USP_20010020443 (1063353)
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US 20010020443A1(19) United States(12) Patent Application Publication (10) Pub. N0.2 US 2001/0020443 A1Shirley(43) Pub. Date:Sep. 13, 2001(54) METHOD AND APPARATUS FORCONTROLLING AIR OVER A SPINNINGMICROELECTRONIC SUBSTRATE(76) Inventor: Paul D. Shirley, Meridian, ID (US)Correspondence Address:Mark W. Roberts, Esq.DORSEY & WHITNEY LLPSuite 34001420 Fifth AvenueSeattle, WA 98101 (US)Publication Classi?cation(51)Int.
Cl? .(52)Us. 01. ............................................. .. 118/52; 118/313(57)1305c 5/00; 1305c 11/02ABSTRACTA method and apparatus for forming a generally uniformliquid layer on a surface of an upper surface microelectronicsubstrate. The apparatus can include a support that engagesless than the entire loWer surface of the microelectronicsubstrate and rotates the microelectronic substrate at aselected rate.
Abarrier can extend over the upper surface ofthe microelectronic substrate and can rotate at about thesame rate as the substrate to separate a rotating air massadjacent to the upper surface and Within the barrier from astationary air mass external to the barrier. The rotating air(21) Appl. No.:09/859,601(22) Filed:May 16, 2001mass can reduce the likelihood for liquid/air interface disRelated US. Application Dataturbances that create non-uniformities in the liquid layer.Accordingly, the method and apparatus can increase therange of thicknesses to Which the liquid layer can be formed(62) Division of application No. 09/384,830, ?led on Aug.27, 1999, noW Pat. NO. 6,261,635.and can reduce the topographical non-uniformities of theliquid layer.I23724 I4814; } //_750725I20I27Patent Application PublicationSep.
13, 2001 Sheet 1 0f 470\25F1' . 1(P175 Art)US 2001/0020443 A1Patent Application PublicationSep. 13, 2001 Sheet 2 0f 4US 2001/0020443 A170020a27300F1 . 2(Prjgr Art)Patent Application Publication5HO\I25\Sep. 13, 2001 Sheet 3 0f 4723US 2001/0020443 A1Patent Application PublicationSep. 13, 2001 Sheet 4 0f 42251225249242 \kles\210E;\US 2001/0020443 A1243I~—2485/40248btif”I I260L59Z20272‘,MQSep. 13, 2001US 2001/0020443 A1METHOD AND APPARATUS FOR CONTROLLINGAIR OVER A SPINNING MICROELECTRONICSUBSTRATETECHNICAL FIELD[0001]The present invention is directed toward methodsand apparatuses for controlling the movement of air over aspinning microelectronic substrate, for example duringapplication of a liquid to the microelectronic substrate.BACKGROUND OF THE INVENTION[0002] During themanufacture of microelectronicdevices, such as memory chips, processor chips and ?eldemission displays, etching processes are often used to formfeatures on a microelectronic substrate or substrate assemblythat forms the foundation of the device.
A typical etchingtechnique includes depositing a layer of a photoresist material on the substrate, masking selected portions of the layerand exposing the unmasked portions to a selected radiation.The selected radiation changes the solubility of theunmasked portions to become either soluble (in the case ofa positive photoresist) or insoluble (in the case of a negativephotoresist) When exposed to a selected solvent. The photoresist layer is then Washed With the selected solvent toremove either the exposed or unexposed photoresist material, exposing a portion of the substrate beneath. The substrate is Washed With an etchant that removes material fromthe exposed portions of the substrate While leaving intact theportions of the substrate covered by the photoresist material.[0003]It is often important to control the uniformity of thethickness to Which the photoresist material is deposited onthe substrate.
For example, if the photoresist material isdeposited to a non-uniform thickness, certain portions of thephotoresist material may he overexposed to the radiationWhile other portions may be underexposed. Where thephotoresist material is overexposed, the edges betWeen themasked and unmasked regions can become blurred, makingthe process unsuitable for forming very small features.Where the photoresist material is underexposed, it may nothave sufficient exposure time to change solubility.
