BONDING APPARATUS AND BONDING METHOD

A bonding apparatus includes a first holder, a second holder, an attracting pressure generator, a pushing member and a controller. The controller attracts a second substrate with a beginning attracting pressure distribution set on multiple regions, when a pressurization of a first substrate by the pushing member is begun. The controller performs a control of performing a switchover from the beginning attracting pressure distribution to a progress attracting pressure distribution between a time point when the pressurization by the pushing member is begun and a contact end point at which an entire bonding surface of the first substrate and an entire bonding surface of the second substrate come into contact with each other. The progress attracting pressure distribution is created by changing at least one attracting pressure of attracting pressures on the multiple regions in the beginning attracting pressure distribution.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No. 2022-147267 filed on Sep. 15, 2022, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The various aspects and embodiments described herein pertain generally to a bonding apparatus and a bonding method.

BACKGROUND

Patent Document 1 discloses a bonding apparatus equipped with an upper chuck for attracting a substrate at an upper side from above and a lower chuck for attracting a substrate at a lower side from below, and configured to bond the two substrate to face each other. To bond the substrates, the bonding apparatus presses a center of the substrate of the upper chuck into contact with a center of the substrate of the lower chuck, bonds the centers of the two substrates to each other by an intermolecular force, and expands this bonding region from the centers to edges of the substrates.

Further, in the bonding apparatus described in Patent Document 1, an attraction surface of the lower chuck is divided into a plurality of regions, and an attracting pressure is set for each of the regions individually during the bonding to increase bonding strength between the substrate of the upper chuck and the substrate of the lower chuck.Patent Document 1: Japanese Patent Laid-open Publication No. 2015-095579

SUMMARY

In one exemplary embodiment, a bonding apparatus includes a first holder configured to hold a first substrate; a second holder, allowed to be disposed at a position facing the first holder, having an attraction surface partitioned into multiple regions configured to attract a second substrate; an attracting pressure generator configured to generate attracting pressures in the multiple regions individually; a pushing member configured to press a central portion of the first substrate toward the second substrate to bond the first substrate to the second substrate; and a controller configured to control the attracting pressure generator and the pushing member. The controller attracts the second substrate with a beginning attracting pressure distribution set on the multiple regions, when a pressurization of the first substrate by the pushing member is begun. The controller performs a control of performing a switchover from the beginning attracting pressure distribution to a progress attracting pressure distribution between a time point when the pressurization by the pushing member is begun and a contact end point at which an entire bonding surface of the first substrate and an entire bonding surface of the second substrate come into contact with each other. The progress attracting pressure distribution is created by changing at least one attracting pressure of the attracting pressures on the multiple regions in the beginning attracting pressure distribution.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In the various drawings, same parts will be assigned same reference numerals, and redundant description will be omitted.

As depicted inFIG.1andFIG.2, a bonding apparatus1according to an exemplary embodiment is an apparatus configured to produce a bonded substrate T by transferring two substrates (a first substrate W1and a second substrate W2) and bonding these two substrates to each other.

At least one of the first substrate W1or the second substrate W2is a substrate on which a plurality of electronic circuits are formed on a semiconductor substrate such as, but not limited to, a silicon wafer or a compound semiconductor wafer. One of the first substrate W1and the second substrate W2may be a bare wafer on which no electronic circuit is formed. Although not particularly limited, the compound semiconductor wafer may be, for example, a GaAs wafer, a SiC wafer, a GaN wafer, or an InP wafer.

The first substrate W1and the second substrate W2are formed on circular plates having substantially the same shape (same diameter). As shown inFIG.3, the bonding apparatus1places the second substrate W2on the negative Z-axis side of (vertically under) the first substrate W1, and bonds the first substrate W1and the second substrate W2. Therefore, hereinafter, the first substrate W1may sometimes be referred to as “upper wafer W1”; the second substrate W2, “lower wafer W2”; and the bonded substrate T, “bonded wafer T”. In addition, hereinafter, among plate surfaces of the upper wafer W1, the plate surface to be bonded to the lower wafer W2will be referred to as “bonding surface W1j”, and the plate surface opposite to the bonding surface W1jwill be referred to as “non-bonding surface W1n”. Likewise, among plate surfaces of the lower wafer W2, the plate surface to be bonded to the upper wafer W1will be referred to as “bonding surface W2j”, and the plate surface opposite to the bonding surface W2jwill be referred to as “non-bonding surface W2n”.

As depicted inFIG.1, the bonding apparatus1is equipped with a carry-in/out station2and a processing station3which are arranged in this order along the positive X-axis direction. The carry-in/out station2and the processing station3are connected as one 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 CS1, CS2and CS3each of which accommodates therein a plurality of (e.g., 25 sheets of) substrates horizontally. The cassette CS1accommodates therein upper wafers W1; the cassette CS2, lower wafers W2; and the cassettes CS3, bonded wafers T. Further, the upper wafers W1and the lower wafers W2are accommodated in the cassettes CS1and the cassette CS2, respectively, with the bonding surfaces W1jand W2jfacing upwards while being aligned in the same direction.

The transfer section20is provided adjacent to the positive X-axis side of the placing table10, and is equipped with 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, and serves to transfer the upper wafers W1, the lower wafers W2, and the bonded wafers T between the cassettes CS1to CS3placed on the placing table10and a third processing block PB3of the processing station3.

The processing station3has, for example, three processing blocks PB1, PB2, and PB3. The first processing block PB1is provided on the rear side (positive Y-axis side ofFIG.1) of the processing station3. The second processing block PB2is provided on the front side (negative Y-axis side ofFIG.1) of the processing station3. The third processing block PB3is provided on the carry-in/out station2side (negative X-axis side ofFIG.1) of the processing station3.

Further, the processing station3is equipped with a transfer section60having a transfer device61in a region surrounded by the first processing block PB1to the third processing block PB3. For example, the transfer device61has a transfer arm 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 section60to transfer the upper wafers W1, the lower wafers W2, and the bonded wafers T to devices within the first processing block PB1, the second processing block PB2, and the third processing block PB3which are adjacent to the transfer section60.

The first processing block PB1includes, for example, a surface modifying apparatus33and a surface hydrophilizing apparatus34. The surface modifying apparatus33is configured to modify the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2. The surface hydrophilizing apparatus34is configured to hydrophilize the modified bonding surfaces W1jand W2jof the upper and lower wafers W1and W2, respectively.

