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Precision silicon optical bench fabricated with combination of anisotropic wet etching and high rate reactive ion etching

IP.com Disclosure Number: IPCOM000019161D
Original Publication Date: 2003-Sep-02
Included in the Prior Art Database: 2003-Sep-02
Document File: 3 page(s) / 208K

Publishing Venue

IBM

Abstract

A method for fabricating a Silicon optical bench for precision alignment of passive optical components such as optical fibers, ball lens and optical isolators using a combination of anisotropic wet etching and high rate reactive ion etching is disclosed. The combination of the two etching methods means that corner compensation structures are not needed and unique structure such as rhomboid shaped cavities for optical isolators, features to aid in assembly such as adhesive cavities, simplified receivers and fiber stops can be readily formed.

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  Precision silicon optical bench fabricated with combination of anisotropic wet etching and high rate reactive ion etching

  For optical communications, it is necessary to precisely align (to about 1 micron accuracy) passive optical components such as optical fibers, ball lens, optical isolators and active components such as laser diodes or photo diodes to convert high speed electrical signals into light and couple the light into optical fibers and to receive the light from said optical fibers and convert it back into high speed electrical signals. This is typically done using a Silicon optical bench (SiOB) where anisotropically etched features are formed to hold passive components such as ball lens, optical fibers etc... A difficulty of this is that convex corners require the use of complicated corner compensation structures which are often difficult to implement in practice. Convex corners are necessary to form a clear optical path connecting the features in the SiOB which contain the passive optical components. The use of high etch rate reactive ion etching (RIE) in addition to anisotropic wet etching can enable a SiOB design which does not require stopping the anisotropic wet etch at a controlled depth to produce a feature with a flat bottom, which avoids corner compensation structures, which can produce arbitrary shaped openings, and which offers cavities with either vertical or sloped edges.

Fig. 1 Schematic drawing of an SiOB formed using a combination of anisotropic wet etching (light gray) and RIE (dark gray).

The first step in forming the disclosed SiOB is to anisotropically wet etch the ball lens pits, optical fiber grooves and other necessary features where each is a closed rectangle in form (light gray in Fig. 1). The next process step is to use a high rate Si dry etching to form a cavity to place the optical isolator in and to form cavities to clear the optical path between the laser diode, ball lens, and the optical fiber (dark gray in Fig. 1). By only using rectangles for the wet etching, the features are self terminating. The cavities for the ball lens need only be etched to a sufficient depth so that the ball lenses have adequate clearance. One of the unique features which can be formed by this

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method is the rhomboid shaped cavity with vertical sides which allows the optical isolator...