Ultrahigh selective nitride etch to form finfet devices

Abstract

A substrate processing system for selectively etching a layer on a substrate includes an upper chamber region, an inductive coil arranged around the upper chamber region and a lower chamber region including a substrate support to support a substrate. A gas distribution device is arranged between the upper chamber region and the lower chamber region and includes a plate with a plurality of holes. A cooling plenum cools the gas distribution device and a purge gas plenum directs purge gas into the lower chamber. A surface to volume ratio of the holes is greater than or equal to 4. A controller selectively supplies an etch gas mixture to the upper chamber and a purge gas to the purge gas plenum and strikes plasma in the upper chamber to selectively etch a layer of the substrate relative to at least one other exposed layer of the substrate.

What is claimed is: 
     
         1 . A method for selectively etching a layer on a substrate, comprising:
 providing a substrate processing chamber including:
 a gas distribution device arranged between an upper chamber region and a lower chamber region, 
 the lower chamber region including a substrate support to support a substrate, and 
 the gas distribution device including a plate including a plurality of holes in fluid communication with the upper chamber region and the lower chamber region,
 wherein a ratio of a surface area of the holes to a volume of the holes is greater than or equal to 4 centimeters −1 ; 
 
   supplying an etch gas mixture to the upper chamber region; and   striking plasma in the upper chamber region thereby selectively etching a silicon nitride layer of the substrate relative to an epitaxial-silicon (epi-Si) layer of the substrate that is exposed to the plasma,   wherein a gap between a lower surface of the gas distribution device and an upper surface of the substrate during the etching is 20 mm to 80 mm.   
     
     
         2 . The method of  claim 1 , further comprising:
 supplying fluid to a cooling plenum in the gas distribution device to control a temperature of the gas distribution device; and   supplying purge gas to a purge gas plenum in the gas distribution device, wherein the purge gas plenum directs the purge gas from the gas distribution device towards the substrate support.   
     
     
         3 . The method of  claim 2 , further comprising transitioning the plasma to a post etch gas mixture after a predetermined etch period, wherein the post etch gas mixture includes a hydrogen species and an oxide species. 
     
     
         4 . The method of  claim 3 , wherein the transitioning from the etch gas mixture to the post etch gas mixture is performed without extinguishing the plasma. 
     
     
         5 . The method of  claim 1 , wherein a thickness of the plate is in a range from 5 mm to 25 mm, a diameter of the holes is in a range from 1 mm to 5 mm, a number of the holes is in a range from 100 to 5000 and a diameter of the plate is in a range from 6″ to 20″. 
     
     
         6 . The method of  claim 1 , wherein the etch gas mixture includes gases promoting nitride etch and passivation of at least one of silicon (Si), silicon germanium (SiGe) and oxide. 
     
     
         7 . The method of  claim 6 , wherein the gases promoting nitride etch include one or more gases selected from a group consisting of nitrogen trifluoride (NF 3 ), difluoromethane (CH 2 F 2 ), tetrafluoromethane (CFO, fluoromethane (CH 3 F), a combination of molecular oxygen, molecular nitrogen, and nitrous oxide (O 2 /N 2 /N 2 O), and combinations thereof. 
     
     
         8 . The method of  claim 6 , wherein the gases promoting passivation include one or more gases selected from a group consisting of fluoromethane (CH 3 F), difluoromethane (CH 2 F 2 ), methane (CH 4 ), carbonyl sulfide (COS), hydrogen sulfide (H 2 S), a combination of molecular oxygen, molecular nitrogen, and nitrous oxide (O 2 /N 2 /N 2 O), and combinations thereof. 
     
     
         9 . A method for selectively etching a layer on a substrate, comprising:
 providing a substrate processing chamber including:
 a gas distribution device arranged between an upper chamber region and a lower chamber region, 
 the lower chamber region including a substrate support to support a substrate, and 
 the gas distribution device including a plate including a plurality of holes in fluid communication with the upper chamber region and the lower chamber region, 
 wherein a ratio of a surface area of the holes to a volume of the holes is greater than or equal to 4 centimeters −1 ; 
 the gas distribution device further including:
 an annular radially-outer portion; 
 a cooling plenum formed in the annular radially-outer portion and to circulate fluid around a periphery of the gas distribution device and control a temperature of the gas distribution device; and 
 a purge gas plenum to direct purge gas from the gas distribution device in a direction into the lower chamber region towards the substrate support; 
 
   selectively enabling purge gas flow to the purge gas plenum;   supplying plasma gas to the upper chamber region thereby selectively etching a silicon nitride layer of the substrate relative to at least one other layer of the substrate that is exposed to the plasma gas, the at least one other layer of the substrate selected from a group consisting of silicon dioxide (SiO 2 ), silicon oxycarbonitride (SiOCN), silicon germanium (SiGe), amorphous silicon (a-Si), and epitaxial-silicon (epi-Si); and   during the etching of the silicon nitride layer of the substrate relative to the at least one other layer of the substrate, controlling the purge gas flow and the plasma gas flow such that a temperature of a mixture of the purge gas and the plasma gas within the upper chamber region is less than 100 degrees Celsius.   
     
     
         10 . The method of  claim 9 , wherein a thickness of the gas distribution device is in a range from 5 mm to 25 mm and a diameter of the holes is in a range from 1 mm to 5 mm. 
     
     
         11 . The method of  claim 9 , wherein a number of the holes is in a range from 100 to 5000 and a diameter of the gas distribution device is in a range from 6″ to 20″. 
     
     
         12 . The method of  claim 9  further comprising generating the plasma gas using a plasma gas mixture including gases promoting nitride etch and promoting passivation of at least one of silicon (Si), silicon germanium (SiGe) and oxide. 
     
     
         13 . The method of  claim 12 , wherein the gases promoting nitride etch include one or more gases selected from a group consisting of nitrogen trifluoride (NF 3 ), difluoromethane (CH 2 F 2 ), tetrafluoromethane (CF 4 ), fluoromethane (CH 3 F), a combination of molecular oxygen, molecular nitrogen, and nitrous oxide (O 2 /N 2 /N 2 O), and combinations thereof. 
     
     
         14 . The method of  claim 13 , wherein the gases promoting passivation include one or more gases selected from a group consisting of fluoromethane (CH 3 F), difluoromethane (CH 2 F 2 ), methane (CH 4 ), carbonyl sulfide (COS), hydrogen sulfide (H 2 S), a combination of molecular oxygen, molecular nitrogen, and nitrous oxide (O 2 /N 2 /N 2 O), and combinations thereof. 
     
     
         15 . The method of  claim 9 , further comprising transitioning from the plasma gas to a post etch gas mixture after a predetermined etch period, wherein the post etch gas mixture includes a hydrogen species and an oxide species. 
     
     
         16 . The method of  claim 15 , wherein the transitioning from the plasma gas to the post etch gas mixture is performed without extinguishing the plasma.