Summary

In the past, poor gate dielectric quality and interface among oxide/semiconductor could results in frequency dispersion, hysteresis, and inferior interface property. Therefore, first of all, we demonstrate the TMA precursor of ALD can achieve more self-cleaning capability than TEMAZ at the oxide/In0.53Ga0.47As interface. Furthermore, various Al2O3 inter-layers with FGA under different PDA conditions have been conferred. According to the electrical characteristics of frequency dispersion and hysteresis, the capacitor under PDA 300 °C with FGA displays the better property than other temperatures. This result indicates that proper temperature of PDA is important due to the higher temperature might produce inferior native oxide like As₂O₅ or InAsO₄ from XPS analysis which gives rise to higher D_it existed in midgap from the extraction of the conductance method. In addition, more Al2O3 cycles inserting among ALD-TMA/ZrO₂ show the optimum electrical performance. It is observed that the interface of ZrO2/In0.53Ga0.47As is effectively passivated by trivalent oxides such as Al₂O₃ and As₂O₃ without generating a large amount of dangling bonds and demonstrate that the interface have better quality.

25

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31

Fig. 2.1 Capacitive equivalent thickness (CET) vs. physical thickness as measured in a MOSCAPs for various ALD dielectrics on In0.53Ga0.47As.

Table 2.1 Band offsets of various dielectrics with respect to In0.53Ga0.47As as measured by synchrotron radiation photoelectron spectroscopy.

Gate dielectric(ALD) △E

v

(eV) △E

c

(eV) E

g

(eV)

ZrO

2

2.63±0.1 2.13±0.3 5.5±0.2

HfO

₂

3.04±0.1 1.8±0.3 5.6±0.2

Al

2

O

3

4.09±0.1 2.8±0.3 7.65±0.2

32

p-In

_0.53

Ga

_0.47

As (100) buffer layer p-InP (100)

p-In

_0.53

Ga

_0.47

As (100) channel layer TEMAZ or TMA/ZrO

₂

Ti/Pt

Ti/Pt

 Surface pretreatment

- Acetone (5min) - Isopropanol (5min)

- HCl : H

₂

O = 1:10 (2min)

 Deposited by ALD at 250 ˚C

- TEMAZ or TMA 10cycles pretreatment - ZrO

2

80 cycles.

 Annealing condition

- PDA (300.400.500˚C/120s)

 Gate electrode patterning and formation(Ti/Pt)

 Backside-contact deposition (Ti/Pt)

 FGA 10% H

2

+90% N

2

(250˚C/30min.)

Fig. 2.2 Process flow of MOSCAPs with different surface pretreatments.

Fig. 2.3 MOSCAPs structure with ALD-TEMAZ or TMA/ZrO2/In0.53Ga0.47As.

33

p-In

_0.53

Ga

_0.47

As (100) buffer layer p-InP (100)

p-In

_0.53

Ga

_0.47

As (100) channel layer ZrO

₂

Ti/Pt

Ti/Pt

TMA/Al

₂

O

₃

1.5.10cycles

 Surface pretreatment

- Acetone (5min) - Isopropanol (5min)

- HCl : H

₂

O = 1:10 (2min)

 Deposited by ALD at 250 ˚C

- TMA 10cycles - Al

2

O

3

1.5.10 cycles - ZrO

₂

80 cycles.

 Annealing condition

- as-deposited or PDA (300.400.500 ˚C/120s)

 Gate electrode patterning and formation(Ti/Pt)

 Backside-contact deposition (Ti/Pt)

 FGA 10% H

2

+90% N

2

(250˚C/30min.)

Fig. 2.4 Process flow of the MOSCAPs with several cycles of Al2O3.

Fig. 2.5 MOSCAPs structure with ALD-TMA/Al2O3/ZrO2/In0.53Ga0.47As.

34

1 0 n m

Fig. 2.6 TEM image of the as-deposited ALD-TMA/Al2O3 10 cycle/ZrO2 on In0.53Ga0.47As with FGA.

