JPH0364811B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a compact and highly accurate sensor constructed by focusing on the fact that an amorphous semiconductor thin film resistor deposited on an insulating substrate changes depending on the ambient temperature. Regarding heating equipment.

In particular, we discovered that it is possible to create an amorphous semiconductor that contains a microcrystalline phase and has an extremely high dark conductivity.By using this material, we can create a circuit configuration that is integrated on any insulating substrate. We have made it possible to provide a compact, high-precision thin-film temperature sensing device that can be connected to peripheral circuits with low impedance.

Here, the amorphous semiconductor refers to a semiconductor that is a substance excluding liquids and gases and does not exhibit three-dimensional periodicity crystallographically. In other words, it refers to a semiconductor that is irregular and amorphous and does not have a diffraction peak that can be identified in an X-ray diffraction pattern.

[Prior Art] Conventionally, thermistors have been mainly used as temperature sensing devices.

Thermistors are generally made of Mn, Co, Ni, Fe, Cu.
It is composed of a composite sintered body of transition metal oxides such as
The shapes are bead, disk, washer, flake, and thick film.

[Problem to be solved by the invention]

The performance and stability of these thermistor elements are greatly influenced by the conditions for forming the sintered body, and the sintered body is formed at a high temperature of around 1000℃ and under pressure. Therefore, microfabrication technology such as photoetching technology cannot be used, so it has the disadvantage that it cannot be incorporated into IC process technology.

There is also a method using a semiconductor thin film deposited by vapor deposition of Ge, Si, etc., but when forming a semiconductor thin film with high conductivity, the substrate temperature is set at 500°C.
It is necessary to do more than that. In this case, since the linear expansion coefficient of the substrate and the linear expansion coefficient of the semiconductor thin film deposited on the substrate by vapor deposition are generally different, when the substrate is returned to room temperature, distortions and cracks are likely to occur in the semiconductor thin film. As a result, from an industrial technology perspective, it was not possible to take full advantage of its performance.

Furthermore, amorphous semiconductors (also called glass semiconductors), which are made by mixing compounds containing multiple group elements such as S, Se, and Te in an appropriate ratio, liquefy the mixture at high temperatures, and then rapidly cool it to solidify, are also sensitive. Generally, the conductivity at room temperature is 10 ^-3 ~
10 ¹⁸ S·cm ^-1 , and when made into a thin film, the element impedance was too large to be practical. In particular, there were difficulties in connecting with peripheral circuits, making it difficult to integrate and easily picking up noise.

[Means to solve the problem]

In view of the above points, in the present invention, an amorphous amorphous semiconductor thin film deposited on an insulating substrate by a glow discharge method contains a microcrystalline phase and has high conductivity, and a high-quality amorphous amorphous semiconductor thin film is deposited on an insulating substrate by a glow discharge method. We focus on the fact that semiconductor thin films can be deposited.

By using an amorphous semiconductor thin film deposited using this glow discharge method in the detection part of a thermistor element, an ultra-small and highly accurate temperature-sensing device can be realized. That is, even if this amorphous semiconductor is formed into a thin film, it is difficult to pick up noise due to its low impedance and can be easily connected to peripheral circuits, making it possible to realize an integrated temperature sensing device.

Furthermore, amorphous semiconductors can be formed on most types of substrates so as to cover their surfaces, and can be particularly incorporated into semiconductor integrated circuits and thin-film hybrid integrated circuits.

[Effect]

Figure 1 shows the conductivity (strictly speaking, dark conductivity) vs. temperature characteristics of p-type and n-type amorphous Si thin films deposited on glass substrates by the DC glow discharge method using a mixed gas of SiF ₄ and H ₂ . It is a figure showing an example.

In the drawings, the + mark indicates p-type, the black circle indicates n-type, the horizontal axis indicates 1/T (T is absolute temperature), and the vertical axis indicates conductivity σ (S·cm ^-1 ) of the amorphous semiconductor thin film.