By way of example, the surfacy modifying apparatus33cuts a SiO2bond on the bonding surfaces W1jand W2jto form a dangling bond of Si, thus allowing the bonding surfaces W1jand W2jto be hydrophilized afterwards. The surface modifying apparatus33excites an oxygen gas as a processing gas into plasma under a decompressed atmosphere, for example. By radiating oxygen ions to the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2, the surface modifying apparatus33plasma-processes the bonding surfaces W1jand W2jto modify them. The processing gas is not limited to the oxygen gas, but it may be a nitrogen gas or the like.

The surface hydrophilizing apparatus34is configured to hydrophilize the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2with, for example, a hydrophilizing liquid such as pure water. The surface hydrophilizing apparatus34also has a function of cleaning the bonding surfaces W1jand W2j. In this surface hydrophilizing apparatus34, 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 is diffused on the bonding surfaces W1jand W2j, and an OH group is attached to the dangling bond of Si, so that the bonding surfaces W1jand W2jare hydrophilized.

As shown inFIG.2, the second processing block PB2includes, for example, a bonding module41, a first temperature control device42, and a second temperature control device43. The bonding module41is configured to bond the hydrophilized upper wafer W1and lower wafer W2to produce the bonded wafer T. The first temperature control device42is configured to adjust a temperature distribution of the upper wafer W1before producing the bonded wafer T. The second temperature control device43is configured to adjust a temperature distribution of the lower wafer W2before producing the bonded wafer T. In addition, in the present exemplary embodiment, although the first temperature control device42and the second temperature control device43are provided separately from the bonding module41, they may be provided as a part of the bonding module41.

The third processing block PB3is equipped with a first position adjusting device51, a second position adjusting device52, and transition devices53and54in this order from top to bottom, for example. Further, the places where the individual devices are disposed in the third processing block PB3are not limited to the example shown inFIG.2. The first position adjusting device51is configured to adjust a direction of the upper wafer W1in a horizontal direction, and invert the upper wafer W1upside down so that the bonding surface W1jof the upper wafer W1faces downwards. The second position adjusting device52is configured to adjust a direction of the lower wafer W2in a horizontal direction. The transition device53is configured to temporarily place therein the upper wafer W1. Further, the transition device54is configured to temporarily place therein the lower wafer W2and the bonded wafer T.

Referring back toFIG.1, the bonding apparatus1is equipped with a control device (controller)90configured to control the individual constituent components. The control device90is a control computer having one or more processors91, a memory92, a non-illustrated input/output interface, and an electronic circuit. The one or more processors91are implemented by one of a CPU, an ASIC, an FPGA, and a circuit composed of a plurality of discrete semiconductors, or a combination thereof, and execute programs stored in the memory92. The memory92forms a storage of the control device90, including a non-volatile memory and a volatile memory.

Now, referring toFIG.4, a bonding method of the present exemplary embodiment will be explained. Processes S101to S109shown inFIG.4are performed under the control of the control device90.

In the bonding method, an operator or a transfer robot (not shown) places the cassette CS1accommodating therein the plurality of upper wafers W1, the cassette CS2accommodating therein the plurality of lower wafers W2, and the empty cassette CS3on the placing table10of the carry-in/out station2.

The bonding apparatus1takes out the upper wafer W1in the cassette CS1by the transfer device22, and transfers it to the transition device53of the third processing block PB3of the processing station3. Thereafter, the bonding apparatus1takes out the upper wafer W1from the transition device53by the transfer device61, and transfers it to the surface modifying apparatus33of the first processing block PB1.

Next, the bonding apparatus1modifies the bonding surface W1jof the upper wafer W1by the surface modifying apparatus33(process S101). The surface modifying apparatus33modifies the bonding surface W1jin the state that the bonding surface W1jfaces upwards. Then, the transfer device61takes out the upper wafer W1from the surface modifying apparatus33, and transfers it to the surface hydrophilizing apparatus34.

Then, the bonding apparatus1hydrophilizes the bonding surface W1jof the upper wafer W1by the surface hydrophilizing apparatus34(process S102). The surface hydrophilizing apparatus34hydrophilizes the bonding surface W1jin the state that the bonding surface W1jfaces upwards. Thereafter, the transfer device61takes out the upper wafer W1from the surface hydrophilizing apparatus34, and transfers it to the first position adjusting device51of the third processing block PB3.

The bonding apparatus1adjusts the direction of the upper wafer W1in the horizontal direction and inverts the upper wafer W1upside down by the first position adjusting device51(process S103). As a result, a notch of the upper wafer W1is directed in a predetermined direction, and the bonding surface W1jof the upper wafer W1is turned to face downwards. Thereafter, the transfer device61takes out the upper wafer W1from the first position adjusting device51, and transfers it to the first temperature control device42of the second processing block PB2.

The bonding apparatus1adjusts the temperature of the upper wafer W1by the first temperature control device42(process S104). The temperature adjustment of the upper wafer W1is performed with the bonding surface W1jof the upper wafer W1facing downwards. Thereafter, the transfer device61takes out the upper wafer W1from the first temperature control device42, and transfers it to the bonding module41.

The bonding apparatus1performs a processing on the lower wafer W2in parallel with the above-described processing on the upper wafer W1. First, the bonding apparatus1takes out the lower wafer W2in the cassette CS2by the transfer device22, and transfers it to the transition device54of the third processing block PB3of the processing station3. Then, the transfer device61takes out the lower wafer W2from the transition device54, and transfers it to the surface modifying apparatus33of the first processing block PB1.

The bonding apparatus1modifies the bonding surface W2jof the lower wafer W2by the surface modifying apparatus33(process S105). The surface modifying apparatus33modifies the bonding surface W2jin the state that the bonding surface W2jfaces upwards. Thereafter, the transfer device61takes out the lower wafer W2from the surface modifying apparatus33, and transfers it to the surface hydrophilizing apparatus34.

The bonding apparatus1hydrophilizes the bonding surface W2jof the lower wafer W2by the surface hydrophilizing apparatus34(process S106). The surface hydrophilizing apparatus34hydrophilizes the bonding surface W2jin the state that the bonding surface W2jfaces upwards. Then, the transfer device61takes out the lower wafer W2from the surface hydrophilizing apparatus34, and transfers it to the second position adjusting device52of the third processing block PB3.

