MEMS device, liquid ejecting head, liquid ejecting apparatus, and MEMS device manufacturing method

A MEMS device includes a wire that is formed of a conductive portion embedded into a recess opened in a first face of a substrate and a bump electrode that is electrically connected to the wire. A total width, in a second direction intersecting a first direction along which the wire extends on the first face, of an opening of the recess in a connection region where the wire and the bump electrode are electrically connected to each other is narrower than a width, in the second direction, of an opening of the recess in a region outside the connection region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. 2016-126306, filed Jun. 27, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a MEMS device such as a liquid ejecting head, a liquid ejecting head, a liquid ejecting apparatus, and a MEMS device manufacturing method. In particular, the invention relates to a MEMS device, a liquid ejecting head, and a liquid ejecting apparatus that include wires formed of conductive portions embedded into recesses formed in a substrate, and a method of manufacturing such a MEMS device.

2. Related Art

Microelectromechanical systems (MEMS) devices including a driving element such as a piezoelectric element, an electronic circuit, or the like on a silicon substrate are applied to various liquid ejecting apparatuses, display devices, vibration sensors, and the like. For example, in a liquid ejecting apparatus, various liquids are ejected (discharged) from a liquid ejecting head that is one form of a MEMS device. In such MEMS devices, a configuration is adopted in which plural substrates used for electrical signals to drive a driving element or the like are electrically connected to each other. One such proposed configuration employs embedded wires that are formed by embedding conductive portions of copper (Cu) or the like, serving as wiring material, into groove-shaped recesses by a plating process, a sputtering process, or the like and then polishing away excess conductive portion that rises outside of the recess openings using, for example, chemical mechanical polishing (CMP) (for example, see JP-A-2005-353633).

However, in configurations in which the above embedded wires are formed on a silicon substrate and such plural embedded wires are provided to the substrate, it is difficult to have the excess portions that rise in a uniform thickness. Thus, when the embedded wire from which an excess portion rises the most is polished until it is even with the substrate surface, as the conductive portions, which are softer than the substrate material (silicon), are more easily removed, a phenomenon called dishing occurs in which the other embedded wires sink below the substrate surface toward the opposite side face. When such dishing occurs, a step arises between the substrate surface and the embedded wires, and therefore there is a risk of disconnections, increased resistance, or the like in wires stacked over the embedded wires, which may result in the MEMS device having diminished reliability.

SUMMARY

An advantage of some aspects of the invention is that a MEMS device, a liquid ejecting head, a liquid ejecting apparatus, and a MEMS device manufacturing method capable of suppressing dishing in embedded wires are provided.

A MEMS device according to an aspect of the invention includes a wire that is formed of a conductive portion embedded into a recess opened in a first face of a substrate and a bump electrode that is electrically connected to the wire. A total width, in a second direction intersecting a first direction along which the wire extends on the first face, of an opening of the recess in a connection region where the wire and the bump electrode are electrically connected to each other is narrower than a width, in the second direction, of an opening of the recess in a region outside the connection region.

According to the above configuration, since the total width of the opening of the recess in the connection region is narrower than the width of the opening of the recess in the region outside of the connection region, dishing in which the conductive portion filled into the recess sinks below the surface of the substrate is able to be suppressed. Accordingly, a step between the surface of the substrate and the conductive portion inside the opening of the recess can be suppressed, and thus disadvantages such as disconnections, increases in the resistance, and the like of wires stacked over the wires at the step can be reduced. Further, in the connection region, variation in the height (the position in the direction of stacking the substrates) of the wire becomes less likely to occur, which enables reduction of the load needed to establish electrical conduction when the bump electrode is pressed against the wire to make electrical connection therewith.

In the above configuration, it is preferable to adopt a configuration in which the wire includes a support portion that supports the bump electrode in the opening of the recess in the connection region.

According to this configuration, since the support portion supports the bump electrode and the support portion bears load when the wire and the bump electrode are connected, electrical conduction is more reliably ensured while reducing load during connection.

In the above configuration, it is preferable to adopt a configuration in which an edge of the opening of the recess in the connection region projects further in the second direction toward an opposing opening edge side than an edge of the opening in the region outside the connection region.

According to this configuration, since the width of the opening of the recess in the connection region is narrower than the width of the opening of the recess outside of the connection region, dishing in which the conductive portion in the recess sinks below the surface of the substrate is suppressed.

In the above configuration, it is preferable to adopt a configuration in which a total width, in the second direction, of the opening of the recess in the connection region is narrower than a total width, in the second direction, inside the recess in the connection region.

