WO2020199640A1

WO2020199640A1 - Multilayer metal film and preparation method therefor

Info

Publication number: WO2020199640A1
Application number: PCT/CN2019/123773
Authority: WO
Inventors: 叶怀宇; 刘旭; 张国旗
Original assignee: 深圳第三代半导体研究院
Priority date: 2019-04-03
Filing date: 2019-12-06
Publication date: 2020-10-08
Also published as: CN109967747B; CN109967747A

Abstract

Disclosed are a multilayer metal film and a preparation method therefor. The multilayer metal film comprises a first organic dielectric material layer, and a second organic dielectric material layer, wherein the first organic dielectric material layer contains nano metal particles of a first size, and the second organic dielectric material layer contains nano metal particles of a second size, with the diameter of the nano metal particle of the first size being different from that of the nano metal particle of the second size. By means of a mechanical press fit, particles of different sizes in different layers are rapidly mixed and mutually fill gaps so as to form a dense sintered metal layer, such that the overall reliability performance of a power device is improved, the feature of easy assembly is provided and the cost can be effectively reduced.

Description

Multilayer metal film and preparation method thereof

Technical field

The invention relates to the field of chip packaging interconnection, and more specifically to a metal film for sintering and its preparation technology.

Background technique

In the field of power semiconductor packaging, the search for interconnect materials with low temperature process, high temperature service, matching thermal expansion coefficient, high thermal conductivity and low cost has become an urgent problem to be solved. The traditional material technology of welding and wire bonding has unsolvable problems such as low melting point, high temperature creep failure, wire winding, parasitic parameters, etc. New interconnect materials are developing from welding to sintering technology. By reducing the size of the sintered particles and lowering the sintering temperature, the nano-metal particle sintering technology has become the most promising technology among the new interconnect materials for power semiconductor devices.

At present, the advanced technology represented by nano-silver sintering has gradually become the mainstream of power semiconductor device packaging interconnection, and major packaging application manufacturers at home and abroad have entered practical and large-scale use. However, nano-silver sintering patents, materials, processes and equipment are mainly controlled by foreign manufacturers, and their development in China is greatly restricted. At the same time, the nano-silver sintering technology also has shortcomings: 1) The high price of silver material itself limits its wide use. 2) The thermal expansion coefficients of the backside materials of silver and SiC chips are different, and other intermediate metal layers need to be added to improve interconnection performance, thereby increasing process complexity and cost. 3) Electromigration exists in the silver layer, which is not conducive to long-term reliable application of power devices. Nano-copper particles similar to nano-silver can be melted under low temperature conditions, and the melting point after sintering is close to copper elemental material (1083°C), which can construct a stable metal interconnection layer. Its single-component metal characteristics avoid the service reliability problem under the thermal cycling effect of alloy materials, realize copper-copper bonding, solve the problem of thermal expansion coefficient matching between the chip and the substrate, and avoid the reliability problem caused by electromigration. Compared with nano-silver particles, it effectively reduces the material and processing costs of interconnect packaging. More importantly, it can further promote the practical application and industrialization of the "All copper" concept from the field of chip packaging applications, and promote the innovative development of the semiconductor industry.

Patent document CN103262172A, its technical scheme is shown in Figure 1. Disclosed are a sintered material and a thin layer prepared from the sintered material, and an adhesion method of the material. The thin layer is composed of metal powder, solder paste, adhesive and solvent. The metal powder includes gold, palladium, silver, copper, aluminum, silver-palladium alloy or gold-palladium alloy, and may further include one or more functional additives. The metal powder includes nanoparticles. The metal powder is applied to the substrate, and the material on the substrate is dried to form a thin layer. The substrate material includes polyester fibers. The disadvantage of the prior art is that the nano-metal layer on the substrate has a single component size, which results in a large porosity after sintering and poor electrical and thermal conductivity.

