Abstract:
An apparatus for processing wafer-shaped articles comprises a rotary chuck and a heating assembly that faces a wafer-shaped article when positioned on the rotary chuck. A liquid dispenser positioned so as to dispense liquid onto a surface of a wafer-shaped article that faces away from the rotary chuck when positioned on the rotary chuck. The heating assembly comprises an array of radiant heating elements distributed among at least five individually controllable groups. The liquid dispenser comprises one or more dispensing orifices configured to move a discharge point from a more central region of the rotary chuck to a more peripheral region of the rotary chuck. A controller controls power supplied to each of the at least five individually controllable groups of radiant heating elements based on a position of the discharge point of the liquid dispenser.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0001]    The invention relates generally to a method and apparatus for processing wafer-shaped articles, such as semiconductor wafers, in an open or in a closed process chamber. 
       2. Description of Related Art 
       [0002]    Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668. 
         [0003]    Alternatively, a chuck in the form of a ring rotor adapted to support a wafer may be located within a closed process chamber and driven without physical contact through an active magnetic bearing, as is described for example in International Publication No. WO 2007/101764 and U.S. Pat. No. 6,485,531. Treatment fluids which are driven outwardly from the edge of a rotating wafer due to centrifugal action are delivered to a common drain for disposal. 
         [0004]    As the device features formed on such wafers continue to decrease in their layout dimensions, with an attendant increase in the aspect ratio of those device features, and as the diameter of such wafers continues to increase, the phenomenon of pattern collapse during drying of the wafers becomes increasingly problematic. Existing techniques for preventing pattern collapse are of limited effectiveness. 
       SUMMARY OF THE INVENTION 
       [0005]    In one aspect, the present invention relates to an apparatus for processing wafer-shaped articles, comprising a rotary chuck adapted to hold a wafer-shaped article of a predetermined diameter thereon. The apparatus comprises a heating assembly that faces a wafer-shaped article when positioned on the rotary chuck, and a liquid dispenser positioned so as to dispense liquid onto a surface of a wafer-shaped article that faces away from the heating assembly when positioned on the rotary chuck. The heating assembly comprises an array of radiant heating elements distributed among at least five individually controllable groups each occupying a respectively different zone extending from a more central region of the rotary chuck to a more peripheral region of the rotary chuck. The liquid dispenser comprises one or more dispensing orifices configured to move a discharge point from a more central region of the rotary chuck to a more peripheral region of the rotary chuck. A controller controls power supplied to each of the at least five individually controllable groups of radiant heating elements based on a position of the discharge point of the liquid dispenser. 
         [0006]    In preferred embodiments of the apparatus according to the present invention, the at least five individually controllable groups of radiant heating elements comprises at least ten individually controllable groups of radiant heating elements. 
         [0007]    In preferred embodiments of the apparatus according to the present invention, the at least five individually controllable groups of radiant heating elements comprises at least fifteen individually controllable groups of radiant heating elements. 
         [0008]    In preferred embodiments of the apparatus according to the present invention, the at least five individually controllable groups of radiant heating elements comprises at least twenty individually controllable groups of radiant heating elements. 
         [0009]    In preferred embodiments of the apparatus according to the present invention, the radiant heating elements are LED heating elements. 
         [0010]    In preferred embodiments of the apparatus according to the present invention, the LED heating elements emit radiation having a maximum intensity in a wavelength range from 380 nm to 650 nm. 
         [0011]    In preferred embodiments of the apparatus according to the present invention, the LED heating elements emit radiation in a wavelength range from 380 nm to 650 nm. 
         [0012]    In preferred embodiments of the apparatus according to the present invention, the heating assembly is positioned relative to the chuck so as to heat a wafer shaped article held on the chuck from one side only and without contacting the wafer shaped article. 
         [0013]    In preferred embodiments of the apparatus according to the present invention, the heating assembly overlies the rotary chuck and is positioned between the rotary chuck and a surface of a wafer-shaped article that faces the rotary chuck when mounted on the rotary chuck. 
         [0014]    In preferred embodiments of the apparatus according to the present invention, the liquid dispenser comprises an arm that is movable relative to the rotary chuck from a more central region of the rotary chuck to a more peripheral region of the rotary chuck. 
         [0015]    In preferred embodiments of the apparatus according to the present invention, a plate that is transparent to radiation emitted by the radiant heating elements is mounted for rotation with the rotary chuck and is positioned between the heating assembly and a wafer-shaped article when positioned on the rotary chuck. 