According to this configuration, by making the total width of the opening of the recess in a connection region narrower than the total width inside the recess in the connection region, the cross-sectional area of the wire can be increased. This enables an increase in electrical resistance due to narrowing the width of the opening of the recess in the connection region to be suppressed.

In the above configuration, it is preferable to adopt a configuration in which the bump electrode is formed of a resilient body composed of resin with a conductive layer formed on a surface of the resilient body.

According to this configuration, since the load needed to establish electrical conduction when the bump electrode is pressed against the wire to make electrical connection therewith can be reduced, disadvantages due to excessive load, such as the electrode layers of the bump electrodes disconnecting, the substrates breaking, or the like are suppressed.

In the above configuration, the substrate may electrically connect, through the wire, a driving circuit and a driving element driven by signals output from the driving circuit, and the electrical connection between the bump electrode and the connection region is a connection between the driving circuit and the substrate or a connection between the substrate and the driving element.

According to this configuration, the driving circuit and the driving element may be more reliably electrically connected, which enables the reliability of the MEMS device to be improved.

A liquid ejecting head according to an aspect of the invention includes one of the above MEMS devices.

A liquid ejecting apparatus according to an aspect of the invention includes the above liquid ejecting head.

According to the above configuration, a more reliable liquid ejecting head and liquid ejecting apparatus may be provided.

A method of manufacturing a MEMS device according to an aspect of the invention is a method of manufacturing a MEMS device including a wire that is formed of a conductive portion embedded into a recess opened in a first face of a substrate made from silicon and a bump electrode that is electrically connected to the wire. The method includes forming a cavity extending in a plate thickness direction from the first face side of the substrate at a position where the recess is intended to be formed on the substrate; forming the recess by anisotropically etching the cavity to expand the cavity in a direction intersecting the plate thickness direction; filling a conductive portion into the recess; and removing excess conductive portion outside of an opening of the recess by polishing.

According to the above manufacturing method, since a cavity extending in the thickness direction of the substrate is expanded in a direction intersecting the plate thickness direction by anisotropic etching, a recess may be formed such that a total width inside the recess is wider than a total width of the opening of the recess in the first face of the substrate. Accordingly, the cross-sectional area of the wire may be increased while narrowing the width of the opening of the recess, and thus an increase in electrical resistance due to narrowing the width of the opening of the recess is suppressed.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Explanation follows regarding embodiments of the invention, with reference to the accompanying drawings. The embodiments described below include various limitations as preferable specific examples of the invention. However, the scope of the invention is not limited thereby unless specifically indicated to be so in the following explanation. Moreover, in the following, explanation is given using examples of an ink jet recording head (hereinafter, recording head), which is one form of a MEMS device according to the invention, and is one form of a liquid ejection head; and an ink jet printer (hereinafter, printer), which is one form of a liquid ejecting apparatus equipped with such a recording head.

Configuration of a printer1is explained with reference toFIG. 1. Printer1is an apparatus that ejects ink (one type of liquid) onto the surface of a recording medium2such as recording paper to record images or the like. The printer1includes a recording head3, a carriage4that is equipped with the recording head3, a carriage moving mechanism5that moves the carriage4along a primary scanning direction, a transport mechanism6that moves the recording medium2along a secondary scanning direction, and the like. The ink is stored in an ink cartridge7that serves as a liquid supply source. The ink cartridge7is installed to the carriage4so as to supply ink stored therein to the recording head3. Note that configuration may be adopted in which the ink cartridge is disposed on a main body side of the printer, and ink is supplied from the ink cartridge to the recording head through ink supply tubing.

The carriage moving mechanism5includes a timing belt8. The timing belt8is driven by a pulse motor9such as a DC motor. Accordingly, when the pulse motor9is actuated, the carriage4is guided along a guide rod10spanning across the printer1, and reciprocates along the primary scanning direction (a width direction of the recording medium2). The position of the carriage4in the primary scanning direction is detected by a linear encoder (not illustrated in the drawings), which is one type of position information detector, and obtained by a controller of the printer1.

Next, explanation is given regarding the recording head3.FIG. 2is a plan view illustrating configuration of the recording head3.FIG. 3is a cross-section taken along line III-III inFIG. 2.FIG. 4is a cross-section taken along line IV-IV inFIG. 2. Note that illustration of a head case16is omitted fromFIG. 2.

