Method of manufacturing a spectral filter for green and longer wavelengths
First Claim
1. A method of making a spectral filter comprising:
- providing a substrate wafer of single-crystal (100)-oriented p-doped silicon having a first surface and a second surface, providing etching starting points at a first surface of said semiconductor wafer, and electrochemically etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethrough, said pores having coherently modulated cross-sections at least over the part of said depth.
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Abstract
A method of manufacture for optical spectral filters with omnidirectional properties in the visible, near IR, mid IR and/or far IR (infrared) spectral ranges is based on the formation of large arrays of coherently modulated waveguides by electrochemical etching of a semiconductor wafer to form a pore array. Further processing of said porous semiconductor wafer optimizes the filtering properties of such a material. The method of filter manufacturing is large scale compatible and economically favorable. The resulting exemplary non-limiting illustrative filters are stable, do not degrade over time, do not exhibit material delamination problems and offer superior transmittance for use as bandpass, band blocking and narrow-bandpass filters. Such filters are useful for a wide variety of applications including but not limited to spectroscopy, optical communications, astronomy and sensing.
27 Citations
37 Claims
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1. A method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal (100)-oriented p-doped silicon having a first surface and a second surface, providing etching starting points at a first surface of said semiconductor wafer, and electrochemically etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethrough, said pores having coherently modulated cross-sections at least over the part of said depth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethrough, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said etching start points are located by producing a photoresist mask on the first surface of the substrate wafer and by a subsequent etching of the first surface through said photoresist mask, and wherein said etching is chosen from the group consisting of chemical etching, reactive ion etching, and ion milling. - View Dependent Claims (13)
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14. A method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethrough, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said surface topology is produced by disposing a layer of material with different chemical properties than those of wafer material on the first surface of substrate wafer, by producing a photoresist mask on the surface of said layer, by etching away the said chemically different material inside the photoresist mask openings and by etching the wafer surface through the thus-formed openings in said disposed chemically different material, and wherein said chemically different layer is removed from the first surface of the wafer after forming said surface topology in the wafer.
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15. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said electrochemical etching occurs in a fluoride-containing, acidic electrolyte, and wherein said electrolyte additionally contains a hydrogen reducing agent selected from the group of chemicals consisting of mono-functional alkyl alcohols, die-functional alkyl alcohols, and tri-functional alkyl alcohols.
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16. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said electrolyte is a fluoride-containing, acidic electrolyte, and, wherein said electrolyte additionally contains a viscosity-modifying agent.
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17. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said electrolyte is a fluoride-containing, acidic electrolyte, and, wherein said electrolyte additionally contains an electrical conductivity-modifying agent.
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18. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said electrolyte is a fluoride-containing, acidic electrolyte, and, wherein said electrolyte additionally contains a wetting agent.
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19. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein said eching occurs in a fluoride-containing, acidic electrolyte, and, wherein the electrolyte additionally contains at least one organic additive. - View Dependent Claims (20)
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21. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein at least one layer of substantially transparent material is deposited onto the pore walls. - View Dependent Claims (22, 23)
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24. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, wherein at least one layer of absorptive and/or reflective material is deposited on the pore walls over at least part of the pore depth. - View Dependent Claims (25)
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26. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, further including the removal of the unetched remainder of the wafer. - View Dependent Claims (27, 28, 29, 30)
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31. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, and further including coating the first, second or both surfaces of said spectral filter with at least one layer of material intended to suppress the reflection from said surfaces of said spectral filter in at least some wavelength ranges inside the transparency wavelength range of said spectral filter. - View Dependent Claims (32, 33)
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34. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, further including sealing said spectral filter with two flat plates of material that is transparent within the transparency range of said spectral filter.
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35. The method of making a spectral filter comprising:
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providing a substrate wafer of single-crystal semiconductor having a first surface and a and a second surface, providing etching start points at a first surface of said semiconductor wafer, and etching the substrate wafer beginning at said start points to produce a structured layer having pores with controlled depths defined at least partially therethroug, said pores having coherently modulated cross-sections at least over the part of said depth, and wherein a roughness suppression procedure is performed subsequently to said etching of the substrate wafer. - View Dependent Claims (36, 37)
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Specification