Patent Application
20250231493
The disclosure relates to a method of operating an optical component having a mirror element, a substrate for carrying the mirror element, an actuator device for tilting the mirror element and a sensor device having a sensor electrode structure for detecting a tilt angle of the mirror element based on changes in capacitance. The disclosure also relates to an optical component and to an optical apparatus having such an optical component. Moreover, the disclosure relates to an illumination optical unit and an illumination system for a projection exposure apparatus, and a projection exposure apparatus.
Depending on the application, micromirrors may be used in different applications, such as for example smartphone projectors, head-up displays, barcode readers, etc.
For EUV lithography systems, adjustable optical paths up to the reticle, also called a mask, which are able to be implemented by a micromirror array in the optical path, are often desirable.
The micromirrors may be provided with a Bragg coating that reflects the central wavelengths well. Wavelengths outside the reflection range can be absorbed and generate heat in the micromirror, which can be dissipated in a targeted manner with the lowest possible temperature resistance.
The positional accuracy of the micromirror can depend on how well the system for positioning the micromirrors works. This depends for example on manufacturing tolerances, temperature stability in combination with temperature variance and long-term stability in combination with product lifetime or the times at which the device is recalibrated.
Document DE 10 2015 204 874 A1 relates to an actuator device for tilting a mirror element.
Document DE 10 2016 213 026 A1 relates to a sensor device for detecting a tilt angle of a mirror element.
The two documents each describe an optical component that comprises an actuator device for tilting a mirror element with two tilting degrees of freedom and a sensor device for detecting a tilt angle of the mirror element. The actuator device comprises an actuator electrode structure having actuator electrodes that are in the form of comb electrodes and form a direct drive for pivoting the mirror element. The sensor device comprises a sensor electrode structure having sensor electrodes that are likewise in the form of comb electrodes. The optical component furthermore comprises a gimbal flexure for mounting the mirror element, wherein the flexure has flexure springs and defines two tilt axes of the mirror element.
A method for operating an optical component is proposed. The optical component comprises a mirror element, a substrate for carrying the mirror element, which may in particular be a micromirror element, an actuator device for tilting the mirror element about one or two tilt axes, having a plurality of active actuator electrodes and one or more passive actuator electrodes. The optical component furthermore comprises a sensor device having a sensor electrode structure for detecting a tilt angle of the mirror element based on changes in capacitance. A tilt angle of the mirror element corresponds to a polar angle of a spherical coordinate system. The tilt angle may in this case be azimuth-dependent.
The sensor electrode structure in this case comprises a plurality of active sensor electrodes, such as for example two, four, six or more, and a plurality of passive sensor electrodes, such as for example two, four, six or more. The active and passive sensor electrodes can be in the form of comb electrodes. The number of active sensor electrodes can be equal to the number of passive sensor electrodes. The number of active sensor electrodes may also be one higher or lower than the number of passive sensor electrodes. Optionally, the passive sensor electrodes are each assigned to an active sensor electrode. The active sensor electrodes in this case comprise sensor transmitter electrodes and sensor receiver electrodes that are each optionally in the form of comb electrodes. The sensor transmitter electrodes, in order to detect the tilt angle of the mirror element, may be subjected to an AC voltage.
According to the disclosure, a method comprises generating a first voltage between a first portion of the active actuator electrodes and the one or more passive actuator electrodes and generating a second voltage between a second portion of the active actuator electrodes and the one or more passive actuator electrodes, wherein a respective potential is applied to the one or more passive actuator electrodes, which potential is different from a reference potential, for example a ground potential, of a voltage source that is used to generate these potentials. The potentials of the one or more passive actuator electrodes can be identical, that is to say they have a common potential. The reference potential is connected to the voltage source and constitutes the reference potential for the potentials applied to the one or more passive actuator electrodes. Optionally, the potentials applied to the one or more passive actuator electrodes are also different from a second potential of the passive sensor electrodes, wherein each of the passive sensor electrodes particularly optionally has the reference potential and/or a ground potential. The latter can help make it possible to reduce noise in signals from the sensor device.
