JP6707420B2 - Joining device and joining system - Google Patents

Description

The disclosed embodiments relate to a joining device and a joining system.

Conventionally, as a bonding apparatus for bonding substrates such as semiconductor wafers, a bonding apparatus for bonding substrates by intermolecular force has been known.

In this type of bonding apparatus, the upper substrate and the lower substrate are arranged so as to face each other, and then the center portion of the upper substrate is pushed down by a striker to make contact with the center portion of the lower substrate. As a result, first, the central portions of the upper substrate and the lower substrate are bonded to each other by the intermolecular force to form a bonding region. After that, a so-called bonding wave occurs in which the bonding area expands toward the outer peripheral portion of the substrate. As a result, the upper substrate and the lower substrate are joined over the entire surface (see Patent Document 1).

As described above, in this type of bonding apparatus, the upper substrate is attached to the lower substrate while being bent by the striker. Therefore, extra stress is applied to the upper substrate, and this stress causes distortion of the substrates after bonding.

Therefore, in recent years, in order to reduce the strain generated in the substrate after bonding, it has been proposed to reduce the deflection of the upper substrate by narrowing the distance between the upper substrate and the lower substrate as much as possible.

JP, 2005-095579, A

However, if the distance between the upper substrate and the lower substrate is narrowed, the air between the substrates becomes difficult to escape due to the viscosity, and stress may be added to the substrates during bonding, which may worsen the distortion of the substrates after bonding. ..

It is an object of one aspect of the embodiment to provide a bonding apparatus and a bonding system that can reduce distortion of substrates after bonding.

The joining device according to one aspect of the embodiment includes a first holding unit, a second holding unit, a lifting mechanism, a partition wall, a gas introduction port, and a gas supply unit. The first holding unit sucks and holds the first substrate from above. The second holding unit is disposed below the first holding unit and sucks and holds the second substrate from below. The elevating mechanism moves the first holding unit or the second holding unit in the vertical direction. The partition wall is provided in the first holding unit or the second holding unit, and forms a processing space in which the bonding process of the first substrate and the second substrate is performed together with the first holding unit and the second holding unit. The gas introduction port introduces an inert gas into the processing space. The gas supply unit supplies an inert gas into the processing space via the gas inlet.

According to one aspect of the embodiment, it is possible to reduce distortion of the substrate after joining.

FIG. 1 is a schematic plan view showing the configuration of the joining system according to the embodiment. FIG. 2 is a schematic side view showing the configuration of the joining system according to the embodiment. FIG. 3 is a schematic side view of the first substrate and the second substrate. FIG. 4 is a schematic plan view showing the configuration of the joining device. FIG. 5 is a schematic side view showing the configuration of the joining device. FIG. 6 is a schematic side sectional view showing the configurations of the upper chuck and the lower chuck. FIG. 7 is a schematic bottom view of the upper chuck. FIG. 8 is a schematic plan view of the lower chuck. FIG. 9 is a flowchart showing a part of the processing executed by the joining system. FIG. 10 is an operation explanatory diagram of the joining process. FIG. 11 is an operation explanatory view of the joining process. FIG. 12 is an operation explanatory diagram of the joining process. FIG. 13 is an operation explanatory diagram of the joining process. FIG. 14 is an operation explanatory diagram of the joining process. FIG. 15 is an operation explanatory diagram of the joining process. FIG. 16 is an operation explanatory diagram of the joining process. FIG. 17 is a schematic side sectional view showing configurations of an upper chuck and a lower chuck according to a modified example. FIG. 18 is a schematic side sectional view showing configurations of an upper chuck and a lower chuck according to a modified example.

Hereinafter, embodiments of a joining device and a joining system disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

<1. Structure of joining system>
First, the configuration of the joining system according to the embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic plan view showing the configuration of the joining system according to the embodiment. FIG. 2 is a schematic side view showing the configuration of the joining system according to the embodiment. FIG. 3 is a schematic side view of the first substrate and the second substrate.

In addition, in each of the drawings referred to below, an orthogonal coordinate system in which an X-axis direction, a Y-axis direction, and a Z-axis direction that are orthogonal to each other are defined and a Z-axis positive direction is a vertically upward direction is shown for easy understanding of the description. There are cases. Further, in each of the drawings including FIGS. 1, 2 and the like, only constituent elements necessary for description are shown, and description of general constituent elements may be omitted.

The bonding system 1 according to the present embodiment shown in FIG. 1 forms the overlapped substrate T by bonding the first substrate W1 and the second substrate W2 (see FIG. 3).

The first substrate W1 is a substrate in which a plurality of electronic circuits are formed on a semiconductor substrate such as a silicon wafer or a compound semiconductor wafer. The second substrate W2 is, for example, a bare wafer on which no electronic circuit is formed. The first substrate W1 and the second substrate W2 have substantially the same diameter. An electronic circuit may be formed on the second substrate W2.

Hereinafter, the first substrate W1 may be referred to as “upper wafer W1”, the second substrate W2 may be referred to as “lower wafer W2”, and the overlapping substrate T may be referred to as “overlapping wafer T”. Further, in the following description, as shown in FIG. 3, among the plate surfaces of the upper wafer W1, the plate surface on the side to be bonded to the lower wafer W2 is referred to as a “bonding surface W1j”, and the plate surface on the side opposite to the bonding surface W1j. The plate surface is described as "non-bonded surface W1n". Further, of the plate surfaces of the lower wafer W2, the plate surface on the side bonded to the upper wafer W1 is referred to as “bonding surface W2j”, and the plate surface opposite to the bonding surface W2j is referred to as “non-bonding surface W2n”. Enter.

As shown in FIG. 1, the joining system 1 includes a loading/unloading station 2 and a processing station 3. The loading/unloading station 2 and the processing station 3 are arranged side by side in the order of the loading/unloading station 2 and the processing station 3 along the X-axis positive direction. Further, the loading/unloading station 2 and the processing station 3 are integrally connected.

