阅读说明：本技术 一种金锡合金薄膜的制备方法 (Preparation method of gold-tin alloy film ) 是由 杨曌 李保昌 李淑华 罗俊尧 沓世我 于 2020-07-28 设计创作，主要内容包括：本发明涉及一种可用于共晶焊接的多层金锡合金薄膜制备工艺,根据理论计算膜层厚度,结合磁控溅射方式加工形成多层结构单质薄膜再经快速后退火处理工艺,制备得到金锡合金化完全和成份均匀的金锡合金薄膜。本发明以单质金属为原料,制备出金锡合金薄膜,有效简化工艺过程；采用磁控溅射制备方法,避免了化学法、真空蒸镀法的缺点,可制备出成分、厚度可控、图形复杂、位置灵活的金锡叠层薄膜,工艺稳定性良好,适用大批量生产；通过层数调节和热退火处理,可以有效调节薄膜层合金化区域,获得合金化均匀的薄膜层；采用RTP快速热退火处理,大大缩短了退火时间,有效提高了生产效率；金锡合金比例可控制在80:20～70:30之间,适用于共晶焊接。(The invention relates to a preparation process of a multilayer gold-tin alloy film for eutectic welding, which is characterized in that the thickness of a film layer is calculated according to theory, a multilayer structure simple substance film is formed by combining a magnetron sputtering mode, and the gold-tin alloy film with complete gold-tin alloying and uniform components is prepared by a rapid post-annealing treatment process. The gold-tin alloy film is prepared by taking simple substance metal as a raw material, so that the process is effectively simplified; the preparation method of magnetron sputtering is adopted, the defects of a chemical method and a vacuum evaporation method are avoided, the gold-tin laminated film with controllable components and thickness, complex pattern and flexible position can be prepared, the process stability is good, and the method is suitable for mass production; the alloying area of the thin film layer can be effectively adjusted through layer number adjustment and thermal annealing treatment, and the thin film layer with uniform alloying is obtained; the RTP rapid thermal annealing treatment is adopted, so that the annealing time is greatly shortened, and the production efficiency is effectively improved; the ratio of the gold to the tin alloy can be controlled to be 80: 20-70: 30, and the method is suitable for eutectic welding.)

1. The preparation method of the gold-tin alloy film is characterized by comprising the following steps:

(1) designing the simple substance gold-tin alloy thin film layer: calculating the thickness ratio of the simple substance gold layer and the tin layer according to a mass density formula M ═ rho V and the gold-tin ratio of the gold-tin alloy film; determining the total thickness of the simple substance gold layer and the tin layer according to the thickness of the gold-tin alloy film, and then determining the thickness of each layer of the simple substance gold layer and the tin layer according to the number of layers of the gold-tin alloy film;

(2) processing the ceramic substrate;

(3) adopting magnetron direct current sputtering to plate simple substance gold layers and tin layers on the ceramic substrate alternately to obtain a film with a laminated structure;

(4) and (4) carrying out thermal annealing treatment on the film with the laminated structure obtained in the step (3) by adopting rapid annealing, and cooling along with the furnace to obtain the gold-tin alloy film.

2. The production method according to claim 1, wherein in the step (1), the number of layers of the gold-tin alloy thin film is not less than 5, and the elemental gold layer is the outermost layer and the number of layers is one more than that of the elemental tin layer.

3. The method according to claim 1, wherein in the step (2), the ceramic substrate is an alumina ceramic sheet.

4. The method according to claim 1, wherein in the step (2), the treatment operation is: and ultrasonically cleaning the ceramic substrate for 10-30 min by sequentially adopting acetone, pure water and ethanol, and then drying at the drying temperature of not less than 100 ℃ for not less than 1 h.

5. The method according to claim 1, wherein in the step (3), the area not covered with the thin film is masked before the coating.

6. The method of claim 5, wherein the mask is a mechanical mask or a photomask mask.

7. The production method according to claim 1, wherein in the step (3), the outermost layer of the thin film of the stacked structure is an elemental gold layer.

8. The method of claim 1, wherein in step (3), the background vacuum during magnetron DC sputtering is not higher than 10^-4Pa, the working pressure of 0.1-0.6 Pa, normal temperature, power of 50-150W, gold layer coating time of 10-150 sec, and tin layer coating time of 10-100 sec.

9. The preparation method according to claim 1, wherein in the step (4), annealing is performed under vacuum, the annealing temperature is 260-320 ℃, the temperature rise time is 20-50 sec, and the heat preservation time is not less than 10 min.

