Annealing Studies on Low Energy As+ and As2+ Implants

ABSTRACT2 keV to 10 keV arsenic, As+, and arsenic dimer ions, As 2+, were implanted into silicon at a dose of le15 cm-2 and 3e 15 cm-2 at 0° and 7°' tilt angles. For bare wafers, a low concentration of oxygen is required to provide sufficient capping during anneal to minimize out-diffusion. In the presence of oxygen, enhanced diffusion occurs during the anneal, the extent of which is a function of the concentration of oxygen and the temperature of anneal. The oxidation enhanced diffusion (OED) is significant at anneal temperatures above 1050°C. The extent of OED is observed to be more significant for the samples with lower energy As+ implants. An alternative technique for minimizing OED, without much out-diffusion, is the use of higher energy, 5 keV implants through a screen oxide. For identical anneal conditions, 5 keV As+ implants through a 40 Å screen oxide offer junction depth and sheet resistance values equivalent to that of 2 keV implants into bare silicon. As the screen oxide is sufficient to cap the out-diffusion of dopants, a nitrogen ambient or a lower temperature could be employed to get shallower junctions without much degradation in the sheet resistance. Further reduction in junction depths can be achieved by using the As 2+ implants.

Download Full-text

Rapid Thermal Process Requirements for The Annealing of Ultra-Shallow Junctions

MRS Proceedings ◽

10.1557/proc-470-299 ◽

1997 ◽

Vol 470 ◽

Cited By ~ 5

Author(s):

Daniel F. Downey ◽

Sonu L. Daryanani ◽

Marylou Meloni ◽

Kristen M. Brown ◽

Susan B. Felch ◽

...

Keyword(s):

Sheet Resistance ◽

Diffusion Mechanism ◽

Complex Surface ◽

Junction Depth ◽

Enhanced Diffusion ◽

Shallow Junctions ◽

Diffusion Mechanisms ◽

Ultra Shallow Junctions ◽

Dopant Loss ◽

Loss Mechanisms

ABSTRACT2. 0 keV 11B+, 2.2 keV 49BF2+ ion implanted and 1.0 kV Plasma Doped (PLAD) wafers of a dose of 1E15/cm2 were annealed at various times and temperatures in a variety of ambiente: 600 to 50,000 ppm O2 in N2; 5% NH3 in N2; N2O; N2 or Ar, in order to investigate the effects of the annealing ambient on the formation of ultra-shallow junctions. RGA data was collected during some (if the anneals to assist in identifying the complex surface chemistry responsible for boron out-diffusion. Subsequent to the anneals, ellipsometric, XPS, four-point probe sheet resistance and SJJVIS measurements were performed to further elucidate the effects of the different ambients on the r etained boron dose, the sheet resistance value, the RTP grown oxide layer and the junction depth. In the cases where oxygen was present, e.g. N2O and O2 in N2, an oxidation enhanced diffusion of the boron was observed. This was most dramatic for the N2O anneals, which at 1050°C 10s diffused the boron an additional 283 to 427 Å, depending on the particular doping condition and species. For the case of BF2 implants and PLAD, anneals in 5% NH3 in N2 reduced the junction depth by a nitridation reduced diffusion mechanism. RGA data indicated that the out-diffusion mechanisms for B and BF2 implanted wafers are different, with the BF2 exhibiting dopant loss mechanisms during the 950°C anneals, producing F containing compounds. B implants did not show doping loss mechanisms, ais observed by the RGA, until the 1050°C anneals and these signals did not contain F containing compounds. Equivalent effective energy boron implants of 8.9 keV BF2 vs. 2.0 keV B, however, indicated that the overall effect of the F in the BF2 implants is very beneficial in the creation of ultra-shallow junctions (compared to B implants): reducing the junction depth by 428 Å, and increasing the electrical activation (determined by SRP) by 11.7%, even though the retained dose (resulting from an increased out-diffusion of B), was decreased by 5.4%.

Download Full-text

Ultra low energy arsenic implant limits on sheet resistance and junction depth

2000 Symposium on VLSI Technology. Digest of Technical Papers (Cat. No.00CH37104) ◽

10.1109/vlsit.2000.852790 ◽

2002 ◽

Cited By ~ 7

Author(s):

R. Kasnavi ◽

P.B. Griffin ◽

J.D. Plummer

Keyword(s):

Sheet Resistance ◽

Low Energy ◽

Junction Depth

Download Full-text

Effect of Ge Pre-amorphization on Junction Characteristics for Low Energy B Implants

MRS Proceedings ◽

10.1557/proc-610-b4.6 ◽

2000 ◽

Vol 610 ◽

Cited By ~ 4

Author(s):

Jinning Liu ◽

Sandeep Mehta

Keyword(s):

Sheet Resistance ◽

Low Energy ◽

Junction Depth ◽

Semiconductor Processing ◽

Rapid Thermal Anneal ◽

Lower Sheet ◽

N Source ◽

Energy Regime ◽

Spike Anneal ◽

Lower Sheet Resistance

AbstractThe drive towards developing deep sub-micron CMOS devices places more challenges on semiconductor processing. From the standpoint of doping technology, the challenge is to achieve ultra-shallow p+/n source/drain extension junctions for PMOS. Among the various approaches being pursued to meet this challenge, pre-amorphization was used to curtail channeling of the as-implanted Boron. The effect of pre-amorphization on junction depth and junction sheet resistance in the ultra-low implant energy regime is investigated in this study. Pre-amorphization was achieved with Ge implant. B was implanted at energies of 250eV to 5keV and at a dose of 1×1015cm−2 into crystalline and pre-amorphized wafers. Both spike anneal at 1050°C and furnace anneal at 500°C to 750°C were performed after B implants. In all spike anneal cases, the pre-amorphized wafers exhibit higher sheet resistance and shallower junction depth than crystalline wafers. In all furnace anneal cases, shallower junction depth as well as lower sheet resistance can be achieved with pre-amorphized wafers. Higher pre-amorphization energy induces lower sheet resistance after both furnace and rapid thermal anneal (RTA).

