Patent Application
20190029496
The present invention relates to a method for manufacturing an optical unit for endoscope in which a plurality of devices are laminated, and an endoscope including the optical unit for endoscope in a rigid distal end portion.
It is important for an optical unit for endoscope arranged in a rigid distal end portion of an endoscope to be downsized for minimization of invasiveness. For example, an area of a light incident surface is several mm2 or smaller, and an area of a very small light incident surface is 1 mm2 or smaller. As a method for manufacturing an extremely small optical unit, there is a method in which a bonded wafer is fabricated by laminating a plurality of device wafers each of which includes a plurality of optical elements, and the bonded wafer is cut and divided. The bonded wafer is cut, for example, after being adhesively fixed to a dicing tape.
Note that the optical unit manufacturing method described above is similar to a multi-memory module manufacturing method disclosed in Japanese Patent Application Laid-Open Publication No. 2014-71932.
In the case of the optical unit with a light incident surface area of several mm2 or smaller, especially in the case of the optical unit with a light incident surface area of 1 mm2 or smaller, an area of being adhesively fixed to a dicing tape is also a very small area of several mm2 or smaller, especially, 1 mm2 or smaller. Therefore, it is not easy to sufficiently fix the optical unit.
A method for manufacturing optical units for endoscope of an embodiment of the present invention includes: a step of fabricating a plurality of device wafers including at least one optical element wafer, each of the plurality of device wafers including a plurality of devices; a step of laminating the plurality of device wafers to fabricate a bonded wafer; a first fixation step of fixing a main face of the bonded wafer to a first substrate; a first cutting step of cutting the bonded wafer along mutually parallel first cutting lines to divide the bonded wafer into slice bodies; a step of removing the slice bodies from the first substrate; a second fixation step of fixing cutting surfaces of the slice bodies to a second substrate; a second cutting step of cutting the slice bodies along mutually parallel second cutting lines orthogonal to the first cutting lines to divide the slice bodies into the optical units for endoscope; and a step of removing the optical units for endoscope from the second substrate; and an area of a side face of each of the optical units for endoscope is larger than an area of a light incident surface, the side face being fixed to the second substrate and being orthogonal to the light incident surface.
An endoscope of an embodiment of the present invention includes an optical unit for endoscope in a rigid distal end portion of an insertion portion; the optical unit for endoscope is manufactured by a manufacturing method including: a step of fabricating a plurality of device wafers including at least one optical element wafer, each of the plurality of device wafers including a plurality of devices; a step of laminating the plurality of device wafers to fabricate a bonded wafer; a first fixation step of fixing a main face of the bonded wafer to a first substrate; a first cutting step of cutting the bonded wafer along mutually parallel first cutting lines to divide the bonded wafer into slice bodies; a step of removing the slice bodies from the first substrate; a second fixation step of fixing cutting surfaces of the slice bodies to a second substrate; a second cutting step of cutting the slice bodies along mutually parallel second cutting lines orthogonal to the first cutting lines to divide the slice bodies into the optical units for endoscope; and a step of removing the optical units for endoscope from the second substrate; and an area of a side face of each of the optical units for endoscope is larger than an area of a light incident surface, the side face being fixed to the second substrate and being orthogonal to the light incident surface.
As shown in
Note that all drawings are schematic, and it should be noticed that a relationship between thickness and width of each portion, a thickness ratio among respective portions and the like are different from actual ones; and, among the drawings, portions having a different mutual dimensional relationship or ratio may be included. Further, there may be a case where some components are not shown.
The image pickup unit 1 is configured with a cover glass element 10, an image pickup device (an imager) 20 and semiconductor devices 30, 40, 50 and 60 having same-size cross sections in a direction orthogonal to an optical path (an optical axis O) and being laminated in that order. As described later, the image pickup unit 1 is a wafer-level optical unit fabricated by cutting a bonded wafer in which a plurality of wafers are laminated, and an external form of the image pickup unit 1 is a rectangular parallelepiped.
As shown in
The cover glass element 10 is formed with transparent material that protects an image pickup surface of the image pickup device 20. The image pickup device 20 and the semiconductor devices 30 to 60 are configured with semiconductors such as silicon.
On an image pickup surface 20SA of the image pickup device 20, a light receiving portion 21 such as a CMOS light receiving element, and electrodes 22 connected to the light receiving portion 21 are formed. The electrodes 22 are connected to electrodes on a back face opposite to the image pickup surface 20SA via a through wiring 25. On the image pickup surface 20SA, the cover glass element 10 is attached via transparent adhesive resin 70.
Semiconductor circuits 31 to 61 are formed on the semiconductor devices 30 to 60, respectively. The semiconductor devices 30 to 60 are mutually connected via through wirings 35, 45, 55 and 65. On a back face 60SB of the semiconductor device 60, a bump 66 connected to the through wiring 65 is arranged. The image pickup unit 1 receives and transmits electrical signals via the bump 66.
Among the image pickup device 20 and the semiconductor devices 30 to 60, insulating resin 71 to 74 is filled for mechanical reinforcement and improvement of bonding reliability.
The image pickup unit 1 is in a rectangular parallelepiped shape having a light incident surface 10SA, the back face 60SB and four side faces 10SS1 to 10SS4.
A cross section orthogonal to the optical axis O, for example, the light incident surface 10SA is in a rectangular shape of 0.7 mm×0.5 mm. That is, an area S1 of the light incident surface 10SA is only 0.35 mm2. Note that a height (a dimension in a Z direction) of the image pickup unit 1 is 1.5 mm. Therefore, areas (S2 and S3) of side faces 10SS1 to 10SS4 are S2=1.05 mm2 and S3=0.75 mm2, which are larger than the area S1 (0.35 mm2) of the light incident surface 10SA.
Though the area S1 of the light incident surface 10SA of the image pickup unit 1 is 0.35 mm2 that is smaller than 1 mm2, there is not a possibility that image pickup units 1 which have been cut come off from a dicing tape and are scattered or that it is not possible to cut along a desired cutting line, during cutting, because the image pickup units 1 are manufactured by a manufacturing method to be described later. Therefore, productivity of the image pickup units 1 is high. Note that the present invention is especially effective for such an image pickup unit that the area S1 of the light incident surface 10SA is 1 mm2 or smaller.
Next, a method for manufacturing image pickup units of the embodiment will be described along a flowchart shown in
As shown in
The device wafer 10W is a glass wafer and can be regarded as an optical element wafer that includes a plurality of cover glass elements 10. The device wafer 10W is only required to be transparent in a light wavelength band for image pickup, and, for example, borosilicate glass, quartz glass, or single crystal sapphire is used.
The image pickup wafer 20W includes a plurality of image pickup devices 20, the light receiving portion 21 and the like being formed on each of the plurality of image pickup devices 20 by a well-known semiconductor manufacturing technique. Readout circuits may be formed on the image pickup wafer 20W. On each of the semiconductor wafers 30W to 60W, a plurality of semiconductor circuits are formed by a well-known semiconductor manufacturing technique. On the image pickup devices 20 of the image pickup wafer 20W and the semiconductor devices 30 to 60 of the semiconductor wafers 30W to 60W, respectively, through wirings 25 to 65 are formed, respectively. The through wirings 25 to 65 may be formed after the plurality of device wafers 10W to 60W are laminated in a bonded wafer fabrication process to be described later.
For example, each semiconductor circuit 31 of the semiconductor wafer 30W includes a plurality of thin film capacitors and performs primary processing of an image pickup signal outputted by the light receiving portion 21. Each semiconductor circuit 41 of the semiconductor wafer 40W performs AD conversion processing of the image pickup signal outputted by the semiconductor circuit 31. Each semiconductor circuit 51 of the semiconductor wafer 50W includes a transmission buffer, a resistance and a capacitor. Each semiconductor circuit 61 of the semiconductor wafer 60W includes a timing adjusting circuit. The number of semiconductor wafers, the kind of semiconductor circuit included in each of the semiconductor wafers, and the like are set according to specifications of the image pickup unit 1. The semiconductor circuits may be formed on both faces of each semiconductor wafer, or the semiconductor circuits may be formed on a back face of each semiconductor wafer.
As shown in
Electrical connection among the wafers may be provided by bump electrodes. Otherwise, the wafers may be electrically connected by through wirings after mechanically bonding the respective wafers by direct bonding via insulating films. The respective wafers may be connected by hybrid bonding in which the insulating films and the connection electrodes are collectively connected, via the connection electrodes embedded in the insulating films.
A main face 70SB of the bonded wafer 70W is adhesively fixed to a dicing tape 80 which is a first substrate. Note that the dicing tape 80 is held by a dicing frame 81. The first substrate is not limited to the dicing tape 80 if the bonded wafer 70W can be fixed. The main face 70SA of the bonded wafer 70W may be fixed to the dicing tape 80. Furthermore, instead of adhesive fixation, the bonded wafer 70W may be fixed using wax.
As shown in
The plurality of slice bodies 90 are removed from the dicing tape 80 which is the first substrate. Since the adhesive force of the dicing tape 80 disappears, for example, when the dicing tape 80 is irradiated by ultraviolet rays or heated, the slice bodies 90 can be easily separated from the dicing tape 80.
As shown in
Note that the dicing tape 80 and the dicing tape 80A may be dicing tapes of a same kind or may be different kinds of fixing members.
