Patent Grant
7436572
The present invention is related generally to the art of microelectromechanical devices, and, more particularly, to micromirrors and methods of making the same.
Spatial light modulators (SLMs) are transducers that modulate an incident beam of light in a spatial pattern in response to an optical or electrical input. The incident light beam may be modulated in phase, intensity, polarization, or direction. This modulation may be accomplished through the use of a variety of materials exhibiting magneto-optic, electro-optic, or elastic properties. SLMs have many applications, including optical information processing, display systems, and electrostatic printing.
An early SLM designed for use in a projection display system is described by Nathanson, U.S. Pat. No. 3,746,911. The individual pixels of the SLM are addressed via a scanning electron beam as in a conventional direct-view cathode ray tube (CRT). Instead of exciting a phosphor, the electron beam charges deflectable reflective elements arrayed on a quartz faceplate. Elements that are charged bent towards the faceplate due to electrostatic forces. Bent and unbent elements reflect parallel incident light beams in different directions. Light reflected from unbent elements is blocked with a set of Schlieren stops, while light from bent elements is allowed to pass through projection optics and form an image on a screen. Another electron-beam-addressed SLM is the Eidophor, described in E.Baumann, “The Fischer large-screen projection system (Eidophor)” 20 J.SMPTE 351 (1953). In that system, the active optical element is an oil film, which is periodically dimpled by the electron beam so as to diffract incident light. A disadvantage of the Eidophor system is that the oil film is polymerized by constant electron bombardment and oil vapors result in a short cathode lifetime. A disadvantage of both of these systems is their use of bulky and expensive vacuum tubes.
A SLM in which movable elements are addressed via electrical circuitry on a silicon substrate is described in K. Peterson, “Micromechanical Light Modulator Array Fabricated on Silicon” 31 Appl. Phys. Let. 521 (1977). This SLM contains a 16 by 1 array of cantilever mirrors above a silicon substrate. The mirrors are made of silicon dioxide and have a reflective metal coating. The space below the mirrors is created by etching away silicon via a KOH etch. The mirrors are deflected by electrostatic attraction: a voltage bias is applied between the reflective elements and the substrate and generates an electrostatic force. A similar SLM incorporating a two-dimensional array is described by Hartstein and Peterson, U.S. Pat. No. 4,229,732. Although the switching voltage of this SLM is lowered by connecting the deflectable mirror elements at only one corner, the device has low light efficiency due to the small fractional active area. In addition, diffraction from the addressing circuitry lowers the contrast ratio (modulation depth) of the display.
Another SLM design is the Grating Light Value (GLV) described by Bloom, et al., U.S. Pat. No. 5,311,360. The GLV's deflectable mechanical elements are reflective flat beams or ribbons. Light reflects from both the ribbons and the substrate. If the distance between surface of the reflective ribbons and the reflective substrate is one-half of a wavelength, light reflected from the two surfaces adds constructively and the device acts like a mirror. If this distance is one-quarter of a wavelength, light directly reflected from the two surfaces will interfere destructively and the device will act as a diffraction grating, sending light into diffracted orders. Instead of using active semiconductor circuitry at each pixel location, the approach in the '360 patent relies on an inherent electromechanical bistability to implement a passive addressing scheme. The bistability exists because the mechanical force required for deflection is roughly linear, whereas the electrostatic force obeys an inverse square law. As a voltage bias is applied, the ribbons deflect. When the ribbons are deflected past a certain point, the restoring mechanical force can no longer balance the electrostatic force and the ribbons snap to the substrate. The voltage must be lowered substantially below the snapping voltage in order for the ribbons to return to their undeflected position. Ceramic films of high mechanical quality, such as LPCVD (low pressure chemical vapor deposition) silicon nitride, can be used to form the ribbons. However, there are several difficulties with the GLV. A problem is that a passive addressing scheme might not be able to provide high frame rates (the rate at which the entire SLM field is updated). In addition, with a passive addressing scheme, the ribbons deflect slightly even when off. This reduces the achievable contrast ratio. Also, even though the device is substantially planar, light is scattered, as in the DMD, from areas between the pixels, further reducing the contrast ratio.
