Bonding interface state monitoring method

Abstract

The invention discloses a method for monitoring the state of a bonding interface, and the method comprises the steps: carrying out the cleaning and plasma activation of the bonding interface of a bonding structure, depositing liquid drops on the bonding interface, measuring the contact angle between the liquid drops and the bonding interface, and determining the state of the bonding interface according to a comparison table of the contact angle and the bonding effect and the contact angle between the liquid drops and the bonding interface. A reference bonding effect of the bonding interface is obtained, and whether the bonding interface meets the bonding requirement or not is determined. According to the technical scheme, the state of the bonding interface of the bonding structure is monitored, and the bonding effect of the bonding structure is improved.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor technology, and in particular relates to a method for monitoring a bonding interface state. Background Art

[0002] In the process of preparing semiconductor devices, the formation of the bonding structure between wafer and wafer, die and wafer is one of the key steps. However, the state of the bonding interface of the bonding structure will be affected by factors such as time, thus affecting the final bonding effect of the bonding structure. How to monitor the state of the bonding interface of the bonding structure before bonding has become an urgent problem to be solved in the field. Summary of the invention

[0003] The present application proposes a method for monitoring the state of a bonding interface, aiming to monitor the bonding interface of a bonding structure before bonding.

[0004] To achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0005] A method for monitoring the state of a bonding interface is provided, the monitoring method comprising: cleaning and plasma activating the bonding interface of a bonding structure, depositing a liquid droplet on the bonding interface, and measuring the contact angle between the liquid droplet and the bonding interface, obtaining a reference bonding effect of the bonding interface according to a comparison table of contact angle and bonding effect and the contact angle between the liquid droplet and the bonding interface, and determining whether the bonding interface meets the bonding requirements.

[0006] In some embodiments, before cleaning and plasma activating the bonding interface of the bonding structure, the monitoring method further includes: cleaning and plasma activating the bonding interfaces of multiple sampled bonding structures, the process conditions for cleaning and plasma activation of the multiple sampled bonding structures are the same, after different waiting times after the cleaning and plasma activation processes are completed, depositing droplets on the bonding interfaces of different sampled bonding structures, and measuring the contact angle between the droplets and the bonding interface, bonding the multiple sampled bonding structures respectively, and testing the bonded multiple sampled bonding structures respectively to obtain the bonding effects of the multiple sampled bonding structures, so as to obtain a comparison table of contact angles and bonding effects at different waiting times.

[0007] In some embodiments, when it is determined that the bonding interface does not meet the bonding requirements, the above-mentioned monitoring method also includes: cleaning and plasma activating the bonding interface of the bonding structure again, adjusting the waiting time of the bonding structure after the cleaning and plasma activation processes are completed, depositing droplets on the bonding interface, and measuring the contact angle between the droplets and the bonding interface, and obtaining a reference bonding effect of the bonding interface according to a comparison table of contact angles and bonding effects, and the contact angle between the droplets and the bonding interface, until it is determined that the bonding interface meets the bonding requirements.

[0008] In some embodiments, before cleaning and plasma activating the bonding interface of the bonding structure, the above-mentioned monitoring method also includes: cleaning and plasma activating the bonding interfaces of multiple sampled bonding structures, the process conditions for cleaning and plasma activation of the multiple sampled bonding structures are different, depositing droplets on the bonding interfaces of the multiple sampled bonding structures, and measuring the contact angle between the droplets and the bonding interface, analyzing the bonding interfaces of the multiple sampled bonding structures, and obtaining information parameters and bonding effects of the bonding interfaces of the multiple sampled bonding structures, so as to obtain a comparison table of contact angles and bonding effects under different process conditions.

[0009] In some embodiments, when it is determined that the bonding interface does not meet the bonding requirements, the above-mentioned monitoring method also includes: adjusting the process conditions of the bonding interface of the bonding structure, depositing droplets on the bonding interface, and measuring the contact angle between the droplets and the bonding interface, and obtaining a reference bonding effect of the bonding interface according to a comparison table of contact angle and bonding effect, and the contact angle between the droplets and the bonding interface, until it is determined that the bonding interface meets the bonding requirements.

