JP3387280B2 - Thin film temperature sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film temperature sensor having a high thermistor constant and a high electric conductivity and capable of miniaturizing an element.

[0002]

2. Description of the Related Art As a conventional temperature sensor, various types such as a thermistor type and a pyroelectric type have been devised and put into practical use. For these, a sensor of a suitable type is used depending on its application. Among them, when considering the application to an image sensor for obtaining image information, it is necessary to miniaturize and highly integrate the sensor element to manufacture a two-dimensional sensor array. However, conventional pyroelectric sensors that have been widely used have limitations in miniaturization and high integration. Therefore, if the thermistor type thin film sensor is used, downsizing and high integration can be easily achieved, and it is considered that the thermistor type thin film sensor is suitable for application to an image sensor.

[0003]

In the conventional thermistor type temperature sensor, in order to improve the thermistor characteristics (hereinafter referred to as B constant), it is necessary to increase the activation energy (Ea) of the thermistor. The relationship between Ea and the conductivity σ is as follows. σ = σ ₀ exp (-Ea / kT) where σ ₀ is the conductivity at a given temperature, k is the Boltzmann constant, and T is the temperature.

Since the B constant B = Ea / k, the above equation is σ = σ ₀ exp (-BT), and the conductivity σ is low in order to obtain a high B constant. In the conventionally used thermistor type temperature sensor, since it was composed of a single material, the relationship of the above equation holds, and the B constant and the conductivity σ cannot be controlled independently. There is a problem that the resistance value becomes so high that it becomes difficult to measure the characteristics of the device.

The present invention has been made in view of the above problems, and an object thereof is to have a high thermistor constant and a high conductivity, and to measure the resistance value even if the element is downsized. It is to provide a structure of a thin film temperature sensor which can be easily manufactured.

[0006]

In order to solve the above problems, a thin film temperature sensor according to claim 1 is a silicon substrate.
A first layer formed of an insulator thin film or a semiconductor thin film, and a second layer formed of an insulator thin film or a semiconductor thin film having a band gap different from that of the first layer and laminated on the first layer A laminated structure having a laminated structure including on the silicon substrate , and in which the first layer and the second layer are laminated.
It has an interface parallel to the control board,
Carrier flow into a layer smaller than the larger layer
To form a carrier accumulation layer near the interface.
In addition, a pair of electrodes is formed on a layer above the laminated structure.

A thin film temperature sensor according to a first aspect of the present invention utilizes the carrier accumulation effect at the interface between two types of insulator thin films or semiconductor thin films having different band gaps. By making the doping amount of the thin film having the larger bandgap of the first layer or the second layer larger than that of the thin film having the smaller bandgap,
Carriers flow from the thin film having the larger band gap to the interface, and the carrier concentration of the accumulation layer at the interface increases. Further, since the thin film having a smaller band gap has a lower impurity concentration, the influence of impurity scattering is small, so that the carrier mobility becomes high. Furthermore, since the activation energy of the thin film having the larger band gap that supplies the carriers to the interface is high, the temperature dependence of the number of carriers becomes large (the change in the number of carriers due to temperature can be increased). That is, the change in the number of carriers (change in resistance value) between the state where the thermistor does not absorb infrared rays and the state where the thermistor absorbs infrared rays and its temperature rises can be increased. From these facts, it is possible to obtain a small-sized thin film temperature sensor which has a high thermistor constant (B constant) and high conductivity and is easy to manufacture.

A thin film temperature sensor according to a second aspect of the present invention is the thin film temperature sensor according to the first aspect, wherein the pair of electrodes is provided on one of the first layer and the second layer having a smaller band gap. It is characterized by being formed. Since the carrier concentration is higher in the layer having a smaller band gap, ohmic contact with the electrode can be established, and therefore the characteristics as a temperature sensor are further improved.

A thin film temperature sensor according to claim 3 is a silicon
A substrate, a first layer composed of an insulator thin film or a semiconductor thin film, and an insulating thin film or a semiconductor thin film having the same bandgap and different activation energies as those of the first layer. A laminated structure including a second layer laminated on the silicon substrate , the first layer and the second layer.
The layer is a field parallel to the silicon substrate formed by stacking.
Has a surface and is smaller than a layer with high activation energy
Carriers flow into the layer, causing carry near the interface.
A to form the storage layer, and above the laminated structure
A pair of electrodes is formed on the layer . The thin film temperature sensor according to claim 3 is different from the thin film temperature sensor according to claim 1 in that the first layer and the second layer are made of the same material having the same band gap, that is, the same material. The activation energy differs depending on the type or doping amount of the material to be doped. In this case, since the first layer and the second layer are made of the same material and have the same conduction band and valence band, a spike (barrier) at the interface cannot be generated and the activation energy is smaller. Since carriers are more likely to move to the thin film, the characteristics as a temperature sensor are further improved.

A thin film temperature sensor according to claim 4 is a silicon
Substrate composed of an insulating thin film or a semiconductor thin film.
Insulation with a different bandgap between the first layer and the first layer
It is composed of body thin film or semiconductor thin film and is laminated on the first layer
A laminated structure including the formed second layer on the silicon substrate.
In addition, the first layer and the second layer are laminated and formed.
Since it has an interface parallel to the recon substrate,
Carriers may flow into a layer smaller than the one with a large cap.
To form a carrier accumulation layer near the interface.
There is a pair on both sides of the laminated structure so that it touches the interface.
The above electrode is formed . In this case, the Schottky barrier at the interface between the insulator or semiconductor and the metal can be reduced, and the characteristics as the temperature sensor are further improved.

The thin film temperature sensor according to claim 5 is a silicon
Substrate, a first layer made of an insulator thin film or a semiconductor thin film, and an insulator thin film or a semiconductor thin film having a band gap different from that of the first layer, and the side faces of the first layer are in contact with each other. A second layer formed on the silicon
On the substrate, and the side surfaces of the first and second layers are in contact with each other.
Has an interface perpendicular to the silicon substrate formed by
Therefore, the layer is smaller than the layer with a large band gap.
Carrier accumulation layer near the interface due to the rear flow
To form the first layer so that it contacts the interface.
And a pair of the electrodes is formed on the upper and lower surfaces of the second layer . With this configuration, the distance between the electrodes is reduced and the resistance value can be reduced, so that the element can be further downsized.

A thin film temperature sensor according to claim 6 is a silicon
A substrate, a first layer composed of an insulator thin film or a semiconductor thin film, and an insulating thin film or a semiconductor thin film having the same bandgap and different activation energies as those of the first layer. And a second layer formed so that their side surfaces are in contact with each other on the silicon substrate, and
Layer and second layer are silicon substrates formed with their side surfaces in contact with each other
It has an interface perpendicular to the
Carriers flow into layers smaller than large layers
It forms a carrier accumulation layer near the interface.
On the upper and lower surfaces of the first layer and the second layer so as to contact the interface of
The above electrode is formed . With this configuration, the distance between the electrodes can be reduced and the resistance value can be reduced, so that the element can be further downsized.

[0013]

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the thin film temperature sensor of the present invention will be described with reference to the sectional view of FIG. In the figure, 1 is a silicon substrate, 2 is an amorphous silicon film (a-Si) which is a first layer formed on the silicon substrate 1,
Reference numeral 3 is an amorphous silicon carbon film (a-SiC) which is a second layer formed on the amorphous silicon film 2. Amorphous silicon carbon has a band gap larger than that of amorphous silicon. Therefore, a laminated structure 4 in which semiconductor thin films having different band gaps are laminated is formed on the silicon substrate 1. Further, 5 is a chromium electrode which is formed on the amorphous silicon carbon film 3 and serves as a pair of electrodes, and 6 is an interface between the amorphous silicon film 2 and the amorphous silicon carbon film. When the laminated structure 4 is formed by plasma CVD by RF discharge, it can be easily formed by changing the reaction gas. In the case of the thin film temperature sensor shown in FIG. 1, the carrier moves mainly in parallel with the silicon substrate 1.

