Summary

In this chapter, MIM capacitors have been successfully fabricated with HfO2 as the dielectric layer. We also discussed Characteristics of HfO2 Gate Dielectrics Deposited on Tantalum Metal. We found out the poorer frequency dispersion for MIM (Ta/HfO2/Ta) structure. Besides, the capacitance density under high frequency is very low, especially at 1 MHz. the voltage coefficients of capacitance (VCC) values of α and β are higher than 100 ppm/V² 1000 ppm/V according to the ITRS roadmap.

Furthermore, conduction mechanism of Ta/HfO2/Ta structure has been studied. The conduction mechanism of Ta/HfO2/Ta structure is Frenkel-Poole Emission.

The measurement results show high capacitance density compared to TiN/Al2O3/TiN structure. The Ta/HfO2/Ta capacitor exhibits the highest capacitance density value of 25.67fF/µm². The leakage currents of Ta/HfO2/Ta capacitors are very small compared to TiN/Al2O3/TiN structure. These show that the HfO2 dielectric is very suitable for MIM applications. Thus indicates that it is very suitable for HfO2 dielectric to use in silicon IC applications.

High-κ Dielectrics

HfO2 ZrO2 Al2O3

Bandgap (eV) 6.02 5.82 8.3

Barrier Height to Si (eV) 1.6 1.5 2.9

Dielectric Constant ~30 ~25 9

Heat of Formation

(Kcal/mol) 271 261.9 399

∆G for Reduction

(MOx + Si → M + SiOx) 47.6 42.3 64.4

Thermal expansion coefficient

(10^-6 K^-1) 5.3 7.01 6.7

Lattice Constant (Å)

(5.43 Å for Si) 5.11 5.1 4.7 - 5.2

Oxide Diffusivity

@ 950^oC (cm²/sec) 1x10^-12 5x10^-25

Table 2-1 Materials properties of high-κ dielectrics, Al2O3, ZrO2, and HfO2

3.5

Figure 2-1 Band alignment of topical high-κ dielectrics.

1. Silicon substrate, RCA clean and HF dip to remove native oxide.

2. SiO2 550 nm film deposited at furnace Wet Oxidation.

3. Bottom electrode Tantalum 100 nm deposited by Reactive Sputter (RS)

4. The HfO2 thin film 5 nm deposited by RS

5. Finally, Top Electrode deposited 100 nm are used to metal mask

Figure 2-2 Flow chart for the fabrication of HfO2 thin films.

Voltage (V)

Figure 2-3 The C-V characteristics of the as-deposited HfO2 gate dielectrics for 5nm, 6nm, and 9nm were deposited difference thickness

40 50 60 70 80 90 100

Figure 2-4 Capacitance density varied with 5nm, 6nm, and 9nm HfO2 dielectric film thickness

Voltage (V)

Figure 2-5 (a) Capacitance-voltage (C-V) and (b) Capacitance-frequency characteristics of HfO2 5nm thin film on MIM capacitors at the frequencies from 1 kHz to 1 MHz.

Figure 2-6 (a) Schematic representation of different mechanisms of polarization [22]

Figure 2-6 (b) Frequency dependence of several contributions to the polarizability [51

]

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Figure 2-7 (a) Normalized C-V curves (△C/Co) of MIM structure (Ta/ HfO2/Ta) with 5 nm thickness

Figure 2-7 (b) DC bias dependence of normalized capacitance (△C/Co) at 100 KHz for 5nm、6nm、9nm MIM capacitor

High-k

material Frequency α (ppm/V²) β (ppm/V)

1K 14215 17200

10K 8277 10536

HfO2(5nm)

100K 5139 7025

Table 2-2 Summary of α and β extracted from MIM structure (Ta/ HfO2/Ta)) with 5nm

Thickness Frequency (Hz)

α (ppm/V²) β (ppm/V)

5nm 5139 7025

6nm 4329 6649

9nm

100K

447 1483

Table 2-3 Summary of Quadratic VCC, α, and linear VCC, β, extracted from MIM structure (Ta/HfO2/Ta) at 100 KHz for 5nm、6nm、9nm MIM capacitor

Voltage (V)

Figure 2-8 (a) Capacitance density of the MIM capacitor with 5nm thickness at 100 kHz from 25°C to 125°C. (b) Capacitance density of the MIM capacitor with 5nm thickness as a function of frequency after thermal stress from 25°C to 125°C.

