PROJECTION EXPOSURE APPARATUS FOR SEMICONDUCTOR LITHOGRAPHY

Abstract

A projection exposure apparatus for semiconductor lithography includes an optical correction element and an electromagnetic heating radiation source for at least partly irradiating an optically active region of the correction element with electromagnetic heating radiation. The optical correction element is provided with at least one electrical heating element outside the optically active region.

Claims

1. An apparatus, comprising: an optical correction element comprising an optically active region; a plurality of electrical heating elements supported by the optical correction element; and an electromagnetic heating radiation source configured to provide electromagnetic heating radiation, wherein: the plurality of electrical heating elements is outside the optically active region; during use of the apparatus: is used light impinges on the optically active region; the electromagnetic heating radiation at least partly irradiates the optically active region; and the plurality of electrical heating elements provide locally adaptable densities of heating power depending heating of the optically active region due to the used light impinging on the optically active region and the electromagnetic heating radiation irradiating the optically active region; and the apparatus is a semiconductor lithography projection exposure apparatus.

2. The apparatus of claim 1, wherein the apparatus does not have an electrical heating element supported by the optical correction element within the optically active region.

3. The apparatus of claim 1, wherein the plurality of electrical heating elements comprises a plurality of resistance wires.

4. The apparatus of claim 3, wherein the resistance wires are at least one micrometer thick.

5. The apparatus of claim 1, wherein the plurality of electrical heating elements is disposed on a surface of the optical correction element.

6. The apparatus of claim 1, wherein, for at least some of the heating elements, different heating elements have different electrical properties.

7. The apparatus of claim 1, further comprising an open-loop/closed-loop control configured to control the plurality of heating elements so that the plurality of electrical heating elements provide the locally adaptable densities of heating power.

8. The apparatus of claim 1, further comprising temperature sensor configured to detect a temperature of the optical correction element.

9. The apparatus of claim 1, wherein the optical correction element comprises a plane-parallel plate.

10. The apparatus of claim 9, wherein the plane-parallel plate has a thickness of from two millimeters to 20 millimeters.

11. The apparatus of claim 1, wherein the optical correction element comprises two plane-parallel plates, and a fluid channel is between the two plane-parallel plates.

12. The apparatus of claim 11, wherein the two plane-parallel plates are arranged parallel to one another at a distance of from 2 millimeters to 50 millimeters.

13. The apparatus of claim 11, wherein a material of the two plane-parallel plates and a wavelength of the electromagnetic heating radiation are configured so that an average absorbed power of the electromagnetic heating radiation over the optically active region is at least 10 Watts.

14. The apparatus of claim 11, wherein a material of the plane-parallel plates and a wavelength of the electromagnetic heating radiation are configured so that an absorptivity of the electromagnetic heating radiation over the optically active region is from 10% to 20% of an incident power of the electromagnetic heating radiation per 100 millimeters of the material.

15. The apparatus of claim 11, further comprising an electrical connection strip contacting the plurality of electrical heating elements, wherein at least sections of the electrical connection strip run parallel to the fluid channel.

16. The apparatus of claim 1, further comprising a common ground line, wherein at least two of the electrical heating elements are connected to the common ground line.

17. The apparatus of claim 1, wherein the used radiation is EUV radiation, and the electromagnetic heating radiation is infrared radiation.

18. The apparatus of claim 1, wherein a wavelength of the used radiation is from one nanometer to 30 nanometers.

19. The apparatus of claim 1, further comprising: an illumination device configured to at least partially illuminate an object in an object plane with the used radiation; and a projection device configured to image the object into an image plane, wherein the projection device comprises the an optical correction element and the plurality of electrical heating elements.

20. An apparatus, comprising: an optical correction element comprising an optically active region; a plurality of heating elements supported by the optical correction element; and an electromagnetic heating radiation source configured to provide electromagnetic heating radiation, wherein: the plurality of heating elements is outside the optically active region; during use of the apparatus: used light impinges on the optically active region; the electromagnetic heating radiation at least partly irradiates the optically active region; and the plurality of heating elements provide locally adaptable densities of heating power depending heating of the optically active region due to the used light impinging on the optically active region and the electromagnetic heating radiation irradiating the optically active region; and the apparatus is a semiconductor lithography projection exposure apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Exemplary embodiments and variants of the disclosure are explained in greater detail below with reference to the drawing, in which:

[0025] FIG. 1 shows a basic illustration of a projection exposure apparatus in which the disclosure can be applied; and

[0026] FIG. 2 shows a basic detailed illustration of the disclosure.