[0010] In some embodiments, multiple bonding structures include a first chip and a wafer, the wafer includes a second chip, the first chip is used to bond with the wafer and is electrically connected to the second chip, the bonding interface between the first chip and the second chip is cleaned and plasma activated, droplets are deposited on the bonding interface of the first chip and the second chip respectively, and the contact angle between the droplets and the bonding interface is measured, and a reference bonding effect of the bonding interface between the first chip and the second chip is obtained according to a comparison table of contact angle and bonding effect, and the contact angle between the droplets and the bonding interface, and it is determined whether the bonding interface between the first chip and the second chip meets the bonding requirements.

[0011] In some embodiments, multiple bonding structures include a first wafer and a second wafer, the first wafer is used to bond with the second wafer, the bonding interface between the first wafer and the second wafer is cleaned and plasma activated, droplets are deposited on the bonding interface of the first wafer and the second wafer respectively, and the contact angle between the droplets and the bonding interface is measured, and a reference bonding effect of the bonding interface between the first wafer and the second wafer is obtained according to a comparison table of contact angle and bonding effect, and the contact angle between the droplets and the bonding interface, and it is determined whether the bonding interface between the first wafer and the second wafer meets the bonding requirements.

[0012] In some embodiments, droplets are respectively deposited on the bonding interface of the first wafer and the second wafer, and the contact angles between the droplets and the bonding interface are measured, including: dividing the bonding interface of the first wafer and the second wafer into multiple regions, depositing multiple droplets in the multiple regions of the bonding interface of the first wafer, and measuring the contact angles between the multiple droplets and the bonding interface; and, depositing multiple droplets in the multiple regions of the bonding interface of the second wafer, and measuring the contact angles between the multiple droplets and the bonding interface.

[0013] The method for monitoring the bonding interface status provided in the embodiment of the present application, after cleaning and plasma activating the bonding interface of the bonding structure, deposits droplets on the bonding interface and measures the contact angle between the droplets and the bonding interface. It is only necessary to look up in a comparison table of contact angles and bonding effects to obtain a reference bonding effect of the bonding interface, so as to determine whether the bonding interface meets the bonding requirements based on the reference bonding effect. The process flow of the monitoring method is simple, the cost is low, and the time to obtain the reference bonding effect is short, which improves the feasibility of the method.

[0014] When the bonding interface meets the bonding requirements, the bonding structure is bonded; when the bonding interface does not meet the bonding requirements, the bonding structure is not bonded. This monitoring of the bonding interface state before bonding enables the screening of bonding structures that meet the bonding requirements before bonding, greatly improving the final bonding effect of the bonding structure and the yield of the final product.

[0015] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 A flow chart of a method for monitoring a bonding interface state provided in an embodiment of the present application;

[0018] Figure 2 to Figure 5 for Figure 1 Diagram of the steps of the monitoring method in

[0019] Figure 6 Schematic diagram of calculating surface tension for Young's contact angle;

[0020] Figure 7 Schematic diagram of the contact angle between the water droplet and the bonding interface;

[0021] Figure 8-Figure 9A diagram showing the steps of forming a bonding structure in an embodiment of the present application;

[0022] Fig.10 A flowchart of a comparison table of contact angles and bonding effects under different waiting times obtained in an embodiment of the present application;

[0023] Fig.11 A detection diagram of the bonding interface of the bonding structure provided in the embodiment of the present application;

[0024] Fig.12 This is a flow chart of obtaining a comparison table of contact angle and bonding effect under different process conditions in the embodiments of the present application. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0026] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0027] In the description of the present application, “plurality” means two or more.

[0028] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0029] When describing some embodiments, the expression "connected" and its derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "electrically connected" indicates, for example, that two or more components are in direct physical or electrical contact, and may also mean that two or more components are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0030] At present, in the process lines of advanced packaging, the commonly used bonding methods are fusion bonding or hybrid bonding. Before two bonding structures are bonded, the bonding interface of the two bonding structures needs to be cleaned and plasma activated to remove surface contaminants on the bonding interface and improve the strength of subsequent bonding. After the bonding is completed, the entire bonding structure is annealed to achieve electrical connection between wafers or chips.