35

36 after FGA under different PDA conditions in N₂ ambience for 120 s (a) 300 °C (b) 400 °C (c) 500 °C

37

38

Pt/Ti/TMA+ZrO₂/In_0.53Ga_0.47As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA conditions in N2 ambience for 120 s (a) 300 °C (b) 400

°C (c) 500 °C

39

(a) (b)

(c) (d)

Fig. 2.11 Multi-frequency C-V curves for p-type Pt/Ti/TMA+Al2O3 1 cycle+ZrO2/In0.53Ga

0.47-As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA

40 Pt/Ti/TMA+Al₂O₃ 1 cycle+ZrO₂/In_0.53Ga_0.47As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA conditions in N2 ambience for 120 s (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

41

(a) (b)

(c) (d)

Fig. 2.13 Multi-frequency C-V curves for p-type Pt/Ti/TMA+Al2O3 5 cycle+ZrO2/In0.53Ga

0.47-As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA

42 Pt/Ti/TMA+Al2O3 5 cycle+ZrO2/In0.53Ga0.47As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA conditions in N₂ ambience for 120 s (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

43

(a) (b)

(c) (d)

Fig. 2.15 Multi-frequency C-V curves for p-type Pt/Ti/TMA+Al2O3 10 cycle+ZrO2/In0.53

Ga-0.47As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA conditions in N2 ambience for 120 s (a) as deposited (b) 300 °C (c) 400 °C (d) 500

44 MHz to 100 Hz after FGA under different PDA conditions in N₂ ambience for 120 s (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

45

(a)

(b) (c)

Fig. 2.17 Multi-frequency C-V curves for various Al2O3 cycles measured from 1 MHz to 100 Hz after FGA under as-deposited (a) Al₂O₃ 1 cycle (b) Al₂O₃ 5 cycle (c) Al₂O₃ 10

46

(a) (b)

(c) (d)

Fig. 2.18 Multi-frequency C-V curves for various Al2O3 cycles measured from 1 MHz to 100 Hz after FGA under PDA 300 °C /120 s (a) TMA pretreatment (Al₂O₃ 0 cycle)

47

(a) (b)

(c) (d)

Fig. 2.19 Multi-frequency C-V curves for various Al2O3 cycles measured from 1 MHz to 100 Hz after FGA under PDA 400 °C /120 s (a) TMA pretreatment (Al₂O₃ 0 cycle) (b)

48

(a) (b)

(c) (d)

Fig. 2.20 Multi-frequency C-V curves for various Al2O3 cycles measured from 1 MHz to 100 Hz after FGA under PDA 500 °C /120 s (a) TMA pretreatment(Al₂O₃ 0 cycle) (b)

49

Table 2.2 Overview of frequency dispersion △C of various pretreatments and several Al2O₃ cycles with FGA under various PDA conditions at Vg = -2 V.

Table 2.3 Overview of hysteresis (V) of various pretreatments and several Al₂O₃ cycles with FGA under various PDA conditions.

△C (@V

_g

= -2 V)

(w/FGA)

as-deposited PDA 300 °C /120 s

PDA 400 °C /120 s

PDA 500 °C /120 s

TEMAZ 99.4% 160.9% 129.5%

TMA 42.7% 84.3% 75.9%

Al

₂

O

₃

1cyc. 43.4% 41.7% 79.4% 55.7%

Al

₂

O

₃

5cyc. 40.9% 37.8% 65.3% 46.7%

Al

2

O

3

10cyc. 25.0% 24.4% 34.8% 33.6%

Hysteresis (V)

(w/FGA)

as-deposited PDA 300 °C /120 s

PDA 400 °C /120 s

PDA 500 °C /120 s

TEMAZ 0.96 0.76 0.61

TMA 0.59 0.74 0.66

Al

₂

O

₃

1cyc. 0.49 0.44 0.70 0.54

Al

2

O

3

5cyc. 0.48 0.43 0.62 0.46

Al

₂

O

₃

10cyc. 0.31 0.29 0.43 0.37

50

Fig. 2.21 Energy band diagram of a n-type MOSCAPs in depletion region is shown in (a). A dc gate bias V_g with a small ac signal of frequency f are applied, causing a band bending ψs in the semiconductor and interface trap response with time constant  . (b) Equivalent circuit of MOSCAPs in depletion region. (c) Measured capacitance Cm and conductance Gm.

