KR101012210B1 - Multiple barrier layers - Google Patents

Abstract

A fluid ejection device (103) comprises a substrate (115) having a first surface; a fluid ejector (201) formed over the first surface; and a cover layer (124) defining a firing chamber (202) formed about the gluid ejector, and defining a nozzle (105) over the firing chamger. The cover layer is formed by at least two SU8 layers.

Description

Multiple barrier layers {PLURALITY OF BARRIER LAYERS}

The present invention relates to a fluid ejection device, and more particularly to a plurality of barrier layers inside the fluid ejection device.

Various inkjet print equipments are known in the art, and such print equipments include both thermally actuated printer heads and mechanically operated printer heads. Thermally actuated printer heads tend to use resistive elements or the like for ejecting ink, while mechanically actuated printer heads tend to be piezoelectric transducers or the like. There is a tendency to use elements.

Representative thermal inkjet printer heads have a plurality of thin film resistors installed on a semiconductor substrate. The barrier layer is deposited over the thin film layer on the substrate. The barrier layer defines a firing chamber for each resistor, a hole corresponding to each resistor and an inlet or fluid channel for each firing chamber. Frequently, ink enters a slot in a substrate and flows into the firing chamber through a fluid channel defined by a nozzle layer. The operation of the exothermic resistor by the "fire signal" heats the ink in the firing chamber corresponding to the resistor and causes the ink to be discharged through the hole corresponding to the resistor.

Continuous adhesion between the nozzle layer and the thin film layer is required. In the case of a print head substrate die, undesirable deformation (eg, nozzle layer cracking) may occur due to mechanical or thermal stresses, especially when the print head substrate die is relatively large or the aspect ratio is high. For example, nozzle layers often have different coefficients of thermal expansion than semiconductor substrates. Thermal stress can cause cracks in the nozzle layer or other thin film layers, which in turn can lead to ink leakage and / or electrical shorts. As a further example, cracks may occur when the die on the assembled wafer is separated. As a further and / or modified example, the nozzle layer may be stressed due to structural adhesive shrinkage that occurs during shrinkage after curing, attachment of the nozzle layer, adjustment of the device, and thermal cycling of the fluid ejection device. have.

summary
The fluid ejection device comprises a substrate having a first surface; A fluid ejector formed on the first surface; And a cover layer defining a firing chamber formed for the fluid ejector and a nozzle on the firing chamber. The cover layer is formed by at least two SU8 layers.
1 is a perspective view of one embodiment of a cartridge 101 that includes a fluid ejection device 103, such as a print head. The cartridge stores a fluid reservoir, such as ink. What is visible on the outer surface of the print head are a number of holes or nozzles through which the fluid is selectively ejected. According to one embodiment, the fluid is ejected at the command of a printer (not shown) in communication with the print head via electrical connection 107.

2 is a cross-sectional view of the printer head 103 of FIG. 1, showing a cross section with a slot 110 formed through the substrate 115. Examples of methods used to form slots through slot regions (or slot areas) in a substrate include wet etching, dry etching, deep reactive ion etching (DRIE), and ultraviolet laser processing.

According to one embodiment, the substrate 115 is silicon. In various embodiments, the substrate is comprised of any one of monocrystalline silicon, polycrystalline silicon, gallium arsenide, glass, silica, ceramic, or semiconductor material. The various materials listed as possible substrate materials do not necessarily have to be compatible and are selected depending on the application in which the materials are used.

According to the embodiment of FIG. 2, a thin film stack 116 (such as an active layer, an electrically conductive layer and layers related to microelectronics) is the front of the substrate 115. Or formed or deposited on the first side (or surface). According to one embodiment, the thin film stack 116 includes a capping layer 117 formed on the first surface of the substrate. The capping layer 117 may be formed of various materials such as, for example, a field oxide layer, silicon dioxide, aluminum oxide, silicon carbide, silicon nitride, and glass (PSG). In this embodiment, layer 119 is deposited or grown on capping layer 117. According to a detailed embodiment, layer 119 is one of titanium nitride, titanium tungsten, titanium, titanium alloys, metal nitride, tantalum aluminum and aluminum silicon.

