JP4622522B2 - Metal resistor material, resistance thin film, sputtering target, thin film resistor, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a metal resistor material, a resistance thin film using the same, a sputtering target, a thin film resistor using the metal resistance material, and a method for manufacturing the same.

  Electronic components such as chip resistors, precision resistors, network resistors, high-voltage resistors, temperature sensors such as resistance temperature detectors, temperature sensitive resistors, and hybrid ICs and their composite module products Thin film resistors using resistive thin films are used.

  In this thin film resistor, a Ta alloy, a TaN compound and a Ni—Cr alloy are often used as a metal resistor material for forming a resistance thin film. Among these, a Ni—Cr alloy is the most common. Has been used.

  A thin film resistor using a Ni—Cr alloy has a small absolute value of the resistance temperature coefficient and has a good resistance temperature characteristic. However, if an aqueous solution containing chlorine such as human sweat or seawater adheres, corrosion occurs during use, that is, when a voltage is applied. For this reason, a thin film resistor using a Ni—Cr alloy has a problem that it is inferior to a conventional thin film resistor using a Ta alloy or a TaN compound in terms of corrosion resistance to chlorine and lacks reliability.

  On the other hand, thin film resistors using conventional Ta alloys or TaN compounds have good corrosion resistance to chlorine, but their resistance temperature coefficient (TCR) is not stable except for a specific film thickness, and thin film resistors with a wide range of resistance values. It was difficult to manufacture the vessel.

  Thin film resistors are also required to have resistance stability at high temperatures (hereinafter referred to as high temperature stability).

  The present invention has been made in view of such problems, and has higher corrosion resistance to chlorine than a conventional thin film resistor using a Ni-Cr alloy, and is equivalent to a thin film resistor using a Ta alloy or a TaN compound. It has a resistance to temperature of about the same magnitude (absolute value) as a conventional thin film resistor using Ni-Cr alloy, and has a resistance temperature coefficient to chlorine. Thin film resistor, thin film resistor having a high temperature stability equal to or higher than that of a thin film resistor using a Ta alloy or TaN compound, and a manufacturing method thereof, and a metal resistor material, sputtering target, and resistance used in the resistive thin film The object is to provide a thin film.

  The metal resistor material according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is made of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1.

  The metal resistor material according to the second aspect of the present invention includes 30 to 60% by mass of Ta and 0 to 8% by mass of Al, the balance is made of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1.

  The sputtering target according to the present invention has substantially the same composition as the metal resistor material, and can be used for forming a resistive thin film.

  The resistive thin film according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is made of Cr and Ni, the mass ratio of Cr to Ni is 0.5 to 1.1, and the surface An oxide film is formed.

  The resistive thin film according to the second aspect of the present invention contains 30 to 60% by mass of Ta and 0 to 8% by mass of Al, the balance is made of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1. 1 and an oxide film is formed on the surface.

  The resistance thin film has a temperature coefficient of resistance of ± 25 ppm / ° C. or less, and the resistance change rate after being held at a high temperature of 155 ° C. for 1000 hours is 0.10% or less. In an electrolytic corrosion test using acidic artificial sweat It is preferable that the melting start voltage is 3.0 V or more.

  The thin film resistor according to the present invention includes the resistive thin film.

  The thin film resistor manufacturing method according to the present invention includes forming a resistive thin film on an insulating material substrate by a sputtering method using the sputtering target according to the present invention, and then forming the resistive thin film in the atmosphere or a small amount of oxygen. Heat treatment is performed at 300 to 650 ° C. for 1 to 5 hours in the contained inert gas. As the insulating material substrate, for example, alumina or the like can be used.

  The resistance thin film according to the present invention has a dense oxide film formed on the surface of the thin film by performing an appropriate heat treatment, so that the corrosion resistance against chlorine is improved and the high temperature stability is excellent. Further, the temperature coefficient of resistance can be stably within ± 25 ppm / ° C.

  By using a thin film resistor including a resistive thin film having such characteristics, reliability in a corrosive environment and a high temperature environment can be ensured even in an electronic device that requires precise accuracy.

