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In integrated circuits (ICs), conductive lines provide electrical interconnection among different parts of the ICs, devices, and the outside. The main applications of metallization are classified by gate, contact, and interconnection. Polysilicon and silicides are commonly applied as gates and interconnects in MOS devices.
Table 2051a shows the summary of 2003 Roadmap, listing the node, gate length, equivalent oxide thickness of high power (CPU) and low standby power devices (mobile), gate oxide material, and gate electrode material.
Table 2051a. Summary of 2003 Roadmap.
Year |
2001 |
2003 |
2005 |
2007 |
2009 |
2012 |
2016 |
2018 |
Node |
130 |
100 |
80 |
65 |
45 |
32 |
22 |
18 |
ASIC 1/2 pitch |
150 |
107 |
80 |
65 |
45 |
32 |
25 |
18 |
Physical gate
length |
65 |
45 |
32 |
25 |
20 |
13 |
9 |
7 |
Tox hi power |
1.5 |
1.3 |
1.1 |
0.9 |
0.8 |
0.6 |
0.5 |
0.5 |
Tox lo power |
|
2.2 |
2.1 |
1.6 |
1.4 |
1.1 |
1.0 |
0.9 |
Gate oxide |
Oxynitride |
HfOx; Si,N |
LaAlO3 |
Gate metal |
Poly Si |
Metal gate, e.g. TaSiNx |
Table 2051b. Metallization selections in ICs.
Application |
Selection |
Gates, interconnection, and
contacts |
Polysilicon, refractory metal silicides (e.g. MoSix, TaSix, WSix, and TiSix), nitrides,aluminum, copper, and/or refractory metals. |
Diffusion barrier layer |
Ti, TiN, Ta, TaN, Ti-W alloy, and/or silicides |
Top level |
Aluminum, and/or copper |
Metallization
on silicon |
Silicides, tungsten, aluminum, and/or copper |
Table 2051c. Comparison between coarse- and fine-grain polycrystalline Si.
|
Coarse-grain poly-Si |
Fine-grain poly-Si |
Deposition temperature |
~640 °C |
~580 °C |
Surface roughness |
> 5 nm |
<1.5 nm |
Grain size
|
Undoped
|
16-32 nm |
Very small |
In situ P-doped
|
24-40 nm |
|
Strain |
-0.007 (compressive) |
-0.007 (compressive) |
Effect of thermal annealing |
Grain size increases; residual strain decreases but remain compressive |
Grain size increases to 10-90 nm; compressive to tensile strain |
Dry and wet etch rate
|
Higher for doped Si |
Higher for doped Si |
Texture
|
<110> as deposited; <311> in situ P-doped |
No texture |
Note that the comparison of the properties between single, polycrystalline, and amorphous Si is listed in page2019.
Table 2051d. Example of structural properties of poly-crystalline Si.
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