Gas-phase tungsten etch

Patent metadata

Field	Value
Publication number	US-9299575-B2
Application number	US-201414215701-A
Country	US
Kind code	B2
Filing date	Mar 17, 2014
Priority date	Mar 17, 2014
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

Methods of evenly etching tungsten liners from high aspect ratio trenches are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor and a high flow of helium. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with tungsten coating a patterned substrate having high aspect ratio trenches. The plasmas effluents react with exposed surfaces and evenly remove tungsten from outside the trenches and on the sidewalls of the trenches. The plasma effluents pass through an ion suppression element positioned between the remote plasma and the substrate processing region. Optionally, the methods may include concurrent ion bombardment of the patterned substrate to help remove potentially thicker horizontal tungsten regions, e.g., at the bottom of the trenches or between trenches.

First claim

The invention claimed is:

1. A method of etching tungsten, the method comprising:
transferring a patterned substrate into a substrate processing region, wherein the patterned substrate has a tungsten lining layer coating a high aspect ratio trench having a depth more than twenty times a width of the high aspect ratio trench;
flowing a fluorine-containing precursor with a fluorine flow rate into a remote plasma region fluidly coupled to a substrate processing region via perforations in a perforated plate;
flowing helium with a helium flow rate into the remote plasma region;
forming a remote plasma in the remote plasma region to produce plasma effluents from the fluorine-containing precursor and the helium, and flowing the plasma effluents into the substrate processing region through the perforations; and
etching the tungsten lining layer, wherein, after etching the tungsten lining layer, a top sidewall thickness of the tungsten lining layer measured on a sidewall of the high aspect ratio trench near the opening of the high aspect ratio trench is within 20% of a bottom sidewall thickness of the tungsten lining layer measured on the sidewall of the high aspect ratio trench near the bottom of the high aspect ratio trench.

2. The method of claim 1 wherein the fluorine-containing precursor comprises at least one precursor selected from the group consisting of atomic fluorine, diatomic fluorine, bromine trifluoride, chlorine trifluoride, nitrogen trifluoride, hydrogen fluoride, sulfur hexafluoride and xenon difluoride.

3. The method of claim 1 wherein the depth of the high aspect ratio trench is greater than one micron.

4. The method of claim 1 wherein the width of the high aspect ratio trench is less than one hundred nanometers.

5. The method of claim 1 wherein a ratio of the helium flow rate to the fluorine flow rate is greater than or about fifteen.

6. The method of claim 1 wherein the helium flow rate and the fluorine flow rate are selected such that a net atomic flow rate ratio of helium to fluorine into the substrate processing region is greater than or about five.

7. The method of claim 1 wherein the remote plasma is formed by applying a remote plasma power greater than 10 watts capacitively to the remote plasma region.

8. The method of claim 1 wherein no bias plasma power is applied during the operation of forming the remote plasma.

9. The method of claim 1 further comprising applying a bias plasma power in the substrate processing region to re-ionize plasma effluents and bombard the patterned substrate with fluorine-containing ions.

10. The method of claim 9 wherein the bias plasma power is between 10 watts and 900 watts.

11. The method of claim 1 wherein a temperature of the patterned substrate is between −30° C. and 300° C. during the operation of etching the tungsten lining layer.

12. The method of claim 1 wherein one or both of the two adjacent stacks comprises at least ten alternating layers of dielectric and tungsten.

13. The method of claim 1 wherein etching the tungsten lining layer reduces a thickness of the tungsten lining layer at a top rate near the outermost portion of the sidewall of the high aspect ratio trench which is within 20% of a bottom rate near the innermost portion of the sidewall of the high aspect ratio trench.

14. The method of claim 1 wherein the fluorine-containing precursor is nitrogen trifluoride.

15. A method of etching tungsten, the method comprising:
transferring a patterned substrate into a substrate processing region, wherein the patterned substrate has a tungsten lining layer coating a high aspect ratio trench having a depth more than twenty times a width of the high aspect ratio trench;
flowing a fluorine-containing precursor into the substrate processing region
flowing nitrogen trifluoride into a remote plasma region fluidly coupled to a substrate processing region via perforations in the perforated plate;
forming a remote plasma in the remote plasma region to produce plasma effluents from the nitrogen trifluoride and flowing the plasma effluents into the substrate processing region through the perforations;
applying local plasma power capacitively between the perforated plate and a substrate susceptor supporting the patterned substrate to create and accelerate re-ionized plasma effluents toward the patterned substrate; and
etching the tungsten lining layer, wherein etching the tungsten lining layer reduces a thickness of the tungsten lining layer on a sidewall of the high aspect ratio trench at a top rate near the outermost portion of the sidewall of the high aspect ratio trench which is within 20% of a bottom rate near the innermost portion the sidewall of the high aspect ratio trench.

Assignees

• Applied Materials Inc

Inventors

• Park Seung
• Wang Xikun
• Liu Jie
• Wang Anchuan
• Kim Sang-Jin

Classifications

• H10P50/267 Primary

  using plasmas · CPC title

• H10P50/242 Primary

  of Group IV materials · CPC title

• H01L21/3065 Primary

  Electricity · mapped topic

• H01J37/32357

  Generation remote from the workpiece, e.g. down-stream · CPC title

• H01J2237/334

  Etching · CPC title