The Research On Properties Of AlN And Its Alloys Deposited By Magnetron Sputtering

In the twenty-first century,with the rapid development of information communication,the demand of high transfer rate and large bandwidth is increasingly urgent..This requires not only the continuous optimization of information transmission protocols,but also the new hardware made of new materials to meet this development demand.As a III-?compound semiconductor material,AlN has the advantages of high temperature resistance,high acoustic wave speed,and wide band-gap.It also has a strong piezoelectric polarization effect,which can be used to prepare surface acoustic wave devices for the application in 5G communication.In addition,by doping Sc element into AlN film,its piezoelectric polarization coefficient can be further increased,thereby increasing the operating frequency,so as to be applied to microwave high-power devices.There are various methods for preparing AlN films currently.Among them,magnetron sputtering technology has the advantages of simple process flow and low growth cost,hence it has huge commercial development potential.Therefore,this paper mainly studied the influence of sputtering conditions on the deposition of AlN films and Al Sc N films and their properties.The main research results are as follows:(1)The effect of working gas argon-nitrogen ratio,DC sputtering power,substrate temperature,and gas pressure on the crystalline quality of AlN films was studied.By analyzing the crystal structure,surface morphology,element composition and thickness of AlN thin films prepared under different sputtering process parameters,it is found that the working gas argon-nitrogen ratio affects the deposition rate of the thin film and the ratio of the aluminum and nitrogen elements,gas pressure affects the mean free path of particles in the sputtering cavity,DC sputtering power affects the degree of ionization of the gas,the kinetic energy and number of sputtered Al atoms sputtered,the substrate temperature affects the migration of AlN particles deposited on the film surface.By synthesizing various sputtering process conditions,when the gas pressure is 2 m Torr,the sputtering power is 130W,the substrate temperature is 570°C,and the argon-nitrogen ratio is 1:1.5,a high-quality AlN film with a preferential orientation of(0002)plane can be prepared with the full width at half maximum(FWHM)of the rocking curve at 1.22°,the atomic percentages of Al and N close to the stoichiometric ratio of AlN,the deposition rate of 3.35 nm/min and the root mean square of the surface roughness at 1.56 nm.(2)Based on the optimal sputtering conditions for depositing AlN thin films,a dual-target magnetron sputtering process is applied to deposit Al Sc N thin films.The effect of Sc doping on the crystal quality of AlN thin films and the enhancement of piezoelectric characteristics were studied.Firstly,The effect of Sc RF power on the crystal quality of Al Sc N thin films was investigated with the sputtering duration at 1 h.By analyzing the crystal structure and thickness of the Al Sc N thin film obtained by sputtering,it is found that Sc doping reduces the crystal quality of the Al Sc N film,and when the Sc RF power is between 50 W and 90 W,the crystal quality of the Al Sc N film obtained by sputtering does not change much.The Al Sc N film mainly presents the AlN(0002)peak,and the FWHM of the peak of the Al Sc N film is slightly higher than that of the AlN film,with optimum of 1.701°.Secondly,the effect of Sc doping on the piezoelectric properties of AlN films was studied.The sputtering time was extended to 6 h and the SAW devices were made.By analyzing the crystal structure,element composition and thickness of the Al Sc N film and AlN film obtained by sputtering,it is found that the prolonged sputtering time leads to a decrease in the crystalline quality and an increase in the content of O impurities in the thin film.A vector network analyzer was used to test the S₁₁ transmission characteristics of SAW devices made of AlN films and Al Sc N films.It is found that Sc doping leads to a slight decrease in the acoustic wave rate of the AlN film,but increases the piezoeletric coefficient from 0.9%to 1.2%.The overall device performance has been improved.