         [0016]    In preferred embodiments of the apparatus according to the present invention, the plate is made of quartz or sapphire. 
         [0017]    In preferred embodiments of the apparatus according to the present invention, each of the at least five individually controllable groups of radiant heating elements is capable of applying a power intensity of at least 2 W/cm 2  to a wafer-shaped article when positioned on the rotary chuck. 
         [0018]    In preferred embodiments of the apparatus according to the present invention, each of the at least five individually controllable groups of radiant heating elements is capable of applying a power intensity of at least 4 W/cm 2  to a wafer-shaped article when positioned on the rotary chuck. 
         [0019]    In preferred embodiments of the apparatus according to the present invention, the at least five individually controllable groups of radiant heating elements are arranged concentrically to an axis of rotation of the rotary chuck. 
         [0020]    In preferred embodiments of the apparatus according to the present invention, the controller is configured to supply full power to one of the at least five individually controllable groups in response to the discharge point of the liquid dispenser being aligned axially with the one of the at least five individually controllable groups. 
         [0021]    In preferred embodiments of the apparatus according to the present invention, the controller is configured to supply an inner intermediate power that is less than the full power to another of the at least five individually controllable groups that is adjacent and radially inward of the one of the at least five individually controllable groups, in response to the discharge point of the liquid dispenser being aligned axially with the one of the at least five individually controllable groups. 
         [0022]    In preferred embodiments of the apparatus according to the present invention, the controller is configured to supply an outer intermediate power that is less than the full power to yet another of the at least five individually controllable groups that is adjacent and radially outward of the one of the at least five individually controllable groups, in response to the discharge point of the liquid dispenser being aligned axially with the one of the at least five individually controllable groups. 
         [0023]    In preferred embodiments of the apparatus according to the present invention, the outer intermediate power is greater than the inner intermediate power. 
         [0024]    In preferred embodiments of the apparatus according to the present invention, the heating assembly comprises an array of light-emitting diodes (LEDs) that is substantially coextensive with a wafer shaped article of the predetermined diameter. 
         [0025]    In preferred embodiments of the apparatus according to the present invention, the rotary chuck comprises a rotatable chuck body surrounding a central stationary post, and the heating assembly is mounted to an upper end of the central stationary post. 
         [0026]    In another aspect, the present invention relates to a method for processing wafers shaped articles, comprising the use of the apparatus having one or more of the aforesaid characteristics, in the manner described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which: 
           [0028]      FIGS. 1 a , 1 b  and 1 c    are an explanatory illustration of the phenomenon of pattern collapse; 
           [0029]      FIG. 2  is a plan view of an apparatus according to a first embodiment of the present invention; 
           [0030]      FIG. 3  is a sectional view along the line III-Ill in  FIG. 2 ; 
           [0031]      FIG. 4  is an enlarged view of the detail IV in  FIG. 3 ; 
           [0032]      FIG. 5  is a plan view of the heating assembly of this embodiment; 
           [0033]      FIGS. 6 a  and 6 b    show preferred processing conditions for use of the embodiment of  FIGS. 1-5 ; 
           [0034]      FIG. 7  shows an apparatus according to a second embodiment of the present invention in a use position; and 
           [0035]      FIG. 8  shows the embodiment of  FIG. 7  in a loading and unloading position. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0036]    Referring now to  FIG. 1 , device features  1  formed on a semiconductor wafer  2  may be fins of doped silicon or any other structures or materials formed or used in the fabrication of semiconductor devices. During processing, the wafer  2  is rinsed, typically first with water and then with isopropyl alcohol IPA, which is shown at  3  in  FIG. 1 a    surrounding the fins  1 . As the wafer is dried, the IPA  3  evaporates; however, owing to surface tension and the high aspect ratio of the fins  1 , the IPA  3  is driven off more slowly from the space between the fins, which results in the formation of a meniscus shown at M in  FIG. 1 b   . As drying of the wafer continues, the surface tension of the IPA  3  pulls the fins  1  toward each other as shown in  FIG. 1 c   , which can impair or prevent the correct performance of the associated semiconductor device. 
         [0037]    Conventional techniques for mitigating the phenomenon of pattern collapse include the use of a rinse liquid having lower surface tension than deionized water, with IPA being the predominant choice, and the use of such rinse liquid at elevated temperature; however, as noted above, such techniques have limited effect on reducing pattern collapse. 