  Conventionally, Ni—Cr alloys, Ta alloys and TaN compounds have been used as resistor materials for thin film resistors. As described above, Ni—Cr alloys have a large resistance temperature coefficient (absolute Although the value was small, the corrosion resistance to chlorine was poor. On the other hand, although the Ta alloy and the TaN compound have good corrosion resistance to chlorine, the resistance temperature coefficient (TCR) is not stable except for a specific film thickness, and it is difficult to manufacture a thin film resistor having a wide resistance value. there were.

  Therefore, the present inventor has found that the temperature coefficient of resistance is as small as that of the Ni—Cr alloy, the corrosion resistance to chlorine equal to or higher than that of the Ta alloy and the TaN compound, the Ni—Cr alloy, the Ta alloy, and the TaN compound. R & D was carried out to obtain a metal resistor material that has equivalent or higher temperature stability.

  As a result, it has been found that a metal resistor material having a plurality of characteristics can be obtained by containing Ta, Ni, and Cr at a predetermined ratio and performing a predetermined heat treatment.

  The metal resistor material according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is made of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1.

  Ta is mainly effective in corrosion resistance, but if it is less than 30% by mass, the effect on corrosion resistance is insufficient, and if it exceeds 60% by mass, the temperature coefficient of resistance becomes negatively large, which is not preferable.

  Cr and Ni are mainly effective in reducing the value of the resistance temperature coefficient. However, if the mass ratio of Cr to Ni is less than 0.5, the effect of reducing the value of the resistance temperature coefficient is reduced, the resistance temperature coefficient is increased, and high-temperature stability is insufficient. On the other hand, when the mass ratio of Cr to Ni exceeds 1.1, the effect of reducing the value of the resistance temperature coefficient is reduced, the resistance temperature coefficient is increased, and the high temperature stability is insufficient. In addition, the reproducibility in production deteriorates.

  The metal resistor material according to the second aspect of the present invention is obtained by further adding Al to the metal resistor material according to the first aspect. Corrosion resistance is improved by adding Al. However, if the amount of Al exceeds 8% by mass, the temperature coefficient of resistance becomes negatively large, which is not preferable.

  Next, the case where a resistive thin film is produced using the metal resistor material according to the first or second aspect of the present invention for a sputtering target will be described.

  A resistive thin film made of Ta—Ni—Cr alloy or Ta—Ni—Cr—Al alloy when sputtering is performed using the metal resistor material according to the first or second aspect of the present invention and a film is formed on an insulating material substrate. Is obtained. The composition of the resistive thin film is substantially the same as that of the metal resistor material used for the target. However, the resistance thin film formed in vacuum does not have sufficient corrosion resistance to chlorine, has a negative resistance temperature coefficient, and has insufficient resistance stability at high temperatures.

  Therefore, it is necessary to perform a predetermined heat treatment in the atmosphere on the resistance thin film formed using the metal resistor material according to the first or second aspect of the present invention. By performing a predetermined heat treatment, the corrosion resistance to chlorine is better than that of a conventional Ni—Cr alloy, the absolute value of the resistance temperature coefficient is smaller than 25 ppm / ° C., and further when the temperature is kept at 155 ° C. for 1000 hours. A resistance thin film having a resistance change rate of 0.10% or less can be obtained.

  Specifically, heat treatment is performed in the atmosphere at 400 ° C. to 650 ° C. for 1 to 5 hours depending on the composition. Thereby, a dense and stable oxide film is formed on the surface of the resistance thin film, and high corrosion resistance against chlorine can be imparted. Further, the temperature coefficient of resistance is adjusted at the same time, and the temperature can be stably within ± 25 ppm / ° C., and good high temperature stability can be obtained. The oxide film is mainly composed of chromium, tantalum and aluminum.

  When the heat treatment temperature is less than 400 ° C., the corrosion resistance and heat resistance are not sufficiently exhibited, and the resistance temperature coefficient remains negatively large. On the other hand, when the heat treatment temperature exceeds 650 ° C., the resistance temperature coefficient becomes positive. When the heat treatment time is less than 1 hour, the corrosion resistance and heat resistance are not sufficiently exhibited, and the resistance temperature coefficient remains negatively large. On the other hand, even if the heat treatment is performed for more than 5 hours, the effect on each property is small and the productivity is deteriorated.

