JP2007059564A - Anode joining device, anode joining method, and manufacturing method for droplet delivery head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable fine joining of boards without executing complicated control while preventing the formation of a void. <P>SOLUTION: An anode joining device includes an anode 2 which is connected electrically to a laminated silicon board 10 to be joined to another board; and cathodes 3A to 3E which are connected electrically to a glass board 20, and apply a voltage to the boards 10, 20 across the cathodes 3A to 3E and the anode 2, in such a voltage distribution that the voltage becomes maximum on given parts of the plane of boards 10, 20, and gets smaller toward the outer periphery of the boards 10, 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for bonding substrates (wafers), for example. In particular, the present invention relates to an anodic bonding apparatus and method for bonding a silicon substrate and a glass substrate, for example, when a microfabricated element (actuator, acceleration sensor, dispenser, etc.) is manufactured.

  When finely processing a silicon substrate or the like to form an element, thickness control is very important. For example, when an adhesive such as a resin is used for bonding the substrates, it is necessary to consider the influence of the thickness of the adhesive. Further, it is necessary to maintain the joined state without being eroded by the chemical solution or the like in subsequent processing and use. In that respect, anodic bonding does not use an adhesive or the like, and the substrates can be bonded to each other at the atomic level, so it is not necessary to consider the thickness of the adhesive or the like, and is a very strong bonding. This is convenient when performing fine processing.

When the anodic bonding is performed, if the adhesion of the stacked substrates is not uniform, the gas remains in the non-adhered portion without being discharged, and voids (voids, bubble accumulations. Resulting in voids that are not joined). For this reason, voids are generated on the joint surface, and an unjoined portion is formed. When a void occurs, for example, when the bonded substrate is ground after bonding, the thin silicon substrate may be damaged. In addition, when processing by wet etching is performed on a bonded substrate, an etchant (etching solution) may be allowed to enter a portion that should not originally enter. Thus, a method for preventing the generation of voids has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 07-183181

  The above-described method controls voltage application to a plurality of concentric cathodes and sequentially performs anodic bonding from the central portion of the substrate toward the outer peripheral edge (outside). Therefore, the control and the apparatus become complicated. Further, in this method, the center portion bent and bent by supporting the silicon substrate from the outer peripheral end portion is brought into close contact with each other, and then gradually brought into close contact with the outer peripheral portion to be joined. . This method is effective when the silicon substrate and the glass substrate are flat. However, for example, when a glass substrate having a concavo-convex surface and a silicon substrate are bonded to each other, the protrusion is in close contact with the protruding portion. A pressure difference may be generated between the concave portions and the voids, and voids may occur.

  Thus, for example, to realize an anodic bonding apparatus and an anodic bonding method that can bond substrates satisfactorily without generating voids even when bonding substrates having irregularities or the like by processing the surfaces. With the goal. Another object of the present invention is to realize a method for manufacturing a droplet discharge head in which substrates are bonded using this apparatus and method.

An anodic bonding apparatus according to the present invention includes a first electrode that is electrically connected to one outer substrate among a plurality of stacked substrates to be bonded, and an electric connection to the other outer substrate of the plurality of substrates. A voltage applied to the substrate with a voltage distribution such that a predetermined portion on the plane of the substrate has a maximum potential and decreases toward the outer peripheral edge of the substrate due to a voltage applied between the first electrode and the first electrode. 2 electrodes.
According to the present invention, by applying a voltage to the substrate in such a voltage distribution that the predetermined portion on the plane of the substrate has the maximum potential and decreases toward the outer peripheral edge of the substrate, the entire substrate is then boosted and heated. To satisfy the conditions of anodic bonding from a predetermined portion and to spread the anodic bonding sequentially to the outer peripheral edge, so that an anodic bonding apparatus in which no void is generated on the bonded substrate can be obtained. . Since the voltage distribution is formed without switching the voltage application for a plurality of electrodes having different arrangement positions, voids can be prevented from being generated without performing complicated voltage control. .

The anodic bonding apparatus according to the present invention further includes voltage control means for controlling a voltage applied between the first electrode and the second electrode.
According to the present invention, by further providing the voltage control means, it is possible to sequentially adhere and bond a plurality of substrates from a predetermined part toward the outer peripheral end while controlling the boosting.

The anodic bonding apparatus according to the present invention further includes a temperature control means for controlling the temperatures of the plurality of substrates.
According to the present invention, by further providing the temperature control means, it is possible to sequentially adhere and bond a plurality of substrates from a predetermined portion toward the outer peripheral end while controlling the temperature rise.

Further, in the anodic bonding apparatus according to the present invention, the second electrode is arranged in a concentric shape in which one of the centers has a circular shape and the other has a ring shape, and the electrical resistance increases from the central portion toward the outside. It comprises a plurality of electrodes.
According to the present invention, the center is arranged in a circular shape and the other is arranged in a ring-like concentric shape, the electric resistance is increased from the center toward the outside, and a voltage having a distribution in which the center becomes the maximum potential is applied to the substrate. As a result, a substrate without voids can be obtained. In particular, in the case of a circular shape, a distribution matched to the wafer can be configured.

In the anodic bonding apparatus according to the present invention, the plurality of electrodes are formed of members made of materials having different resistivity.
According to the present invention, since the plurality of electrodes to be the second electrodes are formed of members made of materials having different resistivity, each electrode can be easily set to a predetermined electric resistance.

In the anodic bonding apparatus according to the present invention, a plurality of electrodes are formed by coating members with films having different resistivity.
According to the present invention, since the plurality of electrodes to be the second electrodes are configured by coating the members with films having different resistivity, each electrode can be easily set to a predetermined electric resistance.

