Aspect ratio controlled etch selectivity using time modulated DC bias voltage

Abstract

A modulated bias power etching method for etching a substrate is disclosed. The method alternatively deposits and etches material from a low aspect area of an integrated circuit device to form a static area while etching material from a high aspect area. The modulation pulse period and repetition rate are adjusted to permit deposition at low aspect ratio and very little or no deposition at high aspect ratio during the deposition cycle and to permit etching of the material deposited on the low aspect ratio area and etching of the material in the high aspect ratio area during the etching cycle.

What is claimed as new and desired to be protected by Letters Patent of the United States is:  
     
         1 . A method for selectively etching a layer of material over a substrate, said method comprising: 
 defining an etching pattern on said layer of material;    placing said substrate containing said layer of material into a reactive chamber;    introducing an etching gas into said chamber;    providing a power to said substrate to induce a plasma in said gas; and    changing the operating parameters of said reactive chamber during the etching of said material to selectively etch said layer of material.    
     
     
         2 . The method according to  claim 1 , wherein said method includes selectively controlling deposition on a first position of a first material having a first aspect ratio while continuously etching a second position of a second material having a second aspect ratio, wherein said first aspect ratio is less than said second aspect ratio.  
     
     
         3 . The method according to  claim 2 , wherein said first aspect ratio is less than or equal to 5.  
     
     
         4 . The method according to  claim 2 , wherein said second aspect ratio is greater than or equal to 3.  
     
     
         5 . The method according to  claim 3 , wherein said first aspect ratio is from about 0.5 to about 5.0.  
     
     
         6 . The method according to  claim 4 , wherein said second aspect ratio is from about 3.0 to about 20.0.  
     
     
         7 . The method according to  claim 1 , wherein said etching gas includes a fluorocarbon gas.  
     
     
         8 . The method according to  claim 1 , wherein said etching gas includes a hydrofluorocarbon gas.  
     
     
         9 . The method according to  claim 1 , wherein said etching gas includes a gas selected from the group consisting of CF 4 , C 2 F 6 , C 4 F 8 , C 3 F 8  and CHF 3.    
     
     
         10 . The method according to  claim 8 , wherein said etching gas includes CHF 3 .  
     
     
         11 . The method according to  claim 1 , wherein method includes etching a self-aligned contact.  
     
     
         12 . The method according to  claim 2 , wherein changing the operating parameters of said reactive chamber during the etching includes changing a DC bias voltage from a first voltage to a second voltage during a predetermined period while etching said material layer.  
     
     
         13 . The method according to  claim 12 , wherein said DC bias voltage is pulsed on a duty cycle of from about 10% to about 90%  
     
     
         14 . The method according to  claim 13 , wherein said pulsed DC bias voltage is obtained by modulating a source power.  
     
     
         15 . The method according to  claim 13 , wherein said pulsed DC bias voltage is obtained by modulating a source power, a bias power voltage or a combination thereof.  
     
     
         16 . The method according to  claim 2 , wherein said predetermined period is calculated according to a first relative deposition rate and a first relative etch rate of said first material, and to a second relative deposition rate and a second relative etch rate of said second material.  
     
     
         17 . The method according to  claim 12 , wherein said DC bias voltage is changed between about 0 volts and about 300 volts.  
     
     
         18 . The method according to  claim 17 , wherein said DC bias voltage is changed between about 10 volts and about 80 volts.  
     
     
         19 . The method according to  claim 12 , wherein said first voltage etches material on said first position of said first material and said second position of said second material and said second voltage deposits material on said first position while continuously etching said second position.  
     
     
         20 . A method for etching a self-aligned contact, comprising: 
 creating a patterned photoresist over a dielectric layer on a substrate, said substrate having spaced structures thereon, said patterned photoresist having an opening in alignment with the space between said spaced structures;    placing said device into a reactive chamber;    introducing an etching gas into said chamber;    providing a DC bias voltage to said substrate; and    changing said DC bias voltage from a first voltage to a second voltage during a predetermined period while etching said self-aligned contact.    
     
     
         21 . The method according to  claim 20 , wherein said method includes controlling deposition on a first position of a first material having a first aspect ratio while continuously etching a second position of a second material with a second aspect ratio between said structures, wherein said first aspect ratio is less than said second aspect ratio.  
     
     
         22 . The method according to  claim 21 , wherein said first aspect ratio is less than or equal to 5.  
     
     
         23 . The method according to  claim 21 , wherein said second aspect ratio is greater than or equal to 3.  
     
     
         24 . The method according to  claim 22 , wherein said first aspect ratio is from about 0.5 to about 5.0.  
     
     
         25 . The method according to  claim 23 , wherein said second aspect ratio is from about 3.0 to about 20.0.  
     
     
         26 . The method according to  claim 20 , wherein said etching gas includes a gas selected from the group consisting of a fluorocarbon gas and a hydrofluorocarbon gas.  
     
     
         27 . The method according to  claim 20 , wherein said etching gas includes a gas selected from the group consisting of CF 4 , C 2 F 6 , C 3 F 8 , C 4 F 8  and CHF 3.    
     
     
         28 . The method according to  claim 26 , wherein said etching gas includes CHF 3 .  
     
