Abstract:
A wafer dryer for drying a wafer includes a chamber and a support adapted to support the wafer in the chamber. A spray nozzle is disposed in the chamber. A source gas supply tank is in fluid communication with the spray nozzle. At least one heater is operable to heat the chamber and the source gas supply tank. A pumping line is in fluid communication with the chamber. Drive means are operable to rotate the chamber and the spray nozzle. A method for drying a wafer using a wafer dryer including a chamber and a revolving spray nozzle includes the steps of: loading the wafer in the chamber; reducing the pressure in the chamber in which the wafer is loaded to a near vacuum state; creating a temperature controlled atmosphere in the pressure-reduced chamber to quicken drying of the wafer; and spraying the source gas on the wafer while rotating the chamber and the revolving spray nozzle in opposite directions in the pressure-reduced temperature controlled atmosphere.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Korean Application No. 00-14552, filed Mar. 22, 2000, the disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to wafer dryers and methods for drying wafers, and more particularly, to spin dryers for drying wafers and methods for using the same. 
     BACKGROUND OF THE INVENTION 
     In a known method for drying a wafer such as a silicon wafer, the wafer is rotated at a high speed using a spin dryer to remove moisture from the surface of the wafer. Friction induced deterioration of high speed spinning parts of the spin dryer may generate particles. Also, particles which are removed from the wafer may be re-absorbed onto the wafer by static electricity induced by friction. Moreover, water marks may remain on the wafer in hydrophobic portions thereof after moisture is removed by the high speed rotation. 
     A widely used method for drying wafers larger than 8″ includes vaporizing isopropyl alcohol (IPA), which is hydrophilic and highly volatile, and removing moisture using the vapor. This method may provide a simple means for drying the wafer. However, reaction by-products such as particles ( e.g., silica) may be formed and coagulate on the wafer, leaving smears on the wafer. The particles may hamper the stability of follow-up processes. For example, locations where metal interconnections should be separated may be bridged by these particles, and intended connections may be broken by these particles. Moreover, as the diameter of the wafer is increased from 8″ to 12″, it becomes difficult to uniformly dry the entire wafer using only the isopropyl alcohol vapor. 
     SUMMARY OF THE INVENTION 
     According to embodiments of the present invention, a wafer dryer for drying a wafer includes a chamber and a support adapted to support the wafer in the chamber. A spray nozzle is disposed in the chamber. A source gas supply tank is in fluid communication with the spray nozzle. At least one heater is operable to heat the chamber and the source gas supply tank. A pumping line is in fluid communication with the chamber. Drive means are operable to rotate the chamber and the spray nozzle. 
     The drive means may be operable to rotate the chamber and the spray nozzle in opposite directions relative to one another. The at least one heater may include an external heater surrounding an upper portion of the chamber and operable to heat the chamber, and an internal heater mounted below the source gas supply tank and operable to heat the source gas supply tank. The wafer dryer may further include a fixed base and the drive means may include a chamber revolving unit operable to rotate the chamber about the fixed base, and a nozzle revolving unit operable to rotate the spray nozzle independently of the chamber. 
     According to further embodiments of the present invention, a wafer dryer for use with a wafer loading means includes a revolving chamber having a wall. The chamber has an interior and an exterior. A support is mounted on an upper part of the wall of the chamber. The support is adapted to support the wafer loading means in the chamber. An external heater surrounds an upper portion of the exterior of the chamber and is operable to heat the chamber. A revolving spray nozzle is disposed in the chamber and has a lower end. A source gas supply tank is connected to the lower end of the revolving spray nozzle by a source gas supply pipe. An internal heater is mounted below the source gas supply tank and is operable to heat the source gas supply tank. A fixed base is disposed below the internal heater. A pumping line passes through the fixed base. A chamber revolving unit is operable to rotate the chamber about the fixed base. 
     According to method embodiments of the present invention, a method for drying a wafer using a wafer dryer including a chamber and a revolving spray nozzle is provided. The method includes loading the wafer in the chamber. The pressure in the chamber in which the wafer is loaded is reduced to a near vacuum state. A temperature controlled atmosphere is created in the pressure-reduced chamber to quicken drying of the wafer. A source gas is sprayed on the wafer while rotating the chamber and the revolving spray nozzle in opposite directions in the pressure-reduced temperature controlled atmosphere. 
     Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention. 
