Apparatus and methods for multi-step chemical mechanical polishing

#The present invention relates to apparatus and methods for chemical mechanical polishing a substrate.

#An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a patterned stop layer, and planarizing the filler layer until the stop layer is exposed. For example, trenches or holes in an insulative layer may be filled with a conductive layer. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs and lines that provide conductive paths between thin film circuits on the substrate.

#Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed against a rotating polishing pad. The polishing pad may be either a “standard” (non-fixed-abrasive) pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles if a standard pad is used, is supplied to the surface of the polishing pad.

#FIG. 1 is a schematic exploded perspective view of a chemical mechanical polishing apparatus.

#FIG. 2 is a top view of the CMP apparatus of FIG. 1.

#FIG. 3A is a top view of the first polishing station of the CMP apparatus of FIG. 1.

#Referring to FIGS. 1 and 2, one or more substrates 10 will be polished by a chemical mechanical polishing apparatus 20. A description of a similar polishing apparatus may be found in U.S. Pat. No. 5,738,574, the entire disclosure of which is incorporated herein by reference. Polishing apparatus 20 includes a machine base 22 with a table top 23 that supports a series of polishing stations, including a first polishing station 25a, a second polishing station 25b, and a final polishing station 25c, and a transfer station 27. Transfer station 27 serves multiple functions, including receiving individual substrates 10 from a loading apparatus (not shown), washing the substrates, loading the substrates into carrier heads, receiving the substrates from the carrier heads, washing the substrates again, and finally, transferring the substrates back to the loading apparatus.

#Each polishing station includes a rotatable platen. At least one of the polishing stations, such as first station 25a, includes a polishing cartridge 102 mounted to a rotatable, rectangular platen 100. The polishing cartridge 102 includes a linearly advanceable sheet or belt of fixed-abrasive polishing material. The remaining polishing stations, e.g., second polishing station 25b and final polishing station 25c, may include “standard” polishing pads 32 and 34, respectively, each adhesively attached to a circular platen 30. Each platen may be connected to a platen drive motor (not shown) that rotates the platen at thirty to two hundred revolutions per minute, although lower or higher rotational speeds may be used. Assuming that substrate 10 is an “eight-inch” (200 mm) diameter disk, then rectangular platen 100 may be about twenty inches on a side, and circular platen 30 and polishing pads 32 and 34 may be about thirty inches in diameter.

#Each polishing station 25a, 25b and 25c also includes a combined slurry/rinse arm 52 that projects over the associated polishing surface. Each slurry/rinse arm 52 may include two or more slurry supply tubes to provide a polishing liquid, slurry, or cleaning liquid to the surface of the polishing pad. For example, the polishing liquid dispensed onto the fixed-abrasive polishing sheet at first polishing station 25a will not include abrasive particles, whereas the slurry dispensed onto the standard polishing pad at second polishing station 25b will include abrasive particles. If final polishing station 25a is used for buffing, the polishing liquid dispensed onto the polishing pad at that station would not include abrasive particles. Typically, sufficient liquid is provided to cover and wet the entire polishing pad. Each slurry/rinse arm also includes several spray nozzles (not shown) which provide a high-pressure rinse at the end of each polishing and conditioning cycle.