EXEMPLARY EMBODIMENTS

[0027] FIG. 1 illustrates an exemplary projection exposure apparatus 1 in which the disclosure can be applied. The projection exposure apparatus 1 serves for imaging structures on a substrate which is coated with photosensitive materials, and which generally consists predominantly of silicon and is referred to as a wafer 2, for the production of semiconductor components, such as computer chips. The projection exposure apparatus 1 in this case substantially includes an illumination device 3, a reticle stage 4 for receiving and exactly positioning a mask provided with a structure, a so-called reticle 5, by which the later structures on the wafer 2 are determined, a wafer stage 6 for holding, moving and exactly positioning the wafer 2 and an imaging device, to be specific a projection lens 7, with a plurality of optical elements 8, which are held by way of mounts 9 in a lens housing 10 of the projection lens 7. The basic functional principle in this case provides that an image of the structures introduced into the reticle 5 is projected onto the wafer 2; the imaging generally being on a reduced scale. The illumination device 3 provides a projection beam 11 in the form of electromagnetic radiation, which is used for the imaging of the reticle 5 on the wafer 2. A laser, a plasma source or the like can be used as the source of this radiation. Optical elements in the illumination device 3 are used to shape the radiation in such a way that, when it is incident on the reticle 5, the projection beam 11 has the desired properties with regard to diameter, polarization and the like. An image of the reticle 5 is produced by the projection beam 11 and transferred from the projection lens 7 onto the wafer 2 in an appropriately reduced form, as already explained above. In this case, the reticle 5 and the wafer 2 can be moved synchronously, so that images of regions of the reticle 5 are projected onto corresponding regions of the wafer 2 virtually continuously during a so-called scanning operation. The projection lens 7 has a multiplicity of individual refractive, diffractive and/or reflective optical elements 8, such as, for example, lens elements, mirrors, prisms, terminating plates and the like, wherein the optical elements 8 can be supplemented or replaced for example by an optical correction device 20 according to the disclosure.

[0028] The disclosure can likewise be used in an EUV apparatus, which is not illustrated. An EUV apparatus is set up in principle like the DUV apparatus 1 described above, wherein in an EUV apparatus predominantly mirrors can be used as optical elements and the light source of an EUV apparatus emits used radiation in a wavelength range of 5 nm to 100 nm, in particular 13.5 nm. In the case where the disclosure is used in an EUV apparatus, a mirror would then be heated outside its optically active region via an electrical heating element.

[0029] FIG. 2 shows a detailed illustration of the disclosure, illustrating a device embodied as a thermal manipulator 20 in a plan view. The manipulator 20 includes an optical element embodied from two plane-parallel plates 21.x. Only the lower 21.1 of the two plane-parallel plates 21.x, which are embodied functionally identically, is illustrated in FIG. 2, the illustration showing a plan view of the surface 24 of the plane-parallel plate 21.1 from above in the direction of the used light. The plane-parallel plate 21.1 includes an optically active region 22, which is impinged on by used radiation (not illustrated) of the projection exposure apparatus. Furthermore, the optically active region 22 is irradiated by electromagnetic heating radiation embodied as laser beams 44.x, the irradiation being coupled into the plane-parallel plate 21.1 through the side surfaces 32.x thereof. The laser beams 44.x are emitted by one or more lasers (not illustrated) and are guided via optical waveguides 41.x to the input coupling points 42.x at the side surfaces 32.x of the plane-parallel plate 21.1. Input coupling optical units 43.x embodied as spherical lens elements, for example, are arranged at the input coupling points 42.x, and shape the laser beams 44.x and couple them into the plane-parallel plate 21.1 perpendicularly to the used radiation. The plane-parallel plate 21.1 is heated by absorption in its material. In order to be able to set local heatings, a plurality of laser beams 44.x are oriented such that they meet at crossover points 45.x in the optically active region 22 of the plane-parallel plate 21.1, at which points the power density can be doubled, as a result of the absorption of two laser beams 44.1, 44.2. Only two laser beams 44.1, 44.2 intersecting at a crossover point 45 are illustrated in FIG. 2, for reasons of clarity. After the beams have passed through the plane-parallel plate 21.1, they are absorbed in light traps (not illustrated) and the heat is dissipated in a manner such that the excess energy does not heat other optical elements or other component parts such as, for example, mounts of the projection exposure apparatus. The input coupling points 42.x can be arranged at all four sides of the plane-parallel plates 21.x, in which case up to 200 laser beams can be coupled in per side, which in turn results in almost 800 adjustable degrees of freedom for correcting imaging aberrations.