The bonding apparatus1adjusts the direction of the lower wafer W2in the horizontal direction by the second position adjusting device52(process S107). As a result, a notch of the lower wafer W2is directed toward a predetermined direction. Thereafter, the transfer device61takes out the lower wafer W2from the second position adjusting device52, and transfers it to the second temperature control device43of the second processing block PB2.

The bonding apparatus1adjusts the temperature of the lower wafer W2by the second temperature control device43(process S108). The temperature adjustment of the lower wafer W2is performed with the bonding surface W2jof the lower wafer W2facing upwards. Thereafter, the transfer device61takes out the lower wafer W2from the second temperature control device43, and transfers it to the bonding module41.

Then, the bonding apparatus1bonds the upper wafer W1and the lower wafer W2in the bonding module41to produce the bonded wafer T (process S109). After the production of the bonded wafer T, the transfer device61takes out the bonded wafer T from the bonding module41, and transfers it to the transition device54of the third processing block PB3.

Finally, the bonding apparatus1takes out the bonded wafer T from the transition device54by the transfer device22, and transfers it to the cassette CS3on the placing table10. Thus, the series of processes are ended.

Now, with reference toFIG.5toFIG.7, an example of the bonding module41will be described. As depicted inFIG.5, the bonding module41is equipped with a processing vessel210having a sealable inside. A carry-in/out opening211is formed on a side surface of the processing vessel210on the transfer section60side, and an opening/closing shutter212is provided at the carry-in/out opening211. The upper wafer W1, the lower wafer W2, and the bonded wafer T are carried in and out through the carry-in/out opening211.

As shown inFIG.6, an upper chuck230(first holder) and a lower chuck231(second holder) are provided inside the processing vessel210. The upper chuck230holds the upper wafer W1from above while allowing the bonding surface W1jof the upper wafer W1to face downwards. Further, the lower chuck231is disposed below the upper chuck230, and holds the lower wafer W2from below while allowing the bonding surface W2jof the lower wafer W2to face upwards.

The upper chuck230is supported by a supporting member280provided on a ceiling surface of the processing vessel210. Meanwhile, the lower chuck231is supported by a first lower chuck mover291provided below the lower chuck231, and can be disposed at a position facing the upper chuck230.

The first lower chuck mover291moves the lower chuck231in a horizontal direction (Y-axis direction) as will be described later. Further, the first lower chuck mover291is configured to be capable of moving the lower chuck231in a vertical direction and rotating it around a vertical axis.

The first lower chuck mover291is mounted to a pair of rails295provided on a bottom surface side of the first lower chuck mover291and extending in the horizontal direction (Y-axis direction). The first lower chuck mover291is configured to be movable along the rails295. The rails295are provided on the second lower chuck mover296.

The second lower chuck mover296is mounted to a pair of rails297provided on a bottom surface side of the second lower chuck mover296and extending in a horizontal direction (X-axis direction). The second lower chuck mover296is configured to be movable along the rails297. In addition, the pair of rails297are disposed on a placing table298which is provided on a bottom surface of the processing vessel210.

The first lower chuck mover291and the second lower chuck mover296constitute a moving mechanism290. The moving mechanism290moves the lower chuck231relative to the upper chuck230. Further, the moving mechanism290moves the lower chuck231between a substrate delivery position and a bonding position.

The substrate delivery position is a position where the upper chuck230receives the upper wafer W1from the transfer device61, the lower chuck231receives the lower wafer W2from the transfer device61, and the lower chuck231delivers the bonded wafer T to the transfer device61. The substrate delivery position is a position where a carry-out of the bonded wafer T produced by the nth(n is a natural number equal to or larger than 1) bonding and a carry-in of the upper wafer W1and the lower wafer W2to be bonded by the (n+1)thbonding are performed in succession. The substrate delivery position is, for example, a position shown inFIG.5andFIG.6.

When handing the upper wafer W1over to the upper chuck230, the transfer device61advances to a space directly below the upper chuck230. Further, when receiving the bonded wafer T from the lower chuck231and handing the lower wafer W2over to the lower chuck231, the transfer device61advances to a space directly above the lower chuck231. The upper chuck230and the lower chuck231are placed sideways apart and a distance between the upper chuck230and the lower chuck231in a vertical direction is large so that the transfer device61advances therebetween easily.

Meanwhile, the bonding position is a position where the upper wafer W1and the lower wafer W2are made to face each other with a preset distance therebetween. The bonding position is, for example, a position shown inFIG.7. At the bonding position, the distance between the upper wafer W1and the lower wafer W2in the vertical direction is narrower than that at the substrate delivery position. Further, at the bonding position, the upper wafer W1and the lower wafer W2overlap each other when viewed from the vertical direction, unlike at the substrate delivery position.

The moving mechanism290moves the relative positions of the upper chuck230and the lower chuck231in horizontal directions (both the X-axis direction and the Y-axis direction) and a vertical direction. Although the moving mechanism290moves the lower chuck231in the present exemplary embodiment, it may move any one of the lower chuck231and the upper chuck230, or both of them. Further, the moving mechanism290may rotate the upper chuck230or the lower chuck231around a vertical axis.

As illustrated inFIG.7, the upper chuck230is divided into a plurality of (for example, three) regions230a,230b, and230calong a radial direction of the upper chuck230. These regions230a,230b, and230care provided in this order from a center of the upper chuck230toward an outer periphery thereof. The region230ais formed in a circular shape when viewed from the top, and the regions230band230care formed in an annular shape when viewed from the top. The regions230band230cmay have a plurality of arc-shaped zones (small regions) along a circumferential direction.

Suction lines240a,240b, and240care independently provided in the regions230a,230b, and230c, respectively. Different vacuum pumps241a,241b, and241care connected to the suction lines240a,240b, and240c, respectively. The upper chuck230is capable of vacuum-attracting the upper wafer W1in each of the regions230a,230b, and230cindividually.

The upper chuck230is provided with a multiple number of holding pins245configured to be movable up and down in a vertical direction. The plurality of holding pins245are connected to a vacuum pump246, and the upper wafer W1is vacuum-attracted to the holding pins235by the operation of the vacuum pump246. The upper wafer W1is vacuum-attracted to lower ends of the plurality of holding pins245. Instead of the plurality of holding pins245, a ring-shaped attraction pad may be used.