The loading/unloading station 2 includes a mounting table 10 and a transfer area 20. The mounting table 10 includes a plurality of mounting plates 11. On each mounting plate 11, cassettes C1, C2, C3 for accommodating a plurality of (for example, 25) substrates in a horizontal state are mounted, respectively. For example, the cassette C1 is a cassette that houses the upper wafer W1, the cassette C2 is a cassette that houses the lower wafer W2, and the cassette C3 is a cassette that houses the overlapped wafer T.

The transfer region 20 is arranged adjacent to the X-axis positive direction side of the mounting table 10. The transport area 20 is provided with a transport path 21 extending in the Y-axis direction, and a transport device 22 movable along the transport path 21. The transfer device 22 is movable not only in the Y-axis direction but also in the X-axis direction and is rotatable about the Z-axis, and is provided with cassettes C1 to C3 mounted on the mounting plate 11 and a processing station 3 described later. The upper wafer W1, the lower wafer W2, and the overlapped wafer T are transferred to and from the third processing block G3.

The number of cassettes C1 to C3 mounted on the mounting plate 11 is not limited to that shown in the figure. In addition to the cassettes C1, C2 and C3, a cassette or the like for collecting the defective substrate may be mounted on the mounting plate 11.

The processing station 3 is provided with a plurality of processing blocks including various devices, for example, three processing blocks G1, G2, G3. For example, a first processing block G1 is provided on the front side of the processing station 3 (Y-axis negative direction side of FIG. 1), and a second processing block G1 is provided on the back side of the processing station 3 (Y-axis positive direction side of FIG. 1). A processing block G2 is provided. Further, a third processing block G3 is provided on the loading/unloading station 2 side of the processing station 3 (X-axis negative direction side in FIG. 1).

In the first processing block G1, a surface reforming device 30 that reforms the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 is arranged. The surface reforming device 30 cuts the bond of SiO2 on the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 to form a single bond of SiO, so that the bonding surface W1j, Modify W2j.

In the surface reforming apparatus 30, for example, oxygen gas or nitrogen gas, which is a processing gas, is excited into plasma and ionized under a reduced pressure atmosphere. Then, the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2 are irradiated with such oxygen ions or nitrogen ions, whereby the bonding surfaces W1j, W2j are plasma-treated and modified.

A surface hydrophilization device 40 and a joining device 41 are arranged in the second treatment block G2. The surface hydrophilization device 40 hydrophilizes the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2 with pure water, for example, and cleans the bonding surfaces W1j, W2j. The surface hydrophilization apparatus 40 supplies pure water onto the upper wafer W1 or the lower wafer W2 while rotating the upper wafer W1 or the lower wafer W2 held by, for example, a spin chuck. As a result, the pure water supplied onto the upper wafer W1 or the lower wafer W2 diffuses on the bonding surfaces W1j, W2j of the upper wafer W1 or the lower wafer W2, and the bonding surfaces W1j, W2j are made hydrophilic.

The bonding apparatus 41 bonds the hydrophilized upper wafer W1 and lower wafer W2 by intermolecular force. The configuration of the joining device 41 will be described later.

In the third processing block G3, as shown in FIG. 2, transition (TRS) devices 50 and 51 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T are provided in two stages in order from the bottom.

Further, as shown in FIG. 1, a transport region 60 is formed in a region surrounded by the first processing block G1, the second processing block G2, and the third processing block G3. A transport device 61 is arranged in the transport area 60. The transfer device 61 has, for example, a transfer arm that is movable in the vertical direction, the horizontal direction, and around the vertical axis. The transfer device 61 moves in the transfer region 60, and the upper wafer W1 and the lower wafer W2 are moved to predetermined devices in the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the transfer region 60. And the superposed wafer T is transported.

Further, as shown in FIG. 1, the joining system 1 includes a control device 70. The control device 70 controls the operation of the joining system 1. The control device 70 is, for example, a computer and includes a control unit and a storage unit (not shown). The control unit includes a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output port, and various circuits. The CPU of the microcomputer realizes the control described below by reading and executing the program stored in the ROM. The storage unit is realized by, for example, a RAM, a semiconductor memory element such as a flash memory, or a storage device such as a hard disk or an optical disk.

The program may be recorded in a computer-readable recording medium, and may be installed in the storage unit of the control device 70 from the recording medium. Computer-readable recording media include, for example, a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO), and a memory card.

<2. Structure of joining device>
Next, the configuration of the joining device 41 will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic plan view showing the configuration of the joining device 41. FIG. 5 is a schematic side view showing the configuration of the joining device 41.

As shown in FIG. 4, the joining device 41 has a processing container 100 capable of sealing the inside. A loading/unloading port 101 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T is formed on the side surface of the processing container 100 on the transfer region 60 side, and the loading/unloading port 101 is provided with an opening/closing shutter 102.

The inside of the processing container 100 is partitioned by the inner wall 103 into a transfer area T1 and a processing area T2. The loading/unloading port 101 described above is formed on the side surface of the processing container 100 in the transport region T1. The inner wall 103 is also formed with a loading/unloading port 104 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T.

In the transfer area T1, the transition 110, the wafer transfer mechanism 111, the reversing mechanism 130, and the position adjusting mechanism 120 are arranged side by side in this order from, for example, the loading/unloading port 101 side.

The transition 110 temporarily mounts the upper wafer W1, the lower wafer W2, and the overlapped wafer T. The transition 110 is formed in, for example, two stages, and any two of the upper wafer W1, the lower wafer W2, and the overlapped wafer T can be simultaneously placed.

As shown in FIGS. 4 and 5, the wafer transfer mechanism 111 has, for example, a transfer arm that is movable in the vertical direction (Z-axis direction), the horizontal direction (Y-axis direction, X-axis direction), and the vertical axis. The wafer transfer mechanism 111 can transfer the upper wafer W1, the lower wafer W2, and the overlapped wafer T within the transfer area T1 or between the transfer area T1 and the processing area T2.

The position adjusting mechanism 120 adjusts the horizontal orientations of the upper wafer W1 and the lower wafer W2. Specifically, the position adjusting mechanism 120 detects the positions of the base 121 having a holding unit (not shown) that holds and rotates the upper wafer W1 and the lower wafer W2, and the positions of the notch portions of the upper wafer W1 and the lower wafer W2. And a detection unit 122 that operates. The position adjustment mechanism 120 detects the positions of the notch portions of the upper wafer W1 and the lower wafer W2 by using the detection unit 122 while rotating the upper wafer W1 and the lower wafer W2 held on the base 121, and thereby the notch portion is detected. Adjust the position of. As a result, the horizontal orientations of the upper wafer W1 and the lower wafer W2 are adjusted.

