JP2009032745A - Substrate heating method, substrate heating apparatus, manufacturing method of piezoelectric element, and manufacturing method of liquid injection head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate heating method and a substrate heating apparatus capable of uniformly heating the entire surface of a substrate. <P>SOLUTION: A film is formed on the substrate. When placing the substrate on which the film is formed on a hot plate for heating, the surface of the hot plate should be convex or concave. The substrate is heated while the interval between the substrate warped by heating and the surface of the hot plate is nearly constant in a direction parallel to the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a substrate heating method and a substrate heating apparatus for a substrate, and more particularly, a method for manufacturing a piezoelectric element having a piezoelectric layer formed by firing a piezoelectric precursor film, and a liquid jet head including the piezoelectric element. It relates to the manufacturing method.

  A piezoelectric element used for a liquid jet head or the like is an element in which a piezoelectric layer made of a ferroelectric material such as a piezoelectric material exhibiting an electromechanical conversion function is sandwiched between two electrodes, and the piezoelectric layer is crystallized, for example. It is composed of piezoelectric ceramics. As a liquid ejecting head using such a piezoelectric element, for example, a part of a pressure generating chamber communicating with a nozzle for ejecting ink droplets is constituted by a diaphragm, and the diaphragm is deformed by the piezoelectric element to generate pressure. There is an ink jet recording head that pressurizes ink in a chamber and ejects ink droplets from nozzles.

  Here, as a piezoelectric layer constituting the piezoelectric element, for example, there is one formed by laminating a plurality of ferroelectric films. The manufacturing method is as follows. First, a ferroelectric precursor film is formed on a lower electrode film provided on a substrate, and then heat-treated at a high temperature for crystallization to form a lowermost ferroelectric film (first ferroelectric film). Form. Next, the first ferroelectric film and the lower electrode film are formed into a predetermined shape by etching the first ferroelectric film and the lower electrode film. Thereafter, a ferroelectric precursor film is formed again and crystallized by heat treatment at a high temperature to form a ferroelectric film. There is a method of forming a plurality of such ferroelectric films to form a piezoelectric layer having a predetermined thickness (see, for example, Patent Document 1).

  When the piezoelectric layer is formed in this way, for example, in the degreasing process, the ferroelectric precursor film is heated by placing the substrate on a hot plate of a heating device and heating it. Various heating devices for heating the substrate (ferroelectric precursor film) have been proposed (see, for example, Patent Document 2).

JP 2005-014265 A JP 2002-198302 A

  However, since the surface of such a hot plate of a heating device is usually flat, there is a problem that the substrate cannot be heated uniformly over the entire surface. Specifically, when a film made of a material having a different linear expansion coefficient, such as a lower electrode film or a ferroelectric film, is formed on the substrate, warping occurs due to the difference in the linear expansion coefficient. End up. On the other hand, the surface of the hot plate is flat. Therefore, there is a problem that a gap is formed between the substrate and the hot plate, resulting in variations in the heating temperature.

  Also, for example, when such a variation in heating temperature occurs when a piezoelectric precursor film (ferroelectric precursor film) formed on a substrate is dried or degreased, the formed piezoelectric layer There is a possibility that the crystallinity will vary and the displacement characteristics of the piezoelectric element will deteriorate.

  This invention is made | formed in view of such a situation, and it aims at providing the board | substrate heating method and board | substrate heating apparatus which can heat a board | substrate uniformly over the whole surface. Furthermore, an object of the present invention is to provide a method for manufacturing a piezoelectric element and a method for manufacturing a liquid ejecting head that can improve the displacement characteristics of the piezoelectric element.

The present invention that solves the above-mentioned problems forms a film on a substrate, and when the substrate on which the film is formed is placed on a hot plate and heated, the surface of the hot plate is formed in a convex shape or a concave shape. And the substrate is heated in a state in which the distance between the substrate warped by heating and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. It is in the substrate heating method.
In the present invention, since the distance between the surface of the hot plate and the substrate placed thereon is always constant during heating, the entire substrate can be heated to a uniform temperature.