Plural substrates and the like are stacked and attached to the head case16to configure the recording head3of the present embodiment. The substrates are stacked in the order of a nozzle plate21, a communication substrate24, and a pressure chamber formation substrate29, and bonded to each other by adhesive or the like so as to form a single unit. A diaphragm31, piezoelectric elements32(one type of driving element of the invention), an interposing substrate33(one type of substrate or wiring substrate of the invention), and a driving IC34(one type of driving circuit of the invention) are stacked on a face on the opposite side of the pressure chamber formation substrate29to the communication substrate24side. Note that for convenience, the stacking direction of the various members is described as the up-down direction.

The head case16is a box shaped member made from synthetic resin, and a liquid entry path18that supplies ink to a common liquid chamber25, described below, is formed inside the head case16. The liquid entry path18, together with the common liquid chamber25, configures a space where ink common to plural pressure chambers30provided in a row in the pressure chamber formation substrate29, described below, is stored. A housing space17is formed in the head case16at a position away from the liquid entry path18. The pressure chamber formation substrate29, the interposing substrate33, the driving IC34, and the like, are housed inside the housing space17. As illustrated inFIG. 4, a wiring insertion port19that communicates with the housing space17is formed in the head case16. A flexible substrate (not illustrated), which transmits drive signals and the like from a control circuit side of the printer1to the driving IC34, is inserted into the wiring insertion port19, and is connected to substrate wire portions46(wires of the invention) formed on the upper face of the interposing substrate33inside the housing space17.

The communication substrate24of the present embodiment is plate member made from silicon. As illustrated inFIG. 3, the communication substrate24is formed with the common liquid chamber25, which is in communication with the liquid entry path18and stores ink common to the pressure chambers30, and plural individual communication ports26that individually supply ink inside the common liquid chamber25to respective pressure chambers30. Nozzle communication ports27that penetrate the communication substrate24in the plate thickness direction are formed in the communication substrate24at positions corresponding to respective nozzles22. Namely, plural nozzle communication ports27are formed along a nozzle row direction so as to correspond to the respective nozzles22.

The nozzle plate21is a substrate made from silicon bonded to the lower face of the communication substrate24(the face on the opposite side to the pressure chamber formation substrate29). In the present embodiment, openings at the lower face side of the space forming the common liquid chamber25are sealed off by the nozzle plate21. Plural of the nozzles22are opened in straight line shapes (in a row) in the nozzle plate21. The plural nozzles22provided in rows (nozzle rows) are provided uniformly spaced along the secondary scanning direction orthogonal to the primary scanning direction, with a pitch from one end side of the nozzles22to another end side of the nozzles22corresponding to a dot formation density.

The pressure chamber formation substrate29is made from a silicon substrate similarly to the communication substrate24and the nozzle plate21. The pressure chamber formation substrate29is anisotropically etched so as to provide plural spaces for forming the pressure chambers30in a row along the nozzle row direction. These spaces are partitioned from below by the communication substrate24and are partitioned from above by the diaphragm31, thereby configuring the pressure chambers30. The pressure chambers30are formed elongated in a direction intersecting the nozzle row direction. One end portions in a longitudinal direction of the respective pressure chambers30are in communication with the individual communication ports26, and the other end portions in the longitudinal direction of the respective pressure chambers30are in communication with the nozzle communication ports27.

The diaphragm31is a thin film member with elastic properties, and is stacked on the upper face of the pressure chamber formation substrate29(the face on the opposite side to the communication substrate24side). The diaphragm31seals off upper openings of the spaces for forming the pressure chambers30. In other words, upper faces (ceiling faces) of the pressure chambers30are partitioned by the diaphragm31. Portions of the diaphragm31corresponding to the upper openings of the pressure chambers30function as displacement portions that are displaced along a direction moving away from, or a direction approaching, the nozzles22accompanying flexural deformation of the piezoelectric elements32. Namely, regions of the diaphragm31corresponding to the upper openings of the pressure chambers30configure driving regions where flexural deformation is permitted. Deformation of the driving regions changes the capacity of the pressure chambers30.

Note that the diaphragm31is, for example, configured from an elastic film composed of silicon dioxide (SiO2) formed on the upper face of the pressure chamber formation substrate29and an insulating body layer composed of a zirconium oxide (ZrO2) formed on the elastic film. The piezoelectric elements32are respectively stacked on regions corresponding to the respective pressure chambers30(namely, driving regions) on the insulating body layer (the face on the opposite side of the diaphragm31to the pressure chamber formation substrate29side). The piezoelectric elements32of the present embodiment are flexural mode piezoelectric elements. The respective piezoelectric elements32are, for example, formed by stacking a lower electrode layer, a piezoelectric body layer, and an upper electrode layer, on the diaphragm31in that sequence. In the piezoelectric elements32configured in this manner, when an electric field is applied between the lower electrode layer and the upper electrode layer according to a potential difference between the two electrodes, the piezoelectric elements32flexurally deform in a direction moving away from, or a direction approaching, the nozzles22. As illustrated inFIG. 2, lead electrodes37extend from respective piezoelectric elements32toward the outside of the piezoelectric elements32(namely, to a non-driving region away from the driving regions). The lead electrodes37are wires for applying drive signals for driving the piezoelectric elements32to the piezoelectric elements32, and are provided extending along a direction intersecting the nozzle row direction from the piezoelectric elements32to an end portion of the diaphragm31.

