Patent Publication Number: US-6334581-B1

Title: Nozzle reposition device used in a resist coating process

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention provides a resist spray nozzle resetting device, namely a device for achieving uniformity of resist coating on a semiconductor wafer. 
     2. Description of the Prior Art 
     In semiconductor manufacturing processes, a semiconductor wafer must go through many coating processes from start to finish, such as lithographic resist and developer coating processes. With the narrowing line width in semiconductor processes, photolithographic technology has become critical, for it is with photolithography that all the MOS components, metallic wires, thin film patterns and dopant regions are made. Moreover, the pattern-transferring process, mandatory in photolithography, is complicated and subtle, and so only a precise pattern of resist can ensure the reliability of later processes. 
     In today&#39;s market, most resist coating processes are performed by spin-coating liquid resist over a wafer to form a resist layer with an even thickness. This forms a light-sensitive photo-emulsion layer. Since the uniformity of the thickness of a resist layer can later affect the resolution, the depth of focus (DOF), and even the quality of the wafer, it is important in wafer production to know how to achieve and maintain the uniformity of the resist layer. 
     Please refer to FIG.  1 . FIG. 1 is a front view of a resist coating device  10  according to the prior art. As shown here, the resist coating device  10  comprises a rotary robotic arm  12  and a spray nozzle  14 . The spray nozzle  14  has a covering nut  16  fastened on the rotary arm  12 . The spray nozzle  14  sprays resist  18  over a wafer&#39;s surface  20  which, positioned on a vacuum rotary station  22 , is kept in rotating motion. Ideally, the spray nozzle aims straight at the midpoint  26  of the wafer  20 ; in other words, it forms a line with the central axis  24 , so that the resist  18  drops directly on the midpoint  26  of the wafer  20  and coats the wafer surface. Unfortunately, sometimes the spray nozzle  14  might move astray from the center axis  24  due to maintenance errors or operating negligence, causing the resist  18  to fall off the midpoint  26 , resulting in a non-uniform resist coating. Even though resetting of the spray nozzle  14  can be done manually, if it is off of the central axis  24 , it wastes both time and money, and alignment errors after manual resetting are not negligible. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to provide a spray nozzle resetting device to correct the weaknesses of the conventional counterpart described above. 
     Another purpose of the present invention is to provide a spray nozzle resetting device to avoid misalignment problems, so as to improve the uniformity of the resist layer. 
     In a preferred embodiment of the present invention, a spray nozzle resetting device comprises a spray nozzle for spraying resist on the midpoint of a wafer, a rotary robotic arm, a resist-delivering duct connected to one end of the spray nozzle, a covering nut, a resetting ring, a fixing ring connecting the covering nut to the rotary robotic arm, and a spring positioned between the covering nut and the resetting ring. The covering nut has an opening of diameter D. The resetting ring has a rotary part with a diameter equal to or less than D, and at last two protrusions. The rotary part fits in the opening of the covering nut. The fixing ring is used to fix the covering nut to the rotary robotic arm, and it has two recesses corresponding to the two protrusions to interact with the two protrusions. 
     In the preferred embodiment, the midpoint of the resetting ring is not aligned with the two protrusions. To move the spray nozzle, the operator can lift up the rotary part of the fixing ring and rotate it to a desired angle, with the spray nozzle rotating along with it. For performing the resist coating process, the operator can rotate the rotary part in the reverse direction until the two protrusions re-catch on the two recesses, so as to again aim the spray nozzle at the midpoint of the wafer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a resist spray nozzle according to the prior art. 
     FIG. 2 is an exploded diagram of a spray nozzle resetting device according to the present invention. 
     FIG. 3A is a side view of a resetting ring of the present invention. 
     FIG. 3B is a front view of a resetting ring of the present invention. 
     FIG. 3C is a rear view of a resetting ring of the present invention. 
     FIG. 4A is a cross-sectional view of a fixing ring of the present invention. 
     FIG. 4B is a front view of a fixing ring of the present invention. 
     FIG. 5 is a perspective view of a spray nozzle resetting device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIG.  2 . FIG. 2 is an exploded diagram of a spray nozzle resetting device  30  according to the present invention. As shown here, the spray nozzle resetting device  30  comprises a spray nozzle  34  bent at a 90 degree angle that is used to spray resist on the midpoint of a wafer, a rotary robotic arm  32  for resist delivery, a covering nut  36  with an opening  36   a  of diameter D, a spring  44 , a resetting ring  38  and a fixing ring  42  for connecting the covering nut  36  to the rotary robotic arm  32 . The spring  44  is located between the covering nut  36  and the resetting ring  38 , and is fixed resiliently on the rotary part  38   a , providing a tightening force between the resetting ring  38  and the fixing ring  42 . The rotary robotic arm  32  has a resist-delivering duct  32   a  connected to one end of the spray nozzle  34 . 
     In the preferred embodiment, the spray nozzle  34  is made of stainless steel, and is bent at  90  degrees. Additionally, the spraying end of the spray nozzle  34  is equipped with a plastic head  34   a . The spray nozzle  34  of the present invention, however, is not restricted to this particular material and bending angle. Other materials and bending angles can be used for the spray nozzle  34 . 
