Advanced MOS Devices Homework #5 Due Wednesday, April 13 1. Transconductance in Saturation Find an expression for the transconductance in saturation gmsat of a MOSFET, as predicted by the Square Law Model and by the Bulk Charge Model. For each case, make a plot of the saturation transconductance as a function of gate voltage. Assume NB = 5 x 1015 cm-3, dox = 50 nm, and W/L = 5. Find the mobility from the tables provided in the notes, and under the assumption that the surface mobility is about half the bulk mobility. Transconductance is given by gIVmsatDsatG. 2. MOS Threshold Adjust Consider a Si MOS system with the following parameters: dox = 600 Å, substrate doping density Na = 8 x 1014 cm-3, Qot = -2 x 10-8 Coul/cm2, and MS = -0.5 V. (a) Find the acceptor ion implant dose DI needed for VT = + 1V. (b) Calculate the body factor . 3. Parameter Extraction On the class web site you will find an Excel spreadsheet (MOSFET Data.xlsx) with the data used to construct the I-V plots for the MC14007 MOSDFET in the Chapter 6 PowerPoint presentation. There are three sets of data: ID – VDS with VG as a parameter; ID1/2 – VGS in saturation; log(ID) – VGS with VD as a parameter. Using this data, reconstruct the plots listed above (i.e., make copies of the plots in the notes). Then, extract the following information from this device by fitting appropriate equations to the data in each case. Since we do not know the oxide thickness or gate dimensions, we simply take kLWCox. Find… - The pre-factor k; - The threshold voltage VT; - The body bias parameter  - The subthreshold slope (this should be the same for either value of VDS). If the gate dimensions are such that W/L = 5 and dox = 20 nm, find the mobility. 4. Generalized IV Calculation Here we will use the Generalized IV model discussed in class to plot I-V curves for the MC14007 MOSFET. We will use the parameter k found in the previous problem. i) Calculate the ID – VDS curves for VG = 2.5 V. Note that to do this, we need the doping density, which we do not have. So, start with a reasonable assumption for what this valuemight be, plot the curve, and compare your results to the data. Then adjust the doping density until the result is reasonably close to the actual data. We do not expect to get a perfect match between theory and experiment, but the overall IV characteristics should be similar. ii) Calculate the ID1/2 – VGS curve assuming the device is in saturation (VDS = VGS) using the doping density you settled on above. For this plot, set VBS = -1.0 V and compare your result to the data. iii) Using the values for k and doping density determined above, plot both the drift and diffusion current components of the ID – VDS curve for VG = 1.5 V. Comment on the relative contribution of each component to the total