PATENT ABSTRACT
A plasma generation apparatus is provided. The plasma generation apparatus includes a chamber defining a reaction space that can be isolated from an external environment, an upper electrode provided in an upper portion of the chamber, a lower electrode provided in a lower portion of the chamber, a sidewall electrode provided at a sidewall of the chamber, a radio frequency (RF) pulse power supplier configured to supply RF pulse power to at least one selected from the upper electrode and the lower electrode, and a direct current (DC) pulse power supplier configured to supply DC pulse power to the sidewall electrode.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Korean Patent Application No. 10-2015-0120546, filed on Aug. 26, 2015 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    Apparatuses, methods and systems consistent with exemplary embodiments relate to plasma generation, and more particularly, to a plasma generation apparatus that is operated by a radio frequency (RF) pulse power supply. 
         [0003]    When wafer processing such as etching and deposition of a wafer is performed using an RF pulse plasma generation apparatus, an electron temperature may be lowered more than a case where continuous wave (CW) plasma is used. Thus, the possibility of the wafer being damaged due to excessive decomposition of injected reactive gas may be reduced. However, a process error that may occur as electrons are concentrated in a specific area in a chamber. 
       SUMMARY 
       [0004]    One or more exemplary embodiments provide a plasma generation apparatus for improving process distribution. 
         [0005]    According to an aspect of an exemplary embodiment, there is provided a plasma generation apparatus including: a chamber defining a reaction space that is isolated from an external environment; an upper electrode provided in an upper portion of the chamber; a lower electrode provided in a lower portion of the chamber; a sidewall electrode provided at a sidewall of the chamber; a radio frequency (RF) pulse power supplier configured to supply RF pulse power to at least one from among the upper electrode and the lower electrode; and a direct current (DC) pulse power supplier configured to supply DC pulse power to the sidewall electrode. 
         [0006]    An on-time of the DC pulse power, during which the DC pulse power is supplied to the sidewall electrode, may be substantially equal to an off-time of the RF pulse power, during which the RF pulse power is not supplied to the upper electrode and the lower electrode. 
         [0007]    A first section of an on-time of the DC pulse power, during which the DC pulse power is supplied to the sidewall electrode, may overlap with an off-time of the RF pulse power, during which the RF pulse power is not supplied to the upper electrode and the lower electrode, and a second section of the on-time of the DC pulse power other than the first section may overlap with a portion of an on-time of the RF pulse power, during which the RF pulse power is supplied to the at least one from among the upper electrode and the lower electrode. 
         [0008]    A voltage value of the DC pulse power may be substantially constant during an on-time of the DC pulse power supplied by the DC pulse power supplier to the sidewall electrode. 
         [0009]    A voltage value of the DC pulse power may vary during an on-time of the DC pulse power supplied by the DC pulse power supplier to the sidewall electrode. 
         [0010]    The DC pulse power supplier may be further configured to, when electron density in a central area of the chamber is higher than an electron density in an outer area of the chamber surrounding the central area, supply the DC pulse power having a positive voltage value to the sidewall electrode. 
         [0011]    The DC pulse power supplier may be further configured to, when electron density in a central area of the chamber is lower than an electron density in an outer area surrounding the central area, supply the DC pulse power having a negative voltage value to the sidewall electrode. 
         [0012]    The plasma generation apparatus may further include a controller configured to supply a first pulse signal to the RF pulse power supplier to control supply of the RF pulse power by the RF pulse supplier and supply a second pulse signal synchronized with the first pulse signal to the DC pulse power supplier to control supply of the DC pulse power by the DC pulse power supplier. 
         [0013]    The plasma generation apparatus may further include a monitoring unit configured to monitor a first electron density in a central region of the chamber and a second electron density in an outer area of the chamber surrounding the central region, and the controller may be further configured to adjust a voltage value of the DC pulse power based on the first electron density and the second electron density. 
         [0014]    The plasma generation apparatus may further include a database configured to store a correlation model between the DC pulse power and an electron density in the chamber, and the controller may be further configured to adjust a voltage value of the DC pulse power based on the correlation model stored in the database. 
         [0015]    According to an aspect of another exemplary embodiment, there is provided a plasma generation apparatus including: a chamber defining a reaction space that is isolated from an external environment; an upper electrode provided in an upper portion of the chamber; a lower electrode provided in a lower portion of the chamber; a sidewall electrode provided at a sidewall of the chamber; a first radio frequency (RF) pulse power supplier configured to supply first RF pulse power to the upper electrode; a second RF pulse power supplier configured to supply second RF pulse power to the lower electrode; and a direct current (DC) power supplier configured to supply DC power to the sidewall electrode during an off-time of the first RF pulse power and an off-time of the second RF pulse power. 
         [0016]    There may be a phase difference between the first RF pulse power and the second RF pulse power, and the DC power supplier may be further configured to supply the DC power to the sidewall electrode when both the first RF pulse power and the second RF pulse power are pulsed off. 
         [0017]    There may be a phase difference between the first pulse power and the second RF pulse power, and the DC power supplier may be further configured to supply the DC power during the off-time of the first RF pulse power or the off-time of the second RF pulse power. 
         [0018]    The plasma generation apparatus may further include a controller configured to supply synchronized first and second pulse signals to the first and second RF pulse power suppliers, respectively. 
         [0019]    The controller may be further configured the DC power so as to be synchronized with on-times and off-times of the first and second RF pulse powers. 
