Patent Description:
An inkjet recording device that discharges ink from multiple nozzles of an inkjet head to record an image on a recording medium is well known. For example, an actuator type inkjet head where a piezo actuator that transforms when voltage is applied is placed in each pressure chamber that connects to a nozzle is well known as an inkjet head. This inkjet head is manufactured using a semiconductor process where pressure chambers, and piezo actuators corresponding respectively to the pressure chambers, are arranged on a silicon wafer.

One problem with this type of inkjet head in that when discharge droplet volumes from the nozzles are not uniform, concentration distribution occurs in an output image and thus image quality drops. To address this problem, measures are taken to correct variations in ink discharge droplet volumes.

For example, a technique to address this problem includes measuring the thickness of a piezoelectric body film, determining widths for individual electrodes based on the amount of deviation between the thickness of the measured piezoelectric body film and a preset reference thickness, and then forming individual electrodes having the determined widths to then correcting variations in the thickness of the piezo electric body film using the widths of the individual electrodes.

Furthermore, another solution to this problem includes forming a cutout portion to reduce an area of a common electrode, placed on an ink pressure chamber corresponding to a nozzle targeted for a discharge rate adjustment, to correspond to a rate adjustment amount to reduce the transformation amount of a piezo electric element in that region, and thus make an ink discharge rate uniform.

The two solutions described above require measurements of variations in the thickness of a piezoelectric body film relative to individual elements and of an ink discharge rate, and thus the correction processes thereof are complex. Additionally, there is also a lack of any technical concept for changing a position of an inflection point of a displacement profile of a piezoelectric element,.

<CIT> discloses the preambles of claims <NUM> and <NUM>.

An inkjet print head according to claim <NUM> and a method of manufacturing a piezoelectric element according to claim <NUM> are described.

The present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only.

In the following description, numerous details are set forth to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

An inkjet print head according to claim <NUM> is disclosed.

Also disclosed is a method for manufacturing a piezoelectric element according to claim <NUM>.

Detailed descriptions of the embodiments of the present invention will be given below in accordance with the attached drawings.

<FIG> illustrates one embodiment of an inkjet head die. Referring to <FIG>, an inkjet head die <NUM> includes a plurality of piezo actuators <NUM> (one example of a piezoelectric element) arranged two dimensionally to correspond to the positions of a plurality of pressure chambers <NUM> (see <FIG>). Piezo actuator columns <NUM>-<NUM> to <NUM>-<NUM> are in the vertical direction and each contains a plurality of piezo actuators <NUM>.

In one embodiment, the plurality of piezo actuators <NUM> are pressure generating elements for discharging ink inside the plurality of pressure chambers <NUM> through each of the nozzles <NUM> (see <FIG>) in communication with the plurality of pressure chambers.

<FIG> illustrates an inkjet head outputting image data. Referring to <FIG>, in one embodiment, inkjet head <NUM> illustrated uses inkjet head die <NUM> of <FIG>. <FIG> illustrates a state where input image data with uniform concentration is output to a form <NUM> by inkjet head <NUM>, and, in this case, the image is output by a single pass method while form <NUM> is being transported in a form feeding direction relative to inkjet head <NUM>. As illustrated in <FIG>, an uneven concentration is being generated in a form feeding orthogonal direction in an output image <NUM>.

<FIG>_is a graph showing the concentration distribution of the output image where the horizontal axis shows the position in the form feeding orthogonal direction of the output image and the vertical axis shows an Optical Density (OD) value (<NUM> bit) measured from the output image in each position. As illustrated in <FIG>, the further the output image is to the right in the form feeding orthogonal direction, the higher the concentration becomes.

On the other hand, <FIG> is a graph showing a displacement amount distribution of piezo actuator <NUM> provided in inkjet head die <NUM> of inkjet head <NUM> where the horizontal axis shows the position of piezo actuator columns <NUM>-k (k = <NUM>, <NUM>,. , n) in the form feeding orthogonal direction and the vertical axis shows the displacement amount (in nanometers) of piezo actuator <NUM>. Here, the average value of the displacement amount of each piezo actuator column <NUM>-k is plotted on the graph.

As illustrated in <FIG>, the unevenness of the concentration of the output image of inkjet head <NUM> correlates to the distribution of the displacement amount of piezo actuator <NUM> of inkjet head die <NUM>. That is, the displacement amount of piezo actuator <NUM> is distributed in the plane of inkjet head die <NUM> and the discharge droplet volume variations caused by nozzles <NUM> (sees <FIG>) are generated by this distribution, thereby causing the unevenness in the concentration of the output image.

