Inkjet print head

Abstract

A printhead for ejecting one or more printable fluids, the printhead comprising a substrate, the substrate defining a plurality of MEMS droplet ejectors arranged in a grid, each comprising a flexible diaphragm, a piezoelectric actuator and at least one MEMS metallization layer, the substrate further defining a CMOS control circuit comprising at least one CMOS metallization layer, the at least one metallization layer comprising one or more of: a conductive connection extending from the CMOS control circuit for actuating the piezoelectric actuator to each piezoelectric actuator; a conductive connection extending through a grid in the at least one metallization layer for conducting an actuator drive waveform; and a plurality of bond pads within an individual zone. The printhead is compact, can be easily manufactured, and has relatively few required wired connections.

Description

Technical Field

[0001] The present invention relates to the field of inkjet printheads formed as a monolithic structure on a substrate. The inkjet printhead ejects printable fluids such as color ink, materials for additional printing, and the like.

Background Art

[0002] In a conventional piezoelectric inkjet printhead in which a high density of individual droplet ejectors are formed on the same substrate, at least one, a number of individual wire connections are required for each droplet. In the case of a 1200 dpi inkjet printhead, this can correspond to 1200 individual wire bonds to enable external off-chip connections.

[0003] It has been proposed to provide an integrated piezoelectric inkjet printhead having a CMOS drive circuit on which a MEMS layer formed on a substrate and including nozzles and MEMS piezoelectric transducers is stacked (WO2018 / 054917, McAvoy). Thereby, the number of external off-chip connections can be significantly reduced. Further, these devices can be formed using a conventional CMOS foundry process without the need for additional assembly steps for coupling the droplet ejector components.

[0004] It is desirable to maximize the density of droplet ejectors and minimize printing artifacts so that adjacent nozzles are affected by consistent physical parameters (such as temperature, pressure). As a result, technical problems arise in the on-chip wiring of individual droplet ejectors, and the maximum density of droplet ejectors may be limited. This is particularly true for devices in which the nozzles are formed in the MEMS layer and the ink chamber is at least partially defined by the substrate. In this case, the holes resulting from penetrating the substrate and at least a part of the surface area required for the piezoelectric transducer cannot be used for routing electrical signals, and the density of droplet ejectors is limited.

[0005] The present invention addresses these problems and aims to provide a compact monolithic print head that can be formed with a high-density droplet ejector, typically using a conventional CMOS foundry process.

Summary of the Invention

[0006] A print head for ejecting one or more printable fluids, the print head comprising a substrate,

[0007] The substrate defines a plurality of MEMS droplet ejectors arranged in a grid for ejecting droplets of one or more printable fluids, each droplet ejector comprising a flexible diaphragm and a piezoelectric actuator for ejecting (respectively) droplets of the printable fluid through a nozzle by moving the flexible diaphragm, and each droplet ejector comprising at least one MEMS metallization layer,

[0008] The substrate further defines a CMOS control circuit comprising at least one CMOS metallization layer, a print head.

[0009] The substrate may comprise conductive connections extending from the CMOS control circuit to each piezoelectric actuator within at least one of the metallization layers (i.e., at least one of the MEMS metallization layers and / or at least one of the CMOS metallization layers) for actuating the piezoelectric actuators.

[0010] The substrate may comprise conductive connections extending through a grid within at least one of the metallization layers (i.e., at least one of the MEMS metallization layers and / or at least one of the CMOS metallization layers) for conducting the actuator drive waveform.

[0011] The substrate may comprise a plurality of bond pads in an individual (e.g., single) zone of the substrate (e.g., along a single edge).

[0012] The substrate (i) at least one conductive connection within said at least one metallization layer (i.e., at least one of said MEMS metallization layer and / or at least one of said CMOS metallization layer) extending from the CMOS control circuit to each piezoelectric actuator for actuating the piezoelectric actuator, and (ii) optionally, one or more of the conductive connections extending through the grid within said at least one metallization layer (i.e., at least one of said MEMS metallization layer and / or at least one of said CMOS metallization layer) for conducting the actuator drive waveform, and / or (iii) may include one or more of a plurality of bond pads within an individual (e.g., single) zone of the substrate (e.g., along a single edge).

[0013] One or more printable fluids may include a plurality of printable fluids, typically at least 3 or at least 4 different printable fluids. The printable fluid may be ink. The inks may be of different colors. The print head may be a multi-channel print head. This refers to a print head having a plurality of different printable fluids and / or a plurality of different grids (droplet ejector zones) and typically having separate printable fluid supply sources.

[0014] The grid may be a parallelogram grid. The grid may be a rhombic grid, a hexagonal grid, a rectangular grid (e.g., a square grid), or an equilateral triangular grid. Thus, a plurality of MEMS droplet ejectors may be arranged in a grid pattern.

[0015] The lattice of the MEMS droplet ejector usually forms a droplet ejector zone on the substrate. The droplet ejector zone usually comprises at least 100 droplet ejectors. The droplet ejector zone is usually elongated. The droplet ejector zone usually has a length and a width. The droplet ejector zone may be rectangular. The droplet ejector zone may be parallelogram-shaped. Usually, the ratio of the length to the width of the droplet ejector zone is at least 5, or at least 10, or at least 20. The length and width refer to the length and width of the rectangle with the smallest area that completely surrounds the droplet ejector zone.

[0016] Usually, the lattice comprises a plurality of rows of MEMS droplet ejectors extending across the width of the lattice. Usually, there are more rows (extending across the width) than the number of MEMS droplet ejectors in any row. Usually, each row (extending across the width) has 4 to 16 MEMS droplet ejectors, more typically 8 to 12.

[0017] Usually, the lattice includes more than 50 rows (usually parallel to each other). The rows can be aligned parallel to the width of the droplet ejector zone. However, this is not essential. For example, in the case of a parallelogram-shaped lattice, the rows are aligned at a slight angle rather than parallel to the width of the droplet ejector zone. Usually, the rows extend at an angle between 45° and 135° with respect to the length of the droplet ejector zone, or between 30° and 120° with respect to the length of the droplet ejector zone, or between 15° and 105° with respect to the length of the droplet ejector zone.

[0018] The substrate may comprise (i) on at least one of said metallization layers, conductive connection portions (actuating conductive connection portions) extending from a CMOS control circuit for actuating the piezoelectric actuators to each piezoelectric actuator.

[0019] In some embodiments, there are one or more separate and distinct conductive connection portions extending from the CMOS control circuit to each piezoelectric actuator to operate each piezoelectric actuator individually. In other embodiments, one or more conductive connection portions for operating the actuators are connected to each of a plurality of piezoelectric actuators to operate each piezoelectric actuator, in which case the CMOS control circuit is typically configured to individually address control signals to each piezoelectric actuator.

