Isotropic atomic layer etch for silicon oxides using no activation

Patent metadata

Field	Value
Publication number	US-2016196969-A1
Application number	US-201514590801-A
Country	US
Kind code	A1
Filing date	Jan 6, 2015
Priority date	Jan 6, 2015
Publication date	Jul 7, 2016
Grant date	—

Abstract

Methods for controlled isotropic etching of layers of silicon oxide and germanium oxide with atomic scale fidelity are provided. The methods make use of NO activation of an oxide surface. Once activated, a fluorine-containing gas or vapor etches the activated surface. Etching is self-limiting as once the activated surface is removed, etching stops since the fluorine species does not spontaneously react with the un-activated oxide surface. These methods may be used in interconnect pre-clean applications, gate dielectric processing, manufacturing of memory devices, or any other applications where accurate removal of one or multiple atomic layers of material is desired.

First claim

1 . A method of controllably etching a semiconductor oxide layer on a substrate, the method comprising:
(a) contacting the substrate housed in a process chamber with excess NO species to modify the surface of silicon or germanium oxide on the substrate by adsorption, forming Si/Ge—O—N—O bonds, such that the oxide on the substrate surface is saturated with NO bonding, preventing etching from occurring; (b) contacting the substrate with an F etchant after the surface of the modified oxide is saturated with Si/Ge—O—N—O bonds; (c) desorbing nitrogen oxide from the surface of the modified oxide, while leaving a surface activated towards etching; (d) allowing the F etchant to etch the activated surface.

2 . The method of claim 1 , wherein the semiconductor is silicon and etching operation (d) comprises desorption of SiF 4 from the oxide surface.

3 . The method of claim 2 , wherein a single cycle of operations (a)-(d) removes about 0.5-10 atomic layers of silicon oxide.

4 . The method of claim 2 , wherein a single cycle of operations (a)-(d) removes about an atomic monolayer of silicon oxide.

5 . The method of claim 2 , comprising performing at least two cycles, wherein each cycle comprises operations (a)-(d).

6 . The method of claim 2 , wherein the NO species is a plasma-excited NO gas.

7 . The method of claim 2 , wherein the NO species is a NO radical generated in a plasma.

8 . The method of claim 2 , wherein the F etchant is selected from the group consisting of F radical, NF 3 , F 2 , CF 4 , C 2 F 6 , HF, and XeF 2 .

9 . The method of claim 2 , wherein the F etchant is introduced into the process chamber coincident with the nitrogen oxide desorption.

10 . The method of claim 2 , wherein the F etchant is introduced into the process chamber before nitrogen oxide is desorbed from the modified surface of silicon oxide.

11 . The method of claim 10 , wherein F etchant chemisorbs on the surface of the Si—O—N—O such that he modified oxide is saturated with Si—O—N—O—F bonds before nitrogen oxide is desorbed as N—O—F, and the activated oxide surface is etched by the chemisorbed F.

12 . The method of claim 2 , wherein the F etchant is introduced into the process chamber after nitrogen oxide is desorbed from the modified surface of silicon oxide as N 2 O, leaving a surface activated towards etching, and the F etchant is allowed to etch the activated surface.

13 . The method of claim 2 , wherein (a)-(d) are performed at a temperature of between about 0-300° C.

14 . The method of claim 2 , wherein operations (a) and (b) comprise continuously supplying NO species into the process chamber, to prevent desorption of nitrogen oxide from the modified surface of silicon oxide.

15 . The method of claim 2 , wherein operations (c) and (d) comprise stopping supplying NO species into the process chamber or reducing supply of NO species to allow nitrogen oxide to desorb from the modified surface of silicon dioxide.

16 . The method of claim 2 , wherein operations (c) and (d) comprises stopping supply of the F etchant into the process chamber.

17 . The method of claim 1 , wherein following step (d) the chamber is purged with an inert gas.

18 . 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.

19 . An etching apparatus for controllably etching a semiconductor oxide on a substrate, the apparatus comprising:
(a) a process chamber having an inlet for introduction of process gases; (b) a substrate support in the process chamber configured for holding the substrate in position during etching of a silicon or germanium oxide on the substrate; and (d) a controller comprising instructions for:
(i) contacting the substrate housed in the process chamber with excess NO species to modify the surface of the oxide on the substrate by forming Si/Ge—O—N—O bonds;
(ii) contacting the substrate with an F etchant after the surface of the modified oxide is saturated with Si/Ge—O—N—O bonds, such that the oxide on the substrate surface is saturated with NO bonding, preventing etching from occurring;
(iii) desorbing nitrogen oxide from the surface of the modified oxide, while leaving a surface activated towards etching;
(iv) allowing the F etchant etch the activated oxide surface.
(v) optionally purging the chamber with an inert gas.

20 . An etching apparatus of claim 19 , wherein the controller comprises instructions for conducting (d)(i)-(v) two or more times.

Assignees

• Lam Res Corp

Inventors

• Berry Iii Ivan L
• Park Pilyeon
• Yaqoob Faisal

Classifications

• H10P76/2041

  Photolithographic processes · CPC title

• H10P70/20

  Cleaning during device manufacture · CPC title

• H10P50/285

  of materials not containing Si, e.g. PZT or Al2O3 · CPC title

• H10P50/283 Primary

  by chemical means · CPC title

• H10P50/73

  using masks for insulating materials · CPC title