EP1647402B1

EP1647402B1 - Ink jet nozzle arrangement with actuator mechanism in chamber between nozzle and ink supply

Info

Publication number: EP1647402B1
Application number: EP05109733A
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: 2008-07-02
Anticipated expiration: 2018-07-15
Also published as: ATE399644T1; EP1647402A1

Abstract

An inkjet nozzle arrangement is provided. The arrangement comprises a nozzle chamber having an ink ejection port defined in a wall of the nozzle chamber, an ink supply channel for the supply of ink to the nozzle chamber, and an actuator located in the nozzle chamber, between the ink supply channel and the ink ejection port. The actuator is adapted to cause ejection of ink from the nozzle chamber upon activation.

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.
DE19516997 describes a printhead where ink is delivered through a hole at right angles to a monocrystalline substrate surrounding a piston with a gap of less than 5 microns. Both ends of the body carrying the piston are fixed to the substrate with interposition of a heating layer between upper and lower insulations.
EP0634273 describes a casing and a nozzle plate forming a hollow cavity in which ink liquid can be filled. A buckling structure body is disposed within this hollow cavity. A nozzle orifice is provided in a nozzle plate at a position corresponding to the buckling structure body. The buckling structure body has a portion extending in a longitudinal direction. Both ends of the buckling structure body in the longitudinal direction are fixedly attached to the casing via an insulative member.
DE19517969 describes a print head having a chamber filled with ink, an ink ejection aperture and an ink delivery aperture connected to the inner chamber. Several inflatable bodies are arranged in the inner chamber between the apertures to place the ink under pressure. A first inflatable body is attached to a first inner surface section via an attachment. The second inflatable body is connected to a second inner surface section so as to face the first inflatable body. When voltage is applied the inflatable bodies expand but are restricted by the attachments, hence exerting pressure on the ink.
DE19639717 discloses an ink-jet print head having a nozzle plate with an orifice that connects with an ink containing chamber. The underside of the chamber is formed by a laminated actuator element that is electrically excited and causes pressure to be applied to the fluid. The top surface is in the form of a flexible diaphragm. A piezo-electric bimorph construction causes a deflection to occur and so produces the ink-jet action.
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

The present invention relates to ink jet nozzle arrangement as set forth in the claims which follow.

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. 263 is a schematic diagram of the conductive layer utilised in the thermal actuator of the ink jet nozzle constructed in accordance with an embodiment;
Fig. 264 is a close-up perspective view of portion A of Fig. 263;
Fig. 265 is a cross-sectional schematic diagram illustrating the construction of a corrugated conductive layer in accordance with an embodiment of the present invention;
Fig. 266 is a schematic cross-sectional diagram illustrating the development of a resist material through a halftoned mask utilised in the fabrication of a single ink jet nozzle in accordance with an embodiment;
Fig. 267 is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with an embodiment;
Fig. 268 is a perspective view of a section of an ink jet print head configuration utilising ink jet nozzles constructed in accordance with an embodiment.
Fig. 269 provides a legend of the materials indicated in Fig. 270 to Fig. 283; and
Fig. 270 to Fig. 283 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.
Fig. 284 to Fig. 286 illustrate basic operation of an embodiments;
Fig. 287 is a sectional view of an embodiment;
Fig. 288 is an exploded perspective view of an embodiment;
Fig. 289 to Fig. 298 are cross-sectional views illustrating various steps in the construction of an embodiment; and
Fig. 299 illustrates a top view of an array of ink jet nozzles constructed in accordance with the principles of the present invention.
Fig. 300 provides a legend of the materials indicated in Fig. 301 to Fig. 312; and
Fig. 301 to Fig. 312 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.

