JPH04297001A - Electroless ni-re-p alloy thin-film resistor - Google Patents

Abstract

PURPOSE:To provide an alloy thin-film resistor through an electroless method stably maintained up to temperatures having high specific resistance value and temperature resistance coefficient and high resistivity and temperature resistance coefficient. CONSTITUTION:An Ni-Re-P alloy thin-film having 5-75wt.% rhenium content and 1-14% phosphorus content is formed onto a base material through an electroless plating method.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to metals, ceramics,
Electroless Ni-R covering the surface of a base material 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 which maintains these electrical resistance characteristics stably up to extremely high temperatures.

0002

[Prior Art] A Ni-P alloy thin film with a phosphorus content of 5 to 15% by weight, produced by electroless plating, is formed of a microcrystalline or amorphous layer, and has a relatively high specific resistance and low temperature resistance. Because it has a coefficient (hereinafter referred to as TCR), it is used as a metal thin film type electrical resistance material in intermittent energizing parts (discrete parts), hybrid ICs, etc. However, this good electrical resistance property is
It is obtained by the microcrystalline structure or amorphous structure of the i-P alloy, and since these structures are thermodynamically metastable, they have the disadvantage of poor heat resistance. This is an extremely important problem considering that the resistive material itself is essentially a heat-generating component and that its manufacturing and assembly processes almost always include a heating process.

[0003] As a method to deal with this problem, studies have been made to eutectoid a high melting point metal such as W or Mo as a third element into the Ni-P alloy. For example, electroless Ni-1
3 wt% P alloy thin film has specific resistance of 140μΩcm, TCR
Although the property of 118 ppm/°C can only be maintained up to 300°C, electroless Ni with W eutectoid-20 wt% W-
6 wt% P alloy thin film has higher specific resistance of 190μΩcm
, and a lower TCR of 56 ppm/°C, yet can maintain these properties up to about 400°C. Furthermore, electroless Ni-19% by weight Mo eutectoid
-1 wt% P alloy thin film has a specific resistance of 150 μΩcm, T
A characteristic of CR 130 ppm/° C. can be maintained up to about 500° C. (the absolute value of the resistance characteristic is inferior to that of the Ni-W-P alloy). For details on these data, see
Osaka, Koiwa, Kawaguchi; Surface technology, 40. 807 (
1989).

However, when comparing the thin film resistance materials produced by these electroless plating methods with the usual metal thin film type resistance materials, it is found that the TCR is slightly inferior (Table 1). Furthermore, it is generally known that as metal materials become thinner, their specific resistance increases and TCR decreases (L
．． I. Maissel and R. ”
Handbook of Thin FilmTech
p. 18-6 (McGraw-H
Ill, 1970), etc.), and considering that the metal resistance materials shown in Table 1 are actually produced using dry film formation methods such as vacuum evaporation and sputtering, it is possible that the metal resistance materials shown in Table 1 exhibit characteristics that exceed those shown in Table 1. It is also possible to do so. On the other hand, wet film formation methods such as electroless plating are superior in terms of cost and mass production compared to dry film formation methods, but the film thickness and physical properties are unstable in the ultra-thin film region. It is difficult to expect improvements in resistance characteristics by making the film thinner. Therefore, the current situation is that the use of thin film resistive materials produced by electroless plating is limited to areas where the resistance value is relatively low and where a high TCR is acceptable.

[0005]

[Table 1]

[0006]

[Problems to be solved by the present invention] However, in order to take advantage of the advantages of electroless plating, such as low cost and excellent mass productivity, and to expand its application to high resistance and high precision areas, the following steps are required. The challenge is to satisfy the stated characteristics. stomach. Developing materials with higher specific resistance values. B. Developing materials with lower temperature coefficient of resistance (TCR). C. These resistivity values and TCR should be maintained stably up to higher temperatures.

[0007]

[Means and effects for solving the problems] The present invention was created based on the above technical background, and has an extremely high specific resistance and a low TCR, and furthermore, these electrical resistance characteristics are maintained even at extremely high temperatures. The purpose is to develop an electroless Ni-based alloy thin film resistance material that can be stably maintained. And, this purpose is for Ni-P alloy, W.M.
This is achieved by producing an electroless Ni-Re-P alloy in which rhenium (hereinafter referred to as Re), which is a metal with a high melting point along with o, is eutectoid as a third element.

