HK1169081B - Protective coating for print head feed slots - Google Patents

Description

Protective coating for printhead feed slot

Background

Printing devices use printheads to selectively deposit fluid (e.g., ink) onto a print medium. In many cases, the print head degrades over time due to ink erosion, thereby reducing print quality.

Drawings

For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings. The drawings are not necessarily to scale unless otherwise indicated.

Fig. 1 is a front view of a printer according to various embodiments.

Fig. 2 is an exploded bottom perspective view of a print cartridge of the printer of fig. 1, in accordance with various embodiments.

Fig. 3A is a cross-sectional view of the cartridge of fig. 2 taken along line 3-3, in accordance with various embodiments.

FIG. 3B is a partial 3D view of a printhead die of the cartridge shown in FIG. 3A, facilitating identification of different surfaces of feed slots and rib structures, in accordance with various embodiments.

Fig. 4A is a schematic diagram of a coating system for producing a protective coating on a printhead chip using self-ionized plasma (SIP) Physical Vapor Deposition (PVD), in accordance with various embodiments.

Fig. 4B is a simplified enlarged view of a printhead die structural assembly for a SIP vapor deposition process, in accordance with various embodiments.

Fig. 5 is an enlarged bottom view of a printhead assembly from the nozzle side after deposition of a protective coating in accordance with various embodiments.

Detailed Description

Certain terms are used throughout the following description and claims to refer to particular system components. Those skilled in the art will appreciate that computer components may refer to components by different names. This document does not intend to distinguish between components that differ in name but not function.

In the following discussion and claims, the words "include" and "comprise" are used in an open-ended fashion, and thus should be understood to mean "including, but not limited to …".

In the present disclosure, the term "coupled" refers to joining two members directly or indirectly to each other. This combination may be fixed in nature or movable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. This coupling may be permanent in nature or alternatively may be removable or releasable in nature. The term "operatively coupled" shall mean that two members are joined, directly or indirectly, such that motion may be transmitted from one member to the other, either directly or via intermediate members.

In this disclosure, unless otherwise specified, the term "protective coating" refers to a coating comprising at least one layer of material that protects the silicon (Si) feed slot from ink erosion (i.e., chemical etching or physical damage to the feed slot by one or more components of the ink and/or the fluid forces of the ink).

In the present disclosure, the expression "sputtering" refers to the direct physical bombardment of gas atoms and ions onto and interaction with target material (metal) species in the form of atoms (neutrals) or ions. Sputter coating refers to the deposition of a target material onto a substrate.

The expression "resputtering" refers to the indirect interaction between the target material and the gaseous species, in that the material is moved away from the substrate and redeposits in other areas of the substrate due to interaction with the accompanying energetic atoms or ions.

In the present disclosure, the term "aspect ratio" refers to the ratio between the vertical (depth) dimension of a structure and the shortest lateral dimension of the structure. For example, the aspect ratio of an inkjet printhead feed slot is the ratio between the depth of the slot and the width of the slot. For the purposes of this disclosure, the term "high aspect ratio" generally refers to structures having a vertical dimension greater than twice the minimum lateral width.

The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. Furthermore, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.

Printing apparatus

Fig. 1 illustrates an example of a printing device 10 according to various embodiments. Printing device 10 is configured to print or deposit ink or other fluid onto a print medium 12 (e.g., paper or other suitable ink-receiving substrate). The printing device 10 includes a media feed 14 and one or more print cartridges 16. The media feeder 14 drives or moves the media 12 relative to the cartridge 16, and the cartridge 16 ejects ink or other fluid onto the media. For ease of reference, ink and other ejectable fluid are hereinafter referred to simply as "ink". In the illustrated example, the cartridge 16 is driven or scanned laterally across the media 12 during printing. In other embodiments, the cartridge 16 may be stationary and may extend substantially across the lateral width of the media 12, such as a pagewidth printhead.

According to various embodiments, print cartridge 16 includes a nozzle plate and a printhead die having a fluid feed slot with a surface provided with a protective coating that does not extend into the firing chamber. The protective coating inhibits or reduces corrosion of the chip due to interaction between the chip and the ink while substantially not interfering with ejection of ink from the firing chamber through the nozzle. Thus, print quality may be improved and extended over the life of the print cartridge 16.

