JP4439675B2 - Substrate bonding method for optical element substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate bonding how the optical element substrate.
[0002]
[Prior art]
Conventional direct bonding techniques between substrates are actively studied as a process of forming an SOI substrate in which a semiconductor layer is formed on a semiconductor substrate via an insulating layer. Conventionally, in the bonding process of semiconductor substrates, in order to prevent bubbles from entering the bonding interface between two semiconductor substrates, the first semiconductor substrate or both the first semiconductor substrate and the second semiconductor substrate are centered. Generally, a method is adopted in which vacuum suction is performed on a semiconductor substrate support having a taper or curvature so as to be convex, and bonding is advanced from the central portion of the semiconductor substrate toward the outer periphery.
[0003]
As such a method, there is a method disclosed in Japanese Patent Publication No. 5-60250. In this method, mirror-polished semiconductor substrates are directly bonded to each other under a clean condition. As shown in FIG. 18, a bonding method in which one substrate is bent from the center and bonded from the center, and one substrate is protruded. Means for joining jigs to warp are disclosed. According to this, there is a technique in which one semiconductor substrate is warped in a convex shape according to the shape of the jig by vacuum suction, and bonding is started from the center portion, so that no bubbles remain at the bonding interface. It is taken.
[0004]
Further, as a method of directly joining two semiconductor substrates, there is a method disclosed in Japanese Patent Laid-Open No. 5-152549 shown in FIG. In this method, when two semiconductor substrates are bonded, a portion near the OF (orientation flat) near the bonding surface is adsorbed by vacuum tweezers, and the bonded surface of the OF portion of the semiconductor substrate adsorbed by the vacuum tweezers The edge on the side is lightly brought into contact, and at that time, the distance between the joining surfaces of the ends located on the opposite side of the OF portions of both semiconductor substrates is set to 1 mm or less, and then the semiconductor substrate is adsorbed by vacuum tweezers. In this bonding method, the state is released and the semiconductor substrate is brought into contact. Also by this method, it is possible to join the bonding interface without remaining bubbles.
[0005]
As a method of joining from the peripheral portion, there is a method disclosed in Japanese Patent Laid-Open No. 7-6937 shown in FIG. When bonding is started from the periphery due to the original warpage state or surface state distribution of the semiconductor substrate, a difference in spreading speed of the bonded portion becomes a problem. Due to the difference in spreading speed of the bonded part, the fast part entrains the slow part, and bubbles remain in the bonded part. For this reason, in Japanese Patent Application Laid-Open No. 7-6937, means for pressurizing from the periphery and means for actively controlling the distance between the two semiconductor substrates on the opposite side to the pressurization start position in accordance with the movement of the pressurizing means. Is disclosed. According to this method, bonding from the peripheral part is performed under pressure, and the distance between the substrates on the opposite side is controlled in accordance with the movement of the pressing means, so that it is possible to actively control the expansion of the bonding region. Therefore, the reliability of the joining process can be increased.
[0006]
As a method for aligning the substrates to be joined, there is a method disclosed in Japanese Patent Laid-Open No. 5-218181 shown in FIG. According to this method, the substrate in which the orientation flat is in contact with the two pins tries to slide while evenly contacting the two pins due to the inclination of the two pins with respect to the horizontal. This is stopped by a third pin for positioning.
[0007]
[Problems to be solved by the invention]
By the way, in joining the substrates, it is important that the surfaces of the substrates are polished to a mirror surface and cleaned, and both surfaces are brought into contact with each other in a state in which no bubbles remain. Of course, if particles or the like enter between the substrates, it may cause a bonding failure. Therefore, it is necessary to avoid particles or the like from entering between the substrates as much as possible.
