U.S. patent application number 11/681021 was filed with the patent office on 2007-09-06 for optical deflecting device, optical deflecting device manufacturing method, and optical projecting device.
Invention is credited to Seiichi Katoh, Takeshi Nanjyo, Koichi Ohtaka.
Application Number | 20070206268 11/681021 |
Document ID | / |
Family ID | 38471211 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070206268 |
Kind Code |
A1 |
Katoh; Seiichi ; et
al. |
September 6, 2007 |
OPTICAL DEFLECTING DEVICE, OPTICAL DEFLECTING DEVICE MANUFACTURING
METHOD, AND OPTICAL PROJECTING DEVICE
Abstract
Bearing portions having an approximately arc shape are provided
on a lower surface of a plate-shaped member. In the bearing
portions, stoppers of a regulating member are embedded. With the
engagement of the lower surface of the plate-shaped member and the
apex of a pivot member and the engagement of an inner surface of
the bearing portions and a lower surface of the stoppers, the
plate-shaped member is rotatably supported with the apex of the
pivot member as a center. With a side surface of the regulating
member 109 facing a side surface of the bearing portions, the
position of the plate-shaped member in a rotation axis direction is
regulated.
Inventors: |
Katoh; Seiichi; (Miyagi,
JP) ; Nanjyo; Takeshi; (Hyogo, JP) ; Ohtaka;
Koichi; (Miyagi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
38471211 |
Appl. No.: |
11/681021 |
Filed: |
March 1, 2007 |
Current U.S.
Class: |
359/291 |
Current CPC
Class: |
G02B 26/0841
20130101 |
Class at
Publication: |
359/291 |
International
Class: |
G02B 26/00 20060101
G02B026/00; A61B 3/00 20060101 A61B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2006 |
JP |
2006-055050 |
Claims
1. An optical deflecting device comprising: a substrate; a pivot
member formed on the substrate; a regulating member formed on the
substrate; a plate-shaped member having an upper surface as a light
reflecting surface; and a group of electrodes formed on the
substrate, wherein the plate-shaped member has a loop-shaped
bearing portion on a lower surface side, the regulating member has
a stopper protruding in approximately parallel to the substrate and
embedded inside the bearing portion, with an engagement of the
lower surface of the plate-shaped member and an apex of the pivot
member and an engagement of an inner surface of the bearing portion
and a lower surface of the stopper, the plate-shaped member is
rotatably supported with the apex of the pivot member as a center,
and a position of the plate-shaped member in a rotation axis
direction is regulated by a side surface of the regulating member
facing a side surface of the bearing portion, and with an
electrostatic force generated between the group of electrodes and
the plate-shaped member, the plate-shaped member is rotated with
the apex of the pivot member as the center, thereby changing a
reflecting direction of a light beam incident to the light
reflecting surface of the plate-shaped member.
2. The optical deflecting device according to claim 1, wherein the
bearing portion and the stopper have an approximately arc-shaped
cross section.
3. The optical deflecting device according to claim 1, wherein the
inner surface of the bearing portion and the surface of the stopper
engaging the inner surface of the bearing portion have an
approximately equal radius of curvature.
4. The optical deflecting device according to claim 1, wherein the
plate-shaped member is formed of film-laminated layers, and a lower
layer of the layers and the bearing portion are conductors.
5. The optical deflecting device according to claim 1, wherein the
plate-shaped member is formed of film-laminated layers, and a lower
layer of the layers and the bearing portion are insulators.
6. The optical deflecting device according to claim 4, wherein the
regulating member and the stopper are conductors.
7. A method of manufacturing the optical deflecting device
according to claim 1, the method comprising: after planarizing a
photoresist serving as a sacrifice layer, forming a concave surface
corresponding to the bearing portion through etching process; next
forming a film made of a material serving as the lower layer of the
plate-shaped member; next forming and patterning a sacrifice layer
along the concave surface; and next forming a film serving as the
stopper of the regulating member.
