### 5.1.6 Summary to: 5.1 Basic Considerations for Process Integration

| Integration means: |  |
It ain't easy!
|  | 1. Produce a large number (up to 1.000.000.000) of transistors (bipolar or MOS) and other electronic elements on a cm2 of Si |
|  | 2. Keep thoses elements electrically insulated from each other. |
|  | 3. Connect those elements in a meaningful way to produce a system / product. |
| An integrated bipolar transistor does not resemble the textbook picture at all, but looks far more complicated Þ. |  |
|  | This is due to the insulation requirements, the process requirements, and the need to interconnect as efficiently as possible. |
|  | The epitaxial layer cuts down on the number of critical diffusions, makes insulation easier, and allows a "buried contact" structure. |
| Connecting transistor / elements is complicated; it has to be done on several levels |  |
|  | Materials used are Al ("old"), Cu ("new"), W, (highly doped) poly-Si as well as various silicides. |
|  | Essential properties are the conductivity s of the conductor, the dielectric constant er of the intermetal dielectric, and the resulting time constant t = s · er that defines the maximum signal transmision frequency through the conducting line. |
| Integrating MOS transistors requires special measures for insulation (e.g. a field oxide) and for gate oxide production |  |
|  | Since a MOS transistor contains intrinsically a capacitor (the gate "stack"), the technology can be used to produce capacitors, too. |
| CMOS allows to reduce power consumption dramatically. |  |
|  | The process, however, is more complex: Wells with different doping type need to be made. |
| Using the third dimension (depth / height) might become necessary for integrating "large" structures into a small projected are (example: trench capacitor in DRAMs Þ). |  |
|  | Unwanted "topology", however, makes integration more difficult. |
|  | Planarized technologies are a must since about 1995! Þ |
| It ain't neither easy nor cheap! |  |
Property | Number
Feature size | 0,2 µm
No. metallization levels | 4 - 7
No. components | > 6 · 108 (Memory)
Complexity | > 500 Process steps
Cost (development and 1 factory) | ca. $ 6 · 109
Questionaire
Multiple Choice questions to all of 5.1

© H. Föll (Electronic Materials - Script)