However, Kilby's invention was not a true monolithic integrated circuit chip since it had external gold-wire connections, which would have made it difficult to mass-produce.[21] Half a year after Kilby, Robert Noyce at Fairchild Semiconductor invented the first true monolithic IC chip.[22][21] More practical than Kilby's implementation, Noyce's chip was made of silicon, whereas Kilby's was made of germanium, and Noyce's was fabricated using the planar process, developed in early 1959 by his colleague Jean Hoerni and included the critical on-chip aluminum interconnecting lines. Modern IC chips are based on Noyce's monolithic IC,[22][21] rather than Kilby's.