Method and structure for preventing corrosion of metal bonding layer in wafer bonding structure

Abstract

The invention discloses a method and a structure for preventing corrosion of a metal bonding layer in a wafer bonding structure, which are applied to the field of chip preparation, and the method comprises the following steps: providing a pretreated bonding wafer; the preprocessed bonding wafer comprises a first substrate, a first device function layer, a bonding metal layer, a second device function layer and a second substrate which are sequentially arranged along a preset direction; the first substrate is of a structure with a part of thickness of the substrate removed from the first surface; the first surface is the surface of one side, back to the bonding metal layer, of the first substrate; etching the edge region in the first surface of the pre-treated bonded wafer inwards by using a dry etching process until the second substrate is exposed, and forming a region to be deposited; the second surface is the surface of one side, back to the bonding metal layer, of the second substrate; and depositing a barrier layer in the to-be-deposited region until the barrier layer exceeds the bonding metal layer. According to the invention, the barrier layer is prepared on the side surface of the bonding metal layer, so that the phenomenon of side digging corrosion of the metal bonding layer during wet etching can be avoided.

Description

Technical Field

[0001] The present invention relates to the field of chip preparation, and particularly to a method and structure for preventing corrosion of a metal bonding layer in a wafer bonding structure. Background Art

[0002] In the chip manufacturing process, two wafers are connected by metal bonding, and then the silicon substrate of one of the wafers is removed to achieve device functionality. Currently, the silicon substrate is usually removed by a grinding device to remove most of the silicon substrate, and when there is a small amount of the silicon substrate remaining, a wet etching method is used to remove the silicon substrate. However, when using the method of first grinding to remove a large amount of the silicon substrate and then using wet etching to remove a small amount of the remaining silicon substrate, when the bonding material is metal, the bonding metal is usually corroded to a certain extent during the wet etching process, resulting in side etching corrosion of the metal bonding layer. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method and structure for preventing corrosion of a metal bonding layer in a wafer bonding structure, which solves the problem of side etching corrosion of the bonding layer in the wafer bonding structure in the prior art after wet etching.

[0004] To solve the above technical problems, the present invention provides a method for preventing corrosion of a metal bonding layer in a wafer bonding structure, including:

[0005] Providing a pre-treated bonded wafer; the pre-treated bonded wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged along a preset direction; the preset direction is the direction of wafer stacking and bonding; the first substrate is a structure in which a part of the thickness of the first surface is removed; the first surface is the surface of the first substrate facing away from the bonding metal layer;

[0006] In the edge region of the first surface of the pre-treated bonded wafer, etching the pre-treated bonded wafer along the direction pointing to the second surface by using a dry etching process, etching at least until the second substrate is exposed to form a deposition region to be formed; the second surface is the surface of the second substrate facing away from the bonding metal layer;

[0007] Depositing a barrier layer in the deposition region to be formed until the height of the deposited barrier layer exceeds the bonding metal layer.

[0008] Optionally, in the edge region of the first surface of the pre-treated bonded wafer, etching the pre-treated bonded wafer along the direction pointing to the second surface by using a dry etching process, etching at least until the second substrate is exposed to form a deposition region to be formed, including:

[0009] In the edge region of the first surface of the pre-processed bonded wafer, in the direction pointing to the second surface, the pre-processed bonded wafer is etched using a dry etching process until a part of the second substrate is removed, and the remaining second substrate corresponding to the edge region and adjacent to the surface of the first substrate is used as the region to be deposited.

[0010] Optionally, a barrier layer is deposited in the region to be deposited until the height of the deposited barrier layer exceeds the bonding metal layer, including:

[0011] The barrier layer is deposited in the region to be deposited until the deposited barrier layer is flush with the surface of the first device functional layer facing away from the bonding metal layer.

[0012] Optionally, the edge region is a region formed by the edge contour of the pre-processed bonded wafer extending at least 3 mm towards the center of the pre-processed bonded wafer in the first surface and the second surface of the pre-processed bonded wafer.

[0013] Optionally, in the edge region of the first surface of the pre-processed bonded wafer, in the direction pointing to the second surface, the pre-processed bonded wafer is etched using a dry etching process until at least the second substrate is exposed to form a region to be deposited, including:

[0014] A photoresist layer is prepared on the first surface of the pre-processed bonded wafer;

[0015] The photoresist corresponding to the edge region in the photoresist layer is removed to expose the pre-processed bonded wafer in the edge region;

[0016] The pre-processed bonded wafer in the edge region is etched using a dry etching process until at least the second substrate is exposed to form the region to be deposited.

