LASER IMPLANTATION OF Fe IN SILICON

(1)

HAL Id: jpa-00219651

https://hal.archives-ouvertes.fr/jpa-00219651

Submitted on 1 Jan 1980

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.

LASER IMPLANTATION OF Fe IN SILICON

Yu. Petrikin, S. Damgaard, M. Oron, J. Petersen, G. Weyer

To cite this version:

Yu. Petrikin, S. Damgaard, M. Oron, J. Petersen, G. Weyer. LASER IMPLANTATION OF Fe IN SIL- ICON. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-423-C1-424. �10.1051/jphyscol:19801164�.

�jpa-00219651�

(2)

JOURNAL Dl3 PHYSIQUE Colloque C1, supplkment au n o 1,

Tome

41, janvier 1980, page C1-423

LASER IMPLANTATION OF

Fe

IN SILICON

Yu, V. petrikin*, S. Damgaard, M. oron*

*,

^J.W.Petersen and G. Weyer I n s t i t u t e of Physics, University o f A&s DK 8000 Aarhus C, Denmark

1. Introduction 3. Experimental results and discussion

As an alternative to diffusion and ion implanh ation techniques, laser irradiation has been ap- plied to incorporate dopants from a deposited layer on the surface into the bulk of silicon [I]. The limit of solid solubility may be exceeded by this method. In contrast to ion implantation, where this

can also be achieved, problems from radiation dam- age are less severe. Here we report on the implantation of iron in silicon by laser irradiation. The location of iron in the silicon lattice is investig ated by conversion electron Mdssbauer spectroscopy.

2. Experimental procedure

Layers of metallic iron (3

-

30 ug/cm2 en- riched in s Fe) were deposited on the <Ill> surface of silicon single crystals (Fz,n-type,5Qcm) by an electron gun evaporation technique. The iron layers were irradiated with (3

-

4 slightly overlasping) light pulses which covered about 1 cm2 ( ~ 1 0 0 ns duration time) from a Nd glass laser (A= 1.06um )

.

^Af-

ter the laser irradiation the surface was cleaned from residual iron with HC1.

Conversion electron M6ssbauer spectra were measured in a backscattering geometry with a paral-

lel-plate avalanche counter 121 where the samples were used as cathodes. A 10 mCi 57Co(Rh) source was moved on a conventional constant acceleration drive system.

To investigate the depth distribution of the implanted iron, surface layers of 100

-

¹⁰⁰⁰fi were stripped off by an anodic oxidation technique.

fpermanent addres~ : Moscow Physical-Engineering Institute, Moscow, 115 409 USSR.

A spectrum of an iron layer (30 ug/cn12) irradiated with a power density of 2.6 J/cm2 is shown in

VELOCITY Cmmlsec I

Figure 1 : Mossbauer spectrum measured at room temperature of a sample (30 g/cm2 Fe) irradiated with 2.6 J/cm2. A surface layer of%100 fi has been stripped off.

figure 1. Similar spectra were obtained for layer thicknesses of 3 to 30 uq/cm2 irradiated with power densities of 2.1 to 3.5 J/cm2. Except for a de- crease in intensity, the spectra did not change upon a stripping of up to 3500 fi from the surface of the samples. The spectra are similar to those found for ion implanted samples of 5 7 ~ e in Si that have been annealed at high temperatures [ 3 ] . The lines are interpreted as a quadrupole split doublet

( 6

-

0.2 mm/sec rel.to 01-Fe, AE = 0.4 mm/sec, Q

r

= 0.4 mm/sec) due to FeSi2

.

The observation of large amounts of iron deep inside the silicon can hardly be accounted for by a diffusion of iron into solid silicon. A diffusion constant of D

2

10-'cm2/sec I41 limits the diffusion length to %I00 A if the diffusion time is not considerably longer than,the duration of the laser

*

%emanent address: Soreq research center,Yavne,Israel.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801164

(3)

C 1-424 JOURNAL DE PHYSIQUE

pulse. It seems more reasonable to assume that a silicon surface layer of several thousand dnqstroms thickness has been molten as an effect of the laser irradiation. These assumptions seem to be justified by recent experiments [5]

.

Thus iron atoms are incorporated as a result of laser induced diffusion in the liquid phase. About 1% 02 the deposited iron layer is implanted yielding an iron concentration several orders of magnitude above the maximum solid solubility.

For an irradiation with a power density of 1.6 J/cm of an iron layer of 30 bg/cm2, a spectrum as displayed in figure 2 is found. An analysis with

,a,.*,

I Î Î Î I

VELOCITY [mm lsecl

Figure 2 : Idbssbauer spectrum measured at room temperature Of a sample ( 3 0 ~-lg/cm*- " ~ e ) irradiated with 1.6 ~/cm'.

three independent lines as indicated in the figure suggests that the spectrum consists of a doublet

( 6 -0.3 mm/sec, A E 0.7 mm/sec,

r

^z 0.5 mm/sec) I!

and an additional single line ( 6 ~ 0 . 2 mm/sec,

r

0.3 mm/sec). No measurable fraction of iron had pen- etrated a surface layer %I00 A. Thus contrary to the higher power density laser irradiations, in this case a fraction of the iron atoms may have dif- Fused into the silicon in the solid state. This spr- cies should then occupy well defined positions in the silicon lattice. These expectations are in agreement with the occurrence of the narrow line at 6 = 0.2 mm/sec in the spectrum. It should be

noted that the concentration of this species ex- ceeds the maximum solid solubility of iron by several orders of magnitude. The parameters of the doublet which are inbetween those found for annealed and non-annealed ion implanted samples [ 3 ] may sup- port the assumption that the temperature of the sample has been lower for this low power density irradiation.

4. Conclusion

The irradiation of thin evaporated layers of iron on silicon with short laser pulses has been de- monstrated to result in an implantation of a substan- tial fraction of the iron atoms into the silicon cry- stal. For high laser power densities, a silicon surface layer is molten; the iron is incorporated in the liquid phase and is found in precipitates after the resolidification. For low laser power densities,iron atoms are implanted in a shallow surface layer. It is proposed that an appreciable amount of the iron atoms diffuse into the silicon in the solid phase. This fraction is related to a single line in the spectra which is attributed to iron in well defined lattice positions.

This work has been supported by the Danish Nat- ural Science Research Council.

References

1 See, e.q., Narayan, J., Young, R.T., Wood, R.F., and Christie, W.H.,Appl.Phys.Lett.z (1978) 3 3 8 2 Weyer, G., Mossb.Eff.Method.(eds,Gruvermann,

I.J. an6 Seidel, C.W.)

10

(1976) 301

3 Damgaard, S., Petersen, J . W . , and Weyer, G., this conference

4 Struthers, J.D., Appl.Phys.3 (1956) 1560 5 Auston,D.H., Surko, C.M., V~nkateson, T.N.C.,

Slushev, R.E., and Golovchenko, J.A., Appl.

Phys.Lett.2 11978) 437