Further, the amorphous silicon film 2 and the amorphous silicon carbon film 3 are doped with boron (B) so as to exhibit p-type characteristics, and the amorphous silicon film has a band gap larger than that of the amorphous silicon film 2. The carbon film 3 has a doping concentration higher than that of the amorphous silicon film 2.

Next, an energy band diagram of the structure shown in FIG. 1 is shown in FIG. As shown in FIG. 2, many holes, which are majority carriers, exist in the amorphous silicon carbon film 3, but move to the amorphous silicon film 2 having smaller activation energy and are accumulated in the accumulation layer. Further, since the amorphous silicon film 2 has a low impurity concentration, carrier scattering of impurities is reduced and mobility is increased, so that the conductivity of the thermistor can be increased. Further, since the activation energy of the amorphous silicon carbon film 3 having the larger band gap that supplies the carriers to the interface 6 is high, the temperature dependence of the number of carriers is increased (change in the number of carriers and the change in resistance value depending on temperature). It is possible to realize a thin film temperature sensor having a high thermistor constant (B constant).

However, since the characteristics of the thin film temperature sensor described above are greatly influenced by the state of the formed interface 6, depending on the state, an accumulation layer is formed as shown in the energy band diagram of FIG. However, even in this case, since carriers move from the amorphous silicon carbon film 3 to the amorphous silicon film 2 which is the thin film having a smaller band gap, a thin film temperature sensor having a high B constant and a high conductivity can be used. Can be realized.

Next, a different embodiment of the thin film temperature sensor of the present invention will be described with reference to the sectional view of FIG. The thin film temperature sensor shown in FIG. 4 is an amorphous silicon film which is a thin film having a smaller bandgap than the thin film temperature sensor shown in FIG. A chrome electrode is formed on top of 2. Since the amorphous silicon film 2 has a higher carrier concentration, ohmic contact with the chromium electrode is established, and the characteristics as a temperature sensor are improved.

Next, the characteristics of the thin film temperature sensor shown in FIG. 4 will be described with reference to the diagram of FIG. The figure is a diagram showing the relation between B constant and conductivity σ of thin film temperature sensor.
The horizontal axis represents the B constant, and the vertical axis represents the conductivity σ. Amorphous silicon carbon film 3 (B
Amorphous silicon film 2 (B constant: 4600, conductivity: 6 × 10 ^-6 S / cm) shown at point B is laminated on the film of constant: 4500, conductivity: 2 × 10 ^-7 S / cm. In this case, since the conductivity of the amorphous silicon carbon film 3 is reduced by one digit or more, assuming that all the carriers flow in the amorphous silicon film 2, the characteristics of the laminated structure 4 are as follows: B constant: 4800 The conductivity was 1.5 × 10 ⁻⁵ S / cm, and the conductivity of the amorphous silicon film 2 was doubled.

Next, still another embodiment of the thin film temperature sensor of the present invention will be described. With the structure shown in FIG.
It is also possible to realize a thin film temperature sensor by using an insulating thin film or a semiconductor thin film having the same band gap but different activation energies as the first layer and the second layer. The energy band diagram in this case is shown in FIG. As shown in FIG. 6, since the first layer and the second layer have the same bandgap, barriers such as spikes are not formed like a general pn junction, and the thin film with smaller activation energy (in FIG. Second
The carrier is more easily transferred to the layer). According to this method, when forming by plasma CVD by RF discharge, it is possible to easily form a laminated structure of semiconductor thin films having different activation energies by changing the doping gas flow rate.

Next, a further different embodiment of the present invention will be described with reference to the sectional view of FIG. However, the same components as those shown in FIG. 1 are designated by the same reference numerals. In the figure, 1 is a silicon substrate, 2 is an amorphous silicon film (a-
Si) and 3 are formed on the amorphous silicon film 2,
Second layer amorphous silicon carbon film (a-SiC
). Further, 7 is a chromium electrode, which is a pair of electrodes, formed on the side surface of the laminated structure 4 so as to be in contact with the interface 6 between the amorphous silicon film 2 and the amorphous silicon carbon film 3. In the structure shown in the figure, for example, after the laminated structure 4 is formed, the laminated structure 4 is etched by a method such as RIE, ion milling, or wet etching to expose the interface 6, and then an electrode is formed thereon. It can be realized by doing.

