KR100689159B1 - Spring-ring micromechanical device - Google Patents

Abstract

The micromachine of the present invention comprises a substrate 104, a rigid deflectable member 302, 314, 326 suspended on the substrate, and at least one spring 328 supported on the substrate and spaced apart from the rigid deflectable member. It is provided. The spring resists deflection of the rigid deflectable member when the rigid deflectable member is deflected and in contact with the spring. The micromachine of the present invention manufactures at least one support structure 116 on a substrate, manufactures at least one spring spaced from the substrate and suspended by at least one of the at least one support structures, the substrate and the spring. By fabricating a deflectable member spaced apart from and suspended by at least one of the at least one support structures. The micromechanical apparatus of the present invention is useful in a projection display system in which the micromirror device selectively reflects incident light as directed by a controller electrically connected thereto and the selectively reflected light is focused on an image plane. The micromirror device comprises an array of micromirror elements each comprising a substrate, a spring supported by the substrate, and a deflectable member supported by the substrate and spaced from the spring. The rigid deflectable member includes a mirror that is deflected toward the spring, the spring resists deflection of the rigid deflectable member.

 Micromachines, deflectable members, springs, elastic strips, mirrors, torsion beam yokes

Description

Micro machinery and its manufacturing method {SPRING-RING MICROMECHANICAL DEVICE}

1 is a perspective view of a portion of a micromirror array according to the prior art;

FIG. 2 is an enlarged perspective view of a single micromirror element from the micromirror array shown in FIG. 1; FIG.

3 is a perspective view of a portion of a spring ring according to an embodiment of the present invention.

4 is an enlarged perspective view of a single micromirror element from the micromirror array shown in FIG.

FIG. 5 is a side view of the single micromirror element shown in FIG. 4, showing that the rotation of the rigidly deflectable member of the micromirror element is stopped by a spring ring prior to contact with the mirror bias / reset metallization layer. FIG.

FIG. 6 is a side view of the single micro-mirror element shown in FIG. 4, illustrating the deformation of the spring ring by rotation of the rigid deflectable member before rotation is stopped by contact between the mirror and the mirror bias / reset metallization layer. FIG. drawing.

FIG. 7 is a side view of the single micro-mirror element shown in FIG. 4, illustrating deformation of the spring ring by rotation of the rigid deflectable member before rotation is stopped by contact between the torsion beam yoke and the mirror bias / reset metallization layer. Figure shown.

8 is an enlarged perspective view of a single microelement with a thick spring extension fabricated on the torsion beam cap.

9 is an enlarged perspective view of a single microelement with a thin spring extension fabricated on a torsion beam cap;

FIG. 10 is an enlarged perspective view of a single microelement with a thin middle portion and a thin spring extension with a thick end; FIG.

11 is an enlarged perspective view of a single micro device with a twist ring spring structure.

12 is a cross sectional view of an antireflective coating on an address electrode and a mirror bias / reset metallization layer.

13 is a cross-sectional view of the spacer, metal and oxide layers used to fabricate the torsion beam supporting spacer vias, torsion beams, torsion beam yokes and spring rings of the spring ring miniature mirror array of FIG.

FIG. 14 is a plan view of the partially completed spring ring miniature mirror device of FIG. 4, showing the torsion beam etch stop, the torsion beam yoke etch stop, and the position of the etch stop used to form the torsion beam spacer via cap and spring ring. FIG. One drawing.

FIG. 15 is a plan view of the partially completed thick cap extension spring micro-mirror device of FIG. 8, used to form a torsion beam etch stop, a torsion beam yoke etch stop, a torsion beam spacer via cap and a thick spring cap extension. A figure which shows the position of an etching stop.

FIG. 16 is a plan view of the partially completed thin torsion beam cap extension spring micromirror of FIG. 9 with a torsion beam etch stop, a torsion beam yoke etch stop, a torsion beam spacer via cap etch stop, and a spring cap extension A figure which shows the position of a sub etching stop.

FIG. 17 is a plan view of the partially completed torsion beam cap extension spring micro-mirror device of FIG. 10 with a torsion beam etch stop, a torsion beam yoke etch stop, a torsion beam spacer via cap etch stop, and a spring cap extension etch Figure showing the position of the stop.

FIG. 18 is a plan view of the partially completed twist ring miniature mirror device of FIG. 11, showing the positions of the torsion beam etch stop, the torsion beam yoke etch stop, the torsion beam spacer via cap etch stop, and the twist ring etch stop. FIG. drawing.

FIG. 19 is a cross sectional view of the metal layers of FIG. 13 showing a state after patterning those metal layers and removing oxide and spacer layers. FIG.

FIG. 20 is an enlarged perspective view of a single micromirror device similar to the micromirror array of FIG. 3 but with a mirror bias / reset metallization layer that enables mirror addressing. FIG.

Figure 21 is a schematic diagram of a micromirror based projection system using an improved micromirror device in accordance with an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

104, 1104: substrate

116: torsion beam support spacer via

delete

302, 1602: mirror

310: address electrode

312, 612, 712: Mirror Bias / Reset Metallization Layer

314: torsion beam yoke

320: torsion beam hinge

322, 922: torsion beam cap

326: mirror support spacer via

328: spring ring

330: Nubs

332: ring structure

334 thin section

delete

834, 934: torsion beam cap extension

922: Torsion Beam Cap

936 edge

938 thin middle

940: thick end

1002: antireflective coating

1102: spacer layer

1106: thin metal layer

1108, 1112: oxide layer

1110, 1208: thick metal layer

1202, 1204, 1206, 1208, 1210, 1212, 1214, 1216, 1220, 1222: Etch stop

1600: Image Projection System

1604: light source

1606: Lens

1608: Optical Trap

1610: projection lens

1612: image plane or screen

1614: controller

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to micromechanical devices, and more particularly to micromechanical devices having deflectable members, and more particularly to digital micromirror devices (DMDs). will be.

Micromachines are devices that use techniques such as optical lithography, doping, metal sputtering, oxide deposition, and plasma etching developed for the manufacture of integrated circuits. A small structure typically fabricated on a semiconductor wafer.

Digital micromirror devices (DMDs), sometimes referred to as deformable micromirror devices, are one form of micromechanical devices. Other types of micromachines include accelerometers, pressure / flow sensors, gears, and motors. Some micromechanical devices such as pressure sensors, flow sensors and DMDs have been commercially successful, while other types of micromechanical devices have not yet been commercially implemented.

Digital subminiature mirror devices are mainly used in optical display systems. In a display system, a DMD is an optical modulator that modulates a light beam by selectively reflecting a portion of the light beam towards the display screen using digital image data. Although operating in analog mode of operation, the DMD typically operates in digital bistable mode of operation, which is a key element in the first true full-color image projection system.

Micromirror devices have developed rapidly over the last 10 to 15 years. Early devices used a deformable reflective membrane that, when electrostatically pulled toward its lower address electrode, dimpled toward that address electrode. Schlieren optics illuminate the membrane and produce an image from the light scattered by the dim portion of the membrane. Shrylene systems allow for image formation by membrane devices, but the resulting images are so faint that their contrast ratio is unsuitable for most image display applications.

