Introduction to plasma and plasma process
Plasma is an ionized gas phase substance that consists of ions, electrons and neutral atoms and/or molecules that grossly maintain charge neutrality.
In DC glow discharge, there is a fixed cathode and a fixed anode. Electrons will be accelerated from cathode to anode and acquire more energy.
Capacitively coupled discharge works similarly as DC glow discharge. They both rely on the electric field created by voltage applied on the electrodes to accelerate free-moving electrons to knock out bonded electrons in neutrals.
Inductively coupled discharge also uses RF power supply like capacitively coupled discharge. Frequency of the power is usually in tens of KHZ to tens of MHz range.
Capacitively coupled discharge and inductively coupled discharge are usually driven by RF power supply with frequency range from tens of KHz to less than 100MHz.
ECR excitation method also use microwave to heat up electrons.
Plasma cleaning is the process of creating energetic plasma to remove nanometer-scale impurities and contaminants from surfaces.
Photoresist ashing or stripping refers to the process of completely removing the photoresist layer on the substrate.
Photoresist descum is the process of removing the photoresist residual in the open trenches or holes after the lithography and developing steps.
Plasma cleaning prior to wire bonding removes organic, oxide and fluoride contaminations on the surface, promotes better interfacial adhesion for wire bond and chip packaging, reduces non-stick-on-pad (NSOP) and bond lifting problems.
Hydrocarbon contamination is a prevalent issue in many high vacuum analytical equipment, such as SEM, FIB, TEM, and XPS systems.