JP4397236B2 - Optical deflection apparatus, optical deflection array, image forming apparatus, and image projection display apparatus - Google Patents

Description

  The present invention relates to an optical deflection apparatus, an optical deflection array, an image forming apparatus, and an image projection display apparatus, and more particularly to an optical deflection apparatus that changes the direction of outgoing light with respect to incident light.

  The technology as an optical deflecting device that changes the reflection direction of light by displacing or deforming a mirror using electrostatic force is described in Larry J. There is a torsion beam type digital micromirror device (hereinafter abbreviated as DMD) disclosed by L. J. Hornbeck et al. This DMD uses a hinge having a mirror beam at the top as a rotation axis, and the beam is torsionally displaced by an electrostatic attraction generated by a potential difference with an opposing electrode through the space, and the reflection direction of the light beam incident on the mirror is changed. It is a device that changes and deflects light. Details of this DMD are described in Non-Patent Document 1. Further, Non-Patent Document 2 describes a projection-type image display device as a product using this DMD. Furthermore, Patent Document 1 discloses a manufacturing method related to DMD and a configuration of a mirror member and a hinge member. In Patent Document 1, the beam corresponds to a mirror, that is, a light reflection region. The hinge is disclosed as 75 nm thick and Al-1% Si-0.2% Ti, the beam contact metal is an aluminum alloy with a thickness of 300 nm, and the beam is disclosed as an aluminum alloy with a thickness of 400 nm. ing. It should be noted that the composition of the beam contact metal and the beam is not clarified. Therefore, the film thickness of the thickest part having such a configuration is 775 nm in total. Patent Document 1 does not disclose means for ensuring the flatness of the beam, which is a mirror, and there is no description regarding the elastic modulus and film stress of each member. The beam functioning as the light reflection region needs to have flatness, and it is assumed that the requirement is satisfied by increasing the film thickness to 400 nm.

  Next, as another prior art, there is a light valve using a diffraction grating. The diffraction grating light valves disclosed in Non-Patent Document 3 and Patent Documents 2 to 4 are called Grating Light Valves (hereinafter abbreviated as GLV), and each element has a plurality of elongated ribbons composed of two groups. This ribbon has a light reflection area on the upper surface, and the diffracted light is generated by changing the height of the ribbons in the two groups by the electrostatic attraction generated by the potential difference between the plurality of ribbons and the electrodes facing each other through the space. A device that modulates light by changing the intensity of reflected light. A projection-type image display device using GLV is disclosed in Patent Document 5. According to the GLV manufacturing method disclosed in Patent Document 3, a ribbon having a light reflecting region is configured to include an elastic material, a thin aluminum layer, and a thin dielectric layer. The elastic material is a silicon nitride film as a preferable material, and the film thickness and film stress are determined by the spring force for returning to the initial height after the ribbon is displaced. The thin aluminum layer is provided in order to increase the reflectance of the ribbon, and is preferably configured with a thickness of 100 nm or less. The thin dielectric layer is primarily intended to protect the underlying aluminum layer during the manufacturing process, and is intended to help suppress electromigration and mechanical distortion of the underlying aluminum layer during light deflection operations. It is preferable to be provided with a thickness of 50 nm or less.

  Further, in the DMD disclosed in Non-Patent Document 1, it is presumed that the flatness of the mirror surface is ensured by making the beam as thick as 400 nm. However, for this purpose, the thickest part of the hinge, beam contactor metal, and beam, which are members having a light reflecting region, is about 775 nm, and the total weight is also increased. Therefore, the optical response performance of the DMD is about 0.1 MHz, which has a problem that high-speed operation is difficult. In addition, due to the heavy weight, the thin film hinge is liable to be broken during the light deflection operation, and the long-term reliability is lowered. Furthermore, since an aluminum alloy is used as the material of the beam, if this beam is made into a thin film of about 200 nm, for example, the elastic modulus (meaning Young's modulus as a physical property value) of the aluminum alloy is as low as 100 GPa or less. And distortion during the optical deflection operation, reducing the flatness. That is, there is a problem that it is difficult to reduce the thickness of the mirror.

  On the other hand, in the GLV disclosed in Patent Documents 2 and 4, a ribbon having a light reflection region is composed of an elastic material, a thin aluminum layer, and a thin dielectric layer. However, since this GLV uses a both-ends fixed beam type ribbon, when the height of the ribbon is changed by electrostatic attraction, that is, when the ribbon is micro-elongated and deformed, for example, the elastic material has a high membrane stress. If the elastic modulus is particularly high, it becomes difficult for the ribbon to be deformed and displaced by electrostatic attraction, and the drive voltage increases. Conversely, in order to reduce the driving voltage, it is necessary to keep the film stress and elastic modulus of the elastic material, which is the main member of the ribbon, relatively low. In general, the residual film stress σ, elastic modulus (physical Young's modulus) E, and strain ε of a thin film have a relationship of ε = σ / E. When a silicon nitride film is used as the elastic material, the elastic modulus E is as high as 250 GPa or more, and the film stress σ needs to be as low as 0.1 GPa or less for low voltage driving. In this case, the strain amount ε inherent in the elastic material is reduced by the film stress σ. On the other hand, the elastic modulus E of the thin aluminum layer is generally as low as 100 GPa or less, and the film stress σ is generally as low as about 0.5 GPa, so that the strain amount ε of the aluminum layer is larger than that of the elastic material due to the film stress σ. Become. That is, a difference occurs in the strain amount between the elastic material and the thin aluminum layer. For example, when the thickness of the elastic material is as thin as about 200 nm, the difference in the amount of strain inherent in each film is caused as a bow of the ribbon film. Therefore, the GLV having a fixed end has a problem that the flatness of the ribbon is lowered. This problem can be solved by increasing the film thickness of the elastic material. In this case, however, there is a problem of increasing the drive voltage. As described above, since the operation of the GLV is accompanied by the elongation deformation of the ribbon, the elastic modulus and residual film stress of the members constituting the ribbon cannot be particularly increased due to the limitation of the driving voltage. Therefore, there is a problem that it is difficult to reduce the thickness of the ribbon while ensuring the flatness of the light reflection region.

