Method and apparatus for anisotropic etching
View Patent ↗There is disclosed a method of treating a substrate material or a film present on the material surface comprising cyclically performing the following steps: (a) etching the material or film; (b) depositing or forming a passivation layer on the surfaces of an etched feature; and (c) selectively removing the passivation layer from the etched feature in order that the etching proceeds in a direction substantially perpendicular to the material or film surface. At least one of the steps (a) or (b) is performed in the absence of a plasma. Also disclosed is an apparatus for performing the method.
1. A method of treating a substrate material or film present on the material surface comprising repeatedly performing an etching process cycle, wherein each etching process cycle increases a depth of an etched feature in the material or film, and wherein each etching process cycle includes performing the following sequential steps:
(a) etching the material or film to increase the depth of the etched feature;
(b) depositing or forming a passivation layer on the surfaces of the etched feature; and
(c) partially and selectively removing the passivation layer from the surfaces of the etched feature in order that the etching of subsequent etching process cycles proceeds in a direction substantially perpendicular to the material or film surface,
wherein at least one of steps (a) or (b) is performed in the absence of a plasma, and wherein step (c) of each cycle is performed separately from step (a) of each next cycle.
2. A method according to claim 1 , wherein step (a) is performed with one or more appropriate chemicals in the absence of a plasma.
3. A method according to claim 1 , wherein the other of steps (a) and (b) is performed in the presence of a plasma.
4. A method according to claim 1 , wherein the material surface has previously had a mask pattern defined thereon.
5. A method according to claim 1 , wherein the material or film is a dielectric.
6. A method according to claim 5 , wherein the material or film is an oxide, preferably of silicon, quartz, glass, pyrex, SiO 2 deposited by CVD, or SiO 2 grown by thermal, plasma or other means to deposit or grow the oxide.
7. A method according to claim 1 , wherein the material or film is etched with HF.
8. A method according to claim 1 , wherein H 2 O and/or an alcohol is present in step (a).
9. A method according to claim 1 , wherein the material or film is a semiconductor, preferably a Si, SiGe or Ge semiconductor.
10. A method according to claim 9 , wherein the material or film is etched with HF, HNO 3 and CH 3 COOH, or with a halogen containing compound, preferably an inter-halogen gas comprising halogen components only.
11. A method according to claim 1 , wherein the material or film is a conductor, preferably an Au or Pt conductor.
12. A method according to claim 11 , wherein the material or film is etched using aqua regia.
13. A method according to claim 1 , wherein N 2 or other inert gas is present in step (a) and/or is used as a purging gas between the steps of the method.
14. A method according to claim 1 , wherein the passivation layer is formed on a surface that is resistant to chemical etch.
15. A method according to claim 1 , wherein the passivation layer is deposited using a polymer.
16. A method according to claim 15 , wherein the polymer is a per-fluoro polymer of formula n(C x F y ), where x and y are suitable values.
17. A method according to claim 1 , wherein, when a plasma is not present in step (b), a photo-enhanced polymerization process in used in the deposition of the passivation layer.
18. A method according to claim 1 , wherein the selective removal of the passivation layer is carried out by surface irradiation.
19. A method according to claim 18 , wherein the irradiation is thermal heating of either the front and/or the rear surface of the material or film to provide thermolytic decomposition, or is provided by a light source of the front of the material or film resulting in photolytic decomposition, or wherein the irradiation source is an excimer laser.
20. A method according to claim 18 , wherein the irradiation is directional or collimated parallel to the direction of etch front propagation.
21. A method according to claim 18 , wherein the surface irradiation is a plasma, wherein the ion energy in the plasma is preferably greater than 10 eV.
22. A method according to claim 21 , wherein the plasma comprises a precursor gas or mixture of precursor gases.
23. A method according to claim 22 , wherein the precursor gas comprises an inert gas which is capable of physically removing the passivation layer and/or a gas which is capable of physically removing the passivation layer with chemical enhancement.
24. A method according to claim 22 , wherein the precursor gas comprises an etchant chemical used in step (a) or a material used for depositing the passivation layer in step (b).
25. A method according to claim 1 , wherein any gases employed are delivered from a point of use delivery system positioned locally to a chamber within which the method is performed.
26. A method according to claim 1 for treating a substrate material or film formed from metallic and magnetic materials, wherein the etching step (a) is operated at pressures above atmosphere and/or at elevated temperatures using as etchant materials any one or more of diketones, ketoimines, halogenated-carboxylic acid, acetic acid, and formic acid chemistries and extensions including hexafluoro-2,4-pentanedione and other fluorinmated acetyl-acetone groups.