CN112097645A - High Aspect Ratio Microstructure Reflection Interferometric Microscopic Nondestructive Measurement Device - Google Patents

Abstract

The invention discloses a reflective interference microscopic nondestructive measurement device for a high-aspect-ratio microstructure, which solves the problem that the depth and the width of a high-aspect-ratio groove structure in a silicon-based MEMS device cannot be measured nondestructively in the prior art. The device fully utilizes the advantage that near infrared light can penetrate through the silicon substrate, and can use a large-numerical-aperture convergent light beam for measurement; aiming at the problem that the large-numerical-aperture light beam converged by a microobjective is modulated by a groove structure of a sample to be detected to reduce the focusing property of the light beam, an exit pupil aberration monitoring light path and an aberration active compensation system of the microobjective are arranged, so that the large-numerical-aperture light beam can be converged to the bottom of a groove; and obtaining the depth and width measurement results of the groove structure of the sample to be measured by using a vertical scanning interference method. The invention overcomes the difficulty that the prior measurement technology can not realize the nondestructive measurement of the high depth-width ratio groove structure of the silicon-based MEMS device, and can carry out the high-precision nondestructive measurement on the depth and the width of the deep groove structure of the sample to be measured.

Description

High Aspect Ratio Microstructure Reflection Interferometric Microscopic Nondestructive Measurement Device

technical field

The invention relates to the technical field of precision optical measurement engineering, in particular to a high-aspect-ratio microstructure reflective interference microscopic nondestructive measurement device, which measures the depth and width of a trench structure of a silicon-based MEMS device, and is especially suitable for high aspect ratio measurement devices. Deep trench structure.

Background technique

With the development of MEMS, the measurement requirements for microstructures are getting higher and higher. In silicon-based MEMS processing technology, aspect ratio is one of the main indicators, which directly affects the performance of MEMS devices; The trench width of the aspect ratio microstructure is 3~10 μm, the depth is 10~300 μm, and the aspect ratio is generally between 10~100:1. The development of this high aspect ratio microstructure is very important for driving MEMS technology. Applications in many fields such as aviation, aerospace, electronics, biology, and medical treatment will play a key role, and corresponding measurement technologies and devices will continue to emerge in the process.

There are roughly two types of geometric measurement methods for high aspect ratio microstructure devices at home and abroad: contact measurement and non-contact measurement; for contact measurement, the most commonly used instruments include scanning electron microscope SEM and atomic force microscope. The bottom of the trench can only be measured when the device is cut from the side. This method of destroying the device structure is not suitable for on-line inspection and has limited help in improving device performance; non-contact measurement mainly refers to interferometric measurement technology, which is based on the principle of light wave interference. , compared with other measurement techniques, interferometry can achieve non-destructive measurement.

In recent years, the contour testing method that has gradually matured using the principle of light wave interference, and the non-contact topography measuring device represented by the white light interferometer, can complete the device without touching the sample to be tested or destroying the device structure. 3D topography measurement. Since the resolution of white light is limited by the numerical aperture NA of the microscope objective, a large NA objective must be used to improve the resolution. However, the white light will be blocked by the high aspect ratio groove of the sample to be tested, so that the large NA probe light cannot reach the groove The bottom, which cannot meet the imaging requirements, as shown in Figure 2(a), for example, a trench with a width of 3 μm, a depth of 60 μm, and an aspect ratio of 20:1 requires NA≤0.025 to illuminate the bottom of this trench, Assuming that the wavelength is 550 nm, the imaging resolution exceeds 14.4 μm at this time, which cannot meet the imaging requirements for the bottom of 3 μm width. Although some people propose to tilt and rotate the sample to be tested so that the beam is irradiated to the bottom of the deep groove, the tilting and rotation process of the sample to be tested is very cumbersome, and the entire bottom cannot be imaged at one time. Therefore, it is impossible to directly measure the high depth and width of silicon-based MEMS using a white light interferometer. than the structure.

Using near-infrared light to penetrate the silicon material to probe the bottom of the trench, as shown in Figure 2(b), but for high aspect ratio structures, the large numerical aperture beam focused by the microscope objective will be modulated by the trench structure and reduce the beam focus. Aberrations are generated, which seriously affect the imaging quality and interference fringes, resulting in huge errors in the measurement results.