The interposing substrate33of the present embodiment is configured from a crystalline substrate, specifically a monocrystalline silicon substrate, and is a member that functions as an interposer. Namely, the interposing substrate33is a substrate that electrically connects the driving IC34, which is one type of a driving circuit, to the piezoelectric elements32, which are one type of driving elements. Bonding resin43is interposed between the interposing substrate33and the diaphragm31, and the interposing substrate33is disposed in a state forming a space that accommodates the piezoelectric elements32. In the present embodiment, the surfaces, namely the upper face and the lower face of the interposing substrate33are made from (100) planes of monocrystalline silicon substrates. The driving IC34, which outputs drive signals for driving of the piezoelectric elements32, is disposed at the upper face side (corresponding to the first face of the invention, which is the face on the opposite side to the piezoelectric elements32side) of the interposing substrate33. Drive signals, ejection data (raster data), and the like from the control circuit are input to the driving IC34through the flexible substrate (not illustrated), and the driving IC34controls the selection of drive pulses, from out of the drive signals, that are respectively output to the piezoelectric elements32based on the ejection data. Input terminals42to which drive signals, drive voltages, and the like from the flexible substrate are input, and output terminals41that are configured from a common terminal shared by the piezoelectric elements32and individual terminals provided so as to correspond to respective piezoelectric elements32, are provided to the lower face (the face on the interposing substrate33side) of the driving IC34.

As illustrated inFIG. 2, plural (four, in the present embodiment) of the input terminals42are provided in a row along an edge of the lower face of the driving IC34at one end in the nozzle row direction. Plural of the output terminals41are also provided in rows along the edges of the lower face of the driving IC34at each end in a direction intersecting the nozzle row direction, so as to correspond to the respective piezoelectric elements32. The input terminals42and output terminals41are both formed of bump electrodes in which a conductive layer has been stacked on a portion of the surface of a resin portion formed from a synthetic resin. Namely, the input terminals42are each formed of a resilient body42aformed projecting along the nozzle row direction, and a conductive layer42bformed following the surface profile of the resilient body42aso as to cross the resilient body42a. The input terminals42are pressed against the substrate wire portions46, described below, of the interposing substrate33to electrically connect to the substrate wire portions46. Similarly, the output terminals41are each formed of a resilient body41aformed projecting along the nozzle row direction, and a conductive layer41bformed following the surface profile of the resilient body41aso as to cross the resilient body41a. The output terminals41are pressed against upper face side wires38, described below, of the interposing substrate33to electrically connect to the upper face side wires38.

The upper face side wires38, electrically connected to the output terminals41of the driving IC34as described above, are formed on the upper face of the interposing substrate33. Plural of the upper face side wires38are formed along the nozzle row direction so as to correspond to the respective piezoelectric elements32. Other end portions of the upper face side wires38, which have respective one end portions that are connected to the output terminals41, are connected to lower face side wires39formed on the lower face of the interposing substrate33through penetrating wires45. The penetrating wires45are wires relaying between the lower face and the upper face of the interposing substrate33, and are configured from a conductor such as metal formed inside penetrating holes that penetrate the interposing substrate33in the plate thickness direction. Connecting electrodes40that are electrically connected to the lead electrodes37of the respective piezoelectric elements32are formed on the lower face (the face on the piezoelectric elements32side) of the interposing substrate33. The connecting electrodes40and the penetrating wires45are connected through the lower face side wires39. Similarly to the input terminals42and output terminals41of the driving IC34, the connecting electrodes40of the present embodiment are each a type of bump electrode formed of a resin portion (a resilient body) and a conductive layer formed on the surface of the resin portion. The connecting electrodes40project toward the diaphragm31side of regions facing the lead electrodes37. These connecting electrodes40are pressed against the lead electrodes37to establish electrical conduction with the lead electrodes37. Note that a configuration may be adopted in which the connecting electrodes40are provided to the lead electrode37side of the diaphragm31(namely, with the lead electrodes37functioning as bump electrodes), and in which the connecting electrodes40and the lower face side wires39of the interposing substrate33are electrically connected.

