Silicon carbide (4H-SiC) devices with blocking voltage rating up to 3.3kV have been successfully commercialized [1]. Two key factors for this are the availability of lower cost, high quality SiC substrates, and the availability of low defect epitaxial layers with a thickness of up to 30 m. SiC devices also have the potential to outperform Si devices for higher voltage applications beyond 6.5kV due to lower power dissipation and superior thermal conductivity [2]. For this, thicker epitaxial layers are required for higher blocking voltage. In-grown stacking faults (IGSF) can be generated during epitaxial growth of SiC and can have a more complex nature in thick epitaxial layers [3]. These IGSFs can cause device leakage and can also result in surface defects that may influence oxide reliability in SiC MOSFETs. Hence, it is essential to investigate their formation and microstructure. In this work, we perform an analysis of IGSFs that were formed at different stages of epitaxial growth, analyze their spectral emission and identify possible formation mechanisms using ultraviolet photoluminescence (UVPL) imaging with spectral content as well as multi-vector X-ray topography (XRT). SiC epitaxial layers with 180m thickness, low n-doping of 5x1014 cm-3 were grown on 150 mm diameter SiC substrates with a 20m thick 1x1018 cm-3 highly n-doped buffer layer using conventional chemical vapor deposition with chlorinated chemistry in a hot-wall epi-reactor. UVPL extended defect mapping was performed on a custom setup with 355nm laser excitation. Several spectral filters with ~10 nm bandpass from 400-700nm are being used to observe luminescence images of various IGSFs. Additionally, -PL mapping of selected defects areas were measured using a customized grating based spectrometer with 325nm laser excitation. XRT measurements were performed using a Rigaku XRTmicron system. Section topography was also performed on selected sample IGSF regions to investigate defect evolution and propagation with depth. IGSFs of various sizes were observed in the wafers as shown in Fig 1. This indicates that they did not form at the substrate / epitaxial interface but at a later stage during epitaxial growth. They also appeared to have a different microstructure. Many of them were a Frank-type IGSF, but there were others that also had Shockley-type regions. XRT imaging of the same defect regions, as shown in Fig. 2, shows contrast that indicates the presence of multiple components of fault vectors for different stacking faults. Spectral UVPL images also correspond with these results and show some regions of the faults having emission in the ~415-420nm range, which corresponds to Shockley stacking faults [4]. Other regions show emission ~430nm, indicating an extrinsic Frank-type fault [5]. Complete details from spectral UVPL imaging and -PL mapping from the IGSFs will be presented to determine the various fault types in more detail. Additionally, depth resolved section XRT will be shown to analyze the origins of the IGSFs during the epitaxial growth process.[1] D. Xing et al., pp 1-6, 2020 WiPDA Asia, doi.org/10.1109/WiPDAAsia49671.2020.9360270. [2] J. Wang, et. al., IEEE Industrial Electronics Magazine, 3, 16-23, (2009). [3] N. A. Mahadik, et. Al., Scripta Materialia 235, 115598, (2023). [4] Sridhara et. al. Appl. Phys. Lett. 79, 3944 (2001) [5] Tsuchida et. al., J. Crys. Growth 310, 757 (2008)