     FIG. 1 is a top plan view of a wafer dryer according to the present invention; 
     FIG. 2 is a sectional view of the wafer dryer of FIG. 1 taken along line  2 — 2 ′ of FIG. 1; 
     FIG. 3 is a plan view of a wafer dryer according to further embodiments of the present invention; 
     FIG. 4 is a sectional view of the wafer dryer of FIG. 3 taken along line  4 — 4 ′ of FIG. 3; and 
     FIG. 5 is a block diagram representing a method according to the present invention for drying a wafer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. Elements of the drawings may be exaggerated for clarity. 
     With reference to FIG. 1, a wafer dryer  38  according to embodiments of the present invention is shown therein. The wafer dryer  38  includes a chamber  40  within which wafer drying is performed. An external heater  42  surrounds the chamber  40 . The external heater  42  is operable to create an atmosphere of an appropriate temperature inside of the chamber  40 , so that a source gas for vaporizing supplied to the inside of the chamber  40  is maintained in a vaporized state. More particularly, the external heater  42  heats the interior of the chamber  40  (primarily an upper portion) so as to create an atmosphere of a predetermined temperature. The temperature controlled atmosphere maintains the source gas in a vaporized state to quicken the reaction of the source gas with moisture on one or more wafers W disposed in the chamber  40 . A revolving spray nozzle  46  and a source gas supply tank  48  connected to the revolving spray nozzle are mounted in the chamber  40 . A revolving plate  50  transfers revolving power, which is generated from a fixed base  52  mounted in the middle of the chamber  40 , to the source gas supply tank  48 . The revolving plate  50 , the source gas supply tank  48 , and the revolving spray nozzle  46  are rotated in the same direction as indicated by arrows in FIG.  1 . 
     First and second wafer loading means  60   a  and  60   b  are connected to the inner wall of the chamber  40 . Preferably, and as illustrated and hereinafter referred to, the first and second wafer loading means  60   a  and  60   b  are wafer cassettes. A plurality of wafers W are held in each of the wafer cassettes  60   a ,  60   b . The wafer cassettes  60   a ,  60   b  are mounted between the inner wall of the chamber  40  and the revolving spray nozzle  46 . In use, the chamber  40  rotates in a direction opposite the direction of rotation of the spray nozzle  46 . As a result, the first and second wafer cassettes  60   a  and  60   b  are rotated in the opposite direction to the revolving spray nozzle  46 . 
     Referring to FIG. 2, an opening  66   a  of the chamber  40  is closed with a removable cover  66 . The cover  66  is connected to one side of the chamber  40  by a hinge  66   b  and can be selectively opened and closed. The chamber  40  is divided into an upper structure above an O-ring  44  and a lower structure below the O-ring  44 . The upper and lower structures center the O-ring  44 . The O-ring  44  seals the interface between the upper structure and the lower structure. An external wall  43  is mounted outside of and surrounds the chamber  40 . The external heater  42  surrounds an upper portion of the external wall  43  and the upper structure of the chamber  40 . Preferably, the external heater  42  is a quartz heater; however, a coil-type or other suitable heater may be used. Preferably, a protective wall (not shown) is mounted outside the external wall  43  and surrounds the entire chamber  40  and the entire external wall  43 . 
     The revolving spray nozzle  46  is mounted below the cover  66 . The revolving spray nozzle  46  is a revolving multi-layer spray nozzle and consists of an upper spray nozzle  46   a  and a lower spray nozzle  46   b , which are connected in parallel to each other. A plurality of spray holes h are formed in the upper and lower spray nozzles  46   a  and  46   b , as shown in FIG.  2 . The revolving spray nozzle  46  is circular and the upper and lower spray nozzles  46   a  and  46   b  are shaped as hollow disks. The spray holes h are formed around the circumferential peripheries of the disks. 
     The first and second wafer cassettes  60   a  and  60   b  are mounted around and adjacent the revolving spray nozzle  46 . The wafer cassettes  60   a ,  60   b  are connected to the chamber  40  by respective supports  61 . The supports are pivotally mounted on the upper ends of the wafer cassettes  60   a ,  60   b  such that the wafer cassettes  60   a ,  60   b  may rotate upward and downward about generally horizontal axes relative to the supports  61  and, thereby, the chamber  40  and the spray nozzle  46 . Before and after drying a wafer, the wafer cassettes  60   a ,  60   b  are rotated upwardly by 90 degrees about the supports  61  from the position shown in FIG.  2 . The wafer cassettes  60   a ,  60   b  are positioned relative to the spray nozzle  46  such that the topmost wafers W are positioned lower than the revolving spray nozzle  46 . 
