Additive method based on tin precipitation in formic acid atmosphere

Abstract

The invention relates to an additive manufacturing method based on tin deposition in a formic acid atmosphere, and aims to solve the problems of high cost, complex equipment, strict operation conditions, process limitation and the like in the traditional film preparation technology. By utilizing a tin evaporation phenomenon in a formic acid atmosphere, efficient deposition of a metal film within a specific thickness range is realized, and the method is particularly suitable for preparing a tin layer in a semiconductor device. According to the method, an expensive high-energy source or complex target material equipment is not needed, operation is easy and convenient, the cost is low, the process flexibility is high, and the requirements for the metal film in various application scenes can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing and thin film deposition, and in particular relates to a method for depositing a metal thin film by tin evaporation in a formic acid atmosphere, which can be widely used in the preparation of a tin layer in the manufacture of semiconductor devices. Background Art

[0002] Traditional methods for forming metal films mainly include chemical vapor deposition (CVD) and physical vapor deposition (PVD) technologies. These methods convert metal source substances into vapor or ions, and then deposit them on the surface of the substrate to form metal films. However, these traditional methods have limitations such as high cost, complex operation, difficult to control film quality, and inability to meet specific application requirements. For example, in the process of chemical vapor deposition and physical vapor deposition, gas flow, temperature gradient, reaction time, etc. need to be precisely controlled, which makes the production process susceptible to external factors.

[0003] Among the existing technical solutions for the formation of metal films, the implementation solution closest to the present invention is a method based on magnetron sputtering. Magnetron sputtering technology is a commonly used physical vapor deposition technology. The process involves placing a metal target in a vacuum chamber, evaporating metal atoms on the surface of the target by electron bombardment and depositing them on the surface of the substrate to form a metal film, which has good film adhesion and controllable preparation of complex structures. However, due to the physical properties and chemical activity of metals such as tin and other factors, magnetron sputtering technology mainly uses metals such as aluminum, titanium, chromium, nickel, etc. to manufacture transparent conductive films, superconducting films, decorative films and other functional films, rather than being mainly used in the preparation of tin layers in semiconductors, and has the disadvantages of high equipment cost, complex operation, low deposition rate and sensitivity to environmental pollution. For the application of tin layers in semiconductors, the magnetron sputtering method mainly has the following challenges and limitations. Specifically, during the magnetron sputtering process, strict requirements are placed on process parameters and environmental conditions, and due to the physical properties and chemical activity of tin, the sputtering rate of tin is low, the deposition process is slow, the target utilization rate is low, and the sputtering yield is not high. In addition, it is difficult to control the uniformity and thickness of the film under the influence of a magnetic field. In the fields of microelectronics, optical devices, and sensors, the thickness of the film produced by magnetron sputtering is usually between ten nanometers and hundreds of nanometers. There are still technical gaps and challenges in the application field where the thickness of the metal layer exceeds several microns.

[0004] Therefore, it is necessary to seek more effective technical solutions. In view of the various challenges and limitations faced by the above conventional metal film forming methods, the present invention proposes a tin layer forming method based on metal precipitation in a formic acid atmosphere. By utilizing the tin evaporation phenomenon in a formic acid atmosphere, the present invention simplifies and improves the metal film forming process, reduces costs, improves film quality, and can meet the needs of specific application fields. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to propose an additive method based on tin precipitation in a formic acid atmosphere, aiming to reduce the many limitations of the traditional method. The advantages of the present invention mainly include low cost, simple operation, superior film quality and wide applicability. The working principle mainly involves the reduction of metal oxides and the generation of metal formate. First, gaseous formic acid reacts with the surface of the metal plate and the tin solder ball through chemical adsorption to promote the reduction of oxides. At this time, formic acid acts as a reducing agent to convert solid tin oxide into tin formate. When it rises to a certain peak temperature, the Sn surface oxide has been partially consumed, and Sn begins to appear on the surface of the solder ball. Solid Sn begins to react with formic acid to generate tin formate. According to research, the expansion area under formic acid atmosphere can be continuously increased, and the film is continuously plated on the Cu substrate. At this time, tin formate can be continuously produced. Subsequently, tin formate evaporates in large quantities in a form similar to a volcanic eruption and precipitates on the surface of the Cu substrate to form a uniform tin layer.

[0006] The invention relates to an additive method based on tin precipitation in a formic acid atmosphere, the key of which lies in the reduction reaction of metals and their oxides in the formic acid atmosphere, and the continuous evaporation and precipitation of tin formate when the metal tin is heated to a certain peak temperature, and the formation of a uniform tin layer.

