Method for improving bonding surface coincidence residual value

Abstract

The application provides a method for improving bonding surface coincidence residual value. The method comprises the following steps: providing a first wafer and a second wafer; performing first photoetching on the first wafer and the second wafer, so that the first wafer and the second wafer are both formed with standard alignment marks; performing second photoetching on the second wafer, and compensating the standard alignment mark of the second wafer according to a pre-acquired alignment mark compensation value, so that the second wafer is formed with a compensated alignment mark; and bonding the first wafer and the second wafer by taking the standard alignment mark of the first wafer and the compensated alignment mark of the second wafer as references, so as to form a wafer bonding structure. The above technical scheme generates the same standard alignment mark on the two wafers through the first photoetching, reduces the difference between the alignment marks of the two wafers, and introduces the second photoetching to compensate the mark on the second wafer, so as to compensate the coincidence residual value caused by the upper chuck and the lower chuck during the bonding.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor, in particular to a method for improving residual value of bonding surface overlay. BACKGROUND

[0002] In semiconductor process, it is more and more common to bond two wafers of different functions together by three-dimensional stacking process of generating covalent chemical bond. In the three-dimensional stacking process, the overlay (OVL) of the bonding surface of the two wafers is an important index. The absolute bonding deviation-free OVL value is 0, and the greater the value is, the greater the deviation is. The OVL residual value refers to the OVL value that cannot be compensated by the bonding machine. With the reduction of device size, the tolerance limit of OVL is also smaller and smaller. However, due to the difference between the two wafers caused by the front-end process and the deformation caused by the bonding process of the bonding machine, there is always a certain OVL residual value.

[0003] The current process control method is to strictly control the OVL of each of the two wafers relative to the front layer during the lithography process of the bonding surface. From the results, if the difference between the two wafers in the front layer is large, such practice will increase the OVL residual value during bonding. Secondly, such practice cannot solve the OVL difference caused by the deformation in the process of the bonding machine.

[0004] Therefore, how to improve the difference between the two wafers caused by the front-end process and the deformation caused by the bonding process of the bonding machine, and then reduce the OVL residual value, is a problem to be solved at present. SUMMARY

[0005] The technical problem to be solved by the present application is to improve the difference between the two wafers caused by the front-end process and the deformation caused by the bonding process of the bonding machine, and then reduce the OVL residual value, and to provide a method for improving the residual value of the bonding surface overlay.

[0006] In order to solve the above problems, the present application provides a method for improving the residual value of the bonding surface overlay, comprising the following steps: providing a first wafer and a second wafer; performing first lithography on the first wafer and the second wafer to form standard alignment marks on the first wafer and the second wafer; performing second lithography on the second wafer, and compensating the standard alignment mark of the second wafer according to the pre-obtained alignment mark compensation value to form a compensated alignment mark on the second wafer; and bonding the first wafer and the second wafer with the standard alignment mark of the first wafer and the compensated alignment mark of the second wafer as references to form a wafer bonding structure.

[0007] The above technical solution reduces the difference in alignment marks caused by the front-end processes of the two wafers by generating the same standard alignment marks on the two wafers in the first photolithography; the second photolithography is introduced to compensate for the standard alignment marks of the second wafer, so as to compensate for the overlap residual value caused by the bonding machine, thereby reducing the overlap residual value of the bonding surface of the two wafers. Attached Figure Description

[0008] Figure 1 The diagram shown is a schematic representation of an embodiment of the wafer bonding process.

[0009] Figure 2 The diagram shown is a flowchart of one embodiment of the method for improving the residual value of bonding surface overlap according to the present invention.

[0010] Figures 3A-3D The diagram shown is a process flow diagram of an embodiment of the method for improving the residual value of bonding surface overlap according to the present invention.

[0011] Figure 4 The diagram shows the steps of the method for detecting the overlap residual value of the bonding machine and lithography machine described in this invention. Detailed Implementation

[0012] The following detailed description, in conjunction with the accompanying drawings, illustrates the specific implementation of the method for improving the residual value of bonding surface overlap provided by the present invention.

