Introduction to Cleanroom

Transcription

1 ECE 541/ME 541 Microelectronic Fabrication Techniques MW 4:00-5:15 pm, Taft Hall 204 Introduction to Cleanroom Zheng Yang ERF 3017, Page 1

2 Semiconductor manufacture particulate contamination. A 2µ x 2µ molecular contaminant captured on KLA-Tencor 8100 CD SEM at 75kX magnification. A 6µ x 6µ molecular contaminant captured on KLA-Tencor 8100 CD SEM at 25kX magnification A 2µ x 2µ molecular contaminant captured on KLA-Tencor 8100 CD SEM at 75kX magnification Page 2

3 The nature of particulate contamination.continued. Page 3

4 Environmental Abundancy The smaller the diameter, the more aerosols are there! The smaller the structures, the harder it is to provide a clean environment. Page 4

5 Federal Standard 209E The number of 0.5μm-diameter-particles in 1 m 3. Particles per cubic foot Particle Size (Microns) Page 5

6 Airborne particulate cleanliness, English system, Fed. Std. 209E Class Chart gives maximum number of particles in a given size range per cubic foot E E E E E E E E E E E E E E E E E+02 # of particles per cubic foot 1.00E E E E E E Particle size (micron) Class 1 Class 10 Class 100 Class 1000 Class Class 100,000 Page 6

7 Metric classification of airborne particulate cleanliness (Fed. 209e). Particles per cubic meter 1.00E E E E E E E E Particle size (micron) M1 M1.5 M2 M2.5 M3 M3.5 M4 M4.5 M5 M5.5 M6 M6.5 M7 Page 7

8 SIA Roadmap for particulate contamination. Page 8

9 Mechanism for particulate filtration. Page 9

10 Filtration efficiency. Page 10

11 Filtration efficiency. Page 11

12 Construction of HEPA filter. Page 12

13 HEPA filter construction. Page 13

14 HEPA filter construction alternate design. Page 14

15 HEPA filters: examples. Page 15

16 Examples of HEPA filtration. Before filtration. After filtration. Page 16

17 Cleanroom Evolution Dry Wet VLF (Vertical Laminar Flow) Hoods (1970 s) Also HLF existent Stand next to each other to pass wafers along inside Page 17

18 Back to the Ballroom Design Back to the Ballroom Design because of more processing steps and more stations. Air Circulation at low speed. (1990 s) Page 18

19 Conventional cleanroom technology: The ballroom concept. Page 19

20 Conventional cleanroom technology: Flow diagram. Page 20

21 Conventional cleanroom: Air supply area. Page 21

22 Cleanroom technology: Mini-environment concept. Page 22

23 Implementaton of mini-environment concepts. Page 23

24 Smif Pods and Mini-Environments Mid 1980 s developed by HP (Agilent) Page 24

25 Mini-Environment System Page 25

26 Mini-environments.example. Page 26

27 Transporting Wafers Page 27

28 Page 28

29 Measurements of particulate contamination. Particle Measuring Systems model 7625 Condensation particle counter. Detectible particle size: 20nm. Concentration range: 2000 particles/sec. Concentration range: 10 6 particles/ft. 3. Page 29

30 Condensation particle counter example. Biral scanning mobility particle Sizer. Page 30

31 Beta attenuation counters. Page 31

32 Page 32

33 This image cannot currently be displayed. Do s and Don t s Page 33

34 Clothing for semiconductor manufacturing environment. Page 34

35 Entering the Cleanroom Adhesive Floor Mats Gowning Area Air Pressure Issues Shoe Cleaner Glove Cleaner Air Shower Double Door Pass Through Static Control Page 35

36 Clothing for clean room: Bunny Suits Page 36

37 Gowning Procedure Page 37

38 Page 38

39 Page 39

40 Page 40

41 Page 41

42 Page 42

43 Page 43

44 Page 44

45 Page 45

46 Static Control Page 46

47 Wafer Cleaning Etch: initial SC-1 Removes Organics SC-2 Removes Alkali Ions, Hydroxides, Metal Complexes 10 Times more diluted they also work fine Page 47

48 1. NH 3 + H 2 O 2 2. HF Wafer Cleaning 3. HCl + H 2 O 2 Most wafer manufacturers use a final cleaning method developed by RCA in The 3-step process starts with a solution of ammonia, hydrogen peroxide and RO/DI water to remove organic impurities and particles from the wafer surface. Next, natural oxides and metal impurities are removed with hydrofluoric acid, and finally, a solution of hydrochloric acid and hydrogen peroxide causes clean new natural oxides to grow up on the surface. Page 48

49 Cryocleaning CO 2 expands and cools down, which ablates dust more efficiently than compressed air Page 49

50 Water Flow Rinsing Controlled flow direction prevents contamination to come from one wafer to the next Page 50

51 Spray-Dump Rinsing The surface of any liquid is usually much dirtier than its bulk. Spraying removes dirt from the wafers, after they are pulled through the surface Page 51

52 Ultrasonic/Megasonic Cleaning Ultrasonic -> 20-50kHz -> Cavities in Water (Bubbles) Megasonic -> 850 khz -> Mobilizes Surface Hydration Layer Page 52

53 Page 54

54 Mind the amount! Page 55

55 Water Oxygen Hydrogen Nitrogen Particles/liter Page 56

56 Clean Design Consideration Page 57

57 Oxidation Layering. Oxidation layering produces a thin layer of silicon dioxide, or oxide, on the substrate by exposing the wafer to a mixture of highpurity oxygen or water at ca C (1800 F). Page 58