Layout design

Layout Design Formats

When you want to create a pattern on a wafer with photolithography, you have to describe or digitize the pattern by geometric shapes, i.e. to distinguish the areas where UV light will expose the photoresist from the areas where it will not. This will be a required step for either the fabrication of a Cr blank mask (to use on a mask-aligner or a stepper), or for exposing the photoresist with a UV laser (direct laser writing).

To create a complete 2D layout, the patterns can be drawn using dedicated computer-assisted design (CAD) softwares, generated using mathematics softwares such as Matlab or Octave, or coded using python/ruby programmed scripts. There exist many layout file formats to describe such layouts. Some are proprietary, some public, some standard. While you can use your preferred CAD software to generate the layout, the design should be exported to formats that are compatible with the Heidelberg Instruments (HIMT) laser writing equipments used in CMi, such as (in order of recommendation):

  • gds, gdsii, gds2, GDSII (Graphic Database System for Information Interchange). The GDS file format is an industry standard and the recommended file format to flawlessly convert your design to the internal language of the HIMT direct laser writing equipment. General information about the GDS format are available here.
  • cif, CIF (Caltech Intermediate Format). The CIF file format is a concise and human readable text based description of the layout. In general, the CIF format is converted without issues but some proprietary text statements introduced in specific layout editors (such a Clewin) may not be interpretated correctly by the HIMT conversion tool. General information about the CIF format are available here.
  • dxf, DXF (Drawing eXchange Format). The DXF file format as been developped by Autodesk to enable data exchange between AutoCAD and related softwares. With many limitations and restrictions, DXF files may be accepted and converted correctly by the HIMT conversion tool. General information about the DXF format are available here.

Layout editors: CAD software

The softwares and tools listed below (in order of preference) can export valid and standardized GDS format files for the HIMT laser writing equipment.

Software Description License/Installation
Tanner L-Edit IC (v2016.2) by Mentor (Siemens), layout editor
Klayout by Matthias Köfferlein, layout editor
  • Free software
LinkCAD (v8) by Bay Technology, layout file formats conversion tool
  • License for CMi users
  • Installed on cmipc27 and cmipc58 in CMi open office BM 1.132
Clewin (v4)

by WieWeb software, layout editor

LayoutEditor by Juspertor GmbH, layout editor
  • Packages: free (limited), reduced (~EUR300), full (~EUR1100)
Glade by Peardrop Design Systems, layout editor
  • Free software
Virtuoso Layout Suite by Cadence, professional layout suite
  • Payed software
Expert by Silvaco, professional layout suite
  • Payed software
AutoCAD by AutoDESK, mechanical drawing software
Solidworks by Dassault Systems, mechanical drawing software

GDSII Toolbox

by Ulf Griesmann, Matlab/Octave GDS import/modify module
  • Free addon/fonctions for Matlab/Octave

Gdspy

by Lucas Heitzmann, Python GDS import/modify module
  • Free addon/fonctions for Python

CMi layout template

CMi user library available for download (gds ziped):

Description of layers used in the template files:

GDS #
Layer function
Notes
50
Wafer frame
This layer shows the 3mm edge frame and flat position of a 100 mm Si wafer wheew it is not recommended to place devices. This layer is normally removed from the layout.
51
Mask frame
This layer shows the frame of a standard 5″ mask plate used in the contact aligners at CMi. This layer is always removed from the layout.
52
CMi logo

The logo of CMi and mask information for identification of mask plates. This layer is normally kept and updated, and can be removed if necessary.
53
Dicing marks

The matrix of crosses show an example guideline set for dicing the wafer into dies. The layer should be kept only if dicing will occur; the step size can be adjusted to adapt layout.
54
MA6BA6 BSA mark
location area
Demonstration of the area visible with the backside objectives on the Süss MA6 or MA6 Gen3 mask-aligners. Alignment marks for BSA should be located in this area.
55
EVG150 robot arm
handling area
Demonstration of the area where the robot arm suction cups will be in contact with the backside of the wafer. This layer should always be removed.
56
SB6 contact area

Demonstration of the area where the fixture and the pin is in contact with the wafers during the bonding process. This layer should always be removed.
57
Resolution test
patterns
Test patterns to determine best achievable resolution; can be used during a lithography process, and mask fabrication. These patterns are adapted to the DWL writing modes, and can be replaced or removed if necessary.
58
Top side layer 1
alignment marks
First layer of structures for top side layer-to-layer alignment. Other marks may also be used. These can be removed if there is no need for alignment.
59
Top side layer 2
alignment marks
Second layer of structures for top side layer-to-layer alignment. Depending on process steps and layout, this layer might need to be inverted for better visibility.
60
Top side layer 3
alignment marks
Third layer of structures for top side layer-to-layer alignment. Depending on process steps and layout, this layer might need to be inverted for better visibility.
61
Back side layer 1
alignment marks
First layer of structures for back side layer-to-layer alignment. Other marks may also be used. These can be removed if there is no need for back side alignment.
62
Back side layer 2
alignment marks
Second layer of structures for back side layer-to-layer alignment.
63
DWL alignment marks

Patterns for alignment with the laserwriter. This layer should only be kept for direct write alignment with the DWL200 or inspiration for VPG200.
64
Wafer edge mask see-throughs. Fiber feedthroughs. E-beam alignment marks,
A 2mm wide edge of a 100mm wafer. Allows to peek through the mask by the means of this visual feedback coarsly align the wafer edge with the design. Primary flat scale allows for good alignment with crystal plane. Feedthrough positions for spectrometer fiber used on MA6Gen3 in SMILE and GSL modes. Set of alignment marks to allow both optical and e-beam lithography with alignment in one process flow. Please contact CMi staff for further information.
65
MLA150 BSA areas, vacuum channels.
The MLA150 chuck has four rectangular holes that allow the back side alignment BSA cameras to look at the wafer from the back side. This is where you must place your alignment marks, if you want to do BSA. The traditional two BSA areas are located along the x-axis, here there are two additional ones along y-axis. Tthe traces of the vacuum clamping channels are given as well.
159
Inverted TSA layer2
Alignment marks of layer 59, inverted, inside a 2mm x 2mm square, so that you see through that opening in the mask the marks on layer 58 on the substrate below
160
Inverted TSA layer3
Alignment marks of layer 60, inverted, inside a 2mm x 2mm square, so that you see through that opening in the mask the marks on layer 58/59 on the substrate below