         [0020]    According to an aspect of another exemplary embodiment, there is provided plasma generation apparatus including: a chamber defining a reaction space; a first electrode provided in an upper or lower portion the chamber; a second electrode provided at a sidewall of the chamber; a radio frequency (RF) pulse power supplier configured to supply RF pulse power to the first electrode, the RF pulse power having an on-time during which the RF power is pulsed on and an off-time during which the RF pulse power is pulsed off; and a direct current (DC) pulse power supplier configured to supply DC pulse power to the second electrode, the DC pulse power having an on-time during which the DC pulse power is pulsed on and an off-time during which the DC pulse power is pulsed off, wherein the on-time of the DC pulse power and the off-time of the RF pulse power overlap each other, and the off-time of the DC pulse power and the on-time of the RF pulse power overlap each other. 
         [0021]    The on-time of the DC pulse power and the on-time of the RF pulse power may not overlap each other. 
         [0022]    The on-time of the DC pulse power and the on-time of the RF pulse power may overlap each other. 
         [0023]    The DC pulse power supplier may be further configured to, when an electron density in a central area of the chamber is higher than an electron density in an area surrounding the central area, supply the DC pulse power having a positive voltage during an on-time of the DC pulse power. 
         [0024]    The DC pulse power supplier may be further configured to, when electron density in a central area of the chamber is lower than an electron density in an area surrounding the central area, supply the DC pulse power having a negative voltage during an on-time of the DC pulse power. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and/or other aspects will be more clearly understood from the following detailed description of exemplary embodiments taken in conjunction with the accompanying drawings in which: 
           [0026]      FIG. 1  is a configuration diagram of a plasma generation apparatus according to an exemplary embodiment; 
           [0027]      FIG. 2  is a timing diagram illustrating operations of an RF pulse power and a DC pulse power and electron density in a chamber which varies depending on the RF pulse power and the DC pulse power, according to an exemplary embodiment; 
           [0028]      FIGS. 3A through 3D  are timing diagrams illustrating operations of an RF pulse power and a DC pulse power, according to exemplary embodiments; 
           [0029]      FIG. 4  is a configuration diagram of a plasma generation apparatus according to another exemplary embodiment; 
           [0030]      FIG. 5  is a timing diagram illustrating operations of an RF pulse power and a DC pulse power and electron density in a chamber which varies depending on the RF pulse power and the DC pulse power, according to an exemplary embodiment; 
           [0031]      FIG. 6  is a configuration diagram of a plasma generation apparatus according to another exemplary embodiment; 
           [0032]      FIG. 7  is a configuration diagram of a plasma generation apparatus according to another exemplary embodiment; 
           [0033]      FIG. 8  is a configuration diagram of a plasma generation apparatus according to another exemplary embodiment; and 
           [0034]      FIGS. 9A and 9C  are timing diagrams illustrating operations of first and second RF pulse powers and a DC pulse power, according to exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0035]    Exemplary embodiments will be described more fully with reference to the accompanying drawings. Like reference numerals refer to like elements throughout. 
         [0036]    The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope to those skilled in the art. In the drawings, lengths and sizes of layers and regions may be exaggerated for clarity. 
         [0037]    It will be understood that, although the terms “first”, “second”, “third”, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings. 
         [0038]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0039]    In a case where a certain embodiment may be implemented in a different way, a specific sequence of processes may be different from a sequence to be described. For example, two processes sequentially described may be simultaneously performed in reality, or may be performed in a sequence opposite to the sequence to be described. 
         [0040]    As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
         [0041]    A plasma generation apparatus according to exemplary embodiments may use a capacitively coupled plasma (CCP) method in which wafers are arranged at a point having an RF voltage applied thereto, a magnetically-enhanced RIE (CCP-MERIE) method in which the possibility of ion generation is increased by applying a magnetic field to a plasma space to thereby perform etching, an electron cyclotron resonance (ECR) method in which resonance is generated by causing a microwave frequency to be incident thereon to thereby ionize neutral particles, a transformer coupled plasma (TCP) method in which an RF coil is used but the RF coil is only wound around an upper portion of a process chamber, an inductively coupled plasma (ICP) method in which an RF coil is used but the RF coil is wound around a side surface of a process chamber, a helical plasma method in which an RF coil is used in a spiral form, a high density plasma (HDP) method in which a portion generating plasma and a portion adjusting ion energy are independently controlled, or the like. However, the inventive concept is not limited thereto, and the plasma generation apparatus may use any method insofar as the plasma generation apparatus may apply RF power in the form of a pulse. 
         [0042]      FIG. 1  is a configuration diagram of a plasma generation apparatus  100  according to an exemplary embodiment. 
         [0043]    Referring to  FIG. 1 , the plasma generation apparatus  100  may include a chamber  110 , an RF pulse power supplier  120 , a DC pulse power supplier  130 , and a controller  140 . 
         [0044]    The chamber  110  provides a plasma reaction space that is isolated from an external environment and may have various sizes and forms depending on a size of a wafer W on which a process is to be performed and on process characteristics. 
         [0045]    In some exemplary embodiments, the chamber  110  may be formed of a metal, an insulator, or a combination thereof. In some exemplary embodiments, the inside of the chamber  110  may be coated with an insulator. The chamber  110  may have a rectangular parallelepiped shape or a cylindrical shape, but the inventive concept is not limited thereto. 