Although the cartridge 16 is illustrated in fig. 1 and 2 as a modular cartridge configured to be removably mounted to or within the printer 10, in other embodiments, the reservoir 18 may include one or more structures that are substantially permanent parts of the printer 10 and that are not removable.

The printer 10 may have other configurations and may include other printing devices that print controlled patterns, images, layouts, etc. of ink onto a surface. Examples of other such printing devices include, but are not limited to, facsimile machines, copiers, multi-function devices that print or eject ink, or other devices.

Fig. 2 shows the cassette 16 in more detail. The cartridge 16 includes a reservoir 18 and a head assembly 20. The reservoir 18 includes one or more structures configured to supply fluid or ink to the head assembly 20. In one embodiment, the reservoir 18 includes a body 22 and a lid 24, the body 22 and lid 24 forming one or more internal fluid chambers containing ink that is expelled through a slot or opening to the head assembly 20. In some embodiments, the one or more internal fluid chambers further comprise a capillary medium (not shown) for exerting a capillary force on the printing fluid to reduce the likelihood of printing fluid leakage. In other embodiments, each internal cavity of the reservoir 18 further includes an internal standpipe (not shown) and a filter spanning the internal standpipe. Any other equivalent configuration of the reservoir 18 may be substituted, if desired. For example, while the reservoir 18 is illustrated as including a self-contained supply of one or more inks, the reservoir 18 may also be configured to receive ink from the ink supply via one or more conduits or tubes.

Printing head

According to some embodiments, the head assembly 20 includes a mechanism coupled to the reservoir 18 by which ink is selectively ejected onto the media. In the embodiment shown in FIG. 2, the head assembly 20 comprises a drop on demand ink jet head assembly. In one embodiment, the head assembly 20 comprises a thermal resistive head assembly. In another embodiment, the head assembly 20 comprises a piezoelectric head assembly. In other embodiments, head assembly 20 may include any other type of device configured to selectively deliver or eject printing fluid onto a medium. The following discussion focuses on thermal inkjet printing as an example; it should be understood, however, that the methods and systems disclosed herein relating to feed slot protective coatings are also applicable to other types of inkjet printing.

In the particular embodiment shown in fig. 2, the head assembly 20 includes a Tab Head Assembly (THA) including a flex circuit 28, a printhead die 30, a firing resistor 32, a package (printhead encapsulation) 34, and an orifice plate 36. The enlarged portion in fig. 2 shows the orifice plate 36 and the nozzle 42. The flex circuit 28 comprises a strip, panel or other structure of flexible, bendable material, such as one or more polymers, wires or traces (not shown) that support or retain the wires, terminate in electrical contacts 38, and are electrically connected to the firing circuits or resistors 32 on the chip 30. The electrical contacts 38 extend generally perpendicular to the chip 30 and include pads configured to make electrical contact with corresponding electrical contacts of a printing device in which the cartridge 16 is employed. As shown in the embodiment of fig. 2, the flexible circuit 28 surrounds the body 22 of the fluid reservoir 18. In other embodiments, flex circuit 28 may be omitted or may have other configurations in which electrical connection to resistor 32 and its associated addressing (or firing circuitry) is accomplished in other ways.

In fig. 2, package 34 comprises one or more materials that encapsulate electrical interconnects that interconnect conductive traces or lines associated with chip 30 with conductive traces or traces of flex circuit 28 that are connected to electrical contacts 38. In other embodiments, the enclosure 34 may have other configurations or may be omitted.

The printhead die 30 (also referred to as a printhead substrate or chip) includes feed slots 40, ribs 41 (fig. 3A), and the spacing between the feed slots. Printhead die 30 delivers fluid to firing chamber 47 and resistors 32 via feed slot 40. In some cases, printhead die 30 supports resistors 32.

Fig. 3A is a cross-sectional view showing the head assembly 20 in detail, with the printhead die 30 between the lower portion of the body 22 of the reservoir 18 and the orifice plate 36. As shown in FIG. 3A, printhead die 30 has a front side 44 bonded to orifice plate 36 by a barrier layer 46. The barrier layer 46 at least partially forms a firing chamber 47 between the resistor 32 and the nozzles 42 of the orifice plate 36. In one embodiment, the barrier layer 46 may comprise a photoresist polymer substrate. In one embodiment, the barrier layer 46 may be made of the same material as the orifice plate 36. In yet another embodiment, the barrier layer 46 may form the pores or nozzles 42, such that the orifice plate 36 may be omitted. In some embodiments, the barrier layer 46 may be omitted.

