A method for building a 3D model of EG-ISFET

Abstract

The present invention discloses a method for building a 3D model of an EG-ISFET, comprising the following steps: obtaining the structural parameters of the EG-ISFET device to be simulated; constructing a 3D simulation model of a gridded EG-ISFET according to the structural parameters of the EG-ISFET device; establishing a pH buffer model and defining new materials through TCAD simulation software according to the physicochemical properties of the electrolyte; setting doping, contact type, interface state, physical model and pH buffer / insulator interface site binding model for the 3D simulation model of the EG-ISFET; setting voltage parameters to obtain output characteristics, transfer characteristic curves and pH characteristic curves, and analyzing the simulation results. Based on this method, a method for verifying the induced voltage conduction theory of the extended gate part in the EG-ISFET is provided, providing theoretical guidance for the development of EG-ISFET devices.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for building a 3D model of an EG-ISFET. Background Art

[0002] ISFET (ion-sensitive field-effect transistor) was first proposed by Bergveld and can be used to detect hydrogen ion concentration or pH. ISFET has the advantages of easy miniaturization, strong specificity, fast detection speed and easy integration, and is widely used in environmental testing, medical testing and biomarker identification.

[0003] When the traditional ion-sensitive field-effect transistor is used for detection, the solution will be in direct contact with the device. After long-term use, not only the surface sensitive layer will be corroded, but the device itself will also be damaged, thus greatly shortening the device life. In 1983, Van der proposed the concept of EG-ISFET (extended gate ion-sensitive field-effect transistor) based on ISFET technology. Unlike ISFET, EG-ISFET is divided into a sensor and a transducer area, in which the transducer area maintains the standard MOSFET (metal oxide semiconductor field-effect transistor) structure, while the sensor area is physically separated from the transducer area.

[0004] In the EG-ISFET structure, only the sensitive film of the sensing area is in direct contact with the solution, and the induced potential generated by the sensing area is transferred to the gate of the transducer area, so the solution will not affect the transducer area, which can greatly extend the service life of the device. This structure has the advantages of low cost, easy packaging, good stability, etc., and can isolate the influence of temperature and light on the device.

[0005] The sensitivity of traditional ISFET is limited by its structure, and the pH sensitivity cannot break through the Nernst limit. The dual-gate structure is used in the transduction region of EG-ISFET, and the pH sensitivity can be significantly improved through the capacitive coupling effect between the bottom gate dielectric layer and the top gate dielectric layer.

[0006] TCAD software is a computer-aided simulation tool that can simultaneously realize semiconductor process research and semiconductor device research. Since the actual preparation cycle of chips is long and the cost is high, TCAD software can be used to verify the structural rationality of the chip, which can reduce the cycle and cost of chip development. TCAD provides process simulators (Athena), structure and grid editors (DevEdit), device simulators (Atlas), etc. Among them, DevEdit can edit the device structure, and can also edit it based on the structure obtained by process simulation, such as re-dividing the grid; Atlas is an easy-to-use, modular and scalable platform that can be used for physical simulation. It is also the core component of TCAD software and can simulate many characteristics of semiconductor devices, including electrical characteristics, optical characteristics and thermal characteristics. The 2D model of EG-ISFET built by TCAD has certain limitations and cannot fully simulate the overall structure and electrical characteristics of the device. The construction of a 3D model can fully describe the structure of the device and simulate and analyze more electrical characteristic parameters, so it is more instructive for device preparation and performance analysis.

[0007] However, there is no report on the 3D model construction method in the prior art, due to the following technical difficulties:

[0008] TCAD software cannot simulate pH buffers.

[0009] In TCAD software, the 3D simulation model only responds to voltage and cannot detect different pH values, that is, the pH sensitivity cannot be directly simulated and calculated. Summary of the invention

[0010] The purpose of the present invention is to provide guidance for the development of EG-ISFET by providing a method for building a 3D model of EG-ISFET.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] (1) First, start DevEdit (structure and mesh editor) and set the basic simulation environment, including the version number of DevEdit, the version number of the library, and the size of the simulation area;

[0013] (2) Then, a 3D model of the basic EG-ISFET is constructed, and the materials and dimensions of the sensing area and the transducing area are defined from bottom to top.

