Wafer bonding process
By using a gas with a Joule-Thomson coefficient less than 0 to activate the wafer bonding surface, the problem of bubble defects at the wafer edge was solved, and the yield of the wafer bonding process was improved.
Patent Information
- Application Number
- CN202610091453.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-05-08
AI Technical Summary
In back-illuminated processes, bubble defects are prone to occur at the edge of the wafer after bonding, which affects product yield.
Gases with a Joule-Thomson coefficient less than 0, such as helium or neon, are used as plasma sources to activate the bonding surfaces of the top and bottom wafers. The atmosphere of this gas is maintained during the bonding process to suppress water vapor condensation.
It reduces the formation of moisture at the wafer edges, lowers the likelihood of bubble defects, and improves product yield.
Smart Images
Figure CN122002929A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of integrated circuit manufacturing, specifically to a wafer bonding process. Background Technology
[0002] In back-side illuminated (BSI) processes, the photosensitive element is located above the metal lines, which improves photosensitive efficiency. For back-side illuminated processes, the bonding process that bonds the device wafer and the carrier wafer together is crucial.
[0003] Currently, the bonding process typically uses air as the atmosphere and is activated by nitrogen plasma. During bonding, air escapes from the wafer center and moves towards the wafer edge, expanding under atmospheric pressure. When the pressure suddenly drops, the air temperature decreases by several degrees, leading to supersaturation of water vapor. This water vapor easily condenses into water droplets at the wafer edge, creating bubble defects in the wafer edge region and affecting product yield. Summary of the Invention
[0004] This application provides a wafer bonding process that can solve the problem of bubble defects in the edge region of the wafer after bonding in related technologies.
[0005] This application provides a wafer bonding process, including: Provide the top-layer wafer and the bottom-layer wafer to be bonded; Using a first gas as the plasma source, the bonding surfaces of the top and bottom wafers are activated. The first gas is a gas with a Joule-Thomson coefficient of less than 0. The top and bottom wafers are surface cleaned; The top wafer and the bottom wafer are bonded under the condition of a first gas atmosphere.
[0006] In some embodiments, the first gas is helium or neon.
[0007] In some embodiments, in the step of activating the bonding surfaces of the top and bottom wafers using a first gas as the plasma source, the low-frequency radio frequency power of the plasma generator is 35~45W and the high-frequency radio frequency power is 50~60W.
[0008] In some embodiments, in the step of activating the bonding surfaces of the top wafer and the bottom wafer using a first gas as a plasma source, the activation process lasts for 5 to 60 seconds.
[0009] In some embodiments, the cleaning solution used in the step of cleaning the surface of the top wafer and the bottom wafer is deionized water.
[0010] The technical solution of this application has at least the following advantages: 1. By using a first gas with a Joule-Thomson coefficient less than 0 as the plasma source to activate the bonding surfaces of the top and bottom wafers, the surface states of the bonding surfaces are changed. In subsequent bonding processes, the bonding processes of the top and bottom wafers are performed under the condition of the first gas with a Joule-Thomson coefficient less than 0. This can reduce the formation of water vapor at the wafer edges during the bonding process and reduce the possibility of bubble defects. Attached Figure Description
[0011] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0012] Figure 1 This is a flowchart of a wafer bonding process provided in an exemplary embodiment of this application; Figure 2 This application provides an exemplary embodiment of a bubble defect detection pattern obtained using an ultrasonic scanning microscope in the prior art; Figure 3 This is an exemplary embodiment of the present application, showing a bubble defect detection pattern obtained using an ultrasonic scanning microscope after wafer bonding using the present application. Detailed Implementation
[0013] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0014] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0015] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0016] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0017] This application provides a wafer bonding process, referring to... Figure 1 The wafer bonding process includes the following steps: S1: Provides the top-layer wafer and bottom-layer wafer to be bonded.
[0018] For example, a top-layer wafer and a bottom-layer wafer are provided for bonding processes.
[0019] S2: Using the first gas as the plasma source, the bonding surfaces of the top and bottom wafers are activated. The first gas is a gas with a Joule-Thomson coefficient of less than 0.
[0020] The bonding surface refers to the surface to be bonded in the subsequent bonding process. In this step, the bonding surface activation treatment can be performed on both the top wafer and the bottom wafer at the same time, or the bonding surface activation treatment can be performed on the top wafer and the bottom wafer separately.
