Abstract:
A plasma generating apparatus having superior plasma generation efficiency that uses a single reaction chamber. The plasma generating apparatus includes a RF generator for providing a RF power, an antenna for generating an electromagnetic field upon receiving the RF power, a reaction chamber for exciting/ionizing a reaction gas via the electromagnetic field, and generating a plasma, and a plasma channel for absorbing the RF power, and allowing a current signal to be induced to the plasma.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2007-0069061, filed on Jul. 10, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present invention relates to a plasma generating apparatus, and more particularly to a plasma generating apparatus for generating a high-density plasma having superior uniformity. 
     2. Description of the Related Art 
     Generally, the plasma is indicative of a highly-ionized gas including positive and negative ions and electrons, and has been widely used for the etching/depositing of the semiconductor fabrication process which forms a fine pattern (e.g., a semiconductor wafer or a glass substrate of the LCD). 
     Recently, as the integration degree of the semiconductor element gradually increases, a line width of the fine pattern gradually decreases, so that there is needed a plasma generating apparatus capable of generating the high-density plasma to improve the plasma uniformity used for the fine pattern. A variety of plasma generating apparatuses have been widely used, and representative examples are an Inductive Coupled Plasma (ICP) generating apparatus and a Capacitive Coupled Plasma (CCP) generating apparatus. Specifically, in the case of providing the electromagnetic energy for generating the plasma, the ICP generating apparatus has the plasma loss less than that of the CCP generating apparatus, and the sample (e.g., the semiconductor wafer or the glass substrate) of the ICP generating apparatus is not affected by the electromagnetic field, so that the ICP generating apparatus has been used more frequently than the CCP generating apparatus, 
     Examples of the above-mentioned ICP generating apparatus are shown in  FIGS. 1 and 2 . 
       FIG. 1  is a cross-sectional view illustrating a conventional plasma generating apparatus.  FIG. 2  is a plan view illustrating a conventional plasma generating apparatus. The plasma generating apparatus of  FIG. 1  or  2  includes at least one ferrite core  41 . 
     The conventional plasma generating apparatus  100  includes a vacuum-state upper reaction container  111  and a vacuum-state lower reaction container  112  coupled to each other. The upper and lower reaction containers  111  and  112  include the plasma generated by the ionized injection gas. 
     The space formed by two reaction containers  111  and  112  is divided into two reaction chambers  113  and  114  by the partitions  121  and  122 , respectively. The reaction chambers  113  and  114  include chucks  131  and  132 , respectively. The sample (e.g., the semiconductor wafer or the glass substrate) is located at the lower chuck  132 . Six toroidal-shaped ferrite cores  141  spaced apart from each other at regular intervals are circularly arranged at the center of each of the reaction chambers  113  and  114 . The coil  142  is wound on each ferrite core  141 . The coil  142 &#39;s winding direction among the neighboring ferrite cores  141  are opposite to each other, so that the induced electromotive forces generated from the neighboring ferrite cores  141  have opposite phases. 
     The reaction chambers  113  and  114  are interconnected via a through-hole  152  formed in the tube  151  passing through the center of the ferrite core  141 . The reaction gas passes via the through-hole  152 , and the through-hole  152  is used as the path of the discharging current signal. In the case of processing the sample, the coil  142  wound on the ferrite core  141  is used as a primary coil, and the plasma is used as a secondary part, so that the high-frequency RF power applied to the primary coil  142  is applied to the plasma acting as the secondary part. The induced electromotive forces of the neighboring ferrite cores  141  has a phase difference of 180°. The path of the current signal induced to the plasma forms a closed path via two neighboring through-holes  152 . The arrows of  FIG. 2  indicate six induced current signals formed among the neighboring through-holes  152 . 
     The conventional plasma generating apparatus  100  must configure the path of the secondary current signal induced to the plasma in the form of a closed circuit in order to increase the plasma generation efficiency, so that it requires two reaction chambers  113  and  114 . Indeed, the conventional plasma generating apparatus  100  has difficulty in using one of the two reaction chambers  113  and  14 , resulting in the loss of plasma and the occurrence of particles. 
