Anisotropic etch method

Abstract

A method to anisotropically etch an oxide/silicide/poly sandwich structure on a silicon wafer substrate in situ, that is, using a single parallel plate plasma reactor chamber and a single inert cathode, with a variable gap between cathode and anode. This method has an oxide etch step and a silicide/poly etch step. The fully etched sandwich structure has a vertical profile at or near 90° from horizontal, with no bowing or notching.

1 . An etching method in a reactor for an oxide layer on a substrate producing a profile in said layer of oxide substantially 90° from a horizontal plane passing through said layer of oxide comprising: 
 providing a parallel plate plasma etch reactor having a first electrode and having an inert second electrode;    mounting said substrate on said first electrode;    providing a high pressure atmosphere within said parallel plate plasma etch reactor, said high pressure atmosphere containing C 2 F 6 , CHF 3 , CF 4 , and He, said C 2 F 6  being predominant in relation to said CHF 3  and said CF 4 ;    establishing a plasma in said high pressure atmosphere, said plasma having a high power density;    exposing said layer of oxide to said plasma having a high power density; and    etching said layer of oxide to expose a subjacent layer on said substrate.    
   
   
       2 . The method of  claim 1 , wherein: 
 said high pressure atmosphere includes a pressure of approximately 2.3 torr and approximately 50 sccm C 2 F 6 , approximately 32 sccm CHF 3 , approximately 40 sccm CF 4 , and approximately 100 sccm He;    said plasma high power density is approximately 1.9 W/cm 2 ; and    a gap of approximately 0.48 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       3 . The method of  claim 1 , wherein: 
 said high pressure atmosphere includes a pressure within approximately 1.8 to 3.0 torr;    said plasma high power density is within approximately 0.18 to 4.0 W/cm 2 ; and    a gap within approximately 0.3 to 0.6 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       4 . The method of  claim 1  wherein: 
 said high pressure atmosphere includes a pressure within approximately 2.2 to 2.3 torr;    said plasma high power density is within approximately 0.18 to 4.0 W/cm 2 ; and    a gap within approximately 0.38 to 0.52 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       5 . The method of  claim 1 , wherein said high pressure atmosphere includes more C 2 F 6  than CF 4  and more CF 4  than CHF 3 .  
   
   
       6 . The method of  claim 1 , wherein said high pressure atmosphere includes at least approximately 5 sccm He.  
   
   
       7 . The method of  claim 1 , wherein said oxide layer includes a mask layer on portions thereof, said mask layer releasing carbon in said plasma having a high power density.  
   
   
       8 . An etching method in a parallel plate reactor for at least one layer in the group of layers consisting of a silicide layer, a poly layer, and a polycide layer located on a portion of a substrate for producing a profile in said layer of oxide of about 90° from horizontal, comprising: 
 providing a first electrode and an inert second electrode in the parallel plate reactor;    mounting said substrate on said first electrode;    providing a high pressure atmosphere within said parallel plate plasma etch reactor, said high pressure atmosphere containing C2F6, CHF3, CF4, and He;    establishing a plasma in said high pressure atmosphere, aid plasma having a high power density; and    exposing said layer of oxide to said plasma having a high power density.    
   
   
       9 . The method of  claim 8 , wherein: 
 said high pressure atmosphere includes a pressure of approximately 2.3 torr and approximately 50 sccm C2F6, approximately 32 sccm CHF3, approximately 40 sccm CF4, and approximately 100 sccm He;    said plasma power density is approximately 1.9 W/cm2; and    a gap of approximately 0.48 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       10 . The method of  claim 8 , wherein: 
 said high pressure atmosphere including a pressure within approximately 1.8 to 3.0 torr;    said plasma power density is within approximately 0.18 to 4.0 W/cm2; and    a gap within approximately 0.3 to 0.6 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       11 . The method of  claim 8 , wherein: 
 said high pressure atmosphere includes a pressure within approximately 2.2 to 2.3 torr;    said plasma power density is within approximately 0.18 to 4.0 W/cm2; and    a gap within approximately 0.38 to 0.52 cm exists between said first electrode and said inert second electrode, said inert second electrode comprising anodized aluminum.    
   