The plurality of holding pins245are protruded from an attraction surface of the upper chuck230as they are lowered by a non-illustrated driving unit. In this state, the plurality of holding pins245receives the upper wafer W1from the transfer device61by vacuum-attracting it. Thereafter, the plurality of holding pins245are raised, allowing the upper wafer W1to come into contact with the attraction surface of the upper chuck230. Then, the upper chuck230vacuum-attracts the upper wafer W1horizontally in the respective regions230a,230b, and230cby the operations of the vacuum pumps241a,241b, and241c, respectively.

In addition, the upper chuck230has, at the center thereof, a through hole243formed through the upper chuck230in a vertical direction. A pushing member250is inserted through the through hole243. The pushing member250presses the center of the upper wafer W1spaced apart from the lower wafer W2, thus bringing the upper wafer W1into contact with the lower wafer W2.

The pushing member250has a pushing pin251and an outer cylinder252serving as an elevation guide for the pushing pin251. The pushing pin251is inserted through the through hole243by, for example, a driving unit (not shown) having a motor therein, and is protruded from the attraction surface of the upper chuck230, pressing the center of the upper wafer W1.

Moreover, the lower chuck231also has a plurality of partitioned regions in an attraction surface300for attracting the lower wafer W2. The configuration of the attraction surface300of the lower chuck231will be described in detail later.

The lower chuck231is provided with a plurality of (for example, three) holding pins265configured to be movable up and down in a vertical direction. The lower wafer W2is placed on upper ends of the plurality of holding pins265. Further, the lower wafer W2may be vacuum-attracted to the upper ends of the plurality of holding pins265.

The plurality of holding pins265are protruded from the attraction surface300of the lower chuck231as they are raised. In this state, the plurality of holding pins265receive the lower wafer W2from the transfer device61. After that, the plurality of holding pins265are lowered, thus allowing the lower wafer W2to come into contact with the attraction surface300of the lower chuck231. Then, the lower chuck231vacuum-attracts the lower wafer W2horizontally in the plurality of regions of the attraction surface300.

Now, with reference toFIG.8toFIG.10C, the process of manufacturing the bonded wafer T in the process S109ofFIG.4will be described in detail. As depicted in FIG.8, the control device90controls the transfer device61to carry the upper wafer W1and the lower wafer W2into the bonding module41(process S111). The relative positions of the upper chuck230and the lower chuck231after being carried in are as shown inFIG.5andFIG.6, that is, they are at the substrate delivery position.

After the carry-in, the control device90controls the moving mechanism290to move the relative positions of the upper chuck230and the lower chuck231from the substrate delivery position to the bonding position shown inFIG.7(process S112). In this process S112, the control device90carries out alignment between the upper wafer W1and the lower wafer W2by using an upper camera S1and a lower camera S2as shown inFIG.9AtoFIG.9C.

The upper camera S1is fixed to the upper chuck230to image the lower wafer W2held by the lower chuck231. Multiple reference points P21to P23are previously formed on the bonding surface W2jof the lower wafer W2. As the reference points P21to P23, patterns of electronic circuits or the like may be used. The number of the reference points is not particularly limited.

Meanwhile, the lower camera S2is fixed to the lower chuck231to image the upper wafer W1held by the upper chuck230. Multiple reference points P11to P13are formed in advance on the bonding surface W1jof the upper wafer W1. As the reference points P11to P13, patterns of electronic circuits or the like may be used. The number of these reference points is not particularly limited.

As depicted inFIG.9A, the bonding module41adjusts the relative positions of upper camera S1and lower camera S2in a horizontal direction through the use of the moving mechanism290. Specifically, the moving mechanism290moves the lower chuck231in the horizontal direction such that the lower camera S2is positioned substantially directly below the upper camera S1. Then, the upper camera S1and the lower camera S2image a common target X and the moving mechanism290finely adjusts the position of the lower camera S2in the horizontal direction such that the positions of the upper camera S1and the lower camera S2in the horizontal direction are coincident.

Subsequently, as shown inFIG.9B, the moving mechanism290moves the lower chuck231vertically upwards to adjust the positions of the upper chuck230and the lower chuck231in the horizontal direction. Specifically, while the moving mechanism290is moving the lower chuck231in the horizontal direction, the upper camera S1sequentially images the reference points P21to P23of the lower wafer W2, and the lower camera S2sequentially images the reference points P11to P13of the upper wafer W1.FIG.9Bshows a state in which the upper camera S1is imaging the reference point P21of the lower wafer W2and the lower camera S2is imaging the reference point P11of the upper wafer W1.

The upper camera S1and the lower camera S2transmit the obtained image data to the control device90. The control device90controls the moving mechanism290based on the image data obtained by the upper camera S1and the image data obtained by the lower camera S2, and adjusts the position of the lower chuck231in the horizontal direction such that the reference points P11to P13of the upper wafer W1and the reference points P21to P23of the lower wafer W2coincide with each other when viewed from the vertical direction.

Thereafter, as illustrated inFIG.9C, the moving mechanism290moves the lower chuck231vertically upwards. As a result, a distance G (seeFIG.7) between the bonding surface W2jof the lower wafer W2and the bonding surface W1jof the upper wafer W1becomes a predetermined distance of, e.g., 80 μm to 200 μm. The adjustment of the distance G is performed by using a first displacement meter S3and a second displacement meter S4.

The first displacement meter S3is fixed to the upper chuck230, and measures the thickness of the lower wafer W2held by the lower chuck231. The first displacement meter S3measures the thickness of the lower wafer W2by, for example, radiating light to the lower wafer W2and receiving reflected light reflected from both top and bottom surfaces of the lower wafer W2. This thickness measurement is performed when the moving mechanism290moves the lower chuck231in the horizontal direction, for example. The first displacement meter S3carries out the measurement by, for example, a confocal method, a spectral interference method, or a triangulation method. A light source of the first displacement meter S3is an LED or a laser.

Meanwhile, the second displacement meter S4is fixed to the lower chuck231, and measures the thickness of the upper wafer W1held by the upper chuck230. The second displacement meter S4measures the thickness of the upper wafer W1by, for example, radiating light to the upper wafer W1and receiving reflected light reflected from both top and bottom surfaces of the upper wafer W1. This thickness measurement is performed when the moving mechanism290moves the lower chuck231in the horizontal direction, for example. The second displacement meter S4carries out the measurement by, for example, a confocal method, a spectral interference method, or a triangulation method. A light source of the second displacement meter S4is an LED or a laser.

