Capacitance fitting method for field plate semiconductor devices

Abstract

The present invention discloses a capacitance fitting method for a field plate type semiconductor device, the capacitance fitting method comprising: S1, fitting the charge amount without field plate and with field plate based on the first function Q(x) and the second function Q'(x); S2, fitting the charge amounts Qgd, Qgs, Qds corresponding to the capacitances Cgd, Cgs, Cds based on the first function Q(x) and / or the second function Q'(x); S3, differentiating the charge amounts Qgd, Qgs, Qds respectively to obtain the capacitances Cgd, Cgs, Cds; S4, obtaining the input capacitance Ciss, the output capacitance Coss and the feedback capacitance Coss according to the capacitances Cgd, Cgs, Cds. The present invention performs nonlinear fitting on the charge amount through a combination of two functions, and on this basis, obtains the change of the capacitance of the field plate type semiconductor device with the drain-source voltage through fitting, and the fitting result is highly consistent with the measured result, providing an accurate basis for circuit design, debugging and verification.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a capacitance fitting method for a field plate type semiconductor device. Background Art

[0002] Gallium nitride (GaN)-based high electron mobility transistors (HEMTs) have been widely used in power electronic devices such as high temperature, high frequency, high voltage, and high power due to the advantages of GaN materials such as large bandgap, large breakdown electric field strength, and high carrier saturation mobility. Since the parasitic capacitance of GaN devices is small, they have faster switching speeds. Currently, GaN devices on the market are mainly used in the field of fast charging, car charging piles, and other fields, and their applications will also increase.

[0003] For application development, circuit simulation can simulate application circuits, which runs through the entire process of circuit design, debugging and verification, shortening the R&D cycle. The importance of simulation models is self-evident. An accurate circuit-level simulation model can produce relatively accurate simulation results, making the application more confident.

[0004] The model research of GaN devices started at the end of the 20th century. The development time is short and the model is not mature. Basically, the mature silicon-based device model is applied. However, due to the difference in working principles between GaN devices and silicon devices and the design of their special field plate structure, their model is different from the traditional silicon device model and must be improved on the basis of the original model.

[0005] The GaN device model is divided into table lookup model, physical model and empirical model according to the modeling method. The empirical model is the equivalent circuit model. According to the physical structure and electrical characteristics of the device, the topology of the equivalent circuit is derived. From the analysis of circuit design requirements, the equivalent circuit model is the most commonly used GaN device model in CAD simulation tools. At present, the equivalent circuit models include Curtice2 / 3 model, EEHEMT model, Angelov model, Tom model, etc. Its basic topology is as follows ( Figure 1 ). When the device works in a large signal state, the component values ​​inside the device will change with the change of bias voltage, and the functional relationship with the gate-source voltage and drain-source voltage is very complicated. The focus of the model is to perform nonlinear modeling on these changing components. The above-mentioned models are more accurate in describing the current, but the fitting effect of the change of capacitance with drain-source voltage is slightly insufficient, especially for GaN devices with added field plates. It is difficult to describe the effect of the field plate on the capacitance of GaN devices.

[0006] Therefore, in view of the above technical problems, it is necessary to provide a capacitance fitting method for a field plate type semiconductor device. Summary of the invention

[0007] In view of this, an object of the present invention is to provide a capacitance fitting method for a field plate type semiconductor device.

[0008] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0009] A capacitance fitting method for a field plate type semiconductor device, the capacitance fitting method comprising:

[0010] S1. Fitting the charge amount without and with the field plate based on the first function Q(x) and the second function Q'(x);

[0011] S2. Fitting the charges Qgd, Qgs, Qds corresponding to the capacitances Cgd, Cgs, Cds based on the first function Q(x) and / or the second function Q'(x);

[0012] S3, differentiate the charges Qgd, Qgs, Qds respectively to obtain the capacitances Cgd, Cgs, Cds;

[0013] S4. Obtain input capacitance Ciss, output capacitance Coss and feedback capacitance Crss according to capacitances Cgd, Cgs and Cds.

[0014] In one embodiment, in step S1 , the first function Q(x) is a composite function based on a power function, and the second function Q′(x) is a composite function based on a hyperbolic tangent function.

