• Polymerization (conventional, molecular) • Plasma Polymerization, (atomic) • Competitive Ablation and Polymerization (CAP) • Plasma Sensitivity of Elements • DC Discharge Polymerization • Field Effects • Influence of Wall Contamination Processes that yield solid deposition from gas phase
• Thermal Activation – Chemical Vapor Deposition (CVD) –Hot Wire CVD – Parylene Polymerization* • Plasma Activation – Plasma Enhanced CVD (PECVD) – Plasma Assisted CVD (PACVD) – Plasma CVD or Plasma Polymerization*
• * Large amount of free radicals are found in the deposition. 2 . CH 2 CH2. CH2 CH2
CH2 CH2
n CH2 CH2 2 CH2 CH2 Trapped free radicals (dangling bonds) in plasma polymer
1500.0
1000.0
500.0
0.0 3B 3A -500.0 3F
-1000.0
-1500.0
-2000.0 Two major mechanisms of polymerization
Chain-Growth Polymerization
Step-growth Polymerization
Molecular Polymerization Need specific chemical structures Building Blocks are monomer molecules Free Radical Chain-Growth Polymerization
Initiation I• + M IM• Propagation IM• + M IMM•
• • IMn + M RM(n+1) • • Termination IMn + IMm IM(n+m)I
No free radical in the product polymer
2 free radicals and 10,000 monomers yields a polymer with the degree of polymerization 10,000 • • • • • • • • •••••••• •• • • • •
∆F = ∆H - T ∆S
S = k ln Ω −Τ ∆S term is positive for polymerization
∆Η is limited by the difference of bond energies
Polymerization does not proceed in gas phase Too many free radicals are formed in plasma, and very small amount of monomer exist in plasma phase.
The degree of polymerization decreases inversely proportional to the concentration of the initiator.
A great number of free radicals exist in plasma polymers.
Plasma polymers are formed by coupling of free radicals.
Not by the free radical chain growth polymerization
What is the mechanism of plasma polymerization? Rapid Step-Growth Polymerization (RSGP) Mechanism
Cycle 1
(1) M i·+M M i-M·
(2) M i· M i·+ · M j M i-M j
M i· (3) M i ·M k -M i + Cross-cycle reaction ·M · Plasma k (4) Excitation ·M k · ·M k ·+ M ·M k -M·
·M k ·+ · M j· ·M k -M j· (5)
Cycle 2 Plasma Polymerization
• “Atomic” Polymerization – No specific chemical structure is necessary. • Fragmentation of monomer molecule • Scrambling of atoms • Building Blocks are not the original monomer molecule, but atoms liberated by the fragmentation of monomer molecule. • Characteristic deposition rate for each element • Key parameter is W/FM in J/kg. – W is wattage, F is volume flow rate, and M is molecular weight. Typical Operational Range of Plasma Polymerization
• W/FM 10 MJ/kg – 10 GJ/kg • F & W depends on the volume of reactor – 100 Liter reactor • 1 – 10 sccm • 5 – 100 watts – The increase of F has the same effect as the decrease of W, and vise versa. • Current density in DC polymerization – Less than 1 mA/cm2, V 0.5 – 1.5 kV Input Energy & Bond Energy
• Input energy is given by W/FM in J/kg. • Specific bond energy of a molecule, which could be defined as Φ = Σ(bond energy)/M, is given also in J/kg. – Ethylene 80 MJ//kg – Tetrafluoroethylene 26 MJ/kg • When W/FM exceeds ~ 20 times Φ, plasma polymerization becomes a typical atomic polymerization, and the molecular structures play little role in determining the characteristics of plasma polymers. Contrast of Polymer Characteristics
