athena疑难解答.doc

疑难解答/FAQ ATHENA Q1 As sheet resistance is a function of W and L of the transistor, then how does DECKBUILD extract the sheet resistance (in ohm/square) if 2D simulation is performed? A1 The sheet resistance (Rs) of a layer with resisitivity, P, and thickness, t, is given by their ratio: Rs = P / t In ATHENA, it is this sheet resistance, Rs that is being extracted. While strictly speaking the units of the sheet resistance is Ohms, one refers to it as being in Ohms per square. This nomenclature comes in handy when the resistance of a rectangular piece of material with length, L, and width W must be obtained. It equals the product of the sheet resistance and the number of squares or: R = Rs * (W/L) where the number of squares equals the length divided by the width. Therefore, once the sheet resistance has been extracted by DECKBUILD, you can compute R (in ohm/square) easily. Q2 When performing process simulation of AlGaAs/GaAs LED, I tried to perform diffusion of Boron. But, the impurity only diffuses through the first GaAs layer, it does not diffuse into the second AlGaAs and third GaAs layer as shown below. Do you have any idea how to solve this problem? ?  A2 This is because the segregation and transport parameters at the interface between AlGaAs and GaAs are not defined. Therefore, the dopant only confine within the top GaAs region. You need to use the IMPURITY statement to define these parameters. An example of how you can define these parameters are as follow: IMPURITY I.BORON ALGAAS /GAAS SEG.0=1 TRN.0=1.66E-7 IMPURITY I.BORON GAAS /ALGAAS SEG.0=1 TRN.0=1.66E-7 After defining the IMPURITY statement, the Net Doping profile of the LED structure is as shown below. ? ? ? ? Top Q3 How to extract the effective channel length of a MOS structure? A3 Take the MOS example as shown below: ? ? ? ? ? To extract the channel length, use the following EXTRACT statement as follows: extract name=junc_source xj silicon mat.occno=1 y.val=0.22 junc.