25 50 75 100 125

Capacitance (fF/um2 )

-10

0 10 20 30 40 50

1K Hz 10K Hz 100K Hz 1M Hz

Temperature (

^o

C)

Figure 2-9 Capacitance density of the MIM capacitor as a function of temperature at frequencies varied from 100Hz to 1MHz.

Voltae (V)

Figure 2-10 The J-V curves of MIM capacitor with 5nm thickness under various temperatures, ranging from 25°C to 150°C.

1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75

ln(J/E) (A/MVcm-1 )

Figure 2-11 Poole-Frenkel plot showing the current density versus electric field characteristics at five measurement temperatures from 25°C to 125°C for Ta/HfO2/Ta

Voltage (V)

Figure 2-12 Compared to the (a) C-V and (b) J-V curves of MIM structure (TiN/Al2O3/TiN) at 8nm and (Ta/HfO2/Ta) at 5nm

CHAPTER 3

Effects of PDA Temperature and Basic Characteristics of Plasma Surface Technology for MIM

3.1 Introduction

Recently, MOSFETs with high-k gate dielectrics such as Al2O3, ZrO2, and HfO2have been studied intensively. However, investigation of these materials shows that oxygen or doping penetration through dielectrics is a significant problem due to the low crystallization temperature [34]. In addition, in crystallized gate dielectric films, grain boundaries may act as high oxygen or doping diffusivity paths, causing device failure with high leakage. For this reason, the high-k materials are expected to have higher crystalline temperature. Consideration of high capacitance density, the MIM capacitors (metal/insulator/metal) have been widely used in radio frequency (RF) circuit for a long time [35-37]. Comparing to conventional MIS structure, there is more carriers in metal electrode than in silicon substrate and can raise charge storage.

Theoretically, we can raise charge storage in the DRAM technology applying the MIM structure.

In previous chapter, we study the basic characteristics of the MIM structures. In this chapter, the effect of post-position annealing (PDA) temperature on the electrical properties and reliability characteristics of Ta/HfO2/Ta capacitor are studied. It is

found that the leakage current increase over PDA temperature at 500°C and the capacitance densities increase with PDA temperature. Moreover, basic characteristics of Ta/HfO2/Ta capacitor with plasma surface treatment are studied. The plasma surface technology is produced by PECVD. Plasma surface technology improved the voltage coefficients of capacitance (VCC) values of α and β.

3.2 Experiment Details

Four inches diameter (150-mm) p-type (100) Si wafers with nominal resistivity of 15 to 25 Ω-cm were used as substrate. Prior to the growth of Ta metal, the native oxide was cleaned by the conventional RCA cleaning and diluted HF etching in sequence for the removal of particles and native oxides. The capacitor area in this measurement about is 5.3×10^–4 cm². After standard RCA cleaning, a 550 nm SiO2

film was grown on Si substrate by wet oxidation, the 100 nm Ta layers were deposited sequentially by dc sputtering to obtain a Ta/SiO2/Si structure for the deposition of HfO2 thin-film capacitors. After that, the HfO2 thin film of approximately for 5 nm thickness was deposited on Ta electrode. In addition, Bottom electrode is defined by mask. After HfO2 deposition, Annealing of HfO2 thin film was carried out by rapid thermal annealing at three different temperatures (400°C, 500°C, 600°C) in a N2 or O2

ambient for 60 sec. Top metal Ta was defined directly by metal mask. Figure 3-1 shows the flow chart of HfO2 thin film fabrication with PDA technology. Before HfO2

deposition, N2O or NH3 plasma by PECVD was carried out on bottom metal at 400°C, 600s. The plasma power is 20W. After that, the HfO2 thin film of approximately for 5 nm thickness was deposited on Ta electrode. Ta gate was defined directly by metal

mask. All these processes are performed at room temperature. Figure 3-2 shows the flow chart of HfO2 thin film fabrication with plasma process.

