JP2866486B2 - Electroless Ni-Re-P alloy thin film resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to metal, ceramics,
Electroless Ni-R covering the surface of a substrate made of synthetic resin, etc.
The present invention relates to a thin-film resistor made of an e-P alloy, which has an extremely high specific resistance and a low temperature coefficient of resistance (TCR), and whose electric resistance characteristics are stably maintained at an extremely high temperature.

[0002]

2. Description of the Related Art A Ni-P alloy thin film having a phosphorus content of 5 to 15% by weight produced by an electroless plating method is formed of a microcrystalline or amorphous layer, and has a relatively high specific resistance and a low temperature resistance. Since it has a coefficient (hereinafter referred to as TCR), it is used as a metal thin-film type electric resistance material for intermittent conduction parts (discrete parts), hybrid ICs, and the like. However, this good electric resistance characteristic is N
It is obtained by a microcrystalline structure or an amorphous structure of the i-P alloy, and these structures have a disadvantage that they are inferior in heat resistance because they are thermodynamically metastable. This is a very important problem in view of the fact that the resistance material itself is essentially a heat-generating component, and that the manufacturing process and the assembling process include a heating process which is almost always required.

As a method for addressing this problem, it has been studied to co-deposit a high melting point metal such as W or Mo as a third element in a Ni-P alloy. For example, electroless Ni-1
For a 3 wt% P alloy thin film, the specific resistance is 140 μΩcm, TCR
Although the characteristic of 118 ppm / ° C. can be maintained only up to 300 ° C., electroless Ni-20 wt% W-
6% by weight P alloy thin film has higher specific resistance 190μΩc
m, and a lower TCR of 56 ppm / ° C., while maintaining these properties up to about 400 ° C. Further, electroless Ni-19% by weight of eutectoid of Mo
Mo-1 wt% P alloy thin film has a specific resistance of 150 μΩc
m, the characteristic of TCR 130 ppm / ° C. can be maintained up to about 500 ° C. (The absolute value of the resistance characteristic is Ni-WP
Inferior to alloys). For details of these data, see “Osaka, Koiwa, Kawaguchi; Surface Technology, 40. 807 (1
989)).

[0004] However, it can be seen that the TCR of the thin-film resistance materials produced by these electroless plating methods is slightly inferior to that of ordinary metal thin-film resistance materials (Table 1). Further, it is generally known that when a metal material is thinned, the specific resistance increases and the TCR decreases (L.
I.Maissel and R.Glang; "Handbook of Thin FilmTechn
ology ", p.18-6 (McGraw-Hill, 1970)), taking into account that the metal resistive materials shown in Table 1 are actually manufactured using a dry film forming method such as vacuum evaporation or sputtering. Then, it is also possible to exhibit the characteristics described above in Table 1. On the other hand, the wet film forming method such as the electroless plating method,
Compared to the dry film formation method, it is superior in cost and mass productivity, but because the film thickness and physical properties in the ultra-thin film region are unstable, it is difficult to expect improvement of the resistance characteristics by thinning. is there. Therefore, at present, the use of the thin film resistance material by the electroless plating method is limited to a region having a relatively low resistance value and a region permitted even if the TCR is high.

[0005]

[Table 1]

[0006]

[Problems to be Solved by the Invention] However, in order to make use of the advantages of the low cost of the electroless plating method and excellent mass productivity, and to expand its application to a high resistance area and a high precision area, the following is required. The challenge is to satisfy the characteristics described. I. Develop materials with higher specific resistance. B. To develop a material with a lower temperature coefficient of resistance (TCR). C. These specific resistance values and TCR must be stably maintained up to higher temperatures.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical background, and has an extremely high specific resistance and a low TCR, and yet has an electric resistance characteristic up to an extremely high temperature. An object of the present invention is to develop an electroless Ni-based alloy thin film resistance material that can be stably maintained. The purpose of this is to use W · M for Ni-P alloy.
Electroless Ni-Re-P in which rhenium (hereinafter referred to as Re), which is a refractory metal similar to o, is eutectoid as a third element.
This is achieved by making an alloy.

