Oxide film etching method

Abstract

The present invention provides an oxide film etching method performed by using an etching apparatus in which an oxide film formed on a target object to be processed is etched by utilizing a plasma generated within the process chamber by application of a high frequency power. The etching gas introduced into the process chamber in the etching step contains a C 4 F 6 gas and an O 2 gas, and the ratio C 4 F 6 /O 2 of the C 4 F 6 gas to the O 2 gas falls within a range of 0.7 and 1.5 so as to increase the etching selectivity of the oxide film relative to a resist film.

What is claimed is:  
     
         1 . An etching method, in which a target object to be processed, which has an oxide film formed on the upper surface thereof, is held within a process chamber capable of maintaining a vacuum environment, and a plasma is generated in the etching gas atmosphere introduced into said process chamber so as to etch said oxide film formed on said target object within the plasma, 
 wherein said etching gas including a C 4 F 6  gas and an O 2  gas, and a ratio C 4 F 6 /O 2  of the C 4 F 6  gas to the O 2  gas falls within a range of 0.7 and 1.5.    
     
     
         2 . The oxide film etching method according to  claim 1 , wherein said etching gas further contains an inert gas in addition to said C 4 F 6  gas and said O 2  gas.  
     
     
         3 . The oxide film etching method according to  claim 1 , wherein the gas pressure within said process chamber is set to fall within a range of 1.3 and 26 Pa (between 10 and 200 mTorr) in the etching step.  
     
     
         4 . The method according to  claim 1 , wherein the total flow rate of the C 4 F 6  gas and the O 2  gas into said process chamber is set to fall within a range of 0.01 and 0.1 L/min in the etching step.  
     
     
         5 . The method according to  claim 1 , wherein the residence time of O 4 F 6  and O 2  ranges from 0.69 msec to 26.3 msec.  
     
     
         6 . The method according to  claim 1 , wherein the plasma density in the etching step is not lower than 3×10 10 /cm 3  and is lower than 2×10 11 /cm 3 .  
     
     
         7 . The method according to  claim 1 , wherein the temperature of said target object is set at 50° C. or higher in the etching step.  
     
     
         8 . The method according to  claim 1 , wherein the silicon nitride film is exposed when the silicon oxide film is etched.  
     
     
         9 . The method according to  claim 8 , wherein the silicon oxide film is etched in a self-alignment contact process.  
     
     
         10 . The method according to  claim 1 , wherein said mechanism for generating a plasma is of a capacity coupled etching type, in which a high frequency electric field is formed between a pair of mutually facing electrodes for generating a plasma.  
     
     
         11 . The method according to  claim 8 , wherein said mechanism for generating a plasma is of a RIE (Reactive Ion Etching) type, in which a high frequency power for generating a plasma is applied to one electrode holding said target object.  
     
     
         12 . The method according to  claim 10 , wherein said mechanism for generating a plasma is of a type, in which different high frequency powers for generating a plasma are applied to both of said electrodes.  
     
     
         13 . The method according to  claim 11 , wherein the etching is performed a magnetic field perpendicular to the electric field in the space between said electrodes.  
     
     
         14 . The method according to  claim 10 , wherein said magnetic field is formed by magnetic field forming means having a dipole ring magnetic in which a plurality of anisotropic segment magnets are arranged to form a ring such that the directions of the magnetization of said anisotropic segment magnets are controlled to form a uniform magnetic field of one direction between the pair of electrodes.  
     
     
         15 . The method according to  claim 9 , wherein the etching selectivity of the oxide film relative to the shoulder portion of the mask pattern formed of a resist film is at least 5.  
     
     
         16 . A method of etching an oxide film, which uses a RIE (Reactive Ion Etching) mechanism in which a process chamber can maintain a vacuum, a high-frequency electric filed is generated between a pair of opposing electrodes and high-frequency power is supplied to one of the electrodes, which holds an object, and in which the object with the oxide film formed on an upper surface is held, a plasma is generated in an atmosphere of an etching gas introduced into the process chamber, the oxide film formed on the object is etched in the plasma, and RIE is performed in the following conditions: 
 C 4 F 6  and O 2  are applied at a total flow rate of 0.01 to 0.04 L/min;    C 4 F 6  is applied in a ratio of 1.0 to 1.5 with respect to O 2 ;    a gas pressure of 1.3 to 26 Pa (10 to 200 mTorr) is maintained in the process chamber ranges during the etching; and    the plasma has a density of at least 3×10 10 /cm 3 , not exceeding 1×10 11 /cm 3 , during the etching.    
     
     
         17 . A method of etching an oxide film, which uses a mechanism in which a high frequency electric filed is applied between opposing two electrodes provided in a process chamber maintained in a vacuum, thereby to supply high frequency power to both electrodes to generate a plasma, a high-frequency electric filed is generated between a pair of opposing electrodes and high-frequency power is supplied to both electrodes an object, and in which the object with the oxide film formed on an upper surface is held, a plasma is generated in an atmosphere of an etching gas introduced into the process chamber, the oxide film formed on the object is etched in the plasma, and RIE is performed in the following conditions: 
 C 4 F 6  and O 2  are applied at a total flow rate of 0.03 to 0.1 L/min;    C 4 F 6  is applied in a ratio of 0.7 to 1.1 with respect to O 2 ;    a gas pressure of 1.33 to 9.97 Pa (10 to 75 mTorr) is maintained in the process chamber ranges during the etching; and    the plasma has a density of at least 5×10 10 /cm 3 , not exceeding 2×10 11 /cm 3 , during the etching.