[0017] Optionally, after etching the pre-processed bonded wafer in the edge region using a dry etching process until at least the second substrate is exposed to form the region to be deposited, it further includes:

[0018] The remaining photoresist layer on the first surface of the pre-processed bonded wafer is removed.

[0019] Optionally, removing the photoresist corresponding to the edge region in the photoresist layer to expose the pre-processed bonded wafer in the edge region includes:

[0020] Using a photoresist edge removal process or a photoresist edge exposure process to remove the photoresist corresponding to the edge region in the photoresist layer to expose the pre-processed bonded wafer in the edge region.

[0021] Optionally, providing a pre-processed bonded wafer includes:

[0022] Providing two wafers, sputtering a metal layer on the surfaces of both wafers facing away from the substrate, and planarizing the surface of the metal layer by chemical mechanical polishing;

[0023] Bonding the two wafers through the metal layer to obtain an initial bonded wafer; the bonded metal layer serves as the bonding metal layer;

[0024] Using a grinding device to remove a partial thickness of the substrate on the first surface of the initial bonded wafer to obtain the pre-processed bonded wafer; the thickness of the removed part of the substrate is greater than the thickness of the remaining part of the substrate.

[0025] The present invention also provides a structure for preventing corrosion of the metal bonding layer in a wafer bonding structure, prepared by the method for preventing corrosion of the metal bonding layer in a wafer bonding structure as described above, including:

[0026] A first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate stacked in sequence along a specified direction; the first substrate has a structure in which a partial thickness of the substrate on the side facing away from the bonding metal layer is removed;

[0027] The bonding metal layer is provided with a barrier layer corresponding to the edge regions of the first substrate and the second substrate to wrap the side surfaces of the bonding metal layer.

[0028] Optionally, the edge region is a region formed by the edge contour of the first substrate surface extending 3 mm towards the center of the first substrate surface among the first substrate surface and the second substrate surface,

[0029] or a region formed by the edge contour of the second substrate surface extending 3 mm towards the center of the second substrate surface.

[0030] It can be seen that the method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the present invention includes providing a pre-treated bonding wafer, which includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate arranged in sequence along a preset direction. The preset direction is the direction of wafer stacking and bonding. The first substrate is a structure with a part of the thickness removed from the first surface, and the first surface is the surface of the first substrate facing away from the bonding metal layer. In the edge region of the first surface of the pre-treated bonding wafer, along the direction pointing to the second surface, the pre-treated bonding wafer is etched using a dry etching process, at least until the second substrate is exposed to form a deposition area. The second surface is the surface of the second substrate facing away from the bonding metal layer. A barrier layer is deposited in the deposition area until the height of the deposited barrier layer exceeds the bonding metal layer. By preparing a barrier layer structure on the side of the bonding metal layer, when the first substrate is removed using a wet etching process, the etching solution will not corrode the bonding metal layer, avoiding the phenomenon of side etching corrosion of the bonding layer after etching and improving the yield of the device.

[0031] In addition, the present invention also provides a structure for preventing corrosion of the metal bonding layer in the wafer bonding structure, which also has the above beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0033] Figure 1 It is a flowchart of a method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiment of the present invention;

[0034] Figures 2 to 4 It is a flow example diagram of a method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiment of the present invention;

[0035] Figure 5 It is a flowchart of another method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiment of the present invention;

[0036] Figure 6 It is a schematic diagram of a structure for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiment of the present invention;

[0037] Figures 2 to 4 , and Figure 6 In, the reference numerals are explained as follows:

[0038] 10 - First substrate;

[0039] 20 - First device functional layer;

[0040] 30 - Bonding metal layer;

[0041] 40 - Second device functional layer;

[0042] 50 - Second substrate;

[0043] 60 - Barrier layer. Detailed implementation mode

[0044] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] In the chip manufacturing process, two wafers are connected by metal bonding, and then the silicon substrate of one of the wafers is removed to achieve device functionality. Currently, the silicon substrate is usually removed by a grinding device to remove most of the silicon substrate, and when there is a small amount of the silicon substrate remaining, a wet etching method is used to remove the silicon substrate. However, when using the method of first grinding to remove a large amount of the silicon substrate and then using wet etching to remove a small amount of the remaining silicon substrate, when the bonding material is metal, substances such as nitric acid, hydrofluoric acid, and oxalic acid that are likely to corrode the metal are usually used during the wet etching process. Therefore, it will cause a certain degree of corrosion to the bonded metal, resulting in the phenomenon of side etching corrosion of the metal bonding layer.

