Fabrication and characterization of Au-Ag alloy thin films resistance random access memory C. C. Kuo1 and J. C. Huang1,*

1Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, ROC

* Corresponding author: Tel: +886 7 5252000 ext 4063; fax: +886 7 5254099, E-mail: jacobc@mail.nsysu.edu.tw

Conductive Bridge Random Access Memory Processes of Porous Materials

X-ray photoelectron spectroscopy

Abstract

The RRAM devices were made into two systems: Au-Ag film and nanoporous Au-Ag film for bottom electrodes. The larger activity of Ag element compared to Au element make Ag element more easily dissolved in nitric acid solution. Hence, the nanoporous Au-Ag films can be prepared by simple chemical dealloying of Au-Ag films fabricated by co-sputtering. The surface morphology, roughness and composition can change by immersing in HNO3 for different time periods. The surface roughness can provide point potential effect of electric field to get more stable electrical properties. For these samples, the surface morphology is investigated by scanning electron microscopy (SEM). The variation of surface composition is identified by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The surface roughness can be measured by Atomic force microscopy (AFM). Finally, the electrical characteristics of samples are measured by Multi-function Semiconductor Parameter Analyzer.

The process of fabricating of a Au-Ag alloy/SiO2/TiN device

Y. Bernard, V. T. Renard, P. Gonon, V. Jousseaume, Microelectron Eng. , 88 (2011) 814-816.

I-V characteristics

Conclusions

RRAM devices were mainly fabricated by sputtering. It is successful to make the Au-Ag alloy/SiO2/TiN device that has RRAM properties. The composition of the Au-Ag alloy is Au30Ag70 that is examined by X-ray photoelectron spectroscopy (XPS). The electrical characteristics, including I-V curves, endurance and retention tests, of the RRAM devices can be measured by multi-function semiconductor parameter analyzer. The electrical properties of the Au-Ag alloy/SiO2/TiN device can be compared with the device with the Ag /SiO2/TiN device. Au-Ag alloy/SiO2/TiN is lower energy consumption and can be easier operation without the appearance of normally “ON” than Ag /SiO2/TiN. Hence, the current conduction mechanism of the Au-Ag alloy/SiO2/TiN device was discussed.

The switching-on process while applying -1 V to a Pt/H2O/Ag cell. (a), (b) and (c) Scanning electron microscope (SEM) images show the process of the metallic Ag dendrite growth after applying -1 V for 1, 2, and 4 s, respectively

(a) Ten consecutive I-V curves between -0.35 and +0.35 V. (b) The related proposed filamentary model.

(a) (b) (c)

(d)

(b)

(a) (b) (c)

X. Guo, C. Schindler, S. Menzel, R. Waser, Applied Physics Letters, 91 (2007) 133513.

Au

Binding Energy (eV)78808284868890

Inte

nsi

ty (

a. u

.)

Ag

Binding Energy (eV)364366368370372374376378

Inte

nsi

ty (

a. u

.)

Si 2p3/2

Binding Energy (eV)98100102104106

Inte

nsi

ty (

a. u

.)

O 1s

Binding Energy (eV)528529530531532533534535536

Inte

nsi

ty (

a. u

.)

(a) (b)

Au Ag

Composition (at. %) 30 70

(c) (d)

Si O

Composition (at. %) 33 67

 (a) A 6-inch silicon substrate with defined via size was TiN electrode, which is provided from Industrial Technology Research Institute (ITRI). (b)The insulator layer (SiO2) was deposited on the TiN substrate by Sputter in the National Science Council Core Facilities Laboratory. (c) The top electrode of a Au-Ag thin film was deposited on the SiO2 layer by self-made magnetron co-sputter in our lab. (d) The photo-resist (PR) on the TiN substrate was lifted off by acetone, then the Au-Ag alloy/SiO2/TiN device is done.

Voltage (V)0 1 2 3 4 5 6 7

Cu

rren

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Forming

Voltage (V)-1.0 -0.5 0.0 0.5 1.0

Cu

rren

t (A

)

10-7

10-6

10-5

10-4

10-3

10-2

Times0 20 40 60 80 100

Res

ista

nce

(

)

103

104

HRSLRS

Resistance ()

0 5000 10000 15000 20000 25000 30000

Per

cen

tage

(%

)

0.5

1

2

5

10

2030

5070

90

9999.9

HRSLRS

(a)Au-4f doublet peaks locate at about 87.5 eV and 83.8 eV. (b) Ag-3d doublet peaks locate at about 374 eV and 368 eV.

(c) The Si-2p single peak locates at about 102.5 eV. (d) The O-1s single peak locates at about 531.8 eV.

Forming

Voltage (V)0 1 2 3 4 5 6 7

Cu

rren

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Forming

Voltage (V)-1.0 -0.5 0.0 0.5 1.0

Cu

rren

t (A

)

10-7

10-6

10-5

10-4

10-3

10-2

Times20 40 60 80 100

Res

ista

nce

(

)

103

104

HRSLRS

Resistance ()

0 5000 10000 15000 20000

Per

cen

tage

(%

)

0.5

1

2

5

10

2030

5070

90

9999.9

HRSLRS

process

Forming process

Forming process

I-V curves of 100 times

I-V curves of 100 times

The memory window

The memory window The weibull distribution

The weibull distribution