JPH06138074A - Humidity detecting element - Google Patents

Abstract

PURPOSE:To stabilize a humidity detecting element for a long period by preventing the deterioration of the insulating property of an insulating film so as to prevent the occurrence of short-circuiting even when a pinhole exists in a humidity sensitive film interposed between an upper and lower electrodes. CONSTITUTION:A lower electrode 12, pad 12a for electrode of the electrode 12, and pad 15a for electrode of an upper electrode 15 are successively formed on a substrate 11 and, after forming an insulating film 13 on the surface of the electrode 12 and giving an insulating property to the film 13, a humidity sensitive film 14 and the upper electrode 15 are successively formed on the film 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type humidity detecting element using an organic polymer resin material as a moisture sensitive film, and more particularly to a contact structure between a lower electrode and a moisture sensitive film.

[0002]

2. Description of the Related Art Heretofore, this type of humidity detecting element has been constructed by laminating a thin film lower electrode, a moisture sensitive film made of an organic polymer resin material and a thin film upper electrode in this order on the surface of a substrate. The change in the capacitance value or impedance between the counter electrodes with respect to the relative humidity of the humidity sensitive film is detected as the change in humidity.

FIG. 3 is a plan view for explaining the structure of a conventionally proposed humidity detecting element of this type. In the figure, first, as shown in the plan view of FIG. 3A, after forming the thin film-shaped lower electrode 2, lower electrode connection terminal 2a and upper electrode connection terminal 4a on the surface of the substrate 1, Figure 3 (b)
As shown in FIG. 3, the moisture sensitive film 3 is formed on the insulating substrate 1 over the entire area except the connection terminal portion. Next, as shown in FIG. 3C, after extending the upper electrode 4 and the extending piece 4b of the upper electrode 4 on the moisture-sensitive film 3 over the upper electrode connection terminal 4a, the moisture-sensitive film 3 is formed as shown in FIG. As shown, the step portion of the moisture sensitive film 3 between the upper electrode connecting terminal 4a and the extending piece 4b is covered with the noble metal film 5 to make electrical connection, and then the upper electrode connecting terminal 4a and the lower electrode The lead wire 6 was connected to the side electrode connection terminal 2a, and a change in the capacitance value or impedance between the upper electrode 4 and the lower electrode 2 with respect to the relative humidity of the moisture sensitive film 3 was extracted as a change in humidity. Note that FIG. 4 is a partially cutaway perspective view of the humidity detecting element thus configured. The structure of this type of humidity sensitive element is disclosed in, for example, Japanese Patent Laid-Open No. 60-2.
It is proposed by No. 39657 and the like.

[0004]

However, in the humidity detecting element thus constructed, a metal thin film, a thick film or a bulk is used for the lower electrode 2,
If the surface of the lower electrode 2 is not subjected to an insulation treatment, the moisture-sensitive film 3 formed on the upper portion of the lower electrode 2 has an insulating property if a minute pinhole is present. There is a problem that the current is reduced, current leaks, and a short circuit with the upper electrode 4 occurs. Further, as a means for solving such a problem, there is a structure in which a silicon single crystal which is a material of the substrate 1 is used as the lower electrode 2 and a thermal oxide film is used as an insulating film to prevent the occurrence of the above-mentioned short circuit. Although proposed, such a structure constrains the substrate material,
The insulating film is also limited to SiO ₂ and the range of material selection is narrowed, so that there is a problem in that it cannot be optimally designed as a humidity detecting element. Further, there is a problem that the capacitance value changes depending on the applied voltage supplied between the lower electrode 2 and the upper electrode 4 and the measurement frequency, which makes it impossible to detect humidity with high accuracy. Further, as another means for solving such a problem, a structure has been proposed in which a corrosion-resistant metal such as Ta that can be anodized is used as the lower electrode 2, and an oxide is formed on the electrode surface by a wet process for insulation treatment. However, in such a structure,
Noble metals such as Pt, Au, and Pd cannot be used for the electrode material of the lower electrode 2, the range of material selection is narrow, and there is a problem that optimal design cannot be performed in terms of long-term stability.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide insulation between the upper electrode and the lower electrode even if a pinhole is present in the moisture sensitive film. The purpose of the present invention is to provide a humidity detecting element capable of realizing long-term stability by preventing deterioration of performance and occurrence of short circuit. Another object of the present invention is to select a substrate material, an electrode material, and a polymer resin material that have the best matching with each other, thereby expanding the design range and improving the reliability. It is to provide a detection element.

