JPH01256101A - Thin film type thermal head - Google Patents

Abstract

PURPOSE:To realize the high speed operation of a thermal head, and improve the high temperature stability, by making the temperature coefficient of resistance of Ta-SiO2 as a thin film heater resistor approximate to zero. CONSTITUTION:The temperature coefficient of resistance TCR of a thin film heating resistor 2 composed of tantalum-silicon oxide (Ta-SiO2) is made 0 to -500ppm in the resistivity range of 1-100mOMEGA.cm. As a result, the TCR can be almost equal to zero, by performing Ta-SiO2 sputtering, wherein a target whose SiO2 mol ratio in the target composition ratio is in a range of 30-70%, and argon gas pressure is kept about 10<-2>Torr. Thereby, the high speed operation of a thermal head is realized, and the improvement of high temperature stability and durability can be easily attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film heating element for a thin film type thermal head used for thermal recording printing.

(Prior art) - The thermal head used for thermal recording printing is absolutely unique! A plurality of heat generating resistors and electrodes for supplying power to the heat generating resistors are provided on a substrate, and a voltage is applied to the electrodes. By applying this, Joule heat is generated in the heating resistor, and numbers, letters, symbols, etc. are printed and recorded on heat-sensitive recording paper.

In recent years, such thermal heads have become faster printing, larger, and
There is a strong demand for characteristics such as low current consumption and high reliability due to high density.

For high-speed printing, recording must be performed using short printing pulses of several milliseconds, and for this purpose it is necessary to apply a large current to the heating resistor to instantaneously generate a temperature of 400° C. or more. In addition, as the size increases, the resistance value of the electrode that supplies power to the heating resistor cannot be ignored compared to the resistance value of the heating resistor, so the amount of heat generated by each heating resistor differs depending on the electrode pattern, resulting in density differences in the recording pattern. Since the number of heating resistors to be driven at once increases due to high density, the current capacity of the drive system such as the heating power source and the switching circuit increases.

To solve these problems, it is necessary for heating resistor materials to have high temperature stability and high resistance, but tantalum nitride (Ta-N), which has been the mainstream of conventional heating element materials, has a low specific resistance. The film thickness is as low as 200 to 300 μΩ, around 200 μΩ, and the optimum resistance value requires a film thickness of about 100.
Control during manufacturing is extremely difficult, and the film quality is also unstable. To avoid this, it is possible to increase the length of the heating element and increase the resistance value by increasing the thickness of Ta-N and forming a meandering pattern, but this method is difficult to manufacture when achieving high resolution. There was a problem that it was extremely difficult and the yield was low.

For this reason, Ta-5iO□ is considered as a heating resistor material that can obtain high resistance, or in other words, has a high specific resistance, instead of Ta-H, but Ta-5iJ has a specific resistance of 1 to 100μ.
The TCP is -500 in the range of about Ω・c111
Since it has a large negative value of ~-1000 pp+m, it has poor high temperature stability and is unsuitable as a thin film heating resistor material for a thermal head.

[Problem to be solved by the invention]

As mentioned above, Ta-5i02 does not have sufficient characteristics for high speed and high temperature stability as a heating resistor material for a thermal helad.

From this point of view, it is an object of the present invention to provide a thin film type thermal head equipped with a thin film heating resistor having characteristics necessary for increasing the speed of the thermal head and achieving high temperature stability.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention controls the conditions at the time of manufacturing the thin film heating resistor to produce Ta as the thin film heating resistor.
The TCR of -5iOz is made close to zero, and a thin film type thermal head equipped with this is constructed.

[Effect]

As mentioned above, when trying to obtain a heating resistor with high specific resistance using Ta-5iO□, there is a problem that TCP increases on the negative side and high temperature stability deteriorates.
By controlling the manufacturing conditions, a thin film heating resistor with high resistivity and TCP close to zero can be obtained, and a thermal head equipped with a thin film heating resistor with excellent high temperature stability can be constructed.