[0013] Figure 1 The diagram shown is a schematic representation of one embodiment of the wafer bonding process. Figure 1 As shown, a first alignment mark 13 is formed on a logic wafer 11, and a second alignment mark 14 is formed on a storage wafer 12. Using the first alignment mark 13 of the logic wafer 11 and the second alignment mark 14 of the storage wafer 12 as references, the two wafers are bonded to form a wafer bonding structure 15. However, since the first alignment mark 13 and the second alignment mark 14 are not identical, there is a certain offset between the first alignment mark 13 and the second alignment mark 14 on the bonded wafer bonding structure 15, resulting in a bonding surface overlap residual. Therefore, this invention provides a method to improve the bonding surface overlap residual, reduce the OVL residual, and obtain a better wafer bonding structure.

[0014] Figure 2The step flow chart of one embodiment of the method for improving the bonding surface coincidence residual value is shown, including the following steps: step S21, providing a first wafer and a second wafer; step S22, performing first photoetching on the first wafer and the second wafer to form standard alignment marks on the first wafer and the second wafer; step S23, performing second photoetching on the second wafer to form compensation alignment marks on the second wafer based on the pre-acquired alignment mark compensation value; and step S24, bonding the first wafer and the second wafer based on the standard alignment marks of the first wafer and the compensation alignment marks of the second wafer to form a wafer bonding structure.

[0015] Figures 3A-3D The process flow chart of one embodiment of the method for improving the bonding surface coincidence residual value is shown.

[0016] Reference Figure 3A In some embodiments, the first wafer 31 is formed with a first original alignment mark 33, and the second wafer 32 is formed with a second original alignment mark 34.

[0017] Continuing to refer to Figure 3B In some embodiments, the first wafer 31 and the second wafer 32 are subjected to first photoetching to form standard alignment marks 35. In some embodiments, a one-time photoetching machine is used to perform the first photoetching on the first wafer 31 and the second wafer 32 to form the standard alignment marks 35. The bonding coincidence residual value from the previous layer is removed in the bonding surface photoetching process when the standard alignment marks 35 are formed by the one-time photoetching machine. After the standard alignment marks 35 are formed, the first original alignment mark 33 and the second original alignment mark 34 are covered. Since the first original alignment mark 33 (shown in Figure 3A ) and the second original alignment mark 34 (shown in Figure 3A ) are different, a coincidence residual value will be generated after wafer bonding. By performing the first photoetching on the first wafer 31 and the second wafer 32 to form the same standard alignment marks 35, the difference between the alignment marks of the first wafer 31 and the second wafer 32 is reduced, thereby reducing the coincidence residual value after the first wafer 31 and the second wafer 32 are bonded.

[0018] Continuing to refer to Figure 3Cand step S23, performing second lithography on the second wafer 32, and compensating the standard alignment mark 33 of the second wafer 32 according to the pre-obtained alignment mark compensation value, so as to form a compensated alignment mark 36 on the second wafer 32. In some embodiments, the compensated alignment mark 36 can be formed by performing displacement compensation on the standard alignment mark 35 according to the pre-obtained alignment mark compensation value. In other embodiments, the compensated alignment mark 36 can be formed by adding a rotation angle to the standard alignment mark 35 according to the pre-obtained alignment mark compensation value. In some embodiments, the compensated alignment mark 36 is formed by performing second lithography on the second wafer 32 by using a compensation lithography machine. The pre-obtained alignment mark compensation value further comprises the following steps: providing two test wafers; performing lithography on the two test wafers so as to form standard alignment marks 35 on the two test wafers; placing the two test wafers in an upper chuck and a lower chuck of a bonding machine, respectively; bonding the two test wafers to form a first test wafer bonding structure; and measuring a coincidence residual value of the standard alignment marks of the two test wafers in the first test wafer bonding structure, wherein the coincidence residual value is used as the alignment mark compensation value. In a three-dimensional stacking process, the coincidence of the bonding surfaces of two wafers is an important index. The absolute coincidence value without deviation is 0, and the greater the value is, the greater the deviation is. The coincidence residual value refers to the coincidence value that cannot be compensated by the bonding machine.

