JPH06213707A - Infrared sensor - Google Patents

Abstract

PURPOSE:To detect true quantity of infrared rays from the differential output between two infrared-sensitive membranes by preventing the infrared rays from impinging on one of a pair of infrared-sensitive membranes positively. CONSTITUTION:Infrared-sensitive membranes 35, 36 are provided on the surface of bridge parts 34a, 34b. Infrared rays radiated from an object to be measured impinges selectively on one infrared-sensitive membrane 36 through a cover 40 applied to the rear surface of a silicon substrate 31. Nickel membranes 46 are applied, as infrared ray shielding membranes, to the side wall faces at hollow sections 32, 33 and the infrared rays incident to one hollow section 33 is prevented from intruding into the other hollow section 35.

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 measuring the temperature of an object to be measured in a non-contact manner, and more particularly to a thermobolometer type infrared sensor.

[0002]

2. Description of the Related Art Recently, various techniques have been developed for producing an infrared sensor suitable for a non-contact thermometer or the like by utilizing a semiconductor fine processing technique. There are various types of infrared sensors such as a thermobolometer type and a thermopile type. Among them, the thermobolometer type infrared sensor forms an infrared sensor sensitive film of a substance having a thermistor effect, and measures the temperature rise due to the received infrared ray by the change of the electric resistance value to know the infrared ray amount,
It is superior to other types in that the sensor can be easily miniaturized.

In this thermobolometer type infrared sensor, if the heat capacity of the infrared thermosensitive film is small and the amount of heat transferred from the infrared thermosensitive film to the outside is small, the temperature rises accordingly and the response sensitivity to a small amount of infrared rays is high. Become.
Therefore, in the conventional structure, a very small bridge portion is formed on the sensor substrate, and an infrared sensitive film is further formed on the bridge portion. That is, the response sensitivity is improved by forming a cross-linked structure in which the heat-sensitive part of the element is floated from the support substrate.

On the other hand, in measuring, since a small amount of infrared rays emitted from the object to be measured is targeted, various measures are required. For example, one sensor is provided with two identical infrared-sensitive films, one infrared-sensitive film is irradiated with infrared light, and the other infrared-sensitive film is shielded so that infrared light does not enter. By constantly comparing the output of the infrared sensitive film on which infrared rays are incident with the output of the infrared sensitive film on which infrared rays are not incident, electrical noise and thermal disturbance are removed to detect the net amount of infrared rays. be able to.

As a concrete structure for performing such a measurement, a structure shown in FIG. 7 can be considered.

In this infrared sensor, for example, two cavities 12, 1 are provided in a silicon substrate 11 as a sensor substrate.
3 is formed. On the upper surfaces of the cavities 12 and 13, for example, 2 with a width of 20 μm, a length of 2 mm and a film thickness of 3 μm.
The insulating film 14 having the bridge portions 14a and 14b of the book is formed. The insulating film 14 is formed of, for example, a silicon oxynitride (SiOxNy) film. Bridge 14
The infrared sensitive films 15 and 1 are provided on the upper surfaces of the central portions of a and 14b.
6 is provided. The infrared sensitive films 15 and 16 are
For example, it is formed of amorphous germanium (a-Ge). Although not shown, one end of an electrode wiring layer formed of an aluminum (Al) film is electrically connected to the infrared sensitive films 15 and 16, and the other end of the electrode wiring layer is connected to the peripheral edge of the silicon substrate 11. It is connected to the formed electrode pads 17 and 18.

A front cover 20 is provided on the upper surface of the silicon substrate 11. The peripheral portion of the front cover 20 is supported by the electrode pads 17 and 18 with an FPC (flexible printed circuit) 19 in between. The front cover 20 is formed of a silicon substrate 21, and infrared reflection preventing films 22a and 22b are provided on both front and back surfaces thereof, respectively. Infrared shielding films 23a and 23b made of, for example, aluminum (Al) are formed on the right half of the infrared reflection preventing films 22a and 22b so as to cover the infrared sensitive film 15.

