Crystallographic Characterization of Poly-Si Thin Films...2003.9.5...

Crystallographic Characterization of Poly-Si Thin Films

Junichi NISHINO, Materials and Devices Development Center, SANYO Electric Co., Ltd.

[email protected]

Poly-Si has been used as a gate electrode material for many years on CMOS LSIs. As smaller and smaller LSIs continue to be

designed, even a minor difference in the crystal structure affects the electric property of MOS transistor. The typical thickness of

gate poly-Si films is about 200nm in 0.18µm rule LSIs. Normally, the poly-Si grains are around the same order of thickness, and

there are cases where a grain becomes a single crystal from the bottom to the top of film. In this case, the Boron penetration effect,

which is a serious problem in making LSIs, can easily occur due to ion channeling during ion implantation. To avoid this effect,

gate poly-Si films are made of double poly-Si layers. It is necessary to analyze the crystal structure of each layer of the double

poly-Si layer. In this experiment, to evaluate the characteristics of the crystal structure near the surface, we examined a test sample

of an amorphous-Si/poly-Si double layer film on Si wafer. The

in-plane X-ray diffraction was applied. The incident X-ray energy

was 10.0keV. Figure 1 shows the in-plane diffraction patterns of the

amorphous-Si/poly-Si double layer film. The thickness of each layer

was the same as 100nm of amorphous-Si and poly-Si. In theω

=0.180 degree case, the diffraction pattern has only an

amorphous-Si structure. In the ω=0.190degree case, the diffraction

pattern has mainly a poly-Si structure. From these results, it has been

shown that it is possible to evaluate crystal structures of poly-Si thin

films in the depth direction by precise control in incident angle.

15 20 25 30 35 40 45 50

２θ (degree)

Inte

nsi

ty (

a.u.)

ω=0.180 deg、p.d.=34nm

ω=0.185 deg、p.d.=101nm

(111)

(311)(220)

ω=0.190 deg、p.d.=143nm

Fig. 1 In-plane XD spectra for amorphous-Si/ Poly-Si

double layer film with various incident angles.

2003.9.5 第3回サンビーム研究研究会 ©SANYO Electric Co., Ltd. 2003

Crystallographic characterization of poly-Si thin films

Materials and Devices Development Center BU,SANYO Electric Co., Ltd.

Junichi NISHINO


1. Introduction

2. Requirement for LSI analysis

3. X-ray diffraction of poly-Si thin film

4. Summary

Contents


Radio network

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OfficeOffice

HomeHomeCarCar

Handy phoneHandy phone

Terrestrial broadcasting

Satellite broadcasting

CATV

Telephone（ISDN,ADSL）

Homeserver

Digital stillcamera

PC

PhoneTV monitor

DVD

Video gameVideocamera

PC

Video printer

Home LAN

Living roomLiving roomBed roomBed room

Digital network worldDigital network world

Introduction

FTTH


Key technology for system LSI

packagepackage devicedevice

designdesign processprocess

SoC（System on Chip）SoC（System on Chip）

calculationcalculation

ＰＣ

imageprocessing

imageprocessing

MPEG

input/outputinput/output

CCD/LCD

Storage media

W-CDMA

tele-communication

tele-communication

memorymemory


Requirement for LSI analysisITRS2002 road map

N added gate oxide

Poly-Sigate Boron diffusion

siliside

Year of production 2001 2004 2007 2010 2013 2016DRAM 1/2 pitch(nm) 130 90 65 45 32 22

Critical perticle size(nm) 43 24 17 12 9 6Junction depth(nm) 27 15 10 7 5 4

Void size in Cu lines(nm) 32.5 22.5 16.25 11.25 8 5.5


View

Element

Structure

Thickness

Analytical technique for LSI development

SEM, TEM, AFM

XRF, SIMS,EPMA, AES

XRD, XAFS

XRR , Ellipsometory

Make precise analytical technique using SR


Shrinkage of MOS-Tr ⇒ Boron diffusion problem

Prevent Boron diffusion ⇒ Double Poly-Si layer

Analyze crystallographic structure of thin Poly-Si films along depth direction

⇒ use X-ray diffractmetor

of BL16XU

Crystallographic characterization of thin films

Boron diffusion


BL16XU XRD・Parallel beam・Small size in incident beam：＜0.2mm□・Energy of incident X-ray：tunable・Intensity：strong 3 order than rotation source・θ-2θ, thin film, in-plane

２θarm ditector

double slitsample


Poly-Si（50nm）diffraction

0

5

1 0

1 5

2 0

2 5

3 0

2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 52 θ （d e g r e e )

coun

t (c

ps)

粉末回折装置　C u K α 1 ：4 0 k V ,3 0 m A

s t e p s c a n : 2 s e c / p o i n t 0 . 1 d e g / s t e pθ - ２θ

Lab.