[0015] In one embodiment, in step S1, the expressions of the first function Q(x) and the second function Q'(x) are:

[0016] Q(x)=(1e-12)*x*[A+B / (C+|(x / D)| E )];

[0017] Q′(x)=(1e-10)*[F*tanh(G*(x+H))];

[0018] Among them, A~H are different parameters, and the variable x is the drain-source voltage Vds.

[0019] In one embodiment, in step S2, the charge amounts Qgd, Qgs, and Qds are the sum of a first function Q(x) and n second functions Q'(x) within different Vds ranges, where n≥0, that is:

[0020] Qgd or Qgs or Qds = Q(x) + Q′(x1) + ... + Q′(x n ).

[0021] In one embodiment, step S2 includes:

[0022] Parameters A to E in the first function Q(x) corresponding to the charges Qgd, Qgs, Qds are determined based on the measured values ​​of the capacitances Cgd, Cgs, Cds of the field plate type semiconductor device at different Vds.

[0023] In one embodiment, the step S2 further includes:

[0024] Determine the number of second functions Q'(x) corresponding to the charges Qgd, Qgs, Qds and the Vds range corresponding to each second function Q'(x) according to the measured values ​​of the capacitances Cgd, Cgs and Cds of the field plate type semiconductor device at different Vds; and,

[0025] The parameters F to H corresponding to the second function Q'(x) within each Vds range are determined according to the measured values ​​of the capacitances Cgd, Cgs, and Cds of the field plate type semiconductor device at different Vds.

[0026] In one embodiment, in step S4, the input capacitor Ciss, the output capacitor Coss, the feedback capacitor Crss and the capacitors Cgd, Cgs, and Cds satisfy:

[0027] Crss = Cgd;

[0028] Ciss=Cgd+Cgs;

[0029] Coss=Cgd+Cds.

[0030] In one embodiment, the step S4 further includes:

[0031] The simulated capacitance curve is obtained according to the fitting formula of the input capacitance Ciss, the output capacitance Coss and the feedback capacitance Crss.

[0032] In one embodiment, the capacitance fitting method is performed in LTSPICE simulation software.

[0033] The present invention has the following beneficial effects:

[0034] The present invention performs nonlinear fitting on the charge quantity by combining two functions, and obtains the variation of the capacitance of the field plate type semiconductor device with the drain-source voltage on this basis. The fitting result has a high degree of consistency with the measured result, which provides an accurate basis for circuit design, debugging and verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a basic topological structure circuit diagram of GaN devices in the prior art;

[0037] Figure 2 It is a schematic flow chart of the capacitance fitting method of a mid-field plate type semiconductor device in the present invention;

[0038] Figure 3 It is a measured Vds-Cgd / Cgs / Cds curve diagram of the field plate type gallium nitride device in Example 1 of the present invention;

[0039] Figure 4 It is a simulated Vds-Cgd / Cgs / Cds curve diagram of the mid-plane gallium nitride device in Example 1 of the present invention;

[0040] Figure 5 It is a measured Vds-Cgd / Cgs / Cds curve diagram of the field plate type gallium nitride device in Example 2 of the present invention;

[0041] Figure 6 It is a simulated Vds-Cgd / Cgs / Cds curve diagram of the field-plate gallium nitride device in Example 2 of the present invention. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] Ginseng Figure 1 As shown, the present invention discloses a capacitance fitting method for a field plate type semiconductor device, comprising:

[0044] S1. Fitting the charge amount without and with the field plate based on the first function Q(x) and the second function Q'(x);

[0045] S2. Fitting the charges Qgd, Qgs, Qds corresponding to the capacitances Cgd, Cgs, Cds based on the first function Q(x) and / or the second function Q'(x);

[0046] S3, differentiate the charges Qgd, Qgs, Qds respectively to obtain the capacitances Cgd, Cgs, Cds;

[0047] S4. Obtain input capacitance Ciss, output capacitance Coss and feedback capacitance Crss according to capacitances Cgd, Cgs and Cds.