In the anodic bonding apparatus according to the present invention, the second electrode is composed of a plurality of concentrically arranged electrodes having a circular shape at the center and a ring shape at the other. A member is provided between each electrode.
According to the present invention, even if it is provided between a plurality of electrodes, in the plane of the substrate, the electric resistance increases from the center toward the outside, and a voltage having a distribution with the center having the maximum potential can be applied to the substrate Can be configured.

In the anodic bonding apparatus according to the present invention, the first electrode is connected to a silicon substrate as an anode, and the second electrode is connected to a glass substrate containing metal as a cathode.
According to the present invention, when the silicon substrate and the glass substrate containing metal are bonded, the above-mentioned effect can be exhibited most.

In the anodic bonding method according to the present invention, a plurality of stacked substrates to be bonded are heated to a temperature necessary for anodic bonding, and a predetermined portion is set to a maximum potential in the substrate plane toward the outer peripheral edge of the substrate. A step of applying a voltage with a lower distribution to the substrate, and boosting at a predetermined rate, applying a voltage necessary for sequentially performing anodic bonding from a predetermined portion toward the outer peripheral edge of the substrate, And a step of bonding.
According to the present invention, a predetermined portion is set to a maximum potential in the substrate plane, and a voltage having a distribution that decreases toward the outer peripheral edge of the substrate is boosted, and voltages necessary for anodic bonding are sequentially applied from the predetermined portion. Since the substrate is sequentially spread to the outer peripheral portion of the substrate, a bonded substrate having no voids in the bonded substrate can be obtained without particularly complicated control.

In addition, the anodic bonding method according to the present invention is a voltage required for anodic bonding to the substrate in a distribution in which the predetermined portion is at the maximum potential and decreases toward the outer peripheral edge of the substrate in the plane of the plurality of stacked substrates. And a step of heating the plurality of substrates at a predetermined rate, sequentially bringing the plurality of substrates into close contact from the predetermined portion toward the outer peripheral edge of the substrate, and bonding them.
According to the present invention, after applying a voltage having a predetermined potential at a predetermined potential in the substrate plane and decreasing toward the outer peripheral edge of the substrate, the temperature of the substrate is raised, and anodic bonding is sequentially required from the predetermined location. Since the temperature is gradually extended to the outer periphery of the substrate, it is possible to obtain a bonded substrate free from voids in the bonded substrate without particularly complicated control.

In the anodic bonding method according to the present invention, a predetermined rate is determined within a range not damaging at least two substrates and a jig for bonding, and temperature rise is controlled.
According to the present invention, since the rate is controlled without damaging the substrate and the jig, the bonding can be performed safely.

In addition, the method for manufacturing a droplet discharge head according to the present invention includes an electrode substrate having a fixed electrode on at least the bottom surface of a concave portion formed using the above-described anodic bonding apparatus, and a distance from the fixed electrode. A cavity substrate having a movable electrode that is opposed to each other and operates by an electrostatic force generated between the fixed electrode and the fixed electrode is joined except for the concave portion.
According to the present invention, since the above-described anodic bonding apparatus is used in manufacturing a droplet discharge head, no void is generated and the droplet discharge head can be manufactured by a method with a high yield.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an anodic bonding apparatus according to Embodiment 1 of the present invention. Usually, an anodic bonding apparatus has a pair of electrodes (anode and cathode) facing each other, and a plurality of substrates (wafers. In this embodiment, for example, a borosilicate-based material including a silicon (Si) substrate and sodium (Na). Two sheets of heat-resistant and hard glass substrate) are aligned and laminated, and placed between the electrodes. Then, for example, the anode is brought into contact with the silicon substrate, the cathode is brought into contact with the glass substrate, a DC voltage is applied between the electrodes (between the substrates), and the substrate is further heated. The silicon substrate is positively charged by voltage application. Further, sodium in the glass substrate becomes sodium ions (Na +: positive ions) and can move in the glass substrate by heating the substrate. Therefore, sodium ions move to the cathode side, and sodium is deposited by receiving supply of electrons (negative charge) to and from the cathode.

  On the other hand, negative ions such as oxygen having unpaired electrons remain in the glass substrate. Negative ions move to the silicon substrate side, and an electric double layer is formed at the bonding interface. A strong electrostatic attractive force is generated by the electric field generated in the electric double layer, and the silicon substrate and the glass substrate are brought into close contact with each other. Further, silicon in the silicon substrate and oxygen in the glass substrate are covalently bonded, and the substrates are bonded to each other. Therefore, strong bonding can be performed by bonding at the atomic level.

  The anodic bonding apparatus in FIG. 1 has a chamber 1. In the chamber 1, an anode 2, cathodes 3A to 3E, a mounting table 4, and a heater 5 are provided. Then, the silicon substrate 10 and the glass substrate 20 to be bonded are aligned and overlapped and placed on the mounting table 4 in the chamber 1 (hereinafter, particularly, the silicon substrate 10 and the glass substrate 20 are superposed as a superposed substrate). If the two are not distinguished, they are referred to as the substrate 30). Here, the type of the chamber 1 is not particularly limited, such as a vacuum chamber. However, as will be described later, for example, when the surface of the glass substrate 20 is processed and there is a recess on the bonding surface, a pressure difference may occur between the gas remaining in the recess and a void may be induced. In such a case, avoid using a vacuum chamber or the like. Moreover, since it does not specifically limit about the method of carrying in and carrying out the board | substrate 30, it does not specifically limit about the position of a carrying-in and a carrying-out port, a structure, etc. The anode 2 is supplied with power from the DC voltage power source 6 and positively charges the silicon substrate 10 that is electrically connected (contacted). Here, the anode 2 has a parallel plate shape so that the entire substrate 30 is sandwiched and brought into contact with the mounting table 4. However, for example, a rod or a cylindrical anode may be partially brought into contact with the silicon substrate 10. Good (still the whole silicon substrate 10 is positively charged).