51

0.0 0.2 0.4 0.6

10¹ 10³ 10⁵ 10⁷ 10⁹

Characteristic Frequency (Hz)

Energy in Bandgap (eV)

300K 250K 200K 150K 100K 77K

h⁺ e

-0.0 0.2 0.4 0.6

10¹ 10³ 10⁵ 10⁷ 10⁹

=1E-15cm²

 =1E-16cm²

 =1E-17cm²

T=300K

Characteristic Frequency (Hz)

Energy in Bandgap (eV)

Fig. 2.22 Behavior of the interface trap time constant at room temperature as a function of capture cross section determines the part of interface traps in the band gap observable in the MOS admittance characteristics.

Fig. 2.23 The trapped charge characteristics for In0.53Ga0.47As under different temperature and corresponding measurement window from 1 MHz to 100 Hz C-V measurement frequency.

52

53

(a) (b)

(c) (d)

Fig. 2.25 Parallel conductance curves of for p-type Pt/Ti/TMA+Al2O3 1 cycle+ZrO2/In0.53

Ga-0.47As MOSCAPs after FGA under different PDA conditions from Vg= -0.35 to +0.1 volts (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

54

55

(a) (b)

(c) (d)

Fig. 2.27 Parallel conductance curves of for p-type Pt/Ti/TMA+Al2O3 5 cycle+ZrO2/In0.53

Ga-0.47As MOSCAPs after FGA under different PDA conditions from Vg= -0.5 to +0.2 volts (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

56 p-type Pt/Ti/TMA+Al2O3 10 cycle+ZrO2/In0.53Ga0.47As MOSCAPs measured from 1 MHz to 100 Hz after FGA under different PDA conditions in N₂ ambience for 120 s (a) as deposited (b) 300 °C (c) 400 °C (d) 500 °C.

57

58

59

(a) (b)

(c) (d)

Fig. 2.31 Comparison of Dit profiles of ALD-TMA/ZrO2/In0.53Ga0.47As MOSCAPs with various Al2O3 inter-layers under different PDA conditions (a) as deposited (b) 300

°C (c) 400 °C (d) 500 °C.

60 Gate Voltage(volt)

Log[Frequency(Hz)]

-2 -1 0 1 2

2 3 4 5 6

1 2 3 4 x 105 ¹³

(a)

(b)

Fig. 2.32(a)(b) The map of normalized parallel conductance, (Gp/ω)/Aq (eV^-1cm^-2) vs. Vg (volt) and the curves for p-type Pt/Ti/TMA+ZrO2/In0.53Ga0.47As MOSCAPs from V_g= -0.25 to +0.1 volts under PDA 300 °C/120 s, w/FGA

10

²

10

³

10

⁴

10

⁵

10

⁶

0

2 4 6 8 10

G

p

/A  q



10

12

eV

-1

cm

-2

)

Frequency (Hz)

Vg= +0.25V

^

Vg= -0.1V PDA 300



C/120s w/FGA TMA 10cycle/ZrO

2

61

-2 -1 0 1 2

0.2 0.4 0.6

0.8 PDA 300C/120s,w/FGA

Capacitance,C(F/cm2 )

Gate Voltage, V_g(volt)

TMA 10cycle/Al₂O₃ T=300K

Gate Voltage,Vg(volt)

Log[Frequency(Hz)]

-2 -1 0 1 2

2 3 4 5 6

1 2 3 4 x 105 ¹³

(a)

(b) (c)

Fig. 2.33 (a)(b)(c) The capacitance curve, the map of normalized parallel conductance, and (Gp/ω)/Aq (eV^-1cm^-2) vs. Vg (volt) and the [(Gp/ω)/Aq] curves for p-type Pt/Ti/TMA+Al₂O₃/In_0.53Ga_0.47As MOSCAPs from V_g= -0.05 to +0.6 volts under PDA 300 °C/120 s, w/FGA

