By Heekyong Yang SEOUL (Reuters) - SK Hynix said on Friday it has completed its internal certification process for next generation high-bandwidth memory 4(HBM4) chips and established a production system for customers as it seeks to retain a lead over rivals. In March, the South Korean chipmaker, a key supplier to AI giant Nvidia, said it had shipped its HBM4 12-layer chip samples to customers, adding that the company aims to complete preparations for mass production of 12-layer HBM4 products within the s ...