This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-126900, filed on Jun. 2, 2010, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate to a MOSFET model output apparatus and method, and recording medium, for example, to a MOSFET model to be used in a SPICE (Simulation Program with Integrated Circuit Emphasis) circuit simulation, such as a SPICE model of a MOSFET used in an analog circuit or an RF circuit.
An example of a MOSFET model for a SPICE circuit simulation is a four-terminal model. In circuit designing of a semiconductor integrated circuit, the SPICE circuit simulation considering a parasitic device is often performed using the four-terminal model or the like.
However, the four-terminal model has such a problem that the high frequency characteristic effect of bias application to a deep N-type well cannot be estimated. Further, since a substrate and a well are not connected on a net list, there is a problem that cross-talk noise analysis through the substrate cannot be performed. The cross-talk noise analysis is very important in circuit designing particular on future mixed signal integrated circuit development. The four-terminal model has a further problem that a connection verification of the deep N-type well cannot be performed in connection verifications after layout designing.
In this technical field, there are various known methods of generating a model for the SPICE circuit simulation considering the parasitic device. However, those methods have a problem that it is difficult to suitably incorporate the effect of the parasitic device into the model.
Embodiments will now be explained with reference to the accompanying drawings.
An embodiment described herein is, for example, a MOSFET model output apparatus configured to output a MOSFET model for a simulation of a semiconductor circuit. The apparatus includes a shape data input part configured to input shape data of a MOSFET. The apparatus further includes a parameter calculation part configured to calculate a parameter of a parasitic device model to be added to the MOSFET model, using the shape data. The apparatus further includes a MOSFET model output part configured to generate and output the MOSFET model added with the parasitic device model, using the parameter of the parasitic device model. Further, the MOSFET model output part adds different parasitic device models to the MOSFET model in a case where the MOSFET is an N-type MOSFET and in a case where the MOSFET is a P-type MOSFET.
Another embodiment described herein is, for example, a MOSFET model output method of outputting a MOSFET model for a simulation of a semiconductor circuit. The method includes inputting shape data of a MOSFET into an information processing apparatus. The method further includes calculating a parameter of a parasitic device model to be added to the MOSFET model by the apparatus using the shape data. The method further includes generating and outputting the MOSFET model added with the parasitic device model by the apparatus using the parameter of the parasitic device model. Further, different parasitic device models are added to the MOSFET model in a case where the MOSFET is an N-type MOSFET and in a case where the MOSFET is a P-type MOSFET.
Another embodiment described herein is, for example, a computer readable recording medium storing a program to cause a computer to execute a MOSFET model output method of outputting a MOSFET model for a simulation of a semiconductor circuit. The method includes calculating a parameter of a parasitic device model to be added to the MOSFET model, using shape data of a MOSFET inputted into the computer. The method further includes generating and outputting the MOSFET model added with the parasitic device model, using the parameter of the parasitic device model. Further, different parasitic device models are added to the MOSFET model in a case where the MOSFET is an N-type MOSFET and in a case where the MOSFET is a P-type MOSFET.
The apparatus of
In each of the examples shown in
In addition,
In the present embodiment, as shown in
Each of
On the other hand, in each of
The operations of the junction diodes DA and DB of
Details of the circuit diagrams of
In the present embodiment, shape data which is data associated with a shape of a MOSFET is inputted to the shape data input part 101 (
In
In
In the present embodiment, the values of those variables (i.e., shape data) are inputted to the shape data input part 101 of
The shape data may be inputted to the shape data input part 101 by a user, or may be inputted to the shape data input part 101 from various recording media or other apparatuses.
In the present embodiment, the parameter calculation part 102 calculates the parameters of the parasitic device model, using the values of the all variables shown in
Hereinafter, the processing performed by the MOSFET parameter calculation part 102A and the parasitic device parameter calculation part 102B shown in
The MOSFET parameter calculation part 102A calculates the parameters of the MOSFET model, using the shape data.
Examples of the parameters of the MOSFET model include a length LOD_L, an area AA_AREA, and a peripheral length AA_PERI of the active area. LOD_L is the length in the Y direction of the active area, as shown in
LOD_L=RF_Length*(RF_NF+2*RF_NF_DG)+Ldiffgg*(RF_NF+2*RF_NF_DG+1)+2*Ldiffga (1),
AA_AREA=LOD_L*RF_Width (2),
AA_PERI=2*(LOD_L+RF_Width) (3).
