JPS5942826B2 - gas detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies to a gas detection device having an average particle size of 10 to 15
It is composed of an aggregate of metal or metal oxide ultrafine particles in the 0A range, and is constructed by combining an ultrafine particle resistance film that is sensitive to external agents such as gas and water vapor, and a semiconductor integrated circuit. The present invention aims to provide a gas detection device that can detect components such as gas and water vapor with high sensitivity.

As a device for detecting leakage of hydrogen gas using a semiconductor chip, a device having the structure shown in Fig. 1 has been proposed (for details, refer to "Rev.
nstrument” magazine, Vol. 46, No. 9 (1975)
(See pages 1206-1208).

First, the outline of this device will be explained.

1 is a semiconductor chip for detecting hydrogen gas, MOS
A Pd vapor deposition film is formed on the gate insulating film of the transistor.

When hydrogen gas comes into contact with the Pd vapor deposited film, the threshold voltage VT of the MOS transistor changes depending on the concentration of hydrogen gas, and its voltage-current characteristics change, so the hydrogen gas concentration can be detected electrically. . At this time, in order to speed up the detection of hydrogen gas, the heating coil 2 is energized to generate heat and the semiconductor chip 1 is heated to 150°C. In order to control this temperature, a thermistor 3 having a resistance value of approximately 100Ω at 150° C. is used. A bridge circuit is constructed with this thermistor 3 as one side, and its output voltage is amplified using an operational amplifier, and the output voltage is applied to a Darlington transistor to control the heater power. 4 is a TO-18 type metal package, and 5 is a transistor socket.

The main features of this device are that the MOS transistor itself detects hydrogen gas, so it can directly output an electrical signal, and that it controls the temperature using a bridge circuit using a thermistor. be.

However, in putting it into practical use, the first problem is that the semiconductor chip 1 and thermistor 3
The temperature of the semiconductor chip cannot be measured accurately because it is far away from the semiconductor chip. The second problem is that the coil 2
Since the shape and number of turns of the coil, its arrangement with respect to the semiconductor chip 1 and the package 4, the holding material and mounting condition of the thermistor 3, the heat capacity of the socket 5, etc. vary from device to device, the power applied to the coil 2 for each device varies. Since it is necessary to correct the correlation between the temperature detected by the thermistor 3 and the temperature of the semiconductor chip 1, this is disadvantageous from an industrial perspective because it increases the number of testing and adjustment steps. The gas detection device according to the present invention solves the above-mentioned problems and integrates an adaptive part and a circuit that operates based on changes in its output.

That is, the major feature of the gas detection device of the present invention is that the sensitive portion is made of an ultrafine particle resistive film whose electrical resistance value changes extremely sensitively depending on the type and concentration of gas or water vapor. The operating temperature detection and control parts, alarms such as buzzers, and parts that drive loads such as display devices are formed by being integrated or divided into one or more semiconductor chips, and are integrated into one substrate or header. It is located at the point above. In addition,
The ultrafine particle resistance film can be formed on a part of the surface of a semiconductor chip, or it can be installed after forming the ultrafine particle resistance film separately on a part of one insulating substrate or forming it as an independent resistor chip. It's okay. With this configuration, it has become possible to manufacture a large quantity of ultra-small gas detection devices that are highly reliable and have uniform characteristics. Hereinafter, details of the apparatus according to the present invention will be explained using the drawings.

FIG. 2 shows an example of the structure, and 11 is a semiconductor integrated circuit chip as described later. Although one chip is shown here to simplify the explanation, a plurality of chips may be used. After this is die-bonded to the header 12 of the package, each bonding pad and lead wires 13, 13' are connected by wires 14, 14', respectively. 15 is a heating coil.

FIG. 3 shows a cross-sectional structure of the semiconductor integrated circuit chip 11.