As shown in
As already described, the area S1 of the light incident surface 10SA of each image pickup unit 1, which is a rectangular parallelepiped, is 0.35 mm2 that is smaller than 1 mm2. However, in the second cutting process, each of the cut image pickup units 1 is fixed to the dicing tape 80A by the side face 10SS1 the area of which is larger than an area of the light incident surface 10SA. That is, the area S2 of the side face 10SS1 is 1.05 mm2, which is three times as large as the area S1.
Since the fixation area is large, during the cutting process the image pickup units 1 which have been cut do not come off from the dicing tape 80A nor are scattered, or it is not possible for the image pickup units 1 not to be cut along a desired cutting line. Therefore, productivity of the image pickup units 1 is high.
Note that in the case of such image pickup units 1 that the area S2 of the side face 10SS orthogonal to the light incident surface 10SA is larger than the area S1 of the light incident surface 10SA, the manufacturing method of the present embodiment has the effects described above. From a viewpoint of productivity, it is preferable that a lower limit of the area S1 of the light incident surface 10SA is, for example, 0.05 mm2 or larger. Note that it is preferable that the area S2 of the side face 1055 is 1.5 times or more larger than the area S1 of the light incident surface 10SA, and it is especially preferable that the area S2 is 2.0 times or more larger. Further, it is preferable that the area S2 of the side face 10SS is more than 1 mm2
Furthermore, the larger the area of the face of each cut image pickup unit 1 fixed to the dicing tape 80A is, the higher the productivity is. Therefore, in a case where the light incident surface 10SA of each of the image pickup units 1 divided by the second cutting process is rectangular, it is preferable that an area of a first side face 10SS1 fixed to the second substrate (the dicing tape 80A) is larger than an area of a second side face 10SS2 orthogonal to the first side face 10SS1.
For example, in each image pickup unit 1, since the area S1 of the side faces 10SS1 and 10SS3 is 1.05 mm2, and the area S2 of the side faces 10SS2 and 10SS4 is 0.75 mm2, it is preferable that the side face 10SS1 or 10SS3, which is the first side face, is fixed to the dicing tape 80A.
The cut image pickup units 1 are removed from the dicing tape 80A which is the second substrate.
Note that it is preferable that, on any of the device wafers, for example, on the device wafer 60W, alignment marks M60 in a configuration almost the same as a configuration of the through wirings 65 are arranged as shown in
The alignment marks M60 are arranged simultaneously with the through wirings 65, and recess portions (through holes) of the device wafer 60W are filled with the same material as material of the through wirings 65, for example, copper. Note that the alignment marks M60 and the through wirings 65 may be different in cross-sectional area and cross-sectional shape.
As shown in
In the slice body 90 shown in
When the alignment marks indicating the positions of the second cutting line C2 are exposed on the cutting surface of the slice body 90, the cutting process is easier. Note that it is sufficient if the alignment marks are arranged on at least one device wafer.
Note that when alignment marks are arranged on each of the plurality of device wafers, the plurality of alignment marks may indicate different positions of the second cutting lines C2 because of lamination errors of the device wafers. In this case, for example, the second cutting process is performed based on average positions or the like of the positions of the second cutting lines C2 indicated by the plurality of alignment marks.
Note that alignment marks are required only to be exposed on the cutting surface of each slice body 90 by the first cutting process and are not required to be penetrated through a device wafer. The alignment marks may be arranged on a surface of a device wafer. A width of the alignment marks may be wider than a width of a cutting margin by the first cutting process, and cutting surfaces of the alignment marks may be exposed on side faces of two slice bodies 90 to be adjoined by cutting.
Next, image pickup units 1A to 1C of modifications of the first embodiment will be described. Since the image pickup units 1A to 1C are similar to the image pickup unit 1 and have the same effects, the same reference numerals will be given to the same components, and description of the components will be omitted.
As shown in
That is, on each slice body 90A the cutting surface 90SA of which is fixed to the second substrate (the dicing tape 80A), the first grooves T90A with an opening width of W1 are formed using a dicing blade 99A with a V-shaped cross section.
Next, as shown in
Since side faces of each image pickup unit 1A are chamfered, and a cross section is hexagonal, a volume is smaller than a volume of the image pickup unit 1, and arrangement into a small space of the rigid distal end portion 9A is easy. Other members can be accommodated in a space of the cutting margin. Therefore, a diameter of the image pickup unit 1A is small.
In a method for manufacturing the image pickup units 1B of a second modification, first, the first grooves T90A are formed on the cutting surface 90SB of each slice body 90A the cutting surface 90SA of which is fixed to the second substrate (the dicing tape 80A) using the dicing blade 99A with a V-shaped cross section as in the case of the image pickup units 1A (same as
Then, the slice body 90A is removed from the second substrate (the dicing tape 80A), and the cutting surface 90SB opposite to the cutting surface 90SA fixed to the second substrate is adhesively fixed to a third substrate (a dicing tape 80B). Then, as shown in
Next, as shown in
All side faces of each image pickup unit 1B are chamfered, and cross sections are octagonal. Therefore, a volume is further smaller than the volume of the image pickup unit 1A, and arrangement into the small space of the rigid distal end portion 9A is easier.
