News Column

Patent Issued for Termination of High Voltage (HV) Devices with New Configurations and Methods

August 27, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- Alpha and Omega Semiconductor Incorporated (Sunnyvale, CA) has been issued patent number 8803251, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Lee, Yeeheng (San Jose, CA); Bobde, Madhur (Sunnyvale, CA); Ding, Yongping (Sunnyvale, CA); Kim, Jongoh (Cupertino, CA); Bhalla, Anup (Santa Clara, CA).

This patent was filed on July 19, 2011 and was published online on August 12, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The invention relates generally to the semiconductor power devices. More particularly, this invention relates to configurations and methods for manufacturing of new and improved edge terminations for high voltage (HV) devices for improved reliability and to reduce the areas occupied by the termination areas while maintaining high breakdown voltages.

"Conventional floating guard rings in the termination area are not sufficient to sustain high breakdown voltages for high-voltage (HV) devices that have heavily doped N regions 110, e.g., doping concentration of 10.sup.16 dopants/cm.sup.3, of about two to five microns in depth below the top surface of the substrate 105 as that shown in FIG. 1. The N-charge in the heavily doped region 110 is too high and the floating guard rings, which are P type doped regions implanted in the heavily doped N region, need charge compensation in order to sustain a higher breakdown voltage in the termination area. The conventional edge termination designs with voltage drop in the oxide lining the trench are not effective in resolving the problems due to the facts that such edge termination can only sustain a breakdown voltage up to approximately 100 volts. The lower breakdown voltage of approximately 100 volts is caused by the gross field crowding effects under the trench. The low breakdown voltage at the edge termination will limit the applications of the high-voltage (HV) devices when a higher voltage operational requirement is necessary.

"Therefore, a need still exists in the art of power semiconductor device design and manufacture to provide new and improved configurations of the edge termination such that the above discussed problems and limitations can be resolved."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "It is therefore an aspect of the present invention to provide a new and improved edge termination configuration to reduce the electrical field crowding effects near the blocking junction at the device edge and provide a compact termination with lower surface electric field that is less sensitive to surface charge. This is achieved with the formation of a plurality of termination trenches formed in the heavily doped region and forming doped regions at the bottom of the termination trenches in the lightly doped region to function as buried guard rings in the edge termination.

"Specifically, an aspect of this invention is to provide a new and improved edge termination configuration for a semiconductor power device by forming a plurality of buried guard rings either underneath or surrounding the areas around a plurality of termination trenches opened in the edge termination areas. Theoretically, the pinch-off of the floating guard rings limits the voltage drop across each mesa between two trenches. Therefore, an important aspect of the present invention is to design the mesa width and space increments between two trenches to achieve breakdown voltage suitable for application of high voltage devices while the buried guard rings result in low sensitivity to the surface charges.

"It is another aspect of this invention to provide the new and improved edge termination configuration for a semiconductor power device by forming a plurality of termination trenches and forming the guard rings at the bottom and around the sidewalls of alternating trenches to overcome the potential issues of the shortening of the adjacent guard rings when the mesa doping is light. Every two guard rings are formed at the bottom of the two termination trenches with an intermediate termination trench not surrounded by a guard-ring doped region. The termination trenches with no guard ring doped region do not have the P-region along the sidewalls and can therefore sustain high breakdown voltage limited by the buried guard ring pinch-off.

"Briefly in a preferred embodiment this invention discloses a semiconductor power device disposed in a semiconductor substrate and having an active cell area and an edge termination area. The edge termination area comprises a plurality of termination trenches lined with an insulation layer and filled with a gate material therein. The edge termination further includes a plurality of buried guard rings formed as doped regions in the semiconductor substrate immediately adjacent to the termination trenches. In an embodiment of this invention, the plurality of buried guard rings formed as doped regions in the semiconductor substrate immediately below a bottom surface of the termination trenches. In another embodiment, the plurality of buried guard rings formed as doped regions in the semiconductor substrate immediately below a bottom surface and surrounding a lower portion of the termination trenches. In another embodiment, the plurality of buried guard rings formed as doped regions in the semiconductor substrate immediately below a bottom surface and surrounding sidewalls of the termination trenches wherein the buried guard rings are disposed around alternate termination trenches with every two of the guard rings separated by a middle termination trench with no buried guard ring underneath.

"These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various drawing figures."

For the URL and additional information on this patent, see: Lee, Yeeheng; Bobde, Madhur; Ding, Yongping; Kim, Jongoh; Bhalla, Anup. Termination of High Voltage (HV) Devices with New Configurations and Methods. U.S. Patent Number 8803251, filed July 19, 2011, and published online on August 12, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8803251.PN.&OS=PN/8803251RS=PN/8803251

Keywords for this news article include: Electronics, High Voltage, Alpha and Omega Semiconductor Incorporated.

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Source: Electronics Newsweekly


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