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).