Patent ID: 12198963

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the various drawings, same or corresponding parts will be assigned same reference numerals, and redundant description may be omitted. In the following description, the X-axis direction, the Y-axis direction and the Z-axis direction are orthogonal to each other, and the X-axis and Y-axis directions are horizontal directions whereas the Z-axis direction is a vertical direction. A rotational direction around a vertical axis is also referred to as “θ direction.” In the present specification, below means vertically below, and above means vertically above.

<Bonding System>

FIG.1is a plan view illustrating a bonding system1according to an exemplary embodiment.FIG.2is a side view illustrating the bonding system1according to the exemplary embodiment.FIG.3is a side view illustrating a state before a first substrate and a second substrate are bonded according to the exemplary embodiment. The bonding system1shown inFIG.1forms a combined substrate T (seeFIG.7B) by bonding a first substrate W1and a second substrate W2.

The first substrate W1is, for example, a semiconductor substrate such as a silicon wafer or a compound semiconductor wafer on which multiple electronic circuits are formed. The second substrate W2is, for example, a bare wafer on which no electronic circuit is formed. The first substrate W1and the second substrate W2have the substantially same diameter. Further, the second substrate W2may have an electronic circuit formed thereon.

In the following description, the first substrate W1may sometimes be referred to as “upper wafer W1”; the second substrate W2, “lower wafer W2”; and the combined substrate T, “combined wafer T.” Further, in the following description, as depicted inFIG.3, among surfaces of the upper wafer W1, a surface to be bonded to the lower wafer W2will be referred to as “bonding surface W1j”, and a surface opposite to the bonding surface W1jwill be referred to as “non-bonding surface W1n”. Further, among surfaces of the lower wafer W2, a surface to be bonded to the upper wafer W1will be referred to as “bonding surface W2j”, and a surface opposite to the bonding surface W2jwill be referred to as “non-bonding surface W2n.”

As depicted inFIG.1, the bonding system1includes a carry-in/out station2and a processing station3. The carry-in/out station2and the processing station3are arranged in this sequence along the positive X-axis direction. Further, the carry-in/out station2and the processing station3are connected as a single body.

The carry-in/out station2includes a placing table10and a transfer section20. The placing table10is equipped with a multiple number of placing plates11. Provided on the placing plates11are cassettes C1, C2and C3each of which accommodates therein a plurality of (e.g., 25 sheets of) substrates horizontally. For example, the cassette C1accommodates therein upper wafers W1; the cassette C2, lower wafers W2; and the cassettes C3, combined wafers T.

The transfer section20is provided adjacent to the positive X-axis side of the placing table10. Provided in the transfer section20are a transfer path21extending in the Y-axis direction and a transfer device22configured to be movable along the transfer path21. The transfer device22is configured to be movable in the X-axis direction as well as in the Y-axis direction and pivotable around the Z-axis. Further, the transfer device22is also configured to transfer the upper wafers W1, the lower wafers W2and the combined wafers T between the cassettes C1to C3placed on the placing plates11and a third processing block G3and the fourth processing block G4of the processing station3to be described later.

Further, the number of the cassettes C1to C3placed on the placing plates11is not limited to the shown example. In addition, besides the cassettes C1to C3, a cassette for collecting a problematic substrate or the like may be additionally provided on the placing plates11.

A multiple number of, for example, four processing blocks G1, G2, G3and G4equipped with various kinds of devices are provided in the processing station3. For example, the first processing block G1is provided at a front side (negative Y-axis side ofFIG.1) of the processing station3, and the second processing block G2is provided at a rear side (positive Y-axis side ofFIG.1) of the processing station3. Further, the third processing block G3is provided at a side of the carry-in/out station2(negative X-axis side ofFIG.1) of the processing station3. In the processing station3, the fourth processing block G4is provided at a side opposite to the carry-in/out station2(positive X-axis side ofFIG.1).

Provided in the first processing block G1is a surface modifying apparatus30configured to modify the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2. In the surface modifying apparatus30, a SiO2bond on the bonding surfaces W1jand W2jof the upper wafer W1and the lower wafer W2is cut to be turned into SiO of a single bond, so that the bonding surfaces W1jand W2jare modified such that these surfaces are easily hydrophilized afterwards.

Furthermore, in the surface modifying apparatus30, for example, an oxygen gas or a nitrogen gas as a processing gas is excited into plasma under a decompressed atmosphere to be ionized. As these oxygen ions or nitrogen ions are irradiated to the bonding surfaces W1jand W2jof the upper wafer W1and the lower wafer W2, the bonding surfaces W1jand W2jare plasma-processed to be modified.

In the second processing block G2, a surface hydrophilizing apparatus40and a bonding apparatus41are disposed. The surface hydrophilizing apparatus40is configured to hydrophilize and clean the bonding surfaces W1jand W2jof the upper wafer W1and the lower wafer W2with, for example, pure water. In this surface hydrophilizing apparatus40, while rotating the upper wafer W1or the lower wafer W2held by, for example, a spin chuck, the pure water is supplied onto the upper wafer W1or the lower wafer W2. Accordingly, the pure water supplied onto the upper wafer W1or the lower wafer W2is diffused onto the bonding surface W1jof the upper wafer W1or the bonding surface W2jof the lower wafer W2, so that the bonding surfaces W1jand W2jare hydrophilized.

The bonding apparatus41is configured to bond the upper wafer W1and the lower wafer W2, which are hydrophilized, by an intermolecular force. A configuration of the bonding apparatus41will be discussed later.

In the third processing block G3, as shown inFIG.2, transition (TRS) devices50and51for the upper wafer W1, the lower wafer W2and the combined wafer T are provided in two levels in this order from below.

Provided in the fourth processing block G4is an alignment measuring device55. The alignment measuring device55is configured to measure a relative position deviation between the upper wafer W1and the lower wafer W2bonded by the bonding apparatus41. The alignment measuring device55outputs measurement data to a control device70to be described later.

Further, the alignment measuring device55may be disposed at an outside of the processing station3as long as it is capable of transmitting the measurement data to the control device70. By way of example, the combined wafer T may be carried out to the outside of the processing station3through the carry-in/out station2from the processing station3, and then subjected to the measurement by the alignment measuring device55.

Further, as illustrated inFIG.1, a transfer section60is formed in a region surrounded by the first processing block G1, the second processing block G2, the third processing block G3and the fourth processing block G4. A transfer device61is provided in the transfer section60. The transfer device61is equipped with, for example, a transfer arm which is configured to be movable in a vertical direction and a horizontal direction and pivotable around a vertical axis. The transfer device61is moved within the transfer section60and transfers the upper wafers W1, the lower wafers W2and the combined wafers T with respect to preset devices within the first processing block G1, the second processing block G2, the third processing block G3and the fourth processing block G4which are adjacent to the transfer section60.

Furthermore, as depicted inFIG.1, the bonding system1includes a control device70. The control device70controls an operation of the bonding system1. The control device70may be implemented by, for example, a computer and includes, as illustrated inFIG.1, a CPU (Central Processing Unit)71, a recording medium72such as a memory, an input interface73and an output interface74. The control device70carries out various kinds of controls by allowing the CPU71to execute a program stored in the recording medium72. Further, the control device70receives a signal from an outside through the input interface73and transmits a signal to the outside through the output interface74.

The program of the control device70is recorded in an information recording medium and installed from the information recording medium. The information recording medium may be, by way of non-limiting example, a hard disc (HD), a flexible disc (FD), a compact disc (CD), a magnet optical disc (MO), or a memory card. Further, the program may be installed by being downloaded from a server through Internet.