[0046] The present invention prepares a barrier layer structure on the side of the bonding metal layer. When using the wet etching process to remove the first substrate, the etching solution will not corrode the bonding metal layer, avoiding the phenomenon of side etching corrosion of the bonding layer after etching and improving the yield rate of the device.

[0047] Embodiment 1

[0048] Please refer to Figure 1 , Figure 1 , which is a flowchart of a method for preventing corrosion of the metal bonding layer in a wafer bonding structure provided by an embodiment of the present invention. The method may include:

[0049] S101: Provide a pre-processed bonded wafer; the pre-processed bonded wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged in a preset direction; the preset direction is the direction of wafer stacking and bonding; the first substrate has a structure with a part of its thickness removed from its first surface; the first surface is the surface of the first substrate facing away from the bonding metal layer;

[0050] S102: In the edge region of the first surface of the pre-processed bonded wafer, etch the pre-processed bonded wafer in the direction pointing to the second surface using a dry etching process, etching at least until the second substrate is exposed to form a deposition region; the second surface is the surface of the second substrate facing away from the bonding metal layer;

[0051] S103: Deposit a barrier layer in the deposition region until the height of the deposited barrier layer exceeds the bonding metal layer.

[0052] In this embodiment, when two wafers are bonded, the substrate of one of the wafers needs to be removed. In this embodiment, the first substrate is used as the wafer whose substrate structure needs to be removed. Before adopting the method for preventing corrosion of the metal bonding layer in the wafer bonding structure of this embodiment, a substrate with a part of its thickness removed from the outer-side facing surface of the first substrate is provided. The specific thickness to be removed can be set according to the manufacturing process and the operator. In this embodiment, in the edge region of the first surface of the pre-processed bonded wafer, the pre-processed bonded wafer is etched in the direction pointing to the second surface using a dry etching process. The objects etched by the dry etching process include the first substrate in the edge region, and can also include a part of the thickness of the second substrate on the side of the edge region close to the first substrate. If the edge region includes the first device functional layer, the bonding metal layer, and the second device functional layer, the objects that can be etched by the dry etching process also include the first device functional layer and the bonding metal layer located in this edge region, and can also include the second device functional layer. In this embodiment, the bottom surface formed after etching by the dry etching process can be used as the deposition region to deposit a barrier layer in this deposition region, ensuring that the bonding metal layer is encapsulated and protected on the side of the bonding metal layer. In order to improve the corrosion resistance of the bonding metal layer, the above deposition region can extend outward away from the pre-processed bonded wafer to increase the thickness of the barrier layer formed on the side of the bonding metal layer.

[0053] This embodiment does not limit the specific setting position of the edge region. As long as the distance between the inner and outer contours in the edge region is greater than or equal to the distance between the edge of the bonding metal layer and the edge of the pre-treated bonding wafer, that is, to ensure that the deposited barrier layer is in close contact with the side surface of the bonding metal layer. This embodiment does not limit the etching cut-off position of the dry etching process along the edge region of the first surface of the pre-treated bonding wafer in the direction pointing to the second surface. As long as the barrier layer can be deposited on the side surface of the bonding metal layer after etching. For example, the etching cut-off position of the dry etching process can be stopped just beyond the bonding metal layer, or the etching cut-off position of the dry etching process can also be stopped in the second substrate. It should be noted that since the side surfaces of the bonding metal layer, the first device functional layer, and the second device functional layer are generally flush, and the side surface profiles of the first substrate and the second substrate exceed the side surface profiles of the bonding metal layer, the first device functional layer, and the second device functional layer, setting the etching cut-off position of the dry etching process beyond the first substrate can ensure that the deposited barrier layer is in close contact with the side surface of the bonding metal layer. This embodiment does not limit the specific material of the barrier layer, as long as it can prevent the etching solution from eroding the bonding metal layer when the first substrate is wet-etched. To make the present invention easier to understand, the above method for preventing the corrosion of the metal bonding layer in the wafer bonding structure can be specifically referred to Figures 2 to 4 , Figures 2 to 4 FIG. Figures 2 to 4 is a flow example diagram of a method for preventing the corrosion of a metal bonding layer in a wafer bonding structure provided by an embodiment of the present invention.

