JP2006068842A - Micro electromechanical element, optical micro electromechanical element, light modulation element, manufacturing method thereof and laser display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize the beam inclination amount while restraining the bending of a beam and improve manufacturing yield in a micro electromechanical element requiring an inclination in the surface shape of the beam and a manufacturing method thereof. <P>SOLUTION: In this micro electromechanical element and the manufacturing method thereof, a lower electrode 43 is provided with a beam 45 opposite thereto through a space 44 and supported at the end parts, and the beam 45 is provided with a step 51 for causing inclination in the width direction of the beam. The inclination amount of the beam 45 is controlled by selection of a step shape, that is, controlling the step width W3 and the step depth H3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrostatically driven microelectromechanical element, an optical microelectromechanical element, a light modulation element, a manufacturing method thereof, and a laser display.

  Microelectromechanical elements utilizing electrostatic driving, so-called MEMS (Micro Electro Mechanical Systems) elements, have been developed. FIG. 13 is a typical example of a general microelectromechanical element. The microelectromechanical element 1 includes a substrate-side electrode (hereinafter referred to as a lower electrode) 3 formed on a substrate 2 and a thin-film vibrating portion (hereinafter referred to as a beam) arranged so as to straddle the lower electrode 3 in a bridge shape. And 5). The beam 5 and the lower electrode 3 are electrically insulated by a space 4 therebetween. The beam 5 is formed in a double-supported beam structure in which both ends thereof are supported by the substrate 2 via support portions 6 [6A, 6B] integral therewith.

  As the substrate 2, for example, a substrate in which an insulating film is formed on a semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs), or an insulating substrate such as a quartz substrate or a glass substrate is used. The lower electrode 3 is formed of a polycrystalline silicon film doped with impurities, a metal film (polycrystalline W, Cr), or the like. The beam 3 includes an insulating film 7 such as a silicon nitride film (SiN film) and a driving side electrode (hereinafter referred to as an upper electrode) 8 made of, for example, an Al film having a thickness of about 100 nm formed on the upper surface thereof. The If an optical microelectromechanical element is used, the Al film 8 functions as a reflective film.

  In the microelectromechanical element 1 having the thin film beam, the beam 5 is displaced by electrostatic attraction or electrostatic repulsion between the lower electrode 3 according to the potential applied between the lower electrode 3 and the upper electrode 8. As shown in the drawing, the lower electrode 3 is displaced in a parallel state (solid line) and a concave state (broken line). For example, considering that this microelectromechanical element 1 is used as an optical microelectromechanical element, the surface of the upper electrode 8 also serving as a light reflecting film is irradiated with light, and the light reflection direction depends on the driving position of the beam. By utilizing the difference, it can be applied as an optical modulation element such as an optical switch having a switch function by detecting one reflected light. Also, the present invention can be applied as a light modulation element in which a plurality of beams are arranged in parallel and the light intensity is modulated using light diffraction.

  Many product developments using optical microelectromechanical elements are currently underway. One of them is a projector using GLV (registered trademark) (Grating Light Valve) developed as an optical modulator by SLM (Silicon Light Machine).

  The GLV is a system in which a plurality of thin beams having a double-supported beam structure are arranged, and the beams reflected by the beam are diffracted by denting every other beam by electrostatic attraction. Thereby, since the reflected light intensity in a certain direction can be continuously changed, application to a projector is expected. A projector using a GLV element has high color reproducibility, high contrast ratio, and high brightness.

In the GLV element, a structure that realizes higher contrast and luminance is a blazed GLV element. In this blaze GLV element, the beam is tilted, and the diffracted light is limited from diffracted light in two directions of ± first order light to diffracted light in one direction of −1st order light or + 1st order light (see Patent Document 1). ).
On the other hand, Patent Document 2 discloses a technique for reducing the film stress by annealing as a technique for reducing the deflection generated in the beam of the microelectromechanical element, which will be described later.

US Pat. No. 6,639,722B2 JP 2002-26007 A

  By the way, in the case of the blaze GLV element in which the beam is tilted as described above, it is necessary to control the beam tilt (Tilt) in addition to the beam deflection (Bow) inherent in the GLV element, so that the optimum structure is realized. It was extremely difficult to do.

  The mechanism for causing the beam to tilt is as shown in FIGS. 12A and 12B. This is a mechanism that tilts the center of the beam by using the tensile stress of the beam 3 itself by providing steps 11 on both sides of one half of the width direction of the beam 3. That is, as shown in FIG. 12A (before stress release), on the side where the step 11 of the beam 3 is present, a force Fb1 that pushes down to a height below the step 11 acts by the tensile stress Fa1. Similarly, a force Fb2 (not shown) that keeps the surface height by the tensile stress Fa2 is applied to the side having no step. Since these two forces Fb1 and Fb2 act as rotational moments on the beam 3, the beam 3 is tilted (see reference numeral 12) as shown in FIG. 12B (after stress release).

  In this structure, the stress of the beam 3 is indispensable, and a resonance frequency of 1 MHz or more is realized by the tensile stress of the beam. However, the fact that the beam 3 has a strong tensile stress conversely causes a beam deflection in the longitudinal direction of the beam. As for the light irradiation surface of the beam 3, a metal film 8 having a high reflectance is usually laminated on an insulating film 7 serving as a base layer. Therefore, the layer including the light irradiation surface of the beam has a laminated structure of at least two layers. Since each layer has its own internal stress (tensile stress or compressive stress), if this stress is not balanced, beam deflection occurs in a direction in which the tensile stress is strong.

