SUSS (1063342), страница 3
Текст из файла (страница 3)
As shown, theaxial shaft 135 has an axially located vacuum chamber118 extending substantially along the length of axialshaft 135 and terminating in a vacuum orifice 119. Vacuum orifice 119 is preferably centrally located on a support surface 104 of bowl 102.[0024] As shown, support surface 104 of bowl 102 ispreferably configured to hold a suitable workpiece. In apreferred embodiment, the work piece is a silicon waferused in the fabrication of semiconductor integrated circuits. However, it should be appreciated that the variousembodiments of the present invention may be equallyapplicable to other technologies where precision chemical spin-coating is desirable (i.e., photoresist, spin-onglass (SOG), compact disc recordable (CDR) dyechemicals, etc.).
Generally, a support ring 126 definesthe outer circumference of support surface 104 of bowl102 and is configured to support a wafer 130, as shownin Figure 2C. In this example, lid 101 will preferably havea circular recessed groove 112 defined in the lower flatsurface 114. Circular recessed groove 112 is preferablyconfigured to mate with a circular protruded lip 124 thatis located around the outer wall portions of bowl 102.[0025] Also shown are a plurality of drain holes 125that are arranged at the outer radius of bowl 102. Preferably, drain holes 125 are vertically lower than supportsurface 104.
In this manner, when wafer 130 is placedover support surface 104, the wafer lies above drainholes 125. Because chemicals that are applied to thesurface of a spinning wafer slide off of the wafer at highrates, the chemicals will preferably be channeled downand along the curved walls to the drain holes 125. Assuch, this curved wall surface is well suited to receivethe chemicals being released from the wafer surface ina manner that directs the chemicals out of the closedbowl system.
Preferably, between about 8 and about 16drain holes 125 are defined around the outer radius ofbowl 102 to enable the applied chemicals to exit duringa spin coating cycle. In this embodiment, drain holes 125are between about 1 mm and about 3 mm in diameter.Of course, the diameter may be modified to suit depending on the viscosity of the applied chemicals and the solvent materials injected in through injection holes 121. Inany event, drain holes 125 are generally large enoughto ensure that a sufficient pathway is defined to drainout the injected solvent and dissolved coating materials.[0026] Figure 2B is a top view of bowl 102 as illustrated in Figure 2A.
As shown, support surface 104 of bowl102 has a plurality of supports 128 that extend radiallyoutward from the centrally located vacuum orifice 119to the support ring 126. Supports 128 are used to support the substrate that is held in place by vacuum suctionsupplied by vacuum orifice 119 and vacuum chamber118.
A plurality of locking pins 122 are shown arrangedaround the top portion of bowl 102 to assist in securinglid 101 to bowl 102. Generally, locking pins 122 are con-51015202530354045505558figured to mate with suitable recessed pin holes 122alocated on lid 101 as shown in Figure 2D below. Ofcourse, other suitable lid attachment techniques willwork as well. This view also provides a good illustrationof a plurality of solvent injector holes 121 that are defined on a solvent ejector ring 127. In one embodiment,about 100 solvent injection holes 121 are definedaround the solvent ejector ring 127 for applying solventchemicals used in back side rinse operations. The backrinse function of solvent injector holes 121 will be described in greater detail with reference to Figure 2E.[0027] Figure 2C shows a wafer 130 placed upon support surface 104 of bowl 102 in accordance with Figures2A and 2B.
As described above, a vacuum supplied bya vacuum pump (not shown) is coupled to the vacuumchamber 118 which leads to the support surface 104 forsecuring wafer 130 during operation. In this view, the lid101 has been coupled to bowl 102 in order to encapsulate wafer 130. Preferably, the lower flat surface 114 oflid 101 is separated from the upper surface 132 of wafer130 by a distance that is small enough to reduce convective vortices from forming near the surface lyingabove the spinning wafer.
