# US 2018/0026176 A1 · Method for manufacturing niobate-system ferroelectric thin-film device

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- Number: US 2018/0026176 A1
- Document ID: US20180026176A1
- Status: Published application
- Kind: A1
- Application number: 15/548,543
- Filed: 2016-01-19
- Published: 2018-01-25
- Earliest claimed: 2015-02-04
- Assignees: Sumitomo Chemical Company, Limited; Kanto Kagaku Kabushiki Kaisha
- Applicants: Sumitomo Chemical Company, Limited; Kanto Kagaku Kabushiki Kaisha
- Inventors: Fumimasa HORIKIRI; Kenji SHIBATA; Kazutoshi WATANABE; Kazufumi SUENAGA; Masaki NOGUCHI; Kenji KUROIWA
- Web page: https://patentgrep.com/patent/US20180026176A1

## CPC

- H10N 30/076: by vapour phase deposition
- C23C 14/08: Oxides (C23C14/10 takes precedence)
- C23C 14/34: Sputtering
- H10N 30/082: by etching, e.g. lithography
- H10N 30/30: with mechanical input and electrical output, e.g. functioning as generators or sensors
- H10N 30/853: Ceramic compositions
- H10N 30/8542: {Alkali metal based oxides, e.g. lithium, sodium or potassium niobates}
- H10P 50/691: {for Group IV materials or Group III-V materials}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

This method for manufacturing a lead-free niobate-system ferroelectric thin film device includes: a lower electrode film formation step of forming a lower electrode film on a substrate; a ferroelectric thin film formation step of forming a niobate-system ferroelectric thin film on the lower electrode film; an etch mask pattern formation step of forming an etch mask in a desired pattern on the niobate-system ferroelectric thin film; and a ferroelectric thin film etching step of shaping the niobate-system ferroelectric thin film into a desired fine pattern by wet etching using an etchant comprising: a predetermined chelating agent including at least one selected from EDTMP, NTMP, CyDTA, HEDP, GBMP, DTPMP, and citric acid; an aqueous alkaline solution containing an aqueous ammonia solution; and an aqueous hydrogen peroxide solution.

## Claims

### Claim 1

A method for manufacturing a niobate-system ferroelectric thin film device comprising:
a lower electrode film formation step of forming a lower electrode film on a substrate;
a ferroelectric thin film formation step of forming a niobate-system ferroelectric thin film on the lower electrode film;
an etch mask pattern formation step of forming an etch mask in a desired pattern on the niobate-system ferroelectric thin film; and
a ferroelectric thin film etching step of shaping the niobate-system ferroelectric thin film into a desired fine pattern by wet etching using an etchant comprising:
a predetermined chelating agent comprising at least one selected from ethylenediamine tetra(methylene phosphonic acid), nitrilotris(methylene phosphonic acid), cyclohexane diamine tetraacetic acid, 1-hydroxyethane-1,1-diphosphonic acid(etidronic acid), glycine-N,N-bis(methylene phosphonic acid), diethylenetriamine penta(methylene phosphonic acid), and citric acid;
an aqueous alkaline solution comprising an aqueous ammonia solution; and
an aqueous hydrogen peroxide solution.

### Claim 2 (depends on 1)

The method according to claim 1,
wherein when the predetermined chelating agent is ethylenediamine tetra(methylene phosphonic acid), nitrilotris(methylene phosphonic acid), cyclohexane diamine tetraacetic acid, 1-hydroxyethane-1,1-diphosphonic acid(etidronic acid), glycine-N,N-bis(methylene phosphonic acid), or diethylenetriamine penta(methylene phosphonic acid), the chelating agent in the etchant has a molarity of 0.001 M or more and 0.5 M or less, and
wherein when the predetermined chelating agent is citric acid, the citric acid in the etchant has a molarity of 0.03 M or more and 1 M or less.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the etch mask is made of a silicon oxide film.

### Claim 4 (depends on 1)

The method according to claim 1, wherein, at the ferroelectric thin film etching step, the etchant has a temperature of 50° C. or higher and lower than 100° C.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the niobate-system ferroelectric thin film is made of potassium sodium niobate or lithium niobate.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the lower electrode film is made of platinum.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the niobate-system ferroelectric thin film has a device-forming surface on which the niobate-system ferroelectric thin film device is formed; the niobate-system ferroelectric thin film includes one or more crystal grains having a crystal system and crystal planes including a (001) crystal plane; the crystal system of the niobate-system ferroelectric thin film is pseudo cubic or tetragonal; the niobate-system ferroelectric thin film is formed by sputtering in such a manner that the (001) crystal plane of the one or more crystal grains is preferentially oriented parallel to the device-forming surface.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the substrate is a silicon substrate having a thermal oxide layer thereon.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the method further comprises:
an upper electrode formation step of forming an upper electrode over a desired fine pattern of the niobate-system ferroelectric thin film; and
a dicing step of dicing the substrate having thereon the niobate-system ferroelectric thin film having thereon the upper electrode into one or more chips.