TWI406772B - Method of forming connection between electrode and actuator in an inkjet nozzle assembly,printhead integrated circuit, and pagewidth inkjet printhead - Google Patents

Abstract

A printhead integrated circuit comprises a substrate (1) having a plurality of inkjet nozzles assemblies (100) formed on a surface of the substrate. The substrate has drive circuitry for supplying power to the nozzle assemblies. Each nozzle assembly comprises: nozzle chamber (5) for containing ink, the nozzle chamber having a nozzle opening defined therein (13) and a wall of insulating material (4) defining a sidewall of the nozzle chamber; an actuator (10) for ejecting ink through the nozzle opening; a pair of electrodes (2) positioned at the surface of the substrate; and a pair of connector posts (8) electrically connecting a respective eledrode (2) to the actuator (10). Each connector post extends linearly from a respective electrode (2) to the actuator (10), and each connector post fills a via defined in the sidewall (4) of the nozzle chamber (5).

Description

A method of forming a connection between an electrode and an actuator in an inkjet nozzle assembly, a printhead integrated circuit, and a pagewidth inkjet printhead

The present invention relates to ink jet nozzle assemblies and methods of making ink jet nozzle assemblies. The present invention has been primarily developed to reduce the loss of electrical power when powering an inkjet actuator.

Many MEMS inkjet nozzles that use thermal bending actuation have been previously described in this application. Thermal bending actuation generally refers to a bending motion associated with another material resulting from thermal expansion of a material through which electrical current passes. Optionally, the resulting bending motion can be used to eject ink from a nozzle opening through the movement of a paddle or blade that creates a pressure wave within the nozzle chamber.

Some representative types of thermally curved inkjet nozzles are exemplified in the patent and patent applications listed in the reference section, the contents of which are hereby incorporated by reference.

An ink jet nozzle having a blade disposed in a nozzle chamber and a thermally curved actuator disposed outside the nozzle is disclosed in U.S. Patent No. 6,416,167. The actuator is in the form of a lower active beam that is fused to a conductive material (eg, titanium nitride) on the upper passive beam of a non-conductive material (eg, cerium oxide). The actuator is coupled to the paddle through an arm that passes through a slot in the wall of the nozzle chamber. When an electric current is passed through the lower active beam, the actuator is bent upward, and the pad is thus moved toward a nozzle opening provided on the top of the chamber of the nozzle chamber, thereby ejecting an ink droplet. One of the benefits of this design is its simple structure. A disadvantage of this design is that the two blades of the blade work against the rather viscous ink in the nozzle chamber.

An ink jet nozzle is disclosed in the applicant's U.S. Patent No. 6,260,953, in which the actuator forms a movable chamber top portion of the nozzle chamber. The actuator is in the form of a crucible core material of a conductive material surrounded by a polymeric substance. Upon actuation, the actuator is bent toward the chamber floor of the nozzle chamber, raising the pressure within the chamber and forcing an ink droplet to exit from the nozzle opening provided on the top of the chamber of the chamber. The nozzle opening is disposed on a stationary portion of the top of the chamber. One benefit of this design is that one side of the roof portion of the activity needs to work against the rather viscous ink in the nozzle chamber. A disadvantage of this design is that the conductive elements surrounded by a polymeric material are difficult to fabricate using MEMS processes.

An ink jet nozzle comprising a nozzle chamber having a movable chamber top portion having a nozzle opening on the top of the chamber is disclosed in U.S. Patent No. 6,623,101. The movable roof portion is coupled to a thermally curved actuator disposed outside the nozzle through an arm. The actuator is in the form of an upper active beam that is spaced apart from the lower passive beam. By spacing the active beam from the passive beam, the thermal bending efficiency is maximized because the passive beam does not act as a heat sink for the active beam. When an electric current is passed through the upper active beam, the movable ceiling portion on which the nozzle opening is opened is urged to rotate toward the nozzle chamber to eject ink from the nozzle opening. Since the nozzle opening moves together with the ceiling portion, the droplet flight direction can be controlled by appropriately changing the shape of the nozzle edge. One benefit of this design is that only one face of the top portion of the activity must work against the relatively viscous ink in the nozzle chamber. Another benefit is that the active and passive beam members are separated to minimize heat loss. A disadvantage of this design is that the active and passive beam members are separated to loosen the structural robustness.

In all MEMS inkjet nozzle designs, there is a need to minimize electrical losses. In the case where the nozzle design is the main disadvantageous structure that causes electrical losses, it is particularly important to minimize the loss of electricity. For example, a relatively long distance between the actuator and a CMOS electrode that supplies current to the actuator can make the loss of electricity more severe. Furthermore, bending or twisting the current path will also make the loss of electricity more serious.