  Next, FIG. 7 shows a configuration of a conventional optical deflecting device, where FIG. 7A is a plan view, and FIG. 7B is a cross-sectional view taken along line BB ′ of FIG. is there. However, the fulcrum member 103 and the electrodes 105a, 105b, 105c, and 105d are described in a transparent manner. A conventional optical deflection apparatus 100 shown in FIG. 7 is an optical deflection apparatus in which a light beam incident on the light reflection area is deflected by changing a reflection direction when a member having the light reflection area is displaced by electrostatic attraction. is there. The conventional optical deflection apparatus 100 includes a substrate 101, a plurality of four regulating members 102 in FIG. 7, a fulcrum member 103, a plate-like member 104, a plurality of electrodes 105, and four electrodes 105a in FIG. , 105b, 105c, 105d. Further, each regulating member 102 has a stopper 102-1 at the upper portion, and is provided at each of a plurality of ends of the substrate 101. The fulcrum member 103 has a top and is provided on the upper surface of the substrate 101. Further, the plate-like member 104 does not have a fixed end, has a light reflection region on the upper surface, has a conductive layer made of a conductive member at least in part, and has a substrate 101, a fulcrum member 103, and a stopper. It is movably arranged in the space between 102-1. The plurality of electrodes 105 a, 105 b, 105 c, and 105 d are provided on the substrate 101, respectively, and substantially face the conductor layer of the plate-like member 104. Such a conventional optical deflection apparatus 100 has the following advantages. That is, since the tilt angle is determined by the contact of the fulcrum member 103, the substrate 101, and the plate member 104, the control of the deflection angle of the mirror is easy and stable. In addition, since the thin plate member 104 is reversed at a high speed by applying different potentials to the opposing electrodes with the fulcrum member 103 as the center, the response speed can be increased. Furthermore, since the plate-like member 104 does not have a fixed end, it can be driven at a low voltage with little long-term deterioration without deformation such as torsional deformation. In addition, since the fine and lightweight plate-like member 104 can be formed by a semiconductor process, there is little impact due to collision with the stopper 102-1, and long-term deterioration is small. Furthermore, the ON / OFF ratio of reflected light, that is, the S / N ratio in the image equipment and the contrast ratio in the video equipment can be improved by arbitrarily determining the configuration of the regulating member 102, the plate-like member 104, and the light reflection area. In addition, since a semiconductor process and apparatus can be used, miniaturization and integration are possible at low cost. Furthermore, by arranging a plurality of electrodes around the fulcrum member 103, light deflection in the uniaxial and biaxial directions is possible.

  Next, FIG. 8 schematically shows how the conventional optical deflection apparatus is driven, and FIG. 9 shows a timing chart of potentials applied to the respective electrodes. FIG. 9 shows a state in which the plate-like member is tilted by driving, taking the conventional optical deflector of FIG. 7 as an example. FIG. 8 (a) shows an AA ′ of FIG. 7 (a) during the OFF operation. 8B is a cross-sectional view taken along the line CC ′ in FIG. 7A during the OFF operation, and FIG. 8C is a cross-sectional view taken along the line A- in FIG. A sectional view taken along line A ′, and FIG. 8D shows a sectional view taken along line CC ′ of FIG. 7A during the ON operation. A light deflection operation occurs by switching the potential applied to the electrodes 105a, 105b, 105c, and 105d shown in FIG. Further, in each of FIGS. 8A to 8D, the electrostatic attractive force generated by the potential applied to the electrodes 105a, 105b, 105c, and 105d is indicated by white arrows.

Hereinafter, based on FIGS. 8 and 9, the driving operation of the conventional optical deflection apparatus and the corresponding tilt displacement operation of the plate-like member 104, that is, the optical deflection operation will be described.
First, in the potential application combination in the OFF operation of FIG. 9, when a high potential a is applied to the electrode 105a, a low potential c is applied to the electrode 105b, and an intermediate potential b is applied to the electrode 105c and the electrode 105d, the conductor layer And the electrically floating plate member 104 facing the electrode group 105 is equal to the intermediate potential b as can be easily inferred from a simple closed circuit calculation. As a result, no electrostatic attractive force is generated on the ON-side electrodes 105c and 105d, and an electrostatic attractive force is generated on the OFF-side electrodes 105a and 105b as shown in FIG. Therefore, the plate-like member 104 is inclined and displaced to the OFF side. This operation may be not only a series of optical deflection operation OFF operations, but also a reset operation performed at the initial stage of the optical deflection operation. Next, in the potential application combination in the ON operation of FIG. 9, when a high potential a is applied to the electrode 105c, a low potential c is applied to the electrode 105d, and an intermediate potential b is applied to the electrodes 105a and 105b, The electrically floating plate-like member 104 having a body layer and facing the electrode group 105 becomes equal to the intermediate potential b as can be easily inferred from simple closed circuit calculations. As a result, no electrostatic attractive force is generated on the OFF-side electrodes 105a and 105b, and an electrostatic attractive force is generated on the ON-side electrodes 105c and 105d as shown in FIG. Therefore, the plate-like member 104 is inclined and displaced to the ON side. The plate member 104 of the conventional optical deflecting device is a single layer, but is not necessarily limited to a single layer, and may have a two-layer structure. In addition, the above-described driving operation of the conventional optical deflecting device and the corresponding tilt displacement operation of the plate-like member 104 have been described as a method of tilting and displace the electrically floating plate-like member 104. 103 is formed of a conductive member, and a potential is applied by contacting the plate-like member 104 via the fulcrum member 103, and the plate-like member 104 is inclined and displaced by electrostatic attraction between the opposing electrode groups 105. There is also a way to make it.

  As an advantage of the conventional optical deflection apparatus, the plate-like member 104 that contributes to optical deflection does not have a fixed end, and the optical deflection operation is not accompanied by deformation deformation of the plate-like member, that is, elongation deformation or torsional deformation. It is. That is, since the plate-like member in the conventional optical deflecting device performs the light deflection operation by the tilt displacement with the fulcrum member as the center, it is clear that the lighter the plate-like member, the lower the voltage can be driven. . In order to obtain a lightweight plate-like member, it is effective to reduce the thickness or size. However, since the size reduction is limited by the required mirror area, it is effective to reduce the thickness. However, easily reducing the thickness of the constituent members of the plate-shaped member may cause warpage of the plate-shaped member, that is, flatness deterioration, adhesion during the manufacturing process, and flatness deterioration during light deflection operation.

  Here, the problem due to the thinning of the plate-like member will be described in detail. First, the case where the plate-like member is a single layer film will be described. Since the plate-like member needs to have high reflectivity, an aluminum film or aluminum Most preferably, it is an aluminum alloy monolayer containing 90 weight percent. In that case, since the elastic modulus of the aluminum film (physical Young's modulus) is as low as 70 to 100 GPa, it is necessary to receive an excessive force on the film during the manufacturing process and during the optical deflection operation to ensure flatness. It becomes difficult.

Next, FIG. 10 shows an example of a manufacturing process of a conventional optical deflecting device. (A)-(i) of the same figure shows the manufacturing process of the conventional optical deflection | deviation apparatus shown in FIG. 7 along with a typical process, and is the BB 'sectional process drawing of (a) of FIG. It is.
First, as shown in FIG. 10A, a silicon oxide film constituting a fulcrum member 103 is deposited on a silicon substrate 101 by a plasma CVD method, and then a photo using a photomask having a density gradation property. A resist pattern having an arbitrary film thickness that is substantially the same as the shape of the fulcrum member 103 is formed by a plate making method or a photoengraving method in which heat deformation is performed after forming a resist pattern. It is formed. A silicon oxide film may be formed on the silicon substrate 101, and a part of the upper layer may be processed in the same manner. Next, as shown in FIG. 10B, electrodes 105a, 105b, 105c, and 105d are formed of a thin film of titanium nitride (TiN) film. The TiN thin film is formed by a DC magnetron sputtering method using Ti as a target, and patterned as a plurality of electrodes 105a, 105b, 105c, and 105d by a photoengraving method and a dry etching method. Then, as shown in FIG. 10C, a silicon oxide film is formed by plasma CVD as the protective film 106 for the electrodes 105a, 105b, 105c, and 105d. Next, as shown in FIG. 10 (d), an amorphous silicon film was deposited by sputtering, and planarized by the processing time control using the CMP technique. At this time, it is important to control the film thickness of the amorphous silicon film remaining on the top of the fulcrum member 103. The remaining amorphous silicon film is the first sacrificial layer 107. As the first sacrificial layer 107, a polyimide film, a photosensitive organic film (a resist film generally used in a semiconductor process), a polycrystalline silicon film, or the like can be used in addition to the amorphous silicon film. As a planarization method, a reflow method by heat treatment or an etch back method by dry etching can be used. Then, as shown in FIG. 10E, a plate-like member 104, which is a feature of the conventional optical deflection apparatus, is deposited and patterned. Since the plate-like member 104 has high light reflectivity and plays a role as a conductor layer, an aluminum film is deposited by a sputtering technique and patterned by a photolithography method and a dry etching method.

  Next, as shown in FIG. 10F, an amorphous silicon film was deposited by sputtering to form the second sacrificial layer 108. In addition to the amorphous silicon film, a polyimide film, a photosensitive organic film (a resist film generally used in a semiconductor process), a polycrystalline silicon film, or the like may be used as the second sacrificial layer 108. it can. Then, as shown in FIG. 10 (g), in order to separate the light deflection devices individually and arrange the regulating member 102 having the stopper 102-1 around the plate-like member 104, photolithography and dry etching are performed. By patterning, the first sacrificial layer 107 and the second sacrificial layer 108 are simultaneously patterned slightly wider than the plate-like member 104. Next, as shown in FIG. 10H, a silicon oxide film constituting the regulating member 102 having a stopper is deposited by a plasma CVD method, and patterned at an arbitrary position by a photoengraving method and a dry etching method. In addition, the regulating member 102 having the stopper 102-1 is not limited to the arrangement shown in FIG. 7, and may be a position that holds the plate-like member 104 in the restricted space. Then, as shown in FIG. 10I, the remaining first sacrificial layer 107 and second sacrificial layer 108 are removed by etching through the openings by wet etching, and the movable range of the plate member 104 is limited. The conventional light deflection apparatus is completed by arranging in the formed space. Note that etching of the sacrificial layer is not limited to wet etching, but can be performed by dry etching depending on the type of the sacrificial layer. Further, since the sacrificial layer is etched in the direction of the substrate plane, it is important to optimize the material of the plate-like member 104 with a material that is difficult to etch.

