Atomic layer etching 3D structures: Si and SiGe and Ge smoothness on horizontal and vertical surfaces

• US 10,727,073 B2
• Filed: 02/02/2017
• Issued: 07/28/2020
• Est. Priority Date: 02/04/2016
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Tan, Samantha, Yang, Wenbing, Kanarik, Keren Jacobs, Lill, Thorsten, Pan, Yang
• Primary Examiner(s): Booth, Richard A
• Application Number:
  US15/423,486
• Publication Number:
  US 20170229314A1
• Time in Patent Office: 1,272 Days
• 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: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01J 37/32651 Shields, e.g. dark space shields, Faraday shields
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/30655 comprising alternated and repeated etching and passivation steps, e.g. Bosch process
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/70 Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof multistep manufacturing processes of assemblies consisting of a plurality of individual semiconductor or other solid state devices H01L25/00; manufacture of assemblies consisting of preformed electrical components H05K3/00, H05K13/00

Abstract

Methods and apparatuses for etching semiconductor material on substrates using atomic layer etching by chemisorption, by deposition, or by both chemisorption and deposition mechanisms in combination with oxide passivation are described herein. Methods involving atomic layer etching using a chemisorption mechanism involve exposing the semiconductor material to chlorine to chemisorb chlorine onto the substrate surface and exposing the modified surface to argon to remove the modified surface. Methods involving atomic layer etching using a deposition mechanism involve exposing the semiconductor material to a sulfur-containing gas and hydrogen to deposit and thereby modify the substrate surface and removing the modified surface.

Claims

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

(a) etching a substrate by removing layers of material using sequential self-limiting reactions by performing n cycles of;

(i) exposing the substrate to a reactive gas to modify a surface of the substrate without etching the surface of the substrate to form a modified surface, wherein the reactive gas comprises a sulfur-containing gas and wherein the surface of the substrate is modified by deposition, and

(ii) after exposing the substrate to the reactive gas, exposing the modified surface of the substrate to a removal species to remove at least some of the modified surface; and

(b) periodically exposing the substrate to an oxygen-containing plasma to passivate the surface of the substrate; and

wherein n is an integer between and including 1 and 100.

2. The method of claim 1, wherein the reactive gas further comprises a second reactive gas selected from the group consisting of hydrogen and a halogen-containing gas.

3. The method of claim 1, wherein the surface of the substrate comprises germanium that is modified by deposition.

4. The method of claim 3, wherein the sulfur-containing gas is selected from the group consisting of sulfur hexafluoride, sulfur dioxide, and hydrogen sulfide.

5. The method of claim 2, wherein the second reactive gas is a halogen-containing gas selected from the group consisting of chlorine, boron chloride, hydrogen chloride, hydrogen bromide, bromine, nitrogen fluoride, and fluorine;

and wherein the surface of the substrate is modified by chemisorption.

6. The method of claim 2, wherein the halogen-containing gas is selected from the group consisting of nitrogen trifluoride, fluorocarbons, and fluorine.

7. The method of claim 6, wherein the fluorocarbons comprise a gas selected from the group consisting of carbon tetrafluoride (CF₄), hexafluoro-2-butyne (C₄F₆), fluoromethane (CH₃F), and combinations thereof.

8. The method of claim 1, wherein the removal species is generated by introducing an activating gas and igniting a plasma using a plasma power between about 50 W and about 1000 W.

9. The method of claim 1, wherein x is a number of cycles for which (i) and (ii) are repeated using a halogen-containing gas as the reactive gas and y is a number of cycles for which (i) and (ii) are repeated using a sulfur-containing gas, and wherein a ratio of x to y is between 2:

1 and 20;

1.

10. The method of claim 1, wherein a bias is not applied during exposure to the removal species and bias power is 0 V.

11. The method of claim 1, wherein a bias is applied during exposure to the removal species to facilitate removal of the at least some of the modified surface.

12. The method of claim 11, wherein bias power is less than about 50 V.

13. The method of claim 11, wherein the bias is applied continuously, and wherein bias power is between about 40V and about 100V.

14. The method of claim 11, wherein the bias is pulsed for a duty cycle between about 5% and about 40% and wherein bias power is between about 300V and about 1000V.

15. The method of claim 11, wherein the bias is pulsed for a duty cycle of about 50%, and wherein bias power is between about 100V and about 300V.

16. The method of claim 1, wherein the oxygen-containing plasma is generated by introducing an oxygen-containing gas selected from the group consisting of oxygen, carbon dioxide, and sulfur dioxide;

and igniting a plasma.

17. The method of claim 1, wherein periodically exposing the substrate to the oxygen-containing plasma to passivate the surface of the substrate comprises depositing an oxide layer on the surface of the substrate by atomic layer deposition.

18. The method of claim 17, wherein etching the substrate by performing the n cycles and periodically exposing the substrate to the oxygen-containing plasma is performed without breaking vacuum.

19. A method of etching a substrate, the method comprising:

removing layers of material of a substrate by using sequential self-limiting reactions by;

(a) exposing a substrate to a halogen-containing gas to modify a first surface of the substrate by chemisorption to form a first modified surface;

(b) after exposing the substrate to the halogen-containing gas, exposing the substrate to a removal gas to remove at least some of the first modified surface;

(c) exposing the substrate to a sulfur-containing gas to modify a second surface of the substrate by deposition to form a second modified surface;

(d) after exposing the substrate to the sulfur-containing gas, exposing the substrate to the removal gas to remove at least some of the second modified surface; and

(e) repeating (a)-(d) and periodically exposing the substrate to an oxygen-containing plasma to passivate surfaces of the substrate; and

wherein the substrate comprises germanium.

20. The method of claim 19, wherein the etching produces atomically smooth vertical surfaces, substantially parallel with etch direction, in features in the substrate.