10² 10³ 10⁴ 10⁵ 10⁶

0 2 4 6 8 10

TMA 10cycle/Al₂O₃ Vg= +0.6V^Vg= -0.05V PDA 300C/120s w/FGA

G p/Aq1012 eV-1 cm-2 )

Frequency (Hz)

62

Fig. 2.34 Comparison of Dit profiles of In0.53Ga0.47As MOSCAPs with various Al2O3 cycle inter-layer and ALD-Al2O3/In0.53Ga0.47As MOSCAPs under PDA 300 °C/120 s, w/FGA.

Table 2.4 Overview of Dit at trap energy Et =0.377eV of ALD-TMA/ZrO2/In0.53Ga0.47As under different thermal conditions and Al2O3/In0.53Ga0.47As MOSCAPs at PDA 300

◦C/120 s, w/FGA.

D

it

(10

¹²

eV

^-1

cm

^-2

) 0cyc 1cyc 5cyc 10cyc Al

₂

O

₃

As-deposited+FGA 9.26 8.70 5.40

PDA 300

^◦

C+FGA 9.37 8.57 7.83 4.99 3.75

PDA 400

^◦

C+FGA 16.87 14.0 7.71

PDA 500

^◦

C+FGA 17.21 16.49 14.71

0.0 0.1 0.2 0.3 0.4 0.5

0 3 6 9 12 E

_V

0cyc 1cyc 5cyc 10cyc Al2O

3

PDA 300C/120s w/FGA

E

i

D

it(

10

12

eV

-1

cm

-2 )

E-E

v

(eV)

T=300K

63

(a)

(b)

1120 1118 1116 1114

Ga 2p_3/2

Al

2

O

3

1cycle

PDA 500C,w/FGA PDA 400C,w/FGA PDA 300C,w/FGA as-deposited,w/FGA

Ga-As Ga2O

Ga2O

3

In tensity (a. u. )

Binding Energy (eV)

447 446 445 444 443 442

In 3d_5/2

Al

₂

O

₃

1cycle

In₂O₃

InAsO₄

In-As

In tensity (a. u. )

Binding Energy (eV)

PDA 500C,w/FGA PDA 400C,w/FGA PDA 300C,w/FGA as-deposited,w/FGA

64

(c)

Fig. 2.35 X-ray photoelectron spectroscopy for p-type Pt/Ti/TMA+Al2O3 1 cycle+ZrO2/In

0.53-Ga_0.47As MOSCAPs after FGA under various PDA conditions (a) Ga 2p_3/2 (b) In 3d5/2 (c) As 2p3/2.

1328 1326 1324 1322

As 2p

3/2

As-Ga

As²⁺

As₂O₃

Al

₂

O

₃

1cycle

as-deposited,w/FGA

As₂O₅ PDA 300C,w/FGA

PDA 400C,w/FGA

PDA 500C,w/FGA

In tensity (a. u. )

Binding Energy (eV)

65

(a)

(b)

1120 1118 1116 1114

Ga 2p_3/2

Ga2O Ga-As

PDA 300  C/120s,w/FGA

In tensity (a. u. )

Al₂O₃ 10 cyc Al₂O₃ 5 cyc Al₂O₃ 1 cyc

TMA TEMAZ

Ga₂O₃

Binding Energy (eV)

447 446 445 444 443 442

In2O

3

In-As

PDA 300  C/120s,w/FGA

InAsO

4

In 3d_5/2

In tensity (a. u. )

Binding Energy (eV)

Al₂O₃ 10 cyc Al₂O₃ 5 cyc Al₂O₃ 1 cyc

TMA TEMAZ

66

(c)

Fig. 2.36 X-ray photoelectron spectroscopy of various pretreatment and several Al2O3 cycles after FGA under PDA 300 °C /120 s (a) Ga 2p3/2 (b) In 3d5/2 (c) As 2p3/2

1328 1326 1324 1322 PDA 300  C/120s,w/FGA

TEMAZ

TMA

Al

2

O

3

1 cyc

Al

2

O

3

5 cyc

In tensity (a. u. )

As 2p

3/2 As-Ga

As²⁺

As2O

3

As₂O₅

Al

2

O

3

10 cyc

Binding Energy (eV)

67

Table 2.5 Ratio of the fitted area from the As 2p3/2 and In 3d5/2 spectra for p-type Pt/Ti/TMA+Al₂O₃ 1 cycle+ZrO₂/In_0.53Ga_0.47As MOSCAPs after FGA under various PDA conditions.

