DEVICE AND METHOD FOR CONTROLLING THE TEMPERATURE OF ELEMENTS IN MICRO-LITHOGRAPHIC PROJECTION EXPOSURE SYSTEMS

Abstract

A micro-lithographic projection exposure system comprises an illumination unit and a projection lens with at least one element which is penetrated at least in regions by a temperature-control fluid line provided for conducting a temperature-control fluid for controlling the temperature of the element. The temperature-control fluid line is connected to a temperature-control fluid storage container. A temperature-control element for controlling the temperature of the temperature-control fluid is provided on or in the temperature-control fluid line. At least two of the elements are independently penetrated by a respective separate at least one of temperature-control fluid lines, or at least two different regions of the at least one element are penetrated independently by a respective separate at least one of the temperature-control fluid lines, or at least two of the elements are penetrated by the temperature-control fluid line. A corresponding method is provided.

Claims

1. An apparatus, comprising: an illumination device; a projection lens comprising first and second elements; a first fluid line at least regionally traversing the first element to guide a fluid to control a temperature of the first element; a first fluid storage container connected to the first fluid line; a first temperature control element configured to control a temperature of the fluid being provided to the first fluid line or a temperature of the fluid in the first fluid line, wherein the apparatus is a microlithographic projection exposure apparatus, and at least one of the following holds: the apparatus comprises a second fluid line at least regionally traversing the second element to guide a fluid to control a temperature of the second element; the first fluid line independently traverses at least two different regions of the first element; and the first fluid line traverses the first and second elements.

2. The apparatus of claim 1, further comprising: a second fluid line connected to the first fluid storage container; and a second temperature control element configured to control a temperature of the fluid being provided to the first fluid line or a temperature of the fluid in the first fluid line.

3. The apparatus of claim 1, further comprising: a second fluid line connected to the first fluid storage container; a first control circuit connected to the first fluid line; and a second control circuit connected to the second fluid line.

4. The apparatus of claim 3, wherein one of the following holds: each of the first and second control circuits is connected to the first fluid storage container; and the apparatus further comprises a second fluid storage container, the first control circuit is connected to the first fluid storage container, and the second control circuit is connected to the second fluid storage container.

5. The apparatus of claim 1, wherein the first and second elements are connected in series and are traversed by the first fluid line.

6. The apparatus of claim 1, further comprising a temperature sensor, wherein the temperature sensor is adjacent the first element to measure a temperature adjacent to the first element, or the temperature sensor is in the first element to measure a temperature in the element.

7. The apparatus of claim 6, further comprising a controller to provide closed-loop control of the first temperature control element based on a temperature measured by the temperature sensor.

8. The apparatus of claim 1, wherein the first and second elements each comprise at least one member selected from the group consisting of a sensor frame, a force frame, a mirror support frame, a mirror, and a cooler and thermal shield.

9. The apparatus of claim 1, further comprising a cooler and thermal shield between the first and second elements.

10. The apparatus of claim 9, wherein the apparatus comprises a mirror, the apparatus is an EUV microlithographic projection exposure apparatus, and a beam path of EUV light and the mirror are accommodated by the cooler and thermal shield.

11. The apparatus of claim 1, wherein the first fluid storage container and the temperature control element are outside of the projection lens.

12. The apparatus of claim 1, wherein the apparatus is an EUV microlithographic projection exposure apparatus.

13. The apparatus of claim 1, wherein the apparatus is a DUV microlithographic projection exposure apparatus range.

14. A method for controlling a temperature of an element in a microlithographic projection exposure apparatus comprising a fluid line to guide a fluid passing through the element, the method comprising: measuring a temperature of the element; comparing the measured temperature of the element with a target temperature of the element; controlling a temperature of the fluid using a control element at or in the fluid line until a difference between the measured temperature of the element and the target temperature of the element is below a specified limit.

15. The method of claim 14, further comprising determining the target temperature of the element.

16. The method of claim 15, wherein the temperature of the element is measured using a temperature sensor at or in the element.

17. The method of claim 16, further comprising using a closed-loop control circuit to control the temperature of the fluid.

18. The method of claim 14, wherein the temperature of the element is measured using a temperature sensor at or in the element.

19. The method of claim 19, further comprising using a closed-loop control circuit to control the temperature of the fluid.

20. The method of claim 14, further comprising using a closed-loop control circuit to control the temperature of the fluid.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0049] FIG. 1 shows a schematic representation of an EUV projection lens from the prior art.

