A method for preparing a copper-diamond packaging substrate

Abstract

The present invention relates to the field of semiconductor preparation technology, specifically a preparation method of a copper-diamond package substrate. Specifically comprising the following steps: Step 1: (1) copper powder and diamond metallization powder are mixed evenly to obtain a copper-diamond mixed powder; (2) a copper sheet is pretreated to obtain a pretreated copper sheet; Step 2: the copper-diamond mixed powder is sprayed onto the pretreated copper sheet, and then reduced in a formic acid atmosphere to obtain a copper-diamond composite body; Step 3: the copper-diamond composite body is electroplated and filled, and then surface grinding and cleaning are performed in sequence to obtain a copper-diamond package substrate. The copper-diamond package substrate prepared by the present invention realizes the close physical bonding of copper and diamond, and compared with the prior art, it avoids the problems of shrinkage pores and looseness caused by high-temperature melting, and diamond does not need to design a jig at the same time, and a high thermal conductivity copper-diamond package substrate is obtained comprehensively.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor preparation, and in particular to a method for preparing a copper-diamond packaging substrate. Background Art

[0002] The development of the third generation of semiconductors has driven power devices to move towards high power, miniaturization, and integration. The power consumption within a limited volume has increased significantly, and the heat accumulation has risen sharply. The heat dissipation problem has become a bottleneck in the development of high-power electronic devices. The packaging substrate of high-power semiconductor devices should have both high thermal conductivity and a thermal expansion coefficient similar to that of the chip. With the marketization of artificial diamonds, metal-based diamond composite materials are favored by the electronic packaging industry. Copper-diamond packaging materials show strong heat dissipation performance and excellent thermal expansion coefficient, and are more ideal packaging substrates for high-power devices.

[0003] The preparation methods of common copper-diamond composite materials on the market are as follows:

[0004] (1) Blank forming method: Add a binder to mix copper and diamond powders evenly, then cold press them into a blank, remove the binder and sinter to achieve copper-diamond powder connection. In this method, copper powder is easily oxidized during processing, the powder distribution is uneven, and large-diamond particles are prone to breakage under high pressure. If these factors are not controlled and eliminated, the natural thermal conductivity advantage of diamond will be greatly reduced.

[0005] (2) Liquid infiltration method: After the diamonds are evenly distributed, the copper matrix is ​​heated to the melting point (above 1000°C), and the molten copper liquid infiltrates into the gaps between the diamond particles to form a composite material, which is then cooled and solidified. This method has extremely high requirements for the selection and design of the mold, and is very likely to cause processing defects such as looseness and holes; in addition, the direct composite of diamond and copper matrix will cause problems such as mutual non-wetting and poor interface bonding, and the thermal conductivity of the composite material will be reduced, so the heat dissipation performance of the copper-diamond packaging substrate cannot reach the best.

[0006] (3) Electroplating deposition method: The diamond surface is chemically copper plated and then placed in the electroplating solution to deposit copper atoms. This method is only applicable to small-sized diamond particles. It has high requirements for particle uniformity and low deposition rate, making it difficult to achieve mass production.

[0007] In summary, in the preparation process of the existing technology of copper-diamond packaging substrate, it is difficult to further improve the heat dissipation performance of the packaging substrate due to the problems of easy oxidation and contamination of copper powder, high production temperature and difficulty in mold design.

[0008] Based on this, a method for preparing a copper-diamond packaging substrate needs to be developed urgently. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing a copper-diamond packaging substrate to solve the problems raised in the above background technology.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] A method for preparing a copper-diamond packaging substrate comprises the following steps:

[0012] Step 1:

[0013] (1) copper powder and diamond metallization powder are mixed uniformly to obtain copper-diamond mixed powder;

[0014] (2) pre-treating the copper sheet to obtain a pre-treated copper sheet;

[0015] Step 2: spraying the copper-diamond mixed powder onto the pretreated copper sheet, and then reducing it in a formic acid atmosphere to obtain a copper-diamond composite body;

[0016] Step 3: electroplating and filling the copper-diamond composite body, and then sequentially grinding and cleaning the surface to obtain a copper-diamond packaging substrate.

