Influence of fluorine preamorphization on the diffusion and activation of low-energy implanted boron during rapid thermal annealing

Abstract

The diffusion and activation of low-energy implanted B in F preamorphized Si during rapid thermal annealing has been studied. Compared with low-energy B or BF2 implant into crystalline Si, low-energy B ion implantation into F preamorphized Si allows the formation of shallow junctions with reduced junction depth and increased B activation. F preamorphization suppresses the B transient enhanced diffusion in the low B concentration region resulting in a steep dopant profile which is necessary for shallow junction formation. Secondary ion mass spectroscopy and cross-sectional transmission electron micrograph results show F accumulation near the surface and at end-of-range defects. The interaction of F with defects is believed to reduce B diffusion in the low B concentration region. Low-energy B implant into F preamorphized Si followed by rapid thermal annealing has been demonstrated as a promising process for shallow junction formation.

Raman spectroscopic study of surface layer in fluorine-implanted Si

“…10,11 A new interest in studying the F ϩ -implanted Si is expected to be still growing. 12 We report some new results on the annealing behaviors of F ϩ -implanted Si sample as studied by Raman scattering in parallel with measurement of sheet resistance.…”

Effect of fluorine implantation dose on boron thermal diffusion in silicon

“…1,7,8 In later work 2-6,9-15,17,18 fluorine was implanted separately to the boron to characterize the effect of the fluorine on boron diffusion. This work showed that the fluorine implant reduced boron transient enhanced diffusion [2][3][4][5]9,11,13,14,[16][17][18] and increased boron activity. 2 However, there have also been contradictory reports in the literature, which showed that fluorine implants had little or no effect on boron transient enhanced diffusion 10 and that fluorine enhanced boron diffusion in preamorphized silicon 6 using a silicon implant.…”

“…18 Finally the interaction of fluorine with silicon interstitials has been widely proposed as a mechanism of suppressing boron transient enhanced diffusion. 2, [4][5][6][7][8][9][10]18 In this paper, experiments are performed to investigate how the fluorine implantation dose influences the thermal diffusion of boron marker layers in silicon. Boron secondary ion mass spectroscopy (SIMS) profiles are studied for different fluorine implantation doses and compared with the corresponding fluorine profiles.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] A chemical interaction between boron and fluorine has been proposed to explain the suppression of boron transient enhanced diffusion by fluorine, 4,9,11,14,16 in which the fluorine combines with interstitial boron reducing its mobility 4,11,14,16 or reduces the probability of formation of a boron interstitial pair. 9,11 Alternatively, the formation of vacancy-fluorine complexes has been proposed, 13,17,18,[23][24][25][26] which act as a barrier for boron diffusion, 13 or suppress the interstitial concentration and hence reduce boron transient enhanced diffusion 17 and thermal diffusion.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] This research has been motivated by the requirement in advanced CMOS technologies to minimize boron diffusion for the formation of shallow source/drain junctions and sharply defined halo profiles. 19,20 The minimization of boron diffusion is also important in bipolar transistors, where boron diffusion limits the achievable base width and hence the value of cutoff frequency that can be obtained.…”