PCD planers for dressing CMP pads: The enabling technology for manufacturing future moore's law semiconductors

Diamond pad conditioners can determine the efficiency of CMP processes and the quality of polished wafers. The polishing rate of a wafer is primarily determined by the amplitude (height) of the asperities on the pad surface. The polishing uniformity is mainly controlled by the frequency (density) of such asperities. Current diamond pad conditioners cannot create effectively the amplitude nor the density of pad asperities. This is because the tips of diamond grits are not leveled to the same height. Moreover, diamond grits are different in shapes and they orient differently, so their cutting behaviors are not predictable. Consequently, the dressed pad surface will show uneven texture with variable asperities. As a result, the wafer polishing is not fully controllable with variations in polishing rate, wafer uniformity, and defect counts. Instead of attaching individual diamond grits to a metal substrate, a revolutionary design of pad conditioners is made by carving the structure out of a strong polycrystalline diamond (PCD) matrix that is sintered at ultrahigh pressure (6 GPa) and high temperature (1350°C). Such Advanced Diamond Disks (ADD) are manufactured by electro discharge machining (EDM) of PCD to form cutting pyramids of a specific size with a designed shape. These pyramids can be distributed in a predetermined pattern. This is not possible with single crystal diamond grits that possess obtuse solid angles for cutting. ADD can produce a much higher density of pad asperities for uniform polishing wafers at high efficiency. The test data confirmed that ADD could dress pad more effectively than conventional pad conditioners. Moreover, the service lives of ADD as well as pad can be both lengthened due to the much milder dressing action. In addition, ADD may be resurfaced after their cutting edges become dull so the pad conditioners can be used over and over again. These unique features of ADD can reduce significantly the cost of consumable (CoC) of CMP for the manufacture of sophisticated semiconductors.