JP4380586B2 - Thin film resistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a thin film resistor used for a thin film chip resistor, a method for producing the same, and a sputtering target that can be used in the production.

  Conventionally, thin film resistors have been used for thin film chip resistors. The thin film resistor is a ceramic substrate formed of a metal such as a Ni—Cr alloy (specific resistance is 100 to 150 μΩ · cm) or a Cr—Si alloy (specific resistance is a maximum of 300 μΩ · cm) by sputtering or vacuum deposition. It can be obtained by depositing on top. The specific resistance of the thin film resistor made of Ni—Cr alloy is 100 to 150 μΩ · cm, and the specific resistance of the thin film resistor made of Cr—Si alloy is 300 μΩ · cm at the maximum. When the thin film resistor is used for a thin film chip resistor, it is processed into a predetermined shape by photolithography or the like. A thin film chip resistor manufactured using such a thin film resistor has a specific resistance of 300 μΩ · cm or less, and a good resistance temperature coefficient (TCR) of −25 ppm / ° C. to +25 ppm / ° C. is obtained in this specific resistance region. It is done. For this reason, a chip resistor manufactured using a thin film resistor made of a Ni—Cr alloy or a Cr—Si alloy is widely used as a high precision chip resistor in various electronic devices.

  On the other hand, a thin film resistor used for a thin film chip resistor or the like is required to have not only a small absolute value of resistance temperature coefficient but also a large specific resistance.

  However, at present, it is difficult to produce a high-precision thin film resistor having a high specific resistance of, for example, 500 μΩ · cm or more and a small absolute value of the resistance temperature coefficient using the metal thin film.

  Therefore, research for developing a thin film resistor having a large specific resistance and a small absolute value of the temperature coefficient of resistance has been continued. For example, Patent Document 1 has a large specific resistance of 2000 μΩ · cm or more, Moreover, a thin film resistor made of Si, C, and Cr is disclosed as a thin film resistor having a small absolute value of resistance temperature coefficient (see Patent Document 1). The specific resistance of this thin film resistor is as high as 2000 μΩ · cm or more, but the composition dependence of the resistance temperature coefficient is large, and it is possible to stably produce a thin film having a resistance temperature coefficient within ± 25 ppm / ° C. Have difficulty.

In Patent Document 2, sputtering is performed using a sputtering target in which a valve metal or a transition metal is added to Cr and Si to obtain a thin film resistor. During the sputtering, N ₂ is mixed into Ar as a reactive gas, and further, after film formation, an aging treatment is performed in an N ₂ gas atmosphere, whereby a specific resistance is 500 to 10,000 μΩ · cm and a resistance temperature coefficient is ±±. It is disclosed that a thin film resistor of about 25 ppm / ° C. can be obtained. However, in general, in a thin film resistor formed by reactive sputtering with N _2, it is difficult to control the composition, and it is difficult to obtain a stable resistance value.

Japanese Patent Laid-Open No. 07-086004 Japanese Patent Laid-Open No. 2002-141001

  The present invention has been made in view of such problems, and an object thereof is to stably provide a thin film resistor having a large specific resistance and a small absolute value of a resistance temperature coefficient.

  The first aspect of the thin film resistor according to the present invention is composed of Ni, Cr, Si and C, the content of Si and C is 40 to 65% by mass, and the mass ratio of Cr to Ni is 0.00. It is 15-1.1.

  The thin film resistor preferably has a specific resistance of 500 to 3000 μΩ · cm and a resistance temperature coefficient of −25 to +25 ppm / ° C.

  The second aspect of the thin film resistor according to the present invention is composed of nickel, chromium, silicon and carbon, the content of silicon and carbon is 40 to 65% by mass, and the mass ratio of chromium to nickel is 0. It is a thin film resistor obtained by heat-treating a thin film of 15 to 1.1 so that the temperature coefficient of resistance is −25 to +25 ppm / ° C.

  A thin film resistor manufacturing method according to the present invention includes a sputtering target composed of nickel, chromium, silicon and carbon, or a sputtering target composed of a nickel-chromium alloy and a sputtering target composed of silicon carbide attached to a sputtering apparatus. A thin film comprising nickel, chromium, silicon and carbon, having a silicon and carbon content of 40 to 65 mass% and a mass ratio of chromium to nickel of 0.15 to 1.1, The thin film is heat-treated to form a thin film resistor having a specific resistance of 500 to 3000 μΩ · cm and a resistance temperature coefficient of −25 to +25 ppm / ° C.

