MLA150 - Design Guidelines - Revision history

John d: /* General CAD Guidelines */ reducing write time

2025-12-20T01:43:40Z

General CAD Guidelines: reducing write time

← Older revision		Revision as of 01:43, 20 December 2025
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	*Make sure the file extension is all lower case (e.g. <code>.gds</code> not <code>.GDS</code>) - some design programs (e.g. Klayout) will create a file with an upper case file extension by default.		*Make sure the file extension is all lower case (e.g. <code>.gds</code> not <code>.GDS</code>) - some design programs (e.g. Klayout) will create a file with an upper case file extension by default.
	*We recommend that your filename starts with your LastnameFirstinitial, similar to job/design names for easy finding later. For example, Demis D. John's GDS files would be named <code>johnd_MyCadDesign_Layer1_v2.gds</code>.		*We recommend that your filename starts with your LastnameFirstinitial, similar to job/design names for easy finding later. For example, Demis D. John's GDS files would be named <code>johnd_MyCadDesign_Layer1_v2.gds</code>.

			=== Reducing Write Time ===

			* If your CAD file has many (eg. thousands/millions) of overlapping polygons, the conversion software can take a long time to process the file. This looks like the tool's write-head writing / pausing / writing / pausing as the tool waits for more data from the computer during the "converting/exposing" operation. You can '''"merge" the polygons''' in KLayout prior to writing to reduce this. We found that a 1hr exposure → 10min with this method!
			* Write time scales directly with write area. If you have large areas to expose with small unexposed regions in between consider using a negative PR and an inverted CAD file to reduce write area.

	==CAD Design File Specifications==		==CAD Design File Specifications==

John d: /* Limitations & Workarounds */

2025-09-19T21:01:14Z

Limitations & Workarounds

← Older revision		Revision as of 21:01, 19 September 2025
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	#'''Alignment - workarounds''':		#'''Alignment - workarounds''':
	As of 2024-11, Heidelberg have added alignment capability to Greyscale exposures, but this hasn’t yet been tested by staff. Please let us know if you try this out.		As of 2024-11, Heidelberg have added alignment capability to Greyscale exposures, but this hasn’t yet been tested by staff. Please let us know if you try this out. - [[Demis D. John\|Demis]]
	##the native software does not have rotational alignment capabilities implemented for greyscale exposures. To prevent the software from silently failing during greyscale exposure, you must ''DIS''able '''[_]''' '''''Expose with''' '''Substrate Angle''''' and/or '''[_] ''Rotation, Scaling and Shearing''''' during exposure or the <u>software will fail to expose</u> (with no error, exposure will begin but then suddenly stop after a few minutes). Workarounds - read ''both'' of the following before proceeding, as you'll need to combine both methods into your CAD file to implement both X-Y and Rotational alignment:		##the native software does not have rotational alignment capabilities implemented for greyscale exposures. To prevent the software from silently failing during greyscale exposure, you must ''DIS''able '''[_]''' '''''Expose with''' '''Substrate Angle''''' and/or '''[_] ''Rotation, Scaling and Shearing''''' during exposure or the <u>software will fail to expose</u> (with no error, exposure will begin but then suddenly stop after a few minutes). Workarounds - read ''both'' of the following before proceeding, as you'll need to combine both methods into your CAD file to implement both X-Y and Rotational alignment:
	###X-Y Alignment workaround:		###X-Y Alignment workaround:

John d: /* Compatibility with Heidelberg's convert software */

2025-06-25T00:44:21Z

Compatibility with Heidelberg's convert software

← Older revision		Revision as of 00:44, 25 June 2025
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	# Your "Editable" version that you can easily edit designs with, that keeps your separated Cells, Arrays, PCells such as Text/Circle objects, and possibly is saved in OASIS format.		# Your "Editable" version that you can easily edit designs with, that keeps your separated Cells, Arrays, PCells such as Text/Circle objects, and possibly is saved in OASIS format.
	# An "exposure" version where you make the file compatible with the heidelberg software by:		# An "exposure" version where you make the file compatible with the heidelberg software by:
	## Save as <code>*.gds</code> with your name at the start of the filename.		## Save as <code>*.gds</code> with your name at the start of the filename, eg. <code>johnd_UCSB_device1_L10_v1.gds</code>.
	## Convert all PCells to Static Cells,		## Convert all PCells to Static Cells,
	## Resolve Arrays - especially orthogonal arrays, which cause issues.		## Resolve Arrays - especially orthogonal arrays, which cause issues.

