Porous silver soldering lug for power device packaging and preparation method and application thereof

Abstract

The invention provides a porous silver soldering lug for packaging a power device as well as a preparation method and application of the porous silver soldering lug. The preparation method of the porous silver soldering lug comprises the following steps that S1, a silicon wafer is pretreated; s2, depositing a silver film on the pretreated silicon wafer; s3, performing plasma oxidation on the silver film to form a silver oxide film with a porous structure; and S4, performing plasma reduction on the silver oxide film to form a silver film with a porous structure, and preparing the porous silver soldering lug for packaging the power device. The prepared porous silver soldering lug has excellent electrical conductivity and thermal conductivity, and the performance and reliability of a power device can be improved; the porous silver soldering lug is suitable for packaging of power devices, the preparation method is simple, cost is low, large-scale production can be achieved, and the porous silver soldering lug has wide industrial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of third-generation semiconductor power device packaging, and in particular to a porous silver solder sheet for power device packaging, and a preparation method and application thereof. Background Art

[0002] At present, electronic information technology is developing rapidly, and semiconductor devices are constantly developing in the direction of high power, high integration, and miniaturization. Especially in the application fields of high-power devices, such as aerospace, electronic communications, inverter conversion of power grids, and power modules of new energy vehicles, the working environment of power devices is more harsh, the load current density is greater, and they need to serve in harsh environments for a long time and maintain performance stability. The third-generation semiconductor materials represented by silicon carbide and gallium nitride have the advantages of high power density, high breakdown voltage, high electron mobility, and small dielectric constant. They can perform more efficient calculations and work stably for a long time in harsh and complex environments. Therefore, they are widely used in some high-power devices.

[0003] Power chips made of third-generation semiconductor materials have higher working efficiency and greater power, but they also generate more heat during service than traditional silicon-based chips, which will cause the operating temperature of the device to rise. As the performance of power devices continues to improve, higher requirements are placed on chip packaging interface materials, namely long-term stable service under high temperature conditions and rapid heat dissipation capabilities.

[0004] Nanosilver sintering technology has become an excellent choice for high-power semiconductor device packaging due to its low-temperature sintering and high-temperature service performance. However, the preparation of nanosilver particles requires a relatively complex process, including nano-processing, surface stabilization, etc. In addition, the stability and dispersibility of silver nanoparticles require special technical guarantees, which increases the cost of materials and processes. Therefore, low-cost, high-reliability chip connection materials for power device packaging are urgently needed to be developed.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a porous silver solder sheet for power device packaging and a preparation method and application thereof. The porous silver solder sheet has excellent electrical conductivity and thermal conductivity and can improve the performance and reliability of the power device.

[0007] The present invention provides a method for preparing a porous silver solder sheet for power device packaging, comprising the following steps:

[0008] S1: pre-processing the silicon wafer;

[0009] S2: depositing a silver film on the pre-treated silicon wafer;

[0010] S3: Plasma oxidation is performed on the silver film to form a silver oxide film having a porous structure;

[0011] S4: Plasma reduction is performed on the silver oxide film to form a silver film with a porous structure, thereby preparing a porous silver solder sheet for power device packaging.

[0012] In step S1, the silicon wafer may be a single-sided polished silicon wafer with a diameter of 4-12 inches; the pretreatment includes cutting and cleaning the silicon wafer, and the cleaning may be performed using an RCA method.

[0013] Specifically, cleaning may include the following steps performed in order:

[0014] A) Soak the silicon wafer in the SPM solution, rinse and dry it after soaking;

[0015] B) Soak the silicon wafer in SC1 solution, rinse and dry it after soaking;

[0016] C) Soak the silicon wafer in SC2 solution, rinse and blow dry after soaking.

[0017] In step A), the SPM solution is composed of H 2 SO 4 and H 2 O 2 The mixture is prepared by mixing (2-4): 1; the soaking temperature is 80-130° C. and the soaking time is 10-20 min; the mixture is rinsed with deionized water and then dried under nitrogen.