     Please refer to FIG. 3A, which is an enlarged side view of the resetting ring  38  according to the present invention. The resetting ring  38  comprises a rotary part  38   a  on one side, and at least two protrusions  38   b  on the opposite side. The rotary part  38   a  fits into the opening  36   a  of the covering nut  36 . Additionally, the rotary part  38   a  has at least one screw hole  38   c  that accommodates a bolt to secure the spray nozzle  34 . The resetting ring  38  has in its center a hole  38   d  to accommodate the spray nozzle  34 . The hole  38   d  extends through the resetting ring  38 , including the rotary part  38   a . There are in the rotary part  38   a  two screw holes  38   c  going through the hole  38   d  for securing the spray nozzle  34  with a screw bolt, making the spray nozzle  34  and the rotary part  38   a  rotate together. 
     Please refer to FIG. 3B, which is a front view of the resetting ring  38  according to the present invention. The rotary part  38   a  is located on one side of the resetting ring  38 , and the two protrusions  38   b  are on the opposite side. The diameter of the rotary part  38  is equal to or less than D, so that it may pass through the opening  36   a  of the covering nut  36 . 
     “Please refer to FIG. 3C, which is a rear view of the resetting ring  38  according to the present invention The two protrusions  38   b  and  38   e  have distances of d 1  and d 2  from the center of the circle, respectively. In the preferred embodiment, d 1  is not equal to d 2 , and d 1  and d 2  are less than the diameter  39  of the resetting ring  38 . Additionally, the two protrusions  38   b  and  38   e  are not aligned together with the center point of the circle.” 
     “Please refer to FIG.  4 A and FIG.  4 B. FIG.  4 A and FIG. 4B are, respectively, a cross-sectional side view and a front view of the fixing ring  42  according to the present invention. As shown in FIG. 4A, the fixing ring  42  comprises a front part  45  and a rear part  46 . The front part  45  is screwed tightly to the covering nut  36 , and the rear part  46  to the rotary robotic arm  32 . In other words, the main function of the fixing ring  42  is to join together the covering nut  36  and the rotary robotic arm  32 . Moreover, the fixing ring  42  has in its center an opening  42   a  that accommodates the spray nozzle  34  and the resist-delivering duct  32   a . There are two screw holes  42   b  in the rear part  46  for securing the resist-delivering duct  32   a , which runs across the rear part.” 
     The fixing ring  42  has an the inner side  47  of the rear part  45  two recesses  42   c , which correspond to and interact with the two protrusions  38   b  of the resetting ring  38 . In the preferred embodiment, the center point of the fixing ring  42  is not aligned with the two recesses  42   c . As shown in FIG.  3 C and FIG. 4B, the diameter  43  of the inner circle of the front part  45  of the fixing ring  42  is slightly longer than the diameter  39  (in FIG. 3C) of the resetting ring  38 . 
     What is worth noticing is that because the distances d 1  and d 2  from the two protrusions  38   b  and  38   c  to the center point of the circle, respectively, are not the same, and because the two protrusions  38   b  and  38   c , and the center point of the resetting ring  38  are not aligned, the spray nozzle can have only one reset position. 
     Please refer to FIG. 5, which is a perspective view of the spray nozzle resetting device  30  according to the present invention. As shown here, to move the spray nozzle  34  for regular maintenance, the operator first pulls out the rotary part  38   a  in the direction of the arrow  51 , and rotates it clockwise or counter clockwise through an angle. Since the spray nozzle  34  has been screwed securely to the rotary part  38   a , the spray nozzle  34  moves together through the same angle as the rotary part  38   a . When the operator releases the rotary part  38   a , the resetting ring  38  and the fixing ring  42  are kept in contact by the force provided by he spring  44 , allowing the spray nozzle  34  and the resetting device  30  to remain in the maintenance position. After the maintenance procedure has been completed, and when the operator needs to run another resist coating process, he or she may rotate the rotary part  38   a  in the reverse direction until the two protrusions  38   b  re-catch the two recesses  42   c , ensuring that the spray nozzle  34  points at the midpoint  86  of the wafer  80 , and aligning it with the center axis. 
     It should be remembered that before using the spray nozzle resetting device  30 , the operator should correct the spray nozzle  34  by aiming it at the midpoint  86  of the wafer  80  and aligning it with the center axis  84 . It is only after the correction that the operator may secure with screw bolts the spray nozzle  34  to the rotary part  38   a  of the resetting ring  38 . In this manner, the operator ensures that the spray nozzle points precisely at the midpoint  86  of the wafer  80  for each run. 
     In comparison to the prior art, the present invention is superior in that it solves the resetting problem of the spray nozzle  34 , which the operator often encounters after a maintenance procedure. Because of this invention, the spray nozzle  34  can now be accurately aimed at the midpoint  86  of the wafer  80  in resist coating processes, thus improving the uniformity of resist and the reliability of the later photolithographic processes. 
     The above disclosure is based on the preferred embodiment of the present invention. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.