8. An optical projecting device comprising: an optical deflecting
device including a substrate; a pivot member formed on the
substrate; a regulating member formed on the substrate; a
plate-shaped member having an upper surface as a light reflecting
surface; and a group of electrodes formed on the substrate, wherein
the plate-shaped member has a loop-shaped bearing portion on a
lower surface side, the regulating member has a stopper protruding
in approximately parallel to the substrate and embedded inside the
bearing portion, with an engagement of the lower surface of the
plate-shaped member and an apex of the pivot member and an
engagement of an inner surface of the bearing portion and a lower
surface of the stopper, the plate-shaped member is rotatably
supported with the apex of the pivot member as a center, and a
position of the plate-shaped member in a rotation axis direction is
regulated by a side surface of the regulating member facing a side
surface of the bearing portion, and with an electrostatic force
generated between the group of electrodes and the plate-shaped
member, the plate-shaped member is rotated with the apex of the
pivot member as the center, thereby changing a reflecting direction
of a light beam incident to the light reflecting surface of the
plate-shaped member; a light source that light up a light
reflecting surface of a plate-shaped member of the optical
deflecting device; and an optical system that projects light
reflected from the light reflecting surface when the plate-shaped
member of the optical deflecting device is tilted in a first
tilting direction, and shields light reflected from the light
reflecting surface and prevents the light from being projected
outside when the plate-shaped member is tilted in a second tilting
direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present document incorporates by reference the entire
contents of Japanese priority document, 2006-055050 filed in Japan
on Mar. 1, 2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an optical deflecting
device that changes the direction of output light with respect to
incident light and a method of manufacturing such an optical
deflecting device, and also relates a technology suitable for image
forming apparatuses, such as electrophotographic printers and
copiers, and projection-type image and vide display apparatuses,
such as projectors and digital theater systems.
[0004] 2. Description of the Related Art
[0005] L. J. Hornbeck has disclosed digital micromirror device with
a torsion beam hinge in Proceedings, The International Society for
Optical Engineering (SPIE), vol. 1150, pp. 86-102 (1989). This
technology has been expanded as disclosed in Proceedings of The
Institute of Electrical and Electronics Engineers (IEEE), vol. 86,
No. 8, pp. 1687-1704 (1998) by P. F. Van Kessl and J. Hornbeck, in
which spatial light modulating device having a group of
micromirrors is disclosed and called a Digital Micromirror Device
(DMD) for use in image projecting device.
[0006] In these micromirror devices, mirrors are generally
supported by a torsion beam called a hinge. By using the hinge, the
reflection area is reduced. However, a DMD from Texas Instruments
Incorporated has a two-storied structure provided with a reflecting
member on the surface separately from the hinge portion. Also, with
the use of the hinge, the actual voltage to be driven is as much as
several tens of volts. However, for control on the order of 5 volts
to 7.5 volts as data for switching the tilting direction, a bias
voltage of several tens of volts to be applied all at one to a
plurality of pixels and a restoring force of a special spring
member are combined to switch the tilt.
[0007] Also, in a micromirror device reported in Micro Opto Electro
Mechanical Systems-MOEMS '99 by Chang-Hyeon Ji and Yong Kweon Kim,
a bearing-shaped hinge on a substrate without stiffness is
used.
[0008] Furthermore, the inventors have submitted a patent
application that discloses an optical deflecting device in which,
with a displacement due to electrostatic attraction according to a
potential applied to a member having a light reflecting area, a
light beam incident to the light reflecting area is deflected with
a reflecting direction being changed. The optical deflecting device
includes a substrate, a plurality of regulating members, a pivot
member, and a plate-shaped member. The regulating members each has
a stopper on an upper portion and are provided to a plurality of
ends. The pivot member has an apex formed of a conductive material
and is provided on an upper surface of the substrate. The
plate-shaped member does not have a fixed end, has the light
reflecting area on an upper surface, and at least partially has a
conductive material layer formed of a conductive member. At least a
contact point making contact with the apex on a back surface is
formed of a conductive member. The plate-shaped member is movably
disposed within a space formed of the substrate, the pivot member,
and the stopper, and provides a potential of the plate-shaped
member through a contact with the pivot member (refer to Japanese
Patent Application Laid-Open No. 2004-78136). Still further, the
inventors have also submitted a patent application that discloses
the invention having a bearing structure in which a plate-shaped
member has formed thereon a notch and a protrusion (refer to
Japanese Patent Application Laid-Open No. 2005-195798).
[0009] Other examples of the conventional technology include those
disclosed in Japanese Patent Application Laid-Open No. 2004-138881,
Japanese Patent No. 3492400, Japanese Patent No. 3411014, and
Japanese National Phase PCT Laid-Open No 2002-525676.
[0010] In the spatial light modulator and optical deflecting device
using a hinge, with the restoring force due to the stiffness of the
hinge, the driving voltage is high, as much as several tens of
volts. In high-definition and high-resolution television, for
example, high-definition and high-resolution is required, and the
number of pixels tend to be increased. When the number of pixels is
increased, the chip size is expanded. In that case, a special
process is required, and material cost is increased. Thus, the
mirror dimension forming a pixel is required to be decreased. With
this, the stiffness of the hinge hanging the mirror is increased,
thereby increasing the driving voltage. For further downsizing, it
is not easy to decrease the stiffness of the hinge because of
limitations of microfabrication accuracy for making the hinge
narrower. Moreover, if the stiffness of the hinge is tried to be
weakened to decrease the driving voltage even for the purpose other
than downsizing, the hinge is bent, and cannot sustain the center
position of the mirror. Still further, when the hinge is used, the
hinge is formed on the surface, and therefore the area that
reflects light is decreased. To get around this problem, a complex
structure has to be adopted in which a reflecting surface is formed
on a driving electrode hanged by the hinge to form a double
structure so as to increase the reflecting area. Still further, a
post is formed to superpose the mirror on the electrode, but since
the post has a hole, the mirror inevitably has an area where light
cannot be reflected, thereby inviting a decrease in reflection
efficiency. From these reason above, in the structure using a
hinge, there is a problem in which downsizing results in a complex
element structure and high manufacturing cost.