[0019] With reference to the foregoing Figure 3D and step S24, bonding the first wafer 31 and the second wafer 32 by using the standard alignment mark 35 of the first wafer 31 and the compensated alignment mark 36 of the second wafer 32 as references, so as to form a wafer bonding structure 37. In some embodiments, the bonding of the first wafer 31 and the second wafer 32 further comprises the following steps: placing the first wafer 31 in an upper chuck and the second wafer 32 in a lower chuck of a bonding machine; and bonding the first wafer 31 and the second wafer 32 to form a wafer bonding structure 37. Due to inherent reasons such as process and equipment, the wafers placed in the upper chuck and the lower chuck will produce a certain deviation during bonding, and a large coincidence residual value will be generated. During the bonding process, the second wafer 32 placed in the lower chuck is not flipped, and there is no axial symmetry difference during lithography. Therefore, placing the second wafer 32 with the compensated alignment mark 36 in the lower chuck can reduce the deviation value. The technical solution described above compensates the standard alignment mark of the second wafer 32 by using the alignment mark compensation value to form the compensated alignment mark 36, and pre-compensates the deviation value generated due to inherent reasons such as process and equipment during the bonding process. Therefore, after bonding, the alignment marks of the two wafers can be aligned, that is, the coincidence residual value is reduced.

[0020] In some embodiments, after the first wafer 31 and the second wafer 32 are bonded, a step of thinning the first wafer 31 from the surface of the second wafer 32 is further included. In wafer processing, a wafer usually needs to be thinned before subsequent etching, chemical deposition, electroplating and other processing procedures. In some embodiments, the method of thinning the wafer includes but is not limited to mechanical grinding, chemical etching and chemical mechanical planarization.

[0021] The above technical solution reduces the difference between the alignment marks of the first wafer 31 and the second wafer 32 by generating the same standard alignment marks 35 on the first wafer 31 and the second wafer 32 through the first photolithography, thereby reducing the residual value of the coincidence degree after the first wafer 31 and the second wafer 32 are bonded.

[0022] In addition, the present application also provides a method for detecting the residual value of the coincidence degree of a bonder and a photolithography machine.

[0023] Figure 4 The figure shows a step flow chart of the method for detecting the residual value of the coincidence degree of the bonder and the photolithography machine, which includes the following steps: step S41, photolithography of at least one wafer to form a standard alignment mark, and the wafer after photolithography as a standard wafer; and step S42, using the standard wafer to detect the coincidence degree of the upper chuck and the lower chuck of the bonder and the photolithography machine.

[0024] Referring to step S41, at least one wafer is photolithographed to form a standard alignment mark, and the wafer after photolithography as a standard wafer. In some embodiments, a one-time photolithography machine is used to photolithograph at least one wafer to form the standard alignment mark. In this embodiment, 100 wafers are photolithographed by a one-time photolithography machine as standard wafers for detecting the bonder and the photolithography machine.

[0025] Step S42, using the standard wafer to detect the coincidence degree of the upper chuck and the lower chuck of the bonder and the photolithography machine. In some embodiments, the coincidence degree detection of the upper chuck of the bonder further includes the following steps: placing the standard wafer on the upper chuck and placing a test wafer on the lower chuck, the test wafer being formed with an initial alignment mark; using the standard alignment mark of the standard wafer and the initial alignment mark of the test wafer as a reference, bonding the standard wafer and the test wafer to form a second test wafer bonding structure; thinning the bonded standard wafer; photolithographing the surface of the test wafer away from the standard wafer to form the standard alignment mark; and measuring the coincidence degree of the test wafer and the standard alignment mark of the standard wafer in the second test wafer bonding structure. The second test wafer bonding structure is used for detecting the upper chuck of the bonder to confirm whether the residual value of the coincidence degree when the upper chuck is bonded has a deviation, thereby ensuring that the residual value of the coincidence degree of wafer bonding in the production process is small.