  The temperature of the heat treatment is preferably a temperature selected according to the composition of the thin film within a range of 400 to 800 ° C., and the heat treatment is more preferably performed so that the temperature coefficient of resistance is −25 to +25 ppm / ° C. preferable.

  The sputtering target according to the present invention is made of Ni, Cr, Si and C, the content of Si and C is 40 to 65 mass%, and the mass ratio of Cr to Ni is 0.15 to 1.1. It is characterized by being.

  The thin film resistor according to the present invention is made of Ni, Cr, Si and C, the content of Si and C is 40 to 65% by mass, and the mass ratio of Cr to Ni is 0.15 to 1.1. By applying an appropriate heat treatment to the thin film, a thin film resistor having a specific resistance of 500 to 3000 μΩ · cm and a resistance temperature coefficient of −25 to +25 ppm / ° C. can be obtained. .

  By applying a thin film resistor having such a specific resistance and a temperature coefficient of resistance to a chip resistor, a high-precision chip resistor having a large specific resistance of 500 to 3000 μΩ · cm and a small absolute value of the resistance temperature coefficient Can be obtained.

  Further, the specific resistance and the temperature coefficient of resistance of the thin film resistor according to the present invention can be controlled only by the film composition and heat treatment conditions. Therefore, by regulating the film composition and appropriate heat treatment conditions corresponding thereto, a thin film resistor having a large specific resistance and a small absolute value of the resistance temperature coefficient can be stably manufactured.

  The thin film resistor according to the present invention is made of Ni, Cr, Si and C. In general, Ni and Cr are conductive components, and are characterized by a low specific resistance and a low resistance temperature coefficient.

  On the other hand, Si and C are insulating components. In the thin film resistor according to the present invention, the molar ratio of C to Si is not particularly limited, but is preferably 0.9 to 1.3.

  The mass ratio of Cr to Ni in the thin film resistor of the present invention is preferably 0.15 to 1.1, more preferably 0.9 to 1.1. If the mass ratio of Cr to Ni is less than 0.15, the temperature coefficient of resistance increases, which is not preferable. In addition, if the mass ratio of Cr to Ni is greater than 1.1, cracks occur when the Ni—Cr alloy or Ni—Cr—Si—C alloy sputtering target used for manufacturing the thin film resistor of the present invention is manufactured. Since it becomes easy, it is not preferable.

  Since Si and C are insulative components, the inclusion of them has the effect of increasing the specific resistance of the thin film resistor. When the content of Si and C is less than 40% by mass, the specific resistance becomes small and a high-resistance thin film resistor having a resistance of 500 μΩ · cm or more cannot be obtained. Moreover, when the content of Si and C exceeds 65% by mass, a high specific resistance can be obtained. However, even if heat treatment is performed, the absolute value of the negative resistance temperature coefficient becomes large, and a highly accurate thin film resistor can be obtained. Can't get.

  Next, a method for manufacturing a thin film resistor according to the present invention will be described. In the method for manufacturing a thin film resistor according to the present invention, a sputtering method is used as means for forming a thin film. The sputtering method is a method capable of manufacturing a film having a desired composition even with a high melting point material, and is suitable for use in manufacturing a high-precision thin film resistor having a small resistance temperature coefficient. The type of sputtering method used is not particularly limited, and may be a direct current sputtering method or a high frequency sputtering method.

  As the sputtering target, a sputtering target made of Ni, Cr, Si and C and having a Si and C content of 40 to 65% by mass can be used. The composition of the thin film resistor formed using the sputtering target is substantially the same as the composition of the sputtering target. In addition, this sputtering target first produces a sputtering target made of SiC, and then engraves a groove in the surface of the sputtering target and embeds a Ni—Cr alloy chip in accordance with the surface area ratio to obtain a desired composition. You may produce by. Moreover, you may use as a sputtering target what mounted the Ni-Cr alloy chip | tip on the sputtering target which consists of SiC.

  Moreover, it is also possible to produce the thin film resistor according to the present invention by simultaneous sputtering using a sputtering target made of a Ni—Cr alloy and a sputtering target made of SiC.

And after setting the said sputtering target in a sputtering device and evacuating the inside of the system of this sputtering device to a vacuum degree of 1.0 * 10 <^-4> Pa or less, Ar gas (purity: 99.999%) in the system The thin film resistor according to the present invention can be manufactured by forming a thin film by sputtering on the substrate at a sputtering pressure of 0.27 to 1.1 Pa.

  Next, in order to stabilize the specific resistance of the thin film and bring the temperature coefficient of resistance close to 0, the thin film obtained as described above is subjected to heat treatment. In the heat treatment for manufacturing the thin film resistor according to the present invention, an appropriate heat treatment temperature is selected in the temperature range of 400 to 800 ° C. according to the composition. By performing this heat treatment, the temperature coefficient of resistance of the thin film resistor can be reduced to −25 ppm / ° C. to +25 ppm / ° C.

