# US 5,706,067 A · Reflective spatial light modulator array > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,067 A - Document ID: US5706067A - Status: Granted - Kind: A - Application number: 08/803,210 - Filed: 1997-02-21 - Granted: 1998-01-06 - Earliest claimed: 1995-04-28 - Assignees: International Business Machines Corporation - Inventors: Evan George Colgan; James Mckell Edwin Harper; Frank Benjamin Kaufman; Margaret Paggi Manny; Robert Lee Melcher; James Louis Speidell - Web page: https://patentgrep.com/patent/US5706067A ## CPC - G02F 1/136277: {formed on a semiconductor substrate, e.g. of silicon} - G02F 1/133553: {Reflecting elements (associated to illuminating devices G02F1/133605)} - G02F 1/136209: {Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element} - G02F 1/13394: {spacers regularly patterned on the cell subtrate, e.g. walls, pillars (G02F1/133377 takes precedence)} - G02F 1/136: Liquid crystal cells structurally associated with a semi-conducting layer or substrate, e.g. cells forming part of an integrated circuit (G02F1/135 takes precedence) - G02F 2203/12: spatial light modulator - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract A reflective spatial light modulator array is described incorporating liquid crystal devices, mirrors, a semiconductor substrate, electrical circuits, and a reflector/absorber layer for blocking light. The invention overcomes the problem of shielding light from semiconductor devices, high optical throughput and contrast, pixel storage capacitance to hold the voltage across the liquid crystal device and precise control of the liquid crystal device thickness without spacers obscuring the mirrors. ## Claims ### Claim 1 A reflective spatial light modulator array for modulating light to form an image, comprising: a lateral arrangement of a plurality of liquid crystal devices positioned on a semiconductor substrate, said liquid crystal devices comprising electrodes and mirrors on a dielectric layer, a plurality of electrical circuits formed in said semiconductor substrate coupled to said liquid crystal devices, respectively, for placing a voltage across its electrodes, said light modulator array being characterized in that at least one of said liquid crystal devices comprises a reflector/absorber layer being arranged such that it shields said plurality of electrical circuits and forms a capacitor together with said electrode and said dielectric layer, said reflector/absorber layer partially overlaps said one electrode such that light passing said electrode is attenuated by multiple reflections between said electrode and reflector/absorber layer thus decreasing the intensity of said light eventually passing into said semiconductor substrate, said reflector/absorber layer being selected from the group consisting of Al, Cr--Cr.sub.x O.sub.y, Ti and TiN.sub.x C.sub.y, and the upper surface of said reflector/absorber layer comprising TiN. ### Claim 2 (depends on 1) The spatial light modulator array of claim 1 wherein said reflector/absorber layer overlaps said edge of said mirror by at least 5.4 .mu.m. ### Claim 3 (depends on 1) The spatial light modulator array of claim 1 wherein said mirrors are formed from a metal layer wherein said metal is selected from the group consisting of Ag, Al and alloys thereof. ### Claim 4 (depends on 1) The spatial light modulator array of claim 1 wherein said mirrors have a supporting layer having a substantially planar upper surface and said mirrors include a respective metal layer for reflecting light on said substantially planar upper surface of said supporting layer. ### Claim 5 (depends on 4) The spatial light modulator array of claim 4 wherein said supporting layer includes dielectric material and electrical vias for electrical connection to said metal layer. ### Claim 6 (depends on 1) The spatial light modulator array of claim 1 wherein said plurality of liquid crystal devices have a thickness determined by a dielectric layer having openings formed over said respective mirrors. ### Claim 7 (depends on 6) The spatial light modulator array of claim 6 wherein said dielectric layer includes material is selected from the group consisting of SiO.sub.2, Si.sub.3 N.sub.4, diamond-like carbon, and polyimide. ### Claim 8 (depends on 6) The spatial light modulator array of claim 6 wherein said respective mirrors form the lower electrode of said plurality of liquid crystal devices and being electrically coupled to respective outputs of said plurality of electrical circuits. ### Claim 9 (depends on 1) The spatial light modulator array of claim 1 wherein said reflector/absorber layer is electrically conductive and forms a blanket layer over said semiconductor substrate with openings therein for electrical vias to said mirrors. ### Claim 10 (depends on 1) The spatial light modulator array of claim 1 wherein said electrical circuits include complementary metal oxide silicon (CMOS) circuits. ### Claim 11 (depends on 1) The spatial light modulator array of claim 1, wherein said mirror and said reflector/absorber layer form a capacitor of about 0.03 pf. ### Claim 12 (depends on 1) The spatial light modulator array of claim 1, wherein said liquid crystal devices are positioned in rows and columns on a pitch in each of two directions of about 17 microns. ### Claim 13 A reflective spatial light modulator array for modulating light to form an image, said modulator array comprising a plurality of electrical circuits formed in a semiconductor substrate and a plurality of liquid crystal devices formed thereon, said liquid crystal devices being coupled to said electrical circuits for placing a voltage across its top and bottom electrodes, each of said liquid crystal devices comprising a mirror layer and a reflector/absorber layer arranged such that both are separated by a dielectric layer together forming a first capacitor wherein said mirror layer serves as upper electrode and said reflector/absorber layer as lower electrode, said reflector/absorber layer has an edge overlapping an edge of said mirror layer to ensure that light passing said mirror layer is attenuated by multiple reflections between said mirror layer and reflector/absorber layer thus decreasing the intensity of said light and shielding said electrical circuits underneath from ambient light, and said mirror layer serves as bottom electrode of said liquid crystal device, each of said liquid crystal devices further comprising a second capacitor situated underneath said first capacitor and being coupled to it to provide a pixel storage capacitance for holding said voltage across said top and bottom electrodes, said second capacitor being formed by an upper and a lower polysilicon layer embedding a dielectric layer. ### Claim 14 (depends on 13) The spatial light modulator array of claim 13 wherein said first capacitor has a capacitance of about 0.03 pf. ### Claim 15 (depends on 13) The spatial light modulator array of claim 13 wherein studs are used for interconnection of layers. ### Claim 16 (depends on 13) The spatial light modulator array of claim 13 wherein said dielectric layer being part of said second capacitor is thermally grown. ### Claim 17 (depends on 13) The spatial light modulator array of claim 13 wherein said dielectric layer being part of said first capacitor is a high dielectric constant material. ### Claim 18 (depends on 17) The spatial light modulator array of claim 17 wherein the dielectric constant of said high dielectric constant material is about 7. ### Claim 19 (depends on 17) The spatial light modulator array of claim 17 wherein said high dielectric constant material is silicon nitride.