Alignment system, alignment method and bonding method of wafer
The offset alignment wafer marking area is calculated by the laser grating and optical signal detection system, which solves the problem of low alignment accuracy in the prior art and achieves high-precision wafer bonding.
Patent Information
- Application Number
- CN202411282999.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2025-01-07
AI Technical Summary
In the prior art, wafer bonding alignment accuracy is low, especially due to the complex optical structure and material absorption problems of infrared alignment systems, the graphical alignment method is poorly robust in dynamic environments, making it difficult to meet high-precision requirements. .
Using laser grating and optical signal detection device, the offset is calculated by diffraction and reflected signals of the optical signal, and the alignment of the wafer marking area with the grating is controlled to improve the alignment accuracy.
It significantly improves the accuracy of wafer bonding alignment, ensures the correct correspondence between metal bumps, and improves the overall performance of three-dimensional system integration.
Smart Images
Figure CN119275159A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of integrated manufacturing technology, and in particular to a wafer alignment system, an alignment method and a bonding method. Background Art
[0002] In three-dimensional system integration, the bonding of multi-layer chips needs to ensure the mutual positional relationship, and this positional correspondence is achieved by alignment. To obtain high-performance devices, it is necessary to ensure high alignment accuracy between the two layers of wafers during bonding, and ensure the correct correspondence and positional relationship between the metal bumps, otherwise the misalignment between the metal bumps will cause interconnection failure or even lead to incorrect interconnection. Therefore, bonding alignment is crucial for three-dimensional system integration. Although the alignment accuracy required by different applications is different, with the development of technology and application prospects, the requirements for alignment accuracy are getting higher and higher.
[0003] There are many factors that affect the bonding alignment accuracy, including the bonding method, alignment method, and the surface fluctuations and warping of the upper and lower cores. Under the same other conditions, different bonding methods have very different effects on accuracy. Direct bonding and metal hot pressing bonding cause less slippage and higher precision after bonding. However, polymer and eutectic bonding, due to the high bonding temperature, cause the bonding layer to soften and melt to a certain extent, which easily leads to slippage of the bonded wafer.
[0004] The existing alignment methods, whether infrared alignment or optical alignment, all belong to the field of optics. Infrared alignment mainly uses the infrared band spectrum to be transparent to materials with a bandgap width greater than 1.1eV. However, due to the influence of infrared imaging and transmission wavelength, the infrared alignment system involves complex optical structures, and is subject to large restrictions on device materials and multi-layer metal interconnects. For example, silicon dioxide and silicon nitride on silicon wafers are both good infrared absorption materials, which greatly reduces the accuracy of infrared alignment.
[0005] Infrared imaging and transmission wavelength are affected. At the same time, the infrared alignment system involves complex optical structures, and is subject to large restrictions on device materials and multi-layer metal interconnections. For example, silicon dioxide and silicon nitride on silicon wafers are good infrared absorption materials, which greatly reduces the accuracy of infrared alignment.
[0006] The main disadvantage of the image-based alignment method is that the alignment accuracy is not high. Optical alignment usually requires the alignment mark to have clear edges and specific textures so that it can be identified and positioned. If the alignment mark features are not clear, the alignment accuracy will be directly reduced. In addition, in a complex dynamic environment, the image direct alignment method is easily affected by external environment disturbances such as vibration and impact, resulting in reduced system robustness. Summary of the invention
[0007] The object of the present invention is to provide a wafer alignment system, an alignment method and a bonding method to improve the alignment accuracy of wafer-level wafer bonding.
[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0009] One aspect of an embodiment of the present invention provides a wafer alignment system, the alignment system comprising: a first grating and a second grating, wherein one side of the first grating is arranged opposite to one side of the second grating, and a first wafer and a second wafer to be aligned are arranged between the first grating and the second grating; a first laser light source and a second laser light source, wherein the first laser light source is arranged on the other side of the first grating, and the second laser light source is arranged on the other side of the second grating, the first laser light source diffracts a light signal to the first wafer through the first grating, and the second laser light source diffracts a light signal to the second wafer through the second grating; an optical signal detection device and a control module, wherein a first detection end of the optical signal detection device is arranged between the first grating and the first wafer, and a second detection end of the optical signal detection device is arranged between the second grating and the second wafer, and the optical signal detection device is connected to the control module.