The reversing mechanism 130 reverses the front and back surfaces of the upper wafer W1. Specifically, the reversing mechanism 130 has a holding arm 131 that holds the upper wafer W1. The holding arm 131 extends in the horizontal direction (X-axis direction). Further, the holding arm 131 is provided with holding members 132 for holding the upper wafer W1 at, for example, four positions.

The holding arm 131 is supported by a drive unit 133 including, for example, a motor. The holding arm 131 is rotatable around the horizontal axis by the driving unit 133. Further, the holding arm 131 is rotatable about the drive unit 133 and is also movable in the horizontal direction (X-axis direction). Below the drive unit 133, another drive unit (not shown) including, for example, a motor is provided. The other drive unit allows the drive unit 133 to move in the vertical direction along the support column 134 extending in the vertical direction.

In this way, the upper wafer W1 held by the holding member 132 can be rotated about the horizontal axis by the driving unit 133 and can be moved in the vertical direction and the horizontal direction. Further, the upper wafer W1 held by the holding member 132 can rotate around the driving unit 133 and move between the position adjusting mechanism 120 and an upper chuck 140 described later.

In the processing area T2, the upper chuck 140 that holds the upper surface (non-bonding surface W1n) of the upper wafer W1 from above and the lower wafer W2 on which the lower surface (non-bonding surface W2n) of the lower wafer W2 is mounted from below. A lower chuck 141 for adsorbing and holding is provided. The lower chuck 141 is provided below the upper chuck 140, and is arranged so as to face the upper chuck 140.

As shown in FIG. 5, the upper chuck 140 is held by the upper chuck holding portion 150 provided above the upper chuck 140. The upper chuck holding unit 150 is provided on the ceiling surface of the processing container 100. The upper chuck 140 is fixed to the processing container 100 via the upper chuck holding unit 150.

The upper chuck holding unit 150 is provided with an upper imaging unit 151 that images the upper surface (bonding surface W2j) of the lower wafer W2 held by the lower chuck 141. A CCD camera, for example, is used for the upper imaging unit 151.

The lower chuck 141 is supported by a first lower chuck moving unit 160 provided below the lower chuck 141. The first lower chuck moving unit 160 moves the lower chuck 141 in the horizontal direction (X-axis direction) as described later. Further, the first lower chuck moving unit 160 is configured to be able to move the lower chuck 141 in the vertical direction and rotate about the vertical axis.

The first lower chuck moving unit 160 is provided with a lower imaging unit 161 that images the lower surface (bonding surface W1j) of the upper wafer W1 held by the upper chuck 140 (see FIG. 5). A CCD camera, for example, is used for the lower imaging unit 161.

The first lower chuck moving unit 160 is provided on the lower surface side of the first lower chuck moving unit 160, and is attached to a pair of rails 162, 162 extending in the horizontal direction (X-axis direction). The first lower chuck moving unit 160 is configured to be movable along the rail 162.

The pair of rails 162, 162 are arranged on the second lower chuck moving portion 163. The second lower chuck moving unit 163 is provided on the lower surface side of the second lower chuck moving unit 163, and is attached to the pair of rails 164 and 164 extending in the horizontal direction (Y-axis direction). The second lower chuck moving unit 163 is configured to be movable in the horizontal direction (Y-axis direction) along the rail 164. The pair of rails 164 and 164 are arranged on a mounting table 165 provided on the bottom surface of the processing container 100.

Next, detailed configurations of the upper chuck 140 and the lower chuck 141 of the joining device 41 will be described with reference to FIGS. 6 to 8. FIG. 6 is a schematic side sectional view showing the configurations of the upper chuck 140 and the lower chuck 141. FIG. 7 is a schematic bottom view of the upper chuck 140. FIG. 8 is a schematic plan view of the lower chuck 141.

As shown in FIGS. 6 and 7, the upper chuck 140 has a main body 170 having the same diameter as the upper wafer W1 or a diameter larger than the upper wafer W1.

The main body 170 is supported by the support member 180 of the upper chuck holder 150. The support member 180 is provided so as to cover at least the upper surface of the main body 170 in a plan view, and is fixed to the main body 170 by, for example, screwing. The support member 180 is supported by a plurality of support columns 181 (see FIG. 5) provided on the ceiling surface of the processing container 100.

A through hole 178 is formed in the center of the support member 180 and the main body 170 so as to penetrate the support member 180 and the main body 170 in the vertical direction. The position of the through hole 178 corresponds to the central portion of the upper wafer W1 that is suction-held by the upper chuck 140. Then, the pressing pin 191 of the striker 190 is inserted into the through hole 178.

The striker 190 is arranged on the upper surface of the support member 180, and includes a pressing pin 191, an actuator portion 192, and a linear motion mechanism 193. The pressing pin 191 is a columnar member extending along the vertical direction, and is supported by the actuator portion 192.

The actuator unit 192 generates a constant pressure in a constant direction (here, vertically downward) by air supplied from an electropneumatic regulator (not shown), for example. The actuator unit 192 can control the pressing load applied to the central portion of the upper wafer W1 by coming into contact with the central portion of the upper wafer W1 by the air supplied from the electropneumatic regulator. In addition, the tip of the actuator portion 192 is vertically movable by the air from the electropneumatic regulator through the through hole 178.

The actuator section 192 is supported by the linear motion mechanism 193. The linear motion mechanism 193 moves the actuator section 192 in the vertical direction by, for example, a drive section having a built-in motor.

The striker 190 is configured as described above, and the movement of the actuator 192 is controlled by the linear motion mechanism 193, and the pressing load of the upper wafer W1 by the pressing pin 191 is controlled by the actuator 192.