         [0046]    A lower electrode  112  may be disposed in a lower portion of the chamber  110 . The lower electrode  112  may function as a wafer chuck. In some exemplary embodiments, the lower electrode  112  may be an electrostatic chuck (ESC) that adsorbs and supports a wafer by an electrostatic force. Alternatively, in some exemplary embodiments, the lower electrode  112  may be a mechanical clamping type chuck or a vacuum chuck that adsorbs and supports a wafer by vacuum pressure. The lower electrode  112  may be provided with a heater that heats the wafer to a process temperature. In some exemplary embodiments, the lower electrode  112  may be grounded. 
         [0047]    An upper electrode  114  may be disposed in an upper portion of the chamber  110 . The pulse power supplier  120  that supplies an RF pulse power to the upper electrode  114  may be connected to the upper electrode  114  to generate plasma of a reaction gas. 
         [0048]    In the current exemplary embodiment, although the RF pulse power supplier  120  is connected to the upper electrode  114  and the lower electrode  112  is grounded, the inventive concept is not limited thereto. For example, unlike the embodiment shown in  FIG. 1 , the upper electrode  114  may be grounded and the RF pulse power supplier  120  may be connected to the lower electrode  112 . 
         [0049]    As the RF pulse power supplier  120  supplies an RF pulse power to the upper electrode  114 , a reaction gas diffused in the chamber  110  may be changed to a plasma state to react with the wafer W disposed on the lower electrode  112 . In other words, the reaction gas is converted into plasma by the RF pulse power, which is applied to the upper electrode  114 , as soon as the reaction gas is diffused in the chamber, and the plasma comes into contact with a surface of the wafer W and thus physically or chemically reacts with the wafer W. Wafer processing processes, such as plasma annealing, etching, plasma-enhanced chemical vapor deposition, physical vapor deposition, and plasma cleaning, may be performed through such reaction. 
         [0050]    In some exemplary embodiments, the RF pulse power supplier  120  may include an RF power generator  122  and a matching unit  124 . For example, the RF power generator  122  may generate a high frequency RF power. The matching unit  124  may output a pulse-modulated RF pulse power by mixing the RF power generated by the RF power generator  122  with a pulse signal output from the controller  140  as will be described below. 
         [0051]    Accordingly, the RF pulse power supplier  120  may be operated in a pulse mode to supply pulse-modulated RF pulse power. In this manner, pulse plasma may be formed by pulsing RF power and applying the pulsed RF power to the upper electrode  114 . In other words, plasma may be generated during an on-time of a pulse and may be extinguished during an off-time of the pulse. By using the pulse plasma for wafer processing, an electron temperature may be lowered as compared to using continuous wave (CW) plasma. Thus, the incidence of wafer damage occurring due to the excessive decomposition of an injected reactive gas may be lowered. 
         [0052]    A plurality of sidewall electrodes  116  may be arranged at sidewalls of the chamber  110 . 
         [0053]    The DC pulse power supplier  130 , which supplies a DC pulse power for adjusting the density of electrons or positive ions of etching gases in the chamber  110 , may be connected to the sidewall electrodes  116 . As the DC pulse power is supplied to the sidewall electrodes  116 , electron density in a central area (C area) of the chamber  110  and electron density in an outside area (E area) surrounding the central area (C area) may be adjusted. This operation will be described in detail below with reference to  FIGS. 2 and 3 . 
         [0054]    The controller  140  may be connected to the RF pulse power supplier  120  and the DC pulse power supplier  130  to control the RF pulse power supplier  120  and the DC pulse power supplier  130 . 
         [0055]    In some exemplary embodiments, the controller  140  may provide a first pulse signal to the RF pulse power supplier  120 . 
         [0056]    The matching unit  124  of the RF pulse power supplier  120  may mix an RF power, generated by the RF power generator  122 , with the first pulse signal, output from the controller  140 , and output a pulse-modulated RF pulse power. In other words, the controller  140  may control the matching unit  124  to turn-on or turn-off of the RF power so that the RF power is pulse-modulated. 
         [0057]    In some exemplary embodiments, the controller  140  may provide a second pulse signal to the DC pulse power supplier  130 . The second pulse signal may be synchronized with the first pulse signal. The DC pulse power supplier  130  may mix a DC power with the second pulse signal output from the controller  140  and output a DC pulse power. 
         [0058]    In some other exemplary embodiments, the controller  140  may control the DC pulse power supplier  130  so that the DC pulse power supplier  130  outputs a DC pulse power, according to an on-time and an off-time of the first pulse signal. For example, the controller  140  may control the DC pulse power suppler  130  so that the DC pulse power suppler  130  supplies a DC power to the sidewall electrodes  116  only during the off-time of the first pulse signal. 
         [0059]      FIG. 2  is a timing diagram illustrating operations of an RF pulse power and a DC pulse power and electron density in a chamber which varies depending on the RF pulse power and the DC pulse power, according to an exemplary embodiment. 
         [0060]    Some elements of the plasma generation apparatus  100  shown in  FIG. 1  may be referred to in descriptions related to  FIG. 2 . 
         [0061]    Referring to  FIG. 2 , an RF pulse power RFPP may be supplied from the RF pulse power supplier  120  to the upper electrode  114 . 
         [0062]    The RF pulse power RFPP may denote that an RF power is supplied in a pulse mode. In other words, the RF power is supplied during on-time RF_To of the RF pulse power RFPP and is not supplied during off-time RF_Tf of the RF pulse power RFPP. Accordingly, plasma is generated during the on-time RF_To of the RF pulse power RFPP and is extinguished during the off-time RF_Tf of the RF pulse power RFPP. 
         [0063]    During the on-time RF_To of the RF pulse power RFPP, a frequency of the RF pulse power RFPP may be about 13.56 MHz. However, the inventive concept is not limited thereto. For example, the frequency of the RF pulse power RFPP may be selected within a frequency range that is equal to or greater than about 1 MHz and is equal to or less than about 100 MHz. 
