JP2004268323A - Substrate joining method, joined substrate body, inkjet head, and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To join substrates well and to realize cost reduction. <P>SOLUTION: In a process (C), a resin layer 46 is formed by applying a resin material as a protecting film against ink to the joining face side of a part of a silicon wafer 24 where an electric thermal conversion body 32 is set. The thickness of the resin layer 46 is 4.5 μm or more. Next, a baking process for the resin layer 46 after the application is carried out. The temperature of the baking process is preferably a glass transition temperature plus 80 °C. In a process (E), the silicon wafer 24 and a silicon wafer 38 are precisely registered with the use of a registration mark 48, and a predetermined pressurization process is carried out to join the silicon wafer 24 and the silicon wafer 38 to each other. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a substrate bonding method, a substrate bonded body, an ink jet head, and an image forming apparatus, and more particularly, to a substrate bonding method, a substrate bonded body, and an ink jet used when manufacturing a functional device manufactured by various micromachine technologies. The present invention relates to a head and an image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a method of joining substrates, a method of joining using an adhesive having adhesive strength is generally used (see Patent Document 1). However, functional devices manufactured by using various micromachine technologies are extremely miniaturized, and in the case of bonding using an adhesive having adhesive strength, protrusion of the adhesive becomes a serious problem.
[0003]
Therefore, Patent Document 2 proposes a technique of selectively applying a thin adhesive to a predetermined position on a substrate as a measure for improving the protrusion of the adhesive.
[0004]
[Patent Document 1]
JP-A-61-230954
[Patent Document 2]
JP-A-63-34152
[0005]
[Problems to be solved by the invention]
However, in recent years, the size of dots in an ink jet head has been remarkably reduced for the purpose of high image quality, and the size of the nozzle serving as an ink liquid ejection port has been significantly reduced due to the reduced size of the dots. Due to these small nozzles, the method proposed in Patent Document 2 has the following problems.
(1) The groove size of the joining surface is significantly reduced due to the use of a small nozzle, and the nozzle and the flow channel are filled with minute protrusion of the adhesive. FIG. 9 is a view showing a nozzle portion of an ink jet head. As shown in FIG. 9A, in a conventional nozzle having a width of about 20 μm that generates ink droplets equivalent to 400 dpi, the ink discharge port 56 is Since it is relatively large, the nozzle does not become buried even when the adhesive 70 applied to the element substrate 26 protrudes. However, as shown in FIG. 9 (B), with a miniaturized nozzle having a width of about 5 μm that generates ink droplets equivalent to 1200 dpi, the entire portion of the opening of the ink discharge port 56 is buried due to the protrusion of the adhesive 70. , Cannot eject ink.
(2) In order to prevent the above-mentioned adhesive from protruding into the flow path, if the thickness of the applied adhesive is reduced, the inter-flow path seal due to insufficient adhesive in a poor adhesion area due to minute unevenness on the substrate bonding surface or substrate warpage. A defect occurs, and as a result, a defect occurs that the pressure generated for ink ejection in the flow path escapes to the adjacent flow path. Therefore, for the purpose of improving the flatness of the bonding surface of the substrate, means such as a flattening step (Japanese Patent Application No. 7-169660) using CMP (Chemical Mechanical Polish) or the like is employed. However, due to the relationship of wafer warpage, particles, and the like, when bonding large-area substrates, an inter-substrate gap (bonding gap) is generated to about 1.0 μm in the above-described poor adhesion region.
(3) When the head is used for a long period of time, the adhesive thin film transferred to the protruding portion or the unjoined portion of the adhesive may peel off, which may cause nozzle clogging or the like. FIG. 10A shows an ink flow path structure of the ink jet head, and FIG. 10B shows a cross-sectional view taken along line XX of FIG. 10A. When the adhesive thin film is transferred to the convex portion formed on the ink flow path substrate 40 and the ink flow path substrate 40 and the element substrate 26 are joined, after the individual flow path 44 corresponding to the bypass flow path section, At the wall, the adhesive is transferred but not joined.
[0006]
In order to solve the above-mentioned problems, various joining techniques such as eutectic bonding and room-temperature interfacial joining without using a so-called adhesive have been proposed. However, eutectic bonding requires the formation of an Au thin film, which increases the manufacturing cost. In addition, room-temperature interface bonding requires special interface treatment using an ultra-high vacuum or an ion beam, and requires a special apparatus.