The Chinese patent "A Micro-Nano Deep Trench Structure Measurement Method and Device" (CN200710053292.5), the method is to project an infrared beam onto the surface of a silicon wafer containing a deep trench structure, and analyze the reflections from each interface of the deep trench structure. The measured reflection spectrum is obtained from the formed interference light; the theoretical reflection spectrum of the optical model of the equivalent multilayer thin film stack of the deep trench structure is constructed by using the equivalent medium theory, and the theoretical reflection spectrum is obtained by using the simulated annealing algorithm and the gradient-based optimization algorithm. Measure the reflection spectrum for fitting, and then extract the collective characteristic parameters such as the depth and width of the groove. The method described in this patent needs to model the groove structure of the sample to be tested in advance and calculate the theoretical reflection spectrum. The measurement results of the groove depth and width are obtained by fitting with the measured spectrum. The accuracy of the measurement results is affected by Due to the influence of pre-established theoretical models, it is difficult to model samples with complex structures or unknown structures, and it is difficult to ensure the accuracy of the measurement results.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-aspect-ratio microstructure reflection type interference microscopic nondestructive measurement device, which is used to solve the problem that the existing interference microscopic nondestructive measurement method cannot measure the depth and width of the MEMS high aspect ratio trench structure. question.

The technical solution to achieve the purpose of the present invention is: a high aspect ratio microstructure reflective interference microscopic nondestructive measurement device, which is characterized in that: it includes a near-infrared short coherent light source, a Koehler illumination system, a first cubic beam splitting prism, a first Optical path refraction system, deformable mirror, first relay lens group, first microscope objective lens, sample to be tested, piezoelectric ceramic PZT, second cube beam splitter prism, tube mirror, first infrared detector, pupil mirror, single A color filter, a second infrared detector, a second optical path folding system, a second plane mirror, a second relay lens group, a second microscope objective lens, and a third plane mirror.

The Koehler illumination system includes a first condenser mirror, a second condenser mirror, a first plane reflection mirror and a third condenser mirror which are arranged in sequence in a common optical path.

The piezoelectric ceramic PZT is connected with the first infrared detector to form a synchronous scanning acquisition system; the deformation mirror and the second infrared detector cooperate to form an aberration monitoring optical path and an active compensation system.

After the beam emitted by the near-infrared short coherent light source passes through the Koehler illumination system to generate uniform illumination light with multiple fields of view, it is divided into test light and reference light by the first cubic beam splitter; Reflected by the deformable mirror, the first optical path refraction system, the first relay lens group and the first microscope objective lens are in turn irradiated to the sample to be tested placed on the piezoelectric ceramic PZT; the reference light passes through the second optical path refraction system It turns to reach the second plane reflector, is reflected by the second plane reflector, passes through the second optical path refraction system, the second relay lens group and the second microscope objective lens in turn, irradiates the third plane reflector, and returns to the original path. Return; after the sample to be tested is illuminated, the reflected light returns to the first cubic beam splitter prism, and through the second cubic beam splitter prism, a part of the light passes through the tube mirror to image the sample to be tested on the first infrared detector, and is combined with the returned The reference light interferes on the first infrared detector; another part of the light passes through the pupil mirror and the monochromatic filter to image the pupil of the microscope objective on the second infrared detector, and is detected with the reference light in the second infrared detector. The optical path of exit pupil aberration monitoring of the microscope objective lens is formed. The piezoelectric ceramic PZT is used to drive the sample to be tested, and the second infrared detector is used to collect 4 phase-shifted interferograms, and the pupil aberration is calculated and obtained; The pupil aberration of the objective lens is fed back to the deformable mirror, and then the shape of the deformable mirror is adjusted to compensate for the pupil aberration; the vertical scanning interferometry method is used to drive the sample to be tested through the piezoelectric ceramic PZT, and the sample to be tested is synchronously received on the first infrared detector The interference fringe pattern of the surface of the sample at different depths, and finally the vertical scanning interference algorithm is used to process the interference pattern to obtain the measurement results of the depth and width of the groove of the sample to be tested.

