Atomic layer etching in continuous plasma

• US 9,991,128 B2
• Filed: 01/31/2017
• Issued: 06/05/2018
• Est. Priority Date: 02/05/2016
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Tan, Zhongkui, Zhang, Yiting, Wu, Ying, Xu, Qing, Fu, Qian, Yamaguchi, Yoko, Cui, Lin
• Primary Examiner(s): Ahmed, Shamim
• Application Number:
  US15/421,189
• Publication Number:
  US 20170229311A1
• Time in Patent Office: 490 Days
• Field of Search: None
• CPC Class Codes: C23C 16/45536 Use of plasma, radiation or electromagnetic fields
• CPC Class Codes: C23C 16/45544 characterized by the apparatus
• CPC Class Codes: C23C 16/52 Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• CPC Class Codes: H01J 2237/332 Coating
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32119 Windows
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/32449 Gas control, e.g. control of the gas flow
• CPC Class Codes: H01J 37/32697 Electrostatic control
• CPC Class Codes: H01J 37/32715 Workpiece holder
• CPC Class Codes: H01J 37/32926 Software, data control or modelling
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/3085 characterised by their behaviour during the process, e.g. soluble masks, redeposited masks
• CPC Class Codes: H01L 21/31122 of layers not containing Si, e.g. PZT, Al2O3
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/32139 using masks
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67259 Position monitoring, e.g. misposition detection or presence detection
• CPC Class Codes: H01L 21/6833 : Details of electrostatic chucks

Abstract

Methods and apparatus for etching substrates using self-limiting reactions based on removal energy thresholds determined by evaluating the material to be etched and the chemistries used to etch the material involve flow of continuous plasma. Process conditions permit controlled, self-limiting anisotropic etching without alternating between chemistries used to etch material on a substrate. A well-controlled etch front allows a synergistic effect of reactive radicals and inert ions to perform the etching, such that material is etched when the substrate is modified by reactive radicals and removed by inert ions, but not etched when material is modified by reactive radicals but no inert ions are present, or when inert ions are present but material is not modified by reactive radicals.

Claims

1. A method of etching a material of a substrate, the method comprising:

exposing a substrate in a processing chamber to a plasma-generated reactive species, and while the substrate is exposed to the plasma-generated reactive species, also exposing the substrate to plasma-generated inert ions to remove a material exposed on the substrate using self-limiting reactions,

wherein an energy threshold for removing a layer of the material modified by the reactive species using the inert ions is less than an energy threshold for sputtering the material exposed on the substrate using the inert ions.

2. The method of claim 1, wherein exposure of the substrate to the reactive species modifies the exposed material of the substrate, and the inert ions generated by the plasma remove the modified substrate material, thereby etching the material of the substrate.

3. The method of claim 1, wherein, during the exposure of the substrate to the reactive species and inert ions, the plasma is delivered continuously such that both source power and bias power are continuously on while etching the material of the substrate.

4. The method of claim 3, wherein the concentration of the inert ions present in the processing chamber during the etch is greater than 99% of all chemical species in the chamber, while the concentration of reactive species is less than about 1%.

5. The method of claim 1, further wherein a mask layer overlies the material of the substrate to be etched, and the energy threshold for removing a layer of the material modified by the reactive species using the inert ions is less than the energy threshold upon which the inert ions have sufficient energy to bombard or sputter onto the surface of a mask layer over the target layer, thereby resulting in physical removal of mask material.

6. The method of claim 1, wherein processing chamber pressure is between about 30 mTorr and about 1000 mTorr.

7. The method of claim 6, wherein processing chamber pressure is between about 100 mTorr and about 500 mTorr.

8. The method of claim 7, wherein processing chamber pressure is between about 200 mTorr and about 300 mTorr.

9. The method of claim 1, wherein the ion density of reactive ions, that are reactive to etch unmodified material on the substrate, is negligible.

10. The method of claim 1, wherein the material of a substrate to be etched is carbon-based.

11. The method of claim 10, wherein the carbon-containing material to be etched is amorphous carbon.

12. The method of claim 11, wherein the reactive species includes species selected from the group consisting of an oxygen-containing plasma, fluorine-containing plasma, chlorine-containing plasma, bromine-containing plasma, or combinations thereof.

13. The method of claim 1, wherein the material of a substrate to be etched is silicon-based.

14. The method of claim 13, wherein the silicon-containing material to be etched is selected from the group consisting of silicon, polysilicon, silicon-germanium, silicon oxide, silicon carbide, silicon-nitride, doped silicon carbide, doped silicon, and combinations thereof.

15. The method of claim 14, wherein the reactive species includes species selected from the group consisting of a fluorine-containing plasma, chlorine-containing plasma, bromine-containing plasma, or combinations thereof.

16. The method of claim 1, wherein the material of a substrate to be etched is metal-based.

17. The method of claim 16, wherein the metal-containing material to be etched is selected from the group consisting elemental metals tungsten and titanium, metal oxide, titanium oxide, metal nitrides, and combinations thereof.

18. The method of claim 17, wherein the reactive species includes species selected from the group consisting of a fluorine-containing plasma, chlorine-containing plasma, bromine-containing plasma, or combinations thereof.

19. The method of claim 1, wherein the inert ions include ions generated from He, Ne, Ar, Kr, Xe, or combinations thereof.