A plurality of pins 171 that come into contact with the back surface (non-bonding surface W1n) of the upper wafer W1 are provided on the lower surface of the main body 170. A rib 172 that supports the outer peripheral portion of the back surface (non-bonding surface W1n) of the upper wafer W1 is provided on the lower surface of the main body 170. The rib 172 is provided in an annular shape on the outer side of the plurality of pins 171.

Further, another rib 173 is provided inside the rib 172 on the lower surface of the main body 170. The rib 173 is provided in an annular shape concentric with the rib 172. The region inside the rib 172 is divided into a first suction region 174a inside the rib 173 and a second suction region 174b outside the rib 173.

A suction tube 175a is provided in the first suction area 174a. A vacuum pump 177a is connected to the suction pipe 175a via a pressure regulator 176a. A suction tube 175b is provided in the second suction area 174b. A vacuum pump 177b is connected to the suction pipe 175b via a pressure regulator 176b.

Then, the suction regions 174a and 174b formed by being surrounded by the upper wafer W1, the main body 170 and the ribs 172 are evacuated through the suction pipes 175a and 175b, respectively, and the suction regions 174a and 174b are decompressed. At this time, since the atmosphere outside the suction regions 174a and 174b is atmospheric pressure, the upper wafer W1 is pushed toward the suction regions 174a and 174b by the atmospheric pressure by the reduced pressure, and the upper wafer W1 is attracted to the upper chuck 140. Retained. The upper chuck 140 is configured to be able to vacuum the upper wafer W1 for each of the first suction region 174a and the second suction region 174b.

In such a case, the rib 172 supports the outer peripheral portion of the back surface (non-bonding surface W1n) of the upper wafer W1, so that the upper wafer W1 is appropriately vacuumed to the outer peripheral portion. Therefore, the entire surface of the upper wafer W1 is adsorbed and held by the upper chuck 140, the flatness of the upper wafer W1 can be reduced, and the upper wafer W1 can be flattened.

Moreover, since the heights of the plurality of pins 171 are uniform, the flatness of the lower surface of the upper chuck 140 can be further reduced. Thus, the lower surface of the upper chuck 140 can be flattened (the flatness of the lower surface can be reduced) to suppress the vertical distortion of the upper wafer W1 held by the upper chuck 140. Further, since the back surface (non-bonding surface W1n) of the upper wafer W1 is supported by the plurality of pins 171, the upper wafer W1 is easily separated from the upper chuck 140 when the upper chuck 140 releases the vacuum of the upper wafer W1. Become.

A partition 200 is provided on the upper chuck 140. The partition wall 200 is provided in an annular shape so as to surround the upper wafer W1 suction-held by the upper chuck 140. The partition wall 200 is a process for performing a bonding process between the upper wafer W1 and the lower wafer W2 when the lower chuck 141 is brought closer to the upper chuck 140 by using the first lower chuck moving unit 160 (see FIG. 5). A space is formed with the upper chuck 140 and the lower chuck 141.

The partition wall 200 includes a ceiling portion 211, a peripheral wall portion 212, and a stretchable portion 213. The ceiling portion 211 is an annular member that surrounds the periphery of the main body portion 170, and is provided, for example, at a stepped portion between the main body portion 170 and the support member 180.

The lower surface of the ceiling portion 211 is provided at the same height as the lower surface of the main body portion 170. That is, the lower surface of the ceiling portion 211 is provided at a position higher than the upper surface of the upper wafer W1 sucked and held by the upper chuck 140.

The peripheral wall portion 212 is a cylindrical member that surrounds the upper wafer W1 on the outer peripheral side of the exhaust port 201 and the gas introduction port 205 of the ceiling portion 211, which will be described later.

The expandable part 213 is a member that is expandable and contractible in the vertical direction, and is made of, for example, a metal bellows. The upper end of the expandable portion 213 is fixed to the lower end of the peripheral wall portion 212. Further, the lower end of the expandable portion 213 contacts the upper surface of the main body 250 when the lower chuck 141 is brought close to the upper chuck 140. A closed processing space is formed by the lower end of the expandable portion 213 contacting the upper surface of the main body 250. The expansion/contraction part 213 has only to be vertically expandable/contractible, and is not limited to a metal bellows.

An exhaust port 201 is formed on the lower surface of the ceiling portion 211. The exhaust port 201 is connected to a vacuum pump 204 via a suction pipe 202 and a pressure regulator 203. The vacuum pump 204 exhausts the atmosphere in the processing space described above through the exhaust port 201. The pressure adjuster 203 and the vacuum pump 204 correspond to an example of a pressure reducing mechanism that exhausts the processing space to reduce the pressure.

A gas inlet 205 is formed on the lower surface of the ceiling portion 211. The gas introduction port 205 is connected to a gas supply source 208 via a gas introduction pipe 206 and a supply device group 207. The gas supply source 208 supplies an inert gas into the above-mentioned processing space via the gas inlet 205. The supply device group 207 is configured to include an opening/closing valve and a flow rate adjusting mechanism, and opens and closes the gas introducing pipe 206 and adjusts the flow rate of the inert gas flowing through the gas introducing pipe 206.

The gas introduction pipe 206, the supply device group 207, and the gas supply source 208 correspond to an example of a gas supply unit that supplies an inert gas into the processing space via the gas introduction port 205.

In the bonding apparatus 41 according to the present embodiment, since the upper wafer W1 is bonded to the lower wafer W2 in a warped state by the striker 190, extra stress is applied to the upper wafer W1, and this stress causes the overlaid wafer T to be distorted. Will occur.

In order to reduce the distortion that occurs in the overlapped wafer T, it is preferable that the distance between the upper wafer W1 and the lower wafer W2 be narrowed to reduce the deflection of the upper wafer W1 as much as possible. However, when the distance between the upper wafer W1 and the lower wafer W2 is narrowed, it becomes difficult for the air between the wafers to escape due to the viscosity. As a result, stress is rather applied to the upper wafer W1 and the lower wafer W2 during bonding, which may worsen the distortion (distortion) of the overlapped wafer T.

Therefore, in the bonding apparatus 41 according to the present embodiment, a processing space sealed by the upper chuck 140, the lower chuck 141, and the partition wall 200 is formed, and the atmosphere of this processing space is replaced with an inert gas having a lower viscosity than air. In this state, the upper wafer W1 and the lower wafer W2 are bonded together.