[0018] In step B), the SC1 solution is composed of NH 3 , H 2 O 2 and H 2 O is mixed in a ratio of 1: (1-2): (5-7); the soaking temperature is 70-80° C. and the soaking time is 5-20 min; deionized water is used for rinsing and then dried under nitrogen.

[0019] In step C), the SC2 solution is composed of HCl, H 2 O 2 and H 2 O is mixed in a ratio of 1: (1-2): (5-7); the soaking temperature is 70-80° C. and the soaking time is 5-20 min; deionized water is used for rinsing and then dried under nitrogen.

[0020] In step S2, magnetron sputtering technology can be used to deposit a silver film on the pretreated silicon wafer in an argon atmosphere, and the thickness of the silver film can be precisely controlled by controlling the sputtering time; specifically, the thickness of the silver film can be 50-500nm.

[0021] In step S3, the plasma oxidation conditions include: using O 2 The plasma is oxidized; the power of the plasma is 2-20W, for example, 6.8-10.5W; the pressure is 0.1-1.0Torr, for example, 0.5Torr; the plasma oxidation time is 1-60min, for example, 10-15min. The deposited silver film is exposed to O 2 In plasma, the silver film is oxidized by adjusting the plasma power, pressure and plasma oxidation time, thereby forming a silver oxide film with a porous structure; compared with the porous structure formed by other methods such as chemical etching, the pore size and distribution of the porous structure of the silver oxide film can be precisely controlled by plasma conditions (power, pressure, time).

[0022] In step S4, the plasma reduction conditions include: using H 2 / Ar plasma reduction, H 2 H / Ar plasma 2 The volume content is 1-100%; the plasma power is 2-20W, for example, 18W; the pressure is 0.1-1.0Torr, for example, 0.5Torr; the plasma reduction time is 1-60min, for example, 3-5min. 2 The silver oxide film is reduced by Ar plasma to remove the oxide and restore the metallic properties of the silver film.

[0023] The invention also provides a porous silver solder sheet for power device packaging, which is prepared according to the preparation method.

[0024] The invention also provides application of the porous silver solder sheet in power device packaging.

[0025] The implementation of the present invention has at least the following advantages:

[0026] 1. Excellent conductivity: The specific porous structure of the porous silver solder sheet increases the surface area of ​​the solder sheet and improves the conductivity.

[0027] 2. Good thermal conductivity: The specific porous structure of the porous silver solder sheet helps to quickly diffuse heat and improves thermal conductivity.

[0028] 3. Enhanced mechanical strength: The specific porous structure of the porous silver solder sheet provides better mechanical stability and enhances the fatigue resistance of the solder sheet.

[0029] 4. Cost-effectiveness: The preparation method of the porous silver solder sheet is simple, the raw materials are easily available, and it can be mass-produced, which reduces the production cost; the porous silver solder sheet is suitable for the packaging of power devices, can improve the performance and reliability of power devices, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] Figure 1 Schematic diagram of silver film deposition;

[0032] Figure 2 Schematic diagram of plasma oxidation-reduction;

[0033] Figure 3 Schematic diagram of the preparation process of porous silver solder sheet;

[0034] Figure 4 Schematic diagram of the microstructure changes during the preparation process of porous silver film. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] 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.

[0038] Example 1

[0039] Combination Figures 1 to 4 As shown, the method for preparing the porous silver solder sheet for power device packaging in this embodiment comprises the following steps:

[0040] S1: Preprocessing

[0041] The silicon wafer uses a single-sided polished silicon wafer with a diameter of 4 inches.

[0042] Clean the silicon wafer according to the following RCA method:

[0043] A) The silicon wafer was placed in a SPM solution (H 2 SO 4 :H 2 O 2 =3:1) for 20 min, then rinse with deionized water and blow dry under nitrogen.

[0044] B) The silicon wafer was heated in SC1 solution (NH 3 :H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0045] C) The silicon wafer was heated at 80°C in SC2 solution (HCl:H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0046] S2: Deposition of silver film

[0047] A silver film with a thickness of 100 nm was deposited on the silicon wafer pre-treated in step S1 using magnetron sputtering technology.

