JP2007109999A - Lamination method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To laminate a wafer with a board for reinforcing without an air bubble included in an adhesive agent. <P>SOLUTION: An underside chuck 11 and an upperside chuck 12 are provided in a processing container 10 so as to face each other. A heater 21 and a coolant flow path 23 are provided to the chuck 11. The chuck 11 is vertically movable with a cylinder 33. An exhaust pipe 90 communicating with a negative-pressure generating device 91 is connected to the processing container 10. At the time of lamination processing, the board S for reinfocing is held by the chuck 11, the wafer W is held by the chuck 12, and a solid-state liquid crystal wax is placed on the board S for reinfocing. The board S for reinfocing is heated by the heater 21 and the liquid crystal wax is melted. The inside of the processing container 10 is depressurized by the exhaust from the exhaust pipe 90 to remove the gaseous matter in the liquid crystal wax. The chuck 11 is lifted to laminate the board S for reinfocing to the wafer W. The liquid crystal wax is cooled and solidified by the coolant flow path 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bonding method in which two substrates are bonded using a hot-melt adhesive.

  In recent years, in the manufacture of semiconductor devices, semiconductor wafers (hereinafter referred to as “wafers”) are becoming larger and thinner. For example, if a thin wafer with a large diameter is transported or polished as it is, the wafer may be warped or cracked. For this reason, for example, in order to reinforce the wafer, the wafer is attached to a reinforcing substrate, for example. Further, in order to reduce the thickness of the wafer, it is necessary to grind the wafer, and it is necessary to attach the wafer to a support substrate.

  For example, the above-described bonding of the wafer and the reinforcing substrate is usually performed using a bonding apparatus. In this bonding apparatus, for example, a wafer and a reinforcing substrate are held so as to be opposed to each other by upper and lower chucks, and for example, liquid crystal wax as a hot-melt adhesive is melted on the wafer by heat. Then, by moving the chuck, the wafer and the reinforcing substrate are pressed together, the liquid crystal wax is spread over the entire surface, and then the liquid crystal wax is cooled and solidified to bond the wafer and the reinforcing substrate (for example, (See Patent Document 1).

JP 2005-51055 A

  However, when the liquid crystal wax is melted as described above, bubbles are generated in the liquid crystal wax, and if the wafer and the reinforcing substrate are bonded together in this state, the adhesion between the wafer and the reinforcing substrate may be reduced. It was. Further, during the heat treatment of the wafer, bubbles in the liquid crystal wax may expand and contract, and the wafer may be damaged. Further, when the wafer is ground with the abrasive, the bubbles are not uniformly ground on the wafer surface, and the wafer may not be flattened properly.

  The present invention has been made in view of the above points. When a hot melt type adhesive such as liquid crystal wax is used to bond two substrates such as a wafer and a reinforcing substrate, the adhesive is included in the adhesive. Its purpose is to prevent bubbles from entering.

  In order to achieve the above object, the present invention is a method of bonding two substrates using a hot-melt adhesive, the step of arranging the two substrates vertically opposite each other, Placing a solid hot-melt adhesive on the substrate, heating and melting the adhesive on the lower substrate, reducing the ambient atmosphere of the molten adhesive, and reducing the pressure Maintaining the two, the step of combining the two substrates sandwiching the melted adhesive, and the step of cooling and solidifying the adhesive between the two substrates, To do.

  According to the present invention, after the adhesive is melted, the ambient atmosphere of the adhesive can be decompressed to remove the bubbles in the adhesive. Therefore, when the two substrates are bonded together, the bubbles are generated in the adhesive. Intrusion can be suppressed. Thereby, two board | substrates can be adhere | attached with high adhesive force. In addition, the substrate can be ground uniformly within the substrate surface. Since bubbles entering the adhesive are reduced, the substrate can be appropriately heat-treated.

  The step of melting the adhesive may be performed by placing the lower substrate and the upper substrate close to each other and heating both the substrates. The heating temperature of the upper substrate may be set higher than the heating temperature of the lower substrate.

  Immediately after combining the two substrates, the ambient atmosphere of the adhesive may be returned to normal pressure.

  According to the present invention, since bubbles are prevented from entering the adhesive between the two substrates, the bonded substrates are appropriately processed.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is an explanatory view of a longitudinal section showing an outline of the configuration of a bonding apparatus 1 in which the bonding method according to the present embodiment is performed.