[0020] Typically, the length of the operating conductive connection portion between the CMOS control circuit and the piezoelectric actuator within a group of piezoelectric actuators is constant. Since the operating conductive connection portions have the same length, thickness, and width, they are subject to similar effects due to voltage drop, parasitic capacitance, antenna effect, etc.

[0021] The length of the conductive connection for operating the piezoelectric actuator between the CMOS control circuit and the piezoelectric actuator within the droplet ejector zone can be constant.

[0022] Typically, the length of the conductive connection portion for operating the piezoelectric actuator between the CMOS control circuit (e.g., ejection transistor) and the piezoelectric actuator within the droplet ejector zone varies within 1 cm or less, preferably 0.1 cm or less. Typically, the length of the conductive connection portion for operating the piezoelectric transducer between the CMOS control circuit and the piezoelectric actuator within the droplet ejector zone varies within 10 times the interval between droplet ejectors along the row of the droplet ejector. Typically, the substrate has an elongated shape with length and width, and the length of the conductive connection portion for operating the piezoelectric transducer between the CMOS control circuit and the piezoelectric actuator within the droplet ejector zone varies within 20% or less, or 10% or less of the width of the substrate. The droplet ejector zone typically includes at least eight droplet ejectors. The droplet ejectors in the droplet ejector zone typically eject the same one printable fluid among a plurality of printable fluids.

[0023] Typically, the conductive connection for actuating a piezoelectric actuator extends through one or more MEMS metallization layers via a connection from a CMOS control circuit in one or more CMOS metallization layers to one or more MEMS metallization layers adjacent to each piezoelectric actuator to the electrodes of the MEMS piezoelectric actuator, and includes metal wires.

[0024] The CMOS metallization layer is a metallization layer that connects CMOS devices in a substrate and is formed as part of a CMOS manufacturing process. The MEMS metallization layer is a metallization layer formed (on top of the CMOS metallization layer) for the purpose of operating MEMS devices and is used. (In the present invention, the MEMS metallization layer may include additional conductors, such as conductive connections for conducting actuator drive waveforms).

[0025] One or more of the piezoelectric transducer, the electrodes, and the MEMS metallization layer may include gold. Gold is excluded from CMOS manufacturing facilities.

[0026] The lattice of the MEMS droplet ejector can form a droplet ejector zone of the substrate. The droplet ejector zone has a length and a width and is in an elongated shape with opposing long sides along the length. The conductive connection for actuating the actuator extends into the lattice from one or both of the opposing long sides of the droplet ejector zone.

[0027] Typically, the conductive connection extends into the lattice with a length less than 1.5 times the width of the droplet ejector zone, usually less than 1.2 times. In some embodiments, the conductive connection extends into the lattice with a length shorter than the width of the droplet ejector zone.

[0028] The CMOS control circuit may include a plurality of drive transistors, and at least one of the plurality of drive transistors is directly connected to at least one electrode of the piezoelectric transducer of each MEMS droplet ejector by the conductive connection portion in order to operate the piezoelectric actuator without interposing a transistor. The plurality of drive transistors are arranged in at least one row adjacent to one or two of the opposing long side surfaces of the droplet ejector zone.

[0029] The conductive connection portion for operating the piezoelectric actuator may extend into the grid between the rows of the MEMS droplet ejectors.

[0030] Generally, the conductive connection portion for operating the piezoelectric actuator extends from one or both of the opposing long side surfaces into the grid between the rows of the MEMS droplet ejectors. Generally, the conductive connection portion for operating the piezoelectric actuator extends laterally into the grid between the rows of the MEMS droplet ejectors.

[0031] With this arrangement, it is ensured that the MEMS droplet ejectors in the same row (parallel to the width) receive control signals from the control circuit at very similar times. This improves the printing quality and / or reduces the complexity of control.

[0032] Generally, the aspect ratio of the length to the width (of the grid / droplet ejector zone) is at least 5, or at least 10, or at least 20.

[0033] The conductive connection portion for operating the piezoelectric actuator may extend into the grid from one or both of the long side surfaces. The conductive connection portion for operating the piezoelectric actuator may extend into the grid from both long side surfaces along the width in some cases.

[0034] The rows of piezoelectric actuators between which the conductive connection portion for operating the piezoelectric transducer extends may be aligned at an angle of at least 45°, usually at least 60° or at least 75° with respect to the length of the droplet ejector zone.

[0035] The actuator drive waveform may include pulses having portions of each polarity. Thus, the direction of the potential difference between each piezoelectric actuator reverses twice within each droplet ejection.

[0036] The CMOS control circuit may be configured to determine, for each MEMS droplet ejector, for each of a plurality of ejection cycles, whether that MEMS droplet ejector should eject a droplet, and the conductive connection for actuating the actuator is connected to an ejector switch (usually a latch) associated with each MEMS droplet ejector, thereby controlling whether an individual MEMS droplet ejector ejects a droplet.

[0037] Thus, the determination of whether each MEMS droplet ejector should eject a droplet is made within the CMOS control circuit (usually in response to digital image data received via a digital interface, usually one or more bond pads). This avoids the need for a large number of individual conductive connections to a control circuit external to the substrate, reducing the difficulty in connecting the substrate. Usually, the determination is made for each MEMS droplet ejector for each of a plurality of ejection cycles. An ejection cycle may include multiple stages, and during each stage, a different subset of MEMS droplet ejectors, if selected, ejects printable fluid.

[0038] The substrate may include a conductive connection that extends through a grid in at least one of the metallization layers to conduct an actuator drive waveform for connecting the MEMS droplet ejector to one or more actuator drive waveform sources.

[0039] The conductive connection can relay different actuator drive waveforms to different groups of MEMS droplet ejectors by connecting different groups of MEMS droplet ejectors to different actuator drive waveform sources among a plurality of actuator drive waveform sources.

[0040] Typically, a MEMS droplet ejector includes a plurality of spatially separated MEMS droplet ejector zones, each zone including a lattice of MEMS droplet ejectors, and each MEMS droplet ejector within the same droplet ejector zone receives the same actuator drive waveform. Typically, in at least two, or at least four, different droplet ejector zones, the droplet ejectors within each zone receive different actuator drive waveforms. Typically, the droplet ejectors of each zone receive printable fluid from the same source. Thus, droplet ejectors ejecting different printable fluids can receive different actuator drive waveforms, while droplet ejectors ejecting the same printable fluid are located in the same droplet ejector zone and can receive the same actuator drive waveform. Thus, the actuator drive waveform can be customized according to the physical properties of each printable fluid.

