Repeating alternating multilayer buffer layer

Patent metadata

Field	Value
Publication number	US-2020295249-A1
Application number	US-201916352542-A
Country	US
Kind code	A1
Filing date	Mar 13, 2019
Priority date	Mar 13, 2019
Publication date	Sep 17, 2020
Grant date	—

Abstract

A buffer layer can be used to smooth the surface roughness of a galvanic contact layer (e.g., of niobium) in an electronic device, the buffer layer being made of a stack of at least four (e.g., six) layers of a face-centered cubic (FCC) crystal structure material, such as copper, the at least four FCC material layers alternating with at least three layers of a body-centered cubic (BCC) crystal structure material, such as niobium, wherein each of the FCC material layers and BCC material layers is between about five and about ten angstroms thick. The buffer layer can provide the smoothing while still maintaining desirable transport properties of a device in which the buffer layer is used, such as a magnetic Josephson junction, and magnetics of an overlying magnetic layer in the device, thereby permitting for improved magnetic Josephson junctions (MJJs) and thus improved superconducting memory arrays and other devices.

First claim

What is claimed is:

1 . A buffer layer comprising:
a stack of at least four layers of a face-centered cubic (FCC) crystal structure material, the at least four FCC material layers alternating with at least three layers of a body-centered cubic (BCC) crystal structure material, wherein each of the FCC material layers and BCC material layers is between about five and about ten angstroms thick.

2 . The buffer layer of claim 1 , wherein the FCC crystal structure material is copper and the BCC crystal structure material is niobium.

3 . The buffer layer of claim 1 , wherein the stack has six layers of the FCC crystal structure material alternating with layers of the BCC crystal structure material.

4 . The buffer layer of claim 3 , wherein the FCC crystal structure material is copper and the BCC crystal structure material is niobium.

5 . A magnetic Josephson junction (MJJ) comprising the buffer layer of claim 1 , the buffer layer being located directly on top of a lower superconducting electrode contact layer of the MJJ and below a magnetic layer of the MJJ, wherein the lower superconducting electrode contact layer is niobium and is at least five hundred angstroms thick.

6 . A superconducting memory comprising a plurality of memory cells each comprising an instance of the MJJ of claim 5 .

7 . A room-temperature magnetoresistive random-access memory (MRAM) comprising the buffer layer of claim 1 .

8 . A hard disk drive reader comprising the buffer layer of claim 1 .

9 . A method of fabricating an electronic device, the method comprising:
depositing a galvanic contact layer having a thickness of greater than five hundred angstroms and a root-mean-square upper surface roughness of between about fifteen angstroms and about twenty angstroms, depositing on top of the galvanic contact layer a face-centered cubic (FCC) crystal structure material between about five and about ten angstroms thick; depositing on top of the FCC crystal structure material a body-centered cubic (BCC) crystal structure material between about five and about ten angstroms thick; and repeating the FCC material deposition at least three more times, alternating with BCC material layers, wherein the repeated alternating FCC material layers and BCC material layers together form a buffer layer having an upper surface that is smoother than the upper surface of the galvanic contact layer.

10 . The method of claim 9 , further comprising depositing a magnetic layer on top of the buffer layer.

11 . The method of claim 9 , wherein the galvanic contact layer is niobium.

12 . The method of claim 11 , wherein the galvanic contact layer is between twelve hundred and two thousand angstroms thick.

13 . The method of claim 12 , wherein the galvanic contact layer is about fifteen hundred angstroms thick.

14 . The method of claim 9 , wherein the FCC crystal structure material is copper and the BCC crystal structure material is niobium.

15 . The method of claim 9 , wherein the electronic device is a magnetic Josephson junction (MJJ).

16 . A superconducting device comprising:
a lower substrate layer of silicon; above the substrate layer, a galvanic contact layer of niobium between about twelve hundred angstroms and about two thousand angstroms thick; and on top of the galvanic contact layer, a buffer layer comprising alternating layers of copper and niobium, the number of alternating copper layers in the buffer layer being N, the number of alternating niobium layers being either N−1 or N, where N is four or greater.

17 . The device of claim 16 , wherein the alternating layers of copper and niobium in the buffer layer each between about five angstroms and about ten angstroms thick.

18 . The device of claim 16 , wherein N is six.

19 . The device of claim 16 , wherein the device is a magnetic Josephson junction (MJJ).

20 . The device of claim 16 , further comprising, on top of the buffer layer, a magnetic layer.

Assignees

• Ambrose Thomas F
• Loving Melissa G
• Northrop Grumman Systems Corp

Inventors

• Ambrose Thomas F
• Loving Melissa G

Classifications

• H10N50/85

  Materials of the active region · CPC title

• G11C11/44

  using super-conductive elements, e.g. cryotron · CPC title

• H01F10/3254

  the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ] · CPC title

• G11C11/161 Primary

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• H01F10/3272

  by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets · CPC title