[0054] Further, in order to ensure that the prepared barrier layer is in close contact with the bonding metal layer and ensure the adaptability of the preparation method, the above-mentioned edge region can be a region formed by extending the edge contour of the pre-treated bonding wafer at least 3 mm towards the center of the pre-treated bonding wafer on the first surface and the second surface of the pre-treated bonding wafer.

[0055] In this embodiment, the distance between the inner and outer contours in the edge contour is set to at least 3 mm, which is adapted to the distance between the outer contour of the bonding metal layer and the outer contour of the substrate in a conventional bonding wafer, and can ensure that the deposited barrier layer is in close contact with the side surface of the metal bonding layer after dry etching. It should be noted that in this embodiment, when the distance between the inner and outer contours in the edge contour is greater than 3 mm, part of the bonding metal layer, the first device functional layer, and the second device functional layer will be etched during dry etching. Therefore, the distance between the inner and outer contours in the edge contour should ensure that the dry etching process is carried out on the basis of not damaging the first device functional layer and the second device functional layer.

[0056] Further, in order to ensure that the dry etching process realizes etching the edge region to obtain a region to be deposited, the above-mentioned dry etching process for etching the pre-treated bonding wafer along the edge region on the first surface of the pre-treated bonding wafer in the direction pointing to the second surface and etching at least until the second substrate is exposed to form a region to be deposited may include the following steps:

[0057] Step S11: Prepare a photoresist layer on the first surface of the pre-treated bonded wafer;

[0058] Step S12: Remove the photoresist in the corresponding edge area of the photoresist layer to expose the pre-treated bonded wafer in the edge area;

[0059] Step S13: Etch the pre-treated bonded wafer in the edge area using a dry etching process, etching at least until the second substrate is exposed to form a deposition area to be formed.

[0060] In this embodiment, by preparing a photoresist layer on the first surface of the pre-treated bonded wafer and patterning and etching the photoresist layer to form a structure in which the pre-treated bonded wafer in the edge area is exposed, it ensures the step of etching the pre-treated bonded wafer in the edge area using a dry etching process to prepare the deposition area to be formed, improving the preparation efficiency.

[0061] Further, in order to ensure the smooth progress of the preparation process, after etching the pre-treated bonded wafer in the edge area using a dry etching process and etching at least until the second substrate is exposed to form a deposition area to be formed, the following steps may further be included:

[0062] Remove the remaining photoresist layer on the first surface of the pre-treated bonded wafer.

[0063] In this embodiment, after forming the deposition area to be formed, removing the remaining photoresist layer can ensure the subsequent smooth removal of the first substrate. Further, in this embodiment, the photoresist layer may also be removed after depositing the barrier layer, and when removing the photoresist layer, the barrier layer deposited outside the remaining photoresist layer can be removed together, further improving the preparation efficiency.

[0064] Further, in order to ensure the smooth removal of the photoresist layer in the edge area, the step of removing the photoresist in the corresponding edge area of the photoresist layer to expose the pre-treated bonded wafer in the edge area may include:

[0065] Use a photoresist edge removal process or a photoresist edge exposure process to remove the photoresist in the corresponding edge area of the photoresist layer to expose the pre-treated bonded wafer in the edge area.

[0066] In this embodiment, using a photoresist edge removal process or a photoresist edge exposure process can adapt to the step of removing the photoresist in the edge area in this solution, improving the removal efficiency of the photoresist in the edge area.

[0067] Further, in order to ensure the efficiency of wafer bonding, providing a pre-treated bonded wafer may include the following steps:

[0068] Step S21: Provide two wafers, sputter a metal layer on the surfaces of the two wafers facing away from the substrate, and planarize the surface of the metal layer by chemical mechanical polishing;

[0069] Step S22: Bond the two wafers through the metal layer to obtain an initial bonded wafer; the bonded metal layer serves as the bonding metal layer;

[0070] Step S23: Use a grinding device to remove a partial thickness of the substrate located on the first surface of the initial bonded wafer to obtain a preprocessed bonded wafer; the removed partial substrate thickness is greater than the remaining substrate thickness.

[0071] In this embodiment, after sputtering the metal layer, the surface of the metal layer is planarized to facilitate the subsequent bonding of the two metal layers. By using a grinding device to grind and remove a part of the thickness of the first substrate, it is possible to facilitate the subsequent etching to form a deposition region to be formed, and to facilitate the deposition of a barrier layer in the deposition region to be formed.

