Analysis and discussion OTFT electric characteristics

Here we focus on the influence of plasma treatment under varied conditions which have different gas of PECVD. They are N

₂

, NH

₃

and no treatment respectively.

As shown from Figure 3-23 to Figure 3-25, design of drain current I

D

versus gate voltage V

D

at various drain voltage V

G

, drain current I

D

versus gate voltage V

_G

at various drain voltage V

_D

and drain current I

_D

versus radical gate voltage V

G

at various drain voltage V

D

with different plasma treatments.

In all figures of different treatment conditions, we can observe that no treatment has best electrical characteristic about I

_D

-V

_G

and NH

₃

treatment has best electrical characteristic about I

D

-V

D

. Additionally, we plot the comparison of I

_D

-V

_D

, I

_D

-V

_G

and ︱ I

_D

︱

^1/2

-V

_G

in the same figure due to observe clearly, they are shown in Figure 3-26. The

magnitude of current at the same operating voltage, NH

₃

> no > N

₂

. Besides, threshold voltage and mobility would be calculated by taking measured data into Eq.(3-1) ~ (3-3). Arrangement of threshold voltage, mobility and on/off ratio is shown in Table 3-3(labeled as no treatment, N

₂

and NH

₃

) and Figure 3-27. The mobility in the saturation region and the threshold voltage and on/off ratio of the OTFT are 0.72 cm

²

/Vs and -0.616 V and ~10

³

, respectively.

To summarize this section, we can know from the experiment the atmospheric-pressure plasma technology silicon dioxide is worth studying. The advantage of the atmospheric-pressure plasma technology is that it needn't vacuum and at general room temperature to deposit insulator. This advantage is an asset condition to fabricate OTFT.

-2 -1 0 1 2

Le a k a g e Cu rre nt (n A)

Bias ( V ) 0.1sccm

1.0sccm 5.0sccm

(b)

Figure 3-1 The (a)C-V and (b)I-V characteristic of MIM structure with different APPT flow rates

-2 -1 0 1 2

L ea k ag e Cur ren t (n A)

Bias (V)

(b)

Figure 3-2 The (a)C-V and (b)I-V characteristic of MIM structure with Al gate

-2 -1 0 1 2

Le akag e Cur rent (n A)

Bias (V)

(b)

Figure 3-3 The (a)C-V and (b)I-V characteristic of MIM structure with Ni gate

-2 -1 0 1 2

L eak age Cur ren t ( nA )

Bias (V)

(b)

Figure 3-4 The (a)C-V and (b)I-V characteristic of MIM structure with TaN gate

-2 -1 0 1 2

Le akag e Cur rent (n A)

Bias (V)

(b)

Figure 3-5 The (a)C-V and (b)I-V characteristic of MIM structure with Ir gate

-2 -1 0 1 2

Le akag e Cur rent (n A)

Bias (V)

(b)

Figure 3-6 The (a)C-V and (b)I-V characteristic of MIM structure with Pd gate

-2 -1 0 1 2

Leak age C u rrent Dens it y ( A/c m 2 )

Pd

TaN Ni Ir

Metal gate Al

In same electric field

(b)

Figure 3-7 The (a)C-V and (b)I-E characteristic of MIM structure with different metal gates at 200℃

Table 3-1: The surface roughness of different conditions 溫度

金屬 100℃ 150℃ 200℃

Al 10.895 nm 9.937 nm 8.601 nm

Ni 11.695 nm 3.778 nm 1.950 nm

TaN 6.421 nm 3.882 nm 2.090 nm

Ir 18.422 nm 4.134 nm 3.013 nm

Pd 3.093 nm 2.075 nm 2.467 nm

(a) (b)

(c)

Figure 3-8 The surface roughness of APPT SiO

2

on Al gate at (a)100, (b)150, (c)200 substrate temperature

(a)

(b)

(c)

Figure 3-9 The surface roughness of APPT SiO

2

on Ni gate at (a)100, (b)150, (c)200 substrate temperature

(a)

(b)

(c)

Figure 3-10 The surface roughness of APPT SiO

2

on TaN gate at (a)100, (b)150, (c)200 substrate temperature

(a)

(b)

(c)

Figure 3-11 The surface roughness of APPT SiO

2

on Ir gate at (a)100, (b)150, (c)200 substrate temperature

(a)

(b)

(c)

Figure 3-12 The surface roughness of APPT SiO

2

on Pd gate at (a)100, (b)150, (c)200 substrate temperature

90 100 110 120 130 140 150 160 170 180 190 200 210 2

4 6 8 10 12 14 16 18 20

0 2 4 6 8 10

0 2 4 6 8 10

RMS

temperature(

^o

C)

Al Ni TaN Ir Pd

Figure 3-13 The trend of surface roughness of different conditions

-2 -1 0 1 2

Leakage Current De nsity (A/ c m

2

)

Bias (V)

(b)

Figure 3-14 The (a)C-V and (b)I-V characteristic of MIM structure by N

2

plasma treatment with different flow rates

-2 -1 0 1 2

Leakage Current De nsity (A/ c m

2

)

Bias (V)

(b)

Figure 3-15 The (a)C-V and (b)I-V characteristic of MIM structure by NH

3

plasma treatment with different flow rates

-2 -1 0 1 2

Leakage Current De nsity (A/ c m

2

)

Bias (V)

(b)

