SUSS (1063342)
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Europäisches Patentamt(19)European Patent Office*EP001015136B1*Office européen des brevets(11)EP 1 015 136 B1EUROPEAN PATENT SPECIFICATION(12)(45) Date of publication and mention(51) Int Cl.7:of the grant of the patent:07.09.2005 Bulletin 2005/36(21) Application number: 98926126.8(22) Date of filing: 29.05.1998B05D 3/12, B05D 3/02,B05C 13/00, B05C 13/02,H01L 21/469, B05C 11/08,B05D 1/00, G03F 7/16,H01L 21/312(86) International application number:PCT/US1998/010958(87) International publication number:WO 1998/053923 (03.12.1998 Gazette 1998/48)(54) METHOD AND APPARATUS FOR SPIN-COATING CHEMICALSVERFAHREN UND VORRICHTUNG ZUM ZENTRIFUGALBESCHICHTEN VON CHEMIKALIENPROCEDE ET APPAREIL DE REVETEMENT DE SUBSTANCES CHIMIQUES PAR ROTATIONRAPIDE(84) Designated Contracting States:• BATCHELDER, William, T.Oakland, CA 94605 (US)AT BE CH DE FR GB IT LI NL(30) Priority: 30.05.1997 US 866832(74) Representative: Vossius & Partner30.05.1997 US 866834Siebertstrasse 481675 München (DE)(43) Date of publication of application:(56) References cited:05.07.2000 Bulletin 2000/27(73) Proprietor: SUSS MicroTec Lithography GmbH85748 Garching (DE)US-A- 4 113 492US-A- 4 838 289US-A- 5 474 807US-A- 4 518 678US-A- 5 439 519US-A- 5 705 223(72) Inventors:EP 1 015 136 B1• MAHNEKE, PeterD-21244 Muchholz (DE)Note: Within nine months from the publication of the mention of the grant of the European patent, any person may givenotice to the European Patent Office of opposition to the European patent granted.
Notice of opposition shall be filed ina written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.99(1) European Patent Convention).Printed by Jouve, 75001 PARIS (FR)1EP 1 015 136 B1DescriptionBACKGROUND OF THE INVENTION1. Field of the Invention5[0001] The present invention relates generally tosemiconductor fabrication, and more particularly, to apparatuses and methods for spin-coating substratesused in the fabrication of semiconductor devices.102. Description of the Related Art[0002] The fabrication of a large variety of solid statedevices such as semiconductors requires the use of planar substrates, otherwise known to those skilled in theart as wafers.
An important consideration in the fabrication of these devices is the final number (i.e., yield) offunctional dies remaining from each manufactured wafer. The functional dies are packaged, undergo testing(both electrical and otherwise), and substantially all ofthe packaged dies that pass the requisite testing aresold.
It is therefore of utmost importance for manufacturers of these products to take advantage of economiesof scale realized by increasing their production yield.Typically, depending on the individual die dimensions,upwards of 1000 or more dies may be fabricated on asingle wafer. These wafers are typically on the order ofsix to twelve inches in diameter.[0003] A typical fabrication process requires numerous steps, where several layers of material are cumulatively applied and patterned on the surface of the wafer.Once complete, these layers form the desired semiconductor structure necessary for the resulting circuit, or device.
As can be appreciated, the final functional yieldcritically depends upon the proper application of eachlayer during the various process steps. Proper application of these layers typically depends, in turn, upon theability to form uniform coatings of material on the surfaceof the wafer in an efficient, environmentally benign, andproduction worthy manner.[0004] Various fabrication process steps implemented in making semiconductor devices utilize photolithography to define the desired patterns on the surface of awafer. As is well known, photolithography is the processwhere light energy is applied through a reticle mask (using a stepper exposure camera) onto a photoresist material that is applied to the wafer to define patterns wheresubsequent etching will occur.
These surface patternsrepresent a two dimensional layout of the desired structure that is fabricated on the surface of the wafer. It istherefore important that the photoresist material be applied in uniformly distributed coatings, while at the sametime ensuring that particulate generation is minimized.As is well known in the art, when particulate generationis minimized or eliminated, it is possible to increase theresolution of the desired patterns, as well as increasepattern density.15202530354045505522[0005] Conventionally, the application of photoresistcoatings on the surface of a wafer is accomplished bycasting a photoresist fluid on a wafer that is spinning athigh speeds within a stationary exhausted bowl.