[0007]
Further, in anodic bonding via glass, a high voltage of several hundred volts needs to be applied, and there is a risk that a transistor or the like may be destroyed on a substrate having an electronic circuit.
[0008]
Furthermore, there is a thermocompression bonding method as a bonding through a resin layer, and high-pressure pressing (4.9 × 10 ⁵ ~ 9.8 × 10 ⁵ Pa) and requires special equipment. Furthermore, since the circuit is pressurized at a high pressure, there is a problem in the reliability of the circuit board, and in the formation of a fine pattern, the same problem as in the use of the adhesive occurs in terms of the thickness of the resin layer and the protrusion.
[0009]
The present invention has been made in order to solve the above-mentioned problems, and a substrate bonding method, a substrate bonded body manufactured by using the substrate bonding method, an inkjet head, and an image capable of realizing a good bonding state. Forming apparatus.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, a substrate bonding method according to the present invention includes heating a resin material, sandwiching the heat-treated resin material having a thickness of 4.5 μm or more between a plurality of opposed substrates, A pressure process is performed between the plurality of substrates to bond the respective substrates.
[0011]
Here, the pressurizing process includes a process including at least pressing in a direction in which a plurality of substrates are bonded, and a process including setting of other conditions such as temperature setting.
[0012]
In the present invention, first, the resin material is subjected to a heat treatment. When the heat treatment is performed, volatile substances contained in the resin material are volatilized and removed. Thus, the substrate can be satisfactorily bonded without being hindered by the volatile substance. If the thickness of the resin material is less than 4.5 μm, a good bonding state cannot be obtained between the substrates after the pressure treatment. However, in the present invention, the thickness of the resin material is set to 4.5 μm or more. Therefore, a good bonding state can be obtained.
[0013]
Note that the upper limit of the thickness of the resin material differs depending on the application of the bonded substrates, the device for bonding, the device for manufacturing the resin material, and the like. For example, when the bonded substrate is used for an ink jet head, the thickness of the resin material is about 50 μm in view of the efficiency of bubbles for repelling ink, but is not limited to this value.
[0014]
Further, in the present invention, any resin material may be used, and an adhesive having so-called tackiness is not required. Therefore, it is possible to prevent the protrusion as in the case of using a resin material having adhesiveness. That is, by using a resin material having no tackiness, it is possible to realize good bonding without protruding the adhesive.
[0015]
Note that as the resin material, a resin material which is cured by heat treatment, such as polyimide or polyamide, is preferable.
[0016]
Further, the temperature of the heat treatment can be characterized by being equal to or lower than the glass transition temperature of the resin material plus 80 ° C.
[0017]
If the temperature of the heat treatment is too high, cracks are likely to occur due to pressurization at the time of joining the substrates, which causes poor joining. By setting the temperature of the heat treatment to be equal to or lower than the glass transition temperature of the resin material plus 80 ° C., good bonding can be obtained. The heating temperature may be equal to or lower than the glass transition point temperature, but is preferably equal to or higher than the temperature at which the resin material is not fluidized (moved by tilting) by the heat treatment.
[0018]
Further, the pressure treatment may include applying a voltage between the plurality of substrates, as described in claim 3. By applying such a voltage, the plus side of the dipole-polarized resin material is attracted to the substrate on the minus electrode side, and the minus side is attracted to the substrate on the plus electrode side by electrostatic attraction. The anchor effect is generated by entering the fine unevenness, and the substrates are joined to each other via the resin material. Furthermore, it is considered that the negative ions move from the resin material to the substrate side and chemically react with the material constituting the substrate by causing a chemical reaction to strengthen the bonding of the substrate. Therefore, better bonding can be obtained.
[0019]
Preferably, the voltage is 5 V or more and 350 V or less.
[0020]
The pressure treatment may be performed by setting the temperature of the plurality of substrates to 200 ° C. or higher. By setting the temperature of a plurality of substrates in this manner, better bonding can be obtained.
[0021]
The highest temperature of the plurality of substrates when the voltage is applied is equal to or lower than the heat-resistant temperature of the resin material and equal to or higher than the glass transition temperature.
When the temperature of the substrate is equal to or higher than the glass transition temperature, the resin material can easily move, a good bonding state can be obtained, and the effect that the residual stress at the end of the bonding is close to zero can be obtained.