In this embodiment, conductive layer 121 is formed by depositing a conductive material on layer 119. The conductive material is variously formed from at least one of several materials including aluminum, aluminum with about 50% copper, copper, gold and aluminum with 20% silicon, and can be deposited by, for example, sputtering and evaporation. have. Conductive layer 121 is patterned and etched to form conductive traces. After forming the conductive traces, a resistive material 125 is deposited on the etched conductive material 121. The resistive material is etched to form the ejection portion 201 such as, for example, a fluid ejector, a resistor, a heating portion and a bubble generator. Suitable resistive materials are variously known to those skilled in the art, including tantalum aluminum, nickel chromium, tungsten nitride and titanium nitride, and resistive materials are optionally doped with impurities such as oxygen, nitrogen and carbon to adjust the resistivity. can do.

As shown in the embodiment of FIG. 2, the thin film stack 116 further includes an insulating passivation layer 127 formed on the resistive material. The protective layer 127 may be formed of a suitable material such as, for example, silicon dioxide, aluminum oxide, silicon carbide, silicon nitride, and glass. In this embodiment, a cavitation layer 129 is added on the protective layer 127. According to a detailed embodiment, the cavitation layer is tantalum.

According to one embodiment, a cover layer 124, such as, for example, a barrier layer, is deposited on thin film stack 116, more particularly cavitation layer 129. According to one embodiment, the cover layer 124 is for example a photosensitive epoxy (SU8 developed by IBM), a fast crosslinked polymer such as a photosensitive polymer, or a photosensitive silicon dielectric such as SINR-3010 manufactured by ShinEtsu ^™ , for example Polyset Co. Inc. epoxy siloxanes such as PCX30 manufactured by Mechanicsville, NY. According to another embodiment the cover layer 124 is made of a mixture of organic polymers that are sufficiently inert to the corrosive action of the ink. Suitable polymers for this purpose include EI DuPont de Nemours and Co. Some products are sold under the trademark "VACREL and RISTON" manufactured by of Wilmington, Del.

An example of the physical arrangement of the cover layer and the basic structure of the thin film is described on page 44 of the February 1994 Hewlett-Packard Journal. Examples of printer heads are described in commonly assigned US Pat. Nos. 4,719,477, 5,317,346, and 6,162,589. Embodiments of the invention include examples having any type and any number of layers formed or deposited on a substrate, depending on the application.

According to a detailed embodiment, the cover layer 124 defines a firing chamber 202 in which the fluid is heated by the corresponding spout 201 and a nozzle hole 105 in which the heated fluid is spouted. Fluid flows into the firing chamber 202 through the channel 203 formed in the cover layer 124 in the slot 110. The current or “ignition signal” through the resistor is transmitted to heat the fluid in the corresponding firing chamber and eject it through the corresponding nozzle 105.

As disclosed in the cross-sectional and perspective views shown in FIGS. 2 and 3, respectively, the cover layer 124 includes two layers 205 and 207. A first layer 205 (such as a primer layer and a bottom layer) is formed on layer 129 and second layer 207 (such as a top coat layer, chamber) ) And nozzle layers) are formed on layer 205. In this embodiment, the first layer 205 at least partially defines the firing chamber 202, and the second layer 207 is the ceiling of the fluid channel, the remaining portion of the firing chamber and wall, and the nozzle 105. To regulate. Although not shown, according to another embodiment, the first layer 205 defines the firing chamber wall and the second layer 207 defines the nozzle.

According to one embodiment, layers 205 and 207 are formed of different materials. In this embodiment, layers 205 and 207 are formed of the same material. In another embodiment, layers 205 and 207 are about the same thickness, layer 207 is thicker than layer 205, or layer 205 is thicker than layer 207. In this embodiment, layer 205 is thinner than layer 207. In one embodiment, layer 205 has a thickness of about 2-15 μm, preferably 2-6 μm, preferably 2 μm. According to one embodiment, layer 207 has a thickness of about 20-60 μm, preferably 30 μm. According to one embodiment, the thickness of the primer layer is less than about 50% of the total thickness of layer 124.

According to one embodiment, the primer layer 205 is a low viscosity SU8 material that is cured at 210 ° C. According to another embodiment, the material of the primer layer 205 is selected according to resistance to ink and adhesion to the thin film stack 116 and the nozzle or chamber layer. According to another embodiment, the primer layer 205 is more flexible than the other layers of the cover layer 124. According to another embodiment, the primer layer 205 has higher ink resistance than other layers of the cover layer 124. According to another embodiment, the primer layer 205 is a NANO ^™ , which is a lower modulus SU8 structure. It is made of SU8 Flex CP. According to another embodiment, the primer layer 205 is a flexible epoxy. According to another embodiment, the primer layer 205 is a polyimide or polyamide layer. According to another embodiment, the primer layer 205 is SU8 comprising an additive which is an optional Photo-Acid-Generator (PAG) that makes the material photosensitive. According to another embodiment, the primer layer 205 is cured at a higher temperature than the other layers in the cover layer 124. As such, the higher the temperature, the more resistance to the ink and the more stress can occur. However, the thickness of layer 205 remains relatively thin to reduce undesirable cracking.

