Patent Application
20080007595
Further advantages of the exemplary embodiments will become apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale, wherein like reference members indicate like elements through the several views, and wherein:
With reference to
In the prior art micro-fluid ejection head 10, a nozzle plate 16 is attached as by an adhesive 18 to a device surface 20 of the substrate 12. In such a micro-fluid ejection head 10, the nozzle plate 16 may be made out of a laser ablated material such as polyimide. The polyimide material is laser ablated to provide a fluid chamber 22 in fluid flow communication with a fluid flow channel 24. Upon activation of the ejector actuator 14, fluid is expelled through a nozzle 26 that is also laser ablated in the polyimide material of the nozzle plate 16. The fluid chamber 22 and fluid flow channel 24 in this embodiment are collectively referred to as “flow features.” A fluid feed slot 28 is formed in the substrate 12, for example, by wet etching, dry etching, laser ablation, grit blasting, and the like, to provide fluid from a fluid reservoir that is in fluid flow communication with the ejection head 10. Fluid provided from the reservoir flows via the fluid flow channel 24 to the fluid chamber 22.
In order to provide the laser ablated nozzle plate 16, the polyimide material is laser ablated from a flow feature side 30 thereof, as shown in
It will be appreciated that the nozzle plate 16 contains a plurality of flow features (22 and 24) laser ablated therein and corresponding to a plurality of ejector actuators 14 as illustrated in plan view in
Another prior art micro-fluid ejection head 34 is illustrated in
A process for making the nozzles 44 in nozzle plate 42 is illustrated in
In order to, for example, improve alignment between nozzles, flow features and/or fluid ejection actuators in a micro-fluid ejection head, an improved micro-fluid ejection head manufacturing process may be used. In such a process, described in more detail below, nozzles in a nozzle plate may be formed after attaching the nozzle plate to a thick film layer using a unique etching process.
Processes for making a micro-fluid ejection head according to the disclosure will now be described with reference to
Next a photoresist material is applied adjacent (e.g., to) the device surface 20 of the substrate 12 to provide a thick film layer 50. In order to apply the photoresist to the device surface 20 of the substrate 12, a substrate wafer may be centered on an appropriate sized chuck of, for example, either a resist spinner or conventional wafer resist deposition track. The photoresist material may be dispensed by hand or mechanically into the center of the wafer, for example. The chuck holding the wafer may then be rotated at a predetermined number of revolutions per minute to evenly spread the mixture from the center of the wafer to the edge of the wafer. The rotational speed of the wafer may be adjusted or the viscosity of the coating mixture may be altered to vary the resulting resin film thickness. Rotational speeds of 2500 rpm or more may be used. The amount of photoresist material applied to device surface 20 should be sufficient to provide the thick film layer 50 having the desired thickness for flow features imaged therein. Accordingly, the thickness of layer 50 after curing may range from about 10 to about 25 microns or more. Other methods that may be used to apply the thick film layer 50 to the substrate 12 include lamination processes, spray coating, blade coating, roll coating, and the like.
A photoresist formulation that may provide the thick film layer 50 may include a difunctional epoxy component, a photoacid generator, a non-reactive solvent, and, optionally, an adhesion enhancing agent. Another photoresist formulation that may be used may include a multi-functional epoxy compound, a difunctional epoxy compound, a photoacid generator, a non-reactive solvent, and, optionally, an adhesion enhancing agent.
In the foregoing photoresist formulations, the difunctional epoxy component may be selected from difunctional epoxy compounds which include diglycidyl ethers of bisphenol-A (e.g. those available under the trade designations “EPOON 1007F”, “P7N1007” and “EPON 1009F”, available from Shell Chemical Company of Houston, Tex. , “DDER-331”, “DER-332”, and “DER-334”, available from Dow Chemical Company of Midland, Mich., 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexene carboxylate (e.g “ERL-4221” available from Union Carbide Corporation of Danbury, Connecticut, 3,4-epoxy-6-methylcyclohexyl methyl-3,4-epoxy-6-methylcyl-clohexene carboxylate (e.g. “ERL-4201” available from Union Carbide Corporation), bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate (e.g. “ERL-4289” available from Union Carbide Corporation) and bis(2,3-epoxycyclopentyl)ether (e.g. “ERL-0400” available from Union Carbide Corporation).
