利用遠程電漿輔助原子氣相沉積技術成長二氧化鉿之氮化與介面工程

Abstract

本論文研究利用遠程電漿輔助原子氣相沉積(Remote Plasma Atomic Layer Deposition，簡稱RP-ALD)技術成長二氧化鉿(HfO2)薄膜作為閘極介電層。針對二氧化鉿(HfO2)閘極介電層，施以不同處理條件，例如電漿瓦數、不同種類含氮的氣氛，以及阻障層(buffer layer)，研究其材料結構的改變，並製作金屬/絕緣層/半導體的電容元件結構探討其電容值、閘極漏電流與其他相關之電性。首先，研究結果發現，對於物理厚度為10 nm的HfO2閘極介電層，經過NH3電漿氣氛處理之後，在電漿瓦數為300W時，可以獲得厚度約為0.3nm的超薄介面層(interfacial layer)、等效介電係數(Keff)約為20.9、漏電流密度為9×10-6A/cm2，以及等效氧化層厚度(Capacitance Equivalent Thickness, CET)為1.9nm；另一方面，經由N2氣氛處理的HfO2閘極介電層，其介面層厚度則高達1.5 nm。此研究結果顯示，經由含H氣氛的氮化處理程序，對於HfO2閘極介電層的電特性有顯著之提升。其次，對於物理厚度為 6 nm的HfO2薄膜，利用原位(in-situ) NH3電漿處理可以有效將CET由2.1nm降低至1.6nm，漏電流密度則由1.5x10-3A/cm2降至6×10-4A/cm2，並且能有效抑制介面厚度的生成。最後，本研究利用RP-ALD技術在HfO2與矽基板之間成長二氧化矽(SiO2)薄膜作為之阻障層，可促進HfO2結晶相的形成，其CET可由2.1 nm降低至1.4 nm，Keff(~由12提高至17)，而漏電流密度可以由1.5x10-3 A/cm2有效抑制至4×10-4A/cm2。

Hafnium oxide (HfO2) gate dielectrics were prepared by the Remote Plasma Atomic Layer Deposition (RP-ALD) technique. The effects of the HfO2 gate dielectrics treated by the different processing conditions, including the radio-frequency (RF) plasma power, different nitrogen-containing atmospheres, as well as the insertion of barrier layer (buffer layer), were investigated. The first part of this thesis reports that significant increase of effective dielectric constant (keff), decrease of capacitance equivalent thickness (CET), reduction in leakage current density, and suppression of the interfacial layer (IL) thickness were observed with an increase of the RF power in the remote NH3 plasma treatment. An ultrathin interfacial layer (~0.3 nm), a high keff (20.9), a low leakage current density (9×10-6A/cm2), and a low CET (1.9 nm) in the nitrided HfO2 film were accomplished. Next, the characteristics of HfO2 gate dielectrics treated by a variety of post-deposition nitridation processes, including remote N2, N2/H2, and NH3 plasma, were investigated. The nitrogen content in the HfO2 thin film treated by remote hydrogen-containing plasma is higher than that treated only by remote nitrogen plasma, indicating that the participation of hydrogen in the nitridation process plays a critical role to improve the electrical properties of HfO2 gate dielectrics. Then the properties of HfO2 gate dielectrics treated by the nitrogen incorporation with different nitridation configurations, including bottom, in-situ, and top nitridation, are reported. The result demonstrates that significant increase of keff, decrease of CET, reduction in leakage current density, and suppression of the IL thickness were observed by the in-situ remote NH3 plasma treatment, with achievement of a low CET (1.6 nm), a high keff (~14.2), and a low leakage current density (6.7×10-4A/cm2). Finally, a SiO2 buffer layer grown by RP-ALD was inserted between HfO2 and the Si substrate to improve the electrical properties of the gate dielectrics. The tetragonal phase in HfO2 and the silicate in the interfacial layer were observed, which results in the increase of the k-value and reduce the gate leakage current. A low CET of 1.4 nm, a high keff of ~17, and a low leakage current density of 4×10-4A/cm2 were achieved in the Pt/HfO2/ALD-SiO2/Si structure.