The present invention also relates to a method of manufacturing a piezoelectric element having an electrode layer and a piezoelectric layer made of a piezoelectric material on a substrate, the film forming step of forming a piezoelectric precursor film on the substrate, A drying step for drying the piezoelectric precursor film by heating to a predetermined temperature; a degreasing step for degreasing the piezoelectric precursor film by heating the substrate to a predetermined temperature; and a degreasing piezoelectric precursor film A piezoelectric layer forming step of forming the piezoelectric layer by a baking step of baking, and the substrate is placed on a hot plate in the piezoelectric layer forming step to heat the piezoelectric precursor film In this case, the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate warped by heating and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. Said piezoelectric precursor in a state In the manufacturing method of the piezoelectric element, characterized in that so as to heat the.
In the present invention, since the distance between the surface of the hot plate and the substrate placed thereon is always constant during heating, the piezoelectric precursor film on the substrate can be uniformly heated. Thereby, since the crystallinity of the piezoelectric layer is improved, the displacement characteristics of the piezoelectric element can be improved.

  Specifically, for example, in the degreasing step, the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate that has been warped by heating and the surface of the hot plate is the substrate. The piezoelectric precursor film is heated in a state that is substantially constant in the in-plane direction. Further, for example, in the drying step, the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate that has been warped by heating and the surface of the hot plate is within the plane of the substrate. The piezoelectric precursor film is heated in a state that is substantially constant in the direction. Thus, the crystallinity of the piezoelectric layer is more reliably improved by heating the piezoelectric precursor film uniformly in the degreasing step or the drying step, or both steps.

  The piezoelectric precursor film is preferably formed by an organometallic pyrolysis method. Thereby, a piezoelectric layer having excellent crystallinity can be formed relatively easily.

  The substrate is preferably composed of a silicon single crystal substrate having a plane orientation (110). Thereby, a piezoelectric element can be favorably formed on a substrate.

  Furthermore, the present invention resides in a method for manufacturing a liquid ejecting head using a piezoelectric element manufactured by such a manufacturing method. Thereby, it is possible to realize a liquid jet head having excellent droplet discharge characteristics.

The present invention also includes a hot plate on which the substrate is placed and a heating means for heating the hot plate to a predetermined temperature, and the surface of the hot plate is formed along the warp of the substrate caused by heating. In the substrate heating apparatus, the substrate is heated in a state where the distance between the substrate and the surface of the hot plate is substantially constant in the in-plane direction of the substrate.
In the present invention, since the distance between the surface of the hot plate and the substrate placed thereon is always constant during heating, the entire substrate can be heated uniformly.

  Here, it is preferable that support pins having the same length to support the substrate are provided on the outer peripheral portion of the hot plate. Thereby, the space | interval of the surface of a hotplate and a board | substrate can be hold | maintained in a substantially constant state comparatively easily.

Hereinafter, the present invention will be described in detail based on an embodiment.
FIG. 1 is an exploded perspective view showing an outline of an ink jet recording head which is an example of a liquid ejecting head, FIG. 2 is a plan view and a cross-sectional view taken along line AA ′ of FIG. 1, and FIG. It is an expanded sectional view which shows the layer structure. As shown in the figure, the flow path forming substrate 10 constituting the ink jet recording head is made of, for example, a silicon single crystal substrate having a plane orientation (110), and an elastic film 50 made of silicon dioxide is formed on one surface thereof. ing. In the flow path forming substrate 10, a plurality of pressure generating chambers 12 partitioned by a partition wall 11 are arranged in parallel in the width direction. An ink supply path 13 and a communication path 14 that are partitioned by a partition wall 11 and communicate with each pressure generation chamber 12 are provided on one end side in the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10. A communication portion 15 that communicates with each communication path 14 is provided outside the communication path 14. The communication portion 15 communicates with a reservoir portion 32 of the protective substrate 30 described later, and constitutes a part of the reservoir 100 common to the pressure generation chambers 12.

  The ink supply path 13 is formed so as to have a narrower cross-sectional area than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 15. Specifically, the ink supply path 13 has a width smaller than the width of the pressure generation chamber 12 by narrowing the flow path on the pressure generation chamber 12 side between the reservoir 100 and each pressure generation chamber 12 in the width direction. Is formed. Each communication path 14 is formed by extending the partition walls 11 on both sides in the width direction of the pressure generating chamber 12 to the communication part 15 side to partition the space between the ink supply path 13 and the communication part 15. The ink supply path 13 is not limited to the above-described configuration, and for example, the width of the flow path may be narrowed from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. As described above, the silicon single crystal substrate is preferably used as the material of the flow path forming substrate 10 as described above. However, the material is not limited to this, and for example, glass ceramics, stainless steel, or the like may be used.