A particularly suitable difunctional epoxy component is a bisphenol-A/epichlorohydrin epoxy resin available from Shell Chemical Company of Houston, Tex. under the trade name EPON resin 1007F having an epoxide equivalent of greater than about 1000 An “epoxide equivalent” is the number of grams of resin containing I gram-equivalent of epoxide. The weight average molecular weight of the difunctional epoxy component is typically above 2500, e.g., from about 2800 to about 3500 weight average molecular weight in Daltons. The amount of difunctional epoxy component in the photoresist formulation may range from about 30 to about 95 percent by weight based on the weight of the cured resin.
A photoacid generator may also be included in the photoresist formulation. The photoacid generator may be selected from a compound or mixture of compounds capable of generating a cation such as an aromatic complex salt which may be selected from onium salts of a Group VA element, onium salts of a Group VIA element, and aromatic halonium salts. Aromatic complex salts, upon being exposed to ultraviolet radiation or electron beam irradiation, are capable of generating acid moieties which initiate reactions with epoxides. The photoacid generator may be present in the photoresist formulation in an amount ranging from about 0.5 to about 15 weight percent based on the weight of the cured resin.
Examples of aryl-substituted onium complex salt photoinitiators which may be used in the formulations according to the first embodiment include, but are not limited to:
triphenylsulfonium tetrafluoroborate,
triphenylsulfonium hexafluorophosphate,
triphenylsulfonium hexafluoroantimonate,
tritolysulfonium hexafluorophosphate,
anisyldiphenylsulfonium hexafluoroantimonate,
4-butoxyphenyidiphenylsulfonium tetrafluoroborate,
4-chlorophenyidiphenylsulfonium hexafluoroantimonate,
4-acetoxy-phenyldiphenylsulfonium tetrafluoroborate,
4-acetamidophlenyldiphenylsulfonium tetrafluoroborate,
diphenyliodonium trifluoromethanesuIfonate,
(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,
diphenyliodonium p-toluenesulfonate,
(p-tert-butoxyphenyl)-phenyliodonium p-toluenesulfonate,
bis(4-tert-butylphenyl)iodonium hexafluorophosphate, and
diphenyliodonium hexafluoroantimonate.
Of the triaryl-substituted sulfonium complex salts which are suitable for use in the formulations of the first embodiment, a particularly useful salt may be a mixture of triarylsulfonium hexafluoroantimonate salt, commercially available from Union Carbide Corporation under the trade name CYRACURE UVI-6974. A particularly suitable iodonium salt for use as a photoacid generator for the photoresist formulations described herein may be a mixture of diaryliodonium hexafluoroantimonate salts, commercially available from Sartomer Company, Inc. of Exton, Pa. under the trade name SARCAT CD 1012.
As set forth above, another photoresist formulation that may be used contains the multifunctional epoxy component. A suitable multifunctional epoxy component for making the photoresist formulation may be selected from aromatic epoxides such as glycidyl ethers of polyphenols. A particularly useful multifunctional epoxy resin may be a polyglycidyl ether of a phenolformaldehyde novolac resin, such as a novolac epoxy resin having an epoxide gram equivalent weight ranging from about 190 to about 250 and a viscosity at 130° C. ranging from about 10 to about 60 poise, which is available from Resolution Performance Products of Houston, Tex. under the trade name EPON RESIN SU-8.
When present in a photoresist formulation, the multi-functional epoxy component may have a weight average molecular weight of from about 3,000 to about 5,000 as determined by gel permeation chromatography, and an average epoxide group functionality of greater than 3, such as from about 6 to about 10. The amount of multifunctional epoxy resin in the photoresist formulation may range from about 30 to about 50 percent by weight based on the weight of the cured thick film layer 50
The photoresist formulations described herein may optionally include an effective amount of an adhesion enhancing agent such as a silane compound. Silane compounds that are compatible with the components of the photoresist formulation typically have a functional group capable of reacting with at least one member selected from the group consisting of the multifunctional epoxy compound, the difunctional epoxy compound and the photoinitiator. Such an adhesion enhancing agent may be a silane with an epoxide functional group such as a glycidoxyalkyltrialkoxysilane, e.g., gamma-glycidoxypropyltrimethoxysilane. When used, the adhesion enhancing agent may be present in an amount ranging from about 0.5 to about 5 weight percent, such as from about 0.9 to about 4.5 weight percent based on total weight of the cured resin, including all ranges subsumed therein. Adhesion enhancing agents, as used herein, are defined to mean organic materials soluble in the photoresist composition which assist the film forming and adhesion characteristics of the thick film layer 50.
