JP2808765B2 - Manufacturing method of thin film type thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin-film thermal head used for a facsimile or the like.

2. Description of the Related Art Conventionally, a thin film type thermal head shown in FIG. 4 has been used. 11 is an insulating substrate, 12 is a heating resistor layer, 13 is a conductor layer (electrode), and 14 is a wear-resistant protective film.

Properties required for the wear-resistant protective film 14 of the thermal head in this configuration include the following.

(1) Excellent in abrasion resistance (mechanical abrasion [hardness and friction coefficient involved] and electrochemical abrasion [abnormal abrasion involving reaction between paper and abrasion-resistant protective film] ).

(2) Good heat resistance (no voids or cracks during heating).

(3) Electrolytic corrosion does not occur on the heating element layer, conductor layer, etc. formed under the wear-resistant protective film under moisture absorption of the paper (good step coverage, pinhole-free, dense No hygroscopicity).

(4) Adhesion with an underlying layer such as a heating resistor layer, a conductor layer, and a substrate is good.

(5) Good electrostatic resistance (static electricity generated when sliding the PET (insulating material), which is a transfer paper used in the thermal transfer method, and the abrasion-resistant protective film causes electrostatic breakdown, especially in dry conditions).

(6) Abnormal current does not flow through the wear-resistant protective film when the resistor breaks, and it does not overheat. As a wear-resistant protective film 14 of a conventional thermal head, tantalum oxide (Ta ₂ O ₅ ), silicon carbide (SiC), silicon nitride (SiN), or the like formed by a sputtering method has been used. However, Ta ₂ O ₅ has low hardness and poor wear resistance, SiC reacts with free carbon and heat-sensitive paper to cause abnormal wear, and SiN has a large stress, so that the film is easily peeled off when the film is thickened.

In general, in the sputtering method, when high power is applied during high-speed film formation, splats are likely to occur.
Since granular projections and pinholes due to their detachment are generated in the wear-resistant protective film 14, and the step coverage of the conductor layer pattern (conductor layer pressure is about 1 μm) is insufficient, the defect of the underlying film is reduced through these defective portions. There are cases where electrolytic corrosion occurs.

In order to solve the above, the plasma CVD (chemical vapor deposition) method is useful. In the plasma CVD method, a gas is used as a raw material, a high frequency is applied to the raw material, and the gas is decomposed in a plasma to deposit a film on a substrate. plasma
Energy (electric power) is higher in CVD than in sputtering.
And small protrusions due to abnormal discharge are unlikely to occur. Further, since it is dense and excellent in step coverage, electrolytic corrosion of the lower layer film hardly occurs, and reliability is remarkably improved.

In addition, a silicon nitride film (hereinafter referred to as a SiN film) is generally used as a protective film using a plasma CVD method. 5μm
Thickening can cause stress cracking. Therefore, a silicon oxynitride film (hereinafter referred to as a SiON film) in which O (oxygen) atoms are added to the SiN film to reduce the stress is used.

However, if this SiON film is used as a thermal transfer recording type thermal head abrasion protection film, the thermal transfer sheet (PET) also becomes SiON.
Since the film (resistivity 10 ¹³ to 10 ¹⁴ Ω · m) is also an insulator, static electricity is generated due to friction during sliding between the two, and the wear-resistant protective film 14
Causes dielectric breakdown.

In view of the above problems, an object of the present invention is to realize a wear-resistant protective film that does not cause dielectric breakdown.

Means for Solving the Problems In order to achieve the above object, the present invention provides a step of providing a number of heating resistor rows on an insulating substrate, and forming an upper wear-resistant protective film on the heating resistor row. Resistivity 10 ⁹ -10 ¹⁰ Ω
・ SiH ₄ or Si ₂ H ₆ as raw material gas and N
₂ , a step of forming by plasma CVD using B ₂ H ₆ or BF ₃ , and before that, a plasma CVD method using SiH ₄ or Si ₂ H ₆ and N ₂ using a lower wear-resistant protective film as a raw material gas Wherein the resistivity of the lower wear-resistant protective film is 10 ² compared to the resistivity of the upper wear-resistant protective film.
The flow rate ratio of the source gas is adjusted so as to be twice or more.

