When a material in a solid phase is heated, the material is changed to a liquid phase and a gas phase in sequence. When energy is further applied to the material in the gas phase through heating or discharging, the gas is dissociated to atoms, ions and electrons which are smaller particles and the particles are mixed. This state is called plasma. Plasma that is industrially used is divided into low-temperature plasma and thermal plasma, and the low-temperature plasma (cold plasma) is widely used in a semiconductor manufacturing process, and the thermal plasma is applied in cutting and spraying.
A plasma generating method that is currently used the most in a semiconductor manufacturing process and display field uses a RF (Radio Frequency), and is largely divided into an inductively coupled plasma (ICP) method and a capacitively coupled plasma (CCP) method. In the inductively coupled plasma method, a coil type antenna is structurally used. When a RF power is applied to the antenna, a current flows in the antenna, and the current forms induced magnetic field around the antenna. At this time, positive charges and negative charges are alternately charged on a surface of the antenna by a RF frequency, so that a secondary induced current is allowed to flow around the antenna. In general, the inductively coupled plasma is generated by an induction coil in a frequency (13.56 MHz) domain generated by a quartz oscillator-type high-frequency generator by using an argon gas as a plasma gas.
In the inductively coupled plasma method, a RF current flows in the antenna for generating the inductively coupled plasma to form the magnetic field, and an induced electric field is formed by a time varying magnetic field to generate the plasma.
FIG. 1 is a diagram illustrating inductively coupled plasma equipment according to the related art, and FIG. 2 is a diagram illustrating an antenna used to generate inductively coupled plasma according to the related art. In FIG. 2, reference numeral “30” denotes a RF power supply.
In inductively coupled plasma equipment 10 according to the related art, a circular antenna 21 is used as illustrated in FIGS. 1 and 2, and efficiency of the entire power system may be decreased and space non-uniform of plasma P may be caused due to capacitive coupling caused by a high potential difference generated between both ends 22 and 23 of the antenna.
As illustrated in FIG. 1, a high voltage is applied between the antenna 21 and a wall 12 of a processing chamber 11, and strong capacitive coupling (CC) is generated between the antenna 21 and the wall 12 of the chamber to cause a loss due to a displacement current. For this reason, the wall 12 of the chamber may be damaged.
Further, the antenna 21 that is directly connected to the power supply 30 in a wired manner generates and controls inductively coupled plasma, and since the antenna is directly connected to the power supply, there is a limitation on an installation position of the antenna. Thus, the entire density of the plasma may be reduced.
In recent years, a size of a processing target or a substrate on which a depositing process or an etching process is performed by the plasma generated by the inductively coupled plasma equipment is gradually increased. However, when a large antenna corresponding to a large substrate is used, a standing wave effect may be exhibited.
Furthermore, as a need for the plasma process on the large substrate is increased, a need for uniformity of the plasma on a surface of the large substrate is also increased. However, when a single antenna is used, it is difficult to uniformly control the plasma, and when a plurality of antenna that is directly connected to the power supply in the wired manner is used, the plasma equipment may be complicated.