The analogy method of radio frequency MOS variodenser
Technical field
The present invention relates to the semiconductor design technology, particularly a kind of analogy method of radio frequency MOS variodenser.
Background technology
MOS varactor (variodenser) is one of critical elements of RF CMOS or BiCMOS integrated circuit, is widely used in the radio-frequency (RF) circuit module such as voltage controlled oscillator.The sectional view of traditional N type MOSvaractor (variodenser) is seen Fig. 1: Lg is the grid stray inductance among the figure, Rg is the grid dead resistance, C_MOS is a mos capacitance, and Rnw is a channel region resistance, and Rnwe is a N+ injection region dead resistance, Rs is source/drain terminal dead resistance, Ls is source/drain terminal stray inductance, and Cfr is that N+ area overlapping partition capacitance is leaked in grid and source, and Dnwi, Dnwe are P type substrate and N trap parasitic diode, Rsub is a P type substrate dead resistance, and Csub is a P type substrate stray capacitance.
Traditional RF MOS varactor device modeling mainly contains two kinds of methods: based on experimental formula (as the coth function), or for N type MOS variodenser employing PMOS device model (its topological structure such as Fig. 2), adopt nmos device model (its topological structure such as Fig. 3) for P type MOS variodenser, among the figure, lg is the grid stray inductance, rg is the grid dead resistance, rnwi is a N type MOS variodenser channel region resistance, rnwe is a N+ injection region dead resistance, rpwi is a P type MOS variodenser channel region resistance, rpwe is a P+ injection region dead resistance, rs is source/drain terminal dead resistance, ls is source/drain terminal stray inductance, cfr is that injection region lap electric capacity is leaked in grid and source, d1, d2 is P type substrate and the N trap parasitic diode of N type MOS, r1, r2 is the P trap dead resistance of P type MOS, and rsub is the substrate dead resistance, csub is the substrate stray capacitance.Adopt the model of experimental formula, be difficult for the equal proportion convergent-divergent of implementation model, extendability is poor; Adopt the PMOS device model for N type MOS variodenser, or for P type MOS variodenser employing nmos device model, owing to need come dummy source to leak floating empty state at the resistance that PMOS device model or nmos device model source leak two high value of two terminations, easily in the circuit simulation process, cause and do not restrain.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of analogy method of radio frequency MOS variodenser, can avoid occurring in the emulation not convergent situation, realize real equal proportion convergent-divergent simultaneously, the extensibility of implementation model, reduce the complexity of radio frequency MOS variodenser modeling, made things convenient for the design of radio frequency integrated circuit.
For solving the problems of the technologies described above, the analogy method of radio frequency MOS variodenser of the present invention, set up a radio frequency MOS variodenser realistic model, utilize described radio frequency MOS variodenser realistic model that radio frequency MOS variodenser is simulated, the characteristic that the capacitance of analog radio frequency MOS variodenser changes with change in voltage, it is characterized in that, the model of the variable capacitance in the topological structure of described radio frequency MOS variodenser realistic model is simulated by MOS device model of the same type, described MOS device model of the same type, the grid end is an end of variable capacitance, the source is leaked and is connect the other end as variable capacitance, body end ground connection.
If described radio frequency MOS variodenser is the N type, then described MOS device model of the same type is the N type.
If described radio frequency MOS variodenser is the P type, then described MOS device model of the same type is the P type.
The analogy method of radio frequency MOS variodenser of the present invention, the model of the variable capacitance in the topological structure of the MOS variodenser realistic model that adopts, utilize traditional nmos device model of the same type, need be at two big resistance of the extra adding of nmos device model source drain terminal of the same type, avoided occurring in the emulation not convergent situation, reduced the complexity of model, realized the equal proportion convergent-divergent simultaneously, effectively realized the extensibility of model, reduce the complexity of radio frequency MOS variodenser modeling, made things convenient for the design of radio frequency integrated circuit.
Description of drawings
The present invention is described in further detail below in conjunction with the drawings and specific embodiments.
Fig. 1 is the sectional view of traditional N type MOS variodenser;
Fig. 2 is the topology diagram that N type MOS variodenser adopts the PMOS device model;
Fig. 3 is the topology diagram that P type MOS variodenser adopts the nmos device model;
Fig. 4 is the topology diagram of radio frequency MOS variodenser realistic model one embodiment in the analogy method of radio frequency MOS variodenser of the present invention;
Fig. 5 is the model that obtains of the analogy method of radio frequency MOS variodenser of the present invention and the match situation map of test data.
