Copper seed layer

Then a very thin barrier layer and a copper seed layer are formed (Figs. 21 (b) and 21 (c)>). In order to conduct the electric current, good conductive material, e.g., copper, will be coated on the surface of the copper seed layer which forms a rough surface as shown in Fig. 21(d). Since multilayer s introduction into IC production, the surface coated with copper must be very smooth, clean, and bare of dielectric stacks... 

Fig. 8. Top view of a 4.7 x 4.7 cm wafer whose surface is coated by a thin seed layer of copper deposited by evaporation. Above the seed layer is a zebra pattern of photoresist black indicates resist and white indicates exposed copper seed layer. (Originally presented at the Fall 1991 Meeting of the Electrochemical Society, Inc. [39]).

Electroless copper seed layer on TaN surfaces for Cu metallization in the back-end-of-line semiconductor fabrication was also investigated.38 After etching in diluted HF solution and activation with PdCb, the electroless deposition of copper (to be used as a seed layer) was carried out from CuSCVEDTA solution containing Triton X-100, tetramethyl ammonium hydroxide (TMAH), and formaldehyde as a reducing agent of Cu(II) ions. 

Copper is electroplated onto a thin (100-1000A), quite resistive copper seed layer... 

Plating experiments were performed on sections of both blanket and patterned wafers. The wafers were p-type device quality wafers subjected to wet oxidation at 1050°C for 1.25 hours to develop 7pm of oxide. A copper seed layer was sputtered at a base pressure of 10 7 Torr and an argon pressure of 5mTorr. The sputtered layers were 30nm thick and exhibited a resistivity of 2.1pO cm. The patterned wafers had a 0.5 pm minimum feature size with a 2 1 aspect ratio. 

Copper is going to replace aluminum as the material of choice for semiconductor interconnects due to its low electrical resistance and high electromigration resistance (1-4). An inlaid interconnect is used for copper metallization in which the insulating dielectric material is deposited first, trenches and vias are formed by patterning and selective dielectric etching, and then diffusion barrier and copper seed layer are deposited into the trenches and vias (5). 

Plating time for the ECD seed was determined by the thickness of desired total copper seed layer. Three different plating baths for ECD seed were examined for conformal plating. Some wafers were plated directly using the acid copper sulfate bath without the ECD seed enhancement and were compared to those processed with ECD seed enhancement. 

Copper interconnection via electrochemical means has received increasing attention. Currently the most acceptable method is based on electrodeposition of copper on top of a copper seed layer which has previously been deposited by CVD or sputtering method 1 . 

The copper deposition observed between TiN barrier layer and acidic copper solution containing F" ions is actually due to reaction between the bare Si material and Cu2+ through cracks in the TiN layer due to etching reaction by the fluoride ions. But other metal ions such as palladium can indeed induce displacement reaction and serve as a possible alternative for copper deposition without copper seed layer by CVD or sputtering. 

Eigure 1 presents a simplified schematic for the fabrication process of the proposed LIGA-Uke technique in SU-8 epoxy resin. Briefiy, a substrate is firstly coated with metal seed layers for the electroforming process (Fig. la). A chromium or titanium layer with a thickness of several hundred angstroms is usually used as the adhesion layer. A gold or copper seed layer of several micrometers in thickness is then deposited on the adhesion layer to be the bottom... 

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