Subsequent micromirror devices use flap or diving board-shaped cantilever beams of silicon or aluminum material combined with dark-field optical systems to produce images with improved contrast ratio. Created. The flap and cantilever beam device used a single metal layer to form the upper reflective layer. However, this single metal layer tends to deform over a large area and scatter light reaching the deformed portion. Torsion beam devices use a thin layer of metal to form a torsion beam called a hinge, and a thick layer of metal typically uses a rigid-like surface with a mirror-like surface. member) or by forming a rigid beam, which concentrates the deformation on a relatively small portion of the DMD surface. Thus, the rigid mirror remains flat while the hinge is deformed, so that the amount of light scattered by the device is minimized, thereby improving the contrast ratio of the device.

In recent miniature mirror structures of hidden-hinge configurations, the contrast ratio is further improved by manufacturing the mirror above the torsion beam. This upper mirror prevents incident light from impacting the torsion beam, the torsion beam support structure and the rigid yoke connecting the torsion beam and the mirror support structure. These support structures tend to scatter light impinging upon them with address electrodes and mirror bias / reset metalization on the device substrate, which scattered light reaches and projects the image screen. Reduces the contrast of the image. The hidden-hinge miniature mirror configuration improves the contrast ratio of the image by preventing most of the light from reaching their support structure.

Positioning the micromirror above the torsion beam and its supporting structure requires a support structure for spacing the torsion beam and the micromirror above it, typically for which a spacer via or a support column is fabricated. Spacer vias are hollow (ie hollow) hollow tubes of metal formed by depositing metal into holes in a sacrificial layer on which mirrors are fabricated. Since the top of this hollow spacer via is open, the surface area of the micromirror is reduced. In addition, there is a sharp edge on the open top of the spacer via, so that the incident light is diffracted to lower the contrast of the projected image.

In addition to improving the contrast of the projected image, micro-mirror designers must also improve the reliability of mirror resets. This mirror reset refers to an operation of restoring the micromirror to the neutral position after the micromirror is rotated to an on position or an off position. Some micromirrors tend to stick to the landing site due to various forces such as van der Waals forces generated by the intermetallic and water vapor present on the device surface. In a technique called dynamic reset, voltage pulses are used to excite the dynamic response of the micromirror and torsion beams, causing the mirror to spring up from the landing site and return to a neutral position.

Unfortunately, however, the amount of adhesion to the landing site of the mirror varies considerably. Sometimes a mirror that is weakly attached to the landing site is released from the landing site by a single reset pulse, but a strongly attached mirror requires several pulses to get enough energy to release from the landing site. A prematurely released mirror even before it gets enough energy may cause several problems. One of those problems is that a prematurely released mirror may be re-landed during the remaining dynamic reset period, if the prematurely released mirror lands very late during the remaining dynamic reset period, Enough energy for the second release from the site will not be available from the reset pulse. Another problem is that the prematurely released micromirror may tend to sway about the axis of the torsion beam, in which case the mirror bias voltage is applied again while the oscillating mirror is rotated toward the inappropriate address electrode. In this case, the mirror is electrostatically latched to the inappropriate address electrode, so that a dark pixel flashes intermittently.

It is therefore an object of the present invention to provide a micromirror device and a method of manufacturing the same, which can improve the contrast of the projected image and at the same time improve the reliability of the micromirror reset operation.

The above and other objects and advantages of the present invention will become apparent from the following description with reference to the drawings, in which they manufacture a micromechanical system and method comprising a spring-based restoring structure and its manufacturing method. Will be achieved by

The micromachine according to an embodiment of the present invention has a substrate, a rigid deflectable member suspended on the substrate, and at least one spring supported on the substrate and spaced apart from the rigid deflectable member, the spring being rigid And when the biasing member is in contact with the spring, an operation to resist the deflection of the rigidly deflectable member.

According to another embodiment of the present invention, a method of manufacturing a micromachined device includes manufacturing at least one support structure on a substrate, and manufacturing at least one spring spaced apart from the substrate and suspended by at least one of the support structures. And manufacturing a deflectable member spaced apart from the substrate and the spring and suspended by at least one of the support structures, wherein the deflectable member is movable in contact with the spring and the spring is no longer of the deflectable member. The operation can be performed to resist movement.

According to another embodiment of the present invention, a display system includes a light source capable of providing a light beam along an optical path, a micromirror device on the optical path, a controller electrically connected to the micromirror device, and a projection located in the projection optical path. A micromirror device comprising an array of micromirror elements, each micromirror device comprising a substrate, a spring supported by the substrate, and a deflectable member supported by the substrate and spaced from the spring; The rigid deflectable member may typically be deflected toward the spring as a mirror disposed in the optical path, which spring resists the deflection of the rigid deflectable member, and the controller applies an electrical signal to the micromirror device to provide a rigid deflectable member. Selectively deflects the selectively deflected rigid deflectable member to Thus selectively reflecting light, and the projection optics can focus the light reflected by the microscopic mirror device on the image plane.

For a more complete understanding of the present invention and its advantages, reference is now made to the following description with reference to the drawings.

According to the micromirror device of the present invention, the contrast ratio of the projected image is improved and the reliability of the mirror reset operation is improved, which is achieved by a spring provided between the micromirror and the substrate below. Although the spring is preferably metal, it is also possible to use an elastic member capable of storing energy upon contact with the deflectable member and upon deformation by the deflecting member. The spring resists movement of the deflectable member upon contact between the deflectable member and the spring, which contact may be through an intermediate member.

A typical hidden-hinge DMD 100 according to the prior art is an orthogonal array of DMD cells or devices, which may include thousands of row DMD devices and column DMD devices. 1 illustrates a portion of a DMD array according to the prior art, where several mirrors 102 are removed to show the mechanical structure of the underlying DMD array. 2 is an enlarged view of a single DMD device according to the prior art to further illustrate the relationship between DMD structures.

DMD is provided on a semiconductor typically silicon substrate 104. Electrical control circuits are typically provided in or on the surface of the semiconductor substrate 104 by standard integrated circuit fabrication processes. This control circuit typically includes memory cells associated with each mirror 102 and typically underneath each mirror 102 and digital logic circuitry for controlling digital data transfer to the memory cells. However, it is not limited to these. On the DMD structure there is also provided a voltage divider circuit for driving bias and reset signals for the mirror superstructure, which may be provided outside of the DMD. Image processing and formatting logic is also formed within the substrate 104 in some configurations. For purposes of explanation, the addressing circuitry shall comprise any circuit used for controlling the direction of rotation of the DMD mirror, for example direct voltage transfer means and a shared memory cell.

Some DMD configurations use a split reset configuration that allows several DMD devices to share a single memory cell, which reduces the number of memory cells required for operation of a very large array, thereby reducing the number of memory cells on a DMD integrated circuit. Provides more space that can be used for potentiometers and image processing circuitry. The division reset is enabled by the bistable operation of the DMD, allowing the contents of the lower memory to be changed without affecting the position of the mirror upon application of a bias voltage to the mirror 102.

