Wafer bonding method and heterogeneous wafer

Abstract

The invention discloses a wafer bonding method and a heterogeneous wafer, and relates to the technical field of semiconductor materials.The wafer bonding method comprises the steps that contact pressing is conducted, at least one of a first wafer and a second wafer is made to rotate around the axis of the first wafer and the second wafer, so that the relative rotation angle of the first wafer and the second wafer in the circumferential direction reaches a preset value, and the first wafer and the second wafer are laminated under a preset pressure, and the preset value is adjusted according to the materials of the first wafer and the second wafer. According to the wafer bonding method, the bonded wafers rotate around the axes of the wafers in the contact pressing step, the chemical matching environment of the bonding interface is improved by adjusting the relative rotation angle of the two wafers in the circumferential direction, the adverse effect on wafer bonding caused by stress generated by lattice mismatch is reduced, the overall bonding quality is improved, and the wafer bonding quality is improved. The bonding strength is greatly improved, and the bonding stability is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a wafer bonding method and a heterogeneous wafer. Background Art

[0002] Wafer bonding technology is a key step in the field of microelectronics and microsystem technology. Through wafer bonding technology, two or more wafers or chips can be stacked vertically together to realize three-dimensional integrated circuits, greatly improve integration, enhance functionality, and thus improve device performance.

[0003] Wafer bonding technology allows wafers of different materials to be combined, expanding the range of material choices. This is particularly important for applications that require special material properties (such as different electrical or thermal properties). However, a major challenge faced by wafer bonding technology when achieving integration between different materials is lattice mismatch. Lattice mismatch refers to the difference in lattice constants between two different crystal materials, which can cause stress and cracks. When the lattice constants of two crystal materials do not match, stress will be generated on the bonding interface. This stress may cause material deformation, cracks or other structural defects, affecting the performance and reliability of the device. Lattice mismatch may also cause defects in the bonding interface, such as dislocations and voids, which will become scattering centers for charge carriers and reduce the performance of electronic devices. By limiting the range of material selection, the impact caused by lattice mismatch will be reduced, but this may hinder the application of new materials or new technologies.

[0004] Therefore, how to reduce the impact of lattice mismatch on wafer bonding technology without affecting the selection range of materials is a technical problem that technicians in this field currently need to solve. Summary of the invention

[0005] The object of the present invention is to provide a wafer bonding method and a heterogeneous wafer. The wafer bonding method provided by the present invention is used to reduce the influence of lattice mismatch on wafer bonding technology without affecting the selection range of materials.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A wafer bonding method, comprising:

[0008] Contact pressing is to rotate at least one of the first wafer and the second wafer around its own axis so that the relative rotation angle of the first wafer and the second wafer in the circumferential direction reaches a preset value, and to fit and press the first wafer and the second wafer together under a preset pressure, wherein the preset value is adjusted according to the material of the first wafer and the second wafer.

[0009] Optionally, in the above-mentioned wafer bonding method, a first twist mark is set on the first wafer, and a second twist mark is set on the second wafer. After rotation, the angle between the first twist mark and the second twist mark is the relative rotation angle of the first wafer and the second wafer.

[0010] Optionally, in the above wafer bonding method, before the contact pressing step, the following steps are further included:

[0011] Surface cleaning: cleaning the surfaces of the first wafer and the second wafer to remove organic pollutants, metal impurities and oxides.

[0012] Optionally, in the above wafer bonding method, after the contact pressing step, the method further comprises the following steps:

[0013] Annealing treatment, performing an annealing process on the first wafer and the second wafer pressed together at a preset temperature;

[0014] Exposing the silicon active layer, after the annealing treatment is completed, treating the side away from the bonding surface by a combination of wet etching and grinding so that the silicon active layer is exposed;

[0015] Polishing and film reduction: polishing the first wafer and the second wafer so that the thickness of the wafers after bonding reaches a preset value.

[0016] Optionally, in the above wafer bonding method, during plasma activated direct bonding, after the surface cleaning step, the method comprises the following steps:

[0017] Plasma treatment: using plasma to treat the surfaces of the first wafer and the second wafer to increase the activity of the surfaces.

[0018] Optionally, in the above wafer bonding method, when hydrophilic bonding is adopted, the surface cleaning further comprises adopting a specific chemical treatment to treat the surface of the first wafer and the second wafer to increase the hydrophilicity of the wafer surface.