Typically, the actuator material in the inkjet nozzle is selected from a material that is capable of meeting several requirements. In the case of mechanical thermal bending actuated nozzles, these requirements include electrical conductivity, coefficient of thermal expansion, Young's modulus, and the like. In the example of a hot bubble forming inkjet nozzle, these requirements include electrical conductivity, oxidation resistance, burst resistance, and the like. Thus, it will be appreciated that the choice of actuator material is often a compromise of multiple characteristics and that the actuator material does not necessarily have optimal conductivity. In the case where the actuator material itself has sub-optimal conductivity, it is particularly important to minimize the loss of electricity in the nozzle assembly.

Finally, any improvements in nozzle design should be compatible with standard MEMS processes. For example, some materials are incompatible with MEMS processes because they can cause contamination at the fab.

From the foregoing, it will be appreciated that there is a need for improvements in the design and manufacture of ink jet nozzles to minimize electrical losses and to provide more efficient droplet ejection of the print head. There is a particular need for improvements in the design and manufacture of mechanical thermal bending actuated ink jet nozzles where electrical losses are exacerbated by the inherent appearance of the nozzle design.

In a first aspect of the invention, the invention provides a method of forming an electrical connection between an electrode and an actuator within an ink jet nozzle assembly, the method comprising the steps of: (a) providing a a substrate having a driving circuit layer, the driving circuit including the electrode for connecting to the actuator; (b) forming an insulating material wall on the electrode; (c) forming a through hole in at least the wall (via) a via hole exposing the electrode; (d) filling a conductive material into the via hole using electroless plating to provide a connector post; and (e) forming at least a portion of the actuator on the connector post Thereby providing an electrical connection between the actuator and the electrode.

The upper ground is selected such that the distance between the actuator and the electrode is at least 5 microns.

Selecting the upper layer, the driving circuit layer is a CMOS layer of a substrate.

Optionally, the drive circuit includes a pair of electrodes for each ink jet nozzle assembly, each electrode being coupled to the actuator with a respective connector post.

Selecting the upper layer, the insulating material wall is composed of cerium oxide.

The upper hole is selected to have a side wall perpendicular to one side of the substrate.

The upper hole is selected to have a minimum cross-sectional diameter of 1 micrometer or more.

Selecting the upper layer, the conductive material is a metal.

Selecting the upper layer, the conductive material is copper.

In another aspect, a method is provided, the method further comprising the step of depositing a catalyst layer on the base of the via prior to the electroless plating.

The upper layer is selected and the catalyst is palladium.

The upper conductive material is selected to be planarized by chemical mechanical planarization prior to forming the actuator.

Selecting the upper body, the actuator is a thermally curved actuator that includes a planar active beam member that mechanically cooperates with a planar passive beam member.

Optionally, the thermal bending actuator at least partially defines a roof of the chamber for the nozzle chamber of the inkjet nozzle assembly.

The upper insulator is selected to define a sidewall of the nozzle chamber.

Selecting the upper layer, step (e) comprises depositing an active beam material on a passive beam material.

The upper beam is selected such that the active beam member of the active beam material extends from the top of the connector post to a plane perpendicular to the column.

In another aspect, the present invention provides a method further comprising the steps of: depositing a first metal pad on top of the connector post prior to deposition of the active beam material, the first metal pad being constructed Current is promoted from the connector post to the active beam member.

Optionally, the planar active beam member comprises a curved or meandering beam member having a first end that is placed over a first connector post and a second end that is placed in a Above the second connector post, the first and second connector posts are adjacent to one another.

In another aspect, the present invention provides a method further comprising the step of depositing one or more second metal pads on the passive beam material prior to deposition of the active beam material, the second metal pad being Placed to promote current flow into the curved region of the beam member.

In a second aspect, the present invention provides a printhead integrated circuit comprising a substrate having a plurality of ink jet nozzle assemblies formed on a surface of the substrate, the substrate having a drive circuit for supplying electricity To the nozzle assemblies, each nozzle assembly includes: a nozzle chamber for containing ink, the nozzle chamber having a nozzle opening defined therein; an actuator for ejecting ink through the nozzle opening; a pair disposed thereon An electrode on the surface of the substrate, the electrodes being electrically connected to the drive circuit; and a pair of connector posts, each connector electrode electrically connecting a further electrode to the actuator, wherein each A connector post extends linearly from the individual electrodes to the actuator.

Selecting the upper layer, each connector post is perpendicular to the surface of the substrate.

The upper ground is selected such that the shortest distance between the actuator and the electrodes is at least 5 microns.

Selecting the upper ground, the connector columns have a minimum cross-sectional diameter of 2 microns or more.

Optionally, the nozzle assemblies are arranged in a plurality of nozzle rows that extend longitudinally along the substrate.

The upper ground is selected such that the distance between adjacent nozzle openings in a nozzle row is less than 50 microns.

Selecting the upper body, the actuator is a thermally curved actuator that includes a planar active beam member that mechanically cooperates with a planar passive beam member.

