JP3056927B2 - Thin film transistor element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor element which can be used for a liquid crystal display device and the like and a method of manufacturing the same.

[0002]

2. Description of the Related Art Thin film transistors (hereinafter referred to as TFs) on an active matrix substrate constituting a conventional liquid crystal display device.
The structure of abbreviated as T), will be described with reference to partial cross-sectional view of FIG.

[0003] Amorphous silicon thin film transistor, Gate electrode 8 consisting of the first electrode such as aluminum on the insulating substrate 1 such as glass or quartz is formed, covering the Gate <br/> gate electrode 8 way aluminum is formed first gate insulating film 9 by anodic oxidation, further amorphous silicon semiconductor layer through the second gate insulating film 10 of silicon nitride (a-Si layer ) 11 and the channel stopper layer 12 is formed, amorphous silicon semiconductor layer source over the source electrode 13a and drain electrode 13b made of titanium and aluminum containing phosphorus (n ⁺ a-Si layer) 11
a, 11b.

[0004] Manufacturing in such a TFT manufacturing method
Figure of process example2As shown in FIG. First, figure2(A)
(Al) is formed on the insulating substrate 1 as described above.
Using photolithography technologyーForm electrode 8
I do. Next figure2(B)ーNecessary part of the electrode 8
Anodizing to aluminum oxide (AlO)
x) the first gameーThe insulating film 9 is formed. Next figure2
As shown in (c), silicon nitride (S
iN_xThe second game consisting ofーInsulating film 10, amorphous semiconductor
Body layer (a-Si layer) 11, channel stopper layer 12 and
And softwareーBetween the drain and drain electrodes 13a, 13b and the semiconductor
OhーN to get Mic contact⁺a-Si layer 11a, 1
1b was continuously formed by plasma CVD.2(D)
Channel storage other than the TFT forming part
Layer 12 and a-Si layer 11 and n⁺a-Si layer 11
a and 11b are removed by etching. Finally figure2(E)
Al is formed as described above, and
ーForming a drain electrode 13a and a drain electrode 13b;
N on the channel section of the FT⁺a-Si layers 11a and 11b
Is removed to complete the TFT.

[0005]

[0005] However, this
The first example is the first gate insulation formed by anodization.
In the film 9, the shape of the channel stopper layer 12 in the post-process
During BHF etching for2(C)
The second gameーAnode due to defective portion 17 of insulating film 10
FIG. 4 shows an exposed portion of the first gate insulating film 9 which is an oxide film.2
As shown in (d), the first gate insulating film 9 is formed by hydrofluoric acid.
Etched,ーThe insulating film 9 becomes thinner
Therefore, there is a problem that a low breakdown voltage portion is generated.

On the other hand, when the first gate insulating film 9 having excellent resistance to hydrofluoric acid is to be formed, there is a problem that the unevenness of the film surface becomes large and the withstand voltage is lowered.

[0007] As a result, the gate electrode 8 drain electrode 13b there is a possibility that a short circuit 15 as shown in FIG.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thin film transistor element capable of achieving the hydrofluoric acid resistance and dielectric strength of the first insulating film and a method of manufacturing the same.

[0009]

According to a first aspect of the present invention, there is provided a thin film transistor element comprising: a first electrode formed on an insulating substrate;
An insulating layer formed on the surface of the first electrode by anodic oxidation, and two or more first insulating films including a layer having hydrofluoric acid resistance, and other than anodizing on the first insulating film Comprising a second insulating film formed by the means, a semiconductor layer including a channel stopper layer formed on the second insulating film, and a second electrode formed on the semiconductor layer It is.

The method of manufacturing a thin-film transistor element according to claim 2 is the method of manufacturing a thin-film transistor element according to claim 1, wherein the first layer is formed in an organic solvent of an electrolytic solution at the time of anodic oxidation for forming a first insulating film. The second layer contains 20 % to 30% of water, and the second layer contains 60% to 80 % of water to form an insulating layer and a layer having hydrofluoric acid resistance.

