Microfluidic architecture

A microfluidic architecture is disclosed. The microfluidic architecture includes a substrate having an edge and a thin film stack established on at least a portion of the substrate adjacent the edge. The thin film stack includes a non-conducting layer and a seed layer, where the seed layer is positioned such that a portion of the non-conducting layer is exposed. A chamber layer is established on at least a portion of the seed layer. The non-conducting layer, the seed layer, and the chamber layer define a microfluidic chamber. A layer having a predetermined surface property is electroplated on the chamber layer and on at least one of another portion of the seed layer and the exposed portion of the non-conducting layer.

BACKGROUND

The present disclosure relates generally to fluidic architectures, and more particularly to microfluidic architectures and methods of making the same.

Fluidic architectures, such as those used in fluid ejection assemblies, utilize a chamber and a plurality of nozzles or apertures through which fluids are ejected. The microfluidic architecture used to form the chamber and nozzles may include a semiconductor substrate or wafer having a number of electrical components provided thereon (e.g., an ink-jetting device may include a resistor for heating ink in the chamber to form a bubble in the ink, which forces ink out through the nozzle).

The chamber and nozzle may be formed from layers of polymeric materials. One potential difficulty with the use of polymeric materials to form the nozzle and chamber is that such materials may become damaged or degraded when used with particular fluids (e.g., inks having relatively high solvent contents, etc.). Another difficulty with the use of polymeric materials is that such materials may become damaged or degraded when subjected to certain temperatures that may be reached during operation of the device in which the architecture is being used.

The chamber and nozzle may also be formed of metals. Certain metals may have desirable material properties, however, these metals may also increase the cost of manufacturing the microfluidic architectures.

Still further, processes for forming and coating architectures are generally not selective processes. As such, substantially the entire architecture is formed from the same material in order to achieve desired surface properties. Further, if a coating is desirable on the architecture, generally a coating should be used that is compatible with the device and/or components that are coated in the process.

As such, it would be desirable to provide a microfluidic architecture that may be selectively coated and relatively inexpensively manufactured.

SUMMARY

A microfluidic architecture is disclosed herein. The microfluidic architecture includes a substrate having an edge and a thin film stack established on at least a portion of the substrate adjacent the edge. The thin film stack includes a non-conducting material layer and a seed layer, where the seed layer is positioned such that a portion of the non-conducting material layer is exposed. A chamber layer is established on at least a portion of the seed layer. The non-conducting material layer, the seed layer, and the chamber layer define a microfluidic chamber. A layer having a predetermined surface property is electroplated on the chamber layer and on at least one of an other portion of the seed layer and the exposed portion of the non-conducting layer.

DETAILED DESCRIPTION

Embodiment(s) of the microfluidic architecture described herein are suitable for use in a variety of devices. Specifically, embodiment(s) of the microfluidic architecture may be incorporated into, for example, ink-jet printheads or cartridges, fuel injectors, microfluidic biological devices, pharmaceutical dispensing devices, and/or the like. Further, an embodiment of the method for forming the architecture allows for selective establishment of the various elements, thus allowing a variety of materials to be used.

Referring now toFIGS. 1A through 1M, two alternate embodiments of forming embodiments of microfluidic architectures10are schematically depicted. Both embodiments of the method include establishing a thin film stack30on a substrate12. The substrate12may be formed of any suitable material. In an embodiment, the substrate12is selected depending, at least in part, on the device in which the architecture10is operatively disposed. Non-limitative examples of substrate materials include semiconductor materials, silicon wafers, quartz wafers, glass wafers, polymers, metals, and the like. It is to be understood that polymeric substrates are generally coated with a seed layer that may act as a cathode. Further, the substrate12may also contain logic and/or drive/power electronics; or the substrate may contain a resistor that interconnects to off die power and logic circuitry.

The thin film stack30includes a non-conducting layer37and a seed layer38. As depicted inFIG. 1A, generally the non-conducting layer37is blanket established on the substrate12, and the seed layer38is blanket established on the non-conducting layer37. The thin film stack30may be established by any suitable technique, including, but not limited to physical vapor deposition (PVD), evaporative deposition, chemical vapor deposition (CVD), plasma enhanced physical vapor deposition, plasma enhanced chemical vapor deposition, spin-coating of appropriate precursor mixtures and baking (i.e. spin on glass), or electroless deposition (i.e. autocatalytic plating), or the like.

The non-conducting layer37may be formed of any suitable non-conducting material. Non-limitative examples of non-conducting materials are dielectric materials. It is to be understood that the dielectric material may be an organic dielectric material, an inorganic dielectric material and/or a hybrid mixture of organic and inorganic dielectric materials. A non-limitative example of the organic dielectric material is poly(vinylphenol) (PVP), and non-limitative examples of the inorganic dielectric material are silicon nitride and silicon dioxide. Other examples of materials suitable for the non-conducting layer37include, but are not limited to tetraethylorthosilicate (TEOS), borophosphosilicate glass, borosilicate glass, phosphosilicate glass, aluminum oxide, silicon carbide, silicon nitride, and/or combinations thereof, and/or the like. It is to be understood that nonstoichiometric forms of these compounds may be used as well.

The seed layer38may include one or more layers, at least one of which acts as a cathode. According to an example embodiment, seed layer38includes one or more metals, such as gold, tantalum, alloys thereof, or combinations thereof. In the embodiment depicted inFIG. 1A, the seed layer38includes a gold layer established on a tantalum layer. According to other embodiments, the seed layer may include any of a variety of other metals or metal alloys such as nickel, nickel-chromium alloys, copper, titantium and gold layers, titanium-tungsten alloys, titanium, palladium, chromium, rhodium, alloys thereof, and/or combinations thereof. According to an example embodiment, seed layer38has a thickness ranging from about 500 angstroms to about 1,000 angstroms. According to other example embodiments, the thickness of seed layer38is between approximately 500 angstroms and 10,000 angstroms.

