JPH05102533A - Manufacture of optical power sensor - Google Patents

Abstract

PURPOSE:To improve the sensitivity of an optical power sensor which detects the heat converted by a photodetector as a thermoelectromotive force with a thermopile. CONSTITUTION:When a thermopile is formed on a substrate by using Au-Ge thermocouples, a Ge film deposited on the substrate is heat-treated at 580-630 deg.C for one minute or more. Thereby the area resistance of the Ge film of the thermocouple element is reduced to be 1/10, so that the number of thermocouples can be remarkably increased by reducing the element width. Hence an optical power sensor of high sensitivity can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical power sensor, and more particularly, to a thermoelectromotive force for converting heat converted by a photoreceptor having a thermopile using gold and germanium as constituent elements of a thermocouple on a substrate. The present invention relates to a method for manufacturing an optical power sensor for detecting as.

[0002]

2. Description of the Related Art FIG. 3 is a plan view showing an arrangement pattern of thermopiles (thermocouple groups) of an optical power sensor conventionally used for measuring optical power, and FIG. 4 is a line AA of FIG. A sectional view is shown.

In FIG. 4, a photoreceptor 31 is adhered onto a calibration heater 32 on the light-receiving side of a substrate 34, and a thermocouple group for measuring the heat generated in the photoreceptor 31 is attached to the sensor side of the substrate 34. ing.

As shown in FIG. 3, the thermocouple group includes a substrate 3
4, the hot junctions 36 are arranged around the heat equalizing film 35 laminated on the surface of the sensor side corresponding to the light receiving body 34 of the light receiving side, and the thermocouples are arranged radially to cool the adjacent thermocouples. The contact 37 is connected in series to form a thermopile, and the thermoelectromotive force is detected from the output terminal 38 at the end thereof.

To manufacture such an optical power sensor, as shown in FIG. 4, a thermocouple element such as bismuth and antimony or gold (Au) and germanium (Ge) is formed on the sensor side of the substrate 34 by CVD, They are arranged next to each other in sequence by vacuum evaporation or the like, and the hot junction 36 and the cold junction 37 are connected in series to form a thermopile, and an output terminal is provided at the end thereof.

[0006]

However, in the conventional optical power sensor manufactured in this manner, when the number of thermocouples in the thermopile is increased, the width of the thermocouple element becomes extremely narrow, and therefore the resistance is increased. There was a limit to the increase in the number of thermocouples, so it was difficult to improve the sensitivity.

[0007]

According to the present invention, a Ge deposited film, which has been conventionally used as an element constituting a thermocouple, is heat-treated at a specific temperature to significantly reduce its resistance, thereby forming a thermopile. It is possible to greatly increase the number of thermocouples and improve the sensitivity of the optical power sensor.

That is, the present invention provides a substrate for manufacturing an optical power sensor which has a thermopile using gold and Ge as constituent elements of a thermocouple on a substrate and which detects heat converted by a photoreceptor as a thermoelectromotive force. 5 Ge deposited on top
It is a method for manufacturing an optical power sensor, characterized by performing a heat treatment at a temperature of 80 to 630 ° C. for at least 1 minute.

FIG. 1 is a plan view of a sensor side of an embodiment of the optical power sensor of the present invention, showing an arrangement pattern of thermocouple groups, and FIG. 2 is a plan view of the light receiving side of FIG.

The structure of the optical power sensor of the present invention may be basically the same as that of the conventional optical power sensor of FIG. 3, but the number of thermocouples constituting the thermopile can be greatly increased.

The number of thermocouples that can be increased depends on the required sensitivity,
Although the total resistance, the element pattern that can be formed, and the like are determined according to practical use, it is usually possible to increase the necessary sensitivity by increasing the logarithm of the conventional thermopile of FIG. 3 as a single layer. Further, if necessary, it is also possible to increase the number of thermoelectron pairs by laminating thermocouple elements via an insulating layer or by forming the thermopile itself into a multilayer.

As shown in FIG. 1, a Ge film 3 as a thermocouple element b and a thermocouple element a, which are radially arranged and arranged around the sensor-side soaking film 2 on the sensor side of the substrate 1. As
The NiCr / Au film 4 is joined to the hot junction 5 and the cold junction 6 to form a thermopile, and output terminals 7 and 8 for measuring thermoelectromotive force are provided at both ends of the thermopile.

