JP2002250655A - Infrared detection element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-sensitivity infrared detection element, using a bolometer layer, having a high resistance-temperature coefficient at room temperature and a low resistance value. SOLUTION: In this bolometer-type infrared detection element, having a light-receiving part supported by bridge parts on a silicon substrate, the light- receiving part includes a wiring layer formed so as to extend through the bridge parts to the light-receiving part, electrode parts electrically connected to the wiring layer, and the bolometer layer formed over the electrode parts. The bolometer layer comprises a layer, composed mainly of a prescribed NTC(negative temperature coefficient) thermistor material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting element and a method of manufacturing the same, and more particularly, to a bolometer type infrared detecting element utilizing a resistance change caused by a temperature change of a light-receiving portion that has absorbed infrared rays and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, in a bolometer type infrared detecting element, the temperature of a light receiving section changes when the light receiving section absorbs infrared rays, and the resistance value of a bolometer layer included in the light receiving section corresponding to this temperature change. Changes. Further, by detecting a change in the resistance value of the bolometer layer as a change in an electric signal, the intensity of the infrared light incident on the light receiving unit is detected. Therefore, as the temperature dependence of the electrical resistance of the bolometer layer increases, that is, as the absolute value of the temperature coefficient of resistance (TCR) increases, the infrared detection sensitivity increases.

FIG. 4 is a cross-sectional view of an infrared detecting element indicated generally by reference numeral 200 described in Japanese Patent No. 2655101. In the infrared detecting element 200, a silicon oxide layer 202 is provided on a silicon substrate 201.
On the silicon oxide layer 202, electrode layers 203 are provided on both sides. Further, the bolometer layer 204 electrically connected to the two electrode layers 203 forms a silicon oxide layer 202.
And on the electrode layer 203. Bolometer layer 2
04, are formed from VO _2. The electrode layer 203
The bolometer layer 204 is connected to a detection circuit (not shown).
The change in the resistance value is detected. On the bolometer layer 204, a protective film 205 made of, for example, silicon nitride is formed.

[0004] A void 206 is provided in the silicon oxide layer 202 below the bolometer layer 204.
A metal reflection layer 207 is provided on the silicon substrate 201 in the gap 206. The region above the gap 206 becomes the light receiving unit 210, and the temperature of the light receiving unit 210 changes due to the infrared light incident on the light receiving unit 210. In response to such a temperature change, the bolometer layer 2 provided in the light receiving unit 210
The resistance value of the light-receiving portion 210 changes and is detected by a detection circuit (not shown), thereby detecting the amount of infrared light incident on the light-receiving portion 210. The infrared light transmitted through the light receiving unit 210 is reflected by the metal reflection film 207 and is incident on the light receiving unit 210 again. This improves the infrared absorption efficiency.

[0005]

However, in order to use it as a high-sensitivity infrared detecting element, the absolute value (| TCR |) of the TCR of the bolometer layer must be at room temperature (298 ° C.).
K) at 2.5 / deg. Above, preferably 3.0 / de
g. It is necessary to be above. On the other hand, | TCR | at room temperature of VO ₂ used as a material of the bolometer layer 204 of the infrared detecting element 200 and V ₂ O ₃ , Si, Ge, and the like conventionally used as a bolometer material is 2.5 / deg. These materials did not make it possible to produce a highly sensitive infrared detecting element.

On the other hand, as a material whose resistance changes in response to a change in temperature, there is another thermistor. Among the thermistors, an NTC thermistor having a negative temperature coefficient (Ne
gative Temperature Coefficient Thermistor is widely used for temperature sensors and the like (for example, Japanese Patent Application Laid-Open No. H10-124).
No. 05), | TCR | at room temperature is 4.0 / de.
g. These are also promising bolometer materials.

However, such an NTC thermistor is generally used at a temperature of 300 ° C. or more at which the resistance becomes low, and the resistivity (ρ) at room temperature is very high at 1 kΩcm or more. For this reason, it has been difficult to apply to a bolometer layer of an infrared detecting element used at room temperature.