[0011] In the device reported by Chang-Hyeon Ji and Yong Kweon Kim,
a simple bearing-shaped hinge is used. However, since the
plated-shaped shaft moves within a rectangular frame, stability is
low. Also, there are problems in which it is difficult to process a
brace of the mirror and it is also difficult to downsize the mirror
to a cube measuring 10 micrometers per side. Ensuring the accuracy
of the bearing-shaped hinge is difficult. When mirrors are arranged
in an array with high density to narrow a space between the
mirrors, which may cause a loss of incident light, a problem of
collision between adjacent mirrors occurs. Even in Japanese Patent
Application Laid-Open No. 2005-195798, a constriction, a hole, and
a protrusion are provided to the plate-shaped member, and therefore
the light reflecting area of the plate-shaped member is
sacrificed.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to at least
partially solve the problems in the conventional technology.
[0013] According to an aspect of the present invention, an optical
deflecting device includes a substrate; a pivot member formed on
the substrate; a regulating member formed on the substrate; a
plate-shaped member having an upper surface as a light reflecting
surface; and a group of electrodes formed on the substrate. The
plate-shaped member has a loop-shaped bearing portion on a lower
surface side, the regulating member has a stopper protruding in
approximately parallel to the substrate and embedded inside the
bearing portion, with an engagement of the lower surface of the
plate-shaped member and an apex of the pivot member and an
engagement of an inner surface of the bearing portion and a lower
surface of the stopper, the plate-shaped member is rotatably
supported with the apex of the pivot member as a center, and a
position of the plate-shaped member in a rotation axis direction is
regulated by a side surface of the regulating member facing a side
surface of the bearing portion, and with an electrostatic force
generated between the group of electrodes and the plate-shaped
member, the plate-shaped member is rotated with the apex of the
pivot member as the center, thereby changing a reflecting direction
of a light beam incident to the light reflecting surface of the
plate-shaped member.
[0014] According to another aspect of the present invention, a
method of manufacturing the optical deflecting device includes,
after planarizing a photoresist serving as a sacrifice layer,
forming a concave surface corresponding to the bearing portion
through etching process; next forming a film made of a material
serving as the lower layer of the plate-shaped member; next forming
and patterning a sacrifice layer along the concave surface; and
next forming a film serving as the stopper of the regulating
member.
[0015] According to still another aspect of the present invention,
an optical projecting device includes the above optical deflecting
device; a light source that light up a light reflecting surface of
a plate-shaped member of the optical deflecting device; and an
optical system that projects light reflected from the light
reflecting surface when the plate-shaped member of the optical
deflecting device is tilted in a first tilting direction, and
shields light reflected from the light reflecting surface and
prevents the light from being projected outside when the
plate-shaped member is tilted in a second tilting direction.
[0016] The above and other objects, features, advantages and
technical and industrial significance of this invention will be
better understood by reading the following detailed description of
presently preferred embodiments of the invention, when considered
in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1A to 1D are drawings of the structure of an optical
deflecting device according to a first embodiment of the present
invention;
[0018] FIG. 2 is a drawing for explaining a rotational supporting
structure of a plate-shaped member;
[0019] FIGS. 3A and 3B are drawings for explaining an optical
deflecting device manufacturing method according to the first
embodiment;
[0020] FIG. 4 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 3B;
[0021] FIG. 5 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 4;
[0022] FIG. 6 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 5;
[0023] FIG. 7 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 6;
[0024] FIG. 8 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 7;
[0025] FIG. 9 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 8;
[0026] FIG. 10 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 9;
[0027] FIG. 11 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 10;
[0028] FIG. 12 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 11;
[0029] FIGS. 13A to 13D are drawings of the structure of an optical
deflecting device according to a second embodiment of the present
invention;
[0030] FIGS. 14A and 14B are drawings for explaining an optical
deflecting device manufacturing method according to the second
embodiment;
[0031] FIG. 15 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 14B;
[0032] FIG. 16 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 15;
[0033] FIG. 17 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 16;
[0034] FIG. 18 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 17;
[0035] FIG. 19 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 18;
[0036] FIG. 20 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 19;
[0037] FIG. 21 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 20;
[0038] FIG. 22 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 21;
[0039] FIG. 23 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 22;
[0040] FIGS. 24A to 24D are drawings of the structure of an optical
deflecting device according to a third embodiment of the present
invention;
[0041] FIGS. 25A and 25B are drawings for explaining an optical
deflecting device according to the third embodiment;
[0042] FIG. 26 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 25B;
[0043] FIG. 27 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 26;
[0044] FIG. 28 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 27;
[0045] FIG. 29 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 28;
[0046] FIG. 30 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 29;
[0047] FIG. 31 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 30;
[0048] FIG. 32 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 31;
[0049] FIG. 33 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 32;
[0050] FIG. 34 is a drawing for explaining continuation of the
manufacturing method shown in FIG. 33; and
[0051] FIG. 35 is a schematic drawing of an optical projecting
device according to a fourth embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] Exemplary embodiments of the present invention are explained
below. To avoid redundancy of explanation, in the drawings referred
to in the following explanation, same portion or corresponding
portions are provided with the same reference numerals.