[0014] (3) The structures of different materials in the 3D model are divided and distinguished through gridding; each grid unit contains only one material and has different state values ​​such as doping concentration, mobility, electric field strength, etc., giving basic physical parameters to different material regions.

[0015] In the preferred technical solution, the grid is then optimized, and the simulation accuracy of different materials is distinguished by different grid densities; in the simulation, different grid densities are selected according to the simulation accuracy requirements of different materials to obtain better convergence and faster simulation speed.

[0016] (4) Then the materials described in the model (there are no corresponding materials in the library) are redefined, and the pH buffer model is established.

[0017] (5) Then, doping is performed on the materials of different parts of the 3D model, and doping data is set, including boron doping, phosphorus doping, doping area color, function type for defining impurity distribution, definition of doping area boundary, area boundary concentration and electron peak, etc. Then, the electrode part of the 3D model of the EG-ISFET is defined.

[0018] The above has preliminarily established a 3D model of EG-ISFET with basic physical parameters.

[0019] (6) Start Atlas (device simulator). Set device simulation conditions, including material contact type, physical model, interface characteristics, site binding model, numerical calculation method, and specify charge trajectory;

[0020] (7) Finally, the voltage conditions are set to obtain the electrical characteristics of the 3D model of the EG-ISFET, including the output characteristics and transfer characteristics; based on the basic electrical characteristics, an analysis is performed to obtain the voltage sensitivity, current sensitivity, threshold voltage, saturation current, switching current ratio, subthreshold swing, and field effect mobility of the 3D model of the EG-ISFET; the internal characteristics of the 3D model of the EG-ISFET are extracted, including the concentration distribution, potential distribution, and current density.

[0021] Further preferably, in the 3D model structure of the EG-ISFET, the transduction area is, from bottom to top, sequentially: back gate electrode, substrate, bottom gate dielectric layer, channel layer, top gate dielectric layer and gate, and the channel layer is located between the bottom gate dielectric layer and the top gate dielectric layer; the source and the drain are located on both sides of the channel layer and are in contact with the channel layer; the sensing area is, from bottom to top, sequentially: back gate electrode, substrate, bottom gate dielectric layer, gate, sensitive layer, pH buffer solution and reference electrode.

[0022] Further preferably, the geometric dimensions of the 3D model of the EG-ISFET include the length, width and thickness of the back gate; the length, width and thickness of the substrate; the length, width and thickness of the bottom gate dielectric layer; the length, width and thickness of the channel; the length, width and thickness of the source; the length, width and thickness of the drain; the length, width and thickness of the top gate dielectric layer; the length, width and thickness of the gate; the length, width and thickness of the sensitive layer; the length, width and thickness of the electrolyte; and the length, width and thickness of the reference electrode.

[0023] Further preferably, the materials of the 3D model structure of the EG-ISFET, such as the back gate electrode, source and drain, may be selected from metal materials such as Ag, Cr / Au, Au, Cu, etc.; the gate may be selected from conductive materials such as ITO, Al, Cu, Ag, etc.; the bottom dielectric layer and the top dielectric layer may be selected from materials such as SiN, SiO2, Si3O4, Ta2O5, HfO2 and Si3N4, etc.; the channel may be selected from semiconductor materials such as InGaZnO, In2O3, silicon, etc.; the sensitive layer may be selected from insulating materials with high dielectric constants such as tin oxide, tantalum oxide, titanium oxide, aluminum oxide, HfO2, etc.

[0024] Further preferably, in the 3D model of the EG-ISFET, each grid unit contains only one material with different state values ​​such as doping concentration, mobility and electric field strength; different grid densities can be set to achieve fast running speed and high precision. For example, a denser grid is set at the contact position of each material to improve the accuracy of the result and reduce the error with the actual result; the grid density distribution can be reduced accordingly in the central area of ​​each material to reduce the running time of the simulation.

