Microelectromechanical Apparatus with Heating Element

Abstract

The invention relates to a microelectromechanical apparatus (100, 200) comprising one or more microelectromechanical devices (130) each having a mirror element (134), an actuator (132) for moving the respective mirror element (134), and a heating element (138, 240) for heating the respective mirror element (134), wherein the microelectromechanical apparatus (100) comprises one or more temperature sensors (135, 145, 210, 212) and an electronic system (125, 225), wherein the control electronic system (125, 225) is configured to determine a temperature value of the respective mirror element (134) using the one or more temperature sensors (135) for each mirror element (134), and the electronic system (125, 225) is further configured to adjust a heating power for each of the heating elements (138, 240). The invention further relates to an illumination optical unit (172), to an illumination system (174) and to a projection exposure apparatus (170), each having a microelectromechanical apparatus (100, 200) according to the invention, and to a method for controlling temperatures of a microelectromechanical apparatus (100, 200) in a closed-loop.

Claims

1. A microelectromechanical apparatus comprising one or more microelectromechanical devices each having a mirror element, an actuator for moving the respective mirror element, and a heating element for heating the respective mirror element, wherein the microelectromechanical apparatus comprises one or more temperature sensors and an electronic system, wherein the electronic system is configured to determine a temperature value of the respective mirror element using the one or more temperature sensors for each mirror element, and the electronic system is furthermore configured to adjust a heating power for each of the heating elements.

2. The microelectromechanical apparatus according to claim 1, wherein each of the one or more microelectromechanical devices has at least one of the one or more temperature sensors.

3. The microelectromechanical apparatus according to claim 2, wherein for each of the one or more microelectromechanical devices a. the at least one temperature sensor is arranged between the respective actuator and the respective heating element; or b. the respective heating element comprises or is identical to the at least one temperature sensor.

4. The microelectromechanical apparatus according to claim 1, wherein for each of the one or more microelectromechanical devices the at least one temperature sensor and/or the heating element is an electrical resistor.

5. The microelectromechanical apparatus according to claim 1, wherein for each of the one or more microelectromechanical devices the heating element is a. arranged between the respective mirror element and the respective actuator; or b. is part of the respective mirror element.

6. The microelectromechanical apparatus according to claim 1, wherein each of the one or more mirror elements comprises a Bragg mirror.

7. The microelectromechanical apparatus according to claim 1, wherein the electronic system is configured for controlling the heating power of each of the heating elements of the one or more microelectromechanical devices in a closed-loop based on the temperature value of the mirror element of the respective microelectromechanical device.

8. The microelectromechanical apparatus according to claim 1, wherein the microelectromechanical apparatus comprises a further temperature sensor, and the electronic system is configured to determine a temperature value for a component of the microelectromechanical apparatus which is not a mirror element, for example for an electronic component, using the further temperature sensor.

9. An illumination optical unit for a projection exposure apparatus for guiding illumination radiation to an object field, comprising one or more microelectromechanical apparatuses according to claim 1.

10. An illumination system for a projection exposure apparatus, comprising an illumination optical unit according to claim 9 and a radiation source, in particular an EUV radiation source, for emitting illumination radiation, wherein illumination radiation emitted from the radiation source is reflected by a mirror element of the microelectromechanical apparatus.

11. A microlithographic projection exposure apparatus comprising an illumination optical unit according to claim 9 and a projection optical unit for projecting a reticle, arranged in the object field of the illumination optical unit, onto a wafer, arranged in an image field of the projection optical unit.

12. A method for controlling temperatures of a microelectromechanical apparatus in a closed-loop, wherein the microelectromechanical apparatus has an electronic system, one or more temperature sensors and one or more microelectromechanical devices, each having a mirror element and a heating element for heating the respective mirror element, wherein the electronic system controls, for each of the one or more microelectromechanical devices, a temperature value, determined by way of the electronic system, for the respective mirror element using the one or more temperature sensors in a closed-loop by adjusting a heating power of the respective heating element to a respectively specified set temperature value.