An insulating film 24 made of a silicon oxynitride film is formed on the lower surface of the silicon substrate 11, and a back cover 25 is provided below the insulating film 24. This back cover 25 is also made of a silicon substrate, and an infrared reflection film 26 is formed on the upper surface thereof.

In this infrared sensor, since the front cover 20 is formed with the infrared shielding films 23a and 23b, infrared rays are selectively incident only on the other infrared sensitive film 16 side.
By obtaining the differential output between the infrared sensitive film 16 on which the infrared rays are incident and the infrared sensitive film 15 on which the infrared rays are not incident,
The true amount of infrared rays can be detected.

[0010]

However, in the above infrared sensor, since the side wall 27 partitioning the cavity 12 and the cavity 13 is made of silicon (silicon single crystal), the side wall 27 is located on the cavity 13 side. The incident infrared rays are reflected by the infrared reflecting film 26, pass through this portion, and enter the infrared sensitive film 15 side. For example,
When the wavelength dependency (FT-IR) is measured by using the above infrared sensor in a tympanic sound thermometer, the single crystal silicon exhibits infrared transmittance of about 53% in the vicinity of 10 μm, which is a main component of infrared rays emitted from the human body. . Therefore, an error occurs in the differential output between the infrared sensitive films 15 and 16, and there is a problem that the true amount of infrared rays cannot be detected.

The present invention has been made in view of the above problems, and an object thereof is to surely prevent infrared rays from entering one infrared sensitive film of a pair of infrared sensitive films. It is to provide an infrared sensor capable of detecting a quantity.

[0012]

An infrared sensor according to the present invention comprises a sensor substrate having at least a pair of bridge portions,
A first infrared-sensitive film formed on one side of the bridge,
A second infrared sensitive film having the same structure as the first infrared sensitive film formed on the other side of the bridge portion, and infrared rays emitted from a measurement target are selectively made incident on the first infrared sensitive film. The infrared selective incident means and the side walls on the infrared sensitive film side different from each other in the lower cavity of each of the bridge portions are provided to the second infrared sensitive film side of the infrared rays incident on the first infrared sensitive film side. And an infrared shielding film that prevents the entry of the infrared rays.

In this infrared sensor, infrared rays radiated from the object to be measured are selectively made incident on the first infrared sensitive film by the infrared selective entrance means, and are transmitted through the side wall between the cavities of the infrared rays. The infrared shielding film prevents the second infrared sensitive film from invading.

As the sensor substrate, a semiconductor substrate made of silicon, germanium or the like is used, but it is preferable to use a silicon substrate which can be easily and inexpensively obtained. The infrared sensitive film is amorphous germanium (a-Ge), amorphous silicon (a-Si).
And a film of polycrystalline silicon or the like. Sputtering, ion beam sputtering, CVD (Chemical Vapor Deposition) and the like are used for forming the infrared sensitive film.

The bridging portion is composed of a silicon oxide film (SiOx), a silicon nitride film (SiNy) and a silicon oxynitride (SiOxN).
y) It can be formed of a film or the like, but it is particularly preferably formed of a silicon oxynitride film. The silicon oxynitride film has the properties of both a silicon oxide film and a silicon nitride film, and therefore has a good stress balance and can form a stable crosslinked structure.

This cross-linking portion forms a silicon oxynitride film on both surfaces of a silicon substrate,
It is possible to form it by anisotropic etching using a hydrazine aqueous solution, potassium hydroxide (KOH) or the like, by previously patterning one surface with a crosslinked structure and the other surface with a window shape of an arbitrary size by etching.

As the infrared shielding film, nickel (Ni) is used.
A film, a laminated film of a chromium (Cr) film and a copper (Cu) film, or the like can be used. These films can be easily formed on the wall surface of the cavity formed by anisotropic etching by the vapor deposition method.