Note that in one embodiment the displacement amount distribution of piezo actuator <NUM> is conceivably caused by an in plane distribution of a film thickness of a piezoelectric film <NUM> (see <FIG>) of inkjet head die <NUM>.

With a given sputtering devices, material sputtered and discharged from a target may deposit more in the center of a silicon wafer <NUM> (see <FIG>) and then more thinly as distance from the center increases. Accordingly, the film thickness of piezoelectric film <NUM> formed by a sputtering method is relatively thick in the center of silicon wafer <NUM> and becomes relatively thinner as distance from the center increases, resulting in a concentric film thickness distribution. The film thickness distribution of piezoelectric film <NUM> affects the displacement amount distribution of piezo actuator <NUM>, controlling the displacement amounts of different portions of the piezoelectric film across inkjet head die <NUM>.

<FIG> is a top view of the piezo actuator <NUM>, and <FIG> is a cross sectional view along line 4b - 4b in <FIG>.

A plurality of inkjet head dies <NUM> (not illustrated in <FIG>) are arranged on silicon wafer <NUM> (an example of a substrate), and the plurality of pressure chambers <NUM> that store ink and an ink flow path (not illustrated) that links the plurality of pressure chambers <NUM> are formed on each of the plurality of inkjet head dies <NUM>. Additionally, the plurality of piezo actuators <NUM> are formed to correspond to the plurality of pressure chambers <NUM>, respectively. Furthermore, overlapping inkjet head die <NUM> of silicon wafer <NUM> and a die of a silicon wafer <NUM> that forms nozzle <NUM> configures inkjet head <NUM> that links pressure chamber <NUM> and nozzle <NUM>.

Piezo actuator <NUM> includes a lower electrode <NUM>, piezoelectric film <NUM>, and an upper electrode <NUM>. The plurality of piezo actuators <NUM> use lower electrode <NUM> (an example of a common electrode) and piezoelectric film <NUM> in common, and one of the upper electrodes <NUM> (an example of an individual electrode) is arranged to correspond to each of piezo actuators <NUM>.

In one embodiment, PZT (Pb (Zr, Ti) O<NUM>: Lead zirconate titanate) is used in piezoelectric film <NUM> (an example of a piezoelectric body film).

In one embodiment, upper electrode <NUM> is centered on a center 132a of pressure chamber <NUM> and is a ring type electrode having an elliptical ring shape that corresponds to the shape of pressure chamber <NUM>. Upper electrode <NUM> can be given an appropriate ring shape such as a circular, polygonal ring shape to correspond to the shape of pressure chamber <NUM>.

The ring width, which is the length in the width direction orthogonal to the circumferential direction of the ring shape of upper electrode <NUM>, is x, and upper electrode <NUM> functions as a ring type electrode having ring width x. In one embodiment, upper electrode <NUM> use oxide electrodes, such as, for example, but not limited to, IrOx (iridium oxide), ITO (indium tin oxide), and RuOx (ruthenium oxide), to suppress reactions with piezoelectric film <NUM> and to improve adhesion.

A wire <NUM> (or other conductor) is connected to upper electrode <NUM>. Wire <NUM> causes piezo actuator <NUM> to function as a pressure generating element, and thus applies a signal voltage to upper electrode <NUM> with lower electrode <NUM> as the reference potential.

In one embodiment, piezo actuator <NUM> configured in this way sets the voltage of the upper electrode <NUM> to off (reference potential) during ink discharge standby, which helps with long term durability thereof.

Furthermore, in one embodiment, the voltage of upper electrode <NUM> is set to on (signal voltage is applied) during ink discharge. When the applied voltage of upper electrode <NUM> is set to on, piezo actuator <NUM> drives the position of inner diameter of the ring shape of upper electrode <NUM> to be displaced in a convex manner in the upward direction in <FIG> (the direction that increases the volume of pressure chamber <NUM>, hereinafter referred to as the reverse direction of pressure chamber <NUM>) as the inflection point of the displacement profile. This makes ink to be sucked inside pressure chamber <NUM> from the supply flow path (not illustrated). Setting the voltage to off from this state allows piezo actuator <NUM> to return to the original shape thereof and cause the ink inside pressure chamber <NUM> to discharge through nozzle <NUM> simultaneously.

The displacement amount of piezoelectric film <NUM> can be suppressed by narrowing the ring width x of upper electrode <NUM>, thereby changing the position of the inflection point of the displacement profile. <FIG> is a cross sectional view that is similar to <FIG>, and illustrates piezo actuator <NUM> where the ring width of upper electrode <NUM> has been narrowed by exactly Δx. In this case, the outer diameter of the ring shape of upper electrode <NUM> is fixed, and thus the ring width of upper electrode <NUM> is set to (x - Δx) by widening the inner diameter of the ring shape by exactly Δx.

