Structure and Method of Forming Trench MOSFET Having A Box Shaped Channel and Improved On Resistance Using Double Charged Channel Implant
Publication Date: 2004-Mar-16
The IP.com Prior Art Database
Keywords Trench, MOSFET, Box Channel, On Resistance (RDSon), Double Charged, Implant, Voltage Threshold (Vt), P-Channel
Trench, MOSFET, Box Channel, On Resistance (RDSon), Double Charged, Implant, Voltage Threshold (Vt), P-Channel
Trench MOSFET device electrical performance is highly dependent upon precisely forming channel regions having optimized doping concentrations and shape. Channel shapes such as “box-shaped” are well known in the art to improve Trench device electrical performance such as RDSon (1, 2). P-channel devices for example rely heavily on costly implantation and anneal manufacturing equipment and use complex and time consuming process to form such shaped channel regions. Unfortunately, existing process exhibit poor repeatability and process control leading to devices having poorly shaped channel with lackluster electrical performance. Thus, for at least the above reasons it is desirable to devise a novel structure and method of forming Trench MOSFET having a box shaped channel and improved on resistance.
A new structure and method of forming Trench MOSFET having a box shaped channel profile achieved by Double Charge Channel Implant (DCCI) without using costly high-energy implanters is disclosed. The box shaped channel profile reduces Rdson and Rdson sensitivity to voltage threshold (Vt) variation. Furthermore, the new method exhibits low process variation which contributes to lower manufacturing costs and higher overall device electrical performance.
Detailed Description of the Figures
Table 1 shows an example of a process flow that could be used to produce the new device including the double charged channel implant step. Note that the typical channel anneal step has been eliminated which reduces processing time as well as eliminates costly process equipment. Also note the step of double charge channel implant. This example flow could be used to produce a p-channel device, although one of average skill in the art could make obvious and well known substitutions to alternatively produce an n-channel device.
Fig. 1 shows a cross section rendering one embodiment of the novel Trench MOSFET. In this embodiment, the Trench MOSFET is of p-channel type.
Fig. 2 shows the positive impact of using the new method on doping profile....