The invention relates generally to methods of manufacturing semiconductor devices and, more particularly, to methods of manufacturing silicon carbide-based devices that utilize a junction termination extension.
Breakdown voltage of the reverse-blocking junction typically defines the maximum reverse voltage that a semiconductor device (having a p-n junction) can withstand. Such a blocking junction may comprise, for example, a p-n junction of a thyristor, a junction barrier schottky (JBS) diode, a bipolar junction transistor (BJT), an insulated-gate bipolar transistor (IGBT), or a corresponding junction in a metal-oxide-semiconductor field-effect transistor (MOSFET). Usually avalanche breakdown occurs in such devices at a voltage substantially less than the ideal breakdown voltage if no termination is present, because excessively high electric fields are present at certain locations (“high field points”) in the device under reverse bias. A high field point of a blocking junction under reverse bias usually occurs at locations where p-n junction is no longer planar, e.g. at a region of curvature, such as that at the periphery or edges of device active area.
In particular, breakdown voltage is critical for high power devices, such as silicon carbide (SiC) devices. Also, properties, such as insensitivity of device design (including termination) to active dose and interface charge variation, are more substantial in SiC devices, than in silicon (Si) based devices due to fundamental structural material differences.
Semiconductor devices may utilize any of various structures and methods to achieve an increase in the breakdown voltage. For example, junction termination extension (JTE) regions may be utilized near edge portions of the p-n junction formed by active area of device. In general, a JTE region may be considered as a more lightly doped extension of a heavily doped semiconductor region that adjoins a lightly doped semiconductor region having opposite type of conductivity to form the foregoing p-n junction. The principal function of the JTE region is to reduce the high concentration of electric field that would otherwise exist in the vicinity of the unterminated portion of the p-n junction, by laterally extending the blocking junction.
In addition to breakdown voltage, the design of the JTE affects a number of critical properties of the semiconductor device, including reliability and surface charge variation tolerance, and many of the affected properties have complex interrelationships. However, typical methods of manufacturing semiconductor devices include multiple implantation steps performed sequentially, which leads to higher implant costs.
Accordingly, there is a need for improved methods of manufacturing semiconductor devices including a JTE design. Further, it may be desirable to provide a JTE design that improves the critical properties of silicon-carbide based semiconductor devices, such as breakdown voltage, charge tolerance to surface charge variation and reliability.