When the ring width is narrowed by exactly Δx in this way, the position of the inner diameter of upper electrode <NUM>, which is the position of the inflection point of the displacement profile of piezo actuator <NUM>, changes according to the size of Δx, and thus the displacement amount decreases. In one embodiment, this characteristic is used to make the displacement amounts of the plurality of piezo actuators <NUM> of inkjet head die <NUM> uniform, and thus makes the discharge droplet volumes uniform. Specifically, the ring width is made relatively narrow where the original displacement amount is high, and the ring width is made relatively wide where the displacement amount is low. In one embodiment, the ring width of upper electrode <NUM> is corrected and the ring width is given a distribution by using correction coefficients that offset the in-plane distribution of the film thickness of piezoelectric film <NUM> of inkjet head die <NUM>.

<FIG> is a diagram illustrating inkjet head die <NUM> in which each of the piezo actuators <NUM> is configured from upper electrodes <NUM>-<NUM> and each has the same ring width. Furthermore, <FIG> is a graph illustrating the distribution of discharge droplet volumes through nozzles <NUM> (not illustrated in <FIG>) corresponding to piezo actuators <NUM> illustrated in <FIG> where the horizontal axis shows the positions of piezo actuator columns <NUM>-k (k equals <NUM>, <NUM>,. , n) that correspond to the form feeding orthogonal direction of the output image, and the vertical axis shows the discharge droplet volumes. In this case, the average value of the discharge droplet volumes for every four rows of piezo actuator columns <NUM>-k is plotted on the graph. As illustrated in <FIG>, the discharge droplet volumes of piezo actuators <NUM> in this case have an in-plane distribution, and the uniformity of the discharge droplet volumes is +<NUM>%.

Furthermore, <FIG> is diagram illustrating inkjet head die <NUM> where each of piezo actuators <NUM> is corrected based on the in-plane position of silicon wafer <NUM> and is configured from upper electrodes <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>, each having a different ring width. Furthermore, <FIG> is a graph illustrating the distribution of discharge droplet volumes through the nozzles <NUM> (not illustrated in <FIG>) corresponding to piezo actuators <NUM> illustrated in 6A where the horizontal axis shows the positions of the piezo actuator columns <NUM>-k (k = <NUM>, <NUM>,. , n) that correspond to the form feeding orthogonal direction of the output image, and the vertical axis shows the discharge droplet volumes. Here, the average value of the discharge droplet volumes for every four rows of the piezo actuator columns <NUM>-k is plotted on the graph. As illustrated in <FIG> , the discharge droplet volumes of piezo actuators <NUM> have been corrected for in-plane distribution in this case, and the uniformity of the discharge droplet volumes is - <NUM>%. Adjusting the ring width of upper electrode <NUM> based on the in-plane position of the silicon wafer <NUM> in this way allows the displacement amounts of the plurality of piezo actuators <NUM> and the discharge droplet volumes through the nozzles <NUM> to be made uniform.

Other aspects of the piezo actuator are described below. Portions that are shared with piezo actuator <NUM> are given the same reference numerals and detailed descriptions thereof are omitted.

<FIG> is a top view of a piezo actuator <NUM> (an example of a piezoelectric element), and <FIG> is a cross sectional view along line 7b - 7b in <FIG>.

A plurality of piezo actuators <NUM> are formed on each of the plurality of inkjet head dies <NUM>. Each of the piezo actuators <NUM> corresponds with one of pressure chambers <NUM> where the ink is captured, respectively, and includes lower electrode <NUM>, piezoelectric film <NUM>, an insulating film <NUM>, and upper electrode <NUM>. In one embodiment, the plurality of piezo actuators <NUM> use lower electrode <NUM> and piezoelectric film <NUM> in common, and one of upper electrodes <NUM> is arranged to correspond to each of piezo actuators <NUM>.

In one embodiment, insulating film <NUM> is in between piezoelectric film <NUM> and upper electrode <NUM>. In one embodiment, center 132a of pressure chamber <NUM> is centered on the center of upper electrode <NUM>, and an opening 146b is provided in insulating film <NUM> with an elliptical ring shape that corresponds to the shape of pressure chamber <NUM>. In one embodiment, opening 146b is given an appropriate ring shape such as, for example, but not limited to, a circular, polygonal ring shape to correspond to the shape of pressure chamber <NUM>.