  Thus, “deflection” and “tilt” are in a trade-off relationship with respect to the film stress of the beam 3. As a technique for reducing only the beam deflection, a technique for reducing the film stress by annealing is disclosed in Patent Document 1 described above. However, it is difficult to obtain the beam tilt using this method. On the other hand, the present applicant has previously proposed a structure in which a stress adjustment layer is added as a technique for reducing beam deflection without reducing the film stress as much as possible (see Japanese Patent Application No. 2004-95872). However, in order to increase the beam tilt while keeping the beam deflection low, some contrivance is required in the structure. In the blaze GLV element, considering the efficiency, it is necessary to control the beam tilt within about ± 10 nm, and a method that can expect accuracy and reproducibility is indispensable.

  Of course, the beam tilt increases as the tensile stress of the beam film increases. However, as described above, if the tensile stress of the film is strong, the deflection of the beam also increases. Is desired.

In view of the above points, the present invention makes it possible to optimize the amount of vibration part inclination while suppressing deflection in a microelectromechanical element that requires an inclination in the surface shape of the vibration part (beam), and further improves the manufacturing yield. The present invention provides a microelectromechanical element, an optical microelectromechanical element, a light modulation element, and a manufacturing method thereof.
The present invention also provides a laser display having this light modulation element and capable of obtaining a projected image with higher brightness.

The microelectromechanical element according to the present invention has a vibrating portion that is opposed to a lower electrode with a space and is supported at an end portion, and has a step formed on the vibrating portion to cause a tilt in the width direction of the vibrating portion. The electromechanical element is characterized in that the width of the step is set to a width corresponding to a substantially maximum value of the tilt amount of the vibration part.
The width of the stepped portion corresponding to the substantially maximum value can be approximately one quarter or substantially three quarters of the width of the vibrating portion.

An optical microelectromechanical element according to the present invention has a vibrating part that is opposed to a lower electrode with a space therebetween and is supported by an end part, and a step is provided on the vibrating part to cause the vibrating part to tilt in the width direction. An optical microelectromechanical element that converts the reflection direction of light reflected by the vibrating part or generates diffracted light by driving the vibrating part, wherein the width of the step is approximately the tilt amount of the vibrating part. It is characterized by being set to a width corresponding to the maximum value.
The width of the stepped portion corresponding to the substantially maximum value can be approximately one quarter or substantially three quarters of the width of the vibrating portion.

In the light modulation element according to the present invention, a plurality of vibrating portions that are opposed to each other with a space between the lower electrode and supported by the end portions are arranged in parallel, and a step is provided on the vibrating portion to cause an inclination in the width direction of the vibrating portion. The light modulation element is configured to generate diffracted light by driving the vibration part, wherein the width of the step is set to a width corresponding to a substantially maximum value of the tilt amount of the vibration part.
The width of the stepped portion corresponding to the substantially maximum value can be approximately one quarter or substantially three quarters of the width of the vibrating portion.

  The method for manufacturing a microelectromechanical element according to the present invention has a vibrating portion that is opposed to a lower electrode with a space therebetween and is supported by an end portion, and a step is provided on the vibrating portion so that the vibrating portion is inclined in the width direction. A method of manufacturing a microelectromechanical element to be generated, characterized in that an inclination amount of a vibrating part is controlled by a shape of a step.

As the control of the amount of inclination of the vibration part, it is possible to control so as to maximize the amount of inclination of the vibration part by controlling at least one of the width in the vibration part width direction and the depth of the step.
As control of the tilt amount of the vibration part, control of at least one of the width of the step in the width direction of the vibration part and the depth of the step minimizes the variation in the tilt amount of the vibration part due to the variation in the etching depth of the step shape. Can be controlled.
As control of the amount of inclination of the vibration part, at least one of the width of the step in the width direction of the vibration part and the depth of the step is controlled to minimize variation in the amount of inclination of the vibration part due to the variation in the etching width of the step shape. Can be controlled.

  The method of manufacturing an optical microelectromechanical element according to the present invention includes a vibrating portion that is opposed to a lower electrode with a space therebetween and is supported by an end portion, and a step is provided on the vibrating portion, and the vibrating portion is inclined in the width direction. And a method of manufacturing an optical microelectromechanical element in which the direction of reflection of light reflected by the vibration part is changed by driving the vibration part, or diffracted light is generated. Controlling at least one of the width of the direction and the depth of the step makes the amount of inclination of the vibration part maximize.

In this method of manufacturing an optical microelectromechanical element, the amount of tilt of the vibration portion is controlled by controlling at least one of the width of the step in the width direction of the vibration portion and the depth of the step to vary the etching depth of the step shape. It is possible to control so as to minimize the variation in the amount of inclination of the vibration part due to.
In this method for manufacturing an optical microelectromechanical element, the amount of tilt of the vibration part is controlled by controlling at least one of the width of the step in the vibration part width direction and the depth of the step, and by varying the etching width of the step shape. Control can be performed so as to minimize variation in the amount of inclination of the vibration part.

