US-12625411-B1 - Two step patterning methods for photonic devices

Abstract

An etching method includes forming a metal oxide layer that is a barium titanate layer or a strontium titanate layer over a substrate, and etching the metal oxide layer using atomic layer etching.

Inventors

• Colleen Shang FENRICH
• George Kovall

Assignees

• Psiquantum, Corp.

Dates

Publication Date

20260512

Application Date

20230420

Claims (20)

1. 1 . An etching method, comprising: forming a metal oxide layer comprising a barium titanate layer or a strontium titanate layer over a substrate; and etching the metal oxide layer using atomic layer etching, wherein: the atomic layer etching comprises a sequence alternating between a first step comprising a self-limiting chemical modification step which forms a passivating layer on the metal oxide layer, and a second step which comprises a self-limiting selective removal step which selectively removes the passivating layer relative to metal oxide layer located under the passivating layer, the first step and the second step are sequentially repeated two or more times; the passivating layer comprises a barium halide or a strontium halide passivating layer; and the second step comprises an acid based wet etching or a water based dissolution step.
2. 2 . The method of claim 1 , wherein the barium halide or the strontium halide passivating layer comprises a barium fluoride, strontium fluoride, barium chloride, strontium chloride, barium chloride fluoride, or strontium chloride fluoride passivating layer.
3. 3 . The method of claim 2 , wherein the first step comprises a fluorine based etch.
4. 4 . The method of claim 3 , wherein the fluorine based etch comprises a fluorine based plasma etch, and the barium halide or the strontium halide passivating layer comprises the barium fluoride or the strontium fluoride passivating layer.
5. 5 . The method of claim 4 , wherein the fluorine based plasma etch comprises a CHF 3 plasma etch or a CF 4 plasma etch.
6. 6 . The method of claim 2 , wherein the first step comprises a chlorine based etch.
7. 7 . The method of claim 6 , wherein the chlorine based etch comprises a chlorine based plasma etch, and the barium halide or the strontium halide passivating layer comprises the barium chloride or the strontium chloride passivating layer.
8. 8 . The method of claim 7 , wherein the chlorine based plasma etch comprises a Cl 2 plasma or a BCl 3 plasma etch.
9. 9 . The method of claim 2 , wherein the first step comprises a combination fluorine and chlorine based etch.
10. 10 . The method of claim 9 , wherein the combination fluorine and chlorine based etch comprises a combination fluorine and chlorine based plasma etch, and the barium halide or the strontium halide passivating layer comprises the barium chloride fluoride or the strontium chloride fluoride passivating layer.
11. 11 . The method of claim 10 , wherein the combination fluorine and chlorine based plasma etch comprises a CHClF 2 , CCl 2 F 2 , CClF 3 , or CCl 3 F plasma etch.
12. 12 . The method of claim 1 , wherein the second step comprises the acid based wet etching step.
13. 13 . The method of claim 12 , wherein the acid based wet etching step comprises a dilute nitric acid, an oxalic acid, a hydrochloric acid, a hydrofluoric acid, a hydroiodic acid, a hydrobromic acid, a perchloric acid, a sulfuric acid, a phosphoric acid, or an acetic acid wet etching step.
14. 14 . The method of claim 2 , wherein the second step comprises the water based dissolution step.
15. 15 . The method of claim 14 , wherein the barium halide or the strontium halide passivating layer comprises the barium chloride passivating layer.
16. 16 . The method of claim 1 , wherein the metal oxide layer comprises a waveguide layer of a Mach-Zehnder interferometer.
17. 17 . The method of claim 1 , wherein the metal oxide layer comprises the barium titanate layer.
18. 18 . The method of claim 17 , further comprising forming a first electrode and a second electrode on the metal oxide layer.
19. 19 . The method of claim 1 , wherein the metal oxide layer comprises the strontium titanate layer.
20. 20 . The method of claim 19 , wherein the step of forming the metal oxide layer comprises forming the strontium titanate layer over a substrate and forming the barium titanate layer over the strontium titanate layer.

Description

FIELD Embodiments herein relate generally to methods for etching materials to generate components of electro-optic devices such as phase shifters and switches. BACKGROUND Electro-optic (EO) modulators and optical switches are useful components for the control and manipulation of optical signals. Some EO modulators utilize free-carrier electro-refraction, free-carrier electro-absorption, the Pockel's effect, or the DC Kerr effect to modify optical properties during operation, for example, to change a phase of light propagating through the EO modulator or switch. Optical phase modulators may be used in integrated optics systems, waveguide structures, integrated optoelectronics, etc. Despite the progress made in the field of EO modulators and switches, there is an ongoing need for improved methods and systems related to patterning and etching wafer stacks for use in EO modulators, switches, and related devices. SUMMARY An embodiment etching method includes forming a metal oxide layer that is a barium titanate layer or a strontium titanate layer over a substrate, and etching the metal oxide layer using atomic layer etching. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of the disclosure, and together with the general description given above and the detailed description given below, serve to explain the features of the disclosure. FIG. 1 is a simplified schematic diagram illustrating an optical switch, according to various embodiments. FIG. 2 is a schematic diagram of a pre-fabricated wafer including stacked layers, according to various embodiments. FIG. 3A is a simplified schematic diagram illustrating a cross section of a waveguide structure that shows the direction of an induced electric field, according to various embodiments. FIG. 3B is a simplified schematic diagram illustrating a cross section of a waveguide structure, according to various embodiments. FIG. 4 is a simplified schematic diagram showing a top view of a waveguide structure, according to various embodiments. FIG. 5 is a schematic diagram of a wafer etching apparatus, according to various embodiments. FIG. 6 is a schematic illustration of an ion milling etch procedure. FIG. 7 is a schematic illustration of using ionized partial gas mixture to etch an electro-optic layer, according to various embodiments. FIG. 8 is a schematic illustration of a thin SiO2 hard mask that may be used to etch a wafer, according to various embodiments. FIG. 9 is a schematic illustration of a thin Si3N4 hard mask that may be used to etch a wafer, according to various embodiments. FIG. 10 is a schematic illustration of a thick SiO2 hard mask that may be used to etch a wafer, according to various embodiments. FIG. 11 is a schematic illustration of a thick Si3N4 hard mask that may be used to etch a wafer, according to various embodiments. FIG. 12A is a vertical cross-sectional view of an intermediate structure that may be used in the formation of an optical component, according to various embodiments. FIG. 12B is a vertical cross-sectional view of a further intermediate structure that may be used in the formation of an optical component, according to various embodiments. FIG. 12C is a vertical cross-sectional view of a further intermediate structure that may be used in the formation of an optical component, according to various embodiments. FIGS. 13A and 13B are vertical cross-sectional view of optical components, according to various embodiments. FIG. 14A is a vertical cross-sectional view of an intermediate structure that may be used in the formation of an optical component, according to various embodiments. FIG. 14B is a vertical cross-sectional view of a further intermediate structure that may be used in the formation of an optical component, according to various embodiments. FIG. 14C is a vertical cross-sectional view of a further intermediate structure that may be used in the formation of an optical component, according to various embodiments. DETAILED DESCRIPTION The various embodiments are described in detail with reference to the accompanying drawings. The drawings are not necessarily to scale, and are intended to illustrate various features of the disclosure. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the disclosure or the claims. It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first electrode layer could be termed a second electrode layer, and, similarly, a second electrode layer could be termed a first electrode laye