The p-type amorphous semiconductor thin film is produced by adding _B2H6 as a doping gas to a mixed gas _{of SiF4} and _H2 , _B2H6 / _SiF4 = _500ppm , and discharge pressure of 0.8~
Deposited at 1.4Torr and substrate temperature of 350℃. From the measurement results, the magnitude of conductivity changes depending on the ambient temperature and is given by the following equation.

σ=σ ₀ e ^-A/KT (1) where σ ₀ is the conductivity at T=T ₀ , k is Boltzmann's constant, and A is a constant.

In addition, the n-type amorphous semiconductor thin film is SiF ₄ and
In the mixture gas of _H2 , _PH3 as doping gas
B ₂ H ₆ /SiF ₄ = 740ppm, discharge pressure
Deposited at 1Torr and substrate temperature of 300℃. From the measurement results, like the p-type amorphous semiconductor thin film, the conductivity of the n-type amorphous semiconductor thin film can be expressed by equation (1).

From the above experimental results, the amorphous semiconductor thin film deposited at low temperature using the glow discharge method is p-type, n-type
Along with its shape, it exhibits high conductivity at room temperature, and its resistance change rate with temperature is over 0.3%/°C, making it ideal as a variable resistance temperature-sensitive material.

〔Example〕

2 and 3 are diagrams showing the configuration of an embodiment of the temperature sensing device according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross section taken along line X-X' in FIG. 2. Show the diagram.

In FIGS. 2 and 3, 1 is an insulating substrate;
2 is a p-type (n-type) amorphous semiconductor thin film, 3 and 3' are an ohmic electrode pair, 4 and 4' are a lead wire pair,
5 indicates a temperature sensing device.

Next, a method for manufacturing the temperature sensing device 5 will be described below.

The material for the insulating substrate 1 is preferably a heat-resistant insulator, or a conductor plate or semiconductor plate with similar properties whose surface is covered with a SiO ₂ film or Si ₃ N ₄ film by CVD method, such as glass plate, quartz plate,
Insulating thin films (for example,
Those covered with a SiO ₂ thin film or Si ₃ N ₄ thin film formed by CVD method are used. After thoroughly cleaning the insulating substrate 1 with an organic solvent or the like, it is instantly dried in a clean atmosphere. Next, an amorphous semiconductor thin film 2 is deposited using SiH ₄ or a mixed gas of SiF ₄ and H ₂ by a DC glow discharge method or an RF glow discharge method. In this case, the higher the conductivity of the amorphous semiconductor thin film resistor, the more desirable it is, and usually σ = 1 (S cm
^-1 ) or more are used. An example of deposition conditions using the DC glow discharge method is a discharge pressure of 0.1
~10Torr, discharge current 1~100mA/ ^cm2 , discharge voltage
500~800V, electrode spacing 3cm, substrate temperature 250~450
°C, SiF ₄ /H ₂ = 1~10, B ₂ H ₆ /SiF ₄ = 100~
2500ppm, _PH3 / _SiF4 =100-2500ppm.
As an amorphous semiconductor thin film deposited under these conditions, a conductivity of σ=20 (S·cm ⁻¹ ) or higher is easily obtained. A common method for increasing the conductivity of a semiconductor thin film is to increase the discharge current or increase the proportion of doping gas. A method of applying a magnetic field is also effective. Si-Ge alloy type amorphous semiconductor thin films also have high conductivity. In this case, _SiF4 and _GeH4
Using a mixed gas with B ₂ H ₆ or PH ₃ , AsH ₃ doping gas added, DC glow discharge method (method of applying direct current voltage) or RF glow discharge method (method of applying high frequency voltage) An amorphous semiconductor thin film (thin film containing microcrystalline grains and exhibiting high dark conductivity; the same applies hereinafter) is deposited using the method. When a semiconductor thin film is deposited using the above method, the amorphous film may contain a fine crystal phase of around 100 Å or exhibit polycrystalline properties, but the conductivity is -
Temperature characteristics are maintained.