Further, according to the present invention, the step of providing a large number of heating resistor rows on the insulating substrate, and the resistivity of the upper wear-resistant protective film with respect to this heating resistor row is 10 ⁹ to 10 ¹⁰ Ω · m As described above, a step of forming by a plasma CVD method using SiH ₄ or Si ₂ H ₆ , N ₂ , B ₂ H ₆ or BF ₃ as a source gas, and prior to that, using a lower wear-resistant protective film as a source gas ₄ or Si
And ₂ H _6, N ₂ and O, and a step of forming by plasma CVD method using N _2, the resistivity of the lower layer of the wear protection layer than the resistivity of the upper layer of wear-resistant protective film There is characterized in that the adjusting of the flow rate ratio of the raw material gas to be greater 10 ³ times or more.

Further, in the present invention, the step of providing a large number of heating resistor arrays on the insulating substrate, and the resistivity of the upper wear-resistant protective film with respect to this heating resistor array is 10 ⁹ to 10 ¹⁰ Ω · m. As SiH ₄ or Si ₂ H ₆ , N ₂ , B ₂ H ₆ or BF ₃
A step of forming by plasma CVD method using SiH ₄ or
A process of forming by plasma CVD method using Si ₂ H ₆ and N ₂ , and an intermediate wear-resistant protective film
H ₄ or Si ₂ H ₆ , N ₂ O, and a step of forming by a plasma CVD method using N ₂ , the abrasion resistance of the intermediate layer compared to the resistivity of the abrasion protection film of the upper layer resistivity of the protective film, the resistivity of the lower layer of the wear protection layer is respectively 10 ³ times or more, 10 ²
The flow rate ratio of the raw material gas is adjusted so as to be twice or more.

According to the present invention, the upper layer made of silicon, nitrogen, and boron (SiBN) in the two- or three-layer wear-resistant protective film
Since boron is a group III element of the layer, the upper layer is given conductivity by acting as an acceptor with silicon in the upper layer. For this reason, static electricity generated between the transfer paper (PET) and the wear-resistant protective film can be released through the wear-resistant protective film, and dielectric breakdown of the wear-resistant protective film can be prevented.

However, since the adhesion between the SiBN layer and the underlying heating resistor layer and conductor layer is poor, the abrasion-resistant protective film may peel off when heated. Therefore, by using a SiN film or SiON film as the lower layer as a buffer layer with good adhesion to the base (heating resistor layer, conductor layer), it has appropriate conductivity (prevents dielectric breakdown) and heat resistance An excellent wear-resistant protective film can be obtained, and a highly reliable thin-film thermal head can be obtained.

Furthermore, if the resistivity of the wear-resistant protective film is too low, the drive IC of the thermal head is broken, and a drive voltage is constantly applied to the heat-generating resistor. And the paper may burn. Therefore, a two-layer structure with a SiON film as the lower layer or a two-layer structure with the above-mentioned SiN film as the lower layer
By forming a three-layer wear-resistant protective film with the ON film as an intermediate layer, it is possible to prevent current from flowing to the wear-resistant protective film, and it is possible to provide a highly safe thin-film thermal head. .

Embodiment An embodiment of the present invention will be described with reference to the drawings.

In this embodiment, first, the properties of a film mainly composed of silicon (Si), nitrogen (N), and boron (B) (hereinafter, referred to as a SiBN film) as an upper layer are described, and then the SiBN film is used as an upper layer. Examples of a thermal head having a wear-resistant protective film formed in a two-layer configuration or a three-layer configuration will be described.

Here, the apparatus used for forming the wear-resistant protective film was a parallel plate type (capacitively coupled) plasma CVD apparatus, and the electrode shape was 300 mm.
φ, electrode spacing 20 mm, RF frequency 13.56 MHz, RF power 500 W, gas pressure 1 Torr. The substrate temperature during film formation was 350 ° C. (constant).

