Abstract:
A cleaning apparatus of an exhaust path of a process reaction chamber used in a manufacturing of articles including a semiconductor or an LCD. The cleaning apparatus of the exhaust path includes a housing having an inflow pipe, connected to an upstream end of the exhaust path, an outflow pipe, connected to a downstream end of the exhaust path, and a connecting pipe disposed between the inflow pipe and the outflow pipe. A radio frequency generator in the housing applies radio frequency power to the inflow pipe and to the outflow pipe via respective coils. Plasma induced within the inflow and outflow pipes from RF power applied via the respective coils causes the generation of radicals from the exhaust gas flowing within. The radicals act to dislodge accumulated particulates within the exhaust path downstream of the cleaning apparatus.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    N/A 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a cleaning apparatus for an exhaust path of a process reaction chamber used in a manufacturing process for semiconductors or LCDs, and more particularly, to a cleaning apparatus for the exhaust path in which an inflow pipe and an outflow pipe are formed inside a housing to which a gas inlet and a gas outlet are attached, radio frequency power from a radio frequency generator is applied to the inflow pipe and the outflow pipe, and a capacitor and a coil for impedance matching are provided. 
         [0003]    In general, a plasma generator is used in a process of depositing or patterning a structure implemented on a semiconductor or a liquid crystal display LCD. Plasma refers to an ionized gas state consisting of ions, electrons, or radicals, and is generated by a high-temperature state, a strong electric field, or a radio frequency (RF) electromagnetic field. 
         [0004]    In particular, the plasma generation by a glow discharge phenomenon is performed by free electrons excited by a direct current (DC) or radio frequency electromagnetic field, and the excited free electrons collide with gas molecules to generate activity groups such as ions, radicals, and electrons. Such activity groups physically or chemically act on the surface of target surfaces to alter the properties thereof. 
         [0005]    In this way, a process of intentionally altering the surface properties of a material by an active group is referred to as a surface treatment, and generally, the surface treatment with plasma refers to cleaning or etching the surface of the material by utilizing the products of a plasma state. In the process reaction chamber for executing the surface treatment of the object using the plasma, an exhaust pipe is connected to the process reaction chamber in which a plasma is generated and from which a gas such as argon gas is discharged to the outside. A vacuum pump connected to or in-line with the exhaust pipe causes the exhaust gas to flow to the outside, while gate valves and a pressure regulating valve implement flow and pressure control of the exhaust gas. A scrubber reduces the concentration of harmful substances in the exhaust gas to a level below an acceptable standard prior to discharge of the exhaust gas to the atmosphere. 
         [0006]    However, solid precipitate generated by the deposition or etching process taking place within the process reaction chamber may enter the exhaust pipe and accumulate on an interior surface of the exhaust pipe. Over time, this accumulation can cause operational failure of the gate valve or the pressure regulating valve or can lead to interference with the smooth emission of the exhaust gas by blocking the exhaust pipe. 
         [0007]    Therefore, an operator needs to manually remove the solid precipitate of the exhaust gas to enable the continuous emission of the exhaust gas. However, since it is necessary to temporarily stop the reaction chamber processing during such manual cleaning, a decrease in productivity results. In addition, since harsh chemicals are used in the manual precipitation removal process, safety risks are also always present. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention solves the conventional problems described above by providing a cleaning apparatus for the exhaust path of a process reaction chamber which can inhibit the accumulation of particulates in the exhaust path, thereby obviating reduced productivity of an associated process reaction chamber. Worker safety is improved because the exhaust path of the process reaction chamber is cleaned through the use of the presently disclosed cleaning apparatus and not through manpower. Excellent cleaning effect is achieved. 
         [0009]    According to an aspect of the present invention, there is provided a cleaning apparatus for the exhaust path of a process reaction chamber. The cleaning apparatus includes an inflow pipe and an outflow pipe formed on the inside of a cleaning apparatus housing to which a gas inlet and a gas outlet are attached. A radio frequency (RF) generator, also disposed within the housing, provides RF energy to the inflow pipe and the outflow pipe. Capacitors and coils for impedance matching are provided in conjunction with the inflow pipe and outflow pipe. 
         [0010]    It should be understood that different embodiments of the invention, including those described under different aspects of the invention, are meant to be generally applicable to all aspects of the invention. Portions of any one embodiment may be combined with portions of any other embodiment. All examples provided herein are intended to be illustrative and non-limiting. 