Next, a metal film for electrodes (for example, NiCr 500 Å/Au 1000 Å) is deposited using a vacuum evaporation method.
Further, unnecessary portions are removed using a photoetching technique to form the electrode pair 3, 3' and the amorphous semiconductor thin film resistor 2. The shape of the thin film resistor 2 is determined by considering the conductivity, film thickness, and output impedance of the amorphous semiconductor thin film.
If the length of the amorphous semiconductor thin film is L and the width is W, then L/W is usually set to 1/10 to 10.

Next, a protective film is deposited on the substrate surface. As the protective film, an SiO ₂ film, a Si ₃ N ₄ film, a polyimide resin, or the like is used by the CVD method. The protective film on the electrode pads is removed using photoetching technology. Finally, connect the lead wire pair 4 to the electrode pair 3, 3'.
Attach to 4' and complete. As a lead wire,
It is constructed using the beam lead method or wire bonding of Au wires, Au ribbon wires, etc.

In the above manufacturing method, a photo-etching technique is used for the semiconductor thin film resistor and the electrode pair, but they can also be formed by a method using a metal mask. In this case, a method is used in which unnecessary parts are covered with a metal master when depositing an amorphous semiconductor thin film or when depositing an electrode metal thin film using a vacuum evaporation method.

4 and 5 are views showing another embodiment of the present invention, with FIG. 4 showing a plan view thereof, and FIG. 5 showing a sectional view taken along line X-X' in FIG. 4. 4 and 5, 11 is an insulating substrate, 12 and 12' are a pair of amorphous semiconductor thin films deposited to form opposite sides of a Wheatstone bridge, and 13 and 13' are Wheatstone bridges. A pair of resistor thin films 14A, 14B, 14C, 1 deposited to constitute opposite sides of the stone bridge
4D denotes two pairs of opposing ohmic electrodes connecting each amorphous semiconductor thin film and each resistor thin film;
5A, 15B, 15C, and 15D are lead wires provided to each ohmic electrode, and 16 is a temperature sensing device.

Materials with extremely small temperature changes are used as resistor thin films, such as tantalum nitride, nichrome, titanium,
1 pair of ohmic electrodes using chromium, tin dioxide, etc.
If fixed pressure Vin is applied between 4A and 14B, the output voltage Vout between ohmic electrode pair 14C and 14D
varies depending on the ambient temperature and is given by the following equation:

Vout≒Vin/2・A・ΔT For example, if the input voltage Vin=2V, the rate of change of the output voltage Vout will be ~3mV/°C.

The temperature sensing device shown in FIG. 4 and FIG. It can be constructed by adding a step of depositing a resistor thin film using vapor deposition or the like.

In this case, photoetching technology or metal mask technology is used for patterning the resistor thin film.

Next, we will briefly discuss the glow discharge method. Glow discharge methods include the DC glow discharge method, which generates glow discharge in a direct current electric field, and the RF glow discharge method, which generates glow discharge in a high frequency electric field. FIG. 6 shows an example of an apparatus for depositing an amorphous Si thin film on an insulating substrate or the like by the RF glow discharge method.

This device heats a vacuum container 38, an anode 39 and a cathode 40 arranged in parallel inside the vacuum container, an air supply port 42 and an exhaust port 43 for supplying or exhausting gas 41 into the vacuum container, and the anode and cathode. It is composed of a heater 44 and the like.

An insulating substrate 45 is placed on the anode. As the gas 41, doping gas (for example _{, PH 3 , AsH 3 ,}
B ₂ H ₆ etc.) is used.

During glow discharge, the vacuum pressure is several Torr, the voltage is almost constant, the current is 1 to 100 mA/cm ² , and most of the gas reactions occur within the positive column (plasma 46).

In particular, in this glow discharge method, the substrate temperature is 400°C.
It has the characteristic of being able to deposit amorphous semiconductor thin films at temperatures as low as ℃ or below (conventional pyrolysis methods for producing thin films require a substrate temperature of 500 to 700℃).
was necessary).

