JP3639920B2 - Manufacturing method of thermal ink jet head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a thermal ink jet head having a plurality of heating elements on a substrate.
[0002]
[Prior art]
In recent years, thermal ink jet printers have been widely used. In this thermal ink jet method, in the process of forming ink droplets to be ejected for printing, (1) a heating element is heated to generate nuclear bubbles on the heating element. (2) Membrane bubbles are formed by combining these nuclear bubbles. {Circle around (3)} This film bubble expands adiabatically and grows, pushing the surrounding ink. {Circle around (4)} The grown film bubbles are contracted by the surrounding ink taking heat. {Circle around (5)} Finally, the film bubbles disappear and the next heater heating is waited for to perform a series of steps instantaneously. The film boiling phenomenon is used in the above steps (1) to (3).
[0003]
The film boiling phenomenon occurs when an object heated to a high temperature, for example, iron quenching, is immersed in a liquid, and when the surface temperature of an object in contact with the liquid is suddenly increased. The film boiling phenomenon used in the above is based on the latter method of “raising the surface temperature of an object in contact with a liquid rapidly”. Such thermal ink jet heads include not only monochrome printing but also full-color printing by ejecting three primary color inks.
[0004]
The ink droplets are ejected in a direction in which the ink droplets are ejected in a direction perpendicular to the heat generating surface of the heat generating element and in a structure in which the ink droplets are ejected in a direction parallel to the heat generating surface of the heat generating element. In the configuration that ejects ink droplets in a direction parallel to the heat generating surface of the heat generating element, the ejection energy of the ink droplets is relatively large, and is approximately 8 to 10 μJ per dot.
[0005]
On the other hand, as a manufacturing method of a thermal ink jet head for full color, which is configured to eject ink droplets in a direction perpendicular to the heat generating surface of the heat generating element, a plurality of heat generating elements, individual drive circuits and inks are utilized by utilizing silicon LSI and thin film technology. There is a method in which discharge nozzles (orifices) are collectively formed in a monolithic manner.
[0006]
According to this method, for example, when a print head having a resolution of 360 dpi (dots / inch) is formed on a silicon chip having a width of 10 mm, 128 heating elements, a drive circuit, and an orifice (generally a waveguide) The terminology used for the energy transmission hole or window formed on the end or wall surface of the like), and if the resolution is 720 dpi, 256 heating elements and drive circuit And an orifice can be formed.
[0007]
[Problems to be solved by the invention]
By the way, there is a step of forming a large number of orifices by forming holes in an orifice plate made of polyimide as a subsequent step of manufacturing the thermal ink jet head as described above. For this purpose, after laminating a metal film such as Al, Ni or Cu on the above polyimide plate, this is patterned, and the polyimide plate is selectively etched using the patterned metal film as a mask.
[0008]
In general, according to a helicon wave etching apparatus having a high plasma density capable of performing etching of 1 μm or more per minute on polyimide, the selection ratio of polyimide to metal film is 1/50 to 1/100. The etching speed and the selection ratio with the metal film vary depending on the gas condition and bias condition of the helicon wave etching.
[0009]
In the case of processing the polyimide of the above orifice plate, it is necessary to set the processing time and stop the etching in a state where the orifice is just processed (nozzle hole penetrates the orifice plate). Otherwise, in a configuration in which ink droplets are ejected in a direction perpendicular to the heat generating surface of the heat generating element, that is, in the roof shooter type thermal ink jet head, the heat generating element formed facing the position of the orifice may be damaged. There is.
[0010]
Etching is performed by putting a single wafer in the above etching apparatus. First, variations in this etching occur first in wafer units. That is, there is no variation in the processing of each orifice of one wafer, but the processing of one wafer is finished, and the next processing after the replacement is not necessarily performed the same processing as the first wafer. Secondly, etching variation occurs due to the difference in orifice plate lots. This is considered to be caused by a subtle difference in the thickness of the orifice plate and a difference in a small amount of components. Third, there are individual differences in etching apparatuses. Etching apparatuses mainly process one wafer with one apparatus, but there are individual differences in etching apparatuses that should have the same characteristics, resulting in variations in etching state.