[0041] The actuator drive waveform source may include one or more actuator drive waveform generators. The actuator drive waveform source may include one or more interfaces such as bond pads of the printhead substrate, typically the plurality of bond pads, for receiving the actuator drive waveform from a source external to the substrate. The external source may be, for example, one or more actuator drive waveform generators disposed within a printing device such as a printer that is not formed on the substrate, is typically separate from the printhead, but also includes the printhead.

[0042] The droplet ejector zone has a length and a width, may have opposite long sides along the length, and a conductive connection for conducting the actuator drive waveform extends into the lattice from one or both of the opposing long sides of the droplet ejector zone.

[0043] The conductive connection for conducting the actuator drive waveform may extend into the grid from one or both of the opposing long sides. The conductive connection for conducting the actuator drive waveform may extend into the grid between the rows of the MEMS droplet ejector from one or both of the opposing long sides. The conductive connection for conducting the actuator drive waveform may extend laterally within the grid between the rows of the MEMS droplet ejector.

[0044] The rows of piezoelectric actuators into which the conductive connection for conducting the actuator drive waveform extends therebetween may be aligned at an angle of at least 45°, usually at least 60° or at least 75° with respect to the length of the droplet ejector zone.

[0045] The substrate may define a plurality of elongated droplet ejector zones, and the conductive connection for conducting the actuator drive waveform may comprise a plurality of separate buses, and for one or more of the elongated droplet ejector zones, the conductor that is part of the bus for conducting the actuator drive waveform to that zone extends across the width of one or more further droplet ejector zones.

[0046] Thus, since the conductive connection for conducting the actuator drive waveform does not need to extend around the (short) edges of each droplet ejector zone, the length of the conductive connection is shortened, and more substrate surface area can be used than would be the case if it were extended around the (short) edges of each droplet ejector zone.

[0047] The substrate may comprise a plurality of bond pads within a single individual zone of the substrate.

[0048] The substrate may comprise a bond pad zone including a plurality of bond pads that are spatially separated from a plurality of MEMS droplet ejectors and usually also spatially separated from a CMOS control circuit. There may be only one bond pad zone. The bond pad zone may be elongated and arranged along a single edge of the substrate. Usually, the substrate has an elongated shape with opposing edges and a short edge therebetween, and the bond pad zone is arranged along the long edge. However, in some embodiments, the bond pad zone may be on the short edge. There may be two bond pad zones that are elongated and usually arranged along opposing long sides of the substrate. The bond pads within the bond pad zone may be spaced along a straight line.

[0049] The substrate may comprise fewer than 75, and further fewer than 50, external electrical connections in total. The ratio of individually controllable MEMS droplet ejectors to external electrical connections may be greater than 1, may be greater than 10, and in some embodiments may be greater than 100. This is made possible by the CMOS control circuit and reduces the complexity of the wiring connections to the substrate as compared to a printing device that requires individual electrical connections for individually controllable MEMS droplet ejectors on the substrate.

[0050] One or more conductive connections for actuator drive signals may be configured to provide potential switching to 100 or more, and further 1000 or more, droplet ejectors. The conductive connections extending from the CMOS drive circuit to the piezoelectric actuator to operate the piezoelectric actuator may each provide potential to 10 or fewer, 4 or fewer, or just one piezoelectric actuator. Thus, a much smaller cross-sectional area of conductive metal may be required compared to the conductive connections for actuator drive signals.

[0051] There may be no transistors within the lattice of MEMS droplet ejectors.

[0052] However, for at least the majority of a plurality of MEMS droplet ejectors, an ejector switch comprising one or more CMOS transistors formed on a substrate can controllably apply a potential difference to the electrodes of the piezoelectric actuator of each MEMS droplet ejector, and one or more of the above conductive connections (conductive connections for operating the piezoelectric actuator and / or conductive connections for conducting the actuator drive waveform and / or conductive connections for connecting each of the MEMS droplet ejectors to two or more different fixed voltages) may be arranged in a grid for electronic communication therewith to cause the MEMS droplet ejector to eject printable fluid. The ejector switch typically includes a latch.

[0053] The ejector switch may be configured to selectively route an actuator drive waveform (voltage and / or current) to respective piezoelectric transducers, and the actuator drive waveform is received via one or more of the above conductive connections within at least one metallization layer.

[0054] Therefore, the power electronics required to generate current for the piezoelectric transducer can be located elsewhere, and the associated heat is also generated elsewhere. In some embodiments, the ejector switch only needs to switch the actuator drive waveform, reducing power consumption on the substrate within the grid.

[0055] Typically, the CMOS control circuit is arranged in one or more individual zones of the substrate, separate from the bond pads and the MEMS droplet ejector.

[0056] Nevertheless, in some embodiments, the ejector switch may be disposed within a grid relative to at least a majority of the plurality of MEMS droplet ejectors. In other embodiments, one or more transistors that function as ejector switches for individual MEMS droplet ejectors are disposed within the CMOS control circuit. Thus, there may be no transistors within the grid of MEMS droplet ejectors, or at least fewer transistors than the MEMS droplet ejectors.

[0057] Each MEMS droplet ejector may comprise a hole that penetrates a substrate for ejecting a printable fluid.

[0058] Thus, the substrate comprises a plurality of holes associated with one of the corresponding MEMS droplet ejectors. The holes typically form a grid. The holes are typically nozzles for the MEMS droplet ejectors. Each nozzle is typically in fluid communication with a printable fluid chamber at least partially defined by the substrate.

[0059] Since each MEMS droplet ejector comprises a hole that penetrates the substrate, the surface area of the substrate available for conductive connections is limited. Typically, the conductive connections extend between rows of holes.

[0060] Typically, each flexible diaphragm extends around the corresponding hole. The conductive connections may extend between the flexible diaphragms without overlapping the flexible diaphragms. The conductive connections may extend between the holes without overlapping 50% of the central surface area of the flexible diaphragm.

[0061] In at least one region of the substrate (typically, at least one region of the substrate within the grid of droplet ejectors, such as a region adjacent to each droplet ejector), one or more MEMS metallization layers may overlap one or more CMOS metallization layers.

[0062] One or more MEMS metallization layers may be formed directly on one or more CMOS metallization layers.

[0063] One or more CMOS metallization layers may be integrated with one or more MEMS metallization layers, for example, at the interface of a CMOS control circuit. Thus, one or more CMOS metallization layers and one or more MEMS metallization layers may be formed simultaneously.

[0064] One or more CMOS metallization layers may be electrically connected to one or more MEMS metallization layers.

[0065] One or more insulating layers may be formed between one or more CMOS metallization layers and one or more MEMS metallization layers. Usually, the one or more insulating layers are thicker than the insulating layers between the CMOS metallization layers. This provides additional electrical insulation and reduces the parasitic capacitance between the metal wiring layers.

