Radiofrequency LDMOS (laterally diffused metal oxide semiconductor) device and manufacturing method thereof

Abstract

The invention discloses a radiofrequency LDMOS (laterally diffused metal oxide semiconductor) device. Drift regions are uneven doping structures; a first drift region, a third drift region and a second drift region are sequentially arranged between a channel and a drain region; the doping concentration of the first drift region is minimum, the strength of an electric field nearby a channel region and a hot carrier effect can be reduced, and the reliability of the device is improved; the doping concentration of the second drift region is high, and the switch-on resistance of the device can be reduced; and by a contra-doping covering layer formed on the surface of the second drift region, the drift regions can run out effectively, the outputting capacitance of the device is reduced, influences of charge and an interface state of shielding dielectric layer without a Faraday shield layer can be avoided, and the characteristics of the device are stable. The second drift region is a transition region, and the driving current of the device can be increased further and the switch-on resistance of the device can be reduced under the condition that the reliability and the outputting capacitance of the device are not affected. The invention also discloses a manufacturing method of the radiofrequency LDMOS device.

Description

technical field [0001] The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a radio frequency LDMOS device; the invention also relates to a method for manufacturing the radio frequency LDMOS device. Background technique [0002] RF Lateral Field Effect Transistor (RF LDMOS) is a common device used in RF base stations and broadcasting stations. High breakdown voltage, low source-drain on-resistance (RDSON) and low source-drain parasitic capacitance (Coss) are device characteristics that RF LDMOS must have. In order to minimize the parasitic capacitance between the source region, the channel and the substrate, a heavily doped substrate material and a lightly doped epitaxial layer are usually used, and tungsten deep contact holes are used to connect the source region, channel, and substrate. epitaxial layer and substrate. Such as figure 1 Shown is a schematic structural diagram of an existing radio frequency LDMOS device. Tak...

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Problems solved by technology

To keep RDSON low, it is necessary to increase the doping concentration of the drift region 103 as much as possible, but this may cause the drift region 103 to not be completely depleted when a high voltage is applied to the drain region 106, resulting in a drop in breakdown voltage

In addition, the main factor restricting the decline of Coss is the junction capacitance from the drift region 103 to the silicon substrate 101. If the concentration of the drift region 103 increases, the junction capacitance will also increase, which is also not conducive to the decline of Coss.

Therefore, the two parameters of RDSON and Coss are mutually restricted, and the existing device structure cannot simply increase the concentration of the drift region to reduce both of them at the same time, so the device characteristics of the existing RF LDMOS are difficult to achieve excellent performance

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