Method for coating a substrate and also a coating system

Abstract

Method for coating a substrate with a coating material is described, in particular with a coating or photoresist, wherein said substrate is provided in said method. Said coating material is applied to said upper side of said substrate. A gas flow is generated, said gas flow being directed from said underside of said substrate to said upper side of said substrate, wherein said gas flow prevents a bead of said coating material forming on said edge of said upper side of said substrate or a previously existing bead is removed by means of said gas flow. In addition, a coating system is described.

Claims

1. Method for coating a substrate with a coating material, in particular a coating or a photoresist, said method having the following steps: a) Providing said substrate, b) Attaching said coating material to said upper side of said substrate, and c) Generating a gas flow that is directed from said underside of said substrate to said upper side of said substrate, wherein said gas flow prevents a bead of said coating material forming on said edge of said upper side of said substrate or a previously existing bead is removed by means of said gas flow.

2. Method as claimed in claim 1, characterized in that said substrate is rotated when applying said coating material so that said coating material that is applied is distributed essentially evenly on said upper side of said substrate.

3. Method as claimed in claim 1, characterized in that said gas flow is generated before said coating material has dried.

4. Method as claimed in claim 1, characterized in that said gas flow impinges at least in part on said underside of said substrate.

5. Method as claimed in claim 1, characterized in that said gas flow impinges on said edge region of said substrate.

6. Method as claimed in claim 1, characterized in that said gas flow generates a negative pressure on said upper side of said substrate.

7. Method as claimed in claim 1, characterized in that said gas flow generates a negative pressure in said edge region of said substrate.

8. Method as claimed in claim 1, characterized in that said gas flow is generated at least in part in such a manner that a possible bead is drawn from said edge region outwards into said gas flow owing to said pressure that occurs.

9. Method as claimed in claim 1, characterized in that said gas flow is generated at least in part in such a manner that a possible bead is drawn from said edge region of said upper side onto said underside of said substrate owing to said pressure that occurs.

10. Method as claimed in claim 1, characterized in that said substrate is rotated when said gas flow is generated.

11. Method as claimed in claim 1, characterized in that said gas flow is free from solvents and/or comprises nitrogen.

12. Method as claimed in claim 11, characterized in that said gas flow consists of nitrogen.

13. Coating system for applying a coating material to an upper side of a substrate, said coating system having an in particular rotatable substrate holder and an outflow device for a gas flow, wherein said substrate holder comprises a support surface for a substrate that is arranged by way of its underside on said support surface of said substrate holder, wherein said outflow device is arranged in relation to said support surface in such a manner that said outflow device generates a gas flow that is directed from said underside of said substrate to said upper side of said substrate wherein said outflow device generates said gas flow such that said gas flow prevents said formation of a bead of said coating material on said edge of said upper side of said substrate and/or removes an already existing bead.

Description

DESCRIPTION OF THE DRAWINGS

[0027] Further advantages and characteristics of the invention are evident in the description hereinunder and the single FIGURE to which reference is made.

DETAILED DESCRIPTION

[0028] In the FIGURE, a coating system 10 for applying a coating to a substrate 12 is illustrated so that a coated substrate is produced with which a photolithography method can be implemented in order to produce microstructured components such as integrated circuits, semiconductor chips or micro-electromechanical systems (MEMS).

[0029] The invention is accordingly explained hereinunder with reference to a specific application example of the invention, a coating system for microstructured components. The fundamental statements can however be transferred in a similar manner to the other application fields.

[0030] The coating system 10 comprises a rotatable substrate holder 14 that comprises a support surface 16 and the substrate 12 is arranged by way of its underside 18 on said support surface.

[0031] In addition, the coating system 10 comprises an application device 20 by way of which coating material of the coating that is to be applied is applied to the upper side 22 of the substrate 12. The coating material that is to be applied is typically in fluid form.

[0032] Furthermore, the coating system 10 comprises an outflow device 24 that is embodied in the illustrated embodiment separately from the substrate holder 14 and the application device 20. A gas flow can be generated by way of the outflow device 24 as is further explained hereinunder.

[0033] The substrate 12 is coated with the coating by means of the coating system 10, wherein a coating bead is simultaneously prevented from forming permanently on the edge 26 of the upper side 22 of the substrate 12.

[0034] The coating material is applied by way of the application device 20 to the upper side 22 of the substrate 12. The substrate holder 14 rotates at a predetermined angular velocity whereby the substrate 12 that is arranged on said substrate holder likewise rotates. The coating material that is applied is distributed as a consequence in a homogenous manner on the upper side 22.

[0035] The coating material migrates to the edge 26 of the upper side 22 of the substrate 12 and would form a bead of coating at that location owing to the centrifugal forces that occur when rotating the substrate 12, said centrifugal forces acting upon the coating material that is applied to the upper side 22.

[0036] In order to prevent this, a gas flow in particular a nitrogen gas flow is generated by way of the outflow device 24 and said gas flow is directed from the underside 18 to the upper side 22 of the substrate 12.

