HAL Id: jpa-00223125
https://hal.archives-ouvertes.fr/jpa-00223125
Submitted on 1 Jan 1983
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
ANNEALING OF HIGH DOSE IMPLANTED GaAs WITH HALOGEN LAMPS
Y. Nissim, B. Joukoff, J. Sapriel, N. Duhamel
To cite this version:
Y. Nissim, B. Joukoff, J. Sapriel, N. Duhamel. ANNEALING OF HIGH DOSE IMPLANTED GaAs WITH HALOGEN LAMPS. Journal de Physique Colloques, 1983, 44 (C5), pp.C5-247-C5-251.
�10.1051/jphyscol:1983539�. �jpa-00223125�
A N N E A L I N G O F H I G H DOSE I M P L A N T E D G a A s W I T H HALOGEN LAMPS
Y.I. Nissim, B. J o u k o f f , J . S a p r i e l and N. Duhamel
C . N . E.T., Laboratoire de Bagneux*, 196 rue de Paris, 92220 Bagneux, France
Resum6 - Le r e c u i t de GaAs implant6 par un systeme de deux lampes halogene m r 6 s e n t e . Le confinement de 1'i.chantillon monte entre une plaque de silicium e t une plaque de quartz permet d'obtenir une protection par con- t a c t . Cette configuration a permis l ' c t u d e par diffusion Raman de l a recons- truction du r6seau c r i s t a l l i n aprgs i r r a d i a t i o n ainsi que l a l i m i t e de d6- gradation en surface du substrat par perte dl arsenic.
Abstract - The use of radiation from two ha1 ogene lamps to anneal impl anted G a A s Z been studied. Contact protection of the substrate i s obtained by mounting i t in a sandwich configuration between a silicon and a quartz pla- t e . This configuration allows to measure by Raman s c a t t e r i n g l a t t i c e recove- ry after i r r a d i a t i o n and substrate surface degradation due to arsenic loss.
INTRODUCTION
The annealing of ion implanted GaAs i s the object of a constant research e f f o r t t o achieve a good control in GaAs devices. Conventional thermal annealing of GaAs often gives unsatisfactory r e s u l t s in both activation of dopants and removal of damage induced by ion impl antation. Furthermore, encapsulation of the substrate or a con- t r o l 1 ed arsenic overpressure are required t o prevent the substrate from surface decomposition (As evaporation) a t elevated temperatures. This procedure i s often d e l i c a t e and can induce e l e c t r i c a l conversion a t the surface of a semi-insulating s u b s t r a t e 111. Therefore GaAs has from the s t a r t been a potential candidate for the application of the beam anneal ing techno1 ogy. The short and local 1 ized heat t r e a t - ment under beam i r r a d i a t i o n was expected to suppress decomposition and thereby im- prove the properties of the annealed layers. However the r e s u l t s t o date on laser annealing of implanted layers in GaAs have not shown substantial improvements as compared to thermal anneal ing . Major d i f f i c u l t i e s arising from the f r a g i l i t y and dissociation of the material under laser i r r a d i a t i o n are responsible for the limited success achieved in earlyattempts .More recently the use of lamps to anneal implan- ted GaAs has brought promising r e s u l t s in e l e c t r i c a l activation of dopants /2,3/.
Similar r e s u l t s were obtained with a graphite s t r i p heater 141. The novelty of the technic i s a more distributed thermal gradient induced a t the surface of the sub- s t r a t e and a longer annealing time (few seconds) as compared t o a laser irradiation.
In t h i s presentation the annealing of high dose implanted GaAs w i t h a system of two 150 watts halogene lamps i s studied. The optimization of i r r a d i a t i o n time has been made for a given induced temperature on the basis of best l a t t i c e recovery and mini - mum surface degradation. The confinement of the sample mounted in a sandwich confi- guration during i r r a d i a t i o n r e s u l t s in the a b i l i t y of measuring both informations within a single Raman scattering investigation.