The present inventors have proposed the eutectoid deposition of Re on an electroless Ni—P alloy and the electroless Ni
A study on thermal change behavior of -Re-P alloy thin film was conducted. The eutectoid of Re was carried out by adding ammonium perrhenate to a conventional electroless plating bath.
With respect to weight% and P, eutectoid became possible in the range of 0 to 16 weight%. This means that the maximum eutectoid content of W is 20% by weight (I. Koiw
a, M. Usuda and T. Osaka; J. Electrochem. Soc., 135, 1
222 (1988)), the maximum eutectoid content of Mo was 22% by weight (I. Koiwa,
M.Usuda, K.Yamada and T.Osaka; J.Electrochem.So
c., 135, 718 (1988), etc.). Hereinafter, these electroless Ni-Re
The electrical resistance characteristics of the -P alloy thin films and their changes due to heating will be outlined.

Although the electroless Ni-Re-P alloy thin film has a higher specific resistance as the Re content in the thin film is larger, its properties are roughly classified into two at 60% by weight. I. When the Re content is 60% by weight or less, the specific resistance gradually increases as the Re content increases. For example, when the Re content is 45% by weight, the specific resistance is about 150 μΩc.
m, the same value as that of a normal electroless Ni-P-based alloy thin film, and at 60% by weight, the specific resistance is about 350 μΩcm.
And an extremely high value. Further, although the TCR is a negative value, it is −30 to −35 ppm / ° C., respectively, which is a normal Ni−
Its absolute value is clearly lower than that of the P-based alloy. When these films are subjected to a heat treatment, the specific resistance gradually decreases with an increase in temperature, but shows a value superior to that of a normal Ni-P alloy up to 500 ° C. In addition, the absolute value of the TCR that has been subjected to heat treatment is lower,
It shows an extremely good value of 20 ppm / ° C. Therefore, it is recommended to perform heat treatment when used for precision applications or when used at high temperatures.

B. When the Re content exceeds 60% by weight In this region, when the Re content in the thin film increases, the specific resistance increases exponentially, and reaches a maximum of about 3600 μΩcm. When such a large specific resistance is exhibited by a normal electroless plating film, cracking of the film or formation of an oxide due to internal stress at the time of plating may be considered, but a scanning electron microscope (SEM) or an X-ray Observations by photoelectron spectroscopy (XPS) and the like did not show any such abnormalities. Although the cause is unknown at present, it is considered that a gas or the like generated at the time of plating was adsorbed to form an insulating layer.
In fact, the thin film in this region has a TCR of -60 to -150 pp.
It shows a large negative value of m / ° C., suggesting semiconductor properties. Moreover, the specific resistance of the film in this region is at most 10
Heating at 0 to 200 ° C. sharply reduces it to about 400 μΩcm, so that it cannot be used as it is. On the other hand, it can be stabilized by performing a heat treatment at 200 to 500 ° C.

A. The specific resistance when heat-treated at the same temperature is lower than that of the film in the region of b. In the case where high specific resistance and stability up to high temperature are required, b. The film in the region should be heat treated and used. About TCR Similarly to the above, the temperature becomes about ± 20 ppm / ° C. by performing the heat treatment, which is an extremely good value.

From the above, it can be understood that the electroless Ni-Re-P alloy thin film resistor has extremely excellent electric resistance characteristics in all cases as compared with the conventional electroless Ni-P alloy thin film resistor. . However, these good electric resistance characteristics can be explained by the fact that the film structure is amorphous, like other Ni-P-based alloy thin films. X-ray diffraction (XRD) and electron beam diffraction (TH
A structural analysis by EED) shows that the amorphous state is maintained even after heat treatment to 500 ° C.

For example, in the case of an electroless Ni—P alloy thin film, 30
Since the amorphous state is lost at 400 ° C. in the electroless Ni—WP alloy thin film at 0 ° C., Re can be said to have an effect of extremely stabilizing the amorphous state. This is because Re has an extremely large amount of eutectoid as compared with W, Mo, etc. as described above, which may be one of the reasons. on the other hand,
The electroless Ni-Mo-P alloy thin film has thermal stability up to 500 ° C like the Ni-Re-P alloy thin film by moderate heat treatment, but this film partially forms a crystalline layer consciously. By doing so, thermal stabilization is achieved, so that the crystalline portion exhibits metallic electrical properties, so that the resistance characteristics are slightly inferior (low specific resistance, high TCR).

