Cross Section of 16 Mbit DRAM and 64 Mbit DRAM
||Below a large SEM micrograph showing the cross-section
of an (early) 16 Mbit DRAM. |
|| || |
| ||Some explanations: |
- The two deep "trenches" (they
holes) contain the capacitors. There dielectric (with ca. 7 nm far too thin to be visible)
is "ONO", a triple layer of Oxide - Nitride - Oxide.
- The trench os
lined with poly-Si as a first electrode and as the second electrode.
- To the
left and right two transistor gates are visible. The sources of both transistors is the (poly-Si
) electrode lining the trench and the diffused areas being contacted by the "Polizid
bitline". "Polizid" means a double layer of poly-Si and MoSi2
- The "poly-Si wordline" runs perpendicular to
the picture and connects the gates of the transistors
- The "BPSG"
layers denote SiO2 doped with B and P that serves as insulating
dielectric. It is essentially a glass.
- Parallel to the word lines are Ti/TiN/AlSiCu
lines. They contact the wordlines every once in a while to decrease the ohmic resistance.
The consist of a layer sequence: Ti, TiN, and Al doped with about 0,5%
of Si and Cu.
- On top of this first metal layer is another one running
across the picture.
- The metals are insulated by the intermetal dielectric composed
of plasma-oxide (PO) that contains spin-on-glass (SOG) in the interstices.
| || Below the successor of the 16 Mbit DRAM, the 64
Mbit DRAM from a development stage around about 1996. |
|| || |
| || ||The structure is essentially the same, but all layers have
been planarized. |
| || || |
Physical Processes for Layer Deposition
5.1.5 Integrated CMOS Technology
6.3.3 CVD for Poly-Silicon, Silicon Nitride and Miscellaneous Materials
6.6.2 Resist and Steppers
© H. Föll (Electronic Materials