On the other hand, the substrate surface is generally cleaned before the substrates are directly bonded. In order to avoid intrusion of particles, etc. and adhesion to the surface in the transition process from the cleaning process to the bonding process, the atmosphere in which the work is performed must be in a particle-free state. Making it smaller is a realistic measure. Furthermore, even in an advanced clean room, if an operator is involved, the operator himself becomes a source of particles and the like. Therefore, a large amount of capital investment is required to realize the atmosphere, for example, by implementing automation other than an advanced clean room to realize an environment in which workers are not accessible.
However, in Japanese Patent Publication No. 5-60250 and Japanese Patent Application Laid-Open No. 5-152549 described as the prior art, the main problem is not to leave bubbles at the bonding interface, such as particles in the process from the cleaning process to the bonding. No problem has been dealt with regarding the problem of penetration into the bonding interface or adhesion to the bonding surface.
Further, the substrate gap control means described in Japanese Patent Application Laid-Open No. 7-6937 or the positioning means described in Japanese Patent Application Laid-Open No. 5-218181 described as the prior art is not always satisfactory.
[0008]
The present invention is aimed at the solve the problems in the conventional ones, the yield by the low cost of equipment to provide a very substrate bonding how good optical element substrate.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a substrate bonding method for an optical element substrate configured as described in the following (1) to ( 6 ).
(1) In the substrate bonding method for an optical element substrate in which the surfaces of the substrates to be bonded to each other are cleaned in the cleaning process, and then the substrates are bonded in the bonding process.
In order to hold the surfaces of the substrates to be bonded facing each other at a constant interval to reduce particle intrusion and adhesion, from the cleaning step to the start of bonding in the bonding step ,
The surface of the substrate to be bonded is cleaned by holding the cleaning jig substantially in parallel with the particles facing each other at a certain interval to reduce the ingress and adhesion of the particles, and
A process of mounting on a joining jig in a state of being held in the cleaning jig;
Substrate bonding method characterized by having a.
( 2 ) After the washing step,
A drying step of drying the substrate while being held in the cleaning jig;
After passing through the drying step, the step of mounting on the joining jig in a state of being held in the cleaning jig,
Substrate bonding method according to the above (1), wherein the performing.
( 3 ) After the step of mounting on the joining jig,
After inserting another member into the space around the substrate held by the cleaning jig, removing the cleaning jig and bringing both substrates close to each other;
Wherein after brought close to both substrates, and performing bonding than the central portion by applying a force to the center of the substrate,
After bonding from the center, removing the separate member and bonding the entire surface of the substrate;
The method for bonding substrates according to ( 1 ) or ( 2 ) above, wherein:
( 4 ) After the step of mounting on the joining jig,
After inserting another member into the space around the substrate held by the cleaning jig, removing the cleaning jig and bringing both substrates close to each other;
A step of aligning the substrates after bringing both the substrates close together;
After aligning the substrate, applying a force to the center of the substrate and joining from the center; and
After the central portion of the substrate is bonded, removing the separate member and bonding the entire surface of the substrate;
The method for bonding substrates according to ( 1 ) or ( 2 ) above, wherein:
( 5 ) The substrate bonding method according to ( 4 ), wherein the step of aligning the substrates is performed by butting two points.
( 6 ) The substrate bonding method according to any one of ( 3 ) to ( 5 ), wherein the separate member is at least two or more plate-like members.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment of the present invention, by applying the above configuration and optimizing the joining process including the cleaning process, it is possible to achieve a joining method and jig that do not require a high working atmosphere, and particles Therefore, it is possible to solve the conventional problem that has been a problem of the cost of environmental maintenance. In other words, by holding the substrate surfaces to be bonded facing each other at regular intervals from the cleaning process to the start of bonding, the probability of intrusion of particles and the like and the probability of adhesion to the bonded surface after cleaning are reduced. Is possible.
In addition, by applying the above configuration, both the cleaning jig and the joining jig are optimally designed, and the two can work together without interfering with each other. Can be realized.
[0011]
【Example】
Hereinafter, a description will be given to an embodiment of the present invention, but the present invention is in no way limited by these examples.