13. The method according to claim 12, wherein, during the closed-loop control of the temperature values to the set temperature values of the mirror elements, irradiation at least of one of the mirror elements with illumination radiation from a radiation source, in particular an EUV radiation source, takes place and the intensity of the illumination radiation is changed one or more times, wherein the set temperature values of the one or more mirror elements remain unchanged here.

14. The method according to claim 12, wherein the closed-loop control of the temperature values of the mirror elements to the set temperature values is carried out taking into account a further temperature value, determined by way of the electronic system by means of a further temperature sensor, for a further component of the microelectromechanical apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0029] In the figures:

[0030] FIG. 1 shows a schematic illustration of a projection exposure apparatus according to the invention; and

[0031] FIG. 2 shows a schematic flowchart for explaining a method according to the invention for controlling temperatures of a microelectromechanical apparatus in a closed-loop.

EMBODIMENTS OF THE INVENTION

[0032] In the following description of the embodiments of the invention, identical or similar elements are designated with the same reference signs, a repeated description of these elements in individual cases being omitted. The figures only schematically illustrate the subject matter of the invention.

[0033] FIG. 1 shows a schematic illustration of an exemplary projection exposure apparatus 170 according to the invention, as can be used for example for EUV lithography. The projection exposure apparatus comprises an irradiation source 180, for example for EUV radiation, a reticle (photomask) 184, a projection optical unit 178 and a microelectromechanical apparatus 100 according to the invention. Furthermore, a wafer 190 is shown, which is intended for irradiation.

[0034] The microelectromechanical apparatus 100 has three microelectromechanical devices 130 with mirror elements 134 in the example shown. These microelectromechanical devices 130 each comprise a heating element 138 for heating the respective mirror element 134. The mirror elements 134 can be moved by means of actuators 132. A temperature sensor 135 arranged between the heating element 138 and the actuator 132 of the microelectromechanical device 130 enables determination of a temperature value of the mirror element 134. The microelectromechanical devices are applied to a layer 140, which can have one or more electronic components 146 such as ASICs, for example, for controlling the actuators 132. A temperature value is also determined for these electronic components 146. This is done via a further temperature sensor 145. The microelectromechanical devices 130 may be attached, together with the layer 140, to a mechanically stabilizing carrier substrate 110, for example consisting of a ceramic. Further electronic components, such as, for example, further ASICS, may be arranged below this carrier substrate 110. FIG. 1 further shows a layer 120 with an electronic system 125, for example implemented by means of an ASIC, which is configured to determine a temperature value of the respective mirror element 134 for each mirror element 134 using the temperature sensors 135. To this end, the temperature signals from the temperature sensors are transmitted to the electronic system 125 via the connections 160. In addition, the electronic system 125 is configured to adjust a heating power of each of the three heating elements 138. Corresponding control signals are transmitted from the electronic system 125 to the heating elements 138 by means of the connections 150. To determine the temperature value for one of the three mirror elements 134, signals from further temperature sensors 135 can additionally also be used, but also information such as calibration data and data regarding the environment of the microelectromechanical apparatus 100 and also signals from further temperature sensors 145 can be used. The electronic system 125 can further be configured to perform closed-loop control of the heating power of the heating elements 135 on the basis of the determined temperature values.

[0035] In the example shown, a temperature value for an electronic component 146, for example an ASIC, is further also determined by means of a further temperature sensor 145, wherein this electronic component 146 is used, for example, to control the actuators 132 of the microelectromechanical devices 130. Since an electronic component 146 likewise generates a relevant waste heat and thus contributes to the heating of the mirror elements, it is advantageous to determine a temperature value for this electronic component 146 by means of the temperature sensor by way of the electronic system 125 and to take it into account for closed-loop control. For this purpose, a corresponding temperature signal is transmitted to the electronic system 125 by means of the connection 162.

[0036] In the case of the exemplary projection exposure apparatus 170 shown, illumination radiation 186, for example EUV radiation, is emitted by a radiation source 180. This radiation travels from the radiation source 180 via the mirror elements 134 of the microelectromechanical apparatus 100 to the reticle 184 and from there to the wafer 190 by means of a projection optical unit 178. In this case, the reticle 184 is located in an object field 176 of the projection optical unit 178 and is projected from there by means of the projection optical unit 178 onto the wafer 178, which is located in an image field 188 of the projection optical unit 178. The projection exposure apparatus 170 and in particular the projection optical unit 178 are shown in FIG. 1 in a very simplified and purely schematic manner. For example, mirrors not shown in FIG. 1 can thus be used for beam guidance and beam shaping; in particular, the projection optical unit 178 may comprise a plurality of mirrors.