  The laminating apparatus 1 has a processing container 10 that can be hermetically closed, for example. In the center of the processing container 10, for example, a lower chuck 11 is provided as a first holding member for placing and holding the reinforcing substrate S. Further, an upper chuck 12 as a second holding member that holds the wafer W, for example, is provided above the lower chuck 11 at a position facing the lower chuck 11. In the present embodiment, the wafer W is a substrate on which a device is formed. The reinforcing substrate S is a substrate having the same diameter as that of the wafer W.

  The lower chuck 11 has, for example, a thick and substantially disk shape. On the upper surface of the lower chuck 11, a horizontal holding surface 11a larger than the diameter of the reinforcing substrate S is formed. The holding surface 11a is subjected to a surface treatment for flattening, and has a center line average roughness of 5 μm or less, for example. A suction port (not shown) is formed in the holding surface 11a of the lower chuck 11, and the reinforcing substrate S can be attracted to the holding surface 11a by suction by the suction port. Accordingly, the lower chuck 11 can hold the reinforcing substrate S on the holding surface 11a with the bonding surface facing upward.

  Inside the lower chuck 11, a heater 21, which is a heating member that generates heat when power is supplied from the power source 20, is built in. The heater 21 can heat the reinforcing substrate S on the lower chuck 11 and the adhesive on the reinforcing substrate S. In the present embodiment, for example, the power source 20 and the heater 21 constitute a heating mechanism.

  Further, inside the lower chuck 11, for example, a refrigerant flow path 23 is formed that is a cooling member through which the refrigerant supplied from the refrigerant supply device 22 flows. Thereby, the reinforcing substrate S on the lower chuck 11 and the adhesive on the reinforcing substrate S can be cooled.

  The lower chuck 11 is supported by a rod 32 via, for example, a heat insulating plate 30 and a support plate 31. The rod 32 moves up and down by a cylinder 33, for example. Thus, the lower chuck 11 is raised to the upper chuck 12 side, and the reinforcing substrate S held by the lower chuck 11 can be pressed against the wafer W held by the upper chuck 12. In the present embodiment, in order to align the wafer W and the reinforcing substrate S, a holding member driving mechanism for moving the lower chuck 11 is constituted by the rod 32 and the cylinder 33.

  The upper chuck 12 has, for example, a thick and substantially disk shape. On the lower surface of the upper chuck 12, a horizontal holding surface 12a larger than the diameter of the wafer W is formed. The holding surface 12a is subjected to a surface treatment for flattening, and has a center line average roughness of 5 μm or less, for example. A suction port (not shown) is formed in the holding surface 12a, and the upper surface of the wafer W can be attracted to the holding surface 12a by suction by the suction port. The upper chuck 12 can hold the wafer W so as to face the reinforcing substrate S of the lower chuck 11 with the bonding surface of the wafer W facing downward.

  Inside the upper chuck 12, a heater 41, which is a heating member that generates heat when power is supplied from the power supply 40, is built in. For example, the wafer W on the lower surface of the upper chuck 12 can be heated by the heater 41. Further, the reinforcing substrate S and the adhesive of the lower chuck 11 can be heated by the radiant heat from the upper chuck 12.

  For example, a disk-shaped heat insulating plate 50 is attached to the upper surface of the upper chuck 12. A support plate 51 is attached to the upper surface of the heat insulating plate 50. The central portion of the support plate 51 is supported by a ball plunger 52 attached to the ceiling surface of the processing container 10. The overall height of the upper chuck 12 can be adjusted by turning the ball plunger 52.

  On the support plate 51, there is provided a pull screw 60 as a lifting member having an upper end attached to the ceiling surface of the processing vessel 10 and a lower end attached to the support plate 51. By turning the pull screw 60, the upper chuck 12 can be lifted upward with the center portion of the support plate 51 with the ball plunger 52 (the center portion of the upper chuck 12) as a fulcrum. On the support plate 51, there is provided a push screw 61 as a push-down member whose upper end is attached to the ceiling surface of the processing vessel 10 and whose lower end is in contact with the upper surface of the support plate 51. By turning the push screw 61, the upper chuck 12 can be pushed downward with the central portion of the support plate 51 as a fulcrum.