  In the method for manufacturing a light modulation element according to the present invention, a plurality of vibrating portions that are opposed to each other with a space between the lower electrode and supported by the end portions are arranged in parallel, a step is provided on the vibrating portion, and the vibrating portion is arranged in the width direction. A method of manufacturing a light modulation element that causes inclination and generates diffracted light by driving a vibration part, and controls at least one of a width in a vibration part width direction of the step and a depth of the step, It is characterized in that the amount of inclination of the vibration part is maximized.

In this method of manufacturing a light modulation element, the tilt amount of the vibration part is controlled by controlling at least one of the width of the step in the vibration part width direction and the depth of the step, and vibration caused by variations in the etching depth of the step shape. It is possible to control so as to minimize the variation in the amount of inclination of the part.
In this method of manufacturing a light modulation element, the amount of tilt of the vibration part is controlled by controlling at least one of the width of the step in the vibration part width direction and the depth of the step, and the vibration part due to variation in the etching width of the step shape. It is possible to control so as to minimize the variation in the inclination amount.

A laser display according to the present invention is a laser display having a laser light source and a light modulation element that is arranged on the optical axis of the laser light emitted from the laser light source and modulates the light intensity of the laser light. The element comprises a lower electrode and a plurality of vibration parts, each vibration part having a step and tilting in the width direction of the vibration part, and driving the vibration part to cause intensity modulation of the diffracted light. Is set to a width corresponding to a substantially maximum value of the amount of inclination of the vibration part.
The width of the stepped portion corresponding to the substantially maximum value can be approximately one quarter or substantially three quarters of the width of the vibrating portion.

  In the micro electro mechanical element, the optical micro electro mechanical element, and the light modulation element of the present invention described above, an inclination occurs in the width direction of the vibration part by providing a step. Then, by setting the width of the step to a width corresponding to the substantially maximum value of the amount of inclination of the vibration part, for example, approximately one quarter or substantially three quarters of the vibration part width, the inclination of the vibration part is maximized. In addition, the change in the tilt amount of the vibration part is small. Moreover, since the amount of vibration part inclination increases without increasing the tensile stress of the vibration part, the deflection of the vibration part is suppressed.

In any of the manufacturing methods of the microelectromechanical element, the optical microelectromechanical element, and the light modulation element of the present invention described above, the vibration part can be inclined in the width direction by adding a step to the vibration part. At this time, by devising the shape of the step, the inclination amount of the vibration part is controlled, and a desired inclination amount is obtained. At this time, since the amount of inclination of the vibration part can be increased without increasing the tensile stress of the vibration part, the deflection of the vibration part is suppressed.
By controlling at least one of the width of the step in the width direction of the vibration part and the depth of the step, the amount of inclination of the vibration part can be maximized.
By controlling at least one of the width of the step in the width direction of the vibration portion and the depth of the step, variation in the amount of inclination of the vibration portion due to variation in the etching depth of the step shape can be minimized.
By controlling at least one of the width of the step in the width direction of the vibration portion and the depth of the step, variation in the amount of inclination of the vibration portion due to variation in the etching width of the step shape can be minimized.

  According to the microelectromechanical element, the optical microelectromechanical element, and the light modulation element according to the present invention, the width of the step corresponds to a substantially maximum value of the tilt amount of the vibration part, for example, approximately four quarters of the width of the vibration part. By setting it to 1 or 3/4, the amount of inclination of the vibration part can be increased and optimized while suppressing the deflection of the vibration part. In addition, the change in the amount of inclination of the vibration part can be reduced.

  According to the method for manufacturing a microelectromechanical element according to the present invention, in the method for manufacturing a microelectromechanical element that requires an inclination in the vibration part to be electrostatically driven, a step is formed in a part of the vibration part, and this step shape is formed. By changing the above, it is possible to control the tilt amount of the vibration part to the optimum value while suppressing the deflection of the vibration part. This produces the following effects.

  It is possible to improve the performance of a microelectromechanical element that has not been able to secure a sufficient amount of vibration part tilt until now. According to the method for manufacturing an optical microelectromechanical element to which this method for manufacturing a microelectromechanical element is applied, an optical microelectromechanical element having a high conversion efficiency in the reflection direction of light is manufactured when applied to an optical switch. be able to. Further, when applied to a diffractive optical element, an optical microelectromechanical element with improved diffraction efficiency can be manufactured. According to the method for manufacturing a light modulation element to which this method for manufacturing a microelectromechanical element is applied, it is possible to manufacture a light modulation element with improved diffraction efficiency and good intensity modulation of diffracted light.

  With the manufacturing method of the present invention, process variations due to the etching depth can be suppressed. Since the etching rate is not always constant, variations in the etching depth of about several percent can usually occur sufficiently. Therefore, a significant improvement can be achieved with respect to yield, which is one of the problems that microelectromechanical elements currently have.

  By the manufacturing method of the present invention, process variations due to the etching width can be suppressed. In particular, in a microelectromechanical element having a minute structure, slight variations in the processing width due to photoresist or side etching greatly affect the structure. In the present invention, however, the yield and uniformity within a chip are particularly affected. It is valid.