[0066] The substrate may further include conductive connections extending through a grid in at least one metallization layer to connect each of the MEMS droplet ejectors (usually, the ejector switches of each MEMS droplet ejector) to two or more different fixed voltages. The CMOS control circuit (usually the ejector switch associated with each MEMS droplet ejector) is configured to selectively connect at least one electrode of the piezoelectric actuator of each droplet ejector to each of two or more different fixed voltages in sequence in response to a control signal from the CMOS control circuit.

[0067] The droplet ejector zone may have a length and a width and may have opposing side surfaces along the length. The conductive connections for connecting each of the MEMS droplet ejectors to two or more different fixed voltages extend into the grid from one or both of the opposing long side surfaces of the droplet ejector zone.

[0068] The conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages may extend into the grid from one or both of the opposing long sides. The conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages may extend into the grid between the rows of the MEMS droplet ejectors from one or both of the opposing long sides. The conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages may extend horizontally into the grid between the rows of the MEMS droplet ejectors.

[0069] The rows of piezoelectric actuators in which the conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages extend therebetween may be aligned at at least 45°, typically at least 60° or at least 75° with respect to the length of the droplet ejector zone.

[0070] The substrate may define a plurality of elongated droplet ejector zones, and the conductive connection portions for connecting each MEMS droplet ejector to two or more different fixed voltages may include a plurality of individual buses, and for one or more of the elongated droplet ejector zones, the conductors that are part of the bus for conducting the actuator drive waveform to that zone extend across the width of one or more additional droplet ejector zones.

[0071] Thus, since the conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages do not need to extend around the (short) edges of each droplet ejector zone, the length of the conductive connection portions is shortened, and instead, more substrate surface area can be used than when extended around the (short) edges of each droplet ejector zone.

[0072] One or more conductive connection portions for connecting each of the MEMS droplet ejectors to two or more different fixed voltages may be configured to provide potential switching to 100 or more, and further 1000 or more, droplet ejectors.

[0073] The ejector switch may be configured to selectively connect each piezoelectric transducer to two or more (or three or more) different fixed voltages in sequence to actuate the ejection of droplets, and the piezoelectric transducer is connected to different fixed voltages via one or more conductive connections in at least one metallization layer.

[0074] The print head may include a first plurality of conductive connections and a second plurality of conductive connections, one of the first plurality of conductive connections and the second plurality of conductive connections includes a conductive connection for actuating a piezoelectric actuator, and the other of the first plurality of conductive connections and the second plurality of conductive connections includes a conductive connection for conducting a droplet ejector waveform or a plurality of different potentials, and at least one first conductive connection and at least one second conductive connection both extend at one or more positions within the grid. Usually, they extend to different metallization layers.

[0075] The at least one first conductive connection and the at least one second conductive connection may be in parallel. The at least one first conductive connection and the at least one second conductive connection may cross each other.

[0076] Usually, at least one conductive connection for conducting a droplet ejector waveform is disposed within a MEMS metallization layer, and at least one conductive connection for actuating a piezoelectric actuator is disposed within a CMOS metallization layer.

[0077] Usually, one of the first plurality of conductive connections and the second plurality of conductive connections extends through one or more MEMS metallization layers, and the other of the first plurality of conductive connections and the second plurality of conductive connections extends through one or more CMOS metallization layers.

[0078] The conductors that conduct the actuation signal to the droplet ejectors may extend between the rows of the droplet ejectors such that they overlap but are located in different metallization layers, for example, different CMOS metallization layers. This enables individual processing of a number of droplet ejectors from one side of the droplet ejector zone.

[0079] At one or more positions within the grid, at least one conductive connection for actuating the piezoelectric actuator and at least one conductive connection for conducting the droplet ejector waveform may extend (usually parallel) between the same adjacent rows of the droplet ejectors.

[0080] The grid may comprise MEMS droplet ejectors in at least a first row, a second row, and a third row (usually with no other rows in between), and a plurality of (usually at least four) conductive connections extend along the length of the second row to respective different droplet ejectors between the droplet ejectors of the first row and the second row, and usually a plurality of (usually at least four) conductive connections extend along the length of the second row to respective different droplet ejectors between the droplet ejectors of the second row and the third row.

[0081] The plurality of (usually at least four) conductive connections that extend to respective different droplet ejectors between the rows of the droplet ejectors may extend through the same or different metallization layers.

[0082] The CMOS control circuit may comprise one or more first zones and one or more second zones, the substrate comprises one or more isolation mechanisms that separate the first zone and the second zone, the one or more first zones comprise transistors that process digital signals, the one or more second zones comprise drive transistors that directly provide a potential to the electrodes of the piezoelectric actuator, and the second zone operates at at least twice the maximum potential of the first zone.

[0083] A CMOS control circuit is formed on a first surface of the substrate, and a flexible diaphragm, a piezoelectric actuator, and a MEMS metallization layer may also be formed on the first surface of the substrate.

[0084] The first surface of the substrate typically includes a nozzle forming layer with a flexible diaphragm and a piezoelectric actuator.

[0085] The substrate may be in an elongated shape having a length and a width, and may define a plurality of adjacent droplet ejector zones isolated orthogonally to those lengths, and between each adjacent droplet ejector zone, there is provided at least one CMOS circuit zone which is also in an elongated shape and aligned in the same direction as the droplet ejector zone. The CMOS circuit zone includes at least one CMOS metallization layer, and the conductive connection extends from the CMOS circuit to the adjacent droplet ejector zone to operate the piezoelectric actuator.

[0086] Typically, the substrate is in an elongated (usually rectangular) shape, and the droplet ejector zones have lengths and widths that match the length and width of the substrate.

[0087] At least one CMOS circuit zone may include both a high voltage region and a low voltage region. The low voltage region includes one or more digital logic gates, and the high voltage region includes ejection transistors directly connected to the piezoelectric transducers of the respective droplet ejectors.

[0088] Typically, the high voltage region and the low voltage region are separated by an isolation mechanism within the substrate.

[0089] The high voltage region and the low voltage region refer to the relative voltages during operation.

[0090] One or more conductive connections for the actuator drive waveform may extend laterally across one or more droplet ejector zones and be connected to the high voltage region of the CMOS circuit zone.

[0091] In a second aspect, the present invention extends to a printing apparatus comprising a print head according to the first aspect of the present invention.