Accordingly, an object of the present invention is to provide an infrared detecting element in which an NTC thermistor having a high resistance temperature coefficient at room temperature and a low resistance value is applied to a bolometer layer, and a method of manufacturing the same.

[0009]

SUMMARY OF THE INVENTION The present invention is a bolometer-type infrared detecting element having a light receiving portion supported on a silicon substrate by a bridge portion, wherein the light receiving portion passes through the bridge portion and receives the light. A wiring layer formed so as to extend to the portion, an electrode portion electrically connected to the wiring layer, and a bolometer layer formed on the electrode portion, wherein the bolometer layer mainly includes an NTC thermistor material. An infrared detecting element comprising a layer as a component. Thus, N
By using a layer mainly composed of the TC thermistor material for the bolometer layer, | TCR | of the bolometer layer can be increased, and the sensitivity of the infrared detecting element can be improved.

The above NTC thermistor material is MnDxO
y (D is one or more elements selected from the group consisting of Ni, Fe, Cr and Co, 0.2 <x <0.9, y = (x
+1.5) × δ (0.7 <δ <1.3)). By using such a material, | TCR | of the bolometer layer can be increased and the resistance at room temperature can be reduced, so that an infrared detecting element with high detection sensitivity can be manufactured.

It is preferable that the bolometer layer is at least partially in an amorphous state. By making at least a part of the bolometer layer have an amorphous structure, the resistivity of the bolometer layer is reduced, and the resistance characteristics of the bolometer layer are made uniform even when a comb-shaped electrode having a distance between the electrodes of several μm or less is used. be able to. Further, the contact resistance between the bolometer layer and the electrode can be reduced.

[0012] The bolometer layer may further include at least one element selected from the group consisting of Li and Cu as an additional element. By adding such an additive element, the electric resistance and TCR of the bolometer film can be controlled to form an infrared detecting element having high detection sensitivity.

Further, the present invention is a method for manufacturing a bolometer-type infrared detecting element for forming a light receiving portion supported by a bridge portion on a silicon substrate, wherein the step of forming the light receiving portion includes a wiring layer. Forming a silicon oxide layer connected to the bridge portion; forming an electrode layer on the silicon oxide layer so as to be electrically connected to the wiring layer; and forming the silicon oxide layer and the electrode on the silicon oxide layer. A bolometer layer forming step of forming a bolometer layer on the layer, wherein the bolometer layer forming step includes MnDxOy (D is Ni, Fe, Cr
And one or more elements selected from the group consisting of
0.2 <x <0.9, y = (x + 1.5) × δ (0.7
<Δ <1.3)), a bolometer layer composed of an oxide of Mn and D having a metal component ratio of Mn: D = 1: x (0.2 <x <0.9). A step of sputtering a target containing a mixture with an oxide or a target containing a composite oxide of Mn and D, and depositing the target on the silicon oxide layer and the electrode layer. Is also a manufacturing method. By using such a method,
A bolometer layer having a high | TCR | and a low electric resistance at room temperature can be formed. As a result, it is possible to manufacture an infrared detecting element having high detection sensitivity. Note that δ indicates a range of the oxygen content that varies depending on the type of the sputtering gas, the combination of the elements constituting the target, and the like. Further, as the sputtering gas, a non-oxidizing gas, a mixed gas of a non-oxidizing gas and oxygen, a mixed gas of a non-oxidizing gas and ozone gas, a mixed gas of oxygen and ozone gas, or the like can be used.

[0014]

FIG. 1 is a cross-sectional view of an infrared detecting element according to the present embodiment, which is designated by the reference numeral 100 in its entirety. In the infrared detecting element 100, on the silicon substrate 1,
A silicon oxide layer 2 is provided. Silicon oxide layer 2
A gap 7 is provided between the silicon substrate 1 for thermal insulation.
Is provided, and a light receiving section 8 is formed above the gap 7. The light receiving section 8 is supported by a bridge section 9. In the silicon oxide layer 2, a wiring layer 3 extending to a light receiving section 8 via a bridge section 9 is provided. The wiring layer 3 is made of, for example, a metal material such as Ti, Al, or Cu. In the light receiving section 8, the silicon oxide layer 2 above the wiring layer 3
Are formed to form an electrode 4 electrically connected to the wiring layer 3. The electrode 4 is formed of, for example, Pt. On the other hand, the other end of the wiring layer 3 is connected to a detection circuit (not shown).

