The growth process of Cu polycrystal films on Si, Ti, W and Ru substrate during isothermal annealing was studied by the molecular dynamics method. We focused on the influence of the adhesion strength between substrate and Cu on crystallinity and orientational order of the film. After structural relaxation at low temperature (50 K), the movements of individual Cu atoms were calculated for different annealing temperatures using the molecular dynamics method. The crystallinity and orientational order of the film were examined by 2D-Fourier transformation of the atomic structure. We found that the system with strong adhesion strength between substrate and Cu showed higher crystallinity and orientational order for (111) oriented Cu film.

In the production of LSIs, annealing is necessary to coarsen the crystal grains in the wires. In this process, wiring breakdown is frequently caused by defect generation at the T-shaped buried wire. To overcome this difficulty, we investigated the conditions for defect generation and the atomic behavior during the annealing process by molecular dynamics simulation. We focused on the influence of the adhesion strength between substrate and wire materials on void generation. As samples for the simulation, a Cu single crystal was buried in three different substrates, Si, Ti, and W. After structural relaxation at low temperature (50 K), the movements of individual Cu atoms were simulated for different annealing temperatures using the molecular dynamics method. The strain of the buried wire was also varied where the thickness of the covered layer, the width and the height of the wire were fixed. We found that the system with strong adhesion strength between substrate and wire materials suppressed void generation.

We carried out experiments on stress-induced void formation in ultrathin Cu wires while varying heat-treatment temperature, wire dimensions, and overlayer thickness. We also did molecular dynamics simulations of void formation in a buried wire of nanometer scale and compared these results with experimental results to clarify details of the void formation mechanism. The experimental and simulation results showed good accordance in explaining the effects of wire width, overlayer thickness, and cooling rate on void formation. ͑1͒ The narrower the wire width, the easier the void formation. ͑2͒ The thicker the overlayer, the easier the void formation. ͑3͒ The larger the cooling rate, the greater the suppression of void formation. From the obtained results, we constructed a void formation model for a buried wire. The basic concept of the model describes how local strain at four trench corners is relaxed in the buried wire in the annealing process. There are two ways to relax the local strain: ͑1͒ structural relaxation to strengthen adhesion between the wire and substrate and ͑2͒ reduction of the surface area to minimize surface energy. The way preferred is dependent on how parameters such as system temperature and wire dimensions are combined. Based on the void formation model, we interpreted the effects of wire strain, wire dimensions, and overlayer thickness.