[0018]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a vertical sectional structure of an infrared sensor according to an embodiment of the present invention. This infrared sensor is of a type in which infrared rays are incident from the back side (lower side in the figure).

In the infrared sensor of this embodiment, the silicon substrate 31 as the sensor substrate has two cavities 32 and 33.
Are formed. On the upper surfaces of these cavities 32 and 33, for example, 2 with a width of 20 μm, a length of 2 mm and a film thickness of 3 μm.
A silicon oxynitride (SiOxNy) film 34 having book bridges 34a and 34b is formed. Bridge 34
The infrared sensitive films 35 and 3 are provided on the upper surfaces of the central portions of a and 34b.
6 is provided. The infrared sensitive films 35 and 36 are
For example, it is formed of amorphous germanium (a-Ge). Although not shown, one end of an electrode wiring layer formed of an aluminum (Al) film is electrically connected to the infrared sensitive films 35 and 36, and the other end of the electrode wiring layer is a peripheral portion on the silicon substrate 31. Are connected to the electrode pads 37 and 38 formed on.

A silicon oxynitride film 44 is formed on the lower surface of the silicon substrate 31, and a lid 40 is provided below the silicon oxynitride film 44.
This lid 40 is formed of a silicon substrate 41,
An infrared antireflection film 42a is formed on each of the front and back surfaces,
42b is provided. These infrared antireflection films 42
In the right half of the figures a and 42b, the infrared sensitive film 35 is provided.
Infrared shielding films 43a and 43b made of, for example, aluminum (Al) are provided so as to cover the.
A lid (not shown) is provided on the upper surface of the silicon substrate 31, and the sensor chip is sealed together with the lid 40 on the back surface. Soldering or anodic bonding methods are used to bond these lids to the infrared sensor chip. In particular, the anodic bonding method can seal the inside of the chip in a vacuum state, so that the effect of air convection is affected. Can be eliminated and the sensor characteristics can be improved.

In this embodiment, nickel (Ni) films 46 as infrared shielding films are formed on the side walls of the cavities 32 and 33, respectively.

In this infrared sensor, infrared rays pass through the lid 40 from the back surface side, pass through the cavity 33, and are selectively incident only on one infrared sensitive film 36 side. The infrared sensitive film 36 on which the infrared rays enter and the infrared sensitive film 3 on which the infrared rays do not enter
The amount of infrared rays is detected by obtaining the differential output with respect to 5 as in the conventional case.

In this infrared sensor, infrared rays which are incident on the side of the cavity portion 33 and permeate through the partition portion 45 between the cavity portions 32 and 33 to enter the side of the infrared sensitive film 35 are nickel provided on the side wall surface. It is shielded by the membrane 46. Therefore, the infrared ray sensitive film 35 completely shields infrared rays, so that the true infrared ray amount can be detected by the differential output between the infrared ray sensitive film 36 and the infrared ray sensitive film 35.

2 to 4 show a manufacturing process of the infrared sensor. The infrared sensitive films 35, 36
Since they have basically the same structure, only the infrared sensitive film 36 side portion will be illustrated and described here.

First, a silicon substrate 31 having a crystal plane orientation (100) as shown in FIG. 2 (A) was prepared. Next, silicon oxynitride films 34 and 44 having a film thickness of 2 μm as shown in FIG. 3B were formed on both surfaces of the silicon substrate 31 by the plasma CVD method. That is,
The silicon substrate 31 is heated to 450 ° C., the film forming conditions are pressure of 0.45 Torr and high frequency output of 400 W,
As reaction gas, monosilane (Si H ₄ ) 15SCCM,
203 SCCM of nitrogen (N ₂ ) and 32 of laughing gas (N ₂ O)
SCCM was flown, and silicon oxynitride was vapor-deposited on both surfaces of the silicon substrate 31 for 20 minutes to form a film.