The physical gate oxide thickness was determined by n&k analyzer 1280. The equivalent oxide thickness (EOT) was extracted by fitting the measured high-frequency capacitance-voltage (C-V) data from Hewlett-Packard (HP) 4284LCR meter under zero-biased. Moreover the capacitance was measure using 4284LCR meter at frequencies 100 KHz. In order investigate the thermal stability of high-k dielectric film. The tunneling leakage current density-voltage (J-V) was measured by semiconductor parameter analyzer HP4145A. After PDA temperature, the micro-roughness of the HfO2 surface was detected by atomic force microscopy (AFM).

3.3 Results and Discussions

3.3.1 Basic characteristic of the MIM with PDA Technology

After PDA process in N2, Figure 3-3 (a) C-V characteristics of MIM structure (Ta/HfO2/Ta) shows difference effects for electric characteristic at 100 KHz. The capacitance densities increase with PDA temperature. It may be due to the PDA processing in N2 ambient provides a reducing interface for oxidized surface layer of the Ta electrode [38]. Figure 3-3 (b) shows the capacitance densities was the highest value at PDA 600°C. The capacitance densities increase with PDA temperature be explained to Grain Boundary Barrier Layer Capacitor structure [39-41]. Effective permittivity of capacitor is related to the ratio of the average thicknesses of grain and

grain boundary. Generally, the ratio of the average thicknesses of grain and grain boundary is very lager, so that the effective permittivity of capacitor is very high.

Figure 3-4 shows J-V curves characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C, 600°C PDA in N2. Leakage current increases over 500°C PDA. It may be to grant growths in the high-k material. The corresponding AFM were presented in Figure 3-5 (a) and (b). Surface roughness of HfO2/Ta structure without PDA was 0.762nm. After PDA process, surface roughness increases from 0.803nm (400°C-60s), 1.115nm (500°C-60s) to 2.774nm (600°C-60s) in Figure 3-6, Figure 3-7, and Figure 3-8 [42]. At 600°C-60s PDA, surface roughness of the high-k material raises greatly. Due to stress relaxation and grain growth during annealing, the grain boundaries become clearly visible after PDA process [43]. For the as-deposited, 400°C, 500°C, and 600°C-annealed samples, higher annealing temperature lead to higher leakage current. Since the higher PDA temperature may trigger the small grains to merge into a large grain. The boundaries around these large grains will provide more short leakage path, which allow the carriers more easily tunneling through from top electrode to bottom electrode and, then, contribute to larger leakage current. Therefore, the crystalline temperature of HfO2 material was presented in our results. It is found that agglomeration effect might lead to higher gate leakage current density [42] and this is consistent with high leakage current in MIM structure we discussed before.

Figure 3-9 shows the relationship between surfaces roughness relate to difference PDA temperature of HfO2/Ta structure, these results were understood clearly for grain growing and crystallizing at temperature.

On the contrary, the capacitance of HfO2 samples annealing in an O2 ambient decreases with the increasing annealing temperature in Figure 3-10(a) and (b) [44].

Therefore, the capacitance decreases after annealing in an O2 ambient. This is because an O2 penetration will induce the increasing of the interfacial layer at HfO2/Ta and

higher annealing temperature increasing will speed up interface layer growth rate [45].

Figure 3-11 shows the J-V curves characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C, 600°C PDA in an O2 ambient. The current density reduces with PDA temperature, it may be to explain that thicker film of HfO2

was produced or oxygen vacancy within high-k material was decreased.

Figure 3-12 the relationship between capacitance densities relate to difference PDA temperature. The comparison of differencePDA temperature in O2 or N2 ambient shows the capacitance densities rise after PDA process in N2 ambient. In the addition, the contrary results were produced after PDA process in O2 ambient. Figure 3-13 shows the leakage current of sample with 400°C PDA was lower than other PDA temperature in N2 ambient. It can be explained to the defects decrease after 400°C annealing in N2 ambient. As mentioned above, PDA process in O2 ambient can cause the leakage current to diminish.