The ring width, which is the length in the width direction orthogonal to the circumferential direction of the ring shape of the opening 146b, is x. Furthermore, upper electrode <NUM> is placed along opening 146b, and piezoelectric film <NUM> and upper electrode <NUM> are electrically connected through opening 146b. Accordingly, the portion of upper electrode <NUM> that is electrically connected to piezoelectric film <NUM> in opening 146b becomes a displacement driving portion, and thus piezo actuator <NUM> substantially functions as a piezoelectric element having a ring like electrode with an electrode width of x. Furthermore, wire <NUM> is connected to upper electrode <NUM>. In this way, piezo actuator <NUM> sets the voltage of upper electrode <NUM> to off (reference potential) during ink discharge standby.

Also, in one embodiment, the voltage of upper electrode <NUM> is set to on (signal voltage is applied) during ink discharge, and the position of the inner diameter of the ring shape of opening 146b is driven to be displaced in a convex manner in the upward direction (reverse direction of the pressure chamber <NUM>) in <FIG> as the inflection point of the displacement profile, and thus ink is sucked from the supply flow path (not illustrated) inside pressure chamber <NUM>. Setting the voltage to off from this state allows piezo actuator <NUM> to return to the original shape thereof and the ink inside pressure chamber <NUM> is discharged through nozzle <NUM>.

The displacement amount of piezoelectric film <NUM> is suppressed by making the ring width of opening 146b narrower in piezo actuator <NUM>. <FIG> is a cross sectional view that is similar to <FIG>, and illustrates piezo actuator <NUM> where the ring width of opening 146b has been narrowed by exactly Δx. In this case, the outer diameter of the ring shape of opening 146b is fixed, and thus the ring width of opening 146b is set to (x - Δx) by widening the inner diameter of the ring shape. Note that the shape of upper electrode <NUM> has not changed.

When the ring width is narrowed by exactly Δx in this way, the position of the inner diameter of opening 146b, which is the position of the inflection point of the displacement profile of piezo actuator <NUM>, changes according to the size of Δx, and thus the displacement amount decreases. This makes the displacement amounts of the plurality of piezo actuators <NUM> of inkjet head die <NUM> uniform, which allows the discharge droplet volumes to be made uniform.

<FIG> is a top view of a piezo actuator <NUM> (an example of a piezoelectric element), and <FIG> is a cross sectional view along line 8b - 8b in <FIG>. Piezo actuator <NUM> includes, relative to piezo actuator <NUM>, an inflection point adjusting layer <NUM> on upper electrode <NUM> (on the side opposite that of piezoelectric film <NUM> of upper electrode <NUM>) through an inflection point adjusting layer forming step. That is, piezo actuator <NUM> substantially functions as a piezoelectric element having a ring type electrode with electrode width x.

In one embodiment, inflection point adjusting layer <NUM> is laminated on the insulating film <NUM> on the outside of the ring shape formed by opening 146b, protruding inward from outside the ring shape relative to the opening 146b to a position (hereinafter referred to simply as the position of inner wall 132b of pressure chamber <NUM>) where an inner wall 132b, which is in the depth direction of silicon wafer <NUM>, of pressure chamber <NUM> extends to opening 146b. Inflection point adjusting layer <NUM>, may be, for example, SU-<NUM> (manufactured by MicroChem, Inc. In this way, piezo actuator <NUM> sets the voltage of upper electrode <NUM> to off (reference potential) during ink discharge standby. Furthermore, the voltage of upper electrode <NUM> is set to on (signal voltage is applied) during ink discharge, and the position of the edge of inflection point adjusting layer <NUM> that protrudes relative to opening 146b is driven to be displaced in a convex manner in the upward direction (reverse direction of the pressure chamber <NUM>) in <FIG> as the inflection point of a specific displacement profile, and thus ink is sucked from the supply flow path (not illustrated) inside pressure chamber <NUM>. Setting the voltage to off from this state allows piezo actuator <NUM> to return to the original shape thereof and ink inside pressure chamber <NUM> to be discharged through nozzle <NUM>.

The displacement amount of piezoelectric film <NUM> is suppressed by making the amount that inflection point adjusting layer <NUM> protrudes relative to opening 146b wider in piezo actuator <NUM>. <FIG> is a cross sectional view that is similar to <FIG>, and illustrates piezo actuator <NUM> where the amount of overlap (the amount protruding from the position of inner wall 132b of pressure chamber <NUM>) between opening 146b and inflection point adjusting layer <NUM> has been widened by exactly Δy. In this way, when the overlap amount is widened by exactly Δy, the position of the edge of inflection point adjusting layer <NUM>, which is the position of the inflection point of the displacement profile of piezo actuator <NUM>, changes according to the size of Δy, and thus the displacement amount of piezo actuator <NUM> decreases. This makes the displacement amounts of the plurality of piezo actuators <NUM> of inkjet head die <NUM> uniform, which allows the discharge droplet volumes to be made uniform.

