i) It is advisable to use a mixed diluent of HF and HCl for the selective etching of the pyroelectric thin film 15 on which O ₃ or the like is deposited, and to use aqua regia or oxytron for the selective etching of the upper electrode 16 on which Au is deposited. .

Next, the thermoelectric material shell 1 is formed on the upper surface insulating thin film 11.
9 and the thermoelectric material Otsu 20 are arranged to form a plurality of thermocouples constituting the thermopile part.
In order to arrange 9 and 20 in a predetermined shape, a photoresist is previously deposited as a dummy in a place other than the place where the thermoelectric material is arranged, and the material is vapor-deposited from one direction,
The lift-off method of removing the material other than the necessary portions together with the photoresist may be repeated. Absorber 27
Deposits a SiO ₂ film on the upper electrode 16 by the CVD method,
Au, Bi, etc. are vapor-deposited thereon in an N ₂ atmosphere, and unnecessary portions are removed by a lift-off method [FIG.
(C)]. Next, a lower surface insulating thin film 28 is formed on the lower surface of the semiconductor substrate 10 by thermal oxidation and the central region is removed by etching.
Using as a mask, the semiconductor substrate layer 10 is etched with an n-type Si etchant such as an alkaline etchant of NaOH or KOH or an aqueous solution of hydrazine. The etching stop time is appropriately controlled to perform etching until the lower surface of the upper insulating thin film 11 is reached to form the cavity region 13 [FIG. 2 (d)]. When the plane orientation of the n-type Si crystal piece of the semiconductor substrate 10 is set to the (100) plane or the (110) plane, and the central portion of the lower surface insulating thin film 28 is etched, the selective etching is performed. By matching the direction of the sides of the rectangle with <110> or <211>, more precise processing can be performed.

The cavity 13 is shown in FIGS. 3 (a), 3 (b) and 3 (c).
The structure shown in FIG. FIG. 3A shows an n-type S.
After forming the pyroelectric element part and the thermopile part on the upper surface insulating thin film 11 of the semiconductor substrate 10 of the i crystal piece, a part of the upper surface insulating thin film 11 is removed by etching, and the n-type Si etchant described above is opened from this window. Shows a part formed by etching a part of the upper surface side of the n-type Si crystal piece using. It is possible to perform more precise processing by using a semiconductor substrate of P-type Si crystal pieces, preliminarily diffusing P or As in the cavity region, and finally selectively etching the n-type region. FIG. 3 (b), first n-type Si surface of the crystal piece covered with the Si ₃ N ₄ film, the central portion the Si ₃ N ₄ to form a cavity region
The film is removed with a phosphoric acid etchant, the exposed n-type Si crystal layer is oxidized and phosphorus is enlarged to form a dummy region of phosphorus glass, and the peripheral Si ₃ N ₄ film is removed. An insulating thin film 11 is formed, and the upper insulating thin film 1 is formed.
1 shows that the phosphor glass of the dummy region is selectively etched with a hydrofluoric acid-based etchant after the pyroelectric element portion and the thermopile portion are formed on the substrate 1. In FIG. 3C, a dummy region of photoresist, polyimide or phosphorus glass is formed in the central portion of the semiconductor substrate 10, an upper insulating thin film is formed on the dummy region, and finally the dummy region is removed by a solvent or an etchant to leave a blank space. The thing which formed the trunk | drum area 13 is shown.

