JP3079003B2 - INK JET PRINT HEAD, ITS MANUFACTURING METHOD, AND DRIVE CIRCUIT - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head, a method of manufacturing the same, and a driving circuit.

[0002]

2. Description of the Related Art Hitherto, various types of driving methods of an ink jet recording head of a type in which bubbling is induced in ink by heating a heater and the ink is ejected by the energy have been proposed. In particular, the type in which a part of the drive circuit is incorporated into a silicon substrate and the heater array is configured on-chip can greatly reduce the number of bonding wires compared to the number of heaters, and various methods have been proposed. ing. Above all, a method disclosed in JP-A-2-283454, in which a diode is connected in series for each heater and driven for each block, so that only a specific heater among heaters arranged in a matrix is driven, is particularly preferable. Are better. FIG.
(A) shows a conceptual diagram of the circuit. N number of heaters and the block respectively, heater R _H1 ... pads V ₁ end to R _Hn via the diode D ₁ ... D _n for voltage application ...
Tied to V _m, the other end of each heater R _H1 ... R _H2 is connected to the pad H ₁ ... H _n for grounding. According to the above method, if the number of heaters is N, the number of external terminals, that is, the number of bonding pads, can be reduced to 2N theoretically. As an example, in the case of a heater array of 64 bits, the number of bonding pads can be driven by 16. However, since one pad for grounding the substrate is required, the number is actually seventeen.

[0003] The reduction in the number of bonding wires is very important in securing the reliability of wiring, and the diode system has been used for a long time in an actual ink jet recording head.

[0004]

However, in the above conventional example, since the diode array is formed on the same substrate, the diodes need to be electrically insulated for each block. Therefore, installation of an insulating region becomes indispensable, and it has an unusually complicated structure for a two-terminal element. First, consider the simplest structure in which the p region and the n region are formed by planar technology. If the supply voltage V _H to the heater is set to a positive potential, the substrate must be grounded, and the conductivity type of the substrate is p-type. Then, a PNP bipolar transistor is formed between the substrate and the diode, and most of the current does not flow to the heater and escapes as the substrate current. For this reason, as a diode of an ink jet recording head which is currently manufactured as a product, an NPN bipolar type in which a collector and a base are short-circuited as shown in FIG. 6B has been used. FIG. 6C shows a specific cross-sectional view of the structure. 10
1 is a p-type silicon substrate, 106 is an n-type buried layer, 107
Is a p-type silicon epitaxial layer, 108 is a deep n-type diffusion layer, 109 is a deep and shallow p-type diffusion layer, and 110 is an n-type deep and shallow diffusion layer. 111 is an insulating film, 112 is a collector / base electrode, 113 is an emitter electrode, and 114 is an isolation electrode.

If only an NPN bipolar is constructed, 3
Although double diffusion is also conceivable, a PNP parasitic bipolar transistor formed between the base, the collector and the substrate operates, and the substrate current does not flow through the heater as in the case of the above-described simple diode, and the current escapes. For the above reasons, a complicated structure as shown in FIG. 6C cannot be avoided, and an expensive manufacturing process has been continuously employed.

As a result, despite the fact that the device is essentially a two-terminal device, four diffusion layers including a buried layer are required, and even the most expensive process of depositing an epitaxial layer is required. It is a manufacturing process.

As described above, the conventional example requires an unnecessarily expensive manufacturing process due to its structural problem.

A first object of the present application is to eliminate the need for a complicated structure as in the conventional example described above, and to eliminate the need for an epitaxial layer deposition step by using a simple structure.
The production cost is reduced to 60% or less of the conventional example.

At the same time, it is another object of the present invention to reduce the arrangement pitch per element by simplifying the structure and to reduce the area occupied by the diode when the number of bits is increased.

[0010]

In order to achieve the above object, an ink jet recording head according to the present invention is provided in a silicon substrate of a first conductivity type having a second substrate different from the first conductivity type.
A plurality of first diffusion layers of the first conductivity type are formed, a plurality of second diffusion layers of the first conductivity type are formed on each of the plurality of first diffusion layers, and ink is heated on each of the plurality of second diffusion layers. The resistors for discharging ink by generating bubbles are connected one by one, and the different sides of the plurality of resistors from the second diffusion layer side are connected to each other for each first diffusion layer. And

A manufacturing method according to the present invention is characterized in that, in the method for manufacturing an ink jet recording head, phosphorus is implanted into a p-type silicon substrate by an ion implantation method to form a first diffusion layer.