<Bonding Apparatus>

FIG.4is a plan view illustrating the bonding apparatus41according to the exemplary embodiment.FIG.5is a side view illustrating the bonding apparatus41according to the exemplary embodiment.

As depicted inFIG.4, the bonding apparatus41includes a processing vessel100having a hermetically sealable inside. A carry-in/out opening101for the upper wafer W1, the lower wafer W2and the combined wafer T is formed on a lateral side of the processing vessel100at a side of the transfer section60. A shutter102for opening/closing the carry-in/out opening101is provided at the carry-in/out opening101.

The inside of the processing vessel100is partitioned into a transfer region T1and a processing region T2by an inner wall103. The aforementioned carry-in/out opening101is formed at a side surface of the processing vessel100in the transfer region T1. Further, a carry-in/out opening104for the upper wafer W1, the lower wafer W2and the combined wafer T is formed at the inner wall103.

In the transfer region T1, a transition110, a wafer transfer device111, an inverting device130and a position adjusting device120are arranged side by side in this sequence from, for example, a carry-in/out opening101side.

The transition110is configured to temporarily place thereon the upper wafer W1, the lower wafer W2and the combined wafer T. The transition110has, for example, two levels, and is capable of holding any two of the upper wafer W1, the lower wafer W2and the combined wafer T.

The wafer transfer device111is equipped with a transfer arm configured to be movable in the vertical direction (Z-axis direction) and the horizontal directions (Y-axis direction and X-axis direction) and also pivotable around a vertical axis, as shown inFIG.4andFIG.5. The wafer transfer device111is capable of transferring the upper wafer W1, the lower wafer W2and the combined wafer T within the transfer region T1or between the transfer region T1and the processing region T2.

The position adjusting device120is configured to adjust a direction of the upper wafer W1(lower wafer W2) in the horizontal direction. To elaborate, the position adjusting device120includes a base121equipped with a non-illustrated holder configured to hold and rotate the upper wafer W1(lower wafer W2); and a detector122configured to detect a position of a notch of the upper wafer W1(lower wafer W2). The position adjusting device120adjusts the position of the notch of the upper wafer W1(lower wafer W2) by detecting the position of the notch with the detector122while rotating the upper wafer W1(lower wafer W2) held by the base121. Accordingly, the position of the upper wafer W1(lower wafer W2) in the horizontal direction is adjusted.

The inverting device130is configured to invert a front surface and a rear surface of the upper wafer W1. To elaborate, the inverting device130is equipped with a holding arm131configured to hold the upper wafer W1. The holding arm131extends in the horizontal direction (X-axis direction). Further, the holding arm131is provided with, at four positions, for example, holding members132configured to hold the upper wafer W1.

The holding arm131is supported by a driving unit133having, for example, a motor or the like. The holding arm131is configured to be rotatable around a horizontal axis by the driving unit133. Further, the holding arm131is rotatable around the driving unit133and movable in the horizontal direction (X-axis direction). Another driving unit (not shown) including, for example, a motor or the like is provided under the driving unit133. The driving unit133can be moved in the vertical direction along a vertically extending supporting column134by this another driving unit.

Further, the upper wafer W1held by the holding members132can be rotated around the horizontal axis by the driving unit133and can also be moved in the vertical direction and the horizontal direction. Further, the upper wafer W1held by the holding members132can be moved between the position adjusting device120and an upper chuck140to be described later by being rotated around the driving unit133.

Provided within the processing region T2are the upper chuck140configured to attract and hold a top surface (non-bonding surface W1n) of the upper wafer W1from above and a lower chuck141configured to place thereon the lower wafer W and attract and hold a bottom surface (non-bonding surface W2n) of the lower wafer W2from below. The lower chuck141is provided under the upper chuck140and configured to be arranged to face the upper chuck140in parallel. The upper chuck140and the lower chuck141are arranged apart from each other in the vertical direction.

As depicted inFIG.5, the upper chuck140is held by an upper chuck holder150which is provided above the upper chuck140. The upper chuck holder150is provided at a ceiling surface of the processing vessel100. The upper chuck140is fixed to the processing vessel100with the upper chuck holder150therebetween.

The upper chuck holder150is equipped with an upper imaging device151configured to image a top surface (bonding surface W2j) of the lower wafer W2held by the lower chuck141. By way of example, a CCD camera is used as the upper imaging device151.

The lower chuck141is supported by a first lower chuck mover160provided below the lower chuck141. The first lower chuck mover160moves the lower chuck141in the horizontal direction (X-axis direction) as will be described later. Further, the first lower chuck mover160is also configured to be capable of moving the lower chuck141in the vertical direction and rotate the lower chuck141around a vertical axis.

The first lower chuck mover160is equipped with a lower imaging device161configured to image a bottom surface (bonding surface W1j) of the upper wafer W1held by the upper chuck140(seeFIG.5). The lower imaging device161may be, by way of example, a CCD camera.

The first lower chuck mover160is fastened to a pair of rails162which is provided at a bottom side of the first lower chuck mover160and extends in the horizontal direction (X-axis direction). The first lower chuck mover160is configured to be movable along the rails162.

The rails162are disposed on a second lower chuck mover163. The second lower chuck mover163is fastened to a pair of rails164which is disposed at a bottom side of the second lower chuck mover163and extends in the horizontal direction (Y-axis direction). The second lower chuck mover163is configured to be movable in the horizontal direction (Y-axis direction) along the rails164. Further, the rails164is disposed on the placing table165which is disposed at a bottom of the processing vessel100.

The first lower chuck mover160, the second lower chuck mover163, and so forth constitute a position adjuster166. The position adjuster166is configured to perform position adjustment in the horizontal direction between the upper wafer W1held by the upper chuck140and the lower wafer W2held by the lower chuck141by moving the lower chuck141in the X-axis direction, the Y-axis direction and the0direction. Further, the position adjuster166is also configured to perform position adjustment in the vertical direction between the upper wafer W1held by the upper chuck140and the lower wafer W2held by the lower chuck141by moving the lower chuck141in the Z-axis direction.

Further, although the position adjuster166of the present exemplary embodiment carries out the position adjustment between the upper wafer W1and the lower wafer W2in the horizontal direction by moving the lower chuck141in the X-axis direction, the Y-axis direction and the0direction, the present disclosure is not limited thereto. The way how the position adjuster166performs this position adjustment in the horizontal direction is not particularly limited as long as the upper chuck140and the lower chuck141are moved relatively to each other in the X-axis direction, the Y-axis direction and the0direction. By way of example, the position adjuster166may perform the position adjustment in the horizontal direction between the upper wafer W1and the lower wafer W2by moving the lower chuck141in the X-axis direction and the Y-axis direction and by moving the upper chuck140in the0direction.

Furthermore, although the position adjuster166of the present disclosure carries out the position adjustment between the upper wafer W1and the lower wafer W2in the vertical direction by moving the lower chuck141in the Z-axis direction, the present disclosure is not limited thereto. The way how the position adjuster166performs this position adjustment in the vertical direction is not particularly limited as long as the upper chuck140and the lower chuck141can be moved relatively to each other in the Z-axis direction. By way of example, the position adjuster166may perform the position adjustment between the upper wafer W1and the lower wafer W2in the vertical direction by moving the upper chuck140in the Z-axis direction.

