4th Lecture Second Semester
4th Lecture Second Semester
4th Lecture Second Semester
Topics:
•Chemical Vapor Deposition
•Physical Vapor Deposition
•Evaporation
•Sputtering
•Strengths and Weaknesses
•Basic Calculations
Issues related to thin film deposition
• Quality:
– Composition
– Defect density (e.g. pinholes)
– Contamination
– Mechanical and electrical properties
– Good adhesion
– Minimum stress
• Topography
– Uniform thickness on non-planar surfaces
– Step coverage
– Conformal coverage: uniform
– Space filling in holes, channels
– Voids
Thin film filling issues:
(a) shows good metal filling of a via or
contact hole in a dielectric layer
(b) silicon dioxide dielectric filling the SEM photo showing typical coverage and
space between metal lines, with poor filling problems
filling leading to void formation
(c) poor filling of the bottom of a via
hole with barrier or metal
Classification of Thin Films
xylene + [Fe(C5H5)2]
Revap
Fk cos k
r 2
Revap
v cos k cos i
Geometries of flux and deposition of small areas on a flat
wafer holder for (a) a point source and (b) a small planar Nr 2
surface source
1/ 2
m 2
Revap 5.83 10 As Pe
T
Deposition rate of evaporated film as function of
position on substrate for point and surface sources. i
= k in this configuration for both point and surface
sources.
kT
Mean free path l: l
2d 2 Pe
k = 1.36 x 10-2 erg/at-K
d≈.4 x 10-8 cm
Pe = partial pressure (torr)
http://en.wikibooks.org/wiki/Microtechnology/Additive_Processes
DC Sputtering
DC Sputtering Schematic
RF Sputter Deposition
RF Sputtering Schematic
Reactive Sputtering
Elements of Thin Film Growth
Growth Modes
Microscopic View of
• Sputtering
The impact of an atom or ion on a surface produces
sputtering from the surface as a result of the
momentum transfer from the incoming particle. Unlike
many other vapor phase techniques there is no melting
of the material.
• History of Sputtering
– The verb to SPUTTER originates from Latin SPUTARE(To
emit saliva with noise).
– Phenomenon first described 150 years ago ...
Grove (1852) and plücker (1858) first reported vaporization
and film formation of metal films by sputtering.
– Key for understanding discovery of electrons and positive
ions in low pressure gas discharges and atom structure (J.J.
Thomson, Rutherford), 1897--
– Other names for SPUTTERING were SPLUTTERING and
CATHODE DESINTEGRATION.
ref: www.gencoa.com
Target Erosion
ref: www.lesker.com
The Latest in UHV Sputtering
http://www.ajaint.com
• A UHV, magnetron sputter source that fits through the port of a 2.75" CF flange
complete with its tilt gimbals assembly.
• The AJA International new A310-XP only needs a 2.75" CF to accommodate the
source head, tilt gimbals and gas injection/isolation chimney.
• This revolutionary new design is true UHV - all ceramic to metal construction.
Ion Implantation
Topics:
•Deposition methods
•Implant
-Depth & Distribution
-Masking effects
•Damage annealing
Manufacturing Methods
Applying a magnetic induction,
B, to speeding atoms causes
them to bend around the curve
of radius R:
½ mv2 = q.v x B
Velocity can be expressed as:
v = √(2E/m) = √(2qVext/m)
B can be expressed as a
Schematic of an ion implanter function of current:
Ion source: Vaporized solids or gases – e.g., - B = aI
- Arsine
Vapors form various species, suchThus
- Phosphine ++ + + +
as B , B , BF , BF2 , along with
neutral atoms √m = q/√2E(aR)I
- BF2
By adjusting current, I, ions
These gases are extremely toxic! Mixed in can be separated by mass
15% concentrations with H2
Neutrals are separated by the electrostatic
deviation of the focus beam
x R p 2
C ( x) C p exp
2 DR
p
2
C ( x, y ) Cvert ( x) exp
y
2DR p2
( x R* ) 2
C * ( xm ) C *p exp C
m p
*2
2DR p B
C *p
xm R*p DR*p 2 ln R*p mDR*p
C
Schematic of masking process, where B
dose Qp penetrates the mask of
thickness xm. * denotes mask 2
Q
x R *p
*
Qp exp dx
2DR p xm 2DR p
*
x Rp
Q
Q 2
C (0, t )
C ( x, t ) exp 2 Dt
2 DR p 2 Dt
2
2 D R 2
p 2 Dt
Actual distributions
Simulation of recombination of
vacancy (V) and interstitial (I) Si interstitials condense into ribbons
damage resulting from of Si atoms (I-dimers) lying on {311}
implantation. At 800 oC, planes and grow by extending in the
recombination takes place very <110> directions. On right is a TEM
quickly. After a short time, only image of clusters
excess interstitial clusters remain
At high temperatures, ribbons condense and grow, creating dislocation
loops that populate the boundary between crystalline and amorphous
silicon.
63
Implantation Processes: Anneal
64
Thermal Annealing
73
Rapid Thermal Annealing (RTA)
Light Ion
Damaged Region
Heavy Ion
75
Implantation Processes: Damage
• Ion collides with lattice atoms and knock
them out of lattice grid
• Implant area on substrate becomes
amorphous structure
76