3.3.2 Basic characteristic of the MIM with Plasma surface Technology

Figure 3-14 (a), (b) shows C-V and J-V characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with N2O, NH3 plasma process on Ta electrode. After plasma process, maybe the capacitance densities both were decreased due to interface layer growing. This interface layer was not understood for us. We need more physical analysis, for example TEM analysis, XRD analysis, and Auger depth profiles analysis.

Leakage current density decreases after plasma processing, which is supposed to be suppressed by thicker interfacial layer on bottom metal. Figure 3-15, Figure 3-16, and Figure 3-17 clarify AFM topography of Ta bottom electrode without plasma process and with N2O, NH3 plasma process. Surface roughness without plasma process was

more than surface roughness with N2O, NH3 plasma process. It may be reason to decrease leakage current density. Figure 3-18 the comparison between surfaces roughness relate to without and with plasma process on Ta electrode. The results of N2O, NH3 plasma process on Ta metal clarify reduce leakage current, but capacitance density degrades.

3.3.3 Analysis Voltage coefficient of capacitance (VCC) on the MIM

Voltage coefficient of capacitance (VCC) are very important parameters for MIM capacitor applications, and can be obtained by using a second order polynomial

equation of ( )− = ₂ + +1

capacitance, αand β represent the quadratic and linear VCC respectively. The requirement of the quadratic coefficient of capacitance α is smaller than 100 ppm/V², and the requirement of the linear coefficient of capacitance β is below 1000 ppm/V according to the ITRS roadmap. Low VCC values cause the capacitance to stability.

Figure 3-19, Figure 3-20, and Figure 3-21 shows Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in N2

for 100 KHz, 10 KHz, and 1KHz respectively. We found the sample exhibits VCC values became lager with increasing PDA temperature. Especially the sample with 500°C PDA in N2 clarifies high VCC values. It may be explained that the dielectric traps located around the metal–insulator interface [46]. Figure 3-22, Figure 3-23, and Figure 3-24 shows Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in O2 ambient for 100 KHz, 10

KHz, and 1KHz respectively. The sample with 500°C PDA in O2 ambient can reduce VCC values compare with the sample with 400°C PDA in O2 ambient. It may be explained that PDA process with 500°C O2 ambient reduces traps around the metal–insulator interface. Figure 3-25 shows measured Quadratic VCC, α, versus difference frequency without PDA , with 400°C、500°C PDA in O2 and N2. It is found that the Quadratic VCC decreases with frequency. It may be explained that the carrier mobility becomes smaller with increase frequency, which lead to a higher relaxation time and a smaller capacitance variation [47]. Table 3-1 Summary of Quadratic VCC, α and linear VCC, β extracted from MIM structure (Ta/HfO2/Ta) without and with 400°C、500°C PDA in N2 and O2 ambient PDA process. Maybe dielectric traps located around the metal–insulator interface cause high VCC values. According to this reason, we use plasma process to improve metal–insulator interface defects [48]. Besides, the rapid △C/Co reduction with increasing frequency may be due to the trapped carriers being unable to follow the high frequency signal [49] [50].

Figure 3-26, Figure 3-27, Figure 3-28 shows Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without plasma and with N2O, NH3 plasma process for 100 KHz, 10 KHz, and 1KHz respectively. We found VCC values of the sample with plasma process become smaller than the sample without plasma process.

It may be explained that plasma process can improve trap defects to reduce VCC values. Figure 3-29 shows measured Quadratic VCC, α, versus difference frequency without plasma and with N2O, NH3 plasma process. The results clarify plasma process can reduce VCC values make the capacitance stability. However the VCC values are still higher than 100 ppm/V² and 1000 ppm/V, not achieve the requirement of the ITRS roadmap. Table 3-2 Summary of Quadratic VCC, α, and linear VCC, β, extracted from MIM structure (Ta/HfO2/Ta) without plasma and with N2O, NH3

plasma process for variant frequency.

