This application claims the benefit of Japanese Patent Application No. 2013-144879, filed on Jul. 10, 2013, in the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference.
The present disclosure relates to a bonding device for bonding substrates together, and a bonding method.
In recent years, semiconductor devices have been under high integration. When many highly-integrated semiconductor devices are arranged in a horizontal plane and are connected by wirings for final fabrication, there are problems of increase in wiring length, wiring resistance and wiring delay.
Under the circumstances, there has been proposed a three-dimensional integration technique for stacking semiconductor devices in three dimensions. This three-dimensional integration technique uses a bonding system to bond two semiconductor wafers (hereinafter abbreviated as “wafers”) together. For example, the bonding system includes a surface modifying device (surface activating device) for modifying bonding surfaces of the wafers, a surface hydrophilizing device for hydrophilizing the surfaces of the wafers modified by the surface modifying device and a bonding device for bonding the wafers having the surfaces hydrophilized by the surface hydrophilizing device. In this bonding system, the surface modifying device modifies the wafer surfaces by plasma-processing the wafer surfaces and the surface hydrophilizing device hydrophilizes the wafer surfaces by supplying pure water onto the wafer surfaces. Then, the bonding device bonds the wafers using a Van der Waals force and hydrogen bonding (an inter-molecular force).
In the bonding device, one wafer (hereinafter referred to as an “upper wafer”) is held by an upper chuck and another wafer (hereinafter referred to as a “lower wafer”) is held by a lower chuck installed below the upper chuck. In this state, the bonding device bonds the upper wafer and the lower wafer together. Prior to bonding the wafers in this way, the horizontal positions of the upper chuck and the lower chuck are adjusted. More specifically, a lower image pickup member, e.g., a visible light camera, is moved in the horizontal direction in order for the lower image pickup member to pick up an image of the front surface of the upper wafer held in the upper chuck. An upper image pickup member, e.g., a visible light camera, is moved in the horizontal direction in order for the upper image pickup member to pick up an image of the front surface of the lower wafer held in the lower chuck. The horizontal positions of the upper chuck and the lower chuck are adjusted such that the reference point of an upper wafer surface and the reference point of a lower wafer surface coincide with each other.
In recent years, there is a demand for bonding three or more wafers in a bonding device. In this case, for example, a lower wafer to be bonded has a configuration in which two wafers are laminated in advance. In such a case, a reference point exists on a bonding surface of two wafers which constitute the lower wafer. That is to say, the reference point exists within the lower wafer and does not exist on the front surface of the lower wafer. For that reason, in the aforementioned method, it is not possible to pick up an image of a reference point of an overlapped wafer with the upper image pickup member and the lower image pickup member. It is therefore impossible to adjust the horizontal positions of the upper chuck and the lower chuck. Thus, there is a fear that the horizontal positions of the wafers to be bonded will be out of alignment.
Furthermore, after an upper wafer and a lower wafer are bonded together, it is desirable to inspect the bonding accuracy of the bonded wafer (hereinafter referred to as an “overlapped wafer”), namely the accuracy of the relative position of the upper wafer and the lower wafer bonded together. In the inspection of the overlapped wafer, inspection is conducted, e.g., as to whether the reference point of the upper wafer and the reference point of the lower wafer coincide with each other. However, in the overlapped wafer, the reference point exists on a bonding surface of the wafers. That is to say, the reference point exists within the lower wafer and does not exist on the front surface of the overlapped wafer. For that reason, it is not possible to pick up an image of the reference point of the overlapped wafer with the upper image pickup member and the lower image pickup member. It is therefore impossible to conduct the inspection of the overlapped wafer. Thus, there is a fear that the horizontal positions of the wafers to be bonded will be out of alignment.
In order to conduct the inspection of the overlapped wafer, it may be desirable to use an inspection device additionally installed outside a bonding device. However, it is costly to additionally install the inspection device. Moreover, time is required from the bonding process performed in the bonding device to the inspection conducted in the inspection device. This makes it impossible to provide timely feed back on the inspection result for the subsequent bonding process.
As set forth above, it is likely that the horizontal positions of the wafers to be bonded will be out of alignment. Accordingly, there is room for improvement in the bonding process of the wafers.
Some embodiments of the present disclosure provide a bonding device and a bonding method capable of appropriately adjusting the horizontal positions of a first holding unit for holding a first substrate and a second holding unit for holding a second substrate and capable of appropriately performing a bonding process of substrates.
In accordance with an aspect of the present disclosure, there is provided a bonding device for bonding substrates together, including: a first holding unit configured to hold a first substrate on a lower surface of the first holding unit; a second holding unit located below the first holding unit and configured to hold a second substrate on an upper surface of the second holding unit; a moving mechanism configured to move the first holding unit or the second holding unit in a horizontal direction and a vertical direction; a first image pickup unit located in the first holding unit and configured to pick up an image of the second substrate held in the second holding unit; and a second image pickup unit located in the second holding unit and configured to pick up an image of the first substrate held in the first holding unit, at least one of the first image pickup unit and the second image pickup unit including an infrared camera.