Further, in the manufacturing method according to the present invention, in the method for manufacturing an ink jet recording head, boron is introduced into the n-type silicon substrate to form the first diffusion layer.

Further, the ink jet recording head according to the present invention is for heating the ink to generate bubbles, thereby controlling the plurality of resistors for discharging the ink, and controlling the energization to each of the plurality of resistors. In the ink jet recording head in which a plurality of functional elements are formed in the same base, the plurality of functional elements are bipolar transistors, and the collectors of the plurality of bipolar transistors are of the same conductivity type as the base and are grounded to each other. One end of the plurality of resistors is connected to each of the emitters of the plurality of bipolar transistors, and the other end of each of the plurality of resistors is configured to apply a voltage to the resistor. It is characterized by being connected to a terminal.

A driving circuit according to the present invention is a driving circuit for an ink jet recording head, wherein a plurality of resistors for heating ink to generate air bubbles in the same substrate, thereby discharging ink, and a plurality of bipolar transistors are provided. Are formed, and the collectors of the plurality of bipolar transistors are of the same conductivity type as the base and are connected to each other at a ground potential, and one end of one of the plurality of resistors is connected to each of the plurality of bipolar transistors. Are connected, and the other end of each of the plurality of resistors is connected to a terminal for applying a voltage to the resistor. Heating a specific resistor by controlling the potential of the base of each of a plurality of bipolar transistors

[0015]

According to the present invention, unlike the conventional example, instead of connecting the diode to the heater resistor in order from the power supply to the heater toward the ground, the connection is made in series from the heater resistor to the diode. For this purpose, a PNP transistor is deliberately formed between the heater and the p-type silicon substrate, and this PNP transistor has a simple diode configuration of a p region and an n region.

In the above configuration, the substrate current, that is, PN
Naturally, a large amount of the collector current of the P transistor is generated, but this current effectively acts as a heater current unlike the arrangement of the conventional example. That is, the substrate current can be positively utilized by reversing the positional relationship between the heater resistance and the diode.

[0017]

FIG. 1 is a drawing showing the features of the present invention best. FIG. 1A is a circuit conceptual diagram of a heater transistor array and a bipolar transistor matrix formed between a voltage supply power supply and a silicon substrate. The transistor grouping is the same as in the conventional example of FIG. FIG.
(B) is a sectional view showing the structure of the bipolar transistor. Here, 101 is a silicon substrate of the first conductivity type, a region corresponding to the collector of the bipolar transistor,
Reference numeral 102 denotes a diffusion layer of the second conductivity type opposite to 101, which corresponds to the base of the bipolar transistor. 103 denotes a diffusion layer of the same first conductivity type as the silicon substrate 101, which corresponds to the emitter and collector contact layers. , 104
Is a second conductive type diffusion layer opposite to the silicon substrate 101 and corresponding to a base contact layer.

An embodiment of the present invention will be described below in detail with reference to the drawings.

For the sake of simplicity, a comparison between the conventional example and the present invention is made using a 2 × 2 matrix. Although a circuit diagram of a conventional example in FIG. 2 (a), considered here to operate the heater R _11. First, by applying a supply voltage V _H to the heater pad V ₁ from the external drive unit, dropping pads H ₁ to the ground potential by an external driving unit. Naturally heater current flows through the heater R _11, R ₁₁ foaming phenomenon in the ink location is arranged to occur. Now consider the potential when the pads V ₂ and the pad H ₂ is in a floating state by the external drive unit. If the voltage V _H is applied to the pad V ₁ , the diode D
Since ₁₂ is the forward direction, increases to naturally pads H ₂ be near V _H potential. The forward if the pad H ₁ is the ground potential diode D ₂₁ is the pad V ₂ → pads H ₁ since pad V
₂ is at ground potential. Therefore pad H ₂ is V _H potential, will pad V ₂ is the ground potential, a voltage is applied to the diode D _22. However, since this orientation is in the opposite direction to the diode D _22, no current flows. Eventually, the current path of the pad V ₁ → D ₁₂ → R ₁₂ → R ₂₂ → D ₂₂ → D ₂₁ → R ₂₁ → pad H ₁ is cut off by the diode D ₂₂ , and the current substantially flows through the pad V ₁ → D ₁₁ → R
₁₁ → which is the passage bamboo pad H _1. As a result, the pad V ₁
It can be a current flows only to the diode R ₁₁ by selecting the pad H _1.