The first displacement meter S3and the second displacement meter S4transmit the measured data to the control device90. The control device90controls the moving mechanism290based on the data obtained by the first displacement meter S3and the data obtained by the second displacement meter S4, and adjusts the position of the lower chuck231in the vertical direction such that the distance G becomes the set value.

Next, the operation of the vacuum pump241ais stopped. As a result, as shown inFIG.10A, the vacuum attraction of the upper wafer W1in the region230ais canceled. Thereafter, the pushing pin251of the pushing member250is lowered to press the center of the upper wafer W1, allowing the upper wafer W1to come into contact with the lower wafer W2(process S113inFIG.8). As a result, the centers of the upper and lower wafers W1and W2are bonded to each other.

Since the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2are modified, a van der Waals force (intermolecular force) is first generated between the bonding surfaces W1jand W2j, so that the bonding surfaces W1jand W2jare bonded to each other. Further, since the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2have been hydrophilized, hydrophilic groups (e.g., OH groups) are hydrogen-bonded, allowing the bonding surfaces W1jand W2jto be firmly bonded to each other.

Subsequently, the control device90stops the operation of the vacuum pump241b, and cancels the vacuum attraction of the upper wafer W1in the region230b, as shown inFIG.10B. Afterwards, the control device90stops the operation of the vacuum pump241c, and cancels the vacuum attraction of the upper wafer W1in the region230c, as shown inFIG.10C.

In this way, the vacuum attraction of the upper wafer W1is released step by step from the center toward a periphery of the upper wafer W1, so that the upper wafer W1drops and comes into contact with the lower wafer W2step by step. Then, the bonding of the upper wafer W1and the lower wafer W2proceeds sequentially toward the peripheries of the upper and lower wafers W1and W2after the centers thereof are bonded (process S114). As a result, the entire bonding surface W1jof the upper wafer W1and the entire bonding surface W2jof the lower wafer W2come into contact with each other, so that the upper wafer W1and the lower wafer W2are bonded together, and the bonded wafer T is obtained. Then, the bonding apparatus1raises the pushing pin251to its original position.

After the bonded wafer T is formed, the control device90controls the moving mechanism290to move the relative positions of the upper chuck230and the lower chuck231from the bonding positions shown inFIG.7to the substrate delivery positions shown inFIG.5andFIG.6(process S115). By way of example, the moving mechanism290first lowers the lower chuck231to widen the distance between the lower chuck231and the upper chuck230in the vertical direction. Then, the moving mechanism290moves the lower chuck231sideways so that the lower chuck231and the upper chuck230are placed sideways apart.

Thereafter, the control device90controls the transfer device61to carry out the bonded wafer T from the bonding module41(process S116). Specifically, the lower chuck231first releases the holding of the bonded wafer T. Then, the plurality of holding pins265are raised to hand the bonded wafer T over to the transfer device61. Thereafter, the plurality of holding pins265are lowered to their original positions.

Now, the configuration of the attraction surface300of the lower chuck231will be described with reference toFIG.11. This technique of the present disclosure is also applicable to the attraction surface of the upper chuck230. InFIG.11, hatched regions are regions in which an attracting pressure is generated. The attraction surface300of the lower chuck231has the plurality of regions that generate the attracting pressure individually.

For example, the attraction surface300is partitioned into a central region A, an intermediate region B, and an outer region C by annular ribs301,302, and303. The central region A, the intermediate region B, and the outer region C are arranged concentrically in this order from a center of the attraction surface300toward an outer periphery thereof. Specifically, the central region A is formed in a circle shape. The intermediate region B is formed in an annular shape at a position outside and adjacent to the central region A. The outer region C is formed in an annular shape at a position outside and adjacent to the intermediate region B. Alternatively, the attraction surface300may not include the intermediate region B, and the outer region C may be positioned outside the central region A to be adjacent thereto. Still alternatively, the attraction surface300may include a plurality of annular intermediate regions B between the central region A and the outer region C.

The intermediate region B is divided into eight arc-shaped zones (small intermediate regions) by a plurality of ribs305that are arranged radially. Likewise, the outer region C is also divided into eight arc-shaped zones (small outer regions) by the ribs305. Here, the number of the divisions of the intermediate region B may be equal to or different from the number of the divisions of the outer region C.

The central region A, the eight zones of the intermediate region B, and the eight zones of the outer region C are configured to be capable of suctioning the lower wafer W2individually. Here, however, in the lower chuck231according to the present exemplary embodiment, ten suction mechanisms311are connected to the total of seventeen zones, and the attraction surface300are suctioned for the zones of ten channels. That is, the attraction surface300has, among the total of seventeen zones, zones in which the suctioning is performed by the same suction mechanism311.

In detail, the central region A is connected to the suction mechanism311set for a single zone ch1. Meanwhile, in the intermediate region B, three zones ch2to ch4are set. The two zones adjacent to each other in the X-axis direction (a left-and-right direction inFIG.11) with the central region A therebetween are the zones ch2. The two zones adjacent to each other in the Y-axis direction (an up-and-down direction inFIG.11) with the central region A therebetween are the zones ch3. Further, in the intermediate region B, the four zones interposed between the zones ch2and the zones ch3are the zones ch4. Meanwhile, in the outer region C, six zones ch5to ch10are set. The one zone adjacent to the intermediate region B in the positive X-axis direction (left side inFIG.11) is the zone ch5. The one zone adjacent to the intermediate region B in the negative X-axis direction (right side inFIG.11) is the zone ch6. The one zone adjacent to the intermediate region B in the negative Y-axis direction (upper side inFIG.11) is the zone ch7. The one zone adjacent to the intermediate region B in the positive Y-axis direction (bottom side inFIG.11) is the zone ch8. Further, in the outer region C, the zone interposed between the zone ch5and the zone ch7and the zone interposed between the zone ch6and the zone ch7are the zones ch9. Likewise, in the outer region C, the zone interposed between the zone ch5and the zone ch8and the zone interposed between the zone ch6and the zone ch8are the zones ch10.

On the X-axis passing through the center of the attraction surface300, the zones of ch5, ch2, ch1, ch2, and ch6are arranged in this sequence from the positive X-axis side toward the negative X-axis side. On the Y-axis passing through the center of the attraction surface300, the zones of ch7, ch3, ch1, ch3, and ch8are arranged in this sequence from the negative Y-axis side toward the positive Y-axis side. Here, however, it should be noted that the attraction surface300can be designed as required for the number and the location of the channels of the respective zones without being limited to the shown example.