John d: /* General CAD Guidelines */ added a "compatiblity" section

2025-06-19T18:00:39Z

General CAD Guidelines: added a "compatiblity" section

← Older revision		Revision as of 18:00, 19 June 2025
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	*Note the Layer(s) to print. The system can select either a single Layer, or can combine multiple layers via Boolean OR.		*Note the Layer(s) to print. The system can select either a single Layer, or can combine multiple layers via Boolean OR.
	*The Origin (0,0) in your file is the reference for all coordinates during exposure, including alignment mark exposure/measurement.		*The Origin (0,0) in your file is the reference for all coordinates during exposure, including alignment mark exposure/measurement.
			**The Origin is usually placed at the ''Center'' of your wafer/substrate. Autofocus usually initializes at this location, so it's important that it's ''not'' at the edge of your wafer where there is badly formed photoresist/cleaved edges.
	*Your file name cannot contain any spaces or special characters except for underscores.		*Your file name cannot contain any spaces or special characters except for underscores.
	*Make sure the file extension is all lower case (e.g. .gds not .GDS) as some design programs (e.g. Klayout) will create a file with an upper case file extension.		*Make sure the file extension is all lower case (e.g. <code>.gds</code> not <code>.GDS</code>) - some design programs (e.g. Klayout) will create a file with an upper case file extension by default.
			*We recommend that your filename starts with your LastnameFirstinitial, similar to job/design names for easy finding later. For example, Demis D. John's GDS files would be named <code>johnd_MyCadDesign_Layer1_v2.gds</code>.

	==CAD Design File Specifications==		==CAD Design File Specifications==

			=== Compatibility with Heidelberg's ''convert'' software ===
			We recommend to keep two versions of your CAD design -

			# Your "Editable" version that you can easily edit designs with, that keeps your separated Cells, Arrays, PCells such as Text/Circle objects, and possibly is saved in OASIS format.
			# An "exposure" version where you make the file compatible with the heidelberg software by:
			## Save as <code>*.gds</code> with your name at the start of the filename.
			## Convert all PCells to Static Cells,
			## Resolve Arrays - especially orthogonal arrays, which cause issues.
			## Turn off any options that reduce compatibility, such as "Save cell context info" etc. MLA software has issues with those.
			## Optionally ''Flatten'' all objects (removes all Cells) and delete all unused Cells
			## Optionally Save ''only'' the Layers to be printed (turn off other layers, and "Save only Visible Layers"). These reduce chances of human-error during the MLA program setup.
			## This is the file you'll upload to the MLA for exposure.

	===GDS aka. GDSii===		===GDS aka. GDSii===
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	*Make note of the "Cell" that you want to print, often called the "top cell" as it can contain a hierarchy of other child/instanced cells.		*Make note of the "Cell" that you want to print, often called the "top cell" as it can contain a hierarchy of other child/instanced cells.
	**This is called "GDS Structure" in the ''Convert'' software.		**This is called "GDS Structure" in the ''Convert'' software.
	*Note the Layer to be printed. ~~You~~ can boolean Union (combine) multiple layers, or print only one layer.		*Note the Layer to be printed. On the MLA, you can boolean Union (combine) multiple layers, or print only one layer.

	===DXF===		===DXF===

John d: /* Alignment Marks */ link to https://wiki.nanofab.ucsb.edu/wiki/MLA150_-_Troubleshooting#Aligning_to_a_quarter-wafer/irregular_piece

2025-04-29T15:59:58Z

Alignment Marks: link to https://wiki.nanofab.ucsb.edu/wiki/MLA150_-_Troubleshooting#Aligning_to_a_quarter-wafer/irregular_piece

← Older revision		Revision as of 15:59, 29 April 2025
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	If your cross does not fill the whole field, you can use the Reduced Detection Area button to make the image detection measure in a smaller area.		If your cross does not fill the whole field, you can use the Reduced Detection Area button to make the image detection measure in a smaller area.

			=== [[MLA150 - Troubleshooting#Aligning%20to%20a%20quarter-wafer/irregular%20piece\|Aligning to a quarter-wafer/irregular piece]] ===
			See the above link for how to align to the cleaved edges of an irregular piece.