[0048] The present invention optimizes the nonlinear fitting modeling method, and establishes a capacitance fitting method for field plate type semiconductor devices through LTSPICE (Simulation Program with Integrated Circuit Emphasis) simulation software, which achieves a more accurate fitting effect for the changes of device parasitic capacitance (Ciss, Coss and Crss) with drain-source voltage (Vds).

[0049] In step S1, the present invention fits the charge without and with the field plate respectively by using the first function Q(x) and the second function Q'(x), and determines the fitting function as follows:

[0050] The first function Q(x) is a composite function based on the power function, and its expression is:

[0051] Q(x)=(1e-12)*x*[A+B / (C+|(x / D)| E )];

[0052] The second function Q'(x) is a composite function based on the hyperbolic tangent function, and its expression is:

[0053] Q′(x)=(1e-10)*[F*tanh(G*(x+H))];

[0054] Among them, A~H are different parameters, and the variable x is the drain-source voltage Vds.

[0055] In step S2, the charge amounts Qgd, Qgs, and Qds are the sum of a first function Q(x) and a second function Q'(x) within n different Vds ranges, where n≥0, that is:

[0056] Qgd or Qgs or Qds = Q(x) + Q′(x1) + ... + Q′(x n ).

[0057] In the present invention, by measuring the values ​​of capacitances Cgd, Cgs, and Cds at different Vds, a Vds-Cgd / Cgs / Cds curve can be obtained, and the final charge amount Qgd / Qgs / Qds can be determined based on the Vds-Cgd / Cgs / Cds curve.

[0058] Determination of the first function Q(x):

[0059] Parameters A to E in the first function Q(x) corresponding to the charges Qgd, Qgs, Qds are determined based on the measured values ​​of the capacitances Cgd, Cgs, Cds of the field plate type semiconductor device at different Vds.

[0060] The first function Q(x) fits the charge amount without the action of the field plate, which corresponds to the downward trend of the Vds-Cgd / Cgs / Cds curve. Parameters A to E can be finally determined based on the maximum value, minimum value, slope, etc. of Cgd / Cgs / Cds.

[0061] Determination of the second function Q'(x):

[0062] Determine the number of second functions Q'(x) corresponding to the charges Qgd, Qgs, Qds and the Vds range corresponding to each second function Q'(x) according to the measured values ​​of the capacitances Cgd, Cgs and Cds of the field plate type semiconductor device at different Vds;

[0063] The parameters F to H corresponding to the second function Q'(x) within each Vds range are determined according to the measured values ​​of the capacitances Cgd, Cgs, and Cds of the field plate type semiconductor device at different Vds.

[0064] The second function Q'(x) fits the amount of charge under the action of the field plate, which corresponds to the change platform in the Vds-Cgd / Cgs / Cds curve (changing the downward trend). According to the Vds-Cgd / Cgs / Cds curve, the number of change platforms n and the Vds range corresponding to each change platform can be obtained, and then the parameters F~H corresponding to the second function Q'(x) in each Vds range can be determined according to each change platform.

[0065] Through the above scheme, the specific functions of Qgd, Qgs, and Qds that vary with Vds can be finally fitted.

[0066] In step S3, the charges Qgd, Qgs, and Qds are differentiated in LTSPICE simulation software to obtain specific functions of the capacitances Cgd, Cgs, and Cds as Vds changes.

[0067] The input capacitor Ciss, the output capacitor Coss, the feedback capacitor Crss and the capacitors Cgd, Cgs, and Cds satisfy:

[0068] Crss = Cgd;

[0069] Ciss=Cgd+Cgs;

[0070] Coss=Cgd+Cds.

[0071] In step S4 , based on the above capacitance relationship, the final input capacitance Ciss, output capacitance Coss and feedback capacitance Crss can be fitted in LTSPICE simulation software.

[0072] Furthermore, the LTSPICE simulation software can output a simulation capacitance curve according to the fitting formula of the input capacitance Ciss, the output capacitance Coss and the feedback capacitance Crss.

[0073] The present invention is further described below in conjunction with specific embodiments.