Next, similarly, consider the potential state of the present invention. FIG. 2B shows a 2 × 2 matrix. Here is applied the supply voltage V _H to the heater pad V ₁ Pad H ₁
Is reduced to the ground potential. PNP bipolar transistor Tr ₁₁ which is an emitter follower state is the ON state, the base current and the collector current (substrate current) flows. At this time, the emitter current is the sum of the base current and the collector current. If a heater current through the heater R ₁₁ is viewed from the transistor Tr _11, since the emitter current, the heater current is obtained by adding the base current and collector current (substrate current). This current without waste supplied to the pad V _1, meant to be consumed as a heater current. Therefore, unlike the conventional example, it is not necessary to suppress the substrate current. Rather, it is possible to reduce the load on the external driving unit of the H-side pad by actively using the substrate.

Next, as in the conventional example, consider the potential of the pad V ₂₁ and the pad H _2. When the voltage V _H is applied to the pad V ₁ , the potential of the pad H ₂ becomes near V _H because the emitter-base of the transistor Tr ₂₁ is in the forward direction. In this case the base and the collector of the transistor Tr ₁₂ is turned reverse junction, the base - collector current if the breakdown voltage of the diode formed between the collector V _H or (substrate current) will not flow. In other words, if the breakdown voltage V _CEO between the collector and the emitter of the transistor Tr ₁₂ is equal to or higher than V _H, there is no current flowing in the path of the pad V ₁ → R ₁₂ → Tr ₁₂ substrate.

Next, since the emitter and base of the transistor Tr ₂₁ are in the forward direction, the pad V ₂ is stabilized at the ground potential, similarly to the pad H ₁ . As a result, conventional exactly the same state, that is, the pad H ₂ potential near V _H, pad V ₂ becomes the ground state. Turning now to the transistor Tr _22,
In the above state, the base is at the potential near V _H , and the emitter and collector are at the ground potential. Here, considering the equivalent circuit of the PNP bipolar transistor, it is as shown in FIG. In other words, when viewed from the base, the diode D in the opposite direction
_EB, is obtained by connecting the D _BC 2 one parallel. Here will be both the withstand voltage of the emitter-base diode D _EB and base-collector diode D _BC current does not flow anywhere if more V _H.

That is, according to the structure of the present invention, the same operation as the conventional example can be obtained with a simple structure.

Hereinafter, the manufacturing process of an 8 × 16 bit ink jet head will be briefly described. Since all the manufacturing processes use a known technique, only main process parameters are described.

The silicon substrate 101 is a p-type 10-20Ω.
Cm, that is, an impurity concentration of about 1 × 10 ¹⁵ cm ⁻³ was selected. The selection of the impurity concentration of the substrate is important in considering the collector-base breakdown voltage and the base-emitter breakdown voltage. Since the substrate is a collector in the structure shown in FIG. 1 or FIG. 4, the lower the impurity concentration, the better the breakdown voltage.
However, if a substrate having an extremely low impurity concentration is used, the collector resistance increases and the collector current stops flowing. In the case of this embodiment, the external drive unit has a margin, and the ON operation may be performed in a state where the collector current is smaller than the base current.
Since the environment of the heater current and the base current was acceptable, a substrate having a relatively low impurity concentration was used.

After selecting the substrate, a common base is formed. In this embodiment, the base is an 8-bit common base. On board 1
An oxide film 103 is formed on the surface of the base region 102.
Is removed by etching only a portion corresponding to.

The impurity was phosphorus, which was implanted by ion implantation through the thin portion 103A of the oxide film 103. The dose was 4 × 10 ¹² ions / cm ² . After the driving, drive-in was performed at 1200 ° C. for 5 hours. As a result, a diffusion layer having a surface impurity concentration of about 8.4 × 10 ¹⁵ cm ^{−3 and a} diffusion depth of 7.8 μm was formed in the base region 102 (FIG. 4A).

Next, portions of the oxide film corresponding to the emitter and collector contact layers were opened, and the emitter and collector contact layers 104 were formed by a solid-phase boron glass diffusion method using BBr ₃ . Of course, Ion
It may be formed by an implantation method. drive·
Injection is performed at 1100 ° C. for 3 hours, and the diffusion depth is 0.2 μm.
About. As described above, the withstand voltage of the emitter-base is required to be higher than the supply voltage to the heater. If the rating is 35 V, the curvature of the emitter needs to be 1 μm or more. In the present embodiment, the emitter edge portion is gently rounded by the drive-in to ensure the withstand voltage.