  According to the laser display of the present invention, since the above-described light modulation element of the present invention is provided as the light modulation element, a sufficient amount of vibration part inclination of the light modulation element can be ensured, and the diffraction efficiency of the laser display can be improved. A projected image with brightness can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, in order to facilitate understanding of the present invention, a microelectromechanical element (FIG. 11A, 11B) is used, in which a step is provided at both ends of a thin-film vibrating portion (hereinafter referred to as a beam) to incline the beam. A comparative example of a so-called MEMS element will be described. The microelectromechanical element 21 of this comparative example includes a lower electrode 23 formed on a substrate 22 and a beam 25 which is arranged so as to straddle the lower electrode 23 and has steps 31 at both ends. . The width W1 in the beam width direction of the step 31 of the beam 25 is half of the normal beam width W2 (W1 = 1 / 2W2). The beam 25 and the lower electrode 23 are electrically insulated by a space 24 therebetween. The beam 25 is formed of a two-layer film, for example, an insulating film 27 such as a silicon nitride film and an upper electrode 28 made of, for example, an Al film on the upper surface, as described above. 26A, 26B] to form a doubly supported beam type structure supported by the substrate 22.

In this microelectromechanical element 21, the mechanism by which the beam 25 having the step 31 is tilted is as described above (see FIG. 12), and the tilt amount of the beam is controlled by the step depth H1. FIG. 3 shows the amount of inclination with respect to the depth H1 of the step 31 of the beam 25 in the microelectromechanical element 21. As shown in FIG. The vertical axis in FIG. 3 indicates the amount of inclination (relative value), and the horizontal axis indicates the step depth (relative value).
As the step depth H1 is increased, the amount of inclination increases, but reaches a peak value at a certain step depth, and thereafter the amount of inclination decreases. In order to obtain an amount of tilt greater than the peak value, the beam film must be a film having a high tensile stress, but the deflection of the beam also increases.

Next, an electrostatic drive type micro electromechanical element (so-called MEMS element) and a manufacturing method thereof according to the present invention will be described. The microelectromechanical device targeted by the present invention is a micro / nanoscale device.
FIG. 1 shows a first embodiment of a microelectromechanical device and a method for manufacturing the same according to the present invention. A microelectromechanical element 41 according to the present embodiment includes a lower electrode 43 formed on a substrate 42, and a beam 45 that is disposed so as to straddle the lower electrode 43 in a bridge shape and has steps 51 at both ends. It consists of The beam 45 and the lower electrode 43 are electrically insulated by a space 44 therebetween. The beam 45 is formed of, for example, a two-layer film of an insulating film 47 and an upper electrode 48 made of a metal film on the upper surface thereof, and both ends thereof are formed on the substrate 42 via support portions 46 [46A, 46B] integral therewith. Formed in a supported doubly supported beam structure.

The support portion 46 [46A, 46B] can be formed integrally with the beam 45 with the same film structure as the beam 45.
As described above, the substrate 42 may be a substrate in which an insulating film is formed on a semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs), or an insulating substrate such as a quartz substrate or a glass substrate. The lower electrode 43 is formed of a polycrystalline silicon film doped with impurities, a metal film (polycrystalline W, Cr vapor deposition film), or the like. The beam 45 is composed of a silicon nitride film (SiN film), a silicon oxide film (SiO2 film), other insulating films, and in this example, physical properties such as strength and elastic constant are suitable for mechanical driving of the beam 45. A membrane is used. The upper electrode 48 can be formed of a polycrystalline Al single film, an Al alloy film (these are collectively referred to as an Al film), and other metal films having good light reflection efficiency.

  In this embodiment, the beam tilt amount is controlled by selecting the shape of the step 51 in particular. That is, the amount of tilt of the beam 45 is controlled by changing the width W3 of the step shape in the beam width direction and the step depth H3.

The step width W3 is normally set to ½ of the beam width W4, but in this embodiment, for example, the step width W3 is set to ½ or more of the width W4 of the beam 45, or ½ or less.
As shown in the graph of FIG. 2, the change in the tilt amount of the beam 45 with respect to the step width W3 has peaks in the vicinity of ¼ and 3/4 of the beam width W4. Therefore, by making the step width W3 close to this peak, the amount of inclination can be increased as compared with the comparative example.
On the other hand, as is apparent from the graph of FIG. 3 described above, when the step width W3 is kept constant and the step depth H3 is changed, there is a characteristic that the slope amount has a peak. Therefore, by setting the step width W3 close to the peak in FIG. 2 and further increasing the step depth H3, the amount of inclination can be further increased.

According to the microelectromechanical element 41 and the manufacturing method thereof according to the first embodiment, a desired beam tilt amount can be obtained by changing the step shape, so-called step width W3 and step height H3. For example, the step width W3 is set to a certain value to control the step depth H3, or the step depth H3 is set to a certain value to control the step width W3, or both the step width W3 and the step depth H3 are set. By controlling, the beam tilt amount can be arbitrarily controlled. Therefore, if the step width W3 and the step depth H3 are controlled to optimum values, the beam tilt amount can be maximized, and a larger beam tilt amount can be obtained as compared with the comparative example.
In this microelectromechanical element 41, the width W3 of the step is set to about one quarter or about three quarters of the width W4 of the beam 45, thereby increasing the beam tilt amount and changing the beam tilt amount. Can be small. Here, approximately one-quarter and approximately three-quarters are such that a margin sufficient in terms of characteristics can be obtained in consideration of the accuracy of a device that uses the quarter and three-quarters as the center, It refers to the step width in a range where an amount of inclination close to the maximum value is obtained. For example, an error range of ± 0.1 μm can be allowed.