A high aspect ratio microstructure reflection type interference microscopic nondestructive measurement method, the steps are as follows:

Step 1. Put the sample to be tested on the piezoelectric ceramic PZT, and obtain an image with aberration and a low-contrast interference fringe pattern on the first infrared detector;

Step 2. Use the second infrared detector to monitor the pupil aberration of the microscope objective, use the piezoelectric ceramic PZT to drive the sample to be tested, and use the second infrared detector to collect 4 phase-shifted interferograms, and calculate and obtain the pupil aberration;

Step 3. Adjust the shape of the deformable mirror according to the monitored pupil aberration, observe the compensation result on the second infrared detector, and observe a clear image and a high-contrast interference fringe pattern on the first infrared detector after compensation;

Step 4, adopting the vertical scanning interferometry method to drive the sample to be tested through the piezoelectric ceramic PZT, the first infrared detector synchronously collects the interference fringe pattern, and using the vertical scanning interferometry algorithm to process the interferogram;

Step 5. Finally, the depth and width measurement results of the trench structure of the sample to be tested are obtained.

Compared with the prior art, the present invention has the following significant advantages:

(1) A near-infrared short coherent light source is used for the samples of silicon-based MEMS high aspect ratio trench structure, which penetrates the deep groove to the bottom, and can use a large NA microscope objective, which solves the problem that the large NA beam cannot detect high aspect ratio trenches. Problems at the bottom of the slot structure.

(2) Aiming at the problem that the large NA beam converged by the microscope objective is modulated by the groove structure of the sample to be tested and reduces the focus of the beam, construct the optical path for the exit pupil aberration monitoring of the microscope objective and an active aberration compensation system, which can monitor the sample due to the sample to be tested. The aberration generated by the deep groove structure is fed back to the deformable mirror to actively compensate the aberration, improve the imaging quality and the contrast of interference fringes, and ensure the measurement accuracy.

Description of drawings

Figure 1 is a schematic diagram of a high-aspect-ratio microstructure reflective interference microscopic nondestructive measurement device.

Figure 2 is a schematic diagram of the bottom of the groove of the sample to be detected by the converging beam, in which Figure (a) is a picture of using white light to detect and is blocked by the side wall; Figure (b) is using near-infrared light to penetrate the side wall to detect the bottom, but the focus of the beam changes. Aberration map; Figure (c) shows that the beam can converge to the bottom of the groove after compensation by the deformed mirror.

Figure 3 is a schematic block diagram of pupil aberration monitoring and active compensation.

Figure 4 is the interferogram collected by the infrared detector, in which Figure (a) is the interferogram before the deformation mirror compensation; Figure (b) is the interferogram after the deformation mirror compensation.

FIG. 5 is a graph showing the measurement results of the high aspect ratio trench structure.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to Figure 1, a high aspect ratio microstructure reflective interference microscopic nondestructive measurement device includes a near-infrared short coherent light source 1, a Koehler illumination system, a first cubic beam splitting prism 6, a first optical path refraction system 7, and a deformable mirror. 8. The first relay lens group 9, the first microscope objective lens 10, the sample to be tested 11, the piezoelectric ceramic PZT12, the second cubic beam splitter prism 13, the tube mirror 14, the first infrared detector 15, the pupil mirror 16, Monochromatic filter 17 , second infrared detector 18 , second optical path refraction system 19 , second plane mirror 20 , second relay lens group 21 , second microscope objective lens 22 , third plane mirror 23 .

The Koehler illumination system includes a first condensing mirror 2 , a second condensing mirror 3 , a first plane reflecting mirror 4 and a third condensing mirror 5 which are arranged in sequence in a common optical path.

The piezoelectric ceramic PZT12 and the first infrared detector 15 are connected to form a synchronous scanning acquisition system; the deformable mirror 8 and the second infrared detector 18 cooperate to form an aberration monitoring optical path and an active compensation system.

