Letter with accents treated as identical when freetagging

I make a freetagging category (no hierarchy, possible to set several tags), create a page, and write "ãr, âr, är, år, ar" in the freetagging field. The page only gets one tag, the first one I write. I can create those different categories if I go to "administer categories", but even then, I can only assign one of them to content while editing content.