Next, a second embodiment of the microelectromechanical element and the manufacturing method thereof according to the present invention will be described. The basic structure of the microelectromechanical element according to the present embodiment is the same as that of the microelectromechanical element 41 according to the first embodiment.
The value of the beam tilt amount with respect to the depth H3 of the step 51 (referred to here as the etching depth because it corresponds to the etching depth at the time of manufacture) is saturated at a certain etching depth H3 as shown in FIG. To do. Near this saturation (near the peak), the change in the beam tilt amount with respect to the etching depth H3 of the step 51 is small.
In forming the beam having a required inclination, the micro electromechanical element and the manufacturing method thereof according to the present embodiment set the step width W3 to a certain value and set the step depth H3 to the above saturation region. The step 51 is formed under the control of conditions.

According to the microelectromechanical element and the manufacturing method thereof according to the second embodiment, the step 51 is formed by controlling the etching depth (step depth) W3 under the condition near the saturation region where the beam tilt amount is saturated. As a result, the variation in the beam tilt amount with respect to the error of the etching depth W3 can be minimized.
This will be further described with reference to FIG. FIG. 4 shows the relationship between the beam tilt amount and the etching depth when the step width is used as a parameter. Curve a is when step width = beam width × 1/4, and curve b is when step width = beam width × 1/2. For example, when it is desired to form a beam having an inclination amount of 80 (relative value) so that the influence of variations in etching depth is as small as possible, the step width is ½ of the beam width and the etching depth is 160 (relative). Value) (see curve a). In curve a, the etching depth 160 is near saturation (near the peak), and therefore the influence of the variation in etching depth on the beam tilt amount is small. On the other hand, when the curve b is used, the elasticity imparting member difference width is ¼ of the beam width, and the etching depth is 120, the beam tilt amount of 80 is achieved. However, since the portion of the etching depth 120 is not near the saturation of the curve b, the beam tilt amount is greatly affected by the variation in the etching depth.
Therefore, in order to design a target beam tilt amount so as to minimize the influence of the etching depth variation, both the step depth (etching depth) and the step width (etching width) may be controlled. . Alternatively, only the step depth is controlled by setting the step width to a certain value, or only the step width is controlled by setting the step depth to a certain value.
When the influence of the etching depth is larger than the etching width (corresponding to the step width) at the time of manufacture as a factor of variation in the beam tilt amount, the variation in the beam tilt amount is reduced by using the second embodiment. It becomes possible.

Next, a third embodiment of the microelectromechanical element and the method for manufacturing the same according to the present invention will be described. The basic structure of the microelectromechanical element according to the present embodiment is the same as that of the microelectromechanical element 41 according to the first embodiment.
As shown in FIG. 2, the value of the beam tilt amount with respect to the width W3 of the step 51 (referred to here as the etching width at the time of manufacture) is about 1/4 of the beam width W4. A maximum value is taken at / 4, and a minimum value is taken at about ½ of the beam width W4. In the vicinity of the maximum value and the minimum value, the change in the beam tilt amount with respect to the etching width W3 of the step 51 is small.
The microelectromechanical element and the manufacturing method thereof according to the present embodiment set the step depth H3 to a certain value and form the etching width W3 in the vicinity of the above-mentioned maximum value when forming a beam having a required inclination. Alternatively, the step 51 is formed under the control near the minimum value.

According to the microelectromechanical element and the manufacturing method thereof according to the third embodiment, etching is performed by forming the step 51 by controlling the etching width W3 near the maximum value of the beam tilt amount or near the minimum value. Variations in the beam tilt amount with respect to the error of the width W3 can be minimized.
That is, in this case as well, both the step depth (etching depth) and the step width (etching width) are controlled in order to design a certain amount of beam tilt so that the influence of the variation in etching width is minimized. do it. Alternatively, only the step depth is controlled by setting the step width to a certain value, or only the step width is controlled by setting the step depth to a certain value.
When the influence of the etching width is larger than the etching depth (corresponding to the step depth) at the time of manufacture as a factor of variation in the beam tilt amount, the variation in the beam tilt amount is reduced by using the third embodiment. It becomes possible to make it. In particular, when the beam 45 has a narrow ribbon structure, the variation in the beam tilt due to the process error of the etching width becomes large, so the method of the third embodiment is effective.

  In the microelectromechanical element and the manufacturing method thereof according to the above-described embodiment, the upper electrode 48 of the beam 45 is used as a light reflection film, and the reflected light in one direction is utilized by utilizing the fact that the reflection direction of the light varies depending on the driving of the beam 45. Can be applied to an optical switch having a switch function by detecting the above, or an optical microelectromechanical element such as a light modulation element. The light modulation element when utilizing light reflection is so-called time modulation in which light intensity is modulated by the amount of reflection in one direction per unit time. The light modulation element when utilizing light diffraction is so-called spatial modulation that modulates the intensity of light reflected by a beam by light diffraction. Furthermore, the microelectromechanical element and the manufacturing method thereof according to the above-described embodiment can be applied to a light modulation element such as a GLV element that modulates light intensity using light diffraction.