[0092] According to a third aspect of the present invention, there is provided a method of forming a print head as claimed in any one of the preceding claims, forming a grid of apertures through the substrate, each aperture at least partially defining a fluid chamber of a droplet ejector; forming a CMOS control circuit comprising at least one CMOS metallization layer on a first surface of the substrate; forming a plurality of droplet ejectors by forming a MEMS layer comprising a flexible diaphragm, a piezoelectric actuator and at least one MEMS metallization layer on the first substrate of the substrate, whereby each droplet ejector is conductively connected to the CMOS control circuit via at least one said metallization layer.

[0093] The method may include forming an insulating layer over the CMOS control circuit before forming at least one MEMS metallization layer.

[0094] The MEMS layer may have holes therein. The holes may function as nozzles of the droplet ejectors.

[0095] Hereinafter, exemplary embodiments of the present invention are shown with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0096]

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DETAILED DESCRIPTION OF THE INVENTION

[0097] FIG. 1 is a plan view showing the layout of an integrated inkjet printhead 100. The printhead is formed on a single semiconductor substrate 102 and has an elongated shape with opposing long edges 104 parallel to its length 106 and opposing short edges 103 parallel to its width 108. A bond pad zone 110 with a plurality of bond pads 112 is arranged along a part of a single long edge. The substrate has a plurality of elongated zones of integrated droplet ejectors 114A, 114B, 114C, 114D, each associated with a different channel and extending longitudinally aligned with the long edge of the substrate. Each zone comprises a droplet ejector having the same printable fluid supply source. In this example, each zone of the integrated droplet ejector has a different color printable fluid supply source, but the present invention is also applicable to multi-channel devices having a single color or a single type of printable fluid supply source. Within each zone, the droplet ejectors are arranged in a lattice (repeating array of dots, e.g., rhombic lattice, square lattice, hexagonal lattice, rectangular lattice, parallelogram lattice, equilateral triangle lattice). In this example, the droplet ejectors are arranged in a parallelogram lattice having rows extending parallel to the length (longitudinal direction) of the substrate and columns extending across the width of the lattice at a slight angle to the width of the lattice. The rows of droplet ejectors extend laterally across each zone of the droplet ejector zone at a small angle to the long edge and length of the droplet ejector zone. This parallelogram arrangement provides droplet ejectors at a wide range of longitudinal positions, improving the maximum print density.

[0098] The substrate is a semiconductor substrate on which a CMOS control circuit is formed. The CMOS control circuit includes a central control circuit 120 (master data path circuit) that executes calculations and determines signal routing, and a drive circuit 122 that includes at least one CMOS drive transistor for each droplet ejector. The drive circuit functions as a latch and provides a wired connection to the electrodes of the piezoelectric actuator of each droplet ejector. The elongated zone of the drive circuit 122 is disposed along the opposing long sides of each zone of the droplet ejector and is interposed between the opposing long sides, and the individual rows of the droplet ejector are configured to be controllably actuated by drive transistors at both ends of the row using conductive connection portions 240 that extend from the opposing long sides into the grid of the droplet ejector so as to actuate the droplet ejector of each zone of the droplet ejector.

[0099] Figure 2 is a schematic diagram of the control circuit of the printhead assembly. In this example, control of the printhead is distributed between a machine controller 220 separate from the substrate and control circuits (e.g., CMOS circuits) 120, 122A - D on the substrate 102. They are partially connected by conductors that extend through single or multiple flexible cable interconnects 218.

[0100] Each piezoelectric actuator 320 within the droplet ejector is controlled by applying a potential to its electrodes 340, 342. These potentials typically vary with time in the form of an actuator drive waveform that is normally repeated for each droplet ejection cycle. The machine controller comprises at least a processor 200, such as a microprocessor or microcontroller, having a memory 202 for storing relevant data and program code. A wired or wireless electronic interface 204 receives input data from an external device driver. Those skilled in the art will understand that the machine controller may be distributed among a plurality of individual components or functional modules, such as one component that converts an image into a pixelated pattern for printing using a dither matrix, or another component that converts the pixelated pattern into a printing pattern for different nozzles.

[0101] The machine controller may comprise at least one waveform generator and a voltage amplifier 208 that provides a continuous pattern of actuator control pulses to the printhead via one or more drive signal conductors 210. A ground conductor 212 also extends from the machine controller to the substrate. (For clarity, the ground connection on the substrate is not shown). The processor 200 typically generates digital control signals 214 as a serial bus and also transmits a clock signal 216 to the printhead that serves to synchronize printing with the movement of the printhead. This connector also provides voltage levels related to the operating voltage of the CMOS control electronics.

[0102] On the substrate 100, bond pads 112 are connected to conductors of the flexible connector, and signals are routed from the bond pads through the metallization layer to the CMOS control circuit 120 and from the CMOS control circuit to the electrodes 320, 340 that activate the individual piezoelectrics 342 within each droplet ejector. The received signals include both a digital control signal encoding image information and an analog actuator control pulse conducted via the actuator drive waveform conductor 250.

[0103] The control circuit 120 on the substrate 102 extends to the drive circuit 122, and the drive circuit 122 includes an ejection switch circuit 220 having an ejection transistor with an output that is directly electrically connected to the electrodes 340, 342 via an electrode drive conductor 240 which is a conductive connection directly connected to the electrode (i.e., without further intervening switching semiconductor junctions). The ejection switch circuit selectively switches the actuator control pulse signals received via the conductor 250 and applies these pulse signals to the respective electrodes via the electrode drive conductor 240. If one of the electrodes remains grounded, the ejection switch circuit can be as simple as a single transistor per actuator or a single transistor per electrode for switching the signal applied to that electrode. In the example shown, two conductors extend to each of the individual piezoelectric actuators, one by one per electrode, but there may also be a single electrode drive conductor 240 extending to each of the individual piezoelectric actuators.

[0104] The ejection switch circuit does not perform power amplification. Instead, it switches the actuator control pulses and determines whether each pulse is relayed to the respective actuator for each pulse. Voltage amplification is performed by the amplifier 208 in the machine controller.

[0105] The ejection switch circuit is controlled by a latch and shift transistor 222 that receives and stores digital data from the control circuit 224. The control circuit 224 processes the received data, for example, converts the received serial data, stores these in the register 226, and determines which actuator to activate during each activation event of successive actuators using the received data. The control circuit 228 also stores trim data that is used to customize the exact timing of the voltage switching of each actuator. This trim data is typically determined during the calibration step at setup and may store configuration data 230 indicating the physical layout of the nozzles, security information, and / or nozzle actuation history information. The control circuit 224 also receives data from sensors 232, 234, 236, some of which are associated with individual actuators, such as nozzle fill level sensors, and some of which sense parameters related to the overall function of the printhead, such as temperature sensors.