Electroless Ni-Re-P object of the present invention
The preferred Re content of the alloy thin film resistor is 5 to 75% by weight, and the P content is 1 to 14% by weight. However, there is no problem even if trace amounts of metal elements such as Co, Cu, Cr, and Fe coexist in the thin film as impurities. Further, considering that other electroless Ni-based thin-film resistance materials have been subjected to a heat treatment for stabilization in actual use, the electroless Ni-Re-P alloy thin-film resistor according to the present invention also has: 200-5 to demand more precise and higher thermal stability
It is recommended to heat-treat at a temperature of 00 ° C. (for example, about 1 hour). In particular, this heat treatment is indispensable for a resistor having a Re content of 60% by weight or more.

[0015]

EXAMPLES (Example 1) <Formation of Ni-45 wt% Re-6 wt% P alloy thin film> An electroless Ni-Re-P alloy thin film resistor was manufactured using 96% α-alumina ceramics as a substrate. .

The steps of manufacturing the electroless Ni-Re-P alloy thin film resistor are as follows. I. Degreasing: The ceramic substrate was immersed in ethanol at room temperature and subjected to ultrasonic cleaning for 10 minutes. B. Activation, washing with water: SnCl ₂ (1 g / l), 36% HC
After being immersed in a 1 (1 ml / l) aqueous solution for 1 minute (normal temperature), the substrate was washed with deionized water. C. Catalysis: PdCl ₂ (0.1 g / l), 36% HCl
(0.1ml / l) After immersing in an aqueous solution for 1 minute (normal temperature),
Deionized water washing was performed. D. Repetitive processing: The processing of (b) and (c) was performed again. E. Electroless plating, water washing: The ceramic substrate after the above treatment is immersed in an electroless Ni-Re-P alloy plating bath,
e content 45% by weight, P content 6% by weight, film thickness 1.5μ
After obtaining a Ni-Re-P alloy film of m, the substrate was washed with deionized water and dried with hot air. The composition of the plating bath is as shown below. The adjustment of the film thickness is performed by selecting the processing time. _{NaH 2 PO 2 · H 2 O} 0.10 mol / L Na 3 C 6 H 5 O 7 · 2H 2 O 0.40 mol / L NiSO 4 · 6H 2 O 0.075 mol / L NH 4 ReO 4 0. 005 mol / L * Note: The pH was adjusted to 9.0 with NaOH and H ₂ SO ₄ . The plating bath temperature was 90 ° C.

Evaluation of resistance characteristics a. The specific resistance was measured by a four-probe DC method. B. TCR is -60 to 70 ° C in a thermostat with refrigerator
The change in resistance with respect to temperature was measured in the temperature range described above, and the slope of the temperature-resistance straight line at that time was divided by the resistance value at 25 ° C. C. The stability of the film to heating is 2 in a vacuum heat treatment furnace.
00, 300, 400, 500, 600, 700, 80
About the film after heat treatment at each temperature of 0 ° C. for 1 hour,
I. Evaluation was made by measuring the specific resistance and TCR described in (b).

Example 2 Ni-60 wt% Re-3
Formation of a wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the NH ₄ ReO ₄ of the electroless plating bath was 0.01 mol /
By setting to L, an electroless Ni-Re-P alloy thin film resistor having a Re content of 60% by weight and a P content of 3% by weight was obtained. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics. In addition, a sufficiently stabilized film is produced by heat treatment at 500 ° C. for 1 hour, and the resistance change during the heating process is continuously measured in a vacuum furnace (temperature rise rate: 10 ° C. /
Min.) Proved the thermal stability more practically.

(Example 3) Ni-70% by weight Re-2
Formation of a wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the NH ₄ ReO ₄ of the electroless plating bath was 0.02 mol /
By setting to L, an electroless Ni-Re-P alloy thin film resistor having a Re content of 70% by weight and a P content of 2% by weight was obtained. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics.