Optionally, the thermal bending actuator at least partially defines a roof for a nozzle chamber of the inkjet nozzle assembly, the nozzle opening being defined on the top of the chamber.

Selecting the upper floor, an insulating material wall defines the side wall of the nozzle chamber.

The upper beam is selected to be electrically connected to the top of the connector posts.

A portion of the active beam member is placed over the top of the connector posts.

In another aspect, the present invention provides a column head integrated circuit further comprising a first metal pad placed between the top of each connector post and the active beam member, each first gapped metal The pads are constructed to facilitate current flow from one of the other connector columns to the active beam member.

The upper beam is selected from the active beam material selected from the group consisting of: aluminum alloy; titanium nitride and titanium aluminum nitride.

The upper beam is selected from the vanadium aluminum alloy.

Selecting the upper ground, the planar active beam member includes a beam member including a curved or meandering member having a first end that is placed over a first connector post and a second end that is placed Above the second connector post, the first and second connector posts are adjacent one another.

In another aspect, the present invention provides a printhead integrated circuit that further includes at least one second metal pad that is placed to facilitate current flow into a curved region of the beam member.

In another aspect, the invention provides a printhead integrated circuit that further comprises an outer surface layer of a hydrophobic polymer on top of the chamber.

The upper surface layer is selected to define a planar ink jet surface of the printhead integrated circuit, the planar ink jet surface having no substantial outline structure other than the nozzle openings.

Optionally, the hydrophobic polymer mechanically seals a gap between the thermally curved actuator and the nozzle chamber.

In another aspect, the present invention provides a pagewidth inkjet printhead comprising a plurality of inkjet head integrated circuits, the inkjet head integrated circuit comprising a substrate having a plurality of inkjet nozzle assemblies formed On the surface of the substrate, the substrate has a drive circuit for supplying power to the nozzle assemblies, each nozzle assembly including: a nozzle chamber for containing ink, the nozzle chamber having a nozzle defined therein An opening; an actuator for ejecting ink through the nozzle opening; a pair of electrodes disposed on the surface of the substrate, the electrodes being electrically connected to the driving circuit; and a pair of connector posts, each connector The posts each electrically connect an additional electrode to the actuator, wherein each connector post extends linearly from the individual electrodes to the actuator.

Figures 1 and 2 show a nozzle assembly as described in U.S. Patent Application Serial No. 11/607,976, the entire disclosure of which is incorporated herein by in. The nozzle assembly 400 includes a nozzle chamber 401 formed on a passivated CMOS layer 402 of a tantalum substrate 403. The nozzle chamber is defined by a chamber top 404 and a sidewall 405 extending from the top of the chamber to the passivated COMS layer 402. The ink is supplied to the nozzle chamber 401 by an ink inlet 406 in fluid communication with the ink supply channel 407, which receives the ink from the substrate 403. Ink is ejected from the nozzle chamber 401 by a nozzle opening 408 defined on the chamber top 404. The nozzle opening 408 is offset from the ink inlet 406.

As best seen in Figure 2, the roof 404 has a movable portion 409 that defines a substantial portion of the total area of the roof. The nozzle opening 408 and the nozzle edge 415 are defined on the movable portion 409 such that the nozzle opening moves with the nozzle edge and the movable portion.

The movable portion 409 is defined by a thermally curved actuator 410 having a planar upper active beam 411 and a planar lower passive beam 412. The active beam 411 is connected to a pair of electrode contacts (positive and ground). Electrode 416 is coupled to a drive circuit in the COMS layer.

When it is desired to eject an ink droplet from the nozzle chamber 401, a current flows through the active beam 411 between the two contacts 416. The active beam 411 is rapidly heated by the current and expands relative to the passive beam 412, thereby causing the actuator 410 (which defines the movable portion 409 of the chamber top 404) to bend downward toward the substrate 403. This movement of the actuator 410 causes ink to be ejected from the nozzle opening by the rapidly increasing pressure within the nozzle chamber 401. When the current is stopped, the movable portion 409 of the chamber top 404 can be returned to its rest position, which can draw ink from the inlet 406 into the nozzle chamber 401 for the next ink jet.

In the nozzle design shown in Figures 1 and 2, the chamber top 404 defining at least a portion of the nozzle 401 is advantageous for the actuator 410. This not only simplifies the overall design and manufacture of the nozzle assembly 400, but also provides a higher ink jet efficiency since only one face of the actuator 410 must operate against the relatively viscous ink within the nozzle chamber. In contrast, a nozzle assembly having an actuator pad disposed within the interior of the nozzle is less efficient because both sides of the actuator must operate with ink in the chamber.

However, in the structure in which the actuator 410 at least partially defines the roof 404 of the chamber 401, there is inevitably a relatively long distance between the active beam 411 and the electrode 411 to which the active electrode 411 is connected. distance. The relatively long distance between electrode 416 and actuator 410, the tortuous current path, and the combination of thin beam materials result in an acceptable electrical loss.