  For example, as shown in FIG. 2, the pull screw 60 and the push screw 61 are sequentially arranged from the center side along the radial direction of the support plate 51 (upper chuck 12) when viewed from above. The pull screw 60 and the push screw 61 are provided at a plurality of locations, for example, at three locations. The pull screw 60 and the push screw 61 are arranged at equal intervals (120 ° intervals) on the same circumference. These pull screws 60 and push screws 61 can adjust the height of the upper chuck 12 to adjust the parallelism between the upper chuck 12 and the lower chuck 11. In the present embodiment, for example, the parallelism adjusting mechanism is configured by the ball plunger 52, the pull screw 60, and the push screw 61.

  A leaf spring 71 is provided on the outer peripheral portion of the support plate 51 as shown in FIG. By this leaf spring 70, the support plate 51 is pressed from the upper surface side. The leaf spring 70 is supported by a support pillar 71 attached to the ceiling surface of the processing container 10, for example. For example, as shown in FIG. 2, the leaf springs 70 are arranged at three positions every 120 °. A pair of pulling screws 60 and pressing screws 61 and leaf springs 70 are alternately arranged at equal intervals.

  Spacers 80 are provided on the outer peripheral portion of the holding surface 11a of the lower chuck 11 as shown in FIG. For example, as shown in FIG. 3, the spacer 80 is formed so as to surround the periphery of the reinforcing substrate S held on the holding surface 11a. The spacer 80 is formed from, for example, four projecting portions 81. For example, the four protrusions 81 are linearly formed with the same height and the same length, and are arranged so as to surround the reinforcing substrate S in a square frame shape. For example, as shown in FIG. 4, the height of each protrusion 81 defines a gap when the lower chuck 11 and the upper chuck 12 approach and the spacer 80 contacts the upper chuck 12. The bonded body B, which is a combination of the wafer W and the adhesive A, is set to have a desired thickness. By this spacer 80, the gap between the lower chuck 11 and the upper chuck 12 at the time of bonding is maintained constant within the holding surface, so that the reinforcing substrate S and the wafer W are bonded in parallel.

  Further, as shown in FIG. 3, a ventilation portion 82 is formed between the protruding portions 81 of the spacer 80. As a result, as shown in FIG. 4, even when the spacer 80 of the lower chuck 11 contacts the upper chuck 12, the region where the joined body B is located and the region outside the spacer 80 communicate with each other. The degassed gas can be discharged to the outside of the spacer 80.

  As shown in FIG. 1, an exhaust pipe 90 is connected to the side wall surface of the processing container 10. The exhaust pipe 90 is connected to a negative pressure generator 91 such as a vacuum pump. Thereby, the inside of the processing container 10 can be depressurized to a predetermined pressure. In the present embodiment, for example, the exhaust pipe 90 and the negative pressure generator 91 constitute a decompression mechanism that decompresses the ambient atmosphere of the liquid crystal wax A.

  For example, the control of the operation of the cylinder 33, the heaters 21 and 41, the refrigerant supply device 22, the negative pressure generation device 91, and the like described above is performed by the control unit 100, for example. The control unit 100 is, for example, a computer, and can control a bonding process by executing a stored program and driving each member or device, for example.

  Next, a method for bonding the reinforcing substrate S and the wafer W using the bonding apparatus 1 configured as described above will be described. FIG. 5 is a time chart regarding the temperature of the reinforcing substrate S, the pressure of the processing container 10 and the position of the lower chuck 11 in the bonding process. Moreover, FIG. 6 is explanatory drawing which shows the mode in the processing container 10 at the time of each process of a bonding process.

  First, as shown in FIG. 1, the reinforcing substrate S and the wafer W are attracted and held by the lower chuck 11 and the upper chuck 12 in the processing container 10 so as to face each other. At this time, as shown in FIG. 5, the reinforcing substrate S is maintained at, for example, room temperature T1 (for example, 23 ° C.). The pressure in the processing container 10 is maintained at normal pressure P1, for example. Further, the lower chuck 11 is disposed at a standby position K1 that is separated from the upper chuck 12. At this time, the distance between the lower chuck 11 and the upper chuck 12 is set to about 5 to 30 mm, more preferably 10 mm or less.

