Method for determining an ion angle distribution function in plasma processes on a substrate surface

Abstract

The invention relates to a method for determining an ion angle distribution function in plasma processes on a substrate surface, comprising a computing unit and a sensor connected thereto with a microelectromechanical system (MEMS) and an ion detector arranged underneath or integrated into the MEMS. The MEMS has a deflectable plate with a perforation through which ions strike the ion detector. The plate is harmonically deflected to a tilt angle by means of at least one actuator.wherein the plate selects the ions based on their ion incidence angle perpendicular to the surface of the plate and, by means of the ion detector, detects an ion current intensity as a function of the ion incidence angle and an amplitude of the tilt angle of the plate and transmits it to the computing unit, and wherein the computing unit iteratively determines a simulated ion current intensity from an assumed or previously determined ion angle distribution function (IADF) in the form of an IADF parameter and an incidence angle-dependent transfer function taking into account the geometric conditions of the perforations in the form of a filter effect,wherein a deviation between the measured ion current at the ion detector and the simulated ion current of the computing unit is compared, and wherein after the comparison of the measured ion current and the calculated ion current, the IADF parameter is adjusted for a new simulation or the iteration is terminated when a specified deviation or a minimum of the deviation is undershot.

Description

[0001] The invention relates to a method for determining an ion angle distribution function in plasma processes on a substrate surface and is particularly used for determining the ion angle distribution function.

[0002] Plasmas are among the most important tools in advanced technology and can be found in a wide range of applications. Of particular importance in this regard are the processes for the dry-chemical structuring of silicon and other materials in microtechnology. Such microstructuring processes are based on the interaction of a plasma with the surface of a substrate, based on the bombardment of the substrate with neutral gas particles, radicals, and ions. In particular, the bombardment of the surface by ions enables the structuring of the substrate surface in the nanometer range necessary for modern microelectronics. The result of the structuring is largely determined by the energy and angular distribution of the ions impinging on the workpiece to be processed. This is because, unlike neutral particles, the ions move in a directed manner due to the resulting electric fields.While the ion energy distribution function (IEDF) determines the etching rate and selectivity, the ion angular distribution function (IADF) influences the etching profile.

[0003] Planar opposing field energy analyzers (RFEAs) are used to determine the ion energy distribution in various plasma processes. The RFEA measures ions from the plasma that are accelerated through the plasma boundary layer to the analyzer inlet. The RFEA consists of a series of electrically isolated but conductive grids and a collector plate for detecting the ion current. By detecting and measuring the ion current detected at the collector plate as a function of the grid potential, an IU characteristic curve is determined. The ion energy distribution is then determined by derivative of the ion current with respect to the voltage.

[0004] Other state-of-the-art methods for measuring IEDF include quadrupole mass spectrometers (QMS) according to the paper by WM Greene et al. “Ion Transit through Capacitively Coupled Ar Sheaths: Ion Current and Energy Distribution”, Journal of Applied Physics 63.5 (1988), electrostatic analyzers according to the paper by Seth J. Thompson et al. “Combined Electrostatic Analyzer-Wien Filter Probe for Characterization of Species Distributions in Hall Thrusters”, Journal of Applied Physics 130.23 (2021), time-of-flight based methods according to Giovanni Ceccio et al. “Ion Energy Distributions from Laser-Generated Plasmas at Two Different Intensities”, EPJWeb of Conferences 167 (2018). Ed. by L. Torrisi and M. Cutroneo, and laser-induced fluorescence according to Nathaniel B. Moore, Walter Gekelman and Patrick Pribyl. “Ion Energy Distribution Function Measurements by Laser-Induced Fluorescence in a Dual Radio Frequency Sheath,” Journal of Vacuum Science & Technology A 34.2 (2016), or RFEAs based on electrostatic lenses as in the publication Junhyeok Hwang et al. “Study and Design of a Lens-Type Retarding Field Energy Analyzer without a Grid Electrode”, Ultramicroscopy 209 (2020), play a minor role and cannot be miniaturized due to their design.