Next, as shown in FIG.
An infrared sensitive film 36 as shown in (C) was formed. That is, sputtering was performed using germanium (Ge) as a target to form an amorphous germanium (a-Ge) film on the silicon oxynitride film 34. This sputtering has a gas flow rate of argon (A
r) = ₂ SCCM, hydrogen (H ₂ ) = 1 SCCM, film formation pressure 3 ×
The test was performed for 10 minutes at 10 ⁻³ Torr and a high frequency output of 200W. Next, annealing treatment was performed at 500 ° C. to promote polycrystallization of amorphous germanium. Subsequently, reactive ion etching was performed to pattern the polycrystallized amorphous germanium film.

Subsequently, after heating to 50 ° C. to form an aluminum film having a film thickness of 0.5 μm on the surface of the silicon substrate 31 by, for example, a vapor deposition method, patterning is performed as shown in FIG.
An electrode wiring layer 51 as shown in (D) was formed.

Next, as shown in FIG. 3A, electrode pads 37 and 38 were formed on the surface of the silicon substrate 31. That is, the film thickness of 0.
A chromium (Cr) film 52 having a thickness of 05 μm and a copper (Cu) film 53 having a thickness of 1.5 μm were sequentially formed. Subsequently, as shown in FIG. 3B, an etching resistant film, for example, a silicon oxynitride film 54 having a film thickness of 1 μm was formed on the surface of the silicon substrate 31.

Next, as shown in FIG. 3C, contact holes 55 and 56 were formed in the silicon oxynitride film 54 corresponding to the electrode pads 37 and 38. Subsequently, as shown in FIG. 3D, the silicon oxynitride film 44 on the back surface is selectively etched to form an opening 57.
Was formed.

Subsequently, the silicon substrate 31 is selectively etched from the back surface through the opening 57, and the silicon substrate 31 is etched as shown in FIG.
The cavity 33 was formed as shown in FIG. For this etching, anisotropic etching using a hydrazine aqueous solution is performed at a temperature of 11
It was performed at 0 ° C. for 1 hour and 30 minutes, and stopped at a position of about 20 μm from the surface of the silicon substrate 31. Note that this anisotropic etching may be performed using a potassium hydroxide aqueous solution.

Next, as shown in FIG. 4B, a nickel film 46 as an infrared shielding film is formed on the wall surface of the cavity 33 by electroless plating, and the electrode pads 37, 3 are formed.
Nickel films 57 and 58 were formed in the contact holes 55 and 56 of No. 8, respectively. In this plating, Top Chemialoy B-1 (manufactured by Okuno Chemical Industries Co., Ltd.) was used as a plating solution and immersed at 65 ° C. for 5 minutes to form nickel films 46, 57 and 58 having a thickness of 1 μm. did.

Then, the silicon on the surface of the silicon substrate 31
Patterning the oxynitride film 34 to form a bridge
34b pattern was formed. This patterning was
For example, by reactive ion etching (RIE),
The process was repeated until the silicon substrate 31 was exposed. This etch
Is used as an etching gas for methane trifluoride (CH
F ₃) And oxygen (O₂) Using CHF₃= 4
7.5 SCCM, O₂= 2.5 SCCM, pressure during etching
The power is 0.075 Torr and the high frequency output is 150 W.
The ching time was 3 hours.

Finally, as shown in FIG. 4C, anisotropic etching is performed on the surface of the silicon substrate 31 at a temperature of 110 ° C.
Then, the bridge portion 34b was formed and the upper portion of the cavity 33 was selectively removed. At this time, since the back surface of the silicon substrate 31 is covered with the etching resistant metal film (nickel film 46), the etching does not proceed.

By such a method, an infrared sensor having an infrared shielding film (nickel film 46) on the side wall of the cavity 33 could be manufactured. Also, according to this method,
A nickel film 5 is formed on each of the electrode pads 37 and 38.
Since 7, 58 are formed, the copper film 53 can be prevented from being oxidized.

FIG. 5 shows another embodiment of the present invention.