According to a third aspect of the present invention, there is provided a method of manufacturing a thin film transistor element according to the first aspect, wherein a current value at the time of anodic oxidation for forming the first insulating film is 1 mA / cm. from the value exceeding cm ² to 10 mA /
cm ² , the second layer is 0.1 mA / cm ² to 1 mA / cm ²
By setting to ² , an insulating layer and a layer having hydrofluoric acid resistance are formed.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a thin film transistor element according to the first aspect, wherein the temperature of the first layer is from 20 ° C. during anodic oxidation for forming the first insulating film. 30 ° C. , the second layer is 50 ° C.
By setting the temperature to 60 ° C. , an insulating layer and a layer having resistance to hydrofluoric acid are formed.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a thin film transistor element according to the first aspect, wherein fluorine is contained in an electrolytic solution at the time of anodic oxidation when forming at least one layer of the first insulating film. Including.

According to a sixth aspect of the present invention, in the method of manufacturing a thin film transistor according to the second, third, fourth, or fifth aspect, the first electrode is a thin film containing Al or Ta as a main component. .

[0015]

According to the thin film transistor element of the first aspect, the first insulating film formed by anodic oxidation on the first electrode,
Since the first insulating film is formed in two or more layers including an insulating layer and a layer having hydrofluoric acid resistance, the first insulating film passes through a defective portion or the like during BHF etching at the time of forming the channel stopper layer due to a defective portion of the second insulating film. Etching and the occurrence of a low withstand voltage portion can be prevented, and therefore, the hydrofluoric acid resistance and the withstand voltage can be simultaneously improved, so that a short circuit between the gate electrode and the source electrode can be prevented.

According to a second aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the organic solvent of the electrolytic solution at the time of anodic oxidation for forming the first insulating film includes One layer contains 20 % to 30% of water, and the second layer contains 60% to 80 % of water to form an insulating layer and a layer having resistance to hydrofluoric acid. Since a thin-film transistor element having no defects can be formed, the yield can be improved.

According to a third aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the current value at the time of anodic oxidation for forming the first insulating film is as follows. From the value exceeding 1 mA / cm ² to 10
mA / cm ² , the second layer is 0.1 mA / cm ² to 1 mA
/ Cm ² to form an insulating layer and a layer having resistance to hydrofluoric acid.

According to a fourth aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the temperature of the first insulating film when forming the first insulating film is set to 20 degrees. C to 30 C and the second layer is 5
By setting the temperature to 0 ° C. to 60 ° C. , an insulating layer and a layer having resistance to hydrofluoric acid are formed, which has the same effect.

According to a fifth aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the electrolytic solution at the time of anodic oxidation for forming at least one layer of the first insulating film is used. Since it contains fluorine, it has the same function as the second aspect.

According to the method of manufacturing a thin film transistor element of claim 6, in claim 2, claim 3, claim 4, or claim 5, the first electrode is made of a thin film containing Al or Ta as a main component. In addition to the effects of claim 2, claim 3, claim 4, or claim 5, the formation of the first insulating film can be facilitated regardless of whether the first electrode is a single layer or a stacked layer.

[0021]

BRIEF DESCRIPTION based first embodiment of the present invention in FIG. That is, FIG. 3 is a partial cross-sectional view showing a manufacturing process of the thin film transistor element. Reference numeral 1 denotes an insulating substrate of the thin film transistor element, which uses a glass substrate. Reference numeral 2 denotes a first electrode which is a gate electrode of a stripe-shaped Al film formed on the insulating substrate 1. Reference numeral 3 denotes an A composed of a pressure-resistant first layer 3a, which is an insulating layer formed on the surface of the first electrode 2 by anodic oxidation, and a hydrofluoric acid-resistant second layer 3b.
This is a first insulating film which is a gate insulating film of l ₂ O ₃ . 4
Is a second insulating film which is a gate insulating film of SiN _x (silicon nitride insulating film) formed on the first insulating film 3 by means other than anodic oxidation. Reference numeral 5 denotes a semiconductor layer of an a-Si layer (amorphous silicon semiconductor layer). Reference numeral 6 denotes a channel stopper layer of a SiN _x film. Reference numeral 7 denotes a second electrode which is a source electrode orthogonal to the first electrode 2.