As shown in FIG. 3A, resistor 32 is supported on a shelf on the underside of the slot spacing and generally opposite nozzle 42 within firing chamber 47. The resistor 32 is electrically connected to contact pads 38 (shown in fig. 2) by conductive wires or traces (not shown) supported by the chip 30. During use, the electrical energy supplied to the resistor 32 causes the ink supplied through the slot 40 to evaporate to form a bubble that pushes or ejects surrounding or adjacent ink through the nozzle 42. In one embodiment, resistor 32 is also connected to firing or addressing circuitry also located on chip 30. In another embodiment, resistor 32 may be connected to firing or addressing circuitry located elsewhere.

Resistors 32 include resistive elements or firing circuits coupled to printhead die 30 and configured to generate heat, thereby causing portions of the ink to evaporate to forcibly expel drops of printing fluid through nozzles 42 in orifice plate 36. In one embodiment, the resistor 32 (shown schematically) is formed by a plurality of thin film layers 33, which thin film layers 33 may also form the transistors, electrical routing lines, air pockets and chemical protective layers and contact pads for such resistor 32. The film includes: materials for resistors, such as tantalum aluminum or tungsten silicon nitride; materials for transistors such as polysilicon, borophosphate glass, and silicon oxide on doped silicon; materials for electrical traces, such as aluminum; materials for cavitation and chemical protective layers, such as tantalum, silicon oxide, silicon nitride, and silicon carbide; and for contact pad materials such as aluminum or gold. In yet other embodiments, the firing circuit may have other configurations.

The body 22 of the reservoir 18 includes an insert or headland (header) 48. Headlands 48 include those structures or portions of body 22 that are connected to chip 30, thereby fluidly sealing one or more chambers of reservoir 18 from second side 50 of chip 30. In the embodiment shown in fig. 3A, headlands 48 connect each of the three independent fluid-containing chambers 51 to each of the three slots 40 of chip 30. For example, in one embodiment, the reservoir 18 may include three separate risers that deliver fluid to each of the three slots 40. In one embodiment, each of the three separate chambers may include a different type of fluid, such as a different color of fluid or ink. In other embodiments, the body 22 of the reservoir 18 may include a greater or lesser number of such headlands 48 depending on the number of slots 40 in the chip 30 for receiving different fluids from different chambers in the reservoir 18.

In the embodiment shown in fig. 3A, side 50 of chip 30 is adhesively bonded to body 22 by adhesive 52. In one embodiment, the adhesive 52 comprises an adhesive or other fluid adhesive. In other embodiments, the headland 48 of the reservoir 18 may be sealed and bonded to the chip 30 in other ways.

Orifice plate 36 comprises a plate or panel having a plurality of orifices that define nozzle openings through which printing fluid is ejected. The orifice plate 36 is mounted or secured on the underside of the slot 40 and its associated firing circuit or resistor 32. In one embodiment, aperture plate 36 includes a photo-imageable epoxy substrate. As shown in fig. 2, orifice plate 36 includes a plurality of orifices or nozzles 42 through which ink or fluid heated by resistors 32 is ejected through orifices or nozzles 42 to print on a print medium. In another embodiment, the orifice plate 36 comprises a nickel substrate. In other embodiments, the orifice plate 36 may be omitted when such orifices or nozzles are additionally provided.

Printhead chip

As shown in fig. 3A and 3B, the head chip 30 includes a groove 40 and a rib 41. The ribs 41 (also referred to as cross-beams) include reinforcing structures configured to reinforce and provide rigidity to those portions of the printhead die 30 (the stems 64) between successive slots 40. Ribs 41 extend across each slot 40 generally perpendicular to the main axis along which each slot 40 extends. In one embodiment, the ribs 41 and the center points of the ribs 41 are formed of silicon and are integrally formed as part of a single unitary body of the printhead die 30. The grooves are formed in the Si wafer using a combination of machining processes, which may include laser micro-machining, silicon dry etching, silicon wet etching with TMAH, and may include a masking process with patterned metal or photoresist. As described in more detail below, the ribs 41 strengthen the chip 30, allowing the slots 40 to be more densely disposed across the chip 30 without significantly degrading print performance or quality. In certain embodiments, these structures also serve to physically separate two different fluids or inks. In some embodiments, the printhead die 30 does not have ribs 41 (or rib structures).

