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US-12622197-B2 - Metal oxide conversion for MEOL and BEOL applications

US12622197B2US 12622197 B2US12622197 B2US 12622197B2US-12622197-B2

Abstract

A method of capping a metal layer includes performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer, exposing the top surface of the metal layer to an oxidizing environment, and performing a removal process to remove the metal sulfide layer.

Inventors

  • Mohammad Mahdi TAVAKOLI
  • Chandan Das
  • Bencherki Mebarki
  • JOUNG JOO LEE
  • JIECONG TANG
  • Avgerinos V. Gelatos

Assignees

  • APPLIED MATERIALS, INC.

Dates

Publication Date
20260505
Application Date
20231023

Claims (17)

  1. 1 . A method of capping a metal layer, comprising: performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer; exposing the top surface of the metal layer to an oxidizing environment; and performing a removal process to remove the metal sulfide layer.
  2. 2 . The method of claim 1 , wherein the metal layer comprises tungsten (W), the metal oxide layer comprises tungsten oxide, and the metal sulfide layer comprises tungsten sulfide (WS 2 ).
  3. 3 . The method of claim 1 , wherein the metal layer comprises molybdenum (Mo), the metal oxide layer comprises molybdenum oxide, the metal sulfide layer comprises molybdenum sulfide (MoS 2 ).
  4. 4 . The method of claim 1 , wherein the conversion process comprises soaking the top surface of the metal layer in a precursor including hydrogen (H 2 ) and hydrogen sulfide (H 2 S).
  5. 5 . The method of claim 4 , wherein the conversion process is performed at a temperature of between 250° C. and 450° C., at a pressure of between 5 Torr and 100 Torr, for a time duration of between 20 minutes and 60 minutes.
  6. 6 . The method of claim 1 , wherein the removal process comprises exposing the top surface of the metal layer to a plasma formed from a process gas including hydrogen (H 2 ) gas and argon (Ar) gas.
  7. 7 . The method of claim 1 , wherein the metal oxide layer has a thickness of 1 nm and 3 nm.
  8. 8 . The method of claim 1 , wherein the metal sulfide layer has a thickness of 1 nm and 4 nm.
  9. 9 . A method of capping a metal layer, comprising: performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a cap layer on the top surface of the metal layer; exposing the top surface of the metal layer to an oxidizing environment; and performing a removal process to remove the cap layer, wherein the metal layer comprises tungsten (W), the metal oxide layer comprises tungsten oxide, and the cap layer comprises tungsten sulfide (WS 2 ), tungsten selenide (WSe 2 ), or tungsten telluride (WTe 2 ).
  10. 10 . The method of claim 9 , wherein the conversion process comprises soaking the top surface of the metal layer in a precursor including hydrogen (H 2 ) and hydrogen sulfide (H 2 S), hydrogen selenide (H 2 Se), or hydrogen telluride (H 2 Te).
  11. 11 . The method of claim 10 , wherein the conversion process is performed at a temperature of between 250° C. and 450° C., at a pressure of between 5 Torr and 100 Torr, for a time duration of between 20 minutes and 60 minutes.
  12. 12 . The method of claim 9 , wherein the removal process comprises exposing the top surface of the metal layer to a plasma formed from a process gas including hydrogen (H 2 ) gas and argon (Ar) gas.
  13. 13 . The method of claim 9 , wherein the metal oxide layer has a thickness of between 1 nm and 3 nm.
  14. 14 . The method of claim 9 , wherein the cap layer has a thickness of between 1 nm and 4 nm.
  15. 15 . A method of capping a metal layer, comprising: performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a cap layer on the top surface of the metal layer; exposing the top surface of the metal layer to an oxidizing environment; and performing a removal process to remove the cap layer, wherein the metal layer comprises molybdenum (Mo), the metal oxide layer comprises molybdenum oxide, the cap layer comprises molybdenum sulfide (MoS 2 ), molybdenum selenide (MoSe 2 ), or molybdenum telluride (MoTe 2 ).
  16. 16 . The method of claim 15 , wherein the conversion process is performed at a temperature of between 250° C. and 450° C., at a pressure of between 5 Torr and 100 Torr, for a time duration of between 20 minutes and 60 minutes.
  17. 17 . The method of claim 15 , wherein the conversion process comprises soaking the top surface of the metal layer in a precursor including hydrogen (H 2 ) and hydrogen sulfide (H 2 S), hydrogen selenide (H 2 Se), or hydrogen telluride (H 2 Te).

Description

BACKGROUND Field Embodiments described herein generally relate to semiconductor device fabrication. More specifically, embodiments of the present disclosure relate to methods for converting a metal oxide layer to form a cap layer in middle-end-of-line (MEOL) and a back-end-of-line (BEOL) applications. Description of the Related Art In fabrication of an integrated circuit, middle-end-of-line (MEOL) and back-end-of-line (BEOL) stages may include forming gate regions of transistors and local interconnect layers with metal, such as tungsten (W) and molybdenum (Mo). Typically, fabrication process flows include vacuum breaks that cause oxidation of metal layers, forming isolating materials at interfaces. Conventionally, metal oxides at the interfaces are removed by a chemical soak using a precursor (e.g., tungsten chloride, tungsten fluoride, molybdenum chloride, molybdenum fluoride) followed by a plasma treatment. However, a chemical soak is a time-consuming process and causes size variation in post-soak features. In addition, a cleaned surface of a metal layer will be oxidized again if the surface of the metal layer undergoes another vacuum break. Therefore, there is a need for efficient methods of removing metal oxides, such as tungsten oxide (WxOy) and molybdenum oxide (MoOx), and protecting metal layers from further oxidation. SUMMARY Embodiments of the present disclosure provide a method of capping a metal layer. The method includes performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer, exposing the top surface of the metal layer to an oxidizing environment, and performing a removal process to remove the metal sulfide layer. Embodiments of the present disclosure provide a method of capping a metal layer. The method includes performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a cap layer on the top surface of the metal layer, exposing the top surface of the metal layer to an oxidizing environment, and performing a removal process to remove the cap layer. Embodiments of the present disclosure provide a method of capping a metal layer. The method includes performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer, and exposing the top surface of the metal layer to an oxidizing environment, wherein the conversion process comprises soaking the top surface of the metal layer in a precursor including hydrogen (H2) and hydrogen sulfide (H2S). BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited features of embodiments of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. FIG. 1 is a schematic top view of a multi-chamber processing system, according to one or more embodiments of the present disclosure FIGS. 2A and 2B are schematic views of an exemplary semiconductor structure. FIG. 3 depicts a process flow diagram of forming a semiconductor structure including a MEOL portion and/or a BEOL portion, according to one or more embodiments of the present disclosure. FIGS. 4A, 4B, and 4C are schematic views of a portion of the semiconductor structure including a metal layer, corresponding to various states of the method of FIG. 3. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. In the figures and the following description, an orthogonal coordinate system including an X-axis, a Y-axis, and a Z-axis is used. The directions represented by the arrows in the drawings are assumed to be positive directions for convenience. It is contemplated that elements disclosed in some embodiments may be beneficially utilized on other implementations without specific recitation. DETAILED DESCRIPTION Embodiments of the present disclosure generally relate to converting a metal oxide layer (e.g., tungsten oxide (WxOy), molybdenum oxide (MoOx)) formed at an interface of a gate region in a middle-end-of-line (MEOL) portion or an interconnect in a back-end-of-line (BEOL) portion of an integrated circuit, into a cap layer that protects the interface from further oxidation. The conversion process may be sulfurization of the metal oxides into metal sulfide (e.g., tungsten sulfide (