JP3464348B2 - Method for producing pyroelectric infrared thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pyroelectric thin film,
Method of manufacturing the pyroelectric infrared thin film for infrared detection infrared detector consisting of an upper electrode and a lower electrode are provided respectively on its upper and lower surfaces are formed on an upper portion of the concave portion of the substrate having a recess in a surface portion Regarding

[0002]

2. Description of the Related Art One of the pyroelectric infrared thin film elements is disclosed in Japanese Patent Application Laid-Open No. 7-55574. In this pyroelectric infrared thin film element, as shown in FIGS. 10A and 10B, a MgO (100) single crystal substrate is used as a substrate 51, and a Pt (platinum) thin film is provided as a lower electrode 52 on the upper layer thereof. The pyroelectric thin film 53 is provided on the upper layer of the pyroelectric thin film 53, and the NiCr (Nichrome) thin film having a small infrared light reflectance is provided as the upper electrode 54 on at least a part of the upper layer of the pyroelectric thin film 53. Hole 5 for etching from the side
The microcavity 56 is provided in the surface layer portion of the substrate 51 by injecting an appropriate etching liquid from 5.

[0003]

According to the pyroelectric infrared thin film element having the above-described structure, the infrared detecting portion 57 is provided where the etching hole 55 overlaps the lower electrode 52, the pyroelectric thin film 53 and the upper electrode 54. Side, that is, substrate 51
Since it is provided on the surface side, it has an advantage that it is easy to perform etching, but has the following drawbacks.

That is, in the above-described conventional pyroelectric infrared thin film element, the holes 55 are only provided at positions symmetrical to each other on the outer peripheral side of the infrared detecting section 57 with the infrared detecting section 57 as the center. When viewed in the direction of the symbol X in FIG. 10A, the cross-sectional shape is as shown in FIG.
As shown in FIG. 1, the minute cavity 56 has a so-called W shape with many irregularities, and the distance (depth) t from the infrared detecting section 57 in the minute cavity 56 directly below the infrared detecting section 57 is extremely small. As described above, when the distance t between the infrared detecting portion 57 in the minute cavity 56 is small, the angle of the minute cavity 5 is small.
Even if 7 is provided, the heat that is incident on the infrared detecting section 57 for infrared rays and is generated in the infrared detecting section 57 is taken by the substrate 51 by radiative cooling, and as a result, the sensitivity of the pyroelectric infrared thin film element is lowered. There are drawbacks such as.

The present invention has been made in consideration of the above-mentioned matters, and is provided directly below the portion of the substrate where the infrared detecting portion is provided.
Make sure to form a recess with a predetermined depth, which
As possible the heat of the infrared detector so as not to diffuse, with high sensitivity, it is an object to provide a method of <br/> manufacturing the pyroelectric infrared thin film having a high-speed response.

[0006]

Pyroelectric infrared rays according to the present invention
A method of manufacturing a thin film element is a pyroelectric film in which an infrared detection part including a pyroelectric thin film and an upper electrode and a lower electrode respectively provided on an upper surface and a lower surface of the thin film element is formed above the concave portion of a substrate having a concave portion in a surface layer portion. the method of manufacturing a mold infrared thin film element, a hole for etching the substrate within the surrounding and infrared detector of the infrared detecting part of the surface portion of the substrate, and smaller than twice the thickness of the spacing of the substrate Setting
Only, by injecting an etchant having a predetermined concentration of these holes
Etching the surface layer of the substrate, directly under the infrared detection part
It is characterized by forming the recess.

Method for manufacturing the pyroelectric infrared thin film element of the present invention
According to the method, not only the area around the infrared
Etching holes are also provided in the outlet and these holes are used.
The infrared detector is retained because the substrate is etched.
Make sure that the surface layer of the substrate has a recess with a predetermined depth.
Formed, the heat in the infrared detector is radiatively cooled
It is prevented from being robbed by the substrate. Therefore, high sensitivity
And to obtain a pyroelectric infrared thin film element with excellent response characteristics.
You can

The upper surface of the MgO single crystal substrate is made of Pt
Form the lower electrode and place a pyroelectric thin film on the upper surface of this lower electrode.
An upper electrode made of Pt is formed on the upper surface of this pyroelectric thin film.
May be formed.