         [0011]    The cleaning apparatus of a process reaction chamber exhaust path of the present invention having a configuration as described has an effect that can obviate a reduction in productivity and can contribute to worker safety by cleaning the exhaust path of the process reaction chamber without the need for manual intervention. 
         [0012]    Further, according to presently disclosed invention, fluorine radicals or chlorine radicals are formed twice in the cleaning apparatus, once in the inflow pipe and once in the outflow pipe, thereby exhibiting excellent cleaning effect. 
         [0013]    Since the radio frequency power applied to the cleaning apparatus of the present invention is a radio frequency in the range of 40 to 100 MHz, the cleaning effect can be enhanced. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0014]    Various aspects of at least one embodiment of the present invention are discussed below with reference to the accompanying figures. It will be appreciated that, for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, however, not every component may be labeled in every drawing. The figures are provided for the purposes of illustration and explanation and are not intended as a definition of the limits of the invention. In the figures: 
           [0015]      FIG. 1  is a schematic diagram of an exhaust path of a process reaction chamber in which a cleaning apparatus of the presently disclosed invention is installed; 
           [0016]      FIG. 2  is a perspective view of the cleaning apparatus of  FIG. 1 ; 
           [0017]      FIG. 3  is an exploded perspective view of the cleaning apparatus of  FIG. 2 ; 
           [0018]      FIG. 4  is a side view of the cleaning apparatus of  FIG. 2 ; 
           [0019]      FIG. 5  is a schematic cross-sectional view of a flow pipe of the cleaning apparatus of  FIG. 2 ; 
           [0020]      FIGS. 6A and 6B  are schematic diagrams of first and second embodiments of RF coils disposed about a gas pipe and an RF feed connected thereto; 
           [0021]      FIGS. 7A, 7B, and 7C  are schematic diagrams of third, fourth, and fifth embodiments of RF coils disposed about a gas pipe and an RF feed connected thereto; 
           [0022]      FIG. 8  is a schematic diagram of an inflow pipe having a pair of coils disposed thereabout, a connecting pipe, an outflow pipe having a pair of coils disposed thereabout, and an RF feed connected to the coils; 
           [0023]      FIG. 9  is a schematic diagram of an RF generator, a matching network, and an RF feed connected to a coil disposed about a pipe; 
           [0024]      FIGS. 10A and 10B  are exemplary embodiments of a matching network for use with the RF generator of  FIG. 9 ; 
           [0025]      FIGS. 11A, 11B, and 11C  are exemplary embodiments of matching network circuits for use with the RF generator of  FIGS. 9, 10A, and 10B . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments of the present invention. It will be understood by those of ordinary skill in the art that these embodiments of the present invention may be practiced without some of these specific details. In some instances, well-known methods, procedures, components and structures may not be described in detail so as not to obscure the embodiments of the present invention. 
         [0027]    Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention. 
         [0028]      FIG. 1  is a schematic diagram of an exhaust path  11  of a process reaction chamber  10  in which the cleaning apparatus  1  of the present invention is installed. As described above, the cleaning apparatus of the present invention is installed on an exhaust pipe  20  connected to the process reaction chamber. 
         [0029]    A first gate valve  30  and a second gate valve  31  for controlling the flow and pressure of the exhaust gas with a pressure regulating valve  50  therebetween are installed in the exhaust pipe  20 . 
         [0030]    Also, a turbo-molecular pump  40  is installed between the first gate valve  30  and the pressure regulating valve  50 . A vacuum pump  60  which provides the negative pressure for the discharge of exhaust gas from the process chamber  10  is installed on a downstream side of the second gate valve  31 . The exhaust gas discharged by the vacuum pump  60  is discharged to the atmosphere through an exhaust port  80  after harmful substances are removed or reduced by a scrubber  70 . 
         [0031]    The cleaning apparatus  1  of the present invention, discussed in detail below and with respect to  FIGS. 2-4 , may be installed at a point (point A) between the pressure regulating valve  50  and the second gate valve  31  of the exhaust part system of the process reaction chamber. Alternatively, the cleaning apparatus  1  of the present invention may be installed at a point (point B) between the vacuum pump  60  and the scrubber  70 . Furthermore, in order to maximize the exhaust path cleaning, instances of the cleaning apparatus  1  can be installed at both points A and B. 