After the beam emitted by the near-infrared short coherent light source 1 passes through the Koehler illumination system to generate uniform illumination light with multiple fields of view, it is divided into test light and reference light by the first cube beam splitter prism 6; The deformable mirror 8 is reflected by the deformable mirror 8, and then irradiated to the sample to be tested 11 placed on the piezoelectric ceramic PZT12 through the first optical path refraction system 7, the first relay lens group 9 and the first microscope objective lens 10 in turn; The reference light is deflected by the second optical path refraction system 19 to reach the second plane mirror 20, reflected by the second plane mirror 20, and then passes through the second optical path refraction system 19, the second relay lens group 21 and the second microscope in turn. The objective lens 22 is irradiated on the third plane mirror 23, and returns to the original path; after the sample to be tested 11 is illuminated, the reflected light returns to the first cubic beam splitter prism 6 on the original path, passes through the second cubic beam splitter prism 13, and a part of the light passes through The tube mirror 14 images the sample to be tested 11 on the first infrared detector 15, and interferes with the returned reference light on the first infrared detector 15; another part of the light passes through the pupil mirror 16 and the monochromatic filter 17 The pupil of the microscope objective is imaged on the second infrared detector 18, and interferes with the reference light on the second infrared detector 18 to form the exit pupil aberration monitoring optical path of the microscope objective, and the piezoelectric ceramic PZT12 is used to drive the Measure the sample 11 and use the second infrared detector 18 to collect 4 phase-shifted interferograms, and calculate the pupil aberration; feedback the pupil aberration of the microscope objective to the deformable mirror 8, and then adjust the shape of the deformable mirror 8 to the pupil The aberration is compensated; the vertical scanning interferometry is used to drive the sample 11 to be tested through the piezoelectric ceramic PZT12, and the first infrared detector 15 receives the interference fringe patterns on the surface of the sample 11 at different depths synchronously. The interferogram is processed to obtain the depth and width measurements of the grooves of the sample to be tested.

The near-infrared short coherent light source 1 is located on the front focal plane of the first condenser lens 2 , and the first condenser mirror 2 , the second condenser mirror 3 and the third condenser mirror 5 are confocal in sequence.

The deformable mirror 8 is located on the back focal plane of the third condenser lens 5, and is conjugated with the pupil of the first microscope objective 10 with respect to the first relay lens group 9. The first relay lens group 9 includes two identical A confocal condenser lens, a diaphragm is placed at the focal position to block stray light, and the test surface of the sample to be tested 11 is located on the focal surface of the first microscope objective lens 10;

The first infrared detector 15 , the confocal plane of the first relay lens group 9 and the sample to be tested 11 are conjugated.

The pupil of the first microscope objective 10 is imaged on the second infrared detector 18 through the first relay lens group 9, the deformable mirror 8, the pupil mirror 16 and the monochromatic filter 17. The pupil of 10, the deformable mirror 8 and the second infrared detector 18 are conjugated, and the central wavelength of the monochromatic filter 17 is the same as the central wavelength of the near-infrared short coherent light source 1; the piezoelectric ceramic PZT12 is used to drive the sample to be tested 11 and The second infrared detector 18 is used to collect 4 phase-shifted interferograms, and the pupil aberration is obtained by calculation; according to the obtained pupil aberration, the deformable mirror 8 is actively adjusted to perform aberration compensation, so that the large numerical aperture beam is affected by the sample to be tested. The groove structure can still converge to the bottom of the groove after modulation.

The optical path refraction system includes three plane reflection mirrors and a cube beam splitting prism.

Further, the direction of the light beam after passing through the first optical path refraction system 7 is perpendicular to the original direction, the front side illuminates the deformable mirror 8 and reflects, and then is reflected by the cube beam splitter prism in the first optical path refraction system 7, and the beam direction is turned to the original direction. Consistent.

Further, after the light beam passes through the second optical path refraction system 19, the rear direction is perpendicular to the original direction, the second plane mirror 20 is irradiated and reflected from the front, and then reflected by the cube beam splitter prism in the second optical path refraction system 19, and the beam direction is changed to same as the original direction.

Referring to Fig. 2, the white light is blocked by the groove structure of the sample to be tested 11, as shown in Fig. 2(a), the near-infrared light penetrates the sample to be tested 11 but is modulated by the groove structure to reduce focusing as shown in Fig. 2(b) As shown in Figure 2(c), the near-infrared large numerical aperture beam can converge to the bottom of the groove after using the deformable mirror 8 to compensate the aberration.