As shown in
Next, as shown in
As shown in
It is easy to accurately arrange the image pickup unit 1C in a long axis direction of another member, for example, the rigid distal end portion 9A with the projecting parts used as a guide.
Since an optical unit for endoscope of a second embodiment is similar to the image pickup units 1 to 1C and has the same effects, the same reference numerals will be given to the same components, and description of the components will be omitted.
The optical unit for endoscope of the second embodiment is a lens unit 2D in which a plurality of optical elements 10D to 50D are laminated.
The lens unit 2D is fabricated by cutting a bonded wafer in which a plurality of device wafers each of which includes a plurality of devices are laminated as in the case of the image pickup unit 1 and the like.
That is, a method for manufacturing the lens units 2D includes: a process of fabricating a plurality of lens device wafers (optical element wafers), each of the plurality of lens device wafers including a plurality of lens devices; a process of laminating the plurality of lens device wafers to fabricate a bonded wafer; a first fixation process of fixing a main face of the bonded wafer to a first substrate; a first cutting process of cutting the bonded wafer along mutually parallel first cutting lines to divide the bonded wafer into slice bodies; a process of removing the plurality of slice bodies from the first substrate; a second fixation process of fixing cutting surfaces of the slice bodies to a second substrate; and a second cutting process of cutting the slice bodies along mutually parallel second cutting lines orthogonal to the first cutting lines to divide the slice bodies into the lens units 2D with a light incident surface area of 1 mm2 or smaller.
The area S2 of the side face 10SS1 of each lens unit 2D fixed to the second substrate 80A is larger than the area S1 of the light incident surface 10SA.
Since the area of fixation of each of the lens units 2D to the second substrate 80A is large, it does not happen during cutting that the lens units 2D which have been cut come off from the dicing tape 80A and are scattered or that it is not possible to cut along a desired cutting line, and, therefore, productivity of the lens units 2D is high.
Furthermore, as shown in
The width W1 of an upper part is wider than the width W2 of a lower part in the cutting margin in the second cutting process. In other words, the area S1 of the side face 10SS1 of the lens unit 2D is larger than the area S3 of the side face 10SS3.
As shown in
Productivity of the lens unit 2D is higher because an area of adhesion to the image pickup substrate 29 is larger. In the image pickup unit 1D in which the lens unit 2D is adhesively fixed to the image pickup substrate 29, it is possible to secure the area of adhesion to the image pickup substrate 29, secure a space in an upward part of the image pickup substrate 29 (a side face part of the lens unit 2D), and enable downsizing of the image pickup unit 1D and downsizing of an endoscope.
Since lens units 2E and 2F of first and second modifications of the second embodiment are similar to the lens unit 2D and have the same effects, the same reference numerals will be given to the same components, and description of the components will be omitted.
As shown in
The light shielding film 95 with a thickness of 10 μm which is, for example, made of metal such as Cr or Ni is coated by a sputtering method or an evaporation method. The light shielding film 95 prevents external light from entering an optical path of the lens unit 2E.
As shown in
Material, a thickness and a coating method of the light shielding film 95 are appropriately selected. Note that instead of the light shielding film 95, an inorganic insulating film of silicon oxide, silicon nitride or the like having a function of a barrier layer against water may be coated on the side faces. Furthermore, the light shielding film 95 and the inorganic insulating film may be coated.
Four side faces of each lens unit 2F of the second modification are covered with the light shielding films 95 (95A and 95B).
As shown in
As shown in
As shown in
Then, as shown in
As shown in
Note that in the image pickup units 1, and 1A to 1C, light shielding films or the like can be coated on the side faces by a method similar to the method for manufacturing the lens units 2E or 2F. Further, in the lens units 2D to 2F, alignment marks can be formed by a method similar to the methods for manufacturing the image pickup units 1A to 1C. The alignment marks can be formed by vapor deposited films having an aperture function, which is formed on the lens device wafers of the lens units 2D to 2F. The alignment marks may be formed by a resin mold for forming a lens device.
It goes without saying that an endoscope provided with any of the image pickup units 1A to 1C or any of the lens units 2D to 2F in a rigid distal end portion of an insertion portion has the same effects as the endoscope 9 and has effects of the respective units.
The present invention is not limited to the embodiments described above, and various modifications, alterations and the like can be made within a range not departing from the spirit of the present invention.
This application is a continuation application of PCT/JP2016/061870 filed on Apr. 13, 2016, the entire contents of which are incorporated herein by this reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2016/061870 | Apr 2016 | US |
| Child | 16151480 | US |