[0025] Further preferably, the redefined TACD library does not have the corresponding material and the required pH buffer. The parameters of the actual material such as material type, electrical dielectric constant, eg300 (bandgap width (eV) at 300K (room temperature 300 degrees Kelvin)), nc300 (conduction band density (cm -3 ))、nv300(valence band density at 300K (cm -3 )), electronic Auger coefficient (cm 6 / s), hole Auger coefficient (cm 6 / s), electron saturation velocity (cm / s), spin degeneration factor, electron affinity (eV), etc. to simulate the required materials. For example, the pH value of the electrolyte is determined according to the Poisson-Boltzmann equation, and the formula is as follows:

[0026]

[0027] Where N C is the conduction band density at 300K, N V is the valence band density at 300K, N A is Avogadro's number, E g is the band gap of the semiconductor, k is the Boltzmann constant, and T is the absolute temperature.

[0028] We then calculated the basic characteristics N of different pH buffers using the Poisson-Boltzmann equation. C and N V, thus establishing the basic variables of the pH buffer model, thus establishing the pH buffer model of pH 1 to pH 14, as shown in Table 1:

[0029] Table 1. pH buffer model parameters

[0030]

[0031] Further preferably, the doping of the 3D model of the EG-ISFET can be divided into N-type and P-type according to the doping material (boron doping, phosphorus doping) and concentration; at the same time, the doping area color and the function type of impurity distribution are defined, including gauss, erfc, dist, log and exp types; the doping area boundary is defined, usually low, high and both; the area boundary concentration and electron peak value, etc.

[0032] Further preferably, the physical model of the 3D model of the EG-ISFET can be divided into five groups: mobility model, recombination model, carrier statistics model, impact ionization model and tunnel model. The selected physical model includes srh (Shockley-Read-Hall recombination model), auger (Auger recombination model) and cvt (mobility recombination model).

[0033] Further preferably, the contact characteristics and interface characteristics of the 3D model of the EG-ISFET: The contact type between the electrode and the semiconductor material is ohmic contact, so the work function parameter is defined as Schottky contact, and the value of the work function is set; the interface characteristics are defined, including the interface charge density and the surface recombination velocity.

[0034] Preferably, a site binding model of pH buffer / insulator is established. Since the device surface response to pH depends on the surface charge, a site binding model of pH buffer / insulator is established according to the surface charge formula, which is as follows:

[0035]

[0036] Where σ0 is the surface charge density, q is the basic charge, p is the carrier concentration, N trap is the number of binding sites per unit area, V n and V p is the thermal velocity of electrons and holes, n is the electron concentration, σ n and σ p are the carrier capture cross sections for electrons and holes, respectively, e nD and e pD is the electron and hole emission rate, e pA is the acceptor hole capture rate.

[0037] Next, the interface trap parameters are used to accurately simulate the surface charge, ionization rate, values ​​of electrons and holes under different pH environments (including carrier capture cross-sections, thermal velocity and emission rate), Fermi level, trap energy level and degeneracy factor of trap centers, and a site binding model of pH buffer / insulator is established, so that the 3D model can simulate and calculate the pH sensitivity.

[0038] Further preferably, the numerical calculation method and charge trajectory of the 3D model of the EG-ISFET. In Atlas, the defined numerical calculation method is used at the grid points of the 3D device model to obtain the device characteristics. The convergence criteria of Newton iteration, Gummel iteration, Block iteration, combined iteration and nonlinear iteration can be selected. Define the charge trajectory: through normal injection at the drain, set parameters including entry and exit areas, radius, charge density, electron lifetime (s) of SRH recombination and hole lifetime (s) of SRH recombination.

[0039] Further preferably, the IV characteristics, i.e., output characteristics and transfer characteristics, simulated by the 3D model of the EG-ISFET are screened out by setting different voltage bias conditions and scanning voltages to select suitable experimental simulation conditions, such as back gate voltage, reference electrode voltage, source voltage, and drain voltage;

[0040] Further preferably, the pH sensitivity of the 3D model of the EG-ISFET is calculated by output characteristics and transfer characteristics curves. The method of improving the sensitivity can improve the pH sensitivity of the device by the capacitive coupling effect of the dual-gate structure on the one hand, and improve the sensitivity by changing the simulated structure size and material on the other hand.

