JPH07120325A - Infrared detector - Google Patents

Abstract

PURPOSE:To provide a transmittance and a reflectance suitable to reduce a stray light and, to reduce narcissi. CONSTITUTION:In this infrared detector small apertures 12A are formed in the slit plate 12 to face infrared-detecting elements 2 set on the surface of the substrate 1 and a cold aperture consisting of a slit plate 12 of a silicon crystal adhering to a surface of a substrate 1 and a frame-like block 11 of a silicon crystal layered on an upper surface of the slit plate 12 is provided. The frame-like block 11 has a rectangular window 11A at a central part thereof which is almost equal in shape to an outer frame of a row of the small aperture of the slit plate 12. A dopant of a group (III) or (IV) element is dispersed in the frame-like block 11 and the slit plate 12 of the cold aperture to a limit between solid and liquid phases.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an infrared detector. The infrared detector cools to an extremely low temperature (around 80K) with liquid nitrogen or a Joule-Thomson cooler in order to eliminate the effect of energy kT (k is the Boltzmann constant, T is the absolute temperature) at room temperature (300K). And is using it.

On the other hand, in order to improve the spatial resolution of the infrared detector, it is necessary to set the viewing angle of the infrared detecting element to a predetermined value and prevent stray light. For the above reasons
Infrared detectors require cold apertures.

[0003]

2. Description of the Related Art FIG. 4 is a perspective view showing a conventional cold door aperture in a separated form, and FIG. 5 is a sectional view of an infrared detector.

In FIG. 4, 1 is a substrate made of sapphire or the like, and 2 is an infrared detecting element arranged on the surface of the substrate 1 at an equal pitch. Each infrared detection element 2
Are strips of HgCdTe or the like (length about 100 μm, width tens of μm), and the output conductor patterns 3 are derived from the opposite side edges.

Reference numeral 12 is a slit plate made of a silicon crystal which has the same shape as the substrate 1 in a plan view and a desired thickness (about 100 μm). The slit plate 12 faces each of the infrared detection elements 2 arranged in parallel on the surface of the substrate 1, and is a small rectangular window similar to the infrared detection elements 2 and slightly larger than the infrared detection elements 2.
12A are arrayed. The small windows 12A adjacent to each other are separated by a thin wall (about 30 μm) of a partition 12B.

Reference numeral 11 denotes a frame-shaped block having the same shape as the slit plate 12 in a plan view and made of a silicon crystal having a desired plate thickness (several hundred μm). At the center of the frame block 11, a rectangular window 11A having a shape substantially equal to the outer frame shape formed by the small window row of the slit plate 12 is provided.

The small window 12A of the slit plate 12 and the rectangular window 11A of the frame block 11 are provided by anisotropic etching, and each specific inner wall is an inclined surface.
The frame-shaped block 11 and the slit plate 12 are non-doped silicon crystals, or silicon crystals doped with a dopant of a Group 3 element or a Group 4 element (for example, boron) at (10 ¹⁵ to 10 ¹⁶ ) / cm ³ .

Then, after applying an adhesive such as an epoxy resin to the entire bonding surface (the upper surface in the figure) of the slit plate 12,
The joint surface of the slit plate 12 and the joint surface of the frame-shaped block 11 (the lower surface in the figure) are aligned and brought into close contact, and the slit plate 12 and the frame-shaped block 11 are adhered with an adhesive to make a cold door aperture.
It is 100.

Further, after the adhesive 4 is applied near the left and right ends of the surface of the substrate 1, the cold door aperture described above is applied.
The lower surface of 100 (the lower surface of the slit plate 12) is aligned and brought into close contact with the surface of the substrate 1, and the cold aperture 100 and the substrate 1 are bonded with an adhesive 4 to form an infrared detector.

The infrared detector constructed as described above is
The light receiving surface of each infrared detecting element 2 is arranged in the small window 12A of the cold aperture 100, and the partition wall 12B of the slit plate 12 is located between the infrared detecting elements 2 adjacent to each other.

In FIG. 5, 5 is a cold door aperture 10.
A bottomed cylindrical inner cylinder made of metal (for example, Kovar) (trade name), glass, etc. on which the substrate 1 with 0 is mounted, 7 is a desired space in the inner cylinder 5 whose inner diameter is sufficiently larger than the outer diameter of the inner cylinder 5. A bottomed cylindrical outer cylinder made of metal (for example, Kovar brand name) that is fitted through the through hole 8 is a window made of germanium or the like fitted in a hole at the center of the ceiling plate portion of the outer cylinder 7.

Further, a wiring pattern 6 is provided from the ceiling plate portion of the inner cylinder 5 to the surface of the peripheral wall. There is.

