A method, device and system for aligning multiple wafers

Abstract

The present invention provides a wafer alignment method, device and system for aligning two stacked wafers, the alignment method comprising: adjusting a microscope lens to make a first wafer image clear, the first wafer being the wafer closest to the microscope lens, fixing the microscope lens, and performing image acquisition and positioning of the first wafer; selecting a glass sheet according to the distance between the second wafer and the first wafer, adding the glass sheet between the microscope lens and the first wafer, making the second wafer image clear in the microscope lens, so as to perform image acquisition and positioning of the second wafer; and performing alignment of the two wafers by image acquisition and positioning of the first wafer and the second wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor processing, and in particular to a wafer alignment method, device and system. Background Art

[0002] In the semiconductor production process, wafer bonding alignment usually involves collecting images of the marks on the two wafers, and then performing positioning alignment based on the images of the positioning marks. Poor visual alignment can damage the wafers and affect subsequent process flows. Therefore, in semiconductor production, the accuracy of alignment between multiple wafers is very important.

[0003] In the prior art, alignment between wafers usually begins with setting an infrared light source below the wafer, and then performing image acquisition through a microscope above the wafer. More specifically, the images of the marks on the upper and lower wafers are acquired respectively, and then positioning and alignment are performed based on the images of these marks. When using infrared technology to acquire images of the upper and lower wafers using a microscope, since the focal depth of the microscope that can clearly image is less than the gap between the two wafers, the microscope needs to be moved up and down to focus on the upper and lower wafers, so that the images of the marks on the upper and lower wafers are clearly displayed. However, in the process of moving the microscope up and down, shaking is inevitable. Even a very slight shake will cause an error relative to the original position, which will affect the alignment accuracy of the wafer and the subsequent process flow.

[0004] In order to overcome the above-mentioned defects of the prior art, the art is in urgent need of a wafer alignment method, device and system to keep the position of the microscope fixed and compensate the light path by adding optical glass, thereby realizing the focusing of the microscope, ensuring that the positioning mark of each wafer is clearly imaged, and thereby improving the accuracy of wafer alignment. Summary of the invention

[0005] A brief summary of one or more aspects is given below to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceived aspects, and is neither intended to identify the key or critical elements of all aspects nor to define the scope of any or all aspects. Its only purpose is to give some concepts of one or more aspects in a simplified form as a prelude to a more detailed description that will be given later.

[0006] In order to overcome the above-mentioned defects in the prior art, the present invention provides a wafer alignment method for aligning two stacked wafers, the alignment method comprising: adjusting a microscope lens to make the image of a first wafer clear, the first wafer being the wafer closest to the microscope lens, fixing the microscope lens, and performing image acquisition and positioning of the first wafer; selecting a glass sheet according to the distance between the second wafer and the first wafer, adding the glass sheet between the microscope lens and the first wafer, making the image of the second wafer clear in the microscope lens for image acquisition and positioning of the second wafer; and performing alignment of the two wafers according to the image acquisition and positioning of the first wafer and the second wafer.

[0007] In one embodiment, preferably, in the wafer alignment method provided by the present invention, the selecting of the glass sheet according to the distance between the second wafer and the first wafer comprises: selecting the glass sheet according to the following formula:

[0008] l=dd / n

[0009] Wherein, l is the distance between the second wafer and the first wafer, d is the thickness of the glass sheet, and n is the refractive index of the glass sheet.

[0010] In one embodiment, preferably, in the method for aligning multiple wafers provided by the present invention, selecting the glass sheet according to the following formula includes: selecting the thickness or refractive index of the glass sheet to satisfy the formula.

[0011] In one embodiment, preferably, in the method for aligning multiple wafers provided by the present invention, the surface flatness of the glass sheet is within λ / 10, where λ is the wavelength of the light source.

[0012] Another aspect of the present invention provides a wafer alignment device for aligning two stacked wafers, the alignment device comprising: a memory; and a processor coupled to the memory, the processor being configured to: adjust a microscope lens to make a first wafer have a clear image, the first wafer being the wafer closest to the microscope lens, fix the microscope lens, and perform image acquisition and positioning of the first wafer; select a glass sheet according to the distance between the second wafer and the first wafer, add the glass sheet between the microscope lens and the first wafer, make the second wafer have a clear image in the microscope lens, and perform image acquisition and positioning of the second wafer; and perform alignment of the two wafers according to the image acquisition and positioning of the first wafer and the second wafer.