Patent document CN105492198A, its technical scheme is shown in Figure 2. A composite and multilayer silver film for electrical and mechanical components is disclosed, in which reinforcing particles or fibers are added to the sinterable silver layer to improve its strength. As shown in Figures 3 and 4, a reinforced metal foil layer is further added to the slightly decomposable silver particle layer. Its composition can be silver, copper, gold or any other metal or any alloy, or metal polymer or ceramic The foil can also be a composite or a coating structure with different metal and alloy layers. The reinforced metal foil layer can be applied in solid, perforated or grid form. However, the problem with the prior art is that the addition of the multilayer composite metal film and the reinforced metal foil layer increases the number of interfaces of the connection layer after sintering, thereby possibly reducing the connection strength; in addition, the single-size silver particle layer is sintered. The porosity is large, which reduces thermal conductivity, electrical conductivity and shear stress, thereby reducing reliability.

Summary of the invention

In order to overcome the shortcomings of the existing technology, avoid the problems of the original silver film with high porosity, low thermal conductivity, high cost, thermal mismatch with Si or SiC-based chips, high electrical mobility, etc., and improve the overall reliability performance of power devices. To achieve the effect of easy assembly and effective cost reduction, the present invention provides a multilayer metal film, including:

The first organic medium material layer,

The second organic medium material layer;

The first organic medium material layer contains first-size nano metal particles,

The first organic medium material layer contains second-size nano metal particles;

The diameter of the first size nano metal particles is different from that of the second size nano metal particles.

Preferably, the nano metal particle material is copper.

Preferably, the nano metal particle material is gold, palladium, silver, copper, aluminum, silver-palladium alloy, gold-palladium alloy, copper-silver alloy, copper-silver-nickel alloy or copper-aluminum alloy.

Preferably, the multilayer metal film further includes a supporting substrate, wherein the supporting substrate includes polyester fiber, ceramic, glass and/or metal material.

Preferably, the contact surface of the supporting substrate and the nano metal particles is coated with silicone.

Preferably, the medium material layer includes an organic medium material, and the organic medium material is an organic solvent, flux, solder paste, and/or adhesive.

Preferably, in the first size nano metal particles and the second size nano metal particles, the diameter of the larger size nano metal particles is 1 nm<D<10um.

Preferably, in the first size nano metal particles and the second size nano metal particles, the diameter of the smaller size nano metal particles is 0.5 nm<d<20 nm.

A method for preparing a multilayer metal film specifically includes the following steps:

Step 1: Configure a nano metal particle solution with a first size and a nano metal particle solution with a second size; the second size nano metal particles have a different diameter from the first size nano metal particles

Step 2: Use the first size nano metal particle solution to prepare a first metal paste, and use the second size nano metal particle solution to prepare a second metal paste;

Step 3: Use the first metal paste to prepare a first metal film; use the second metal paste to prepare a second metal film;

Step 4: bonding the first metal film and the second metal film.

Preferably, the step 3 further includes:

The first metal paste is disposed on the first supporting substrate, and then dried to form a first metal film.

Preferably, the step 3 further includes:

The second metal paste is disposed on the second supporting substrate, and then dried to form a second metal film.

Preferably, the metal paste is applied to the supporting substrate by screen printing, spraying or coating methods.

Preferably, the nano metal particle material is copper.

Preferably, the supporting substrate material is polyester fiber, ceramic, glass and/or metal material.

Preferably, the nano metal particle solution contains an organic medium material, and the organic medium material is an organic solvent, a flux, a solder paste, and/or an adhesive.

Step 3: Use the first metal paste to prepare the first metal film;

Step 4: Apply a second metal paste on the first metal film.

Preferably, the step 3 further includes:

Disposing the first metal paste on the first supporting substrate, and then performing a drying process to form a first metal film;

The preparation method further includes step 5: after coating the second metal paste on the first metal film, drying is performed to form the second metal film.

Preferably, the nano metal particle material is copper.

A method for interconnecting a chip and a substrate using a multilayer metal film specifically includes the following steps:

Step 1: Paste the multilayer metal film to the bottom of the chip to be interconnected;

Step 2: Heating the chip with the multi-layer metal film attached, and mixing the layers of the multi-layer nano metal film to obtain a multi-layer metal film chip;

Step 3: Interconnect the substrate and the multilayer metal film chip.

Preferably, step 1 includes obtaining a multilayer metal film with the same shape as the chip, and the obtaining method is

Cutting the multilayer metal film according to the shape of the chip to be interconnected;

Or, the chip is placed on the heated multilayer metal film so that the multilayer metal film with the same shape as the chip adheres to the chip.

Preferably, step 1 also includes: selecting whether to have pressure assistance during bonding.

