ETCH METHOD IN THE MANUFACTURE OF A SEMICONDUCTOR DEVICE
The present invention provides a method for forming a transistor on a silicon substrate, the method comprising: providing a substrate comprising: a gate electrode with a liner comprising silicon and oxygen, and with a sidewall spacer, and source and/or drain region(s) in the substrate adjacent to the gate electrode, a layer at least 5 nm thick comprising silicon dioxide covering at least the source and/or drain regions; etching the layer comprising silicon and oxygen from at least the source and/or drain regions; and forming contacts for the source and/or drain region(s), characterized in that the layer comprising silicon and oxygen is etched from the substrate by steps comprising: forming an etchant from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia; exposing the substrate to the etchant; and annealing the substrate.
1 . A method for forming a transistor on a silicon substrate, the method comprising:
providing a substrate comprising a gate electrode with a liner comprising silicon and oxygen, and with a sidewall spacer, and source and/or drain region(s) in the substrate adjacent to the gate electrode, a layer at least 5 nm thick comprising silicon dioxide covering at least the source and/or drain regions;
etching the layer comprising silicon and oxygen from at least the source and/or drain regions; and
forming contacts for the source and/or drain region(s),
wherein etching the layer comprising silicon and oxygen is etched from the substrate by steps comprising comprises:
forming an etchant from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia;
exposing the substrate to the etchant; and
annealing the substrate.
2 . The method according to claim 1 , wherein the source and/or drain contacts are formed by:
depositing a metal or metal alloy layer over the source and/or drain regions; and
annealing the substrate to form metal silicide source and/or drain contacts.
3 . The method according to claim 1 , wherein the source and/or drain contacts are formed from silicon, nickel, and optionally platinum.
4 . The method according to claim 1 , wherein etching the layer comprising silicon and oxygen comprises:
exposing the substrate to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia, and annealing the substrate;
followed by exposing the substrate again to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia, and annealing the substrate.
5 . The method according to claim 1 , wherein etching the layer comprising silicon and oxygen comprises:
etching the substrate with a hydrogen fluoride solution;
forming an etchant formed from a mixture comprising nitrogen trifluoride and ammonia; and
exposing the substrate to the etchant.
6 . The method according to claim 5 , wherein the etching with a hydrogen fluoride solution is carried out before exposing the substrate to an etchant formed from a gas mixture comprising nitrogen trifluoride and ammonia.
7 . The method according to claim 1 , wherein the layer comprising silicon and oxygen is less than 300 nm in thickness.
8 . The method according to claim 1 , wherein the plasma is formed at a power density of between 10 and 1000 mW/cm3.
9 . The method according to claim 1 , wherein the layer comprising silicon and oxygen is covered by a second layer comprising a nitride of silicon.
10 . The method according to claim 9 , wherein the layer comprising a nitride of silicon is from 5 to 50 nm in thickness.
11 . The method according to claim 1 , wherein the layer comprising silicon and oxygen is formed as a blanket layer over the surface of the substrate.
12 . The method according to claim 11 , wherein a layer that is stable to the conditions in the etching steps is formed over part of the blanket layer.
13 . The method according to claim 1 , wherein the layer comprising silicon and oxygen comprises an oxide of silicon, for example silicon dioxide.
14 . The use of an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia in the prevention of undercutting of a sidewall spacer in etching of a layer comprising silicon and oxygen in the manufacture of a semiconductor device.
15 . (canceled)
16 . The method according to claim 2 , wherein the source and/or drain contacts are formed from silicon, nickel, and optionally platinum.
17 . The method according to claim 2 , wherein etching the layer comprising silicon and oxygen comprises:
exposing the substrate to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia, and annealing the substrate;
followed by exposing the substrate again to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride.
18 . The method according to claim 3 , wherein etching the layer comprising silicon and oxygen, comprises:
exposing the substrate to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride and ammonia, and annealing the substrate;
followed by exposing the substrate again to an etchant formed from a plasma formed from a mixture comprising nitrogen trifluoride.
19 . The method according to claim 2 , wherein etching the layer comprising silicon and oxygen comprises:
etching the substrate with a hydrogen fluoride solution;
forming an etchant formed from a mixture comprising nitrogen trifluoride and ammonia; and
exposing the substrate to the etchant.
20 . The method according to claim 3 , wherein etching the layer comprising silicon and oxygen comprises:
etching the substrate with a hydrogen fluoride solution;
forming an etchant formed from a mixture comprising nitrogen trifluoride and ammonia; and
exposing the substrate to the etchant.
21 . The method according to claim 2 , wherein the layer comprising silicon and oxygen is less than 300 nm in thickness.