First Principle Study On The Formation,Evolution And Performance Of AlN/Al

AIN ceramic is the most widely studied high-performance ceramic substrate and packaging material because of its corrosion resistance,high temperature resistance,excellent heat transfer,high resistivity,low dielectric constant and low dielectric loss Moreover,as one of the most important engineering materials,Al is also widely used in the field of electronic packaging materials due to its light weight,high strength,high thermal conductivity and high conductivity.Therefore,as a typical ceramic/metal interface,AlN/Al interface has been widely studied in structure and propertiesAt present,there are great differences in the research results of AlN/Al interface,there is no clear interface structure,and there is no systematic study on the relationship between interface structure and interface strength.Moreover,due to the limitation of experimental observation conditions,there are few reports about the atomic behavior in the formation of AlN/Al interface.There are only a few atomic layers in the AlN/Al interface.The most important factors affecting the structure and properties of the interface are the adsorption,migration,nucleation and growth of atoms at the interface.The key to understand the formation process of the AlN/Al interface is to study the atomic behavior at the interfaceIn this paper,the first principle calculation method based on density functional theory is used.Firstly,the adsorption and desorption behaviors of Al and N atoms on AIN surface are studied at atomic scale,and the most stable AIN terminal structure is determined.Then,the formation and evolution of Al island on AIN surface are analyzed,and the stable interface formed by AlN/Al is analyzed.Finally,the mechanical properties of AlN/Al stable interface are studied.This paper provides an important theoretical reference for revealing the formation mechanism of AlN/Al interface,and also provides a theoretical basis for obtaining high-strength AlN/Al interface.The main results are as follows(1)The surface stable terminal structure of AIN(0001)was defined.There is no obvious difference between the surface energy of Al-Ter and N-Ter.In terms of adsorption performance,both Al-Ter and N-Ter have strong adsorption capacity for heteroatoms,but the adsorption capacity of Al-Ter for similar atoms is stronger than that of N-Ter.In addition,it is found that N atoms on the surface of AIN tend to combine with the surrounding N atoms to form N2 and escape from the surface after evaporation,resulting in the instability of N-Ter.At high temperature,after the surface N atoms escape,the AIN surface reconstructs the structure(?)R30°.After the reconstruction,the arrangement order of the Al atoms in the surface layer is the same as that in the third layer,forming the Hcp like structure.The calculation also shows that the reconstructed transition barrier is 3.2eV.Therefore,Al-Ter is more suitable for the terminal structure of AIN.(2)The evolution process of Al atom forming atomic island on the surface of AIN is obtained.On the surface of AIN,the most stable adsorption position of single Al atom is the Hcp position;on the adsorption of double Al atom,the lowest energy position of the system is the Hcp position and its adjacent Fcc position;on the adsorption of three Al atoms,the original position of Fcc+Hcp is all changed to the Hcp position;with the increase of the number of adsorption atoms,the structure of Al island on the surface of Al-Ter is also changing;when a layer of Al is full After atoms,the position of Fcc is the most stable adsorption strueture,and the activation energy of adsorption strueture transition is 1.41eV.The evolution process of Al island is similar to that of surface adsorption when the second and third layers of Al atoms are adsorbed.Therefore,when the Al atomic layer continues to stack into periodic arrangement,its arrangement form is ABC strueture,forming the AlN/Al interface structure with continuous Fcc arrangement.(3)Finally,the mechanical properties of AlN/A1 interface strueture are analyzed based on the obtained AlN/Al interface structure.By calculating the elastic constant of AlN/Al interface strueture,the result is close to that of crystal Al,and the value of elastic modulus is between Al and AIN crystal.Further,the ideal tensile strength at the interface is studied.It is found that the AlN/Al interface strain is in the stage of elastic deformation before 0 to 0.012,at this time,the stress-strain shows a linear relationship,and the stress increases with the increase of strain.When the strain is greater than 0.012,with the increase of strain,the atomic spacing increases,and the stress drops sharply.So the bond at the AlN/Al interface is broken and the tensile strength of AlN/Al interface is 530MPa.