JP5386795B2 - Joining apparatus and joining method - Google Patents

Description

  The present invention relates to a bonding apparatus and a bonding method for at least two substrates (for example, semiconductor wafers) on which a plurality of connection portions (for example, semiconductor devices) are formed.

  Although miniaturization of semiconductor circuits has progressed, preparations for manufacturing devices of 45 nm nodes are being delayed. The main causes are a delay in development of a high-k material for a gate insulator and a low-k material for wiring, an increase in device heat generation, and the like. In addition, problems such as a prolonged development period of a necessary exposure apparatus and a price increase are expected, and the speed of circuit miniaturization, which has been conventionally performed, is inevitably reduced in the future.

  Even under such circumstances, market demands such as improvement in operation speed of semiconductor devices, enhancement of functions, and increase in capacity continue, and it is necessary to respond to these demands.

  One effective means for solving these problems is three-dimensional stacking of wafers. By laminating wafers with conductive wires penetrating inside the semiconductor substrate and connecting and thinning the conductive wires, the circuit derailment length can be shortened, and the device can be sped up and the heat generation can be reduced. Further, by increasing the number of layers of the wafer stack, the function of the circuit can be improved and the capacity of the memory can be increased.

To perform three-dimensional stacking of wafers, a bonding electrode is formed on the surface of the wafer after circuit formation, and positioning is performed so that the electrodes of two wafers or an already stacked wafer and the next wafer to be stacked are aligned with each other. Need to be contacted. This is performed by a wafer bonding apparatus (see, for example, Patent Document 1).
JP 2005-302858 A

  In the conventional bonding apparatus, the patterns on the two wafers are relatively aligned, and after that, the electrodes on the two wafers are bonded by pressurizing and heating the stacked two wafers. And unite. However, when pressurizing or heating, there is a problem that the position is shifted due to the force that shifts the relative relationship between the two wafers.

In order to solve the above problems, the present invention provides:
A joining apparatus for joining the two substrates after facing and aligning the connecting portions of the two substrates formed with a plurality of connecting portions,
And two members each having a respective direct or plane indirect contact with the substrate of the two bodies,
When pressing and heating treatment of the substrate of the two bodies, the boards of the static friction force between the at least one surface and said at least a surface of the substrate in contact with one side substantially parallel the surface to the substrate And a static friction reducing means for reducing the static friction force between the surfaces in contact with each other.

The present invention also provides:
A step of facing and aligning the connection parts of the two substrates on which a plurality of connection parts are formed, and temporarily fixing;
Via two members each having a respective direct or plane indirect contact with the substrate of the two bodies, the steps of pressurizing and heating a substrate of the two bodies,
During the pressurization and heat treatment , a static friction force between at least one of the surfaces substantially parallel to the substrate and a surface of the substrate in contact with the at least one surface is contacted between the substrates by static friction reducing means. Provided is a joining method characterized in that it is smaller than the static friction force between the surfaces to be joined.

  According to the present invention, it is possible to provide a bonding apparatus and a bonding method in which the alignment accuracy does not deteriorate over the entire wafer surface.

  Next, a joining apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a process flow of substrate (hereinafter referred to as a wafer) bonding in the bonding apparatus according to the embodiment. FIG. 2 is a block diagram of a pressurizing / heating device used for wafer bonding. In the following description, a case where the electrode portions of a semiconductor wafer on which a plurality of semiconductor devices are formed is bonded will be described as a representative. However, the wafer is not limited to the semiconductor wafer, and the bonding portion is also limited to the electrode portion. It goes without saying that there is nothing.

  The joining device 1 according to the embodiment is roughly divided into two device sections. One is an alignment device (not shown) that aligns the electrode portions of two wafers facing each other, and the other is pressurizing and heating two wafers aligned by the alignment device. It is a pressurizing / heating device section 2 to be described later for performing bonding of electrode portions. Between the alignment device unit and the pressurizing / heating device unit 2, two wafers that are aligned and temporarily held by a transfer device such as a wafer carrier (not shown) are transferred. Hereinafter, the joining process based on the joining apparatus 1 shown in FIG. 2 will be described with reference to FIGS. 1 and 2.

(Step S1)
The back surface of the wafer WA (the surface on which no device is formed) is adsorbed to the wafer holder 12A via a wafer transfer device (not shown). For the adsorption here, electrostatic adsorption by electrostatic force or vacuum adsorption by vacuuming is used. In the case of electrostatic attraction, an electrostatic chuck is used for the wafer holder 12A, and in the case of vacuum attraction, a vacuum chuck is used for the wafer holder 12A. The electrostatic attraction force and the vacuum attraction force are controlled by the respective control units so that the attraction force can be generated or stopped.