[0006]

In order to achieve such an object, the humidity detecting element according to the present invention is provided with a thin insulating film on the lower electrode.

[0007]

In the insulating film of the present invention, since the surface of the lower electrode is subjected to insulation treatment, even if minute pinholes are present in the moisture sensitive film interposed between the upper electrode and the lower electrode, Less likely to be affected.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1A and 1B are diagrams showing a configuration of an embodiment of a humidity detecting element according to the present invention. FIG. 1A is a plan view and FIG. 1B is a cross section taken along the line BB 'in FIG. 1A. Figure, Figure 1
FIG. 1C is a sectional view taken along the line CC ′ of FIG. In the figure, 11 is a substrate formed of, for example, non-alkali glass, thermally-oxidized silicon single crystal, quartz, sapphire, alumina, etc., and 12 is about 500 on this substrate 11.
For example, Pt deposited to a thickness of about 5000 Å,
The lower electrode 12a made of a noble metal such as Au or Pd is provided on the substrate 11 on the electrode pad forming region.
Lower electrode pad integrally formed by connecting with 2.
3 is a film thickness of about 100 to 10,000 on the surface of the lower electrode 12.
For example, AlO _x , Si deposited to a thickness of about Å
_{O X, SiN X, SiO X} N Y, TaO X, nitrides such as NbO _X, a thin film-shaped insulating film made of oxide, 14 thickness of about a thickness of about 1~10μm on the insulating film 13 A moisture-sensitive film made of an organic polymer resin material deposited on the substrate 14a is a step portion formed by processing the moisture-sensitive film 14 on the electrode pad forming region side in an inclined shape.

Further, 15 is a film thickness of 20 on the moisture sensitive film 14.
The upper electrode 15a formed in the range of 0 to 2000Å is an upper electrode pad of the upper electrode 15 formed in an island shape in the same step as the lower electrode 12 in the electrode pad forming region on the substrate 11, 15b. Part of the upper electrode 15 is the moisture sensitive film 1
4 is an extension part that covers a part of the inclined stepped portion 14a of FIG. 4 and extends integrally on the upper electrode pad 15a, and the extension part 15b is laminated on the upper electrode pad 15a. The upper electrode electrode terminal 16 having a two-layer structure is configured. Reference numeral 17 is a lead wire connected and fixed by solder 18 on the upper electrode electrode terminal 16 and the lower electrode pad 12a.

In such a structure, by providing the insulating film 13 having a film thickness of about 100 to 10000Å on the surface of the lower electrode 12, the surface of the lower electrode 12 that contacts the moisture sensitive film 14 is completely covered. Since insulation treatment is performed, even if there are pinholes in the moisture-sensitive film 14, the insulation of the moisture-sensitive film 14 is deteriorated, and the moisture-sensitive film 14 is electrically connected to cause a short circuit with the upper electrode 15. It is possible to obtain reliable electrical insulation without any occurrence of defects, and it is possible to reliably prevent the occurrence of initial insulation failure, short-circuit failure, etc. Therefore, the occurrence of insulation failure, short-circuit failure over time and long-term. However, the stability and reliability can be improved.

Further, in such a structure, the insulating film 1
3 is, for example, AlO _x , SiO _x , SiN _x , SiO _x N _y ,
TaO _X, nitrides such as NbO _X, by forming an insulating material comprising an oxide, depends on the combination of the polymeric resin material constituting the electrode material and the moisture sensitive film 14 made of a noble metal constituting the lower electrode 12 Without lower electrode 1
Since it becomes possible to insulate the surface of No. 2, the design margin can be greatly expanded.

Further, in such a structure, the insulating film 1
The case where the film thickness of 3 is formed in the range of 100 to 10000Å has been described. However, if this film thickness is less than 100Å, pinholes and the like are likely to occur, and a film having high insulation property should be formed on the lower electrode 12. And the film thickness is 1
When it exceeds 0000Å, internal stress of the insulating film is generated, and a film having no adhesion and no crack can be obtained. Therefore, by forming the film thickness of the insulating film 13 in the range of 100 to 10000Å, it is possible to obtain good matching with the electrode material and the polymer resin material and to secure the reliable insulating property.

FIG. 2 is a cross-sectional view of the steps for explaining an embodiment of the method of manufacturing the humidity detecting element according to the present invention. In FIG. 1, first, as shown in FIG. 2A, a substrate having a thickness of about 0.5 mm, which is made of an insulator such as alkali-free glass, quartz, sapphire, or alumina, or a semiconductor such as silicon single crystal with an oxide film. A metal layer consisting of at least one noble metal such as Pt, Au, Pd, etc. is formed on the electrode forming surface of No. 11 by vapor deposition or sputtering by 500-
It is deposited to a thickness of about 5000Å and patterned to simultaneously form the lower electrode 12, the electrode pad 12a (not shown) and the upper electrode pad 15a.

Next, as shown in FIG. 2B, on the surface of the lower electrode 12, for example, AlO _x , SiO _x , SiN _x ,
Insulating materials such as SiO _x N _y , TaO _x , NbO _x such as nitrides and oxides are deposited by vapor deposition, sputtering, ion plating or CVD method to 100 to 10,000.
A thin insulating film 13 is formed by depositing it to a thickness of about Å and patterning it by masking, lift-off or photolithography.

Next, as shown in FIG. 2C, the lower electrode 12 having an insulating film 13 formed on the surface thereof, and the electrode pad 12 thereof.
a and the upper electrode pad 15a formed on the substrate 11
A solution in which an oligomer is dissolved as an organic polymer resin material is dropped onto the above, and spin-coating by spin coating at a rotation speed of about 1000 to 5000 rpm, dip coating, or plasma polymerization is applied, and then dried.
Heat treatment is performed at ˜450 ° C. for 1 to 100 hours in a one-step or multi-step temperature profile. As a result, the oligomer is polymerized to form a stable moisture sensitive film 14 as a moisture sensitive material having a film thickness of about 1 to 10 μm.

Next, the moisture-sensitive film 14 thus formed
Is wet etching by photolithography,
By patterning by dry etching or lift-off method, the moisture sensitive film 14 in the electrode pad forming region on the substrate 11 is removed as shown in FIG. 2D, and the lower electrode pad 12a (not shown). And upper electrode pad 1
5a is exposed.

When patterning is performed by, for example, a dry etching method, as shown in FIG. 2D, an opening is formed in a portion for forming an electrode terminal made of non-alkali glass, quartz or sapphire on the moisture sensitive film 14. The mask 20 having a portion is disposed, and the moisture sensitive film 14 in the electrode pad formation region portion is removed by performing dry etching from above the substrate 11 from the direction of arrow A under the following conditions, and the lower electrode pad 12a ( (Not shown) and upper electrode pad 15
Expose a. Accordingly, the step portion 14 of the moisture sensitive film 14
a is formed with a smooth inclined surface. The dry etching conditions in this case are that the gas species is O ₂ , Ar, CF ₄ ,
Etc. were used alone or in combination, the pressure was 0.1 to several Torr, and the high frequency output was 100 to 500 W.

Next, after removing the mask 20 on the moisture sensitive film 14, Au, P are formed on the substrate 11 as shown in FIG.
Moisture-sensitive film is formed by depositing a metal such as t or Pd having high corrosion resistance and moisture permeability under the following conditions to a thickness of about 100 to 2000Å by vapor deposition, sputtering or ion plating, and patterning. 14,
The upper electrode 15 is formed over the inclined step portion 14a of the moisture sensitive film 14 and the main surface of the upper electrode pad 15a. As a result, the extending portion 15b of the upper electrode 15 is laminated on the upper electrode pad 15a, and the upper electrode connecting terminal 16 having a two-layer structure is formed.

