CN115799118A - Wafer bonding machine and wafer bonding method - Google Patents

Abstract

The invention provides a wafer bonding machine and a wafer bonding method, which are used for bonding an upper wafer and a lower wafer, wherein the wafer bonding machine comprises: the upper chuck is used for adsorbing the upper wafer; the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area; at least three light detectors arranged at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and whether the upper layer wafer generates slip relative to the lower layer wafer after bonding is judged according to the emergent light and the reflected light. The technical scheme of the invention can avoid damaging mechanical parts in the wafer bonding machine and avoid damaging the upper wafer.

Description

Wafer bonding machine and wafer bonding method

Technical Field

The present invention relates to the field of semiconductor integrated circuit manufacturing, and more particularly, to a wafer bonding machine and a wafer bonding method.

Background

In semiconductor manufacturing technology, bonding two wafers together using bonding technology has been widely used in order to effectively increase the number of devices per unit area.

Before bonding, the upper chuck is fixed on the upper bearing table, the lower chuck is fixed on the lower bearing table, the upper layer wafer is adsorbed on the upper chuck, and the lower layer wafer is adsorbed on the lower chuck. The bonding step comprises: firstly, moving an upper bearing table and a lower bearing table from an initial position to a set position for carrying out bonding; then, the upper bearing table is moved downwards to bond the upper wafer on the lower wafer; the upper and lower stages are then moved back to the initial position. When an upper wafer is bonded to a lower wafer, a slip sheet (i.e., the upper wafer is shifted relative to the lower wafer) may occasionally occur, and at present, the slip sheet detection is performed after the upper and lower load bearing tables are moved back to the initial positions, which has a delay property.

Therefore, how to detect whether a slip occurs in time to avoid damaging mechanical components and wafers is a problem that needs to be solved.

Disclosure of Invention

The invention aims to provide a wafer bonding machine and a wafer bonding method, which can avoid damage to mechanical parts in the wafer bonding machine and damage to an upper wafer.

In order to achieve the above object, the present invention provides a wafer bonding machine for bonding an upper wafer and a lower wafer, the wafer bonding machine comprising:

the upper chuck is used for adsorbing the upper wafer;

the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area;

at least three light detectors arranged at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and whether the upper layer wafer generates slip sheets relative to the lower layer wafer after bonding is judged according to the emergent light and the reflected light.

Optionally, at least three of the photodetectors are uniformly disposed in an edge region of the lower chuck.

Optionally, the light detector comprises a range finder or a light intensity sensor.

Optionally, a horizontal distance between the photodetector and an edge of the lower wafer is less than 3mm.

Optionally, the wafer bonding machine further includes:

the upper bearing table is used for bearing the upper chuck;

and the lower bearing table is used for bearing the lower chuck.

Optionally, the wafer bonding machine further includes:

and the ejector pin is used for applying pressure to the upper-layer wafer after penetrating through the upper chuck so as to bond the upper-layer wafer to the lower-layer wafer.

The invention also provides a wafer bonding method, which comprises the following steps:

providing an upper chuck and a lower chuck, wherein the lower chuck is provided with an adsorption area and an edge area positioned at the periphery of the adsorption area, an upper wafer is adsorbed on the upper chuck, a lower wafer is adsorbed on the adsorption area of the lower chuck, and at least three photodetectors are arranged in the edge area of the lower chuck;

bonding the upper wafer to the lower wafer;

and adopting the light detector to emit and receive reflected light reflected by the emitted light so as to detect whether the upper layer wafer generates slip relative to the lower layer wafer.

Optionally, the upper chuck is fixed on an upper bearing table, and the lower chuck is fixed on a lower bearing table; before bonding the upper wafer to the lower wafer, the wafer bonding method further includes:

and moving the upper bearing table and the lower bearing table from respective initial positions to a set position for bonding so that the upper chuck and the lower chuck are oppositely arranged.

Optionally, after bonding the upper wafer to the lower wafer, the wafer bonding method further includes:

and respectively moving the upper bearing table and the lower bearing table from the set positions back to the respective initial positions, and detecting whether the upper layer wafer slides relative to the lower layer wafer by using the light detector in the moving process.

Optionally, the reference value is stored in the photodetector; the photodetector is a distance meter, and the step of detecting whether the upper layer wafer slides relative to the lower layer wafer comprises the following steps:

the distance meter emits emergent light and receives reflected light reflected by the emergent light so as to measure the vertical distance between the distance meter and the reflected position of the emergent light; the reference value is a vertical distance between the distance measuring instrument and the upper wafer when no slip occurs after bonding, and if the vertical distance measured by at least one distance measuring instrument is smaller than or equal to the reference value, the slip occurs on the upper wafer relative to the lower wafer;

or, the light detector is a light intensity sensor, and the step of detecting whether the upper layer wafer slides relative to the lower layer wafer comprises:

the light intensity sensor emits outgoing light and receives reflected light reflected by the outgoing light so as to measure the light intensity difference between the outgoing light and the reflected light; and if the light intensity difference measured by at least one light intensity sensor is smaller than or equal to the reference value, the upper layer wafer generates slip sheets relative to the lower layer wafer.

