Browse Prior Art Database

New Etch Process for Luna ES1 Shallow Trench Isolation (IT Etch)

IP.com Disclosure Number: IPCOM000114433D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Maccagnan, R: AUTHOR

Abstract

Disclosed is a dry etch process designed to improve the quality of the shallow trench isolation for advanced semiconductor products such as 16 Mbits DRAM chips.

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New Etch Process for Luna ES1 Shallow Trench Isolation (IT Etch)

      Disclosed is a dry etch process designed to improve the quality
of the shallow trench isolation for advanced semiconductor products
such as 16 Mbits DRAM chips.

      This new process uses a low pressure NF3/N2/CHF3 chemistry -
when the conventional NF3/N2 chemistry is used, four main defects
have been detected as illustrated in Fig. 1:
  o  Nitride node remainings,
  o  Possible negative profiles,
  o  Mask deformation (wafer edge),
  o  Possible Pad Nitride erosion (wafer edge).

      A new NF3/N2/CHF3 chemistry is disclosed to avoid these
defects.  First, the use of an additional CHF3 flow leads to a thin
polymer deposition along the etched surfaces.  This thin layer
protects the Isolation Trench (IT) profiles against lateral etching,
avoiding negative profiles.  Next, changing NF3/CHF3 ratio allows an
IT slope and center-to-edge depth uniformity control.  CHF3 increases
nitride etch rate, so that nitride nodes are etched faster than
silicon and polysilicon and eliminated.  CHF3 decreases resist etch
rate: etch-bias and dimensionnal are more stable.

      New IT profile leads to a better oxyde fill, which in turn,
improve IT isolation and reduces the number of dislocations.
Electrical parameters related to IT have shown a clear improvement on
wafers processed with new plasma parameters as illustrated in Fig. 2.