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Method for the reduction of keff in semiconductor devices using a bilayer as the etch-stop layer

IP.com Disclosure Number: IPCOM000009255D
Publication Date: 2002-Aug-13
Document File: 3 page(s) / 99K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the reduction of the overall effective dielectric constant (keff) in semiconductor devices using separate materials to form the interface with Cu interconnects and act as the etch-stop (ES) layer. Benefits include improved performance and improved manufacturability.

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Method for the reduction of keff in semiconductor devices using a bilayer as the etch-stop layer

Disclosed is a method for the reduction of the overall effective dielectric constant (keff) in semiconductor devices using separate materials to form the interface with Cu interconnects and act as the etch-stop (ES) layer. Benefits include improved performance and improved manufacturability.

Background

      The effective dielectric constant of interlayer materials increases when using a thick diffusion barrier / etch stop, leading to higher resistance/capacitance (RC) delay.

      Conventionally, a single material is used as both an etch stop and a diffusion barrier in one layer. The required thickness is determined by the etch selectivity. Lower dielectric-constant (k) materials may have similar, or better, etch selectivity but have other integrated issues, such as poor adhesion or poor copper diffusion resistance. The act of depositing the etch stop film may also damage the underlying substrate if oxidizing conditions are used during deposition.

General description

      The disclosed method is the reduction of keff in semiconductor devices using bilayer to enable etch-stop layer integration. The key elements of the method include:

·        Reduction of the effective dielectric constant, keff, in a semiconductor device by using a bilayer for the  etch-stop, instead of using a single material.  The lower layer can be tailored to improve device reliability and lifetime.  The upper layer can be tailored to maximize etch selectivity or minimize dielectric constant.  A lower keff reduces RC delay and improves device performance.

·        The lower layer defines the interface with the metal / interlayer dielectric (ILD) substrate that is the underlying layer.  The lower layer material can be chosen for adhesion, to protect the substrate from damage, or to enable past technology optimization of the interface to be carried forward while minimizing the impact to the keff of the device.

·        The lower layer may or may not act as a diffusion barrier.  Diffusion barriers are generally a high-density material with a dielectric constant >5, can be thinned to as few as 1-2 monolayers minimizing any increase in keff.

·        The etch stop layer can be made with a low-dielectric (low-k) material, minimizing any increase in keff.

 


Advantages

      The disclosed method provides advantages, including:

·        Improved performance due to an improved effective dielectric constant

·        Interfaces with metal layer (Cu) and ILD remain unchanged, reducing the risk of the integration approach

·        Improved manufacturability due to the capability to use precursors or process conditions that would conventionally damage/corrode the underlying substrate (Cu or interlayer dielectric) for depositing low-k interlayer dielectric layers

Detailed description

      The disclosed method is the reduction of keff in semiconductor devices using separate materials for the diffusion-barrier layer...