JP2003080754A - Thermal head and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal head with high insulating property reliability of an inter-layer insulating layer while providing a common electrode with a multi-layer wiring, and a production method for high yield production. SOLUTION: This thermal head comprises conductive layers 14, 15 provided on the upper surface of a heat retaining layer 12, inter-layer insulating layers 17, 18 provided on the upper surface of the conductive layers 14, 15, a plurality of heat generating elements 23 provided on the upper surface of the inter-layer insulating layers 17, 18, and a protection layer 26 for covering at least the upper surface of the heat generating elements 23, wherein a common electrode 21 is connected electrically with the conductive layer 15 and the heat generating elements 23, and the inter-layer insulating layers 17, 18 have a three layer structure including two layers made of two different insulating materials laminated on the upper surface of the conductive layer 15 and one layer (third inter-layer insulating layer) made of an insulating material laminated on the two layers as the inter-layer insulating layer on the individual electrode 22 side area contacted with the heat generating elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used for a thermal printer or the like and having a multi-layered common electrode, and a method for manufacturing the same, and particularly to a thermal head having a highly reliable insulating layer. And a manufacturing method thereof.

[0002]

2. Description of the Related Art In general, a thermal head as a recording head mounted on a thermal transfer printer or the like has a plurality of heating elements composed of heating resistors arranged in a line on a substrate.
According to the print information, each heating element is selectively energized to generate heat, so that color recording is performed on the thermosensitive recording paper,
Alternatively, the ink of the ink ribbon is melted and transferred and recorded on plain paper, OHP paper or the like to record on various recording media.

In such a conventional thermal head, the ridges are formed in the vicinity of the ends of the heat retaining layer laminated on the upper surface of the heat dissipation substrate, and the common conductive layer and the common conductive layer are formed on the upper surface of the heat retaining layer. An interlayer insulating layer is laminated, and a lower layer individual electrode that is connected to the common conductive layer through a contact hole and conducts electricity to a heating resistor is laminated on the upper surface of the interlayer insulating layer, and heat is generated on the upper surface of the lower layer individual electrode. A real-edge thermal head is used in which a resistor and an upper-layer individual electrode are laminated and the surface of these is covered with a protective layer, and a common electrode is multilayered.

To explain such a conventional thermal head with reference to FIG. 3, a heat insulating layer 2 made of glass or the like is formed on the entire surface of a heat radiating substrate 1 made of an insulating ceramic such as alumina. . A ridge portion 3 of the heat insulating layer 2 is formed near the one end portion 1a of the heat dissipation substrate 1 by means such as etching.

A first common conductive layer 4a made of a metal such as Cr and having a film thickness of approximately 1 μm is formed on the upper surface of the ridge portion 3, and T
A second common conductive layer 4b made of cermet or the like made of a mixture of Ta such as aSiO2 and an insulator and having a film thickness of about 1 μm is sequentially formed by sputtering or the like.

On the upper surface of the second common conductive layer 4b, an oxidation resistant mask layer made of an oxidation resistant material such as an alloy having oxidation resistance, ceramics or cermet is formed by sputtering or the like to have a film thickness of about 0.2 μm. To form. Then, the oxidation-resistant mask layer is etched to form an oxidation-resistant mask layer having a predetermined shape only in the formation position of a contact hole 6 described later near the one end portion 1a of the heat dissipation substrate 1. In this state, the entire surface of the heat dissipation substrate 1 is thermally oxidized at a temperature of about 700 ° C., so that the surface of the second common conductive layer 4b which is not masked by the oxidation resistant mask layer becomes an insulating oxide ceramic layer. Become. The insulating oxide ceramic layer forms the first interlayer insulating layer 5a having a film thickness of several thousand angstroms.

On the upper surface of the first interlayer insulating layer 5a, there is formed a second insulating ceramic such as SiO2 having a high insulating property.
The interlayer insulating layer 5b is laminated. By thus forming the interlayer insulating layers 5a and 5b in the two-layer structure, the reliability of the interlayer insulating property is further enhanced. In the second interlayer insulating layer 5b, the contact hole 6 is formed by etching the portion where the oxidation resistant mask layer is formed, and at the same time, the oxidation resistant mask layer is also etched, and the second common conductive layer 4b as the lower layer is formed. Is exposed.