	==High-Resolution Writing==		==High-Resolution Writing==

John d: /* General CAD Guidelines */

2025-02-13T22:39:55Z

General CAD Guidelines

← Older revision		Revision as of 22:39, 13 February 2025
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	*GDS / GDSii is the preferred file format (fewest errors). DXF, CIF, BMP and Gerber are also available.		*GDS / GDSii is the preferred file format (fewest errors). DXF, CIF, BMP and Gerber are also available.
	*Note the Cell that you want to print. Only one Cell may be ~~printed~~, so use Cell Instancing to create combinations of Cells.		*Note the Cell that you want to print. Only one Cell may be selected in the software, so use Cell Instancing to create combinations/hierarchy of Cells to print.
	*Note the Layer(s) to print. The system can select either a single Layer, or can combine multiple layers via Boolean OR.		*Note the Layer(s) to print. The system can select either a single Layer, or can combine multiple layers via Boolean OR.
	*The Origin (0,0) in your file is the reference for all coordinates during exposure, including alignment mark exposure/measurement.		*The Origin (0,0) in your file is the reference for all coordinates during exposure, including alignment mark exposure/measurement.

John d: /* Limitations & Workarounds */

2025-01-12T20:44:01Z

Limitations & Workarounds

← Older revision		Revision as of 20:44, 12 January 2025
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	#'''Time''': Your will need to sign up for significantly more time to run a greyscale exposure. The software requires an initial “conversion” of the CAD file - which takes 45-60min for a 100mm wafer with 50% fill. (Be patient - the progress bar may not indicate it is working, but it is!) Once that is complete the Design shows up in the list for exposure - you can expose it any time thereafter. The exposure is also much longer than binary: 50% fill on a 100mm wafer took 12 hours. (Small substrates should be much shorter.) Staff did the Conversion and Exposure two separate sessions, on different days to accomplish the full litho. Contact Staff if you need to book the tool overnight for such a session.		#'''Time''': Your will need to sign up for significantly more time to run a greyscale exposure. The software requires an initial “conversion” of the CAD file - which takes 45-60min for a 100mm wafer with 50% fill. (Be patient - the progress bar may not indicate it is working, but it is!) Once that is complete the Design shows up in the list for exposure - you can expose it any time thereafter. The exposure is also much longer than binary: 50% fill on a 100mm wafer took 12 hours. (Small substrates should be much shorter.) Staff did the Conversion and Exposure two separate sessions, on different days to accomplish the full litho. Contact Staff if you need to book the tool overnight for such a session.
	#'''File size''' can be an issue. We have found that for full-wafers, DXF is the only format that works - BMP files that cover an entire 100mm wafer result in file sizes too large for the ''Convert'' software to handle, it will silently fail/crash.		#'''File size''' can be an issue. We have found that for full-wafers, DXF is the only format that works - BMP files that cover an entire 100mm wafer result in file sizes too large for the ''Convert'' software to handle, it will silently fail/crash.
	#'''Minimum Dose''': In order to expose at low doses, you may need to enable the 15% filter in the exposure menu. Use this if the software disallows entering below a certain Dose that you'd like to access.		#'''Minimum Dose''': In order to expose at low doses, you may need to enable the 15% filter in the exposure menu. Use this if the software disallows entering below a certain Dose that you'd like to access. We think you will have to calculate the actual exposure yourself, and calibrate your exposure with this filter enabled.

	===Greyscale BMP===		===Greyscale BMP===

John d: /* Greyscale DXF */

2025-01-12T20:42:58Z

Greyscale DXF

← Older revision		Revision as of 20:42, 12 January 2025
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	Each grey-level should be on a separate layer, where the layer name should be a number corresponding to the grey-level to print (layers numbers/levels #1-255). We recommend using a scripting method such as [https://pypi.org/project/gdspy/ GDSpy] to generate the DXF file.		Each grey-level should be on a separate layer, where the layer name should be a number corresponding to the grey-level to print (layers numbers/levels #1-255). We recommend using a scripting method such as [https://pypi.org/project/gdspy/ GDSpy] to generate the DXF file.

	Y-oriented ridges will still be present on the PR due to lateral stitching. Post-develop reflow (via hotplate) might be required for smoothing steps, but may also affect the PR profile.		Y-oriented ridges will still be present on the PR due to lateral stitching (approx 7% lower dose on the stitching boundaries - small but will be easily visible due to corresponding PR thickness changes). Post-develop reflow (via hotplate) might be required for smoothing steps, but may also affect the PR profile.