In accordance with another aspect of the present disclosure, there is provided a bonding method for bonding substrates with a bonding device which includes a first holding unit configured to hold a first substrate on a lower surface of the first holding unit, a second holding unit located below the first holding unit and configured to hold a second substrate on an upper surface of the second holding unit, a moving mechanism configured to move the first holding unit or the second holding unit in a horizontal direction and a vertical direction, a first image pickup unit located in the first holding unit and configured to pick up an image of the second substrate held in the second holding unit, and a second image pickup unit located in the second holding unit and configured to pick up an image of the first substrate held in the first holding unit, at least one of the first image pickup unit and the second image pickup unit including an infrared camera. The method includes: picking up images of the second substrate not yet bonded and the first substrate not yet bonded by the first image pickup unit and the second image pickup unit, respectively; and adjusting horizontal positions of the first holding unit and the second holding unit by the moving mechanism based on the images thus picked up.
In accordance with another aspect of the present disclosure, there is provided a bonding method for bonding substrates with a bonding device which includes a first holding unit configured to hold a first substrate on a lower surface of the first holding unit, a second holding unit located below the first holding unit and configured to hold a second substrate on an upper surface of the second holding unit, a moving mechanism configured to move the first holding unit or the second holding unit in a horizontal direction and a vertical direction, a first image pickup unit located in the first holding unit and configured to pick up an image of the second substrate held in the second holding unit, and a second image pickup unit located in the second holding unit and configured to pick up an image of the first substrate held in the first holding unit, at least one of the first image pickup unit and the second image pickup unit including an infrared camera. The method includes: obtaining an image for inspection of an overlapped substrate obtained by bonding the first substrate and the second substrate using the infrared camera; and adjusting horizontal positions of the first holding unit and the second holding unit with the moving mechanism based on the image for inspection obtained from the infrared camera.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
Embodiments of the present disclosure will now be described in detail.
The bonding system 1 is used to bond two substrates, for example, wafers WU and WL, together, as shown in
As shown in
A cassette mounting table 10 is installed in the carry-in/carry-out station 2. A plurality of, e.g., four, cassette mounting boards 11 are installed in the cassette mounting table 10. The cassette mounting boards 11 are arranged in a line along a horizontal X-direction (an up-down direction in
In the carry-in/carry-out station 2, a wafer transfer part 20 is installed adjacent to the cassette mounting table 10. A wafer transfer device 22 movable along a transfer path 21 extending in the X-direction is installed in the wafer transfer part 20. The wafer transfer device 22 is movable in a vertical direction and about a vertical axis (in a θ direction) and is capable of transferring the upper wafer WU, the lower wafer WL and the overlapped wafer WT between the cassettes CU, CL and CT mounted on the respective cassette mounting boards 11 and the below-mentioned transition devices 50 and 51 of a third processing block G3 of the processing station 3.
A plurality of, e.g., three, processing blocks G1, G2 and G3 provided with various types of devices are installed in the processing station 3. For example, the first processing block G1 is installed at the front side of the processing station 3 (at the negative side in the X-direction in
For example, a surface modifying device 30 configured to modify the front surfaces WU1 and WL1 of the upper and lower wafers WU and WL is arranged in the first processing block G1. In the surface modifying device 30, an oxygen gas as a process gas is excited, converted to plasma and ionized under, e.g., a depressurized atmosphere. The oxygen ions are irradiated on the front surfaces WU1 and WL1, whereby the front surfaces WU1 and WL1 are plasma-processed and modified.
For example, in the second processing block G2, a surface hydrophilizing device 40 configured to hydrophilize and clean the front surfaces WU1 and WL1 of the upper and lower wafers WU and WL using, e.g., pure water, and a bonding device 41 configured to bond the upper and lower wafers WU and WL are arranged side by side in the named order from the side of the carry-in/carry-out station 2 along the horizontal Y-direction.
In the surface hydrophilizing device 40, pure water is supplied onto the upper and lower wafers WU and WL while rotating the upper and lower wafers WU and WL held in, e.g., a spin chuck. The pure water thus supplied is diffused on the front surfaces WU1 and WL1 of the upper and lower wafers WU and WL, whereby the front surfaces WU1 and WL1 are hydrophilized. The configuration of the bonding device 41 will be described later.
For example, in the third processing block G3, transition devices 50 and 51 for the upper and lower wafers WU and WL and the overlapped wafers WT are installed in two stages one above another from below as shown in
As shown in
The wafer transfer device 61 includes a transfer arm which can move, e.g., in the vertical direction (in the Z-direction), in the horizontal direction (in the Y-direction and the X-direction) and about the vertical axis. The wafer transfer device 61 can move within the wafer transfer region 60 and can transfer the upper and lower wafers WU and WL and the overlapped wafer WT to a specified device existing within the first processing block G1, the second processing block G2 or the third processing block G3 disposed around the wafer transfer region 60.
