JPS5853484B2 - thin film resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film resistor, and aims to provide a thin film resistor with small resistance change, which can be used as a fixed resistor or in combination with a brush as a variable resistor. It is something.

Conventional thin film fixed resistors are widely used either alone or integrated with other circuit elements.

However, the characteristics of this resistor collector change significantly over time, and no protective material suitable for preventing or suppressing this change has been obtained.

Moreover, in thin film resistors for variable resistors, their change over time is particularly serious.

That is, since the brush slides on the thin film resistor while maintaining electrical contact, the thin film resistor has many opportunities to come into contact with the outside air and is strongly influenced by it.

The present invention has been able to effectively suppress such changes in thin film resistors over time, and in particular, in variable resistors, the change over time can be effectively suppressed without substantially damaging the electrical contact between the thin film resistor and the brush. This made it possible to significantly reduce the change in resistance.

The feature is that Hf and Nb are formed on the thin film resistor.
.

Ta, Mo, W, Re tRu, Rh, I
The present invention is characterized in that a protective film containing at least one selected from r and at least one of silicon carbide and silicon nitride is formed.

Here, the thin film resistor in the present invention should be contrasted with a body resistor, and the thin film resistor is a glaze resistive film formed using printing technology, a composite nitride resistive film, a nichrome resistive film, etc. It means a film-like resistor.

Hereinafter, the thin film resistor according to the present invention will be described in detail based on one embodiment when used as a variable resistor.

FIG. 1 shows the structure of this embodiment, in which 1 is an insulating substrate such as alumina porcelain that serves as a supporting base, 2 is a thin film resistor formed thereon, 3 and 3' are electrodes, 4 is a protective film, 5 is a brush.

The protective film 4 covers the thin film resistor 2 and a portion of the electrodes 3, 3', and the brush 5 comes into contact with this protective film 4 and slides in the direction of the arrow.

Regarding the thin film resistor 2, there are no particular restrictions regarding its material.

As mentioned above, the protective film 4 is made of Hf, Nb, and Ta.

It consists of at least one metal component selected from MotW, Re, Ru, Rh, and Ir, a compound component of at least one of silicon carbide and silicon nitride.

In order to obtain properties more suitable for thermal theory and purpose of use, or to further enhance properties, other components may be additionally introduced therein.

And 1. It is desirable to form the protective film 4 so that the resistance between the electrodes 3 and 3' is sufficiently higher than that of the thin film resistor 2. For example, the resistance value, resistance temperature coefficient, noise, etc. are determined by the thin film resistor 2, and the protective film 4 has virtually no relation to them.

Furthermore, the resistance in the film thickness direction is
It is desirable to form the protective film 4 so that the resistance is sufficiently lower than the resistance between .

By doing this, the resistance value between the electrode 3 or 3' and the brush 5 is determined by that of the portion of the thin film resistor 2 located therebetween, in view of the conditions mentioned above.

Next, the effects of the above configuration will be described.

As the thin film resistor 2, composite nitride resistors having various resistance values were used, and as the protective film 4, a protective film composed of Mo and silicon carbide and having a thickness of approximately 0.3 μm was used.

Then, a carbon brush was used as the brush 5, and the brush was placed at the center of the electrode terminals 3, 3' to examine the rate of change in resistance value.

The results are shown in the table below.

In the table, R1 is the resistance value of the thin film resistor 2 between the electrode terminals 3 and 3' before the protective film 4 is formed, and R2 is the resistance between the electrodes 3 and 3' after the protective film 4 is formed. The value R3 is the sheet resistance value of the protective film 4 itself.

Moreover, Mo/(Mo+SiC) is Mo and Si of the protective film 4.
ΔR1/R1 and ΔR2/R2 are the respective resistance change rates when aged in air for 1 hour at the temperature shown in the table below.

As is clear from the above table, due to the presence of the protective film 4, the change in resistance value as a fixed resistor or as a variable resistor is necessarily small.