[0013] In one embodiment, preferably, in the wafer alignment device provided by the present invention, the processor is further configured to: select the glass sheet according to the following formula:

[0014] l=dd / n

[0015] Wherein, l is the distance between the second wafer and the first wafer, d is the thickness of the glass sheet, and n is the refractive index of the glass sheet.

[0016] In one embodiment, preferably, in the wafer alignment device provided by the present invention, the processor is further configured to: select the thickness or refractive index of the glass sheet to satisfy the formula.

[0017] In one embodiment, preferably, in the wafer alignment device provided by the present invention, the surface flatness of the glass sheet is within λ / 10, where λ is the wavelength of the light source.

[0018] The present invention also provides a computer-readable medium having a computer program stored thereon, and when the computer program is executed by a processor, the wafer alignment method described in any one of the above items is implemented.

[0019] The present invention also provides a wafer alignment system, comprising: a microscope, an infrared light source and a plurality of glass sheets. Under the irradiation of the infrared light source, the microscope performs image acquisition and positioning on two stacked wafers respectively. The plurality of glass sheets are used to be added between the microscope and the first wafer to adjust the focusing position of the microscope, thereby making the image of each wafer clear for image acquisition, positioning and alignment work. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above features and advantages of the present invention can be better understood after reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings. In the drawings, the components are not necessarily drawn to scale, and components with similar related properties or features may have the same or similar reference numerals.

[0021] Figure 1 is a schematic diagram of a method flow of a wafer alignment method according to one aspect of the present invention;

[0022] Figure 2 It is a schematic diagram of the principle of optical path change after adding a glass sheet for optical path compensation in a wafer alignment method according to one aspect of the present invention;

[0023] Figure 3 is a schematic diagram of the structure of a wafer alignment device according to another aspect of the present invention; and

[0024] Figure 4 FIG. 4 is a schematic diagram of the system composition of a wafer alignment system according to another aspect of the present invention.

[0025] For the sake of clarity, a brief description of the reference numerals is given below:

[0026] 201 Glass

[0027] 202 First Wafer

[0028] 203 Second Wafer

[0029] 401 Microscope

[0030] 402 Infrared light source

[0031] 403 Glass

[0032] 404 Wafer DETAILED DESCRIPTION

[0033] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description.

[0034] 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.

[0035] In addition, the terms "upper", "lower", "left", "right", "top", "bottom", "horizontal" and "vertical" used in the following description should be understood as the directions shown in the paragraph and the related drawings. Such relative terms are only used for the convenience of description and do not mean that the device described therein must be manufactured or operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0036] It is understood that although the terms "first", "second", "third", etc. may be used herein to describe various components, regions, layers and / or parts, these components, regions, layers and / or parts should not be limited by these terms, and these terms are only used to distinguish different components, regions, layers and / or parts. Therefore, the first component, region, layer and / or part discussed below may be referred to as a second component, region, layer and / or part without departing from some embodiments of the present invention.

[0037] In order to overcome the above-mentioned defects of the prior art, the present invention provides a wafer alignment method, device and system, which keep the position of the microscope fixed and compensate the light path by adding optical glass, thereby realizing the focusing of the microscope, ensuring that the positioning mark of each wafer is clearly imaged, and thus improving the accuracy of wafer alignment.

[0038] The wafer alignment method provided by the present invention is used for aligning two wafers placed in a stacked manner, and can be combined with reference to Figure 1 .

[0039] Figure 1 FIG. 4 is a schematic diagram of a method flow of a wafer alignment method according to one aspect of the present invention.

[0040] like Figure 1 As shown, the wafer alignment method 100 provided by the present invention includes:

[0041] Step 101: adjusting a microscope lens to make a first wafer image clear, the first wafer being the wafer closest to the microscope lens, fixing the microscope lens, and performing image acquisition and positioning of the first wafer;

[0042] Step 102: selecting a glass sheet according to the distance between the second wafer and the first wafer, and adding the glass sheet between the microscope lens and the first wafer, so that the second wafer is imaged clearly in the microscope lens to perform image acquisition and positioning of the wafer; and

[0043] Step 103: performing alignment of the two wafers according to the image acquisition positioning of the first wafer and the second wafer. For example, the corresponding wafer positions can be adjusted according to the position difference of the positioning marks on the two wafers to achieve alignment between the wafers.

[0044] For the purpose of explanation, an embodiment of the present invention is described by taking the alignment of two wafers placed horizontally in the vertical direction as an example. An illumination light source, such as an infrared light source, is disposed below the two wafers, and a microscope is located above the two wafers. Through illumination by the light source, the alignment marks on the wafers are imaged in the microscope to perform alignment work.