FIG.6is a cross sectional view illustrating the upper chuck and the lower chuck according to the exemplary embodiment, showing a state immediately before the upper wafer and the lower wafer are bonded.FIG.7Ais a cross sectional view illustrating a state in the middle of bonding between the upper wafer and the lower wafer according to the present exemplary embodiment.FIG.7Bis a cross sectional view illustrating a state upon the completion of the bonding between the upper wafer and the lower wafer according to the present exemplary embodiment. Solid-lined arrows inFIG.6,FIG.7AandFIG.7Bindicate a direction in which air is suctioned by a vacuum pump.

The upper chuck140and the lower chuck141are, for example, vacuum chucks. In the present exemplary embodiment, the upper chuck140corresponds to a first holder described in claims, and the lower chuck141corresponds to a second holder described in the claims. The upper chuck140has, at the surface (bottom surface) thereof facing the lower chuck141, an attraction surface140ato which the upper wafer W1is attracted. Meanwhile, the lower chuck141has, at the surface (top surface) facing the upper chuck140, an attraction surface141ato which the lower wafer W2is attracted.

The upper chuck140has a chuck base170. The chuck base170has a diameter equal to or larger than a diameter of the upper wafer W1. The chuck base170is supported by a supporting member180. The supporting member180is disposed to cover at least the chuck base170when viewed from the top, and is fixed to the chuck base170by, for example, screws. The supporting member180is supported by a plurality of supporting columns181(seeFIG.5) provided at the ceiling surface of the processing vessel100. The supporting member180and the plurality of supporting columns181constitute the upper chuck holder150.

A through hole176is formed through the supporting member180and the chuck base170in the vertical direction. A position of the through hole176corresponds to a central portion of the upper wafer W1attracted to and held by the upper chuck140. A push pin191of a striker190is inserted into this through hole176.

The striker190is provided on a top surface of the supporting member180and is equipped with the push pin191, an actuator unit192and a linearly moving mechanism193. The push pin191is a columnar member extending along the vertical direction and is supported by an actuator unit192.

The actuator unit192is configured to generate a constant pressure in a certain direction (here, a vertically downward direction) by air supplied from, for example, an electro-pneumatic regulator (not shown). By the air supplied from the electro-pneumatic regulator, the actuator unit192is capable of controlling a press load applied to the central portion of the upper wafer W1as it is brought into contact with the central portion of the upper wafer W1. Further, a leading end of the push pin191is movable up and down in the vertical direction through the through hole176by the air from the electro-pneumatic regulator.

The actuator unit192is supported at the linearly moving mechanism193. The linearly moving mechanism193moves the actuator unit192in the vertical direction by a driving unit including a motor, for example.

The striker190is configured as described above, and controls a movement of the actuator unit192by the linearly moving mechanism193and controls the press load upon the upper wafer W1from the push pin191by the actuator unit192.

The striker190presses the upper wafer W1attracted to and held by the upper chuck140and the lower wafer W2attracted to and held by the lower chuck141to allow the upper wafer W1and the lower wafer W2to come into contact with each other. To elaborate, the striker190transforms the upper wafer W1attracted to and held by the upper chuck140, thus allowing the upper wafer W1to be pressed in contact with the lower wafer W2. The striker190corresponds to a pressing unit described in the claims.

A plurality of pins171is provided on a bottom surface of the chuck base170, and these pins171are in contact with the non-bonding surface Win of the upper wafer W1. The upper chuck140is composed of the chuck base170, the plurality of pins171, and so forth. The attraction surface140aof the upper chuck140which attracts and holds the upper wafer W1is divided into multiple regions in a diametrical direction, and generation of an attracting pressure and release of the attracting pressure are performed for divided regions individually.

Further, the lower chuck141may be configured the same as the upper chuck140. The lower chuck141has a plurality of pins in contact with the non-bonding surface W2nof the lower wafer W2. The attraction surface141aof the lower chuck141which attracts and holds the lower wafer W2is divided into multiple regions in the diametrical direction, and generation of an attracting pressure and release of the attracting pressure are performed for divided regions individually.

<Bonding Method>

FIG.8is a flowchart illustrating a part of a processing performed by the bonding system according to the exemplary embodiment. Further, the various processes shown inFIG.8are performed under the control of the control device70.

First, a cassette C1accommodating a plurality of upper wafers W1, a cassette C2accommodating a plurality of lower wafers W2and an empty cassette C3are placed on the preset placing plates11of the carry-in/out station2. Then, an upper wafer W1is taken out of the cassette C1by the transfer device22and is transferred to the transition device50of the third processing block G3of the processing station3.

Subsequently, the upper wafer W1is transferred into the surface modifying apparatus30of the first processing block G1by the transfer device61. In the surface modifying apparatus30, an oxygen gas as the processing gas is formed into plasma to be ionized under the preset decompressed atmosphere. The oxygen ions are irradiated to the bonding surface W1jof the upper wafer W1, and the bonding surface W1jis plasma-processed. As a result, the bonding surface W1jof the upper wafer W1is modified (process S101).

Then, the upper wafer W1is transferred into the surface hydrophilizing apparatus40of the second processing block G2by the transfer device61. In the surface hydrophilizing apparatus40, the pure water is supplied onto the upper wafer W1while rotating the upper wafer W1held by the spin chuck. The supplied pure water is diffused on the bonding surface W1jof the upper wafer W1, and hydroxyl groups (silanol groups) adhere to the bonding surface W1jof the upper wafer W1modified in the surface modifying apparatus30, so that the bonding surface W1jis hydrophilized (process S102). Further, the bonding surface W1jof the upper wafer W1is cleaned by this pure water used to hydrophilize the bonding surface W1j.

Thereafter, the upper wafer W1is transferred into the bonding apparatus41of the second processing block G2by the transfer device61. The upper wafer W1transferred into the bonding apparatus41is then delivered into the position adjusting mechanism120via the transition110by the wafer transfer mechanism111. Then, the direction of the upper wafer W1in the horizontal direction is adjusted by the position adjusting mechanism120(process S103).

Subsequently, the upper wafer W1is delivered from the position adjusting mechanism120onto the holding arm131of the inverting mechanism130. Then, in the transfer region T1, by inverting the holding arm131, the front surface and the rear surface of the upper wafer W1are inverted (process S104). That is, the bonding surface Wij of the upper wafer W1is turned to face down.

Afterwards, the holding arm131of the inverting mechanism130is rotated to be located under the upper chuck140. Then, the upper wafer W1is delivered to the upper chuck140from the inverting mechanism130. The non-bonding surface Win of the upper wafer W1is attracted to and held by the upper chuck140in the state that the notch of the upper wafer W1is oriented to a predetermined direction (process S105).

While the above-described processes S101to S105are being performed on the upper wafer W1, a processing of the lower wafer W2is performed. First, the lower wafer W2is taken out of the cassette C2by the transfer device22and transferred into the transition device50of the processing station3by the transfer device22.

Thereafter, the lower wafer W2is transferred into the surface modifying apparatus30by the transfer device61, and the bonding surface W2jof the lower wafer W2is modified (process S106). Further, the modification of the bonding surface W2jof the lower wafer W2in the process S106is the same as the above-stated process S101.

Then, the lower wafer W2is transferred into the surface hydrophilizing apparatus40by the transfer device61, and the bonding surface W2jof the lower wafer W2is hydrophilized (process S107). Further, the bonding surface W2jis cleaned by the pure water used to hydrophilize the bonding surface W2j. The hydrophilizing of the bonding surface W2jof the lower wafer W2in the process S107is the same as the hydrophilizing of the bonding surface W1jof the upper wafer W1in the above-described process S102.

