EP1652671B1

EP1652671B1 - Ink jet nozzle having two fluid ejection apertures and a moveable paddle vane

Info

Publication number: EP1652671B1
Application number: EP05109763A
Authority: EP
Inventors: Kia Silverbrook; Gregory Mcavoy
Original assignee: Silverbrook Research Pty Ltd
Current assignee: Silverbrook Research Pty Ltd
Priority date: 1997-07-15
Filing date: 1998-07-15
Publication date: 2008-05-14
Anticipated expiration: 2018-07-15
Also published as: EP1652671A1

Description

Field of Invention

The present invention relates to the field of ink jet printing systems.

Background of the Art

Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988).
Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
US Patent 3596275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilised by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al )
Piezo-electric ink jet printers are also one form of commonly utilised ink jet printing device. Piezo-electric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970 ) which utilises a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970 ) which discloses a squeeze mode of operation of a piezo electric crystal, Stemme in US Patent No. 3747120 (1972 ) discloses a bend mode of piezo-electric operation, Howkins in US Patent No. 4459601 discloses a Piezo electric push mode actuation of the ink jet stream and Fischbeck in US 4584590 which discloses a sheer mode type of piezo-electric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979 ) and Vaught et al in US Patent 4490728 . Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilising the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. JP-A-58116165 is an example of an inkjet nozzle having two ejection apertures.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handling such precision devices often adds a substantially expense in manufacturing.
Additionally, side shooting ink jet technologies ( U.S. Patent No. 4,899,181 ) are often used but again, this limit the amount of mass production throughput given any particular capital investment.
Additionally, more esoteric techniques are also often utilised. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation ( U.S. Patent No. 5,208,604 ), micro-punching, etc.
The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.
It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.
Further, during the construction of micro electromechanical systems, it is common to utilize a sacrificial material to build up a mechanical system, within the sacrificial material being subsequently etched away so as to release the required mechanical structure. For example, a suitable common sacrificial material includes silicon dioxide which can be etched away in hydrofluoric acid. MEMS devices are often constructed on silicon wafers having integral electronics such as, for example, using a multi-level metal CMOS layer. Unfortunately, the CMOS process includes the construction of multiple layers which may include the utilization of materials which can be attacked by the sacrificial etchant. This often necessitates the construction of passivation layers using extra processing steps so as to protect other layers from possible unwanted attack by a sacrificial etchant.
In micro-electro mechanical system, it is often necessary to provide for the movement of objects. In particular, it is often necessary to pivot objects in addition to providing for fulcrum arrangements where a first movement of one end of the fulcrum is translated into a corresponding measurement of a second end of the fulcrum. Obviously, such arrangements are often fundamental to mechanical apparatuses.
Further, When constructing large integrated circuits or micro-electro mechanical systems, it is often necessary to interconnect a large number of wire to the final integrated circuit device. To this end, normally, a large number of bond pads are provided on the surface of a chip for the attachment of wires thereto. With the utilization of bond pads normally certain minimal spacings are utilized in accordance with the design technologies utilised. Where are large number of interconnects are required, an excessive amount of on chip real estate is required for providing bond pads. It is therefore desirable to minimize the amount of real estate provided for bond pads whilst ensuring the highest degree of accuracy of registration for automated attachment of interconnects such as a tape automated bonding (TAB) to the surface of a device.

Summary of the invention

Accordingly the invention provides a nozzle arrangement as in claim 1 with advantageous embodiments provided in the dependent claims. A printhead according to claim 13 is also provided.

Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 452 to Fig. 456 illustrate schematically the principles operation of an embodiment;
Fig. 457 is a perspective view, partly in section of one form of construction of an embodiment;
Fig. 458 to Fig. 475 illustrate various steps in the construction of an embodiment; and
Fig. 476 illustrates an array view illustrating a portion of a printhead constructed in accordance with an embodiment.
Fig. 477 provides a legend of the materials indicated in Fig. 478 to Fig. 493; and
Fig. 478 to Fig. 494 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.
Fig. 495 to Fig. 499 comprise schematic illustrations of the operation of an embodiment;
Fig. 500 illustrates a perspective view, of a single nozzle arrangement of an embodiment;
Fig. 501 illustrates a perspective view, partly in section of a single nozzle arrangement of an embodiment;
Fig. 502 to Fig. 520 are cross sectional views of the processing steps in the construction of an embodiment;
Fig. 521 illustrates a part of an array view of a printhead as constructed in accordance with the principles of the present invention.;
Fig. 522 provides a legend of the materials indicated in Fig. 523 to Fig. 541; and
Fig. 523 to Fig. 541 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.

Description of the Preferred and Other Embodiments

The preferred embodiments and other embodiments will be discussed under separate headings with the heading including an IJ number for ease of reference. The headings also include a type designator with T indicating thermal, S indicating shutter type and F indicating a field type.

A Description of IJ37 T

In an embodiment, an inkjet printing system is provided for the projection of ink from a series of nozzles. In an embodiment a single paddle is located within a nozzle chamber and attached to an actuator device. When the nozzle is actuated in a first direction, ink is ejected through a first nozzle aperture and when the actuator is activated in a second direction causing the paddle to move in a second direction, ink is ejected out of a second nozzle. Turning initially to Fig. 452 to Fig. 456, there will now be illustrated in a schematic form, the operational principles of an embodiment.
Turning initially to Fig. 452, there is shown a nozzle arrangement 3701 of an embodiment when in its quiescent state. In the quiescent state, ink fills a first portion 3702 of the nozzle chamber and a second portion 3703 of the nozzle chamber. The ink fills the nozzle chambers from an ink supply channel 3705 to the point that a meniscus 3706, 3707 is formed around corresponding nozzle holes 3708, 3709. A paddle 3710 is provided within the nozzle chamber 3702 with the paddle 3710 being interconnected to a actuator device 3712 which can comprise a thermal actuator which can be actuated so as to cause the actuator 3712 to bend, as will be become more apparent hereinafter.
In order to eject ink from the first nozzle hole 3709, the actuator 3712, which can comprise a thermal actuator, is activated so as to bend as illustrated in Fig. 453. The bending of actuator 3712 causes the paddle 3710 to rapidly move upwards which causes a substantial increase in the pressure of the fluid, such as ink, within nozzle chamber 3702 and adjacent to the meniscus 3707. This results in a general rapid expansion of the meniscus 3707 as ink slows through the nozzle hole 3709 with result of the increasing pressure. The rapid movement of paddle 3710 causes a reduction in pressure along the back surface of the paddle 3710. This results in general flows as indicated 3717, 3718 from the second nozzle chamber and the ink supply channel. Next, while the meniscus 3707 is extended, the actuator 3712 is deactivated resulting in the return of the paddle 3710 to its quiescent position as indicated in Fig. 454. The return of the paddle 3710 operates against the forward momentum of the ink adjacent the meniscus 3707 which subsequently results in the breaking off of the meniscus 3707 so as to form the drop 3720 as illustrated in Fig. 454. The drop 3720 continues onto the print media. Further, surface tension effects on the ink meniscus 3707 and ink meniscus 3706 result in ink flows 3721 - 3723 which replenish the nozzle chambers. Eventually, the paddle 3710 returns to its quiescent position and the situation is again as illustrated in Fig. 452.
Subsequently, when it is desired to eject a drop via ink ejection hole 3708, the actuator 3712 is activated as illustrated in Fig. 465. The actuation 3712 causes the paddle 3710 to move rapidly down causing a substantial increase in pressure in the nozzle chamber 3703 which results in a rapid growth of the meniscus 3706 around the nozzle hole 3708. This rapid growth is accompanied by a general collapse in meniscus 3707 as the ink is sucked back into the chamber 3702. Further, ink flow also occurs into ink supply channel 3705 however, hopefully this ink flow is minimised. Subsequently, as indicated in Fig. 456, the actuator 3712 is deactivated resulting in the return of the paddle 3710 to is quiescent position. The return of the paddle 3710 results in a general lessening of pressure within the nozzle chamber 3703 as ink is sucked back into the area under the paddle 3710. The forward momentum of the ink surrounding the meniscus 3706 and the backward momentum of the other ink within nozzle chamber 3703 is resolved through the breaking off of an ink drop 3725 which proceeds towards the print media. Subsequently, the surface tension on the meniscus 3706 and 3707 results in a general ink inflow from nozzle chamber 3705 resulting, in the arrangement returning to the quiescent state as indicated in Fig. 452.
It can therefore be seen that the schematic illustration of Fig. 452 to Fig. 456 describes a system where a single planar paddle is actuated so as to eject ink from multiple nozzles.
Turning now to Fig. 457, there is illustrated a sectional view through one form of implementation of a single nozzle arrangement 3701. The nozzle arrangement 3701 can be constructed on a silicon wafer base 3728 through the construction of large arrays of nozzles at one time utilising standard micro electro-mechanical processing techniques.
An array of nozzles on a silicon wafer device and can be constructed from the utilising semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed.
For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.
One form of construction will now be described with reference to Fig. 458 to Fig. 455. On top of the silicon wafer 3728 is first constructed a CMOS processing layer 3729 which can provide for the necessary interface circuitry for driving the thermal actuator and its interconnection with the outside world. The CMOS layer 3729 being suitably passivated so as to protect it from subsequent MEMS processing techniques. The walls eg. 3730 can be formed from glass (SiO₂). Preferably, the paddle 3710 includes a thinned portion 3732 for more efficient operation. Additionally, a sacrificial etchant hole 3733 is provided for allowing more effective etching of sacrificial etchants within the nozzle chamber 3702. The ink supply channel 3705 is generally provided for interconnecting an ink supply conduit 3734 which can be etched through the wafer 3728 by means of utilisation of a deep anisotropic trench etcher such as that available from Silicon Technology Systems of the United Kingdom.
The arrangement 3701 further includes a thermal actuator device eg. 3712 which includes two arms comprising an upper arm 3736 and a lower arm 3737 formed around a glass core 3738. Both upper and lower arm heaters 3736, 3737 can comprise a 0.4µm film of 60% copper and 40% nickel hereinafter known as (Cupronickel) alloy. Copper and nickel is used because it has a high bend efficiency and is also highly compatible with standard VLSI and MEMS processing techniques. The bend efficiency can be calculated as the square of the coefficient of the thermal expansion times the Young's modulus, divided by the density and divided by the heat capacity. This provides a measure of the amount of "bend energy" produced by a material per unit of thermal (and therefore electrical) energy supplied.
The core can be fabricated from glass which also has many suitable properties in acting as part of the thermal actuator. The actuator 3712 includes a thinned portion 3740 for providing an interconnect between the actuator and the paddle 3710. The thinned portion 3740 provides for non-destructive flexing of the actuator 3712. Hence, when it is desired to actuate the actuator 3712, say to cause it to bend downwards, a current is passed down through the top cupronickel layer causing it to be heated and expand. This in turn causes a general bending due to the thermocouple relationship between the layers 3736 and 3738. The bending down of the actuator 3736 also causes thinned portion 3740 to move downwards in addition to the portion 3741. Hence, the paddle 3710 is pivoted around the wall 3741 which can, if necessary, include slots for providing for efficient bending. Similarly, the heater coil 3737 can be operated so as to cause the actuator 3712 to bend up with the consequential movement upon the paddle 3710.
A pit 3739 is provided adjacent to the wall of the nozzle chamber to ensure that any ink outside of the nozzle chamber has minimal opportunity to "wick" along the surface of the printhead as, the wall 3741 can be provided with a series of slots to assist in the flexing of the fulcrum.
Turning now to Fig. 458 to Fig. 475, there will now be described one form of processing construction of an embodiment of Fig. 457. This can involve the following steps:

1. Initially, as illustrated in Fig. 458, starting with a fully processed CMOS wafer 3728 the CMOS layer 3729 is deep silicon etched so as to provide for the nozzle ink inlet 3705.
2. Next, as illustrated in Fig. 459, a 7 layer of a suitable sacrificial material (for example, aluminium), is deposited and etched with a nozzle wall mask in addition to the electrical interconnect mask.
3. Next, as illustrated in Fig. 460, a 7 layer of low stress glass is deposited 3743 and planarised utilising chemical planarization.
4. Next, as illustrated in Fig. 461, the sacrificial material is etched to a depth of 0.4 micron and the glass to at least a level of 0.4 micron utilising a first heater mask.
5. Next, as illustrated in Fig. 462, the glass layer is etched 3745, 3746 down to the aluminium portions of the CMOS layer 3704 providing for an electrical interconnect utilising a first heater via mask.
6. Next, as illustrated in Fig. 463, a 3 micron layer of 50% copper and 40% nickel alloy is deposited eg. 3748 and planarised utilising chemical mechanical planarization.
7. Next, as illustrated in Fig. 464, a 4 micron layer of low stress glass is deposited and etched 3749 to a depth of 0.5 micron utilising a mask for the second heater.
8. Next, as illustrated in Fig. 465, the deposited glass layer is etched 3750 down to the cupronickel utilising a second heater via mask.
9. Next, as illustrated in Fig. 466, a 3 micron layer of cupronickel is deposited 3751 and planarised utilising chemical mechanical planarization.
10. As illustrated in Fig. 467, next, a 7 micron layer low stress glass 3752 is deposited.
11. The glass is etched, as illustrated in Fig. 468 to a depth of 1 micron utilising a first paddle mask.
12. Next, as illustrated in Fig. 469, the glass is again etched to a depth of 3 micron utilising a second paddle mask with the first mask utilised in Fig. 468 etching away those areas not having any portion of the paddle and the second mask as illustrated in Fig. 469 etching away those areas having a thinned portion. Both the first and second mask of Fig. 468 and Fig. 469 can be a timed etch.
13. Next, as illustrated in Fig. 470, the glass is etched to a depth of 7 micron using a third paddle mask. The third paddle mask leaving the nozzle wall 3730, baffle 3711, thinned wall 3741 and end portion 3754 which fixes one end of the thermal actuator firmly to the substrate.
14. The next step, as illustrated in Fig. 465, is to deposit an 11 micron layer 3755 of sacrificial material such as aluminium and planarize the layer utilising chemical mechanical planarization.
15. As illustrated in Fig. 472, a 3 micron layer of glass is deposited and etched to a depth of 1 micron utilising a nozzle rim mask.
16. Next, as illustrated in Fig. 473, the glass is etched down to the sacrificial layer utilising a nozzle mask so as to form the nozzle structure eg. 3758.
17. The next step, as illustrated in Fig. 474, is to back etch an ink supply channel 3734 utilising a deep silicon trench etcher such as that available from Silicon Technology Systems. The printheads can also be diced by this etch.
18. Next, the sacrificial layers are etched away by means of a wet etch and wash.

