HK1108865B - Substrate and method of forming substrate for fluid ejection device - Google Patents

Description

Substrate and method of forming a substrate for a fluid ejection device

Technical Field

The present invention relates to a method of forming a substrate for a fluid ejection device and a substrate for a fluid ejection device.

Background

In some fluid ejection devices, such as printheads, drop ejecting elements are formed on a front side of a substrate and fluid is directed to ejection chambers of the drop ejecting elements through openings or slots in the substrate. Typically, the substrate is a silicon wafer, and the slots are formed in the wafer by chemical etching. Prior methods of forming a slot through a substrate include etching into the substrate from a backside of the substrate defined as the side of the substrate opposite from where the drop ejecting elements are formed to a front side of the substrate. Unfortunately, etching into the substrate from the back side all the way to the front side can cause misalignment of the slots of the front side and/or variations in the width of the front side slots.

Disclosure of Invention

According to one aspect of the present invention, there is provided a method of forming a substrate for a fluid ejection device, the substrate having a first side and a second side opposite the first side, the method comprising:

abrasive machining into the substrate from the second side toward the first side at a first etch rate, followed by a second etch rate less than the first etch rate, including forming a first portion of a fluid channel within the substrate; and

abrasive machining into the substrate from the first side toward the second side, including forming a second portion of the fluid channel within the substrate;

wherein forming one of the first portion or the second portion includes communicating one of the first portion of the fluid channel and the second portion of the fluid channel with the other of the first portion of the fluid channel and the second portion of the fluid channel.

According to another aspect of the present invention, there is provided a substrate for a fluid ejection device, the substrate comprising:

a first side;

a second side opposite the first side; and

a fluid passage in communication with the first side and the second side, the fluid passage including a first portion in communication with the first side and a second portion in communication with the second side, and a neck portion between the first portion and the second portion, wherein the neck portion defines a minimum dimension of the fluid passage.

Drawings

FIG. 1 is a block diagram illustrating one embodiment of an inkjet printing system;

FIG. 2 is a schematic cross-sectional view illustrating an embodiment of a portion of a fluid ejection device;

FIG. 3 is a schematic cross-sectional view of one embodiment of a portion of a fluid ejection device formed on one embodiment of a substrate;

figures 4A-4H illustrate one embodiment of forming an opening through a substrate.

Detailed Description

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the drawings being described. Because components described herein can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of this disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

FIG. 1 illustrates one embodiment of an inkjet printing system 10. Inkjet printing system 10 constitutes one embodiment of a fluid ejection system that includes a fluid ejection assembly, such as inkjet printhead assembly 12, and a fluid supply assembly, such as ink supply assembly 14. In the depicted embodiment, inkjet printing system 10 also includes a mounting assembly 16, a media transport assembly 18, and an electronic controller 20.

Inkjet printhead assembly 12, as one embodiment of a fluid ejection assembly, includes one or more printheads or fluid ejection devices that eject drops of ink or fluid through orifices or nozzles 13. In one embodiment, the drops are directed toward a medium, such as print media 19, for printing onto print media 19. Print media 19 is any type of suitable sheet material such as paper, card stock, transparencies, mylar, fabric, and the like. In general, nozzles 13 are arranged in one or more rows or columns such that, in one embodiment, properly sequenced ejection of ink from nozzles 13 causes characters, symbols, and/or other graphics or images to be printed upon print medium 19 as inkjet printhead assembly 12 and print medium 19 are moved relative to each other.

Supply assembly 14, which is one embodiment of a fluid supply assembly, supplies ink to inkjet printhead assembly 12 and includes a reservoir 15 for storing ink. Thus, in one embodiment, ink flows from reservoir 15 to inkjet printhead assembly 12. In one embodiment, inkjet printhead assembly 12 and ink supply assembly 14 are housed together in an inkjet or fluid ejection cartridge or pen. In another embodiment, ink supply assembly 14 is separate from inkjet printhead assembly 12 and supplies ink to inkjet printhead assembly 12 via an interface connection, such as a supply tube.

