Method and apparatus for stopping mechanical and chemical-mechanical planarization of substrates at desired endpoints

#The present invention is related to mechanical and chemical-mechanical planarization of substrates, and more particularly, to a method and apparatus for consistently stopping planarization of substrates at a desired endpoint.

#Chemical-mechanical planarization ("CMP") processes remove material from the surface of a semiconductor wafer in the production of integrated circuits. FIG. 1 schematically illustrates a CMP machine 10 with a platen 20, a wafer carrier 30, a polishing pad 40, and a planarizing liquid 44 on the polishing pad 40. The polishing pad 40 may be a conventional polishing pad made from a continuous phase matrix material (e.g., polyurethane), or it may be a new generation fixed-abrasive polishing pad made from abrasive particles fixedly dispersed in a suspension medium. The planarizing liquid 44 may be a conventional CMP slurry with abrasive particles and chemicals that remove material from the wafer, or the planarizing liquid 44 may be a planarizing solution without abrasive particles.

#The CMP machine 10 also may have an under-pad 25 attached to an upper surface 22 of the platen 20 and the lower surface of the polishing pad 40. A drive assembly 26 rotates the platen 20 (as indicated by arrow A), or it reciprocates the platen 20 back and forth (as indicated by arrow B). Since the polishing pad 40 is attached to the under-pad 25, the polishing pad 40 moves with the platen 20.

#FIG. 1 is a schematic cross-sectional view of a chemical-mechanical planarization machine in accordance with the prior art.

#FIG. 2 is a partial schematic cross-sectional view of a chemical-mechanical planarizing machine in accordance with an embodiment of the invention.

#FIG. 3 is a partial cross-sectional view of the chemical-mechanical planarization machine of FIG. 2 at one point in accordance with an embodiment of a method of the invention.

#The preferred embodiment of the present invention is an apparatus and method for consistently stopping CMP processing at desired endpoints on semiconductor wafers, baseplates for field emission displays, and other related substrates. An important aspect of the preferred embodiment of the invention is to provide a substrate with a hydrophobic polish-stop stratum at a desired endpoint of the substrate and a hydrophilic cover layer over the hydrophobic polish-stop stratum. The hydrophobic polish-stop stratum and the hydrophilic cover layer also preferably have the desired electrical properties to be component parts of the integrated circuits formed on the semiconductor substrate. Another important aspect of the preferred embodiment of the invention is to planarize the substrate on a polishing pad with a hydrophobic planarizing surface. In operation, planarization virtually stops at exposed areas of the hydrophobic polish-stop stratum because the hydrophobic stratum and the hydrophobic planarizing surface repel aqueous solutions to substantially inhibit the chemicals and the abrasive particles in the aqueous solutions from contacting exposed areas of the hydrophobic polish-stop stratum. Therefore, the preferred embodiment of the invention provides a self-limiting endpoint for CMP processing that consistently stops planarization at the hydrophobic polish-stop stratum. FIGS. 2-4, in which like reference numbers refer to like parts throughout the various views, illustrate a planarizing system and a method of using the planarizing system in accordance with a preferred embodiment of the invention.

#FIG. 2 is a schematic cross-sectional view of a preferred embodiment of a chemical-mechanical planarization machine 110 and a substrate 150. The chemical-mechanical planarization machine 110 has a platen 120, an underpad 125 attached to the platen 120, a polishing pad 140 attached to the underpad 125, and a wafer carrier 130 positioned over the polishing pad 140. As discussed above with respect to FIG. 1, an actuator 126 moves the platen 120 and another actuator 136 moves a wafer holder 131 of the wafer carrier 130. The substrate 150 is mounted to the wafer holder 131, and the wafer carrier 130 moves the substrate 150 across the polishing pad 140 to remove material from the substrate 150. In the preferred embodiment of the invention, the polishing pad 140 and the substrate 150 interact with one another to selectively self-limit planarization of areas on the substrate at the desired endpoint.

#The polishing pad 140 preferably has a hydrophobic planarizing surface 142 facing the substrate 150. The polishing pad 140 may be wholly made from a hydrophobic material, or just an upper portion of the polishing pad 140 at the planarizing surface 142 may be hydrophobic. The planarizing surface 142 accordingly lacks affinity to water in the slurry 44 such that the surface tension of the slurry 44 inhibits the slurry from uniformly wetting the planarizing surface 142. Depending upon the hydrophobicity of the planarizing surface, the slurry 44 may "bead" on top of the planarizing surface 142 (shown in FIG. 2). In a preferred embodiment of the invention, the polishing pad is either a non-porous or a porous hydrophobic pad. One suitable non-porous hydrophobic pad is a non-porous polymeric polishing pad, and one suitable hydrophobic porous pad is the Rodel IC-1000 polishing pad, both of which are manufactured by Rodel Corporation of Newark, Del.