---
title: Optical Thickness and Flatness Measurement of Bonded Silicon Wafer Assemblies
description: "Lumetrics Engineering Application Note: Optical thickness and flatness measurement of bonded silicon wafer assemblies by Kyle Hadcock"
---

[Blog | Lumetrics ](https://www.lumetrics.com/blog)

# [Optical Thickness and Flatness Measurement of Bonded Silicon Wafer Assemblies](https://www.lumetrics.com/blog/non-contact-thickness-measurement/optical-thickness-and-flatness-measurement-of-bonded-silicon-wafer-assemblies)

 Written by [Kristin Hart Daly](https://www.lumetrics.com/blog/author/kristin-hart-daly) | January 18, 2017

***<https://www.lumetrics.com/hubfs/Imported_Blog_Media/optical-thickness-and-flatness-measurement.png>Abstract*—**The silicon wafer manufacturing process relies heavily on precision polished wafers that have uniform thickness and, depending on the application, also control parallelism to a secondary wafer after bonding.  
 Lumetrics’ low coherence interferometer, commercially marketed as OptiGauge II, is a device capable of measuring the simultaneous wafer thickness, adhesive thickness, and parallelism between surfaces to sub-micron precision. Combined with custom software and a precision XY raster scanner, a wafer or wafer assembly can be fully characterized with respect to layer thicknesses and surface parallelism.  
**Index Terms**—adhesive, flatness, interferometry, metrology, optical thickness measurement, parallelism, silicon, wafer

I. Introduction:

Lumetrics is the market leader in providing high-precision, non-contact optical thickness measurements to medical, scientific, and ophthalmic industries.

A unique capability of our flagship thickness measurement device, OptiGauge II, is its ability to measure the individual layer thickness of a multiple-layer sample.

The OptiGauge II measures using a 1310nm wavelength. This is an ideal wavelength for measuring through nearly all visually transparent and semi-transparent objects.

A visually opaque material that is highly transmissive at 1310nm is silicon. This makes silicon an ideal sample for optical thickness measurement.

[Download the application note now!](https://info.lumetrics.com/optical-thickness-and-flatness-measurement-app-note)

[View full post](https://www.lumetrics.com/blog/non-contact-thickness-measurement/optical-thickness-and-flatness-measurement-of-bonded-silicon-wafer-assemblies)

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