The silicon substrate 104 and any necessary metal interconnect layers are insulated from the DMD superstructure by an insulating layer 106, which is typically a deposited silicon dioxide layer over which a DMD superstructure is formed. Holes or vias are formed in the silicon dioxide layer, allowing the DMD superstructure to be electrically connected with the electrical circuit formed in the substrate 104.

The first layer of the DMD structure is a metallization layer, which is typically referred to as M3 since it is typically the third metallization layer. Two metallization layers, first and second, are needed to interconnect the circuits provided on the substrate. The third metallization layer is deposited on the insulating layer and forms the address electrode 110 and the mirror bias / reset connecting means 112 by patterning. Some subminiature mirror configurations have other structures electrically connected to the landing electrodes separated from each other and to the mirror bias connection means 112. For illustrative purposes, a landing structure, such as a landing electrode, will be considered part of the device substrate. Thus, the contact between the deflectable structure and the landing site on the substrate is considered to be the contact between the deflecting structure and the substrate. The landing electrode limits the rotation of the mirror 102 to prevent the rotated mirror 102 or hinge yoke 114 from contacting the address electrode 110 with a voltage potential relative to the mirror 102. When the mirror 102 contacts the address electrode 110, the torsion beam hinge 120 may melt or the mirror 102 may melt on the address electrode 110 due to the resulting short circuit. In any case, the DMD becomes obsolete.

Since the same voltage is always applied to the landing structure and the mirror 102, it is preferable to combine the mirror bias connection means and the landing electrode into a single structure if possible. The combination between the landing electrode and the mirror bias connection means 112 refers to areas for mechanically limiting the rotation of the mirror 102 by contact with the mirror 102 or the hinge yoke 114, referred to as mirror bias connection means or landing site. By providing it on another area of the substrate. In some cases, the landing site may be coated with a material selected to reduce the tendency of the mirror 102 and torsion beam hinge yoke 114 to adhere to the landing site.

The transfer of the mirror bias / reset voltage to the mirror 102 is through a combination of the mirror bias / reset metallization layer 112 and paths using torsion beams of the mirror and adjacent mirror elements. In the split reset configuration, the array of mirrors must be divided into a plurality of sub arrays each having independent mirror bias connection means. The landing electrode / mirror bias 112 configuration shown in FIG. 1 is ideally suited for split reset applications, in which the DMD elements are electrically insulated by simply isolating the subarrays with a mirror bias / reset layer. Or because it can be easily separated into rows. Mirror bias / reset metallization layer 112 of FIG. 1 is divided into rows of mutually insulated mirrors.

The supporting members of the first layer, typically called spacer vias, are provided on the metal layer forming the address electrode 110 and the mirror bias connection means 112. These spacer vias include torsion beam support spacer vias 116 and top address electrode spacer vias 118, which typically have a thin spacer layer over the address electrodes 110 and mirror via connecting means 112. It is formed by rotary deposition. This thin spacer layer is typically a 1 μm thick positive photoresist layer. After depositing this photoresist layer, the layer is exposed and patterned and then cured with high UV to form holes. Spacers will later be formed in this hole. Such thin spacer layers and thick spacer layers used in subsequent manufacturing processes are called sacrificial layers because these layers are used only as a mold during the manufacturing process and are removed prior to device operation.

A thin metal layer is sputtered on the spacer layer and also in the hole. An oxide is then deposited on this thin metal layer, which is then patterned to form an etch mask over the area where the hinge 120 will later be formed. Next, a thick metal layer of aluminum alloy is typically sputtered over the thin metal layer and the oxide etch mask. Another oxide layer is then deposited and patterned to define hinge yoke 114, hinge cap 122, and top address electrode 124. After patterning this second oxide layer, two rigid metal layers are etched simultaneously and the oxide etch stop is removed to form a thick rigid hinge yoke 114, hinge cap 122 and top formed by the two metal layers. A thin flexible torsion beam 120 formed by only the address electrode 124 and a thin torsion beam metal layer remains.

Next, a thick spacer layer is deposited and patterned over the thick metal layer to define the holes in which the mirror support spacer vias 126 will be formed. The thick spacer layer is typically a 2 μm thick positive photoresist layer. Mirror metal layers of aluminum alloys are typically sputtered on the surface of the thick spacer layer and also in the holes in the thick spacer layer. This metal layer is then patterned to form the mirror 102. After formation of the mirror 102, both spacer layers are removed by plasma etching.

Once the two spacer layers are removed, the mirror is free to rotate about the axis formed by the torsion beam hinge 120. Electrostatic attraction between the address electrode 110 and the deflectable rigid member forming the two electrode plates of the air gap capacitor is used for the rotation of the mirror structure. Depending on the configuration of the micromirror device, the deflectable rigid member may be a torsion beam yoke 114, a beam or mirror 102, a beam directly attached to the torsion beam, or a combination thereof. The upper address electrode 124 also electrostatically attracts the deflectable rigid member.

The force generated by the voltage potential is a function of the inverse of the distance between the two pole plates. As the rigid member rotates due to electrostatic torque, the torsion beam hinge 120 deforms and resists its rotation with a restoring torque that is approximately a linear function of the angular deflection of the torsion beam 120. Rotation of this structure continues until the restored torsion beam torque becomes equal to the electrostatic torque or until the rotation is mechanically blocked by contact between the rotating structure and the substrate. Here, the substrate includes a landing site or a landing electrode. As will be described later, most of the micro mirror devices operate in the digital mode. In this digital mode of operation, a bias voltage large enough to fully deflect the micromirror superstructure is used.

Subminiature mirror devices are generally operated in one of two modes of operation. The first mode of operation is often an analog mode called beam steering, in which the address electrode is charged to a voltage corresponding to the desired degree of mirror deflection. Impinging light of the micromirror device is reflected by the mirror at an angle determined by the mirror deflection. Depending on the voltage applied to the address electrode, the light reflected by the individual mirrors is oriented outwardly or partially into the opening of the projection lens or partially into the opening. The reflected light is focused onto the image plane by the projection lens. Each individual mirror corresponds to a specific location on the image plane. When the reflected light is moved from being completely oriented into the projection lens to being completely oriented out of the opening, the image position corresponding to the mirror is blurred to produce a continuous luminance level.

The second mode of operation is a digital mode, where each subminiature mirror is fully deflected in any of two directions about the torsion beam axis when operating digitally. In digital operation, a relatively large voltage is used for complete deflection of the mirror. A standard logic voltage level is applied to the address electrode, but a large bias voltage of typically + 24V is applied to the mirror metal layer. A sufficiently large mirror bias voltage, i.e., a voltage higher than the device breakdown voltage, causes the mirror to deflect to the nearest landing electrode even in the absence of an address voltage. Therefore, with a large mirror bias voltage, the address voltage only needs to be large enough to slightly deflect the mirror.

