Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
2001-05-16
2003-09-09
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S307000, C106S003000
Reexamination Certificate
active
06616717
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention described in this patent pertains to the polishing and planarization of integrated circuit surfaces, particularly those comprising a metal, a barrier layer, and an insulating layer.
2. Discussion of Related Art
Chemical/Mechanical Planarization (or polishing), or CMP, is an enabling technology used in the semiconductor industry to remove/planarize various thin films from the surface of semiconductor substrates during the production of integrated circuits. While initial applications of this technology focused on the polishing of dielectric films (such as SiO
2
), polishing of metal films used for circuit interconnects is undergoing rapid growth. Currently, tungsten and aluminum are the most common metals used for interconnect structures. However, copper interconnects, coupled with low-k dielectrics, have the potential (when compared to Al/SiO
2
) to increase chip speed, reduce the number of metal layers required, minimize power dissipation, and reduce manufacturing costs.
However, the challenges associated with the successful integration of copper interconnects are not trivial. A typical copper interconnect structure contains a trench formed in silicon dioxide (typically 10,000 angstroms deep and 1-100 microns wide) formed above the silicon substrate. A barrier layer of material (used to improve adhesion of the copper as well as inhibit the diffusion of copper into the dielectric structure) is typically deposited after the trench is formed, and is usually composed of either tantalum, tantalum nitride, titanium, or titanium nitride. This barrier material is also deposited on the horizontal dielectric surface above the trench. The barrier layer is typically <1000 angstroms thick. Copper is then deposited by chemical vapor deposition or electroplating on top of this structure in order to fill the trench structure. To insure complete filling of the trench, an overlayer of copper of 10,000-15,000 angstroms is usually required. CMP is then used to remove the overburden of copper above the trench and the horizontal barrier material above the trench. In order to do this successfully and economically, the copper removal should be as fast as possible, typically above 3000 angstroms/minute. Also, to avoid removal of the copper within the trench (typically referred to as “dishing”), removal of the barrier layer at rates comparable to that of the copper film are necessary. Additionally, to avoid degradation of the SiO
2
film beneath the barrier layer (typically referred to as “erosion”), and to improve global planarization, the removal rate of the underlying dielectric film should be as low as possible. In summary, the selectivity for the removal rate of the barrier film (tantalum, tantalum nitride, titanium, or titanium nitride) should be high with respect to the copper film, while the selectivity for the removal rate of the dielectric film (SiO
2
) should be low (preferably <100:1).
To accomplish these requirements, a two-step polishing process using two different slurries has been proposed. In U.S. Pat. No. 5,676,587, Selective Polish Process for Titanium, Titanium Nitride, Tantalum, and Tantalum Nitride, a two-step process using first (1) a slurry to remove the majority of the metal film (such as tungsten or copper) and second (2) a slurry to remove the barrier film is proposed.
To suppress the removal rate of silicon dioxide during CMP processes, various additives have been previously suggested that passivate the silicon dioxide surface. In U.S. Pat. No. 5,614,444, Method of using Additives with Silica-Based slurries to Enhance Selectivity in Metal CMP, an additive comprising at least one polar component and one apolar component is suggested to suppress oxide removal. This patent lists a number of compounds containing both polar and non-polar groups, which are either anionic (potassium butylsulphate), cationic (tetrabutyl ammonium hydroxide), or non-ionic (butanol). However, this patent claims as a necessity both a polar and apolar component (group) to be present.
In U.S. Pat. No. 5,876,490 polyelectrolytes are used to coat the abrasive particles in a slurry. The polyelectrolytes impart normal stress effects to the slurries. In solution, the polyelectrolytes exhibit normal stress effects and their adsorption on the abrasive particles impart the same behavior to the particles.
According to U.S. Pat. No. 5,876,490, in order to achieve planarization, the quantity of polyelectrolyte in the abrasive suspension is such that a fraction of the particles will be coated with the polyelectrolyte, while another fraction of the abrasive particles will remain uncoated. In order to achieve this, the weight percent of the polyelectrolyte should be about 5 to about 50 percent, preferably about 15 to about 30 percent by, weight, and most preferably about 20 percent by weight of the abrasive particles in the slurry. These ratios depend somewhat on the relative size of the abrasive particles and the polyelectrolyte.
The slurry compositions of U.S. Pat. No. 5,876,490 that contain the polyelectrolyte are preferably prepared by adding the polyelectrolyte to the slurry already containing the abrasive particles, thereby coating a fraction of the abrasive particles “in situ.” In an alternative procedure, a fraction of the abrasive particles can be precoated and then admixed with the slurry containing the remaining abrasive particles which will be uncoated. In addition, it may be desirable to pretreat a portion of the abrasive particles to render them more susceptible to adsorption of the polyelectrolyte from the slurry.
U.S. Pat. Nos. 5,391,258; 5,476,606; 5,738,800; 5,770,103 describe compounds which in CMP slurries provide attenuation of silicon dioxide removal. These patents are hereby incorporated by reference and made a part of this specification.
SUMMARY OF THE INVENTION
The present invention is directed to one or more organic polymers which have surprisingly been found to attenuate the removal of the oxide film during metal CMP and offers an improvement over earlier slurries. This organic polymer is a high molecular weight organic polymer containing a carbon backbone with functional moieties extending from the backbone. The functional moieties interact strongly with the silicon dioxide surface so as to provide a protective layer that inhibits the removal of the silicon dioxide film at appreciable levels. The mechanism of interaction between the functional moieties and the hydroxyl surface is, though not limited to, that observed in the hydrogen bonding of polar species (such as the interaction of hydroxyl groups). The organic polymer is further defined as a high molecular weight organic material, having a degree of polymerization of at least 3 (i.e., 3 monomeric units polymerized into a molecule), more preferably more than 10, and most preferably greater than 50. The organic polymer comprises a plurality of moieties having affinity to surface groups (i.e., silanol and siloxane) contained on silicon dioxide surfaces. These moieties are commonly polar moieties, such as, but not limited to, hydroxy, carboxy, carbonyl, alkoxy, sulphonyl, and phosphonyl. Examples of this type of organic polymer molecule includes polyvinyl alcohol, polyvinylpyrrolidone, polymethylmethacrylate, polyformaldehyde, polyethylene oxide, polyethylene glycol, and polymethacrylic acid.
Many of these same compounds are mentioned as being useful for coating abrasive particles in U.S. Pat. No. 5,876,490 as discussed above. Their use as a silicon dioxide rate suppressant is not mentioned in '490. Moreover, the polyelectrolytes of the present invention have been found to be effective as a silicon dioxide rate suppressant at concentrations below about 5 percent by weight of the abrasive particles in a slurry. They have also been found to be effective when having a molecular weight of greater than about 10,000.
Another aspect of the present invention is a method of polishing a substrate comprising a metal and an insulator wherein the substrate is pressed against
Burke Peter A.
Gettman David
Lack Craig D.
Lane Sarah
Langlois Elizabeth A. (Kegerise)
Benson Kenneth A.
Biederman Blake T.
Kita Gerald K.
Marcheschi Michael
Rodel Holdings Inc.
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