Compositions – Etching or brightening compositions
Reexamination Certificate
1997-08-29
2001-05-01
Lund, Jeffrie R. (Department: 1763)
Compositions
Etching or brightening compositions
C252S079200, C252S079300, C252S079400
Reexamination Certificate
active
06224785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to chemical formulations used in semiconductor wafer fabrication and particularly to chemical formulations that are utilized to remove residue from wafers following a resist plasma ashing step.
2. Description of the Prior Art
The prior art teaches the utilization of various chemical formulations to remove residue and clean wafers following a resist ashing step. Some of these prior art chemical formulations include akaline compositions containing amines and/or tetraalkyl ammonium hydroxides, water and/or other solvents, and chelating agents. Still other formulations are based on acidic to neutral solutions containing ammonium fluoride. The various prior art formulations have drawbacks which include unwanted removal of metal or insulator layers and the corrosion of desirable metal layers, particularly aluminum and aluminum-copper alloys and titanium nitride features. There is therefore a need for chemical formulations which effectively remove residue following a resist ashing step which do not attack and potentially degrade delicate structures which are meant to remain on a wafer.
SUMMARY OF THE INVENTION
A semiconductor wafer cleaning formulation for use in post plasma ashing semiconductor fabrication comprising the following components in the percentage by weight ranges shown:
Ammonium fluoride and/or a derivative thereof;
1-21%
an organic amine or mixture of two amines;
20-55%
water;
23-50%
a metal chelating agent or mixture of chelating agents.
0-21%
It is an advantage of the present invention that it effectively removes inorganic residues following a plasma ashing step.
It is another advantage of the present invention that it effectively removes metal halide and metal oxide residues following plasma ashing.
It is a further advantage of the present invention that it effectively removes slurry particles of aluminum oxides and other oxides remaining after CMP (chemical mechanical polishing).
It is yet another advantage of the present invention that it provides better stripping performance with less corrosivity than formulations containing ammonium fluoride without amines and amines without ammonium fluoride.
It is yet a further advantage of the present invention that it provides better stripping performance at lower processing temperatures than conventional amine-containing formulations.
It is still a further advantage of the present invention that it includes a chelating agent to prevent metal corrosion and increase stripping effectiveness.
These and other features and advantages of the present invention will become understood to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention comprises formulations that are suitable for stripping inorganic wafer residues which originate from high density plasma etching followed by ashing with oxygen-containing plasmas. The formulations are also suitable for removing slurry particles of aluminum oxides and other oxides remaining after CMP (chemical mechanical polishing). The formulations contain ammonium fluoride or a derivative of ammonium fluoride, an amine or mixture of amines, water and, optionally, one or more metal chelating agents.
The preferred formulations utilize the following components (percentages are by weight):
Ammonium fluoride and/or a derivative thereof:
1-21%
An organic amine or mixture of two amines
20-55%
Water
23-50%
A Metal chelating agent or mixture of chelating agents:
0-21%
The Preferred Amines are:
Diglycolamine (DGA)
Methyldiethanolamine (MDEA)
Pentamethyldiethylenetriamine (PMDETA)
Triethanolamine (TEA)
Triethylenediamine (TEDA)
Other Amines that are Effective Include:
Hexamethylenetetramine
3, 3-Iminobis (N,N-dimethylpropylamine)
Monoethanolamine
The Preferred Fluoride Sources are:
Ammonium fluoride
Triethanolammonium fluoride (TEAF)
Other Fluoride Sources that are Effective Include:
Diglycolammonium fluoride (DGAF)
Tetramethylammonium fluoride (TMAF)
Triethylamine tris (hydrogen fluoride) (TREAT-HF)
The Metal Chelating Agents that are Effective Include:
Acetoacetamide
Ammonium carbamate
Ammonium pyrrolidinedithiocarbamate (APDC)
Dimethyl malonate
Methyl acetoacetate
N-Methyl acetoacetamide
2,4-Pentanedione
Tetramethylammonium thiobenzoate
Tetramethylammonium trifluoroacetate
Tetramethylthiuram disulfide (TMTDS)
The combination of ammonium fluoride or a substituted fluoride source as identified above with an amine (other than as a surfactant in an amount of 1% or less) provides better stripping performance with less corrosivity than formulations containing ammonium fluoride without amines and formulations containing amines without ammonium fluoride. In addition, the resulting alkaline solutions were effective at lower processing temperatures (21°-40° C.) than conventional amine-containing formulations.
The use of 1,3-dicarbonyl compounds as chelating agents and to prevent metal corrosion also appears to increase effectiveness.
In the prior art amines are limited to 1% or less of the formulation and serve only as surfactants, or amines are not utilized as formulation ingredients at all. Also, the prior art formulations are acidic (pH<7). In the formulations of the present invention the amines are present as major components and play major roles in stripping, and the formulations are basic (pH>7).
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Fine Daniel N.
Fine Stephen A.
Guan George
Wojtczak William A.
Advanced Technology & Materials Inc.
Guillot Robert O.
Lund Jeffrie R.
Zitzmann Oliver A. M.
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