The conditions for forming the SiBN film are as follows: SiH ₄ flow rate 20 sccm, N ₂ flow rate 400 sccm
(Constant), and the flow rate of B ₂ H ₆ was changed (other film formation conditions were as described above).

FIG. 2 shows the resistivity B ₂ H ₆ of the SiBN film in the present invention.
/ SiH ₄ shows the flow rate-dependent, indicates the B ₂ H ₆ / SiH ₄ flow ratio dependence of Vickers hardness of SiBN film in Figure 3. B ₂ H ₆ flow rate is 0sc
It can be seen that the resistivity at cm, that is, the resistivity of the order of 10 ¹² Ω · m in the SiN film decreases as the flow rate of B ₂ H ₆ increases. In this case, the resistivity reaches a minimum of 10 ⁹ Ω · m,
The resistivity was significantly lower than the resistivity of the iON film in the order of 10 ¹³ Ω · m. FIG. 3 shows the hardness when the flow rate of B ₂ H ₆ is changed. Hardness does not change much with B ₂ H ₆ flow rate, 1500
The value was about kg / mm ² . From the above, the above SiBN
It was found that the film can enhance the static electricity resistance of the wear-resistant protective film.

Hereinafter, examples of the thermal head wear-resistant protective film using the above-described SiBN film as the upper layer will be described.

Example 1 In this example, SiH ₄ and N ₂ were used as a source gas of a SiN film containing silicon (Si) and nitrogen (N) as main components as a two-layer wear-resistant protective film of the present invention, and an upper layer was formed. A case where a film is formed by a plasma CVD method using SiH ₄ , N ₂ , and B ₂ H ₆ as a source gas of a SiBN film containing silicon (Si), nitrogen (N), and boron (B) as main components will be described. The film formation conditions were as described above, and the film was formed sequentially by switching the source gas.

FIG. 1A shows the configuration of the thermal head of this embodiment. In FIG. 1 (a), reference numeral 1 denotes an insulating substrate made of a glazed alumina substrate having a glass glaze layer provided on alumina, on which a heating resistor layer 2 and a conductor layer (electrode) 3 are formed. After forming a desired pattern, the lower layer 5 (SiN) mainly containing silicon and nitrogen is formed by plasma CVD.
Layer) and an upper layer 6 mainly composed of silicon, nitrogen and boron (SiBN
A), a wear-resistant protective film 7 having a two-layer structure is formed.

As described above, the upper layer 6 (SiBN layer) can improve the anti-static property. However, if the SiBN film is brought into direct contact with the heating resistor layer 2 and the conductor layer 3, if the heating is performed due to poor adhesion, the deterioration may be accelerated. A wear-resistant protective film with only one SiBN film is not sufficiently reliable. Therefore, it is necessary to provide an intermediate layer having high adhesion between the heating resistor layer 2 and the conductor layer 3 and the upper layer 6. As this intermediate layer, a Si-rich SiN film is preferable. In other words, the adhesion is improved by the generation of silicide at the interface with the metal of the conductor layer, which is effective and has high heat resistance.

Therefore, the lower layer 5 is made of a Si-rich (N / Si <1.33) SiN film, and the upper layer 6 is made of a two-layered abrasion-resistant protective film 7 made of a SiBN film. Can be simultaneously achieved, and extremely high reliability can be secured.

However, in order to obtain these properties, what is necessary in the structure of the two-layered protective layer is to make the film thickness of the upper SiBN layer as thick as possible and to make the film thickness of the lower SiN layer as thin as possible. In particular, from the viewpoint of conductivity, the thickness of SiN, which is an insulator, needs to be at most 1 μm or less.

