Mixing manifold for multiple inlet chemistry fluids

#The general field of technology to which the present invention belongs is wafer manufacture and substrate processing equipment.

#Wafers or substrates with exemplary characteristics must first be formed prior to the formation of circuit devices. In determining the quality of the semiconductor wafer, the flatness of the wafer is a critical parameter to customers since wafer flatness has a direct impact on the subsequent use and quality of semiconductor chips diced from the wafer. Hence, it is desirable to produce wafers having as near a planar surface as possible by utilizing polishing and grinding apparatus.

#In a current practice, cylindrical boules of single-crystal silicon are formed, such as by Czochralski (CZ) growth process. The boules typically range from 100 to 300 millimeters in diameter. These boules are cut with an internal diameter (ID) saw or a wire saw into disc-shaped wafers approximately one millimeter (mm) thick. The wire saw reduces the kerf loss and permits many wafers to be cut simultaneously. However, the use of these saws results in undesirable waviness of the surfaces of the wafer. For example, the topography of the front surface of a wafer may vary by as much as 1-2 microns (μ) as a result of the natural distortions or warpage of the wafer as well as the variations in the thickness of the wafer across its surface. It is not unusual for the amplitude of the waves in each surface of a wafer to exceed fifteen (15) micrometers. The surfaces need to be made more planar (planarized) before they can be polished, coated or subjected to other processes.

#FIG. 1 is a simplified side view of a mixing apparatus and polishing system according to one embodiment of the present invention;

#FIG. 2 is a side view of the mixing manifold according to the one embodiment of the invention;

#FIG. 3 is an overall view of a mixing element for use in FIG. 2.

#The wafer shaping process requires multiple chemicals to be delivered to the wafer/pad interface. To reduce the number of chemistry holes entering the polishing platen, a manifold is used to combine the chemistries. The manifold has multiple inlets for coupling to multiple chemistry lines. For example, one inlet and line may be used for each chemical or fluid in the mixture. The manifold has a single output, although in other embodiments can have more than one output. A static mixer element, in one embodiment, is incorporated into the manifold to ensure appropriate mixing of the chemistries. Combining the static mixer element within the manifold, as opposed to in a separate mixer apparatus, reduces the linear distance of travel of the mixed chemistry. Hence, the time the chemicals spend in intimate contact with each other also is reduced. It is advantageous to reduce the time the chemicals are in contact due to the above noted use of a supplemental alkaline steam and the resultant instability in the slurry solution.

#By bringing together and thoroughly mixing the several components of the polishing chemistry in a single, compact, low-volume unit, the necessary degree of mixing is achieved while reducing or minimizing the risks associated with excessive chemical interaction time.

#In conjunction with the figures, one embodiment of the present invention will be described. As shown in FIG. 1, water, such as deionized water 34, and one or more chemistries (shown as blocks 31, 32, and 33) are delivered to the mixing manifold 20. In one embodiment, each chemistry is delivered to the mixing manifold by a separate line or tube which is coupled to the manifold with a fitting. Alternatively, two or more chemistries may be premixed and delivered to the manifold together, provided the premixed chemistries are stable and do not cause the colloidal silica particles to agglomerate and fall out of the suspension. The lines are coupled to the manifold with an appropriate number and type of fittings.