Please enter valid numeric values for all fields. Time cannot be zero.
Calculation Results
Total Material Removed:
Etch Rate (Å/min):
Etch Rate (nm/min):
Etch Rate (μm/min):
Rate per Second (Å/sec):
Understanding Etch Rate Calculations in Semiconductor Fabrication
In semiconductor manufacturing and materials science, calculating the etch rate is a fundamental process control step. Whether you are performing wet etching (using chemical baths) or dry etching (plasma etching like RIE), knowing precisely how fast material is being removed is critical for defining feature sizes and ensuring the integrity of the underlying layers.
What is Etch Rate?
Etch rate is the measure of how quickly a material is removed from the surface of a wafer or substrate during an etching process. It is typically expressed in units of distance per time, such as Angstroms per minute (Å/min) or Nanometers per minute (nm/min).
Etch Rate Formula
The calculation for etch rate is straightforward. It represents the change in film thickness divided by the duration of the etch process.
Etch Rate (R) = (Tinitial – Tfinal) / t
Where:
Tinitial = Thickness of the layer before etching.
Tfinal = Thickness of the layer after etching.
t = Duration of the etch process (time).
How to Use This Calculator
This tool normalizes unit conversions automatically, allowing you to input measurements in Angstroms, Nanometers, or Microns, and time in Seconds or Minutes. Here is a step-by-step guide:
Measure Initial Thickness: Use ellipsometry or reflectometry to measure the film thickness before the process.
Perform Etch: Record the exact duration of the etch process.
Measure Final Thickness: Measure the remaining film thickness. If the film cleared completely, check for over-etch time, though this simple calculator assumes a stop at the substrate interface or partial removal.
Calculate: Input these values to determine the rate.
Example Calculation
Imagine you are etching a Silicon Dioxide (SiO2) layer.
Initial Thickness: 5000 Å
Final Thickness: 3500 Å
Time: 2 minutes (120 seconds)
First, calculate the amount removed: 5000 Å – 3500 Å = 1500 Å.
Then, divide by the time in minutes: 1500 Å / 2 min = 750 Å/min.
Factors Affecting Etch Rate
Several variables can influence the etch rate, causing it to drift over time:
Concentration: In wet etching, the depletion of the etchant (chemical reactant) slows down the rate.
Temperature: Higher temperatures generally increase chemical reaction rates exponentially (Arrhenius relationship).
Agitation: Stirring or sonicating the bath improves the transport of fresh etchant to the surface.
Loading Effect: In dry etching, a larger exposed surface area can deplete reactants faster, lowering the rate (micro-loading).
Why Precision Matters
Accurate etch rate calculations ensure selectivity and prevent over-etching. If the rate is underestimated, the process may not remove enough material (under-etch), leaving circuits shorted. If overestimated, the etch may dig into the substrate or damage underlying device structures.
function calculateEtchRate() {
// Get input elements
var initialInput = document.getElementById('initialThickness');
var finalInput = document.getElementById('finalThickness');
var timeInput = document.getElementById('etchTime');
var initUnit = document.getElementById('initialUnit').value;
var finalUnit = document.getElementById('finalUnit').value;
var timeUnit = document.getElementById('timeUnit').value;
// Get output elements
var resultBox = document.getElementById('results');
var errorMsg = document.getElementById('errorMsg');
var removedRes = document.getElementById('removedRes');
var rateAngstromMin = document.getElementById('rateAngstromMin');
var rateNmMin = document.getElementById('rateNmMin');
var rateMicronMin = document.getElementById('rateMicronMin');
var rateAngstromSec = document.getElementById('rateAngstromSec');
// Parse values
var tInit = parseFloat(initialInput.value);
var tFinal = parseFloat(finalInput.value);
var timeVal = parseFloat(timeInput.value);
// Validation
if (isNaN(tInit) || isNaN(tFinal) || isNaN(timeVal)) {
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
}
if (timeVal = 10000) {
removedDisplay = (removedAngstrom / 10000).toFixed(4) + " μm";
} else if (Math.abs(removedAngstrom) >= 100) {
removedDisplay = (removedAngstrom / 10).toFixed(2) + " nm";
} else {
removedDisplay = removedAngstrom.toFixed(2) + " Å";
}
removedRes.innerText = removedDisplay;
rateAngstromMin.innerText = rateAperMin.toFixed(2);
rateNmMin.innerText = rateNmPerMin.toFixed(3);
rateMicronMin.innerText = rateMicronPerMin.toFixed(5);
rateAngstromSec.innerText = rateAperSec.toFixed(2);
resultBox.style.display = 'block';
}
function convertToAngstrom(value, unit) {
if (unit === 'angstrom') {
return value;
} else if (unit === 'nm') {
return value * 10; // 1 nm = 10 A
} else if (unit === 'um') {
return value * 10000; // 1 um = 10,000 A
}
return value;
}