Abstract:
An apparatus for treating a disc-shaped article comprises a spin chuck and at least three individually controllable infrared heating elements. The infrared heating elements are mounted in a stationary manner with respect to rotation of said spin chuck. The infrared heating elements are arranged in a nested configuration so as to define individually controllable inner, middle and outer heating zones adjacent a disc-shaped article when positioned on the spin chuck.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an apparatus for liquid treatment of disc-shaped articles, and to a heating system for use in such an apparatus. 
         [0003]    2. Description of Related Art 
         [0004]    Liquid treatment includes both wet etching and wet cleaning, wherein the surface area of a wafer to be treated is wetted with a treatment liquid and a layer of the wafer is thereby removed or impurities are thereby carried off. A device for liquid treatment is described in U.S. Pat. No. 4,903,717. In this device the distribution of the liquid may be assisted by the rotational motion imparted to the wafer. 
         [0005]    Techniques for processing a surface of a disc-shaped article are typically used in the semiconductor industry on silicon wafers, for example of 300 mm or 450 mm diameter. However, such techniques may be applied for other plate-like articles such as compact discs, photo masks, reticles, magnetic discs or flat panel displays. When used in semiconductor industry they may also be applied for glass substrates (e.g. in silicon-on-insulator processes), III-V substrates (e.g. GaAs) or any other substrate or carrier used for producing integrated circuits. 
         [0006]    When using heated process liquids, there is a problem in achieving temperature uniformity across the surface of the wafer, and the need to address that problem becomes more acute as wafer diameters increase. 
         [0007]    In particular, as the wafer diameter increases, so too will the temperature differential between a liquid at the point where it is applied in a central region of the wafer and the same liquid after it has travelled radially outwardly to the periphery of the wafer. This results in varied etch rates as a function of the distance from the center of the wafer, and hence poor process uniformity. 
         [0008]    Conventional approaches to alleviate this problem have included dispensing process liquid from movable arms, so-called “boom swing” dispensers; however, this involves an increase in the cost and complexity of the device as well as its operation. The problem can be addressed to some extent by increasing the flow of process liquid, and/or by dispensing a high temperature liquid such as deionized water on the opposite side of the wafer; however, these techniques result in higher consumption of process liquids. 
         [0009]    Commonly-owned co-pending application U.S Patent Application Pub. No. 2013/0061873 describes improved apparatus equipped with an infrared heater for heating a wafer to enhance process uniformity. Although the devices of that patent application represent an improvement over conventional techniques, there remains a need to provide further enhanced process uniformity and control. 
       SUMMARY OF THE INVENTION 
       [0010]    Thus, in one aspect, the present invention relates to an apparatus for treating a disc-shaped article, comprising a spin chuck for holding a disc-shaped article in a predetermined orientation relative to an upper surface of the spin chuck, and at least three individually controllable infrared heating elements mounted above the upper surface of the spin chuck and below a disc-shaped article when mounted on the spin chuck. The infrared heating elements are mounted in a stationary manner with respect to rotation of the spin chuck. The at least three individually controllable infrared heating elements are arranged in a nested configuration so as to define individually controllable inner, middle and outer heating zones adjacent a disc-shaped article when positioned on the spin chuck. 
         [0011]    In preferred embodiments of the apparatus according to the present invention, each of the heating elements has at least one of a shape and a position such that each of the heating elements heats regions of differing distance from the axis of rotation of the spin chuck. 
         [0012]    In preferred embodiments of the apparatus according to the present invention, each of the heating elements comprises a curved portion that extends generally along an arc of a circle that is eccentric to the axis of rotation of the spin chuck. 
         [0013]    In preferred embodiments of the apparatus according to the present invention, each of the heating elements comprises two curved portions interconnected by a straight portion, such that each of the heating elements is generally C-shaped. 
         [0014]    In preferred embodiments of the apparatus according to the present invention, a first one of the two curved portions extends generally along an arc of a first circle and a second one of the two curved portions extends generally along an arc of a second circle, the first and second circle having centers that are offset from one another. 
         [0015]    In preferred embodiments of the apparatus according to the present invention, each of the two curved portions extends generally along an arc of a same circle. 
         [0016]    In preferred embodiments of the apparatus according to the present invention, each the heating element comprises two straight portions interconnected by a curved portion. 
         [0017]    In preferred embodiments of the apparatus according to the present invention, the two straight portions are parallel to one another. 