The plurality of active actuator electrodes and the one or more passive actuator electrodes are configured to exert electrostatic force so as to tilt the mirror element. The active actuator electrodes and the at least one passive actuator electrode can be in the form of comb electrodes. All of the active actuator electrodes are furthermore optionally arranged along a common plane, which is also referred to as actuator plane. This means that one end of each active actuator electrode is arranged in this common plane. The individual active actuator electrodes may in this case have different dimensions, in particular different lengths. The actuator device may form a direct drive for tilting the mirror element. The first and the second portion of the active actuator electrodes are located here on different sides of one of the one or two tilt axes. The two voltages (the first voltage and the second voltage) are selected to be different in order to generate a torque about the corresponding tilt axis. Accordingly, the passive actuator electrodes, in the case of a plurality of passive actuator electrodes, may also be divided into a first and a second portion, which are located on different side of the tilt axis. A direct drive should be understood here to mean a drive in which the actuator device is able to exert a force directly on the mirror to be displaced. In particular, no force transmission mechanism is required. In other words, the drive is force-transmission-mechanism-free.
Applying one or more potentials different from the reference potential to the passive actuator electrodes makes it possible to increase the torque generated by the different voltages. This is determined as:
In this case, UN1 is the potential applied to a first portion of the passive actuator electrodes, UN2 accordingly denotes the potential applied to a second portion of the passive actuator electrodes, each with respect to the reference potential. Or in the case of a single passive actuator electrode, a single common potential UN=UN1=UN2 can be involved here. The variables U1, respectively U2, accordingly denote the potentials of the first, respectively second portion of the active actuator electrodes, likewise with respect to the reference potential. The factors ∂CAi/∂θ, i=1, 2 are the motor constants with respect to the corresponding portion of the actuator electrodes that has a capacitance of CAi, which is dependent on the tilt angle θ. The motor constants thus describe the magnitude of the change in capacitance CAi as a function of the tilt angle θ.
Active actuator electrodes should be understood here to mean the actuator electrodes that, in order to tilt the mirror element, are subjected to a variable, for example controllable, for example regulatable potential, that is to say are used primarily to control the mirror element. The active actuator electrodes are accordingly typically connected to a control unit for controlling the corresponding actuator device. Actuator electrodes that are subjected to a fixed, that is to say constant, potential optionally for longer periods than the active actuator electrodes are also referred to as passive actuator electrodes. A change in the potential applied to the passive actuator electrodes may, according to the disclosure, lead to a change in the generated torque about a tilt axis. The passive actuator electrodes may thus be used to support the control of the mirror element. A method according to the disclosure is desirable, for example, when a circuit for generating the potential for the active actuator electrodes that is used for control purposes, that is to say for example a control unit for controlling the corresponding actuator device, is not able to generate a suitably high potential in comparison with the reference potential.
The active actuator electrodes can be attached to the substrate and the one or more passive actuator electrodes are attached to the mirror element. In this case, the active actuator electrodes are also referred to as actuator stator electrodes, while the passive actuator electrodes are also referred to as actuator mirror electrodes.
The active sensor electrodes can be attached to the substrate and the passive sensor electrodes are attached to the mirror element. In this case, the active sensor electrodes are also referred to as sensor stator electrodes, while the passive sensor electrode is also referred to as sensor mirror electrode.
The active sensor electrodes can be arranged along the common plane along which the active actuator electrodes are also arranged. The active sensor electrodes may also have different dimensions, in particular different lengths. The active sensor electrodes can be each assigned to an active actuator electrode.
The number of active sensor electrodes may be equal to the number of active actuator electrodes. By way of example, each active actuator electrode may be assigned to an active sensor electrode. The number of active sensor electrodes may also be different from the number of active actuator electrodes. By way of example, the number of active actuator electrodes may be greater than the number of active sensor electrodes.
The actuator device may be part of a displacement device for displacing the mirror element, or the displacement device itself. The sensor device may likewise be part of the displacement device. The sensor electrode structure may thus be integrated into the actuator electrode structure.
The actuator device may be configured to tilt the mirror element with a single tilting degree of freedom. The mirror element is in this case tilted about a tilt axis. The tilt axis makes it possible to divide the common plane into two sectors, that is to say regions. By way of example, the first portion of the active actuator electrodes may be arranged in the first of the two sectors and the second portion of the active actuator electrodes may be arranged in the second of the two sectors. A corresponding arrangement may be present for the passive actuator electrodes. The active and passive actuator and sensor electrodes may in this case be arranged symmetrically about the tilt axis.
