Study Of The Small Scale LDMOS With Strained

With the emergence of the MOS transistors and the MOS integrated circuits, themicroelectronic industry has a great development. In1965, the law of the developmentof the MOS integrated circuits was summarized by G. Moore: the number of transistorson the integrated circuits doubles approximately every18months-"Moore’s law".Nowadays, the development of the integrated circuits still follows the law. And, therapid development of the integrated circuits could not be separated with scaling down ofthe feature size of the devices. But, as the feature size of the devices comes into thenanometer level, many physical and technology problems will limit the development ofthe integrated circuits which use the scaling rule. The small scale LDMOS deviceswhich are applied in the P, L-band have the same problems. The strained silicontechnology has been widely used, because it can adjust the energy band structure of Simaterial and enhance the carrier mobility, so as to raises the driving ability of the MOSintegrated circuits.Firstly, for the stress in the drift region may reduce the breakdown voltage of theLDMOS device, the LDMOS device which is introduced the local strain is proposed.For the LDMOS device, the breakdown voltage is mainly borne by the low doped driftregion. For the strain would narrow the material’s energy band, if large stress isintroduced into the drift region, the breakdown voltage of the LDMOS device coulddecrease. Therefore, it should be avoided to introduce large stress into the drift region.LDMOS devices which are covered with SiN thin films in the different areas introducelarge stress into the channel and small stress into the drift region. The local strainedLDMOS devices enhance the device’s electrical characteristics and almost have noeffect on the breakdown voltage. And, this technology can be introduced into the smallscale LDMOS devices.Secondly, the local strain method is introduced into the small scale LDMOS device.The small scale LDMOS device has low breakdown voltage. The breakdown voltage ofthe small scale LDMOS device is promoted to17-18V with the STI structure, but it will degrade the performance of the device’s saturation characteristic. For the SOItechnology can improve the saturation characteristic of the device, the STI and SOIstructure are applied in the small scale strained LDMOS device. Thus, the straineddevice improves the breakdown voltage, and the output characteristic of the device hasno degradation.