Define and inspect an LDF fabrication process

Before starting

Use the fabrication owner’s approved process for real devices. The complete example below is a public microstrip teaching stack. Download its shared three-file example or use the inline-geometry guide for the matching IXI and circuit files. Do not substitute this stack for a protected or calibrated process.

Steps

1. Open process.ldf in Studio. Review its source and process inspection view. Save an editable working copy and identify its process revision before changes.
2. Set Units for geometry and thickness, then define Parameters and Layer records using name = value and $End. An open legacy-format LDF can omit a header; do not invent protected-file metadata.
3. Keep Number (layout layer ID), Name (logical material) and Order (vertical construction order) distinct. Here M0 is number 17/order 0, I0 is number 2/order 1 and M1 is number 5/order 2.
4. Review thickness, mask polarity and material type for every layer. Review penetration depth and height-filament settings for the superconducting conductors.
5. Return to strip.ixi, check its Process reference and run that project. A syntactically valid LDF or a nominal stack drawing does not prove the intended physical model.

Complete process.ldf

* Public microstrip teaching stack; dimensions use Units below
$Parameters
  Units = 1e-6
  SegmentSize = 2.0
  AbsMin = 0.025
  GPOverhang = 5.0
  ProcessHasGroundPlane = TRUE
  GPLayer = 17
  TermLayer = 19
  TextLayer = 18
  HFilaments = 1
  TerminalInRange = 1.0
  UnitL = 1
$End
$Layer
  Number = 17
  Name = M0
  Thickness = 0.2
  Lambda = 0.09
  Order = 0
  Mask = -1
  Filmtype = S
  HFilaments = 2
$End
$Layer
  Number = 2
  Name = I0
  Thickness = 0.15
  Order = 1
  Mask = -1
  Filmtype = I
$End
$Layer
  Number = 5
  Name = M1
  Thickness = 0.25
  Lambda = 0.09
  Order = 2
  Mask = 1
  Filmtype = S
  HFilaments = 3
$End

Understand this stack

Units = 1e-6 makes one coordinate/thickness unit equal to 1 µm. Nominal unetched stack positions are M0 from 0 to 0.20 µm, I0 from 0.20 to 0.35 µm and M1 from 0.35 to 0.60 µm. The production editor’s nominal process snapshot reproduces these positions; it is not an etched-layout cross-section.

Filmtype S describes the superconductors; I describes the insulator. Lambda = 0.09 means 0.09 µm in this process. Material properties must come from the actual process, with temperature/frequency/model assumptions reviewed for the intended analysis.

M0 uses a negative mask and the declared ground-plane layer; GPOverhang bounds the generated ground region around the conductor model. M1 uses a positive mask. TermLayer = 19 and TextLayer = 18 identify annotation layers rather than deposited films.

SegmentSize and HFilaments control different mesh dimensions. Halving the planar segment size is a refinement change, not a process calibration or a guarantee of accuracy.

Coordinate units and result units

Changing Units changes the physical sizes represented by the same coordinate and thickness numbers. UnitL instead normalizes inductance values and design values. Do not use one as a substitute for the other.

In the checked example UnitL = 1 uses henries and L1 1 2 3.9e-12. Setting UnitL = 1e-12 and the design value to 3.9 gives the same physical result displayed as 3.896479063 pH. Change the design-value convention consistently with the result-unit convention.

Check the result

The checked 100 × 10 µm example gives L1 = 3.896479063e-12 H (3.896479063 pH), approximately 0.09028% below its 3.9 pH design value. Its mesh bytes and extracted value match the maintained GDS microstrip. This comparison is specific to these exact inputs and runtime.

Verify the intended ground plane, material layers, terminals and current-run units before comparing numbers. Use a justified refinement plan for real structures.

The detailed current CLI output/elements.txt contains the value quoted above in the configured UnitL units. The human-readable summary rounds this example to 3.89648 pH. Match units and printed precision before treating different displays as a numerical change.

If the problem remains

The production editor rejects a Layer record missing required Thickness in this teaching stack; restore the real value before proceeding. The CLI rejects the missing process and undefined material-layer cases and recovers after correction.

The current candidate can flag TERM/TEXT with IXI_CROSS_UNKNOWN_LAYER even though these annotation aliases are accepted by the checked Core run and resolved to TermLayer/TextLayer. This focused mismatch is tracked as KB-GUI-005. Check the actual alias and declared layer numbers; do not rename conductor layers or ignore unrelated warnings.

Keep protected files intact. Obtain the correct process revision, access and validity from the issuer when required; editing metadata or copying an unrelated LDF does not repair a missing fabrication model.

Actual Studio unit-change check

The native scenario saved UnitL = 1e-12 in the real process editor and changed the netlist design value to 3.9. The next normal GUI run showed Inductance [pH] with L1 = 3.89648. Restoring both conventions returned the original result and exact original input bytes.