Patent Publication Number: US-2007110636-A1

Title: Device supplying process gas and related method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Embodiments of the invention relate to a device adapted to supply reaction gas and a related method. More particularly, embodiments of the invention relate to reaction gas supply device adapted to sense errant operation of a related mass flow controller.  
      This application claims priority to Korean Patent Application No. 10-2005-0110106, filed Nov. 17, 2005, the subject matter of which is hereby incorporated by reference in its entirety.  
      2. Description of the Related Art  
      Generally, semiconductor devices are manufactured by performing a complex sequence of fabrication processes. Exemplary fabrication processes include processes related to photolithography, diffusion, etching, oxidation, chemical vapor deposition, and metallic wire formation, etc. Many of these fabrication processes require the application of one or more reaction gases, transport gases, cleaning gases, etc. These gases must be introduced into (i.e., supplied), reacted within, and subsequently removed (i.e., exhausted) from certain specialized process chambers adapted to various fabrication processes in a highly controlled manner.  
      In order accomplish the selective supply and exhaust of gases from a process chamber, the chamber is typically configured with a so-called gas supplying device and a gas exhausting device. Conventional reaction gas supplying devices comprise a gas supplying element, a gas supply line adapted to supply the reaction gas to the process chamber, and a mass flow controller (MFC). In many instances, different reaction gases will each be associated with corresponding gas supplying devices.  
      Supplying gas at a desired flow rate to a process chamber during a defined time interval is an important factor in the successful manufacture of semiconductor devices. Recognizing that the fabrication of any particular semiconductor device is actually a carefully controlled sequence of different processes, the sequence is usually defined by a timed series of intervals during which one or more gases is supplied to the process chamber at defined flow rates. For example, a 100-second process interval may be defined such that a first gas having a flow rate of 30 LPM is supplied to the process chamber for the first 20 seconds, a second gas having a flow rate of 50 LPM is supplied to the process chamber for the next 40 seconds, and a third gas having a flow rate of 80 LPM is supplied to the process chamber for the next 40 seconds. A single MFC may be used in conjunction with a single gas supply line to introduce multiple gases at a different flow rate into a process chamber in a highly controlled manner. Since even a slight variation in the gas flow rate may greatly influence the constituent fabrication process being performed in the chamber, gas flow rate must be carefully controlled.  
       FIG. 1  is a schematic view showing a conventional reaction gas supplying device adapted for use in the fabrication of semiconductor devices. The conventional reaction gas supplying device is connected to a process chamber  10 . Since most fabrication processes requires a very high level of gas purity, process chamber  10  is manufactured to isolate the various processes from the external environment. The conventional reaction gas supplying device comprises a gas supplying element  12 , a main valve  14 , a main pressure regulator and gauge  16 , a secondary pressure regulator  18 , a digital pressure gauge  20 , and an MFC  22 . Process chamber  10  receives one or more gases related to a current fabrication process. Gas supplying element  12  stores a process gas, and main valve  14  controls the supply of the process gas. When main valve  14  is open, main pressure regulator and gauge  16  primarily adjusts the pressure (i.e., main pressure) of the process gas being supplied through a gas supply line  24  and displays the adjusted pressure using an analog display. Secondary pressure regulator  18  secondarily adjusts the pressure of the gas supplied through main pressure regulator and gauge  16 . Digital pressure gauge  20  digitally displays the secondarily adjusted pressure of gas received from secondary pressure regulator  18 . MFC  22  further controls amount of process gas supplied to process chamber  10  and precisely controls the supply interval of the process gas.  
      As shown in  FIG. 1 , gas supply line  24  is connected at one end to process chamber  10  in order to supply the process gas. MFC  22  is disposed along gas supply line  24  and adjusts the supply amount and the supply interval of the process gas. Gas supplying element  12  is disposed at the other end of gas supply line  24  and stores the process gas to be supplied to process chamber  10 .  
      Main valve  14  will be closed during maintenance periods for gas supply line  24 , process chamber  10 , and MFC  22 , but is usually open otherwise. As noted above, when main valve  14  is open, main pressure regulator and gauge  16  and secondary pressure regulator  18  cooperate to adjust the supply pressure to MFC  22 . In one embodiment, primary pressure may be adjusted to a range of about 8 kgf/cm 2 , and secondarily pressure may be adjusted to 3 kgf/cm 2 .  
      The amount of process gas supplied to process chamber  10  will vary by process, gas concentration, gas density, and reaction time of the materials on a wafer being processed. In order to avoid over-reactions and under-reactions between the process gas and the wafer materials, and thereby impair the quality of the material layers on the wafer, the operation of MFC  22  must be very precise and a sufficiently durable over extended periods to ensure proper supply flow rates and well controlled supply intervals.  
