JPH0258801A - Platinum resistance thermometer and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a platinum thermistor made of a thin platinum film and having a high resistance temperature coefficient by forming the platinum film on an insulating film of a different kind of material formed on the surface of a substrate and forming the insulating film of zirconium oxide. CONSTITUTION:After a ZrO2 film 12 is formed on the surface of an Al2O3 substrate 11 heated to 250 deg.C by evaporating Ti by a reactive ion plating method, a platinum film 13 having a thickness of 0.4-1.6mum is produced on the surface of the film 12 by vacuum deposition or sputtering. After patterning the platinum film 13 to a desired form, the film 13 is subjected to heat-treatment at 900-950 deg.C and resistance value adjustment by trimming. Then the substrate 11 is devided into pieces and lead wires 14 are connected to each piece. Therefore, a platinum film which is thinner in thickness and higher in stable resistance temperature coefficient than the conventional example can be obtained and the using quantity of highly expensive platinum can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a temperature sensing resistor whose main component is platinum, which is used as a temperature sensor, and a method for manufacturing the same.

Conventional technology Platinum has long been used as a temperature sensor material because it is chemically stable and easy to obtain with high purity, and its electrical resistance has a large temperature dependence (temperature coefficient of resistance = TCR). ing. An ultra-fine platinum wire wound spirally around an insulator such as mica and inserted into a protective tube is widely used as a resistance temperature detector, and its specifications are specified in detail in JISC-1604. Although this type of platinum resistor has high precision, ■ it has weak mechanical strength.

■ Due to its structure, it takes time to manufacture.

■ Large shape.

■ It is expensive.

It had many drawbacks.

Temperature measuring resistors using thick or thin film platinum that eliminate these drawbacks have been actively developed in recent years, and some are commercially available. However, because thick-film platinum resistance thermometers are manufactured using screen printing technology, it is difficult to produce fine patterns of 100 μm or less, and there are large manufacturing variations.Due to the material composition, it is difficult to obtain high TCR characteristics. have.

On the other hand, the thin film platinum resistance thermometer is (1) a metal with a composition of 100%, and has high TCR characteristics.

■ Since the pattern can be easily miniaturized, miniaturization can be achieved, and high sensitivity can be achieved by increasing the resistance.

■ Strong mechanical strength.

■ Wafer processing can reduce variations, making it suitable for mass production and reducing costs.

It has the following advantages.

As a method for manufacturing a resistance temperature sensor using thin film platinum, first,
A platinum thin film with a thickness of several thousand angstroms is produced on an insulating substrate by vacuum evaporation, sputtering, etc., and then finely patterned by wet etching, dry etching, etc. It is common to perform high temperature heat treatment at ℃. Thereafter, the resistance value is adjusted by trimming, chipping is performed, and lead wires are attached to form a resistance temperature detector.

However, the temperature coefficient of the platinum thin film produced by such a method varies greatly depending on the heat treatment conditions, and heat treatment at a high temperature is required to make the resistance temperature coefficient equivalent to that of the bulk material. Possible reasons for this are as follows.

That is, among the characteristics of such a thin film as a material, size effects and structural defects are among those that greatly affect the physical properties. The size effect is an effect that appears on the so-called electron transport phenomenon, which is caused by an effective reduction in the mean free path of electrons due to inelastic scattering of electrons in a thin film.

The effect becomes particularly noticeable when the film thickness is equal to or less than the mean free path of electrons.

In addition, the thin film formation process often involves rapid agglomeration from a gas layer to a solid layer in a space where gas molecules and ions, more or less unrelated to the thin film substance, exist. Various structural defects inherent in crystals such as vacancies, interstitial atoms, various dislocations, lattice defects, and grain boundaries are introduced, and foreign atoms and molecules are mixed in as impurities, causing electron scattering. Due to these effects, characteristics such as the specific resistance of the thin film become larger than that of the bulk appear, and therefore the temperature coefficient of resistance of the platinum thin film becomes lower than that of the bulk.
This causes the sensitivity of the resistance temperature detector to decrease.

In order to improve this, heat treatment is performed as described above in the manufacturing process of platinum resistance temperature detectors, but the thickness of the produced platinum film is 1 μm.
m or less, if the heat treatment temperature exceeds 11oo'C, the platinum film will aggregate during the heat treatment, forming an island-like non-uniform film, etc.
Characteristics as a resistance temperature sensor could not be obtained.

Therefore, in order to stably obtain a high temperature coefficient of resistance, the thickness of the platinum film must be 1 μm or more, and it has not been industrially satisfactory to produce a thick layer of platinum, which has a high unit cost.

Problems to be Solved by the Invention It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a platinum resistance thermometer having a thin platinum film and a high temperature coefficient of resistance.

Means to solve problems The inventors have developed a type of supporting substrate that produces platinum films.

After examining various structures, we discovered that by forming a 2102 layer on the surface of the substrate, the platinum film formed on the surface can obtain a high temperature coefficient of resistance with a thinner film than in the case of other substrate materials. It is something.

Effect Table 1 shows the crystallinity of the platinum film formed on the ZrO2 layer formed on the Al2O substrate and the platinum film formed directly on the Aβ205 substrate after heat treatment according to the present invention using X-ray diffraction method. The results are shown below.