[0005] The special test structures mentioned in the publication Jia Hu et al. “In-Situ Measurement of Ion Angular Distribution in Bulk Titanium DRIE for Modeling the Etch Profile”, The 8th Annual IEEE International Conference on Nano / Micro Engineered and Molecular Systems. 2013 8th IEEE International Conference on Nano / Micro Engineered and Molecular Systems (NEMS) allow the analysis of the ion angular distribution function using downstream cross-sectional analyses using electron microscopy in combination with simulations of the ion trajectories. For this purpose, cavities with a defined entrance opening are first created using conventional silicon technology. This entrance opening acts as a pinhole during ion bombardment. Depending on the angular distribution of the incident ions, a specific etching profile results at the bottom of the cavity. This etching profile is then examined on the cross-section using suitable analytical methods (e.g. electron microscopy).Finally, ion angle parameters such as the maximum ion incidence angle are determined based on the structure.

[0006] Beyond geometric considerations, a combination with simulations of ion bombardment is also conceivable. This would require using the IADF as an input parameter in an etching simulation, e.g., using particle-in-cell simulations, and iteratively adjusting it until the measured etch profile for the selected geometry of the test structure is approximately obtained.

[0007] Reusability of the test structures is not given for the following reasons.

[0008] Typically, the etch profile is examined using a cross-section scanned by electron microscopy. This cross-section is destructive. Furthermore, the ion bombardment structures the etching substrate at the bottom of the test structure, leaving no flat surface for further testing.

[0009] Another option for determining the IADF is ring electrodes in combination with a small entrance opening (aperture) according to the publication by Shailesh Sharma et al. "Ion Angle Distribution Measurement with a Planar Retarding Field Analyzer", Review of Scientific Instruments 86.11 (2015). However, due to its design, this approach does not allow for continuous angle measurements, as each ring electrode only detects a specific angular range. The angular ranges can only be refined in terms of their width by using narrower ring electrodes. However, as this negatively influences the signal-to-noise ratio, a compromise must be made in the design of the ring electrodes. When measuring the IADF using lateral field drifts in specially designed opposing field analyzers, fixed angular ranges result because the grid potentials cannot be varied independently of one another, but rather only specific ratios can be approached.

[0010] Special equipment or modifications are required for solutions that cannot be miniaturized to the dimensions of typical substrates. Microelectronic manufacturing standards limit the substrate to a diameter of up to 30 cm and a height of no more than 5 mm. This lack of miniaturization is due to the following reasons: Quadrupole mass spectrometers rely on the periodic oscillation of ions caused by electric fields. Miniaturizing the systems would require stronger electric fields to achieve the same ion deflection over a shorter distance. This would lead to electrical breakdowns.

[0011] Pinhole systems rely on geometric angle selection based on the pinhole aperture, the distance between the pinhole and the detector, and the detector's acceptance angle. The pinhole aperture cannot be arbitrarily reduced with regard to the expected ion current, as excessive reduction would result in a low signal-to-noise ratio. The same applies to the detector's acceptance angle, e.g., ring electrodes, mass spectrometers, CCD detectors (Keita Ichikawa et al., "Angular Distribution Measurement of High-Energy Argon Neutral and Ion in a 13.56 MHz Capacitively-Coupled Plasma," Applied Physics Express 14.12 (2021)), and Faraday cups. Therefore, a certain distance between the pinhole and the detector is always necessary to achieve a sufficiently high angular resolution of the overall system. This requires differential pumping of such systems, which requires a corresponding amount of space below the substrate holder or behind the pinhole.

[0012] Tiltable systems such as mass spectrometers (Joachim Janes and Christoph Huth. “Energy-resolved Angular Distributions of O + Ions at the Radio-frequency-powered Electrode in Reactive Ion Etching”, Journal of Vacuum Science Technology A: Vacuum, Surfaces, and Films 10.5 (1992)), microchannel plates (RL Stenzel et al. “Directional Velocity Analyzer for Measuring Electron Distribution Functions in Plasmas”, Review of Scientific Instruments 54.10 (1983)), and Faraday cups (Ch. Huth et al. “Divergence Measurements for Characterization of the Micropatterning Quality of Broad Ion Beams”, Journal of Vacuum Science & Technology A 8.6 (1990)) also require special equipment, as corresponding mechanical elements (e.g. feedthroughs) must be present in order to tilt the elements. This is cost-intensive and very space-consuming.

[0013] The object of the invention is therefore to develop a method for determining an ion angle distribution function in plasma processes on a substrate surface, in particular for the continuous and solid angle-resolved measurement of the ion angle distribution on substrate surfaces, with which the disadvantages of the prior art are eliminated.

[0014] The main drawback of the tiltable microchannel plate, as known in the prior art, is the need for a mechanical feedthrough to tilt the plate. Such feedthroughs exist only in systems specifically built or modified for this purpose.