      However, as the performance of MFC  22  deteriorates with age or use, it becomes increasingly difficult to reliably determine its exact operating nature. Often, a failing MFC  22  is first noticed when one or more processed wafers turns up malformed.  
     SUMMARY OF THE INVENTION  
      Embodiments of the invention provide a reaction gas supplying device and related method of operation adapted to sense errant operation of a mass flow controller (MFC) before damage to processed wafers can occur.  
      In one embodiment, the invention provides a reaction gas supplying device comprising a gas supply line disposed between a process chamber and a gas supplying element; a mass flow controller disposed on the gas supply line and adapted to control a supply amount and a supply time of a gas, wherein the gas supplying element supplies the gas to the mass flow controller; and a digital pressure gauge adapted to measure the pressure of the gas and digitally display a measured pressure value of the gas. The device further comprises a database adapted to store a standard pressure value corresponding to a set flow rate; and a controller adapted to generate a first flow rate control signal, output the first flow rate control signal to the mass flow controller, receive a detected flow rate of the gas from the mass flow controller, compare the measured pressure value of the gas with a standard pressure value stored in the database corresponding to the first flow rate control signal, and output an alarm generation control signal when the measured pressure value of the gas is outside of a set error range around the standard pressure value.  
      In another embodiment, the invention provides a reaction gas supplying device comprising a gas supply line disposed between a process chamber and a gas supplying element; a mass flow controller disposed on the gas supply line and adapted to control a supply amount and a supply time of a gas, wherein the gas supplying element supplies the gas to the mass flow controller; and a digital pressure gauge adapted to measure the pressure of the gas and digitally display a measured pressure value of the gas. The device further comprises a controller adapted to generate a first flow rate control signal, output the first flow rate control signal to the mass flow controller, receive a detected flow rate of the gas from the mass flow controller, compare the measured pressure value of the gas with a standard pressure value corresponding to the first flow rate control signal, and output an alarm generation control signal when the measured pressure of the gas is outside of a set error range around the standard pressure value; and an alarm generator adapted to generate an alarm signal in response to the alarm generation control signal.  
      In yet another embodiment, the invention provides a method for sensing an error in a mass flow controller in a semiconductor fabrication device, the method comprising supplying a gas to a gas supply line disposed between a process chamber and a gas supplying element, controlling a supply amount and a supply time of the gas supplied by the gas supplying element using a mass flow controller in order to control a flow rate of the gas, and measuring a pressure of the gas in the gas supply line, wherein the pressure of the gas corresponds to the flow rate of the gas controlled by the mass flow controller. The method further comprises comparing the measured pressure with a standard pressure value, and determining whether there is an error in the mass flow controller in accordance with the compared result. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Embodiments of the invention will now be described with reference to the accompanying drawings, in which like reference symbols denote like elements. In the drawings:  
       FIG. 1  is a schematic view showing a conventional reaction gas supplying device of a semiconductor device fabrication device.  
       FIG. 2  is a schematic view illustrating a reaction gas supplying device of a semiconductor device fabrication device in accordance with an exemplary embodiment of the present invention;  
       FIG. 3  is a more detailed illustration of the MFC shown in  FIG. 2 ; and,  
       FIG. 4  is a flow chart that illustrates a method for the controller of  FIG. 2  for detecting whether there is an error in the MFC of  FIG. 2  in accordance with an exemplary embodiment of the present invention. 
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS  
       FIG. 2  is a schematic view illustrating a reaction gas supplying device of a semiconductor device fabrication device in accordance with an exemplary embodiment of the present invention.  
      Referring to  FIG. 2 , a reaction gas supplying device  160  comprises a process chamber  150 , a gas supplying element  140 , a main valve  142 , a main pressure regulator and gauge  144 , a secondary pressure regulator  146 , a mass flow controller (MFC)  148 , a digital pressure gauge  152 , a database  158 , a controller  154 , and an alarm generator  156 . A gas supply line  162  is disposed between process chamber  150  and gas supplying element  140 . Process chamber  150  receives a gas and performs a fabrication process in an enclosed space within process chamber  150 , and gas supplying element  140  stores the gas (i.e., the process gas). Main valve  142  controls whether the gas stored in gas supplying element  140  is provided to other elements in reaction gas supplying device  160 . When main valve  142  is open, main pressure regulator and gauge  144  primarily adjusts the pressure (i.e., the main pressure) of the gas supplied through gas supply line  162  to give the gas a first adjusted pressure. Main pressure regulator and gauge  144  also displays the first adjusted pressure of the gas through an analog display (i.e., a gauge). Secondary pressure regulator  146  secondarily adjusts the pressure of the gas it receives from main pressure regulator and gauge  144 . MFC  148  is disposed along gas supply line  162 , receives the gas from secondary pressure regulator  146 , and controls the supply flow rate and supply interval of the gas into process chamber  150 . Digital pressure gauge  152  displays the pressure of the gas, which has been regulated by secondary pressure regulator  146 , as a digital value.  