[0031] During the process of cleaning and plasma activation of the bonding interface of the two bonding structures, the bonding interface of the bonding structure presents different states according to the different solvents selected for cleaning, the particles selected for subsequent plasma activation, and the activation process conditions. The bonding interface can be divided into two categories: hydrophilic bonding and hydrophobic bonding.

[0032] The formation of the hydrophilic bonding interface mainly uses a mixed aqueous solution of ammonia and hydrogen peroxide (RCA) or piranha solution (a mixed solution of concentrated sulfuric acid and hydrogen peroxide) to clean the clean and polished wafer surface, forming a hydrophilic surface with a high density of hydroxyl (-OH), so that water molecules in the atmospheric environment are easily adsorbed on the hydrophilic surface. In the subsequent plasma activation process, argon (Ar) or nitrogen (N2) plasma is used to activate the wafer surface. Under subsequent room temperature conditions, when two wafers with hydrophilic surfaces are bonded together, the following reaction will occur: Si-OH+HO-Si→Si-O-Si+H2O. In the subsequent high-temperature annealing process, the weak intermolecular forces (van der Waals forces and hydrogen bonds) between the bonding interfaces of the two wafers will be converted into stronger Si-O-Si covalent bonds, thereby obtaining a strong bonding interface.

[0033] The formation of a hydrophobic interface mainly uses hydrofluoric acid (HF) to treat the dielectric layer on the surface of the wafer. The surface of the wafer is covered with silicon-hydrogen bonds (Si-H) with hydrophobic properties. At the same time, the wafer surface is subsequently activated by Ar and N2 plasma. The wafers are first directly bonded at room temperature, and the subsequent heating annealing process follows the following reaction: Si-H+H-Si→Si-Si+H2↑. Si-Si covalent bonds are formed between the bonding interfaces of the two wafers, thereby obtaining a strong bonding interface.

[0034] In the process of melt bonding, the bonding interface is all dielectric film layer structure. In addition to the bonding accuracy, melt bonding only needs to complete the structural connection, that is, it only needs to ensure the strength of the bonding interface. In the process of hybrid bonding, the bonding interface has a dielectric film layer and a copper structure, where the copper structure ensures the electrical connection between the bonded wafers. Since the information transmission rate (Transmission Rate) of copper in hybrid bonding is less than 10%, most of the area of ​​the bonding interface is the dielectric film layer. Therefore, the structural connection between the wafers, that is, the bonding strength in hybrid bonding also depends on the connection between the dielectric film layers. In summary, the bonding quality between the dielectric film layers determines the bonding strength of the bonding structure in melt bonding and hybrid bonding, that is, it determines the bonding strength between the bonding structures.

[0035] However, due to the influence of factors such as the film morphology after chemical mechanical planarization, the material of the dielectric film layer used for bonding, the type of cleaning solution, the plasma activation process, the waiting time after cleaning and plasma activation, and the bonding process, the bonding strength of the dielectric film layer will change, thereby affecting the subsequent bonding effect.

[0036] In order to solve the above problems, the present application proposes a method for monitoring the bonding interface state. Figure 1 A flow chart of a method for monitoring a bonding interface state provided in an embodiment of the present application, Figure 2 to Figure 5 for Figure 1 Diagram of the steps in the monitoring method.

[0037] The bonding interface in the embodiments provided in the present application can be a bonding interface between wafers or a bonding interface between chips and wafers. Figure 1 The flowchart in the figure is applicable to the bonding structure of wafer-to-wafer bonding and also to the bonding structure of chip-to-wafer bonding. First, the bonding structure of wafer-to-wafer bonding is used for explanation. Before starting the monitoring of the bonding interface status, the following steps need to be completed:

[0038] Step S11: Figure 2 As shown, a first dielectric film layer 11 is deposited on the surface of a first wafer 1. The first dielectric film layer 11 may be silicon oxide (SiO2), silicon nitride (SiN), silicon carbon nitride (SiCN), etc. The first dielectric film layer 11 is used as a bonding medium. At the same time, a Damascus process is used to manufacture a bonding copper plate (Pad) and a via (Via) to obtain a first copper structure 12, thereby obtaining a first bonding structure A. In the same manner, a second dielectric film layer 21 is formed on the surface of a second wafer 2, and a second copper structure 22 is manufactured using the Damascus process to obtain a second bonding structure B.

