JPH054362A - Method of manufacturing thermal head - Google Patents

Abstract

(57) [Summary] [Purpose] In the conventional protective film of a thermal head, the conventional protective film mainly containing silicon, boron, and nitrogen is used as a method of covering only the necessary portion, and heat is applied to the unnecessary portion before the protective film is laminated. However, this method has caused pinhole defects due to paste dust. An object of the present invention is to prevent the occurrence of this defect and to obtain a more reliable thermal head. [Structure] The wear-resistant protective film 7 containing silicon, boron, and nitrogen as main components is laminated on the entire surface of the thermal head, and then the unnecessary portion 10 of the protective film is removed by plasma etching or wet etching. Further, the present invention can be applied to a case in which a lower wear-resistant protective film 12 containing silicon, oxygen, and nitrogen as main components is formed to form a multilayer protective film, and the conventional method can eliminate many pinhole defects.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thermal head used in a printer of office automation (OA) equipment such as a facsimile and a video printer.

[0002]

2. Description of the Related Art A wear-resistant protective film made of a material containing silicon, boron and nitrogen as main components has conductivity (about 10 ⁹ Ωm), and thus prevents electrostatic charge. This is a material that is effective as a wear-resistant protective film of a thermal head mounted in a thermal transfer type printer that easily causes electrostatic breakdown due to the generation of static electricity, and thus is mainly used for a thermal transfer thermal head. In addition, a material film containing silicon, oxygen, and nitrogen as main components is formed on the first layer, and silicon is formed on the second layer on the material film.
The two-layer wear-resistant protective film formed with a material film containing boron and nitrogen as main components has the characteristics of the above-mentioned single-layer wear-resistant protective film containing silicon, boron and nitrogen as main components, as well as silicon and oxygen. , Nitrogen-based material film is insulating (10 ¹²
Since it is more than Ωm), it is possible to prevent the phenomenon that the drive current flowing through the heating resistor flows to the abrasion-resistant protective film side and causes abnormal heat generation (smoke phenomenon), and for a thermal head that requires anti-static property and smoke prevention property. used.

Here, conventionally, when the wear-resistant protective film for such a thermal head is formed, since these are formed by a method such as sputtering or plasma CVD method, the wear-resistant protective film is formed only on a specific portion. It cannot be formed and is formed over the entire surface. Therefore, in order to prevent the wear-resistant protective film from being formed on the external lead portion of the wiring electrode required for the mounting process and the connecting portion to the driving semiconductor element, that is, the portion where the electrode must be exposed, the unnecessary portion is removed by etching. Although there is a method of removing it, a method of etching a material film containing silicon, boron, and nitrogen as main components has not been performed so much. Therefore, a method of removing an unnecessary portion of the abrasion resistant protective film is performed by the following method. Before forming the wear-resistant protective film (or 11, 12), a water-soluble paste is applied to a portion where the wear-resistant protective film is not desired to be formed with the resistors, electrodes and the like exposed. After drying this, a wear-resistant protective film is formed by sputtering, plasma CVD or the like. After that, when the thermal head substrate on which the abrasion-resistant protective film is formed is immersed in water, the abrasion-resistant protective film in the portion coated with the paste is peeled off and the unnecessary abrasion-resistant protective film is removed.

Here, the water-soluble paste is composed mainly of bentonite, which is a kind of clay containing montmorillonite as a main component containing silica, alumina and magnesia as a main component, and is heat resistant. Since it is excellent in heat resistance and can be easily peeled off with water, it may be used as a mask material for a high temperature film as described above.

[0005]

However, the above conventional methods have the following problems. Originally, a very strict clean environment is required in the process until the abrasion-resistant protective film is formed, but in the conventional method, when the abrasion-resistant protective film is formed of a high temperature film (about 300 ° C), Applying the above-mentioned paste as a mask material to the unnecessary portion before forming the abrasion-resistant protective film is a major obstacle to achieving the required clean environment. In fact, the thermal head manufactured by the conventional method may have many pinholes in the wear-resistant protective film due to the dust caused by the paste, and such a thing does not serve as the wear-resistant protective film. , Treated as defective.

