JPS58151549A - Electrostatic capacity type humidity sensitive element - Google Patents

Abstract

PURPOSE:To make a humidity sensitive element small-sized and also responsive in a high speed by decreasing floating capacity, by using only electrostatic capacity constituted by a humidity sensitive material placed between a diffusion layer and water permeable electrode for humidity detection. CONSTITUTION:A humidity sensitive element is constituted by providing a diffusion layer 2 on a part of a semiconductor substrate 1 and providing a insulation film 3 on the layer 2 and moreover, providing an ohmic electrode 4 on a part of said layer 2. This electrode is used for giving electric potential to the layer 2 from the outside. Next, a humidity sensitive film 5 is provided on the layer 2 through the film 3 and a water permeable electrode 6 and a take-out electrode 7 insulated from the substrate 1 through the film 3 and separated from the electrode 4 each other, are provided on the substrate 1 and then, electrostatic capacity is constituted. Accordingly, variation quantity of humidity in the outside atmosphere is detected as the variation quantity of dimensions of the electrostatic capacity brought out by the film 5 placed between both electrodes 4, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moisture sensing element that is constructed using a porous moisture material on a semiconductor substrate and detects humidity in the atmosphere or gas as a change in capacitance.

Most of the small humidity needles currently in use have two types of humidity sensing elements. One is fI
It utilizes the phenomenon in which the resistance component changes due to changes in l&, and materials that exhibit this phenomenon include electrolyte, ceramic, and glue. The other is people/,0. It is a capacitive type that uses a porous membrane, as typified by the above, and utilizes the phenomenon that the value of capacitance changes when moisture is adsorbed and desorbed by the porous membrane. A humidity sensing element that utilizes changes in resistance components exhibits a phenomenon in which the resistance value decreases as glv increases, and on the other hand, the resistance value becomes extremely high in areas of low humidity. For this reason, it is unsuitable for detecting minute amounts of humidity, and is usually used as a humidity sensing element in high humidity areas of 10-100%. On the other hand, as an element that utilizes changes in capacitance, porous A1 is used in the comb-shaped polarization provided on the oxide insulating film covering the 8i substrate. There are those constructed by sandwiching alpha oxide, and those constructed by oxidizing the surface of an Al substrate and covering it with a water-permeable electrode. These capacitance-type humidity sensing elements have a large amount of change in capacitance even in areas with low humidity; :Can detect even trace amounts of moisture. However, in order to measure humidity using these capacitive humidity sensing elements, a capacitance value of at least a certain value (for example, 19 F) is required due to restrictions imposed by the measuring circuit. However, in the moisture sensitive element having the above structure, the capacitance value per unit area is small, so it is necessary to increase the area of the element. In addition, in the case of a moisture-sensitive element having a structure in which the moisture-sensitive material is formed by oxidizing the surface of the AJ substrate, the film thickness of the moisture-sensitive material is 1.
It has the disadvantage that the response is slow because it is as thick as oIIIm.

Therefore, these temperature-sensitive elements are not suitable as small-sized moisture-sensitive elements having high-speed response, which is the need of the times. In order to overcome the drawbacks of the above-mentioned moisture sensing elements, the present invention is an inexpensive and small-sized moisture sensing element constructed using conventional semiconductor technology.

The present invention also relates to a moisture-sensitive element having high-speed response.

The moisture-sensitive element of the present invention includes a diffusion layer provided with an ohmic electrode on a semiconductor substrate, a moisture-sensitive material provided on the diffusion layer with an insulating film interposed therebetween, and a moisture-sensitive material provided to cover the moisture-sensitive material. The water-permeable electrode includes a water-permeable electrode, and an extraction electrode connected to the water-permeable electrode.

Embodiments of the moisture-sensitive element of the present invention are shown in FIGS. 1 and 2. The moisture sensing element includes a diffusion layer (2) provided on a part of the semiconductor substrate fl1, an insulator 1[+a+] provided on the diffusion layer, and an ohmic electrode (4) provided on a part of the diffusion layer. This electrode is used to apply a potential to the diffusion layer from the outside. Next, a moisture sensitive film (5) is provided on the diffusion layer with an insulating film interposed therebetween, and a moisture sensitive film (5) is connected to the semiconductor substrate through an insulating film to form a scent and a capacitance. Therefore, the humidity sensing method is characterized in that a change in humidity in the external atmosphere is detected as a change in the capacitance provided by the humidity sensitive film (5) sandwiched between the electrodes (4) and fi+. It is element. A porous Ajs Oa film obtained by anodizing AI is usually used as the moisture sensitive film.

A method for manufacturing a moisture sensitive element according to the present invention is shown in FIG. First, the surface of the nfpJ type 8i substrate +11 is thermally oxidized 8i0*.
l[(8) is deposited (state (a)). Next, thermal oxidation 8i0. i[) Open a window, diffuse into the Si substrate (1), form a diffusion layer (p (n) (see ml in (A)), and then remove the film (8) onto the thermally oxidized F3r. A gate oxide 5iol film (3) is deposited on the Si substrate (1) (shape II in (ri)). Next, M is etched so that the diffusion layer (1) remains (shape It in (1)).