  On the opening surface side of the flow path forming substrate 10, a nozzle plate 20 in which a nozzle 21 communicating with the vicinity of the end portion of each pressure generating chamber 12 on the side opposite to the ink supply path 13 is formed is an adhesive or a heat welding film. And so on. The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, or stainless steel (SUS).

  On the other hand, the elastic film 50 is formed on the side opposite to the opening surface of the flow path forming substrate 10 as described above, and the insulator film 55 is formed on the elastic film 50. Further, on the insulator film 55, a piezoelectric element 300 including a lower electrode film 60, a piezoelectric layer 70 having a thickness of about 1.0 to 5.0 μm, and an upper electrode film 80 is formed. . Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one of the electrodes of the piezoelectric element 300 is used as a common electrode, and the other electrode is patterned together with the piezoelectric layer 70 for each pressure generating chamber 12 to form individual electrodes. In the present embodiment, the lower electrode film 60 is used as a common electrode of the piezoelectric element 300 and the upper electrode film 80 is used as an individual electrode of the piezoelectric element 300. However, there is no problem even if this is reversed for convenience of a drive circuit and wiring. In the above-described example, the elastic film 50, the insulator film 55, and the lower electrode film 60 substantially function as a vibration plate, but only the lower electrode film 60 is provided without providing the elastic film 50 and the insulator film 55. The lower electrode film 60 may be left as a diaphragm. Further, the piezoelectric element 300 itself may substantially serve as a diaphragm.

  Here, the lower electrode film 60 constituting the piezoelectric element 300 is patterned in the vicinity of both end portions of the pressure generating chamber 12 and continuously provided along the direction in which the pressure generating chambers 12 are arranged side by side. In the present embodiment, the end surface of the lower electrode film 60 in the region facing each pressure generation chamber 12 is an inclined surface that is inclined with respect to the insulator film 55 at a predetermined angle. Note that the end surface of the lower electrode film 60 is not necessarily an inclined surface, and may be a surface substantially perpendicular to the insulator film 55.

  The piezoelectric layer 70 is provided independently for each pressure generating chamber 12, and as shown in FIG. 3, for example, a plurality of layers of piezoelectric films 71 (71a) made of a piezoelectric material such as lead zirconate titanate (PZT). The first piezoelectric film 71a, which is the lowermost layer among them, is provided only on the lower electrode film 60. The end surface of the first piezoelectric film 71 a is an inclined surface that continues from the end surface of the lower electrode film 60. In addition, the second to fourth piezoelectric films 71b to 71d formed on the first piezoelectric film 71a are the first piezoelectric films from the first piezoelectric film 71a to the insulator film 55. 71a and the lower electrode film 60 are provided so as to cover the inclined end faces. The first piezoelectric film 71a and the lower electrode film 60 are formed in a region facing the longitudinal direction of the pressure generating chamber 12, and the second to fourth piezoelectric films 71b to 71d are configured to generate pressure. The chamber 12 extends from a region facing the longitudinal end of the chamber 12 to the outside of the region.

  The upper electrode film 80 is provided independently for each pressure generation chamber 12 as in the piezoelectric layer 70. Each upper electrode film 80 is connected to one end side of a lead electrode 90 made of, for example, gold (Au) or the like, and the other end side of the lead electrode 90 extends to the insulator film 55.

  A protective substrate 30 having a piezoelectric element holding portion 31 for protecting the piezoelectric element 300 is bonded onto the flow path forming substrate 10. The piezoelectric element holding portion 31 may be sealed, but may not be sealed. Further, the protective substrate 30 is provided with a reservoir portion 32 that constitutes at least a part of the reservoir 100 serving as an ink chamber common to the pressure generating chambers 12. On the protective substrate 30, a compliance substrate 40 including a sealing film 41 made of a material having low rigidity and flexibility and a fixing plate 42 made of a hard material such as metal is joined. A region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, and one surface of the reservoir 100 is sealed only by the sealing film 41.

  In such an ink jet recording head, ink is taken in from an external ink supply means (not shown), filled with ink from the reservoir 100 to the nozzle 21, and then passed through external wiring in accordance with a recording signal from a drive circuit (not shown). By applying a voltage between each of the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generation chamber 12 and bending the piezoelectric element 300 and the diaphragm, the pressure in each pressure generation chamber 12 is changed. The ink droplets are ejected from the rising nozzle 21.

