Analysis on Hot Carrier Reliability for High Voltage MOS Device with Different Processes

摘要

In this thesis we investigated devices is High Voltage MOSFETs (HV-MOSFETs) and analysis hot carrier reliability for different Si recess depth In our study we have HV-MOSFETs with three different Si recess depth The deepest to the shallowest range is about 15 nm First we introduced the structure of HV-MOSFETs its advantage and disadvantage Moreover hot carrier effect mechanism and reduce hot carrier effect methods were be introduced Then we introduced the measurement method and the setting of bias condition in this thesis and explained the formation reason of Si recess structure We will present the measurement results for ID-VG ID-VD and ISUB-VG in terms of the basic electrical characteristics of the HV-MOSFETs The main contents of this thesis are the study of substrate current for the amount of hot carrier degradation Based on the unexpected results of our experimental measurements this device with a Si recess structure has an abnormal hot carrier degradation In general the larger substrate current the device hot carrier degradation should also be larger However we measured the degradation trend is that the larger substrate current induced hot carrier degradation is smaller For the abnormal degradation we analysis of experimental data and computer-aided simulation (TCAD) software we can find that the substrate current caused by the larger part of the reason is its internal electric field and impact ionization rate is larger However we have purposed three reasons to explain this abnormal phenomenon First a deeper Si recess depth is caused by excessive etching induced more defects where below spacer Secondly the topology difference induced this phenomenon Thirdly the linear region drain current of a deeper Si recess depth is closer to interface (Si/SiO2) than shallower Si recess depth Therefore the current path of a deeper Si recess device is affected by interface state more than shallower Si recess device So a deeper Si recess device has more degradation than shallower Si recess device According to our measurement data and simulation results it can be found that Si recess has little effect on the basic electrical performance of devices but this structure is not ignore issue in hot carrier reliability Because the depth of Si recess increases the amount of hot carrier degradation of the device is increases Therefore it is an important challenge to reduce the production of Si recess structure in the process of device

獎項日期	2017 7月 3
原文	English
監督員	Jone-Fang Chen (Supervisor)