• Conventional free-radical polymerization – Free-radical chain-growth polymerization • Linear polymer with no dangling bonds • Soluble and fusible • Positive temperature dependence of polymerization • Semi-crystalline • Plasma polymerization – Free-radical recombination step-growth polymerization • Tight three dimensional network with dangling bonds • Insoluble & infusible • Negative temperature dependence of deposition/polymerization • Amorphous C-H, Si-H, Si-C-H, etc. Electronegativity Values for Some Elements
H 2.1
C N O F 2.53.03.54.0
Si P SCl 1.8 2.1 2.5 3.0 Each Element Has Its Own Characteristic Polymerization Rate
Reactive Species in Normal Plasma and LTCAT Insulating Cathode Coolant Material Metal Channel Disk Normal plasma LTCAT
- + - -
------Arc generator CathodeSubstrate Anode Anode Plasma Substrate Jet Ground state atom Positive ion - Negative electron Excited state atom
0.4 Methane Butane HMDSO 0.3 TMDSO TMS Si 0.2
0.1
Normalized(DR), A/s*sccm C
0.0 Cascade Arc Reactor 0e+0 1e+5 2e+5 3e+5 W*(FM)c/(FM)m, W CH3
H-Si-CH3
CH3
a-SiHx a-CHx
a-(Si-C)Hx Total number of gaseous species could increase in spite of the deposition of plasma polymers depending on the fragmentation pattern.
TMS, Closed system, DC 80
60
40 Plasma off
20 System Pressure,mtorr
Plasma on 0 0 2 4 6 8 10 12 14 Discharge Time, min The change of selected RGA peak intensity with plasma time Closed System, TMS, DC
120
100
80 CH3+
60 C2H2+ HSi(CH3)2+ 40 Si(CH3)3+
Relative Intensity, % H2+ 20
0 0 100 200 300 400 500 Plasma Time, sec Change of the gas phase species changes the composition of plasma deposition
TMS, DC, Closed system (cs) and Flow system (fs)
5.0 Tcs 4.0 Tfs
3.0
2.0 C/Si Atomic Ratio
1.0
0.0 -100 200 500 800 1100 1400 1700 2000 Ar + Sputter Time (sec) Competitive Ablation and Polymerization (CAP) Principle
• Combination of two observations made in two processes aimed to achieve opposing results.
• Formation of polymers of an etching gas (CF4) in etching of silicon wafer (Kay’s group at IBM).
• Weight loss observed in plasma polymerization of C2F4 in high energy input domain (Yasuda’s group at RTI).
• Ablation and polymerization simultaneously occur in a plasma process, but the respective contribution depends on the conditions of discharge. STARTING MATERIAL Escaping from the system
(1) (4)
Stable Plasma Phase Molecules
(2) (3) MONOMER UNREACTED MONOMER
If Chain-Growth Polymerization could occur in vacuum
The structure of polymer is determined by the structure of the monomer Plasma Polymerization by Precursor Concept
STARTING MATERIAL NON-POLYMER- FORMING GASES
POLYMERIZATION
Precursor iN – Out Rule
Fragmentation of molecules in gas phase and also in solid phase, which contact with plasma, follows the rule of thumb of Nitrogen in and Oxygen out.
Oxygen incorporation into a plasma polymer and that into a plasma-treated polymer are largely due to post-plasma reaction of free radicals with oxygen.
Nitrogen has high tendency to be incorporated into a plasma polymer (not in the original forms), and N in a N2 plasma to the treated polymer.
