CN106991201B - Method for determining total dose model parameters of SOI MOSFET - Google Patents

Abstract

The invention provides a method for determining parameters of a total dose model of an SOI MOSFET (silicon on insulator MOSFET), which comprises the following steps of: s1: acquiring transfer characteristic data and transmission characteristic data of the SOI MOSFET under the irradiation of different doses in two working states of on and off; s2: screening the data obtained in the step S1, and importing the test data into parameter extraction software; s3: extracting equivalent transistor parameters of the upper edge angle and equivalent transistor parameters of the field oxide side wall; s4: exporting a total dose intensive model card file; s5: and importing the total dose model of each single point into the parameter extraction software to generate a total dose Bin model card file of the whole region. The method adopts a mode of separating from the main transistor to extract parameters, refines the sensitive parameters of each region in the physical model, improves the accuracy of parameter fitting, can accurately fit out hump effect generated in a sub-threshold region when the SOI MOSFET is influenced by total dose radiation effect, and can simulate the total dose effect of a full-region size device because the model exists in the form of a Bin model card.

Description

A Determination Method of SOI MOSFET Total Dose Model Parameters

technical field

The invention belongs to the technical field of device intensive model parameter extraction, in particular to a method for determining parameters of a SOI MOSFET total dose model.

Background technique

With the continuous development of space technology, electronic products used in the information society are more and more widely used in space exploration and space navigation. And all kinds of rays existing in space will cause irreversible damage to electronic products, thus causing the failure of space instruments. SOI (Silicon-On-Insulator) is a silicon-on-insulator technology, which can well reduce radiation effects such as single-event flipping and single-event latch-up caused by ground-space particles to circuits. The silicon oxide interface (shallow trench isolation field oxygen, buried oxygen) causes radiation particles to generate a large number of redundant charges at these interfaces, which further causes electronic devices to fail to work in the normal working area. Therefore, it is necessary to carry out radiation process reinforcement and design reinforcement for circuits based on SOI devices.

MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide Semiconductor Field-Effect Transistor) intensive model is a model that describes the physical effects of MOSFET devices as mathematical equations, and forms a model for large-scale EDA simulation of circuits through parameter extraction . The SOI MOSFET intensive model is an intensive model that can be used to simulate SOI devices. The high-precision and high-speed intensive model can narrow the difference between the circuit designer's design and the tape-out product, which can greatly improve the design accuracy and shorten the development cycle.

The SOI MOSFET total dose intensive model is a kind of model that can reflect the influence of the total dose in SOI MOSFET, and can accurately reflect the change of the electrical characteristics of the circuit through simulation. This model can provide circuit designers with a feasible and reliable radiation-hardened circuit design scheme, reduce the number of radiation tests, and greatly shorten the design cycle and R&D capital investment.

The existing SOI MOSFET total dose intensive model is a macro model based on the basic idea of adding sub-circuits around the main transistor. The establishment of the macro model must be through the extraction of parameters in order to obtain the intensive model of the corresponding process that can be used for simulation. It includes two parts: device irradiation test data acquisition and parameter extraction. The existing SOI MOSFET total dose intensive model has the problem of complicated parameter extraction process.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for determining the parameters of the SOI MOSFET total dose model, which is used to solve the problems in the prior art that the SOI MOSFET total dose intensive model parameter extraction process is complex and the accuracy is not high. question.

In order to achieve the above-mentioned purpose and other related purposes, the present invention provides a method for determining the parameters of a SOI MOSFET total dose model, comprising the following steps:

S1: Obtain the transfer characteristic data and transfer characteristic data of the SOI MOSFET under two working states of ON and OFF under different dose irradiation;

S2: filter the data obtained in step S1, and import the test data into the parameter extraction software;

S3: Extract the equivalent transistor parameters of the upper corner and the equivalent transistor parameters of the field oxygen sidewall;

S4: Export the total dose intensive model card file;

S5: Import the total dose model of each single point into the parameter extraction software, and generate the total dose Bin model card file of the whole area.