In one embodiment, the distance is between about 1 mm and about 10 mm, andmore preferably, between about 1.5 mm and about 3mm, and most preferably about 2 mm.[0028] During a spin coating operation, a coating material is preferably applied to the inner radius of the upper surface 132 of wafer 130 before lid 101 is securedto the bowl 102. After the coating material has been applied, lid 101 is secured to bowl 102 by mating circularrecessed groove 112 to circular protruded lip 124 as described above. In one embodiment, axial shaft 135 isconnected to a motor (not shown) that preferably rotatesaxial shaft 135 to operational speeds sufficient to spreadthe coating materials.[0029] To ensure that lid 101 remains secured to bowl102 during rotation, a locking shaft 160 is secured to lid101.
In addition, locking shaft 160 is used to mechanically apply and remove lid 101 from bowl 102 during andbetween spin coating cycles. As shown by Figure 2D,opening 113 defines a shape that is configured to receive locking shaft 160 (having a similar shape) into hollow internal region 111. Once the locking shaft 160 islowered into hollow internal region 111, locking shaft 160is rotated approximately 120 degrees in either direction.In this manner, the now opposing shapes of the lockingshaft 160 and opening 113 prevent lid 101 from detaching during spin coating. From this top view of lid 101, theplurality of recessed pin holes 122a are shown definedalong the outer diameter of lid 101 such that the pluralityof pins 122 illustrated in Figures 2A and 2B mate withthe plurality of pin holes 122a.[0030] As described above and illustrated in Figure2E, bowl 102 includes a plurality of solvent injectionholes 121.
Solvent injection holes 121 have one end E1defined within a solvent injector ring 123 that is locateda radial distance r1 from the center of rotation of bowl9EP 1 015 136 B1102. Further, an internal end E2 of the solvent injectionholes 121 is located at about a radial distance r2 fromthe center of rotation of bowl 102.
Generally, radial distance r1 is less than radial distance r2, therefore the injector holes 121 form angled conduit paths (e.g., between about 30 and 50 degrees) through bowl 102, connecting solvent injector ring 123 and solvent ejector ring127. In a preferred embodiment, solvent ejector ring 127has a diameter that extends about 150 mm. As described above, solvent that is passed in through the injector holes are well suited to complete back side rinsingof wafer 130, thereby reducing the possibility of edgebead formation.[0031] It should also be appreciated that wafer 130 ispositioned a distance "Hw" above drain holes 125. Inone embodiment, the distance Hw is at least betweenabout 3 mm and about 5 mm, and more preferably atleast between about 3 mm and about 4 mm, and mostpreferably at least about 3 mm. In this manner, chemicals that are spun off of the surface of wafer 130 arepreferably not reflected back onto the surface of wafer130.
As described above, the inner wall surface of bowl102 is preferably curved enough to allow chemicals toslide off wafer 130 and down the wall surface towarddrain holes 125. A further advantage of having the drainholes 125 below the top surface 132 of wafer 130 is thatany turbulence flows produced near the inner edge ofbowl 102 is preferably contained below wafer 130.When turbulent flows are directed away from the surfaced wafer 130, the spun on coatings are produced withimproved uniformity, thereby reducing yield reducing imperfections.[0032] Figure 2F shows a cross sectional view of wafer 130 during a typical spin coat procedure. As bowl102 rotates, the produced centrifugal forces assist thecoating material in spreading over the surface 132 ofwafer 130, thereby forming a coating layer 140.
Unfortunately, the typical coating procedure produces a beading 150 at the edge of wafer 130. As described above,beading 150 presents a number of undesirable yield reducing problems. To reduce the possibility of beading150, a solvent material is injected in through solvent injector 121 and applied as a temporary solvent coating141.
In this example, the solvent coating 141 is causedto spread out towards the beading 150 by the same centrifugal forces that spread coating layer 140. Accordingly, the solvent coating 141 assists in dissolving beading150 to produce a more uniformly coated edge. The dissolved coating material and excess solvent will then flowout of bowl 102 through drain holes 125 as describedabove. Figure 2G is a diagrammatic cross sectional viewof wafer 130 having the spun on coating material layer140 after the solvent coating 141 was applied to removebeading 150.
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