Simulation analysis method for salient point forming in chip flip-chip bonding

Abstract

The invention discloses a simulation analysis method for salient point forming in chip flip bonding, and belongs to the field of chip integration. The method comprises the following steps: establishing a three-dimensional finite element model of single salient point flip-chip bonding; performing finite element division on the three-dimensional finite element model to obtain a plurality of grids; and setting the bonding pressure, the bonding time and the bonding temperature according to the bonding process parameters, generating a function image and system stress distribution corresponding to the plurality of grids, and obtaining a simulation analysis result of the salient points. Therefore, more comprehensive analysis and rule summarization can be synchronously carried out on a plurality of parameters of the bonding process, manpower and time costs are greatly saved due to simulation repeatability, and the precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chip integration, and in particular to a simulation analysis method for bump forming in chip flip-chip bonding. Background Art

[0002] With the rapid development of wireless communications in recent years, the improvement of functions and performance requirements has made the current optical network system increasingly complex, which in turn has led to problems such as increased energy consumption. In order to solve these problems, people have turned their attention to the field of photonic integration. Compared with traditional discrete devices, photonic integration has huge advantages in size, energy consumption, etc.

[0003] Photonic integration involves a wide variety of optical devices, including lasers, electro-optic modulators, photodetectors, optical attenuators, optical multiplexers, demultiplexers, and optical amplifiers. Flip-chip bonding technology is a very important part of it. Under current technical conditions, bonding III-V lasers on silicon substrates is a common method. Bonding is to combine two wafers or devices through an intermediate layer or directly by heating or pressurizing, avoiding direct contact between semiconductor atoms, thereby effectively solving the problem of III-V materials growing on silicon.

[0004] However, the bumps may fail, that is, the bumps cannot effectively connect the laser to the silicon wafer. This is related to the height, diameter and other parameters of the bumps. The reliability of bumps of different heights and diameters varies significantly. At the same time, experimental research will cause many problems due to the small size of the bumps. First, it is difficult to accurately measure small changes in diameter and height; second, it is difficult to measure covered bumps; finally, it is impossible to analyze the stress and strain changes of the bumps and gold electrodes during the bonding process in real time. Summary of the invention

[0005] The invention provides a simulation analysis method for bump forming in chip flip-chip bonding, establishes a three-dimensional finite element model of single bump flip-chip bonding for simulation, and improves simulation efficiency and quality.

[0006] The embodiment of the present invention provides a simulation analysis method for bump forming in chip flip-chip bonding, comprising the following steps:

[0007] Establish a three-dimensional finite element model of single bump flip-chip bonding;

[0008] Performing finite element division on the three-dimensional finite element model to obtain a plurality of grids;

[0009] The bonding pressure, bonding time and bonding temperature are set according to the bonding process parameters, and the function images and system stress distribution corresponding to multiple grids are generated to obtain the simulation analysis results of the bumps.

[0010] Optionally, in one embodiment of the present invention, the three-dimensional finite element model consists of five parts: a substrate, an electrode, a bump, a laser and a tooling, and in the simulation, the load force is used instead of the tooling.

[0011] Optionally, in one embodiment of the present invention, the three-dimensional finite element model is divided into finite elements using a mapped mesh method.

[0012] Optionally, in one embodiment of the present invention, when performing finite element division, appropriate mesh division is performed according to the position, size relationship and analysis focus between the blocks.

[0013] The simulation analysis method for bump forming in chip flip-chip bonding according to the embodiment of the present invention has the following beneficial effects:

[0014] 1. The modeling is relatively simple: the model consists of five parts: substrate, electrode, bump, laser and tooling. It has fewer components but complete key components. The size, material and other parameters are set according to the required simulation device to avoid cumbersome modeling process.

