Method of photolithographically defining three regions with one mask step and self aligned isolation structure formed thereby

US5972570A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• James A. Bruce · Williston, US
• Steven J. Holmes · Colchester, US
• Robert K. Leidy · Burlington, US
• Walter E. Mlynko · South Burlington, US
• Edward W. Sengle · South Burlington, US

Key dates

• Filing date: Jul 17, 1997
• Grant date: Oct 26, 1999
• Expiry date: Jul 17, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01L21/762
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

The preferred embodiment of the present invention provides a method for defining three regions on a semiconductor substrate using a single masking step. The preferred embodiment uses a photoresist material having, simultaneously, both a positive tone and a negative tone response to exposure. This combination of materials can provide a new type of resist, which we call a hybrid resist. The hybrid resist comprises a positive tone component which acts at a first actinic energy level and a negative tone component which acts at a second actinic energy level, with the first and second actinic energy levels being separated by an intermediate range of actinic energy. When hybrid resist is exposed to actinic energy, areas of the resist which are subject to a full exposure cross link to form a negative tone line pattern, areas which are unexposed form remain photoactive and form a positive tone pattern, and areas which are exposed to intermediate amounts of radiation become soluble and wash away during development. This exposes a first region on the mask. By then blanket exposing the hybrid resist, the positive tone patterns become soluble and will wash away during development. This exposes …