[0039] Step S12: Figure 3As shown, the first surface 110 of the first dielectric film layer 11 away from the first wafer 1 and the second surface 210 of the second dielectric film layer 21 away from the second wafer 2 are planarized, while the copper plates used for bonding in the first copper structure 12 and the second copper structure 22 are kept to form a certain dishing morphology, wherein the first surface 110 and the second surface 210 serve as the bonding interfaces of the subsequent first bonding structure A and the second bonding structure B, respectively.

[0040] After completing the above steps S11 to S12, the bonding interface state is monitored, such as Figure 1 As shown, the monitoring method includes the following steps S1 to S3:

[0041] Step S1: Figure 4 As shown, the bonding interface of the first bonding structure A and the second bonding structure B is cleaned and plasma activated using Ar, N2 plasma, etc. For the first dielectric film layer 11 of the first wafer 1 and the second dielectric film layer 21 of the second wafer 2, the cleaning and plasma activation process can increase the dangling bonds on the bonding surface while removing the contaminants on the bonding surface, generating more radicals, thereby improving the subsequent bonding strength of the first wafer 1 and the second wafer 2. For the first copper structure 12 of the first wafer 1 and the second copper structure 22 obtained from the second wafer 2, cleaning can remove the contaminants on the surface of the copper structure, and plasma activation can react with copper to generate copper nitride (Cu x N), copper nitride can protect the copper inside the first dielectric film layer 11 and the second dielectric film layer 21 from being oxidized. In the subsequent bonding process, Cu x N can be decomposed into Cu by heating, so as to complete the electrical connection between the first wafer 1 and the second wafer 2.

[0042] Step S2: Figure 4 and Figure 5 As shown, the first surface 110 of the first bonding structure A is the bonding interface, the second surface 210 of the second bonding structure B is the bonding interface, droplets 3 are deposited on the two bonding interfaces respectively, and the contact angle θ between the droplets 3 and the bonding interfaces is measured. Figure 5 Taking the illustration of the second bonding structure B as an example, a droplet 3 is deposited on the second surface 210 . In the local enlarged view of the position M where the droplet 3 is located, the contact angle θ between the droplet 3 and the bonding interface can be seen.

[0043] Taking droplet 3 as a water droplet as an example, from a macroscopic perspective, the surface micro-roughness, active groups, dangling bonds and other subtle characteristics of the bonding interface after cleaning and plasma activation processes will change the surface tension of the bonding interface. Water droplets are deposited on the bonding interface, and the contact angle between the water droplet and the bonding interface can be measured using technologies such as a contact angle meter. This contact angle is the Young's contact angle. Figure 6Schematic diagram of calculating surface tension for Young's contact angle, such as Figure 6 As shown, given the surface tension of air and water droplets, the surface tension of the bonding interface can be calculated to determine the hydrophilicity and hydrophobicity of the bonding interface, as well as the changes in the microstructure.

[0044] is a schematic diagram of the contact angle between the water droplet and the bonding interface, as shown in Figure 7 As shown, the contact angle θ between the water droplet and the bonding interface can be similar to cases a, b, c, d, etc. in the figure.

[0045] From a microscopic point of view, the strength of the interaction between the water droplet molecules and the surface molecules of the bonding interface determines the hydrophilicity and hydrophobicity of the bonding interface surface. For example, a microscopic quantity w can be defined to reflect the surface hydrophilicity and hydrophobicity of the bonding interface. w is the ratio of hydrogen bond energy to (single molecule) adsorption energy, and (single molecule) adsorption energy better represents the strength of the surface binding to water molecules in the water molecule structure. Qualitatively speaking, w = 1 is a rough dividing line between the hydrophilic area and the hydrophobic area. And we get a rough relationship between the microscopic w and the macroscopic contact angle θ: θ = 180°-108° / w. Therefore, by the size of the contact angle θ, combined with the relationship between w and θ, it can be judged whether the bonding interface is hydrophilic or hydrophobic.

[0046] In summary, the change in the structure of the bonding interface 41 can be determined by the contact angle θ between the droplet 3 and the bonding interface 41 . In combination with the above discussion, the state of the bonding interface 41 can be determined by the following steps.

