CMP slurry for polymeric interlayer dielectric planarization

This application claims priority to U.S. Provisional Patent Application No. 60/594,309, filed Mar. 28, 2005, the contents of which are herein incorporated by reference.

The present invention relates to a chemical mechanical polishing slurry. More particularly, this invention relates to a nanoparticle-based CMP slurry for polymeric dielectric planarization utilizing Zicronium-dioxide and Tetraethylorthosilicate TEOS-derived silica nanoparticle abrasives.

The semiconductor industry is constantly striving to improve the Integrated Circuits (IC) by: 1) reducing their operating delay, 2) adding more functionality and complexity, 3) adding more versatility, and 4) reducing the size. The complete and flawless global planarization of the thin film materials that form the wiring of the present day integrated circuit (IC) is one of the most prominent challenges in front of the semiconductor industry today.

With the incorporation of polymeric low dielectric constant materials (low k) in the IC wiring to increase the circuit speed, the demand for effective planarization has increased dramatically. Chemical Mechanical Polishing (CMP) process is universally used to planarize the constituent thin films of the IC interconnect wiring scheme. Compared to the other materials in the IC (e.g. Silicon, Tungsten, Silica, etc.), polymeric low k materials are much softer as compared to the abrasive particles used in the chemical active solution used (CMP Slurry) during the polishing process.

Hence, controlling polymeric ILD polishing to meet the stringent demands of the semiconductor industry and producing IC wiring without: 1) micro/nano scratching, 2) over polish, pattern damage, trough formation, etc, 3) material delamination, etc. is of paramount importance to make more sophisticated and cost effective chips of tomorrow.

The present invention provides a slurry for polymeric interlayer dielectric planarization comprising a colloidal suspension of TEOS-derived silica and ZrO 2 in a chemically active medium. In an advantageous embodiment the TEOS-derived silica and ZrO 2 are nanoparticles ranging in size from about 10 nm to about 200 nm and can have a particle concentration of the nanoparticles of TEOS-derived silica and ZrO 2 that range from about 2% to about 12% by weight. The slurry can employ one or more catalysts. Advantageous catalysts include TiO 2 , ZnO and SnO 2 . The slurry may also contain polyamide in the solution to prevent recombination of Si radical with BCB. Lastly, it is found advantageous to include one or more inorganic acids in the slurry. Preferred acids include TRIS-HCl, HNO 3 and H 2 SO 4 .

This invention is further illustrated by the following examples which should not be construed as limiting. The proposed slurry promises to be helpful in achieving the aforementioned demands of the semiconductor industry within the strict tolerances prescribed. Thus, this new technology will facilitate in the achievement of the widely published objectives of the semiconductor industry. Additionally this proposed slurry does not require any special conditions for operation.

These and other advantages will significantly bring down the cost of ownership (COO) of the CMP operations. The universal benefits of this technology include: 1) decrease in the IC cost, 2) wide implementation of the IC, 3) more versatility and faster operation the next current electronic products.

The proposed slurry has been used polishing and planarization of polymeric ILD materials specifically BCB. BCB is a highly thermostatic structure with inorganic —Si— linkage in the polymer which provides toughness and increases the glass transition temperature (Tg). The slurry consists of similar and variable sized Zicronium-dioxide (ZrO 2 ) and Tetraethylorthosilicate (TEOS)-derived silica nanoparticle abrasives ranging from 10 nm to 200 nm.

Each type of particle is employed on a stand-alone basis or in combination for the purpose of abrasion of the surface layer complex formed during CMP. The particle concentration of the slurry solution ranges from 2 to 12% by weight. The primary objective of the slurry is to precisely control the desired CMP output variables and prevent defects such as: 1) high surface roughness, 2) micro/nano scratching, 3) dishing, erosion or pattern damage, 4) delamination, 5) local non-planarity. The slurry solution is made of DI water and inorganic acids specifically TRIS-HCl, HNO 3 , H 2 SO 4 for surface reaction and active dissolution of the polymeric ILD being polished. The pH of the slurry is maintained between 2.0 to 12.0. The surface reactions are carried out in presence of catalysts such a TiO 2 , ZnO, SnO 2 , other metal oxides, ceramics, and elements and compounds derived and modified from them.

The abrasion of the material is carried out by maintaining the aforementioned abrasives along with formation of a nanoporous silica film as a result of the breaking Si—BCB linkage. The nanoporous silica also forms a protective thin film on the surface of the ILD materials, there by protecting it from the adverse effects of heat generation due to exothermic chemical reactions and mechanical abrasion.

The thin film has also shown to inhibit the heat transfer of the process to the polishing pad. This prevents the adverse process effects that may be caused due to pad surface heating and viscoelastic material reflow which inevitably leads to pad compliance and loss in planarity.

The slurry also contains polyamide in the solution to prevent recombination of Si radical with BCB. Finally, the complex salts formed as a result of the reaction also make the surface hydrophobic by reacting with the oxygen and nitrogen of the sample surface.