Study On Processing Parameters, Morphologies And Deposition Principle Of Electroless Plating Nanocrystalline Copper

Electroless plating is a technology by which metals can be deposited on an activated substrate surface through reoxy reaction in solution without external current. Surface etching was commonly used in electroless Cu plating on the surfaces of glass, conductor and semi-conductor, which can improve adhesion strength on substrate, which has, however, some limits. A variety of additives have been used to improve quality and adhesion strength. Sodium dodecyl benzene sulfonate (SDBS) is a kind of anion surfactant and has been applied to electodeposition of metals and alloys, but were less used in electroless plating. The electroless plated Cu films were extensively used as the seed layer of Ultra-Large-Scale-Integration (ULSI). The morphologies, microstructure (e.g. grain size and texture) and resistivity etc. of the seed layer have important effects on microstructure and properties of subsequent electrodeposited layers. Therefore, experimental and theoretical investigations are highly desired to understand the above problems. In this dissertation, the following research work was carried out: 1. Bath composition and processing parameters of the electroless plated nc-Cu on the glass were optimized through systematical tests.2. Morphologies and microstructure on the glass were characterized by XRD, SEM, FESEM.3. The electrical resistivity and optical transmittance of nanocrystalline (nc) -Cu film on two substrate were tested. The relationship among electrical resistivity, grain size and film thickness were analyzed based on the existing theoretical models of the electrical resistivity.4. The effect of substrate surface structure and SDBS on the deposition process and resultant structure were investigated.The above work led to the following conclusions:1. The bath composition and processing parameters of the electroless Cu plating were determined by investigating their effects on deposition rate and bath stability, which are: CuSO4:10-20g/L, NaKC4H4O6: 30-50g/L, HCHO:15-20g/L, pH:12-13, SDBS:0.4-0.5g/L,35-40°C.2. XRD analysis showed that the grain size of the Cu films on the glass increases with increasing deposition time and keeps approximately constant at 28nm when the deposition time is larger than 10min. An obvious {111} texture exits in the Cu films on the glass. The ratio of I(111)/I(100) increases from 1.82 to 5.5 with increasing deposition time. The transition from a random grain growth to one preferred on (111) plane and the expense of the (111) orientated grains are responsible for this texture development in the Cu film.3. Morphologies observations of FESEM that the Cu film on the glass was composed of small nodules which composed of several grains. The number and size of these nodules increase with the deposition time and a dense Cu film formed. The growth of the Cu films follows the Volmer-Weber model. The RMS of the Cu films on the glass increases with increasing the deposition time.4. The electrical resistivity of the Cu film on the glass decreases rapidly when the film thickness is smaller than 100nm and keep approximately constant as the film thickness is increased further. The Cu film below 100nm exhibits the optical transmittance and the highest transmittance occurs at the wavelength of about 570nm. A good adhesion strength exits between the Cu film and the glass substrate.