An electrically detected magnetic resonance study of performance limiting defects in SiC metal oxide semiconductor field effect transistors

Abstract

In this study, we utilize electrically detected magnetic resonance (EDMR) techniques and electrical measurements to study defects in SiC based metal oxide semiconductor field effect transistors (MOSFETs). We compare results on a series of SiC MOSFETs prepared with significantly different processing parameters. The EDMR is detected through spin dependent recombination (SDR) in most cases. However, in some devices at a fairly high negative bias, the EDMR likely also involves spin dependent trap-assisted tunneling (SDT) between defects on both sides of the SiC/SiO2 interface. At least three different defects have been detected in the magnetic resonance measurements. The defects observed include two at the SiC/SiO2 interface or on the SiC side of the SiC/SiO2 interface: one is very likely a vacancy center with a distribution which extends into the bulk of the SiC and the other is likely a “dangling bond” defect. A third defect, located on the SiO2 side of the SiC/SiO2 interface, has a spectrum very similar to that previously reported for an oxygen deficient silicon coupled to a hydrogen atom. In nearly all cases, we observe a strong dominating single line EDMR spectrum with an isotropic g≈2.0027. In some samples, this strong central line is accompanied by two pairs of considerably weaker side peaks which we link to hyperfine interactions with nearby Si and C atoms. The pattern is physically reasonable for a silicon vacancy in SiC. We therefore tentatively assign it to a silicon vacancy or silicon vacancy associated defect in the SiC. In one set of devices with very high interface trap density we observe another dominating spectrum with g∥=2.0026 and g⊥=2.0010 with the symmetry axis coincident with the [0001] and nearly the SiC/SiO2 interface normal. We ascribe this EDMR spectrum to a “dangling bond” defect. A third EDMR spectrum shows up in some devices at a fairly large negative gate bias. The phase of this spectrum is quite consistently opposite to that of the SDR detected EDMR at other biases. Part of this inverted phase spectrum involves two narrow lines which are separated by ≈10.5 G. Since the center responsible for this spectrum is almost certainly in the SiO2, it is likely due to the so called 10.4 G doublet center, an unpaired electron residing on an oxygen deficient silicon atom coupled to a hydrogen in SiO2. The likely presence of one oxygen deficient silicon defect suggests that other oxygen deficient silicon atom defect sites in the oxide may also be important in SiC/SiO2 devices. Oxygen deficient silicon defects in SiO2 are typically called E′ centers. Our results collectively demonstrate considerable complexity in both the chemical composition and physical distribution of performance limiting defects in SiC transistors, with defects observed on both sides of the SiC/SiO2 interface. Our results most strongly indicate that fairly high densities of intrinsic deep-level defects, likely due to a Si vacancy or a closely related defect, extend into the bulk of the SiC in all but one of the devices prepared utilizing a fairly wide range of processing parameters.

Electrically detected magnetic resonance of carbon dangling bonds at the Si-face 4H-SiC/SiO2 interface

“…The first one is the carbon dangling bond (P bC ) center [9][10][11][12][13][14][15] and the second one is the silicon vacancy (V Si ). [16][17][18][19][20][21][22] In this study the EDMR spectra obtained from differently processed 4H-SiC n-channel MOSFETs are compared and simulated spectra based on the reported hyperfine (HF) parameters of the P bC and V Si defects are discussed. While the dominant defect in the studied devices has been tentatively assigned to the V Si in previous studies, 23,24 the comparison to the simulations demonstrates that the P bC center is a more suitable candidate for the observed interface defect.…”

Progress in SiC MOSFET Reliability

“…2(c)). Each type of packaging shows larger negative V T shifts than positive V T shifts, indicating that hole injection is a significant issue, similar to concerns in SiO 2 on Si where holes are trapped at oxygen vacancies (E' centers) (8) with analogous models being developed for SiO 2 on SiC (9). Negative V T shifts appear to be slightly worse for plastic-packaged parts, but the differences are so small it is likely that packaging has no significant effect on ∆V T .…”

Electrically detected magnetic resonance study of defects created by hot carrier stress at the SiC/SiO2 interface of a SiC n-channel metal-oxide-semiconductor field-effect transistor

“…With EDMR, it is possible to measure the atomic structure of defects that eventually limit the device performance in a fully processed semiconductor device. [18][19][20] It provides high resolution and limits the response to electrically active regions within the device. Applying a quasi-static magnetic field to a paramagnetic defect results in a Zeeman splitting of its electron energy levels.…”