* L a b o r a t o i r e a s s o c i g a u CNRS (LA 250)
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983539
JOURNAL DE PHYSIQUE
ANNEALING APPARATUS AND SAMPLE MOUNTING CONFIGURATION
A system of two 150 W halogen lamps as described in ref
/5/was redesigned for the annealing of 111-V compounds. The filament of the lamps of t h i s system draws 10A a t 15V and has an emission spectrum t h a t corresponds to the blackbody radiation emis- sion a t 3400K with a peak a t 800
rim.The lamps are mounted in a b u i l t in gold coated r e f l e c t o r t h a t focuses the filament 19mn away from the edge of the r e f l e c t o r . The average power density radiated by each lamp a t full i n t e n s i t y was measured i n
/5/t o be 100W/cm2. The annealing s e t up i s schematically drawn i n Fig.1. Two lamps facing each other and a s i l i c o n sample holder are mounted each on a disk t h a t can be trans- 1 ated on a vertical graduated pole. The lower lamp i s strongly defocussed with r e s - pect t o the sample holder and i s u t i l i z e d to prepare i t a t a constant i n i t i a l tempe- rature
( =300°C). This procedure i s necessary to reduce the thermal s t r e s s i n the semiconductor when the elevated annealing temperature i s suddenly induced. The upper lamp i s then lighted to ramp the sample t o i t s final temperature (800 t o 1100°C).
The temperature induced on the irradiated sample was carefully measured with a thermocouple i n mechanical contact with the sample holder. The spatial temperature p r o f i l e indicates t h a t the temperature i s re1 ativel y uniform across the studied samples (4x4mn). The temporal temperature p r o f i l e i s shown in Fig.2. I t indicates t h a t the final temperature induced by the lamps due t o the experimental choice of the upper lamp position i s 1000°C and t h a t 8 secondes of t r a n s i e n t regime are ne- cessary to reach thermal equil ibrium.
The GaAs substrate need t o be protected from sudden surface decomposition a t t h i s temperature. A closed contact configuration was choosen for protection w i t h the sample sandwiched between the s i l i c o n sample holder and a quartz plate. The GaAs sample i s placed upside down on a floating s i l i c o n wafer so t h a t the two polished surfaces are i n contact. As shown i n the i n s e t of Fig.1. A heavy quartz p l a t e covers t h e structure and press i t t i g h t . Similar sandwiched configuration has been used successfully t o protect 11-VI compounds during an annealing cycle
/6/. Finally as anextra protection the whole system i s kept in a clean nitrogen environment.
SCHEMATIC OF THE ANNEALING APPARATUS
IPREHEATI S A M P L E CONFIGURATION
Fig.1
: Schematic of the annealing apparatus and sample mounting configuration.sample by the ha1 ogen lamp system.
TIME i s I
EXPERIMENTAL RESULTS
The l a t t i c e reconstruction under i r r a d i a t i o n of heavily damaged GaAs layers has been
studied. Chromium doped
( 1 0 0 )GaAs substrates were implanted with Te+ ions
( 1 ~ 1 0 ~ ~ / c r n ~ ~a t 250 key) resulting in a 1000
Aamorphous layer. Both single crystal and implanted
samples were ramped t o 1000°C i n the lamp system described above for a t o t a l time (including r i s i n g time) varying between 5 and 60 sec. This i s i l l u s t r a t e d i n Fig.2.
The f i r s t experiments were carried out on c r y s t a l l i n e GaAs to check the degradation induced by i r r a d i a t i o n . Raman scattering investigation showed the formation of crys- t a l l i n e arsenic t r a c e s a t the surface of the sample for total i r r a d i a t i o n time above 30 secondes. Crystalline arsenic belongs t o the point group 3m and there are two atoms in the u n i t rhombohedra1 c e l l . There are three optical modes which are Raman a c t i v e
:the single mode Alg (LO) and the doubly degenerate Eg (TO) modes. A clear increase in the As peaks could be measured with increasing exposure time. The pre- sence of traces of c r y s t a l l i n e As can be a t t r i b u t e d either t o an evaporation and r e c r y s t a l l i z a t i o n of As a t the surface of the wafer due t o the confinement of the pressed sandwiched configuration of the sample, or to a thermal oxydation with As retained in the i n t e r f a c i a l region during growth. This l a s t p o s s i b i l i t y has been reported in ref./7/.