[0017] Furthermore, the copper-diamond mixed powder comprises the following components: by mass fraction, 50-65% copper powder and 35-50% diamond metallization powder; wherein the copper powder particle size is 5-20 μm, and the diamond metallization powder particle size is 5-60 μm.

[0018] Furthermore, the copper sheet has the following parameters: purity ≥ 99.99% and surface hardness 20-45 HV.

[0019] Furthermore, the pretreatment method of the pretreated copper sheet is: washing the copper sheet with a 30wt% nitric acid solution for 30 to 60 seconds, then washing it with pure water for 1 to 3 minutes, and finally drying it to obtain the pretreated copper sheet.

[0020] Furthermore, the spraying is cold spraying, and the specific parameters are: spraying distance 0.2-1 mm, spraying temperature ≤35° C., duty cycle ≤10%, and spraying thickness 10-800 μm.

[0021] Furthermore, the formic acid flow rate in the formic acid atmosphere reduction is 5 to 50 L / min.

[0022] Furthermore, the electroplating solution used for the electroplating filling includes the following concentration components: 80-110 g / L of copper sulfate pentahydrate, 40-55 g / L of ethylenediamine, 40-55 g / L of sodium sulfate decahydrate, 40-55 g / L of ammonium sulfate, and the rest is pure water.

[0023] Furthermore, the surface roughness of the copper-diamond packaging substrate is Ra≤1.5 μm.

[0024] Furthermore, the copper-diamond packaging substrate is used in semiconductor devices.

[0025] The key of the present invention is:

[0026] (1) Within the scope of meeting the requirements of cold spraying technology, the particle size of copper and diamond powders is controlled, and the diamond copper mixed powder with equivalent thickness is sprayed, which can meet the close connection between multiple layers of diamond to form a diamond three-dimensional heat transfer network structure, and the thermal conductivity of the copper-diamond composite is high;

[0027] (2) Formic acid atmosphere invades the spray layer within the duty cycle, reducing the copper powder that is oxidized and surface contaminated during the mixing and spraying operations, ensuring the quality of electroplating filling and higher density;

[0028] (3) In the present invention, the copper sheet can be sprayed on one side or both sides. When the single-side spraying method is adopted, the non-sprayed surface still remains in the state of high-purity copper, without diamond particle protrusions, and has good direct surface chemical nickel or nickel-gold plating ability, meeting the solderability requirements of the packaging substrate.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention embeds the copper-diamond mixed powder into the copper matrix through cold spraying so that the matrix and the diamond are tightly combined, and the diamond particles in the inner layer of the spray layer overlap each other to form an effective three-dimensional network for heat transmission; at the same time, formic acid reduction treatment is performed, and the formic acid atmosphere invades the internal structure of the spraying to reduce the copper powder that is oxidized and surface-contaminated during the mixing and spraying operations, so that the electroplating filling is highly densified, and the physical bonding of copper and diamond is achieved. Compared with the prior art, the problems of shrinkage pores and looseness caused by high-temperature melting are avoided. At the same time, diamond does not need to design a jig, and the preparation of a high thermal conductivity copper-diamond packaging substrate is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 It is a schematic diagram of the preparation process of the present invention;

[0032] Figure 2 This is the spraying surface morphology in step 2 of Example 1;

[0033] Figure 3 This is the spray cross-sectional morphology in step 2 of Example 1;

[0034] Figure 4 This is the surface morphology of the electroplating filling in step 3 of Example 1;

[0035] Figure 5 This is the surface morphology of titanium-coated diamond in step 1 of Example 2;

[0036] Figure 6 This is the surface morphology of the copper-diamond packaging substrate sample obtained in Comparative Example 1. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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] It should be noted that the purchasers of all raw materials involved in the present invention include, without any special restrictions, the following examples:

[0039] Spherical copper powder was purchased from Zhongnuo New Materials Technology Co., Ltd.;

[0040] MBD8 artificial diamond metallized powder (titanium-coated diamond) was purchased from Henan Huanghe Cyclone Co., Ltd.;

[0041] Chemical silver plating solution was purchased from Anhui Yizhufeng Electronic Technology Co., Ltd.