Therefore, in order to eliminate this defect (pinholes caused by dust from the paste), the present invention eliminates the step of using the paste, and then wear-protects the protective film by high-temperature film formation such as sputtering or plasma CVD. Is selectively formed to obtain a highly reliable thermal head.

[0007]

In order to achieve the above-mentioned object, the present invention provides silicon on the entire surface of a substrate having a plurality of resistors patterned in a predetermined shape and wiring electrodes for energizing the resistors. , A step of forming a wear-resistant protective film containing boron and nitrogen as a main component, and a unnecessary portion of the wear-resistant protective film formed in the previous step is plasma-treated using a gas containing sulfur hexafluoride and oxygen as a main component. And a step of removing by etching.

The unnecessary portion of the wear-resistant protective film may be wet-etched with a solution containing phosphoric acid as a main component.

[0009]

According to the method of the present invention, a wear-resistant protective film can be formed only on a necessary portion without using a paste, and therefore, pinholes caused by the dust due to the paste can be eliminated, and a process for forming the wear-resistant protective film can be performed. Therefore, the defect rate can be reduced.

[0010]

EXAMPLE An example of a method of manufacturing a thermal head according to the present invention will be described below with reference to FIGS. 1 (a) to 1 (c) and 2 (a).
An explanation will be given using (e).

In the figure, 1 is an alumina substrate, 2 is a glaze layer, 3 is a ceramic layer, 4 is a heating resistor layer, 5 is an individual electrode, 6 is a common electrode, 7 is a wear-resistant protective film, 8 is a heating portion,
Reference numeral 9 is a protective film required portion, 10 is a protective film unnecessary portion, 11 is an upper abrasion resistant protective film, 12 is a lower abrasion resistant protective film, and 13 is a mask.

In the method of the present embodiment, the wear-resistant protective film is formed in a state where the individual electrodes 5, the common electrode 6, the heating resistor layer 4, etc. are exposed as shown in FIGS. 1 (a) and 2 (a). , Plasma C
A single layer type wear-resistant protective film 7 made of a material containing silicon, boron and nitrogen as main components by the VD method, the sputtering method or the like.
Are formed as shown in FIG. In the case of the two-layer type, the upper wear-resistant protective film 11 containing silicon, boron and nitrogen as main components and the lower wear-resistant protective film 12 containing silicon, oxygen and nitrogen as main components are shown in FIG. As described above, the protective film required portion 9 and the protective film unnecessary portion 10 are formed over the entire surface. In the present embodiment, a gas mainly containing silane, nitrogen and oxygen is used as a raw material for the lower wear resistant protective film 12 by the plasma CVD method. And a gas having silane, diborane, and nitrogen as main components is formed as a raw material on the upper wear-resistant protection film 11 to form a two-layer structure wear-resistant protection film. Of the abrasion-resistant protective film thus formed, the protective film unnecessary portion 10 to be removed is, as shown in FIG. It is a part.

In this embodiment, as described in claim 1 and claim 3, the protective film unnecessary portion 10 is removed by a plasma etching method using a gas containing sulfur hexafluoride and oxygen as main components. The wear-resistant protective film can be applied to either a single-layer film or a two-layer film, but this embodiment shows an example of the above-mentioned two-layer film. First, a mask 13 made of aluminum is provided to etch only the protective film unnecessary portion 10. It is sufficient to form about 1000 angstroms at room temperature by vacuum evaporation on the necessary portion 9 of the mask 13 protective film made of aluminum. The mask 13 is used here.
Is aluminum, but is not particularly limited,
There is no particular problem as long as it is not affected by the gas plasma of sulfur hexafluoride and oxygen. Other than this, it is possible to use an etching resist, a photoresist, or the like.