  Note that the atmosphere in which the heat treatment is performed may be an inert gas containing a small amount of oxygen instead of the air. Further, before the heat treatment in the atmosphere, the resistance temperature coefficient may be adjusted by heat treatment in a vacuum.

  By using a thin film resistor including a resistive thin film having such characteristics, reliability in a corrosive environment and a high temperature environment can be ensured even in an electronic device that requires precise accuracy.

(Examples 1 to 7, Comparative Examples 1 to 5 , Conventional Examples 1 and 2, Reference Example 1)
Thin film resistors having the compositions of Reference Example 1, Examples 1 to 5 and 7, and Comparative Examples 1 to 5 shown in Table 1 were prepared by a ternary simultaneous cathode sputtering method using a nichrome target, an aluminum target, and a tantalum target.

  The nichrome target was produced as follows. First, each of nickel nickel (made by Sumitomo Metal Mining Co., Ltd.) and electrolytic chromium (made by Toyo Soda Co., Ltd.) was used as a raw material, and the mass ratio of nickel to chromium was changed to a predetermined value using a vacuum melting furnace. 2 kg of nickel chrome alloy ingots were obtained. Next, each nickel chrome alloy ingot obtained was homogenized, and then a round plate having a thickness of 5 mm and a diameter of 150 mm was cut out by wire cutting. And the upper and lower surfaces were ground to make a nichrome target.

  Commercially available aluminum targets and tantalum targets having a purity of 99.99% were used. The aluminum target is manufactured by Sumitomo Metal Mining Co., Ltd., and the tantalum target is manufactured by Toshima Seisakusho Co., Ltd.

  In Conventional Examples 1 and 2, Nichrome targets (trade names Ni-50Cr and SMS-NC7A) manufactured by Sumitomo Metal Mining Co., Ltd. were used.

  In Example 6, electric nickel (manufactured by Sumitomo Metal Mining Co., Ltd.), electrolytic chromium (manufactured by Toyo Soda Co., Ltd.), aluminum particles (reagent) (manufactured by Hirano Kiyemon Corporation), tantalum plate (manufactured by Tokyo Electrolytic Co., Ltd.) An alloy ingot having a diameter of 80 mm and a thickness of 10 mm was obtained by melting argon plasma using a raw material as a raw material, and then a round plate having a thickness of 5 mm and a diameter of 60 mm was cut by wire cutting, and was vertically ground to form a sputtering target. And one sputtering target is used, and the ternary simultaneous cathode sputtering method is not used. The target having the composition of the present invention can also be obtained by using electron beam (EB) melting or the like.

Using the target described above, film formation was performed by the cathode sputtering method. An alumina substrate is placed in a vacuum chamber and evacuated to 1 × 10 ⁻⁴ Pa. Then, an argon gas having a purity of 99.9995% is introduced and maintained at a pressure of 0.3 Pa, and the sputtering power is set appropriately for each cathode. By controlling the film thickness, the film was formed on the alumina substrate so that the film thickness was 500 mm.

An Au electrode having a thickness of 5000 mm was formed on both sides of the obtained resistance thin film by the cathode sputtering method in the same manner as described above to obtain a substrate on which the resistance thin film and the Au electrode were formed. After forming the resistive film and Au electrodes on the substrate of Reference Example 1, Comparative Examples 1-4 and Examples 1-3, at 400 ° C. to 450 ° C. in air, and a heat treatment for 3 hours, Comparative Example 5 and About Examples 4-7, it heat-processed at 450 degreeC-650 degreeC in air | atmosphere for 3 hours, and about conventional example 1 and 2, it heat-treats at 300 degreeC in air | atmosphere for 3 hours, and each thin film resistor Got. A schematic diagram of the thin film resistor obtained is shown in FIG.

  In addition, as a film forming method, an electron beam evaporation method, a resistance heating evaporation method, or the like can be used.