[0015] 2. More reasonable meshing: Using mapped meshing, the mesh size and shape can be precisely controlled, the simulation accuracy can be improved, and it is more realistic. At the same time, the meshing is properly divided according to the position, size relationship and analysis focus of each block, which greatly reduces the meshing work, reduces the amount of calculation, and shortens the time required for solution.

[0016] 3. Easy to change parameters: Due to the repeatability of simulation, the bonding process parameters studied can be adjusted multiple times, which is convenient for obtaining the optimal solution in continuous testing. Compared with experimental methods, it reduces the difficulty of data measurement, experimental costs, and greatly improves accuracy.

[0017] 4. The results are concise and intuitive: The corresponding function graphs and stress distribution diagrams generated by the simulation results are concise, clear and intuitive, which greatly increases the readability of the results and facilitates researchers to extract and summarize the rules, greatly improving efficiency.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0020] Figure 1 A flowchart of a simulation analysis method for bump forming in chip flip-chip bonding provided according to an embodiment of the present invention;

[0021] Figure 2 A three-dimensional perspective view of a model of an embodiment of the present invention;

[0022] Figure 3 This is a front view of a model of an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of mapping grid division according to an embodiment of the present invention;

[0024] Figure 5 It is an overall simulation schematic diagram of an embodiment of the present invention;

[0025] Figure 6 A schematic diagram of an indium column simulation according to an embodiment of the present invention;

[0026] Figure 7 It is a line graph of the applied pressure and the compression amount of the indium column height according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, examples of which 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 intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0028] Figure 1 The present invention is a flowchart of a simulation analysis method for bump forming in chip flip-chip bonding according to an embodiment of the present invention.

[0029] like Figure 1 As shown, the simulation analysis method for bump forming in the chip flip-chip bonding includes the following steps:

[0030] In step S101, a three-dimensional finite element model of a single bump flip-chip bonding is established.

[0031] In an embodiment of the present invention, a three-dimensional finite element model of a single bump flip-chip bonding is established using the ANSYS Workbench platform for simulation. Figure 2 and Figure 3 As shown in the figure, the three-dimensional finite element model consists of five parts, namely, substrate, electrode, bump, laser and tooling. According to the actual needs and without affecting the authenticity and accuracy of the simulation results, the model size can be flexibly adjusted, which can greatly improve the applicability and extensibility of this simulation analysis method, and can be applied to more bumps and lasers of different sizes for simulation testing.

[0032] Considering that the tooling is actually a force-applying object, the load force can be directly used to replace the tooling, and then the required size, material and other parameters of each part can be set.

[0033] In step S102, finite element division is performed on the three-dimensional finite element model to obtain a plurality of meshes.

[0034] There are three ANSYS / LS-DYNA meshing methods for finite element partitioning of three-dimensional finite element models. In order to ensure the accuracy of the solution results and reduce the time required for the solution, the present invention chooses to use mapped meshing. In addition, since directly applying load force to linear elastic materials does not conform to the process of applying pressure through a fixture structure in reality, a fixture structure is used in the modeling process.

[0035] When using mapped meshing for finite element models, the mesh should be divided appropriately according to the position, size relationship and analysis focus of each block. For example, if the stress and strain at the bumps need to be analyzed in detail, the mesh at the bumps will be more densely divided, while the substrates, lasers and tooling that are much larger than the bumps can be divided more sparsely.

[0036] In step S103, the bonding pressure, bonding time, and bonding temperature are set according to the bonding process parameters, and function images and system stress distribution corresponding to a plurality of grids are generated to obtain simulation analysis results of the bumps.

[0037] The bonding pressure, bonding time, and bonding temperature are set according to the bonding process parameters, and the data table is calculated using the ANSYS software, and the system stress distribution is generated at the same time to obtain the simulation analysis results of the bumps. Since the function graph automatically generated by the ANSYS software is relatively rough, the limitations of choosing other mapping software for drawing are relatively small, easy to personalize, and visually clearer, so the embodiments of the present application can use other software for drawing.