The methods further include selectively etching the thin film stack30such that a portion of the substrate12and a portion of the non-conducting layer37are exposed, as depicted inFIG. 1B. It is to be understood that the seed layer38may be etched prior to etching the non-conducting layer37. Any suitable etching process may be used for the seed layer38. The non-conducting layer37is generally etched using a resist pattern that protects the seed layer38while exposing the non-conducting layer37areas that are to be etched. In an embodiment, etching is accomplished by plasma etching (e.g. reactive ion etching or sputter etching) or wet chemical etching. After the etching is complete, in a non-limitative example, the thin film stack30is established adjacent the edge(s) of the substrate12.

FIGS. 1C through 1Gdepict the formation of one embodiment of the microfluidic architecture10, andFIGS. 1H through 1Mdepict the formation of another embodiment of the microfluidic architecture10.

Referring now toFIG. 1C, an embodiment of the method includes establishing a sacrificial layer172(i.e. sacrificial structure) on the exposed portions of the substrate12and non-conducting layer37. It is to be understood that any suitable sacrificial material172may be used. Non-limitative examples of suitable sacrificial materials include photoresists, tetraethylorthosilicate (TEOS), spin-on-glass, polysilicon, and/or combinations thereof.

The sacrificial layer172may be established via spray coating, spin coating, or a lamination process if, for example, the sacrificial layer172is a resist. In another embodiment, the sacrificial layer172may be established via chemical vapor deposition or physical vapor deposition, and/or the like.

It is to be understood that the sacrificial material172may be formed or patterned in any pattern that is desirable for the subsequently established chamber layer50. The chamber layer50is established such that it substantially overlies the thin film stack30in an area not covered by the sacrificial layer172, for example, the seed layer38. As such, the sacrificial material172acts as a mandrel or mold around which the chamber layer50may be established. The sacrificial material172also acts to mask portions of the underlying elements (e.g. substrate12and non-conductive layer37) from having the chamber layer50established thereon. While chamber layer50is shown as being deposited such that its top surface is substantially planar with the top surface of sacrificial material172, chamber layer50may be deposited to a level higher than the top surface of sacrificial structure172and polished or etched such that it is coplanar with the top surface of sacrificial structure172.

According to an example embodiment, chamber layer50is formed of nickel or a nickel alloy. According to various other example embodiments, chamber layer50may include other metals or metal alloys such as one or more of nickel, iron, cobalt, copper, chromium, zinc, palladium, gold, platinum, rhodium, silver, alloys thereof (non-limitative examples of which include iron-cobalt (Fe—Co) alloys, palladium-nickel (Pd—Ni) alloys, gold-tin (AuSn) alloys, gold-copper (AuCu) alloys, nickel-tungsten (NiW) alloys, nickel-boron (NiB) alloys, nickel-phosphorous (NiP) alloys, nickel-cobalt (NiCo) alloys, nickel-chromium (NiCr) alloys, silver-copper (AgCu) alloys, palladium-cobalt (PdCo) alloys, and others), and/or mixtures thereof. In a non-limitative example, the metal or metal alloy utilized for chamber layer50may be established by an electroplating or electroless deposition process. It is to be understood that the chamber layer50may also be established via a PVD or CVD process.

In an embodiment, chamber layer50has a thickness ranging from about 20 micrometers to about 100 micrometers. According to other example embodiments, chamber layer50has a thickness ranging from about 1 micrometer to about 50 micrometers.

Referring now toFIG. 1D, the sacrificial layer172is removed subsequent to the establishment of the chamber layer50. The removal of the sacrificial layer172may be accomplished via any suitable technique. It is to be understood that the technique may be selected, in part, depending on the sacrificial material172used. In an embodiment, the sacrificial material172is removed via solvent stripping processes, acidic solutions (non-limitative examples of which include sulfuric acid, hydrochloric acid, and the like), basic solutions (non-limitative examples of which include tetramethyl ammonium hydroxide, potassium hydroxide, and the like), or combinations thereof. It is to be understood that oxygen plasma etching may be used to remove polymeric sacrificial materials.

As depicted inFIG. 1D, a microfluidic chamber70is formed upon the removal of the sacrificial material172. In an embodiment, the chamber70is defined by the substrate12, the thin film stack30, and the chamber layer50. The chamber70may contain, but is not limited to containing, biological fluids, inks, fuels, pharmaceutical fluids, and the like. It is to be understood that the architecture(s)10may also contain means for supplying and removing such liquids from the chamber70, however such means are not depicted here for clarity.

FIG. 1Dalso depicts the establishment of the layer54having a predetermined surface property on the chamber layer50. It is to be understood that this layer54may be selectively electroplated such that it is adjacent a top surface of the chamber layer50in addition to being adjacent those portions of the chamber layer50and the seed layer38that are exposed to the chamber70. It is to be understood that the selectivity of the electroplating advantageously allows the layer54to come to rest on the non-conductive layer37without being exposed to the substrate12.

The layer54having the predetermined surface property may be selected to provide corrosion resistance to the chamber layer50and the seed layer38. Other properties that the layer54may include, but are not limited to surface hardness, wettability, surface roughness, brightness, predetermined density, predetermined surface finish (e.g. substantially crack free), predetermined porosity, and/or combinations thereof.

In an embodiment where the surface appears to have relatively shiny deposits, the average surface roughness ranges from about 2 nm to about 20 nm. In an alternate embodiment where the surface appears to have relatively rough deposits or a matted appearance, the average surface roughness is greater than about 0.5 μm. Where a softer surface is desired, layer54may have a hardness ranging from about 80 VHN (Vickers Hardness) to about 120 VHN, and where a harder surface is desired, layer54may have a hardness greater than about 600 VHN. Regarding the wettability of layer54, a contact angle (when measured with water) may be greater than about 50°, and in an alternate embodiment, the contact angle may be greater than about 90°. It is to be understood that when a high wetting surface is desired, the contact angle may be less than about 10°.