  FIG. 2 is a view of the mounting table 4 (particularly, the cathodes 3A to 3E) as viewed from above. The mounting table 4 is provided with a heater 5 for heating the cathodes 3A to 3E and the substrate 30 (the heater 5 is incorporated). The substrate 30 is placed on the mounting table 4 so that the surface of the glass substrate 20 faces the cathodes 3A to 3E. The glass substrate 20 and the cathodes 3A to 3E are in electrical contact (connection). The cathode 3A is circular and the cathodes 3B to 3E are arranged on the mounting table 4 in the same ring shape as the cathode 3A. The cathodes 3A to 3E have different electric resistances, the electric resistance at the center (cathode 3A) is small, and the electric resistance increases as the cathode becomes the outer side. That is, when the electrical resistances of the cathodes 3A to 3E are Ra, Rb, Rc, Rd, and Re, the relationship of Ra <Rb <Rc <Rd <Re is satisfied. The specific resistance value of each cathode varies depending on the substrate to be joined, the temperature, and the method of controlling the applied voltage, and is arbitrarily determined in accordance with them.

  In order to make each electric resistance different, for example, the cathodes 3 </ b> A to 3 </ b> E are made of members having different resistivities. Moreover, the electrical resistance of each cathode can be adjusted by coating at least the contact surface of the electrode member of the same or different material with the glass substrate 20 with films having different resistivity. In addition, the electrical resistance can be adjusted even if the electrode member constituting each cathode, the cross-sectional area of the film, and the diameter (circumference length) of the circle or ring are adjusted and disposed on the mounting table 4. Can do.

  FIG. 3 is a diagram illustrating a circuit model in anodic bonding according to the present embodiment. When the electric resistances of the cathodes 3A to 3E are different, the distribution of the electric resistance in the plane of the mounting table 4 parallel to the bonding surface varies depending on the location. Here, when the electrical resistance at the cathode increases, the voltage drop also increases, and the voltages associated with CGl and RGl decrease accordingly. Accordingly, the movement of sodium ions (positive charge) in the glass substrate 20 is not uniform in the plane, and the movement of sodium ions is the largest in the cathode 3A having a low electrical resistance at the center, and the smaller the movement toward the outer peripheral edge. The distribution is a so-called mountain shape having a gradient of (at least in this distribution, there should be no portion where the gradient is positive (upward portion)). The movement of ions is the movement of electric charges. Therefore, the voltage of the glass substrate 20, the electric field at the bonding interface of the substrate 30, and the electrostatic attraction also have a mountain-shaped distribution. Therefore, the voltage applied between the electrodes (the anode 2 and the cathodes 3A to 3E) is controlled so that the portion of the cathode 3A has the highest potential so that the electrostatic attraction necessary for adhesion is obtained first, and anodic bonding is performed. The anodic bonding is performed in order toward the outer peripheral edge. Hereinafter, the cathodes 3 </ b> A to 3 </ b> E are referred to as the cathode 3 when it is not particularly necessary to distinguish them.

  Here, in the present embodiment, the distance between the cathodes (the outer peripheral edge of the cathode located on the center side and the inner circumferential edge of the cathode located on the outer side) is within 5 mm (when the electrode member is used as a ring shape) The inner electrode and the outer electrode are 2.5 mm + 2.5 mm, so that they are within 5 mm). This is because it has been confirmed by experiments that about 2.5 to 3.0 mm width from the end of the cathode can be joined in the same manner as the portion immediately above the cathode (the portion in contact with the cathode) due to the influence of the cathode. is there.

  The heater 5 is incorporated in the mounting table 4, for example, and heats the substrate 30 by heating the mounting table 4. The DC voltage power supply 6 supplies electric charges for applying a voltage (generating a potential difference) between the electrodes (between the anode 2 and the cathodes 3A to 3E). The voltage control means 7 controls the DC voltage power supply 6 to control the voltage applied between the electrodes. The temperature control means 8 controls power supply from another power source (not shown), controls heating of the heater 5, and controls the temperature of the substrate 30 (mounting table 4). Further, the main control means 9 such as a computer transmits a signal such as an instruction to the voltage control means 7 and the temperature control means 8 based on an ammeter (not shown) and a temperature sensor (not shown) to generate a DC voltage. By controlling the power source 6 and the heater 5, the voltage and temperature are comprehensively controlled.

  Next, the anodic bonding method in the present embodiment will be described. In the present embodiment, the voltage applied to the DC voltage power supply 6 is controlled by the voltage control means 7 based on an instruction from the main control means 9. In the present embodiment, it is assumed that the temperature control means 8 performs temperature control based on an instruction from the main control means 9 so that the temperature of the substrate 30 during bonding becomes 350 ° C. Here, in this embodiment, the temperature is set to 350 ° C., but the temperature at which sodium ions in the glass substrate 20 can move (hereinafter referred to as ion movement start temperature) is about 280 ° C., and thus does not affect the substrate 30. The temperature may be controlled at a temperature higher than 280 ° C., which is the ion movable start temperature. Since the coefficient of expansion of each substrate due to heat varies depending on the temperature, it becomes easy to control the positional deviation between the substrates by keeping the temperature constant.

