Discussion on effective methods and technologies for improving adhesion of sapphire metallized layer
In the manufacture of modern semiconductor and optoelectronic devices, sapphire, as an important substrate material, is widely used in LED, laser and various high-efficient optoelectronic devices. However, when attaching the metal layer to the sapphire surface, how to improve the adhesion of the metallized layer is still a technical problem. The improvement of the adhesion of the metallized layer not only relates to the stability and performance of the device, but also directly affects the production efficiency and cost. This article will discuss several improvements Sapphire metallization The method of layer adhesion provides useful reference for researchers and engineers in related fields.
1、 Surface treatment of sapphire
Surface treatment is a key step to improve the adhesion of sapphire metallized layer. During the processing of sapphire surface, a layer of aluminum oxide film is often formed, which will affect the adhesion between metal and sapphire. Therefore, removing surface oxides, increasing surface roughness and improving surface chemical environment are all effective means to improve adhesion.
1.1 Laser cleaning
Laser cleaning technology uses high-energy laser beam to act on the surface of sapphire to remove surface oxides and pollutants. This method can not only avoid environmental pollution caused by traditional chemical cleaning, but also accurately control the depth and scope of treatment, making the surface state more suitable for the attachment of metallized layer.
1.2 Chemical treatment
Chemical treatment mainly includes acid washing and alkali washing. The oxide layer or other impurities on the surface of sapphire are removed through acid or alkali solution. Common acid solutions include hydrofluoric acid, sulfuric acid, etc. They can effectively remove surface oxides and increase the hydrophilicity of the surface, thus improving the adhesion between metal and sapphire.
1.3 Mechanical sand blasting
Sand blasting can effectively increase the roughness of sapphire surface and provide a larger surface area for metal adhesion. The surface roughness can be precisely adjusted through the sand particles with different particle sizes, and then the adhesion effect of the metallized layer can be optimized.
2、 Selection of metallized layer materials
In addition to surface treatment, the choice of metallized layer materials also has an important impact on adhesion. Generally, the metallized layer of sapphire uses titanium, aluminum, nickel and other materials, but the adhesion ability of different metals on the surface of sapphire is different. Choosing appropriate metal materials and optimizing them will help significantly improve adhesion.
2.1 Aluminum titanium alloy layer
The alloying treatment of aluminum and titanium can improve the adhesion of the metallized layer. Titanium has a strong affinity and can form a strong chemical bond with the sapphire surface, while aluminum helps to reduce the thermal expansion coefficient of the metallized layer and reduce the adhesion decline caused by temperature difference.
2.2 Nickel metallization
Nickel metallization is a widely used method at present. Nickel has strong oxidation resistance and can maintain stable adhesion at high temperature. By optimizing the nickel deposition conditions, a uniform and dense metallized layer can be formed on the surface of sapphire, thus improving the adhesion.
3、 Optimization of annealing process
Annealing is another important step to improve the adhesion of the metallized layer. After the metallization layer is deposited, annealing treatment can promote the combination between the metal layer and the sapphire surface. Annealing temperature, time and atmosphere have significant effects on adhesion.
3.1 Temperature control
The annealing temperature is usually set according to the characteristics of the metallized layer material. Too high a temperature may cause the chemical bond between the metal layer and sapphire to break, while too low a temperature cannot form a firm bond. By precisely controlling the annealing temperature, a strong adhesion layer can be formed between the metallized layer and the sapphire.
3.2 Atmosphere optimization
The atmosphere during annealing is also crucial to the improvement of adhesion. Common annealing atmospheres include nitrogen, argon or hydrogen. The specific atmosphere selection will depend on the type of metallized layer and the surface characteristics of sapphire. By optimizing the atmosphere, metal oxidation can be effectively avoided, and the combination between the metal layer and the sapphire surface can be promoted.
4、 Thin film deposition technology
The deposition process of thin films directly affects the quality and adhesion of metal layers. A uniform metal layer with strong adhesion can be formed on the surface of sapphire by using appropriate deposition technology.
4.1 Evaporative deposition
Evaporative deposition is a common metallization process. It heats the metal material to the evaporation state, and then condenses on the sapphire surface to form a film. Adopting high-quality evaporation source and optimizing deposition parameters can improve the adhesion of metal layer and make it have better coverage and uniformity.
4.2 Sputtering deposition
Sputtering deposition is another commonly used metallization method. The metal target is placed in the gas environment, and its atoms are deposited on the surface of sapphire by bombarding the metal target with high-energy particles. This method can achieve a uniform metallized layer at a lower temperature, which helps to improve adhesion and reduce thermal stress.
epilogue
Improving the adhesion of the sapphire metallized layer is a multifaceted technical challenge, involving many links such as surface treatment, metal selection, annealing process and film deposition. By reasonably selecting appropriate processing methods and technical means, the bonding force between the metallized layer and the sapphire surface can be effectively improved, thus improving the stability and performance of the device. In future research, it is still an important direction to explore more efficient and economical technologies to improve adhesion.