Donor Reactivation Kinetics and Hydrogen Redistribution in the Space Charge Layer of N-Type Silicon
- PDF / 303,271 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 31 Downloads / 191 Views
DONOR REACTIVATION KINETICS AND HYDROGEN REDISTRIBUTION IN THE SPACE CHARGE LAYER OF N-TYPE SILICON Y.-A. WUa),b), G. ROOSa), N. M. JOHNSONa), AND C. HERRINGa),b)
a) Xerox Palo Alto Research Center, Palo Alto, CA 94304 b) Department of Applied Physics, Stanford University, Stanford, CA 94305
ABSTRACT The passivation and reactivation of As donor dopants in n-type Si was studied with both monatomic hydrogen and deuterium. Hydrogenated Schottky diodes were characterized with C-V and DLTS measurements. The reactivation kinetics of the As-H and As-D complexes were studied in the spacecharge layer of reverse biased diodes in the temperature range from 60*C to 120°C. These bias-anneals yield dissociation time constants for As-H, from which an averaged activation energy of 1.17±0.1 eV was determined. Although the dissociation of the As-H complex is appreciably slower than that previously measured for P-H, the activation energy is within about 0.05 eV of
that determined previously for the P-H complex (1.2 eV). The depth redistribution of the As-H complexes after bias-annealing agrees with the previous conclusion that hydrogen can assume a negative charge state in n-type Si. INTRODUCTION The ability of monatomic hydrogen to passivate shallow acceptors and donors in crystalline semiconductors as well as to passivate electrically active deep-level defects in both amorphous and crystalline semiconductors is now well established (1). Lagging these developments has been the quantitative determination of the the parameters that describe the kinetics of passivation and dissociation. In addition, in general the microscopic structure of dopanthydrogen complexes and the charge states of migrating hydrogen require further study. Hydrogenation of single-crystal silicon has received considerable attention, in part due to the importance of the material in the integratedcircuit industry. In 1982 it was shown that hydrogen passivates shallow acceptors (e.g., B) in Si (2, 3), and in 1986 the same phenomenon was demonstrated for shallow donors (e.g., P) (4). In recent years several studies have been reported on the dissociation kinetics of hydrogen-acceptor and hydrogen-donor complexes (see i.e. ref. 1 and refs therein). The earliest attempts utilized simple annealing studies and were later found to yield only upper limits for the dissociation energies because the hydrogen atoms are usually released in the charge state opposite to that of Mat. Res. Soc. Symp. Proc. Vol. 262. 01992 Materials Research Society
450
the dopant (i.e., H+ in p-type and H- in n-type Si). Because of the Coulombic attraction a significant amount of recapture occurs, which if ignored results in an over estimation of the dissociation energy. This complication and been successfully overcome by determining the annealing characteristics within the space-charge layer of reverse biased Schottky diodes (5-8). The high electric field causes the charged hydrogen atom to drift away from the dopant (and out of the space-charge layer). Suppression of the recapture process per
