Preparation method and application of all-intermetallic compound film

Abstract

The invention relates to the technical field of electronic packaging, in particular to a preparation method and application of an all-intermetallic compound film. Comprising the following steps that (1) in an inert atmosphere, a double-target double-beam pulse laser deposition technology is adopted to deposit a metal particle film on the surface of a wafer, and a main target and an auxiliary target selected for deposition are both made of metal; in the initial deposition stage, the heating temperature of the wafer is 260-300 DEG C, and the air pressure is 50-500 Pa; in the later stage of deposition, the heating temperature of the wafer is 220-260 DEG C, and the air pressure is 500-1500 Pa; and (2) carrying out heat treatment on the deposited wafer to obtain the full IMC film covering the surface of the wafer. According to the preparation method provided by the invention, the deposition speed of full IMC film preparation can be increased, the film quality can be improved, the energy consumption and the equipment complexity can be greatly reduced, and the reliability and the performance stability of a device can be remarkably improved when the prepared full IMC film is applied to electronic packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic packaging, and in particular to a preparation method and application of a full intermetallic compound film. Background Art

[0002] In recent years, with the sharp increase in the service temperature requirements of power devices, traditional Sn-based solders are no longer applicable. All-intermetallic compound (all-IMC) joints have become a very economical and feasible packaging technology route due to their low cost, high service temperature, high strength and good thermal and electrical conductivity. However, in the preparation methods of all-IMC joints, the traditional transient liquid phase method (TLP) and solid-liquid interdiffusion bonding method (SLID) face the problem of long preparation time. For this reason, some researchers have shortened the preparation time of joints by applying external energy fields, such as external ultrasonic assistance, current assistance and inductive heating, but these methods are not suitable for actual production due to their cost and device installation problems. Some people have also proposed a method for forming a sintered all-IMC joint using IMC nanoparticles, but there will be organic residue problems when the joint is sintered at low temperature. If all-IMC films can be directly applied to electronic packaging, it will be an efficient means. However, existing thin film preparation technologies such as electroplating, chemical vapor deposition (CVD) and sputtering have many limitations. Although the traditional electroplating method is low-cost, it often leads to uneven film thickness due to uneven current density distribution. Although CVD technology can achieve good film quality, it has complex processes, high equipment costs, and slow deposition speed. These shortcomings limit the application of all-IMC films in efficient and large-scale production. Therefore, it is urgent to propose an all-IMC preparation method that can increase the deposition speed, improve film quality, and significantly reduce energy consumption and equipment complexity. Summary of the invention

[0003] The first object of the present invention is to provide a method for preparing a full intermetallic compound film, which is simple to operate, has low equipment cost, fast deposition speed, and the prepared film has good uniformity and integrity. The second object of the present invention is to provide an application of the full intermetallic compound film.

[0004] The present invention provides a method for preparing a full intermetallic compound film, comprising the following steps:

[0005] (1) Deposition: In an inert atmosphere, a dual-target dual-beam pulsed laser deposition technique is used to deposit a metal particle film on the surface of the wafer. The materials of the main target and the auxiliary target used for deposition are both metals. In the initial stage of deposition, the heating temperature of the wafer is 260-300°C and the gas pressure is 50-500Pa. In the later stage of deposition, the heating temperature of the wafer is 220-260°C and the gas pressure is 500-1500Pa. The initial stage of deposition is the process of deposition thickness from zero to one-half of the total thickness, and the later stage of deposition is the process of deposition thickness from one-half of the total thickness to the end.

[0006] (2) Heat treatment: The wafer with the metal particle film deposited thereon is heat treated to obtain a full intermetallic compound film covering the surface of the wafer.

[0007] Preferably, the main target material in step (1) is one of Cu, Ni, Ag, Au, and Pa, and the secondary target material is one of Sn, In, Ga, and Bi.

[0008] Preferably, the inert atmosphere in step (1) is one of Ar, He, N2, and CO2, and the gas pressure is 100-1000 Pa.

[0009] Preferably, in the dual-target dual-beam pulsed laser deposition technology in step (1), the power of the two laser beams used is 8-100 W and the frequency is 100-600 kHz.

[0010] Preferably, the deposition thickness of the metal particle film in step (1) is 10-30 μm.

[0011] Preferably, in step (2), the heat treatment temperature is 100-220° C., and the heat treatment time is 3-30 minutes.

[0012] The present invention provides an application of a full intermetallic compound film prepared by the above preparation method in electronic packaging, comprising the following steps:

[0013] S1 Cutting and Filming: Cut the wafer covered with full intermetallic compound film and apply UV film on its surface; diamond saw blade or laser cutting can be used;

[0014] S2 chip sintering: After tearing off the UV film, place it on the part of the substrate to be sintered, and sinter it in the sintering equipment to obtain an electronic package.