As other examples of the parameters of the MOSFET model, there are an area AREA_DNWPS and a peripheral length PERI_DNWPS of the deep N-type well, and an area AREA_DNWPW and a peripheral length PERI_DNWPW of the P-type well. In the following expressions (4) to (7), those parameters are represented by the variables shown in
AREA—DNWPS=(LOD_L+2*(LDY—PW+LDY—DNW))*(RF_Width+2*(LDX—PW+LDX—DNW)) (4),
PERI—DNWPS=2*((LOD_L+2*(LDY—PW+LDY—DNW))+(RF_Width+2*(LD X—PW+LDX—DNW))) (5),
AREA—DNWPW=(LOD_L+2*LDY—PW)*(RF_Width+2*LDX—PW) (6),
PERI—DNWPW=2*((LOD_L+2*LDY—PW)+(RF_Width+2*LDX—PW)) (7).
The MOSFET parameter calculation part 102A calculates the parameters of the MOSFET model, using the shape data and the above expressions. Note that the expressions (2) to (7) are represented using LOD_L shown in the expression (1).
Then, the parasitic device parameter calculation part 102B calculates the parameters of the parasitic device model, using the parameters of the MOSFET model. Examples of the parameters of the parasitic device model include a junction capacitance component CJ, a diode saturation current component IS, and a series parasitic resistance component RS of the parasitic device.
The parasitic device parameter calculation part 102B calculates those parameters of the parasitic device models between the P-type well and the deep N-type well and between the deep N-type well and the P-type substrate. Examples of the parasitic device model between the P-type well and the deep N-type well are the junction diode model DA and its equivalent circuit model. Examples of the parasitic device model between the deep N-type well and the P-type substrate are the junction diode model DB and its equivalent circuit (see
In the following expressions (8) to (10), the parameters of the parasitic device model between the deep N-type well and the P-type substrate are represented by the parameters of the MOSFET model shown in the expressions (4) to (7).
CJ=CJA
—
PSDNW*AREA—DNWPS+CJP—PSDNW*PERI—DNWPS (8),
IS=ISA
—
PSDNW*AREA—DNWPS+ISP—PSDNW*PERI—DNWPS (9),
RS=RSA
—
PSDNW*AREA—DNWPS+RSP—PSDNW*PERI—DNWPS+RSUB (10).
In the expressions (8) to (10), CJA_PSDNW, ISA_PSDNW, RSA_PSDNW, CJP_PSDNW, ISP_PSDNW, and RSP_PSDNW are constants. Examples of the values of those constants are, respectively, 7.53×10−4, 9.56×10−7, 4.15×10+8, 4.05×10−10−10, 1.63×10−13, and 71.4. The substrate resistivity RSUB in the expression (10) is represented by the following expression (11):
RSUB=RSUBCONST*AREA—DNWPW/AREA—DNWPS (11).
RSUBCONST represents the value of RSUB when one value from each of RF_Length, RF_Width, and RF_NF is selected. For example, when RF_Length=0.3 μm, and RF_Width*RF_NF=500 μm, RSUBCONST=500.
In the following expressions (12) to (14), the parameters of the parasitic device model between the P-type well and the deep N-type well are represented by the parameters of the MOSFET model shown in the expressions (4) to (7).
CJ=CJA
—
PWDNW*AREA—DNWPW+CJP—PWDNW*PERI—DNWPW (12),
IS=ISA
—
PWDNW*AREA—DNWPW+ISP—PWDNW*PERI—DNWPW (13),
RS=RSA
—
PWDNW*AREA—DNWPW+RSP—PWDNW*PERI—DNWPW (14).
In the expressions (12) to (14), CJA_PWDNW, ISA_PWDNW, RSA_PWDNW, CJP_PWDNW, ISP_PWDNW, and RSP_PWDNW are constants. Examples of the values of those constants are, respectively, 2.21×10−4, 6.81×10−6, 4.94×10+8, 4.97×10−10, 4.04×10−12, and 77.9.
The parasitic device parameter calculation part 102B calculates the parameters of the parasitic device models, using the parameters of the MOSFET model and the above expressions.
Then, the MOSFET model output part 103 generates and outputs the MOSFET model added with the parasitic device models, using the parameters of the parasitic device models.
In the present embodiment, the MOSFET model output part 103 generates the MOSFET model, using the values of CJ, IS, and RS of the parasitic device model between the P-type well and the deep N-type well, and the values of CJ, IS, and RS of the parasitic device model between the deep N-type well and the P-type substrate. However, the MOSFET model output part 103 may generate the MOSFET model by using some of the six values, for example, only the values of CJ and RS of those parasitic device models.
As described above, the MOSFET model output apparatus of the present embodiment generates and outputs the MOSFET model of the five-terminal model. However, the above description premises that the MOSFET is the N-type MOSFET.
In the present embodiment, when the MOSFET is the N-type MOSFET, the MOSFET model of the five-terminal model is generated and outputted. On the other hand, when the MOSFET is the P-type MOSFET, the MOSFET model of the four-terminal model is generated and outputted. Hereinafter, details of such processing will be described with reference to
On the other hand,
In the present embodiment, it is assumed that the N-type MOSFET 201 is formed on the P-type substrate 211 through the deep N-type well 212 and the P-type well 213. On the other hand, it is assumed that the P-type MOSFET 202 is formed on the P-type substrate 211 only through the deep N-type well 212.
