HIgh speed semiconducror devices proccess of crystal growth and wafer slicing and preparation process

1. CRYSTAL GROWTH
AND
WAFER
PREPARATION
PRESENTED BY
M.DAVID VINOD
20304015

2. CONTENTS:
1.Introduction
2.Crystal structure examples
3. Crystal Directions and Planes
4.Defects in crystals
5. Ways of Forming Single Crystal
6. Czochralski Crystal Growth Method
7. Float-Zone Crystal Growth Method
8. Wafer Preparation
9.Wafer Identification
10. Sliced Wafers
11. Chemical Mechanical Polishing (CMP) Process
12. Preparation of silicon wafer
13. Wafer etching
14. Wafer planarization
15. Wafer polishing
16.conclusion

3. INRODUCTION
A crystal is a solid material whose
constituent atoms, molecules, or ions
are arranged in an orderly repeating
pattern extending in all three spatial
dimensions. Crystal growth is a major
stage of a crystallization process, and
consists in the addition of new atoms,
ions, or polymer strings into the
characteristic arrangement of the
crystalline lattice.

4. CRYSTAL STRUCTURE
EXAMPLES:

5. CRYSTAL DIRECTIONS AND
PLANES:

6. SILICON CRYSTAL
STRUCTURE:

7. DEFECTS IN CRYSTALS:
• Point Defects : e.g. V
acancies(V), Interstitials (I)
• LineDefects : e.g. Dislocations
• Area Defects : e.g. StackingFaults
•Volume Defects : e.g. Precipitates, Collection of V
acancies

8. WAYS OF FORMING CRYSTAL:
Natural crystal: Diamond, Jade, Ruby etc...
formed by millions of years under the earth
pressure and temperature.
Man made crystal: Si, Ge and many other
technologically important materials as well
as
engineered quantum structures.
Making of such man-made crystal is called
Crystal growth.

9. Starting material…….

10. CZOCHRALSKI CRYSTAL GROWTH
METHOD:

11. • 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.
• Seed crystal is introduced into the molten poly-EGS
to begin crystallization.
CZOCHRALSKI CRYSTAL GROWTH
METHOD

14. FLOAT-ZONE CRYSTAL GROWTH
METHOD:
This is an alternative technique which can be used for refining or
single crystal growth.

15. WAFER
PREPARATION:
• Shapingthe boule to a uniform diameter
• Formation of “Flats”alongboule’s length
• Sawingof the boule into individual wafers
• Mechanical Lappingof individual wafers
• ChemicalEtchingin a mixture of nitric and
hydrofluoric acids
• ChemicalMechanical Polishing(CMP) usinga
slurry consistingsilicondioxide particles (~ 10
nm) in aqueous solution of NaOH

16. WAFER
PREPARATION

18. SLICED WAFERS:

19. CHEMICAL MECHANICAL POLISHING
(CMP) PROCESS

20. Polished Wafer of
300 mm Diameter

21. PREPARATION OF SILICON WAFER

22. WAFER ETCHING:

23. WAFER PLANARIZATION:

24. WAFER POLISHING:

25. CONCLUSION
Thus,wafer, also called a slice or substrate , is a thin slice of semiconductor
material, such as a crystalline silicon , used in electronics for the fabrication
of integrated circuits and in photovoltaics for conventional, wafer-based
solar cells . The wafer serves as the substrate for microelectronic devices built
in and over the wafer and undergoes many microfabrication ,process steps
such as doping or ion implantation, etching, deposition of various materials,
and photolithographic patterning. Finally, the individual microcircuits are
separated and packaged.Therefore ,this presentation show how wafer can
be prepared