Hereinafter, a method for manufacturing an ink jet recording head according to the present embodiment, in particular, a method for forming a piezoelectric element will be described with reference to FIGS. First, as shown in FIG. 4A, a silicon dioxide film 51 that becomes an elastic film 50 is formed on a flow path forming substrate wafer 110 that is a silicon wafer that becomes a flow path forming substrate 10. Next, as shown in FIG. 4B, an insulator film 55 made of zirconium oxide (ZrO ₂ ) is formed on the elastic film 50 (silicon dioxide film 51). Next, as shown in FIG. 4C, the lower electrode film 60 is formed on the insulator film 55. The material of the lower electrode film 60 is not particularly limited. However, when lead zirconate titanate (PZT) is used as the piezoelectric layer 70, it is desirable that the material has little change in conductivity due to diffusion of lead oxide. . For this reason, platinum, iridium or the like is preferably used as the material of the lower electrode film 60.

  Next, a piezoelectric layer forming step for forming the piezoelectric layer 70 on the lower electrode film 60 is performed. As described above, the piezoelectric layer 70 is formed by stacking a plurality of piezoelectric films 71a to 71d. For example, in the present embodiment, the piezoelectric film 71 is formed by a so-called MOD (Metal-Organic Decomposition) method. That is, after an organometallic compound such as a metal alkoxide is dissolved in alcohol and a colloid solution obtained by adding a hydrolysis inhibitor or the like to this is applied onto the object to form the piezoelectric precursor film 72, Each piezoelectric film 71 is obtained by drying and degreasing the piezoelectric precursor film 72 to release organic components, followed by firing and crystallization.

In addition, as a material of the piezoelectric layer 70, for example, a piezoelectric material such as lead zirconate titanate (PZT) is used. In addition, a piezoelectric material containing excess lead (lead exceeding the stoichiometric ratio) is used in order to prevent lead chipping in the piezoelectric layer 70 formed by firing. Of course, the material of the piezoelectric layer 70 is not limited to lead zirconate titanate (PZT). For example, a relaxor ferroelectric material in which a metal such as niobium, nickel, magnesium, bismuth or yttrium is added to lead zirconate titanate (PZT) may be used. The composition may be appropriately selected in consideration of the characteristics, use, etc. of the piezoelectric element 300. For example, PbTiO ₃ (PT), PbZrO ₃ (PZ), Pb (Zr _x Ti _1-x ) O ₃ (PZT) ), Pb (Mg _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ (PMN-PT), Pb (Zn _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ (PZN—PT), Pb (Ni ₁ ) _{/ 3} Nb _2/3 ) O ₃ -PbTiO ₃ (PNN-PT), Pb (In _1/2 Nb _1/2 ) O ₃ -PbTiO ₃ (PIN-PT), Pb (Sc _1/2 Ta _{1/2 ) O 3 -PbTiO 3 (PST-} PT), Pb (Sc 1/2 Nb 1/2) O 3 -PbTiO 3 (PSN-PT), BiScO 3 -PbTiO 3 (BS-PT), BiYbO 3 -PbTiO 3 (BY-PT) and the like. In the present embodiment, each piezoelectric film 71 constituting the piezoelectric layer 70 is formed by the MOD method. However, the present invention is not limited to this, and may be formed by a so-called sol-gel method. .

  Specifically, as a procedure for forming the piezoelectric layer 70, first, as shown in FIG. 5A, a crystal seed (layer) 65 made of titanium or titanium oxide is formed on the lower electrode film 60 by, for example, sputtering. Form by the method. This crystal seed (layer) 65 may be formed as necessary. Next, as shown in FIG. 5B, an uncrystallized piezoelectric precursor film 72a is formed to have a predetermined thickness by a coating method such as a spin coating method (film forming step). The body precursor film 72a is dried to evaporate the solvent (alcohol) (drying step). The temperature at which the piezoelectric precursor film 72a is dried is, for example, preferably 150 ° C. or higher and 200 ° C. or lower, and preferably about 180 ° C. The drying time is preferably, for example, from 5 minutes to 15 minutes, and preferably about 10 minutes.

