Selective porosification and dissolution of n-InP surfaces after focused ion beam im-plantation of Si++

U. Schlierf, P. Schmuki

In previous investigations it has been shown, that porous Si can be produced electrochemically at defined surface locations of a Si substrate by sensitizing the surface with implanted Si++ ions [1]. The same was shown for GaAs [2]. Also for InP it is known, that it can be electrochemically porosified [3]. In cooperation with the National Research Council of Canada it has been shown now, that InP surfaces can also be sensitized and selective porosificated by a writing process using focused ion beam technology combined with elec-trochemistry.

Selective porosification takes place at defect surface areas, such as scratches, by an elec-trochemical polarization lower than a treshold potential (the pore formation potential (PFP)). Highly defined defect patterns can be created using FIB ion bombardment. At these defect patterns a subsequent electrochemical dissolution reaction can be triggered selectively.

The work shows that not only a selective porosification (Fig. 1, 2) can take place but also, by varying the parameters, a total removal of the pattern could be achieved (Fig. 3). Finally only a small range of potential, time and implantation dosage combinations was found to lead to a local porous surface, in most other cases the patterns were completely dissolved. To obtain detailed information of the pore formation process, further investigations on InP samples had been carried out [4].

Fig.1: SEM image of a selective porousificated InP sample implanted with 1.75e14 ions/cm2 Si++ (160keV) after polarizing in 1M HF from -0.5V to 0.3V.

Fig.2: AFM image of a selective porousificated InP sample implanted with 1.75e14 ions/cm2 Si++ (160keV) after polarizing in 1M HF from -0.5V to 0.3V.

Fig.3: AFM image of a selective porousificated InP sample implanted with 1.75e14 ions/cm2 Si++ (160keV) after polarizing in 1M HF from -0.5V to 0.5V.

References:

[1] A. Spiegel, L.E. Erickson, and P. Schmuki, Selective Growth of Porous Silicon on Fo-cused Ion Beam Patterns; Journal of The Electrochemical Society, 147 (2000) 2993

[2] P. Schmuki, L.E. Erickson, D.J. Lockwood, B.F. Mason, J.W. Fraser, G. Champion, and H.J. Labbé, Predefined Initiation of Porous GaAs Using Focused Ion Beam Sur-face Sensitization; Journal of The Electrochemical Society, 146 (1999) 735

[3] P. Schmuki, L. Santinacci, T. Djenizian, and D.J. Lockwood, Pore Formation on n-InP; phys. Stat. Sol. (a), 182 (2000) 51

[4] P. Schmuki, U. Schlierf, T. Herrmann, G. Champion, Pore Initiation and Growth on n-InP(100); Electrochim. Acta, submitted (2001)