Then, using the two-layered protective film of this embodiment as a wear-resistant protective film for the thermal head, thermal transfer was performed using transfer paper (PET) with a pulse width of 3.6 msec., A line cycle of 10 msec./line, and an applied power of 0.3 w / dot. The head and the transfer paper were slid for a long distance. In this case, the upper SiBN layer is 4 μm thick, and the lower SiN layer is 1 μm thick. The upper SiBN layer was prepared under the conditions of various values shown in FIG.
μm).

As a result, in the case of a single SiN film, that is, a film having a resistivity of about 10 ¹² Ω · m, white spots occurred due to damage of the heating resistor dots due to static electricity, whereas B ₂
As increasing H ₆ flow rate, i.e., reduce the electrostatic breakdown as the conductivity is imparted, becomes ^{10 9} ~10 10 Ω · m or less of the resistivity of the electrostatic breakdown is no longer occur at all.

In addition, a corrosion test was performed on the SiBN single-layer film and the two-layer wear-resistant protective film of the present example under high temperature and high humidity.
In the single-layer SiBN film, the heating resistor layer and the conductor layer part were partially corroded, and peeling occurred at the interface between the SiBN film and the conductor layer. No corrosion or peeling occurred.

Embodiment 2 In this embodiment, the lower layer 5 of the wear-resistant protective film 7 having a two-layer structure in FIG. 1A is formed of a SiON film containing silicon (Si), oxygen (O) and nitrogen (N) as main components. The other components are the same as those in the first embodiment. A film formed by a plasma CVD method using SiH ₄ , N ₂ , and N ₂ O as a raw material gas for the SiON film will be described. The conditions for forming the wear-resistant protective film are as described above, and the wear-resistant protective film is sequentially formed by switching the source gas.

As described in the first embodiment, the use of the SiBN film for the upper layer 6 can improve the electrostatic resistance.
If the film and the heat-generating resistor layer 2 and the conductor layer 3 are brought into direct contact with each other, the adhesiveness is deteriorated, and if heated, the deterioration may be accelerated. Therefore, the wear-resistant protective film having only one SiBN film has insufficient reliability. In addition, if the abrasion-resistant protective film is too conductive, if the drive IC connected to the thermal head latches up, a drive voltage is always applied to the heating resistor of the thermal head in a DC manner. This causes the heating resistor to break, but the wear-resistant protective film becomes more conductive as the temperature rises, so it behaves as if the wear-resistant protective film is a heating resistor, and the paper is overheated and emits smoke. A (burning) phenomenon (hereinafter referred to as a smoke phenomenon) occurs.

In order to prevent the above, the heating resistor layer 2, the conductor layer 3
It is necessary to provide an intermediate layer having high adhesion and low conductivity (high resistivity) between the SiBN film. SiON film has a resistivity of 10 ¹³
1010 ¹⁴ Ω · m, which is high and has high heat resistance, and is therefore preferred as an intermediate layer. Therefore, the lower layer 5 is made of a SiON film and the upper layer 6
Is a two-layered abrasion-resistant protective film 7 made of SiBN film, whereby it is possible to simultaneously provide conductivity by the upper SiBN film, enhance adhesion by the lower SiON film, and prevent smoke generation, which is extremely high. Reliability can be ensured. However, in order to obtain these properties, what is necessary in the configuration of the two-layered protective film is to make the thickness of the upper SiBN layer as thick as possible
One example is to reduce the thickness of the SiN film as much as possible.
In particular, from the viewpoint of conductivity, the thickness of the SiON insulator must be at most 1 μm or less.

Then, using the two-layered protective film of this embodiment as a wear-resistant protective film for the thermal head, thermal transfer was performed using transfer paper (PET) with a pulse width of 3.6 msec., A line cycle of 10 msec./line, and an applied power of 0.3 w / dot. The head and the transfer paper were slid for a long distance. In this case, the upper SiBN layer is 4 μm thick and the lower SiON layer is 1 μm thick. The upper SiBN layer was prepared under the conditions of various values shown in FIG.
μm).