The printheads can then be inserted in an ink chamber moulding, tab bonded and a PTFE hydrophobic layer evaporated over the surface so as to provide for a hydrophobic surface.
In Fig. 476, there is illustrated a portion of a page with printhead including a series of nozzle arrangements as constructed in accordance with the principles of an embodiment. The array 3760 has been constructed for three colour output having a first row 3761 a second row 3762 and a third row 3763. Additionally, a series of bond pads, eg. 3764, 3765 are provided at the side for tab automated bonding to the printhead. Each row 3761, 3762, 3763 can be provided with a different colour ink including cyan, magenta and yellow for providing full colour output. The nozzles of each row 3761 - 3763 are further divided into sub rows eg. 3768, 3769. Further, a glass strip 3770 can be provided for anchoring the actuators of the row 3763 in addition to providing for alignment for the bond pad 3764, 3765.
The CMOS circuitry can be provided so as to fire the nozzles with the correct timing relationships. For example, each nozzle in the row 3768 is fired together followed by each nozzle in the row 3769 such that a single line is printed.
It could be therefore seen that an embodiment provides for an extremely compact arrangement of an inkjet printhead which can be made in a highly inexpensive manner in large numbers on a single silicon wafer with large numbers of printheads being made simultaneously. Further, the actuation mechanism provides for simplified complexity in that the number of actuators is halved with the arrangement of an embodiment.
One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. Relevant features of the wafer at this step are shown in Fig. 478. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. Fig. 477 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the ink inlet hole.
3. Etch silicon to a depth of 15 microns using etched oxide as a mask. The sidewall slope of this etch is not critical (75 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in Fig. 479.
4. Deposit 7 microns of sacrificial aluminum.
5. Etch the sacrificial layer using Mask 2, which defines the nozzle walls and actuator anchor. This step is shown in Fig. 480.
6. Deposit 7 microns of low stress glass and planarize down to aluminum using CMP.
7. Etch the sacrificial material to a depth of 0.4 microns, and glass to a depth of at least 0.4 microns, using Mask 3. This mask defined the lower heater. This step is shown in Fig. 481.
8. Etch the glass layer down to aluminum using Mask 4, defining heater vias. This step is shown in Fig. 482.
9. Deposit 1 micron of heater material (e.g. titanium nitride (TiN)) and planarize down to the sacrificial aluminum using CMP. This step is shown in Fig. 483.
10. Deposit 4 microns of low stress glass, and etch to a depth of 0.4 microns using Mask 5. This mask defines the upper heater. This step is shown in Fig. 484.
11. Etch glass down to TiN using Mask 6. This mask defines the upper heater vias.
12. Deposit 1 micron of TiN and planarize down to the glass using CMP. This step is shown in Fig. 485.
13. Deposit 7 microns of low stress glass.
14. Etch glass to a depth of 1 micron using Mask 7. This mask defines the nozzle walls, nozzle chamber baffle, the paddle, the flexure, the actuator arm, and the actuator anchor. This step is shown in Fig. 486.
15. Etch glass to a depth of 3 microns using Mask 8. This mask defines the nozzle walls, nozzle chamber baffle, the actuator arm, and the actuator anchor. This step is shown in Fig. 487.
16. Etch glass to a depth of 7 microns using Mask 9. This mask defines the nozzle walls and the actuator anchor. This step is shown in Fig. 488.
17. Deposit 11 microns of sacrificial aluminum and planarize down to glass using CMP. This step is shown in Fig.489.
18. Deposit 3 microns of PECVD glass.
19. Etch glass to a depth of 1 micron using Mask 10, which defines the nozzle rims. This step is shown in Fig. 490.
20. Etch glass down to the sacrificial layer (3 microns) using Mask 11, defining the nozzles and the nozzle chamber roof. This step is shown in Fig. 491.
21. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.
22. Back-etch the silicon wafer to within approximately 10 microns of the front surface using Mask 12. This mask defines the ink inlets which are etched through the wafer. The wafer is also diced by this etch. This etch can be achieved with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems. This step is shown in Fig. 492.
23. Etch all of the sacrificial aluminum. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in Fig. 493.
24. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.
25. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
26. Hydrophobize the front surface of the print heads.
27. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 494.

