System for cleaning semiconductor wafers

#The present invention generally relates to semiconductor wafer cleaning, and more particularly, to wet cleaning methods and apparatus employing controlled sonic energy.

#Semiconductor devices are manufactured or fabricated on semiconductor wafers employing a sequence of processing steps to create transistors and interconnection elements. These transistors are traditionally built in two dimensions but more recently in three dimensions, such as finFET transistors, as well. The interconnection elements include conductive (e.g., metal) trenches, vias, and the like formed in dielectric materials.

#In forming these transistors and interconnection elements, semiconductor wafers undergo multiple masking, etching, and deposition processes to form desired structures for the semiconductor devices. For example, multiple masking and plasma etching steps are performed to form recessed areas in a dielectric layer on a semiconductor wafer that serve as fins for a finFET transistor and trenches and vias for the interconnection elements. In order to remove particles and contaminations in fin structures and/or trench and via post etching or photoresist ashing, a wet cleaning step is necessary. However, a wet cleaning with chemicals may result in side wall loss. When device manufacture node migrates down to 14 or 16 nm and beyond, reducing side wall loss in fins, trenches and vias becomes crucial for maintaining critical dimensions. In order to reduce or eliminate the side wall loss, it is important to use moderate or diluted chemicals and sometimes even de-ionized water only. However, the moderate or diluted chemicals or de-ionized water are usually not efficient enough to remove particles in the fin structures and/or trenches and vias. As a result, mechanical force generated by ultra or mega sonic energy, for instance, is needed in order to remove those particles efficiently. Ultra sonic or mega sonic waves generate bubble cavitation to apply mechanical force to the wafer structures under cleaning.

#The drawings accompanying and forming part of this specification are included to depict certain aspects of the present disclosure. A clearer conception of the present disclosure, and of the components and operation of systems provided with the present disclosure, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The present disclosure may be better understood by reference to one or more of these drawings in combination with the description presented herein. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale.

#FIGS. 1A and 1B illustrate a wafer cleaning apparatus using ultra or mega sonic device according to an embodiment of the present invention.

#FIGS. 2A-2G illustrate various shapes of an ultra or mega sonic transducer.

#One aspect of the disclosure relates to controlling bubble cavitation in semiconductor wafer cleaning with sonic energy. Embodiments of the present disclosure will be described hereinafter with reference to the attached drawings.

#FIGS. 1A and 1B illustrate a wafer cleaning apparatus using ultra or mega sonic device according to an embodiment of the present invention. FIG. 1A is a cross-sectional view of the wafer cleaning apparatus that includes a wafer chuck 1014 holding a wafer 1010, a rotation driving module 1016 driving the wafer chuck 1014, and a nozzle 1012 delivering cleaning liquid 1032 to the surface of the wafer 1010. The cleaning liquid 1032 may be cleaning chemicals or de-ionized water. The wafer cleaning apparatus also includes an ultra or mega sonic device 1003 situated above the wafer 1010, so that with rotation of the wafer 1010 and a constant flow of the cleaning liquid 1032 from the nozzle 1012, a film of the cleaning liquid 1032 with thickness d is maintained between the wafer 1010 and the sonic device 1003. The sonic device 1003 further includes a piezoelectric transducer 1004 acoustically coupled to a resonator 1008 in contact with the cleaning liquid. The piezoelectric transducer 1004 is electrically excited to vibrate and resonator 1008 transmits high frequency sound energy into the cleaning liquid 1032. Bubble cavitation generated by the high frequency sound energy causes foreign particles, i.e., contaminants, on surfaces of the wafer 1010 to vibrate and break loose therefrom.

#Referring again to FIG. 1A, the wafer cleaning apparatus also include an arm 1007 coupled to the sonic device 1003 for moving the sonic device 1003 in a vertical direction Z, thereby changing the liquid film thickness d. A vertical driving module 1006 drives vertical movement of the arm 1007. Both the vertical driving module 1006 and the rotation driving module 1016 are controlled by a controller 1088.