   
       12 . The method of  claim 8 , wherein said high pressure atmosphere includes more C 2 F 6  than CF 4  and more CF 4  than CHF 3 .  
   
   
       13 . The method of  claim 8 , wherein said high pressure atmosphere includes at least approximately 5 sccm He.  
   
   
       14 . The method of  claim 8 , wherein said oxide layer includes a mask layer on portions thereof, said mask layer releasing carbon in said plasma having a high power density.  
   
   
       15 . An anisotropic etching method for at least one layer in the group of layers consisting of silicide, poly, and polycide located on a substrate in a parallel plate reactor, said anisotropic etching method producing a profile of about 90° from horizontal, said method comprising: 
 providing a first electrode and having an inert second electrode comprised of anodized aluminum;    providing a gap of approximately 1.0 cm between said first electrode and said inert second electrode;    mounting said substrate on said first electrode; and    providing a plasma atmosphere within said parallel plate plasma reactor, said plasma atmosphere including a pressure of approximately 0.325 torr, including Cl 2  at a rate of approximately 90 seem, He at a rate of approximately 70 seem, and a plasma power density of approximately 0.57 W/cm 2 .    
   
   
       16 . A method to anisotropically etch at least one layer in the group of layers consisting of a silicide layer, a poly layer, and polycide layer located on a substrate, said anisotropical etch producing a profile at or near 90° from horizontal with respect to said substrate in a parallel plate plasma etch reactor having a first electrode and an inert second electrode comprised of anodized aluminum, said method comprising: 
 forming between said first electrode and said inert second electrode a gap within the range of approximately 0.5 cm to 2.5 cm;    mounting said substrate on said first electrode; and    providing a plasma atmosphere within said parallel plate plasma reactor including Cl 2  and He, a pressure within the range of approximately 0.200 to 0.550 torr, a plasma power density within the range of approximately 0.18 to 2.0 W/cm 2 .    
   
   
       17 . An anisotropic etch for a structure in situ to produce a profile of about 90° from horizontal with respect to said structure, said structure including a first layer of an oxide of silicon on a second layer selected from the group consisting silicide, poly, and polycide, said structure located on a substrate, said etch comprising: 
 providing a parallel plate plasma etch reactor having a first electrode and an inert second electrode comprising anodized aluminum;    placing said substrate on said first electrode;    providing a first high pressure atmosphere within said parallel plate reactor, said first high pressure atmosphere including C 2 F 6 , CHF 3 , CF 4 , and He;    exposing the first layer to a first plasma having a first high power density to expose at least a portion of said second layer;    providing a second pressure atmosphere within said reactor including Cl 2  and He; and    exposing the second layer to a second plasma having a second high power density.    
   
   
       18 . The method of  claim 17 , wherein: 
 said first high pressure atmosphere includes a pressure of approximately 2.3 torr, C 2 F 6  at the rate of approximately 50 sccm, CHF 3  at the rate of approximately 32 sccm, CF 4  at the rate of approximately 40 sccm, and He at a rate of approximately 100 sccm;    said first plasma including a power density of approximately 1.9 W/cm2;    a gap of approximately 0.48 cm between said first electrode and said inert second electrode for said first plasma power density;    said second high pressure atmosphere including a pressure of approximately 0.325 torr and Cl 2  at a rate of approximately 90 sccm and He at a rate of approximately 70 sccm;    said second plasma including a power density of approximately 0.57 W/cm2; and    a gap of approximately 1.0 cm between said first electrode and said inert second electrode for said second plasma power density.    
   
   
       19 . The method of  claim 17 , wherein: 
 said first high pressure atmosphere including a pressure within the range of approximately 1.8 torr to 0.3.0 torr;    said first plasma including a power density within the range of approximately 0.18 to 4.0 W/cm2;    a gap within the range of approximately 0.3 to 0.6 cm between said first electrode and said inert second electrode for said first plasma power density;    said second high pressure atmosphere including a pressure within the range of approximately 0.200 torr to 0.550 torr;    said second plasma including a power density within the range of approximately 0.18 to 2.0 W/cm2; and    a gap within approximately 0.5 to 2.5 cm between said first electrode and said inert second electrode for said second plasma high density.    
   