[0009]

[0010]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the drawings. 1 to 3 show an example of a pyroelectric infrared thin film element S of the present invention, FIG. 1 is a diagram showing a planar shape of the pyroelectric infrared thin film element S, and FIG. FIG. 4 is a cross-sectional view showing a cross-sectional shape taken along line I along with an enlarged view, and FIG. 3 is an exploded perspective view of a pyroelectric infrared thin film element S.

In these figures, 1 is a single crystal substrate made of MgO (magnesium oxide), and 2 is a minute recess formed in the surface layer of the substrate 1 by etching. Reference numeral 3 denotes a pyroelectric thin film, which is made of, for example, a PZT-based ferroelectric thin film or a PLZT ferroelectric thin film. This pyroelectric thin film 3
An upper electrode 4 and a lower electrode 5 made of, for example, Pt (platinum) are provided on the upper and lower surfaces of the so as to correspond to each other. 4a and 4b are a plurality of holes for etching formed in the upper electrode 4, and the hole 4a is substantially at the center position of the upper electrode 4,
A plurality of holes 4b are arranged around the hole 4a.
Reference numeral 5a is a protrusion formed on the lower electrode 5. The portion where the electrodes 4 and 5 and the pyroelectric thin film 3 overlap each other when viewed in the direction of the arrow Z is referred to as an infrared detection unit 6.

Reference numeral 7 denotes an infrared absorbing film provided so as to cover the upper surface of the upper electrode 4 serving as a light receiving electrode of the infrared detecting section 6. The photosensitive organic thin film capable of photolithography is provided with an infrared absorbing material such as carbon black. It is appropriately mixed. 8 is formed around the infrared detector 6,
An insulator thin film that holds the infrared detector 6 to the substrate 1, and is made of an organic insulator thin film such as a polyimide resin thin film or an inorganic insulator thin film such as a SiO ₂ thin film. 8a
Is a hole for etching formed in the insulator thin film 8, and the hole 8
A plurality of a are arranged so as to surround the infrared detecting section 6. Reference numerals 9 and 10 denote an upper extraction electrode and a lower extraction electrode, which are connected to the upper electrode 4 and the lower electrode 5, respectively.

A method of forming the pyroelectric infrared thin film element S will be described with reference to FIGS. 6 to 8, a diagram schematically showing a cross-sectional shape and a diagram schematically showing a plane shape are shown in parallel. In addition, a symbol ('dash) is attached to a code representing a portion corresponding to each member before the final shape.

(1) M having an appropriate thickness (for example, 500 μm)
A gO (100) single crystal substrate 1 is prepared (see FIG. 5A).

(2) Pt of 0.2 μm is formed as the lower electrode 5 ′ on the upper surface of the substrate 1 by, for example, sputtering.
A film having a thickness of m is formed (step S1 in FIG. 4 and FIG.
(See (B)).

(3) A PZT-based ferroelectric thin film (or PL) is formed on the upper surface of the lower electrode 5'as a pyroelectric thin film 3'by, for example, MOCVD (metalorganic chemical vapor deposition).
A ZT ferroelectric thin film) is formed to a thickness of about 2 μm (FIG. 4).
Step S2 of FIG. 5 and FIG. 5C).

(4) On the upper surface of the pyroelectric thin film 3 ', 0.2 Pt is formed as the upper electrode 4'by sputtering.
A film having a thickness of μm is formed (step S3 in FIG. 4, FIG.
(D) and FIGS. 6A and 6B).

(5) A resist is applied to the upper electrode 4 ', and the resist is patterned by photolithography.
After that, the upper electrode 4 is patterned by etching, and then the resist is removed to form a shape having a plurality of holes 4a and 4b (step S4 in FIG. 4 and FIG. 6).
(See (C) and (D)).

(6) Next, a resist is applied to the pyroelectric thin film 3 ', and the resist is patterned by photolithography. After that, the pyroelectric thin film 3 is patterned by etching, the resist is removed, and the holes 4 of the upper electrode 4 are removed.
It is formed into a shape having a plurality of holes at positions corresponding to a and 4b (see step S5 of FIG. 5 and FIGS. 6E and 6F). In this embodiment, the pyroelectric thin film 3 has a diameter slightly larger than that of the upper electrode 4.

(7) Next, a resist is applied to the lower electrode 5 ', and the resist is patterned by photolithography. After that, the lower electrode 5'is patterned by etching, and then the resist is removed to form the lower electrode 5 and the lower electrode protruding portion 5a continuous with the lower electrode 5 (see step S6 in FIG. 5 and FIGS. 7A and 7B). ). In this embodiment, the lower electrode 5 is formed to have the same diameter as the pyroelectric thin film 3, but the diameter may be slightly larger than this.

(8) An insulator thin film 8 having a thermal conductivity smaller than that of a metal is formed around the infrared detecting section 6 and the upper surface of the substrate 1 (step S7 in FIG. 5 and FIG. 7).
(See (C) and (D)). The insulator thin film 8 may be either an organic insulator thin film or an inorganic insulator thin film, a polyimide resin thin film is suitable as the organic insulator thin film, and a SiO ₂ thin film is suitable as the inorganic insulator thin film.

(9) Au by, for example, sputtering
The upper electrode lead-out portion 9 and the lower electrode lead-out portion 10 are formed (step S8 in FIG. 5 and FIG. 7 (E),
(See (F)).

(10) Then, a photosensitive organic thin film such as a negative resist material mixed with an infrared absorbing material such as carbon black of about 3 wt% is appropriately provided on the upper surface of the upper electrode 4 of the infrared detecting section 6. After being applied to a thickness, patterning is performed to cover the upper surface of the upper electrode 4 with the infrared absorbing film 7 (see step S9 in FIG. 5 and FIGS. 8A and 8B).

A phosphoric acid solution having a predetermined concentration is injected as an etching solution through the holes 4a and 4b in the infrared detecting section 6 and the holes 8a in the insulating thin film 8 to remove the substrate 1 immediately below the infrared detecting section 6 by etching. Recess (small cavity)
2 (step S10 of FIG. 5 and FIG. 8).
(See (C) and (D)). In this case, the recess 2 is formed so as to be larger than the infrared detector 6, but since the insulator thin film 8 is formed over the periphery of the infrared detector 6 and the upper surface of the substrate 1, the infrared detector 6 is The insulator thin film 8 holds the upper surface of the recess 2 in a state of being levitated.
That is, the pyroelectric infrared thin film element S as shown in FIGS. 1 to 3 and FIGS. 8C and 8D is obtained.

By the way, in etching the substrate 1 of the pyroelectric infrared thin film element S, phosphoric acid (H ₃
PO ₄ ) is used, but the etching of the MgO substrate 1 by this phosphoric acid proceeds isotropically. That is, it is considered that the etching progresses from the etching holes in the depth direction (vertical direction) and in the lateral direction (horizontal direction) almost equally. However, since phosphoric acid has a high viscosity, it is considered that the lateral spread does not proceed further than the depth direction, and the depth direction ≧ the lateral direction, but here, the depth direction =
Assuming the lateral direction, consideration will be added below with reference to FIG. 9.

FIG. 9 schematically shows the substrate 1 in the pyroelectric infrared thin film element S, in which the length between the two etching holes 8a, 8a is d, and the depth direction (horizontal direction) The length (direction) is A, and the distance (gap) between the infrared detector 6 and the closest portion of the concave portion 2 is t, (2A-d) / 2 = t (1) ) Is established, and from this, the relation of t = A−d / 2 (2) or A = (2t−d) / 2 (3) is derived.

When the above etching is performed, if the distance d between the etching holes 8a is larger than twice the thickness L of the substrate 1, that is, d ≧ 2L, in the process of etching the substrate 1, Even if the recess 2 is etched to exceed the thickness L, the adjacent holes 8a are not connected, and thus the infrared detecting section 6 is damaged by mechanical stress. Therefore, the relationship of d <2L (4) is established.

In order to secure the strength of the infrared detecting section 6, the etching depth A is less than half the thickness L of the substrate 1,
That is, it is necessary to establish the relationship of A ≦ L / 2 (5). Therefore, from the equations (3) and (5), (2t-d) / 2≤L / 2 is obtained, and from this, the relationship t≤ (Ld) / 2 (6) is derived.

In order to set the thickness L of the substrate 1 to 0.5 mm and the size of the gap t to 0.1 mm or more, L = 0.5 and t = 0.1 in the equation (6). By
d ≦ 0.3. That is, the distance between the etching holes 8a needs to be 0.3 mm or less. for that reason,
The length of the shorter side of the surface of the infrared detection unit 6 is 0.3 mm
If it is longer, as shown in FIGS. 1, 2, 7C to 8F, and 8A to 8D, not only around the infrared detection unit 6 but also inside the infrared detection unit 6. Also, it is necessary to provide the hole 4a for etching.