Post-plasma incorporation of N does not occur. N found in a plasma polymer, of which monomer has no N, is due to contamination of the reactor in which N-containing monomer was used. Plasma Sensitivity Series of Elements
• Ionization of organic molecules does not follow the same path of ionization of simple atoms. • Fragmentation of an organic molecules precedes the ionization of fragmented species. • In-out rule seems to reflect the trends of plasma fragmentation of organic molecules which contain different elements other than C and H. Types of Monomers for Plasma Polymerization
• Nearly all organic and organo-metallic compounds polymerize in plasma. •Type 1 – Triple bond, aromatic & hetero aromatic •Type 2 – Double bond, cyclic •Type 3 – Linear & branched aliphatic •Type 4 – Oxygen containing aliphatic Polymerization characteristics based on the types of monomers
• Polymerization rate – Type 1 > Type 2 > Type 3 > Type 4 • Photo-emission – Type 4 > Type 3 > Type 2 > Type 1 • Free radicals in polymer substrate – Type 4 > Type 3 > Type 2 > Type 1 • Dangling bonds in plasma polymer – Type 1 > Type 2 > Type 3 > Type 4 Difference of photo-emission at the same energy input level, 40 kHz, with magnetic enhancement Type 2 Type 4 TMS TMS+O2
W/FM=722MJ/kg W/FM=762MJ/kg Correlation between photon emission and polymerization
Deactivation Photon Emission
Excitation of Deactivation a Plasma Gas Photon Emission
Excitation of Deactivation a Reactive Gas (no emission) Polymerization or Deactivation Surface Modification (no emission) Deposition Rates
Local deposition parameters (at a specific place of substrate)
k1 mass deposition rate (kg/m2 s)
ρ k2 = k1/ thickness growth rate (m/s)
ρ = specific gravity (kg/m3)
k0 = k1/FM specific mass deposition rate (1/m2) mass flow rate corrected deposition rate In the monomer deficient domain
k1 =k’ FM
k1/FM = k’ F: volume or molar flow rate
M: molecular weight of monomer In the power deficient domain
k1 = k”W
k1/FM = k” (W/FM)
k0 = k1/FM
k0 = k” (W/FM)
Deposition rate is independent of pressure Dependence of deposition rate on operational parameters and domains of plasma polymerization
120 W 5.7 cm3/min 70 W
50 W 3.1 cm3/min
1.5 cm3/min
3 0.82 cm /min 20 W 0.23 cm3/min
Dependence of deposition rate of plasma polymer of tetramethyldisiloxane on discharge wattage at the flowing monomer Dependence of deposition rate of the plasma polymer of flow rates (cm3/min). tetramethyldisiloxane on discharge power at a fixed flow rate
5.7 cm3/min
3.1 cm3/min
1.5 cm3/min
0.82 cm3/min
0.23 cm3/min
Dependence of deposition rate of the plasma polymer of Dependence of plasma polymerization domains on tetramethyldisiloxane on W/FM at different flow rates deposition rate and W/FM at various flow rates. Deposition characteristics in glow discharge, in energy deficient domain
2.5 CH 1.3sccm C H 0.7sccm 4 4 10 CH 2.9sccm C H 1.3sccm 2.0 4 4 10 CH4 5.2sccm
RF
1.5
1.0
AF
0.5
0.0 0.0 1.0 2.0 3.0 W/FM (GJ/kg) Schematic presentation of D.C. glow discharge in a plasma polymerization reactor, (a) System pressure < 6.66 Pa (50 mTorr), (b) > 13.33 Pa (100 mTorr). Distribution profile of electron temperature in an argon D.C. glow discharge in a plasma polymerization reactor Distribution profile of electron density in an argon D.C. glow discharge in a plasma polymerization reactor Dependence of DC cathodic polymerization on operational parameters