Preferably, step 2 also includes: selecting whether to have pressure assistance during heating.

Preferably, step 3 includes:

Step 3.1: Peel off the supporting substrate.

Step 3.2: Place the multilayer metal film chip on the substrate;

Step 3.3: Heat the multi-layer metal film chip in the sintering furnace, select whether to have pressure assistance, and interconnect the substrate and the multi-layer metal film chip.

The present invention constructs a nano metal film for interconnection by arranging multiple layers and layers of nano copper particles of different sizes stacked on top of each other. During sintering, small size nano metal particles move and fill the gaps of large size nano metal particle clusters. The organic medium will volatilize, and the multilayer film will be sintered to form a complete metal interconnection layer. Compared with a sintered metal film with a single structure and a single number of layers, this technical solution will increase the density of the metal layer, thereby improving the electrical and thermal conductivity of the interconnection layer. nature. It is also optional to use pressure assist and enhance the diffusion mixing effect.

Description of the drawings

FIG. 1 is a structural diagram of a nano-silver thin layer after sintering in the first prior art.

FIG. 2 is a structure diagram of a single-layer nano-silver thin film in the second prior art.

FIG. 3 is a structure diagram of a double-layer nano silver film in the second prior art.

Fig. 4 is a structure diagram of a three-layer nano-silver film of prior art 2.

FIG. 5 is a schematic diagram of the structure of the multilayer nano metal film described in the technical scheme of the present invention.

Figure 6 is a flow chart of the preparation of the multilayer metal film of the present invention.

Fig. 7 is a schematic diagram of the preparation process of the multilayer metal film.

FIG. 8 is a process flow diagram of using the metal film to sinter and interconnect the chip and the substrate.

Fig. 9 is a schematic diagram of the sintered interconnection process flow.

Fig. 10 is a flow chart of preparing multiple single-layer metal films with different nano metal sizes according to the present invention.

Figure 11 is a schematic diagram of the metal film preparation process.

Serial number in the figure: small size copper nano particles in copper film 1, large size copper nano particles in copper film 2, supporting substrate 3, organic medium 4, large size copper nano particles in nano copper paste 5, small size Nano copper particles 6 in nano copper paste, printing squeegee 7, small size nano copper paste 8 in printing, large size nano copper paste 9 in printing, multi-size multilayer metal film 10, chip to be interconnected 11 , Substrate 12, sintering equipment 13, single-layer copper film 14 with large-size copper particles, single-layer copper film 15 with small-size nano particles.

detailed description

The following is a detailed description of the specific implementation of the present invention. It is necessary to point out that the following implementation is only for further description of the present invention, and cannot be understood as a limitation of the protection scope of the present invention. Some non-essential improvements and adjustments made still belong to the protection scope of the present invention.

The multilayer metal film structure provided by the present invention is shown in Figure 5 and includes:

At least 2 layers of organic dielectric materials;

The organic medium material has nano metal particles;

The sizes of the nano metal particles in each organic medium material layer are different.

Among them, the nano metal particles can be metal mixtures including gold, palladium, silver, copper, aluminum, silver-palladium alloys, gold-palladium alloys, copper-silver alloys, copper-silver-nickel alloys or copper-aluminum alloys; copper materials are preferably used instead of gold , Silver materials thus significantly reduce costs, and can effectively avoid high electron migration and high thermal mismatch after the sintering of the nano-silver film.

The metal film also includes a supporting substrate including polyester fiber, ceramic, glass and/or metal material. Organic media materials include organic solvents (such as amines, alcohols, fatty acids, mercaptans, and surfactants, etc.), rosin flux, solder paste, and/or adhesives.

Example one

Fig. 6 shows the preparation method and process of the multilayer metal film provided by the present invention, including the following steps:

1. Configure the nano metal particle solution with the first size in proportion to prepare the first metal paste;

2. Disposing a nano metal particle solution with a second size different from the first size according to the ratio to prepare a second metal paste;

3. Laminating the first metal paste and the second metal paste.

In the preparation process of the multilayer metal film containing the supporting substrate, it can be implemented in two ways:

(1) Two, three or more layers of metal metal films of different sizes of nanoparticles are directly arranged on the supporting substrate. As shown in Figure 7, a release coating is applied in advance on the surface of the supporting substrate, and step one is performed. Prepare a layer of metal paste of small size nano metal particles and set it on the supporting substrate, and then perform step 2 to prepare a layer of metal paste of larger size nano metal particles; if you want to build more layers of metal film, follow this order By analogy, more layers of metal pastes with nanoparticles of different sizes are prepared alternately.