BL16XU

0

5 0

1 0 0

1 5 0

2 0 0

2 5 0

3 0 0

2 0 2 5 3 0 3 5 4 0 4 5 5 0２ θ ( d e g r e e )

coun

t (c

ps)

S P r i n g - 8 B L 1 6 X UE = 1 0 . 0 k e V

d o u b u l e s l i t : 0 . 0 9 d e gs t e p s c a n : 2 s e c / p o i n t 0 . 1 d e g / s t e p

i n c i d e n t a n g l e : 0 . 1 8 d e g


Layout of in-plane diffraction

Incident angle : about 0.18°

sample

diffraction

２θditector

Side view

Top view

Incident slit

double slit

Incident X-ray


Measurement condition

Incident X-ray・Energy 10.0KeV ・Beam size 0.1mmW×0.2mmH

Sample setting・Incident angle 0.170～0.200 degree

（precise angle control by tangent goniometor）・sample sticking to stage by oil

Detection・Detector： Scintillation counter・double slit 1.0mm + 1.0mm 0.29°

Measurement mode・２θ scan （θ fixed）


Total reflection on Si surfaceunder critical angle

over critical angle

almost reflected by sample surface

Penetrate into sample

Need precise incident angle control⇒ under 0.001°

penetration depth


X-ray reflectivity of Si surface

0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.10 0.20 0.30 0.40incident angle (degree)

refle

ctiv

ity

E=10.0keV

θc = 0.180 deg


X-ray penetration depth into Si

1

10

100

1000

0.10 0.14 0.18 0.22 0.26incident angle (degree)

pene

trat

ion

dept

h (n

m)

E=10.0keV

θc = 0.180 degpenetration depth = 34nm


Sample setting accuracy (sample height)

Effective vertical beam width90μm

height accuracy : 1μm

X-ray monitor

sample

Incident X-ray

1.25 1.30 1.35 1.40 1.45sample height (mm)

inte

nsity

(a.

u.)

half position : 1.358mm


Sample setting accuracy (zero angle)

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04φtan (deg)

inte

nsity

(a.

u.)

zero position : +0.001deg

angle accuracy : 0.001°

X-ray monitor

sample

Incident X-ray


Test piece 1(Amo/Poly double layer)

a-Si 100nm

SiO2 25nm

Si wafer

Poly-Si 100nm


Incident angle dependence

As depo

15 20 25 30 35 40 45 50２θ (degree)

Inte

nsity

(a.

u.)

ω=0.180 deg、p.d.=34nm

ω=0.185 deg、p.d.=101nm

(111)

(311)(220)

ω=0.190 deg、p.d.=143nm


Test piece 2(Amo/Poly double layer)

a-Si 150nm

SiO2 25nm

Si wafer

Poly-Si 50nm

Thick amorphous Si layer to measure annealing effect


Crystallographic change by annealing

15 20 25 30 35 40 45 50２θ (degree)

Inte

nsity

(a.

u.)

ω＝0.170 deg

ω＝0.200 deg

(111)

(220) (311)

As depo


15 20 25 30 35 40 45 50２θ (degree)

Nor

mal

ized

Inte

nsity

(a.

u.)

ω＝0.170 deg

ω＝0.200 deg

(111)

(220) (311)


After 1000℃ 5sec N2



49nm

53nm

12nm

---

grain size

82nm

82nm

13nm

---

grain size

FWHMgrain size

FWHMFWHM

52nm

52nm

14nm

---

0.200°

0.170°

0.200°

0.170°

Incident angle

index

0.13°0.13°0.08°9.5nm

after anneal

---------9.5nmas

depo

0.14°0.13°0.08°204nm

0.6°0.5°0.5°204nm

311220111Penetra

tion depth

FWHMs of each index are almost same value after anneal treatment

⇒ change uniform crystallographic structure in depth direction


・High S/N in-plane XRD measurement forthin film is available using BL16XU XRDsystem.

・It is possible to evaluate crystal structures of poly-Si thin films in the depth direction byprecise control in incident angle of 0.001°.

・Crystallographic characterization of SOI and epitaxial layer is next step.

Summary

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