  After attracting wafer WA to wafer holder 12A, the relative positional relationship between alignment marks 13A1 and 13A2 formed on wafer holder 12A and an alignment mark (not shown) formed on wafer WA or a predetermined pattern of the device is measured. To do. The measurement result is sent to a control device (not shown), and the control device determines the relative positional relationship between the wafer WA and the alignment marks 13A1 and 13A2, and stores it as relative position information.

(Step S2)
The back surface of the wafer WB (the surface on which no device is formed) is attracted to the wafer holder 12B via a wafer transfer device (not shown). The adsorption here is the same as that of the wafer WA.

  After the wafer WB is attracted to the wafer holder 12B, the relative positional relationship between the alignment marks 14B1 and 14B2 formed on the wafer holder 12B and an alignment mark (not shown) formed on the wafer WB or a predetermined pattern of the device is measured. To do. The measurement result is sent to a control device (not shown), and the control device determines the relative positional relationship between the wafer WB and the alignment marks 14B1 and 14B2, and stores it as relative position information.

(Step S3)
While the wafer WA is attracted to the wafer holder 12A, the wafer holder 12A is rotated so that the surface of the wafer WA (the surface on which the device is formed) is oriented substantially parallel to the surface of the wafer WB. Whether the wafer WA is moved, the wafer WB is moved, or both are moved is appropriately changed according to the design of the bonding apparatus 1.

(Step S4)
The surfaces of the wafer WA and the wafer WB are placed close to each other and face each other. At this time, the gap between the wafers is set to such a distance that the wafers WA and WB do not come into contact with each other even if they are relatively moved. For example, the gap value is set to a constant value between 10 μm and 50 μm. In this gap, the alignment mark 13A1 on the wafer holder 12A and the alignment mark 14B1 on the wafer holder 12B are in a state in which the relative position can be measured by one measurement system. Further, the alignment mark 13A2 and the alignment mark 14B2 are also in a state in which the relative position can be measured by one measurement system.

(Step S5)
The wafer WA and the wafer WB should be bonded using the relative position information for the wafer WA alignment marks 12A1 and 12A2 and the relative position information for the wafer WB alignment marks 14B1 and 14B2 obtained in steps S1 and S2. The position of the pattern (for example, electrode part) in the horizontal plane is aligned by driving the wafer holders 12A and 12B by an actuator device (not shown).

(Step S6)
After the alignment of the wafer WA and the wafer WB is completed, the wafer WA and the wafer WB are shrunk to contact the bonding part, and after applying pressure, the wafer holder 12A and the wafer holder 12B are temporarily attached with a fixing jig (not shown). Fasten. In this state, the wafer holder 12A and the wafer holder 12B are handled as one block M.

(Step S7)
The temporarily retained block M is transported to a pressurizing / heating device section via a transport device (not shown) and placed in the pressurizing / heating device section 2. At this time, the wafer holder 12A and the wafer holder 12B, which are temporarily held, are transported and placed with great care so as not to shift.

  As shown in FIG. 2, the pressurizing / heating device section 2 includes a heater section (also referred to as a top plate) 11 </ b> A, a heater section (also referred to as a top plate) 11 </ b> B, and a pressurizing section 15 in a sealed structure with a column 10. Has been. The block M temporarily holding the wafer holder 12A and the wafer holder 12B is inserted between the heater part 11A and the heater part 11B, and when the block M is inserted, the inside of the column 10 is depressurized.

  Next, pressure is applied by the pressure unit 15 to press the wafer WA and the wafer WB through the wafer holders 12A and 12B and the heater units 11A and 11B. Further, the wafers WA and WB are uniformly heated by the heater units 11A and 11B via the wafer holders 12A and 12B, respectively, and the contact portions of the wafer WA and the wafer WB are joined. The pressurizing force, heating temperature, duration, etc. are controlled by a control device (not shown). Thereby, the wafer WA and the wafer WB are completely bonded. In addition, when a contact part is a metal electrode, copper etc. are mentioned as a material of a metal electrode. Moreover, a thermosetting resin material etc. are mentioned as a contact part.

  In addition, it can select suitably whether it heats after starting to pressurize, or pressurizes after starting to heat. Further, whether or not to stop the electrostatic chucking or vacuum chucking of the wafer when pressurization or heating starts can be selected as appropriate.

(Step S8)
After the pressurization and heating are finished, cooling water is introduced into the heated portion in the column 10 to cool the block M, and the block M containing the bonded wafers WA and WB is taken out.

