Method for manufacturing bonded structure and method for manufacturing liquid ejection head

Abstract

To provide a manufacturing method of a joint structure having two substrates jointed to each other through an adhesive layer, which can suppress an adhesive from protruding toward concave parts when transferring the adhesive layer onto a surface of the substrates having the concave parts such as grooves and then blocking openings of the concave parts.SOLUTION: The manufacturing method of a joint structure performs a transferring step in which a support body 3 having an adhesive layer 4 formed on a surface thereof is closely contacted with a surface of a first substrate 1, then the support body 3 is peeled off along a separating direction which is parallel to the surface of the first substrate 1 and the support body 3 is separated from the first substrate 1 so as to transfer the adhesive layer onto the surface of the first substrate, where the transferring step is performed in a condition that a width of the concave part in a direction orthogonal to the separating direction is larger than wavelengths of uneven waves formed, by a fingering instability phenomenon, on the surface of the adhesive layer in the surface of the first substrate 1 except for the concave part (such as a groove 2).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a bonded structure formed by bonding two substrates, and a method for manufacturing a liquid ejection head using this manufacturing method. [Background technology]

[0002] Bonded structures formed by bonding two substrates via an adhesive layer are used in various electronic devices, for example, in liquid ejection heads used in liquid ejection devices such as inkjet recording devices. In liquid ejection heads, a bonded structure is used in which a substrate having an energy generating element and a flow path structure is bonded to another substrate corresponding to the first substrate to form a flow path with a complex three-dimensional structure. When bonding two substrates in the manufacture of a bonded structure, an adhesive layer must be formed at the bonding interface to prevent bonding failure or adhesive overflow. Patent Document 1 discloses a method for bonding two substrates by bringing an adhesive applied to a flat support into contact with one substrate, and then peeling and separating the support, thereby transferring a portion of the adhesive to a convex portion on the surface of the other substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-318750 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method described in Patent Document 1, when the surface of the substrate is uneven, the adhesive is transferred only to the convex portions, and should not be transferred to the concave portions such as grooves and holes located between the convex portions. However, a film of adhesive is formed to cover the concave portions, which may result in the flow of liquid through these concave portions being obstructed.

[0005] The object of the present invention is to provide a method for manufacturing a bonded structure that prevents the adhesive from overflowing toward the recesses and blocking the openings of these recesses when an adhesive layer is transferred to the surface of a substrate having recesses such as grooves, and a method for manufacturing a liquid ejection head using the same. [Means for solving the problem]

[0006] The method for manufacturing a bonded structure of the present invention is a method for manufacturing a bonded structure in which a second substrate is bonded to a first substrate having a recess on its surface via an adhesive layer, and includes a transfer step of closely adhering a support having an adhesive layer formed on its surface to the surface of the first substrate, and then separating the support from the first substrate along a separation direction parallel to the surface of the first substrate to transfer the adhesive layer to the surface of the first substrate. a condition setting step of determining the transfer condition parameters before the transfer step is performed, using the conditions used in the transfer step as transfer condition parameters; and a condition that the width of the recess in the direction perpendicular to the separation direction is larger than the wavelength of the unevenness undulation formed on the surface of the adhesive layer on the surface of the first substrate excluding the recess. Transfer by Implement the copying process The condition setting step includes acquiring a width d of the recess in the first substrate in a direction perpendicular to the separation direction, and repeating the steps of bringing a support having an adhesive layer formed thereon into close contact with the surface of the test area while changing transfer condition parameters, separating the support from the test area, transferring the adhesive layer to the surface of the test area, and observing the wavelength λ of the uneven undulations formed on the surface of the test area until a predetermined condition formula is satisfied, and the transfer condition parameters when the predetermined condition formula is satisfied are defined as conditions to be used in the transfer step. do. [Effects of the Invention]

[0007] According to the present invention, in the manufacture of a bonded structure, when an adhesive layer is transferred to the surface of a substrate having recesses such as grooves, it is possible to prevent the adhesive from spilling out toward the recesses and blocking the openings of these recesses. [Brief explanation of the drawings]

[0008] [Figure 1] 3A to 3C are schematic cross-sectional views illustrating a method for manufacturing a joint structure according to the first embodiment. [Figure 2] FIG. 10 is a diagram illustrating the transfer of an adhesive layer. [Figure 3] FIG. 10 is a diagram illustrating the relationship between the wavelength of the waviness and the width of the groove. [Figure 4] FIG. 10 is a diagram illustrating the relationship between the wavelength of the waviness and the width of the groove. [Figure 5] 10A and 10B are diagrams illustrating the relationship between the shape of a groove and the width of the groove. [Figure 6]1 is a flowchart showing a method for manufacturing a bonded structure. [Figure 7] FIG. 10 is a diagram illustrating a change in film thickness due to unevenness and waviness. [Figure 8] FIG. 10 is a diagram illustrating the swell wavelength at each measurement point. [Figure 9] 10 is a graph showing the relationship between transfer condition parameters and waviness wavelength λ. [Figure 10] FIG. 2 is a diagram illustrating a liquid ejection head. [Figure 11] 5A to 5C are schematic cross-sectional views illustrating a method for manufacturing a liquid ejection head. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described with reference to the drawings. A manufacturing method according to the present invention is a method for forming a bonded structure in which a first substrate and a second substrate are bonded together with an adhesive by forming an adhesive layer on the surface of a first substrate and then placing a second substrate on the adhesive layer. In the bonded structure of the present invention, the surface of the first substrate used for bonding to the second substrate is provided with recesses such as grooves and holes. When the bonded structure is a liquid ejection head, the recesses provided in the first substrate are often provided to allow liquid to flow between the first substrate and the grooves and holes provided in the second substrate. Therefore, when forming an adhesive layer on the surface of the first substrate, it is necessary to prevent the opening of the recess from being covered and blocked by the adhesive. Even in bonded structures used in general electronic devices other than liquid ejection heads, yields can be reduced due to the adhesive overflowing into the microfabricated recess space. The manufacturing method of the bonded structure according to the present invention can suppress defects such as adhesive film forming over the recess opening when transferring the adhesive layer to the first substrate. In the following, embodiments to which the present invention can be applied will be described, and in each embodiment, the recessed portion provided in the first substrate is a groove. Of course, the present invention can also be applied to substrates having recessed portions other than grooves.