Optionally, in the step S1, the MOSFET is a PMOS or an NMOS.

Optionally, in the step S1, a cobalt 60 irradiation source is used to perform the irradiation test.

Optionally, in the step S1, the radiation dose ranges from 0 to 1000 k rad/SiO ₂ .

Optionally, in the step S1, at least two radiation doses are used for the irradiation test.

Optionally, in the step S1, in the ON state, the voltage applied to each port is V_drain=V_source=V_body=V_substrate=0V, V_gate=VDD, and in the OFF state, the voltage applied to each port is V_drain=V_source=V_body=V_substrate=V_gate=0V, where V_drain is the drain voltage, V_source is the source voltage, V_body is the body voltage, V_substrate is the substrate voltage, V_gate is the gate voltage, and VDD is the working voltage.

Optionally, in the step S2, the data obtained in the screening step S1 includes the following steps: calculating the threshold voltage of each dose point of each group of test data, if the threshold voltage of the group of data changes to monotonically decrease as the dose increases. , select this group of data.

Optionally, in the step S2, the parameter extraction software is TIDFit.

Optionally, in the step S2, the step of setting process parameters, geometric parameters and type parameters of the device is further included.

Optionally, it also includes the steps of simulating the device transfer characteristics before no irradiation, and revising the sub-threshold slope parameter in the process parameters according to the obtained sub-threshold slope value, and re-simulating the background current after the modification.

Optionally, in the step S3, the step of adjusting the equivalent transistor parameters of the upper corners and the equivalent transistor parameters of the field oxygen sidewalls to correct the fitting details of the curve is further included.

Optionally, in the step S3, the upper corner equivalent transistor parameters include upper corner gate oxide thickness, upper corner threshold voltage, upper corner threshold voltage offset, upper corner mobility, upper corner dose saturation factor, upper corner One or more of angular saturation velocity and upper corner width; the field oxygen sidewall equivalent transistor parameters include field oxygen sidewall gate oxide thickness, field oxygen sidewall threshold voltage, field oxygen sidewall threshold voltage offset, One or more of field oxygen sidewall mobility, field oxygen sidewall dose saturation factor, field oxygen sidewall saturation velocity, field oxygen sidewall width and weak inversion coefficient.

Optionally, in the step S4, at least four single-point models of SOI MOSFETs of different sizes are derived.

Optionally, step S6 is also included, using the total dose physical model description file, the circuit netlist file and the total dose Bin model card file to simulate the device transfer characteristics.

Optionally, in the step S6, the variation curve of the leakage current of the SOI MOSFET with the front gate voltage is simulated under the irradiation of different doses.

As mentioned above, the SOI MOSFET total dose model parameter determination method of the present invention has the following beneficial effects: (1) Compared with the traditional parameter extraction method, the present invention adopts the method of separating the parameters from the main transistor (the main transistor Parameter extraction can use industry standard process for parameter extraction, the total dose model parameter extraction will not affect the main transistor model parameters, the two are independent), refine the sensitive parameters of each area in the physical model, and improve parameter fitting (2) The present invention can accurately fit the bump effect generated in the sub-threshold region when SOI MOSFET is affected by the total dose radiation effect; (3) The model exists in the form of a Bin model card, which can simulate the size of the whole area Device (ie, devices of various sizes) total dose effect.

Description of drawings

FIG. 1 shows a flow chart of the method for determining the parameters of the SOI MOSFET total dose model of the present invention.

FIG. 2 shows the parameter adjustment and curve fitting diagram of the shallow trench isolation gate oxide region.

Figure 3 shows the parameter adjustment and curve fitting diagram for the upper corner area.

Figure 4 shows a comparison of the simulation results of the device transfer characteristics with the test results.