Detailed description

In an embodiment, a drop on demand inkjet printer is provided which allows for the ejection of ink on demand by means of a thermal actuator which operates to eject the ink from a nozzle chamber. The nozzle chamber is formed directly over an ink supply channel thereby allowing for an extremely compact form of nozzle chamber. The extremely compact form of nozzle chamber allows for minimal area to be taken up by the printer head device thereby resulting in an improved economics fabrication.
Turning initially to Fig. 284 to Fig. 286, they will now describe the operation of an embodiment. In Fig. 284, there is illustrated a sectional view of two ink jet nozzles 3110, 3111 which are formed on a silicon wafer eg. 3112 which includes a series of through wafer ink supply channels eg. 3113.
Located over a portion of the wafer 3112 and over the ink supply channel 3113 is a nozzle actuator device 3114 which is actuated so as to eject ink from the corresponding nozzle chamber eg. 3111. The actuator 3114 is placed substantially over the ink supply channel 3113. In the quiescent position, the ink fills the nozzle chamber 3111 and an ink meniscus 3115 forms across the output nozzle of the chamber 3111.
When it is desired to eject a drop from the chamber 3111, the thermal actuator 3114 is activated by means of passing a current through the actuator. The actuation causes the actuator 3114 to rapidly bend upwards as indicated in Fig. 285. The movement of the actuator 3114 results in an increase in the ink pressure around the nozzle of the chamber 3111 which in turn causes a significant bulging of the meniscus 3115 and the flow of ink out of the nozzle chamber 3111. The actuator 3114 can be constructed so as to impart sufficient momentum to the ink to cause the direct ejection of a drop. Alternatively, as indicated in Fig. 286, the activation of actuator 3114 can be timed so as to turn the actuation current off at a predetermined point so as to cause the return of the actuator 3114 to its original position thereby resulting in a consequential backflow of ink 3117 into the chamber 3111 thereby causing a necking and separation of a body of ink 3118 which has a continuing momentum and continues towards the output media, such as paper, for printing thereof. Subsequently, the actuator 3114 returns to its quiescent position and surface tension effects result in a refilling of the nozzle chamber 3111 via ink supply channel 3113 as a consequence of surface tension effects on the meniscus 3115. In time, the arrangement returns to that depicted in Fig. 284.
Turning now to Fig. 287 and Fig. 288, there is illustrated the structure of a single nozzle chamber 3110 in more detail. Fig. 287 illustrates partly in section with Fig. 288 showing a corresponding exploded perspective. Inkjet nozzles can be formed, many print head at a time, on a selected wafer base 3112 utilising standard semi-conductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed.
On top of the silicon wafer layer 3112 is formed a CMOS layer 3120. The CMOS layer 3120 can, in accordance with standard techniques, include multi-level metal layers sandwiched between oxide layers and preferably at least a two level metal process is utilised. In order to reduce the number of necessary processing steps, the masks utilised include areas which provide for a build up of an aluminium barrier 3121 which can be constructed from a first 3122 and second 3123 level aluminium layer. Additionally, aluminium portions eg. 3124 are provided for providing electrical contacts to a subsequent heater layer. The aluminium barrier portion 3121 is important in providing an effective barrier to the possible subsequent etching of the oxide within the CMOS layer 3120 when a sacrificial etchant is utilised in the construction of a nozzle chamber 3111 with the etchable material preferably being glass layers.
On top of the CMOS layer 3120 is formed a nitride passivation layer 3126 which is formed to protect the lower CMOS layers from sacrificial etchants and ink erosion. Above the nitride layer 3126 there is formed a gap 3128 in which an air bubble forms during operation. The gap 3128 can be constructed by a means of laying down a sacrificial layer and subsequently etching the gap as will be explained hereinafter.
On top of the air gap 3128 is constructed a polytetrafluroethylene (PTFE) heater layer 3129 which really comprises to PTFE layers sandwiched between a gold serpentine heater layer 3130. The gold heater 3130 is constructed in a serpentine form to allow it to expand on heating. The heater layer 3130 and PTFE layer 3129 together comprise the thermal actuator 3114 of Fig. 284.
The outer PTFE layer 3129 has an extremely high coefficient of thermal expansion (approximately 77010^-6, or around 380 times that of silicon). The PTFE layer 3129 is also normally highly hydrophobic which results in an air bubble being formed under the actuator in the region 3128 due to out-gassing etc. The top PTFE surface layer is treated so as to make it hydrophilic in addition to those areas around ink supply channel 3113. This can be achieved with a plasma etch in an ammonia atmosphere. The heater layer 3130 is also formed within the lower portion of the PTFE layer.
The heater layer 3130 is connected at ends eg. 3131 to the lower CMOS drive layer 3120 which contains the drive circuitry (not shown). For the purposes of actuation of actuator, a current is passed through the gold heater element 3130 which heats the bottom surface of actuator 3114. The bottom surface of actuator 3114, in contact with air bubble 3128 remains heated while any top surface heating is carried away by the exposure of the top surface of actuator 3114 to the ink within chamber 3132. Hence, the bottom PTFE layer expands more rapidly resulting in a general rapid bending upwards of actuator 3114 (as illustrated in Fig. 285) which consequentially causes the ejection of ink from ejection of ink from ink ejection port 3135.
The actuator 3114 can be deactivated by turning off the current to heater element 3130. This will result in a return of the actuator 3114 to its rest position.
On top of the actuator is formed the nitride nozzle plate comprising side wall portions 3133 and top portion 3134. The nozzle plate can be formed via a dual damascene process utilising a sacrificial layer. The top of the nozzle plate is etched to have nozzle ink ejection hole 3133 in addition to a series of etchant holes eg. 3136 which are of a relatively small diameter and allow for effective etching of lower sacrificial layers when utilising a sacrificial etchant. The etchant holes 3136 are made small enough such that surface tension effects restrict the possibilities of ink being ejected from the chamber 3132 via the etchant holes 3136 rather than the nozzle hole 3133.
Turning now to Fig. 289 to Fig. 298, there will now be explained the various steps involved in the construction of an array of ink jet nozzles:

1. Turning initially to Fig. 289, the starting position comprises a silicon wafer 3112 including a CMOS layer 3120 which has been nitride passivated 3126 and surface finished with a chemical - mechanical planarisation process.
2. The nitride layer is masked and etched as illustrated in Fig. 290 so as to define portions of the nozzle chamber and areas for interconnection between any subsequent heater layer and a lower CMOS layer.
3. Next, a sacrificial oxide layer is deposited, masked and etched as indicated in Fig. 291 with the oxide layer being etched in those areas that a subsequent heater layer electronically contacts the lower layers.
4. As illustrated in Fig. 292, next a 1µm layer of PTFE is deposited and firstly masked and etched for the heater contacts to the lower CMOS layer and secondly masked and etched for the heater shape.
5. Next, as illustrated in Fig. 293, the gold heater layer 3130, 3131 is deposited. Due to the fact that it is difficult to etch gold, the layer can be conformally deposited and subsequently portions removed utilising chemical mechanical planarisation so as to leave those portions associated with the heater element. The processing steps 4 and 5 basically comprising a dual damascene.
6. Next, a top PTFE layer is deposited and masked and etched down to the sacrificial layer as illustrated in Fig. 294 so as to define the heater shape. Subsequently, the surface of the PTFE layer is plasma processed so as to make it hydrophilic. Suitable processing can including plasma damage in an ammonia atmosphere. Alternatively, the surface could be coated with a hydrophilic material.
7. A further sacrificial layer is then deposited and etched as illustrated in Fig. 295 so as to form the structure for the nozzle chamber properly. The sacrificial oxide being masked and etched in order to define the nozzle chamber walls.
8. Next, as illustrated in Fig. 296, the nozzle chamber is formed by conformally depositing three microns of nitride and etching a mask nozzle rim to a depth of one micron for the nozzle rim (the etched depth not being overly time critical). Subsequently, a mask is utilised to etch the nozzle holes 3135 in addition to the sacrificial layer etchant holes 3136.
9. Next, as illustrated in Fig. 297, the backside of the wafer is masked for the ink channels and plasma etched through the wafer. A suitable plasma etching process can include a deep anisotropic trench etching system such as that available from SDS Systems Limited (See) "Advanced Silicon Etching Using High Density Plasmas" by J.K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology).
10. Next, as illustrated in Fig. 298, the sacrificial layers are etched away utilising a sacrificial etchant such as hydrophilic acid. Subsequently, the portion underneath the actuator which is around the ink channel is plasma processed through the backside of the wafer to make the panel end hydrophilic.