A Description of IJ38 T

An embodiment of the present invention includes an inkjet arrangement wherein a single actuator drives two output nozzles. When the actuator is driven in the first direction, ink is ejected out of a first nozzle and when the actuator is driven in a second direction, ink is ejected out of a second nozzle. The paddle actuator is interconnected via a slot in the nozzle chamber wall to a rigid thermal actuator which can be actuated so as to cause the ejection of ink from the ink ejection holes.
Turning initially to Fig. 500 and Fig. 501, there is illustrated a nozzle arrangement 3801 of an embodiment with Fig. 501 being a sectional view through the line VII-VII of Fig. 500. The nozzle arrangement 3801 includes two ink ejection ports 3802, 3803 for the ejection of ink from within a nozzle chamber. The nozzle chamber further includes first and second chamber portions 3805, 3806 in addition to an etched cavity 3807 which, during normal operation, are normally filled with ink supplied via an ink inlet channel 3808. The ink inlet channel 3808 is in turn connected to an ink supply channel 3809 etched through a silicon wafer. Inside the nozzle chamber is located an actuator paddle 3810 which is interconnected through a slot 3812 in the chamber wall to an actuator arm 3813 which is actuated by means of thermal actuators 3814, 3815 which are in turn connected to a substrate 3817 via an end block portion 3818 with the substrate 3817 providing the relevant electrical interconnection for the heaters3814, 3815.
Hence, the actuator arm 3813 can be actuated by the thermal actuators 3814, 3815 to move up and down so as to eject ink via the nozzle holes 3802 or 3803. A series of holes eg. 3820 - 3822 are also provided in top of the nozzle plate. As will become more readily apparent hereinafter, the holes 3820 - 3822 assist in the etching of sacrificial layers during construction in addition to providing for "breathing" assistance during operation of the nozzle arrangement 3801. The two chambers 3805, 3806 are separated by a baffle 3824 and the paddle arm 3810 includes a end lip portion 3825 in addition to a plug portion 3826. The plug portion 3826 is designed to mate with the boundary of the ink inlet channel 3808 during operation.
Turning now to Fig. 495 to Fig. 499, there will now be explained the operation of the nozzle arrangement 3801. Each of Fig. 495 to Fig. 499 illustrate a cross sectional view of the nozzle arrangement during various stages of operation. Turning initially to Fig. 495, there is shown the nozzle arrangement 3801 when in its quiescent position. In this state, the paddle 3810 is idle and ink fills the nozzle chamber so as to form menisci 3829 - 3833 and 3837.
When it is desired to eject a drop out of the nozzle port 3803, as indicated in Fig. 497, the bottom heater 3815 is actuated. The heater 3815 can comprise a 60% copper and 40% nickel alloy which has a high bending efficiency where the bending efficiency is defined as: $bend efficiency = \frac{Youngʹs Modules \times (Coefficient of Thermal expansion)}{Density \times Specific Heat Capacity}$
The two heaters 3814, 3815 can be constructed from the same material and normally exist in a state of balance when the paddle 3810 is in its quiescent position. As noted previously, when it is desired to eject a drop out of nozzle chamber 3803, the heater 3815 is actuated which causes a rapid upwards movement of the actuator paddle 3810. This causes a general increase in pressure in the area in front of the actuator paddle 3810 which further causes a rapid expansion in the meniscus 3830 in addition to a much less significant expansion in the menisci 3831 - 3833 (due to their being of a substantially smaller radius). Additionally, the substantial decrease in pressure around the back surface of the paddle 3810 causes a general inflow of ink from the nozzle chamber 3808 in addition to causing a general collapse in the meniscus 3829 and a corresponding flow of ink 3835 around the baffle 3824. A slight bulging also occurs in the meniscus 3837 around the slot in the side wall 3812.
Turning now to Fig. 498, the heater 3815 is merely pulsed and turned off when it reaches its maximum extent. Hence, the paddle actuator 3810 rapidly begins to return to its quiescent position causing the ink around the ejection port 3803 to begin to flow back into the chamber. The forward momentum of the ink in the expanded meniscus and the backward pressure exerted by actuator paddle 3810 results in a general necking of the meniscus and the subsequent breaking off of a separate drop 3839 which proceeds to the print media. The menisci 3829, 3831, 3832 and 3833 each of a generally concave shape exert a further force on the ink within the nozzle chamber which begins to draw ink in from the ink inlet channel 3808 so as to replenish the nozzle chamber. Eventually, the nozzle arrangement returns to the quiescent position which is as previously illustrated in respect of Fig. 495.
Turning now to Fig. 498, when it is desired to eject a droplet of ink out of the ink ejection port 3802, the thermal actuator 3814 is actuated resulting in a general expansion of the thermal actuator 3814 which in turn causes a rapid downward movement of the actuator paddle 3810. The rapid downward movement causes a substantial increase in pressure within the cavity 3807 which in turn results in a general rapid expansion of the meniscus 3829. The end plug portion 3826 results in a general blocking of the ink supply channel 3808 stopping fluid from flowing back down the ink supply channel 3808. This further assists in causing ink to flow towards the cavity 3807. The menisci 3830 - 3833 of Fig. 495 are drawn generally into the nozzle chamber and may unite so as to form a single meniscus 3840. The meniscus 3837 is also drawn into the chamber. The heater 3814 is merely pulsed, which as illustrated in Fig. 499 results in a rapid return of the paddle 3810 to its quiescent position. The return of the paddle 3810 results in a general reduction in pressure within the cavity 3807 which in turn results in the ink around the nozzle 3802 beginning to flow 3843 back into the nozzle chamber. The forward momentum of the ink around the meniscus 3829 in addition to the backflow 3843 results in a general necking of the meniscus and the formation of an ink drop 3842 which separates from the main body of the ink and continues to the print media.
The return of the actuator paddle 3810 further results in plugging portion 3826 "unplugging" the ink supply channel 3808. The general reduction in pressure in addition to the collapsed menisci 3840, 3837 and 3829 results in a flow of ink from the ink inlet channel 3808 into the nozzle chamber so as to cause replenishment of the nozzle chamber and return to the quiescent state as illustrated in Fig. 496.
Returning now to Fig. 500 and Fig. 501, a number of other important features of an embodiment include the fact that each nozzle eg. 3802, 3803, 3820, 3821, 3822, 3812 etc. includes a nozzle rim around its outer periphery. The nozzle rim acts to stop wicking of the meniscus formed across the nozzle rim. Further, the actuator arm 3813 is provided with a wick minimisation protrusion eg. 3844 in addition to a series of pits eg. 3845 which were again shaped so as to minimise wicking along the surfaces surrounding the actuator arms 3813.
The nozzle arrangement of an embodiment can be formed on a silicon wafer utilising standard semi-conductor fabrication processing steps and micro-electromechanical systems (MEMS) construction techniques.
For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.
Preferably, a large wafer of printheads is constructed at any one time with each printhead providing a predetermined pagewidth capabilities and a single printhead can in turn comprise multiple colors so as to provide for full color output as would be readily apparent to those skilled in the art.
Turning now to Fig. 501 - Fig. 519 there will now be explained one form of fabrication of an embodiment. An embodiment can start with a CMOS processed silicon wafer 3850 which can include a standard CMOS layer 3851 of the relevant electrical circuitry etc. The processing steps can then be as follows:

1. As illustrated in Fig. 501 a deep silicon etch is performed so as to form the nozzle cavity 3807 and ink inlet 3808. A series of pits eg. 3845 are also etched down to an aluminium portion of the CMOS layer.
2. Next, as illustrated in Fig. 502, a sacrificial material layer is deposited and planarised using a standard Chemical Mechanical Planarization (CMP) process before being etched with a nozzle wall mask so as to form cavities for the nozzle wall, plug portion and interconnect portion. A suitable etchant material is aluminium which is often utilised in MEMS processes as a sacrificial material.
3. Next, as illustrated in Fig. 503, a 3 micron layer of low stress glass is deposited and planarized utilising CMP.
4. Next, as illustrated in Fig. 504, the sacrificial material 3852 is etched to a depth of 1.1 micron and the glass 3853 is further etched at least 1.1 micron utilising a first heater mask.
5. Next, as illustrated in Fig. 505, the glass is etched eg. 3855 down to an aluminium layer eg. 3856 of the CMOS layer.
6. Next, as illustrated in Fig. 506, a 3 micron layer of 60% copper and 40% nickel alloy is deposited 3857 and planarized utilising CMP. The copper and nickel alloy hereinafter called "cupronickel" is a material having a high "bend efficiency" as previously described.
7. Next, as illustrated in Fig. 507, a 3 micron layer 3860 of low stress glass is deposited and etched utilising a first paddle mask.
8. Next, as illustrated in Fig. 508, a further 3 micron layer of aluminium eg. 3861 is deposited and planarized utilising chemical mechanical planarization.
9. Next, as illustrated in Fig. 509, a 2 micron layer of low stress glass is deposited and etched 3863 by 1.1 micron utilizing a heater mask for the second heater.
10. As illustrated in Fig. 510, the glass is etched 3864 down to the cupronickel layer so as to provide for the upper level heater contact.
11. Next, as illustrated in Fig. 511, a 3 micron layer of cupronickel alloy is deposited and planarized 3865 utilizing CMP.
12. Next, as illustrated in Fig. 512, a 7 micron layer of low stress glass 3866 is deposited.
13. Next, as illustrated in Fig. 513 the glass is etched 3868 to a depth of 2 micron utilizing a mask for the paddle.
14. Next, as illustrated in Fig. 514, the glass is etched to a depth of 7 micron using a mask for the nozzle walls, portions of the actuator and the post portion.
15. Next, as illustrated in Fig. 515, a 9 micron layer of sacrificial material is deposited 3870 and planarized utilising CMP.
16. Next, as illustrated in Fig. 516, a 3 micron layer of low stress glass is deposited and etched 3871 to a depth of 1 micron utilizing a nozzle rim mask.
17. Next, as illustrated in Fig. 517, the glass is etched down to the sacrificial layer eg. 3872 utilising a nozzle mask.
18. Next, as illustrated in Fig. 518, an ink supply channel 3873 is etched through from the back of the wafer utilizing a silicon deep trench etcher which has near vertical side wall etching properties. A suitable silicon trench etcher is the deep silicon trench etcher available from Silicon Technology Systems of the United Kingdom. The printheads can also be "diced" as a result of this etch.
19. Next, as illustrated in Fig. 519, the sacrificial layers are etched away utilising a wet etch so as release the structure of the printhead.