         [0038]    The present inventors have discovered that rapid localized heating of the wafer along a moving front can serve to evaporate the rinse liquid sufficiently quickly that a meniscus as shown in  FIG. 1 b    is not formed, and the attendant pattern collapse shown in  FIG. 1 c    is thereby avoided. 
         [0039]      FIG. 2  shows a first embodiment of an apparatus designed to implement that discovery, in which a rotary chuck  10  is designed to hold and rotate a wafer W of a predetermined diameter, for example 300 mm or 450 mm. Wafer W is held by a circular series of gripping pins  16 , which in this embodiment are six in number. Pins  16  pass through openings in a transparent plate  25  made of quartz or sapphire. Plate  25  is secured to chuck  10  by screws  26  and rotates with the chuck  10 . When a wafer W is positioned on the chuck, it is held above the plate  25  so that the lower surface of the wafer is parallel to the plate  25  and spaced therefrom by a small gap. 
         [0040]    Beneath the transparent plate  25  is mounted a radiant heating assembly  50 , which will be described in greater detail below. 
         [0041]    Adjacent the chuck  10  a boom swing arm  30  is mounted for pivotal motion about its drive motor  34 . Arm  30  is supplied with process and/or rinse liquid, which is discharged downwardly through its discharge nozzle  32 . Boom swing arm  30  is movable between a standby position shown in solid line in  FIG. 2 , and a central position shown in broken line. Discharge nozzle  32  can therefore scan across the full radius of a wafer W, and when a wafer W is rotated by chuck  10 , thereby dispense liquid onto its entire upwardly-facing surface. 
         [0042]    Turning now to  FIG. 3 , it can be seen that the rotary chuck  10  is made up of a lower chuck body  12  and an upper chuck body  14 , which are secured to one another and are journalled for rotation about a stationary central post  20 . The pins  16  and transparent plate  25  also rotate with the chuck  10  in this embodiment, as does the ring gear  18  which is in continuous meshing engagement with each of the gripping pins  16  via gear teeth provided at the bases of these latter. Ring gear  18  can also rotate relative to the chuck  10  to a limit extent. thereby to rotate pins  16  about their respective axes and move the uppermost eccentric gripping portions between their open and closed positions, in a manner well known per se. 
         [0043]    The stationary post  20  is mounted on a machine frame  40  of the apparatus, as is a stator  44 , whereas rotor  42  is secured to the lower chuck body  12 , with the stator  44  and rotor  42  constituting a magnetic motor that drives the chuck  10  in rotation. Further particulars of the overall chuck structure are described for example in commonly-owned U.S. Pat. No. 9,245,777. 
         [0044]    Radiant heating assembly  50  in this embodiment is mounted on the stationary post  20 , and therefore does not rotate, whereas it is enveloped by the rotating structure of the chuck comprising elements  25 ,  14 ,  16 . Radiant heating assembly  50  in this embodiment comprises a multiplicity of blue LEDs  51  mounted facing the transparent plate  25 , and a controller  52  (e.g. an on-board controller (not shown) mounted on the underside of heating assembly  50 ). Controller  52  controls the turning on and off, as well as the power, of the blue LEDs  51 , and also communicates wirelessly with the motor  34  of the boom swing arm  30 . 
         [0045]    As shown in  FIG. 4 , the radiant heating assembly  50  is composed of an aluminum substrate made up of upper and lower pieces  54  and  55  that are brazed together, the aluminum substrate serving as a heat sink to prevent excessive heating of the structure beneath the blue LED elements  51 . A printed circuit board  53  is mounted on top of upper piece  54 , on which the traces for the LED elements are formed and on which the LED elements  51  are mounted. 
         [0046]    Onboard chips  56  are mounted on a printed circuit board  60  secured to the underside of lower piece  55 . Wires  58  interconnecting the output pins of onboard chips  56  and the input terminals of the traces formed on PCB  53  are accommodated in pockets  57  that pass through the aluminum substrate  53 ,  54 . 
         [0047]    As shown in  FIG. 5 , the PCB  53  of this embodiment is formed in four quadrants, which are joined together by connectors  59 . The LED elements  51  are formed in groups of sixteen, i.e., the arrangement of onboard chips  56  and the connections from those chips to PCB  53 , along with the onboard controller  52 , permit the LEDs to be powered individually in groups as small as sixteen. 