      Database  158  stores standard pressure values that correspond to set flow rates, and controller  154  generates a first flow rate control signal and outputs the first flow rate control signal to MFC  148  in accordance with a set flow rate. As used herein, a “set flow rate” is a flow rate at which controller  154  commands MFC  148  to maintain the gas. Thus, the first flow rate control signal that controller  154  provides to MFC  148  communicates a set flow rate to MFC  148 . Controller  154  receives a detected flow rate of the gas from MFC  148 . Controller  154  also compares a pressure measured by digital pressure gauge  152  with the standard pressure value, which is stored in database  158  and corresponds to the first flow rate control signal, and thus corresponds to the set flow rate that corresponds to the first flow rate control signal as well. Controller  154  outputs an alarm generation control signal when the compared result is outside a set error range. Alarm generator  156  generates an alarm signal in response to an alarm generation control signal provided by controller  154 .  
       FIG. 3  is a more detailed illustration of MFC  148  shown in  FIG. 2 . Mass flow controller  148  comprises a gas introduction port  120 , an opening portion  122 , a capillary tube  128 , a flow rate sensor  130 , a hollow chamber  126 , a bypass valve  124 , a flow rate control valve  132 , an exhausting passage  134 , a gas exhausting port  136 , a control board  138 , and a check valve (not shown). Gas introduction port  120  is connected to a gas supply pipe (i.e., gas supply line  162  of  FIG. 2 ). Opening portion  122  is connected to gas introduction port  120 , and comprises a closed space therein. Gas from opening portion  122  passes through capillary tube  128 , and flow rate sensor  130  detects the flow rate of the gas that passes through capillary tube  128 . Hollow chamber  126  is connected to capillary tube  128 , and also comprises a closed space. Bypass valve  124  is disposed between opening portion  122  and hollow chamber  126  and passes the gas so that it flows through capillary tube  128 . Flow rate control valve  132  is connected to hollow chamber  126  and controls the flow rate of the gas in accordance with a second flow rate control signal. Exhausting passage  134  is connected to flow rate control valve  132 , which provides the gas controlled by flow rate control valve  132  to exhausting passage  134 . In accordance with the flow rate detected by flow rate sensor  130 , control board  138  outputs the second flow rate control signal to flow rate control valve  132  to maintain the gas at a constant pressure. Additionally, the check valve prevents the gas from flowing in reverse, that is, flowing from exhausting passage  134  to gas introduction port  120  in MFC  148 .  
       FIG. 4  is a flow chart that illustrates a method for controller  154  for detecting whether there is an error in MFC  148  in accordance with an exemplary embodiment of the present invention. Hereinafter, an operation of an exemplary embodiment of the present invention will be described with reference to  FIGS. 2 through 4 .  
      Referring to  FIG. 2 , the gas supply line is connected to process chamber  150 , which is isolated from the external environment. Gas supply line  162  is connected to process chamber  150  and is adapted to supply the gas to process chamber  150 . MFC  148  is disposed along gas supply line  162  and adjusts the supply flow rate and supply interval of the gas supplied to process chamber  150 . Gas supplying element  140  is disposed at an end of the gas supply line and stores the gas.  
      When main valve  142  is opened, the gas stored in gas supplying element  140  is supplied through gas supply line  162 . Main valve  142  is closed during maintenance times for gas supply line  162 , process chamber  150 , and MFC  148 , but is open otherwise. When main valve  142  is open, main pressure regulator and gauge  144  primarily adjusts the pressure (i.e., the main pressure) of the gas supplied through gas supply line  162 , and displays the adjusted pressure value of the gas using an analog display. For example, the primarily adjusted pressure of the gas may have a value of 8 kgf/cm 2 . Secondary pressure regulator  146  secondarily adjusts the pressure of the gas received from main pressure regulator and gauge  144 . For example, the secondarily adjusted pressure of the gas may have a value of 3 kgf/cm 2 . The secondarily adjusted pressure of the gas is displayed digitally through digital pressure gauge  152 . Secondary pressure regulator  146  then supplies the gas having the secondarily adjusted pressure to MFC  148 , which supplies the gas to process chamber  150  and controls the supply flow rate and supply interval of the gas supplied to process chamber  150 .  
