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'''Feedback to this page''': '''[mailto:e-beam@danchip.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.danchip.dtu.dk/index.php?title=Specific_Process_Knowledge/Lithography click here]'''
'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Lithography/EBeamLithography/BEAMER click here]'''
 
Content and illustration by Thomas Pedersen, DTU Nanolab unless otherwise noted.


=Beamer guide=
=Beamer guide=
All users of the JEOL 9500 system must have their pattern converted to the JEOL52 V3.0 (V30) format,  this conversion is done using Beamer. Beamer can however do many other operations than this simple format conversion. Proper pattern processen in Beamer can significantly enhance the quality of the lithographical result from an EBL process. As a minimum users should become familar with PEC. In this section we will describe some of the most frequently used nodes and also provide a few node setups for specialized tasks.  
All users of the JEOL 9500 system must have their pattern converted to the JEOL52 V3.0 (V30) format,  this conversion is done using Beamer (via the export node). Beamer can however do many other operations than this simple format conversion. Proper pattern processen in Beamer can significantly enhance the quality of the lithographical result from an EBL process. As a minimum users should become familar with PEC. In this section we will describe some of the most frequently used nodes and also provide a few node setups for specialized tasks.  
 
 
For a more in depth look at Beamer please refer to GenISys own [https://www.genisys-gmbh.com/in-action.html learning material found here.]
 
 
Currently the content below is a mix of Beamer 6 and 7, we are working towards changing it all to Beamer 7. The difference is mostly visual though.
 


==Beamer nodes==
==Beamer nodes==
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|+ Important Beamer modules and methods
|+ Important Beamer modules and methods
|-
|-
! Module/method !! Short description
! Node/module !! Short description
|-
|-
| Import || Layout import
| Import || Layout import
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===Import node===
===Import===
The import node is used to import geometry into Beamer. While we recommend GDS for import Beamer supports the following formats: GDSII, DXF, OASIS, CIF, TXL, LEDB, PNG, STL, JEOL51, JEOL52, Raith (VB6, FRE, GPF, IWFL), NuFlare, MEBES, Micronic, NPI, HIMT and ADVANTEST. The options available are:
The import node is used to import geometry into Beamer. While we recommend GDS for import Beamer supports the following formats: GDSII, DXF, OASIS, CIF, TXL, LEDB, PNG, STL, JEOL51, JEOL52, Raith (VB6, FRE, GPF, IWFL), NuFlare, MEBES, Micronic, NPI, HIMT and ADVANTEST. Import options differ somewhat between formats, for GDS import the options available are:
 
''Layer Set:'' Allows import of only a selected range of layers.


''Import Zero Width Paths:'' Allows polygonal paths to be imported with a defined width, i.e. convert a 1D wire to a 2D structure.
''Import Zero Width Paths:'' Allows polygonal paths to be imported with a defined width, i.e. convert a 1D wire to a 2D structure.
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''Import Boxes:'' Some design tools use "area boxes", a special type of geometry that is not considered a polygon. These can be converted to polygons with this option.
''Import Boxes:'' Some design tools use "area boxes", a special type of geometry that is not considered a polygon. These can be converted to polygons with this option.
''Ignore text, Load Text, Text as Polygon:'' Either ignores text objects, imports them as text objects or converts them to polygons. Notice that text defined in CleWin is not saved as text objects but as polygons when saving the file as GDS and hence this option is not necesarry if the design originates from CleWin.
''Generic curve:'' Allows the detection of curved structures such as arcs or circles. Opens the "Approximation accuracy" field where the user can input the highest allowable deviation from the drawn polygonal structure. If curved elements are found Beamer will determine the right amount of vertices to fit the curved structure.


''Keep Order of Elements:'' Preserves the order in which elements are drawn/listed in the import file.
''Keep Order of Elements:'' Preserves the order in which elements are drawn/listed in the import file.