With reference to Fig. 3, Fig. 4 and Fig. 5, a reflection interference microscopic nondestructive measurement method of high aspect ratio microstructure, the steps are as follows:

Step 1. Put the sample 11 to be tested on the piezoelectric ceramic PZT12, and obtain an image with aberration and a low-contrast interference fringe pattern on the first infrared detector 15, as shown in Figure 4(a);

Step 2. Use the second infrared detector 18 to monitor the pupil aberration of the microscope objective, use the piezoelectric ceramic PZT12 to drive the sample to be tested 11 and use the second infrared detector 18 to collect 4 phase-shifted interferograms, and calculate the pupil image. Difference;

Step 3. The deformable mirror 8 adjusts the shape according to the detected pupil aberration, observes the compensation result on the second infrared detector 18, and observes a clear image and high-contrast interference fringes on the first infrared detector 15 after compensation. Figure, as shown in Figure 4(b);

Step 4, using the vertical scanning interferometry method to drive the sample to be tested 11 through the piezoelectric ceramic PZT12, the first infrared detector 15 synchronously collects the interference fringe pattern, and uses the vertical scanning interferometry algorithm to process the interference pattern;

Step 5: Finally, the depth and width measurement results of the trench structure of the sample to be tested 11 are obtained, as shown in FIG. 5 .

Claims (10)