[0050] FIG. 2 shows a schematic representation of an element from an EUV system that is subject to temperature control according to the disclosure.

[0051] FIG. 3 shows a schematic illustration of an EUV projection lens according to the disclosure with a parallel connection.

[0052] FIG. 4 shows a schematic illustration of an EUV projection lens according to the disclosure with a series connection.

[0053] FIG. 5 shows a schematic representation of a DUV projection lens from the prior art.

[0054] FIG. 6 shows a schematic illustration of a DUV projection lens according to the disclosure.

[0055] FIG. 7 shows a microlithographic projection exposure apparatus provided for the EUV range.

[0056] FIG. 8 shows a microlithographic projection exposure apparatus provided for the DUV range.

EXEMPLARY EMBODIMENTS

[0057] FIG. 2 shows a schematic representation of an element 930 from an EUV system that is subject to temperature control according to the disclosure. This is a parallel connection 900 of two temperature control circuits. By way of example, the element 930 can be a sensor frame, force frame or a mirror support frame. The temperature control fluid line 919 passes through the lower region of the element 930. The temperature control fluid line 921 passes through the upper region of the element 930. The temperature sensor 907 measures the temperature in the lower region of the element and transmits the measured temperature value to the controller 902, the latter controlling the temperature control element 906 which is arranged at the temperature control fluid line 919. The temperature control fluid line 919 is fed by the temperature control fluid storage container 920 and includes a temperature control fluid inlet 904 and a temperature control fluid outlet 908. Should the temperature control element 906 be designed for simplicity to be able to heat only, it would be desirable to integrate into the arrangement what is known as a recooler system, or synonymously a recooler unit. The temperature control fluid would heat continuously without this recooler system. For the sake of clarity, this recooler system is not shown in FIG. 2.

[0058] The temperature sensor 917 measures the temperature in the upper region of the element 930 and transmits the measured temperature value to the controller 912, the latter controlling the temperature control element 916 which is arranged at the temperature control fluid line 921. The temperature control fluid line 921 is likewise fed by the temperature control fluid storage container 920 and includes a temperature control fluid inlet 914 and a temperature control fluid outlet 918. Each of the two temperature control circuits has a dedicated temperature control fluid storage container in an embodiment not shown here.

[0059] FIG. 3 shows a schematic illustration of an EUV projection lens 340 according to the disclosure with a parallel connection. To reduce the thermally induced drifts and wavefront aberrations, the five problems portrayed in the prior art (see the explanations in relation to FIG. 1) are solved according to the disclosure by a plurality of different temperature control and shielding systems. The heat flows Q3 in the direction of the sensor frame 372 and Q4 in the direction of the mirror 392 are depicted merely in exemplary fashion. The mirrors 391, 392, 393, 394 are fastened to active mechanical bearings 395. The temperature control fluid line 302 passes through the force frame 382. A temperature sensor 804 measures the temperature in the force frame 382. A temperature control element 704 controls the temperature of the temperature control fluid until the target value of the temperature of the force frame 382 is reached. The control used to this end is not shown in FIG. 3 for reasons of overall clarity. With regard to the closed-loop control, reference is made to the illustration of FIG. 2. The temperature control fluid line 306 passes through the cooler and thermal shield 398. The cooler and thermal shield 398 thermally shields the sensor frame 372. The temperature control line 304 passes through the mirror support frame 397. The sensor frame 372 is traversed by the temperature control fluid line 308, which is fed by its own fluid storage container 516. The mirror 393 is traversed by its own temperature control fluid line 310, which is fed by its own fluid storage container 519. Each element comprises at least one temperature sensor 804. A common fluid storage container 515 is assigned to all aforementioned temperature control fluid lines 302, 304, 306. The EUV light 502 from the structure-bearing mask 120 (not depicted in FIG. 3) is reflected at the mirrors and leaves the lens as EUV light 504 in the direction of the wafer 124 (not depicted in FIG. 3). In summary, the following should be noted: [0060] The thermal stabilization of the force frame 382 is achieved by controlled water cooling. The latter may consist of a plurality of cooling circuits. [0061] The temperature control of the mirror surround is achieved by water cooling of the mirror support frames 390, 396, 397, 399. [0062] The beam path and the optical surfaces of the mirror are housed by a single or multiple layer, actively cooled cooling shield 398 such that stray light and thermal conduction from the beam path to the sensor frame 372 are suppressed. This has not been depicted in FIG. 3 for reasons of clarity. The thermal output from the force frame 382 to the sensor frame 372 is shielded by an active or passive cooling shield (CS) 398. [0063] Thermally controlling the sensor frame 372 is implemented by way of actively controlled water cooling of the sensor frame 372.