In an embodiment, the layer54is palladium, nickel, cobalt, gold, platinum, rhodium, alloys thereof, and/or mixtures thereof. Without being bound to any theory, it is believed that because the layer54is selectively electroplated independent of the rest of the architecture10elements, a variety of materials may be selected (e.g. a nickel chamber layer50and a palladium layer54), thereby allowing manufacturing to be relatively inexpensive while maintaining the surface integrity of the architecture10.

The layer54is generally a thin layer. In an embodiment, the thickness of the layer54ranges from about 0.05 μm to about 4 μm. In a non-limitative example, the thickness of the layer54is about 1 μm.

In one embodiment, a second seed layer (i.e. thin adhesion layer)52(described further hereinbelow in reference toFIGS. 2D-2K) may be established on the chamber layer50prior to the deposition of the layer54.

Referring now toFIG. 1E, another sacrificial layer172′ is established in a predetermined pattern in the chamber70. This sacrificial layer172′ is generally patterned such that the subsequently deposited nozzle layer60has an opening defined therein. It is to be understood that the sacrificial layer172′ substantially covers the chamber70such that the nozzle layer does not penetrate the chamber70.

FIG. 1Fdepicts the establishment of the nozzle layer60. In an embodiment, the nozzle layer60is selectively electroplated such that it substantially overlies the layer54in an area not covered by the sacrificial layer172′, for example, directly above the chamber layer50. As such, the sacrificial material172′ acts as a mandrel or mold upon which and/or around which the nozzle layer60may be established.

According to an example embodiment, nozzle layer60includes the same material as is used to form chamber layer50. According to other example embodiments, chamber layer50and nozzle layer60may be formed of different materials.

Referring now toFIG. 1G, the second sacrificial layer172′ is removed in a manner such as those previously described. Upon the removal of sacrificial layer172′, the nozzle layer60is formed having opening62(e.g., an aperture or hole is provided in nozzle layer60to define opening62) defined therein and chamber70is exposed. It is to be understood that the nozzle layer60may be further patterned to define opening62. According to an example embodiment, opening62is formed as a relatively cylindrical aperture through nozzle layer60, and may have a diameter ranging from about 1 micrometer to about 20 micrometers. According to other example embodiments, the diameter of opening62is between approximately 4 and 45 micrometers. It is to be understood that opening62may allow fluid to enter and/or exit the microfluidic chamber70.

It is to be understood thatFIG. 1Galso depicts one embodiment of the microfluidic architecture10.

Referring now toFIGS. 1H through 1M, another embodiment of the method of forming a microfluidic architecture10is depicted. After the etching of the thin film stack30(shown inFIG. 1B), the sacrificial layer172is established on a portion of the seed layer38, the exposed portion of the non-conducting layer37, and the exposed portion of the substrate12.FIG. 1Halso depicts the electrodeposited chamber layer50. In this embodiment, the chamber layer50is established on a portion of the seed layer38, and another portion of the seed layer38is covered by the sacrificial layer172.

FIG. 11depicts the removal of the sacrificial layer172, thereby forming an exposed portion of seed layer38, non-conducting layer37, and substrate12. The removal of the sacrificial layer172forms the chamber70defined by the thin film stack30, the chamber layer50, and the substrate12.

FIG. 1Jdepicts the selective electroplating of the layer54having the predetermined surface property. As depicted, in this embodiment, the layer54conforms to a top surface of chamber layer50, in addition to those areas of the chamber layer50and the seed layer38adjacent the chamber70. It is to be understood that in this embodiment, a portion of the layer54may rest on the seed layer38, in addition to, or in place of the non-conducting layer37.

Together,FIGS. 1K through 1Mdepict the formation of the nozzle layer60and the final microfluidic architecture10.FIG. 1Kdepicts the establishment of the second sacrificial layer172′ having a predetermined pattern,FIG. 1Ldepicts the electroplated nozzle layer60, andFIG. 1Mdepicts the microfluidic architecture10after removal of the second sacrificial layer172′, such that the chamber70is open, and the nozzle layer60has an aperture62defined therein which leads to the chamber70.

Referring now toFIGS. 2A through 2K, another embodiment of the method of forming a microfluidic architecture10is depicted.FIGS. 2A and 2Bare similar toFIGS. 1A and 1Bin that after the non-conducting layer37and the seed layer38are established, they are etched such that portions of the substrate12and the non-conducting layer37are exposed.

FIG. 2Cdepicts the addition of the chamber layer50and the sacrificial layer172. WhileFIG. 2Cdepicts the chamber layer50established on a portion of the seed layer38, the chamber layer50may be established on the entire seed layer38as described hereinabove.

Referring now toFIG. 2D, a second seed layer52may be established on the chamber layer50and the sacrificial layer172. Second seed layer52is adapted or configured to promote adhesion between an overlying nozzle layer60and chamber layer50. According to an example embodiment, seed layer52includes nickel or a nickel alloy. According to other embodiments, seed layer52may include any of the metals or metal alloys described above with respect to chamber layer50. Seed layer52has a thickness ranging from approximately 500 to 1,000 angstroms according to one example embodiment, and a thickness ranging from approximately 500 to 3,600 angstroms (or greater than 3,600 angstroms) according to various other embodiments.

While seed layer52is shown inFIG. 2Das being formed as a single layer of material, according to other example embodiments, such a seed layer52may include more than one layer of material. For example, the seed layer52may be formed of a first layer comprising tantalum followed by a second layer comprising gold. According to such an embodiment, the tantalum may be utilized to promote adhesion of the gold layer to the underlying chamber layer (e.g., chamber layer50).

Referring now toFIG. 2E, a second sacrificial layer/structure164is established on a predetermined portion of second seed layer52using, for example, photolithography masking and deposition methods. It is to be understood that the sacrificial layer164may be provided substantially overlying second seed layer52and patterned to form a sacrificial structure or pattern164. Sacrificial structure164may include a photoresist material, such as a positive or negative photoresist material, and may be provided according to any suitable means (e.g., lamination, spinning, etc.). According to other example embodiments, other sacrificial materials may be used for the sacrificial material, such as tetraethylorthosilicate (TEOS), spin-on-glass, and polysilicon.