  FIG. 4 is a diagram illustrating the relationship between the voltage applied between the electrodes and time. First, the superposed substrate 30 is placed on the placing table 4. Here, in this embodiment, the substrate 30 is placed so that the center of the substrate 30 is directly above the cathode 3A. The temperature control means 8 heats the heater 5 while controlling the temperature of the substrate 30 to be about 350 ° C.

  In the first stage (step), the voltage control means 7 sets the voltage necessary for sodium ions to start moving between the anode 2 and the cathode 3 (in this embodiment, for example, 500 V). This voltage is referred to as a movable start voltage). Here, in the present embodiment, boosting to the movable start voltage is performed over 30 seconds. It is even better if the voltage can be boosted linearly. This is due to the relaxation of distortion caused by bonding.

  The application at the movable start voltage is maintained for 5 minutes after the pressure increase. Sodium ions start moving to the portion in contact with the cathode 3A. At this time, for example, portions other than between the anode 2 and the cathode 3A do not reach the ion startable voltage.

  When the application for 5 minutes is completed, the voltage is increased linearly, for example, by 100 V over 30 seconds. Further, the application at that voltage is maintained for 5 minutes. This is repeated until the necessary effective voltage is applied to the glass substrate 20 located immediately above the cathode 3E, and the strong bonding by anodic bonding as usual is completed. The required effective voltage refers to a voltage applied to the glass substrate 20 in order to make anodic bonding effective. Although it varies depending on time, temperature, etc., it is usually about 500V to 1000V. Here, in this embodiment, the required effective voltage is 1000V.

  By repeating the pressure increase, a portion to which a negative charge of a level at which sodium ions can be moved and anodic bonded can be supplied from the center (cathode 3A) side to the outside (cathode 3E) side of the substrate 30 gradually. To spread. The silicon substrate 10 and the glass substrate 20 are brought into close contact with each other toward the outer peripheral end portion in order from the center portion, so that a gas escape path is always provided toward the outer peripheral end portion to prevent generation of voids. Therefore, it is necessary to always join in order from the central portion, and there is no positive portion (upward portion) of the charge distribution slope on the plane of the mounting table 4 when the outer peripheral end portion side is viewed from the central side. This is particularly important in the present embodiment.

  As described above, according to the first embodiment, the cathodes 3A to 3E are provided, and the electric resistance of each cathode is set to Ra <Rb <Rc <Rd <Re, whereby the glass on the surface (bonding surface) of the mounting table 4 is obtained. By making the in-plane distribution of the voltage applied to the substrate 20 the highest in the potential of the cathode 3A portion and sequentially lowering toward the outer peripheral end, the same distribution is obtained with respect to electrostatic attraction, etc. By gradually increasing the voltage between the electrodes, the substrates can be brought into close contact with and bonded to each other at a voltage capable of anodic bonding sequentially from the cathode 3A. By setting the apparatus in such a manner that the distribution is different in advance, it is possible to sequentially surround the outer periphery from a predetermined portion (part in contact with the cathode 3A) of the glass substrate 20 without individually controlling the voltage application by the cathodes 3A to 3E. Since the gas can be brought into close contact with the end portion and pushed out toward the outer peripheral end portion without being sandwiched between the substrates, bonding can be performed, so that anodic bonding can be performed without generating voids. In particular, the present invention is effective when anodic bonding is performed by electrically contacting the anode 2, the silicon substrate 10, the cathodes 3A to 3E, and the glass substrate 20 containing sodium (metal). In the present embodiment, in particular, the voltage between the electrodes is sequentially increased so that the contact and bonding are first performed at the portion in contact with the cathode 3A and spread toward the outer peripheral end portion. In this regard, it is possible to perform bonding in a constant state within a temperature at which anodic bonding is possible (the temperature does not need to be raised or lowered during bonding).

  In addition, since the materials constituting the cathodes 3 </ b> A to 3 </ b> E are made different from each other to make the electric resistances different, it is possible to easily form a plurality of cathodes whose electric resistances are changed. Similarly, a plurality of cathodes having different electric resistances can be easily formed by forming the cathodes 3A to 3E by coating with films having different electric resistances. In the present embodiment, the cathode 3A at the center is circular, the cathodes 3B to 3E are ring-shaped, and are arranged concentrically, so that the voltage distribution can be made symmetrical about the cathode 3A. it can. Further, it is particularly convenient because it conforms to the shape of the wafer (substrate).

Embodiment 2. FIG.
FIG. 5 is a diagram showing the relationship between the temperature and time of the substrate 30 according to the second embodiment of the present invention. In the first embodiment, the applied voltage is changed without changing the temperature of the substrate 30. In order to perform anodic bonding effectively, a predetermined voltage and temperature are required, and in order to activate the movement of ions in the glass substrate 20, the voltage must be increased (the charge on the electrode is increased). In addition, it is conceivable to increase the temperature of the glass substrate 20. Therefore, in this embodiment, after changing the temperature without changing the applied voltage, anodic bonding is gradually performed from the center (cathode 3A) side toward the outer peripheral end. The apparatus is the same as that of the above-described first embodiment, and a description thereof will be omitted.

  In the present embodiment, the voltage control means 7 controls the voltage applied to the glass substrate 20 to be 1000 V (which is a necessary effective voltage). In the present embodiment, the temperature of the substrate 30 is changed, but the temperature control is performed by the voltage control means 7. And the temperature of the board | substrate 30 in the first step shall be 280 degreeC which is ion movement start temperature mentioned above.