On the upper surface of the second interlayer insulating layer 5b, M
A lower common electrode 7a connected to the second common conductive layer 4b through the contact hole 6 and a lower individual electrode 8a by stacking an electrode material composed of a refractory metal group such as o, Cr, and W by sputtering or the like. Electrode patterns are respectively formed. A heating resistor 9 made of Ta cermet or the like is laminated on the upper surfaces of the lower common electrode 7a and the lower individual electrode 8a by sputtering or the like. In this heating resistor 9, heating elements 9a are formed between the lower-layer common electrode 7a and the lower-layer individual electrode 8a, and a plurality of heating elements 9a are linearly arranged according to the number of dots. Further, on the upper surface of the heating resistor 9, an upper layer common electrode 7b and an upper layer individual electrode 8b made of Al, Cu or the like and having a thickness of about 2 μm and an upper layer individual electrode 8b are laminated by sputtering or the like in order to supply electric power energy. There is.

Further, the heating resistor 9, the upper common electrode 7b,
Also, on the upper surface of the upper layer individual electrode 8b, excluding the driving element of the external circuit, in order to prevent oxidation and wear, it is made of a material having high oxidation resistance and hardness such as sialon and has a film thickness of about 5 μm. The protective layer 10 is laminated and coated by sputtering or the like. Then, after a post-process such as a terminal plating process, the heat dissipation substrate 11 is diced to manufacture a block (chip) -shaped thermal head.

In such a thermal printer using a conventional thermal head, when the recording medium is a normal recording paper, it is pressed against the recording paper via a thermal transfer ink ribbon (not shown). Based on predetermined print information, the upper layer individual electrode 8b is energized to heat the desired heating resistor element 9a, whereby the ink of the ink ribbon is melted and transferred onto the recording paper to perform the desired image printing. It has become. When the recording medium is thermal paper, the thermal head is pressed against the thermal paper to cause the thermal paper to develop color and print.

[0011]

In the conventional thermal head as described above, when the contact hole 6 is formed by etching the second interlayer insulating layer 5b, the second portion other than the portion where the contact hole 6 is formed is formed. Interlayer insulating layer 5b
In some cases, there may be a through hole connecting to the lower first interlayer insulating layer 5a. Then, since the first interlayer insulating layer 5a has a very thin film thickness of several thousand angstroms, the reliability of the insulating property of the first interlayer insulating layer 5a in the portion where the through hole is generated becomes low, and the second common electrode layer 4b is formed. There is a possibility that a defect such as a short circuit may occur between the lower individual electrode 8a and the lower individual electrode 8a.

In addition, the heat insulating layer 2 and the first and second conductive layers 4
If the surface roughness of b or the like is rough and there are projections or the like on the surface, the projections reduce the withstand voltage performance of the first and second interlayer insulating layers 5a and 5b formed on the second conductive layer 4b, Dielectric breakdown was likely to occur even when a practical operating voltage was applied. In particular, since the heat-dissipating substrate 1 on the side where the upper layer individual electrode 8b is formed has a large area, it is generated in the heat retaining layer 2, the first and second conductive layers 4a, 4b, etc. on the side of the upper layer individual electrode 8b. The number of protrusions is extremely larger than that on the side where the upper-layer common electrode 7b is formed. Therefore, the second common conductive layer 4b and the heating element 9a
Alternatively, short-circuiting with the lower-layer individual electrode 8a may occur more frequently, and the manufacturing yield of the thermal head may be deteriorated. The present invention has been made in view of these points, and provides a thermal head having a highly reliable insulation property of an interlayer insulating layer and a thermal head manufacturing method with a good manufacturing yield while using a common electrode as a multilayer wiring. The purpose is to

[0013]

As a first solving means for solving the above-mentioned problems, a thermal head of the present invention comprises a heat retaining layer formed on the upper surface of a heat dissipation substrate and a conductive layer formed on the upper surface of this heat retaining layer. A layer, an interlayer insulating layer having a contact hole provided on the upper surface of the conductive layer, a plurality of heating resistors provided on the upper surface of the interlayer insulating layer, and a plurality of heating elements formed in alignment with individual electrodes and common electrodes. A protective layer covering at least an upper surface of the heating element, the common electrode being electrically connected to the conductive layer inside the contact hole and connected to the plurality of heating elements, and the interlayer insulation. The layer is formed by stacking two layers made of different insulating materials on the upper surface of the conductive layer, and the interlayer insulating layer in a region on the side where the individual electrodes connected to the plurality of heating elements are formed, of Further a structure in which the three layers by laminating one layer made of a material of the insulating properties to. Therefore, the withstand voltage performance on the individual electrode side can be improved by forming the interlayer insulating layer in the region on the side where the individual electrode having a large area is formed into three layers.

