Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to improved apparatus for fabricating semiconductor devices having a nozzle and a spin chuck, and more particularly, to an apparatus with a cover, spaced apart from and confronting the wafer surface, for protecting wafers from solutions used to fabricate the semiconductor devices. 
     2. Description of the Related Art 
     Generally, semiconductor devices are created by depositing various insulating or metallic layers on a semiconductor wafer to form a multiple layer structure. Desired circuit patterns are formed on the layers according to the properties of the respective semiconductor devices. 
     The circuit patterns are formed by photolithography processes, which generally comprise coating a photoresist on the wafer, aligning a photo mask having the circuit pattern formed thereon with the wafer, and then exposing selected areas of the photoresist consistent with the pattern. The exposed portion of the photoresist is removed using a developing solution so as to form a photoresist pattern. Thereafter, an etching process is performed using the photoresist pattern as an etching mask to thereby form the desired circuit pattern. 
     During the photolithography process, specific solutions (e.g., solutions used in the semiconductor device fabrication process or developing solutions) are sprayed onto the substrate using a nozzle and a spin chuck as shown in FIG.  1 . The spin chuck  12  secures the wafer W thereon, usually via vacuum suction, and rotates it at a specific speed. A specific solution  13  is sprayed through the nozzle  14  and onto the wafer W surface. More than one nozzle  14  may be provided, and the nozzle locations may be varied according to the process steps and operating conditions. 
     As the solution  13  is sprayed through the nozzle  14 , the wafer W is rotated by rotating the spin chuck  12 , so that the solution  13  is uniformly dispersed or coated along the entire wafer surface. However, as the solution  13  reaches the edge portion of the wafer W, it is scattered due to the centrifugal force of the rotating wafer W. 
     A bowl  18 , provided inside a process chamber  16 , surrounds the spin chuck  12 , nozzle  14 , and wafer W, to prevent the solution  13  supplied onto the wafer W from being scattered onto the inner wall of the process chamber  16 . However, some of the solution  13  contacting the bowl  18  is undesirably reflected back onto the wafer W, as shown by the arrows in FIG. 1, which serves as a source for particle generation. The unwanted solution  13  reflected from the bowl  18  may cause pattern bridges and profile failures during the formation of the pattern. Such defects require the wafer W to be rejected or reworked, thereby resulting in a reduction in productivity. 
     To minimize the unwanted reflected solution, conventional procedures seek to precisely control the process parameters, such as the viscosity of the solution  13  or the rotation speed of the spin chuck  12 . However, such process control parameters must take into account the desired parameters of the overall fabrication process, and as such, the process control ranges are limited. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for fabricating semiconductor devices with a nozzle, a cover and a spin chuck that minimizes the occurrence of pattern formation failures during the semiconductor device fabrication process. 
     To achieve this and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, the apparatus for fabricating semiconductor devices comprises a spin chuck configured for mounting a wafer thereon and operative to rotate the wafer. A nozzle is arranged above the spin chuck, through which a solution is supplied to a surface of the wafer mounted on the spin chuck. A bowl surrounds the spin chuck, the bowl have a width greater than a diameter of the wafer mounted to the spin chuck, and a height greater than a combined height of the wafer mounted to the spin chuck. A cover is spaced apart from and confronts the spin chuck having the wafer mounted thereon. The cover has an opening through which a distal end of the nozzle passes so as to spray the solution onto the wafer surface while the cover is disposed over the wafer surface. The cover prevents any solution reflected back from the bowl from reaching the wafer surface. 
     The spin chuck and wafer cover may each be capable of vertical movement. The cover is preferably spaced 2 mm to 3 mm from the wafer surface. 
     If a plurality of nozzles are employed, the cover would have a corresponding plurality of openings to accommodate the nozzles passing there through. One or more of the openings may be radially elongated, thereby forming a slot in the cover, so that the nozzle may move back and forth in the radial direction along the slot. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a side view of a conventional apparatus for fabricating semiconductor devices with a nozzle and a spin chuck; 
     FIG.  2  and FIG. 3 are side views of an apparatus for fabricating semiconductor devices with a cover over the wafer surface according to embodiments of the present invention; 
     FIG. 4 is a perspective view of the cover according to the present invention; and 
     FIG. 5 is a perspective view of the cover according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     Referring to FIG. 2, there are provided a spin chuck  42 , which is capable of rotating a wafer W mounted thereon at a certain speed. The wafer W is typically secured to the spin chuck  42  via vacuum suction. A nozzle  44  is positioned above the spin chuck  42 . One end of the nozzle  44  is connected to a source of solution  43  (e.g., photoresist, a developing solution, a thinner, etc.) used in manufacturing semiconductor devices. The particular solution  43  is sprayed through the distal end of the nozzle  44  and onto the wafer W mounted on the spin chuck  42 . The spin chuck  42  rotates the wafer W as the nozzle  44  sprays the solution  43  onto the wafer surface. The spin chuck  42  may be constructed such that it moves up/down with respect to the orientation shown in FIG. 2, using any suitable means to effect the vertical movement. 
     In addition, the nozzle  44  may be constructed such that it may be moved up/down or right/left, with respect to the orientation shown in FIG. 2, such that the nozzle  44  may be directed to a specific location on the wafer W. If one nozzle  44  is employed, it would have the capability of being connected to various source of solution  43  (e.g., photoresist, a developing solution, a thinner, etc.). 
     Alternatively, if a plurality of nozzles  44  are employed, each nozzle  44  could be connected to a different source of solution  43 , and each nozzle  44  would be capable of moving up/down or right/left, with respect to the orientation shown in FIG. 2, using any suitable means to effect the vertical and horizontal movement. 
