Patent Publication Number: US-2011049111-A1

Title: Color system for etching gas

Description:
CROSS REFERENCE 
     This application claims foreign priority under Paris Convention and 35 U.S.C. §119 to Korean Patent Application No. 10-2009-0080216, filed Aug. 28, 2009 with the Korean Intellectual Property Office. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a control system for etching gas applied to a plasma etching device. More particularly, the present invention relates an etching gas control system, for not only improving an etching rate and etching uniformity of a wafer surface but also being capable of controlling a Critical Dimension (CD) difference between a central part of a wafer and an edge part, by building a tuning gas control system (e.g., a Supplementary Gas Control (SGC) system) capable of independently controlling and selectively supplying a supplementary gas and tuning gas capable of controlling plasma uniformity or distribution to an upper gas injector and a side gas injector. 
     2. Description of the Related Art 
     In general, a semiconductor Integrated Circuit (IC) device selectively removes only part of a wafer or a thin film deposited on the wafer, thereby forming an ultra miniature structure of a desired form on a surface to form a circuit of a complex structure. At this time, thin film manufacturing is implemented through many manufacturing processes such as a rinse process, a deposition process, a photolithography process, a plating process, an etching process, etc. 
     Among the various processes, the etching process is a process of removing desired materials from a wafer surface through a chemical reaction by jetting an etching gas (e.g., carbon tetrafluoride (CF 4 ), chlorine gas (Cl 2 ), Hydrogen Bromide (HBr), etc.) into a chamber installing a wafer therein using a gas injector. The etching process selectively removes a portion not coated with a photoresist using a photoresist pattern formed in the photolithography process as a mask, thereby forming a minute circuit on a substrate. 
     Thus, it is of importance to maintain the same etching rate on the whole surface of a wafer and also, vertically form an etching section shape to form a thin film in the same pattern as the photoresist pattern formed in the photoresist. 
     However, the etching process induces a difference of an etching speed due to a chemical and physical reaction, thus resulting in a phenomenon of a failure to form a uniform etching rate or CD throughout the surface of the wafer. 
     In order to solve this, the conventional art installs a gas injector at a top of a chamber of an etching equipment, and performs an etching process of controlling an etching gas supplied to the gas injector by means of a flow rate controller to control an amount and distribution of an etching gas input into the chamber. 
     Also, the gas injectors are installed at a top and side of the chamber, respectively, and selectively control a jet amount and flow of an etching gas, thereby controlling an ion density and distribution of the etching gas to control wafer etching uniformity. 
     However, the conventional etching equipment has the following problems. 
     Firstly, the etching equipment has a limitation in obtaining a uniform etching rate throughout the surface of a recent large-size wafer of 12 inches (300 mm). 
     Secondly, the etching equipment cannot independently control a supplementary gas (e.g., argon (Ar), helium (He), xenon (Xe), etc.) that is an inert gas used for controlling a dilution or residual time of an etching gas. 
     Thirdly, because of the absence of an independent tuning gas supply means capable of minutely controlling the ion density or distribution of the etching gas, the etching equipment neither sufficiently secures an etching uniformity nor corrects the CD difference between the central part and edge part of the wafer or artificially generates a CD difference. 
     Secondly, because the baffle plate is not effectively grounded to the chamber, there is a problem that there occurs a plasma flickering phenomenon in which plasma between the vents is irregularly flickered. 
     Thirdly, because of the absence of a control means for controlling aperture ratios of the vents, there is a problem that it is impossible to minutely control an etching rate of the substrate through control of a gas flow or exhaust flow within the chamber. 
     SUMMARY OF THE INVENTION 
     An aspect of exemplary embodiments of the present invention is to address at least the problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of exemplary embodiments of the present invention is to provide a control system for etching gas, for controlling an etching rate and etching uniformity of a wafer surface, by independently controlling and selectively supplying a supplementary gas and tuning gas capable of controlling plasma uniformity within a chamber to an upper gas injector and a side gas injector. 
     Another aspect of exemplary embodiments of the present invention is to provide a control system for etching gas, for compensating a Critical Dimension (CD) difference between a central part of a wafer surface and an edge part or artificially generating a CD difference, by selectively diversely controlling a jet amount and input path of a supplementary gas and tuning gas to control an ion density and distribution of plasma within a chamber. 
