Temperature control of plasma density probe

Abstract

An apparatus for measuring a plasma parameter in a plasma processing reactor comprises a probe including a dielectric tube, a coaxial cable inserted in the dielectric tube, the coaxial cable having an open antenna tip, and a plurality of spacers disposed between the coaxial cable and the dielectric tube. The plurality of spacers define a plurality of ducts through which a cooling fluid is adapted to be circulated to control a temperature of the probe.

1 . An apparatus for measuring a plasma parameter in a plasma processing: reactor, comprising: 
 a probe including a dielectric tube, a coaxial cable inserted in the dielectric tube, the coaxial cable having an open antenna tip, and a plurality of spacers disposed between the coaxial cable and the dielectric tube,    wherein said plurality of spacers define a plurality of ducts through which a cooling fluid is adapted to be circulated to control a temperature of the probe.    
   
   
       2 . The apparatus according to  claim 1 , wherein the dielectric tube is configured to isolate the coaxial cable and the antenna tip from the plasma.  
   
   
       3 . The apparatus according to  claim 1 , wherein a dielectric permittivity of a dielectric material of the dielectric tube is selected to correspond to an expected plasma density range.  
   
   
       4 . The apparatus according to  claim 3 , wherein the dielectric material comprises quartz, ceramic or a combination thereof.  
   
   
       5 . The apparatus according to  claim 1 , wherein the plurality of spacers are disposed in a spiral configuration around the coaxial cable.  
   
   
       6 . The apparatus according to  claim 1 , wherein the plurality of spacers maintain a space between the coaxial cable and the tube.  
   
   
       7 . The apparatus according to  claim 6 , wherein the spacers substantially center the coaxial cable inside the tube.  
   
   
       8 . The apparatus according to  claim 7 , wherein said space is substantially constant.  
   
   
       9 . The apparatus according to  claim 6 , wherein a diameter of the plurality of spacers is equal approximately half of a difference between an internal diameter of the tube and an external diameter of the coaxial cable.  
   
   
       10 . The apparatus according to  claim 1 , wherein the cooling fluid is adapted to be circulated through a first duct in the plurality of ducts from a first end of the tube to a second end of the tube and through a second duct in the plurality of ducts from the second end of the tube to the first end of the tube.  
   
   
       11 . The apparatus according to  claim 10 , wherein the first duct is connected to a cooling fluid inlet and the second duct is connected to a cooling fluid outlet.  
   
   
       12 . The apparatus according to  claim 1 , wherein the probe further comprises a base and the plurality of spacers are connected to the base.  
   
   
       13 . The apparatus according to  claim 1 , further comprising a perforated end-piece disposed at an end of the probe, wherein the end-piece is configured to hold the plurality of spacers to the coaxial cable at the end of the probe.  
   
   
       14 . The apparatus according to  claim 1 , wherein each spacer in the plurality of spacers consists of an elongated element.  
   
   
       15 . The apparatus according to  claim 14 , wherein the elongated element includes plastic, metal, or ceramic materials, or any combination of two or more thereof.  
   
   
       16 . The apparatus according to  claim 15 , wherein the material is polytetrafluoroethylene.  
   
   
       17 . The apparatus according to  claim 1 , wherein the cooling fluid is a liquid or a gas.  
   
   
       18 . The apparatus according to  claim 1 , wherein the cooling fluid includes a fluorinated cooling liquid, liquid nitrogen, liquid carbon dioxide, air, argon, helium, nitrogen gas, or any combination of two or more thereof.  
   
   
       19 . The apparatus according to  claim 1 , further comprising a temperature sensor disposed in the probe.  
   
   
       20 . The apparatus according to  claim 19 , wherein the temperature sensor is attached to the coaxial cable.  
   
   
       21 . The apparatus according to  claim 19 , wherein the temperature sensor is configured to measure the temperature of the probe.  
   
   
       22 . The apparatus according to  claim 19 , wherein the temperature sensor provides a temperature signal, said temperature signal being used as a feedback signal to control pressure, flow rate or temperature of the cooling fluid, or any combination of two or more thereof.  
   
   
       23 . The apparatus according to  claim 22 , further comprising a valve controller, wherein said feedback signal is provided to said valve controller so as to control the flow rate of the cooling fluid.  
   
   
       24 . The apparatus according to  claim 22 , further comprising a pressure control system, wherein said feedback signal is provided to said pressure control system so as to control the pressure of the cooling fluid.  
   
   
       25 . The apparatus according to  claim 22 , further comprising a cooling system, wherein said feedback signal is provided to said cooling system so as to increase or decrease a temperature of the cooling fluid.  
   
