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Overlay disposition/control methodology for (1:4) nonconcentric field clustering in device manufacturing

IP.com Disclosure Number: IPCOM000004674D
Publication Date: 2001-Mar-30
Document File: 2 page(s) / 27K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a methodology to disposition production material and to control stepper alignment based on an overlay analysis tool when the current layer is printed in a different field size (4X) from the previous layer. Benefits of this methodology include improved disposition of production material, improved stepper control, and optimized sampling locations of raw measurement with a minimized uncertainty

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Overlay disposition/control methodology for (1:4) nonconcentric field clustering in device manufacturing

Disclosed is a methodology to disposition production material and to control stepper alignment based on an overlay analysis tool when the current layer is printed in a different field size (4X) from the previous layer. Benefits of this methodology include improved disposition of production material, improved stepper control, and optimized sampling locations of raw measurement with a minimized uncertainty.

The key elements of the disclosed methodology are:

A methodology to disposition production material based on a predicted maximum overlay from the analysis tool

A methodology to control stepper alignment based on a predicted adjustment of stepper components

An overlay analysis tool which:

Takes a limited number of measurements on a wafer, of which the sampling locations are chosen to minimize uncertainty

Uses a modeling algorithm based on a set of non-redundant parameters to predict the overlay at the unmeasured locations

Models with a pre-determined set of stepper components to maximize the ability to control overlay at the current layer

The disclosed methodology addresses the problem of overlay control and disposition on layers printed on a stepper which has different field size (4X) from that of the previous layer. Conventional solutions to this problem include:

Measuring excessively at various locations on a wafer and dispositioning based on the worst-case raw measurement or against a statistically determined limit.

Analyzing the raw overlay measurement with a concentric field clustering model which assumes same field sizes for the current and previous layers and does not correctly account for contributions from various stepper components.

The technical advantages of this invention include:

Dispositioning of production material against maximum overlay error predicted by the analysis tool

Stepper control based on the suggested adjustment from the analysis tool, which models with a stepper component set that maximizes the adjustment at the current layer

Optimization of the sampling locations of raw measurement with a minimized uncertainty

Wide-field steppers are used in the printing of noncritical layers. With a larger print size

(44 mm X 44 mm), the stepper enhances the run-rate by printing multiple fields in a single exposure. In optimized case of the flash manufacturing process, a single exposure on the stepper covers four smaller fields (22 mm X 22 mm) on the previous layer printed on another scanner. This mode of alignment is known as 1:4 field clustering.

Different from 1:1 clustering which has the same field sizes for the current and previous layers, 1:4 field clustering is nonconcentric. The field center of the current layer is not aligned to the field center of the previous layer. This n...