[0042] Example 1: A method for preparing a copper-diamond packaging substrate:

[0043] Step 1: (1) adding spherical copper powder with a particle size of 6 to 10 μm and MBD8 artificial diamond metallized powder with a particle size of 8 to 15 μm (titanium-plated diamond, titanium layer thickness of 10 nm, thermal conductivity of 2000 W / m·k) into a ball mill at a mass ratio of 60:40, setting the ball mill speed to 350 r / min, and ball milling and stirring for 5 hours to obtain a copper-diamond mixed powder; (2) washing a 0.2 mm thick high-purity copper sheet (purity ≥99.99%, surface hardness 35 HV) with a 30 wt% nitric acid solution for 45 seconds, then washing with pure water for 2 minutes, and finally drying with hot air to obtain a pretreated copper sheet;

[0044] Step 2: Spray the copper-diamond mixed powder onto the pretreated copper sheet on one side (spraying parameters: nozzle-copper sheet distance 0.3 mm, temperature 28 ° C, duty cycle 5%, spraying thickness 450 μm); after spraying, place it in a reflow oven and reduce it in formic acid atmosphere (formic acid flow rate 15 L / min) to obtain a copper-diamond composite body (specific sprayed surface and cross-sectional morphology as shown in Figure 2 , Figure 3 shown);

[0045] Step 3: (1) preparing the electroplating solution: the concentration components of the electroplating solution are: 90 g / L copper sulfate pentahydrate, 45 g / L ethylenediamine, 45 g / L sodium sulfate decahydrate, 45 g / L ammonium sulfate, and the rest is pure water;

[0046] (2) The copper-diamond composite body was cut into 10 mm × 20 mm rectangles and immersed in the electroplating solution at a current density of 2 A / mm 2 Electroplating filling is performed under the following conditions (the surface morphology of the electroplating filling is as follows Figure 4 shown);

[0047] (3) After electroplating filling, the substrate was ground with 3000 mesh water-abrasive paper, then cleaned with 10 wt % HCl solution for 5 seconds, cleaned with pure water for 2 minutes, and dried with hot air to obtain a copper-diamond packaging substrate with a spray surface Ra of 1.2 μm and an unsprayed surface Ra of 0.5 μm;

[0048] Example 2: A method for preparing a copper-diamond packaging substrate:

[0049] Step 1: (1) Spherical copper powder with a particle size of 8 to 15 μm and MBD8 artificial diamond metallized powder with a particle size of 40 to 45 μm (titanium-coated diamond, titanium layer thickness of 8 nm, thermal conductivity of 1800 W / m·k, and surface morphology as shown in the following example) are mixed. Figure 5 (2) a 0.3 mm thick high-purity copper sheet (purity ≥ 99.99%, surface hardness 38 HV) was cleaned with a 30 wt % nitric acid solution for 45 s, then cleaned with pure water for 2 min, and finally dried with hot air to obtain a pretreated copper sheet;

[0050] Step 2: Spray the copper-diamond mixed powder onto the pretreated copper sheet on one side (spraying parameters: nozzle-copper sheet distance 0.4 mm, temperature 30° C., duty cycle 8%, spraying thickness 500 μm); after spraying, place in a reflow oven for reduction in formic acid atmosphere (formic acid flow rate 20 L / min) to obtain a copper-diamond composite body;

[0051] Step 3: (1) preparing the electroplating solution: the concentration components of the electroplating solution are: 90 g / L copper sulfate pentahydrate, 45 g / L ethylenediamine, 45 g / L sodium sulfate decahydrate, 45 g / L ammonium sulfate, and the rest is pure water;

[0052] (2) The copper-diamond composite body was cut into 10 mm × 20 mm rectangles and immersed in the electroplating solution at a current density of 3 A / mm 2 Electroplating filling is performed under the following conditions;

[0053] (3) After electroplating filling, the substrate was ground with 3000 mesh water-abrasive paper, then cleaned with 10 wt % HCl solution for 5 s, cleaned with pure water for 2 min, and dried with hot air to obtain a copper-diamond packaging substrate with a sprayed surface Ra of 1.45 μm and an unsprayed surface Ra of 0.43 μm.