As shown in FIG. 2C, a thermal head having a mask 13 formed thereon is set in a high frequency plasma etching apparatus, the substrate temperature is low from room temperature to about 150 ° C., and the gas species and gas flow rate are For example, if sulfur hexafluoride is 300 sccm and oxygen is 100 sccm, the pressure is 500 to 1
RF power of 500 W is applied at about 000 mTorr for etching. Here, if the temperature is raised too much, the etching rate becomes too fast, and it is difficult to determine the etching end point, so the temperature is set to the above level,
If there is no problem, it is possible to raise the temperature further.
In this way, after etching the abrasion-resistant protective film having a two-layer structure of about 5 μm, if the mask 13 is removed with an acid or the like, the abrasion-resistant protective film is formed only on the protective film necessary portion 3 as shown in FIG. 2 (e). You can leave. Further, it is obvious that these can be performed by the same method even in the case of a single layer film containing silicon, boron and nitrogen as main components as shown in FIG.

The electrode material generally used in the thermal head is aluminum, copper, gold or the like, but these are not plasma-etched with sulfur hexafluoride or oxygen gas used in this embodiment. The electrode material used in this example has a two-layer structure of chromium and copper.

Next, another embodiment of the present invention will be described. As in the first embodiment, after the wear-resistant protective film is formed on the entire surface, the removing step of the protective film unnecessary portion 4 is a method of etching with a solution as described in claims 2 and 4. A heat-drying resist for hydrofluoric acid is used as the mask 13, and the resist is applied only to the protective film required portion 3. First, an etching solution of phosphoric acid 85% at 150 ° C. or higher is used for etching the upper wear-resistant protective film 11 containing silicon, nitrogen, and boron as main components. Phosphoric acid is used to etch the lower wear-resistant protective film 12 containing silicon, nitrogen, and oxygen as main components.
A solution obtained by heating a mixed solution of ammonium fluoride to about 90 ° C is used. First, after etching the upper wear-resistant protective film 11 with an etching solution of phosphoric acid 85% at 150 ° C. or higher (FIG. 2D).
), The lower wear-resistant protective film 12 is etched with an etching solution of a mixed solution of phosphoric acid and ammonium fluoride, and finally the resist 13 is removed with a solvent, so that only the necessary portion 3 of the wear-resistant protective film can be left. (See FIG. 2 (e)). Here, since the etching ratio of the mixture of phosphoric acid and ammonium fluoride is different depending on the composition ratio of silicon, nitrogen, and oxygen of the lower wear-resistant protective film 12, the wear-resistant wear-resistant film to be formed is Mix so that the etching rate is the fastest. The approximate ratio is between 5/95 and 20/80 for ammonium fluoride / phosphoric acid, for example 10 / for the wear-resistant protective film formed by the plasma CVD method of this time.
The mixing ratio of 90 is good. Here, since the phosphoric acid-based solution may be corroded by aluminum, chromium, etc., it is necessary to carefully control the etching end time. If possible, it is desirable to use a material that is not corroded by these etching solutions as the electrode material, but in this embodiment, a mixture of ammonium fluoride / phosphoric acid used for the protective film containing silicon, oxygen, and nitrogen as the main components is used. Since the solution has a relatively low etching rate for chromium and copper, the control of the etching end time was relatively easy.