In order to evaluate the resistance temperature characteristics of the thin film resistors of Examples 1 to 7, Comparative Examples 1 to 5 , Conventional Examples 1 and 2 and Reference Example 1 produced as described above, while raising the temperature in a constant temperature bath, Resistance measurement was performed at 25 ° C. and 125 ° C., and a temperature coefficient of resistance was calculated.

  Moreover, in order to evaluate high temperature stability, each thin film resistor was hold | maintained in the 155 degreeC thermostat for 1000 hours, and the change rate of resistance was measured.

  Furthermore, the corrosion resistance to chlorine was evaluated by a water drop test using an acidic artificial sweat (JIS L0848). Specifically, first, the initial resistance value of the resistance film is measured by a four-terminal method using a digital multimeter, and then, as shown in FIG. 2, only 30 μL of artificial sweat is placed in the center of the resistance film with a microsyringe. The voltage applied between the gold electrodes was adjusted so that the voltage applied to both ends of the water droplet was 1.5 V. The voltage applied between the gold electrodes is determined by 1.5 × (distance between the gold electrodes / water droplet diameter). After holding for 3 minutes with voltage applied, the water droplets were washed away with water and dried with a dryer, and then the resistance value was measured by a four-terminal method. When the film is dissolved, the resistance value increases.

  Then, the resistance change rate (%) was determined by dividing the difference between the resistance value after the test and the initial resistance value by the initial resistance value.

  Next, a new resistance film sample was used, a voltage was applied so that the voltage applied to both ends of the water droplet was 1.75 V, the same test was performed, and the resistance change rate was obtained. In this way, the test was performed by sequentially increasing the voltage applied to both ends of the water droplets by 0.25V. And the voltage of the both ends of a water droplet when a resistance change rate exceeded 0.2% was calculated | required, and this voltage was made into dissolution start voltage. In addition, in the vicinity of the dissolution start voltage, the increase in voltage applied to both ends of the water droplet was reduced to 0.1 V to improve accuracy. FIG. 3 shows the relationship between the voltage and the resistance change rate in Example 6 and Conventional Example 1.

  Table 1 shows the measurement results of the temperature coefficient of resistance, the rate of change in resistance, and the dissolution start voltage.

  All of the thin film resistors of Examples 1 to 7 have a melting start voltage of 3.0 V or more, which is a marked improvement over the melting start voltage of 1.9 V of Conventional Example 1, which is a conventional nickel chrome thin film resistor. Has been. Moreover, as for the thin film resistor of Examples 1-7, all have the absolute value of a resistance temperature coefficient of 25 ppm / degrees C or less, and its resistance temperature characteristic is also favorable. Furthermore, the thin film resistors of Examples 1 to 7 all have a resistance change rate of 0.10% or less after being held at 155 ° C. for 1000 hours, and have high temperature stability.

  In Examples 4 to 7 in which aluminum is added by 8% by mass or less, the melting start voltage is 4.2 to 4.6 V, and the melting start voltage of Examples 1 to 3 in which aluminum is not added (3 .6 to 4.3 V), and the corrosion resistance to chlorine is better.

  The resistive thin film of Reference Example 1 is made of tantalum and chromium. The melting start voltage is as large as 3.9 V and the corrosion resistance against chlorine is good, but the temperature coefficient of resistance is as extremely high as 398 ppm / ° C., so that it is difficult to use for a thin film resistor. Further, the rate of change in resistance after holding at 155 ° C. for 1000 hours is 0.15%, which exceeds 0.10%, and the high-temperature stability is not sufficient.

  The resistive thin film of Conventional Example 1 is made of nickel and chromium. Although the temperature coefficient of resistance is as small as 7 ppm / ° C. and good, the melting start voltage is as small as 1.9 V, which is below 3.0 V, and the corrosion resistance against chlorine is poor. Further, the resistance change rate after holding at 155 ° C. for 1000 hours is 0.42%, greatly exceeding 0.10%, and the high temperature stability is also inferior.

