WO2002005010A1

WO2002005010A1 - Grating type spatial light modulators and method of manufacturing grating type spatial light modulators

Info

Publication number: WO2002005010A1
Application number: PCT/US2001/021762
Authority: WO
Inventors: Charles F. Hester; Charles A. Whitehead
Original assignee: Opts, Inc.
Priority date: 2000-07-10
Filing date: 2001-07-10
Publication date: 2002-01-17
Also published as: AU2002218787A1; WO2002005010A9

Abstract

A spatial light modulator having grating bars in parallel with each other and with underlying substrate. According to one embodiment of the invention, a spatial light modulator (601) is provided that employs B number of parallel bars (403) arranged to form a grating, where B is a number greater than 1, but only has S number of support posts (411) supporting the bars, where S ≤ 2B-1. Another embodiment of the invention provides a method for manufacturing a grating-type spatial light modulator that requires fewer manufacturing steps that conventional manufacturing methods.

Description

GRATING TYPE SPATIAL LIGHT MODULATORS

AND METHOD OF MANUFACTURING GRATING TYPE SPATIAL LIGHT MODULATORS

Related Application Information

This application incorporates (1) U.S. Patent Application No. 60/183,793, filed on February 22, 2000, entitled "Point Probe Memory With Light Modulator Readout," naming Dr. Charles Hester and Charles Whitehead as inventors, which application is incorporated entirely herein by reference; (2) U.S. Provisional Patent Application No. 60/142,931, entitled "Analog Compressive Network," naming Charles F. Hester and Marshal K. Quick as inventors, filed on July 9, 1999, which application, along with the entirety of its attached Appendix, is incorporated entirely herein by reference; (3) the U.S. Patent Application entitled "Deformable Grating Modulator Capable Of Both Phase And Amplitude Modulation," naming Charles F. Hester as inventor, filed on July 10, 2000, which application is incorporated entirely herein by reference; (4) the U.S. Patent Application entitled "Microelectromechanical Deformable Grating For Binary Optical Switching," naming Charles F. Hester as inventor, filed on July .10, 2000, which application is incorporated entirely herein by reference; and (5) the U.S. patent application entitled "Adaptive Compressive Network," naming Charles F. Hester and Marshall K. Quick as inventors, filed on July 10, 2000.

Background Of The Invention

Field Of The Invention The invention relates to a new structure for a spatial light modulator that requires less power and provides a more accurate modulation. The invention also relates to new methods for forming variously structured spatial light modulators. These methods require fewer manufacturing steps than conventional methods. In addition, these methods permit a spatial light modulator to be formed separate from the substrate upon which it is to be mounted.

Discussion Of The Prior Art A frequently used component in optical processing and computing is the spatial light modulator. A spatial light modulator is a structure that allows a light beam to be controllably spatially (as opposed to frequency) modulated. For example, spatial light modulators are used for inputting information into an optical processor, for modulating carrier light during an optical computation, such as in a Fourier filter, as a neural network interconnect, and as light beam switches. Particularly useful are programmable spatial light modulators that can be reconfigured in response to electrical or optical signals.

There are many different types of programmable spatial light modulators, including, for example, modulators employing liquid crystal devices, magneto optical materials, acousto optical materials. Various types of spatial light modulators are described in "Two-Dimensional Spatial Light Modulators: A Tutorial" by John A. Neff et al., Proceedings of the IEEE, Vol. 78, No. 5 (May 1990), pages 826-855, which is incorporated entirely herein by reference. One particular type of spatial light modulator is the two dimensional grating spatial light modulator, which uses a set of parallel bars forming a grating.

Referring to Figs. 1-3, this type of modulator 101 has a number of parallel bars 103 suspended above a reflective surface 105. Each bar 103 is covered with a reflective material, and supported on either end by a support post 107. The modulator 101 also has one or more electrodes 201 corresponding to the bars 103.