[0030] In contrast to the optically active region 22, the region outside the optically active region 22, also referred to as edge region 23, is heated by electrical heating elements 25.x. The heating elements 25.x are arranged on the surface 24 of the lower plane-parallel plate 21.1 and each include a supply line 27.x, a heating structure 26.x and an outgoing line 28.x, the outgoing lines 28.x of the heating elements 25.x in the example shown all being connected to a common ground 29. In this case, the supply lines 27.x are embodied such that the electrical resistance is as low as possible in order to minimize unwanted heating in the region of the supply lines 27.x. The same also applies to the outgoing lines 28.x and the ground line 29. The heating structures 26.x are arranged in the regions in which heating by the heating elements 25.x is desired, the heating structures being distinguished by an increased resistance on account of a small cross section and/or a different material and being arranged in a specific region in a meandering fashion on the surface 24 of the plane-parallel plate 21.1. As a result, in the region of the heating structures 26.x the power density is higher by a multiple than in the region of the supply lines 27.x and outgoing lines 28.x and also the ground line 29. The supply lines 27.x all originate on a connection strip 30, which is arranged on the right-hand side of the plane-parallel plate 21.1 in FIG. 2. A fluid channel is embodied between the lower plane-parallel plate 21.1 and the upper plane-parallel plate 21.2 (not illustrated), air as cooling medium flowing through the fluid channel. The cooling gas flow 31 is indicated by three arrows in FIG. 2. The side elements of the cooling channel are not illustrated in FIG. 2, for reasons of clarity. The cooling medium serves as a heat sink which dissipates again the power introduced by the laser beams 44.x and the electrical heating elements 25.x and thus has a thermally neutral effect in relation to the other optical elements of the projection optical unit, with the result that only a temperature distribution within the plane-parallel plates is brought about which brings about the predetermined correction effect by way of the dependence of the refractive index on temperature. In the example shown, the plane-parallel plate 21.1 furthermore includes four temperature sensors 33.x, which are arranged outside the optically active region 22 and are illustrated merely schematically by circles in FIG. 2. On the basis of the values detected by the temperature sensors 33.x, the temperature distribution in the plate can be determined by an open-loop or closed-loop control (not illustrated). the temperature distribution is used for determining the power to be introduced by the electromagnetic heating radiation 44.x and the electrical heating elements 25.x. The powers thus determined are passed on to the open-loop control or closed-loop control of the lasers and of the heating elements, with the result that a predetermined temperature distribution is established in the plane-parallel plates 21.x.

LIST OF REFERENCE SIGNS

[0031] 1 Projection exposure apparatus [0032] 2 Wafer [0033] 3 Illumination device [0034] 4 Reticle stage [0035] 5 Reticle [0036] 6 Wafer stage [0037] 7 Projection lens [0038] 8 Optical element [0039] 9 Mount [0040] 10 Lens housing [0041] 11 Projection beam [0042] 20 Thermal manipulator (device) [0043] 21 Plane-parallel plate (optical element) [0044] 22 Optically active region [0045] 23 Edge region [0046] 24 Surface [0047] 25.x Heating elements [0048] 26.x Heating structure [0049] 27.x Supply line [0050] 28.x Outgoing line [0051] 29 Ground line [0052] 30 Connection strip [0053] 31 Cooling gas flow [0054] 32.1-32.2 Side surface [0055] 33.1-33.4 Temperature sensor [0056] 41.1-41.10 Optical waveguide [0057] 42.1-42.10 Input coupling points [0058] 43.1-43.10 Input coupling optical unit [0059] 44.1,44.2 Laser beam (electromagnetic heating radiation) [0060] 45 Crossover point