Silicon photodetector structure for direct coupling of optical fibers to integrated circuits

Ade, R. W.; Harstead, Edward E.; Amirfazli, Alidad; Cacouris, T.; Fossum, E. R.; Prucnal, Paul R.; Osgood, Richard M.

doi:10.1109/t-ed.1987.23082

Cited by 9 publications

(2 citation statements)

References 10 publications

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“…The etching is carried serially, by scanning a laser beam to remove a sequence of small volumes, making these processes slow but avoiding crystalplane dependencies. A laser-driven wet-etching process for silicon has also been described by Ade et al [58].…”

Section: ) Control Of Surface Roughnessmentioning

confidence: 99%

Bulk micromachining of silicon

Kovacs

Maluf²,

Petersen³

1998

Proc. IEEE

656

374

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Bulk silicon etching techniques, used to selectively remove silicon from substrates, have been broadly applied in the fabrication of micromachined sensors, actuators, and structures. Despite the more recent emergence of higher resolution, surfacemicromachining approaches, the majority of currently shipping silicon sensors are made using bulk etching. Particularly in light of newly introduced dry etching methods compatible with complementary metal-oxide-semiconductors, it is unlikely that bulk micromachining will decrease in popularity in the near future. The available etching methods fall into three categories in terms of the state of the etchant: wet, vapor, and plasma. For each category, the available processes are reviewed and compared in terms of etch results, cost, complexity, process compatibility, and a number of other factors. In addition, several example micromachined structures are presented.

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Section: ) Control Of Surface Roughnessmentioning

confidence: 99%

Bulk micromachining of silicon

Kovacs

Maluf²,

Petersen³

1998

Proc. IEEE

656

374

View full text Add to dashboard Cite

show abstract

“…We have previously used laser-etched vertical cavities in photodetector structures designed to facilitate high den sity optical interconnection (4). As a processing alterna tive, orientation dependent etching of vertical shafts in (110) Si has been investigated.…”

Section: Methodsmentioning

confidence: 99%

Limitations of Orientation Dependent Microstructure Etching in Silicon

Ade

Fossum

1987

J. Electrochem. Soc.

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Anisotropic orientation dependent etching has been used extensively in the formation of silicon-based micro structures. The technique exploits differences between the etch rates of the low index crystallographic planes for some wet chemical etchants. In particular, solutions of KOH in water have been shown to etch jIll! planes up to several hundred times more slowly than (110) and 11001 planes. This allows fabrication of precise three-dimen sional structures in (110) and (100) oriented silicon wa fers (1, 2). The resulting structures are typically cavities with sidewalls formed by the slow-etching 1111! planes. When the edge of a masking material is aligned with the trace of a (Ill! plane (i.e., its intersection with the surface of the wafer), the etch proceeds with minimal under cutting and the shape of the cavity's opening remains sharply defined.The trace of any plane is a line parallel to the cross product of the vectors normal to the plane and to the wa fer. The angle of intersection between the plane and the wafer's surface is determined by the scalar product of the normal vectors. Thus, vector algebra can be used to find the proper mask orientation and to predict the ge ometry of the cavity. For example, the structure of (100) Si V-grooves (3) is based on the following:(i) the planes (111) and(1 II) both intersect the (100) sur face at an angle(ii) the traces of these planes lie parallel to the direc tionwhich is typically indicated by a flat on the wafer perime ter. Thus, an orientation dependent etch (ODE) per formed through a long rectangular mask opening ori ented parallel to the flat yields a V-shaped groove with a depth-to-width ratio equal to tan (54.7°)/2 = '1'2/2. ExperimentIn this note, we report on an attempt to employ the ODE technique for batch fabrication of cavities suitable for vertically coupling optical fibers to silicon circuitry. We have previously used laser-etched vertical cavities in photodetector structures designed to facilitate high den sity optical interconnection (4). As a processing alterna tive, orientation dependent etching of vertical shafts in (110) Si has been investigated. The cavity provides a me chanical seat for the optical fiber, and should consume a minimum amount of on-chip real estate. Cavities with cross sections approximating that of a single mode fiber core (~10 ",m in diameter) and depths greater than 20 ",m are suitable for this application. All sidewalls must be vertical, and adjacent walls must meet in a sharp edge (a [110] vector), where the transition between [111: planes does not cause deviations from verticality.Previous demonstrations of microstructures etched perpendicular to (110) Si surfaces, such as sets of parallel trenches (5), usually involved one-dimensional mask ge ometries. In these cases, as in the above example of (100) Si V-grooves, the crystallographic structure of the walls at the ends of the long mask openings may be ignored. When two-dimensional mask features were employed, e.g., to fabricate cavities for use as ink wells (6) or as m...

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MEMS Wet-Etch Processes and Procedures

Burns¹

2011

MEMS Reference Shelf

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Silicon photodetector structure for direct coupling of optical fibers to integrated circuits

Cited by 9 publications

References 10 publications

Bulk micromachining of silicon

Bulk micromachining of silicon

Limitations of Orientation Dependent Microstructure Etching in Silicon

MEMS Wet-Etch Processes and Procedures

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