Method and apparatus for anisotropic tungsten etching

Patent metadata

Field	Value
Publication number	US-2016196985-A1
Application number	US-201514589424-A
Country	US
Kind code	A1
Filing date	Jan 5, 2015
Priority date	Jan 5, 2015
Publication date	Jul 7, 2016
Grant date	—

Abstract

Methods for anisotropically etching a tungsten-containing material (such as doped or undoped tungsten metal) include cyclic treatment of tungsten surface with Cl 2 plasma and with oxygen-containing radicals. Treatment with chlorine plasma is performed while the substrate is electrically biased resulting in predominant etching of horizontal surfaces on the substrate. Treatment with oxygen-containing radicals passivates the surface of the substrate to etching, and protects the vertical surfaces of the substrate, such as sidewalls of recessed features, from etching. Treatment with Cl 2 plasma and with oxygen-containing radicals can be repeated in order to remove a desired amount of material. Anisotropic etching can be performed selectively in a presence of dielectric materials such as silicon oxide, silicon nitride, and silicon oxynitride.

First claim

1 . A method of anisotropically etching a tungsten-containing material on a semiconductor substrate in a plasma etching apparatus, the method comprising:
(a) providing a semiconductor substrate comprising a tungsten-containing material to a plasma etching process chamber; (b) introducing a first process gas comprising Cl 2 to the plasma etching process chamber and forming a plasma to react the tungsten-containing material with a plasma-activated chlorine; (c) removing the first process gas from the plasma etching process chamber after (b); (d) introducing a second process gas comprising an oxygen radical source to the plasma etching process chamber and forming a plasma comprising oxygen radicals to passivate a surface of the tungsten-containing material and thereby form a passivation layer comprising a compound that includes tungsten and oxygen; and (e) removing the second process gas from the plasma etching process chamber after (d), wherein the method predominantly etches the tungsten-containing material in a selected direction.

2 . The method of claim 1 , wherein forming a plasma in (b) comprises providing a bias of at least about 500 V to a substrate-holding support.

3 . The method of claim 1 , wherein the first process gas consists essentially of Cl 2 .

4 . The method of claim 1 , wherein the first process gas comprises Cl 2 and an inert gas selected from the group consisting of N 2 , He, Ar, H 2 , and combinations thereof.

5 . The method of claim 1 , wherein (b) comprises pulsing the plasma.

6 . The method of claim 1 , wherein (b) comprises pulsing the plasma with a duty cycle of between about 5-50%.

7 . The method of claim 1 , wherein the second process gas comprises a source of oxygen radicals selected from the group consisting of O 2 , O 3 , CO, CO 2 , COS, SO 2 and mixtures thereof.

8 . The method of claim 1 , wherein the source of oxygen radicals is O 2 .

9 . The method of claim 1 , wherein operations (b)-(e) are repeated.

10 . The method of claim 1 , wherein operations (b)-(e) are repeated at least 3 times.

11 . The method of claim 1 , wherein operations (b) and (c) are performed before operations (d) and (e).

12 . The method of claim 1 , wherein operations (d) and (e) are performed before operations (b) and (c).

13 . The method of claim 1 , wherein the semiconductor substrate further comprises an exposed layer of a dielectric material selected from the group consisting of silicon oxide, silicon nitride, and silicon oxynitride.

14 . The method of claim 1 , wherein the semiconductor substrate further comprises an exposed layer of a dielectric material selected from the group consisting of silicon oxide, silicon nitride, and silicon oxynitride, and wherein the tungsten-containing material is etched with an etch selectivity of at least about 2:1.

15 . The method of claim 1 , wherein the semiconductor substrate comprises a recessed feature comprising an exposed layer of tungsten-containing material at the bottom of the recessed feature, and wherein the etching removes the tungsten-containing material from the bottom of the recessed feature without substantially altering the width or diameter of the recessed feature.

16 . The method of claim 1 , wherein the method comprises etching a layer of tungsten-containing material having a thickness of between about 1000-7000 Å.

17 . The method of claim 1 , wherein the semiconductor substrate comprises a recessed feature comprising an exposed layer of tungsten-containing material at the bottom of the recessed feature, wherein the width or diameter of the recessed feature is less than about 150 nm.

18 . The method of claim 1 , wherein a single sequence of operations (b)-(e) removes between about 10-50 nm of the tungsten-containing material.

19 . The method of claim 1 , further comprising:
applying photoresist to the substrate; exposing the photoresist to light; patterning the photoresist and transferring the pattern to the substrate; and selectively removing the photoresist from the substrate.

20 . A plasma etching apparatus for anisotropically etching a tungsten-containing material on a semiconductor substrate, the apparatus comprising:
(a) a process chamber having an inlet for introduction of a process gas; (b) a substrate support in the process chamber configured for holding the semiconductor substrate in position during etching of the tungsten-containing material, wherein the substrate support is configured to be biased at least during a portion of the etching; (c) a system configured for forming a plasma in the process chamber; and (d) a controller comprising instructions for predominantly etching the tungsten-containing material in a selected direction, the instructions comprising program instructions for:
(i) introducing a first process gas comprising Cl 2 to the plasma etching process chamber and forming a plasma to react the tungsten-containing material with a plasma-activated chlorine;
(ii) removing the first process gas from the plasma etching process chamber after (i);
(iii) introducing a second process gas comprising an oxygen radical source to the plasma etching process chamber and forming a plasma comprising oxygen radicals to passivate a surface of the tungsten-containing material and thereby form a passivation layer comprising a compound that includes tungsten and oxygen; and
(iv) removing the second process gas from the plasma etching process chamber after (iii).

21 . The method of claim 1 , wherein the compound that includes tungsten and oxygen is selected from the group consisting of WO x and WOCl x .

Assignees

• Lam Res Corp

Inventors

• Tan Zhongkui
• Fu Qian
• Hsiao Huai-Yu

Classifications

• H10P72/0421

  for drying etching · CPC title

• H10P50/269

  pre- or post-treatments, e.g. anti-corrosion processes · CPC title

• H10P50/71

  using masks for conductive or resistive materials · CPC title

• H10P50/267 Primary

  using plasmas · CPC title

• H10P50/00 Primary

  Etching of wafers, substrates or parts of devices · CPC title