To date, MEMS fabrication of inkjet nozzles has relied primarily on PECVD (plasma enhanced chemical vapor deposition) and mask/etch steps to build a nozzle structure. The use of PECVD to simultaneously deposit the active beam 411 with the connection to the electrode 416 is advantageous from the point of view of MEMS fabrication, but inevitably results in a thin, tortuous connection which is disadvantageous in terms of current loss. . The current loss is further aggravated when the beam material does not have the best conductivity. For example, vanadium-aluminum alloys have excellent thermoelastic properties compared to aluminum, but have poor electrical conductivity.

Another disadvantage of PECVD is that a via 418 having sloped sidewalls is required to effect deposition on the sidewalls. Because of the directional nature of the plasma, PECVD cannot deposit material on vertical sidewalls. There are several problems with the side walls of the inclined through holes. First, there is a need for a scaffold with slanted sidewalls, which is typically achieved by using an unfocused photoresist exposure, which inevitably results in some loss of accuracy. Second, the total footprint area of the nozzle assembly is increased, thereby reducing the density at which the nozzles are brought together, and this increase in area is more severely degraded as the height of the nozzle chamber is increased.

One attempt to mitigate current loss within the nozzle assembly 400 is to introduce a highly conductive intermediate layer 417, such as titanium or aluminum, between the electrode contact 416 and the active beam material 411 (see Figure 1). This intermediate 417 helps to reduce some current losses, but there is still significant current loss.

Another disadvantage of the nozzle assembly shown in Figures 1 and 2 is that the ink jet face of the printhead is non-planar due to the relationship of the electrode vias 418. The non-planarity of the inkjet surface can cause structural weaknesses and problems during printhead maintenance.

In view of the foregoing, the applicant has developed a method of making a mechanical thermal bending inkjet nozzle assembly that does not rely on PECVD to form a connection from a CMOS junction to the actuator. As will be explained in detail, the resulting ink jet nozzle assembly has the least amount of current loss and its planar ink jet surface has an additional structural advantage. Although the invention has been described with reference to a mechanical thermal bending inkjet nozzle assembly, it will be appreciated that the invention can be applied to any type of inkjet nozzle manufactured using MEMS technology.

3 through 26 show a series of MEMS fabrication steps for the inkjet nozzle assembly 100 shown in Figs. The starting point for this MEMS fabrication is a standard CMOS wafer with CMOS component circuitry formed on top of a wafer. At the end of the MEMS fabrication process, the wafer is slit into individual printhead integrated circuits (ICs), each of which contains a drive circuit and a plurality of nozzle assemblies.

As shown in Figures 4 and 5, a basic term 1 has an electrode 2 formed on its upper portion. The electrode 2 is one of a pair of adjacent electrodes (positive and ground) for supplying electric power to the actuator of the inkjet nozzle 100. The electrodes receive power from a CMOS drive circuit (not shown) located on the upper layer of the substrate 1.

The other electrode 3 shown in Figures 4 and 5 is for providing power to an adjacent ink jet nozzle. In general, the figure shows a MEMS fabrication step of a nozzle assembly that is one of an array of nozzle assemblies. The following description focuses on the manufacturing steps of one of these nozzle assemblies. However, it should be understood that the corresponding steps are performed simultaneously on all of the nozzle assemblies formed on the wafer. This can be omitted where an adjacent nozzle assembly is partially shown in the figure. Thus, electrode 3 and adjacent nozzle assemblies will be described in detail herein. For the sake of clarity, certain MEMS fabrication steps will not be displayed on adjacent nozzle assemblies.

Turning now to Figures 3 through 5, the first series of MEMS fabrication steps begins with a CMOS wafer. An 8 micron thick layer of ruthenium dioxide is initially deposited on the substrate 1. The depth of the cerium oxide defines the depth of the nozzle chamber 5 of the ink jet nozzle. The cerium oxide layer may have a depth of between 4 microns and 20 microns, or between 6 microns and 12 microns, depending on the size of the desired nozzle chamber 5. An advantage of the present invention is that the present invention can be used to make nozzle assemblies having relatively deep (e.g., greater than 6 microns) nozzle chambers.

After depositing the cerium oxide (SiO ₂ ) layer, it is etched to define the wall 4 which will become the sidewall of the nozzle chamber 5, as shown in FIG. The dark shade mask of Figure 3 is used to pattern a photoresist (not shown) that will define this etch. Any non-isotropic DRIE (e.g., C ₄ F ₈ /O ₂ plasma) suitable for the standard of cerium oxide can be used for this etching step. Furthermore, any depositable insulating material (e.g., tantalum nitride, hafnium oxynitride, aluminum oxide) can be used in place of the ceria. Figures 4 and 5 show wafers after the first series of cerium oxide deposition and etching steps.