Table 2.6 Ratio of the fitted area from the As 2p3/2 and In 3d5/2 spectra at various pretreatment and several Al₂O₃ cycles after FGA under PDA 300 °C/120 s.

Al

₂

O

₃

1cycle As

²⁺

/As

2

O

5

As

2

O

3

/As

2

O

5

In

2

O

3

/InAsO

4

As-deposited+FGA 0.393 1.145 0.458

PDA 300

^◦

C /120 s+FGA 0.417 1.156 0.488

PDA 400

^◦

C /120 s+FGA 0.225 0.910 0.283 PDA 500

^◦

C /120 s+FGA 0.219 0.902 0.274

PDA 300 °C/120 s

w/FGA As

²⁺

/As

2

O

5

As

2

O

3

/As

2

O

5

In

2

O

3

/InAsO

4

TEMAZ 0.210 0.867 0.228

TMA 0.225 0.916 0.364

Al

2

O

3

1cyc. 0.417 1.156 0.488

Al

2

O

3

5cyc. 0.915 1.543 0.501

Al

2

O

3

10cyc. 1.068 1.624 0.703

68

(a)

(b)

Fig. 2.37 Comparison of Dit and ratio of the fitted area from the As 2p3/2 and In 3d5/2 spectra profiles of ALD-TMA/ZrO2/In0.53Ga0.47As MOSCAPs (a) with Al2O3 1 cycle inter-layer (b) with PDA 300 °C /120 s, w/FGA.

0cycle 1cycle 5cycle 10cycle

69

Chapter 3

The Extraction of Border Traps for ZrO

₂

/In

_0.53

Ga

_0.47

As MOSCAPs by a Distributed Bulk-Oxide Traps Model

3.1 Introduction

The concept of border traps has been introduced by Dan Fleetwood in 1992 [1] to define traps in the gate dielectrics of high-k/III-V MOS devices, which result in frequency dispersion at the accumulation region. The traps have been attributed to trapped-holes [2] or to oxygen deficiency defects [3]. As a rule, the density of border traps increases when the quality of the oxide decreases, due to poor stoichiometry or the presence of strained bonds at the interface [4]. However, the conventional interface states whose time constant in such bias regions is far shorter than the period of typical measurement frequencies can’t be used to explain this dispersion phenomenon. On the other hand, the trap states reside the high-κ dielectric, which are called border traps or slow oxide traps, have long time constants when thay exchange charge with the channel [5]. Furthermore, the frequency dispersion of conductance doesn’t follow the renowned peak deportment when the conventional conductance method [6] for the interface states is applied to the high to low transition (the maximum slope) of the C-V data.

In addition, comparing the experimental C-V curve with the ideal case demonstrates that the density of interface state far surpass which is extracted from the dispersion in that region.

Such variance can be resolved by a border trap model in which the low frequency portion give rise to the stretch-out C-V curve is stronger than the high-frequency portion for the dispersion.

In this chapter, the distributed border traps model is completed by adding integration of

70

the trap density with respect to energy for calculating the equivalent admittance. A differential equation is derived and numerically solved to produce frequency-dependent capacitance and conductance of the MOS devices. The model is validated and calibrated by the experimental data of p-type ALD- ZrO₂/ Al₂O₃ /In_0.53Ga_0.47As MOSCAPs in accumulation region.

在文檔中 原子層沉積二氧化鋯/三氧化二鋁於砷化銦鎵金氧半電容之電性與表面化性分析的研究 (頁 43-89)