|Budget Amount *help
¥3,920,000 (Direct Cost : ¥3,500,000、Indirect Cost : ¥420,000)
Fiscal Year 2007 : ¥1,820,000 (Direct Cost : ¥1,400,000、Indirect Cost : ¥420,000)
Fiscal Year 2006 : ¥2,100,000 (Direct Cost : ¥2,100,000)
The mechanism of wet etching of copper in a ferric chloride solution is studied using an agitated vessel. First, the etching rate of a plate-shaped copper specimen is measured to confirm the rate-limiting step. The effects of the agitation speed and solution temperature on the etching rate are investigated. The etching rate has an approximately 0.7 order dependence on the agitation speed that is the same in the case of benzoic acid-water system. Moreover, it is clear the temperature dependence of the etching rate is small. From this dependence, it was found that the apparent activation energy is about 25kJ/mol. From the results of these, it can be concluded that the liquid-phase mass-transfer process is the rate-limiting step in wet etching of copper. In addition, the dissolution rate of CuCl is also found to be controlled by mass transfer. From the comparison of those rates, it is thought that the etching rate is controlled by the diffusion rate of Fe^<3+> in an agitated vessel, the same as the dissolution rate of CuCl.
Second, line-patterned copper specimens are etched to study the cavity formation. From the results, it is clear that the etching rate decreases with time and is found to decrease with decreasing line spacing. Furthermore, etch factor that means etching depth divided by undercut also decreases with the relative depth. Those results mean reaction species hard to enter the cavity with narrowing the line spacing and depth of the cavity.
Therefore, in the near future, a mass transfer model should be developed to estimate the cavity formation during wet etching of line-patterned copper specimen using the results of this study.