Because the rib structure is a support for reinforcing the feed groove; they are particularly useful when the chip size shrinks. "chip size shrink" or "chip shrink" generally refers to the practice of modifying a chip design of a given size by reducing the width of each feed slot and non-slot area and increasing the number of chips on a wafer or increasing the total number of feed slots in a chip. One possible advantage of using a printhead with an increased number of feed slots and nozzles is that higher resolution and better image quality of the printed image is possible. The spacing of the feed slots may be reduced by using a rib structure to shrink the chip size. Alternatively, the number of feed slots can be increased by decreasing the spacing using the same size chip. Thus, the number of ink colors in a given application can be increased by storing different inks in different feed slots. In some embodiments, the rib structure 41 extends through the full depth of the feed slot (through the rib), while in other embodiments, the rib structure extends only partially in the vertical dimension (as shown in fig. 3A).

Feed slots without ribs may also be used for chip size shrinkage. These feed slots typically have a high aspect ratio (e.g., greater than 2) so that a sufficient amount of ink can be stored in the slots and a sufficient number of slots can be included in the chip. In some cases, the feed slot may have an aspect ratio greater than 3.

As shown in the embodiment of fig. 3A, the slot 40 includes a fluid channel 70 or fluid opening or passage through which fluid is delivered to the resistor 32. The slots 40 are of sufficient depth to deliver fluid to each of the resistors 32 and their associated nozzles 42 within the respective firing chambers 47. In some embodiments, the slots 40 have tapered or sloped ends, thereby defining the fluid passages 70. In one embodiment, the slots 40 have a width between 70 and 700 microns and in some cases in the range of 200 to 300 microns. In the embodiment shown in fig. 3A, in which the firing circuitry or resistive addressing circuitry is disposed directly on the chip or chip 30, the slots 40 have a centerline-to-centerline spacing of about 0.8 mm. In embodiments where the firing or addressing circuitry is not provided on the chip or chip 30, the slots 40 may have a centerline-to-centerline spacing of about 0.5 mm. In other embodiments, the slots 40 may have other suitable dimensions and relative spacing.

Protective coating

It has been found that over time, many fluids or inks (particularly high performance inks) tend to corrode one or more materials of the printhead die 30. For example, it has been found that many high performance inks tend to corrode the silicon forming the chip 30. The ribs 41 in the grooves 40 have a high surface area and may be susceptible to ink corrosion. High performance inks typically contain one or more potentially corrosive substances, such as buffer solutions that may contain functional dispersions or have a high PH. The corroded and decomposed silicon contaminates the fluid or ink and may affect the ejection of the ink by affecting the quality of the ink itself or by depositing on the resistor 32 or other component from which the ink is ejected. It has also been found that decomposed silicon contaminants in the fluid or ink subsequently precipitate from the ink and deposit in the openings 70 or 42 to at least partially block such openings. In some cases, silicon growth in the nozzle openings 42 may create nozzle orientation problems and reduce print quality. Thus, in some applications, ink compositions known to corrode Si may be included in the ink used to coat the printhead assembly.

As further shown in fig. 3A and 3B, the printhead die 30 also includes a protective coating 60 (exaggerated for purposes of illustration). Protective coating 60 solves the above-described problems and expands the range of ink compositions that can be used in a printhead by protecting the substrate (e.g., silicon forming chip 30 and ribs 41) from potentially corrosive fluids or inks. Thus, in many embodiments, the coating 60 reduces or prevents silicon growth around the nozzle opening 42 and reduces the likelihood that the fluid or ink will be contaminated. Thus, in many applications, print quality may be maintained and the useful life of printhead assembly 20 may be extended.

And (3) coating materials. Coating 60 comprises one or more layers of one or more materials that are impermeable to the ink components. Coating 60 has an outermost surface that is substantially inert to fluid directed through slot 40 of print chip 30. Suitable coating materials include titanium (Ti), titanium nitride (TiN), tungsten (W), tantalum (Ta) or tantalum nitride (TaN). The protective coating may comprise a homogeneous single layer of a particular material, or multiple layers comprising a combination of materials. In one embodiment, the protective coating comprises a Ti layer. In another embodiment, the protective coating comprises a TiN layer. In a further embodiment, the protective coating comprises a W layer. In yet another embodiment, the protective coating comprises a Ta layer. In one embodiment, the protective coating comprises a TaN layer. In one embodiment, the protective coating includes a Ti layer and a TiN layer, wherein the TiN layer is the outermost surface. In another embodiment, the protective coating comprises a Ta layer and a TaN layer, wherein the TaN layer is the outermost surface. In yet another embodiment, the protective coating includes a Ti layer and a W layer, wherein the W layer is the outermost surface.