When an object moves or stops in front of an element having a structure such as the upper region, infrared rays emitted from the object are incident on the upper part of the cavity region 13 through the optical system. Then, the infrared rays are converted into heat at the relevant part. At this time, since there is no conductor through which heat escapes, the upper part of the cavity region 13 has a large thermal resistance and becomes high in temperature. Further, since the upper part of the contact region 12 has a small thermal resistance, even if heat is conducted from the upper part of the cavity region 13, it is kept at a low temperature, that is, at about room temperature. Therefore, the same area 1
The temperature in the vicinity of the upper electrode 16 of the pyroelectric element portion formed on the upper part of 3, and in the vicinity of the pyroelectric thin film 15 and the hot junction 17 of the thermopile portion immediately below the temperature are high. Furthermore, a higher temperature can be obtained by the effect of the absorber 27 that is appropriately provided. Here, if the incident infrared ray is stationary from the stationary object, a steady temperature difference is generated between the hot junction 17 and the cold junction 18 of the thermopile part, and a thermoelectromotive force corresponding to this is obtained. In the case where a plurality of thermocouples are connected in series as in the present embodiment, the detection signals increased by a plurality of times can be obtained from the electrode pads 22 and 23. Furthermore, if the method of processing in an external circuit is taken into consideration in consideration of the emissivity distance of the object, the temperature of the object can be measured without contact. When an object is moving and the emitted infrared rays change with time,
Electric charges are induced between the upper electrode 16 and the lower electrode 14 of the pyroelectric element portion by the pyroelectric effect of the pyroelectric thin film 15, and detection signals are obtained from the electrode pads 24 and 25.

As described above, when the object is stationary and the emitted infrared rays are stationary, a highly sensitive detection signal is obtained from the thermopile part, and the infrared rays emitted by the object are moving. When it changes with time, a highly sensitive detection signal is obtained from the pyroelectric element unit. That is, even when the object is stopped, the single element can detect the object with high sensitivity.

FIGS. 4A and 4B show another embodiment of the present invention. 4A is a plan view and FIG. 4B is FIG.
In the cross-sectional view taken along the line BB of (a), the same reference numerals as those in FIG. 1 denote the same or corresponding portions. The difference from the embodiment shown in FIG. 1 is that the upper insulating thin film 2 made of a SiO ₂ film is formed by a CVD method so as to cover at least the upper electrode 16 of the pyroelectric element portion.
9 is formed, and the thermoelectric material shell is formed through the upper insulating thin film 27,
The points B and 19 are arranged in a non-contact structure with the pyroelectric element portion, and the hot junction 17 is formed on the cavity region 13 as close to the center portion as possible. In this embodiment, a more sensitive detection signal can be obtained from the thermopile part.

The shapes of the pyroelectric element portion and the thermopile portion are not limited, and as shown in FIG. 5A, the pyroelectric thin film 15 may be shaped so as to cover the entire surface of the upper insulating thin film 11. Further, as shown in FIG. 5B, the lower electrode 14 may cover the entire surface of the upper insulating thin film 11 and the pyroelectric thin film 15 may cover the entire lower electrode 14, or the upper insulating thin film 2 may be formed.
The shape of 9 may cover the entire surfaces of the upper electrode 16 and the pyroelectric thin film 15. These shapes can be flexibly selected in consideration of the required infrared detection characteristics and the manufacturing cost. That is, as described above, the infrared rays emitted from the object are in the cavity region 13
Although the light is received at the upper part of the above and converted into heat, the thinner the pyroelectric thin film 15 and the upper insulating thin film 29 between the region and the contact region 12, the smaller the heat capacity and the thermal resistance, and the greater the detection sensitivity. This can be achieved by performing a photoetching process many times and selectively processing the above-mentioned thin film, but naturally the cost is high. It is cheaper to form these thin films to cover the entire surface by selectively processing them. For the above reasons, the lower electrode 14, the pyroelectric thin film 15, the upper electrode 1
The shape of 6 does not need to be limited, and may be an optimum shape according to the usage situation.

FIGS. 6A and 6B show an embodiment in which two pyroelectric element parts are provided in one element. 6A is a plan view, and FIG. 6B is a cross-sectional view taken along the line CC of FIG. 6A. In a region above the cavity region 13 of the upper surface insulating thin film 11, a rectangular lower electrode 14a, a pyroelectric thin film 15b, and an upper electrode 16a having the same shape as the first pyroelectric element portion 14 are formed.
The second pyroelectric element section composed of b, 15b and 16b is provided so that detection signals can be obtained from the electrode pads 24a, 25a and 24b, 25b respectively from the first and second pyroelectric element sections. In this embodiment, when the infrared radiation emitted from the moving object moves from right to left, the detection signal appears first on the electrode pads 24a and 25a, and then on the electrode pads 24b and 25b. . When the incident infrared ray moves from left to right, the electrode pad 24
The detection signal appears first on b and 25b, and thereafter the detection signal appears on the electrode pads 24a and 25a. Therefore, the moving direction of the object can be detected by discriminating whether the detection signal from the first pyroelectric element unit precedes in time or the detection signal from the second pyroelectric element unit.