[0022]
Further, the present invention can be characterized in that at least one of the plurality of substrates is made of silicon.
[0023]
According to the present invention, the pressure between the plurality of substrates can be increased at least in two or more stages in the process of increasing the temperature of the plurality of substrates. According to this substrate bonding method, the pressure applied between the substrates is increased with respect to the contraction of the resin material due to the temperature rise, so that a better bonding state can be obtained while maintaining a gap at the bonding surface to some extent. .
[0024]
Further, according to the present invention, a metal pattern made of metal can be provided on at least one of the bonding surfaces of the plurality of substrates with the bonding surface interposed therebetween.
[0025]
When the metal pattern is provided in this manner, the potential on the substrate by applying a voltage becomes substantially constant, and a uniform and favorable bonding state can be obtained.
[0026]
In addition, the bonded substrate according to claim 10 has a thickness of 4.5 μm or more, and includes a heat-treated resin material, and a plurality of substrates opposed to each other and bonded via the resin material. It is comprised including.
[0027]
The bonded substrate of the present invention is bonded via a heat-treated resin material. Since volatile substances are volatilized and removed from the heat-treated resin material, the bonding is not hindered by the volatile substances when bonding the substrates, and a favorable bonding state can be secured. If the thickness of the resin material is less than 4.5 μm, a good bonding state cannot be obtained between the substrates after the pressure treatment. However, in the present invention, the thickness of the resin material is set to 4.5 μm or more. Therefore, a good bonding state can be obtained.
[0028]
Further, in the present invention, any resin material may be used, and an adhesive having so-called tackiness is not required.
[0029]
An ink jet head according to an eleventh aspect is configured to include the substrate joined body according to the tenth aspect.
[0030]
By forming the ink jet head including the substrate assembly according to claim 10, it is possible to prevent the adhesive from protruding to the ink discharge port, and to obtain an ink jet head capable of obtaining good ink discharge. .
[0031]
Further, in the ink jet head according to the present invention, a pair of substrates is constituted by at least two of the plurality of substrates, and one of the substrate pairs has an ink flow channel. May be formed, and a pattern including a plurality of circuits may be formed on the other side.
[0032]
With such a configuration, a substrate on which a pattern including fine ink flow channel grooves is formed and a substrate on which a pattern including a plurality of circuits is formed can be separately manufactured.
[0033]
Further, the image forming apparatus of the present invention can be configured to include the ink jet head according to the eleventh or twelfth aspect.
[0034]
By using the inkjet head, good ink ejection can be obtained, and the image quality to be formed can be improved.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a substrate bonding method according to the present invention will be described with reference to the drawings. In the present embodiment, a description will be given as a substrate bonding method used when manufacturing an inkjet head.
[0036]
As shown in FIG. 1, in a bonding apparatus 10 used in the present embodiment, a mounting unit 12 for mounting a substrate to be bonded and a pressing unit 14 for pressing the substrate are covered by an outer wall 18. A vacuum pump 20 arranged inside the joining device 10 for evacuating the inside of the joining device 10 is connected to the outer wall 18. Also, a power supply 16 for applying a voltage to the substrate is connected. The bonding apparatus 10 used in the present embodiment does not require any special equipment, and is generally commercially available for anodic bonding (EV500 series manufactured by Electronic Visions, substrate bonder SB6 manufactured by Carl Seuss, Etc.) can be used.
[0037]
FIG. 2 shows a manufacturing process of the inkjet head 54 formed in the present embodiment. In the step (A), a plurality of element substrates 26 are formed on the silicon wafer 24 by an LSI process. On each element substrate 26, a signal processing circuit 28, a driver circuit 30, an electro-thermal converter 32, an electric signal connection pad 34, and electric wiring (not shown in the figure) for connecting them are formed. .
[0038]
In the step (B), a plurality of ink flow path substrates 40 are formed on the silicon wafer 38. An ink supply port 42 and an individual ink flow path 44 are formed in each ink flow path substrate 40, and these are formed by anisotropic etching (ODE), RIE (Reactive Ion Etching) technology, or the like. .
[0039]
In the step (C), first, a resin material is applied as a protective film for ink on the bonding surface side of the portion of the silicon wafer 24 where the electro-thermal converter 32 is provided to form a resin layer 46. Here, a photosensitive resin (trade name: Durimide7520, Probideide HTR-3-200, Photones UR5100FX, LthocoatPI-400, or the like) that can easily perform the patterning step is used.