[0041] Further preferably, the performance index of the 3D model of the EG-ISFET is calculated by the IV characteristics simulated by the 3D model of the EG-ISFET, and the performance indexes such as the source-drain current, threshold voltage, subthreshold swing, field effect mobility and switch current ratio of the 3D model are calculated; the pH sensitivity and the corresponding performance indexes are used to evaluate the quality of the 3D model. The source-drain current is the response signal of the EG-ISFET device, which is divided into a linear region and a saturation region; the threshold voltage is the gate voltage of the channel layer to form a strong inversion layer, which is calculated by the transfer characteristics in the IV characteristics, and the tangent with the largest slope in the transfer characteristic curve is taken. The intersection of the x-axis and the tangent is the threshold voltage, and the smaller the threshold voltage, the smaller the gate voltage of the device is turned on; the switch current ratio is calculated by the transfer characteristic curve, which is the ratio of the on-state current to the off-state current. The larger the switch current ratio, the better the device performance; the subthreshold swing is a performance index that measures the mutual conversion rate between the on and off states of the device. It represents the change in gate voltage required for the source-drain current to change tenfold. The calculation formula is as follows:

[0042]

[0043] Among them I DS represents the source-drain current, V GS Represents the gate voltage. Also known as the S factor, the smaller the S, the faster the ON / OFF rate. The field effect mobility μ represents the mobility of the carrier, and the calculation formula is as follows:

[0044]

[0045] Where L is the channel length, C B is the gate dielectric capacitance per unit area, V DS is the source-drain voltage, I DS represents the source-drain current, V GS Indicates the source-drain voltage. Field effect mobility represents the conductivity of the device. The larger μ is, the better the conductivity of the device is.

[0046] Beneficial effects of the present invention

[0047] 1. The technical solution provided by the present invention performs 3D modeling on EG-ISFET, and establishes a 3D model through TCAD software. Compared with the 2D model, the construction of the 3D model can fully describe the structure of the device, and can simulate and analyze more electrical characteristic parameters, and can also more flexibly change different parameters for simulation comparison, such as structure, material and size parameters. A pH buffer model and a pH buffer / insulating layer site combination model are established, and the performance indicators of EG-ISFET under different parameters are simulated and analyzed, so as to quickly obtain the optimization method of EG-ISFET design, thereby reducing the cost of device development and shortening the development cycle.

[0048] 2. The solution provided by the present invention models the structure of EG-ISFET and verifies that the induced voltage of the sensing area to the solution can be transmitted to the gate of the transducing area, which can provide guidance for the extended gate device conduction theory. In the simulation, a voltage is applied to the reference electrode, and the solution to be tested will cause an induced potential on the surface of the sensitive layer, while the extended gate transmits the induced potential to the gate of the transducing area. At the same time, voltage is applied to the source and drain, thereby generating a current signal between the source and drain. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a flow chart of building a 3D model of an EG-ISFET provided by an embodiment of the present invention;

[0050] Figure 2 is a structural diagram of a 3D model of an EG-ISFET provided in an embodiment of the present invention;

[0051] Figure 3The 3D model of EG-ISFET provided by the embodiment of the present invention is Figure 2 A cross-sectional view of the sensing area along line AA;

[0052] Figure 4 The 3D model of EG-ISFET provided by the embodiment of the present invention is Figure 2 A cross-sectional view of the transducing region along line BC;

[0053] Figure 5 It is a simulation result diagram (output characteristic curve) of the 3D model building method of EG-ISFET provided in an embodiment of the present invention;

[0054] Figure 6 It is a simulation result diagram (transfer characteristic curve) of the 3D model building method of EG-ISFET provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] The 3D model building method of EG-ISFET provided in the embodiment of the present invention is combined with Figure 1 , specifically including the following steps:

[0057] (1) First, start DevEdit and set the basic simulation environment, including the version number of DevEdit, the version number of the library, and the size of the simulation area;

[0058] (2) Next, construct a basic 3D model of the EG-ISFET, and define the materials and dimensions of the sensing area and the transducing area from bottom to top. The dimensions include the length, width and thickness of the back gate; the length, width and thickness of the substrate; the length, width and thickness of the bottom gate dielectric layer; the length, width and thickness of the channel; the length, width and thickness of the source; the length, width and thickness of the drain; the length, width and thickness of the top gate dielectric layer; the length, width and thickness of the conductive layer; the length, width and thickness of the sensitive layer; the length, width and thickness of the pH buffer; and the length, width and thickness of the reference electrode. The 3D model of the EG-ISFET is as follows: Figure 2 shown.

