Laser recrystallized polysilicon for high performance I2L

A key process innovation that has the potential to make very significant improvements in the performance of (integrated injection logic) I
²
L is proposed and demonstrated. The process is based on replacing the p
⁺
extrinsic base-n
^-
substrate parasitic diode with an oxide capacitor, This would eliminate injection current losses to the underlying substrate, thus improving the current gain, the minimum propagation delay time, and the speed-power product of the structure. A buried oxide I
²
L structure of this type may be realized via the use of pulsed or CW laser recrystallization of polysilicon. An interesting feature of the proposed method is that the crystal material over SiO
2
would not be used for the active transistor area, thus relaxing the stringent material requirements of bipolar devices. The polysilicon may be deposited on a p
⁺
base patterned thermal oxide by LPCVD or by deposition in a high temperature epitaxial reactor. The realization of such structures is demonstrated here specifically for the case of pulsed laser annealing of polysilicon deposited by either of the above mentioned ways.