Metal resistance material, resistance thin film, sputtering target, thin film resistor and manufacturing methods thereof

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.

For chip resistors, precision resistors, network resistors, resistors such as high-voltage resistors, temperature sensors such as temperature measuring resistors and temperature-sensitive resistors, and electronic components such as hybrid ICs and their composite module products. A thin film resistor using a resistor thin film is used.

In this thin film resistor, Ta alloy, TaN compound and Ni-Cr alloy are often used as the metal resistor material for forming the resistance thin film, and Ni-Cr alloy is the most common among them. Is used as a target.

A thin film resistor using a Ni-Cr alloy has a small absolute value of the temperature coefficient of resistance and has good resistance temperature characteristics. However, if an aqueous solution containing chlorine such as human sweat or seawater is attached, corrosion occurs during its use, that is, when a voltage is applied. Therefore, the thin film resistor using a Ni-Cr alloy has a problem that it is inferior to the 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, conventional thin film resistors using Ta alloys or TaN compounds have good corrosion resistance to chlorine, but the temperature coefficient of resistance (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.

The thin film resistor is also required to have resistance stability at high temperature (hereinafter referred to as high temperature stability).

<p> The present invention has been made in view of such a problem, and has higher corrosion resistance to chlorine than a conventional thin film resistor using a Ni-Cr based alloy, and is equivalent to a thin film resistor using a Ta alloy or a TaN compound. It has a degree of corrosion resistance to chlorine, has a resistance temperature coefficient of the same magnitude (absolute value) as a thin film resistor using a conventional Ni-Cr alloy, and uses a conventional Ni-Cr alloy. Thin-film resistors, thin-film resistors with high-temperature stability equal to or higher than those using Ta alloys or TaN compounds, and methods for manufacturing them, as well as metal resistor materials, sputtering targets, and resistors used for the resistance thin films. An object of the present invention is to provide a thin film.</p>

<p> The metal resistor material according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is composed of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1.</p><p> The metal resistor material 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, and the balance is composed of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1. is there.</p><p> The sputtering target according to the present invention has substantially the same composition as the above-mentioned metal resistor material, and can be used for forming a resistance thin film.</p><p> The resistance thin film according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is composed of Cr and Ni, the mass ratio of Cr to Ni is 0.5 to 1.1, and an oxide film is formed on the surface. It is formed.</p><p> The resistance 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, and the balance is composed of Cr and Ni, and the mass ratio of Cr to Ni is 0.5 to 1.1. Moreover, an oxide film is formed on the surface.</p><p> The resistance thin film has a resistance temperature coefficient of ± 25 ppm / ° C or less, a resistance change rate of 0.10% or less after being held at a high temperature of 155 ° C for 1000 hours, and in an electrolytic corrosion test using an acidic artificial sweat solution. The melting start voltage is preferably 3.0 V or higher.</p><p> The thin film resistor according to the present invention includes the resistance thin film.</p><p> In the method for manufacturing a thin film resistor according to the present invention, a resistance thin film is formed on an insulating material substrate by a sputtering method using the sputtering target according to the present invention, and then the resistance thin film is used in the atmosphere or with a small amount of oxygen. It is characterized by being heat-treated at 300 to 650 ° C for 1 to 5 hours in the containing inert gas. As the insulating material substrate, for example, alumina or the like can be used.</p>

<p> Since the resistant thin film according to the present invention has a dense oxide film formed on the surface of the thin film by appropriate heat treatment, the corrosion resistance to chlorine is improved and the high temperature stability is excellent. Furthermore, the temperature coefficient of resistance can be stably within ± 25 ppm / ° C.</p><p> By using a thin film resistor provided with a resistance thin film having such characteristics, it is possible to ensure reliability in a corrosive environment and a high temperature environment even in an electronic device that requires precise accuracy.</p>

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

Therefore, the present inventor has a resistance temperature coefficient as small as that of Ni-Cr alloys, corrosion resistance to chlorine equal to or higher than that of Ta alloys and TaN compounds, and Ni-Cr alloys and Ta alloys and TaN compounds. We proceeded with research and development to obtain a metal resistor material that has the same or higher temperature stability.

As a result, they have found that a metal resistor material having the above-mentioned plurality of properties can be obtained by containing Ta, Ni, and Cr in a predetermined ratio and performing a predetermined heat treatment, and have reached the present invention.

The metal resistor material according to the first aspect of the present invention contains 30 to 60% by mass of Ta, the balance is composed 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 mainly have the effect of reducing the value of the temperature coefficient of resistance. However, if the mass ratio of Cr to Ni is less than 0.5, the effect of reducing the value of the temperature coefficient of resistance becomes small, the temperature coefficient of resistance becomes large, and the high temperature stability becomes insufficient. On the other hand, when the mass ratio of Cr to Ni exceeds 1.1, the effect of reducing the value of the temperature coefficient of resistance becomes small, the temperature coefficient of resistance becomes large, and the high temperature stability becomes insufficient. In addition, the reproducibility in manufacturing 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 added exceeds 8% by mass, the temperature coefficient of resistance becomes negatively large, which is not preferable.