<FIG> illustrate one embodiment of a method for producing exposure masks having correction coefficients for correcting the displacement amounts of the piezo actuators. For purposes of illustrating the method, an example that uses piezo actuator <NUM> will be described.

Referring to <FIG>, first, a plurality of exposure masks having different ring widths of opening 146b are prepared (step S1). As illustrated in <FIG>, the ring width fixes the outer diameter of the ring shape of opening 146b, and thus the ring width of opening 146b is narrowed by widening the inner diameter of the ring shape by exactly Δx. Accordingly, a plurality of exposure masks that are different by Δx may be prepared.

Next, a plurality of exposure masks is used relative to each of silicon wafers <NUM> to produce piezo actuator <NUM> (step S2), and then a displacement volume of piezo actuator <NUM> is derived for each ring width (step S3). After deriving the displacement volumes for each ring width, the ring widths that correspond to the correction coefficients are generated (step S4).

<FIG> illustrates the displacement volumes of piezo actuators <NUM>, formed to the degree possible in locations close to the film thickness of piezoelectric film <NUM> (not illustrated in <FIG>), are compared using a piezo actuator <NUM> that has been exposed and formed using an exposure mask as reference where Δx = <NUM> (herein, the mask of mask No. <NUM>) and a piezo actuator <NUM> that has been exposed and formed using an exposure mask where Δx > <NUM> (new mask). In this case, the same voltage signal is applied to each of piezo actuators <NUM>, and the displacement volume of each is then derived by measuring the displacement amounts using a scanning laser Doppler meter. This operation is repeated to find the ring widths that achieve the correction coefficients as the target values (step S4 of <FIG>).

<FIG> illustrates that there is a nearly linear relationship between the ring width and the displacement volume. Referring to <FIG>, as the ring width is increased, the displacement volume increase nearly linearly.

<FIG> illustrates the ring widths of the masks of an example of finally determined correction coefficients and simultaneously illustrates the displacement volume measured value and resonant frequency in each of the exposure masks. Note that the displacement volume measured values and resonant frequencies illustrate values that have been normalized using the value of exposure mask No. <NUM> as reference where the correction coefficient is <NUM> (Δx = <NUM>). In this way, exposure masks No. <NUM> to No. <NUM> (an example of a plurality of exposure masks) with correction coefficients ranging from <NUM> to <NUM> in - <NUM> stages are produced in one embodiment. The number of the exposure masks and correction coefficient steps may be are not limited to those described in <FIG>; other numbers of exposure masks and correction coefficients may be used and determined as appropriate.

Note that, in one embodiment, there is almost no change in resonant frequency from piezo actuator <NUM> with a correction coefficient of <NUM> to piezo actuator <NUM> with a correction coefficient of <NUM> is <NUM>%.

<FIG> is a diagram illustrating an example of the positions of a plurality of inkjet head dies <NUM> on an element forming surface of silicon wafer <NUM>. Here, silicon wafer <NUM> is divided into ten inkjet head dies <NUM> labelled Die <NUM> to Die <NUM>. Furthermore, in the exposure step in the manufacturing process, each of inkjet head dies <NUM> is divided into four zones from Zone <NUM> to Zone <NUM> and then stepper exposed. That is, each zone is an exposure region from one stepper exposure, and one of the inkjet head dies <NUM> can use four desired exposure masks that are different for each zone.

Furthermore, as illustrated in <FIG>, in one embodiment, the plurality of piezo actuators <NUM> are provided two dimensionally on the inkjet head dies <NUM>, and plurality of piezo actuators <NUM> are located in piezo actuator columns <NUM>-k (k=<NUM>, <NUM>,. , n), respectively, in the vertical direction of the figure. Furthermore, piezo actuator columns <NUM>-k are arranged at fixed intervals in the width direction of <FIG>.

<FIG> illustrates a method for producing correction coefficient maps for each in plane position on silicon wafer <NUM> configured in this way in accordance with one embodiment. In this case, in one embodiment, correction coefficients are calculated by zone (by exposure region), which is one exposure region of a stepper exposure for the inkjet head dies <NUM>.

Referring to <FIG>, the shapes and processing requirements for lower electrode <NUM>, piezoelectric film <NUM>, upper electrode <NUM>, and insulating film <NUM> are consolidated, and then the piezo actuators <NUM> are produced over the entire surface of silicon wafer <NUM> (step S11). At this point, a film thickness distribution is generated in the plane of silicon wafer <NUM> in piezoelectric film <NUM>.