For image generation by the micromirror device, the light source is placed at an angle equal to twice the angle of rotation, such that the mirror rotated toward the light source reflects the light in a direction perpendicular to the surface of the micromirror device and into the aperture of the projection lens. Create luminance pixels on the plane. The mirror rotated away from the light source reflects light away from the projection lens, leaving the corresponding pixel dark. The intermediate luminance level is created by pulse width modulation that rotates the mirror rapidly on / off. The duty cycle of the mirror determines the amount of light that reaches the image plane. The human eye integrates light pulses and the human brain perceives a medium luminance level without flashing.

Full color images are single micromirror devices illuminated by light beams passing through three color filters mounted on a rotating color wheel or by generating three monochrome images using three micromirrors. By sequentially forming three monochrome images.

3 and 4 show a hidden-hinge subminiature mirror according to a recently developed spring ring structure. In the present specification, the present invention is mainly described with respect to the micromirror device, but the concept of the present invention can be applied to other types of micromachines.

As shown in FIGS. 3 and 4, the ring-shaped spring 328 is provided at a torsion beam yoke level extending around the torsion beam yoke 314. The spring ring 328 has a nub 330 at its outer circumference. During deflection, the bottom of the mirror 302 contacts the nub 330 and pushes the spring ring 328 downward. As the mirror 302 pushes the spring ring 328 downward, the spring ring 328 generates a restoring force that pushes the mirror 302 upward.

The sufficiently large mirror bias voltage spring ring 328 stores energy upon deflection by the mirror 302 and releases the stored energy when the mirror 302 is restored to an unbiased state. Once the electrostatic force deflecting the mirror 302 is removed or sufficiently reduced, the stored potential energy snaps the spring ring 328 back into the non-deflected state, restoring the mirror 302 back to its neutral position. . The force of the spring ring 328 helps to relieve or at least resolve the sticking state between the mirror 302 or yoke 114 and the spring ring 328 or mirror bias / reset metallization layer 112 to provide a mirror ( 302 is freed to allow the torsion beam hinge 320 to restore the mirror 302 to a neutral position. Combined with a dynamic reset to reposition the mirror by causing the mirror to be driven toward its opposite address electrode via its neutral position, the spring ring 328 reliably resets all mirrors 302 in the array, thereby Visual defects due to sticking or premature liberation of the body are eliminated.

According to a preferred embodiment of the present invention, the restoring force caused by the deflection of the spring ring 328 is such that the mirror 302 or yoke 314 metallizes the address electrode 310 or mirror bias / reset metallization on the substrate 104 surface. It is sufficient to stop the rotation of the mirror 302 before contacting the layer 312. 5 is a side view of the deflected hidden-hinge microminiature mirror element according to the present invention, illustrating the relationship between the deflected spring ring 328 and the mirror 302. In FIG. 5, the restoring force caused by the deflection of the spring ring 328 is determined by the mirror (302) before the mirror 302 contacts the address electrode 310 or the mirror bias / reset metallization layer 312 on the substrate 104 surface. It is enough to stop the rotation of 302.

According to another preferred embodiment of the present invention, the restoring force caused by the deflection of the spring ring 328 is such that the mirror 302 or yoke 314 has the address electrode 310 or mirror bias / reset metal on the substrate 104 surface. It is insufficient to stop the deflection of the mirror 302 before contacting the fire layer 312. 6 and 7 are cross-sectional views of the deflected hidden-hinge subminiature mirror element according to the present invention, illustrating the relationship between the deflected spring ring 328 and the mirror 302.

In FIG. 6, the restoring force caused by the deflection of the spring ring 328 is insufficient to stop the rotation of the mirror 302 before the mirror 302 contacts the mirror bias / reset metallization layer 612. Although the rotation of the mirror 302 is interrupted by contact with the mirror bias / reset metallization layer 612, the spring ring 328 is still in the mirror 302 and the spring ring 328 and the mirror bias / reset Insufficient restoring force is provided to break the stuck state between the metallization layers 612.

In FIG. 7, the restoring force caused by the deflection of the spring ring 328 is insufficient to stop the rotation of the mirror before the torsion beam yoke 314 contacts the mirror bias / reset metallization layer 712. As in FIG. 6, although the rotation of the mirror 302 is stopped by contact with the mirror bias / reset metallization layer 612, the spring ring 328 is still in the mirror 302 and the spring ring 328. And insufficient restoring force to break the stuck state between the mirror bias / reset metallization layers 612.

The present invention discloses a spring that is not rigidly attached to the deflectable member, unlike a conventional device comprising a spring extension made as part of a torsion beam yoke. The structure disclosed herein preferably has a spring structure made as part of an intermediate layer between the substrate and a portion of the rigid deflection member.

The previous description focused on a new structure known as a spring ring, but this spring ring structure is only one example of a micromechanical device having a spring member that can be operated to inhibit the movement of a separate deflectable element. Many other structures also use springs to stop the movement of separate deflectable elements.

8, 9, 10 and 11 show examples of another spring structure. Like the spring ring structures of FIGS. 3 and 4, these structures also provide an energy storage member capable of assisting the resistance of the torsion beam hinge to the mirror to restore the mirror 302 to an unbiased position. Two other spring structures shown in FIGS. 8 and 9 use leaf springs or spring extensions that are cantilevered from the torsion beam support column. The third other spring structure uses a ring shaped structure with at least one thin torsion beam section, wherein the thin torsion beam section is capable of twisting upon contact between the ring shaped structure and the deflectable member.

8 shows an extension 834 extending from the torsion beam cap 322. The thick extension 834 consists of a thin metal torsion beam layer and a thick metal layer used to form the torsion beam yoke 314 and the torsion beam cap 322. The thick extension 834 deforms upon contact with the rotating mirror 302 and returns to the non-deflected position when the electrostatic attraction between the deflectable rigid member and the address electrode 110 is removed.

9 shows an extension 934 extending from the torsion beam cap 322. The thick extension 934 consists of a thin torsion beam metal layer that deforms upon contact with the rotating mirror 302. This deformation causes energy to be stored in the extension 934, which is used to cause the mirror 302 to bounce toward the non-deflected position when the electrostatic attraction between the deflectable rigid member and the address electrode 110 is removed. .

One difficulty in using a thin flexible extension 934 extending from the torsion beam cap 922 is to avoid contact with the bottom of the mirror 302. Since the extension 934 is thin, it must be relatively short to maintain the strength required to restore the mirror 302 to the unbiased position. However, if the flexible extension is short, there are cases where the extension deforms to allow the bottom of the mirror 302 and the edge 936 of the thick torsion beam cap 922 to contact. To avoid contact between the bottom of the mirror 302 and the edge 936 of the thick torsion beam cap 922, in the embodiment shown in FIG. 10, a spring having a thick end 940 and a thin middle portion 938. Provide an extension. In deflection, the bottom of the mirror 302 contacts the thick end to minimize contact between the mirror 302 and the spring extension while the thin middle portion 938 is deformed.

It is difficult to provide the constant mirror rotation necessary to produce high quality images using thin flexible extensions. As described above, the luminance of the pixel depends on the amount of reflected light by the mirror entering the opening of the display lens. Therefore, if the rotation of the mirror is excessive or insufficient and a part of the reflected light is outside the opening, the luminance of all the pixels will not be the same and the display quality will be degraded. This problem also occurs when the mirror twists along the torsion beam axis instead of twisting about the torsion beam axis. Thus, each mirror in each array must rotate exactly the same amount every time the mirror rotates for the lifetime of the device.