80 30
DC CH 0.7sccm 4 CH4 1.4sccm CH 2.8sccm 60 CH full size 4 4 CH 5.2sccm CH 1/4 size 4 4 20 C H full size 4 10 C H 1/4 size 40 4 10
10 20
DC 1/4 size
0 0.0 1.0 2.0 3.0 4.0 5.0 0 0.0 0.2 0.4 0.6 0.8 1.0 W/FM (GJ/kg) Current Density (mA/cm2)
80 5.0
with magnetron without magnetron CH4 full size 2.8sccm CH4 full size 2.8sccm 4.0 CH4 1/4 size 0.7sccm CH4 1/4 size 2.8sccm CH 1/4 size 1.4sccm C H full size 0.8sccm 60 4 4 10 CH4 1/4 size 2.8sccm C4H10 1/4 size 0.8sccm CH 1/4 size 5.2sccm 4 CH full size 3.0 C H full size 0.8sccm 4 4 10 CH 1/4 size C H 1/4 size 0.8sccm 4 4 10 40 C H full size 4 10 C H 1/4 size 4 10 2.0
20 1.0
DC DC 0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 2 Current Density (mA/cm2) Current Density (mA/cm ) Cathodic polymerization (deposition on the cathode surface)
k1/[CM] = kc[I] [I] : current density
k1 = kc[I][CM] [CM] : mass concentration
k1 = k’c[I] p p : system pressure Deposition rate is dependent on pressure and independent of flow rate. 2.6
DC 2.4
2.2 DC with magnetron
CH4 full size CH 1/4 size 2.0 4 C4H10 full size C4H10 1/4 size DC without magnetron
1.8 CH4 full size CH 1/4 size AF 4 C4H10 full size C H 1/4 size 1.6 4 10 AF
RF RF 1.4 0.0 1.0 2.0 3.0 4.0 5.0 W/FM (GJ/kg) Si wafer w/ electrical contact
3000 DC 2500 AF RF 2000
1500
1000
500 Deposition Rate, A/min Rate, Deposition 0 0 20 40 60 80 100 120 System Pressure, mTorr
The system pressure dependence of deposition rate of TMS on Si wafer with electrical contact to the substrate as powered electrode in DC cathodic polymerization, AF (40 kHz) and RF (13.5 MHz) plasma polymerization processes. Plasma conditions are 1 sccm TMS, 5 W power input. DC
3000 Si on cathode w/ 2500 electrical contact Si on cathode w/o 2000 electrical contact Floating substrate 1500
1000 Deposition Rate, A/min Deposition
500
0 0 20 40 60 80 100 120 System Pressure, mTorr
The system pressure dependence of deposition rate of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in DC cathodic glow discharge polymerization,. Plasma conditions are 1 sccm TMS, 5 W power input. DC
1.9
1.8
1.7
1.6
1.5 Refractive Index
1.4 Si on cathode w/ electrical contact Si on cathode w/o electrical contact 1.3 Floating substrate 0 20 40 60 80 100 120 System Pressure, mTorrr
The system pressure dependence of refractive index of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in DC cathodic glow discharge polymerization,. Plasma conditions are 1 sccm TMS, 5 W power input. AF
2000 Si on electrode w/ electrical contact 1500 Si on electrode w/o electrical contact Floating substrate 1000
500 Deposition Rate,A/min
0 0 20 40 60 80 100 120 System Pressure, mTorr
The system pressure dependence of deposition rate of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in AF plasma polymerization processes. Plasma conditions are 1 sccm TMS, 5 W power input. AF
1.9
1.8
1.7
1.6
1.5 Refractive Index
1.4 Si on electrode w/ electrical contact Si on electrode w/o electrical contact Floating substrate 1.3 0 20 40 60 80 100 120 System Pressure, mTorr
The system pressure dependence of refractive index of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in AF plasma polymerization processes. Plasma conditions are 1 sccm TMS, 5 W power input. RF
100
80 Si on electrode w/ 60 electrical contact Si on electrode w/o 40 electrical contact Floating substrate 20
Deposition Rate, A/min Rate, Deposition 0 0 20 40 60 80 100 120 System Pressure, mTorr