Next, a fourth embodiment in which the microelectromechanical element and the manufacturing method thereof according to the present invention are applied to a GLV element that is a light modulation element using diffracted light will be described.
In the GLV element 61 according to the present embodiment, as shown in FIG. 5, a common lower electrode 63 is formed on a substrate 62, and a plurality of, in this example, five, crossing the lower electrode 63 and straddling a bridge shape. Beams 65 [651, 652, 653, 654, 655] are arranged in parallel. Of this beam 65, one alternate beam, polycrystalline beams 651, 653, 655 act as fixed beams, and the other alternate beam 652, 654 acts as a movable beam. As described above, the substrate 62 is formed of a substrate in which an insulating film is formed on a semiconductor substrate, an insulating substrate, or the like. The lower electrode 63 is also formed of a polycrystalline silicon film, a metal film, or the like. The beam 65 is formed on the surface parallel to the lower electrode 53 of the bridge member 67 made of an insulating film such as a silicon nitride film (SiN film), for example, an upper electrode (hereinafter referred to as a reflective film made of an Al film of about 70 nm). 68) (referred to as a reflective film and upper electrode). The beam 65 is a portion called a ribbon.

  In the present embodiment, the same step 51 as described above is formed at both ends of the beam 65. As will be apparent from the manufacturing process described later, this step 51 is formed by performing partial etching on the sacrificial layer to be formed to obtain a hollow structure, and forming each film to be a beam thereon. Is done. Since the beam 65 has this step shape, it is arranged with a desired beam inclination.

  In the GLV element 61, when a minute voltage is applied between the lower electrode 63 and the reflective film / upper electrode 68, every other beam 652, 654 approaches the lower electrode 63 due to the electrostatic phenomenon described above, and When the application of the voltage is stopped, the voltage returns to the original position. The height of the reflection / upper electrode 68 is changed by the operation of approaching and separating each of the plurality of beams 652 and 654 of the plurality of beams 65 with respect to the lower electrode 63, and is emitted from the upper electrode 68 by light diffraction. The light intensity is modulated.

  As described in the first to third embodiments, the GLV element and the manufacturing method thereof according to the present embodiment change the step width and step depth of the step 51 to control the beam tilt amount to the optimum value. To make. The optimum value of the beam tilt amount in the GLV element 61 is ¼ of the light source laser wavelength. In the present embodiment, since the errors in the etching width (step width) and the etching depth (step depth) of the step portion 51 both affect the variation in the beam tilt amount, the second and third embodiments are applied. Thus, variations in the beam tilt amount are minimized.

  According to the GLV element 61 and the manufacturing method thereof according to the fourth embodiment, it is expected that the beam tilt amount can be suppressed within ± 10 nm, and the improvement of the light efficiency, the stabilization, and the improvement of the manufacturing yield are achieved. The Further, when the beam 65 becomes thinner as the GLV element 61 becomes smaller, it is necessary to further increase the tilt angle of the beam 65. At this time, this can be realized by using the first embodiment.

  6-9 shows an example of the manufacturing method of the GLV element 61 of 4th Embodiment. In this manufacturing method, the five beams of the GLV element 61 are formed at the same time. However, for convenience of explanation, only two beams are used, and the remaining three beams are the same and are omitted.

  First, as shown in FIG. 6A, a lower electrode 63 common to a plurality of beams to be formed later is formed on a substrate 62. The substrate surface other than the lower electrode 63 is covered with an insulating film so that the lower electrode 63 and the surface of the substrate 62 are flush with each other. In the illustrated example, the lower electrode 63 is embedded in the substrate 62.

  Next, as shown in FIG. 6B, a sacrificial layer 72 is selectively formed on the substrate 62 including the lower electrode 63 so as to have a width wider than the width corresponding to the beam length direction of the lower electrode 63. To do. The sacrificial layer 72 is formed of a lower electrode 63, a substrate surface, a material that can take an etching ratio with a later beam material, in this example, an amorphous silicon film.

  Next, as shown in FIG. 7C, selective etching is performed on the sacrificial layer 72 using photolithography technology and etching technology, and etching is performed with a width W3 'and a depth H3' at a position corresponding to the stepped portion of the beam. A recess 71 'is formed. That is, in the sacrificial layer 72, etching recesses 71 'having a width W3' narrower than the width W4 'corresponding to the beam width and a depth H3' are formed at both ends of the surface of the region corresponding to each beam. This etching recess 71 'corresponds to a beam step 71 described later, and the width W3' and depth H3 'of the etching recess 71' correspond to the step width W3 and step depth H3 of the beam step 71.

  Next, as shown in FIG. 7D, an insulating film 67 ′ made of, for example, a silicon nitride film that serves as a bridge member is deposited on the entire surface of the substrate including the surface of the sacrificial layer 72. Subsequently, as shown in FIG. 8E, for example, an Al film 68 'serving as a reflective film and upper electrode is deposited on the insulating film 67'.

  Next, as shown in FIG. 8F, the Al film 68 ′ and the insulating film 67 ′ are patterned using a photolithography technique and an etching technique, and are divided into beams. That is, each beam 65 [651, 652,...] Having a step 71 at both ends is formed.