〔Effect of the invention〕

In this invention, the amorphous semiconductor thin film constituting the temperature sensing device contains microcrystals with a particle size of around 100 Å and has a high dark conductivity of 1 S cm ^-1 or more. By adopting a thin film, the following effects were obtained.

(1) The dark conductivity of conventionally known amorphous semiconductors, that is, amorphous semiconductors based on compounds containing multiple group elements such as S, Se, and Te, is 10 ^-2 S cm ^- Temperature-sensitive devices, which are circuit elements with significantly lower impedance than those of ¹ , can now be realized as ultra-small thin film devices.

(2) Amorphous semiconductor thin films can be formed on almost any type of substrate surface; (3) the temperature-sensitive device of the present invention exhibits low impedance and therefore induces less noise; (4) and Since no special interface circuit elements are required for connection with peripheral circuits, it has become easier to incorporate into semiconductor integrated circuits and thin-film hybrid integrated circuits.

(5) For example, by configuring a resistor thin film with an extremely small rate of change in resistance due to temperature and a Wheatstone bridge on the same insulating substrate, an ultra-small and highly accurate thin-film thermosensor can be constructed.

(6) Since the method for manufacturing a temperature-sensitive element of the present invention is compatible with the IC process, a temperature-sensing device is incorporated into the IC chip to measure the local temperature distribution of the IC chip. It can be configured by integrating the

(7) Since microfabrication technology represented by photoetching technology can be used, it is possible to construct an ultra-small temperature-sensing device required for integrated circuit formation, making it possible to realize, for example, a temperature measurement system with a thin-film hybrid IC structure.

(8) Since the manufacturing method is easy, an inexpensive temperature sensing device can be manufactured.

(9) Since the rate of change in resistance due to temperature is large, it is easy to configure the output amplifier and correction circuit.

(10) Since an amorphous semiconductor thin film resistor is used, which has a large rate of change in resistance due to temperature and high conductivity, a highly sensitive thin film temperature sensing device can be constructed.

As mentioned above, the temperature sensing device according to the present invention has many advantages over conventional ones.

[Brief explanation of drawings]

Figure 1 shows the conductivity-temperature characteristics of p-type and n-type amorphous semiconductor thin films, Figures 2 and 3
The figures are views showing an embodiment of the temperature sensing device according to the present invention, in which Fig. 2 is a plan view and Fig. 3 is a line X--
A cross-sectional view at X' is shown. 4 and 5 are views showing another embodiment of the temperature sensing device, with FIG. 4 being a plan view and FIG. 5 being a sectional view taken along line X-X' in FIG. FIG. 6 is a diagram showing an example of an apparatus related to the glow discharge method. In the figure, 1 and 11 are insulating substrates, 2 and 1
2, 12' are amorphous semiconductor thin film resistors, 13,
13' is a resistor thin film, 3, 3', 14A, 14B,
14C, 14D are each electrode pair, 4, 4', 15A,
15B, 15C, 15D are each lead wire pair, 5, 1
6 is a temperature sensing device, 39 is an anode, and 40 is a cathode.

Claims (1)

[Scope of Claims] 1. An insulating substrate 1; an amorphous semiconductor thin film 2 deposited on the substrate; and a pair of ohmic electrodes each in contact with the amorphous semiconductor thin film and separated by a predetermined distance. 3 and 3', wherein the amorphous semiconductor thin film is an amorphous semiconductor thin film containing a microcrystalline phase and having a dark conductivity of 1S cm ^-1 or more. Device. 2. an insulating substrate 11; a pair of amorphous semiconductor thin films 12, 1 deposited on the substrate so as to constitute opposite sides of a Wheatstone bridge, respectively;
2' and a pair of resistor thin films 13, 13'; two pairs of opposing ohmic electrodes 14A, 14B connecting the amorphous semiconductor thin film and the resistor thin film;
14C and 14D: the amorphous semiconductor thin film is an amorphous semiconductor thin film containing a fine crystalline phase and having a dark conductivity of 1S·cm ^-1 or more, and the resistor thin film is sensitive to temperature changes. A temperature sensing device characterized by an extremely small resistance element.