     SUMMARY 
     Therefore, it is an aspect of the invention to provide a plasma generating apparatus which has a superior plasma generation efficiency simultaneously while using a single reaction chamber. 
     It is another aspect of the invention to provide a plasma generating apparatus for maximizing the inductive coupling using a toroidal-shaped ferrite core and a tube-shaped channel, increasing a plasma generation efficiency, and uniformly distributing the high-density plasma. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     In accordance with the invention, the above and/or other aspects can be achieved by the provision of a plasma generating apparatus including: a RF generator for providing a RF power; an antenna for generating an electromagnetic field upon receiving the RF power; a reaction chamber for exciting/ionizing a reaction gas via the electromagnetic field, and generating a plasma; and a plasma channel for absorbing the RF power, and allowing a current signal to be induced to the plasma. 
     The antenna may include: a high-frequency antenna coil for providing the RF power having a high-frequency band so as to perform ignition of the plasma; and a low-frequency antenna coil for receiving the RF power having a low-frequency band to perform inductive coupling of the plasma. 
     The apparatus may further include: a window for transmitting the electromagnetic field of the antenna to an inner part of the reaction chamber, wherein the high-frequency antenna coil is arranged on the window. 
     The high-frequency band of the high-frequency antenna coil may be in the range from 2 MHz to several hundreds of MHz. 
     The low-frequency band of the low-frequency antenna coil may be in the range from several tens of KHz to 2 MHz. 
     The low-frequency antenna coil may be wound on each of several ferrite cores arranged in the form of a toroidal shape so as to transmit the electromagnetic field to the plasma. 
     Each of the ferrite cores arranged in the form of the toroidal shape may include a plasma channel, so that the plasma current signal forms a closed circuit and passes the circuit. 
     The plasma channels arranged in the ferrite cores may be regularly arranged on a circumference of the reaction chamber. 
     The plasma channel may be configured in the form of            shape.
     The            -shaped plasma channel may be connected to a          -shaped wall of the reaction chamber so as to reduce the loss of the plasma.
     In accordance with another aspect of the present invention, there is provided a plasma generating apparatus including: a reaction chamber for generating a plasma; a RF generator for providing a RF power to generate the plasma; an antenna system generating an electromagnetic field upon receiving the RF power; and a plasma channel for absorbing the RF power, and allowing a current signal to be induced to the plasma. 
     The antenna system may include: a high-frequency antenna system for providing the RF power having a high-frequency band so as to perform ignition of the plasma; and a low-frequency antenna system for receiving the RF power having a low-frequency band to perform inductive coupling of the plasma. 
     The apparatus may further include: a window for transmitting the electromagnetic field of the antenna to an inner part of the reaction chamber, wherein the high-frequency antenna system is arranged on the window. 
     The high-frequency band of the high-frequency antenna system may be in the range from 2 MHz to several hundreds of MHz. 
     The low-frequency band of the low-frequency antenna coil may be in the range from several tens of KHz to 2 MHz. 
     The low-frequency antenna system may arrange several ferrite cores in the form of a toroidal shape so as to transmit the electromagnetic field to the plasma, and each of the ferrite cores arranged in the form of the toroidal shape may include a plasma channel, so that the plasma current signal forms a closed circuit and passes the circuit. 
     The low-frequency antenna system may further include a DC brake to cut off the current signal induced on the plasma channel. 
     The apparatus may further include: a controller for controlling uniformity of the plasma by adjusting an input RF power of the high-frequency and low-frequency antenna systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a cross-sectional view illustrating a conventional plasma generating apparatus; 
         FIG. 2  is a plan view illustrating a conventional plasma generating apparatus; 
         FIG. 3  is a cross-sectional view illustrating a plasma generating apparatus according to one embodiment of the present invention; and 
         FIG. 4  is a plan view illustrating a plasma generating apparatus according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
     Recently, as the size of a semiconductor wafer or a glass substrate is rapidly increasing to improve the productivity of semiconductor fabrication based on the plasma, the necessity of the plasma generating apparatus for generating high-density plasma having superior uniformity is also rapidly increasing. 