Subsequently, the wafer contained a number of the ink jet printer heads can be separated into separate print heads and each print head is bonded into an injection moulded ink supply channel and the electrical signals to the chip can be tape automated bonded (TAB) to the print head for subsequent testing. Fig. 299 illustrates a top view of jet nozzles constructed on a wafer so as to provide for page width multicolour output.
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. 301. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. Fig. 300 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Deposit 1 micron of low stress nitride. This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface.
3. Deposit 3 micron of sacrificial material (e.g. polyimide).
4. Etch the sacrificial layer using Mask 1. This mask defines the actuator anchor point. This step is shown in Fig. 302.
5. Deposit 0.5 microns of PTFE.
6. Etch the PTFE, nitride, and CMOS passivation down to second level metal using Mask 2. This mask defines the heater vias. This step is shown in Fig. 303.
7. Deposit and pattern resist using Mask 3. This mask defines the heater.
8. Deposit 0.5 microns of gold (or other heater material with a low Young's modulus) and strip the resist. Steps 7 and 8 form a lift-off process. This step is shown in Fig. 304.
9. Deposit 1.5 microns of PTFE.
10. Etch the PTFE down to the sacrificial layer using Mask 4. This mask defines the actuator paddle and the bond pads. This step is shown in Fig. 305.
11. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated.
12. Plasma process the PTFE to make the top and side surfaces of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity.
13. Deposit 10 microns of sacrificial material.
14. Etch the sacrificial material down to nitride using Mask 5. This mask defines the nozzle chamber. This step is shown in Fig. 306.
15. Deposit 3 microns of PECVD glass. This step is shown in Fig. 307.
16. Etch to a depth of 1 micron using Mask 6. This mask defines the nozzle rim. This step is shown in Fig. 308.
17. Etch down to the sacrificial layer using Mask 7. This mask defines the nozzle and the sacrificial etch access holes. This step is shown in Fig. 309.
18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 8. This mask defines the ink inlets which are etched through the wafer. The wafer is also diced by this etch. This step is shown in Fig. 310.
19. Back-etch the CMOS oxide layers and subsequently deposited nitride layers and sacrificial layer through to PTFE using the back-etched silicon as a mask.
20. Plasma process the PTFE through the back-etched holes to make the bottom surface of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity, but maintains a hydrophobic surface underneath the actuator portion of the paddle. This hydrophobic section causes an air bubble to be trapped under the paddle when the nozzle is filled with a water based ink. This bubble serves two purposes: to increase the efficiency of the heater by decreasing thermal conduction away from the heated side of the PTFE, and to reduce the negative pressure on the back of the actuator section of the paddle.
21. 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. 311.
22. 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.
23. 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.
24. Hydrophobize the front surface of the print heads.
25. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 312.

Claims

An ink jet nozzle arrangement including:
a nozzle chamber having an ink ejection port defined in a wall of said nozzle chamber, for the ejection of ink;

an ink supply channel for the supply of ink to said nozzle chamber; and

an actuator located in said nozzle chamber, between said ink supply channel and said ink ejection port, said actuator comprising a substantially planar thermal actuator and being displaceable towards said ink ejection port, and
characterized in that:
said actuator is connected at one end to a CMOS drive layer and an opposite free end bends upwards upon activation, thereby causing ejection of ink from said nozzle chamber.
An ink jet nozzle as claimed in claim 1 wherein said thermal actuator includes a serpentine conductive heater element layer encased within an expansive layer such that, upon activation, said thermal actuator is caused to bend towards said ink ejection port so as to cause the expulsion of ink from said nozzle chamber.
An ink jet nozzle as claimed in any one of the preceding claims wherein said nozzle chamber is formed on a silicon wafer and said ink channel supply means is formed by back etching said silicon wafer.
An ink jet nozzle as claimed in any one of the preceding claims wherein said nozzle is formed on a CMOS substrate.
An ink jet nozzle as claimed in claim 2 wherein said conductive heater material is constructed so as to concertina upon expansion of said expansive layer so as to allow substantially unhindered expansion of said expansive layer during heating.
An ink jet nozzle as claimed in any one of the preceding claims wherein an outer surface of said ink chamber includes a plurality of small etchant holes, provided so as to allow a more rapid etching of sacrificial layers during construction.
An ink jet nozzle as claimed in claim 2, wherein said expansion layer is comprised of PTFE.