The bonding module41is equipped with an attracting pressure generator310configured to generate an attracting pressure in the respective zones of the ten channels of the attraction surface300individually. The suction mechanisms311of the attracting pressure generator310have suction lines312connected to the predetermined zones, and a suction pump313, an opening/closing valve314and a pressure controller315are provided on each of these suction lines312. The attracting pressure generator310is connected to the control device90so as to communicate with it, and operates the respective suction mechanisms311under the control of the control device90.

Each suction mechanism311opens the opening/closing valve314by operating the suction pump313of the suction line312, thus generating an attracting pressure (negative pressure) in the zone to which the suction line312is connected. The magnitude of the attracting pressure is controlled by the pressure controller315. Further, each suction mechanism311releases the attracting pressure of the zone by closing the opening/closing valve314of the suction line312and introducing air through the pressure controller315.

The lower chuck231configured as described above is capable of applying the attracting pressure to the non-bonding surface W2nof the lower wafer W2in the respective zones of ch1to ch10. For example, in the lower chuck231, one or more channels among the zones of ch1to ch10may be set to have a first attracting pressure, while the other one or more channels may be set to have a second attracting pressure different from the first attracting pressure. Further, in the lower chuck231, the attracting pressures in the zones of ch1to ch10may be set to be all different from each other.

As an example, the bonding apparatus1sets the attracting pressures of the respective zones of the attraction surface300to be of values shown inFIG.12Abefore the pressurization of the upper wafer W1by the pushing member250(before the bonding) and after the start of the pressurization (after the beginning of the bonding of the upper wafer W1and the lower wafer W2). In detail, the zones of1chand4chto10chare set to the first attracting pressure of −100 kPa, and the zones of ch2and ch3are set to the second attracting pressure of −20 kPa. The attracting pressure is expressed as a negative pressure based on an atmospheric pressure. The smaller the negative pressure (the larger the absolute value of the negative pressure) is, the stronger the attracting pressure may be, and the larger the negative pressure (the smaller the absolute value of the negative pressure) is, the weaker the attracting pressure may be. Hereinafter, a distribution of the attracting pressures (the first attracting pressure and the second attracting pressure) of the respective zones of the attraction surface300at the beginning of the bonding will be referred to as a “beginning attracting pressure distribution”.

In this way, by setting the attracting pressures of the zones ch2and ch3, which are the zones of the intermediate region B in the X-axis direction and the Y-axis direction, to be weaker than the attracting pressures of the other zones, the lower wafer W2is weakly fixed near the center thereof. For this reason, the lower wafer W2is easily moved under the influence of the bonding force with the upper wafer W1, so it is smoothly bonded to the upper wafer W1.

If, however, the second attracting pressure weaker than the first attracting pressure is continuously applied to the zones of ch2and ch3, distortion of the lower wafer W2tends to occur easily due to a difference in the attracting pressure between these zones and the other zones. In particular, in the bonding of the upper wafer W1and the lower wafer W2, when the bonding progresses from the centers toward the outer peripheries of the wafers, the distortion tends to easily occur at the outer peripheral side of the lower wafer W2.

To solve the problem, the bonding apparatus1according to the present exemplary embodiment adopts a configuration in which the pressure distribution of the respective zones of the attraction surface300is changed to a pressure distribution different from the beginning attracting pressure distribution when the bonding progresses. Hereinafter, the pressure distribution of the attraction surface300changed when the bonding progresses will be referred to as a “progress attracting pressure distribution”. For example, in the progress attracting pressure distribution, the zones of2chand3ch, which are set to have the second attracting pressure (−20 kPa) at the beginning of the bonding, are changed to have the first attracting pressure (−100 kPa), as illustrated inFIG.12B. Therefore, the attracting pressures of the respective zones of1chto10chof the attraction surface300are equalized to −100 kPa.

In this way, in the bonding apparatus1, by increasing the attracting pressures of the zones of2chand3chduring the bonding, the vicinity of the outer periphery of the lower wafer W2is strongly fixed when the bonding progresses. As a result, the distortion that may occur in the vicinity of the outer periphery of the lower chuck231can be suppressed, so that the upper wafer W1and the lower wafer W2can be bonded with high precision.

Hereinafter, a bonding method by the bonding module41and a configuration according to the bonding method will be described in detail. As described above, in the bonding apparatus1, the upper wafer W1is delivered on the plurality of holding pins245by the transfer device61, and the upper wafer W1is held by being attracted to the upper chuck230(upper wafer holding process: seeFIG.6as well). Further, in the bonding apparatus1, the lower wafer W2delivered from the transfer device61onto the plurality of holding pins265is lowered, and attracted to the attraction surface300of the lower chuck231(lower wafer holding process). Thereafter, the lower chuck231is moved to the bonding position by the moving mechanism290(seeFIG.7). After the lower chuck231is placed at the bonding position, the control device90adjusts the attracting pressures of the attraction surface300of the lower chuck231to the beginning attracting pressure distribution, as shown inFIG.12A. Accordingly, the attracting pressure generator310performs the attraction by setting the attracting pressures of the respective zones of ch1and ch4to ch10to the first attracting pressure (−100 kPa) while setting the attracting pressures of the zones of ch2and ch3to the second attracting pressure (−20 kPa). In addition, the adjustment to the beginning attracting pressure distribution may be performed when the lower chuck231is moved, for example.

Thereafter, the bonding apparatus1begins a bonding process between the upper wafer W1and the lower wafer W2. At the beginning of the bonding between the upper wafer W1and the lower wafer W2, the control device90releases the vacuum attraction of the region230aof the upper chuck230, and presses the pushing member250onto the center of the upper wafer W1with the pushing pin251, as stated above (seeFIG.10Aas well). Further, upon the lapse of a predetermined time, the control device90releases the vacuum attraction of the region230bof the upper chuck230(seeFIG.10B).

Here, as shown inFIG.13A, when the upper wafer W1and the lower wafer W2are bonded, the bonding apparatus1monitors the position of the upper wafer W1with a plurality of upper displacement sensors S5provided in the upper chuck230. The plurality of upper displacement sensors S5may include a first sensor S51disposed in the region230bin the X-axis direction, a second sensor S52disposed in the region230cin the X-axis direction, and a third sensor S53disposed in the region230cin the diagonal direction between the X-axis direction and the Y-axis direction. The number and the layout of the upper displacement sensors S5are not limited to the shown example. By way of example, a plurality of sensors may be provided near the pushing member250(at the center of the upper chuck230) or on the Y-axis side thereof.