      An operation of MFC  148  will now be described with reference to  FIGS. 2 and 3 . Gas supplying element  140  supplies a gas to opening portion  122  through gas introduction port  120 . The gas provided to opening portion  122  is induced to flow into capillary tube  128  by means of bypass valve  124 . The gas induced to flow into capillary tube  128  is transferred to hollow chamber  126 . The gas transferred to hollow chamber  126  is then provided to flow rate control valve  132 , which adjusts the flow rate of the gas, if necessary. The gas having the adjusted flow rate is then supplied to process chamber  150  through exhausting passage  134  and gas exhausting port  136 . Flow rate sensor  130  detects the flow rate of the gas flowing through capillary tube  128  and provides the detected flow rate to control board  138 . control board  138  receives a first flow rate control signal from controller  154  and control the amount of the gas that flows from flow rate control valve  132  in accordance with the first flow rate control signal. Control board  138  then receives a detected flow rate of the gas, as detected by flow rate sensor  130 , and controls flow rate control valve  132 , which controls the amount of gas that flows through exhausting passage  134 . Database  158  stores standard pressures that correspond to various flow rates, as illustrated in table 1.  
                       TABLE 1                           Flow rate detected   Digital standard       Set flow rate (LPM)   by MFC (LPM)   pressure (kgf/cm 2 )                  20   19˜29   2.98˜2.99       30   29˜30   2.94˜2.95       40   39˜40   2.92       50   49˜50   2.90˜2.91       60   59˜60   2.88       70   69˜70   2.86˜2.87       80   79˜80   2.84                  
 
      As illustrated in Table 1, there is a one-to-one correspondence between pressure of gas supply line  162  and set flow rates.  
      Consequently, MFC  148  sets the flow rate of the gas that will be used in a fabrication process, wherein the flow rate corresponds to a pressure value of gas supply line  162 . By setting the flow rate of the gas, the pressure of the gas is set with a set error range (i.e., margin of error) of about ±0.01 kgf/cm 2 . Controller  154  compares a pressure value detected by digital pressure gauge  152  with a standard pressures value, which corresponds to the set flow rate for the gas and is stored in database  158 , and determines whether there is an error in MFC  148  (i.e., whether MFC  148  is in an error operation state) based on the result of the comparison. For example, when controller  154  generates and provides a first flow rate control signal of 80 LPM (i.e., a first flow rate control signal corresponding to a set flow rate of 80 LPM) to control board  138  of MFC  148 , control board  138  sends a signal indicating that the gas has a flow rate ranging from 79 to 80 LPM to controller  154 , as shown in Table 1.  
      Digital pressure gauge  152  measures and displays the pressure value of the gas in gas supply line  162  and provides a signal indicating the measured pressure value to controller  154 . Controller  154  receives the measured pressure value from digital pressure gauge  152 , and controller  154  then compares the measured pressure value with the standard pressure value of 2.84 kgf/cm 2 , which corresponds to 80 LPM (i.e., the set flow rate). When the measured pressure value received from digital pressure gauge  152  is 2.75 kgf/cm 2 , for example, controller  154  determines that there is an error in MFC  148  and outputs an alarm generation control signal. Alarm generator  156  generates an alarm signal in response to the alarm generation control signal received from controller  154 .  
       FIG. 4  is a flow chart illustrating a method for controller  154  for detecting an error in MFC  148  in accordance with an exemplary embodiment of the present invention.  
      Referring to  FIG. 4 , controller  154  generates a first flow rate control signal and applies the first flow rate control signal to MFC  148  ( 101 ). When the first flow rate control signal corresponds to a set flow rate of 50 LMP (i.e., commands MFC  148  to control the flow rate of the gas at 50 LPM), for example, control board  138  of MFC  148  controls flow rate control valve  132  in order to adjust the flow rate of the gas, if necessary, so that the flow rate is set to 50 LPM. That is, control board  138  controls flow rate control valve  132  in accordance with the measured flow rate of the gas, detected by flow rate sensor  130 , so that the flow rate of the gas is adjusted to 50 LPM.  
      After the flow rate of the gas has been adjusted, if necessary, as described previously, flow rate sensor  130  detects the flow rate of the gas and provides the resulting detected flow rate of the gas to controller  154 . Next, controller  154  receives the detected flow rate of the gas from flow rate sensor  130  and determines whether the flow rate of the gas is normal (i.e., whether it corresponds to the first flow rate control signal) ( 102 ). Then, digital pressure gauge  152  provides controller  154  with a measured pressure value that corresponds to the flow rate of the gas, which is being controlled in accordance with the first flow rate control signal ( 103 ).  