  After maintaining at the ion movable start temperature for 5 minutes, the temperature is raised to 20 ° C. and maintained for another 5 minutes. This is repeated until 360 ° C is reached. Although the temperature is set to 360 ° C. in the present embodiment, it is not limited to this. Eventually, the temperature may be a temperature at which the substrate 30 has a temperature of 350 ° C. and the applied voltage between the electrodes is 800 V, and can be as strong as the anodic bonding performed in an environment (normal anodic bonding). Is performed within the range of 180 ° C to 500 ° C and 200V to 1000V). However, it is desirable not to exceed 450 ° C. in consideration of damage due to thermal expansion of the substrate 30 and residual stress.

  In the present embodiment, the temperature is raised at a rate of 5 ° C./min (min) when each step of raising the temperature by 20 ° C. is performed. That is, the temperature is raised by 20 ° C. over 4 minutes. This is for suppressing the generation of distortion in the silicon substrate 10 or the glass substrate 20, the mounting table 4, the cathodes 3A to 3E, and the like due to heating. Here, the rate is 5 ° C./min (min), but the rate is not limited to this rate within the range of the purpose of suppressing the occurrence of distortion.

  As described above, according to the second embodiment, the cathodes 3A to 3E are provided in the same manner as in the first embodiment described above, and the cathode 3A portion has the highest potential and gradually decreases toward the outer peripheral end. A voltage is applied to the glass substrate 20 and the temperature of the substrate 30 is sequentially increased so that the cathode 3A portion is brought into close contact and bonding earliest, and the close contact and bonding are directed toward the outer peripheral edge. Thus, anodic bonding that does not generate voids can be performed without individually controlling the voltage application by the cathodes 3A to 3E.

Embodiment 3 FIG.
In the above-described embodiment, cathodes 3A to 3E having different electric resistances are used. However, it is not limited in view of the purpose of preventing the generation of voids by differentiating the charge distribution on the plane of the mounting table 4. For example, even if the electric resistances of the cathodes are the same, the electric charge distribution can be adjusted, for example, by making the electric resistances of the materials partitioning the cathodes different (in the first embodiment, an insulator).

Embodiment 4 FIG.
In the above-described embodiment, the silicon substrate 10 and the glass substrate 20 have been described as being anodic bonded from the central portion toward the outside. Here, the present invention aims to prevent the generation of voids during bonding, and therefore it is not always necessary to perform strong anodic bonding from the central portion toward the outside. For example, an appropriate electrostatic attractive force is generated from the central portion toward the outside to bring the silicon substrate 10 and the glass substrate 20 into close contact with each other, so that a temporary fixing (temporary bonding) state is established. The necessary effective voltage is applied to the entire substrate 20, and it is only necessary that the same anodic bonding can be performed on the entire surface at 350 ° C. and in an environment of 800V. Furthermore, although five cathodes 3A to 3E are used in the above-described embodiment, the number of cathodes is not limited to this.

  In the first embodiment described above, pressure control for performing anodic bonding is performed in a step (step) in which 100 V is boosted in 30 seconds and maintained for 5 minutes. In the second embodiment, temperature control is performed in which the temperature is raised to 20 ° C. over 4 minutes and maintained for 5 minutes. However, the present invention is not particularly limited to this pressure control and temperature control. As described above, the conventional anodic bonding can be performed at a rate that does not affect the substrate 300 and the apparatus, and can perform bonding as strong as bonding performed in an environment of 350 ° C. and 800 V. If so, the number of steps, time, etc. can be set arbitrarily.

Embodiment 5. FIG.
In the above-described embodiment, it has been described on the assumption that the center of the superimposed substrate 30 comes directly above the cathode 3A. However, if the order of bonding can be maintained and generation of voids can be prevented, the substrate is not necessarily provided. And the apex portion of the distribution of electric charges (voltage applied to the glass substrate 20) may not be the same. Also, the shape of the cathode is not limited to a circle or a ring as long as the generation of voids can be prevented. For example, it can be a rectangle or the like. Moreover, although the width | variety of the part which the glass substrate 20 of each cathode contacts was made into the same width, it is not limited to this.

Embodiment 6 FIG.
FIG. 6 is an exploded view of a droplet discharge head according to the sixth embodiment of the present invention. The cavity substrate 40 manufactured by processing a silicon substrate and the electrode substrate 50 made of a glass substrate can be subjected to anodic bonding. Here, when a void is generated during anodic bonding, various adverse effects such as chemical solution intrusion and substrate breakage occur in various processes in the manufacturing process of a droplet discharge head or the like, or an electrostatic actuator. Also, during anodic bonding, the substrate floats due to air bubbles, and as described below, discharge occurs between the electrode 51 and the like formed on the electrode substrate 50 and the silicon substrate, and the electrode is altered, made foreign, In addition, adverse effects such as adsorption of silicon (vibration plate 41) to the electrode 51 occur. Therefore, in the present embodiment, the cavity substrate 40 and the electrode substrate 50 are bonded by the anodic bonding apparatus and method described in the above-described embodiments to prevent generation of voids during anodic bonding.

  In FIG. 6, a cavity substrate 40 manufactured by processing a silicon substrate is configured by using, for example, a silicon single crystal substrate (hereinafter, simply referred to as a silicon substrate) whose surface is approximately (110) plane with a thickness of about 50 μm as a main material. ing. This silicon substrate is subjected to anisotropic wet etching (hereinafter referred to as wet etching) and the like, and is used for each member of the droplet discharge head. A recess serving as a reservoir 43 for storing the liquid to be discharged is formed. The cavity substrate 40 has an electrode terminal 46 for supplying a charge opposite to that of the electrode 51 on the electrode substrate 50 to the silicon substrate (vibrating plate 41).