As a result, in the case of a single-layer SiON film, that is, with a resistivity of about 10 ¹³ Ω · m, white spots due to damage of the heating resistor dots due to static electricity were remarkably generated, whereas B ₂ H ₆ as shown in FIG. As the flow rate was increased, that is, as the conductivity was increased, the electrostatic breakdown was reduced. When the resistivity became 10 ⁹ to 10 ¹⁰ Ω · m or less, the electrostatic breakdown did not occur at all.

Further, a corrosion test was performed on the wear-resistant protective film having a single-layer structure of SiBN and the wear-resistant protective film having a two-layer structure of the present embodiment under high temperature and high humidity. Corrosion occurred partially in the conductor layer portion, and peeling occurred at the interface between the SiBN film and the conductor layer, whereas no corrosion occurred in the two-layer wear-resistant protective film 7.

Furthermore, for a thermal head with a SiON single-layer structure, a SiBN single-layer structure, and a two-layer structure as a wear-resistant protective film, when a 24V DC voltage is continuously applied using thermal paper, the SiBN single-layer wear-resistant protective film produces smoke. While the phenomenon occurred,
Regarding the wear-resistant protective film having a single-layer SiON structure and the wear-resistant protective film having the two-layer structure, no smoke phenomenon was observed, and it can be said that this two-layer structure is excellent in terms of safety.

Embodiment 3 In this embodiment, as the wear-resistant protective film having a three-layer structure of the present invention, the lower layer 5 composed of silicon (Si) and nitrogen (N) as main components is used.
As a source gas for N layers, as SiH _4, using N _2, silicon intermediate layer 8 (Si), oxygen (O), in the raw material gas of the SiON layer mainly composed of nitrogen (N), SiH _4, N ₂ , N ₂ O, and silicon (Si) containing silicon (Si), nitrogen (N), and boron (B) as main components of the upper layer 6.
Plasma CV using SiH ₄ , N ₂ , B ₂ H ₆ as source gas for BN layer
The case where the film is formed by the method D will be described. The film formation conditions were as described above, and the film was formed sequentially by switching the source gas.

FIG. 1 (b) shows a third embodiment of the present invention. In FIG. 1 (b), reference numeral 1 denotes an insulating substrate made of a glazed alumina substrate having a glass glaze layer provided on alumina, on which a heating resistor layer 2 and a conductor layer (electrode) 3 are formed. After a desired pattern is formed, a lower layer 5 (SiN layer) mainly containing silicon and nitrogen, an intermediate layer 8 (SiON layer) mainly containing silicon, oxygen and nitrogen, and silicon, nitrogen and boron are formed by a plasma CVD method. A wear-resistant protective film 9 having a three-layer structure of an upper layer 6 (SiBN layer) whose main component is.

As described in the first embodiment, it is necessary to provide the lower layer 5 (SiN layer) in order to increase the adhesion to the heating resistor layer 2 and the conductor layer 3. Further, as described in Example 2, from the viewpoint of preventing smoke emission, it is better to use a SiON film having a higher resistivity (more insulating property) than a SiN film, in which case the SiN film is slightly more likely to be used. Since the adhesion to the underlying layers (heating resistor layer 2 and conductor layer 3) is good, it is more effective to provide a SiON film as an intermediate layer on the lower SiN film.

Therefore, the lower layer 5 is made of a SiN film, the intermediate layer 8 is made of a SiON film, and the upper layer 6 is made of a SiBN film. Prevention and enhancement of adhesion by the lower SiN film can be achieved at the same time, and extremely high reliability and safety can be secured.

However, in order to obtain these properties, it is necessary to make the thickness of the upper SiBN layer as thick as possible and to make the thickness of the intermediate SiON layer and the lower SiN film as thin as possible in the structure of the three-layered protective film. Is mentioned. In particular, from the viewpoint of conductivity, the total thickness of both the SiN layer and the SiON layer, which are insulators, must be at most 1 μm or less.

