Boosted by Seagate Technology's (STX.O) earnings report, US memory chip stocks rose in after-hours trading. Western Digital (WDC.O) rose 6.5%, SK Hynix (SKHY.O) rose 2.5%, Micron Technology (MU.O) rose 0.8%, SanDisk (SNDK.O) rose 1%, and Seagate Technology (STX.O) once rose 9%.