[0037] The gas flow impinges at least in part on the underside 18 of the substrate 12 and flows in part past the side of the substrate 12 that connects the underside 18 to the upper side 22. The gas flow generates a negative pressure on the upper side 22 in particular in its edge region 26 and the coating material that is still soft or moist is at least moved by the gas flow owing to said negative pressure. As a consequence, a coating bead is effectively prevented from forming on the edge 26.

[0038] If a coating bead has already formed, said bead is accordingly removed by the gas flow.

[0039] Irrespective of whether a coating bead (temporarily) occurs during the coating procedure, it is ensured with the coating method owing to the gas flow that a coating bead is not present at the end of the coating procedure.

[0040] In dependence upon the angle of the gas flow with respect to the upper side 22 of the substrate 12, it is possible to set whether the coating material is at least in part swept away by the gas flow and/or whether the coating material is at least in part displaced from the upper side 22 of the substrate 12 onto the lower side 18 of said substrate owing to the pressure that is generated. As a consequence, a coating bead is effectively prevented from forming permanently on the edge 26 of the upper side 22.

[0041] By way of example, it can be provided that a part of the coating material is swept away and another part of the coating material is displaced onto the underside.

[0042] The angle with which the gas flow that is generated by the outflow device 24 is generated in relation to the substrate 12 can preferably be set in order to generate different effects owing to the pressure that occurs.

[0043] Alternatively, the gas flow can also flow out of the outflow device 24 in such a manner that said gas flow does not impinge on the underside 18 of the substrate 12, but rather merely flows past the side of the substrate 12. However, a fine adjustment is necessary in order to generate on the edge 26 of the upper side 22 a negative pressure that prevents a coating bead on the edge 26 from forming or removes a previously existing coating bead.

[0044] In general, the outflow device 24 is arranged below the plane that is defined by means of the support surface 16. The gas flow that starts from the outflow device 24 is oriented in such a manner as to flow away from the support surface 16 possibly at an angle.

[0045] When generating the gas flow by way of the outflow device 24, the substrate 12 can likewise be rotated by way of the substrate holder 14 in order to ensure that the entire edge 26 is exposed to the effects of the gas flow in as homogenous a manner as possible, in other words is exposed to the negative pressure that is consequently generated on the upper side 22. The rotation speed is however clearly lower when generating the gas flow than the speed when applying the photoresist by way of the application device 20. By way of example, the rotation speed is less than ten revolutions per minute when the gas flow is being generated.

[0046] The rotation speed when generating the gas flow can even be zero. It is preferred that the gas flow is then generated by an annular outflow device 24 so that an essentially annular gas flow in each case flows along on the peripheral edge of the substrate 12.

[0047] It is possible with the method in accordance with the invention and the coating system 10 in accordance with the invention that coating beads do not form on the edge 26 of the upper side 22 of the substrate 12.

[0048] In general, gas mixtures other than pure nitrogen can be used in order to generate the gas flow. By way of example, an oxygen-nitrogen mixture, so-called clean dry air (CDA) or air.

[0049] The gas mixture is preferably solvent-free so that residues of the solvent cannot be deposited on the coated upper side 22 of the substrate 12.

[0050] It is preferred that the gas flows from the outflow device 24 with a pressure of multiple bar. As a consequence, inter alia the speed of the gas flow can be influenced, said speed being decisive in generating a negative pressure on the upper side 22 of the substrate 12.

[0051] Furthermore, it is possible that the coating in the edge 26 is even removed by means of a low rotation speed or a long total application time of the gas flow. Accordingly, so to speak a thinning of the coating that is applied in the edge 26 is achieved.

[0052] The outflow device 24 can comprise one outflow nozzle, multiple nozzles, an outflow slot, a so-called airblade or similar, by way of which inter alia another profile of the gas flow is achieved. This is in particular of importance for non-round substrates, by way of example square substrates.

[0053] In addition, the speed of the gas flow can be influenced by way of the specific embodiment of the outflow device 24.

[0054] If the coating material is swept away by the gas flow, the coating system 10 can comprise a retention tank for the coating material that is removed so that this coating material on the one hand does not contaminate the chamber and on the other hand can be reused.

[0055] In general, the gas flow that is generated by the outflow device 24 accordingly does not directly impinge on the upper side 22 of the substrate 12 but rather impinges on the underside 18 in an essentially perpendicular manner or the gas flow flows past essentially parallel to the axis of rotation of the substrate holder 14 on the substrate 12 in order to generate a negative pressure or a vacuum on the upper side 22 of the substrate 12, in particular on the edge 26 of the upper side 22.

[0056] The negative pressure ensures that the coating material that is collecting on the edge 26 does not form a permanent bead on the edge 26 that would also be present after the coating procedure. A coating bead that occurs temporarily during the coating procedure is accordingly removed by the gas flow.