[Example 1]
1 to 7 show a configuration according to Embodiment 1 of the present invention. FIG. 1 is a view showing a state where a substrate is held by a cleaning jig, and FIG. 2 is a side view of FIG.
In FIG. 1, 1 is a glass substrate A, 2 is a glass substrate B, 3 is a cleaning jig A, and 4 is a cleaning jig B.
In FIG. 3, reference numeral 6 denotes a joining jig, the parts constituting the joining jig are 7 a substrate mounting slope, 8 a substrate positioning pin, 9 a blade, 10 a joining start arm, and 11 a pressing point.
In FIG. 6, 12 is a guide pin, 13 is a spring, and 14 is a spring stopper.
In FIG. 7, reference numeral 15 denotes a spin dryer chuck.
[0012]
The cleaning jig is composed of two members, the cleaning jig A of 3 and the cleaning jig B of 4. The arm formed at the fork of the cleaning jig A of 3 and the arm formed on the cleaning jig B of 4 The glass substrate is held at three points, and projections are provided on the three arm portions to prevent the substrate from moving. In addition, the protrusions between the two substrates prevent the substrates from contacting each other. The above-mentioned 3 cleaning jigs A and 4 above-mentioned cleaning jigs B are movable, and can be fixed after holding the substrate by a fixing mechanism (not shown).
[0013]
Next, cleaning of the substrate will be described. The cleaning jig maintains a state in which the substrate is brought close to and opposed at a constant interval even during the cleaning process. Cleaning is more effective when laminar flow is caused such that the cleaning liquid flows along the substrate surface by oscillating ultrasonic cleaning or a cleaning jig.
[0014]
At the end of the washing process, running water was washed with pure water. The substrate that has been cleaned is dried by a spin dryer. At this time, as shown in FIG. 7, the chuck of the spin dryer has a shape in which the arm portions in the three directions of the cleaning jig can be fitted. The substrate is set on the chuck of the spin dryer together with the cleaning jig, and moisture is removed by rotating the chuck.
[0015]
As shown in FIG. 3, the bonding jig has an inclined surface on which the substrate is mounted.
The surface on which the substrate is mounted is mirror polished by the substrate mounting slope 7. There are substrate positioning pins 8 for fixing the substrate mounted on the slope. The substrate after the spin drying is mounted on the joining jig while being held by the cleaning jig.
[0016]
Here, FIG. 4 shows a mounted state. Although not shown in FIG. 4, the blades 9 positioned on both sides of the substrate mounting slope 7 are inserted between the substrates as shown in FIG. 3 while the substrate is held by the cleaning jig. As shown in FIG. 6, the blade 9 can rotate around the pin 12, and has a structure in which the blade 9 is in close contact with the substrate by a spring 13. Further, the blade 9 has a structure that stops against the lower substrate due to its shape.
[0017]
Only after the blade 9 is inserted is the cleaning jig removed. The lower substrate is supported by the substrate mounting slope 7 and the upper substrate is supported by a blade inserted between the lower substrate and the lower substrate. Further, since the substrate mounting slope 7 is inclined, the substrate tends to slide due to gravity. The substrate is also supported by substrate positioning pins 8 arranged below the substrate mounting slope 7. Further, the substrate is positioned by abutting against the substrate positioning pins 8 using a force with which the substrate slides due to gravity. FIG. 5 shows this state observed from the direction perpendicular to the substrate surface.
[0018]
Each glass substrate to be bonded is processed within tolerances. The substrate abutted against the substrate positioning pin 8 is supported with the center coincident within a negligible error.
Subsequently, when the joining start arm 10 is lowered and the central portion of the substrate is pressurized by the pressurizing point 11, the joining is started from the central portion of the substrate. Joining is completed except for the part where the blade 9 is inserted in three places. When the blade 9 is removed from this state, the joining region spreads over the entire surface and joining is completed.