   
       26 . An apparatus for measuring a plasma parameter in a plasma processing reactor, comprising: 
 a dielectric tube;    a sensor disposed in the dielectric tube;    a connector disposed in the dielectric tube and coupled to the sensor; and    a plurality of spacers disposed between the connector and the dielectric tube,    wherein said plurality of spacers define a plurality of ducts through which a cooling fluid is adapted to be circulated to control a temperature of the probe.    
   
   
       27 . The apparatus according to  claim 26 , wherein the dielectric tube is configured to isolate the connector and the sensor from the plasma.  
   
   
       28 . The apparatus according to  claim 26 , wherein the dielectric material comprises quartz, ceramic or a combination thereof.  
   
   
       29 . The apparatus according to  claim 26 , wherein the plurality of spacers are disposed in a spiral configuration around the connector.  
   
   
       30 . The apparatus according to  claim 26 , wherein the plurality of spacers maintain a space between the connector and the tube.  
   
   
       31 . The apparatus according to  claim 30 , wherein the spacers substantially center the connector inside the tube.  
   
   
       32 . The apparatus according to  claim 30 , wherein said space is substantially constant.  
   
   
       33 . The apparatus according to  claim 30 , wherein a diameter of the plurality of spacers is equal approximately half of a difference between an internal diameter of the tube and an external diameter of the connector.  
   
   
       34 . The apparatus according to  claim 26 , wherein the cooling fluid is adapted to circulate through a first duct in the plurality of ducts from a first end of the tube to a second end of the tube and is adapted to circulate back through a second duct in the plurality of ducts from the second end of the tube to the first end of the tube.  
   
   
       35 . The apparatus according to  claim 34 , wherein the first duct is connected to a cooling fluid inlet channel and the second duct is connected to a cooling fluid outlet channel.  
   
   
       36 . The apparatus according to  claim 26 , wherein the probe further comprises a base and the plurality of spacers are connected to the base.  
   
   
       37 . The apparatus according to  claim 26 , further comprising a perforated end-piece disposed at an end of the connector, wherein the end-piece is configured to hold the plurality of spacers at the end of the connector.  
   
   
       38 . The apparatus according to  claim 26 , wherein each spacer in the plurality of spacers consists of an elongated element.  
   
   
       39 . The apparatus according to  claim 38 , wherein the elongated element includes plastic, metal, or ceramic materials, or any combination of two or more thereof.  
   
   
       40 . The apparatus according to  claim 39 , wherein the material is polytetrafluoroethylene.  
   
   
       41 . The apparatus according to  claim 26 , wherein the cooling fluid is a liquid or a gas.  
   
   
       42 . The apparatus according to  claim 26 , wherein the cooling fluid includes a fluorinated cooling liquid, liquid nitrogen, liquid carbon dioxide, air, argon, helium, nitrogen gas, or any combination of two or more thereof.  
   
   
       43 . The apparatus according to  claim 26 , further comprising a temperature sensor disposed in the probe.  
   
   
       44 . The apparatus according to  claim 43 , wherein the temperature sensor is attached to a surface of the connector.  
   
   
       45 . The apparatus according to  claim 43 , wherein the temperature sensor is configured to measure the temperature of the cooling fluid.  
   
   
       46 . The apparatus according to  claim 43 , wherein the temperature sensor provides a temperature signal, said temperature signal being used as a feedback signal to control pressure, flow rate or a temperature of the cooling fluid, or any combination of two or more thereof.  
   
   
       47 . A plasma apparatus comprising: 
 a chamber having a wall configured to house a substrate;    a source of gas connected to said chamber;    a plasma source; and    a plasma parameter measuring apparatus, comprising: 
 a probe including a dielectric tube, a coaxial cable inserted in the dielectric tube, the coaxial cable having an open antenna tip, and a plurality of spacers disposed between the coaxial cable and the dielectric tube, said plurality of spacers defining a plurality of ducts through which a cooling fluid is adapted to be circulated to control a temperature of the probe,  
   wherein said plasma parameter measuring apparatus is configured to measure a density of said plasma.    
   
   
       48 . A plasma apparatus comprising: 
 a chamber having a wall configured to house a substrate;    a source of gas connected to said chamber;    a plasma source; and    a plasma parameter measuring apparatus, comprising: 
 a dielectric tube;  
 a sensor disposed in the dielectric tube;  
 a connector disposed in the dielectric tube and coupled to the. sensor; and  
 a plurality of spacers disposed between the connector and the dielectric tube, said plurality of spacers define a plurality of ducts through which a cooling fluid is adapted to circulate to control a temperature of the probe,  
   wherein said plasma parameter measuring apparatus is configured to measure a parameter of said plasma.