Polishing machine, workpiece supporting table pad, polishing method and manufacturing method of semiconductor device

This application is a Divisional of U.S. patent application Ser. No. 11/652,132, filed on Jan. 11, 2007, which is a Divisional of application Ser. No. 11/320,073, filed on Dec. 29, 2005, which is now U.S. Pat. No. 7,258,599, issued Aug. 21, 2007 and is based upon and claims priority of Japanese Patent Application No. 2005-268274, filed on Sep. 15, 2005 and Japanese Patent Application No. 2005-283802, filed on Sep. 29, 2005, the contents being incorporated herein by reference.

1. Field of the Invention

The present invention relates to a polishing machine of polishing a workpiece with a slurry, a workpiece supporting table pad, and a polishing method. Specifically, the present invention relates to a polishing machine including a machine for temporarily placing and holding a pre-polished or post-polished workpiece on a workpiece supporting table; a workpiece supporting table pad; and a polishing method.

The present invention also relates to a manufacturing method of a semiconductor device which is manufactured using CMP (chemical mechanical polishing) and a polishing machine suitable for CMP used for manufacturing a semiconductor device and, more particularly to a manufacturing method of a semiconductor device and a polishing machine whereby an abrasive adhered to a polished surface is cleaned quickly.

2. Description of the Prior Art

In recent years, as semiconductor devices have been increasingly miniaturized, surfaces of wafers (semiconductor substrates) on which insulating films and conductor films are formed are required to be smoothed with precision. In order to meet the needs, chemical mechanical polishing (CMP) machines are widely used nowadays. CMP machines are used in various processes for manufacturing semiconductor devices, such as polishing silicon wafers which are going to be turned into substrates, forming interconnects by use of the damascene method, and smoothing insulating films. In addition, CMP machines are used for manufacturing hard discs (magnetic recorders), manufacturing multichip modules (MCMs: hybrid integrated circuits), polishing lenses, and doing the like.

FIG. 1 is a schematic diagram showing an outline of a CMP machine used for manufacturing semiconductor devices. As shown in FIG. 1, the CMP machine includes a platen (table) 10, a polishing head (polishing carrier) 14, a slurry supplying nozzle 15 and a conditioning disc 12.

An abrasive pad (abrasive cloth) 11 is mounted on the platen 10. This platen 10 is fixed to a rotary shaft 10a, and rotates in response to rotation of the rotary shaft 10a. The polishing head 14 is disposed above the platen 10. A member for adsorbing and holding a wafer 13 is provided to the underside of this polishing head 14, and this member is termed as a membrane. The polishing head 14 is fixed to a rotary shaft 14a, and rotates in response to rotation of the rotary shaft 14a.

A conditioning disc 12 is also disposed above the platen 10. This conditioning disc 12 is fixed to a rotary shaft 12a, and rotates in response to rotation of the rotary shaft 12a. This conditioning disc 12 is used for keeping the surface of the abrasive pad 11 in a condition optimal for polishing the wafer during and after the polish. The conditioning disc 12 is also termed as a conditioner, and as a dresser.

The slurry supplying nozzle 15 is connected to a slurry supplying machine (not illustrated) through a tube 15a. A slurry is dropped from the slurry supplying nozzle 15 to the abrasive pad 11. A slurry dropped to the top of the abrasive pad 11 is supplied to the interstice between the abrasive pad 11 and the wafer 13 by means of rotation of the platen 10. Furthermore, a surface of the wafer 13 is mechanically and chemically polished with an abrasive (abrasive grains) and a chemical fluid contained in the slurry and the abrasive pad 11.

FIG. 2 is a perspective view of the CMP machine. FIG. 3 is a diagram showing a cross-section view of a load cup (also termed as a load/unload station or an HCLU) of the CMP machine and a partial cross-section view of the polishing head of the CMP machine. Detailed descriptions will be provided for the CMP machine by use of these figures.

