Actuator

In one embodiment an electrostatic actuator includes: a first conductor associated with each chamber; a second conductor having a plurality of flexible first parts supported by a plurality of second parts, each flexible first part forming at least part of a wall of each chamber and each flexible first part located opposite a corresponding one of the first conductors across a gap; and a voltage source operatively connected to each of the first conductors for selectively applying a voltage between each of the first conductors and the second conductor In another embodiment, an electrostatic actuator includes: a plurality of rigid conductors arranged adjacent to one another along a chamber; and a flexible conductor disposed opposite to and spanning the plurality of first conductors across a gap, the flexible conductor forming at least part of one wall of the chamber such that flexing the flexible conductor flexes the wall to change the volume of the chamber.

BACKGROUND

Piezoelectric actuated inkjet printheads are used for very large format inkjet printing applications, such as the industrial printing market for large signage. Piezoelectric materials, however, are difficult to process using conventional semiconductor wafer fabrication techniques. In conventional piezo actuator fabrication, a saw is used to pattern the material for subsequent etching. Lengthy saw times are used and the size of piezo features is limited by the saw tooling.

DESCRIPTION

Embodiments of the new electrostatic actuator and fabrication process were developed in an effort to produce an inkjet printhead actuator suitable for very large format inkjet printing applications using standard semiconductor wafer processing tools and techniques. Some embodiments of the new actuator, therefore, will be described with reference to inkjet printing. Embodiments of the present disclosure, however, are not limited to inkjet printing. Other forms, details, and embodiments may be made and implemented. Hence, the following description should not be construed to limit the scope of the present disclosure, which is defined in the claims that follow the description.

FIG. 1is a block diagram illustrating an inkjet printer10that includes an array12of printheads14, an ink supply16, a print media transport mechanism18and an electronic printer controller20. Printhead array12inFIG. 1represents generally multiple printheads14and the associated mechanical and electrical components for ejecting drops of ink on to a sheet or strip of print media22. An electrostatic inkjet printhead14may include one of more ink ejection orifices each associated with a corresponding ink channel. Electrostatic forces generated by conductors in the printhead flex one wall of the ink channel back and forth rapidly to alternately expand and contract the ink channel to eject drops of ink through the corresponding orifice. (Ink ejection orifices are also commonly referred to as ink ejection nozzles.) In operation, printer controller20selectively energizes the conductors in a printhead, or group of printheads, in the appropriate sequence to eject ink on to media22in a pattern corresponding to the desired printed image.

Printhead array12and ink supply16may be housed together as a single unit or they may comprise separate units. Printhead array12may be a stationary larger unit (with or without supply16) spanning the width of print media22. Alternatively, printhead array12may be a smaller unit that is scanned back and forth across the width of media22on a moveable carriage. Media transport18advances print media22lengthwise past printhead array12. For a stationary printhead array12, media transport18may advance media22continuously past the array12. For a scanning printhead array12, media transport18may advance media22incrementally past the array12, stopping as each swath is printed and then advancing media22for printing the next swath. Controller20may receive print data from a computer or other host device23and, when necessary, process that data into printer control information and image data. Controller20controls the movement of the carriage, if any, and media transport18. As noted above, controller20is electrically connected to printhead array12to energize the conductors to eject ink drops on to media22. By coordinating the relative position of array12and media22with the ejection of ink drops, controller20produces the desired image on media22according to the print data received from host device23.

FIGS. 2-3are perspective and plan views, respectively, illustrating one example embodiment of a printhead24such as might be used as a printhead14in array12of the printer10shown inFIG. 1. The printhead array in a large format inkjet printer may contain hundreds or thousands of individual printheads24. Referring toFIGS. 2 and 3, printhead24is an assembly composed of an ink channel structure26affixed to an actuator die28. Ink channel structure26and actuator die28are fabricated separately and then bonded together or otherwise affixed to one another to form printhead24. In the embodiment shown, three ink channels30are formed in structure26. Ink channels30are recessed into or otherwise exposed along a surface32of structure26. Each ink channel30includes a rear fill chamber34joined to a front ejection chamber36by a narrow part38that defines a transition between the two chambers34and36. An ink ejection orifice40(also called a nozzle) is located at the forward end of each ejection chamber36, as shown inFIG. 3. In the embodiments described in detail below, a portion of the ejection chamber36of each ink channel30is also formed in the actuator die28. Although it is expected that ink channel structure26will typically be formed in a silicon substrate using conventional silicon wafer processing techniques (e.g., photolithographic patterning, etching and die cutting), other fabrication materials and techniques may be used. For example, structure26may be formed from plastics molded or machined into the desired structural configuration as long as the plastic may be securely affixed to actuator die28.