Optionally, the step of bonding the upper wafer to the lower wafer includes:

and penetrating the upper chuck by using a thimble, and applying downward pressure to the upper layer wafer so as to bond the upper layer wafer on the lower layer wafer.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the wafer bonding machine of the invention comprises: the upper chuck is used for adsorbing the upper wafer; the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area; at least three light detectors arranged at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and judging whether the upper wafer is subjected to slip sheet relative to the lower wafer after bonding according to the emergent light and the reflected light, so that damage to mechanical parts in the wafer bonding machine table can be avoided, and damage to the upper wafer can be avoided.

2. According to the wafer bonding method, the upper chuck and the lower chuck are provided, the lower chuck is provided with an adsorption area and an edge area located at the periphery of the adsorption area, the upper chuck adsorbs an upper wafer, the adsorption area of the lower chuck adsorbs a lower wafer, and the edge area of the lower chuck is provided with at least three photodetectors; bonding the upper wafer to the lower wafer; the optical detector is adopted to emit and receive reflected light reflected by the emitted light so as to detect whether the upper wafer slides relative to the lower wafer, so that mechanical parts in the wafer bonding machine can be prevented from being damaged, and the upper wafer is prevented from being damaged.

Drawings

FIG. 1 is a schematic top view of a photodetector in an embodiment of the invention in a lower chuck;

FIG. 2 is a side view of a photodetector in a lower chuck according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an embodiment of the present invention when no slipping occurs;

FIG. 4 is a schematic view of an embodiment of the present invention when slipping occurs;

fig. 5 is a flowchart illustrating a wafer bonding method according to an embodiment of the invention.

Wherein the reference numerals of figures 1 to 5 are as follows:

11-lower chuck; 111-reference line; 12-a light detector; 13-upper wafer; 14-lower level wafer.

Detailed Description

In order to make the objects, advantages and features of the present invention more apparent, the wafer bonding machine and the wafer bonding method of the present invention are further described in detail below. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

An embodiment of the present invention provides a wafer bonding machine for bonding an upper wafer and a lower wafer, the wafer bonding machine including: the upper chuck is used for adsorbing the upper wafer; the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area; at least three photodetectors disposed at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and whether the upper layer wafer generates slip sheets relative to the lower layer wafer after bonding is judged according to the emergent light and the reflected light.

The wafer bonding machine provided by the present embodiment is described in detail with reference to fig. 1 to 4.

The upper chuck (not shown) is used to chuck the upper wafer 13.

The lower chuck 11 is disposed below the upper chuck, the lower chuck 11 is configured to adsorb a lower wafer 14, a surface to be bonded of the upper wafer 13 faces downward, and a surface to be bonded of the lower wafer 14 faces upward.

The lower chuck 11 and the upper chuck both comprise an adsorption area for placing a wafer and an edge area located at the periphery of the adsorption area, the upper layer wafer 13 and the lower layer wafer 14 are both placed in the adsorption area, and preferably, the diameter of the adsorption area is larger than the diameters of the upper layer wafer 13 and the lower layer wafer 14. Taking the lower chuck 11 as an example, as shown in fig. 1, a reference line 111 is disposed on a top surface of the lower chuck 11, an area within the reference line 111 is an absorption area for placing the lower layer wafer 14, a diameter of the absorption area is slightly larger than a diameter of the lower layer wafer 14, and an area outside the reference line 111 is an edge area.

Preferably, the suction region is recessed inward relative to the edge region, so that a groove is formed on each of the upper chuck and the lower chuck 11, and the upper wafer 13 and the lower wafer 14 are respectively placed in the groove of the upper chuck and the groove of the lower chuck 11, so as to prevent the placement positions of the upper wafer 13 and the lower wafer 14 from shifting.

The wafer bonding machine further comprises:

an upper bearing table (not shown) for bearing the upper chuck, wherein the upper chuck is fixed on the upper bearing table and can drive the upper chuck to move;

and the lower bearing table (not shown) is used for bearing the lower chuck 11, the lower chuck 11 is fixed on the lower bearing table, and the lower bearing table can drive the lower chuck 11 to move.

The upper and lower stages can be moved from their respective initial positions to a set position for performing bonding before bonding the upper wafer 13 to the lower wafer 14, so that the upper and lower chucks 11 are disposed opposite to each other, and the distance between the upper and lower chucks 11 reaches a set distance required for bonding.