3.4 Summary

In this chapter, we studied PDA effect on MIM structure at first. We met a few questions of large leakage current density under high temperature annealing in N2

ambient. Because of grain growing, we found surface roughness increase with PDA temperature. High Surface roughness gives rise to large leakage current density.

Moreover, PDA temperature increases to cause the capacitance go up, it was attributed grain boundary effect. On condition PDA in O2 ambient, after annealing O2

ambient the leakage current density reduces and capacitance rises were attributed thicker high-k film producing and interface layer growing.

Secondly, we used plasma process improve electric characteristics on MIM. It was found that leakage current density decreases one order, but ensues to reduce capacitance density after plasma process. Especially N2O plasma process reduces capacitance density more than NH3 plasma process. It may be explained that surface roughness with N2Oplasma process was higher than NH3 plasma process.

Finally, form analysis VCC on MIM, we found out that PDA process in N2

ambient causes Quadratic VCC and linear VCC become higher than without PDA and with PDA process in O2 ambient. Especially Quadratic VCC and linear VCC become smaller after 500°C PDA process in O2 ambient. Besides, plasma process can reduce Quadratic VCC, but still not achieve the requirement of the ITRS roadmap.

2. SiO2 550 nm film deposited at furnace Wet Oxidation.

3. Bottom electrode Tantalum 100 nm deposited by Reactive Sputter (RS) and is patterned by mask

4. The HfO2 thin film 5 nm deposited by RS

5. Post deposit annealing, PDA: 400°C, 500°C, 600°C, in N² or O2 60 sec.

6. Finally, Top Electrode deposited 100 nm by RS and is patterned by metal mask

Figure 3-1 Flow chart for the fabrication of HfO2 thin films with PDA Technology

1. Silicon substrate, RCA clean and HF dip to remove native oxide.

2. SiO2 550 nm film deposited at furnace Wet Oxidation.

3. Bottom electrode Tantalum 100 nm deposited by Reactive Sputter (RS) and is patterned by mask

4. Plasma N2O and NH3 treatment on Bottom electrode

5. The HfO2 thin film 5 nm deposited by RS

6. Finally, Top Electrode deposited 100 nm by RS and is patterned by metal mask

Figure 3-2 Flow chart for the fabrication of HfO2 thin films with Plasma Technology

Voltage (V)

Figure 3-3 The comparison of (a) and (b) C-V characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C , 600°C PDA in N2.

Voltae (V)

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

J (A/cm2 )

10

^-9

10

^-8

10

^-7

10

^-6

10

^-5

10

^-4

10

^-3

10

^-2

10

^-1

10

⁰

10

¹

AS

N₂ 400oC N₂ 500oC N₂ 600oC

Figure 3-4 The J-V curves characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C, 600°C PDA in N2

(a)

(b)

Figure 3-5 (a) and (b) AFM topography of HfO2/Ta structure without PDA.

(a)

(b)

Figure 3-6 (a) and (b) AFM topography of HfO2/Ta structure with 400°C PDA in N2

(a)

(b)

Figure 3-7 (a) and (b) AFM topography of HfO2/Ta structure with 500°C PDA in N2

(a)

(b)

Figure 3-8 (a) and (b) AFM topography of HfO2/Ta structure with 600°C PDA in N2

AS-dep. 400 500 600

RMS (A)

5 10 15 20 25 30

Figure 3-9 the relationship between surfaces roughness relate to difference PDA temperature of HfO2/Ta structure

Voltage (V)

Figure 3-10 (a) and (b) C-V characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C, 600°C PDA in O2

Voltage (V)

Figure 3-11 the J-V curves characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with 400°C, 500°C, 600°C PDA in O2

PDA Temperature (

^o

C)

AS-dep. 400 500 600

Figure 3-12 the relationship between capacitance densities relate to difference PDA temperature

PDA Temperature (

^o

C)

AS-dep. 400 500 600

J (A/cm2 ) @ -1V

10

^-11

10

^-10

10

^-9

10

^-8

10

^-7

10

^-6

10

^-5

10

^-4

10

^-3

10

^-2

10

^-1

N2 O2 AS-dep.

