Patent Publication Number: US-2018040502-A1

Title: Apparatus for processing wafer-shaped articles

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to an apparatus for processing wafer-shaped articles, such as semiconductor wafers. 
     2. Description of Related Art 
     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. 
     The chucks of the aforementioned patents support a wafer on a cushion of gas, according to Bernoulli&#39;s principle. However, in conventional Bernoulli chucks it is difficult or inconvenient to dispense liquid onto the peripheral region of the underside of a wafer. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention relates to an apparatus for processing wafer-shaped articles comprises a rotary chuck having a series of contact elements surrounding a wafer-shaped article when mounted on the rotary chuck. A non-rotating plate is positioned interiorly of the series of contact elements. The plate includes a gas supply that is configured to supply gas so as to support a wafer-shaped article without contacting the non-rotating plate according to the Bernoulli principle. 
     In preferred embodiments of the apparatus according to the present invention, the gas supply is an annular gas supply directed radially outwardly in relation to an axis of rotation of the rotary chuck. 
     In preferred embodiments of the apparatus according to the present invention, the non-rotating plate is secured on a stationary central post. 
     In preferred embodiments of the apparatus according to the present invention, the non-rotating plate is generally circular and mounted coaxially with an axis of rotation of the rotary chuck, the rotary chuck having a diameter that is greater than the predetermined diameter. 
     In preferred embodiments of the apparatus according to the present invention, the contact surface faces radially inwardly in the contact position and is parallel to the rotational axis of the rotary chuck. 
     In preferred embodiments of the apparatus according to the present invention, the rotary chuck comprises a chuck base body mounted for rotation about the central post, the chuck base body surrounding a fluid distribution manifold comprising the non-rotating plate. 
     In preferred embodiments of the apparatus according to the present invention, each of the series of contact elements comprises a shaft projecting from the chuck base body, and the contact surface projects radially inwardly from a distal end of the shaft so as to overlie the non-rotating plate in the contact position. 
     In preferred embodiments of the apparatus according to the present invention, the gas supply is an annular array of gas supply nozzles comprising a circular series of bores that open on a surface of the non-rotating plate that faces a wafer-shaped article when mounted on the rotary chuck, each of the circular series of bores extending from the surface interiorly of the non-rotating plate at an oblique angle relative to an axis of rotation of the rotary chuck. 
     In preferred embodiments of the apparatus according to the present invention, the non-rotating plate further comprises a plurality of liquid-dispensing nozzles positioned radially outwardly of the gas supply, and directed toward an edge region of a wafer-shaped article when positioned on the rotary chuck. 
     In preferred embodiments of the apparatus according to the present invention, the plurality of liquid dispensing nozzles are comprised by a modular nozzle block that is attachable to and detachable from the non-rotating plate. 
     In preferred embodiments of the apparatus according to the present invention, the series of contact elements is a series of pins, each of the series of pins being rotatable about a respective pin axis so as to move a contact surface of a corresponding pin from a radially outer loading position to a radially inner contact position. 
     In preferred embodiments of the apparatus according to the present invention, a liquid dispenser is positioned so as to dispense liquid onto a side of a wafer-shaped article that faces away from the non-rotating plate when positioned on the rotary chuck. 
     In preferred embodiments of the apparatus according to the present invention, the gas supply comprises an annular array of gas supply nozzles or an annular gas supply nozzle. 
     In preferred embodiments of the apparatus according to the present invention, a supply of inert gas is in communication with the gas supply. 
     In preferred embodiments of the apparatus according to the present invention, a supply of process liquid is in communication with the plurality of liquid-dispensing nozzles. 
     In preferred embodiments of the apparatus according to the present invention, a supply of process liquid is in communication with the liquid dispenser. 
     In preferred embodiments of the apparatus according to the present invention, a radiant heating assembly is positioned such that a wafer-shaped article when mounted on the rotary chuck is positioned between the radiant heating assembly and the non-rotating plate. 
     In preferred embodiments of the apparatus according to the present invention, the radiant heating assembly comprises multiple LED lamps, and wherein the non-rotating plate comprises portions formed from quartz or sapphire. 