     For example, in an apparatus for fabricating semiconductor devices having three nozzles  44 , two nozzles  44  would be positioned over the wafer W to spray photoresist thereon, and one nozzle  44  would be positioned in close proximity to the circumferential edge of the wafer W for spraying a rinsing solution, such as thinner, to rinse the peripheral portion of the wafer W after the spraying of the photoresist. 
     As shown in FIG. 2, a bowl  48  surrounds the spin chuck  42  and wafer W mounted thereon. Note that the bowl  48  has a width greater than a diameter of the wafer W mounted on the spin chuck  42 , and a height greater than a combined height of the wafer W mounted on the spin chuck  42 . This configuration prevents the solution  43  that is sprayed onto the wafer W from being scattered toward the inner wall of the process chamber  46 . 
     The bowl  48  may be comprised of various shapes, for example, tubular, cylindrical, or square shaped. In the embodiment shown in FIG. 2, the upper ends of the bowl  48  are inclined inwardly toward the central vertical axis of the wafer W to further prevent solution  43  from being scattered toward the inner wall of the process chamber  46 . 
     In order to protect the wafer W from any solution  43  that is reflected back from the inner wall of the bowl  48  (see arrows in FIG.  2 ), a cover  50  is provided over the wafer W mounted on the spin chuck  42 . In other words, the cover  50  is spaced apart from and confronts the wafer surface. The distance between the cover  50  and the wafer W mounted on the spin chuck  42  is determined with reference to the final thickness of the solution  43  sprayed on the wafer W. Preferably, the distance is between about 2 mm to 3 mm. Of course, distances of less than 2 mm or greater than 3 mm are contemplated within the scope of this invention. 
     Preferably, the cover  50  is constructed so as to be movable up/down with respect to the orientation shown in FIG. 2 so as to facilitate efficient loading of the wafer W on the spin chuck  42 . Such up/down movement of the cover  50  can be achieved using any suitable moving apparatus, such as a lifter. Alternatively, if a robot arm is used, the cover  50  may be moved up/down as well as right/left. 
     The various locations of the moving apparatus, for example, inside the process chamber  46  or the outside thereof, the particular moving apparatus itself, and the range or degree of movement for the cover  50 , are variations that can be made by one of ordinary skill in the art within the scope of the present invention. 
     As shown in FIG. 2, the cover  50  is attached to the side to the of the process chamber  46 , using a fixed member  55  connected to a fixing device  54 . Any suitable means of providing an attachment between the cover  50  and the process chamber  46  may be utilized. Preferably, the attachment means would include a slide mechanism to allow the cover  50  to be moved up/down. 
     FIG. 3 depicts an alternate embodiment, wherein the cover  60  is attached to the upper end of the bowl  48  via a fixing device  64 . As with the embodiment of FIG. 2, any suitable means of providing an attachment between the cover  60  and the bowl  48  may be utilized. Preferably, the attachment means would include a slide mechanism to allow the cover  60  to be moved up/down. The same reference numerals in FIG. 3 refer to the like elements in FIG. 2, and the discussion of these elements is thus omitted as redundant. 
     The cover  50 ,  60  of the present invention can be installed in various manners based on the diameter of the wafer W mounted on the spin chuck  42 , and as in the embodiment of the present invention, the cover  50 ,  60  may have the same diameter as that of the wafer W or slightly larger. 
     As shown in FIG. 4, the cover  50 ,  60  has openings  52  formed therein so that the distal end of the nozzle(s)  44  may pass there through to supply the solution  43  to the surface of the wafer W with the cover  50 ,  60  installed. The number of openings  52  preferably corresponds to the number of nozzles  44  employed in the various process steps. Note also that the openings  52  are radially spaced along the cover  50 ,  60  to correspond to the spacing of the nozzles  44  over the wafer W. FIG. 4 also depicts the fixing means  54 ,  64  for attaching the cover  50 ,  60  to the process chamber  46  or bowl  48 , respectively. 
     FIG. 5 depicts another embodiment of the present invention in which a radially elongated slot  72  is formed in the cover  70 . With such a configuration, a nozzle  44  may be moved horizontally along the surface of the wafer W as it sprays a solution  43  onto the wafer surface. Similar fixing devices  54 ,  64  as shown in FIGS. 2-4 may be used to attached the cover  70  to either the process chamber  46  or bowl  48 . One or more of the slots  72  may be incorporated in the cover  50 ,  60  of FIG.  4 . 
     The apparatus of the present invention having the cover  50 ,  60 ,  70  can be employed in wide variety of semiconductor device fabricating equipment, including equipment for coating photoresist on a wafer W, for spraying a developing solution onto a wafer W, and for spraying a rinsing solution, such as thinner, onto the wafer W. The cover  50 ,  60 ,  70  is preferably made of transparent material in order to effectively check the solution  43  spraying operations, and to facilitate cleaning of any scattered solution  43 . For example, a transparent chemically-resistant material, such as TEFLON™ (DuPont Co.), can be used because it will withstand not only the solutions  43 , but the cleaning solutions used to remove the solutions  43  adhered to the cover  50 ,  60 ,  70 . 
     Therefore, according to the present invention, the cover  50 ,  60 ,  70  prevents any solution  43  reflected back from the bowl  48  from reaching the surface of the wafer W. Accordingly, a source of particle contamination is eliminated, and the occurrence of pattern bridges and profile failures during the formation of the pattern is reduced or eliminated, thereby increasing productivity since there are fewer wafers that are rejected or that need to be reworked. 
     Note also that the process failures are reduced, and productivity is increased, by the alteration of the physical structure of the apparatus, not by the control of the process conditions, or parameters, such as the viscosity of the solution  43  or the rotation speed of the spin chuck  42 . 
     While the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.

Technology Category: 3