Method for improving wafer bonding strength based on BSI process

Abstract

The invention discloses a method for improving wafer bonding strength based on a BSI process, belonging to the technical field of semiconductor manufacturing, and comprising the following steps: forming an oxide layer on a bonding surface of one of a first wafer or a second wafer and flattening the oxide layer, and then arranging a silicene layer on the flattened bonding surface; then forming an oxide layer on the bonding surface of the other wafer and flattening the oxide layer; contacting and bonding the bonding surfaces of the two wafers, and obtaining a strengthened bonding structure after annealing; on the basis of an existing oxidation activation layer, the invention provides a good silicon-oxygen bonding condition for the bonding surface by arranging a silicene layer on the bonding surface, thereby improving the wafer bonding strength.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a method for improving wafer bonding strength based on a BSI process. Background Art

[0002] CMOS Image Sensor (CIS) is a sensor that can convert the color and brightness of light captured by the lens into electronic signals and transmit them to the processor. Therefore, the image sensor plays the role of the "eyes" of mobile devices such as smartphones or tablets. In recent years, with the rise of virtual reality (VR), augmented reality (AR), and autonomous driving, CIS technology has become a key technology for industrial development. It is expected that CIS technology will not only serve as the "eyes" of the device, but will also have further development in terms of functionality.

[0003] Early CIS product pixels used a front-illuminated (FSI) structure, which placed an optical structure on a circuit based on a CMOS process. This technology is suitable for most CIS solutions with a pixel size of 1.12μm and above, and is widely used in mobile devices, CCTV, dashcams, digital SLR cameras, automotive sensors and other products. As for the FSI structure, this structure is more susceptible to diffraction due to the influence of the metal wiring layer in the lower circuit. Even if the FSI pixel size is reduced, the area covered by the metal remains unchanged. Therefore, the area through which light passes becomes smaller, and the diffraction phenomenon is enhanced, resulting in color mixing in the image. For this reason, a back-illuminated (BSI) process was proposed to eliminate metal interference by flipping the wafer to utilize its back side; as for BSI technology, all circuit parts are first made on one side of the wafer, and then the wafer is flipped upside down to create an optical structure that can collect light on the back side, which can eliminate the interference caused by the metal lines in the FSI, and the space for light to pass is larger under the condition of the same size pixel, thereby improving quantum efficiency.

[0004] The process steps of the BSI structure are relatively complicated. One of the steps is to flip the device wafer with the photodiode and combine it with another wafer carrier as a supporting structure. The bonding process uses the atomic bonding force on the surfaces of the two wafers. After treatment, the atoms on the surfaces of the two wafers react to produce covalent bonds to achieve the desired connection strength. The current bonding process is mostly direct bonding after oxidation activation, but the bonding strength of the wafer is not enough, which can easily cause the wafer to fall off. Therefore, improving the bonding strength of the wafer is a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for improving wafer bonding strength based on the BSI process.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0008] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0009] (2) forming an oxide layer on a bonding surface of one of the first wafer or the second wafer and planarizing the oxide layer, and then providing a silicene layer on the planarized bonding surface;

[0010] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing a planarization process on the oxide layer;

[0011] (4) The bonding surfaces of the first wafer and the second wafer are brought into contact and bonded, and a strengthened bonding structure is obtained after annealing.

[0012] In some preferred embodiments, in step (1), the bonding surface of the first wafer and / or the second wafer is cleaned.

[0013] In some preferred embodiments, the oxide layer in step (2) and step (3) is formed by plasma oxidation or thermal oxygen oxidation.

[0014] In some preferred embodiments, the thickness of the oxide layer in step (2) and step (3) is 10-5000 angstroms.

[0015] In some preferred embodiments, the gas medium of the plasma oxidation and the thermal oxygen oxidation includes one or both of oxygen and ozone.

[0016] In some preferred embodiments, the silicene layer in step (2) is formed by laying or deposition.

[0017] In some preferred embodiments, the laying comprises the following steps: firstly growing the silicene layer on a substrate material, then peeling off the generated silicene layer, and then laying the peeled silicene layer on the oxide layer.

