Thin film forming method and thin film forming apparatus

[0066] [Example 1]

[0067] figure 1 A schematic diagram of the thin film forming apparatus of Example 1 is shown in FIG. A stage 22 is supported on the platform 20 by a moving mechanism 21. On the upper surface (holding surface) of the stage 22, a substrate 50 such as a printed wiring board is held. The direction parallel to the holding surface of the stage 22 is set to the X direction and the Y direction, and the normal direction of the holding surface is set to the Z direction to define the XYZ rectangular coordinate system. The moving mechanism 21 moves the stage 22 in the X direction and the Y direction.

[0068] The beam 32 is supported above the platform 20 by the pillar 31. The nozzle unit support mechanism 29 and the imaging device 30 are attached to the beam 32. The nozzle unit 23 is supported on the nozzle unit support mechanism 29. The imaging device 30 and the nozzle unit 23 are opposed to the substrate 50 held on the stage 22. The imaging device 30 images a wiring pattern, an alignment mark, a thin film pattern formed on the substrate 50, and the like formed on the surface of the substrate 50. The image data obtained by shooting is input to the control device 40. The nozzle unit 23 ejects droplets of a photocurable (for example, ultraviolet curable) thin film material, for example, droplets of solder resist or the like, toward the substrate 50 from a plurality of nozzle holes. The discharged thin film material adheres to the surface of the substrate 50.

[0069] The nozzle unit 23 can be fixed to the platform 20 and the stage 22 can be moved instead of moving the nozzle unit 23 relative to the stage 22 and the platform 20.

[0070] The control device 40 controls the movement mechanism 21, the nozzle unit 23, and the imaging device 30. The control device 40 stores therein image data in a raster format that defines a thin film pattern to be formed on the substrate 50 and the like. The operator inputs various instructions (commands) or numerical data required for control to the control device 40 through the input device 41. The input device 41 uses, for example, a keyboard, a touch panel, a pointing device, and the like. The control device 40 outputs various information from the output device 42 to the operator. As the output device 42, a liquid crystal display or the like is used.

[0071] figure 2 A is a perspective view of the nozzle unit 23. Multiple (for example, four) nozzle heads 24 are mounted on the nozzle holder 26. A plurality of nozzle holes 24 a are formed in each nozzle head 24. The nozzle holes 24 a are arranged in the X direction, and the four nozzle heads 24 are arranged in the Y direction and fixed to the nozzle holder 26.

[0072] Ultraviolet light sources 25 are respectively arranged between the nozzle heads 24 and outside the nozzle heads 24 at both ends. The ultraviolet light source 25 faces the substrate 50 ( figure 1 ) Irradiate ultraviolet rays. In addition, when a material cured by light components outside the wavelength region of ultraviolet rays is used as the film material, a light source that emits light including wavelength components capable of curing the film material is used instead of the ultraviolet light source 25.

[0073] figure 2 B shows a bottom view of the nozzle head 24 and the ultraviolet light source 25. Two nozzle rows 24 b are arranged on each bottom surface (surface facing the substrate 50) of the nozzle head 24. Each nozzle row 24b is composed of a plurality of nozzle holes 24a arranged at a pitch (period) of 8P in the X direction. One of the nozzle rows 24b is deviated in the Y direction relative to the other nozzle rows 24b, and is deviated only by the pitch 4P in the X direction. That is, when focusing on one nozzle head 24, the nozzle holes 24a are distributed at equal intervals with a pitch of 4P in the X direction. The pitch 4P corresponds to a resolution of 300 dpi, for example.

[0074] The four nozzle heads 24 are arranged in the Y direction, and are mutually offset in the X direction, and are mounted on the nozzle holder 26 ( figure 2 A). figure 2 In B, when the leftmost nozzle head 24 is used as a reference, the second, third, and fourth nozzle heads 24 deviate by only 2P, P, and 3P in the negative direction of the X axis, respectively. Therefore, when focusing on the four nozzle heads 24 (as the entire nozzle head), the nozzle holes 24a are arranged at equal intervals in the X direction at a pitch P (a pitch equivalent to 1200 dpi).

[0075] Ultraviolet light sources 25 are respectively arranged between the nozzle heads 24 and on the outside with respect to the outermost nozzle head 24 in the Y direction. The ultraviolet light source 25 is attached to the substrate 50 ( figure 1 ) The liquid film material solidifies.