Thereafter, the lower wafer W2is transferred into the bonding apparatus41by the transfer device61. The lower wafer W2transferred into the bonding apparatus41is then sent into the position adjusting mechanism120via the transition110by the wafer transfer mechanism111. Then, the direction of the lower wafer W2in the horizontal direction is adjusted by the position adjusting mechanism120(process S108).

Afterwards, the lower wafer W2is transferred onto the lower chuck141by the wafer transfer mechanism111and attracted to and held by the lower chuck141(process S109). At this time, the non-bonding surface W2nof the lower wafer W2is attracted to and held by the lower chuck141in the state that the notch of the lower wafer W2is oriented to the same direction as the notch of the upper wafer W1.

Thereafter, the position adjustment in the horizontal direction between the upper wafer W1held by the upper chuck140and the lower wafer W2held by the lower chuck141is performed (process S110). In this position adjustment, the alignment marks W1a, W1band W1c(seeFIG.9AtoFIG.9C) previously formed on the bonding surface W1jof the upper wafer W1and the alignment marks W2a, W2band W2cpreviously formed on the bonding surface W2jof the lower wafer W2(seeFIG.9AtoFIG.9C) are used.

An operation of the position adjustment of the upper wafer W1and the lower wafer W2in the horizontal direction will be elaborated with reference toFIG.9AtoFIG.9C.FIG.9Ais a diagram for describing an operation of performing the position adjustment between the upper imaging device and the lower imaging device according to the present exemplary embodiment.FIG.9Bis a diagram for describing an imaging operation through which the upper imaging device images the lower wafer and an imaging operation through which the lower imaging device images the upper wafer according to the present exemplary embodiment.FIG.9Cis a diagram for describing an operation of performing the position adjustment between the upper wafer and the lower wafer according to the present exemplary embodiment.

First, as shown inFIG.9A, the position adjustment between the upper imaging device151and the lower imaging device161in the horizontal direction is performed. To elaborate, the lower chuck141is moved in the horizontal direction by the position adjuster166to allow the lower imaging device161to be located under the upper imaging device151approximately. Then, a common target149is checked by the upper imaging device151and the lower imaging device161, and a position of the lower imaging device161in the horizontal direction is finely adjusted so that the positions of the upper imaging device151and the lower imaging device161in the horizontal direction are coincident.

Then, as depicted inFIG.9B, the lower chuck141is moved in the vertically upward direction by the position adjuster166. Then, while moving the lower chuck141in the horizontal direction by the position adjuster166, the alignment marks W2c, W2band W2aon the bonding surface W2jof the lower wafer W2are imaged in sequence by using the upper imaging device151. Concurrently, while moving the lower chuck141in the horizontal direction, the alignment marks W1a, W1band W1con the bonding surface W1jof the upper wafer W1are imaged in sequence by using the lower imaging device161.FIG.9Bshows a state in which the alignment marks W2cof the lower wafer W2is imaged by the upper imaging device151and the alignment mark W1aof the upper wafer W1is imaged by the lower imaging device161.

The obtained image data are output to the control device70. Based on the image data obtained by the upper imaging device151and the image data obtained by the lower imaging device161, the control device70controls the position adjuster166to adjust the position of the lower chuck141in the horizontal direction. This horizontal position adjustment is carried out such that the alignment marks W1a, W1band W1cof the upper wafer W1and the alignment marks W2a, W2band W2cof the lower wafer W2are respectively overlapped, when viewed in the vertical direction. In this way, the horizontal positions of the upper chuck140and the lower chuck141are adjusted, and the horizontal positions (for example, including positions in the X-axis direction, the Y-axis direction and the0direction) of the upper wafer W1and the lower wafer W2are adjusted.

Thereafter, as indicated by solid lines inFIG.9C, the position adjustment in the vertical direction between the upper wafer W1held by the upper chuck140and the lower wafer W2held by the lower chuck141is performed (process S111). To elaborate, the position adjuster166moves the lower chuck141in the vertically upward direction, thus allowing the lower wafer W2to approach the upper wafer W1. Accordingly, as shown inFIG.6, a distance S between the bonding surface W2jof the lower wafer W2and the bonding surface W1jof the upper wafer W1is adjusted to, e.g., 50 μm to 200 μm.

Subsequently, after releasing the attracting and holding of the central portion of the upper wafer W1by the upper chuck140(process S112), the push pin191of the striker190is lowered, so that the central portion of the upper wafer W1is pressed down (process S113), as shown inFIG.7A. If the central portion of the upper wafer W1comes into contact with the central portion of the lower wafer W2and the central portion of the upper wafer W1and the central portion of the lower wafer W2are pressed against each other with a preset force, the central portion of the upper wafer W1and the central portion of the lower wafer W2which are pressed against each other are begun to be bonded. Then, a bonding wave whereby the upper wafer W1and the lower wafer W2are gradually bonded from the central portions toward the peripheral portions thereof is generated.

Here, since the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2are modified in the processes S101and S106, respectively, a Van der Waals force (intermolecular force) is generated between the bonding surfaces W1jand W2j, so that the bonding surfaces W1jand W2jare bonded. Further, since the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2are hydrophilized in the processes S102and S107, respectively, hydrophilic groups between the bonding surfaces W1jand W2jare hydrogen-bonded, so that the bonding surfaces W1jand W2jare firmly bonded.

Thereafter, while pressing the central portion of the upper wafer W1and the central portion of the lower wafer W2with the push pin191, the attracting and holding of the entire upper wafer W1by the upper chuck140is released (process S114). Accordingly, as depicted inFIG.7B, the entire bonding surface W1jof the upper wafer W1and the entire bonding surface W2jof the lower wafer W2come into contact with each other, and the upper wafer W1and the lower wafer W2are bonded. Thereafter, the push pin191is raised up to the upper chuck140, and the attracting and holding of the lower wafer W2by the lower chuck141is released.

Subsequently, the combined wafer T is transferred to the alignment measuring device55in the fourth processing block G4by the transfer device61. In the alignment measuring device55, a relative position deviation between the alignment marks W1a, W1band W1cformed on the upper wafer W1and the alignment marks W2a, W2band W2cformed on the lower wafer W2are measured (process S115).

Thereafter, the combined wafer T is transferred to the transition device51of the third processing block G3by the transfer device61, and then is transferred into the cassette C3by the transfer device22of the carry-in/out station2. Through these processes, the series of operations of the bonding processing are completed.

<Alignment Measurement and Use of Measurement Data>

FIG.10is a cross sectional view illustrating the alignment measuring device according to the exemplary embodiment. The alignment measuring device55is configured to measure the relative position deviation (hereinafter, simply referred to as “position deviation”) between the alignment marks W1a, W1band W1c(seeFIG.9AtoFIG.9C) formed on the upper wafer W1and the alignment marks W2a, W2band W2c(seeFIG.9AtoFIG.9C) formed on the lower wafer W2. In the present specification, the position deviation implies a position deviation when viewed in the vertical direction with respect to the bonding surfaces W1jand W2jof the upper wafer W1and the lower wafer W2. The alignment measuring device55corresponds to a measuring unit described in the claims.

The alignment measuring device55is equipped with, for example, a combined wafer holder901configured to hold the combined wafer T horizontally; an infrared imaging unit902configured to acquire an infrared image of the combined wafer T held by the combined wafer holder901; and an infrared irradiating unit903configured to irradiate infrared ray to a region of the combined wafer T from which the infrared image is obtained.

The infrared imaging unit902and the infrared irradiating unit903are provided at the opposite sides with the combined wafer holder901therebetween. By way of example, the infrared imaging unit902is disposed above the combined wafer holder901, and the infrared irradiating unit903is disposed under the combined wafer holder901.

