Study On The Technology Of Double Ion Implantation Ge To Form PN Junction

In Si-based CMOS technology,the improvement of integration in the chip depends on the scale reduction of transistor size,but the resulting intensification of short channel effect makes traditional Si materials gradually approach their physical limits.Germanium(Ge)materials,with their high hole and electron mobility,are considered likely to replace silicon in future technology nodes.However,due to the low solubility,fast diffusion rate and low activation rate of n-type doped elements(P,As,Sb,etc.)in Ge,the source leakage in Ge MOSFET has a large parasitic resistance and is difficult to form shallow junction.In order to improve these problems in Ge n MOSFET,double ion implantation is a possible solution.In this paper,SiO₂ was deposited on Ge chip by PECVD,followed by cleaning,lithography and etching,ion implantation and activation,growth and etching of contact electrode,etc.,to form n+/p junction on p Ge.By the above method,n+/p junction with switch ratio of 10³ is obtained on germanium.As,P double ion implantation was used to improve the performance of n+/P junction.The injection sequence of As and P was changed respectively,and the injection energy was changed within the range of As 25?65 keV/P 20?35 keV to test its influence on the rectifying characteristics of n+/p junction.The results show that the sequence of As and P injection has no effect on the rectifying characteristics of n+/p junction.When the energy of As is increased,the open current(Ion)of n+/p junction increases and the ideal factor decreases.Increasing the energy injected into P increases the open state current of n+/p junction,but the ideal factor increases instead.Meanwhile,the injection sequence of As and P was changed,and the injection energy was changed in the range of As 25?65 keV/P 20?35 keV.The junction depth of n+/p junction after double ion implantation was simulated by TRIM simulation tool,and the metal-semiconductor contact resistance and n+germanium block resistance after different ion implantation processes were measured by TLM(transmission length method)model.This series of studies showed that,with the increase of As and P energy injected,the junction depth of n+/p junction increased(the range was from20 nm to 50 nm).With the increase of As injection energy,the contact resistance of metal-semiconductor and the block resistance of Ge were basically unchanged.However,with the increase of P injection energy,both the metal-semiconductor contact resistance and the block resistance of Ge have a downward trend.The value of n+germanium resistivity generated by injection is obtained through the value of block resistance and the simulation result of TRIM for junction depth.It can be found that with the increase of As energy injected,the resistivity of n+germanium formed by injection increases.However,with the increase of P energy,the resistivity of n+germanium decreased.Therefore,it is considered in this paper that the injected energy of P in As/P dual injection process should be increased As much As possible in order to obtain a lower parasitic resistance of source leakage.