[0010] In some embodiments, the alignment system further includes a first stage and a second stage, the first wafer is disposed on the first stage, and the second wafer is disposed on the second stage.
[0011] In some embodiments, a first adjustable distance is set between the first wafer and the first grating, and between the second wafer and the second grating.
[0012] In some embodiments, a second adjustable distance is set between the first wafer and the second wafer.
[0013] In some embodiments, the first grating includes a plurality of first light-shielding rods arranged in sequence, and a first light-transmitting area is provided between two adjacent first light-shielding rods; the second grating includes a plurality of second light-shielding rods arranged in sequence, and a second light-transmitting area is provided between two adjacent second light-shielding rods.
[0014] In some embodiments, the widths of the plurality of first light-shielding rods are the same, and the widths of the plurality of first light-transmitting regions are the same; the widths of the plurality of second light-shielding rods are the same, and the widths of the plurality of second light-transmitting regions are the same.
[0015] An aspect of an embodiment of the present invention provides a wafer alignment method, which is applied to the alignment system as described above, and includes: obtaining a first optical signal diffracted by a first laser light source through a first grating through an optical signal detection device, and obtaining a second optical signal diffracted by a second laser light source through a second grating through an optical signal detection device; obtaining a first reflected optical signal of the first wafer through the optical signal detection device, and obtaining a second reflected optical signal of the second wafer through the optical signal detection device; calculating a first offset of a marking area of the first wafer relative to the first grating based on the first optical signal and the first reflected optical signal, and calculating a second offset of a marking area of the second wafer relative to the second grating based on the second optical signal and the second reflected optical signal; controlling the alignment of the marking area of the first wafer with the optical signal diffracted by the first grating based on the first offset, and controlling the alignment of the marking area of the second wafer with the optical signal diffracted by the second grating based on the second offset.
[0016] In some embodiments, before obtaining the first light signal diffracted by the first laser light source through the first grating through the light signal detection device and obtaining the second light signal diffracted by the second laser light source through the second grating through the light signal detection device, the alignment method also includes: placing the first grating and the second grating horizontally, obtaining the first horizontal plane coordinates of the first grating and the second horizontal plane coordinates of the second grating; comparing the first horizontal plane coordinates and the second horizontal plane coordinates with the preset horizontal plane coordinates, respectively, and when the first horizontal plane coordinates and the second horizontal plane coordinates are not at the position of the preset horizontal plane coordinates, correcting the horizontal plane coordinates of the first grating and the second grating to the preset horizontal coordinates.
[0017] In some embodiments, before controlling the alignment of the marking area of the first wafer with the light signal diffracted by the first grating according to the first offset and controlling the alignment of the marking area of the second wafer with the light signal diffracted by the second grating according to the second offset, the alignment method also includes: flipping the first wafer and the second wafer.
[0018] One aspect of an embodiment of the present invention provides a wafer bonding method, wherein the bonding method includes the alignment method as described above, and a first wafer and a second wafer are bonded using a direct bonding process.
[0019] According to an embodiment of the present invention, a wafer alignment system, alignment method and bonding method have at least the following beneficial effects: the control module detects and obtains the first optical signal, the second optical signal, the first reflected optical signal and the second reflected optical signal, calculates the first offset of the first wafer relative to the first grating according to the first optical signal and the first reflected optical signal, calculates the second offset of the second wafer relative to the second grating according to the second optical signal and the second reflected optical signal, and then controls the alignment of the marking area of the first wafer with the optical signal diffracted by the first grating according to the first offset, and controls the alignment of the marking area of the second wafer with the optical signal diffracted by the second grating according to the second offset. This improves the alignment accuracy of wafer-level wafer bonding.
[0020] It is to be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0022] Figure 1 FIG. 4 is a partial cross-sectional structural schematic diagram of an alignment system according to an embodiment.