The manufacture of the thin torsion beam cap extension 934 is easy, but it is very difficult to manufacture the thin torsion beam cap extension 934 which provides a constant mirror deflection. The strength of the torsion beam cap extension 934 is approximately equal to three squares of the thickness to length ratio. The metal layer forming the torsion beam is nominally 600 mm thick, while the thick metal layer forming the torsion beam yoke and cap is nominally 4000 mm thick. Since the metal layer used to form the torsion beam hinge 320 and the torsion beam cap extension 934 is thin relative to the length of the torsion beam cap extension 934, the thickness variations typically encountered during production manufacturing processes The strength of the extension 934 can vary greatly. In embodiments where the rigid deflectable structure is not stopped by the mirror bias / reset metallization layer, large variation in the strength of the cap extension 934 may significantly change the range in which the deflectable structure is rotated. As mentioned above, such mirror rotation fluctuations significantly degrade the image generated by the micromirror device.

The thicker the spring, the smaller the influence on the spring strength due to the thickness variation. Thus, the thick torsion beam cap extension 834 shown in FIG. 8 provides a constant strength over a range of metal thickness variations over the thin torsion beam cap extension 934 shown in FIG. 9. The short, thick torsion beam cap extension 834 shown in FIG. 8 may be too thick to provide a constant strength, but may not provide the resilient springs needed to return the mirror 302 to an unbiased position.

The spring ring DMD configuration provides stable mirror deflection while providing the resilient force needed to return the mirror 302 to the unbiased position. Since the spring ring is formed of a thin torsion beam metal layer and a thick torsion beam cap metal layer, the manufacturing thickness variation is not large compared to its nominal thickness and does not affect the spring strength. In addition, since the strength is reduced by the length of the spring ring, the spring can be bent to store enough energy to drive the mirror to an unbiased position.

Compared to the thick torsion beam cap extension 834, the compliance of the spring ring 328 is increased because the length of the spring ring 328 is increased. The shape of the spring ring 328 also provides additional desirable features for long thick torsion beam cap extensions. First, the spring ring 328 is connected with an extension extending from each torsion beam cap 322, so that a small difference in the compliance of each separated extension causes the mirror 302 to be perpendicular to the torsion beam axis. Will not tilt. Second, by providing a nub 330 on the outermost side of the spring ring 328, the contact point between the spring ring 328 and the mirror 302 is minimized and controlled.

Although one nub 330 is shown, due to a defect in the current mirror undercut process that removes the sacrificial spacer layer, using two closely spaced nubs or a single notched nub It is advantageous. The undercut process tends to leave very small irregular ridges of spacer material along the diagonal centerlines of the micromirror elements, which are on the top and bottom of the torsion hinge, the hinge cap and the hinge yoke and also on the bottom of the mirror. exist.

The ridge has a thickness of only about 1.2 μm, but this small thickness is sufficient to reduce the rotation of the large deflected mirror by as much as 1 °. Since the ridge reduces the rotation of certain mirrors, the light reflected by the insufficiently rotated mirror does not completely enter the opening of the projection lens, so that the brightness of the pixel corresponding to the insufficiently rotated mirror is reduced. A small insufficient rotation of 0.5 ° can be noticed, and an insufficient rotation of 1 ° is clearly visible as a spot on the projected image. To avoid image deterioration caused by ridges of residual spacer material, the nubs 330 are notched to avoid contact with the ridges or use two nubs, one on each side of the ridges.

FIG. 11 illustrates in detail another embodiment of a micromechanical apparatus having a spring based return structure. In FIG. 11, two thin portions 334, one on each side of the thick nub 330, are provided on both sides of the ring structure 332. The entire ring structure 328 of FIGS. 3 and 4 is configured to deform upon contact with the bottom of the mirror 302, while the ring structure 332 of FIG. 11 has only a thin portion 334 of which deflection of the nub 330. Deformation by twisting as possible.

In all the devices described above, a spring is attached to the torsion beam support spacer via 116 and extends directly under the mirror 302. In these embodiments, the spring and support structures are provided under the mirror 302, which would be desirable in applications that form images using micromechanical devices because they do not cause reflections that degrade image quality. There is no need to hide it so that it is not exposed to light. In these other applications, a spring may be provided over the deflectable element so that the deflectable element contacts the bottom of the spring. It is also possible to provide a spring support structure outside the outer periphery of the micromirror 302 but allow the spring to extend inwardly towards the deflectable element. In addition, some micromechanical elements may have deflectable elements that move laterally relative to the substrate rather than being moved up and down by the twist of the torsion hinge. The spring is typically provided on the side of the deflectable element that is in lateral motion to position the spring in a position that can constrain the motion of the deflectable element.

One problem affecting current DMD configurations is torsion beam hinge memory or hinge creep. Torsion beam hinge memory occurs when the metal that forms the torsion beam is permanently twisted after the mirror has been repeatedly rotated in a given direction. Sometimes the twist caused by the movement along the intercrystalline slip plane biases the mirror in one direction of rotation. For a given deflection, the problem with the high compliant spring structure in the hinge memory is less.

  If the electrostatic attraction between the address electrode and the deflectable member is insufficient to overcome the bias created by the torsion hinge memory, the mirror is torsion beam upon application of the mirror bias voltage regardless of the data applied to the address electrode. It will always rotate in the direction of the hinge memory. It is rare that the torsion beam hinge memory rises to a level where the address electrode cannot overcome the torsion beam hinge memory, but the torsion beam hinge memory reduces the address margin and generates an error intermittently. Intermittent mirror rotation errors are quite often observed as glare effects in dark areas of the image.

In the spring-based configuration, high compliance hinges can be used, resulting in less chance of hinge creep. The spring ring 328 not only functions to move the mirror 302 to an unbiased neutral region or, in the case of a dynamic reset, to cause the mirror 302 to cross the neutral region, as well as the torsion beam 320 is rigidly deflected. Resisting electrostatic rotation of the possible member ultimately assists in stopping the rotation. Since the torsion beam 320 no longer provides any resistive and restorative torque, the compliance of the torsion beam 320 can be increased and at the same time the spring ring 328 provides sufficient resistive and restorative torque to be maintained. have.

Torsion beam compliance is determined by the length, width and thickness of the torsion beam hinge and also by the torsion beam forming material. All these parameters are limited by the manufacturing process capability or by physical constraints on the size of the miniature mirror element. Perhaps the best way to increase torsion beam compliance is to reduce the thickness of the torsion beams. Decreasing the thickness of the torsion beam from 635 ms to 600 ms increases the compliance of the hinge. Further reduction in the thickness of the torsion beam will further increase compliance, but it is difficult to reduce the thickness of the torsion beam to less than 600 Hz.