The wiring pattern 6 is cut at a center line portion of the ceiling plate portion, that is, a portion corresponding to the center line of the substrate 1. The substrate 1 is placed on the ceiling plate portion of the inner cylinder 5 with the infrared detecting element 2 on the upper side so as to bridge the respective wiring patterns 6 facing each other, and is bonded by using an adhesive to bond the substrate 1 to the inner cylinder 5. It is installed in.

Further, wires such as gold wires are wire-bonded to connect the respective output conductor patterns 3 and the wiring patterns 6 of the infrared detecting element 2. In addition, a circuit board (not shown) made of a hollow disk-shaped ceramic whose inner diameter is larger than the outer diameter of the inner cylinder 5 and whose outer diameter is larger than the outer diameter of the outer cylinder 7.
Is provided so as to be fitted to the lower portion of the inner cylinder 5, the wiring pattern 6 on the peripheral wall of the inner cylinder 5 and the pattern on the surface of the circuit board are connected, and the output of the infrared detection element 2 is set outside the outer cylinder 7. It is derived.

On the other hand, in the infrared detector, in order to eliminate the influence of the energy kT (k is the Boltzmann constant, T is the absolute temperature) at room temperature (300 K), the liquid is provided on the back side of the ceiling plate inside the inner cylinder 5. The infrared detecting element 2 is cooled to an extremely low temperature (around 80K) and used by utilizing the so-called Joule-Thomson effect of ejecting a high-pressure gas such as nitrogen or argon gas.

The space between the inner cylinder 5 and the outer cylinder 7 is evacuated to prevent heat from being transferred from the outer cylinder 7 side to the substrate 1. Since the infrared rays are configured as described above, the infrared rays pass through the window 8 and the cold aperture 100, and the infrared ray detecting element 2
Is incident on the light receiving portion of the infrared ray detector, and the infrared ray detecting element 2 converts the infrared ray energy into an electric signal. Then, through the bonding wire, the wiring pattern 6, and the pattern on the surface of the circuit board, it is led out from the bonding pad outside the circuit board.

At this time, since the cold aperture 100 composed of the frame block 11 and the slit plate 12 having a desired thickness is fixed to the surface of the substrate 1 on which the infrared detecting elements 2 are arranged, the infrared detecting elements 2 receive light. The distance between the surface and the rectangular window 11A of the frame block 11 is predetermined by the slit plate 12 to determine the viewing angle of the infrared detecting element 2 and prevent stray light to improve the spatial resolution of the infrared detector. There is.

[0018]

As described above, the non-doped silicon crystal or the dopant of the group 3 element or the group 4 element (for example, boron) is (10 ¹⁵ to 10 ¹⁶ ) / cm 2.
Cold aperture made of ^3- doped silicon crystals (frame block 11 and slit plate 12) has a transmittance of 40%.
There was a problem that it was not enough to block stray light because it had a large reflectance of 50% to 50% and a reflectance of 50% to 55%.

On the other hand, in the infrared detector, if the reflectance of the upper surface of the frame-shaped block and the reflectance of the surface of the ceiling plate portion of the inner cylinder are not substantially equal, the narcissus (shadow of the infrared detecting element operating at low temperature is photographed). There is a problem in that the detection capability of the infrared detector decreases due to the occurrence of a phenomenon that is displayed on the image surface).

The present invention was created in view of the above points, and an object thereof is to provide an infrared detector having a transmittance and a reflectance suitable for reducing stray light. Another object is to provide an infrared detector having a relatively high reflectance and reduced narcissus.

[0021]

In order to achieve the above object, the present invention, as illustrated in FIG. 1, arranges small windows 12A facing an infrared detecting element 2 provided on the surface of a substrate 1. It is laminated on the upper surface of the formed slit plate 12 having a silicon crystal slit plate 12 adhered to the surface of the substrate 1 and a rectangular window 11A at the central portion, which has a rectangular window 11A having substantially the same shape as the outer frame of the small window row of the slit plate 12. An infrared detector having a cold aperture made up of a frame block 11 made of silicon crystal, which is a frame block 11 and a slit plate 12 of the cold aperture.
In addition, the dopant of Group 3 element or Group 4 element is diffused to the solid solution limit.

Alternatively, as illustrated in FIG. 2, it is assumed that the anodic oxide film 20 is formed on the entire surfaces of the frame block 11 and the slit plate 12 of the cold aperture. Alternatively,
As illustrated in FIG. 3, a metal film 30 is formed on the upper surface of the frame block 11 of the cold aperture.

[0023]

In the infrared detector of the present invention, the dopant of the group 3 element or the group 4 element is contained in the cold aperture until the solid solution limit,
That is, (10 ¹⁹ to 10 ²⁰ ) / cm ^{3 is} doped.

