Quality Control Of Aluminum Nitride Films Based On Magnetron Sputtering

AlN film is the third generation of semiconductor materials,with wide band gap,excellent acoustic characteristics,high thermal conductivity,excellent stability and other characteristics,has a broad application prospect in photoelectric,medical and other fields.Al N films not only have excellent properties,but also can act as a buffer layer to relieve the mismatch stress and prepare high performance Al N based devices.However,there are still some difficulties in epitaxial Al N films.On the one hand,due to the lack of homogeneous substrates and the limited production cost,Al N films are generally epitaxial on heterogeneous sapphire substrates.However,there are differences in lattice constants and thermal expansion coefficients between the heterogeneous substrates and epitaxial films,resulting in a large mismatch stress in the epitaxial Al N films.On the other hand,the low mobility of Al atoms leads to a higher dislocation density in epitaxial films.These factors limit the further application of Al N films,so how to effectively improve the quality of Al N films,which is a challenge for semiconductor epitaxial technology.At present,there are many researches on Al N films with small miscut angles,but there are almost no researches on Al N films with high miscut angles along different orientations and quality control of Al N films with different polarities.Base on this background,this paper takes Al N films with different miscut angles and different polarities as the research object,combines magnetron sputtering technology with high temperature annealing technology to significantly improve the quality of Al N films,obtains high quality Al N films while revealing the micro mechanism of the film quality improvement.The main research contents and results are as follows:(1)In the first part of the work,we adopt magnetron sputtering technology to deposit high miscut angles Al N thin films on the sapphire substrate with different miscut angles and misorientations,introduces the atomic steps,explores the substrate orientation and miscut angles to affect the quality of thin film.The quality of Al N epitaxial films increases first and then decreases with the increase of substrate miscut angles.Subsequently,the microscopic mechanism of miscut angles Al N films during 1400 ℃‐1650 ℃ annealing was further explored.It is found that thin films during high temperature annealing actually occurs recrystallization,accompanied by the change of stress state and the increase of grain size.XRD,Raman,SEM,XPS and other characterization methods reveal that the essence of high temperature annealing to improve the film quality lies in the annihilation of grain boundaries during recrystallization.Among them,C-A 4°film has the best crystal quality.After high temperature annealing,the full width at half maximum(FWHM)of(0002)and(10-12)rocking curves decrease from1285.2 arcsec to 219.6 arcsec,and from 2898 arcsec to 720 arcsec,respectively.In this work,the optimal substrate orientation of miscut angles Al N films with high quality was obtained,and the quality of films was improved efficiently,which is of great significance for the epitaxial growth of films.(2)The research background of the second part is mainly based on slowing down the polarization effect of devices and expanding the application field of semi‐polar and non-polar Al N films.We deposited polar,semi-polar and nonpolar Al N thin films on sapphire substrates of a plane(11-20),m plane(10-10)and r plane(1-102)plane by magnetron sputtering technology.At the same time,Materials Studio was used for modeling and cleaving surfaces.Through crystal plane structure and XPS test,it was found that the reason for the different quality of films with different polarities is the difference in the content of oxygen impurities in the films.The quality control mechanism of Al N films with different polarity has been explored by combining thermal annealing technology.After high temperature annealing,the quality of Al N films with different polarity has different degree of improvement,and has different impurity concentration and stress.It is found that the high temperature annealing process can not only effectively reduce the dislocation in the film,but also reduce the anisotropy of the semi-polar and non-polar films,so that the numerical difference of the FWHM in the two vertical directions of the film decreases from 48 arcmin to 1 arcmin,and the stacking fault of the film is reduced.These results provide important reference value for the preparation of high quality semi-polar and non-polar films and the reduction of the polarization effect of devices.