Next, the oxide film 103A is removed to provide a new oxide film, a portion corresponding to the base contact region is opened, and the diffusion layer 104 for making a base contact is formed by thermal diffusion using phosphoryl chloride POCl _3. Formed by the method. It may be formed using a solid phase diffusion method of PSG,
Of course, it may be formed using an ion implantation method. The diffusion layer 104 was a shallow diffusion layer and was driven at 1000 ° C. for 10 minutes without any problem. Subsequently, the oxide film was removed to form a new oxide film 103B (FIG. 4B).

Hereinafter, contact holes are opened using well-known ordinary silicon fabrication techniques, and emitters E _{1 to} E ₈ ,
Aluminum wiring for base B and collector C was provided (FIG. 4C).

FIG. 5 shows a schematic diagram of the wiring of one block.

The heater array R ₁ to R ₈ using tantalum nitride and hafnium boride, common base region including a base B ₁ .about.B _8, the driving voltage V _H supply line and the collector connection lines are shown. Considering an ink jet head of about 360 DPI (dots per inch), one pitch is 70 μm, and the emitter-emitter spacing can be set to about 65 μm pitch even considering the presence of the collector region. Therefore, the emitters E _{1 to} E ₈ can be arranged in a line, and if the emitter width is set to about 1 mm, the VF becomes sufficiently low (1.5 V or less), and complete compatibility with the conventional diode array can be obtained. .

When the potential supplied to the heater is a negative potential, the polarity of all the transistors may be reversed.

FIG. 7 is a schematic perspective view showing a head assembly (assembly) using the ink jet recording head according to the present invention.

The assembly 20 includes a head 21 having a large number of ink discharge ports 23 and an ink tank 22 for storing ink. The ink tank contains an ink absorber (not shown) for holding ink. The head 21 and the ink tank 22 may be either integral or detachable from each other.

FIG. 8 is a block diagram of a control system of the ink jet recording apparatus having the assembly 20.

The head assembly 20 includes a drive control circuit 2
From 5, the control signal for performing image recording is sent together with the image data. On the other hand, the head assembly 20 is reciprocated by the carriage drive circuit 26 in one main scanning direction of the recording medium PP. Reference numeral 30 denotes a roller as a transport unit for transporting the medium PP in the sub-scanning direction.

Reference numeral 27 denotes a control circuit for controlling the entire apparatus, which has a microprocessor unit (MPU).

Reference numeral 28 denotes an input interface circuit serving as an interface between the input terminal 29 for image data and the control circuit 27.

FIG. 9 is a plan view of a substrate of an ink jet recording head according to the present invention. In FIG. 9, heaters for heating ink are provided at 31 locations, and a driving section shown in FIG. Here, the wiring is omitted.

FIG. 10 is a diagram showing a method of assembling the ink jet recording head.

Reference numeral 21A denotes a head of a type for ejecting ink substantially parallel to the heat generating surface of the heater.
A top plate 35 having a groove 23a is attached to the top plate 01. One heater RH corresponds to one groove 23a, and forms one ink liquid path (nozzle).

Reference numeral 21B denotes a head for ejecting ink in a direction intersecting the heat generating surface of the heater, and a top plate 35 having a groove 23b and an ink ejection port 23 is bonded on a substrate 101. One heater RH corresponds to one ink ejection port, and forms one ink liquid path (nozzle).

The ink tank and the ink liquid path communicate with each other through an ink flow path (not shown), and the ink is supplied to the ink liquid path.

FIG. 11 is a schematic view showing an ink injection step in the manufacturing process of the ink jet recording head of the present invention.

Reference numeral 35 denotes an ink injector for containing ink therein. The ink is supplied to the ink absorber in the tank 22 by a user through an ink injection port or an air communication port 34 provided in the ink tank 22. To absorb.

This step is the same as the ink replenishment step when the amount of ink in the tank 22 is low.

[0048]

As described above, according to the present invention,
A circuit having the same heater selection characteristics as that of the conventional example can be configured only by forming three diffusion layers without using a complicated and expensive manufacturing process that requires an epitaxial layer as in the conventional example. As a result, it was possible to reduce the cost by 35% even though the elements had the same performance.

Further, according to the present invention, it is possible to reduce the interval between element pitches, and it is possible to arrange drive elements in a line at 360 DPI.