[0023] The accompanying drawings are marked as follows: 1. first wafer; 2. second wafer; 3. first laser light source; 4. second laser light source; 5. optical signal detection device; 6. control module; 7. first stage; 8. second stage; 9. first light-shielding rod; 10. first light-transmitting area; 11. second light-shielding rod; 12. second light-transmitting area. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0025] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "horizontal", etc. indicate orientations or positional relationships based on the orientations 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 orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0026] The terms "first", "second", and "third" 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. Thus, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.
[0027] 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0028] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.
[0029] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these example embodiments are provided so that the description of the present disclosure will be more comprehensive and complete and the concepts of the example embodiments will be fully conveyed to those skilled in the art. The accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.
[0030] The following is a brief description of the wafer alignment system of the embodiment of the present application:
[0031] According to some embodiments, Figure 1 As shown, the present application provides a wafer alignment system, the alignment system comprising:
[0032] A first grating and a second grating, one side of the first grating is arranged opposite to one side of the second grating, and a first wafer 1 and a second wafer 2 to be aligned are arranged between the first grating and the second grating;
[0033] A first laser light source 3 and a second laser light source 4, wherein the first laser light source 3 is disposed on the other side of the first grating, and the second laser light source 4 is disposed on the other side of the second grating. The first laser light source 3 diffracts the light signal to the first wafer 1 through the first grating, and the second laser light source 4 diffracts the light signal to the second wafer 2 through the second grating;
[0034] The optical signal detection device 5 and the control module 6 , the first detection end of the optical signal detection device 5 is arranged between the first grating and the first wafer 1 , the second detection end of the optical signal detection device 5 is arranged between the second grating and the second wafer 2 , and the optical signal detection device 5 is connected to the control module 6 .
[0035] In some specific embodiments, Figure 1 As shown, Figure 1 The schematic diagram of the partial cross-sectional structure of the alignment system of the present application is shown in FIG. The first laser light source 3, the first grating, the first wafer 1, the second wafer 2, the second grating and the second laser light source 4 are arranged horizontally from top to bottom in sequence. The optical signal detection device 5 detects and obtains the first optical signal diffracted by the first laser light source 3 and the first reflected optical signal of the first wafer 1 through the first detection end, and detects and obtains the second optical signal and the second reflected optical signal diffracted by the second laser light source 4 through the second detection end, and transmits the first optical signal, the second optical signal, the first reflected optical signal and the second reflected optical signal to the control module 6. The control module 6 calculates the first offset of the first wafer 1 relative to the first grating according to the first optical signal and the first reflected optical signal, and calculates the second offset of the second wafer 2 relative to the second grating according to the second optical signal and the second reflected optical signal, and then controls the alignment of the marking area of the first wafer 1 with the optical signal diffracted by the first grating according to the first offset, and controls the alignment of the marking area of the second wafer 2 with the optical signal diffracted by the second grating according to the second offset. This improves the alignment accuracy of wafer-level wafer bonding.
[0036] The following is combined with the appendix of this manual Figure 1 , the wafer alignment system of the present application is further elaborated in detail.
[0037] According to some embodiments, Figure 1 As shown, the alignment system further includes a first stage 7 and a second stage 8 , the first wafer 1 is disposed on the first stage 7 , and the second wafer 2 is disposed on the second stage 8 .
[0038] When the marking area of the first wafer 1 is controlled to be aligned with the light signal diffracted by the first grating according to the first offset, the control module 6 controls the first stage 7 to move to align the marking area of the first wafer 1 with the light signal diffracted by the first grating; when the marking area of the second wafer 2 is controlled to be aligned with the light signal diffracted by the second grating according to the second offset, the control module 6 controls the second stage 8 to move to align the marking area of the second wafer 2 with the light signal diffracted by the second grating.
[0039] According to some embodiments, a first adjustable spacing is provided between the first wafer 1 and the first grating and between the second wafer 2 and the second grating, which can be used to adjust the diffraction effect of the grating.
[0040] According to some embodiments, a second adjustable distance is provided between the first wafer 1 and the second wafer 2 to facilitate displacement adjustment between the first wafer 1 and the second wafer 2 and to provide a certain space for subsequent bonding of the first wafer 1 and the second wafer 2.