Actuator die28includes an electrostatic actuator42adjacent to each ink ejection chamber36. Each actuator42includes control conductors44(FIG. 3), electrical contact pads46and signal traces/wiring48. These and other components of actuator42are described in detail below. Ink entering each channel30at fill chamber34passes through narrows38into ejection chamber36, from which it is ejected through orifice40at the urging of the corresponding actuator42. Other configurations for ink channel structure26and actuator die28are possible. The number and shape of the ink channels30in printhead24and the corresponding actuators42, for example, may vary from that shown depending on performance criteria for the individual printheads, the characteristics of the printhead array and the printer, as well as fabrication tooling and processing techniques.

FIGS. 4A and 4Bare simplified section views along an ejection chamber36showing the operative components of an actuator die28. To better illustrate the operative features of each actuator42, some of the structural features of die28and actuator42have been omitted fromFIGS. 4A and 4B.FIG. 4Ashows actuator42in a flexed position in which ink ejection chamber36is expanded.FIG. 4Bshows actuator42in a flexed position in which ink ejection chamber36is contracted to eject an ink drop. Actuator42uses a MEMS (micro-electromechanical system) capacitor49that is integrated into actuator die28. One conductor on capacitor49is attached to the flexible membrane/wall of ink channel30and the other/opposite conductor is attached to or part of a rigid substrate. A varying voltage signal applied across the conductors alternately pulls the membrane toward the conductor substrate and releases the membrane to flex back into the original position to pump ink out through orifice40.

Referring toFIGS. 4A and 4B, capacitor49in actuator42includes a first, non-flexing conductor50along actuator die substrate52and a second, flexing conductor54operatively connected to a flexible wall56of ink channel ejection chamber36. Flexible wall56is sometimes referred to as a membrane or a vibration plate. Conductor54“operatively connected” to wall56means that conductor54is affixed to or otherwise constrained so that a deformation in conductor54creates a corresponding deformation in wall56. Conductors50and54extend along ink channel ejection chamber36opposite one another across a gap58. Non-flexing conductor50may itself be flexible or inflexible. If conductor50is flexible, then it will be affixed to substrate52or another suitable support to achieve the desired rigidity. The extent of flexible wall56and/or the extent to which conductor54covers wall56may vary depending on other characteristics of chamber36. However, it is expected that flexible wall56will usually extend substantially the full length and span substantially the full width of ejection chamber36, and conductor54will usually cover substantially all of the flexible portion of wall56.

Each conductor50and54is connected to a signal generator or other suitable voltage source60and62, as indicated by signal lines64and66. Generating a voltage difference between the two conductors50and54across gap58creates electrostatic forces that can be used to flex conductor54, and correspondingly wall56, back and forth to alternately expand and contract ejection chamber36. Varying the voltage difference in a desired pattern controls the ejection of ink drops through orifice40. Any suitable drive circuitry and control system may be used to create the desired forces. The drive circuitry shown in which varying voltages may be applied to each conductor50and54through a separate signal generator60and62is just one example configuration. Other configurations are possible. For example, one of the conductors50or54may be held at a ground voltage (typically flexing conductor54) and varying voltages applied to the other “control” conductor50or54(typically non-flexing conductor50) to achieve the desired forces. Hence, conductors “operatively connected” to a voltage source as used in this document means connected in such a way that a voltage difference may be generated between the conductors, specifically including but not limited to the connections described above.

FIG. 5is a simplified view representing a section along ejection chamber36showing the operative components of another embodiment of an electrostatic actuator42. In the embodiment shown inFIG. 5, multiple control, non-flexing conductors50a-50iare used in capacitors49a-49ito generate a wave in flexible wall56of ink ejection chamber36. (Only part numbers49aand49iare referenced onFIG. 5.) In the embodiment shown inFIG. 5, ink drops are ejected through orifice40from a continuous pulsing wave, rather than from a series of discrete incremental pulses as in the single conductor embodiment shown inFIGS. 4A and 4B. The resulting peristaltic pumping may be used to control the meniscus at orifice40and help reduce (1) ingesting air bubbles through orifice40and/or (2) drooling ink or other fluid out of orifice40. As used in this document, peristaltic pumping means moving fluid by waves of contraction and/or expansion. One example voltage/signal pulse progression is illustrated by the time lines t1-t7inFIG. 5. In this example progression, flexing conductor54is held at a ground voltage while a signal generator60simultaneously pulses four conductors through, for example, a series of gates or switches68a-68i, in a predetermined pattern and the pulse pattern shifts by one conductor with each increment of time. At time t1, pulses are applied to conductors50d/50eand50h/50i; at time t2, pulses are applied to conductors50c/50dand50g/50h; and so on. The state of switches68a-68ishown inFIG. 5corresponds to the pulse pattern shown at time t7. The pulse pattern and progression may be set and/or varied as desired to achieve the proper flow of ink drops through orifice40.