[0021] For example, this step is performed in the plasma activation chamber of the bonding machine. A first gas with a Joule-Thomson coefficient less than 0 is introduced into the plasma activation chamber, and a plasma generator (e.g., a radio frequency power supply) is used to ionize the first gas into high-energy plasma. The high-energy plasma formed by ionization bombards the bonding surface. On the one hand, it can remove impurities on the bonding surface, achieving cleaning of the bonding surface. On the other hand, it can also introduce a large number of unsaturated active groups into the bonding surface, thereby activating the bonding surface and facilitating subsequent bonding processes. At the same time, when the first gas enters the vacuum plasma activation chamber from the atmospheric pressure pipeline through a throttling valve, it undergoes throttling expansion. Since the Joule-Thomson coefficient of the first gas is less than 0, the temperature of the first gas spontaneously increases, inhibiting the adsorption and condensation of water vapor on the wafer surface.
[0022] Furthermore, in some embodiments, the first gas is helium or neon.
[0023] Furthermore, in some embodiments, during the activation process, the low-frequency radio frequency power of the plasma generator in the plasma activation chamber is set to 35~45W and the high-frequency radio frequency power is set to 50~60W.
[0024] Furthermore, in some embodiments, the activation treatment lasts for 5 to 60 seconds. Preferably, the activation treatment lasts for 20 seconds.
[0025] S3: Perform surface cleaning on the top and bottom wafers.
[0026] For example, the activated top wafer and / or bottom wafer are transferred to the wafer cleaning unit of the bonding machine and surface cleaning is performed in the wafer cleaning unit.
[0027] Furthermore, in this step, deionized water is used as the cleaning solution. The bonding surface is rinsed by overflow or spraying with deionized water to remove plasma activation byproducts and tiny particulate impurities from the bonding surface.
[0028] Furthermore, in this step, the bonding surface can be rinsed with deionized water as the cleaning solution first, and then high-purity nitrogen gas can be introduced to purge the bonding surface to quickly dry the residual moisture on the bonding surface and avoid water stain contamination.
[0029] S4: Under the condition that the atmosphere is the first gas, perform bonding process on the top wafer and the bottom wafer.
[0030] For example, the top and bottom wafers are transferred to the bonding chamber of a bonding machine, where they are aligned, bonded, pressurized, and cured. The bonding process uses a first gas; that is, during the bonding process, the first gas is introduced into the bonding chamber and maintained at a constant pressure. Because the Joule-Thomson coefficient of the first gas is less than 0, during the bonding process, when the first gas passes through a throttling device under adiabatic conditions, its temperature increases as the pressure decreases, reducing the possibility of water vapor condensation and thus reducing the likelihood of bubble defects at the wafer edge. (Refer to...) Figure 2 and Figure 3 ,in, Figure 2 This shows a prior art pattern of bubble defect detection obtained using ultrasonic scanning microscopy. Figure 3 The image shows a bubble defect detection pattern obtained using an ultrasonic scanning microscope after employing the wafer bonding process described in this application. The comparison shows that the bubble defect (i.e., the green spots in the image) is significantly reduced after using the wafer bonding process described in this application.
[0031] The wafer bonding process provided in this application embodiment activates the bonding surfaces of the top and bottom wafers by using a first gas with a Joule-Thomson coefficient less than 0 as a plasma source, thereby changing the surface states of the bonding surfaces. In subsequent bonding processes, the bonding process is performed on the top and bottom wafers under the condition of the first gas with a Joule-Thomson coefficient less than 0. This can reduce the formation of moisture at the wafer edges during the bonding process, reduce the possibility of bubble defects, and reduce wafer yield loss.
[0032] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.
Claims
1. A wafer bonding process, characterized in that, include: Provide the top-layer wafer and the bottom-layer wafer to be bonded; Using a first gas as the plasma source, the bonding surfaces of the top and bottom wafers are activated. The first gas is a gas with a Joule-Thomson coefficient of less than 0. The top and bottom wafers are surface cleaned; The top wafer and the bottom wafer are bonded under the condition of a first gas atmosphere.
2. The wafer bonding process according to claim 1, characterized in that, The first gas is helium or neon.
3. The wafer bonding process according to claim 1, characterized in that, In the step of activating the bonding surfaces of the top and bottom wafers using a first gas as the plasma source, the low-frequency radio frequency power of the plasma generator is 35~45W and the high-frequency radio frequency power is 50~60W.
4. The wafer bonding process according to claim 1, characterized in that, In the step of activating the bonding surfaces of the top and bottom wafers using a first gas as the plasma source, the activation process lasts for 5 to 60 seconds.
5. The wafer bonding process according to claim 1, characterized in that, In the step of cleaning the surfaces of the top and bottom wafers, the cleaning solution used is deionized water.