In such a manufacturing process, particularly in the etching of the first sacrificial layer 107 and the second sacrificial layer 108 shown in FIG. 10I, when the plate-like member 104 is the above-mentioned aluminum-based film single layer, the thickness is 200 nm or less. If it is a thin film, the aluminum-based single layer film will cause a defect (adhesion) sticking to the protective film 106 and the regulating member 102 in the sacrificial layer wet etching process. Therefore, when the plate-like member 104 is formed of the above-described aluminum-based film single layer, it is preferable that the thickness is about 400 to 500 nm.
Patent 3,383,031 specification Patent No. 2,941,952 Patent No. 3,016,871 Patent No. 3,164,824 JP 2002-131838 A Proc. SPIE Vol.1150, pp.86-102 (1989) "A MEMS-Based Projection Display" PROCEEDINGS OF THE IEEE. VOL.86, N0.8, AUGUST 1998, page 1687-1704 Optics Letters, Vol.7, No.9, pp688〜pp690

  However, when the plate-like member is a thin film, a problem may occur during the light deflection operation. This defect will be described. FIG. 11 is a cross-sectional view showing a state of a defect that has occurred after the ON operation, and is a cross-sectional view taken along line B-B ′ of FIG. In FIG. 11, after the ON operation, the inclined plate-like member 104 comes close to the portion facing the electrodes 105c and 105d. Therefore, a relatively large electrostatic attractive force acts. At this time, when an aluminum-based single layer film having a relatively low elastic modulus is used as the plate-like member 104 with a thin film having a thickness of 200 nm or less, the plate-like member 104 bends as shown in FIG. A phenomenon that does not return to the original state after refusal, generally a phenomenon of sticking, occurs. Therefore, the flatness of the plate-like member 104 is deteriorated. As described above, this is a problem when the plate-like member is formed of a single layer and is thinned. Needless to say, this problem is not limited to a single layer film but also a multilayer film.

Next, a problem that becomes prominent when the plate-like member is a multilayer will be described below. Note that a case in which the film is typically formed of two layers and thinned will be described as an example.
In general, a film deposited on an arbitrary substrate has a residual stress in the film depending on the difference in thermal expansion coefficient with the substrate, the deposition method, the temperature during deposition, and the bonding state of elements in the film. . The residual film stress or film stress described later represents this. The residual film stress is ideally desired to be uniform in the film thickness direction, but may be non-uniform in the film thickness direction depending on the deposition method. Furthermore, this film has a specific Young's modulus depending on its composition and deposition technique. The elastic modulus described later represents this. Since a film having a specific elastic modulus has a residual film stress, as shown in the above-described ε = σ / E, the film has inherent strain. The amount of distortion described later represents this. The conventional optical deflector of FIG. 7 is characterized in that the plate-like member 104 does not have a fixed end. In the etching of the sacrificial layer in FIG. When the second sacrificial layer 108 is removed by etching, the plate-like member 104 is released from the strain and stretched according to the film stress and the elastic modulus. At this time, unless the film stress is non-uniform in the film thickness direction, the single-layer film releases the strain uniformly, so that the plate-like member 104 does not greatly warp. That is, the flatness does not deteriorate. On the other hand, when the plate-like member 104 is composed of two layers, each film releases the amount of strain according to the elastic modulus and film stress of each film. FIG. 12 schematically shows a state in which the plate-like member is composed of two layers and the strain is released during the sacrifice layer etching. In FIG. 12, when the constituent films 201 and 202 have elastic moduli E1 and E2 and residual tensile stresses σ1 and σ2, respectively, the respective strain amounts are σ1 / E1 and σ2 / E2. As shown by the size of the white arrow, when the constituent film 201 is larger, the plate-like member receives a bending moment as shown by the black arrow in FIG. 12, and warps to the 201 side. It becomes. That is, the flatness of the plate member is reduced. This defect becomes more prominent as the total film thickness of the plate-like member becomes thinner. For example, when the total film thickness is 300 nm or less, it is considered an important problem.

  The present invention is for solving these problems, the optical deflecting device, which can be thinned while ensuring the flatness of the plate-like member of the optical deflecting device, achieve a lightweight mirror, and can achieve low voltage driving, An object is to provide a light deflection array, an image forming apparatus, and an image projection display apparatus.

In order to solve the above problems, the optical deflection apparatus of the present invention includes a substrate, a plurality of regulating members, a fulcrum member, a plate member, and a plurality of electrodes. Each of the plurality of restricting members has a stopper at the top, and is provided at each of the plurality of end portions of the substrate. The fulcrum member has a top and is provided on the upper surface of the substrate. Further, the plate-like member does not have a fixed end, is disposed so as to contact the top of the fulcrum member, has a light reflection region on the upper surface, and has a conductor layer made of a conductive member at least partially. and is movably arranged in the space between the substrate and the fulcrum member and the stopper, the plurality of electrodes are provided on the substrate substantially opposite the conductive layer of the plate member. In the optical deflecting device of the present invention having such a configuration, the plate-like member is tilted and displaced by electrostatic attraction around the fulcrum member, so that the light beam incident on the light reflecting region changes the reflection direction and deflects the light. . Furthermore, in the optical deflecting device of the present invention, the plate-like member is constituted by a two-layer laminated structure of a first film having elasticity and a second film having a reflecting surface , and the film stress of the first film. The direction of the second film stress and the direction of the second film stress are the same, and the amount of strain caused by the film stress of the first film is equal to the amount of strain caused by the film stress of the second film. . Therefore, the reflected light with respect to the incident light can be efficiently reflected by the second film, and the deformation of the plate-like member during the manufacturing process or the light deflection operation, that is, the decrease in flatness can be suppressed by the first film. Therefore, it is possible to provide a thin-film optical deflecting device that achieves both high reflectivity and high flatness.