[0106] Figure 3 is a cross-sectional view of a region of an integrated inkjet printhead 100 comprising a silicon substrate 102 having an insulator layer 302 (thus, a silicon-on-insulator or silicon-on-insulator-on-silicon substrate). The integrated CMOS circuits 120, 122 overlap on the CMOS metallization layer 306 and are formed on the first surface 304 of the silicon substrate with a passivation layer 308 such as SiO2, SiN, SiON interposed therebetween. Those skilled in the art will understand that the CMOS circuit includes both the doped regions of the substrate and the metallization layer on which the interconnections are formed on the first surface of the substrate. The number of CMOS metallization layers is variable but is typically at least three layers.

[0107] The CMOS circuit is divided into a central control circuit 120 that is digital and operates at a standard CMOS digital logic voltage such as 5V, and a drive circuit 122 that processes digital logic signals and operates at a voltage higher than the central control circuit to switch analog signals, particularly actuator control pulse signals. The CMOS circuit operating at two different voltage levels is separated by a deep trench isolation (DTI) barrier 310. The cross-connector 312 extends across the DTI barrier and connects the ejection transistor in the drive circuit 112 to the electrode drive conductor 240 that extends into the grid of the droplet ejector. The bond pad 112 is formed on the substrate and communicates mainly with the central control circuit through a path in the CMOS metallization layer to process digital signals, but one or more bond pads conduct the analog actuator control pulse signal to the drive circuit.

[0108] The print head further includes a piezoelectric actuator including a piezoelectric body 320, which in this example is formed of AlN or ScAlN, but can be formed of another suitable piezoelectric material that can be processed at a temperature below 450°C so as not to damage the underlying CMOS structure. The piezoelectric actuator 320 forms a diaphragm with a layer of a material such as silicon, silicon oxide, silicon nitride, or derivatives thereof, and has a passivation layer 322 (sometimes called the nozzle defining layer 322) that prevents the applied potential from contacting the fluid. Thus, the MEMS layers 320, 322, 323, 340, 342, 350, 352, 362 overlap the CMOS layers 120, 122, 306, 307, 312, and the MEMS layers and the CMOS layers are integrally formed.

[0109] The CMOS metallization layer 306 comprises interconnects that conduct external signals, signals to and from the central control circuit, and signals within the drive circuit. The drive circuit is configured to apply a potential difference across the piezoelectric actuator electrodes 340 and 342 during use via connections to one or more MEMS metallization layers 350 adjacent to the CMOS metallization layer 306 and the droplet ejector. In this example, the MEMS metallization layer shown is connected to the CMOS metallization layer via vias 352 that extend through a passivation layer 354 between the MEMS structure and the CMOS metallization layer. An electrode drive conductor 240 that extends to one of the electrodes 342 shown in FIG. 4 is partially formed by conductive tracks 307 within the MEMS metallization layer 350 and the CMOS metallization layer.

[0110] The piezoelectric actuator 320 and passivation layers 322, 323, 354 define the walls of a fluid chamber 360 that receives a printing agent such as ink (in the case of an inkjet printer) or another printable fluid (e.g., in the case of an additive manufacturing printer) via a conduit (not shown). During operation, when a droplet ejection voltage waveform is applied, the piezoelectric actuator flexes and ejects fluid through respective nozzles 344.

[0111] It can be seen that the cross-section of the semiconductor has distinct zones. Zone 370 includes both CMOS and MEMS metallization (as well as metal wiring) and CMOS transistors. Zone 372 does not include CMOS metallization or transistors and includes only MEMS metallization. Zone 374 includes both CMOS and MEMS metallization (as well as metal wiring) but does not include CMOS transistors.

[0112] This actuator configuration is compact and energy efficient, but the presence of holes (chambers and nozzles) and flexible regions (piezoelectric actuators) limits the surface area available for routing conductive connections and thus may limit nozzle density.

[0113] Referring back to FIG. 1, the ejection switch circuit extends along the long side surface of the elongated grid of the droplet ejector, and the electrode driving conductors from the ejection transistor to the electrodes extend from both sides within the grid of the droplet ejector. As a result, the connection from the ejection transistor to the electrodes is short (less than the width of the elongated grid) and has the same length as each other.

[0114] Referring to FIG. 4, the electrode driving conductor 240 extends within the grid of the droplet ejector along the row from the driver transistor between the piezoelectric actuators 320. (Note that FIG. 4 is rotated 90° with respect to FIG. 1 and the width 108 is shown for reference). As can be seen from FIG. 4, when making the density of the droplet ejector as high as possible, due to the presence of the nozzles 344 which are basically holes penetrating the substrate and the desire to avoid the piezoelectric actuators 320, the space within a single two-dimensional plane available for the electrode driving conductor 240 is very limited. However, in practice, the overlap with the actuator is possible in a limited amount.

[0115] FIG. 5 is a plan view of eight rows of actuators connected to the respective drive circuits 122 on both sides of these rows via the electrode driving conductors 240 extending into the grid from the opposing long side surfaces.

[0116] FIG. 6 is a plan view of an embodiment in which eight rows of actuators are connected to the drive circuit 122 arranged along one side of the row. Different regions of the electrode driving conductors 240, 240' are arranged within two different CMOS metallization layers (for example, M3 and M1). In this plan view, the electrode driving conductors of the layer farther from the substrate 240 cover the conductors closer to the substrate 240', making them partially unclear.

[0117] In these arrangements, the electrode drive conductors (the conductive connections for operating the piezoelectric actuator) are relatively short and of a constant length. Thus, they operate the piezoelectric actuator in a constant time. Each electrode drive conductor may be shorter than 1.5 times the width of the droplet ejector zone, or even shorter than the width of the droplet ejector zone. The electrode drive conductors do not need to extend around the edge of the droplet ejector zone, which would occupy space on the substrate, reduce the density of the entire nozzle, and cause variations in the timing of the actuation signals.

[0118] FIG. 7 is a plan view of selected components from a portion of the printhead on the left side of FIG. 1. The long side surface of the substrate includes a bond pad 112 and a main CMOS control circuit zone 120 used for control timing, data decoding, distribution, etc. The first nozzle zone 114 with a lattice of droplet ejectors is located between elongated zones of a drive circuit 122 that includes high-voltage transistors surrounded by DTI isolation pockets 310. A strip of CMOS digital control logic 121 is part of the CMOS control circuit zone and extends between strips of the drive circuit.

[0119] The actuator drive waveform conductors 250 are arranged as a two-dimensional grid and extend across the droplet ejector zone over each elongated zone of the drive circuit. Due to the current that can pass through these drive waveform conductors during operation, these drive waveform conductors require a relatively large surface area, and the waveform signals are efficiently distributed by a grid of multiple parallel drive waveform conductors. Some actuator drive waveform conductors 250 are parallel to the electrode drive conductors 240 but are found to extend (horizontally) through the lattice of droplet ejectors in a different metallization layer than the electrode drive conductors 240 (only the connections to three rows are shown for clarity).

