劉致為臺灣大學：電子工程學研究所陳自強Chen, Tze-ChiangTze-ChiangChen2007-11-272018-07-102007-11-272018-07-102006http://ntur.lib.ntu.edu.tw//handle/246246/57636本論文中，利用高介電材料(氧化蛤和蛤之矽氧化物)作為二極體之介電層來研究其光及電方面的特性。首先在外部量子效率方面，利用氧化蛤的發光二極體可以觀察到2E-6的量子效率,比上利用傳統的二氧化矽的發光二極體高了四倍(0.5E-6)。其原因應該是由於在矽與高介電層的介面可以累積較多的電洞，這是由於氧化蛤有較高的介電常數，根據電通量不變定律，使得矽基板在靠近氧化蛤的介面可以獲得較高的電場。在這樣的元件結構中，由於介面的缺陷較多,我們也觀察到不同於矽能階的長波長發光。 熱穩定性對於高介電材料一直非常重要的課題，所以我們也探討了氧化蛤在應變矽鍺及矽基板上的熱穩定性。實驗結果發現，處與氧化蛤和矽的介面層厚度會隨著熱處理的溫度增加而增加，要增加介面層必須要提供氧原子，其來源有可能是在加熱腔體中殘存的氧原子，或者是存在氧化蛤之中的氧原子。介面缺陷密度在經過600oC處理之後，在矽鍺元件介面有7.5E12 cm-2eV-1，在矽元件介面有1.8E11 cm-2eV-1。為了要得到適合的介面特性，在熱處理的過程中導入氘氣或是氫氣來改善介面特性。結果無論在發光特性及電性上的可靠度都有改善。 為了要量測氧化蛤的薄膜特性，我們創新一種新式的量測方法，可以直接得到薄膜的特性，無須應用任何外加的裝置，應用這樣的方法，可以量到960, 900, 820 cm-1 的峰值來自Hf-O-Si鍵結的吸收，因此可以暸解氧化蛤和氧化矽在經過熱處理後，會形成蛤矽氧化物，而且再經由750cm-1 這個峰值的大小，來獲得氧化蛤薄膜的結晶程度。在氧化蛤和氧化矽之間經由熱處理會形成蛤矽氧化物這個現象也由X-ray光電子譜儀來加以確認。 最後再利用鍺元素埋在高介電材料中來做成發光二極體可以獲得可見光 (610 nm) 及紅外光 (760 nm) 的頻譜。奈米級的鍺量子點已經經由穿隧式電子顯微鏡和拉曼頻譜確認出來。由於不同的高介電材料有著不一樣的能隙，導致不同的位能井，使得營光量測上看到不一樣的量子點的發光波長，這個現象也是有在博士的研究過程中發現。In this thesis, the metal-insulator-silicon diode using a high dielectric constant material (HfO2 or Hf-silicate) is studied for optical and electrical properties. First, the external quantum efficiency for light emission at room temperature from the MIS LED was observed to be 2.0×10-6, as compared to 0.5×10-6 for the metal-oxide-silicon (MOS) LED. The large hole concentration at the Si/HfO2 interface created by the high dielectric constant of HfO2 may be responsible for the enhancement. Moreover, the Al/HfO2/Silicon LED with a high interface trap density has a continuous spectrum below the Si gap beside the electron-hole plasma emission, probably due to the radiative recombination between the electrons and holes via the interface states. It is very important to realize the thermal stability of high-k material. The thermal stability of strained Si0.8Ge0.2 and Si devices with HfO2 gate dielectrics is also studied. The thickness of the interfacial layer increases with increasing annealing temperature due to trace oxygen in the chamber or oxygen in HfO2 dielectric. The capacitance equivalent thickness increases with increasing post-deposition annealing temperature because of the increase of the interfacial layer. The interfacial trap density for the SiGe and Si devices with the PDA temperature of 600℃ are estimated to be 7.5 × 1012 cm-2eV-1 and 1.8 × 1011 cm-2eV-1, respectively. In order to obtain appropriate interface properties, incorporation deuterium and hydrogen treatment during post-metallization annealing is employed to improve both the electrical and optical reliability of Pt/HfO2 gate stack. For comparison, deuterium-treated technology provides slightly better reliability improvement on both the electrical and optical reliability of Pt/HfO2 gate stack devices. A novel method of FTIR measurement is created for high–k thin film. The peaks of Fourier transform infrared spectra at 960, 900 and 820 cm-1 originate from Hf-O-Si chemical bonds revealing that an Hf-silicate interfacial layer began to form at the HfO2/SiO2 interface after post-deposition-annealing process at 600 oC for 1 min. Moreover, the intensity of the peak at 750 cm-1 can indicate the degree of crystallization of HfO2. The