Another diffraction-based SLM is the Microdisplay, described in P. Alvelda, “High-Efficiency Color Microdisplays” 307 SID 95 Digest. That SLM uses a liquid crystal layer on top of electrodes arrayed in a grating pattern. Pixels can be turned on and off by applying appropriate voltages to alternating electrodes. The device is actively addressed and potentially has a better contrast ratio than the GLV. However, the device, being based on the birefringence of liquid crystals, requires polarized light, reducing its optical efficiency. Furthermore, the response time of liquid crystals is slow. Thus, to achieve color, three devices—one dedicated for each of the primary colors—must be used in parallel. This arrangement leads to expensive optical systems.
A silicon-based micro-mechanical SLM with a large fractional optically active area is the Digital Mirror Device (DMD), developed by Texas Instruments and described by Hornbeck, U.S. Pat. No. 5,216,537 and other references.
Therefore, what is needed is a spatial light modulator that has a high resolution, a high fill factor, and a high contrast ratio.
Disclosed herein is a micromirror device having one or more exposed posts to incident light to be modulated. The objects and advantages of the present invention will be obvious, and in part appear hereafter and are accomplished by the present invention that provides a method and apparatus for operating pixels of spatial light modulators in display systems. Such objects of the invention are achieved in the features of the independent claims attached hereto. Preferred embodiments are characterized in the dependent claims. In the claims, only elements denoted by the words “means for” are intended to be interpreted as means plus function claims under 35 U.S.C. §112, the sixth paragraph.
While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:
The micromirror of the present invention comprises a reflective deflectable mirror plate attached to a deformable hinge that is held on a substrate. The mirror plate and the hinge of the micromirror are constructed such that, when used as a member of a micromirror array in a spatial light modulator for modulating a light beam incident thereon, the hinge is exposed to the incident light. Specifically, the hinge blocks a portion of the incident light beam onto the mirror plate. Alternatively, the micromirror can be constructed such that the hinge and the mirror plate are in different planes, and the plane of the hinge is closer to the incident light than the plane of the mirror plate.
The micromirror of the present invention can compose a micromirror array of a spatial light modulator that can be used in many applications, such as in display systems.
The illumination system provides primary color light that are sequentially applied to the spatial light modulator. In an exemplary configuration, the illumination system light source 102, which can be an arc lamp, lightpipe 104 that can be any suitable integrator of light or light beam shape changer, and color filter 106, which can be a color wheel. In this particular configuration, the color wheel is positioned after the light source and lightpipe on the propagation path of the illumination light from the light source. Of course, other optical configurations can also be used, such as placing the color wheel between the light source and the lightpipe. Optical element 108, which can be a condensing lens, directs the primary color light onto the spatial light modulator in which the primary color light is reflected either into or away from projection lens 109 so as to generate a desired image pattern in the display target. The set of primary colors can comprise any set of three or more colors used to render the output image.
In a number of embodiments of the invention, the micromirror array of the spatial light modulator micromirror array has millions of micromirrors depending upon the desired resolution of the display system. For example, the spatial light modulator may have a resolution of 1024×768 or higher, or 1280×1024 or higher, or 1640×1280 or higher. Of course, the micromirror array device may have a fewer number of micromirrors than in display, or other applications, such as optical switching.
The micromirror array, especially used for display systems, can be constructed having a pitch (the center-to-center distance between adjacent micromirrors) of 25 micrometers or less, or 10.16 micrometers or less, or from 4.38 to 10.16 micrometers. The gap between adjacent micromirrors is approximately of 0.5 micrometers or less, or from 0.1 to 0.5 micrometer. And the mirror plate of the micromirror has a dimension of from 20 micrometers to 10 micrometers.
According to the invention, the micromirror array comprises at least a micromirror whose hinge is exposed to the incident light, and such hinge blocks a portion of the incident light onto the mirror plate. As a way of example,
Referring to
Hinge 208 is held on substrate 233 and connected to the substrate by posts 207. Mirror plate 203 is attached to the hinge via hinge contact 209 such that the mirror plate can rotate above the substrate. The hinge, mirror plate, and the substrate are formed on separate planes. Specifically, as shown in the figure, the mirror plate is formed above the substrate and spaced gap1 from the substrate. The hinge is formed above the mirror plate and spaced gap2 from the mirror plate. The hinge, however is exposed to the incident light, and the hinge plane is placed closer to the incident light than the plane of the mirror plate. The hinge blocks a portion of the incident light onto the mirror plate. The two gaps may or may not be the same. However, gap1 between the hinge and the mirror plate is preferably smaller than gap2 between the mirror plate and the substrate. For example, gap2 can be 0.45 microns or less, or from 0.15 to 0.45 microns, as set forth in U.S. patent application Ser. No. 10/627,303 to Patel, filed on Jul. 24, 2003, now U.S. Pat. No. 6,980,347, issued Dec. 27, 2005, the subject matter being incorporated herein by reference.