As a second means for solving the above-mentioned problems, the two interlayer insulating layers are formed of a thermal oxide film of a refractory metal cermet film in order from the conductive layer side. An interlayer insulating layer and a second interlayer insulating layer made of highly insulating ceramic are laminated and formed, and a second layer made of a highly insulating resin is formed on the upper surface of the second interlayer insulating layer in the region where the individual electrodes are formed. A structure in which three interlayer insulating layers are laminated is formed. Therefore, it is possible to further improve the withstand voltage performance of the area on the individual electrode side having a large area.

As a third means for solving the above-mentioned problems, the heating element is formed by the common electrode and the partially formed first individual electrode on the upper surface of the second interlayer insulating layer. , The heating element, the common electrode,
The third interlayer insulating layer is formed on a portion excluding the first individual electrode, and the second individual electrode connected to the first individual electrode and the driving element is formed on the upper surface of the third interlayer insulating layer. Was laminated. Therefore, the withstand voltage performance between the second individual electrode and the conductive layer can be improved.

As a fourth means for solving the above-mentioned problems, the first individual electrode is partially formed in the range of 200 to 1000 μm from the heating element.

As a fifth means for solving the above-mentioned problems, in the method of manufacturing a thermal head of the present invention, a heat retaining layer formed on the upper surface of the heat dissipating substrate and a conductive layer formed on the upper surface of this heat retaining layer. An interlayer insulating layer having a contact hole formed on the upper surface of the conductive layer, individual electrodes connected to a plurality of heating elements, the heating element, and the conductive layer inside the contact hole. And a common electrode electrically connected to the heat insulating layer in the first polishing step, the surface of the heat insulating layer is smoothed, and an insulating undercoat layer is laminated on the smoothed upper surface of the heat insulating layer. A first conductive layer made of refractory metal is laminated on the upper surface of the coat layer, a second conductive layer made of refractory metal cermet is laminated on the upper surface of the first conductive layer, and the second conductive layer is formed by the second polishing step. Conductive layer surface A mask pattern of an oxidation resistant mask layer made of an oxidation resistant ceramic is formed on the smoothed upper surface of the second conductive layer at the position where the contact hole is formed, and the surface of the second conductive layer is thermally oxidized. The second
An insulating first interlayer insulating layer is formed on the upper surface of the conductive layer, and a third insulating layer is formed.
The surface of the first interlayer insulating layer is smoothed in a polishing step, and an insulating second interlayer insulating layer made of a material different from that of the first interlayer insulating layer is formed on the smoothed upper surface of the first interlayer insulating layer. Then, the contact hole is formed by removing the second interlayer insulating layer in the portion where the mask pattern is formed, and at least the plurality of heat generating elements and the protective layer are formed on the upper surface of the second interlayer insulating layer. I made it like this. Therefore, the surfaces of the heat insulating layer, the second conductive layer, the first interlayer insulating layer, etc. can be smoothed in the polishing step.

As a sixth means for solving the above problems, the second interlayer insulating layer is formed by dividing the second interlayer insulating layer made of insulating ceramic into film formation / cleaning / film formation. The method was such that a film was formed.

Further, as a seventh means for solving the above-mentioned problems, the heating element is partially formed with the common electrode on the upper surface of the heating resistor formed on the second interlayer insulating layer. A third interlayer insulating layer made of an insulating organic material is laminated on the upper surface of the second interlayer insulating layer except the heating element, the common electrode, and the first individual electrode. The method is such that the second individual electrode connected to the first individual electrode electrode is laminated on the upper surface of the interlayer insulating layer. Therefore, the withstand voltage performance of the large-area area on the individual electrode side can be improved by the three-layered interlayer insulating layer.

As an eighth means for solving the above-mentioned problems, the oxidation-resistant mask layer and the second interlayer insulating layer are formed by laminating the same material, and a part of the second interlayer insulating layer is deleted. Then, at the same time when the contact hole is formed, the oxidation resistant mask layer is removed to expose the underlying second conductive layer.

As a ninth means for solving the above problems, a method of smoothing the surface of the second interlayer insulating layer and chamfering the hole angle of the contact hole in the fourth polishing step. And

Further, as a tenth means for solving the above-mentioned problems, the first to fourth polishing steps are chemical polishing with a strong alkaline polishing liquid containing colloidal silica.

As an eleventh solving means for solving the above-mentioned problems, the third polishing step is performed at least immediately before forming the second interlayer insulating layer, and the fourth polishing step is performed at least in the second The method was performed such that the interlayer insulating layer was formed immediately after formation.

As a twelfth means for solving the above problems, the second interlayer insulating layer, the oxidation-resistant mask layer, and the undercoat layer are each made of SiO 2.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION A thermal head and a method for manufacturing the same according to the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of an essential part of a thermal head according to the present invention, and FIG. 2 is a process diagram illustrating a manufacturing method according to the present invention.