[0072] Applying the method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiments of the present invention, which includes providing a preprocessed bonding wafer. The preprocessed bonding wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged along a preset direction. The preset direction is the direction of wafer stacking and bonding. The first substrate is a structure with a part of the thickness removed from the first surface, and the first surface is the surface of the first substrate facing away from the bonding metal layer. In the edge region of the first surface of the preprocessed bonding wafer, along the direction pointing to the second surface, the preprocessed bonding wafer is etched using a dry etching process, at least etching until the second substrate is exposed to form a deposition region to be formed. The second surface is the surface of the second substrate facing away from the bonding metal layer. A barrier layer is deposited in the deposition region to be formed until the height of the deposited barrier layer exceeds the bonding metal layer. By preparing a barrier layer structure on the side surface of the bonding metal layer in the present invention, when the first substrate is removed using a wet etching process, the etching solution will not corrode the bonding metal layer, avoiding the phenomenon of side etching corrosion of the bonding layer after etching and improving the yield of the device. In addition, in the embodiments of the present invention, by setting the distance between the inner and outer contours in the edge profile to at least 3 mm, which is adapted to the distance between the outer contour of the bonding metal layer and the outer contour of the substrate in the conventional bonding wafer, it can ensure that after dry etching, the prepared barrier layer fits the side surface of the metal bonding layer; by preparing a photoresist layer on the first surface of the preprocessed bonding wafer and patterning and etching the photoresist layer to form a structure in which the edge region of the preprocessed bonding wafer is exposed, the preparation efficiency is improved; after the deposition region to be formed is formed, the remaining photoresist layer is removed, which can ensure the subsequent smooth removal of the first substrate; using a photoresist edge removal process or a photoresist edge exposure process can adapt to the step of removing the photoresist in the edge region in this solution and improve the removal efficiency of the photoresist in the edge region; by using a grinding method to remove a part of the thickness of the first substrate, the subsequent steps are ensured, and the efficiency of removing a part of the thickness of the first substrate is ensured.

[0073] Embodiment 2

[0074] Please refer to Figure 5 , Figure 5 which is a flowchart of another method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiments of the present invention. The method may include:

[0075] S201: Provide a preprocessed bonding wafer; the preprocessed bonding wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged along a preset direction; the preset direction is the direction of wafer stacking and bonding; the first substrate is a structure with a part of the thickness removed from the first surface; the first surface is the surface of the first substrate facing away from the bonding metal layer;

[0076] S202: In the edge region of the first surface of the pre-processed bonded wafer, etch the pre-processed bonded wafer in the direction pointing to the second surface using a dry etching process until a part of the second substrate is removed. The remaining edge region of the second substrate, and the surface facing the first substrate, is used as the region to be deposited; the second surface is the surface of the second substrate facing away from the bonding metal layer.

[0077] S203: Deposit a barrier layer in the region to be deposited until the height of the deposited barrier layer exceeds that of the bonding metal layer.

[0078] In this embodiment, etching a part of the second substrate and using the remaining edge region of the second substrate, and the surface facing the first substrate as the region to be deposited can ensure the flatness of the surface of the region to be deposited, facilitate the subsequent deposition of the barrier layer, and can protect the side surface of the second device functional layer to avoid contact between the etching solution and the second device functional layer. The thickness of the second substrate etched away in this embodiment is not limited as long as it can ensure that the deposited barrier layer can protect the side surface of the bonding metal layer.

[0079] Further, in order to improve the protection effect of the barrier layer on the wafer bonding structure, the above step of depositing a barrier layer in the region to be deposited until the height of the deposited barrier layer exceeds that of the bonding metal layer may include:

[0080] Deposit a barrier layer in the region to be deposited until the deposited barrier layer is flush with the surface of the first device functional layer facing away from the bonding metal layer.

[0081] In this embodiment, by setting the deposited barrier layer to have a surface flush with the surface of the first device functional layer facing away from the bonding metal layer, the formed barrier layer can protect the first device functional layer and avoid contact between the etching solution and the first device functional layer when wet etching the first substrate. It should be noted that in this embodiment, the deposited barrier layer can also be set to exceed the surface of the first device functional layer facing away from the bonding metal layer.

