Electron-beam-induced-current study of artificial twist boundaries in bonded Si wafers

Several pairs of (1 0 0)Si wafers were directly bonded with known misorient ation angles, between 0.1 and 11 degrees, to form artificial twist boundari es. The structure and electrical property of these boundaries were studied by means of transmission electron microscopy (TEM) and electron-beam-induce d-current (EBIC) method. TEM images showed that the dominant defects at bou ndaries were screw dislocations which compensate the twist component. All t he twist boundaries were EBIC active at room temperature and their contrast values have increased with the increase in the twist angle. The EBIC profi les of twist boundaries were well fitted with the Donolato's model. Althoug h EBIC contrasts of all the boundaries increased with decreasing temperatur e, the increase of 0.1 degrees boundary was the most significant. Such temp erature dependencies indicates that shallow levels are dominant in the smal ler angle boundaries, while certain amounts of deep levels are introduced i n larger angle boundaries due to dislocation interaction. (C) 2000 Elsevier Science B.V. All rights reserved.