Mounting assembly 16 positions inkjet printhead assembly 12 relative to media transport assembly 18, and media transport assembly 18 positions print medium 19 relative to inkjet printhead assembly 12. Thus, print zone 17 is defined adjacent to nozzles 13 in an area between inkjet printhead assembly 12 and print media 19. In one embodiment, inkjet printhead assembly 12 is a scanning type printhead assembly, and mounting assembly 16 includes a cassette for moving inkjet printhead assembly 12 relative to media transport assembly 18. In another embodiment, inkjet printhead assembly 12 is a non-scanning type printhead assembly, and mounting assembly 16 fixes inkjet printhead assembly 12 in a predetermined position relative to media transport assembly 18.

Electronic controller 20 communicates with inkjet printhead assembly 12, mounting assembly 16, and media transport assembly 18. Electronic controller 20 receives data 21 from a host system, such as a computer, and may include memory for temporarily storing data 21. Data 21 may be sent to inkjet printing system 10 along an electronic, infrared, optical, or other information transfer path. The data 21 represents, for example, a file and/or document to be printed. Accordingly, data 21 forms a print job for inkjet printing system 10 and includes one or more print job instructions and/or instruction parameters.

In one embodiment, electronic controller 20 provides control of inkjet printhead assembly 12 including timing control for ejection of ink drops from nozzles 13. Electronic controller 20, therefore, defines a pattern of ejected ink drops that form characters, symbols, and/or other graphics or images on print media 19. Timing control and the pattern of ejected ink drops is determined by the print job instructions and/or instruction parameters. In one embodiment, logic and drive circuitry forming a portion of electronic controller 20 is located on inkjet printhead assembly 12. In another embodiment, the logic and drive circuitry forming a portion of electronic controller 20 is located external to inkjet printhead assembly 12.

FIG. 2 illustrates one embodiment of a portion of a fluid ejection device 30. Fluid ejection device 30 includes an array of drop ejecting elements 31. Drop ejecting elements 31 are formed on substrate 40 having a fluid (or ink) feed slot 41 formed therein. Thus, fluid feed slot 41 provides a feed of liquid (ink) to drop ejecting elements 31. The substrate 40 is formed of, for example, silicon, glass, or ceramic.

In one embodiment, each drop ejecting element 31 includes a thin film structure 32 having a resistor 34 and an orifice layer 36. Thin-film structure 32 has a fluid (ink) feed hole 33 formed therein that communicates with fluid feed slot 41 of substrate 40. Orifice layer 36 also has a nozzle chamber 39 formed therein that communicates with nozzle opening 38 and fluid supply hole 33 of thin-film structure 32. Resistor 34 is positioned within nozzle chamber 39 and includes leads 35 that electrically connect resistor 34 to the drive signal and ground.

Thin-film structure 32 is formed, for example, by one or more passivation or insulation layers of silicon dioxide, silicon carbide, silicon nitride, tantalum, polysilicon glass, or other materials. In one embodiment, thin-film structure 32 also includes a conductive layer that defines resistors 34 and conductive lines 35. The conductive layer is formed, for example, from aluminum, gold, tantalum-aluminum, or other metals and metal alloys.

In one embodiment, during operation, fluid flows from fluid feed slot 41 to nozzle chamber 39 via fluid feed hole 33. Nozzle opening 38 is operably associated with resistor 34 such that droplets of fluid are ejected from nozzle chamber 39 (e.g., perpendicular to the plane of resistor 34) and toward the media via nozzle opening 38 when resistor 34 is energized.

Exemplary embodiments of fluid ejection device 30 include a thermal printhead, a piezoelectric printhead, a flextensional printhead, as described above, or any other type of fluid ejection device known in the art. In one embodiment, fluid ejection device 30 is a fully integrated thermal inkjet printhead.

