crystal structure ,crystal growth and wafer preparation process.

1. Crystal Growth and
Wafer Fabrication
Mr. Imran Ahmad
Assistant Professor
JETGI

2. Crystal Structure
Crystals are characterized by a unit cell which repeats in
the x, y, z directions.

3. Silicon Crystal Structure

4. Defects in Crystals
I. Point Defects e.g. Vacancies (V), Interstitials (I)
II. Line Defects e.g. Dislocations
III. Area Defects e.g. Stacking Faults
IV. Volume Defects e.g. Precipitates, Collection of Vacancies

6. Czochralski Crystal Growth Method

7. 1. Essentially all Si wafers used for ICs today come from
Czochralski grown crystals.
2. Polysilicon material is melted, held at close to 1417
°C, and a single crystal seed is used to start the
growth.
Czochralski Crystal Growth Method
3- Pull rate, melt temperature and rotation rate are all
important control parameters.

9. Wafer Preparation

10. Chemical Mechanical Polishing (CMP)
Process