SEMI-KLEEN Sapphire downstream RF plasma cleaner

SEMI-KLEEN plasma cleaner

• Tabletop controller with embedded microcomputer and LCD touchscreen user interface
• Low particle source design, qualified for semiconductor application where PWP is a concern.
• PC remote control software with intuitive user interface
• 60-recipe support in microcontroller
• 75W RF power supply with fixed RF impedance matching (IE-SEMI105. Upgrade to 150W RF power supply)
• Plasma sensor for plasma strength monitor
• Electronic gas flow control with pressure sensor feedback control
• Smart-Schedule feature for automatic cleaning
• Intelligent safe and expert operation mode 15 feet high-quality, high-power RF cable; D-Sub 9 PC control cable; D-Sub 15 source control cable

Definition of an RF plasma

A radio frequency (RF) plasma is an ionised gas phase substance that consists of ions, electrons, and neutral atoms and/or molecules that grossly maintain charge neutrality. Electrons and ions should be close enough so that each of them can influence many nearby charged particles within a radius called the Debye screening length. As a result, charged particles in the RF plasma respond collectively to external electromagnetic fields. With a high density of free-moving ions and electrons, plasma is highly electrically conductive. With the exception of boundary regions between the plasma and electrodes, a plasma contains the same amount of positive and negative charges. There is no space charge within the bulk of the plasma.

Plasma sheath

Electron temperature is usually equal to or higher than that of ions. Since electrons are much lighter than ions, they can escape from a plasma at a much faster speed than ions, providing there is no confining potential barrier. Once electrons are nearly depleted from the boundary interface between the plasma and electrodes or specimen, a region with only positive ions and neutrals will be formed. This usually dark boundary region is called plasma sheath. Positive charges in the plasma sheath can push more ions to diffuse out of the plasma. It also creates a potential barrier to prevent electrons from diffusing out of the plasma. Eventually, the loss rate of electrons and ions will reach an equilibrium state. The plasma sheath also creates a positive plasma potential with respect to the grounded chamber walls. The voltage drop across the plasma sheath can accelerate ions and create an ion sputtering effect in many applications.

How an RF plasma is generated

Electrons and ions in plasmas can disappear through diffusion or recombination. To sustain a stable RF plasma, external excitation is required to create more electrons and ions so that their creation rate can reach a balance with the loss rate. Most RF plasma generation methods rely on heating free electrons to high enough energy to break down neutral atoms or molecules into ions and electrons.

PIE Scientific specialise  in developing advanced plasma systems for plasma etching, cleaning, surface treatment, ion and electron beam production applications. The company was founded by alumni of the Plasma and Ion Source Technology group in the Lawrence Berkeley National Laboratory. After 15 years of experience in developing advanced semiconductor capital equipment in Silicon Valley, they realized that many existing low-cost plasma cleaners and plasma treatment systems were still using decades-old technology. Therefore, they decided to bring state-of-the-art plasma technology developed for the semiconductor industry and nuclear research into affordable plasma instruments. Their SmartClean™ technology has been well-received by customers.