[0076] By making the substrate 50 ( figure 1 ) The droplets of the thin film material are discharged from each nozzle hole 24a of the nozzle unit 23 while moving in the Y direction, so that the thin film pattern can be formed with a resolution of 1200 dpi in the X direction. By shifting only P/2 in the X direction to scan twice, the resolution in the X direction can be doubled to 2400 dpi. The second scan can be realized by scanning back and forth in which the directions of the first scan and the second scan are reversed. The resolution in the Y direction is determined by the moving speed of the substrate 50 and the discharge period of the droplets from the nozzle hole 24a.

[0077] image 3 A plan view of the substrate 50 and the nozzle unit 23 on which the thin film pattern is formed is shown in FIG. On the surface of the substrate 50, a thin film pattern 55 is formed. The substrate 50 is a spliced ​​substrate in which a plurality of printed wiring boards are arranged in the surface. As an example, printed wiring boards are arranged in rows and columns of 4 rows and 2 columns on the surface of the substrate 50. The film pattern 55 is defined corresponding to the printed wiring board. The thin film pattern 55 is formed of, for example, a solder resist.

[0078] While the substrate 50 is moving in the Y direction, the action of ejecting droplets of the thin film material from the nozzle unit 23 is called “scanning”. The area where the droplets of the thin film material can be landed by one scan is called the unit scan area 56. The size (width) of the unit scanning area 56 in the X direction is represented by W. As an example, the width W of the unit scanning area 56 is 1/4 of the size of the substrate 50 in the X direction.

[0079] Refer to Figure 4A ~ Figure 4L and Figure 5 A~ Figure 5 C, the thin film forming method of Example 1 will be described. Figure 4A~Figure 4L image 3 The substrate 50 shown in is representative and only shows an area corresponding to one printed wiring board. In addition, for the convenience of description, two square and four circular openings are arranged in the film pattern, but in fact, a large number of finer openings are arranged.

[0080] FIG. 4A shows a plan view of the substrate 50 and the nozzle unit 23 before and after the first scan. Fig. 4B shows a cross-sectional view taken along the chain line 4B-4B in Fig. 4A. Figure 5 A shows a cross-sectional view of the one-dot chain line 5A-5A in FIG. 4A.

[0081] As shown in FIG. 4A, the substrate 50 is scanned in the negative direction of the Y axis. At this time, make the nozzle head 24 ( Figure 5 The droplets of the film material of A) land on the outermost edge of the film pattern 55 and the edge of the opening. During scanning, the ultraviolet light source 25 ( Figure 5 A) The substrate 50 is irradiated with ultraviolet rays. Therefore, after the droplets of the thin film material land on the substrate 50, the surface layer portion of the thin film material is immediately solidified. The light energy density of the ultraviolet rays radiated from the ultraviolet light source 25 on the surface of the substrate is not sufficient, so the inside of the film material is in an uncured state. The reaction in which only the surface layer portion of the film material is cured is called "temporary curing", and the reaction in which the material is cured to the inside is called "main curing". Through the first scan, scan area 56 in 1 unit ( image 3 The outermost edge of the film pattern in) and the edge of the opening form a linear edge pattern 60 made of a temporarily cured film material.

[0082] 4C shows a plan view of the substrate 50 and the nozzle unit 23 before and after the second scan. Fig. 4D shows a cross-sectional view taken along the chain line 4D-4D in Fig. 4C. As shown in FIG. 4C, the substrate 50 is moved in the negative direction of the X axis by a distance equal to the width W of the unit scanning area 56. After that, the second scan is performed by moving the substrate 50 in the positive direction of the Y axis. In the second scan, the droplets of the thin film material are also made to land on the outermost edge and the edge of the opening of the thin film pattern 55 from the nozzle unit 23, and the thin film material is temporarily cured immediately after landing.

[0083] The edge pattern 61 temporarily cured is formed on the outermost edge of the thin film pattern 55 and the edge of the opening in the unit scanning area 56 adjacent to the unit scanning area 56 where the edge pattern 60 is formed through the first scan.

[0084] FIG. 4E shows a plan view of the substrate 50 and the nozzle unit 23 before and after the third scan. 4F shows a cross-sectional view of the one-dot chain line 4F-4F in FIG. 4E, Figure 5 B shows a cross-sectional view of the one-dot chain line 5B-5B in FIG. 4E. After the second scan is completed, the third scan is performed by moving the substrate 50 in the negative direction of the Y axis. In the third scan, the droplets of the thin film material are removed from the nozzle head 24 ( Figure 5 B) Landing on the film pattern 55 ( image 3 ) Inside of the area (the full area). A planar pattern 62 having an edge pattern 61 formed in the second scan as an edge is formed. Ultraviolet light source 25 in the third scan ( Figure 5 B) is closed. Therefore, the planar pattern 62 remains in an uncured state.