An embodiment of the thermal head of the present invention will be described with reference to FIG. 1. A heat radiating substrate 11 made of a Si substrate or a metal substrate is disposed in the lower portion, and the heat radiating substrate 11 is illustrated. A ridge 11b having a predetermined height is formed near the one end 11a on the left side. And the ridge portion 11
On the right side of b in the figure, the other end side (not shown) is formed with a large area so that a drive element or the like can be mounted. On the upper surface of the heat dissipation substrate 11, a low heat conductivity heat insulation layer 12 made of Si, a transition metal, oxygen and the like is laminated to a thickness of about 20 μm by sputtering deposition or the like.

The heat insulating layer 12 has a smooth surface, and a highly insulating undercoat layer 13 made of SiO 2 or the like is formed on the upper surface of the smooth heat insulating layer 12 by sputtering vapor deposition or the like. It is laminated to a thickness of 5 μm.
On the upper surface of the undercoat layer 13, a high-strength first conductive layer 14 made of a metal such as Cr is stacked to a thickness of 0.2 to 0.5 μm by sputtering deposition or the like, and the first conductive layer 14 is formed by photolithography. The pattern of layer 14 has been formed. On the upper surface of the first conductive layer 14, a second conductive layer 15 made of cermet such as Ta-SiO2 is laminated to a thickness of about 1 μm by sputtering deposition or the like, and the first conductive layer 14 is formed by photolithography technique. The pattern of the second conductive layer 15 is formed so as to include the pattern.

The surface of the second conductive layer 15 is finished to be smooth, and the oxidation-resistant mask layer 16 made of SiO 2 having oxidation resistance is formed on the upper surface of the smooth second conductive layer 15.
The oxidation-resistant mask layer 1 made of SiO 2 is laminated by sputtering deposition or the like to a thickness of about 0.2 μm, and is formed by a photolithography technique at a contact hole 19 formation position described later.
6 patterns are partially formed. Then, after forming the pattern of the oxidation resistant mask layer 16, 700 to 800 ° C.
By performing the thermal oxidation treatment at the temperature of the second conductive layer 1
A first interlayer insulating layer 17 having a thickness of about 0.5 μm, which is integrated with the surface of No. 5, is formed.

The surface of the first interlayer insulation layer 17 is finished to be smooth, and the second interlayer insulation layer made of a material such as SiO 2 which is a highly insulating material is formed on the upper surface of the smooth first interlayer insulation layer 17. 18 is laminated by sputtering vapor deposition or the like to a thickness of about 2 μm, and has high reliability of insulation with few defects. The heat dissipation substrate 1 is formed on the second interlayer insulating layer 18.
A contact hole 19 is formed by a photolithography technique at a position near the one end 11a of No. 1 and the underlying oxidation-resistant mask layer 16 is simultaneously removed by etching. Therefore, the second conductive layer 1 is formed inside the contact hole 19.
5 is exposed.

The surface of the second interlayer insulating layer 18 is finished to be smooth, and the contact holes 19 are chamfered to have a rounded corner. By chamfering the corner angle of the contact hole 19, the breakage of the common electrode 21, which will be described later, is prevented. Further, on the upper surface of the second interlayer insulating layer 18 including the inner surface of the contact hole 19, a heating resistor 20 made of Ta-SiO2 or the like is formed by sputtering deposition or the like to a thickness of about 0.
The heating resistors 20 are stacked to have a thickness of 3 μm, and the pattern of the heating resistors 20 is formed by the photolithography technique.

On the upper surface of the heating resistor 20, a common electrode 21 and a first individual electrode 22 made of a refractory metal such as Cr.
And are formed with a predetermined gap. A heating element 23 is formed on the heating resistor 20 in the portion sandwiched between the common electrode 21 and the first individual electrode 22. That is, the common electrode 21 is electrically connected to the second conductive layer 15 inside the contact hole 19, and the plurality of heat generating elements 23.
It is connected to the. The first individual electrode 22 is formed so as to be limited to the range of the dimension A from the center S of the heating element 23. The dimension A is in the range of 200 to 1000 μm.

The third interlayer insulating layer made of a highly insulating resin such as polyimide resin is provided on the upper surface of the second interlayer insulating layer 18 except the portions where the heating element 23, the common electrode 21, and the first individual electrode 22 are formed. 24 is laminated to have a thickness of 2 to 5 μm. That is, the interlayer insulating layer in the region on the side where the first individual electrode 22 connected to the plurality of heating elements 23 is formed is
One layer made of an insulating material is further laminated on the second interlayer insulating layers 17 and 18 to form three layers. On the upper surface of the third interlayer insulating layer 24, Al, Cu, which has high electrical conductivity,
The electrode material made of Au or the like is
The pattern of the second individual electrode 25 is formed on the upper surface of the third interlayer insulating layer 24 by a photolithography technique.

