Study On Preparation And Properties Of HfO₂ And ZrO₂ Films With High Dielectric Constant

With the development of large scale integrated circuits,higher requirements for the properties and fabrication technology of semiconductor materials need more development.Integrated circuit technology is accompanied by the reduction of the size of a single electronic device,and the thickness of the gate dielectric layer is one of the decisive factors that affect the size of the electronic device.SiO₂ is widely used as the gate dielectric material for electronic devices.However,with the reduction of the characteristic size of the devices,the thickness of the traditional SiO₂ grid material is close to the physical thickness of the material,which leads to a large increase in the power consumption of the devices,so it is difficult to meet the requirements of the stability of the microelectronic devices.It is an effective technique to improve the stability of electronic devices by looking for high dielectric constant（High K）materials to replace the traditional SiO₂ grid layer,and to reduce the tunneling effect by increasing the physical thickness of the dielectric layer.ZrO₂ and HfO₂ films have moderate dielectric constant（K²5）,and have excellent characteristics that are compatible with traditional silicon based integrated circuit technology.They are considered to be the two new gate dielectric materials with the most promising prospects.The RF magnetron sputtering technique was used to prepare ZrO₂ and HfO₂ gate dielectric thin films on P doped single crystal silicon（100）substrates with high purity（4N grade）zirconia and hafnium oxide sputtering target as raw materials.The influence of sputtering power on the deposition rate and thickness of the dielectric thin film was investigated.The surface roughness,morphology and structure of the gate dielectric thin film were analyzed and characterized by atomic force microscopy（AFM）,field emission scanning electron microscopy（FE-SEM）and X ray diffractometer（XRD）.On this basis,the Si-ZrO₂-Pd and Si-HfO₂-Pd capacitors were designed and prepared.The impedance analyzer（IA）was used to test the J-V and C-V characteristics of the capacitor,so as to characterize the electrical properties of the gate dielectric thin film.The main results of the study are as follows:ZrO₂ gate dielectric thin films were prepared on P doped monocrystalline silicon（100）substrates by RF Reactive Magnetron sputtering system.With the increase of sputtering power,the RMS value and thickness of ZrO₂ gate dielectric films increase gradually.When the sputtering power reaches 90 W,a high quality ZrO₂ dielectric thin film with a thickness of 152 nm and uniform is obtained.The RMS value of the thin film is 0.968.The deposition rate of ZrO₂ gate dielectric film increased significantly with the increase of sputtering power,rising from 1.36 nm/min at 60 W to 3.04 nm/min at 90 W.When the sputtering power is selected in the range of 60 W⁹0 W,the crystalline state of the ZrO₂ gate dielectric thin film has not changed obviously.The film exists in the form of amorphous oxide,and shows excellent amorphous stability.The leakage current of the thin film decreases with the increase of sputtering power,and the dielectric constant K of thin films is between 23.2²4.6.Comprehensive comparison,when the sputtering power is 80 W,the ZrO₂ gate dielectric thin film with high deposition rate,smooth surface,no crystallization and good electrical properties can be obtained.The K value of the film reaches 24.5 and the leakage current is 3.6×10^-3 A·cm^-2.A uniform high quality HfO₂ film was prepared on P doped monocrystalline silicon（100）substrate by RF Reactive Magnetron sputtering system.The RMS value,thickness and deposition rate of HfO₂ gate dielectric thin films increase with the increase of sputtering power.When sputtering power is 90 W,HfO₂ gate dielectric film with a thickness of 252 nm can be obtained.The RMS value of the film is 0.699,and the deposition rate is 5.04 nm/min.Under the same process conditions,the deposition rate and thickness of HfO₂ gate dielectric film is higher than that of ZrO₂ gate dielectric film,but the RMS value of two kinds of films is similar.When the sputtering power in the range of 60 W⁹0 W,the HfO₂ gate dielectric film exists in the form of amorphous oxide and exhibits excellent amorphous stability.The leakage current of the thin film decreases with the increase of sputtering power,and the dielectric constant k of the thin film is between 23.3²4.7.Above all,when the sputtering power is 80 W,the HfO₂ gate dielectric thin film with high deposition rate,smooth surface,no crystallization and good electrical properties can be obtained.The K value of the film reaches 24.7 and the leakage current is 3.31×10^-5 A·cm^-2.The ZrO₂ and HfO₂ gate dielectric thin films prepared by this experiment is about 25,which is significantly higher than the dielectric constant of the traditional gate dielectric material SiO₂（about 3.9）,and the leak current has reached the demand of application.Compared with ZrO₂ gate dielectric thin film,HfO₂ gate dielectric thin film has lower RMS value,gate leakage current and higher sputtering deposition rate.The research results provide a basis for future selection of ZrO₂ and HfO₂ materials as gate dielectric films.