One embodiment of the structure of actuator die28and one example process for fabricating die28and printhead24will now be described with reference toFIGS. 6-14.FIG. 13is a crosswise section illustrating a view taken along the line13-13inFIG. 3showing printhead24.FIG. 14is a lengthwise section illustrating a view taken along the line14-14inFIG. 3showing printhead24.FIGS. 6-12are crosswise section views showing process steps in the fabrication of actuator die28and printhead24. The structures shown inFIGS. 6-14are not to scale nor do they correlate exactly to the corresponding structures shown inFIG. 3. Rather, the structures shown inFIGS. 6-14are presented in an illustrative manner to help show pertinent structural and processing features of this embodiment of the present disclosure.

Referring first toFIG. 6, a thin oxide layer70is formed on a silicon substrate72by, for example, thermally oxidizing the surface of substrate72to form a layer of silicon dioxide. An oxide layer70works well as a hard mask for the subsequent spacer etch and it provides a good bonding surface. Hence, while it is expected that an oxide layer will be used many applications, other configurations are possible. For example, an unoxidized silicon substrate72may provide an acceptable bonding surface in which case a photoresist may be used for the spacer etch. In addition, although the formation of the components of a single actuator die are shown, the components of many such dies may be formed simultaneously on a silicon wafer (substrate72) and the individual dies subsequently cut or otherwise singulated from the wafer. Also, while the present disclosure will be described in terms of Metal Oxide Semiconductor (MOS) technology, which remains one of the most commonly used integrated circuit technologies, other suitable technologies may be used. A layer of tantalum aluminum (TaAl) or another suitable conductive material is deposited or otherwise formed on thin oxide70. The conductive layer is selectively removed to form control conductors74and contact pads76(conductors44and contact pads46inFIG. 3) by, for example, patterning and etching the conductive layer.

The formation of integrated circuits often includes photolithographic masking and etching. This process consists of creating a photolithographic mask containing the pattern of the component to be formed, coating the wafer with a light-sensitive material called photoresist, exposing the photoresist coated wafer to ultra-violet light through the mask to soften or harden parts of the photoresist, depending on whether positive or negative photoresist is used, removing the softened parts of the photoresist, etching to remove the materials left unprotected by the photoresist and stripping the remaining photoresist. This photolithographic masking and etching process is referred to herein as “patterning and etching.” Although it is expected that the selective removal of materials will typically be achieved by patterning and etching, other selective removal processes could be used. Hence, the reference to patterning and etching in the example fabrication process described and shown should not be construed to limit the processes that may be used for the selective removal of material in the claims that follow this description.

Referring toFIG. 7, sacrificial spacers78are formed over conductors74. Spacers78are removed later to define the electrostatic gaps between the flexing and non-flexing printhead conductors (i.e., between the capacitor conductors). Each spacer78may be constructed as a single body of amorphous silicon, or other suitable material, deposited on the underlying structure and then patterned and etched into the desired shape. Alternatively, spacers78may be constructed as a composite of more than one layer of material. For example, spacers78may be formed by first depositing a layer of amorphous silicon on the underlying structure to approximately the thickness of conductors74. This first silicon layer is planarized to conductors74, by chemical-mechanical polishing for example. The planarization may extend to conductors74as necessary or desirable to help ensure a flat surface for further processing and for a uniform electrostatic gap. A thin layer of silicon nitride is then formed on the underlying structure and a thick layer of amorphous silicon is deposited on the silicon nitride. The silicon/nitride/silicon stack is patterned and etched to form spacers78, each including a thin layer of silicon nitride82sandwiched between silicon sidewalls80and silicon cap84. While any suitable spacer material may be used, it is desirable to use materials that are selectively etchable with respect to conductors74and oxide70to help control the spacer release etch described below.