[0019] Optionally, in the above wafer bonding method, when hydrophobic bonding is adopted, the surface cleaning further includes treating the surfaces of the first wafer and the second wafer by using a silane compound to increase the hydrophobicity of the surfaces.

[0020] Optionally, in the above-mentioned wafer bonding method, in the surface cleaning step, ultrasonic cleaning is performed using acetone or isopropyl alcohol as a solvent to remove organic contaminants, and after ultrasonic cleaning, the surfaces of the first wafer and the second wafer are rinsed with deionized water, and wet cleaning is performed using an acid or alkaline solution to remove metal impurities and oxides.

[0021] Optionally, in the above wafer bonding method, the plasma treatment step uses O 2 , Ar or N 2 The surfaces of the first wafer and the second wafer are processed by plasma.

[0022] The wafer bonding method provided by the present invention is used to reduce the influence of lattice mismatch on wafer bonding technology without affecting the selection range of materials. In the contact pressing step, at least one of the first wafer and the second wafer is rotated around its own axis so that the relative rotation angle of the first wafer and the second wafer in the circumferential direction reaches a preset value, and the first wafer and the second wafer are bonded and pressed together under a preset pressure, and the preset value is adjusted according to the materials of the first wafer and the second wafer. In the wafer bonding method provided by the present invention, the bonded wafers are rotated around their own axes in the contact pressing step, and the relative rotation angle of the two wafers in the circumferential direction is adjusted to improve the chemical matching environment of the bonding interface, reduce the adverse effects of stress generated by lattice mismatch on wafer bonding, improve the overall bonding quality, greatly improve the bonding strength, and enhance the bonding stability.

[0023] A heterogeneous wafer is made by stacking multiple layers of wafers through a wafer bonding method, wherein the wafer bonding method is the wafer bonding method as described in any one of the above items, and the wafers in the multiple layers of wafers include bulk silicon wafers or SOI wafers.

[0024] The heterogeneous wafer provided by the present invention has all the technical effects of the above-mentioned wafer bonding method, and will not be described in detail herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 A schematic diagram of the cooperation between the first wafer and the second wafer disclosed in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of the surface activation treatment of a SiC wafer disclosed in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of surface activation treatment of Si wafer disclosed in an embodiment of the present invention.

[0029] Reference numerals:

[0030] 100 is the first wafer;

[0031] 200 is the second wafer;

[0032] 300 is the relative rotation angle of the first wafer and the second wafer along the circumferential direction. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0036] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] The core of the present invention is to provide a wafer bonding method for reducing the influence of lattice mismatch on wafer bonding technology without affecting the selection range of materials;

[0039] Another core of the present invention is to provide a heterogeneous wafer prepared by the above-mentioned wafer bonding method.

[0040] An embodiment of the present invention discloses a wafer bonding method, which is used to reduce the influence of lattice mismatch on wafer bonding technology without affecting the selection range of materials, and specifically includes the following steps:

[0041] Step S10, contact pressing;

[0042] During the wafer pressing process, at least one of the first wafer 100 and the second wafer 200 to be bonded is rotated with its own axis system as the rotation center, so that the relative rotation angle 300 of the first wafer 100 and the second wafer 200 along the circumferential direction reaches a preset value, and the preset value is adjusted accordingly according to the different materials used by the first wafer 100 and the second wafer 200. After the relative rotation angle 300 of the first wafer 100 and the second wafer 200 is adjusted, a preset pressure is applied to the first wafer 100 and the second wafer 200 to ensure that the first wafer 100 and the second wafer 200 are in good contact with each other for pressing. Compared with the prior art, the wafer bonding method provided in this embodiment adjusts the relative rotation angle 300 of the two wafers along the circumferential direction to improve the chemical matching environment of the bonding interface, reduce the adverse effects of stress caused by lattice mismatch on wafer bonding, improve the overall bonding quality, greatly improve the bonding strength, and enhance the bonding stability.

[0043] like Figure 1 As shown, the first wafer 100 is provided with a first twist mark, and the second wafer 200 is provided with a second twist mark. Before rotation, the first twist mark of the first wafer 100 is aligned with the second twist mark of the second wafer 200 and then rotated. At this time, the angle formed between the orthographic projections of the first twist mark and the second twist mark on the plane perpendicular to the axis is the relative rotation angle 300 of the first wafer 100 and the second wafer 200 along the circumferential direction, so as to facilitate the rotation angle of the first wafer 100 and the second wafer 200 to quickly and accurately turn to the preset value. In a specific embodiment, a groove is provided on the cylindrical surface of the first wafer 100 and the cylindrical surface of the second wafer 200, so that the groove serves as the first twist mark of the first wafer 100 and the second twist mark of the second wafer 200.

