Experimental research of high transconductance MOS field effect transistors fabricated by SIMOX technology

在本年度，对近两年来采用SIMOX（Separation by Implanted OXygen）技术设计和制造的环形振荡器和分频器进行了电特性和性能的测定。SOI衬底的主要特点是埋入氧化层的厚度从500 nm减少到80 nm。作为减薄的埋氧层的结果，它已被证实，短沟道效应已被成功地抑制，因为从漏电极的电通量的屏蔽效果的衬底。对环形振荡器的测量结果表明，当栅长小于0.2 μ m时，环形振荡器延迟时间的减小达到饱和，这是由于栅电极侧和漏/源电极之间的杂散电容相对于本征栅氧化层电容起主导作用。这意味着栅极电极的垂直缩放对于栅极长度小于0.2 μ m的小型器件是首要的。还对四种类型的分频器进行了测量，其中显示出四个中的一个新电路在性能上是最好的。新电路的栅极长度为0.15 μ m，工作频率高达1 GHz，在1 V电源电压下功耗为50 uW。这是由于低杂散电容的witing，以及减少在新的分频器中使用的FET的数量。

In this year, measurement of ring oscillators and frequency dividers, which have been designed and fabricated using SIMOX (Separation by IMplanted OXygen) technology during last two years, have been carried out for evaluating their electric characteristics and performance.Main features of the SOI substrates are their thinness of the buried oxide layers of 80 nm, compared to the previous ones of 500 nm. As a result of thinned buried oxide layers, it has been verified that the short channel effects have been successfully suppressed because of the shielding effect of electric flux from drain electrode by the substrate. Measurement results of the ring oscillators showed that the decrease of the delay time of scaled ring oscillators saturates at the gate length of 0.2 um and less. Thissaturation is considered to take place, as the stray capacitance between gate electrode sides and drain/source electrode becomes dominant, compared with the intrinsic gate oxide capacitance. This implies that the vertical scaling of the gate electrode is first important for the small devices with gate length less than 0.2 um.Measurement that also been carried out for four types of frequency dividers, witch showed that a new circuit out of four is best in performance. The new circuit with 0.15 um gate length operated as high as 1 GHz with power consumption of 50 uW at the supply voltage of 1 V. This is due to the low stray capacitance of witing, as well as reduction in the number of FETs used in the new divider.