''Flatten Layout:'' Flattens the layout to one layer and one cell.
''Flatten Layout:'' Flattens the layout to one layer and one cell.
''Load Text Elements:'' Imports text objects. Notice that text defined in CleWin is not saved as text objects but as polygons when saving the file as GDS and hence this option is not necesarry if working with CleWin.
''Convert Elements to Polygons:'' Allows read text elements to be converted to polygons of a chosen size.
''Curve Detection:'' Detects curves and allows refinement of curve accuracy.


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
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| [[image:BEAMER_Impot.png|r400px]]
| [[image:BEAMER7_Import.png|400px]]
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===Export node===
===Export===
The export node will export the pattern data to the machine specific format. For exposure on JEOL 9500 export to V30. For exposure on Raith E-line export to Raith EBL File (GDS). Export to V30 has multiple options distributed on the three main panes, ''General'', ''Advanced'' and ''Multipass'', while export to Raith GDS has almost no export options.
The export node will export the pattern data to the machine specific format. For exposure on JEOL 9500 export to V30. For exposure on Raith E-line export to Raith EBL File (GDS). Export to V30 has multiple options distributed on the three main panes, ''General'', ''Advanced'' and ''Multipass'', while export to Raith GDS has almost no export options.


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''Size:'' Size of the main writing field, maximum size is 1000 x 1000 µm.
''Size:'' Size of the main writing field, maximum size is 1000 x 1000 µm.


''Fracturing mode:'' This can be used to alter the way Beamer fractures the geometry into trapezoidal shapes. The options in the export module are fairly limited, much more control can be gained by using a ''Fracture'' node.
''Fracture mode:'' This can be used to alter the way Beamer fractures the geometry into trapezoidal shapes. The options in the export module are fairly limited, much more control can be gained by using a ''Fracture'' node. See the ''Fracture'' node for more details.


''Feature Sorting in Field:'' Can be used to alter the writing order of pattern elements in each writing field. The actual result of these choices can be somewhat hard to predict. After export the result can be seen in the Viewer under ''Tool'' and either ''Show Traversal Path'' or ''Show Writing Order''.
''Feature Sorting in Field:'' Can be used to alter the writing order of pattern elements in each writing field. The actual result of these choices can be somewhat hard to predict. After export the result can be seen in the Viewer under ''Tool'' and either ''Show Traversal Path'' or ''Show Writing Order''.
'''Important notice:''' If using the ''Fracture'' node to define the fracturing it is important in the ''Export'' node to explicitly choose not to fracture the layout during export. To ensure this select ''Cell To Field'' in the ''Field Ordering'' menu and ''NoCompaction'' in the ''Feature Sorting in Field'' of the export node.




{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
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| [[image:BEAMER_Export1.png|300px]] | [[image:BEAMER_Export2.png|300px]] | [[image:BEAMER_Export3.png|300px]]
| [[image:BEAMER7_Export1.png|400px]] | [[image:BEAMER7_Export2.png|400px]] | [[image:BEAMER7_Export3.png|400px]]
|-  
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===Extract node===
===Extract===
The extract node allows one to extract only parts of a design for further processing and export. This is very powerful if different parts of a pattern should be treated differently or if only part of a pattern should be exposed, for instance for dose test of the most critical features of a design. The available options are:
The extract node allows one to extract only parts of a design for further processing and export. This is very powerful if different parts of a pattern should be treated differently or if only part of a pattern should be exposed, for instance for dose test of the most critical features of a design. The available options are:


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''Extraction type:'' Allows extraction of single cells of a design or a drawn region. In the example shown below a region has been drawn in the viewer by simply Shift-left clicking to select the region. The corners of a region can also be entered nummerically. Multiple regions can be defined for extraction. By clicking the ''Exclude Region(s)/Instance'' the selected parts can be omitted from the rest of the pattern instead.
''Extraction type:'' Allows extraction of single cells of a design or a drawn region. In the example shown below a region has been drawn in the viewer by simply Shift-left clicking to select the region. The corners of a region can also be entered nummerically. Multiple regions can be defined for extraction. By clicking the ''Exclude Region(s)/Instance'' the selected parts can be omitted from the rest of the pattern instead.
''Region Layer:'' A layer of the design can be used to define regions for extraction.