The actuator device can be configured to tilt the mirror element with two tilting degrees of freedom. In this case, the mirror element may be tilted about two tilt axes, which can be oriented perpendicular to one another, simultaneously or in temporal succession. In this case, the two tilt axes make it possible to divide the common plane into four sectors, also referred to as quadrants. The actuator and sensor electrode structure may in this case exhibit radial symmetry. In other words, the actuator or sensor electrodes may be arranged symmetrically about a centre point, which is also referred to as tilt point of the mirror element. Such a design can help make it possible to improve the displacement of the mirror element. Similarly to the case of a single tilt axis, the active and the passive actuator electrodes may be divided into four portions, corresponding to the four quadrants. Four potentials U1, U2, U3, U4 for the four portions of the active actuator electrodes may be provided in order to generate torques for the two tilt axes. The same applies to the four portions of the passive actuator electrodes; four potentials UN1, UN2, UN3, UN4 may be applied here. Or in the case of a single passive actuator electrode, a single common potential UN=UN1=UN2=UN3=UN4 can be also involved here.
In the context of this disclosure, a displacement should be understood to mean, in general, a displacement in view of a specific degree of freedom. For example, the displacement of the mirror element may be pivoting, which is also referred to as tilting. In general, the displacement may also comprise linear displacements and/or twisting of the mirror element in a mirror plane. The optical component may in this case comprise a gimbal flexure for mounting the mirror element, wherein the flexure has flexure springs and defines two tilt axes of the mirror element.
For details regarding an actuator device for tilting the mirror element with two tilting degrees of freedom and a sensor device for detecting the tilt angle of the mirror element, reference may be made to DE 10 2015 204 874 A1 and DE 10 2016 213 026 A1, which are hereby incorporated in full into the present application as part thereof.
Optionally, the application of one, optionally each, potential to the one or more passive actuator electrodes is performed only at a certain time and/or in the presence of defined conditions, for example when the first voltage exceeds a first limit value and/or the second voltage exceeds a second limit value. Likewise, one, optionally each, of the potentials applied to the one or more passive actuator electrodes may be changed, for example deactivated or increased or reduced, at a certain time and/or when defined conditions are met, for example when the first voltage exceeds a third limit value and/or the second voltage exceeds a fourth limit value. For example, one, optionally each of the potentials applied to the one or more passive actuator electrodes may be regulated, for example on the basis of one or more setpoint values for one or more voltages between the passive and the active actuator electrodes and/or one or more setpoint values for one or more tilt angles.
A second aspect of the disclosure is the provision of an optical component that is configured to carry out the method according to the disclosure. The optical component in this case comprises a mirror element, a substrate for carrying the mirror element, an actuator device for tilting the mirror element about one or two tilt axes, having a plurality of active actuator electrodes and a plurality of passive actuator electrodes, and a sensor device for detecting a tilt angle of the mirror element.
A method according to the disclosure can be carried out using the optical component proposed according to the disclosure. Accordingly, features described within the scope of the optical component can apply to the method and, conversely, features described within the scope of the method can apply to the optical component. Multiple optical components according to the disclosure may together form a mirror array.
According to a third aspect, what is proposed is an optical apparatus comprising a plurality of optical components according to the disclosure, which can form a mirror array. The optical apparatus furthermore comprises a voltage source for applying one or more potentials to the passive actuator electrodes of the actuator devices of the one or more optical components and a control unit for controlling each of the actuator devices of the one or more optical components by applying potentials to the active actuator electrodes and controlling these potentials, wherein the control unit and the voltage source are connected to a common reference potential, for example a ground potential. Such an apparatus may for example be designed such that different potentials for the passive actuator electrodes may be applied for different optical components. It is thereby possible for example to partially compensate for different spring stiffnesses of a flexure that is used, these possibly being caused for example by production fluctuations.
Furthermore proposed is an illumination optical unit for a projection exposure apparatus for guiding illumination radiation to an object field, which illumination optical unit comprises at least one mirror array according to the disclosure.
Also proposed is an illumination system for a projection exposure apparatus, which illumination system comprises an illumination optical unit according to the disclosure and a radiation source, in particular an EUV radiation source.
Additionally proposed is a microlithographic projection exposure apparatus that comprises an illumination optical unit according to the disclosure and a projection optical unit for projecting a reticle arranged in an object field into an image field.
For details regarding a possible projection exposure apparatus, reference may be made to DE 10 2015 204 874 A1 and DE 10 2016 213 026 A1, which are hereby incorporated in full into the present application as part thereof.
