/ 
Physics-Etch-0.01
/ README.md

Physics::Etch

A Perl module that models both wet (isotropic, chemically driven) and dry (anisotropic, plasma / RIE / ion) semiconductor etch processes, with a small built-in database of materials and etch recipes.

It computes etch rate, anisotropy, feature profile (undercut, etch bias, sidewall angle, aspect ratio), clear time and over-etch, mask selectivity / survival, substrate over-etch, and across-wafer uniformity — and prints a readable process report.

It also includes a pattern / reactor toolkit that models pattern-dependent anisotropy and loading: a self-contained GDSII reader/writer for the resist mask, layout geometry analysis (open area, per-feature CD, density map), a chamber model (reactor geometry → DC bias, ion energy, mean free path, residence time), loading effects (macro, micro and aspect-ratio-dependent ARDE / RIE-lag), and a simulation that ties them together for per-feature results.

Disclaimer: the embedded rates, activation energies and selectivities are illustrative, order-of-magnitude teaching values, not process specifications. Every value is overridable at call time.

Layout

lib/Physics/Etch.pm            facade + material/recipe database + factories
lib/Physics/Etch/Material.pm   material (film / mask / substrate)
lib/Physics/Etch/Etchant.pm    etchant / chemistry descriptor
lib/Physics/Etch/Process.pm    base class: geometry, selectivity, reporting
lib/Physics/Etch/WetEtch.pm    wet model  (Arrhenius, isotropic)
lib/Physics/Etch/DryEtch.pm    dry model  (power/pressure/bias, anisotropic)
lib/Physics/Etch/GDSII.pm      GDSII stream reader/writer (+ hierarchy flatten)
lib/Physics/Etch/Layout.pm     mask geometry: open area, CDs, density map
lib/Physics/Etch/Chamber.pm    reactor geometry -> plasma conditions
lib/Physics/Etch/Loading.pm    macro / micro loading + ARDE (RIE lag)
lib/Physics/Etch/Simulation.pm pattern+chamber+loading -> per-feature etch
examples/                      runnable scripts (one per material + toolkit)
t/                             Test::More suite (145 tests)

Quick start

use Physics::Etch;

# Patterned copper, wet ferric-chloride etch
my $cu = Physics::Etch->wet_etch('copper',
    thickness      => 500,     # nm
    temperature    => 40,      # degC  (Arrhenius speed-up)
    feature_cd     => 3000,    # nm mask opening
    mask_thickness => 1500,
    overetch       => 0.30,
);
print $cu->report;

# Silicon-nitride RIE
my $sin = Physics::Etch->dry_etch('silicon_nitride',
    thickness => 200, feature_cd => 250,
    power => 250, pressure => 25, bias => 300,
);
print $sin->report;

Run a full report from the command line:

perl -Ilib examples/etch_copper.pl

The physics

Wet etch (WetEtch) — chemical, essentially isotropic:

R(T) = rate * exp( (Ea/kB) * (1/Tref - 1/T) ) * concentration * agitation
lateral = R * isotropy            # isotropy defaults to 1.0 -> full undercut

Isotropy makes lateral rate ≈ vertical rate, so undercut ≈ etch depth and sidewalls are sloped/rounded (~45°). Strong temperature activation (Arrhenius) is the main rate knob.

Dry etch (DryEtch) — directional plasma / RIE, tunable anisotropy:

Rv = rate * (P/Pnom)^0.8 * (p/pnom)^0.3 * (Vb/Vbnom)^0.5 * loading * arrhenius
A_eff  = 1 - (1 - A_nom) * (p/pnom) * (Vbnom/Vb)      # clamped to [0,1]
lateral = Rv * (1 - A_eff)

Directional ion bombardment (high DC bias, low pressure) drives vertical etching and steep sidewalls; high pressure / low bias lets radicals attack laterally, lowering anisotropy and increasing undercut. An optional Arrhenius term models hot dry etches (e.g. Cu in Cl₂).

Derived by the base class (Process): time_to_clear, etch_time (clear × (1 + over-etch)), etch_depth, undercut, anisotropy, profile (top/bottom width, etch bias, sidewall angle, aspect ratio), mask_loss / mask_survives, substrate_overetch, uniformity_report, and report.

Pattern-dependent anisotropy, loading & chamber tools

The toolkit models how the resist pattern (from a GDSII file) and the reactor combine to make etching feature-dependent.

use Physics::Etch;
use Physics::Etch::Loading;

my $etch    = Physics::Etch->dry_etch('silicon_nitride', thickness => 200);
my $chamber = Physics::Etch->chamber(
    wafer_diameter_mm => 200, gap_cm => 2.5,
    pressure_mtorr => 20, power_w => 300, flow_sccm => 80,
    gas => 'SF6', gas_mass_amu => 146, gas_diameter_m => 4.8e-10);
my $layout  = Physics::Etch->layout_from_gds('mask.gds',
    layer => 1, structure => 'TOP', tone => 'clear', field => [200,200]);
my $loading = Physics::Etch::Loading->from_chamber($chamber, arde_length => 5);

my $sim = Physics::Etch->simulate(
    process => $etch, chamber => $chamber,
    layout  => $layout, loading => $loading);
print $sim->report;               # per-CD anisotropy, undercut, RIE lag

Examples

| Script | Material | Process shown | |---|---|---| | etch_copper.pl | Patterned copper | wet FeCl₃ vs dry Ar ion-mill (undercut) | | etch_photoresist_strip.pl | Photoresist | wet solvent / piranha strip | | etch_photoresist_ash.pl | Photoresist | dry O₂ plasma ash + RIE trim | | etch_aluminum_silicide.pl | Aluminum silicide | dry Cl₂/BCl₃ RIE (vs wet PAN undercut) | | etch_tantalum.pl | Tantalum | dry SF₆ RIE (pressure/bias tuning) | | etch_titanium.pl | Titanium | wet dilute-HF (SiO₂ selectivity) | | etch_silicon_nitride.pl | Silicon nitride | wet hot H₃PO₄ (high Ea) + CF₄/O₂ RIE | | etch_polyimide.pl | Polyimide | dry O₂ RIE thick-film via etch | | make_sample_mask.pl | — | writes sample_mask.gds (mixed CDs + densities) | | etch_gdsii_simulation.pl | Silicon nitride | GDSII-driven per-feature anisotropy + RIE lag | | etch_loading_effect.pl | Aluminum silicide | macro (open-area) & micro (density) loading | | etch_chamber_geometry.pl | Silicon nitride | reactor geometry → bias / mfp / anisotropy |

Running the tests

prove -Ilib t/

Install locally

With ExtUtils::MakeMaker:

perl Makefile.PL
make
make test
make install

On Windows with Strawberry Perl, use gmake instead of make if needed.

Build and upload to CPAN

  1. Build a release archive:
perl Makefile.PL
make dist

This creates Physics-Etch-0.01.tar.gz.

If make dist fails because gzip is unavailable on Windows, create it with:

perl -MIO::Compress::Gzip=gzip -e "gzip 'Physics-Etch-0.01.tar' => 'Physics-Etch-0.01.tar.gz' or die $IO::Compress::Gzip::GzipError"
  1. Upload the tarball to PAUSE:

After indexing completes, install from CPAN with:

cpanm Physics::Etch

Extending

Add a material to %MATERIAL and a recipe hash to @RECIPE in lib/Physics/Etch.pm, or bypass the database entirely and construct Physics::Etch::WetEtch / Physics::Etch::DryEtch directly with your own rate, Ea, anisotropy, etc.