         [0032]    Hereinafter, the configuration and operation of the cleaning apparatus of the exhaust path of the presently disclosed invention, installed in a process reaction chamber exhaust path as described above, will be described in further detail with reference to  FIGS. 2 to 4 .  FIG. 2  is a perspective view of the cleaning apparatus  1  of the present invention,  FIG. 3  is a partially exploded perspective view of the cleaning apparatus of the present invention, and  FIG. 4  is a side cutaway view of the cleaning apparatus of the present invention. 
         [0033]    Referring to  FIGS. 2-4 , the cleaning apparatus  1  includes a hexahedral-shaped housing  100  which has a front plate  101 , side plates  102 , a top plate  103 , and a gas inlet  210  and a gas outlet  220  attached to the front plate  101  of the housing  100 . The gas inlet is in mechanical and fluid communication with an upstream portion of the exhaust pipe  20 , while the gas outlet is in mechanical and fluid communication with a downstream portion of the exhaust pipe. The exhaust gas flow thus extends from the exhaust pipe, into the gas inlet, through the cleaning apparatus as described below, out the gas outlet and back into a downstream portion of the exhaust pipe. 
         [0034]    An inlet mounting plate  211  and an inlet coupling  212 , which attach the gas inlet  210  to the front plate  101 , are mounted to the rear end of the gas inlet  210 . This direction is also considered downstream of the inlet. 
         [0035]    One, upstream side of an inflow pipe  213 , through which gas introduced into the gas inlet  210  flows, is connected to the inlet coupling  212 , while the other, downstream side of the inflow pipe is connected to a connecting block  214  attached to a connecting pipe  250 . 
         [0036]    The connecting pipe  250  is a pipeline which allows the gas introduced from the inflow pipe  213  to flow to an outflow pipe  223 . As noted above, one end of the connecting pipe is connected to the inflow pipe  213  through an inflow connecting block  214 . The other end of the connecting pipe is connected to the outflow pipe  223  through an outflow connecting block  224 . 
         [0037]    An outlet block  230  and an outlet connecting pipe  240  are attached to the rear end of the gas outlet  220 . An outlet mounting plate  221  and an outlet coupling  222 , attached to the outlet connecting pipe  240 , are mounted to the front plate  101 . One, downstream end of the outflow pipe  223  is coupled to an opposite side of the outlet coupling, thereby allowing the gas flowing through the connecting pipe  250  to flow to the gas outlet  220 . 
         [0038]    Disposed about each of the inflow pipe  213  and the outflow pipe  223  are electrical conductors configured as paired RF coils  340 ,  350 . The first pair of coils  340  is wound around an outer circumferential surface of the inflow pipe  213  several times, and the second pair of coils  350  is wound around an outer circumferential surface of the outflow pipe  223  several times. In the illustrated embodiment of  FIGS. 3 &amp; 4 , each coil of each pair has four turns. 
         [0039]    Radio frequency (RF) power is applied to a first end of the first pair of coils  340  via a matching network  500  and a terminal on a plate-like connector  360 . Radio frequency power is applied to a first end of the second coil  350  via the matching network and another terminal on the plate-like connection. The second end of the first and second coils are connected to ground. 
         [0040]    A variety of coil configurations are contemplated. RF power may be divided among coils in two, four, or more paths in order to define plural current paths about a pipe or pipes, all with a common reference. The flux lines for each of the coils are aligned so as to enhance the magnetic fields within the respective pipes. With such configurations, low impedance for VHF frequency resonance is presented and the area for sustaining a plasma within the pipes is enlarged. Low impedance enhances the ability to achieve desired impedance matching while high current values enhance plasma generation. 
         [0041]    In  FIGS. 6A and 6B , RF power is applied to first and second coils  402 ,  404  via an RF feed  410 . For example, the RF feed may be the plate-like connector  360  as shown in  FIG. 3 . As may be seen in these figures, a variety of physical configurations are possible, each with the effect of generating plasma-inducing magnetic fluxes as shown by the arrows in the respective pipes  400 . 
         [0042]    In  FIGS. 7A and 7B , a split pipe  406  is provided. In  FIG. 7A , the serial coil  402 ,  404  configuration of  FIG. 6A  is employed, with serial magnetic flux lines generated. In  FIG. 7B , coils  412 ,  414  are disposed on either side of the split pipe  406 , generating lines of flux that are parallel. 
         [0043]    In  FIG. 7C , the embodiments of  FIGS. 7A and 7B  are combined, resulting in four flux lines for greater plasma generation. 
