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ANISO-/ISO-/ANISOTROPIC VIA PROCESS FOR SUBMICRON DEVICE METAL INTERCONNECT

IP.com Disclosure Number: IPCOM000006976D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-13
Document File: 2 page(s) / 71K

Publishing Venue

Motorola

Related People

Ping Wang: AUTHOR

Abstract

In VLSI device metal interconnect, the metal step coverage strongly depends on the sidewall slope and aspect ratio of the via. As device feature sizes are scaling down to micron regime, the aspect ratios become larger, it is important and challenging to obtain a good metal step coverage at the via holes.

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MOTOROLA INC. Technical Developments Volume 19 June 1993

ANISO-/ISO-/ANISOTROPIC VIA PROCESS FOR SUBMICRON DEVICE METAL INTERCONNECT

by Ping Wang

  In VLSI device metal interconnect, the metal step coverage strongly depends on the sidewall slope and aspect ratio of the via. As device feature sizes are scaling down to micron regime, the aspect ratios become larger, it is important and challenging to obtain a good metal step coverage at the via holes.

  One of the most widely used via processes for metal interconnect today is an isotropic etch (round etch) followed by an anisotropic etch. The purpose of the aniso- tropic etch is to obtain a desired critical dimension (CD) at the bottom of the via holes. The purpose of the round isotropic etch is to obtain a sloped profde at the top of the interlevel dielectric (ILD) layer for better metal step coverage. It is desirable that the sloped portion of via side wall is increased. However, the amount of the iso- tropic etch portion is limited by the top opening CD.

  The advantage of this disclosed aniso-/iso-/aniso- tropic via process is the increase of the sloped sidewall portion of the via without increasing top via CD. The new process consists of three steps: the anisotropic etch, the isotropic etch and the anisotropic etch (see Figure
1). The fast step removes about l/3 of the ILD material an&tropically. The second isotropic round etch step takes off about another 113 of the ILD material. The purpose of the first and se...