Further, on the silicon oxide layer 2 of the light receiving section 8, a bolometer layer 5 electrically connected to the two electrodes 4 is provided.
Are formed. Such a bolometer layer 5 is, for example,
MnDxOy (D is at least one element selected from the group consisting of Ni, Fe, Cr and Co, 0.2 <x <0.
9, y = (x + 1.5) × δ (0.7 <δ <1.3))
Is formed from an oxide material whose main component is. In the present embodiment, Mn ₁ Co _{0. 3} Ni _0.3 O _2.1 was applied to the material of the bolometer layer 5.

As a material of the bolometer layer 5, for example,
1) When at least one element selected from elements having atomic numbers 39 and 62 to 71 is Q, and at least one element selected from Sc, Cr, Mn, Fe and Co is M, at least Q, A material containing perovskite-type crystal particles containing M and Ti, and a bilochlore-type crystal particle containing at least Q, M, and Ti. 2) CoAl ₂ O ₄ , NiAl ₂ O ₄ , MgCr which are p-type semiconductors
_{2 O 4, Mg (Al,} Cr, Fe) 2 O 4, and 3) n
It is also possible to use an NTC thermistor material such as MgFe ₂ O ₄ which is a type semiconductor.

The surfaces of the bolometer layer 8 and the silicon oxide layer 4 are covered with a protective film 6 made of, for example, silicon oxide or silicon nitride.

In the infrared detecting element 100, when the light receiving section 8 is irradiated with infrared rays, the temperature of the light receiving section 8 supported by the bridge section 9 rises, thereby increasing the temperature of the bolometer layer 5.
Changes the resistance value. A fixed bias voltage is applied between the two electrodes 4 via the wiring layer 3. Therefore, in response to the change in the resistance value of the bolometer layer 5, the electrode 4
The amount of current flowing therebetween changes, and by detecting this, the amount of infrared light incident on the light receiving unit 8 can be detected.

In FIG. 1, the infrared detecting element 100 including one light receiving section 8 is described. However, the infrared detecting element 100 in which the light receiving sections 8 are provided in a matrix on the silicon substrate 1 can be used. is there.

Next, a method of manufacturing the infrared detecting device 100 according to the present embodiment will be briefly described. First,
A silicon substrate 1 is prepared. Subsequently, a sacrificial layer (not shown) is formed on the silicon substrate 1 in a region that will become the void 7 in the future. The sacrificial layer is made of, for example, an amorphous silicon layer deposited by a sputtering method.

Next, a lower layer portion of the silicon oxide layer 2 is formed using, for example, a plasma CVD method so as to cover the sacrificial layer.

Next, for example, Ti is deposited on the lower layer portion of the silicon oxide layer 2 and patterned to form the electrode layer 2.

Next, an upper layer portion of the silicon oxide layer 2 is formed by using, for example, a plasma CVD method. Thus, the wiring layer 3 embedded in the silicon oxide layer 2 is formed.

Next, the silicon oxide layer 2 on the wiring layer 3 of the light receiving section 8 is opened, and two electrode sections 4 electrically connected to the wiring layer 3 are formed. The electrode unit 4 is formed using a general vapor deposition method and a patterning method.

Next, so as to cover the silicon oxide layer 2 and the like,
Mn ₁ Co _0.3 Ni _0.3 O _2. A bolometer material layer containing ₁ as a main component is deposited by a sputtering method, and the bolometer layer 5 is formed by patterning the bolometer material layer. The bolometer layer 5 is formed between the two electrodes 4 while being electrically connected to the electrodes 4. Note that preferable sputtering conditions for the bolometer material layer will be described later.

Next, a protective film 6 made of silicon oxide or silicon nitride is deposited on the entire surface. Subsequently, the light receiving unit 8,
The protection film 6 and the silicon oxide film 2 on the sacrificial layer are removed by ion milling, leaving the bridge portion 9, and the sacrificial layer is selectively removed by etching. Thereby, the infrared detecting element 100 having the bridge portion 9 and the light receiving portion 8 supported by the bridge portion 9 is formed.