As shown in Fig. 2, when the electrodes 201 are inactive, the distance d between the bars 103 and the reflective surface 105 is λ/2 (or an integral multiple of λ 2), where λ/2 is the wavelength of the light to be modulated. Thus, the light 203 reflected from the upper reflective surface of the bars 103 is in phase with the light 205 reflected from the reflective surface 105, so the modulator 101 acts as a mirror. When the electrodes 201 are activated, however, the charge on the electrodes 201 pulls the bars 103 toward the reflective surface 105, as can be seen in Fig. 3. If the bars 103 are pulled to a distance d of λ/4 (or an integral multiple of λ/4) from the reflective surface 105, then the light 303 reflected from the reflective surface of the bars 103 is opposite in phase from the light 305 reflected from the reflective surface 105. Thus, when the electrodes 201 pull the bars 103 to this position, destructive interference between light 203 and light 205 prevents the modulator 101 from reflecting light.

As previously noted, each bar 103 is supported at either end by a support post 107. This arrangement prevents the bars 103 from flexing at their ends. Accordingly, the electrodes 201 must carry a large amount of electric charge in order to sufficiently flex the bars 103. In addition, manufacturing differences between each post cause may prevent the bars 103 from being parallel to each other (relative to the reflective surface 105), thereby reducing the operational effectiveness of the modulator 101.

This type of spatial light modulator has many useful applications. In one such application, the operation of the spatial light modulator is controlled by an underlying charge- coupled device (CCD). That is, the charge in the charge wells of the CCD is employed to flex the bars of the grating. With this application of the spatial light modulator, the modulator is manufactured directly onto the surface of the CCD. This technique presents a problem, however, if the there is an error in manufacturing. A mistake in manufacturing the modulator will ruin the much more expensive underlying CCD.

Summary Of The Invention

It is therefore desirable to have a grating-type spatial light modulator that requires less power to flex the grating bars. Still further, it is desirable to have a grating type spatial light modulator where the bars are as parallel as possible with each other and with the underlying substrate. According to one embodiment of the invention, a spatial light modulator is provided that employs B number of parallel bars arranged to form a grating, where B is a number greater than 1, but only has S number of support posts supporting the bars, where S < 2B-1. For example, various embodiments of the invention have gratings with four or more bars supported by only one or two support posts. It is also desirable to have an improved method for manufacturing grating-type spatial light modulators, particularly for applications where the spatial light modulator is going to be controlled by a CCD. Accordingly, another embodiment of the invention provides a method for manufacturing a spatial light modulator separate from the substrate on which it will be mounted for use. Still further, an embodiment of the invention provides a method for manufacturing a grating-type spatial light modulator that requires fewer manufacturing steps than conventional manufacturing methods. It is further desirable to form large two-dimensional arrays of these spatial light modulators.

Brief Description Of The Drawings Fig. 1 is a top view of a conventional micromechanical mirror type spatial light modulator. Fig. 2 is a cross-sectional view of the spatial light modulator shown in Fig. 1 taken along section line 2-2'.

Fig. 3 is a cross-sectional view of the spatial light modulator shown in Fig. 1 taken along section line 3-3'. Figs.4A and 4B illustrate a side and top view, respectively, of a spatial light modulator according to one embodiment of the invention.

Fig. 5 illustrates a top view of a spatial light modulator according to yet another embodiment of the invention.

Fig. 6 shows a top view of a spatial light modulator according to still another embodiment of the invention.

Fig. 7 illustrates a top view of a spatial light modulator according to still yet another embodiment of the invention.

Fig. 8 illustrates a top view of a spatial light modulator according to yet another embodiment of the invention. Fig. 9 illustrates a top view of a tiling pattern for spatial light modulators according to still yet another embodiment of the invention.

Fig. 10 illustrates a top view of a tiling pattern for spatial light modulators according to another embodiment of the invention.

Fig. 11-17 illustrate the process of forming a spatial light modulator according to one embodiment of the invention.

Figs 18-24 illustrate the process of forming a spatial light modulator according to another embodiment of the invention.

Fig.25 is a side view of a spatial light modulator according to yet another embodiment of the invention. Fig. 26 is a side view of a spatial light modulator according to still yet another embodiment of the invention.

