JPH01163648A - Humidity sensing element and its manufacture - Google Patents

Abstract

PURPOSE:To make a humidity-sensitive material thin and to eliminate thermal deterioration by outputting variation in electric characteristics of a humidity sensing material film corresponding to external humidity variation through a bonding pad provided to each electrode. CONSTITUTION:An upper gold electrode 24 is filmed on the humidity sensing film 23 of 1-2mum in film thickness every thinly to hundreds of Angstrom so as to increase permeability to moisture, etc. This electrode 24 is formed by vapor deposition, etc., so a lead-down electrode united with the side taper part of the film 23 is formed simultaneously with the formation of the electrode 24. If moisture which is an external factor permeates the upper gold electrode 24 and is absorbed by the humidity sensing film 23, the dielectric constant varies, but this variation is outputted in the form of variation of an electric signal through bonding pads 22a and 24a as variation in the electrostatic capacity between the upper gold electrode 24 and a lower gold electrode 22, so that an external detecting circuit detects the humidity.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention detects changes in humidity in an external atmosphere using a material whose dielectric constant or electrical properties such as permittivity change depending on humidity. The present invention relates to a moisture sensitive element and a method for manufacturing the same.

(Prior Art) For example, there are conventional humidity sensing elements shown in FIGS. 4 and 5 used for sensing humidity in air conditioners and the like.

The device shown in FIG. 4 has a lower gold electrode 2 on a moisture-sensitive device substrate 1.
, a moisture-sensitive film 3 made of an organic material whose dielectric constant changes with changes in humidity, an upper gold electrode 4, and bonding parameters 1 to 6 and 6 for connecting the upper gold electrode 4 to an external circuit. It consists of a grater electrode 5.

In this humidity-sensitive element, the humidity-sensitive film 3 senses changes in external humidity through the upper gold electrode 4. Therefore, the upper gold electrode 4 is made as thin as several hundred amperes to allow moisture to pass through it as easily as possible. . In addition, the humidity sensitive film 3 has a thickness of about 1 to 2 μm in order to obtain sufficient dielectric capacity and stable humidity sensing ability, and therefore, as shown in the figure, the pull-down electrode 5 has to cross a considerable level difference. It is necessary to reach the bonding pad 6. Therefore, if the pull-down electrode 5 is thin, cracks are likely to occur on the sides of the moisture-sensitive membrane 3, and therefore the pull-down electrode 5 must have a thickness equal to or greater than that of the moisture-sensitive membrane 3.

The device shown in FIG. 5 consists of two independent ICs on a moisture-sensitive substrate 1.
A lower gold electrode 1.12 and a humidity sensitive film 13 are formed, and the humidity sensitive film 1
3. An extremely thin upper gold electrode 14 similar to the device shown in FIG.
The structure is coated with

In this device, unlike the device shown in FIG. 4, the upper gold electrode 1/'l does not function as a capacitance extraction electrode, but rather increases the capacitance between the upper and lower electrodes 11-14 and 14-12, respectively. The composite capacitance is taken out between the lower gold electrodes 11 and 12.

(Problems to be Solved by the Invention) The conventional moisture-sensitive elements as described above each have the following problems.

First, in the device shown in FIG. 4, it is necessary to form the downtrend electrode 5 quite thickly, so that the moisture sensitive film 3 is exposed to high temperature for a long time when the electrode is formed by vapor deposition or sputtering. However, since the moisture-sensitive film 3 is made of an organic material that is relatively heat-resistant, it is likely to deteriorate when exposed to high temperatures for a long period of time. Furthermore, due to the difference in linear expansion coefficient between the drawer electrode 5 and the moisture-sensitive element substrate 1, stress is generated between the two during high-temperature heating, which tends to cause cracks and the like, resulting in failure. Generally speaking, since ordinary humidity sensing elements are intended to be used in particularly humid places, gold, which is resistant to corrosion, is used for the electrodes, but since the drawer electrode 5 is quite thick, a large amount of expensive gold is used. This is a major cause of high costs.

Since the device shown in FIG. 5 does not require a grater electrode, many of the problems described above are overcome. However, as mentioned above, this element extracts the capacitance change of the moisture sensitive membrane 13 by connecting two capacitors in series between the electrodes 11-14 and 1/1-12, and therefore Compared to the one shown in Figure 4, the output efficiency is less than half that for the same area of the moisture-sensitive membrane.

This invention overcomes the above-mentioned problems with conventional moisture-sensitive elements, has low manufacturing costs,
The object of the present invention is to provide a high-output moisture sensing element with excellent moisture sensing ability and stable characteristics, and an effective manufacturing method thereof.