The coating 60 has a thickness sufficient to ensure the integrity (e.g., continuity, without cracking or breaking) of the protective coating formed on the surface of the feed slot 40. At the same time, the coating 60 is sufficiently thin to avoid or minimize cracking or delamination of the coating 60 during use due to tensile stresses. In some applications, the total thickness of the protective coating is in the range of from about 50 to about 300 angstroms. In some applications, the coating has a thickness of from about 75 to about 250 angstroms. In other applications, the coating has a thickness of from about 90 to about 210 angstroms. When the protective coating is very thin (e.g., less than about 300 angstroms), it is transparent in visible light and facilitates downstream chip inspection. In some other applications, the total thickness of the protective coating is up to 1000 angstroms. In other applications, the total thickness of the protective coating is up to 2000 angstroms.

In some applications, when the protective coating includes multiple layers, the stress in the protective layer is balanced to zero. For example, the Ti layer has a compressive stress, and the TiN layer has a tensile stress. The combination of these two layers results in a zero stress protective coating that also resists delamination. The stress of the deposited film is readily determined by measuring the wafer curvature after film deposition using known methods and taking into account the substrate thickness, the young's modulus of the substrate, and the thickness of the deposited film. The compressive stress film makes the substrate bend convex, and the tensile stress film makes the substrate bend concave.

And coating the region. Coating 60 covers all surfaces associated with feed slot 40, including all surfaces of the rib structure. In fig. 3A and 3B, the coating 60 is formed and extends across the side surfaces of the die 30, the side surfaces 61 (including the inclined/tapered surfaces) of the feed slot 40 that define the opening 70, the side surfaces 66 of the ribs 41, the top surfaces 68 of the ribs 41, the bottom surfaces 69 of the ribs 41, and the back surface 74 of the die 30. Thus, the coating 60 provides a protective coating on the surface areas associated with the grooves 40 that may come into contact with the ink as the fluid travels through the grooves 40.

In one embodiment, coating 60 covers a back surface 74 of chip 30 (the back side of the wafer including chip 30). Thus, coating 60 also protects the top surface of die 30 during contact with fluid from cavity 51. In addition, those portions of chip 30 that are bonded to headland 48 by adhesive 52 also benefit. Specifically, coating 60 improves the adhesion of the chip 30 material to the structural adhesive 52. In alternative embodiments, the coating 60 either coats a portion of the back surface 74 of the die 30 or does not coat the back surface 74 of the die 30.

As shown in fig. 3A, coating 60 does not extend significantly into firing chamber 47 so as to not interfere with the ejection of ink from the chamber. In one embodiment, coating 60 extends along opening 70 and die 30 up to opening 70 and die 30. In other embodiments, the coating 60 may also extend onto the portion of the orifice plate 36 directly opposite the opening 70. However, even in these embodiments, the coating 60 does not extend substantially laterally into the firing chamber 47 or across the resistor 32 or nozzle 42. FIG. 5 is a bottom view of an embodiment of the printhead assembly from the nozzle side after deposition of a protective coating. The coating 460 does not extend into the firing chamber 447 more than 5 microns (shaded area, 460'). In some cases, coating 460 does not extend into firing cavity 447 more than 4 microns. In some cases, coating 460 does not extend into firing cavity 447 more than 7 microns. The coating 460/460' does not interfere with the function of the resistor 432, the nozzle 442, or the barrier layer 446.

Since the coverage of the coating 60 is controlled and limited so as not to extend significantly into the firing chamber 47, as described below under the "SIP" approach, the coating 60 does not interfere with the firing properties (e.g., the switch-on energy) of the resistor 32 or those fluid ejection characteristics achieved by the overall firing system. This is particularly important when coating 60 is formed of a material having a relatively low thermal conductivity (much lower than the material forming resistor 32) that would otherwise affect the fluid ejection within each firing chamber 47.