   
       20 . The method of  claim 17 , wherein: 
 said first high pressure atmosphere including a pressure within the range of approximately 2.2 torr to 2.4 torr;    said first plasma including a power density within the range of approximately 0.18 to 4.0 W/cm2;    a gap within approximately 0.38 to 0.52 cm between said first electrode and said inert second electrode for said first plasma power density;    said second high pressure atmosphere including a pressure within the range of approximately 0.300 torr to 0.425 torr;    said second plasma including a power density within the range of approximately 0.18 to 2.0 W/cm2; and    a gap within approximately 0.8 to 1.5 cm between said first electrode and said inert second electrode for said second plasma power density.    
   
   
       21 . The method of  claim 17 , wherein: 
 said first high pressure atmosphere includes more C 2 F 6  than CF 4  and more CF 4  than CHF 3 ;    said first high pressure atmosphere includes at least approximately 5 sccm He; and    said second high pressure atmosphere includes He at the rate of at least approximately 50 sccm.    
   
   
       22 . The method of  claim 17 , wherein the structure includes a mask layer that releases carbon when subjected to a plasma and resists chlorine.  
   
   
       23 . A method to etch a structure including a silicide on a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, said method comprising: 
 providing a parallel plate plasma etch reactor as said reactor, said parallel plate plasma etch reactor having a first electrode and having a second electrode that is non-erodible by said plasma generated in said gas in said reactor;    transferring said substrate into said parallel plate plasma etch reactor upon said first electrode located therein;    introducing a first atmosphere of said gas into said parallel plate plasma etch reactor, said first atmosphere comprising predominantly C 2 F 6  gas;    generating a first plasma using said predominantly C 2 F 6  gas as said first atmosphere in said parallel plate plasma etch reactor by the application of said power thereto;    etching said silicide in said parallel plate plasma etch reactor using said first plasma of said first atmosphere comprising C 2 F 6  as the predominant gas forming said first atmosphere in said parallel plate plasma etch reactor, thereby forming a plasma having a quantity of CF x  species formed therein and having relatively few fluorine radicals formed therein as compared with the quantity of said CF x  species, thereby, in turn, reducing micromasking from carbon depositing on said wafer, by achieving etching selectively without proportionally increasing polymer buildup, thereby, in turn, reducing areas of said silicide on a said layer of polycrystalline silicon which are not etched;    introducing a second atmosphere within said parallel plate plasma reactor prior to removing said wafer therefrom, said second atmosphere comprising:    constituents of Cl 2 ; and     an inert carrier gas, said inert carrier gas of said second atmosphere including at least 50 sccm He therein;    generating a second plasma using said second atmosphere introduced in said parallel plate plasma etch reactor by the application of said power thereto; and    exposing said structure to said second plasma in said second atmosphere thereby causing further etching of said structure.    
   
   
       24 . The method of  claim 23 , wherein, 
 said second atmosphere has a pressure of at least 0.325 torr and includes at least 90 sccm Cl 2 , and at least 70 sccm He as said inert carrier gas;    a power density of said second plasma in said second atmosphere is at least 0.57 W/cm 2 ;    a gap of at least 1.0 cm exists between said first and second electrodes in said second atmosphere; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       25 . The method of  claim 23 , wherein: 
 said second atmosphere has a pressure in the range of 0.200 to 0.550 torr;    a power density of said second plasma in said second atmosphere is in the range of 0.18 to 2.0 W/cm 2 ;    a gap in the range of 0.5 to 2.5 cm exists between said first and second electrodes in said second atmosphere; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       26 . The method of  claim 23 , wherein: 
 said second atmosphere has a pressure in the range of 0.300 to 0.425 torr;    a power density of said second plasma in said second atmosphere is in the range of 0.18 to 2.0 W/cm 2 ;    a gap in the range of 0.8 to 1.5 cm exists between said first and second electrodes in said second atmosphere; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       27 . The method of  claim 23 , wherein said second atmosphere includes at least approximately 50 sccm He.  
   
   
       28 . The method of  claim 23 , wherein said layer is masked with a mask layer that releases a carbon compound as said mask layer erodes.  
   
   
       29 . The method of  claim 23 , wherein said silicide comprises tungsten silicide.  
   