[0037] The mirror elements 134 heat up during operation due to absorption of the EUV radiation and due to the waste heat of the electronic component 146. In this case, the heating during the irradiation of a wafer 190 by means of the EUV radiation is typically not constant but fluctuating, since in the course of a typical irradiation process, the intensities of the illumination radiation 186 vary and/or they are partially completely deactivated. The temperature should also be kept as constant as possible between irradiation processes in order to avoid longer start-up times for the projection exposure apparatus 170. The aim here is to maintain the mirror elements 134 at a constant operating temperature by controlling the heating power of the heating elements 138 optimal for the operation of the projection exposure apparatus 170 in a closed-loop, meaning that errors, for example due to temperature changes of curving mirrors are minimized during the irradiation of the wafer 190.

[0038] FIG. 2 shows a schematic flowchart for explaining an exemplary method according to the invention for controlling temperatures of a microelectromechanical apparatus 200 in a closed-loop, wherein the microelectromechanical apparatus 200 comprises an electronic system 225, one or more temperature sensors 210 and one or more microelectromechanical devices 130, each having a mirror element 134, an actuator 132 for moving the respective mirror element 134, and a heating element 240 for heating the respective mirror element 134. Set temperature values 250 are provided for each of the mirror elements 134 of the one or more microelectromechanical devices 130. These can be stored, for example, in a memory of the electronic system 225. These set temperature values 250 can correspond to intended operating temperatures of the mirror elements 134, i.e. to the temperatures at which the mirror elements 134 have the desired optical properties, that is to say in particular at which the mirror elements 134 deflect incident illumination radiation 186 of a defined wavelength as desired.

[0039] For the respective mirror element 134 of each of the one or more microelectromechanical devices 130, a determination 220 of a temperature value takes place using at least one of the one or more temperature sensors 210 by way of the electronic system 225. For this purpose, temperature signals 211 from the one or more temperature sensors 210 are transmitted to the electronic system 225, wherein each temperature sensor 210 can be assigned exactly to one mirror element 134. Subsequently, an adjustment 230 of a respective heating power for the heating element 240 of each of the one or more microelectromechanical devices 130 is carried out in dependence on the temperature value determined for the respective mirror element 134 and on the respective specified set temperature value 250 by way of the electronic system 225 by means of transmitting corresponding control signals 235 from the electronic system 225 to the heating elements 240. These steps of determining 220 and adjusting 230 can be repeated as often as desired, wherein the mirror elements 134 and thus the temperature sensors 210 are heated by the heating elements 240 (arrow 245), thus a change in the heating power affects the temperature values for the mirror elements 134. This means that the set temperature values 250 are controlled in a closed-loop. This closed-loop control can also be carried out taking into account a temperature value for a further component 146 of the microelectromechanical apparatus 200, which value is evaluated by means of a further temperature sensor 212 by way of the electronic system 125. For this purpose, a temperature signal 213 from the further temperature sensor 212 is transmitted to the electronic system 225.

[0040] Independently of this, irradiation 280 of each of the mirror elements 134 with the temperature sensors 210 can be carried out by means of illumination radiation 186 from a radiation source 180, wherein the intensity of the illumination radiation 186 can change over time, that is to say in particular also the radiation source 180 can be activated and/or deactivated. The closed-loop control of the temperature values via the heating elements 240 to the set temperature values 250 ensures that, despite the changing intensity of the illumination radiation 186, the temperatures of the mirror elements 134 are kept constant and unwanted deformations and/or shifts of the mirror elements 134 are counteracted.

[0041] The invention is not limited to the exemplary embodiments described here and to the aspects highlighted therein. On the contrary, a large number of modifications that are within the ability of a person skilled in the art are possible within the scope specified by the claims.