Figure 3 illustrates another embodiment of a portion of a fluid ejection device 130 of inkjet printhead assembly 12. Fluid ejection device 120 includes an array of drop ejecting elements 131. Drop ejecting elements 131 are formed on substrate 140 having fluid (ink) feed slot 131 formed therein. Thus. Fluid feed slot 141 provides a feed of fluid (ink) to drop ejecting elements 131. The substrate 140 is formed of, for example, silicon, glass, or ceramic.

In one embodiment, each drop ejecting element 131 includes a thin film structure 132 having a resistor 134 and an orifice layer 136. Thin-film structure 132 has a fluid (ink) feed hole 133 formed therein that communicates with fluid feed slot 141 of substrate 140. Orifice layer 136 also has nozzle chambers 139 formed therein that communicate with respective nozzle openings 138 and fluid supply holes 133. In one embodiment, orifice layer 136 includes a barrier layer 1361 that defines nozzle chambers 139 and a nozzle plate 1362 that defines nozzle openings 138.

In one embodiment, during operation, fluid flows from fluid feed slot 141 to nozzle chamber 139 via fluid feed hole 133. Nozzle openings 138 are operably associated with respective resistors 134 such that droplets of fluid are ejected from nozzle chamber 139 and toward the media via nozzle openings 138 when resistors 134 are energized.

As shown in the embodiment of fig. 3, substrate 140 has a first side 143 and a second side 144. Second side 144 is opposite first side 143 and, in one embodiment, is oriented substantially parallel to first side 143. Thus, fluid feed hole 133 communicates with first side 143 of substrate 140, and fluid feed slot 141 communicates with second side 144 of substrate 140. Fluid feed holes 133 and fluid feed slots 141 communicate with each other to form fluid channels or openings 145 through substrate 140. Thus, fluid feed slot 141 forms a portion of opening 145, and fluid feed hole 133 forms a portion of opening 145. In one embodiment, opening 145 is formed in substrate 140 by abrasive machining as described below.

Figures 4A-4H illustrate one embodiment of an opening 150 through a substrate 160. In one embodiment, substrate 160 is a silicon substrate, and opening 150 is formed in substrate 160 by abrasive machining, as described below. Substrate 160 has a first side 162 and a second side 164. Second side 164 is opposite first side 162 and, in one embodiment, is oriented substantially parallel to first side 162. The opening 150 communicates with a first side 162 and a second side 164 of the substrate 160 to provide a channel or channel through the substrate 160. Although only one opening 150 is shown as being formed in substrate 160, it should be understood that any number of openings 150 may be formed in substrate 160.

In one embodiment, first side 162 forms a front side of substrate 160 and second side 164 forms a back side of substrate 160 such that fluid flows through opening 150 and substrate 160 from the back side to the front side. Thus, openings 150 provide fluid channels that communicate fluid (ink) to drop ejecting elements 131 via substrate 160.

In one embodiment, as shown in fig. 4A and 4B, thin-film structure 132 including resistor 134 is formed on substrate 160 prior to formation of opening 150 through substrate 160, and as shown in the embodiment of fig. 4A, oxide layers 170 and 172 are formed on first side 162 and second side 164, respectively, of substrate 160 prior to formation of thin-film structure 132. In one embodiment, oxide layers 170 and 172 are formed by growing oxide on first side 162 and second side 164. The oxide may include, for example, silicon dioxide (SiO2) or Field Oxide (FOX).

Next, as shown in FIG. 4B, thin-film structure 132 is formed on first side 162 of substrate 160. More particularly, thin-film structure 132 is fabricated on oxide layer 170 formed on first side 162 of substrate 160. As described above, thin-film structure 132 includes one or more passivation or insulating layers formed from silicon dioxide, silicon carbide, silicon nitride, tantalum, polysilicon glass, or other materials. In addition, thin-film structure 132 also includes a conductive layer that defines resistor 134 and corresponding conductive pathways and wires. The conductive layer is formed, for example, from aluminum, gold, tantalum-aluminum, or other metals and metal alloys.

Also, as shown in the embodiment of fig. 4B, oxide layer 170 is patterned so as to define or determine where to form opening 150 (fig. 4H) within and in communication with first side 162 of substrate 160. The oxide layer 170 may be patterned, for example, by photolithography and etching, so as to define exposed portions of the first side 162 of the substrate 160.