Next, the upper electrode 1 thus formed
In FIG. 5, the upper electrode 15 is set to an electrode area that secures a predetermined capacitance value by irradiating a laser from above as shown by the arrow A direction and performing patterning by trimming as shown in FIG. be able to. Further, the capacitance value can be arbitrarily set by trimming the moisture sensitive film 13 simultaneously with the trimming of the upper electrode 15. Further, instead of trimming the upper electrode 15 by laser irradiation, trimming by mechanical peeling such as scratching can be performed, and the same effect as described above can be obtained.

According to such a method, by performing trimming by laser irradiation or mechanical peeling, it is possible to manufacture a large number of compatible elements having substantially constant capacitance values without any problem in terms of quality and reliability.

According to this method, the upper electrode connection terminal 15 has a two-layer structure in which the extended portion 14b of the upper electrode 14 is formed on the upper electrode pad 14a.
Since it can be formed by a series of steps that are formed in the same step as the step of forming No. 4, the manufacturing process can be simplified and the productivity can be improved.

Further, according to such a method, the moisture sensitive film 1
Since the alignment with the reference point of the substrate 11 becomes extremely easy by using the mask 20 when performing the dry etching on the No. 4, it is possible to process a plurality of wafers at a time with high positional accuracy in a batch process. It is possible to improve the sex.

Further, according to such a method, the moisture sensitive film 1
By using dry etching for the pattern processing of No. 4, there is no contact with the resist solution of the moisture-sensitive film 14 and its stripping solution, and no contact with dust or the like due to the processing.
The moisture sensitive film 14 having a clean surface is obtained.

Further, according to such a method, the moisture sensitive film 1
Since the step portion 14a of No. 4 is formed to have a smooth inclined surface, the extending portion 15b of the upper electrode 15 is formed on the moisture sensitive film 14
Are formed in close contact with each other along the inclined surface of the stepped portion 14a, and a thin film is formed on the smooth inclined surface. Therefore, a steep polymer step is not formed, so that step coverage is improved and a short circuit or the like does not occur. .

According to such a method, the upper electrode 15 has good adhesion to the moisture sensitive film 14, and therefore the upper electrode 1
Since the adhesive strength in the vicinity of the step portion 14a of the moisture sensitive film 14 of No. 5 and the mechanical strength can be improved, peeling or the like can be eliminated.

[0026]

As described above, according to the present invention,
Since a thin insulating film is provided on the lower electrode and the surface of the lower electrode is insulated, minute pinholes exist in the moisture sensitive film interposed between the upper electrode and the lower electrode. However, since it is hardly affected by this, neither insulation failure nor short-circuit failure will occur over time and in the long term, stable quality and reliability can be obtained for a long time, and various insulation films can be obtained. It is not affected by the combination of the substrate material, electrode material, and polymer resin material, and it is possible to select and combine the ones with good matching. It has an extremely excellent effect such as being obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a humidity detecting element according to the present invention.

FIG. 2 is a cross-sectional view of a manufacturing process illustrating an embodiment of the method of manufacturing the humidity detecting element according to the present invention.

FIG. 3 is a plan view of a manufacturing process illustrating a conventional method for manufacturing a humidity detecting element.

FIG. 4 is a perspective view showing a configuration of a conventional humidity detecting element.

[Explanation of symbols]

 11 Substrate 12 Lower Electrode 12a Lower Electrode Connection Terminal 13 Insulating Film 14 Moisture Sensitive Film 14a Step Part 15 Upper Electrode 15a Upper Electrode Connection Terminal 15b Extension 16 Upper Electrode Electrode Terminal 17 Lead Wire 18 Solder 20 Mask

Claims (3)

[Claims] 1. A humidity detecting element in which a lower electrode, a moisture sensitive film made of an organic polymer resin material and a moisture permeable upper electrode are sequentially laminated on a substrate, wherein an insulating film formed as a thin film on the lower electrode. A humidity detecting element characterized by being provided. 2. The AlO film formed on the insulating film according to claim 1.
_X , SiO _X , SiN _X , SiO _X N _Y , TaO _X , NbO _X
A humidity detecting element characterized by using. 3. The humidity detecting element according to claim 1, wherein the thickness of the insulating film is in the range of 100 to 10000Å.