Nanoscale Wiring by Cu - PowerPoint Presentation

Slide1

Nanoscale Wiring by Cu Electrodeposition in Supercritical CO2 Emulsified Electrolyte withContinuous-Flow Reaction System

Valencia, Spain, September 27th, 2016Separation Technique 2016, OMICS International

Masato Sone,* Tso-Fu Mark Chang, Tetsuya Shimizu and Nao Shinoda

Institute of Innovative Research,

Tokyo Institute of Technology

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Table of Contents1. IntroductionMain issues for IC technology and solution2. Cu electroplating reaction using supercritical carbon dioxide suspension (EP-SCS) with Cu particles

3. Design & manufacture of Cu wiring contentious flow system using Sc-CO2 4. Summary and future works2/28

Slide3

Two Problems for Next Integrated Circuit TechnologyIC：Market Magnitude 267 Billion

$ (Japan 44 Billion$) / 2016 McClean Report

Environmental technological problem1. High Elution of Waste Water2. High Drying Process Energy3. High Elution of CO2

IC Technology Problems

1. Super-fine Wiring (

Hp

≦

10 nm

)

2. Void-less, Crystal controlled wiring

3. Nondestructive Cleaning

(

Hp

≦

32 nm

)

a) Barrier Layer Formation

b) Seed Layer Formation

Defective wiring

32nm

c) Cu

Deposition

void

Excessive deposit

dissolution

Electrolyte

Refinement of Design Rule

Dissolution of Seed Layer

Surface Tension

150nm

3/28

Slide4

How to solve the problems?

Supercritical Nanoplating (SNP)1. Washing & Cleaning with CO2　　 ・Utilize CO

2 for Washing Solvent （Waste water :6 m3/h）　　 ・ Nondestructive Cleaning into Nano-scale　　2. Recycling of CO2　　・ Purification of CO2 can be easily conducted.IC Technological Problems

32nm

80nm

a) Barrier Layer Formation

b) Seed Layer Formation

c) Cu

Deposition

Emulsion

（

Electrolyte + Sc-CO

2

）

ScCO

2

Washing

1. Electrodeposition with CO

2

Emulsion

　

　 ・

Enhancement of gap-fill characteristic by Sc-CO

2

Emulsion

　　 ・

Non-pinhole & High Uniformity

Environmental technological problem

Green

＆

Technological Innovation

4/28

Slide5

5

Temperature [K]

LIQUIDPressure　[MPa]

20

10

０

１００

２００

SOLID

Supercritical state

３００

４００

GAS

Critical point

Triple point

T

c

=302K P

c

=7.38MPa

Phase diagram for CO

2

S

upercritical carbon dioxide(Sc-CO

2

)

5/28

Slide6

Model of Supercritical Nano-Plating (SNP)

Degreasing, Drying, Washing

Sc-CO2

Electrolyte

+

Surfactant

Sc-CO

2

Electroplating in Supercritical CO

2

Emulsion

(EP-SCE)

Application of Sc-CO

2

on Surface Finishing

E

lectrolyte

Sc-CO

2

6/28

Slide7

Conventional

Anti-corrosive Test

（1mol/L H2SO4 sol., RT, 2weeks)

EP-SCE

SEM image

Optical Microscopic image

EP-SCE-Au

　

/

　

High Anti-Corrosive Thin Au Film

Thickness

　

300nm

Corrosive point

7/28

Slide8

2. Cu electroplating reaction using suspension of supercritical carbon dioxide in electrolyte with Cu particles (EP-SCS)

Precision & Intelligence Laboratory,Tokyo Institute of Technology

8/28

Slide9

ObjectiveTo propose a new method for filling of nanoscale holes with high aspect ratio.Cu electroplating in sc-CO

2 emulsion (EP-SCE)Cu electroplating in sc-CO2 suspension(EP-SCS)

9/28

Slide10

Experimental ApparatusHigh pressure autoclave for supercritical CO2

PI

PEEK coating

CO

2

gas tank

CO

2

liquidization unit

Programmable power supply

Backpressure regulator

Trap

10/28

Slide11

Experimental Conditions

Sc-CO

2

Current density

1.0A/dm

2

Anode: Pt

Cathode

:

Cu or

hole Test Element Group

Volume 50ml

313K, 15MPa, 10min or 1h

Copper-sulfate-based electrolyte

Surfactant(C

12

H

25

O(C

2

H

5

O)

15

H) 1.0vol.%

with respect to volume of electrolyte

Cu seed layer

Si

SiO

2

TiN

barrier layer

11/28

Slide12

Current efficiency

Electroplating in Sc-CO2 Emulsion (EP-SCE)

Sc-CO2(10 MPa, 323 K)Hexane(0.1 MPa, 323 K)