     The source gas supply tank  48  and an internal heater H, are located in a lower part of the chamber  40  and are sequentially mounted below the revolving spray nozzle  46 . The source gas supply tank  48  is adapted to supply source gas for drying the wafers W to the spray nozzle  46  and is connected to the lower spray nozzle  46   b  through a source gas supply pipe  62 . The internal heater H contacts the bottom of the source gas supply tank  48  and heats the source gas supply tank  48  to vaporize a liquid source S with which the source gas supply tank  48  is filled. The liquid source S may be, for example, isopropyl alcohol (IPA). 
     A nozzle revolving unit  49  is mounted below the internal heater H. The nozzle revolving unit  49  generates torque for rotating the internal heater H and the revolving spray nozzle  46 . The revolving unit  49  includes a revolving plate  50  in contact with the bottom of the internal heater H and a motor  54  in contact with the bottom of the revolving plate  50 . The revolving plate  50  contacts the entire bottom of and partly surrounds the internal heater H. The revolving plate  50  transmits revolving power generated by the motor  54  to the internal heater H. 
     The nozzle revolving unit  49  is mounted on a fixed base  52  which is fixed in the middle of the bottom of the chamber  40 . The fixed base  52  is mounted to allow independent rotation of the internal heater H and the revolving spray nozzle  46  with respect to the rotation of the chamber  40 . The revolving spray nozzle  46  may thereby be rotated in the same direction as the chamber  40  or the opposite direction to that of the chamber  40 . 
     A pumping line  63  passes through the fixed base  52  and around the revolving means  54  and connects the inside and outside of the chamber  40 . The pumping line  63  is connected to a pump (not shown) for use in reducing the pressure in the chamber  40  to a near vacuum state. 
     In order to supply the liquid source S to the source gas supply tank  48 , a liquid source supply pipe  64  passes through the bottoms of the revolving unit  49  and the source gas supply tank  48 . The liquid source supply pipe  64  is connected to a liquid source supply source (not shown) outside of the chamber  40  and has a T-type end  64   a  extending into the source gas supply tank  48 . In order to supply the liquid source while the source gas supply tank  48  is being rotated, the liquid source S is preferably supplied downwardly from a higher position than the surface level S′ of the liquid source S in the source gas supply tank  48 . The T-type end  64   a  is also positioned at a higher position than the surface level S′ of the liquid source S in the source gas supply tank  48 . The liquid source supply pipe  64  passes through a portion R of the bottom of the source gas supply tank  48  to prevent the liquid source S in source gas supply tank  48  from contacting the liquid source supply pipe  64 . The portion R is convex and projects upwardly from the bottom of the tank  48  so that the portion R extends above the upper surface S′ of the liquid source S. As a result, the portion R is positioned above other portions of the bottom of the tank  48 . 
     With reference to FIG. 2, the chamber  40  rotates in the direction A 1 . The revolving spray nozzle  46  and the source gas supply tank  48  rotate in the direction A 2 , opposite the direction of rotation A 1  of the chamber  40 . A chamber revolving unit  68  for rotating the chamber  40  is secured to the bottom of the chamber  40  and is mounted around the fixed base  52 . The revolving unit  68  transmits internally generated revolving power to the chamber  40 . 
     Because the fixed base  52  is fixed, when the chamber  40  rotates, friction occurs between the two. In order to prevent or reduce frictional damage at the interface between the fixed base  52  and the chamber  40  as the chamber  40  rotates, a bearing B 1  is mounted between the fixed base  52  and the bottom of the chamber  40 . A bearing B 2  is also mounted between the revolving plate  50  and the liquid source supply pipe  64 . Holes are formed in the internal heater H so that the liquid source supply pipe  64  may pass through the middle of the internal heater H and the internal heater H does not directly contact the liquid source supply pipe  64 . 
     With reference to FIGS. 3 and 4, a wafer dryer  38   a  according to further embodiments of the present invention is shown therein. The wafer dryer  38   a  is constructed in the same manner as the wafer dryer  38 , except as described hereinbelow. The wafer dryer  38   a  differs from the wafer dryer  38  with respect to the rotation of the spray nozzle  46 . 
     The wafer dryer  38   a  includes a revolving unit  70  for revolving the spray nozzle  46  instead of the revolving plate  50  of the wafer dryer  38 . As a result, rotation of the source gas supply tank  48  is unnecessary, and accordingly, the nozzle revolving unit  49  is unnecessary. 