[Brief description of the drawings]

FIG. 1 is a circuit diagram and a structural cross-sectional view that best illustrate the features of the present invention.

FIG. 2 is an explanatory diagram of a potential relationship of a conventional example and the present invention in a 2 × 2 matrix.

FIG. 3 is an equivalent circuit diagram of a PNP transistor.

FIG. 4 is a manufacturing process diagram of one embodiment of the present invention.

FIG. 5 is a conceptual diagram of wiring according to one embodiment of the present invention.

FIG. 6 is a circuit diagram and a structural cross-sectional view of a conventional example.

FIG. 7 is a schematic perspective view showing a head assembly using the inkjet recording head according to the present invention.

FIG. 8 is a block diagram of a control system of the inkjet recording apparatus having the head assembly.

FIG. 9 is a plan view of a substrate of the inkjet recording head according to the present invention.

FIG. 10 is a diagram illustrating a method of assembling the inkjet recording head according to the present invention.

FIG. 11 is a view showing an ink injection step of the ink jet recording head according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS 101 Silicon substrate of first conductivity type 102 Base region with diffusion layer of second conductivity type opposite to silicon substrate 104 Emitter and collector contact region with diffusion layer of first conductivity type 105 Second Base contact region 106 of conductive type diffusion layer 106 n-type buried layer 107 p-type silicon epitaxial layer 108 deep n-type diffusion layer 109 p-type diffusion layer 110 n-type diffusion layer

Claims (12)

(57) [Claims] A first conductive type silicon substrate;
A plurality of first diffusion layers of a second conductivity type different from the first conductivity type are formed, and a plurality of second diffusion layers of the first conductivity type are formed on each of the plurality of first diffusion layers. Resistors for discharging ink by heating the ink to generate air bubbles are connected one by one, and the different sides of the plurality of resistors from the second diffusion layer side are connected to each other for each first diffusion layer. An ink jet recording head, comprising: 2. The ink jet recording head according to claim 1, wherein said resistor is made of tantalum nitride and hafnium boride. 3. A third diffusion layer of a second conductivity type and a higher concentration than the first diffusion layer is disposed between each of the plurality of second diffusion layers in the same first diffusion layer. The ink jet recording head according to claim 1, wherein: 4. The method for manufacturing an ink jet recording head according to claim 1, wherein phosphorus is implanted into the p-type silicon substrate by an ion implantation method to form a first diffusion layer. A method comprising: 5. The method according to claim 4, wherein a second diffusion layer containing boron as an impurity is formed in the p-type silicon substrate by an ion implantation method or a solid phase diffusion method. 6. The method for manufacturing an ink jet recording head according to claim 1, wherein boron is introduced into the n-type silicon substrate to form the first diffusion layer. . 7. The method according to claim 6, wherein a second diffusion layer containing phosphorus as an impurity is formed in the n-type silicon substrate by an ion implantation method or a solid phase diffusion method. 8. A plurality of resistors for heating the ink to generate bubbles, thereby discharging the ink, and a plurality of functional elements for controlling energization of each of the plurality of resistors are the same. In the ink jet recording head formed in the base, the plurality of functional elements are bipolar transistors,
The collectors of the plurality of bipolar transistors are of the same conductivity type as the base and are connected to each other at a ground potential. One end of the plurality of resistors is connected to each of the emitters of the plurality of bipolar transistors. The other end of each of the resistors is connected to a terminal for applying a voltage to the resistor. 9. An ink jet recording head according to claim 8, wherein said plurality of bipolar transistors have emitters of individual bipolar transistors in the same common base. 10. The ink jet recording head according to claim 8, wherein a breakdown voltage between an emitter and a base of the bipolar transistor is higher than a supply voltage to the resistor. 11. A driving circuit for an ink jet recording head, wherein a plurality of resistors and a plurality of bipolar transistors for heating ink to generate bubbles and thereby discharge ink are formed in the same base. The collectors of the plurality of bipolar transistors are of the same conductivity type as the base, and are connected to each other at a ground potential. One end of each of the plurality of resistors is connected to each of the plurality of bipolar transistors. The other end of each of the plurality of resistors is connected to a terminal for applying a voltage to the resistor, and application of a supply voltage to the resistor from driving means external to the recording head and application of a voltage to the plurality of bipolar transistors. By controlling the potential of each base, a specific resistor is heated, and the ink jet recording De of the drive circuit. 12. The drive circuit according to claim 11, wherein the total number of bonding pads provided on the base is smaller than the number of resistors in the base.