0.385

0.677

3.03×10

1

3.10×10

2

η

(μPa

･

s)

ρ

(g/ml)

■

Conventional electrolyte

○

Hexane emulsion

◆

Sc-CO

2

emulsion(EP-SCE)

(1.0A/dm

2

, 323K, 15MPa, 1h)

Volume fraction of CO

2

or hexane

Transport properties

of dispersion phase

This is not enough

to explain

decreasing current efficiencies.Current efficiencies decreased with increase in CO

2 volume fraction.Current efficiencies of sc-CO2 emulsion decreased compared with that of hexane emulsion.12/28

Slide13

One of the Reasons of Current Efficiencies Loss

This is caused by dissolution of Cu substrate in electrolyte.Martyak et al. reported damage of Cu seed layer in sulfuric-acid-based electrolyte (2003)→Sc-CO2 emulsion accelerate dissolution of Cu?

13/28

Slide14

Dissolution of Cu in Electrolyte

: pH3.0 conventional electrolyte◆:Sc-CO2 emulsion using pH 3.2 electrolyte: pH 3.2 conventional electrolyte

Weight of Cu substrate lossCu substrate was immersed in different solutions.→ Sc-CO2 emulsion accelerated the dissolution of Cu.→Weight of Cu loss in sc-CO2 emulsion is the same as that in pH 3.0 electrolyte approximately.14/28

Slide15

CO2+H2O⇄H2CO3・・・[1]H2CO

3⇄H++HCO3-・・・[2]HCO3-⇄H++CO3

2-・・・[3]CuO+2H+ ⇄Cu2++H2O・・・[4]Cu+2H+⇄Cu2++H2・・・[5]→Dissolution of Cu substrate may be accelerated by increased H+ (decreased in pH)Chemical Reaction in Sc-CO2 Emulsion

We propose “

Sc-CO2

suspension”

by addition of Cu particles.

→

In order to inhibit dissolution of Cu seed layer

・・・

15/28

Slide16

Electroplating in Sc-CO2 Suspension (EP-SCS)

■Conventional electrolyte△Sc-CO2

suspension (EP-SCS) with Cu particles 1.7g/L◆Sc-CO2 emulsion(EP-SCE)

Sc-CO2

suspension by addition of Cu particles (Avg. 63mm).

(1.0A/dm

2

, 323K, 15MPa, 1h)

Current efficiencies increased

because

Cu particles dissolved in electrolyte and dissolution of Cu substrate

was inhibited

.

Current efficiency

16/28

Slide17

Cu plating on Hole TEG

Hole TEG(Cu seed layer)

EP-SCE(Dissolution of Cu seed ) EP-SCS

(Cu deposit

）

17/28

Slide18

Application of EP-SCS into Nanoscale Holes. 1Electroplating : 1.0 A/dm

2 and 10min, Cu particles : 0.6g/L

CuSi100nm

Cu

Si

100nm

(b)EP-SCS (Cu particles:0.6g/L)

(a)Conventional method

Holes of 70nm in

diameter with a

spect

ratio of 2

Many voids

No

void

→

High viscosity

High surface tension

→

Low viscosity

Low surface tension

18/28

Slide19

Filling of all the holes with Cu by EP-SCS is completed with no void→Because of the low viscosity and low surface tension.

Cu

Si

70nm

350nm

(a)

(b)

(c)

Electroplating

: 1.0 A/dm

2

and 10min, Cu particles : 0.6g/L

Holes of 70nm in

diameter with a

spect

ratio of

5

Application of EP-SCS into Nanoscale Holes. 2

19/28

Slide20

Electroplating in the sc-CO2 suspension (EP-SCS) can fill nano holes with high aspect ratio with no void and no pinhole. Because of the low viscosity of sc-CO2 and the suppressed dissolution of Cu seed layer.EP-SCS can be applied and contribute in progress of Cu interconnects technology.

2. Summary20/28

Slide21

3. Design & Manufacture of Cu Wiring Flow Reaction System using Sc-CO2 Emulsion

Precision & Intelligence Laboratory,Tokyo Institute of Technology

21/28

Slide22

Exit

Reaction Chamber

Canned Pump

CO

2

Line B for mixing

Electrolyte

Flow

Storing Chamber

Line A for reaction

Experimental

apparatus for continuous flow reaction system by using canned motor pump.

EP-SCS system for large area Cu wiring

22/28

Slide23

Exit

Entry

Electrolyte

anode

cathode

Exit

Entry

Entry

Detailed

structure of the reaction chamber.

System for large area Cu wiring

Anode

structure and positions of entrees and

outlet

Geometry

of electrodes, four entrees and exit.