[0044] In a specific embodiment disclosed in the present invention, in order to ensure the quality of wafer bonding, step S00 is further included before step S10.

[0045] Step S00, surface cleaning;

[0046] The surface of the first wafer 100 and the surface of the second wafer 200 are cleaned to remove organic pollutants, metal impurities and oxides, so as to ensure that the surface of the first wafer 100 and the surface of the second wafer 200 have good cleanliness. In a specific embodiment, in the surface cleaning step, organic pollutants are removed by ultrasonic cleaning, acetone or isopropyl alcohol can be used as a solvent, and after ultrasonic cleaning, the surface of the first wafer 100 and the surface of the second wafer 200 are rinsed with deionized water, and then wet cleaned with an acid or alkaline solution to remove metal impurities and oxides.

[0047] In addition, after step S10, the following steps are also included:

[0048] Step S20, annealing treatment;

[0049] The first wafer 100 and the second wafer 200 are subjected to an annealing process at a preset temperature to further enhance the strength of the bonding interface between the first wafer 100 and the second wafer 200 and improve the stability of the bonding between the wafers.

[0050] Step S30, exposing the silicon active layer;

[0051] After the first wafer 100 and the second wafer 200 are bonded and annealed, a surface of the first wafer 100 or the second wafer 200 facing away from the bonding surface is processed by a combination of wet etching and grinding to expose the silicon active layer.

[0052] Step S40, polishing and reducing the film;

[0053] The bonded first wafer 100 and second wafer 200 are polished and reduced by methods such as CMP (Chemical Mechanical Polishing) and smart stripping, so that the overall thickness of the bonded wafers reaches a preset value.

[0054] When the wafer bonding method provided in this embodiment is applied to plasma activated direct bonding, after the wafer surface is processed in step S00, the method further includes:

[0055] Step S01, plasma treatment;

[0056] The surfaces of the first wafer 100 and the second wafer 200 are treated with plasma to increase the activity of the surfaces. After the plasma treatment, a roughened surface can be observed at a microscopic level, which increases the surface energy and helps to improve the contact of the bonding interface. 2 , Ar or N 2 Alternatively, those skilled in the art may select other plasmas for treatment according to actual needs, which will not be described in detail herein.

[0057] In a specific implementation, the specific steps of directly bonding the Si wafer and the SiC wafer by plasma activation are as follows:

[0058] Step S00, surface cleaning;

[0059] The surfaces of the Si wafer and the SiC wafer are ultrasonically cleaned using acetone or isopropyl alcohol as a solvent to remove organic pollutants, and then the surfaces of the Si wafer and the SiC wafer are rinsed using deionized water. Finally, an acid or alkaline solution is used for wet cleaning to remove metal impurities and oxides.

[0060] Step S01, plasma treatment;

[0061] like Figure 2 and Figure 3 As shown, using O 2 , Ar or N 2 Plasma is used to treat the surface of Si wafers and SiC wafers to increase the surface activity. After plasma treatment, a roughened surface can be observed at the microscopic level, which increases the surface energy and helps improve the contact of the bonding interface.

[0062] Step S10, contact pressing;

[0063] After completing the above steps, under clean room conditions, the surfaces of the Si wafer and the SiC wafer to be bonded are aligned with each other, and the grooves of the Si wafer and the grooves of the SiC wafer are aligned with each other. Then the SiC wafer remains stationary, the Si wafer is rotated around its own axis, and the angle between the grooves of the Si wafer and the grooves of the SiC wafer is determined to determine the relative rotation angle of 300 between the Si wafer and the SiC wafer in the circumferential direction to reach a preset value, so as to improve the chemical matching environment of the bonding interface, reduce the adverse effects of stress caused by lattice mismatch on wafer bonding, improve the overall bonding quality, greatly improve the bonding strength, and enhance the bonding stability. Finally, slowly and gently apply pressure to the Si wafer and the SiC wafer and reach the preset pressure value to ensure that the two are in good contact for bonding.

[0064] Step S20, annealing treatment;

[0065] In a nitrogen environment, the bonded Si wafer and SiC wafer are annealed at a preset temperature to enhance the bonding strength of the bonding interface and improve the stability of the bonding between the wafers.

