<i>In Situ </i>Nitrogen and Aluminum Doping in Migration Enhanced Embedded Epitaxial Growth of 4H-SiC

Abstract

The in-situ doping of aluminum and nitrogen in migration enhanced embedded epitaxy (ME3) is investigated with the aim to apply it to the realization and fabrication of all-epitaxial, normally-off 4H-SiC JFET devices. This ME3 process consists of the epitaxial growth of an n-doped channel and a highly p-doped top gate in narrow trenches. We found that the nitrogen doping in the n-channel (a-face) is a factor 1.5 higher than layers grown with the same process on Si-face wafers. Due to the low C/Si ratio and the low silane flow rate used in the ME3 process, the growth of the p-doped top gate needs high flow rates of the aluminum precursor trimethylaluminum for several hours, which contaminates the CVD reactor and causes aluminum memory effects. These aluminum memory effects can be reduced by an extra high temperature bake-out run.

An empirical growth window concerning the input ratio of HCl/SiH4gases in filling 4H-SiC trench by CVD

“…[2][3][4] Therefore, epitaxial growth by refilling an epilayer into the SiC trench is thought to be highly practicable, 5,6) and some preliminary studies have been implemented with chemical vapor deposition (CVD) in a conventional gas system: SiH 4 :C 3 H 8 :H 2 . [6][7][8][9][10][11][12] The use of a high temperature (1650 °C), 6,7) a relatively high pressure of up to 38 kPa, 13) and a reduced flow rate of the H 2 carrier gas has been found helpful for increasing the filling rate (R G ). These techniques applied together produce R G ∼1.5 µm=h for 5-µm-deep trenches.…”

Filling 4H-SiC trench towards selective epitaxial growth by adding HCl to CVD process

“…7) Therefore, trench filling by epitaxially filling doped SiC into trenches of the opposite conductivity type is considered the preferable method for constructing SiC-SJ structures. [8][9][10][11][12][13][14] In previous literature, 4H-SiC trenches with depths of up to 7 µm and aspect ratios of about 2-4 have been completely or half-filled by using hot-wall chemical vapor deposition (HWCVD) with a conventional gas system, SiH 4 : C 3 H 8 : H 2 . [8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches.…”

“…[8][9][10][11][12][13][14] In previous literature, 4H-SiC trenches with depths of up to 7 µm and aspect ratios of about 2-4 have been completely or half-filled by using hot-wall chemical vapor deposition (HWCVD) with a conventional gas system, SiH 4 : C 3 H 8 : H 2 . [8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches. 13) Though few details have been released, it is conjectured that the motivation for minimizing the growth outside of the trenches was to avoid the potential risk of void formation (fast closing around the trench's top corner) during long-duration growth.…”

“…[8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches. 13) Though few details have been released, it is conjectured that the motivation for minimizing the growth outside of the trenches was to avoid the potential risk of void formation (fast closing around the trench's top corner) during long-duration growth.…”

Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics

“…Further, we have to take care for a geometric confinement of the channel in the semiconductor. A vertical confinement is predefined by an epitaxially grown layered pn junction 38 that leaves the top surface of the wafer as low doped conducting n-type layer of 2.9 µm depth (out of which graphene is grown). The space charge region of the pn junction suppresses any charge carrier density below this conducting layer.…”