This makes it possible to reduce the distortion (distortion) of the overlapped wafer T by narrowing the gap between the upper wafer W1 and the lower wafer W2 while eliminating the influence of the viscous resistance of gas at the time of bonding. Further, since the upper wafer W1 is less likely to receive resistance from the gas during the bonding process, it is possible to suppress the elongation of the upper wafer W1 that occurs during bonding. Therefore, it is possible to reduce the positional deviation (scaling) between the bonded upper wafer W1 and lower wafer W2.

Here, as the inert gas supplied to the processing space, for example, helium gas, nitrogen gas, argon gas or the like can be used. Of these, when helium gas is used, in addition to the effect of reducing the viscous resistance, it is possible to obtain the effect of reducing the voids (edge voids) generated at the peripheral portion of the overlapped wafer T due to dew condensation.

Specifically, the atmosphere between the upper wafer W1 and the lower wafer W2 is pushed out from the central portion of the upper wafer W1 and the lower wafer W2 to the outer peripheral portion as the bonding area between the upper wafer W1 and the lower wafer W2 is expanded. Go As a result, the atmospheric pressure between the upper wafer W1 and the lower wafer W2 decreases, and the decrease in atmospheric pressure causes a temperature change.

Since the Joule-Thomson coefficient of nitrogen gas or argon gas is positive, the temperature decreases as the atmospheric pressure decreases. As a result, dew condensation occurs and edge voids occur at the peripheral edge of the overlapped wafer T. On the other hand, the Joule-Thomson coefficient of helium gas is negative, and since the temperature rises when the atmospheric pressure decreases, dew condensation does not occur. Therefore, the use of helium gas as the inert gas supplied to the processing space can prevent the generation of edge voids.

Subsequently, the configuration of the lower chuck 141 will be described. As shown in FIGS. 6 and 8, the lower chuck 141 adopts a pin chuck method like the upper chuck 140. The lower chuck 141 has a main body 250 having the same diameter as the lower wafer W2 or a diameter larger than that of the lower wafer W2. A plurality of pins 251 that come into contact with the back surface (non-bonding surface W2n) of the lower wafer W2 are provided on the upper surface of the main body portion 250. Further, on the upper surface of the main body portion 250, a rib 252 that supports the outer peripheral portion of the back surface (non-bonding surface W2n) of the lower wafer W2 is provided. The rib 252 is annularly provided outside the plurality of pins 251.

Further, another rib 253 is provided on the upper surface of the main body 250 inside the rib 252. The rib 253 is provided in an annular shape concentric with the rib 252. The area inside the rib 252 is divided into a first suction area 254a inside the rib 253 and a second suction area 254b outside the rib 253.

A suction tube 255a is provided in the first suction area 254a. The suction pipe 255a is connected to a vacuum pump 257a via a pressure regulator 256a. A plurality of suction pipes 255b are provided in the second suction area 254b. A vacuum pump 257b is connected to the plurality of suction pipes 255b via a pressure regulator 256b.

Then, the suction regions 254a and 254b formed surrounded by the lower wafer W2, the main body 250 and the ribs 252 are evacuated through the suction pipes 255a and 255b, respectively, and the suction regions 254a and 254b are depressurized. At this time, since the atmosphere outside the suction regions 254a, 254b is atmospheric pressure, the lower wafer W2 is pushed toward the suction regions 254a, 254b by the reduced pressure, and the lower wafer W2 is attracted to the lower chuck 141. Retained. The lower chuck 141 is configured to be able to vacuum the lower wafer W2 for each of the first suction region 254a and the second suction region 254b.

In this case, the ribs 252 support the outer peripheral portion of the back surface of the lower wafer W2, so that the lower wafer W2 is appropriately evacuated to the outer peripheral portion. Therefore, the entire surface of the lower wafer W2 is suction-held by the lower chuck 141, the flatness of the lower wafer W2 can be reduced, and the lower wafer W2 can be flattened.

Further, since the back surface of the lower wafer W2 is supported by the plurality of pins 251, the lower wafer W2 is easily peeled off from the lower chuck 141 when the vacuuming of the lower wafer W2 by the lower chuck 141 is released.

As shown in FIG. 8, in the vicinity of the central portion of the main body 250 of the lower chuck 141, through holes 258 penetrating the main body 250 in the thickness direction are formed at, for example, three places. An elevating pin provided below the first lower chuck moving section 160 is inserted into the through hole 258. A guide member 259 that prevents the lower wafer W2 and the like from jumping out or slipping off the lower chuck 141 is provided on the outer peripheral portion of the main body 250. The guide members 259 are provided on the outer peripheral portion of the main body 250 at a plurality of locations, for example, four locations at equal intervals.

<3. Specific operation of joining system>
Next, a specific operation of the joining system 1 will be described with reference to FIGS. 9 to 16. FIG. 9 is a flowchart showing a part of the processing executed by the joining system 1. 10 to 16 are operation explanatory diagrams of the joining process. The various processes shown in FIG. 9 are executed under the control of the control device 70.

First, the cassette C1 accommodating a plurality of upper wafers W1, the cassette C2 accommodating a plurality of lower wafers W2, and the empty cassette C3 are mounted on a predetermined mounting plate 11 of the loading/unloading station 2. After that, the upper wafer W1 in the cassette C1 is taken out by the transfer device 22 and transferred to the transition device 50 of the third processing block G3 of the processing station 3.

Next, the upper wafer W1 is transferred by the transfer device 61 to the surface reforming device 30 of the first processing block G1. In the surface reforming apparatus 30, oxygen gas, which is a processing gas, is excited into plasma and ionized under a predetermined reduced pressure atmosphere. The bonding surface W1j of the upper wafer W1 is irradiated with the oxygen ions, and the bonding surface W1j is plasma-processed. As a result, the bonding surface W1j of the upper wafer W1 is modified (step S101).