Next, the same voltage signal is applied to the plurality of piezo actuators <NUM> of each zone, and then the distribution of the in-plane displacement amounts of piezo actuators <NUM> on silicon wafer <NUM> are determined. In one embodiment, this determination is made by measuring the displacement amounts using a scanning laser Doppler meter (step S12, an example of a displacement amount measuring step). This obtains the film thickness distribution of piezoelectric film <NUM>. An example of the displacement amounts for piezo actuators <NUM> by zone of a given inkjet head die <NUM> are illustrated in <FIG>.

Next, the average value of the displacement amounts (average displacement amount) of the plurality of piezo actuators <NUM> is calculated by zone, and then the average displacement amount of each zone is normalized using the minimum value of the average displacement amounts of all of the zones (step S13). The average displacement amount for each zone is illustrated in <FIG>. Referring to <FIG>, the average displacement amounts are <NUM> for Zone <NUM>, <NUM> for Zone <NUM>, <NUM> for Zone <NUM>, and <NUM> for Zone <NUM>.

Lastly, in one embodiment, the reciprocals for the normalized average displacement amounts are calculated, and a correction coefficient map, with these values as the correction coefficients in the zones, is completed (step S14, an example of a correction coefficient calculating step).

In one embodiment, based on the generated correction coefficient maps, exposure masks that are closest to the calculated correction coefficients are selected and used by zone during an exposure step of an actual manufacturing process. For example, as illustrated in <FIG>, the correction coefficient for Zone <NUM> is <NUM>. Accordingly, the exposure mask of mask No. <NUM> may be used relative to Zone <NUM>, as illustrated in <FIG>. In the same way, the correction coefficients of Zones <NUM>, <NUM>, and <NUM> are <NUM>, <NUM>, and <NUM>, respectively. Accordingly, the exposure masks of masks No. <NUM>, <NUM> and <NUM> may be used relative to Zones <NUM>, <NUM>, and <NUM>, respectively, as illustrated in <FIG>.

Selecting and using the exposure masks in this way sets the positions of the inflection points of the displacement profiles of piezo actuators <NUM> of each zone to correspond to in plane positions on silicon wafer <NUM>, and thus the displacement amounts of piezo actuators <NUM> are made to be uniform.

An alternative method for producing exposure masks having correction coefficients that correspond to the displacement amounts of the piezo actuators may be used. This method will be described in conjunction with the piezo actuator <NUM> of <FIG>. In this case, a plurality of exposure masks having different protruding amounts for inflection point adjusting layer <NUM> are prepared, and piezo actuators <NUM> are produced on silicon wafer <NUM>. As illustrated in <FIG>, the position of inner wall 132b of pressure chamber <NUM> is used as a reference for the protruding amount. For the purpose of this example, in one embodiment, the thickness of inflection point adjusting layer <NUM> is assumed to be <NUM> micrometers. Furthermore, in this case, the displacement volumes of piezo actuators <NUM> are derived by protruding amount to find the protruding amount that achieves the correction coefficient as the target value.

<FIG> illustrates an example of the protruding amounts of the masks of the finally determined correction coefficients and the displacement volume measured value and resonant frequency in each of the exposure masks. Note that the displacement volume measured values and resonant frequencies illustrate values that have been normalized using the value of exposure mask No. <NUM> where the correction coefficient is <NUM>. Referring to <FIG>, exposure masks No. <NUM> to No. <NUM> with correction coefficients ranging from <NUM> to <NUM> in - <NUM> steps have been produced. Note that the change in resonant frequency from the piezo actuator <NUM> with a correction coefficient of <NUM> to the piezo actuator <NUM> with a correction coefficient of <NUM> is <NUM>%, and thus, while the change amount is larger than piezo actuator <NUM>, it is found that the degree of the change is not a problem in practical terms.

<FIG> illustrates another embodiment of a method for producing correction coefficient maps for silicon wafer <NUM>. In one embodiment, a correction coefficient map that corresponds to a distance from a reference point on silicon wafer <NUM> is produced.

Referring to <FIG>, piezoelectric film <NUM> is produced over the entire surface of silicon wafer <NUM> as part of the process for forming piezo actuator <NUM> (step S21). At this point, the film thickness distribution is generated in the plane of silicon wafer <NUM> in piezoelectric film <NUM> formed.