In a second series of steps, the nozzle chamber 5 is filled with a photoresist or polyamidoamine 6, which acts as a sacrificial support for subsequent deposition steps. It is important to ensure that the top surface of the polyamidoamine 6 is coplanar with the top surface of the ceria wall 4 when preparing the next deposition step. It is also important to ensure that the top surface of the ceria wall 4 is clean after CMP, and a brief cleaning etch can be used to ensure that the above requirements are met.

In the third series of steps, the chamber top member 7 of the nozzle chamber 5 is formed, and the highly conductive connector post 8 is formed to be lowered to the electrodes 2. Initially, a 1.7 micron thick layer of cerium oxide was deposited on the polyamine 6 and wall 4. This ruthenium dioxide layer defines the roof element 4 of the nozzle chamber 5. Next, a pair of vias are formed on the wall up and down to the electrodes 2 by using standard RDRIE. The shade of the mask in Figure 8 is used to form a photoresist (not shown) pattern that defines the etch. The etching is non-isotropically etched such that the sidewalls of the vias are preferably perpendicular to the surface of the substrate 1. This means that any depth of the nozzle chamber can be achieved without affecting the total footprint of the nozzle assembly on the wafer. This etching allows the pair of electrodes 2 to be exposed through the via holes.

Next, the vias are filled with a highly conductive metal such as copper by using electroless plating. Copper electroless plating methods are well known in the art and can be readily incorporated into a foundry. Typically, an electrolyte comprising a copper complex, an acetaldehyde (e.g., formaldehyde) and a hydroxide, deposit a copper coating on the exposed surface of the substrate. There is typically a very thin seed metal (e.g., palladium) coating (e.g., 0.3 microns or less) prior to electroless plating that catalyzes the plating process. Therefore, the electrolessness of the via is preceded by the deposition of a suitable CVD catalyst seed layer (e.g., palladium).

In the final step of the third series of steps, the deposited copper is subjected to a CMP process and stopped on the ceria chamber top member 7 to provide a planar structure. Figures 9 and 10 show the nozzle assembly after this third series of steps. As can be seen from the figure, the copper connector posts 8 formed during electroless copper plating meet the respective electrodes 2 to provide a linear conductive path to the chamber top member 7. The conductive path is not bent or kinked and has a minimum cross-sectional diameter of at least 1 micron, at least 1.5 microns, at least 2 microns, at least 2.5 microns, or less than 3 microns. Thus, the copper connector posts 8 have minimal current loss when supplying power to the actuators within the inkjet nozzle assembly.

In a fourth series of steps, conductive metal pads 9 are formed which are constructed to minimize power loss in any possible high resistance region. These regions are typically located at the joint of the connector post 8 with the thermoelastic member and at any bend on the thermoelastic member. The thermoelastic member is formed in a subsequent step and the function of the metal pad 9 will be more readily understood when the nozzle assembly is described in a state in which it is fully formed.

The metal pad 9 is started by depositing a 0.3 micron aluminum layer on the chamber top member 7 and the connector post 8. Any highly conductive metal (eg, aluminum, titanium, etc.) can be used and deposited to a thickness of about 0.5 microns or less so as not to have a severe effect on the overall flatness of the nozzle assembly. . After deposition of the aluminum layer, a standard metal etch (e.g., Cl ₂ /BCl ₃ ) is used to define the metal pad 9. The brightly colored mask of Figure 11 is patterned with a photoresist (not shown) that will define this etch.

Figures 12 and 13 show the nozzle assembly after the fourth series of steps, wherein the metal pad 9 is formed on the connector post 8 in a predetermined "bending zone" of the subsequently formed thermoelastic active beam member and On the top member 7. For the sake of clarity, the metal pads 9 are not shown on the laterally adjacent nozzle assemblies of Figure 13. However, it will be appreciated that all of the nozzle assemblies in this array are simultaneously produced and in accordance with the manufacturing steps described herein.

In the fifth series of steps shown in Figs. 14 to 16, a thermoelastic active beam member 10 is formed on the ceria chamber top member 7. A portion of the ceria chamber top member 7 acts as a lower passive beam member 16 of a mechanical thermal bending actuator because it is fused to the active beam member 10, the active beam 10 and the passive beam 16 is defined. The thermoelastic active beam member 10 can be constructed of any suitable thermoelastic material such as titanium titanium nitride titanium nitride and aluminum alloy. Vanadium-aluminum alloys are preferred materials as described in the U.S. Patent Application Serial No. 11/607,976, the entire disclosure of which is incorporated by reference in its entirety in The advantageous properties of high Young's modulus.

In order to have the active beam member 10, a 1.5 micron active beam material was initially deposited by standard PECVD. The beam material is then etched using standard metal etching to define the active beam member 10. The brightly colored mask of Figure 14 is patterned to define a photoresist (not shown) that defines this etch.