1. A high aspect ratio microstructure reflective interference microscopic nondestructive measurement device, characterized in that it comprises a near-infrared short coherent light source (1), a Koehler illumination system, a first cubic beam splitting prism (6), a first optical path refracting Rotation system (7), deformable mirror (8), first relay lens group (9), first microscope objective lens (10), sample to be tested (11), piezoelectric ceramic PZT (12), second cubic beam splitter Prism (13), tube lens (14), first infrared detector (15), pupil mirror (16), monochromatic filter (17), second infrared detector (18), second optical path deflection a system (19), a second plane mirror (20), a second relay lens group (21), a second microscope objective lens (22), and a third plane mirror (23); The Koehler illumination system includes a first condenser (2), a second condenser (3), a first plane reflection mirror (4) and a third condenser (5) that are arranged in sequence in a common optical path; The piezoelectric ceramic PZT (12) and the first infrared detector (15) are connected to form a synchronous scanning acquisition system; the deformable mirror (8) and the second infrared detector (18) cooperate to form an aberration monitoring optical path and an active compensation system; After the beam emitted by the near-infrared short coherent light source (1) passes through the Koehler illumination system to generate uniform illumination light with multiple fields of view, it is divided into test light and reference light by the first cubic beam splitter prism (6); the test light is refracted by the first optical path The system (7) turns to reach the deformable mirror (8), is reflected by the deformable mirror (8), and passes through the first optical path folding system (7), the first relay lens group (9) and the first microscope objective lens (10) in turn , irradiates the sample to be tested (11) placed on the piezoelectric ceramic PZT (12); the reference light is deflected by the second optical path refraction system (19) and reaches the second plane mirror (20), through the second plane mirror (20) Reflection, through the second optical path refraction system (19), the second relay lens group (21) and the second microscope objective lens (22) in turn, irradiated to the third plane mirror (23), and the original After the sample to be tested (11) is illuminated, the reflected light returns to the first cube beamsplitter prism (6) in the same way, passes through the second cube beamsplitter prism (13), and part of the light passes through the tube mirror (14) to separate the sample to be tested. (11) is imaged on the first infrared detector (15), and interferes with the returned reference light on the first infrared detector (15); another part of the light passes through the pupil mirror (16) and the monochromatic filter (17) imaging the pupil of the microscope objective on the second infrared detector (18), and interfering with the reference light on the second infrared detector (18) to form an optical path for monitoring the exit pupil aberration of the microscope objective, Use the piezoelectric ceramic PZT (12) to drive the sample to be tested (11) and use the second infrared detector (18) to collect 4 phase-shifted interferograms, calculate and obtain the pupil aberration; feed back the pupil aberration of the microscope objective to the Deformable mirror (8), and then adjust the shape of the deformable mirror (8) to compensate pupil aberration; adopt vertical scanning interferometry to drive the sample to be tested (11) through piezoelectric ceramic PZT (12), at the first infrared detector (15) The upper synchronously receives the interference fringe patterns of the surface of the sample to be tested (11) at different depths, and finally uses the vertical scanning interference algorithm to process the interference patterns to obtain the depth and width measurement results of the grooves of the sample to be tested. 2 . The high aspect ratio microstructure reflective interference microscopic nondestructive measurement device according to claim 1 , wherein the near-infrared short coherent light source ( 1 ) is located at the front focal plane of the first condenser lens ( 2 ). 3 . Above, the first condenser (2), the second condenser (3) and the third condenser (5) are confocal in sequence. 3. A high aspect ratio microstructure reflection type interference microscopic nondestructive measurement device according to claim 1, characterized in that: the deformable mirror (8) is located on the back focal plane of the third condenser (5), and The pupil of the first microscope objective (10) is conjugated with respect to the first relay lens group (9), the first relay lens group (9) includes two identical and confocal condenser lenses, and the focal position is placed with an aperture stop For stray light, the test surface of the sample to be tested (11) is located on the focal plane of the first microscope objective lens (10). 4. A high aspect ratio microstructure reflection type interference microscopic nondestructive measurement device according to claim 1, characterized in that: the first infrared detector (15) and the first relay lens group (9) have The confocal plane is conjugated to the sample to be tested (11). 5. A high aspect ratio microstructure reflection type interference microscopic nondestructive measurement device according to claim 1, characterized in that: the pupil of the first microscope objective lens (10) passes through the first relay lens group ( 9), the anamorphic mirror (8), the pupil mirror (16) and the monochromatic filter (17) are imaged on the second infrared detector (18), the pupil of the first microscope objective (10), the anamorphic mirror (8) is conjugated with the second infrared detector (18), the central wavelength of the monochromatic filter (17) is the same as the central wavelength of the near-infrared short coherent light source (1); the piezoelectric ceramic PZT (12) is used to drive the The sample (11) is measured and the second infrared detector (18) is used to collect four phase-shifted interferograms, and pupil aberration is obtained by calculation; according to the obtained pupil aberration, the deformable mirror (8) is actively adjusted to perform aberration compensation, The large numerical aperture light beam can still converge to the bottom of the groove after being modulated by the groove structure of the sample to be tested (11). 6 . The high aspect ratio microstructure reflective interference microscopic nondestructive measurement device according to claim 1 , wherein the optical path refraction system comprises three plane mirrors and a cube beam splitting prism. 7 . 7. A high aspect ratio microstructure reflective interference microscopic nondestructive measurement device according to claim 6, characterized in that: the direction of the light beam after passing through the first optical path refraction system (7) is perpendicular to the original direction, and the frontal irradiation is deformed The mirror (8) is reflected, and then reflected by the cube beam splitter prism in the first optical path refraction system (7), and the beam direction is turned to be consistent with the original direction. 8. A high aspect ratio microstructure reflection type interference microscopic nondestructive measurement device according to claim 6, characterized in that: the direction of the light beam after passing through the second optical path refraction system (19) is perpendicular to the original direction, and the frontal irradiation of the first light beam is perpendicular to the original direction. The two plane mirrors (20) are reflected, and then reflected by the cubic beam splitting prism in the second optical path refraction system (19), and the beam direction is turned to be consistent with the original direction. 9. A high aspect ratio microstructure reflective interference microscopic nondestructive measurement method, characterized in that the steps are as follows: Step 1. Place the sample to be tested (11) on the piezoelectric ceramic PZT (12), and obtain an image with aberrations and a low-contrast interference fringe pattern on the first infrared detector (15); Step 2. Use the second infrared detector (18) to monitor the pupil aberration of the microscope objective, use the piezoelectric ceramic PZT (12) to drive the sample to be tested (11), and use the second infrared detector (18) to collect 4 amplitude shifts. Interferogram, calculate and obtain pupil aberration; Step 3. The deformable mirror (8) adjusts the shape according to the detected pupil aberration, observes the compensation result on the second infrared detector (18), and observes a clear image on the first infrared detector (15) after compensation and high-contrast interference fringe patterns; Step 4. Using the vertical scanning interferometry method to drive the sample to be tested (11) through the piezoelectric ceramic PZT (12), the first infrared detector (15) synchronously collects the interference fringe pattern, and uses the vertical scanning interference algorithm to process the interference pattern; Step 5. Finally, the depth and width measurement results of the trench structure of the sample to be tested (11) are obtained. The reflective interference microscopic nondestructive measurement method for high aspect ratio microstructures according to claim 9, wherein the sample to be measured (11) is a silicon-based MEMS device with a high aspect ratio trench structure.

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