Embodiment
The analogy method of radio frequency MOS variodenser of the present invention, set up a radio frequency MOS variodenser realistic model, utilize described radio frequency MOS variodenser realistic model radio frequency MOS variodenser to be simulated the characteristic that the capacitance of analog radio frequency MOS variodenser changes with change in voltage; The model of the variable capacitance in the topological structure of described radio frequency MOS variodenser realistic model is simulated by the MOS device model of (N type or P type) of the same type, the MOS device model of described (N type or P type) of the same type, the grid end is an end of variable capacitance, the source is leaked and is connect the other end as variable capacitance, body (Bulk) end ground connection.
Topological structure one embodiment of described radio frequency MOS variodenser realistic model as shown in Figure 4, Figure 4 shows that the topological structure of a N type MOS variodenser realistic model, lg is the grid stray inductance among the figure, rg is the grid dead resistance, rnwi is a channel region resistance, rnwe is a N+ injection region dead resistance, rs is source/drain terminal dead resistance, ls is source/drain terminal stray inductance, cfr is that N+ area overlapping partition capacitance is leaked in grid and source, d1, d2 are P type substrate and N trap parasitic diode, and rsub is that P type substrate dead resistance, csub are P type substrate stray capacitance.Figure 4 shows that the topological structure of a N type radio frequency MOS variodenser realistic model, the model of the variable capacitance in the N type radio frequency MOS variodenser realistic model uses traditional nmos device model, grid (Gate) end is an end of variable capacitance, source/leakage (Source/Drain) also connects the other end as variable capacitance, body (Bulk) end ground connection.
For P type radio frequency MOS variodenser, the model of the variable capacitance in the P type radio frequency MOS variodenser realistic model uses traditional PMOS device model, method of attachment is consistent with N type radio frequency MOS variodenser, PMOS device model grid ends (Gate) are as an end of variodenser, (Source/ receives together the other end as variodenser, substrate terminal ground connection to the source drain terminal.
The analogy method of radio frequency MOS variodenser of the present invention, the model of the variable capacitance in the topological structure of radio frequency MOS variodenser realistic model, by MOS device model of the same type the model of the variable capacitance in the topological structure of radio frequency MOS variodenser realistic model is simulated, described MOS device model of the same type, the grid end is an end of variable capacitance, the source is leaked and is connect the other end as variable capacitance, body end ground connection, because MOS device model (BSIM3 as the industry member standard, BSIM4 etc.), be based on the device model of device physics, have good scalability and extensibility, can simulate the current/voltage of device of the certain size scope of different process platform, capacitor voltage characteristic, therefore can utilize the scalable performance of described MOS device model of the same type to realize the scalability of radio frequency MOS variodenser realistic model, need not insert big resistance resistance, avoid in circuit simulation, occurring not convergent situation at MOS device model source drain terminal.Utilize the MOS device parameter of the same type match of implementation model and data easily simultaneously, reduced the difficulty that radio frequency MOS variodenser realistic model is set up, and radio frequency MOS variodenser realistic model has the extensibility that has been equipped with MOS device model of the same type concurrently, is easy to be applied on the different technique platforms.
The analogy method of radio frequency MOS variodenser of the present invention, utilize radio frequency MOS variodenser realistic model that radio frequency MOS variodenser is simulated, the characteristic that the capacitance of analog radio frequency MOS variodenser changes with change in voltage, the match situation of model and test data is seen Fig. 5, wherein realize the representative simulation family curve, the triangle line is the actual measured property line, as can see from Figure 5, the analogy method of radio frequency MOS variodenser of the present invention, the fitting effect to data in than the range of size of broad is all relatively good.
The analogy method of radio frequency MOS variodenser of the present invention, the model of the variable capacitance in the topological structure of the MOS variodenser realistic model that adopts, utilize traditional nmos device model of the same type, need be at two big resistance of the extra adding of nmos device model source drain terminal of the same type, avoided occurring in the emulation not convergent situation, reduced the complexity of model, realized the equal proportion convergent-divergent simultaneously, effectively realized the extensibility of model, reduce the complexity of radio frequency MOS variodenser modeling, made things convenient for the design of radio frequency integrated circuit.