# US 8,785,238 B2 · Nonvolatile memory element and method for manufacturing same

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- Number: US 8,785,238 B2
- Document ID: US8785238B2
- Status: Granted
- Kind: B2
- Application number: 13/704,663
- Filed: 2011-06-30
- Published: 2013-04-18
- Granted: 2014-07-22
- Earliest claimed: 2010-07-01
- Assignees: Panasonic Corporation
- Applicants: Yoshio Kawashima; Takumi Mikawa
- Inventors: Yoshio Kawashima; Takumi Mikawa
- Web page: https://patentgrep.com/patent/US8785238B2

## CPC

- H10N 70/061: {Shaping switching materials}
- H10N 70/063: {by etching of pre-deposited switching material layers, e.g. lithography}
- H10N 70/24: {based on migration or redistribution of ionic species, e.g. anions, vacancies}
- H10N 70/25: {based on bulk electronic defects, e.g. trapping of electrons}
- H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices}
- H10N 70/8833: {Binary metal oxides, e.g. TaOx}
- H10B 63/30: {comprising selection components having three or more electrodes, e.g. transistors}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

The method includes: forming a lower electrode layer above a substrate; forming a variable resistance layer on the lower electrode layer; forming an upper electrode layer on the variable resistance layer; forming a hard mask layer on the upper electrode layer; forming a photoresist mask on the hard mask layer; forming a hard mask by performing etching on the hard mask layer using the photoresist mask; and forming a nonvolatile memory element by performing etching on the upper electrode layer, the variable resistance layer, and the lower electrode layer, using the hard mask. In the forming of a photoresist mask, the photoresist mask is formed to have corner portions which recede toward the center portion in planar view.

## Claims

### Claim 1

A method of manufacturing a nonvolatile memory element having variable resistance, the method comprising:
forming a lower electrode layer above a substrate;
forming a variable resistance layer on the lower electrode layer, the variable resistance layer comprising an oxygen-deficient transition metal oxide;
forming an upper electrode layer on the variable resistance layer;
forming a hard mask layer on the upper electrode layer;
forming a photoresist mask on the hard mask layer, the photoresist mask having a rounded shape in planar view;
forming a hard mask by performing etching on the hard mask layer, using the photoresist mask; and
forming a nonvolatile memory element including the upper electrode layer, the variable resistance layer, and the lower electrode layer, by performing etching, using the hard mask, on the upper electrode layer, the variable resistance layer, and the lower electrode layer, with an etching gas that contains an oxygen deficiency-suppressing gas, the nonvolatile memory element having a rounded shape in planar view.

### Claim 2 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a photoresist mask, the photoresist mask is formed by projecting, on an exposure subject region, a rectangular shape drawn on a reticle, with a coherence factor during photolithography being smaller than one.

### Claim 3 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a photoresist mask, the photoresist mask is formed by projecting, on an exposure subject region, a rectangular shape drawn on a reticle, with a coherence factor during photolithography being smaller than 0.5.

### Claim 4 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a photoresist mask, the photoresist mask is formed by performing photolithography using a reticle on which a shape is drawn, the shape having an angle larger than 90 degrees formed by two adjacent edge surfaces.

### Claim 5 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a variable resistance layer, the variable resistance layer is formed using a tantalum oxide TaOx where 0<x<2.5.

### Claim 6 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of an upper electrode layer, the upper electrode layer is formed using any one of platinum, iridium, and palladium.

### Claim 7 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a hard mask layer, the hard mask layer is formed using aluminum titanium nitride.

### Claim 8 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a nonvolatile memory element, the oxygen deficiency-suppressing gas reduces change in oxygen content on an etching edge surface of the variable resistance layer.

### Claim 9 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a nonvolatile memory element, the nonvolatile memory element is formed to have sides to which a component included in the oxygen deficiency-suppressing gas adheres as a result of the etching using the etching gas that contains the oxygen deficiency-suppressing gas.

### Claim 10 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a photoresist mask, the photoresist mask is formed to have corner portions in planar view, the corner portions receding toward a center portion of the photoresist mask relative to a corner portion having an angle of 90 degrees.

### Claim 11 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein, when the variable resistance layer has a resistance value which changes according to change in oxygen content and the etching gas does not contain the oxygen deficiency-suppressing gas, the oxygen content of the etched variable resistance layer changes.

### Claim 12 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein the oxygen deficiency-suppressing gas contains a bromine compound.

### Claim 13 (depends on 1)

The method of manufacturing a nonvolatile memory element according to claim 1,
wherein in the forming of a nonvolatile memory element, the nonvolatile memory element is formed by performing etching, using the etching gas that contains the oxygen deficiency-suppressing gas, while causing a component included in the oxygen deficiency-suppressing gas to adhere to sides of the variable resistance layer.