|Copper metallization by electroplating.|
Sputter Cu-Metallization Cu-Anneal Cu-CMP low-k Nitride
In the manufacturing of semiconductor devices copper lines and copper vias are used more and more instead of aluminium, although the metal contamination risk is much higher, the wall adhesion on dielectrics is worse, and the corrosion resistance of Cu is poor. However the conductivity of copper is much higher, which is an important fact for high-integrated devices. Electromigration resistance is higher for copper.
Damascene technology is used for the deposition of copper. This technology is named after an ancient technology used for the multi-layer manufacturing of swords in Damascus.
|Sputtering of the
|Electro plating of
the copper layer
On the silicon diffusion barriers, in some cases etch stop layers,
and dielectric layers are deposited. Then lines and vias are patterned and etched,
followed by the deposition of a copper seed layer. Diffusion barrier layers of titanium nitrid,
tantalum or tantalum nitride as well as copper seed layers are deposited on the wafer
by sputter technology. The openings are filled with copper,
using electroplating technology. The growth of the copper layer is polycrystalline.
The size of the grains depends on the substrate surface,
the growth conditions as well as on the size of the graves and vias.
In order to improve the properties of the copper layer an Cu anneal step is absolutely necessary. Finally the excess copper has to be removed. This is done by chemical mechanical polishing CMP.
Finally the cupper layer is encapsulated by a silicon nitride layer.
The complete process is repeated up to 8 times in order to build a multilayer structure.
For the deposition of copper on a barrier layer, it is necessary to
create first a seed layer of copper, which is usually deposited by sputter technology.
In the electroplating equipmment the first step is wetting of the sample. During this
process step all trenches and vias should be filled with water without any bubbles remaining.
This can be done with assistance of detergents or by ultasonic support. Very well works
wettening after evacuation.
The main process of galvanic copper deposition takes place in the cup, where the wafer is mounted topside down on a cathode chuck. The wafer is then flooded by fountain type electrolyte flow or sprayed by a rotating set of nozzles from below. This process requires exact temperature control. The backside of the wafer is protected by the cup design and will not be coated. The copper ions will be discharged and deposited on the seed layer, which works as cathode. Finally the wafer will be cleaned and dried in a spin dryer unit by DI water and/or acid. After each process step, the reaction chamber and the electrodes will be cleaned automatically.
Electroplating equipment for copper metallization consist of a wetting chamber, one of several cups of galvanic deposition of copper, chemical supply unit, controller and rectifier for the galvanic deposition. Deposition is done wafer by wafer, but several deposition chambers can be installed in one unit as required by the customer.
Beside copper metallization, also other metals like nickel, indium, gold, silver, palladium, rhodium, ruthenium or iridium can be plated.
Please contact us in order to receive more information about our copper electroplating equipment.
|Crystec Technology Trading GmbH
✉ 84503 Altoetting, Zinngiesserstr. 7, Germany, ✆ +49 8671 882173