     According to one aspect of the present invention, a control system for etching gas is provided. The system includes a mass flow control unit, a flow rate control unit, and a tuning gas control unit. The mass flow control unit controls a mass flow of an etching gas input to a chamber. The flow rate control unit distributes the etching gas to an upper gas injector and a side gas injector connected with the mass flow control unit and installed in the chamber, respectively. The tuning gas control unit distributes and supplies a supplementary gas and tuning gas controlling an ion density and distribution of plasma within the chamber, to the mass flow control unit and the flow rate control unit, respectively. 
     The flow rate control unit includes a flow rate controller and a gas distribution duct. The gas distribution duct includes a plurality of outlet ducts, first and second supply ducts branched from the one-side outlet duct and connected to a center nozzle and side nozzle of the upper gas injector, respectively, and third and fourth supply ducts branched from the other-side outlet duct and connected to the side nozzle and the side gas injector, respectively. 
     The second and third supply ducts are integrated into a fifth supply duct and is connected to the side nozzle. 
     Open/close valves are installed in outlet ducts provided in the mass flow control unit and the first, second, third, and fourth supply ducts, respectively. 
     The tuning gas control unit includes a supplementary gas supplier for supplying a supplementary gas to the mass flow control unit, and a tuning gas supplier for supplying a tuning gas to the flow rate controller. 
     The tuning gas control unit includes a plurality of tuning gas flow controllers supplying one or more different tuning gases, respectively. 
     The tuning gas supplier includes a first tuning gas flow controller for supplying a plasma active gas, and a second tuning gas flow controller for supplying a supplementary etching gas. 
     The supplementary gas supplier connects to the outlet ducts of the mass flow control unit through a sixth supply duct, and the first tuning gas flow controller and second tuning gas flow controller connect to the gas distribution duct through a seventh supply duct. 
     The flow rate control unit includes a flow rate controller and a gas distribution duct. The gas distribution duct includes a plurality of outlet ducts, first and second supply ducts branched from the one-side outlet duct and connected to a center nozzle and side nozzle of the upper gas injector, respectively, and third and fourth supply ducts branched from the other-side outlet duct and connected to the side nozzle and the side gas injector, respectively. The second and third supply ducts are integrated into a fifth supply duct and connected to the side nozzle. The seventh supply duct installs a branch point (D), and the branch point installs branch ducts connected to the first, fourth, and fifth supply ducts, respectively. 
     Open/close valves are installed in outlet ducts provided in the first tuning gas flow controller and second tuning gas flow controller and the branch ducts, respectively. 
     The sixth supply duct installs a branch point (C), and has a connection duct connecting the branch point (C) and the seventh supply duct. 
     Open/close valves are installed in the sixth supply duct branched from the branch point (C) and the connection duct, respectively. 
     The active gas can be an O 2  or N 2  gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic cross section illustrating a plasma etching device including an upper gas injector and a side gas injector; 
         FIG. 2  is a diagram illustrating a construction of a control system for an etching gas according to the present invention; 
         FIG. 3  is a graph illustrating a variation of an etching rate of a wafer in case that oxygen (O 2 ), one of active gases, is not supplied and in case that O 2  is supplied through a different path; and 
         FIG. 4  is a graph illustrating a variation of an etching rate of a wafer in case that carbon fluoride (CF 4 ), one of supplementary etching gases, is not supplied and in case that CF 4  is supplied through a different path. 
     
    
    
     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures. 
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Exemplary embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness. 
     A description is made below in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic cross section illustrating a plasma etching device including an upper gas injector and a side gas injector.  FIG. 2  is a diagram illustrating a construction of a control system for an etching gas according to the present invention. 
     As illustrated in  FIG. 1 , the plasma etching device includes a chamber  200  forming a plasma reaction space therein, an upper gas injector  210  installed at a top and center of the chamber  200 , and a side gas injector  220  installed at a side of the chamber  200 . 
     A wafer  300  is loaded on an upper surface of a stage  230  installed at a center of the chamber  200 . 
     The upper gas injector  210  and the side gas injector  220  inject an etching gas into the chamber  200 . 
     The upper gas injector  210  includes a center nozzle jetting an etching gas in a downward direction and a side nozzle jetting the etching gas in a lateral direction. Thus, the upper gas injector  210  simultaneously injects the etching gas in the central and lateral direction of the chamber  200 . The side gas injector  220  is installed to inject the etching gas in a lateral direction of the wafer  300 . 
