n Junction Produced by Plasma Immersion Ion ...

Boron Profile Sharpening in Ultra‐Shallow p + ‐n Junction Produced by Plasma Immersion Ion Implantation from BF 3 Plasma V. Lukichev, K. Rudenko, A. Orlikovsky, A. Pustovit, and A. Vyatkin Citation: AIP Conference Proceedings 1066, 481 (2008); doi: 10.1063/1.3033668 View online: http://dx.doi.org/10.1063/1.3033668 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1066?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Local Resistance Profiling of Ultra‐Shallow Junction with Spike Lamp and Laser Annealing Using Scanning Spreading Resistance Microscopy AIP Conf. Proc. 1066, 83 (2008); 10.1063/1.3033689 PULSION®: A Versatile 200 to 300 mm Bridge Tool Plasma Immersion Ion Implanter for Ultra‐Shallow Doping and Nanotechology Applications. AIP Conf. Proc. 1066, 484 (2008); 10.1063/1.3033669 Fabrication of Ultra‐Shallow Junctions on 300 mm Wafers Using the Plasma Immersion Implanter PULSION® Followed by Spike Annealing Using LEVITOR Furnace AIP Conf. Proc. 1066, 477 (2008); 10.1063/1.3033666 Ultra‐Shallow Junctions Fabrication by Plasma Immersion Implantation on PULSION® Followed by Laser Thermal Processing AIP Conf. Proc. 1066, 473 (2008); 10.1063/1.3033665 Basic Aspects of the Formation and Activation of Boron Junctions Using Plasma Immersion Ion Implantation. AIP Conf. Proc. 1066, 461 (2008); 10.1063/1.3033662

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Boron Profile Sharpening in Ultra-Shallow p^-n Junction Produced by Plasma Immersion Ion Implantation from BF3 Plasma V. Lukichev\ K. Rudenko^ and A. Orlikovsky^ A. Pustovit^ and A. Vyatkin^ Institute of Physics and Technology (FTIAN), Russian Academy of Sciences, Nakhimovsky prosp. 34, Moscow, Russia Institute of Microelectronics Technology (IMT), Chemogolovka, Russia Abstract. We have investigated plasma immersion ion implantation (PI^) of boron with energies of 500 eV (doses up to 2x10 cm" ) from BF3 plasma with He pre-amorphizing implantation (PAI) (energy 3 keV, dose 5x10 cm-^). Implanted samples were subjected to RTA (T = 900 to 1050 °C, t = 2 to 24 sec and spike anneal). SIMS analysis of boron profiles revealed its anomalous behavior. For short RTA times the profile tail (below 5xlO" cm"^) moves toward the surface and then, as in the usual diffusion, toward the bulk at longer annealing times. Keywords: plasma immersion ion implantation, pre-amorphizing implantation PACS: 52.77.Dq amorphization dose of 5x10^ cm" was reached within 100 seconds.

INTRODUCTION The demand of ITRS (2007 Ed.) for ultra-shallow p-n junction depth is about half of the channel length. In the sub-100 nm technology, node plasma immersion ion implantation (PI^) is a promising technique to meet the demand and is considered as potential solution of doping for Front End Processes.

I

EXPERIMENTAL The processes of ultra-shallow plasma doping were studied in an experimental implanter designed at IPT RAS. The processing chamber (Figure 1) uses an ICPplasma source with a planar inductor designed in this laboratory. It possesses a scalability property and is equipped with a permanent magnetic system to tune plasma uniformity in the plane near the chilled wafer chuck. The feeding of small helium flow under the wafer significantly improves the thermal contact and prevents the heating of the wafer over 100 °C. The samples in the experiments were blank 150 mm wafers with n-doping up to the level of 2x10^^ cm"^. It is well known that to avoid boron channeling the step of pre-amorphizing implantation (PAI) is needed. In our previous work [1] we used Ar^ or Xe^ for this purpose. In these experiments we have investigated the PI^ process with He^ as PAI because of specific properties of amorphized silicon under He ion implantation [2, 3]. The process parameters for PAI step are shown in Table 1. A required

:elerating Potential

Cooled chuck

Afloat -

FIGURE 1. Processing.

Scheme of Experimental Chamber for PI^

TABLE 1. Pre-Amorphizing Implantation Step Process parameter Value PAI Source He Plasma (Ions He ) Accelerating Pulse Voltage 3kV Pulse Duration 10 )isec Pulse Repetition Rate IkHz Dose for Si Amorphization 5x10" cm"^ Boron implantation was carried out immediately after the PAI step by changing the feeding gas by BF3. The process conditions are represented in Table 2. The time for a 2x10^' cm"^ boron dose was 20 seconds. The plasma composition was monitored by optical emission spectroscopy (OES).

CPIO66, Ion Implantation Technology, edited by E. G. Seebauer, S. B. Felch, A. Jain, and Y. V. KondratenJio © 2008 American Institute of Pliysics 978-0-7354-0597-4/08/$23.00

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Our previous analysis [1] carried out by fitting of boron PI^ experimental profiles from BF3 plasma with the Pearson distribution shows two distinguished regions with different ranges and straggling. The ratio of these two ranges ratio is due to simultaneous implantation of molecular BF2^ ions and atomic B^ from plasma without separation. This leads to the deterioration of doping profile steepness in junction location (Xj) formed by this technique.

TABLE 2. Boron Implantation Step Process parameter Value BF3 Plasma Boron-Containing Source (Ions BF2+, BF+, B-) Accelerating Pulse Voltage 0.5 kV Pulse Duration 10 )rsec Pulse Repetition Rate IkHz Dose for Boron Implantation 2x10'^ cm'^ Implanted samples were subjected to rapid thermal annealing (RTA) at different temperatures in the range of 900 to 1050 °C. We have applied the different annealing duration of 2 to 24 sec at flat temperature section, and have tested spike annealing with ramp-up rate of 250 °C/s and down rate of 100 °C/s). The details of RTA process are listed in Table 3.

1

Value 900-1050 °C 2 - 2 4 sec 250 °C/sec 100°C/sec High Purity Ar

g

2x10"0

1E18-

20

30

40

iiiWPP"M»*i|i'iii,,, 60 70 80 90 100 110 120 130 140 150

50

A detailed SIMS investigation of annealed samples has shown an abnormal behavior of boron profile evolution for implanted structures using PAI with He^ in comparison with samples when Ar^ PAI was applied for silicon [1]. The main unusual effect is that at short RTA times the profile tail (below 5 x 1 0 " cm"^) moves toward the surface, and then the tail diffusion changes its direction toward the bulk because it becomes controlled by ordinary diffusion laws (Figure 2, 3). The alternation of B-diffusion direction was observed in the whole annealing temperature range, but the diffusion rate significantly increased at high temperatures both for the retrograde and forward diffusion. At T = 1050 °C the shift of the boron tail toward the surface takes place instantaneously even in spike RTA for the ramp-up and ramp-down time. It can be seen that estimated Xj are shifted to the surface due the retrograde diffusion approximately by a constant value of 20 nm and do not depend on annealing temperature.

level of n-doping

li

Level of n-dopIng

FIGURE 3. SIMS Boron profiles for series of RTA process time illustrating retrograde and forward movement of profile tails for T = 1050 °C.

RTA, T=900 ° C , t=24 s e c

Itoj

10'°-

1E19-

Depth, nm

RTA, T=900 ° C , t = 1 2 sec

10"-