1. Mix 0 to 5% resin or polymer, 0 to 1% film former and 30% solvent mixture in a tank to obtain a homogeneous solution. Add 0 to 2% wetting agent, 0 to 2% organic peroxide to this mixture.

2. Add 90% of the aforementioned small-sized copper powder (that is, have an average longest dimension from 0.5nm<d<20nm) and use an orbital mixer to mix at 1000rpm;

3. After mixing, grind in a grinder and mix for several minutes to obtain a uniform paste;

4. Use the same ratio and method to configure the copper paste with large size (that is, the average longest dimension from 1nm<D<10um);

5. Apply the metal paste with small particles to, for example, silicone-coated polyester sheets, ceramics or glass supporting substrates;

6. By drying at 100-130°C for 10-15 minutes, a metal film A with small size particles is formed on the supporting substrate;

7. Apply large-size nano copper paste on the surface of the metal film A;

8. By drying at 100-130°C for 10-15 minutes, a double-layer nano copper film B is formed;

9. Apply a small size nano copper paste on the surface of the metal film B;

10. After drying at 100-130°C for 10-15 minutes, a three-layer nano copper film C is formed.

In a preferred embodiment of the present invention, the copper film C is cut into a small copper film c according to the chip size in the above-mentioned manner; the process flow of sintering and interconnection of the obtained copper film c is shown in FIGS. 8 and 9. The specific steps include: 1) contact the bottom end of the chip to be interconnected with the multilayer composite copper film; 2) choose whether to use pressure assistance to make the top of the copper film adhere to the bottom of the chip; 3) remove the supporting substrate at the bottom of the copper film 4) Place the chip covered with a multilayer composite copper film on the surface of the carrier board; 5) Through a pressure or non-pressure sintering process, the chip is effectively connected to the carrier board, and the organic matter in the interconnecting copper layer is volatilized at the same time, different sizes The nano-copper particles are filled with each other and sintered into a mass, and finally a dense interconnected metal layer is formed.

Example two

A simpler preparation process of a multi-layer metal film containing a supporting substrate (2) is shown in Figures 10 and 11. On the supporting substrate with a release coating applied in advance, a single layer of small size is set by performing step one For nano metal particle metal paste, before step 3 is performed, a single layer of metal paste of larger size nano metal particles is set on another supporting substrate. When in use, two layers of metal paste can be sequentially bonded to the bottom of the chip. The sintering process enables the particles in the two films to mix with each other during the sintering process to achieve the purpose of filling voids and improving compactness. This solution reduces the difficulty of operation to a greater extent.

4. Use the same ratio and method to configure the copper paste with a large size (that is, with an average longest dimension from 1nm<D<10um).

5. Apply two pieces of metal paste with large and small particles to, for example, silicone-coated polyester sheet, ceramic or glass supporting substrate;

6. By drying at 100-130°C for 10-15 minutes, metal films A and D of large and small size particles are formed on the supporting substrate;

Example three

As shown in FIG. 8, the present invention further provides a method for sintering and interconnecting a chip and a substrate by using the multilayer nano metal film. Specifically include the following steps:

1. Cut the copper film C into a small copper film c according to the chip size;

2. Pasting the multilayer metal film on the bottom of the chip to be interconnected;

3. Optionally heat and press the chip and copper film system to mix the multilayer copper film; peel off the supporting substrate;

4. Place the chip/copper film system on the substrate;

5. The system is optionally heated and pressurized in the sintering furnace to make the substrate and the chip interconnect.

