ie3d教程chap6.docx

1、ie3d教程chap6Chapter 6 Modeling of MMIC, RFIC and PCB StructuresWe have learned the basic skills to create and simulate structures on the IE3D in the previous chapters. In this chapter, we will discuss the applications of IE3D in designing MMIC, RFIC and PCB structures. IE3D is a general purpose EM si

2、mulator with extreme capability, flexibility, accuracy and efficiency in modeling different kinds of high frequency structures. It is widely used in MMIC, RFIC and PCB design as well as antenna design. In this chapter, we will concentrate on modeling of MMIC and RFIC structures. Most MMIC and RFIC s

3、tructures are quite complicated. The layout may be done in other layout tools and we need to import them into IE3D and perform the high accuracy EM simulations on them. We will start this chapter on importing.Section 1. Different Import and Export Formats Available on IE3D. The most popular layout f

4、ormats in the electronic industry are the GDSII (Calma Stream) format, DXF (AutoCad) format, GERBER format and ACIS format. IE3D has been able to import and export files in GDSII format and CIF (CalTech Intermediate Form) format directly. Recently, we have implemented the ADIX Format Converter. It c

5、an perform bi-directional IE3DGDSIIDXFGERBERACIS conversion. On the File-Export command, we have the following options: (1) DXF; (2) GDS; (3) 3D Text (Zeland); (4) ACIS; (5) GERBER; (6) CIF; (7) FIDELITY. The 3D Text is a format created by Zeland Software, Inc. Basically, it allows you to write a st

6、ructure as a script file. The 3D Text format is discussed in Appendix O. The FIDELITY format is for export only. Basically, you can export a geometry in MGRID into the FIDELITY format for our FIDELITY simulator. It allows you to define thickness to polygons for 3D objects. Only horizontal polygons (

7、z-directed), x- and y-directed polygons can be exported. Polygons of other orientation will be omitted. Exported FIDELITY structures normally need clean up on FIDELITY because a simulation can be done. More automated exporting will be available in the future. In the last one-year, we have implemente

8、d the Automatic Geometry to IE3D Flow (or AGIF). AGIF can do 3 jobs: (1) Convert GDSII layout into IE3D models directly. After the conversion, the IE3D geometry can be a full-3D model containing vias, wire bonds, solder balls, and ports and ready for simulation. Users can create one template for one

9、 MMIC or RFIC process. The template can be used for all different GDSII files of the same process to do batch IE3D simulations directly from GDSII files. (2) Perform IE3D simulation on a cell or selected part of a cell from Cadence Virtuoso Custom IC Design Platform. Cadence Virtuoso is the most pop

10、ular RFIC design layout tool. AGIF can simplify EM simulations of RFIC significantly. In the automatic conversion, AGIF can clean the structure for high efficiency IE3D EM simulations without losing accuracy. For example, pin-vias are parts of many semiconductor processes. Simulating the pin-vias ex

11、actly is prohibiting because of the large number of pin vias can kill the simulation easily. AGIF can allow the users to merge pin vias into large vias without changing the electrical properties of the structure. The process is done automatically with specifications from users. There are many other

12、advanced editing capabilities of IE3D fully automated into AGIF for streamlined IE3D simulations from GDSII and Cadence Virtuoso. (3) Create IE3D models directly from Cadence Allegro Interconnect Design Platform and Cadence APD. Cadence Allegro is a PCB tool and APD is a packaging tool. AGIF allows

13、users to define selected nets as critical nets, reference nets and coupled nets. Then, it can automatically build the IE3D model for the critical nets including the reference nets. The created model can be ready for simulation. There is a separate documentation on AGIF. In this menu, we may give a s

14、imple example of using AGIF for automated IE3D simulation. In the last couple years, we have also implemented the EMSocket together with Applied Wave Research, Inc. EMSocket basically allows users to create layouts from Microwave Office of AWR, perform IE3D full-wave EM simulations seamless from MWO

15、. The advantages of IE3D and MWO are combined together to make it convenient for designers. EMSocket is available automatically to IE3D and MWO users free of charge. In the next section, we will show the importing of a GDSII file. We will use a simple MIM capacitor as an example. The procedure for i

16、mporting a DXF file is similar except you may need to scale the imported structure after importing because a DXF file may not carry absolute dimensional information.Section 2. Importing an MIM Capacitor in GDSII Format.The shape of the MIM capacitor is shown in Figure 6.1. The bottom plate is on a 1

