What is the discharge principle and characteristics of inductively coupled plasma cleaning machine

• Categories:Technical Support
• Author:plasma cleaning machine-surface treatment equipment-CRF plasma machine-Sing Fung Intelligent Manufacturing
• Origin:
• Time of issue:2020-09-21
• Views:

(Summary description)Inductively coupled vacuum (low pressure) plasma cleaning machine is developed with the process requirements of the semiconductor industry, the main use is in wafer manufacturing photoresist removal and etching. Strictly speaking, plasma etching has been another category of process equipment, today we will discuss the induction coupling plasma cleaning machine discharge principle, model and characteristics. When a spiral coil is fed with a high-frequency current, two kinds of electric fields exist simultaneously in its space. The first is the axial electric field E1 established by the high-frequency potential difference between the two ends of the coil, which is the electric field of e-type discharge. The second is the vortex electric field E0 generated by the magnetic field changing in the discharge space, that is, the H-type electric field. The ratio of these two fields varies according to the way the coil is wound. We will see an interesting phenomenon, when the plasma density is low, discharge is capacitive mode; At high density, the discharge shifts to perceptual mode. An induced electric field is used to accelerate electrons to maintain the plasma. The plasma produced in this way is called the induction-coupled plasma ICP, whose neutral gas pressure is generally lower than one atmosphere, 102~104Pa, and sometimes even reaches atmospheric pressure. Inductive discharge plasmas are generated by applying rf power to a non-resonant coil. There are two common structures which are more suitable for low aspect ratio discharge systems. The first common structure of inductively coupled plasma sources is a cylindric helical coil type (helical type for short). The second common type of inductively coupled plasma source structure is the planar coil type (disc-type for short). Drive the output of the rf source inductance coil impedance of 50 Ω, its frequency is 13.56 MHz or lower. There is a capacitive matching network between the RF source and the inductor coil. The obtained plasma density is 1017~1018m-3, the electron temperature is 2~4eV, and the diameter is up to 30cm. ICP has been widely used in semiconductor plasma processing in recent years because it is easy to obtain large-diameter and high-density plasma over a wide pressure range (1~40Pa). By c=,13.56MHz electromagnetic wave wavelength is 22m, greater than the length of the antenna, so you can ignore the displacement current, the use of quasi-static method to deal with the core do field. The electrons in the plasma are accelerated by this electric field, thus creating eddy currents in the plasma in the direction that neutralizes the antenna's current magnetic field. Although electrons are sometimes accelerated and sometimes slowed by an induced electric field, if this effect is averaged over time, the net energy expenditure in the non-collision condition is zero, and power cannot enter the plasma. Nu e for electrons and neutral particles, ion collision frequency, can calculate the conductor "plasma" DC conductivity. In general, when an alternating magnetic field is applied to a conductive plate of conductivity, a vortex current flows through the conductor causing joule heating. In this case, the magnetic field decays exponentially from the surface to the inside of the conductor, so the depth into the conductor is limited (skin effect). In the low pressure (argument e/omega < < 1), high plasma density (omega p > > omega), skin depth is expressed as the delta = c/p omega. In the physical sense omega p is a measure of how fast electrons respond to collective motion. Less than omega p, the electrons' motion prevents the wave's electric field from entering the plasma, which is called plasma shielding. The wave will travel along the surface of the plasma, and the surface wave can also be used to generate a high-density plasma. Once entered into a state of depression, the resistance of the plasma will be small variations, skin depth will drop, so the joule heating effect cannot make plasma power input, therefore under pressure to maintain high density such as Yu daughter must be another mechanism, the mechanism of thermal motion of electrons is this: local electric field caused by an abnormal skin effect. Consider the collision free process: the electrons, moving at the thermal speed, return to the plasma no matter how far they go into the edgedepth delta region of the induced electric field. When the electron through this electric field area of time/nu is roughly equal to or slightly less than the high frequency voltage cycle 2 / nu, electron acceleration, deceleration is random, after the statistical average electron can obtain energy efficiently, this is the abnormal skin effect. Through the above principle analysis, we can understand some basic principles and characteristics of inductively coupled plasma, but in the design of plasma cleaning machin