Sacrificial layer164may be formed of the same material as used to form sacrificial layer(s)172,172′, or may differ therefrom. This sacrificial layer164is generally patterned such that the subsequently deposited nozzle layer60has an opening62defined therein.

FIG. 2Fdepicts the establishment of the nozzle layer60. In an embodiment, the nozzle layer60is selectively electroplated such that it substantially overlies the second seed layer52in an area not covered by the sacrificial layer164, for example, directly above the chamber layer50. As such, the sacrificial material164acts as a mandrel or mold upon which and/or around which the nozzle layer60may be established.

Referring now toFIG. 2G and 2H, the nozzle opening62and the chamber70are formed. As shown inFIG. 2G, sacrificial layer164is removed to form an aperture62in the nozzle layer60. The sacrificial layer164may be removed by any suitable method, including, but not limited to a solvent develop process, an oxygen plasma, an acid etch, or the like.

As also shown inFIG. 2G, a predetermined portion of second seed layer52underlying aperture62is removed to expose an upper or top surface of sacrificial layer172. Removal of the predetermined portion of seed layer52may be accomplished using a wet or dry etch or other process. In a non-limitative example, the seed layer52is nickel, and a dilute nitric acid etch is utilized to remove the predetermined portion. In another non-limitative example, the seed layer52is gold, and a potassium iodide etch may be utilized to remove the predetermined portion. Any of a variety of etchants may be utilized that are suitable for removal of the portion of second seed layer52(e.g., depending, at least in part, on the composition of the layer52, etc.).

After the top or upper surface of sacrificial layer172is exposed (as shown inFIG. 2G), sacrificial layer172is removed, as shown inFIG. 2H. Removal of sacrificial layer172may be accomplished using a similar method as described herein. As depicted inFIG. 2H, removal of the sacrificial layers164,172results in the formation of chamber70and nozzle aperture62.

Referring now toFIG. 2I, the layer54having the predetermined surface property is established on the nozzle layer60and on those portions of the second seed layer52, the chamber layer50and the seed layer38that are exposed to the chamber70.

The layer54may be selectively electroplated in the interior of the chamber70via the aperture62. It is to be understood that the electroplating process may be performed such that the layer54does not contact the substrate12and comes to rest on the non-conducting layer37.

In an alternate embodiment as depicted inFIGS. 2J and 2K, one or more feed channel(s)15may be formed in the substrate12prior to the establishment of the layer54. The feed channels15may extend from an exterior of the substrate12through to the chamber70. It is to be understood that these feed channels15may be used, in addition to the aperture62, for selectively electroplating the layer54on those areas adjacent the chamber70. Without being bound to any theory, it is believed that the combination of the aperture62and the feed channels15allows for substantially better mass transport of the layer54during the electroplating process.

It is to be further understood that the aperture62and the feed channels15may be used as an ingress and egress for fluids in and out of the chamber70.

Referring now toFIGS. 3A through 3D, four alternate embodiments (formed by the methods previously described) of the microfluidic architecture10are depicted. Each of the embodiments generally includes the substrate12, the thin film stack30, the chamber layer50, the layer54having a predetermined surface property, the nozzle layer60, and nozzle aperture62. It is to be understood that in the embodiments, the chamber70and/or the nozzle aperture62are adapted to contain fluids therein.

The embodiment depicted inFIG. 3Aillustrates the chamber layer50established on substantially the entire seed layer38, such that the layer54is adjacent the top of the chamber layer50and those portions of the chamber layer50and the seed layer38that are exposed to the chamber70. In this embodiment, the layer54may come to rest on the non-conductive layer37, and may not be exposed to the substrate12.

The embodiment depicted inFIG. 3Billustrates the chamber layer50established on a portion of the seed layer38, such that the layer54is again adjacent the top surface of the chamber layer50and those portions of the chamber layer50and the seed layer38that are exposed to the chamber70. In this embodiment, however, the layer54may rest on the seed layer38in addition to, or in place of, the non-conductive layer37. It is to be understood that the layer54may not be exposed to the substrate12.

The embodiment depicted inFIG. 3Cillustrates a second seed layer52established between the chamber layer50and the nozzle layer60. The layer54is electroplated such that it is adjacent the top surface of the nozzle layer60and those portions of the second seed layer52, the chamber layer50and the seed layer38that are exposed to the chamber70. In this embodiment, the layer54may rest on the seed layer38in addition to the non-conductive layer37. It is to be understood that the layer54may not be exposed to the substrate12.

The embodiment depicted inFIG. 3Dillustrates the second seed layer52established between the chamber layer50and the nozzle layer60. The layer54is electroplated such that it is adjacent the top surface of the nozzle layer60and those portions of the second seed layer52, the chamber layer50and the seed layer38that are exposed to the chamber70. In this embodiment, the chamber layer50is established on the entire seed layer38, such that layer54rests on the non-conductive layer37. The layer54may not be exposed to the substrate12.

It is to be understood that the non-conductive layer37electrically isolates the seed layer38from the underlying substrate12or films. Without being bound to any theory, it is believed that the isolation of the seed layer38and the chamber layer50substantially prevents the layer54from plating onto other exposed surfaces of the substrate12.

The microfluidic architectures10depicted inFIGS. 3A through 3Dare capable of being operatively disposed in various devices11, including electronic devices (non-limitative examples of which include fuel injectors (for use in many devices, including but not limited to internal combustion engines), ink-jet printheads, microfluidic biological devices, pharmaceutical devices, and/or the like).

According to an example embodiment, a method or process for producing or manufacturing a printhead (e.g., a thermal ink jet printhead) includes utilizing a sacrificial structure as a mold or mandrel for a metal or metal alloy that is deposited thereon, after which the sacrificial structure is removed. The sacrificial structure defines a chamber and manifold for storing ink and a nozzle in the form of an aperture or opening (e.g., an orifice) through which ink is ejected from the printhead. According to an example embodiment, the metal or metal alloy is formed using a metal deposition process, nonexclusive and nonlimiting examples of which include electrodeposition processes, electroless deposition processes, physical deposition processes (e.g., sputtering), and chemical vapor deposition processes.