Component label description

S1～S5 steps

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

See Figures 1 through 4. It should be noted that the drawings provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the drawings only show the components related to the present invention rather than the number, shape and the number of components in actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

As shown in FIG. 1 , it is a flowchart of the method for determining the parameters of the SOI MOSFET total dose model of the present invention, including the following steps:

Step S1: Acquire transfer characteristic data and transfer characteristic data of the SOI MOSFET under two operating states of ON and OFF under irradiation with different doses.

Specifically, the MOSFET is PMOS or NMOS. The transfer characteristic data includes the relationship between the front gate voltage and the source-drain current, and the transfer characteristic data includes the relationship between the source-drain voltage and the source-drain current.

Specifically, at least four sizes of MOSFETs can be selected for testing. The dimension parameters include a width W and a length L, wherein the width W refers to the length of the gate perpendicular to the channel direction, and the length L refers to the channel length.

In this step, SOI MOSFETs of various sizes are selected for testing, and the total dose model of the whole area can be obtained. For each size of MOSFET, at least two radiation doses are used for the radiation test, the radiation dose range is 0 ~ 1000krad/SiO ₂ . Here, the radiation energy received per unit mass of matter is called dose, and rad or Gray is commonly used as a unit of measurement. The relationship between them and other commonly used energy units is: 1rad=100erg/g= 6.24×1013eV/g, 1Gray=1J/kg=100rad. In the case of a certain radiation intensity, the received radiation dose is related to the atomic density of the material itself; the higher the density, the higher the dose, and the lower the density, the lower the dose. For example, for several common microelectronic materials, the relationship between the doses is: 1rad/Si=0.58rad/SiO ₂ =0.94rad/GaAs. The sum of the radiation doses received by the entire material or device is called the total dose (TID). In this embodiment, the total radiation dose received by the device is in units of rad/SiO ₂ .

Step S2: Screen the data obtained in Step S1, and import the test data into the parameter extraction software.

Specifically, the data obtained in the screening step S1 includes the following steps:

1) Calculate the threshold voltage of each dose point of each group of test data by using the industry general method;

2) If the threshold voltage variation of this group of data decreases monotonically with increasing dose, select this group of data.

The parameter extraction software includes but is not limited to software such as TIDFit. Among them, TIDFit is a parameter extraction software specially developed for SOIMOSFET total dose modeling.

In this step, the step of setting process parameters, geometric parameters and type parameters of the device is also included.

Further, this step also includes the steps of simulating the transfer characteristics of the device before no irradiation, and revising the sub-threshold slope parameter in the process parameters according to the obtained sub-threshold slope value, and re-simulating the background current after the modification.

Step S3: Extracting the equivalent transistor parameters of the upper corner and the equivalent transistor parameters of the field oxygen sidewalls.

Specifically, the upper corner equivalent transistor parameters include upper corner gate oxide thickness, upper corner threshold voltage, upper corner threshold voltage offset, upper corner mobility, upper corner dose saturation factor, upper corner saturation velocity and upper corner width One or more of the field oxygen sidewall equivalent transistor parameters include the field oxygen sidewall gate oxide thickness, the field oxygen sidewall threshold voltage, the field oxygen sidewall threshold voltage offset, the field oxygen sidewall mobility, the field oxygen sidewall threshold voltage One or more of oxygen sidewall dose saturation factor, field oxygen sidewall saturation velocity, field oxygen sidewall width and weak inversion coefficient.

Step S4: Export the total dose intensive model card file.

Specifically, single-point models of SOI MOSFETs of different sizes are derived respectively. Here, the single-point model refers to a model corresponding to a single size.

Step S5: Import the total dose model of each single point into the parameter extraction software, and generate the total dose Bin model card file of the whole area.

Specifically, the Bin model card is obtained by using the Bin model generation method in the industry standard model BSIM3.3.