[0064] Design measures for suppressing a thermal draft of the sensor frame 372 can be divided as follows in terms of their effect over time: [0065] Disturbances with time constants of more than one hour can be suppressed by thermal control of the sensor frame and/or force frame. [0066] Disturbances of the sensor frame with time constants below one hour can be suppressed by shielding the sensor frame by way of cooled or passive cooling shields between the force frame and the sensor frame.

[0067] Cooling the sensor frame with water is very sluggish, that is to say has a long time constant. That is to say, the disturbance can be subject to long wavelength compensation.

[0068] High-frequency disturbances are suppressed by the inner cooler; thermal output would act on the sensor frame without the inner cooler.

[0069] Moreover, different control tasks within the EUV projection lens, for example absolute temperature stability in the case of the mirror support frame and/or drift stability (force frame, mirror, sensor frame) in the case of the cooling shield, can be followed with largely independent control loops. This allows a reduction in the thermally induced drifts and wavefront aberrations.

[0070] FIG. 4 shows a schematic illustration of an EUV projection lens according to the disclosure with a series connection. A single temperature control fluid storage container 1020 feeds the only temperature control fluid line 1007. A temperature control element 1006 is arranged on the temperature control fluid line 1007 downstream of the temperature control fluid inlet 1004. Three elements of a series are connected in exemplary fashion. In the present example, the fluid initially flows through the cooler and temperature shield 1010, which is also referred to as an inner cooler. Then, the fluid flows through the force frame 1012. Last, the fluid flows through the mirror support frame 1014. The inner cooler 1010 is subject to temperature control first as it is arranged closest to the thermally most sensitive sensor frame. The element with the highest thermal load, the mirror support frame 1014—on account of the mirror preheating and the exhaust heat of the actuators—is located at the end to avoid dragging the thermal output within the entire system by way of the temperature control fluid. The force frame 1012 is placed therebetween.

[0071] FIG. 6 shows a schematic illustration of a DUV projection lens according to the disclosure. Two independent temperature control fluid lines 476, 486 pass through the cooler and sensor shield 451. The upper temperature control fluid line 476 is fed by the temperature control fluid storage container 470. The lower temperature control fluid line 486 is fed by the temperature control fluid storage container 480. Thus, two regions of the cooler and sensor shield 451 can be subject to temperature control independently of one another. Each of the two regions has a temperature sensor 806 and a temperature control element 706. The upper temperature control fluid line 476 has an inlet 474 and an outlet 478. The lower temperature control fluid line 486 has an inlet 484 and an outlet 488. Controlling the temperatures of the two regions is not depicted in FIG. 6 for reasons of clarity.

[0072] The EUV lithography apparatus 100 depicted in FIG. 7 comprises a beam-shaping and illumination system 102 and a projection system 104. The beam-shaping and illumination system 102 and the projection system 104 are each provided in a vacuum housing, indicated in FIG. 7, with each vacuum housing being evacuated with the aid of an evacuation device (not shown). The vacuum housings are surrounded by a machine room (not depicted), in which the drive equipment for mechanically moving or setting the optical elements are provided. Furthermore, electrical controllers and the like may also be provided in the machine room.

[0073] The EUV lithography apparatus 100 comprises an EUV light source 106. A plasma source (or a synchrotron) which emits radiation 108 in the EUV range, for example in the wavelength range of between 5 nm and 20 nm, can be provided, for example, as the EUV light source 106. In the beam-shaping and illumination system 102, the EUV radiation 108 is focused and the desired operating wavelength is filtered out from the EUV radiation 108. The EUV radiation 108 generated by the EUV light source 106 has a relatively low transmissivity through air, for which reason the beam-guiding spaces in the beam-shaping and illumination system 102 and in the projection system 104 are evacuated.