  When the reinforcing substrate S and the wafer W are held by the lower chuck 11 and the upper chuck 12, a solid liquid crystal wax A, which is a hot-melt adhesive, is placed at the center of the reinforcing substrate S ((( a)). Thereafter, for example, the heater 21 generates heat, and the temperature of the reinforcing substrate S is raised to a bonding temperature T3 (for example, 170 ° C.) exceeding the melting point temperature T2 (for example, 148 ° C.) of the liquid crystal wax A, as shown in FIG. The The bonding temperature T3 is set, for example, to a temperature about 5 ° C. to 30 ° C. higher than the melting point temperature T2. Further, due to the heat generated by the heater 41, the wafer W is also heated to a temperature that is equal to or higher than the melting temperature T2, for example, and a difference from the bonding temperature T3 within 10 ° C., for example, about 5 ° C. higher than the bonding temperature T3. . By heating the reinforcing substrate S and the wafer W, the liquid crystal wax A melts above the melting point temperature T2 ((b) of FIG. 6). The melting of the liquid crystal wax A is performed by, for example, heat transfer from the reinforcing substrate S and radiant heat from the wafer W. Thereafter, the temperature of the reinforcing substrate S is maintained at the bonding temperature T3 as shown in FIG.

  Subsequently, the pressure in the processing container 10 is reduced from the normal pressure P1 to a low pressure P2 of, for example, 20 kPa or less by exhausting from the exhaust pipe 90. By this decompression, bubbles in the liquid crystal wax A are removed ((c) in FIG. 6).

  Thereafter, the lower chuck 11 is raised to the bonding position K2 while the inside of the processing container 10 is maintained in a reduced pressure atmosphere, the reinforcing substrate S is pressed against the wafer W, and the reinforcing substrate S and the wafer W are aligned. ((D) of FIG. 6). As the lower chuck 11 is raised at this time, the spacer 80 comes into contact with the upper chuck 12, the gap between the upper chuck 12 and the lower chuck 11 is kept constant within the holding surface, and the reinforcing substrate S and the wafer W are parallel to each other. Maintained. As a result, the thickness of the bonded body B composed of the reinforcing substrate S, the liquid crystal wax A, and the wafer W becomes uniform within the wafer surface.

  After the reinforcing substrate S and the wafer W are pressurized with each other, as shown in FIG. 5, the pressure in the processing container 10 is returned from the low pressure P2 to the normal pressure P1 and maintained. As a result, the liquid crystal wax A is prevented from leaking and scattering from between the reinforcing substrate S and the wafer W due to a pressure difference. Further, after that, for example, by flowing a coolant through the cooling flow path 23, the reinforcing substrate S is cooled, and the temperature of the reinforcing substrate S is the final temperature T5 (which is lower than the solidification temperature T4 (eg, 113 ° C.) of the liquid crystal wax A. For example, the temperature is gradually lowered to 103 ° C. The liquid crystal wax A is solidified at the solidification temperature T4, and the reinforcing substrate S and the wafer W are bonded. The temperature fluctuation rate during cooling is set to be lower than the temperature fluctuation rate during heating, for example, 5 ° C./min or less.

  When the reinforcing substrate S is cooled to the final temperature T5, the suction of the wafer W on the upper chuck 12 is released. Thereafter, as shown in FIG. 5, the lower chuck 11 is lowered to the standby position K1, and the lower chuck 11 and the upper chuck 12 are separated ((e) of FIG. 6). Thus, the bonding process between the reinforcing substrate S and the wafer W is completed. The series of bonding processes is performed by the control unit 100 controlling the operations of the cylinder 33, the heaters 21, 41, the refrigerant supply device 22, the negative pressure generation device 91, and the like.

  According to the embodiment described above, after the liquid crystal wax A is melted on the reinforcing substrate S, the inside of the processing container 10 is depressurized, so that bubbles mixed in the melted liquid crystal wax A are reinforced with the wafer W. The liquid crystal wax A can be removed before the substrate S is bonded. Thereby, bubbles do not remain in the liquid crystal wax A after bonding, and a strong adhesive force between the wafer W and the reinforcing substrate S can be secured. Further, the bubbles do not expand and contract due to heat, and the heat treatment after bonding can be performed appropriately. Furthermore, the grinding process after bonding can be performed uniformly within the wafer surface.