And the upper and lower stages can move from the set positions to the initial positions after bonding the upper wafer 13 to the lower wafer 14, the lower stage can move to the initial positions with the bonded wafers, and the upper stage only moves to the initial positions with the upper chuck.

The wafer bonding machine further comprises:

the thimble, set up in the center of going up the chuck, the thimble is used for passing it is right behind the upper chuck upper wafer 13 exerts pressure, makes upper wafer 13's central zone to lower floor's wafer 14 direction is close to and contacts 13 deformation in-process of upper wafer, the bonding wave is followed 13 centers of upper wafer move to the edge, and then release in proper order by center to edge the upper chuck is right upper wafer 13's absorption vacuum, thus make upper wafer 13 with lower floor's wafer 14 accomplishes the bonding under the bonding wave effect.

At least three photodetectors 12 are disposed at intervals in an edge region of the lower chuck 11.

The light detector 12 does not extend beyond the top surface of the lower chuck 11, so as to prevent the upper wafer 13 from being damaged by the portion of the light detector 12 extending beyond the top surface of the lower chuck 11 when the upper wafer 13 slips relative to the lower wafer 14.

Preferably, at least three photodetectors 12 are uniformly spaced from each other in an edge region of the lower chuck 11 so that they can be detected when the upper wafer 13 slips in any direction.

In the embodiment shown in fig. 1, four photodetectors 12 are disposed in an edge region of the lower chuck 11, and the four photodetectors 12 are uniformly distributed. In the embodiment shown in fig. 2, the top surface of the photodetector 12 is flush with the top surface of the lower chuck 11; when the top surface of the photodetector 12 is lower than the top surface of the lower chuck 11, the distance between the top surface of the photodetector 12 and the top surface of the lower chuck 11 may be, for example, 1mm to 2mm.

Preferably, a horizontal distance between the photodetector 12 and an edge of the lower wafer 14 in a radial direction of the lower wafer 14 is less than 3mm. The horizontal distance between each of the photodetectors 12 and the edge of the lower wafer 14 is not limited to the above range, and may be defined according to the specification of the offset distance of the upper wafer 13 with respect to the lower wafer 14.

The photodetector 12 is configured to emit an outgoing light, and when the outgoing light is reflected by a structure above the photodetector 12, the photodetector 12 can receive a reflected light, so as to determine whether a slip occurs in the bonded upper wafer 13 relative to the lower wafer 14 according to the outgoing light and the reflected light.

In this embodiment, the occurrence of slipping of the upper wafer 13 relative to the lower wafer 14 means that the deviation of the upper wafer 13 relative to the lower wafer 14 exceeds a predetermined specification, and the absence of slipping of the upper wafer 13 relative to the lower wafer 14 means that the deviation of the upper wafer 13 relative to the lower wafer 14 does not exceed the predetermined specification. Wherein the set specification is related to performance of the devices bonded together.

Preferably, the outgoing light from the photodetector 12 is laser light.

The light detector 12 comprises a range finder or a light intensity sensor.

The reasons for the slipping of the upper wafer 13 relative to the lower wafer 14 may include: 1) The downward movement of the thimble is not smooth enough, and the downward pressure applied within a specified time is not applied to the surface of the upper wafer 13 or the applied force is insufficient, so that the upper wafer 13 is not yet contacted with the lower wafer 14 or bonded together, that is, the vacuum adsorption of the upper chuck on the upper wafer 13 is released, and the upper wafer 13 falls or deviates; 2) In the process that the thimble is pushed downwards, the thimble moves eccentrically, so that the force acting on the surface of the upper layer wafer 13 is uneven; 3) When the upper wafer 13 is moved downward to approach the lower wafer 14, bonding is started when the vertical distance between the upper wafer 13 and the lower wafer 14 has not reached a set distance, so that the upper wafer 13 cannot contact the lower wafer 14, and at this time, the vacuum adsorption of the upper chuck on the upper wafer 13 is released, so that the upper wafer 13 falls. The reason for the slip sheet is not limited to the above.

If the upper wafer 13 slips relative to the lower wafer 14, the upper wafer 13 may scratch mechanical components (e.g., guide rails, etc.) in the wafer bonding machine or the upper wafer 13 may be damaged by collision during the process of moving the lower stage from the set position back to the initial position. Accordingly, the photo detector 12 is used to detect and confirm whether the upper wafer 13 slips relative to the lower wafer 14 after the upper wafer 13 is bonded to the lower wafer 14 and before the lower stage is moved from the set position back to the initial position.