As shown in Table 1, the platinum film produced on the substrate of the present invention has a strong peak intensity on the (111) plane and a small half-width, indicating that it has a high orientation. As described above, according to the present invention, the crystallinity of the platinum film increases during heat treatment due to the influence of the substrate material, and as a result, the TCR characteristics are improved.

(Space below) Table 1 Analysis results of platinum thin film by X-ray diffraction method (after heat treatment) Examples The present invention will be specifically described below with reference to the drawings.

(Example-1) Figure 1 is a cross-sectional view of a platinum resistance temperature detector showing the first example of the present invention, and Figures 2e) to (0) show the manufacture of the resistance temperature detector shown in Figure 1. FIG. 3 is a cross-sectional view at a stage.

Mu71!20. heated to 260℃. A pressure of 3×105 (
Torr), Ti was evaporated by electron beam heating in an oxygen:argon mixed atmosphere with a partial pressure ratio of 1:1, and the temperature was approximately 1μ.
After forming the ZrO2 film 12 of 0.4 to 1.0 m (Fig. 2 &), its surface is coated with a film of 0.4 to 1.0 m by vacuum evaporation or sputtering.
A platinum film 13 of 6 μm is produced (FIG. 2b).

After patterning the platinum film 13 into a desired shape (FIG. 2C)
), heat treatment is performed at 900 to 950'C, and after adjusting the resistance value by trimming, it is divided into individual pieces, and the lead wires 14 are connected.

(Example 2) FIG. 3 is a sectional view of a platinum resistance temperature detector showing a second example of the present invention.

As in Example-1, the surface of the Mu1203 substrate 110 heated to 250'C was subjected to electron beam heating in an oxygen:argon mixed atmosphere with a pressure of 3X10 (Torr) and a partial pressure ratio of 1=1 using the reactive ion blating method. pTi by law
After evaporating and forming a ZrO2 film of about 1 μm,
The surface is coated with 0.0% by vacuum evaporation method or sputtering method.
After generating the platinum film 13 with a thickness of 4 to 1.6 μm, the platinum film 13
is patterned into a desired shape together with the ZrO2 layer 12, and
Heat treatment is performed at 00 to 950°C, and after adjusting the resistance value by trimming, it is divided into individual pieces, and lead wires 14 are connected.

(Comparative Example) FIG. 4 is a sectional view of a platinum resistance temperature detector showing a comparative example of the present invention.

The surface of the λ6205 substrate 11 used in Examples 1 and 2 was coated with a thickness of 0.4 to 1.6 μm by vacuum evaporation or sputtering.
After forming a platinum film 13 and patterning the platinum film 13 into a desired shape, heat treatment is performed at 900 to 960'C, and after adjusting the resistance value by trimming, it is divided into individual pieces, and lead wires 14 are connected.

A stain current is passed through both ends of the obtained platinum resistance temperature sensor, and o'C
Measure the change in resistance value between temperatures of ~100'C,
As a result of calculating the temperature coefficient of resistance (TCR), as shown in Table 2, the platinum resistance temperature detector according to the present invention can obtain a higher value than the comparative example that does not use the ZrO2 layer.

(Left below) Table 2 Relationship between the substrate material of the present invention and TCR characteristics (platinum film thickness 0.4
μ) Furthermore, when examining the relationship between the platinum film thickness and TCR for the platinum resistance thermometers in Examples 1 and 2 and Comparative Example, the relationship between the platinum film thickness and TCR is as shown in Fig. 6.According to the present invention, , high TCR can be obtained even with a thin platinum film.

Effects of the Invention As described above, according to the present invention, a platinum thin film can stably obtain a high temperature coefficient of resistance with a thinner film than conventional ones, and it is possible to reduce the amount of platinum used, which has a high unit cost. Second, a highly sensitive thin film platinum resistance temperature sensor can be provided at low cost. Another advantage of the present invention is that the base material of the substrate can be freely selected, making it possible to control the thermal characteristics of the substrate such as heat capacity and specific heat, thereby achieving thermal responsiveness, which is the second characteristic required of a resistance thermometer. This makes it possible to easily improve the resistance temperature and provide a low-cost, high-performance resistance temperature detector.

In addition, the effect of the present invention can be obtained by applying 2 on an insulating substrate (human β203)
Although the explanation has been given using an example of a substrate on which 102 layers are formed, the substrate may be a semiconductor (for example, Si, etc.) or a conductor (for example, human β).

Similar effects can be obtained even in the case of Zr, etc.). Further, the method of forming the ZrO2 layer and the method of forming the platinum film are not limited to the examples of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a platinum resistance temperature detector according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of the temperature detector of FIG. 1 at a manufacturing stage, and FIG. FIG. 4 is a cross-sectional view of a platinum resistance temperature detector according to the example, FIG. 5 is a cross-sectional view of the platinum resistance temperature detector according to the example and comparison example, and FIG. FIG. 2 is a characteristic diagram showing the relationship between (TCR) and platinum film thickness. 11...Person 1205 board, 12...Z
rO2 film, 13...Platinum film, 14...Lead wire. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (2)

[Claims] (1) A platinum resistance thermometer, characterized in that a different type of insulating layer is formed on the surface of a base, a platinum film is formed on the insulating layer, and the insulating layer is made of zirconium oxide (ZrO_2). (2) A method for manufacturing a platinum resistance thermometer, characterized in that a zirconium oxide (ZrO_2) layer and a platinum film are sequentially formed on a substrate, and then the platinum film and ZrO_2 are patterned into the same shape.