Figure 3-16 The (a)C-V and (b)I-V characteristic of MIM structure by N

2

plasma treatment with different time

-2 -1 0 1 2

Leakage Current De nsity (A/ c m

2

)

Bias (V)

(b)

Figure 3-17 The (a)C-V and (b)I-V characteristic of MIM structure by NH

3

plasma treatment with different time

1 2 3

L e akage Cur rent Den s it y ( A/cm 2 )

Plasma treatment

NH 3

N 2

no

In the same electric field

Figure 3-18 The I-E characteristic of MIM structure with different plasma treatment

Table 3-2: The surface roughness, contact angle and the film thickness of different conditions

Plasma

(a)

(b)

(c)

Figure 3-19 The roughness of (a)no, (b)N

₂

, (c)NH

₃

plasma treatment

2 20

22 24 26

contact angle thickness

Plasma treatment Co nt a c t ang le (

o

)

NH

3

N

2

no

12.2 12.3 12.4 12.5 12.6

T h ickness (n m )

Figure 3-20 The film thickness and the contact angle of different plasma treatments

(a)

(b)

(c)

Figure 3-21 The contact angel of (a)no, (b)N

₂

, (c)NH

₃

plasma treatment

(a)

(b)

(c)

Figure 3-22 The film thickness of (a)no, (b)N

₂

, (c)NH

₃

plasma treatment

Table 3-3 The s threshold voltage, mobility and on/off ratio of different conditions

Plasma treatment

threshold

voltage(Volt) Mobility(cm

²

/V·s) on/off ratio no -0.616 V 0.56 cm

²

/V·s 0.81×10

³

N

2

-0.953 V 0.59 cm

²

/V·s 0.47×10

³

NH

₃

-0.886 V 0.72 cm

²

/V·s 0.41×10

³

0.0 -0.5 -1.0 -1.5 -2.0

Figure 3-23 I

_D

-V

_D

for different plasmas treatments (a) no treatment (b) N treatment (c) NH treatment

-2.6 -2.4 -2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2

Figure 3-24 I

_D

-V

_G

for different plasmas treatments (a) no treatment (b) N treatment (c) NH treatment

-2.6 -2.4 -2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0

| Drain Current |1/2(A)

(a)

| Drain Current |1/2(A)

(b)

| Drain Current |1/2(A)

(c)

Figure 3-25 ︱ I

_D

︱

^1/2

-V

_G

for different plasmas treatments (a) no treatment (b) N

2

treatment (c) NH

3

treatment

0.0 -0.5 -1.0 -1.5 -2.0

| Drain Current |1/2(A)

(c)

Figure 3-26 The comparison of (a) I

_D

-V

_D

(b) I

_D

-V

_G

(c) ︱ I

_D

︱

^1/2

-V

_G

with different treatments

2

Figure 3-27 The s threshold voltage, mobility and on/off ratio of different conditions

Chapter 4

Conclusions and Future work

4.1 Conclusions

We can know from the experiment the flow of carrier gases will influence the quantity that the TEOS gas comes out. The increasing of the flow rate about carrier gases leads to the increasing of released TEOS gas.

But depositing is too quickly to make good quality of insulator.

And we can learn from the experiment the nickel is most suitable for using APPT to deposit the oxidize layer.

After plasma treatment, the insulator surface characteristic is caused to have exiguity changes. For example, there are the change of the surface roughness and contact angle. And the plasma treatment has the effect to reduce leakage current.

In summary, OTFT using pentacene as an active layer are fabricated on insulator deposited by APPT. The mobility in the saturation region and the threshold voltage and on/off ratio of the OTFT are 0.72 cm

²

/Vs and -0.616 V and ~10

³

, respectively. The advantage of the atmospheric-pressure plasma technology is that it needn't vacuum and at general room temperature to deposit insulator. This advantage is an asset condition to fabricate OTFT.

4.2 Future work

The new method, for example, use plastics substrate as the base, so

that it’s more suitable for OTFT which is flexibility and lightness.

Spinning organic polymeric gate dielectrics on oxide which is deposited by APPT achieve the result of reducing roughness.

Simultaneously, we can improve the hydrophilic and hydrophobic question for organic semiconductor by organic polymeric gate dielectrics.

Because pentacene OTFT is sensitive to ambient conditions.

Protection from the environment by encapsulation is critical to the stability of pentacene OTFT. Therefore, using a suitable material as passivation to protect pentacene film from environmental effect is another important topic.

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簡 歷

姓 名 : 徐明頤 性 別 : 男

出生日期 : 民國 73 年 04 月 26 日 出 生 地 : 台灣省新竹縣

住 址 : 新竹縣竹東鎮水之路 9 號 學 歷 : 私立上智天主教小學

(民國 79 年 09 月～民國 85 年 06 月) 竹東國中

(民國 85 年 09 月～民國 88 年 06 月) 國立新竹高級中學

(民國 88 年 09 月～民國 91 年 06 月) 國立中興大學物理學系

(民國 91 年 09 月～民國 95 年 06 月) 國立交通大學電子工程研究所碩士班 (民國 95 年 09 月～民國 97 年 07 月)

碩士論文 : 常壓式電漿系統沈積之二氧化矽在有機薄膜電晶體應上之研究 The study on the silicon dioxide deposited by

Atmospheric-Pressure Plasma Technology for Organic Thin-Film Transistor application

在文檔中 常壓式電漿系統沈積之二氧化矽在有機薄膜電晶體應用上之研究 (頁 50-0)