The system pressure dependence of deposition rate of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in RF plasma polymerization processes. Plasma conditions are 1 sccm TMS, 5 W power input. RF
1.9
1.8 Si on electrode w/ electrical contact Si on electrode w/o electrical contact Floating substrate 1.7
1.6
1.5 Refractive Index
1.4
1.3 0 20406080100120 System Pressure, mTorr
The system pressure dependence of refractive index of TMS on Si wafer with electrical contact and without electrical contact to powered electrode or floating substrate in RF plasma polymerization processes. Plasma conditions are 1 sccm TMS, 5 W power input. 250 2 On Anode surface
200 1.8
150 1.6
100 1.4
DR, A/min Refractive Index
Deposition Rate, A/min Refractive Index 50 1.2
0 1 0 20 40 60 80 100 120 System Pressure, mTorr
The pressure dependence of plasma polymer deposition rate and Refractive index in TMS DC polymerization (on anode). Conditions are 1sccm TMS, DC 5 W. 250
200
150
100 Deposition Rate, A/min 50 50 mTorr 100 mTorr 0 -10 -5 0 5 10 (a) Vertical Posistion, cm
The plasma polymer deposition profile on anode surface in TMS DC cathodic polymerization. Conditions are 1sccm TMS, DC 5 W. 1200
1000 15.2 cm 800 Cathode 3 cm 7.6 cm 600 Floating Substrate 2 cm
400 17.8 cm Anode Deposition Rate, A/min 200
0 -10 -5 0 5 10 Vertical Position, cm
1/2 piece of Al panel in front of Anode
The effect of the floating panels positioned in front of the anode on the deposition rate on Anode surface and Cathode surface in DC cathodic polymerization. Conditions are: 1 sccm TMS, 50 mTorr, DC 5 W, d = 100 mm. 1200
1000
15.2 cm 800 Cathode 3 cm 15.2 cm 600 Floating 2 cm Substrate 400
Deposition Rate, A/min 17.8 cm Anode 200
0 -10 -5 0 5 10 Vertical Position, cm
1 whole piece of Al panel in front of Anode
The effect of the floating panels positioned in front of the anode on the deposition rate on Anode surface and Cathode surface in DC cathodic polymerization. Conditions are: 1 sccm TMS, 50 mTorr, DC 5 W, d = 100 mm. Dark polymerization in cathode region & plasma polymerization in the negative glow
• Dark polymerization (on the cathode surface) – Much faster polymerization – Yields film with high refractive index – Deposition rate is pressure-dependent. • Glow discharge polymerization (on floating surface) – Slower polymerization – Yields film with lower refractive index – Deposition rate is flow-rate dependent (pressure-independent) • Anode is a passive surface, which collects the same glow polymers. Effect of Electrical Field
• Edge effect – Sputtering by Ar plasma – Deposition on the cathode surface • Un-balanced surface areas of cathode and anode – Deposition rate onto a small cathode or powered electrode is higher. • Effect of magnetic confinement – Reduce the edge effect on sputtering – Over correct the edge-effect in the depositon Schematic diagram of bell jar reactor system Structure of anode magnetron electrode Oxygen DC plasma without magnetron enhancement Oxygen DC plasma with anode magnetron Temperature of cathode (substrate) & anode
Substrate Temperature 300 Plasma Treatment Evacuation [2B](Ace/O)/T [2B](Ace/AH)/T
) 269 [7B](Ace/O)/T 250 149 (Ar+H2, 80 watts, 50 mtorr ) [7B](Ace/AH)/T [2B](Alk)/T
TMS Monomer Start [2B](Ace/AH)/T 200 188 C) o Evacuation Cathodic Ecoat (
150 Plasma Polymer Deposition