  The reason why the heat treatment temperature is limited to the temperature range of 400 to 800 ° C. is that, in any composition range, if the heat treatment temperature is less than 400 ° C., the resistance temperature coefficient becomes more negative than −25 ppm / ° C. On the other hand, if the temperature exceeds 800 ° C., the temperature coefficient of resistance becomes more positive than 25 ppm / ° C. It is preferable to set the heat treatment temperature for each composition of the thin film so that the absolute value of the resistance temperature coefficient is minimized, and the heat treatment temperature is in the temperature range of 400 to 800 ° C.

  The atmosphere for the heat treatment does not have to be a special atmosphere, and can be performed in an inert atmosphere such as vacuum, argon, nitrogen, or the like.

  As described above, the thin film resistor manufacturing method according to the present invention can control the specific resistance and the temperature coefficient of resistance only by the film composition and the heat treatment condition. It can contribute to manufacturing a resistor stably.

Example 1
The thin film resistor was produced by simultaneous sputtering of a Ni—Cr alloy sputtering target and a SiC sputtering target.

  First, using electric nickel and electrolytic chromium as raw materials, each was weighed so that the mass ratio of Cr to Ni was 1.0, and an ingot of about 2 kg of Ni—Cr alloy was prepared in a vacuum melting furnace. After the ingot was homogenized, a round plate having a thickness of 5 mm and a diameter of 150 mm was cut by wire cutting, and the upper and lower surfaces were ground to obtain a Ni—Cr alloy sputtering target.

  This Ni-Cr alloy sputtering target and SiC sputtering target (Purebeta S manufactured by Bridgestone, diameter 154.2 mm, thickness 5 mm) are set in a DC sputtering apparatus (SBH2206 manufactured by ULVAC) and as a substrate on which a film is formed, Kyocera Corporation Alumina substrate manufactured and graded: A476 (hereinafter referred to as “substrate”) was set in the apparatus.

After the inside of the system was evacuated to 1.0 × 10 ⁻⁴ Pa or less, Ar gas (purity: 99.999%) was introduced, the sputtering pressure was set to 0.3 Pa, and simultaneous sputtering was performed on the substrate. A thin film was formed. The output of the Ni—Cr alloy sputtering target was 0.6 A, the output of the SiC sputtering target was 1.46 A, and a film having a thickness of 50 nm was formed by adjusting the sputtering time. After performing sputtering for a predetermined time, the substrate on which a thin film was formed was taken out from the chamber after cooling for 30 minutes or more. Note that pre-sputtering was performed for 10 minutes or more with the shutter closed before forming a film on the substrate by sputtering.

  The thus obtained thin film resistor of Example 1 was quantitatively analyzed by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). As a result, the content of Ni and Cr was 50% by mass. The Si and C contents were 50 mass%, and the mass ratio of Cr to Ni was 1.0.

The thin film resistor formed on the substrate is placed in a vacuum furnace, and in a vacuum (7.0 × 10 ⁻³ Pa or less), the temperature condition is changed at intervals of 100 ° C. within a temperature range of 300 to 900 ° C. for 30 minutes. A thin film resistor sample was prepared by performing heat treatment and changing the heat treatment temperature. The rate of temperature increase was 10 ° C./min up to 10 ° C. before each heat treatment temperature, and the temperature from that temperature to the temperature for heat treatment was 1 ° C./min. And it hold | maintained for 30 minutes at each heat processing temperature.

  A thin film resistor sample that was heat-treated in vacuum and a thin film resistor that was not heat-treated were deposited on both sides of Ni with a thickness of 50 nm by sputtering, and Au with a thickness of 300 nm was further deposited thereon by sputtering. A thin film resistor sample on which Ni / Au electrodes were formed was obtained. The substrate was placed in an atmospheric furnace and subjected to a heat treatment in the atmosphere at 300 ° C. for 3 hours for stabilization treatment. The heating rate was 10 ° C./min from 290 ° C. and 1 ° C./min from 290 ° C. to 300 ° C.

  About the thin film resistor sample taken out from the atmospheric furnace, the film thickness t (cm), the length L (cm), the width W (cm) are measured, and further the resistance R (Ω) is measured by the DC four-terminal method, The specific resistance was determined from the following formula 1.

