Upload
themadagen
View
982
Download
3
Tags:
Embed Size (px)
Citation preview
Clean production
for (ultra) high vacuum applications
Anton de Jong, Anton Duisterwinkel
2011-03-11
Themadag Schoon Produceren
1
Cleaning : Strategy
Step by step cleaning
1. Pre cleanRemoves film, visible dirt, gross contamination.
Can be manual, industrial dish washer is preferred
2. Particle removalRemoves particles and droplets to required level
Often involves wet cleaning, ultrasonic.
Rinsing is critical.
3. Molecular cleaningRemoves last molecules,
Drives off absorbed contaminants.
Preferably done shortly before use.
2011-03-11
Themadag Schoon Produceren
2
Wet cleaningfilm removal by ultrasonic (US) cleaning
Result HV (UHV when combined with baking)
Procedure (after pretreatment)Place object well separated in rack; degas the water
Use optimized program (e.g.: ~ 50 kHz + sweep function;
low detergent concentration, 60-80 °C, 5-15 min)
Rinse plentiful with demiwater
first step with US but beware of cavitation
final step 60-80°C, but beware of oxidation
Blow dry with clean and filtered N2
Monitor program (T, t); water quality (pH, conductivity)
Damagedue to cavitation
Damage due to oxidation
2011-03-11
Themadag Schoon Produceren
3
Cleaning molecular contamination
Pre clean is a must!
(for example wet cleaning, IPA rinse)
Baking in/of vacuum system
+ standard, proven; - high T, low P
Plasma
+ relatively cool; quick - low P, crevices
Solvent and vapour degreasing
+ good for high volume - environment, k€
UV-ozon (optical components)
+ low T, 1 bar, quick - line of sight, O3
2011-03-11
Themadag Schoon Produceren
4
Bake out systems
Typical: 80-200 °C
Time : 5-50 hour
Clean air or nitrogen
Clean oven interior
Requirements bake out systems
• Stainless Steel interior
• Low or high vacuum pumping system
• Oil free: no polymers allowed (except for door seal)
2011-03-11
Themadag Schoon Produceren
5
Qualification bake out systems
How to qualify chambers?
Outgassing measurement in case of HV system
Tenax testing with absorbent and GC/MS analysis
Witness sample with NVR testing, XPS analysis or FTIR spectroscopy
Requirements:
Outgassing: PCxHy < 10-12 mbar
Tenax: < LDL
Witness sample: <LDL
2011-03-11
Themadag Schoon Produceren
6
What is a plasma?
Plasma is an ionized gas consisting of free electrons, ions, reactive
atoms, neutral molecules and photons
The plasma state can be reached by supplying sufficient energy
(heat or electric power) to a gas or mixture of gases
Cool plasma can be operated at low or at atmospheric pressures
Solid Liquid Gas Plasma
Add energy
H2O (s) H2O (l) H2O (g)
H,H2,H+,e-,H2
-
O,O2,O3,O-,O2
-H2O
2011-03-11
Themadag Schoon Produceren
7
Plasma cleaning
Plasma + -Affordable Can attack surfaces (polymers!)
Can be cool (~40°C) Needs development/application
quick not for crevices, potholes, L>D
Options
Many different gas combinations
Different plasma production technology
Caging for milder plasma
Procedure
Develop proper process
Preclean
Monitoring is not straightforward (e.g. p, T, t, gas composition)
2011-03-11
Themadag Schoon Produceren
8
Plasma generation
Typical pressure: either 0.1 and 10 mbar or 1 bar (atmospheric)
Plasma can be generated by several excitation sources:
RF (kHz and MHz)
MW (GHz)
DC
Several active species possible:
O2 (oxidative)
H2 (reducing)
Ar (sputtering)
SF6 (chemically)
He or air (atmospheric treatments)
2011-03-11
Themadag Schoon Produceren
9
Plasma generation
Materials and components to be processed need to be checked for
compatibility with active species and generation process:
O2 can damage thin layers (silver coatings)
RF fields can induce eddy currents (CD in microwave oven) and damage
electronics
Plasma can be generated remotely or object is immersed directly in
plasma. Remote plasma is more gentle and slower
From open air / small reactor to container size commercially available
(but no cleaning recipe or process included)
2011-03-11
Themadag Schoon Produceren
10
Product cleanliness qualification
Dedicated set-up built for automated
baking and testing of assemblies
(including report generation)
Small system for testing components,
materials and electronic devices
TNO TNO
Baking Small RGA set up
2011-03-11