A portion 21 on the left side of the figure is a gas/humidity detection portion, and an ultrafine particle resistance film 25 is formed across comb-shaped electrodes 23 and 24 formed on a SlO2 film 22 as an insulating film. The comb-shaped electrodes 23 and 24 are shown in FIG. 4A, and the state in which the ultrafine particle resistance film 25 is formed is shown in FIG.
Shown below. The comb-shaped electrode structure is just one example, and it goes without saying that there are various modifications to the electrode structure. A portion 26 on the right side of the figure is a part of the active portion of the semiconductor integrated circuit, and a typical example thereof shows the structure of an Npn transistor. By forming a plurality of transistors, resistors, etc. having such a structure and wiring them appropriately using a metal vapor deposition film, a temperature detection and control section, a section for driving an alarm device or a display device, etc. can be constructed. Such a circuit configuration itself is not shown here because a well-known circuit configuration is sufficient. An n-type epitaxial layer 2 is formed on one side of the P-type silicon substrate 27.
8 is formed, and an n-type island region 30 is formed by penetrating this layer 28 and forming a final diffusion region 29. In this region 30, a P-type pace region 31 and an NJ cedar emitter region 32 are formed. 33, 34, 35
are the emitter, base, and collector electrodes, respectively.

In the device having the above structure, elements constituting an integrated circuit such as a transistor or a resistor are not formed below the gas or humidity sensitive portion 21, but as shown in FIG. It can also be provided on the circuit portion 26.

However, in this case, after forming the electrodes 33, 34, 35, a SlO2 film 36 is formed on the entire surface by CVD method,
Thereon, electrodes 23, 24 and an ultrafine particle resistance film 25 are formed as in the case of FIG. At this time, the electrode extraction portions 237, 24' shown in FIG.
It is connected to any part (not shown) of the wiring electrode formed at the same time. One method of connection will be explained. After forming the SlO2 film 36 on the entire surface by CVD method, a part of it is selectively removed to form the electrodes 33, 34.
, 35 is formed, and then a metal for forming an electrode is deposited on the entire surface, and then the metal deposited film is selectively removed by Kowa's photolithography method, and an SlO2 film is formed from the window part. An extraction electrode can be formed over the top of 36. The structure of this extraction electrode part is the fifth
Not shown. It is well known that the electrical characteristics of semiconductor diodes and transistors are temperature dependent. For example, the base and collector of a transistor are electrically connected, and between the emitter and base there is a
A small current of about μA is passed, and the voltage E between the base and emitter is
If you measure B, the value of VEB will change approximately 2 with the temperature.
Since the temperature increases at a rate of m/°C, the temperature of the semiconductor chip can be measured. By feeding back the value of VEB, which has a one-to-one correlation with this temperature, to the control circuit for the power applied to the coil 15, the temperature of the semiconductor chip and the ultrafine particle resistance film can be kept constant at a predetermined temperature. . Note that the SiO2 films 22 and 36 shown in FIG. 5 are at most 1 μm thick, and the temperature difference between the inside of the semiconductor chip and the ultrafine particle resistance film portion can be ignored.

Here, as a method of heating the ultrafine particle film, we have described a method of heating the ultrafine particle film by passing current through a coil to generate heat.
The film may be heated by applying power to a thin film resistor, a diffused resistor, an ion implanted resistor, a thin film resistor, etc. installed in a part of a semiconductor integrated circuit chip to generate heat, or at least a portion including the film may be heated. It may be heated by irradiating with infrared rays.

Alternatively, heating may be performed using a combination of any of the above.
Furthermore, in order to reduce heating power, it is preferable to place the ultrafine particle film above a portion of a semiconductor integrated circuit chip that generates a lot of heat, such as a portion where a power transistor such as a drive circuit is formed. . Next, gas and humidity dependence of the electrical resistance of the ultrafine particle resistance film 25 will be explained.

The ultrafine particle resistance film is composed of ultrafine particles of a metal such as Pd or a metal oxide such as SnO2, ZnO, TiO2, NiO, etc., with an average particle size of about 10 to 150λ. As an example, a case will be described in which a tin oxide ultrafine particle resistance film is formed. Ultrafine particle resistance films are essentially different from vapor-deposited thin film resistance films; they are an aggregate of ultrafine particles, each of which is a single crystal, and are characterized by an order of magnitude higher surface energy and surface activity. It resists and changes extremely sensitively to changes in gas and water vapor.