Therefore, infrared rays are absorbed by this large amount of dopant, the transmittance of the cold aperture becomes approximately 10%, and the reflectance of the cold aperture becomes approximately 30%. Therefore, stray light is blocked.

On the other hand, by providing an anodic oxide film on the entire surface of the frame block and slit plate of the cold aperture, the reflectance of the cold aperture can be made 10% to 20%, so that stray light can be almost completely eliminated. Can be stopped.

Further, by providing the metal film 30 on the upper surface of the frame-shaped block doped with the dopant to the solid solution limit, the reflectance of the upper surface of the frame-shaped block, that is, the upper surface of the cold door aperture is adjusted to the ceiling plate of the inner cylinder. Part surface reflectance (30
% Or more).

Therefore, the occurrence of narcissus is prevented.

[0028]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a sectional view of another embodiment of the present invention, and FIG. 3 is a sectional view of yet another embodiment of the present invention. As shown in FIG. 1, the infrared detecting elements 2 are arrayed at equal pitches on the surface of a substrate 1 made of sapphire or the like.

Each infrared detecting element 2 is a strip of HgCdTe or the like (length about 100 μm, width tens of μm), and output conductor patterns (not shown) are derived from opposite side edges. There is.

A cold aperture 10 is adhered to the surface of the substrate 1 in order to set the viewing angle of each infrared detecting element 2 to a predetermined value and to prevent stray light. The cold aperture 10 is formed by stacking a frame block 11 on a slit plate 12.

More specifically, the slit plate 12 is made of a silicon crystal plate having the same shape as the substrate 1 in plan view and a thin plate thickness as desired, and an infrared detecting element arranged in parallel with the surface of the substrate 1 at the central portion. Infrared detecting element 2 facing each of 2
A small rectangular window 12A that is similar to and slightly larger than
It is formed by anisotropic etching.

The frame-shaped block 11 is a silicon crystal plate having the same shape in plan view as the slit plate 12 and having a desired plate thickness, and has an outer frame shape formed by a row of small windows of the slit plate 12 in the central portion. The rectangular windows 11A having substantially the same shape are formed by anisotropic etching.

Then, a dopant of a Group 3 element or a Group 4 element (for example, boron) is vapor-deposited on the entire surface of the frame-shaped block 11 and the slit plate 12, and it is held at about 1200 ° C. for 20 to 30 hours for thermal diffusion. Solubility limit of dopant, ie (10 ¹⁹ -10 ²⁰ )
/ Cm ^{3 is} doped.

The diffusion depth of the dopant is 30 μm to 50 μm.
μm. Further, the vapor deposition layer remaining on the surface after diffusion is removed by polishing or the like. After doping the frame-shaped block 11 and the slit plate 12 with a dopant of Group 3 element or Group 4 element,
The bonding surface of the frame-shaped block 11 (lower surface in the drawing) and the bonding surface of the slit plate 12 (upper surface in the drawing) are bonded with an adhesive 9 to form a cold door aperture 10.

An infrared detector is constructed by mounting the cold aperture 10 as described above on the surface of a substrate on which infrared detecting elements are arranged, and the infrared detector is made of metal, as shown in FIG. The ceiling plate portion of the bottomed cylindrical inner cylinder 5 made of glass or the like is mounted.

A bottomed cylindrical outer cylinder 7 having an inner diameter sufficiently larger than the outer diameter of the inner cylinder 5 is fitted onto the inner cylinder 5 through a desired space. In addition, a wiring pattern 6 made of a plurality of parallel (equal to the number of infrared detection elements) gold films or the like having a reverse U-shape in side view is provided from the ceiling plate portion of the inner cylinder 5 to the surface of the peripheral wall. The starting end portion of 6 and each output conductor pattern of the infrared detection element 2 are connected by wire bonding a wire such as a gold wire.

The wiring pattern 6 is led out of the outer cylinder 7 as described in the prior art. On the other hand, in order to eliminate the influence of the energy kT (k is the Boltzmann constant, T is the absolute temperature) at room temperature (300K), the infrared detector is equipped with liquid nitrogen or argon on the back side of the ceiling plate inside the inner cylinder 5. Infrared detecting element 2 utilizing the so-called Joule-Thomson effect of ejecting high-pressure gas such as gas
Is cooled to an extremely low temperature (around 80K) before use.

Therefore, the infrared rays enter the light receiving portion of the infrared detecting element 2 through the window of the outer cylinder 7 and the cold door aperture 10, and the infrared detecting element 2 converts the infrared energy into an electric signal. And the above-mentioned bonding wire,
After passing through the wiring pattern 6 and the pattern on the surface of the circuit board, it is led out from the bonding pad outside the circuit board.