[0040]
FIG. 3 is a graph showing the relationship between the thickness of the polyimide and the bonding property. The bonding property was evaluated by bonding Yield (%). As is clear from this graph, when the thickness of the polyimide is 4.5 μm or less, the bonding state is deteriorated due to floating or peeling. Almost the same results were obtained for other resin materials. Therefore, the thickness of the formed resin layer 46 needs to be 4.5 μm or more.
[0041]
Next, a baking process is performed on the resin layer 46 after the application. The baking temperature is preferably equal to the glass transition point plus 80 ° C. This is because if the temperature of the baking treatment is too high, cracks are likely to occur due to the pressurization at the time of bonding the substrates, which causes poor bonding. The heating temperature may be equal to or lower than the glass transition point, but is preferably equal to or higher than a temperature at which the resin material is not fluidized (moved by tilting) by the heat treatment.
[0042]
Then, in the same manner as in a normal LSI process, patterning is performed by performing exposure and development.
[0043]
The thickness of the resin layer 46 differs depending on the material, but is provided for a portion of the resin layer 46 corresponding to the electric-heat converter 32 and the electric signal connection pad 30 due to film shrinkage in the baking process. The vicinity of the opening has a convex shape with respect to a region having no other opening. For example, when the average film thickness of the resin layer 46 after the baking treatment is about 5 μm, the occurrence of a convex shape of about 1.0 μm has been confirmed. Further, the silicon wafer 24 before the resin layer 46 is provided with irregularities due to circuit formation (approximately 3 μm). Although the resin layer 46 is applied to a certain level, it is hardened by the above-described curing. The upper surface of the resin layer 46 as the bonding surface including the protrusions has irregularities of about 2 μm. Therefore, in order to improve the unevenness, it is preferable to perform a flattening process on the resin layer 46 by CMP to obtain a flattened surface of about 0.5 μm or less with the unevenness.
[0044]
In the present embodiment, a photosensitive resin is used for the resin layer 46 used for bonding. However, the present invention is not limited to this. Non-photosensitive resin (trade name: Sumitomo Bakelite's CRC-6061C, Semico Fine SP740, U varnish S, PIX-3400, etc.) can also be used, and furthermore, a dry film resin can be used.
[0045]
In the step (E), the silicon wafer 24 and the silicon wafer 38 are precisely aligned and temporarily fixed using the alignment marks 48 provided for each wafer. The alignment at this time is performed such that the electro-thermal converter 32 and the individual ink flow path 44 face each other.
[0046]
Conventionally, a step of transferring the adhesive 70 to the silicon wafer 38 has been performed (see step (D) in FIG. 12). This step uses a method proposed in Japanese Patent Application Laid-Open No. 63-34152 or the like to apply a spin coating method or the like on a film on the convex portion of the surface of the silicon wafer 38 where the individual ink flow path 44 is provided. This is to transfer the thinly applied adhesive 70. In this embodiment, the step (D) is unnecessary.
[0047]
Next, the silicon wafer 24 and the silicon wafer 38 are bonded. In this bonding, first, the wafer pair 52 including the temporarily fixed silicon wafer 24 and the silicon wafer 38 is mounted on the mounting unit 12 of the bonding apparatus 10. At this time, the wafer pair 52 is set so that the silicon wafer 24 side is a negative electrode and the silicon wafer 38 side is a positive electrode. Next, the vacuum pump 20 is operated to reduce the environment of the wafer inside the bonding apparatus 10, and at the same time, energize a heater (not shown) to raise the temperature of the wafer pair 52. When the pressure in the bonding apparatus 10 reaches a predetermined value and the temperature of the wafer pair 52 reaches a predetermined temperature, the pressing unit 14 presses the wafer pair 52 in a direction orthogonal to the bonding surface of the wafer pair 52, and Is applied with a predetermined voltage. After a predetermined time, the applied voltage is turned off, and the heater is turned off to lower the temperature. Thereafter, the pressure applied to the wafer pair 52 is reduced, the vacuum pump 20 is turned off, and the inside of the bonding apparatus 10 is opened to the atmospheric pressure. Finally, the pressure applied to the wafer pair 52 is released, the wafer pair 52 is taken out of the apparatus, and the step (E) for bonding is completed.