	===Conversion===		===Conversion===

John d: /* Limitations & Workarounds */ mentioned software update for GS Alignment

2025-01-12T20:38:25Z

Limitations & Workarounds: mentioned software update for GS Alignment

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 Greyscale exposure has the following limitations that we have identified:
 #'''Stitching''': Because our tool is the higher-throughput version that exposes a ~20µm field at a time (not a single spot), greyscale exposures will typically see the stitching boundaries between fields. The fast-scan axis is in Y, so you generally will see Y-oriented ridges with something like ~4-7% lower dose. This primarily manifests for greyscale because photoresist is being only partially exposed. (For regular binary exposure, users typically overexpose which hides this stitching boundary.)
 #'''Time''': Your will need to sign up for significantly more time to run a greyscale exposure. The software requires an initial “conversion” of the CAD file - which takes 45-60min for a 100mm wafer with 50% fill. (Be patient - the progress bar may not indicate it is working, but it is!) Once that is complete the Design shows up in the list for exposure - you can expose it any time thereafter. The exposure is also much longer than binary: 50% fill on a 100mm wafer took 12 hours. (Small substrates should be much shorter.) Staff did the Conversion and Exposure two separate sessions, on different days to accomplish the full litho.  Contact Staff if you need to book the tool overnight for such a session.

John d: /* Limitations & Workarounds */ added screenshot of "Set Zero" button

2024-02-04T22:41:45Z

Limitations & Workarounds: added screenshot of "Set Zero" button

← Older revision		Revision as of 22:41, 4 February 2024
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	###Once you are at the '''''Exposure''''' portion of the procedure, drive the microscope and crosshair to the feature that you designated as (0,0) on your CAD file. Use the ['''⨁'''] button to use precise positioning via clicking on the microscope image.		###Once you are at the '''''Exposure''''' portion of the procedure, drive the microscope and crosshair to the feature that you designated as (0,0) on your CAD file. Use the ['''⨁'''] button to use precise positioning via clicking on the microscope image.
	###Click '''[Set Zero]''' to set the origin (0,0) of your CAD file at that location of the crosshair.		###Click '''[Set Zero]''' to set the origin (0,0) of your CAD file at that location of the crosshair.
			####[[File:MLA Set Zero button IMG 2352.jpg\|alt=Screenshot showing MLA150 "Set Zero" button.]]
	###(See below for Rotation alignment correction - to be performed ''before'' the X-Y alignment set, but also requires editing the CAD file.)		###(See below for Rotation alignment correction - to be performed ''before'' the X-Y alignment set, but also requires editing the CAD file.)
	##Rotation Alignment workaround:		##Rotation Alignment workaround:
	###Load your substrate onto the vacuum chuck and run [Load Substrate] function.		###Load your substrate onto the vacuum chuck and run [Load Substrate] function.
	####'''''IMPORTANT''''': <u>Do not unload your substrate</u> until the exposure is complete! We will be correcting the misalignment with respect to the substrate's load position, so once you have loaded the substrate, you do not want to release vacuum or otherwise allow the substrate to move w/r/to the vacuum chuck.		####'''''IMPORTANT''''': <u>Do not unload your substrate</u> until the exposure is complete! We will be correcting the misalignment with respect to the substrate's load position, so once you have loaded the substrate, you do not want to release vacuum or otherwise allow the substrate to move w/r/to the vacuum chuck.
	###Run a dummy binary-design design as a "normal" 2nd-Layer exposure with Alignment, and align to a few marks on your wafer. In the "Exposure" screen it'll show your the resulting ''Rotation (and Scaling/Shearing)'' values calculated from your alignment marks.		###Run a dummy binary-design design as a "normal" 2nd-Layer exposure with Alignment, and align to a few marks on your wafer. In the "Exposure" screen it'll show your the resulting ''Rotation (and Scaling/Shearing)'' values calculated from your alignment marks.
	###Record the ''Rotation'' value (Scaling/Shearing are optional - if they are far from nominal, you may want to account for these as well).		###Record the ''Rotation'' value (Scaling/Shearing are optional - if they are far from nominal, you may want to account for these as well).
	###Do ''NOT'' run the exposure, but instead exit the Exposure and go back to the '''[''<< Setup'']''' screen.		###Do ''NOT'' run the exposure, but instead exit the Exposure and go back to the '''[''<< Setup'']''' screen.
	###Edit your CAD file and apply the rotation to the CAD file. (Recommended: put your entire design into a [[KLayout Design Tips#Cells .26 Instances of Cells\|sub-Cell]] and apply the rotation to that [[KLayout Design Tips#Cells .26 Instances of Cells\|Cell Instance]]. Not you'll likely have to convert between µRadians --> Degrees).		###Edit your CAD file and apply the rotation to the CAD file. (Recommended: put your entire design into a [[KLayout Design Tips#Cells .26 Instances of Cells\|sub-Cell]] and apply the rotation to that [[KLayout Design Tips#Cells .26 Instances of Cells\|Cell Instance]]. Not you'll likely have to convert between µRadians --> Degrees).