Creation of multiple gate oxide with high thickness ratio in flash memory process

US6147008A · kind A · utility

Assignee

• Chartered Semiconductor Manufacturing LTD · SG

Inventors

• Siow Lee Chwa · Singapore, SG
• Ying Jin · Shanghai, CN
• Yung-Tao Lin · Singapore, SG

Key dates

• Filing date: Nov 19, 1999
• Grant date: Nov 14, 2000
• Expiry date: Nov 19, 2019

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/981

Abstract

A new method is provided for the creation of an oxide layer that contains three different thicknesses. A first layer of oxide is grown on the surface of a substrate; a first layer of photoresist is deposited and patterned thereby partially exposing the surface of the underlying first layer of oxide. A nitrogen implant is performed into the surface of the underlying substrate; the photoresist mask of the first layer of photoresist is removed. A second layer of photoresist is deposited and patterned, the first layer of oxide is removed from above and surrounding the implanted regions of the substrate. The second mask of resist is removed. The first layer of oxide is reduced in thickness, its thickness is restored to a first thickness by a blanket growth of a second layer of oxide over the exposed surface of the substrate (where no ion implant has been performed) to a third thickness, over the surface of the substrate where the ion implant has been performed to a second thickness and over the surface of the first layer of oxide thereby restoring this layer of oxide to its original first thickness.