Post metal etch photoresist strip method

Details Post metal etch photoresist strip method Post metal etch photoresist strip method

2000-06-26

2001-08-07

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S710000, C438S725000, C430S330000

Reexamination Certificate

active

06271115

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a method of fabrication used for semiconductor integrated circuit devices, and more specifically to an improved method of post-metal etch stripping of a photoresist mask and removal of residual corrosion inducing components.
(2) Description of Related Art
In the fabrication of semiconductor integrated circuits metal conductor lines are used to interconnect the many components in device circuits. Due to shrinkage in size of semiconductor components and increased circuit density, the complexity of interconnecting the many components in the dense circuits requires that the fabrication processes used to define the metal interconnect patterns provide precise dimensional control. Advances in lithography and masking techniques and dry etching processes, such as RIE (Reactive Ion Etching) and other plasma etching processes, allow production of sub-micron width conducting patterns with spacings also in the sub-micron range. In general, as illustrated in
FIG. 1
, the process steps used to pattern metal conductor patterns comprise: Step
10
, deposition of a conducting layer; Step
11
, formation by standard lithographic techniques of a photoresist mask or other mask, such as titanium oxide, silicon oxide or silicon oxynitride, in the form of the desired metal interconnection pattern; Step
12
, loading the substrate to an etch tool; Step
13
, dry etching to remove the conducting layer from areas not covered by the mask; Step
14
, transferring the substrate to a photoresist strip chamber; Step
15
, removing the photoresist mask layer, exposing the top surface of the metal layer; and then, Step
16
, unloading the substrate from the etch tool.
As is well known in the industry, dry etching processes for metal layers composed of aluminum or aluminum alloys use chlorine and chlorine compounds as reactive components in the etchant gas. During the etching process the chlorine and chlorine compounds, as well as chlorine bearing reaction products, become embedded in and/or attached to the masked pattern sidewalls and other surfaces on the substrate. For example, chlorine and chlorine compounds and chlorine bearing reaction products become embedded into the photoresist mask on top of the etched metal pattern and attached to the sidewalls of the etched pattern. If the chlorine, chlorine compounds, and chlorine bearing reaction products are not removed or passivated before the substrate is exposed to the atmosphere of the manufacturing plant, then the residual chlorine causes corrosion and attack of the etched metal pattern. This corrosion is unacceptable, thereby reducing the yield of the metal etch process. Additionally, if the corrosion is not immediately detected, it will show up later as a cause for a device failure or as a contributing factor in a reliability failure mechanism. Therefore, it is extremely important that following a metal etch process the residual chlorine, chlorine compounds, and chlorine bearing reaction products be removed from all surfaces of the substrate and sidewalls of the etched metal pattern. The challenge in the industry is to provide post-metal etch processes which efficiently and effectively strip the photoresist mask and, also, remove residual chlorine, chlorine compounds, and chlorine bearing reaction products.
It is a well known fact that O
2
can be used to remove or etch photoresist, as shown in U.S. Pat. No. 4, 732,658 entitled “Planarization Of Silicon Semiconductor Devices” granted Mar. 22, 1988 to Eddie C. Lee, which shows a dielectric planarization process in which a photoresist layer is deposited over a dielectric layer having topographical features and then etching back all of the photoresist and enough of the dielectric layer to form a substantially planar surface of the dielectric material. The etchback process, using CHF
3
and O
2
, etches photoresist and the dielectric at substantially the same rate. However, this patent does not address the removal of chlorine, chlorine compounds, or chlorine bearing reaction products following dry etching of an aluminum interconnection pattern.
U.S. Pat. No. 5,792,672 entitled “Photoresist Strip Method” granted Aug. 11, 1998 to Lap Chan et al. describes a two step photoresist strip method in which after etching a conducting material the substrate containing the etched pattern is transferred to a second heated chamber and the photoresist is stripped first in a plasma containing O
2
and H
2
O and second in a plasma containing O
2
. While this process offers an improvement to state-of-the-art photoresist stripping, there continues to remain a challenge to devise effective methods to strip photoresist masks from etched aluminum or aluminum-copper interconnection patterns subsequent to etching the pattern in a chlorine containing plasma and to remove chlorine, chlorine compounds, or chlorine bearing reaction products following the dry etching of the aluminum or aluminum-copper interconnection pattern.
U.S. Pat. No. 5,824,604 entitled “Hydrocarbon-Enhanced Dry Stripping Of Photoresist” granted Oct. 20, 1998 to Ronny Bar-Gadda describes a method of stripping photoresist using a microwave stripper and a plasma containing an oxidizing gas, a fluoride-containing compound, and a hydrocarbon-containing reactive species.
The present invention is directed to a novel method of stripping a photoresist mask from the surface of an aluminum or aluminum-copper pattern formed by dry etching processes using gaseous Cl
2
and BCl
3
etchants by using alternating steps for passivation and photoresist stripping which sequentially passivate the etched aluminum or aluminum-copper surfaces and remove the photoresist. Superior results are obtained using a five step process which combines passivation and photo-resist stripping in Step
1
, followed by photoresist stripping in Step
2
, followed by passivation in Step
3
, followed by photoresist stripping in Step
4
, followed by passivation in Step
5
.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved method for removing a photoresist mask from an etched aluminum or aluminum-copper pattern after etching the pattern in a chlorine containing plasma.
Another object of the present invention is to provide an improved method for removing residual chlorine containing fragments from the surfaces and sidewalls of an aluminum or aluminum-copper pattern after etching the pattern in a chlorine containing plasma.
In accordance with the present invention, the above and other objectives are realized by using a method of fabrication of a conductive interconnection layer in an integrated circuit comprising the steps of: loading a wafer cassette, containing substrates having a photoresist mask pattern formed over a conductive material layer, to a plasma etcher apparatus; etching the conductive material layer by vertical anisotropic etching; transferring the substrate to a second heated chamber; and first stripping, using a microwave generated plasma, the photoresist mask in the second heated chamber in a first plasma containing O
2
and H
2
O.
A second embodiment of the present invention comprises the steps of: loading a wafer cassette, containing substrates having a photoresist mask pattern formed over a conductive material layer, to a plasma etcher apparatus; etching the conductive material layer by vertical anisotropic etching; transferring the substrate to a second heated chamber; and first stripping, using a microwave generated plasma, the photoresist mask in the second heated chamber in a first plasma containing O
2
and H
2
O and one or more gases from the group comprising nitrogen, hydrogen, fluorine, fluorocarbons, fluorine-substituted hydrocarbons, hydrogen bromide, forming gas and argon or other inert gases.
A third embodiment of the present invention comprises the steps of: loading a wafer cassette, containing substrates having a photoresist mask pattern formed over a conductive material layer, to a plasma etcher apparatus; etching the conductive material layer by v

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