In order to provide the thick film layer 50 on, for example, the device surface 20 of the substrate 12 (
Once the thick film layer 50 is spin coated onto the substrate wafer, the resulting substrate wafer having the thick film layer 50 is then removed from the chuck, manually or mechanically, and placed on a temperature controlled hotplate or in a temperature controlled oven at a temperature of about 90° C. for about 30 seconds to about 1 minute until the material is “soft” baked. This step can be used to remove at least a portion of the solvent from the thick film layer 50, resulting in a partially dried film. The wafer may be removed from the heat source and allowed to cool to room temperature.
According to an exemplary embodiments prior to imaging and developing the thick film layer 50, the fluid feed slot 28 is formed in the substrate, such as by an etching process. An exemplary etching process is a dry etch process such as deep reactive ion etching or inductively coupled plasma etching. During the etching process, the thick film layer 50 may act as an etch stop layer.
In order to define flow features in the thick film layer 50, such as a fluid chamber 52 and fluid flow channel 54 (
In
The foregoing procedure is similar to a standard semiconductor lithographic process. The mask 56 may be a clear, flat substrate (usually glass or quartz) with opaque areas 60 defining the areas to be removed from the layer 50 (ie. a negative acting photoresist layer 50). The opaque areas 60 prevent the ultraviolet light from cross-linking the layer 50 masked beneath it. The exposed areas of the layer 50 provided by the substantially transparent areas 58 of the mask 56 are subsequently baked at a temperature of about 90° C. for about 30 seconds to about 10 minutes, such as from about 1 to about 5 minutes, to complete the curing of the thick film layer 50.
The non-imaged areas of the thick film layer 50 are then solubilized by a developer and the solubilized material is removed, leaving the imaged and developed thick film layer 50, as shown in
With reference now to
An exemplary process for etching the nozzle plate 64 according to the disclosure is illustrated in
As in the process used to define the flow features (22 and 24) in the thick film layer 50, a mask 68 containing transparent areas 70 and opaque areas 73 may be used to define the location for nozzles in the nozzle plate 64. The procedures for imaging the photoresist layer 66 are similar to the procedures described above with respect to imaging the thick film layer 50 and thus will not be repeated.
However, after imaging the photoresist layer 66, developing of the imaged photoresist layer 66 is omitted. Instead, a step of silylating the photoresist layer is conducted, as illustrated in
Silylation of the portion of the photoresist layer 66 provides a silicon containing film-resist matrix specific only to exposed areas 74 and 76 of the photoresist layer 66 as provided by mask 68 (
Since the substrate 12 having the thick film layer 50, nozzle plate 66, and photoresist layer 66 is already in the etching chamber, organic etchants 80 containing oxidizing chemistries may next be introduced into the etching chamber as shown in
Once the nozzle 82 is formed, the substrate 12 having the thick film layer 66, newly etched nozzle plate 64 and photoresist layer 66 may be exposed to a developing solvent which is effective to remove the photoresist layer 66 containing the silylated portion 72 from the nozzle plate 64. A resulting micro-fluid ejection head 84 is illustrated in
In an exemplary alternative process, a negative photoresist material may be used in place of positive photoresist material 66. In that case, the mask 68 has opaque areas 70 and transparent area 73. Only the masked areas 74 and 76 of the negative photoresist material are silylated while area 78 remains unsilylated as before. Formation of nozzles 82 may then proceed as in
In yet another alternative process a reverse acting positive photoresist material may be used. In this process the same mask as describe above with respect to the negative photoresist material may be used to provide masked areas 74 and 76 and unmasked area 78. After baking to cross-link the unmasked area 78, the photoresist material is silylated to provide areas 74 and 76 that are silylated and area 78 that remains unsilylated. Formation of the nozzles using the reverse acting positive photoresist material may then proceed as described above.
Another alternative process that may be used includes the use of an electron-beam photoresist material 90. A portion of a process for using an electron-beam photoresist material is illustrated in
After fabricating the micro-fluid ejection head structure 110, the micro-fluid ejection head 110 may be attached to a fluid supply reservoir 112 as illustrated in
It is contemplated and will be apparent to those skilled in the art from the preceding description and the accompanying drawings that modifications and/or changes may be made in the embodiments of the disclosure Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of exemplary embodiments only, not limiting thereto and that the true spirit and scope of the present disclosure be determined by reference to the appended claims.
