Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-10-15
2001-07-31
Quach, T. N. (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S688000, C438S717000, C438S720000
Reexamination Certificate
active
06268287
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to a method of photolithographic etching of metal lines, and more particularly, to a method of photolithographic etching of metal lines without polymer residue in the manufacture of integrated circuits.
(2) Description of the Prior Art
Aluminum and aluminum alloys are often used to form metal lines in integrated circuit processing. To prevent aluminum spiking, a barrier metal layer comprising titanium, titanium nitride, titanium tungsten, or the like, is deposited underlying the aluminum layer. A second barrier metal layer also comprising titanium or titanium nitride is deposited overlying the aluminum layer as both a barrier and an anti-reflective coating layer. An oxide hard mask layer is typically formed over the metal stack. In opening the oxide hard mask, the second barrier metal layer serves as the etch stop. During this etching, a polymer will be generated which includes titanium atoms. This metallic polymer has small solubility to alkaline stripper and thus remains as residue. It is desired to remove all of the polymer to obtain a polymerless hard mask metal etching.
U.S. Pat. No. 4,915,779 to Srodes et al discloses a PE-oxide hard mask for metal etching. U.S. Pat. No. 5,665,641 to Shen et al teaches a silicon oxide or silicon nitride hard mask wherein the hard mask etching chemistry comprises CHF
3
and CF
4
. U.S. Pat. No. 5,369,053 to Fang discloses a silicon oxynitride hard mask wherein the first etching comprises fluorine-based chemistry and etches through both the hard mask layer and the top barrier metal layer. None of these patents mentions the problem of metallic polymers.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide an effective and very manufacturable method of etching metal lines.
Another object of the present invention is to provide a method of etching metal lines without polymer residue.
A further object of the present invention is to provide a method of etching metal lines using a composite hard mask.
Yet another object of the present invention is to provide a method of etching metal lines using a composite hard mask and two-step hard mask etching process.
A still further object of the present invention is to provide a method of etching metal lines using a composite hard mask and two-step hard mask etching process to prevent the inclusion of titanium atoms within the polymer formed during hard mask etching.
Yet another object of the present invention is to provide a method of etching metal lines without polymer residue using a composite hard mask and two-step hard mask etching process.
In accordance with the objects of this invention a new method of etching metal lines without polymer residue using a composite hard mask and two-step hard mask etching process is achieved. An insulating layer is provided on a semiconductor substrate. A first barrier metal layer is deposited overlying the insulating layer. A metal layer is deposited overlying the barrier metal layer. A second barrier metal layer is deposited overlying the metal layer. A composite hard mask layer is deposited overlying the second barrier metal layer. A photoresist mask is formed overlying the composite hard mask layer having openings where openings are to be made within the metal layer. First, the composite hard mask layer is partially etched away where it is not covered by the photoresist mask. Second, most of the composite hard mask layer is overetched away leaving a patterned hard mask and a portion of the hard mask layer within the openings whereby a polymer is formed within the openings. Since the second barrier metal layer is covered by the hard mask layer within the openings, the polymer does not contain metallic atoms. The polymer is removed. Thereafter, the photoresist mask is removed. The metal layer and barrier metal layers not covered by the patterned hard mask are etched away to form metal lines wherein the hard mask layer within the openings is also removed.
REFERENCES:
patent: 4915779 (1990-04-01), Srodes et al.
patent: 5277750 (1994-01-01), Frank
patent: 5369053 (1994-11-01), Fang
patent: 5665641 (1997-09-01), Shen et al.
patent: 5847463 (1998-12-01), Trivedi et al.
patent: 5968711 (1999-10-01), Lee et al.
patent: 5981398 (1999-11-01), Tsai et al.
patent: 6043163 (2000-03-01), Tsai et al.
patent: 6080529 (2000-06-01), Ye et al.
patent: 11-214370 (1999-08-01), None
Park, C.K., et al., “Sub-Quarter-Micron Al Etching Technology Using SiON Hard Mask . . . ,” Microprocesses and Nanotechnology Conference, 1999, Digest of Papers, pp. 218-219.*
Ravijumar, R., et al., “Challenges of Aluminum RIE Technology at sub 0.45&mgr; Pitches,” Interconnect Technology, IEEE International Conference, 1999, pp. 203-205.
Huang Ming-Hsin
Tsai Chia-Shiung
Young Bao-Ju
Ackerman Stephen B.
Pike Rosemary L. S.
Quach T. N.
Saile George O.
Taiwan Semiconductor Manufacturing Company
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