Detailed Description Of Preferred Embodiments Of The Invention

A first embodiment of a grating type spatial light modulator will now be described with reference to Figures 4A and 4B. As seen in these figures, a single grating 401 includes an array of nine parallel bars 403 positioned above a substrate 405. Preferably, each of the bars 403 has the same width and is spaced at a same distance from the adjacent bar 403. Also, in addition to being parallel with each other, the bars 403 are parallel to an underlying substrate 405. As shown in Figure 4B, one end of each of bars 403(a)-403(h) is connected to a connection beam 407(a), while the opposite end of each of bars 403(b)-403(i) is connected to a second connection beam 407(b). In this fashion, the bars 403 are connected together by at least one connection beam 407 so as to form a single unit.

The end bar 403(a) is longer than the bars 403(b)-403(h), and extends to connect to a support beam 409(a). Similarly, the end bar 403(i) is longer than the bars 403(b)-403(h), and extends to connect to a support beam 409(b). A support post 411(a) then supports support beam 409(a), while a support post 411(b) supports the support beam 409(b). Thus, with the embodiment illustrated in Figures 2A and 2B, nine grating bars are supported by only two support posts.

Because the bars 403 are formed as a single unit connected by the connection beams 407, all of the bars 403 can be manufactured to be more parallel to each other relative to the plane of the underlying substrate 405 (i.e., all of the bars 403 will have a similar degree of tilt relative to the plane of the substrate 405). Further, as the bars 403 are connected to the support posts 41 1 by only the two support beams 409, the bars 403 can be moved by only little charge on the electrodes. With conventional grating-type spatial light modulators, the electrodes must exert enough force to flex each of the bars. With the embodiment of the invention shown in Figs. 4(A) and 4(B), the electrodes need only exert enough force to flex the support beams 409.

Another embodiment of the invention is shown in Fig. 5. This spatial light modulator 501 has seventeen grating bars 503. All of the bars 503 have the same width, and are spaced apart.at the same distance from the adjacent bar. Each of the bars 503 is connected one end to a first connection beam 505(a), and connected on the opposite end to a second connection beam 505(b). In this fashion, all of the bars are connected into a single unit.

A single, straight support beam 507 connects the bars 503 to a single support post 509. Fig. 5 illustrates the support beam 507 connecting to the middle of an end bar 503, but the support beam 507 could be connected to the end bar 503 at any point along its length. Further, the support beam 507 could be connected to either of the connection beams 505. Of course, while the illustrated embodiment of the invention employs only the single support beam 507 and support post 509, alternate embodiments of the invention could have additional support beams and support posts.

Yet another embodiment of the invention is shown in Fig. 6. Like the previously described embodiment, the spatial light modulator 601 shown in Fig. 6 has a series of bars 603 that are connected on either end to connection beams 605(a) and 605(b). A single support beam 607 then connects the bars 603 to a single support post 409. The support beam 607 is not straight, however, as with the previous embodiment. Instead, it loops around the bars 603 to reach the support post 609. Preferably, the two portions of the support beam 607 that run alongside the end bars 603 have the same width as the bars 603, and are the same distance from the adjacent end bar 603 as the bars 603 are from each other. In this manner, these two portions of the support beam 607 act as additional grating bars.

Fig. 7 illustrates a spatial light modulator 701 according to still another embodiment of the invention. Unlike the previously described embodiments, the grating bars 703 are not connected together with a single connection beam. Instead, each bar 703 is connected at one end to an adjacent bar by a connection beam 705, and connected to the opposite end to an opposite adjacent bar by another connection beam 705. For example, as seen in the figure, bar 703(b) is connected at one end to bar 703(a) by a connection beam 705(a), and connected at the opposite end to bar 703(c) by connection beam 705(b). Similarly, bar 703(d) is connected at one end to bar 703(c) by connection beam 705(c), and connected at the opposite end to bar 703(e) by connection beam 705(d). Also unlike the previously described embodiments, the bar 703 are note connected to the support posts 707 by a support beam. Rather, end bar 703(a) is directly connected to support post 707(a), while the opposite end bar 703(i) is directly connected to support post 707(b). Of course, those of ordinary skill in the art will appreciate that one or more support beams can be employed with this embodiment of the invention. Similarly, the bars 703 may be supported by only one support post 707.

