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An attempt was made to refine the grain structure of 200 mm wide sheets of AA7475 based aluminum alloys containing zirconium by employing a new warm rolling method under the control of both roll temperature and material temperature. The warm rolled sheets as solution heat treated had subgrain structures through the thickness with a high proportion of low angle boundary less than 15. The average subgrain diameter was approximately 3 mm. The strength of the warm rolled sheets in T6 condition was about 10% higher than that of conventional AA7475 alloy sheets produced by cold rolling. As the most remarkable point in the warm rolled sheets, the high Lankford (r) value of 3.5 was measured in the orientation of 45 to rolling direction, with the average r-value of 2.2. The high r-value would be derived from well developedfiber textures, especially with the strong f011gh211i Brass component. The warm rolled sheets also had high resistance to SCC. From Kikuchi lines analysis and TEM images, it was found that PFZs were hardly formed along the low angle boundaries of the warm rolled sheets in T6 condition. This would be a factor to lead to the improvement of resistance to SCC because of reducing the difference in electrochemical property between the grain boundary area and the grain interior.

Wet cleaning of deep trenches, 4 ~m deep and 0.5 ~m wide, was studied using a two-dimensional wet cleaning simulation including both flow and diffusion effects. It has turned out that the diffusion effect is a dominant factor during wet cleaning. When the flow velocity of the rinse water increases, the rate at which solution in trenches is replaced becomes higher. In our simulation, the solution in the deep trench is diluted to 1 ppm by rinse water within several seconds. This result shows that deep trenches with submicron width can be cleaned by a wet cleaning process. Uniform etch rates of oxide in deep trenches suggest the diffusion mechanism is predominant.

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