As shown In FIG. 2, generally-used CMP machines are provided with a plurality of platens 10 (three platens 10 in the figure) and a load cup 20 on a base 2. A slurry supplying arm 31 provided with slurry nozzles at the end of the slurry supplying arm 31 and a conditioning disc driving arm 32 to which a conditioning disc 12 is attached are arranged around each of the platens 10. In addition, the polishing head 14 is attached to a head unit 30 supported by a rotary shaft 30a. In the case of the CMP machine shown in FIG. 2, three platens 10 and one load cup 20 are arranged around the rotary shaft 30a. The head unit 30 is provided with four polishing heads 14 corresponding to the three platens 10 and the lord cup 20. Wafers are transferred to the tops of the respective platens 10 by means of causing the head unit 30 to rotate while the wafers are adsorbed and held by the polishing head 14. Incidentally, the rotary shafts 14a of the polishing heads 14 are designed to reciprocate in the direction of a radius in which the head unit 30 rotates as shown by arrows in FIG. 2.

As shown in FIG. 3, the inside the load cup 20 is provided with a pedestal (workpiece supporting table) 21 for temporarily holding the wafers 13 (workpieces) which are going to be polished, or which have been polished. The inside of this pedestal 21 is a hollow, and the top of the pedestal 21 is provided with a plurality of nozzles (holes) 21a connecting with the hollow. The unfilled space (hollow) inside the pedestal 21 is connected with an internal unfilled space inside a hollowed shaft 22 supporting the pedestal 21. This internal unfilled space of the shaft 22 is connected to a source of supply of nitrogen gas, a source of supply of pure water and a vacuum pump through a plurality of selector valves (not illustrated).

Furthermore, the inside of the load cup 20 is provided with a positioning member (not illustrated) for aligning the wafers 13 respectively to the polishing heads 14. Incidentally, in the case of the CMP machine shown in FIGS. 2 and 3, the periphery of the pedestal 21 is provided with nozzles 23 for ejecting pure water to the polishing heads 14. These nozzles 23 are connected to the source of supply of pure water through piping 24.

The bottom of each of the polishing heads 14 is provided with an adsorbing member including a membrane 16 made of a thin film of rubber. This adsorbing member is connected to an air pressure regulating system. When the inner unfilled space of the adsorbing member is placed under a negative pressure, the membrane 16 is depressed upwards, and thus adsorbs the wafer 13. Such a configuration of CMP machines has been known heretofore (see Japanese Patent Laid-open Official Gazette Nos. 2003-71709 and Hei. 9-174420, and Japanese Patent Official Gazette No. 3439970, for example).

It should be noted that, as shown in a side view of FIG. 4A, a pedestal pad 25 is arranged on the pedestal 21 for the purpose of preventing the surface of the wafer 13 from being scratched. This pedestal pad 25 is made of a soft material. Specifically, the pedestal pad 25 is a two-layered configuration, where the upper layer is a vertical foam made of polyurethane, and the lower layer is a layer obtained by impregnating a non-woven fabric made of polyurethane fibers with polyurethane resin. Moreover, as shown in a plan view of FIG. 4B, the pedestal pad 25 is provided with holes 25a at positions matching with the nozzles 21a provided to the pedestal 21.

Incidentally, it is known that copper to be used for interconnects is prevented from being oxidized and corroded by means of keeping wafers, which have been polished by CMP, in an aqueous solution of benzotriazole (BTZ) (see Japanese Patent Laid-open Official Gazette No. 2000-277470, for example).

Generally, aluminum is used as a material for interconnects of semiconductor devices. However, in the case of highly-integrated and highly-performing semiconductor devices, copper is more used as the material for interconnects than aluminum, since copper has a smaller resistivity than aluminum and copper less causes electro-migration than aluminum. Chemical reaction makes greater contribution in a case where copper is polished by CMP than in a case when insulating films are polished by CMP. Incidentally, copper is more likely to be oxidized and corroded. In addition, the surface of copper which has been polished by CMP is extremely active, and oxidation and corrosion easily occurs in the surface. For this reason precautions are necessary for not only selection of a slurry and a cleaning fluid, but also treatment of wafers which have been polished.