formed Hf-silicate layer between HfO2 and SiO2 is also confirmed by X-ray photoelectron spectroscopy. Finally, a metal/HfAlO/Si light emitting diode with Ge nanocrystals embedded in HfAlO has the visible light emission (610 nm) and the infrared emission (760 nm). The lattice structure and Ge content are measured by the transmission electron microscopy and Raman spectroscopy. The photoluminescence of Ge nanocrystals embedded in HfAlO has a peak at 700 nm, while the peak at 725 nm is observed for Ge nanocrystals embedded in HfO2. The difference may be due to the larger band gap of HfAlO as compared to HfO2.Contents List of Tables III List of Figures IV Chapter 1 Introduction 1 1.1Motivation 1 1.2 Basic Needs for Scaling 3 1.3 Scaling Challenges 4 1.4 Scaling Limitation for SiO2 5 1.5 Motivation to High-k Gate Dielectrics 9 1.6 Requirements for High-k Dielectrics 10 1.7 Researches on High-k Dielectrics 12 1.8 Thesis Organization 13 Reference 15 Chapter 2 Light emission from Al/HfO2/Si Diodes 20 2.1 Introduction 20 2.2 Device Fabrication 21 2.3 Characteristics of High-k LED 22 2.3.1 High-k LED Structure 22 2.3.2 High-k LED Operation 23 2.3.3 Optical Properties of High-k LED 25 2.4 Summary 31 Reference 32 Chapter 3 The Characteristics of HfO2 on Strained SiGe 34 3.1 Introduction 34 3.2 Device Fabrication and Experimental Setup 36 3.3 Results and Discussions 37 3.3.1 Structure of HfO2 on Strained SiGe 37 3.3.2 Electrical Properties of Strained SiGe Device 41 3.4 Conclusions 47 Reference 48 Chapter 4 Electrical and Optical Reliability Improvement of HfO2 Gate Dielectric by Deuterium and Hydrogen Incorporation 52 4.1 Introduction 52 4.2 HfO2 Device Fabrication 54 4.3 Electrical Characteristics of HfO2 Device 56 4.4 Optical Characteristics of HfO2 Device 61 4.5 Summary 62 Reference 63 Chapter 5 Characterization of the Ultra-Thin HfO2 and Hf-Silicate Films Grown by Atomic Layer Deposition 65 5.1 Introduction 65 5.2 High-k Thin Film Formation and Experiment 67 5.3 Results and Discussions 68 5.3.1 FTIR Analysis 68 5.3.2 Structural Analysis 74 5.3.3 Electroluminescence 81 5.3.4 Electrical Properties 83 5.4 Summary 87 Reference 88 Chapter 6 Luminescence from the Ge nanocrytals in high-k dielectrics 92 6.1 Introduction 92 6.2 Device Fabrications 94 6.3 Experimental Results and Discussion 95 6.4 Summary 103 Reference 102 Chapter 7 Summary and Future Work 105 7.1 Summary 105 7.2 Future Work 108 List of Tables Table 1-1 ITRS 2004 for EOT, Jg and Mobility requirements. 9 Table 3-1 Keff values for Si devices and SiGe devices. 46 Table 5-1 Details of the XRR model simulated data as compared to TEM and AFM results. 80 List of Figures Fig. 1-1 Schematic representation leakage and drive current components of MOSFET devices at On and Off states. 3 Fig. 1-2 Direct tunneling leakage current mechanism for thin SiO2. 6 Fig. 1-3 Fig. 1-3 Gate leakage versus gate voltage for various oxide thicknesses. 6 Fig. 1-4 Jg,limit versus Jg,simulated for High-Performance Logic. 7 Fig. 1-5 Schematic Diagram showing SiO2 and High-k based gate oxides. It could be made physically thicker for the same capacitance 9 Fig. 2-1 Cross-section TEM micrograph of HfO2 on p-type Si wafer, after 1 min post deposition annealing at 600 ℃. 