Yet another embodiment of the invention is shown in Fig. 8. This spatial light modulator 801 is formed of two separate portions. The first portion 803 is formed of five parallel bars 805. The bars 805 are connected at one end to a connection beam 807 so as to form a single unit. Preferably, the width of each bar 805 is the same, and the distance between adjacent bars 805 is three times the width of a bar 805. A first support beam 809 then connects one end of the connection beam 807 to a support post 811, while a second support beam 813 connects the opposite end of the connection beam 807 to another support post 815.

Similarly, the second portion 817 has five parallel bars 819 that are connected at one end to a connection beam 821. Preferably, each bar 819 has the same width as the bars 805, and the distance between each bar 819 is three times the width of a bar 819. A first support beam 823 connects one end of the connection beam 821 to a support post 825, while a second support beam 827 connects the opposite end of the connection beam 821 to a support post 829. The two portions 803 and 817 are juxtaposed so that the bars 805 of the first portion 803 are evenly interleaved with the bars 819 of the second portion 817. The two sets of bars 805 and 819 are interleaved so that they are parallel with each other, and that distance between each adjacent bar is the same (preferably equal to the width of the bars 805 and 819).

As seen in Fig. 8, each support beam 809, 813, 823 and 827 is U-shaped. Preferably, the sides of the U-shape (sections 809(a), 809(c), 813(a), 813(c), 823(a), 823(c), 827(a), and 827(c)) are formed parallel to the bars.803 and 819. These sides are also formed to have the same width as the bars 803 and 819, and to have the same distance between them as the distance between bars 803 and adjacent bars 819. With this arrangement, the sides of the U-shaped support beams 809, 813, 823 and 827 can function as additional bars for the grating. Of course, the support beams 809, 813, 823 and 827 may alternately be of any desirable shape, size and length, and may be of different shapes, sizes and lengths. It should be noted that, because the grating shown in Fig. 8 has two independently controllable and interleaved sets of bars 805 and 819, this grating can perform both amplitude and phase modulation as discussed in the copending U.S. Patent Application entitled "A Grating Type Spatial Light Modulator That Provides Both Amplitude And Phase Modulation," naming Charles Hester at inventor, filed concurrently herewith, which application is incorporated entirely herein by reference.

Thus, a spatial light modulator according to the invention may few supporting posts than grating bars being supported by the posts. That is, a spatial light modulator according to the invention may employ B number of grating bars, where B is a number greater than 1, but only has S number of support posts supporting the bars, where S < 2B-1. The previously described embodiments of the invention have been directed toward individual spatial light modulators. As shown in Figs. 9 and 10, however, individual spatial light modulators can be tiled together to form arrays of multiple modulators. In Fig. 9, spatial light modulators like those shown in Fig. 5 are interleaved to form an array of modulators. Similarly, Fig. 10 illustrates an array of spatial light modulators that are variations of the embodiment shown in Figs. 4(A) and 4(B). Novel methods of forming grating-type spatial light modulators will now be described with reference to Figs. 11-20. These methods can be employed to form both conventional grating-type spatial light modulators and grating-type spatial light modulators according to the invention.

First, as shown in Fig. 11, a planarizing layer 1101 is formed on the upper passivation layer 1103 of a charge coupled device 1105. The planarizing layer 1 101 can be formed from, for example, BCB, spin-on glass, polyimide or any combination thereof. Preferably, the planarizing layer 1101 is formed with a thickness of l-2μm, but it may alternately be formed of any thickness deemed appropriate for the application. Once the planarizing layer 1 101 is formed, it can be polished to a flatness of approximately lOOOA across its surface. As seen in Fig. 11 , the charge coupled device 1105 forms a backplane 1107 with active pads 1109 underlying the passivation layer 1103. Next, as shown in Fig. 12, vias 1201 are formed through the planarizing layer 1101 and the passivation layer 1103 to reach the active pads. The vias 1201 can be formed according to any conventional method known in the art, such as photolithography and etching. Preferably, the vias 1201 should be positioned so that they will be under support posts for the grating bars, in order to maximize the use of the surface area of the spatial light modulator.