         [0064]    A duty ratio of the RF pulse power RFPP may be, for example, 50% or more. The duty ratio may denote the ratio between the on-time RF_To and the off-time RF_Tf. For example, when the duty ratio is 60%, the on-time RF_To is 60% of the sum of the on-time RF_To and the off-time RF_Tf, and the off-time RF_Tf is 40% of the sum. When the duty ratio is 50%, the on-time RF_To is equal to the off-time RF_Tf. The duty ratio may be changed depending on a required wafer processing process, and the change of the duty ratio may have an influence on characteristics of pulse plasma to be generated. 
         [0065]    A DC pulse power DCPP 1  may be supplied from the DC pulse power supplier  130  to the sidewall electrodes  116 . 
         [0066]    The DC pulse power DCPP 1  may be synchronized with the RF pulse power RFPP. For example, the DC pulse power DCPP 1  may not be pulsing (hereinafter, referred to “pulsed off”) during the on-time RF_To of the RF pulse power RFPP and may be pulsing (hereinafter, referred to “pulsed on”) during the off-time RF_Tf of the RF pulse power RFPP. In other words, on-time DC 1 _To of the DC pulse power DCPP 1  may be substantially equal to the off-time RF_Tf of the RF pulse power RFPP, and off-time DC 1 _Tf of the DC pulse power DCPP 1  may be substantially equal to the on-time RF_To of the RF pulse power RFPP. 
         [0067]    When the on-time RF_To of the RF pulse power RFPP is equal to the off-time RF_Tf of the RF pulse power RFPP, the duty ratio (DC 1 _To/(DC 1 _To+DC 1 _Tf) of the DC pulse power DCPP 1  may be substantially equal to the duty ratio (RF_To/(RF_To+RF_Tf)) of the RF pulse power RFPP. 
         [0068]    During the on-time RF_To of the RF pulse power RFPP, electrons existing in the chamber  110  may be trapped in plasma generated by the RF pulse power RFPP. However, during the off-time RF_Tf of the RF pulse power RFPP, the plasma may be extinguished and thus the electrons may freely move without being trapped. When a DC power is supplied to the sidewall electrodes  116  during the off-time RF_Tf of the RF pulse power RFPP, as in the current embodiment, the freely movable electrons may move in a direction (+X direction or −X direction of  FIG. 1 ) parallel to the upper surface of the wafer W, depending on the DC power. Specifically, a positive (+) voltage may be applied to the sidewall electrodes  116  during the on-time DC 1 _To of the DC pulse power DCPP 1 , and thus, the electrons in the chamber  110  may be affected by an attractive force from the sidewall electrodes  116 . Accordingly, as shown in  FIG. 2 , central electron density Cd in the central area (C area) of the chamber  110  decreases according to time, and outside electron density Ed in the outside area (E area) of the chamber  110  increases according to time. 
         [0069]    When the DC pulse power DCPP 1  having a positive (+) voltage is supplied to the sidewall electrodes  116  in this manner, a phenomenon in which the electrons in the chamber  110  are concentrated in the central area (C area) may be mitigated, and thus, a process distribution in a central area and an edge area of the wafer W may be improved. 
         [0070]      FIGS. 3A through 3D  are timing diagrams illustrating operations of an RF pulse power and a DC pulse power, according to exemplary embodiments. 
         [0071]    Repeated descriptions reference labels in  FIGS. 3A through 3D  that are the same as those of  FIG. 2  are omitted for simplification of description. 
         [0072]    In addition, some elements of the plasma generation apparatus  100  shown in  FIG. 1  may be referred to in descriptions related to  FIGS. 3A through 3D . 
         [0073]    Referring to  FIG. 3A , an RF pulse power RFPP may be supplied from the RF pulse power supplier  120  to the upper electrode  114 , and a DC pulse power DCPP 2  may be supplied from the DC pulse power supplier  130  to the sidewall electrodes  116 . 
         [0074]    The DC pulse power DCPP 2  may be supplied to the sidewall electrodes  116  while being synchronized with the RF pulse power RFPP and being shifted by a delay time td compared to the RF pulse power RFPP. In other words, the DC pulse power DCPP 2  may not be pulsed on directly after the RF pulse power RFPP enters into the off-time RF_Tf from the on-time RF_To, but may be pulsed on after a lapse of the delay time td. In addition, the DC pulse power DCPP 2  may not be pulsed off directly after the RF pulse power RFPP enters into the on-time RF_To from the off-time RF_Tf, but may be pulsed off after a lapse of the delay time td. 
         [0075]    When the DC pulse power DCPP 2  is supplied to the sidewall electrodes  116  while being shifted, a DC power may be supplied to be suitable for a pulse off-time even if the phase of the RF pulse power RFPP varies due to process variation. 
         [0076]    Referring to  FIG. 3B , an RF pulse power RFPP may be supplied from the RF pulse power supplier  120  to the upper electrode  114 , and an DC pulse power DCPP 3  may be supplied from the DC pulse power supplier  130  to the sidewall electrodes  116 . 
         [0077]    The DC pulse power DCPP 3  may be supplied to the sidewall electrode  116  while being synchronized with the RF pulse power RFPP, and may be pulsed on in a portion of the on-time RF_To as well as the off-time RF_Tf of the RF pulse power RFPP. In other words, a first section X 1  of on-time DC 3 _To of the DC pulse power DCPP 3  may overlap with the off-time RF_Tf of the RF pulse power RFPP, and a remaining second section X 2  and X 3  other than the first section X 1  in the on-time DC 3 _To of the DC pulse power DCPP 3  may overlap with a portion of the on-time RF_To of the RF pulse power RFPP. 
