Magnetron Sputtering Technology
Release Date[2013-9-25 15:46:02]    Total access[504]Times
 

Basic Sputtering Process

                There are many different ways to deposit materials such as metals, ceramics, and plastics onto a surface (substrate) and to form a thin film.  Among these is a process called SPUTTERING that has become one of the most common ways to fabricate thin films.  Sputtering is a physical vapor deposition (PVD) process used for depositing materials onto a substrate, by ejecting atoms from such materials and condensing the ejected atoms onto a substrate in a high vacuum environment.

                The basic process is as follows.  A target, or source of the material desired to be deposited, is bombarded with energetic ions, typically inert gas ions such as Argon (Ar+).  The forceful collision of these ions onto the target ejects target atoms into the space.  These ejected atoms then travel some distance until they reach the substrate and start to condense into a film.  As more and more atoms coalesce on the substrate, they begin to bind to each other at the molecular level, forming a tightly bound atomic layer.  One or more layers of such atoms can be created at will depending on the sputtering time, allowing for production of precise layered thin-film structures.

                Though the basic idea of operation is seemingly simple, the actual mechanisms at play are intricately complex.  Electrically neutral Argon atoms are introduced into a vacuum chamber at a pressure of 1 to 10 mTorr.  A DC voltage is placed between the target and substrate which ionizes Argon atoms and creates a plasma, hot gas-like phase consisting of ions and electrons, in the chamber.  This plasma is also known as a glow discharge due to the light emitted.  These Argon ions are now charged and are accelerated to the anode target.  Their collision with the target ejects target atoms, which travel to the substrate and eventually settle. Electrons released during Argon ionization are accelerated to the anode substrate, subsequently colliding with additional Argon atoms, creating more ions and free electrons in the process, continuing the cycle.

Magnetron Sputtering Process

                There are a number of ways to enhance this process.  One common way to do this is to use what is known as a magnetron sputtering system.  The main difference between this and a basic DC sputtering system described above is the addition of a strong magnetic field near the target area.  This field causes traveling electrons to spiral along magnetic flux lines near the target instead of being attracted toward the substrate.  The advantage of this is that the plasma is confined to an area near the target, without causing damages to the thin film being formed. Also, electrons travel for a longer distance, increasing the probability of further ionizing Argon atoms. This tends to generate a stable plasma with high density of ions. More ions mean more ejected atoms from the target, therefore, increasing the efficiency of the sputtering process. The faster ejection rate, and hence deposition rate, minimizes impurities to form in the thin-film, and the increased distance between the plasma and substrate minimizes damage caused by stray electrons and Argon ions.

                A way to measure target deposition rate is something called the SPUTTERING YIELD.  The sputtering yield is defined as the number of target atoms released per incident Argon ion with certain kinetic energy.  For example, if two target atoms are released per collision with an Argon ion, the sputtering yield is two.  For a comprehensive list of different sputtering yields for different targets, click here.

                To sputter conducting targets, a DC power supply is generally used.  For insulating or semiconducting targets, an RF power supply is required with an automatic or manual impedance matching network between the power supply and the sputtering gun.  Micro Magnetics recommends an automatic network for an RF power supply. Micro Magnetics magnetron sputtering guns are designed to work with any DC and RF power supplies for sputtering applications. We do recommend customers use the DC and RF power supplies marketed on our online store.They offer excellent functionality, ease of use, stability, and compatibility.

 

 


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