[Structure of the Invention] Means for Solving Problems) In order to solve the above problems, the moisture sensitive element of the present invention includes an insulating substrate, a lower gold electrode formed on the insulating substrate, and a lower gold electrode formed on the insulating substrate. , a moisture-sensitive material film formed relatively thickly on the lower gold electrode and having tapered side edges; and a moisture-sensitive film having a thin enough thickness to allow moisture to pass through from the outside. an upper gold electrode having a thickness that maintains sufficient conductivity and covering the upper surface of the moisture-sensitive material film and the tapered side surface and further extending onto the insulating substrate; The gist of the present invention is to have as constituent elements a bonding pad formed on a portion extending on an insulating substrate and connected to an external circuit.

The present invention further provides a manufacturing method for forming a humidity sensitive element whose electrical characteristics change in response to changes in external humidity, comprising: forming a lower gold electrode on an insulating substrate; forming a moisture-sensitive material film by coating the lower gold electrode with a material that changes its electrical characteristics in response to changes in external humidity; one end of the moisture-sensitive material film is tapered; forming a relatively thin metal film having a shape; using the metal film as a mask for buttering, etching the moisture-sensitive material film by applying 02 ash to form a taper at the side edges thereof; removing the metal mask after the edge puffing process; and depositing or sputtering a pot on the moisture-sensitive material after removing the metal mask to form a thin upper gold electrode extending over the tapered portion and the insulating substrate. The gist of the manufacturing method is to form a bonding pad on a part of the lower gold electrode and a part of the upper gold electrode extending on the insulating substrate, respectively.

<Function> In the moisture-sensitive element of the present invention, the side end portion of the moisture-sensitive material film provided between the upper and lower gold electrodes is configured to be tapered, so that the gold electrode extending into this tapered portion is The electrode does not break due to the difference in level between the upper gold electrode and the upper gold electrode. Therefore, the upper gold electrode, including this tapered part, can be made extremely thin, and the thick draw-down metal electrodes used in conventional elements are not required. No deterioration of the membrane occurs. Therefore, variations in characteristics between elements during manufacturing are prevented, and manufacturing yield and reliability are improved.

In addition, in the manufacturing method, a metal mask with tapered side edges is placed on the moisture-sensitive material film, and the difference in oxygen permeability depending on the thickness of the metal mask is used to create the sensitivity using the 02 asher. When etching a wet material film, the etching speed varies depending on the thickness of the metal mask, so as a result, one end of the moisture sensitive material film is etched into a tapered shape. A film of moisture sensitive material is formed having side edges of the shape.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a moisture sensitive element according to an embodiment of the present invention. In the figure, 21 is an oxide layer 2 on the silicon substrate surface.
22 is a lower gold electrode having a bonding pad 22a, 23 is a moisture sensitive film formed with one side tapered, and an organic moisture sensitive material is attached to the substrate 21 by a spin cord. , is formed by coating on the electrode 22. 24 is the upper gold electrode, J shown in the figure is the side tapered part of the sea urchin moisture sensitive film 23 and the substrate 21-
It is formed over the entire length of the electrode, and is integrally formed with a so-called pull-down electrode. Note that 24a is a bonding pad for connection with an external circuit.

In the above configuration, the upper gold electrode 24 is formed of a thin film of several hundred layers in order to increase the transmittance of humidity and the like, whereas the moisture sensitive film 23 normally has a film thickness of 1 to 2 μm. This electrode 23 is generally formed by vapor deposition or sputtering, and therefore, the pull-down electrode integrally formed on the side tapered portion of the membrane 23 can be easily formed at the same time as the electrode 24 is formed.

In this element, moisture, which is an external factor, passes through the upper gold electrode 24 and is absorbed by the moisture sensitive film 23, causing a change in its dielectric constant. This change is caused by the upper gold electrode 24 and the lower mold 4@
The change in the capacitance (a) that is applied between the two is outputted as a change in an electrical signal via the bonding pads 22a and 24a, and the humidity is detected by an external detection circuit.

FIGS. 2 and 3 are diagrams showing the manufacturing process of the above-mentioned first embodiment element of the present invention. Next, the structure of the device of the present invention will be further clarified while explaining the manufacturing process with reference to the drawings.

In the manufacturing process shown in FIG. 2, first J:
An oxide film 21a is formed on the surface of the silicon substrate 21,
Furthermore, a lower gold electrode 22 is provided thereon.

Thereafter, as shown in Figure (b), a moisture sensitive material made of an organic substance is applied onto the lower gold electrode 22 by spin coating. The thickness of the moisture sensitive material P31-film 25 is 1 to 2 μm. Next, on a part of the moisture-sensitive material film 25, metal such as A1 is vapor-deposited in multiple layers in stages so that the side edges are tapered as shown in Figure (C). The thickness of this metal film 26 is about 500 at most, and the position where the taper is formed corresponds to the position where the taper is formed on the moisture sensitive film. After the metal film 26 with stepped side edges is formed in this way, the moisture-sensitive material film 25 is etched using the metal film 26 as a mask. At this time, the transmittance of the metal mask to oxygen (02) differs depending on the film thickness, and the thinner the metal mask, the faster the etching rate.As a result, the moisture-sensitive film 25 is patterned, and as shown in FIG. A moisture sensitive film 23 having tapered ends is formed. After that, as shown in Figure (1), the metal mask 26 is removed, and a gold electrode 24 on the moisture sensitive film is formed by vapor deposition or sputtering of gold (Figure e).
.

