EP0438586A1 - Procede de fabrication d'une microlentille optique binaire sur un reseau de detecteurs - Google Patents

Procede de fabrication d'une microlentille optique binaire sur un reseau de detecteurs

Info

Publication number
EP0438586A1
EP0438586A1 EP90913424A EP90913424A EP0438586A1 EP 0438586 A1 EP0438586 A1 EP 0438586A1 EP 90913424 A EP90913424 A EP 90913424A EP 90913424 A EP90913424 A EP 90913424A EP 0438586 A1 EP0438586 A1 EP 0438586A1
Authority
EP
European Patent Office
Prior art keywords
mask
radiation
microlens
back surface
set forth
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90913424A
Other languages
German (de)
English (en)
Inventor
Paul R. Norton
Timothy D. Wise
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Santa Barbara Research Center
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Santa Barbara Research Center filed Critical Santa Barbara Research Center
Publication of EP0438586A1 publication Critical patent/EP0438586A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0232—Optical elements or arrangements associated with the device
    • H01L31/02327—Optical elements or arrangements associated with the device the optical elements being integrated or being directly associated to the device, e.g. back reflectors

Definitions

  • This invention relates generally to radiation detectors and, in particular, relates to methods of fabricating a binary optics microlens array as an integral part of a backside-illuminated, one or two-dimensional detector array.
  • Each individual microlens is fabricated such that it is disposed relative to an individual detector element of the array for concentrating incident radiation into a relatively small area at the plane of the detectors.
  • Conventional arrays of radiation detectors have been known to include detectors adhesively bonded, for example, to separately fabricated optical elements (or vice-versa) , the optical elements comprising lenticular surfaces or lenses. Typical arrangements have included molded, cast or embossed patterns of lenses. Curved lens surfaces have also been used. Also known are integrating cavities or cones which perform much the same function. "Faceplate” technology employs micrjolenses, the lens patterns being processed on or into a structure separate from the array of detectors. One type -of faceplate technology has been suggested that would provide a binary optics microlens array in proximity to a detector array, but not fabricated in the detector array substrate itself.
  • a binary optic microlens array directly within a radiation receiving surface of an array of detectors would provide a number of advantages over the separately provided lens arrays. For example, the ruggedness of the detector array would be increased while the overall cost related to assembly and fabrication would be reduced. Furthermore, such a lens/detector arrangement would provide for a backside illuminated detector array wherein incident radiation could be focussed to a relatively small spot size at the plane of the detectors, thereby enabling the detector active area to be decreased without sacrificing signal quality. As is known, a reduced area photovoltaic detector is desirable in that it typically exhibits a reduced junction capacitance, an increased operating speed and an improved resistance to ionizing radiation. However, until the integral microlens/detector array fabrication method taught by the invention these benefits were not readily attainable.
  • a binary optics microlens array that is fabricated as an integral part of a backside-illuminated, one or two-dimensional radiation detector array.
  • a three dimensional binary optic microlens structure is created within the radiation receiving back surface of the substrate of a radiation detecting array.
  • the microlens has a structure predetermined to achieve a concentration of optical radiation within a desired spot size at the plane of the detectors, thereby facilitating the provision of detectors of reduced active area.
  • the incident radiation may be planar or may be prefocused by externally provided optics.
  • the method of the invention determines a binary optic microlens solution to a Fresnel lens which achieves the desired optical concentration, the method further providing at least one fabrication masking layer upon the back surface of the array and the selective removal of material from or addition of material to the back surface of the array to create the microlens structure.