         [0078]    Specifically, the DC pulse power DCPP 3  may be pulsed on for a delay time td 1  before the RF pulse power RFPP enters into the off-time RF_Tf from the on-time RF_To, and may be pulsed off for a delay time td 2  after the RF pulse power RFPP enters into the on-time RF_To from the off-time RF_Tf. In this case, the on-time DC 3 _To of the DC pulse power DCPP 3  may be longer than the off-time RF_Tf of the RF pulse power RFPP. 
         [0079]    When the on-time DC 3 _To of the DC pulse power DCPP 3  overlaps with a portion of the on-time RF_To of the RF pulse power RFPP in this manner, a sufficient DC power may be supplied even while the RF pulse power RFPP may be distorted or offset due to a reflected wave. 
         [0080]    Referring to  FIG. 3C , an RF pulse power RFPP may be supplied from the RF pulse power supplier  120  to the upper electrode  114 , and a DC pulse power DCPP 4  may be supplied from the DC pulse power supplier  130  to the sidewall electrodes  116 . 
         [0081]    The DC pulse power DCPP 4  may be supplied to the sidewall electrode  116  while being synchronized with the RF pulse power RFPP, and may be pulsed on only in a portion of the off-time RF_Tf of the RF pulse power RFPP. For example, the DC pulse power DCPP 4  may be pulsed on for a delay time td 3  after the RF pulse power RFPP enters into_the off-time RF_Tf from the on-time RF_To, and may be pulsed off for a delay time td 4  before the RF pulse power RFPP enters into the on-time RF_To from the off-time RF_Tf. 
         [0082]    When the DC pulse power DCPP 4  is pulsed on only in a portion of the off-time RF_Tf of the RF pulse power RFPP, the DC pulse power DCPP 4  may be supplied within a range that does not have an influence on a plasma processing process that may be performed during the on-time RF_To of the RF pulse power RFPP. 
         [0083]    Referring to  FIG. 3D , an RF pulse power RFPP may be supplied from the RF pulse power supplier  120  to the upper electrode  114 , and an DC pulse power DCPP 5  may be supplied from the DC pulse power supplier  130  to the sidewall electrodes  116 . 
         [0084]    When the DC pulse power DCPP 5  is supplied to the sidewall electrode  116 , as in the current embodiment, electrons, which may freely move during the off-time RF-Tf of the RF pulse power RFPP, may move in a direction (+X direction or −X direction of  FIG. 1 ) parallel to the upper surface of the wafer W, depending to the DC pulse power DCPP 5 . Specifically, a negative (−) voltage may be applied to the sidewall electrodes  116  during the on-time DC 5 _To of the DC pulse power DCPP 5 , and thus, electrons in the chamber  110  may be affected by a repulsive force from the sidewall electrodes  116 . Accordingly, as shown in  FIG. 3D , central electron density Cd in the central area (C area) of the chamber  110  increases according to time, and outside electron density Ed in the outside area (E area) of the chamber  110  decreases according to time. 
         [0085]    When the DC pulse power DCPP 5  having a negative (−) voltage is supplied to the sidewall electrodes  116  in this manner, a phenomenon in which the electrons in the chamber  110  are concentrated in the outside area (E area) may be mitigated, and thus, a process distribution in a central area and an edge area of the wafer W may be improved. 
         [0086]    In the current embodiment of  FIG. 3D , although the DC pulse power DCPP 5  is pulsed off during the on-time RF-To of the RF pulse power RFPP and is pulsed on during the off-time RF-Tf of the RF pulse power RFPP, the DC pulse power DCPP 5  may be supplied to the sidewall electrodes  115  while being more shifted by a certain time than the RF pulse power RFPP, similar to the case described above with reference to  FIG. 3A . 
         [0087]    In some exemplary embodiments, the DC pulse power DCPP 5  may be pulsed on in a portion of the on-time RF-To as well as the off-time RF-Tf of the RF pulse power RFPP, similar to the case described above with reference to  FIG. 3B . 
         [0088]    In some other exemplary embodiments, the DC pulse power DCPP 5  may be pulsed on in a portion of the off-time RF-Tf of the RF pulse power RFPP, similar to the case described above with reference to  FIG. 3C . 
         [0089]      FIG. 4  is a configuration diagram of a plasma generation apparatus  200  according to another exemplary embodiment.  FIG. 5  is a timing diagram illustrating an operation of an RF pulse power and an operation of a DC pulse power according to an exemplary embodiment and electron density in a chamber which varies depending on the RF pulse power and the DC pulse power. 
         [0090]    Referring to  FIGS. 4 and 5 , the plasma generation apparatus  200  may include a chamber  110 , an RF pulse power supplier  120 , a DC pulse power supplier  230 , a controller  240 , and a monitoring unit  250 . 
         [0091]    The monitoring unit  250  may monitor the density of electrons existing in the chamber  110 . For example, the monitoring unit  250  may monitor central electron density Dc in a central area (C area) of the chamber  110  and outside electron density Ed in an outside area (E area) of the chamber  110  in real time. 
         [0092]    In some exemplary embodiments, the monitoring unit  250  may transmit data, which relates to the central electron density Cd and the outside electron density Ed, to the controller  240 . The controller  240  may adjust a voltage value of a DC pulse power DCPP 6  that is supplied to the sidewall electrodes  116  by the DC pulse power supplier  230 , based on the central electron density Cd and the outside electron density Ed received from the monitoring unit  250 . 