Rather than forming the mirror plate and the hinge on the same substrate as shown in
Though the relative geometric positions of the mirror plate and the hinge of a micromirror are preferably configured as discussed with reference to
Referring to
Micromirror array 210 comprises a plurality of micromirror devices, such as the micromirror device shown on
According to an embodiment of the invention, the micromirror plate is attached to the zigzagging multi-layered hinge structure such that the micromirror plate can rotate along an axis that is parallel to but offset from a diagonal of the micromirror plate. The hinge structures are formed above the semiconductor wafer and the mirror plates such that the hinge structures are exposed to the incident light as illustrated in the figure. As a way of example, micromirror plate 203 has a well defined geometrical diagonal 206. However, the rotation axis of the micromirror plate is along direction 205 that is parallel to but offset from diagonal 206. Such a rotation axis can be achieved by attaching the hinge structure to the mirror plate at a point not along the mirror plate diagonal 206. The point of attachment can be at least 0.5 um, at least 1 um, or at least 2 um away from the diagonal 206. In one embodiment, the point of attachment is from 1/40 to ⅓ the length of the diagonal away from diagonal 206, or from 1/20 to ¼ if desired—although any desired distance away from the diagonal is possible if so desired in the present invention. In the present invention, the micromirror preferably has a substantially four-sided shape. Whether the micromirror is a rectangle, square, rhombus or trapezoid, even if the corners are rounded or “clipped” or if an aperture or protrusion is located on one or more of the sides of the micromirror, it is still possible to conceptually connect the four major sides of the micromirror shape and take a diagonal across the middle of the micromirror. In this way, a center diagonal can be defined even if the micromirror plate is substantially but not perfectly a rhombus, trapezoid, rectangle, square, etc. However, the rotation axis of the micromirror plate is not along the center diagonal but is along direction 205 that is parallel to but offset from diagonal 206. By “parallel to but offset from the diagonal” it is meant that the axis of rotation can be exactly parallel to or substantially parallel to (±19 degrees) the diagonal of the micromirror. This type of design benefits the performance of the micromirror device in a number of ways. One advantage of this asymmetric offset arrangement is that the micromirror plate can rotate at a larger angle than the rotation angle that can be achieved in a symmetrical arrangement (with a mirror plate—substrate gap being the same). The length of the diagonal of the mirror plate is preferably 25 microns or less.
In order to hold the micromirror plate and meanwhile, provide a rotation axis for the micromirror plate for rotating above the substrate, each hinge structure, such as hinge structure 204, further comprises posts 207, hinge 208, and contact 209 as shown in
In this embodiment of the invention, the two posts are formed on the substrate. The hinge (e.g. hinge 204) is supported by the two posts above the substrate and attached to the micromirror plate via the contact (e.g. contact 209). In this configuration, the micromirror plate can pivot below the hinge and above the substrate.
Instead of forming the hinge structures on the semiconductor wafer, the hinge structures can be formed on another substrate, such as glass that is positioned proximate to semiconductor substrate 233, as shown in
The hinge structure can take other suitable forms as desired.
The hinge structure can also be formed on a substrate other than the semiconductor substrate, as shown in
Referring to
In the embodiments discussed above, the hinge-supports of all micromirror devices form a continuous hinge-support frame for all micromirror plates, but that is not an absolute requirement. Moreover, the posts of each hinge structure are not required to be formed along a diagonal of the micromirror plate. Referring to
A top view of a micromirror of the micromirror array in
Referring to
There is a variety of ways to construct the micromirror devices described above. Exemplary processes will be discussed in the following with references to
Referring to
First sacrificial layer 290 is deposited on substrate 280. First sacrificial layer 290 may be any suitable material, such as amorphous silicon, or could alternatively be a polymer or polyimide, or even polysilicon, silicon nitride, silicon dioxide, etc. depending upon the choice of sacrificial materials, and the etchant selected. If the first sacrificial layer is amorphous silicon, it can be deposited at 300-350° C. The thickness of the first sacrificial layer can be wide ranging depending upon the micromirror size and desired title angle of the micro-micromirror, though a thickness of from 500 Å to 50,000 Å, preferably around 10,000 Å, is preferred. The first sacrificial layer may be deposited on the substrate using any suitable method, such as LPCVD or PECVD.
