1700伏特碳化矽平面式金氧半場效電晶體設計與模擬

Abstract

本論文以1700伏特碳化矽平面式垂直金氧半場效電晶體之結構設計為主軸，並使用TCAD Sentaurus模擬軟體進行電性模擬。在主動區結構中，透過調整磊晶濃度、厚度，以確立元件之崩潰電壓大小，並且為防止元件因突波電壓而毀損，使用2100 V作為模擬之耐壓基準。另一方面，本文對閘極氧化層之厚度做電性模擬，使元件不論順、逆向運作時，皆有相當的可靠度。除了以上的基礎製程參數設計之外，為降低元件之特徵導通電阻，本文在電晶體內部加入電流擴散層，包含不同類型的離子佈植、摻雜濃度峰值分佈與磊晶方式，並進行模擬分析。從結果可以得知，在元件中使用磊晶式的電流擴散層，不僅能夠在相同崩潰電壓下降低阻值至3.01 mΩ∙cm2，此種結構在逆向操作時的氧化層電場也是最小的。此外，為在逆向操作時保護元件之主動區，本文亦針對電晶體的邊緣終端保護結構進行設計，包含接面終端延伸(JTE)、內環(P+ Rings)以及外環結構(MFZ, JTE rings)。其中未加入P+ rings時，整體終端區僅有一最佳化崩潰電壓，對JTE植入劑量的變化相當敏感，透過不同數量Rings的加入，並配合MFZ區域之大小最佳化，使終端區下方的電場分佈呈現均勻遞減，不僅能夠提高RAJTE的崩潰電壓至約2400 V，且能夠提高此種結構的製程誤差容忍度。

This work focuses on the design of the 1700 V planar VDMOSFET. The TCAD Sentaurus is used for simulation. In the active area of the device, the breakdown voltage, BV, is simulated with adjusting the epitaxial concentration and thickness. Also, the approval BV standard is set to be 2100 V, preventing the device from being damaged due to pulse voltage. Considering the reliability of the MOSFET, different thickness of the gate oxide layer is also simulated to understand the forward, reverse characteristics. Except for the basic structural design, the study introduces the current spreading layer (CSL) to reduce the specific on-resistance, Ron,sp, of the device. The CSL analysis is conducted with different approaches, including various types of ion implantation, doping concentration peak distribution and multiple epitaxial layer. It turns out that the application of an epitaxial CSL in the MOSFET not only reduce the Ron,sp to 3.01 mΩ∙cm2 with the same breakdown voltage, BV, but also maintain the lowest oxide field during reverse bias. On the other hand, to protect the device during reverse operation, the edge termination structure of the MOSFET is also designed, including junction termination extension (JTE), inner P+ rings and outer ring structure (JTE rings). The MFZJTE is the JTE structure without P+ rings added, and it is quite sensitive to the variation of JTE implantation dose. The RAJTE is the MFZJTE with the addition of P+ rings. By optimizing the numbers of P+ rings and the size of the MFZ area, the electric field distribution is more uniformly distributed. Therefore, the BV of RAJTE is about 2400 V, and the process tolerance is greatly improved.