[0041] According to some embodiments, the first grating includes a plurality of first light shielding rods 9 arranged in sequence, and a first light-transmitting area 10 is provided between two adjacent first light shielding rods 9;
[0042] The second grating includes a plurality of second light shielding rods 11 arranged in sequence, and a second light-transmitting area 12 is arranged between two adjacent second light shielding rods 11 .
[0043] In some specific embodiments, the widths of the plurality of first light shielding rods 9 are the same, and the widths of the plurality of first light transmission areas 10 are the same, that is, the spacing between any two consecutive first light shielding rods 9 is the same; the spacing between any two consecutive first light transmission areas 10 is the same.
[0044] The widths of the second light shielding rods 11 are the same, and the widths of the second light transmission areas 12 are the same, that is, the spacing between any two consecutive second light shielding rods 11 is the same; the spacing between any two consecutive first light transmission areas 10 is the same.
[0045] The following is an explanation of the wafer alignment method of the embodiment of the present application:
[0046] According to some embodiments, the present application provides a wafer alignment method, the alignment method is applied to the alignment system as described above, and the alignment method includes:
[0047] Step 101, the control module 6 detects and obtains the first light signal diffracted by the first grating of the first laser light source 3 through the light signal detection device 5, and also detects and obtains the second light signal diffracted by the second grating of the second laser light source 4 through the light signal detection device 5;
[0048] Step 102, the control module 6 detects and obtains a first reflected light signal reflected from the first wafer 1 through the optical signal detection device 5, and also detects and obtains a second reflected light signal reflected from the second wafer 2 through the optical signal detection device 5;
[0049] Step 103, the control module 6 calculates a first offset of the marking area of the first wafer 1 relative to the first grating according to the first optical signal and the first reflected optical signal, and calculates a second offset of the marking area of the second wafer 2 relative to the second grating according to the second optical signal and the second reflected optical signal;
[0050] In step 104, the control module 6 controls the movement of the first stage 7 according to the first offset so that the marking area of the first wafer 1 is aligned with the light signal diffracted by the first grating, and also controls the movement of the second stage 8 according to the second offset so that the marking area of the second wafer 2 is aligned with the light signal diffracted by the second grating.
[0051] In some specific embodiments, in step 101, before obtaining the first light signal diffracted by the first grating from the first laser light source 3 through the light signal detection device 5 and obtaining the second light signal diffracted by the second grating from the second laser light source 4 through the light signal detection device 5, the alignment method further includes:
[0052] Step 91, the first grating and the second grating are both placed horizontally, and the first horizontal plane coordinates of the first grating and the second horizontal plane coordinates of the second grating are obtained;
[0053] In step 92, the first horizontal plane coordinate and the second horizontal plane coordinate are respectively compared with the preset horizontal plane coordinate. When the first horizontal plane coordinate and the second horizontal plane coordinate are not at the position of the preset horizontal plane coordinate, the horizontal plane coordinates of the first grating and the second grating are corrected to the preset horizontal coordinate. Then, step 101 is entered. Since the position of the grating has been adjusted to the ideal position in steps 91 and 92, the wafer and the grating can be aligned by only adjusting the wafer according to the position of the grating in steps 101 to 104.
[0054] The preset horizontal plane coordinates may be set according to actual needs. In some embodiments, the preset horizontal plane coordinates are set to 0 on the X axis and 0 on the Y axis, that is, the origin coordinates (0, 0).
[0055] According to some embodiments, before step 104, controlling the alignment of the marking area of the first wafer 1 with the light signal diffracted by the first grating according to the first offset, and controlling the alignment of the marking area of the second wafer 2 with the light signal diffracted by the second grating according to the second offset, the alignment method further includes:
[0056] Step 1031, flip the first wafer 1 and the second wafer 2, and then perform an alignment operation.
[0057] According to some embodiments, the present application provides a wafer bonding method, wherein the bonding method includes the alignment method as described above, and a direct bonding process is used to bond a first wafer 1 and a second wafer 2 .
[0058] Among them, wafers using direct bonding technology have higher alignment accuracy. For direct bonding, the accuracy can reach above 0.25um. For indirect bonding using an intermediate, the accuracy cannot reach 2 microns.
[0059] 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.