[0015] Preferably, the specific operation in step S2 is as follows: tear off the UV film on the surface, place it on the part to be sintered on the substrate, and then place it on the heating plate of the sintering equipment, evacuate the cavity, and at a vacuum degree of 1×10 -2When the temperature is 0.04 Pa, an inert gas is introduced to a positive pressure, and then the heating plate is heated to a heating temperature and pressurized. After the pressurization is completed, the pressure is cooled to room temperature to obtain an electronic package.

[0016] Preferably, in step S2, the heating rate of the heating plate is 40-60°C / min, and the heating temperature is 160-220°C.

[0017] Preferably, the pressurizing pressure in step S2 is 1-15 MPa, and the pressurizing time is 2-5 minutes.

[0018] In summary, compared with the prior art, the present invention has the following advantages:

[0019] The technical solution of the present invention deposits a metal particle film on the surface of a wafer through a dual-target dual-beam pulsed laser deposition technology. The main target material and the auxiliary target material selected for deposition are both metals. The deposition rate and ratio of the two target materials can be controlled simultaneously, and the target intermetallic compound phase can be accurately generated. During the deposition process, the deposition parameters can also be dynamically adjusted to ensure the uniformity and integrity of the film, which can increase the deposition speed, improve the film quality, and greatly reduce energy consumption and equipment complexity. The metal particle film contains intermetallic compounds and metal elements. After heat treatment, the intermetallic compound phase diffuses more evenly in the film, further improving the uniformity of the film. The full IMC film prepared by the method provided by the present invention is applied to electronic packaging, which can significantly improve the reliability and performance stability of the device, solve the problems of slow speed, high energy consumption and complex equipment in preparing full IMC joints by traditional methods, and is particularly suitable for electronic packaging of high-power, high-frequency and high-temperature devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The process flow chart of the preparation of the all-metallic compound film and electronic packaging in the present invention;

[0022] Figure 2 It is a schematic diagram of the operation of the dual-target dual-beam pulsed laser deposition system of the present invention;

[0023] Figure 3 is a scanning electron microscope image of the surface of the full intermetallic compound film in Example 1 of the present invention;

[0024] Figure 4 is a temperature curve diagram of the electronic packaging process in Example 1 of the present invention;

[0025] Figure 5 is a schematic structural diagram of an electronic package in Embodiment 2 of the present invention;

[0026] Figure 6 XRD pattern of the full IMC film prepared in the test example of the present invention;

[0027] Figure 7 A cross-sectional view of a joint prepared for a test example of the present invention;

[0028] Figure 8 A cross-sectional view of a joint prepared in a comparative example of the present invention;

[0029] Fig. 9 It is a comparison diagram of the force-displacement curves of the joints prepared in the test example of the present invention and the comparative example during shearing. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, 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 connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The appended Figure 1 The combined schematic diagram of the preparation method of the full intermetallic compound film (abbreviated as full IMC film) and its application process in electronic packaging is shown in the figure. The pre-treated wafer is placed in the cavity of the dual-target dual-beam pulsed laser deposition system for deposition. After deposition, the wafer is heat treated to obtain a wafer with full IMC film deposited on the surface. Then, the wafer is cut, filmed, and sintered to obtain an electronic package. The equipment used in the dual-target dual-beam pulsed laser deposition technology used in the present invention is basically the same as the pulsed laser deposition equipment in the prior art, except that the present invention uses dual beams to simultaneously ablate two metal targets, such as Figure 2 As shown, it is described in detail through the following specific embodiments:

[0034] Example 1

[0035] A method for preparing a full intermetallic compound film, the specific process is as follows:

[0036] (1) Deposition: A dual-target dual-beam pulsed laser deposition technique was used to deposit a thin film of metal particles on the surface of the wafer. The deposition was carried out in an Ar atmosphere with a gas pressure of 500 Pa. The wafer entered the chamber and reached the specified position. The main target material used for deposition was Cu, the laser power was 55 W, the frequency was 400 kHz, and the target-substrate distance was 50 mm. The secondary target material was Sn, the laser power was 12 W, the frequency was 400 kHz, and the target-substrate distance was 50 mm. The deposition thickness was 30 μm. When the deposition thickness was 0-15 μm, the heating temperature of the wafer was 280 °C and the gas pressure was 500 Pa. When the deposition thickness was 16-30 μm, the heating temperature of the wafer was 240 °C and the gas pressure was 1500 Pa.

[0037] (2) Heat treatment: The heating temperature of the wafer with the metal particle film deposited thereon is lowered to 180°C and maintained for 10 minutes to obtain a full IMC film covering the surface of the wafer. The surface of the full IMC film is as follows: Figure 3 shown.