As shown in
Next, description will be made on the configuration of the aforementioned bonding device 41. As shown in
The interior of the processing vessel 100 is divided into a transfer region T1 and a processing region T2 by an internal wall 103. The carry-in/carry-out gate 101 is formed on the side surface of the processing vessel 100 corresponding to the transfer region T1. A carry-in/carry-out gate 104 through which the upper and lower wafers WU and WL and the overlapped wafer WT are carried is also formed in the internal wall 103.
A transition 110 is located at the X-direction positive side of the transfer region T1 for temporarily mounting the upper and lower wafers WU and WL and the overlapped wafer WT. The transitions 110 is installed in, e.g., two stages, and are capable of simultaneously mounting two of the upper and lower wafers WU and WL and the overlapped wafer WT.
A wafer transfer mechanism 111 is installed in the transfer region T1. As shown in
A position adjustment mechanism 120 configured to adjust the horizontal direction orientations of the upper and lower wafers WU and WL is located in the X-direction negative side of the transfer region T1. As shown in
In the transfer region T1, as shown in
As shown in
As shown in
As shown in
An upper image pickup unit 151 is located in the upper chuck support unit 150 as a first image pickup unit for picking up an image of the front surface WL1 of the lower wafer WL held in the lower chuck 141. That is to say, the upper image pickup unit 151 is located adjacent to the upper chuck 140.
As shown in
By opening and closing the shutters 156, 158 and 160, the upper image pickup unit 151 can perform an image pickup operation using the micro lens 155 of the infrared camera 152, an image pickup operation using the micro lens 155 of the visible light camera 153 and an image pickup operation using the macro lens 159 of the visible light camera 153.
As shown in
A lower image pickup unit 171 is located in the first lower chuck moving unit 170 as a second image pickup unit for picking up an image of the front surface WU1 of the upper wafer WU held in the upper chuck 140. That is to say, the lower image pickup unit 171 is located adjacent to the lower chuck 141.
As shown in
By opening and closing the shutters 175 and 177, the lower image pickup unit 171 can perform an image pickup operation using the micro lens 174 and an image pickup operation using the macro lens 176.
As shown in
The rails 178 are arranged in a second lower chuck moving unit 179. The second lower chuck moving unit 179 is located on a pair of rails 180 located at the lower surface side of the second lower chuck moving unit 179 and extending in the horizontal direction (the X-direction). The second lower chuck moving unit 179 is configured to move along the rails 180. That is to say, the second lower chuck moving unit 166 is configured to move the lower chuck 141 in the horizontal direction (the X-direction). The rails 180 are arranged on a mounting table 181 located on the bottom surface of the processing vessel 100.
In the present embodiment, the first lower chuck moving unit 170 and the second lower chuck moving unit 179 constitute a moving mechanism of the present disclosure.
Next, description will be made on the detailed configuration of the upper chuck 140 and the lower chuck 141 of the bonding device 41.
As shown in
Suction holes 194 for vacuum-drawing the upper wafer WU in an inner region 193 of the outer wall portion 192 (hereinafter sometimes referred to as a “suction region 193”) are formed on the lower surface of the body portion 190. The suction holes 194 are formed at, e.g., two points, in the outer peripheral portion of the suction region 193. Suction pipes 195 installed within the body portion 190 are connected to the suction holes 194. A vacuum pump 196 is connected to the suction pipes 195 through joints.
The suction region 193 surrounded by the upper wafer WU, the body portion 190 and the outer wall portion 192 is vacuum-drawn from the suction holes 194, whereby the suction region 193 is depressurized. At this time, the external atmosphere of the suction region 193 is kept at atmospheric pressure. Thus, the upper wafer WU is pressed by the atmospheric pressure toward the suction region 193 just as much as the depressurized amount. Consequently, the upper wafer WU is sucked and held by the upper chuck 140.
In this case, it is possible to reduce the flatness of the lower surface of the upper chuck 140 because the pins 191 are uniform in height. By making the lower surface of the upper chuck 140 (by reducing the flatness of the lower surface of the upper chuck 140) flat in this manner, it is possible to suppress vertical distortion of the upper wafer WU held in the upper chuck 140. Since the rear surface WU2 of the upper wafer WU is supported on the pins 191, the upper wafer WU is easily detached from the upper chuck 140 upon releasing the vacuum-drawing of the upper wafer WU performed by the upper chuck 140.
A through-hole 197 extending through the body portion 190 in the thickness direction is formed in the central portion of the body portion 190. The central portion of the body portion 190 corresponds to the central portion of the upper wafer WU adsorptively held by the upper chuck 140. A pressing pin 201 of a pressing member 200 to be described below is inserted into the through-hole 197.