     In preferred embodiments of the apparatus according to the present invention, the contact surfaces are configured to contact an edge of a wafer-shaped article only at a side surface thereof. 
     In preferred embodiments of the apparatus according to the present invention, the contact surfaces face inwardly and are parallel to the rotational axis of the rotary chuck. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a plan view of a rotary chuck for use in an apparatus according to a first embodiment of the present invention; and 
         FIG. 2  is a cross-sectional view of an apparatus according to a first embodiment of the present invention, in which the rotary chuck is sectioned along the line II-II of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , a rotary chuck  10  comprises a circular series of contact elements  12 , which in this embodiment are eight in number, but which may be any desired number of three or more. A series of six contact elements  12  is preferred. The contact elements  12  each comprise a contact surface  14  at a distal end thereof, which contacts a wafer W when the chuck  10  is in use. The contact elements  12  could be gripping pins, but more preferably the contact surfaces  14  are smooth and parallel to the axis of rotation of the rotarty chuck  10 , as they need to provide only lateral but not subjacent support for a wafer W. 
     The contact surfaces  14  of the contact elements  12  are eccentric to the axes of rotation of the contact elements  12 , so that the surfaces  14  are movable between a radially outer non-contact position, for loading and unloading a wafer W, and a working position, as shown. The positioning of the contact elements  12  is such that the chuck  10  is configured to hold a wafer of a predetermined diameter, for example a 300 mm diameter or 450 mm diameter semiconductor wafer. 
     A stationary fluid distribution manifold  20  is positioned within the circle described by the contact elements  12 , and beneath a wafer W when one is positioned on the chuck  10 . Manifold  20  comprises an upper plate  25  that is likewise stationary, and in which are formed an inner series of discharge nozzles  22 , and an outer series of discharge nozzle  24 . Either or both of the series of nozzles  22 ,  24  could be formed instead as a single continuous annular nozzle, or a circular series of arcuate nozzles. 
     Three modular liquid nozzle assemblies  26 ,  30  are removably attached to the manifold  20  and upper plate  25 , and each includes a series of liquid discharge orifices  28 ,  31  positioned so as to discharge process liquid upwardly, and, if desired, radially outwardly, onto the downwardly-facing surface of a wafer W, in the peripheral area thereof. 
     Turning now to  FIG. 2 , it can be seen that the rotary chuck  10  comprises a chuck base body made up of a lower part  11  and an upper part  13  that are rigidly interconnected. The chuck base body is mounted for motation about a stationary central post  50 , which in turn is mounted on a support frame  36  of the apparatus. Also mounted on the support frame  36  is a stator  32 , which cooperates with a rotor  34  secured to the chuck base body so as to drive the chuck  10  in rotation. 
     The fluid distribution manifold  20  including upper plate  25  is rigidly mounted to the stationary central post  50 . The chuck  10  surrounds manifold  20 . Chuck  10  also includes a ring gear  15  sandwiched between elements  11  and  13 , which comprises a ring of outwardly projecting teeth coaxial with the chuck  10  and simultaneously engaging complementary teeth formed at the base of each contact element  12 . Rotation of the chuck base body and ring gear  15  thereby rotates the series of contact elements  12  in unison. 
     As can be seen in  FIG. 2 , the contact elements  12  of this embodiment are crank-shaped, such that their upper and lower ends overlap the manifold  20  when viewed from above, but also include a radially-outwardly projecting intermediate portion that provides clearance for the contact elements  12  relative to the manifold  20 . 
     Central post  50  comprises liquid conduits  56  and  57 , which are supplied with process liquid from a supply thereof. Liquid conduits  56 ,  57  communicate with liquid conduits  27  and  29 , respectively, formed in the fluid distribution manifold  20 , which in turn communicate with the liquid nozzle assemblies  26  and  30 , respectively, shown in  FIG. 1 . The modular nature of the assemblies  26  permits them to be easily removed and exchanged for cleaning, and for providing differently sized and shaped discharge orifices according to the process in question. 
     Central post  50  also includes gas conduits  54 , which are connected to a source of gas, which is preferably nitrogen. Conduits  54  open at their downstream ends into the chamber  23  formed in manifold  20 . Chamber  23  communicates with the circular series of discharge nozzles  24 , which, as shown in  FIG. 2 , are bores formed in plate  25  that extend obliquely from a radially inner inlet to a radially outer outlet. 