[0120] Figs. 8 and 9 are plan views of an electrical connection portion including both an electrode driving conductor extending across the grid of the droplet ejector and actuator driving waveform conductors 250A, 250B, 250C, 250D. In this example, conductor 250A conducts a first actuator driving waveform for the magenta ink ejector, conductor 250B conducts a second actuator driving waveform for the cyan ink ejector, and conductors 250C, 250D conduct third and fourth actuator driving waveforms for the yellow and black ink ejectors, respectively. Each is part of a bus that distributes its respective actuator driving waveform. The actuator driving waveform conductors may be wider than the electrode driving conductors and in this example are disposed on top of (i.e., further away from the first surface of the substrate) the electrode driving conductors. In Fig. 9, only the lateral conductor 250A of the magenta driving waveform is shown as being connected to the longitudinal conductor running along the drive circuit 122. As shown in the plan view of Fig. 10, the conductors for the other channels / inks extend across the grid of the droplet ejector, and the conductors for each channel are connected to the drive circuits on both sides of the ejectors for that channel.

[0121] Fig. 11 is a cross-sectional view of a print head substrate according to the present invention along a cross-section different from that of Fig. 3. At the center of the image, the MEMS metallization layer 250 is the actuator driving waveform conductor 250 (or one of 250A, 250B, 250C, 250D) that overlaps the two electrode driving conductors 240, 240' located at M3 and M1 of the CMOS metallization layer.

[0122] Fig. 12 is a cross-sectional view of the print head substrate according to Fig. 3 along a longitudinal cross-section (the cross-section passing through A-A in Fig. 8) extending between two actuator driving waveform conductors 250C, 250D. Below the MEMS layers 354, 322 and the actuator driving waveform conductors 250C, 250D are a plurality of smaller electrode driving conductors 240, 240' located at M3 and M1 of the CMOS metallization layer 306.

[0123] Figures 13 and 14 correspond to Figures 3 and 11, and show another cross-section of an electrode driving conductor 240 connected to a lower (side closer to the substrate) electrode 342 of a droplet ejector, and an actuator driving waveform conductor 250 overlapping the electrode driving conductors 240, 240'.

[0124] Accordingly, the electrode driving conductors 240 extend a short distance from the ejection transistors and each drive only a single droplet ejector. The actuator driving waveform conductors must each drive across one or more zones of the droplet ejector. There may be a need to drive 100 or more, and even 1000 or more, droplet ejectors. Accordingly, they need to have a considerably larger cross-sectional area than the electrode driving conductors. They are accommodated in the MEMS metallization layer and are wider than the electrode driving conductors of the CMOS metallization layer. Thereby, the actuator driving waveform conductors extend in a grid across the zones of the droplet ejector and along the CMOS drive circuits extending longitudinally between the zones of the droplet ejector. Accordingly, routing of signals, particularly of the actuator driving waveform conductors, around the ends of the zones of the droplet ejector (i.e., along the short sides 103 of the substrate) can be minimized or avoided.

[0125] Figure 15 shows a flowchart showing a method of manufacturing a print head module. The method 400 of manufacturing a print head module includes a step 410 of forming an integrated circuit (for example, a CMOS control circuit 224 and a metal interconnect layer 306) on a substrate 102. The CMOS circuit is formed by a standard CMOS processing method including ion implantation into a p-type or n-type substrate, and the interconnect layer is also formed by standard processes such as ion implantation, chemical vapor deposition, physical vapor deposition, etching, chemical mechanical planarization, and / or electroplating.

[0126] Thereafter, the substrate having the integrated CMOS circuit is transferred from the CMOS foundry to the MEMS foundry (step 420). Using a continuous thin film deposition technique, additional material layers are formed on the substrate to form a MEMS device comprising electrodes 340 and 342 together with the intervening piezoelectric 320. Thus, the method further includes step 430 of forming a plurality of actuators (usually piezoelectric actuators), each in electrical communication with the integrated circuit. At each step, it is necessary to avoid damaging the CMOS control circuit. The piezoelectric is formed of a material such as AlN or ScAlN that can be deposited by PVD (including low temperature sputtering) at a temperature below 450°C. The electrodes are formed of, for example, titanium, platinum, aluminum, tungsten, or alloys thereof.

[0127] This method further includes step 440 of forming a nozzle exit 344 associated with each actuator. In other words, a plurality of nozzle exits are formed. Each nozzle exit is associated with each of the plurality of actuators. Each nozzle exit extends through the substrate. Typically, each nozzle exit further extends through one or more additional layers on the substrate. This method also includes step 450 of forming a print agent manifold for sending the print agent towards the plurality of nozzle exits. The print agent manifold can be formed before or after the formation of the nozzle exits. The print agent manifold can be formed before or after the formation of the plurality of actuators. The print agent manifold is a fluid channel that defines a fluid communication path between the print agent inlet of the print head module and the plurality of nozzle exits. The fluid channels and openings through the substrate can be formed using an etching procedure such as DRIE. The channel defining layer can be formed using DRIE etching and wafer bonding of the silicon MEMS substrate. The nozzle defining layer can be formed of a metal, a silicon MEMS wafer, or a plastic material by deposition or adhesion on the channel defining layer. Each droplet ejector tip is connected to the machine controller via a flexible interconnect 218 having a limited number of conductors, usually less than 75 or less than 50, and in some cases less than 25 conductors.

[0128] Since it is necessary to avoid damage to the CMOS control circuit in which the piezoelectric actuator including the piezoelectric body is formed, the material forming the piezoelectric body must not be PZT and is not PZT. Therefore, the piezoelectric actuator has a piezoelectric constant d that is much lower than that of PZT, usually at least one order of magnitude, and in some cases two orders of magnitude smaller, depending on its exact composition. 31 has.

[0129] In the above-described embodiment, one or more analog actuator drive waveforms (e.g., one for each printable fluid type or ink color) are generated off-chip, conducted to the substrate, and distributed there via the drive waveform conductor 250. In an alternative embodiment, instead, a plurality of voltage rails of different potentials, e.g., at least three different potentials, are provided, which extend through the substrate to the drive circuit instead of the drive waveform conductor, and the drive circuit includes a plurality of transistors for each droplet ejector and switches the voltage rail connected to each electrode of each droplet ejector over time during each ejection cycle in which the droplet ejector is selected. For example, there may be a positive voltage, a negative voltage, and a ground that are switched in sequence to provide a droplet ejection waveform.