The pressing member 200 configured to press the central portion of the upper wafer WU is installed on the upper surface of the upper chuck 140. The pressing member 200 has a cylindrical structure. The pressing member 200 includes the pressing pin 201 and an outer cylinder 202 serving as a guide when the pressing pin 201 is moved up and down. By virtue of a drive unit (not shown) provided with, e.g., a motor therein, the pressing pin 201 can be moved up and down in the vertical direction through the through-hole 197. When bonding the upper and lower wafers WU and WL in the below-mentioned manner, the pressing member 200 can bring the central portion of the upper wafer WU into contact with the central portion of the lower wafer WL and can press the central portion of the upper wafer WU against the central portion of the lower wafer WL.
As shown in
Suction holes 214 for vacuum-drawing the lower wafer WL in an inner region 213 of the outer wall portion 212 (hereinafter sometimes referred to as a “suction region 213”) are formed on the upper surface of the body portion 210. Suction pipes 215 installed within the body portion 210 are connected to the suction holes 214. For example, two suction pipes 215 are installed within the body portion 210. A vacuum pump 216 is connected to the suction pipes 215.
The suction region 213 surrounded by the lower wafer WL, the body portion 210 and the outer wall portion 212 is vacuum-drawn from the suction holes 214, whereby the suction region 213 is depressurized. At this time, the external atmosphere of the suction region 213 is kept at atmospheric pressure. Thus, the lower wafer WL is pressed by the atmospheric pressure toward the suction region 213 just as much as the depressurized amount. Consequently, the lower wafer WL is adsorptively held by the lower chuck 141.
In this case, it is possible to reduce the flatness of the upper surface of the lower chuck 141 because the pins 211 are uniform in height. In addition, for example, even if particles exist within the processing vessel 100, it is possible to suppress the existence of particles on the upper surface of the lower chuck 141 when the interval of the adjoining pins 211 is appropriate. By making the upper surface of the lower chuck 141 (by reducing the flatness of the upper surface of the lower chuck 141) flat in this manner, it is possible to suppress vertical distortion of the lower wafer WL held in the lower chuck 141. Since the rear surface WL2 of the lower wafer WL is supported on the pins 211, the lower wafer WL is easily detached from the lower chuck 141 upon releasing the vacuum-drawing of the lower wafer WL performed by the lower chuck 141.
Through-holes 217 extending through the body portion 210 in the thickness direction are formed at, e.g., three points, in and around the central portion of the body portion 210. Lift pins installed below the first lower chuck moving unit 170 are inserted into the through-holes 217.
Guide members 218 configured to prevent the upper or lower wafer WU or WL or the overlapped wafer WT from jumping out and sliding down from the lower chuck 141 are installed in the outer peripheral portion of the body portion 210. The guide members 218 are installed at a plurality of points, e.g., four points, at a regular interval in the outer peripheral portion of the body portion 210.
The operations of the respective parts of the bonding device 41 are controlled by the aforementioned control unit 70.
Next, description will be made on a process of bonding the upper and lower wafers WU and WL performed by the bonding system 1 configured as above.
First, the cassette CU accommodating a plurality of upper wafers WU, the cassette CL accommodating a plurality of lower wafers WL and the empty cassette CT are mounted on the specified cassette mounting boards 11 of the carry-in/carry-out station 2. Thereafter, the upper wafer WU is taken out from the cassette CU by the wafer transfer device 22 and is transferred to the transition device 50 of the third processing block G3 of the processing station 3.
Then, the upper wafer WU is transferred to the surface modifying device 30 of the first processing block G1 by the wafer transfer device 61. In the surface modifying device 30, oxygen gas as a process gas is excited, converted to plasma and ionized under a specified depressurized atmosphere. The oxygen ions thus generated are irradiated on the front surface WU1 of the upper wafer WU, whereby the front surface WU1 is plasma-processed. Thus, the front surface WU1 of the upper wafer WU is modified (Step S1 in
Next, the upper wafer WU is transferred to the surface hydrophilizing device 40 of the second processing block G2 by the wafer transfer device 61. In the surface hydrophilizing device 40, pure water is supplied onto the upper wafer WU while rotating the upper wafer WU held in a spin chuck. The pure water thus supplied is diffused on the front surface WU1 of the upper wafer WU. Hydroxyl groups (silanol groups) adhere to the front surface WU1 of the upper wafer WU modified in the surface modifying device 30, whereby the front surface WU1 is hydrophilized. Furthermore, the front surface WU1 of the upper wafer WU is cleaned by the pure water (Step S2 in
Then, the upper wafer WU is transferred to the bonding device 41 of the second processing block G2 by the wafer transfer device 61. The upper wafer WU carried into the bonding device 41 is transferred to the position adjustment mechanism 120 through the transition 110 by the wafer transfer mechanism 111. The horizontal direction orientation of the upper wafer WU is adjusted by the position adjustment mechanism 120 (Step S3 in
Thereafter, the upper wafer WU is delivered from the position adjustment mechanism 120 to the holding arm 131 of the inverting mechanism 130. Subsequently, in the transfer region T1, the holding arm 131 is inverted to thereby invert the front and rear surfaces of the upper wafer WU (Step S4 in
Thereafter, the holding arm 131 of the inverting mechanism 130 rotates about the first drive unit 134 and moves to below the upper chuck 140. Then, the upper wafer WU is delivered from the inverting mechanism 130 to the upper chuck 140. The rear surface WU2 of the upper wafer WU is adsorptively held by the upper chuck 140 (Step S5 in
During the time when the processing of steps S1 to S5 is performed with respect to the upper wafer WU, processing with respect to the lower wafer WL is also performed. First, the lower wafer WL is taken out from the cassette CL by the wafer transfer device 22 and is transferred to the transition device 50 of the processing station 3.
