The rate of Cu dissolution from a Si(111) wafer into an SC-1 process solution was measured by total reflection X-ray spectroscopy. The Cu surface concentration decreased logarithmically with time, demonstrating that dissolution of Cu into an SC-1 solution is a first-order process, probably kinetically limited by surface reaction. The rate constant al room temperature and a mixing ratio of 5:1:0.1 H2O:H2O2:NH4OH is approximately 2.7 x 1(0-)2 s(-1).