USP_6261635 (1063343)
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US006261635B1(12) United States Patent(10) Patent N0.:US 6,261,635 B1(45) Date of Patent:Jul. 17, 2001Shirley(54)METHOD FOR CONTROLLING AIR OVERA5,238,713 *SPINNING MICROELECTRONIC5,472,502 * 12/1995 Batchelder ............ ..8/1993 Sago et a1. ......................... .. 427/240118/52SUBSTRATE5,518,542 *118/525/1996 Matsukawa et a1.5,688,322 * 11/1997(75) Inventor:Paul D.
Shirley, Meridian, ID (US)(73) Assignee: Micron Technology, Inc., Boise, ID(US)(*)Notice:Subject to any disclaimer, the term of thispatent is extended or adjusted under 35U'S'C' 154(k)) by 0 days‘Motoda et a1. ...................... .. 118/524 Cited by examinerPrimary Examiner—Shrive BeckAssistant Examiner—Jennifer Calcagni(74) Attorney, Agent, or Firm—Dorsey & Whitney LLP(57)ABSTRACTAmethod for forming a generally uniform liquid layer on asurface of an upper surface microelectronic substrate. The(21)(22)Appl- NOJ 09/384,830Filed:Aug 27’ 1999apparatus can include a support that engages less than theentire loWer surface of the microelectronic substrate and(51)(52)Int. Cl.7 ...................................................... ..
B05D 3/12US. Cl. ........................ .. 427/240; 427/425; 438/780;rotates the microelectronic substrate at a selected rate. Abarrier can extend over the upper surface of the microelectronic substrate and can rotate at about the same rate as the438/782substrate to separate a rotating air mass adjacent to the upper(58)Field of Search ............................... .. 427/240, 385.5,errrfree and within the barrier from a stationary err rrrree427/425; 118/52, 320; 438/758, 778, 780,782, 909, 928external to the barrier.
The rotating air mass can reduce thelikelihood for liquid/air interface disturbances that createnon-uniformities in the liquid layer. Accordingly, the method(56)References Citedcan increase the range of thicknesses to Which the liquidlayer can be formed and can reduce the topographicalU'S' PATENT DOCUMENTS4,800,836 *1/19895,211,753 *5/1993 Swain ................................... .. 118/52non-uniformities of the liquid layer.Yamamoto et a1.
................. .. 118/5233 Claims, 4 Drawing Sheets742I10723724 748I25I22x736U.S. PatentJul. 17, 2001Sheet 1 014US 6,261,635 B1$20F1. . 1(Pn'g Art)U.S. PatentJul. 17, 2001Sheet 2 014I002/300F1‘ . 2(P115 Art)US 6,261,635 B1U.S. PatentJul. 17, 2001Sheet 3 014US 6,261,635 B1125I24 748'4?) f74,760740750f/251441/ / f 155L)‘VAA‘K446\’\\z55\752I54725\150f/56/A DKI22U.S. PatentJul. 17, 2001Sheet 4 014US 6,261,635 B12251225349242 \M210m\*248"245$247IMr277f\'/256A248bI260ii”US 6,261,635 B112Yet another draWback With this technique is that theMETHOD FOR CONTROLLING AIR OVER ASPINNING MICROELECTRONICSUBSTRATEviscosity selected for the liquid photoresist material mustThe present invention is directed toward methods andaccount 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 desiredapparatuses for controlling the movement of air over athickness.
Such a liquid may be too viscous for smallerTECHNICAL FIELDsubstrates. Accordingly, conventional techniques typicallyspinning microelectronic substrate, for example duringapplication of a liquid to the microelectronic substrate.BACKGROUND OF THE INVENTION10use 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 thisDuring the manufacture of microelectronic devices, suchas memory chips, processor chips and ?eld emissiondisplays, etching processes are often used to form featureson a microelectronic substrate or substrate assembly that 15forms the foundation of the device.
A typical etching technique includes depositing a layer of a photoresist material onapproach 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 toexposing the unmasked portions to a selected radiation. Thecontrol the thickness of the liquid layer (for example, byincreasing the angular velocity to reduce the layerthickness), this technique is limited because at high angularselected radiation changes the solubility of the unmaskedvelocities, the liquid can form Waves or other disturbances,portions to become either soluble (in the case of a positivephotoresist) 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 photoresistmaterial, exposing a portion of the substrate beneath.
