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Method for improving mask defect yield using multipass wafer exposures

IP.com Disclosure Number: IPCOM000022274D
Publication Date: 2004-Mar-03
Document File: 7 page(s) / 170K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for improving mask defect yield using multipass wafer exposures. Benefits include improved performance and yield.

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Method for improving mask defect yield using multipass wafer exposures

Disclosed is a method for improving mask defect yield using multipass wafer exposures. Benefits include improved performance and yield.

Background

In integrated circuit (IC) manufacturing, a mask pattern is projected by the exposure tool onto the wafer so that the wafer area is tiled with the pattern (see Figure 1). The mask must not have any printable defects because they are replicated on the wafer. A printable defect on the mask in a critical area of the circuit can destroy every chip on the wafer. Making the mask free of defects, accounts for significant technical challenges and costs, in mask manufacturing. In some cases, making a defect free mask may not be possible. For instance, in extreme ultraviolet (EUV) lithography, a perfect multi-layer coated mask blank may not be possible to produce. No pellicles are available to keep the EUV mask free of defects during wafer exposure. Additionally, the production of functional circuits in the early phase of process development when the mask process is not yet free of defects may be beneficial.

Conventionally, significantly printable defects on the masks used to expose wafers are prevented by using mask defect inspection and repair. When the mask is fabricated with no appreciably printable defects, it is protected from particles and contamination by a pellicle. For EUV lithography, making defect-free masks is very challenging because defects can be embedded in the multilayer coating that makes the mask reflective to EUV light. No proven methods exist to repair defects in the EUV multilayer. Furthermore, no pellicles are available to keep the EUV mask free of defects during the wafer exposure.

General description

The disclosed method exposes wafers with the same mask pattern multiple times to minimize the effect of mask defects.

The disclosed method is especially applicable in extreme ultraviolet lithography (EUVL) or in early part of the development cycle where ensuring that the masks can be made free of defects is difficult.

         The key elements of the method include:

•         Wafer exposure strategy that takes advantage of multiple identical dice on a mask

•         Exposing each die on a wafer using the multiple copies of the desired pattern on the mask

•         Mask defect dispositioning strategy employing defect specifications that depend on the number of identical dice on the mask and on the wafer exposure strategy

Advantages

         The disclosed method provides advantages, including:

•         Improved performance due to mitigating the effect of defects that may be present

•         Improved yield due to reducing printing errors from mask imperfections

•         Improved cost effectiveness due to enabling defect specifications to be relaxed

Detailed description

The disclosed method is a wafer exposure strategy that employs the multiple identical dice on a mask to mitigate the effect of defects that may be present. Each wafer die is exposed using the multiple cop...