In the embodiment shown, and referring now toFIG. 8, the flexible parts86(FIGS. 12-14) of the wall along each ink channel are constructed as a conducting layer90sandwiched between insulating layers88and92. Flexible wall part86is also sometimes referred to in this document as a membrane86. A thin insulating layer88is formed on the underlying structure, a tantalum aluminum (TaAl) layer90or another suitable conductor is deposited on insulating layer88, and a second thin insulating layer92is formed on conductive layer90. Although it is expected that insulating layers88and92will often be formed by depositing silicon dioxide using a tetraethylorthosilicate low temperature chemical vapor deposition (TEOS) process, other suitable materials and processes could also be used. The insulated conductor stack94is patterned and etched to form membrane86and to expose contact pads76. Unlike some conventional electrostatic printheads, in which part of the sacrificial spacer is left to partition the control conductors, stack94is used to separate the control conductors74from one another in both the crosswise direction (FIGS. 8-13) and in the lengthwise direction (FIG. 14), thus allowing for the complete removal of spacer78in the release etch. That portion of stack94that drops down to the substrate (at oxide layer70) between control conductors74, designated by part number95, also supports membrane86(the horizontal, flexible parts of stack94) after the release etch. This configuration for the membrane layer in printhead24, therefore, has two significant advantages over conventional printheads. First, the membrane layer is self supporting and, second, it may be used to separate the control conductors.

Referring toFIG. 9, second sacrificial spacers96are formed over insulated conductor stack94. Spacers96are removed later to define the width of membrane86. Each spacer96may be constructed as a single body of amorphous silicon, or other suitable material, deposited on the underlying structure and then patterned and etched into the desired shape. Again, while any suitable spacer material may be used, it is desirable to use a material that is selectively etchable with respect to oxide layer92to help control the release etch.

Referring toFIG. 10, a thick TEOS oxide or other suitable insulating layer98is formed over the underlying structure. Insulating layer98is planarized by, for example, chemical-mechanical polishing to provide a flat, smooth surface for bonding the actuator die28to ink channel structure26. Insulating layer98is patterned and etched to expose sacrificial spacers96and partially form the extension99(FIG. 11) of the ink channels into actuator die28. This etch may continue, as shown inFIG. 11, to expose contact pads76and to open a hole100to expose sacrificial spacers78and to fully form ink channel extensions99. Alternatively, a second masking/patterning and etching step may be used to expose contact pads76and to open a hole100to expose sacrificial spacers78. A so-called “release” etch is then performed to remove spacers96and78, forming the structure shown inFIG. 11. TEOS layers92and98, oxide layer88and metal control conductors74serve as etch stops while etching silicon spacers78and96to help allow for the complete removal of spacers78and96without also degrading surrounding structures. That is to say, the release etch is selective to remove the amorphous silicon spacer material but not the oxides and metals. Hence, the timing of the release etch is not substantially significant to defining either the electrostatic gap58formed by the removal of spacers78or the actuator width defined by the removal of spacers96.

Insulating layer88, which faces control conductors74, provides electrical insulation between conductors74and90and helps prevent shorting between the conductors. Insulating layer92, which faces ink channel30, insulates conductor90against chemical attack by the ink. However, depending on the selection of a variety of design factors in printhead24, specifically including the electostatic displacement of conductive membrane86, the size of gap58, and the use of stiction bumps or other short preventing structures, insulating layer88may be omitted. Similarly, if conductive layer90is not susceptible to chemical degradation from the inks that may be used in printhead24, then insulating layer92may be omitted. Hence, it may be possible to form membrane86from an uninsulated conductive layer90which is ink resistant and otherwise configured to not short to control conductors74.

Ink channel structure26is bonded to the completed actuator die28by plasma bonding or another suitable bonding process, as shown inFIG. 12, to mate each ink channel30with the corresponding membrane86and to cover clear hole100. That portion of ink channel structure26over contact pads76(pads46inFIGS. 2 and 3) is then removed by, for example, saw cutting to expose pads76.

The completed printhead24is shown inFIGS. 13 and 14. (FIG. 14is a lengthwise section view taken along the line14-14inFIG. 3.) Capacitors49, typical at each location of conductor44, are specifically designated by part number only once in each ofFIGS. 13 and 14. The particular dimensions of the various layers and components described above can vary widely depending on the printing application. Nevertheless, for an electrostatic inkjet printhead24used in an array12(FIG. 1) in a very large format printing application in which the array includes hundreds of printheads, the following is one example of the nominal sizes of some of the components in a printhead24printing at a resolution of 600 dpi (dots per inch). Each ink channel30and corresponding membrane86is about 30 micrometers wide. The electrostatic gap58and membrane86are each about 200 nanometers thick (conductor90is about 100 nanometers thick and each TEOS oxide layer is about 50 nanometers thick). Ejection chamber36in each ink channel30is about 100 micrometers deep (including parts formed in both structure26and die28).