A method proposed according to the disclosure can increase a torque for tilting a mirror element, which torque is generated by an actuator device, by applying potentials that are different from a reference potential to passive actuator electrodes. This can be desirable because it is often the case that suitable control units for controlling the actuator device, which may be implemented for example by way of one or more ASICs (ASIC: application-specific integrated circuit), are not able to provide sufficiently high voltages. However, high voltages can be desirable because they can help make it possible for example also to compensate for high spring stiffnesses of a flexure that is used and/or to achieve greater deflections of the mirror element. For example, cross sections of springs of the flexure may thus be made larger, which reduces the thermal resistance of the springs, which in turn leads to better heat dissipation and lower mirror temperatures when illuminating the mirror element of an optical component according to the disclosure. This also can help make it possible to reduce electrical resistance, and any photocurrents that may occur during illumination may thus be minimized.
Electrostatic softening may also be amplified in a targeted manner by applying different potentials for the passive actuator electrodes of different optical components of an optical apparatus according to the disclosure, such that production-related fluctuations in the spring stiffness of the springs are able to be compensated for. Electrostatic softening in the context of this disclosure should be understood to mean an angle-dependent modification of a spring constant of a resetting spring by applying an additional voltage to electrodes of an optical component.
Certain embodiments of the disclosure are explained in more detail with reference to the drawings and the following description. In the drawings:
In the following description of certain embodiments of the disclosure, identical or similar elements are designated with the same reference signs, a repeated description of these elements in individual cases being omitted. The figures illustrate the subject matter of the disclosure only schematically.
The optical component 100 in this case comprises a mirror element 20 and a substrate 30 for carrying the mirror element 20. The mirror element 20 is in this case mounted on an articulation device 80. To displace the mirror element 20, the optical component 100 comprises a displacement device 200, which has an actuator device 40 for tilting the mirror element 20 and a sensor device 50 for detecting a tilt angle 9 of the mirror element 20.
The optical component 100 is arranged, for illustrative purposes, in a three-dimensional Cartesian coordinate system 90. The three-dimensional Cartesian coordinate system 90 comprises an x-axis, a y-axis and a z-axis. The x-axis runs perpendicular to the plane of the drawing towards the observer in
The mirror element 20 comprises a reflection surface 22 having a surface normal 24 that is perpendicular to the reflection surface 22. Here in the left-hand illustration in
In this case, the substrate 30 is arranged on an x-y plane 92 (cf.
The actuator device 40 in this case comprises an actuator electrode structure 42 having two active actuator electrodes 421 (cf.
The actuator electrodes 421, 422 are configured to exert electrostatic force. They can be in the form of comb electrodes. The active actuator electrodes 421 and the passive actuator electrodes 422 in this case can each comprise multiple comb fingers.
The sensor device 50 in this case comprises a sensor electrode structure 52. It may be seen in
The control unit 310, for example an ASIC, is designed to apply potentials U1, respectively U2, to the active actuator electrodes 421 and to control them, for example to regulate them. By virtue of the voltage source 320, potentials UN1 and UN2 may be applied to the passive actuator electrodes 422 to the left (first portion of the passive actuator electrodes) and to the right (second portion of the passive actuator electrodes) of the surface normal 24. This can help enable significantly higher voltages between the passive actuator electrodes 422 and the active actuator electrodes 421. Optionally, UN1 and UN2 are identical, and so a common potential UN=UN1=UN2 is involved. Both the control unit 310 and the voltage source 320 are connected to a common reference potential G. The same applies to the passive sensor electrodes 522. The control unit 310 may furthermore be designed to control and/or to read out the active sensor electrodes 521.
The optical component 100 in
As illustrated in
The tilt axis 28 thus divides the active actuator and sensor electrodes 421, 521 into two electrode pairs 202, 204, which are each arranged in a sector 32, 34. A first electrode pair 202 in this case comprises an active actuator electrode 421a in the first sector 32 and an active sensor electrode 521a in the first sector 32, while a second electrode pair 204 comprises an active actuator electrode 421b in the second sector 34 and an active sensor electrode 521b in the second sector 34. It may also be seen in
The passive actuator and sensor electrodes 422, 522 not illustrated in
During operation of the optical component 100 according to
The disclosure is not limited to the exemplary embodiments described here and 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 211 335.7 | Oct 2022 | DE | national |
The present application is a continuation of, and claims benefit under 35 USC 120 to, international application No. PCT/EP2023/079432, filed Aug. 7, 2023, which claims benefit under 35 USC 119 of German Application No. 10 2022 211 335.7, filed Oct. 26, 2022. The entire disclosure of each of these applications is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2023/079432 | Oct 2023 | WO |
| Child | 19171128 | US |