The infrared imaging unit902and the infrared irradiating unit903are arranged on the same axis. The infrared ray output from the infrared irradiating unit903passes through an opening of the combined wafer holder901having a ring shape to be vertically incident upon the combined wafer T held by the combined wafer holder901. The infrared ray which has penetrated the combined wafer T is received by the infrared imaging unit902.

Each infrared image obtained by the infrared imaging unit902includes at least one alignment mark of the upper wafer W1and at least one alignment mark of the lower wafer W2. Therefore, the relative position deviation between the alignment mark of the upper wafer W1and the alignment mark of the lower wafer W2can be measured on each infrared image.

The alignment measuring device55is further equipped with a mover (not shown) configured to move the combined wafer holder901in the X-axis direction, the Y-axis direction and the0direction. By moving the combined wafer holder901, the region of the combined wafer T from which the infrared image is obtained can be changed, so that the position deviation can be measured at multiple positions of the combined wafer T.

Further, though the mover moves the combined wafer holder901in the present exemplary embodiment, the mover only needs to move the combined wafer holder901and the infrared imaging unit902relatively. Whether the combined wafer holder901is moved or the infrared imaging unit902is moved, the region of the combined wafer T from which the infrared image is obtained can be changed, so that the position deviation can be measured at the multiple positions of the combined wafer T.

FIG.11is a functional block diagram illustrating constituent components of the control device according to the exemplary embodiment. Individual functional blocks shown inFIG.11are conceptual and may not necessarily be physically configured exactly the same as shown inFIG.11. All or a part of the functional blocks may be functionally or physically dispersed or combined on a unit. All or a part of processing functions performed in the respective functional blocks may be implemented by a program executed by the CPU or implemented by hardware through a wired logic.

As depicted inFIG.11, the control device70includes a measurement data analyzer701, a position adjustment controller702, a distortion controller703, and a determination unit704. The measurement data analyzer701is configured to analyze the measurement data obtained by the alignment measuring device55. The position adjustment controller702is configured to control a position adjustment within a horizontal plane between the upper wafer W1held by the upper chuck140and the lower wafer W2held by the lower chuck141in the currently performed bonding processing based on a position deviation generated in the previously performed bonding processing. The distortion controller703is configured to control a distortion of the lower wafer W2held by the lower chuck141in the currently performed bonding processing based on the position deviation generated in the previously performed bonding processing. The determination unit704is configured to determine, through a statistical analysis, whether there is a meaningful difference between the position deviation generated in the previously performed bonding processing and the position deviation generated in the currently performed bonding processing. If a statistical value falls out of a preset range, the determination unit704makes a determination that there is a meaningful difference. If the statistical value falls within the preset range, the determination unit704makes a determination that there is no meaningful difference.

FIG.12AandFIG.12Bare explanatory diagrams illustrating a processing performed by the measurement data analyzer according to the exemplary embodiment.FIG.12Ais a diagram illustrating the position deviation at multiple positions on an xy coordinate system fixed on the combined wafer according to the exemplary embodiment. InFIG.12A, the x-axis and the y-axis are orthogonal to each other and parallel to the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2. InFIG.12A, the x-axis fixed to the upper wafer W1and the x-axis fixed to the lower wafer W2are overlapped, and the y-axis fixed to the upper wafer W1and the y-axis fixed to the lower wafer W2are overlapped.FIG.12Bis an explanatory diagram illustrating the position deviation at each position after parallel translation and rotation are performed to minimize a size and a non-uniformity of the position deviation shown inFIG.12A. The x-axis and the y-axis indicated by solid lines inFIG.12Bare ones fixed to the upper wafer W1, and the x-axis and the y-axis indicated by dashed lines are ones fixed to the lower wafer W2.

First, the measurement data analyzer701first calculates the position deviations at the multiple positions on the xy coordinate system fixed to the combined wafer T, as shown inFIG.12A. In this calculation, the relative position deviations between the alignment marks W1a, W1band W1cof the upper wafer W1and the alignment marks W2a, W2band W2cof the lower wafer W2on the images obtained by the infrared imaging unit902and horizontal positions (an X-axis position, a Y-axis position and a θ-directional position) of the combined wafer holder901with respect to the infrared imaging unit902at the moment when the images are obtained are used.

Further, the number of the positions where the position deviation are measured is not limited to three but may be more than three. Furthermore, the shape of each alignment mark for measuring the position deviation is not limited to a cross-shape.

Then, the measurement data analyzer701calculates parallel translations Δx and Δy and a rotation Δθ of the lower wafer W2with respect to the upper wafer W1to minimize the size and the non-uniformity of the position deviation therebetween, as depicted inFIG.12B. The parallel translations and the rotation are performed so that a maximum value of the position deviation is reduced or a standard deviation of the position deviation is minimized, for example. Further, the non-uniformity may be represented by a difference between the maximum value and the minimum value of the position deviations instead of the standard deviation.

At this time, the measurement data analyzer701calculates a position deviation at each position after the parallel translations and the rotation are performed. The calculation of the optimal parallel translation/rotation and the calculation of the position deviation at each position after the optimal parallel translation/rotation are performed are carried out substantially at the same time.

Further, though the lower wafer W2is parallel-translated and rotated in the present exemplary embodiment, the lower wafer W2may be parallel-translated, and the upper wafer W1may be rotated. Alternatively, the upper wafer W1may be parallel-translated and rotated.

FIG.13is a flowchart illustrating a processing of deciding settings of the bonding apparatus based on the measurement data of the alignment measuring device according to the exemplary embodiment. Processes after a process S201ofFIG.13are performed under the control of the control device70and carried out in response to, for example, a correction instruction for the position adjustment. The correction instruction for the position adjustment is created when a production condition (including a production lot) of the upper wafer W1or the lower wafer W2is changed, for example.

First, the bonding system1bonds the upper wafer W1and the lower wafer W2by performing the processes S101to S114ofFIG.8(process S201). Then, the alignment measuring device55measures the relative position deviation between the upper wafer W1and the lower wafer W2at each of the multiple positions, the same as in the process S115ofFIG.8(process S202).

Thereafter, the measurement data analyzer701calculates the parallel translations Δx and Δy and the rotation Δθ to minimize the non-uniformity and the size of the position deviation (process S203). Further, the measurement data analyzer701calculates the position deviation at each position after the parallel translations and rotation calculated in the process S203are performed (process S204).

Further, the calculation of the parallel translations and the rotation (process S203) and the calculation of the position deviation at each position after the parallel translations and the rotation are performed (process S204) are carried out substantially at the same time.

Afterwards, the measurement data analyzer701checks whether the cumulative number of the calculation data is equal to or larger than a preset number (process S205). The calculation data refers to data regarding the parallel translations Δx and Δy and the rotation Δθ and the position deviation at each position after the parallel translations and the rotation are performed. For example, the preset number is set to be equal to or larger than a value (e.g., 20) which allows a distribution of the calculation data to be a normal distribution.

If the cumulative number of the calculation data is less than the preset number (process S205: No), the cumulative number of the calculation data has not reached a sufficient number for statistical analysis, and there is a concern that the non-uniformity in the distribution of the calculation data has been caused by an accidental disturbance. Thus, in this case, the control device70returns to the process S201and repeats the process S201and the subsequent processes. That is, the processes S201to S204are repeated until the number of combined wafers T reaches a preset number.

Meanwhile, if the cumulative number of the calculation data is equal to or larger than the preset number (process S205: Yes), the cumulative number of the calculation data has reached the sufficient number for the statistical analysis. Therefore, the control device70proceeds to a process S206and performs the process S206and subsequent processes.