After the metal etching is completed and as shown in FIGS. 15 and 16, the active beam member 10 includes a portion of the nozzle opening 11 and a beam member 12, the ends of which are electrically connected to the positive electrode and the electrode electrode 2 through the connector post 8. The planar beam member 12 extends from the top of a first (positive) connector post and is bent 180 degrees for returning to the top of a second (ground) connector post. It is of course also within the scope of the invention to describe the beam element structure of the crucible as described in the Applicant's U.S. Patent Application Serial No. 11/607,976.

As clearly shown in Figures 15 and 16, the metal pad 9 is placed in a region that promotes current flow into the higher resistance. A metal pad 9 is disposed in a curved region of the beam member 12 and is sandwiched between the active beam member 10 and the passive beam member 16. Other metal pads 9 are disposed between the top of the connector post 8 and the end of the beam member 12. It will be appreciated that the metal pad 9 can reduce the electrical resistance in these areas.

In the sixth series of steps shown in Figures 17 through 19, the ceria chamber top member 7 is etched to completely define a nozzle opening 13 and the movable portion 14 of the chamber top. The dark tone mask of Figure 17 is patterned with a photoresist (not shown) that will define this etch.

As clearly shown in Figures 18 and 19, the movable portion 14 of the chamber defined by the etching comprises a thermally curved actuator 15 which is itself comprised of the active beam member 10 and the underlying passive beam. The component 16 is composed of. The nozzle opening 13 is also defined on the movable portion 14 of the chamber such that the nozzle opening moves with the actuator during actuation. Thus, the nozzle opening 13 is immovable relative to the movable portion 14, and of course described in U.S. Patent Application Serial No. 11/607,976, is also incorporated herein by reference.

A peripheral gap 17 in the vicinity of the movable portion 14 at the top of the chamber separates the movable portion 14 of the roof from the stationary portion 18. This gap 17 allows the movable portion 14 to be bent into the nozzle chamber 5 and towards the substrate 1 during actuation of the actuator 15.

In the seventh series of steps illustrated in Figures 20-23, a 3 micron thick optically patterned hydrophobic polymer layer 19 is deposited over the entire nozzle assembly and patterned to redefine the nozzle opening 13. A dark-tone mask in Fig. 20 is used to optically pattern the hydrophobic polymer 19.

The use of an optically patternable polymer to coat the nozzle assembly array is disclosed in U.S. Patent No. 11/685,084, filed on March 12, 2007, and No. 11/740,925, issued Apr. 27, 2007. The detailed description of the contents of the two applications is hereby incorporated by reference in its entirety in its entirety. Typically, the hydrophobic polymer is a modified polydimethylsiloxane (PDMS), or a perfluoropolyethylene (PFPE). These polymers are particularly advantageous because they are optically patternable, have a high hydrophobicity and a low Young's modulus.

The exact sequence of MEMS fabrication steps comprising the hydrophobic polymer is quite flexible, as described in the aforementioned U.S. Patent Application. For example, it is absolutely reasonable to etch the nozzle opening 13 after depositing the hydrophobic polymer 19, and the polymer is used as a mask for etching the mask. It will be appreciated that variations in the actual order of the MEMS fabrication steps are within the foreseeable scope of those skilled in the art and are included within the scope of the present invention.

The hydrophobic polymer layer 19 performs several functions. First, it provides a mechanical seal to the peripheral gap 17 in the vicinity of the movable portion 14 of the roof. The low Young's modulus (<1000 MPa) of the polymer means that it does not significantly inhibit the bending of the actuator while preventing the ink from leaking out through the gap during actuation. Second, the polymer has a very high hydrophobicity which minimizes the tendency of the ink to spill out of the relatively hydrophilic nozzle chamber and spill over onto the ink jet face 21 of the printhead. Furthermore, the polymer acts as a protective layer which aids in the maintenance of the printhead.

In the final eighth series of steps shown in Figures 24-26, an ink supply channel 20 is etched through the nozzle chamber 5 from the back side of the substrate 1. The shade of the mask in Figure 24 is used to pattern the photoresist (not shown) that defines this etch. Although the ink supply channel 20 is shown aligned with the nozzle opening 13 in Figures 25 and 26, it can also be offset from the nozzle opening, such as the nozzle assembly 400 shown in FIG.

After the ink supply channel is etched, the polyamidoamine 6 filled into the nozzle chamber 5 is treated by ashing treatment with oxygen plasma, whether it is ash on the front side or ash on the back side. The nozzle assembly 100 is removed for providing.

The resulting nozzle assembly 100 as shown in Figures 25 and 26 has several advantages over the nozzle assembly 400 shown in Figures 1 and 2. First, the nozzle assembly 100 has minimal current loss on the connection line between the active beam 10 and the electrode 2 of the actuator. The copper connector post 8 has excellent electrical conductivity. This is because of its relatively large cross-sectional diameter (>1.5 microns); the inherent high electrical conductivity of copper; and no bending on the connecting line. Thus, the copper connector post 8 can maximize circuit transmission from the drive circuit to the actuator. Conversely, the corresponding connecting lines in the nozzle assembly 400 of Figures 1 and 2 are relatively thin, meandering, and are made of the same material as the active beam 411.

Second, the surface of the connector post 8乖 substrate 1 extends vertically, allowing the height of the nozzle chamber 5 to be increased without affecting the total footprint of the nozzle assembly 100. Conversely, the nozzle assembly 400 requires a tapered connecting line between the electrode 416 and the active beam member 411 such that the connecting line can be formed by PECVD. This slope will inevitably affect the total footprint of the nozzle assembly 400, which would be particularly disadvantageous if the height of the nozzle chamber 401 would be increased (e.g., to provide improved droplet ejection characteristics). . In accordance with the present invention, nozzle chambers having a relatively large volume can be arranged in columns with a nozzle pitch of less than 50 microns.

Third, the nozzle assembly 100 has an ink jet surface 21 having a high degree of flatness without pits or through holes in the region of the electrodes. The flatness of the inkjet face is advantageous for printhead maintenance because it represents a smooth and wipeable surface for any service device. Moreover, there is no risk that the particles will be permanently trapped within the electrode vias or other curved features of the inkjet face.

Of course, it is to be understood that the invention has been described by way of example only, and the details of the invention may be made within the scope of the invention as defined by the following claims.

400. . . Nozzle assembly

401. . . Nozzle chamber

402. . . Passive CMOS layer

403. . . Bismuth substrate

404. . . Roof

405. . . Side wall

406. . . Ink inlet

407. . . Ink supply channel

408. . . Nozzle opening

409. . . Active part

415. . . Nozzle edge

410. . . Thermal bending actuator

411. . . Active beam

412. . . Passive beam

416. . . Electrode contact

418. . . Through hole

417. . . middle layer

2. . . electrode

1. . . Substrate

100. . . Inkjet nozzle

3. . . electrode

5. . . Nozzle chamber

4. . . Cerium oxide (SiO ₂ ) wall

6. . . Polyamine

7. . . Room top

8. . . Connector column

9. . . Metal pad

10. . . Active beam

16. . . Passive beam

12. . . Beam

13. . . Nozzle opening

14. . . Active part

17. . . gap

18. . . Immobile part

19. . . Hydrophobic polymer

twenty one. . . Inkjet surface

20. . . Ink supply channel

Figure 1 is a side cross-sectional view of a thermally curved actuated ink jet nozzle assembly having a thin, meandering connection between an electrode and an actuator; Figure 2 is a cutaway view of the nozzle assembly of Figure 1. 3 is a side view of a portion of the ink jet nozzle assembly for the first step of forming the sidewall of the nozzle chamber; FIG. 4 is a side cross-sectional view of the ink jet nozzle assembly after the first series of steps forming the side wall of the nozzle chamber; a perspective view of a portion of the ink jet nozzle assembly; Figure 6 is a side cross-sectional view of the portion of the ink jet nozzle assembly after the second series of steps of filling the nozzle chamber with polyamidoride; A perspective view of a portion of the ink jet nozzle assembly shown in FIG. 6; FIG. 8 is a mask for through hole etching; and FIG. 9 is a portion of the third series after the connector post is formed to reach the top of the chamber. Side cross-sectional view of the ink jet nozzle assembly; Fig. 10 is a perspective view of the ink jet nozzle assembly shown in Fig. 9; Fig. 11 is a mask for metal plate etching; Fig. 12 is a conductive metal plate Side profile view of a portion of the inkjet nozzle assembly formed after the fourth series of steps Figure 13 is a perspective view of a portion of the ink jet nozzle assembly shown in Figure 12; Figure 14 is a mask for active beam etching; Figure 15 is an active beam member of a thermally curved actuator A side cross-sectional view of a portion of the ink jet nozzle assembly that is formed after the fifth series of steps is formed; FIG. 16 is a perspective view of the portion of the ink jet nozzle assembly shown in FIG. 15; a top-piece etched mask; Figure 18 is a side cross-sectional view of a portion of the inkjet nozzle assembly after a sixth series of steps including the movable top portion of the thermally curved actuator; Figure 19 A perspective view of a preferred ink jet nozzle assembly for the portion shown in Figure 18; Figure 20 is a mask for patterning an optically patternable hydrophobic polymer; Figure 21 is for the hydrophobic polymer layer A side cross-sectional view of a portion of the ink jet nozzle assembly after the seventh series of steps that are deposited and optically patterned; FIG. 22 is a perspective view of the portion of the ink jet nozzle assembly shown in FIG. 21; 23 is a perspective view of FIG. 22, in which the underlying MEMS layer is shown by a dotted line FIG 24 is a mask for etching the backside of the ink supply channel; is a side sectional view of the inkjet nozzle assembly 25 according to the present invention; and FIG. 26 is a cut perspective view of the inkjet nozzle assembly shown in FIG. 25.

