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SSPD_Chapter 6_Part 7_Introduction to ATHENA 5 deals with specification of electrodes and saving the structure file.

SSPD_Chapter 6_Part 7_Introduction to ATHENA2

SECTION 7.7 Background of ATHENAcontinued.

7.7.2. Creating Device Structure using ATHENA

7.7.2.8 Specification of Electrodes in ATHENA

The ultimate goal of an ATHENA simulation is usually to create a device structure (material layers plus doping), which then can be used by a device simulator (usually ATLAS) for electrical characterization. Although ATLAS is able to specify the locations of electrodes, in many cases specifying electrodes must be done in ATHENA. For example, it is impossible to specify an electrode location in ATLAS when the electrode does not consist of straight segments. Also, when specifying electrodes in ATHENA, it is useful to transfer electrode layer information from layout to electrical tests in a device simulator

ATHENA can attribute an electrode to any metal, silicide, or polysilicon region. A special case is the backside electrode, which can be placed at the bottom of the structure without having a metal region there. If you deposit 0.1 µm aluminum layer on the full structure after reflection using:

DEPOSIT ALUMIN THICK = 0.1

and etched the following part of the layer between x= -0.8 and x= 0.8, using the Any Shape specification in the Athena Etch Menu (See Figure 7.26):

ETCH ALUMINUM START X= -0.8 Y= -1.0

ETCH CONT X= -0.8 Y= 1.0

ETCH CONT X= 0.8 Y= 1.0

ETCH DONE X= 0.8 Y= -1.0

you will now have the structure shown in Figure 7.30

You can now use the ATHENA Electrode menu (see Figure 7.31) by selecting Commands→Structure→ Electrode....

To set an electrode at a specified position, select the Specified Position button, type in the X Position (e.g., -0.9) and Name (for example, source), and press the Write button. The following statement will appear in the input file:

ELECTRODE NAME=SOURCE X= -0.9

Similarly, specify the drain electrode:

ELECTRODE NAME=DRAIN X= 0.9

The polysilicon gate electrode specification has the same format. For this structure it can be done the same way as for source or drain:

ELECTRODE NAME= GATE X= 0.0

If the polysilicon layer is not the topmost layer at x=0, the Y Position can be specified. In this case, check the Y Position checkbox and type in a y coordinate within the polygate layer (e.g., -0.2). If Y is not specified and the electrode is not on top, ATHENA will look for the electrode in the underlying layers. If it fails, an error will be reported.

To specify a backside electrode, select Backside from the Electrode Type field and type in a name (see Figure 7.31) .

The following backside electrode statement will appear in the input file:

ELECTRODE NAME=BACK BACKSIDE

If an electrode name is not specified, DECKBUILD issues the error message:

NO ELECTRODE NAME SPECIFIED and the command is not written to the input file.

If an incorrect position for electrode is specified, for example:

ELECTRODE NAME=JUNK X=0.6

ATHENA will output the following warning message: Cannot find the electrode for this structure. Electrode statement ignored and ignores the statement.

7.7.2.9. Saving a Structure File for Plotting or Initializing an ATHENA Input file for Further Processing

As mentioned in the “Standard Structure File Format” Section, the DECKBUILD history function saves structure files after each process step. In many cases, however, you need to save and initialize structures independently. There are several reason why it’s needed to save and initialize structures independently.

The first reason is because the stack for the history files is limited (50 by default). The second reason is because it is usually undesirable to keep dozens of history files on disc (each of which occupy hundreds of Kbytes) after the DECKBUILD session ends. The third reason is because users often want to save the structure information generated after key process steps (e.g., final structure)

To save or load a structure, use the ATHENA File I/O Menu (See Figure 7.32) by selecting Commands → File I/O.... Specify a file name (the file extension.str is recommended for all ATHENA structure files) and press the Save button. The following line will appear in the input file:

STRUCT OUTFILE=TUTOR.STR

You can reload this file (tutor.str) back into ATHENA at any time during the current DECKBUILD session or during any subsequent session. To reload the structure file, press the Load button on the ATHENA File I/O menu. The following INIT statement will appear:

INIT INFILE=TUTOR.STR

Note: Only the structure will be reloaded if ATHENA is restarted before this INIT statement. Any parameters or coefficients that were set during previous simulations must be reset if they are needed. This structure file can also be used by any device simulator or DEVEDIT.

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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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