Then, using a thermal head having the three-layered film of Example 3 as a wear-resistant protective film, a transfer paper (PET) with a pulse width of 3.6 msec., A line cycle of 10 msec./line, and an applied power of 0.3 w / dot.
The thermal head and the transfer paper were slid over a long distance by using.
In this case, the upper SiBN layer is 4 μm, and the intermediate SiON layer is 0.5 μm.
m, the lower SiN layer is 0.5 μm thick. The upper SiBN layer used was formed under the conditions of various values shown in FIG.

In the single-layer SiN film (resistivity of about 10 ¹² Ω · m) and single-layer SiON film (resistivity of about 10 ¹³ Ω · m), white spots due to damage of the heating resistor dots due to static electricity (especially many in the single-layer SiON film) On the other hand, the thermal head of the present embodiment increases the flow rate of B ₂ H ₆ when forming the upper layer 6 (SiBN layer) as shown in FIG. When the breakdown was reduced and the resistivity became 10 ⁹ to 10 ¹⁰ Ω · m or less, no electrostatic breakdown occurred at all.

A corrosion test was performed on the single-layer SiBN film and the three-layer wear-resistant protective film of Example 3 under a high temperature and high humidity.
In the single-layer film, the heating resistor layer 2 and the conductor layer 3 were partially corroded and peeled off at the interface between the SiBN film and the conductor layer. No corrosion or peeling occurred.

In the above embodiment, SiH ₄ , N ₂ , and B ₂ H ₆ were used as source gases. However, if Si ₂ H ₆ is used instead of SiH ₄ , Si ₂ H ₆ → SiH ₂
+ SiH ₄ reaction occurs, and the film formation rate can be increased.
In this case, it is necessary to increase the flow rates of other N ₂ and B ₂ H ₆ and to keep the composition of the film constant. When BF ₃ is used, hydrogen (H) in the film is reduced by the reaction of H + F → HF ↑, heat resistance is improved, and hardness is further increased.

When the lower layer is formed and then the upper layer is formed, or when the lower layer is formed and then the intermediate layer is formed, or when the intermediate layer is formed and then the upper layer is formed, the composition is rapidly changed. The adhesion between layers deteriorates. In particular, the effect is large when the thickness of the upper layer is increased. However, in this embodiment,
The source gas for the BN film is obtained by adding B ₂ H ₆ or BF ₃ to the source gas for the SiN film, and the source gas for the SiON film is N ₂ O as the source gas for the SiN film.
Therefore, if the source gas is switched continuously by changing the flow rate or by changing the amount of change to a small amount and changing it intermittently, the composition gradually changes, and it is possible to improve the adhesion. Needless to say.

In this embodiment, the substrate temperature during film formation was set to 350 ° C., for the following reason. When the thermal head generates heat, if the film contains hydrogen bonded to silicon (Si), the bond is broken by thermal energy because the Si-H bond is small, and the hydrogen is released, causing cracks and bubbles in the film. . Therefore, if the substrate is kept at a high temperature (about 350 ° C.) in advance, hydrogen is released from the film at the film formation stage, and it is difficult for hydrogen to be taken into the film. Further, when the amount of hydrogen in the film decreases, the density of the film increases, and accordingly, the hardness increases. As described above, in order to improve heat resistance and hardness, it is necessary to increase the substrate temperature. Further, the adhesion to the base such as the resistor and the electrode can be improved.

As described above, according to the present embodiment, the thermal head abrasion protection film for the thermal transfer recording system can be formed by the plasma CVD method, and the electrostatic resistance can be increased and the performance can be improved.

Effects of the Invention As described above, according to the present invention, dielectric breakdown due to static electricity generated between a thermal transfer sheet and a thermal head can be prevented, and heat resistance can be improved. Furthermore, it is possible to prevent the smoke generation phenomenon, improve the adhesion to the underlying layer (heating resistor layer, conductor layer, etc.), and prevent corrosion of the heating resistor layer and conductor layer.

