Si基Si_3N_4/SiO_2双层驻极体薄膜的电荷储存稳定性和电荷输运特性

The Stability of Charge Storage and Property of Charge Transport of Si_3N_4/SiO_2 Double Layer Electret Based on Si Substrate

非晶态二氧化硅 (SiO2 )具有优良的驻极体性质 ,可制成微型化、集成化和机敏化的高灵敏度的传感器。但是 ,热氧化SiO2 驻极体膜的高压应力引起微结构变形 ,对薄膜储电特性形成复杂的影响。利用氮化硅薄膜的高张应力研制成氮化硅 /二氧化硅 (Si3 N4 /SiO2 )双层膜 ,可使其内应力相互补偿。本文讨论了双层膜驻极体的电荷储存稳定性及电荷输运特性。实验结果表明 ,Si3 N4 /SiO2 双层膜具有比单层膜更优异的电荷储存稳定性 ,Si3 N4 /SiO2 双层膜系统的电荷寿命比SiO2 驻极体约高两个数量级。常温恒压电晕充电 ,电荷被储存在Si3 N4 /SiO2 双层膜的近自由面附近 ,随着充电温度的提高 ,平均电荷重心向驻极体内部迁移。但是在低于 3 0 0℃的充电温度下 ,平均电荷重心不能达到Si3 N4 和SiO2 的界面处。电荷输运受缓慢再捕获效应控制。

Subminiatureintegratedelectretsensorscanbeobtainedbyusingamorphoussilicondioxide (SiO2 )becauseofitsexcellentelectret properties .Butthedistortofmicrostructurecausedbyhighcompressivestressinthermallygrowingelectretfilminfluencesthepropertyofchargestorageinthefilmcomplexly .Aselectretmembranesinelectretsensors ,Si3 N4 /SiO2 doublelayerscouldleadtocompensatetensile stressforcompressivestressesencounteredinsinglelayersofSi3 N4 andSiO2 .Inthispaper ,thechargestorageandtransportpropertiesare discussed .TheexperimentalresultsshowthestabilityofchargestorageinSi3 N4 /SiO2 doublelayerelectretlayerismuchbetterthanthatof singleoneanditschargelifeisabouttwoordersofmagnitudeofthatofsingleone .Theresultsprovethatthechargelayersituatednearthe freesurfaceafterconstantvoltagecoronachargingforSi3 N4 /SiO2 doublelayersample .Themeanchargedepthgoesdeeperintothebulkof thefilmwiththeincreaseofchargingtemperature .However ,themeanchargedepthwillnotreachtheinterfaceofSi3 N4 andSiO2 whenthe chargingtemperatureislowerthan 3 0 0℃ .Thechargetransportiscontrolledbytheslowretrappingeffect.