Method of plasma-enhanced atomic layer etching

• US 9,396,956 B1
• Filed: 01/16/2015
• Issued: 07/19/2016
• Est. Priority Date: 01/16/2015
• Status: Active Grant

• Current Assignee: ASM IP Holding B.V. (ASM International NV)
• Original Assignee: ASM IP Holding B.V. (ASM International NV)
• Inventors: Fukazawa, Atsuki
• Primary Examiner(s): Lu, Jiong-Ping
• Application Number:
  US14/598,532
• Publication Number:
  US 20160211147A1
• Time in Patent Office: 550 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01J 37/32091 the radio frequency energy being capacitively coupled to the plasma
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• CPC Class Codes: H01J 37/32449 Gas control, e.g. control of the gas flow
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/31111 by chemical means
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/32137 of silicon-containing layers
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

A method for etching a layer on a substrate includes at least one etching cycle, wherein an etching cycle includes: continuously providing an inert gas into the reaction space; providing a pulse of an etching gas into the continuous inert gas flow upstream of the reaction space to chemisorb the etching gas in an unexcited state on a surface of the substrate; and providing a pulse of RF power discharge between electrodes to generate a reactive species of the inert gas in the reaction space so that the layer on the substrate is etched.

Claims

1. A method for etching a layer on a substrate placed between electrodes in a reaction space by an atomic layer etching (ALE) process which comprises at least one etching cycle, wherein an etching cycle comprises:

continuously providing an inert gas flowing at least as a carrier gas for an etching gas into the reaction space, wherein the carrier gas flows through a mass flow controller and then through a gas manifold disposed upstream of the reaction space, said inert gas referring to a gas that does not etch the substrate in an unexcited state;

providing a pulse of an etching gas into the continuous inert gas flow upstream of the reaction space to chemisorb the etching gas in an unexcited state on a surface of the substrate in the reaction space, wherein the etching gas flows through a mass flow controller and is converged into the carrier gas flow downstream of the mass flow controller for the carrier gas and upstream of the gas manifold;

continuously providing a reactant gas other than the carrier gas and the etching gas into the reaction space, wherein each reaction gas flows through a mass flow controller and is then converged into the etching gas with the carrier gas at the gas manifold; and

providing a pulse of RF power discharge between the electrodes to generate a reactive species of the inert gas in the reaction space and to contact the etching gas-chemisorbed surface of the substrate with the reactive species so that the layer on the substrate is etched.

2. The method according to claim 1, wherein the etching gas is a halogen-containing gas and/or hydrocarbon gas.

3. The method according to claim 1, wherein the carrier gas functions also as a reactant gas.

4. The method according to claim 1, wherein the inert gas is selected from the group consisting of a noble gas and nitrogen gas.

5. The method according to claim 1, wherein the reactant gas includes at least one gas which is selected from the group consisting of a noble gas, nitrogen gas, oxidizing gas, and reducing gas.

6. The method according to claim 1, wherein the reactant gas includes at least one gas which is selected from the group consisting of oxidizing gas and reducing gas.

7. The method according to claim 1, wherein the ALE process is conducted at a temperature of 0°

C. to 200°

C.

8. The method according to claim 1, wherein the pulse of the etching gas and the pulse of RF power discharge do not overlap.

9. The method according to claim 7, wherein a purging period is taken between the pulse of the etching gas and the pulse of RF power discharge to remove excess etching gas from the reaction space, and a purging period is taken after the pulse of RF power discharge to remove reaction products from the reaction space.

10. The method according to claim 1, wherein no gas other than a halogen-containing gas flows as the etching gas throughout the ALE process.

11. The method according to claim 1, wherein the layer of the substrate has a recess pattern.

12. The method according to claim 11, wherein at least one of the following conditions is employed during the ALE process:

(i) a flow rate of the inert gas is 3,000 sccm or higher, (ii) an RF power is 250 W or higher, and (iii) a pressure is 300 Pa or higher.

13. The method according to claim 1, wherein the inert gas is a noble gas, and the layer of the substrate is etched anisotropically by supplying the inert gas to the reaction space.

14. The method according to claim 1, wherein the etching cycle is repeated multiple times.

15. The method according to claim 1, wherein the reaction space is formed in a reaction chamber for film-forming or dry-etching.

16. The method according to claim 1, wherein the layer of the substrate is a silicon-containing dielectric layer, and an etching rate is at least 0.015 nm/min.