Themadag Schoon Produceren
11
Most commonly used is a Quadrupole Mass Spectrometer
(QMS), also known as a Residual Gas Analyser (RGA)
How does a mass spectrometer work:
Ionise molecules
Filter ions according to
the mass/charge ratio
Detect ions
Rest Gas Analysis
RGA head and controller
2011-03-11
Themadag Schoon Produceren
12
Slide 12 |
RGA interpretation
Peaks can be several components and
one component can have several sources
2011-03-11
Themadag Schoon Produceren
13
Typical result of RGA measurement
Ion current per mass (one or more compo-nents)
H+ H2+ H2O
N2CO2
Logaritmic scale: ten times more H2
than CO2
Measured with total pressure gauge
2011-03-11
Themadag Schoon Produceren
14
Interpretation of RGA measurements (1)
Mass spectrum after 8h pumping(pressure corrected)
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1 21 41 61 81 101 121 141 161 181
Mass [amu]
Pre
ss
ure
[m
ba
r]
Sample + background Background
CF3+ C2F4+
C2F3O+
C2F5+C2F5O+
C3F6+
C3F5+
C3F5O+
C3F7+
C3F7O+
leak
(N2:O2~4:1 & Ar)
leak
(N2:O2~4:1 & Ar)
slight permeation
through O-ring
RGA-plot of seal with additional o-ring
Compare to background (blue)
Peaks at distinct masses point to distinct contaminants
High peaks of N2,O2 and Ar:air leaking in, butnot at “air” ratio’s
2011-03-11
Themadag Schoon Produceren
15
Results
KF 10 blind flange made from SS316 with
Laser sintering (Rapid Manufacturing)
Mass spectrum after 10h pumping(pressure corrected)
1.E-15
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
0 20 40 60 80 100 120 140 160 180 200
Mass [amu]
Pre
ss
ure
[m
ba
r]
Sample + background Background
Outgassing versus time
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
0 2 24
Time [hours]
Q [
mb
ar.
l/s
]Integrated
CxHy
Integrated (background)
CxHy (background)
2011-03-11
Themadag Schoon Produceren
16
RGA: typical uses
Qualification of vacuum systems
Compare results to requirements
Leak detection
Look for typical air peaks (N2, O2 and Ar)
Scan He for leak searching
System cleanliness
Look for CH2-bumps and specific components
Outgassing tests
Dedicated chamber with known background
2011-03-11
Themadag Schoon Produceren
17
Theoretical
efftottot SPQ *=
Total outgassing:
Water outgassing:
Hydrocarbon outgassing:
Other combinations possible
efftot
i
SPP
PQ *
200
1
18
18
∑=
efftot
i
i
HC SPP
PQ
yx*
200
1
100
44
∑
∑=
No correction for ionisation efficiencies
Results are in nitrogen equivalent pressures
Volatile hydrocarbons:
Non volatile hydrocarbons:
efftot
i
i
HC SPP
PQ
yx*
200
1
200
44
∑
∑= efftot
i
i
HC SPP
PQ
yx*
200
1
200
101
∑
∑=
2011-03-11
Themadag Schoon Produceren
18
A typical system
• Magnetic turbo for hydrocarbon free
pumping
• Granville Phillips Stabil Ion
pressure gauge
• Pump speed reduced to 25 l/s
• Pfeiffer QMG422 RGA
• Load lock
• Heated sample holder
• Electrical connections for testing
devices under power
Pult = 5*10-9 Pa
2011-03-11
Themadag Schoon Produceren
19
Measurement procedure
Vent loadlock with dry nitrogen
Open loadlock
Place sample on transporter
After 5 minutes close loadlock and
start pump
When pressure is below 1*10-4 Pa
transfer sample to Main Chamber
Start measurement for 10 hours
minimum
Background measurement performed
with empty sampleholder
Laser sintered KF10 blind flange made with Rapid Manufacturing
2011-03-11
Themadag Schoon Produceren
20
RGA: operating tips
Do NOT use RGA when total pressure > 1*10-4 mbar, this will cause
filament burn-out
If equiped with Secondary Electron Multiplier do not operate this
above 1*10-6 mbar
A RGA needs to warm up before accurate measurements can be
taken (> half hour)
Selection, use and interpretation of RGA is specialist job!
Beware: RGA is a source of
Heat (due to filament)
electric fields (due to magnetic field for separation)
Light (due to heated filament)
2011-03-11
Themadag Schoon Produceren
21
RGA: what you need to remember
Partial pressure = how much of each component makes up of total
pressure
RGA is very useful to determine gas composition (partial pressures)
Used for qualification of systems and parts and leak testing
Only determines partial pressure
Spectrum analysis is a specialist job
Years of experience and training needed
Do NOT switch on RGA when pressure > 10-4 mbar