[0053] FIGS. 1A to 1D and 2 are drawings of the structure of an
optical deflecting device according to the present embodiment.
FIGS. 3A, 3B, and 4 to 12 are drawings for explaining an optical
deflecting device manufacturing method according to the present
embodiment.
[0054] FIG. 1A is a schematic plan view of the optical deflecting
device (a plate-shaped member acting as a movable mirror is
omitted). FIG. 1B is an A-B schematic cross-section view. FIG. 1C
is a C-D schematic cross-section view. FIG. 1D is a schematic side
view. Here, in FIG. 1A, the plate-shaped member acting as a movable
mirror is omitted because it covers the entire surface. Also in
FIG. 1D, the plate-shaped member is omitted.
[0055] The optical deflecting device according to the present
embodiment includes a silicon substrate 101. On this silicon
substrate 101, an oxide film 102 is formed for insulation, on which
a pivot member 105 is formed. Also, a group of electrodes 103 is
formed, and is then covered with an insulating film 104, such as an
oxide film. A conductive plate-shaped member 106 having a light
reflecting area is provided. This plate-shaped member 106 has a
structure in which it is rotatably supported like a seesaw, with
the apex of the pivot member 105 as a pivot. This plate-shaped
member 106 is tilted in a direction depicted in FIG. 1B (first
tilting direction) or in a reverse direction (second tilting
direction). The tilt angle is an approximately arcsin (arcsine) of
a value obtained by dividing the height of the pivot member 105 by
the half of the length of the plate-shaped member 106.
[0056] The plate-shaped member 106 is formed of two layers, that
is, an upper layer and a lower layer. On a lower layer 107, a pair
of bearing portions 108 formed in a loop is formed for rotatably
supporting the plate-shaped member 106. In the present embodiment,
the bearing portions 108 have an arc cross-section. Here, the
bearing portions 108 are disposed on an end side not engaging the
pivot member 105 of the plate-shaped member 106. As most clearly
depicted in FIG. 1D, a pair of regulating members 109 is provided
so as to correspond to the pair of bearing portions 108. The
regulating members 109 each has a stopper 109a protruding
externally in approximately parallel to the silicon substrate 101.
This stopper 109a has a positional relation as depicted in FIG. 1C
in which the stopper 109a enters the bearing portion 108 from the
inside and engages the inner surface of the bearing portion 108.
Also, the stopper 109a has an arc-shaped cross-section, and its
radius of curvature is approximately equal to the radius of
curvature of the inner surface of the bearing portion 108.
[0057] FIG. 2 is a drawing for explaining a rotational supporting
scheme of the plate-shaped member 106. As depicted in the drawing,
with the contact between the bearing portion 108 and the stopper
109a and the contact between the plate-shaped member 106 and the
pivot member 105, the rotation center of the plate-shaped member
106 is determined. Since the radius of curvature of the inner
surface of the bearing portion 108 is approximately equal to the
radius of curvature of the stopper 109a, the plate-shaped member
106 can smoothly rotate with the apex of the pivot member 105 as
the rotation center. Movement of the plate-shaped member 106 in a
rotation axis direction is regulated by vertical side surfaces of
the regulating members 109 facing the side surfaces of the bearing
portions 108.
[0058] Here, the loop-shaped bearing portions 108 preferably have
an arc cross-section as in the present embodiment, but can have a
polyhedron cross-section. Also, the lower layer 107 of the
plate-shaped member 106 is a conductor, such as metal, but can be
an insulator.
[0059] With the regulating members 109 and the stoppers 109a being
conductors and their potential being equal to the potential of the
pivot member 105, even when the plate-shaped member 106 is
separated from the pivot member 105 at the time of rotation, the
bearing portions 108 and the stopper 109a are in contact with each
other, thereby making the potential of the plate-shaped member 106
equal to the potential of the pivot member 105. The probability of
the plate-shaped member 106 electrically making contact with the
pivot member 105 and the stoppers 109a is higher compared with the
probability of the plate-shaped member 106 electrically making
contact with only the pivot member 105, thereby allowing more
stable operation. By controlling the potential of the pivot member
105, the potential of the plate-shaped member 106 is established.