Claims

Claim 1 A printhead for ejecting one or more printable fluids, the printhead comprising a substrate, the substrate defining a plurality of MEMS droplet ejectors arranged in a grid and ejecting droplets of the one or more printable fluids, each droplet ejector comprising a flexible diaphragm and a piezoelectric actuator for ejecting droplets of the printable fluid through a nozzle by moving the flexible diaphragm, and each droplet ejector comprising at least one MEMS metallization layer, the substrate further defining a CMOS control circuit comprising at least one CMOS metallization layer, the substrate (i) at least one conductive connection within the at least one metallization layer extending from the CMOS control circuit to each piezoelectric actuator for actuating the piezoelectric actuator, and (ii) a printhead further comprising one or more of conductive connections extending through the grid within the at least one metallization layer for conducting an actuator drive waveform. Claim 2 The printhead according to claim 1, wherein the substrate comprises (i) at least one of the metallization layers with a conductive connection extending from the CMOS control circuit to each piezoelectric actuator for actuating the piezoelectric actuator. Claim 3 The printhead according to claim 2, wherein the length of the conductive connection for actuating the piezoelectric actuator is constant between the CMOS control circuit and the piezoelectric actuator within a group of droplet ejectors. Claim 4 The grid of the MEMS droplet ejector forms a droplet ejector zone on the substrate. The droplet ejector zone has a length and a width and is in an elongated shape with opposing long sides along the length. The conductive connection for actuating the actuator extends into the grid from one or both of the opposing long sides of the droplet ejector zone. Usually, the CMOS control circuit includes a plurality of drive transistors, and at least one of the plurality of drive transistors is directly connected to at least one electrode of the piezoelectric transducer of each MEMS droplet ejector by the conductive connection for actuating the piezoelectric actuator without an intervening transistor. The plurality of drive transistors are arranged in at least one row adjacent to one or both of the opposing long sides of the droplet ejector zone. The print head according to claim 2 or claim 3.

5. The conductive connection for actuating the piezoelectric actuator extends into the grid between rows of MEMS droplet ejectors. The print head according to claim 4.

6. (ii) The conductive connection extends through the grid in at least one of the metallization layers to conduct an actuator drive waveform for connecting the MEMS droplet ejector to one or more actuator drive waveform sources. The print head according to any one of claims 1 to 5.

7. The conductive connection relays different actuator drive waveforms to different groups of MEMS droplet ejectors by connecting different groups of MEMS droplet ejectors to different actuator drive waveform sources among a plurality of actuator drive waveform sources. The print head according to claim 6.

8. The droplet ejector zone has a length and a width and has opposing long sides along the length. The conductive connection for conducting an actuator drive waveform extends into the grid from one or both of the opposing long sides of the droplet ejector zone. The print head according to claim 6 or claim 7.

9. Each MEMS droplet ejector includes a hole penetrating the substrate for ejecting a printable fluid. The print head according to any one of claims 1 to 8.

10. The substrate further includes a conductive connection portion extending through the grid in at least one metallization layer for connecting each of the MEMS droplet ejectors to two or more different fixed voltages, and the CMOS control circuit is configured to selectively connect at least one electrode of the piezoelectric actuator of each droplet ejector to each of the two or more different fixed voltages in sequence in response to a control signal from the CMOS control circuit. The print head according to any one of claims 1 to 9.

11. The print head according to any one of claims 1 to 10, wherein in at least a region of the substrate, the one or more MEMS metallization layers overlap the one or more CMOS metallization layers.

12. Comprising a first plurality of conductive connection portions and a second plurality of conductive connection portions, one of the first plurality of conductive connection portions and the second plurality of conductive connection portions includes the conductive connection portion for operating the piezoelectric actuator, and the other of the first and second plurality of conductive connection portions includes a conductive connection portion for conducting a droplet ejector waveform or a plurality of different potentials. At one or more positions within the grid, at least one first conductive connection portion and at least one second conductive connection portion both extend, but extend into different metallization layers. The print head according to any one of claims 1 to 11.

13. The print head according to any one of claims 1 to 12, wherein at one or more positions within the grid, at least one conductive connection portion for operating the piezoelectric actuator and at least one conductive connection portion for conducting a droplet ejector waveform extend parallel between the same adjacent rows of the droplet ejector.

14. The grid includes at least MEMS droplet ejectors in a first row, a second row, and a third row, and the plurality of conductive connection portions extend between the droplet ejectors in the first row and the second row to respective different droplet ejectors along the length of the second column. The print head according to any one of claims 1 to 13.

15. The print head according to claim 14, wherein the plurality of conductive connection portions extend between the droplet ejectors in the second row and the third row to respective different droplet ejectors along the length of the second row.

16. The CMOS control circuit includes one or more first zones and one or more second zones. The substrate includes one or more isolation mechanisms that separate the first zone and the second zone. The one or more first zones include transistors that process digital signals. The one or more second zones include drive transistors that directly supply a potential to the electrodes of the piezoelectric actuator. The second zone operates at at least twice the maximum potential of the first zone. The print head according to any one of claims 1 to 15.

17. The substrate has an elongated shape having a length and a width, and defines a plurality of adjacent droplet ejector zones spaced apart orthogonally to their length. Between each adjacent droplet ejector zone, there is provided at least one CMOS circuit zone that is also elongated and aligned in the same direction as the droplet ejector zone. The CMOS circuit zone includes at least one CMOS metallization layer. The conductive connection extends from the CMOS circuit into the adjacent droplet ejector zone to operate the piezoelectric actuator. The print head according to any one of claims 1 to 16.

18. The at least one CMOS circuit zone includes both a high voltage region and a low voltage region. The low voltage region includes one or more digital logic gates. The high voltage region includes ejection transistors directly connected to the piezoelectric transducers of the respective droplet ejectors. The high voltage region and the low voltage region are separated by an isolation mechanism within the substrate. Usually, one or more conductive connections for the actuator drive waveform extend laterally across one or more droplet ejector zones and are connected to the high voltage region of the CMOS circuit zone. The print head according to claim 17.

19. The substrate of the individual zone includes a plurality of bond pads. The print head according to any one of claims 1 to 18.

20. A printing apparatus comprising the print head according to any one of claims 1 to 19.

21. A method of forming the print head or the printing apparatus according to any one of claims 1 to 20, forming a grid of openings through the substrate, each opening at least partially defining a fluid chamber of a droplet ejector, Forming the CMOS control circuit comprising at least one CMOS metallization layer on the first surface of the substrate; Forming the plurality of droplet ejectors by forming a MEMS layer comprising a flexible diaphragm, a piezoelectric actuator, and at least one MEMS metallization layer on the first substrate of the substrate; Thereby, each droplet ejector is conductively connected to the CMOS control circuit via at least one of the metallization layers, a method.

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