[0059] (3) Then, the different material structures in the 3D model are divided and distinguished through gridding; each grid cell contains only one material and has different state values ​​such as doping concentration, mobility, and electric field strength, giving basic physical parameters to different material regions.

[0060] Next, the grid is optimized, and the simulation accuracy of different materials is distinguished by different grid densities; different grid densities are selected according to the simulation accuracy requirements of different materials in the simulation to obtain better convergence and faster simulation speed. For the contact surface between the channel, sensitive layer and material, the grid density can be increased to improve the simulation accuracy; for the substrate and other material middle parts, the grid density can be reduced to reduce the simulation time.

[0061] (4) Then, the material (there is no corresponding material in the library) is redefined. According to the physical and chemical properties of the material, the relevant material parameters are set, including the basic material selection, the electrical dielectric constant of the material, eg300 (bandgap width (eV) at 300K (room temperature 300 degrees Kelvin)), nc300 (conduction band density (cm) at 300K -3 ))、nv300(valence band density at 300K (cm -3 )), electronic Auger coefficient (cm 6 / s), hole Auger coefficient (cm 6 / s), electron saturation velocity (cm / s), spin degeneration factor and electron affinity (eV), etc.

[0062] Subsequently, the pH buffer was redefined. The material properties of the pH buffer were set, including the base material selection, the material's electrical dielectric constant, eg300 (bandgap width (eV) at 300K (room temperature 300 degrees Kelvin)), nc300 (conduction band density (cm -3 ))、nv300(valence band density at 300K (cm -3 )), electronic Auger coefficient (cm 6 / s), hole Auger coefficient (cm 6 / s), electron saturation velocity (cm / s) and spin degeneration factor, etc. Then, different pH buffers were simulated according to the Poisson-Boltzmann equation, and different pH buffer materials were obtained by changing parameters such as nc300 and nv300. The Poisson-Boltzmann equation is as follows:

[0063]

[0064] Where N C is the conduction band density at 300K, N V is the valence band density at 300K, N A is Avogadro's number, E gis the band gap of the semiconductor, k is the Boltzmann constant, and T is the absolute temperature. The electrolyte base material is Electrolyte, the material type is semiconductor, the electron affinity is 3.9eV, the dielectric constant is 80, and the band gap width at 300K is 1.5eV. For example, when pH = 6, the conduction band density at 300K can be set to 2.33×10 27 The valence band density at 300K is 2.33×10 25 .

[0065] (5) Then, doping is performed on the materials of different parts of the 3D model, and doping data is set, including boron doping, phosphorus doping, doping area color, function type for defining impurity distribution, definition of doping area boundary, area boundary concentration and electron peak value, etc. The doping is determined according to the requirements of N-type and P-type. For example, the substrate is doped with P type and the appropriate doping concentration is set; the channel is doped with N type and the appropriate doping concentration is set; the function type for defining impurity distribution is Multiply; the boundary concentration is 0. Then the source, drain, reference electrode and back gate electrode parts are defined.

[0066] (6) Next, start Atlas. In Atlas, the contact type between the electrode and the semiconductor material is ohmic contact, so the work function is defined as Schottky contact and the work function value is set; select physical models, including srh (Shockley-Read-Hall composite model), auger (Auger composite model) and cvt (mobility composite model); define interface characteristics, including interface charge density and surface recombination velocity; establish a site binding model, and solve the problem that the 3D model cannot simulate and calculate pH sensitivity by establishing a site binding model of the pH buffer / insulator interface; define the digital calculation method, and use the defined numerical calculation method at the grid points of the 3D device model in Atlas to obtain the device characteristics, and select the Newton iteration method; define the charge trajectory: normal injection through the drain, set parameters including the entry and exit areas, radius of 0.05, set appropriate charge density, electron lifetime of SRH recombination and hole lifetime of SRH recombination;

[0067] In this embodiment, since the device surface response to pH depends on the surface charge, a site binding model of the pH buffer / insulator is established according to the surface charge formula, which is as follows:

[0068]

[0069] Where σ0 is the surface charge density, q is the basic charge, p is the carrier concentration, N trap is the number of binding sites per unit area, V n and V p is the thermal velocity of electrons and holes, n is the electron concentration, σ nand σ p are the carrier capture cross sections for electrons and holes, respectively, e nD and e pD is the electron and hole emission rate, e pA is the acceptor hole capture rate.