SIP method

The coating material may be deposited using self-ionized plasma (SIP) physical vapor deposition techniques known in the art. For example, the SIP deposition apparatus and process described in U.S. patent application No. 20040112735 may be suitably used for this purpose.

In some cases, coating 60 needs to be kept away from certain surfaces of the printhead assembly (e.g., resistive surfaces). This can be accomplished by conventional techniques such as shadow masking or lift-off, which are methods known in the art. For Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD), masking or stripping is typically required to avoid extending the coating to unwanted areas. However, masking or stripping is not necessary for the SIP vapor deposition method disclosed herein. Thus, the SIP vapor deposition method reduces the complexity of the coating process.

In one embodiment, the printhead die with feed slot is sputtered prior to assembly with the printhead structure (including firing chambers, nozzles, and other related structures). In some embodiments, the chip is similar to chip 30 shown in FIG. 3A, without thin film layer 33, resistor 32, barrier layer 46, orifice plate 36, firing chamber 47, or nozzle 42.

In another embodiment, as shown in FIG. 4A, the printhead die with feed slot 140 is sputtered after the printhead structure (including firing chambers, nozzles, and other related structures) is attached to the die. The chip having the structure is referred to as a chip architecture assembly (DAA) 130'. In fig. 4B, a portion 300 of DAA 130' in fig. 4A is enlarged to illustrate the relative dimensions of slot 340 and the distance between slot opening 370 and orifice plate 336. For example, the width of the slot 340 is about 200 microns, the width of the opening 370 is about 100 microns, and the distance between the slot opening 370 and the orifice plate 336 is about 15 microns. Since the distance between the slot openings 370 and the orifice plate 336 is much smaller compared to the slot and slot opening dimensions, the SIP vapor deposition process used herein does not extend the protective coating into the firing chamber more than 5 microns (FIG. 5). In some cases, the coating does not extend into the firing chamber more than 4 microns. In some cases, the coating does not extend into the firing chamber more than 7 microns. The coating material plasma may pass through the opening 370 and coat a portion of the plate 336. But due to the small distance between 370 and 336 very little coating material is resputtered laterally. Thus, the protective coating does not extend significantly into the firing chamber. In addition, coating the bottom surface of the rib structure may be facilitated by the secondary sputtering plate 336 through the opening 370.

Referring again to fig. 4A, the SIP reactor includes a sealed vacuum chamber 270. The vacuum cavity wall 271 is typically made of metal and is electrically grounded. In some cases, an inert gas (e.g., argon) is flowed into the chamber in a controlled manner (not shown in fig. 4A). The reactor also includes a target 290 having at least a surface portion formed of the material to be sputter deposited on the DAA 130'. The DC magnetron 280 is coupled to a target 290 and generates a plasma in close proximity to the target for sputtering the target and ionizing the sputter-deposited material. The DC magnetron is powered by a DC power supply 260. The magnetron is scanned around the back of the target and projects its magnetic field into the portion of the reactor near the back to increase the plasma density. Target 290 is typically negatively biased to attract ions generated in the plasma to sputter the target.

The pedestal electrode 220 has a support surface 225 that supports the DAA 130 'and biases the DAA 130' to attract the ionized deposition material. The DAA 130' is removably secured to the support surface 225 of the base electrode 220 on its front side or orifice plate 145. The base electrode 220 is powered by an AC power source 250. Resistive heaters, refrigerant channels, and heat transfer gas chambers may be configured in the pedestal 220 to allow the temperature of the pedestal to be controlled at a temperature of less than 40 ℃, thereby allowing the chip temperature to be similarly controlled. The DAA 130' is disposed on the base electrode 220 with the wide portion of the feed slot facing the target 290.

The SIP PVD reactor includes a controller 210, in some cases the controller 210 controls a magnetron 280, a DC power source 260, and an AC power source 250. In one embodiment, the process conditions of the SIP vapor deposition process are a chamber pressure in the range of 0.5 to 2 mTorr, an argon gas flow into the chamber in the range of 10 to 15 SCCM, a pedestal gas flow in the range of 3 to 6 SCCM, a pedestal temperature in the range of-50 ℃ to 130 ℃, a DC power in the range of 8 to 25 kilowatts, an AC bias in the range of 230 to 270 watts, and a deposition time in the range of 5 to 90 seconds based on the target thickness and the process conditions.