The second individual electrode 25 is the first individual electrode 2
One end is laminated on the right end in FIG. 2 to be electrically connected, and the other end is extended on the heat dissipation substrate 11 having a large area on the right side in the drawing to form a driving element (not shown). And an external circuit (not shown). Further, at least on the upper surfaces of the heating element 23, the common electrode 21, the first and second individual electrodes 22, 25, a protective layer 26 made of sialon or the like for preventing them from oxidation or wear is formed by sputtering evaporation or the like. Is laminated and coated to a thickness of about 5 μm.

A method of manufacturing the thermal head of the present invention having such a structure will be described with reference to the process chart shown in FIG.
First, in the substrate forming step 31, on the surface of the heat-dissipating substrate 11 made of a single crystal Si wafer or a metal plate having excellent heat dissipation, a photolithography technique or a press technique is used.
The ridges 11b are formed with a height of 10 to 100 μm. Next, in the heat retaining layer forming step 32, the heat retaining layer 12 made of sputter-deposited material such as Si, a transition metal, and oxygen, which has excellent heat insulating properties, is formed on the upper surface of the heat dissipation substrate 11 by sputter deposition.
The layers are formed to have a thickness of about 20 μm.

Next, in the first polishing step 33, the surface of the heat retaining layer 12 is chemically polished with a strong alkaline polishing liquid containing colloidal silica to remove projections and foreign matters on the surface, and the surface of the heat retaining layer 12 is removed. Make it smooth. Next, in the undercoat layer forming step 34, the undercoat layer 13 made of SiO 2 is laminated on the upper surface of the heat retaining layer 12 to a thickness of about 0.5 μm by sputtering deposition or the like. Next, in the first conductive layer forming step 35, the first conductive layer 14 made of a refractory metal such as Cr or Mo is formed on the upper surface of the undercoat layer 13 by sputtering deposition or the like to have a thickness of 0.2 to 0.5 μm. To stack. The first conductive layer 14 is formed by photolithography as a lower-layer common electrode of a desired pattern over substantially the entire area within the outer peripheral edge of the heat dissipation substrate 11.

Next, in the second conductive layer forming step 36,
Second made of high melting point metal cermet such as Ta-SiO2
The conductive layer 15 is laminated on the upper surface of the first conductive layer 14 to a thickness of about 1 μm by sputtering deposition or the like. Then, the second conductive layer 15 is patterned by photolithography so as to include the outer shape of the first conductive layer 14, and the first conductive layer 14 is formed.
It has a role of antioxidant. Next, in the second polishing step 37, the surface of the second conductive layer 15 is chemically polished with the same strong alkaline polishing liquid containing colloidal silica as in the first polishing step 33 to remove protrusions and foreign matters, and Conductive layer 1
Finish the surface of No. 5 smoothly.

Next, in the oxidation-resistant mask layer forming step 38, the oxidation-resistant mask layer 16 made of SiO 2 is laminated on the upper surface of the second conductive layer 15 to a thickness of about 0.2 μm by sputtering deposition or the like. Then, by etching using a photolithography technique, the oxidation resistant mask layer 1 is partially formed at the position where the contact hole 19 is formed near the one end 11a of the heat dissipation substrate 11.
6 is formed. Next, in the first interlayer insulating layer forming step 39, the entire heat dissipation substrate 11 is heated to 700 ° C. in an oxidizing atmosphere.
By performing thermal oxidation treatment at a temperature of ~ 800 ° C, the second
The surface of the conductive layer 15 is forcibly oxidized to form a first interlayer insulating layer 17 integral with the second conductive layer 15 with a thickness of about 0.5 μm.

Next, in the third polishing step 40, the surface of the first interlayer insulating layer 17 is chemically polished with the same strong alkaline polishing liquid containing colloidal silica as in the second polishing step 37,
By removing the protrusions and foreign substances, the surface of the first interlayer insulating layer 17 is finished to be smooth. Next, in the second interlayer insulating layer forming step 41, the second interlayer insulating layer 18 made of SiO 2 is formed on the upper surfaces of the oxidation resistant mask layer 16 and the first interlayer insulating layer 17 to a thickness of about 2 μm by sputtering deposition or the like. Form a stack. The second interlayer insulating layer 18 is formed by first suspending the film formation where SiO 2 is laminated to a thickness of about 1 μm, and letting the heat dissipation substrate 11 pass through a brush cleaning device (not shown). Foreign matter or the like that is a defect and is attached to the interlayer insulating layer 18 is removed. Then, SiO 2 is laminated again to a thickness of about 1 μm, and the second interlayer insulating layer 18 is formed by laminating SiO 2 to a thickness of about 2 μm.