One advantageous feature of utilizing metals to form the nozzle and chamber layers of the printhead is that such metals may be relatively resistant to inks (e.g., high solvent content inks) that may degrade or damage structures conventionally formed of polymeric materials and the like. Another advantageous feature is that such metal or metal alloy layers may be subjected to higher operating temperatures than can conventional printheads. For example, polymeric materials used in conventional printheads may begin to degrade at between 70° C. and 80° C. In contrast, metal components will maintain their integrity at much higher temperatures.

FIG. 4is a semi-schematic cross-sectional view of a portion of a microfluidic architecture10, and in particular a thermal ink jet printhead10′ according to an example embodiment. Printhead10′ includes a chamber70that receives ink from ink feed channels15. Ink is ejected from chamber70through an opening62, which in one embodiment is a nozzle, onto a print or recording medium such as paper when printhead10′ is in use.

Printhead10′ includes a substrate12such as a semiconductor or silicon substrate. According to other embodiments, any of a variety of semiconductor materials may be used to form substrate12. For example, a substrate may be made from any of a variety of semiconductor materials, including silicon, silicon-germanium, (or other germanium-containing materials), or the like. The substrate may also be formed of glass (SiO2), according to other embodiments.

A member or element in the form of a resistor14is provided above substrate12. Resistor14is configured to provide heat to ink contained within chamber70such that a portion of the ink vaporizes to form a bubble within chamber70. As the bubble expands, a drop of ink is ejected from opening62. Resistor14may be electrically connected to various components of printhead10′ such that resistor14receives input signals or the like to selectively instruct resistor14to provide heat to chamber70to heat ink contained therein.

According to an example embodiment, resistor14includes WSixNy. According to various other example embodiments, the resistor14may include any of a variety of materials, including, but not limited to TaAl, TaSixNy, and TaAlOx.

A layer of material20(e.g., a protective layer) is provided substantially overlying resistor14. Protective layer20is intended to protect resistor14from damage that may result from cavitation or other adverse effects due to any of a variety of conditions (e.g., corrosion from ink, etc.). According to an example embodiment, protective layer20includes tantalum or a tantalum alloy. According to other example embodiments, protective layer20may be formed of any of a variety of other materials, such as tungsten carbide (WC), tantalum carbide (TaC), and diamond like carbon.

The resistor14may be established by depositing a resistor material on the substrate12and then patterning the material using photolithography and etching. Conductor traces (which connect the resistor14to the drive and firing electronics) may then be established via deposition, patterning, and etching. Further, the resistor protective layer20may then be deposited over the resistor14and conductor traces, and then patterned and etched. It is to be understood that the resistor protective layer20may be composed of a single material or may be a combination of multiple thin film layers.

A plurality of thin film layers30(a non-limitative example of which is thin film stack30described hereinabove) are provided substantially overlying protective layer20. According to the example embodiment shown inFIG. 4, thin film layers30comprise four layers32,34,36, and38. It is to be understood that the thin film layers30may include the non-conducting layer37and the seed layer38as previously described. According to other embodiments, a different number of layers (e.g., greater than four layers, etc.) may be provided. Layers20,32,34,36, and38(FIG. 4) may protect the substrate from inks used during operation of the printhead and/or act as adhesion layers or surface preparation layers for subsequently deposited material. According to other example embodiments, additional layers of material may be provided intermediate or between layer20and substrate12. Such additional layers may be associated with logic and drive electronics and circuitry that are responsible for activating or firing resistor14.

As shown inFIG. 4, layer38is seed layer38(previously described) that may be used as a cathode during electrodeposition of overlying metal layers.

The various layers (e.g., layers32,34,36,38, and any additional layers provided intermediate layer20and substrate12) can include conductors such as gold, copper, titanium, aluminum-copper alloys, and titanium nitride; tetraethylorthosilicate (TEOS) and borophosphosilicate glass (BPSG) layers provided for promoting adhesion between underlying layers and subsequently deposited layers and for insulating underlying metal layers from subsequently deposited metal layers; silicon carbide and SixNyfor protecting circuitry in the printhead10′ from corrosive inks; silicon dioxide, silicon, and/or polysilicon used for creating electronic devices such as transistors and the like; and any of a variety of other materials.

Chamber layer50is provided substantially overlying thin film layers30. It is to be understood that the chamber layer50may be formed of any suitable material and by any suitable process, examples of which are previously described.

In an embodiment, the layer54having a predetermined surface property may be established on the chamber layer50as previously described. In an alternate embodiment, second seed layer52is provided substantially overlying chamber layer50.

Nozzle layer60may be provided substantially overlying chamber layer50and seed layer52, or overlying chamber layer50and layer54. In another embodiment, nozzle layer60is provided substantially overlying chamber layer50and seed layer52and is substantially covered by layer54. According to an example embodiment, nozzle layer60has a thickness of between approximately 5 and 100 micrometers. According to other example embodiments, nozzle layer60has a thickness ranging between approximately 1 and 30 micrometers.

FIGS. 5A through 5Gare semi-schematic cross-sectional views of a portion of a thermal ink jet printhead10′ similar to that shown inFIG. 5showing the steps of a manufacturing process according to an example embodiment.

As shown inFIG. 5A, a thin film layer130is provided above a substratum112. Thin film layer130may be similar to thin film layer30shown inFIG. 4, and may include a seed layer and any of a number of additional thin film layers such as those described with respect toFIG. 4. Thin film layer130is provided substantially overlying a resistor and protective layer (not shown) such as that shown inFIG. 4as resistor14and protective layer20, as are known in the art.