At this time, a gold electrode 24b simultaneously covers the side of the moisture sensitive film 23 and reaches the position where the bonding pad 24a is formed.
is formed. The thickness of the upper gold electrode 24 is thin enough to maintain sufficient permeability to the moisture-sensitive membrane 23 for moisture, etc., and also thick enough to maintain sufficient conductivity. good.

In the manufacturing method shown in Figure 3, Figures (a) and (b)
The process of forming the moisture-sensitive material film 25 on the lower gold electrode 22 shown in FIG. 2 and the process of forming the upper gold electrode on the etched moisture-sensitive film 23 shown in FIGS. This is the same manufacturing method as shown in FIG. On the other hand, in this manufacturing method, in the process of forming the metal mask 26 shown in FIG. This method differs from the manufacturing method shown in FIG. 2 in that a taper is formed at the side end portion of the metal mask 2C for film patterning.

In the above example, a silicon substrate on which an oxide film is formed is used as the substrate of the moisture-sensitive element, but it is of course possible to use an insulating substrate such as glass.

Further, although the above-mentioned moisture-sensitive material film changes its dielectric constant in response to external moisture, it may also change its conductivity.

[Effect of the Invention 1] As explained above with reference to the embodiments, in the moisture-sensitive element of the present invention, the moisture-sensitive film 83 sandwiched between the upper and lower gold electrodes has a tapered side end surface. In this case, there is no fear of electrode breakage, and manufacturing yield and reliability can be improved.

Furthermore, the electrode over this tapered portion is formed at the same time as the upper gold electrode, and can be made extremely thin (same thickness as the upper gold electrode). Therefore, there is no thermal deterioration of the moisture-sensitive material due to the formation of extremely thick pull-down electrodes as in the case of conventional elements, and variations in electrical characteristics among the elements do not occur, improving manufacturing yield. In addition, there is no increase in cost due to the formation of thick gold-plated electrodes, and since the dielectric capacity can be increased by the area of the moisture-sensitive film, a high-output device can be obtained.

In addition, in the method of manufacturing the device of the present invention, etching is performed using a 02 asher using a metal mask with tapered side edges, taking advantage of the fact that the oxygen permeability varies depending on the thickness of the metal film. Therefore, it is possible to easily form a moisture-sensitive material film having a tapered shape at the negative end.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the moisture-sensitive element according to the present invention, FIG. 2 is a process diagram showing an example of the manufacturing process of the element shown in FIG. 1, and FIG. 3 is the same as shown in FIG. 1. FIGS. 4 and 5 are process diagrams showing other examples of the manufacturing process of the device, and are cross-sectional views showing conventional examples of the moisture-sensitive device. 21...Silicon substrate 21a...Oxygen film 22...
・Lower gold electrode 23...@Wet material film 24...Upper mold 4#A 25...Moisture sensitive material layer 26...Metal mask

Claims (2)

[Claims] (1) An insulating substrate, a lower gold electrode formed on the insulating substrate, and a material made of a substance whose electrical characteristics change in response to changes in external humidity; a moisture-sensitive material film formed relatively thickly with tapered side edges, and a thickness that is thin enough to allow moisture from the outside to pass through the moisture-sensitive material film and maintain sufficient conductivity. an upper gold electrode formed to cover the upper surface of the moisture-sensitive material film and the tapered side surface and further extend onto the insulating substrate; and an insulating substrate on the lower gold electrode and the upper gold electrode. a bonding pad formed on each of the upwardly extending portions and connected to an external circuit, and a bonding pad provided on each of the electrodes to change the electrical characteristics of the moisture-sensitive material film in response to changes in external humidity. A moisture sensing element characterized by outputting through. (2) A manufacturing method for forming a humidity-sensitive element whose electrical characteristics change in response to changes in external humidity, the method comprising: forming a lower gold electrode on an insulating substrate; A step of forming a moisture-sensitive material film by coating a gold electrode with a material whose electrical characteristics change in response to changes in external humidity; and forming a tapered end on one side of the moisture-sensitive material film. A process of forming a relatively thin metal film, and using the metal film as a mask for patterning.
_2 A step of etching the moisture-sensitive material film by applying an asher to form a taper at its side edge; a step of removing the metal mask after the etching step; and a step of removing the moisture-sensitive material after removing the metal mask. forming a thin upper gold electrode extending over the tapered portion and the insulating substrate by depositing or sputtering gold on the film; and a portion of the upper gold electrode extending over the tapered portion and the insulating substrate. 1. A method for manufacturing a moisture-sensitive element, comprising: forming a bonding pad on each portion.