     The high-density plasma generating apparatus includes an antenna system. The antenna system includes a low-frequency RF power to generate the plasma, and a high-frequency RF power for providing the high-frequency RF power to draw the ions or radicals of the plasma toward the semiconductor wafer or glass substrate. In this case, the low-frequency RF power is called a source power, and the high-frequency RF power is called a bias power. 
     In the case of using the source power (about 2 MHz˜several hundreds of MHz) of the antenna system, the size of the plasma generating apparatus gradually increases, so that the plasma uniformity becomes deteriorated due to the transmission line effect. Therefore, in the case of using a low-frequency RF power (about several tens of KHz˜2 MHz) of the antenna system, the line transmission effect can be removed, so that the above-mentioned antenna system can be highly compatible with a large-area high-density plasma generating apparatus. 
     However, induced electromotive force (E) generated from the antenna for the plasma generation is proportional to the magnetic field (B) of the antenna and the frequency (ω) of the power-supply voltage. So, in the case of using the power-supply voltage, the plasma generation efficiency becomes deteriorated. 
     Individual steps have different pressure conditions in their reaction chambers, because different reaction gases are received in the reaction chambers according to the individual steps. If the RF power having a relatively low-frequency RF power is used, it is difficult to stably generate the plasma in the plasma ignition step, so that the plasma generating apparatus has difficulty in plasma ignition. 
     Therefore, the present invention includes the low-frequency antenna system and the high-frequency antenna system, so that it can effectively perform the plasma ignition using the high-frequency antenna system which uses the high-frequency power-supply voltage advantages to the plasma ignition under various pressure conditions, and at the same time increases the inductive coupling efficiency between the low-frequency antenna and the plasma using the low-frequency antenna system composed of both a multi-ferrite core having a high transmission rate and a plasma channel, resulting in the increase of plasma generation efficiency. 
       FIG. 3  is a cross-sectional view illustrating a plasma generating apparatus according to one embodiment of the present invention.  FIG. 4  is a plan view illustrating a plasma generating apparatus according to one embodiment of the present invention. 
     In  FIG. 3 , the plasma generating apparatus according to the present invention includes a vacuum-state reaction chamber  10 , a high-frequency antenna system  20 , a low-frequency antenna system  30 , and a controller  40 . 
     The reaction chamber  10  includes the plasma generated by the ionized injection gas. The high-frequency antenna system  20  is arranged at the center of an upper part of the reaction chamber  10 . The low-frequency antenna system  30  is arranged at the outside of the upper part of the reaction chamber  10 . The controller  40  adjusts the input RF power of the high-frequency and low-frequency antenna systems  20  and  30  so as to control the plasma uniformity. 
     The reaction chamber  10  forms a process area in which the semiconductor fabrication process based on the plasma is conducted, and maintains the process area in a vacuum state at a predetermined temperature. The reaction chamber  10  includes a pair of gas nozzles  11  for injecting the reaction gas from the external part, and a gas outlet  12  for discharging the reaction gas to the outside after the reaction has been completed. The reaction chamber  10  includes a trimmer chuck  13  on which the sample  14  (e.g., the semiconductor wafer or the glass substrate) is seated. 
     The dielectric window  15  is arranged among the reaction chamber  10  and the high-frequency and low-frequency antenna systems  20  and  30 , so that it transmits the electromagnetic field of the high-frequency and low-frequency antenna systems  20  and  30  to the inside of the reaction chamber  10 . The window  15  is made of a dielectric material such as alumina or quartz. 