[0019]
In our experiment, a 250 μm blade was used on a substrate with a diameter of 200 mm and a thickness of 0.95 mmt, and it was possible to bond well. When the substrate is thick, the amount of deflection generated even with the same pressure is reduced. In this case, it is desirable that the blade is thinner. For a substrate having a diameter of 200 mm and a thickness of about 1 mmt, deformation due to its own weight is expected to be about 10 μm. Therefore, if the blade thickness is larger than the amount of deformation of its own weight, the substrates can be brought close to each other without being joined against the will.
[0020]
In this embodiment, the glass substrate can be bonded with a high yield by using a cleaning jig that can clean the substrates to be bonded while facing and close to each other and a bonding jig that can be mounted while being held by the jig. In addition, by using the abutting alignment method using two pins, it was possible to achieve good alignment accuracy in a simple manner. In addition, by adopting a simple structure alignment method such as the abutment method, it is easy to mount a jig that holds the substrate in a state of facing the substrate consistently from cleaning to the bonding jig while holding the substrate. became.
[0021]
[Example 2]
8 and 9 show a configuration according to the second embodiment. In FIG. 8, 16 is a rectangular substrate cleaning jig A, 17 is a rectangular substrate cleaning jig B, and 18 is a rectangular substrate.
Both substrates to be joined are square. The cleaning jig was contacted at four points so that the substrate could be held securely. The blades 9 were installed at four locations. FIG. 9 is a diagram showing a state where the substrate is mounted on the slope where the substrate is installed as in the first embodiment. The both-type substrates are positioned by contacting the substrate positioning pins 8. The steps before and after joining are the same as those in Example 1.
[0022]
[Example 3]
FIG. 10 shows a configuration according to the third embodiment. FIG. 10 is a diagram in which each ABC looks at the cleaning jig from each direction, and in particular, C shows a cross section of only the cleaning jig for explanation. In the figure, 19 is a cleaning jig C, 20 and 21 are first and second substrates, 22 and 23 are substrate chucks, and 33 is an opening.
[0023]
In the cleaning jig of Example 3, a part to be a frame of the jig is formed on the outer periphery of the substrate. Since the hinge is configured, the jig is split into two when holding and releasing the substrate. In addition, an opening 33 is formed on the side surface so as to sufficiently wrap around the surface to which the chemical solution is bonded during cleaning. When it is considered that bubbles or the like remain when the substrate is put into the chemical solution in the cleaning process and the chemical solution is not sufficiently circulated, a jig having the shape shown in FIG. 17 may be used.
[0024]
The feature of the cleaning jig of Example 3 is that the surface opposite to the surface to be joined is largely exposed. Thereby, the joining method shown in FIG. 11 can be performed. In FIG. 11, the substrate chucks 22 and 23 are arranged from the upper and lower surfaces. The substrate chuck 22 is a flat substrate chuck having a convex shape so that the substrate chuck 23 deforms the central portion into a convex shape. In order to exaggerate in the figure, the radius of curvature is considerably smaller than the actual one, but in reality, even with a substrate having a diameter of 200 mm, the protruding amount of the convex shape is several tens of μm at the center with respect to the periphery of the substrate. After being supported from both sides by both chucks, the cleaning jig is removed. Thereafter, when both substrates are brought close to each other, the substrate chuck 23 causes the central portion to be convex and the lower substrate is warped, so that bonding is performed from the central portion (FIG. 12). If the suction of the substrate chuck 23 is gradually released after the central portion is bonded, the bonding region is spread over the entire surface and the bonding process is completed.
[0025]
[Example 4]
13 and 14 show a configuration according to the fourth embodiment. Reference numeral 24 in FIG. 13 denotes an adsorption site of the vacuum tweezers, reference numeral 25 in FIG. 14 denotes vacuum tweezers, and reference numerals 26 and 27 denote arms that support the vacuum tweezers. Reference numeral 28 denotes a structure that supports the arms and also serves as a guide for controlling movement.
