Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1999-02-24
2001-07-17
Wojciechowicz, Edward (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S356000, C257S358000, C257S630000, C257S773000
Reexamination Certificate
active
06262454
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a protection structure for high-voltage integrated electronic devices.
BACKGROUND OF THE INVENTION
One of the main problems encountered in the production of high-voltage electronic devices is due to the establishment of high electrical fields on the surface of the device, which can cause premature breakdowns between high and low voltage regions (for example between sink and source terminal of high voltage MOS transistors), and instability of the electrical parameters of the device during its life, owing to charges outside the component (e.g., polarization of the passivation material, ionic contamination, and polarization of the resin of the package).
Various solutions have been proposed in order to reduce the surface electrical fields. Among these, a technique which is widely used at present in the production of lateral devices uses a lightly doped layer (epitaxial layer optionally doped by implantation), which makes it possible to considerably decrease the surface electrical fields, and thus to obtain higher breakdown voltages. However, this solution causes the device to be highly sensitive to charges localized outside of the device, for example in the package resin, in the passivation oxide layers, and in the dielectric layers deposited at the end of the production process.
In addition, when the high voltage devices are connected to other components, it is difficult to connect the high voltage biased terminal using standard techniques (e.g., metallization extending on the insulation surface), without inducing premature breakdowns.
Structures have thus been proposed to protect the device surface and to distribute the electrical potential as uniformly as possible over extensive areas, so as to reduce crowding of electrical field lines. In particular, the use of spiral-shaped resistive components has been proposed, extending between high voltage regions and low voltage regions, so as to generate linear equal distribution of the potential, beginning from the center to the periphery of the device (see for example U.S. Pat. No. 5,349,232, EP-A-574,643, U.S. Pat. No. 5,382,825, U.S. Pat. No. 5,382,826 and the article “A 500V 1A 1-Chip Inverter IC with a New Electric Field Reduction Structure” by Koichi Endo, Yoshiro Baba, Yuso Udo, Mitsuru Yasui and Yoshiyuki Sano, Proc. of the 6th Internat. Symposium on Power Semiconductor Devices & ICs, Davos, Switzerland, May 31-Jun. 2, 1994). A variant in the use of resistive components includes the use of silicon junction diode chains (again see U.S. Pat. No. 5,382,825 and U.S. Pat. No. 5,349,232), or of a dielectric capacitor chain (see U.S. Pat. No. 5,040,045).
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a further protection structure which functions efficiently in preventing establishment of localized electrical fields inside the device, generated by external charges. According to principles of the present invention, a substrate of semiconductor material is provided with a plurality of protection regions of increased doping concentration. In one embodiment, the doping concentration is of the opposite conductivity type as the substrate. The doped region in the substrates are concentrically formed arranged in close lines, one inside another. Each ring is contiguous with each adjacent ring along at least a portion of each respective ring. Preferably, the contiguous portion alternates on either side of the respective ring so that the rings are connected reciprocally in series. In a first embodiment, the rings are cylindrical in nature, but in other embodiments they are oval, square, or other acceptable shape for forming the desired protection regions that extend along closed lines, arranged one inside the other.
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Endo et al., “A 500V 1A 1-Chip Inverter IC With A New Electric Field Reduction Structure,” inProc. of the 6th Internat. Sympos. on Power Semiconductor Devices&IC's,Davos, Switzerland, May 31-Jun. 2, 1994.
Legnani Marco Alessandro
Pidutti Albino
Galanthay Theodore E.
Rupnick Charles J.
Seed Intellectual Property Law Group PLLC
STMicroelectronics S.r.l.
Wojciechowicz Edward
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