Figure 3-13 leakage current characteristics as a function of PDA temperatures with 400°C, 500°C and 600°C deposition in N2 andO2.

Voltage (V)

Figure 3-14 the comparison of (a) C-V and (b) J-V characteristics of MIM structure (Ta/HfO2/Ta) without PDA and with N2O, NH3 plasma process on Ta electrode.

Figure 3-15 AFM topography of Ta bottom electrode without plasma process

Figure 3-16 AFM topography of Ta bottom electrode with N2O plasma process, 600s

Figure 3-17 AFM topography of Ta bottom electrode with NH3 plasma process, 600s

AS-dep. N2O Plasma NH3 Plasma

RMS (A)

6 8 10 12 14

Figure 3-18 the relationship between surfaces roughness relate to without and with plasma process on Ta electrode

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Figure 3-19 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in N2 for 100 KHz

Figure 3-20 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in N2 for 10 KHz

Figure 3-21 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in N2 for 1 KHz

Figure 3-22 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in O2 for 100 KHz

Figure 3-23 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to

Figure 3-24 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without PDA and with 400°C、500°C PDA in O2 for 1 KHz

Frequency (Hz)

1K 10K 100k

α (ppm/V2 )

0 5000 10000 15000 20000 25000 30000 35000 40000

AS-dep.

O₂ 400⁰C O₂ 500⁰C N₂ 400⁰C N₂ 500⁰C

Figure 3-25 Quadratic VCC, α, versus difference frequency without PDA , with 400°C、500°C PDA in N2 and 400°C、500°C PDA in O2

Frequency(Hz) α (ppm/V²) β (ppm/V)

Table 3-1 Summary of Quadratic VCC, α and linear VCC, β extracted from MIM structure (Ta/HfO2/Ta) without and with 400°C、500°C in N2, 400°C、500°C in O2

PDA.

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Figure 3-26 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without plasma and with N2O, NH3 plasma process for 100 KHz

dC/C 0 (ppm)

Figure 3-27 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to

without plasma and with N2O, NH3 plasma process for 10 KHz

Figure 3-28 Normalized C-V curves (△C/Co) of MIM structure (Ta/HfO2/Ta) relate to without plasma and with N2O, NH3 plasma process for 1 KHz

Figure 3-29 Quadratic VCC, α, versus difference frequency without plasma and α (ppm/V2 )

2 3

Frequency (Hz)

α (ppm/V²) β (ppm/V)

1K 14215 17200

10K 8277 10536

As-dep.

100K 5139 7025

1K 4961 19557

10K 2910 12374

N2O Plasma Treatment

100K 1908 8869

1K 6776 19037

10K 3914 11834

NH3 Plasma Treatment

100K 2402 8045

Table 3-2 Summary of Quadratic VCC, α, and linear VCC, β, extracted from MIM structure (Ta/HfO2/Ta) without plasma and with N2O, NH3 plasma process for variant frequency.

CHAPTER 4

Conclusions and Suggestions

For Future Work

4.1 Conclusions

In the first part of this thesis, MIM capacitors have been successfully fabricated with HfO2 as the dielectric layer. Describe as follows

Firstly, we also discussed Characteristics of HfO2 Gate Dielectrics Deposited on Tantalum Metal. We found MIM (Ta/HfO2/Ta) structure achieve a high capacitance density (~25.67fF/cm²). However, the poorer frequency dispersion for MIM (Ta/HfO2/Ta) structure was produced especially at 1 MHz. Besides, we speculate that the conduction mechanism of MIM structure is Frenkel-Poole Emission. The leakage currents of Ta/HfO2/Ta capacitors are very small compared to TiN/Al2O3/TiN structure. The capacitance density of Ta/HfO2/Ta capacitors is higher than TiN/Al2O3/TiN structure.

In the second part of this thesis, we deposited HfO2 thin film on Ta metal electrode using these optimum conditions. Several important phenomena were observed and summarized follows. Firstly, we focused on PDA effect on MIM

structure. Large leakage current density was observed under high temperature

structure. Large leakage current density was observed under high temperature

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