         [0093]    Referring to the timing diagram shown in  FIG. 5 , if the central electron density Cd is higher than the outside electron density Ed at the moment (for example, at times ta 1 , ta 2 , and ta 4 ) when the RF pulse power RFPP that is supplied by the RF pulse power supplier  120  enters into the off-time RF_Tf from the on-time RF_To (ta 1 , ta 2 , ta 3 , and ta 4 ), the DC pulse power DCPP 6  may supply a positive (+) voltage during a pulse on-time thereof. On the contrary, if the central electron density Cd is lower than the outside electron density Ed at the moment (for example, at times ta 3 ) when the RF pulse power RFPP enters into the off-time RF_Tf from the on-time RF_To (ta 1 , ta 2 , ta 3 , and ta 4 ), the DC pulse power DCPP 6  may supply a negative (−) voltage during a pulse on-time thereof. 
         [0094]    By monitoring the density of electrons existing in the chamber  110  and adjusting a voltage value of the DC pulse power DCPP 6  based on the monitored density of electrons, a process distribution in a central area and an edge area of the wafer W may be improved. 
         [0095]      FIG. 6  is a configuration diagram of a plasma generation apparatus  300  according to another exemplary embodiment. 
         [0096]    Referring to  FIG. 6 , the plasma generation apparatus  300  may include a chamber  110 , an RF pulse power supplier  120 , a DC pulse power supplier  330 , a controller  340 , and a memory storing a database  360 . 
         [0097]    A correlation model between a DC pulse power, which may be supplied by the DC pulse power supplier  330 , and an electron density (for example, the central electron density Cd and the outside electron density Ed of  FIG. 5 ) may be stored in the database  360 , and the correlation model may be obtained through a test. 
         [0098]    The correlation model between the DC pulse power and the electron density may include a correlation established by a non-modeling approach, such as a decision tree analysis algorithm, as well as a modeling approach such as a neural network algorithm. 
         [0099]    In some exemplary embodiments, the correlation model between the DC pulse power and the electron density may be established through any of various algorithms, such as a multiple linear regression algorithm, a multiple nonlinear regression algorithm, a neural network algorithm, a support vector regression algorithm, a K nearest neighbor (KNN) regression algorithm, and a design of experiment (DOE) algorithm. 
         [0100]    The database  360  may transmit the correlation model between the DC pulse power and the electron density to the controller  340 . The controller  340  may control the DC pulse power, which is supplied to the sidewall electrode  116  by the DC pulse power supplier  330 , based on the correlation model between the DC pulse power and the electron density. 
         [0101]    By controlling the DC pulse power, which is supplied to the sidewall electrode  116  by the DC pulse power supplier  330 , based on the correlation model between the DC pulse power and the electron density, the electron density in the central area (C area) and the electron density in the outside area (E area) may be controlled. 
         [0102]      FIG. 7  is a configuration diagram of a plasma generation apparatus  400  according to another exemplary embodiment. 
         [0103]    Referring to  FIG. 7 , the plasma generation apparatus  400  may include a chamber  410 , first and second RF pulse power suppliers  420 _ 1  and  420 _ 2 , a DC pulse power supplier  430 , and a controller  440 . 
         [0104]    The chamber  410  may include a lower electrode  412 , an upper electrode structure  414 , a plurality of sidewall electrodes  416 , and a gas-discharging unit  418 . 
         [0105]    The upper electrode structure  414  may include a gas-supplying unit  414   a,  a nozzle  414   b,  and an upper electrode  414   c.  In some embodiments, the gas-supplying unit  414   a  may be disposed in the upper electrode structure  414 , as shown in  FIG. 7 . However, the inventive concept is not limited thereto. For example, the gas-supplying unit  414   a  may be disposed outside the chamber  410 , independent of the upper electrode structure  414 . 
         [0106]    The gas-supplying unit  414   a  may supply a reaction gas to the chamber  410  via the nozzle  414   b,  and a gas may be exhausted via the gas-discharging unit  418  to maintain the chamber  410  in a vacuum state. 
         [0107]    The first RF pulse power supplier  420 _ 1  for applying a first RF pulse power to the upper electrode  414   c  may be connected to the upper electrode  414   c.    
         [0108]    In some embodiments, the first RF pulse power supplier  420 _ 1  may include a first RF power generator  422 _ 1  and a first matching unit  424 _ 1 . 
         [0109]    In some exemplary embodiments, an RF power generated by the first RF power generator  422 _ 1  and a pulse signal output from the controller  440  may be mixed in the first matching unit  424 _ 1  to generate a pulse-modulated RF pulse power. 
         [0110]    The first RF pulse power that is supplied by the first RF pulse power supplier  420 _ 1  may be, for example, a source power. 
         [0111]    In some exemplary embodiments, the first RF pulse power may be, for example, a high frequency (HF) pulse in a frequency range that is equal to or greater than about 13.56 MHz and is less than about 60 MHz or a very high frequency (VHF) pulse in a frequency range that is equal to or greater than about 60 MHz and is less that about several hundred MHz. 
         [0112]    In some other embodiments, the first RF pulse power may be an RF pulse obtained by mixing multiple frequencies. For example, the first RF pulse power may be variously changed by mixing the VHF pulse and the HF pulse. 