The spring ring configuration also improves the mechanical reliability of the micro mirror array. One potential high-load action point of the micromirror superstructure is the connection between the mirror support spacer via 326 and the torsion beam yoke 314, which is a mirror support where the vertical spacer via walls intersect the horizontal base of the spacer via. The spacer via 326 is weakened due to poor metal distribution in the mirror support spacer via 326. The metal distribution at this boundary is called step coverage. The problem of step coverage is caused by the inherent difficulty in depositing metal into the holes in the spacer vias, the problem being described in the United States entitled "Support Post Architecture for Micromechanical Devices", which was issued December 30, 1997. It is discussed in detail in patent 5,703,728.

Without strengthening the connection between the mirror support spacer via 326 and the torsion beam yoke 314, the "soft landing" provided by the spring ring 328 is the mirror support spacer via 326 and the torsion beam. The stress on the connection between the yokes 314 is reduced to improve the reliability of the device. There are several factors that reduce this stress. One of them is mirror 302 by spring ring, unlike the sudden stop of mirror 102 which occurs when torsion beam yoke 114 or mirror 102 impinges on the mirror bias / reset metallization layer. ) Will gradually stop.

Another of the above factors is due to the mirror inertia of the connection between the mirror support spacer via 326 and the torsion beam yoke 314 by the spring ring 328 contacting the mirror 302 and stopping the mirror. The destructive effects are excluded. The mirror 302 accounts for about 60% of the inertia of the rigidly deflectable member because of its relatively large weight. In the prior art device for landing the torsion beam yoke 114 to the mirror bias / reset metallization layer 112, the large inertia force due to the length portion of the mirror support spacer via 126 being used as the lever arm is the mirror support. A large torsional force was generated at the connection between the spacer via 126 and the torsion beam yoke 114. On the other hand, in the present invention where the mirror 302 directly lands on the spring ring, such inertial forces are eliminated and instead a relatively small torque is generated by the electrostatic attraction between the address electrode 310 and the torsion beam yoke 314. Is generated.

The stress on the mirror support spacer via 326 is reduced due to the soft landing features and the stress relief due to the mirror inertia. As a result, as shown in the spacer vias 326 shown in Figs. 3 and 4, the diameter of the spacer can be made significantly smaller. The spacer vias occupy some space, which is space to be used as the active mirror area when not used as the spacer via space. Since the top of the spacer via is open, it cannot reflect light impinging on the spacer via region to the image plane. Therefore, if the spacer via is made small, the active mirror area can be increased and the light efficiency of the ultra-small mirror device can be increased.

When the spacer via is made small, in addition to improving image brightness, the contrast ratio of the projected image is increased. Light impinging on the spacer via is scattered regardless of the tilt direction of the mirror. Some of the scattered light reaches the projected image. Since the scattered light reaching the image is randomly diffused throughout the image, the scattered light lowers the contrast ratio by brightening the dark areas of the image and losing the image.

When the light scattered by the boundary between the mirror 302 and the mirror support spacer via 326 is scattered by the straight edge, in particular when the straight edge is parallel to the axis of the torsion beam hinge 320, the scattered light is The opening is likely to eventually reach the projected image. In order to reduce the influence of the scattered light and also to strengthen the mirror support spacer vias, conventional support mirrors have used a mirror support spacer via having a rectangular cross section and a side portion parallel to the torsion beam is shorter than the side portion perpendicular to the hinge. As shown in FIGS. 1 and 2, the width of the mirror support spacer via is about 4 μm in the direction perpendicular to the torsion beam 120 and about 3 μm in the direction parallel to the torsion beam 120.

By reducing the outer periphery of the mirror support spacer via 326, the amount of light scattered by the boundary is reduced by reducing the length of the boundary between the mirror 302 and the mirror support spacer via 326. When the spacer via 326 is made sufficiently small, the response of the photosensitive spacer material in which the mirror support spacer via 326 is formed and the diffraction by the photolithography process round the angled corners of the mirror support spacer via 326, thereby projecting it. Exclude or greatly reduce straight edges that are likely to reflect light into the system aperture. Spacer vias of 2.6 μm diameter are large enough to provide the required strength and small enough to be suitable for photolithographic processes that round the corners.

Several other advantages include the side effect of the mirror 302 not landing on the M3 metallization layer, one of which is the use of antireflective coatings on the structure underneath the mirror 302. Light passing through the gap between the mirrors is scattered by the M3 metallization layer on the mirror support spacer and the substrate 104 surface, some of which eventually passes back through the gap between the mirrors in the reverse direction and the projection lens system. It enters into the aperture of and reduces the contrast of the image produced by the miniature mirror array. One way to improve the contrast is to provide an antireflective coating on the bottom surfaces of the mirror, which antireflective coating 1002 shown in FIG. 12 reduces the reflection component from the coated surface to degrade the quality of the projected image. To reduce stray light.

Unfortunately, it is easy to apply to address electrode 310 and mirror bias / reset metallization layer 312 and provides sufficient resistance to abrasive dynamic reset and mirror bias / reset metallization layer 312 and mirror ( There is no known antireflective coating 1002 that may provide between 302 or yoke 314. However, the spring based subminiature mirror configuration allows the use of the antireflective coating 1002 by excluding contact between the mirror 302 and the M3 layer.

Excluding contact between the mirror 302 and the mirror bias / reset metallization layer 312 can also improve the electrical reliability of the device and resistance to mechanical breakage. When the rotation of the mirror 302 is stopped by the spring ring 328, no separate landing site is needed on the mirror bias / reset metallization layer 112. Excluding the landing site, which typically stops the rotation of the mirror by contact with the torsion beam yoke 114 or the mirror 102, leaves additional space available on the M3 metallization layer.

In particular, additional space in the layer portion furthest from the hinge axis can be used to enlarge the address electrode. Additional space can also be used to enlarge the gap between the address electrode and the mirror bias / reset metallization layer. The larger the gap, the short circuit caused by the particles is eliminated in the device and the tolerance to manufacturing defects is increased, thereby increasing the manufacturing yield of the device. In addition, some of the additional space may be used to simplify the routing of the mirror bias / reset signal, particularly when using a separate reset address method.

Increasing the address electrode 310 increases the capacity of the air capacitor formed by the rigid deflectable member and the address electrode. Extending the address electrode 310 away from the axis of the torsion beam 320 increases the torque generated by the electrostatic attraction between the address electrode 310 and the rigid deflectable member. This increased capacity and torque cooperatively increases the operational reliability of the device, thereby lowering the voltage required for device operation.

In addition to making the operation of the device more consistent, improving the electrostatic margin by increasing the address electrode 310 results in an electrostatic margin between the upper address electrode 124 and the mirror 102 as shown in FIGS. 1 and 2. There is no need for the upper address electrode 124 needed to generate miracle attraction. Even without the upper address electrode 124, the height of the mirror spacer spacer 326 may be increased to increase the height of the support spacer via 126 in order to prevent contact between the mirror 102 and the upper address electrode 124. It does not have to be as large as in the prior art configuration which should be. Excluding the upper address electrode 124 also makes the torsion beam yoke 314 larger, which increases the electrostatic torque generated by the device.