Then, as shown in Fig. 13, electrodes 1301 are formed over the planarizing layer 1 101, so that each electrode 1301 is electrically connected to one of the active pads 1 109 through a via 1201. While a variety of materials can be used to form the electrodes, aluminum is preferably employed, as it is low stress, relatively easy to work with, and optically efficient. If aluminum is used, it is preferably sputtered on in a layer approximately 200 nm thick. It is then patterned by an etch process to actually form the electrodes 1301.

As shown in Fig. 14, a sacrificial layer 1401 is then formed over the electrodes 1301. This sacrificial layer 1401 may be, for example, a polyimide layer approximately 1.5 μm, but any material that can easily be removed in a subsequent step can be employed. This sacrificial layer 1401 performs several functions. First, it initially insulates the electrodes from the grating bars that are subsequently formed over the electrodes. Second, it planarizes the electrode layer. Third, portions of the insulative layer 1401 will form the support posts for supporting the grating bars over the electrodes.

A metal layer 1501 is then formed over the insulative layer 1301, as shown in Fig. 15. The metal layer 1501 may be formed from aluminum having a thickness of approximately 200 nm, but any other reflective and conductive material or structure may be employed. The metal layer 1501 then is etched using any conventional method to form the grating bars 1601, as shown in Fig. 16. Preferably, the residual stress in the bars 1601 is relatively low, and, more preferably in the range of 5 - 15 MPa tensile. A larger tensile stress tends to force the grating bars 1601 too far away from the electrodes 1301 while compressive stress causes the useable modulating distance of the bars 1601 to be reduced by pushing them too close to the electrodes 1301.

Lastly, the bars 1601 are released by removing portions of the insulative layer 1401, as shown in Fig. 17. The portions of the insulative layer 1401 can be removed by any conventional method, but are preferably removed by a controlled plasma etch process. Still another method of manufacturing grating type spatial light modulators will now be described with reference to Figs. 18-24. This method is advantageous in that it allows a grating (or an array of gratings) to be formed on a transparent substrate, and subsequently bonded to another structure (e.g., a backplane of a CCD device) after completion.

As shown in Fig. 18, a layer 1801 of transparent conductive material, such as Indium Tin Oxide (ITO), is formed as the last layer of an anti-reflective V-coating on the a surface of a transparent substrate 1801; such as waferglass. Next, as shown in Fig. 19, a layer 1901 of insulative material is formed over the transparent electrode layer 1801. The layer 1901 may be formed from, e.g., silicon dioxide, silicon nitride, spin-on glass, or any other suitable material. For some preferred embodiments of the invention, the layer 1901 has a thickness of approximately 100 nm. Also, the layer 1901 may be patterned (not shown) to expose the layer 1801 to the subsequently formed grating bars, as will be understood by those of ordinary skill in the art.

Then, as shown in Fig. 20, a layer 2001 of sacrificial material is formed over the layer 1901 (and any exposed portion of the layer 1801). This sacrificial layer 2001 may be formed of any material that can easily be removed, such as spun-on polyimide. If spun-on polyimide is used for the layer 2001 , then the layer 2001 may have a thickness of 1.5 μm for some preferred embodiments of the invention.

Next, vias 2101 are then formed through the layer 2001 of sacrificial material, as shown in Fig. 21. As will be explained below, these vias 2101 should reach as far through the layer 1901 of insulative material as possible without extending to the electrode layer 1801. The vias 2101 should not extend to the electrode layer 1801, however, to prevent electrical contact between the subsequently formed 2401 bars and the electrode layer 1801.

