Experimental Setup

General remarks

Silicon electrochemistry, especially in electrolytes containing HF, is used to etch porous silicon. We use a standard three electrode arrangement. The cell is made of Teflon. In addition the electrolyte can be circulated through the cell with a peristaltic pump. The electrolyte-temperature is controlled. A Personal-Computer controlls the wohl etch-system.For pore-ecthing an anodic potential is applyed at the silicon-sample. For etching p-type-silicon no backside illumination is needed.
 
 


Figure 1 - General experimental setup

N-type silicon

N-type-silicon is etch in contact to an aqueous HF solutions. The charateristic i-v-curve is shown in the figure. By n-Si the current-density is controlled by the illumination-intensity.
 
 


Figure 2 - IV Curve

For etching n-type-silicon a photogeneration of holes is need by back-side-illumination. The photo-current (back-side-illumination intensity) is lower than the cirtical current-density Ips. The anodic etch-potential has to be higher than the critical voltage U(Ips).
 
 


Figure 3 - Current limitation


P-type silicon

For etching p-type -silicon no backside-illumination is need. Macropores in p-Si were usually etch in organic electrolytes. Often used organic solutions with HF for etching p-type silicon are: acetonitril (MeCN), dimetyhlsufloxid (DMSO) and dimetyhlformamid (DMF). The Figure 4 shows the i-v-curve of n-Si in contact to an aqueous HF-solution. Macropores on p-type-silicon can also be etch in pure aqeuos HF solutions by applying very low etching-potentials (see Fig).
 
 


Figure 4 - Macropores in aqu. electrolyte

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Last modified: 08/16/02
URL: http://www.marc-christophersen.de