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1.双外延材料选取原则400兆50瓦硅大功率管选用外延平面工艺制作,对外延层提出了要求.首先要求BV_(ceo)较高,这就要求外延层的电阻率高,厚度厚些为好.但同时要求大电流工作时h_(FE)和f_T高,这又要求外延层的电阻率低,厚度薄些为好.这对外延层的要求是一对矛盾.如何调和这对矛盾是外延材料选取的中心环节.根据外延平面工艺的特点,分析BV_(ceo)更多地受表层电阻率的限制,而大电流下工作的h_(FE)和f_T特性主要取决于正对发射区电阻率,如图1斜线部分.所以我们考虑选用n~-/n/n~+的双外延结构来调和这对矛盾.
1. Double-epitaxial material selection principle 400 megawatt 50-watt silicon high-power tube made by epitaxial planar process, the requirements of the epitaxial layer requirements first higher BV_ (ceo), which requires the high resistivity of the epilayer, the thickness of the thicker As well, but at the same time require high-current work h_ (FE) and f_T high, which in turn requires the low resistivity of the epitaxial layer, the thinner the thickness of the better.This requirement for the epitaxial layer is a pair of contradictions .How to reconcile the contradiction Is the central part of the selection of epitaxial materials.According to the characteristics of the epitaxial planar process, BV ceo is more limited by the resistivity of the surface, while the h FE and f T characteristics of the work under high current mainly depend on the positive emission area Resistivity, as shown in Figure 1. Therefore, we consider the use of n ~ - / n / n ~ + double epitaxial structure to reconcile the contradiction.