23/28

Slide24

System for large area Cu wiring

24/28

Slide25

(

a) 1.41 A/dm2

(b) 2.83 A/dm2Photographic images of 300 mm diameter round-type hole TEG electroplated by Cu - EP-SCS.

System for large area Cu wiring

25/28

Slide26

Cu

SiO2

(c) 300 nm in depth, 2.83 A/dm2

・

At current density of 2.83 A/dm2

, complete Cu filling into 60 nm diameter hole

s was observed

.

・

At current density of

4.24

A/dm

2

, the incomplete filling was obtained because of complete covering of Cu on substrate.

(a) 120 nm in depth,

2.83

A/dm

2

Cross sectional SEM images of electroplated Cu filled in

f

60 nm holes on 300 mm diameter substrate by EP-SCS.

(b

)

300

nm in depth, 1.41

A/dm

2

Cu

SiO

2

(d

) 300 nm in depth,

4.24 A/dm2Cu

SiO2Complete filling of all the holes with electrodeposited Cu was observed without voids Cu

SiO2

EP-SCS for large area Cu wiring

26/28

Slide27

Si

Cu

SiO2300mm hole TEG

Exit

Reaction Chamber

CO

2

Line B for mixing

Electrolyte

Flow

Storing Chamber

Line A for reaction

Canned Pump

3.Summary: Continuous

flow reaction

system

for nanoscale

wiring

Cu

TEM image of Cu wired into holes of 60nm

f

& 120 nm depth

27/28

Slide28

4. Summary and Future works

Gap-fill capability:

Electroplating in the sc-CO2 suspension (EP-SCS) can fill nano holes with high aspect ratio with no void and no pinhole. Impurity: From GDOES results, carbon and oxygen concentration were about the same between conventional Cu plating and EP-SCS. System & Apparatus: We proposed a continuous flow reaction system for nanoscale wiring using Sc-CO2

Future

works

:

(1)

Application into

TSV

(2)

3D integration by combination with Sc-CO

2

cleaning method

Acknowledgement:

This work has been

supported by

Funding Program for CREST program by JST, NEXT Program GN037 by Cabinet Office (CAO) and Next

genaeration

technology program by New Energy and Industrial Technology Development Organization (NEDO), Japan.

28/28

Slide29

Slide30

Batch System for EP-SCS

PI

PEEK coating

CO

2

gas tank

CO

2

liquidization unit

Programmable power supply

Backpressure regulator

Trap

Difficult to homogenize sc-CO

2

emulsion

Slide31

Contamination of C contents by GDOES

Conventional EP-SCEEP-SCS

Conv. with Surf.

Electrodeposits

Electrodeposits

Electrodeposits

Electrodeposits

Slide32

Si

Cu

SiCuSiO2

SiO

2

60nm

120nm

（

μm

）

Single Crystalline, (111) Bottom-Up Growth Wiring

Application of EP-SCS into Nanoscale Holes. 3

TEM image of Cu Wiring into Superfine Hole (60nm

f

, 120nm depth)

Slide33

Self-annealing of CuEP-SCS as electrodeposited

Two months after electrodeposited

Slide34

1. Washing & Cleaning with Sc-CO2

Reduction of waste water Nondestructive cleaning of nanoscale 3D structures2

. Recycling of CO2Pure CO2 can be easily extracted.IC technological problems

32nm

a) Barrier Layer Formation

b) Seed Layer Formation

c) Cu

Deposition

Emulsion

（

Electrolyte +

Sc-CO

2

）

Sc-CO

2

Washing

1.

Electroplating in Sc-CO

2

Emulsion (EP-SCE)

Improvement

of gap-fill

ability by sc-CO

2

Void-free

&

pinhole-free

Environmental

problems

Supercritical CO

2

Solution

Low

viscosity

・

Low

surface tension

Cheap and Green

Slide35

Conventional EP-SCE

EP-SCSConv. with Surf.

Electrodeposits

Electrodeposits

Electrodeposits

Electrodeposits

Contamination of O contents by GDOES

Slide36

Cross-sectional SEM images of Cu wired by EP-SCS method （70nmf, Aspect ratio 2）

Conformal Growth

Bottom-up Growth

Cu

Si

CO

2

rich

CO

2

poor

Crystal Growth in Cu Wiring

by EP-SCS

ａ）

Conformal Growth

ｂ）

Bottom Up Growth

Cu

Seed

Layer

Insulator

Barrier

Layer

Cu

Slide37

Crystal Growth in Cu Wiring for Integrated Circuits

ａ）

Conformal Growth

ｂ）

Bottom Up Growth

On the conventional Cu electroplating for IC wiring, various additives play important roles to control the crystal growth. However, additives cause impurities in wired Cu.

Cu

Seed

Layer

Insulator

Barrier

Layer

(TaN)

Cu