Next, another embodiment of the present invention will be described. After forming the abrasion-resistant protective film on the entire surface similarly to the first embodiment, the unnecessary abrasion-resistant protective film removing step is performed by combining the above-mentioned two methods of plasma etching and wet etching. It is a thing. As an example, in the case of the wear-resistant protective film having the two-layer film structure as in the first embodiment, for example, after forming the mask 13 made of aluminum, the wear-resistant protective film of the upper layer containing silicon, nitrogen and boron as the main components is formed. For No. 11, plasma etching was performed using a gas containing sulfur hexafluoride and oxygen as in the first embodiment, and then the lower layer containing silicon, nitrogen and oxygen was used as a main component. The wear protection film 12 is formed by removing the protection film unnecessary portion 10 by wet etching with a mixed solution of ammonium fluoride and phosphoric acid as in the second embodiment. According to this method, the upper wear-resistant protective film 11 is more conveniently etched by plasma etching than the wet-etching method, which is convenient, and when the lower wear-resistant protective film 12 is plasma-etched. It is possible to prevent adverse effects on the resistor layer 7, the CERALOY layer 8 and the like below the wear-resistant protective film, and it becomes easy to operate and control the etching end point. Furthermore, since the number of lots of thermal heads that can be etched at one time can be easily increased by wet etching, it is preferable to use wet etching for the lower wear-resistant protective film 12 that requires a relatively short time for wet etching. Can handle larger amounts. Further, since the upper wear-resistant protection film 11 is hardly attacked by the etching solution for the lower wear-resistant protection film 12, the upper layer wear-resistant protection film 11 is plasma-etched and then the mask 1 is used as it is.
3 can be used as a resist mask for the wet etching of the lower wear-resistant protective film 12. Therefore, there is an advantage that it is not necessary to use the heat-drying type resist as in the second embodiment for wet etching.

[0018]

According to the present invention, since a paste has been conventionally used to form a pattern of a wear-resistant protective film, pinhole defects often occur. However, the paste use process can be eliminated. It is possible to prevent pinhole defects due to paste dust.

[Brief description of drawings]

FIG. 1A to FIG. 1C are process diagrams showing a series of flows of a method of manufacturing a thermal head according to an embodiment of the present invention.

2A to 2E are process diagrams showing a series of flows of a method of manufacturing a thermal head according to another embodiment of the present invention.

[Explanation of symbols]

1 Alumina substrate 2 glaze layer 3 CERAROI layer 4 Heating resistor layer 5 individual electrodes 6 common electrode 7 Anti-wear protection film 8 heating section 9 Protective film required part 10 Protective film unnecessary part 11 Wear-resistant protective film on the upper layer 12 Lower wear-resistant protective film 13 masks

Claims (5)

[Claims] 1. A wear-resistant protective film containing silicon, boron, and nitrogen as main components is formed on the front surface of a substrate having a plurality of resistors patterned in a predetermined shape and wiring electrodes for energizing the resistors. A method of manufacturing a thermal head, which comprises a step and a step of removing an unnecessary portion of the abrasion-resistant protective film formed in the previous step by plasma etching using a gas containing sulfur hexafluoride and oxygen as main components. 2. The method of manufacturing a thermal head according to claim 1, wherein the step of removing an unnecessary portion of the wear-resistant protective film is performed by wet etching with a solution containing phosphoric acid as a main component. 3. A lower wear-resistant protective film containing silicon, oxygen, and nitrogen as main components on the entire surface of a substrate having a plurality of resistors patterned in a predetermined shape and wiring electrodes for energizing the resistors. And further forming an upper wear-resistant protection film mainly composed of silicon, boron, and nitrogen, and removing unnecessary portions of the upper and lower wear-resistant protection films formed in the previous step by 6 A method of manufacturing a thermal head, comprising a step of removing by plasma etching using a gas containing sulfur oxide and oxygen as main components. 4. The step of removing an unnecessary portion of the wear-resistant protective film is carried out by wet etching the upper wear-resistant protective film with a solution containing phosphoric acid as a main component, and the lower wear-resistant protective film is made of phosphoric acid or ammonium fluoride. The method of manufacturing a thermal head according to claim 3, wherein the method is performed by wet etching with a solution containing the main component. 5. In the step of removing an unnecessary portion of the wear-resistant protective film, the wear-resistant protective film in the upper layer is plasma-etched using a gas containing sulfur hexafluoride and oxygen as main components, and the wear-resistant protective film in the lower layer is removed. The method of manufacturing a thermal head according to claim 3, wherein is by wet etching with a solution containing phosphoric acid and ammonium fluoride as a main component.