[0074] Embodiment 1:

[0075] Based on the capacitance fitting method of the present invention, the capacitance fitting of the field plate type gallium nitride device GPI65060DFN is performed in this embodiment. The measured Vds-Cgd / Cgs / Cds curve is as follows: Figure 3 shown.

[0076] The charges obtained by fitting the Vds-Cgd / Cgs / Cds curve are as follows:

[0077] The charge Qgd includes a first function Q(x) and two second functions Q'(x), specifically:

[0078] Qgd=Q(x)+Q′(x1)+Q′(x2)

[0079] =(1e-12)*x*[7+75 / (0.4+|(x / 60)| 1 )]+(1e-10)*[8*tanh(0.04*(x+35))]+(1e-10)*[5*tanh(0.04*(x+80))]

[0080] Among them, the value range of x is 0~500V.

[0081] The charge Qgs includes a first function Q(x), which is:

[0082] Qgs=(1e-12)*x*[420+0 / (C+|(x / D)| E )] = (1e-12)*x*420

[0083] The value range of x is 0 to 500 V. Since parameter B is 0, the values ​​of parameters C, D, and E do not need to be limited.

[0084] The charge Qds includes a first function Q(x) and two second functions Q'(x), specifically:

[0085] Qds=Q(x)+Q′(x1)+Q′(x2)

[0086] =(1e-12)*x*[(-50)+800 / (1+|(x / 400)| 1 )]+(1e-10)*[90*tanh(0.03*(x+35))]+(1e-10)*[4*tanh(0.14*(x+90))]

[0087] Among them, the value range of x is 0~500V.

[0088] In the LTSPICE simulation software, Qgd, Qgs, and Qds are differentiated to obtain capacitances Cgd, Cgs, and Cds, and Crss, Ciss, and Coss can be obtained according to Crss = Cgd, Ciss = Cgd + Cgs, and Coss = Cgd + Cds. Finally, the simulation Vds-Cgd / Cgs / Cds curve output by the LTSPICE simulation software is Figure 4 shown.

[0089] contrast Figure 3 , Figure 4 It can be seen that the simulated Vds-Cgd / Cgs / Cds curve ( Figure 4 ) and the measured Vds-Cgd / Cgs / Cds curve ( Figure 3 ) are basically consistent.

[0090] Embodiment 2:

[0091] Based on the capacitance fitting method of the present invention, another field plate gallium nitride device GPI65060DFN is subjected to capacitance fitting in this embodiment. The measured Vds-Cgd / Cgs / Cds curve is shown as follows: Figure 5 shown.

[0092] The charges obtained by fitting the Vds-Cgd / Cgs / Cds curve are as follows:

[0093] The charge Qgd includes a first function Q(x) and five second functions Q'(x), specifically:

[0094] Qgd=Q(x)+Q′(x1)+Q′(x2)+Q′(x3)+Q′(x4)+Q′(x5)

[0095] =(1e-12)*x*[3+120 / (0.8+|(x / 130)| 1)]+(1e-10)*[4*tanh(0.07*(x+25))]+(1e-10)*[4*tanh(0.035*(x+75))]+(1e-10)*[6*tanh( 0.035*(x+100))]+(1e-10)*[4*tanh(0.03*(x+180))]+(1e-10)*[2.3*tanh(0.035*(x+200))]

[0096] Among them, the value range of x is 0~500V.

[0097] The charge Qgs includes a first function Q(x), which is:

[0098] Qgs=(1e-12)*x*[40+0 / (C+|(x / D)| E )] = (1e-12)*x*40

[0099] The value range of x is 0 to 500 V. Since parameter B is 0, the values ​​of parameters C, D, and E do not need to be limited.

[0100] The charge Qds includes a first function Q(x), which is:

[0101] Qds=(1e-12)*x*[3+0 / (C+|(x / D)| E )]=(1e-12)*x*3

[0102] The value range of x is 0 to 500 V. Since parameter B is 0, the values ​​of parameters C, D, and E do not need to be limited.

[0103] In the LTSPICE simulation software, Qgd, Qgs, and Qds are differentiated to obtain capacitances Cgd, Cgs, and Cds, and Crss, Ciss, and Coss can be obtained according to Crss = Cgd, Ciss = Cgd + Cgs, and Coss = Cgd + Cds. Finally, the simulation Vds-Cgd / Cgs / Cds curve output by the LTSPICE simulation software is Figure 6 shown.