10. The preparation method according to claim 1, wherein in the step (4), the weight ratio of gold to tin in the gold-tin alloy film is 80: 20-70: 30.

Technical Field

The invention relates to a preparation method of a gold-tin alloy film, in particular to a preparation process of a gold-tin alloy film which has a multi-layer structure and can be used for eutectic welding and has adjustable components, belongs to the technical field of microelectronic technology and semiconductor packaging, and is mainly applied to high-reliability packaging of products such as a film circuit, a ceramic heat sink, a single-layer capacitor and the like.

Background

Compared with the traditional welding and packaging process, the Au-Sn eutectic solder has the advantages of excellent physical properties, such as high strength of a welding head, moderate welding temperature, good wetting property, no need of soldering flux, corrosion resistance and the like, and is widely applied to the semiconductor welding process with high requirements on heat dissipation and reliability. In recent years, attention has been paid to the fields of radio frequency, optical communication, MEMS, and the like. Among them, the traditional way of presetting the gold-tin alloy sheet is no longer applicable to products such as thin film circuits, ceramic heat sinks, single-layer capacitors and the like. On one hand, the thickness of the preset gold-tin alloy sheet is not less than 25 μm at the thinnest, which far exceeds the requirement of a welding functional layer (2-5 μm) in the product, and the automation degree is low, thereby improving the cost; on the other hand, the pattern requirement of the welding position of the product is complex, the position is flexible, the precision is high, and the preset gold-tin alloy sheet cannot be met. Therefore, the gold-tin alloy layer with controllable components and thickness prepared by adopting the thin film process is an important process method for obtaining high-reliability welding of the products.

At present, the methods for preparing the gold-tin alloy film mainly comprise electroplating and vacuum plating. The electroplating process is complex, the parameter control requirement is extremely high, the uniformity of the film-forming thickness and components is poor, the process controllability is poor, and the industrial production is not facilitated. Compared with an electroplating method, the vacuum coating method has a more controllable process, high film forming stability and environmental protection, and mainly comprises an evaporation method and a magnetron sputtering method. The former has the defects of low utilization rate of evaporation materials, low thickness control precision and the like, and is not widely used in industrial production. The latter is suitable for mass production with higher control precision and better repeatability. For the heat treatment process after coating, a tube furnace with longer treatment time is conventionally adopted.

In conclusion, the magnetron sputtering method and the rapid annealing (RTP) treatment different from the conventional method are adopted, so that the controllability of the components and the thickness and the precision of the alloy film can be effectively improved, the uniform alloying of the film layer is ensured, meanwhile, the process repeatability is good, the cost performance is high, and the method is suitable for the preparation and the batch production of the gold-tin alloy film for eutectic welding.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the preparation method of the gold-tin alloy film, and the gold-tin alloy film prepared by the method has the advantages of adjustable components, good adhesive force, uniform thickness, accurate control and capability of meeting the eutectic welding requirement.

In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of a gold-tin alloy film comprises the following steps:

(1) designing the simple substance gold-tin alloy thin film layer: calculating the thickness ratio of the simple substance gold layer and the tin layer according to a mass density formula M ═ rho V and the gold-tin ratio of the gold-tin alloy film; determining the total thickness of the simple substance gold layer and the tin layer according to the thickness of the gold-tin alloy film, and then determining the thickness of each layer of the simple substance gold layer and the tin layer according to the number of layers of the gold-tin alloy film;

(2) processing the ceramic substrate;

(3) adopting magnetron direct current sputtering to plate simple substance gold layers and tin layers on the ceramic substrate alternately to obtain a film with a laminated structure;

(4) and (4) carrying out thermal annealing treatment on the film with the laminated structure obtained in the step (3) by adopting rapid annealing, and cooling along with the furnace to obtain the gold-tin alloy film.

The technical problem to be solved in the application is that the alloying of the gold-tin film is uniform, through the design of a multilayer structure simple substance film material, a multilayer structure gold-tin film is prepared on different substrates by adopting magnetron sputtering equipment, the gold-tin films with different compositions are prepared, then annealing treatment is carried out by adopting a heat treatment process, and the prepared gold-tin alloy film has controllable components and thickness, is uniform in film alloying and is suitable for batch production.

The invention relates to a preparation process of a multilayer gold-tin alloy film for eutectic welding, which is characterized in that the thickness of a film layer is calculated according to theory, a multilayer structure simple substance (gold and tin) film is formed by combining a magnetron sputtering mode, and then the gold-tin alloy film with complete gold-tin alloying and uniform components is prepared by a rapid post-annealing treatment process.