Also, with an electrostatic force from a difference with the
potential provided to the group of electrodes 103, the tilting
direction of the plate-shaped member 106 can be switched between
the first tilting direction and the second tilting direction.
Therefore, the direction in which the light beam incident to the
plate-shaped member 106 is reflected can be switched. Here, such a
mechanism of driving of the plate-shaped member 106 is disclosed in
detail in Japanese Patent Application Laid-Open No. 2004-78136, and
therefore is not explained further more.
[0060] The bearing portions 108 are formed on the lower layer 107
side opposite to the light reflecting surface of the plate-shaped
member 106. Therefore, since the upper surface of the plate-shaped
member 106 does not have a hole or the like, the entire upper
surface of the plate-shaped member 106 can be used as a light
reflecting area. Thus, when the optical deflecting devices
according to the present embodiment are disposed in a
two-dimensional array and a light beam is launched from an external
light source, a ration of reflecting the incident light beam is
determined by the area of the plate-shaped member 106 of each
optical deflecting device and a space area between each of the
plate-shaped members 106 of adjacent optical deflecting devices,
and can be increased to, for example, approximately 91 percent.
[0061] Next, a typical process of manufacturing an optical
deflecting device explained above is explained. Here, it is assumed
that the size of the plate-shaped member 106 measures 10
micrometers per side and its tilt angle is 10 degrees.
[0062] Step a: As depicted in FIG. 3A, on a silicon wafer serving
as the silicon substrate 101, an insulating film 102 is formed.
[0063] Step b: As depicted in FIG. 3B, an Al film serving as the
group of electrodes 103 is formed through spattering so as to have
a thickness of 200 nanometers, and is then patterned through
photolithography by using an organic resist. Then, etching is
performed through Reactive Ion etching (RIE) with Cl.sub.2 gas to
form electrodes. Through a plasma chemical-vapor deposition (CVD)
with mixed gas of SiH.sub.4 and N.sub.2O, an oxide film, which is a
protective insulating film 104, is formed so as to have a thickness
of 250 nanometers.
[0064] Step c: As depicted in FIG. 4, the protective insulating
film 104 is etched through photolithography and RIE with mixed gas
of CF.sub.4 and H.sub.2 to open the insulating film. A tungsten W
film is then formed so as to have a thickness of 1 micrometer and,
by using a photomask with gradation, the pivot member 105 is formed
through photolithography so as to have a height of 0.87
micrometers.
[0065] Step d: As depicted in FIG. 5, a novolac photoresist serving
as a sacrifice layer 201 is applied, and is then planarized through
Chemical Mechanical Polishing (CMP). By using the photomask with
gradation, a concave surface 202 is formed from the photoresist so
as to have an arc-shaped cross-section. This concave surface 202
serves as a basic pattern of the loop shape of the bearing portions
108 on the lower layer 107 of the plate-shaped member 106. At this
time, the gradation of the photomask is set so that the concave
surface 202 has a predetermined curvature.
[0066] Step e: As depicted in FIG. 6, a metal film 203, such as Al
or Al--Ti alloy, for example, serving as the lower layer 107 of the
plate-shaped member 106 is formed so as to have a thickness of 100
nanometers, and is then etched through photolithography and RIE
with Cl.sub.2 gas.
[0067] Step f: As depicted in FIG. 7, a photoresist is applied
through spraying so as to have a thickness of 200 nanometers (film
formation through organic film vapor deposition is also possible).
Through plasma CVD with mixed gas of SiH.sub.4 and N.sub.2O, an Si
oxide film is formed so as to have a thickness of 100 nanometers.
Through photolithography and RIE with mixed gas of CF.sub.4 and
H.sub.2, the Si oxide film is then opened. Through RIE with
O.sub.2, the photoresist is then etched.
[0068] Step g: As depicted in FIG. 8, through plasma CVD with mixed
gas of SiH.sub.4 and N.sub.2O, an Si oxide film is formed so as to
have a thickness of 300 nanometers.
[0069] Step h: As depicted in FIG. 9, etching is performed through
photolithography and RIE with mixed gas of Cf.sub.4 and
H.sub.2.
[0070] Step i: As depicted in FIG. 10, a photoresist is applied,
and is then planarized through CMP.
[0071] Step j: As depicted in FIG. 11, a metal film 204, such as Al
or Al--Ti alloy, for example, serving as the upper layer of the
plate-shaped member 106 is formed so as to have a thickness of 100
nanometers, and is then etched through photolithography and RIE
with Cl.sub.2 gas. In a plan view included in FIG. 11, the
plate-shaped member 106 covers the entire surface, and therefore
part of device is omitted.