[0011]
For this reason, due to the variation in etching described above, it is often the case that the orifice is not sufficiently drilled and the hole does not penetrate the orifice plate. In this case, an inefficient operation is performed in which the wafer is again set in the vacuum apparatus and etched.
[0012]
On the other hand, in the formation of the heating element, there is almost no variation depending on the position of film formation in one wafer when the heating resistor is formed on the wafer. There is also a problem that variation occurs between the membrane devices.
[0013]
An object of the present invention is to provide a method for manufacturing a thermal ink jet head that reliably processes an orifice and eliminates variation in heating elements in view of the above-described conventional situation.
[0014]
[Means for Solving the Problems]
First, in the method of manufacturing a thermal ink jet head according to the first aspect of the present invention, a plurality of heating elements are provided on a substrate, ink supplied onto the heating elements is heated by the heating elements, and the ink and the heating are generated. A method of manufacturing a thermal ink jet head that discharges ink droplets from an orifice provided opposite to the heating element by generating bubbles at an interface of the element, wherein the orifice plate is provided opposite to the heating element. While performing the orifice machining, the resistance value of the heating element is monitored, and when the resistance value obtained by the monitoring reaches a predetermined value, the orifice machining is finished.
[0015]
For example, the heating element whose resistance value is monitored is organized so as to be a specific heating element among the plurality of heating elements.
Next, according to a third aspect of the present invention, there is provided a thermal ink jet head manufacturing method comprising: providing a plurality of heat generating elements on a substrate; heating the ink supplied on the heat generating elements with the heat generating elements; A method of manufacturing a thermal ink jet head that ejects ink droplets from an orifice provided opposite to a heating element by generating bubbles at an interface of the heating element, wherein the method is separate from the heating element that discharges the ink. A resistor dedicated for monitoring is provided in the same manner as the heating element, and the resistance value of the resistor is monitored while performing orifice processing on an orifice plate provided opposite to the heating element, and the resistance obtained by the monitoring is obtained. When the value reaches a predetermined value, the knitting is performed so as to end the orifice processing.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 (a), (b), (c) and FIGS. 2 (a), (b), (c) are diagrams showing a method of manufacturing a thermal ink jet head in one embodiment in the order of steps. 1 (a), (b), and (c) show a schematic plan view and a cross-sectional view, respectively. The upper part of FIGS. 2 (a), (b), and (c) is shown in FIGS. (b), (c) is a partially enlarged view showing a part of the plan view in detail, the middle is a cross-sectional view of the upper AA 'cross section (see (a)), the lower is the upper B- It is a B 'cross-sectional view (refer to the figure (a)). The cross-sectional views shown below in FIGS. 1 (a), (b) and (c) are the same as the cross-sectional views shown in the middle of FIGS. 2 (a), (b) and (c). is there.
[0017]
In these drawings, for convenience of explanation, only one heating head of the thermal ink jet head for full color (same as the configuration of the monochrome ink jet head) is shown, but actually, as will be described later, A plurality of such heat generating heads (usually four) are formed on a single substrate (silicon chip), and a large number of such substrates are formed on a single silicon wafer. .
[0018]
First, a basic manufacturing method will be described. First, as step 1, a driver circuit having electrode wiring and its terminals are formed on a silicon substrate of 4 inches or more by LSI formation processing, and an oxide film having a thickness of 1 to 2 μm is formed. Next, as a step 2, using a thin film technique, a resistive protective film made of Ta—Si—O or the like (which serves as both a resistance film for forming a heating element and a protective film for protecting a lower layer) is sputtered. To form a film having a thickness of 4000 mm, and forming each electrode film of a common electrode and individual wiring electrodes of Al or Ni. Furthermore, a conductive protective film made of W-Al (or W-Ti, W-Si) or the like and each electrode film made of Au may be laminated.
[0019]
Then, the pattern of the wiring part is formed on the electrode film by the photolithography technique (and the conductive protective film, if a conductive protective film is formed), and the resistive protective film has a substantially square fine heating part (heating A pattern of a resistor and a heating element is formed. The resistance of each heating resistor is set to be thicker than the final thickness in consideration of later adjustment, that is, the resistance value is set to a resistance value lower than the final resistance value, for example, 230Ω. In this step, the position of the heating element is determined.