As shown in FIG. 2, a calibration heater 9 and heater input terminals 10 and 11 are provided on the light receiving side opposite to the substrate 1. The calibration heater 9 has a soaking plate on the sensor side on the surface thereof. The light receiver 12 (omitted) is adhered to the corresponding position.

The manufacturing method of the present invention will be described below.

The substrate 1 of the optical power sensor of the present invention has an insulating property, and its material is mica, ceramics,
Although glass, mylar, etc. can be mentioned, alumina is preferable in terms of mechanical strength and time constant, and zirconia which is excellent in toughness and thermal conductivity makes the thickness of the substrate 1 50 μm or less. It is particularly preferable because it is possible to improve the resolution of the sensor.

The constituent elements of the thermocouple of the present invention include Au and
A combination of Ge is used. First, Ge as thermoelectric element b is used.
Is deposited on the sensor side of the substrate 1 by means such as vapor deposition or CVD. The thickness of the deposited layer is about 2 μm, and its sheet resistance is 1
It is preferably about 20.

The amorphous or microcrystalline Ge film deposited to a thickness of about 2 μm on the substrate 1 is in an inert gas such as nitrogen or in vacuum at a temperature of 580 to 630 ° C. for 1 to 5 minutes, preferably 2
After heating for ~ 3 minutes, it is slowly cooled down to 100 ℃ or less. By this heat treatment, the resistance value of the Ge film is
It can be reduced to 1/10, enabling the thermopile to be finely patterned.

In the above heat treatment, when the heating temperature is lower than the above range, the decrease in the resistance value of the Ge film is insufficient,
Further, even if the heat treatment is performed at a temperature higher than the above range, the reduction of the resistance value is insufficient. Heating and cooling are performed at a rate of about 1 ° C / sec, and rapid heating and rapid cooling are not preferable.

The heat-treated Ge film is subjected to patterning necessary for the thermoelectric element b of FIG. 1, and then the surface of the patterned Ge film 3 is covered with a protective film for the next light-receiving side treatment. Insulating silicon nitride is preferable as the protective film.

Next, the calibration heater 9 and the lead wire are attached to the opposite side (light receiving side) of the substrate 1 by sputtering, vapor deposition or the like. The heater material is arbitrary, but tantalum nitride (Ta ₂ N)
A film such as the above is used, and the conductive wire is drawn from both ends of the ring-shaped pattern.

The protective film is removed from the hot and cold junctions of the Ge film pattern on the sensor side and the portion corresponding to the uniform heating film 2 at the center.

On top of that, Au with Ni-Cr as a base is laminated,
A thermopile is formed by patterning the thermocouple element a, the output terminal and the heat equalizing film 2 of FIG.

For stacking and patterning each of these patterns, a stacking means such as vapor deposition, sputtering, and CVD, patterning and etching with a resist, etc. are combined depending on the respective materials.

Finally, a photoreceptor is adhered onto the calibration heater on the light receiving side corresponding to the heat equalizing film 2 on the sensor side, and after a necessary inspection is conducted, lead wires (not shown) are connected to the thermopile output terminal and the heater terminal. And the optical power sensor is completed.

The light receiving body used as the optical sensor element in the present invention may be any one as long as it absorbs light and converts the energy into heat energy. Generally, a black treated metal thin film with a small heat capacity is used,
Electroless nickel / phosphorus plating with gold black coating or black coating is used, but from the viewpoint of sensitivity as a sensor and strength in use, electroless nickel with black coating with extremely low total reflectance is used. A copper thin film having phosphorous plating is preferable, and especially Japanese Patent Application Nos. 63-231760 and 63-231761.
A metal thin film having a nickel-phosphorus alloy-based black coating described in JP-A No. 1994-242242 is preferable.

Although the size of the photoreceptor is arbitrary, for example, the diameter
A circular copper foil with a thickness of 6 mm and a thickness of 20 m is electrolessly plated with nickel-phosphorus with a thickness of 50 m, and a black film is formed by oxidation treatment. This photoreceptor is a heater 9 for calibration.
Alternatively, an insulating film may be provided on the calibration heater 9, and a copper layer and an electroless nickel / phosphorus plating layer may be laminated on the surface by a means such as plating or vapor deposition. The surface may be blackened.