22 Fig. 2-2 A schematic energy band diagram of a MIS diode on p-type Si wafer at accumulation bias. The dash line and solid line represent the band alignments of HfO2 and SiO2 devices, respectively. 24 Fig. 2-3 Electric field at different gate bias by numerical simulation. 25 Fig. 2-4 The measured electroluminescence spectra of HfO2 LED with the fitting curves by the electron-hole plasma recombination model. 26 Fig. 2-5 External quantum efficiency of the HfO2 and SiO2 devices. 27 Fig. 2-6 The electroluminescence spectrum of HfO2 LED with a long tail at the energy lower than the Si bandgap at room temperature. 28 Fig. 2-7 Integrated intensity ratio vs gate current density. 29 Fig. 2-8 Fig. 2-8 The comparison of the normalized electroluminescence spectra of the HfO2 and SiO2 LEDs. 30 Fig. 3-1 XRD results for compressive strained Si0.8Ge0.2/Si. No strain relaxation is observed after high temperature processes. 38 Fig. 3-2 Fig. 3-2 Cross-sectional TEM micrographs of HfO2 on Si and Si0.8Ge0.2 after different PDA temperatures. (a) PDA 600℃ on Si. (b) PDA 600℃ on SiGe. (c) PDA 900℃ on Si. (d) PDA 900℃ on SiGe. 40 Fig. 3-3 High-frequency (100 kHz) C-V characteristics of Pt/HfO2/Si MIS capacitors at different PDA temperatures. The area of the MIS capacitor is 3 × 10-4 cm2. 41 Fig. 3-4 High-frequency (100 kHz) C-V characteristics of Pt/HfO2/Si0.8Ge0.2/Si MIS capacitors (gate area: 3 × 10-4 cm2) at different PDA temperatures. 42 Fig. 3-5 Flat band voltage and interface trap density of HfO2/Si and HfO2/SiGe devices as a function of PDA temperature. The SiGe devices have worse thermal stability due to the higher Dit. 44 Fig. 3-6 Frequency dependence of interface trap density for Si and SiGe MIS capacitors. 45 Fig. 3-7 Leakage current and CET vs PDA temperature of HfO2 on Si and SiGe. 46 Fig. 4-1 Cross-section TEM micrograph of HfO2 on p-type Si wafer, after 300 sec post deposition annealing at 600 ℃. 55 Fig. 4-2 Jg -Vg curves of HfO2 gate stack MIS capacitors incorporating H2 treatment. 56 Fig. 4-3 Jg -Vg curves of HfO2 gate stack MIS capacitors incorporating D2 treatment. 57 Fig. 4-4 Time evolutions of gate current of HfO2 gate stack MIS capacitors incorporating H2 and D2 treatment under -3 V constant voltage stress. 58 Fig. 4-5 Interface trap density of Pt/HfO2 gate stack MIS structure before/after H2 (D2) treatment and after stress, respectively. 59 Fig. 4-6 Recoverable Jg -Vg curves incorporating H2 treatment with constant current stress at 100 mA for 104 sec. 60 Fig. 4-7 Recoverable Jg -Vg curves incorporating D2 treatment with constant current stress at 100 mA for 104 sec. 60 Fig. 4-8 Time evolutions of light emission intensity for (a)H2- and (b)D2-treated devices under constant current stress at 100 mA. 61 Fig. 5-1 A scheme of FTIR measurement structure. 69 Fig. 5-2 FTIR spectra of HfO2 after PDA at 600 ℃ for 1 min in flowing N2 measured by “Face to Face” structure. The intensity of IR signal with ultra-thin high-k layer can be enhanced by the “Face to Face” method. 69 Fig. 5-3 FTIR spectra of ultra-thin HfO2 films as-deposited, annealed at 600 ℃ for 1 min, and annealed at 1000 ℃ for 5 min in N2 ambient. The positions of the peaks in the three curves are indicated by dashed lines. The intensity of the peak at 750 cm-1 is clearly seen to increase the thermal budget. 