By shortening the mirror support spacer via 326, several advantages can be obtained. First, reducing the gap between the mirror 302 and the address electrode 310 increases the electrostatic force generated by the given voltage difference between the mirror 302 and the address electrode 310, further improving the electrostatic performance of the device. Second, since the mirror support spacer via 326 is an additional moment arm for inertia of the mirror, reducing the height of the mirror support spacer via 326 connects the mirror support spacer via 326 to the torsion beam yoke. The stress on is reduced.

In addition, shortening the mirror support spacer via 326 reduces the amount of light that can pass between the mirrors 302, further improving the contrast ratio of the image. Shortening the mirror support spacer via 326 reduces the gap between the mirrors 302 upon rotation of the mirror, thereby reducing the amount of light passing through the gap. Light passing through the gap between the mirrors 302 is reflected by the underlying structure and the mirror bias / reset metallization layer. Some of the light reflected by the underlying structure passes back through the mirror gap in the reverse direction to reach the image plane, thereby reducing the contrast of the display by losing the projected image.

Since the torsion beam yoke 314 no longer contacts the mirror bias / reset metallization layer 312, the height of the torsion beam support spacer via 116 no longer depends on the final tilt angle of the mirror 302. In addition, since the height of the torsion beam support spacer vias 116 does not affect the tilt angle of the mirror and the electrostatic performance of the device is greatly improved by the exclusion of the landing site and the upper address electrode, The height can be varied over a relatively large range.

The height of the torsion beam support spacer via 116 is determined in consideration of the electrostatic performance and resistance to fragmentation. Shortening the torsion beam support spacer vias 116 increases the electrostatic attraction between them by reducing the gap between the torsion beam yoke 314 and the address electrode 310. However, if the gap between the torsion beam yoke 314 and the address electrode 310 is made small, the possibility of device failure due to debris inside the device package increases. The fragments between the torsion beam yoke 314 and the address electrode 310 mechanically limit the rotation of the mirror 302 as well as electrically short the torsion beam yoke 314 and the address electrode 310.

The height of the torsion beam support spacer via 116 and the mirror support spacer via 326 is determined by the thickness of the spacer layer used to form the support spacer via. In the prior art device, torsion beam support spacer vias 116 are formed using spacers of 1.18 μm height and mirror support spacer vias 126 are formed using spacer layers of 2.15 μm height. These spacer layers are combined with a 0.32 μm thick torsion beam yoke to form a 3.65 μm high mirror. In one embodiment using a spring recovery structure, a torsion beam support spacer via 116 and a mirror support spacer via 326 are formed using a spacer layer of 1.46 μm. This embodiment forms a 3.28 μm high mirror in combination with a 0.36 μm thick torsion beam yoke 314. Although the gap between the torsion beam yoke 314 and the address electrode 310 is enlarged, according to the device of the present invention, the electrostatic performance is improved and the resistance to debris is increased. In addition, according to the present invention, the contrast ratio of the image can be increased by lowering the mirror height and providing an antireflective coating to the mirror bias / reset metallization layer 312.

No further steps are necessary to manufacture the device according to the invention. According to one manufacturing method, the yoke extension, or the landing spring, with the torsion beam yoke 314, whether it is the torsion beam cap extensions 834, 934, the spring ring 328 or the twist ring 332 It is manufactured simultaneously with the torsion beam cap 322. It is only necessary to modify the torsion beam etch stop photolithography mask or torsion beam cap and yoke photolithography mask or both to produce the landing spring.

FIG. 13 is a cross-sectional view of the spacer, metal and oxide layers used to fabricate the torsion beam support spacer via 116, torsion beam 320, torsion beam yoke 314 and spring ring 328 of FIG. 3. As shown in FIG. 13, the spacer layer 1102 is typically a 0.8 μm thick positive photoresist layer, which is deposited on the integrated circuit board 1104 and then patterned to form holes or vias. Subsequent torsion beam support spacer vias are formed in the holes or vias. Prior to depositing this spacer layer 1102, any necessary electrical circuits, metal circuit connection members, address electrodes and mirror bias / reset metallization layers are formed on the substrate.

Next, a thin metal layer 1106 is sputtered over the spacer layer 1102 and in the via, which layer forms the torsion beam 320. An oxide layer 1108 is then deposited and patterned over the thin metal layer 1106 to form an etch stop over the regions of the thin metal layer 1106 that will later form a torsion beam. Additional etch stops are formed over thin spring structure forming regions such as the thin torsion beam cap extension 934 shown in FIG. 9 and the thin portion 334 of the twist ring 332 shown in FIG.

Next, the thick metal layer 1110 is sputtered over the thin metal layer 1106 and the etch stop. Next, a second oxide layer 1112 is deposited and patterned over the thick metal layer 1110 to form the torsion beam support spacer via 116, the torsion beam support cap 322 and the torsion beam yoke 314. An etch stop is formed over the thick metal layer 1110 regions. Additional etch stops include the spring ring 328 and nub 330 shown in FIG. 3, the thick torsion beam cap extension 834 shown in FIG. 8, and the thick portion 334 of the twist ring 332 shown in FIG. 11. And thick spring structure forming regions such as nubs 330.

14 is a plan view of the partially completed spring ring miniature mirror device of FIG. 4, used to form a torsion beam etch stop 1202, a torsion beam yoke etch stop 1204, and a torsion beam spacer via cap and spring ring. It is a figure which shows the position of the etching stop 1206 which becomes. In Figure 14, the etch stops used to form the torsion beam yoke, spacer vias and spring rings cover a thick metal layer 1208 and a thin metal layer, and the etch stop 1202 forming the torsion beam is between the two metal layers. It is shown by the dotted line as located.

FIG. 15 is a plan view of the partially completed micromirror device of FIG. 8, used to form a torsion beam etch stop 1202, a torsion beam yoke etch stop 1204, a torsion beam spacer via cap, and a thick spring cap extension. It is a figure which shows the position of the etching stop 1220 which becomes. In FIG. 15, the etch stops used to form the torsion beam yoke, spacer via cap and spring cap extension cover a thick metal layer 1208 and a thin metal layer, and the etch stop 1202 forming the torsion beam is formed of two metals. It is shown by the dotted line as located between the layers.

FIG. 16 is a plan view of the partially completed thin torsion beam cap extension spring miniature mirror device of FIG. And the spring cap extension etch stop 1412. As shown in FIG. 16, the etch stops used to form the torsion beam yoke and spacer via caps cover the thick metal layer 1208 and the thin metal layer, and the etch stop 1202 and the spring cap to form the torsion beam. Etch stops forming 1412 are shown in dashed lines as being located between two metal layers.

FIG. 17 is a plan view of the partially completed micromirror device of FIG. 10, used to form a torsion beam etch stop 1202, a torsion beam yoke etch stop 1204, and a torsion beam spacer via cap and spring cap extension. Figure shows the location of the etch stop 1222 and the etch stop 1210 used to form the thick end of the spring cap extension. Etch stop 1212 determines the shape of the thin portion of the spring extension. As shown in FIG. 17, the etch stops used to form the torsion beam yoke, spacer via cap, and spring cap extension cover a thick metal layer 1208 and a thin metal layer and cover the thin portion of the torsion beam and spring extension. The forming etch stop 1202 is shown in dashed lines as being located between the two metal layers.