Next, the lower wafer WL is transferred to the surface modifying device 30 by the wafer transfer device 61. The front surface WU of the lower wafer WL is modified in the surface modifying device 30 (Step S6 in
Thereafter, the lower wafer WL is transferred to the surface hydrophilizing device 40 by the wafer transfer device 61. The front surface WL1 of the lower wafer WL is hydrophilized and cleaned in the surface hydrophilizing device 40 (Step S7 in
Thereafter, the lower wafer WL is transferred to the bonding device 41 by the wafer transfer device 61. The lower wafer WL carried into the bonding device 41 is transferred to the position adjustment mechanism 120 through the transition 110 by the wafer transfer mechanism 111. The horizontal direction orientation of the lower wafer WL is adjusted by the position adjustment mechanism 120 (Step S8 in
Thereafter, the lower wafer WL is transferred to the lower chuck 141 by the wafer transfer mechanism 111. The rear surface WL2 of the lower wafer WL is adsorptively held by the lower chuck 141 (Step S9 in
Next, as shown in
In Step S10, the lower chuck 141 is moved in the horizontal direction (in the X-direction and the Y-direction) by the first lower chuck moving unit 170 and the second lower chuck moving unit 179 such that the lower image pickup unit 171 is positioned substantially below the upper image pickup unit 151. The visible light camera 153 of the upper image pickup unit 151 and the visible light camera 172 of the lower image pickup unit 171 identify a common target T. The horizontal position of the lower image pickup unit 171 is finely adjusted such that the horizontal positions of the upper image pickup unit 151 and the lower image pickup unit 171 coincide with each other. At this time, it is only necessary to move the lower image pickup unit 171 because the upper image pickup unit 151 is fixed to the processing vessel 100. This makes it possible to appropriately adjust the horizontal positions of the upper image pickup unit 151 and the lower image pickup unit 171.
Next, as shown in
A plurality of, e.g., three, predetermined reference points A1 to A3 are defined on the front surface WU1 of the upper wafer WU. Similarly, a plurality of, e.g., three, predetermined reference points B1 to B3 are defined on the front surface WL1 of the lower wafer WL. The reference points A1 and A3 and the reference points B1 and B3 are reference points of the outer peripheral portions of the upper wafer WU and the lower wafer WL, respectively. The reference points A2 and B2 are reference points of the central portions of the upper wafer WU and the lower wafer WL, respectively. For example, specific patterns formed on the upper wafer WU and the lower wafer WL are used as the reference points A1 to A3 and the reference points B1 to B3.
In Step S11, the lower chuck 141 is moved in the horizontal direction (in the X-direction and the Y-direction) by the first lower chuck moving unit 170 and the second lower chuck moving unit 179. Images of three points of the outer peripheral portion of the front surface WU of the lower wafer WL are picked up by the macro lens 159 of the visible light camera 153 of the upper image pickup unit 151. The control unit 70 measures the horizontal positions of three points based on the picked-up images and calculates the horizontal position of the central portion of the front surface WL1 of the lower wafer WL based on the measurement result. Thereafter, the lower chuck 141 is moved in the horizontal direction, and an image of the central portion (the centrally-located chip) of the front surface WL1 of the lower wafer WL is picked up. Subsequently, the lower chuck 141 is further moved in the horizontal direction, and an image of the chip located adjacent to the centrally-located chip is picked up. Then, the control unit 70 calculates the slope of the lower wafer WL based on the image of the centrally-located chip and the image of the chip located adjacent to the centrally-located chip. By acquiring the horizontal position of the central portion of the lower wafer WL and the slope of the lower wafer WL in this way, it is possible to acquire approximate coordinates of the lower wafer WL. The horizontal position of the lower chuck 141 is roughly adjusted based on the approximate coordinates of the lower wafer WL. The horizontal positions of the upper wafer WU and the lower wafer WL are roughly adjusted in the aforementioned manner.