[0008] The present inventors have discovered the eutectoid of Re in an electroless Ni-P alloy, and the electroless Ni produced thereby.
A study was conducted on the thermal change behavior of -Re-P alloy thin films. Co-deposition of Re was performed by adding ammonium perrhenate to a conventional electroless plating bath, but by optimizing the plating bath, Re was 0 to 75% by weight and P was 0 to 16% by weight. Co-deposition became possible within the range of weight %. This is the maximum eutectoid amount of W of 20% by weight (I.Ko
iwa, M. Usuda and T. Osaka;
J. Electrochem. Soc. , 135,
1222 (1988), etc.), maximum eutectoid amount of Mo22
Weight% (I. Koiwa, M. Usuda, K.Y.
amada and T. Osaka; J. Elec
trochem. Soc. , 135, 718 (1
988), etc.), it can be said that this is a dramatic amount of eutectoid. The electrical resistance characteristics of these electroless Ni-Re-P alloy thin films and their changes due to heating will be summarized below.

The electroless Ni-Re-P alloy thin film has a higher resistivity as the Re content in the thin film increases, but its properties can be broadly classified into two categories at 60% by weight. stomach. 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 μΩcm,
It shows the same value as a normal electroless Ni-P alloy thin film, and 6
At 0% by weight, the specific resistance shows an extremely high value of about 350 μΩcm. Further, although the TCR is a negative value, the absolute value is clearly lower than that of a normal Ni-P alloy, which is -30 to -35 ppm/°C. Furthermore, when these films are subjected to heat treatment, the resistivity value gradually decreases as the temperature rises, but up to 500°C they show a value superior to that of ordinary Ni-P alloys. Moreover, the absolute value of TCR is lower when heat treatment is applied, 10 to 20 ppm/
℃, which shows an extremely good value. Therefore, heat treatment is recommended when using for precision purposes or when using at high temperatures.

B. When the Re content exceeds 60% by weight, in this region, as the Re content in the thin film increases, the specific resistance increases exponentially and reaches a maximum of about 3600 μΩcm. If a normal electroless plated film exhibits such a large resistivity, it may be due to cracking of the film due to internal stress during plating or the formation of oxides. According to observation using photoelectron spectroscopy (XPS), etc., no abnormalities like these were observed. The cause of this is currently unknown, but it is thought that gases generated during plating were adsorbed and formed an insulating layer. In fact, thin films in this region have a TCR of -60 to -150pp.
It shows a large negative value of m/°C, suggesting semiconducting properties. Moreover, the specific resistance value of the film in this region is at most 10
When heated at 0 to 200°C, the resistance rapidly decreases to about 400 μΩcm, so it cannot be used as is. On the other hand, it can be stabilized by heat treatment at 200 to 500°C.

[0011]B. Compared to the film in the region of , the resistivity when heat treated at the same temperature is . Since the value is larger in the region of , if high resistivity and stability up to high temperatures are required, choose region . The film in the area should be heat treated before use. Regarding TCR, see i. Similarly, by applying heat treatment, the value becomes about ±20 ppm/°C, which is an extremely good value.

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

For example, in an electroless Ni-P alloy thin film, 30
Since an electroless Ni-W-P alloy thin film at 0°C loses its amorphous state at 400°C, it can be said that Re has the effect of extremely stabilizing the amorphous state. This is probably due to the fact that, as mentioned earlier, Re has an extremely large eutectoid amount compared to W, Mo, etc. 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 applying appropriate heat treatment. Thermal stabilization is achieved by forming
Since the crystalline portion exhibits metallic electrical properties, the resistance characteristics are somewhat inferior (low specific resistance, high TCR).

Electroless Ni-Re-P targeted by the present invention
The preferred Re content of the alloy thin film resistor is 5 to 75% by weight.
, 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. Furthermore, considering that other electroless Ni-based thin film resistance materials are subjected to heat treatment for stabilization in actual use, the electroless Ni-Re-P alloy thin film resistor according to the present invention also has 200-50 for more precision and requiring higher thermal stability
It is recommended to perform heat treatment at a temperature of 0° C. (for example, for about 1 hour). In particular, this heat treatment is essential for resistors with a Re content of 60% by weight or more.