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

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, a resistance thin film composed of a Ta-Ni-Cr alloy or a Ta-Ni-Cr-Al alloy is formed. Is obtained. The composition of the resistance thin film is substantially the same as the composition of the metal resistor material used for the target. However, the resistance thin film as it is formed in vacuum does not have sufficient corrosion resistance to chlorine, has a negative temperature coefficient of resistance, 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 by 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 the conventional Ni-Cr alloy, the absolute value of the temperature coefficient of resistance is smaller than 25 ppm / ° C, and the temperature is maintained at 155 ° C for 1000 hours. It is possible to obtain a resistance thin film having a resistance change rate of 0.10% or less.

Specifically, depending on the composition, heat treatment is performed at 400 ° C to 650 ° C for 1 to 5 hours in the air. As a result, a dense and stable oxide film is formed on the surface of the resistance thin film, and high corrosion resistance to chlorine can be imparted. At the same time, the temperature coefficient of resistance is adjusted so that it 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.

If the heat treatment temperature is less than 400 ° C, corrosion resistance and heat resistance are not sufficiently developed, and the temperature coefficient of resistance remains negatively large. On the other hand, when the heat treatment temperature exceeds 650 ° C, the temperature coefficient of resistance becomes positively large. If the heat treatment time is less than 1 hour, corrosion resistance and heat resistance are not sufficiently developed, and the temperature coefficient of resistance 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.

The atmosphere for heat treatment may be an inert gas containing a small amount of oxygen instead of the atmosphere. Further, before the heat treatment in the atmosphere, the heat treatment may be performed in a vacuum to adjust the temperature coefficient of resistance.

By using a thin film resistor provided with a resistance thin film having such characteristics, it is possible to ensure reliability in a corrosive environment and a high temperature environment even in an electronic device that requires precise accuracy.

(Examples 1 to 7, Comparative Examples 1 to 6, Conventional Examples 1 and 2, Reference Example 1) Reference Example 1 and Table 1 are shown by a three-way simultaneous cathode sputtering method using a nichrome target, an aluminum target and a tantalum target. Thin film resistors having the compositions of Examples 1 to 5 and 7 and Comparative Examples 1 to 5 were prepared.

The nichrome target was prepared as follows. First, electric nickel (manufactured by Sumitomo Metal Mining Co., Ltd.) and electrolytic chromium (manufactured by Toyo Soda Co., Ltd.) were used as raw materials, and the mass ratio of nickel to chromium was changed to a predetermined value using a vacuum melting furnace. 2 kg each of nickel-chromium alloy ingots was obtained. Next, each of the obtained nickel-chromium alloy ingots 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. Then, the upper and lower surfaces were ground to obtain a nichrome target.

Commercially available aluminum targets and tantalum targets with 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 Manufacturing 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 granules (reagent) (manufactured by Seizaemon Hirano Co., Ltd.), and tantalum plate (manufactured by Tokyo Electrolytic Co., Ltd.). After obtaining an alloy ingot with a diameter of 80 mm and a thickness of 10 mm by dissolving argon plasma from the raw material, a round plate with a thickness of 5 mm and a diameter of 60 mm is cut out by wire cutting and ground up and down to form a film using a sputtering target. This method uses one sputtering target and does not use the ternary simultaneous cathode sputtering method. The target of the composition of the present invention can also be obtained by using electron beam (EB) dissolution or the like.

Using the targets described above, film formation was performed by the cathode sputtering method. Alumina substrate is placed in the vacuum chamber, and 1 x 10^-4After exhausting to Pa, argon gas with a purity of 99.9995% is introduced, the pressure is maintained at 0.3 Pa, and the sputtering power is appropriately controlled at each cathode so that the film thickness becomes 500 Å on the alumina substrate. A film was formed in.

Au electrodes having a thickness of 5000 Å were 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 Au electrodes were formed. After forming the resistance thin film and Au electrode on the substrate, Reference Example 1, Comparative Examples 1, 5, 6 and Examples 1 to 3 are heat-treated in the air at 400 ° C to 450 ° C for 3 hours. Comparative Examples 3 and 4 and Examples 4 to 7 were heat-treated in the air at 450 ° C to 650 ° C for 3 hours, and Conventional Examples 1 and 2 were heat-treated in the air at 300 ° C for 3 hours. By doing so, each thin film resistor was obtained. A schematic diagram of the obtained thin film resistor is shown in FIG.

As the film forming method, an electron beam vapor deposition method, a resistance heating type vapor deposition method, or the like can also be used.

In order to evaluate the resistance temperature characteristics of the thin film resistors of Examples 1 to 7, Comparative Examples 1 to 6, Conventional Examples 1 and 2, and Reference Example 1 produced as described above, while raising the temperature in a constant temperature bath, the temperature was increased. The resistance temperature coefficient was calculated by measuring the resistance at 25 ° C and 125 ° C.

In addition, in order to evaluate the high temperature stability, each thin film resistor was held in a constant temperature bath at 155 ° C for 1000 hours, and the rate of change in resistance was measured.