[0054] Comparative Example 1: A copper-diamond packaging substrate was prepared by hot pressing and infiltration method, specifically:

[0055] Diamonds were placed in a mold of a vacuum hot press furnace with a stacking thickness of 3.5 mm. After preheating it to 1050°C, molten copper at 1100°C was poured into the mold. The surface of the copper was directly acted on by a pressure head to make the copper penetrate into the diamond. After the furnace was cooled, the mold was demolded to obtain a copper-diamond packaging substrate (surface morphology as shown in Figure 2). Figure 6 shown).

[0056] Performance test: Since the copper layer is easily polluted by oxidation, causing problems such as poor welding, in actual applications, the copper surface will be further silver-plated. Therefore, in the scheme, during the performance test, the copper-diamond packaging substrates prepared in Examples 1 to 2 and Comparative Example 1 were silver-plated (silver-plating treatment: at 85°C, the copper-diamond packaging substrate was immersed in chemical silver plating solution for 35 minutes; the thickness of the silver plating layer was 0.4 μm), and then the copper-diamond packaging substrate was subjected to macroscopic observation, microscopic observation and thermal conductivity test.

[0057] Test results: The surface of the copper-diamond packaging substrate sample prepared in Comparative Example 1 has a large number of diamond embossed particles. After slight grinding, it is microscopically observed that there are many defects such as pores on its surface, and the surface cannot be silver-plated. The thermal conductivity test value is 394.5 W / m·k, and it cannot meet the commercial requirement of ≥500 W / m·k. The surface of the copper-diamond packaging substrate sample prepared in Examples 1 to 2 still retains the characteristics of copper, and the surface can be silver-plated. The thermal conductivity test value is 570.5 W / m·k, and the heat dissipation performance meets commercial requirements.

[0058] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0059] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a copper-diamond packaging substrate, characterized in that: The following steps are involved: Step 1: (1) copper powder and diamond metallization powder are mixed evenly to obtain copper-diamond mixed powder; (2) pre-treating the copper sheet to obtain a pre-treated copper sheet; Step 2: Spraying the copper-diamond mixed powder onto the pretreated copper sheet, and then reducing it in a formic acid atmosphere to obtain a copper-diamond composite body; Step 3: electroplating and filling the copper-diamond composite body, and then sequentially grinding and cleaning the surface to obtain a copper-diamond packaging substrate; The copper-diamond mixed powder comprises the following components: by mass fraction, 50-65% copper powder and 35-50% diamond metallization powder; wherein the copper powder particle size is 5-20 μm, and the diamond metallization powder particle size is 5-60 μm; The pretreatment method of the pretreated copper sheet is as follows: the copper sheet is cleaned with a 30wt% nitric acid solution for 30 to 60 seconds, then cleaned with pure water for 1 to 3 minutes, and finally dried to obtain the pretreated copper sheet; The spraying is cold spraying, and the specific parameters are: spraying distance 0.2-1 mm, spraying temperature ≤35° C., duty cycle ≤10%, spraying thickness 10-800 μm; the formic acid flow rate in the formic acid atmosphere reduction is 5-50 L / min; The electroplating solution used for the electroplating filling includes the following concentration components: 80-110 g / L of copper sulfate pentahydrate, 40-55 g / L of ethylenediamine, 40-55 g / L of sodium sulfate decahydrate, 40-55 g / L of ammonium sulfate, and the rest is pure water.

2. The method for preparing a copper-diamond packaging substrate according to claim 1, characterized in that: The surface roughness Ra of the copper-diamond packaging substrate is less than or equal to 1.5 μm. 3 . The copper-diamond packaging substrate prepared by the method for preparing a copper-diamond packaging substrate according to any one of claims 1 to 2 .

4. Use of the copper-diamond packaging substrate according to claim 3 in a semiconductor device.

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