In the process S206, by statistically analyzing the calculation data, the measurement data analyzer701sets correction data ΔX, ΔY and ΔΘ to be used in the position adjustment in the horizontal direction between the upper wafer W1and the lower wafer W2which is performed before the bonding is carried out. As the correction data ΔX, ΔY and ΔΘ, average values of the calculation data Δx, Δy and Δθ may be used, for example.

Further, if the distribution of the calculation data does not become a normal distribution even if the cumulative number of the calculation data has reached the preset number, median values of the calculation data Δx, Δy and Δθ may be used as the correction data ΔX, ΔY and ΔΘ.

Then, the measurement data analyzer701predicts a position deviation when the position adjustment in the horizontal direction is performed by using the correction data (process S207). For the purpose, the average values (or the median values) of the calculation data may be used, for example.

Then, the measurement data analyzer701sets a parameter which generates a distortion of the lower wafer W2to reduce the predicted position deviation (process S208). Besides (1) an attracting pressure on the attraction surface141aof the lower chuck141for attracting the lower wafer W2, (2) a temperature of the lower wafer W2or (3) a shape of the attraction surface141aof the lower chuck141may be used as the parameter which causes the distortion of the lower wafer W2.

(1) If a distribution of the attracting pressure on the attraction surface141aof the lower chuck141is varied, a distribution of a stress applied to the lower wafer W2is changed, causing a shape of the lower wafer W2to be changed. Thus, by controlling the distribution of the attracting pressure on the attraction surface141aof the lower chuck141, the distortion of the lower wafer W2can be controlled. The attraction surface141aof the lower chuck141is partitioned into multiple regions, and the attracting pressure is set for each of the multiple regions individually. When the lower wafer W2is attracted by the attraction surface141aof the lower chuck141, the attracting pressure may be generated in the entire attraction surface141aof the lower chuck141, or only in a part of the attraction surface141aof the lower chuck141. While maintaining the temperature of the lower wafer W2constant, it is possible to control the distortion of the lower wafer W2.

(2) If the temperature distribution of the lower wafer W2is changed, the shape of the lower wafer W2is changed as the lower wafer W2is locally contracted or expanded. Therefore, by controlling the temperature distribution of the lower wafer W2, the distortion of the lower wafer W2can be controlled. The control of the temperature distribution of the lower wafer W2is carried out in the state that the attraction of the lower wafer W2by the lower chuck141is released, for example. Subsequently, the lower chuck141attracts the lower wafer W2in the state that there is generated non-uniformity in the temperature distribution of the lower wafer W2. Then, the shape of the lower wafer W2is fixed until the attraction of the lower wafer W2is released again. During a period until the attraction of the lower wafer W2is released again, the shape of the lower wafer W2, which is made when there is the non-uniformity in the temperature distribution of the lower wafer W2, is maintained even if the temperature distribution of the lower wafer W2becomes uniform.

(3) If the shape of the attraction surface141aof the lower chuck141is changed after the lower wafer W2is attracted to the attraction surface141aof the lower chuck141, the shape of the lower wafer W2is changed to follow the change of the attraction surface141a. Thus, by controlling the shape of the attraction surface141aof the lower chuck141, the distortion of the lower wafer W2can be controlled. The attraction surface141aof the lower chuck141may be transformed between, for example, a flat surface and a curved surface. By way of example, the curved surface has an upwardly protruding dome shape. If the attraction surface141aof the lower chuck141is transformed from the flat surface to the curved surface after the lower wafer W2is attracted to the attraction surface141aof the lower chuck141, the lower wafer W2is also transformed to have the upwardly protruding dome shape. Accordingly, the lower wafer W2can be expanded in a diametrical direction, so that the size of the lower wafer W2and the size of the upper wafer W1can be made equal. The upper wafer W1is bent to have a downwardly protruding dome shape by the striker190and thus expanded in the diametrical direction.

The distortion of the lower wafer W2may be controlled by controlling one of the above-described parameters (1) to (3), or by controlling a plurality of the parameters (1) to (3). When controlling the distortion of the lower wafer W2by using the plurality of the parameters, a combination of the parameters is not particularly limited.

Furthermore, the correction data ΔX, ΔY and ΔΘ to be used in the position adjustment in the horizontal direction between the upper wafer W1and the lower wafer W2performed before the bonding is carried out may be reset based on the setting of the parameter(s) which causes the distortion of the lower wafer W2.

Through the above-described processes, the processing of deciding the settings for use in the bonding apparatus41based on the measurement data obtained by the alignment measuring device55is completed.

FIG.14is a flowchart illustrating an operation of the bonding apparatus based on the measurement data of the alignment measuring device according to the exemplary embodiment. Processes from a process S301inFIG.14are performed under the control of the control device70in response to an instruction for bonding the upper wafer W1and the lower wafer W2after the completion of the series of processes shown inFIG.13, for example.

First, the bonding system1bonds the upper wafer W1and the lower wafer W2by performing the processes S101to S114ofFIG.8according to the settings obtained in the processes S206and S208ofFIG.13(process S301).

By way of example, the distortion controller703performs the attracting and holding of the lower wafer W2in the process S109ofFIG.8based on the setting of the attracting pressure obtained in the process S208ofFIG.13. Further, besides the attracting pressure, the distortion of the lower wafer W2may be controlled by using the shape of the attraction surface, the temperature, or the like, as stated above.

Further, the position adjustment controller702performs the position adjustment in the horizontal direction in the process S110ofFIG.8based on the settings of the correction data ΔX, ΔY and ΔΘ obtained in the process S206ofFIG.13. To elaborate, the position adjustment controller702carries out the position adjustment in the horizontal direction based on the image data obtained by the upper imaging unit151, the image data obtained by the lower imaging unit161and the correction data. A difference between a position of the lower chuck141after the position adjustment in the horizontal direction based on both image data and the correction data and a position of the lower chuck141after the position adjustment in the horizontal direction based on only both image data is the same as, for example, the correction data. Furthermore, though the position adjustment in the horizontal direction is carried out by moving the lower chuck141in the present exemplary embodiment, it can be achieved by moving the upper chuck140instead or by moving both the upper chuck140and the lower chuck141, as mentioned above.

Subsequently, the alignment measuring device55measures the relative position deviation between the upper wafer W1and the lower wafer W2at multiple positions, the same as in the process S202ofFIG.13(process S302).

Then, the measurement data analyzer701calculates the parallel translations Δx and Δy and the rotation Δθ to minimize the size and the non-uniformity of the position deviation therebetween, the same as in the process S203ofFIG.13(process S303). Further, the measurement data analyzer701calculates a position deviation at each position after the parallel translations and the rotation calculated in the process S303are performed (process S304).

Further, the calculation of the parallel translations and the rotation (process S303) and the calculation of the position deviation at each position after the parallel translations and the rotation are performed are carried out substantially at the same time.

Afterwards, the determination unit704determines, through the statistical analysis, whether there is the meaningful difference between the position deviation generated in the previously performed bonding processing and the position deviation generated in the currently performed bonding processing (process S305). It may be determined through the statistical analysis whether there is a meaningful difference between a position deviation generated in the previously performed bonding processings and a position deviation generated in the most recent bonding processings (including the current one). For the statistical analysis, t-test (student's t-test) or F-test may be used, for example.

In this determination, the parallel translations Δx and Δy and the rotation Δθ calculated in the process S203ofFIG.13and at least one selected from the position deviation at the individual positions calculated in the process S204ofFIG.13may be used as the position deviation generated in the previously performed bonding processing, for example. Either Δx or Δy may be used.