(Step S9)
The temporary holding jig is removed from the block M, the wafer holder 12A is removed from the wafer WA, and the wafer holder 12B is removed from the wafer WB.

  Through the above steps, the bonding apparatus 1 bonds the electrodes while the wafer WA and the wafer WB maintain a predetermined positional relationship.

  Thereafter, the bonded wafer WA and wafer WB are placed on a sample holder (not shown), and the sample holder is carried out to the next processing step.

  Thus, the bonding of the wafer WA and the wafer WB by the bonding apparatus 1 according to the embodiment is completed.

  In the conventional bonding apparatus, there has been a problem that in the pressurization and heat treatment process in step S7, the electrode portions of the wafer WA and the wafer WB in a predetermined alignment state are displaced, resulting in a bonding failure. The problem is that the positional relationship between the wafer WA and the wafer WB is shifted mainly due to the difference in thermal expansion between the wafer WA and the wafer holder 12A, the wafer WB and the wafer holder 12B, or the heater portions 11A and 11B during heating. There is.

  For example, when the static frictional force between the wafer WA and the wafer holder 12A and between the wafer WB and the wafer holder 12B is larger than the static frictional force between the wafer WA and the wafer WB, the contact portion between the wafer WA and the wafer WB due to deformation due to a difference in thermal expansion. The cause is that the part is shifted. In the bonding apparatus 1 according to the present embodiment, it is possible to suppress the occurrence of the above-described deviation and suppress the occurrence of bonding failure.

  Hereinafter, examples of the joining device according to the embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 3A shows a partial view of the joining apparatus according to the first embodiment. 3 (b) and 3 (c) show modifications of the first embodiment. The process is the same as in FIG. 1 and the description thereof is omitted, and description will be made mainly with respect to the time point of step S7. Further, the column 10 shown in FIG.

  In FIG. 3A, a DLC (Diamond Like Carbon) film X for reducing static frictional force is formed on the surface of the wafer holder 112A where the wafer WA is attracted and contacted. Further, in the wafer holder 112B, the DLC film X for reducing the static frictional force is formed on the surface where the wafer WB is attracted and contacted.

  Thus, by providing the DLC film on the contact surfaces of the wafer WA and the wafer holder 112A and the wafer WB and the wafer holder 112B, the static friction force between the wafer WA and the wafer holder 112A and the static friction force between the wafer WB and the wafer holder 112B are provided. Can be made smaller than the contact frictional force between the wafer WA and the wafer WB, the static frictional force between the wafer holder 112A and the heater unit 11A, and the static frictional force between the wafer holder 112B and the heater unit 11B. It is possible to prevent the occurrence of deviation between the wafer WA and the wafer WB due to the above. That is, before the contact surface between the wafer WA and the wafer WB is deviated, the contact surface between the wafer WA and the wafer holder 112A and the contact surface between the wafer WB and the wafer holder 112B are shifted to eliminate the difference in thermal expansion, and the contact between the wafer WA and the wafer WB. Surface displacement can be prevented.

  FIG. 3B is a modified example of FIG. 3A, and shows a case where a DLC film is formed on the surface of the wafer holder 112A that contacts the heater unit 11A and the surface of the wafer holder 112B that contacts the heater unit 11B. In this case, the static friction force on the contact surface between the wafer holder 112A and the heater unit 11A and the static friction force on the contact surface between the wafer holder 112B and the heater unit 11B can be made smaller than the static friction force on the contact surface between the wafer WA and the wafer WB. Further, it is possible to prevent the occurrence of deviation between the wafer WA and the wafer WB due to the difference in thermal expansion during heating.

  FIG. 3C is a modification of FIG. 3B, and shows a case where a DLC film is formed on the surface of the heater unit 111A that contacts the wafer holder 12A and the surface of the heater unit 111B that contacts the wafer holder 12B. Also in this case, the static friction force on the contact surface between the wafer holder 12A and the heater unit 111A and the static friction force on the contact surface between the wafer holder 12B and the heater unit 111B can be made smaller than the static friction force on the contact surface between the wafer WA and the wafer WB. It is possible to prevent the occurrence of a deviation between the wafer WA and the wafer WB due to a difference in thermal expansion during heating.

  As described above, the DLC film for reducing the static frictional force is provided on at least one surface of the wafer holder 112A and the heater unit 111A, and at least one surface of the wafer holder 112B and the heater unit 111B, so that the interface at which the DLC is provided is stationary. It is possible to configure the bonding apparatus 1 that reduces the frictional force as compared with the static frictional force between the contact surfaces of the wafer WA and the wafer WB and prevents a shift during wafer bonding.

  Further, when the DLC film is formed, it is possible to prevent the wafer WB and the wafer holder 11A or the wafer WB and the wafer holder 11B from sticking after pressing and heating. Moreover, since DLC has high hardness, it is possible to prevent the surface of the wafer holder 11A or the wafer holder 11B from being damaged. In addition, it can be expected to prevent dust from adhering to the wafer holders 11A and 11B or to improve the durability of the wafer holder.

  The static friction force reducing means for reducing the static friction force can use an inorganic material film other than DLC. In the first embodiment, the timing for stopping electrostatic chucking or vacuum chucking of the wafer can be selected as appropriate. Further, it is more preferable to stop the electrostatic chucking or vacuum chucking of the wafer at the time when pressure is applied and heating is started, because the static frictional force between the wafer and the wafer holder can be reduced.

(Second embodiment)
FIG. 4 is a partial view of the joining apparatus according to the second embodiment.

  In the joining apparatus 1 according to the second embodiment, the aligned block M shown in FIG. 4 is inserted into the column 10 shown in FIG. 2 and subjected to pressure and heat treatment. The process is the same as in FIG.

  In the second embodiment, after the block M is pressurized by the pressure unit 15, the electrostatic adsorption force between the wafer WA and the wafer holder 12A and the electrostatic adsorption force between the wafer WB and the wafer holder 12B are measured by the static electricity control unit 30. To stop. As a result, the electrostatic attraction force on the wafer WA and the wafer holder 12A and the wafer WB and the wafer holder 12B is eliminated, and the static frictional force at the interface between the wafer WA and the wafer holder 12A and between the wafer WB and the wafer holder 12B can be reduced. As a result, the contact friction force at the interface between the wafer WA and the wafer holder 12A and the static friction force at the interface between the wafer WB and the wafer holder 12B can be made smaller than the static friction force at the contact surface between the wafer WA and the wafer WB. It is possible to prevent the occurrence of deviation between the wafer WA and the wafer WB due to the difference in thermal expansion during heating.

(Third embodiment)
FIG. 5 shows a partial view of the joining apparatus according to the third embodiment.

  In the bonding apparatus 1 according to the third embodiment, the bonding apparatus 1 having a static frictional force reducing means when the wafer holder is vacuum suction is shown. The process is the same as in FIG. Note that the configurations of the wafer holder for attracting the wafer WA and the wafer holder for attracting the wafer WB in FIG. To do.

  In FIG. 5, after aligning the wafer WB and the wafer WA (not shown), the two wafer holders are temporarily fastened, and the wafer WB is kept in the wafer holder 18 until it is transferred to the pressurizing / heating unit 2 (see FIG. 2). Are held by a static frictional force between the electrostatic force and the wafer WA (not shown). After being carried into the column 10 of the pressurizing / heating device 2, the hole 19 provided in the wafer holder 18 is joined to the pipe 20 by the pipe joint 25. The hole 19 continues from the pipe joint portion 25 and branches in the middle, and the branched hole is connected to holes distributed over the entire wafer WB.

  Reference numeral 24 denotes an exhaust part, and 22 denotes an inert gas supply part. As the inert gas, a gas such as nitrogen, helium, neon, or argon is used. Reference numeral 21 denotes an air supply valve, and 23 denotes an exhaust valve, which are closed until the pipe joint 25 is attached to the wafer holder 18. When the pipe joint 25 is joined to the hole 19, the valve 23 connected to the exhaust part 24 is opened, and the inside of the pipe 20 and the hole 19 is exhausted. By this exhaust, the wafer WB is vacuum-sucked to the wafer holder 18 and the electrostatic suction is stopped. After this evacuation, the block M (see FIG. 2) composed of the wafer WB and the wafer WA is placed in the column 10 and the atmosphere in the column 10 is evacuated. After exhausting the atmosphere, the web block M is pressurized by the pressure unit 15.

  Next, the exhaust valve 23 is closed and the air supply valve 21 is opened. The inert gas flows from the air supply valve 21 into the pipe 20 and the hole 19, and the pressure of the inert gas is applied to the back surface of the wafer WB. Thereby, the static frictional force between the wafer WB and the wafer holder 18 is reduced. Thereafter, the temporarily fixed wafer WB and the entire wafer WA are heated to join the contact portions.

According to this configuration of Fig. 1 step, even if stresses due to granulation physicians and temperature unevenness of the linear expansion coefficient of each part at the time of heating is generated, slip between the between the wafer WB and the wafer holder 18 or the wafer WA and the wafer holder, the wafer It is possible to prevent slipping between the WA and the wafer WB. When the heating is finished, the air supply valve 21 is closed and the atmosphere is returned to the atmospheric pressure.