Next, a CVD Siα film is deposited on the entire surface, and the 8i0° film is etched using a photoetching technique to cover the two electrodes t41 and ('11) to form an 8iα film ((o) shape It ).Next, gate oxide 81α film (8
), a window is opened using a photo-etching technique, M is vapor deposited on the entire surface, and A/, O, are formed using an anodic oxidation method. Leave the moisture sensitive film (country) through the gate oxidized 5iOfi film (3) on the diffusion layer (2) using the photo-etching technique.
The remaining kl and Oa are removed (state of (force)) 0 After this step, some of the St (% film) covering the M ohmic electrode (4) on the diffusion layer, and the moisture sensitive film (5) are removed. Take-out electrode (7
) of the extraction electrode (7)! ! A wet smell (5
Photoetch a part of the 8iα film on the ) side (state of (g)). Next, apply resist to the entire surface.

A water-permeable electrode (6) is formed to cover the S-well (5). Next, the extraction electrode (7) and the water permeable electrode (6)
) The thin film is thickened using electrolytic plating so that a part of the area becomes completely conductive. Finally, Daishin 2 Technique Next, the operating principle of the moisture sensing element in the embodiment of the present invention will be explained using FIGS. 1 and 2. First, voltage is applied to the two electrodes of the ohmic M electrode (4) on the diffusion layer formed on the water-permeable electrode (1) and the semiconductor substrate (1).Now, moisture in the atmosphere or gas is applied to the water-permeable electrode. Upon contact, moisture passes through this membrane and enters the α moisture-sensitive membrane (5).Since the moisture contains ions, it acts as an electrolyte, and the moisture-sensitive membrane (5)
change the dielectric constant of Changes in humidity can be measured by detecting changes in capacitance caused by this change.

Next, an embodiment of the one-guest detection device constructed using the humidity sensing element according to the present invention will be described with reference to FIG. First, an integrating circuit is constructed by the humidity sensing element whose capacitance value changes according to the present invention and resistor 0.

Next, another integral circuit α for comparison is provided in the apparatus. These two circuits generate a rectangular pulse signal at the entrance of the pulse generating circuit and add a rectangular pulse signal thereto, and detect the difference signal between the two circuits using a differential amplifier α◆. When moisture passes through the permeable electrode and enters the humidity sensing element, it changes the capacitance of the humidity sensing element and changes the difference signal output from the differential amplifier I.Changes in this difference signal. Humidity measurement can be carried out by detecting a large value of the amount and making it correspond to the humidity.To hold the maximum value of the difference signal, the maximum value holding circuit 4 is a reset pulse circuit synchronized with the cycle of the pulse signal. Operate at αe.Using such a circuit, it is possible to detect changes in humidity.Also, using the circuit described above, it is possible to measure humidity intermittently, and it can also be operated with a finite micro-power such as a battery. be able to.

The principle and embodiments of the moisture sensitive element of the present invention have been explained above according to the drawings. The moisture-sensitive element of the present invention uses only the capacitance formed by the moisture-sensitive material sandwiched between the diffusion layer and the water-permeable electrode for humidity detection, and has a structure in which the stray capacitance caused by the lead-out electrode portion is reduced. Highly sensitive moisture sensing elements can be made. Furthermore, since it is a planar type element, it can be connected to other circuits on a semiconductor substrate using only M wiring. For example, a measurement circuit and a humidity sensing element are installed on the same board.
Can be easily connected by wiring. Therefore, by providing the detection section and the measurement circuit section on the same substrate, an integrated sensor can be obtained.

In addition, in the moisture sensing element of the present invention, the thickness of the moisture sensing material can be made as thin as 0.2 mm, so the moisture sensing element can be made much smaller than conventional ones, and it can also provide a high-speed response moisture sensing element. can be made. Furthermore, since it is manufactured using semiconductor manufacturing technology, it is possible to manufacture an inexpensive moisture-sensitive element with good reproducibility. As described above, the present invention has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a front view of a configuration in an embodiment of the present invention. FIG. 2 is a sectional view taken along the line XX in FIG. 1, FIG. 3 is an explanatory diagram showing an example of the method for manufacturing a humidity sensing element according to the present invention, and FIG. 4 is a humidity sensor using the humidity sensing element according to the present invention. FIG. 2 is a circuit diagram showing an example of a detection device. 1... Semiconductor substrate, 2... Diffusion layer, 3
...Insulating film, 4...Ohmic electrode,
5...Moisture sensitive material, 6...19. Water permeable electrode, 7
...Extracting electrode, 8...Thermal oxidation #6i (
l JjlE, 9...CV D SsO
*@, 103.9. = CV D 8i0* membrane. 11...Resistor, 12...Comparison integration circuit,! 3- Pulse generation circuit for..., 14...
Differential multiplier, 15...Maximum value holding circuit, 16
・・・・・・Reset pulse circuit agent Patent attorney Kobu ■Tabe Figure 1 Figure 2

Claims (1)

[Claims] Semiconductor substrate (1): A diffusion layer provided on a part of the semiconductor substrate (1); Ohmic electrode (nodule) provided on a part of the diffusion layer; A cough insulating film and a water-permeable electrode 41 (f8) provided covering the moisture-sensitive material so as to sandwich the moisture-sensitive material to form a capacitance; and a water-permeable electrode provided on the insulating film; Connected unloading electrode (
7) An electrostatic sensing element consisting of.