A Wet Process Based On Porous Silicon To Form SiO₂ Insulating Layer And Its Application

Three dimensional electronic packaging based on TSV technology is the development trend for the future.With the rapid development of electronic industry,it is difficult for traditional method to prepare high quality insulating layer in smaller and deeper TSV.In this article,in order to reduce production cost,lower oxidizing temperature and enhance the step coverage,a wet process method based on porous silicon is developed to form silicon dioxide?SiO₂?insulating layer.The research content contains three parts.The first part explores the influence of the preparation parameters on the microstructure of the porous silicon.Research has found that the thickness of the porous silicon is proportional to the etching time and the current density is positively correlated,which is helpful to control the thickness of SiO₂ insulating layer.In addition,an increase in the aperture of the porous silicon is obtained,if the etching current density and etching time are increased or if the HF concentration is decreased.It is also found that the microstructure of porous silicon is affected by the concentration of HF solution.Results show that there are two types of porous silicon,one is formed in the concentrated HF solution with disordered pores and entitled with sponge-like porous silicon,while the other is formed in the dilute HF solution with straight pores and called fence-like porous silicon.The second part investigates the influence of oxidation parameters on the performance of anodized silicon and analyzes the process of the electrochemical oxidation of porous silicon.For highly doped p-type wafer,increasing oxidizing voltage and time is beneficial to electrochemically oxidize silicon,but the oxidizing temperature almost has no effect.What's more,it is proved that the electrochemical oxidation starts from the top of the porous silicon layer to the bottom of it step by step.During the oxidation process,the thickness of pore wall is crucial to decide whether the porous silicon grain can be completely oxidized or not.At the end of this paper,the wet process of fabricating SiO₂ is applied to the TSV field.The result reveals that the step coverage of this wet process can up to 90%in high aspect ratio?100?m diameter by 500?m depth?via.But in TSV wet etching field,more efforts should be made to solve the lateral erosion problem.