Selective and isotropic etch of silicon over silicon-germanium alloys and dielectrics; via new chemistry and surface modification

12272,558

17/964601

October 12, 2022

Selective protection and etching is provided which can be utilized in etching of a silicon containing layer with respect to a Ge or SiGe layer. In an example, the layers are stacked, and an oxide is on a side surface of the layers. A treatment is utilized to provide a modified surface or termination surface on side surfaces of the Ge/SiGe layers, and a heat treatment is provided after the gas treatment to selectively sublimate layer portions on side surfaces of the Si containing layers. The gas treatment and heat treatment are preferably in non-plasma environments. Thereafter, a plasma process is performed to form a protective layer on the Ge containing layers, and the Si containing layers can be etched with the plasma.

TOKYO ELECTRON LIMITED (Tokyo, JP)

Tokyo Electron Limited (Tokyo, JP)

1. A method for processing a semiconductor substrate, the method comprising: receiving the semiconductor substrate that comprises a film stack, the film stack comprising a first germanium-containing layer, a second germanium-containing layer, and a first silicon layer positioned between the first germanium-containing layer and the second germanium-containing layer; removing an oxide layer from the film stack and forming a termination layer on the first germanium-containing layer and the second germanium-containing layer by: treating the film stack with a treatment gas comprising fluorine and oxygen, and heat-treating the film stack; and exposing the film stack to a plasma comprising fluorine and nitrogen, the plasma selectively etching the first silicon layer and converting the termination layer to an etch protection layer that inhibits etching of the first germanium-containing layer and the second germanium-containing layer during exposure of the film stack to the plasma.

2. The method of claim 1 , wherein the exposing the film stack to the plasma includes: exposing the film stack to a first plasma comprising nitrogen but not fluorine, and exposing the film stack to a second plasma comprising the fluorine and the nitrogen.

3. The method of claim 2 , further comprising sequentially repeating at least once the steps of exposing the film stack to the first plasma and exposing the film stack to the second plasma.

4. The method of claim 2 , wherein the exposing the film stack to the first plasma and the exposing the film stack to the second plasma comprises: forming the first plasma with nitrogen and hydrogen, and exposing the film stack to the first plasma for a predetermined amount of time, and after the predetermined amount of time, continuing to introduce the nitrogen and hydrogen and also introducing fluorine to form the second plasma, the second plasma being continuous with the first plasma.

5. The method of claim 4 , wherein the predetermined amount of time is 5 seconds or longer.

6. The method of claim 4 , wherein the predetermined amount of time is in a range from 5 seconds to 25 seconds, and after the predetermined amount of time, the fluorine containing gas is introduced.

7. The method of claim 1 , wherein the treating is performed in the absence of a plasma, wherein the treatment gas includes aerosolized water or water vapor, and wherein the plasma further comprises hydrogen.

8. The method of claim 2 , wherein the first plasma is generated from gases comprising nitrogen and hydrogen and without fluorine, and the second plasma is formed with gases comprising nitrogen, hydrogen and fluorine.

9. The method of claim 1 , wherein the plasma is generated from a gas combination comprising: nitrogen trifluoride (NF 3) and ammonia (NH 3); NF 3 , NH 3 , and nitrogen (N 2); NF 3 , NH 3 , and argon (Ar); NF 3 and hydrogen (H 2); NF 3 , H 2 , and N 2 ; or NF 3 , H 2 , NH 3 , and N 2 .

10. The method of claim 1 , wherein the etch protection layer formed on exposed surfaces of the first germanium-containing layer and the second germanium-containing layer comprises germanium nitride.

11. The method of claim 1 , wherein the first germanium-containing layer and the second germanium-containing layer are both germanium layers or are both silicon-germanium layers, wherein the plasma selectively etching the first silicon layer comprises selectively etching an end portion of the first silicon layer to form an indent in the film stack between the first germanium-containing layer and the second germanium-containing layer, as the first silicon layer is selectively etched, additional surfaces of the first germanium-containing layer and the second germanium-containing layer are exposed, and the plasma forms a passivation layer on the additional surfaces.

