Difference between RF sputtering and DC sputtering | RF sputtering vs DC sputtering
This page compares RF sputtering vs DC sputtering and mentions difference between RF sputtering and DC sputtering.
What is Sputtering:
Sputtering is highly versatile vacuum coating system which is used for deposition of various coating materials.
Plasma gas is used ti knock atoms out of the target. As a result, atoms gets deposited on wafers as shown. Higher pressure generates better coverage. The excess energy of metal ions helps to increase surface mobility (i.e. movement of atoms on surface).
• In DC sputtering, source of power is DC (Direct Current) type.
• DC power is usually preferred for electrically conductive target materials as it is easy to control DC power.
• chamber pressure is usually 1 to 100 mTorr
• It is chaper technique when large quantities of large substrates are dealt with.
• In this technique, positively charged sputtering gas is accelerated towards the target. This results in ejection of atoms which gets deposited on substrate.
• In RF sputtering, source of power is AC (Alternating Current).
Instead of DC voltage to cathode, RF at about 13.5 MHz is being applied.
• RF peak to peak voltage is 1000 V, electron densities are 109 to 1011 Cm-3 and chamber pressure is 0.5 to 10 mTorr
• RF power is suitable for all the materials but most commonly used for depositing films from dielectric target materials.
• Deposition rate is low compare to DC sputtering.
• It is used for smaller substrate sizes due to high cost factor of RF power supplies.
• The RF sputtering consists of two processes. In the first cycle, target material is negatively charged. This causes polarization of atoms. The sputtering gas atoms are attracted towards source where they knock out source atoms. Here source atoms and ionized gas ions remain at target surface due to polarization of target.
• In the second cycle, target is positively charged. This causes ejection of gas ions and source atoms due to reverse polarization. These are accelerated toward substrate and hence deposition will occur.
Following table summarizes core difference between RF sputtering and DC sputtering.
|Features||DC Sputtering||RF Sputtering|
|Sputtering type||magnetron only||magnetron or diode|
|Target materials||conductive only||All the targets|
|Sputtering rate||100% of DC||20% of DC, no magnetron|
|cost and complexity||Best||Very Good|
|Compaign length (i.e. loss of anode)||Good||Excellent|
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