Transcript عرض تقديمي من PowerPoint - The Minerals, Metals

Sufian Abedrabbo
TMS Educational Resource Awards
OUTLINE

Abstract
 Introduction
 Ion Beam Mixing in Materials Research
 Experimental Setup – Ion-Beam Mixing,
Rutherford Backscattering
 Conclusions
 Acknowledgment
ABSTRACT

An overview of processes enabled by the
Availability of Accelerators (Van de Graaff) / Ion
Implanters.

In particular Results of:
- Ion Beam Assisted Surface Modification (IM) of
Semiconductors,
- Silicon-on-Insulators Formation are Briefed.
- Structural Analysis Capabilities - Rutherford
Backscattering (RBS).
INTRODUCTION

Van de Graaff accelerator is one of many types of accelerators
available today.

In a University, Accelerators / Implanters provide tremendous
capabilities:
a) Ion Beam Assisted Surface Modification (IM) is a very powerful
technique by which non-equilibrium or meta-stable alloys and intermetallic compounds on surfaces can be formed. This process is
typically preceded by low-cost layer deposition.
b) Direct Implantation of gaseous species to form an electrically
modified active region.
c) Direct Implantation of Oxygen or Nitrogen followed by a long
annealing process to form Silicon-on-Insulator.
d) Van de Graaff accelerator provides RBS capability to structurally
characterize processed samples.
APPLICATIONS
Ion-Beam Mixing in Materials Research

At Jordan University, we have utilized the Van de Graaff
accelerator in forming:
a) Silicon-Germanium structures (using - IM) that have the potential to
serve the Photovoltaic Industry, display and communication industries,
and in fabricating advanced Hetero-junction-Bipolar-ComplementaryMetal-Oxide Semiconductor (Bi-CMOS)
b) Rare-Earth Impurity Centers (using - IM) in Silicon, thus forming
promising Silicon light emitting diodes (Si-LED).
c) Silicon on Nitrides and Silicon on Oxides by direct implantation of O
and N followed by Rapid Thermal Annealing (RTA).
Experimental Setup
Schematic of a Beam-Line in a Van de Graaff Accelerator
Experimental Setup
Schematic diagram
representing the setup for
RBS and Ar-Irradiation
Experimental Setup - RBS Set-up
RBS - Fundamentals
E  kE o  E1
 k dE

 cos1 dx
Eo

x
kEo 

1 dE

cos dx
 k

1

  Eo  
  kE o   Nx
cos 2
 cos1

=   o  Nx
2
m

m
E1  M cos  1   M  sin  
k

m

Eo 
1 M


2
2
APPLICATIONS - I
Why Si-Ge !!
Si-Ge Alloys:
• Comprises 38% of the copmpound semiconductor
market competing with GaAs;
• Becoming a major player in high frequency
applications - cellular phones;
• Dominant in forming high-performance strained silicon
layers featuring high-mobility;
• Permits band gap engineering from 1.12-0.66eV;
• Ge nano-clusters (alone or when oxidized) can form
promising light emission centers and vice versa
improved photovoltaics
Temperature and concentration dependence of the fundamental
indirect energy gaps for Si1-xGex
R. Braunstein et.al,
Phys. Rev.,
pg.695, vol. 109
(1958)
Normalized photocurrent spectra for 4 samples; The energies
indicate te lowest quadratic threshold for each sample
D.V. Lang et al. Appl. Phys. Lett., pg.1333, vol.47 (12) (1985)
Experimental Details
Germanium and silicon thin films were deposited in a chamber at
a pressure of 10-4 Pa , on silicon substrates to form a multi-layer
configuration of
Sample 1
Si(Substrate)
Ge
Si
500
1000
1730
Sample 2
Si(Substrate)
Ge
Si
830
500 900
Ge
Si
500
Si(Substrate)
Ge
Si
1730
1000
As-Deposited
1E16
1E17
1400
1200
Y Axis Title
1000
800
600
400
200
0
350
400
450
500
550
X axis title
600
650
700
750
Results and Discussions





Ge peak most right, next hump surface-Si, down
edge of the step is the Si-Substrate
Small doses (1E16ion/cm2) do not change the the
structure significantly
Evidence of mixing is clear at the dose
1E17ion/cm2, Ge-peak yield is decreasing and
depth is increasing
Si peak’s yield is increasing indicating that
scattered ions from Ge are losing more energy, and
hence diffusing into substrate.
Next figure indicate the same result
Si-Peak
Top Si layer's
relative
concentration
Near-surface
relative Ge
concentration
Ge Peak
1
0.8
0.6
0.4
0
5
10
15
20
Dose (x1E16)
Near surface Ge
concentration as
function of Ar dose
25
1.2
1
0.8
0.6
0
5
10
15
20
Dose (x1E16)
Top Si layer
concentration as function
of dose.
25
RESULTS and DISCUSSIONS

Rutherford manipulation program (RUMP)
yielded:
(50nm) Si/ (50nm) Si0.99Ge0.01 / (60nm) Si0.656Ge0.328Ar0.017/ (80nm) Si
0.52Ge0.43Ar0.044/