As an optional feature of the embodiment, anti-reflection layer 285 may be deposited on the surface of the substrate for one embodiment of the invention. The anti-reflection layer is deposited for reducing the reflection of the incident light from the surface of the substrate. Alternatively, other optical enhancing layers may be deposited on either surface of the glass substrate as desired.
After depositing the first sacrificial layer, a plurality of structure layers will be deposited and patterned as appropriate. According to the invention, a structural layer is a layer that will not be removed after the removal of the sacrificial layers. The first structural layer deposited on the first sacrificial layer is micromirror plate layer 300 for forming a micromirror. Because the micromirror is designated for reflecting incident light in the spectrum of interest (e.g. visible light spectrum), it is preferred that the micromirror plate layer comprises of one or more materials that exhibit high reflectivity (preferably 90% or higher) to the incident light.
In accordance with one embodiment of the invention, micromirror plate layer 300 can be a multi-layered structure, as shown in
In fact, one or more protecting layers can be provided regardless whether the light reflecting layer is conducting or not. For example, a protecting layer (e.g. protecting layer 301) can be deposited on the light reflecting layer for protecting the light reflecting layer. In addition, another protecting layer (e.g. protecting layer 307) can be provided, on which the enhancing layer can be deposited. In this way, the light reflecting layer and the enhancing layers are laminated between the outmost protecting layers.
The protecting layers can be made of any suitable materials, preferably a material of electrically and/or mechanically stable. For example, the protecting layer may be SiOx with a preferred thickness of 400 Å. Of course, other suitable materials may also be employed herein.
In depositing the micromirror plate layer(s), PVD is preferably used at 150° C. The thickness of the micromirror plate layer can be wide ranging depending upon the desired mechanical (e.g. elastic module), the size of the micromirror, desired titled angle and electronic (e.g. conductivity) properties of the micromirror plate and the properties of the materials selected for forming the micromirror plate. According to the invention, a thickness of from 500 Å to 50,000 Å, preferably around 2500 Å, is preferred.
The micromirror plate layer 300 is then patterned into a desired shape, as shown in
After the formation of the micromirror plate, further structural layers are deposited and patterned. Specifically, a plurality of layers of the hinge structure will be deposited and patterned for forming the hinge structure. Referring to
In accordance with the operation mechanism of the micromirror plate and the constructional design, it is desired that the posts comprise materials that are insusceptible to elastic deformation (e.g. fatigue, creep, dislocation motion) during the operation of the device. It is also preferred that such materials have large elastic modulus and exhibits high stiffness. Opposite to that of the posts, the materials of the hinge are expected to be more compliant because the hinge deforms while the micromirror plate pivots. Moreover, the hinge is desired to be electrically conducting such that the micromirror plate can be held at a particular voltage level.