The second interlayer insulating layer 18 is formed by etching the contact hole 19 formation position near the one end portion 11a of the heat dissipation substrate 11 by photolithography. In the etching for forming the contact hole 19, the oxidation resistant mask layer 16 is also etched at the same time, and the second conductive layer 15 is exposed at the bottom of the contact hole 19. Next, the fourth polishing step 4
2, the surface of the second interlayer insulating layer 18 is chemically polished with the same strong alkaline polishing liquid containing colloidal silica as in the third polishing step 40 to remove protrusions and foreign matter, To make it smooth. The fourth polishing step 4
2, the contact hole 19 is chamfered at the same time to have a rounded shape, for example.

Next, in the heating resistor forming step 43,
The heating resistor 20 made of Ta-SiO2 or the like is formed on the upper surface of the second interlayer insulating layer 18 by sputtering deposition or the like to have a thickness of about 0.3 μm.
Then, a desired resistor pattern is formed by photolithography technique. Next, in the first electrode forming step 44, the common electrode 21 made of Cr or the like having a high melting point and the first individual electrode 22 are formed on the upper surface of the heating resistor 20 by sputtering deposition or the like to have a thickness of about 0.1 μm. Stack. A desired electrode pattern is formed on each of the common electrode 21 and the first individual electrode 22 by a photolithography technique, and a heating element 23 is formed in a portion sandwiched between the common electrode 21 and the first individual electrode 22. The pattern of the first individual electrode 22 is formed in a range from the heating element 23 to the dimension A from the center line S of the heating element 23. The dimension A
In the range of 200 to 1000 μm, the rate of occurrence of interlayer insulation failure is remarkably reduced.

Next, in the third interlayer insulating layer forming step 45, the third interlayer insulating layer 24 made of a highly insulating resin such as photosensitive polyimide is formed on the second interlayer insulating layer 18, the common electrode 21,
2 to 5 μm on the upper surface of the first individual electrode 22 and the heating element 23
Of common electrode 2 by photolithography technology
The pattern is formed in a range excluding the first, first individual electrode 22, and heating element 23. Next, in the second electrode forming step 46, the second individual electrode 25 made of Al, Cu, Au or the like having excellent conductivity is formed on the upper surface of the third interlayer insulating layer 24 by sputtering deposition or the like to have a thickness of 1 to 2 μm. It is laminated on the substrate and formed into a desired pattern by photolithography technology, and one end of the
The individual electrodes 22 are laminated and connected to the end portion on the right side in the drawing, and the other end portion is connected to a mounting terminal of a drive element or an external connection terminal (not shown). Next, in the protective layer forming step 47, the protective layer 26 is formed on the substantially entire surface of the heat dissipation substrate 11 excluding the driving element and the external connection terminal by sialon or the like by sputtering deposition or the like in order to prevent oxidation or wear. 5 μm
It is laminated and coated to the thickness of.

As described above, according to the thermal head and the method of manufacturing the same of the present invention, the area is large even if it is a real edge type in which the heating element 23 is formed to be offset toward the one end 11a of the heat dissipation substrate 11. First formed,
Since the common electrode 21 is connected to the second conductive layers 14 and 15 through the contact hole 19, it becomes easy to make the resistance value of the common electrode 21 small and uniform, and the print density unevenness due to the common drop of the common electrode 21 becomes easy. It is possible to eliminate the occurrence of the occurrence of high quality printing.

Further, the common electrode 21 and the first individual electrode portion 22
Are formed by two layers made of a hard inorganic ceramic material having excellent insulating properties, heat resistance and stress resistance, and the conductive layers 14 and , 15 and the common electrode 21 are made of hard refractory metal to have a thin film thickness. Therefore, even if the pressure contact force with the platen (not shown) on the printer side is increased to concentrate the pressure on the heating element 23 and the common electrode 21 near the one end 11a of the heat dissipation substrate 11, the protection layer 26 can be easily formed. The thermal head of the present invention can have a long printing life without causing stress fracture, and high quality printing quality can be obtained.