     
         29 . The method according to  claim 20 , wherein said DC bias voltage is modulated on a duty cycle of from about 10% to about 90%  
     
     
         30 . The method according to  claim 29 , wherein said DC bias voltage is obtained by modulating a source power.  
     
     
         31 . The method according to  claim 29 , wherein said DC bias voltage is obtained by modulating a source power, a bias power or combinations thereof.  
     
     
         32 . The method according to  claim 20 , wherein said pulsing period is calculated according to a first relative deposition rate and a first relative etch rate of said first material, and to a second relative deposition rate and a second relative etch rate of said second material.  
     
     
         33 . The method according to  claim 20 , wherein said DC bias voltage is modulated between about 0 volts and about 300 volts.  
     
     
         34 . The method according to  claim 33 , wherein said DC bias voltage is modulated between about 10 volts and about 80 volts.  
     
     
         35 . The method according to  claim 20 , wherein said first voltage etches material on a first position of a first material having a first aspect ratio and a second position having a second aspect ratio, wherein said first aspect ratio is less than said second aspect ratio, and said second voltage deposits material on said first position while continuously etching said second position.  
     
     
         36 . An integrated circuit device wherein said device is selectively etched by a method, comprising: 
 placing said device into a reactive chamber;    introducing into said chamber an etching gas;    providing a DC bias voltage to said substrate; and    modulating said DC bias voltage from a first voltage to a second voltage for a predetermined pulsing period to selectively etch said device.    
     
     
         37 . The device according to  claim 36 , wherein said method includes controlling deposition on a first position of a first material having a first aspect ratio while continuously etching a second position of a second material with a second aspect ratio, wherein said first aspect ratio is less than said second aspect ratio.  
     
     
         38 . The device according to  claim 37 , wherein said first aspect ratio is less than or equal to 5.  
     
     
         39 . The device according to  claim 37 , wherein said second aspect ratio is greater than or equal to 3.  
     
     
         40 . The device according to  claim 38 , wherein said first aspect ratio is from about 0.5 to about 5.0.  
     
     
         41 . The device according to  claim 39 , wherein said second aspect ratio is from about 3.0 to about 20.0.  
     
     
         42 . The device according to  claim 36 , wherein said etching gas includes a fluorocarbon gas.  
     
     
         43 . The device according to  claim 36 , wherein said etching gas includes a hydcrofluorocarbon gas.  
     
     
         44 . The device according to  claim 36 , wherein said etching gas includes a gas selected from the group consisting of CF 4 , C 2 F 6 , C 3 F 8 , C 4 F 8  and CHF 3.    
     
     
         45 . The device according to  claim 43 , wherein said etching gas includes CHF 3 .  
     
     
         46 . The device according to  claim 36 , wherein said device includes a self-aligned contact etched thereon.  
     
     
         47 . The device according to  claim 36 , wherein said bias voltage is modulated on a duty cycle of from about 10% to about 90%  
     
     
         48 . The device according to  claim 36 , wherein said modulated DC bias voltage is obtained by modulating a source power.  
     
     
         49 . The device according to  claim 36 , wherein said modulated DC bias voltage is obtained by modulating a source power, a bias power or combinations thereof.  
     
     
         50 . The device according to  claim 36 , wherein said predetermined pulsing period is calculated according to a first relative deposition rate and a first relative etch rate of said first material, and to a second relative deposition rate and a second relative etch rate of said second material.  
     
     
         51 . The device according to  claim 36 , wherein said bias voltage is modulated between about 0 volts and about 300 volts.  
     
     
         52 . The device according to  claim 51 , wherein said bias voltage is modulated between about 10 volts and about 80 volts.  
     
     
         53 . An apparatus for aspect controlled selective etching comprising; 
 a plasma etching chamber including a supported electrode;    a plasma induced bias voltage on said electrode; and    a bias voltage modulator for modulating the DC bias voltage between a first voltage and a second voltage, wherein said first voltage is greater than the voltage at which no etching occurs and said second voltage less that the voltage at which no etching occurs.    
     
     
         54 . The apparatus according to  claim 53 , wherein said apparatus is a high voltage plasma apparatus.  
     
     
         55 . The apparatus according to  claim 53 , wherein said high power plasma apparatus has a source power of from about 400 to about 1500 watts.  
     
     
         56 . The apparatus according to  claim 54 , wherein said apparatus is an inductively coupled plasma apparatus.  
     
     
         57 . The apparatus according to  claim 54 , wherein said apparatus is an electron cyclotron resonance apparatus.  
     
     
         58 . The apparatus according to  claim 53 , wherein said apparatus operates at a pressure of from about 2 to about 40 mTorr.  
     
     
         59 . The apparatus according to  claim 53 , wherein said bias voltage modulator has a duty cycle of from about 10% to about 90%.  
     
     
         60 . The apparatus according to  claim 53 , wherein said bias voltage is varied from between about 0 volts and about 300 volts.  
     
     
         61 . The apparatus according to  claim 53 , wherein said plasma is a fluorocarbon gas provided to said reactive plasma chamber by a plasma source.  
     
     
         62 . The apparatus according to  claim 53 , wherein said bias voltage modulator modulates the source power.  
     
     
         63 . The apparatus according to  claim 53 , wherein said bias voltage modulator modulates the bias power.