Study On Preparation Methods And Principles Of Ultra High-k At Sub 14nm Technology Node

With the feature size of CMOS devices entering the 45nm and below technology nodes,HfO₂ high-k materials have attracted wide attention and applications.Pure HfO₂ is generally an amorphous or monoclinic phase under low temperature annealing conditions,the k value is only about 20,and it can only meet the development requirements of several technical nodes.At the same time,the researchers found that the crystal of HfO₂ plays a decisive role in its k value,for example,the theoretical k value of the tetragonal phase HfO₂ can reach 70.However,pure HfO₂ needs to be transformed into a tetragonal phase or a cubic phase and requires a high temperature of 1000 to 2000℃.Therefore,how to transform Hf02 crystal phase at low temperature and increase its k value has become a new research hotspot.This article begins with the concept and definition of the dielectric constant,analyzes the research on high-k materials in recent years,studies the development and regularity of high-k materials,and determines the use of trace Al-doped HfO₂ structures as sub-14nm ultra-high k candidate material.Then,the preparation process of the MOS capacitor is introduced,and the process methods and principles required in the preparation process are analyzed and discussed.According to the advantages and disadvantages of each process,the shallow trench isolation,interface layer growth,and high-k deposition are formulated and developed.Other key process modules ensure the successful preparation of MOS capacitors.Then,based on the preparation process of MOS capacitors,the electrical properties of Al-doped Hf02 high-k materials are analyzed in detail.The influence of the annealing process on the crystal phase,the k value,and the defects of the gate dielectric layer was studied,and the optimum high-k preparation and annealing process was confirmed.At the same time,k-values are extracted for the high-k material in the MOS capacitor under the minimum EOT condition.Under the two conditions of anneal at 650℃ for 30s and annealing at 700℃ for 15s in N2 environment,the EOT of Al-doped HfO₂ high-k material is only 0.88nm,and the k values are 35 and 35.5,respectively.Finally,annealing at 700℃ for 15s in N2 environment is considered as the best condition for the preparation of sub-high-k materials with sub-14nm nodes.The obtained material properties meet the requirements of sub-14nm technology nodes for high-k materials.