In one embodiment, as shown in FIG. 4C, centering slot 152 is formed in first side 162 before opening 150 or a portion of opening 150 is formed in substrate 160; in one embodiment, centering slots 152 control where openings 150 communicate with first side 162 of substrate 160 when openings 150 are formed in substrate 160. In one embodiment, centering slots 152 are formed in substrate 160 by chemically etching into substrate 160 from first side 162, including, for example, dry, plasma, or reactive ion etching.

In one embodiment, as shown in fig. 4C, masking layer 180 is formed on first side 162 of substrate 160 in order to form centering slots 152 in substrate 160. More particularly, masking layer 180 is formed over thin-film structure 132 and resistor 134. Thus, masking layer 180 serves to selectively control or block etching of first side 162.

In one embodiment, masking layer 180 is deposited and patterned by photolithography and etching to define exposed portions of first side 162, and more particularly to include exposed portions of oxide layer 170 formed on first side 162. Masking layer 180 is thus patterned to determine and define where centering slots 152 are to be formed in substrate 160 from first side 162.

In one embodiment, centering slots 152 are formed in substrate 160 by chemical etching. Mask layer 180 is thus formed of a material that is resistant to the etchant used to etch centering slots 152 into substrate 160. Examples of suitable materials for masking layer 180 include silicon dioxide, silicon nitride, photoresist. After centering slots 152 are formed, masking layer 180 is removed or stripped.

In one embodiment, as shown in fig. 4D, a portion of sacrificial layer 136, more particularly barrier layer 1361 including orifice layer 136, is formed on first side 162 of substrate 160. Barrier layer 1361 is formed over thin-film structure 132 and patterned to define nozzle chamber 139 (fig. 3). Barrier layer 1361 is formed of a photoimageable epoxy such as SU 8.

Next, as shown in the embodiment of FIG. 4E, masking layers 182 and 184 are formed on substrate 160 before opening 150 is formed in substrate 160. More particularly, masking layer 182 is formed on first side 162 of substrate 160 and masking layer 184 is formed on second side 164 of substrate 160. In one embodiment, masking layer 182 is formed over barrier layer 1361 and thin-film structure 132 including resistor 134, and masking layer 184 is formed over oxide layer 172. Masking layers 182 and 184 are used to selectively control and block abrasive machining of first side 162 and second side 164 of substrate 160, respectively, while forming portions of opening 150 as described above.

In one embodiment, masking layers 182 and 184 are formed by deposition or spray coating and patterning by photolithography and etching to define exposed areas of substrate 160. More particularly, masking layers 182 and 184 are patterned to determine where portions of opening 150 (fig. 4H) are formed in substrate 160 from first side 162 and second side 164. In one embodiment, openings 150 are formed in substrate 160 by abrasive machining, as described below. Thus, masking layers 182 and 184 are formed of a material that resists abrasive machining. In one embodiment, the material of masking layers 182 and 184, for example, comprises a photoresist.

As shown in the embodiment of fig. 4F, first portion 154 of opening 150 is formed in substrate 160 after masking layers 182 and 184 are formed and patterned. In one embodiment, the first portion 154 is formed by an abrasive machining process. More particularly, first portion 154 is formed by abrasive machining the exposed area of substrate 160 defined by masking layer 184 from second side 164 toward first side 162.

In one embodiment, the abrasive machining process includes directing a flow of compressed gas, such as air, and abrasive particulate material at substrate 160. Accordingly, the stream of abrasive particulate material impinges on substrate 160 and abrades or erodes exposed areas of substrate 160 defined by masking layer 184 (and/or masking layer 182 as described below). Abrasive particulate materials may include, for example, sand, alumina, silicon carbide, quartz and diamond dust and other suitable abrasive materials in particulate form or particulate materials having suitable abrasive properties for abrading substrate 160.