[0070] Next, the interface trap parameters are used to accurately simulate the surface charge, ionization rate, values ​​of electrons and holes under different pH environments (including carrier capture cross-sections, thermal velocity and emission rate), Fermi level, trap energy level and degeneracy factor of trap centers, and a site binding model of pH buffer / insulator is established, so that the 3D model can simulate and calculate the pH sensitivity.

[0071] (7) Finally, the voltage conditions are set to obtain the electrical characteristics of the 3D model of the EG-ISFET, including the output characteristics and transfer characteristics. Based on the basic electrical characteristics, an analysis is performed to obtain the voltage sensitivity, current sensitivity, threshold voltage, saturation current, switching current ratio, subthreshold swing and field effect mobility of the 3D model of the EG-ISFET. The internal characteristics of the 3D model of the EG-ISFET are extracted, including the concentration distribution, potential distribution and current density.

[0072] Figure 2-Figure 4 A specific example of building a 3D model of EG-ISFET is given, in which the transduction area is, from bottom to top, back gate electrode 1, substrate 2, bottom gate dielectric layer 3, channel layer 4, top gate dielectric layer 7 and gate 8, and the channel layer is located between the bottom gate dielectric layer and the top gate dielectric layer; the source 5 and the drain 6 are located on both sides of the channel layer and are in contact with the channel layer; the sensing area is, from bottom to top, back gate electrode 1, substrate 2, bottom gate dielectric layer 3, conductive layer 8, sensitive layer 9, pH buffer solution 10 and reference electrode 11.

[0073] from Figure 5 We can see from the simulation that the output characteristic curve of the 3D model under the condition of pH=7 has obvious linear and saturation regions, which is consistent with the basic characteristics of ISFET. Figure 6 We can see from the transfer characteristic curve under the simulation condition of pH=7 that we can see an obvious turn-on voltage, which proves the rationality of the 3D model; in summary, the feasibility of our pH buffer and site binding model is proved.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for building a 3D model of an EG-ISFET, characterized in that: The method comprises the following steps: Step 1: Start DevEdit and set the basic simulation environment, including the version number of DevEdit, the version number of the library, and the size of the simulation area; Step 2: Construct a 3D model of the basic EG-ISFET; Obtaining structural parameters of the EG-ISFET device to be simulated, including: geometric dimensions and materials of the model transducer region, geometric dimensions and materials of the model sensing region; Step 3: Mesh the 3D model of the basic EG-ISFET, including the geometric models of the transducer and sensor regions; Step 4: For the material described in step 2, if there is no corresponding material in the library, the characteristics of the material are redefined and combined to obtain different materials; the material includes a buffer material, and a pH buffer model in the TCAD software is established by the Poisson-Boltzmann equation to simulate the buffer material; Step 5: Perform doping treatment on the materials at different parts of the 3D model to obtain different types of EG-ISFET simulation models, including N-type and P-type; and define the electrodes of the 3D model of the EG-ISFET; Step 6: Start Atlas, set the device simulation conditions, including material contact type, physical model, interface characteristics, site binding model, numerical calculation method, and specify the charge trajectory; Step 7: Obtain device characteristics, set source-drain, back-gate, and top-gate voltage conditions, obtain the electrical characteristics of the 3D model of the EG-ISFET, and obtain the internal information of the device.

2. The method according to claim 1, characterized in that The transduction region is composed of, from bottom to top: a back gate electrode, a substrate, a bottom gate dielectric layer, a channel layer, a top gate dielectric layer and a gate, wherein the channel layer is located between the bottom gate dielectric layer and the top gate dielectric layer; the source and the drain are located on both sides of the channel layer and are in contact with the channel layer; the geometric dimensions of the model transduction region include the length, width and thickness of the back gate electrode; the length, width and thickness of the substrate; the length, width and thickness of the bottom gate dielectric layer; the length, width and thickness of the channel; the length, width and thickness of the source; the length, width and thickness of the drain; and the length, width and thickness of the top gate dielectric layer.