[0082] Applying the method for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiments of the present invention includes providing a pre-treated bonding wafer. The pre-treated bonding wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged along a preset direction. The preset direction is the direction of wafer stacking and bonding. The first substrate is a substrate structure with a part of its thickness removed from the first surface, and the first surface is the surface of the first substrate facing away from the bonding metal layer. In the edge region of the first surface of the pre-treated bonding wafer, along the direction pointing to the second surface, the pre-treated bonding wafer is etched using a dry etching process until a part of the second substrate is removed. The corresponding edge region of the remaining second substrate and the surface facing the first substrate are used as the deposition region to be deposited. The second surface is the surface of the second substrate facing away from the bonding metal layer. A barrier layer is deposited in the deposition region to be deposited until the height of the deposited barrier layer exceeds the bonding metal layer. By preparing a barrier layer structure on the side of the bonding metal layer in the present invention, when the first substrate is removed using a wet etching process, the etching solution will not corrode the bonding metal layer, avoiding the phenomenon of side etching corrosion of the bonding layer after etching, and improving the yield of the device. By using the corresponding edge region of the remaining second substrate and the surface facing the first substrate as the deposition region to be deposited, the flatness of the surface of the deposition region to be deposited can be ensured, facilitating the subsequent deposition of the barrier layer, and protecting the side surface of the second device functional layer. In addition, by setting the surface of the barrier layer prepared by deposition to be flush with the surface of the first device functional layer facing away from the bonding metal layer in the embodiments of the present invention, the formed barrier layer can protect the first device functional layer.

[0083] To make the present invention easier to understand, the above method for preventing corrosion of the metal bonding layer in the wafer bonding structure may specifically include the following steps:

[0084] Step S1: Provide two wafers, sputter a metal layer on the surfaces of the two wafers facing away from the substrates, and perform planarization treatment on the surface of the metal layer using chemical mechanical polishing;

[0085] Step S2: Bond the two wafers through the metal layer to obtain an initial bonded wafer; the bonded metal layer is used as the bonding metal layer;

[0086] Step S3: Use a grinding device to remove a part of the thickness of the first substrate on the first surface of the initial bonded wafer to obtain a pre-treated bonded wafer; the removed substrate thickness is greater than the remaining substrate thickness; the pre-treated bonded wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate sequentially arranged along a preset direction; the preset direction is the direction of wafer stacking and bonding; the first substrate is a substrate structure with a part of its thickness removed from the first surface; the first surface is the surface of the first substrate facing away from the bonding metal layer;

[0087] Step S3: Prepare a photoresist layer on the first surface of the preprocessed bonded wafer;

[0088] Step S4: Use a photoresist edge removal process or a photoresist edge exposure process to remove the photoresist in the corresponding edge region of the photoresist layer to expose the preprocessed bonded wafer in the edge region; the edge region is a region formed by extending the edge contour of the preprocessed bonded wafer at least 3 mm towards the center of the preprocessed bonded wafer on the first surface and the second surface of the preprocessed bonded wafer;

[0089] Step S5: Along the direction pointing to the second surface, use a dry etching process to etch the preprocessed bonded wafer in the edge region until part of the second substrate is removed, and the surface of the remaining second substrate corresponding to the edge region and adjacent to the first substrate is used as the region to be deposited; the second surface is the surface of the second substrate facing away from the bonding metal layer;

[0090] Step S9: Remove the remaining photoresist layer on the first surface of the preprocessed bonded wafer;

[0091] Step S7: Deposit a barrier layer in the region to be deposited until the deposited barrier layer is flush with the surface of the first device functional layer facing away from the bonding metal layer.

[0092] The structure for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiment of the present invention is introduced below. The structure for preventing corrosion of the metal bonding layer in the wafer bonding structure described below is prepared by the method for preventing corrosion of the metal bonding layer in the wafer bonding structure described above, and can be mutually corresponding and referenced with the method for preventing corrosion of the metal bonding layer in the wafer bonding structure described above.

[0093] Specifically, please refer to Figure 6 , Figure 6 which is a schematic diagram of a structure for preventing corrosion of the metal bonding layer in a wafer bonding structure provided by an embodiment of the present invention, and may include:

[0094] A first substrate 10, a first device functional layer 20, a bonding metal layer 30, a second device functional layer 40, and a second substrate 50 stacked in sequence along a specified direction; the first substrate 10 is a structure of a substrate with a part of its thickness removed on the side facing away from the bonding metal layer 30;

[0095] A barrier layer 60 is provided in the edge regions of the bonding metal layer 30 corresponding to the first substrate 10 and the second substrate 50 to wrap the side surfaces of the bonding metal layer 30.

