Ultra-Shallow Junction Formation on 3D Silicon and ...Steeper profile is expected as FLA or LA will be applied Enhanced P Level of Plasma-Assisted Doping on Ge After RTP 600C, 30 sec

© 2017 Lam Research Corp. | EAG 2017 1

YS Kim & Hyuckjun Kown

CTD, Lam Research

Ultra-Shallow Junction Formation on 3D Silicon and Germanium Device Structures

by Ion Energy Decoupled Plasma Doping


► Introduction and challenges Challenges on device

USJ on 3D structure

► Plasma-assisted doping (PaD) on Si Previous work for plasma-assisted doping on Si

► Annealing vs Doping on Si PaD vs ALD vs GaP vs SOD

► Plasma-assisted doping on Ge Various annealing for junction depth and P level

Plasma-assisted doping on Ge

► Summary

Overview



USJ on 3D structure for <10 nm node


► Annealing vs Doping on Si



► Summary

Overview


AlphaGo handily beat world Go champions

AlphaGo: employs 1200 CPU’s and 280 GPU’s in 2016

Human brain: 12W!

Man Made “Intelligent” but Power Inefficient System

12W74,000W

15% power reduced in 2017


Demands on Surface Engineering Due to Increasing of Both R and C Components on <10 nm Node Device

imec 2015

To reduce Rc: or or : the Schottky barrier height N : the electrically active dopant density at the interfaceA : contact area

Source: Chipworks




► Plasma-assisted doping (PaD) Previous work for plasma-assisted doping on Si




► Summary

Overview


► Doping on 3D structure will be a challenge due to its directionality during implantation

► To form shallow junction on 3D structure, reducing ion energy and increasing ion scattering will be necessary

► Monolayer doping by deposition of dopant will be an alternate option

Comparison of Conformality for 3D USJ with Various Doping Schemes

Beamline I2P PLAD(Plasma Doping)

PaD(Plasma-assisted Doping)

MLD(Mono-Layer Doping)

V. S. Basker et al, VLSI Tech. Symp., 2010


Comparison of PaD with Typical PLAD (with Bias)Y.Kim et al, IWJT 2016

* Data Source from S Qin, IEEE Trans Electron Dev 62 (2015)

Plasma Doping with Bias

Lam result with no-Bias(with pre-treatment)

Rs from pre-treat but no bias power added is compatible with PLAD

Before doping

Si

After PaD








► Summary

Outline


► Junction depth can be optimized by annealing condition to form USJ

► Dopants activation confirmed with Rs measurement and SRP

Various Annealing on PaD Processed Si Samples

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

0 50 100

P C

ON

CEN

TRAT

ION

(ato

ms/

cc)

DEPTH (nm)

SIMS

SRP

715 /sq

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

0 50 100

P C

ON

CEN

TRAT

ION

(ato

ms/

cc)

DEPTH (nm)

SIMS

SRP

83 /sq

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

0 100 200P

CO

NC

ENTR

ATIO

N (a

tom

s/cc

)DEPTH (nm)

SRPSIMS

38 /sq

Anneal A Anneal B Anneal C


Xj with Various Doping Technique vs. Annealing

1.0E+17

1.0E+18

1.0E+19

1.0E+20

1.0E+21

1.0E+22

0 5 10 15 20 25

P Co

nc@

Si S

urfa

ce (

atom

/cm

3 )

Xj (nm)

ALD P_RTP ALD P_LAALD P_FLA PaD_RTPPaD_LA PaD_FLAPaD_as doped GaD_RTPGaD_as doped SOD_10nm_RTPSOD_10nm_FLA SOD_as dep

► Junction depth can be optimized by optimizing annealing condition to form USJ Dopants activation confirmed by SRP

► Shallowest Xj can be produced by either ALD or MLD (GaD here) Dopant level with ALD is higher than MLD due to encapsulated surface to reduce out-diffusion