''Dose Classification:'' The dose modulation table (if any is present from PEC) can be truncated with the ''Shrink'' option to reflect the extracted region.
''Dose Classification:'' The dose modulation table (if any is present from PEC) can be truncated with the ''Shrink'' option to reflect the extracted region.
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| [[image:BEAMER_Extract.png|800px]]
| [[image:BEAMER7_Extract.png|800px]]
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===Fracture===
The ''Fracture'' node has changed considerably between Beamer 6 and Beamer 7. In Beamer 7 all features related to field placement has been moved into a new ''Field'' node. To gain the same functionality as in Beamer 6 simply put a ''Field'' node after the ''Fracture'' node in Beamer 7.


===Fracture node===
Before pattern writing the shapes/polygons of a design must be fractured into trapezoids filled with beam/shot positions. Careful setup of how a design is fractured and shots are placed can greatly enhance the end result both in terms of critical dimension accuracy, line edge roughness and pattern stitching between writing fields.


===ChipPlace - easy dose test setup===
A pattern can easily be set up for a dose test using the ChipPlace module. In ChipPlace one can set up a pattern to be instanced a number of time and easily assign each instance a dose. The dose can be manually set or be linearly interpolated between a start and end value for the instanced array. The output of ChipPlace is a single pattern file with all array elements assigned to individual doses (shot ranks). This also works with patterns that already have PEC applied. In that case ChipPlace will create a combined modulation of the PEC modulation and the dose test modulation. In the example below we demonstrate how to set up dose test without PEC. If PEC is needed a PEC node can simply be added before the ChipPlace node. In the example we will use the '''Array_dots''' pattern found in the examples pane. It is a simple array of dots in a 100 x 100 µm<sup>2</sup> box. The procedure is
*Import a design
*Add the ChipPlace node
*In the '''Substrate''' tab define the substrate size. This is purely for visualization of how the pattern fits on the substrate


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
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| [[image:BEAMER_1.png|800px]]  
| [[image:BEAMER7_Fracture.png|400px]]
|-  
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This example uses the '''Array_dots''' pattern supplied with Beamer. Image: Thomas Pedersen.
The ''Fracture'' node in Beamer.
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''Maintain grid:'' Check this to fracture at the database grid size, in most cases 1 nm. If unchecked the fracturing resolution can be changed in the ''Resolution'' field. The fracture resolutions should be set to the writing grid resolution, in most cases 1 nm.
''Beam Step Size Correction:'' If checked, the program will attempt to preserve original shape outlines when beam shots are placed.
''Fracturing Type:''
*''Hierarchical:'' This mode will preserve the hierarchical layout structure.
*''Flat:'' This mode will remove the hierarchy in the pattern while preserving the layer information of the shapes.
''Fracturing mode'' determines the method used for fracturing.
*''Conventional:'' The conventional algorithm performs mainly horizontal fractures at polygon vertices that maintain the original design intent as good as possible. This leads to many slices of trapezoids to best represent the original layout.
*''Large Rectangle Fine Trapezoid:'' The LRFT algorithm attempts to minimize the number of shapes using very large rectangles for large areas and fine trapezoids for smaller features. In other words, this mode fractures the polygons with as many large rectangles as possible and completes the filling with small trapezoids.
*''Curved:'' This algorithm should typically be used to fracture circles and rings. This mode allows BEAMER to shift the vertices along curves to get fractures consistent with the specified resolution and beam step size. In other words, this mode will try to detect curves in the given polygons and fracture these curves within a specified tolerance consistent with the specified resolution and beam step size.
*''Symmetric Fracturing:'' This will attempt to perserve as high symmetry across the x- and y-axis as possible.


