Undercut-free patterned aluminum nitride structure and methods for forming the same

Patent metadata

Field	Value
Publication number	US-2022018009-A1
Application number	US-202016931574-A
Country	US
Kind code	A1
Filing date	Jul 17, 2020
Priority date	Jul 17, 2020
Publication date	Jan 20, 2022
Grant date	—

Abstract

A microstructure may be provided by forming a metal layer such as a molybdenum layer over a substrate. An aluminum nitride layer is formed on a top surface of the metal layer. A surface portion of the aluminum nitride layer is converted into a continuous aluminum oxide-containing layer by oxidation. A dielectric spacer layer may be formed over the continuous aluminum oxide-containing layer. Contact via cavities extending through the dielectric spacer layer, the continuous aluminum oxide-containing layer, and the aluminum nitride layer and down to a respective portion of the at least one metal layer may be formed using etch processes that contain a wet etch step while suppressing formation of an undercut in the aluminum nitride layer. Contact via structures may be formed in the contact via cavities. The microstructure may include a micro-electromechanical system (MEMS) device containing a piezoelectric transducer.

First claim

What is claimed is:

1 . A microstructure comprising:
at least one metal layer formed within interlayer dielectric material layers that overlie a substrate, wherein the interlayer dielectric material layers comprise an aluminum nitride layer overlying a topmost metal layer of the at least one metal layer; and at least one contact via structure contacting a respective one of the at least one metal layer and including a respective top portion that is vertically spaced from the interlayer dielectric material layers by an aluminum oxide-containing layer and a respective dielectric spacer structure which comprises a dielectric material that is essentially free of a metallic element, wherein the aluminum oxide-containing layer contacts a respective portion of a top surface of the aluminum nitride layer.

2 . The microstructure of claim 1 , wherein the aluminum oxide-containing layer comprises a graded aluminum nitride-oxide layer having a compositional gradient in which an oxygen atomic concentration increases from zero at an interface with a topmost aluminum nitride layer to a percentage in a range from 50% to 60% at a distal surface that is spaced from the interface with the topmost aluminum nitride layer.

3 . The microstructure of claim 2 , wherein:
the aluminum oxide-containing layer comprises an aluminum oxide layer that contacts the graded aluminum nitride-oxide layer at the distal surface; and the oxygen atomic concentration is 60% at the distal surface.

4 . The microstructure of claim 2 , wherein the distal surface contacts a bottom surface of the dielectric spacer structure.

5 . The microstructure of claim 1 , wherein dielectric spacer structure comprises a silicon oxide material.

6 . The microstruture of claim 1 , wherein the aluminum oxide-containing layer has a thickness in a range from 3 nm to 60 nm.

7 . A micro-electromechanical system (MEMS) device, comprising:
at least one metal layer formed within interlayer dielectric material layers that overlie a substrate, wherein the interlayer dielectric material layers comprise an aluminum nitride layer overlying a topmost metal layer of the at least one metal layer; and at least two contact via structures contacting a respective portion of the at least one metal layer and including a respective top portion that is vertically spaced from the interlayer dielectric material layers by a respective dielectric spacer structure and an aluminum oxide-containing layer, wherein the MEMS device comprises a piezoelectric transducer that uses the at least two contact via structures as electrical nodes and uses the aluminum nitride layer as a piezoelectric conversion element.

8 . The MEMS device of claim 7 , wherein:
the at least one metal layer comprises a plurality of metal layers; one of the at least two contact via structures contacts the topmost metal layer; and another of the at least two contact via structures contacts a metal layer selected from the plurality of metal layers other than the topmost metal layer.

9 . The MEMS device of claim 8 , wherein the interlayer dielectric material layers comprise at least one additional aluminum nitride layer located between the topmost metal layer and the substrate.

10 . The MEMS device of claim 8 , wherein the plurality of metal layers comprise a plurality of molybdenum layers having a respective thickness in a range from 5 nm to 100 nm.

11 . The MEMS device of claim 7 , wherein the dielectric spacer structure contacts a top surface of the aluminum oxide-containing layer, and comprises a dielectric material that is essentially free of a metallic element.

12 . The MEMS device of claim 11 , wherein the aluminum oxide-containing layer comprises a graded aluminum nitride-oxide layer having a compositional gradient in which an oxygen atomic concentration increases from zero at an interface with a topmost aluminum nitride layer to a percentage in a range from 50% to 60% at a distal surface that is spaced from the interface with the topmost aluminum nitride layer.

13 . The MEMS device of claim 11 , wherein:
the aluminum oxide-containing layer comprises an aluminum oxide layer that contacts the graded aluminum nitride-oxide layer at the distal surface; and the oxygen atomic concentration is 60% at the distal surface.

14 . The MEMS device of claim 11 , wherein the distal surface contacts a bottom surface of the dielectric spacer structure.

15 . The MEMS device of claim 7 , wherein:
the dielectric spacer structure comprises a silicon oxide material; and the aluminum oxide-containing layer has a thickness in a range from 3 nm to 60 nm.

16 . A method of patterning a microstructure, comprising:
forming at least one metal layer over a substrate; forming an aluminum nitride layer on a top surface of the metal layer; converting a surface portion of the aluminum nitride layer into a continuous aluminum oxide-containing layer by oxidizing the surface portion; forming a dielectric spacer layer over the continuous aluminum oxide-containing layer; forming contact via cavities extending through the dielectric spacer layer, the continuous aluminum oxide-containing layer, and the aluminum nitride layer and down to a respective portion of the at least one metal layer using etch processes that contain a wet etch step that etches physically exposed portions of the aluminum nitride layer while suppressing formation of an undercut in the aluminum nitride layer; and forming contact via structures in the contact via cavities.

17 . The method of claim 16 , further comprising:
depositing a conductive material layer in the contact via cavities and over the dielectric spacer layer; and patterning the conductive material layer and the dielectric spacer layer, wherein patterned portions of the conductive material layer comprise the contact via structures; and wherein patterned portions of the dielectric spacer layer comprise dielectric spacer structures that laterally surround a vertically-extending portion of a respective one of the contact via structures.

18 . The method of claim 16 , further comprising performing a plasma oxidation process that converts the surface portion of the aluminum nitride layer into the continuous aluminum oxide-containing layer, wherein the continuous aluminum oxide-containing layer comprises a graded aluminum nitride-oxide layer having a compositional gradient in which an oxygen atomic concentration increases from zero at an interface with the aluminum nitride layer to a percentage in a range from 50% to 60% at a distal surface that is spaced from the interface with the aluminum nitride layer.

19 . The method of claim 16 , wherein:
the metal layer comprises a molybdenum layer having a respective thickness in a range from 5 nm to 100 nm; and the aluminum nitride layer has a thickness in a range from 3 nm to 60 nm after the surface portion is converted into the aluminum oxide-containing layer.

20 . The method of claim 16 , wherein the microstructure comprises a micro-electromechanical system (MEMS) device containing a piezoelectric transducer that uses a subset of the contact via structures as electrical nodes and uses the aluminum nitride layer as a piezoelectric conversion element.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Hsieh Yuan-Chih
• Wang Yi-Ren
• Lin Hung-Hua

Classifications

• H10W20/071

  of dielectric parts thereof · CPC title

• H10W20/43

  Layouts of interconnections · CPC title

• H10W20/093

  by modifying materials of the dielectric parts · CPC title

• H10W20/42 Primary

  Vias, e.g. via plugs · CPC title

• B81C1/00095

  Interconnects · CPC title