[0104] contrast Figure 5 , Figure 6 It can be seen that the simulated Vds-Cgd / Cgs / Cds curve ( Figure 6 ) and the measured Vds-Cgd / Cgs / Cds curve ( Figure 5 ) are basically consistent.

[0105] It can be seen from the above technical solutions that the present invention has the following advantages:

[0106] The present invention performs nonlinear fitting on the charge quantity by combining two functions, and obtains the variation of the capacitance of the field plate type semiconductor device with the drain-source voltage on this basis. The fitting result has a high degree of consistency with the measured result, which provides an accurate basis for circuit design, debugging and verification.

[0107] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0108] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A capacitance fitting method for a field plate type semiconductor device, characterized in that: The capacitance fitting method comprises: S1. Fitting the charge without the field plate and with the field plate based on the first function Q(x) and the second function Q'(x), wherein the first function Q(x) fits the charge without the field plate, and the second function Q'(x) fits the charge with the field plate; S2. Fitting the charges Qgd, Qgs, Qds corresponding to the capacitances Cgd, Cgs, and Cds based on the first function Q(x) or based on the first function Q(x) and the second function Q'(x); S3, differentiate the charges Qgd, Qgs, Qds respectively to obtain the capacitances Cgd, Cgs, Cds; S4, obtaining input capacitance Ciss, output capacitance Coss and feedback capacitance Crss according to capacitances Cgd, Cgs and Cds; In step S1, the first function Q(x) is a composite function based on a power function, and the second function Q'(x) is a composite function based on a hyperbolic tangent function; In step S1, the expressions of the first function Q(x) and the second function Q'(x) are: Q(x)=(1e-12)*x*[A+B / (C+|(x / D)| E )]; Q′(x)=(1e-10)*[F*tanh(G*(x+H))]; Among them, A~H are different parameters, and the variable x is the drain-source voltage Vds; In step S2, the charge amount Qgd is a first function Q(x), or a first function Q(x) and a second function Q'(x) within at least one different Vds range, the charge amount Qgs is a first function Q(x), or a first function Q(x) and a second function Q'(x) within at least one different Vds range, and the charge amount Qds is a first function Q(x), or a first function Q(x) and a second function Q'(x) within at least one different Vds range; The step S2 also includes: determining the number of second functions Q'(x) corresponding to the charges Qgd, Qgs, Qds and the Vds range corresponding to each second function Q'(x) according to the measured values ​​of the capacitances Cgd, Cgs and Cds of the field plate semiconductor device at different Vds.

2. The capacitance fitting method of a field plate type semiconductor device according to claim 1, characterized in that: The step S2 further comprises: Parameters A to E in the first function Q(x) corresponding to the charges Qgd, Qgs, Qds are determined based on the measured values ​​of the capacitances Cgd, Cgs, Cds of the field plate type semiconductor device at different Vds.

3. The capacitance fitting method of a field plate type semiconductor device according to claim 2, characterized in that: The step S2 further comprises: The parameters F to H corresponding to the second function Q'(x) within each Vds range are determined according to the measured values ​​of the capacitances Cgd, Cgs, and Cds of the field plate type semiconductor device at different Vds.

4. The capacitance fitting method of a field plate type semiconductor device according to claim 1, characterized in that: In step S4, the input capacitor Ciss, the output capacitor Coss, the feedback capacitor Crss and the capacitors Cgd, Cgs, and Cds satisfy: Crss = Cgd; Ciss=Cgd+Cgs; Coss=Cgd+Cds.

5. The capacitance fitting method of a field plate type semiconductor device according to claim 1, characterized in that: The step S4 further includes: The simulated capacitance curve is obtained according to the fitting formula of the input capacitance Ciss, the output capacitance Coss and the feedback capacitance Crss.

6. The capacitance fitting method of a field plate type semiconductor device according to claim 1, characterized in that: The capacitance fitting method is performed in LTSPICE simulation software.

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