Grooved polishing pads and methods of use

#The present invention relates to the field of making polishing pads, and more specifically to providing macrotextured surfaces on polishing pads used in the chemicalmechanical planarization (CMP) of semiconductor substrates.

#Chemical-mechanical polishing has been used for many years as a technique for polishing optical lenses and semiconductor wafers. More recently, chemical-mechanical polishing has been developed as a means for planarizing intermetal dielectric layers of silicon dioxide and for removing portions of conductive layers within integrated circuit devices as they are fabricated on various substrates. For example, a silicon dioxide layer may cover a metal interconnect conformably such that the upper surface of the silicon dioxide layer is characterized by a series of non-planar steps corresponding in height and width to the underlying metal interconnects.

#The step height variations in the upper surface of the intermetal dielectric layer have several undesirable characteristics. Such non-planar dielectric surfaces may interfere with the optical resolution of subsequent photolithographic processing steps, making it extremely difficult to print high resolution lines. Another problem involves the step created in the coverage of a second metal layer over the intermetal dielectric layer. If the step height is relatively large, the metal coverage may be incomplete such that open circuits may be formed in the second metal layer.

#The features, operation, and advantages of the invention may be better understood from the following detailed description of the preferred embodiments taken in conjunction with the attached drawings, in which:

#FIG. 1 is an elevational view of the invention in partial section and in which its major components are illustrated diagrammatically;

#FIG. 2 is a planar cross-sectional view as taken along line 2—2 of FIG. 1;

#The polishing pad grooving method and apparatus of the present invention are illustrated best in FIGS. 1-3. The polishing apparatus has a platen 10 on which a polishing pad 12 is supported and held in a fixed radial position by a plurality of holding posts 14. Each of the holding posts 14 fits within a channel or recess 16 (FIG. 4) formed within the pad body or in the pad periphery and extending parallel to the central axis C of the pad so that the pad may be guided for axial movement away from the surface of the platen, as illustrated by the arrows Z and the air gap 17 shown in FIG. 3. However, for axially adjustable routers and/or flexible pads of sufficiently large diameter and small thickness to permit movement of the portion thereof being grooved, the holding posts 14 may be replaced by non-guiding clamps.

#Positioned opposite to the working surface 22 of pad 12 is a router bit 24 replaceably held in a chuck 26 and driven in rotation by a router motor 28. Router motor 28 is carried by a frame 30 surrounded by a casing 32, such that an annular space 34 is provided between the concentric walls of the frame and the casing, both of which are preferably cylindrical. A vacuum, represented by arrows V, V is provided in the annular space 34 by a blower 36 attached to the casing 32 by a flexible hose 38. The platen 10 is carried for rotation in either direction by a drive shaft 18 driven by a platen motor 20. Motors 20 and 28 may both be of the reversible type, such that the router bit 24 may be rotated in either direction, as indicated by the arrow R1, and the platen 10 also may be rotated in either direction, as indicated by the arrow R2.

#Mounted on the bottom wall 31 of the frame 30 adjacent to a passage 35 for the router bit 24 is a plurality of stop pins 33, which project parallel to the router bit for a distance that is less than the projecting distance of the router bit itself. The difference between the projecting distance of the pins 33 and the projecting distance of the router bit define the length of an end portion 37 of the bit equal to the desired depth of the groove to be cut by this end portion, as described more fully below in connection with operation of the invention. The projecting length of bit end portion 37 may be changed by rotating a pair of pinions 27, 27 that engage a corresponding pair of racks 29, 29 mounted on router motor 28 as shown in FIG. 1. The pins 33 are preferably threaded into the bottom wall 31 for axial adjustment, as an alternative means for changing the projecting length of bit end portion 37. Pins 33 may have a hex head portion 39 permitting engagement for rotation by a corresponding tool.