Katsumi Okashita

Conformal doping mechanism for fin field effect transistors by self-regulatory plasma doping with AsH3 plasma diluted with He

Key parameters for achieving n-type conformal doping desirable for source/drain extension regions of Si n-channel fin field effect transistors (FinFETs) have been determined for self-regulatory plasma doping using an AsH3 plasma diluted with He. Two-dimensional scanning spreading resistance microscopy revealed that this technique is advantageous for conformal doping of fin structures. An excellent resistivity conformality was obtained with the ratio of the resistivity of fin sidewall to that of the fin top surface being 0.85. A high total gas flow rate and a high AsH3 concentration were found to be important conditions for realizing conformal doping. The results revealed that a short gas residence time and high molar concentrations of AsH3 and He in the process chamber are essential physical parameters for realizing large amounts of dopant species with finite decomposition times. When these conditions are realized, a sufficiently large amount of As is supplied to both the top surface and the sidewall so t...

Doping Effects from Neutral B2H6 Gas Phase on Plasma Pretreated Si Substrates as a Possible Process in Plasma Doping

In a low-energy plasma doping process, the contribution of not only ionized species but also neutral species to the doping process should be considered. To investigate such a contribution, experiments involving gas phase doping combined with Ar plasma pretreatment were carried out. As a result, a significant increase in boron dose from a neutral gas phase was observed when the substrate surface was subjected to Ar plasma pretreatment prior to exposure to neutral B2H6/He gas. Through a comprehensive study of the effects of plasma pretreatment and gas exposure conditions on the boron dose from the neutral gas phase, the substrate temperature at which the surface was exposed to the neutral B2H6/He gas after the plasma pretreatment was observed to significantly increase the boron dose.