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.  
Integrated bipolar transistor
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  
Multi layer metalilzation
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  
Integrated MOS transistors
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.  
Inverter Integrated CMOS
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).  
Planarization in DRAMs
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 5.1
 
     
 
Exercise 5.1-6
All Questions to 5.1
 
With frame Back Forward as PDF

© H. Föll (Semiconductor Technology - Script)