- Sheet resistance RS is defined as

Here rho represents resistivity, and t represents thickness of conductive (metal) layer.

- So thickness of conductive layer t is

- Since correlation between conductivity σ and resistivity ρ is as followed

Metal Layer Thickness Measurement by Eddy Current Testing

Eddy current thickness gauges are applied across many industries measuring film thicknesses from a few nanometers to hundreds of micrometers or even millimeters. The underlying principle relies on the induction of eddy currents in metal films in all vertical present conductive elements. Each vertically stacked metal atom within a metal film contributes to the metal film's ability to transport electrical currents. This ability is described as sheet resistance and it correlates with metal thickness. Very thin metal films are analyzed by high frequency eddy current (< 100 MHz) sensors and very thick material films by low frequency eddy current sensors (> 10 kHz). Eddy current thickness gauges are calibrated directly to metal thicknesses of specific metal materials or use the metal thickness correlation to the sheet resistance. System deliveries are typically ready-to-use for various metal thickness measurement tasks. Especially, thick metal films are often measured by eddy current testing since optical measurements such as ellipsometry and reflectometry cannot be applied because they rely on a certain non-transparency. The user value derives especially from its robustness and its ability to measure in a contactless mode. The key benefits are:

√  Contact-free

√  Robustness

√  Well automatable for inline and in tool measurements

√  Ultra fast (20 ms / measurement)

√  Transmission mode and reflective mode gauges

√  High repeatability and accuracy

√  Measurement through encapsulation

√  Measurement of non-transparent metal films

√  Large measurement range 2 nm to 2 mm (depending on conductivity)

Benchtop Device

for Single Point Measurements

Tasks:

Fast and high-precision,stationary random sample measurement of production quality at incoming and outgoing goods or before and after a production step to determine product quality in order to draw conclusions about process quality and stability. particularly large elements.

Handling:

The specimen is positioned centered on the measuring field.The measured value is displayed immediately in the software.

If several measuring points on the specimen are of interest,the software supports the creation of a manual mapping with an input matrix.

Result:

The result is a single mearurement value,a manual multiple measurement in the form of a matrix or even a line profile.

Benchtop Device

for Full Area Images

Tasks:

Very detailed because full surface information of the product quality,in order to draw conclusions on the process quality and stability,as well as for the optimizaton of the process (use of resources,process speed) and the product (improvement of homogeneity,adherence to minimum values).

Handling:

The sample is positioned centered on the measuring field.Prefabricated holders are available for wafers,which guarantee centered support.Insert the sample.Close the flap and press"Start measurement".

Result:

The result is a false image representation of entire layere to be measured consisting of many thousands of individual measured values.

Handheld Device

for Single Point Measurements

Tasks:

Fast random measurements of product quality at good receipt and after production of particularly large elements.

Handling:

The handheld uints is placed on the object to be examined.Then the"Measure"button is pressed and after one second the measured value appears on the dispaly.

Result:

The result of a mearurement is the value of the measured point.

Inline-System

for Continuous Single Point

Measurements

Tasks:

Continuous information acquisition about process quality and stability as well as product quality before and/or after a production step.

production automation based on sensor information.

Handling:

The inline system is integrated into existing production line.The operator starts the measurement recording and the software stores all data in a datebase.

Result:

Depending on the configuraion,the result is one or more line profiles,centered or at noralgic points on the layer to be examined.

Typical coatings are

- Aluminum Al, Aluminum-Titanium Al-Ti, Aluminum oxide Al2O3

- Cadmium Telluride CdTe, Cadmium Selenide CdSe, Cadmium Sulphide CdS

- Chromium Cr, Chromium-Molybdenum Cr-Mo, Chromium-Titanium Cr-Ti, Chromium-Tungsten Cr-W,  Chromium-Vanadium Cr-V, Chromium-Molybdenum-Tantalum Cr-Mo-Ta

- Cobalt Co, Cobalt-Chromium-Tantalum-Boron, Cobalt-Iron-Boron Co-Fe-B

- Copper Cu, Copper alloys

- Indium Tin oxide (ITO, In2O3-SnO2)

- Iron Fe, Iron-Cobalt-Boron Fe-Co-B, Iron-Tantalum-Carbon Fe-Ta-C

- Gold Au, Gold-Silver Au-Ag, Gold-Palladium Au-Pd, Gold-Platinum Au-Pt

- Molybdenum Mo, Molybdenum-Tungsten Mo-W, Molybdenum-Niobium Mo-Nb, Molybdenum-Silicon Mo-Si

- Niobium Nb,

- Nickel Ni, Nickel-Chromium Ni-Cr, Nickel alloys

- Platinum Pt, Platinum-Palladium Pt-Pd, Platinum-Silver Pl-Ag

- Ruthenium Ru, Ruthenium-Aluminum Ru-Al

- Silicon Si, Silicon-Aluminum Si-Al, Silicon dioxide SiO2

- Silver Ag

-Tantalum Ta, Tantalum pentoxide Ta2O5, Tantalum-Silicon TaSi

-Tin Sn

- Titanium Ti, Titanium oxide TiOx, Titanium-Aluminum Ti-Al, Titanium-Tungsten Ti-W

- Terbium-Iron-Cobalt Tb-Fe-Co and many other alloys.

- Tungsten W, Tungsten-Silicon W-Si

- Zinc Zn, Zinc sulfide ZnS, Zinc-Aluminum Zn-Al

- Zirconium Zr, Zirconium boride ZrB2