Theas discussed above.the substrate, masking selected portions of the layer andFIG. 1 is a partially schematic, partially cutaWay sideelevation vieW of a conventional device 10 that can addresssome of the foregoing problems for rectangular substrates.25The device 10 includes a motor 30 having a shaft 32connected to a chuck 33 and a boWl 20. A substrate 12substrate is Washed With an etchant that removes materialhaving a rectangular platform shape is releasably mounted tofrom the exposed portions of the substrate While leavingintact the portions of the substrate covered by the photoresistthe chuck 33 and both the substrate 12 and the boWl 20 spinas the shaft 32 rotates. Accordingly, the air adjacent to thesubstrate 12 is partially contained Within the spinning boWlmaterial.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 nonuniform thickness, certain portions of thephotoresist material may be overexposed to the radiationWhile other portions may be underexposed. Where thepholoresist 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 the photoresistant layer relatively small to increasethe resolution of the features formed With this technique.The photoresist material is typically deposited on thesubstrate or substrate assembly by disposing the material inliquid 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 adjacent20 so that at least a portion of the air Will spin at the same35rate as the substrate 12. A ?uid supply conduit 23 disposesa liquid onto the substrate 12 through an aperture 24 and theliquid spreads out over the surface of the substrate 12 as thesubstrate 12 spins. Excess liquid is collected in the boWl 20as it runs over the edges of the substrate 12 and can beremoved from the boWl via a drain 21.
Air can be exhaustedfrom the boWl 20 through an exhaust port 22.One potential draWback With the device 10 shoWn in FIG.1 is that the boWl 20 can be heavy and difficult to spinsmoothly at high rates of speed. Furthermore, the drain 21and the exhaust port 22 may be coupled to a drain line 23aand an exhaust line 23b, respectively, Which must be securedto the boWl 20 With ?uid-tight rotating couplings. Still45further, the boWl 20 is partially open so that it may be timeconsuming to bring the air mass adjacent to the substrate 12up to the same rotational speed as the substrate 12, particularly Where the substrate 12 rotates at high speed.FIG.
2 is a partially schematic, partially cutaWay sideelevation vieW of another conventional device 10a thatair mass, creating Waves or other disturbances in the phoincludes a motor 30a coupled With a shaft 32a to a chucktoresist material that affect the uniformity of the layer33a. The chuck 33a includes a rectangular recess 36 forthickness.
This problem can become more acute When thereceiving the rectangular substrate 12. A cover 40 is releasably placed on the chuck 33a to rotate With the chuck 33avelocity of the substrate increases, for example, When thesubstrate is rotated at a high angular velocity and/or When55the substrate has a large radius so that at even moderateangular velocities, the linear speed toWard the edge of thesubstrate is high.and 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 furtherinclude a collection vessel 20a ?xed relative to the motor30a and having a drain 21 and an exhaust port 22 forAnother draWback With this technique is that the convective heat transfer rate can vary over the surface of theremoving liquid and gas from the region adjacent to thesubstrate because the relative linear velocity betWeen thesubstrate and the adjacent air mass varies With the distancesubstrate 12.One problem With the device 10a shoWn in FIG. 2 is thatthe liquid disposed on the substrate 12 can become trappedbetWeen the loWer surface of the substrate 12 and the Wallsof the recess 36 into Which the substrate 12 is placed. Afurther draWback is that the recess 36 is siZed for rectangularsubstrates 12, making it unsuitable for or unusable Withfrom the substrate center. The variation in heat transfer ratescan 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.65US 6,261,635 B134round substrates, particularly Where the diameter of theembodiment of the invention.
The substrate 112 can have around substrate exceeds the Width of the recess 36.generally round platform shape and a diameter of at leastapproximately eight inches. For example, in oneSUMMARY OF THE INVENTIONembodiment, the substrate 112 can have a diameter ofThe present invention is directed toWard methods andapparatuses for uniformly distributing a liquid over a surfaceof a spinning microelectronic substrate. An apparatus insubstrate 112 can have other diameters and shapes so long asit can be adequately supported by the apparatus 110 and soaccordance With one aspect of the invention can include aa uniform manner.approximately tWelve inches and in other embodiments thelong as the liquid can be distributed on the substrate 112 insupport having an engaging portion for engaging the microelectronic substrate and rotating the microelectronic sub10strate at a ?rst rate.
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