         [0018]    In preferred embodiments of the apparatus according to the present invention, each of the heating elements comprises a curved portion extending along an arc of a circle, and wherein the circle for each heating element is concentric with the circle for at least two others of the heating elements. 
         [0019]    In preferred embodiments of the apparatus according to the present invention, a circle circumscribing emitting portions of any one of the at least three individually controllable infrared heating elements does not intersect a circle circumscribing emitting portions of any others of the at least three individually controllable infrared heating elements. 
         [0020]    In preferred embodiments of the apparatus according to the present invention, the apparatus includes a plate that is transparent to infrared radiation emitted by the at least three individually controllable infrared heating elements, said plate being positioned between said at least three individually controllable infrared heating elements and a disc-shaped article when positioned on the spin chuck. 
         [0021]    In preferred embodiments of the apparatus according to the present invention, the plate is part of a housing that surrounds the at least three individually controllable infrared heating elements. 
         [0022]    In preferred embodiments of the apparatus according to the present invention, the housing is mounted in a stationary manner with respect to rotation of the spin chuck. 
         [0023]    In another aspect, the present invention relates to an infrared heating assembly for use in an apparatus for treating a disc-shaped article. The infrared heating assembly comprises at least three individually controllable infrared heating elements mounted in a common frame connector. The at least three individually controllable infrared heating elements are arranged in a nested configuration so as to define individually controllable inner, middle and outer heating zones. Each of the heating elements has at least one of a shape and a position such that each of the heating elements extends over regions of differing distance from the center of a circle circumscribing the infrared heating assembly. 
         [0024]    In preferred embodiments of the infrared heating assembly according to the present invention, each of the at least three individually controllable infrared heating elements comprises at least one curved portion and at least one straight portion. 
         [0025]    In preferred embodiments of the infrared heating assembly according to the present invention, the curved portions of adjacent infrared heating elements extend along concentric circles and the straight portions of adjacent heating elements are parallel to one another. 
         [0026]    In preferred embodiments of the infrared heating assembly according to the present invention, the common frame connector comprises a plurality of electrical connectors equal in number to the at least three individually controllable infrared heating elements, thereby to permit individual connection of each of the at least three individually controllable infrared heating elements to a controller for individually energizing each of the at least three individually controllable infrared heating elements. 
         [0027]    In preferred embodiments of the infrared heating assembly according to the present invention, the assembly includes a housing surrounding the at least three individually controllable infrared heating elements, the housing comprising a plate forming an upper portion thereof, the plate being transparent to the infrared radiation emitted by the at least three individually controllable infrared heating elements. 
         [0028]    In yet another aspect, the present invention the present invention relates to an infrared lamp for use in heating a disc-shaped workpiece in such a way that the infrared lamp radiates light onto the disc-shaped workpiece while the infrared lamp and the disc-shaped workpiece rotate relative to each other. The infrared lamp comprises an arc-shaped emitting part generally describing a circle that is eccentric in relation to an axis of rotation of the disc-shaped workpiece, and an adjoining emitting part disposed inside the circle and extending from the arc-shaped emitting part generally along a chord of the circle. 
         [0029]    In preferred embodiments of the infrared lamp for use in heating a disc-shaped workpiece according to the present invention, the adjoining emitting part has a linear shape. 
         [0030]    In preferred embodiments of the infrared lamp for use in heating a disc-shaped workpiece according to the present invention, the lamp includes a second arc-shaped emitting part at an end of the adjoining emitting part opposite the arc-shaped emitting part. 
         [0031]    In preferred embodiments of the infrared lamp for use in heating a disc-shaped workpiece according to the present invention, the adjoining emitting part is integrally connected to an end of the arc-shaped emitting part. 
         [0032]    In preferred embodiments of the infrared lamp for use in heating a disc-shaped workpiece according to the present invention, the arc-shaped emitting part and the adjoining emitting part are integrally formed and each is round in cross-section. 
         [0033]    In yet another aspect, the present invention relates to a heating apparatus comprising an infrared lamp positioned facing a disc-shaped workpiece, the heating apparatus heating the disc-shaped workpiece in such a way that the infrared lamp radiates light onto the disc-shaped workpiece while the infrared lamp and the disc-shaped workpiece rotate relative to each other. The infrared lamp comprises an arc-shaped emitting part generally describing a circle that is eccentric in relation to an axis of rotation of the disc-shaped workpiece, and an adjoining emitting part disposed inside the circle and extending from the arc-shaped emitting part generally along a chord of the circle. The heating apparatus comprises a plurality of the infrared lamps, wherein the arc-shaped emitting parts of the infrared lamps are positioned concentrically to one another. 