[0026] In some embodiments, the alignment detection of the bonder lower chuck further comprises the following steps: placing a test wafer on the upper chuck and a standard wafer on the lower chuck, the test wafer being formed with initial alignment marks; bonding the standard wafer and the test wafer with the standard alignment marks of the standard wafer and the initial alignment marks of the test wafer as references to form a third test wafer bonding structure; thinning the bonded test wafer; performing photolithography on the surface of the test wafer away from the standard wafer to form the standard alignment marks; and measuring the alignment of the test wafer and the standard alignment marks of the standard wafer in the third test wafer bonding structure. The third test wafer bonding structure is used for the detection of the bonder lower chuck to confirm whether the alignment residual of the lower chuck bonding has a deviation, thereby ensuring that the alignment residual of wafer bonding in the production process is small.

[0027] In some embodiments, the photolithography machine comprises a one-time photolithography machine, and the alignment detection of the photolithography machine further comprises the following steps: performing photolithography on a test wafer with the one-time photolithography machine to form the standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks of the standard wafer and the standard alignment marks of the test wafer as references to form a fourth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fourth test wafer bonding structure. The fourth test wafer bonding structure is used for the detection of the one-time photolithography machine to confirm whether the standard photolithography marks on the wafer surface photolithographed by the one-time photolithography machine have a deviation, thereby ensuring that the alignment residual of wafer bonding in the production process is small.

[0028] In some embodiments, the photolithography machine comprises a compensation photolithography machine, and the alignment detection of the photolithography machine further comprises the following steps: performing photolithography on a test wafer with the compensation photolithography machine to form the standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks of the standard wafer and the standard alignment marks of the test wafer as references to form a fifth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fifth test wafer bonding structure. The fifth test wafer bonding structure is used for the detection of the compensation photolithography machine to confirm whether the compensation photolithography marks on the wafer surface photolithographed by the compensation photolithography machine without setting the alignment mark compensation value have a deviation.

[0029] In some embodiments, the photolithography machine comprises a compensation photolithography machine, and the step of performing overlay detection on the photolithography machine further comprises the following steps: performing photolithography on the test wafer by using the compensation photolithography machine to form the compensation alignment mark; bonding the test wafer and the standard wafer by using the standard alignment mark of the standard wafer and the compensation alignment mark of the test wafer as a reference to form a sixth test wafer bonding structure; and detecting the overlay of the alignment marks of the test wafer and the standard wafer in the sixth test wafer bonding structure. The sixth test wafer bonding structure is used for detection of the compensation photolithography machine to confirm whether there is a shift in the compensation photolithography mark on the surface of the photolithography wafer when the compensation photolithography machine sets the compensation value of the alignment mark, thereby ensuring that the residual value of the overlay of the wafer bonding in the production process is small.

[0030] The above technical solution ensures the accuracy of the operation of the machine by detecting the upper chuck and the lower chuck of the bonder and the photolithography machine, and updates the compensation value data in real time to ensure the overlay of the wafer bonding in the production process and reduce the residual value of the overlay of the wafer bonding.