Next, the upper wafer W1 is transferred to the surface hydrophilization device 40 of the second processing block G2 by the transfer device 61. The surface hydrophilization device 40 supplies pure water onto the upper wafer W1 while rotating the upper wafer W1 held by the spin chuck. Then, the supplied pure water diffuses on the bonding surface W1j of the upper wafer W1, and a hydroxyl group (silanol group) is attached to the bonding surface W1j of the upper wafer W1 modified by the surface reforming apparatus 30 to cause the bonding surface. W1j is made hydrophilic. Further, the bonding surface W1j of the upper wafer W1 is washed with the pure water (step S102).

Next, the upper wafer W1 is transferred by the transfer device 61 to the bonding device 41 of the second processing block G2. The upper wafer W1 carried into the bonding apparatus 41 is transferred to the position adjusting mechanism 120 by the wafer transfer mechanism 111 via the transition 110. Then, the position adjusting mechanism 120 adjusts the horizontal direction of the upper wafer W1 (step S103).

After that, the upper wafer W1 is transferred from the position adjusting mechanism 120 to the holding arm 131 of the reversing mechanism 130. Subsequently, in the transfer region T1, the holding arm 131 is turned over, so that the front and back surfaces of the upper wafer W1 are turned over (step S104). That is, the bonding surface W1j of the upper wafer W1 is directed downward.

After that, the holding arm 131 of the reversing mechanism 130 rotates to move below the upper chuck 140. Then, the upper wafer W1 is transferred from the reversing mechanism 130 to the upper chuck 140. The upper wafer W1 has its non-bonded surface W1n adsorbed and held by the upper chuck 140 with its notch portion facing in a predetermined direction (step S105).

While the processing of steps S101 to S105 described above is performed on the upper wafer W1, the processing of the lower wafer W2 is performed. First, the lower wafer W2 in the cassette C2 is taken out by the transfer device 22 and transferred to the transition device 50 of the processing station 3.

Next, the lower wafer W2 is transferred to the surface modification device 30 by the transfer device 61, and the bonding surface W2j of the lower wafer W2 is modified (step S106). The modification of the bonding surface W2j of the lower wafer W2 in step S106 is the same as in step S101 described above.

After that, the lower wafer W2 is transferred to the surface hydrophilizing device 40 by the transfer device 61, the bonding surface W2j of the lower wafer W2 is hydrophilized, and the bonding surface W2j is cleaned (step S107). The hydrophilicity and cleaning of the bonding surface W2j of the lower wafer W2 in step S107 are the same as in step S102 described above.

Then, the lower wafer W2 is transferred to the bonding device 41 by the transfer device 61. The lower wafer W2 loaded into the bonding apparatus 41 is transferred to the position adjusting mechanism 120 by the wafer transfer mechanism 111 via the transition 110. Then, the position adjusting mechanism 120 adjusts the horizontal direction of the lower wafer W2 (step S108).

After that, the lower wafer W2 is transferred to the lower chuck 141 by the wafer transfer mechanism 111 and suction-held on the lower chuck 141 (step S109). In the lower wafer W2, the non-bonding surface W2n is suction-held by the lower chuck 141 with the notch portion oriented in a predetermined direction.

Next, the position adjustment of the upper wafer W1 held by the upper chuck 140 and the lower wafer W2 held by the lower chuck 141 in the horizontal direction is performed (step S110).

Next, the vertical positions of the upper wafer W1 held by the upper chuck 140 and the lower wafer W2 held by the lower chuck 141 are adjusted (step S111). Specifically, the first lower chuck moving unit 160 moves the lower chuck 141 vertically upward to bring the upper chuck 140 and the lower chuck 141 close to a first distance.

As a result, the lower end of the expansion/contraction portion 213 of the partition wall 200 abuts the upper surface of the main body 250 of the lower chuck 141 to form the processing space R (see FIG. 10).

Next, exhaust and decompression of the processing space R are performed (step S112). Specifically, the vacuum pump 204 and the pressure regulator 203 are controlled to exhaust the atmosphere in the processing space R from the suction pipe 202 (see FIG. 11).

Next, the inert gas is introduced into the processing space R (step S113). Specifically, the supply device group 207 is controlled to supply the inert gas into the processing space R from the gas inlet 205. As a result, the atmosphere in the processing space R is replaced with the inert gas atmosphere (see FIG. 12).

Here, the control device 70 controls the pressure adjuster 203 and the supply device group 207 to make the inside of the processing space R an inert gas atmosphere whose pressure is lower than atmospheric pressure. At this time, the controller 70 controls the pressure regulators 176a, 176b, 256a, 256b so that the vacuum degree of the suction regions 174a, 174b, 254a, 254b becomes higher than the vacuum degree of the processing space R. This can prevent the upper wafer W1 from dropping and the lower wafer W2 from being displaced or warped.

In order to compensate for the suction force on the lower wafer W2 that is reduced due to the decompression of the processing space R, an electrostatic chucking unit that sucks and holds the lower wafer W2 by an electrostatic force may be built in the lower chuck 141. In this case, for example, when the pressure in the processing space R falls below a predetermined threshold value or after the pressure reduction in the processing space R is started (that is, after the processing of step S112 is started), a predetermined time has elapsed. At this time, the lower wafer W2 may be attracted and held by the electrostatic attraction unit.

Next, by using the first lower chuck moving unit 160 (see FIG. 5) to raise the lower chuck 141, the upper chuck 140 and the lower chuck 141 are shorter than the first distance as shown in FIG. The second distance, that is, the distance at the time of bonding is approached (step S114). Specifically, the upper chuck 140 and the lower chuck 141 are brought close to each other until the distance between the upper wafer W1 and the lower wafer W2 becomes less than 50 μm.

Next, as shown in FIG. 14, by lowering the pressing pin 191 of the striker 190, the central portion of the upper wafer W1 is pushed down, and the central portion of the upper wafer W1 and the central portion of the lower wafer W2 are pressed with a predetermined force. Press with (step S115). At this time, the vacuum pump 177a is stopped to release the suction holding of the upper wafer W1 in the first suction area 174a.

