Browse Prior Art Database

PSM Library and Place and Route

IP.com Disclosure Number: IPCOM000007571D
Publication Date: 2002-Apr-05

Publishing Venue

The IP.com Prior Art Database

Abstract

An approach to laying out features in a layer of material in an IC designed for use with phase shifting masks (PSMs) is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 34% of the total text.

PSM Library and Place and Route

BACKGROUND

Field of the Invention 5

[0001] This invention relates to the field of semiconductor devices. More particularly, the

invention relates to a method and apparatus for placement and routing of circuit layouts for phase

shifting masks.

Description of the Related Art

[0002] One approach to manufacturing an integrated circuit (IC) is to use lithographic

processes. Using lithography, light (frequently ultra-violet, deep-ultraviolet, extreme ultraviolet,

and more recently x-ray and other non-visible light) sources are used to expose a photosensitive

resist coating that has been applied to a semiconductor wafer. The exposure of the resist to light

occurs through a mask (or reticle) that includes light transmissive and non-transmissive regions.

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[0003] The wavelength of the light used in the lithographic process can limit the

minimum resolvable feature size on the resultant IC. However, using the destructive interface

properties of light it is possible to consistently produce smaller features than would otherwise be

possible. Masks designed to make use of such destructive interference are sometimes referred to

as phase shifting masks.

[0004] One approach to defining IC features using phase shifting masks is described in

United States Patent No. 5,858,580 entitled "Phase Shifting Circuit Manufacture and Apparatus"

having inventors Yao-Ting Wang, et. al.

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[0005] It would be desirable to have a method and apparatus for laying out features in a

layer of material in an IC that is designed to account for definition of some of those features

using a phase shifting mask.

SUMMARY

[0006] An approach to laying out features in a layer of material in an IC designed for use

with phase shifting masks (PSMs) is disclosed.

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BRIEF DESCRIPTION OF THE FIGURES

[0007] FIG. 1 is a process flow diagram for placement and routing accounting for phase

shifting masks.

[0008] FIG. 2 show a layout arranged according to an embodiment of the invention.

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DETAILED DESCRIPTION

[0009] FIG. 1 is a process flow diagram for placement and routing accounting for phase

shifting masks. According to one embodiment of the invention, the process starts at step 100

with the identification of features in an already existing design (e.g. a layout, e.g. in GDS-II

format, or some other representation). 5

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[0010] Critical features are simply those features that the designer prefers to be defined

in the integrated circuit (IC) using a phase shifting mask (PSM). In some embodiments, the

identification of critical features occurs automatically, e.g. according to one or more rules. In

another embodiment, the critical features are manually selected by the designer.

[0011] Next, at step 110, the layout is placed and routed (or re-done if an existing layout

was provided at step 100) in accordance with the critical feature information. Embodiments of

the invention orient substantially all critical features in a single orientation (...