[0045] It should be noted that the position and placement direction of each device in the alignment system is only an exemplary description, the purpose of which is to better explain the working principle and effect of the wafer alignment method provided by the present invention, rather than to limit the protection scope of the present invention. In fact, the various devices in the alignment system provided by the present invention do not have to be placed vertically, and the wafer calibration work can also be performed in other directions such as the horizontal direction according to actual process requirements. The above-mentioned method devices similar to the alignment method of the present invention can be applied to the wafer alignment method provided by the present invention, and should also be included in the protection scope of the present invention.

[0046] Figure 2 The diagram is a schematic diagram of the principle of optical path change for optical path compensation after adding a glass sheet in a wafer alignment method according to one aspect of the present invention.

[0047] Please refer to Figure 2 In this embodiment, the first wafer 202 and the second wafer 203 are stacked in a vertical direction. Figure 2 The arrow in the middle shows the imaging light path of the microscope. Figure 2 As shown, the wafer alignment method provided by the present invention realizes focusing of the microscope by adding a glass sheet 201 between the microscope and the first wafer 202 .

[0048] It is easy for a person skilled in the art to understand that, since the refractive index of glass is greater than that of air, light is refracted by the added glass sheet, which causes the position of the light convergence point to change, thereby achieving adjustment of the focus position of the microscope lens.

[0049] The step 102 of selecting a glass sheet for the distance between the second wafer and the first wafer includes: selecting the glass sheet according to the following formula:

[0050] l=dd / n

[0051] Wherein, l is the distance between the second wafer and the first wafer, d is the thickness of the glass sheet, and n is the refractive index of the glass sheet.

[0052] like Figure 2 As shown, the distance between the first wafer 202 and the second wafer 203 is l, the thickness of the selected glass sheet 201 is d, and the refractive index is n. After the first wafer 202 is imaged clearly, the microscope is kept fixed and a glass sheet 201 is added to compensate the optical path. The d and n of the glass sheet 201 satisfy the above quantitative relationship, so that the focusing position of the microscope can be exactly on the surface to be measured of the second wafer 203, and then the second wafer 203 can also achieve clear imaging, thereby avoiding the error introduced by the movement of the microscope during the focusing process and improving the alignment accuracy of the wafer.

[0053] In practical applications, when selecting a glass sheet, the thickness or refractive index of the glass sheet can be selected to satisfy the formula. For example, multiple glass sheets can be prepared according to the common distance between wafers. The glass sheets can have the same thickness but different refractive indices, the same refractive index but different thicknesses, or different refractive indices and thicknesses. As long as the physical relationship between the two can be selected to satisfy the above formula, the distance between wafers can be adapted to achieve focus alignment.

[0054] It is easy to understand that, for example, when two wafers are gradually approaching and the gap between them is reduced, observation can be performed by changing glass sheets of different thicknesses, thereby achieving the focusing of the microscope.

[0055] In one embodiment, the surface flatness of the glass sheets is within λ / 10, where λ is the wavelength of the light source. It is easy to understand that glass sheets with high surface flatness can further reduce errors and improve the accuracy of alignment work.

[0056] Although the above methods are illustrated and described as a series of actions for simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in a different order and / or concurrently with other actions from those illustrated and described herein or not illustrated and described herein but understandable to those skilled in the art.

[0057] Figure 3 FIG. 4 is a schematic diagram of the structure of a wafer alignment device according to another aspect of the present invention.

[0058] According to another aspect of the present invention, an embodiment of a wafer alignment device 300 is also provided herein.

[0059] like Figure 3 As shown, the wafer alignment device 300 provided in this embodiment may include a memory 301 and a processor 302 coupled to the memory 301. The processor 302 may be configured to implement any one of the above-mentioned methods for aligning multiple wafers.

[0060] Figure 4 FIG. 4 is a schematic diagram of the system composition of a wafer alignment system according to another aspect of the present invention.

[0061] Please refer to Figure 4The present invention also provides a wafer alignment system, including: a microscope 401, an infrared light source 402 and a plurality of glass sheets 403. Under the irradiation of the infrared light source 402, the microscope 401 performs image acquisition and positioning on two wafers 404 respectively. The plurality of glass sheets 403 are used to be added between the microscope 401 and a first wafer, and the first wafer is the wafer closest to the microscope lens, so as to adjust the focus position of the microscope 401, so as to make the image of each wafer clear for image acquisition, positioning and alignment.

[0062] According to another aspect of the present invention, an embodiment of a computer storage medium is also provided herein.