The diameter of the infrared detecting portion 6 is equal to that of the substrate 1.
As shown in FIGS. 1 and 7,
As shown in (D), (F) and FIGS. 8 (B), (D), an appropriate hole 4 is centered on the hole 4a in the infrared detecting section 6.
It is also necessary to provide b.

As described above, in the above-described embodiment, not only the hole 8a around the infrared detecting portion 6 is used as a hole for etching the surface layer portion of the substrate 1 to form the recess 2.
Since the holes 4a and 4b are also provided in the infrared detecting section 6,
The recess 2 having a predetermined depth can be reliably formed. Therefore, the heat in the infrared detecting section 6 is prevented from being taken by the substrate 1 by the radiation cooling, and the pyroelectric infrared thin film element S having desired high sensitivity and excellent response characteristics can be obtained.

Further, the etching holes 8a, 4a,
It goes without saying that the upper surface of the concave portion 2 can be made substantially flat by increasing the number of 4b and narrowing the interval.

[0033]

The present invention is implemented in the above-described modes and has the following effects.

Method for manufacturing pyroelectric infrared thin film according to the present invention
The method is to form a recess by etching the surface layer of the substrate.
In addition to the holes around the infrared detector,
Since a hole is also provided in the part, a concave part with a predetermined depth can be securely
Can be formed. Therefore, the infrared detector
The heat generated by radiant cooling is prevented from being taken by the substrate.
Pyroelectric infrared with excellent high sensitivity and desired response characteristics
A thin film element can be obtained.

Further, according to the above manufacturing method, the substrate is protected.
Immediately below the infrared detector to be held, a recess having a predetermined depth
The heat generated in the infrared detector is radiatively cooled.
It is possible to prevent the board from being robbed of the product by the
To obtain a pyroelectric infrared thin film element with excellent degree and response characteristics
be able to.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a pyroelectric infrared thin film element of the present invention.

FIG. 2 is a cross-sectional view taken along the line I-I in FIG. 1 and a partially enlarged view thereof.

FIG. 3 is an exploded perspective view of the pyroelectric infrared thin film element.

FIG. 4 is a flowchart showing a method for manufacturing the pyroelectric infrared thin film element.

FIG. 5 shows a manufacturing process of the pyroelectric infrared thin film element together with FIGS. 6 to 8, and shows a beginning portion thereof.

FIG. 6 is a diagram showing the manufacturing process following FIG. 5;

FIG. 7 is a diagram showing a manufacturing process that follows FIG. 6;

FIG. 8 is a diagram showing a manufacturing process that follows FIG. 7.

FIG. 9 is a schematic view for explaining a concave portion formed by etching in the surface layer portion of the substrate of the pyroelectric infrared thin film element.

10A and 10B are views for explaining a conventional technique, in which FIG. 10A is a plan view and FIG. 10B is a sectional view.

FIG. 11 is a cross-sectional view seen from the arrow X direction in FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... Recess, 3 ... Pyroelectric thin film, 4 ... Upper electrode,
5 ... Lower electrodes, 4a, 4b, 8a ... Holes for etching,
S ... Pyroelectric infrared thin film element, d ... Hole spacing, L ... Substrate thickness, t ... Distance between infrared detector and concave surface.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-55575 (JP, A) JP-A-58-182523 (JP, A) JP-A-7-55574 (JP, A) JP-A-7- 43215 (JP, A) JP-A-8-136343 (JP, A) JP-A-8-145799 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01J 5/00-5 / 62 G01J 1/00-1/60

Claims (2)

(57) [Claims] 1. A pyroelectric thin film and its top and bottom surfaces
Red consisting of upper electrode and lower electrode provided respectively
The outside line detection part is on the surface of the concave part of the substrate having the concave part
In the manufacturing method of the pyroelectric infrared thin film element formed on the bottom
Around the infrared detection portion of the surface layer of the substrate and
Hole for etching the substrate inside the infrared detector
With a gap smaller than twice the thickness of the board.
The etching solution of a specified concentration is injected through these holes to
The surface layer is etched, and the layer is formed directly below the infrared detecting section.
Pyroelectric infrared thin film element characterized by forming recesses
Manufacturing method. 2. The upper surface of the MgO single crystal substrate is formed of Pt.
Lower electrode, and a pyroelectric thin film on the upper surface of this lower electrode.
On the upper surface of this pyroelectric thin film, and
The pyroelectric infrared thin film element according to claim 1, which forms a pole.
Production method.