[0015]

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

The manufacturing process of the electroless Ni-Re-P alloy thin film resistor is as follows. stomach. Degreasing: The ceramic substrate was immersed in ethanol at room temperature and subjected to ultrasonic cleaning for 10 minutes. B. Activation, water washing...SnCl2 (1g/l), 36%H
After being immersed in a Cl (1 ml/l) aqueous solution for 1 minute (at room temperature), it was washed with deionized water. C. Catalysis...PdCl2 (0.1g/l), 36%HC
1 (0.1 ml/l) aqueous solution for 1 minute (at room temperature), and then washed with deionized water. D. Repetitive processing: The above-mentioned processes B and C were performed again. Ho. Electroless plating, water washing...The ceramic substrate after the above treatment is immersed in an electroless Ni-Re-P alloy plating bath, and R
E content 45% by weight, P content 6% by weight, film thickness 1.5μ
After obtaining a Ni-Re-P alloy film of m, it was washed with deionized water and dried with hot air. The plating bath composition is as shown below. Note that the film thickness is adjusted by selecting the processing time. NaH2PO2・H2O
0.10 mol/L
Na3C6H5O7・2H2O
0.40 mol/L N
iSO4・6H2O
0.075 mol/L NH4ReO
4 0.
005 mol/L *Note: pH was adjusted to 9.0 with NaOH and H2SO4. The plating bath temperature was 90°C.

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

(Example 2) Ni-60% by weight Re-
Formation of 3 wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, 0.01 mol of NH4ReO4 in the electroless plating bath
/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. Furthermore, the same method as in Example 1 was used for evaluating the resistance characteristics. In addition, a sufficiently stabilized film was prepared by heat treatment at 500°C for 1 hour, and the resistance change during the heating process was continuously measured in a vacuum furnace (heating rate: 10°C).
/min) to demonstrate thermal stability more practically.

(Example 3) Ni-70% by weight Re-
Formation of 2 wt% P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, 0.02 mol of NH4ReO4 in the electroless plating bath
/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. Furthermore, the same method as in Example 1 was used for evaluating the resistance characteristics.

(Example 4) Ni-75% by weight Re-
Formation of 1 wt % P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, 0.03 mol of NH4ReO4 in the electroless plating bath
/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. Furthermore, the same method as in Example 1 was used for evaluating the resistance characteristics.

(Comparative Example 1) Formation of Ni-15% by weight P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, electroless plating was performed using the bath shown below to obtain an electroless Ni--P alloy thin film resistor with a P content of 15% by weight. Furthermore, the same method as in Example 1 was used to evaluate the resistance characteristics. However, the heat treatment temperature was only 300°C. NaH2PO2・H2O
0.15 mol/L
(NH4)2SO4
0.50 mol/L
Na3C6H5O7・2H2O
0.20 mol/L Ni
SO4・6H2O 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-20wt W-6wt% 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-
A P alloy thin film resistor was obtained. Furthermore, the same method as in Example 1 was used to evaluate the resistance characteristics. However, the heat treatment temperature was only 400°C. In addition, this film was heated to 400°C for 1
It was stabilized by heat treatment for a period of time, and the resistance change during continuous temperature rise in the vacuum heat treatment furnace performed in Example 2 was also measured. NaH2PO2・H2O
0.10 mol/L
Na3C6H5O7・2H2O
0.60 mol/L N
iSO4・6H2O
0.075 mol/L Na2WO4
・2H2O 0.60
mol/L *Note: pH was adjusted to 9.0 with NaOH. The plating bath temperature was 90°C.

(Comparative Example 3) Ni-19% by weight Mo-
Formation of 1 wt % P alloy thin film A sample was prepared basically in the same manner as in Example 1. However, electroless plating was performed using the bath shown below, and electroless Ni-M with 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. Furthermore, the same method as in Example 1 was used to evaluate 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 change in resistance during continuous temperature rise in the vacuum heat treatment furnace performed in Example 2 was also measured. NaH2PO2・H2O
0.20 mol/L
Na3C6H5O7・2H2O
0.10 mol/L C2H4O
3
0.20 mol/L NiSO4・
6H2O 0.10
mol/L Na2MoO4・2H2O
0.01 mol/L *Note: pH was adjusted to 9.0 with NaOH. The plating bath temperature was 90°C.