The relative performance comparison of the nano metal film obtained by the present invention and the prior art is as follows:

Table 1

In the packaging field, the diameter of nano metal particles prepared by chemical methods is usually above 30 nm, and it is difficult to achieve the preparation and subsequent stable retention of nano metal particles with a diameter of less than 20 nm or even less than 1 nm. In addition, the nano metal particles prepared by chemical preparation methods, despite the strict control of the operation and environment, the particle size range prepared in the same batch still has the technical problems of poor distribution concentration and large dispersion, which will affect the metal film to varying degrees After sintering performance. The physical method used in the present invention to prepare the nano metal particle size range is 0-20nm. In order to overcome the bottleneck of sintering performance caused by the limitation of the particle size prepared by the chemical method, the small size metal nano metal particles prepared by the physical method are combined with The chemically prepared large-size metal particles are combined with a sintered thickness of 90um to achieve the technological breakthrough of high thermal conductivity, electrical conductivity and high shear force as shown in the above table.

The specific selection of the larger and smaller sizes of the nano metal particles of the present invention makes the small size nano metal particles have a good filling effect in the gaps of the large size nano metal particles, and the compactness is significantly improved. The above-mentioned metal particle size design achieves the effects of improving the density of the metal layer and reducing the porosity after sintering, which cannot be achieved by the combination of nano metal particles of other diameter sizes. When copper particles are used to replace precious metal materials such as nano-silver materials, the nano-copper particles can be melted under low temperature conditions, and the melting point after sintering is close to the copper elemental material (1083°C), which can build a stable metal interconnection layer. Its single-component metal characteristics avoid the service reliability problem under the thermal cycling effect of alloy materials, realize copper-copper bonding, solve the problem of thermal expansion coefficient matching between the chip and the substrate, and avoid the reliability problem caused by electromigration. Compared with nano silver particles, it can effectively reduce the material and processing cost of interconnection packaging. The sintering nano-copper film made of nano-copper powder and paste has the excellent characteristics of copper materials, but also has the portability and easy formability of metal sintered films. It is the first choice for the next generation of electrical interconnection.

Although the exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will understand that they can be modified in form and details without departing from the scope and spirit of the invention disclosed in the appended claims. Various modifications, additions and substitutions are made, and all these changes shall fall within the protection scope of the appended claims of the present invention, and the various steps in the various departments and methods of the products claimed by the present invention can be combined in any combination. Forms are combined together. Therefore, the description of the embodiments disclosed in the present invention is not intended to limit the scope of the present invention, but to describe the present invention. Accordingly, the scope of the present invention is not limited by the above embodiments, but by the claims or their equivalents.

Claims

A multilayer metal film, characterized in that it comprises:

The first organic medium material layer,

The second organic medium material layer;

The first organic medium material layer contains first-size nano metal particles,

The first organic medium material layer contains second-size nano metal particles;

The diameter of the first size nano metal particles is different from that of the second size nano metal particles.
8. The multilayer metal film of claim 1, wherein the nano metal particle material is copper.
The multilayer metal film of claim 1, wherein the nano metal particle material is gold, palladium, silver, copper, aluminum, silver-palladium alloy, gold-palladium alloy, copper-silver alloy, copper-silver-nickel alloy or Copper aluminum alloy.
The multilayer metal film according to any one of claims 1 to 3, wherein the multilayer metal film further comprises a supporting substrate, wherein the supporting substrate comprises polyester fiber, ceramics, glass and/or metal materials .
The multilayer metal film according to any one of claims 1 to 3, wherein the contact surface of the supporting substrate and the nano metal particles is coated with silicone.
The multilayer metal film according to any one of claims 1 to 3, wherein the dielectric material layer comprises an organic dielectric material, and the organic dielectric material is an organic solvent, flux, solder paste, and/or adhesive mixture.
The multilayer metal film according to any one of claims 1 to 3, wherein, in the first size nano metal particles and the second size nano metal particles, the larger size of the nano metal particles has a diameter of 1 nm <D<10um.
The multilayer metal film according to any one of claims 1 to 3, wherein, in the first size nano metal particles and the second size nano metal particles, the smaller size of the nano metal particles has a diameter of 0.5 nm<d<20nm.
A method for preparing a multilayer metal film is characterized in that it specifically includes the following steps:

Step 1: Configure a nano metal particle solution with a first size and a nano metal particle solution with a second size; the second size nano metal particles have a different diameter from the first size nano metal particles;

Step 2: Use the first size nano metal particle solution to prepare a first metal paste, and use the second size nano metal particle solution to prepare a second metal paste;

Step 3: Use the first metal paste to prepare a first metal film; use the second metal paste to prepare a second metal film;

Step 4: bonding the first metal film and the second metal film.
9. The method for preparing a multilayer metal film according to claim 9, wherein said step 3 further comprises:

The first metal paste is disposed on the first supporting substrate, and then dried to form a first metal film.
9. The method for preparing a multilayer metal film according to claim 9, wherein said step 3 further comprises:

The second metal paste is disposed on the second supporting substrate, and then dried to form a second metal film.
The method for preparing a multilayer metal film according to claim 10 or 11, wherein the metal paste is applied to the supporting substrate by screen printing, spraying or coating methods.
9. The method for preparing a multilayer metal film according to claim 9, wherein the nano metal particle material is copper.
The method for preparing a multilayer metal film according to claim 9, wherein the nano metal particle material is gold, palladium, silver, copper, aluminum, silver palladium alloy, gold palladium alloy, copper silver alloy, copper silver Nickel alloy or copper aluminum alloy.
9. The method for preparing a multilayer metal film according to claim 9, wherein the supporting substrate material is polyester fiber, ceramic, glass and/or metal material.
The method for preparing a multilayer metal film according to claim 9, wherein the nano metal particle solution contains an organic medium material, and the organic medium material is an organic solvent, flux, solder paste, and/or adhesive. mixture.
A method for preparing a multilayer metal film is characterized in that it specifically includes the following steps:

Step 1: Configure a nano metal particle solution with a first size and a nano metal particle solution with a second size; the second size nano metal particles have a different diameter from the first size nano metal particles;

Step 2: Use the first size nano metal particle solution to prepare a first metal paste, and use the second size nano metal particle solution to prepare a second metal paste;

Step 3: Use the first metal paste to prepare the first metal film;

Step 4: Apply a second metal paste on the first metal film.
17. The method for preparing a multilayer metal film according to claim 17, wherein said step 3 further comprises:

Disposing the first metal paste on the first supporting substrate, and then performing a drying process to form a first metal film;

The preparation method further includes step 5: after coating the second metal paste on the first metal film, drying is performed to form the second metal film.
The method for preparing a multilayer metal film according to claim 18, wherein the metal paste is applied to the supporting substrate by screen printing, spraying or coating methods.
The method for preparing a multilayer metal film according to claim 18, wherein the nano metal particle material is copper.
The method for preparing a multilayer metal film according to claim 18, wherein the nano metal particle material is gold, palladium, silver, copper, aluminum, silver palladium alloy, gold palladium alloy, copper silver alloy, copper silver Nickel alloy or copper aluminum alloy.
The method for preparing a multilayer metal film according to claim 18, wherein the supporting substrate material is polyester fiber, ceramic, glass and/or metal material.
The method for preparing a multilayer metal film according to claim 18, wherein the nano metal particle solution contains an organic medium material, and the organic medium material is an organic solvent, flux, solder paste, and/or adhesive. mixture.
A method for interconnecting a chip and a substrate by using a multilayer metal film is characterized in that it specifically includes the following steps:

Step 1: Paste the multilayer metal film to the bottom of the chip to be interconnected;

Step 2: Heating the chip with the multi-layer metal film attached, and mixing the layers of the multi-layer nano metal film to obtain a multi-layer metal film chip;

Step 3: Interconnect the substrate and the multilayer metal film chip.
The method of using a multilayer metal film to interconnect a chip and a substrate according to claim 24, wherein step 1 comprises obtaining a multilayer metal film with the same shape as the chip, and the obtaining method is

Cutting the multilayer metal film according to the shape of the chip to be interconnected;

Or, the chip is placed on the heated multilayer metal film so that the multilayer metal film with the same shape as the chip adheres to the chip.
The method for interconnecting a chip and a substrate by using a multi-layer metal film according to claim 24, wherein step 1 further comprises: selecting with or without pressure assistance during bonding.
The method for interconnecting a chip and a substrate by using a multilayer metal film according to claim 24, wherein step 2 further comprises: selecting whether to have pressure assistance during heating.
The method for interconnecting a chip and a substrate using a multilayer metal film according to claim 24, wherein step 3 includes:

Step 3.1: Peel off the supporting substrate;

Step 3.2: Place the multilayer metal film chip on the substrate;

Step 3.3: Heat the multi-layer metal film chip in the sintering furnace, select whether to have pressure assistance, and interconnect the substrate and the multi-layer metal film chip.