[0060] Although the present disclosure has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present disclosure can be implemented in a variety of forms without departing from the spirit or essence of the present application, it should be understood that the above-mentioned embodiments are not limited to any of the foregoing details, but should be widely interpreted within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.
Claims
1. A wafer alignment system, characterized in that: The alignment system comprises: A first grating and a second grating, wherein one side of the first grating is arranged opposite to one side of the second grating, and a first wafer and a second wafer to be aligned are arranged between the first grating and the second grating; a first laser light source and a second laser light source, wherein the first laser light source is disposed on the other side of the first grating, and the second laser light source is disposed on the other side of the second grating, the first laser light source diffracts a light signal to the first wafer through the first grating, and the second laser light source diffracts a light signal to the second wafer through the second grating; An optical signal detection device and a control module, wherein the first detection end of the optical signal detection device is arranged between the first grating and the first wafer, the second detection end of the optical signal detection device is arranged between the second grating and the second wafer, and the optical signal detection device is connected to the control module.
2. The alignment system according to claim 1, characterized in that The alignment system further includes a first stage and a second stage, the first wafer is disposed on the first stage, and the second wafer is disposed on the second stage.
3. The alignment system according to claim 1, characterized in that A first adjustable distance is set between the first wafer and the first grating, and between the second wafer and the second grating.
4. The alignment system according to claim 3, characterized in that A second adjustable distance is set between the first wafer and the second wafer.
5. The alignment system according to claim 1, characterized in that The first grating includes a plurality of first light shielding rods arranged in sequence, and a first light-transmitting area is arranged between two adjacent first light shielding rods; The second grating includes a plurality of second light shielding rods arranged in sequence, and a second light-transmitting area is arranged between two adjacent second light shielding rods.
6. The alignment system according to claim 5, characterized in that The widths of the plurality of first light-shielding rods are all the same, and the widths of the plurality of first light-transmitting areas are all the same; The widths of the plurality of second light-shielding rods are all the same, and the widths of the plurality of second light-transmitting areas are all the same.
7. A wafer alignment method, characterized in that: The alignment method is applied to the alignment system according to any one of claims 1 to 6, and the alignment method comprises: Acquire a first light signal diffracted by the first grating from the first laser light source through an optical signal detection device, and acquire a second light signal diffracted by the second grating from the second laser light source through an optical signal detection device; Acquire a first reflected light signal of the first wafer through an optical signal detection device, and acquire a second reflected light signal of the second wafer through an optical signal detection device; Calculate a first offset of a marking area of a first wafer relative to a first grating according to the first optical signal and the first reflected optical signal, and calculate a second offset of a marking area of a second wafer relative to a second grating according to the second optical signal and the second reflected optical signal; The marking area of the first wafer is controlled to be aligned with the light signal diffracted by the first grating according to the first offset, and the marking area of the second wafer is controlled to be aligned with the light signal diffracted by the second grating according to the second offset.
8. The alignment method according to claim 7, characterized in that: Before obtaining the first light signal diffracted by the first grating from the first laser light source through the light signal detection device and obtaining the second light signal diffracted by the second grating from the second laser light source through the light signal detection device, the alignment method further includes: The first grating and the second grating are both placed horizontally, and a first horizontal plane coordinate of the first grating and a second horizontal plane coordinate of the second grating are obtained; The first horizontal plane coordinate and the second horizontal plane coordinate are respectively compared with the preset horizontal plane coordinates. When the first horizontal plane coordinate and the second horizontal plane coordinate are not at the positions of the preset horizontal plane coordinates, the horizontal plane coordinates of the first grating and the second grating are corrected to the preset horizontal coordinates.
9. The alignment method according to claim 7, characterized in that: Before controlling the alignment of the marking area of the first wafer with the light signal diffracted by the first grating according to the first offset, and controlling the alignment of the marking area of the second wafer with the light signal diffracted by the second grating according to the second offset, the alignment method further includes: The first wafer and the second wafer are turned over.
10. A wafer bonding method, characterized in that: The bonding method comprises the alignment method as claimed in any one of claims 7 to 9, and a direct bonding process is used to bond the first wafer and the second wafer.