      Thereafter, controller  154  compares the measured pressure value received from digital pressure gauge  152  with the standard pressure value that corresponds to the first flow rate control signal (and the set flow rate) and determines whether the measured pressure value falls outside of the set error range around the standard pressure value ( 104 ). When the measured pressure value is outside of the set error range around the standard pressure value, controller  154  generates an alarm generation control signal to thereby drive alarm generator  156  to generate an alarm signal ( 105 ). Alternatively, when the measured pressure value is within the set error range around the standard pressure value, a normal operation is performed ( 106 ). The set error range around the standard pressure value may be, for example, ±0.01 kgf/cm 2 . When the measured pressure value is outside of the range of ±0.01 kgf/cm 2  around the standard pressure value that corresponds to the set flow rate, controller  154  determines that there is an error in MFC  148 . When the set flow rate provided to MFC  148  (i.e., provided via a first flow rate control signal) is 20 LPM, the standard pressure preferably ranges from 2.98 to 2.99 kgf/cm 2 . Accordingly, when the pressure detected in digital pressure gauge  152  is 2.97 kgf/cm 2  or 3.0 kgf/cm 2 , for example, controller  154  determines that there is an error in MFC  148 . As another example, when the set flow rate provided to MFC  148  is 30 LPM, the standard pressure preferably ranges from 2.94 to 2.95 kgf/cm 2 . Accordingly, when the pressure detected by digital pressure gauge  152  is 2.93 kgf/cm 2  or 2.96 kgf/cm 2 , for example, controller  154  determines that there is an error in MFC  148 . Additionally, when the set flow rate provided to MFC  148  is 40 LPM, the standard pressure is preferably 2.92 kgf/cm 2 . Accordingly, when the pressure detected by digital pressure gauge  152  is 2.91 kgf/cm 2  or 2.93 kgf/cm 2 , for example, controller  154  determines that there is an error in MFC  148 . When the set flow rate provided to MFC  148  is 50 LPM, the standard pressure preferably ranges from 2.90 kgf/cm 2  to 2.91 kgf/cm 2 . Accordingly, when the pressure detected by digital pressure gauge  152  is 2.89 kgf/cm 2  or 2.92 kgf/cm 2 , for example, controller  154  determines that there is an error in MFC  148 .  
      As set forth above, when the flow rate of the gas is adjusted and supplied using MFC  148 , when gas supply line  162  is in an abnormal state, for example, when the pressure of gas exhausting port  136  of MFC  148  becomes greater than that of gas introduction port  120  due to atmospheric exposure or a gas leak, a check value disposed at exhausting passage  134  prevents the gas from flowing in reverse. This feature prevents gas supply line  162  from being polluted and maintains the purity of the gas in gas supply line  162 .  
      The amount of a process gas introduced into process chamber  150  for a given fabrication process depends on concentration, density, and reaction time in accordance with a reaction degree on a wafer. Ultra-thin films are treated on a wafer during etching, diffusion, oxidation, or chemical vapor deposition. Accordingly, when the amount of gas introduced into process chamber  150  or the amount of time during which gas is introduced into process chamber  150  is even slightly greater than the required amount or time, an over-reaction occurs. On the other hand, when the amount of gas introduced into process chamber  150  or the amount of time during which gas is introduced into process chamber  150  is even slightly less than the required amount or time, an under-reaction occurs, and physical properties of chemical compounds on the wafer vary and a circuit is improperly formed as a result. For these reasons, MFC  148 , which adjusts the amount of process gas supplied into process chamber  150 , must be very precise and sufficiently durable so that the flow rate is not changed due to frequent flow rate control operations.  
      As mentioned above, a gas supplying device, in accordance with the present invention, detects and compares a standard pressure value corresponding to a set flow rate of a gas controlled by the MFC of a semiconductor production device with a measured pressure value. When the measured pressure value is outside of a set error range around the standard pressure value, the gas supplying device determines that there is an error in the MFC and generates an alarm. Therefore, the present invention is adapted to prevent a process error due to a failure of the MFC in order to reduce semiconductor device fabrication cost.  
      The present invention has been described with reference to exemplary embodiments. However, it will be understood that the scope of the invention is not limited to the disclosed embodiments. Rather, various modifications and alternative arrangements within the capabilities of persons skilled in the art are within the scope of the present invention, as described in the accompanying claims. Therefore, the scope of the claims should be accorded the broadest possible interpretation to encompass all such modifications and similar arrangements.