12. A method for processing a substrate comprising: providing the substrate having a Ge containing layer and a Si containing layer, one of the Ge containing layer or the Si containing layer being above another of the Ge containing layer or the Si containing layer, the Si containing layer including either no Ge or Ge in a percentage amount lower than the Ge containing layer, and wherein the Ge containing layer and the Si containing layer each have an oxide on side surfaces; performing a non-plasma treatment which removes the oxide from side surfaces of the Si containing layer and which provides a modified surface on side surfaces of the Ge containing layer; and performing a plasma process which etches side surfaces of the Si containing layer and which converts the modified surface of the Ge containing layer to a protective surface which includes germanium nitride to prevent etching of the Ge containing layer.

13. The method according to claim 12 , wherein the plasma process comprises: forming a first plasma with a nitrogen containing gas which does not include fluorine; exposing the substrate to the first plasma for 5 seconds or longer; after the exposing to the first plasma, introducing fluorine to the first plasma while continuing to supply the nitrogen containing gas to form a second plasma; and exposing the substrate to the second plasma.

14. The method according to claim 12 , wherein after the plasma process, the Si containing layer is indented with respect to the Ge containing layer so that an outer dimension of the Si containing layer is smaller than an outer dimension of the Ge containing layer.

15. The method according to claim 12 , wherein the non-plasma treatment includes: a treatment with a fluorine containing gas and a hydrogen containing gas, to form the modified surface on side surfaces of the Ge containing layer; and raising a temperature of the substrate to perform a heat treatment, wherein the modified surface includes hydrogen, silicon, germanium and fluorine, wherein during a first part of the plasma process, the modified surface reacts with nitrogen in a plasma to form the protective surface which includes germanium nitride, the plasma during the first part of the plasma process not including a halogen, and wherein during a second part of the plasma process, fluorine is introduced into the plasma and the Si containing layer is etched while the Ge containing layer is protected by the protective surface.

16. The method according to claim 15 , wherein the hydrogen containing gas includes aerosolized water or water vapor, and the heat treatment removes water residues and removes residual oxide layer portions remaining on side surfaces of the Si containing layer while the modified surface on side surfaces of the Ge containing layer is not removed.

17. A method for selective etching comprising: providing a substrate having a Ge containing layer and an Si containing layer, the Ge containing layer having a larger percentage of Ge than the Si containing layer, wherein one of the Ge containing layer or the Si containing layer is vertically above another of the Ge containing layer or the Si containing layer, and wherein a side surface layer is on side surfaces of both the Ge containing layer and the Si containing layer; treating the side surface layer in a non-plasma with process gases which include hydrogen, oxygen and fluorine; after the treating, selectively sublimating portions of the side surface layer so that after the selectively sublimating the side surface layer is removed from side surfaces of the Si containing layer, and a modified side surface layer is present on side surfaces on the Ge containing layer; after the selectively sublimating, exposing the substrate to a first plasma which includes hydrogen and nitrogen and which does not include a halogen or oxygen; and after the exposing to the first plasma, exposing the substrate to a second plasma which includes hydrogen, nitrogen and a halogen.

18. The method of claim 17 , wherein the modified side surface layer includes hydrogen, silicon, germanium and fluorine, the substrate is exposed to the first plasma for a first time period in a range of 5 seconds to 25 seconds, the substrate is exposed to the second plasma for a second time period in a range of 8 seconds to 25 seconds, after the second time period, at least one of plasma power is turned off or introduction of the halogen is discontinued for a third time period, and hydrogen and nitrogen continue to be introduced during the third time period, after the third time period, plasma power is turned on and the halogen is introduced for a fourth time period in a range of 8 seconds to 25 seconds.

19. The method of claim 18 , wherein the halogen includes fluorine, and during the second time period a ratio of fluorine to nitrogen introduced is in a range from 1:5 to 1:10, during the first time period and the second time period, oxygen is not introduced, and temperature is maintained in a range of −50° C. to 25° C.

20. The method according to claim 17 , wherein the treating is performed in a first process chamber, the selectively sublimating is performed in a second process chamber, and the exposing to the first and second plasmas is performed in a third process chamber.

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