The first sensor S51, the second sensor S52, and the third sensor S53are configured to measure a position (displacement) of the non-bonding surface W1nof the upper wafer W1during the progress of the bonding, and transmits information of measurement results to the control device90. Accordingly, the control device90acquires detection values of the respective sensors, as shown in a graph ofFIG.13B. In the graph ofFIG.13B, a horizontal axis represents time, and a vertical axis indicates the position of the upper wafer W1.

A time point t0in the graph is a timing when the pressurization on the center of the upper wafer W1by the pushing member250is begun (the beginning point of the bonding). After the time point to, the first sensor S51detects the position of the non-bonding surface W1nas the center of the upper wafer W1is lowered. At this time, the first sensor S51detects the position of the upper wafer W1which is rapidly lowered from the time point t0. Then, upon the lapse of time from a time point t1at which the attraction of the region230bis released, a portion of the upper wafer W1near the position detected by the first sensor S51comes into contact with the lower wafer W2. Therefore, the first sensor S51outputs a substantially constant detection value.

Meanwhile, a detection value of the second sensor S52located at the outer side than the first sensor S51in the X-axis direction gradually decreases at a value (position) higher than the detection value of the first sensor S51after the time point t0. Then, the detection value of the second sensor S52becomes substantially constant from a time point t1′ after a certain time further elapses from the time point t1at which the attraction of the region230bis released. That is, when the bonding between the upper wafer W1and the lower wafer W2progresses from the centers toward the outer peripheries thereof, a deformation (lowering) of the upper wafer W1is temporarily stopped as the outer periphery of the upper wafer W1is attracted to the region230cof the upper chuck230.

At the time point t2upon the lapse of a certain time after the deformation of the upper wafer W1is temporarily stopped, the control device90releases the attraction of the region230c. Accordingly, the second sensor S52outputs a detection value indicating that the upper wafer W1is rapidly lowered immediately after the time point t2. Then, a time point t3slightly after the time point t2becomes a contact end point at which the entire bonding surface W1jof the upper wafer W1and the entire bonding surface W2jof the lower wafer W2finally come into contact with each other.

Moreover, a detection value of the third sensor S53provided in the diagonal direction also falls gradually at a value (position) higher than the detection value of the second sensor S52after the bonding begins. Here, in the region230cof the upper chuck230according to the present exemplary embodiment, the upper wafer W1is attracted at four places (indicated by hatching inFIG.13A) in the diagonal direction. The third sensor S53, which is provided in the same region230cas the second sensor S52, detects the displacement of the upper wafer W1strongly attracted by the upper chuck230. Thus, even if the third sensor S53performs the detection at the same timing as the second sensor S52, the detection value of the third sensor S53becomes higher than the detection value of the second sensor S52. Then, the detection value of the third sensor S53also becomes substantially constant at the time point t1′ after the certain time further elapses from the time point t1.

The control device90switches the attracting pressure distribution of the attraction surface300of the lower chuck231from the beginning attracting pressure distribution to the progress attracting pressure distribution after the time point t1′ at which the detection value of the second sensor S52and the detection value of the third sensor S53become substantially constant. Below, a timing at which this switching is performed is referred to as a “switching time point tr”.

In a process S1prior to the switching time point tr, the lower chuck231attracts the lower wafer W2with the aforementioned beginning attracting pressure distribution. Then, after the switching time point tr, the control device90performs a process S2in which the attracting pressure distribution is switched to the progress attracting pressure distribution. In the progress attracting pressure distribution, the attracting pressures of all the channels are set to −100 kPa, as depicted inFIG.12B. Accordingly, the lower chuck231firmly fixes the lower wafer W2from its middle portion in a radial direction to the vicinity of the outer periphery thereof.

Further, even in a process S3after the time point t2at which the attraction of the region230cis released, the lower chuck231maintains the progress attracting pressure distribution, so that the lower wafer W2can be strongly fixed continuously. As a result, the lower chuck231enables the outer periphery of the upper wafer W1and the outer periphery of the lower wafer W2to be bonded with high precision.

The aforementioned change in the attracting pressure distribution during the progress of the bonding will be described in more detail with reference toFIG.14AtoFIG.15B. At the beginning (time point t0inFIG.13B) of the bonding shown inFIG.14A, the control device90attracts the lower wafer W2with the beginning attracting pressure distribution. That is, the attraction surface300of the lower chuck231attracts the lower wafer W2at −100 kPa in the zones of ch1and ch4to ch10, and attracts the lower wafer W2at −20 kPa in the zones of ch2and ch3.

When the attraction of the region230bof the upper chuck230is released and the time point t1′ is reached (seeFIG.13B), the lowering of the upper wafer W1, that is, the progress of the bonding between the upper wafer W1and the lower wafer W2is temporarily stopped as the region230cis attracting the upper wafer W1. Specifically, as shown inFIG.14B, at a position in the middle of the intermediate region B, the bonding of the upper wafer W1and the lower wafer W2is stopped.

When the progress of the bonding is temporarily stopped, there is formed a boundary point BP (inflection point) at which a bonding portion on the center sides of the upper wafer W1and lower wafer W2and a separation portion on the outer peripheral sides of the upper wafer W1and lower wafer W2are distinguished, as indicated by a thick line inFIG.14B. As shown inFIG.15A, at this boundary point BP, the lower wafer W2is pulled toward the upper wafer W1, so that the lower wafer W2is contracted. For example, when the attracting pressures of the zones of ch2and ch3are not strengthened (when −20 kPa is continued), the lower wafer W2may be greatly contracted, causing the distortion.

To solve the problem, the control device90performs a switchover from the beginning attracting pressure distribution to the progress attracting pressure distribution as shown inFIG.14Cafter the progress of the bonding is temporarily stopped. That is, the switching time point tr is set between the timing when the progress of the bonding is temporarily stopped and the time point t2at which the attraction of the region230cis released (seeFIG.13B). In the progress attracting pressure distribution, the attraction surface300of the lower chuck231is set to have the attracting pressure of −100 kPa in all the zones, so that the portion of the lower wafer W2at the outer side than the boundary point BP is firmly attracted to the lower chuck231. As a result, as shown inFIG.15B, the contraction of the lower wafer W2is suppressed, and the distortion of the lower wafer W2can be alleviated.