3. The method according to claim 1, characterized in that The sensing area is, from bottom to top, back gate electrode, substrate, bottom gate dielectric layer, conductive layer, sensitive layer, pH buffer solution, and reference electrode; the geometric dimensions of the sensing area of ​​the model include the length, width and thickness of the conductive layer; the length, width and thickness of the sensitive layer; the length, width and thickness of the pH buffer solution; the length, width and thickness of the reference electrode; in the 3D model of EG-ISFET, the sensing area and the transducing area are separated, and the sensed induced potential is transmitted to the transducing area through the conductive layer, so as to achieve the purpose of separating the pH solution and the transducing area.

4. The method according to claim 1, characterized in that In step 3, different material structures in the 3D model are divided and distinguished by gridding; each grid unit contains only one material and has different state values; the state values ​​include doping concentration, mobility, and electric field strength; different grid densities are used to distinguish the simulation accuracy of different materials; different grid densities are selected according to the simulation accuracy requirements of different materials during simulation to obtain better convergence and faster simulation speed.

5. The method according to claim 1, characterized in that: In step 4, the material properties include: base material selection, electrical dielectric constant of the material, bandgap width eg300 at room temperature 300 degrees Kelvin, conduction band density nc300 at room temperature 300 degrees Kelvin, valence band density nv300 at room temperature 300 degrees Kelvin, electron Auger coefficient, hole Auger coefficient, electron saturation velocity, spin degeneration factor, and electron affinity; By changing the value of a certain characteristic parameter of the material and combining them, different materials can be obtained.

6. The method according to claim 1, characterized in that: In step 4, the pH buffer model is as follows: Where N C is the conduction band density at 300K, N V is the valence band density at 300K, N A is Avogadro's number, E g is the band gap of the semiconductor, k is the Boltzmann constant, and T is the absolute temperature.

7. The method according to claim 1, characterized in that: In step 5, the materials of different parts in the 3D model are doped, and the doping data are set, including boron doping, phosphorus doping, doping area color, function type for defining impurity distribution, definition of doping area boundary, area boundary concentration and electron peak.

8. The method according to claim 1, characterized in that: In step 6, in Atlas, the contact type between the electrode and the semiconductor material is ohmic contact, so the work function is defined as Schottky contact, and the value of the work function is set; select physical models, including SRH, Auger, and CVT; define interface characteristics, including interface charge density and surface recombination velocity; establish a site binding model, and calculate pH sensitivity by establishing a site binding model of the pH buffer / insulator interface; define a numerical calculation method, and use the defined numerical calculation method at the grid points of the 3D device model in Atlas to obtain the characteristics of the device; define the charge trajectory: inject normally through the drain, and set parameters including the entry and exit areas, radius, charge density, electron lifetime of SRH recombination, and hole lifetime of SRH recombination; in step 6, the site binding model of the pH buffer / insulator interface is as follows: Where σ0 is the surface charge density, q is the basic charge, p is the carrier concentration, N trap is the number of binding sites per unit area, V n and V p is the thermal velocity of electrons and holes, n is the electron concentration, σ n and σ p are the carrier capture cross sections for electrons and holes, respectively, e nD and e pD is the electron and hole emission rate, e pA is the acceptor hole capture rate.

9. The method according to claim 1, characterized in that: In step 7, based on the establishment of a complete 3D model of the EG-ISFET, voltage conditions are set to obtain the electrical characteristics of the 3D model of the EG-ISFET, including output characteristics and transfer characteristics; analysis is performed on the basis of the basic electrical characteristics to obtain the voltage sensitivity, current sensitivity, threshold voltage, saturation current, switching current ratio, subthreshold swing and field effect mobility of the 3D model of the EG-ISFET; internal characteristics of the 3D model of the EG-ISFET are extracted, including concentration distribution, potential distribution and current density.

10. The method according to claim 1, characterized in that Step 3 also includes: optimizing the grid, distinguishing the simulation accuracy of different materials by different grid densities; and selecting different grid densities according to the simulation accuracy requirements of different materials during simulation.

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