  On the lower surface of the cavity substrate 40 (the surface opposite to the electrode substrate 50), a TEOS film (herein, Tetraethyl orthosilicate Tetraethoxysilane: an SiO2 film formed using tetraethoxysilane (ethyl silicate)) 44 is formed. Is formed by a plasma CVD (Chemical Vapor Deposition: TEOS-CVD) method. By forming the TEOS film 44 by plasma CVD, a dense film can be formed at a relatively low temperature process, and breakdown of the insulating film and short circuit when the droplet discharge head is driven can be prevented. Further, a SiO 2 film (including a TEOS film) to be the liquid protective film 45 is formed on the upper surface of the cavity substrate 40 (the surface facing the nozzle plate 3) by a plasma CVD method or a sputtering method. This is to prevent the channel from being corroded by a liquid such as ink.

  The electrode substrate 50 has a thickness of about 1 mm, and is a substrate bonded to the lower surface of the cavity substrate 40 when viewed in FIG. In the present embodiment, a borosilicate heat-resistant hard glass substrate is used as the electrode substrate 50 in order to perform anodic bonding with the above-described apparatus and method. Here, the electrode substrate 50 is provided with a recess 52 having a depth of about 0.2 μm by etching in accordance with each discharge chamber 42 formed in the cavity substrate 40. Then, an individual electrode 51, a lead portion 53, and a terminal portion 54 (hereinafter referred to as the electrode 51 together when there is no need to distinguish between them) are provided inside the recess 52. In the present embodiment, transparent ITO (Indium Tin Oxide) doped with tin oxide as an impurity is used as the material of the electrode 51, and the inside of the recess 52 has a thickness of 0.1 μm, for example, by sputtering. Shall be formed. At that time, in anodic bonding, the cavity substrate 40 (silicon substrate) and the electrode 51 are made equipotential. Therefore, the equipotential contact pattern 56 of the contacts (hereinafter referred to as equipotential contacts) that electrically connect them is also the electrode 51. At the same time, a film is formed. In addition, the electrode substrate 50 is provided with an ink supply port 55 that communicates with the reservoir 43 and serves as a flow path from an external tank (not shown) to the reservoir 43.

  The nozzle plate 60 is made of, for example, a silicon substrate having a thickness of about 180 μm, and is joined to the cavity substrate 40 on the surface opposite to the electrode substrate 50 (upper surface in the case of FIG. 1). Since this bonding is bonding between silicon, bonding using an adhesive, for example, is used instead of anodic bonding. 1, nozzle holes 61 are formed on the upper surface of the nozzle plate 60, and liquid such as ink pressurized by the discharge chamber 42 is discharged as droplets. Further, an orifice 62 is formed on the lower surface, and the discharge chamber 42 and the reservoir 43 are communicated. Here, the nozzle plate 60 having the nozzle holes 61 is described as the upper surface, and the electrode substrate 50 is described as the lower surface. However, in practice, the nozzle plate 60 is often used as the lower surface than the electrode substrate 50. Further, the nozzle plate 60 is provided with a diaphragm 63 for buffering the pressure applied in the direction of the reservoir 43 when the vibration plate 41 is bent.

  FIG. 7 is a cross-sectional view of the droplet discharge head. FIG. 7B is an enlarged view of the equipotential contact pattern 56. In FIG. 7, the discharge chamber 42 stores liquid to be discharged from the nozzle hole 61. By deflecting the vibration plate 41 which is the bottom wall of the discharge chamber 42, the pressure in the discharge chamber 42 is increased, and droplets are discharged from the nozzle holes 61. Here, in the present embodiment, a high-concentration boron-doped layer that can be used as a movable electrode, has an extremely low etching rate, and can be processed with high thickness accuracy during an etching process, is formed on a silicon substrate. The diaphragm 41 is composed of a boron-doped layer.

  The oscillation circuit 80 is electrically connected to the terminal portion 54 and the electrode terminal 46 through a wire, FPC (Flexible Print Circuit) or the like (referred to as FPC) 81, and the electrode 51 and the cavity substrate 40 (vibration plate 41) are charged ( (Power) supply and stop. The oscillation circuit 80 supplies a charge by applying a pulse potential to the electrode 51, for example. When the oscillation circuit 80 is driven to oscillate, when an electric charge is supplied to the electrode 51 to be positively charged and the vibration plate 41 is relatively negatively charged, the electrode 51 is attracted to the electrode 51 by an electrostatic force to bend. Thereby, the volume of the discharge chamber 42 is expanded. When the charge supply is stopped, the vibration plate 41 returns to the original state, but the volume of the discharge chamber 42 at that time also returns to the original state, and the differential droplet 82 is discharged by the pressure. For example, printing such as printing is performed when the droplet 82 lands on a recording sheet 83 to be recorded. The sealing material 71 is provided to block the gap from the outside air and seal it so that foreign matter, moisture (water vapor) or the like does not enter the gap. Usually, the droplet discharge heads are made in units of wafers, and finally separated into each droplet discharge head (head chip).

  FIG. 8 is a diagram illustrating a manufacturing process of the droplet discharge head according to the sixth embodiment. A manufacturing process of the droplet discharge head will be described with reference to FIG. In practice, a plurality of droplet discharge heads from a silicon wafer are processed for manufacturing, but only a part of them is shown in FIG.

