JP3246131B2 - Manufacturing method of infrared detecting element - Google Patents

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 infrared detecting element, and more particularly to a thermal infrared detecting element for detecting infrared light by detecting a change in temperature due to absorption of infrared light.

[0002]

2. Description of the Related Art There are two types of infrared detecting elements, so-called quantum type and thermal type. Although the quantum type infrared detecting element has a very high sensitivity, it needs to be cooled and used at a low temperature, is difficult to handle, and has a high manufacturing cost.

[0003] Although the thermal type infrared detecting element is inferior to the quantum type in terms of sensitivity, it does not require cooling, has a simple structure and is inexpensive to manufacture, and is widely used in various practical applications. I have.

There are three main types of thermal type infrared detecting elements, those using a pyroelectric element, those using a thermocouple, and those using a resistor. Converts the thermal behavior, that is, the temperature change into an electrical change, and detects infrared rays.

A thermistor bolometer is used as an element for detecting the amount of incident infrared light by using a resistor, which is described in detail in the prior art of Japanese Patent Application Laid-Open No. 2-201229.

As shown in FIG. 5, the inventors of the present invention have formed an infrared detector comprising a thin-film resistor 14 as a heat-sensitive layer, a pair of electrodes 15 and 15 above and below the thin-film resistor 14, and an uppermost infrared absorption layer 17. It has a sandwich type structure. Then, as shown in FIG. 6, a bridge circuit is formed in which four infrared detecting units a are configured to have four sides, and the infrared rays incident through the lens are narrowed by the movement of the heat source.
The infrared detecting unit a to be irradiated is changed so that the fine movement of the heat source can be detected. In addition, with respect to the change in the environmental temperature, the infrared rays are always irradiated to all the four infrared ray detection units a, and thus are not detected.

[0007]

In such an infrared detecting element, errors must be increased unless the thin-film resistor 14 as the four heat-sensitive layers has uniform electrical and temperature characteristics. In addition, variations in sensitivity and characteristics as a sensor also increase. However, if the components of the infrared detecting section a are formed on the wafer as a thin film and then separated into individual infrared detecting sections a by patterning, the thin film resistor 1
The electrical characteristics and temperature characteristics of No. 4 are almost uniform within the same wafer, and the above-mentioned problems have been almost solved.

However, when higher detection accuracy is required, a slight variation in the resistance value between the four infrared detectors a becomes a problem. Is greatly reduced.

The present invention has been made in view of the above points, and has as its object to provide a method of manufacturing an infrared detecting element capable of producing an infrared detecting element having high detection accuracy and good yield. Is to provide.

[0010]

According to the first aspect of the present invention,
A method of manufacturing an infrared detecting element in which a thin film resistor and four infrared detecting sections each including a pair of electrodes and an infrared absorbing layer configured to sandwich the thin film resistor and the infrared absorbing layer are assembled in a bridge circuit,
After making the shape of the upper electrode of the four infrared detectors comb-shaped, measuring the resistance of the four infrared detectors and examining the variation in the resistance, the upper side of each infrared detector is checked by laser cutting. A part of the electrodes is cut so as to adjust the electrode area, and the facing area between the upper and lower electrodes of each infrared detecting unit is changed, so that the distance between the four infrared detecting units is reduced. Is characterized in that the variation of the resistance value is eliminated.

[0011]

[0012]

According to the method of manufacturing an infrared detecting element of the present invention, the resistance of each infrared detecting section as described above is measured, and the variation of the four infrared detecting sections assembled in the bridge circuit is examined. The electrodes are processed so that the facing area between the upper and lower electrodes is 4
By changing the direction in which there is no variation between the four infrared detection units, the resistance values of the four infrared detection units are uniform.
An infrared detection element with good detection accuracy can be manufactured.

When the area of the electrode is adjusted by laser cutting, the area can be adjusted with one scanning line by forming the electrode in a comb shape, thereby facilitating the processing. Further, since the scanning length of the laser can be shortened, damage to the base can be minimized.

[0014]

An embodiment according to the present invention will be described below with reference to the drawings. FIG. 4 shows the entire structure of the infrared detecting device, and FIG. 5 shows the detailed structure of the infrared detecting element.

By the way, the resistance value of the infrared detecting element, of course, changes depending on the characteristics of the heat-sensitive portion. However, in the infrared detecting element having the sandwich structure as described above,
It can be easily changed by changing the facing area between the upper electrode and the lower electrode. Therefore, 4
If the electrode area can be changed after measuring the resistances of the four infrared detection units, the resistance values of the four infrared detection units can be made uniform.