The MOSFET models of the N-type MOSFET 201 and the P-type MOSFET 202 will be described.
In the present embodiment, when the MOSFET is the N-type MOSFET 201, the MOSFET model of the five-terminal model is generated. At that time, the structure shown in
When the MOSFET is the N-type MOSFET 201, the parasitic device model between the P-type well 213 and the deep N-type well 212, and the parasitic device model between the deep N-type well 212 and the P-type substrate 211 are added to the MOSFET model. The junction diode model DA and its equivalent circuit model are examples of the former parasitic device model. The junction diode model DB and its equivalent circuit model are examples of the latter parasitic device model (see
On the other hand, in the present embodiment, when the MOSFET is the P-type MOSFET 202, the MOSFET model of the four-terminal model is generated. At that time, the structure shown in
When the MOSFET is the P-type MOSFET 202, the parasitic device model between the deep N-type well 212 and the P-type substrate 211 is added to the MOSFET model. However, the parasitic device model between the P-type well 213 and the deep N-type well 212 is not added. For example, in terms of the example shown in
As described above, in the present embodiment, different parasitic device models are added to the MOSFET model, in the case where the MOSFET is the N-type MOSFET 201, and in the case where the MOSFET is the P-type MOSFET 202. Consequently, the difference between the parasitic devices of the N-type MOSFET 201 and the P-type MOSFET 202 can be reflected on the MOSFET model.
In the present embodiment, the MOSFET model other than the five-terminal model may be applied to the N-type MOSFET 201, and the MOSFET model other than the four-terminal model may be applied to the P-type MOSFET 202. For example, the MOSFET model of a six-terminal model may be applied to the N-type MOSFET 201, and another MOSFET model (e.g., MOSFET model of five-terminal model) may be applied to the P-type MOSFET 202.
The effects of the present embodiment will be described.
As described above, in the present embodiment, the parameters of the parasitic device model to be added to the MOSFET model are calculated using the shape data of the MOSFET. Then, the MOSFET model added with the parasitic device model is generated and outputted using the parameters of the parasitic device model.
Further, in the present embodiment, different parasitic device models are added to the MOSFET model, in the case where the MOSFET is the N-type MOSFET 201, and in the case where the MOSFET is the P-type MOSFET 202.
According to the above configuration, in the present embodiment, the difference between the parasitic devices of the N-type MOSFET 201 and the P-type MOSFET 202 can be reflected on the MOSFET model. Consequently, it is possible to generate a high-accuracy MOSFET model suitably incorporating the effects of the parasitic devices.
In the present embodiment, for example, when the MOSFET is the N-type MOSFET 201, the MOSFET model of the five-terminal model is used. In this case, the parasitic device model between the P-type well 213 and the deep N-type well 212 and the parasitic device model between the deep N-type well 212 and the P-type substrate 211 are added to the MOSFET model.
On the other hand, when the MOSFET is the P-type MOSFET 202, the MOSFET model of the four-terminal model is used. In this case, the parasitic device model between the deep N-type well 212 and the P-type substrate 211 is added to the MOSFET model. However, the parasitic device model between the P-type well 213 and the deep N-type well 212 is not added.
Consequently, in the present embodiment, the structures shown in
There will be described the effects obtained when the five-terminal model is applied to the N-type MOSFET 201, and the parasitic device model is added to the five-terminal model.
As the first effect, the bias dependence of the deep N-type well 212 can be considered, whereby the accuracy of the simulation using the MOSFET model can be enhanced.
As the second effect, the substrate and the well are connected on the net list, whereby the cross-talk noise analysis important in mixed-signal circuit designing can be performed. According to the present embodiment, analysis of the parasitic effect of the substrate, and a verification of digital noise wrapped around through the substrate are enabled.
As the third effect, in the connection verifications after the layout designing, the connection verification of the deep N-type well 212 can be performed.
In the present embodiment, the parameters of the parasitic device model are calculated, using the functions including the variables shown in
In the present embodiment, the net list of the MOSFET model added with the parasitic device model is generated and outputted. The net list can be used in the SPICE circuit simulation performed inside or outside the apparatus of
The processing performed by the apparatus of
Although the MOSFET model outputted from the apparatus of
As described above, embodiments described herein can provide a MOSFET model output apparatus and method, and a recording medium which can generate a high-accuracy MOSFET model suitably incorporating the effects of the parasitic device.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel apparatuses, methods and media described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatuses, methods and media described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2010-126900 | Jun 2010 | JP | national |