## 4.4 Summary

### 4.4.1 Summary to: 4. Getting Started

| Semiconductor technology happens in factories. They need special materials, "reticles" (= structures), "know-how" and huge amoundt of money (= capital) as major inputs |  |
|  | It's always about money! Only mass production will recover large investments. |
|  | The materials side always contains semiconductor substrates ("wafers") and often very dangerous special "raw" materials. |
|  | A number tells it all: 500 - 1.000 wafers /day are processed in a large Si "wafer fab" |
| Three big steps to Si wafers |  |
Sand (SiO2) Metallurgical Si Poly-Si | Þ Þ Þ | Metallurgical Si clean (doped) poly-Si. Single crystal / wafer
--- | --- | ---
|  | Si single crystal growth is done by "Czochralski process" (CZ). |
|  | Dislocation-free crystals are possible but "bulk microdefects" and impurities cannot be totally avoided. |
|  | Nearly perfect 300 mm wafers are standard. |

| Growing single crystals of compound semiconductors is far more difficult than for elemental semiconductors |  |
GaAs: 150 mm wafers, encapsulation technique, disl. density (103 - 106) cm–2 GaP, InP as GaAs but smaller and more expensive SiC: 100 mm wafers, sublimation technique, several polytypes available, "pipe" defects
|  | Precise stoichiometry is important |
|  | Vapor pressures if the constituents at the melting point might be very different |
|  | New kinds of defects might be encountered |
|  | Polytypie might be encountered |  |
| Major techniques are Encapsulated CZ Sublimation growth |  |
Exercise 4.4-1
All Questions to 4.
Questionnaire
Multiple Choice questions to 4.

© H. Föll (Semiconductor Technology - Script)