1. Field of the Invention
The invention relates in general to a manufacturing method for a transistor, and more particularly to a manufacturing method for a high voltage transistor.
2. Description of the Related Art
With the development of the semiconductor technology, a high voltage transistor has been developed. A deep well doped with ions is formed on a substrate, and the high voltage transistor is disposed in the deep well to obtain the higher reference withstanding voltage (also referred to as a breakdown voltage).
In many applications, designers have to increase the breakdown voltage of the high voltage transistor through various manufacturing processes. However, it is not easy to increase the breakdown voltage of the high voltage transistor. Under various factors, the stable results of the substrate current (Isub) and the specific turn-on resistance (Ronsp) of the high voltage transistor cannot be obtained.
In addition, the high voltage transistor also often encounters the problem of Kirk's effect. Kirk's effect represents that the cut-off frequency descends while the drain current of the transistor ascends. Since a lot of carriers are injected, the width of the depletion layer on the junction of the drain and the source is decreased, and the dummy increase of the source width is caused.
The above-mentioned phenomena are the great bottlenecks encountered in the current high voltage transistor technology. Thus, it is an important target in the current semiconductor industry to develop the new technology to improve the above-mentioned phenomena.