(Test Results) FIGS. 1 and 2 show changes in resistivity and 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 resistivity value in Figure 1, the resistivity value of the films of Examples 1 and 2 (films with a Re content of 60% by weight or less) gradually decreases as the heat treatment temperature increases, and exceeds 500°C. It can be seen that there is an even greater decrease. On the other hand, Examples 3 and 4
A film with a Re content of more than 60% by weight shows extremely high resistivity as plated, but
It decreases rapidly by heat treatment at ℃, and then gradually decreases up to 500℃. Then, when the temperature exceeds 500°C, it decreases significantly again. The changes at temperatures above 500°C are more obvious when looking at the changes in TCR shown in FIG. The films of Examples 1 and 2 maintained a value close to zero up to a heat treatment temperature of 500°C, and
It increases rapidly when the temperature exceeds 00°C. In addition, Examples 3 and 4
The film takes a large negative value in the as-plated state, but it stabilizes around zero at 200 to 500°C, and the value of 50
It increases rapidly when it exceeds 0°C.

[0025] From the above results, the following matters stated in "Means and effects for solving the problems" are verified. 1) Films with Re content of 60% by weight or less have a temperature of 500% from room temperature.
It has stable resistance characteristics over °C. 2) Films with a Re content of more than 60% by weight are unstable as plated and require heat treatment at 200 to 500°C, but have a higher specific resistance than films with a Re content of 60% by weight or less. Similarly, the resistance characteristics are stable up to 500°C.

Next, Table 2 compares the electrical resistance characteristics (specific resistance, TCR) of the coatings produced in each of the Examples and Comparative Examples as-plated and after heat treatment. In Table 2 (
) indicates the value 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-W-P alloy,
For Ni-Mo-P alloy it is 500°C.

From Table 2, it is clear that 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. In addition, in the film shown in the comparative example, the absolute value of TCR increases by heat treatment, but on the contrary, it decreases in the Ni-Re-P alloy thin film, and the effect of heat treatment for stabilization is more remarkable. It has been shown that

[0028]

[Table 2]

Table 2 Specific resistance and TCR of various electroless Ni-P alloy thin films. Values after heat treatment are shown in parentheses. Furthermore, FIG. 3 shows the continuous resistance change with respect to temperature increase for the films of Example 2 (Ni-Re-P), Comparative Example 2 (Ni-W-P), and Comparative Example 3 (Ni-Mo-P). showed that. According to this, as can be seen from the above specific resistance measurements, etc., Example 2 maintains a high specific resistance in the entire temperature range, and there is almost no change in the resistance value until the temperature exceeds 500°C. On the other hand, in Comparative Example 2, the temperature was 300 to 400°C.
A slight oscillation in the resistivity value is observed in the vicinity, and it decreases rapidly when the temperature exceeds 400°C. Furthermore, in Comparative Example 3, although no decrease in specific resistance is observed up to 500° C., a continuous increase in specific resistance value due to the large TCR is observed.

[0030]

Effects of the Invention As is clear from the above description, the electroless Ni-Re-P alloy thin-film resistor has a higher level of performance compared to the conventional electroless Ni-based alloy thin-film resistor. B. has a specific resistance value of about 1.5 to 2 times. It has an extremely low TCR, and its absolute value approaches zero after heat treatment.
C. 500℃ by applying heat treatment for stabilization
It has the advantage of having heat resistance up to These factors have expanded the scope of application of electroless plated thin film resistors, which were previously limited to low resistance applications, as mentioned above.
This expands the range to higher resistance areas and areas where more precision is required.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the change in specific resistance after heat treatment at various temperatures in order to demonstrate the thermal stability of the electroless Ni-Re-P alloy thin film resistor according to the present invention (black triangles: examples). 1,
△: Example 2, ●: Example 3, ○: Example 4), FIG. 2 is a diagram showing TCR changes after heat treating the electroless Ni-Re-P alloy thin film according to the present invention at various temperatures. (Black triangle: Example 1, △: Example 2, ●: Example 3, ○:
Example 4), Figure 3 shows the electroless Ni-Re-P alloy thin film (Example 2) that was heat-treated for stabilization at the optimum temperature (500°C for 1 hour) to investigate the actual thermal stability of the film. Electrolytic N
i-W-P alloy thin film (Comparative Example 2, heat treated at 400°C for 1 hour) and electroless Ni-Mo-P alloy thin film (Comparative Example 3, 500°C
FIG. 2 is a diagram showing changes in specific resistance when the temperature is continuously raised in a vacuum heating furnace, in comparison with heat treatment (heat treatment at 1 hour at °C).

Claims (1)

[Claims] Claim 1: Formed on a base material by electroless plating, rhenium content 5-75% by weight, phosphorus content 1-14%.
wt% Ni-Re-P alloy thin film resistor.