Moreover, since insufficient bonding force between the upper wafer 13 and the lower wafer 14 may occur when the upper wafer 13 is bonded to the lower wafer 14, and thus the upper wafer 13 may be separated from the lower wafer 14 by inertia of movement during the process of moving the lower stage from the set position back to the initial position, thereby generating a slip sheet, it is preferable that the photodetector 12 is further configured to detect whether or not the upper wafer 13 slips relative to the lower wafer 14 in real time during the process of moving the lower stage from the set position back to the initial position.

When the upper wafer 13 does not slip relative to the lower wafer 14, all the photodetectors 12 are not shielded by the upper wafer 13, and the emergent light emitted by all the photodetectors 12 is reflected by a mechanical component in the wafer bonding machine; when the upper wafer 13 slips relative to the lower wafer 14, at least one of the photodetectors 12 is blocked by the upper wafer 13 that is shifted, the emergent light emitted by the photodetector 12 blocked by the upper wafer 13 is reflected by the upper wafer 13, and the emergent light emitted by the photodetector 12 not blocked by the upper wafer 13 is reflected by a mechanical component in the wafer bonding machine. After bonding, when the upper chuck or the upper carrying table and the lower chuck 11 are still overlapped in the vertical direction, the mechanical component in the wafer bonding machine can be the upper chuck or the upper carrying table, and the emergent light emitted by the light detector 12 which is not shielded by the upper layer wafer 13 is reflected by the upper chuck or the upper carrying table.

Taking the example that four photodetectors 12 are disposed in the lower chuck 11 at the periphery of the lower wafer 14, when no slip occurs in the upper wafer 13 relative to the lower wafer 14, as shown in fig. 1 and 3, the upper wafer 13 covers the lower wafer 14, none of the photodetectors 12 is shielded by the upper wafer 13, and all of the emitted light (i.e., arrows) emitted by the photodetectors 12 are reflected by mechanical components in the wafer bonding machine; when the upper wafer 13 slips relative to the lower wafer 14, as shown in fig. 4, one of the photodetectors 12 is blocked by the upper wafer 13 that is shifted, the emitted light from this photodetector 12 is reflected by the upper wafer 13, three photodetectors 12 are not blocked by the upper wafer 13, and the emitted light (i.e., arrows) from three photodetectors 12 is reflected by mechanical components in the wafer bonding machine.

A reference value is stored in the photodetector 12; when the light detector 12 is a distance meter, the distance meter is used for emitting emergent light and receiving reflected light reflected by the emergent light so as to measure the vertical distance between the distance meter and the reflected position of the emergent light; the reference value is a vertical distance between the distance meter and the upper layer wafer 13 when no slip sheet occurs after bonding, and if the vertical distance measured by at least one distance meter is smaller than or equal to the reference value, it indicates that the emergent light emitted by at least one distance meter is reflected by the upper layer wafer 13, namely at least one distance meter is shielded by the upper layer wafer 13, and the upper layer wafer 13 generates a slip sheet relative to the lower layer wafer 14.

Or, when the light detector 12 is a light intensity sensor, the light intensity sensor is configured to emit outgoing light and receive reflected light reflected by the outgoing light, so as to measure a light intensity difference between the outgoing light and the reflected light; the reference value is a light intensity difference between the emergent light and the reflected light obtained by reflecting the emergent light by the upper wafer 13 when no slip occurs after bonding, if the light intensity difference measured by at least one light intensity sensor is smaller than or equal to the reference value, it is indicated that the emergent light emitted by at least one light intensity sensor is reflected by the upper wafer 13, namely at least one distance meter is shielded by the upper wafer 13, and the upper wafer 13 generates a slip relative to the lower wafer 14.

The photodetector 12 may transmit the reference value, the measured vertical distance, and the measured light intensity difference to a control module in the wafer bonding machine, and the control module compares the reference value, the measured vertical distance, and the measured light intensity difference to determine whether the upper wafer 13 slides relative to the lower wafer 14.

And when the upper wafer 13 is judged to slide relative to the lower wafer 14, the control module can control to stop moving the lower bearing table and/or control to send out a warning signal to prompt a manufacturer to process.

As can be seen from the above, the wafer bonding machine of the present invention includes at least three photodetectors disposed at intervals in the edge region of the lower chuck, and the photodetectors are configured to emit an emitting light and receive a reflected light reflected by the emitting light, so as to determine whether a slip occurs in the bonded upper wafer relative to the lower wafer according to the emitting light and the reflected light, so that it is possible to detect whether a slip occurs in the bonded upper wafer relative to the lower wafer immediately after the upper wafer is bonded to the lower wafer, and thus it is possible to prevent the shifted upper wafer from scratching mechanical components in the wafer bonding machine and prevent the upper wafer from being damaged in the subsequent process of moving the lower carrier table from a set position where bonding is performed back to the initial position.