Download Full-text

The Effects of Small Concentrations of Oxygen in RTP Annealing of Low Energy Boron, BF2 and Arsenic Ion Implants

MRS Proceedings ◽

10.1557/proc-525-263 ◽

1998 ◽

Vol 525 ◽

Cited By ~ 21

Author(s):

Daniel F. Downey ◽

Judy W. Chow ◽

Wilfried Lerch ◽

Juergen Niess ◽

Steven D. Marcus

Keyword(s):

Scanning Force Microscopy ◽

Low Energy ◽

Junction Depth ◽

Force Microscopy ◽

Enhanced Diffusion ◽

Low Concentrations ◽

Shallow Junctions ◽

Scanning Force ◽

Dopant Loss ◽

Anneal Temperature

ABSTRACTIon implants of 1.0 keV 11B+, 5 keV BF 2+, and 2.0 keV As+ at a dose of IeI5/cm2 were rapid thermal annealed (RTA) in a STEAG AST-2800µ with varying percents of oxygen in N2, ranging from 0-lppm to 50,000 ppm to investigate the effects of low concentrations of oxygen during anneal. Sheet resistance (Rs), ellipsometry, SIMS, Tapered Groove Profilometry (TGP), and Scanning Force Microscopy (SFM) were employed to characterize these layers. For each of these implant cases, an optimal RTA condition is established which maximizes retained dose while still producing shallow junctions. As a function of O2 content, anneal temperature and implant condition, three regimes are observed that affect after anneal retained dose. These regimes are: dopant loss to the ambient resulting from etching of Si, dopant loss by out-diffusion from evaporation/chemical reactions, a capping regime that minimizes out-diffusion. In this later regime the dopant loss results from consumption into the RTA grown oxide. In addition, this paper also discusses oxidation enhanced diffusion (OED) and identifies its extent as a function of temperature and O2 content of the anneal for the three implant conditions investigated. For example, a 1.0 keV 11B+wafer annealed at 1050°C lOs in a controlled 33 ppm of O2 in N2 yields a SIMS junction depth 320 Å shallower than previously reported by others.

Download Full-text

Implant Dose and Spike Anneal Temperature Relationships

MRS Proceedings ◽

10.1557/proc-669-j8.1 ◽

2001 ◽

Vol 669 ◽

Cited By ~ 1

Author(s):

K. K. Bourdelle ◽

A. T. Fiory ◽

H.-J. L. Gossmann ◽

S. P. McCoy

Keyword(s):

Sheet Resistance ◽

Junction Depth ◽

Enhanced Diffusion ◽

Coupled Diffusion ◽

Temperature Trends ◽

Transient Enhanced Diffusion ◽

Physically Based ◽

Spike Anneal ◽

Spike Annealing ◽

Anneal Temperature

ABSTRACTThe method of ion implantation and spike annealing for preparing shallow junctions suitable for the extension regions bridging the channel and source/drain contacts of CMOS transistors are studied by annealing blanket implants. Junction depths at a given sheet resistance for low energy B implants are minimized for the combination of a fast ramp with a sharp-spike anneal. This is shown to be physically based on activation energy phenomenology. The fraction of electrically activated B is insensitive to implant dose, unlike the case of transient enhanced diffusion. Arsenic implants show higher activation fraction than comparably annealed P implants, without the large transient enhanced diffusion which is attributed to P and Si-interstitial coupled diffusion. For targeted sheet resistance and junction depth, spiking temperature trends lower with implant dose, concomitant with decreasing fraction of activated dopant.

Download Full-text

The influence of "off-axis" from [100] oriented Si wafers on junction depth and sheet resistance for low-energy implantation and rapid thermal annealing

2000 International Conference on Ion Implantation Technology Proceedings. Ion Implantation Technology - 2000 (Cat. No.00EX432) ◽

10.1109/iit.2000.924121 ◽

2003 ◽

Author(s):

W. Lerch ◽

D.F. Downey ◽

E.A. Arevalo ◽

R. Ostermeir

Keyword(s):

Sheet Resistance ◽

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Low Energy ◽

Junction Depth

Download Full-text

Ultra Shallow Junction Formation by B+/BF2+ Implantation at Energy of 0.5 KEV

MRS Proceedings ◽

10.1557/proc-532-13 ◽

1998 ◽

Vol 532 ◽

Cited By ~ 1

Author(s):

M. Kase ◽

Y Kikuchi ◽

H. Niwa ◽

T. Kimura

Keyword(s):

Junction Depth ◽

Shallow Junction ◽

Enhanced Diffusion ◽

Transient Enhanced Diffusion ◽

Junction Formation

ABSTRACTThis paper describes ultra shallow junction formation using 0.5 keV B+/BF2+ implantation, which has the advantage of a reduced channeling tail and no transient enhanced diffusion. In the case of l × 1014 cm−2, 0.5 keV BF2 implantation a junction depth of 19 nm is achieved after RTA at 950°C.

Download Full-text