Next, as shown in FIG. 9G, the sacrificial layer 72 is selectively removed by etching to form a space 64 between each beam 65 and the lower electrode 63.
In this way, as shown in FIG. 9H, the lower electrode 63 is formed on the substrate 62, the space 64 is sandwiched with respect to the lower electrode 63, the steps 71 are formed at both ends, and the reflective film and upper electrode is formed on the surface. Thus, a target GLV element 61 having a plurality of 68 formed with five beams 65 [651 to 655] in this example is obtained.

  FIG. 10 shows an embodiment of an optical apparatus using the GLV element 61 as the light modulation element of the present invention. In this example, the present invention is applied to a laser display. The laser display 81 according to the present embodiment is used, for example, as a large screen projector, particularly as a digital image projector, or as a computer image projector.

As shown in FIG. 10, the laser display 81 has red (R), green (G), and blue (B) laser light sources 82R, 82G, and 82B on the respective optical axes with respect to the laser light sources. Sequentially provided mirrors 84R, 84G, 84B, each color illumination optical system (lens group) 86R, 86G, 86B, and the above-described GLV elements 88R, 88G, 88B functioning as light modulation elements. .
The laser light sources 82R, 82G, and 82B, for example, emit lasers of R (wavelength 642 nm, light output about 3 W), G (wavelength 532 nm, light output about 2 W), and B (wavelength 457 nm, light output about 1.5 W), respectively. To do.

  Further, the laser display 81 includes a color synthesis filter 90 that synthesizes red (R) laser light, green (G) laser light, and blue (B) laser light whose light intensity is modulated by the DLV elements 88R, 88G, and 88B, respectively. A spatial filter 92, a diffuser 94, a mirror 96, a galvano scanner 98, a projection optical system (lens group) 100, and a screen 102 are provided. The color synthesis filter 90 is constituted by, for example, a dichroic mirror.

In the laser display 81 of the present embodiment, the RGB laser beams emitted from the laser light sources 82R, 82G, and 82B pass through the mirrors 84R, 84G, and 84B, respectively, and the GLV elements 88R from the respective color illumination optical systems 86R, 86G, and 86B. , 88G, 88B.
Further, each laser beam is spatially modulated by being diffracted by the GLV elements 88R, 88G, and 88B, the diffracted light of these three colors is synthesized by the color synthesis filter 90, and then only the signal component is extracted by the spatial filter 92. It is.
Next, this RGB image signal is reduced in laser speckle by the diffuser 94, passes through a mirror 96, is developed in space by a galvano scanner 98 synchronized with the image signal, and is projected as a full-color image on the screen 102 by the projection optical system 100. Projected.
According to the laser display 81 of this embodiment, the beam tilt amounts of the GLV elements 88R, 88G, and 88B can be sufficiently secured, so that the diffraction efficiency is improved and a projected image with higher brightness can be obtained.

According to the micro electro mechanical element, the optical micro electro mechanical element, the light modulation element and the manufacturing method thereof according to the above-described embodiment, the step shape provided on the beam is devised, that is, the step width and the step depth are selectively controlled. By doing so, the beam tilt amount can be further increased while suppressing the beam deflection, and a sufficient beam tilt amount can be secured and optimized.
As a result, it is possible to improve the performance of the microelectromechanical element, which has conventionally been unable to secure a sufficient beam tilt amount. According to the light modulation element to which the micro electromechanical element is applied, the light reflection direction can be efficiently converted. According to the light modulation element to which the micro electro mechanical element is applied, the diffraction efficiency can be improved. If the projector is provided with the GLV element as the light modulator, the diffraction efficiency is improved, so that projection with higher luminance is possible.

  According to the second embodiment, process variations due to the etching depth when forming the beam step can be suppressed. Since the etching rate is not always constant, variations in the etching depth on the order of several percent can usually occur sufficiently. Therefore, a significant improvement is expected with respect to the yield, which is one of the problems of the conventional microelectromechanical elements.

  According to the third embodiment, process variations due to the etching width when forming the beam step can be suppressed. In particular, micro electromechanical elements having a micro beam structure, photoresist, and slight variations in processing width due to side etching greatly affect the structure. This embodiment is particularly effective for yield and uniformity within the chip.

1A is a perspective view showing an embodiment of a microelectromechanical element according to the present invention. FIG. B is a plan view showing an embodiment of a microelectromechanical element according to the present invention. FIG. It is a graph which shows the relationship between a level | step difference width and beam inclination amount. It is a graph which shows the relationship between level | step difference depth and beam inclination amount. It is a graph which shows the relationship between the step depth (etching depth) and the beam tilt amount with the step width as a parameter. It is a block diagram which shows embodiment which applied this invention to the GLV element. A, B Manufacturing process figure (the 1) which shows one Embodiment of the manufacturing method of the light modulation element (GLV element) of this invention. C, D Manufacturing process figure (the 2) which shows one Embodiment of the manufacturing method of the light modulation element (GLV element) of this invention. E, F Manufacturing process figure (the 3) which shows one Embodiment of the manufacturing method of the light modulation element (GLV element) of this invention. G, H Manufacturing process figure (the 4) which shows one Embodiment of the manufacturing method of the light modulation element (GLV element) of this invention. It is a block diagram which shows the example of the laser display using the GLV element which is a light modulation element which concerns on this invention. A is a perspective view of a microelectromechanical element according to a comparative example. B is a plan view of a microelectromechanical element according to a comparative example. A is a stress distribution diagram before releasing stress of a beam having a step. B is a stress distribution diagram after releasing stress of a beam having a step. It is a perspective view which shows the representative example of the conventional double-supported beam type microelectromechanical element.