         [0044]      FIG. 8  is a simplified schematic of the coil embodiment employed in  FIG. 3 . The first coil pair  340  is disposed about the inflow pipe  213  and the second coil pair  350  is disposed about the outflow pipe  223 . Both coil pairs are energized by RF power coupled through the plate-like connector  360  serving as the RF feed. 
         [0045]    In all of these exemplary configurations, multiple coils are closely spaced, resulting in an amplification of the applied magnetic flux, deeper penetration into the gas flowing through the pipe, and higher density of resulting plasma. 
         [0046]    In the abstract and with reference to  FIG. 9 , each coil, such as one of the first pairs of coils  340 , is driven by connection to an RF feed  504 , such as the plate-like connector  360 . The RF feed is driven by an RF generator, phase shift, and power divide circuit  90  via a matching network  500 . Exemplary embodiments are shown in  FIGS. 10A and 10B , where an RF generator, comprised of a voltage/current (V/I) sensor  508  and an RF power supply  506 , drive load coils  510 ,  512  via a matching network comprised of the first and second capacitors  320 ,  330  and dual load coils. Other circuit configurations are contemplated. 
         [0047]    Capacitors  320 ,  330  form the matching network  500  and are wired to the first coil  340  and the second coil  350  for impedance matching of the radio frequency power applied from a radio frequency generator  90 . In the example of the present invention, the first capacitor  320  and the second capacitor  330  are connected to the first coil  340  and the second coil  350  through the connector  360  to form an LC network, thereby performing the impedance matching of the radio frequency power. 
         [0048]    With reference to  FIGS. 11A, 11B, and 11C , various configurations of the capacitors realizing the matching network  500  may be employed. The embodiments of  FIGS. 10A and 10B  are preferably augmented by a third variable capacitor C c    333 , inductor L  335  or L  337 , and second ground GND 2 , in addition to the primary ground GND 1  directly grounded to the chassis. The additional variable capacitor C C  enables a balanced flow of VHF currents in the matching network and the second ground GND 2  acts as a ground for an internal current I RFIN . The inductor L value is selected within the range of 0.15 μH to 0.425 μH, and more preferably within the range of 0.17 μH to 0.35 μH. Tuning for impedance matching is impossible if the value for the inductor L is out of these ranges, or absent altogether. Thus, these inductor value ranges are important aspects of the matching network  500 . 
         [0049]    The circuit of  FIG. 11A  is preferable for load coils in which the load impedance is low, whereas the circuit of  FIG. 11B  is preferable for load coils in which the load impedance is high. 
         [0050]    A further embodiment of the matching network  500  is illustrated in  FIG. 11C . Here, a current/voltage (I/V) sensor  339  is introduced into the circuit of  FIG. 11A . The RF power is analyzed in the sensor. The magnitude of the received current (I) is used for adjusting the capacitance value of the first capacitor C A    320 , while the magnitude of the detected voltage (V) is used to adjust the capacitance value of the second capacitor C B    330 . A delta measurement (A), representing the ratio of current to voltage, is used to adjust the capacitance value of the third capacitor C C    333 . Specifically, when the value of Δ&gt;0, a high current state, the capacitance value of the third capacitor C C  is adjusted downward. When the value of Δ&lt;0, a low current state, the capacitance value of the third capacitor C C  is adjusted upward. When Δ=0, the capacitance value of the third capacitor C C  is not adjusted. Actual adjustment of the capacitors is achieved through the use of a control circuit and motors, as described subsequently. 
         [0051]    Preferably, as shown in  FIGS. 11A, 11B, and 11C , the first capacitor  320  and the second capacitor  330  are variable capacitors, as well as the third capacitor  333 , if employed. With reference to  FIG. 4 , a first adjusting pin  311  and a second adjusting pin  312  for adjusting the capacitance of the first capacitor  320  and the second capacitor  330  are installed in a regulation box  310  attached to the top plate  103  of the housing  100 . Other physical configurations are envisioned. Motors  315 ,  317 , whose rotation is controlled by the adjusting pins, adjust the capacitance of the first capacitor  320  and the second capacitor  330 , respectively, and are provided in the adjusting box  310  between the adjusting pins and the capacitors themselves. A control circuit  319  for controlling a rotation amount of the motors is mounted thereon. Since the control circuit is a known control circuit, further detailed description will not be provided. The control circuit may be under the control of, for instance, the IN Sensor  339  shown in  FIG. 11C  for achieving automated control over the capacitor settings. 