The rough adjustment of the horizontal positions in Step S11 is performed into such positions where, at least in Step S12 to be described below, the upper image pickup unit 151 can pick up the images of the reference points B1 to B3 of the lower wafer WL and the lower image pickup unit 171 can pick up the images of the reference points A1 to A3 of the upper wafer WU.
In Step S12 performed subsequently, the lower chuck 141 is moved in the horizontal direction (in the X-direction and the Y-direction) by the first lower chuck moving unit 170 and the second lower chuck moving unit 179. The images of the reference points B1 to B3 of the front surface WL1 of the lower wafer WL are sequentially picked up using the micro lens 155 of the visible light camera 153 of the upper image pickup unit 151. At the same time, the images of the reference points A1 to A3 of the front surface WU1 of the upper wafer WU are sequentially picked up using the micro lens 174 of the visible light camera 172 of the lower image pickup unit 171.
During the fine adjustment of the horizontal positions performed in Step S12, the orientation of the lower chuck 141 is also finely adjusted by moving the lower chuck 141 in the horizontal direction (in the X-direction and the Y-direction) as described above and by rotating the lower chuck 141 using the first lower chuck moving unit 170.
Thereafter, as shown in
Next, a process of bonding the upper wafer WU held in the upper chuck 140 and the lower wafer WL held in the lower chuck 141 is performed.
First, as shown in
Then, bonding begins to occur between the central portion of the upper wafer WU and the central portion of the lower wafer WL pressed against each other (see the portion indicated by a thick line in
Thereafter, as shown in
Thereafter, as shown in
Next, as shown in
In Step S16, while moving the lower chuck 141 in the horizontal direction (in the X-direction and the Y-direction) by the first lower chuck moving unit 170 and the second lower chuck moving unit 179, the images of the reference points C1 to C3 located within the overlapped wafer WT are sequentially picked up using the infrared camera 152 of the upper image pickup unit 151. At this time, since the infrared rays are transmitted through the overlapped wafer WT, the infrared camera 152 can pick up the images of the reference points C1 to C3 located within the overlapped wafer WT.
In the inspection of the overlapped wafer WT performed in Step S16, the coincidence of the reference points A1 to A3 and the reference points B1 to B3 includes not only a case where the reference points completely coincide with each other but also a case where the positional deviation of the respective reference points falls within a desired range.
Thereafter, the horizontal positions of the upper chuck 140 and the lower chuck 141 are adjusted based on the inspection results of Step S16 (Step S17 in
In Step S17, the horizontal positions of the upper chuck 140 and the lower chuck 141 are not adjusted if the inspection results are normal. On the other hand, if the inspection results are abnormal, namely if the upper wafer WU and the lower wafer WL are bonded in a horizontally deviated state, a correction value corresponding to the deviation is stored in the control unit 70. Then, after Step S12 is performed with respect to the next wafers WU and WL, the lower chuck 141 is moved just as much as the correction value by the first lower chuck moving unit 170 and the second lower chuck moving unit 179. By doing so, the horizontal position of the lower chuck 141 is appropriately adjusted. This makes it possible for the bonding process of the wafers WU and WL to be performed subsequently.
Thereafter, the overlapped wafer WT subjected to the inspection is transferred to the transition device 51 by the wafer transfer device 61 and is then transferred to the cassette CT located on one of the specified cassette mounting boards 11 by the wafer transfer device 22 of the carry-in/carry-out station 2. As a result, the bonding process of the wafers WU and WL is finished.
According to the embodiment described above, the infrared rays are transmitted through the overlapped wafer WT when inspecting the overlapped wafer WT in Step S16. Thus, the images of the reference points C1 to C3 can be picked up by the infrared camera 152 of the upper image pickup unit 151. As a result, in Step S17 to be performed subsequently, the upper chuck 140 and the lower chuck 141 can be feedback controlled based on the inspection results such that, in the overlapped wafer WT, the reference points A1 to A3 of the upper wafer WU coincide with the reference points B1 to B3 of the lower wafer WL. Accordingly, it is possible to appropriately adjust the horizontal positions of the upper chuck 140 and the lower chuck 141. This makes it possible to appropriately perform the subsequent bonding process of the wafers WU and WL.
As mentioned above, the inspection of the overlapped wafer WT can be performed within the bonding device 41. There is no need to additionally install an inspection device outside the bonding device 41. It is therefore possible to save the device manufacturing cost. In addition, since the overlapped wafer WT can be inspected just after the wafers WU and WL are bonded to each other, it is possible to feed back the inspection results to the subsequent bonding process at an appropriate timing. This enhances the accuracy of the bonding process.