[0020]
FIG. 1A and FIG. 2A show a state immediately after the above steps 1 and 2 are completed. That is, on the silicon substrate 1, the common electrode 2, the common electrode power supply terminal 3 (see FIG. 1A), the individual wiring electrode 4, a large number of heating resistors (heating elements) 5, the drive circuit 6 and the drive circuit terminal 7. (See FIG. 1 (a)).
[0021]
Subsequently, as step 3, a partition member made of an organic material such as photosensitive polyimide is formed to have a height of about 20 μm by coating so as to form an ink groove corresponding to each heating element 5, and this is patterned, 30 minutes to 60 minutes, optionally 2 hours, curing (dry curing, baking) applying heat at 300 ° C. to 400 ° C., and forming a partition with the above-mentioned photosensitive polyimide having a height of 10 μm on the silicon substrate after curing. Secure. Further, as step 4, a groove-like ink supply path is formed on the surface of the silicon substrate by wet etching or sand blasting, and an ink feed hole which is open to the lower surface in communication with the ink supply path is formed.
[0022]
FIG. 1B and FIG. 2B show a state immediately after the above-described step 3 and step 4 are finished. That is, the groove-shaped ink supply path 8 and the ink supply hole 10 are formed, the common electrode 2 portion located on the left side of the ink supply path 8, the portion where the right individual wiring electrode 4 is disposed, and A partition wall 9 (9, 9-1, 9-2) is formed between each heating resistor 5 and the heating resistor 5. The portion of the partition wall 9 that is laminated between the heat generating resistors 5 is a portion 9-2 that extends between the heat generating resistors 5 if the portion 9-1 on the individual wiring electrode 4 is a comb body. It has a shape corresponding to the tooth. As a result, the comb teeth are used as partition walls, and as many fine ink grooves as the heat generating resistors 5 are located at the base portion between the teeth are formed. By changing the length of the comb teeth, the conductance of the ink changes, and it also affects the interference between the inks flowing in the adjacent ink grooves.
[0023]
Thereafter, as step 5, an orifice plate of a film made of polyimide having a thickness of 10 to 30 μm is coated with a thermoplastic polyimide as an adhesive on one side thereof to an extremely thin thickness of, for example, 2 to 5 μm. Affixed to the uppermost layer, the ink groove formed by the partition wall 9-2 is covered, thereby forming individual fine passages (ink groove pits). And it pressurizes, heating at 200-300 degreeC, and an orifice plate is fixed. Subsequently, a metal film having a thickness of about 0.5 to 1 μm such as Ni, Cu or Al is formed.
[0024]
Further, as step 6, a metal film on the orifice plate is patterned to form a mask for selectively etching polyimide, and then the orifice plate is subjected to the above-described metal film mask by a helicon wave etching apparatus or the like. A large number of nozzle holes (orifices) are formed at once by making holes of 40 μmφ to 20 μmφ. This will be described in more detail later.
[0025]
FIG. 1C and FIG. 2C show a state immediately after the above-described step 5 and step 6 are finished. That is, the orifice plate 11 covers the entire area except for the drive circuit 6 and the power supply terminals 3 and 7, and the ink groove is also covered on the top so that the height of the partition wall 9 corresponds to the thickness of 10 μm. Ink grooves (ink supply paths) 12 are formed. In the orifice plate 11, nozzle holes (orifices) 13 are formed by etching in portions corresponding to the heating resistors 5, thereby completing a monocolor head 14 having one row of nozzle holes 13. .
[0026]
By pasting the orifice plate 11 in this way and then processing the nozzle hole (orifice) in accordance with the position of the underlying pattern, that is, the heating resistor 5, rather than pasting the orifice plate in which the orifice has been processed in advance, It is a far more productive and practical method. In the case of dry etching, a metal / Ni film such as Ni, Cu, or Al is used as the mask, so that a selectivity ratio between the resin and the metal film is approximately 100. Therefore, it is sufficient to form a mask with a metal film of 1 μm or less for etching a polyimide film of 20 to 40 μm.
[0027]
Up to this point, the wafer is processed. Finally, as step 7, cutting is performed using a dicing saw or the like, and the unit is individually divided, die-bonded to a mounting board, and terminal-connected to complete.