Next, an example of the detection signal of each embodiment will be shown. This is the case where the speed of the moving object is 10 m / s. Figure 1
In the example of the structure shown in FIG.
The detection signal of 1.2 × 10 ⁴ V / W from the pyroelectric element part is 5.5 × 10 from the thermopile part when the object is stopped.
A detection signal of ² V / W was obtained. Further, in the embodiment shown in FIG. 4, when the object is moved, 5.0 × 10 5
^When the detection signal of ³ V / W is stationary, the detection signal of 9.6 × 10 ² V / W was obtained from the thermopile part. In the embodiment shown in FIG. 6, when the object moves from right to left, the detection signal from the second pyroelectric element unit becomes the detection signal from the first pyroelectric element unit as shown in FIG. 7A. When the object is obtained in advance and moves in the opposite direction, the detection signal from the first pyroelectric element unit precedes the detection signal from the second pyroelectric element unit as shown in FIG. 7B. It was possible to detect the moving direction of the object. Further, when the object was stopped, a detection signal of 9 × 10 ³ V / W was obtained from the thermopile part.

[0018]

As described above, according to the present invention, it becomes possible to detect infrared rays from an object stopped and a moving object with a single element with high sensitivity, and the installation space is smaller than before. Well, it also has the effect of lowering costs.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing method of the embodiment shown in FIG.

FIG. 3 is a diagram showing a cavity region having a different structure.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing an example in which the shape of the pyroelectric element portion is different.

FIG. 6 is a diagram showing an embodiment having two pyroelectric element parts.

FIG. 7 is a diagram showing an example of infrared detection signals from the moving object of the embodiment shown in FIG.

FIG. 8 is a diagram showing a basic structure of a thermopile.

FIG. 9 is a diagram showing a basic structure of a pyroelectric element.

[Explanation of sign]

 10 Semiconductor Substrate 11 Top Insulating Thin Film 12 Adhesion Area 13 Cavity Area 14 Lower Electrode 15 Pyroelectric Thin Film 16 Upper Electrode 17 Hot Junction 18 Cold Junction 19 Thermoelectric Material A 20 Thermoelectric Material Otsu 22, 23 Electrode Pad 24, 25 Electrode Pad 26 Metal frame 27 Absorber 28 Bottom insulating thin film

Claims (3)

[Claims] 1. A lower part arranged in a laminated structure on an upper surface insulating thin film formed on a surface of a semiconductor substrate and having a cavity region formed by removing a semiconductor substrate layer below a central region surrounded by a peripheral portion thereof. An infrared sensor, comprising: a pyroelectric element portion including electrodes, a pyroelectric thin film, and an upper electrode; and a thermopile portion including a plurality of thermocouples arranged in a non-contact structure with the pyroelectric element portion. 2. The infrared sensor according to claim 1, wherein a plurality of thermocouples forming the thermopile portion are arranged in a non-contact structure with the pyroelectric element portion via a gap or an insulating thin film. 3. A step of forming an upper surface insulating thin film on at least one surface of a semiconductor substrate, and a lower electrode, a pyroelectric thin film and an upper electrode arranged in a laminated structure on the upper surface insulating thin film to provide a pyroelectric element section. A step of forming a thermopile part by disposing a plurality of thermocouples on the outer upper insulating thin film in a non-contact structure with the pyroelectric element part, and a pyroelectric element part and a thermopile part on the upper insulating thin film. And forming a cavity region by removing the semiconductor substrate layer below the central region surrounded by the peripheral portion of the upper insulating thin film after forming the above.