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
|-
|-
| [[image:BEAMER_2.png|800px]]
| [[image:BEAMER_Conventional.png|300px]] | [[image:BEAMER_LRFT.png|300px]] | [[image:BEAMER_Curved.png|300px]]
|-  
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| colspan="1" style="text-align: center;|
| colspan="3" style="text-align:center;|
Choose a substrate size to visualize placement within the substrate in ChipPlace. Image: Thomas Pedersen.
Illustration of the three different fracture modes on a 400 nm diameter circle. From left to right the fracture modes are ''Conventional'', ''LRFT'' and ''Curved''.
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*Go to the '''Array and Data tab'''
*Click '''Add Array'''
*In '''Data to place''' choose '''Chip'''. It will then take the pattern connected to the ChipPlace module
*Fill in array data in '''Repitition''' and '''Pitch''' to create as many dose test instance as you want. In this case we create a 10 x 2 array
*Choose '''Center''' in '''Position Mode''' to have everything centered in the final output pattern (V30 file)
*Click '''Assign Dose''' to open up the dose assignment page
*Choose '''Dose Series''' and enter a start and end value. This is relative dose, i.e. a multiplier on the base dose defined by RESIST in the SDF file
*Choose '''Raster X''' in '''Deploy Mode''' to increase dose from left to right for all rows
*Click '''OK''' in both open windows to see the result


This will produce a 10 x 2 array of the pattern with a relative dose from 1 to 2. Remember this dose factor is acting as a multiplier onto the base dose defined by '''RESIST''' in the SDF file. Thus if a base dose of 200 is defined by '''RESIST''' this setup will start at 200 µC/cm<sup>2</sup> and end at 400 µC/cm<sup>2</sup>.
===Fields===
 
 
The ''Advanced'' pane allows one to divide a design into different regions and apply different fracturing methods to different regions. Simply shift-click in the layout to draw out regions. It can also be used to assign different methods by layer. Multiple setups can be added with the ''+'' button.
 


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
|-
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| [[image:BEAMER_3.png|800px]]
| [[image:BEAMER_A1.png|300px]] [[image:BEAMER_A2.png|300px]] [[image:BEAMER_A3.png|300px]] [[image:BEAMER_A4.png|300px]]  
|-  
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| colspan="2" style="text-align: center;|
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The array and dose assignment can be set up with just a few inputs. Image: Thomas Pedersen.
Advanced pane of the ''Fracture'' node.
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''Field Traversal:'' ''Fixed'', ''Floating'' or ''Fields Follow Geometry''. The ''Fixed'' traversal will lay out main fields in a perfect grid starting from the bottom left feature of the design. The ''Floating'' field option will attempt to place geometry in the center of writing fields and is best used for sparse layouts. ''Fields Follow'' will attempt to lay out fields and their writing order such that they follow geometry. This is a good choice for waveguides and spiral structures.
''Multipass Mode:'' In order to mitigate beam fluctations it is possible to divide an exposure into multiple exposures of each writing field. It is a simple averaging technique whare each pattern element is written n times, each time with 1/n of the total dose. Options are ''Single Pass'', ''Two Passes'', ''Four Passes'' and ''Dose Selective''. In the first three cases the pattern is written in either one pass (i.e. not multipass), two passes or four passes. In the dose selective approach it is possible to set the number of passes based on the dose using the table in the bottom of the window. When using multipass one must assign either a ''Mainfield Offset'', a ''Subfield Offset'' or both, such that elements are written at different placements of the writing field.
''Overlap Method:'' Allows one to setup a pattern overlap between main fields to mitigate stiching problems. The overlap dimension is controlled with the ''Size'' fields. The methods available are:
*''Share between fields:'' This method divides pattern elements at main field boundaries and assigns the entire dose of an element to a single writing field. An overlap region can be defined such that small elements within this overlap are placed in a single writing field to avoid stitching.
*''Split Dose between Fields:'' The dose is split evenly across neighbouring fields over the designated distance.
*''Interleaving:'' In this method an interleave is made between writing field boundaries over the distance set by ''Size''. The width of the interleaved strips is set in the ''Element Size Interleaving''.
*''Interleaving + extra field:'' This method is somewhat similar to ''Interleave'' but in addition it creates an extra writing field with the interleaving part only. Thus, the interleaving part is written at 50% dose in each of the neighbouring fields and then written at 50% dose in a third (floating) writing field.