  • Fig. la is an elevational view of a back surface of a radiation detector array showing several binary optic microlens structures
  • Fig. lb is a cross-sectional view, not to scale, taken through one of the binary optic microlens elements of Fig. la;
  • Fig. 2a is an enlarged cross-sectional view of a conventional Fresnel lens showing three Fresnel zone plates;
  • Figs. 2b-2d illustrate a cross-sectional view of a one mask, two mask and four mask binary optic microlens approximation, respectively, of the Fresnel zone plates of Fig. 2a;
  • Fig ⁇ . 3a and 3b schematically illustrate a f/1 embodiment of the binary optic microlens
  • Figs. 4a and 4b schematically illustrate a f/2 embodiment of the binary optic microlens
  • Figs. 5a-5d illustrate steps of a method of the invention of fabricating a binary optic microlens on a back surface of a radiation detector array substrate.
  • a backside radiation receiving surface of a radiation detector array 10 The back surface can be seen to be filled with a plurality of Fresnel-type microlens structures which, in accordance with the invention, are comprised of binary optic microlens elements 12. Incident IR radiation (A) is concentrated by the lens elements 12 upon a detector 18 which is disposed on an opposite surface 14 of a transparent substrate 16.
  • Each microlens 12 has an associated unit cell width (W) which, in one illustrative embodiment of the invention, is approximately 50 microns.
  • the width (w) of an associated photovoltaic detector 18 is generally reduced in relation to the unit cell width and may be on the order of 12 microns.
  • the thickness of the substrate 16 can vary over a substantially wide range of thicknesses from, for example, 50 microns to 450 microns.
  • the detector 18 is responsive to IR radiation and the substrate 16 comprises material that is substantially transparent to the wavelengths of interest, such as CdTe or CdZnTe, while the surface 14 is a surface of an epitaxial HgCdTe radiation absorbing layer wherein the photovoltaic detector 18 is formed.
  • a conventional Fresnel lens which is comprised of a plurality of Fresnel zone plates 20.
  • Each spherically curved zone plate 20 defines the spatial extent of a region wherein incident radiation makes a (2 pi) phase shift.
  • the fabrication of the spherical curvature of the Fresnel zone plates 20 within- the confines of a 50 micron unit cell is extremely difficult if not impossible to accomplish with presently known fabrication techniques.
  • a binary optic lens solution is employed to approximate the desired shape of the Fresnel zone plates 20 upon the back surface of an array of radiation detectors.
  • the binary optic lens solution is accomplished by the application of one or more masking layers of predetermined shape in conjunction with the selective removal of material from the back surface of the array.
  • the one or more masking layers define the position, shape and resolution of the resulting binary optic approximation of the Fresnel zone plates.
  • Fig. 2b shows a one-mask embodiment of a binary optic microlens
  • Fig. 2c shows a two mask embodiment
  • Fig. 2d shows an enlarged view of one zone plate approximation resulting from a four mask embodiment.
  • a binary optic microlens 22 which forms a f/1 microlens element.
  • the radiation concentration required is such that approximately 80% of the flux falls within a 6 micron spot at the plane of the detector 24.
  • the overall optical gain of the microlens 22 is approximately 69.
  • a two mask embodiment of microlens 22 achieves an 81% optical efficiency.
  • Table 1 shows the radial dimensions in microns, referenced to the center of the microlens 22, of the first and the second fabrication masks, mask 1 and mask 2.
  • the higher order mask in this case mask 2
  • mask 2 is preferably applied and processed first in order that the finer resolution microlens features are applied to a substantially planar surface.
  • FIG. 4a and 4b there is shown another example of a binary optic microlens 26 which provides an f/2 lens for use with 10 micron wavelength f/2 prefocussed radiation and a 50 micron width unit cell.
  • the CdTe substrate thickness is 100 microns and the microlens 26 achieves an 80% flux concentration within a 10 micron diameter spot at the plane of the detector 28.