The interposing substrate33and the pressure chamber formation substrate29(specifically, the pressure chamber formation substrate29onto which the diaphragm31has been stacked) are bonded to each other by the bonding resin43in a state in which the connecting electrodes40are interposed therebetween. In addition to functioning as an adhesive agent that bonds the interposing substrate33and the pressure chamber formation substrate29to each other, the bonding resin43functions as a spacer that forms a gap between the interposing substrate33and the pressure chamber formation substrate29, the gap being to the extent that the driving of the piezoelectric elements32is not obstructed, and the bonding resin43functions as a sealing member that encloses the region where the piezoelectric elements32are formed such that the region is sealed off. Note that, for example, a thermosetting resin having an epoxy resin, an acrylic resin, a phenol resin, a polyimide resin, a silicone resin, a styrene resin, or the like as its primary component, and that includes a photopolymerization initiator or the like, may be suitably employed as the bonding resin43.

In the recording head3formed as described above, ink from the ink cartridge7is introduced to the pressure chambers30through the liquid entry path18, the common liquid chamber25, and the individual communication ports26. In this state, drive signals are selectively applied to the piezoelectric elements32from the output terminals41of the driving IC34through the penetrating wires45and other respective wires and the like, in accordance with discharge data input to the driving IC34from the flexible substrate through the substrate wire portions46and the input terminals42. The piezoelectric elements32are thereby driven such that pressure fluctuations occur in the pressure chambers30, and these pressure fluctuations are controlled to eject ink droplets from the nozzles22.

FIG. 5is a plan view illustrating configuration of the substrate wire portion46on the interposing substrate33.FIG. 6is a cross-section taken along line VI-VI inFIG. 5.FIG. 7is a cross-section taken along line VII-VII inFIG. 5. Note that illustration of a conductive film49is omitted fromFIG. 5. A substrate surface (upper face) of the interposing substrate33is illustrated by hatching inFIG. 5. The substrate wire portions46are formed on the upper face of the interposing substrate33, electrically connected to the input terminals42of the driving IC34, and electrically connected to the flexible substrate (not illustrated). Plural of the substrate wire portions46are provided in a row on the upper face of the interposing substrate33, for each input terminal42of the driving IC34. The conductive film49, described below, is formed in a region where each substrate wire portion46is electrically connected to the respective input terminal42(a connection region). Herein, a connection region means a region where a substrate wire portion46(wire) and an input terminal42(bump electrode) are in contact, and in cases in which a width (a dimension in a second direction intersecting a first direction in which each substrate wire portion46extends) of the contact region is narrower than a width of the opening of a recess47, the region is a connection region of a range encompassing the contact region and extends virtually along the second direction to the edges of the opening of the recess47.

As illustrated inFIG. 4, plural groove-shaped recesses47(trenches) that extend along a direction (the first direction) intersecting the array direction (the second direction) of the substrate wire portions46are formed in strips in the upper face of the interposing substrate33so as to be separated by predetermined intervals along the terminal array direction. Etching processing (dry etching and wet etching) is performed on the monocrystalline silicon substrate that is the interposing substrate33, as described below, to form the recesses47. The recesses47are open at the upper face of the interposing substrate33. A conductive portion48composed of a metal such as copper (Cu) or the like is filled into each recess47by plating or the like (namely, is embedded into the interposing substrate33). Note that an insulating film (not illustrated) composed of a silicon oxide film or the like may be provided between each recess47and the respective conductive portion48. Besides an insulating film, a diffusion prevention film or an adhesion film may also be provided.

A conductive film49composed of a conductive material such as gold (Au) or the like is deposited on the upper face of the interposing substrate33so as to cover the conductive portion48exposed at the opening of each recess47in the respective connection region. Each substrate wire portion46is formed of a respective conductive portion48and conductive film49. The conductive film49is formed of stacking an adhesion layer51of titanium-tungsten (TiW), nickel-chromium (NiCr), or the like and a conductive layer52of gold (Au) or the like. The substrate wire portions46extend along a direction intersecting (orthogonal to) the terminal array direction on the upper face of the interposing substrate33from positions facing the input terminals42of the driving IC34, through regions connected to wiring electrode terminals of the flexible substrate, to an end (edge) of the interposing substrate33. Accordingly, the dimension (overall length) of each substrate wire portion46is sufficiently longer than the dimensions of the wiring electrode terminals of the flexible substrate and the input terminals42of the driving IC34along the direction intersecting the terminal array direction.

Each substrate wire portions46of the present embodiment is formed with a column shaped support portion50that supports the respective input terminal42at a position in the connection region with the input terminal42. Namely, in plan view, the support portion50is provided inside the opening of the recess47. The support portion50is a portion formed by causing silicon to remain, which is the base material of the interposing substrate33, in a column shape when the recess47is formed by etching. In the present embodiment, the support portion50is not formed in a region outside of the connection region. Accordingly, in the connection region, the total width of the opening of the recess47in the second direction intersecting the first direction in which the substrate wire portion46extends, is narrower than the width of the opening of the recess47outside of the connection region. Herein, a total width means a dimension of the opening of the recess47along the second direction, and excludes the range of the support portion50inside the opening. Namely, as illustrated inFIG. 5andFIG. 6, the total width W1of the opening of the recess47in the connection region along the second direction (left-right direction in the figures) is the sum of widths W1aand W1bof the opening at both sides of the support portion50. Providing the support portion50causes the total width W1to be narrower than the total width W2of the opening of the recess47outside the connection region by a corresponding amount.

By thus narrowing the width of the opening of the recess47in the connection region, after the conductive portion48is filled into the recess47by plating or the like as described below, so-called dishing, in which the conductive portion48sinks below the surface of the interposing substrate33during a polishing process, can be suppressed. Accordingly, a step between the surface (upper face) of the interposing substrate33and the conductive portion48inside the opening of the recess47can be suppressed, and thus the risk of the conductive film49disconnecting at the step can be reduced. Accordingly, it is also possible to suppress an increase in resistance or the occurrence of migration or the like due to the step. Further, in the connection regions, variation in the height (the position in the stacking direction of the substrates) of the substrate wire portions46becomes less likely to occur, which enables reduction of the load needed to establish electrical conduction when the input terminals42composed of bump electrodes are pressed against the substrate wire portion46to make electrical connection therewith. Variation in the height of the substrate wire portions46is not limited to variation in the heights between substrate wire portions46. Variation can also be suppressed between the substrate wire portions46and other wire portions on the interposing substrate33. Accordingly, when respective substrates are stacked and load is applied in a direction for both substrates to mutually approach each other such that respective wires on both substrates are connected by the bump electrodes, it is possible to suppress disadvantages due to excessive load such as the electrode layers of the bump electrodes disconnecting, the substrates breaking, or the like. Additionally, in the present embodiment, when the input terminals42and the substrate wire portions46are connected, the input terminals42are supported by the support portions50composed of the base material of the interposing substrate33, which enables electrical conduction to be reliably ensured while reducing the aforementioned load. Adopting such a configuration enables a more reliable recording head3(MEMS device) and printer1to be provided.

Narrowing the width of the opening of each recess47in the connection region (narrowing the opening surface area) causes a corresponding increase in an electrical resistance component. In the present embodiment, to suppress this, as illustrated inFIG. 6, the total width W1(W1a+W1b) along the second direction of the opening of each recess47in the connection region is narrower than the total width W3(W3a+W3b) inside (partway along the thickness direction of the interposing substrate33) the recess47in the connection region. In other words, the total width W3inside each recess47in the connection region is wider than the total width W1of the opening of the recess47in the connection region. Similarly, as illustrated inFIG. 7, the total width W4inside each recess47in a region outside of the connection region is wider than the total width W2of the opening of the recess47in this region. By making the widths inside each recess47wider than the widths of the openings of the recess47, even though the width of the openings of each recess47on the substrate surface is narrowed, the cross-sectional area of the respective substrate wire portion46can be increased, which enables an increase in electrical resistance due to narrowing the width of the opening of each recess47in the connection region to be suppressed.

FIG. 8toFIG. 13are process diagrams describing a process for forming each substrate wire portion46on the interposing substrate33, and illustrate a cross-section at a position in the connection region. First, as illustrated inFIG. 8, a first mask54and a second mask55are formed on a face that will become a mounting face (first face) of a monocrystalline silicon substrate that is the material of the interposing substrate33(a mask forming process). These masks may be, for example, a resist or the like composed of a silicon oxide film, a silicon nitride film, or a photosensitive resin, so long as they function as masks in a dry etching process and a wet etching process explained below. Mask openings57are formed in the first mask54by exposure and developing (seeFIG. 9). The mask openings57are openings employed in a wet etching process. Similarly, mask openings58are formed in the second mask55(seeFIG. 8). The mask openings58are openings employed in a dry etching process. Since the support portions50are provided at portions in the connection region in the present embodiment, the portions corresponding to the support portions50are masked. Note that the opening surface area of the mask openings58is set smaller than the opening surface area of the mask openings57.