The printheads can then be washed and inserted in an ink chamber moulding for providing an ink supply to the back of the wafer so to allow ink to be supplied via the ink supply channel. The printhead can then have one edge along its surface TAB bonded to external control lines and preferably a thin anti-corrosion layer of ECR diamond-like carbon deposited over its surfaces so as to provide for anti corrosion capabilities.
Turning now to Fig. 520, there is illustrated a portion 3880 of a full colour printhead which is divided into three series of nozzles 3881, 3882 and 3883. Each series can supply a separate color via means of a corresponding ink supply channel. Each series is further subdivided into two subrows 3886, 3887 with the relevant nozzles of each subrow being fired simultaneously with one subrow being fired a predetermined time after a second subrow such that a line of ink drops is formed on a page.
As illustrated in Fig. 520 the actuators a formed in a curved relationship with respect to the main nozzle access so as to provide for a more compact packing of the nozzles. Further, the block portion (3 818) of Fig. 495 is formed in the wall of an adjacent series with the block portion of the row 3883 being formed in a separate guide rail 3890 provided as an abutment surface for the TAB strip when it is abutted against the guide rail 3890 so as to provide for an accurate registration of the tab strip with respect to the bond pads 3891, 3892 which are provided along the length of the printhead so as to provide for low impedance driving of the actuators.
One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer, Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in Fig. 523. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. Fig. 522 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the pit underneath the paddle, the anti-wicking pits at the actuator entrance to the nozzle chamber, as well as the edges of the print heads chip.
3. Etch silicon to a depth of 20 microns using etched oxide as a mask. The sidewall slope of this etch is not critical (60 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in Fig. 524.
4. Deposit 23 microns of sacrificial material (e.g. polyimide or aluminum). Planarize to a thickness of 3 microns over the chip surface using CMP.
5. Etch the sacrificial layer using Mask 2, which defines the nozzle walls and actuator anchor. This step is shown in Fig. 525.
6. Deposit 3 microns of PECVD glass and planarize using CMP.
7. Etch the sacrificial material to a depth of 1.1 microns, and glass to a depth of at least 1.1 microns, using Mask 3. This mask defined the lower heater. This step is shown in Fig. 526.
8. Etch the glass layer down to aluminum using Mask 4, defining heater vias. This step is shown in Fig. 527.
9. Deposit 3 microns of heater material (e.g. cupronickel [Cu: 60%, Ni: 40%] or TiN). If cupronickel, then deposition can consist of three steps - a thin anti-corrosion layer of, for example, TiN, followed by a seed layer, followed by electroplating of the cupronickel.
10. Planarize down to the sacrificial layer using CMP. Steps 7 to 10 form a 'dual damascene' process. This step is shown in Fig. 528.
11. Deposit 3 microns of PECVD glass and etch using Mask 5. This mask defines the actuator arm and the second layer of the nozzle chamber wall. This step is shown in Fig. 529.
12. Deposit 3 microns of sacrificial material and planarize using CMP.
13. Deposit 2 microns of PECVD glass.
14. Etch the glass to a depth of 1.1 microns, using Mask 6. This mask defined the upper heater. This step is shown in Fig. 530.
15. Etch the glass layer down to heater material using Mask 7, defining the upper heater vias. This step is shown in Fig. 531.
16. Deposit 3 microns of the same heater material as step 9.
17. Planarize down to the glass layer using CMP. Steps 14 to 17 form a second dual damascene process. This step is shown in Fig. 532.
18. Deposit 7 microns of PECVD glass. This step is shown in Fig. 533.
19. Etch glass to a depth of 2 microns using Mask 8. This mask defines the paddle, actuator, actuator anchor, as well as the nozzle walls. This step is shown in Fig. 534.
20. Etch glass to a depth of 7 microns (stopping on sacrificial material in exhaust gasses) using Mask 9. This mask defines the nozzle walls and actuator anchor. This step is shown in Fig. 535.
21. Deposit 9 microns of sacrificial material and planarize down to glass using CMP. This step is shown in Fig. 536.
22. Deposit 3 microns of PECVD glass.
23. Etch glass to a depth of 1 micron using Mask 10, which defines the nozzle rims. This step is shown in Fig. 537.
24. Etch glass down to the sacrificial layer (3 microns) using Mask 11, defining the nozzles and the nozzle chamber roof. This step is shown in Fig. 538.
25. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.
26. Back-etch silicon wafer to within approximately 15 microns of the front surface using Mask 8. This mask defines the ink inlets which are etched through the wafer. The wafer is also diced by this etch. This etch can be achieved with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems. This step is shown in Fig. 539.
27. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in Fig. 540.
28. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.
29. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
30. Hydrophobize the front surface of the print heads.
31. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 541.