The invention solves the current situation that the existing total dose model has a complicated parameter extraction process, provides a simplified parameter extraction process, and ensures the accuracy of the model. The model exists in the form of a Bin model card, which can simulate the total dose effect of a full-area-sized device.

Further, the SOI MOSFET total dose model parameter determination method of the present invention further includes step S6: using the total dose physical model description file, the circuit netlist file and the total dose Bin model card file to simulate device transfer characteristics.

Specifically, the variation curve of the leakage current I _Drain of the SOI MOSFET with the front gate voltage V _FrontGate under different doses of irradiation is simulated. Among them, the description file of the total dose physical model is expressed in verilog-A language and is written according to the physical model. This file does not need to be modified in the whole process of extracting parameters. It is a given file and has nothing to do with parameter extraction. However, this file is required for circuit simulation after the parameter extraction is completed. The circuit netlist file is a file written by a circuit designer. This file is written in SPICE language and contains all the information of the circuit to be simulated. This file has nothing to do with parameter extraction, but is needed for circuit simulation.

As an example, taking 1.2V NMOS in the 0.13-micron SOI CMOS process as an example, the extraction of SOI MOSFET total dose model parameters includes the following processes:

1) Select four sizes of NMOS devices with a width-to-length ratio W/L=10/10, 10/0.13, 0.15/10, 0.15/0.13 (units are all microns) for packaging, and the Drain (drain), Gate (gate) Electrode), Source (source), Body (body region), Substrate (substrate) are all drawn out with gold wires.

In this embodiment, four sizes of NMOS devices are selected for testing. In other embodiments, devices with more sizes can also be selected for testing as required.

2) The irradiation test is carried out with a cobalt 60 irradiation source, and all devices use two test bias states of ON (on) and OFF (off). When biased ON, the voltage of each port is V_drain=V_source=V_body=V_substrate=0V, V_gate=1.2V (operating voltage), and when biased OFF, the voltage of each port is V_drain=V_source=V_body=V_substrate=V_gate=0V, radiation The time is determined according to different dose rates, to ensure that the total radiation dose received by the device is 100k, 400k, 700k, 1000k (units are rad/SiO ₂ ).

3) Remove the device that has reached the specified dose, and use a semiconductor parameter tester to measure two sets of data of the device's transfer characteristics and transmission characteristics. The transfer characteristic data includes the relationship between the front gate voltage and the source-drain current, and the transfer characteristic data includes the relationship between the source-drain voltage and the source-drain current.

4) Repeat steps 2)-3) to collect data at the next dose point until the total dose reaches 1000k rad/SiO ₂ .

5) Import the filtered data into the parameter extraction software TIDFit. Then set the process parameters, geometric parameters and type parameters of the device, wherein the process parameters of the device include body factor switch (isgammaset), main transistor gate oxide thickness (toxref), sub-threshold slope (ss), body region doping concentration (Nsub ), effective source-drain voltage parameter (delta) and other parameters; the geometric parameters include gate perpendicular to the channel direction length (W) and channel length (L); the type parameters include operating voltage (VDD).

6) Simulate the transfer characteristics of the device before irradiation (the relationship between the front gate voltage and the source-drain current), and modify the ss parameter according to the obtained sub-threshold slope value, and re-simulate the background current after the modification.

7) Adjust the equivalent transistor parameters of the field oxygen sidewall so that the curve (the change curve of the current in the field oxygen sidewall region with the voltage) fits the test data of the field oxygen sidewall region (shallow trench isolation gate oxide region) better. As an example, the field oxygen sidewall equivalent transistor parameters include the field oxygen sidewall gate oxide thickness (toxsti2), the field oxygen sidewall threshold voltage (vth0sti2), the field oxygen sidewall threshold voltage offset (voffsti2), the field oxygen sidewall threshold voltage (voffsti2), the field oxygen sidewall threshold voltage Wall mobility (usti2), field oxygen sidewall dose saturation factor (taosti2), field oxygen sidewall saturation velocity (SATsti2), field oxygen sidewall width (wsti2) and weak inversion coefficient (MINV).