In addition, the resistor sample was put in a thermostat, the resistance value R ₂₅ [Ω] at ₂₅ ° C. and the resistance value R ₁₂₅ [Ω] at 125 ° C. were measured, and the temperature coefficient of resistance was obtained from the following formula 2.

  Table 1 shows the measurement results of the specific resistance and resistance temperature coefficient of the thin film resistor of Example 1 when the heat treatment temperature in vacuum is varied in the range of 300 to 900 ° C. at intervals of 100 ° C.

  As can be seen from Table 1, when the heat treatment temperature in vacuum is in the range of 300 to 900 ° C., the specific resistance does not depend greatly on the heat treatment temperature, but tends to increase as the heat treatment temperature increases.

  On the other hand, the temperature coefficient of resistance greatly depends on the heat treatment temperature. The lower the heat treatment temperature, the larger the resistance temperature coefficient becomes, and the higher the heat treatment temperature, the larger the resistance temperature coefficient. When the heat treatment temperature is 500 ° C., the absolute value of the resistance temperature coefficient is the smallest.

  Therefore, when the manufacturing method according to the above-described conditions is used, the thin film resistor having the above composition is preferably subjected to heat treatment at 500 ° C.

(Example 2)
A thin film is formed in the same manner as in Example 1 except that the output of the Ni—Cr alloy sputtering target is 0.6 A, the output of the SiC sputtering target is 0.98 A, and the film formation rate of Si and C is smaller than that of Example 1. A resistor was produced.

  The obtained thin film resistor of Example 2 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 60% by mass, the content of Si and C was 40% by mass, and the mass of Cr with respect to Ni The ratio was 1.0.

  For the thin film resistor of Example 2 obtained, the heat treatment temperature when the resistance temperature coefficient became the smallest when the heat treatment temperature in vacuum was varied in the range of 300 to 900 ° C. at intervals of 100 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Example 3)
Implementation was performed except that the output of the Ni—Cr alloy sputtering target was 0.3 A, the output of the SiC sputtering target was 1.36 A, and the output of the Ni—Cr alloy sputtering target relative to the output of the SiC sputtering target was smaller than that of Example 1. A thin film resistor was produced in the same manner as in Example 1.

  The obtained thin film resistor of Example 3 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 35% by mass, the content of Si and C was 65% by mass, and the mass of Cr with respect to Ni The ratio was 1.0.

  For the thin film resistor of Example 3 obtained, the heat treatment temperature when the resistance temperature coefficient became the smallest when the heat treatment temperature in vacuum was varied in the range of 300 to 900 ° C. at intervals of 100 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Example 4)
A Ni—Cr alloy was produced so that the mass ratio of Cr to Ni was 0.15, and a Ni—Cr alloy sputtering target was produced using this. And the thin film resistor was produced like Example 1 except the output of the Ni-Cr alloy sputtering target being 0.6A, and the output of the SiC sputtering target being 1.45A.

  The obtained thin film resistor of Example 4 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 50% by mass, the content of Si and C was 50% by mass, and the mass of Cr with respect to Ni The ratio was 0.15.

  For the thin film resistor of Example 4 obtained, the heat treatment temperature when the resistance temperature coefficient became the smallest when the heat treatment temperature in vacuum was swung at 100 ° C. in the range of 300 to 900 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Example 5)
A Ni—Cr alloy was produced so that the mass ratio of Cr to Ni was 1.1, and a Ni—Cr alloy sputtering target was produced using this. A thin film resistor was produced in the same manner as in Example 1 except that the output of the Ni—Cr alloy sputtering target was 0.6 A and the output of the SiC sputtering target was 1.46 A.

  The obtained thin film resistor of Example 5 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 50 mass%, the content of Si and C was 50 mass%, and the mass of Cr with respect to Ni The ratio was 1.1.

  For the thin film resistor of Example 5 obtained, the heat treatment temperature when the resistance temperature coefficient was the smallest when the heat treatment temperature in vacuum was varied in the range of 300 to 900 ° C. at intervals of 100 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Comparative Example 1)
A thin film resistor was fabricated in the same manner as in Example 1 except that the output of the Ni—Cr alloy sputtering target was 1.0 A and the output of the SiC sputtering target was 1.05 A.

  The obtained thin film resistor of Comparative Example 1 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 70% by mass, the content of Si and C was 30% by mass, and the mass of Cr with respect to Ni The ratio was 1.0.

  For the thin film resistor of Comparative Example 1 obtained, the heat treatment temperature when the temperature coefficient of resistance became the smallest when the heat treatment temperature in vacuum was varied in the range of 300 to 900 ° C. at intervals of 100 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Comparative Example 2)
A thin film resistor was fabricated in the same manner as in Example 1 except that the output of the Ni—Cr alloy sputtering target was 0.2 A and the output of the SiC sputtering target was 1.14 A.

