Transmission-mode optical microscope images of micropipes that run in different directions in (a, b) two different regions of a 4H–SiC wafer and in (c) a single region of a 4H–SiC wafer. The major flat is at the bottom of each image.
Map of the micropipe distribution and orientation in a 4H–SiC wafer. The dot indicates the top of the pipe where it intersects the top surface, and the line segment is the projection of the pipe as viewed from above. Micropipes aligned to the axis should be horizontal, with their tops on the left side.
Semilogarithmic plots of (a) (at high forward current) and (b) as a function of device area in wafer A. Some data points with are not visible in part (a) in order to show the main part of the distributions more clearly. Circles represent individual devices; lines are exponential fits to the deciles (10th through 90th percentiles) of each distribution (for a given device size) as a function of area. The actual decile values (not shown) are somewhat more scattered.
(a) Correlation between ideality factor and barrier height for all the Schottky diodes on wafer A. Circles represent individual devices. The solid line is a linear fit to the data points with , corresponding to the equation , yielding an extrapolated at . The correlation coefficient is 0.91. (b) Correlation between leakage current density at and ideality factor at high forward current for devices on wafer A. (In some cases, the current is limited by the compliance setting on the bias source.) Open circles represent devices containing D3 and/or D8 with micropipes; filled triangles, filled squares, and filled diamonds represent devices containing D5, D21, and D26 without micropipes, respectively; crosses represent devices containing relatively benign defects (i.e., D3, D8, or D25 defects without micropipes) and open squares represent devices without any visible defects.
(a, b) NDIC and (c) contact-mode AFM images of D8 defects of various subtypes. The step flow direction is from left to right. The scan size is and the depth scale is in the AFM image.
(a) Electroluminescence due to defects (spots A and B correspond to D8 defects, and spot C corresponds to a D5 defect, all with micropipes); (b) enlarged NDIC image of circle A in (a); (c) enlarged NDIC image of circle B in (a).
NDIC images of (a) two D3 defects with micropipes; (b) defect D25; (c) defect D26; and (d) defect D21. Step flow direction is from left to right.
NDIC images of triangular defects. (a) Defect D5 with a micropipe; (b) defect D5 without a micropipe; (c) defect D24; and (d) defect D16.
NDIC images of (a) a D11 defect and (c) three D17 defects. (b) A back-reflection topograph of six devices on wafer B, showing the micropipes terminating in D11 and D17 defects (“MP” denotes micropipes). (d) Contact-mode AFM images of D17 defects. The step flow direction is from left to right. The scan size is and the depth scale is in the AFM image.
EBIC images of four Schottky diodes on wafer C. The number of dark spots (including comets) and ideality factor are 12 and 1.168 in device 3-1 A, 15 and 1.184 in 4-4 A, 18 and 1.237 in 2-3 A, and 27 and 1.342 in 1-4 A, respectively.
Correlation between density of dark spots observed by EBIC and ideality factors for (triangles), (squares) and (circles) diameter Schottky diodes on wafer C. The solid line is a least squares fit to the data points for both 240- and diodes, corresponding to the equation , with a correlation coefficient . The long- and short-dashed lines are separate linear fits to the data for the 300- and devices only, corresponding to and , respectively.
Properties of observed morphological defects in 12 SiC wafers.
Summary of the electrical effects of various morphological defects in wafer A.
Summary of the electrical effects of various morphological defects in wafer B.
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