         [0052]    In  FIG. 4 , an RF generator, phase shifter, and power divider circuit  90  is illustrated within the housing  101 , proximate a regulation box  310  containing tuning elements for the capacitors, as described above. The location of the circuit  90  may be selected as a matter of convenience. As shown in  FIGS. 2 and 3 , a display  252  such as an LCD or an LED screen which displays the capacitance of the first and second capacitors  320 ,  330  is provided in conjunction with the housing  100 . An air variable capacitor (AVC) or a vacuum variable capacitor (VVC), both of which are conventional variable capacitor elements, may be used as the first capacitor  320  and the second capacitor  330 . The capacitors  320 ,  330  are illustrated mounted to the top plate  103  of the housing  100 . 
         [0053]    The phase shifter of the RF generator, phase shift, and power divider circuit  90  is utilized to place the first capacitor  320  out of phase with the second capacitor  330 , thereby generating a persistent plasma that extends from the inlet to the outlet. The power divider of this circuit  90  is functionally programmed to control the ratio of power applied to each of the first and second capacitors. 
         [0054]    The impedance to the radio frequency power applied through the LC circuit network between the first coil  340  and the second coil  350 , connected in parallel to each other, is impedance matched by adjusting the capacitance of the first capacitor  320  and the second capacitor  330 . This is achieved through the use of the adjusting pins  311 ,  312  projecting from the regulation box  310 , or by use of the control circuit described above. The adjusted capacitance values are then displayed on the display  252 . 
         [0055]    The operation of the cleaning apparatus of the process reaction chamber exhaust path of the presently disclosed invention is now described. Exhaust gas containing fluorine or chlorine flows from the exhaust pipe  20  into the gas inlet  210  of the cleaning apparatus  1  of the present invention. The fluorine or chlorine gas includes perfluorocarbon (PFC) gases such as NF 3 , C 3 F 8 , C 4 F 8  and SF 6 , C 1   2 , HCl, BCl 3  and CCl 4 , O 2 , and Ar. 
         [0056]    The fluorine gas or chlorine gas flowing into the gas inlet  210  flows through the inflow pipe  213 , the connecting pipe  250 , and the outflow pipe before exiting the gas outlet  220  and returning to the exhaust pipe  20 . During this transition, the fluorine gas or chlorine gas is converted into a fluorine radical gas or a chlorine radical gas by the radio frequency power from the radio frequency generator  90  applied to the coils about the inflow pipe  213  and the outflow pipe  223 . 
         [0057]    In order to allow the fluorine gas or chlorine gas to flow through the inflow pipe  213  and outflow pipe  223  at a constant rate, as illustrated in  FIG. 5 , an inner diameter r 1  of the inlet side inner wall  223   a  of the outflow pipe  223  is smaller than an inner diameter r 2  of a central portion of the outflow pipe  223 , and thereafter, an outlet side inner wall  223   b  of the outflow pipe  223  is formed in a shape which gradually slopes inward in the direction of the outlet, i.e., in an inwardly tapered shape. Thus, the inflow pipe and the outflow pipe are designed so that the gas speed increases in a small-diameter portion of the inlet side of the outflow pipe  223  then slightly decreases at the center of the outflow pipe  223 , allowing the RF energy to effect the gas for a longer time period due to the slower speed. The gas containing fluorine or chlorine radicals can then be discharged from the pipeline of the outflow pipe  223  with increased speed on the outlet side. This configuration of the outflow pipe  223  may also be applied to the configuration of the inflow pipe  213 . 
         [0058]    The fluorine radical gas or the chlorine radical gas generated as described above etches and removes the solid precipitate generated from the process reaction chamber  10 , while sequentially passing through the exhaust path elements downstream of the cleaning apparatus. 
         [0059]    By cleaning the exhaust path of the process reaction chamber by application of RF power as described above rather than by manual intervention, it is possible to prevent a reduction in productivity and to provide enhanced worker safety. 
         [0060]    Further, since the cleaning apparatus of the exhaust part of the present invention generates fluorine radicals or chlorine radicals twice, once through the inflow pipe  213  and once through the outflow pipe  223 , the generated gas can exhibit an enhanced cleaning effect. 
         [0061]    The radio frequency energy applied to the cleaning apparatus of the present invention is in the 40 to 100 MHz range. In one particular embodiment, a frequency of 60 MHz is used. Such a high frequency RF power results in VHF frequency resonance and the resulting high density plasma exhibits an excellent cleaning effect with low power consumption. 
         [0062]    While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.