[0010] [First embodiment] FIG. 1 is a schematic cross-sectional view showing the manufacturing process of a bonded structure according to the first embodiment. FIG. 1(a) shows a cross section of a first substrate 1. A groove 2 is formed as a recess on the surface of the first substrate 1. The groove 2 may penetrate, not penetrate, or only partially penetrate the first substrate 1. A plurality of linear grooves 2 may be formed parallel to one another on the surface of the first substrate 1. In FIG. 1, the left-right direction of the paper is the X-direction, the depth direction of the paper is the Y-direction, and the thickness direction of the first substrate 1 is the Z-axis. Hereinafter, the X, Y, and Z directions of the first substrate 1 will be defined in this manner. When the groove 2 is formed linearly, the Y-direction is, for example, the extension direction of the groove 2. However, as will be described later, the extension direction of the groove 2 may be oblique to the Y-direction. The width of the groove 2 is defined as d.

[0011] Assuming that a first substrate 1 is prepared as shown in FIG. 1(a), a support 3 is prepared, with an adhesive layer 4 formed on one surface with a predetermined thickness. As shown in FIG. 1(b), the support 3 is pressed against the first substrate 1 so that the adhesive layer 4 faces the first substrate 1, thereby adhering the support 3 to the first substrate 1. As a result, the adhesive layer 4 adheres to the surface of the first substrate 1 in areas other than the grooves 2. Then, as shown in FIG. 1(c), the support 3 is separated from the first substrate 1 so that a portion of the adhesive layer 4 remains on the surface of the first substrate 1 in areas where the adhesive layer 4 adheres to the surface of the first substrate 1. In other words, the support 3 is peeled off from the surface of the first substrate 1 so that the adhesive layer 4 is transferred to areas other than the grooves 2 on the surface of the first substrate 1. This process is called the transfer process. The adhesive layer 4 is not formed in the areas that will become openings above the grooves 2. When the adhesive constituting the adhesive layer 4 is liquid, separation generally occurs within the adhesive layer 4 during the process of separating the support 3 from the first substrate 1, and a wavy shape 7 is generated on the surface of the adhesive remaining on the first substrate 1 after the support 3 is separated. Here, the wavelength (i.e., the distance between peaks) of the wavy shape 7 of the adhesive layer 4 formed in the region of the second wall portion 6, which is the relatively wider wall portion, is defined as λ. In reality, when the wavy shape 7 is formed on the surface of the adhesive layer 4, the wavelength λ varies, but for convenience, it is assumed here that wavy shapes with repeated concave and convex portions are formed with the same wavelength. Details of the transfer process of the adhesive layer 4 and the generation of the wavy shape 7 will be described later.

[0012] After the transfer process, as shown in FIG. 1(d), the second substrate 8 is bonded to the first substrate 1 via the adhesive layer 4 remaining on the surface of the first substrate 1. Then, a curing process of the adhesive constituting the adhesive layer 4 is performed, bonding the first substrate 1 and the second substrate 8 together, completing the bonded structure. During this process, the adhesive is crushed, causing adhesive overflow 9 into the groove 2, as shown in FIG. 1(e). The amount of adhesive overflow tends to increase as the amount of adhesive near the groove 2 increases. In particular, in grooves 2 where the adhesive layer 4 should not be formed, the adhesive layer 4 may cover the top surface of the opening formed in the surface of the first substrate 1 by the groove 2, resulting in a defect in which the adhesive layer 4 forms a film. This defect, in which the adhesive layer 4 forms a film over the opening formed by the recess, blocking the opening, is called a film formation defect. In this embodiment, a method for suppressing film formation defects when manufacturing a bonded structure is described. The method for manufacturing a bonded structure of this embodiment is described in detail below.

[0013] First, the transfer process of the adhesive layer 4 will be described using FIG. 2. FIG. 2 generally illustrates the transfer process, showing that the support 3, on whose surface the adhesive layer 4 is formed, is brought into close contact with the substrate 20, and then the support 3 is separated, thereby transferring the adhesive layer 4 to the surface of the substrate 20. In the example shown in FIG. 2, the surface of the substrate 20 is assumed to have no irregularities such as grooves. The a and b directions are defined as being orthogonal to each other within the plane of the substrate 20. The c direction is the direction perpendicular to the surface of the substrate 20. FIG. 2(a) is a schematic perspective view illustrating the transfer process. The surface of the support 3 on which the adhesive layer 4 is formed is not visible from the perspective shown in FIG. 2(a), so the adhesive layer 4 is not shown in FIG. 2(a). From a position on the edge side of the substrate 20, the support 3, which is in close contact with the surface of the substrate 20, is lifted upward (in the c direction) as indicated by arrow 21, and then peeled off in the -b direction as indicated by arrow 22. The -b direction is the separation direction (peeling direction) of the support 3. At this time, the support 3 may be separated in stages by moving the pressure member 24 in the -a direction while pressing the support 3 with the pressure member 24, which may be a roller, and lifting the support 3 upward on the rear side of the moving direction of the pressure member 24. In the following, the separation speed or peeling speed of the support 3 may be referred to, but the separation speed or peeling speed is the speed when the pressure member 24 is moved in the -b direction.