In the optical deflecting device of the present invention, the plate-like member has a laminated structure of a first film having elasticity , a second film having a reflecting surface , and at least one strain amount adjusting film. The direction of the film stress of the first film is the same as the direction of the second film stress, and the direction of the film stress of the strain adjustment film is opposite to the direction of the first and second film stresses, It is characterized in that the difference between the strain amount caused by the film stress of the first film and the strain amount caused by the film stress of the second film is offset by the strain amount caused by the film stress of the strain amount adjustment film. Therefore, it is possible to provide a light deflecting device having a higher planarity and a thin film by eliminating a slight displacement of the strain amount of the first film or the second film.

Furthermore , by using a silicon nitride film, an aluminum nitride film, an aluminum alloy nitride film, a chromium film or a chromium alloy film as the first layer , a plate member having high tensile stress can be provided, and the plate member can be made thin. In addition, high flatness can be ensured.

Further, by using a silicon oxide film or a chromium oxide film as a strain amount adjusting film, it is possible to provide a distortion amount adjustment film having a low compressive stress, the film thickness in any order of the first film and the second film Can be laminated, and thus the planarity of the plate-like member can be improved.

  Another feature of an optical deflection array according to another invention is that a plurality of the optical deflection devices described above are arranged in a one-dimensional or two-dimensional array on an arbitrary substrate. Therefore, an optical deflection array that can be driven at a low voltage can be provided.

  Furthermore, an image forming apparatus as another invention is characterized in that the above-described optical deflection array is used as an optical writing unit which is a line exposure type latent image forming means. Therefore, an image forming apparatus that can be driven at a low voltage can be provided.

  According to another aspect of the present invention, an image projection display device is characterized in that the light deflection array described above is used as a display unit that reflects a light beam from a light source in a target direction according to image information.

  According to the present invention, the planarity of the plate-like member can be improved by optimizing the film type and film characteristics (elastic modulus and film stress) constituting the plate-like member of the light deflection apparatus and adjusting the strain amount of each film. The film can be thinned while being secured. As a result, it is possible to provide a light deflecting device that is lightweight, and to reduce the driving voltage for tilting displacement of the light deflecting device that does not have a fixed end, and to provide a thin film light deflecting device that achieves both high reflectivity and high flatness. And low voltage drive can be achieved.

According to the present invention, a conductor layer made of a member that does not have a fixed end and is disposed so as to be in contact with the top of the fulcrum member, has a light reflection region on the upper surface, and has conductivity at least partially. and a movably arranged plate-shaped member in the space between the substrate and the fulcrum member and the stopper, a first film having elasticity, a stacked structure of two layers of the second film having a reflective surface The amount of strain caused by the film stress of the first film, the direction of the film stress of the first film being the same as the direction of the film stress of the first film, and the strain caused by the film stress of the second film Make the amount equal.

  FIG. 1 is a diagram showing a configuration of an optical deflecting device according to a first embodiment of the present invention. FIG. 1 (a) is a plan view, and FIG. 1 (b) is a diagram of FIG. It is a BB 'line sectional view. However, the fulcrum member 103 and the electrodes 105a, 105b, 105c, and 105d are described in a transparent manner. 1, the same reference numerals as those in FIG. 7 denote the same components. The optical deflecting device 300 of this embodiment shown in FIG. 1 has a first member 302 having a high elastic modulus as a component different from the conventional optical deflecting device shown in FIG. The second member 303 is composed of two layers. Further, the amount of strain caused by the film stress of the first member 302 having a high elastic modulus and the amount of strain caused by the film stress of the second member 303 having a high reflectance constituting the plate-like member 301 are as follows. Almost the same. Further, a silicon nitride film, an aluminum nitride film or an aluminum alloy nitride film, or a chromium film or a chromium alloy film is used as the first member 302 having a high elastic modulus. The configuration and the manufacturing method of the optical deflecting device of this embodiment are the same as those of the conventional optical deflecting device shown in FIG.

  In FIG. 2, the plate-like member 301 is configured by stacking a second member 303 having a high reflectance and a first member 302 having a high elastic modulus. By adopting such a configuration, a mirror having high reflectivity can be formed with a thin film having a total film thickness of 300 nm or less while ensuring flatness. The reason why a member having a high elastic modulus can suppress adhesion during a manufacturing process, sticking during a light deflection operation, and poor flatness will be briefly described below. As described above, the elastic modulus is Young's modulus, and the high elastic modulus is 200 GPa or more. The above-mentioned ε = σ / E does not correspond only to the residual film stress in the film, but can also represent strain with respect to an external force. That is, when the elastic modulus of the film is doubled for a certain external force, the strain is halved. That is, deformation can be suppressed accordingly, and this is the reason for suppressing the above-described poor flatness.

  Next, Table 1 below lists the elastic modulus and film stress of a film used as a film having a high elastic modulus, and the amount of strain calculated from the above-mentioned ε = σ / E.