  • the optical gain of this two mask configuration is approximately 25 and the optical efficiency is again approximately 81%.
  • Table 2 shows the mask radial dimensions in microns for the first and the second mask. - Table 2
  • Example 2 employs three micron rule lithography whereas Example 1 above employs 1.6 micron rule lithography. 5
  • Example 3 provides a binary optical microlens for 4.6 micron wavelength f/2 0 prefocussed radiation and a 75 micron width unit cell.
  • This microlens concentrates approximately 80% of the incident flux within an approximately 1.9 micron spot 5 at the plane of the detector and provides an optical gain of approximately 15.6. Again, an 81% optical efficiency is achieved with two masks.
  • Table 3 illustrates the radial dimensions of the two ° masks.
  • the masks are fabricated with 1.8 micron rule lithography.
  • Table 2 illustrates the radial dimensions of the two ° masks. The masks are fabricated with 1.8 micron rule lithography. Table 2
  • Figs 5a-5d there is illustrated, in accordance- with a method of the invention, the fabrication of the binary optic microlens 22 of Example 1 above.
  • the substrate index of refraction and thickness, the desired detector 24 active area, and the detector center-to-center spacing _j s known beforehand.
  • the wavelength of the radiation and the degree of prefbcussing, if any, of the incident radiation are also known beforehand. Based on this information, a Fresnel lens that would provide for the required amount of radiation concentration within the detector 24 active area is arrived at by a conventional lens design.
  • the spherical curvature of the zone plates is evaluated. From this evaluation a binary optic lens design is determined that most closely approximates the spherical curvature of the Fresnel zone plates within the limitations of the photolithographic and other processing restrictions in effect. After the number of masks and the resolution of each mask is determined the masks are fabricated and the binary optic lens elements are fabricated upon the surface of the substrate.
  • a substrate 30 has a substantially planar surface 32 to which the highest order mask is applied and processed by known techniques to deposit a masking layer 34.
  • the masking layer 34 may be comprised of photoresist or any suitable type of material.
  • the radial dimensions of the portion of the masking layer 34 that is illustrated in Fig. 5a correspond to that shown in Table 1.
  • the surface is etched with, preferably, a dry etch method such as an ion beam etch to selectively remove the substrate 30 material which is not covered by the masking layer 34.
  • a dry etch method such as an ion beam etch
  • n is the index of refraction of the substrate material and N is the mask number or order.
  • Fig. 5b it can be seen that the masking layer 34 has been stripped away and that the surface 32 of the substrate 30 includes a number of depressions 34a.
  • Fig. 5c a coarser mask, mask 1 of Example 1, is applied and processed to produce the masking layer 36.
  • the surface of the substrate 30 is once more etched.
  • Fig. 5d illustrates the substrate surface after the removal of the masking layer 36. It can be seen that after the second etching step that portions of the substrate 30 have not been etched (32) , portions have been etched once (38) and other portions have been etched twice (34) and, hence, have a greater depth than the once-etched portions.
  • a three dimensional binary optic microlens structure is created within the radiation receiving back surface of the substrate of a radiation detecting array.
  • the microlens has a structure predetermined to achieve a concentration of optical radiation within a desired spot size at the plane of the detectors, thereby facilitating the provision and operation of detectors of reduced active area.
  • the incident radiation may be planar or may be prefocused by externally provided optics.
  • the method of the invention determines a binary optic microlens solution to a Fresnel lens which achieves the desired optical concentration, the method further providing at least one fabrication masking layer upon the back surface of the array and the selective removal of material from the back surface of the array to create the microlens structure.