The substrate is cleaned using the same cleaning jig as in Example 1. Then, the state which mounted the board | substrate on the joining jig is FIG. Here, the cleaning jig is rotated 90 degrees as compared with the first embodiment, which indicates that the mounting direction of the cleaning jig may be any. Here, an area indicated by 24 in FIG. 13 indicates the suction site of the vacuum tweezers shown in FIG. After the substrate is mounted on the joining jig and adsorbed by the vacuum tweezers 25, the cleaning jig is removed. Here, when the arm 26 supporting the vacuum tweezers 25 is raised, the upper substrate is slightly inclined with respect to the lower substrate.
[0026]
The figure is exaggerated for easy understanding. The inclination here is an angle uniquely determined by the arm 27 supporting the arm 26 having a stopper structure. The arm 27 is guided to the support portion 28 and can move downward. When the arm 27 moves downward, the arm 26 and the substrate move along with it, and bonding is started from the vicinity near the place where the vacuum tweezers attracted. If the negative pressure of the vacuum tweezers is gradually released after the bonding is started, the bonding region is spread over the entire surface by its own weight, and the bonding process is completed.
[0027]
[Example 5]
15 and 16 show a configuration according to the fifth embodiment. In FIG. 15 and FIG. 1, 29 is a structure for positioning the substrate, 30 is an elastic body, and 31 is a support pin on a joining jig that supports the first substrate. The substrate is cleaned / dried by the same cleaning jig as in the first embodiment. Then, although mounted on a joining jig, the board | substrate installation surface of the joining jig of a present Example is horizontal. A blade 29 and a substrate positioning structure 29 are provided at positions at which the outer peripheral portion is evenly distributed. Here, the first substrate is configured to be supported by three support pins provided on the substrate installation surface. However, the first support is provided via concentric annular protrusions provided on the plate installation surface. The substrate may be supported.
[0028]
The substrate positioning structure 29 is shown in FIG. 16, and has a mechanism for introducing air pressure. The introduced gas pressure causes the elastic body 30 to expand. At the point where the elastic body swells, there is a first substrate supported by the support pins 31 and a second substrate spaced by a blade. The substrate 29 has a common pressure supply source so that the gas pressure is equal at three locations. Thus, the centers of the two substrates pressed by the elastic body from three sides coincide with each other within an error determined by the processing accuracy of the original diameter.
[0029]
[Example 6]
When the optical element was bonded using the cleaning and bonding process of the present application, good bonding was realized.
The optical element is a diffractive optical element, which is manufactured using semiconductor lithography on a transparent substrate having a thickness of less than 1 mmt. Although the diffractive optical element has a thickness of 1 mmt and a size of a little over 200 mm in diameter, deformation due to its own weight or holding has occurred. Such deformation is a problem because it leads to performance degradation of the optical system.
However, the strength could be increased by carrying out the cleaning process and bonding process of the present application, and bonding to a transparent substrate having a thickness of 15 mm. Therefore, problems such as deformation are not generated.
Furthermore, when the diffractive optical element of this example was mounted on an optical system of a semiconductor exposure apparatus, good optical characteristics could be exhibited.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible yield is achieved a very substrate bonding how good optical device substrate by a low equipment cost.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining Example 1 of the present invention.
FIG. 2 is a diagram for explaining Example 1 of the present invention.
FIG. 3 is a diagram for explaining Example 1 of the present invention.
FIG. 4 is a diagram for explaining a work process according to the first embodiment of the present invention.
FIG. 5 is a diagram for explaining a work process according to the first embodiment of the present invention.
FIG. 6 is a diagram for explaining a work process according to the first embodiment of the present invention.
FIG. 7 is a diagram for explaining a work process according to the first embodiment of the present invention.
FIG. 8 is a diagram for explaining the configuration of a second embodiment of the present invention.