[0048] S3: Plasma oxidation

[0049] The silver film was exposed to 6.8W, 0.5Torr O 2 After oxidizing in plasma for 10 min, a silver oxide film with a porous structure is formed.

[0050] S4: Plasma reduction

[0051] The silver oxide film was exposed to 18W, 0.5Torr H 2 / Ar plasma (H 2 The silver film having a porous structure is formed by reducing the silver solder sheet with a volume proportion of 10% for 3 minutes, thereby obtaining a porous silver solder sheet for power device packaging.

[0052] Example 2

[0053] The method for preparing the porous silver solder sheet for power device packaging in this embodiment comprises the following steps:

[0054] S1: Preprocessing

[0055] The silicon wafer uses a single-sided polished silicon wafer with a diameter of 4 inches.

[0056] Clean the silicon wafer according to the following RCA method:

[0057] A) The silicon wafer was placed in a SPM solution (H 2 SO 4 :H 2 O 2 =3:1) for 20 min, then rinse with deionized water and blow dry under nitrogen.

[0058] B) The silicon wafer was heated in SC1 solution (NH 3 :H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0059] C) The silicon wafer was heated at 80°C in SC2 solution (HCl:H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0060] S2: Deposition of silver film

[0061] A silver film with a thickness of 200 nm was deposited on the silicon wafer pre-treated in step S1 using magnetron sputtering technology.

[0062] S3: Plasma oxidation

[0063] The silver film was exposed to 10.5W, 0.5Torr O 2 After oxidizing in plasma for 15 min, a silver oxide film with a porous structure is formed.

[0064] S4: Plasma reduction

[0065] The silver oxide film was exposed to 18W, 0.5Torr H 2 / Ar plasma (H 2 The silver film having a porous structure is formed by reducing the silver solder sheet with a volume proportion of 10% for 5 minutes, thereby obtaining a porous silver solder sheet for power device packaging.

[0066] Example 3

[0067] The method for preparing the porous silver solder sheet for power device packaging in this embodiment comprises the following steps:

[0068] S1: Preprocessing

[0069] The silicon wafer uses a single-sided polished silicon wafer with a diameter of 4 inches.

[0070] Clean the silicon wafer according to the following RCA method:

[0071] A) The silicon wafer was placed in a SPM solution (H 2 SO 4 :H 2 O 2 =3:1) for 20 min, then rinse with deionized water and blow dry under nitrogen.

[0072] B) The silicon wafer was heated in SC1 solution (NH 3 :H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0073] C) The silicon wafer was heated at 80°C in SC2 solution (HCl:H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0074] S2: Deposition of silver film

[0075] A silver film with a thickness of 100 nm was deposited on the silicon wafer pre-treated in step S1 using magnetron sputtering technology.

[0076] S3: Plasma oxidation

[0077] The silver film was exposed to 3.6W, 0.5Torr O 2 After oxidizing in plasma for 5 minutes, a silver oxide film with a porous structure is formed.

[0078] S4: Plasma reduction

[0079] The silver oxide film was exposed to 12W, 0.5 Torr H 2 / Ar plasma (H 2 The silver film having a porous structure is formed by reducing the silver solder sheet with a volume proportion of 10% for 2 minutes, thereby obtaining a porous silver solder sheet for power device packaging.

[0080] Comparative Example 1

[0081] The preparation method of the porous silver solder sheet for power device packaging in this comparative example comprises the following steps:

[0082] S1: Preprocessing

[0083] The silicon wafer uses a single-sided polished silicon wafer with a diameter of 4 inches.

[0084] Clean the silicon wafer according to the following RCA method:

[0085] A) The silicon wafer was placed in a SPM solution (H 2 SO 4 :H 2 O 2 =3:1) for 20 min, then rinse with deionized water and blow dry under nitrogen.

[0086] B) The silicon wafer was heated in SC1 solution (NH 3 :H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0087] C) The silicon wafer was heated at 80°C in SC2 solution (HCl:H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0088] S2: Deposition of silver film

[0089] A silver film with a thickness of 100 nm is deposited on the silicon wafer pretreated in step S1 by using magnetron sputtering technology, thereby obtaining a porous silver solder sheet for power device packaging.

