Research On Design,Preparation And Performance Of CMOS Inverter Based On Molybdenum Sulfide

Two-dimensional transition metal chalcogenide(TMDC)has become the most promising material for the continuation of Moore's Law in the post-Moore era due to its atomic-level thickness and excellent semiconductor properties.Molybdenum sulfide(MoS₂)is a typical representative among them.Compared with the zero bandgap of graphene,MoS₂has an adjustable bandgap width.The single-layer MoS₂ is a direct band gap semiconductor with a bandgap width of 1.8 e V.With the increase of layers,it can become indirect semiconductor.TMDC has broad application prospects in the construction of logic gate circuits,photoelectric detection,information storage,and many other aspects.The inverter is the most basic logic gate circuit.This article designs and prepares MoS₂ CMOS inverters.We use the optimized CVD process to prepare N-type MoS₂ thin films,the size of which is mostly around 150?m,and the film density is very high.The prepared bottom-gate N-FET based on MoS₂ has a threshold voltage of 2.64V,a current on-off ratio of 10⁴,a subthreshold swing of 3.12V/dec,and carrier mobility of 40cm²V^-1s^-1,showing a good N-type semiconductor characteristic.P-type doping of MoS₂is carried out using oxygen plasma doping technology.The prepared bottom-gate P-FET has a hole mobility of 120 cm²V^-1s^-1,a current on-off ratio of 10⁶,and a subthreshold swing of 488.15m V/dec,which shows excellent P-type semiconductor performance.In this thesis,a CMOS inverter based on MoS₂ is designed and prepared,and it shows excellent electrical performance.Under the condition of Vdd=5V,the measured peak voltage gain is 7.48,the maximum static power consumption is 37.7n W,the noise margin low is0.45Vdd,the noise margin high is 0.32Vdd,and the input-output voltage matching is realized.At the same time,we studied the influence of the plasma doping time and the aspect ratio in the FET on the performance of the inverter device.The analysis results show that as the treatment time increases,the oxygen plasma doping concentration gradually increases,causing the carrier mobility to decrease,and the corresponding threshold voltage of the P-FET increases,so that the inverter's high-level output voltage decreases.The research on the P-FET aspect ratio shows that the VM can be closer to Vdd/2 by improving the FET aspect ratio.At this time,the transmission curve is more symmetrical and the noise tolerance of the corresponding device is higher.These two studies both show the impact of matching the threshold voltage of N-FET and P-FET on device performance.This thesis also studied the change of the inverter voltage output curve with time.After placing the device in an air environment for 42 days,due to the drop in the threshold voltage of the N-FET,the inverter Vout was reduced by 3.75%in the case of low-level input..In the case of high-level input,thanks to the high stability of the oxygen plasma doping MoS₂,the low-level output is unchanged.