1. SEMINAR PRESENTATION ON IC FABRICATION PROCESS
PREPARED BY: GUIDED BY:
VAIBHAV RAJPUT(12BEC102) Dr. USHA MEHTA
SOURABH JAIN(12BEC098)

2. CONTENTS
PROCESS OVERVIEW
DETAILED EXPLANATION OF EACH STEP
REFERENCES

3. PROCESS IN THE “REAL SENSE”

4. HOW DO THEY DO IT ?
Si used for crystal growth is purified from SiO2 (sand) through refining, fractional distillation and CVD.
The raw material contains < 1 ppb impurities. Pulled crystals contain O (» 1018 cm-3) and C (» 1016 cm-3), plus any added dopants placed in the melt.
Essentially all Si wafers used for ICs today come from Czochralski grown crystals.
Polysilicon material is melted, held at close to 1417 °C, and a single crystal seed is used to start the growth.
Pull rate, melt temperature and rotation rate are all important control parameters.

5. CZOCHRALSKI PROCESS

6. HERE SIZE DO MATTER !

7. <100> p-type is used for IC fabrication
Wafer: 10 cm to 30 cm (~4 to ~12 inches) and 1 mm thick.

8. OXIDE GROWTH Oxidation layering
-> Creates a layer of SiO2 for insulation.
Wet Oxidation uses water vapour and Dry Oxidation uses high- purity oxygen and hydrogen at ~1000 degrees C.
SiO2 growth consumes silicon, grows into the substrate.
SiO2 is twice the volume of Si, projects above the substrate as well.

9. Etched Field Oxide Isolation
First grow field oxide and then create active regions (where transistors will be created) by etching
LOCOS (Local Oxidation of Silicon)
First define active regions and then grow the oxide layers in remaining areas

10. Fabricate thin SiO2 layer adjacent to THICK SiO2 layers.
Transition from THICK to thin SiO2 layers fabricated WITHOUT creating sharp vertical transitions.

11. SPINNING OF ORGANIC COATING
Photoresist coating : A light-sensitive polymer (latex) is evenly spread (thickness 1 mm) by spinning the wafer.
Negative photoresist: Unexposed photoresist soluble in organic solvent, light exposure causes cross-linking making exposed regions insoluble.
Positive photoresist: Originally insoluble, exposure makes it soluble. Positive photoresist has higher resolution compared to negative resolution

14. n-Type Si

15. SiO2
n-Type Si

16. photoresist
SiO2
n-Type Si

17. UV-light
MASK
photoresist
SiO2
n-Type Si

18. ETCHING
Wet etching
Material is selectively removed from areas that are not covered by photoresist using acids, bases and caustic solutions.
Chemicals used here can be very dangerous to humans and the environment.
Hydrofluoric acid (HF) is used for SiO2.
Dry etching or plasma etching
popular.
Here, wafer is given a negative charge in a chamber heated to 100 degrees C under vacuum.
A positively charged plasma is introduced (usually a mix of nitrogen, chlorine and boron trichloride).
Rapidly moving plasma causes a chemical sandblasting action in the well defined direction of the electric field.
Clean vertical cuts can be etched using this method.

19. Sputtering (a)
Wet etching: by chemical like HF acid (b)
Dry etching : by plasma
Ion enhanced energetic (c)
Ion-enhanced-inhibitor(d)

20. photoresist
SiO2
n-Type Si

21. photoresist
SiO2
n-Type Si

22. SiO2
n-Type Si

23. THE NEXT BIG Q
WHAT ARE THE METHODS OF INSERTING IMPURITY ATOMS INTO Si SUBSTARTE ?
THE ANSWER IS-
1)Diffusion (impurity applied at Si surface, high temperature and long time, control of doping concentration not very precise)
2)Ion implantation (impurity applied by scanning a high energy focussed ion beam at Si surface, low temperature, acceleration, precise control of doping concentration)

24. SiO2
p-Type BORON
n-Type Si

25. p-Type BORON
n-Type Si

26. LITHOGRAPHY TECHNIQUES

27. FUTURE AGENDA 3-D IC FABRICATION PROCESS 3-D PHOTOLITHOGRAPHY
CURRENT TRENDS IN FABRICATION
SOI-THE TECHNOLOGY OF FUTURE
BLOG ON HOW IT IS MADE?

28. REFERENCES CMOS FABRICATION PROCESS BY Dr. USHA MEHTA
IC FABRICATION PROCESS- INTEL CORPORATION
IC FABRICATION PROCESS ANIMATION-
PHTOLITHOGRAPHY-
HOW WE MAKE OUR PRODUCTS BY LEXAR
HOW PROCESSORS ARE MADE FROM MICROCHIPS-

29. THANK YOU