SPICE Model Of Nonuniform Substrate Doping MOSFET

In the CMOS technology the device modeling is the important domain which for many years has studied. From the multitudinous model independent develop to the uniform models which suitable to the circuit simulation. For IC designer, the semiconductor make engineer, development engineers CAD, the model researches and develops between engineer's highly effective cooperation, and reduced the IC production cost and so on to get up the count for much promoter action. However, when device reduced to deep submicron, its work mechanism has had the very big change. So building suitable device model is critical to analyze device. Non-uniform substrate doping places great influence to MOSFET. It makes threshold voltage reduced, the ratio of threshold voltage and drain voltage increased, enhances the two dimensional parasitic effect. In the same time, the device electric field and current density becomes greater and be more sensitive to device defaults. Therefore, it is important to consider non-uniform substrate doping when building MOSFET models.The effective method to analyze non-uniform doping MOSFET is numerical analysis. However, there are at least two disadvantages. First is no analytical model can be obtained, the other is great amount of calculation. It is impossible to only use numerical analysis. In this work, we combine these two methods to derive the non-uniform doping MOSFET models which similar to SPICE models.Firstly, we introduce some effect when device' s size has reduced. How the Substrate non- uniform doping influences to threshold voltage this important parameter. Generally, threshold voltage is defined as the gate voltage which makes surface inversion generated. It consists of flat-band voltage, surface potential and electron charge. We describe the electron charge share model when the bias voltage is zeroand others. The basic CMOS process is introduced which demonstrated the substrate of MOSFET is non-uniform doping in reality. The doping distribution is Gauss distribution. In order to solve channel depletion layer boson equation, we converted it to integration expression. By numerical methods we get channel surface potential. Then we can obtain the channel depletion layer width. The long channel MOSFET threshold voltage model is derived which was directly influenced by substrate non-uniform doping. Based on those, we derived the short channel threshold voltage model. At last, An example which according to the reference is calculated. In the result and the reference observed value has carried on the comparison, these two results was consistent, explained this model correction.In view of electric circuit simulator in MOSFET model insufficiency. Proposed the MOSFET threshold value voltage analytical model which can be used in the circuit simulation. This model to the non-uniform doping substrate, unifies with the numerical analysis and the analysis method. We derived the MOSFET models which is similar to SPICE models. The parameter has completely used the numerical method to produce, and the concept is clear, the computation quantity is small, the precision is high.