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US-20260130128-A1 - High Critical Temperature Metal Nitride Layer with Oxynitride Seed Layer

US20260130128A1US 20260130128 A1US20260130128 A1US 20260130128A1US-20260130128-A1

Abstract

A superconducting device includes a substrate, a metal oxide or metal oxynitride seed layer on the substrate, and a metal nitride superconductive layer disposed directly on the seed layer. The seed layer is an oxide or oxynitride of a first metal, and the superconductive layer is a nitride of a different second metal.

Inventors

  • Zihao Yang
  • Mingwei Zhu
  • Shriram Mangipudi
  • Mohammad Kamruzzaman CHOWDHURY
  • Shane LAVAN
  • Zhebo Chen
  • Yong Cao
  • Nag B. Patibandla

Assignees

  • APPLIED MATERIALS, INC.

Dates

Publication Date
20260507
Application Date
20241104

Claims (17)

  1. 1 . A superconducting device, comprising: a dielectric or semiconductive substrate; a metal oxynitride seed layer on the substrate, the seed layer being an oxynitride of a first metal other than niobium; and a niobium nitride superconductive layer disposed directly on the seed layer and patterned to form a wire.
  2. 2 . The device of claim 1 , wherein the seed layer provides a higher critical temperature to the niobium nitride superconductive layer than a metal nitride layer of the first metal.
  3. 3 . The device of claim 1 , wherein the metal oxynitride seed layer is disposed directly on the substrate.
  4. 4 . The device of claim 1 , comprising a distributed Bragg reflector between the substrate and the metal oxynitride seed layer.
  5. 5 . The device of claim 1 , comprising an optical waveguide between the substrate and the metal oxynitride seed layer to receive light propagating substantially parallel to the top surface of the substrate.
  6. 6 . The device of claim 1 , wherein the niobium nitride superconductive layer comprises δ-phase NbN.
  7. 7 . The device of claim 1 , wherein the first metal is aluminum nitride (AlN), hafnium nitride (HfN), chromium nitride (CrN), or nitride of an alloy of aluminum and either hafnium or scandium.
  8. 8 . The device of claim 7 , wherein the first metal is aluminum.
  9. 9 . The device of claim 1 , where the metal oxynitride seed layer has a thickness less than 2 nm.
  10. 10 . The device of claim 1 , wherein the metal oxynitride seed layer has a thickness of 3-50 nm.
  11. 11 . The device of claim 1 , comprising a metal nitride layer between the metal oxynitride seed layer and the substrate.
  12. 12 . The device of claim 11 , wherein the metal nitride layer is a nitride of the first metal.
  13. 13 . The device of claim 12 , wherein the metal nitride layer has a thickness of 3-50 nm.
  14. 14 . The device of claim 1 , further comprising a capping layer on the superconductive layer.
  15. 15 . The device of claim 14 , wherein the capping layer is aluminum nitride, aluminum oxide, silicon oxide, or silicon nitride.
  16. 16 . The device of claim 1 , comprising a single superconductive layer.
  17. 17 . The device of claim 1 , wherein the niobium nitride superconductive layer has a thickness of 4 to 50 nm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application No. Ser. No. 18/177,096, filed on Mar. 1, 2023, which is a continuation of U.S. application No. Ser. No. 17/178,187, filed on Feb. 17, 2021, which claims priority to U.S. application No. 62/980,079, filed on Feb. 21, 2020, the disclosure of which is incorporated by reference. BACKGROUND Technical Field The disclosure concerns use of a seed layer to improve the superconducting critical temperature of a metal nitride layer. Background Discussion In the context of superconductivity, the critical temperature (TC) refers to the temperature below which a material becomes superconductive. Niobium nitride (NbN) is a material that can be used for superconducting applications, e.g., superconducting nanowire single photon detectors (SNSPD) for use in quantum information processing, defect analysis in CMOS, LIDAR, etc. The critical temperature of niobium nitride depends on the crystalline structure and atomic ratio of the material. For example, referring to FIG. 1, cubic δ-phase NbN has some advantages due to its relatively “high” critical temperature, e.g., 9.7-16.5 K (the indicated process temperatures are for a particular fabrication process, and not necessarily applicable other process and deposition chamber designs). Niobium nitride can be deposited on a workpiece by physical vapor deposition (PVD). For example, a sputtering operation can be performed using a niobium target in the presence of nitrogen gas. The sputtering can be performed by inducing a plasma in the reactor chamber that contains the target and the workpiece. SUMMARY In one aspect, a superconducting device includes a substrate, a metal oxide or metal oxynitride seed layer on the substrate, and a metal nitride superconductive layer disposed directly on the seed layer. The seed layer is an oxide or oxynitride of a first metal, and the superconductive layer is a nitride of a different second metal. In another aspect, a superconducting device includes a substrate, a lower seed layer on the substrate, an upper seed layer disposed directly on the lower seed layer, and a superconductive layer disposed directly on the upper seed layer. The lower seed layer is a nitride of a first metal, the upper seed layer is an oxide or oxynitride of the first metal, and the superconductive layer is a nitride of a different second metal. Implementations may provide, but are not limited to, one or more of the following advantages. The critical temperature of the metal nitride layer, e.g., the NbN layer, can be increased. This permits fabrication of devices, e.g., SNSPDs, with superconductive wires with a higher critical temperature. The larger difference between the operating temperature (2-3 K) and the critical temperature provides superior detection efficiency, lower dark count, and possibly faster temporal response. It should be noted that “superconductive” indicates that the material becomes superconducting at the operating temperature of the device, e.g., 2-3° K. The material is not actually superconducting during fabrication of the device at or above room temperature or when the device is not being cooled for operation. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other potential aspects, features, and advantages will become apparent from the description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 diagram illustrating phase of niobium nitride as a function of processing temperature and atomic percentage nitrogen. FIG. 2A is a schematic cross-sectional view of a device that includes a metal nitride lower seed layer, a metal oxide or oxynitride upper seed layer, and a superconductive metal nitride layer. FIG. 2B is a schematic cross-sectional view of the device of FIG. 2A in which the superconductive layer has been etched to form superconductive wires. FIGS. 3A-3C are flow charts of a method of fabricating the device of FIG. 2A or 2B. FIG. 4A is a schematic cross-sectional view of a device that includes a metal oxide or oxynitride seed layer and a superconductive metal nitride layer. FIG. 4B is a schematic cross-sectional view of the device of FIG. 4A in which the superconductive layer has been etched to form superconductive wires. FIG. 5 is a flow chart of a method of fabricating the device of FIG. 4A or 4B. FIG. 6A is a schematic cross-sectional view of a device that includes a metal nitride seed layer and a superconductive metal nitride layer. FIG. 6B is a schematic cross-sectional view of the device of FIG. 6A in which the superconductive layer has been etched to form superconductive wires. FIG. 7 is a flow chart of a method of fabricating the device of FIG. 6A or 6B. FIG. 8A is a schematic top view of a SNSPD that includes a distributed Bragg reflector. FIG. 8B is a schematic cross-sectional side view of the device of FIG. 8A. FIG. 9A is a schematic top view of a SNSPD that in