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Film Thickness Uniformity Calculator
Paste your thickness measurements and see half-range, range, and sigma uniformity in a single view. The same wafer data produces three different percentages — this tool shows all of them so you can compare directly.
Any unit, one shared unit. Separate with commas, spaces or new lines.
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How it is calculated
Enter thickness values separated by commas, spaces, or new lines. Any unit works as long as every value shares that unit. You need at least two points.
The calculator reports count (n), mean, min, max, and range (max − min), then derives three uniformity metrics. Half-range: (max − min) / (2 × mean) × 100 %, expressed as ± %. Range: (max − min) / (max + min) × 100 %. Sigma: 1σ / mean × 100 % and 3σ / mean × 100 %, where 1σ is the sample standard deviation (n − 1 denominator).
Range-based formulas — half-range and range — depend only on the two extreme values, so a single outlier swings the result. Sigma-based uniformity uses every measurement point and reflects the full distribution.
Because the three formulas return different numbers for identical data, always state which formula you used, the number of measurement points and their pattern, edge exclusion, and whether the result is within-wafer (WIW) or wafer-to-wafer (WTW). Also specify whether you report uniformity or non-uniformity.
Limits to keep in mind
- The 1σ here is the sample standard deviation (n − 1 denominator). Some metrology tools use the population standard deviation (n denominator); with few measurement points the two can differ noticeably.
- This calculator processes the numbers you enter. It does not account for measurement noise, wafer orientation, or spatial patterns in the data.
FAQ
- What is the difference between half-range and range uniformity?
- Half-range divides the spread (max − min) by twice the mean and is written as ± %. Range divides the same spread by (max + min). For the same data the two give slightly different numbers.
- Should I report uniformity or non-uniformity?
- Conventions vary by fab and tool. Some print uniformity (how similar values are), others print non-uniformity (how spread out they are). Always specify which convention you used.
- Why does sigma-based uniformity differ from range-based?
- Sigma uses every data point to compute the standard deviation, while range-based metrics use only the maximum and minimum. A single outlier shifts range-based results heavily but affects sigma less.
- How many measurement points do I need?
- The minimum is two, but more points give a more representative result. Report the point count and measurement pattern alongside your uniformity number.
Read the full article
Need the map, not just the number? Semi Process Lab predicts a 300 mm uniformity map from your CVD conditions and shows which variables drive it.
Predict the full wafer map