Example 4 Ni-75 wt% Re-1
Formation of a wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the NH ₄ ReO ₄ of the electroless plating bath was 0.03 mol /
By setting to L, an electroless Ni-Re-P alloy thin film resistor having a Re content of 75% by weight and a P content of 1% by weight was obtained. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics.

Comparative Example 1 Formation of Ni-15 wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the electroless plating was performed using the following bath to obtain an electroless Ni-P alloy thin film resistor having a P content of 15% by weight. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics. However, the heat treatment temperature was only 300 ° C. _{NaH 2 PO 2 · H 2 O} 0.15 mol / L (NH 4) 2 SO 4 0.50 mol / L Na 3 C 6 H 5 O 7 · 2H 2 O 0.20 mol / L NiSO 4 · 6H 2 O 0.10 mol / L * Note: pH was adjusted to 6.0 with NaOH. The plating bath temperature was 90 ° C.

Comparative Example 2 Formation of Ni-20 wt% W-6 wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the electroless plating was performed using the bath shown below, and the electroless Ni—W— having a W content of 20% by weight and a P content of 6% by weight was used.
A P alloy thin film resistor was obtained. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics. However, the heat treatment temperature was only 400 ° C. Further, this film was heated at 400 ° C. for 1 hour.
It was stabilized by heat treatment for a period of time, and the resistance change during continuous temperature increase by the vacuum heat treatment furnace performed in Example 2 was also measured. _{NaH 2 PO 2 · H 2 O} 0.10 mol / L Na 3 C 6 H 5 O 7 · 2H 2 O 0.60 mol / L NiSO 4 · 6H 2 O 0.075 mol / L Na 2 WO 4 · 2H ₂ O 0.60 mol / L * Note: The pH was adjusted to 9.0 with NaOH. The plating bath temperature was 90 ° C.

Comparative Example 3 Ni-19 wt% Mo-1
Formation of a wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, the electroless plating was performed using the following bath, and the electroless Ni-M having a Mo content of 19% by weight and a P content of 1% by weight was used.
An o-P alloy thin film resistor was obtained. In addition, the same method as in Example 1 was used for evaluating the resistance characteristics. However, the heat treatment temperature was only 500 ° C. Further, this film was stabilized by heat treatment at 500 ° C. for 1 hour, and the resistance change during continuous temperature increase by the vacuum heat treatment furnace performed in Example 2 was also measured. _{NaH 2 PO 2 · H 2 O} 0.20 mol / L Na 3 C 6 H 5 O 7 · 2H 2 O 0.10 mol / L C 2 H 4 O 3 0.20 mol / L NiSO 4 · 6H 2 O _{0.10 mol / L Na 2 MoO 4} · 2H 2 O 0.01 mol / L * Note: the pH was adjusted to 9.0 by NaOH. The plating bath temperature was 90 ° C.

(Test Results) FIGS. 1 and 2 show the changes in the specific resistance and the TCR of the electroless Ni-Re-P alloy thin film resistors described in Examples 1 to 4 after heat treatment at various temperatures. Looking at the change in the specific resistance in FIG. 1, the coatings of Examples 1 and 2 (the coatings having a Re content of 60% by weight or less) gradually decrease in specific resistance as the heat treatment temperature increases, and exceed 500 ° C. It can be seen that it is further reduced. On the other hand, Examples 3 and 4
(A film having a Re content of more than 60% by weight) shows an extremely large specific resistance when plated,
It decreases sharply by heat treatment at ℃, and then gradually decreases to 500 ℃. Then, when the temperature exceeds 500 ° C., the temperature greatly decreases again. The change above 500 ° C. is more apparent from the TCR change in FIG. The coatings of Examples 1 and 2 maintain a value close to zero up to a heat treatment temperature of 500 ° C.
When the temperature exceeds 00 ° C., it rapidly increases. Examples 3 and 4
The film of (1) takes a large negative value in the as-plated state, but stabilizes to almost zero at 200 to 500 ° C.
When the temperature exceeds 0 ° C., it rapidly increases.

From the above results, the following items described in "Means and Actions for Solving the Problems" are proved. 1) A film having a Re content of 60% by weight or less is from room temperature to 500%.
It has stable resistance characteristics up to ℃. 2) A film having a Re content of more than 60% by weight is unstable when plated, and therefore requires a heat treatment at 200 to 500 ° C., but has a higher specific resistance than a film having a Re content of 60% by weight or less. , And the resistance characteristics are similarly stable up to 500 ° C.

Next, Table 2 compares the electrical resistance characteristics (specific resistance, TCR) of the films prepared in each of the examples and comparative examples as they are after being plated and after the heat treatment. In Table 2 (
The values in parentheses indicate the values after heat treatment. Here, the maximum heat-resistant temperature of each film was adopted as the heat treatment temperature. That is, Ni-
500 ° C for Re-P alloy, 300 ° C for Ni-P alloy, 400 ° C for Ni-WP alloy,
The temperature is 500 ° C. for the Ni—Mo—P alloy.

From Table 2, it is apparent that the electroless Ni-Re-P
It can be seen that the alloy thin films have high specific resistance and low TCR, and their resistance characteristics are stable up to high temperatures.
Further, in the film shown in the comparative example, the absolute value of TCR is increased by the heat treatment, but is decreased in the Ni-Re-P alloy thin film, and the heat treatment effect for stabilization is more remarkable. It has been shown.

[0028]

[Table 2]

Table 2 Specific resistance and TCR of various electroless Ni-P alloy thin films. The value after heat treatment is shown in parentheses. Further, in FIG. 3, for the coatings of Example 2 (Ni-Re-P), Comparative Example 2 (Ni-WP), and Comparative Example 3 (Ni-Mo-P), a continuous resistance change with increasing temperature was performed. showed that.
According to this, as can be seen from the above-described specific resistance measurement and the like, Example 2 maintains a high specific resistance in the entire temperature range, and its resistance value hardly changes until the temperature exceeds 500 ° C. On the other hand, in Comparative Example 2, 300 to 400 ° C.
A slight oscillation of the specific resistance value is observed in the vicinity, and when the temperature exceeds 400 ° C., the value rapidly decreases. Further, in Comparative Example 3, although the specific resistance did not decrease until 500 ° C., a continuous increase in the specific resistance due to the large TCR was observed.

[0030]

As is apparent from the above description, the electroless Ni-Re-P alloy thin film resistor has the following advantages as compared with the conventional electroless Ni-based alloy thin film resistor. Having a specific resistance of about 1.5 to 2 times; It has an extremely low TCR and its absolute value approaches almost zero by heat treatment.
C. 500 ° C by performing heat treatment for stabilization
This has the advantage of having heat resistance up to. These facts extend the application range of the electroless plated thin film resistor, which has been conventionally limited to low-resistance applications, to a higher resistance region and a region where higher precision is required, as described above.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in specific resistance after heat treatment at various temperatures in order to show the thermal stability of an electroless Ni-Re-P alloy thin film resistor according to the present invention (solid triangles: Examples). 1,
Δ: Example 2, ●: Example 3, ○: Example 4), and FIG. 2 shows the TCR change after heat-treating the electroless Ni—Re—P alloy thin film according to the present invention at various temperatures. (Black triangle: Example 1, Δ: Example 2, ●: Example 3, ○:
Example 4), FIG. 3 shows the results of a test to determine the actual thermal stability of a film obtained by stabilizing and heat-treating an electroless Ni—Re—P alloy thin film (Example 2) at an optimum temperature (500 ° C. for 1 hour). Electrolysis N
i-WP alloy thin film (Comparative Example 2, heat treatment at 400 ° C. for 1 hour) and electroless Ni—Mo—P alloy thin film (Comparative Examples 3, 50)
FIG. 3 is a diagram showing a change in specific resistance when the temperature is continuously increased in a vacuum heating furnace, as compared with (heat treatment at 0 ° C. for 1 hour).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01C 7/00 H01C 7/06

Claims (1)

(57) [Claims] 1. A rhenium content of 5 to 75% by weight and a phosphorus content of 1 to 1 formed on a substrate by an electroless plating method.
4% by weight of a Ni-Re-P alloy thin film resistor.