As shown in Figure 2, it shows the parameter adjustment and curve fitting diagram of the field oxygen sidewall area, in which the ordinate is the logarithmic current (A), the abscissa is the voltage (V), the solid dots represent the test data, and the solid line represents the fitted curve. The parameters of the field oxygen sidewall region can affect the off-state leakage current of the device.

8) Adjust the equivalent transistor parameters of the upper corner so that the curve (the change curve of the current in the upper corner region with the voltage) fits the test data of the upper corner region better. As an example, the upper corner equivalent transistor parameters include upper corner gate oxide thickness (toxsti1), upper corner threshold voltage (vth0sti1), upper corner threshold voltage offset (voffsti1), upper corner mobility (usti1), upper corner dose Saturation factor (taosti1), upper corner saturation velocity (SATsti1) and upper corner width (wsti1).

As shown in Figure 3, it is displayed as a graph of parameter adjustment and curve fitting in the upper corner area, wherein the solid dots represent the test data, and the solid lines represent the fitting curve. Here, the upper corner region refers to the corner of the interface between the main transistor and the field oxide sidewall region, and the parameters of this region affect the hump effect. Among them, the hump effect means that in addition to the increase of off-state leakage current of the MOSFET after irradiation, a "bulge" will also appear in the sub-threshold region. The existing total dose model cannot express this effect, but can only express off-state leakage. current increases.

9) Repeat steps 7)-8) to correct the fitting details of the curve.

It should be pointed out that in the process of repeating steps 7)-8), the entire curve does not need to be in good agreement, as long as the final superimposed total current is in agreement with the test result. Among them, step 7) adjusts the current in the sidewall area, and step 8) adjusts the current in the corner area. When adjusting the currents of these two areas respectively, the accuracy of the current matching in one area may be improved, but the addition of the current in the other area After the current, the accuracy decreases, so repeat operations 7)-8) to improve the total current accuracy, so as to determine the following parameters: (1) The equivalent transistor parameters of the upper corner, including the upper corner gate oxide thickness, the upper corner threshold voltage, One or more of parameters such as upper corner threshold voltage shift, upper corner mobility, upper corner dose saturation factor, upper corner saturation velocity and upper corner width; (2) Field oxygen sidewall equivalent transistor parameters: including field Oxygen Sidewall Gate Oxide Thickness, Field Oxygen Sidewall Threshold Voltage, Field Oxygen Sidewall Threshold Voltage Offset, Field Oxygen Sidewall Mobility, Field Oxygen Sidewall Dose Saturation Factor, Field Oxygen Sidewall Saturation Velocity, Field Oxygen Sidewall Width and one or more of the parameters such as weak inversion coefficient.

10) Export the single-point model (total dose intensive model card file) of SOI MOSFET of each size obtained through the above steps, and import the software to generate the total dose Bin model card file of the whole area. Among them, each single point model corresponds to only one size, and the total dose Bin model of the whole area can cover devices of various sizes, and can simulate the total dose effect of the size devices of the whole area.

11) Call the total dose model card Bin file generated through the above steps and the existing total dose physical model description file and circuit netlist file to simulate the device transfer characteristics.

As an example, Figure 4 shows a comparison of simulation results (solid lines) and test results (solid dots) for the transfer characteristics of a device with dimensions W/L=0.15/0.13. It can be seen that the SOI MOSFET total dose model parameter determination method of the present invention has high parameter fitting accuracy. At the same time, it can be seen from the -0.2V-0.1V region in Fig. 4 that the present invention can accurately fit the bump effect generated in the subthreshold region when the SOI MOSFET is affected by the total dose radiation effect.

