NOBLE GAS BOMBARDMENT TO REDUCE SCALLOPS IN BOSCH ETCHING

• US 20150069581A1
• Filed: 09/11/2013
• Published: 03/12/2015
• Est. Priority Date: 09/11/2013
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Chang, Che-Ming, Tseng, Lee-Chuan, Lin, Shih-Wei, Chan, Chih-Jen, Hsieh, Yuan-Chih, Liu, Ming Chyi, Chou, Chung-Yen
• Granted Patent: US 9,224,615 B2
• Time in Patent Office: Days
• US Class Current: 257/622
• CPC Class Codes: H01L 21/2633 for etching, e.g. sputteretching
• 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 27/00 Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate details thereof H01L23/00, H01L29/00 - H10K10/00; assemblies consisting of a plurality of individual solid state devices H01L25/00

Abstract

A method of etching a trench in a substrate is provided. The method repeatedly alternates between using a fluorine-based plasma to etch a trench, which has trench sidewalls, into a selected region of the substrate; and using a fluorocarbon plasma to deposit a liner on the trench sidewalls. The liner, when formed and subsequently etched, has an exposed sidewall surface that includes scalloped recesses. The trench, which includes the scalloped recesses, is then bombarded with a molecular beam where the molecules are directed on an axis parallel to the trench sidewalls to reduce the scalloped recesses.

Claims

1. A method, comprising:

forming a trench having an axis extending into a semiconductor body, wherein the trench has a sidewall surface exhibiting scallops having respective troughs which are arranged at different depths in the trench and which meet at respective crests; and

bombarding the semiconductor body with a molecular beam directed along or in parallel with the axis to reduce heights of the crests and thereby establish a plateau having a planar or substantially planar surface which extends between neighboring troughs corresponding to remnants of neighboring scallops.

2. The method of claim 1, wherein the molecular beam comprises an ionized noble gas.

3. The method of claim 1, wherein the molecular beam comprises ionized argon.

4. The method of claim 2, wherein the roughness is made up of a series of scalloped recesses having a height defined between a scallop crest and a scallop trough.

5. The method of claim 4, wherein bombarding the semiconductor body with ionized Argon reduces the height by at least half.

6. The method of claim 1, wherein forming the trench and bombarding the semiconductor body are both carried out in a process chamber of a plasma etching tool.

7. The method of claim 6, wherein fluorine is present in the process chamber while the semiconductor body is bombarded with the molecular beam.

8. A method, comprising:

providing a substrate;

repeatedly alternating between;

using a fluorine-based plasma to etch a trench, which has trench sidewalls, into a selected region of the substrate and using a fluorocarbon plasma to deposit a liner on the trench sidewalls, wherein at least one of the trench sidewalls or the liner exhibit scallops having respective troughs which are arranged at different depths in the trench and which meet at respective crests; and

bombarding the trench with a molecular beam, which is directed along an axis that is parallel to the trench sidewalls, to reduce heights of the crests and thereby establish a plateau having a planar or substantially planar surface which extends between remnants of neighboring troughs.

9. The method of claim 8, wherein the molecular beam is made up of inert gas molecules.

10. The method of claim 9, wherein the inert gas molecules comprise argon gas molecules.

11. The method of claim 9, wherein prior to bombarding the trench with the inert gas molecules, the roughness comprises neighboring scalloped recesses which have a height of approximately 4000 angstroms as measured between a crest of a scallop and a trench sidewall surface.

12. The method of claim 11, wherein after bombarding the trench with the inert gas molecules, the roughness is reduced so smoothed scalloped recesses have a height of approximately 1000 angstroms or less as measured between a crest of a scallop and trench sidewall surface.

13. The method of claim 8, wherein the trench has a depth to width aspect ratio of between approximately 3:

1 and approximately 15;

1.

14. The method of claim 8, wherein SF₆ is a source gas used for the fluorine based plasma.

15. The method of claim 14, wherein octofluorocyclobutane (c-C₄F₈) is a source gas used for the fluorocarbon plasma.

16. An integrated circuit comprising:

a semiconductor body having a trench therein, wherein the trench has a sidewall trench surface and a bottom trench surface, wherein the sidewall trench surface exhibits first and second scallops having first and second troughs, respectively, which are arranged at different depths and which meet a plateau having a planar or substantially planar surface which extends between nearest edges of the first and second troughs; and

an inert gas doped region proximate to the bottom trench surface and disposed within the semiconductor body.

17. The integrated circuit of claim 16, wherein the inert gas doped region has a first dopant concentration, which is approximately constant over a central region of the bottom trench surface, and a second dopant concentration which is lower than the first dopant concentration near an edge of the bottom trench surface adjacent to the sidewall trench surface.

18. The integrated circuit of claim 17, wherein the sidewalls of the trench are substantially smooth.

19. The integrated circuit of claim 17, wherein an amplitude or height between a trough and the plateau is less than 500 angstroms.

20. The integrated circuit of claim 17, wherein the sidewalls near the bottom trench surface have an inert gas dopant concentration that is less than the first dopant concentration.