GCA 6300 Mask Making Guidance
Work In Progress
This article is still under construction. It may contain factual errors. Content is subject to change.
|To Do: In progress, this page is not ready to use yet - needs corrections, still includes copied ASML instructions. Biljana 2019-06|
Mask Layout / Alignment Marks / Ordering from Photronics / Specifications
1) Mask specifications to Photronics using old Connexant order form
The following material should be sent to them to do a job:
1. Mask file in GDSII format, upload by FTP. Site: “dragon.photronics.com or 184.108.40.206”, Get your own Username/Password from Photronics.
2. The mask file should be the same scale size as will appear on the mask (ie. 5x scale). The features on the wafer will be 5 x smaller. L-Edit has a feature to scale dimensions so that the original mask file can be made with the correct on-wafer dimensions and then the job can be scaled and saved as a separate file. Each layer in the document must have a unique GDSII number assigned to it. These numbers are used by Photronics.
3. You must send a purchase order and put a part number on the order form. The part number is anything you make up and will appear on the mask.
4. You need to fill out a Connexant Photomask Order form (2 pages). Most fields you will fill in are obvious. Here are the meanings of the not-so-obvious ones.
Media Type : “FTP” is the answer for electronically sent data.
Data Scale : “1 x” is the correct answer if the mask layout dimensions sent are those that will be on the mask (remember that the GCA Steppers will shrink these dimensions by 5 times on the wafer)
Material : Quartz
Material Size: 5” x 5” x .09”
C.D. Feature Type: “rectangle” is usually the correct answer
Data Extents Xlow, Ylow, Xhigh, and Yhigh: In the L-edit mask file, these are the box coordinates, in microns from the origin, of a box that just contains all of the features in the mask.
Reticle/Mask Level I.D: The name of the level
|To Do: clarify what this is called in L-Edit or KLayout terminology|
Topcell Structure Name: The Name of the Cell in the GDS file that contains the data to be printed on the mask.
Add. Unit: This is the address unit size (step size) of the raster-scanned beam used by Connexant to shoot the mask. This will affect the price.
Chrome Side Down Reading: “Right” is usually correct. This specifies that when the Chrome is facing down, all features will appear as in the GDS file. Also that the text will be readable when looking at the plate with chrome down (away from user).
Polarity: “Clear” for a positive pattern (i.e. GDS objects will be chrome and block light) “Dark” for the opposite polarity.
|To Do: please check that this is correct, sounds opposite|
CD: Size of critical dimension in microns. They will print a test structure of this size to automatically measure to see if the print is within spec. Choose any size for this, usually the smallest feature size on the reticle.
Overlay Registration to grid: See price list. This sets the guaranteed precision of one mask level feature relative to another.
Pellicle Req’d: “No” is the correct answer.
Connexant PRMIS Lot No: Leave blank.
Special Instructions: “Use tucsbgca.jb alignment marks for masks”, “See attached drawings for CD placement and specifications for each layer and for text information to include at the outside of each mask”
5. The location of the critical dimension (CD) features, what they look like, and what the dimensions are should be included for each layer in which CDs are important.
6. Also include any text that you want to be written at the outside of the usable mask area for each layer for your own purposes. For example, the mask name, layer name, Key Offset for Global Alignment in X and Y (i.e. One could ask for the text KOGX 25um to specify a key offset in X of 25um for global alignment, etc.), the key offset for local alignment in X and Y, and the repeat step distance in X and Y would be good to include on each layer.
2) Alignment marks in exposure field, Global, Local (DFAS). To learn more about how these alignment marks work with the system, see the reticle handbook. In our system we mainly use manual global alignment to get +/- 0.25 or better alignment tolerance. Local alignment can be used but needs some characterization for each process.
Global alignment marks: These marks and how to place them on the mask are described on page 5-44 to 5-47 of the reticle handbook and are included as an attachment to this document. The difference of our system from the manual is that the objectives are 38.1 mm apart, not 76.2 mm as indicated in the manual. The distance of this mark (or marks) to the center of the cell in X and Y should be noted, this is the key offset and will be required when exposing a job. (Positive offset values are left for X and up for Y)
Local alignment marks: These marks and how to place them on the mask are described on page 5-33 to 5-34 of the reticle handbook and are included as an attachment to this document. If possible use one of each type if you desire to try to use local alignment. These can be light or dark field in nature. The distance of the center point of this mark (or marks) to the center of the cell in X and Y should be noted, this is the key offset and will be required when exposing a job.