The rate at which material is sputtered can be controlled by controlling the power of the source that biases the target. Since relatively thin layer deposition is generally desired, low sputtering rates are generally used to facilitate control of the deposition thickness. Thus, the power level of the target bias source may be set relatively low to facilitate achieving the desired thin layer deposition. For example, at a sufficiently high plasma density near the target, a sufficiently high density of target metal ions can be generated that ionize the additional metal sputtered from the target. As mentioned above, such a plasma is known as a self-ionized plasma (SIP). Sputtered metal ions may be accelerated along the plasma sheath and toward the biased substrate, thus increasing the directionality of the sputtered material. In this case, the biased substrate is DAA 130'. The impinging ions and the increased energy of the deposited material on the non-vertical plane of the substrate/trench allow for the re-sputtering of material onto the vertical sidewalls. The coating of vertical sidewalls is a challenge in conventional Physical Vapor Deposition (PVD) systems, especially in high aspect ratio structures. Thus, the present SIP method can improve sidewall and bottom coverage in deep, narrow trenches.

The SIP is capable of depositing material into the bottom surface 69 of the high aspect ratio feed slot and rib structure 41 (fig. 3A). This is because of the high degree of ionization of the SIP forming atoms; the bias on the substrate allows the formed ions to be accelerated toward the substrate so that a sufficient amount of ions reach the bottom of the high aspect ratio structures. In addition, ion bombardment resputtering from the accelerated ions resputters material from non-vertical planes to coat sidewalls 61 and 66, as shown in FIGS. 3A and 3B. As shown in fig. 3A and 3B, protective coating 60 is deposited on surfaces 61, 66, 68, and 69 by a SIP PVD process. The coating of the rib underside (rib surface 69) is difficult in conventional PVD methods due to shadowing of the structure during any orientation. The double sputtering in the SIP method allows this protection and in turn prevents ink attacks on the surface.

When the resulting coated chip is used for printing, protective coating 60 (fig. 3A) allows printhead assembly 20 to maintain a desired level of quality over an extended period of time. Coating 60 inhibits or prevents fluid or ink from corroding chip 30. The coating 60 inhibits contamination of the fluid or ink by decomposition of the chip material. Coating 60 also inhibits deposition, accumulation, or growth of decomposed material of die 30 around opening 70 or nozzle opening 42 and on resistor 32. At the same time, the coating 60 does not interfere with fluid ejection from the printhead. Coating 60 facilitates printing of fluids or inks that may be more corrosive to the material of chip 30, possibly providing enhanced performance. The coating 60 provides greater flexibility in selecting fluid or ink formulations. In some applications, coated chip arrays are used to assemble pagewidth printheads. In some applications, the coated chip is used as a component of an inkjet cartridge.

In one embodiment, a method of fabricating a corrosion resistant printhead die is described. The method comprises the following steps: forming a self-ionized plasma (SIP) of the coating material; establishing a bias on a printhead chip comprising a plurality of feed slots (40), each feed slot (40) comprising a sidewall surface (61); and plasma depositing a coating material on the surface to form a protective coating, wherein at least a portion of the coating material is deposited on at least a portion of the surface by double sputtering. In some cases, the feed slot has an aspect ratio greater than 2. In some other embodiments, the feed slot comprises at least one rib (41), each rib (41) comprises a top surface (68), a lower surface (69) and two side surfaces (66), and the formed protective coating is deposited on the top surface (68), the lower surface (69) and the two side surfaces (66) of each rib (41).

In some cases, the coating material is selected from the group consisting of: titanium (Ti), titanium nitride (TiN), tungsten (W), tantalum (Ta), tantalum nitride (TaN), and combinations thereof. In some cases, the protective coating includes at least two layers of material. For example, the protective coating includes a titanium (Ti) layer and a titanium nitride (TiN) layer, wherein the titanium nitride (TiN) layer is outermost. In some embodiments, the protective coating is formed with zero stress. In application, the protective coating is capable of protecting the coated surface from ink corrosion. In some applications, the protective coating is transparent under visible light.