Another embodiment of the structure of actuator die28and another example process for fabricating die28and printhead24will now be described with reference toFIGS. 15-22.FIG. 21is a lengthwise section illustrating a view taken along the line21-21inFIG. 15showing printhead24.FIG. 22is a crosswise section illustrating a view taken along the line22-22inFIG. 15showing printhead24.FIGS. 16-20are lengthwise section views showing process steps in the fabrication of actuator die28and printhead24. As described in detail below, in this embodiment, stiction bumps are formed between control electrodes and the membrane layer drops down to the substrate between control electrodes in the crosswise direction only. The structures shown inFIGS. 16-22are not to scale nor do they correlate exactly to the corresponding structures shown inFIG. 15. Rather, the structures shown inFIGS. 16-22are presented in an illustrative manner to help show pertinent structural and processing features of this embodiment of the present disclosure.

Referring first toFIG. 15, so-called “stiction” bumps102are formed in actuator die28between control electrodes44along the length of each channel30. Stiction bumps are used in MEMS devices to help reduce unwanted STicking and friCTION (hence, the name “stiction”) and/or to provide a mechanical stand-off that keeps conductors physically separated to help prevent electrical shorting between the conductors. “Stiction bumps” as used in this document refers to bumps configured to perform either or both of these functions. The other components shown inFIG. 15are the same as those shown and described above with reference toFIG. 3. Printhead24is an assembly composed of ink channel structure26affixed to actuator die28. Ink channel structure26and actuator die28are fabricated separately and then bonded together or otherwise affixed to one another to form printhead24. Each ink channel30includes a rear fill chamber34joined to a front ejection chamber36by a narrow part38that defines a transition between the two chambers34and36. An ink ejection orifice40(also called a nozzle) is located at the forward end of each ejection chamber36. Actuator die28includes an electrostatic actuator42adjacent to each ink ejection chamber36. Each actuator42includes control conductors44, electrical contact pads46and signal traces/wiring48.

Referring now toFIG. 16, a thin oxide layer70is formed on a silicon substrate72by, for example, thermally oxidizing the surface of substrate72to form a layer of silicon dioxide. An oxide layer70works well as a hard mask for the subsequent spacer etch and it provides a good bonding surface. Hence, while it is expected that an oxide layer will be used many applications, other configurations are possible. For example, an unoxidized silicon substrate72may provide an acceptable bonding surface in which case a photoresist may be used for the spacer etch. A layer of tantalum aluminum (TaAl) or another suitable conductive material is deposited or otherwise formed on thin oxide70. The conductive layer is selectively removed to form control conductors74(conductors44inFIG. 15) and stiction bump blockers104by, for example, patterning and etching the conductive layer. While it is expected that it may be convenient to form bump blockers104at the same time, and from the same material, as control conductors74, blockers104might also be formed separately and from another material, including an insulating material.

Referring toFIG. 17, a sacrificial spacer78is formed over conductors74. Spacer78is removed later to define the electrostatic gaps between the flexing and non-flexing printhead conductors (i.e., between the capacitor conductors). In the embodiment shown, spacer78includes a thin layer of silicon nitride82sandwiched between silicon sidewalls80and silicon cap84. While any suitable spacer material may be used, it is desirable to use materials that are selectively etchable with respect to conductors74and oxide70to help control the spacer release etch described below. A recess106is etched or otherwise formed in the upper surface of spacer78(silicon cap84) at the desired location of stiction bumps102over each bump blocker104.

Referring toFIG. 18, in this embodiment, conductive membrane86is constructed from a single conducting layer90. Conductive layer90is patterned and etched to form membrane86and to expose contact pads46(seeFIG. 22). Conductive layer90filling each recess106forms stiction bumps102. Also in this embodiment, conductor layer90separates the control conductors44from one another in only the crosswise direction as best seen by comparingFIGS. 21 and 22. That portion of conductor90that drops down to the substrate (at oxide layer70) between control conductors74/44inFIG. 22also supports membrane86(the horizontal, flexible parts of conductor90) after the release etch.