Furthermore, the corrosion resistance to chlorine was evaluated by a water drop test using an acidic artificial sweat solution (JIS L0848). Specifically, first, the initial resistance value of the resistance film is measured by the four-terminal method using a digital multimeter, and then, as shown in FIG. 2, 30 μL of artificial sweat solution is applied to 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 droplets would be 1.5V. The voltage applied between the gold electrodes is calculated by 1.5 × (distance between gold electrodes / diameter of water droplets). After holding for 3 minutes with a voltage applied, the water droplets were rinsed with water, dried with a dryer, and then the resistance value was measured by the four-terminal method. The resistance value increases when the membrane is dissolved.

Then, the difference between the resistance value after the test and the initial resistance value was divided by the initial resistance value to obtain the resistance change rate (%).

Next, using a sample of a new resistance film, a voltage was applied so that the voltage applied to both ends of the water droplet was 1.75 V, and the same test was performed to determine the rate of change in resistance. In this way, the test was carried out by sequentially increasing the voltage applied to both ends of the water droplet by 0.25V. Then, the voltage across the water droplet when the resistance change rate exceeded 0.2% was obtained, and this voltage was used as the dissolution start voltage. In the vicinity of the melting start voltage, the increase width of the voltage applied to both ends of the water droplet was reduced to 0.1V to improve the accuracy. FIG. 3 shows the relationship between the voltage and the resistance change rate of Example 6 and Conventional Example 1.

Table 1 below shows the measurement results of the temperature coefficient of resistance, the rate of change in resistance, and the starting voltage for melting.

<tables num="1"><img file="JP2006190871A_D0001.tif" /></tables>

The thin film resistors of Examples 1 to 7 all have a melting start voltage of 3.0 V or more, which is significantly improved as compared with the conventional nickel chromium-based thin film resistor of the conventional example 1 having a melting start voltage of 1.9 V. There is. Further, all of the thin film resistors of Examples 1 to 7 have an absolute value of the temperature coefficient of resistance of 25 ppm / ° C or less, and have good resistance temperature characteristics. Further, all of the thin film resistors of Examples 1 to 7 have a resistance change rate of 0.10% or less after being held at 155 ° C for 1000 hours, and have good high temperature stability.

In Examples 4 to 7 in which aluminum is added in an amount of 8% by mass or less, the melting start voltage is 4.2 to 4.6V, and the melting start voltage (3.6 to 4.3V) in Examples 1 to 3 in which aluminum is not added is 4.2 to 4.6V. ), And has better corrosion resistance to chlorine.

The resistance thin film of Reference Example 1 is composed of tantalum and chromium. The melting start voltage is as large as 3.9V and the corrosion resistance to chlorine is good, but the temperature coefficient of resistance is extremely large as 398ppm / ° C, making it difficult to use for thin film resistors. In addition, 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 resistance thin film of Conventional Example 1 is composed of nickel and chromium. Although the temperature coefficient of resistance is as small as 7 ppm / ° C and is good, the melting start voltage is as small as 1.9 V, which is lower than 3.0 V, and the corrosion resistance to chlorine is inferior. In addition, the rate of change in resistance after holding at 155 ° C for 1000 hours is 0.42%, which greatly exceeds 0.10%, and the high temperature stability is also inferior.

The resistance thin film of Conventional Example 2 is composed 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 good. In addition, the rate of change in resistance after holding at 155 ° C for 1000 hours is as small as 0.05%, which is 0.10% or less, which is good. However, the melting start voltage is as small as 2.1V, which is lower than 3.0V, and the corrosion resistance to chlorine is inferior.

In Comparative Example 1, the tantalum content is 26.3% by mass, which is lower than the lower limit of 30% by mass in the range of the present invention. Therefore, the melting start voltage is as small as 2.7V, which is lower than 3.0V, 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 in the range of the present invention. Therefore, the temperature coefficient of resistance is as large as -28ppm / ° C, and the absolute value exceeds 25ppm / ° C.

In Comparative Example 3, the Cr / Ni mass ratio is 0.47, which is below the lower limit of 0.5 in the range of the present invention. Therefore, the temperature coefficient of resistance is as large as 55 ppm / ° C, and the absolute value exceeds 25 ppm / ° C. In addition, the melting start voltage is as small as 2.8V, which is lower than 3.0V, and the corrosion resistance to chlorine is insufficient. Furthermore, the rate of change in resistance after holding at 155 ° C for 1000 hours is 0.13%, which exceeds 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 of the range of the present invention. Therefore, the temperature coefficient of resistance is as large as -32ppm / ° C, and the absolute value exceeds 25ppm / ° C. In addition, the rate of change in resistance after holding at 155 ° C for 1000 hours is 0.11%, which exceeds 0.10%, and the high temperature stability is not sufficient.

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

<figref num="1">It is the schematic of the manufactured thin film resistor.</figref><figref num="2">It is a figure which shows the outline of the water drop test.</figref><figref num="3">It is a graph which shows the relationship between the voltage applied to both ends of the water droplet of Example 6 and the prior art Example 1 and the resistance change rate measured by the water drop test.</figref>

Code description

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