Old-school lithium niobate engineering: diamond scribers and cowboy-style HF acid etching

jwt0625 · x · 2026-11-08

The author shows a bare wafer sitting on an optical breadboard as a "wafer level test setup" — uLEDs still on the sapphire wafer, driven with a probe and Mini-Circuits bias tee — illustrating how differently things are done across eras and industries.
Industry anecdotes: before thin-film lithium niobate (TFLN) replaced bulk LN, engineers scribed chip/wafer names on the wafer backside with a diamond scriber; proper lithography labels are standard now.
Even wilder: to inspect poling domains via HF etch (etch rates differ along +z vs -z crystal axes), engineers would place the wafer on paper, pour HF on it, and rely on surface tension to keep the acid contained — a genuinely cowboy-style process.

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