In the infrared detector provided with the cold aperture 10 as described above, since the dopant of the Group 3 element or the Group 4 element is doped to the solid solution limit, infrared rays are absorbed by the dopant and transmitted through the cold aperture. The reflectance is about 10% and the reflectance is about 30%.

Therefore, the stray light incident on the infrared detecting element is reduced. Further, since the cold aperture 10 is provided with the desired deep rectangular window 11A having a desired shape, the viewing angle of the infrared detecting element is set to a predetermined value.

The cold aperture 10 shown in FIG.
The entire surface of the frame-shaped block 11 and the slit plate 12 doped with a Group 3 element or Group 4 element dopant to the solid solution limit,
By providing the anodic oxide film 20, the reflectance of the cold aperture is reduced to 10% to 20% (transmittance is about 10%).

Since the reflectance of the cold aperture is small as described above, stray light incident on the infrared detecting element 2 can be almost completely prevented. Incidentally, the anodic oxide film 20 is, for example, a frame-shaped block 11 and a slit plate in an electrolytic solution such as potassium hydroxide.
Oxide film (SiO ₂ ) on the surface by immersing 12 and anodizing
Are easily formed.

The cold aperture 10 shown in FIG.
A metal film 30 is formed on the upper surface of the frame-shaped block 11 which is doped with a Group 3 element or 4th group element dopant to the solid solution limit, and the reflectance of the upper surface of the frame-shaped block 11 is adjusted to the ceiling plate of the inner cylinder. (The inner cylinder 5 shown in FIG. 5) is almost equal in reflectance to the surface.

When the material of the inner cylinder 5 is metal (for example, Kovar product name), the metal film 30 is used as an aluminum film to improve the reflectance.
It is about 40%. As described above, by making the reflectance of the upper surface of the frame-shaped block 11 substantially equal to the reflectance of the surface of the ceiling plate portion of the inner cylinder, the narcissus of the image of the infrared distribution detected by the infrared detector is reduced.

The formation of the metal film 30 is obtained as follows. First, resist is applied to the entire surface of the frame-shaped block 11 and the frame-shaped block 11 is formed by photolithography.
Remove the resist on the upper surface of the.

Next, a desired metal is vapor-deposited on the surface of the frame block 11. After that, by removing the resist, the metal film can be formed only on the upper surface of the frame-shaped block 11.

[0048]

As described above, according to the present invention, a dopant of a Group 3 element or a Group 4 element is diffused into the cold aperture to the solid solution limit, so that the transmittance and the reflectance of the cold aperture can be desirably reduced. This has the effect of reducing stray light incident on the infrared detecting element and improving the performance of the infrared detector.

Further, by forming the anodic oxide film, the reflectance of the cold aperture becomes smaller, and the stray light hardly enters the infrared detecting element, so that the performance of the infrared detector is improved.

On the other hand, when the dopant of Group 3 element or Group 4 element is diffused into the cold aperture to the solid solution limit and a metal film is formed on the upper surface of the frame block, the reflectance of the upper surface of the frame block is increased. Can be made substantially equal to the reflectance of the surface of the ceiling plate portion of the inner cylinder, and the narcissus of the image of the infrared distribution detected by the infrared detector is reduced, and the image becomes clear.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of another embodiment of the present invention.

FIG. 3 is a sectional view of still another embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional example in a separated form.

FIG. 5: Cross-sectional view of infrared detector

[Explanation of symbols]

1 Substrate 2 Infrared Detector 3 Output Conductor Pattern 4, 9 Adhesive 5 Inner Cylinder 6 Wiring Pattern 7 Outer Cylinder 8 Window 10,100 Cold Door Aperture 11 Frame Block 11A Square Window 12 Slit Board 12A Small Window 12B Partition 15 Dopant 20 Anodized Film 30 metal film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Hirota 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Hiroyuki Tsuchida 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (3)

[Claims] 1. An infrared detection element provided on the surface of a substrate (1)
The substrate having small windows (12A) arranged in an array facing the substrate (2).
Silicon crystal slit plate that adheres to the surface of (1) (12)
And a rectangular window (11A) having a rectangular window (11A) approximately equal to the shape of the outer frame of the small window row of the slit plate (12) at the center, and a silicon crystal frame-shaped block (11) laminated on the upper surface of the slit plate (12). ), And an infrared detector having a cold aperture, wherein the frame block (11) and the slit plate (12) of the cold aperture have a solid solution limit of a Group 3 element or a Group 4 element dopant. Infrared detector characterized by being diffused up to. 2. An infrared detector comprising an anodic oxide film (20) formed on the entire surfaces of the frame block (11) and the slit plate (12) of the cold aperture according to claim 1. 3. An infrared detector characterized in that a metal film (30) is formed on the upper surface of the frame block (11) of the cold door aperture according to claim 1.