In the preferred embodiment of the invention, the micromirror plate layer comprises an aluminum layer, and the second sacrificial layer is silicon. This design, however, can cause defects in the hinge structure due to the diffusion of the aluminum and silicon at the edges of the micromirror plate, wherein the aluminum is exposed to the silicon. To solve this problem, a protection layer (not shown) may be deposited on the patterned micromirror plate before depositing the second sacrificial silicon layer such that the aluminum layer can be isolated from the silicon sacrificial layer. Then the protection layer is patterned according to the shape of the micromirror plate. After the patterning, segments of the protection layer (e.g. segment 211 in
The deposited second sacrificial layer is patterned afterwards for forming one deep-via area 320 and a shallow via area 330 using standard lithography technique followed by etching, as shown in
Referring to
After the deposition, layers 340 and 350 are patterned into a desired configuration (e.g. hinge 204 in
After etching layers 340 and 350, a post 260 and a contact area 330 are formed. The bottom segment of contact area 330 is removed by etching and the part of the micromirror plate underneath the contact area is thus exposed. The exposed part of micromirror 203 will be used to form an electric-contact with external electric source. The sidewalls (e.g. 335) of contact area 330 are left with residues of layers 340 and 350 after etching. The residue 335 has a slope measured by angle θ approximately 75 degrees, but may vary between 0 and 89 degrees. The residue on the sidewalls helps to enhance the mechanical and electrical properties of the hinge that will be formed afterwards. In other embodiments, there can be more post on either side of the mirror forming a continuous element with the posts corresponding to the adjacent micromirror in an array as shown in
After the completion of patterning and etching of layers 340 and 350, hinge layer 360 is deposited and then patterned as shown in
A hinge is expected to function both as a reliable mechanical element and as a robust electrical conductor. Conductors on MEMS devices are generally metals (e.g. Al, Ti, W, Cu, or Ta), metal alloys (e.g. Al—1 wt. % Cu, or Al—1 wt. % Si—1 wt % Cu), metal nitrides (e.g. TiN or TaN) or metal silicides (e.g. TiSi2, WSi2, or TaSi2). These materials are often poor mechanical elements, especially over long times and large numbers of cycles and in MEMS applications where the amount of strain required for failure is very small. The purpose of this embodiment is to reduce the residual displacement in a composite hinge in the rest state by choosing a conductor with a very low elastic modulus compared to that of the robust mechanical element(s) that makes up the rest of the hinge. In an embodiment of the invention, the hinge comprises a TiNx (e.g. 100 Å in thickness) layer and SiNx layer (e.g. 400 Å in thickness), although the material could include silicon nitride, silicon dioxide, polysilicon, or any suitable material. The hinge may further comprise a conductive polymer formed on top of the SiNx layer. Any conductive polymer might be used, such as polypyrrole, polyaniline, or poly (3,4-ethylenedioxythiophene)poly(styrenesulfonate). Alternatively, the conductive layer could be any conductive material that is compliant including metals formed with a distribution of pores, very compliant metals, or any suitable material.
After all structural layers are deposited and patterned according to the desired configuration, the sacrificial layers and the removable barrier layers are removed using a spontaneous vapor phase chemical etchant. According to the invention, the etchant is selected from a group comprising interhalogen (e.g. bromine trifluoride), noble gas halide (e.g. xenon difluoride) and HF, and more preferably xenon difluoride. It is further preferred that the chemical etchant is mixed with a diluent gas, which is preferably an inert gas selected from N2, He, Ne, Ar, Kr, and Xe, and more preferably He and N2, as set forth in U.S. patent applications, Ser. No. 09/427,841 to Patel, filed Oct. 26, 1999; Ser. No. 09/649,569 to Patel, filed Aug. 28, 2000; and Ser. No. 10/269,149 to Patel, filed Oct. 12, 2002, the subject matter of each being incorporated herein by reference. A cross-sectional view of the released micromirror device is presented in
In the above described exemplary fabrication process, the processes for forming the hinge support (e.g. processes described in
Another exemplary process for constructing the micromirror devices described above will be discussed in the following with references to
Referring to
First sacrificial layer 290 is deposited on substrate 280. First sacrificial layer 290 may be any suitable material, such as amorphous silicon, or could alternatively be a polymer or polyimide, or even polysilicon, silicon nitride, silicon dioxide, etc. depending upon the choice of sacrificial materials, and the etchant selected. If the first sacrificial layer is amorphous silicon, it can be deposited at 300-350° C. The thickness of the first sacrificial layer can be wide ranging depending upon the micromirror size and desired title angle of the micro-micromirror, though a thickness of from 500 Å to 50,000 Å, preferably around 10,000 Å, is preferred. The first sacrificial layer may be deposited on the substrate using any suitable method, such as LPCVD or PECVD.
As an optional feature of the embodiment, anti-reflection layer 285 may be deposited on the surface of the substrate for one embodiment of the invention. The anti-reflection layer is deposited for reducing the reflection of the incident light from the surface of the substrate. Alternatively, other optical enhancing layers may be deposited on either surface of the glass substrate as desired.
After depositing the first sacrificial layer, a plurality of structure layers will be deposited and patterned as appropriate. According to the invention, a structural layer is a layer that will not be removed after the removal of the sacrificial layers.