Next, the film thickness of piezoelectric film <NUM> is measured in a plurality of positions from the edge to the center of silicon wafer <NUM>. This may be performed using an optical interference film thickness measuring device (step S22, an example of a piezoelectric body film measuring step). In the example illustrated in <FIG>, the film thickness of piezoelectric film <NUM> is measured at five points, being center 120a (an example of a reference point) of silicon wafer <NUM> and measuring points P1, P2, P3, and P4, which are positions at distances of <NUM>, <NUM>, <NUM> and <NUM> (units: millimeters) from the center 120a, respectively (an example of by distance from a reference point).

After measuring the piezoelectric film thickness, the film thicknesses of the piezoelectric film <NUM> of the five measured points are normalized using the minimum value, and the reciprocal of the normalized value is taken as the correction coefficient (step S23, an example of correction coefficient calculating step). The distances and the film thicknesses of piezoelectric film <NUM> from center 120a of silicon wafer <NUM>, with the numeric values normalized using the minimum value, and the reciprocals thereof (correction coefficients) are illustrated in <FIG>.

Additionally, using distance r from center 120a of silicon wafer <NUM> as a variable, an approximate expression F(r) is derived based on the distances from center 120a of silicon wafer <NUM> and the correction coefficients illustrated in <FIG> (step S24). In one embodiment, a quadratic function is used and this approximate expression is typically sufficient and can be expressed as follows.

Next, distances r from center 120a of silicon wafer <NUM> to the centers of the zones of inkjet head dies <NUM> are calculated (step S25). These distances r are calculated from mask design CAD data.

Finally, the correction coefficients for the zones of the inkjet head dies <NUM> are calculated relative to the calculated distances r using Expression <NUM> (step S26). The distances from the center 120a of the silicon wafer <NUM> and the correction coefficients in Zones <NUM> to <NUM> of the inkjet head die <NUM> of Die <NUM> and in Zones <NUM> and <NUM> of the inkjet head die <NUM> of Die <NUM> are illustrated in <FIG>.

In one embodiment, based on calculated correction coefficients, exposure masks that are closest to the correction coefficients are selected and used by zone during an exposure step of an actual manufacturing process. This sets the positions of the inflection points of the displacement profiles of piezo actuators <NUM> of each zone to correspond to in plane positions on silicon wafer <NUM>, and thus makes the displacement amounts of piezo actuators <NUM> uniform.

Note that this embodiment derives the correction coefficients based on the assumption that the film thickness of piezoelectric film <NUM> and the displacement amount of piezo actuator <NUM> are proportionally related. The relationship between the thickness of piezo actuator <NUM> and the displacement amount of piezo actuator <NUM> is ascertained to more accurately correct the displacement amount.

<FIG> illustrates another embodiment of a method for manufacturing a piezo actuator having a ring type electrode. As an example, <FIG> are used to illustrate the method for manufacturing piezo actuator <NUM>.

Referring to <FIG>, silicon wafer <NUM> is prepared by forming a plurality of pressure chambers <NUM> and an ink flow path that links the plurality of pressure chambers <NUM> on silicon wafer <NUM> through a pressure chamber forming step (step S31, see <FIG>).

Next, lower electrode <NUM> is formed as a film on silicon wafer <NUM> (step S32, an example of common electrode forming step). In one embodiment, this is performed by a sputtering method.

After forming lower electrode <NUM>, piezoelectric film <NUM> is formed as a film on the side where lower electrode <NUM> of silicon wafer <NUM> has been formed as a film (step S33, an example of a piezoelectric body film forming step, see <FIG>). In one embodiment, this is performed by a sputtering method. In this manner, lower electrode <NUM> is formed on one surface of piezoelectric film <NUM>.

Furthermore, as mentioned above, the film thickness distribution of piezoelectric film <NUM>, which is at least partially the cause of the displacement amount distribution of piezo actuator <NUM>, is generated in this sputtering film formation.

After forming piezoelectric film <NUM>, insulating film <NUM> is formed as a film on the side where piezoelectric film <NUM> of silicon wafer <NUM> has been formed as a film (step S34, see <FIG>). Insulating film <NUM> may comprise, for example, SiN (silicon nitride), SiO<NUM> (silicon oxide). In alternative embodiments, insulating film <NUM> is formed by a Chemical Vapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) method.

After forming insulating film <NUM>, a photoresist <NUM> is applied (step S35, lithography process, see <FIG>). In one embodiment, photoresist <NUM> is applied by a spin coating method and baking is performed on the side where insulating film <NUM> of silicon wafer <NUM> has been formed as a film. Additionally, exposure (exposure step) and developing are performed to remove the region of opening 146b of insulating film <NUM> (step S36, see <FIG>).

