Strain Mechanism And Stress Models Of Wafer-level Strained SOI

Strain Si and SOI(silicon-on-insulator)are recognized as two key technologies for maintaining Moore's Law in deep submicron and nanotechnology.Wafer-level strained SOI integrates strain technology and SOI characteristics,and possesses the advantage that does not influenced by the process conditions,which will become the preferred process of the military integrated circuit with high-performance and high reliability.A new method of wafer-level strained SOI with high stress Si N thin films was proposed based on the theory of structural properties of SOI materials,the stress characteristics of Si N films and the elasto-plastic mechanics.The method used the stress introduced by deposited high stress Si N thin film into the SOI,and adopted the ion implantation and the high temperature annealing process to enhance the stress and keep the stress.The generation,introduction and maintaining mechanism of stress of the method were described based on the theory of elasto-plastic mechanics and the yield characteristics of SOI materials.The experimental scheme and process flow of the high stress Si N wafer-level strained SOI were designed based on the strain mechanism of the new method.On the basis of the strain mechanism of the new method,the experimental scheme and process flow of the high stress Si N wafer-level strained SOI were designed,and the experimental study on wafer-level strained SOI was carried out leveraging on PECVD technique.This paper established the stress model of wafer-level strained SOI of Si N thin films based on this method and the theory of elasticity and the theory of pure bending.The stress calculation of wafer-level strained SOI caused by Si N thin films was also studied.In this paper,the mechanical and thermal properties of SOI layers were studied in detail.Different nanoindentation experiments were designed in terms of the structural characteristics,mechanics and thermal properties of SOI,thus obtaining the hardness and Young's modulus of SOI layers and giving the relationship of changes between the mechanical properties of SOI material and the depth of indentation.The experimental model of nanoindentation was established based on the finite element analysis software.The change of multiple parameters of material is simulated based on this mode and the dimensionless function of the measured material is obtained by means of dimensional function analysis,thus the yield strength and tangent modulus of the material were obtained.The experiment of high stress Si N thin film was carried out on the basis of PECVD technology and a 50 nm thickness of Si N film with 1.2 GPa tensile stress and 1.5Gpa compressive stress was fabricated.This paper designed the experimental scheme and process steps of wafer-level strained SOI based on the new method of high-stress Si N thin film induced wafer-level strain SOI,combining with ion implantation process and stress memory technology,PECVD process and different annealing processes were adopted to conduct experimental studies of preparation of high-stress Si N thin film induced wafer-level strain SOI,thus the wafer-level tensile strain SOI and compressive SOI samples were fabricated.The stress model was validated by different experimental model and different experimental samples.Raman characterization results showed that the strain amount of silicon on the top layer of the wafer SOI was 0.231%,and the calculated result by the model was 0.261%.The experimental value was consistent with the theoretical calculation.The experimental results showed that the ion implantation process and the improvement of the annealing conditions were conducive to the increase of the strain of the wafer-level strained SOI.