         [0034]    In preferred embodiments of the heating apparatus according to the present invention, the adjoining emitting part of each of the infrared lamps does not intersect a circle circumscribing the arc-shaped emitting part of the corresponding adjacent inner infrared lamp. 
         [0035]    In preferred embodiments of the heating apparatus according to the present invention, the infrared lamp further comprises a second arc-shaped emitting part at an end of the adjoining emitting part opposite the arc-shaped emitting part. 
         [0036]    In preferred embodiments of the heating apparatus according to the present invention, ends of the arc-shaped emitting part and the second arc-shaped emitting part define an angle whose vertex is on an axis of rotation of the disc-shaped article. 
         [0037]    In preferred embodiments of the heating apparatus according to the present invention, the adjoining emitting part of each of the infrared lamps is integrally connected to an end of the corresponding arc-shaped emitting part. 
         [0038]    In preferred embodiments of the heating apparatus according to the present invention, the adjoining emitting part of each of the infrared lamps does not extend outwardly from the circle described by the corresponding arc-shaped emitting part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    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: 
           [0040]      FIG. 1  is an exploded perspective view of an apparatus for treating disc-shaped articles according to an embodiment of the present invention; 
           [0041]      FIG. 2  is top plan view of the embodiment of  FIG. 1 ; 
           [0042]      FIG. 3  is an axial section through the chuck depicted in  FIGS. 1 and 2 , taken along the line III-III of  FIG. 2 ; 
           [0043]      FIG. 4  is a view similar to that of  FIG. 2 , of another embodiment of an apparatus according to the present invention; 
           [0044]      FIG. 5  is a view similar to that of  FIG. 2 , of yet another embodiment of an apparatus according to the present invention; 
           [0045]      FIG. 6  is a view similar to that of  FIG. 2 , of still another embodiment of an apparatus according to the present invention; 
           [0046]      FIG. 7  is an explanatory view for better understanding the relative shapes and sizes of the lamps utilized in the embodiment of  FIG. 6 ; 
           [0047]      FIG. 8  is a graph showing the depth of material etched when using the lamp assembly of the  FIGS. 1-3  embodiment with all three IR lamps turned off; 
           [0048]      FIG. 9  is a graph showing the depth of material etched when using the lamp assembly of the  FIGS. 1-3  embodiment with all three IR lamps turned on; 
           [0049]      FIG. 10  is a graph showing the depth of material etched when using the lamp assembly of the  FIGS. 1-3  embodiment with the inner and middle IR lamps turned on and the outer IR lamp turned off; and 
           [0050]      FIG. 11  is a graph showing the depth of material etched when using the lamp assembly of the  FIGS. 1-3  embodiment with the inner and middle IR lamps turned off and the outer IR lamp turned on. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0051]    Referring now to the drawings,  FIGS. 1 and 2  depict an apparatus made up of two principal subassemblies, namely, a base spin chuck  10  and a modular infrared heating assembly  20 . The spin chuck  10  comprises a rotary main body  12  that is mounted for rotation about a stationary central hollow post  14 . This post  14  in turn comprises a central nozzle  18  for dispensing process liquid or gas onto the underside of a wafer when mounted on the spin chuck, as well a series of female electrical sockets  15  in a shoulder of the post  14 , which sockets receive corresponding male connectors (not shown) that depend downwardly from the heating assembly  20 , and which supply driving current to the IR heating lamps inside that assembly  20 . 
         [0052]    The chuck body  12  has mounted therein a series of gripping pins  16 , which operate generally as described in the above-referenced U.S. Pat. No. 4,903,717, in that the pins  16  are driven in unison by a common ring gear between a radially outer open position and a radially inner closed position in with the upper ends of these pins engage the edge of a disc-shaped article to be treated. 
         [0053]    The heating assembly  20  in this embodiment is formed as a modular unit comprising a lower dished housing or shell  22  that contains the IR lamps  21 ,  23 ,  25 . A cover  24  is screwed onto the lower housing  22  by a series of peripheral screws  26 , which are six in number in this embodiment. 
         [0054]    The cover  24  in this embodiment is a plate formed from a material that is transparent to the wavelengths of IR radiation emitted by the lamps  21 ,  23 ,  25 , and this plate  24  may be formed for example of sapphire or quartz glass, as is known to those skilled in this art. The plate  24  has a small central opening  19  formed therein, to permit passage of the upper end of dispensing nozzle  18 . 