1. . . Substrate

2. . . electrode

4. . . Cerium oxide (SiO ₂ ) wall

6. . . Polyamine

7. . . Room top

Claims (29)

A method of forming an electrical connection between an electrode and an actuator in an inkjet nozzle assembly, the method comprising the steps of: (a) providing a substrate having a drive circuit layer, the drive circuit including the An electrode is connected to the actuator; (b) an insulating material wall is formed on the electrode, the insulating material wall defines a sidewall of a nozzle chamber; and (c) a via is formed on at least the wall, The via exposes the electrode; (d) electroless plating is used to fill a conductive material into the via to provide a connector post; and (e) at least a portion of the actuator is formed on the connector post An electrical connection is provided between the actuator and the electrode. The method of claim 1, wherein the distance between the actuator and the electrode is at least 5 microns. The method of claim 1, wherein the driving circuit layer is a CMOS layer of a substrate. The method of claim 1, wherein the drive circuit includes a pair of electrodes for each of the ink jet nozzle assemblies, each of the electrodes being coupled to the actuator with a respective connector post. The method of claim 1, wherein the insulating material wall is composed of cerium oxide. The method of claim 1, wherein the through hole has a side wall perpendicular to one side of the substrate. The method of claim 1, wherein the conductive material is copper. The method of claim 1, further comprising the step of depositing a catalyst layer on the base of the through hole before the electroless plating. The method of claim 8, wherein the catalyst is palladium. The method of claim 1, wherein the electrically conductive material is planarized by chemical mechanical planarization prior to forming the actuator. The method of claim 1, wherein the actuator is a thermally curved actuator comprising a planar active beam member that mechanically cooperates with a planar passive beam member. The method of claim 11, wherein the thermally curved actuator at least partially defines a roof of the nozzle chamber for the inkjet nozzle assembly. The method of claim 11, wherein the step (e) comprises depositing an active beam material on a passive beam material. The method of claim 13, wherein the active beam member of the active beam material extends from a top of the connector post to a plane perpendicular to the column. A print head integrated circuit comprising a substrate having a plurality of ink jet nozzle assemblies formed on a surface of the substrate, the substrate having a drive A circuit for supplying power to the nozzle assemblies, each nozzle assembly including: a nozzle chamber for containing ink, the nozzle chamber having a nozzle opening defined thereon, the insulator wall defining a sidewall of the nozzle chamber An actuator for ejecting ink through the nozzle opening; a pair of electrodes disposed on the surface of the substrate, the electrodes being electrically connected to the drive circuit; and a pair of connector posts, each connector post Each of the other electrodes is electrically connected to the actuator, wherein each connector post extends linearly from the individual electrodes to the actuator, wherein: each connector post is filled in the nozzle chamber A through hole defined in the side wall. A print head integrated circuit as in claim 15 wherein each connector post is perpendicular to the surface of the substrate. The print head integrated circuit of claim 15 or 16, wherein the shortest distance between the actuator and the electrodes is at least 5 microns. The print head integrated circuit of claim 15 wherein the connector posts have a minimum cross-sectional diameter of 2 microns or more. The print head integrated circuit of claim 15 wherein the nozzle assemblies are arranged in a plurality of nozzle rows extending longitudinally along the substrate. The printhead integrated circuit of claim 19, wherein the distance between adjacent nozzle openings in a nozzle row is less than 50 microns. A print head integrated circuit as in claim 15 wherein the actuator is a thermally curved actuator comprising a planar active beam member that mechanically cooperates with a planar passive beam member. The printhead integrated circuit of claim 21, wherein the thermally curved actuator at least partially defines a chamber top of the nozzle chamber, the nozzle opening being defined on the top of the chamber. A print head integrated circuit as claimed in claim 21, wherein the active beam member is electrically connected to the top of the connector posts. A print head integrated circuit as in claim 23, wherein a portion of the active beam member is placed over the top of the connector posts. The print head integrated circuit of claim 24, further comprising a first interstitial metal pad placed between the top of each connector post and the active beam member, each A first voided metal pad is constructed to facilitate current flow from one of the other connector posts to the active beam member. The print head integrated circuit of claim 21, wherein the active beam member is selected from the group consisting of: aluminum alloy; titanium nitride; titanium aluminum nitride; and vanadium-aluminum alloy The composition of the beam material. The print head integrated circuit of claim 21, wherein the planar active beam member comprises a beam member comprising a curved or meandering member, the beam member having a first end disposed at a first The connector post and a second end are placed over a second connector post, the first and second connector posts being adjacent one another. For example, the print head integrated circuit of claim 15 of the patent scope, wherein The sidewall is composed of a material selected from the group consisting of cerium oxide, cerium nitride, cerium oxynitride, and alumina. A pagewidth inkjet printhead comprising a plurality of printhead integrated circuits as described in claim 15 of the patent application.