[0047] In some embodiments, in the above step S2, in which the droplets 3 are deposited on the two bonding interfaces respectively and the contact angle θ between the droplets 3 and the bonding interface is measured, the first surface 110 of the first bonding structure A and the second surface 210 of the second bonding structure B can be divided into a plurality of regions, a plurality of droplets are deposited in the plurality of regions of the first surface 110, and the contact angles between the plurality of droplets and the bonding interface 41 are measured. It can be understood that the deposition of a plurality of droplets in the plurality of regions of the first surface 110 can be performed by dividing the first surface 110 into different regions according to different radii, and measuring a plurality of groups of contact angle data in different regions to improve the accuracy of the monitoring result of the bonding interface of the first bonding structure A.

[0048] Furthermore, multiple droplets are deposited in multiple regions of the second surface 210, and the contact angles between the multiple droplets and the bonding interface are measured. It can be understood that multiple droplets are deposited in multiple regions of the second surface 210. Similarly, the second surface 210 can be divided into different regions according to different radii, and several groups of contact angle data are measured in different regions to improve the accuracy of the monitoring result of the bonding interface of the second bonding structure B.

[0049] Step S3: According to the comparison table of contact angle θ and bonding effect, and the contact angle θ between the droplet 3 and the bonding interface, the reference bonding effect of the two bonding interfaces is obtained, and it is determined whether the two bonding interfaces meet the bonding requirements. The "reference bonding effect" refers to the expected effect after bonding the bonding interface when the bonding interface is not bonded.

[0050] For example, Figure 8-Figure 9 FIG. 1 is a step diagram for forming a bonding structure in an embodiment of the present application. When both bonding interfaces meet the bonding requirements, as shown in FIG. Figure 8 As shown, the first bonding structure A and the second bonding structure B are bonded to obtain a complete bonding structure, and then as shown Fig. 9 As shown, the first bonding structure A and the second bonding structure B after bonding are annealed to form more chemical bonds between the first dielectric film layer 11 and the second dielectric film layer 12 to ensure the bonding strength, so that the dish-shaped (Dishing) morphology of the copper plates used for bonding in the first copper structure 12 and the second copper structure 22 is expanded by heat and contacts each other, thereby completing the electrical connection between the first wafer 1 and the second wafer 2.

[0051] The method for monitoring the bonding interface status provided in the embodiment of the present application, after cleaning and plasma activating the bonding interface of the bonding structure, deposits droplets on the bonding interface and measures the contact angle between the droplets and the bonding interface. It is only necessary to look up in a comparison table of contact angles and bonding effects to obtain a reference bonding effect of the bonding interface, so as to determine whether the bonding interface meets the bonding requirements based on the reference bonding effect. The process flow of the monitoring method is simple, the cost is low, and the time to obtain the reference bonding effect is short, which improves the feasibility of the method.

[0052] When the bonding interface meets the bonding requirements, the bonding structure is bonded; when the bonding interface does not meet the bonding requirements, the bonding structure is not bonded. This monitoring of the bonding interface state before bonding enables the screening of bonding structures that meet the bonding requirements before bonding, greatly improving the final bonding effect of the bonding structure and the yield of the final product.

[0053] In some embodiments, the comparison table of contact angle θ and bonding effect may be a comparison table of contact angle θ and bonding effect under different waiting times, and a comparison table of contact angle θ and bonding effect under different process conditions.

[0054] In some embodiments, Fig.10 In order to obtain a flow chart of a comparison table of contact angle and bonding effect under different waiting times, before cleaning and plasma activation of the bonding interface of the first bonding structure A and the second bonding structure B, as shown in FIG. Fig.10As shown, the monitoring method further includes the following steps S101 to S103, for obtaining a comparison table of contact angle θ and bonding effect under different waiting times:

[0055] Step S101: providing a plurality of sampling bonding structures, illustratively, the structures of the plurality of sampling bonding structures are the same as the first bonding structure A or the second bonding structure B, and performing cleaning and plasma activation on the bonding interfaces of the plurality of sampling bonding structures, wherein the process conditions for cleaning and plasma activation of the plurality of sampling bonding structures are the same, and the process conditions include the surface bonding material of the bonding interface, the solution for cleaning the bonding interface, and the conditions for plasma activation, etc.