Anodic Ecoat (107) (O2 , 40 watts, 100 mtorr )
100Temperature ( Anode Temperatur
40 50 28 25
0 0 5 10 15 20 25 30 35 Time (min) Sputter Cleaning of Cathode Coated with TMS Plasma Polymer Sputter Cleaning of Cathode Coated with TMS Plasma Polymer
(a): The CRS Panel Coated by TMS Plasma (70 nm)
Cleaned Steel (Fe)
(b): Interelectrode (c): Interelectrode distance of 50 mm distance of 100 mm or 75 mm to 175 mm
Schematic diagram of different magnetic field configuration. • parallel magnetic field configuration (PM), • (b) opposite magnetic field configuration (OM) and • (c) no magnetron on the backside of anode electrodes. 2000 1800 DC PM DC OM 1600 DC NM 1400 1200 1000 800 600 400 200
Deposition rate (Å/min.) 0 0 1020304050607080 Radial distance (mm)
Dependence of the deposition rate distribution on the magnetic field configuration (DC, TMS, 5 w, 50 mtorr, d=100 mm, 1 sccm) 1000 900 AF PM AF OM 800 AF NM 700 600 500 400 300 200
Deposition rate (Å/min.) 100 0 0 1020304050607080 Radial distance (mm)
Dependence of the deposition rate distribution on the magnetic field configuration (AF, TMS, 5 w, 50 mtorr, d=100 mm, 1 sccm) 500 450 RF, PM 400 RF, OM 350 RF, NM 300 250 200 150 100
Deposition rate (Å/min.) Deposition rate 50 0 0 1020304050607080 Radial distance (mm)
dependence of the deposition rate distribution on the magnetic field configuration (RF, 5 w, 50 mtorr, d=100 mm, 1 sccm) 2000 1800 DC 1600 AF 1400 RF 1200 1000 800 600 400
Deposition rate (Å/min.) 200 0 0 1020304050607080 Radial distance (mm)
Dependence of deposition rate on power supplies (OM, TMS, 50 mtorr, 1 sccm, 5 w, d = 100 mm) 2000 1800 PM, d=100 mm 1600 PM, d=80 mm 1400 PM, d=60 mm 1200 PM, d=40 mm 1000 OM, d=100 mm 800 600 OM, d=80 mm 400 OM, d=60 mm
Deposition rate (Å/min.) 200 OM, d=40 mm 0 020406080 Radial distance (mm)
The influence of electrode distance on the deposition rate (DC. TMS, 50 mtorr, 1 sccm, 5 w) 1400 AF, PM, d=100mm
1200 AF, PM, d=80 mm AF, PM, d=60 mm 1000 AF, OM, d=100mm
800 AF, OM, d=80 mm AF, OM, d=60 mm 600 RF, PM, d=100mm
400 RF, PM, d=80 mm RF, PM, d=60 mm 200 Deposition rate (Å/min.) rate Deposition RF, OM, d=100 mm
0 RF, OM, d=80 mm 0 1020304050607080 RF, OM, d=60 mm Radial distance (mm)
The influence of electrode distance on the deposition rate (AF or RF, TMS, 50 mtorr, 1 sccm, 5 w) 2000 6*6 inch2 PM 1800 6*6 inch2 OM 1600 6*6 inch2 NM 1400 3*6 inch2 PM 3*6 inch2 OM 1200 3*6 inch2 NM 1000 800 600 400
Deposition rate (Å/min.) 200 0 0 1020304050607080 Radial distance (mm)
The influence of substrate area on the deposition rate (DC, TMS, 50 mtorr, 1 sccm, 5 W) 900 6*6 inch2 PM 800 6*6 inch2 OM 700 6*6 inch2 NM 600 3*6 inch2 PM 500 3*6 inch2 OM 400 3*6 inch2 NM 300 200
Deposition rate (Å/min.) 100 0 0 1020304050607080 Radial distance (mm)
The influence of substrate area on the deposition rate (AF, TMS, 50 mtorr, 1 sccm, 5 W) 2500 p=30 mtorr, OM 2000 p=50 mtorr, OM 1500 p=100 mtorr, OM p=30 mtorr, 1000 NM p=50 mtorr, 500 NM p=100 mtorr, NM Deposition rate (Å/min.) 0 0 1020304050607080 Radial distance (mm)
Dependence of deposition rate distribution on system pressure DC glow discharge (TMS, 5 W, d=100 mm, 1 sccm) 1600 p=30 mtorr, 1400 OM p=50 mtorr, 1200 OM 1000 p=100 mtorr, OM 800 p=30 mtorr, 600 NM p=50 mtorr, 400 NM 200 p=100 mtorr, NM 0 Deposition rate (Å/min.) 0 1020304050607080 Radial distance (mm)
dependence of deposition rate distribution on system pressure AF glow discharge (TMS, 5 W, d=100 mtorr, 1 sccm). 1400
