JPH0640522B2 - Thin film resistor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film resistor, in particular, a heating resistor for a thermal head of a thermal recording device of a facsimile, a resistor for a hybrid integrated circuit, and a device using another thin film resistor. The present invention relates to a thin film resistor that can be applied to.

2. Description of the Related Art Tantalum nitride thin film resistors have been widely used in thermal heads and hybrid integrated circuits up to now, but their long resistance has been limited mainly because of their low resistance. In particular, thin film resistors for thermal heads are used under severe conditions, and therefore, thermally stable thin film resistors having high resistance and excellent oxidation resistance are required.

Problems to be Solved by the Invention There is a demand for a highly reliable thermal head for heat-sensitive recording capable of high-definition and high-speed (high efficiency) printing. Since the rate is low, it is necessary to reduce the film thickness of the heating element segment to obtain a predetermined electric resistance value to 1000 Å or less,
It was difficult to obtain a stable thin film of good quality. Owing to the thin film thickness, the oxidation resistance was inferior, and the resistance was largely changed over time, resulting in low reliability. Further, a hard thick protective film layer is required to prevent the above-mentioned oxidation and to improve the wear resistance of the surface of the heating element, and this is one of the causes of deteriorating the thermal efficiency.

The present invention is intended to obtain a thermally stable thin film having high resistivity and high hardness.

Means for Solving the Problems Using a mixed target of SiC and TiC or ZrC, a thin film formed by a sputtering method is used as a resistor.

Action A compound of the transition elements of Groups 4 to 6 of the periodic table and non-metal atoms Si, B, C and N having a small atomic radius is known as a hard alloy and has high hardness and low resistivity. Thermodynamic stability is generally high for those containing a Group 4 transition element such as Ti or Zr.

The resistance of these compounds is generally too low for a resistor thin film for a thermal head. Therefore, it is possible to increase the resistance by compounding with another hard and high resistivity compound.

Of the above hard alloys, TiN and Z, which have high thermodynamic stability
A thin film resistor made by using rN and forming a composite thin film of each of them with SiC having high resistance, high hardness, and excellent oxidation resistance by a sputtering method has higher resistivity than conventional It is hard and thermally stable, and is excellent in oxidation resistance due to the thickness effect of the thin film together with the material.

Example SiC and TiN powder were used as starting materials and mixed in various weight ratios. A ceramic plate was formed by forming and heat-treating to prepare a sputtering target.

The target was sputtered using a high frequency magnetron sputtering device to form a thin film on the glazed alumina substrate. Typical sputtering conditions are shown below.

Sputtering power: 2 KW / 20 cm diameter target Sputtering gas and gas pressure: Ar, 3 × 10 ^-2 Torr Substrate temperature: 400 ° C. Substrate-target distance: 6 cm Under the above conditions, for example, a target of TiN: SiC = 1: 2 weight ratio is 10 When sputtered for a minute, a thin film having a metallic luster having a film thickness of 0.95 μm was obtained. Considering the general operating temperature of the thermal head of 350 ° C, the substrate temperature during sputtering was set to 400 ° C, which is slightly higher than that.
It was possible to obtain a similar thin film having metallic luster even when the temperature was changed in the range of 700 ° C. The composition of the thin film and the target was found to be almost the same by Auger spectroscopy and atomic absorption spectroscopy, but the thin film shows a halo peak by X-ray diffraction, and the crystal phase cannot be identified. However, various hard alloys TiN, TiC, Si ₃ composed of four elements of Ti, N, Si and C ₃
It is considered to be a composite alloy thin film having a bond such as N ₄ , SiC and TiSi ₂ .

As a result of measuring the hardness of the thin film, it was found that the dependence on the composition was small and a Knoop hardness of 2000 was obtained, which was very hard as the SiC alone. This means that the protective film layer conventionally provided on the heating resistor can be eliminated or made as thin as possible if the resistor has oxidation resistance, and the thermal head can be made highly efficient. A thin film was formed by changing the composition of the target variously, and the resistivity was measured. The results are shown in the figure.

