**4. Types of sputtering deposition**

There are many sputtering deposition processes like Gas flow sputtering/Glow discharge sputtering deposition, Ion beam sputter deposition (IBSD), Reactive sputter deposition, Ion-assisted deposition, Magneton sputter deposition and Radio frequency (RF) sputter deposition etc.

Few mechanisms of sputtering deposition are explained in detail.

#### **4.1 Ion beam sputtering deposition (IBSD)**

Ion beam sputter deposition (IBSD) can solve a variety of problems. IBSD, unlike other PVD processes, provides a unique desirable ability to modify properties of thin film such as dense film, fewer flaws, higher purity, greater adhesion etc.

A setup is depicted in the **Figure 8**. An ion beam source, target, and substrate holder make up the ion beam sputter deposition setup. To sputter a target, IBSD uses a wide beam ion source with low energy ions. A film forms when the powder (emitted particles) condenses on a sample. Primary particles also disperse on target to provide aid in the formation of a thin coating. Dispersed primary particles as well as the sputtered target particles, both play an important role in the film formation process. The essential process parameters are geometric parameters and ion beam parameters, such

**Figure 8.** *Ion beam sputtering.*

#### **Figure 9.**

*Schematic diagram of ion surface interaction and resulting implantation, scattering and sputtering process.*

as ion's angle of incidence, polar emission angle, angle of scattering and ion energy EIon etc. When these parameters are changed, energy distributions of the particles that make up film are also changed.

When an energetic particle collides with a target, the momentum and energy are transmitted from primary to the target particle. Sputtering, dispersion, and implantation are all significant processes in IBSD as in **Figure 9**. The retreating target particles and the scattered primary particles can collide further, creating a collision cascade or leaving the target. If target particles at the surface have acquired enough energy to overcome the binding energy of the surface, they can escape the target. The dispersed primary particles can either scatter or stay on the target. The dispersed particles are known as scattered particles.

Two particle collision is shown in **Figure 10**. Here, α is the Ion Incident angle, β is the Polar emission angle and γ is Scattering angle γ. Angle of incident plays an important role to decide either the resulting process will be scattering or sputtering.

Additional features must be addressed in order to fully utilize IBSD's potential. To begin with, the ion beam is always slightly divergent. As a result, the primary particles will collide with the chamber's components and walls. The forming film can be contaminated by eroded particles, so the chamber size must be large enough to reduce or avoid this. Second, the vacuum system's pumping speed must be high enough to prevent the background gas particle coverage of the target surface. The background pressure, current density of ion beam, and target body all play a role in surface coverage.

Ion beam sputtering deposition (IBSD**)** disadvantages include a slower growth and more difficult scaling. In addition, ion beam sources are extra complex than magnetrons, incorporating peripheral components [12].

#### **4.2 Magnetron sputtering deposition**

In the Magnetron sputtering technique, permanent magnets are used. As illustrated in the **Figure 11**, these magnets are placed behind the target to generate a

#### **Figure 10.**

*Two particle collision (a) direct scattering and (b) direct sputtering processes.*

**Figure 11.** *Magnetron sputter deposition.*

magnetic field. As ions are heavier than electrons so ions are scarcely influenced directly by the magnetic field. But the magnetic field causes the electrons to flow on a spiral course, extending their residence duration in the plasma. Now the likelihood of electrons colliding with background gas atoms will raise, causing a significant number of gas atoms to ionize.