[0096] In this embodiment, by providing a barrier layer 60 in the edge regions of the bonding metal layer 30 corresponding to the first substrate 10 and the second substrate 50, it is possible to ensure that the side surfaces of the bonding metal layer 30 are wrapped by the barrier layer 60, avoiding corrosion of the side surfaces of the bonding metal layer 30 when etching the first substrate 10 using a wet etching process. This embodiment does not limit the specific position where the barrier layer 60 is provided. For example, the barrier layer 60 can be provided only in the edge regions of the bonding metal layer 30 corresponding to the first substrate 10 and the second substrate 50, that is, at the positions corresponding to the edge regions in the side surfaces of the bonding metal layer 30. It should be noted that the edge regions in the side surfaces of the bonding metal layer 30 are in contact with the bonding metal layer 30; or the barrier layer 60 can also be provided at the positions corresponding to the edge regions in the side surfaces of the bonding metal layer 30, the second device functional layer 40, and a part of the second substrate 50, or the barrier layer 60 can further be provided at the positions corresponding to the edge regions in the side surfaces of the first device functional layer 20, the bonding metal layer 30, the second device functional layer 40, and a part of the second substrate 50. It should be noted that in this embodiment, a part of the second substrate 50 is the substrate with a partial thickness on the side facing the bonding metal layer 30. In this embodiment, the edge region is a region formed by extending a preset distance along the outer contour of the substrate surface towards the center of the substrate surface, and this preset distance is equal to the spacing formed between the edge of the current bonding metal layer 30 and the edge of the substrate.

[0097] Further, in order to ensure that the device functional layer is not damaged, the above-mentioned edge region can be a region formed by extending the edge contour of the surface of the first substrate 10 towards the center of the surface of the first substrate 10 by 3 mm in the surfaces of the first substrate 10 and the second substrate 50,

[0098] or a region formed by extending the edge contour of the surface of the second substrate 50 towards the center of the surface of the second substrate 50 by 3 mm.

[0099] It should be noted that the distance between the edge contour of the conventionally unmodified bonding metal layer 30 and the edge contour of the unmodified substrate is generally 3 mm. In this embodiment, by using the region formed by extending the edge contour of the substrate surface towards the center of the substrate surface by 3 mm as the edge region, it can be ensured that when dry etching the substrate in the edge region to form a region to be deposited, the device functional layer will not be etched away, ensuring the excellent rate of the wafer bonding structure. That is, the spacing between the inner and outer contours of the edge region is the same as the spacing between the edge contour of the bonding metal layer 30 when unmodified and the edge contour of the substrate when unmodified. In this embodiment, the bonding metal layer 30 and the substrate when unmodified are the wafer bonding structure before etching to form a region to be deposited using a dry etching process.

[0100] Applying the structure for preventing corrosion of the metal bonding layer in the wafer bonding structure provided by the embodiments of the present invention, which includes a first substrate 10, a first device functional layer 20, a bonding metal layer 30, a second device functional layer 40, and a second substrate 50 that are sequentially stacked along a specified direction. The first substrate 10 is a structure with a part of its thickness removed on the side facing away from the bonding metal layer 30. The bonding metal layer 30 is provided with a barrier layer 60 corresponding to the edge regions of the first substrate 10 and the second substrate 50 to wrap the side surfaces of the bonding metal layer 30. By preparing the barrier layer 60 structure on the side surfaces of the bonding metal layer 30 in the present invention, when the first substrate 10 is removed by a wet etching process, the etching solution will not cause corrosion to the bonding metal layer 30, avoiding the phenomenon of side etching corrosion of the bonding layer after etching and improving the yield of the device. In addition, in the embodiments of the present invention, the region formed by extending the edge contour of the substrate surface 3 millimeters towards the center of the substrate surface corresponding to the size of the device functional layer is used as the edge region, which can ensure that when the substrate in the edge region is dry etched to form the region to be deposited, the device functional layer will not be removed, ensuring the yield of the wafer bonding structure.

[0101] The various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0102] Finally, it should also be noted that in this article, relationships such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device.

