Methods of code programming a mask ROM

US6875659B2 · kind B2 · utility

Assignee

• MACRONIX INTERNATIONAL CO., LTD. · TW

Inventors

• Ta-Hung Yang · Hsinchu, TW
• Ching-Yu Chang · Taipei, TW

Key dates

• Filing date: Jul 3, 2003
• Grant date: Apr 5, 2005
• Expiry date: Jul 3, 2023

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10B20/383

Abstract

A method of code programming a mask read only memory (ROM) is disclosed. According to the method, a first photoresist layer is formed over word lines and a gate oxide layer of a substrate already having implanted bit lines. The first photoresist layer is patterned to develop pre-code openings over all of the memory cells, which correspond to intersecting word and bit lines. The first photoresist layer is then hardened using either a treatment implant or a treatment plasma. Subsequently, a second photoresist layer is formed over the first photoresist layer and patterned to develop real-code openings over memory cells which are actually to be coded with a logic “0” value. Each memory cell to be coded is then implanted with implants passing through the pre-code openings and the real code openings and into the memory cell.