FIG. 9 is a diagram for explaining the configuration of a second embodiment of the present invention.
FIG. 10 is a diagram for explaining the configuration of a third embodiment of the present invention.
FIG. 11 is a diagram for explaining a work process according to a third embodiment of the present invention.
FIG. 12 is a diagram for explaining a work process according to a third embodiment of the present invention.
FIG. 13 is a diagram for explaining the configuration of a fourth embodiment of the present invention.
FIG. 14 is a diagram for explaining the configuration of a fourth embodiment of the present invention.
FIG. 15 is a diagram for explaining the configuration of a fifth embodiment of the present invention.
FIG. 16 is a diagram for explaining the configuration of a fifth embodiment of the present invention.
FIG. 17 is a diagram for explaining the configuration of a third embodiment of the present invention.
FIG. 18 is a diagram for explaining a method of bonding substrates in a conventional example.
FIG. 19 is a diagram for explaining a method of bonding substrates in a conventional example.
FIG. 20 is a diagram for explaining a method of bonding substrates in a conventional example.
FIG. 21 is a diagram for explaining a substrate alignment method in a conventional example.
[Explanation of symbols]
1: Substrate A
2: Substrate B
3: Cleaning jig A
4: Cleaning jig B
6: Joining jig 7: Board mounting slope 8: Board positioning pin 9: Blade 10: Joining start arm 11: Pressing point 12: Guide pin 13: Spring 14: Spring stopper 15: Chuck of spin dryer 16: For rectangular board Cleaning jig A
17: Cleaning jig B for rectangular substrate
18: Rectangular substrate 19: Cleaning jig C
20: First substrate 21: Second substrate 22, 23: Substrate chuck 24: Vacuum tweezer suction part 25: Vacuum tweezers 26, 27: Arms for supporting vacuum tweezers 28: Support portion 29: Substrate positioning 30: Elastic body 31: Support pin 32: Cleaning jig 33: Opening

Claims (6)

In the substrate bonding method of an optical element substrate in which the surfaces of the substrates to be bonded to each other are cleaned in the cleaning process, and then the substrates are bonded in the bonding process.
In order to hold the surfaces of the substrates to be bonded facing each other at a constant interval to reduce particle intrusion and adhesion, from the cleaning step to the start of bonding in the bonding step ,
The surface of the substrate to be bonded is cleaned by holding the cleaning jig substantially in parallel with the particles facing each other at a certain interval to reduce the ingress and adhesion of the particles, and
A process of mounting on a joining jig in a state of being held in the cleaning jig;
Substrate bonding method characterized by having a. After the washing step,
A drying step of drying the substrate while being held in the cleaning jig;
After passing through the drying step, the step of mounting on the joining jig in a state of being held in the cleaning jig,
Substrate bonding method according to claim 1, wherein the performing. After the step of mounting on the joining jig,
After inserting another member into the space around the substrate held by the cleaning jig, removing the cleaning jig and bringing both substrates close to each other;
Wherein after brought close to both substrates, and performing bonding than the central portion by applying a force to the center of the substrate,
After bonding from the center, removing the separate member and bonding the entire surface of the substrate;
Substrate bonding method according to claim 1 or claim 2, wherein the performing. After the step of mounting on the joining jig,
After inserting another member into the space around the substrate held by the cleaning jig, removing the cleaning jig and bringing both substrates close to each other;
A step of aligning the substrates after bringing both the substrates close together;
After aligning the substrate, applying a force to the center of the substrate and joining from the center; and
After the central portion of the substrate is bonded, removing the separate member and bonding the entire surface of the substrate;
Substrate bonding method according to claim 1 or claim 2, wherein the performing. The substrate bonding method according to claim 4 , wherein the step of aligning the substrates is performed by abutment of two points. The substrate joining method according to claim 3, wherein the separate member is at least two or more plate-like members.

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