It would therefore be evident that an embodiment provides for a compact form of manufacture of an inkjet printhead which includes a dual nozzle single actuator system.

Claims

An ink jet nozzle arrangement comprising:
a nozzle chamber having at least two fluid ejection apertures (3708, 3709) defined in a wall of said chamber; and characterized by:
a moveable paddle vane (3710) located within said chamber; and

an actuator mechanism (3712) attached to said moveable paddle vane,

wherein said actuator mechanism vane is adapted to move said paddle vane in a first direction so as to cause the ejection of fluid out of a first fluid ejection aperture and to further move said paddle vane in a second alternative direction so as to cause the ejection of fluid out of a second fluid ejection aperture.
An ink jet nozzle arrangement as claimed in claim 1, wherein said paddle vane is located between said fluid ejection apertures.
An ink jet nozzle arrangement as claimed in any one of the preceding claims wherein said paddle vane and said actuator are joined at a fulcrum pivot point, said fulcrum pivot point comprising a thinned portion of said nozzle chamber wall.
An ink jet nozzle arrangement as claimed in any one of the preceding further comprising:
a fluid supply channel connecting said nozzle chamber with a fluid supply for supplying fluid to said nozzle chamber, said connection being in a wall of said chamber substantially adjacent the quiescent position of said paddle vane.
An ink jet nozzle arrangement as claimed in claim 4 wherein said connection comprises a slot defined in the wall of said chamber, said slot having similar dimensions to a cross-sectional profile of said paddle vane.
An ink jet nozzle arrangement as claimed in claim 1, wherein said paddle vane is located in a plane adjacent a rim of a first one of said fluid ejection apertures.
An ink jet nozzle arrangement as claimed in claim 6 further comprising:
a baffle located between said first and second fluid ejection apertures,
wherein said paddle vane moving in said first direction causes an increase in pressure of said fluid in the volume adjacent said first aperture and a simultaneous decrease in pressure of said fluid in the volume adjacent said second aperture.
An ink jet nozzle arrangement as claimed in claim 6 wherein said paddle vane moving in said second direction causes an increase in pressure of said fluid in the volume adjacent said second aperture and a simultaneous decrease in pressure of said fluid in the volume adjacent said first aperture.
An ink jet nozzle arrangement as claimed in claim 6 wherein said paddle vane and said actuator are interconnected so as to pivot about a wall of said chamber and said apparatus further comprises:
a fluid supply channel connecting said nozzle chamber with a fluid supply for supplying fluid to said nozzle chamber said connection being in a wall of said chamber substantially adjacent the pivot point of said paddle vane.
An ink jet nozzle arrangement as claimed in any one of the preceding claims, wherein said actuator comprises a thermal actuator having at least two heater elements with a first of said elements being actuated to cause said paddle vane to move in a first direction and a second heater element being actuated to cause said paddle vane to move in a second direction.
An ink jet nozzle arrangement as claimed in claim 10 wherein said heater elements are arranged on opposite sides of a central arm, said central arm having a low thermal conductivity.
An apparatus as claimed in claim 11 wherein said central arm comprises substantially glass.
An ink jet printhead comprising a plurality of ink jet nozzle arrangements according to any one of the preceding claims.