Backscattering of MeV 4He ions has been used to analyze the Ga and As content in SiO2 and Si3N4 dielectric layers deposited on single-crystal GaAs substrates. Changes in impurity concentrations and distributions are seen after isothermal annealing at both 750 and 800°C. Evidence for Ga outdiffusion is clear.
-c h a r g e c o n t r o l ' i n MOS s t r u c t u r e s f o r t h r e s h o l d s h i f t , a u t o r e g i s t r a t i o n , and complementary w e l l s and 2) d i s t r i b u t i o n cont r o l i n microwave and bipolar structures. Another f e a t u r e t h a t has n o t been e x t e n s i v e l y e x p l o i t e d i s t o combine the advantages o f t h e h i g h r e s o l u t i o n c a p a b i l i t i e s o f e l e c t r i c beam p a t t e r n d e l i n e a t i o n w i t h t h e l o w l a t e r a l s p r e a d i n h e r e n t i n t h e implantation process. This talk reviewssome o f t h e g e n e r a l f e a t u r e s o f t h e c h a r a c t e r i s t i c s o f implanted layers i n
terms o f d e p t h d i s t r i b u t i o n , r a d i a t i o n damage and e l e c t r o n a c t i v i t y .I m p l a nt a t i o n p r o c e s s e s i n s i l i c o n a r e r e a s o n a b l y w e l l understood. There remain areas which require f u r t h e r c l a r i f i c a t i o n , F o r compound semiconductors, p a r t i c u l a r l y GaAs, implantation techniques offer a t t r a c t i v e p o s s i b i l i t i e s f o r t h e f a b r i c a t i o n of substrate temperature during implantation and t h e high frequency devices. In these materials , t h e d i e l e c t r i c c o a t i n g r e q u i r e d t o p r e v e n t d i s s o c i a t i o n during thermal anneal play major roles.
Although Au–Ge has often been used in making Ohmic contacts to GaAs, the alloying behavior of this system has not been well characterized and understood. In this paper the behavior of Au and Au–Ge layers on GaAs was investigated as a function of processing temperature (400–600°C) and time by backscattering and channeling-effect measurements with 2-MeV 4He ions. Scanning electron microscopy and current-voltage evaluations were also made. Similarities are found in both systems: There is a deeply penetrating component of Au into the GaAs that remains essentially unaltered once the surface Au has been consumed; a disordered region near the surface is found, the amount of which increased with increased process times. No significant amount of Au is found on substitutional or tetrahedral interstitial sites within about 3000 Å of the surface. The presence of the Ge does have a significant effect: Complete alloying occurs at lower temperatures, and Ohmic contacts are formed. Scanning-electron-microcope displays indicate that surface pits are formed; the depth of these increase with increased amounts of Au. Optical micrographs of a sectioned sample indicate a deep Au penetration.
Backscattering and channeling effect measurements with MeV 4He ions were used to determine the depth dependence of the composition of amorphous silicon nitride layers on singlecrystal silicon. The composition was stoichiometric over the entire layer for high ratios of NHs to SiH 4 used in the deposition reaction at 850°C. For lower ratios, a silicon excess was found, and in extreme cases, the silicon excess was located predominantly near the interface.
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