FIG. 2 is a perspective view of another infrared detecting element 110 according to the present embodiment, which is generally denoted by reference numeral 110. 2, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. FIG. 2 shows a state in which the silicon oxide layer 2, the bolometer layer 5, and the protective film 9 provided thereon are removed so that the shapes of the wiring layer 3 and the electrode portion 4 can be understood. The electrodes 3 have a comb shape facing each other, and the electrode width W (the length in the x direction) and the distance L between the electrodes are W / L = 70 μm / 1 μ.
m. By using the electrode 3 having such a shape, 2
The length of the region where the three electrodes 3 are arranged facing each other is increased, and the resistance value of the infrared detecting element 110 can be further reduced.

Next, the sputtering conditions for forming the bolometer layer will be discussed. In the infrared detection device 100 used for the study, a layer mainly composed of Mn ₁ Co _0.3 Ni _0.3 O _2.1 was used as the bolometer layer 5.
The bolometer layer 5 was formed by a sputtering method without heating and cooling the silicon substrate 1.

First, as a target used in the sputtering method, a mixed powder of Mn ₂ O ₃ , NiO, and CoO was press-formed into a disk having a diameter of 3 inches and a thickness of 10 mm, and was pressed in air at 1300 ° C. for 24 hours. A sintered body obtained by firing for a time was used. On the other hand, Ar and O
₂ or a mixed gas of O ₂ and O ₃ was used. The sputtering conditions were such that the degree of vacuum in the chamber was maintained at 0.5 Pa, and neither heating nor cooling of the silicon substrate 1 was performed.

The ratio of the partial pressures of the sputtering gases is as follows: (A) Ar: O ₂ = 1: 0, (B) Ar: O ₂ = 5: 1, (C) Ar: O ₂ = 3: 2, D) Ar: O ₂ = 1: 5, (E) Ar: O ₂ = 0: 1, (F) O ₂ : O ₃ = 9: 1 A bolometer layer is formed using six kinds of sputtering gases, Infrared detecting elements were produced. Five infrared detecting elements were formed under each sputtering condition.
The manufacturing conditions other than the sputtering conditions are the same. The electrode portion was a comb-shaped electrode having an electrode width (W) / inter-electrode distance (L) = 70 μm / 1 μm as shown in FIG.

FIG. 3 is a schematic view of a measuring jig 20 for measuring the electric resistance of the infrared detecting element. Measurement jig 20
Has a fixed base 21 made of metal or the like, and a temperature sensor 22 for measuring the surface temperature of the fixed base 21 on the fixed base 21.
Is provided. The electrode pad 2 on which the electrode portion 24 to which the lead wire 23 is connected is mounted on the fixing base 21.
5 are provided.

In the infrared detecting element 100 manufactured under each of the sputtering conditions (A) to (F), the silicon substrate 1 is attached to the fixing base 21 using an instant adhesive, and Fixed. Further, the wiring layers of the infrared detecting device 100 were connected to the electrode portions 24 by bonding wires 26, respectively.

The electric resistance between the electrodes of the infrared detecting element 100 was measured by using a direct current two-terminal method. In the DC two-terminal method, first, the current flowing through the lead wire 23 was adjusted to a constant value so that the voltage applied between the wiring layers of the infrared detecting element 100 became 3.5 V at 30 ° C. Subsequently, the electric resistance between the wiring layers was measured. The fixing table 9 is
Put in a constant temperature bath where the temperature can be set arbitrarily up to ℃,
The electrical resistance was measured at a plurality of set temperatures. This allows
The electrical resistance between the wires of the infrared detecting element 100 at a plurality of set temperatures (including room temperature) was measured.

Subsequently, a TCR (temperature coefficient of resistance) was obtained from the following equation (1) based on the measurement result of the electric resistance.

TCR = ((Δρ / Δt) / t) × 100 (1) where t represents temperature (K) and ρ (Ωcm) represents resistivity.