[0066] Step S30, exposing the silicon active layer;

[0067] After the Si wafer and the SiC wafer are bonded and annealed, the back side of the Si wafer is processed by a combination of wet etching and grinding to expose the silicon active layer.

[0068] Step S40, polishing and reducing the film;

[0069] The bonded Si wafer and SiC wafer are polished and reduced by CMP, smart stripping and other methods so that the overall thickness of the bonded wafer reaches the preset value.

[0070] When the wafer bonding method provided in this embodiment is applied to hydrophilic bonding, the surface cleaning in step S00 also includes using specific chemical treatment, such as using nitric acid or hydrochloric acid to treat the surface of the first wafer 100 and the second wafer 200 to increase the hydrophilicity of the wafer surface.

[0071] In a specific implementation, the specific steps of hydrophilic bonding of Si wafer and SiC wafer are as follows:

[0072] Step S00, surface cleaning;

[0073] The surfaces of the Si wafer and the SiC wafer are ultrasonically cleaned using acetone or isopropanol as a solvent to remove organic pollutants, and then the surfaces of the Si wafer and the SiC wafer are rinsed with deionized water, and then wet cleaned with an acid or alkaline solution to remove metal impurities and oxides. Finally, nitric acid or hydrochloric acid is used for chemical treatment to increase the hydrophilicity of the wafer surface, which is beneficial to the formation of abundant hydroxyl groups on the surfaces of the Si wafer and the SiC wafer.

[0074] Step S10, contact pressing;

[0075] After completing the above step S00, under clean room conditions, the surfaces of the Si wafer and the SiC wafer to be bonded are aligned with each other, and the grooves of the Si wafer and the grooves of the SiC wafer are aligned with each other. Then the Si wafer remains stationary, the SiC wafer is rotated around its own axis, and the relative rotation angle of 300 between the Si wafer and the SiC wafer along the circumferential direction is determined by the angle between the grooves of the Si wafer and the grooves of the SiC wafer to reach a preset value, so as to improve the chemical matching environment of the bonding interface, reduce the adverse effects of stress on wafer bonding caused by lattice mismatch, improve the overall bonding quality, greatly improve the bonding strength, and enhance the bonding stability. Finally, the Si wafer and the SiC wafer are slowly and gently applied with pressure to reach the preset pressure value to ensure that the two are in good contact for bonding.

[0076] Step S20, annealing treatment;

[0077] In a nitrogen environment, the bonded Si wafer and SiC wafer are annealed at a preset temperature to promote the conversion of hydrogen bonds between hydroxyl groups at the interface into more stable covalent bonds.

[0078] Step S30, exposing the silicon active layer;

[0079] After the Si wafer and the SiC wafer are bonded and annealed, the back side of the Si wafer is processed by a combination of wet etching and grinding to expose the silicon active layer.

[0080] Step S40, polishing and reducing the film;

[0081] The bonded Si wafer and SiC wafer are polished and reduced by CMP, smart stripping, etc., so that the overall thickness of the bonded wafer reaches the preset value.

[0082] When the wafer bonding method provided in this embodiment is applied to hydrophilic bonding, the surface cleaning in step S00 also includes treating the surface of the first wafer 100 and the surface of the second wafer 200 with a silane compound to increase the hydrophobicity of the surface to reduce the number of hydroxyl groups on the wafer surface, thereby reducing the hydrophilicity.

[0083] In a specific implementation, the specific steps of hydrophobic bonding of Si wafer and SiC wafer are as follows:

[0084] Step S00, surface cleaning;

[0085] The surfaces of the Si wafer and the SiC wafer are ultrasonically cleaned using acetone or isopropyl alcohol as a solvent to remove organic pollutants, and then the surfaces of the Si wafer and the SiC wafer are rinsed with deionized water, and then wet cleaned with an acid or alkaline solution to remove metal impurities and oxides. Finally, a hydrophobic silane compound is used for treatment to increase the hydrophobicity of the wafer surface, thereby reducing the number of hydroxyl groups on the wafer surface and thus reducing the hydrophilicity.

[0086] Step S10, contact pressing;

[0087] After completing the above steps, under clean room conditions, the surfaces of the Si wafer and the SiC wafer to be bonded are aligned with each other, and the grooves of the Si wafer and the grooves of the SiC wafer are aligned with each other. Then the SiC wafer remains stationary, the Si wafer is rotated around its own axis, and the angle between the grooves of the Si wafer and the grooves of the SiC wafer is determined to determine the relative rotation angle of 300 between the Si wafer and the SiC wafer in the circumferential direction to reach a preset value, so as to improve the chemical matching environment of the bonding interface, reduce the adverse effects of stress caused by lattice mismatch on wafer bonding, improve the overall bonding quality, greatly improve the bonding strength, and enhance the bonding stability. Finally, slowly and gently apply pressure to the Si wafer and the SiC wafer and reach the preset pressure value to ensure that the two are in good contact for bonding.

