Systems and methods for etching a high aspect ratio structure
A method for etching a stack is described. The method includes etching a first nitrogen-containing layer of the stack by applying a non-metal gas and discontinuing the application of the non-metal gas upon determining that a first oxide layer is reached. The first oxide layer is under the first nitrogen-containing layer. The method further includes etching the first oxide layer by applying a metal-containing gas. The application of the metal-containing gas is discontinued upon determining that a second nitrogen-containing layer will be reached. The second nitrogen-containing layer is situated under the first oxide layer. The method includes etching the second nitrogen-containing layer by applying the non-metal gas.
1 . A method for etching a stack, comprising:
etching a first nitrogen-containing layer of the stack by applying a non-metal gas;
discontinuing the application of the non-metal gas upon determining that a first oxide layer is reached, wherein the first oxide layer is under the first nitrogen-containing layer;
etching the first oxide layer by applying a metal-containing gas;
discontinuing the application of the metal-containing gas before the etching of the first oxide layer is complete and before a second nitrogen-containing layer is reached, wherein the second nitrogen-containing layer is situated under the first oxide layer; and
etching the second nitrogen-containing layer by applying the non-metal gas.
2 . The method of claim 1 , wherein the first oxide layer is reached when the first oxide layer is being etched, wherein the first oxide layer is being etched when a pre-determined depth from a top surface of the oxide layer is reached.
3 . The method of claim 1 , wherein the non-metal gas includes a hydrofluorocarbon.
4 . The method of claim 1 , wherein the application of the metal-containing gas is discontinued while the first oxide layer is etched.
5 . The method of claim 1 , wherein said etching the first nitrogen-containing layer continues until a recess is formed in the first oxide layer, wherein the application of the non-metal gas is discontinued upon determining that the recess is formed in the first oxide layer.
6 . The method of claim 5 , wherein the recess is of a pre-determined depth.
7 . The method of claim 1 , further comprising:
discontinuing the application of the non-metal gas used to etch the second nitrogen-containing layer;
applying the metal-containing gas to etch a second oxide layer, wherein the second oxide layer is located under the second nitrogen-containing layer.
8 . The method of claim 7 , further comprising:
discontinuing the application of the metal-containing gas used to etch the second oxide layer upon determining that a pre-determined level proximate to a third nitrogen-containing layer is reached, when the third nitrogen-containing layer is located under the second oxide layer; and
etching the third nitrogen-containing layer by applying the non-metal gas after said discontinuing the application of the metal-containing gas used to etch the second oxide layer.
9 . The method of claim 1 , wherein the metal-containing gas includes carbonyl or a metal fluoride.
10 . The method of claim 9 , wherein the metal fluoride is tungsten hexafluoride.
11 . The method of claim 9 , wherein the metal-containing gas is applied with a fluorocarbon or nitrogen trifluoride (NF 3 ).
12 . The method of claim 1 , further comprising:
supplying a low frequency radio frequency (LF RF) signal having a first primary parameter level and a second primary parameter level for said etching the first nitrogen-containing layer;
modifying the first primary parameter level to a third primary parameter level and the second primary parameter level to a fourth primary parameter level when etching the first oxide layer.
13 . The method of claim 12 , wherein the second primary parameter level is lower than the first primary parameter level and the fourth primary parameter level is lower than the third primary parameter level, wherein the third primary parameter level is greater than the first primary parameter level and the fourth primary parameter level is greater than the second primary parameter level.
14 . The method of claim 12 , further comprising:
supplying a high frequency RF (HF RF) signal having a first secondary parameter level and a second secondary parameter level for said etching the first nitrogen-containing layer;
modifying the first secondary parameter level to a third secondary parameter level and the second secondary parameter level to a fourth secondary parameter level when etching the first oxide layer.
15 . The method of claim 14 , wherein the second secondary parameter level is lower than the first secondary parameter level and the fourth secondary parameter level is lower than the third secondary parameter level, wherein the third secondary parameter level is greater than the first secondary parameter level and the fourth secondary parameter level is greater than the second secondary parameter level.
16 . The method of claim 15 , wherein a ratio of the first primary parameter level to the first secondary parameter level is between 0.75 and 1.25, wherein a ratio of the second primary parameter level to the second secondary parameter level is between 0.75 and 1.25.
17 . The method of claim 15 , wherein a ratio of the third primary parameter level to the third secondary parameter level is between 2 and 4, wherein a ratio of the fourth primary parameter level to the fourth secondary parameter level is between 2 and 4.
18 . A method for etching a stack, comprising:
etching an oxide layer by applying a metal-containing gas;
discontinuing the application of the metal-containing gas before the etching of the oxide layer is complete and before a silicon-containing layer is reached, wherein the silicon-containing layer is situated under the oxide layer; and
etching the silicon-containing layer by applying a non-metal gas.
19 . The method of claim 18 , wherein the oxide layer is reached when the oxide layer is being etched, wherein the oxide layer is being etched when a pre-determined depth from a top surface of the oxide layer is reached.
20 . The method of claim 18 , wherein the silicon-containing layer is a silicon-nitride layer or a polysilicon layer.
21 . The method of claim 18 , wherein the metal-containing gas is applied with a fluorocarbon or nitrogen trifluoride (NF 3 ).
22 . The method of claim 18 , wherein the non-metal gas includes a hydrofluorocarbon.
23 . The method of claim 18 , wherein the application of the metal-containing gas is discontinued while the oxide layer is etched.
24 . The method of claim 18 , wherein the metal-containing gas includes carbonyl or a metal fluoride.
25 . The method of claim 24 , wherein the metal fluoride is tungsten hexafluoride.