     With reference to FIG. 4, the revolving unit  70  is fixedly mounted at the source gas supply pipe  62  between the revolving spray nozzle  46  and the source gas supply tank  48 . A revolving apparatus capable of revolving the revolving spray nozzle  46 , for example, a motor, is mounted in the revolving unit  70 , and the revolving power of the motor is transmitted only to the revolving spray nozzle  46 . As a result, only the revolving spray nozzle  46  is rotated with the source gas supply pipe  48  remaining fixed. The chamber  40  rotates in the direction opposite the rotating direction of the revolving spray nozzle  46 . More particularly, the direction of rotation of the revolving spray nozzle  46  is indicated by the arrow A 4  and the direction of rotation of the chamber  40  is indicated by the arrow A 3 . 
     In the wafer dryer  38   a , because it is not necessary to rotate the source gas supply tank  48  during the drying process, friction between the source gas supply pipe  48  and the liquid source supply pipe  64  is not a concern, and only the seal between the two need be considered. Accordingly, in the wafer dryer  38   a , the source gas supply tank  48  and the liquid source supply pipe  64  are easily combined, and it is not necessary to modify the middle portion of the bottom of the source gas supply tank  48 . Also, because a revolving means corresponding to the revolving unit  49  is not required, the assembly on the fixed base  52  is simplified. The internal heater H may be maintained in the same shape as in the wafer dryer  38 . 
     Additionally, in the wafer dryer  38   a , rather than passing the liquid source supply pipe  64  through the bottom of the source gas supply tank  48 , the liquid source supply pipe  64  can be connected to the upper portion of the tank  48  above the liquid source S, as indicated in dashed lines and by reference numeral  80 . In this configuration, because the pipe  64  does not pass through the bottom of the tank  48 , the liquid source supply pipe  64  is prevented from contacting the liquid source S in the source gas supply tank  48 , and it is possible to use a disk-type heater for the internal heater H rather than a brass-coin type heater. 
     With reference to FIG. 5, the following method according to embodiments of the present invention may be used for drying a wafer using a wafer dryer according to the present invention. The method may be executed using either of the wafer dryers  38  and  38   a ; however, the method will be described hereinafter with reference to the wafer dryer  38   a  and FIGS. 3 and 4. Suitable modifications to the method to use the wafer dryer  38  will be apparent to those of ordinary skill in the art upon reading the description herein. 
     The wafers W are first loaded into the chamber  40  (Block  100  of FIG.  5 ). More particularly, the wafers W, which have preferably first undergone a cleaning process, are loaded into the first and second wafer cassettes  60   a  and  60   b . The chamber cover  66  is opened, the first and second wafer cassettes  60   a  and  60   b  are loaded into the chamber  40  through the opening  66   a  and mounted on the supports  61 . The chamber cover  66  is thereafter re-placed over the opening  66   a  to close the chamber  40 . 
     The liquid source S is supplied from the liquid source supply source outside of the chamber  40  to the source gas supply tank  48  through the liquid source supply pipe  64 , to fill the source gas supply tank  48  to an appropriate level with the liquid source S. During the drying process, the liquid source S is continuously supplied to the source gas supply tank  48  so that the level of the source gas supply tank  48  is maintained at approximately the original level. Preferably, alcohol-group chemicals having an excellent vaporizing capability are used for the liquid source S. For example, isopropyl alcohol (IPA) may be used for the liquid source S. 
     The pressure in the chamber  40  is then reduced to a high vacuum state by operating the pump mounted outside of the chamber  40  (Block  200  of FIG.  5 ). 
     A vaporizing atmosphere is created in the chamber  40  to prevent condensation in the chamber  40  (Block  300  of FIG.  5 ). More particularly, after the internal pressure of the chamber  40  is lowered to a high vacuum state, the inside of the chamber  40  is heated by operating the external heater  42 . Because the external heater  42  surrounds the upper region of the chamber  40 , the upper region is mainly heated. Heating the inside of the chamber  40  in this way serves to keep the source gas vaporized until the source gas supplied from the source gas supply tank  48  to the upper region of the chamber  40  completely reacts with and thereby evaporates moisture from the surfaces of the wafers W. 
     The chamber  40  is heated using the external heater  42  until the internal temperature of the chamber  40  reaches the temperature vaporization range of the liquid source S supplied to the source gas supply tank  48 . For example, if isopropyl alcohol (IPA) is selected as the liquid source S, its range of vaporizing temperature is from about 70-90 degrees Celsius. After the internal temperature of the chamber  40  reaches the vaporizing temperature range, the chamber  40  is continuously heated until the process is complete so that the internal temperature of the chamber  40  does not drop below the vaporizing temperature range. 