[0088] Step S20, annealing treatment;

[0089] The bonded Si wafer and SiC wafer are annealed at a preset temperature in a nitrogen environment to promote van der Waals forces or other types of chemical bonding between the hydrophobic surfaces.

[0090] Step S30, exposing the silicon active layer;

[0091] After the Si wafer and the SiC wafer are bonded and annealed, the back side of the Si wafer is processed by a combination of wet etching and grinding to expose the silicon active layer.

[0092] Step S40, polishing and reducing the film;

[0093] The bonded Si wafer and SiC wafer are polished and reduced by CMP, smart stripping and other methods so that the overall thickness of the bonded wafer reaches the preset value.

[0094] The embodiment of the present invention further discloses a heterogeneous wafer, which is made by stacking multiple layers of wafers through the above-mentioned wafer bonding method, wherein the silicon wafers in the multiple layers of wafers include two types of wafers, namely, bulk silicon wafers or SOI (Silicon-On-Insulator) wafers. Since the heterogeneous wafer has the above-mentioned wafer bonding method, it has all the technical effects of the above-mentioned wafer bonding method, which will not be described in detail herein.

[0095] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0096] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A wafer bonding method, characterized in that: include: Contact pressing is to rotate at least one of the first wafer and the second wafer around its own axis so that the relative rotation angle of the first wafer and the second wafer in the circumferential direction reaches a preset value, and to fit and press the first wafer and the second wafer together under a preset pressure, wherein the preset value is adjusted according to the material of the first wafer and the second wafer.

2. The wafer bonding method according to claim 1, characterized in that: A first twist mark is provided on the first wafer, and a second twist mark is provided on the second wafer. After rotation, an angle between the first twist mark and the second twist mark is a relative rotation angle between the first wafer and the second wafer.

3. The wafer bonding method according to claim 1, characterized in that: Before the contact pressing step, the method further comprises the following steps: Surface cleaning: cleaning the surface of the first wafer and the surface of the second wafer to remove organic pollutants, metal impurities and oxides.

4. The wafer bonding method according to claim 1, characterized in that: After the contact pressing step, the method further comprises the following steps: Annealing treatment, performing an annealing process on the first wafer and the second wafer pressed together at a preset temperature; Exposing the silicon active layer, after the annealing treatment is completed, treating the side away from the bonding surface by a combination of wet etching and grinding so that the silicon active layer is exposed; Polishing and film reduction: polishing the first wafer and the second wafer so that the thickness of the wafers after bonding reaches a preset value.

5. The wafer bonding method according to claim 3, characterized in that: In the case of plasma activated direct bonding, after the surface cleaning step, the steps include: Plasma treatment: using plasma to treat the surfaces of the first wafer and the second wafer to increase the activity of the surfaces.

6. The wafer bonding method according to claim 3, characterized in that: When hydrophilic bonding is adopted, the surface cleaning further comprises treating the surfaces of the first wafer and the second wafer by adopting a specific chemical treatment to increase the hydrophilicity of the wafer surfaces.

7. The wafer bonding method according to claim 3, characterized in that: When hydrophobic bonding is adopted, the surface cleaning further comprises treating the surface of the first wafer and the surface of the second wafer with a silane compound to increase the hydrophobicity of the surface.

8. The wafer bonding method according to claim 3, characterized in that: In the surface cleaning step, ultrasonic cleaning is performed using acetone or isopropanol as a solvent to remove organic pollutants, and after ultrasonic cleaning, the surface of the first wafer and the surface of the second wafer are rinsed with deionized water, and wet cleaning is performed using an acid or alkaline solution to remove metal impurities and oxides.

9. The wafer bonding method according to claim 5, characterized in that: In the plasma treatment step, O2, Ar or N2 plasma is used to treat the surfaces of the first wafer and the second wafer.

10. A heterogeneous wafer, characterized in that: The multi-layer wafer is stacked by a wafer bonding method, wherein the wafer bonding method is the wafer bonding method as described in any one of claims 1 to 9, and the wafers in the multi-layer wafer include bulk silicon wafers or SOI wafers.

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