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
|-
|-
| [[image:BEAMER_4.png|800px]]
| [[image:BEAMER_Share2.png|400px]]  [[image:BEAMER_Share1.png|400px]]  
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| colspan="2" style="text-align:center;|
Indicated for each element in the viewport is relative dose X and array number (x,y). Image: Thomas Pedersen.
Illustration of ''Share between Fields'' overlap. On the left side the overlap distance is 0, i.e. no overlap. The rods are simply divided along the main field boundary. On the right side an overlap has been introduced such that the line of rods at the boundary is entirely placed in either of the writing fields and hence will not be stitched across two fields.
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To make analysis of the post exposure result easier let us add a dose label to each array element. This dose label will be exposed along with the pattern and thus when inspecting the result in SEM the (relative) dose will be visible next to the pattern. It is very easy to add:
*Go to the '''Texts''' pane in the bottom window
*Enter '''$DOSE_REL(3)$''' to have the relative dose printed with 3 decimals accuracy
*Choose array 1 in '''Array ID''' to assign the text label to that array
*Assign text labels to all array elements with the '''(*,*,2)''' command. The "2" sets the relative dose of the labels to 2
*Assign an y-axis offset of for instance -100 µm to avoid having the label printed on top of the pattern itself
*Assign a decent size in the '''Size''' window, 20 µm will work for most cases
*Click '''OK''' in the bottom of the window to return to the Beamer view
*Run the ChipPlace node to see the result
*Add an '''Export''' node and export the result as normal


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
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| [[image:BEAMER_5.png|800px]]
| [[image:BEAMER_Split.png|400px]]  
|-  
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| colspan="1" style="text-align: center;|
| colspan="2" style="text-align:center;|
Final result of the ChipPlace node with relative doses from 1 to 2, ready for export to V30. Image: Thomas Pedersen.
Illustration of ''Split between fields'' overlap. Over a defined distance at the writing field boundary the geometry is present in both fields but only written with half the dose, as can bee seen by the color of the overlap.
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|}


{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
{| style="border: none; border-spacing: 0; margin: 1em auto; text-align: center;"
|-
|-
| [[image:BEAMER_6.png|800px]]
| [[image:BEAMER_Interleave1.png|400px]] [[image:BEAMER_Interleave2.png|400px]]  
|-  
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| colspan="1" style="text-align: center;|
| colspan="2" style="text-align:center;|
Example of the added dose labels. Image: Thomas Pedersen.
Illustration of the ''Interleave'' overlap methods. On the left side ''Interleaving'' is used to interleave the structures at the main field boundary between the fields. On the right side "Interleaving + extra field'' is used to interleave but also add an additional writing field for the interleaved part.
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|}


== Beamer ==
The following is a short walkthrough of the most frequently used features of Beamer. For a more in depth look at Beamer please refer to GenISys own [https://www.genisys-gmbh.com/in-action.html learning material found here.]
The BEAMER software is used to convert files from GDSII format to v30-format. The BEAMER software is manufactured by GenISys (www.genisys-gmbh.de) and the software is installed on the ebprep computer.


The main functions of BEAMER are:
The ''Fields'' pane is very simple and can be used to limit the main or subfield dimensions. The maximum main field size is 1000 x 1000 µm<sup>2</sup> and the maximum subfield size is 4 x 4 µm<sup>2</sup>.


<pre>
Module      Function
Import      Imports a GDS, CIF or v30-file
Export      Exports to GDS, CIF or v30-format
Grid     Modifies the base unit of the imported file
Fracture    Optimizes the fracturing of the layout
Heal     Removes overlaps in the layout and joins abutting polygons
Bias     Adds or subtracts geometrical bias to the pattern
Merge     Merges two layouts
Minus     Subtracts two layouts
PEC     Proximity Error Correction
Split     Splits the output in two
</pre>


[[File:beamer11.jpg|500px]] [[File:beamer10.jpg|250px]]
'''Important notice:''' The export node will re-fracture the layout with other parameters unless one selects ''Cell To Field'' in the ''Field Ordering'' menu and ''NoCompaction'' in the ''Feature Sorting in Field'' of the export node.


To use the modules, they are dragged to the process flow area.
===ChipPlace===
 
The inputs and outputs of each module are illustrated by white tags. Two modules are coupled to each other by positioning the input of e.g. the Export module on top of the output of the Import module. The input/output tags turns black when they are connected.
 
By clicking on active modules, the layout of the file becomes visible in the layout view area.
 
 
<br clear="all" />
 
==Node setups and usage examples==
 
= Proximity Effect Correction =
Apart from conversion to V30 the prime use of Beamer is to do Proximity Effect Correction (PEC). This is done through the PEC node. The PEC node has a quite a few options and different ways to define a Point Spread Function (PSF). The PSF is a radially symmetric function around the beam spot that defines dose received by the resist both due to the incident beam but also from scattered electrons. The PSF used in Beamer can be defined in two ways; either based on gaussian functions where the user supplies the parameters used to define the functions, or the PSF can be based on Monte Carlo simulations of electron scattering. In any case the PSF is mainly dependent on beam energy (acceleration voltage) and substrate material. The JEOL 9500 system is always used at 100 kV, the Raith eLine system can however be used at any acceleration voltage between 1 and 30 kV. The PSF changes drastically with acceleration voltage and it is very important to use a PSF generated at the correct acceleration voltage. Beamer comes with its own Monte Carlo simulator called Tracer. In Tracer one can set up a substrate material stack and simulate electron scattering at the desired acceleration voltage. The PSF can be output as a file and loaded into Beamer for PEC.
 
=ChipPlace - easy dose test setup=
A pattern can easily be set up for a dose test using the ChipPlace module. In ChipPlace one can set up a pattern to be instanced a number of time and easily assign each instance a dose. The dose can be manually set or be linearly interpolated between a start and end value for the instanced array. The output of ChipPlace is a single pattern file with all array elements assigned to individual doses (shot ranks). This also works with patterns that already have PEC applied. In that case ChipPlace will create a combined modulation of the PEC modulation and the dose test modulation. In the example below we demonstrate how to set up dose test without PEC. If PEC is needed a PEC node can simply be added before the ChipPlace node. In the example we will use the '''Array_dots''' pattern found in the examples pane. It is a simple array of dots in a 100 x 100 µm<sup>2</sup> box. The procedure is
A pattern can easily be set up for a dose test using the ChipPlace module. In ChipPlace one can set up a pattern to be instanced a number of time and easily assign each instance a dose. The dose can be manually set or be linearly interpolated between a start and end value for the instanced array. The output of ChipPlace is a single pattern file with all array elements assigned to individual doses (shot ranks). This also works with patterns that already have PEC applied. In that case ChipPlace will create a combined modulation of the PEC modulation and the dose test modulation. In the example below we demonstrate how to set up dose test without PEC. If PEC is needed a PEC node can simply be added before the ChipPlace node. In the example we will use the '''Array_dots''' pattern found in the examples pane. It is a simple array of dots in a 100 x 100 µm<sup>2</sup> box. The procedure is


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== Beamer ==
===Visual-Job===
The following is a short walkthrough of the most frequently used features of Beamer. For a more in depth look at Beamer please refer to GenISys own [https://www.genisys-gmbh.com/in-action.html learning material found here.]
Visual Job is essentially a graphical interface where one can setup a job consisting of multiple patterns. After setup Visual Job vil write the corresponding SDF and JDF files. A short video guide to [https://youtu.be/Mi_HimB0Xa8?si=7WemvXTKJMGLY2jb Visual Job is available here.] Notice that the video is from Beamer 6.2, there is only a few minor changes in Beamer 7.


The BEAMER software is used to convert files from GDSII format to v30-format. The BEAMER software is manufactured by GenISys (www.genisys-gmbh.de) and the software is installed on the ebprep computer.  
===PEC===
Apart from conversion to V30 the prime use of Beamer is to do Proximity Effect Correction (PEC). This is done through the PEC node. The PEC node has a quite a few options and different ways to define a Point Spread Function (PSF). The PSF is a radially symmetric function around the beam spot that defines dose received by the resist both due to the incident beam but also from scattered electrons. The PSF used in Beamer can be defined in two ways; either based on gaussian functions where the user supplies the parameters used to define the functions, or the PSF can be based on Monte Carlo simulations of electron scattering. In any case the PSF is mainly dependent on beam energy (acceleration voltage) and substrate material. The JEOL 9500 system is always used at 100 kV, the Raith eLine system can however be used at any acceleration voltage between 1 and 30 kV. The PSF changes drastically with acceleration voltage and it is very important to use a PSF generated at the correct acceleration voltage. Beamer comes with its own Monte Carlo simulator called Tracer. In Tracer one can set up a substrate material stack and simulate electron scattering at the desired acceleration voltage. The PSF can be output as a file and loaded into Beamer for PEC.


The main functions of BEAMER are:
==Node setups and usage examples==
 
<pre>
Module      Function
Import      Imports a GDS, CIF or v30-file
Export      Exports to GDS, CIF or v30-format
Grid     Modifies the base unit of the imported file
Fracture    Optimizes the fracturing of the layout
Heal     Removes overlaps in the layout and joins abutting polygons
Bias     Adds or subtracts geometrical bias to the pattern
Merge     Merges two layouts
Minus     Subtracts two layouts
PEC     Proximity Error Correction
Split     Splits the output in two
</pre>
 
[[File:beamer11.jpg|500px]] [[File:beamer10.jpg|250px]]
 
To use the modules, they are dragged to the process flow area.
 
The inputs and outputs of each module are illustrated by white tags. Two modules are coupled to each other by positioning the input of e.g. the Export module on top of the output of the Import module. The input/output tags turns black when they are connected.
 
By clicking on active modules, the layout of the file becomes visible in the layout view area.
 
 
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= Simple conversion from GDSII to v30 =
 
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| Import a GDSII-file by dragging the 'Import' module to the process flow area. Select the file. In the 'Import Layout' window, type the layer number to import or type * if you wish to import all layers. || Export the GDSII file to v30 by dragging an 'Export' module on top of the 'Import' icon. An 'Export JEOL' window appears.  || In the tab 'General' of this export window, choose JBX9500FS (100kV). In the tab 'Advanced', type the correct field size (maximum is 1000 mm in both X and Y). The fields will be distributed automatically by choosing 'Fixed'. In case you have small patterns, is it recommended to tick 'Center to Field'.
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'''If your pattern is larger than one field size''', it will be stitched by several fields. In the tab 'Multipass', you can choose to smooth the stitching errors by overlapping the fields to be stitched or by multipass method.
 
There are 3 types of '''overlap''' methods; for all 3 methods you define an overlap width:
 
'''a)''' standard: the overlap will be exposed with half dose both of field 1 and field2; <br>
'''b)''' interleaving: the overlap will be finger-jointed by field 1 and field 2; <br>
'''c)''' interleaving with extra field: the overlap will be finger-jointed by field 1, field 2 and an extra field 3, as illustrated to the right. <br>
 
The '''multipass''' method smooths the field stitching errors by writing the pattern with half dose in different areas of the main deflector; by this method, pattern located in the corner of a writing field will be written partly by the corner of a writing field and partly by the central part of the writing field.
 