         [0113]    The lower electrode  412  may function as a wafer chuck. In some embodiments, the lower electrode  412  may be an ESC that adsorbs and supports a wafer by an electrostatic force. In some other embodiments, the lower electrode  412  may be a mechanical clamping type chuck or a vacuum chuck that adsorbs and supports a wafer by vacuum pressure. 
         [0114]    In some exemplary embodiments, a second RF pulse power supplier  420 _ 2  may be connected to the lower electrode  412 . The second RF pulse power supplier  420 _ 2  may include a second RF power generator  422 _ 2  and a second matching unit  424 _ 2 . 
         [0115]    In some exemplary embodiments, an RF power generated by the second RF power generator  422 _ 2  and a pulse signal output from the controller  440  may be mixed in the second matching unit  424 _ 2  to generate a pulse-modulated RF pulse power. 
         [0116]    The second RF pulse power that is supplied by the second RF pulse power supplier  420 _ 1  may be a bias power. 
         [0117]    The second RF pulse power supplier  420 _ 2  may supply the second RF pulse power in a frequency that is lower than that of the first RF pulse power that is supplied by the first RF pulse power supplier  420 _ 1 . For example, the second RF pulse power may be a low frequency (LF) pulse in a frequency range that is equal to or greater than about 0.1 MHz and is less than about 13.56 MHz. 
         [0118]    The plasma generation apparatus  400  may use a CCP method. Specifically, when the first RF pulse power is supplied to the upper electrode  414   c  and the second RF pulse power is supplied to the lower electrode  412 , an electric field may be induced between the upper electrode  414   c  and the lower electrode  412 . At this time, when a reaction gas is injected in the chamber  410  via the gas-supplying unit  414   a  installed in the top of the chamber  410 , the reaction gas may be changed to a plasma state due to an electric field induced inside the chamber  410 . A wafer processing process, such as an etching or thin film deposition process for a wafer W, may be performed by using the generated plasma. 
         [0119]    In some exemplary embodiments, the first RF pulse power that is supplied to the upper electrode  414   c  may perform a function of igniting plasma, and the second RF pulse power that is supplied to the lower electrode  412  may perform a function of controlling plasma. 
         [0120]    The plurality of sidewall electrodes  416  may be arranged at sidewalls of the chamber  410 . The DC pulse power supplier  430 , which supplies a DC pulse power for adjusting the density of electrons or positive ions of etching gases in the chamber  410 , may be connected to the sidewall electrodes  416 . 
         [0121]    The controller  440  may control the first and second RF pulse power suppliers  420 _ 1  and  420 _ 2  and the DC pulse power supplier  430 . 
         [0122]    In some exemplary embodiments, RF powers generated by the first and second RF power generators  422 _ 1  and  422 _ 2  and a DC power generated in the DC pulse power supplier  430  may be pulse-modulated by the control of the controller  440 . In addition, first and second RF pulse powers that are supplied by the first and second RF pulse power suppliers  420 _ 1  and  420 _ 2  and a DC pulse power that is supplied by the DC pulse power supplier  430  may be synchronized by the control of the controller  440 . 
         [0123]      FIG. 8  is a configuration diagram of a plasma generation apparatus  500  according to another exemplary embodiment. 
         [0124]    Referring to  FIG. 8 , the plasma generation apparatus  500  may include a chamber  510 , first and second RF pulse power suppliers  420 _ 1  and  420 _ 2 , a DC pulse power supplier  430 , and a controller  440 . 
         [0125]    The chamber  510  may include a lower electrode  412 , an upper electrode structure  514 , a plurality of sidewall electrodes  416 , and a gas-discharging unit  418 . 
         [0126]    The upper electrode structure  514  may include a gas-supplying unit  514   a,  a nozzle  514   b,  an insulating plate  514   c,  and an antenna  514   d.  In some embodiments, the gas-supplying unit  514   a  may be disposed in the upper electrode structure  514 , as shown in  FIG. 8 . However, the inventive concept is not limited thereto. For example, the gas-supplying unit  514   a  may be disposed outside the chamber  510 , independent of the upper electrode structure  514 . 
         [0127]    The gas-supplying unit  514   a  may supply a reaction gas to the chamber  510  via the nozzle  514   b,  and a gas may be exhausted via the gas-discharging unit  518  to maintain the chamber  510  in a vacuum state. 
         [0128]    The plasma generation apparatus  500  may use an ICP method. Specifically, after the chamber  510  is exhausted by the gas-discharging unit  518 , a reaction gas for generating plasma is supplied from the gas-supplying unit  514   a  to the chamber  510 . Furthermore, a first RF pulse power from the first RF pulse power supplier  420 _ 1  is applied to the antenna  514   a.  As the first RP pulse power is applied to the antenna  514   d,  lines of magnetic force may be formed around the antenna  514   d.  An induced electric field may be formed inside the chamber  510  due to the lines of magnetic force, and the induced electric field may heat electrons to generate ICP. 
         [0129]    In some exemplary embodiments, the insulating plate  514   c  may be disposed between the antenna  514   d  and the lower electrode  412 . The insulating plate  514   c  may facilitate transmission of energy supplied from the first RF pulse power supplier  420 _ 1  to plasma by an inductive coupling by reducing a capacitive coupling between the antenna  514   d  and the plasma. 
         [0130]    The antenna  514   d  may have one or more spiral coil shapes as seen in a plan view. However, the inventive concept is not limited thereto. For example, the antenna  514   d  may have various shapes other than the spiral coil shape. 
         [0131]      FIGS. 9A through 9C  are timing diagrams illustrating operations of first and second RF pulse powers and an operation of a DC pulse power according to exemplary embodiments. 