[0072] Step k: Isotropic etching is performed with O.sub.2 plasma
and the sacrifice layer of the novolac photoresist is removed,
thereby completing an optical deflecting device. In a plan view
included in FIG. 12, the plate-shaped member 106 covers the entire
surface, and therefore part of device is omitted.
[0073] FIGS. 13A to 13D are drawings of the structure of an optical
deflecting device according to the present embodiment. FIGS. 14A,
14B, and 15 to 23 are drawings for explaining an optical deflecting
device manufacturing method according to the present
embodiment.
[0074] FIG. 13A is a schematic plan view of the optical deflecting
device (a plate-shaped member acting as a movable mirror is
omitted). FIG. 13B is an A-B schematic cross-section view. FIG. 13C
is a C-D schematic cross-section view. FIG. 13D is a schematic side
view. Here, in FIG. 13A, the plate-shaped member acting as a
movable mirror is omitted because it covers the entire surface.
Also in FIG. 13D, the plate-shaped member is omitted.
[0075] In the optical deflecting device according to the present
embodiment, the regulating members 109 and the stoppers 109a are
conductors. Other than that, the second embodiment is similar to
the first embodiment.
[0076] Next, a typical process of manufacturing an optical
deflecting device explained above is explained. Here, it is assumed
that the size of the plate-shaped member 106 measures 10
micrometers per side and its tilt angle is 10 degrees.
[0077] Step a: As depicted in FIG. 14A, on a silicon wafer serving
as the silicon substrate 101, the insulating film 102 is
formed.
[0078] Step b: As depicted in FIG. 14B, an Al film serving as the
group of electrodes 103 is formed through spattering so as to have
a thickness of 200 nanometers, and is then patterned through
photolithography by using an organic resist. Then, etching is
performed through RIE with Cl.sub.2 gas to form electrodes. Through
a plasma CVD with mixed gas of SiH.sub.4 and N.sub.2O, an oxide
film, which is the protective insulating film 104, is formed so as
to have a thickness of 250 nanometers.
[0079] Step c: As depicted in FIG. 15, the protective insulating
film 104 is etched through photolithography and RIE with mixed gas
of CF.sub.4 and H.sub.2 to open the insulating film. A tungsten W
film is then formed so as to have a thickness of 1 micrometer and,
by using a photomask with gradation, the pivot member 105 is formed
through photolithography so as to have a height of 0.87
micrometers.
[0080] Step d: As depicted in FIG. 16, a novolac photoresist
serving as the sacrifice layer 201 is applied, and is then
planarized through Chemical Mechanical Polishing (CMP). By using
the photomask with gradation, the concave surface 202 is formed
from the photoresist so as to have an arc-shaped cross-section.
This concave surface 202 serves as a basic pattern of the loop
shape of the bearing portions 108 formed on the lower layer 107 of
the plate-shaped member 106. At this time, the gradation of the
photomask is set so that the concave surface 202 has a
predetermined curvature.
[0081] Step e: As depicted in FIG. 17, the metal film 203, such as
Al or Al--Ti alloy, for example, serving as the lower layer 107 of
the plate-shaped member 106 is formed so as to have a thickness of
100 nanometers, and is then etched through photolithography and RIE
with Cl.sub.2 gas.
[0082] Step f: As depicted in FIG. 18, a photoresist is applied
through spraying so as to have a thickness of 200 nanometers (film
formation through organic film vapor deposition is also possible).
Through spattering, an Al or Al--Ti alloy film is formed so as to
have a thickness of 100 nanometers. Through photolithography and
RIE with Cl.sub.2, the metal film is then opened. Through RIE with
O.sub.2, the photoresist is then etched.
[0083] Step g: As depicted in FIG. 19, through spattering, an Al or
Al--Ti alloy film is formed so as to have a thickness of 300
nanometers.
[0084] Step h: As depicted in FIG. 20, etching is performed through
photolithography and RIE with Cl.sub.2.
[0085] Step i: As depicted in FIG. 21, a photoresist is applied,
and is then planarized through CMP.
[0086] Step j: As depicted in FIG. 22, the metal film 204, such as
Al or Al--Ti alloy, for example, serving as the upper layer (light
reflecting layer) of the plate-shaped member 106 is formed so as to
have a thickness of 100 nanometers, and is then etched through
photolithography and RIE with Cl.sub.2. In a plan view included in
FIG. 22, the plate-shaped member 106 covers the entire surface, and
therefore part of device is omitted.
[0087] Step k: As depicted in FIG. 23, isotropic etching is
performed with O.sub.2 plasma and the sacrifice layer of the
novolac photoresist is removed, thereby completing an optical
deflecting device. In a plan view included in FIG. 23, the
plate-shaped member 106 covers the entire surface, and therefore
part of device is omitted.
[0088] FIGS. 24A to 24D are drawings of the structure of an optical
deflecting device according to the present embodiment. FIGS. 25A,
25B, and 26 to 34 are drawings for explaining an optical deflecting
device manufacturing method according to the present
embodiment.
[0089] FIG. 24A is a schematic plan view of the optical deflecting
device. FIG. 24B is an A-B schematic cross-section view. FIG. 24C
is a C-D schematic cross-section view. FIG. 24D is a schematic side
view. Here, in FIG. 24A, the plate-shaped member acting as a
movable mirror is omitted because it covers the entire surface.
Also in FIG. 24D, the plate-shaped member is omitted.
[0090] In the optical deflecting device according to the present
embodiment, the lower layer 107 of the plate-shaped member 106 and
the bearing portions 108 formed thereon are insulators. Also, as
the group of electrodes 103, two electrodes "a" and "b" are formed
in the first tilting direction of the plate-shaped member, whilst
two electrodes "c" and "d" are formed in the second tilting
direction thereof. In a driving scheme, when a voltage is applied
between the electrodes "a" and "b" in the first tilting direction,
an intermediate potential is induced to the plate-shaped member
106. when the intermediate potential between the electrodes "a" and
"b" in the first tilting direction is provided to the electrodes
"c" and "d" in the second tilting direction, there is no potential
difference between the plate-shaped member 106 and the electrodes
"c" and "d" in the second tilting direction, thereby preventing an
electrostatic force to act. Therefore, the plate-shaped member 106
is tilted in the first direction. Here, such a induced-type driving
scheme is disclosed in detail in Japanese Patent Application
Laid-Open No. 2004-78136, and therefore is not explained further
more.
[0091] Next, a typical process of manufacturing an optical
deflecting device explained above is explained. Here, it is assumed
that the size of the plate-shaped member 106 measures 10
micrometers per side and its tilt angle is 10 degrees.
[0092] Step a: As depicted in FIG. 25A, on a silicon wafer serving
as the silicon substrate 101, the insulating film 102 is
formed.
[0093] Step b: As depicted in FIG. 25B, an Al film serving as the
group of electrodes 103 is formed through spattering so as to have
a thickness of 200 nanometers, and is then patterned through
photolithography by using an organic resist. Then, etching is
performed through RIE with Cl.sub.2 gas to form electrodes. Since a
dielectric voltage can be ensured on the lower layer 107 of the
plate-shaped member 106, the protective insulating film 104 of the
first and second embodiments can be omitted.
[0094] Step c: As depicted in FIG. 26, the insulating film 102 is
etched through photolithography and RIE with mixed gas of CF.sub.4
and H.sub.2 to open the insulating film 102. A polysilicon film is
then formed through CVD so as to have a thickness of 1 micrometer
and, by using a photomask with gradation, the pivot member 105 is
formed through photolithography so as to have a height of 0.87
micrometers.
[0095] Step d: As depicted in FIG. 27, a novolac photoresist
serving as the sacrifice layer 201 is applied, and is then
planarized through Chemical Mechanical Polishing (CMP). By using
the photomask with gradation, the concave surface 202 is formed
from the photoresist so as to have an arc-shaped cross-section.
This concave surface 202 serves as a basic pattern of the loop
shape of the bearing portions 108 formed on the lower layer 107 of
the plate-shaped member 106. At this time, the gradation of the
photomask is set so that the concave surface 202 has a
predetermined curvature.
[0096] Step e: As depicted in FIG. 28, the metal film 203, such as
a SiN (silicon nitride) film, serving as the lower layer 107 of the
plate-shaped member 106 is formed through CVD, and is then etched
through photolithography and RIE with mixed gas of CHF.sub.3 and
H.sub.2.
[0097] Step f: As depicted in FIG. 29, a photoresist is applied
through spraying so as to have a thickness of 200 nanometers (film
formation through organic film vapor deposition is also possible).
Through plasma CVD with mixed gas of SiH.sub.4 and N.sub.2O, a Si
oxide film is formed so as to have a thickness of 100 nanometers.
Through photolithography and RIE with CF.sub.4 and H.sub.2, the Si
oxide film is then opened. Through RIE with O.sub.2, the
photoresist is then etched.
[0098] Step g: As depicted in FIG. 30, through plasma CVD with
mixed gas of SiH.sub.4 and N.sub.2O, a Si oxide film is formed so
as to have a thickness of 300 nanometers.
[0099] Step h: As depicted in FIG. 31, the insulating film is
etched through photolithography and RIE with mixed gas of Cf.sub.4
and H.sub.2. Step i: As depicted in FIG. 32, a photoresist is
applied, and is then planarized through CMP.
[0100] Step j: As depicted in FIG. 33, the metal film 204, such as
Al or Al--Ti alloy, for example, serving as the upper layer (light
reflecting layer) of the plate-shaped member 106 is formed, and is
then etched through photolithography and RIE with Cl.sub.2. In a
plan view included in FIG. 33, the plate-shaped member 106 covers
the entire surface, and therefore part of device is omitted.
[0101] Step k: As depicted in FIG. 34, isotropic etching is
performed with O.sub.2 plasma and the sacrifice layer of the
novolac photoresist is removed, thereby completing an optical
deflecting device. In a plan view included in FIG. 34, the
plate-shaped member 106 covers the entire surface, and therefore
part of device is omitted.
[0102] FIG. 35 depicts the structure of an optical projecting
device 800 using the optical deflecting device explained above. In
FIG. 35, with light having an angle of divergence emitted from a
light source 802, an optical deflecting device 801 (or its
two-dimensional array) according to the present invention is
radiated through, for example, a rotational color filer 805.
Reflected light from a light reflecting surface of a plate-shaped
member of the optical deflecting device 801 is projected through
projection lenses 803 and 806 forming an optical system together
with a light shielding unit 804 onto a projection screen 810 when
the plate-shaped member is tilted in the first tilting direction.
This is an ON state. However, when the plate-shaped member of the
optical deflecting device 801 is tilted in the second tilting
direction, reflected light from the light reflecting surface is
shielded by the light shielding unit 804 serving as a diaphragm,
and cannot be projected onto the projection screen. This is an OFF
state.
[0103] When the two-dimensional array of the optical deflecting
device 801 is used, with this ON or OFF, an image can be formed
onto the projection screen 810. The optical deflecting device 801
can be used as an optical switching unit of a display (that is,
pixel light and dark display) device. Therefore, excellent light
and dark control of pixels (that is, ON/OFF control of the optical
switch) can be achieved. Also, stray light (reflected light from an
adjacent element occurring at the time of distortion in a
reflecting direction) can be suppressed. Furthermore, a high-speed
operation can be achieved. Still further, high reliability can be
achieved for a long time. Still further, driving can be made with
low voltage. Still further, a contrast ratio can be increased.
[0104] According to an aspect of the present invention, the
plate-shaped member can smoothly rotate with the apex of the pivot
member as a pivot. Also, its rotation axis tends not to be shifted,
thereby allowing stable rotation of the plate-shaped member.
Furthermore, there is no hole or the like one the upper surface
(light reflecting surface) of the plate-shaped member. Therefore,
the entire upper surface of the plate-shaped member can be used as
a light reflecting surface.
[0105] According to an aspect of the present invention, the bearing
portion and the stopper have an approximately arc-shaped
cross-section. Therefore, the bearing portion smoothly slides with
respect to the stopper, thereby allowing smooth rotation of the
plate-shaped member. In particular, According to an aspect of the
present invention, the inner surface of the bearing portion and the
lower surface of the stopper engaging the inner surface have an
approximately equal radius of curvature. Therefore, friction of the
bearing portion with respect to the stopper can be further reduced,
thereby allowing more smooth rotation of the flat-plate member.
[0106] According to an aspect of the present invention, the lower
layer of the plate-shaped member is a conductor. Therefore, when
the pivot member is a conductor, the potential of the plate-shaped
member can be established with an electrical contact between the
pivot member and the plate-shaped member.
[0107] According to an aspect of the present invention, the lower
layer of the plate-shaped member is an insulator. Therefore, an
insulating film for insulating the group of electrodes from the
plate-shaped member does not have to be formed. This leads to
reduction in cost and optical deflecting apparatus manufacturing
procedure.
[0108] According to an aspect of the present invention, the bearing
portion, the regulating member, and the stopper are conductors.
Therefore, with electrical contacts among these, even if the pivot
member and the plate-shaped member are electrically separated, the
potential of the plate-shaped member can be established.
[0109] According to an aspect of the present invention, the radius
of curvature of the cross-section of the bearing portion and that
of the stopper can be approximately equalized.
[0110] According to an aspect of the present invention, excellent
light and dark control of pixels through ON/OFF control of the
optical deflecting device can be achieved. Also, a high-speed
operation can be achieved. Furthermore, high reliability can be
achieved for a long time. Still further, driving can be made with
low voltage. Still further, a contrast ratio can be increased.
Therefore, an optical projecting device capable of high-definition
image projection with a high contrast ratio can be achieved.
[0111] Although the invention has been described with respect to a
specific embodiment for a complete and clear disclosure, the
appended claims are not to be thus limited but are to be construed
as embodying all modifications and alternative constructions that
may occur to one skilled in the art that fairly fall within the
basic teaching herein set forth.
* * * * *