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Method for an oval array contact for advanced flash technologies

IP.com Disclosure Number: IPCOM000132124D
Publication Date: 2005-Dec-01
Document File: 6 page(s) / 126K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an oval array contact for advanced flash technologies. Benefits include improved functionality, improved performance, improved reliability, and improved sort yield.

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Method for an oval array contact for advanced flash technologies

Disclosed is a method for an oval array contact for advanced flash technologies. Benefits include improved functionality, improved performance, improved reliability, and improved sort yield.

Background

              The industry trend is for contact resistance to increase and for the contact-to-gate distance to decrease as the critical dimensions of flash technologies shrink. As a result, specification limits are tightened for in-line parameters that affect the contact-to-gate distance. Affected parameters include contact registration, contact dimension, and word-line dimension (see Figure 1).

              The conventional array contact is circular. With shrinkage, the contact-to-gate distance is shortened, which increases the failure rate (see Figure 2).

              For a contact in an array, the direction of the wordline has a strong and clear correlation with the reliability of the flash device. For advanced technology at 0.13 micron and below, a preferential dimension for the array contacts is beneficial. The array should be wider in the direction parallel to the wordline, so the contact can expand more in one direction than the other.

              Contact-to-gate electrical shorts are a significant reliability failure for conventional flash technologies. These shorts occur due to high voltage applied between the gate and the contact during the erase operation (bulk erase). Additionally, the distance between the contact and gate is short.

General description

              The disclosed method includes an oval-shaped flash-array contact. The total contact area between the bottom of the contact and the silicon is larger, which lowers the contact resistance. The contact has a smaller diameter in the direction perpendicular to the wordline and a longer diameter in the direction parallel to the wordline. As a result, the oval contact lowers the contact resistance without increasing the contact-to-gate distance. When a larger contact-to-gate distance is required, it can be increased without increasing the contact resistance.

              The key elements of the disclosed method include:

•             Oval contact shape

•             Increased surface area usage, especially for flash arrays where all components are very close together

•             Increased array width in the direction parallel to the wordline

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing an oval array contact
•             Improved performance due...