Further, the second interlayer insulating layer 18 according to the present invention.
Is about 1μ in the first film forming operation by dividing the film forming process into two.
A film thickness of m is formed, and then the surface is washed. Then, in the second film forming operation, a film thickness of approximately 1 μm is formed again to form the second interlayer insulating layer 18 having a film thickness of approximately 2 μm. Therefore, the insulation resistance of the second interlayer insulating layer 18 is improved. Can be improved. Further, the second individual electrode 25 side having the largest pattern formation area has many protrusions and foreign matters, and therefore the occurrence rate of short circuits is high, but the first and second interlayer insulating layers 17, 18 on the second individual electrode 25 side are high. The third interlayer insulating layer 24 made of an organic resin having an excellent interlayer insulating property is selectively laminated on the above to form three interlayer insulating layers.
It is possible to prevent the short circuit between the heating elements 4 and 15 and the heating element 23 or the second individual electrode 25 at an unnecessary portion. Therefore, a long-life thermal head having excellent manufacturing quality and manufacturing yield can be obtained.

Further, polishing is performed in a plurality of polishing steps to improve the smoothness of each film surface and to eliminate sharp protrusions, so that variations in withstand voltage due to electric field concentration can be reduced and practical application voltage can be reduced. On the other hand, a highly reliable thermal head that does not cause dielectric breakdown can be obtained. Further, since the contact hole 19 of the second interlayer insulating layer 18 is chamfered in the fourth polishing step to have a rounded shape, the common electrode 21 is prevented from being broken and is connected to the conductive layers 14 and 15. Reliability has been increased.

Further, since the abrasives used in the first to fourth polishing steps and the sputtering material such as SiO2 and Cr are commonly used, the number of materials and the equipment investment can be reduced and the productivity is improved. Manufacturing cost can be reduced. In addition,
The present invention is not limited to the above-described embodiments, but can be modified as necessary. For example,
It is also possible to use a glaze alumina substrate as the material of the heat dissipation substrate 11. Such a glaze heat insulation layer,
Since the thermal diffusivity is large as compared with the vapor deposition heat insulating layer of the present invention,
Although the thermal response is inferior, since the heat insulating layer forming step by sputtering vapor deposition and the polishing step can be omitted, the manufacturing cost can be reduced.

The polishing step according to the present invention has been described with reference to the first to fourth four polishing steps in order to obtain the highest production yield. For example, the first, second and third polishing steps are described. Of the first interlayer insulating layer 17 before the second interlayer insulating layer 18 is laminated, and the second interlayer insulating layer 18 is formed after the second interlayer insulating layer 18 is formed. The step of polishing the surface of 18 may be performed twice. The number of such polishing steps can be changed as necessary.

In the embodiment of the method for manufacturing a thermal head of the present invention, the second individual electrode 2 having a large area is used.
The interlayer insulation layer in the region on the fifth side is replaced with the first to third interlayer insulation layers 1
Although the three-layer structure of 7, 18, and 24 has been described, each surface of the heat retaining layer 12, the second conductive layer 15, the first interlayer insulating layer 17, and the second interlayer insulating layer 18 is polished to be smooth. Thus, the withstand voltage performance can be improved even if the interlayer insulating layer in the region on the second individual electrode 25 side has a two-layer structure of the first and second interlayer insulating layers 17 and 18. That is, the method of manufacturing the thermal head of the present invention may be any method as long as at least a plurality of heating elements and protective layers are formed on the upper surface of the second interlayer insulating layer 18.

[0049]

As described above, according to the thermal head and the method of manufacturing the same of the present invention, the insulation property of the interlayer insulating layer is high, and the common electrode can have a multi-layer structure. It is possible to provide a thermal head that has an extremely excellent effect that the printing quality and the printing life can be reliably maintained for a long period of time, and the manufacturing yield and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a thermal head according to the present invention.

FIG. 2 is a process diagram illustrating a method of manufacturing a thermal head of the present invention.

FIG. 3 is a sectional view of a main part of a conventional thermal head.

[Sharp sign]

11 Heat dissipation board 12 Insulation layer 13 Undercoat layer 14 First conductive layer 15 Second conductive layer 16 Oxidation-resistant mask layer 17 First interlayer insulating layer 18 Second interlayer insulating layer 19 contact holes 20 Heating resistor 21 common electrode 22 First individual electrode 23 Heating element 24 Third interlayer insulating layer 25 Second individual electrode 26 Protective layer

Claims (12)

