Clean Room, Lab safety Nano Lab tour. David Haviland Nanotechnology SU course FK7018 KTH course SK2730

Transcription

1 Clean Room, Lab safety Nano Lab tour. David Haviland Nanotechnology SU course FK7018 KTH course SK2730

2 Fabrication in a Machine Shop Making hand held parts out of metal, ceramics with cutting tools, lathe, welding, etc. Oil and Grease, metal flakes and shavings, dust dirt and grime!

3 Fabrication in a Nano Lab Very small structures made with Lithography One small dirt grain can spoil a sample.

4 Molecular Self Assembly Clean, very flat crystalline surfaces, very sensitive to contamination. Assembly of molecules in a solvent on the surface. Jonas Rundqvist,Nanostructure Physics, KTH

5 What is a clean room? Minimizing airborne particles Minimizing particles on surfaces

6 Side view of industry standard clean room This is the basic design of the facility MC2 at Chalmers

7 high grade clean room suite, bunny suite Intel Corporation About 43 steps to put on before you enter!

8 Albanova Nano Fab Lab Simpler clothing: coat, shoes and hair cover.

9 Sample Yield and Clean room requirements Probability of good sample depends on clean room standard Sample handling procedure critical area of sample and stage of process If this piece of dirt lands on the sample after a critical stage, the device may still work Pentium chip with 106 transistors in 1cm2 has much more stringent requirements than one, single electron transistor which occupies area (100 nm)2 Yield = Money. Clean room is expensive. Required level of clean room determined by cost benefit analysis.

10 Cost of Yield Analysis a rational approach to your work Your time is money how much do you cost? You lab costs money how much does it cost (equipment, space)? What is your required yield? Research: a small number of working samples Industry: the volume needed by the market Ways to reduce cost and increase yield Standardize structures (e.g. contacts) wafer process these. Use photo lithography (parallel) when you can, E beam lithography (serial) only for high resolution. Make many structures in one process step, use parameter spreads. Know and understand you tools learn the theory of operation. For an Industry example of COY see

11 Albanova Nano Fabrication Facility 320 m2 total, 270m2 clean environment, paying users Laminar flow benches Light Microscopes Wet bench, hood 2 Photo Lithography Surface Profilometer 3 Reactive Io Etchers E beam lithography Scanning Probe Microscope Scanning Electron Microscope Focused Ion Beam System 4 Vacuum Deposition Systems Wire Bonder ~30M SEK of equipment K A Wallenberg Foundation

12 Albanova Nano Fab Lab Process lab for chemical work, sample handeling Pre filter Fan HEPA HEPA Service area HEPA Over pressure indicator Door Over pressure Sticky mat Over pressure (less)

13 Albanova Nano Fab Lab Fume hood and laminar flow benches deminish the over pressure. Important to close fume hood and shut off benches after use! Fume hood Laminar flow bench with partial exhaust Laminar flow bench with partial exhaust

14 Close fume hood after use. Do not open more than safety level!

15 Homework Problem The clean room fume hood exhaust air at a maximum rate of 350 liters/min, (at standard temperature and pressure, i.e. 300 K, 1 Atm. ) This air is vented directly to the outside world. Assume that the air is replaced by cold air from the outside at 0 deg. C, which needs to be warmed up to room temperature of 20 deg. C. Calculate the energy wasted when a careless user leaves the hood full open overnignt. Give your answer in kwhr.

16 Albanova Nano Fab Lab Deposition and E beam lithography labs AC unit AC unit Over pressure indicator E beam and SPM Deposition Service room

17 HEPA filters High Efficiency Particulate Air filter captures 99.97% airborne particles 0.3 microns in diameter at 85 litres per minute (Lpm). It is not only acting like a sieve, Particles coming within one radius of a fiber gets caught, interception. Larger particles embed in fibers due to curving air stream, inertial impaction. Brownian motion (diffusion) of smaller particles (<0.1 um) causes them to have higher probability to get caught on a fiber,

18 Air filter modules In process lab, above mask aligner and projection mask camera

19 Laminar flow (clean air) benches, with partial exhaust Local clean areas, lowest particle count

20 Laminar flow (clean air) benches, without partial exhaust

21 Do not block air intake of laminar flow benches Air barrier at front protecting the inner clean volume

22 Particle count in Albanova Nano Lab

23 Particle counter Sample inlet Sensor Control electronics Flow monitor Filter Outlet Pump

24 Clean room standards US FED STD 209E cleanroom standards particles/ft³ Class 0.1 µm 0.2 µm 0.3 µm 0.5 µm 5 µm ,000 1, ,000 ISO cleanroom standards 10, particles/m³ 100,000 Class 0.1 µm 0.2 µm 0.3 µm 0.5 µm 1 µm 5 µm 100, ISO ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 1, , ,000 1,000, ,200 2,930 2,370 23, ,000 1,020 10, , ,520 35, , ,000

25 Storage and use of chemicals All bottles must be clearly labeled with their contents, even harmless substances (e.g. H2O). A labeler is available. Bottles must be tightly sealed and stored in a ventilated cabinet. Used chemicals put in proper waist container. Handel so that you do not breathe fumes (use in hood). Use eye protection always as a habbit. Know where emergency shower is. Think about what you are doing, take your time, don t rush. If you don t know what you should do ASK and LEARN

26 Think about this... Acids can BURN Solvents EXPLODE Use thick latex golves, with long arm and wrist covers. Don t spill, slow and careful. If spill evacuate, notify manage. Wear eye protection goggles. A small drop on your shirt will burn a big hole. Will burn the skin, black mark, pain. Rinse with water. When mixed with air (oxygen) small spark sets off a bomb. Solvent on hot plate = fumes = explosion risk. Fumes are dangerous to breath. Acetone slightly carcinogenic, eats latex gloves. IPA is much more mild us it when you can.

27 Clean Water for many processes De ionized water, Albanova supply Millipore MilliQ Academic, 18 Mohm cm, 1.5 liter / min Millipore Elix 3, Mohm cm, 3 liter / min, 30 liter tank, tap outlet in one laminar flow bench

28 Cleaning Routine for Nano Lab Central vacuum hose facility, exhaust in service corridor. Cleaned every other week with lintfree wipes and special detergent. All floors are vacuumed and wiped. All horisontal surfaces are wiped. Work surfaces are always clutter free users responsible for cleaning Work in progress is labelled with a lint free cloth, write on it when you will return to clean it up. A clean lab is a safe lab.

29 Some Basic Work Routines Leave ordinary shoes before bench in entrance, step over bench in entrance. Change to coat, clean shoes and put on hair cover. Wear clean room gloves when necessary (handling vacuum parts, samples). Wash up used glass ware, de ionized water and detergent Wipe off spill from work surfaces, avoid acetone on plastic, yellow film Do not leave glass ware in or beside sink, hang up to dry Do not leave glass ware, etc. in fume hood, very limited space Waste baskets may be overfull, please empty them Change of garments and many users make personal hygiene more noticeable Notify the lab manager when general supplies nearly run out Knowing how to use a machine means knowing what state to leave it in.