1200
1000
800
600
400 d = 60 mm
Deposition Rate, A/min Rate, Deposition d = 100 mm 200 d = 160 mm no anode assembly 0 0 1020304050607080 Vertical Position, mm
The influence of electrode distance on the deposition rate on Cathode surface in DC cathodic polymerization. Conditions are: 1 sccm TMS, 50 mTorr, DC 5 W, d is the distance between two anodes (the cathode is placed in the middle of the two anodes). Effect of Wall Contamination
• Because of CAP principle, wall contamination could change the deposition pattern. • Elements with high electro negativity in the wall contamination cause the most pronounced change in the deposition. – Change from the super adhesion system to no adhesion system caused by F containing wall contaminants. Scanned image of the surface of two alloy panels showing adhesion failure caused by the omission of O2 plasma treatment of the substrate prior to plasma film deposition and application of the primer (Deft 44-GN-72 MIL-P-85582 Type I Waterbased Chromated ® Control Primer). a) Panel after Skydrol LD4 fluid resistance test, which had the O2 plasma treatment prior to film deposition and primer application. b) Panel after scribed wet (24- hour immersion in tap water) tape test, which had not been treated with the O2 plasma treatment prior to film deposition and primer application. Sequence of processes in the normal operation
Evac./O2 /TMS /(HFE+H2)/ Evac./ O2 / TMS /(HFE+H2)/
New substrate New substrate
The first batch The second batch
Sequence of Plasma Polymerization
TMS Plasma/(HFE+H2) Plasma Sequence of processes in the abnormal operation
Evac./TMS /(HFE+H2)/ Evac./ TMS /(HFE+H2)/
New substrate New substrate
The first batch The second batch
Sequence of Plasma Polymerization
(HFE+H2) Plasma/TMS Plasma
Previous batch Plasma polymer
Spray primer
Al alloy Adhesion failure occurred at the interface of the plasma polymer and the substrate alloy
XPS Analysis 1.4
Plasma polymer adhering to metal 1.2 surface
1
0.8
0.6 Plasma polymer/metal
Silicon/Carbon Ratio interface Delaminated paint 0.4
0.2
0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Ar+ Sputter Time (sec) 30 HFE Line Disconnected O2 or Ar plasma treated no plasma treatment 25
20 Liquid N2 Trap Reactor Cleaned 15 Pump Oil Changed 10 Approximate Fluorine Atomic % Fluorine Atomic Approximate 5
0 0 5 10 15 20 25 30
Date of Sample Preparation, days Formation of stable molecules in plasma • Stable molecules escape from the system. • Stable molecules shorten the kinetic-path length of plasma polymerization. – Increase the oligomer content in plasma polymer. – Change elemental composition of plasma polymer. • Stable molecules formation change the balance of ablation and polymerization. – Stable molecules formation such as SiF4 is the basis for plasma etching of silicon, and HF for polymerization of etching gas. – Depending the source of element to form stable molecules, adhesion and/or barrier characteristics of plasma polymer could be completely damaged. Si In Plasma C Placing a new substrate in a contaminated reactor
Substrate F C
Reactor Wall Evacuation of Reactor
Migration of oligomeric contaminants, and chemi-sorption on the substrate
Substrate
Reactor Wall Si C
In Plasma
F C O2 plasma treatment of contaminated substrate
CO2
O2
F C Si C In Plasma
Plasma- Inablatable F
Substrate or plasma polymer