Further, when no infrared light was incident on the infrared detecting element 100, the element noise was measured. The device noise was measured by detecting a voltage generated when the bias current was controlled so that a DC voltage of 3.5 V was applied between the wiring layers by a frequency spectrum detector. The measurement was performed by measuring the device noise at a frequency of 2 KHz for each infrared detecting device. The element noise has a property of being inversely proportional to the sensitivity of the infrared detecting element.

Table 1 shows the absolute value (| TCR) of the TCR of the infrared detecting element 100 manufactured under the above conditions (A) to (F).
|), Measurement results of device resistance (R) and device noise at room temperature (300 K). As can be seen from Table 1, |
TCR | is (D) except for a part of Ar: O ₂ = 1: 5,
All were 3.0% / K or more, which was good. The element resistances are (A) Ar: O ₂ = 1: 0 and (B) Ar: O ₂ =
For elements other than 5: 1, it is 100 kΩ or less,
It was good. The element noise is (C) Ar: O ₂
= 3: 2 and (D) Ar: O ₂ = 1: 5, the devices were good at 100 nV / √Hz or less.

According to the experimental results shown in Table 1, the element resistance of the infrared detecting element was reduced by adopting a comb-shaped electrode for the electrode part and adjusting the conditions for forming the bolometer layer (sputter gas component and gas partial pressure ratio). In a detection circuit using such an infrared detection element, an operable level of 100
kΩ or less. In addition, a high | TCR | of 3.0% / K or more can be obtained. Furthermore, 100
It is also possible to obtain a low device noise of nV / √Hz or less.

Next, Mn ₁ Co _0.3 Ni _0.3 O _2.1 produced by using the sputtering gases (A) to (F).
An experiment was conducted to examine the difference in crystallinity of the bolometer layer mainly composed of. In such an experiment, first, a thermal oxide film SiO ₂ was formed on a Si substrate, and a Mn ₁ Co _0.3 Ni _0.3 O _2.1 thin film was formed thereon under the conditions of (A) to (F). Was formed. X of the bolometer thin film formed under each condition
The line diffraction pattern was analyzed.

As a result, for the films of (C) Ar: O ₂ = 3: 2 and (D) Ar: O ₂ = 1: 5, the diffraction peak of the (400) plane of the spinel type crystal structure and the amorphous structure A pattern that overlaps with the broad pattern caused by was observed. In particular, in the film of (D) Ar: O ₂ = 1: 5, the diffraction peak of the (400) plane of the spinel-type crystal structure appeared strongly. As for the other films, only a broad pattern due to the amorphous structure was observed.

With respect to these thin films whose X-ray diffraction patterns were examined, the fine structure of the film surface was further examined with an atomic force microscope (A
FM), (C) Ar: O ₂ = 3:
2 and (D) for films other than Ar: O ₂ = 1: 5,
It was found that the structure had high surface smoothness on which fine particles having a particle size of 30 nm or less were deposited. Further, (C) A
The film of r: O ₂ = 3: 2 has a particle size of 50 nm to 100 nm.
And (D) Ar: O ₂ =
The 1: 5 film was found to be a structure in which particles having a particle size of 100 nm to 200 nm were deposited.

From the results of the above X-ray diffraction and structure observation,
A film having an amorphous structure (for example, the film of (A))
Due to the structure having high surface smoothness in which fine particles having a particle size of 30 nm or less are deposited, when a bolometer layer is deposited on the electrode portion, the contact resistance at the interface between the bolometer layer and the electrode is small. It is considered that the element noise is reduced.

[0043]

[Table 1]

In Table 1, Mn ₁ Co _0.3 Ni _0.3 O
_2.1 An example in which a thin film is applied to a bolometer layer is shown,
The bolometer layer is made of MnDxOy (D is Ni, Fe, Cr
And one or more elements selected from the group consisting of
0.2 <x <0.9, y = (x + 1.5) × δ (0.7
<Δ <1.3)), when the ratio of the partial pressure of the sputtering gas is controlled, | TCR | is high, and the element resistance and the element noise are low. A film in an amorphous state can be formed.

For such a bolometer layer,
By adding additives such as Li and Cu, the device resistance can be further reduced.