[0085] Although the planar pattern 62 is in an uncured state, the edge pattern 61 formed in the region corresponding to the edge of the thin film pattern 55 blocks the diffusion of the thin film material in the in-plane direction. Therefore, the uncured film material does not penetrate into the inside of the opening. Unit scan area 56 ( image 3 On the boundary line 63 of ), there is no edge pattern that blocks the uncured film material. Therefore, the thin film material diffuses to reach an equilibrium state according to the wettability with the substrate on the boundary line 63 of the unit scanning area 56.

[0086] FIG. 4G shows a plan view of the substrate 50 and the nozzle unit 23 before and after the fourth scan. Fig. 4H shows a cross-sectional view taken along the chain line 4H-4H in Fig. 4G. After the third scan, the substrate 50 is moved in the positive direction of the X axis by only the unit scan area 56 ( image 3 ) The width W is equal to the distance. The fourth scan is performed by moving the substrate 50 in the positive direction of the Y axis in this state. The fourth scan is the same as the third scan, and the droplets of the thin film material are landed on the thin film pattern 55 ( image 3 ) Inside the area. A planar pattern 64 having the edge pattern 60 formed in the first scan as an edge is formed. Ultraviolet light source 25 in the fourth scan ( Figure 5 B) It is also closed. Therefore, the planar pattern 64 remains uncured.

[0087] Since the planar pattern 62 formed in the third scan and the planar pattern 64 formed in the fourth scan are both in an uncured state, the thin film materials are mixed with each other near the boundary between the two. Therefore, the boundary line 63 of the unit scanning area 56 becomes almost unrecognizable.

[0088] FIG. 4I shows a plan view of the substrate 50 and the nozzle unit 23 before and after the fifth scan. Fig. 4J shows a cross-sectional view of the one-dot chain line 4J-4J in Fig. 4I. Figure 5 C shows a cross-sectional view of the one-dot chain line 5C-5C in FIG. 4I. After the fourth scan, the fifth scan is performed by moving the substrate 50 in the negative direction of the Y axis. In the 5th scan, the nozzle head 24 ( Figure 5 C) The droplets of the thin film material are discharged, and the ultraviolet light is irradiated only through the ultraviolet light source 25. The planar pattern 64 in the uncured state is temporarily cured by ultraviolet irradiation. In Figure 4I, dense hatching is added to the temporarily cured area, and sparse hatching is added to the uncured area. The same applies to other drawings shown later.

[0089] 4K shows a plan view of the substrate 50 and the nozzle unit 23 before and after the sixth scan. Fig. 4L shows a cross-sectional view of the one-dot chain line 4L-4L in Fig. 4K. After the fifth scan, the substrate 50 is moved in the negative direction of the X axis by only the unit scan area 56 ( image 3 ) The width W is equal to the distance. The sixth scan is performed by moving the substrate 50 in the positive direction of the Y axis in this state. The nozzle head 24 ( Figure 5 C) The droplets of the thin film material are discharged, and the ultraviolet light is irradiated only through the ultraviolet light source 25. The planar pattern 62 in the uncured state is temporarily cured by ultraviolet irradiation.

[0090] reference Image 6 A and Image 6 B describes the effect of the thin film forming method of Example 1. Image 6 A and Image 6 In B, cross-sectional views of thin film patterns formed by the methods of Comparative Example and Example 1 are respectively shown.

[0091] Image 6 In the comparative example shown in A, the film pattern 55 ( image 3 ) On the edges and inside to form a film pattern. When scanning the substrate 50, the ultraviolet light source 25 is turned on in advance ( figure 2 A. figure 2 B), the film material is temporarily cured immediately after the film material falls. Such as figure 2 A and figure 2 As shown in B, the ultraviolet light source 25 is arranged between the nozzle heads 24. Therefore, after the droplets of the thin film material discharged from one nozzle head 24 land on the substrate 50, before the droplets of the thin film material discharged from the next nozzle head 24 land on the substrate 50, the deposited thin film material is temporarily solidified.