[0018] In some preferred embodiments, the substrate material is gold, silver, iridium or zirconium boride.

[0019] In some preferred embodiments, the thickness of the silicene layer in step (2) is 10-5000 angstroms.

[0020] In some preferred embodiments, the bonding pressure of the contact bonding in step (4) is 1-20 N / cm 2 The annealing temperature is 200-400° C., and the annealing time is 1-4 hours.

[0021] The beneficial effects of the present invention are:

[0022] In view of the problem of low wafer bonding strength in the existing BSI process technology, the present invention provides a bonding structure and method that can improve the bonding strength. Specifically, on the basis of the existing oxidation activation layer, the present invention sets a silicene layer on the bonding surface, utilizes the electrophilicity of silicene in the p-orbital direction and the oxidizing environment of the wafer oxidation surface, provides good silicon-oxygen bonding conditions for the bonding surface under annealing conditions, and thus improves the wafer bonding strength. DETAILED DESCRIPTION

[0023] The present invention is further described in conjunction with the following examples.

[0024] Example 1

[0025] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0026] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0027] (2) forming an oxide layer on the bonding surface of one of the first wafer or the second wafer and performing a mechanical grinding and flattening treatment on the oxide layer, and then providing a silicene layer on the flattened bonding surface;

[0028] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0029] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing;

[0030] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0031] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 100 angstroms;

[0032] The silicene layer in step (2) is formed by laying;

[0033] The laying comprises the following steps: firstly epitaxially growing the silicene layer on the surface of the substrate material Ag (111), then peeling off the generated silicene layer, and then transferring and laying the peeled silicene layer on the oxide layer, wherein the thickness of the silicene layer is 100 angstroms;

[0034] The bonding pressure of the contact bonding in step (4) is 5N / cm 2 The annealing temperature is 300° C. and the annealing time is 1.5 h.

[0035] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 3.2 J / m 2 .

[0036] Example 2

[0037] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0038] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0039] (2) forming an oxide layer on the bonding surface of one of the first wafer or the second wafer and performing a mechanical grinding and flattening treatment on the oxide layer, and then providing a silicene layer on the flattened bonding surface;

[0040] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0041] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing;

[0042] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0043] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 100 angstroms;

[0044] The silicene layer in step (2) is formed by laying;

[0045] The laying comprises the following steps: firstly epitaxially growing the silicene layer on the surface of the substrate material Ag (111), then peeling off the generated silicene layer, and then transferring and laying the peeled silicene layer on the oxide layer, wherein the thickness of the silicene layer is 1000 angstroms;

[0046] The bonding pressure of the contact bonding in step (4) is 5N / cm 2The annealing temperature is 300° C. and the annealing time is 1.5 h.

[0047] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 3.1 J / m 2 .

[0048] Example 3

[0049] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0050] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0051] (2) forming an oxide layer on the bonding surface of one of the first wafer or the second wafer and performing a mechanical grinding and flattening treatment on the oxide layer, and then providing a silicene layer on the flattened bonding surface;

[0052] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0053] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing;

[0054] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0055] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 1000 angstroms;

[0056] The silicene layer in step (2) is formed by laying;

[0057] The laying comprises the following steps: firstly epitaxially growing the silicene layer on the surface of the substrate material Ag (111), then peeling off the generated silicene layer, and then transferring and laying the peeled silicene layer on the oxide layer, wherein the thickness of the silicene layer is 1000 angstroms;

[0058] The bonding pressure of the contact bonding in step (4) is 10N / cm 2 The annealing temperature is 300° C. and the annealing time is 1.5 h.

[0059] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 2.9 J / m 2 .