         [0048]    It will be seen in  FIG. 5  that the LEDs  51  are arranged in twenty concentric circles, and that the number of LEDs in each circle is a multiple of sixteen. Thus, each concentric circle can be individually controlled as a separate heating zone, by virtue of the arrangement described above. 
         [0049]    The blue LED lamps  51  have a maximum intensity at a wavelength of about 450 nm. Other sources of radiation could be used, but it is preferred to use sources emitting radiation having a maximum intensity in a wavelength range from 390 nm to 550 nm and more preferably in a wavelength range from 400 nm to 500 nm. 
         [0050]    Whereas radiation of that wavelength characteristic is largely transmitted by the plate  25 , that same radiation is largely absorbed by the semiconductor material of the wafer W, especially when the wafer W is silicon. 
         [0051]    This arrangement allows very fast local heating of the wafer W, in a manner that causes evaporation of rinse liquid before the damaging meniscus has a chance to form. For example, each LED  51  may have a power consumption of 10 W and provides a light power of 3 W, which light power can be generated nearly instantaneously. Additionally, lesser light powers can be generated for selected LEDs  51  when desired, for examples by pulsing the power supply to selected LEDs  51  at for example 500 Hz, in a manner known per se. 
         [0052]      FIGS. 6 a  and 6 b    show a preferred example of operation of the apparatus of this embodiment. The wafer W can be considered to be divided into N zones  1 ,  2 ,  3 ,  4 , . . . N, corresponding to the number of individually controllable concentric zones of the heating assembly  50 , such that the abscissa in  FIG. 6 b    represents the number of zones as well as the radial distance from the center to the edge of the wafer. 
         [0053]    In the region A shown in  FIG. 6 a   , liquid L remains on the surface of wafer W, and the objective is to heat that liquid L, which in this example is isopropyl alcohol (IPA) to a temperature that is elevated but which does not cause premature drying of the wafer W. That temperature corresponds to the heat flux of the heater in zones  4  through N being maintained at level  2 , as shown on the ordinate in  FIG. 6   b.    
         [0054]    On the other hand, in the region B, corresponding to zone  3  of the radiant heating assembly  50 , the temperature of the wafer W is elevated substantially so as to cause the evaporation rate of the IPA to be sufficiently high that there is no meniscus (i.e., a flat or 90° meniscus) between closely adjacent device features, so as to avoid pattern collapse as described above. Within region C, corresponding to heater zones  1  and  2 , the already dried wafer is maintained at a lower but still elevated temperature, to ensure complete evaporation of rinse liquid and to prevent condensation on the dried wafer surface. 
         [0055]    It will be appreciated that the control of the power supplied to the various concentric zones of the heating assembly corresponds to the radial position of the discharge nozzle  32  of the rinse fluid, and thus controller  52  controls the power supply to the LEDs  51  of the relevant zones based on the radial position of the discharge nozzle. 
         [0056]      FIGS. 7 and 8  show an alternative embodiment in which the chuck is a magnetic ring rotor  70  positioned within a closed chamber  80 , and driven in rotation by a stator  72  positioned outside of the chamber  80 . A wafer W is held by gripping elements  71  that project downwardly from the ring rotor  70 . 
         [0057]    The chamber  80  can be opened for loading and removal of a wafer W as shown in  FIG. 8 . The heating assembly  50 ′ is incorporated into the lower part of housing  80 , and is generally similar to that described in connection with the preceding embodiment, except that in this embodiment the transparent plate  25 ′ is stationary and does not rotate with the magnetic rotor  70 . 
         [0058]    Furthermore, in this embodiment, instead of a radially movable liquid dispenser  30 , there is provided a series of fixed liquid dispensing nozzles  74  fed by a manifold  73 . Rinse liquid can be supplied serially to these nozzles  74 , starting with the most central and continuing to the most peripheral, so as to approximate the dispensing action of the boom swing arm  30  of the preceding embodiments. In this case, therefore, the controller  52  would control the power supply to the selected groups of LEDs  51  based on which nozzle  74  was dispensing liquid. 
         [0059]    While the present invention has been described in connection with various preferred embodiments thereof, it is to be understood that those embodiments are provided merely to illustrate the invention, and that the invention is not limited to those embodiments, but rather includes that which is encompassed by the true scope and spirit of the appended claims.