Since the resistance value can be measured after the upper electrode is formed, the measurement is performed, and the variation in the resistance values of the four infrared detection units is checked. If the area of the exposed upper electrode before formation is adjusted in a direction that eliminates variations by a method such as laser cutting, an infrared detection element having a uniform resistance value between the four infrared detection units is obtained. be able to.

When the electrode area is adjusted by laser cutting, the area can be adjusted with one scanning line by making the electrode shape comb-shaped.

As shown in FIG.
Has a thickness of 30 on the surface of the silicon single crystal (100) plane.
On a surface of a substrate 11 having a thickness of 0 μm, a heat insulating film 12 having a thickness of 1.0 μm and comprising a composite film of silicon nitride and silicon oxide is formed. A part of the substrate 11 is removed from the back side of the substrate 11 until the thermal insulation film 12 is reached.
It has become. At the position of the heat separation space 13, the heat insulating film 12 is in a hollow state, and only the outer periphery thereof is supported by the substrate 11, forming a so-called thin film bridge b.

On the thin film bridge b, a thin film resistor 14 made of amorphous silicon having a thickness of 1.0 μm and a thin film resistor 14 made of chromium having a thickness of 0.2 μm
A pair of electrodes 15, 15 arranged vertically above and below are formed by patterning. The resistance value of the thin film resistor 14 can be detected by the electrodes 15 and 15 and taken out to an external circuit. The electrodes 15, 15 are extended outward on the thin film bridge b, and electrode terminals 16, 16 are provided on the heat insulating film 12 of the substrate 11. Over the infrared detecting portion a having a sandwich structure of the thin film resistor 14 and the upper and lower electrodes 15, 15, the infrared absorbing layer 17 made of silicon oxide enhances the infrared absorption, and the temperature rise of the infrared absorbing portion a is good. To be done.

Next, an example of a method for manufacturing an infrared detecting element having the above structure will be described. First, a thermal insulating film 12 made of silicon nitride and silicon oxide is formed on one surface of a silicon substrate 11 by a plasma CVD method. At this time, monosilane and ammonia, and monosilane and carbon monoxide were used as the introduced gas, and the substrate temperature was set to 40 °.
C, a processing condition of a frequency of 13.56 MHz was employed. On the opposite surface of the substrate 11, a thin film of silicon nitride is formed by the same means as described above.

On the thermal insulating film 12 of the substrate 11, chromium having a thickness of 0.2 μm is deposited at a substrate temperature of 150 ° C. by a vacuum evaporation method. A resist layer is formed and patterned on the chromium layer to be the electrodes 15 and 15 by using a normal photolithography technique. Using this resist pattern as a mask, the chromium layer is etched with an etching solution containing cerium ammonium nitrate to form an electrode 15 on the lower side of the predetermined pattern. After the etching, unnecessary resist patterns are removed.

Next, the thin film resistor 1 is formed by a plasma CVD method.
An amorphous silicon layer 4 is deposited. A resist pattern is formed on the amorphous silicon layer by the same means as described above, and the amorphous silicon layer is etched with an etching solution containing nitric acid, acetic acid, and hydrofluoric acid using the resist pattern as a mask. Is formed.

The upper electrode 15 made of chromium is formed on the thin film resistor 14 through the same steps as those for the lower electrode 15.

However, the upper electrode is patterned into a shape as shown in FIGS. 41, 51, 6
Reference numeral 1 denotes a laser cutting surface of each electrode. Here, after measuring the resistance value of each infrared detection unit a, the upper side of the four infrared detection units a assembled in the bridge circuit whose resistance value variation is ± 2% or more is removed so that the variation is eliminated. A part of the electrode film is cut by a laser cutter device using a Xe laser, and the opposing areas of the upper and lower electrodes are adjusted to make the resistance value between the four infrared detection units a uniform.

The thin film resistor 14 and the electrode 15,
A thin layer of silicon oxide to be the infrared absorbing layer 17 is deposited on the layer 15 by the same plasma CVD method as in the step of forming the thermal insulating film 12. Further, after forming a resist pattern, the silicon oxide layer is etched with an etchant comprising hydrofluoric acid and ammonium fluoride to form an infrared absorbing layer 17 having a predetermined pattern.

Further, an aluminum layer having a thickness of 1.5 μm is deposited thereon at a substrate temperature of 150 ° C. by using a vacuum evaporation method. After a resist pattern serving as a mask is formed, the aluminum layer is etched with an etching solution containing phosphoric acid, acetic acid, and nitric acid to form electrode terminals 16 having a predetermined pattern.