Next, the dried piezoelectric precursor film 72a is degreased at a predetermined temperature (degreasing step). The degreasing referred to here is to release the organic component of the piezoelectric precursor film 72a as, for example, NO ₂ , CO ₂ , H ₂ O or the like. In addition, it is preferable that the heating temperature of the wafer 110 for flow path formation substrates at the time of degreasing is about 300 to 500 degreeC. For example, in this embodiment, the flow path forming substrate wafer 110 is heated to about 400 ° C. to degrease the piezoelectric precursor film 72a. If the heating temperature is too high, crystallization of the piezoelectric precursor film 72a starts, and if the temperature is too low, sufficient degreasing may not be performed.

  Next, the flow path forming substrate wafer 110 is put into, for example, an RTA (Rapid Thermal Annealing) apparatus and the like, and the piezoelectric precursor film 72a is baked and crystallized at a high temperature of about 700 ° C. A first piezoelectric film 71a which is a piezoelectric film is formed (firing process).

  Next, the lower electrode film 60 and the first piezoelectric film 71a are patterned simultaneously. First, as shown in FIG. 5C, a resist is applied onto the first piezoelectric film 71a, and a resist film 150 having a predetermined pattern is formed by exposure and development. Here, the resist is formed, for example, by applying a negative resist by a spin coating method or the like, and the resist film 150 is formed by performing exposure, development, and baking using a predetermined mask. Of course, a positive resist may be used instead of the negative resist. In the present embodiment, the end surface of the resist film 150 is formed to be inclined at a predetermined angle.

  Then, as shown in FIG. 6A, patterning is performed by ion milling the lower electrode film 60 and the first piezoelectric film 71a through such a resist film 150. At this time, the lower electrode film 60 and the first piezoelectric film 71a are patterned along the inclined end surfaces of the resist film 150, and these end surfaces become inclined surfaces inclined at a predetermined angle with respect to the diaphragm. .

  Next, as shown in FIG. 6B, the resist film 150 on the first piezoelectric film 71a is peeled off, and then, on the first piezoelectric film 71a, as shown in FIG. 6C. Then, the piezoelectric precursor film 72b is formed to have a predetermined thickness by a spin coating method or the like (film forming process). Next, the above-described drying process, degreasing process, and firing process are performed. In the present embodiment, the piezoelectric precursor film 72b having a desired thickness is obtained by applying, drying, and degreasing three times. Thereafter, the piezoelectric precursor film 72b is fired and crystallized to form a second piezoelectric film 71b.

  Then, the remaining piezoelectric film is formed by repeating such a film formation process, a drying process, a degreasing process, and a baking process. That is, by repeating the step of forming the piezoelectric precursor film by three times of coating and the step of drying and degreasing the piezoelectric precursor film and then baking and forming the piezoelectric film, the remaining number of times is obtained. Third and fourth piezoelectric films 71c and 71d, which are piezoelectric films, are formed. As a result, a piezoelectric layer 70 composed of a plurality of layers of piezoelectric films 71a to 71d is formed (FIG. 6D).

  As described above, in the piezoelectric layer forming step, the piezoelectric layer 70 is formed by repeating the film forming step, the drying step, the degreasing step, and the firing step a plurality of times. As will be described in detail later, in this piezoelectric layer forming step, the piezoelectric precursor film 72 is heated by placing the flow path forming substrate wafer 110 on a hot plate of a substrate heating apparatus. For example, in the present embodiment, the piezoelectric precursor film 72 is heated by the hot plate in this way in the drying step and the degreasing step.

  Here, the flow path forming substrate wafer 110 on which the lower electrode film 60 or the piezoelectric film 71 is formed includes the flow path forming substrate wafer 110 and each layer (for example, the lower electrode film 60) formed thereon. Due to the difference in linear expansion coefficient between the lower electrode film 60 and the lower electrode film 60, a slight warpage is generated. On the other hand, when the flow path forming substrate wafer 110 is heated, a warp in which the lower electrode film 60 side is convex occurs in the flow path forming substrate wafer 110 due to a difference in linear expansion coefficient. For example, in the case of a 6-inch wafer, the amount of warpage is about several hundred μm at the maximum.

  In the present invention, when the flow path forming substrate wafer is placed on the hot plate and the piezoelectric precursor film is heated, the gap between the flow path forming substrate wafer and the surface of the hot plate that is warped by heating. However, it is made substantially constant in the in-plane direction of the flow path forming substrate wafer. Specifically, the flow path forming substrate wafer is placed on a hot plate of a substrate heating apparatus described below to heat the piezoelectric precursor film.

