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Method for wafer orientation for optimal detection of STI voids

IP.com Disclosure Number: IPCOM000130415D
Publication Date: 2005-Oct-24
Document File: 3 page(s) / 185K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for wafer orientation for optimal detection of shallow trench isolation (STI) voids. Benefits include improved functionality and improved performance.

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Method for wafer orientation for optimal detection of STI voids

Disclosed is a method for wafer orientation for optimal detection of shallow trench isolation (STI) voids. Benefits include improved functionality and improved performance.

Background

              Conventionally, inspection recipes on darkfield (AIT type) toolsets were set up for front end inspection with the incident direction of the laser perpendicular to the predominant feature of the Flash Cell.  This creates constructive interference. The signal is mixed with noise and defects, such as STI voids, and cannot be detected during inspection (see Figure 1).

Description

              The disclosed method includes the optimal wafer orientation for flash die inspection with a darkfield defect inspection toolset. The direction of the incident laser beam must be parallel to direction of the predominant linear feature of the flash cell. (see Figure 2).

      The method orients the wafer parallel to the incident beam focused on the dominant feature of the flash lines for steps subsequent to Poly 2 etch. The method prevents the scattering of the light of a diffraction grating in which the dominant features of the flash array are the grating. Because less constructive interference is generated when the dominant features are oriented parallel to the direction of the incident beam, less noise generated. As a result, the signal-to-noise ratio is increased (see Figure 3).

              The key elements of the disclosed method...