And the photodetector can also be used for detecting whether the upper wafer slides relative to the lower wafer in real time in the process of moving the lower bearing table from the set position back to the initial position, so that whether sufficient bonding force exists between the upper wafer and the lower wafer can be judged, and meanwhile, the mechanical part in the wafer bonding machine table can be prevented from being scratched by the deflected upper wafer and the damage of the upper wafer can be avoided.

In summary, the present invention provides a wafer bonding machine, including: the upper chuck is used for adsorbing the upper wafer; the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area; at least three light detectors arranged at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and whether the upper layer wafer generates slip relative to the lower layer wafer after bonding is judged according to the emergent light and the reflected light. The wafer bonding machine table provided by the invention can avoid damaging mechanical parts in the wafer bonding machine table and avoid damaging an upper wafer.

Based on the same inventive concept, an embodiment of the present invention provides a wafer bonding method, referring to fig. 5, as can be seen from fig. 5, the wafer bonding method includes:

the method comprises the following steps that S1, an upper chuck and a lower chuck are provided, the lower chuck is provided with an adsorption area and an edge area located on the periphery of the adsorption area, an upper wafer is adsorbed on the upper chuck, a lower wafer is adsorbed on the adsorption area of the lower chuck, and at least three photodetectors are arranged in the edge area of the lower chuck;

s2, bonding the upper wafer to the lower wafer;

and S3, adopting the light detector to emit and receive reflected light reflected by the emitted light so as to detect whether the upper layer wafer generates slip relative to the lower layer wafer.

The wafer bonding method provided in this embodiment is described in detail with reference to fig. 1 to 4.

According to the step S1, an upper chuck (not shown) and a lower chuck 11 are provided, the upper chuck having an upper wafer 13 adsorbed thereon, the lower chuck 11 having a lower wafer 14 adsorbed thereon, the upper wafer 13 having a surface to be bonded facing downward, and the lower wafer 14 having a surface to be bonded facing upward.

The upper chuck is fixed on an upper bearing table (not shown), and the upper bearing table can drive the upper chuck to move; the lower chuck 11 is fixed on a lower bearing table (not shown), and the lower bearing table can drive the lower chuck 11 to move.

The lower chuck 11 and the upper chuck both comprise an adsorption area for placing a wafer and an edge area located at the periphery of the adsorption area, the upper layer wafer 13 and the lower layer wafer 14 are both placed in the adsorption area, and preferably, the diameter of the adsorption area is larger than the diameters of the upper layer wafer 13 and the lower layer wafer 14. Taking the lower chuck 11 as an example, as shown in fig. 1, a reference line 111 is disposed on a top surface of the lower chuck 11, an area within the reference line 111 is an absorption area for placing the lower layer wafer 14, a diameter of the absorption area is slightly larger than a diameter of the lower layer wafer 14, and an area outside the reference line 111 is an edge area.

Preferably, the suction region is recessed inward relative to the edge region, so that a groove is formed on each of the upper chuck and the lower chuck 11, and the upper wafer 13 and the lower wafer 14 are respectively placed in the groove of the upper chuck and the groove of the lower chuck 11, so as to prevent the placement positions of the upper wafer 13 and the lower wafer 14 from shifting.

The center of the upper chuck is further provided with a thimble (not shown) capable of applying downward pressure to the upper wafer 13 through the upper chuck, so that the upper wafer 13 is bonded with the lower wafer 14.

At least three photodetectors 12 are arranged in an edge region of the lower chuck 11.

The photodetector 12 does not extend beyond the top surface of the lower chuck 11, so as to prevent the upper wafer 13 from being damaged by the portion of the photodetector 12 extending beyond the top surface of the lower chuck 11 when the upper wafer 13 slips relative to the lower wafer 14.

Preferably, at least three photodetectors 12 are uniformly disposed in an edge region of the lower chuck 11 at intervals, so that the upper wafer 13 can be detected when slipping occurs in any direction.

In the embodiment shown in fig. 1, four photodetectors 12 are disposed in an edge region of the lower chuck 11, and the four photodetectors 12 are uniformly distributed. In the embodiment shown in fig. 2, the top surface of the photodetector 12 is flush with the top surface of the lower chuck 11; when the top surface of the photodetector 12 is lower than the top surface of the lower chuck 11, the distance between the top surface of the photodetector 12 and the top surface of the lower chuck 11 may be, for example, 1mm to 2mm.

Preferably, a horizontal distance between the photodetector 12 and an edge of the lower wafer 14 in a radial direction of the lower wafer 14 is less than 3mm. The horizontal distance between each of the photodetectors 12 and the edge of the lower wafer 14 is not limited to the above range, and may be defined according to the specification of the offset distance of the upper wafer 13 with respect to the lower wafer 14.