[0048]
In this step, the wafer environment inside the bonding apparatus is depressurized by the vacuum pump 20 at the time of bonding, which prevents discharge at the time of applying a high voltage, and prevents a chemical reaction at a high temperature and a trace amount from the resin layer 46. This is to prevent the device from being contaminated by the exhaust gas, which is not an essential condition in this step, and can be performed in an inert gas environment without depressurizing the wafer environment.
[0049]
Further, in the present embodiment, the voltage is applied to the wafer bear 52, but the application of this voltage is not always necessary, and the bonding can be performed without applying the voltage. In particular, by applying a voltage, a better bonding state can be obtained. This is because, as shown in FIG. 11A, by applying a voltage between the silicon wafer 24 and the silicon wafer 38, the ions showing the dipolar polarization inside the resin layer 46 are directed in a certain direction and become negative. The interface between the charged silicon wafer 24 and the plus side of the resin layer 46 attracts by electrostatic attraction, and the interface of the positively charged silicon wafer 38 and the minus side of the resin layer 46 attract by electrostatic attraction. Therefore, it is considered that the resin material moves and enters the minute unevenness of the bonding surface, and the bonding force due to the anchor effect is generated. At the bonding interface attracted by electrostatic attraction, negative ions move from the resin layer 46 side to the silicon wafer 38 side, and a chemical bond (Si-O-, etc) occurs to generate a chemical bonding force. It is considered that it is.
[0050]
In the step (F), the wafer pair 52 bonded in the above-described steps is cut and separated into chips by dicing or the like, and is subjected to washing and inspection as necessary, thereby obtaining a large number of inkjet heads 54. Since the resin layer 46 is exposed to the nozzle portion 56, burrs are generated at the time of cutting by dicing in the resin layer 46 in the vicinity of the nozzle portion 56. However, the resin layer 46 is preferably removed by the processing method proposed in Japanese Patent No. 2827884. Can be.
[0051]
Further, as shown in FIG. 4, a metal pattern can be provided on the element substrate 26 of the above embodiment. FIG. 4A is a plan view of the element substrate 26, and FIG. 4B is a cross-sectional view. If aluminum or another metal pattern 60 is provided at least in a region below the resin layer 46 where the resin layer 46 is formed, a voltage is applied to the back surface of the element substrate 26 on the side where the resin layer 46 is formed. When the voltage is applied, the inside of the region of the metal pattern 60 has substantially the same potential. As described above, by providing the metal pattern 60, when a voltage is applied between the wafer pairs 52 in the bonding process, the potential distribution (electric field distribution) on the surface of the wafer bonded to the resin layer 46 can be made substantially uniform. Since a potential distribution (electric field distribution) difference in the resin layer 46 due to a circuit, a wiring pattern, or the like formed on the wafer is eliminated, it is possible to prevent bonding unevenness between bonding planes and movement of the resin layer 46 in the bonding plane. Uniform and good bonding can be achieved.
[0052]
As described above, according to the present embodiment, the volatile substance contained in the resin material used as the adhesive is volatilized and removed by the baking treatment, and the baking treatment inhibits the volatile substance. Thus, the substrate can be satisfactorily bonded between the silicon wafer 24 and the silicon wafer 38. Further, since the thickness of the resin material is set to 4.5 μm or more, a good bonding state between the substrates after the pressure treatment can be obtained. Furthermore, in the present embodiment, since an adhesive having tackiness is not required, the adhesive does not protrude, and good bonding can be obtained. Further, the conventional adhesive application step (D) can be omitted, and the resin layer 46 as the protective film is used for bonding as it is, so that it is not necessary to add a new step, and low cost can be realized. Further, since no sticky adhesive is used, there is no clogging of the nozzle due to a piece of the adhesive that has been peeled off during long-term use, and the head reliability is improved.
[0053]
The bonding method according to the present embodiment is closest in process to anodic bonding between Si and glass, but since the substrate on which the resin layer is provided and the substrate on which the resin layer is bonded are the same, misalignment due to a difference in coefficient of thermal expansion. No worry about warping. In the case of glass, it is necessary to apply a high voltage of several hundred volts. However, in this embodiment, since bonding can be performed at several tens of volts, there is a risk that transistors and the like may be destroyed even on a substrate on which an electronic circuit is mounted. Absent.
