Browse Prior Art Database

Multi-functional Embedded Layer

IP.com Disclosure Number: IPCOM000101318D
Original Publication Date: 2005-Mar-16
Included in the Prior Art Database: 2005-Mar-16
Document File: 5 page(s) / 15K

Publishing Venue

IBM

Abstract

This is a solution to the often observed bottom edge of the metal line roughness caused in the reactive ion etching of porous low-k dielectric materials. We define an embedded etch stop that also facilitates the placement of an under layer of a thin non porous dielectric such as SiLK. A dielectric layer of porous SiLK, ( to be generated by subsequent porogen decomposition), is placed under the Multi-functional Embedded Layer (MEL). A porous SiLK dielectric layer to contain a line is placed over the MEL. This Multi-functional Embedded Layer (MEL) acts as an etch stop as well as a semipermeable barrier to control porogen out-gassing and may be composed of a bi-layer ( Silk lower, Hosp upper ) or a single layer of a dense carbon rich film such as SiLk, Flare, or BCB. The MEL prevents over etch and the non porous SiLK prevents line defects from replicating into the porous dielectric below as well as eliminating the replication of porous topographic features of the porous dielectric into the bottom surface of the line. Features: 1. Adhesion is enhanced by under curing the polymer stack until the completion of the stack. Final curing of the full stack is performed prior to the RIE etch step. 2. The cure profile is designed to optimize diffusion of the porogen. This will facilitate the diffusion of the porogen out of the stack without forming pores in the etch stop and non porous SiLk layers above the SiLk containing the porogen. 3. The etch stop and non porous SiLk etch at an optimized rate to prevent over etch of side walls and bottom of trench. 4. Defects in the line are prevented by the SiLk coating sealing the pores of the dielectric below the line.

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Multi-functional Embedded Layer

Main Idea

Purpose: To provide an Multi-functional Embedded Layer (MEL) that facilitates the placement of an under layer of a thin non porous dielectric such as SiLK.

A dielectric layer of porous SiLK, generated by porogens, is placed under the non porous layer of SiLK. A porous SiLK dielectric layer to contain a line is placed over the etch stop.

The MEL prevents over etch and the non porous SiLK prevents line defects from replicating into the porous dielectric below as well as eliminating the replication of porous topographic features of the porous dielectric into the bottom surface of the line.

Features:

1. Adhesion is enhanced by under curing the polymer stack until the completion of the stack. Final curing of the full stack is performed prior to the RIE etch step.
2. The cure profile is designed to optimize diffusion of the porogen. This will facilitate the diffusion of the porogen out of the stack without forming pores in the etch stop and non porous SiLk layers above the SiLk containing the porogen.
3. The etch stop and non porous SiLk etch at an optimized rate to prevent over etch of side walls and bottom of trench.
4. Defects in the line are prevented by the SiLk coating sealing the pores of the dielectric below the line.

Structural Description:

Porous-SiLk ( with porogen) - trench for line in this layer

MEL: Etch Stop polymer layer (ESL) & Embedded Pore Sealing Layer (EPSL):

--- Desired properties:

-- Etch rate simular to the bulk etch rate of the porous material

      -- This film should have good adhesion to the layer below

      -- This film should provide for good adhesion to any subsequent layer

-- If a bilayer is used:

1

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- the upper layer is thin and a strong RIE etch

stop

         - the lower layer is a pore sealer and adhesion promoter

-- a typical Single layer MEL could be SiLk without porogen [SiLk-D (non porous)]

--- other materials could be Flare or BCB

--- a typical bi-layer MEL

--- a typical upper layer in a bilayer construction would be HOSP or thin MSQ

--- a typical lower layer in a bilayer construction would be SiLk, Flare, or BCB

Porous-SiLk ( with porogen)

use a non-porous dielectric so smooth out the jagged wire trench bottoms induced by RIE etching a porous dielectric:

porous dielectric

non-porous dielectric

porous dielectric

Diel.

W ire

Diel.

Wire

Prior Art This Invention

Figure 1: Cross-sectional drawing showing the broadest embodiment of this invention (i.e. embedding a non-porous dielec...