Tokyo stocks opened sharply higher Thursday as a weaker yen lifted exporters and semiconductor-linked shares got a boost from a stronger-than-expected earnings outlook by U.S. chip giant Micron Technology Inc. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 649.81 points, or 1.72 percent, from Wednesday to 38,520.07. The broader Topix index was up 34.02 points, or 1.28 percent, at 2,684.52. On the top-tier Prime Market, gainers were led by metal product, miscellaneous product, and electric appliance shares. At 9 a.m., the U.S. dollar fetched 144.70-71 yen compared w…