[0054]
In a conventional thermocompression bonding method via a resin layer, high-pressure pressing (4.9 × 10 ⁵ ~ 9.8 × 10 ⁵ Pa), a special device is required, and a high pressure is applied, which causes a problem in the reliability of the circuit board, and furthermore, a problem in which the resin layer protrudes. If this is the case, a device commercially available for anodic bonding can be generally used as a bonding device, and furthermore, both temperature and pressure can be performed at a lower temperature and lower pressure compared to the thermocompression bonding method. .
[0055]
In this embodiment, an example in which the substrate is used as a substrate bonding method in manufacturing an inkjet head has been described. However, the present invention is not limited to this, and a substrate bonding method in manufacturing a micromachine such as a pressure sensor or a micropump is described. Can be used as
[0056]
【Example】
An example of the step of bonding the silicon wafer 24 and the silicon wafer 38 in the step (E) of the embodiment will be described with reference to the drawings.
[Example 1]
In the present embodiment, as shown in FIG. 5, the wafer environment inside the bonding apparatus 10 was reduced in pressure, and a heater (not shown) was energized to raise the temperature of the wafer pair 52 (see FIG. 3A). . The pressure in the joining device 10 is 10 ^-3 mbar or less, and when the temperature of the wafer pair 52 reaches about 300 ° C., the pressure unit 14 applies about 9.8 × 10 ⁴ A pressure of Pa was applied (see FIG. 5B), and a voltage of about 100 V was applied to the wafer pair 52 (see FIG. 5C). After the voltage was applied, the current flowing through the wafer pair 52 was monitored. When the current value became equal to or less than a constant value, the applied voltage was turned off, and the heater was turned off to lower the temperature (see FIG. 5 (4)). Thereafter, the pressure on the wafer pair 52 is increased to 1.96 × 10 ⁴ The pressure was reduced to Pa (see FIGS. 5-4), and when the temperature became below a certain level, the vacuum pump 20 was turned off to open the inside of the bonding apparatus 10 to atmospheric pressure (FIG. 5-5). reference). Finally, the pressure applied to the wafer pair 52 was released, and the wafer pair 52 was taken out of the apparatus (see FIG. 5 (6)).
[0057]
According to the present embodiment, a wafer pair 52 in a good bonding state was obtained.
[0058]
[Example 2]
In this embodiment, as shown in FIG. 6, the vacuum pump 20 is operated to start reducing the pressure of the wafer environment in the bonding apparatus 10, and energize a not-shown apparatus heater to raise the temperature of the wafer pair 52. Was. At this point, the wafer pair 52 should have a minimum pressure of about 1.96 × 10 ⁴ Pa was added to ensure contact with the temperature control section of the device. (Fig. 6 (1))
The pressure in the joining device 10 is 10 ^-3 When the temperature of the wafer pair 52 reaches less than mbar and the temperature of the wafer pair 52 reaches 300 ° C., about 9.8 × 10 ⁴ Pressure was applied by Pa ((2) in FIG. 6), and then a voltage of about 40 V was applied to the wafer pair 52. (Fig. 6 (3)).
[0059]
After the voltage was applied, the current flowing between the two wafer pairs 52 was monitored, and when the current value became constant (eg, 1 mA) or less, the apparatus heater was turned off to lower the temperature. (Fig. 6-4)
When the temperature falls below 200 ° C., the applied voltage is turned off (FIG. 6 (5)), the pressure between wafers is reduced to the initial value, and the vacuum pump 20 is turned off to increase the inside of the bonding apparatus. It was released to atmospheric pressure (Fig. 6 (6)). Finally, the pressing force of the wafer pair 52 was released, and the wafer pair 52 was taken out of the apparatus (FIG. 6 (7)).
[0060]
In the present embodiment, the maximum temperature at the time of applying a voltage is set to 300 ° C. or higher. However, the temperature is not limited to this temperature. If the temperature is about +10 to 60 ° C., a good bonding state can be obtained. By setting this temperature, the resin layer 46 transferred to the silicon wafer 24 becomes easy to move, and even if there is a small amount of bonding gap, good bonding can be achieved. Therefore, good bonding can be performed. If the maximum temperature at the time of voltage application is too high with respect to the glass transition point, the amount of movement of the resin material is too large, and the resin material moves largely in the direction of the bonding plane even with a weak potential difference, so that desired bonding quality cannot be obtained.
