All commands in this menu list are declarative! This means that selecting an item will not result in its immediate execution. This is done for two reasons. The first one is to give the user a chance to change his/her mind and cancel the selected process via the "Unselect Process" command in the Edit menu or simply select another process. The second is that very often the user is required to specify additional information after a process has been selected. For instance, if the user has selected "Etching", then the etch rates for all materials making up the structure will have to be subsequently defined (see the "Material’s Data" command in the Edit menu). Another example is, if the user has selected "Resist Deposition" then the thickness of the resist will have to be additionally specified (see "Resist Deposition" below).
N.B. EXECUTION of a process starts only when the "Start" command from the Simulation menu is selected or equivalently the "Start" button in the Command bar is pressed. During process execution the whole "Process" menu is disabled.
A process is completed automatically without requiring user's further interaction, unless the user wishes to "Pause" or "Abort" it.
Some processes are interdependent and are hence enabled in a specific order. For instance, the "Mask definition" process can only be executed after a "Resist deposition" process. Similarly, a "Resist development" process can only be executed after a "Mask definition" process has been completed (see below).
The number of processes executed is virtually unlimited (that is, until the program eventually runs out of memory as the complexity of the structure increases.
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1. The "Etching" command:
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Selects "Etching" as the next process. A dialog box entitled "Enter Etching Process Information" automatically opens in which the user needs to specify some general information such as duration of the process and which combination of the three fundamental etch types will be employed.
The user can choose any combination from the following three fundamental etch process types:
a) Isotropic:
If some materials are going to be etched isotropically then the type "Isotropic" will have to be checked.
b) Directional:
If some of the materials are going to be etched in a manner such that the flux of etching species arrives at the surface along a predetermined direction(s) (so that geometrical shadowing may occur), then the type "Directional" will have to be checked. As a result of the latter action two new fields appear allowing the user to specify the angle of incidence of the "flux" and its divergence in degrees. It should be noted that the incidence angle is measured with respect to the vertical direction and clearly should be in the range -90 to +90 degrees, since the structure is infinite in the lateral directions and hence the flux cannot originate from underneath. The same holds for the divergence, that is, if a flux component lies outside the above angular range it is discarded. The divergence actually is the maximum angular deviation from the incidence direction. The total spread of the flux is twice the divergence!
See "To Remember" for a further discussion!
c) Anisotropic:
If some of the materials are going to be etched in an anisotropic fashion then the type "Anisotropic" will have to be checked. (A typical example for an anisotropic etching process is when the etch rate is dependent on the crystallographic orientation of the material).
N.B. A material can be subjected to all three types of etching simultaneously. However, the actual definition of the etch rates for each particular material is done after closing successfully the above dialog box, using the "Material’s Data" command from the Edit menu or simply by double clicking over the desired regions.
Speed considerations: Do not check a process type if it is never used!
-> Press the "Start" button to commence execution of the "Etching" process when finished with the input data for all materials which will be etched.
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2. The "Deposition" command:
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Selects "Deposition" as the next process.
The user can:
a) Define the duration of the deposition process.
b) Define the name of the material to be deposited.
c) Select a color of the material to be deposited.
d) Check "Isotropic" and specify a growth rate if the deposition process has an isotropic component.
e) Check "Directional" and specify a deposition rate if the deposition process has a directional component. See the "Directional" type in the "Etching" command above for definition of the angle of incidence and divergence.
N.B. It is important to note that the deposition rate one specifies is the one which corresponds to zero divergence, that is, this would be the growth rate corresponding to a fully collimated flux J. Specifying a non-zero divergence is equivalent to angularly spreading the incidence deposition flux in a uniform fashion in an angular range equal to twice the divergence. In other words the integral of the incident flux over the angular range is exactly equal to J.
See "To Remember" for a further discussion!
f) Check "Anisotropic" and specify a deposition rate (or rather a coefficient) if the deposition process has an anisotropic component. This means a deposition component such that the growth rate depends on the surface orientation only.
Checking the "Anisotropic" type enables a button named "Select(ed) file for Angular dependence [Anisotropic only]", which button allows the user to select a file containing the required angular dependence (see I/O Formats).
Remember that the erosion data in the file selected is multiplied by the above coefficient. The latter is provided for greater freedom - inclusion of synergistic effects, etc.