[0038] The full IMC film prepared in this embodiment is used for electronic packaging to produce a single-tube MOS power device. The specific process is as follows:

[0039] S1 Cutting and filming: Use laser to cut the wafer covered with the full IMC film obtained in step (2) into suitable sizes and patterns, and mount UV film on its surface.

[0040] S2 patch sintering: tear off the UV film and place it on the substrate to be sintered. Before sintering begins, place the sample on the lower heating plate of the sintering equipment, evacuate the chamber, and place the sample on the lower heating plate of the sintering equipment. -2Pa, N2 gas was introduced to positive pressure, and then the lower heating plate was heated at a rate of 60℃ / min to 220℃. The temperature curve is as follows Figure 4 As shown. When the temperature reaches 220°C, pressurization is performed at a pressure of 10 MPa for 3 minutes. After pressurization, an electronic package is obtained and cooled to room temperature in a N2 gas environment. After testing, the shear strength of the electronic package is 106 MPa.

[0041] Example 2

[0042] A method for preparing a full intermetallic compound film, the specific process is as follows:

[0043] (1) Deposition: A dual-target dual-beam pulsed laser deposition technique is used to deposit a thin film of metal particles on the surface of the wafer. The deposition is carried out in a N2 atmosphere with a gas pressure of 1000Pa. The wafer enters the cavity and reaches the specified position. The main target material used for deposition is Ag, the laser power is 35W, the frequency is 400kHz, and the target-substrate distance is 50mm. The secondary target material is In, the laser power is 8W, the frequency is 400kHz, and the target-substrate distance is 50mm. The deposition thickness is 20μm. When the deposition thickness is 0-10μm, the heating temperature of the wafer is 260℃ and the gas pressure is 500Pa. When the deposition thickness is 11-20μm, the heating temperature of the wafer is 220℃ and the gas pressure is 1000Pa.

[0044] (2) Heat treatment: The heating temperature of the wafer with the metal particle film deposited thereon is lowered to 160°C and maintained for 5 minutes to obtain a full IMC film covering the wafer surface.

[0045] The full IMC film prepared in this embodiment is used for electronic packaging to produce a certain SiC diode. The specific process is as follows:

[0046] S1 cutting and film mounting: Use laser to cut the wafer covered with the full IMC film obtained in step (2) into suitable sizes and patterns to obtain chips, and mount UV film on the surface.

[0047] S2 patch sintering: tear off the UV film and place it on the DBC substrate to be sintered. Before sintering begins, place the sample on the lower heating plate of the sintering equipment. Evacuate the inner cavity of the packaging equipment. -2 N2 gas is introduced to positive pressure, and then the lower heating plate is heated at a rate of 65℃ / min to 220℃. When the temperature reaches 220℃, pressurization is applied at a pressure of 10Mpa for 3min. After pressurization, the electronic package is obtained and cooled to room temperature in the N2 gas environment. The structure of the electronic package is shown in the figure. Figure 5 As shown, the DBC substrate is located at the bottom layer, the SIC chip is located at the top layer, and the middle connection layer is a full IMC film. After testing, the shear strength of the electronic package is 65MPa.

[0048] Test Case

[0049] The process provided by the present invention is used to prepare the joint, and the connecting material is directly deposited on the chip. The specific process is as follows: the main target material is Cu, the laser power is 55W, the frequency is 400kHz, the target-substrate distance is 50mm, the secondary target material is Sn, the laser power is 12W, the frequency is 400kHz, and the target-substrate distance is 50mm. The deposition thickness is 30μm, and the heating temperature of the wafer is 280°C and the air pressure is 500Pa when the deposition thickness is 0-15μm; the heating temperature of the wafer is 240°C and the air pressure is 1500Pa when the deposition thickness is 16-30μm. At this time, the ratio of Cu and Sn atoms in the metal particle film is 5:5. After the deposition is completed, the substrate heating temperature drops to 220°C and is maintained for 5 minutes to obtain a full IMC film. The XRD test results of the film structure are as shown in the figure. Figure 6 As shown, it can be seen that the film obtained at this time is entirely composed of Cu-SnIMC particles, including Cu6Sn5 and Cu3Sn.

[0050] After the deposition is completed, the sintering package is carried out, and the connection temperature is 220℃, the connection pressure is 15MPa, and the connection time is 3min. The backscattering characterization of the prepared joint cross section is as follows Figure 7 As shown, it can be seen that the joint connection layer has a uniform structure. Under this composition design, the diffusion of the Cu element of the substrate during the sintering process makes the connection layer become a full Cu3Sn structure.

[0051] Comparative Example

[0052] The common Cu-Sn mixed solder paste was used to prepare the joint. The ratio of Cu and Sn atoms in the solder paste was also 5:5. The connection process parameters were consistent with the above parameters. The two connection processes can be seen in Table 1. The backscattering characterization of the prepared joint cross section is shown in Figure 8 As shown, it can be found that when the traditional solder paste is used to prepare the joint, the joint structure is not uniform, and the connection layer is composed of two phases, Cu6Sn5 and Cu3Sn. The uneven structure will lead to a decrease in the reliability of the joint.

[0053] pass Fig. 9 Comparison of the shear strengths of the two joints shows that the joint connection strength obtained by the preparation method provided by the present invention is more than twice that of the comparative example. The joint strength prepared by the test example of the present invention is 86 MPa, while that of the comparative example is 39 MPa.

[0054] Table 1 Comparison of two connection process parameters

[0055] Material Cu:Sn atomic ratio Chip size Connection temperature Connection time Connection pressure Test film 5:5 3×3mm 220℃ 3min 15MPa Common solder paste 5:5 3×3mm 220℃ 3min 15MPa

[0056] The present invention can accurately control the deposition ratio of multiple materials in a short time by innovatively improving the pulsed laser deposition technology, and form a full IMC film with excellent performance. Due to its chemical stability and high melting point, the full IMC connection layer shows excellent service performance under high temperature conditions, which can significantly improve the reliability of electronic packaging. By accurately adjusting the power ratio of the dual-beam laser, quantitative deposition of different materials is achieved. At the same time, by controlling the substrate temperature and introducing a suitable gas environment during the deposition process, the formation and growth of the full IMC phase are promoted, so that the final prepared full IMC film shows significant advantages in thickness uniformity, interface performance, electrical conductivity and thermal conductivity. It can be used in the field of electronic packaging and can greatly shorten the preparation time of the full IMC joint. The full IMC film prepared by the preparation method provided by the present invention is particularly suitable for high-density integrated circuits, miniaturized electronic devices and high-power electronic packaging applications, and can significantly improve the reliability and performance stability of the device, solving the problems of slow speed, high energy consumption and complex equipment in preparing full IMC joints by traditional methods.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a full intermetallic compound film, characterized in that: The following steps are involved: (1) Deposition: In an inert atmosphere, a dual-target dual-beam pulsed laser deposition technique is used to deposit a metal particle film on the wafer surface. The materials of the main target and the auxiliary target used for the deposition are both metals; In the initial stage of deposition, the wafer is heated at a temperature of 260-300°C and a gas pressure of 50-500 Pa; in the later stage of deposition, the wafer is heated at a temperature of 220-260°C and a gas pressure of 500-1500 Pa; (2) Heat treatment: The wafer with the metal particle film deposited thereon is heat treated to obtain a full intermetallic compound film covering the surface of the wafer.

2. The preparation method according to claim 1, characterized in that: The main target material in step (1) is one of Cu, Ni, Ag, Au, and Pa, and the auxiliary target material is one of Sn, In, Ga, and Bi.

3. The preparation method according to claim 1, characterized in that: The inert atmosphere in step (1) is one of Ar, He, N2, and CO2, and the gas pressure is 100-1000 Pa.

4. The preparation method according to claim 1, characterized in that: The dual-target dual-beam pulsed laser deposition technology in step (1) uses two laser beams with a power of 8-100 W and a frequency of 100-600 kHz.

5. The preparation method according to claim 1, characterized in that: The deposition thickness of the metal particle film in step (1) is 10-30 μm.

6. The preparation method according to claim 1, characterized in that: In the step (2), the heat treatment temperature is 100-220° C., and the heat treatment time is 3-30 minutes.

7. An application of a full intermetallic compound film prepared by the preparation method according to any one of claims 1 to 6 in electronic packaging, characterized in that: The following steps are involved: S1 cutting and filming: cutting the wafer covered with full intermetallic compound film and mounting UV film on its surface; S2 chip sintering: After tearing off the UV film, place it on the part of the substrate to be sintered, and sinter it in the sintering equipment to obtain an electronic package.

8. The use according to claim 7, characterized in that: The specific operation in step S2 is as follows: tear off the UV film on the surface, place it on the part to be sintered on the substrate, and then place it on the heating plate of the sintering equipment, evacuate the cavity, and sinter the substrate at a vacuum degree of 1×10 -2 When the temperature is 0.04 Pa, an inert gas is introduced to a positive pressure, and then the heating plate is heated to a heating temperature and pressurized. After the pressurization is completed, the pressure is cooled to room temperature to obtain an electronic package.

9. The use according to claim 8, characterized in that: In step S2, the heating rate of the heating plate is 40-60°C / min, and the heating temperature is 160-220°C.

10. The use according to claim 8, characterized in that: The pressurization pressure in step S2 is 1-15 MPa, and the pressurization time is 2-5 minutes.

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