The infrared detectors manufactured using the conditions (A) to (F) shown in Table 1 have improved infrared detection sensitivity as compared with conventional infrared detectors.

[0047]

As is apparent from the above description, in the infrared detecting element according to the present invention, the bolometer layer is made of NTC.
When the bolometer layer is formed from a layer containing a thermistor material as a main component, | TCR | of the bolometer layer can be increased and the element resistance near room temperature can be reduced, so that an infrared detecting element with high detection sensitivity can be manufactured.

In particular, the material of the NTC thermistor is MnDx
Oy (D is one or more elements selected from the group consisting of Ni, Fe, Cr and Co, 0.2 <x <0.9, y =
By using an oxide material containing (x + 1.5) × δ (0.7 <δ <1.3)) as a main component, an infrared detecting element with high detection sensitivity can be manufactured.

Further, by making the bolometer layer at least partly in an amorphous state, the resistance characteristics become uniform, the contact resistance between the bolometer layer and the electrode portion is reduced, and the device noise can be reduced.

The element resistance can be further reduced by adding Li or Cu to the bolometer layer.

Further, in the method of manufacturing an infrared detecting element according to the present invention, in the bolometer layer forming step, the TCR and the element resistance can be controlled by controlling the sputtering conditions to produce an infrared detecting element having high detection sensitivity. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an infrared detecting element according to an embodiment of the present invention.

FIG. 2 is a perspective view of the infrared detecting element according to the embodiment of the present invention.

FIG. 3 is a schematic view of a measuring jig used in the embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional infrared detecting element.

[Explanation of symbols]

1 silicon substrate, 2 silicon oxide layer, 3 wiring layer,
4 electrode part, 5 bolometer layer, 6 wiring layer, 7 void section, 8 light receiving section, 9 bridge section, 100 infrared detecting element.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2G065 BA12 BA32 BC01 CA12 DA20 2G066 BA09 BA51 BA55 BB07 4M118 AA01 AB10 BA01 CA01 CA21 CA32 CA35 CA40 CB20 HA30

Claims (5)

[Claims] 1. A bolometer-type infrared detecting element having a light receiving portion supported by a bridge portion on a silicon substrate, wherein the light receiving portion is formed to extend to the light receiving portion through the bridge portion. A wiring layer, an electrode portion electrically connected to the wiring layer, and a bolometer layer formed on the electrode portion, wherein the bolometer layer is made of a layer mainly composed of an NTC thermistor material. Characteristic infrared detector. 2. The method according to claim 1, wherein the NTC thermistor material is MnDx.
Oy (D is one or more elements selected from the group consisting of Ni, Fe, Cr and Co, 0.2 <x <0.9, y =
2. The infrared detecting element according to claim 1, wherein the infrared detecting element is made of an oxide material having (x + 1.5) * [delta] (0.7 <[delta] <1.3)) as a main component. 3. The infrared detecting element according to claim 1, wherein the bolometer layer is at least partially in an amorphous state. 4. The bolometer layer further comprises Li, Cu
The infrared detecting device according to claim 1, further comprising at least one element selected from the group consisting of: 5. A method for manufacturing a bolometer-type infrared detecting element for forming a light receiving portion supported by a bridge portion on a silicon substrate, wherein the step of forming the light receiving portion includes a step of forming the light receiving portion on the bridge portion including a wiring layer. Forming a connected silicon oxide layer; forming an electrode layer on the silicon oxide layer so as to be electrically connected to the wiring layer; and forming the electrode layer on the silicon oxide layer and the electrode layer. A bolometer layer forming step of forming a bolometer layer, wherein the bolometer layer forming step includes MnDxOy (D is Ni,
One or more elements selected from the group consisting of Fe, Cr and Co, 0.2 <x <0.9, y = (x + 1.5) × δ
A bolometer layer having (0.7 <δ <1.3) as a main component has a metal component ratio of Mn: D = 1: x (0.2 <x <
0.9), a target including a mixture of an oxide of Mn and an oxide of D or a target including a composite oxide of Mn and D is sputtered on the silicon oxide layer and the electrode layer. A method of manufacturing an infrared detecting element, wherein the method is a step of depositing on an infrared ray.