CMOS-compatible optical bench

Details CMOS-compatible optical bench CMOS-compatible optical bench

1999-01-22

2001-01-02

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

With optical coupler

Particular coupling structure

C385S014000, C385S050000, C385S052000, C385S088000

Utility Patent

active

06169833

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of optical communications and in particular to a complementary metal-oxide-semiconductor (CMOS) electronic chip having an optical fiber directly attached thereto and a method of preparing same.
BACKGROUND OF THE INVENTION
Optical fiber is increasingly used in a variety of applications ranging from long distance voice and data transmission to interconnection of electronic devices, subassemblies, or assemblies. In many applications of optical fiber, it is necessary to couple the optical fiber to an optoelectronic device.
The desirability of providing efficient and compact means for optically coupling an optoelectronic device to an optical fiber has become recognized. Desirably, such means are compatible with integrated circuit (IC) fabrication and mounting technology since such compatibility may simplify assembly and therefore result in significant cost reduction. For an example of an advanced mounting technique see, for instance, U.S. Pat. No. 4,675,717, incorporated herein by reference.
Another fiber-to-device coupling assembly that is compatible with IC fabrication technology is disclosed in U.S. Pat. No. 4,779,946, filed Feb. 14, 1986 for R. J. Pimpinessa and J. M. Segelken and incorporated herein by reference. This prior art assembly utilizes a Si chip comprising a through-aperture to maintain the end of an optical fiber in coupling relationship with an optoelectronic component mounted on the chip. The chip exemplary is produced by a process that comprises selective etching of one face of a Si wafer to form sloped-wall through-apertures, formation of metallization patterns on the other face of the wafer in precise alignment with respect to these apertures, and dicing of the wafer. The end of an optical fiber is inserted into the aperture and maintained therein by appropriate means, and an appropriate optoelectronic device, i.e., transducer, is aligned with the metallization pattern and conductively attached thereto.
Alignment between the core of the optical fiber and the active area of the transducer results from the precise placement of the metallization pattern and the alignment of the transducer with the pattern. The thus formed assembly can then be mounted on an appropriate substrate (e.g., a Si wafer with appropriate metallization thereon) substantially in the same manner as ordinary IC chips, e.g., by means of a face-down solder ball technique.
Finally, an optical integrated circuit having passively aligned fibers was disclosed in U.S. Pat. No. 5,703,973 that issued to Mettler et al. on Dec. 30, 1998 is incorporated herein by reference. As disclosed therein, an optical integrated circuit and an optical array are joined using index matching material and mounted on a planar bridging structure to form a device that can be connected to other devices using optical connectors. The optical integrated circuit and the fiber array include multiple silicon substrates having bottom surfaces that have reference areas and top sides that have a plurality of optical paths. These optical paths are positioned above each reference area and bottom sides of the optical integrated circuit and the fiber array include alignment features that are etched into their substrates and bear a predetermined horizontal relation to the optical paths. Consequently, when the optical integrated circuit and the fiber array are positioned upon an additional substrate that mates with the alignment features of the optical integrated circuit and the fiber array, the resulting overall device is in proper, optical alignment.
Although providing a significant advance over other prior art assemblies, the above-described assembly has some shortcomings. In particular, the assembly requires several individual parts, i.e, the fiber array, the optical integrated circuit and the underlying substrate, that must be mechanically aligned and assembled into a unitary structure. Additionally, the prior art has focussed on attaching an optical fiber to an optoelectronic device, not an electronic device. In view of this, it will be apparent that simple structures and methods for coupling optical fibers to electronic integrated circuits as well as devices so constructed are highly desirable. We disclose herein such a method and device.
SUMMARY OF THE INVENTION
We have developed a method of aligning, placing, and attaching an optical fiber directly to an electronic chip (i.e., complementary, metal-oxide-semiconductor (CMOS)) chip that uses alignment features defined during the CMOS fabrication. Specifically, the method involves the steps of: i) defining, during the fabrication of an electronic CMOS device, one or more shallow grooves upon the electronic device substrate; ii) disposing an optical fiber within the defined groove(s); and iii) securing the optical fiber within the groove(s). Advantageously, the method may be practiced using a variety of fabrication techniques and apparatus that are compatible with conventional CMOS devices. A distinguishing characteristic of our inventive method and apparatus, is that while the prior art has shown how to attach an optical fiber to an optical device, we have shown how to attach an optical fiber to an electronic device using electronic fabrication techniques.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawing.


REFERENCES:
patent: 4675717 (1987-06-01), Herrero et al.
patent: 4779946 (1988-10-01), Pimpinella et al.
patent: 5703973 (1997-12-01), Mettler et al.
patent: 5909523 (1999-06-01), Sakaino et al.
patent: 5972232 (1999-10-01), Lee et al.
patent: 6058234 (2000-05-01), Tachigori

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