In one embodiment, as shown in fig. 4F, first portion 154 of opening 150 includes a first region 1541 and a second region 1542. First region 1541 is in communication with second side 164 of substrate 160 and, in one embodiment, defines a maximum dimension of first portion 154 of opening 150 at second side 164 of substrate 160. Additionally, second region 1542 is in communication with first region 1541 and, in one embodiment, defines a minimum dimension of first portion 154 of opening 150.

In one embodiment, first region 1541 and second region 1542 of first portion 154 are formed by different erosion rates of an abrasive machining process. For example, first region 1541 is formed by abrasive machining at a first erosion rate, followed by abrasive machining of second region 1542 at a second erosion rate that is less than the first erosion rate. In one embodiment, abrasive machining at a first erosion rate is performed for a first time period, and abrasive machining at a second erosion rate is performed for a second time period. In one exemplary embodiment, the first time period and the second time period are approximately equal. Thus, a lower erosion rate of second region 1542 abrades less material for second region 1542.

As shown in the embodiment of fig. 4G, second portion 156 of opening 150 is formed within substrate 160. In one embodiment, the second portion 156 is formed by an abrasive machining process as described above. More particularly, second portion 156 of opening 150 is formed by abrasive machining the exposed area of substrate 160 defined by masking layer 182 from first side 162 toward second side 164.

In one embodiment, as shown in FIG. 4G, abrasive machining of substrate 160 from first side 162 toward second side 164 is performed after centering slots 152 and removing any portions of substrate 160 previously remaining between centering slots 152. Thus, in one embodiment, second portion 156 of opening 150 includes a first region 1561 defined by centering slot 152 and a second region 1562 defined by an abrasive machining process. First region 1561 is in communication with first side 162 of substrate 160 and, in one embodiment, defines a maximum dimension of second portion 156 of opening 150 at first side 162 of substrate 160. Additionally, second region 1562 communicates with first region 1561 and, in one embodiment, defines a minimum dimension of second portion 156 of opening 150.

In one embodiment, as shown in fig. 4F and 4G, first portion 154 of opening 150 is formed within substrate 160 before second portion 156 of opening 150 is formed within substrate 160. In other embodiments, however, first portion 154 of opening 150 is formed after second portion 156 is formed, or first portion 154 and second portion 156 are formed at substantially the same time (i.e., second portion 156 of opening 150 is formed at the same time that first portion 154 of opening 150 is formed).

As shown in the embodiment of fig. 4H, masking layers 182 and 184 are stripped or removed after formation of opening 150, including, in particular, first portion 154 and second portion 156 of opening 150. Subsequently, a nozzle plate 1362 is disposed on the first side 162 of the substrate 160. More particularly, in one embodiment, nozzle plate 1362 is formed separately from and secured to barrier layer 1361 formed on thin-film structure 132. Nozzle plate 1362 defines nozzle openings 138 and, in one embodiment, is formed of one or more layers of material including, for example, a metallic material such as nickel, copper, iron/nickel alloy, palladium, gold, or rhodium.

As shown in the embodiment of FIG. 4H, the first portion 154 and the second portion 156 of the opening 150 communicate and form a neck 158 of the opening 150. In one embodiment, neck 158 defines a minimum dimension of first portion 154 and a minimum dimension of second portion 156. Thus, the maximum dimension of the neck 158 is less than the maximum dimension of the first portion 154 and less than the maximum dimension of the second portion 156. In one embodiment, the position of neck 158 relative to first side 162 and second side 164 of substrate 160 is controlled by the relative duration of abrasive machining of substrate 160 from first side 162 toward second side 164 and abrasive machining of substrate 160 from second side 164 toward first side 162.