[0027]

[Function] When the Ge film formed by deposition is heat-treated, its sheet resistance is reduced to 1/10, so the logarithm of the thermopile is increased to decrease the resistance of the Ge film element due to the decrease in width and increase in the total length. Even if the increase is expected, the total resistance of the thermopile can be made lower than before, and the sensitivity of the optical power sensor can be greatly improved.

[0028]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 On an alumina substrate 1 having a size of 22 mm square and a thickness of 50 μm, a thickness of about 2
A μm Ge film was deposited by the plasma CVD method. The sheet resistance of the deposited layer was 125 Ω / Sq.

This deposition substrate 1 was placed in an electric furnace and was heated at 1 ° C./sec.
It is heated to 600 ℃ at a heating rate of, held at this temperature for 2 minutes, and then cooled at a cooling rate of 1 ℃ per second.
After the temperature reached ℃, it was naturally cooled to 100 ℃ or less in the furnace.
The sheet resistance of the Ge film layer of the taken-out substrate 1 was lowered to 10 Ω / Sq.

The heat-treated Ge film on the substrate 1 is photoetched to pattern the thermocouple element b of FIG.
Further, a SiN _x protective film was deposited on the surface by ultraviolet CVD.

Then, TaN is deposited on the light-receiving side of the substrate 1 by sputtering with Ar + N ₂ using metallic Ta as a target, and
NiCr / Au deposition was combined with photoetching patterning to form the heater circuit of FIG.

The protective film on the sensor side is patterned to expose the circular heat equalizing film 2 part, the hot junction and the cold junction of the Ge film element, and the vapor deposition film of NiCr.Au is formed on it to form the NiCr.Au film. Was patterned to form the heat equalizing film 2 and the thermocouple element a in FIG. 1 to complete the thermopile.

Table 1 shows the results obtained by adhering a nickel-phosphorus alloy black coating light-receiving element on the light-receiving side heater and measuring various properties as an optical power sensor.

Comparative Example 1 As an example of a conventional product, an optical power sensor having 6 pairs of thermocouples shown in FIG. 3 was manufactured.

The photoreceptor, the heater 9 for calibration, the substrate 1, and the thermocouple elements a and b are the same as those of the first embodiment, and the thickness of the thermocouple elements is substantially the same as that of the first embodiment, but the thermocouple element b is used. Was not heat treated. The various properties are shown in Table 1.

The sensitivity and resistance values in the table are actual measured values of the sensor itself, the noise voltage is the output voltage when there is no sensor input, and the resolution is the minimum measurable input,
In all cases, the value of Comparative Example 1 was set to 1 and shown as a comparative value.

[0038]

[Table 1]

Example 2 An optical power sensor was manufactured in the same manner as in Example 1 except that a zirconia plate having a thickness of 30 μm was used as the substrate 1.
As shown in Table 1, the noise voltage and the resistance value are the same as those in the first embodiment, but the sensitivity and the resolution are significantly improved as the effect of the substrate 1.

[0040]

The optical power sensor according to the method of the present invention is
Since the resistance value of the Ge film of the thermocouple element b becomes extremely small by heat treatment, and the resistance value of Au of the other element a is originally extremely small, the pattern width of the element can be made narrower than before, and the number of thermocouples of the thermopile can be greatly increased. It can be increased, and the resistance value of the whole thermopile is not increased. As a result, the output is increased without increasing noise, and an optical power sensor with improved sensitivity and resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a sensor side plan view of an optical power sensor of the present invention.

FIG. 2 is a plan view of a light receiving side of the optical power sensor of FIG. 1, in which a light receiving film is omitted.

FIG. 3 is a plan view of a sensor obtained by partially removing the conventional optical power sensor.

4 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 substrate 2 soaking film 3 Ge film film 4 NiCr / Au film 5 hot junction 6 cold junction 7 output terminal 8 output terminal 9 calibration heater 10 heater input terminal 11 heater input terminal 12 photoreceptor

Claims (2)

[Claims] 1. In the manufacture of an optical power sensor having a thermopile using gold and germanium as constituent elements of a thermocouple on a substrate and detecting heat converted by a photoreceptor as a thermoelectromotive force, it is deposited on the substrate. Germanium
A method for manufacturing an optical power sensor, which comprises heat-treating at a temperature of 580 to 630 ° C. for at least 1 minute. 2. The optical power sensor according to claim 1, wherein zirconium is used as the substrate.