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Bombardment of Si substrates in vacuum byA r ions is widely employed for ion cleaning of Si substrates. A r bombardment is also used in ion, ion-plasma, and ion-chemical etching of Si substrates. This bombardment influences the electrical properties of Si structures and devices. A change of I-U characteristics of Si structures subjected to 10 keV 111 and 1 keV 1 2 , 31 A r ion bombardment is observed. Deep levels created during A r bombardment are connected with these changes. DLTS spectra of Mo-Si diodes prepared after cleaning of Si substrates by (1 to 3.5)keV A r ions before electron beam evaporation of Mo on Si substrates are studied in 141. However, as shown in 151, electron beam evaporation of Mo on the Si substrate alone creates deep levels in the Si substrate. Therefore, in order to study the deep levels created in Si substrates after ion cleaning by A r bombardment one needs to measure the DLTS spectra of Si Schottky structures prepared by thermal evaporation of metal on Si substrates cleaned in this way. Phosphorous-doped low ohmic Si substrates with n-type epitaxial layers of thickness (10 to 1 5 ) p m and electron concentration (d4 to 10 were used. Ion cleaning of the Si surface was performed by rf sputtering in vacuum of 4 Pa A r pressure, with 1 keV 1 3 . 5 MHz rf voltage for 5 min. After this cleaning Au dot contacts were evaporated on the surface of the Si epitaxial layer. For better adhesion after Au evaporation the Si substrates were heated in H2 ambient at 150 OC for 5 min. Control experiments have shown that the deep level concentration in these Au-Si Schottky structures is practically the same after this annealing. This result is in accord with the results of I51 where after subsequent annealing steps of 25 K for 10 min up to 15OoC the concentration of deep levels at Et = E -0.22 eV decreases by 10 %, at Et = Ec -0.39 eV by 1 2 30, and at Et = E -0.42 eV by 1 2 % and with the results of I61 where subsequent steps of 50 K fzr 10 min up to 15OoC decreases the concentration of deep levels at Et Ec -0.44 eV by 25 %.DLTS spectra were measured by a Semitrap DLS-81 apparatus of the Research Institute of Technical Physics (Hungary). Typical DLTS spectra of phosphorousdoped Si substrates, subjected to ion cleaning are given in Fig. 1. The electron emission rate at the maximum of the DLTS signal, e,(Tmax), is given by 15 ') Boul. Lenin 72, BG-1784, Sofia, Bulgaria.

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