[0092] Therefore, from the nozzle hole 24a ( figure 2 A. figure 2 B) The discharged droplets 55a of the thin film material overlap each other in a distinguishable state. Concavities and convexities are formed on the surface of the thin film pattern 55 corresponding to the respective droplets 55a. The unevenness can be regarded as a band-shaped pattern extending in the Y direction.

[0093] Such as Image 6 As shown in B, in the method of Embodiment 1, the edge patterns 60 and 61 are formed on the edges of the thin film pattern 55, and the planar patterns 62 and 64 are formed inside the thin film pattern 55. The film materials that make up the edge patterns 60 and 61 and Image 6 The same is true in the case of A, and the droplets 55a overlap each other in a distinguishable state. That is, on the thin film material that has landed on the substrate 50 and has been temporarily cured, other droplets are landed in a partially overlapping manner, and temporarily cured. Therefore, it is possible to obtain the edge patterns 60 and 61 that are higher than the height of the thin film material formed by temporarily curing one droplet. However, the planar patterns 62 and 64 are formed by spreading a plurality of droplets of thin film material in the in-plane direction of the substrate to form a film (FIG. 4G) having a substantially uniform thickness, and then temporarily curing (FIG. 4I and FIG. 4K ). Therefore, the surfaces of the planar patterns 62 and 64 become substantially flat.

[0094] In order to make the surface of the planar patterns 62 and 64 flat, it is preferable that in the step of FIG. 4E, the thin film material landing on the substrate spreads in the direction of the substrate surface, and the thin film materials landing on multiple landing points are continuous, making it impossible to distinguish each other. After the adjacent landing points, in the step of FIG. 4K, the thin film material of the planar pattern 62 is cured.

[0095] In Embodiment 1, as shown in FIGS. 4A and 4B, through one single pass scan, a scan area 56 ( image 3 The edge regions of the film pattern 55 in) form edge patterns 60 and 61. The deviation in the X direction is equivalent to the pitch P ( figure 2 B) 1/2 of the distance, and by scanning back and forth, the resolution in the X direction can be increased to 2 times.

[0096] In the step of forming the planar pattern 62 shown in FIG. 4E and the step of forming the planar pattern 64 shown in FIG. 4G, it is not necessary to make the droplets of the thin film material land on the fullness of the image data in the raster format defining the thin film pattern 55 All pixels in the cloth area. As an example, the arrangement pitch of the pixels is about 10 μm, and a circular pattern with a diameter of about 50 μm is formed by droplets that land on one pixel. Therefore, the impact points can be extracted by spacing pixels in the area. That is, the distribution density of the impact points when the planar patterns 62 and 64 are formed can be made lower than the distribution density of the impact points when the edge patterns 60 and 61 are formed. In addition, the distribution density of the impact points when the planar patterns 62 and 64 are formed can be further reduced, and the discharge from the nozzle hole 24a per discharge can also be increased ( figure 2 A) The droplet volume. By increasing the volume of the droplet, even if the distribution density of the impact point is reduced, the planar patterns 62 and 64 can be set to a desired thickness.

[0097] [Example 2]

[0098] Next, referring to FIGS. 7A to 7E, the thin film forming method of Example 2 will be described. Hereinafter, the differences from Embodiment 1 will be described, and the description of the same structure will be omitted. Through the first scan, the edge pattern 60 shown in FIG. 4A of Example 1 is formed.

[0099] FIG. 7A shows a plan view of the substrate 50 and the nozzle unit 23 before and after the second scan. After the first scan, the substrate 50 is moved in the positive direction of the Y axis to perform the second scan. In the second scan, in the unit scan area 56 where the edge pattern 60 is formed ( image 3 ) In the same unit scanning area 56, an uncured planar pattern 64 is formed.

[0100] FIG. 7B shows a plan view of the substrate 50 and the nozzle unit 23 before and after the third scan. After the second scan, the third scan is performed by moving the substrate 50 in the negative direction of the Y axis without deviating in the X direction. In the third scan, droplets of the thin film material are not ejected from the nozzle unit 23, and only the ultraviolet light source 25 ( figure 2 A. figure 2 B) Irradiation of ultraviolet rays. Thus, the planar pattern 64 is temporarily cured.

