JP3237176B2 - Thermal inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a thermal ink jet head.

[0002]

2. Description of the Related Art Conventionally, as a structure of a thermal ink jet head, a structure as described in Japanese Patent Publication No. 33648/1987 is known. FIG. 9 is a cross-sectional view for explaining the outline. In the figure, 11 is a substrate, 12 is an oxide film, 13 is a heater, 14 is an insulating film, 15 is a wiring layer, 16 is a Si ₃ N ₄ film, 17 is a Ta film, and 18 is PSG.
The film, 19 is a layer having pits formed thereon, 20 is a channel wafer, 22 is an ink reservoir, 23 is a channel portion, 26 is a dicing groove, and 27 is a pit.

In a channel wafer of such an ink jet head, anisotropic etching (ODE: Orientation Depth) is performed using a Si wafer.
With the “ended etching”, a channel portion for discharging ink and an ink reservoir for supplying ink from outside are formed. In the anisotropic etching, even if a square or rectangular pattern can be formed with high accuracy, if the shapes are connected, the accuracy of the connected portion is reduced. Therefore, since the ink reservoir 22 and the channel portion 23 are formed separately, an unetched portion shown by a dotted line exists at a boundary portion between the ink reservoir 22 and the channel portion 23. In order to remove the unetched portion and form a flow path connecting the ink reservoir 22 and the channel portion 23,
A groove is formed in the portion indicated by 6 by dicing, and the ink reservoir 22 and the channel portion 23 are connected. Therefore, a dicing process for connecting the ink reservoir 22 and the channel portion 23 is required. The dicing groove is formed so as to penetrate to the end of the head, and the portion of the connecting groove formed at the chip edge of the head must be filled, which requires a filling and repairing operation. There is a problem.

In order to solve the above problem, FIG.
As shown in FIG. 2, a layer 19 in which pits of a heater plate are formed facing an unetched portion between an ink reservoir 22 and a channel portion 23 in a channel wafer 20.
A so-called bypass pit structure has been proposed in which a groove (bypass pit) 21 is formed in the through hole and the ink reservoir 22 and the channel portion 23 are connected through the groove (for example,
JP-A-62-80054 and JP-A-1-14856.
No. 0). However, the structure employing the bypass pit has a problem that the life of the head is short.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to provide a thermal ink jet head having a long life bypass pit structure.

[0006]

According to the present invention, a pit is formed on an upper portion of a heater, and a protective layer is formed on the heater.
And, the ink reservoir and the channel portion are connected via a groove portion formed at a position corresponding to a boundary portion between the ink reservoir and the channel portion of the layer in which the pits are formed, and the groove is formed. In a thermal ink jet head having a protective layer provided at the bottom of a portion, the protective layer provided at the bottom of the groove and the protective layer of the heater are formed in the same process. is there.

[0007]

According to the present invention, since the protective layer is provided at the bottom of the bypass pit, ink can be directly supplied to the bottom of the bypass pit,
For example, the bottom of the bypass pit can be prevented from deteriorating without touching the PSG film, thereby preventing corrosion of the internal circuit and the like. This makes it possible to achieve a longer life of the head.

[0008]

FIG. 1 is a sectional view of a thermal ink jet head according to the present invention. In FIG. 1, the same portions as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. 24 is Si ₃ N ₄
The film 25 is a Ta film. The Si ₃ N ₄ film 24 and the Ta film 25 form a protective layer at the bottom of the bypass pit 21.

This protective layer does not need to be formed of a Si ₃ N ₄ film and a Ta film.
Any material may be used as long as the material can be protected.
Further, it is not necessary to have two layers, and it may be one layer.

In this embodiment, the protective layer at the bottom of the bypass pit 21 is the same as the protective layer of the heater 13. The reason is that the protective layer of the heater 13 is
Since the protective layer is formed at the same time as the bottom portion of the bypass pit 21 at the time of manufacturing, the protective layer is formed not only on the bottom portion of the pit 27 provided on the heater 13 but also on the bottom portion of the bypass pit 21 during etching. This is because a protective layer can be formed on the bypass pit 21 only by leaving Therefore, the bypass pit 21
The protective layer at the bottom and the protective layer of the heater 13 are formed in the same step. Subsequently, a pit 27 and a bypass pit 21 are opened by coating a polyimide layer. By doing so, a protective layer can be formed at the bottom of the bypass pit 21 without adding a special process to the head manufacturing process, and the head can be manufactured without reducing productivity.