The upper image pickup unit 151 and the lower image pickup unit 171 are provided with the visible light cameras 153 and 172, respectively. Therefore, in Steps S10 to S12, the images of the lower wafer WL and the upper wafer WU can be picked up by the visible light cameras 153 and 172. By doing so, the horizontal positions of the upper chuck 140 and the lower chuck 141 can be appropriately adjusted based on the visible light images thus picked up. Accordingly, it is possible to appropriately perform the bonding process of the upper wafer WU and the lower wafer WL in Steps S14 and S15.
In addition, since the upper image pickup unit 151 and the lower image pickup unit 171 are respectively provided with the micro lens 155 and 174 and the macro lens 159 and 176, it is possible to adjust, in a stepwise manner, the horizontal positions of the upper chuck 140 and the lower chuck 141 in Steps S11 and S12. Accordingly, it is possible to efficiently adjust the horizontal positions of the upper chuck 140 and the lower chuck 141.
The upper chuck 140 is fixed to the processing vessel 100, and the upper image pickup unit 151 is also fixed to the processing vessel 100. Thus, there is no possibility that the upper chuck 140 and the upper image pickup unit 151 are moved over time. In Step S10, it is only necessary to move the lower image pickup unit 171 because the upper image pickup unit 151 is fixed to the processing vessel 100. This makes it possible to appropriately adjust the horizontal positions of the upper image pickup unit 151 and the lower image pickup unit 171. In Steps S11 and S12, it is only necessary to move the lower chuck 141 because the upper chuck 140 is fixed to the processing vessel 100. This makes it possible to appropriately adjust the horizontal positions of the upper chuck 140 and the lower chuck 141. That is to say, it is possible to enhance the accuracy of the adjustment of the horizontal positions of the upper chuck 140 and the lower chuck 141.
The bonding system 1 includes not only the bonding device 41 but also the surface modifying device 30 for modifying the front surfaces WU1 and WU of the wafers WU and WL and the surface hydrophilizing device 40 for hydrophilizing and cleaning the front surfaces WU1 and WL1. Thus, the bonding of the wafers WU and WL can be efficiently performed within one system. Accordingly, it is possible to increase the throughput of the wafer bonding process.
The bonding device 41 of the aforementioned embodiment may be used in a case where three or more wafers are bonded together. Description will now be made on a case where another wafer WZ is bonded to the overlapped wafer WT1 bonded in the aforementioned embodiment. The overlapped wafer WT1 may be made thinner by polishing the rear surface WU2 of the upper wafer WU or the rear surface WL2 of the lower wafer WL. In the present embodiment, the wafer WZ is a first substrate and the overlapped wafer WT1 is a second substrate.
The wafer WZ is subjected to Step S1 to S5 described above. The wafer WZ is adsorptively held by the upper chuck 140. On the other hand, the overlapped wafer WT1 is subjected to Steps S6 to S9 described above. The overlapped wafer WT1 is adsorptively held by the lower chuck 141. Thereafter, in Step S10 described above, the horizontal positions of the upper image pickup unit 151 and the lower image pickup unit 171 are adjusted as shown in
Performed next is Step S11 where the horizontal positions of the upper chuck 140 and the lower chuck 141 are roughly adjusted using the macro lens 159 of the visible light camera 153 of the upper image pickup unit 151 and the macro lens 176 of the visible light camera 172 of the lower image pickup unit 171.
Next, in Step S12, the horizontal positions of the upper chuck 140 and the lower chuck 141 are adjusted as shown in
In Step S12, while moving the lower chuck 141 in the horizontal direction (in the X-direction and the Y-direction) by the first lower chuck moving unit 170 and the second lower chuck moving unit 179, the images of the reference points C1 to C3 located within the overlapped wafer WT1 are sequentially picked up using the infrared camera 152 of the upper image pickup unit 151. At this time, since the infrared rays are transmitted through the overlapped wafer WT1, the infrared camera 152 can pick up the images of the reference points C1 to C3 located within the overlapped wafer WT1. At the same time, while moving the lower chuck 141 in the horizontal direction, the images of the reference points D1 to D3 on the front surface of the wafer WZ are sequentially picked up using the micro lens 174 of the visible light camera 172 of the lower image pickup unit 171.
Thereafter, Step S13 described above is performed to adjust the vertical positions of the upper chuck 140 and the lower chuck 141. Then, Steps S14 and S15 described above are performed to carry out the bonding process of the wafer WZ held in the upper chuck 140 and the overlapped wafer WT1 held in the lower chuck 141.
Next, in Step S16, an overlapped wafer WT2 obtained by bonding the wafer WZ and the overlapped wafer WT1 is inspected as shown in
Thereafter, based on the inspection results of Step S16, Step S17 described above is performed to adjust the horizontal positions of the upper chuck 140 and the lower chuck 141. That is to say, for the subsequent processing on the wafers WU and WL, the upper chuck 140 and the lower chuck 141 are feedback controlled.
