Lamb acoustic wave resonator and filter with self-aligned cavity via

Patent metadata

Field	Value
Publication number	US-2018287587-A1
Application number	US-201715478941-A
Country	US
Kind code	A1
Filing date	Apr 4, 2017
Priority date	Apr 4, 2017
Publication date	Oct 4, 2018
Grant date	—

Abstract

A method for forming a lamb acoustic wave resonator and filter and the resulting device are provided. Embodiments include forming a sacrificial layer over a substrate; forming a first electrode over the sacrificial layer; forming a piezoelectric thin film over the first electrode; forming a second electrode over the piezoelectric thin film; forming a hardmask over the second electrode; etching through the hardmask and the second electrode down to the piezoelectric thin film forming self-aligned vias; forming and patterning a photoresist layer over the self-aligned vias; etching through the photoresist layer forming cavities extending through the vias and to the sacrificial layer; and removing the sacrificial layer forming a cavity gap under the cavities and first metal electrode.

First claim

What is claimed is:

1 . A method comprising:
forming a sacrificial layer over a substrate; forming a first electrode over the sacrificial layer; forming a piezoelectric thin film over the first electrode; forming a second electrode over the piezoelectric thin film; forming a hardmask over the second electrode; etching through the hardmask and the second electrode down to the piezoelectric thin film forming self-aligned vias; forming and patterning a photoresist layer over the self-aligned vias; etching through the photoresist layer forming cavities extending through the vias and to the sacrificial layer; and removing the sacrificial layer forming a cavity gap under the cavities and first metal electrode.

2 . The method according to claim 1 , comprising:
forming a dielectric hardmask over the second metal electrode.

3 . The method according to claim 1 , comprising:
reactive ion etching (RIE) through the photoresist layer forming the cavities.

4 . The method according to claim 1 , comprising:
removing the sacrificial layer by mechanical and/or chemical etching.

5 . The method according to claim 1 , further comprising:
removing the photoresist layer after the cavity gap is formed.

6 . The method according to claim 1 , comprising:
forming the piezoelectric thin film of aluminum nitride (AlN), scandium-doped AlN (ScAlN), zinc oxide (ZnO), lithium niobate/tantalate (LiNbO3/LiTaO3), or lead zirconate titanate (PZT).

7 . The method according to claim 1 , comprising:
forming the first and second electrodes of metal comprising molybdenum (Mo), chromium (Cr), or tungsten (W).

8 . The method according to claim 1 , comprising:
forming the second electrode as an interdigital transducer (IDT) electrode.

9 . The method according to claim 8 , further comprising:
forming an upper support; and forming another cavity gap between the support and the second electrode.

10 . A device comprising:
a substrate; a first electrode formed over the substrate; a first cavity gap disposed between the substrate and first electrode; a piezoelectric thin film formed over the first electrode; a patterned second electrode formed over the piezoelectric thin film; first and second self-aligned cavities extending through the patterned second electrode down to the cavity gap, wherein the first cavity gap connects the first and second self-aligned cavities; an upper support formed over the patterned second electrode; and a second cavity gap disposed between the patterned second electrode and the upper support.

11 . The device according to claim 10 , further comprising:
a patterned hardmask formed over the patterned second electrode, wherein a pattern of the hardmask is the same as a pattern of the second electrode, wherein the first electrode and the second patterned electrode comprise a metal selected from molybdenum (Mo), chromium (Cr), or tungsten (W).

12 . The device according to claim 10 , wherein:
the device is an acoustic resonator filter, the piezoelectric thin film forms an acoustic layer, the second metal electrode transduces an acoustic signal from the acoustic layer and determines a central resonance frequency of the filter, and the first and second self-aligned cavities provide frequency control of a resonance frequency of the acoustic resonator filter by fixing a distance between the second metal electrode and the first and second self-aligned cavities.

13 . The device according to claim 10 , wherein the piezoelectric thin film comprises aluminum nitride (AlN) scandium-doped AlN (ScAlN), zinc oxide (ZnO), lithium niobate/tantalate (LiNbO3/LiTaO3), or lead zirconate titanate (PZT).

14 . The device according to claim 10 , wherein the patterned second electrode comprises an interdigital transducer (IDT) electrode.

15 . The device according to claim 10 , wherein the patterned second electrode includes over etched regions in an upper surface over the first and second self-aligned cavities.

16 . A method comprising:
forming a sacrificial layer over a substrate; forming a first electrode over the sacrificial layer; forming a piezoelectric thin film over the first electrode; forming a second electrode over the piezoelectric thin film; etching through the second electrode down to the piezoelectric thin film forming self-aligned vias; forming and patterning a photoresist layer over the self-aligned vias; etching through the photoresist layer, forming cavities extending through the vias and to the sacrificial layer, wherein an over etch is formed in the second electrode over the cavities; and removing the sacrificial layer forming a cavity gap under the cavities and first metal electrode.

17 . The method according to claim 16 , comprising:
reactive ion etching (RIE) through the photoresist layer forming the cavities; and removing the sacrificial layer by mechanical and/or chemical etching. removing the photoresist layer after the cavity gap is formed.

18 . The method according to claim 16 , comprising:
forming a piezoelectric thin film of AlN, ScAlN, ZnO, LiNbO 3 /LiTaO 3 , or PZT; forming the first and second electrodes of metal comprising molybdenum (Mo), chromium (Cr), or tungsten (W); and forming the second electrode as an interdigital transducer (IDT) electrode.

19 . A device comprising:
a self-aligning hardmask comprising a conductive material and including an outer edge and an opening disposed within a perimeter of the edge, wherein the opening is positioned over a patterned layer that defines a cavity via.

20 . The device according to claim 19 , wherein:
the edge has an oval shape, elliptical shape or polygonal shape, and the conductive material comprises molybdenum (Mo), chromium (Cr), or tungsten (W).

21 . The device according to claim 20 , further comprising:
an electrode comprising Mo, Cr, or W, wherein the self-aligning hardmask and electrode are formed of the same conductive material, and patterned with the same processing step to pattern the electrode and ensure self alignment between the cavity via and the electrode.

Assignees

• Globalfoundries Sg Pte Ltd

Inventors

• Campanella Pineda Humberto
• Stamper Anthony Kendall
• Maling Jeffrey C
• Poikayil Satheesh Sharath
• Qian You
• Kumar Rakesh

Classifications

• H03H2003/021

  the resonators or networks being of the air-gap type · CPC title

• H03H9/02228

  Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer · CPC title

• H03H3/02 Primary

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H01L41/18

  Electricity · mapped topic

• H03H9/54 Primary

  comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64) · CPC title