While thin film layer130is shown as a continuous layer, a portion of thin film layer130may be removed above the resistor, as shown in the example embodiment shown inFIG. 4. Removal of a portion of thin film layer130may occur either before or after the processing steps shown inFIGS. 5A through 5G. For example, where such a portion is removed before the processing steps described inFIGS. 5A through 5G, photoresist material may fill the removed portion during processing prior to its subsequent removal to form a chamber and nozzle such as chamber70and opening62such as those shown inFIG. 4. It should also be noted that the removal of a portion of similar thin film layers230and330may be performed before or after the process steps shown and described with respect toFIGS. 6A-6Eand7A-7D, respectively. For simplicity, each of the embodiments shown andFIGS. 5A-5G,6A-6E and7A-7D will be described as if removal of a portion of the film layers130,230and330occurs after the formation of the chamber and nozzle.

As shown inFIG. 5A, a sacrificial material is provided substantially overlying thin film layer130and patterned to form a sacrificial structure or pattern172. Sacrificial structure172may comprise a photoresist material, such as a positive or negative photoresist material, and may be provided according to any suitable means (e.g., lamination, spinning, etc.). According to one example embodiment, the sacrificial material used to form sacrificial structure172is a positive photoresist material such as SPR 220, commercially available from Rohm and Haas of Philadelphia, Pa. According to another example embodiment, the sacrificial material is a negative photoresist material such as a THB 151N material commercially available from JSR Micro of Sunnyvale, Calif. or an SU8photoresist material available from MicroChem Corporation of Newton, Mass.

According to other example embodiments, other sacrificial materials may be used for the sacrificial material, such as tetraethylorthosilicate (TEOS), spin-on-glass, and polysilicon. One advantageous feature of utilizing a photoresist material is that such material may be relatively easily patterned to form a desired shape. For example, according to an example process, a layer of photoresist material may be deposited or provided substantially overlying thin film layer130and subsequently exposed to radiation (e.g., ultraviolet (UV) light) to alter (e.g., solubize or polymerize) a portion of the photoresist material. Subsequent removal of exposed or nonexposed portions of the photoresist material (e.g., depending on the type of photoresist material utilized) will result in a relatively precise pattern of material.

Subsequent to the formation or patterning of sacrificial structure172, a layer150of metal is provided inFIG. 5Bsubstantially overlying thin film layer130in areas not covered by sacrificial structure172. In this manner, sacrificial structure172acts as a mandrel or mold around which metal may be deposited. Sacrificial structure172also acts to mask a portion of the underlying layers from having metal of layer150provided therein. While layer150is shown as being deposited such that its top surface is substantially planar with the top surface of sacrificial structure172, layer150may be deposited to a level higher than the top surface of sacrificial structure172and polished or etched such that it is coplanar with the top surface of sacrificial structure172.

According to an example embodiment, layer150is intended for use as a chamber layer such as chamber layer50shown inFIG. 4. Accordingly, layer150may be formed from any of a variety of metals and metal alloys such as those described above with respect to chamber layer50. For example, according to one example embodiment, layer150comprises nickel or a nickel alloy. One method by which nickel may be provided for layer150(or for any other layer described herein which may include nickel) is the use of a Watts bath containing nickel sulphate, nickel chloride and boric acid in aqueous solution with organic additives (e.g., saccharine, aromatic sulphonic acids, sulfonamides, sulphonimides, etc.).

Layer150is deposited using an electrodeposition process according to an example embodiment. According to one example embodiment, layer150is deposited in a direct current (DC) electrodeposition process using Watts nickel chemistry. In such an embodiment, electrodeposition is conducted in a cup style plating apparatus. According to other embodiments, electrodeposition can be carried out in a bath style plating apparatus. The Watts nickel chemistry is composed of nickel metal, nickel sulfate, nickel chloride, boric acid and other additives that have a compositional range from 1 milligrams per liter to 200 grams per liter for each component.

According to the example embodiment, a resist pattern is first prepared on the wafer surface (which may include any of a variety of thin film layers such as layers32,34,36, and38shown inFIG. 4), after which the wafer is prepared for deposition by dipping for 30 seconds in sulfuric acid. Other acids or cleaning techniques such as plasma etching or UV ozone cleaning may be utilized in other embodiments. The wafer is then placed in the plating apparatus and electrodeposition begins by setting the DC power source to plate at a current density of approximately 3 amperes per square decimeter (amps/dm2). In other embodiments, electrodeposition can utilize a current density range of between approximately 0.1 to 10° amps/dm2 depending on the plating chemistry used and the desired plating rates (higher current densities can result in higher plating rates). These conditions can be used for deposition of the chamber and nozzle layers described with respect to the embodiment shown inFIGS. 5A-5Fand in either of the embodiments illustrated inFIGS. 6A-6EandFIGS. 7A-7D.

According to another example embodiment, layer150may be provided in an electroless deposition process or any other process by which metal may be deposited onto thin film layer130(e.g., physical vapor deposition techniques such as a sputter coating, chemical vapor deposition techniques, etc.).

As shown inFIG. 5C, a layer of metal152(e.g., a seed layer) is provided substantially overlying both sacrificial structure172and layer150. According to another example embodiment, layer152may be omitted. Layer152may be formed of similar materials as described with respect to layer52with regard toFIG. 4. Layer152may be deposited in any suitable process (e.g., physical vapor deposition, evaporation, electroless deposition, etc.). As described above with respect to layer52, layer152may comprise a single layer of material or multiple layers of material (e.g., a first layer comprising tantalum and a second layer comprising gold, etc.).

InFIG. 5D, sacrificial structure164is provided substantially overlying layer152and aligned with sacrificial structure172using conventional photolithography masking and deposition methods. Sacrificial structure164may be formed of the same material as used to form sacrificial structure172, or may differ therefrom. As with sacrificial structure172, sacrificial structure164is formed by photolithographic methods from a layer of sacrificial material (e.g., positive or negative photoresist, etc.).