[0061]
Also in this example, a good bonding state was obtained.
[0062]
[Example 3]
The present embodiment is applied to the case where the curing process performed on the resin layer 46 of the above embodiment is performed at a temperature equal to or lower than the temperature at which the resin layer is completely cured. For example, if the resin material is normally cured at 400 ° C., the curing treatment is performed at a temperature sufficiently lower than that (for example, about 120 ° C.). As a result, a state in which the resin layer 46 has almost no hardness and no irregularities due to the curing process is obtained.
[0063]
As shown in FIG. 7, the vacuum pump 20 was operated to reduce the pressure of the wafer environment inside the bonding apparatus 10, and at the same time, a heater (not shown) was energized to raise the temperature of the wafer pair 52 (FIG. 7 (1)). ). During the process of raising the wafer temperature, the wafer pair 52 was gradually applied with pressure in a direction perpendicular to the bonding surface of the wafer (about 9.8 × 10 at 100 ° C.). ⁴ Pa, 14.7 × 10 at 200 ° C. ⁴ Pa, 19.6 × 10 at 300 ° C. ⁴ Pa, 24.5 × 10 at 350 ° C. ⁴ Pa ((1)-(2) in FIG. 7)). The purpose of this is to maintain a gap equal to or less than a certain value on the bonding surface against the contraction of the resin layer 46 due to the temperature rise, and to perform the bonding satisfactorily. In this embodiment, when the temperature is increased because the resin layer 46 is in an uncured state, the curing proceeds, and a constant gas is generated. Therefore, the environmental pressure reduction curve is different from those of the above-described first and second embodiments (FIG. 7). (See the Chamber Pressure curve of FIG. 1: Although gas varies depending on the material, gas is generated from about 200 ° C., and the degree of vacuum is reduced first order.)
[0064]
After the wafer temperature reaches a desired temperature (a value in the vicinity of the curing temperature recommended by the resin material manufacturer: for example, 350 ° C.), the wafer environmental pressure becomes 10− ³ When the voltage reached below mbar, a voltage was applied between the wafer pair 52. At this time, the power supply was set to a maximum of 200 V, and a power supply voltage with a limiter (constant current source) of about 15 mA was applied (FIG. 7 (3)). The voltage was fluctuated within 200 V while controlling the current so as not to flow over a certain amount by this power supply.
[0065]
After the voltage is applied, the voltage applied to the wafer pair 52 is monitored, and the voltage becomes constant (200 V) or more, and the wafer environmental pressure becomes constant (10 or less). ^-4 When the pressure became stable at mbar, that is, when the outgassing from the material of the resin layer 46 almost disappeared, the apparatus heater was turned off to lower the temperature. In FIG. 7, the wafer environmental pressure is 10 ^-4 When the pressure reaches less than mbar, the outgassing from the resin layer disappears, and it is estimated that the curing reaction of the resin layer 46 is almost completed (FIG. 6-4). In addition, depending on the performance of the vacuum pump 20, even if outgas is generated, ^-4 Although it is possible to reach less than mbar, it can be estimated at which point the curing reaction of the resin layer 46 has been completed by comparing with a vacuum degree profile in a state where there is no outgas.
[0066]
When the temperature falls below a certain level (100 ° C.), the applied voltage is turned off (FIG. 7 (5)), and then the pressure between wafers is reduced to the initial value, and the vacuum pump 20 is turned off to reach atmospheric pressure. It was released (Fig. 7 (6)). Finally, the pressure applied to the wafer pair 52 was released, and the wafer pair 52 was taken out of the apparatus (FIG. 7 (7)).
[0067]
In this embodiment, the power supply voltage is a constant current power supply. However, as in the first and second embodiments, a constant voltage power supply may be used. However, when the curing reaction of the resin layer 46 is simultaneously performed in the bonding step as in the present embodiment, a temperature considerably higher than the glass transition temperature of the resin layer 46 is often required. When a constant voltage source is used, a large current may flow or the resin layer 46 may move so much that desired bonding may not be achieved.
[0068]
Further, in this embodiment, the time when the voltage value becomes equal to or higher than a certain value, and in the first and second embodiments, the time when the current value becomes lower than or equal to the certain value is the time when the apparatus temperature starts to be reduced. Even if almost no voltage rise (this embodiment) and current decrease (embodiments 1 and 2) are observed, the bonding step is performed in a certain time to prevent excessive movement of the resin layer 46 and to shorten the process time. It can also end (see FIG. 8).
[0069]
According to this embodiment, a good bonding state can be obtained. Further, since the uncured resin layer 46 is cured during the joining process, a resin layer flattening step such as a CMP step as a pre-joining process can be omitted.
[0070]
【The invention's effect】
As described above, according to the present invention, since the resin material used as the adhesive medium is subjected to the heat treatment, volatile substances contained in the resin material are volatilized and removed. Thus, the substrate can be satisfactorily bonded without being hindered by the volatile substance. If the thickness of the resin material is less than 4.5 μm, a good bonding state cannot be obtained between the substrates after the pressure treatment. However, in the present invention, the thickness of the resin material is set to 4.5 μm or more. Therefore, a good bonding state can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a bonding apparatus according to the present embodiment.
FIG. 2 is a diagram illustrating a flow of a process of manufacturing an inkjet head according to the present embodiment.
FIG. 3 is a graph showing the relationship between the thickness of polyimide and the bonding property.
FIG. 4A is a schematic front view of an element substrate according to a modification of the embodiment, and FIG.
FIG. 5 is a diagram showing bonding conditions in Example 1.
FIG. 6 is a diagram showing bonding conditions in Example 2.
FIG. 7 is a diagram showing bonding conditions in Example 3.
It is a schematic sectional drawing.
FIG. 8 is a view showing another joining condition of the third embodiment.
FIG. 9 is a cross-sectional view of the vicinity of an ink discharge port of an inkjet head when a conventional adhesive is used.
10A is a diagram illustrating a structure of an ink jet head using a conventional adhesive thin film when viewed from above, and FIG. 10B is a cross-sectional view taken along line XX of FIG. 10A. .
FIG. 11 is a diagram showing a bonding state by electron transfer according to the present embodiment.
FIG. 12 is a diagram illustrating a flow of a process of manufacturing an inkjet head when a conventional adhesive is used.
[Brief description of reference numerals]
10 Joining equipment
14 Pressing section
16 Power supply
18 outer wall
20 vacuum pump
24 Silicon wafer
26 Element substrate
38 Silicon wafer
40 ink flow path substrate
42 Ink channel
46 resin layer
60 metal pattern

Claims (13)

Heat-treat the resin material,
The heat-treated resin material having a thickness of 4.5 μm or more is sandwiched between a plurality of opposing substrates,
A substrate bonding method of performing pressure processing on the plurality of substrates and bonding the respective substrates. 2. The method according to claim 1, wherein a temperature of the heat treatment is equal to or lower than a glass transition point temperature of the resin material plus 80.degree. 3. The method according to claim 1, wherein the pressing includes applying a voltage between the plurality of substrates. 4. 4. The method according to claim 3, wherein the voltage is 5 V or more and 350 V or less. 5. The substrate bonding method according to claim 1, wherein the pressing is performed at a temperature of the plurality of substrates of 200 ° C. or higher. 6. The substrate according to any one of claims 1 to 5, wherein a maximum temperature of the plurality of substrates when the voltage is applied is equal to or higher than a glass transition point temperature and equal to or lower than a heat-resistant temperature of the resin material. Joining method. The substrate bonding method according to claim 1, wherein at least one of the plurality of substrates is made of silicon. 8. The method according to claim 1, wherein the pressurization between the plurality of substrates is performed at a pressure set in at least two or more stages in a process of increasing the temperature of the plurality of substrates. The substrate bonding method according to the above section. The substrate bonding method according to any one of claims 1 to 8, wherein a metal pattern made of metal is provided on at least one of the bonding surfaces of the plurality of substrates. A heat-treated resin material having a thickness of 4.5 μm or more, and a plurality of substrates facing each other and joined via the resin material;
A substrate joined body comprising: An ink jet head comprising the substrate assembly according to claim 10. A pair of substrates is formed of at least two of the plurality of substrates, and a pattern including an ink flow channel is formed on one of the pair of substrates, and a pattern including a plurality of circuits is formed on the other. The inkjet head according to claim 11, wherein the inkjet head is formed. An image forming apparatus comprising the inkjet head according to claim 11.

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