High selectivity CMP slurry

Details High selectivity CMP slurry High selectivity CMP slurry

2002-06-03

2003-09-09

Hail, III, Joseph J. (Department: 3723)

Abrading

Abrading process

Abradant supplying

C451S036000, C451S446000, C451S041000, C438S690000, C438S691000, C438S692000, C438S693000, C252S079100, C252S079200, C252S079400, C252S079500, C216S089000, C216S090000, C216S099000

Reexamination Certificate

active

06616514

ABSTRACT:

FIELD OF THE INVENTION
The present invention provides a chemical mechanical polishing slurry and, more particularly, a chemical mechanical polishing slurry that exhibits a high selectivity for silicon dioxide in preference to silicon nitride over a broad pH range.
BACKGROUND OF THE INVENTION
Hosali et al., U.S. Pat. No. 5,738,800, disclose a slurry for chemical mechanical polishing (CMP) a composite comprised of silicon dioxide and silicon nitride. The CMP slurry according to Hosali et al. comprises an aqueous medium, abrasive particles, a surfactant, and a complexing agent having two or more functional groups each having a dissociable proton that complexes with the silicon dioxide and silicon nitride. The surfactant used in conjunction with the complexing agent in the CMP slurry according to Hosali et al. does not perform the usual function of surfactants (i.e., the stabilization of the particulate dispersion), but rather it is believed by the inventors to affect the rate of removal of silicon nitride from the composite surface. The chemistry of the interaction between the surfactant and the complexing agent is not explained. The composition according to Hosali et al. exhibits selectivity better than conventional CMP slurries, but only within a narrow range of pH (from about 6 to about 7).
Grover et al., U.S. Pat. No. 5,759,917, disclose a CMP slurry for selectively polishing a silicon dioxide overfill in preference to a silicon nitride film stop layer during the manufacture of integrated circuit's and semiconductors. The CMP slurry according to Grover et al. comprises a carboxylic acid, a salt, and a soluble cerium compound at a pH within the range of from about 3 to about 11. The specification of Grover et al. states that a silicon dioxide to silicon nitride removal selectivity of from about 5 to about 100 is obtainable, but the highest reported selectivity in any of the examples in Grover is 34.89, and the substantial majority of the examples yield a selectivity of less than 20.
Kodama et al, EP 0 786 504 A2, disclose a CMP polishing composition comprising silicon nitride particles, water, and an acid. The CMP polishing composition according to Kodama et al. is said to exhibit high selectivity for polishing silicon dioxide relative to silicon nitride. The highest selectivity reported in any of the examples in Kodama et al. is 32.5, and the substantial majority of the examples yield a selectivity of less than 20.
Ronay, EP 0 846 740 A1, discloses a CMP slurry for shallow trench isolation (STI) processing that contains abrasive particles and a polyelectrolyte having a molecular weight of between about 500 and 10,000 such as, for example, polyethylenimine. The pH of the slurry must be kept between 9 to 11, and there is no information provided regarding whether the CMP slurry according to Ronay provides any degree of selectivity between silicon dioxide and silicon nitride.
Morrison et al., EP 0 853 335 A2, disclose a CMP slurry for STI processing that comprises a mixture of a conventional CMP slurry (typically colloidal silica suspended in an aqueous medium) to which has been added tetramethyl ammonium hydroxide and hydrogen peroxide. The modified CMP slurry according to Morrison et al. is said to improve the typical silicon dioxide to silicon nitride selectivity of 4 to as high as 30. The pH of the slurry must be maintained within a rather narrow range of from about 11 to 12.9.
Several literature references also discuss CMP slurries for use in STI processing. For example,
A High Oxide:Nitride Selectivity CMP Slurry for Shallow Trench Isolation
, by Sharath Hosali and Ray Lavoie, in Electromechanical Society Proceedings Volume 98-7 (1998), pages 218-234, discloses a slurry that is said to enhance the selectivity rate between silicon oxide and silicon nitride removal by CMP processes. The slurry disclosed in that reference includes cerium oxide as an abrasive with an undisclosed proprietary solution that inhibits the removal rate of the silicon nitride. This references reports that a high rate of selectivity can be obtained for unpatterned silicon wafers. However, the selectivity reported for the slurry on a patterned silicon wafer was almost the same as with the conventional CMP slurry it was compared against.
Another literature reference,
Application of Ceria
-
based High Selectivity Slurry to STI CMP For Sub
0.18
&mgr;m CMOS Technologies
, by Ki-Sik Choi, Sang-Ick Lee, Chang-II Kim, Chul-Woo Nam, Sam-Dong Kim, and Chung-Tae Kim, CMP-MIC Conference, Feb. 11-12, 1999, pages 307-313, discloses the use of a ceria-based CMP slurry in the process of forming an STI structure, but no specific information is provided regarding how to prepare the slurry. This reference teaches that dummy patterns are required in order to minimize a phenomena known as dishing, which is the formation of shallow depressions in the silicon dioxide filled trenches below the plane of the top surface of silicon nitride stop layer during CMP processing. This reference also reported that there were some problems related to scratches being formed by the ceria abrasive which required filtering to correct.
Yet another literature reference,
A Production
-
Proven Shallow Trench Isolation
(
STI
)
Solution Using Novel CMP Concepts
, by Raymond R. Jin, Jeffery David, Bob Abbassi, Tom Osterheld, and Fritz Redeker, CMP-MIC Conference on Feb. 11-12, 1999, pages 314-321, discusses the problem of having to use dummy patterns to reduce dishing. The solution offered is to employ a low selectivity, or no selectivity, CMP slurry for minimizing dishing during CMP processing in combination with a special system, apparatus, and polishing heads.
Finally, yet another literature reference,
A Wide Margin CMP and Clean Process For Shallow Trench Isolation Applications
, by Brad Withers, Eugen Zhoa, Rahul Jairath, CMP-MIC Conference on Feb. 19-20, 1998, pages 319-327, addresses the problems of process cost and complexity due to the need for block masks, pattern resist etch, high selectivity material overlays or implementation of dummy active areas. No solutions for these problems are provided.
It should be readily apparent from the foregoing that there remains a need within the art for a method of chemical mechanical polishing and a slurry that exhibits high selectivity for silicon dioxide in preference to silicon nitride and that has a wide working range of pH.
SUMMARY OF THE INVENTION
The present invention provides a chemical mechanical polishing slurry that is effective over a wide range of pH for selectively removing silicon dioxide in preference to silicon nitride from a surface of an article by chemical mechanical polishing. The aqueous slurry according to the present invention comprises an abrasive, an aqueous medium, and an organic polyol that does not dissociate protons, said organic polyol comprising a compound having at least three hydroxyl groups that are not dissociable in the aqueous medium, or a polymer formed from at least one monomer having at least three hydroxyl groups that are not dissociable in the aqueous medium. In a preferred embodiment, the abrasive comprises ceria particles and the organic polyol comprises one or more selected from the group consisting of mannitol, sorbitol, mannose, xylitol, sorbose, sucrose, and dextrin. The aqueous slurry according to the invention can optionally include acids or bases for adjusting the pH within an effective range of from about 2 to about 12.
The present invention also provides a method of selectively removing a first substance such as silicon dioxide in preference to silicon nitride from a surface of an article by chemical-mechanical polishing. The method of the present invention comprises polishing a surface of an article using a polishing pad, an abrasive, an aqueous medium, and an organic polyol that does not dissociate protons, said organic polyol comprising a compound having at least three hydroxyl groups that are not dissociable in the aqueous medium, or a polymer formed from at least one monomer having at least three hydroxyl groups that are not disso

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