[0015] This problem is solved with the features of the first patent claim.

[0016] The method for determining an ion angle distribution function in plasma processes on a substrate surface comprises a computing unit and a sensor connected thereto with a microelectromechanical system (MEMS) and an ion detector arranged underneath or integrated into the MEMS. The MEMS has a deflectable plate with a perforation through which ions strike the ion detector. According to the method according to the invention, the plate is harmonically deflected to a tilt angle by means of at least one actuator. The plate selects the ions based on their ion incidence angle perpendicular to the surface of the plate. Using the ion detector, an ion current intensity is detected as a function of the ion incidence angle and the amplitude of the tilt angle of the plate and transmitted to the computing unit.The computing unit iteratively determines a simulated ion current from an assumed or previously determined ion angle distribution function (IADF) in the form of an IADF parameter and an angle-of-incidence-dependent transfer function that takes the geometric conditions of the perforations into account in the form of a filter effect. After the ion current is calculated, a deviation between the measured ion current at the ion detector and the simulated ion current of the computing unit is compared. After comparing the measured ion current and the calculated ion current, the IADF parameter is adjusted for a new simulation, or the iteration is terminated when the deviation falls below a specified value or a minimum deviation.

[0017] The assumed or previously determined ion angle distribution function is typically a normal (Gaussian) distribution. Alternatively, any other distribution can be used. The distribution used depends on the specified assumptions. For example, there are setups for depositing materials using physical vapor deposition (PVD) with more than one source. If two sources are used, for example, this can be considered as a superposition of two normal distributions in the evaluation algorithm.

[0018] The IADF parameter can, for example, affect the centroid and / or the width / half-width of the normal distribution and can be varied in each calculation to achieve the minimum of the deviation.

[0019] The transfer function describes the geometry and filtering effect of the perforation in the plate. Depending on the angle of incidence of an assumed ideal ion beam, in which all ions have the same angle of incidence, the proportion of ions that can pass through the plate varies between 0 and 1. At an angle of 0°, all ions pass through, resulting in a result of 1. The larger the angle of incidence of the ions, the fewer ions pass through the tiltable plate. The electric fields in the sensor system also influence the transfer function. These are advantageously taken into account in the calculations. The transfer function takes the ion trajectories into account. This means that due to the electric fields, ions in the edge area of ​​the perforation of the plate are attracted to the side walls.

[0020] The transfer function relates to the filtering effect of the perforation, for example, of honeycombs. It can be calculated geometrically and depends on the width of the opening d Si , the thickness of the material t Si and the angle of incidence of the ions ϕ Ion away.

[0021] Preferably, the simulated ion current strength at the ion detector below the plate is determined as a function of the tilt angle of the plate by convolving the assumed or previously determined ion angle distribution function and the transfer function.

[0022] In an advantageous embodiment, the plate is deflected into a periodic oscillation with a fixed amplitude (maximum tilt angle) by an actuator excitation signal. Furthermore, the period duration and amplitude can be varied.

[0023] Typical ion angle distributions are a few degrees wide. If the MEMS only achieves a maximum tilt angle of less than one degree statically, the MEMS is operated resonantly. Typical resonance frequencies are in the kilohertz range.

[0024] The resonant operating mode allows any tilt amplitude. However, care must be taken to ensure that the plate is not tilted so far that ions can bypass the tilted plate and hit the ion detector surface.

[0025] Preferably, the temporal variation of the ion current is recorded during an amplitude from the ion current strength of the plate deflected at a tilt angle. Subsequently, an effective value of the current strength (time averaging) is determined using the computing unit. Calculating the effective value serves to improve the signal-to-noise ratio.

[0026] Preferably, several measurements are carried out, whereby by means of several measurements with different amplitudes of the plate, the effective value of the ion current strength forms a measurement curve as a function of the amplitudes of the plate.

[0027] In an advantageous embodiment of the invention, the iterative approximation of the ion angle distribution function is output when the specified deviation or the minimum of the deviation is undershot.

[0028] Due to layer stress and dynamic effects, the MEMS plate is deformed and not flat both in the static and oscillating states. This particularly affects the edge regions of the plate. As a result, a certain portion of the perforation used to filter the ion incidence angles does not "face" the tilt direction of the MEMS plate, but deviates from this tilt angle. To compensate for this, a deformation parameter is preferably considered. The deformation parameter accounts for the deformation of the plate in the oscillating state and thus the deviation of the ion incidence angles in the calculation of the ion angle distribution function.