[0014] 2(b), 2(c), and 2(d) are cross-sectional schematic diagrams showing the details of the transfer process of the adhesive layer 4. When the support 3 is lifted to separate it, the liquid adhesive layer 4 separates into a portion adhering to the support 3 and a portion adhering to the substrate 20. This process generates a syrup-like string 23, and the adhesive portion stretched as the string 23 breaks when it exceeds its displacement threshold. This phenomenon occurs repeatedly, resulting in separation in the adhesive layer 4. As the separation in the adhesive layer 4 progresses, the support 3 separates from the substrate 20, as shown in FIG. 2(b). When this separation occurs, the adhesive layer 4 after separation develops a streak-like undulation 7, with protrusions or depressions extending in a direction parallel to the peeling direction (direction b). Along the direction perpendicular to the peeling direction (direction a), the adhesive layer 4 repeatedly increases and decreases in thickness. Focusing on this repeated increase and decrease in thickness, the undulation 7 can be considered an uneven undulation. The phenomenon that generates the undulation pattern 7 is commonly referred to as fingering instability. This phenomenon is caused by the inflow of low-viscosity air into the adhesive layer 4, which is a high-viscosity liquid. Figures 2(c) and 2(d) show schematic cross-sections of the streaky undulation pattern 7 in the orthogonal direction (direction a). In the fingering instability phenomenon, the undulation wavelength λ varies depending on the transfer conditions. For example, if the thickness of the adhesive layer 4 before separation is thick, the undulation wavelength λ increases, as shown in Figure 2(c). Conversely, if the thickness of the adhesive layer 4 is thin, the undulation wavelength λ decreases, as shown in Figure 2(d). Furthermore, as described below, the undulation wavelength λ increases with increasing temperature or decreasing viscosity, and decreases with increasing separation speed (peeling speed). The undulation wavelength λ is the distance from one peak to the next in the undulating pattern 7, which is an uneven undulation, and is also called the undulation period.

[0015] The above describes how the fingering instability phenomenon causes the undulations 7 in the adhesive layer 4. Next, we will explain how the occurrence of film formation defects can be suppressed by utilizing the occurrence of the undulations 7 in the manufacturing process of the bonded structure described with reference to FIG. 1 . FIG. 3 is a diagram illustrating how the adhesive layer 4 on the first substrate 1 differs depending on the relationship between the undulation period in the adhesive layer 4 on the first substrate 1 and the width d of the grooves 2 on the first substrate 1. Here, we will explain how a substantially circular silicon substrate is used as the first substrate 1, how a bonded structure is formed by bonding a second substrate 8 to the silicon substrate, and how multiple chips 25 are then cut out from the bonded structure. The first substrate 1 has multiple (three in this case) elongated grooves 2 extending parallel to each other for each chip 25. These grooves 2 are already formed before bonding to the second substrate 8. Therefore, when transferring the adhesive layer 4 to the first substrate 1 in the manufacturing process of the bonded structure, it is necessary to prevent film formation defects due to the adhesive in the grooves 2. In the chip 25, the relatively large flat area surrounding the area where the multiple grooves 2 are formed is referred to as the peripheral area. Figure 3(a) is a schematic plan view of the first substrate 1, which is a silicon substrate 1, and Figure 3(b) is a schematic plan view of the first substrate 1 corresponding to one chip 25. The X, Y, and Z directions are defined as described above with reference to Figure 1. Here, the separation direction of the support 3 during the transfer process, i.e., the -a direction shown in Figure 2, corresponds to the -Y direction in the XYZ coordinate system shown in Figure 1. Therefore, in Figure 3, the -Y direction indicates the separation direction, and the direction of the arrangement of the unevenness in the undulation shape 7 due to the fingering instability phenomenon corresponds to the X direction. The c direction shown in Figure 2 and the Z direction in Figure 3 correspond to the thickness direction of the substrate, so the c direction and the Z direction coincide.

[0016] In the example shown in FIG. 3, since the extending direction (longitudinal direction) of the elongated groove 2 formed on the surface of the first substrate 1 is orthogonal to the separation direction, the width d of the groove 2 along the direction orthogonal to the separation direction (i.e., the X direction) is sufficiently large. FIG. 3(c) is a schematic cross-sectional view taken along the C-C line of FIG. 3(b) for the first substrate 1 after the transfer process, and FIG. 3(d) is a schematic cross-sectional view taken along the D-D line of FIG. 3(b). FIG. 3(c) shows the cross-sectional shape in a region where the surface of the first substrate 1 is flat over a relatively wide range. Here, in the adhesive layer 4, undulations with an undulation wavelength λ occur. On the other hand, at the position that becomes the opening above the groove 2, as shown in FIG. 3(d), the adhesive layer 4 is not formed. When separating the support 3 in a state where the relationship λ < d holds, the position where the adhesive layer 4 becomes thin due to undulations (the position of the valley) is necessarily in an overlapping positional relationship with somewhere in the groove 2. When the position of the valley in the adhesive layer 4 overlaps with the groove 2, there is a high possibility that the adhesive layer 4 is divided at this position. The divided adhesive layer 4 is pulled to both ends of the groove 2 by surface tension or the like. As a result, the occurrence of film stretching failure in the groove 2 is suppressed.