  (A) A recess 52 having a depth of 0.2 μm is formed on one surface of a glass substrate of about 1 mm in accordance with the shape pattern of the electrode 51. The portion where the equipotential contact pattern 56 of the equipotential contact is formed is left without being etched. After the formation of the recess 52, the electrode 51 and the equipotential contact pattern 56 having a thickness of 0.1 μm are simultaneously formed by using, for example, a sputtering method. Finally, the ink supply port 55 is formed by a sandblasting method or a cutting process. Thereby, the electrode substrate 50 is produced.

  (B) On the other hand, one surface of the silicon substrate 90 having a (110) plane orientation and low oxygen concentration (becomes the bonding surface side with the electrode substrate 50) is mirror-polished to produce a substrate having a thickness of 220 μm. Then, boron is diffused on the surface side to form a boron doped layer 91. A TEOS film 44 having a thickness of 0.1 μm is formed on the surface on which the boron doped layer 91 is formed by plasma CVD. Further, a window is formed in a part of the TEOS film 44 in order to bring the equipotential contact pattern 56 into contact with the silicon substrate 90.

FIG. 9 is a diagram illustrating the relationship between the silicon substrate 90 and the electrode substrate 50.
(C) As shown in FIG. 9, the positions of the silicon substrate 90 and the overlapped substrate are anodically bonded so that the side on which the TEOS film 44 is formed faces the side on which the electrode 51 of the electrode substrate 50 is formed. It mounts on the mounting base 4 of an apparatus. The anode 2 of the anodic bonding apparatus and the silicon substrate 90 are brought into contact with each other, and the electrode substrate 50 and the cathodes 3A to 3E are brought into contact with each other. By applying a voltage between the anode 2 and the cathode 3 and performing heating in the procedure described in the above embodiment, anodic bonding is performed without generating voids. It should be noted that if the heating rate is too fast, damage will be added. At the time of anodic bonding, glass may be decomposed electrochemically and oxygen may be generated as a gas at the interface between the silicon substrate 90 and the electrode substrate 50. In addition, gas (gas) adsorbed on the surface may be generated by heating. In this case, pressurization of gas in the recess 52 can be prevented by providing an air opening hole communicating with the outside so as not to seal the recess 52.

  (D) About the bonded substrate after anodic bonding, the silicon substrate 90 is subjected to grinding or the like, so that the thickness of the silicon substrate 90 is about 50 μm.

  (E) Next, a TEOS etching mask (hereinafter referred to as a TEOS etching mask) 92 is formed on the wet etched surface by plasma CVD. Thereafter, resist patterning is performed in order to etch the TEOS etching mask 92 in the portion that becomes the discharge chamber 42 and the reservoir 43. Then, the TEOS etching mask 92 is patterned and the resist is removed. Here, depending on the case, the depths of the portions to be the discharge chambers 42 and the reservoirs 43 are made different, so that the etching depth of the corresponding TEOS etching mask 92 may be made different.

  (F) Next, the bonded substrate is immersed in an aqueous solution of potassium hydroxide having a concentration of 35 wt% and 3 wt%, and wet etching is performed until the thickness of the portion that becomes the discharge chamber 42 becomes about 10 μm. By using two types of potassium hydroxide aqueous solutions having different concentrations, the surface roughness of the diaphragm 41 can be suppressed and the thickness accuracy can be increased. When the wet etching is finished, the bonded substrate is immersed in a hydrofluoric acid aqueous solution, and the TEOS etching mask 92 on the surface of the silicon substrate 90 is peeled off.

  (G) Next, the silicon portion of the silicon substrate 90 which becomes the electrode outlet 70 is removed, and a liquid protective film 45 of TEOS film is formed on the upper surface of the cavity substrate 40 by plasma CVD method to a thickness of 0.1 μm. As described above, the liquid protective film 45 may be formed of a SiO2 film formed by a sputtering method other than the plasma CVD method. Further, the liquid protective film 45 remaining in the electrode outlet 25 is removed. Then, a sealing material 71 made of, for example, epoxy resin is poured along the end portion of the electrode outlet 70 (the opening portion of the gap formed between the cavity substrate 40 and the concave portion of the electrode substrate 50) to seal the gap. Stop. Thereby, the processing performed on the bonded substrate is completed.

  (H) The previously produced nozzle plate 60 is bonded from the cavity substrate 40 side of the bonded substrate, for example, with an epoxy adhesive. Then, dicing is performed along the dicing line 27 and cut into individual droplet discharge heads, thereby completing the droplet discharge heads.

  As described above, according to the sixth embodiment, when the droplet discharge head (electrostatic actuator) is manufactured, bonding is performed by the anodic bonding apparatus and method described in the above-described embodiment. No voids are generated at the time of bonding, and there is no breakage of the silicon substrate 90, infiltration of chemicals, or the like at the time of processing, and the yield can be improved. In particular, this is an anodic bonding apparatus and method that are effective even when the surface is processed and the electrode substrate 50 and the silicon substrate 90 each having a recess are bonded in advance.

Embodiment 7 FIG.
FIG. 10 is an external view of a printer 100 that is a droplet discharge device using the droplet discharge head manufactured in the above embodiment. The printer 100 in FIG. 10 is intended for printing on paper by a droplet discharge method (inkjet method). In a normal printer, liquid is discharged onto paper as ink, but the liquid discharged from the droplet discharge head is not limited to ink. For example, in an application to be discharged onto a substrate to be a color filter, a light emitting element is used in an application to be discharged onto a substrate of a display panel (OLED or the like) using an electroluminescent element such as a liquid containing a color filter pigment or an organic compound. For example, a liquid containing a compound and a liquid containing a conductive metal may be discharged from a droplet discharge head provided in each device. In addition, when the droplet discharge head is used as a dispenser and is used for discharging onto a substrate that is a microarray of biomolecules, DNA (Deoxyribo Nucleic Acids: deoxyribonucleic acid), other nucleic acids (for example, Ribo Nucleic Acid: ribonucleic acid, Peptide (Nucleic Acids: peptide nucleic acids, etc.) A liquid containing a probe such as a protein may be discharged. In addition, it can also be used for discharging dyes such as cloth.