According to one embodiment, layer 207 has high resolution photolithographic properties. According to one embodiment, layer 207 is cured at 170 ° C.

According to the embodiment shown in FIGS. 4A-4D, the process of forming the barrier layer 124, two layers 205 and 207, is shown. The embodiment of FIG. 5 discloses a flow chart according to the process shown in FIGS. 4A-4D. Primer layer 205 is coated in step 500 and exposed in step 510. The nozzle layer material 207a is coated over the primer layer 205 in step 520 as shown in FIG. 4A. In step 530 the nozzle layer 207 is exposed in two masks as shown in FIGS. 4B and 4C. In step 540, the remaining unexposed nozzle layer material 207a is developed and removed as shown in FIG. 4D. The nozzle layer forms a firing chamber 202 and a nozzle 105.

According to the embodiment shown in FIG. 6, an additional top coat 209 is formed on the nozzle layer 207. According to one embodiment, the topcoat 209 is photodefinable with light. According to one embodiment, the top coat 209 is formed of SU8. According to one embodiment, the topcoat is non-wetting. According to another embodiment, the topcoat 209 is a flattening layer that usually flattens the outline of the rough nozzle layer. According to another embodiment, the topcoat 209 is a mask drawn to make countersunk bore to reduce puddling. According to another embodiment, the topcoat 209 has a low surface energy. According to another embodiment, the topcoat 209 is a siloxane based material. According to another embodiment it is a fluoropolymer based material. According to one embodiment, the thickness of layer 209 is in the range of about 0.5 to 5 μm, preferably 1.1 μm.

According to the embodiment disclosed in FIGS. 7A-7H, the process of forming the barrier layer 124, three layers 205, 206, and 208, is shown. 8 is a flowchart corresponding to the process shown in FIGS. 7A-7H. In step 800 a thin film 116 that produces a fluid ejector is deposited on the substrate. In step 810, the primer layer 205 is spun on and patterned on the thin film layer 116. In step 820, the material 206a forming the chamber layer is spun on, as shown in FIG. 7A. As shown in FIG. 7B, the material 206a is patterned or exposed to form the chamber layer 206. As shown in FIG. 7C, the material 206a is developed and removed at step 820. As shown in FIG. 7D, in step 830 a filling material 300 such as, for example, resist coats the chamber layer 206. As shown in FIG. 7E, in step 840 the fill material 300 is planarized in a manner such as, for example, mechanical-chemical polishing (CMP), patterning and development of the material. As shown in FIG. 7F, in step 850, the chamber layer 206 and the planarized material 300 are coated with a material 208a forming the nozzle layer. The nozzle layer 208 is exposed as shown in FIG. 7G. In step 850 material 208a is developed. As shown in FIG. 7H, the filling material (eg, resist) is removed at step 860. The method shown in FIGS. 7A-7H and shown in the flow chart of FIG. 8 is also referred to as a lost wax method.

In this embodiment the primer layer of FIG. 7H has a thickness of about 2-15 μm, specifically 2-6 μm, more specifically 2 μm. In this embodiment, chamber layer 206 and nozzle layer 208 each have a thickness in the range of about 10-30 μm. In a more detailed embodiment at least one of the layers 206 and 208 has a thickness in the range of about 15-20 μm. According to another embodiment, at least one of the layers 206 and 208 has a thickness of 15 or 20 μm.

According to one embodiment, the nozzle layer 208 is formed of a material similar to the layer 207 described above. According to one embodiment, chamber layer 206 is formed of a material similar to layer 207 described above. According to another embodiment, the chamber layer 206 is formed of SU8 comprising a photobleachable dye for z-contrast. According to one embodiment z-contrast refers to a direction perpendicular to a sufficiently flat substrate. According to a more detailed embodiment, z-contrast means disposing an absorbing material so as to dissipate light intensity from top to bottom. In this embodiment, 'contrast' means the sharpness of the transition between the concentration of photo acid in which the SU8 material is not dissolved by the developer and the concentration of the mine dissolved by the developer. do. According to one embodiment, the sharper the variation, the more rectangular the shape. In this embodiment the photobleaching die becomes bleached and transparent with sufficient administration of electromagnetic energy.