[0017] Similar to FIG. 3, FIG. 4 illustrates how the adhesive layer 4 on the first substrate 1 differs depending on the relationship between the waviness wavelength λ in the adhesive layer 4 on the first substrate 1 and the width d of the grooves 2 on the first substrate 1. The example shown in FIG. 4 shows multiple elongated grooves 2 of the same shape and size as those shown in FIG. 3 formed on the surface of the first substrate 1, but differs from that shown in FIG. 3 in that the extension direction of the grooves 2 is parallel to the separation direction (Y direction). FIG. 4(a) is a schematic plan view of the entire silicon substrate serving as the first substrate 1, FIG. 4(b) is a schematic plan view of a chip 25, FIG. 4(c) is a cross-sectional view taken along line CC in FIG. 4(b), and FIG. 4(d) is a cross-sectional view taken along line DD in FIG. 4(b). Note that FIGS. 4(c) and 4(d) are cross-sectional views that include not only one chip 25 but also the adjacent portions. As with FIG. 3, the X, Y, and Z directions are defined in FIG. 4. In this case, too, uneven undulations with a undulation wavelength λ are generated on the surface of the adhesive layer 4 in the flat region of the first substrate 1 over a relatively wide area. In the example shown in FIG. 4, the extension direction (longitudinal direction) of the elongated grooves 2 formed on the surface of the first substrate 1 is parallel to the separation direction, so the width d of the grooves 2 along the direction perpendicular to the separation direction (i.e., the X direction) is small, and λ > d. When λ > d, there is a certain probability that a positional relationship will occur in which the grooves 2 are contained within the mountain-shaped portions of the undulations of the adhesive layer 4. For example, in the region 26 surrounded by the dashed line in FIG. 4(d), the convex portions (mountains) of the undulations of the adhesive layer 4 are exactly aligned with the center of the grooves 2 in the width direction, and the concave portions (valleys) on both sides of the convex portions are located on the top surfaces of the wall portions on both sides that define the grooves 2. In this positional relationship, the adhesive layer 4 is prevented from being separated at the positions of the grooves 2, thereby increasing the possibility of poor adhesive film formation in the grooves 2.

[0018] From the above, when forming a bonded structure using the first substrate 1 having the groove 2 formed on its surface, it can be seen that the transfer process of the adhesive layer 4 may be performed under the transfer condition that the undulation wavelength λ of the adhesive is smaller than the width d of the groove 2 along the direction orthogonal to the separation direction of the support 3. By performing the transfer process in this way, the adhesive layer 4 is effectively segmented at the position above the groove 2, and the occurrence of film stretching defects of the adhesive can be suppressed. Then, when the second substrate 8 is brought into contact with and bonded to the adhesive layer 4, the occurrence of defects in which the groove 2 and the opening are blocked by excess adhesive can be suppressed. Thereby, according to the present embodiment, a bonded structure can be manufactured with high yield.

[0019] Here, the width d of the groove 2 in the direction orthogonal to the separation direction of the support 3 corresponding to the shape of the groove 2 will be described. Depending on the shape of the groove 2, the end of the groove may be circular or acute-angled, and the width of the groove may gradually change. In such a case, as shown in FIG. 5(a), for one groove 2, the maximum width in the direction (X direction) orthogonal to the separation direction of the support 3 can be defined as the width of the groove 2 in the direction orthogonal to the separation direction of the support 3. There may also be a case where the longitudinal direction of the elongated groove 2 is inclined (oblique) to the separation direction. In such a case, as shown in FIG. 5(b), for the inclined groove 2, the maximum groove width d in the direction orthogonal to the separation direction is defined. Assuming that the width d of the groove is defined in this way, for a groove 2 having a shape in which the width d is not constant, if there is a place where λ < d even at one point along the length direction of the groove 2, the effect of suppressing the occurrence of film stretching defects can be obtained. However, it is preferable that the relationship of λ < d holds in a region of 50% or more of the total length of the groove 2.

[0020] Conditions for suppressing film formation defects when transferring an adhesive layer 4 formed on a support 3 to the surface of a first substrate 1 and then bonding a second substrate to the first substrate 1 have been identified. These conditions can be met by appropriately setting the transfer condition parameters, which refer to, for example, the film thickness of the adhesive layer 4 on the support 3, the separation speed, and the temperature when separating the support 3. Next, we will explain how to manufacture a bonded structure while suppressing film formation defects by setting the transfer condition parameters. Figure 6 is a flowchart showing a method for manufacturing a bonded structure. In the following explanation, the first substrate 1 that constitutes the bonded structure to be actually manufactured is referred to as a product substrate. In contrast, a substrate that is identical to the first substrate 1 except for the lack of grooves is referred to as a planar substrate. A planar substrate is a flat substrate made of the same material as the first substrate 1. When the first substrate 1 actually used, i.e., the product substrate, is obtained by micromachining a silicon wafer, the planar substrate is an unprocessed silicon wafer.

[0021] First, in step 101, the width d of the groove 2 on the product substrate is obtained. Next, in step 102, transfer condition parameters are provisionally set, and in step 103, adhesive is applied to the surface of the support 3 to form an adhesive layer 4. After that, in step 104, the support 3 is brought into close contact with the planar substrate and then peeled off and separated from the planar substrate, thereby transferring the adhesive layer 4 to the surface of the planar substrate. The transfer conditions at this time are represented by the transfer condition parameters set in step 102.

[0022] Next, in step 105, the surface undulations 7 of the adhesive layer 4 transferred to the surface of the planar substrate are observed, and the wavelength λ of the uneven waviness is obtained. The surface shape of the adhesive layer 4 is obtained, and a cross-sectional profile in a direction perpendicular to the separation direction is extracted from the surface shape. The waviness wavelength can be determined as the distance between the peak positions of two adjacent peaks in the cross-sectional profile. To obtain the surface shape of the adhesive layer 4, a measuring device such as a white light interferometer surface profiler or a white light interferometer three-dimensional profiler can be used. As described below, in reality, the waviness spacing and peak-to-valley shape are not uniform even within the same substrate, but vary. Therefore, measurements can be taken at multiple points and the average of these measurements can be used to determine the waviness wavelength λ. For example, it is preferable to measure the peak-to-valley distance at 10 or more points, double it, and then calculate the average of these measurements to determine λ.

[0023] Once the waviness wavelength λ on the surface of the adhesive layer 4 transferred onto the flat substrate is obtained, next in step 106, it is determined whether the predetermined conditional expression λ < d holds. If this conditional expression holds, in step 107, the transfer condition parameters tentatively set in step 102 earlier are formally determined as the formal transfer condition parameters to be used for the product substrate. Then in step 108, the transfer of the adhesive layer 4 and the separation of the support 3 are carried out according to the formally determined transfer condition parameters, so as to manufacture a bonded laminate using the product substrate, and then this series of processes is terminated. On the other hand, when the condition of λ < d does not hold in step 106, the process returns to step 102 to reset the transfer condition parameters again, and the above processes are repeated until this condition holds. Thereby, a bonded structure having the product substrate as the first substrate 1 and in which the occurrence of film stretching defects is suppressed can be obtained. Incidentally, considering variations in the waviness wavelength and the like, a conditional expression indicating a stronger condition than λ < d, for example, λ < 0.7d, may be used. The process of executing the processes of steps 101 to 107 is called a condition setting process. In the above description, the condition setting process is carried out using a flat substrate prepared separately from the product substrate, but the condition setting process can also be carried out for a relatively wide area on the product substrate where no grooves are formed. The area on the product substrate that is the target of the condition setting process and the flat substrate are collectively called a test area. For example, in the examples shown in FIGS. 3 and 4, the outer peripheral area of the chip 25 or the area on the first substrate 1 where the chip 25 is not formed can be used as the test area instead of the flat substrate.

[0024] As described above, examples of the transfer condition parameters include the film thickness of the adhesive layer on the support, the separation speed, and the temperature when separating the support 3. Below, the results of examining the relationship between the change in the value of each of these parameters and the ripple wavelength λ will be described. CYCLOTENE (registered trademark) 3022 manufactured by The Dow Chemical Company was applied as an adhesive on the support, and this support was adhered to a flat substrate, which is a mirror-finished silicon wafer. Then, the support 3 was separated to transfer the adhesive layer onto the flat substrate. And the ripple wavelength λ was evaluated using a white interference surface shape measuring device. The results are shown in Fig. 7. The measurement of the ripple wavelength λ was performed at multiple points, and the results at each individual measurement point are shown as small circles in Fig. 7. In Fig. 7, the average of the measured values at multiple points is also shown.

[0025] Fig. 7(a) shows the change in the ripple wavelength λ when the film thickness of the adhesive layer on the support was changed to 2.9 μm, 10.5 μm, 12.5 μm, and 18.5 μm with the temperature at 100°C and the separation speed at 3 mm / sec. It can be seen that as the film thickness increases, the ripple wavelength λ tends to increase. Fig. 7(b) shows the change in the ripple wavelength λ when the temperature when separating the support was changed to 100°C, 120°C, and 140°C with the film thickness of the adhesive layer on the support at 3.3 μm and the separation speed at 3 mm / sec. It can be seen that as the temperature increases, that is, as the viscosity of the adhesive decreases, the ripple wavelength λ tends to increase. Fig. 7(c) shows the change in the ripple wavelength λ when the separation speed was changed to 0.1 mm / sec, 3 mm / sec, and 10 mm / sec with the film thickness of the adhesive layer on the support at 3.3 μm and the temperature at 120°C. It can be seen that as the separation speed increases, the ripple wavelength λ tends to decrease. Thus, by changing at least one of the film thickness, temperature, and separation speed of the adhesive layer on the support, the ripple wavelength λ also changes. Using one of these parameters or combining two or more of them, the ripple wavelength λ can be adjusted to satisfy the condition of λ < d.