The light detector 12 may be a range finder or a light intensity sensor, the light detector 12 being capable of emitting outgoing light and the light detector 12 being capable of receiving reflected light when the outgoing light is reflected back by a structure above the light detector 12.

According to step S2, the upper wafer 13 is bonded to the lower wafer 14.

Before bonding the upper wafer 13 to the lower wafer 14, the wafer bonding method further includes: moving the upper and lower stages from their respective initial positions to a predetermined position for bonding, wherein the movement includes moving the upper and lower stages horizontally and vertically, so that the upper and lower chucks 11 are disposed opposite to each other, and the distance between the upper and lower chucks 11 reaches a predetermined distance required for bonding, and further, after the upper wafer 13 and the lower wafer 14 are aligned, the ejector pins apply downward pressure, so that the upper wafer 13 and the lower wafer 14 are bonded together.

The bonding process comprises the following steps: and applying pressure downwards by adopting the ejector pin to enable the central area of the upper layer wafer 13 to approach and contact the lower layer wafer 14, wherein in the deformation process of the upper layer wafer 13, the bonding wave moves from the center to the edge of the upper layer wafer 13, and then the adsorption vacuum of the upper chuck on the upper layer wafer 13 is released from the center to the edge in sequence, so that the upper layer wafer 13 and the lower layer wafer 14 are bonded under the action of the bonding wave.

After bonding the upper wafer 13 to the lower wafer 14, the wafer bonding method further includes: and respectively moving the upper bearing table and the lower bearing table from the set positions back to the initial positions, wherein the lower bearing table drives the bonded wafer to move to the initial position, and the upper bearing table only drives the upper chuck to move back to the initial position.

According to the step S3, after the upper wafer 13 is bonded to the lower wafer 14, the photodetector 12 is used to emit an emitting light and receive a reflected light reflected by the emitting light, so as to detect whether a slip occurs on the upper wafer 13 relative to the lower wafer 14.

Preferably, the outgoing light from the photodetector 12 is laser light.

In this embodiment, the occurrence of slip of the upper wafer 13 with respect to the lower wafer 14 means that the deviation of the upper wafer 13 with respect to the lower wafer 14 exceeds a predetermined specification, and the absence of slip of the upper wafer 13 with respect to the lower wafer 14 means that the deviation of the upper wafer 13 with respect to the lower wafer 14 does not exceed the predetermined specification. Wherein the set specification relates to performance of the devices bonded together.

The reasons for causing the upper wafer 13 to slip with respect to the lower wafer 14 may include: 1) The downward movement of the thimble is not smooth enough, and the downward pressure applied within a specified time is not applied to the surface of the upper layer wafer 13 or the force is insufficient, so that the upper layer wafer 13 is not yet contacted with the lower layer wafer 14 or is not bonded together, that is, the vacuum adsorption of the upper chuck on the upper layer wafer 13 is released, and the upper layer wafer 13 falls or shifts; 2) In the process that the thimble is pushed downwards, the thimble moves eccentrically, so that the force acting on the surface of the upper layer wafer 13 is uneven; 3) When the upper wafer 13 is moved downward to approach the lower wafer 14, bonding is started when the vertical distance between the upper wafer 13 and the lower wafer 14 has not reached a set distance, so that the upper wafer 13 cannot contact the lower wafer 14, and at this time, the vacuum adsorption of the upper chuck on the upper wafer 13 is released, so that the upper wafer 13 falls. The reason for the slip sheet is not limited to the above.

If the upper wafer 13 slips relative to the lower wafer 14, the upper wafer 13 may scratch mechanical components (e.g., guide rails, etc.) in the wafer bonding machine or the upper wafer 13 may be damaged by collision during the process of moving the lower stage from the set position back to the initial position. Therefore, it is necessary to check and confirm whether the upper wafer 13 slips relative to the lower wafer 14 after the upper wafer 13 is bonded to the lower wafer 14 and before the lower stage is moved from the set position back to the initial position.

Further, when the upper wafer 13 is bonded to the lower wafer 14, a bonding force between the upper wafer 13 and the lower wafer 14 may be insufficient, and thus, in the process of moving the lower stage from the set position back to the initial position, the upper wafer 13 may be separated from the lower wafer 14 by inertia of the movement, thereby generating a slip sheet, and therefore, it is preferable that the photodetector 12 is also used to detect whether or not the upper wafer 13 slips with respect to the lower wafer 14 in real time in the process of moving the lower stage from the set position back to the initial position.