[0029] The tilt angle, and thus the deflection of the plate, is between 0 and 45°, depending on the design and control of the MEMS and the plate. For an oscillating measurement, the angle of the plate is specifically between 0 and 45°. For a static measurement, the angle is between 0 and 12°.

[0030] In an advantageous embodiment of the method, the plate is attached to two bending beams, each with two points, with one beam serving as the actuator and the other as the tilt sensor. Subsequently, the tilt angle can be determined using a calibration curve as a function of the sensor signal. Tilting the plate around two axes enables spatially resolved measurement of the ion angle distribution.

[0031] The deflection of the plate and the detection of the tilt angle (MEMS) are preferably carried out by means of at least one actuator based on electrothermal, electrostatic, piezoelectric, or electromagnetic forces, or on shape memory alloys. The deflection can also be extrapolated based on the ambient parameters, in particular pressure, by the excitation of the actuator. In this case, a sensor for detecting the tilt angle can be dispensed with.

[0032] A reusable sensor for measuring the ion angle distribution function using a microelectromechanical system according to the method according to the invention essentially comprises the following three elements: An aperture whose surface is exposed to a plasma, with ions entering the sensor system through a perforated area. The perforation opening must be selected so that the openings are smaller than the Debye length to avoid disturbing the plasma boundary layer and to simulate a flat substrate surface. The thickness of the perforated area must be selected to create openings with a low aspect ratio, so that no angular selection occurs at this perforation.

[0033] MEMS describes an element used for angular ion selection. A perforation of a tilted element, referred to as a plate, selects the ion incidence angles based on their angle of incidence perpendicular to the plate's surface. For this purpose, the plate's perforation must consist of hole structures with a high aspect ratio. Ions with an angle of incidence greater than the acceptance angle of the holes are absorbed by the sidewalls of the holes and cannot reach the ion detector. To record the ion angle distribution function, the plate is tilted along one or two axes using microelectromechanical principles. Tilting the plate around two axes enables spatially resolved measurement of the ion angle distribution. Possible actuators can be based on electrothermal, electrostatic, piezoelectric, electromagnetic forces, and shape memory alloys.The tilt of the plate can be static or dynamic. The ion angle distribution function is derived directly from the tilt angle-dependent measurement signal of the ion current at an ion detector or from a time-averaged measurement and the subsequent fitting of the measurement signal to indirectly determine the ion angle distribution function.

[0034] Furthermore, an ion detector is used, which serves as an element for detecting the ions. Detection occurs, for example, by means of the absorption of the ions on a metallic surface and the electrical measurement of the ion current. Optionally, the ion detector can also be placed on the back of the plate being tilted. The design of the ion detector can include suitable measures to suppress secondary electrons, e.g., adequate selection of the ion detector material, shielding electrodes around the ion detector surfaces, or a grid to control the secondary electrons.

[0035] These three elements are mounted and aligned one above the other using suitable techniques. Since all three elements are realized at the wafer level, the height of the individual elements corresponds to the thickness of the wafers used (e.g., 300...775 µm).

[0036] This results in a total height of the fully integrated system of a few millimeters.

[0037] To enhance functionality, a grid stack can be inserted at various points in the system, serving as an opposing field analyzer. This enables the simultaneous measurement of the ion angle distribution function and the ion energy distribution function. This corresponds to a measurement of the ion angle energy distribution function.

[0038] Possible positions for this grid stack are: • Integration into the aperture • Between the aperture and the surface of the tilting plate. • On the surface of the tilting plate • On the back of the tilting plate • Between the back of the tilting plate and the ion detector • Integration into the ion detector.

[0039] The system can be operated autonomously using appropriate electronics and energy storage. Alternatively, it can be connected to the control unit via cables and a flange on the chamber floor, which is also found in industrial systems.

[0040] The invention overcomes this deficiency in the prior art by integrating the perforated plate for angle selection into a micro-electro-mechanical system (MEMS) rather than traditionally tilting it mechanically. Due to their small dimensions in the millimeter range, these systems can be integrated into existing plasma systems without additional modifications. They can be placed on the substrate holder instead of the substrate itself, enabling the measurement of the ion angle distribution.

[0041] The invention is explained in more detail below using an embodiment and associated drawings.