According to the present embodiment, when adjusting the horizontal positions of the upper chuck 140 and the lower chuck 141 in Step S12, the infrared rays are transmitted through the overlapped wafer WT1. Therefore, the infrared camera 152 of the upper image pickup unit 151 can pick up the images of the reference points C1 to C3 located within the overlapped wafer WT1. On the other hand, the images of the reference points D1 to D3 of the wafer WZ can be picked up using the visible light camera 172 of the lower image pickup unit 171. Accordingly, it is possible to appropriately adjust the horizontal positions of the upper chuck 140 and the lower chuck 141. Thereafter, in Steps S14 and S15, the bonding process of the wafer WZ and the overlapped wafer WT1 can be appropriately performed.
Even when inspecting the overlapped wafer WT2 in Step S16, the infrared rays are transmitted through the overlapped wafer WT2. Thus, the images of the reference points D1 to D3 located within the overlapped wafer WT2 can be picked up by the infrared camera 152 of the upper image pickup unit 151. By doing so, in Step S17, the upper chuck 140 and the lower chuck 141 can be feedback controlled based on the inspection results. Accordingly, it is possible to appropriately adjust the horizontal positions of the upper chuck 140 and the lower chuck 141. This makes it possible to appropriately perform the bonding process of the subsequent wafers WU and WL.
In the aforementioned embodiment, description has been made on a case where three wafers are bonded in the bonding device 41. However, four or more wafers may be bonded in the bonding device 41.
In the bonding device 41 of the aforementioned embodiment, the sensor 154 of the infrared camera 152 and the sensor 157 of the visible light camera 153 are independently installed in the upper image pickup unit 151. Alternatively, a sensor capable acquiring both an infrared image and a visible light image may be installed in common.
Although the infrared camera 152 is installed in the upper image pickup unit 151 in the aforementioned embodiment, it may be possible to install the infrared camera 152 in the lower image pickup unit 171. Alternatively, two infrared cameras 152 may be separately installed in the upper image pickup unit 151 and the lower image pickup unit 171. If the infrared cameras 152 are installed in the upper image pickup unit 151 and in the lower image pickup unit 171, both the upper chuck 140 and the lower chuck 141 can hold an overlapped wafer obtained by laminating a plurality of wafers. Thus, the degree of freedom of the bonding process is enhanced.
In the bonding device 41 of the aforementioned embodiment, the upper chuck 140 is fixed to the processing vessel 100 and the lower chuck 141 is moved in the horizontal direction and the vertical direction. In contrast, the upper chuck 140 may be moved in the horizontal direction and the vertical direction and the lower chuck 141 may be fixed to the processing vessel 100. Alternatively, both the upper chuck 140 and the lower chuck 141 may be moved in the horizontal direction and the vertical direction.
In the bonding system 1 of the aforementioned embodiment, after the wafers WU and WL are bonded by the bonding device 41, the overlapped wafer WT thus bonded may be heated (annealed) to a predetermined temperature. By heating the overlapped wafer WT in this way, it is possible to strongly join the bonding interface.
According to the present disclosure, since the infrared rays are transmitted through the overlapped wafer, the infrared camera can pick up the images of the reference points located within the overlapped wafer.
In a case of bonding three or more wafers together, for example, bonding a single wafer as a first substrate and an overlapped wafer a second substrate together, reference points located within the second substrate can be picked up using an infrared camera. In addition, reference points on the front surface of the first substrate can be picked up using various types of cameras. In this case, the horizontal positions of the first holding unit and the second holding unit can be appropriately adjusted based on thus picked-up images such that, the reference points of the first substrate and the reference points of the second substrate coincide with each other.
In addition, in a case of inspecting an overlapped wafer obtained by bonding the first substrate and the second substrate together, for example, reference points located within the overlapped wafer can be picked up using the infrared camera. In this case, the first holding unit and the second holding unit can be feedback controlled based on the inspection results such that, in the overlapped wafer, the reference points of the first substrate coincide with the reference points of the second substrate. Accordingly, it is possible to appropriately adjust the horizontal positions of the first holding unit and the second holding unit.
In addition, the inspection of the overlapped wafer can be performed within the bonding device. There is no need to additionally install an inspection device outside the bonding device. It is therefore possible to save the device manufacturing cost. In addition, since the overlapped wafer can be inspected just after the wafers are bonded to each other, it is possible to feed back the inspection results to the subsequent bonding process at an appropriate timing. This enhances the accuracy of the bonding process.
According to the present disclosure, it is possible to appropriately adjust the horizontal positions of a first holding unit for holding a first substrate and a second holding unit for holding a second substrate and to appropriately perform a bonding process of substrates.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures. The present disclosure may be applied to a case where the substrate is not a wafer but another substrate such as a FPD (Flat Panel Display), a mask reticle for a photo mask or the like.
Number | Date | Country | Kind |
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2013-144879 | Jul 2013 | JP | national |