[Brief description of the drawings]

FIG. 1 (a) is a cross-sectional view of a thin-film thermal head having a two-layer wear-resistant protective film of the present invention, and FIG. 1 (b) is a thin-film thermal head having a three-layer wear-resistant protective film of the present invention. sectional view of a thermal head, for the second figure characteristic diagram showing the dependency on B ₂ H ₆ / SiH ₄ flow ratio of SiBN film, FIG. 3 is B ₂ H ₆ / SiH ₄ flow ratio of Vickers hardness of the SiBN layer Characteristic diagram showing dependency,
FIG. 4 is a sectional view of a conventional thin film thermal head. DESCRIPTION OF SYMBOLS 1 ... Insulating board, 2 ... Heating resistor layer, 3 ... Conductor layer (electrode), 5 ... Lower layer, 6 ... Upper layer, 7 ... Abrasion-resistant protective film, 8 ... Intermediate layer, 9 ... ... Abrasion-resistant protective film.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takashi Hirao 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-148569 (JP, A) JP-A-61-291154 (JP, A) JP-A-63-157311 (JP, A) JP-A-62-156822 (JP, A) JP-A-61-44401 (JP, A) JP-A-61-267328 (JP, A) JP-A-63-265423 (JP, A) JP-A-63-299322 (JP, A) JP-A-60-263121 (JP, A) Japanese Utility Model 1-67047 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B41J 2/335

Claims (3)

(57) [Claims] A step of providing a large number of heating resistor rows on an insulating substrate; and adjusting the resistivity of the upper wear-resistant protective film to the heating resistor row to be 10 ⁹ to 10 ¹⁰ Ω · m. in a SiH ₄ or Si ₂ H ₆ as a source gas, and N _2, SiH ₄ and forming a B ₂ H ₆ or a plasma CVD method using a BF _3, the lower wear protection film prior to it as a raw material gas Or Si ₂ H
_6, and a step of forming by plasma CVD method using N _2, the resistivity of the lower layer of the wear protection layer increases 10 ² times or more than the resistivity of the upper layer of wear-resistant protective film The method of manufacturing a thin-film thermal head, wherein the flow rate ratio of the source gas is adjusted as described above. 2. A process of providing a plurality of heating resistor arrays on an insulating substrate, such that the resistivity of an upper wear-resistant protective film for the heating resistor arrays is 10 ⁹ to 10 ¹⁰ Ω · m. in a SiH ₄ or Si ₂ H ₆ as a source gas, and N _2, SiH ₄ and forming a B ₂ H ₆ or a plasma CVD method using a BF _3, the lower wear protection film prior to it as a raw material gas Or Si ₂ H
_6, and N ₂ O, and a step of forming by plasma CVD method using N _2, the resistivity of the lower layer of the wear protection layer than the resistivity of the upper layer of wear-resistant protective film 10 ^A method for manufacturing a thin-film thermal head, wherein the flow rate ratio of the source gas is adjusted to be ^three times or more. 3. A step of providing a large number of heating resistor rows on an insulating substrate, such that the resistivity of the upper wear-resistant protective film with respect to the heating resistor rows is 10 ⁹ to 10 ¹⁰ Ω · m. in a SiH ₄ or Si ₂ H ₆ as a source gas, and N _2, SiH ₄ and forming a B ₂ H ₆ or a plasma CVD method using a BF _3, the lower wear protection film prior to it as a raw material gas Or Si ₂ H
₆ and a step of forming by a plasma CVD method using N _2, and a plasma CVD method using SiH ₄ or Si ₂ H ₆ , N ₂ O and N ₂ using a wear-resistant protective film of an intermediate layer as a source gas thereon. Forming a resist by a method, wherein the resistivity of the wear-resistant protective film of the intermediate layer and the resistivity of the wear-resistant protective film of the lower layer are each 10 ³ compared to the resistivity of the wear-resistant protective film of the upper layer. more than doubled, the method of manufacturing a thin film type thermal head and adjusting the flow rate of the material gas so as to increase 10 ² times or more.