Next, as illustrated inFIG. 9, a dry etching process is performed through the mask openings58of the second mask55, and cavities60, which are portions from which formation of the recesses47will originate, are formed at positions where the recess47is intended to be formed. The cavities60, for example, are formed partially in the thickness direction of the base material of the interposing substrate33by an etching process such as the Bosch process. Namely, a plasma etching process and a process of forming a protective film on inner peripheral walls of holes are sequentially repeated to form the cavities (vertical holes)60extending along the thickness direction of the interposing substrate33. The cavities60are respectively formed at both sides of the region where the support portion50is intended to be formed in the connection region. In regions where the recesses47outside of the connection region are intended to be formed, the cavities60are set wider than the cavities60in the connection region. The cross-sectional area of each cavity60along an orientation parallel to the orientation of the upper and lower faces of the base material of the interposing substrate33is smaller than the cross-sectional area (the cross-sectional area at completion) of the later-formed recess47, and in the present embodiment, is adjusted so as to be smaller than the opening surface area (opening surface area at completion) of the recess47in the upper face of the base material. The depth of each cavity60is adjusted to the depth needed for the recess47. Note that the method of forming the cavities60is not limited to the example illustrated, and although various procedures, such as a method employing a laser, may be adopted, it is preferable that the depth of the cavities60is able to be desirably adjusted. After forming the cavities60, the second mask55is removed.

When the cavities60have been formed, next, a wet etching process is performed by introducing an etching solution composed of potassium hydroxide (KOH) through the mask openings57of the first mask54. In the present embodiment, the etching rate of a (110) plane orthogonal to a (100) plane that is parallel to the substrate surface of the interposing substrate33is faster than the etching rate of a (111) plane. Thus, as illustrated inFIG. 10, as the wet etching process progresses, the cavities60expand toward the sides (in a direction intersecting the plate thickness direction of the interposing substrate33), and both inclined faces61formed of (111) planes inclined approximately 55° with respect to a (100) plane that is parallel to the substrate surface of the interposing substrate33, and side faces62formed of (110) planes orthogonal to the (100) plane, are formed. Recesses47having a wider internal total width than a total width of openings in the substrate surface of the interposing substrate33are thereby formed. In the present embodiment, the wet etching process is completed when a support portion50of a desired shape and size has been formed at the position corresponding to the connection region. In the present embodiment, although the side faces62remain when the wet etching process has been completed, depending on the shape and size of the planned recess47, the wet etching process may be performed until the side faces62have disappeared. After forming the recess47, the first mask54is removed. Note that although an example has been given in the present embodiment of configuration in which the upper and lower faces of the interposing substrate33are (100) planes, even when, for example, the upper and lower faces of the interposing substrate33are (110) planes, by performing a process similar to the above, recesses can be formed that have a wider internal total width than a total width of openings in the substrate surface of the interposing substrate33. However, in such a case, the angle of the inclined faces with respect to the substrate surface of the interposing substrate33differs (60°).

When the wet etching process has been completed, then, as illustrated inFIG. 11, a conductive material such as copper (Cu) or the like is filled into the recesses47by a plating process to form the conductive portion48. When this is performed, a bulge portion48′ is formed where the conductive material rises out from the opening of each recess47. Accordingly, after forming the conductive portion48, a polishing process is performed to remove the excess bulge portions48′. Namely, the upper face of the interposing substrate33where the bulge portions48′ are formed is polished using CMP. As illustrated inFIG. 12, the upper face of the interposing substrate33is mostly planarized. When this is performed, since the total width of the openings of each recess47in the connection region is formed so as to be narrower than the opening width of the recess47outside the connection region, dishing in which the conductive portion48sinks below the surface of the interposing substrate33due to excessive planarizing of the conductive portion48, which is softer than the base material (silicon) of the interposing substrate33, is suppressed in at least the connection region. Additionally outside the connection region, by causing the width inside each recess47to be wider than the width of the opening of the recess47, the width of the opening of the recess47in this region can be narrowed without inviting an increase in electrical resistance, which enables dishing to be suppressed.

Then, as illustrated inFIG. 13, a conductive film49is formed at a position where each connection region will be formed, so as to cover the surfaces of the conductive portion48exposed at the openings of the recess47and the surface of the support portion50. In this process, an adhesion layer51is deposited, and then a conductive layer52is deposited in a configuration stacked over the adhesion layer51. In the present embodiment, the adhesion layer51is, for example, made from titanium-tungsten (TiW) and the conductive layer52is, for example, made from gold (Au). A sputtering process, CVD process, plating process, or the like may be adopted as the deposition method. Then, the adhesion layer51and the conductive layer52are patterned using a photolithographic technique and the conductive film49is formed. Through the above processes, the substrate wire portions46are formed on the mounting face of the interposing substrate33.