In general, the stationary exhausted bowl is used to catch anyexcess fluids and remove particulates. Once the photoresist fluid is applied, the centrifugal force that resultfrom the high rotational speed of the wafer overcomesthe surface tension of the photoresist fluid, which causes the photoresist fluid to spread over the surface of thewafer.[0006] A side effect of spinning the wafer is the inducement of air flows in the air immediately above andadjacent to the wafer surface. Unfortunately, this air flowtends to induce particles of photoresist to leave the wafer surface at the wafer's edge.
When the photoresistleaves the wafer's edge, the free floating photoresistparticulates have the potential to back contaminate theremainder of the wafer surface where a fresh coating ofphotoresist has just been applied. Although these particles may be removed by an exhaust system that maybe part of the stationary bowl, the exhaust has the undesirable effect of drying out photoresist solvent filmsunevenly and, thus, producing a non-uniform coating ofphotoresist over the surface of the wafer during the spinning process. Back side contamination of the photoresist film with photoresist particulates and uneven dryingof the photoresist film are therefore, undesirable yieldreducing side effects of conventional spin-coating processes.[0007] Another problem associated with conventionalspin coating methods is photoresist fluid beading at theouter edge of the spinning wafer.
Specifically, it is believed that surface tension and adhesion of the photoresist film to the wafer surface experienced during spinning causes the photoresist to from a "zone of increasedthickness" at the edge of the wafer. This beading cantypically contribute to a significant loss in functional devices that lie at and near the outer edge of the wafer.[0008] Yet another problem associated with the beading effect at the edges of the wafers is that wafers arecommonly stored in cassettes and, the increased thickness at the edges has the unfortunate effect of fracturingthe wafers when they come in contact with the storagecassette. Of course, when wafers are fractured in anyway, an instant loss in yield is experienced.[0009] Figure 1 is an illustration of a conventionalopen bowl apparatus 10 for spin coating a wafer 16.
Awafer 16 is typically placed upon a rotatable chuck 14which is rigidly connected to a spinning motor unit 20 bya shaft 18. As shown, the spinning chuck 14 and thewafer 16 are located within an open stationary bowl 12.The open stationary bowl 12 may include suitable exhaust passages 22 that are used to purge out particulates that may be produced within open stationary bowl12 during a spin coating process. Unfortunately, conventional methods for removing particulates producedduring spin coating operations have been less than ad-3EP 1 015 136 B1equate.[0010] During a spin coating operation, a number ofair flows 17 may be produced in the air immediatelyabove and adjacent to the spinning chuck 14. As described above, the air flows 17 tend to produce particlesof photoresist that further complicate the back contamination problems described above.[0011] In view of the foregoing, there is a need for apparatuses and methods that facilitate the application ofsubstantially uniform spin coated materials over the surface of a wafer while reducing the amount of yield reducing particulates.510SUMMARY OF THE INVENTION15[0012] Broadly speaking, the present invention fillsthese needs by providing a method and an apparatusfor uniformly spin-coating materials over the surface ofa substrate, such as wafers.[0013] According to the present invention, an apparatus for spin coating chemicals over a substrate is disclosed as defined in appended claim 1.
The apparatusincludes a bowl having a raised support for holding thesubstrate. The bowl includes curved walls that define acavity capable of holding a fluid near an outer region ofthe bowl. The apparatus further includes a lid configuredto mate with the curved walls. The lid preferably has asubstantially flat underside that is positioned in closeproximity to a top surface of the substrate.
Further, theapparatus includes fluid injector holes defined along anejection ring that is defined under the substrate. The fluid injector holes are directed at an underside of the substrate that is near the outer diameter of the substrate.The apparatus also includes a plurality of drain holesthat are defined on a floor region of the bowl. The plurality of drain holes are spaced apart from the outer region of the bowl to enable the cavity to hold a fluid whilethe bowl is spinning, and to drain the fluid when the bowlbegins to come to a substantial stop.[0014] A method for spin coating a substrate in accordance with the present invention is also disclosed asdefined in appended claim 28. The method includes applying a chemical to be spin coated over a substrate thatis supported within a bowl. The bowl has a fluid retainingcavity at an outer edge of the bowl.
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