As a result, bonding is started between the pressed central portion of the upper wafer W1 and the pressed central portion of the lower wafer W2. Specifically, since the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 are modified in steps S101 and S106, respectively, first, the Van der Waals force (intermolecular force) is applied between the bonding surfaces W1j and W2j. Force) and the joining surfaces W1j and W2j are joined together. Furthermore, since the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 are hydrophilized in steps S102 and S107, respectively, the hydrophilic groups between the bonding surfaces W1j and W2j are hydrogen-bonded, and the bonding surfaces W1j and W2j are bonded. The two are firmly joined together.

After that, the bonding region between the upper wafer W1 and the lower wafer W2 expands from the central portion of the upper wafer W1 and the lower wafer W2 to the outer peripheral portion.

Here, in the bonding apparatus 41 according to the present embodiment, since the atmosphere in the processing space R is replaced with an inert gas, it is possible to reduce the distance between the upper wafer W1 and the lower wafer W2 to a narrow gap of less than 50 μm. Even if it exists, it is not easily affected by the viscous resistance of gas. Therefore, according to the bonding apparatus 41 according to the present embodiment, it is possible to reduce the distance between the upper wafer W1 and the lower wafer W2 and reduce the distortion of the overlapped wafer T.

In addition, in the bonding apparatus 41 according to the present embodiment, the upper wafer W1 and the lower wafer W2 are bonded together in a state where the processing space R is in an inert gas atmosphere whose pressure is lower than atmospheric pressure. By thus reducing the pressure in the processing space R, the resistance that the upper wafer W1 receives from the gas during the bonding process can be further reduced, so that the distortion (distortion) of the overlapped wafer T can be further reduced. .. Further, by combining the pressure reduction and the substitution, the degree of vacuum in the processing space R does not need to be so high, in other words, the degree of vacuum is such that the upper wafer W1 and the lower wafer W2 can be suction-held by vacuuming. Even if there is, the resistance that the upper wafer W1 receives from the gas can be sufficiently reduced.

Then, as shown in FIG. 15, the operation of the vacuum pump 177b is stopped, and the suction holding of the upper wafer W1 in the second suction region 174b is released (step S116). Then, the outer peripheral portion of the upper wafer W1 falls onto the lower wafer W2. As a result, the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 come into contact with each other, and the upper wafer W1 and the lower wafer W2 are bonded (step S117).

After that, as shown in FIG. 16, the pressing pin 191 is raised to the upper chuck 140, the inert gas atmosphere in the processing space R is discharged from the exhaust port 201 and opened to the atmosphere, and the lower chuck 141 adsorbs the overlapped wafer T. Release the hold. After that, the overlapped wafer T is transferred to the transition device 51 by the transfer device 61, and then transferred to the cassette C3 by the transfer device 22 of the loading/unloading station 2. In this way, a series of joining processes is completed.

By the way, as shown in FIG. 14, when the center portion of the upper wafer W1 is pressed by the pressing pin 191, a space (hereinafter, referred to as “intermediate space”) is formed between the upper chuck 140 and the upper wafer W1. It

Therefore, in the joining device 41, the pressure in the intermediate space may be reduced as in the processing space R. Specifically, the control device 70 controls the pressure regulator 176a and the vacuum pump 177a to reduce the pressure in the intermediate space.

The intermediate space may be decompressed at least to a pressure lower than the atmospheric pressure, but it is preferable to decompress the intermediate space to a pressure substantially the same as the processing space R. It should be noted that the term “substantially the same” as used herein includes that they are completely the same, and if the pressure difference between them is within an allowable range, the pressures are regarded as “substantially the same”.

Thereby, the pressure difference between the intermediate space and the processing space R can be reduced, and the stress applied to the upper wafer W1 can be further reduced by reducing the pressure difference. Therefore, the distortion of the overlapped wafer T can be further reduced. In addition, by reducing the pressure difference between the intermediate space and the processing space R, it is possible to prevent the pressure difference from acting as a disturbance and adversely affecting the bonding accuracy of the upper wafer W1 and the lower wafer W2. it can. In addition, the elongation of the upper wafer W1 can also be suppressed.

As described above, in the bonding device 41 according to the present embodiment, the upper chuck 140 (an example of the first holding unit), the lower chuck 141 (an example of the second holding unit), and the first lower chuck moving unit 160. It is provided with (an example of an elevating mechanism), a partition wall 200, a gas inlet 205, a supply device group 207 and a gas supply source 208 (an example of a gas supply unit). The upper chuck 140 sucks and holds the upper wafer W1 (an example of the first substrate) from above. The lower chuck 141 is arranged below the upper chuck 140 and sucks and holds the lower wafer W2 from below. The first lower chuck moving unit 160 moves the lower chuck 141 along the vertical direction. The partition wall 200 is provided on the upper chuck 140 and forms a processing space R in which the upper wafer W1 and the lower wafer W2 are bonded together, together with the upper chuck 140 and the lower chuck 141. The gas inlet 205 introduces an inert gas into the processing space R. The supply device group 207 and the gas supply source 208 supply an inert gas into the processing space R via the gas introduction port 205.

Therefore, according to the bonding apparatus 41 according to the present embodiment, the gap between the upper wafer W1 and the lower wafer W2 can be narrowed to reduce the strain of the overlapped wafer T.

<4. Modification>
In the above-described embodiment, the bonding device 41 includes the striker 190, and the striker 190 pushes down the center of the upper wafer W1 to bring the center of the upper wafer W1 and the center of the lower wafer W2 into contact with each other. The wafers W1 and W2 are bonded. However, the method of joining the two wafers W1 and W2 is not limited to the method using the striker 190.

This point will be described with reference to FIGS. 17 and 18. 17 and 18 are schematic side sectional views showing the configurations of the upper chuck and the lower chuck according to the modified example. In the following description, the same parts as those already described will be denoted by the same reference numerals as those already described, and redundant description will be omitted.

As shown in FIG. 17, the upper chuck 140A according to the modification is formed such that the portion holding the upper wafer W1 is convex downward. In addition, the lower chuck 141A according to the modification is formed such that the portion holding the lower wafer W2 is convex upward.

More specifically, the upper chuck 140A is formed such that the height of the pin 171A provided at the central portion of the main body 170A is higher than the height of the pin 171A provided at the outer peripheral portion. The height of the rib 173A is also higher than that of the rib 172A. Therefore, the upper wafer W1 is adsorbed and held by the upper chuck 140A in a state of being warped in a convex shape downward.