(70nm) Si0.45Ge0.45Ar0.1/ (25nm) Si0.48Ge0.48Ar0.048
Total penetration depth agrees with the Stopping
and Range of Ions in Matter (SRIM-2003)
calculations (330nm) for multilayered Si/Ge
Structure.
Si(Substrate)
Ge
Si
830 500
Ge
Si
900 500
As-deposited
1E16
5E16
1E17
2E17
1000
900
800
Y Axis Title
700
600
500
400
300
200
100
0
350
400
450
500
550
X axis title
600
650
700
1.1
R-Peak-Ge
1
L-Peak-Ge
0.9
R-Peak-Si
0.8
L-Peak-SI
0.7
0
5
10
15
20
25
Concentration of Si and Ge layers as function of
the dose.
RESULTS and DISCUSSIONS
•
•
•
Valley between two Ge peaks diminishes
indicating mixing
The two Ge-peaks remain separated meaning
Ar+ ions pushes both layers deeper into
subsequent layer/substrate
Trailing tail of the second Ge peak (lower
channel number) shifts strongly deeper,
enhancing the background of the surface Si
RESULTS and DISCUSSIONS
•
RUMP yielded:
(30nm) Si/ (50nm) Si0.5Ge0.5/ (85nm) Si0.37Ge0.57Ar0.06/ (80nm)
Si0.6Ge0.3Ar0.1/ (60nm) Si0.07Ge0.71Ar0.21/ (40nm) Si0.83Ge0.17/(50nm)
Si0.8Ge0.2/ (100nm) Si0.9Ge0.1
•
•
•
Total actual penetration depth surpasses that
using SRIM-2003 by close to 30%. due to the
radiation enhanced diffusion (RED).
Evidence is the large shift of the trailing edge of
the Ge second peak towards deeper regions.
The second Ge layer can be used as a process
monitoring indicator
APPLICATIONS - II
Rare-Earth Impurity Centers

R.E. features have been studied in Solids for sometime.

Form base for Erbium doped Fiber Amplifiers (EDFA),
which is unavoidable in Optical communications
networks
 Proved to improve Si emission by over 10 folds *. To
put a figure on this, ST scientists are claiming an
external quantum efficiency of 10 to 20 percent, while
others talking about 0.2-6% @ RT.
*S. Coffa, F. Franzo, and F. Priolo, Materials Research
Society Bulletin, 23, pp. 25-32, (1998)
Advantages of Efficient Si-LED

Easy to integrate with other Si-based
circuitries
 Processes needed are the same as those in
electronic industry
 Upon utilizing cascading of LED high
power diodes for machinery
 Automotive industry
 Possible tunable source upon using proper
R.E. co-dopants
Rare-Earth Metals Radiative and
Non-Radiative Transitions
PREPARED SAMPLES
Si(Substrate)
Si(Substrate)
Si-Er Si
80nm 10nm
60nm
Si-Yb
Si-Er
50nm
Si(Substrate)
Si-Er
Si-Er
80nm
70nm
Ge-Si-Er
80nm
RBS Spectra of Sample # 1
RBS Spectra of Sample # 2
RBS Spectra of Sample # 3
Photoluminescence of Three Prepared Samples
Evidence of Efficient Mixing for Sample
#1, Using Ar-Irradiation
Results and Discussions

Ion-Beam Mixing proved to be an efficient,
and low-cost process to enable fabrication
of Si-Rare-Earth.
 Rare-Earth Metals concentrations above
solubility level have been achieved.
 Light output of reasonable intensity is
yielded from various structures; thus
indicating that segregation of Rare-Earth is
not dominant.
APPLICATIONS - III
Silicon-on-Insulators, Why

To enhance the performance of Si-devices, SOI is
considered, especially when recognizing that only a thin
layer from a face of the wafer is used for making the
electronic components; the rest essentially serves as a
mechanical support.

The major role of SOI is to electronically insulate a fine
layer of the mono-crystalline silicon from the rest of the
silicon wafer, beside the ever growing role of W.G.

Embedded layer of insulation enables the SOI-based chips
to function at significantly higher speeds (30 to 40% more)
while reducing electrical losses. The result is an increase in
performance and a reduction in power consumption by up to
up to 50%
Why Silicon-on-Insulators

Circuits built in SOI wafers have reduced parasitic
capacitance when compared to bulk or epi-wafers.

Useful for space application as they are immune to
radiation-induced single event upset (SEU).

Free of latch-up.

Number of masks are reduced by as much as 30%.

Lower junction leakage and higher carrier mobility.
Comparison Between Schematics of CMOS
Processed on SOI and Regular CMOS
Left CMOS transistor is directly situated on Substrate
while the CMOS built on a silicon-on-insulator substrate is
isolated. The Latter is immune to current leackage.
RBS Spectra for Si-on-Oxide and
Si-on-Nitride
Depth Profile for the Two
Prepared Samples
FT-IR Absorbance Spectra of
Si-on-Oxide Indicating Major SiO Peaks
FT-IR Absorbance Spectra of
Si-on-Nitride Indicating Major SiN Peaks
Results and Discussions

Van de Graaff accelerator has proved once again a
powerful tool for fabricating Silicon on Insulators.

Various dielectric-film structures has been
achieved with different density / porosity.

Rapid Thermal Annealing can achieve Silicon-onNitrides of high quality.
Conclusion
•A college-Based Van de Graaff Accelerator has been utilized to
process various structures by Ion-Beam Mixing and direct
implantations techniques.
•Novel Si-Ge Structures containing more than 50% of Ge have
been processed, with the possibility of annealing without
worrying about lattice mismatch problems at the interfaces due
to the method of preparation.
•Unique Rare-Earth in Silicon structures have been processed
using IM. High mixing efficiency is achieved while maintaining
above solubility level concentrations.
•Silicon-on-Insulators are processed by direct implantation of O
and N followed by RTA.
Acknowledgment

I would like to acknowledge and give my special
thanks to Mr. Khalil El-Borno for his innovation
with figures.

I am indebted to the crew of the Van de Graaff
accelerator for their continuous support

Many thanks to Dr. J.C. Hensel who supplied part
of the materials utilized in this research