The deposited first sacrificial layer is patterned for forming one deep-via area 320 using standard lithography techniques followed by etching, as shown in
The first structural layer deposited on the first sacrificial layer is hinge layer 360 for forming a hinge structure. Because the hinge provides a rotation axis for the micromirror plate, it is natural to expect that the hinge layer comprises a material that is at least susceptible to plastic deformation (e.g. fatigue, creep, and dislocation motion). Furthermore, when the hinge layer is also used as electric contact for the micromirror plate, it is desired that the material of the hinge layer is electrically conductive. Examples of suitable materials for the hinge layer are silicon nitride, silicon oxide, silicon carbide, polysilicon, Al, Ir, titanium, titanium nitride, titanium oxide(s), titanium carbide, CoSiNx, TiSiNx, TaSiNx, or other ternary and higher compounds. When titanium is selected for the hinge layer, it can be deposited at 100° C. Alternatively, the hinge layer may comprise of multi-layers, as previously explained.
After deposition, the hinge layer is then patterned as desired using etching as shown on
Referring to
The second sacrificial layer 310 is afterwards patterned for forming shallow-via area 330 using standard lithography techniques followed by etching, as shown in
The last structural layer deposited on the second sacrificial layer is micromirror plate layer 300 for forming a micromirror. Because the micromirror is designated for reflecting incident light in the spectrum of interest (e.g. visible light spectrum), it is preferred that the micromirror plate layer comprises of one or more materials that exhibit high reflectivity (preferably 90% or higher) to the incident light. According to the embodiment of the invention, micromirror plate layer 300 is a multi-layered structure as shown in
According to another embodiment of the invention, the light reflecting layer 305 is an electro-conducting layer that comprises a material having a resistivity less than 10,000 μΩ·cm. Layers 301 and 307 are insulators with resistivities greater than 10,000 μΩ·cm. And layer 303 is an electro-conducting layer with a resistivity also less than 10,000 μΩ·cm.
Micromirror plate layer 300 is then patterned into a desired shape, as shown in
In order to release the micromirror plate for pivoting along the hinge, the sacrificial layers (e.g. layers 290 and 310) are removed by etching as discussed below. A cross-sectional view of the released micromirror device is presented in
It will be appreciated by those of skill in the art that a new and useful spatial light modulator has been described herein. In view of the many possible embodiments to which the principles of this invention may be applied, however, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of invention. For example, those of skill in the art will recognize that the illustrated embodiments can be modified in arrangement and detail without departing from the spirit of the invention. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4566935 | Hornbeck | Jan 1986 | A |
| 4615595 | Hornbeck | Oct 1986 | A |
| 5061049 | Hornbeck | Oct 1991 | A |
| 5083857 | Hornbeck | Jan 1992 | A |
| 5784190 | Worley | Jul 1998 | A |
| 5835256 | Huibers | Nov 1998 | A |
| 6028690 | Carter et al. | Feb 2000 | A |
| 6046840 | Huibers | Apr 2000 | A |
| 6224216 | Parker et al. | May 2001 | B1 |
| 6522454 | Meier et al. | Feb 2003 | B2 |
| 6523961 | Ilkov et al. | Feb 2003 | B2 |
| 6529310 | Huibers et al. | Mar 2003 | B1 |
| 6804039 | Doan et al. | Oct 2004 | B1 |
| 6867897 | Patel et al. | Mar 2005 | B2 |
| 6873450 | Patel et al. | Mar 2005 | B2 |
| 20020024641 | Ilkov et al. | Feb 2002 | A1 |
| 20030214639 | Patel | Nov 2003 | A1 |
| 20040004753 | Pan | Jan 2004 | A1 |
| 20040125346 | Huibers | Jul 2004 | A1 |
| 20040156089 | Doan | Aug 2004 | A1 |
| 20040156090 | Patel et al. | Aug 2004 | A1 |
| 20040233505 | Huibers et al. | Nov 2004 | A1 |
| 20050018091 | Patel et al. | Jan 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| WO 2004000720 | Dec 2003 | WO |
| WO 2004001487 | Dec 2003 | WO |
| WO 2004001717 | Dec 2003 | WO |
| WO 2004109363 | Dec 2004 | WO |
| WO 2004109364 | Dec 2004 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20060044519 A1 | Mar 2006 | US |