The infrared sensor of this embodiment is of a type in which infrared rays are incident from the surface side (upper side in the figure),
The same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the lid 40 is provided on the upper surface of the silicon substrate 11, and the peripheral portion of the lid 40 is FP.
It is supported by the electrode pads 37 and 38 with a C (flexible printed circuit) 61 in between. On the other hand, a lid 62 is provided on the lower surface of the silicon substrate 11. The lid 62 is formed of a silicon substrate, and an infrared reflection film 63 is formed on the upper surface thereof.

In this embodiment, a laminated film 47 is formed as an infrared shielding film on the side walls of the cavities 32 and 33, respectively. The laminated film 47 has a two-layer structure of a chromium film and a copper film.

In this infrared sensor, the infrared rays that are incident on the cavity portion 33 side and reflected by the infrared reflecting film 63 are shielded by the laminated film 47 provided on the side wall surface. Therefore, similarly to the embodiment of FIG. 1, the infrared ray sensitive film 35 completely shields the infrared ray, so that the true infrared ray amount can be detected by the differential output between the infrared ray sensitive film 36 and the infrared ray sensitive film 35. .

FIG. 6 shows the manufacturing process of the infrared sensor of this embodiment. It should be noted that the description up to FIG. 4A is omitted because it is similar to the above-described embodiment.

In this embodiment, after the cavity 33 is formed by anisotropic etching as described with reference to FIG. 4A, the silicon substrate 3 is formed by the vacuum evaporation method as shown in FIG. 6A.
Chromium and copper are sequentially vapor-deposited from the back surface of 1 to a film thickness of 0.0
5 μm chromium film 71 and 1.5 μm thick copper film 72
The laminated film 47 of was formed.

Next, the silicon oxynitride film 34 on the surface of the silicon substrate 31 is patterned to form the bridge portion 3.
The pattern of 4b was formed. This patterning was performed, for example, by reactive ion etching (RIE) until the underlying silicon substrate 31 was exposed. This etching was performed under the same conditions as shown in FIG.

Finally, as shown in FIG. 6B, anisotropic etching was performed from the surface of the silicon substrate 31 to form the bridge portion 34b and selectively remove the upper portion of the cavity 33. At this time, since the back surface of the silicon substrate 31 is covered with the etching resistant metal film (laminated film 47), the etching does not proceed.

In the above embodiment, the infrared sensor having the pair of infrared sensitive films 35 and 36 on one surface of the silicon substrate 31 has been described.
The present invention is not limited to this, and for example, a pair of infrared sensitive films 35 and
It is also applicable to the type having 36.

[0045]

As described above, according to the infrared sensor of the present invention, since the infrared shielding films are provided on the different infrared sensitive films of the two cavities, the infrared rays to the second infrared sensitive film are provided. Is reliably prevented, and the true infrared ray amount can be obtained by the differential output between the first infrared sensitive film and the second infrared sensitive film.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an infrared sensor according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 3 is a vertical cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 4 is a vertical cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 5 is a vertical cross-sectional view of an infrared sensor according to another embodiment of the present invention.

6 is a vertical cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 7 is a vertical sectional view showing an infrared sensor for extracting a differential output.

[Explanation of symbols]

 31 Silicon Substrate (Sensor Substrate) 32, 33 Cavity 34, 34b Crosslink 35, 36 Infrared Sensitive Film 46 Nickel Film 47 Laminated Film

Claims (1)

[Claims] 1. A sensor substrate having at least a pair of bridges, a first infrared-sensitive film formed on one of the bridges, and a first infrared-sensitive film formed on the other of the bridges. A second infrared-sensitive film having the same structure, an infrared selective-injection means for selectively injecting infrared rays emitted from the object to be measured into the first infrared-sensitive film, and a cavity portion below each of the bridge portions. And an infrared shielding film which is provided on a side wall of a different infrared sensitive film side and which prevents infrared rays incident on the first infrared sensitive film side from entering the second infrared sensitive film side. Infrared sensor.