  The obtained thin film resistor of Comparative Example 2 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 30% by mass, the content of Si and C was 70% by mass, and the mass of Cr with respect to Ni The ratio was 1.0.

  For the thin film resistor of Comparative Example 2 obtained, the heat treatment temperature when the temperature coefficient of resistance became the smallest when the heat treatment temperature in vacuum was varied at intervals of 100 ° C. in the range of 300 to 900 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

(Comparative Example 3)
A Ni—Cr alloy was produced so that the mass ratio of Cr to Ni was 0.1, and a Ni—Cr alloy sputtering target was produced using this. A thin film resistor was fabricated in the same manner as in Example 1 except that the output of the Ni—Cr alloy sputtering target was 0.6 A and the output of the SiC sputtering target was 1.45 A.

  The obtained thin film resistor of Comparative Example 3 was quantitatively analyzed by ICP-AES. As a result, the content of Ni and Cr was 50% by mass, the content of Si and C was 50% by mass, and the mass of Cr with respect to Ni The ratio was 0.1.

  For the thin film resistor of Comparative Example 3 obtained, the heat treatment temperature when the temperature coefficient of resistance becomes the smallest when the heat treatment temperature in vacuum is in the range of 300 to 900 ° C. at intervals of 100 ° C., and this heat treatment Table 2 shows the specific resistance and temperature coefficient of resistance of the thin film resistor heat-treated by temperature.

  As can be seen from Table 2, in Examples 1 to 5, which are within the scope of the present invention, the specific resistance falls within the range of 500 to 3000 μΩ · cm by appropriately setting the heat treatment temperature in vacuum. In addition, the temperature coefficient of resistance is in the range of −25 to +25 ppm / ° C.

  In contrast, in Comparative Example 1, the contents of Si and C are 30% by mass, which is lower than the lower limit of 40% by mass of the present invention. For this reason, even if heat treatment is performed in vacuum at an optimum temperature, the specific resistance is 350 μΩ · cm, lower than 500 μΩ · cm, and the resistance temperature coefficient is 50 ppm / ° C., −25 to +25 ppm Not within the range of / ° C.

  In Comparative Example 2, the contents of Si and C are 70% by mass, which exceeds the upper limit of 65% by mass of the present invention. For this reason, although the specific resistance was as large as 20000 μΩ · cm, the resistance temperature coefficient was −1500 ppm / ° C. even when heat treatment in vacuum was performed at the optimum temperature, which was greatly deviated from the range of −25 to +25 ppm / ° C. ing.

  In Comparative Example 3, although the contents of Ni and Cr and Si and C are within the scope of the present invention, the mass ratio of Cr to Ni is 0.1, which is the lower limit of 0.15 of the present invention. Is below. For this reason, even if it heat-processes in vacuum at optimal temperature, a resistance temperature coefficient is 100 ppm / degrees C, and is not in the range of -25- + 25 ppm / degrees C.

It is a schematic diagram of the thin film resistor sample in which the Ni / Au electrode was formed.

Explanation of symbols

1 Alumina substrate 2 Thin film resistor 3 Ni electrode 4 Au electrode

Claims (3)

  It consists of nickel, chromium, silicon and carbon, the silicon and carbon content is 40 to 65 mass%, the mass ratio of chromium to nickel is 0.15 to 1.1, and the specific resistance is 500 to A thin film resistor having a resistance of 3000 μΩ · cm and a temperature coefficient of resistance of −25 to +25 ppm / ° C.   A thin film made of nickel, chromium, silicon and carbon, having a silicon and carbon content of 40 to 65% by mass and a mass ratio of chromium to nickel of 0.15 to 1.1, has a resistance temperature coefficient. The thin film resistor according to claim 1 obtained by heat-treating so that it may become -25- + 25 ppm / degrees C.   A sputtering target made of nickel, chromium, silicon and carbon, or a sputtering target made of nickel-chromium alloy and a sputtering target made of silicon carbide are mounted on a sputtering apparatus, and made of nickel, chromium, silicon and carbon by a sputtering method. And a carbon content of 40 to 65% by mass and a mass ratio of chromium to nickel of 0.15 to 1.1 is formed, and then the composition of the thin film within a range of 400 to 800 ° C. The thin film is heat-treated at a temperature selected according to the above, to form a thin film resistor having a specific resistance of 500 to 3000 μΩ · cm and a resistance temperature coefficient of −25 to +25 ppm / ° C. A method for manufacturing a thin film resistor.

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