Referring toFIG. 19, a second sacrificial spacer96is formed over conductor90. Spacer96is removed later to define the width of membrane86(seeFIG. 22). Then, a thick TEOS oxide or other suitable insulating layer98is formed over the underlying structure. Insulating layer98is planarized by, for example, chemical-mechanical polishing to provide a flat, smooth surface for bonding the actuator die28to ink channel structure26. Insulating layer98is patterned and etched to expose sacrificial spacer96and partially form the extension of the ink channels into actuator die28, as described above with reference toFIGS. 10 and 11. This etch may continue, as shown inFIG. 22, to expose contact pads46and to open holes100to expose sacrificial spacer78. Alternatively, a second masking/patterning and etching step may be used to expose contact pads76and to open clear holes100.

A release etch is then performed to remove spacers96and78, forming the structure shown inFIG. 20. Ink channel structure26is bonded to the completed actuator die28by plasma bonding or another suitable bonding process, as shown inFIGS. 21 and 22to mate each ink channel30with the corresponding membrane86and to cover clear holes100. That portion of ink channel structure26over contact pads76(pads46inFIGS. 2-3and22) is then removed by, for example, saw cutting to expose pads76. Referring toFIG. 21, stiction bumps102provide a mechanical stand-off that keeps conductive membrane86and control conductors44physically separated when membrane86flexes down toward conductors44to help prevent electrical shorting between conductors86and44. Where bump blockers104are conductive, blockers104and bumps102are held at the same voltage so that conductors102and104also do short to one another.

In one embodiment, an inkjet printhead comprises:a first structure having a plurality of first ink channels formed at a bonding surface of the first structure, the first ink channels arranged generally parallel to one another across the first structure bonding surface;a second structure having a plurality of second ink channels formed at a bonding surface of the second structure, the second ink channels arranged generally parallel to one another across the second structure bonding surface, the first and second structures bonded to one another at their respective bonding surfaces such that each of the first ink channels is aligned with a corresponding one of the second ink channels to form a plurality of ink chambers, and the second structure including an electrostatic actuator that includes:a first conductor having a plurality of flexible first parts supported by a plurality of second parts, each flexible first part defining at least part of one wall of each of the second ink channels; anda plurality of second conductors each aligned across a gap opposite a corresponding one of the first parts of the first conductor; andan orifice in each ink chamber through which fluid may be ejected from the chamber at the urging of the actuator.

In this inkjet printhead embodiment, a second conductor second part may be disposed between each pair of first conductors positioned adjacent to one another. In this inkjet printhead embodiment, the actuator may further include a voltage source operatively connected to each of the second conductors for selectively applying a voltage between each of the second conductors and the first conductor.

In one embodiment, an inkjet printer comprises:an ink supply;an array of printheads operatively connected to the ink supply, each printhead in the array including an electrostatic actuator for ejecting ink drops from a plurality of ink chambers in the printhead, the actuator comprising:a plurality of first conductors each associated with one of the ink chambers;an insulated second conductor having a plurality of flexible first parts and a plurality of second parts, each flexible first part forming at least part of a wall of the chamber and each flexible first part located opposite a corresponding one of the first conductors across a gap, and each second part separating one of the first conductors from another of the first conductors; anda voltage source operatively connected to each of the second conductors for selectively applying a voltage between each of the second conductors and the first conductor;an electronic controller operatively connected to the printheads for selectively activating the electrostatic actuators in the printheads; anda print media transport mechanism configured to move print media past the printhead array at the urging of the controller.

In one embodiment, a method of forming an electrostatic actuator comprises:forming a first layer of spacer material over the structure and over the first conductors;selectively removing parts of the first layer of spacer material to form first spacers covering each of the first conductors and to expose the structure between the first spacers;covering the first spacers and the exposed structure between the first spacers with an insulated second conductor;forming a second layer of spacer material over the insulated second conductor;selectively removing parts of the second layer of spacer material to form second spacers on the insulated second conductor directly over each of the first conductors;covering the second spacers and the insulated conductor with an insulating material;selectively removing parts of the insulating material to expose the second spacers along channels in the insulating material; andremoving the first and second spacers.

In this method of forming embodiment, the structure may include a silicon structure and covering the first spacers and the exposed structure between the first spacers with a second conductor may include covering the first spacers and the exposed structure between the first spacers with an insulated second conductor.

As noted at the beginning of this Description, the example embodiments shown in the figures and described above illustrate but do not limit the claimed subject matter. Other forms, details, and embodiments may be made and implemented. Therefore, the foregoing description should not be construed to limit the scope of the claimed subject matter, which is defined in the following claims.