Furthermore, it may be desirable to keep the overall thickness of thephotoresistant layer relatively small to increase the resolution of the features formed With this technique.can cause the surface temperature of the substrate to vary, inturn causing the evaporation rate of the ?uid (and thereforethe thickness of the ?uid) to vary over surface of thesubstrate.[0006] Yet another draWback With this technique is that theviscosity selected for the liquid photoresist material mustaccount for the diameter and rotation speed of the substrate.For example, a relatively viscous liquid may be selected forlarge substrates to prevent the liquid from ?ying off theedges of the substrate before accumulating to the desiredthickness.
Such a liquid may be too viscous for smallersubstrates. Accordingly, conventional techniques typicallyuse liquids With different viscosities to form layers havingdifferent thicknesses. For example, less viscous liquids canbe used to form thinner layers and more viscous liquids canbe used to form thicker layers. One problem With thisapproach is that it requires controlling and/or adjusting theviscosity of the liquid and/or providing multiple sources ofthe liquid, each having a different viscosity. Furthermore,While the angular velocity of the substrate can be used tocontrol the thickness of the liquid layer (for example, byincreasing the angular velocity to reduce the layer thickness), this technique is limited because at high angularvelocities, the liquid can form Waves or other disturbances,as discussed above.[0007] FIG.
1 is a partially schematic, partially cutaWayside elevation vieW of a conventional device 10 that canaddress some of the foregoing problems for rectangularsubstrates. The device 10 includes a motor 30 having a shaft32 connected to a chuck 33 and a boWl 20. A substrate 12having a rectangular planform shape is releasably mountedto the chuck 33 and both the substrate 12 and the boWl 20spin as the shaft 32 rotates.
Accordingly, the air adjacent tothe substrate 12 is partially contained Within the spinningboWl 20 so that at least a portion of the air Will spin at thesame rate as the substrate 12. A ?uid supply conduit 23disposes a liquid onto the substrate 12 through an aperture24 and the liquid spreads out over the surface of the substrate12 as the substrate 12 spins. Excess liquid is collected in theboWl 20 as it runs over the edges of the substrate 12 and canbe removed from the boWl via a drain 21.
Air can beexhausted from the boWl 20 through an exhaust port 22.[0008]One potential draWback With the device 10 shoWn[0004] The photoresist material is typically deposited onthe substrate or substrate assembly by disposing the materialin FIG. 1 is that the boWl 20 can be heavy and di?icult toin liquid form at the center of the substrate and spinning thesubstrate about its center to spread the material outWardly bycentrifugal force.
One draWback With this technique is thatthe liquid photoresist material can interact With the adjacentair mass, creating Waves or other disturbances in the photoresist material that affect the uniformity of the layer21 and the exhaust port 22 may be coupled to a drain line23a and an exhaust line 23b, respectively, Which must bethickness. This problem can become more acute When the12, particularly Where the substrate 12 rotates at high speed.velocity of the substrate increases, for example, When thesubstrate is rotated at a high angular velocity and/or Whenthe substrate has a large radius so that at even moderateangular velocities, the linear speed toWard the edge of thesubstrate is high.[0005] Another draWback With this technique is that thespin smoothly at high rates of speed.
Furthermore, the drainsecured to the boWl 20 With ?uid-tight rotating couplings.Still further, the boWl 20 is partially open so that it may betime consuming to bring the air mass adjacent to thesubstrate 12 up to the same rotational speed as the substrate[0009] FIG.
2 is a partially schematic, partially cutaWayside elevation vieW of another conventional device 10a thatincludes a motor 30a coupled With a shaft 32a to a chuck33a. The chuck 33a includes a rectangular recess 36 forreceiving the rectangular substrate 12. A cover 40 is releasably placed on the chuck 33a to rotate With the chuck 33asubstrate because the relative linear velocity betWeen thesubstrate and the adjacent air mass varies With the distanceand the substrate 12. The cover 40 includes an aperture 41that alloWs ?uid to pass from the ?uid supply conduit 23 tothe surface of the substrate 12. The apparatus 10a can furtherfrom the substrate center.
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