1. DC Sputtering principle: (Suitable for sputtering of conductor materials)
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In the vacuum sputtering chamber, Ar is injected and a few KV direct current is added to the electrode, thus generating a glow discharge.
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Glow discharge will produce Ar(?) Plasma? In plasma? It accelerates due to the cathode potential drop (the cathode is negatively charged), collides with the target surface, sputtering particles on the target surface, and the sputtered particles are deposited on the substrate to form a film.
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How to calculate the number of sputtered particles to substrate? If the total amount of sputtering particles Q is sputtered into substrate, then?
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? : Constant,? : Total evaporation of target, P: gas pressure for sputtering, d: distance from target to substrate.
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? :target ion current, e: electron charge, s: sputtering rate, A: sputtering atomic weight, N:? In general, the discharge current during sputtering? ,? For the discharge voltage, so? ,? Depends on the target.
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Therefore, the amount of sputtering in substrate is proportional to the power consumption of the sputtering device. ), inversely proportional to the gas pressure and the distance from the target to the substrate.
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Two, RF Sputtering principle: (suitable for all solid materials sputtering)
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If the target is an insulator, because the target surface has a positive potential (target is negatively charged (cathode)), the potential difference between the target surface and the anode disappears, and the discharge will not continue, and the glow discharge effect cannot be generated, so if the DC power supply is changed to RF power supply, the target of the insulator can also maintain glow discharge.
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After the RF power supply is connected, the electron mobility in the plasma will be greater than the ion mobility, excess electrons will accumulate on the target surface, and the DC bias on the target surface will be negative potential, so that sputtering can be done.
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An impedance matching circuit is inserted between the high frequency power supply and the electrode in order to fully discharge the power. The impedance matching circuit and the target electrode are connected in series to the capacitor, and the insulator target will also arouse negative potential bias. This negative potential is about the peak value of the applied voltage at high frequency sputtering. Times).
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Target applies RF high voltage at the same time when water cooling, so the water cooling pipe should use insulation such as teflon, and use cooling water with high resistance, and the discharge impedance is generally 1 to 10? To integrate the matching circuit into a power supply of 50? .
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Assume that the flow target current density of the sputtering device is?
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C: Electrostatic capacity between plasma and target? Is the change of target surface potential with respect to time.
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Note: The RF frequency should not be too high, otherwise it will not be easy to supply power to the target.
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? The more you increase, the easier it is to sputter. (That is to say, the more the surface negative potential increases in a shorter period of time, the easier it is to sputter, so within the RF power supply frequency tolerance range, increasing the RF frequency brigade can increase the film formation rate)
Sputtering, usually referred to as magnetic sputtering, is a high-speed and low-temperature sputtering method.
The process requires a vacuum degree of about 1×10-3Torr, that is, 1.3×10-3Pa vacuum state filled with the inert gas argon (Ar), and added high voltage direct current between the plastic substrate (anode) and the metal target (cathode), due to glow discharge (glow discharge) generated by the electron excitation of the inert gas, A plasma is generated, which blasts atoms from the metal target and deposits them onto the plastic substrate.
principle
Charged particles with tens of electron volts or more of kinetic energy are bombarded with the surface of the material, causing it to sputter out into the gas phase, which can be used for etching and coating. The number of atoms sputtered by an incident ion is called the sputtering Yield. The higher the yield, the faster the sputtering speed. Cu,Au,Ag is the highest, Ti,Mo,Ta,W is the lowest. Generally in the range of 0.1-10 atoms\/ions. The ions can be produced by glow discharge, at a vacuum of 10-1-10 Pa, a high voltage is applied between the poles to produce discharge, and the positive ions will bombard the negative target and sputter the target, and then be plated on the substrate.
The current density of normal glow discharge is related to the cathode material and shape, gas type and pressure. It should be kept as stable as possible when sputtering. Any material can be sputtered, even high-melting materials are easy to sputter, but the non-conductor target must be sputtered with RF or pulse; Due to poor electrical conductivity, the sputtering power and speed are low. Metal sputtering power up to 10W\/cm2, non-metal < 5W\/cm2