InFIG. 5E, a layer160of metal (similar to that provided as nozzle layer60inFIG. 4) is provided substantially overlying layer152in areas not covered by sacrificial structure164. Layer160may be formed of a material similar to that used for nozzle layer60described with respect toFIG. 4.

A chamber170and nozzle162are formed as shown inFIGS. 5F and 5G. As shown inFIG. 5F, sacrificial structure164is removed to form a nozzle162. According to an example embodiment, sacrificial structure164is removed using any of a variety of methods. For example, sacrificial structure164may be removed with a solvent develop process, an oxygen plasma, an acid etch, or any of a variety of other processes suitable for removal of sacrificial structure164.

As also shown inFIG. 5F, a portion of layer152underlying nozzle162is removed to expose an upper or top surface of sacrificial structure172. Removal of the portion of layer152may be accomplished using a wet or dry etch or other process. According to an example embodiment in which layer152is formed of nickel or a nickel alloy, a dilute nitric acid etch may be utilized. According to another example embodiment in which gold or a gold alloy is used to form layer152, a potassium iodide etch may be utilized. Any of a variety of etchants may be utilized that are suitable for removal of the portion of layer152(e.g., depending on the composition of layer152, etc.). One consideration that may be utilized in choosing an appropriate etchant is the goal of avoiding damage to the metal utilized to form layers150and160.

After the top or upper surface of sacrificial structure172is exposed (as shown inFIG. 5F), sacrificial structure172is removed as shown inFIG. 5G. Removal of sacrificial structure172may be accomplished using a similar method as described above with respect to sacrificial structure164.

As shown inFIG. 5G, removal of sacrificial structures164and172and etching of a portion of layer152results in a structure including a chamber170for storage of ink for printhead100and a nozzle162for ejection of ink from chamber170. WhileFIG. 5Gshows chamber170provided substantially overlying thin film layers130, all or a portion of thin film layers130underlying chamber170may be removed in a subsequent etching step. According to another example embodiment, thin film layers130may be etched prior to deposition of sacrificial structures172and164. Other components of printhead100may also be formed prior to or after the formation steps described with respect toFIGS. 5A through 5G. For example, one or more ink feed channels15may be formed to provide ink to chamber170prior or subsequent to the formation of the structure shown inFIG. 5G.

FIGS. 6A through 6Eare semi-schematic cross-sectional views of a portion of a thermal ink jet printhead200similar to that shown inFIG. 4showing the steps of a manufacturing process according to another example embodiment. In contrast to the example embodiment described with respect toFIGS. 5A through 5G, the example embodiment shown inFIGS. 6A through 6Eutilizes a sacrificial structure that is formed prior to metal deposition used to form a chamber layer and a nozzle layer. In this embodiment, a metal layer such as a seed layer152(see, e.g.,FIGS. 5A through 5F) is not required between a chamber layer and a nozzle layer.

As shown inFIG. 6A, a first layer of sacrificial material is provided or formed substantially overlying a thin film layer230similar to that described above with respect to thin film layer130. Once deposited, the first layer of sacrificial material will be patterned to define regions to be removed and regions to remain (i.e., that will be used to form a portion of a sacrificial structure). According to an example embodiment in which a negative photoresist material is provided substantially overlying thin film layer230, the photoresist material is patterned by exposing the photoresist material to radiation such as ultraviolet light to form exposed portion272and unexposed portions273. In this embodiment, exposed portions272polymerize in response to the exposure to ultraviolet light, and will act as a portion of a sacrificial structure to be used in the formation of a chamber and nozzle (seeFIG. 6E). According to another embodiment, in which a positive photoresist is utilized, portion272may be unexposed and portions273may be exposed to ultraviolet light.

A second layer of sacrificial material is provided substantially overlying the first layer of sacrificial material and patterned to define at least one portion or region to be removed and to define a portion or region that will remain to form another portion of a sacrificial structure. Patterning may be accomplished in a manner similar to that described with reference to the first layer of sacrificial material, such as by exposing a portion of the second layer of sacrificial material to radiation such as ultraviolet light. In this manner, an exposed portion264and an unexposed portion265(or vice-versa where a positive photoresist material is utilized) is formed in the second layer of sacrificial material.

Subsequent to the exposure of portions of the first and second layers of sacrificial material, portions of each of the first and second layers are removed to form a sacrificial structure that may be used to define a chamber and nozzle for the printhead. InFIG. 6C, portions273and265are removed according to an example embodiment. The removal of portions of the photoresist results in the formation of a sacrificial structure266having a top or upper portion264to be used in the formation of a nozzle for printhead200and a bottom or lower portion272to be used in the formation of an ink chamber and ink manifold for printhead200.

According to an example embodiment, the first and second layers of sacrificial materials used to form portions264and272are formed of the same material and are deposited in two separate deposition steps. In another example, the first and second layers of sacrificial materials are formed of a single layer of material formed in a single deposition step. In yet another example, the first and second layers of sacrificial materials used to form portions264and272are formed of different materials (e.g., a positive photoresist for one layer and a negative photoresist for the other layer).

As shown inFIG. 6D, a layer250of metal is provided or deposited substantially overlying the thin film layer230and adjacent to portions264and272of sacrificial structure266. According to an example embodiment, metal used to form layer250may be material similar to that described with respect to chamber layer50and nozzle layer60described with regard toFIG. 4. Metal used to form layer250may be provided using any acceptable deposition method, including electrodeposition, electroless deposition, physical vapor deposition, chemical vapor deposition, etc. According to an example embodiment in which the metal used to form layer250is deposited in a direct current electrodeposition (DC) process, the metal is provided such that it is level or slightly below the level of the top or upper surface of portion264of the sacrificial structure266. As shown inFIG. 6D, the metal used to form layer250increases in thickness at distances away from portion264. One reason for this is that as layer250thickens beyond the height of portion272, the metal is deposited both vertically and laterally on top of portion272, thus slowing the vertical deposition rate in the vicinity of portion272. Once the lateral deposition of layer250stops, the deposition rate of layer250is the same everywhere (including substantially overlying portion272and adjacent portion264).

