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Computational lithography and proximity correction software

Lithography simulation, proximity correction and model calibration, fitted to your measured wafers. The mask you release prints the pattern you drew, and the first wafer run confirms it.

Talk to our Technical Experts See Process Proximity Compensation

What is computational lithography?

Computational lithography is the software that predicts how a mask pattern will print on a wafer and changes the mask so the printed result matches the design. Process proximity correction is its core step. It models how exposure, resist and etch distort each feature, shifts mask edges to offset that distortion, then checks the corrected mask in simulation.

  • The problem

    The wafer doesn't print what you drew. Below the exposure wavelength, diffraction, resist and etch each drag an edge off target. Lines thin. Corners round. Line ends pull back. A perfect layout can still produce the wrong silicon.

  • What the software does

    It predicts that drift with a model calibrated on your silicon, corrects the layout, and simulates the result back before any data reaches the mask shop.

  • When you use it

    When you qualify a new node and need to know whether a layer can print at all. At tape-out, on every critical layer. And in a yield ramp, when one layer keeps missing its critical dimension and nobody can say why yet.

From drawn layout to measured silicon, and back

What one layer measures on silicon improves the correction on the next.

  1. Design intent Your layout, as drawn
  2. Litho model Aerial and resist image
  3. PPC correction Edges shifted to compensate
  4. Mask data Corrected and ready to write
  5. Verification Simulated back, rule-checked
  6. Silicon result Measured on the wafer
  7. Calibration Model refit against your data

The return arrow is the point. Refit the model to your own measurements and the fix lands on target.

Four jobs in one correction flow

See what a mask will print before you pay to make one. Physics-based litho models predict the aerial and resist image for each feature.

Correct the layout against the calibrated model, correct-by-construction instead of by trial and error. Source-mask optimization tunes the illumination with the mask, and hybrid SRAF placement widens the process window.

Fit the model to your wafer or CD-SEM measurements. Silvaco's predictive process model includes resist, etch and mask behavior as well as optics, so the dimension you correct to is the one that reaches silicon.

Re-simulate the corrected mask and compare the printed contour with the target. Mask rule checks then confirm every shape is writable before release.

Lithography tools

Silvaco added Process Proximity Compensation from Cadence in March 2025. DimensionPPC handles curvilinear masks.

  • Process Proximity Compensation (PPC)

    Builds and verifies the mask your layout needs.

    • Third-generation suite designed for correct-by-construction OPC, with patented optimization
    • Source and source-mask optimization with hybrid SRAF placement
    • Pipelined, distributed runs on general-purpose hardware; recipes by GUI or script
    View product

  • DimensionPPC

    Curvilinear correction for layers that rectilinear masks can't print cleanly.

    • Curvilinear mask synthesis and optimization
    • Simulation-based verification of the curvilinear mask
    • Mask rule checks written for curvilinear shapes
    View product

Where holding the pattern gets hard

Same physics everywhere. What changes is which distortion eats your error budget.

Foundries, nodes, formats and platforms

Foundries and nodes

PPC runs in production from large geometries to the most advanced processes. The PDK table covers Silvaco's analog and custom IC tools; ask us directly about lithography coverage.

Check the PDK table See foundry partners

Operating systems and compute

Synthesis and verification are pipelined across general-purpose hardware, so a full-layer job spreads over your cluster.

Named customer work

  • DRAM Curvilinear OPC

    Micron

    Presented curvilinear OPC on DimensionPPC for DRAM layers, covering mask synthesis, simulation-based verification and mask rule checks.

    Nobue Kosa, Member of Technical Staff, Advanced Mask Development, Recipe and Tool Development, Micron

    Watch the SURGE 2026 session

Lithography and TCAD process simulation

Lithography settles which shapes reach the wafer. TCAD process simulation picks them up from there, through etch, deposition and implant, and into a working device.

Explore TCAD simulation

Lithography papers and sessions

Read any of it without filling in a form.

  • Conference session2026

    Curvilinear OPC Applications

    Micron's curvilinear OPC work on DRAM layers, using DimensionPPC.

  • Journal articleFebruary 2006

    Athena/Optolith Simulation of Proximity Lithography

    Archival. Proximity printing without a projection system, and why the aerial image in the resist comes out as a distorted copy of the mask: the same effect proximity correction exists to cancel.

  • Journal articleFebruary 2003

    Optical Lithography Models in ATHENA

    Archival. The model set behind contact, proximity and projection lithography — Helmholtz solutions for complex refractive indices, beam propagation, and non-linear resist behavior.

  • Journal articleAugust 2000

    Exposure in complex nonplanar resist-substrate structures

    Archival. Reflection and notching over topography, and dose-dependent refractive index — the effects that make patterning over an existing structure harder than patterning on a flat wafer.

Licensing and support for lithography tools

  • Licensing options

    Time-Based Licensing: floating seats on terms of one to three years, with updates and technical support in the fee.

    See licensing options

  • Installation and OS support

    Licenses run from a server on your network; the installation guide covers setup.

    Read the installation guide

  • Documentation

    User manuals, reference guides and release notes for PPC and DimensionPPC.

    Browse documentation

  • Support portal

    File a case and follow its status in the portal; access needs a current maintenance contract.

    Go to Support and Downloads

Talk to our technical experts about one layer

Bring the layer, its node and whatever metrology you have. An application engineer will scope the calibration with you.

Talk to our Technical Experts

Lithography questions

Process proximity correction (PPC) makes a printed feature match its drawing. Exposure, resist and etch each move a feature's edges, so a line never prints exactly as drawn. PPC predicts that movement and pre-distorts the mask by the opposite amount. Silvaco's product for it is Process Proximity Compensation.

Optical proximity correction (OPC) corrects for what the optics do during exposure. PPC also accounts for resist, etch and mask effects, which shift the final dimension too. Silvaco's Process Proximity Compensation is an OPC suite whose process model covers that wider set, so it corrects toward the dimension you'll measure.

Computational lithography makes sub-wavelength features print correctly, which at an advanced node means every critical layer. Teams rely on it while qualifying a node, while preparing mask data for tape-out, and when a yield ramp stalls on a layer that won't hold its dimension.

Against your own measurements. You print test patterns, measure them with CD-SEM or other metrology, and adjust the model until its simulation reproduces the wafer. Silvaco's predictive process model fits resist, etch and mask behavior this way, so it describes your process, not a generic one.

They sit on either side of the same wafer. Lithography sets the printed pattern; Silvaco TCAD, including Victory Process, models what the fab does to it next. Both belong to Silvaco's AI-Driven Manufacturing unit alongside FTCO, which brings TCAD physics to fab engineers in real time.

Silvaco's PDK table lists support for its analog and custom IC tools. Lithography sits outside it, so for a mask flow the useful question is whether your layer type has been corrected before. Ask us that.

Published so far: PPC distributes synthesis and verification across general-purpose hardware. Share your cluster size and layer count and we'll size a run for you.

Silvaco's University Program licenses its tools to more than 200 universities for research and teaching, separately from commercial sales. Contact the program with your group's project to check.