According to this embodiment, the first insulating film 3 formed on the first electrode 2 includes the first layer 3a having a pressure resistance and the second layer 3b having a hydrofluoric acid resistance by anodic oxidation. For,
Second by an insulating film 4 of the defect portion 17 through the defect 17 in the BHF etching for the formation of the channel stopper layer 6 is first insulating film 3 is etched low-breakdown-voltage portion as shown in FIG. 3 (d) is This can prevent the occurrence of hydrofluoric acid and improve the resistance to hydrofluoric acid and dielectric strength at the same time, so that a short circuit between the first electrode 2 serving as the gate electrode and the second electrode 7 serving as the source electrode can be prevented.

Note that the first insulating film 3 may be formed of two or more layers.

Next, a method of manufacturing the thin film transistor will be described. That is, as shown in FIG. 3 , an Al film is formed on a glass substrate as the insulating substrate 1 to a thickness of 300 nm.
Formed, thereby completing the Gate electrodes as shown in FIGS. 3 (a) as the first electrode 2 by photolithography and etching. By anodic oxidation, and the Al ₂ O ₃ film as shown in FIG. 3 (b) as a first layer 3a of the first insulating film 3 (the anodic oxide film of Al) and 100nm formed. Anodic oxidation conditions as a main component ammonium citrate, an electrolytic solution containing ethylene glycol as the solvent heated to 30 ° C., a current density of 5 mA / c
The test was performed at a constant current up to m ² and a predetermined voltage of 70 V. Then the second
3 as a layer 3b 100 an Al ₂ O ₃ film as a (c)
nm. Anodization conditions are as follows: ammonium citrate as a main component, an electrolytic solution using water as a solvent is heated to 30 ° C.,
The current density was 0.5 mA / cm ² , and a constant voltage was applied to a predetermined voltage of 140 V. After reaching 140 V, the current was extended at a constant voltage until the current value dropped to 1% of the initial value.

Next, FIG.3Plasma CVD as shown in (d)
The second insulating film 4 isーInsulating film SiN
_x(Silicon nitride insulating film)
A-Si (amorphous silicon semiconductor layer) of the semiconductor layer 5
Is 50 nm, and the channel stopper provided thereon is
SiN of layer 6_xThe film was continuously formed at 100 nm. This tea
SiN of the channel stopper layer 6_xSelectively etch film
Then figure3The channel stopper layer 6 is formed as shown in FIG.
Was. 300 nm of Al was formed by sputtering.
Later, by photolithography and etching,3
A source electrode 7 is formed as shown in FIG.
Device was completed.

For comparative measurement, a sample in which the first insulating film 3 was either the first layer 3a or the second layer 3b was prepared.

[0027] For these samples, Gate electrode 2
And it was measured short-preparative incidence upon 50V applied between the source over the source electrode 7. The number of cross points used was 100,000 per sheet. As a result, Table 1 shows the relationship between the configuration of the first insulating film 3 and the number of defects.

[0028]

[Table 1]

Here, the sample of the first embodiment is the first sample.
The number of defects when the layer 3a is aqueous and the second layer 3b is non-aqueous,
The first layer 3a shows the number of defects when the second layer 3b is non-aqueous and the second layer 3b shows the number of defects when the second layer 3b is aqueous. The sample for comparison shows the number of defects in the case of non-aqueous and water. From Table 1, it was found that the first insulating film 3 having a two-layer structure was good.

