We have developed an alkaline barrier slurry （named FA/O slurry） for barrier removal and evaluated its chemical mechanical planarization （CMP） performance through comparison with a commercially developed barrier slurry. The FA/O slurry consists of colloidal silica, which is a complexing and an oxidizing agent, and does not have any inhibitors. It was found that the surface roughness of copper blanket wafers polished by the FA/O slurry was lower than the commercial barrier slurry, demonstrating that it leads to a better surface quality. In addition, the dishing and electrical tests also showed that the patterned wafers have a lower dishing value and sheet resistance as compared to the commercial barrier slurry. By comparison, the FA/O slurry demonstrates good planarization performance and can be used for barrier CMP.
The oxidation induced stacking faults （OISFs） exposed on the surface of polished silicon substrate are harmful to the electrical performance and reliability of the device region located on the wafer surface. This work investigates the characteristics of the novel nano colloidal silica alkaline slurry, including polyamine and complex non-ions surface surfactant. The experimental results show that when the pH value is higher than 10.1, the removal rate can be higher than 750 nm/min and the surface roughness can be lower than 0.3 nm （10 × 10 μ2）. The surface OISFs existing on the wafer are efficiently controlled with the slurry, and the defect density on the polished wafer surface decreases greatly as well.
In order to decrease the consumption of reagents and silicon during removal of surface contamination before silicon texturing in solar cell manufacturing industry, a new low-cost surface treatment approach of electrochemical cleaning technique(ECT) is reported. In this technique, a powerful oxidizing electrolyte was obtained from the electrochemical reaction on Boron-doped Diamond(BDD) electrodes, and applied during removal of surface contaminations on silicon wafer surfaces. The slightly polished monocrystalline silicon surfaces after cleaning were compared with the ones of primal silicon wafers. The measurement results show that ECT is quite efficient in removing NaCl and organic contaminants. After cleaning, the contrast test was conducted for the textured silicon wafers with/without pre-treatment(polish) separately. The results show that the size of pyramids on the surface without traditional polishing process is homogeneous and smaller than 4μm, and the average surface reflectance is much lower in the wavelength range from 400nm to 800nm. Therefore, the new technique can save silicon material, and effectively avoid optical losses for improving photoconversion effect of solar cells.