In Table 1, + of the film stress indicates tensile stress, and-indicates compressive stress. Further, + of the strain amount is a strain amount acting on the contraction direction due to the tensile stress, and-is a strain amount acting on the stretch direction due to the compressive stress. The film stress is a stress value after undergoing a thermal process in the manufacturing process after deposition of the first member 302 and the second member 303. In Table 1 above, the aluminum nitride film 1 is a film formed by reactive sputtering with a mixed gas of Ar and N ² using aluminum as a target by a DC magnetron sputtering method. The aluminum nitride film 2 is a film formed by reactive sputtering using a mixed gas of Ar and N ^{2 with} an aluminum 3 titanium 1 alloy (Al ³ Ti) as a target by a DC magnetron sputtering method. The aluminum nitride film 3 is a film formed by reactive sputtering with a mixed gas of Ar and N ² using an aluminum-neodymium alloy as a target by a DC magnetron sputtering method. Further, the silicon nitride film 1 is a film formed at a high temperature of 830 ° C. using silane and ammonia gas as raw materials by a low pressure CVD method. The silicon nitride film 2 is a film formed at a low temperature of 300 ° C. using silane and ammonia gas as raw materials by a low-temperature high-density plasma CVD method. The chromium film is a film formed by sputtering with Ar gas using chromium as a target by a DC magnetron sputtering method. As described in Table 1 above, a member having an arbitrary elastic modulus of 200 to 380 GPa can be provided. In addition to this member, an aluminum oxide film having a high elastic modulus of 400 GPa and a silicon carbide film having a high elastic modulus of 450 GPa can be used as necessary. The film | membrane which has the high elasticity modulus of the said Table 1 is used by the film thickness of 250 Nm or less.

  Next, Table 2 below shows the amount of strain calculated from the reflectance, elastic modulus, film stress, and ε = σ / E of the film used as a film having a high reflectance.

Here, the reflectance is a relative value in which the reflectance with respect to incident light with a wavelength of 400 to 800 nm of an aluminum film generally used as a highly reflective mirror film is 100%. The elastic modulus and film stress are the same as in Table 1. The aluminum film is a film formed by sputtering with Ar gas using aluminum as a target by a DC magnetron sputtering method. The aluminum alloy film 1 is a film formed by sputtering with Ar gas using an aluminum-silicon alloy as a target by a DC magnetron sputtering method. The aluminum alloy film 2 is a film formed by sputtering with Ar gas using an aluminum-neodymium alloy as a target by a DC magnetron sputtering method. While the film described in Table 2 has a high reflectance of 97% or more, several strains due to the film stress can be selected. The film having a high reflectance is not limited to the film composition described in Table 2 above. For example, an aluminum-silicon-copper alloy film, an aluminum-silicon-titanium alloy film, or an aluminum-titanium alloy film may be used. By selecting each composition, the amount of strain due to film stress can be arbitrarily selected from 3.0 to 6.0 × 10 ⁻³ while ensuring high reflectance. The film having high reflectivity is formed with a film thickness of 30 nm or more in order to ensure reflectivity, and is used with a film thickness that makes the total film thickness of the plate-like member 300 nm or less. The film having high reflectivity also has conductivity, which is a requirement required for the plate-like member of the optical deflecting device of this embodiment, due to being an aluminum-based alloy film. . Table 3 below shows the configurations of specific examples 1 and 2 and the actual warpage of the plate-like member in the optimum combinations from Tables 1 and 2 above. In Table 3, the warpage of the plate-like member is 10 μm × 10 μm, which is a typical mirror size after the plate-like member having no fixed end, which is a feature of the optical deflector, is released after the sacrifice layer etching. It is the value which measured the curvature amount of the plate-shaped member of a magnitude | size.

  In Specific Example 1, the chromium film described in Table 1 and the aluminum film described in Table 2 were used as the first member 302 and the second member 303 of the plate-shaped member 301. In Specific Example 2, the chromium film described in Table 1 was used. The silicon nitride film 1 and the aluminum alloy film 1 listed in Table 2 were used as the first member 302 and the second member 303 of the plate member 301. By adopting a configuration in which the amount of strain caused by the film stress is the same for both members, there is no difference in the amount of strain in the laminated film as schematically shown in FIG. No black arrow) occurred, and the warpage amount of the plate-like member (the definition of the warpage amount is shown in FIG. 12) was as small as 0.1 μm or less.

  As the film having a high elastic modulus, a chromium film having conductivity, an aluminum nitride film having insulation, and a silicon nitride film are selected as necessary.

  Next, FIG. 3 is a diagram showing a configuration of an optical deflection apparatus according to the second embodiment of the present invention, in which (a) of FIG. 3 is a plan view, and (b) of FIG. It is BB 'sectional view taken on the line of a). However, the fulcrum member 103 and the electrodes 105a, 105b, 105c, and 105d are shown in a transparent manner. The main difference from the first embodiment is that the plate member 401 has a first member 402 having a high elastic modulus, a second member 403 having a high reflectance, and a strain amount adjusting member 404 having at least one layer. The difference in the amount of distortion within or between each member constituting the plate-like member 401 is corrected by the strain amount of the strain amount adjusting member 404. Further, a silicon oxide film or a chromium oxide film is used as the strain amount adjusting member 404. In FIG. 3, the strain amount adjusting member 404 is provided between the first member 402 and the second member 403, but it may be an upper layer of the first member 402 or the second member 403. It may be a lower layer. Further, it is not always necessary to have one layer. In the first embodiment described above, the planarity of the plate-like member 301 is improved by making the amount of strain of the first member 302 having a high elastic modulus and the second member 303 having a high reflectance substantially equal. However, there may be a case in which the improvement is not necessarily achieved only by matching the strain amounts of the first member 302 and the second member 303. For example, this is a case where the first member 402 and the second member 403 have a distribution of film stress in the respective film thickness directions depending on the deposition means and film type. This tendency becomes conspicuous when the difference in thermal expansion coefficient from the base substrate is large. When the film thickness of the first member 402 and the second member 403 is reduced to, for example, 100 nm or less, the influence becomes large. It may not be improved only by the configuration. Further, there may be a case where the amount of distortion of the first member 402 and the second member 403 is slightly shifted. In such a configuration, the strain amount adjusting member 404 is disposed in order to suppress the warpage of the plate-like member 401. As can be seen from Table 2 above, when an aluminum-based alloy is used as the second member 403 having a high reflectance, the film has a low tensile stress. The first member 402 having a high elastic modulus is also desired to have a relatively strong tensile stress as described above. That is, it is preferable that both the first member 402 and the second member 403 are composed of tensile stress members, and it is desirable that the film stress has a compressive stress as an effective film for adjusting the amount of strain. . That is, the strain amount adjusting member 404 is preferably a film having a compressive stress. Table 4 below shows the configuration of specific example 3 using a chromium oxide film as a strain amount adjusting member and the configuration of specific example 4 using a silicon oxide film and the amount of warpage of the plate member.