     Thus, by simultaneously jetting the etching gas in an upper and lateral direction of the wafer  300 , an ion density or distribution of a plasma state can be relatively uniformly formed compared to a case that only the upper gas injector  210  is installed. 
     As illustrated in  FIG. 2 , the etching gas control system according to the present invention includes a mass flow control unit  10 , a flow rate control unit  40 , and a tuning gas control unit  70 . 
     The mass flow control unit  10  controls a mass flow of an etching gas supplied into the chamber  200 , and includes a Mass Flow Controller (MFC)  11  and an outlet duct  12 . 
     The mass flow controller  11  connects with a gas supply device (not shown) for etching gas through a gas inlet duct  15 , and connects with a Flow Rate Controller (FRC)  20  of the flow rate control unit  40  through the outlet duct  12 . So, the mass flow controller  11  receives the etching gas from the gas supply device and inputs a suitable mass flow to the flow rate controller  20 . 
     Generally, the etching gas may be a gas such as hydrogen bromide (HBr), chlorine (Cl 2 ), tetra fluoro methane (CF 4 ), octa fluoro cyclo butane (C 4 F 8 ), hexafluoro-1,3-butadiene (C 4 F 6 ), tri fluoro methane (CHF 3 ), di fluoro methane (CH 2 F 2 ), sulfur hexa fluoride (SF 6 ), etc. 
     The mass flow controllers  11  can be plurally installed in parallel with each other in the mass flow control unit  10  to selectively supply several kinds of different main etching gases. Open/close valves  180  and  110  are installed in the gas inlet duct  15  and the outlet duct  12 , which are connected to the mass flow controller  11 , respectively, to make etching gas supply and cutoff possible. 
     Accordingly, the mass flow control unit  10  can selectively supply a different etching gas to the flow rate control unit  40  using the respective mass flow controllers  11  and open/close valves  110 . 
     The flow rate control unit  40  includes the flow rate controller  20  and a gas distribution duct  30 . 
     The flow rate controller  20  distributes and supplies a main etching gas to the upper gas injector  210  and side gas injector  220  installed in the chamber  200 , and connects with the outlet duct  12  of the mass flow control unit  10 . 
     Accordingly, the flow rate control unit  40  receives an etching gas through the outlet duct  12  from the mass flow controller  11  and supplies the received etching gas to the upper gas injector  210  and side gas injector  220  through the gas distribution duct  30 . At this time, the flow rate control unit  40  diversely controls an amount of an etching gas to distribute and supply the etching gas to the upper gas injector  210  and the side gas injector  220 , respectively. 
     The gas distribution duct  30  includes two outlet ducts  32  each installed in the flow rate controller  20 , and includes first, second, third, fourth, and fifth supply ducts  33 ,  34   35 ,  36 , and  37 . 
     The outlet ducts  32  form branch points (A) and (B), respectively and thus, the outlet ducts  32  are branched into the first, second, third, and fourth supply ducts  33 ,  34 ,  35 , and  36 , respectively. 
     The first supply duct  33  connects to the center nozzle of the upper gas injector  210 . The second and third supply ducts  34  and  35  connect to the side nozzle of the upper gas injector  210 . The fourth supply duct  36  connects to the side gas injector  220 . 
     Thus, an etching gas going through the first supply duct  33  is downwardly jet to a center of the chamber  200  through the center nozzle of the upper gas injector  210 . Etching gases going through the second and third supply ducts  34  and  35  are jet in the lateral direction of the chamber  200  through the side nozzle of the upper gas injector  210 . An etching gas going through the fourth supply duct  36  is jet from the side of the chamber  200  to the center of the wafer  300  through the side gas injector  220 . 
     The second and third supply ducts  34  and  35  are integrated into the fifth supply duct  37  and simultaneously, can connect to the side nozzle of the upper gas injector  210 . 
     Open/close valves  120 ,  121 ,  122 , and  123  can be installed in the first, second, third, and fourth supply ducts  33 ,  34 ,  35 , and  36 , respectively. 