   
       30 . A method to etch a structure including tungsten silicide on a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, comprising: 
 masking said layer with a mask layer that erodes;    providing a parallel plate plasma etch reactor as said reactor, said parallel plate plasma etch reactor having a first electrode and having a second electrode that is non-erodible by said plasma;    transferring said substrate into said parallel plate plasma etch reactor upon said first electrode located therein;    providing an atmosphere within said parallel plate plasma etch reactor, said atmosphere comprising:     a gas having primary constituents of Cl 2  and an inert carrier gas, said atmosphere having a pressure within said parallel plate plasma etch reactor in the range of 0.200 to 0.550 torr;    generating a plasma by the application of said power to said gas in said parallel plate plasma etch reactor in the range of 0.18 to 2.0 W/cm 2 ; and    exposing said structure to said plasma when generated by the application of said power to said gas in said parallel plate plasma etch reactor in the range of 0.18 to 2.0 W/cm 2 , thereby etching said tungsten silicide.    
   
   
       31 . The method of  claim 30 , wherein: 
 a gap in the range of 0.3 to 0.6 cm exists between said first and second electrodes; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       32 . The method of  claim 30 , wherein said atmosphere includes at least 5 sccm He as said inert carrier gas.  
   
   
       33 . A method to etch a structure including a silicide on a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, comprising: 
 providing a parallel plate plasma etch reactor as said reactor, said reactor having a first electrode and having a second electrode that is non-erodible by said plasma generated in said reactor;    transferring said substrate formed as a wafer upon said first electrode of said parallel plate plasma etch reactor;    introducing a first atmosphere of said gas into said parallel plate plasma etch reactor comprising predominantly C 2 F 6  gas;    generating a first plasma using said predominantly C 2 F 6  gas as said first atmosphere in said parallel plate plasma etch reactor by the application of said power thereto;    etching said silicide in said parallel plate plasma etch reactor using said first plasma of said first atmosphere comprising C 2 F 6  as the predominant gas forming said first atmosphere in said parallel plate plasma etch reactor, thereby providing a plasma having a quantity of CF x  species formed therein and having relatively few fluorine radicals formed therein as compared with the quantity of said CF x  species, thereby, in turn, reducing micromasking from carbon depositing on said wafer, by achieving etching selectively without proportionally increasing polymer buildup, thereby, in turn, reducing areas of said silicide on a said layer of polycrystalline silicon which are not etched;    introducing a second atmosphere within said parallel plate plasma reactor prior to removing said wafer therefrom, said second atmosphere comprising:     constituents of Cl 2  and an inert carrier gas, said inert gas carrier including at least 50 sccm He therein;    generating a second plasma using said second atmosphere in said parallel plate plasma etch reactor by the application of said power thereto; and    exposing said structure to said second plasma in said second atmosphere, said second atmosphere having a pressure in the range of 0.200 to 0.550 torr, a power density of said second plasma in said second atmosphere is in the range of 0.18 to 2.0 W/cm 2 , a gap in the range of 0.5 to 2.5 cm exists between said first and second electrodes of said parallel plate plasma etch reactor in said second atmosphere introduced therein, and said non-erodible second electrode of said parallel plate plasma etch reactor comprises anodized aluminum.    
   
   
       34 . The method of  claim 33 , wherein: 
 said second atmosphere has a pressure in the range of 0.300 to 0.425 torr;    a power density of said second plasma is said second atmosphere is in the range of 0.18 to 2.0 W/cm 2 ;    a gap in the range of 0.8 to 1.5 cm exists between said first and second electrodes in said second atmosphere; and    d) said non-erodible second electrode comprises anodized aluminum.    
   
   
       35 . The method of  claim 33 , wherein the layer is masked with a mask layer that releases a carbon compound as it erodes.  
   
   
       36 . The method of  claim 33 , wherein the metal silicide is tungsten silicide.  
   