According to the embodiment shown in FIG. 9, an additional topcoat 209 is formed on the nozzle layer 208. Topcoat 209 is similar to topcoat 209 described in connection with FIG. 6.

According to the embodiment shown in FIGS. 10A-10F, the process of forming the barrier layer 124, which is four layers 205, 1206, 1000, and 1208, is shown. The embodiment of FIG. 11 discloses a flowchart corresponding to the process shown in FIGS. 10A-10F. In steps 1100 and 10A, a material 1206a for forming the chamber layer is coated on the primer layer 205. In steps 1110 and 10B, the chamber layer 1206 is exposed to form a wall to the chamber, leaving the unexposed material 1206a in the chamber area. In steps 1120 and 10C, a material 1000a for forming a photon barrier layer is coated on the chamber layer 1206 and the material 1206a. In steps 1130 and 10D, the material 1208a for the nozzle layer is coated on the photon barrier layer material 1000a. In steps 1140 and 10E, the nozzle layer 1208 and the photon barrier layer 1000 are exposed. Material 1206a remains in chamber 202 and materials 1000a and 1208a remain in nozzle 105. In steps 1150 and 10F, materials 1206a, 1000a and 1208a are developed and removed from the chamber and nozzle.

In this embodiment, the photon barrier layer 1000 comprises a solution comprising at least one of an epoxy or acrylic resin, a binder, a solvent, a PAG (photosensitive), and an i-line dye (photon barrier). Is formed from. According to one embodiment, the thickness of the photon barrier layer 1000 is in the range of about 0.5 to 2 μm, preferably 0.5 μm. According to another embodiment, the photon barrier layer is minimized but has sufficient absorbent.

According to one embodiment, chamber layer 1206 and nozzle layer 1208 are formed of a material similar to layer 207 described above. According to one embodiment, layer 1206 comprises a material similar to layer 206. According to another embodiment, the photon barrier layer 1000 is formed of SU8 comprising a photobleachable dye similar to that described with respect to the embodiment of the layer 206 described above. According to one embodiment, SU8 comprising a photobleachable dye allows for easier orientation and more straight edges. For example, as shown in FIG. 10F, the corner edge between the chamber and the nozzle is an almost square edge.

According to the embodiment shown in FIG. 12, an additional topcoat 209 is formed on the nozzle layer 1208. Topcoat 209 is similar to topcoat 209 described in connection with FIG. 6.

According to one embodiment, at least one of the layers included in the cover layer 124 described in one of the embodiments described above is formed of the same initial basic coating material. However, the material undergoes different processes to have different properties from other layers in cover layer 124. For example, according to one embodiment, one layer is exposed to a different amount of electromagnetic energy than the remaining layers of cover layer 124 or is cured at a different temperature.

According to one embodiment, the material forming the layers in cover layer 124 is selected for at least one of the following characteristics: coefficient of thermal expansion (CTE matching), ink resistance, stress relief ( stress relief, hydrophobic (non-wetting ability), hydrophilicity (wetting ability), ability to photocure, high resolution processing capability, smooth surface, compatibility and blending Intermixing capability.

According to one embodiment, at least one of the layers included in the cover layer 124 described in one of the above embodiments is formed of a patterned or etched material using at least one of the following methods: abrasive sand Blasting, dry etching, wet etching, UV induced wet etching, exposure and development, DRIE and UV laser processing. According to one embodiment, at least one of the layers in the cover layer 124 described in one of the embodiments described above is formed of a dry film.

According to one embodiment, the material forming the primer, chamber and / or nozzle layer is photodefined via i-line exposure. i-line exposure is a type of exposure, more particularly exposure to wavelengths of about 365 nm. According to one embodiment, this photoimaged pattern is covered with a resist material. According to one embodiment, the resist is a positive photoresist, and according to a more detailed embodiment is SPR-220. The resist is baked into a convection oven at a temperature between 110 ° C. and 190 ° C. to stabilize the resist for the next level of planarization and hole or nozzle layer treatment. In some embodiments, a solvent development process is also used to remove the unexposed chamber and nozzle layer to remove the resist.