[0056] Step S102: after different waiting times for the cleaning and plasma activation processes to be completed, droplets are deposited on the bonding interfaces of different sampled bonding structures, and contact angle data of multiple groups of droplets and the bonding interfaces are measured by a measurement technique such as an antenna meter.

[0057] Step S103: Bonding the plurality of sample bonding structures respectively, then annealing the plurality of sample bonding structures, and then detecting the bonding interfaces of the plurality of bonding structures after annealing respectively, to obtain the following: Fig.11 The bonding accuracy measurement (Bonding OVL) result (a) and the ultrasonic bubble defect detection (CSAM Bubble Defect) result (b) are shown. By analyzing the above two detection results, the bonding effects of multiple bonding structures can be obtained, so as to obtain a comparison table of contact angle and bonding effect under different waiting times.

[0058] In some embodiments, in the above step S3, whether the bonding effects of multiple bonding structures meet the process requirements is judged according to the comparison table of contact angles and bonding effects at different waiting times. When the bonding interface does not meet the bonding requirements, the bonding interface of the bonding structure that does not meet the bonding requirements is cleaned and plasma activated again, and the waiting time of the bonding structure after the cleaning and plasma activation process is adjusted. Then, droplets are deposited on the bonding interface, and the contact angle between the droplets and the bonding interface is measured. According to the comparison table of contact angles and bonding effects at different waiting times and the contact angle between the droplets and the bonding interface, a reference bonding effect of the bonding interface is obtained until it is determined that the bonding interface meets the bonding requirements.

[0059] Since the comparison table of contact angle and bonding effect under different waiting times has been obtained, when there is a bonding interface that does not meet the bonding requirements, after obtaining the contact angle between the bonding interface that does not meet the bonding requirements and the droplet, it can be compared with the comparison table to optimize the waiting time of the bonding structure after the cleaning and plasma activation process is completed. In addition, the bonding effect of the bonding structure can be directly judged by the contact angle, without the need for subsequent bonding, annealing, bonding bubble detection, and bonding strength detection, which greatly simplifies the process flow.

[0060] In some embodiments, Fig.12 In order to obtain a flow chart of a comparison table of contact angle and bonding effect under different process conditions, before cleaning and plasma activation of the bonding interface of the first bonding structure A and the second bonding structure B, as shown in FIG. Fig.12 As shown, the monitoring method further includes the following steps S111 to S113, for obtaining a comparison table of contact angles and bonding effects under different process conditions:

[0061] Step S111: cleaning and plasma activating the bonding interfaces of the plurality of sample bonding structures, but the process conditions for cleaning and plasma activation of the plurality of sample bonding structures are different, wherein the process conditions include the solvent selected for cleaning, the particles selected for plasma activation, the activation process conditions, etc.

[0062] Step S112: depositing droplets on the bonding interfaces of the plurality of sampled bonding structures, and measuring data of contact angles between the plurality of groups of droplets and the bonding interfaces by using a measurement technique such as an antenna meter.

[0063] Step S113: Analyze the bonding interfaces of multiple sampled bonding structures, for example, by characterizing and analyzing the bonding interfaces through XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope), TEM (transmission electron microscope), etc., to obtain information parameters and bonding effects of the bonding interfaces of the multiple sampled bonding structures, so as to obtain a comparison table of contact angles and bonding effects under different process conditions.

[0064] In some embodiments, in the above step S3, according to the comparison table of contact angle and bonding effect under different process conditions, it is judged whether the bonding effect of multiple bonding structures meets the process requirements. In the case that the bonding interface does not meet the bonding requirements, after adjusting the process conditions of the bonding interface of the bonding structure, the bonding interface of the bonding structure that does not meet the bonding requirements is cleaned and plasma activated again, and then droplets are deposited on the bonding interface, and the contact angle between the droplets and the bonding interface is measured. According to the comparison table of contact angle and bonding effect, and the contact angle between the droplets and the bonding interface that has been cleaned and plasma activated again, the contact angle is compared with the comparison table to obtain a reference bonding effect of the bonding interface, until it is determined that the bonding interface meets the bonding requirements.