When the upper wafer 13 does not slip relative to the lower wafer 14, all the photodetectors 12 are not shielded by the upper wafer 13, and the emergent light emitted by all the photodetectors 12 is reflected by a mechanical component in the wafer bonding machine; when the upper wafer 13 slips relative to the lower wafer 14, at least one of the photodetectors 12 is blocked by the upper wafer 13 that is shifted, the emergent light emitted by the photodetector 12 blocked by the upper wafer 13 is reflected by the upper wafer 13, and the emergent light emitted by the photodetector 12 not blocked by the upper wafer 13 is reflected by a mechanical component in the wafer bonding machine. After bonding, when the upper chuck or the upper carrying table and the lower chuck 11 are still overlapped in the vertical direction, the mechanical component in the wafer bonding machine can be the upper chuck or the upper carrying table, and the emergent light emitted by the light detector 12 which is not shielded by the upper layer wafer 13 is reflected by the upper chuck or the upper carrying table.

Taking the example that four photodetectors 12 are disposed in the lower chuck 11 at the periphery of the lower wafer 14, when no slip occurs in the upper wafer 13 relative to the lower wafer 14, as shown in fig. 1 and 3, the upper wafer 13 covers the lower wafer 14, none of the photodetectors 12 is shielded by the upper wafer 13, and all of the emitted light (i.e., arrows) emitted by the photodetectors 12 are reflected by mechanical components in the wafer bonding machine; when the upper wafer 13 slips relative to the lower wafer 14, as shown in fig. 4, one of the photodetectors 12 is shielded by the upper wafer 13 that is shifted, the emitted light from this photodetector 12 is reflected by the upper wafer 13, three photodetectors 12 are not shielded by the upper wafer 13, and the emitted light (i.e., arrows) from the three photodetectors 12 is reflected by mechanical components in the wafer bonding machine.

A reference value is stored in the photodetector 12; when the light detector 12 is a range finder, the step of detecting whether the upper wafer 13 slips relative to the lower wafer 14 includes: the distance meter emits emergent light and receives reflected light reflected by the emergent light so as to measure the vertical distance between the distance meter and the reflected position of the emergent light; the reference value is a vertical distance between the distance meter and the upper layer wafer 13 when no slip sheet occurs after bonding, and if the vertical distance measured by at least one distance meter is smaller than or equal to the reference value, it indicates that the emergent light emitted by at least one distance meter is reflected by the upper layer wafer 13, namely at least one distance meter is shielded by the upper layer wafer 13, and the upper layer wafer 13 generates a slip sheet relative to the lower layer wafer 14.

Or, when the light detector 12 is a light intensity sensor, the step of detecting whether the upper wafer 13 slips relative to the lower wafer 14 includes: the light intensity sensor emits emitting light and receives reflected light reflected by the emitting light so as to measure the light intensity difference between the emitting light and the reflected light; the reference value is a light intensity difference between the emergent light and the reflected light obtained by reflecting the emergent light by the upper wafer 13 when no slip occurs after bonding, if the light intensity difference measured by at least one light intensity sensor is smaller than or equal to the reference value, it is indicated that the emergent light emitted by at least one light intensity sensor is reflected by the upper wafer 13, namely at least one distance meter is shielded by the upper wafer 13, and the upper wafer 13 generates a slip relative to the lower wafer 14.

The photodetector 12 may transmit the reference value and the measured vertical distance or the light intensity difference to a control module in the wafer bonding machine, and the control module compares the reference value and the measured vertical distance or the light intensity difference to determine whether the upper wafer 13 slips relative to the lower wafer 14.

And when the upper wafer 13 is judged to slide relative to the lower wafer 14, the control module can control to stop moving the lower bearing table and/or control to send out a warning signal to prompt a manufacturer to process.

In addition, if it is determined that the upper wafer 13 does not slip relative to the lower wafer 14, after the lower susceptor is moved from the set position back to the initial position, the wafers bonded together are taken away by a robot arm, so as to perform a subsequent process.

As can be seen from the above, in the wafer bonding method of the present invention, the photodetector is adopted to emit the emergent light and receive the reflected light reflected by the emergent light immediately after the upper wafer is bonded to the lower wafer, so as to detect whether the upper wafer slips relative to the lower wafer, so that whether the upper wafer slips relative to the lower wafer can be detected at the first time, and thus, it is possible to prevent the upper wafer from scratching the mechanical components in the wafer bonding machine and prevent the upper wafer from being damaged in the subsequent process of moving the lower susceptor from the set position where bonding is performed to the initial position.

And in the process of moving the lower bearing table from the set position back to the initial position, the photodetector is also adopted to detect whether the upper wafer slides relative to the lower wafer in real time, so that whether sufficient bonding force exists between the upper wafer and the lower wafer can be judged, and meanwhile, the deflected upper wafer can be prevented from scratching mechanical parts in a wafer bonding machine table and being damaged.

