10 Questions You Should to Know about tantalum sputtering targets

The life of a sputter target is typically quantified in terms of units of power and time, like kilowatt/hours. For a target being sputtered at 500 watts for a total duty cycle of 100 hours that’s 50 kilowatt/hours. Target life is also a function of the sputter yield of the material or how many target atoms are ejected for each gas ion (typically argon) that strikes the surface. For example when an argon ion with a mass of 39.948, hits a light material, like carbon, with an atomic mass of 12.01, about 3 carbon atoms are ejected. For materials like platinum with an atomic mass of 195.09, nearly 5 argon ions have to strike the target to get one platinum atom out (Ref 1).

Other factors that affect sputter yield include the bias voltage used to accelerate the argon ion to the target surface and the incident angle of the collision. In addition, there are big differences in sputter yield for metals verses oxides. Typically oxides will last many more kilowatt/hours than metals like aluminum.

One of our resident thin film deposition experts, Rob Belan, recommends that a target be replaced when the trench depth of the race track is ¾ of the total target thickness. For a ¼″ thick target there will be 0.062″ of material remaining at the bottom of the trench. He adds that if you are particularly careful you may be able to sputter the trench to a thickness of 0.031″, but beyond that you are risking a complete burn through.

A handy online calculator for sputter yield can be found at TU Wein’s Institute fur Angewandte Physik. I’m not sure how accurate it is, but it does list out several single element metals and their yields:

https://www.iap.tuwien.ac.at/www/surface/sputteryield

For a list of sputter yields using other ions, such as xenon and neon, there is an expansive data base on the web site of the National Physical Laboratory. Their data base also includes sputter yields at various powers (Ref 2).

So to determine when it is time to change out a sputter target you will need to have a depth gauge, either digital or dial. Check the depth of the trench in the race track after every deposition until you get a feel for the number of kilowatt/hours it takes to thin the target out to 25% of its original thickness (Ref 3). For those looking for an in-situ, real time method for measuring target thickness during sputtering, check out the publication from Alex Leybovich of TOSOH SMD who used ultrasonic time of flight measurements to monitor the health of sputter targets and target bonding during thin film depositions (Ref 4).

References:

1. Argonne National Laboratory, “Noble Gas Sputtering Calculations using TRIM,” https://www.osti.gov/biblio/
2. National Physical Laboratory of the UK, http://www.npl.co.uk/science-technology/surface-and-nanoanalysis/services/sputter-yield-values
3. MSC Direct, https://www.mscdirect.com/browse/Measuring-Inspecting/Dimensional-Measuring-Tools/Depth-Gages/?navid=&cid=ppc-bing-New%20-%20Measuring%20%26%20Inspecting%20-%20Product%20-%20PPC%20-%20Exact_I4PUCfCI_depth%20gauge_be__c_&mkwid=I4PUCfCI|dc&pcrid=&utm_source=bing&utm_medium=cpc&utm_campaign=New%20-%20Measuring%20%26%20Inspecting%20-%20Product%20-%20PPC%20-%20Exact&utm_term=depth%20gauge&utm_content=Depth%20Gages
4. In-situ real time sputtering source health monitoring using ultrasonics, Alex Leybovich, TOSOH SMD, Grove City, OH, , https://www.sciencedirect.com/science/article/pii/S?via%3Dihub

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Category: Deposition Equipment

Sub-Category: Sputtering Targets

Related Topics: Sputtering, Process

When it comes to thin film deposition techniques like sputtering, the choice of material for sputtering targets is crucial. Each material brings its unique properties and advantages to the table, making it suitable for specific applications.

One type of sputtering target includes pure metal targets. In this post, we will briefly explore different types of sputtering targets, highlighting their characteristics and common uses.

What Are Pure Metal Targets?

Pure metal sputtering targets, as opposed to alloy sputtering targets, are made out of elemental metals. These are typically available in very high-purity grades, such as 99.999% purities, which ensures minimal contamination in thin film sputtering processes. For coatings that need to have a specific degree of hardness, flexibility, or wear-resistance, you may want to look at the different properties of pure metal coatings.

Image: sputter coater process in a lab

Metals have a wide range of characteristics, but generally, different metals are used for precise depositions of coatings for their high electrical conductivity for electronics. Another common utilization is for their reflective properties, making them see use for optical device manufacturing.

For more details, here are some types of metal sputtering targets that see widespread use:

Chromium Targets

Material Characteristics: Chromium (Cr): Known for their excellent corrosion resistance and hardness. They form a protective oxide layer when exposed to air, making them ideal for applications requiring durability and resistance to wear.

Common Uses: Chromium sputtering targets are often used in the aerospace and automotive industries to create protective coatings on components, such as engine parts and decorative trim.

If you want to learn more, please visit our website graphite target.

Copper Targets

Material Characteristics: Copper (Cu): Highly conductive and have good adhesion properties. They are also known for their thermal conductivity and are relatively easy to work with.

Common Uses: Copper sputtering targets are widely used in the semiconductor industry to create interconnects and circuitry on integrated circuits (ICs) and printed circuit boards (PCBs).

Gold Targets

Material Characteristics: Gold (Au): Renowned for their superior electrical conductivity and optical properties. They have excellent reflectivity in the visible and infrared spectra.

Common Uses: Gold sputtering targets are used in various industries, including electronics, aerospace, and optics, for applications such as producing conductive coatings, reflective layers, and decorative finishes.

Iron Targets

Material Characteristics: Iron (Fe): Fundamental in the deposition of ferromagnetic thin films.

Common Uses: Iron sputtering targets contribute to applications in electronics, data storage, and sensing. This includes devices such as hard drives and magnetic sensors.

Tantalum Targets

Material Characteristics: Tantalum is valued for its high melting point and excellent conductivity. This material is also highly resistant to corrosion and have low vapor pressure, making it suitable for high-temperature applications.

Common Uses: Because of this, tantalum sputtering targets find their place in the electronics industry, where they are used to create thin films for capacitors and semiconductors.

Tungsten Targets

Material Characteristics: Tungsten (W): Boasts an extremely high melting point, excellent mechanical strength, and low vapor pressure. They are ideal for applications that require resistance to high temperatures and wear.

Common Uses: Tungsten sputtering targets are crucial in the aerospace, automotive, and solar industries for depositing films that provide thermal protection and durability, as well as in creating high-temperature superconductors.

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