JPH02129901A - Positive temperature coefficient thin film thermistor - Google Patents

Abstract

PURPOSE:To realize a compact element without requiring a large area by forming an electrode on one or both sides of a flat supporting substrate and by applying and forming a barium titanate composition thin film to the one side. CONSTITUTION:An Ni layer 2 is formed on one or both sides of an n-Si substrate 1 through electroless plating, EB deposition, ion plating, etc., and Au or Pt 3 is deposited thereon to secure an ohmic contact. Metal alkoxide solution which is adjusted to a specified concentration is dropped to one side of the substrate 1. A thin film containing an element which constitutes barium titanate composition such as Ti, Ba, Sr is formed through a spin coat method, etc., and a ceramic semiconductor of a barium titanate composition thin film 4 is acquired by firing it. An electrode 5 such as Ni, Au, Pt is formed thereon through a similar means. A small-sized element can be thereby acquired without requiring a large area.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a positive characteristic (PTC characteristic) thermistor whose electrical resistance increases significantly when the Curie temperature is exceeded, and in particular to a film of a barium titanate-based composition. This invention relates to a PTC thin film thermistor that is a thin film.

[Conventional technology]

Conventionally, in semiconductor ceramic materials made by adding rare earth elements such as Y, La, and Dy or transition metal elements such as Nb and Ta to barium titanate and firing them in the atmosphere at 1200 to 1400°C, the electrical resistance value at the Curie point is It is known that it exhibits a so-called PTC characteristic that increases suddenly. Heaters, temperature sensors, and the like have been manufactured using this characteristic. In addition, by partially replacing Ba sites with Sr, the Curie point can be shifted to the lower temperature side.
By replacing it with pb, the Curie point can be shifted to the high temperature side, and can be arbitrarily changed to some extent within the range of -30°C to 300°C.

[Problem to be solved by the invention]

However, conventional PTC thermistors employ a method in which oxides of constituent elements such as Ti and Ba are mixed to a predetermined concentration and then fired, which inevitably results in a large thickness. Therefore, the resistance value at room temperature is large, and when making an electric circuit, this problem has been addressed by increasing the area and lowering the resistance. Therefore, if a PTC thermistor can be made thinner, the device can be made smaller without taking up a large area. In addition, the current used was small, and there were many expectations from a practical standpoint.

[Means to solve the problem]

That is, the present invention is a characteristic thin film thermistor characterized in that electrodes are formed on one or both sides of a flat support substrate, and a thin film of a barium titanate-based composition is further coated on one side.
Moreover, the thickness of the barium titanate-based composition thin film is 0.005 to 5.
It is a positive characteristic thin film thermistor with a positive characteristic of
a, 5rSS i, sb, Mn; or T t,,
Consisting of Ba, Sr, S tSDy, and Mn, the composition ratio is Ba=1-0.5.5 when the number of Ti atoms is 1.
r=O~0.5, and Ti/(Ba+Sr) is 1.0
02 to 1.015, and St, Sb, Dy=0.0005 to 0.005, Mn=
A positive characteristic thin film thermistor in which the barium titanate composition is in the range of 0.0001 to 0.001, and a positive characteristic thin film thermistor in which a barium titanate-based composition is formed by coating and firing a uniform solution or uniform dispersion of each metal alkoxide. , and is also a positive characteristic thin film thermistor in which a uniform solution or dispersion of a metal alkoxide is applied by spin coating.

That is, the basic concept of the present invention is to form a thin film on a flat support substrate, preferably by applying a uniform solution or dispersion of various metal alkoxides, preferably by a spin coating method, and then baking this. This method produces a thin film device exhibiting excellent PTC characteristics.

[Detailed disclosure of the invention]

The present invention will be explained in detail below.

In the present invention, a relatively inexpensively available Si substrate, AItos substrate, Stow substrate, or the like is used as the flat support substrate. Further, when using a back electrode, a low resistance Si substrate is suitable.

The metals forming the barium titanate composition are Ti, B
a, Sr, S f, SbSMn; or Ti, Ba
, Sr, S t, and DySMn, the composition ratio of which is T
When the number of i atoms is 1 (hereinafter, the amount of metal used is T
(indicates the valence when the number of i atoms is 1), Ba=1-0.5.5r=O~0.5, and Ti/(
Ba+Sr) is in the range of 1.002 to 1.015,
Also, Si, Sb, Dy=0.0005 to 0.005, Mn=
It is in the range of 0.0001 to 0.001(7).

The barium titanate composition can be made into a thin film by coating, preferably by spin coating, a uniform solution or dispersion of alkoxides such as methoxide, ethoxide, propoxide, butoxide of each of the metals mentioned above. Ru. The thin film obtained at this time is kept at a relatively low temperature, e.g.
It can be fired for about 2 to 20 hours at a temperature of about 0 to 200°C, resulting in a semiconductor ceramic made of a barium titanate composition.

Ceramic semiconductors obtained by conventional sintering and firing of oxide powder generally have a considerably large particle size, and when made into a thin film, particle size growth occurs and does not exhibit sufficient performance. Use trace amounts of additives. As a result of various studies on additives, we found that Si is 0.0005 to 0.0 relative to Ti as suitable for this purpose.
The particle size can be reduced by adding 0.05, preferably 0.001 to 0.01. This is based on new findings that we have discovered.