Embodiment 8 FIG.
In the sixth and seventh embodiments described above, examples of applying the anodic bonding apparatus and method of the first to fifth embodiments to a droplet discharge head and a droplet discharge device have been described. However, the present invention is not limited to this. Absent. For example, the present invention can also be applied to anodic bonding in the case of manufacturing microfabricated elements using MEMS (Micro Electro Mechanical System) including actuators and sensors.

It is a figure showing the anodic bonding apparatus which concerns on Embodiment 1 of this invention. It is the figure which looked at the mounting base 4 from the upper surface. It is a figure showing the circuit model in the anodic bonding of this Embodiment. It is a figure showing the relationship between the voltage applied between electrodes, and time. It is a figure showing the relationship between the temperature of the board | substrate 30 which concerns on Embodiment 2, and time. FIG. 10 is an exploded view of a droplet discharge head according to a sixth embodiment. It is sectional drawing of a droplet discharge head. It is a figure showing the manufacturing process of the droplet discharge head which concerns on 6th Embodiment. 4 is a diagram illustrating a relationship between a silicon substrate 90 and an electrode substrate 50. FIG. It is an external view of a droplet discharge device using a droplet discharge head.

Explanation of symbols

1 chamber, 2 anode, 3, 3A, 3B, 3C, 3D, 3E cathode, 4 mounting table, 5 heater, 6 DC voltage power supply, 7 voltage control means, 8 temperature control means, 9 main control means, 10 silicon substrate, 20 glass substrate, 30 substrate, 40 cavity substrate, 41 diaphragm, 42 discharge chamber, 43 reservoir, 44 TEOS film, 45 liquid protective film, 46 electrode terminal, 50 electrode substrate, 51 electrode, 52 recess, 53 lead portion, 54 Terminal part, 55 Ink supply port, 56 Equipotential contact pattern, 60 Nozzle plate, 61 Nozzle hole, 62 Orifice, 63 Diaphragm, 70 Electrode outlet, 71 Sealing material, 80 Oscillator circuit, 81 FPC, 82 Droplet, 83 Recording paper, 90 silicon substrate, 91 boron doped layer, 92 TEOS etching mask, 100 printer.

Claims (12)

A first electrode that is electrically connected to one of the plurality of stacked substrates to be bonded;
A predetermined portion on the plane of the substrate is at a maximum potential due to a voltage applied between the substrate and the other outer side of the plurality of substrates and applied to the first electrode, and toward a peripheral edge of the substrate. And a second electrode that applies a voltage to the substrate with a voltage distribution that is low.   2. The anodic bonding apparatus according to claim 1, further comprising a voltage control unit that controls a voltage applied between the first electrode and the second electrode.   The anodic bonding apparatus according to claim 1, further comprising temperature control means for controlling temperatures of the plurality of substrates.   The second electrode is formed of a plurality of electrodes arranged concentrically with one center having a circular shape and the other having a ring shape, and increasing in electrical resistance from the central portion toward the outside. The anodic bonding apparatus according to any one of claims 1 to 3.   The anodic bonding apparatus according to claim 4, wherein the plurality of electrodes are made of members made of materials having different resistivity.   6. The anodic bonding apparatus according to claim 4, wherein the plurality of electrodes are formed by coating members with films having different resistivity.   The second electrode is composed of a plurality of electrodes arranged in a concentric shape with the center being circular and the other being ring-shaped, and resistance members made of materials having different electrical resistances are provided between the electrodes. The anodic bonding apparatus according to claim 1.   The anodic bonding apparatus according to claim 1, wherein the first electrode is connected to a silicon substrate as an anode, and the second electrode is connected to a glass substrate containing a metal as a cathode. A plurality of stacked substrates to be bonded are heated to a temperature necessary for anodic bonding, and a voltage having a distribution that becomes a maximum potential in the substrate plane and decreases toward the outer peripheral edge of the substrate is applied to the substrate. Process,
A step of increasing the pressure at a predetermined rate, applying a voltage necessary for sequentially performing anodic bonding from the predetermined portion toward the outer peripheral edge of the substrate, bringing the plurality of substrates into close contact with each other, and performing bonding An anodic bonding method characterized by the above. A step of applying a voltage necessary for anodic bonding to the substrate in a distribution such that a predetermined portion has a maximum potential and decreases toward the outer peripheral edge of the substrate in the plane of the plurality of superimposed substrates;
And anodic bonding, comprising: heating the plurality of substrates at a predetermined rate, and sequentially bonding the plurality of substrates toward the outer peripheral edge of the substrate from the predetermined portion to perform bonding. Method.   11. The anodic bonding method according to claim 10, wherein the predetermined rate is determined within a range not damaging at least the two substrates and the jig for bonding, and the temperature rise is controlled. Using the anodic bonding apparatus according to any one of claims 1 to 8,
An electrode substrate made of glass containing metal and having a fixed electrode on at least the bottom surface of the formed recess,
A droplet discharge head characterized by bonding a cavity substrate having a movable electrode facing the fixed electrode at a distance and operating by electrostatic force generated between the fixed electrode, excluding the concave portion. Manufacturing method.

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