〔Example〕

FIG. 1 shows a sectional view of a thin film type thermal head according to the present invention.

In FIG. 1, a thin film heating resistor 2 made of Ta-5iJ is formed on an electrically insulating substrate l by spuckling,
On top of this is an electrode 3 for supplying power to the thin film heating resistor.
After forming a pattern, a pattern is formed using photolithography technology, and on top of this, a Fjl) 1j4 heating resistor is used to prevent oxidation during heat generation and to prevent abrasion with the recording paper that heats up during printing.
It has a structure in which an I film 4 is formed.

Sputtering of Ta-3iO□ was performed by conventional sputtering, and a TTa-5in sintered body was used as a target. Among the sputtering conditions, the target composition ratio and argon gas pressure are controlled to improve the temperature coefficient of resistance (TCR).
) are shown in FIGS. 2 and 3.

FIG. 2 shows the change in TCP with respect to the 5iOz molar ratio in the target composition ratio, with sputtering conditions other than the Targetera 1411 composition ratio fixed.

Although the specific resistance decreases as the 5iOz molar ratio decreases, the TCR approaches zero as shown in the figure. In addition, Figure 3 shows that sputtering conditions other than argon gas pressure are fixed.
This shows the change in TCP with respect to argon gas pressure. TCP approaches zero as argon gas pressure increases, and TCP shifts to the positive side from around 5 X 10-"Torr. At this time, the specific resistance changes with argon gas pressure. rise,
It suddenly becomes larger than 10-tTorr.

Next, a continuous pulse application test was conducted using a thermal head equipped with Ta-5iO□ thin film heating resistors with different TCPs.

For sputtering, a Ta-3iO□ sintered body target with a SiO□ molar ratio in the target composition ratio of 30% was used, and the argon gas pressure was changed to apply thin film heating resistors with different TCPs. A comparison was made of thermal heads equipped with

Thin film heating resistors A and B are shown in the table below.

Table I Fjl film heating resistor test conditions are pulse width 1m5ec + pulse period l
Q++pec+ Applied power 4 (V/ms”)
Figure 4 shows the rate of change from the initial resistance value. From this result, it can be seen that the closer the TCR is to 01111m, the smaller the rate of change in resistance cm and the significantly better durability.

As mentioned above, in Ta-5iO□ sputtering, the 5iOz molar ratio in the target m acid ratio is 30 to 7.
Using a target in the 0% range, the argon gas pressure was 10%.
-" When carried out on a Torr stand, the TCP is close to zero and has good durability, so a thin film thermal head equipped with this is extremely reliable and can easily handle high speed and high temperature stability.

In this example, Ta-5 was used as the sputtering target.
Although an iJ sintered body was used, it goes without saying that similar results can be obtained using a composite target of Ta and 5i(h), and that similar results can also be obtained by magnetron sputtering.

〔Effect of the invention〕

As described above, the present invention controls the sputtering conditions in the Ta-5ift heating resistor material so that the TCP is 0.
This is a thin film thermal head equipped with a thin heating resistor of ~-500ppm, which makes it easy to increase the speed, high temperature stability, and durability of the thermal head, and its industrial value is extremely high. .

[Brief explanation of the drawing]

Figure 1 is a sectional view of the thin film thermal head according to the present invention, Figure 2 is a relationship between TCP and SiO□ molar ratio in the target Vt ratio, and Figure 3 is a diagram of TCP versus argon gas pressure.
The CP relationship diagram, FIG. 4, is a diagram showing the continuous pulse application life as an embodiment of the present invention. Applicant: Seiko Electronics Industries Co., Ltd.

Claims (1)

[Claims] (1) Thin film type equipped with a thin film heating resistor made of tantalum-silicon oxide (Ta-SiO_2), the temperature coefficient of resistance of the thin film heating resistor being 0 to -500 ppm in a specific resistance range of 1 to 100 mΩ·cm thermal head.