         [0055]    Within the housing of the heating assembly  20 , that is, inside the lower housing  22  and beneath the transparent plate  24 , there is mounted a set of three infrared heating lamps  21 ,  23 ,  25 , which are carried by a common frame  29  that also incorporates the associated electrical supply wiring (not shown). The assembly formed by the housing formed of lower shell  22  and upper plate  24 , frame  29  and lamps  21 ,  23 ,  25  in this embodiment is rigidly mounted to the stationary post  14 . 
         [0056]    Referring now to  FIG. 2 , it can be seen that the wafer W is now supported by the ends of pins  16  projecting adjacent the outer periphery of the heating assembly  20 . The phantom line in  FIGS. 2 and 3  designates the position of a wafer W when held by the apparatus, with the underside of wafer W being spaced by a small defined gap from the cover  24 . 
         [0057]    The wafer W is centered above the heating assembly  20 , which in turn is centered on the axis of rotation of the underlying spin chuck. It will be appreciated that the spin chuck  10  is therefore designed to hold a wafer W of a specified diameter. In the embodiments described herein, that diameter is 300 mm, which is a common diameter of silicon wafer at present. However, the apparatus may of course be designed to hold disc-shaped articles of other diameters, such as 200 mm and 450 mm. 
         [0058]    In the plan view of  FIG. 2  it can be seen that each of the three heating elements in this embodiment is made of two curved portions ( 25 - 1  and  25 - 3  in the case of the outer heating element  25 ) interconnected by a straight portion ( 25 - 2  in the case of the outer heating element  25 ). The middle and inner heating elements  23  and  21 , respectively, have the same shape. The heating elements  21 ,  23 ,  25  of this embodiment are thus generally C-shaped. Moreover, while the curved portions (e.g.,  25 - 1 ,  25 - 3 ) of these heating elements generally follow a circular arc, and while the adjacent curved portions of all three heating elements are preferably substantially concentric, the circles described by those curved portions are not in this embodiment concentric with the center of the heating assembly  20  and hence are not concentric with the axis of rotation of the spin chuck. 
         [0059]    Consequently, in this embodiment, both the position and shape of the heating elements  21 ,  23 ,  25  is such that, as the wafer W is rotated by the chuck  10  relative to the stationary heating elements  21 ,  23 ,  25 , each heating element effectively “travels” radially relative to the rotating wafer W, in that each heating element heats an annular region whose radial extent is significant greater than the cross-sectional diameter of the heating elements. For the present embodiment, those zones are delimited by the circles shown in broken line in  FIG. 2 , and those zones are designated Z 1 , Z 2  and Z 3  in  FIG. 2 . 
         [0060]    It will be appreciated that each heating element also contributes to some extent to the heating in the zone or zones adjacent thereto. The broken line circles in  FIG. 2  thus delineate the position at which the predominant heating effect changes from one heating element to the next. 
         [0061]    In  FIG. 3 , it can be seen that the frame  29  is supported within the housing  22 ,  24 , with the housing of the heating assembly  20  being in this embodiment rigidly secured to the stationary post  14 , and thus with the frame  29  and lamps  21 ,  23 ,  25  also being mounted in a stationary manner to the post  14 . The upwardly-facing surface of the lower housing part or shell  22  is preferably provided with a suitable IR reflective coating  31 , to aid in directing the IR radiation emitted by lamps  21 ,  23 ,  25 , upwardly through the transparent plate  24  and onto the downwardly facing surface of the wafer W. 
         [0062]    The stationary post  14  is mounted onto the frame  32  of the apparatus, which in this embodiment also carries a stator  34 . Stator  34  in turn drives rotor  36 , which is attached to the body  12  of spin chuck  10 . Also visible in  FIG. 3  is the ring gear  11  mentioned above, which drives the gripping pins  16  in unison. 
         [0063]    It will be appreciated that in the embodiments described herein, the entire heating assembly is mounted in a stationary manner on the post  14 , as is described for example in connection with the heating assembly disclosed in commonly-owned co-pending application U.S Patent Application Pub. No. 2013/0061873. 