After the vias 2101 are formed, a support material 2201 is formed inside the vias 2101, such that the support material 2201 extends well beyond the surface of the sacrificial layer 2001. This material 2201 is preferably strong, as it forms a support for the spatial light modulator when the modulator is subsequently pressed against a structure (e.g., a CCD backplane) for bonding. With some preferred embodiments, the support material 2201 should extend as close to the conductive transparent layer 1801 as possible without contacting it, as the transparent conductive layer will be the most rigid layer of material for these embodiments. With other preferred embodiments of the invention, the support material 2201 will additionally serve as a connection between the subsequently formed grating bars 2401 and the control electrodes on the subsequently attached structure (e.g., a CCD backplane). In these embodiments, the support material 2201 should be both conductive and act as a bonding material (e.g., a bump bonding material). As shown in Fig. 23, second layer 2301 of conductive material is formed over the sacrificial layer 2001. This second layer 2301 may be an evaporated aluminum layer approximately 200 nm thick, but other conductive and reflective materials or structures may be used. This layer 2301 is patterned with a lift-off process to form the grating bars 2401. Again, the residual stress in the bars is preferably relatively low, and, more preferably in the range of 5 - 15 MPa tensile. Lastly, the sacrificial layer 2001 is removed, as shown in Fig. 24, leaving the bars 2401 free to move toward and away from the layer 1801 of transparent conductive material. After the sacrificial layer 1901 has been removed, releasing the bars 2203, then the electrostatic modulation of the modulator can be characterized. As shown in this figure, if the support material 2201 is used to connect the bars 2401 to the control electrode of a subsequently attached structure, the bars 2401 will preferably contact the support material 2201. After the grating has been completed as described above, it can be bonded (e.g., bump- bonded) to, for example, a CCD backplane or other structure for use. As previously noted, some preferred embodiments of the invention use the support material 2201 to connect the grating bars 2401 to control electrodes on the attached structure (e.g., active portions of a CCD backplane). Thus, with these embodiments, if a grating has a single set of controllable bars 2401 , a single unit of supporting material 2201 can be used to connect the bars 2401 to a control electrode. Similarly, if a grating has two sets of independently controllable bars 2401 A and 240 IB, two separate units of supporting material 2201 are used to connect the bars 2401 A and 240 IB to two separate control electrodes. Likewise, if an array of gratings employs this embodiment of the invention, then a corresponding array of units of support material 2201 will be formed that can be matched to the control electrodes (e.g., active portions of a CCD backplane) of the attached structure.

Still other spatial light modulators 2501 and 2601 according to yet other embodiments of the invention are shown in Figs. 25 and 26, respectively. These spatial light modulators 2501 and 2601 are similar to the conventional spatial light modulator 101 shown in Fig. 3. That is, they both have gratings 103 supported by support posts 107 over a substrate 105. Unlike that conventional modulator shown in Fig. 3, however, the electrodes 201 ', 201 A' and 201 B' of the spatial light modulators 2501 and 2601 are positioned on the opposite side of the grating bars 103 from the substrate. That is, the electrodes 201', 201 A' and 20 IB' are formed over the grating bars 103 rather than under the grating bars 103.

With the particular embodiment shown in Fig. 25, the electrode 201 ' must be formed from a transparent conductive material, such as Indium Tin Oxide (ITO). For the embodiment shown in Fig. 26, however, the electrodes 201 A' and 20 IB' are formed at either end of the bars 103. Thus, these electrodes 201A' and 201B' do not block light from being reflected off of the bars 103. Instead, the electrodes 201 A' and 201B' overhang the bars 103 by only a sufficient distance necessary to modulate the bars.

The present invention has been described above by way of specific exemplary embodiments, and the many features and advantages of the present invention are apparent from the written description. Thus, it is intended that the appended claims cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the specification is not intended to limit the invention to the exact construction and operation ad illustrated and described. For example, the invention may include any one or more elements from the apparatus and methods described herein in any combination or subcombination. Accordingly, there are any number of alternative combinations for defining the invention, which incorporate one or more elements from the specification (including the drawings, claims, and summary of the invention) in any combinations or subcombinations. Hence, all suitable modifications and equivalents may be considered as falling within the scope of the appended claims.

Claims

We claim: I claim:

1. A spatial light modulator, comprising: B number of parallel bars arranged to form a grating, where B is a number greater than 1 ; and

S number of supports for supporting the bars above a substrate, where S < 2B-1.