     Thus, the flow rate control unit  40  can distribute and supply a suitable amount of etching gas to the upper gas injector  210  and side gas injector  220 , and can selectively open the open/close valves  120 ,  121 ,  122 , and  123  to variously control an input path of an etching gas through the first, second, third, and fourth supply ducts  33 ,  34 ,  35 , and  36  as well. 
     Also, the flow rate control unit  40  can variously control amounts of etching gases jet from the center nozzle and side nozzle of the upper gas injector  210  and the side gas injector  220 , by relatively controlling amounts of etching gases supplied to the first, second, third, and fourth supply ducts  33 ,  34 ,  35 , and  36  using the flow rate controller  20 . 
     The tuning gas control unit  70  connects to the mass flow control unit  10  and the flow rate control unit  40  to supply a supplementary gas and tuning gas to the mass flow control unit  10  and the flow rate control unit  40 . The tuning gas control unit  70  includes a supplementary gas supplier (e.g., a Supplementary Gas Controller (SGC))  50  and a tuning gas supplier  60 . 
     The supplementary gas supplier  50  supplies a supplementary gas for controlling a dilution or residual time of an etching gas. Here, the supplementary gas can be an inert gas such as argon (Ar), helium (He), xenon (Xe), etc. 
     The supplementary gas supplier  50  can install a mass flow controller  10  to supply or cut off a suitable amount of supplementary gas. 
     The supplementary gas supplier  50  connects to the outlet duct  12  of the mass flow control unit  10  by means of a sixth supply duct  56 . Also, an open/close valve  130  is installed in the sixth supply duct  56  to make supplementary gas supply and cutoff possible. 
     Thus, the supplementary gas supplier  50  can mix a supplementary gas with an etching gas through the sixth supply duct  56  and supply the mixed gas to the flow rate controller  20 . The etching gas and the supplementary gas are mixed with each other and are distributed and supplied to the upper gas injector  210  and the side gas injector  220  through the flow rate controller  20  and the gas distribution duct  30 , respectively. 
     The tuning gas supplier  60  connects to the gas distribution duct  30  to supply a plasma active gas or supplementary etching gas. The tuning gas supplier  60  includes a first tuning gas flow controller (e.g., a SGC)  61  and a second tuning gas flow controller  65 . 
     However, the tuning gas supplier  60  is not limited to the first tuning gas flow controller  61  and the second tuning gas flow controller  65 , and can include a plurality of tuning gas flow controllers supplying different active gases or supplementary etching gases, respectively. 
     The first tuning gas flow controller  61  connects to a seventh supply duct  67  through an outlet duct  62  to supply an active gas (O 2  or N 2 ) to the gas distribution duct  30  through the seventh supply duct  67 . 
     At this time, the active gas is mixed with an etching gas in the gas distribution duct  30  and is supplied to the upper gas injector  210  and the side gas injector  220 , thereby activating plasma of the etching gas within the chamber  200  and controlling an ion density or distribution of the plasma, thus improving an etching rate. 
     Here, it is desirable that the first tuning gas flow controller  61  installs an open/close valve  160  in the outlet duct  62  to make active gas supply and cutoff possible. 
     The second tuning gas flow controller  65  additionally supplies a supplementary etching gas to improve an etching rate. The second tuning gas flow controller  65  connects to the seventh supply duct  67  through an outlet duct  66  to supply the supplementary etching gas to the gas distribution duct  30  through the seventh supply duct  67 . 
     An open/close valve  170  can be installed in the outlet duct  66 . 
     The seventh supply duct  67  connects to the gas distribution duct  30  of the flow rate control unit  40  such that an active gas or a supplementary etching gas is supplied to the upper gas injector  210  or the side gas injector  220 . The seventh supply duct  67  installs a branch point (D) and forms a plurality of branch ducts  68 . After that, the branch ducts  68  are connected to the first, fourth, and fifth supply ducts  33 ,  36 , and  37  of the gas distribution duct  30 , respectively. 
     Also, open/close valves  140  are installed in the branch ducts  68 , respectively. 
     Accordingly, the seventh supply duct  67  selectively supplies an active gas or supplementary etching gas, which is a tuning gas, to the upper gas injector  210  and the side gas injector  220  through the first, fourth, and fifth supply ducts  33 ,  36 , and  37  via the branch ducts  68 . 
     The sixth supply duct  56  provided in the supplementary gas supplier  50  can connect with the seventh supply duct  67  through a connection duct  80  in which an open/close valve  150  is installed. 
     Thus, the supplementary gas supplier  50  closes the open/close valve  150  of the connection duct  80  such that a supplementary gas can be mixed with an etching gas and supplied through the flow rate controller  20 . Or, the supplementary gas supplier  50  closes the open/close valve  130  of the sixth supply duct  56  and opens the open/close valve  150  of the connection duct  80  such that a supplementary gas can be mixed with an active gas or supplementary etching gas and supplied to the gas distribution duct  30  through the seventh supply duct  67 . 
     Accordingly, the present invention can either mix a supplementary gas with a main etching gas and supply the mixed gas to the upper gas injector  210  and the side gas injector  220  through the flow rate controller  20  and the gas distribution duct  30 , or can mix a supplementary gas with an active gas or supplementary etching gas and supply the mixed gas through the seventh supply duct  67  and the gas distribution duct  30 . Also, the present invention can selectively open or close the open/close valves  140  of the branch ducts  68  to independently control a supplementary gas and tuning gas, thus selectively supplying the supplementary gas and tuning gas to each of the upper gas injector  210  and the side gas injector  220 . 
     Experiment results of an exemplary embodiment of the present invention are described below with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a graph illustrating respective Etching Rates (E/R) of a wafer  300  in case that O 2 , one of active gases, is not supplied and in case that O 2  is selectively supplied through a different path.  FIG. 4  is a graph illustrating etching rates in case that a supplementary etching gas (CF 4 ) is not supplied and in case that a supplementary etching gas (CF 4 ) is selectively supplied through a different path. 
     In  FIGS. 3 and 4 , horizontal axes denote left and right positions based on a central part ‘0’ between edge parts ‘−147’ and ‘+147’ of the wafer  300 , and vertical axes denote etching rates (E/R) dependent on a corresponding position on the wafer  300  shown in horizontal axis. 
     In  FIG. 3 , it can be appreciated that, in ‘E’ case that an active gas (O 2 ) is not supplied, the central and edge parts of the wafer  300  have no great difference in etching rate and, unlike this, in ‘F’ case that the active gas (O 2 ) flows through the seventh supply duct  67  and the branch duct  68  and is supplied to the center nozzle of the upper gas injector  210  through the first supply duct  33 , the central part of the wafer  300  has a relatively high etching rate compared to the edge parts of the wafer  300 . 
     Also, it can be appreciated that, in ‘G’ case that the active gas (O 2 ) is supplied to the side nozzle of the upper gas injector  210  through the fifth supply duct  37  and in ‘H’ case that the active gas (O 2 ) is supplied to the side gas injector  220  through the fourth supply duct  36 , the edge parts of the wafer  300  have a relatively high etching rate compared to the central part of the wafer  300 . 
     In  FIG. 4 , it can be appreciated that, even in case that a supplementary etching gas (CF 4 ) instead of the active gas (O 2 ) is supplied to the same path as that of an exemplary embodiment of  FIG. 3 , a difference of an etching rate between the central part and edge parts of the wafer  300  shows the same trend as that of the graph of  FIG. 3 . 
     That is, the active gas (O 2 ) activates plasma in a jet position within the chamber  200 , thus increasing the etching rate. The supplementary etching gas (CF 4 ) improves an ion density of plasma in the jet position, thus improving the etching rate. 
     Accordingly, by selectively supplying or cutting off a supplementary gas, an active gas, and a supplementary etching gas using a tuning gas control unit, the present invention can variously control a jet amount and flow of a tuning gas, control an ion density or distribution of plasma in a desired position, and control etching rates of a central part of a wafer  300  and edge parts. By doing so, the present invention can control an etching rate and etching uniformity of a surface of a wafer  300  and, in addition, the present invention can compensate a CD difference between the central part and edge parts or artificially control a CD difference. 
     As described above, firstly, the present invention has an effect of, by variously controlling a jet amount and input path of a supplementary gas or tuning gas, being capable of forming the optimum etching condition through a control of an ion density or distribution of plasma within a chamber to improve an etching rate and etching uniformity of a wafer surface, minimizing an error rate of a wafer. Secondly, the present invention has an effect of, even in case that a large size wafer is input, not only securing an etching uniformity of a central part and edge parts of a wafer but also compensating a CD difference or artificially generating a CD difference, thus improving process efficiency. 
     While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.