Next, the heat separation space 13 is provided on the surface of the substrate 11 on the back side of the surface on which the infrared absorbing portion a is formed.
Is formed to form a resist pattern. Using this resist pattern as a mask, the silicon nitride layer previously formed on the surface of the substrate 11 is patterned by a plasma etching method. The plasma etching conditions at this time were as follows: power 200 W, gas pressure 400 mTorr.
Carbon tetrafluoride is used as the introduced gas.

After removing the resist, the silicon forming the substrate 11 is etched by a so-called anisotropic etching method using the patterned silicon nitride layer as a mask to form a thermal isolation space 13. The conditions of the anisotropic etching treatment are as follows: potassium hydroxide is used as an etchant;

The infrared detecting element 10 manufactured as described above is used in a state of being housed in a package 20, as shown in FIG.

The infrared detecting element 10 is bonded to a metallic stem 21 with an adhesive 22. Lead terminal 2 installed through upper and lower surfaces of stem 21
3 and 23, the electrode terminal 16 of the infrared detecting element 10;
16 are connected by bonding with gold wires 24, 24, and the resistance of the thin film resistor 14 is
23 to the outside.

A metal cap 25 is placed over the stem 21, and the outer peripheral portion is welded and sealed to the stem 21.
In the cap 25, at a position facing the infrared detecting section a of the infrared detecting element 10, infrared light of a specific wavelength is selectively applied.
Incident window 27 provided with a filter 26 that transmits light
Are formed. The filter 26 is made of the silicon substrate 11
Produced by depositing a permselective membrane on the surface of
A material having the following cut characteristics is used and bonded to the infrared incident window 27 of the cap 25 using low-melting glass.

In this embodiment, as described above, by performing trimming adjustment of the upper electrode area by the laser cutter, the variation yield of the four infrared detectors a in the bridge circuit (variation is within ± 2%). If there is a good product,
If it is more than that, the defective product is reduced from about 50%
It was dramatically increased to 0% or more.

[0033]

As described above, the infrared detecting element of the present invention has a sandwich structure in which a thin film resistor and an electrode are formed in a sandwich structure. It is possible to eliminate the variation in the resistance of the four infrared detection units formed by combining the above, and to greatly improve the yield due to the variation. In addition, when laser cutting is used to adjust the electrode area, the electrode shape is made comb-shaped, making processing easier,
Damage to the groundwork can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the shape of an upper electrode according to one embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a shape of an upper electrode according to another embodiment of the present invention.

FIG. 3 is a schematic view showing an example of the shape of an upper electrode according to another embodiment of the present invention. .

FIG. 4 is a cross-sectional view of the entire structure of the infrared detection device.

FIG. 5 is an enlarged sectional view of an infrared detecting element.

FIG. 6 is a configuration diagram of a bridge circuit of the infrared detection element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Infrared detecting element 11 Substrate 12 Thermal insulating film 13 Thermal isolation space 14 Thin film resistor 15 Electrode 16 Electrode terminal 20 Package 21 Stem 25 Cap 41, 51, 61 Laser cutting surface a Infrared detecting part b Thin film bridge c Enclosure space

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01S 3/00 G01J 1/02 C // G01J 1/02 H01L 29/44 F (72) Inventor Takayoshi Awai Kadoma, Osaka 1048 Ojimon Kadoma Matsushita Electric Works Co., Ltd. (72) The inventor Keiji Kakite 1048 Ojidoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (56) References JP 5-164604 (JP, A) JP -201229 (JP, A) JP-A-56-12521 (JP, A) JP-A-5-205905 (JP, A) JP-A-5-135914 (JP, A) JP-A-53-128752 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01J 1/02 G01J 5/02 G01J 5/12 G01J 5/20-5/24 G01K 7/16 H01C 7/00 H01L 29/41 H01L 21/28-21/288 H01L 21/44-21/445 H01L 29/40-29/64 H01L 31/00-31/02 H01L 31/08 H01L 37/00-37/02 H01S 3/00 H01C 7 / 02-7/22

Claims (1)

(57) [Claims] 1. A method of manufacturing an infrared detecting element, comprising: a thin film resistor, a pair of electrodes configured to sandwich the thin film resistor, and four infrared detecting sections each including an infrared absorbing layer in a bridge circuit. four upper electrodes of the infrared detection portion shape and a comb shape, after examining the variation in the resistance values by measuring the resistance value of the four infrared detection unit, laser
By cutting, one of the upper electrodes of each infrared detector
In order to eliminate the variation in resistance between the four infrared detectors, the parts are cut and processed to adjust the electrode area, and the facing area between the upper and lower electrodes of each infrared detector is changed. A method for manufacturing an infrared detecting element.