INTERACTIONS OF HYDROGEN MOLECULES WITH BOND-CENTERED INTERSTITIAL OXYGEN AND ANOTHER DEFECT CENTER IN SILICON

Infrared spectra obtained from Czochralski (CZ) silicon heated in the range 1100 less than or equal to T less than or equal to 1300 degrees C in H-2, D-2, or mixtures of the two gases, show vibrational absorpti on at 1075 cm(-1) due to perturbed bond-centered interstitial oxygen a toms O-i. Deconvolutions of these absorption profiles imply that the o bserved perturbations to the O-i atom are due to adjacent defects inco rporating two H atoms. This interpretation is confirmed by detection o f modes nu(1) (nu(1HH),nu(1HD),nu(1DD)) with nu(1HH)=3789 cm(-1) and n u(2) (nu(2HH),nu(2HD),nu(2DD)) with nu(2HH)=3731 cm(-1), that both cor relate in strength with that of the 1075 cm(-1) absorption. A third se t of modes nu(3) (nu(3HH),nu(3HD),nu(3DD)), with nu(3HH)=3618 cm(-1) d etected in heat-treated CZ and float zone silicon and not related to t he absorption at 1075 cm(-1), must be due to H-H pair defects trapped at an unknown impurity or lattice defect. The frequencies of the nu(1H D), nu(2HD), and nu(3HD) modes imply that the three defects are H-2 mo lecules with weakened bonds and small dipole moments resulting from in teractions with either adjacent oxygen atoms (nu(1), nu(2)) or a secon d type of trap (nu(3)). Annealing treatments imply that isolated O-i-H -2 complexes can dissociate for T greater than or equal to 70 degrees C allowing interstitial H-2 molecules to diffuse away but they can be retrapped during a subsequent anneal at T less than or equal to 50 deg rees C.