[0063] The computer storage medium stores a computer program, which, when executed by a processor, can implement the steps of any one of the above-mentioned wafer alignment methods.

[0064] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or a combination of the two. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. The technician may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as resulting in a departure from the scope of the present invention.

[0065] The processor described in this case can be implemented using electronic hardware, computer software or any combination thereof. Whether such processors are implemented as hardware or software will depend on the specific application and the overall design constraints imposed on the system. As an example, the processor presented in this disclosure, any part of the processor, or any combination of processors can be implemented with a microprocessor, a microcontroller, a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic device (PLD), a state machine, a gated logic, a discrete hardware circuit, and other suitable processing components configured to perform various functions described throughout this disclosure. The functionality of the processor presented in this disclosure, any part of the processor, or any combination of processors can be implemented with software executed by a microprocessor, a microcontroller, a DSP or other suitable platforms.

[0066] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read and write information from / to the storage medium. In an alternative, a storage medium may be integrated into a processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components.

[0067] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented as a computer program product in software, each function may be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any medium that facilitates the transfer of a computer program from one place to another. Storage media may be any available medium that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, a server, or other remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disk often reproduces data magnetically, while disc reproduces data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0068] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wafer alignment method for aligning two stacked wafers, wherein an infrared light source and a microscope are respectively located on both sides of the two wafers in the axial direction of the wafers, and the microscope receives light transmitted through the two wafers by the infrared light source to collect a positioning image, and the alignment method comprises: Adjusting the microscope lens to make the image of the first wafer clear, the first wafer being the wafer closest to the microscope lens, fixing the microscope lens, and performing image acquisition and positioning of the first wafer; A glass sheet is selected according to the distance between the second wafer and the first wafer, and the glass sheet is added between the microscope lens and the first wafer, so that the second wafer is imaged clearly in the microscope lens to perform image acquisition and positioning of the second wafer, further comprising: The glass sheets are selected according to the following formula: l=dd / n Wherein, l is the distance between the second wafer and the first wafer, d is the thickness of the glass sheet, n is the refractive index of the glass sheet, and the surface flatness of the glass sheet is within λ / 10, where λ is the wavelength of the light source; and The alignment of the two wafers is performed according to the image acquisition positioning of the first wafer and the second wafer.

2. The alignment method according to claim 1, characterized in that: The selecting the glass sheet according to the following formula includes: selecting the thickness or refractive index of the glass sheet to satisfy the formula.

3. A wafer alignment device, used for aligning two stacked wafers, the alignment device comprising an infrared light source, a microscope, and a glass sheet, wherein: The infrared light source and the microscope are respectively located at two sides of the two wafers in the axial direction of the wafers, and the microscope receives the light transmitted through the two wafers by the infrared light source to collect positioning images. The alignment device also includes: a memory; and a processor coupled to the memory, the processor being configured to: Adjusting the microscope lens to make the image of the first wafer clear, the first wafer being the wafer closest to the microscope lens, fixing the microscope lens, and performing image acquisition and positioning of the first wafer; A glass sheet is selected according to the distance between the second wafer and the first wafer, and the glass sheet is added between the microscope lens and the first wafer, so that the second wafer is imaged clearly in the microscope lens to perform image acquisition and positioning of the second wafer, further comprising: The glass sheets are selected according to the following formula: l=dd / n Wherein, l is the distance between the second wafer and the first wafer, d is the thickness of the glass sheet, n is the refractive index of the glass sheet, and the surface flatness of the glass sheet is within λ / 10. where λ is the wavelength of the light source; and The alignment of the two wafers is performed according to the image acquisition positioning of the first wafer and the second wafer.

4. The alignment device according to claim 3, characterized in that The processor is further configured to: The thickness or refractive index of the glass sheet is selected to satisfy the formula.

5. A computer readable medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the wafer alignment method according to any one of claims 1 to 2 is implemented.

6. A wafer alignment system, comprising: A microscope, an infrared light source, and a plurality of glass sheets, wherein under the irradiation of the infrared light source, the microscope performs image acquisition and positioning on two stacked wafers respectively, wherein the infrared light source and the microscope are respectively located on both sides of the two wafers in the axial direction of the wafers, and the microscope receives the light transmitted through the two wafers by the infrared light source to acquire positioning images; The multiple glass sheets are used to be added between the microscope and the first wafer. The first wafer is the wafer closest to the microscope lens. By adding or replacing the glass sheets to adjust the focus position of the microscope, the image of each wafer can be made clear for image acquisition positioning and alignment.

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