         [0064]      FIG. 4  depicts another embodiment, in which the infrared lamps  21 ′,  23 ′,  25 ′ are shaped differently than in the preceding embodiments. In particular, each lamp comprises two straight portions  21 - 1 ′,  21 - 3 ′,  23 - 1 ′,  23 - 3 ′,  25 - 1 ′,  25 - 3 ′, and one straight portion  21 - 2 ′,  23 - 2 ′,  25 - 2 ′. The shape and position of the straight portions of these elements contribute to the creation of heating zones as described in connection with the preceding embodiments. 
         [0065]      FIG. 5  depicts yet another embodiment, in which each of the three heating elements  41 ,  43 ,  45  is a continuous curved tubular element. Moreover, while these heating elements generally follow a circular arc, and while all three heating elements are preferably substantially concentric, the circles described by those heating elements are not in this embodiment concentric with the center of the heating assembly  20  and hence are not concentric with the axis of rotation of the spin chuck. 
         [0066]    Consequently, in this embodiment, both the position and shape of the heating elements  41 ,  43 ,  45  is such that, as the wafer W is rotated by the chuck  10  relative to the stationary heating elements  41 ,  43 ,  45 , each heating element also heats an annular region whose radial extent is significant greater than the cross-sectional diameter of the heating elements, as in the preceding embodiments. 
         [0067]      FIGS. 6 and 7  illustrate a still further approach to the design of the heating lamps. In this embodiment, four individually controllable IR heating lamps  51 ,  53 ,  55 ,  57  are mounted on a suitable carrier frame  59  in the manner as generally as described in connection with the preceding embodiments. The housing  20  and spin chuck  10  are as previously described. 
         [0068]    The conceptual diagram of  FIG. 7  reveals the interrelationship between the shapes and sizes of these lamps  51 ,  53 ,  55 ,  57 . In particular, the outer periphery of the curved part of lamp  53  describes a circle R 1  that is also coincident with the inner periphery of the curved part of lamp  51 . Similarly, the outer periphery of the curved part of lamp  55  describes a circle R 2  that is also coincident with the inner periphery of the curved part of lamp  53 , and the outer periphery of the curved part of lamp  57  describes a circle R 3  that is also coincident with the inner periphery of the curved part of lamp  55 . Furthermore, the outer periphery of the largest lamp  51  approximately coincides with a one-fourth quadrant of the circular housing  20 . 
         [0069]    Therefore, when the lamps  51 ,  53 ,  55 ,  57  are mounted as shown in  FIG. 6 , there are effectively no gaps in the heated regions of the wafer W, as the wafer is rotated in relation to the stationary lamps. 
         [0070]    It is to be noted that the heating lamps in each of the preceding embodiments are preferably individually controllable. It is particularly preferred that each lamp can be not only switched on and off independently of the others, but also that the wattage to each lamp can be independently varied. This permits a variety of advantageous process control. 
         [0071]    For example,  FIG. 8  shows, for purposes of comparison, etching profiles achieved when using the heating lamp assembly of  FIGS. 1-3  but without powering any of the three IR lamps  21 ,  23 ,  25 . As can be seen, there is a markedly greater removal of material from the wafer in the central region of the wafer as compared to the peripheral region. This is because etchant dispensed centrally of the wafer has cooled substantially as it travels radially outwardly across a 300 mm diameter wafer. Moreover, this undesired etching profile is largely the same regardless of whether the etching chemistry, temperature and flow are selected to etch 4 Å or material or 9 Å of material. In either case, the material removed at the outer periphery of the wafer is less by about 2Å. 
         [0072]    By contrast,  FIG. 9  shows etching profiles achieved by appropriately powering all three of the lamps  21 ,  23 ,  25 . The etching profiles have been nearly inverted relative to those of  FIG. 8 . It should be noted also that these profiles are attained at lower flow rates and shorter processing times than for the data of  FIG. 8 . It should also be noted that for many process specifications, the ideal etching profile is not necessarily flat; instead, as in  FIG. 9 , a desired etching profile will often call for “overetching” of the peripheral wafer region, e.g., removing approximately 10% more material at the wafer edge than at the wafer center. As can be seen in  FIG. 9 , the apparatus and heating assemblies of the present invention are particularly well-suited to such applications. 
         [0073]      FIG. 10  shows the profile attained when only the lamps  21 ,  23  are powered, whereas  FIG. 11  shows the profile attained when only the lamp  25  is powered. In neither case does the resulting profile resemble those of  FIG. 9 . 
         [0074]    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 should not be used as a pretext to limit the scope of protection conferred by the true scope and spirit of the appended claims.