 
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=Dose variations=
 
 
== Dose variation defined by datatype or layertype ==
 
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When designing your pattern, you can define a dose variation either by defining different areas in different GDS datatype or in different layertype.
 
In both cases you import the GDS-file as usual into BEAMER, importing all layers. The layers should be visible when you view the GDSfile:
 
If you defined different doses by different GDS layers, you should tick 'Datatype to Class' under 'Advanced' when you convert to v30.
 
If you defined different doses by different layer type, you should tick 'Layer to Class' under 'Advanced' when you convert to v30.
 
View the v30-file and make sure all variations have been converted correctly.
 
In the jdf-file, manually create a shot modulation (similar to the jdi-file created by PEC) that fits to the number of layers in your v30-file. This shot modulation should be defined in the end of the jdf-file (see the sdf- and jdf-file manual). In the example below, the three layers (green, blue and red in the BEAMER viewer to the right) are defined to have shot modulation from -20 % to + 20 % of the base-dose:
 
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<pre>
 
JOB/W  'TEST',4        ; 4 inch wafer
PATH DTU5M
  ARRAY    (0,1,0)/(10000,3,10000)
    ASSIGN  P(1)-> ((*,*),SHOT1)     
  AEND
PEND
 
 
LAYER    1
P(1)  'fredrikpnov1507prox.v30'
SPPRM 4.0,,,,1.0,1
STDCUR 0.22  ;nA
 
SHOT1:  MODULAT  (( 0, -20) , ( 1, 0) , ( 2, 20))
 
END
 
</pre>
 
== Dose variation defined by an array in jdf file ==
 
Another even faster way to define dose modulation (if you have less than 10-15 different doses) is to repeat the pattern (v30-file) in an array with different doses in the jdf file, just type the dose modulation you wish to apply to every chip in the array:
 
<pre>
 
JOB/W  'TEST',4        ; 4 inch wafer
PATH DTU5M
  ARRAY    (-10000,2,10000)/(10000,1,10000)
    ASSIGN  P(1)-> ((1,1),SHOT1)
    ASSIGN  P(1)-> ((1,2),SHOT2)
    ASSIGN  P(1)-> ((2,1),SHOT3)
    ASSIGN  P(1)-> ((2,2),SHOT4)     
  AEND
PEND
 
 
LAYER    1
P(1)  'tjulahej.v30'
SPPRM 4.0,,,,1.0,1
STDCUR 0.22  ;nA
 
SHOT1:  MODULAT  (( 0, -20))
SHOT2:  MODULAT  (( 0, -10))
SHOT3:  MODULAT  (( 0, 0))
SHOT4:  MODULAT  (( 0, 10))
 
END
 
</pre>
 
== Proximity Error Correction (PEC) ==
 
BEAMER has a built-in proximity error correction simulation program; import the GDS-file as usual and connect the 'PEC' module to its output. In the 'Proximity Error Correction' window you can either type Beta and Eta manually or import a point spread function (PSF).
 
 
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| Add a PEC-module on top of the import module. A Proximity Error Correction parameter window opens. Here, you can either type in values of alpha, beta and eta or load a point spread function.|| After converting to v30-format, the dose variation is illustrated in your pattern || BEAMER has at this point created a jdi-file in the same folder as the v30-file. This jdi-file is the shot modulation that should be inserted in the jdf-file. The jdi-file opens with SuperEdi.
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= Bulk and sleeve =
 
If you have structures with both bulky and fine parts that you wish to pattern either with different doses or different currents, you can use BEAMER to divide the structures in different layers or different v30-files.
 
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| An illustration of how the 'bulk & sleeves' technique this is done by using the Bias and Minus modules; the Bias function subtracts in this case 1 micron from the pattern, defining layer 0 (red layer). Layer 1 (green) is the original pattern minus layer 0. ||In the flow to the left, the two layers are exported separately in two different v30-files. In the flow to the right, the two layers are combined in one single v30-file
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