HYDROGENATION STUDIES OF DEFORMED n-Si

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HYDROGENATION STUDIES OF DEFORMED n-Si

B. Pohoryles

To cite this version:

B. Pohoryles. HYDROGENATION STUDIES OF DEFORMED n-Si. Journal de Physique Colloques,

1983, 44 (C4), pp.C4-359-C4-362. �10.1051/jphyscol:1983443�. �jpa-00223063�

HYDROGENATION STUDIES OF DEFORMED n-Si

B. Pohoryles

I n s t i t u t e of Physics, Polish Academy of Sciences, AZ. Lotnik6w 32, 02-668 Warsaw, PoZand

RBsumd

-

Nous prdsentons de nouveaux rdsultars sur l'hydrogdnation du silicium de type n dgformd. Nous montrons que la profondeur de passiva- tion par l'hydrogzne est plus grande que 10 vm.

Abstract

-

New results on hydrogenation of dislocated n-Si are present- ed. Hydrogen passivation depth was found to be more than 10 pm.

Hydrogen bonded chemically i n both c r y s t a l l i n e and amorphous S i produces s i g n i f i c a n t changes i n e l e c t r i c a l p r o p e r t i e s of these materials. This f a c t caused t h e upsurge i n i n t e r e s t i n hydrogenation s t u d i e s of Si. I n the previous paper

^C13

the e f f e c t i v e hydrogen- passivation of d e f e c t s associated with d i s l o c a t i o n s in n-Si was reported.

The s a p l e s studded

in

t h i s work were of 1.15 a ^{cm P-doped}

^l?Z

^siUcon.

Dislocations were introduced a t 650

C

by u n i a x i a l compression ( f i n a l s t r a i n

E =

3.4%) , p a r a l l e l t 8

^the

4 2 1 j > direction. IPhe samples underwent hydrogenation a t 350

C

i n 3 'Porr, 3

MHz;

hydrogen p l a s m . llhe hydrogenation process was optimieed t o t h e point where a l l measurable by

DL=

technique defects,except f o r one

w i t h

i o n i s a t i o n energy 0.45 eV, , r e r e removed t o the depth of 10 p.

P i $ . 1

- Hydrogen penetration

depth

Ihe hydrogen penetration depth was investigated by subsequent polishing of the sample surface i n i t i a l l y subjected t o H-plasma.

llhe r e l a t i o n -

^SM

100%

( S

- i n i t i a l

DL'I'S

s i g n a l amplitude,

SH

-

amplitude a f t e r %ydrogenatio& Results a r e s h c m

in Fig. 1,

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983443

C4-360 JOURNAL DE PHYSIQUE

The n o t a t i o n E 3,

E 4

and

E

5 corresponds

w i t h

t h e one used

in

Fig.

2,

!&e

S

and a r e the amplitudes of

DL'PS

spectrum

in

the temperature points deno % ed by the respective arrows.

A s it i s

seen from Fig.

1

a s deep a s 40 pu beneath the surface which underwent hydrogenation 4536 of i n i t i a l l y d&ectable d e f e c t s is

still

passivated.

This

re-

sult

shows t h a t hydrogenation can have a p r a c t i c a l a p p l i c a t i o n in conventional device processing. There is a l s o another information concerning the d e f e c t configuration in dislocated S i a v a i l a b l e from the s t u d i e s of

H

penetration depth. !be s i m i l a r passivation depth f o r t h e d e f e c t s

E

3,

^E 4

and

E

5 i n d i c a t e s t h e common d i f f u s i o n path which is followed by H before it is trapped on these defects. The simplest i n t e r p r e t a t i o n assumes t h e

H

a i f f u s i o n along the d i s l o c a t i o n cores and the l o c a t i o n of t h e defects seen i n DLTS spectrum ( o r a t l e a s t 3 of them)

in

the v i c i n i t y of d i s l o c a t i o n l i n e s ( i n agreement with 123

)

.

Fig. 2 shows: the i n i t i a l DLTS spectrum of

investigated

sample,

the spectrum a f t e r hydrogenation, and spectra obtained a f t e r a s e r i e s of i s o c h r o m t i c

⁽ l h )

h e a t treatments a t indicated temperatures,

Another spectrum seen i n Fig. 2a belongs t o

a

reference-sample which underwent the same h e a t treatments but was not hydrogenated,

It is

seen

in

Fig.