[0038] In an embodiment of the present invention, indium can be selected as the bump material, and parameters such as bonding pressure, bonding time, and bonding temperature can be set according to the bonding process parameters to obtain the change in the size of the indium column during the indium column bonding and molding process and the stress-strain analysis results. This allows for a more comprehensive analysis and law summary of multiple parameters of the bonding process to be performed simultaneously. The repeatability of the simulation also greatly saves manpower and time costs and improves accuracy.

[0039] Specifically, when setting parameters such as bonding pressure, bonding time, and bonding temperature according to the bonding process parameters under study, do not exceed the melting point of each material, otherwise the results will be invalid. The corresponding function graph and system stress distribution generated can be used to more intuitively adjust parameters and summarize rules.

[0040] The simulation analysis method for bump forming in chip flip-chip bonding of the present invention is described below through specific embodiments.

[0041] like Figure 2 and Figure 3As shown, by modeling the physical object to be simulated, setting the size and material, and completing the preliminary preparations, a pressure test is carried out. Here, as a demonstration, the substrate is a prism with a square cross-section made of Si material, with a side length of 0.2mm and a thickness of 0.05mm; the electrode is a thin layer with a square cross-section made of Au material, with a side length of 0.1mm and a thickness of 1μm; the bump is made of In material, which is a co-central axis cylinder with a diameter of 60μm and a height of 6μm. The laser is made of Si material, with a square cross-section prism, a side length of 0.1mm and a thickness of 0.05mm.

[0042] Mapping meshing is performed on the three-dimensional finite element model, such as Figure 4 As shown in Figure 2, according to the different research objects, the model can be analyzed as a whole and locally, such as Figure 5 and Figure 6 As shown in the figure, macroscopic and microscopic observation and analysis of the indium column as a whole and individually can help to draw a more comprehensive conclusion. Figure 5 It can be seen that for the contact surface, the stress at the edge is the largest, the stress at the center is the smallest, and the stress gradually increases from the center to the edge in a radial shape.

[0043] In view of the influence of different environments and bonding parameters, the time, temperature, bonding pressure and other data in the simulation process can be directly set, which is much more efficient than repeated tests. Figure 7 As shown, a function graph of the applied pressure and the height compression of the indium column at T = 150°C is obtained. It can be clearly seen that the compression of the indium column basically increases with the increase of the applied pressure. The changes in the diameter of the indium column can also be plotted in the same way, so that the conclusion can be summarized more intuitively.

[0044] According to the simulation and analysis method for bump forming in chip flip-chip bonding proposed in an embodiment of the present invention, a three-dimensional finite element model of a single bump flip-chip bonding is established for simulation, and the modeling process and the meshing method used are refined, which reduces a large amount of calculation and greatly improves the simulation efficiency. At the same time, the adjustable parameters of the bonding process make the method of the present invention applicable to more application scenarios and conditions, reduces manpower and time costs, and enhances applicability and scalability.

[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 invention. In this specification, the schematic representations of the above terms do 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 N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0047] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

Claims

1. A simulation analysis method for bump forming in chip flip-chip bonding, characterized in that: The following steps are involved: Establish a three-dimensional finite element model of single bump flip-chip bonding; Performing finite element division on the three-dimensional finite element model to obtain a plurality of grids; The bonding pressure, bonding time and bonding temperature are set according to the bonding process parameters, and the function images and system stress distribution corresponding to multiple grids are generated to obtain the simulation analysis results of the bumps.

2. The method according to claim 1, characterized in that The three-dimensional finite element model consists of five parts: substrate, electrode, bump, laser and tooling. In the simulation, the load force is used instead of the tooling.

3. The method according to claim 1, characterized in that The three-dimensional finite element model is divided into finite elements using a mapped mesh method.

4. The method according to claim 1 or 3, characterized in that: When performing finite element division, the grid is divided into appropriate density according to the position, size relationship and analysis focus of each block.

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