  In addition, by ejecting the inert gas to the back surface of the wafer WB, minute dust existing between the wafer WB and the wafer holder 18 can be removed, and the wafer WB and the wafer WA can be bonded more flatly.

  Further, the first to third embodiments are not required to be mutually exclusive, and can be performed simultaneously or in combination.

  As described above, in the bonding apparatus according to the present embodiment, the static frictional force between the wafer and the wafer holder or the static frictional force between the wafer holder and the heater unit (top plate) is determined based on the static frictional force on the bonding surface between the wafers. Can be reduced, and deviation between wafers can be prevented during bonding.

  In the above description, the case where the static friction force reducing means is provided in the members related to both wafers has been described, but the static friction force reducing means may be provided only in the member related to one wafer.

  In the first to third embodiments, it is preferable that the timing for releasing the electrostatic adsorption or the vacuum adsorption is performed at least before heating.

  In addition, in order to be affected by disturbances such as temperature changes and acceleration applied after the wafers are aligned and temporarily fixed, the temporary transfer alignment unit and the conveyance part to the pressure / heating unit, It is more desirable to have a device configuration in which the temperature before pressing and heating of the heating unit is made uniform to minimize temperature unevenness and temperature change. Further, it is desirable that the wafer and the wafer holder are not subjected to an impact during transportation.

  The above-described embodiment is merely an example, and is not limited to the above-described configuration and shape, and can be appropriately modified and changed within the scope of the present invention.

The process flow of the board | substrate (wafer) joining in the joining apparatus concerning embodiment is shown. The block diagram of the pressurizing / heating device used for wafer bonding is shown. (A) shows the partial view of the joining apparatus concerning 1st Example, (b) shows the modification of (a), (c) has shown the modification of (b), respectively. The fragmentary view of the joining device concerning the 2nd example is shown. The fragmentary view of the joining device concerning the 3rd example is shown.

Explanation of symbols

1 Joiner 10 Column 11A, 11B, 111A, 111B Heater (top plate)
12A, 12B, 112A, 112B, 18 Wafer holder 13A1, 13A2, 14B1, 14B2 Alignment mark 15 Pressurization part 19 Hole 20 Pipe 21 Supply valve 22 Inert gas supply part 23 Exhaust valve 24 Exhaust part 25 Pipe joint part 30 Static electricity Control unit WA, WB Wafer X DLC (Diamond Like Carbon)
M block

Claims (10)

A joining apparatus for joining the two substrates after facing and aligning the connecting portions of the two substrates formed with a plurality of connecting portions,
And two members each having a respective direct or plane indirect contact with the substrate of the two bodies,
When pressing and heating treatment of the substrate of the two bodies, the boards of the static friction force between the at least one surface and said at least a surface of the substrate in contact with one side substantially parallel the surface to the substrate And a static friction reducing means for reducing the static friction force between the surfaces in contact with each other . 2. The joining apparatus according to claim 1, wherein the static frictional force reducing means comprises a DLC (abbreviation of diamond-like carbon) film formed on the at least one surface . The member holds the substrate by electrostatic force,
The joining apparatus according to claim 1, wherein the static frictional force reducing unit includes an electrostatic control unit that controls an electrostatic force applied to the member. The member holds the substrate by vacuum suction,
3. The joining apparatus according to claim 1, wherein the static frictional force reducing means includes gas ejection means for ejecting gas toward the substrate from a vacuum suction hole of the member.   The bonding apparatus according to claim 1, wherein the member includes a substrate holder that adsorbs the substrate.   5. The bonding apparatus according to claim 1, wherein the member includes a heater portion that contacts the substrate holder. A step of facing and aligning the connection parts of the two substrates on which a plurality of connection parts are formed, and temporarily fixing;
Via two members each having a respective direct or plane indirect contact with the substrate of the two bodies, the steps of pressurizing and heating a substrate of the two bodies,
During the pressurization and heat treatment , a static friction force between at least one of the surfaces substantially parallel to the substrate and a surface of the substrate in contact with the at least one surface is contacted between the substrates by static friction reducing means. The joining method is characterized in that it is smaller than the static frictional force between the surfaces to be machined.   The joining method according to claim 7, wherein the static frictional force reducing means is a DLC (diamond-like carbon) film formed on the at least one surface.   The member holds the substrate by electrostatic force,
  The joining method according to claim 7 or 8, wherein the static friction force reducing means reduces the static friction force by reducing an electrostatic force to the member.   The member holds the substrate by vacuum suction,
  The joining method according to claim 7 or 8, wherein the static friction force reducing means reduces the static friction force by ejecting a gas from the vacuum suction hole of the member toward the substrate.

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