[0028]
In the above example, the drive circuit 6 is exposed, but a protective film is actually formed. In addition, the protective film is not formed afterwards, and the orifice plate 11 is extended to the right side of FIG. 1 (c) (the same applies to FIG. 2 (c)) and laminated to drive the orifice plate 11. The protective film of the circuit 6 may also be used.
[0029]
The monocolor head 14 having the nozzle holes 13 in one row has a monochrome ink jet head configuration. However, in full-color printing, yellow (Y), magenta (M), cyan (subtractive three primary colors) are usually used. A total of four colors of ink are required by adding black (Bk) dedicated to the black portion of characters and images to the three colors of C). Therefore, at least four nozzle rows are necessary. According to the manufacturing method described above, the four rows of heat generating heads can be configured monolithically, and the positional relationship of each row can be accurately arranged by today's semiconductor manufacturing technology.
[0030]
FIG. 3A is a diagram showing a state in which the above-described mono-color heads 14 are arranged side by side to form a full-color thermal inkjet head 15, and FIG. 3B is a diagram showing a substrate (chip) of the thermal inkjet head 15. FIG. 6 is a view showing a state where a large number of silicon wafers 17 are formed. FIG. 6A shows a type in which the orifice plate 11 is also used as the protective film of the drive circuit 6 (see FIGS. 1C and 2C).
[0031]
As shown in FIG. 3A, the thermal inkjet head 15 is formed by arranging four monocolor heads 14 (14a, 14b, 14c, 14d) side by side on a slightly larger substrate 16. The thermal inkjet head 15 is configured to eject magenta, cyan, yellow, and black inks, for example, sequentially from right to left.
In the thermal ink jet head 15, during printing, the heating resistor 5 (see FIGS. 2A and 2B) is selectively energized according to the printing information, and instantaneously generates heat to generate a film boiling phenomenon. Ink droplets are ejected from the nozzle holes 13 corresponding to the heating resistors 5. In such a thermal ink-jet head, ink droplets are ejected in a substantially spherical shape having a size corresponding to the diameter of the nozzle hole 13, and are printed on the paper surface with a diameter that is approximately twice that of the nozzle hole 13.
[0032]
If the resolution is 360 dpi, the full-color inkjet head obtained in this way can be equipped with 128 nozzles × 4 rows = 640 nozzles on a chip of approximately 8.5 mm × 19.0 mm. In addition, if the resolution is 720 dpi, 256 nozzles × 4 rows = 1280 nozzles can be formed in a chip having a size of approximately 8.5 mm × 19.0 mm.
[0033]
By the way, in the manufacturing method of the thermal ink jet head 15 described above, as a feature in the present embodiment, a special contrivance is made in the formation of the orifice and the rating of the heat generation characteristics of the heat generating element. As a result, variations in each etching apparatus and variations in each orifice plate are absorbed, so that stable orifice processing (perforation processing) and a desired resistance value of the heating element are obtained, and as a result, desired heat generation characteristics are obtained. I am trying to do it. This will be described below.
[0034]
FIG. 4A is an enlarged side sectional view showing the orifice 13 formed in the step 6 of manufacturing the thermal ink jet head 15 in the present embodiment and the heating element 5 formed at a position facing the orifice 13. FIG. 5B is a plan view showing the state of the heating element 5 with the orifice plate 11 removed for easy understanding. In FIGS. 1A and 1B, the same parts as those shown in FIGS. 1 to 3 are the same as those shown in FIGS. A number is given.
[0035]
In the manufacture of the thermal ink jet head in the present embodiment, first, in the above-described step 2, a resistive protective film made of Ta—Si—O or the like is formed slightly thick, that is, 4000 mm by thin film technology (FIG. 4A). The heat generating part (heat generating element) 5 is formed by the photolithography technique (see FIG. 4B). Thereafter, the orifice plate 11 is heat-pressed.
[0036]
The orifice plate 11 is coated with a thermoplastic polyimide 11-2 very thinly on the lower surface of the main body polyimide film 11-1, and a mask metal film 11-3 is deposited on the upper surface. Then, dry etching is performed according to the patterned mask of the metal film 11-3. In general, with respect to a polyimide material such as the orifice plate 11 used in this example, the selection ratio is 1/50 to 1/100 under an etching condition that provides an etching rate of 1.5 μm or more per minute.