3) Vernier Scales: These can be included to quantify the alignment offset after an exposure is done. The reticle handbook has an example of vernier scales on pages 5-49 to 5-53. You should include them for any layers that require critical alignment.
4) Resolution: If you have room in the mask layout, it is good to have features that can give the resolution of a given exposure. The resolution should show both “pillars” and “trenches” in the resist so that you can see whether the focus or exposure needs some tweaking for your particular process.
|To Do: delete the following section|
|To Do: ASML INSTRUCTIONS from WIKI:|
- Use commercial mask/reticle houses: Photronics, Toppan, Compugraphics, etc.
- Instruct vendor that this will be used on an ASML 5500/300 system with 4x reduction. They have all outer templates to make your mask match our system. You just provide them the data you want printed, at wafer-scale (1X), and they'll scale it up 4x and insert it into the template.
- Reduction is 4X, instruct the mask makers to scale your CAD data to 4X size, which will determine price. Scale your mask critical dimensions (CD) and tolerances from the product quotes accordingly.
- Masks must be Quartz, 6" x 6" x 0.25” thick.
- Layer-to-layer alignment marks are provided by a calibration mask in our system. No need to put alignment marks on your CAD file.
- Spacing between mask-plate fields : 1mm of Chrome between fields (at wafer scale) in order for the reticle masking blades to blank off unwanted areas.
- Field Sizes Available (at Wafer-Scale, 1x):
- The full field useable exposure area is limited to the intersection of a 31mm diameter circle and a rectangle of dimensions 22mm x 27mm. See the schematic below for an illustration. Schematic of lens/aperture illumination. Fit a rectangle within this field to get the aforementioned rectangular field sizes.
- For High Resolution 0.63 NA: 21mm in X, 21mm in Y
- For 0.4 to 0.57 NA: 22mm in X, 22mm in Y
- Other rectangular sizes available, that fit within the lens/aperture intersection:
- 21mm x 23mm (X width x Y height)
- 20mm x 24mm
- 19mm x 25mm
- 18mm x 25.5mm
- 17mm x 26mm
- 16mm x 26.5mm
- 15mm x 27mm
- In general, 250nm resolution will resolve over the entire field. Anything smaller than this may not resolve closer to the edges of the field where lens quality degrades, and will also have a smaller viable process window (tolerance of exposure/bake/develop parameters). A number of users have shot ~150nm features.
When submitting the photo mask order, the following notes apply:
- Although you will submit your CAD file at 1x wafer scale, the actual reticle is printed 4x larger. Make sure to choose your reticle grade accounting for this; eg. If I want to shoot 1.0µm lines, I should choose a photomask grade better/equal to 4.0µm.
- “GDS Level” is also knows as “layer number”
- Barcode text for the plate must be 12 characters or less. Avoid special characters, a-z/0-9 only. This text is what you type into the job program.
- “Min. Feature on Mask” refers to minimum clear or chrome feature, assuming features similar to lines/spaces.
- “Min. Contact” refers to features with aspect ratio close to 1:1, eg. Squares and circles. These have a separate spec due to the manufacturing process, so make sure to choose the appropriate grade of photomask with this in mind.
- Choose a Critcal Dimension “CD” similar to your most critical feature (scaled to the 4x reticle scale), so they will print & measure & guarantee test structures at that size.
- For UCSB purchases: you will need to submit your order in UCSB Procurement Gateway first (as a "Non-Catalogue Item"), with the cost estimate from our negotiated quote, so that you can get the Purchase Order (PO) Number (usually in the same day). Then submit the order form to the photomask vendor with this PO number entered on their order form.
- When programming your job at the tool, you can fill out this Spreadsheet using your CAD file before starting your job programming:
- ASML Reticle Programming Params - MyReticleBarCode v1.xlsx
- GDS CAD file for for the ASML on-wafer alignment marks: