JPH0330281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a thin film platinum temperature sensor.

Conventionally, a laser trimming method or a mask evaporation method has been used as a method for forming a resistance pattern of a thin film platinum temperature sensor.

With the laser trimming method, it is possible to form fine and precise resistance patterns, making it possible to create small, high resistance, and highly accurate resistance values. However, on the other hand, it is not possible to form a large number of resistance patterns at once. There are difficulties in mass production.

On the other hand, with the mask vapor deposition method, it is possible to easily form a large number of resistance patterns at once, but it is not possible to form fine patterns. Therefore, in order to make a high resistance one, the shape of the sensor itself must be enlarged, making it difficult to obtain accurate resistance values. Too bad.

On the other hand, we aimed to obtain a method for manufacturing a thin film platinum temperature sensor that can compensate for the shortcomings of both the laser trimming method and the mask evaporation method and form a large number of fine resistance patterns at once. A manufacturing method has been proposed in which a photoresist pattern is formed on a thin film and a desired resistance value pattern is created by etching the platinum thin film. However, since platinum is a chemically very stable metal, it is difficult to etch it into a precise resistance pattern using a normal etching solution (aqua regia). In etching using aqua regia, the etching reaction does not proceed unless it is heated to 80 to 90°C, so hot aqua regia has been used, but the heat accelerates the reaction in which the resist is attacked by chemicals. Since the resist pattern was thus different from the intended pattern, a platinum thin film with a precise pattern could not be obtained.

In order to solve the above-mentioned drawbacks, the present invention etches a platinum thin film with an etching solution mainly composed of hydrochloric acid and hydrogen peroxide, or aqua regia and hydrogen peroxide,
It is characterized by creating a required resistance pattern. In the etching solution of the present invention, the etching reaction is promoted by adding hydrogen peroxide, so that sufficient etching can be achieved at room temperature. Therefore,
Since no heating is applied that would accelerate the reaction of the resist being attacked by chemicals, the resist pattern is not damaged and a platinum thin film with a precise pattern can be obtained.This allows us to produce a large number of thin film platinum temperature sensors with high resistance accuracy. We were able to produce it.

An embodiment of the present invention will be described below based on the drawings. In Figures 1 and 2, the width is 3mm and the length is 10mm.
Approximately 1 μm of platinum is placed on the alumina substrate 1 with a thickness of 1 mm and a thickness of 1 mm.
A film is deposited to a thickness of m, and then the platinum is etched into a desired pattern by photo-etching to form a resistive film 2, and a lead wire 4 is connected to a lead wire extraction electrode portion 3 formed at the end of the resistive film 2. Furthermore, a protective film 5 covering the resistive film 2 is provided.

The process of photoetching the platinum film is divided into two steps: forming a photoresist pattern and etching the platinum film. There are negative type and positive type photoresists, and a positive type resist with excellent acid resistance (for example, OFPR-2 manufactured by Tokyo Ohka Co., Ltd.) was used. First, in order to improve the adhesion between the substrate 1 and the photoresist, remove dust with an organic solvent such as acetone.
After degreasing, dry at 150°C for 1 hour. After that, set the substrate on a spinner, drop about 3 c.c. of resist, and rotate at 300 rpm for 30 seconds until the thickness is approx.
A 1.5 μm resist is formed, and then prebaked and dried at 80° C. for 10 minutes. Next, using a prescribed mask, the exposed portions of the resist are removed by irradiating with ultraviolet rays for 20 seconds and immersing in a developer for 3 minutes. Further, after washing with water, hot baking is performed at 125°C for 30 minutes to form a required resist pattern. In this example, a resist pattern having a platinum resist width of 50 μm and a groove width of 30 μm was formed through such steps.

As the etching solution for platinum, a mixture containing hydrochloric acid and hydrogen peroxide as the main components or a mixture containing aqua regia and hydrogen peroxide as the main components is suitable, but in this example,
By etching with a mixture of hydrochloric acid and hydrogen peroxide (volume ratio 5:1) at room temperature for about 5 minutes, platinum other than the required pattern was completely removed, and the etching was completed to a 500Ω
We were able to obtain a resistance value of ±10Ω.

In addition, as another example, by etching with a mixed solution of aqua regia and hydrogen peroxide (volume ratio of hydrochloric acid, nitric acid, and hydrogen peroxide 6:2:1) at room temperature for about 7 minutes, a 500Ω± I was able to obtain a resistance value of 10Ω.

Further, by laser trimming the resistance value fine adjustment portion 6 provided on the resistive film 2, a more accurate resistance value can be obtained.

As described above, according to the present invention, the required resistance pattern of the thin platinum film is formed by photoetching, and the platinum thin film is etched with a solution containing hydrochloric acid and hydrogen peroxide or aqua regia and hydrogen peroxide as main components. , it is possible to etch precise resistor patterns. In addition, it has the advantage of being able to easily form a large number of resistor patterns at once, making mass production easy and reducing costs, as well as being able to form fine patterns and producing small, high-resistance, and highly accurate products. .

Furthermore, if a resistance value fine adjustment portion is formed in the resistive film and laser correction is performed, it is possible to manufacture a resistor with higher precision.

[Brief explanation of the drawing]

1 and 2 are a plan view showing an example of a resistor pattern of a thin film platinum temperature sensor and a sectional view of the thin film platinum temperature sensor for explaining the manufacturing method of the present invention. 1...Alumina substrate, 2...Platinum resistance film, 3...
...Lead wire extraction electrode part, 4...Lead wire,
5...Protective film.

Claims (1)

[Claims] 1. A photoresist pattern is formed on a platinum thin film formed on an insulating substrate, and the platinum thin film is etched with an etching solution mainly composed of hydrochloric acid and hydrogen peroxide, or aqua regia and hydrogen peroxide to obtain the required resistance. A method for manufacturing a thin film platinum temperature sensor that creates a pattern.