[0031] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method of improving the bonding face coincidence residual value, characterized by, The method comprises the following steps: providing a first wafer and a second wafer; performing first photoetching on the first wafer and the second wafer to form standard alignment marks on the first wafer and the second wafer; performing second photoetching on the second wafer, compensating the standard alignment mark of the second wafer according to a pre-obtained alignment mark compensation value, and forming a compensated alignment mark on the second wafer; and bonding the first wafer and the second wafer according to the standard alignment mark of the first wafer and the compensated alignment mark of the second wafer to form a wafer bonding structure. Photoetching at least one wafer to form a standard alignment mark, and the wafer after photoetching is used as a standard wafer. The standard wafer is used to detect the coincidence degree of an upper chuck and a lower chuck of a bonding machine and a photoetching machine. The step of detecting the coincidence degree of the upper chuck of the bonding machine by using the standard wafer further comprises the following steps: placing the standard wafer on the upper chuck and placing a test wafer on the lower chuck, the test wafer is formed with an initial alignment mark; bonding the standard wafer and the test wafer according to the standard alignment mark on the standard wafer and the initial alignment mark of the test wafer to form a second test wafer bonding structure; thinning the bonded standard wafer; photoetching the surface of the test wafer away from the standard wafer to form a standard alignment mark; and measuring the coincidence degree of the standard alignment mark of the test wafer and the standard wafer in the second test wafer bonding structure.

2. The method of claim 1, wherein, The first photoetching on the first wafer and the second wafer is performed by using a one-time photoetching machine.

3. The method of claim 1, wherein, The step of pre-obtaining the alignment mark compensation value further comprises the following steps: providing two test wafers; photoetching the two test wafers to form standard alignment marks on the two test wafers; placing the two test wafers on an upper chuck and a lower chuck of a bonding machine respectively; bonding the two test wafers to form a first test wafer bonding structure; measuring the coincidence degree residual value of the standard alignment marks of the two test wafers in the first test wafer bonding structure; and using the coincidence degree residual value as the alignment mark compensation value.

4. The method of claim 1, wherein, The step of bonding the first wafer and the second wafer further comprises the following steps: placing the first wafer on an upper chuck of a bonding machine and placing the second wafer on a lower chuck of the bonding machine; and bonding the first wafer and the second wafer to form a wafer bonding structure.

5. The method of claim 4, wherein, After bonding the first wafer and the second wafer, the step of thinning the first wafer from the surface of the first wafer away from the second wafer is further included.

6. The method of claim 1, wherein, In the step of photoetching at least one wafer to form a standard alignment mark, a one-time photoetching machine is used to photoetch at least one wafer to form the standard alignment mark.

7. The method of claim 1, wherein, The alignment detection method further comprises the following steps: placing a test wafer on the upper chuck and placing the standard wafer on the lower chuck, the test wafer being formed with initial alignment marks; bonding the standard wafer and the test wafer with the standard alignment marks on the standard wafer and the initial alignment marks of the test wafer as references to form a third test wafer bonding structure; and thinning the bonded test wafer. The surface of the test wafer away from the standard wafer is subjected to photolithography to form standard alignment marks; and the alignment of the test wafer and the standard alignment marks of the standard wafer in the third test wafer bonding structure is measured.

8. The method of claim 1, wherein, The photolithography machine comprises a one-time photolithography machine, and the alignment detection method further comprises the following steps: performing photolithography on a test wafer with the one-time photolithography machine to form standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks on the standard wafer and the standard alignment marks of the test wafer as references to form a fourth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fourth test wafer bonding structure.

9. The method of claim 1, wherein, The photolithography machine comprises a one-time photolithography machine, and the alignment detection method further comprises the following steps: performing photolithography on a test wafer with the one-time photolithography machine to form standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks on the standard wafer and the standard alignment marks of the test wafer as references to form a fourth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fourth test wafer bonding structure.

10. The method of claim 1, wherein, The photolithography machine comprises a one-time photolithography machine, and the alignment detection method further comprises the following steps: performing photolithography on a test wafer with the one-time photolithography machine to form standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks on the standard wafer and the standard alignment marks of the test wafer as references to form a fourth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fourth test wafer bonding structure. The photolithography machine comprises a one-time photolithography machine, and the alignment detection method further comprises the following steps: performing photolithography on a test wafer with the one-time photolithography machine to form standard alignment marks; bonding the test wafer and the standard wafer with the standard alignment marks on the standard wafer and the standard alignment marks of the test wafer as references to form a fourth test wafer bonding structure; and detecting the alignment of the test wafer and the standard alignment marks of the standard wafer in the fourth test wafer bonding structure.

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