[0074] The beam shaping and illumination system 102 illustrated in FIG. 7 has five mirrors 110, 112, 114, 116, 118. After passing through the beam-shaping and illumination system 102, the EUV radiation 108 is directed onto the photomask (reticle) 120. The photomask 120 is likewise in the form of a reflective optical element and may be arranged outside the systems 102, 104. Furthermore, the EUV radiation 108 may be directed onto the photomask 120 via a mirror 122. The photomask 120 has a structure which is imaged onto a wafer 124 or the like in a reduced fashion via the projection system 104.

[0075] The projection system 104 (also referred to as projection lens) has six mirrors M1-M6 for imaging the photomask 120 onto the wafer 124. It should be noted that the number of mirrors of the EUV lithography apparatus 100 is not restricted to the number illustrated. More or fewer mirrors could also be provided. The force frame 380, which substantially carries the mirrors of the projection lens, and the sensor frame 370, which substantially serves as a reference for the position of the mirrors of the projection lens, are shown roughly schematically. Furthermore, the mirrors, as a rule, are curved on their front side for beam shaping.

[0076] FIG. 8 shows a schematic illustration of a microlithographic projection exposure apparatus according to the disclosure for the DUV range 400. The DUV projection exposure apparatus 400 comprises a beam shaping and illumination device 402 and a projection lens 404. In this case, DUV stands for “deep ultraviolet” and denotes a wavelength of the working light of between 30 and 250 nm.

[0077] The DUV projection exposure apparatus 400 comprises a DUV light source 406. For example, an ArF excimer laser that emits radiation 408 in the DUV range at for example 193 nm, may be provided as the DUV light source 406.

[0078] The beam shaping and illumination device 402 illustrated in FIG. 8 guides the DUV radiation 408 onto a photomask 420. The photomask 420 is formed as a transmissive optical element and may be arranged outside the beam shaping and illumination device 402 and the projection lens 404. The photomask 420 has a structure of which a reduced image is projected onto a wafer 424 or the like via the projection lens 404.

[0079] The projection lens 404 has a number of lens elements 428, 440 and/or mirrors 430 for projecting an image of the photomask 420 onto the wafer 424. In this case, individual lens elements 428, 440 and/or mirrors 430 of the projection lens 404 may be arranged symmetrically in relation to the optical axis 426 of the projection lens 404. It should be noted that the number of lens elements and mirrors of the DUV projection exposure apparatus 400 is not restricted to the number shown. More or fewer lens elements and/or mirrors may also be provided. Furthermore, the mirrors are generally curved on their front side for beam shaping.

[0080] An air gap between the last lens element 440 and the wafer 424 may be replaced by a liquid medium 432 which has a refractive index of >1. The liquid medium 432 may be for example high-purity water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

[0081] Even though the disclosure has been described on the basis of specific embodiments, numerous variations and alternative embodiments will be apparent to a person skilled in the art, for example through combination and/or exchange of features of individual embodiments. Accordingly, it will be apparent to a person skilled in the art that such variations and alternative embodiments are also encompassed by the present disclosure, and the scope of the disclosure is restricted only within the scope of the appended patent claims and the equivalents thereof.

[0082] The following terms are used synonymously:

[0083] EUV system is used synonymously with EUV projection exposure apparatus and with microlithographic projection exposure apparatus for the EUV range. DUV system is used synonymously with DUV projection exposure apparatus and microlithographic projection exposure apparatus for the DUV range. Where cooling is used, temperature control, that is to say cooling and/or heating, should also be comprised. Thus, fluid, temperature control fluid and cooling fluid are used synonymously. Additionally, cooling shield and cooler and temperature shield are used synonymously. Photomask and reticle are used (synonymously. Wafer and substrate coated with a light-sensitive layer (photoresist) are used synonymously. Sensor frame is abbreviated SFr. Force frame is abbreviated FFr. Mirror support frame is abbreviated MSF.

LIST OF REFERENCE SIGNS

[0084] 100 (Microlithographic) projection exposure apparatus for the EUV range (=EUV system) [0085] 102 EUV (beam shaping and) illumination device [0086] 104 EUV projection lens having six mirrors (M1 to M6) [0087] 106 EUV light source [0088] 108 EUV radiation [0089] 110, 112, 114, 116, 118 Mirrors of the EUV illumination device 102 [0090] 120 Photomask, reticle (reflective) [0091] 122 Mirror [0092] 124 Wafer (=substrate coated with a light-sensitive layer (photoresist)) [0093] 302, 304, 306, 308, 310 Temperature control fluid line [0094] 340 EUV projection lens having four mirrors (391, 392, 393, 394) [0095] 370, 371, 372 Sensor frame (SFr) [0096] 380, 381, 382 Force frame (FFr) [0097] 390 Mirror support frame (MSF) [0098] 395 Active mechanical bearing [0099] 396 Mirror support frame (MSF) [0100] 397 Mirror support frame (MSF) [0101] 398 Cooler and thermal shield (CS) [0102] 399 Mirror support frame (MSF) [0103] 400 (Microlithographic) projection exposure apparatus for the DUV range (=DUV system) [0104] 402 DUV (beam shaping and) illumination device [0105] 404 DUV projection lens [0106] 406 DUV light source [0107] 408 DUV light at the entry to the DUV projection lens 404 [0108] 420 Photomask, reticle (transmitting) [0109] 424 Wafer [0110] 426 Optical axis of the projection lens 404 [0111] 428 Lens elements [0112] 430 Mirror [0113] 432 Liquid medium [0114] 440 Last lens element [0115] 450 DUV cooler and thermal shield (prior art) [0116] 451 DUV cooler and thermal shield [0117] 452 Temperature control fluid line [0118] 454 Temperature control fluid inlet [0119] 456 Temperature control fluid outlet [0120] 458 DUV light to the wafer [0121] 460 Temperature control fluid storage container [0122] 470 Temperature control fluid storage container [0123] 474 Temperature control fluid inlet [0124] 476 Temperature control fluid line [0125] 478 Temperature control fluid outlet [0126] 480 Temperature control fluid storage container [0127] 484 Temperature control fluid inlet [0128] 486 Temperature control fluid line [0129] 488 Temperature control fluid outlet [0130] 502 EUV light from the structure-bearing mask 321 [0131] 504 EUV light in the direction of the wafer 124 [0132] 507 Force frame temperature control inlet [0133] 508 Surface temperature control inlet [0134] 509 Sensor frame temperature control inlet [0135] 510 Sensor frame temperature control outlet [0136] 511 Surface temperature control outlet [0137] 512 Mirror support frame temperature control inlet [0138] 513 Mirror support frame temperature control outlet [0139] 514 Force frame temperature control outlet [0140] 515 Fluid storage container for FFr/MSF/CS [0141] 516 Fluid storage container for SFr [0142] 517 Mirror temperature control inlet [0143] 518 Mirror temperature control outlet [0144] 519 Fluid storage container for mirror [0145] 525 Position measurement [0146] 602 Temperature control fluid line [0147] 607 Force frame temperature control inlet [0148] 614 Force frame temperature control outlet [0149] 615 Fluid storage container for force frame [0150] 625 Position measurement [0151] 640 EUV projection lens having four mirrors (691, 692, 693, 694) [0152] 695 Active mechanical bearing [0153] Q1 Heat flows in the direction of the sensor frame 371 [0154] Q2 Heat flows in the direction of the mirror 692 [0155] Q3 Heat flows in the direction of the sensor frame 372 [0156] Q4 Heat flows in the direction of the mirror 392 [0157] Q5 Heat flows of consumers (DUV) [0158] Q6 Heat flows from the DUV projection lens 404 [0159] 702 Temperature control element [0160] 704 Temperature control element [0161] 706 Temperature control element [0162] 802 Temperature sensor (EUV, prior art) [0163] 804 Temperature sensor (EUV) [0164] 806 Temperature sensor (DUV) [0165] 900 Parallel connection [0166] 902 Controller [0167] 904 Temperature control fluid inlet [0168] 906 Temperature control element [0169] 907 Temperature sensor [0170] 908 Temperature control fluid outlet [0171] 912 Controller [0172] 914 Temperature control fluid inlet [0173] 916 Temperature control element [0174] 917 Temperature sensor [0175] 918 Temperature control fluid outlet [0176] 919 Temperature control fluid line [0177] 920 Temperature control fluid storage container [0178] 921 Temperature control fluid line [0179] 930 Element (SFr, FFr, MSF) [0180] 1000 Series connection [0181] 1004 Temperature control fluid inlet [0182] 1006 Temperature control element [0183] 1007 Temperature control fluid line [0184] 1008 Temperature control fluid outlet [0185] 1010 Element 1, for example cooler and thermal shield [0186] 1012 Element 2, for example force frame [0187] 1014 Element 3, for example mirror support frame [0188] 1020 Temperature control fluid storage container