[0060] Example 4

[0061] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0062] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0063] (2) forming an oxide layer on the bonding surface of one of the first wafer or the second wafer and performing a mechanical grinding and flattening treatment on the oxide layer, and then providing a silicene layer on the flattened bonding surface;

[0064] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0065] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing;

[0066] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0067] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 10 angstroms;

[0068] The silicene layer in step (2) is formed by laying;

[0069] The laying comprises the following steps: firstly epitaxially growing the silicene layer on the surface of the substrate material Ag (111), then peeling off the generated silicene layer, and then transferring and laying the peeled silicene layer on the oxide layer, wherein the thickness of the silicene layer is 10 angstroms;

[0070] The bonding pressure of the contact bonding in step (4) is 2N / cm 2 The annealing temperature is 400° C. and the annealing time is 1 h.

[0071] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 2.5 J / m 2 .

[0072] Example 5

[0073] A method for improving wafer bonding strength based on a BSI process comprises the following steps:

[0074] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0075] (2) forming an oxide layer on the bonding surface of one of the first wafer or the second wafer and performing a mechanical grinding and flattening treatment on the oxide layer, and then providing a silicene layer on the flattened bonding surface;

[0076] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0077] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing;

[0078] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0079] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 5000 angstroms;

[0080] The silicene layer in step (2) is formed by laying;

[0081] The laying comprises the following steps: firstly epitaxially growing the silicene layer on the surface of the substrate material Ag (111), then peeling off the generated silicene layer, and then transferring and laying the peeled silicene layer on the oxide layer, wherein the thickness of the silicene layer is 5000 angstroms;

[0082] The bonding pressure of the contact bonding in step (4) is 20N / cm 2 The annealing temperature is 200° C. and the annealing time is 4 hours.

[0083] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 2.2 J / m 2 .

[0084] Comparative Example

[0085] A wafer bonding method based on a BSI process comprises the following steps:

[0086] (1) Providing a first wafer having a photodiode circuit structure and metal wiring formed thereon and a second wafer serving as a support structure;

[0087] (2) forming an oxide layer on a bonding surface of one of the first wafer or the second wafer and performing mechanical grinding and planarization processing on the oxide layer;

[0088] (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing mechanical grinding and planarization treatment on the oxide layer;

[0089] (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and performing annealing treatment;

[0090] Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned with deionized water;

[0091] The oxide layer in step (2) and step (3) is formed by ozone plasma oxidation, and the thickness of the oxide layer is 100 angstroms;

[0092] The bonding pressure of the contact bonding in step (4) is 5N / cm 2 The annealing temperature is 300° C. and the annealing time is 1.5 h.

[0093] In this embodiment, the bonding strength formed by bonding the first wafer and the second wafer is 1.4 J / m 2 .

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for improving wafer bonding strength based on BSI process, characterized in that: The following steps are involved: (1) providing a first wafer on which a photodiode circuit structure and metal wiring are formed and a second wafer as a support structure; (2) forming an oxide layer on a bonding surface of one of the first wafer or the second wafer and planarizing the oxide layer, and then providing a silicene layer on the planarized bonding surface; (3) forming an oxide layer on a bonding surface of another wafer different from the wafer in step (2) and performing a planarization process on the oxide layer; (4) contacting and bonding the bonding surfaces of the first wafer and the second wafer, and obtaining a strengthened bonding structure after annealing; The silicene layer in step (2) is formed by laying, and the laying comprises the following steps: firstly growing the silicene layer on a substrate material, then peeling off the generated silicene layer, and then laying the peeled silicene layer on the oxide layer.

2. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: Step (1) The bonding surface of the first wafer and / or the second wafer is cleaned.

3. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: The oxide layer in step (2) and step (3) is formed by plasma oxidation or thermal oxygen oxidation.

4. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: The thickness of the oxide layer in step (2) and step (3) is 10-5000 angstroms.

5. The method for improving wafer bonding strength based on BSI process according to claim 3, characterized in that: The gas medium of the plasma oxidation and the thermal oxygen oxidation includes one or both of oxygen and ozone.

6. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: The substrate material is gold, silver, iridium or zirconium boride.

7. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: The thickness of the silicene layer in step (2) is 10-5000 angstroms.

8. The method for improving wafer bonding strength based on BSI process according to claim 1, characterized in that: The bonding pressure of the contact bonding in step (4) is 1-20N / cm 2 The annealing temperature is 200-400° C., and the annealing time is 1-4 hours.