[0065] Since the comparison table of contact angle and bonding effect under different process conditions has been obtained, when there is a bonding interface that does not meet the bonding requirements, after obtaining the contact angle between the bonding interface that does not meet the bonding requirements and the droplet, it can be compared with the comparison table, and the bonding interface can be reworked (rework) by solvent cleaning, plasma activation and other processes. In addition, the bonding effect of the bonding structure can be directly judged by the contact angle, without the need for subsequent bonding, annealing, bonding bubble detection and bonding strength detection, which greatly simplifies the process flow.

[0066] In some embodiments, the chip-to-wafer bonding process may also be applied as follows Figure 1 The monitoring method shown in the flow chart monitors the bonding interface between the chip and the wafer, such as Figure 1 As shown, the method for monitoring the bonding interface state of the chip and wafer bonding process includes the following steps S1 to S3:

[0067] Step S1: provide a plurality of bonding structures, the plurality of bonding structures comprising a first chip and a wafer, the wafer comprising a second chip, the first chip being used for bonding with the wafer, and the first chip being electrically connected to the second chip on the wafer, after the first chip and the second chip are prepared, the bonding interface between the first chip and the second chip is cleaned and plasma activated.

[0068] Step S2: depositing droplets on the bonding interfaces of the first chip and the second chip respectively, and measuring the contact angles of the droplets with the bonding interface of the first chip and the contact angles of the droplets with the bonding interface of the second chip respectively.

[0069] Step S3: According to the comparison table of contact angle and bonding effect under different waiting times, or the comparison table of contact angle and bonding effect under different process conditions, the contact angle between the droplet and the bonding interface is compared with the above two comparison tables to obtain a reference bonding effect of the bonding interface between the first chip and the second chip, and determine whether the bonding interface between the first chip and the second chip meets the bonding requirements.

[0070] Since in the process of bonding the first chip to the wafer, each first chip needs to be bonded to the wafer in turn, the process time is very long. Therefore, before bonding the first chip to the wafer, the contact angle of the droplet is tested on the bonding interface using the monitoring method provided in the embodiment of the present application. By comparing with the reference table, the reference bonding effect can be obtained in advance, so as to determine whether the first chip needs to be reworked, thereby greatly improving the bonding effect of the subsequent bonding of the first chip to the wafer and improving the yield of the final product.

[0071] Exemplarily, the contact angle between the droplet and the bonding interface is compared with a comparison table of contact angles and bonding effects at different waiting times. When the reference bonding effect obtained by comparison does not meet the requirements, the bonding interface of the bonding structure that does not meet the bonding requirements is re-cleaned and reworked by plasma activation, and then the droplet is deposited on the bonding interface, and the contact angle between the droplet and the bonding interface is measured, and the contact angle is compared with the comparison table until the reference bonding effect that meets the bonding requirements is obtained.

[0072] Exemplarily, the contact angle between the droplet and the bonding interface is compared with a comparison table of contact angles and bonding effects under different process conditions. When the reference bonding effect obtained by comparison does not meet the requirements, the process conditions of the bonding interface of the bonding structure are adjusted, and then the bonding interface of the bonding structure that does not meet the bonding requirements is cleaned and plasma activated again. Then, the droplet is deposited on the bonding interface, and the contact angle between the droplet and the bonding interface is measured. The contact angle is compared with the comparison table until the reference bonding effect that meets the bonding requirements is obtained.

[0073] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for monitoring a bonding interface state, characterized in that: include: Cleaning and plasma activation of the bonding interface of the bonded structure; depositing a liquid droplet on the bonding interface, and measuring a contact angle between the liquid droplet and the bonding interface; According to the comparison table of contact angle and bonding effect and the contact angle between the liquid droplet and the bonding interface, a reference bonding effect of the bonding interface is obtained, and it is determined whether the bonding interface meets the bonding requirements.