  Since the reduced pressure is maintained when the wafer W and the reinforcing substrate S are put together, the bubbles can be removed even while the liquid crystal wax A diffuses between the wafer W and the reinforcing substrate S. Further, due to the reduced pressure, an external force acts on the liquid crystal wax A to assist the diffusion of the liquid crystal wax A. As a result, the liquid crystal wax A is spread uniformly between the wafer W and the reinforcing substrate S in a shorter time.

  Since the upper wafer W is heated when the reinforcing substrate S is heated, the liquid crystal wax A is heated from both sides by the reinforcing substrate S and the wafer W. For this reason, only the lower surface of the liquid crystal wax A which is a contact portion with the reinforcing substrate S is not melted, and the liquid crystal wax A does not slide on the reinforcing substrate S. As a result, the liquid crystal wax A melts at the central portion of the reinforcing substrate S and is spread uniformly on the reinforcing substrate S by the subsequent pressurization. Since the heating temperature of the wafer W is set higher than the heating temperature of the reinforcing substrate S, the surface side of the liquid crystal wax A can be sufficiently melted by the radiant heat.

  Immediately after the wafer W and the reinforcing substrate S are combined, the pressure in the processing container 10 is returned to the normal pressure, so that the liquid crystal wax A is not pulled outward by the reduced pressure, and the liquid crystal wax A is removed from the wafer. It is possible to prevent leakage and scattering from between W and the reinforcing substrate S.

  The preferred embodiment of the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to such an example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the spirit described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  For example, in the above embodiment, the lower chuck 11 is provided with a cooling function, and the liquid crystal wax A is actively cooled when the liquid crystal wax A is solidified. However, natural cooling may be used. In the above embodiment, the lower chuck 11 moves up and down to bond the reinforcing substrate S and the wafer W, but the upper chuck 12 may move up and down. Further, both the upper chuck 12 and the lower chuck 11 may move up and down. In the above embodiment, the reinforcing substrate S is held on the lower chuck 11 side and the wafer W is held on the upper chuck 12 side. Furthermore, the present invention can also be applied when holding the wafer W on both sides of the lower chuck 11 and the upper chuck 12 and bonding the wafers together. The present invention can also be applied to bonding of substrates other than the wafer W and the reinforcing substrate S. The present invention can also be applied when a hot-melt adhesive other than liquid crystal wax is used.

  The present invention is useful when two substrates are bonded together so that bubbles do not enter the adhesive.

It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the bonding apparatus. It is a top view of an upper chuck | zipper. It is a top view of a lower chuck. It is sectional drawing of the upper chuck | zipper and lower chuck | zipper explaining the state at the time of bonding. (A) is explanatory drawing which shows the state which put the liquid crystal wax on the board | substrate for reinforcement. (B) is explanatory drawing which shows the state which liquid crystal wax melt | dissolved. (C) is explanatory drawing which shows a mode that it defoams from liquid crystal wax. (D) is explanatory drawing which shows the state which bonded the board | substrate for reinforcement and the wafer. (E) is explanatory drawing which shows the state which separated the wafer from the upper chuck | zipper. It is a time chart which shows the control of the temperature of the board | substrate for a reinforcement | strengthening in a bonding process, the pressure in a processing container, and the position of a lower chuck | zipper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bonding apparatus 10 Processing container 11 Lower chuck 11a Holding surface 12 Upper chuck 21 Heater 33 Cylinder 90 Exhaust pipe 91 Negative pressure generator S Reinforcing substrate W Wafer A Liquid crystal wax

Claims (4)

A method of bonding two substrates using a hot-melt adhesive,
A process of arranging two substrates facing each other vertically;
Placing a solid hot-melt adhesive on the lower substrate;
Heating and melting the adhesive on the lower substrate;
Reducing the ambient atmosphere of the melted adhesive;
In a state where the reduced pressure is maintained, the step of combining the two substrates with the melted adhesive sandwiched therebetween,
And a step of cooling and solidifying the adhesive between the two substrates. 2. The bonding method according to claim 1, wherein the step of melting the adhesive is performed by placing the lower substrate and the upper substrate close to each other and heating the two substrates. The bonding method according to claim 2, wherein a heating temperature of the upper substrate is set higher than a heating temperature of the lower substrate. The bonding method according to claim 1, wherein the ambient atmosphere of the adhesive is returned to normal pressure immediately after the two substrates are combined.

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