A different embodiment of the thin film temperature sensor of the present invention will be described with reference to FIG. First, FIG.
The structure will be described based on (d). In the figure, 8 is a silicon substrate, 9 is a lower chrome electrode formed on the silicon substrate 8, 10 is an amorphous silicon film which is a first layer locally formed on the lower chrome electrode 9, and 11 is amorphous silicon. The amorphous silicon carbon film, which is the second layer, is formed so as to be in contact with the film 10 on its side surfaces. Further, 12 is an upper chrome electrode, which is formed so as to form a pair with the lower chrome electrode 9 so as to sandwich the interface 13 between the amorphous silicon film 10 and the amorphous silicon carbon film 11. With this configuration, the distance between the electrodes is reduced and the resistance value can be reduced, so that the element can be further downsized.

Next, an embodiment of the manufacturing method will be described with reference to FIGS. First, as shown in (a), a lower chromium electrode 9 is formed on a silicon substrate 8, one thin film (amorphous silicon film 10) is formed, and then a part of the film is removed by etching.
Thereafter, as shown in (b), another thin film (amorphous silicon carbon film 11) is formed on the surface, and then etching is performed to expose the amorphous silicon film 10 as shown in (c). Finally, as shown in (d), the upper chromium electrode 12 is formed on the interface 13 between the amorphous silicon film 10 and the amorphous silicon carbon film 11.

A further different embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 8, the first
As the layer and the second layer, an insulating thin film or a semiconductor thin film having the same band gap but different activation energies may be used. When such a material is used, the thin film temperature sensor having the structure shown in FIG. 8 can be formed by a simpler method than the manufacturing method described with reference to FIG. Specifically, as shown in FIG. 9, on the silicon substrate 14,
After forming the lower chromium electrode 15, an amorphous silicon carbon film 16 which is a first layer is formed, and the first layer forming portion on the amorphous silicon carbon film 16 is formed.
The mask 17 is covered and the second layer formation location is doped by a method such as ion implantation to form a second layer to form a laminated structure. With this manufacturing method, it is possible to more easily realize a thin film temperature sensor having desired characteristics.

Next, a further different embodiment of the thin film temperature sensor of the present invention will be described with reference to FIG. In the figure, 18 is a silicon substrate, 19 is a lower chrome electrode formed on the silicon substrate 18, and 20 is a lower chrome electrode 1.
9 is an amorphous silicon film which is a first layer formed on 9; 21 is a granular amorphous silicon carbon region formed in the amorphous silicon film 20; and 22 is an upper chromium electrode formed on the amorphous silicon film 20. is there. The upper chrome electrode 22 is the lower chrome electrode 1
9 and 9 are formed so as to sandwich a plurality of interfaces 23 between amorphous silicon and amorphous silicon carbon. Amorphous silicon film 2 having granular amorphous silicon carbon regions 21 shown in FIG.
0 is, for example, ECR plasma CVD method by microwave,
It can be realized by a method of forming a microcrystal by controlling the flow rate of the reaction gas or the dilution gas.

The thin film temperature sensor according to the present invention is not limited to the materials described in the embodiments. Further, as the laminated structure, a two-layer structure is shown.
The embodiment is not limited as long as it includes a structure in which a layer and a second layer are laminated.

[0027]

As described above, according to the thin film temperature sensor of claims 1 to 6 , it is possible to realize a thin film temperature sensor which has a high thermistor constant and a high conductivity and can be miniaturized. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a thin film temperature sensor of the present invention.

FIG. 2 is a band gap diagram of an embodiment of the thin film temperature sensor of the present invention.

FIG. 3 is a band gap diagram of one embodiment of the thin film temperature sensor of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the thin film temperature sensor of the present invention.

FIG. 5 is a diagram showing the performance of different embodiments of the thin film temperature sensor of the present invention.

FIG. 6 is a bandgap diagram of a different embodiment of the thin film temperature sensor of the present invention.