71 Fig. 5-4 FTIR absorption spectra of Hf-silicate. The samples in (a) were not annealed and in (b) and (c) were annealed in N2 ambient for 1 min at 600 ℃ and for 5 min at 1000 ℃, respectively. There are only two peaks (at 600 and 512 cm-1) in as-deposited nano-mixed HfO2-SiO2, indicating no Hf-silicate formation. 73 Fig. 5-5 XPS results of the (a) Hf 4f and (b) O 1s peaks for HfO2 films as-grown and annealed at 1000 ℃ for 5 min in N2 ambient. The shift of the Hf 4f and O 1s peaks to higher binding energy is due to the formation of a Hf-silicate layer. 75 Fig. 5-6 HRTEM cross section images of HfO2 (a) as-deposited, and after (b) 600 ℃/1 min/N2 annealing and (c) 1000 ℃/5 min/N2 annealing. The thickness of the interfacial layer between HfO2 and Si is increased by annealing. 77 Fig. 5-7 XRR spectra of HfO2 film, as-deposited, after 1 min annealing in N2 at 600 ℃ and 5 min annealing in N2 at 1000 ℃. The inset is the surface roughness for HfO2 samples by AFM. The roughness of the HfO2 surface is lower than 0.5 nm even after high temperature annealing. 79 Fig. 5-8 The electroluminescence spectra of Hf0.66Si0.34O2 LED at 320 K, 150 K, and 105 K. 82 Fig. 5-9 Normalized intensity of high-k LED as a function of Hf concentration. 82 Fig. 5-10 High-frequency (100 kHz) C-V characteristics of Pt/HfO2/Si and Pt/Hf-silicate/Si MIS capacitors following PDA at 600 ℃ for 1 min and PMA at 400 ℃ for 15 min. The inset shows the device structure. The C-V curve without PMA would be stretched out due to a large number of interface states (not shown). 83 Fig. 5-11 The relation between leakage current and EOT of the HfO2 and Hf-silicate devices. The SiO2 trend line is also shown (dashed line). 84 Fig. 5-12 Fig. 5-12 The flat-band voltage and Neff of the HfO2 device, and Hf-silicate devices with Pt electrodes. The ideal VFB is 0.4 volt, assuming that the work function of Pt is 5.3 eV and the doping concentration of the p-type Si substrate is 3×1015 cm-3. 85 Fig. 5-13 The Dit of HfO2 and Hf-silicate devices with Pt electrodes before and after PMA. The Dit value of all high-k samples with PMA is below 1012 eV-1cm-2. 86 Fig. 6-1 Schematic of the device structure. 94 Fig. 6-2 Cross-section TEM micrograph of the Ge NCs in HfAlO dielectrics. 95 Fig. 6-3 The Raman spectra of Ge NCs in HfAlO layer on Si substrate. Ge-Ge TO peak with phonon confinement is found at 298.4 cm-1. 97 Fig. 6-4 The Raman spectrum of bulk Ge for reference. 97 Fig. 6-5 Current-voltage characteristics of the MIS diode. The Ge NCs can increase the current due to the trap assistant tunneling. 98 Fig. 6-6 The electroluminscence spectrum of the MIS LED with Ge in HfAlO structure. The current as the EL measurement is 200 mA, and the bias voltage is -18V. 99 Fig. 6-7 Photoluminescence spectra of the Ge NCs embedded in HfO2 and HfAlO after annealing at 700 oC. The PL intensity of the HfAlO sample is stronger than that of the HfO2 sample due to more Ge NCs. 1002317244 bytesapplication/pdfen-US高介電材料矽發光可見光傅立葉轉換器high-k dieletric materialSi LEDvisible lightFTIRthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/57636/1/ntu-95-D90943015-1.pdf