Research On CMOS Insulated Gate Based On DPN Technology

With the CMOS key size smaller, the traditional pure silicon dioxide gate can’t meet the key dimensions of 0.35um as well as the following requirements. So we must change the traditional gate structure or introduce new material. For 0.13 μm to 65nm CMOS process, the traditional method is to use nitrogen-doped silicon oxide as gate dielectric. For below 65nm CMOS process people use new high-k material replace the traditional pure silicon dioxide.The traditional nitrogen-doped way is anneal with nitric oxide or nitrogen dioxide in certain time and annealing to the aim of nitrogen. But the oxide layer is thin in 0.13um CMOS process and below. So the drain current gate growth fast and then reducing the charge carrier mobility in gate channel. In order to inhibit this effect, the most common method is DPN (Decoupled Plasma Nitridation) on the surface of pure silicon dioxide. DPN technology is act on the thin oxide layer by nitridation. Only on the surface of oxide of nitrogen doped and will not affect the interface between silicon and oxide.In order to obtain high quality SiO2 before DPN process, people uses ISSG (in-situ-steam generation) technology to get the high quality SiO2. ISSG technology is growth the high quality silicon dioxide in high temperature and low pressure condition with in the certain hydrogen and oxygen. There are four main factors which affect the growing of ISSG. It is difficult to get the high quality silicon dioxide mixed all four condition. This paper will discuss the balance point from the optimal experiment.DPN is an advanced process that doping nitrogen to silicon dioxide.It is very important to control the distribution of nitrogen concentration in the process of doping. The nitrogen distribution in depth and concentration in insulated gate not changed when changes the condition of the experiment with DPN. The change of nitrogen concentration is only affected by radio frequency power of DPN and not associated with pressure. Compare traditional nitrogen-doped silicon to the doping silicon with DPN technology especially for the flicker noise and NBTI (negative bias temperature instability).The conclusion is the DPN method can reduce flicker noise and reduce the effect of NBTI and deduced the nitrogen distributed on surface of silicon dioxide from DPN way. This paper also introduces the rapid thermal anneal(RTA) after DPN process.It is most effective to repair oxide defect after DPN for RTA choosing a certain proportion of nitrogen and oxygen gas.The advantage is very obvious for DPN to improve the NBTI and reduce the flicker noise.