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Solid State Image Pick-Up Elements (AREA)

Abstract

Une structure de microlentille optique binaire tridimensionnelle (12) est fabriquée dans une contre-surface de réception de rayonnement d'un substrat (16) d'un réseau (10) de détecteurs de rayonnement. La microlentille possède une structure prédéterminée pour obtenir une concentration de rayonnement optique dans un spot de taille désirée au niveau du plan de détecteur (18) facilitant ainsi l'utilisation de détecteurs de zone active réduite. Le rayonnement incident peut être un rayonnement plan ou peut être préfocalisé par des optiques externes. Le procédé de l'invention détermine une solution de microlentille binaire sur une lentille de Fresnel qui permet d'obtenir la concentration optique désirée, le procédé consistant en outre à placer au moins une couche de masquage de fabrication sur la contre-surface du réseau ainsi que l'élimination sélective de matière de la contre-surface du réseau pour créer la structure de la microlentille.
EP90913424A 1989-08-11 1990-08-06 Procede de fabrication d'une microlentille optique binaire sur un reseau de detecteurs Withdrawn EP0438586A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US39275189A 1989-08-11 1989-08-11
US392751 1989-08-11

Publications (1)

Publication Number Publication Date
EP0438586A1 true EP0438586A1 (fr) 1991-07-31

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP90913424A Withdrawn EP0438586A1 (fr) 1989-08-11 1990-08-06 Procede de fabrication d'une microlentille optique binaire sur un reseau de detecteurs

Country Status (3)

Country Link
EP (1) EP0438586A1 (fr)
JP (1) JPH04502233A (fr)
WO (1) WO1991002380A1 (fr)

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US5300788A (en) * 1991-01-18 1994-04-05 Kopin Corporation Light emitting diode bars and arrays and method of making same
US6627953B1 (en) 1990-12-31 2003-09-30 Kopin Corporation High density electronic circuit modules
US6593978B2 (en) 1990-12-31 2003-07-15 Kopin Corporation Method for manufacturing active matrix liquid crystal displays
US5258325A (en) * 1990-12-31 1993-11-02 Kopin Corporation Method for manufacturing a semiconductor device using a circuit transfer film
US6143582A (en) 1990-12-31 2000-11-07 Kopin Corporation High density electronic circuit modules
US5376561A (en) * 1990-12-31 1994-12-27 Kopin Corporation High density electronic circuit modules
US5256562A (en) * 1990-12-31 1993-10-26 Kopin Corporation Method for manufacturing a semiconductor device using a circuit transfer film
US5499124A (en) 1990-12-31 1996-03-12 Vu; Duy-Phach Polysilicon transistors formed on an insulation layer which is adjacent to a liquid crystal material
GB2278723B (en) * 1991-01-17 1995-04-26 Honeywell Inc Binary optical microlens detector array
US5310623A (en) * 1992-11-27 1994-05-10 Lockheed Missiles & Space Company, Inc. Method for fabricating microlenses
FR2729789B1 (fr) * 1993-09-10 1998-03-20 Thomson Csf Detecteur a puits quantique et procede de realisation
DE19518303C2 (de) * 1995-05-18 1997-04-10 Forschungszentrum Juelich Gmbh Optische Linsen-/Detektoranordnung
DE19545484C2 (de) * 1995-12-06 2002-06-20 Deutsche Telekom Ag Bildaufnahmeeinrichtung
US6665014B1 (en) * 1998-11-25 2003-12-16 Intel Corporation Microlens and photodetector
US6236508B1 (en) 1999-03-03 2001-05-22 The Boeing Company Multicolor detector and focal plane array using diffractive lenses
CN101052910B (zh) * 2004-09-14 2010-05-05 Cdm光学有限公司 低高度成像***及相关方法
WO2006055094A1 (fr) * 2004-09-14 2006-05-26 Cdm Optics, Inc. Systeme d’imagerie de basse hauteur et procedes associes
TW200717678A (en) * 2005-05-05 2007-05-01 Koninkl Philips Electronics Nv Method for analyzing an integrated circuit, apparatus and integrated circuit
DE102005033746A1 (de) * 2005-07-15 2007-01-25 Schott Ag Kompaktes Objektiv zur digitalen Bilderfassung sowie Bilderfassungsvorrichtung
CN100444381C (zh) * 2006-10-13 2008-12-17 中国科学院上海技术物理研究所 背向集成微透镜红外焦平面探测器及微透镜的制备方法
US9507985B2 (en) 2014-03-31 2016-11-29 Symbol Technologies, Llc Optical lens for using in illumination system of imaging scanner

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JPS60191548A (ja) * 1984-03-12 1985-09-30 Hitachi Ltd イメ−ジセンサ
JPS61145861A (ja) * 1984-12-19 1986-07-03 Mitsubishi Electric Corp 固体撮像素子
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Also Published As

Publication number Publication date
WO1991002380A1 (fr) 1991-02-21
JPH04502233A (ja) 1992-04-16

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