Further, the lower chuck 141A is formed such that the height of the pin 251A provided in the central portion of the main body 250 is higher than the height of the pin 251A provided in the outer peripheral portion. The height of the rib 253A is also higher than that of the rib 252A. Therefore, the lower wafer W2 is sucked and held by the lower chuck 141A in a state of being convex upward.

Then, in the bonding apparatus 41 according to the modification, for example, by raising the lower chuck 141A by using the first lower chuck moving unit 160, as shown in FIG. 18, the central portion of the upper wafer W1 and the lower wafer W2. Can be brought into contact with the central part of the. Thereafter, the bonding area between the upper wafer W1 and the lower wafer W2 is expanded from the central portion to the outer peripheral portion of the upper wafer W1 and the lower wafer W2, so that the upper wafer W1 and the lower wafer W2 are bonded.

In this way, by bending both the upper wafer W1 and the lower wafer W2, the stress states of the two wafers W1 and W2 can be made uniform, so that, for example, between the upper wafer W1 and the lower wafer W2 due to the stretching of the wafer. Positional deviation (scaling) can be reduced.

In the embodiment described above, the example in which the partition wall 200 is provided on the upper chuck 140 has been described, but the partition wall 200 may be provided on the lower chuck 141, or may be divided into the upper chuck 140 and the lower chuck 141. It may be provided.

Further, in the above-described embodiment, the example in which the lower chuck 141 is moved up and down by using the first lower chuck moving unit 160 has been described. An upper chuck moving unit may be provided.

Further, in the above-described embodiment, the partition wall 200 includes the elastic portion 213 at the lower end portion of the peripheral wall portion 212, but the partition wall 200 does not include the peripheral wall portion 212 and the elastic portion 213 is provided on the lower surface of the ceiling portion 211. The configuration may be provided. That is, the peripheral wall portion may be entirely configured by the stretchable portion 213. Further, the partition wall 200 does not necessarily need to include the expansion/contraction portion 213, and may be configured to include, for example, an O-ring or the like instead of the expansion/contraction portion 213.

Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the particular details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

T Overlapping wafer W1 Upper wafer W2 Lower wafer 41 Bonding device 140 Upper chuck 141 Lower chuck 160 First lower chuck moving part 190 Striker 200 Partition wall 201 Exhaust port 202 Suction pipe 203 Pressure regulator 204 Vacuum pump 205 Gas introduction port 206 Gas introduction Pipe 207 Supply equipment group 208 Gas supply source 211 Ceiling part 212 Peripheral wall part 213 Expansion part

Claims (5)

A first holding unit that holds the first substrate by suction from above;
A second holder arranged below the first holder and sucking and holding the second substrate from below;
An elevating mechanism for moving the first holding part or the second holding part along the vertical direction,
A partition wall that is provided in the first holding unit or the second holding unit and forms a processing space in which the bonding process of the first substrate and the second substrate is performed together with the first holding unit and the second holding unit; ,
A gas inlet for introducing helium gas into the processing space,
A gas supply unit for supplying helium gas into the processing space through the gas inlet,
An exhaust port provided in any of the first holding unit, the second holding unit, and the partition wall for exhausting the processing space;
A decompression mechanism connected to the exhaust port to evacuate and decompress the processing space,
By controlling the decompression mechanism to decompress the processing space, and by controlling the gas supply unit to replace the atmosphere in the processing space with helium gas, the atmosphere of helium gas decompressed below atmospheric pressure. And a control unit that performs a bonding process between the first substrate and the second substrate ,
The control unit is
While the bonding region between the first substrate and the second substrate expands from the central portion of the first substrate and the second substrate toward the outer peripheral portion, the first holding portion and the first substrate A joining device , wherein the joining process is performed in a state in which a gap generated therebetween is depressurized . The partition wall is
The joining apparatus according to claim 1, further comprising a stretchable portion that is stretchable in a vertical direction. The control unit is
After forming the processing space by controlling the elevating mechanism to bring the first holding unit and the second holding unit close to each other by a first distance, the decompression mechanism is controlled to decompress the processing space. And controlling the gas supply unit to replace the atmosphere in the processing space with helium gas , and then controlling the elevating mechanism to move the first holding unit and the second holding unit to the first holding unit. The joining apparatus according to claim 2 , wherein the joining process is performed by approaching to a second distance shorter than the distance. A striker for pressing the central portion of the first substrate from above to contact the second substrate,
The control unit is
One any of claims 1 to 3, characterized in that the bonding process the gap in a state of reduced pressure generated between the first substrate and the first holding portion by the pressing of the first substrate by said striker joining apparatus according to One. A surface modification device for modifying the surfaces of the first substrate and the second substrate;
A surface hydrophilizing device for hydrophilizing the surfaces of the modified first substrate and second substrate;
A bonding device that bonds the first substrate and the second substrate that have been hydrophilized by an intermolecular force,
The joining device is
A first holding portion for sucking and holding the first substrate from above;
A second holder arranged below the first holder and sucking and holding the second substrate from below;
An elevating mechanism for moving the first holding part or the second holding part along the vertical direction,
A partition wall that is provided in the first holding unit or the second holding unit and forms a processing space in which the bonding process of the first substrate and the second substrate is performed together with the first holding unit and the second holding unit; ,
A gas inlet for introducing helium gas into the processing space,
A gas supply unit for supplying helium gas into the processing space through the gas inlet,
An exhaust port provided in any of the first holding unit, the second holding unit, and the partition wall for exhausting the processing space;
A decompression mechanism connected to the exhaust port to evacuate and decompress the processing space,
By controlling the decompression mechanism to decompress the processing space and controlling the gas supply unit to replace the atmosphere in the processing space with helium gas, the atmosphere of helium gas decompressed below atmospheric pressure. And a control unit that performs a bonding process between the first substrate and the second substrate ,
The control unit is
While the bonding region between the first substrate and the second substrate expands from the central portion of the first substrate and the second substrate toward the outer peripheral portion, the first holding portion and the first substrate A joining system , wherein the joining process is performed in a state in which a gap generated therebetween is depressurized .

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