Overvoltage protection device and manufacturing process for the same
An overvoltage protection device has a voltage-limiting region parallel to its central junction to produce a transverse junction breakdown. The spacing between the voltage-limiting region and the central junction defines the breakdown voltage. Via varying the size and location of the voltage-limiting region, the protection device can has various-breakdown voltages and lower breakover currents. Thereby, the sensitivity of the protection device can be improved.
1. A method for manufacturing an overvoltage protection device, wherein a voltage-limiting region surrounds a base region of the overvoltage protection device to control a breakdown voltage and a breakover current, the method comprising:
forming a first shading layer on a substrate;
etching the first shading layer to form a plurality of shading blocks to define a first region and a second region;
forming the base region in the second region;
forming the voltage-limiting region in the first region, wherein a breakdown region is formed between the voltage-limiting region and the base region and the breakover current passes through the breakdown region;
forming an emitter region on the base region; and
forming an electrode region on the emitter region;
whereby, the breakdown voltage is determined according to the spacing between the base region and the voltage-limiting region.
2. The method as claimed in claim 1 , wherein the voltage-limiting region has a first impurity concentration larger than a second impurity concentration of the substrate.
3. The method as claimed in claim 1 , wherein the voltage-limiting region and the base region produce a transverse breakdown phenomenon therebetween.
4. The method as claimed in claim 1 , wherein the base region is completely or partially surrounded by the voltage-limiting region with a continuous shape or a segmented shape.
5. The method as claimed in claim 1 , wherein the step for forming the base region, the voltage-limiting region or emitter region is performed via a diffusion process or an ion implantation process.
6. The method as claimed in claim 1 , wherein the substrate, the voltage-limiting region or the emitter region is made of an N-type semiconductor and the base region is made of a P-type semiconductor.
7. The method as claimed in claim 1 , wherein the voltage-limiting region or the emitter region is made of a P-type semiconductor and the base region is made of an N-type semiconductor.
8. The method as claimed in claim 1 , wherein a structure of the overvoltage protection device is manufactured repeatedly to form a bi-directional or multi-directional overvoltage protection device.