[0101] FIG. 7C shows a plan view of the substrate 50 and the nozzle unit 23 before and after the fourth scan. After the third scan, make the substrate 50 deviate from the unit scan area 56 ( image 3 ) The width W is equal to the distance. After that, the fourth scan is performed by moving the substrate 50 in the positive direction of the Y axis. In the fourth scan, the unit scan area 56 (with the edge pattern 60 and the planar pattern 64 formed in the first to third scans) image 3 ) In the adjacent unit scanning area 56, an edge pattern 61 corresponding to the edge of the thin film pattern 55 is formed. The edge pattern 61 is temporarily cured during the 4th scan.

[0102] As shown in FIG. 7D, by performing the fifth scan, an uncured planar pattern 62 is formed. As shown in FIG. 7E, the planar pattern 62 is temporarily cured by performing the sixth scan. The steps of FIGS. 7D and 7E are the same as the steps of forming the planar pattern 64 shown in FIGS. 7A and 7B.

[0103] In Example 1, the film pattern 55 ( image 3 After forming the edge patterns 60 and 61 (FIGS. 4A to 4D) at the edges of ), the planar patterns 62 and 64 are formed (FIGS. 4E to 4L ). In the second embodiment, one unit scanning area 56 ( image 3 After the edge pattern and planar pattern in ), the edge pattern and planar pattern in the unit scanning area 56 on the side are formed. In Example 2, as in the case of Example 1, the surfaces of the planar patterns 62 and 64 became flat.

[0104] In Example 2, after temporarily curing the planar pattern 64 (FIG. 7B ), the planar pattern 62 in the unit scanning area 56 on the side (FIG. 7D) is formed. Therefore, compared with Example 1, it becomes easier to observe the boundary line 63 of the unit scanning area 56 (FIG. 7E ). However, a large number of band-shaped patterns corresponding to the number of nozzle holes 24a cannot be observed.

[0105] [Example 3]

[0106] With reference to FIGS. 8A to 8D, the thin film forming method of Example 3 will be described. Hereinafter, the differences from Embodiment 2 will be described, and the description of the same structure will be omitted. The nozzle unit 23 of the thin film forming apparatus used in Example 2 ( figure 2 A) Including 4 nozzle heads 24. The nozzle unit 23 of the thin film forming apparatus used in Example 3 includes eight nozzle heads 24.

[0107] FIG. 8A shows a plan view of the substrate 50 and the nozzle unit 23 before and after the first scan. The nozzle unit 23 is composed of two subunits 23A and 23B. The respective structures of the subunits 23A and 23B are the same as those of the nozzle unit 23 ( figure 2 A) The structure is the same. The subunits 23A and 23B are arranged at a certain interval in the Y direction. The subunit 23A is arranged on the positive side of the Y axis than the subunit 23B.

[0108] The first scan is performed by moving the substrate 50 in the negative direction of the Y axis. In the first scan, the edge pattern 60 is formed by the subunit 23A. The ultraviolet light source 25 of the subunit 23A is turned on in advance. Therefore, the formed edge pattern 60 becomes a temporarily cured state.

[0109] During the first scan, the subunit 23B is further used to form the planar pattern 64. The ultraviolet light source 25 of the subunit 23B is turned off in advance. Therefore, the formed planar pattern 64 is in an uncured state. After the edge pattern 60 is temporarily cured, the thin film material for forming the planar pattern 64 is discharged from the sub-unit 23B. Since the edge pattern 60 blocks the thin film material discharged from the subunit 23B, the thin film material does not penetrate into the opening.

[0110] FIG. 8B shows a plan view of the substrate 50 and the nozzle unit 23 before and after the second scan. After the first scan, the substrate 50 is moved in the positive direction of the Y axis without deviating in the X direction, so that the second scan is performed. In the second scan, the ultraviolet light source 25 of at least one of the subunits 23A and 23B is turned on in advance. Thus, the planar pattern 64 is temporarily cured.

[0111] As shown in FIG. 8C, after the second scan, the substrate 50 is moved in the negative direction of the X-axis only by the unit scan area 56 ( image 3 ) The width W is equal to the distance. By performing the third scan in this state, the temporarily cured edge pattern 61 and the uncured planar pattern 62 are formed. The third scan is the same as the first scan shown in FIG. 8A.

[0112] As shown in FIG. 8D, the fourth scan is performed in the same manner as the second scan shown in FIG. 8B. Through the fourth scan, the planar pattern 62 is temporarily cured.

[0113] In the second embodiment, the scanning area 56 ( image 3 ) To form a thin film pattern. In the third embodiment, it is possible to scan the area 56 ( image 3 ) To form a thin film pattern.