A Quantitative Study of Chemical Etching of InP

Abstract

Chemical etching of InP with HCI is used on a large scale, but limited information is available in the literature on the quantitative and mechanistic aspects of this reaction. A higher reaction rate is observed in alcoholic HCI than in aqueous HCI solutions. Also, a decrease of the reaction rate is observed with an increase in the degree of dissociation of HCI in aqueous solutions. We confirm that chemical etching depends on the concentration of nondissociated HCI molecules and that the reaction does not occur below a critical concentration. A first-order rate was obtained in aqueous and in alcoholic HCI solutions. The Arrhenius plot indicated an activation energy greater than 40 kJ . tool -I, indicating a kinetically controlled process. Scanning electron microscopy also showed profiles characteristic of a kinetically controlled process.There is great interest in the use of indium-phosphorus alloys in optoelectronic devices. During fabrication and quality control of these devices we must use robust and reproducible processes. Chemical etching is used in several steps during the production of such semiconductor devices. Although this technique has been applied since the beginning of this century, I it is our opinion that empiricism dominates and etching is still more art than science.Gerischer et al. 2.3 and Notten 4 have shown that the dissolution reaction of semiconductors may occur by a purely chemical mechanism. In such a case, the material surface suffers an attack by reactive solute molecules, as for example halogens and hydrogen halides. These are capable of forming, simultaneously, two new chemical bonds with the semiconductor surface. This concerted action distinguishes such a mechanism from the more usual electrochemical control. The reaction products are dissolved in the etching solution or escape as gases. We view the etching of InP with HC1 solutions as an example of this mechanism InPcs I + 3HCI(~q~ ---> InCl3(aql + PH3rThis work was carried out to contribute to the quantitative interpretation of the chemical processes occurring during etching of InP with HC1. ExperimentalThe crystals of InP used here were all from single batches of wafers. Samples were doped with Sn and, in some cases, with S. The crystalline orientation of the polished face of the wafers wa_s (001). After cutting small samples from the wafer, the (001) surface was submitted to a mechanochemical polishing with a 2 % bromine ethanolic solution at room temperature. Before each etching procedure the samples were extracted with trichloroethytene, acetone, and methanol in a quartz Soxhlet extractor for 10 min and subsequently washed with isopropanol, deionized water, and dried with a high purity nitrogen stream.To obtain the etching profiles we use a positive photoresist (Shipley S 1400-26) defining 5-~m wide lines by photolithography.All etching solutions were prepared by dilution of a 12M HC1 stock solution (standard 37% electronic reagent grade). The etching reactions were performed in a thermostated water bath (5 to 35 -+ 0. I~ in 15...

Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics

“…Note that in the particular alloy example in Equation (3), aluminium is not required for selective etching, but it can accelerate etching of the sacrificial layer. Moreover, because only undissociated HCl molecules interact with phosphide, the throughput is greatly enhanced by using concentrated HCl with the new ELO process 20,23,24 . The use of HCl as an etchant also poses significantly lower risks compared with highly lethal and corrosive HF.…”

Fabrication of microrods and microtips of InP by electrochemical etching

“…As can be concluded from Fig. 6(a), most of the microtips were bounded with four {3 2 2} facets, instead of the more stable {1 1 1} or {0 1 1} facets [7,14,16]. The left of Fig.…”

“…Now many techniques have been employed to fabricate semiconductor microstructure, like metal-organic chemical vapor deposition [1][2][3][4][5], molecular beam epitaxy [6], liquid-phase epitaxy [7] and electrochemical techniques [8][9][10][11][12][13][14][15][16]. Among these techniques the electrochemical techniques have their own advantages, such as their low processing temperature, low damage, low-cost and versatility.…”

“…The microtips of InP were gotten in strong HCl solutions [13] and in the ternary HBr-K 2 Cr 2 O 7 -H 2 O solutions [14]. In addition, triangle pillars were obtained based on n-InP (1 1 1) [14,15], and V-shaped groove of InP was formed based on n-InP (0 0 1) [16]. The nanoporous InP arrays with uniform and straight walls were fabricated by electrochemical etching [17].…”

Electrochemical structuring of mechanically activated n‐InP(100) surfaces

“…Etch stop was observed at {111} planes of the material [33,34]. Other research [35] described chemical etching in acid solutions and the development of a surface roughness, which gave the samples a white appearance. Work on photoelectrochemical (PEC) etching of InP described a strong surface roughness, which develops on n-type InP(100) etched in HCl solutions, whereas PEC etching in HBr and HF solutions leads to smooth (electropolished) surfaces [36].…”