In Table 4, the layer of the first member 402 and the layer of the second member 403 of the specific example 3 are the same film type as each layer of the first example of the specific example 1, and the layer of the second member 403 This shows a case where the film thickness of the film is reduced. Further, the layer of the first member 402 and the layer of the second member 403 in Example 4 are the same film type as each layer of Example 2 described above, and the film thickness of the layer of the second member 403 is reduced. Shows the case. The warpage of the plate-like member 401 in Table 4 is based on the same evaluation means as in Table 3. It can be seen that in both the specific example 3 and the specific example 4, the warpage is suppressed to about 0.1 μm regardless of the total film thickness of the plate-like member 401 being about 150 nm. The chromium oxide film of the strain amount adjusting member 404 used in the specific example 3 is a film formed by reactive sputtering using a mixed gas of Ar and O _{2 with} chromium as a target by RF magnetron sputtering. It is a film having a high compressive stress of about 0 GPa as a film stress. This film is not only a very thin film and the amount of strain can be adjusted, but when a chromium film is used as a film having a high elastic modulus, there is an advantage that it can be processed by the same wet etching. The silicon oxide film of the strain amount adjusting member 404 used in the specific example 4 is a film deposited at a film forming temperature of 300 ° C. using silane dioxygen dioxide gas as a raw material by a plasma CVD method, and is −0.4 GPa. It is a film having a low compressive stress as a film stress. Since this film has a relatively low stress value, there is an advantage that the strain amount adjustment can be easily controlled by the film thickness. According to FIG. 3B schematically showing the effect of disposing the strain adjusting member, the film thickness distribution of the film stress of the first member 402 having a high elastic modulus that becomes conspicuous by thinning is adjusted for the amount of strain. By arranging and canceling the member 404, the bending moment is not generated and the warp is suppressed. Since the warpage suppression by the strain amount adjusting member is suppressed when the total film thickness of the plate-like member is small, that is, suppression in the thin film, optimization of the film thickness is important.

  Next, FIG. 4 is a plan view showing the configuration of an optical deflection array according to another embodiment of the present invention. An optical deflection array according to the present invention is obtained by arranging a plurality of the optical deflection devices described above in a one-dimensional or two-dimensional array. FIG. 4A is a plan view of an optical deflection array in which a plurality of the optical deflection devices of FIG. 1 are arranged in a line in a direction perpendicular to the optical deflection surface direction, that is, a one-dimensional array. . FIG. 4B is a plan view of a light deflection array in which a plurality of the light deflection devices in FIG. 1 are aligned in the direction perpendicular to the light deflection surface and arranged in an array, that is, a two-dimensional array. Thus, by arranging a plurality of the above-described optical deflection devices in a one-dimensional or two-dimensional array, an optical deflection array that can be driven at a low voltage can be provided.

  Next, FIG. 5 is a schematic sectional view showing the structure of an image forming apparatus according to an embodiment of another invention. The image forming apparatus 500 of this embodiment shown in the figure uses the optical deflection array 503 that is the optical deflection array shown in FIG. 4 as the optical writing unit 502 that is a line exposure type latent image forming means. An image forming apparatus 500 that forms an image by performing optical writing by an electrophotographic process holds the formed image so as to be rotatable in the direction of arrow D in the figure, and includes an image carrier 501 that is a drum-shaped photoconductor. A latent image is formed by performing optical writing on the image carrier 501 that is uniformly charged by the charging unit 504 by the optical writing unit 502 including the optical deflection array 503. The latent image is formed as a toner image on the image carrier 501 by the developing unit 505, and then the toner image is transferred to the transfer target 507 by the transfer unit 506, and the toner image transferred to the transfer target 507 is transferred. After fixing by the fixing unit 508, the transfer target 507 is discharged onto the discharge tray 509 and stored. On the other hand, the image carrier 501 after the toner image is transferred to the transfer target 507 by the transfer unit 507 is cleaned by the cleaning unit 510 to prepare for image formation in the next process. The optical writing unit 502 irradiates the light deflection array 503 with the incident light beam 512 from the light source 511 via the first lens system 513, and each light deflection device is tilted and displaced in accordance with the image information to change the reflected light direction. The incident light beam 512 is imaged on the surface of the image carrier 501 through the second lens system 514. As described above, by using the optical deflection array shown in FIG. 4 as an optical writing unit, an image forming apparatus capable of low voltage driving can be provided.