         [0132]    Some elements of the plasma generation apparatus  400  shown in  FIG. 7  may be referred to in descriptions referred to  FIGS. 9A through 9C . 
         [0133]    Referring to  FIG. 9A , a first RF pulse power RFPP 1  may be supplied from the first RF pulse power supplier  420 _ 1  to the upper electrode  414   c,  a second RF pulse power RFPP 2  may be supplied from the second RF pulse power supplier  420 _ 2  to the lower electrode  412 , and a DC pulse power DCPP 7  may be supplied from the DC pulse power supplier  430  to the sidewall electrodes  416 . 
         [0134]    The first RF pulse power RFPP 1  and the second RF pulse power RFPP 2  may be synchronized with each other. In some embodiments, the first RF pulse power RFPP 1  and the second RF pulse power RFPP 2  may be simultaneously pulsed on and pulsed off without having a phase difference. Accordingly, the on-time RF 1 _To and the off-time RF 1 _Tf of the first RF pulse power RFPP 1  may be substantially the same as the on-time RF 2 _To and the off-time RF 2 _Tf of the second RF pulse power RFPP 2 , respectively. 
         [0135]    The DC pulse power DCPP 7  may be synchronous with the first RF pulse power RFPP 1  and the second RF pulse power RFPP 2 . 
         [0136]    For example, as shown in  FIG. 9A , the DC pulse power DCPP 1  may be pulsed off during the on-times RF 1 _To and RF 2 _To of the first and second RF pulse powers RFPP 1  and RFPP 2 , and may be pulsed on during the off-times RF 1 _Tf and RF 2 _Tf of the first and second RF pulse powers RFPP 1  and RFPP 2 . In other words, the on-time DC 7 _To of the DC pulse power DCPP 7  may be substantially the same as the off-times RF 1 _Tf and RF 2 _Tf of the first and second RF pulse powers RFPP 1  and RFPP 2 , and the off-time DC 7 _Tf of the DC pulse power DCPP 7  may be substantially the same as the on-times RF 1 _To and RF 2 _To of the first and second RF pulse powers RFPP 1  and RFPP 2 . 
         [0137]    Referring to  FIG. 9B , a first RF pulse power RFPP 1  may be supplied from the first RF pulse power supplier  420 _ 1  to the upper electrode  414   c,  a second RF pulse power RFPP 2  may be supplied form the second RF pulse power supplier  420 _ 2  to the lower electrode  412 , and a DC pulse power DCPP 8  may be supplied from the DC pulse power supplier  430  to the sidewall electrodes  416 . 
         [0138]    The first RF pulse power RFPP 1  and the second RF pulse power RFPP 2  may be synchronized with each other, but may be supplied with having a phase difference. In other words, the second RF pulse power RFPP 2  may be shifted by a delay time td 5  compared to the first RF pulse power RFPP 1 . Specifically, the second RF pulse power RFPP 2  may not be pulsed off directly after the first RF pulse power RFPP 1  enters into the off-time RF_Tf from the on-time RF_To, but may be pulsed off after a lapse of a delay time td 5 . In addition, the second RF pulse power RFPP 2  may not be pulsed on directly after the first RF pulse power RFPP 1  enters into the on-time RF_To from the off-time RF_Tf, but may be pulsed on after a lapse of a delay time td 6 . 
         [0139]    In some embodiments, as shown in  FIG. 9B , the DC pulse power DCPP 8  may be pulsed on when both the first RF pulse powers RFPP 1  and the second RF pulse power RFPP 2  are pulsed off, that is, only in a period in which the off-time RF 1 _Tf of the first RF pulse powers RFPP 1  and the off-time RF 2 _Tf of the second RF pulse power RFPP 2  overlap each other. 
         [0140]    In this case, the on-time DC 8 _To of the DC pulse power DCPP 8  may be shorter than the off-time RF 1 _f of the first RF pulse power RFPP 1  or the off-time RF 2 _Tf of the second RF pulses power RFPP 2 , and the off-time DC 8 _Tf of the DC pulse power DCPP 8  may be longer than the on-time RF 1 _To of the first RF pulse power RFPP 1  or the on-time RF 2 _To of the second RF pulses power RFPP 2 . 
         [0141]    Referring to  FIG. 9C , a first RF pulse power RFPP 1  may be supplied from the first RF pulse power supplier  420 _ 1  to the upper electrode  414   c,  a second RF pulse power RFPP 2  may be supplied form the second RF pulse power supplier  420 _ 2  to the lower electrode  412 , and a DC pulse power DCPP 9  may be supplied from the DC pulse power supplier  430  to the sidewall electrodes  416 . 
         [0142]    As described with reference with  FIG. 9B , the second RF pulse power RFPP 2  may be shifted by a delay time td 5  compared to the first RF pulse power RFPP 1 . 
         [0143]    In some embodiments, the DC pulse power DCPP 9  may be pulsed on during the off-time of one selected from the first and second RF pulse powers RFPP 1  and RFPP 2 . For example, the DC pulse power DCPP 9  may be pulsed on during the off-time RF 1 _Tf of the first RF pulse power RFPP 1 . 
         [0144]    In this case, the on-time DC 9 _To of the DC pulse power DCPP 9  may be substantially equal to the off-time RF 1 _Tf of the first RF pulse power RFPP 1 , and the off-time DC 9 _Tf of the DC pulse power DCPP 9  may be substantially equal to the on-time RF 1 _To of the first RF pulse power RFPP 1 . 
         [0145]    While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.