As a consequence, the lower chuck231attracts the lower wafer W2with the attracting pressures as shown inFIG.14Dduring the progress of the bonding. That is, the lower chuck231attracts the lower wafer W2with a weak attracting pressure on the center side of the zones of ch2and ch3of the intermediate region B, thus allowing the upper wafer W1and the lower wafer W2near the center to be smoothly bonded. Further, the lower chuck231fixes the lower wafer W2with a strong attracting pressure on the outer peripheral side of the zones of ch2and ch3of the intermediate region B, thus suppressing the deviation between the bonding surface W1jof the upper wafer W1and the bonding surface W2jof the lower wafer W2to thereby bond them with high precision.

As described above, the bonding apparatus1performs the switchover from the beginning attracting pressure distribution to the progress attracting pressure distribution during the progress of the bonding, thus allowing the lower wafer W2to be appropriately fixed as the bonding of the upper wafer W1and the lower wafer W2progresses. As a result, the bonding apparatus1is able to suppress the distortion that may be caused to the lower wafer W2during the progress of the bonding, thus capable of bonding the two sheets of substrates (the upper wafer W1and the lower wafer W2) with high precision.

In addition, by setting the switching time point tr to the timing after the progress of the bonding is temporarily stopped, the bonding apparatus1is capable of bonding the lower wafer W2to the upper wafer W1appropriately until the progress of the bonding from the centers of the upper wafer W1and the lower wafer W2is temporarily stopped. Then, by setting the progress attracting pressure distribution to be maintained until the upper chuck230releases the attraction of the outer periphery of the upper wafer W1, the bonding apparatus1is capable of smoothly suppressing the distortion that may occur at the outer peripheral side of the lower wafer W2after the attraction is released.

Further, by switching from the beginning attracting pressure distribution to the progress attracting pressure distribution at the time when the boundary point BP between the upper wafer W1and the lower wafer W2is located in the intermediate region B, the bonding apparatus1is capable of appropriately adjusting the influence of the attracting pressure of the intermediate region B during the progress of the bonding. Further, in the beginning attracting pressure distribution, by setting the zones of ch1and ch4to ch10to the first attracting pressure while setting the other zones of ch2and ch3to the second attracting pressure, the lower wafer W2can be easily moved according to the bonding force of the upper wafer W1. Therefore, the bonding at the centers of the upper wafer W1and the lower wafer W2can be carried out more stably.

Meanwhile, in the progress attracting pressure distribution, by setting all the regions to have the same attracting pressure (first attracting pressure), the bonding apparatus1is capable of uniformly fixing the entire non-bonding surface W2nof the lower wafer W2. Thus, the distortion of the lower wafer W2that may be caused by different attracting pressures can be more reliably avoided.

In addition, the bonding apparatus1and the substrate processing method of the present disclosure are not limited to the above-described exemplary embodiment, and various modifications may be made. For example, the switchover between the beginning attracting pressure distribution and the progress attracting pressure distribution is not limited to being performed between the time point t1′ at which the progress of the bonding is temporality stopped and the time when the attraction of the region230cis released. For example, it may be performed earlier than the time point t1′.

Furthermore, in the beginning attracting pressure distribution, the attracting pressures of the zones of ch1and ch4to ch10are not limited to −100 kPa, and may be appropriately set according to the internal pressure of the processing vessel210or the like. Likewise, in the progress attracting pressure distribution, the second attracting pressure of the zones of ch2and ch3may be arbitrarily set by a user in the range of, e.g., about 0 kPa to about −40 kPa as long as it is weaker than the attracting pressures of the adjacent zones ch1, ch4, and ch5to ch8.

The second attracting pressure in the beginning attracting pressure distribution is not limited to the zones of ch2and ch3. For example, the zone of ch2alone or the zone of ch3alone may be set to have the second attracting pressure, or the zone of ch4may be set to have the second attracting pressure. The bonding apparatus1may set the zone of ch1to have the second attracting pressure. The bonding apparatus1may automatically change the channels of the second attracting pressure according to, for example, a bending state of the lower wafer W2measured by a bending measuring device5(seeFIG.1). Thus, only any one of the zones in the intermediate region B may be set to have the second attracting pressure, or all the zones in the intermediate region B may be set to have the second attracting pressure. In addition, in the beginning attracting pressure distribution, the bonding apparatus1may set some of the zones of the outer region C to have the second attracting pressure.

Alternatively, the bonding apparatus1may set three or more types of attracting pressures in the beginning attracting pressure distribution. By way of example, the central region A (ch1) may be set to have a third attracting pressure different from the attracting pressure (−20 kPa) of the zones of ch2and ch3of the intermediate region B and the attracting pressure (−100 kPa) of the zone of ch4. Likewise, the outer region C (ch5to ch10) may be set to have a fourth attracting pressure different from the attracting pressure of the intermediate region B. On the contrary, the bonding apparatus1may set the first attracting pressure common to all the zones in the beginning attracting pressure distribution, and may change all or some of the zones to have the second attracting pressure different from (stronger than) the first attracting pressure in the progress attracting pressure distribution.

Also, the progress attracting pressure distribution is not limited to setting the attracting pressures of all the zones to a single type of attracting pressure (first attracting pressure), but the zones may have different attracting pressures. For example, the attracting pressures of the zones of ch2and ch3in the beginning attracting pressure distribution only needs to be stronger than −20 kPa, so they may be set to be stronger than the first attracting pressure (−100 kPa) or may set to be weaker than the first attracting pressure.

In short, as long as the lower chuck231can appropriately fix the lower wafer W2during the bonding, the attracting pressures in the beginning attracting pressure distribution and the attracting pressures in the progress attracting pressure distribution may be arbitrarily set by the user. By way of example, there may be performed a control of attracting the lower wafer W2with a strong attracting pressure in each region in the beginning attracting pressure distribution, and then switching to an attracting pressure weaker than that of the beginning attracting pressure distribution in each region in the progress attracting pressure distribution.

Here, it should be noted that the bonding apparatus1and the bonding method according to the above-described exemplary embodiments are illustrative in all aspects and are not anyway limiting. In fact, the above-described exemplary embodiments can be embodied in various forms. Further, the above-described exemplary embodiments may be omitted, replaced and modified in various ways without departing from the scope and the spirit of claims.

According to the exemplary embodiment, the two sheets of substrates can be bonded to each other with high precision.