[0042] They show: Fig. 1 schematic representation of the elements of the sensor, Fig. 2 the perforation of the MEMS plate, Fig. 3 the functions for simulating the measurement curve, Fig. 4 a function of the deviation due to deformation with a measurement curve each with measured and simulated measured values, Fig. 5 a function of deviation due to deformation, Fig. 6 a measurement curve representing an external tilt.

[0043] In Fig. 1 shows a sensor for implementing the method according to the invention. The sensor consists of three elements: an aperture 1, a MEMS 2, and a detector base 3. An ion detector 3.1, in the form of a metallic plate, is arranged on the detector base 3 and measures the incident ions. The detector base 3 is designed in the form of a printed circuit board. The aperture 1 is exposed to the plasma, with ions entering the sensor system through a perforated area 1.1. The openings of the perforation 1.1 are arranged centrally on the aperture and allow the ions to pass toward the MEMS 2.

[0044] The MEMS 2 located behind aperture 1 has a tiltable plate 2.1 that is deflected by an actuator 2.2. A piezoelectric tilt angle sensor 2.3 is arranged on the side opposite the actuator 2.2 to measure the deformation. The plate 2.1 is connected to the actuator 2.2 and sensor 2.3 via connecting elements 2.4. The actuator 2.2 and tilt sensor 2.3 are designed as pincer-shaped structures in the form of piezoelectric bending beams. Each of the bending beams is connected to the plate at two points.

[0045] If the plate 2.1 is tilted by the actuator 2.2, the sensor cantilever is also deformed. This, in turn, induces charges in the tilt angle sensor 2.3 due to the piezoelectric effect, which can be converted into the current tilt angle using a calibration curve. The plate 2.1 also has a perforation 2.5 through which the ions hit the detector base 3.

[0046] The Fig. Figure 2 shows a representation of perforation 1.1 of aperture 1. Perforation 1.1 has a honeycomb design. Perforation 2.5 can also have a honeycomb design. For both perforations, honeycomb structures were patterned into 30 µm-thick silicon using dry etching. Since typical low-pressure plasmas have a Debye length of more than 60 µm, perforations with an opening of 30 µm and an area of ​​4.8×4.8 mm² were realized for aperture perforation 1.1. For perforation 2.5 of MEMS 2 for angle selection, holes with an opening of 2 µm were realized on an area of ​​700×700 µm². These holes were integrated into the 30 µm-thick, tiltable plate 2 of a piezoelectric MEMS.

[0047] The process of simulating a measurement curve is described in the Fig. 3. The process is divided into six steps. In the first step (I), a Gaussian ion angle distribution (IADF) is assumed, whereby the ion current intensity is determined as a function of the ion incidence angle. In the second step (II), the filtering efficiency (GT) of the perforated plate is taken into account. The filtering efficiency of the perforation can be calculated geometrically and depends on the width of the opening (d). Si , the thickness of the material, for example silicon t Si and the angle of incidence of the ions ϕ Ion away.

[0048] The angle-dependent current I(Φ) below the plate at the ion detector results from the superposition or convolution of the assumed ion angle distribution IADF with the filter effect GT of the tiltable plate.

[0049] The resulting function is shown in step III. Since the plate has a harmonic oscillation ϕ(t, ϕ Max, ω), this is taken into account in the function under step IV.

[0050] In step V, the combination of the angle-dependent current I and harmonic oscillation ϕ is shown, from which the temporal course of the ion current at the ion detector for a fixed amplitude ϕ MaX and frequency ω.

[0051] The measurement curve is shown in step VI, where the effective value (average of the ion current from step V) of the ion current is shown for different amplitudes. This corresponds to a simulated measurement curve for dynamic sensor operation.

[0052] The amplitude-dependent ion current values ​​obtained by the sensor, as well as the resulting ion angle distribution, are shown in Fig. 4. The iteration of the calculation of the ion angle distribution ends when the deviation between the measured values ​​and the simulated values ​​falls below a specified value or a minimum.

[0053] The tiltable plate of the MEMS is not completely flat. Due to layer stress and dynamic effects, the plate is deformed both in the resting and oscillating state. As a result, a certain portion of the aperture for filtering the ion incidence angle does not "face" the tilt direction of the MEMS, but deviates from this tilt angle. This deviation is in the Fig. 5 shown.

[0054] An external tilt of the MEMS sensor relative to the plasma boundary layer of approximately 4° is reflected in a shift of the center of gravity of the IADF. Such a measurement curve resulting from a tilt is shown in the Fig. 6 shown.