[0007] Taking copper substrate and Sn metal source as an example, it mainly involves metal oxide reduction and metal formate formation, including the following steps:

[0008] S1: Prepare metal source and substrate: Select the required metal source (eg, tin) and substrate (eg, glass, silicon wafer, etc.).

[0009] S2: Prepare formic acid atmosphere: Establish formic acid (HCOOH) atmosphere in the reaction chamber, ensuring appropriate atmospheric conditions and temperature.

[0010] S3: Control coating conditions: Optimize the formation process and quality of the metal film by controlling the temperature and pressure of the formic acid atmosphere and the heating conditions of the metal source.

[0011] S4: Heating the metal source: placing the metal source (eg, tin) in a formic acid atmosphere and converting it into a vapor or gas state by heating.

[0012] S5: coating the substrate surface: placing the substrate to be coated in a reaction chamber, and allowing the vapor or gaseous state of metal formate (such as tin formate) to be deposited on the substrate surface to form a metal film.

[0013] Through the chemical adsorption and reduction of formic acid, gaseous formic acid chemically adsorbs on the Cu substrate and the surface of the Sn solder ball, thereby promoting the reduction of the oxide. Formic acid, as a reducing agent, reduces the solid Sn oxide to generate solid tin formate and H2, H2O, etc., as shown in formula (1) and formula (2).

[0014] When the temperature reaches a certain peak value, the Sn surface oxide has been partially consumed, and Sn begins to appear on the surface of the solder ball. Solid Sn begins to react with formic acid to generate tin formate. Studies have shown that the expansion area in the formic acid atmosphere can continue to increase, and the coating continues. At this time, tin formate can be continuously generated, as shown in formula (3).

[0015] Subsequently, tin formate evaporates and precipitates, similar to a volcanic eruption. A large amount of solid tin formate evaporates and becomes gaseous and deposits on the lower surface of the copper substrate, forming a uniform tin layer, as shown in formula (4).

[0016] The specific chemical reaction can be expressed as:

[0017] SnO+iHCOOH (g) →Sn(COOH) i(s) +H2O (g) (1)

[0018] SnO2+iHCOOH (g) →Sn(COOH) i(s) +H 2(g) +O 2(g) (2)

[0019] Sn (s) +iHCOOH (g) →Sn(COOH) i(s) +H 2(g) (3)

[0020] Sn(COOH) i(s) →Sn(COOH) i(g) (4)

[0021] The present invention has the following beneficial effects:

[0022] 1. Low cost and simplified equipment: The precipitation method under formic acid atmosphere does not require expensive high energy sources and special targets, which reduces production costs. The equipment is relatively simple, the operating conditions are easy to control, and the equipment maintenance cost is low.

[0023] 2. Flexible process conditions: The precipitation method under formic acid atmosphere has flexible requirements on process parameters and environmental conditions and has higher process stability.

[0024] 3. Wide applicability: This method is applicable to a variety of substrates and application scenarios. It is not only suitable for nano-scale thin films, but also can prepare metal films with a thickness of micrometers or above at low cost. It can be used not only for the application of tin layers in semiconductors, but also for optical devices and other fields with high precision requirements, and has broad application prospects.

[0025] 4. Environmentally friendly: Formic acid is a low-toxic, biodegradable organic acid, which reduces the impact on the environment and improves the environmental friendliness and operational safety of the process. Compared with traditional methods, the present invention greatly reduces energy consumption, improves resource utilization efficiency, and helps achieve sustainable development goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a vapor deposition experimental device in one embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of the evaporation effect in one embodiment of the present invention; DETAILED DESCRIPTION

[0028] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0029] In this technical solution, Sn corresponds to the metal element tin, and Cu corresponds to the metal element copper. Figure 1 to Figure 2 ,like Figure 1 The figure shows the schematic diagram of the evaporation experimental equipment. Figure 2 : is a schematic diagram of a specific evaporation effect. This embodiment provides an additive method based on tin precipitation in a formic acid atmosphere. The system structure description and preparation steps are as follows:

[0030] The system structure of the present invention mainly includes a reaction chamber, a heating device, a formic acid supply device, an exhaust device, a metal source and a substrate.

[0031] 1. Reaction chamber and heating device: A reaction chamber is provided for placing the metal source and the substrate, and a heating device is provided for heating the metal source.