2. The monitoring method according to claim 1, characterized in that: Before cleaning and plasma activating the bonding interface of the bonding structure, the monitoring method further comprises: Cleaning and plasma activating the bonding interfaces of the plurality of sample bonding structures, wherein the cleaning and plasma activation process conditions of the plurality of sample bonding structures are the same; depositing droplets on bonding interfaces of different sample bonding structures after different waiting times after the cleaning and plasma activation processes are completed, and measuring contact angles between the droplets and the bonding interfaces; Bonding the plurality of sampling bonding structures respectively; The plurality of bonded sample bonding structures are tested respectively to obtain bonding effects of the plurality of bonded sample bonding structures, so as to obtain a comparison table of contact angles and bonding effects under different waiting times.

3. The monitoring method according to claim 2, characterized in that: In the case where it is determined that the bonding interface does not meet the bonding requirements, the monitoring method further includes: cleaning and plasma activating the bonding interface of the bonding structure again; adjusting a waiting time of the bonding structure after the cleaning and plasma activation processes are completed, depositing a droplet on the bonding interface, and measuring a contact angle between the droplet and the bonding interface; According to the comparison table of contact angle and bonding effect and the contact angle between the liquid droplet and the bonding interface, a reference bonding effect of the bonding interface is obtained until it is determined that the bonding interface meets the bonding requirements.

4. The monitoring method according to claim 1, characterized in that: Before cleaning and plasma activating the bonding interface of the bonding structure, the monitoring method further comprises: Cleaning and plasma activating the bonding interfaces of the plurality of sampling bonding structures, wherein the cleaning and plasma activation process conditions of the plurality of sampling bonding structures are different; Depositing liquid droplets on bonding interfaces of the plurality of sampling bonding structures, and measuring contact angles between the liquid droplets and the bonding interfaces; The bonding interfaces of the plurality of sampled bonding structures are analyzed to obtain information parameters and bonding effects of the bonding interfaces of the plurality of sampled bonding structures, so as to obtain a comparison table of contact angles and bonding effects under different process conditions.

5. The monitoring method according to claim 4, characterized in that: In the case where it is determined that the bonding interface does not meet the bonding requirements, the monitoring method further includes: Adjusting the process conditions of the bonding interface of the bonding structure; depositing a liquid droplet on the bonding interface, and measuring a contact angle between the liquid droplet and the bonding interface; According to the comparison table of contact angle and bonding effect and the contact angle between the liquid droplet and the bonding interface, a reference bonding effect of the bonding interface is obtained until it is determined that the bonding interface meets the bonding requirements.

6. The monitoring method according to claim 1, characterized in that: The plurality of bonding structures include a first chip and a wafer, wherein the wafer includes a second chip; the first chip is used to bond with the wafer and is electrically connected to the second chip; Cleaning and plasma activating the bonding interface between the first chip and the second chip; Depositing droplets on the bonding interfaces of the first chip and the second chip respectively, and measuring contact angles between the droplets and the bonding interfaces; According to the comparison table of contact angle and bonding effect, and the contact angle between the droplet and the bonding interface, a reference bonding effect of the bonding interface between the first chip and the second chip is obtained, and it is determined whether the bonding interface between the first chip and the second chip meets the bonding requirements.

7. The monitoring method according to claim 1, characterized in that: The plurality of bonding structures include a first wafer and a second wafer, wherein the first wafer is used for bonding with the second wafer; Cleaning and plasma activating the bonding interface between the first wafer and the second wafer; Depositing droplets on bonding interfaces of the first wafer and the second wafer respectively, and measuring contact angles between the droplets and the bonding interfaces; According to the comparison table of contact angle and bonding effect, and the contact angle between the droplet and the bonding interface, a reference bonding effect of the bonding interface between the first wafer and the second wafer is obtained, and it is determined whether the bonding interface between the first wafer and the second wafer meets the bonding requirements.

8. The monitoring method according to claim 7, characterized in that: Depositing droplets on bonding interfaces of the first wafer and the second wafer respectively, and measuring contact angles between the droplets and the bonding interfaces, comprising: dividing a bonding interface between the first wafer and the second wafer into a plurality of regions; A plurality of droplets are deposited in a plurality of regions of the bonding interface of the first wafer, and contact angles between the plurality of droplets and the bonding interface are measured; and a plurality of droplets are deposited in a plurality of regions of the bonding interface of the second wafer, and contact angles between the plurality of droplets and the bonding interface are measured.

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