According to one embodiment, at least one of the embodiments described above maximizes trajectory control by reducing deformation of the hole-chamber arrangement.

According to one embodiment, the proportion of the raw materials, the additives and the molecular weight of the SU8 oligomer are adjusted to give a range in the properties of the above mentioned materials.

It is to be understood that the present invention may be practiced in other forms than described in detail. For example, the present invention is not limited to heat-operated fluid ejection devices, and may include, for example, fluid ejection devices operated by piezoelectric materials and other mechanically operated printer heads and other fluid ejection devices. According to a further embodiment, the cover layer 124 of the present invention includes a plurality of layers, such as four layers, five layers, six layers, and the like. Each of these layers may have the same or different material composition from one another, depending on the application. Accordingly, it is to be understood that the embodiments of the invention are illustrative and not restrictive, the scope of the invention being indicated by the appended claims in addition to the foregoing description. In referring to equivalent elements of "a" or "first" in a claim, such claims are to be understood to include combinations of one or more elements, and not to claim or exclude two or more elements.

1 is a perspective view of one embodiment of a fluid ejection cartridge of the present invention.

FIG. 2 is a cross-sectional view of one embodiment of a fluid ejection device shown through region 2-2 of FIG.

3 is a perspective view of one embodiment of a barrier island and a firing chamber therefor;

4A-4D are cross-sectional views of one embodiment of a process for the present invention.

5 is a flow chart for the view of FIGS. 4A-4D.

FIG. 6 is a cross-sectional view of one embodiment of the present invention including a layer added to that shown in FIG. 4D. FIG.

7A-7H are cross-sectional views of one embodiment of the process of the present invention.

8 is a flow chart of the diagram of FIGS. 7A-7H.

FIG. 9 is a cross-sectional view of one embodiment of the present invention including a layer added to that shown in FIG. 7H. FIG.

10A-10F are cross-sectional views of one embodiment of the process of the present invention.

FIG. 11 is a flow chart of the diagram of FIGS. 10A-10F.

12 is a cross-sectional view of one embodiment of the present invention including a layer added to that shown in FIG. 10F.

Claims (12)

As a fluid ejecting device, A substrate comprising a first surface; A fluid ejector formed on the first surface; And A cover layer defining a firing chamber defined for the fluid ejector and defining a nozzle on the firing chamber, And the cover layer is formed by at least two SU8 layers. The fluid ejection device of claim 1 wherein each of the SU8 layers is formed of the same material. The fluid ejection device of claim 2 wherein each of the SU8 layers is treated differently. The fluid ejection device of claim 1 wherein the cover layer has a primer layer and a nozzle layer, the primer layer having a thickness that is less than 50% of the thickness of the cover layer. The fluid ejection device of claim 4 wherein the primer layer is a low viscosity SU8 cured at 210 ° C. 6. 2. The fluid ejection device of claim 1 wherein the cover layer comprises at least three layers comprising a primer layer coating the thin film layers, a chamber layer defining the firing chamber, and a nozzle layer defining the nozzle. The fluid ejection device of claim 1 further comprising a top coat layer formed on the cover layer. The fluid ejection device of claim 1 wherein at least one of the layers forming the cover layer is formed by a lost wax method. The method of claim 1, wherein the materials for the layers forming the cover layer are CTE matching, ink resistance, stress relief, non-wetting ability, and hydrophilicity. A fluid ejection device selected for at least one of ability, ability to photocure, processing capability, smooth surface, compatibility and intermixing capability. The fluid ejection apparatus of claim 1, wherein at least one of the layers forming the cover layer is formed of a dry film. 2. The cover layer of claim 1, wherein the cover layer comprises at least four layers including a primer layer coating the thin film layers, a chamber layer defining the firing chamber, and a photon barrier layer comprising a nozzle layer defining the nozzle. Fluid ejection device. As a method of forming a fluid ejecting device, Coating a thin film stack comprising a fluid ejector with a first material; Exposing the first material to form a first SU8 cover layer; Coating the first material with a second material; Exposing the second material to form a second SU8 cover layer defining a chamber; Developing and removing the unexposed second material from the chamber; Filling the chamber with resist; Planarizing the resist; Coating the resist with a third material; Exposing the third material to form a third SU8 cover layer defining a nozzle; And Developing and removing the resist and the third material Method of forming a fluid ejecting device comprising a.

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