The LO and TO modes of c r y s t a l l i n e GaAs (292 and 267
cm-Irespectively) are s u f f i -
c i e n t l y separated from the LO and TO modes of c r y s t a l l i n e arsenic (257 and 199 cm-l
respective1 y ) t o a1 1 ow ready i d e n t i f i c a t i o n of the separated species. I t i s then
possible to carry the experiments on the amorphi zed substrate and follow simul tane-
ousl y the l a t t i c e reconstruction and the surface decomposition. The Raman scattering
measurements weremade with the probing 1 aser beam a t Brewster incidence t o minimize
unwanted s c a t t e r i n g from surface i r r e g u l a r i t i e s . The s c a t t e r i n g geometry was
Z(X+Y, X + Y ) Z in order t o detect the LO peak of c r y s t a l l i n e GaAs ( t h e only GaAs
Raman active peak allowed i n t h i s configuration). The increase of the LO ( 2 9 2 ~ m - ~ )
peak i s c l e a r l y an indication of l a t t i c e reconstruction since t h i s peak i s complete-
l y inexista1nt in the s t a r t i n g amorphous material .
JOURNAL DE PHYSIQUE
---
AMORPHOUS REFERENCE-
IRRADIATED FOR 30 sI - IRRADIATED FOR 45 s
t
300 250 200 150 '
'
FREClUENCY SHIFT (cm-'
Fig.3
:Raman scattering spectra of samples "over irradiated". The As peaks are the two low frequency peaks (199 and 257
an-1 ).
---
AMORPHOUS REFERENCE -IRRADIATED FOR 30 sIRRADIATED FOR 15 s A
-IRRADIATED FOR 5 s
POLARlZATlON . Z(X+Y,X+Y1 Z
- : -
FREQUENCY
SHIFT [cm-' )Fig. 4
:Raman scatter.ing spectra of sam- plesMunder irradiated'! The GaAs peaks are the two high frequency peaks (267 and 292
cm-'1.When the sample i s i r r a d i a t e d for times longer than 30 secondes the resulting spec- t r a are shown in Fig.3. The As peak i n t e n s i t i e s are increasing with annealing time and the GaAs peaks are present. A well defined LO peak and a small TO peak a t t r i b u - ted to residual disorder appear. I t can be concluded t h a t annealing times over 30 secondes r e s u l t i n r e c y r s t a l l i z a t i o n of the amorphous layer b u t induce a too impor- t a n t surface decomposition. When the exposure time i s reduced below 30 secondes the resulting Raman spectra are shown in Fig.4. I t can be seen t h a t no c r y s t a l l i n e As ( o r only a very small amount) can be detected and t h a t the highest GaAs LO peak i s obtained for 30 secondes exposure time. When t h i s time i s reduced be1 ow 15 secondes, the spectrum shows the evidence of a resulting GaAs disorder s t a t e /8/ intermediate between amorphous and c r y s t a l l i n e phases. The optimum (highest LO for GaAs and lowest As peaks) total annealing time for an induced temperature of 1000°C i s then around 30 secondes. In t h i s case the i n t e n s i t y of
t h eGaAs LO peak i s 60
%of a single crystal reference with comparable position and p r o f i l e .
As a conclusion i t has been shown t h a t heavily damaged by ion implantation GaAs
1 ayer s coul d be reconstructed with an ha1 ogen 1 amp anneal and t h a t Raman scattering i s
an elegant method t o follow simultaneously t h i s reconstruction and the surface de-
gradation. Further work t o f u l l y caracterise the annealed crystal structure and to
measure e l e c t r i c a l activation i s on the way and will be reported l a t t e r .
[I] DONNELLY J.P., BOZLER C:O. and LINDLEY W.T., Solid. S t a t e E l e c t r o n 20 (1977)
273
-
[2]
ARAI M., NISHIYAMA K. and WATANABE N., Jap. J. o f Appl. Phys.20
(1981) L124 [ 3 ] KUZUHARA M., KOHZU H. and TAKAYAMA Y., Appl. Phys. L e t t . 41, (1982) 755-
[ 4 ] CHAPMAN R.L., FAN J .C.C., DONNELLY J .P. and TSAUR B.Y., Appl
.
Phys. L e t t . 40 (1982) 805[ 5 ] VU D.P., YAOND M. TERNISIEN D'OUVILLE T., PER10 A. and MINGAM H., E l e c t r o n i c s L e t t .
-
19 (1983) 4[6]
CONWAY K.L.,
OPYD -W.G., GREINER M.E., GIBBONS J.F.,
SIGMOM T.W., and BUBULAC L.O., Appl.
Phys. L e t t .-
41 (1982) 750[ 7 ] SCHWARTZ G.P., GRIFFITHS J .E., DISTEFANO D., GUALTIERI G.J. and SCHWARTZ B., Appl
.
Phys. L e t t .-
34 (1979) 742[8] SAPRIEL J