[0103] The above has introduced in detail a method and a structure for preventing corrosion of the metal bonding layer in a wafer bonding structure provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preventing corrosion of a metal bonding layer in a wafer bonding structure, characterized in that, Comprising: Providing a pre - treated bonded wafer; The pre - treated bonded wafer includes a first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate arranged in sequence along a preset direction; the preset direction is the direction of wafer stacking and bonding; the first substrate has a structure in which a part of the thickness is removed from the first surface; the first surface is the surface of the first substrate facing away from the bonding metal layer; In the edge region of the first surface of the pre - treated bonded wafer, along the direction pointing to the second surface, the pre - treated bonded wafer is etched using a dry etching process, at least etching until the second substrate is exposed to form a deposition - waiting area; The second surface is the surface of the second substrate facing away from the bonding metal layer; A barrier layer is deposited in the deposition - waiting area until the height of the deposited barrier layer exceeds the bonding metal layer.

2. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 1, wherein In the edge region of the first surface of the pre - treated bonded wafer, along the direction pointing to the second surface, the pre - treated bonded wafer is etched using a dry etching process, at least etching until the second substrate is exposed to form a deposition - waiting area, including: In the edge region of the first surface of the pre - treated bonded wafer, along the direction pointing to the second surface, the pre - treated bonded wafer is etched using a dry etching process until a part of the second substrate is removed, and the remaining second substrate corresponding to the edge region and facing the surface of the first substrate is used as the deposition - waiting area.

3. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 1, wherein, Depositing a barrier layer in the deposition - waiting area until the height of the deposited barrier layer exceeds the bonding metal layer, including: Depositing the barrier layer in the deposition - waiting area until the deposited barrier layer is flush with the surface of the first device functional layer facing away from the bonding metal layer.

4. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 1, wherein, The edge region is a region formed by the edge contour of the pre - treated bonded wafer extending at least 3 mm towards the center of the pre - treated bonded wafer in the first surface and the second surface of the pre - treated bonded wafer.

5. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 1, wherein In the edge region of the first surface of the pre - treated bonded wafer, along the direction pointing to the second surface, the pre - treated bonded wafer is etched using a dry etching process, at least etching until the second substrate is exposed to form a deposition - waiting area, including: Preparing a photoresist layer on the first surface of the pre - treated bonded wafer; Removing the photoresist corresponding to the edge region in the photoresist layer to expose the pre - treated bonded wafer in the edge region; Etching the pre - treated bonded wafer in the edge region using a dry etching process, at least etching until the second substrate is exposed to form the deposition - waiting area.

6. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 5, wherein After etching the pre - treated bonded wafer in the edge region using a dry etching process, at least etching until the second substrate is exposed to form the deposition - waiting area, it further includes: Removing the remaining photoresist layer on the first surface of the pre - treated bonded wafer.

7. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 5, characterized in that, Removing the photoresist corresponding to the edge region in the photoresist layer to expose the pre - treated bonded wafer in the edge region, including: Using a photoresist edge removal process or a photoresist edge exposure process, the photoresist in the photoresist layer corresponding to the edge region is removed to expose the pre-processed bonded wafer in the edge region.

8. The method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 1, wherein Provided is a pre-processed bonded wafer, including: Two wafers are provided. A metal layer is sputtered on the surfaces of the two wafers facing away from the substrate, and the surface of the metal layer is planarized by chemical mechanical polishing. The two wafers are bonded through the metal layer to obtain an initial bonded wafer; the bonded metal layer is used as the bonding metal layer. Using a grinding device, a part of the thickness of the substrate on the first surface of the initial bonded wafer is removed to obtain the pre-processed bonded wafer; the thickness of the removed part of the substrate is greater than the thickness of the remaining part of the substrate.

9. A structure for preventing corrosion of a metal bonding layer in a wafer bonding structure, characterized in that, Prepared by the method for preventing corrosion of the metal bonding layer in the wafer bonding structure according to any one of claims 1 to 8, including: A first substrate, a first device functional layer, a bonding metal layer, a second device functional layer, and a second substrate are sequentially stacked in a specified direction; the first substrate has a structure in which a part of the thickness of the substrate on the side facing away from the bonding metal layer is removed. The bonding metal layer is provided with a barrier layer corresponding to the edge regions of the first substrate and the second substrate to wrap the side surfaces of the bonding metal layer.

10. The structure for preventing corrosion of the metal bonding layer in the wafer bonding structure according to claim 9, characterized in that, The edge region is a region formed by the edge contour of the first substrate surface extending 3 mm towards the center of the first substrate surface in the first substrate surface and the second substrate surface, Or a region formed by the edge contour of the second substrate surface extending 3 mm towards the center of the second substrate surface.

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