In particular, the effect becomes more pronounced as the aging temperature increases.

Typically, such a variable resistor has a resistance of 15
When left at a temperature of 0° C. for 100 hours, the rate of change in resistance value is required to be within ±3%.

Taking the example of a variable resistor with Ω shown in 8 in the table above, when tested under the above conditions, 6 when no protective film 4 is formed.
~9% compared to 3 when it was formed.
% or less.

The effect of the protective film 4 tends to decrease the change in resistance value as it becomes thicker, and in practical terms it becomes noticeable when the thickness is 1000 angstroms or more.

As shown in FIG. 2, the sheet resistance of the protective film 4 decreases as the volume ratio of Mo increases.

Practically speaking, considering the relationship with the sheet resistance value of the thin film resistor 2, the value of Mo/(Mo+5ic) should exceed 30% by volume so that the similar resistance value of the protective film 4 is 10Ω/or more. The composition ratio may be selected within a range where there is no difference.

Furthermore, in the samples in the above table, the contact resistivity when the protective film 4 is formed is 0.5 to 2%, and this value is almost the same as the contact resistivity when the protective film 4 is not formed. .

The contact resistivity was measured using a hemispherical carbon brush with a radius of 1 as the brush 5.

As described above, by using the protective film 4, the increase in resistance value due to aging can be reduced without affecting the resistance value and contact resistivity of the thin film resistor 2.

The detailed reason for this is not fully elucidated at present (1), but considering that the increase in resistance due to aging is due to the formation of a surface oxidation layer on the thin film resistor 2, the protective film 4 is This is because the body 2 is prevented from coming into direct contact with oxygen in the air, and the contact of oxygen with the thin film resistor 2 is reduced to the extent that it comes into contact with the oxygen that diffuses through the inside of the protective film 4. it is conceivable that.

Further, the contribution of the protective film 4 to the contact resistivity is considered to be a resistance valve in the film thickness direction, and since the film thickness is thin, the resistance valve is so small that it can be ignored.

Above, we have described the protective film 4 made of Mo and SiC, but in addition to Mo, Hf tNb,
Ta 2 , W, Re tRu +Rh , and I r can be used, and two or more of these including Mo can also be used in combination.

Furthermore, silicon nitride, or silicon carbide and silicon nitride may be used instead of silicon carbide.

All of these metals are high melting point metals and have similar electrical properties, and all of their compounds have high melting points and similar crystal structures.

Therefore, even if the above components are selected and combined, equivalent characteristics can be obtained.

That is, this is considered to be because the protective films have similar structures regardless of the combination of the metals and compounds.

As described above, the thin film resistor of the present invention has extremely stable resistance characteristics not only as a variable resistor but also as a fixed resistor.

The thin film resistor and the protective film can be sufficiently manufactured using currently used manufacturing techniques.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of an embodiment of a thin film resistor according to the present invention, and FIG. 2 is a diagram showing the relationship between the composition of the protective film and the sterilization resistance. 1... Insulating substrate, 2... Thin film resistor, 3, 3'... Electrode, 4... Protective film,
5...Brush.

Claims (1)

[Scope of Claims] 1. A thin film resistor and a protective film are sequentially laminated on an insulating support base, and the protective film includes Hf and Nb. Ta tMo , W t Re , Ru , Rh t
A thin film resistor comprising at least one metal component selected from Ir and a compound component of at least one of silicon carbide and silicon nitride. 2. In the thin film resistor according to claim 1,
The protective film is characterized in that the metal component is contained in an amount that does not exceed 30% by volume of the total amount of the metal component and the compound component. 3. The thin film resistor according to claim 1 or 2, characterized in that the thin film resistor is provided with electrodes and the resistance between the electrodes is utilized. 4. The thin film resistor according to claim 1 or 2, characterized in that the thin film resistor is provided with an electrode and a brush is brought into contact with the protective film to make the resistance variable. .