The innovation of the application is as follows: 1. the elemental metal film with a multilayer structure is adopted, so that the component segregation of the sputtering of the alloy target is avoided; 2. the magnetron sputtering process which is efficient, high in film forming stability and environment-friendly is adopted as the film preparation method; 3. the rapid thermal annealing treatment is adopted, so that the post-annealing process time can be effectively prolonged; 4. the alloy film with the weight ratio of gold to tin of 80:20 is actually prepared and can be used for gold-tin welding.

As a preferred embodiment of the preparation method of the present invention, in the step (1), the number of layers of the gold-tin alloy thin film is not less than 5, and the elemental gold layer is an outermost layer and the number of layers is one layer more than that of the elemental tin layer.

The thickness of each layer can be equally divided according to the area of the film layer needing alloying, and the film layer thickness can also be divided according to different density degrees.

As a preferred embodiment of the preparation method of the present invention, in the step (2), the ceramic substrate is an alumina ceramic sheet.

As a preferred embodiment of the preparation method of the present invention, in the step (2), the treatment operation is: and ultrasonically cleaning the ceramic substrate for 10-30 min by sequentially adopting acetone, pure water and ethanol, and then drying at the drying temperature of not less than 100 ℃ for not less than 1 h.

As a preferred embodiment of the preparation method of the present invention, in the step (3), a mask is used to block an area that is not to be covered with a thin film before plating.

As a preferred embodiment of the preparation method of the present invention, the mask shielding is mechanical mask shielding or photomask shielding.

Mechanical masking is the direct attachment of a mechanical mask to an alumina ceramic substrate.

As a preferable embodiment of the preparation method of the present invention, in the step (3), the outermost layer of the stacked structure thin film is an elemental gold layer. In order to prevent oxidation, the outermost layer of the stacked-structure thin film, i.e., the outermost layer away from the substrate, should be an elemental gold layer.

As a preferred embodiment of the preparation method of the present invention, in the step (3), during the magnetron DC sputtering process, the background vacuum is not higher than 10^-4Pa, the working pressure of 0.1-0.6 Pa, normal temperature, power of 50-150W, gold layer coating time of 10-150 sec, and tin layer coating time of 10-100 sec. Magnetron sputtering methods include, but are not limited to, DC, RF, co-sputtering.

In the step (4), annealing is performed under vacuum, wherein the annealing temperature is 260-320 ℃, the temperature rise time is 20-50 sec, and the heat preservation time is not less than 10 min.

In a preferred embodiment of the preparation method of the present invention, in the step (4), the weight ratio of gold to tin in the gold-tin alloy thin film is 80:20 to 70: 30.

The structure for equally dividing the thickness of the simple substance film layer can obtain a gold-tin film with uniform alloying, and when the weight ratio of gold to tin in the alloy film is controlled to be 80: 20-70: 30, the gold-tin film can be used for eutectic welding; the structure of the thickness of the simple substance film layer is split for different density degrees, so that the locally alloyed gold-tin film can be obtained, and the locally alloyed area can be arranged above, in the middle, below or at any specified position of the film layer.

Compared with the prior art, the invention has the beneficial effects that: the gold-tin alloy film is prepared by taking simple substance metal as a raw material, so that the process is effectively simplified; the preparation method adopts magnetron sputtering, avoids the defects of a chemical method and a vacuum evaporation method, can prepare the gold-tin laminated film with controllable components and thickness, complex pattern and flexible position, has good process stability and is suitable for mass production; the alloying area of the thin film layer can be effectively adjusted through layer number adjustment and thermal annealing treatment, and the thin film layer with uniform alloying is obtained; the RTP rapid thermal annealing treatment is adopted, so that the annealing time is greatly shortened, and the production efficiency is effectively improved; the ratio of the gold to the tin alloy can be controlled to be 80: 20-70: 30, and the method is suitable for eutectic welding.

Drawings

FIG. 1 is a structural diagram of a Au-Sn alloy thin film according to the present invention.

FIG. 2 is a scanning electron microscope photograph of a tin alloy thin film in example 1.

FIG. 3 is a cross-sectional view and a composition diagram of the Au-Sn alloy thin film after the rapid annealing in example 1.

FIG. 4 is a cross-sectional profile and composition diagram of the Au-Sn alloy thin film after the rapid annealing in example 2.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.

The structure of the gold-tin alloy film of the present invention is shown in FIG. 1.