Highest dopant level can be produced by PaD with LA or FLA

As doped/dep < 5 nm

Laser annealed < 7 nm

Flash annealed <12 nm

RTP annealed <21 nm


► Dopant level at Si surface can be increased by plasma-assisted doping, while GaD/MLD shows the lower level due to its limited dopant source Highest dopant level can be produced by PaD with LA or FLA

Dopants activation confirmed by 4pt-pb & SRP

► Shallowest Xj can be produced by laser annealing with the similar surface P level

Dopant Level and Junction Depth (Xj)Doping vs. Annealing Technique

1.0E+16

1.0E+17

1.0E+18

1.0E+19

1.0E+20

1.0E+21

ALD PaD GaD SOD

Surf

ace

P Co

nc(a

tom

/cc)

Doping Technique

0

5

10

15

20

As-doped LA FLA RTA

Junc

tion

Dep

th (

Xj,

nm)

Annealing Technique

Average Surface Dopant Level of P Avg Junction Depth with Various Annealing

PaD, ALD, SOD, GaDPost annealing








► Summary

Outline


► Fast diffusion of n-dopant is unfavorable to for USJ on Ge

► Efficient strategies to be developed To constrain the diffusion of n-type

dopants

To increase the level of electrical activation, i.e., to hinder the formation of dopant defect cluster

Issue of N Dopants on Ge

Flash or Laser Anneal

co-Doping


► Plasma doping (no bias power, PH3) produces ~5 nm junction depth, while no plasma (gas only) could not produce any

► No significant effect of wafer temperature is seen on plasma-assisted doping level at Ge surface

Plasma-Assisted Doping for P Doping on GeWith vs. Without Plasma: As Doped

Dopants Level vs. Plasma

With Plasma

No Plasma

With vs. Without Plasma @ 45C

Plasma-assisted Doping

1.E+17

1.E+18

1.E+19

1.E+20

1.E+21

1.E+22

1.E+23

0 200 400

Surf

ace

Dop

ant

Leve

l (at

om/c

c)

Chuck Temp(C)

Ds_plasma

Ds_no plasma


► P level after annealing by RTP is < 3E19

► Flash or P Enhancement will be the option to increase the level

To Increase P Level on GeAnnealing Variation and Other Enhancement

Expected P Concentration with Enhancement + Flash Annealing

0E+00

1E+01

2E+01

3E+01

4E+01

5E+01

6E+01

7E+01

8E+01

9E+01

1E+02

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

0 50 100

Ge

INTE

NS

ITY

(arb

itrar

y un

its)

P C

ON

CE

NTR

ATI

ON

(ato

ms/

cc)

DEPTH (nm)

Ge->

RTP 60sec

No annealing

P Enhanced +RTP

P Enhanced + FLA

Xj vs. RTP Temp

Pre and Post RTP on PaD Ge


► P level after activation annealing by RTP is ~1E21

► P Enhancement with other annealing will be the option to increase the level

► Steeper profile is expected as FLA or LA will be applied

Enhanced P Level of Plasma-Assisted Doping on Ge After RTP 600C, 30 sec

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

1E+22

1E+23

P CO

NCE

NTR

ATIO

N (

atom

s/cc

)

Normalized DEPTH (nm)

Si->

O->

P

N->

<10 nm Xj3 nm slope

SiN cap

P Doping on Ge with Enhancement


► Novel process approach has been developed to form USJ on 3D structure of Si and Ge using plasma

► Novel approaches increase P dopant level and lowers Rs further, therefore, conformal doping on 3D structure can be enabled without bias power No structure damage has been observed

Confirmed that doping with no bias power forms shallow Xj depth of <7 nm on 3D structure

► Finally various annealing could reduce Xjto <5 nm

Executive Summary

Doping on 3D Structure

Annealing vs. Xj

P

Ultra-Shallow Junction Formation on 3D Silicon and ...Steeper profile is expected as FLA or LA will be applied Enhanced P Level of Plasma-Assisted Doping on Ge After RTP 600C, 30 sec

Documents