  As shown in FIG. 7, the substrate heating apparatus 200 according to this embodiment includes a hot plate 202 in which a heater 201 as a heating unit is provided, and the hot plate 202 is disposed in a housing 203. (FIG. 7B). Moreover, the surface of this hot plate 202 is formed in the convex curved surface in this embodiment, for example. That is, the surface of the hot plate 202 is formed in a convex curved surface along the warp of the flow path forming substrate wafer 110 that occurs during heating. As a result, the distance between the heated flow path forming substrate wafer 110 and the hot plate 202 is made substantially constant in the in-plane direction of the flow path forming substrate wafer 110.

  In the present embodiment, a plurality (for example, three) of support pins 204 that support the flow path forming substrate wafer 110 are provided at a peripheral portion of the hot plate 202 with a certain length. The flow path forming substrate wafer 110 is placed on the hot plate 202 through the support pins 204, and the surfaces of the flow path forming substrate wafer 110 and the hot plate 202 supported by the plurality of support pins 204. Is set to be substantially constant in the in-plane direction of the flow path forming substrate wafer 110.

  As described above, the flow path forming substrate wafer 110 is warped so that the lower electrode film 60 side is convex at room temperature, but when it is placed on the hot plate 202 heated to a predetermined temperature, the temperature rises rapidly. Accordingly, the warping state changes, and the distance between the flow path forming substrate wafer 110 and the surface of the hot plate 202 becomes substantially constant. Then, the piezoelectric precursor film 72 is heated while holding the state where the distance between the flow path forming substrate wafer 110 and the surface of the hot plate 202 is substantially constant for a predetermined time.

  As a result, the entire piezoelectric precursor film 72 formed on the flow path forming substrate wafer 110 can be heated uniformly, and the piezoelectric film 71 (piezoelectric layer 70) constituting each piezoelectric element 300 can be heated. Variation in crystallinity can be prevented. Therefore, the piezoelectric layer 70 constituting each piezoelectric element 300 is uniformized with good crystallinity. Therefore, the displacement characteristics of the piezoelectric element 300 can be improved. In addition, since variation in displacement characteristics of each piezoelectric element 300 formed on one flow path forming substrate wafer 110 is prevented, the yield can be improved and the manufacturing cost can be reduced. It should be noted that such an effect is particularly easily obtained by heating the piezoelectric precursor film 72 as described above in the degreasing step.

  It should be noted that the distance between the heated flow path forming substrate wafer 110 and the surface of the hot plate 202 may be constant so that the variation in the heating temperature is within the allowable range. That is, the distance between the heated flow path forming substrate wafer 110 and the surface of the hot plate 202 may be substantially constant in the in-plane direction of the flow path forming substrate wafer 110.

  Further, when the piezoelectric layer 70 is formed of a plurality of piezoelectric films 71a to 71d as in the present embodiment, the warp of the flow path forming substrate wafer 110 in the step of forming the piezoelectric films 71a to 71d. The amount may vary. That is, the thicker the piezoelectric film 71 formed in each process, the greater the warpage. Further, since the heating temperature is different between the drying step and the degreasing step, the warpage amount of the flow path forming substrate wafer 110 may also change. When the amount of change is relatively large, it is preferable that the hot plate 202 having a different curvature radius of the surface shape is appropriately selected and used in the step of forming each piezoelectric film 71. Thereby, the crystallinity variation of the piezoelectric film 71 (piezoelectric layer 70) can be more reliably prevented.

  The surface shape of the hot plate 202 is determined based on the measurement result obtained by heating the flow path forming substrate wafer 110 on a trial basis and heating the piezoelectric precursor film 72 to measure the amount of warpage. do it. The amount of warpage of the substrate varies depending on the material of the film formed thereon, the thickness, the film forming conditions such as the region where the film is formed, or the heating conditions such as the heating temperature and the heating time. Is constant, the amount of warpage of the substrate is always constant.

  In the present embodiment, since the silicon single crystal substrate having the plane orientation (110) is used as the flow path forming substrate wafer 110, the amount of warpage varies depending on the crystal direction. Specifically, the warpage amount of the flow path forming substrate wafer 110 is maximum in the (001) direction and is minimum in the (1-10) direction, which is a direction orthogonal to the (001) direction. Therefore, when heating such a substrate, it is preferable to change the radius of curvature in each direction on the surface of the hot plate 202 in accordance with the amount of warpage. Such a difference in warpage amount may also occur due to a difference in heating temperature. For example, in a drying process where heating is performed at a relatively low temperature, the warping amount is constant regardless of the crystal direction, but in a degreasing process where heating is performed at a relatively high temperature, the warping amount may vary depending on the crystal direction as described above. In such a case, it is preferable that the hot plate 202 is appropriately selected and used in each step.