Next, a ring-shaped opening 146b is formed in insulating film <NUM>. In one embodiment, ring shaped opening 146b is formed by a dry etching method in accordance with an opening in photoresist <NUM> (step S37, an example of an insulating film forming step, see <FIG>), and then photoresist <NUM> is removed (step S38, see <FIG>).

After forming ring-shaped opening 146b, upper electrode <NUM> is formed as a film. In one embodiment, upper electrode <NUM> is formed by a sputtering method on the side where the insulating film <NUM> of the silicon wafer <NUM> has been formed as a film (an example of a surface opposite one surface of a piezoelectric body film) (step S39, see <FIG>). Then, just as with insulating film <NUM>, a photoresist is applied, baking, exposure and developing are performed, a desired shape is formed by a dry etching method, and the resist is removed to form a plurality of upper electrodes <NUM> that correspond to the plurality of pressure chambers <NUM>, respectively (step S40, an example of an individual electrode forming step, see <FIG>).

After performing the method of <FIG>, piezo actuator <NUM> is produced. As for piezo actuator <NUM>, upper electrode <NUM> substantially functions as a ring type electrode with an electrode width x, and this electrode width x is determined based on the width of opening 146b of insulating film <NUM>. The width of opening 146b is determined in the exposure step for the photoresist <NUM> in step S6. By selecting and using the desired exposure mask from among a plurality of exposure masks by zone for inkjet head dies <NUM> (an example of an inflection point setting step, and an example of a mask selecting step) in the exposure step, the width of opening 146b is given a desired width. This sets the positions of the inflection points of the displacement profiles of piezo actuators <NUM> in desired positions, and makes the displacement amounts of piezo actuators <NUM> uniform.

Accordingly, in one embodiment, as for inkjet head die <NUM> (an example of an integrated circuit) where the plurality of piezo actuators <NUM> have been formed, the positions of the inflection points of the displacement profiles of the plurality of piezo actuators <NUM> are set in positions in at least one zone, which is one exposure region by stepper exposure, in positions that are different from other zones.

Note that the method for manufacturing inkjet head <NUM> is configured of the pressure chamb forming step described above and the piezoelectric element forming step for forming the plurality of piezo actuators <NUM> to correspond to the plurality of pressure chambers, respectively, using the method for manufacturing piezo actuators shown in steps S31 to S40. Furthermore, a die that forms a plurality of the nozzles <NUM> is overlapped to correspond to the plurality of pressure chambers <NUM>.

In one embodiment, lower electrode <NUM>, piezoelectric film <NUM>, and then upper electrode <NUM> are laminated on the element forming surface of silicon wafer <NUM> in order to form piezo actuator <NUM>; however, in another embodiment, the order of in which they are laminated is upper electrode <NUM>, piezoelectric film <NUM>, and then lower electrode <NUM>.

In the embodiments described above, examples that applied to an inkjet recording device for graphic printing are described; however, the scope of application of the present invention is not limited to these examples. For example, the techniques described herein can be applied broadly to ink jet devices for drawing a variety of shapes and patterns using liquid functional materials such as wire drawing devices for drawing the wire patterns of electronic circuits, devices for manufacturing all types of devices, resist recording devices that use resin solutions as functional liquids for discharge, devices for manufacturing color filters, and microstructure forming devices for forming microstructures using materials for material deposition.

Some portions of the detailed descriptions above are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated.

Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus.

Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language.

A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory ("ROM"); random access memory ("RAM"); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc..

Claim 1:
An inkjet print head comprising:
a plurality of jets, wherein each of the plurality of jets comprises
a nozzle (<NUM>),
a substrate (<NUM>) that forms part of a pressure chamber (<NUM>) connected with the nozzle (<NUM>),
a common electrode (<NUM>) on top of the substrate, the common electrode being used by multiple jets of the plurality of jets;
a piezoelectric body (<NUM>) comprising a piezoelectric film that is on top of the common electrode (<NUM>), wherein the inkjet print head is characterized in that each of the plurality of jets comprises an individual ring shaped electrode (<NUM>) having an inner diameter and an outer diameter coupled to the piezoelectric body (<NUM>) to cause displacement of the piezoelectric body (<NUM>) to apply pressure to the pressure chamber (<NUM>) in response to a voltage applied to the electrode (<NUM>), and wherein individual ring shaped electrodes (<NUM>) of two or more of the plurality of jets have different ring widths between the inner diameter and the outer diameter (x, x - Δx) to cause their associated piezoelectric bodies to have a uniform displacement amount when the voltage is applied to the individual ring shaped electrodes (<NUM>), wherein the ring width of the individual ring shaped electrode (<NUM>) is adjusted by widening the inner diameter of the individual ring shaped electrode.