     The high-frequency antenna system  20  includes a high-frequency antenna coil  21 , a high-frequency RF generator  22 , and an impedance matching unit  23 . The high-frequency RF generator  22  provides the high-frequency antenna coil  21  with the RF power having the high-frequency band (2 MHz˜several hundreds of MHz). 
     The impedance matching unit  23  transmits the RF power of the high-frequency RF generator  22  to the high-frequency antenna coil  21  without any loss. The high-frequency antenna coil  21  may be composed of a serial antenna configured in the form of a spiral shape or a serial/parallel antenna. 
     The low-frequency antenna system  30  includes a ferrite core  31 , a low-frequency antenna coil  32 , a low-frequency RF generator  33 , and an impedance matching unit  34 . The low-frequency antenna coil  32  is wound on the ferrite core  31 . The low-frequency RF generator  33  provides the low-frequency antenna coil with the RF power having a low-frequency band (several tens of KHz˜2 MHz). The impedance matching unit  34  transmits the RF power of the low-frequency RF generator  33  to the low-frequency antenna coil  32  without any loss. The ferrite core  31  is composed of a toroidal-shaped multi-ferrite core  31  for effectively applying the electromagnetic field created by a primary current signal of the low-frequency antenna coil  32  to a secondary plasma. 
     The low-frequency antenna system  30  includes the plasma channel  35  contained in each ferrite core  33 . The plasma channel  35  configures the path of a high-frequency current induced to the secondary plasma in the form of a closed circuit, so that it absorbs the RF power supplied from the low-frequency RF generator  33 . The plasma channel  35  is formed of a metal tube or a ceramic tube. If the plasma channel  35  is formed of a metal tube, a DC brake  36  is used. This DC brake  36  prevents the plasma current signal from being induced, so that it can effectively apply the RF power to the plasma. 
     The path of the high-frequency current signal induced to the secondary plasma may correspond to the plasma channel  35  and the reaction chamber  10 . In order to reduce the plasma loss of the plasma channel  35 &#39;s area, the            -shaped wall of the reaction chamber  10  is connected to the          -shaped plasma channel  35 , so that the size of the plasma channel  35  is minimized.
     Each ferrite core  31  and the plasma channel  35  configure the plasma source module  37 , so that at least two plasma source modules  37  are regularly arranged on a circumference of the reaction chamber  10 . 
     The controller  40  controls the RF power ratio of the high-frequency and low-frequency RF generators  22  and  33  to adjust the RF power applied to the high-frequency and low-frequency antenna systems  20  and  30 . 
     Operations and effects of the above-mentioned plasma generating apparatus will hereinafter be described. 
     Initially, the plasma generating apparatus discharges the gas to the outside using the vacuum pump (not shown), and receives the reaction gas to generate the plasma via the gas nozzle  11 , so that it maintains the necessary pressure. 
     Then, if the RF power having the high-frequency band (2 MHz˜several hundreds of MHz) is applied from the high-frequency RF generator  22  to the high-frequency antenna coil  21  of the high-frequency antenna system  20  so as to perform the plasma ignition, the current signal flowing in the high-frequency antenna coil  21  forms the sine-wave electromagnetic field, so that an induced electric field is formed in the process area of the reaction chamber  10 . The induced electric field accelerates particles of the reaction gas contained in the reaction chamber  10 , excites/ionizes the reaction gas, so that the plasma ignition is conducted and the plasma occurs in the center of the reaction chamber  10 . In this case, during the plasma generation, the plasma generating apparatus applies the low-frequency RF power to the low-frequency antenna system after igniting the plasma using the high-frequency antenna system  20 . 
     If the RF power having the low-frequency band (several tens of KHz˜2 MHz) is applied from the low-frequency RF generator  33  to the low-frequency antenna coil  32  of the low-frequency antenna system  30 , the current signal flowing in the low-frequency antenna coil  32  forms the sine-wave electromagnetic field, and an induced electric field opposite to the current signal of the low-frequency antenna coil  32  is formed in the process area of the reaction chamber  10 . The induced electric field accelerates particles of the reaction gas contained in the reaction chamber  10 , excites/ionizes the reaction gas, so that the plasma is generated outside of the reaction chamber  10 . The sample  14  seated on the chuck  13  contained in the reaction chamber  10  is deposited on a thin film by the plasma or is etched by the plasma. 