[0055] Another measurement option would be a statically operated sensor to directly measure the ion angle distribution. A corresponding MEMS can enable a static tilt angle of more than 30°.

[0056] The advantages achieved with the method according to the invention are, in particular, that, in contrast to obvious solutions according to the prior art, no special equipment or modifications are necessary and that the ion angle distribution can be measured continuously.

[0057] The invention enables the measurement of the ion angle distribution function (IADF) using a microelectromechanical system (MEMS). Additional modules can be used to extend the invention to include the ability to measure the ion energy distribution function (IEDF), allowing the ion energy angle distribution function (IEADF) to be measured. This is a previously unknown measurement principle. List of reference symbols 1 aperture 1.1 Perforation 2 MEMS 2.1 Plate 2.2 Actuator 2.3 Tilt angle sensor 2.4 Connecting element 2.5 Perforation 3 Detector base 3.1 Metallic plate / ion detector

Claims

[1] Method for determining an ion angle distribution function in plasma processes on a substrate surface, comprising a computing unit and a sensor connected thereto with a microelectromechanical system (MEMS, 2) and an ion detector arranged underneath or integrated into the MEMS (2), wherein the MEMS (2) has a deflectable plate (2.1) with a perforation (2.5) through which ions strike the ion detector (3.1), wherein the plate (2.1) is harmonically deflected into a tilt angle by means of at least one actuator (2.2), wherein the plate (2.1) selects the ions based on their ion incidence angle perpendicular to the surface of the plate (2.1) and, by means of the ion detector, determines an ion current strength as a function of the ion incidence angle and an amplitude of the tilt angle of the plate (2.1) and transmits it to the computing unit, and wherein the computing unit iteratively determines a simulated ion current strength from an assumed or previously determined ion angle distribution function (IADF) in the form of an IADF parameter and an angle-of-incidence-dependent transfer function taking into account the geometric conditions of the perforations (2.5) in the form of a filter effect, wherein a deviation between the measured ion current strength at the ion detector (3.1) and the simulated ion current strength of the computing unit is compared, and wherein after the measured ion current strength and the calculated ion current strength have been compared, the IADF parameter is adjusted for a new simulation, or the iteration is terminated when the deviation falls below a specified deviation or a minimum of the deviation. [2] Method according to claim 1, characterized bythat the simulated ion current intensity is determined as a function of the tilt angle of the plate (2.1) by convolving the assumed or previously determined ion angle distribution function and the transfer function. [3] Method according to claim 1, characterized by that the plate (2.1) is deflected by an excitation signal of the actuator (2.2) in a periodic oscillation with a fixed amplitude and a defined tilt angle. [4] Method according to claim 3, characterized by that the period and amplitude are varied. [5] Method according to claims 3 and 4, characterized by that the oscillation occurs in resonance with a resonance frequency in the kilohertz range. [6] Method according to one of claims 3 to 5, characterized by that an effective value is determined as an average value over at least one oscillation of the ion current strength by means of the computing unit below the deflected plate (2.1). [7] Method according to claim 6, characterized by that by means of several measurements with different amplitudes of resonant oscillations of the plate (2.1) the effective value of the ion current intensity forms a measurement curve as a function of the amplitude of the plate (2.1). [8] Method according to one of the preceding claims, characterized by that the ion angle distribution function is output when the specified deviation or the minimum of the deviation is undershot. [9] Method according to one of the preceding claims, characterized in that a deformation parameter takes into account the deformation of the plate (2.1) in the oscillating state and thus the deviation of the ion incidence angles in the calculation of the ion angle distribution function. [10] Method according to one of the preceding claims, characterized by that the tilt angle and thus the deflection of the plate (2.1) is between 0 and 45°. [11] Method according to one of the preceding claims, characterized bythat the plate (2.1) is attached to two bending beams, each with two points, one bending beam being used as an actuator (2.2) and one bending beam as a piezoelectric sensor, and that by tilting the actuator (2.2) the sensor is deformed, wherein depending on the deformation of the sensor charges are induced in the sensor due to the piezoelectric effect, wherein the tilt angle is determined as a function of the charge by means of a calibration curve. [12] Method according to one of the preceding claims, characterized by that the at least one actuator (2.2) is based on electrothermal or electrostatic or piezoelectric or electromagnetic forces or on shape memory alloys.

Images