FIG. 18 is a plan view of the partially completed spring ring miniature mirror device of FIG. 11, with a torsion beam etch stop 1202, a torsion beam yoke etch stop 1204, and a thick end of the torsion beam spacer via cap and twist ring. Figure 2 shows the location of the etch stop 1214 used to form the etch stop 1214 and the etch stop 1216 used to form the nub of the twist ring. As shown in FIG. 18, the etch stops used to form the thick portion of the torsion beam yoke, the spacer via cap and the twist ring and the twist ring nubs cover the thick metal layer 1208 and the thin metal layer, and the torsion beam and Etch stops 1202 and 1218 forming the thin portion of the twist ring are shown in dashed lines as being located between the two metal layers.

FIG. 19 is a cross-sectional view of the metal layers of FIG. 13 showing the state after patterning those metal layers and removing the oxide and spacer layers. After the formation of the metal layers and the patterning of the oxide etch stop, a single etch stop is used to remove all thick and thin metal layer regions not covered by the etch stop. After etching the metal layers, the oxide etch stop is removed. The spacer layer is not removed until a mirror support spacer via and a mirror are formed thereon. Once the spacer layers have been removed, the rigid deflectable member can freely rotate about an axis formed by the torsion beams.

20 is an enlarged perspective view of a single DMD element with the spring ring structure of FIG. The apparatus of FIG. 20 replaces the mirror bias / reset metallization layer 312 with torsion beam support pads 338 and interconnects the address electrodes 310 to implement another mirror addressing scheme. In a typical DMD addressing scheme, a unique address voltage and its complementary components are applied to each address pair according to the desired direction of rotation and a common bias voltage is applied to the mode mirror. In the mirror addressing scheme enabled by the mirror bias / reset metallization layer of FIG. 20, each mirror is unique while a two-device wide bias signal is applied to address electrodes 310 on both sides of the torsion beam axis. The address voltage of can be received.

The shape and position of the address electrode 310 in FIG. 20 are the same as the shape and position of the address electrode 310 shown in FIG. 4. If the address electrodes 310 are kept the same, the operation of the micromirror device will be the same regardless of which addressing scheme is used. The interconnect member 336 connects all address electrodes 310 on either side of the torsion beam axis with the address electrodes 310 on the other in the device row. Connections between device rows, on the other hand, are made outside the active portion of the array.

21 is a schematic diagram of an image projection system 1600 using an ultra-small mirror 1602 modified in accordance with the present invention. In FIG. 21, light from the light source 1604 is focused on the micro mirror 1602 by the lens 1606. Although shown as a single lens, lenses 1606 are typically lenses and mirror groups that focus light from light source 1604 and orient them towards the surface of subminiature mirror 1602. Image data and control signals from the controller 1614 cause some mirrors to rotate to the on position and others to the off position. The mirrors on the micromirror device rotated to the off position reflect light toward the light trap 1608 and the mirrors rotated to the on position reflect toward the projection lens 1610, for the sake of simplicity only a single lens is shown. The projection lens 1610 focuses the light modulated by the microscopic mirror device 1602 on the image plane or screen 1612.

Although a specific embodiment has been described so far with a micromechanical device having a spring restoring structure, a manufacturing method of a micromechanical device having a spring restoring structure, and a display using a micromirror device having a spring mirror restoring structure, the scope of the present invention Is not to be limited by the specific embodiments thereof except as set forth in the claims. In addition, while the present invention has been described with reference to specific embodiments thereof, as those skilled in the art will appreciate, other variations are possible and are intended to be included within the scope of the claims.

As described above, according to the present invention, the contrast of the projected image is improved and the reliability of the miniature mirror reset operation is improved.

Claims (22)

In an improved micromachine, Board; A rigid deflectable member suspended on the substrate; And At least one spring supported on the substrate and spaced apart from the rigid deflectable member, The spring is operable to resist the deflection of the rigid deflectable member when the rigid deflectable member and the spring are in contact by deflection of the rigid deflectable member. The micromachine according to claim 1, wherein said spring is operable to prevent contact between said substrate and said rigid deflectable member. The micromachine according to claim 1, wherein said rigidly deflectable member is capable of contacting said substrate by overcoming resistance by said spring. The micromachine according to claim 1, wherein the spring comprises a leaf spring supported on the substrate. The micromachine according to claim 1, wherein the spring comprises an elastic strip suspended over the substrate between two support members on the substrate. 6. The micromachine according to claim 5, wherein said elastic strip is operable to deflect upon contact with said deflectable member. 6. The micromachine according to claim 5, wherein said elastic strip is operable to twist upon contact with said deflectable member. The micromachine according to claim 1, wherein said rigid deflectable member comprises a mirror. 2. The rigid deflectable member of claim 1, wherein the rigid deflectable member is supported on the substrate by at least one torsion beam and is operable to rotate in one of two directions about an axis formed by the torsion beam. Micromechanism. 10. The micromachine of claim 9, wherein the at least one spring comprises at least one spring on each side of the shaft. 10. The microminiature apparatus of claim 9, wherein the spring comprises a ring-shaped spring supported by at least two support structures. 12. The microminiature apparatus of claim 11, wherein the ring-shaped spring further comprises at least one nub extending therefrom. 12. The microminiature apparatus of claim 11, wherein the ring-shaped spring further comprises at least one thin portion, the thin portion being operable to twist upon contact between the ring-shaped spring and the deflectable member. The method of claim 1, wherein the rigid deflectable member, Torsion beam yoke, Mirror support spacers, mirror Micro mechanical device comprising a. 15. The micromachine according to claim 14, wherein the deflection of the rigid deflectable member is limited by the contact between the substrate and the torsion beam yoke. 15. The micromachine according to claim 14, wherein the deflection of the rigid deflectable member is limited by the contact between the substrate and the mirror. In a method of manufacturing an improved micromachine, Fabricating at least one support structure on the substrate, Manufacturing at least one spring spaced apart from the substrate and supported by at least one of the at least one support structures; Manufacturing a deflectable member spaced from the substrate and the spring and supported by at least one of the at least one support structures Including; And said biasable member is movable to contact said spring, said spring being operable to resist further movement of said biasable member. 18. The method of claim 17 wherein the at least one spring is made between the deflectable member and the substrate. 18. The method of claim 17 wherein the deflectable member and the at least one spring are fabricated on at least one common support structure. 18. The method of claim 17 wherein fabricating the at least one spring comprises fabricating a metal strip extending from at least one of the at least one support structures. 18. The method of claim 17 wherein fabricating the at least one spring comprises fabricating a metal strip suspended between at least two of the at least one support structures. 18. The method of claim 17, wherein fabricating the at least one spring comprises fabricating a metal strip suspended between at least two of the at least one support structures, wherein the metal strip is deflected with the metal strip. And have a thin portion operable to twist upon contact between the releasable members.

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