To sum up, the method for determining the parameters of the SOI MOSFET total dose model of the present invention adopts the method of separating the parameters from the main transistor to extract the parameters, refines the sensitive parameters of each area in the physical model, and improves the accuracy of parameter fitting; The invention can accurately fit the bump effect generated in the sub-threshold region when SOI MOSFET is affected by the total dose radiation effect; in the invention, the model exists in the form of a Bin model card, which can simulate the total dose effect of the full area size device. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (14)

1. A method for determining total dose model parameters of SOIMOSFET is characterized by comprising the following steps:

s1: acquiring transfer characteristic data and transmission characteristic data of an SOI MOSFET under and under two working states of different doses of irradiation, wherein in the on working state, the voltage applied to each port is V _ drain-V _ source-V _ body-V _ substrate-0V and V _ gate-VDD, in the off working state, the voltage applied to each port is V _ drain-V _ source-V _ body-V _ substrate-V _ gate-0V, wherein V _ drain is a drain voltage, V _ source is a source voltage, V _ body is a bulk voltage, V _ substrate is a substrate voltage, V _ gate is a gate voltage and VDD is a working voltage;

s2: screening the data obtained in the step S1, and importing the test data into parameter extraction software;

s3: extracting equivalent transistor parameters of the upper edge angle and equivalent transistor parameters of the field oxide side wall;

s4: exporting a total dose intensive model card file;

s5: and importing the total dose model of each single point into the parameter extraction software to generate a total dose Bin model card file of the whole region.

2. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S1, the MOSFET is PMOS or NMOS.

3. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S1, an irradiation test is performed using a cobalt 60 irradiation source.

4. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in the step S1, the radiation dose is in the range of 0-1000 k rad/SiO₂。

5. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S1, at least two radiation doses are used for the irradiation test.

6. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S2, the data obtained in the screening step S1 includes the following steps: and calculating the threshold voltage of each dose point of each group of test data, and selecting the group of data if the threshold voltage change of the group of data is monotonously reduced along with the increase of the dose.

7. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S2, the parameter extraction software is tidbit.

8. The SOI MOSFET total dose model parameter determination method of claim 1, characterized by: in step S2, a step of setting process parameters, geometric parameters and type parameters of the device is further included.

9. The SOIMOSFET total dose model parameter determination method of claim 8, wherein: the method also comprises the steps of simulating the transfer characteristics of the device before irradiation, correcting the sub-threshold slope parameter in the process parameters according to the obtained sub-threshold slope value, and re-simulating the background current after correction.

10. The method for determining total SOIMOSFET dose model parameters of claim 1, wherein: in step S3, the method further includes adjusting the top corner equivalent transistor parameter and the field oxide sidewall equivalent transistor parameter to correct the fitting details of the curve.

11. The method for determining total SOIMOSFET dose model parameters of claim 1, wherein: in step S3, the upper corner equivalent transistor parameters include one or more of an upper corner gate oxide thickness, an upper corner threshold voltage offset, an upper corner mobility, an upper corner dose saturation factor, an upper corner saturation velocity, and an upper corner width; the field oxygen sidewall equivalent transistor parameters comprise one or more of field oxygen sidewall gate oxide thickness, field oxygen sidewall threshold voltage deviation, field oxygen sidewall mobility, field oxygen sidewall dose saturation factor, field oxygen sidewall saturation velocity, field oxygen sidewall width and weak inversion coefficient.

12. The method for determining total SOIMOSFET dose model parameters of claim 1, wherein: in step S4, a single-point model of at least four soi mosfets of different sizes is derived, where the single-point model is a model corresponding to a single size.

13. The method for determining total SOIMOSFET dose model parameters of claim 1, wherein: and step S6, performing device transfer characteristic simulation by using the total dose physical model description file, the circuit netlist file and the total dose Bin model card file.

14. The SOI MOSFET total dose model parameter determination method of claim 13, wherein: in step S6, a variation curve of the drain current of the soi mosfet with the front gate voltage under different dose irradiation is simulated.

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