  Incidentally, for example, a silicon single crystal substrate having a plane orientation (100) is isotropic, and the amount of warpage in each direction in the plane is constant. When such a substrate is heated, the radius of curvature on the surface of the hot plate 202 may be constant in each direction.

  After the piezoelectric layer 70 is formed in this way, as shown in FIG. 8A, for example, an upper electrode film 80 made of iridium (Ir) is laminated and the piezoelectric layer 70 and the upper electrode film 80 are formed. Patterning is performed in a region facing each pressure generating chamber 12 to form the piezoelectric element 300 (FIG. 8B). Next, as shown in FIG. 9A, after forming a metal layer 91 made of gold (Au) over the entire surface of the flow path forming substrate 10, for example, through a mask pattern (not shown) made of resist or the like. The lead electrode 90 is formed by patterning the metal layer 91 for each piezoelectric element 300. Next, as shown in FIG. 9B, a protective substrate wafer 130 on which a plurality of protective substrates 30 are integrally formed is bonded onto the flow path forming substrate wafer 110 with an adhesive 35. Here, a piezoelectric element holding portion 31, a reservoir portion 32, and the like are formed in advance on the protective substrate wafer 130. Next, as shown in FIG. 9C, after the flow path forming substrate wafer 110 is polished to a certain thickness, the flow path forming substrate wafer 110 is further etched to a predetermined thickness by wet etching with hydrofluoric acid. To.

  Next, as shown in FIG. 10A, a protective film 52 made of, for example, silicon nitride (SiN) is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape. Then, as shown in FIG. 10B, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) through the protective film 52, so that the pressure generating chamber is formed in the flow path forming substrate wafer 110. 12, an ink supply path 13, a communication path 14, and a communication portion 15 are formed. Thereafter, the nozzle plate 20 having the nozzles 21 formed on the surface of the flow path forming substrate wafer 110 opposite to the protective substrate wafer 130 is bonded, and the compliance substrate 40 is bonded to the protective substrate wafer 130. The ink jet type recording head having the above-described structure is manufactured by dividing the flow path forming substrate wafer 110 and the like into a single chip size flow path forming substrate 10 as shown in FIG.

(Other embodiments)
As mentioned above, although one Embodiment of this invention was described, the structure of this invention is not limited to what was mentioned above. For example, in the above-described embodiment, the example in which the surface of the hot plate 202 is configured by a curved surface has been described. However, the surface of the hot plate 202 only needs to be substantially curved. For example, as shown in FIG. 11, it may be a substantially curved surface formed by a plurality of steps. Of course, if each step is too large, the heating temperature of the substrate may vary, which is not preferable.

  Further, for example, in the above-described embodiment, the surface of the hot plate 202 is formed in a convex shape, but of course, the hot plate 202 may have a surface formed in a concave shape. This shape should just be formed along the curvature of a board | substrate to the last. For example, in the above-described embodiment, an example in which a plurality of support pins 204 are provided on the hot plate 202 as the substrate heating device has been described. However, the support pins 204 are not necessarily provided. Of course, even when the support pins 204 are not provided, the distance between the flow path forming substrate wafer 110 and the surface of the hot plate 202 is substantially constant. That is, the distance between the two is substantially zero and constant, and the entire surface of the flow path forming substrate wafer 110 is substantially in contact with the hot plate 202. For example, in the above-described embodiment, the example in which the piezoelectric precursor film 72 is heated by the hot plate 202 in each of the drying step and the degreasing step has been described. Of course, the hot plate 202 is used only in one step. The piezoelectric precursor film 72 may be heated.

  Further, for example, in the above-described embodiment, the piezoelectric films 71b to 71d on the piezoelectric film 71a are each formed by applying, drying, and degreasing three times to form the piezoelectric precursor film 72, and then the piezoelectric precursor film 72. Of course, each piezoelectric film is formed by firing a piezoelectric precursor film formed by coating, drying, and degreasing once, twice, or four times or more. You may make it do.