As shown inFIG. 6E, sacrificial structure266is removed after layer250is provided. Removal of sacrificial structure266may be accomplished using methods similar to those described above with respect to sacrificial structures164and172. As described above with respect toFIGS. 5A through 5F, other processing steps may be utilized either prior or subsequent to the formation of the structure shown inFIG. 6E.

According to an example embodiment, the top or upper surface of metal layer250may be planarized using a chemical mechanical polish technique or other similar technique. One advantageous feature of performing such a planarization step is that the entire surface of printhead200will have a relatively flat or planar characteristic around the nozzle.

FIGS. 7A to 7Dare semi-schematic cross-sectional views of a portion of a printhead300similar to that shown inFIG. 4showing the steps of a manufacturing process according to another example embodiment. Similar to the embodiment shown with respect toFIGS. 6A to 6E, one feature of the embodiment shown inFIGS. 7A to 7Dis the formation of an entire sacrificial structure prior to the deposition of metal used to form a printhead structure.

As shown inFIG. 7A, a sacrificial structure366having a top or upper portion364and a bottom or lower portion372is formed substantially overlying a thin film layer330. As with structures264and272described above with respect toFIGS. 6A to 6E, top portion364is utilized to form a nozzle and bottom portion372is utilized to form an ink chamber or ink manifold. The sacrificial structure366may be formed in a manner similar to that described above with respect toFIGS. 6A to 6E(i.e., utilizing the successive deposition, patterning and removal of a portion of two separate photoresist layers).

As also shown inFIG. 7A, a layer390of metal is provided substantially overlying the sacrificial structure366and the surface of thin film layers330not covered by sacrificial structure366. Any of a variety of deposition methods may be used to form layer390, including physical vapor deposition, evaporation, chemical vapor deposition, electrodeposition, electroless deposition, autocatalytic plating, etc. Layer390is intended to act as a seed layer for overlying metal layers used to form the printhead structure. According to an example embodiment, layer390may have a thickness of between approximately 500 and 3,000 angstroms. According to other example embodiments, layer390may have a thickness of between 500 angstroms and 2 micrometers.

Layer390may include a relatively inert metal such as gold, platinum and/or gold and platinum alloys. According to other embodiments, layer390may include palladium, ruthenium, tantalum, tantalum alloys, chromium and/or chromium alloys.

As shown inFIG. 7B, a layer350of metal is provided or deposited substantially overlying layer390(i.e., substantially overlying and around sacrificial structure366and substantially overlying portions of thin film layers330not covered by sacrificial structure366). The material used to form layer350may be similar to that used to form chamber layer50and the nozzle layer60as shown inFIG. 4. As shown inFIG. 7B, a portion of the metal used to form layer350extends substantially overlying a top surface of a top portion364of sacrificial structure366.

According to an example embodiment shown inFIG. 7C, a planarization process is used to planarize the top surface of layer350and sacrificial structure366. According to an example embodiment, a chemical mechanical polish technique is utilized to planarize the top surface of layer350and sacrificial structure366.

Sacrificial structure366is removed as shown inFIG. 7Dusing methods similar to those described above with respect to sacrificial structure266. The result is the formation of a chamber370and a nozzle362similar to chamber70and opening62shown inFIG. 4. As described above, additional processing steps may be performed prior or subsequent to the formation of the structure shown inFIG. 7D.

As an optional step (not shown), a layer of metal similar or identical to that used to form layer390may be provided substantially overlying a top surface of layer350. One advantageous feature of such a configuration is that layer350may be effectively encapsulated or clad to prevent damage from inks or other liquids. In this manner, relatively inert metals (e.g., gold, platinum, etc.) may be utilized to form the wall or surface that is in contact with ink used by the printhead, while a relatively less expensive material (e.g., nickel) may be used as a “filler” material to form the structure for the chamber and nozzle.

FIGS. 8 through 11are scanning electron micrographs illustrating the formation of ink jet printhead chambers according to example embodiments.FIG. 8shows a chamber level sacrificial structure formed of a positive photoresist, magnified at 500 times.FIG. 9shows a similar chamber level sacrificial structure formed from a negative photoresist material magnified at 1,000 times.FIGS. 10 and 11show the formation of chambers subsequent to the removal of the sacrificial photoresist structures shown inFIGS. 8 and 9, respectively.FIG. 8illustrates the initial shape of the resist mandrel created from the SPR220 resist. The shape of the walls of the plated material inFIG. 10conforms to the initial shape of the plating resist shown inFIG. 8.FIGS. 9 and 11show that nickel plated around the JSR THB 151N resist also conforms well to the resist shape.FIGS. 10 and 11also illustrate that it is possible to deposit structures that have a relatively flat or planar surface.

FIG. 12is a scanning electron micrograph illustrating the formation of a microfluidic architecture having the layer54thereon. As shown, the layer54conforms to the chamber layer50and the nozzle layer60, and comes to rest on seed layer38. As depicted, the layer54does not contact the substrate12.

It is to be understood that any of the various embodiments disclosed herein may include the layer54having the predetermined surface characteristic. It is to be further understood that the layer54may be positioned on the chamber layer50(also depicted as150,250,350), the nozzle layer60(also depicted as160), and/or those areas/elements (generally excluding the substrate12) that are adjacent the microfluidic chamber70(also depicted as170,370).

The embodiment(s) disclosed offer many advantages, including, but not limited to the following. The selective electroplating of the layer54having a predetermined property and the chamber layer50allow the cost of manufacturing to be relatively inexpensive while maintaining the desired surface integrity of the architecture10. Further, a variety of materials may be selected for the various architecture elements (e.g. layer54, chamber layer50, nozzle60), as they are established individually. Still further, embodiment(s) of the microfluidic architecture(s)10described herein are advantageously suitable for use in a variety of devices, such as for example, ink-jet printheads, fuel injectors, microfluidic biological devices, pharmaceutical dispensing devices, and/or the like.