For example, in an atmosphere of a reducing gas such as isobutane, the electrical resistance value of an ultrafine particle resistive film formed from ultrafine tin oxide particles with an average particle size of approximately several + A becomes logarithmic as the gas concentration increases. decreases to The same applies to alcohol gas. Furthermore, when measured at room temperature, the value of electrical resistance decreases logarithmically with increasing relative temperature.

As for how to detect it, you can directly measure its resistance or
Alternatively, it and a reference resistor may be connected in series, a constant voltage may be applied across the resistor, and the partial voltage may be measured. However, it goes without saying that the coil 15 may be energized to generate heat to heat the semiconductor chip 11 immediately before measuring the relative humidity. In this case, as clear from the above, it is possible to directly measure whether the semiconductor chip 11 has cooled to room temperature. The example described above is an example for explaining the gist of the present invention, and it goes without saying that there are various modifications.

In short, the key point of the configuration of the present invention is that at least one semiconductor integrated circuit chip having an ultrafine particle resistive film formed in a portion thereof, or at least one semiconductor integrated circuit chip and an ultrafine particle resistive film are integrated into one header. Alternatively, it may be installed integrally on the board. More preferably, the operating temperature of the ultrafine particle resistive film is determined from the voltage-current characteristics of a semiconductor diode or transistor or the temperature dependence of resistance, and the operating temperature is automatically controlled.

According to this device, there is no need to separately install a thermistor as in the conventional example shown in FIG.

Further, unlike the conventional example, there is no need to newly create various control circuit parts. In this respect, the characteristics of the gas sensing device of the present invention tend to be essentially uniform. Furthermore, since ordinary semiconductor integrated circuit manufacturing techniques can be used as is, they can be manufactured in large quantities relatively easily.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the main part of a conventional gas detection device, FIG. 2 is a diagram showing the configuration of the main part of an embodiment of the gas detection device according to the present invention, and FIG. 3 is a diagram showing the structure of the main part of the gas detection device according to the present invention. FIGS. 4A and 4B are plan views for explaining the structure of the sensitive portion, and FIG. 5 is a sectional view showing another example of the structure of the semiconductor chip. 11... Semiconductor chip, 12... Header 1, 13, 13'... Lead wire, 14, 14
'... Wire, 15... Heating coil, 21... Sensing part, 22... SlO
2 membranes, 23, 24...electrodes, 25...
Ultrafine particle film, 26... Semiconductor integrated circuit part, 2
7... Silicon substrate, 28... Epitaxial layer.

Claims (1)

[Scope of Claims] 1. An ultrafine particle resistive film composed of an aggregate of ultrafine metal or metal oxide particles having an average particle size in the range of 10 to 150 Å, and means for detecting the operating temperature of the resistive film. A semiconductor integrated circuit including at least one of a circuit for controlling the operating temperature or a load driving circuit is formed on a semiconductor substrate or an insulating substrate, and has means for heating the resistive film, and Gas or water vapor is detected by utilizing the characteristic that the electrical resistance value of the resistive film heated to a predetermined operating temperature by a heating means changes depending on the type and concentration of the gas to be detected. Detection device. 2. The gas detection device according to claim 1, wherein the ultrafine particle resistance film is provided on one surface of a semiconductor integrated circuit chip with an insulating film interposed therebetween. 3. The means for detecting the operating temperature of the resistive film is to detect the temperature by utilizing the characteristic that the Pn junction voltage of a transistor or diode formed in the semiconductor integrated circuit changes depending on the temperature, or to detect the temperature in the integrated circuit. 2. The gas detection device according to claim 1, wherein the gas detection device detects temperature by utilizing a property that the electrical resistance value of a resistor formed therein changes depending on temperature.