  In the above-described embodiment, the ink jet recording head that ejects ink is exemplified as the liquid ejecting head. However, the present invention is widely intended for the liquid ejecting head. Examples of the liquid ejecting head include a recording head used for an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (field emission display). Electrode material ejecting heads used in manufacturing, bioorganic matter ejecting heads used in biochip production, and the like. The present invention is not limited to a method for manufacturing a piezoelectric element used in a liquid ejecting head, but also a method for manufacturing a piezoelectric element mounted on any other device, for example, a microphone, sounding body, various vibrators, an oscillator, and the like. Needless to say, it can also be applied.

  Furthermore, the substrate heating method of the present invention can be applied when heating a substrate on which a film made of a material having a different linear expansion coefficient is formed. For example, for manufacturing a color filter used for a liquid crystal monitor or the like. Can also be applied, and the object is not particularly limited. Of course, the substrate heating apparatus of the present invention can also be used for heating a wide variety of substrates.

FIG. 3 is an exploded perspective view illustrating the recording head according to the first embodiment. 2A and 2B are a plan view and a cross-sectional view illustrating the recording head according to the first embodiment. 3 is an enlarged cross-sectional view showing the piezoelectric element according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. It is the schematic top view and sectional drawing which show the substrate heating apparatus which concerns on Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. It is a schematic sectional drawing which shows the substrate heating apparatus which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 13 Ink supply path, 14 Communication path, 15 Communication part, 20 Nozzle plate, 30 Protection board, 40 Compliance board, 50 Elastic film, 55 Insulator film, 60 Lower electrode film, 70 Piezoelectric Layer, 71 Piezoelectric Film, 72 Piezoelectric Precursor Film, 80 Upper Electrode Film, 90 Lead Electrode, 100 Reservoir, 110 Channel Forming Substrate Wafer, 130 Protective Substrate Wafer, 150 Resist Film, 200 Substrate Heating Apparatus, 201 heater, 202 hot plate, 203 housing, 204 support pin, 300 piezoelectric element

Claims (9)

When a film is formed on a substrate and the substrate on which this film is formed is placed on a hot plate and heated,
In the state where the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate and the surface of the hot plate warped by heating is substantially constant in the in-plane direction of the substrate. A substrate heating method characterized by heating a substrate. A method of manufacturing a piezoelectric element having an electrode layer and a piezoelectric layer made of a piezoelectric material on a substrate,
A film forming step of forming a piezoelectric precursor film on the substrate; a drying step of drying the piezoelectric precursor film by heating the substrate to a predetermined temperature; and heating the substrate to a predetermined temperature to form the piezoelectric A degreasing step of degreasing the body precursor film, and a firing step of further firing the degreased piezoelectric precursor film, and a piezoelectric layer forming step of forming the piezoelectric layer,
When the substrate is placed on a hot plate and the piezoelectric precursor film is heated in the piezoelectric layer forming step, the surface of the hot plate is formed into a convex shape or a concave shape. Manufacturing of the piezoelectric element characterized in that the piezoelectric precursor film is heated in a state where the distance between the warped substrate and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. Method.   In the degreasing step, the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate warped by heating and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. 3. The method of manufacturing a piezoelectric element according to claim 2, wherein the piezoelectric precursor film is heated in a state where   In the drying step, the surface of the hot plate is formed in a convex or concave shape, and the distance between the substrate warped by heating and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. 4. The method of manufacturing a piezoelectric element according to claim 2, wherein the piezoelectric precursor film is heated in a state of   The method for manufacturing a piezoelectric element according to any one of claims 2 to 4, wherein the piezoelectric precursor film is formed by an organic metal pyrolysis method.   6. The method for manufacturing a piezoelectric element according to claim 2, wherein the substrate is made of a silicon single crystal substrate having a plane orientation (110).   A method for manufacturing a liquid jet head, comprising using the piezoelectric element manufactured by the manufacturing method according to claim 1. A hot plate on which the substrate is placed and a heating means for heating the hot plate to a predetermined temperature;
The surface of the hot plate is formed along the warp of the substrate caused by heating, and the substrate is heated in a state where the distance between the substrate and the surface of the hot plate is substantially constant in the in-plane direction of the substrate. A substrate heating apparatus.   The substrate heating apparatus according to claim 8, wherein a support pin having the same length for supporting the substrate is provided on an outer peripheral portion of the hot plate.

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