Sputtering Targets

Precious metals for physical vapor deposition (PVD) has historically been the realm of juggernaut corporations with customer service and product pricing to match. Experience the difference with a focused, financially strong company built on customer responsiveness.

Tell us what technical and commercial variables for thin film coatings are most important for your company. Whether it be fabrication cost, metal management, grain structure, material purity, something else, or a combination thereof, RSC delivers a sputter target that best meets our customer’s needs, not our convenience.

Standard Available Rotatable Targets

• Gold (Au) Targets – 4N (99.99%), higher purities available on request
• Silver (Ag) Targets – 4N (99.99%), higher purities available on request
• Platinum (Pt) Targets – 4N (99.99%)
• Palladium (Pd) Targets – 3N5 (99.95%)

Technical & Quality Considerations

Reliable Corporation employs processes designed to achieve a homogeneous grain structure to maximum sputter rate uniformity on to your substrate. Processes also minimize incorporation of oxygen into the target. We use proprietary quality controls to characterize and lock-in specific processes for specific part numbers. The same quality controls can be used to certify product is free from voids, inclusions, and meets purity requirements.

Technical Capabilities

We specialize in rotatable targets ranging in length from 500 mm to 3,897 mm (approximately 20 inches to 153 inches). Target thicknesses of up to 15 mm are also within our capabilities. However, it is important to consider the total weight of the target during equipment design and process planning, as longer silver rotatable targets can become quite heavy.

• In architectural glass coaters using targets that are 3,191 mm or longer, very thick silver coatings can sometimes lead to slight sagging in the middle of the target due to weight. This can affect coating uniformity. Fortunately, this issue is generally not a concern for shorter targets under 2 meters in length.

Our thermal spray process has been specifically selected and optimized to maintain low oxygen content in the coatings. After evaluating a range of manufacturing methods—including thermal spray, cold spray, casting, and other rotatable target production techniques—we chose this process for its optimal balance of cost-efficiency and desirable technical properties.

Available Targets

Applications

Applications include web coaters and large area glass coaters, where our silver rotary targets have been successfully used in low-E glass coating stacks, window films, anti-bacterial coatings, and high temperature superconductors.

Additional Considerations

Reclaim of residual coatings is also a part of the complete cost of ownership. In some instances, it’s also economical to re-use the backing tubes. Silver alloys with gold, indium, tin, copper and other elements are possible.

What is Evaporation for Thin Film Coatings?

Evaporation is a form of physical vapor deposition (PVD) where material is heated to a high vapor pressure, often in molten state. The vapors are then condensed on to a substrate to form a desired thickness of a thin film. In our case, a thin film precious metal coating. The heating is typically accomplished via resistive heating or by E-beam (electron beam).

Why Use Materials Engineered Specifically for Evaporation?

Engineered pellets or slugs are manufactured with specific form factors intended to vaporize at known rates. Often during evaporation processes, “spitting” results in liquid droplet material splattering on to the substrate. Engineered pellets are made with specified metal purities and processes intended to minimize incorporated gases and impurities to mitigate “spitting” in process.

Technical Notes / Parameters

A quartz crystal microbalance (QCM) is widely used to monitor deposition thickness during process. A QCM is based on a reverse piezoelectric effect such that a mechanical strain or deflection occurs when an electric field (voltage) is applied to the quartz. In the case of a QCM, the electric field is alternating in voltage, thus causing the crystal to vibrate at its resonant frequency inherent to quartz. As a thin film coating builds on the quartz crystal, its mass changes. This results in a change in the vibration or frequency of oscillation.

Two additional factors come into place in order to correct the QCM. The QCM is designed to be in the chamber aside from the substrate, otherwise one or the other would shadow the deposition of the other.

• The tooling factor is a situation or design specific factor which is a consequence of the chamber design and specifically the placement of the sensor and substrate in relation to each other.  The tooling factor is a calibration of deposition rate on the sensor compared to what is actually occurring on the substrate.
• The Z-factor, also known as z-ratio, is inherent to the material being evaporated.  The Z-factor is essentially a correction factor to account for the fact that the resonant frequency and density of a particular material deposited on the quartz crystal is not the same as quartz, but rather at some ratio to quartz.

What is Target Bonding?

Target bonding involves securely attaching (bonding) a sputtering target to a backing plate to ensure stability, optimal heat transfer, and good electrical contact. Without proper bonding, the target may crack, warp, or delaminate resulting in poor film quality, process interruption, substrate and equipment damage. RSC employs ultrasonic scanning of the bond to ensure good quality control of the bonding layer.

Why Proper Target Bonding is Important for Deposition Materials

• Enhanced Heat Dissipation: A bonded target enables good heat transfer to the cooled backing plate, preventing overheating, and allowing higher sputtering power and faster deposition rates.
• Mechanical Stability: Choice of backing plate and type of bonding can accommodate and minimize thermal expansion mismatches between the backing plate and target material. There can also be substantial cooling water pressure on the backside of the backing plate. A rigid backing plate of sufficient thickness can allow good thermal contact to the backside cooling while be rigid enough to avoid warping.
• Economics: Especially with precious metals, for cost and working capital reasons it is often desirable to have a thin target material. An appropriate backing plate becomes the rigid base for the thin target material.
• Common Approach: C10100 grade of copper (Cu) is commonly used for a backing plate material, especially for precious metals. This alloy code designates high purity Cu >99.99% pure. It is often known as OFE (oxygen free electronic) Cu or otherwise known as OFHC Cu (oxygen free high conductivity). The bonding agent is typically an indium based material.
  • Other backing plate materials, Cu alloys, or different bonding agents can be considered for particular challenges. Please call and speak with an engineer to discuss specific circumstances.