Furthermore, in this determination, the parallel translations Δx and Δy and the rotation Δθ calculated in the process S303ofFIG.14and at least one selected from the position deviation at the individual positions calculated in the process S304ofFIG.14may be used as the position deviation generated in the currently performed bonding processing, for example. Either Δx or Δy may be used.

If there is the meaningful difference between the position deviation generated in the previously performed bonding processing and the position deviation generated in the currently performed bonding processing (process S305; Yes), a quality of the combined wafer T may fall out of a tolerance range, and there is a likelihood that a problem such as an attraction failure may be generated. Thus, in such a case, the determination unit704makes a determination that there is abnormality (process S306), and the current processing is ended.

Further, if the determination unit704makes the determination of the abnormality, the control device70may notify an alarm to a user of the bonding system1. The alarm is outputted in the form of an image, a sound or a buzzer. After the user repairs the bonding system1, the processing from the process S301is resumed. As stated, by stopping the bonding processing when there is a problem such as the attraction failure, production of defective products, which is a waste, can be suppressed.

Meanwhile, if there is no meaningful difference between the position deviation generated in the previously performed bonding processing and the position deviation generated in the currently performed bonding processing (process S305; No), the quality of the combined wafer T falls within the tolerance range. In such a case, the determination unit704makes a determination of normality (process S307), and the current processing is ended.

As stated above, according to the present exemplary embodiment, the position adjustment in the horizontal direction in the currently performed bonding processing is controlled based on the position deviation between the alignment marks generated in the previously performed bonding processing. Thus, the position deviation between the alignment marks, which is not solved in the position adjustment in the horizontal direction performed based on only the image data of the upper imaging unit151or the lower imaging unit161, can be reduced.

Moreover, according to the present exemplary embodiment, the distortion of the lower wafer W2in the currently performed bonding processing is controlled based on the position deviation between the alignment marks generated in the previously performed bonding processing. Accordingly, the position deviation between the alignment marks, which is not solved in the relative parallel translations or rotation between the upper wafer W1and the lower wafer W2, can be reduced.

In addition, according to the present exemplary embodiment, it is determined through the statistical analysis whether there is the meaningful difference between the position deviation between the alignment marks generated in the previously performed bonding processing and the position deviation between the alignment marks generated in the currently performed bonding processing. Accordingly, it is possible to determine whether the quality of the combined wafer T falls out of the tolerance range, and it can be determined whether a problem such as the attraction failure has occurred. In case that the problem such as the attraction failure is generated, by stopping the bonding processing, the production of defective products, which is a waste, can be suppressed.

<Control Over Distortion of Lower Wafer>

FIG.15is a diagram illustrating the attraction surface of the lower chuck according to the exemplary embodiment. The lower chuck141shown inFIG.15has, on the attraction surface141aconfigured to attract the lower wafer W2, multiple regions (for example, circular arc regions A1, circular arc regions A2, circular arc regions B1, circular arc regions B2and a circular region C) in which the attracting pressure (for example, a vacuum pressure) for attracting the lower wafer W2is controlled independently. The circular arc regions A1and A2are arranged alternately in a circumferential direction, forming a ring region A. Inside this ring region A in a diametrical direction, the circular arc regions B1and B2are arranged alternately in the circumferential direction, forming a ring region B. Inside this ring region B, the circular region C is formed. That is, the attraction surface141ais divided into the ring region A, the ring region B and the circular region C as it goes inwards in the diametrical direction. The ring region A is divided into multiple circular arc regions A1and A2in the circumferential direction. Likewise, the ring region B is divided into multiple circular arc regions B1and B2in the circumferential direction.

One vacuum pump251is connected to the multiple circular arc regions A1via pipelines which are equipped with one electro-pneumatic regulator261(inFIG.15, only a pipeline connected to the single circular arc region A1is illustrated). Likewise, one vacuum pump252is connected to the multiple circular arc regions A2via pipelines which are equipped with one electro-pneumatic regulator262(inFIG.15, only a pipeline connected to the single circular arc region A2is illustrated). Further, one vacuum pump253is connected to the multiple circular arc regions B1via pipelines which are equipped with one electro-pneumatic regulator263(inFIG.15, only a pipeline connected to the single circular arc region B1is illustrated). Likewise, one vacuum pump254is connected to the multiple arc regions B2via pipelines which are equipped with one electro-pneumatic regulator264(inFIG.15, only a pipeline connected to the single circular arc region B2is illustrated). Furthermore, one vacuum pump255is connected to the single circular region C via a pipeline which is equipped with one electro-pneumatic regulator265.

If the control device70operates the vacuum pump251, the vacuum pump251generates the vacuum pressure in each of the circular arc regions A1. This vacuum pressure is maintained at a predetermined set value by the electro-pneumatic regulator261, so that an attracting pressure corresponding to this set value is generated in each of the circular arc regions A1. If the control device70stops the operation of the vacuum pump251, each circular arc region A1is turned back into an atmospheric pressure, so that the generation of the attracting pressure in each circular arc region A1is stopped. Since the generation and the release of the attracting pressure in the other circular arc regions A2, B1and B2and in the circular region C are the same as the generation and the release of the attracting pressure in the circular arc regions A1, redundant description thereof will be omitted here.

The vacuum pumps251to255, the electro-pneumatic regulators261to265, and so forth constitute an attracting pressure distribution adjuster250. The attracting pressure distribution adjuster250is configured to adjust a distribution of the attracting pressure of the lower chuck141configured to attract the lower wafer W2, thus generating the distortion of the lower wafer W2. The distribution of the attracting pressure can be varied by selecting operating target vacuum pumps from the vacuum pumps251to255or by changing the set values for the electro-pneumatic regulators261to265. This changing of the settings is performed by the distortion controller703. Further, the layout of the regions in which the attracting pressures are controlled independently is not limited to the example shown inFIG.15.

Further, though the lower chuck141is configured to vacuum-attract the lower wafer W2in the present exemplary embodiment, the lower chuck141may be configured to attract the lower wafer W2electrostatically. In this case, the attracting pressure distribution adjuster250includes multiple internal electrodes embedded in the lower chuck141; a power supply configured to supply a power to the internal electrodes; and so forth. The power supply may be a step-down DC/DC converter, a step-up DC/DC converter, or the like. The distribution of the attracting pressure can be varied by altering, among the multiple internal electrodes, the internal electrode which supplies the power, by changing the power to be fed, and so forth.

FIG.16is a side view illustrating the upper chuck, the lower chuck and a temperature distribution adjuster according to the exemplary embodiment. The upper chuck140and a temperature distribution adjuster500are fixed to a common horizontal frame590, and the lower chuck141is disposed below the upper chuck140and the temperature distribution adjuster500.

The temperature distribution adjuster500causes the distortion of the lower wafer W2by adjusting the temperature distribution of the lower wafer W2held by the lower chuck141. The temperature distribution adjuster500includes a main body510having a bottom surface of a diameter larger than a diameter of the lower wafer W2; a supporting member520configured to support the main body510from above it; and an elevating unit530configured to move the supporting member520in the vertical direction.

The main body510is configured to be movable up and down under the horizontal frame590. The elevating unit530is fixed to the horizontal frame590and configured to move the main body510up and down with respect to the horizontal frame590. Accordingly, a distance between the main body510and the lower chuck141can be adjusted.

FIG.17is a side cross sectional view illustrating the main body of the temperature distribution adjuster according to the exemplary embodiment. The main body510includes, as depicted inFIG.17, a cooling unit550and a heating unit560.