[0037]
In this example, the over-etching is performed after allowing for a margin of about 3 minutes after the penetration. This over-etching is 200 mm / min when the selection ratio with respect to the resistance film (heating resistor 5) is 1/75, and when the film thickness at the time of forming the resistance film is 4000 mm as described above, As shown in FIG. 4 (a), a recess 5-1 of about 600 mm is formed in the central portion of the heating resistor 5 arranged immediately below the orifice 13, as shown in FIG. 4 (b). That is, the resistance film (heating resistor 5) is partially thinned and the resistance value is increased.
[0038]
FIG. 5 is a chart showing a change in resistance value when the resistance film (heating resistor 5) is processed 10% or 20% thinner than the initial thickness (overetching). As shown in the figure, the resistance value changes depending on the relationship between the size of the heating resistor 5 and the orifice 13. For example, in the first row of the figure, the size of the heating resistor is a 40 μm mouth, This shows the case where the diameter of the opposed orifice is 30 μmφ. In this case, if the resistance film (heating resistor 5) is made 10% thinner, that is, 400 mm thinner in this example, the resistance value increases by 5%. In addition, when the thickness is 20% thinner (800 mm thinner), the resistance value increases by 11%.
[0039]
Also, the second line in the figure shows that even if the heating resistor has the same size of 40 μm, and the orifice diameter is 35 μmφ, the resistance value is reduced by making the heating resistor 10% thinner (400 mm thinner). It shows that the resistance value increases by 15% when it increases by 8% and thins by 20% (thickness of 800 mm).
[0040]
According to this, since the initial value is set to 200Ω, in the case of the configuration shown in the first row, it is possible to adjust from 241Ω to 255Ω. By utilizing the change in the resistance value of the heating resistor when this over-etching is performed, in this example, when dry etching is completed, the orifice is surely formed through the orifice plate, and the resistance film The resistance value of the heat generating portion (heat generating resistor) is made constant to a desired value even if there is a variation in film thickness or variation between lots.
[0041]
FIG. 6A schematically shows an etching apparatus and a control apparatus that performs etching while measuring and monitoring the change in resistance value of the heating resistor 5 when the over-etching is performed. These are figures explaining the timing until the completion | finish of the etching process of the orifice including the over-etching to the said heating resistor.
[0042]
As shown in FIG. 3A, a wafer (see FIG. 3B) is mounted in the etching apparatus 20 and etching is performed. At this time, etching is performed while monitoring (monitoring) the resistance value of the heating resistor 5 between the common electrode 2 and one individual wiring electrode 4. In this case, it has been found that the etching variation does not usually occur between the plurality of heating resistors 5. Therefore, on the assumption of this, only one heating resistor 5 for monitoring the resistance value is sufficient.
[0043]
As shown in FIG. 6B, the initial resistance value Ωu (200Ω in this example) of the heating resistor 5 is from the time t0 when the etching is started to the time t1 when the orifice 13 penetrates the orifice plate 11. It does not change as shown by the solid line a in b). However, the resistance value changes from the moment when the orifice 13 passes through the orifice plate 11 as shown by the solid line b in FIG. As a result of the above monitoring, when the resistance value of the heating resistor 5 reaches the desired resistance value Ωa at time t2, the control device 21 causes the etching device 20 to finish etching.
[0044]
Variation in wafer lots during resistance film formation in Step 2 described above is unavoidable, but the resistance value of the heat generation part is obtained by processing the heat generation part of the resistance film during orifice processing by the method described above. A thermal ink jet head having a uniform thickness can be produced, and the orifice 13 is formed so as to penetrate the orifice plate 11 when the etching is completed. Therefore, there is no problem that a double labor such as re-opening the hole because the orifice does not penetrate is caused.
[0045]
In the above manufacturing method, an example in which the drive circuit is integrated with the drive circuit has been shown. However, the present invention is not limited to this, and only the thermal ink jet head portion (electrode wiring, heating resistor, partition, ink groove, ink hole, orifice) Can be applied to a substrate such as a silicon substrate or a glass substrate. In the above example, one heating resistor used for the head is monitored. However, the present invention is not limited to this, and a monitor-dedicated resistor other than the printing heating resistor is formed for monitoring. You may make it do.