     Central post  50  still further includes gas conduit  52 , which is likewise connected to a source of gas, which again is preferably nitrogen. Conduit  52  opens at its downstream end into the chamber  21  formed in manifold  20 . Chamber  21  communicates with the circular series of discharge nozzles  22 , which, as shown in  FIG. 2 , are bores formed in plate  25  that extend axially through plate  25 . 
     Also shown in  FIG. 2  is a liquid dispenser  45  for dispensing liquid onto the upwardly-facing surface of wafer W. Dispenser  45  may for example take the form of a boom swing arm that moves the downwardly-depending discharge nozzle along an arc above the upper surface of a wafer to be processed, as well as to a rest position. 
       FIG. 2  also shows a heater  40 , which is preferably a radiant heating assembly. More preferably, heater  40  comprises a multiplicity of blue LED heating elements  42 , which are shielded from the process environment by a plate  44  that is made of material transparent to the radiation emitted by the LEDs  42 , such as quartz or sapphire. 
     It will be observed in  FIG. 2  that the surface  14  of contact elements  12  that touch the wafer W do so only at the outer peripheral edge of the wafer. In this embodiment, those surfaces are parallel to the rotation axis of chuck  10 . As such, the contact elements  12  check the wafer W against lateral displacement, but do not provide subjacent support to the wafer. This arrangement allows a wafer W to be gripped in different positions at different axial distances from the upper plate  25 . 
     In use, gas is supplied through conduits  54  into chamber  23  and discharged through nozzles  24 . A wafer W is positioned above and parallel to the upper plate  25 , preferably at a distance in the range of 0.3 to 3.0 mm. The flow rate of gas through the nozzles is adjusted so that the wafer W is supported according to the Bernoulli principle. 
     Loading and unloading of a wafer W may be assisted by supplying gas through conduit  52 , which passes into chamber  21  and is discharged through the axial nozzles  22 . Gas supply through nozzles  22  may be controlled independently of gas supply through nozzles  24 . The supply may be alternate or simultaneous. 
     The above-described configuration of contact surface  14  aids in achieving a stable support of the wafer W in this manner, because the distance to the non-rotating plate is an equilibrium depending on the gas flow and the weight of the wafer-shaped article (further depending on gravity and mass). The parallel contact surface  14  can for example be a vertical plane or cylinder with generatrices parallel to the rotational axis of the rotary chuck. Consequently, the radial bearing of the wafer-shaped article is provided by the gripping elements, whereas the axial bearing is provided by the gas cushion. A horizontal notch in the contact surface would tend to limit axial displacement of the wafer W, and is preferably avoided. However, if a notch is utilized in the contact elements, it should be in the position corresponding to the equilibrium predicted for the gas flow and wafer weight in question. 
     The contact elements  20  are then closed by causing relative rotation of gear ring  15  and chuck base body  11 ,  13  in a manner known per se, whereafter the wafer W may be rotated by rotating the chuck base body  11 ,  13  and contact elements  12  in unison. 
     A typical process to be performed on the illustrated apparatus would be a bevel etch of a wafer, either alone or together with a backside etch. In such a process, a wafer W is positioned on the chuck with its device side facing down and its backside facing up. Etching liquid supplied through the conduits  56 ,  27  and discharged by discharge nozzles  28  of nozzle assemblies  26  will impinge on a defined peripheral region of the device side, thereby to provide a bevel etch. Thereafter rinsing liquid is supplied through the conduits  57 ,  29  and discharged by discharge nozzles  31  of nozzle assemblies  30 . 
     If it is also desired to etch the backside of the wafer W, which faces upwardly, then process liquid can be dispensed from the dispenser  45 . Etching is promoted by heating of the wafer, which is performed with heater  40 . 
     Different wafers might require a different extent of bevel etch, for example, 2, 3 or 4 mm. The provision of the modular liquid nozzle assemblies  26  also permits the rapid exchange of assemblies whose nozzles are positioned differently depending on the radial extent of the desired bevel etch. 
     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.