[0090] Comparative Example 2

[0091] The preparation method of the porous silver solder sheet for power device packaging in this comparative example comprises the following steps:

[0092] S1: Preprocessing

[0093] The silicon wafer uses a single-sided polished silicon wafer with a diameter of 4 inches.

[0094] Clean the silicon wafer according to the following RCA method:

[0095] A) The silicon wafer was placed in a SPM solution (H 2 SO 4 :H 2 O 2 =3:1) for 20 min, then rinse with deionized water and blow dry under nitrogen.

[0096] B) The silicon wafer was heated in SC1 solution (NH 3 :H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0097] C) The silicon wafer was heated at 80°C in SC2 solution (HCl:H 2 O 2 :H 2 The samples were immersed in 4% paraformaldehyde (OD) (1:1:5) for 20 min, then rinsed with deionized water and dried under nitrogen.

[0098] S2: Deposition of silver film

[0099] A silver film with a thickness of 100 nm was deposited on the silicon wafer pre-treated in step S1 using magnetron sputtering technology.

[0100] S3: Preparation of porous structures

[0101] The porous structure was prepared as follows:

[0102] A) Etchant preparation: Prepare 0.5 M nitric acid solution as the etchant solution.

[0103] B) Etching reaction: The silver film was immersed in an etchant solution and reacted for 60 minutes.

[0104] C) Cleaning and drying: The silver film is taken out from the etchant solution, rinsed with deionized water to remove the residual etchant, and then the silver film is blown dry in nitrogen or dry air to form a silver film with a porous structure, that is, a porous silver solder sheet for power device packaging is prepared.

[0105] 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 porous silver solder sheet for power device packaging, characterized in that: The steps include: S1: pre-processing the silicon wafer; S2: depositing a silver film on the pre-treated silicon wafer; S3: Plasma oxidation is performed on the silver film to form a silver oxide film having a porous structure; S4: Plasma reduction is performed on the silver oxide film to form a silver film with a porous structure, thereby preparing a porous silver solder sheet for power device packaging.

2. The preparation method according to claim 1, characterized in that: Pretreatment includes cleaning; cleaning includes the following steps in the following order: A) Soak the silicon wafer in the SPM solution, rinse and dry it after soaking; B) Soak the silicon wafer in SC1 solution, rinse and dry it after soaking; C) Soak the silicon wafer in SC2 solution, rinse and blow dry after soaking.

3. The preparation method according to claim 2, characterized in that: In step A), the SPM solution is prepared by mixing H2SO4 and H2O2 in a ratio of (2-4):1; the soaking temperature is 80-130°C and the soaking time is 10-20 minutes.

4. The preparation method according to claim 2, characterized in that: In step B), the SC1 solution is prepared by mixing NH3, H2O2 and H2O in a ratio of 1:(1-2):(5-7); the soaking temperature is 70-80°C and the soaking time is 5-20 min.

5. The preparation method according to claim 2, characterized in that: In step C), the SC2 solution is prepared by mixing HCl, H2O2 and H2O in a ratio of 1:(1-2):(5-7); the soaking temperature is 70-80°C and the soaking time is 5-20 minutes.

6. The preparation method according to claim 1, characterized in that: The thickness of the silver film is 50-500nm.

7. The preparation method according to claim 1, characterized in that: The plasma oxidation conditions include: using O2 plasma for oxidation; the plasma power is 2-20W, the pressure is 0.1-1.0Torr, and the plasma oxidation time is 1-60min.

8. The preparation method according to claim 1, characterized in that: The plasma reduction conditions include: using H2 / Ar plasma for reduction, the volume content of H2 in the H2 / Ar plasma is 1-100%; the plasma power is 2-20W, the pressure is 0.1-1.0Torr, and the plasma reduction time is 1-60min.

9. A porous silver solder sheet for power device packaging, characterized in that: Prepared according to any one of the preparation methods of claims 1-8.

10. Use of the porous silver solder sheet according to claim 9 in power device packaging.

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