[0026] This section describes an example of measuring the undulations formed on the surface of an adhesive layer when the adhesive layer was transferred to a flat substrate. A mirror-finished silicon wafer was used as the flat substrate (first substrate 1). CYCLOTENE® 3022 (manufactured by The Dow Chemical Company) was applied to a support as an adhesive, and the support was then attached to the flat substrate to transfer the adhesive layer. A white-light surface profilometer was then used to measure the surface profile of an area of ​​2576 μm × 985 μm (3520 × 1344 pixels) on the flat substrate, as well as the cross-sectional profile at Y=0. Figure 8(a) shows the results when the thickness of the adhesive layer formed on the support before transfer was 2.0 μm. Similarly, Figure 8(b) shows the results when the thickness was 9.6 μm, and Figure 8(c) shows the results when the thickness was 20 μm. In these figures, the measured surface profile is shown as a grayscale image on the left, and the cross-sectional profile is shown on the right. Next, in the cross-sectional profile shown in Figure 8, the distance between adjacent peaks and valleys, and between valleys and peaks, was measured in the direction of increasing X from the position where X = 0 (the left end of the graph). This distance is the difference between the X coordinate value of the upward convex inflection point and the X coordinate value of the downward convex inflection point on the graph. Doubling this distance value is considered to be a measurement of the waviness wavelength λ at one point. Figure 9(a) shows the wavelength λ values ​​at each measurement point for each thickness of the adhesive layer on the support. The numbers on the horizontal axis identify the measurement point. While there are some differences depending on the thickness of the adhesive layer, it can be seen that there are no extreme changes in the wavelength of the waveform (i.e., the uneven waviness) appearing in the cross-sectional profile, and that all are average. It can also be seen that the waviness wavelength λ increases with film thickness.

[0027] Figure 9(b) shows the results of calculating the average wavelength at an increasing number of measurement points. As the number of measurement points increases and the amount of data used to calculate the average increases, the average wavelength value converges. Furthermore, Figure 9(c) shows the rate of change of the average wavelength calculated from the measurement points as the number of measurement points increases. When the number of measurement points is small, the average value itself fluctuates significantly. However, when the number of measurement points is 10 or more, the rate of change is kept to 95% to 105% under all film thickness conditions. From the above, it can be seen that it is preferable to acquire surface shape data using an angle of view large enough to repeat the peak-valley shape 10 or more times, measure 10 or more consecutive adjacent points, and calculate the average value to determine the waviness wavelength λ.

[0028] In the method for manufacturing a bonded structure of this embodiment, the transfer step is performed under conditions such that the recesses of the uneven undulations are always positioned over the openings of the recesses (e.g., grooves 2) in the first substrate 1. As described above, there is variation in the beat wavelength λ, so in order to more reliably suppress film formation defects, the transfer condition parameters can be set so as to satisfy, for example, the condition λ<0.7d or λ<0.5d using the waviness wavelength λ obtained as the average value.

[0029] [Second embodiment] As an example of application of the manufacturing method of a bonded structure according to the present invention, an example in which this manufacturing method is used to manufacture a liquid ejection head will be described. Figure 10 shows a liquid ejection head, with Figure 10(a) being a schematic perspective view of the liquid ejection head and Figure 10(b) being a cross-sectional view taken along line BB in Figure 10(a). A plurality of energy generating elements 13 are arranged on a first surface of a first substrate 1 made of a silicon substrate, and an ejection port forming member 12 is laminated thereon. A recess is provided for each energy generating element 13 on the surface of the ejection port forming member 12 facing the energy generating elements 13, forming a pressure chamber 14. The pressure chamber 14 has an ejection port 10 formed as a through hole. The energy generating elements 13 generate energy for ejecting liquid from the ejection port 10. The ejection port forming member 12 may contain an organic material such as epoxy resin to improve dimensional flexibility in its formation. The ejection port forming member 12 is bonded to the first substrate 1 via an adhesive. A plurality of grooves 2 are formed on the second surface of the first substrate 1, and the grooves 2 communicate with pressure chambers 14 via supply ports 15 or recovery ports that penetrate to the first surface of the first substrate 1. A recording element substrate is made up of the first substrate 1, the ejection port forming member 12, and the energy generating elements 13. The ejection port forming member 12 is provided with a plurality of ejection port arrays 11, each consisting of a plurality of ejection ports 10. The grooves 2 are formed in an elongated shape with the direction in which the ejection port arrays 11 extend as the longitudinal direction. The width of the grooves 2 in the direction perpendicular to the longitudinal direction is defined as d.

[0030] On the second substrate 8, an opening 16 is provided for supplying liquid to the groove 2 in communication with the groove 2 of the first substrate 1 and recovering the liquid from the groove 2. The second substrate 8 is joined to the second surface of the first substrate 1 via an adhesive layer 4, and a liquid ejection head which is a joined structure is formed by the first substrate 1 which is a recording element substrate and the second substrate 8. The liquid ejection head is configured to eject different types of liquids, for example, inks of different colors, for each ejection port row 11. In this liquid ejection head, since it is necessary for the liquid to flow between the opening 16 of the second substrate 8 and the groove 2 of the first substrate 1, it is required to suppress the occurrence of poor film formation of the adhesive in the groove 2. Therefore, when joining the first substrate 1 and the second substrate 8 via the adhesive layer 4, the manufacturing method of the joined structure described above is used. Further, in the manufacture of the liquid ejection head, it is common to use a first substrate 1 having a size corresponding to a plurality of liquid ejection heads, join the second substrate 8 thereto, and then cut out a portion (referred to as a chip) corresponding to each individual liquid ejection head. Hereinafter, the manufacturing method of the liquid ejection head of the present embodiment will be described with reference to FIG. 11.

[0031] First, as shown in FIG. 11(a), a first substrate 1 to which an ejection port forming member 12 is joined is prepared. A plurality of grooves 2 are already formed in the first substrate 1. At this stage, the first substrate 1 has a size corresponding to a plurality of chips. Next, a support 3 having an adhesive layer 4 formed on one surface is prepared, and as shown in FIG. 11(b), the support 3 is pressed against the first substrate 1 so that the adhesive layer 4 faces the first substrate 1 and brought into close contact. Then, as shown in FIG. 11(c), the support 3 is separated from the first substrate 1 so that a part of the adhesive layer 4 remains on the surface of the first substrate 1 in the region where the surface of the first substrate 1 and the adhesive layer 4 are in close contact. When separating the support 3 from the first substrate 1, the transfer condition parameters are set so that the undulation wavelength λ in the adhesive layer 4 satisfies λ < d. The separation direction is the direction in which the ejection port row 11 extends, that is, the direction parallel to the longitudinal direction of the groove 2.