  The resistive thin film of Conventional Example 2 is made of nickel, chromium, and aluminum. The temperature coefficient of resistance is as small as 15 ppm / ° C., and the absolute value is 25 ppm / ° C. or less, which is favorable. Further, the rate of change in resistance after being held at 155 ° C. for 1000 hours is as small as 0.05%, which is good at 0.10% or less. However, the melting start voltage is as small as 2.1 V, which is lower than 3.0 V, and the corrosion resistance against chlorine is poor.

  In Comparative Example 1, the tantalum content is 26.3% by mass, which is lower than the lower limit of 30% by mass of the range of the present invention. For this reason, the melting start voltage is as small as 2.7 V, which is lower than 3.0 V, and the corrosion resistance to chlorine is insufficient.

  In Comparative Example 2, the tantalum content is 62.4% by mass, which exceeds the upper limit of 60% by mass of the range of the present invention. For this reason, the temperature coefficient of resistance is as negative as −28 ppm / ° C., and the absolute value exceeds 25 ppm / ° C.

  In Comparative Example 3, the Cr / Ni mass ratio is 0.47, which is lower than 0.5 which is the lower limit value of the range of the present invention. For this reason, the resistance temperature coefficient is as large as 55 ppm / ° C., and the absolute value exceeds 25 ppm / ° C. Moreover, the melting start voltage is as small as 2.8V, and is less than 3.0V, and the corrosion resistance to chlorine is insufficient. Furthermore, the resistance change rate after holding at 155 ° C. for 1000 hours exceeds 0.13% and 0.10%, and the high-temperature stability is not sufficient.

  In Comparative Example 4, the Cr / Ni ratio is 1.26, which exceeds 1.1 which is the upper limit value of the range of the present invention. For this reason, the temperature coefficient of resistance is as negative as −32 ppm / ° C., and the absolute value exceeds 25 ppm / ° C. In addition, the rate of change in resistance after holding at 155 ° C. for 1000 hours exceeds 0.11% and 0.10%, and the high-temperature stability is not sufficient.

  In Comparative Example 5, the aluminum content is 8.5% by mass, which exceeds the upper limit of 8% by mass of the range of the second aspect of the present invention. For this reason, the temperature coefficient of resistance is as negative as −30 ppm / ° C., and the absolute value exceeds 25 ppm / ° C.

It is the schematic of the produced thin film resistor. It is a figure which shows the outline | summary of a water drop test. It is a graph which shows the relationship between the voltage applied to the both ends of the water droplet of Example 6 and the prior art example 1, and resistance change rate measured by the water drop test.

Explanation of symbols

1 Alumina substrate 2 Resistive film 3 Gold electrode 4 Water drop 5 Constant voltage power supply

Claims (8)

  A metal resistor material containing 30 to 60% by mass of Ta, the balance being Cr and Ni, and the mass ratio of Cr to Ni being 0.5 to 1.1.   A metal resistor material containing 30 to 60% by mass of Ta and 0 to 8% by mass of Al, the balance being made of Cr and Ni, wherein the mass ratio of Cr to Ni is 0.5 to 1.1.   A sputtering target for forming a resistance thin film using the metal resistor material according to claim 1.   A resistive thin film containing 30 to 60% by mass of Ta, the balance being Cr and Ni, the mass ratio of Cr to Ni being 0.5 to 1.1, and an oxide film being formed on the surface.   30 to 60% by mass of Ta, 0 to 8% by mass of Al, the balance being made of Cr and Ni, the mass ratio of Cr to Ni being 0.5 to 1.1, and an oxide film on the surface The formed resistive thin film.   The temperature coefficient of resistance is within ± 25 ppm / ° C., the rate of change in resistance after being held at a high temperature of 155 ° C. for 1000 hours is 0.10% or less, and the dissolution initiation voltage is 3 in the electrolytic corrosion test using acidic artificial sweat The resistance thin film according to claim 4 or 5, wherein the resistance thin film is 0.0 V or more.   A thin film resistor using the resistive thin film according to claim 4.   A resistance thin film is formed on an insulating material substrate by a sputtering method using the sputtering target according to claim 3, and then the resistance thin film is 300 to 650 ° C. in the atmosphere or in an inert gas containing a small amount of oxygen. A method of manufacturing a thin film resistor, wherein the heat treatment is performed for 1 to 5 hours.

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