[0032] 2. Formic acid supply device: a device for providing formic acid atmosphere, including a storage and supply system for liquid formic acid, to ensure that the atmosphere in the reaction chamber contains an appropriate amount of formic acid.

[0033] 3. Metal source, substrate and metal plate to be coated: Select a suitable metal source (such as tin) and substrate (such as glass, silicon wafer), and place them in the reaction chamber, and place the metal plate to be coated (such as Cu metal plate) at a certain height above them.

[0034] 4. Heating and reaction process: The heating device heats the metal source to convert it into steam or gas. At the same time, the liquid formic acid supply device delivers formic acid gas to the reaction chamber to react with the heated metal source.

[0035] The preparation steps are as follows:

[0036] S1: Prepare metal source and substrate: Select the required metal source (eg, tin) and substrate (eg, glass, silicon wafer, etc.).

[0037] S2: Prepare formic acid atmosphere: Establish formic acid (HCOOH) atmosphere in the reaction chamber, ensuring appropriate atmospheric conditions and temperature.

[0038] S3: Control coating conditions: Optimize the formation process and quality of the metal film by controlling the temperature and pressure of the formic acid atmosphere and the heating conditions of the metal source.

[0039] S4: Heating the metal source: placing the metal source (eg, tin) in a formic acid atmosphere and converting it into a vapor or gas state by heating.

[0040] The present invention proposes a method for forming a tin layer based on metal precipitation in a formic acid atmosphere. By utilizing the tin evaporation phenomenon in a formic acid atmosphere, the present invention simplifies and improves the metal film forming process, reduces costs, improves film quality, and can meet the needs of specific application fields.

[0041] The key points of this technical solution are as follows:

[0042] 1. Metal precipitation additive technology in formic acid atmosphere: The key of the present invention is to utilize the metal precipitation phenomenon in formic acid atmosphere, and generate metal formate such as tin formate Sn(COOH)2 by reacting formic acid gas with heated metal source, and the metal formate is further gasified to form an ultra-thin tin layer. This deposition process is the key step of the present invention to achieve low-cost and high-efficiency preparation of tin layer.

[0043] 2. Simplified operation process: Compared with the traditional metal film forming method, the present invention has the advantages of simple operation and clear process. It does not require complex equipment and precise operation, and only needs to provide formic acid atmosphere and appropriate heating conditions to achieve high-quality addition of metal film.

[0044] 3. Reduce preparation costs: The present invention utilizes common formic acid atmosphere as a reducing agent, avoiding the problem of expensive equipment and special materials required in traditional methods, thereby reducing the cost of metal film preparation and improving economy and scalability.

[0045] 4. Wide applicability: The additive method of metal deposition under formic acid atmosphere has the characteristics of wide applicability and can be flexibly applied to the formation of thin films of different metals and substrate materials, especially for the application of tin layers in semiconductors. At the same time, it can meet the special requirements of metal film formation in specific application fields and has strong application prospects and market competitiveness.

[0046] The above disclosure is only a preferred embodiment of the method for preventing tin from drifting in a formic acid atmosphere of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. An additive method based on tin precipitation in a formic acid atmosphere, characterized by comprising the following steps: S1: prepare metal source and substrate; S2: establishing a formic acid atmosphere in the reaction chamber; S3: Control the temperature and pressure of formic acid atmosphere; S4: heating the metal source to generate tin formate; S5: precipitate tin formate onto the surface of the substrate to form a metal film.

2. The method according to claim 1, wherein the metal source includes but is not limited to tin and its alloy materials, the substrate on which the metal source is placed includes but is not limited to glass or silicon wafer, and the metal plate to be coated includes but is not limited to a Cu substrate.

3. The method according to claim 1 is suitable for forming an ultra-thin tin layer in semiconductor device manufacturing, and the thickness of the formed metal film can be controlled in the nanometer level and above. The method according to claim 1 , wherein the metal film has high uniformity and stability.

5. The method according to claim 1 is suitable for forming a metal film under specific atmosphere and temperature conditions, wherein the heating temperature of the metal source is adjusted according to the characteristics of the metal to ensure effective generation and precipitation of the metal. The method according to claim 1 , further comprising annealing the metal film to improve its properties.

7. The method according to claim 1, further comprising optimizing the growth rate and quality of the metal film by adjusting the flow rate and composition of the formic acid atmosphere, wherein the formic acid metal compound is generated by exposing the metal source to formic acid vapor for a catalytic reaction.

8. The method according to claim 1, wherein the forming process of the metal film comprises stacking multiple metal films to achieve specific physical and chemical properties.

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