[0046]
【The invention's effect】
As described above in detail, according to the present invention, the resistance film is formed thicker and the resistance value of the heat generating portion is set to be smaller than a desired value, and the hole is formed in the polyimide during dry etching of the orifice. Then, the heat generating portion of the resistance film is etched, and the resistance value of the heat generating portion is monitored during the etching, and the dry etching is stopped when the resistance value reaches a predetermined value. When etching is completed, not only the orifice is surely formed through the orifice plate, but also the resistance value of the heat generating part is adjusted to the desired value including the lot-to-lot variation even if the film thickness of the resistance film varies. This makes it possible to keep the driving conditions of the driving circuit constant without adjusting for each thermal ink jet head. Te, not applied troublesome adjustments after chip, it is possible to make a thermal ink jet head having uniform characteristics.
[Brief description of the drawings]
FIGS. 1A, 1B, and 1C are a schematic plan view and a cross-sectional view showing a method of manufacturing a thermal ink-jet head in one embodiment in order of steps.
Fig. 2 (a), (b), (c) is an enlarged view of the top plan view of Fig. 1 (a), (b), (c). AA 'cross-sectional arrow view, the lower stage is an upper BB' cross-section arrow view.
3A is a diagram showing a state in which four monocolor heads are arranged side by side to form a full-color thermal inkjet head, and FIG. 3B is a diagram showing a state in which a large number of chips of the thermal inkjet head are formed on a silicon wafer. FIG.
4A is an enlarged side sectional view showing an orifice and a heating element formed in an embodiment, and FIG. 4B is a plan view showing an orifice plate removed for easy understanding of the state of the heating element. It is.
FIG. 5 is a chart showing a change in resistance value when a resistance film (heating resistor) is processed to be 10% or 20% thinner than the initial thickness.
6A is a diagram schematically showing a control device that performs etching while measuring and monitoring a change in resistance value of the heating resistor when overetching with the etching device, and FIG. 6B is a diagram showing a heating resistor. It is a figure explaining the timing until the completion | finish of the etching process of an orifice including the over-etching to.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Common electrode 3 Common electrode feeding terminal 4 Individual wiring electrode 5 Heating resistor (heating element)
6 Drive circuit 7 Drive circuit terminal 8 Ink supply path 9 (9-1, 9-2) Partition 10 Ink feed hole 11 Orifice plate 13 Nozzle hole (orifice)
14 (14a, 14b, 14c, 14d) Mono-color head 15 Full-color thermal inkjet head 16 Substrate (chip)
17 Silicon wafer 20 Etching device 21 Control device

Claims (3)

A plurality of heat generating elements are provided on the substrate, the ink supplied onto the heat generating elements is heated by the heat generating elements, and bubbles are generated at the interface between the ink and the heat generating elements to face the heat generating elements. A method of manufacturing a thermal ink jet head that discharges ink droplets from an orifice provided,
While performing orifice processing on an orifice plate provided facing the heating element, the resistance value of the heating element is monitored, and when the resistance value obtained by the monitoring becomes a predetermined value, the orifice processing is performed. A method for producing a thermal ink jet head, comprising: ending. 2. The method of manufacturing a thermal ink jet head according to claim 1, wherein the heating element whose resistance value is monitored is a specific heating element among the plurality of heating elements. A plurality of heat generating elements are provided on the substrate, the ink supplied onto the heat generating elements is heated by the heat generating elements, and bubbles are generated at the interface between the ink and the heat generating elements to face the heat generating elements. A method of manufacturing a thermal ink jet head that discharges ink droplets from an orifice provided,
Provided in the same manner as the heating element, a resistor dedicated to monitoring, separate from the heating element that discharges the ink,
While performing the orifice processing on the orifice plate provided facing the heating element, the resistance value of the resistor is monitored, and when the resistance value obtained by the monitoring becomes a predetermined value, the orifice processing is performed. A method for producing a thermal ink jet head, comprising: ending.

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