With the composition containing only TiN, a thin film having a resistivity of 1 × 10 ⁻⁴ Ω · cm was obtained. This resistivity is almost the same as that of the conventional resistor thin film, and the thickness of the heating element segment cannot be made larger than that of the prior art. At least 1 × 10 ^-3 Ω
A value of cm or more is required. For that purpose, it is understood from the figure that the content of SiC should be 0.35 weight ratio or more. S
As the content of iC increases, the resistivity increases, and 0.8% by weight of S
When iC is included, it becomes 1 × 10 ⁻¹ Ω · cm. In this way, the resistivity of the resistance film can be changed in an analog manner by changing the composition, which is very advantageous in designing the heating element of the thermal head. This is also one of the characteristics of the thin film resistor of the present invention.

If the SiC content exceeds 0.8 weight ratio, the thickness of the heating element thin film of the thermal head becomes several μm or more, and the etching process becomes difficult. Generally, in terms of composition, the greater the amount of SiC, the more difficult etching is. Therefore, a suitable composition range of 0.35 to 0.8 by weight ratio of SiC is suitable as a resistor thin film for a thermal head.

Next, the maximum temperature of the heating element of the thermal head is 400 ° C
Then, an aging test of oxidation resistance was performed. A thin film having a thickness of 3000 Å was formed on an A ₂ O ₃ substrate provided with a pair of gold electrode films, which was held in air at a temperature of 400 ° C., and the change in resistance was examined with time. As a result, the resistance increase within 20% was observed after 2000 hours for various composition films. On the other hand, the resistance of the tantalum nitride film formed with the same structure doubled after 24 hours. From this, it is understood that the resistor thin film of the present invention is a material having excellent oxidation resistance as compared with the conventional tantalum nitride film.

Further, the SiC-ZrN system was examined by almost the same method as the above-mentioned SiC-TiN system. ZrN is very similar in electrical and chemical properties to TiN. As with TiN, thin films having metallic luster were obtained with various compositions, the X-ray diffraction pattern had a halo peak, and the hardness was the same as that of TiN. However, the resistivity with respect to the composition is somewhat higher, and the change is shown by the broken line in the figure as well. ZrN
1.2 × 10 ⁻⁴ Ω · cm alone, 20 compared to TiN
Although the resistivity is increased by%, when the SiC content increases, the Si content increases.
It approaches the composition versus resistivity change of the C-TiN system. 1 x 10 ^-3
A resistivity of Ω · cm or more can be obtained with a SiC content of 0.35 weight ratio or more. The oxidation resistance aging test also obtained the same result as that of the SiC-TiN system.

The resistor thin film excellent in high resistivity, high hardness and oxidation resistance described above is naturally applied not only to the above thermal head but also to other applications such as a resistor for a hybrid integrated circuit and a device using a thin film heater. I will get it.

Effects of the Invention The resistor thin film of the present invention is 1 × 10 ⁻³ to 1 × 10 ⁻¹ Ω · cm.
The desired resistance value can be selected by changing the composition. According to the above resistivity, for example, 10
A heating element for a thermal head having a thickness of 00Å to several μm, which is thicker than the conventional one, can be prepared. Therefore, a thin-film heating resistor having excellent oxidation resistance, that is, high reliability due to the thickness effect as well as the stable characteristics of the material itself can be obtained. The hardness is SiC
Since it is the same as the above, either remove the protective layer on the surface of the heating resistor,
It is possible to create a thermal head that is as thin as possible and has high thermal efficiency. It is possible to provide a resistor having various stable resistivities even for a device using another thin film resistor.

[Brief description of drawings]

The figure is a graph showing the composition change of the resistivity of the thin film resistor prepared from the targets with different mixing ratios of SiC and TiN and SiC and ZrN.

Claims (2)

[Claims] 1. A thin-film resistor formed by a sputtering method using a mixed target of SiC and TiN or ZrN. 2. The thin film resistor according to claim 1, wherein the weight ratio of SiC to TiN or ZrN is in the range of 3.5: 6.5 to 8: 2.