2b

t h a t hydrogen d i f f u s e s i n t o S i under exposure t o t h e H-plasma removing e l e c t r o n traps, m e concentration of the only d e f e c t detectable a f t e r hydrogenation (0.45 eV), decreased over

2

orders of magffitude i n comparison

w i t h i t s

i n i t i a l value. After anneal a t 350

C

the reconstruction of 0.42 eV defect

is

most pronoun- ced.

The most s t r i k i n g f e a t y e of the DLTS-spectrum measured with t h e sample annealed a t 450

C

is the appearance of 0.53 eV peak a t re- l a t i v e l y high temperature indicating unusually small capture cross- s e c t i o n of t h e defect concerned. This i n d i c a t e s t h a t t h e a d d i t i o n

of H

c r e a t e s new

structurel~osnfigurations in

deformed

Si.

The r e s u l t s of a n n e p n g a t 5 5 0 8 and 6 5 0 ' ~ do not d i f f e r very much.

After anneal a t

650 C

t h e re-appearance of

liiost of the s p e c t r a l

f e a t u r e s of t h e deformed sample is c m p l e t e except f o r E

4

and perhaps

E

5 defect. The difference between t h e spectra shown

in

Fig.

2a and

2f

reveal a l s o t h e inhomogenity of t h e sample.

It

r e s u l t s from the f a c t t h a t before subsequent h e a t treatments the l a g e r of about

2 pm

t h i c k was taken o f f t o remove Au contact. Nevertheless in a l l investigated samples

(

a s a l s o reported in

^L13)

t h e re-appea- rance of E

4

defect was incomplete.

Spegtrum of t h e reference sample d i d not c h p e u n t i l anneal a t 750

C.

!I!he DLTS spectra a f t e r anneal a t 750

C

f o r both reference and hydrogenated samples a r e ahown i n

Pig. 2g,

Clear d i f f e r e n c e between these spectra i n d i c a t e s t h a t i n s p i t e of such a

high

tem- perature

in disordered samples a p a r t of H is

r e t a i n e d i n the c r y s t a l l a t t i c e . Much of t h i s hydrogen does not merely passivate dangling S i bonds Once trapped, t h e

H

i n h i b i t s t h e annealing of c e r t a i n d e f e c t s f~ 6) and enhances t h e annealing of others

(

e,g.

E

3,

E

4).

After anneal a t 850% onl one d i s t i n c t peak

E 4

remains i n the

spectrum of non-hydrogene 5 ed sample

(

a s i n

C

3

1 )

, whereas i n the

spectrum of hydrogenated sample the amplitude of

E 6

peak s t i l l

exceeds t h e one of

E 4

peak. Further anneal a t 9 0 0 ~ ~ b r i n g s verg

l i t t l e change in non-hydrogenated sample spectrum but f u r t h e r de-

creases

E 4

peak

in

hydrogenated sample spectrum.

C4-362 JOURNAL DE PHYSIQUE

It

is

not possible on t h e base of t h e above r e s u l t s t o a t t r i b u t e e x p l i c i t l y t h e peaks of DWS spectra t o t h e d e f i n i t e d e f e c t s in deformed n-Si. More research is a l s o required t o understand t h e s t r u c t u r e of Si-H bonds and t h e i n t e r r e l a t i o n between t h e s t r u c t u r e and t h e e l e c t r i c a l p r o p e r t i e s of t h i s material. The EPR and s p i n dependent photoconductivity ( sDP) measurements a r e under-way in order t o c o r r e l a t e t h e b r e s u l t s with DLTS r e s u l t s o

The experimental p a r t of t h i s work was done i n t h e I n s t i t u t ftlr Metallphysik and I V Physikalische I n s t i t u t in GUttingen, An award o f t h e A.v, Humboldt Foundation which enabled me t o c a r r y out t h i s work in W. Germany

is

acknowledged. I wish t o express my appreciat- i o n t o prof. T. F i g i e l s k i f o r c r i t i c a l r e v i s i o n of t h i s paper.

References

1, POHORYLES,

B.,

phys,stat,sol

a

¹⁹⁸¹

K . 5

2, SZKIEXJKO, W., ~IfCENSTEIN, O., P CKEXKEIN, R., C r y s t a l Res.

'Pechnolo 16 1981 197

3.

PATEL, J,=, KIMBLING, L.C., C r y s t a l Res. Technol.

16

1981 187