  Next, FIG. 6 is a schematic diagram showing the configuration of an image projection display device according to another embodiment of the present invention. The image projection display device 600 uses the light deflection array shown in FIG. 4 as a display unit 603 that reflects the light beam 608 from the light source 601 in a target direction according to image information. In FIG. 6, a light source 601 is a cheap light source such as a white light source as compared with a laser light source. The optical system 602 is an illumination optical system that guides the light beam 608 from the light source 601 to the light deflection array 603. The optical deflection array 603 is the optical deflection array shown in FIG. Projection optical systems 604 and 605 are projections for enlarging and projecting light beams deflected in a target direction by a light deflection array 603 arranged two-dimensionally corresponding to the vertical pixel columns and the horizontal pixel columns of the display screen. It is an optical system. The control system 606 is a control system that controls the operation of the light deflection array 603 and is configured by an electronic circuit. Although a part of a light beam 608 indicated by a dotted line is shown in the drawing, the light emitted from the light source 601 is guided onto the light deflection array 603 by the illumination optical system 602, and the light beam deflected by the light deflection array 603 is projected optically. Projected as a two-dimensional image by the systems 604 and 605. In FIG. 6, a rotating color wheel 607 is used to select the wavelength of the incident light beam guided to the light deflection array 603. As described above, according to the image projection display device of the present invention, since the above-described light deflection array is used as a display unit, low voltage driving is possible.

  Each invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

It is a figure which shows the structure of the optical deflection | deviation apparatus based on 1st Example of this invention. It is sectional drawing which shows the structure of a plate-shaped member. It is a top view which shows the structure of the optical deflection | deviation apparatus based on 2nd Example of this invention. It is a top view which shows the structure of the optical deflection | deviation array which concerns on one Example of another invention. It is a schematic sectional drawing which shows the structure of the image forming apparatus which concerns on one Example of another invention. It is the schematic which shows the structure of the image projection display apparatus which concerns on one Example of another invention. It is a figure which shows the structure of the conventional optical deflection | deviation apparatus. It is a figure which shows the mode of the drive of the conventional optical deflection | deviation apparatus. It is a figure which shows the relationship between the timing of the electric potential applied to each electrode, and the inclination displacement of a plate-shaped member. It is process sectional drawing which shows an example of the manufacturing process of the conventional optical deflection | deviation apparatus. It is sectional drawing which shows the mode of the malfunction which occurred after ON operation. It is sectional drawing which shows a mode that the plate-shaped member was comprised by 2 layers and distortion was released at the time of sacrificial layer etching.

Explanation of symbols

300; light deflection device; 301, 401; plate-like member;
302, 402; first member, 303, 403; second member,
304, 404; distortion amount adjusting member, 500; image forming apparatus,
503, 603; light deflection array, 600; image projection display device.

Claims (7)

A substrate, a plurality of restricting members, a fulcrum member, a plate-like member, and a plurality of electrodes, each of the plurality of restricting members having a stopper on the top and provided at each of a plurality of ends of the substrate The fulcrum member has a top and is provided on the upper surface of the substrate, the plate-like member does not have a fixed end and is disposed so as to contact the top of the fulcrum member , and has a light reflection region on the upper surface. A conductive layer made of a conductive member at least partially, and is movably disposed in a space between the substrate, the fulcrum member, and the stopper, and the plurality of electrodes are in the form of a plate The plate member is provided on the substrate substantially opposite to the conductor layer of the member, and the plate member is inclined and displaced by electrostatic attraction around the fulcrum member, so that the light beam incident on the light reflecting region changes the reflection direction. In an optical deflection device that deflects light Te,
The plate-like member, the first and the membrane, consists of a two-layer structure of the second film having a reflecting surface, orientation as the second layer of film stress of the first film having an elastic and the amount of distortion direction of stress caused by the film stress of the first film have the same light deflecting device, characterized in that equal the amount of distortion caused by the film stress of the second film. A substrate, a plurality of restricting members, a fulcrum member, a plate-like member, and a plurality of electrodes, each of the plurality of restricting members having a stopper on the top and provided at each of a plurality of ends of the substrate The fulcrum member has a top and is provided on the upper surface of the substrate, the plate-like member does not have a fixed end and is disposed so as to contact the top of the fulcrum member , and has a light reflection region on the upper surface. A conductive layer made of a conductive member at least partially, and is movably disposed in a space between the substrate, the fulcrum member, and the stopper, and the plurality of electrodes are in the form of a plate The plate member is provided on the substrate substantially opposite to the conductor layer of the member, and the plate member is inclined and displaced by electrostatic attraction around the fulcrum member, so that the light beam incident on the light reflecting region changes the reflection direction. In an optical deflection device that deflects light Te,
The plate-like member has a laminated structure of a first film having elasticity , a second film having a reflective surface , and at least one strain amount adjusting film, and the film stress of the first film And the direction of the second film stress is the same, and the direction of the film stress of the strain adjustment film is opposite to the direction of the first film stress and the second film stress. An optical deflection apparatus characterized in that the difference between the strain amount caused by the film stress of the second film and the strain amount caused by the film stress of the second film is offset by the strain amount caused by the film stress of the strain amount adjustment film.   3. The optical deflecting device according to claim 1, wherein a silicon nitride film, an aluminum nitride film, an aluminum alloy nitride film, a chromium film, or a chromium alloy film is used as the first film.   The optical deflection apparatus according to claim 2, wherein a silicon oxide film or a chromium oxide film is used as the strain amount adjusting film.   An optical deflection array comprising a plurality of optical deflection devices according to claim 1 arranged in a one-dimensional or two-dimensional array on an arbitrary substrate.   6. An image forming apparatus, wherein the optical deflection array according to claim 5 is used as an optical writing unit which is a line exposure type latent image forming means.   6. An image projection display device, wherein the light deflection array according to claim 5 is used as a display unit that reflects a light beam from a light source in a target direction according to image information.

Images