     In this case, the primary current signal flowing in each low-frequency antenna coil  32  and the current signal induced to the secondary plasma are opposite to each other, so that the plasma generating apparatus prevents the electromagnetic field from being lost, increases the electromagnetic field of the process area, so that it increases the plasma generation efficiency although the low-frequency RF power is used. 
     Therefore, in the case of using the above-mentioned low-frequency antenna system  30 , the plasma generating apparatus can remove the transmission line effect using the RF power having a relatively low-frequency band (several tens of KHz˜2 MHz), so that it can uniformly generate the high-density plasma. The plasma generating apparatus uses the toroidal-shaped multi-ferrite core  31  having a high transmission rate, so that it increases the inductive coupling efficiency between the low-frequency antenna system  30  and the plasma. So, the plasma generating apparatus can increase the plasma generation efficiency using the RF power having a relatively low-frequency. 
     The low-frequency antenna system  30  is formed of a toroidal-shaped multi-ferrite core  31  in order to effectively transmit the electromagnetic field created by the primary current of the low-frequency antenna coil  32  to the secondary plasma. As shown in the dotted circle of  FIG. 3 , the secondary plasma allows the path of the plasma current signal to form a closed circuit, and absorbs the RF power generated from the low-frequency RF generator  33  using the closed circuit, so that the plasma density increases by two or more times as compared to the conventional art. In this case, the plasma channel  35  is formed of a metal tube or a ceramic tube. If the plasma channel  35  is formed of the metal tube, the DC brake  36  is required for the plasma generating apparatus, so that the DC brake  36  prevents the current signal from being induced on the plasma channel  35 , and the RF power can be effectively applied to the plasma. 
     The path of the high-frequency current signal induced to the secondary plasma may correspond to the plasma channel  35  and the reaction chamber  10 . In order to reduce the plasma loss of the plasma channel  35 &#39;s area, the            -shaped wall of the reaction chamber  10  is connected to the          -shaped plasma channel  35 , so that the size of the plasma channel  35  is minimized.
     However, as described above, different reaction gases are injected into the reaction chamber  10  according to individual steps, and the individual steps have a variety of pressure conditions in the reaction chamber  10 , so that the low-frequency antenna system  30  employing the relatively low-frequency RF power has difficulty in the initial plasma ignition. In order to solve this problem, the high-frequency antenna system  20  can easily ignite the plasma under a variety of pressure conditions. The electrostatic field caused by the high voltage of the high-frequency antenna coil  21  accelerates the seed electrons, so that it induces the initial discharging. 
     Therefore, the plasma generating apparatus always ignites the plasma using the high-frequency antenna coil  21  during the plasma generation, and then applies the RF power to the low-frequency antenna system  30 . In this case, the controller  40  adjusts the input RF power of the high-frequency and low-frequency antenna systems  20  and  30 , so that it controls the plasma uniformity. 
     Therefore, the plasma generating apparatus has no unnecessary reaction chamber  10 , generates the large-area/high-density plasma, so that it can be highly compatible with a variety of commercial devices. Specifically, the plasma generating apparatus is applied to the HCPCVD or the etcher device, so that it reduces the process time below a critical dimension (CD) of 100, and can also be easily applied to the plasma processing device of the flat panel display (FPD) such as a LCD. 
     As is apparent from the above description, the plasma generating apparatus has no unnecessary reaction chamber because it uses only one reaction chamber, and has a superior plasma generation efficiency, so that it can be highly compatible with all the processing devices based on the plasma. 
     The plasma generating apparatus maximizes the inductive coupling using a toroidal-shaped ferrite core and a tube-shaped channel, increases a plasma generation efficiency, and uniformly distributes the high-density plasma. 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.