A New Process for Manufacturing Arrays of Microlenses N.P. Eisenberg, A. Karsenty, J. Broder Jerusalem College of Technology - Israel M. Abitbol, N. Ben Yossef Hebrew University of Jerusalem - Israel ABSTRACT The need for microlenses with a wide -range of focal lengths from 10μ to 100mm and with a di- ameter varying from 10μ to 1mm lead to the development of various techniques which are able to generate these lenses in a photoresist substrate. The existing techniques are reviewed and a new one proposed. In this technique a positive or negative photoresist layer is exposed to a tailored light intensity distribution. After development of the photoresist, its surface is identical to the spatial intensity light distribution. Photoresist with an index of refraction of n =1.6 in the visible spectrum, can be used as a lens. 1. INTRODUCTION Microlenses are now widely used and the trend is for wider applications. Microlenses are used in color CCD cameras [1], in facsimilia systems, in CCD image sensors for enhancement of quantum yield [2], solar energy collection [3], and for optical computing, imaging and communication [4]. Therefore the specifications for microlenses for example focal length, F /number, geometrical size are diverse, so the existing techniques to generate microlenses are generally unable to cover the whole range of specifications. Moreover the trend today is toward fabrication techniques similar to those used in the production of integrated circuits, in order to integrate the microlens and microelectronic devices. In this article most of the published techniques for generating microlenses and analysis of their advantages and disadvantages will be briefly reviewed. A new technique has been developed and will be compared to existing methods. The goal of the project was to develop a technique enabling the fabrication of microlenses with focal length varying from microns to hundred of millimeters. The process should also be compatible with IC fabrication techniques. In addition, as opposed to the other methods, the microlenses fabricated by this technique should meet the design's specification. 2. EXISTING TECHNIQUES Four different techniques for microlens fabrication are reviewed : a) Mechanical method b) Distributed index planar microlens [6] [7] [8] [9] [10] c) Resin thermal flow technique [2] [11] d) Photoresist developed vs. exposure technique [3] [5] 2.a Mechanical method The classical methods for generating optical surfaces by mechanical means - Turning, Polishing or Molding - are limited in their ability to meet the requirements mentioned above. 388 / SPIE Vol 1038 Sixth Meeting in Israel on Optical Engineering (1988) A New Process for Manufacturing Arrays of Microlenses N.P. Eisenberg, A. Karsenty, J. Broder Jerusalem College of Technology - Israel M. Abitbol, N. Ben Yossef Hebrew University of Jerusalem - Israel ABSTRACT The need for microlenses with a wide-range of focal lengths from 10/z to 100mm and with a di- ameter varying from 10/i to 1mm lead to the development of various techniques which are able to generate these lenses in a photoresist substrate. The existing techniques are reviewed and a new one proposed. In this technique a positive or negative photoresist layer is exposed to a tailored light intensity distribution. After development of the photoresist, its surface is identical to the spatial intensity light distribution. Photoresist with an index of refraction of n=1.6 in the visible spectrum, can be used as a lens. 1. INTRODUCTION Microlenses are now widely used and the trend is for wider applications. Microlenses are used in color CCD cameras [1], in facsimilia systems, in CCD image sensors for enhancement of quantum yield [2], solar energy collection [3], and for optical computing, imaging and communication [4]. Therefore the specifications for microlenses for example focal length, F/number, geometrical size are diverse, so the existing techniques to generate microlenses are generally unable to cover the whole range of specifications. Moreover the trend today is toward fabrication techniques similar to those used in the production of integrated circuits, in order to integrate the microlens and microelectronic devices. In this article most of the published techniques for generating microlenses and analysis of their advantages and disadvantages will be briefly reviewed. A new technique has been developed and will be compared to existing methods. The goal of the project was to develop a technique enabling the fabrication of microlenses with focal length varying from microns to hundred of millimeters. The process should also be compatible with 1C fabrication techniques. In addition, as opposed to the other methods, the microlenses fabricated by this technique should meet the design's specification. 2. EXISTING TECHNIQUES Four different techniques for microlens fabrication are reviewed : a) Mechanical method b) Distributed index planar microlens [6] [7] [8] [9] [10] c) Resin thermal flow technique [2] [11] d) Photoresist developed vs. exposure technique [3] [5] 2.a Mechanical method The classical methods for generating optical surfaces by mechanical means - Turning, Polishing or Molding - are limited in their ability to meet the requirements mentioned above. 388 / SPIE Vol. 1038 Sixth Meeting in Israel on Optical Engineering (1988)