[Claims] 1. A heat insulating layer formed on the upper surface of the heat dissipation substrate,
A conductive layer formed on the upper surface of the heat insulating layer, an interlayer insulating layer having a contact hole provided on the upper surface of the conductive layer, a plurality of heating resistors provided on the upper surface of the interlayer insulating layer, individual electrodes, and a common electrode. A plurality of heating elements aligned and formed by
A protective layer covering at least the upper surface of the heating element, the common electrode being electrically connected to the conductive layer inside the contact hole and connected to the plurality of heating elements, and the interlayer insulating layer. Is formed by stacking two layers made of different insulating materials on the upper surface of the conductive layer, and forming the two layers of the interlayer insulating layer on the side where the individual electrodes connected to the plurality of heating elements are formed. A thermal head characterized in that one layer made of an insulating material is further laminated thereon to form three layers. 2. The two interlayer insulating layers are, in order from the conductive layer side, a first interlayer insulating layer made of a thermal oxide film of a refractory metal cermet film and a second interlayer insulating layer made of a highly insulating ceramic. An insulating layer is laminated, and a third interlayer insulating layer made of a highly insulating resin is laminated on the upper surface of the second interlayer insulating layer in the region on the side where the individual electrode is formed. Item 1. The multilayer wiring thermal head according to Item 1. 3. The heating element is formed by the common electrode and the partially formed first individual electrode on the upper surface of the second interlayer insulating layer, and the heating element, the common electrode,
The third interlayer insulating layer is formed on a portion excluding the first individual electrode, and the second individual electrode connected to the first individual electrode and the driving element is formed on the upper surface of the third interlayer insulating layer. The thermal head according to claim 2, wherein the thermal head is formed by stacking. 4. The thermal head according to claim 3, wherein the first individual electrode is partially formed within a range of 200 to 1000 μm from the heating element. 5. A heat insulating layer formed on the upper surface of the heat dissipation substrate,
A conductive layer formed on the upper surface of the heat insulating layer, an interlayer insulating layer having a contact hole formed on the upper surface of the conductive layer,
A separate electrode connected to the plurality of heating elements and a common electrode connected to the heating element and electrically connected to the conductive layer inside the contact hole,
The surface of the heat retaining layer is smoothed in a polishing step, an insulating undercoat layer is laminated on the smoothed upper surface of the heat retaining layer, and a first conductive layer made of a refractory metal is laminated on the upper surface of the undercoat layer. The second conductive layer formed by laminating a second conductive layer made of a refractory metal cermet on the upper surface of the first conductive layer and smoothing the surface of the second conductive layer in a second polishing step. A mask pattern of an oxidation resistant mask layer made of an oxidation resistant ceramic is formed on the upper surface of the second conductive layer at a position where the contact hole is formed, and the surface of the second conductive layer is thermally oxidized to insulate the upper surface of the second conductive layer from the insulating property. The first interlayer insulating layer is formed, and the surface of the first interlayer insulating layer is smoothed in a third polishing step, and the upper surface of the smoothed first interlayer insulating layer is
An insulating second layer made of a material different from that of the first interlayer insulating layer
An interlayer insulating layer is formed, the second interlayer insulating layer in the portion where the mask pattern is formed is removed to form the contact hole, and at least the plurality of heating elements are formed on the upper surface of the second interlayer insulating layer. And a method for manufacturing a thermal head in which a protective layer is formed. 6. The second interlayer insulating layer is formed by dividing the second interlayer insulating layer made of insulating ceramic into film forming / cleaning / film forming. Manufacturing method of thermal head. 7. The heating element is provided on the upper surface of a heating resistor formed on the second interlayer insulating layer by the common electrode and a partially formed first individual electrode, and the heating element and the common electrode are provided. A third interlayer insulating layer made of an insulating organic material is laminated on the upper surface of the second interlayer insulating layer excluding the first individual electrode, and is connected to the first individual electrode electrode on the upper surface of the third interlayer insulating layer. 7. The method of manufacturing a thermal head according to claim 5, wherein the second individual electrode is formed so as to be laminated. 8. The oxidation resistant mask layer and the second interlayer insulating layer are formed of the same material, and a portion of the second interlayer insulating layer is removed to form the contact hole, and at the same time, the oxidation resistant layer is formed. 8. The mask layer is removed so that the underlying second conductive layer is exposed.
The method for manufacturing a thermal head according to any one of 1. 9. A fourth polishing step, wherein the surface of the second interlayer insulating layer is made smooth and the corners of the contact hole are chamfered.
The method for manufacturing a thermal head according to any one of 1. 10. The method of manufacturing a thermal head according to claim 9, wherein in the first to fourth polishing steps, chemical polishing is performed with a strong alkaline polishing liquid containing colloidal silica. 11. The third polishing step is performed at least immediately before forming the second interlayer insulating layer, and the fourth polishing step is performed at least immediately after forming the second interlayer insulating layer. Claim 9 or claim 10
A method for manufacturing the thermal head described. 12. The manufacturing of a thermal head according to claim 5, wherein the second interlayer insulating layer, the oxidation resistant mask layer and the undercoat layer are each made of SiO 2. Method.