17、00-micron GaAs substrate. The dielectric between the two plates is of thickness 0.2 microns and dielectric constant 6.7. The dimensions of the top plate are 100 microns by 100 microns. The air bridge is at 102-micron level. The GDSII file is in .ie3dsamplesmimcap.gds.Step 1 Run MGRID. Select File-Im

18、port command. MGRID will prompt you the Import Options dialog. Select GDSII for Import Format. Many of the options are grayed out because they are for the DXF conversion. For DXF import, you may have to select Length Unit. You also need to define Circular Min Radius (Rmin) and the Segment (Smin), Ci

19、rcular Max Radius (Rmax) and the Segment (Smax). The parameters are for converting circular structures to polygons which are the only objects accepted by IE3D. When we encounter a circular shape with radius R, we will convert it into a polygon with S-number of segment. The S is calculated based upon

20、 the formulas in Table 6.1. It is basically a linear interpolation based upon R, Rmin, Rmax, Smin and Smax. We should choose the Rmin, Rmax, Smin and Smax values wisely. For some applications, the circular shapes can be electrically large, we should choose Smin and Smax as 12, 16, 24, 36 or even 64.

21、 For some applications, the circular shapes are normally for vias and they are electrically very small. We can choose Smin and Smax as 4, 6 or 8. Normally, 6 is a good number. Choosing too big a number will cause IE3D create too many unknowns and the simulation time will increase substantially while

22、 the accuracy is not improved.(a) Original structure with two plates (b) Z-direction magnified by a factor of 30Figure 6.1 The shape of the MIM capacitor to be built from importing.Table 6.1 The formula for Segments (S) based upon Radius (R).R RangeS FormulaR RminS = SminRmin R RmaxS = SmaxStep 2 Fo

23、r GDSII structure, circular shapes are already converted into polygon shapes. We do not need to worry about it. Please select OK to continue. MGRID will prompt you for the GDSII file. Select file .ie3dsamplesmimcap.gds. Select OK continue. MGRID will import the structure from the file. It comes up w

24、ith the Import Data Options dialog (see Figure 6.2). It will list all the structures detected in the file. There might be multiple structures in a GDSII file. You can select which structure you want to import. For this particular GDSII file, there is only one structure: mimcap and it is checked. All

25、 the layers detected in the structure are shown in the list box at the right. There are many parameters you need to enter. The first group of parameters you need to enter the Basic Parameters for the structure. They contain the substrates and the metallic strip types and the meshing parameters etc.

26、The second group of parameters you need to enter are the layer information. A GDSII file contains only the layer information and the (X, Y) coordinates. It does not contain the Z-coordinates. We need to map the layers to Z-coordinates. It is also possible a GDSII file use polygons to define the shap

27、es of vias. However, they do not contain the third dimensional information about how the vias are connecting the layers. Figure 6.2 The Import Data Options dialog before the template file .ie3dsamplesmimcap.ctp is loaded.We need to define all the above data in the Basic Parameters dialog from the bu

28、tton, the layer information dialog at the right and the Automatic Via list box at the lower right corner of Figure 6.2. Certainly, we can define some temporary data first. After we import the geometry into MGRID, we can change the layer z-coordinates, redefine the Basic Parameters, and build the via

29、s using the polygon shapes using the Adv Edit-Build Holes and Vias from Selected Polygons command. It can be a tedious process. Fortunately, we have implemented the Import Template File (.ctp) to ease the process.Step 3 We have already created the Import Template File: .ie3dsamplesmimcap.ctp file fo

30、r you. Please select Load button. Select the .ie3dsamplesmimcap.ctp file. MGRID will load the .ctp file and use the information in the .ctp file to define the Basic Parameters and the Layer Information dialog (see Figure 6.3). All the layers are placed at the supposed z-coordinates they should be on

31、. The Basic Parameters are also defined. If you choose the Basic Parameters button, it will show you the GaAs substrate configuration. In case you have to manually enter the import option parameters, after you define all the data, you can select the Save button to save the defined data into an Impor

32、t Template File (.ctp). You can use the .ctp file for future importing of similar structures without going through the same procedure. In fact, we are doing so using the mimcap.ctp file here now.Figure 6.3 The import Data Options dialog after the template file is loaded.Step 4 Please un-check the Merge Polygons option. If you check it, it will try to merge the imported polygons if they are connected. For this case, we would like not to do so. Select OK to continue. MGRID will import the structure with all the Basic Param