Furthermore, by making the film thickness sufficiently thin and adding 0.001 to 0.01 sb to Ti, the resistance value at room temperature can be reduced. Note that by adding Mn, a steep resistance temperature characteristic and a resistance temperature change rate of 10%/'C or more can be obtained.

In the present invention, the minimum film thickness exhibiting PTC characteristics is 0.
．． 005 μm, and when thinning the film by spin coating, the maximum film thickness of 5 μm is required due to film uniformity and operability.
It is about μm. The barium titanate composition layer has a thickness of 5 μm.
It was confirmed that a thin film thermistor exhibiting sufficient PTC characteristics could be obtained even if the following conditions were used. In addition, especially when trying to obtain stable characteristics, a film thickness of 0.1 to 1 μm is preferable.

(Embodiment) Specific examples of embodiments of the present invention will be explained below with reference to the drawings. In FIG. Au or Pt3 is formed on the proboscis.
is deposited to ensure ohmic contact. In addition,
When electroless plating is performed using such a substrate, N
A metal alkoxide solution prepared to a predetermined concentration is dropped onto one side of this substrate, and titanium such as Ti, Ba, Sr, etc. A thin film containing elements constituting the barium acid composition is formed and fired to obtain a barium titanate composition thin film 4 which is a ceramic semiconductor. Furthermore, an electrode 5 of Ni, Au, Pt, etc. is formed thereon by the same means as described above, and the PTC of the present invention is
This is an Ei film thermistor-mister element.

〔Example〕

Further, more specific embodiments will be explained with reference to Examples.

(Example 1) Mirror-finished n-3i substrate (specific resistance 0.005Ωcm)
Commercially available electroless N1-P plating was performed. This was annealed for 1 hour at 750'C in N2 gas containing 5% H2 to form a Ni layer of about 1 .mu.m which brought the coating layer closer together. Furthermore, after electroless plating with NiP, Au was formed on one side by a vacuum method to a thickness of 0.1 μm μm, and then Ti/Ba/S r was formed on the Au.
/ S i / S b / M n is 110.836
10.16,10.00110.00110.0002
Each isoroboxide was prepared by dissolving it in isopropyl alcohol and then added dropwise to form a thin film of 200 (0.02 μN) by spin coating. This was heated to 800'C at a rate of 180'C/hr.
After raising the temperature to 30℃/hr, leave it for about 5 hours.
Cool down to room temperature at a rate of Au vapor deposition was performed on the obtained barium titanate composition to form an electrode.

(Example 2) Mirror-finished n-3i substrate (specific resistance 0.005 Ωcm)
Then, Ni evaporation and Pt evaporation are performed to form a lower electrode layer each having a thickness of 0.1 μm. Then, T i / on pt
B a / S r / S i / D y / M
n is 110.83610.1610.00110.0
0110.0002 was prepared by dissolving each isorboxoxide in isopropyl alcohol, and a thin film of 200 layers (0.02 μm) was formed by spin coating. This was heated to 1000°C at a rate of 180°C/hr, left for about 5 hours, and heated to 30°C.
The temperature is lowered to room temperature at a rate of °C/hr. PT vapor deposition was performed on the obtained barium titanate composition to form an electrode.

[Effect]

In Example 1, the resistance was measured as a function of temperature 2 using a sandwich-type electrode with the Ni layer on the back surface of the Si substrate as one electrode, and the PTC characteristics were evaluated. In addition, in Example 2, 7
Similar evaluations were performed using a Brunner type electrode. The results showed typical PTC characteristics as shown in Figure 2, and it was confirmed that the product was sufficient for use as a PTC thin film thermistor.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a specific example of an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between temperature and resistance value of an element in an example of the present invention. In the figure, 1n-3i substrate, ZNi layer, 3...Au or PT layer, 4--barium titanate based composition, 5Ni, Au or PT electrode are shown.

Claims (5)

[Claims] (1) A positive characteristic thin film thermistor characterized in that an electrode is formed on one or both sides of a flat support substrate, and a thin film of a barium titanate composition is further coated on one side. (2) Thickness of barium titanate-based composition thin film is 0.00
The positive characteristic thin film thermistor according to claim 1, which has a diameter of 5 to 5 μm. (3) The metal forming the barium titanate composition is T
i, Ba, Sr, Si, Sb, Mn; or Ti, B
a, Sr, Si, Dy, and Mn, whose composition ratio is T
When the number of i atoms is 1, Ba=1 to 0.5, Sr=
0 to 0.5, and Ti/(Ba+Sr) is 1.002
-1.015, and Si, Sb, Dy=0.0005-0.005, Mn=
2. The positive characteristic thin film thermistor according to claim 1, wherein the positive temperature coefficient is in the range of 0.0001 to 0.001. (4) The positive characteristic thin film thermistor according to claim 1, wherein the barium titanate composition is formed by coating and firing a uniform solution or dispersion of each metal alkoxide. (5) The positive characteristic thin film thermistor according to claim 4, wherein a uniform solution or dispersion of the metal alkoxide is applied by spin coating.