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ALGORITHM FOR BREAKUP AND CHECKING OF LINES TO COMBAT DISHING IN MULTILEVEL DAMASCENE BEOL

IP.com Disclosure Number: IPCOM000019649D
Original Publication Date: 2003-Sep-24
Included in the Prior Art Database: 2003-Sep-24
Document File: 3 page(s) / 140K

Publishing Venue

IBM

Abstract

Disclosed is a method and structure which achieves automated control of Damascene interconnect resistances, regardless of linewidth, in such a manner as to combat dishing and erosion from the chemical mechanical polishing process.

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  ALGORITHM FOR BREAKUP AND CHECKING OF LINES TO COMBAT DISHING IN MULTILEVEL DAMASCENE BEOL

  Disclosed is a method and structure which achieves automated control of Damascene interconnect resistances, regardless of linewidth, in such a manner as to combat dishing and erosion from the chemical mechanical polishing process. This is achieved by clamping the maximum metal pattern factor without requiring changes to the interconnect width or spacing layout design.

  It is well known that the damascene process has limits in its planarization capability as a function of metal pattern factor (PF, defined as the ratio of metal area to total area in the plane of the wiring level). Metal erosion typically starts to increase strongly as pattern factor exceeds ~60%, and the resulting sheet resistance grows beyond tolerable limits, especially for pattern factors above 90%. However, it is still desirable to design very wide lines at small spacings, which would normally exceed tolerable pattern factors. Increasing spacings may alleviate some of the problem, but would preclude legacy design migration and has limits as to maximum linewidth allowed due to intraline erosion.

  Figure 1a) shows pairs of lines at minimum spacing for increased linewidth, where spacing has had to be increased in order to limit pattern factor to less than 80%. There is a maximum linewidth, beyond which erosion within each line overcomes increased spacings, and effective pattern factor exceeds limits. Layout area has had to increase to accommodate the wider lines.

  Figure 1b) shows the same pairs of lines with the present algorithm employed, to "tile" lines beyond a certain linewidth with unit cells containing blank spots or perforations in the metal pattern. Staggered perforations in dimensions shown limit pattern factor to ~80% and have reduced impact to sheet resistance (rule of thumb is 3:1 spacing:width for perforations in the line current axial direction). These perforations effectively lim...