FIG. 7 is a sectional view showing still another embodiment of the thin film temperature sensor of the present invention.

FIG. 8 is a sectional view showing still another embodiment of the thin film temperature sensor of the present invention.

FIG. 9 is a cross-sectional view showing the manufacturing method of still another embodiment of the thin film temperature sensor of the present invention.

FIG. 10 is a sectional view showing still another embodiment of the thin film temperature sensor of the present invention.

[Explanation of symbols]

2,16,20 Amorphous silicon film (first layer) 3,11 Amorphous silicon carbon film (second layer) 4 Laminated structure 5,7 Chrome electrode (electrode) 6,13,23 Interface 9,15,19 Lower chromium electrode (Electrode) 12,22 Upper chrome electrode (Electrode) 21 Amorphous silicon carbon area (Area)

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 5/00-5/62 H01C 7/02-7/04

Claims (6)

(57) [Claims] 1. A silicon substrate, a first layer formed of an insulator thin film or a semiconductor thin film, and an insulator thin film or a semiconductor thin film having a band gap different from that of the first layer, and the first layer is formed on the first layer. A laminated structure including a laminated second layer
The first layer and the second layer are provided on the silicon substrate , and
An interface parallel to the silicon substrate formed by stacking
The layer with a smaller band gap than the layer with a larger band gap.
Carriers accumulate near the interface as they flow in.
What is claimed is: 1. A thin film temperature sensor for forming a laminate, wherein a pair of electrodes is formed on a layer above the laminate structure. 2. The thin film temperature sensor according to claim 1, wherein the pair of electrodes is formed on one of the first layer and the second layer having a smaller bandgap. 3. A silicon substrate, a first layer composed of an insulator thin film or a semiconductor thin film, and an insulator thin film or a semiconductor thin film having the same band gap and different activation energies as the first layer. A laminated structure including a second layer laminated on the first layer on the silicon substrate ,
Moreover, the silicon formed by stacking the first layer and the second layer
It has an interface parallel to the substrate and the activation energy
Carrier flow into a layer smaller than the larger layer
A carrier accumulation layer is formed closer to the interface.
And a pair of electrodes formed on a layer above the laminated structure. 4. A silicon substrate and an insulating thin film or a semiconductor.
The first layer composed of the body thin film and the first layer are
Consist of an insulator thin film or a semiconductor thin film with different caps
And a laminated structure including a second layer laminated on the first layer.
The first layer and the second layer are provided on the silicon substrate, and
An interface parallel to the silicon substrate formed by stacking
The layer with a smaller band gap than the layer with a larger band gap.
Carriers accumulate near the interface as they flow in.
It forms a stack, and stacks so that it touches the interface.
A feature that a pair of the electrodes is formed on both side surfaces of the layer structure
Thin film temperature sensor to. 5. A silicon substrate, a first layer composed of an insulator thin film or a semiconductor thin film, and an insulator thin film or a semiconductor thin film having a band gap different from that of the first layer, and the first layer. A second layer formed so that its side surfaces are in contact with each other, and the second layer is formed on the silicon substrate;
The second layer is opposed to the silicon substrate formed by contacting the side surfaces with each other.
Has a vertical interface and has a large band gap
Interface is created by carriers flowing into a layer smaller than the layer
It forms a carrier accumulation layer in the vicinity and its interface
On the upper and lower surfaces of the first layer and the second layer so as to be in contact with
A thin film temperature sensor having electrodes formed thereon. 6. A silicon substrate, a first layer composed of an insulator thin film or a semiconductor thin film, and an insulator thin film or a semiconductor thin film having the same bandgap and different activation energies as the first layer. A first layer and a second layer formed so that the side surfaces are in contact with each other on the silicon substrate.
And the sides of the first and second layers are in contact with each other.
It has an interface perpendicular to the silicon substrate formed.
Carry in a layer smaller than the layer with large activation energy.
As a result, the carrier accumulation layer near the interface
To be formed, and the first layer and
And a pair of the electrodes formed on the upper and lower surfaces of the second layer .