In another embodiment, a printhead is disclosed. The print head includes: a chip (30), the chip (30) comprising a plurality of feed slots (40) having an aspect ratio greater than 2, each feed slot (40) comprising a sidewall surface (61); a protective coating disposed on each of said surfaces; and a plurality of firing chambers (47) each in fluid communication with the feed slot (40), wherein the protective coating does not extend more than 5 microns into the firing chambers (47). In some cases, each feed slot of the printhead further includes at least one rib (41), each rib (41) including a top surface (68), a lower surface (69), and two side surfaces (66), the protective coating being disposed on the top surface (68), the lower surface (69), and the two side surfaces (66) of each rib (41).

In some cases, the protective coating has substantially zero stress. In some cases, the protective coating is formed by self-ionized plasma physical vapor deposition. In some embodiments, the protective coating is formed from a material selected from the group consisting of: titanium (Ti), titanium nitride (TiN), tungsten (W), tantalum (Ta), tantalum nitride (TaN), and combinations thereof. In some cases, the protective coating includes at least two layers of material.

In yet another embodiment, an inkjet cartridge is disclosed, comprising: a printhead assembly comprising a printhead and printing circuitry as described herein; and an ink reservoir attached to the assembly.

Although the present invention has been described with reference to exemplary embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different exemplary embodiments may be described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described exemplary embodiments or in other alternative embodiments. Not all variations of the techniques are foreseeable, as the techniques of this disclosure are relatively complex. The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, although the foregoing description has focused on SIP PVD, any other suitable coating technique that achieves the same result may be substituted. Moreover, it should be understood that coating materials that serve the same purpose and that can be similarly applied, other than as specifically described herein, may be substituted. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Claims (15)

1. A method for forming a protective coating on a printhead feed slot, comprising:

forming a self-ionized plasma (SIP) of the coating material;

establishing a bias on a printhead chip comprising a plurality of feed slots (40), wherein each feed slot (40) delivers fluid to a respective firing chamber, each feed slot (40) comprising a sidewall surface (61); and

depositing a coating material on the surface to form a protective coating, wherein at least a portion of the coating material is deposited on at least a portion of the surface by double sputtering.

2. The method of claim 1, wherein each of the feed slots has an aspect ratio greater than 2.

3. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein each of the feed slots further comprises at least one rib (41), each rib (41) comprising a top surface (68), a lower surface (69) and two side surfaces (66), an

Wherein the formed protective coating is deposited on the top surface (68), lower surface (69) and two side surfaces (66) of each rib (41).

4. The method of claim 1, wherein the coating material is selected from the group consisting of: titanium (Ti), titanium nitride (TiN), tungsten (W), tantalum (Ta), tantalum nitride (TaN), and combinations thereof.

5. The method of claim 1, wherein a protective coating comprises at least two layers of the coating material.

6. The method of claim 1, wherein the protective coating comprises a titanium (Ti) layer and a titanium nitride (TiN) layer, wherein the titanium nitride (TiN) layer is outermost.

7. The method of claim 1, wherein the protective coating formed has zero stress.

8. The method of claim 1, wherein the protective coating is transparent under visible light.

9. A printhead, comprising:

a chip (30), said chip (30) comprising a plurality of feed slots (40) having an aspect ratio greater than 2, wherein each feed slot (40) delivers fluid to a respective firing chamber, each said feed slot (40) comprising a sidewall surface (61);

a protective coating disposed on each of said surfaces; and

a plurality of firing chambers (47) respectively in fluid communication with the feed slot (40),

wherein the protective coating does not extend more than 5 microns into the firing chamber (47).

10. A printhead as in claim 9, wherein the printhead is,

wherein each of the feed slots further comprises at least one rib (41), each rib (41) comprising a top surface (68), a lower surface (69) and two side surfaces (66), an

Wherein a protective coating is provided on the top surface (68), lower surface (69) and two side surfaces (66) of each rib (41).

11. The printhead of claim 9, wherein the protective coating has substantially zero stress.

12. The printhead of claim 9 wherein the protective coating is formed by self-ionized plasma physical vapor deposition.

13. The printhead of claim 9, wherein the protective coating is formed from a material selected from the group consisting of: titanium (Ti), titanium nitride (TiN), tungsten (W), tantalum (Ta), tantalum nitride (TaN), and combinations thereof.

14. The printhead of claim 9, wherein the protective coating comprises at least two layers of the material.

15. An ink jet cartridge comprising:

a printhead assembly comprising a printhead according to claim 9 and printing circuitry; and

an ink reservoir attached to the printhead assembly.