Question

Can DC sputtering be used for depositing dielectrics? Why? ..... What is the alternative method for depositing dielectrics? Why?

I need the answer in obvious script not by handwriting please.
thanks

Answer 1

Yes, DC sputtering can be used for depositing dielectrics.

DC or Direct Current Sputtering is a Thin Film Physical Vapor Deposition (PVD) Coating technique where a target material to be used as the coating is bombarded with ionized gas molecules causing atoms to be “Sputtered” off into the plasma. These vaporized atoms are then deposited when they condense as a thin film on the substrate to be coated.

DC Sputtering is the most basic and inexpensive type of sputtering for PVD metal deposition and electrically conductive target coating materials. Two major advantages of DC as a power source for this process is that it is easy to control and is a low cost option if you are doing metal deposition for coating.

Magnetron Cathode Magnet Array Target High Density Plasma - Magnetic Field Target Material 1696 Sputtered Film Substrate Holder lonized Argon Y Plasma Generated by Neutralization Argon Soo MFC -Substrate + Anode Throttle Valve Vac Pump

While DC Sputtering is the economical solution of choice for many types of metal coatings, its primary limitation is that non-conducting dielectric insulating materials take on a charge over time which can result in quality issues like arcing, or the poisoning of the target material with a charge that can result in the complete cessation of sputtering.

To overcome these limitations of DC Sputtering, several more complicated technologies have been developed such as RF or Radio Frequency Sputtering, and HIPIMS or High Power Impulse Magnetron Sputtering. RF Sputtering alternates the electrical charge at Radio Frequency so as to prevent a charge buildup on the target or coating material. HIPIMS utilizes a very high voltage, short duration burst of energy focused on the target coating material to generate a high density plasma that results in a high degree of ionization of the coating material in the plasma.

Despite the relative simplicity of DC Sputtering it usually has low deposition rates compared to more complicated HIPIMS that is the result of lower plasma densities and higher gas densities.

Traditional DC Sputtering is a cost effective way of applying metal target coatings that are electrical conductors like gold. However, DC Sputtering is limited when it comes to dielectric target materials – coatings which are non-conducting insulating materials that can take on a polarized charge. Examples of common dielectric coating materials used in the semiconductor industry include Aluminum Oxide, Silicon Oxide and Tantalum Oxide.

RF or Radio Frequency Sputtering is the technique involved in alternating the electrical potential of the current in the vacuum environment at radio frequencies to avoid a charge building up on certain types of sputtering target materials, which over time can result in arcing into the plasma that spews droplets creating quality control issues on the thin films – and can even lead to the complete cessation of the sputtering of atoms terminating the process.

DC AC RF RF HIPIMS - V Power Source i I - Cathode o q e Cathode Target Atom of Target Material Neutralized Atom Co lonized TOTO doo Argon Plasma Generated by Neutralization Sputtered Film Substrate Holder Substrate + Anode

DC AC RF RF HIPIMS - V Power Source i I - Cathode o q e Cathode Target Atom of Target Material Neutralized Atom Co lonized TOTO doo Argon Plasma Generated by Neutralization Sputtered Film Substrate Holder Substrate + Anode

As with DC Sputtering, RF Sputtering runs an energetic wave through an inert gas in a vacuum chamber which becomes ionized. The target material or cathode which is to become the thin film coating is bombarded by these high energy ions sputtering off atoms as a fine spray covering the substrate to be coated. RF Magnetron sputtering uses magnets behind the negative cathode to trap electrons over the negatively charged target material so they are not free to bombard the substrate, allowing for faster deposition rates.

Over time, positive ions are produced which accumulate on the surface of the target face giving it a positive charge. At a certain point this charge can build up and lead to a complete secession of sputtering atoms being discharged for coating.

By alternating the electrical potential with RF Sputtering, the surface of the target material can be “cleaned” of a charge buildup with each cycle. On the positive cycle electrons are attracted to the target material or cathode giving it a negative bias. On the negative portion of the cycle - which is occurring at the radio frequency of 13.56 MHz used internationally for RF power supply equipment - ion bombardment of the target to be sputtered continues.

RF Sputtering offers several advantages depending upon your specific application. RF plasmas tend to defuse throughout the entire chamber rather than concentrating around the cathode or target material as with DC Sputtering.

RF Sputtering can sustain a plasma throughout the chamber at a lower pressure (1-15 mTorr). The result is fewer ionized gas collisions equaling more efficient line-of-site deposition of the coating material.

Because with RF Sputtering the target material is being “cleaned” with each cycle from building up a charge it helps reduce arcing. Arcing is where there is an intensely focused and localized discharge emanates from the target material or cathode into the plasma that creating droplets and problems with non-uniform film deposition. RF Sputtering greatly reduces the buildup of a charge in a specific location on the surface of the target material that leads to the sparks that creates the arc which causes numerous quality control issues.

Another advantage of RF Sputtering is that there is no disappearing anode effect when the substrate to be coated becomes insulated and acquires a charge as with DC Sputtering. All surfaces develop a charge in a plasma as a result of electrons moving much faster than ions due to their smaller size and kinetic energy.