Transparent pattern characterization by DHM® is a unique solution to measure 3D topography and thicknesses of transparent structures on a reflective substrate.
The 3D topography as well as the thicknesses and refractive indices of patterned transparent samples are retrieved by a dedicated post-analysis software by computing the complete reflected wavefront based on the laws of physics. Therefore DHM® provides a solution to measure the correct topography while measurements with alternative optical profilometer are affected by the multiple reflections of the light signal occurring in transparent materials. Structures of Transparent materials such SiO2 and thin metal layers, widely used in coating, isolating, protective or structuring layers in semiconductor and MEMS industries, are typical samples easily characterized by DHM®. Dynamical topography of liquids on microfluidics devices and on functional surfaces is critical to characterize because of multiple interferences occurring between the liquid and the substrate. DHM® with the Reflectometry analysis software enables to provide accurate dynamical measurements. This solution encompasses a holographic microscope instrument by Lyncée Tec with a full range of microscope objectives, the dedicated Koala acquisition and analysis software and the dedicated Reflectometry post-analysis software.
DHM® technology and its dedicated Reflectometry post-analysis software offer significant benefits.
Features | DHM® | Mechanical profilometer |
Non-damaging | ||
Non-scanning | ||
Soft materials & liquids | ||
Topography measurement | no scanning | XY scanning |
Measurement of refractive index | ||
Measurement of dynamical and moving sample |
Features | DHM® | Ellipsometer |
Non-scanning | ||
Thickness measurement | [10nm – 50μm] transparent materials |
[0.1nm – 0.01mm] non-metals
[0.1nm – 50nm] metals
|
Measurement of refractive index | ||
Topography measurement | w/o scanning | XY scanning |
Measurement of dynamical and moving sample | ||
Lateral resolution | ++ objective resolution | – limited by laser spot diameter |
Cost competitive | ++ | – |
Spectral Reflectance (SR) analyzes reflected light and determines the thickness and dielectric constant of films. The main difference between Ellipsometry and SR is that the first one uses light reflected at low incident angle, while the second uses light reflected perpendicular (normal) to the surface of the sample. SR is a simple and low-cost instrument but measurements are not instantaneous since a spectral analysis has to be performed. Moreover, it requires a lateral XY scanning to retrieve 3D information. SR usual application is films with a limited numbers of layers, and with thickness larger than 10 μm.
Features | DHM® | Spectral Reflectance |
Non-scanning | ||
Thickness measurement | [10nm – 50μm] transparent materials |
[1nm – 1mm] non-metals
[0.5nm – 50nm] metals
|
Measurement of refractive index | ||
Topography measurement | w/o scanning | XY scanning |
Measurement of dynamical and moving sample | ||
Lateral resolution | ++ objective resolution | – limited by laser spot diameter |
DHM® Reflectometry analysis does not require discrimination of each layer interface. It considers the global reflected signal and uses the laws of optics to provide accurate measurement of thicknesses from a few nanometers to several microns. Moreover, without any scanning, DHM® retrieves the 3D topography of transparent patterns with interferometric resolution as well as the refractive index.
Features | DHM® | CLSM |
Non-scanning | ||
Thickness range | 10nm – μm | >um |
Topography measurement | ||
Measurement of refractive index | ||
Measurement of dynamical and moving sample | ||
Complete reflected signal considered |
Features | DHM® | WLI |
Use of monochromatic light source | ||
Non-scanning | ||
Thickness range | 10nm – μm | >um |
Topography measurement | ||
Measurement of refractive index | limited | |
Measurement of dynamical and moving sample | ||
Large collection of objectives from standard optical microscopy |
In 2009, on request of a DHM® user measuring SIMS, Lyncée Tec has developed the solution to interpret optical measurement of samples with transparent structures. Since then, the Reflectometry analysis software has been continuously improved with new features and tools. Among many samples, Lyncée Tec has published the comparative measurements of geometrical topography for the following sample configurations: