Fast gas switching plasma processing apparatus

Abstract

A plasma chamber with a plasma confinement zone with an electrode is provided. A gas distribution system for providing a first gas and a second gas is connected to the plasma chamber, wherein the gas distribution system can substantially replace one gas in the plasma zone with the other gas within a period of less than 1 s. A first frequency tuned RF power source for providing power to the electrode in a first frequency range is electrically connected to the at least one electrode wherein the first frequency tuned RF power source is able to minimize a reflected RF power. A second frequency tuned RF power source for providing power to the plasma chamber in a second frequency range outside of the first frequency range wherein the second frequency tuned RF power source is able to minimize a reflected RF power.

1 . A plasma wafer processing tool, comprising: 
 a plasma chamber with a plasma confinement zone with a volume and at least one electrode;    a gas distribution system for providing a first gas and a second gas, wherein the gas distribution system can substantially replace one of the first gas and the second gas in the plasma zone with the other of the first gas and the second gas within a period of less than 1 s, wherein a first plasma formed in the plasma zone from the first gas provides a first impedance load and wherein a second plasma formed in the plasma zone from the second gas provides a second impedance load different than the first impedance load;    a first frequency tuned RF power source for providing power to the at least one electrode in a first frequency range wherein the first frequency tuned RF power source is able to receive reflected RF power and tune an output RF frequency to minimize the reflected RF power; and    a second frequency tuned RF power source for providing power to the plasma chamber in a second frequency range outside of the first frequency range wherein the second frequency tuned RF power source is able to receive reflected RF power and tune an output RF frequency to minimize the reflected RF power.    
   
   
       2 . The plasma wafer processing tool, as recited in  claim 1 , wherein the first frequency tuned RF power source is able to provide a first frequency to impedance match the first impedance load and a second frequency to impedance match the second impedance load, wherein the first frequency is different than the second frequency.  
   
   
       3 . The plasma wafer processing tool, as recited in  claim 2 , wherein the second frequency tuned RF power source is able to provide a third frequency to impedance match the first impedance load and a fourth frequency to impedance match the second impedance load, wherein the fourth frequency is different than the first, second, and third frequency.  
   
   
       4 . The plasma wafer processing tool, as recited in  claim 3 , wherein the gas distribution system can substantially replace the first gas or the second gas in the plasma zone with the other of the first gas or the second gas within a period of less than 200 ms.  
   
   
       5 . The plasma wafer processing tool, as recited in  claim 4 , wherein the plasma chamber further comprises: 
 a substrate support for supporting a wafer within the plasma chamber; and    a chamber top spaced apart less than 3 cm. from the substrate support.    
   
   
       6 . The plasma wafer processing tool, as recited in  claim 5 , further comprising confinement rings spaced apart between the chamber top and substrate support.  
   
   
       7 . The plasma wafer processing tool, as recited in  claim 6 , wherein interiors of the confinement rings, the substrate support, and chamber top define the plasma zone.  
   
   
       8 . The plasma wafer processing tool, as recited in  claim 7 , wherein the first frequency turned RF power source and the second frequency tuned RF power source tune the output RF frequency over a range of less than 1 MHz.  
   
   
       9 . The plasma wafer processing tool, as recited in  claim 1 , wherein the gas distribution system comprises: 
 a first gas passage and a second gas passage adapted to be in fluid communication with a first gas line;    a third gas passage and a fourth gas passage adapted to be in fluid communication with a second gas line, the first and third gas passages being adapted to supply gas to the vacuum chamber, and the second and fourth gas passages being adapted to supply gas to a by-pass line;    a first fast switching valve arranged along the first gas passage;    a second fast switching valve arranged along the second gas passage;    a third fast switching valve arranged along the third gas passage;    a fourth fast switching valve arranged along the fourth gas passage;    the first and fourth fast switching valves being adapted to receive signals to open while the second and third fast switching valves are closed so that the first gas is supplied to the vacuum chamber via the first gas line and the first and third gas passages while the second gas is supplied to the by-pass line via the second gas line and the second and fourth gas passages; and    the second and third fast switching valves being adapted to receive signals to open while the first and fourth fast switching valves are closed so that the second gas is supplied to the vacuum chamber via the second gas line and the third gas passage while the first gas is supplied to the by-pass line via the first gas line and the second gas passage.    
   
   
       10 . The plasma wafer processing tool, as recited in  claim 9 , wherein the gas distribution system further comprises: 
 a first flow restrictor adapted to be arranged along the first gas line upstream of the first and second fast switching valves; and    a second flow restrictor adapted to be arranged along the second gas line upstream of the third and fourth fast switching valves;    wherein the first and second flow restrictors are adapted to maintain an approximately constant gas pressure in a region of the first and second gas lines upstream of and proximate the first and second flow restrictors.    
   
   
       11 . The plasma wafer processing tool, as recited in  claim 10 , wherein the first gas line has a volume between the first flow restrictor and the first and second fast switching valves of less than about 10 cm 3 , and the second gas line has a volume between the second flow restrictor and the third and fourth fast switching valves of less than about 10 cm 3 .  
   
   
       12 . The plasma wafer processing tool, as recited in  claim 9 , further wherein the gas distribution system further comprises: 
 a third flow restrictor adapted to be arranged along the first gas passage downstream of the first fast switching valve;    a fourth flow restrictor adapted to be arranged along the second gas passage downstream of the second fast switching valve;    a fifth flow restrictor adapted to be arranged along the third gas passage downstream of the third fast switching valve; and    a sixth flow restrictor adapted to be arranged along the fourth gas passage downstream of the fourth fast switching valve;    wherein the third, fourth, fifth and sixth flow restrictors are adapted to maintain an approximately constant gas pressure in a region of the first, second, third and fourth gas passages upstream of and proximate the respective first, second, third, fourth, fifth and sixth flow restrictors.    
   
   
       13 . The plasma wafer processing tool, as recited in  claim 9 , further comprising a controller which is operable to control the opening and closing of the first, second, third and fourth fast switching valves.  
   
   
       14 . The plasma wafer processing tool, as recited in  claim 9 , wherein the first, second, third and fourth fast switching valves can be opened and/or closed within a period of less than about 100 ms after receiving a signal.  
   
   
       15 . The plasma wafer processing tool, as recited in  claim 1 , further comprising a gas distribution member having an inner zone and outer zone, which are flow insulated from each other.  
   
   
       16 . The plasma wafer processing tool, as recited in  claim 15 , wherein the gas distribution system comprises: 
 a gas supply system, which provides the first gas and the second gas;    a flow control system in fluid communication with the gas supply system, which splits a flow of the first gas into an inner zone flow of the first gas and an outer zone flow of the first gas and which splits a flow of the second gas into an inner zone flow of the second gas and an outer zone flow of the second gas; and    a switching section, which is in fluid connection between the flow control system and the inner zone and outer zone of the gas distribution member, and wherein the switching section switches flow to the inner zone of the gas distribution member between the inner zone flow of the first gas and the inner zone of the second gas and wherein the switching section switches flow to the outer zone of the gas distribution member between the outer zone flow of the first gas and the outer zone flow of the second gas.    
   
   
       17 . The plasma wafer processing tool, as recited in  claim 16 , further comprising a by-pass line, wherein the switching section also switches the inner zone flow of the first gas, the inner zone of the second gas, the outer zone flow of the first gas, and the outer zone flow of the second gas to the by-pass line.  
   
   
       18 . The plasma wafer processing tool, as recited in  claim 17 , wherein the flow control system further comprising a tuning gas source in fluid connection to at least one of the first gas inner zone flow or first gas outer zone flow after the flow of the first gas is split into the inner zone flow of the first gas and the outer zone flow of the first gas.  
   
   
       19 . A plasma processing apparatus, comprising: 
 a plasma processing chamber including a showerhead electrode assembly having the inner and outer zones and an interior volume of about ½ liter to 4 liters;    the gas distribution system in fluid communication with the inner and outer zones of the showerhead electrode assembly, wherein the gas distribution system being operable to substantially replace a first process gas or a second process gas in the plasma confinement zone with the other of the first process gas or the second process gas within a period of less than about 1 s, comprising:    a gas supply system, which provides the first process gas and the second process gas;    a flow control system in fluid communication with the gas supply system, which splits a flow of the first process gas into an inner zone flow of the first process gas and an outer zone flow of the first process gas and which splits a flow of the second process gas into an inner zone flow of the second process gas and an outer zone flow of the second process gas; and    a switching section, which is in fluid connection between the flow control system and the inner zone and outer zone of the gas distribution member, and wherein the switching section switches flow to the inner zone of the gas distribution member between the inner zone flow of the first process gas and the inner zone of the second process gas and wherein the switching section switches flow to the outer zone of the gas distribution member between the outer zone flow of the first process gas and the outer zone flow of the second process gas;    a first frequency tuned RF power source for providing power to the plasma processing apparatus in a first frequency range wherein the first frequency tuned RF power source is able to receive reflected RF power and tune an output RF frequency to minimize the reflected RF power; and    a second frequency tuned RF power source for providing power to the plasma processing apparatus in a second frequency range outside of the first frequency range wherein the second frequency tuned RF power source is able to receive reflected RF power and tune an output RF frequency to minimize the reflected RF power.    
   