In summary, the present invention provides a wafer bonding method, including: providing an upper chuck and a lower chuck, wherein the lower chuck is provided with an adsorption area and an edge area positioned at the periphery of the adsorption area, an upper wafer is adsorbed on the upper chuck, a lower wafer is adsorbed on the adsorption area of the lower chuck, and at least three photodetectors are arranged in the edge area of the lower chuck; bonding the upper wafer to the lower wafer; and adopting the light detector to emit light and receive reflected light reflected by the emitted light so as to detect whether the upper layer wafer generates slip sheets relative to the lower layer wafer. The wafer bonding method provided by the invention can avoid damaging mechanical parts in the wafer bonding machine and damage of an upper wafer.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.

Claims (11)

1. A wafer bonding machine for bonding an upper wafer to a lower wafer, the wafer bonding machine comprising:

the upper chuck is used for adsorbing the upper wafer;

the lower chuck is arranged below the upper chuck and is provided with a suction area for sucking the lower layer wafer and an edge area positioned at the periphery of the suction area;

at least three light detectors arranged at intervals in an edge region of the lower chuck; the optical detector is used for emitting emergent light and receiving reflected light reflected by the emergent light, and whether the upper layer wafer generates slip relative to the lower layer wafer after bonding is judged according to the emergent light and the reflected light.

2. The wafer bonding machine of claim 1, wherein at least three photodetectors are uniformly disposed in an edge region of the lower chuck.

3. The wafer bonding machine of claim 1, wherein the light detector comprises a range finder or an intensity sensor.

4. The wafer bonding machine of claim 1, wherein a horizontal distance between the photodetector and an edge of the underlying wafer is less than 3mm.

5. The wafer bonding machine of claim 1, wherein the wafer bonding machine further comprises:

the upper bearing table is used for bearing the upper chuck;

and the lower bearing table is used for bearing the lower chuck.

6. The wafer bonding machine of claim 1, wherein the wafer bonding machine further comprises:

and the ejector pin is used for applying pressure to the upper-layer wafer after penetrating through the upper chuck so as to bond the upper-layer wafer to the lower-layer wafer.

7. A wafer bonding method, comprising:

providing an upper chuck and a lower chuck, wherein the lower chuck is provided with an adsorption area and an edge area positioned at the periphery of the adsorption area, an upper wafer is adsorbed on the upper chuck, a lower wafer is adsorbed on the adsorption area of the lower chuck, and at least three photodetectors are arranged in the edge area of the lower chuck;

bonding the upper wafer to the lower wafer;

and adopting the light detector to emit and receive reflected light reflected by the emitted light so as to detect whether the upper layer wafer generates slip relative to the lower layer wafer.

8. The wafer bonding method according to claim 7, wherein the upper chuck is fixed on an upper susceptor, and the lower chuck is fixed on a lower susceptor; before bonding the upper wafer to the lower wafer, the wafer bonding method further includes:

and moving the upper bearing table and the lower bearing table from respective initial positions to a set position for bonding so that the upper chuck and the lower chuck are oppositely arranged.

9. The wafer bonding method of claim 8, wherein after bonding the upper wafer to the lower wafer, the wafer bonding method further comprises:

and respectively moving the upper bearing table and the lower bearing table from the set positions to the respective initial positions, and detecting whether the upper layer wafer slides relative to the lower layer wafer by using the light detector in the moving process.

10. The wafer bonding method according to claim 7, wherein the photodetector has a reference value stored therein; the photodetector is a distance meter, and the step of detecting whether the upper layer wafer slides relative to the lower layer wafer comprises the following steps:

the distance meter emits emergent light and receives reflected light reflected by the emergent light so as to measure the vertical distance between the distance meter and the reflected position of the emergent light; the reference value is a vertical distance between the distance measuring instrument and the upper wafer when no slip occurs after bonding, and if the vertical distance measured by at least one distance measuring instrument is smaller than or equal to the reference value, the slip occurs on the upper wafer relative to the lower wafer;

or, the light detector is a light intensity sensor, and the step of detecting whether the upper wafer slides relative to the lower wafer comprises:

the light intensity sensor emits outgoing light and receives reflected light reflected by the outgoing light so as to measure the light intensity difference between the outgoing light and the reflected light; and if the light intensity difference measured by at least one light intensity sensor is less than or equal to the reference value, the upper layer wafer generates slip relative to the lower layer wafer.

11. The wafer bonding method of claim 7, wherein the step of bonding the upper wafer to the lower wafer comprises:

and penetrating the upper chuck by using a thimble, and applying downward pressure to the upper layer wafer so as to bond the upper layer wafer on the lower layer wafer.

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