2. The spatial light modulator of claim 1, wherein B > 4.

3. The spatial light modulator of claim 2, wherein S < 2.

4. The spatial light modulator of claim 3, wherein S = 1.

5. The spatial light modulator of claim 1 , wherein B > 8.

6. The spatial light modulator of claim 2, wherein S < 2.

7. The spatial light modulator of claim 3, wherein S = 1.

8. The spatial light modulator of claim 1, further including a cross piece connecting at least two of the bars.

9. The spatial light modulator of claim 1, further including an electrode for exerting an electrical force on at least one of the bars so as to control a position of the bar relative to .the substrate.

10. The spatial light modulator of claim 9, wherein the electrode is positioned at a side of the controllable bar opposite the substrate.

11. The spatial light modulator of claim 10, wherein the electrode is transparent.

12. The spatial light modulator of claim 11, wherein the electrode covers a surface of the grating.

13. The spatial light modulator of claim 10, wherein the electrode is positioned in a periphery of the grating.

14. The spatial light modulator of claim 9, wherein the electrode is positioned on a same side of the controllable bar as the substrate.

15. The spatial light modulator of claim 14, further including the substrate, and wherein the electrode is positioned below the substrate relative to the controllable bar.

16. A method of manufacturing the spatial light modulator of claim 1 on a charge coupled device, comprising: forming a planarizing layer to an upper passivation layer of a charge coupled device, the charge coupled device having a backplane with active pads underlying the passivation layer; forming vias through the planarizing layer to the active pads; forming electrodes over the planarizing layer so that the electrodes are electrically connected to the active pads through the vias; forming an insulative layer over the electrodes; forming vias through the insulative layer to the electrodes; forming bars over the insulative layer, such that the bars are arranged to form a grating; and releasing the bars by removing one or more portions of the insulative layer.

17. The method of claim 16, including forming the planarizing layer from one or more of the group consisting of BCB, polyimide, and spin-on glass.

18. The method of claim 16, including forming the planarizing layer to have a thickness of lμm - 2μm.

17. The method of claim 16, further including polishing the planarizing layer to a flatness of lOOOA.

18. The method of claim 16, further including forming the electrodes of aluminum.

19. The method of claim 16, further including forming the electrodes to have a thickness of approximately 200 nm.

20. The method of claim 16, further including forming the insulative layer of polyimide.

21. The method of claim 16, further including forming the insulative layer with a thickness of approximately 1.5 μm.

22. The method of claim 16, further including forming the bars from aluminum.

23. The method of claim 23, further including forming the bars to have a thickness of approximately 200 nm.

24. The method of claim 16, further including forming the bars such that residual stress for the bars is within the range of 5 - 15 MPa tensile.

25. The method of claim 16, further including removing the one or more portions of the insulative layer such that one or more remaining portions of the insulative layer provide one or more support posts for supporting the bars above the electrodes.

26. The method of claim 25, further including removing the one or more portions of the insulative layer such that at least one of the one or more support posts is positioned over one of the vias between the electrodes and the charge-coupled device backplane.

27. A method of manufacturing the spatial light modulator of claim 1, comprising: forming a transparent electrode layer over a first surface of a transparent substrate; forming an insulative layer over the transparent electrode layer; forming a sacrificial layer over the insulative layer; forming vias through the sacrificial layer into the insulative layer; forming bars over the sacrificial layer, such that the bars are arranged to form a grating; and releasing the bars by removing one or more portions of the sacrificial layer.

28. The method of claim 27, including forming the transparent electrode from ITO.

29. The method of claim 27, including forming the transparent electrode into a multilayer V-coat design.

30. The method of claim 27, wherein the insulative layer is formed from a material, selected from the group consisting of: silicon dioxide, silicon nitride, and spin-on glass.

31. The method of claim 27, including forming the insulative layer to have a thickness of approximately 100 nm.

32. The method of claim 27, including forming the sacrificial layer from polyimide.

33. The method of claim 27, including forming the sacrificial layer with a thickness of 1.5 μm.

34. The method of claim 27, wherein the sacrificial layer is formed with a thickness greater than or equal to λ/4, where λ is a wavelength of light to be modulated by the spatial light modulator.