FIG. 14andFIG. 15are diagrams illustrating configuration of a substrate wire portion64of a second embodiment of the invention.FIG. 14is a plan view, andFIG. 15is a cross-section taken along line XV-XV inFIG. 14. Although an example was given in which the substrate wire portion46in the first embodiment above has a configuration in which the opening of the recess47is provided with an island shaped support portion50, there is no limitation thereto. The substrate wire portion64of the present embodiment differs from the first embodiment in that, in the connection region with the input terminals42, edges of the opening of a recess67respectively project further in the second direction toward the opposing opening edge side than edges of the opening in a region outside the connection region, so as to form projections68. By providing the projections68at a portion corresponding to the connection region of the substrate wire portion64in this manner, the width of the opening of each recess67along the second direction in the connection region becomes narrower than the width of the opening of the recess67in a region outside the connection region. Namely, the opening width (total width of the opening) W1′ of the recess67along the second direction (the left-right direction in the figures) in the connection region is narrower than the opening width W2of the recess67outside the connection region by an amount corresponding to the provision of the projections68to both sides of the recess67. Thus, by causing the opening width of the recess67in the connection region to be narrower than the opening width of the recess67outside the connection region, similarly to in the first embodiment above, during a polishing process after a conductive portion65has been filled into the recess67by plating or the like, dishing, in which the conductive portion65sinks below the surface of the interposing substrate33due to the conductive portion65being excessively planed, is suppressed. Additionally, similarly to the support portion50of the first embodiment above, the projections68bear load during connection with the input terminals42, which enables electrical conduction to be more reliably ensured.

In each of the above embodiments, explanation was given using an example in which the electrical connection between a bump electrode and a connection region of a wire is a connection between a substrate wire portion46, which is one type of wire on the interposing substrate33, and an input terminal42, which is one type of bump electrode on the driving IC34, which is one type of driving circuit, (the electrical connection between the bump electrode and the connection region of a wire is a connection between a driving circuit and a substrate); however, there is no limitation thereto. For example, the invention may be applied to a connection between a lead electrode37of a piezoelectric element32, which is one type of driving element, and a lower face side wire39of the interposing substrate33. In such a case, configuration may be made in which a bump electrode is provided to each lead electrode37, and the lower face side wires39are wires having similar structure to that of the substrate wire portions46. Namely, in this structure, the electrical connection between the bump electrodes and the connection regions of the wires is a connection between a substrate and a driving element. In this configuration, dishing of the lower face side wires39is also suppressed, thereby enabling more reliable electrical conduction to be ensured between the lead electrodes37and the lower face side wires39. As a result, since a more reliable electrical connection can be ensured between the driving circuit and the driving element, the reliability of the MEMS device can be improved.

Moreover, the invention can be applied to configurations not including an interposing substrate33. Namely, the invention can be applied to a portion electrically connecting a driving element and a driving circuit in a configuration in which the driving circuit is stacked on a substrate provided with the driving element.

Moreover, there is no limitation to the shape or the size of the support portion50and the projections68given as examples in the above embodiments. For example, each support portion50may be an elongated island shape extending along the extension direction of the respective substrate wire portion46(the first direction). As illustrated inFIG. 14, the projections68are also not limited to being substantially trapezoidal shaped in plan view, and may be any shape that reduces the opening width of the recess47in the substrate wire portion46.

Moreover, the invention can be applied to any MEMS devices in which the electrode terminals of plural substrates are electrically connected to each other. For example, the invention can be applied to MEMS devices such as sensors that detect pressure changes, vibration, displacement, or the like in movable regions.

In the above embodiments, although explanation has been given regarding an example in which an ink jet recording head3serves a liquid ejecting head, the invention can be applied to other liquid ejecting heads in which the electrode terminals of plural substrates are electrically connected to each other. For example, the invention can be applied to colorant ejecting heads employed in the manufacture of color filters for liquid crystal displays or the like, electrode material ejecting heads employed to form electrodes of organic electroluminescent (EL) displays, field emission displays (FEDs), or the like, bioorganic matter ejecting heads employed in the manufacture of biochips (biochemical elements), and the like. In colorant ejecting heads for display manufacturing apparatuses, solutions of R (red), G (green), and B (blue) colorants are each ejected as respective types of liquid. In electrode material ejecting heads for electrode forming apparatuses, a liquid electrode material is ejected as one type of liquid, and in bioorganic matter ejecting heads for chip manufacturing apparatuses, a bioorganic matter solution is ejected as one type of liquid.