The cooling unit550is, for example, a flow path formed within the main body510and is connected to an inlet line551through which a coolant such as cooling water is introduced into the cooling unit550and an outlet line552through which the coolant is flown out from the cooling unit550. By circulating the temperature-controlled coolant in this cooling unit550, the entire surface of the lower wafer W2can be cooled in a uniform manner.

Meanwhile, the heating unit560is configured to heat the lower wafer W2locally. To elaborate, the heating unit560includes multiple independent heating regions561a, and by heating these heating regions561aselectively, a part of or the entire of the lower wafer W2can be heated. The selection of the heating regions561ais carried out by the distortion controller703.

According to the present exemplary embodiment, the local heating of the lower wafer W2by the heating unit560and the temperature adjustment of the lower wafer W2by the cooling unit550can be performed at the same time. Further, though the local heating of the lower wafer W2is performed in the present exemplary embodiment, the local cooling of the lower wafer W2may be performed. Any of various heating or cooling methods can be adopted as long as the non-uniform temperature distribution of the lower wafer W2can be created.

By way of example, the adjustment of the temperature distribution of the lower wafer W2is performed in the state that the attraction of the lower wafer W2by the lower chuck141is released. Then, in the state that there is created the non-uniformity in the temperature distribution of the lower wafer W2, the lower wafer W2is attracted by the lower chuck141. Thereafter, the bonding between the lower wafer W2and the upper wafer W1is performed, and the shape of the lower wafer W2is fixed until the attraction of the lower wafer W2is released again.

FIG.18AandFIG.18Bare side cross sectional views illustrating a lower chuck according to a modification example.FIG.18Aillustrates a state when an attraction surface141aof a lower chuck141is a flat surface, andFIG.18Billustrates a state when the attraction surface141aof the lower chuck141is an upwardly protruding dome-shaped curved surface. The lower chuck141according to the present modification example includes an elastic transformation member610having the attraction surface141aconfigured to attract the lower wafer W2; and a base member620configured to support the elastic transformation member610.

The elastic transformation member610has suction grooves601on the attraction surface141awhich attracts the lower wafer W2. A layout of the suction grooves601may be selected as required. The suction grooves601are connected to a vacuum pump603via suction lines602. If the vacuum pump603is operated, the lower wafer W2is vacuum-attracted to a top surface of the elastic transformation member610. Meanwhile, if the operation of the vacuum pump603is stopped, the vacuum-attraction of the lower wafer W2is released.

The elastic transformation member610is formed of alumina ceramic or a ceramic material such as, but not limited to, SiC. Further, the base member620is also formed of alumina ceramic or a ceramic material such as, but not limited to, SiC, the same as the elastic transformation member610.

The base member620is disposed under the elastic transformation member610, and a fixing ring630is provided around the elastic transformation member610. A peripheral portion of the elastic transformation member610is fixed to the base member620by the fixing ring630.

A sealed pressure-variable space640is formed between a bottom surface of the elastic transformation member610and a top surface of the base member620. An attraction surface transforming unit650is configured to adjust a shape of the attraction surface141aof the elastic transformation member610by adjusting an air pressure within the pressure-variable space640.

The attraction surface transforming unit650has an air feed/exhaust line651, and the air feed/exhaust line651is connected to an air feed/exhaust opening621formed at a top surface of the base member620. An electro-pneumatic regulator653configured to supply air into the pressure-variable space640and a vacuum pump654configured to exhaust the air from the pressure-variable space640are connected to the air feed/exhaust line651via a switching valve652. The switching valve652is switched into between a state (A) and a state (B): (A) a flow path connecting the switching valve652and the vacuum pump654is opened for the air feed/exhaust opening621, and a flow path connecting the switching valve652and the electro-pneumatic regulator653is closed for the air feed/exhaust opening621; and (B) the flow path connecting the switching valve652and the vacuum pump654is closed for the air feed/exhaust opening621, and the flow path connecting the switching valve652and the electro-pneumatic regulator653is opened for the air feed/exhaust opening621.

As depicted inFIG.18A, if the inside of the pressure-variable space640is decompressed (for example, −10 kPa) by being evacuated through the vacuum pump654, the elastic transformation member610is attracted to the base member620. In this state, the top surface of the elastic transformation member610becomes the flat surface.

Meanwhile, as shown inFIG.18B, if the inside of the pressure-variable space640is pressurized (for example, 0 kPa to 100 kPa) by supplying the air thereinto through the electro-pneumatic regulator653, the elastic transformation member610is pressed from below it. Since the peripheral portion of the elastic transformation member610is fixed to the base member620by the fixing ring630, a central portion of the elastic transformation member610is protruded higher than the peripheral portion thereof, and the top surface of the elastic transformation member610becomes the curved surface. This curved surface is of an upwardly protruding dome shape. A radius of curvature of this curved surface can be controlled by adjusting the air pressure within the pressure-variable space640. Changing of the setting of the air pressure within the pressure-variable space640is carried out by the distortion controller703.

If the shape of the attraction surface141aof the lower chuck141is changed after the lower wafer W2is attracted to the attraction surface141aof the lower chuck141, the shape of the lower wafer W2is changed to conform to the attraction surface141a. Thus, by changing the shape of the attraction surface141aof the lower chuck141, the distortion of the lower wafer W2can be controlled.

<Modifications and Improvements>

So far, the exemplary embodiment of the bonding system and the bonding method have been described. However, the present disclosure is not limited to the above-described exemplary embodiment or the like. Various changes, corrections, replacements, addition, deletion and combinations may be made within the scope of the claims, and all of these are included in the scope of the inventive concept of the present disclosure.

In the above-described exemplary embodiment and modification example, the attracting pressure distribution adjuster250, the temperature distribution adjuster500or the attracting surface transforming unit650is used as a distortion generator. Under the control of the distortion controller703, the distortion generator is configured to generate the distortion of the lower wafer W2attracted to the lower chuck141. The attracting pressure distribution adjuster250, the temperature distribution adjuster500and the attraction surface transforming unit650may be used individually or in combinations. Here, the combinations are not particularly limited.

The distortion controller703according to the above-described exemplary embodiment and modification example controls the distortion of the lower wafer W2attracted to the lower chuck141. However, the distortion controller703may control the distortion of the upper wafer W1attracted to the upper chuck140. That is, though the upper wafer W1, the upper chuck140, the lower wafer W2and the lower chuck141correspond to the first substrate, the first holder, the second substrate and the second holder, respectively, in the above-described exemplary embodiment and modified example, the upper wafer W1, the upper chuck140, the lower wafer W2and the lower cuck141may correspond to the second substrate, the second holder, the first substrate and the first holder, respectively. Furthermore, the distortion controller703may control both the distortion of the lower wafer W2and the distortion of the upper wafer W1.

This application claims the benefit of Japanese Patent Application No. 2018-008892 filed on Jan. 23, 2018, the entire disclosures of which are incorporated herein by reference.

According to the exemplary embodiments, it is possible to improve accuracy of position adjustment between a substrate at an upper side and a substrate at a lower side in the horizontal direction, which is performed before bonding of the two substrates is carried out.

The claims of the present application are different and possibly, at least in some aspects, broader in scope than the claims pursued in the parent application. To the extent any prior amendments or characterizations of the scope of any claim or cited document made during prosecution of the parent could be construed as a disclaimer of any subject matter supported by the present disclosure, Applicants hereby rescind and retract such disclaimer. Accordingly, the references previously presented in the parent applications may need to be revisited.