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Etch Rate And Time Calculator

Work out etch rate and time instantly with clear inputs, formula shown and shareable results.

About Etch Rate And Time Calculator

Etch time is target depth divided by etch rate, but selectivity and uniformity determine whether the result is usable: mask loss is depth divided by selectivity, and rate non-uniformity across the wafer means some die are over-etched while others are under-etched at the same endpoint.

Formula

Etch time

t = depth / rate; mask loss = depth / selectivity; variation = depth x non-uniformity

Worked example

With the default values below, Etch Rate And Time Calculator returns Etch time of 7.08. Change any input above and every figure here is recalculated in your browser.

Inputs used

Target etch depth
850 nm
Etch rate
120 nm/min
Selectivity to mask
15 :1
Rate non-uniformity
4 %

Results

Etch time
7.08 min
Mask consumed
56.67 nm
Depth variation across wafer
34.00 nm
Recommended over-etch
42.50 s

Step by step

  1. 1Values used
  2. 2Etch time
  3. 3Etch time= 7.08 min
  4. 4Mask consumed= 56.67 nm
  5. 5Depth variation across wafer= 34.00 nm
  6. 6Recommended over-etch= 42.50 s

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why over-etch at all?

To clear residue in the slowest-etching regions. A 10% over-etch is typical, but it consumes more mask and can undercut or damage the underlying layer.

What limits selectivity?

The chemistry's ability to attack the film while sparing the mask and the stop layer. High-aspect-ratio features also suffer from aspect-ratio-dependent etch slowdown.

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