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 2007 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/435114
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=12107671&cid=ppc-bing-New%20-%20Measuring%20%26%20Inspecting%20-%20Product%20-%20PPC%20-%20Exact_I4PUCfCI_depth%20gauge_be_73667346999721_c_&mkwid=I4PUCfCI|dc&pcrid=73667346999721&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, 2007, https://www.sciencedirect.com/science/article/pii/S0257897206008905?via%3Dihub
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Category: Deposition Equipment
Sub-Category: Sputtering Targets
Related Topics: Sputtering, Process
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Link to Acetron The lifetime of a sputtering target is typically quantified in terms of units of power and time, such as kilowatt/hours. The life of a sputter target depends on the power at which it is being sputtered and the total duty cycle. For example, a target being sputtered at 500 watts for a total duty cycle of 100 hours would result in 50 kilowatt/hours of usage. The size and shape of sputtering targets can vary greatly depending on the nature of the thin film being created. The smallest targets can be less than one inch (2.5 cm) in diameter, while the largest rectangular targets can reach lengths well over one yard (0.9 m). In some cases, larger sputtering equipment may require segmented targets that are connected by special joints. Manufacturing processes for sputtering targets depend on the properties of the target material and its application. Common fabrication methods include vacuum melting and rolling, hot-pressed, special press-sintered process, vacuum hot-pressed, and forged. Sputtering targets can be fabricated into various shapes and sizes, with circular and rectangular targets being the most common. Other shapes, such as square and triangular designs, can also be produced. The sputter yield is an important factor in the lifetime of a sputtering target. The sputter yield refers to the average number of atoms ejected from the surface of the target material by the collision of each ion. The energy of sputtered atoms can vary widely, typically ranging from tens of electron volts to 600 eV. Approximately one percent of the ions that hit the surface of the target material have a ballistic impact and return to the substrate, causing re-sputtering. Overall, the lifetime of a sputtering target depends on factors such as power usage, duty cycle, target material properties, and sputter yield. Manufacturers are continuously researching and developing new types of sputtering targets, such as rotatory targets, to achieve higher utilization rates and improve the efficiency of sputter coating processes. Looking for high-quality sputtering targets for your laboratory? Look no further than KINTEK! With our wide range of sizes and shapes, we have the perfect target for your sputtering equipment. Our targets are designed to have a long lifetime, measured in kilowatt/hours, ensuring efficiency and cost-effectiveness. Whether you need small, one-inch targets or large, rectangular ones, we have got you covered. Trust KINTEK for all your sputtering target needs. Contact us today to learn more! For more planar sputtering targetsinformation, please contact us. We will provide professional answers.