[0032] After the support 3 is separated, the second substrate 8 is bonded to the first substrate 1 via the adhesive layer 4 remaining on the surface of the first substrate 1, as shown in FIG. 11(d). An opening 16 is formed in the second substrate 8. The adhesive constituting the adhesive layer 4 is cured, bonding the first substrate 1 and the second substrate 8 together, as shown in FIG. 11(e). Then, chips corresponding to individual liquid ejection heads are separated from the bonded structure. When a liquid ejection head is manufactured using this process, the waviness wavelength d is shorter than the width d of the groove 2 in the direction perpendicular to the separation direction. This facilitates the separation of the adhesive layer 4 at the position of the groove 2 during transfer, thereby suppressing the occurrence of film formation defects. As a result, the flow of liquid between the opening 16 of the second substrate 8 and the groove 2 of the first substrate 1 is not impeded. The manufacturing method of this embodiment enables the manufacture of liquid ejection heads with high yield. In the above description, the second substrate 8 is bonded to the first substrate 1 on which the ejection port forming member 12 is already provided, but the timing of bonding the ejection port forming member 12 to the first substrate 1 does not affect the effects obtained by this embodiment. Therefore, the ejection port forming member 12 may be formed on the first substrate 1 after bonding the first substrate 1 and the second substrate 8. [Example]

[0033] [Example 1] The steps shown in FIGS. 1(a) to 1(c) were carried out. As the first substrate 1, as shown in FIG. 3(a), a silicon substrate on which a plurality of chips 25 were arranged was prepared. In the region of each chip 25, a plurality of rectangular grooves 2 with a width of 180 μm and a length of 20000 μm were formed so as to be parallel to each other. On a polyethylene terephthalate (PET) film as the support 3, as an adhesive, CYCLOTENE (registered trademark) 3022 manufactured by The Dow Chemical Company was spin-coated to form an adhesive layer 4 with a film thickness of 9.6 μm. The first substrate 1 was placed on a heating stage set at 120° C., and the support 3 was arranged at a certain distance above it so that the adhesive layer 4 faced downward. Then, a transfer process was carried out using a roller that scanned at a pressure of 0.2 MPa and a speed of 3 mm / sec, and the adhesive layer 4 was transferred onto the surface of the first substrate 1. At this time, the scanning direction of the roller, that is, the separation direction of the support 3, was set to be perpendicular to the longitudinal direction of the groove 2. As a result, the width d of the groove 2 in the direction perpendicular to the separation direction was 20000 μm.

[0034] The unevenness of the surface of the adhesive formed in the outer peripheral region of the chip 25 was measured by a white interference three-dimensional shape measuring device. The distance between the peak and valley in the unevenness was measured at 10 points, each measured value was doubled, and then their average was obtained as the average value of the wavelength λ of the unevenness, which was 200 μm. That is, the relationship of λ < d was established. When each groove 2 of the plurality of chips 25 onto which the adhesive was transferred was observed in this way, no chip 25 with film stretching failure was found, and the occurrence rate of film stretching failure was 0%.

[0035] [Example 2] The steps shown in FIGS. 1(a) to 1(c) were carried out. As the first substrate 1, as shown in FIG. 4(a), a silicon substrate on which a plurality of chips 25 were arranged was prepared. In the region of each chip 25, a plurality of rectangular grooves 2 having a width of 220 μm and a length of 40000 μm were formed so as to be parallel to each other. The scanning direction of the roller, that is, the separation direction of the support 3, was set to a direction parallel to the longitudinal direction of the groove 2. The transfer process was carried out in the same manner as in Example 1 in other respects, and the adhesive layer 4 was transferred onto the surface of the first substrate 1. In this Example 2, the width d of the groove 2 in the direction orthogonal to the separation direction was 220 μm. Thereafter, in the same manner as in Example 1, the average value of the wavelength λ of the undulation and the presence or absence of the occurrence of film stretching failure were confirmed. As a result, the wavelength λ of the undulation was about 200 μm, and the relationship of λ < d was satisfied. Also, no chip 25 in which film stretching failure occurred was found, and the occurrence rate of film stretching failure was 0%.

[0036] [Comparative Example 1] The transfer process was carried out in the same manner as in Example 2 except that the size of the groove 2 was a width of 180 μm and a length of 20000 μm, and the adhesive layer 4 was transferred onto the surface of the first substrate 1. In this comparative example, the width d of the groove 2 in the direction orthogonal to the separation direction was 180 μm. Thereafter, in the same manner as in Example 2, the average value of the wavelength λ of the undulation and the presence or absence of the occurrence of film stretching failure were confirmed. As a result, the wavelength λ of the undulation was about 200 μm, and the relationship of λ > d was satisfied. Also, chips 25 in which film stretching failure occurred were found, and the occurrence rate of failure obtained by dividing the number of chips in which film stretching failure occurred by the total number of chips was 89%. The results are summarized in Table 1. As shown in Table 1, by making the relationship of d < λ hold, it was possible to suppress the occurrence of film stretching failure of the adhesive in the recess represented by the groove.

[0037]

Table 1

Explanation of Signs

[0038] 1 First substrate 2 Groove 3 Support 4 Adhesive layer 5 First wall 6 Second wall 7. Wavy shape 8 Second board

Claims

1. A method for manufacturing a bonded structure in which a second substrate is bonded to a first substrate having a recess on a surface thereof via an adhesive layer, comprising: a transfer step of closely adhering a support having an adhesive layer formed on its surface to the surface of the first substrate, and then separating the support from the first substrate along a separation direction parallel to the surface of the first substrate to transfer the adhesive layer to the surface of the first substrate; a condition setting step of determining the transfer condition parameters before carrying out the transfer step, the conditions to be used in the transfer step being set as transfer condition parameters; and carrying out the transfer step under conditions in which the width of the recess in a direction perpendicular to the separation direction is greater than the wavelength of the unevenness undulations formed on the surface of the adhesive layer on the surface of the first substrate excluding the recess; The condition setting step includes: acquiring a width d of the recess in a direction perpendicular to the separation direction in the first substrate; repeating the steps of: while changing the transfer condition parameters, bringing the support on which the adhesive layer is formed into close contact with the surface of a test area, separating the support from the test area, transferring the adhesive layer to the surface of the test area, and observing the wavelength λ of the unevenness undulations formed on the surface of the test area until a predetermined conditional formula is satisfied; and The method for manufacturing a bonded structure uses the transfer condition parameters that satisfy the predetermined conditional formula as conditions to be used in the transfer step.

2. A method for manufacturing a bonded structure in which a second substrate is bonded to a first substrate having a recess on its surface via an adhesive layer, a transfer step of attaching a support having an adhesive layer formed on a surface thereof to the surface of the first substrate, and then separating the support from the first substrate along a separation direction parallel to the surface of the first substrate to transfer the adhesive layer to the surface of the first substrate; A method for manufacturing a bonded structure, wherein the transfer step is carried out under conditions in which, on the surface of the first substrate excluding the recess, a width of the recess in a direction perpendicular to the separation direction is larger than a wavelength of unevenness and undulations formed on the surface of the adhesive layer, A method for manufacturing a bonded structure, wherein the wavelength of the uneven undulations is a wavelength in a direction perpendicular to the separation direction.

3. A condition setting step of determining, before carrying out the transfer step, conditions used in the transfer step as transfer condition parameters, the transfer condition parameters; The condition setting step includes: acquiring a width d of the recess in a direction perpendicular to the separation direction in the first substrate; repeating the steps of: while changing the transfer condition parameters, bringing the support on which the adhesive layer is formed into close contact with the surface of a test area, separating the support from the test area, transferring the adhesive layer to the surface of the test area, and observing the wavelength λ of the unevenness undulations formed on the surface of the test area until a predetermined conditional formula is satisfied; and The method for manufacturing a bonded structure according to claim 2 , wherein the transfer condition parameters that satisfy the predetermined conditional formula are used as conditions in the transfer step.

4. The method for manufacturing a joint structure according to claim 1 or 3, wherein the predetermined conditional expression is λ<d.

5. 5. A method for manufacturing a bonded structure according to claim 1, wherein the surface of the test area is a surface of a flat substrate made of the same material as the first substrate, or a surface of an area of ​​the first substrate where the recess is not formed.

6. 6. The method for manufacturing a bonded structure according to claim 4 or 5, wherein the transfer condition parameters include at least one of a film thickness of the adhesive layer on the support, a separation speed along the separation direction when peeling off the support, and a temperature when separating the support.

7. The method for manufacturing a bonded structure according to claim 1 , wherein after the transferring step, the second substrate is bonded to the first substrate via the adhesive layer on the surface of the first substrate.

8. The method for manufacturing a joint structure according to claim 1 , wherein the recessed portion is made up of a plurality of linear grooves parallel to each other.

9. A method for manufacturing a liquid ejection head having an ejection port for ejecting a liquid and an energy generating element for generating energy for ejecting the liquid from the ejection port, comprising: a method for manufacturing a bonded structure in which a second substrate is bonded to a first substrate having a recess on a surface thereof via an adhesive layer, thereby bonding the first substrate, which is a recording element substrate having the energy generating elements, to the second substrate having an opening corresponding to the recess provided in the first substrate; The method for manufacturing the bonded structure includes: a transfer step of attaching a support having an adhesive layer formed on a surface thereof to the surface of the first substrate, and then separating the support from the first substrate along a separation direction parallel to the surface of the first substrate to transfer the adhesive layer to the surface of the first substrate; A method for manufacturing a liquid ejection head, in which the transfer process is carried out under conditions in which the width of the recess in a direction perpendicular to the separation direction is greater than the wavelength of the uneven undulations formed on the surface of the adhesive layer on the surface of the first substrate excluding the recess.

10. A method for manufacturing a liquid ejection head as described in Claim 9, wherein after the transfer process, the second substrate is bonded to the first substrate via the adhesive layer on the surface of the first substrate.

11. A method for manufacturing a liquid ejection head as described in claim 9 or 10, wherein the recess consists of a plurality of linear grooves parallel to each other.

12. A method for manufacturing a liquid ejection head having an ejection port for ejecting a liquid and an energy generating element for generating energy for ejecting the liquid from the ejection port, comprising: A method for manufacturing a liquid ejection head, comprising: carrying out the method for manufacturing a bonded structure described in any one of claims 1 to 8; and bonding the first substrate, which is a recording element substrate having the energy generating element, to the second substrate, which has an opening corresponding to the recess provided in the first substrate.

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