   
       37 . A method of etching a structure including a layer of silicide and a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, comprising: 
 masking said silicide layer with a mask layer that erodes;    providing a parallel plate plasma etch reactor as said reactor, said parallel plate plasma etch reactor having a first electrode and having a second electrode that is non-erodible by said plasma;    transferring said substrate into said parallel plate plasma etch reactor upon said first electrode located therein;    providing an atmosphere within said parallel plate plasma etch reactor, said atmosphere comprising:     a gas having primary constituents of Cl 2  and an inert carrier gas;    generating a plasma by the application of said power to said gas in said parallel plate plasma etch reactor; and    exposing said structure to said plasma in generated by the application of said power to said gas in said parallel plate plasma etch reactor thereby etching said layer of silicide.    
   
   
       38 . The method of  claim 37 , wherein: 
 a gap in the range of 0.3 to 0.6 cm exists between said first and second electrodes; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       39 . The method of  claim 37 , wherein said atmosphere includes at least 5 sccm He as said inert carrier gas.  
   
   
       40 . A method of etching a structure including a layer of silicide and a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, comprising: 
 masking said silicide layer with a mask layer that erodes;    providing a parallel plate plasma etch reactor as said reactor, said parallel plate plasma etch reactor having a first electrode and having a second electrode that is non-erodible by plasma;    transferring said substrate into said parallel plate plasma etch reactor upon said first electrode located therein;    providing an atmosphere within said parallel plate plasma etch reactor, said atmosphere comprising:     a gas having primary constituents of Cl 2  and an inert carrier gas, said atmosphere having a pressure within said parallel plate plasma etch reactor in the range of 0.200 to 0.550 torr;    generating a plasma by the application of said power to said gas in said parallel plate plasma etch reactor in the range of 0.18 to 2.0 W/cm 2 ; and    exposing said structure to said plasma in generated by the application of said power to said gas in said parallel plate plasma etch reactor in the range of 0.18 to 2.0 W/cm 2 , thereby etching said layer of silicide.    
   
   
       41 . The method of  claim 40 , wherein: 
 a gap in the range of 0.3 to 0.6 cm exists between said first and second electrodes; and    said non-erodible second electrode comprises anodized aluminum.    
   
   
       42 . The method of  claim 40 , wherein said atmosphere includes at least 5 sccm He as said inert carrier gas.  
   
   
       43 . A method of etching a structure including a silicide on a layer of polycrystalline silicon on a substrate formed as a wafer, said etch performed by a plasma generated by the application of power to a gas forming a portion of an atmosphere in a reactor, comprising: 
 providing a parallel plate plasma etch reactor as said reactor, said reactor having a first electrode and having a second electrode that is non-erodible by said plasma generated in said reactor;    transferring said substrate formed as a wafer upon said first electrode of said parallel plate plasma etch reactor;    introducing a first atmosphere of said gas into said parallel plate plasma etch reactor comprising predominantly C 2 F 6  gas;    generating a first plasma using said predominantly C 2 F 6  gas as said first atmosphere in said parallel plate plasma etch reactor by the application of said power thereto;    etching said silicide in said parallel plate plasma etch reactor using said first plasma of said first atmosphere comprising C 2 F 6  as the predominant gas forming said first atmosphere in said parallel plate plasma etch reactor thereby selectively etching of said substrate;    introducing a second atmosphere within said parallel plate plasma reactor prior to removing said wafer therefrom, said second atmosphere comprising:     constituents of Cl 2  and an inert carrier gas, said inert gas carrier including He therein;    generating a second plasma using said second atmosphere in said parallel plate plasma etch reactor by the application of said power thereto; and    exposing said structure to said second plasma in said second atmosphere, wherein:    said second atmosphere has a pressure in the range of 0.200 to 0.550 torr, a power density of said second plasma in said second atmosphere is in the range of 0.18 to 2.0 W/cm 2 , a gap in the range of 0.5 to 2.5 cm exists between said first and second electrodes of said parallel plate plasma etch reactor in said second atmosphere introduced therein, and said non-erodible second electrode of said parallel plate plasma etch reactor comprises anodized aluminum.    
   
   
       44 . The method of  claim 43 , wherein: 
 said second atmosphere has a pressure in the range of 0.300 to 0.425 torr;    a power density of said second plasma is said second atmosphere is in the range of 0.18 to 2.0 W/cm 2      a gap in the range of 0.8 to 1.5 cm exists between said first and second electrodes in said second atmosphere; and    said non-erodible second electrode comprises anodized aluminum.