In one embodiment, as shown in fig. 4H, the profile of the opening 150 through the substrate 160 converges from the second side 164 toward the first side 162 to the neck 158 and diverges from the neck 158 to the second side 162. More specifically, first portion 154 of opening 150 converges from second side 164 toward first side 162 to neck 158, and second portion 156 of opening 150 diverges from neck 158 to first side 162. In one embodiment, first region 1541 of first portion 154 converges from second side 164 toward second side 162 at a first gradient, and second region 1542 of first portion 154 converges from first region 1541 toward first side 162 at a second gradient that is greater than the first gradient of first region 1541. Additionally, in one embodiment, second regions 1562 of second portion 156 diverge from neck 158 toward first side 162 at a first gradient, and first regions 1561 of second portion 156 diverge from second regions 1562 to first side 162 at a second gradient that is less than the first gradient of second regions 1562.

In one embodiment, as shown in fig. 4H, the first portion 154 and the second portion 156 of the opening 150 formed by abrasive machining include concave sidewalls. More particularly, first region 1541 and second region 1542 of first portion 154 include concave sidewalls, and second region 1562 of second portion 156 includes concave sidewalls. In one embodiment, first region 1561 of second portion 156 includes linear sides defined by centering slots 152 (fig. 4C).

While the above description refers to a substrate 160 including an opening 150 formed in an inkjet printhead assembly, it is understood that the substrate 160 having the opening 150 formed therein may be incorporated into systems including other fluid ejection systems for non-printing applications or other applications having fluid channels through the substrate, such as medical devices or other micro-electromechanical systems (MEMS devices). Thus, the methods, structures, and systems described herein are not limited to printheads and may be applied to any substrate having a slot. Additionally, while the above description refers to directing a fluid or ink through the opening 150 of the substrate 160, it should be understood that any flowable material including a liquid such as water, ink, blood, or resist, or flowable solid particles including, for example, talc powder or drug powder, or air may be supplied or directed through the opening 150 of the substrate 160.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This disclosure is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.

Claims (12)

1. A method of forming a substrate (160) for a fluid ejection device, the substrate having a first side (162) and a second side (164) opposite the first side, the method comprising:

abrasive machining into the substrate from the second side toward the first side at a first erosion rate, followed by a second erosion rate that is less than the first erosion rate, including forming a first portion (154) of a fluid channel (150) in the substrate; and

abrasive machining into the substrate from the first side toward the second side, including forming a second portion (156) of a fluid channel within the substrate;

wherein forming one of the first portion or the second portion includes communicating one of the first portion of the fluid channel and the second portion of the fluid channel with the other of the first portion of the fluid channel and the second portion of the fluid channel.

2. The method of claim 1, wherein forming one of the first portion or the second portion comprises forming a fluid passage neck (158).

3. The method of claim 2, wherein the neck of the fluid passageway defines a minimum dimension of the first portion and a minimum dimension of the second portion.

4. The method of claim 1, wherein a maximum dimension of the first portion is greater than a maximum dimension of the second portion.

5. The method of claim 1, further comprising:

prior to abrasive machining into the substrate from the first side, a chemical etch is performed into the substrate from the first side toward the second side, including a second portion that partially forms the fluid channel.

6. A substrate (160) for a fluid ejection device, the substrate comprising:

a first side (162);

a second side (164) opposite the first side; and

a fluid channel (150) in communication with the first side and the second side, the fluid channel including a first portion (154) in communication with the first side and a second portion (156) in communication with the second side, and a neck (158) between the first portion and the second portion, wherein the neck defines a minimum dimension of the fluid channel.

7. The substrate of claim 6, wherein a maximum dimension of the first portion of the fluid channel is greater than a maximum dimension of the second portion of the fluid channel.

8. The substrate of claim 7, wherein the first portion of the fluid channel comprises a first region (1541) defined by a largest dimension portion of the first portion and a second region (1542) defined by a smallest dimension portion of the neck.

9. The substrate of claim 8, wherein the first region comprises a first concave sidewall and the second region comprises a second concave sidewall.

10. The substrate of claim 8, wherein the first region converges from the second side toward the first side with a first gradient, and the second region converges from the first region toward the first side with a second gradient that is greater than the first gradient.

11. The substrate of claim 6, wherein the second portion of the fluid channel includes at least one region (1562) defined by a smallest dimension portion of the neck.

12. The substrate of claim 11, wherein the at least one region diverges from the neck toward the first side.