Optical interference effect on chip’s temperature distribution in the optical annealing process

In the optical annealing process, temperature distributions of chips on a silicon wafer tend to be inhomogeneous. One of sources to generate the temperature inhomogeneities should be an optical interference effect of the incident lights where the incident lights are interfered by chip’s circuit patterns which are small enough compared to the wavelength. The optical interference effect disturbs optical absorption distribution of a chip, which makes the temperature distributions inhomogeneous. To estimate the optical absorption distribution of a chip, the optical absorptions against various circuit patterns are calculated with RCWA (Rigorous Coupled Wave Analysis) simulations. With the estimated optical absorption distribution, the temperature distribution is calculated by a heat diffusion simulation. The simulated temperature distribution agreed well with experimental result. This fact showed that the optical interference effect should be the main source of the temperature inhomogeneities. Moreover, our method proved to be appropriate to predict the temperature distributions of chips with good accuracy.