     Thereafter, the spray nozzle  46  is rotated and the source gas is sprayed to dry the wafers W (Block  400  of FIG.  5 ). More particularly, after the source gas vaporizing atmosphere is created in the chamber  40 , the liquid source S in the source gas supply tank  48  is heated by operating the internal heater H. The internal heater H may have a maximum heating capability of between about 20 and 300 degrees Celsius. The source gas supply tank  48  is heated at an appropriate temperature corresponding to the vaporizing temperature of the liquid source S. For example, if the liquid source S is isopropyl alcohol, the source gas supply tank  48  is preferably heated at about 70-90 degrees Celsius. The liquid source S in the gas supply tank  48  is thereby vaporized. 
     As the source gas supply tank  48  is heated, the chamber  40  and the revolving spray nozzle  46  are rotated by operating the revolving unit  68  and the revolving unit  70 , respectively. Preferably, the chamber  40  and the revolving spray nozzle  46  are rotated in opposite directions. The source gas then flows into the rotating spray nozzle  46  through the source gas supply pipe  62  and the revolving unit  70 . The drying gas is sprayed through the spray holes h and onto the wafers W in the wafer cassettes  60   a ,  60   b . 
     When the revolving spray nozzle  46  is in a revolving state, the travel distance of the drying gas sprayed from the revolving spray nozzle  46  may be adjusted to accommodate the particular diameter of the wafers W by adjusting the rate of rotation (e.g., revolutions per minute (RPM)) of the spray nozzle  46 . That is, when the wafers W have a relatively small diameter, the travel distance of the drying gas is reduced by lowering the rate of rotation of the revolving spray nozzle  46 . When the wafers W have a relatively large diameter, the travel distance of the drying gas is increased by increasing the rate of rotation of the revolving spray nozzle  46 . In this way, it is possible to dry the entireties of the wafers W loaded in the wafer cassettes  60   a ,  60   b  regardless of the diameters of the wafers W. 
     The drying gas sprayed onto the wafers W reacts with moisture smeared on the surface of each wafer W. The upper region of the chamber  40  in which the wafer cassettes  60   a ,  60   b  are mounted is maintained at an appropriate temperature to maintain the drying gas in the vapor state. The reaction of moisture smeared on the wafer W and the drying gas is thereby expedited. As a result, water marks left on the wafer W when moisture is vaporized are minimized or eliminated. Reaction by-products such as particles formed on the wafer W are removed by centrifugal force generated by rotation of the chamber  40 . 
     Various modifications to the wafer dryers  38 ,  38   a  as described above may be desired. For example, various revolving spray nozzles such as a semicircle or a ring-type may be employed instead of the circular first and second revolving spray nozzles  46   a  and  46   b , and three or more of the revolving spray nozzles may be used. Also, the technical spirit of the invention may be applied to sheet-fed dryers, in which case, the revolving spray nozzle  46  may be formed of one layer. Also, the external heater  42  may be a quartz heater or a coil-type heater surrounding the wall of the chamber  40 . 
     In the method for drying a wafer, the travel distance of the drying gas may also be increased by increasing the spraying pressure and thereby the velocity of the spraying gas rather than adjusting the rate of rotation of the revolving spray nozzle  46 . For this purpose, the diameters of the spray holes h may be reduced, or a separate pressurizing means may be provided. 
     As described above, the wafer dryers  38 ,  38   a  each include a revolving chamber and wafer loading means (e.g., wafer cassettes) attached to the inside of the revolving chamber and so that wafers held in the wafer loading means are rotated with the chamber. Accordingly, the reaction by-products (e.g., particles) formed on the surface of the wafer in the drying process are removed from the wafer by centrifugal force. Also, the wafer dryers each include a revolving spray nozzle which is rotated independently of the rotation of the revolving chamber and with an adjustable rotation speed. The travel distance of the drying gas sprayed from the revolving spray nozzle can be adjusted in accordance with the diameter of the wafer so that the entire wafer can be uniformly dried. 
     Because each of the wafer dryers also includes the external heater surrounding the upper portion of the revolving chamber, the temperature in the internal region of the chamber where the wafer is located can be maintained at an appropriate temperature for the drying gas and moisture to react during the process of drying a wafer. The efficiency of drying the entire wafer can thereby be increased, particularly for wafers of relatively large diameter. 
     As a result of the foregoing effects and advantages, the stability of follow-up processes such as forming metal interconnections can be ensured. For example, the reduction or elimination of reaction by-products remaining on the surface of the wafer reduces or solves the problem of undesirable bridges being formed between metal interconnections. Similarly, unintentional severing of metal interconnections formed by a photolithographic process as a result of such reaction by-products may be reduced or eliminated. 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.