(To unselect a file press the "Option" key and click over the file selection button.)
g) If the material to be deposited is going be at the same time subject to an erosion process press the "Simultaneous Etching..." control button to define the details of the erosion process. A new dialog box, almost identical to that opened via the "Material's Data" command, opens, which allows the user to select any combination from all three fundamental etch process types and specify etch rates and angular dependence files exactly in the same way as he/she would normally do in an Etching process (see the "Material's Data" command in the Edit menu).
N.B. This last option introduces a powerful feature in 2Dinese for the simulation of various types of ion assisted deposition processes, as well as high density plasma deposition processes.
-> To execute the "Deposition" process close the dialog via the "OK" button and press the "Start" button! Make sure that the "Duration" is not zero and that there is at least one non-zero deposition rate.
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3. The "ChemMech Polish" command:
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Selects a Chemical-Mechanical Polishing process. Highly idealised this process polishes everything above a specified height. Selecting this command will transform the cursor appropriately, while the Message line will display the height above which polishing will occur. Specifying the desired height is done by moving the mouse vertically while keeping it pressed.
Note that one can always and independently use the magnification options (see N.B. after the "Zoom in" command in the Edit menu.), which allows precise determination of the polishing height.
The height at which the mouse is last released is taken to be the desired height.
-> To execute the process press the "Start" button!
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4. The "Resist Deposition" command:
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Selects a Resist deposition process. A dialog box opens automatically allowing the user to select the color, name and type of the resist. Again, highly idealised this process will result in the deposition of an ideally flat resist layer. The program automatically creates a resist layer with a minimum thickness of 2 spatial units. Changing its thickness is done similarly to the previous process, namely by keeping the mouse pressed and moving it vertically. Note that one can always and independently use the magnification options (see N.B. after the "Zoom in" command in the Edit menu.), which allows precise determination of the resist thickness. The height and the resist thickness will be displayed in the Message line. If the desired thickness is greater than what the window allows then locating the mouse within the Message line (while still pressed) will cause the graphic to be scrolled automatically downwards, thus increasing the thickness of the resist.
-> To execute the process press the "Start" button!
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5. The "Mask Definition" command:
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Selects a procedure for the definition of a mask to be used in a subsequent resist development process. It works as follows. The cursor initially is pointing to the right. Clicking anywhere over the graphic will cause the formation of a dark zone the right hand side coordinate of which is where the mouse click occurred. At this point the cursor is changed to point to the left. Clicking repeatedly over the graphic from left to right results in the formation of dark and color (unchanged) zones in the resist layer, thus defining the areas which will be exposed (the color zones) and those which will be masked (the dark zones). For precise coordinate definition the user can use the following tools:
- Dragging (left or right) the mouse before releasing it allows more precise definition of the position
- Keeping the "Option" and "Command" keys simultaneously will change the cursor to a "cross" allowing the user to change the position of any particular line. Note that one can always and independently use the magnification options (see N.B. after the "Zoom in" command in the Edit menu.) which allows precise definition of the line widths.
N.B. This command is only activated if the previously executed process has been "Resist Deposition"!
-> To finish the mask definition process press the "Start" button!
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6. The "Resist Development" command:
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This command is automatically selected after execution of the previous "Mask Definition" command since it is most logical, that after resist deposition and mask definition (resist exposure) there follows resist development. Again, the process is extremely idealized. The exposure is assumed to be ideal and follow with geometrical precision the mask pattern, the resist is also assumed to be ideal, so that as a result of the development process the walls in the developed resist are vertical.
N.B. This command is only activated if the previous process has been "Mask Definition"!
-> To finish the "Resist Development" process press the "Start" button!
Remark: As seen processes 3, 4, 5 and 6 are highly idealised and developed at a very basic level. They are primarily included for completeness as well as to provide elementary tools for complete wafer processing.
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7. The "Remove..." command:
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This command allows a specified material to be completely removed from the structure. However, only those regions, which have access to the surface, will be removed. In other words, regions made of the same material and which are completely isolated from the surface by other materials will not be removed. It is implied that the user can apply a highly selective etching process, which erodes the specified material only. It is also noted that it may happen that the removal of a given material may result in a complete lift off of other materials, which are completely separated from the structure as a result of the removal process. The user does not need to specify that a lift off is to occur in such cases (see "Lift off" in the Simulation menu).
Normally, the name of the material will be displayed next to the "Remove" command, as well as in the Message line.
This command is only activated when a region is selected (outlined).
-> To execute the process press the "Start" button!
Copyright 1996 I.V.Katardjiev. All rights reserved.
