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A DC Electron Plasma for the Sealing of Porous Low-Dielectric Constant ILD Materials

IP.com Disclosure Number: IPCOM000030144D
Publication Date: 2004-Jul-29
Document File: 3 page(s) / 48K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a DC electron plasma (in the presence of a radical reactive species) to stimulate reactions from ILD (inter-layer dielectric) surfaces and seal porous low-dielectric constant materials. Benefits include a solution that is less expensive and eliminates ion bombardment damage.

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A DC Electron Plasma for the Sealing of Porous Low-Dielectric Constant ILD Materials

Disclosed is a method that uses a DC electron plasma (in the presence of a radical reactive species) to stimulate reactions from ILD (inter-layer dielectric) surfaces and seal porous low-dielectric constant materials. Benefits include a solution that is less expensive and eliminates ion bombardment damage.

Background

As the semiconductor industry moves below the 65nm technology node, low-dielectric constant ILD materials (k ≤ 2.2) are needed to mitigate capacitance effects and increase speed as interconnect dimensions continually shrink. The main approach to lowering the dielectric constant (k-value) of ILD materials is to increase porosity. The ILD pores are comprised of air, which has a dielectric constant of one.   

However, increasing porosity is not without a cost. In the dual damascene flow, a barrier is needed between the ILD and the copper deposition to prevent metal diffusion. In a porous material, the barrier itself can diffuse into the ILD, negating the dielectric constant benefit from the pores.  In order to realize the k-value advantage from a porous ILD, the surface pores must be effectively sealed prior to the metallization process.

Currently, a non-porous carbon-doped ILD is used. This ILD is not particularly porous and will not be extendible to lower dielectric constant needs. Several different methods of creating pores and then sealing them are currently being examined.  No path has been fully realized and each has drawbacks. The following is a partial list of list of approaches:

§         Thin film deposition. This creates concerns about conformal deposition in small structures.

§         RF plasma sealing. This is possibly too aggressive because it creates concerns about ion damage to the surface and directionality of the plasma.

§         Electron beam sealing. The electron gun or flood method. This may only be directional and not capable of integrating reactive species into the process area.

§         Surface Pre-treatment. This may depend on subsequent interactions with the barrier layer.

General Description

The disclosed method is a new method for sealing the pores in low-dielectric constant ILD.  Figures 1 and 2 show that without appropriate sealing, the effective k-value of the ILD may be compromised.  A DC electron plasma is a better approach when compared with other proposed methods:

§         The application of an RF plasma to an ILD is useful for pore...