The reason for providing the protective layer will be described. In the bypass pit structure shown in FIG. 10, when ink flows from the ink reservoir 22 to the channel section 23, a protective film exposed at the bottom of the bypass pit 21, that is, a PSG film (a phosphorus-added CVD) in this embodiment. The ink directly contacts the oxide film 18. The present inventors have found that this PSG film is deteriorated by ink. When the PSG film 18 of the protective film exposed at the bottom of the bypass pit 21 is eroded by the ink, the ink penetrates into the element from that location, corrodes the internal circuit, and shortens the life of the head. As shown in FIG. 1, a protective layer is provided at the bottom of the bypass pit 21 to prevent the bottom of the bypass pit 21 from being exposed, prevent ink from entering the inside of the element, and prevent corrosion of the internal circuit due to the ink. You can try. The same applies to the case where a material having low resistance to ink is used for the insulating film, not limited to the PSG film.

A method for manufacturing the thermal ink jet head described with reference to FIG. 1 will be described. 2 to 8 are process diagrams in each manufacturing stage. First, as conventionally performed, an oxide film 12 of about 1.5 μm is formed on a substrate 11.
Is formed by a thermal oxidation method. On the oxide film 12, a Poly-Si pattern corresponding to the heater section 13 is formed. Subsequently, the entire surface is covered with an insulating film 14 by a CVD method, and is further flattened by a heat treatment (FIG. 2).

After forming the connection holes for the electrodes, an Al film as a wiring material is deposited to a thickness of about 1.5 μm by sputtering, and the wiring layer 15 is patterned by etching (FIG. 3).

Then, using photoresist as a mask, B
The insulating film 14 is etched in an HF (buffered hydrofluoric acid) solution, and the insulating film 14 on the heater 13 is removed by patterning (R-VIA patterning). At this time, the Poly-Si pattern of the heater 13 is exposed at the bottom of the R-VIA patterning (FIG. 4).

Subsequently, as a protective layer of the heater 13, S
A laminated film of the i ₃ N ₄ film 16 and the Ta film 17 is deposited. Si
₃ N ₄ film is 2000Å about by the plasma CVD method, T
The film a is deposited to about 5000 ° by a sputtering method (FIG. 5).

The stacked film of the Si ₃ N ₄ film 16 and the Ta film 17 is patterned by dry etching with CF ₄ gas plasma so as to remain at the location where the heater section and the bypass pit are formed. At this time, since the Si ₃ N ₄ film 16 and the Ta film 17 have substantially the same etching rate, the laminated film can be etched at once without using a special method (FIG. 6).

Further, a protective layer is formed by depositing the PSG film 18 to a thickness of about 1.2 μm by the CVD method, and only the Al electrode portion, the R-VIA portion, and the bypass pit 21 are etched and opened by BHF ( (FIG. 7).

Finally, as a layer 19 on which pits are formed, photosensitive polyimide is applied to a thickness of about 40 to 50 μm, and a pattern corresponding to the pits 27 is provided at a position above the heater, and at a boundary between the ink reservoir and the channel. A pattern corresponding to the bypass pit 21 is formed at a corresponding position, and curing is performed to form a heater wafer (FIG. 8).

It is obvious that other known methods may be used for the method of forming, patterning, and etching each layer in the above manufacturing process. Further, the material and thickness of each layer are not limited to the above-described embodiment, and can be appropriately changed.

[0020]

As is apparent from the above description, according to the present invention, since the protective layer is provided at the bottom of the bypass pit, deterioration of the bottom of the bypass pit can be prevented, and ink can be prevented from entering inside. Can be prevented. Therefore, damage to the inside of the device can be prevented, and a long-life thermal inkjet head can be provided. In addition, since the protective layer at the bottom of the bypass pit and the protective layer of the heater are formed in the same process, a protective layer is formed at the bottom of the bypass pit without adding a special process to the head manufacturing process. Thus, there is an effect that the head can be manufactured without lowering the productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of a thermal inkjet head of the present invention.

FIG. 2 is a process chart in each manufacturing stage of the head shown in FIG.

FIG. 3 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 4 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 5 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 6 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 7 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 8 is a process chart in each manufacturing stage of the head shown in FIG. 1;

FIG. 9 is a cross-sectional view of a conventional thermal inkjet head having dicing grooves.

FIG. 10 is a sectional view of a conventional thermal inkjet head having bypass pits.

[Explanation of symbols]

Reference Signs List 11 substrate, 12 oxide film, 13 heater, 14 insulating film, 15 wiring layer, 16, 24 Si ₃ N ₄ film, 1
7, 25 Ta film, 18 PSG film, 19 pit formed layer, 20 channel wafer, 21 bypass pit, 22 increment reservoir, 23 channel section, 26
Dicing groove.

Claims (1)

(57) [Claims] 1. A pit is formed on an upper portion of a heater, a protective layer is formed on the heater, and an ink reservoir and a channel portion are defined by a boundary between the ink reservoir and the channel portion of the layer on which the pit is formed. In a thermal ink jet head, which is connected via a groove portion formed at a position corresponding to the portion and a protective layer is provided at the bottom of the groove portion, the protective layer provided at the bottom of the groove portion and A thermal inkjet head, wherein the protective layer of the heater is formed in the same step.