Explanation of symbols

  41..Electrostatic drive type MEMS element 42..Substrate, 43..Lower electrode 44..Space, 45..Vibration part (beam), W3..Step width, W4 ..Vibration part (beam) Width, H3 ··· Step depth, 61 · · GLV element, 62 · · Substrate, 63 · · Lower electrode, 65 [651, 652, 653, 654, 655] · · Vibrating part (beam), 67 · · Insulation Film, 68 ... Reflective film and upper electrode

Claims (18)

It has a vibrating part that is opposed to the lower electrode across the space and supported by the end part,
A micro-electromechanical element that creates a step in the vibration part and causes the vibration part to tilt in the width direction,
The micro electromechanical element, wherein a width of the step is set to a width corresponding to a substantially maximum value of an inclination amount of the vibrating portion. The micro electromechanical element according to claim 1, wherein a width of the step is approximately a quarter or a quarter of the width of the vibrating portion. It has a vibrating part that is opposed to the lower electrode across a space and supported by the end part,
A step is added to the vibrating part to cause an inclination in the width direction of the vibrating part,
An optical microelectromechanical element configured to change a reflection direction of light reflected by the vibration part or generate diffracted light by driving the vibration part,
The optical microelectromechanical element, wherein the width of the step is set to a width corresponding to a substantially maximum value of an inclination amount of the vibrating portion. The optical microelectromechanical element according to claim 3, wherein a width of the step is approximately ¼ or approximately ¾ of the width of the vibrating portion. A plurality of vibration parts that are opposed to each other with a space between the lower electrode and supported by the end part are arranged in parallel,
A step is added to the vibrating part to cause an inclination in the width direction of the vibrating part,
A light modulation element configured to generate diffracted light by driving the vibration unit,
The width of the step is set to a width corresponding to a substantially maximum value of the tilt amount of the vibration part. 4. The light modulation element according to claim 3, wherein a width of the step is approximately ¼ or approximately ¾ of a width of the vibrating portion. It has a vibrating part that is opposed to the lower electrode across the space and supported by the end part,
A method of manufacturing a microelectromechanical element in which a step is provided on the vibration part to cause a tilt in the width direction of the vibration part,
A method of manufacturing a microelectromechanical element, wherein the amount of inclination of the vibrating portion is controlled by selecting a step shape. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing a microelectromechanical element according to claim 7, wherein the amount of inclination of the vibrating portion is maximized. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing a microelectromechanical element according to claim 7, wherein variation in the amount of inclination of the vibration portion due to variation in the etching depth of the step shape is minimized. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing a microelectromechanical element according to claim 7, wherein variation in the amount of inclination of the vibration portion due to variation in the etching width of the step shape is minimized. It has a vibrating part that is opposed to the lower electrode across a space and supported by the end part,
A step is added to the vibrating part to cause an inclination in the width direction of the vibrating part,
A method of manufacturing an optical microelectromechanical element that converts a reflection direction of light reflected by the vibration part or generates diffracted light by driving the vibration part,
A method of manufacturing an optical microelectromechanical element, wherein the amount of inclination of the vibration part is maximized by controlling at least one of the width of the step in the vibration part width direction and the depth of the step. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing an optical microelectromechanical element according to claim 11, wherein variations in the amount of inclination of the vibration part due to variations in the etching depth of the step shape are minimized. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing an optical microelectromechanical element according to claim 11, wherein variations in the amount of inclination of the vibration part due to variations in the etching width of the step shape are minimized. A plurality of vibration parts that are opposed to each other across the space between the lower electrodes and supported by the end parts are arranged in parallel,
A step is added to the vibrating part to cause an inclination in the width direction of the vibrating part,
A method of manufacturing a light modulation element configured to generate diffracted light by driving the vibration unit,
A method of manufacturing a light modulation element, wherein the amount of inclination of the vibration part is maximized by controlling at least one of the width of the step in the vibration part width direction and the depth of the step. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing a light modulation element according to claim 14, wherein variations in the amount of inclination of the vibration portion due to variations in the etching depth of the step shape are minimized. Control at least one of the width of the step in the vibration part width direction and the depth of the step,
The method of manufacturing a light modulation element according to claim 14, wherein variation in the amount of inclination of the vibration portion due to variation in the etching width of the step shape is minimized. A laser display having a laser light source and a light modulation element that is arranged on the optical axis of the laser light emitted from the laser light source and modulates the light intensity of the laser light,
The light modulation element is:
A light modulation element comprising a lower electrode and a plurality of vibration parts, each vibration part having a step and tilting in the width direction of the vibration part, and causing the intensity modulation of diffracted light by driving the vibration part,
The width of the step is set such that the width of the step corresponds to a substantially maximum value of the amount of inclination of the vibrating portion. 18. The laser display according to claim 17, wherein a width of a step of the vibration part in the light modulation element is approximately ¼ or approximately ¾ of the width of the vibration part.

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