   
       20 . The plasma processing apparatus, as recited in  claim 19 , further comprising a by-pass line, wherein the switching section also switches the inner zone flow of the first process gas, the inner zone of the second process gas, the outer zone flow of the first process gas, and the outer zone flow of the second process gas to the by-pass line.  
   
   
       21 . The plasma processing apparatus, as recited in  claim 20 , wherein the flow control system further comprising a tuning gas source in fluid connection to at least one of the first process gas inner zone flow or first process gas outer zone flow after the flow of the first process gas is split into the inner zone flow of the first process gas and the outer zone flow of the first process gas.  
   
   
       22 . The plasma processing apparatus, as recited in  claim 21 , wherein the first frequency tuned RF power source is able to provide a first frequency to impedance match a first impedance load of a plasma formed from the first process gas and a second frequency to impedance match a second impedance load of a plasma formed from the second plasma gas, wherein the first frequency is different than the second frequency and wherein the second frequency tuned RF power source is able to provide a third frequency to impedance match the first impedance load and a fourth frequency to impedance match the second impedance load, wherein the fourth frequency is different than the first, second, and third frequency.  
   
   
       23 . A method of processing a semiconductor structure in a plasma processing chamber, comprising: 
 a) supplying a first process gas into the plasma processing chamber while diverting a second process gas to a bypass-line, the plasma processing chamber containing a semiconductor substrate including at least one layer and a patterned resist mask overlying the layer;    b) energizing the first process gas to produce a first plasma with a first impedance load and (i) etching at least one feature in the layer or (ii) forming a polymer deposit on the mask;    c) frequency tuning a first RF power source to a first frequency to match the first impedance load;    d) frequency tuning a second RF power source to a second frequency different than the first frequency to match the first impedance load;    e) switching the flows of the first and second process gases so that the second process gas is supplied into the plasma processing chamber while diverting the first process gas to the by-pass line, the first process gas being substantially replaced in a plasma confinement zone of the plasma processing chamber by the second process gas within a period of less than about 1 s;    f) energizing the second process gas to produce a second plasma with a second impedance load different from the first impedance load and (iii) etching the at least one feature in the layer or (iv) forming a polymer deposit on the layer and the mask;    g) frequency tuning the first RF power source to a third frequency different than the first and second frequencies to match the second impedance load;    h) frequency tuning the second RF power source to a fourth frequency different than the first, second, and third frequencies to match the second impedance load;    i) switching the flows of the first and second process gases so that the first process gas is supplied into the plasma processing chamber while diverting the second process gas to the by-pass line, the second process gas being substantially replaced in the plasma confinement zone of the plasma processing chamber by the first process gas within a period of less than about 1 s; and    j) repeating b)-i) a plurality of times with the substrate.    
   
   
       24 . The method, as recited in  claim 23 , wherein the periods of less than about 1 s is less than 200 ms.  
   
   
       25 . The method, as recited in  claim 23 , wherein the polymer deposit is formed to a maximum thickness of less than about 100 angstroms after repeating a)-i) a plurality of times with the substrate.  
   
   
       26 . The method, as recited in  claim 23 , further comprising: 
 splitting a flow of the first process gas into an inner zone flow and an outer zone flow, wherein the supplying the first process gas into the plasma processing chamber provides the inner zone flow to an inner zone of the processing chamber and the outer zone flow to an outer zone of the processing chamber.    
   
   
       27 . The method, as recited in  claim 26 , further comprising providing a tuning gas to at least one of the inner zone flow of the first process gas and the outer zone flow of the first process gas, wherein the tuning gas is provided after the splitting of the flow of the first process gas.  
   
   
       28 . The method of  claim 27 , wherein the first plasma etches the at least one feature in the layer, and the second plasma forms the deposit on the layer and the mask, the deposit repairing striations in the mask.  
   
   
       29 . The method of  claim 23 , wherein the plasma confinement zone has a volume of about ½ liter to about 4 liters.  
   
   
       30 . The method, as recited in  claim 23 , wherein: 
 the first layer is of SiO 2 ;    the mask is a UV-resist mask;    the first process gas comprises a mixture of C 4 F 8 , O 2  and argon and the first plasma etches the layer; and    the second process gas comprises a mixture of CH 3 F, argon, and optionally O 2  and the second plasma forms the polymer deposit on the feature and the mask.    
   
   
       31 . The method, as recited in  claim 23 , wherein the frequency tuning the first RF power source to a first frequency to match the first impedance load, and the frequency tuning the first RF power source to a third frequency to match the second impedance load use a matchbox to partially match the first impedance load and third impedance load and use frequency tuning to provide a final match of the first impedance load and second impedance load.