Therefore, according to this method of manufacturing a thin film transistor element, a thin film transistor element having no short circuit between the gate electrode 2 and the source electrode 7 can be formed because the layer having pressure resistance and the layer having hydrofluoric acid resistance are formed. The yield can be improved by obtaining a dense first insulating film 3 having no defect.

A method for manufacturing a thin film transistor device according to a second embodiment of the present invention will be described. That is, an Al: Ta film is formed on a glass substrate as the insulating substrate 1 by 300 n.
formed by photolithography and etching.
As electrodes 2 were formed Gate electrodes. First insulating film 3
Table 2 shows the first layer 3a and the second layer 3b of the Al ₂ O ₃ film shown in FIG.
As shown in (1), each was formed to have a thickness of 100 nm by focusing on various anodic oxidation conditions, in particular, the relationship between the liquid composition of the solvent of the electrolytic solution (water: organic solvent) and the HF resistance. The anodizing condition at this time was a temperature of 30 ° C. and a current density of 1 mA / cm ² using a non-aqueous solution of ammonium adipate. Others are the same as the first embodiment.

The quality of the first insulating film 3 was evaluated by observing the amount of etching with a BHF solution used for forming the channel stopper layer 6 and the unevenness of the film surface. First layer 3
a and the second layer 3b are determined to be good or bad by determining that the remaining amount of the anodic oxide film after immersion for 2 minutes is 3 with the etching amount of the BHF solution.
A sample having a size of 0 nm or more was rated as ０, a size greater than 0 and less than or equal to 20 nm was rated as Δ, and a value of 0 or less was rated as x. Regarding the irregularities on the film surface, those that felt cloudy by visual inspection were evaluated as x. Those satisfying both of these two points were rated as "good".

[0033]

[Table 2]

Referring to Table 2, the first layer 3a and the second layer 3
The composition of the liquid composition of b is 20: 80/60: 40, 20: 80/8 as the first layer (water: organic solvent) / second layer (water: organic solvent).
Good results were obtained with four types: 0:20, 30: 70/60: 40, and 30: 70/80: 20.

[0035] Then, a thin film transistor element likewise four layered structure of Example 1, short-preparative generation upon 50V applied between Gate electrode 2 and the source over the source electrode 7 for these samples The number was measured. As a result, the number of defects was zero in each case.

Therefore, the first layer 3a is replaced with an organic solvent as a solvent of the electrolytic solution at the time of anodic oxidation for forming the first insulating film 3.
It can be seen that by containing 30% or less of water and the second layer 3b containing 60% or more of water, a layer having pressure resistance and a layer having resistance to hydrofluoric acid can be formed. Thereby, the same effect as that of the first embodiment can be obtained.

A method for manufacturing a thin film transistor device according to a third embodiment of the present invention will be described. That is, similarly to Example 2, an Al: Ta film was formed on a glass substrate to a thickness of 300 nm.
Formed, to form a Gate electrode as the first electrode 2 by photolithography and etching. As shown in Table 3, the first layer 3a and the second layer 3b of the Al ₂ O ₃ film of the first insulating film 3 are focused on various anodic oxidation conditions, in particular, the relationship between current density and HF resistance. , Each having a thickness of 100 nm. The anodic oxidation was performed at a temperature of 30 ° C. using a non-aqueous solution of ammonium adipate. Others are the same as the first embodiment. The evaluation of the film quality is the same as in Example 2.

[0038]

[Table 3]

Referring to Table 3, the first layer 3a and the second layer 3
construction of b is, as the density of the current density / second layer of the first ^{layer, 5mA / cm 2 /0.1mA/cm 2,} 5mA / cm 2 /0.5mA/cm 2, 5m
^{A / cm 2 / 1mA / cm} 2, 10mA / cm 2 /0.1mA/cm 2, 10mA / cm 2 /
Good results were obtained with six types, 0.5 mA / cm ² and 10 mA / cm ² cm ² .

Further to prepare a thin film transistor element likewise six laminated structure as in Example 1, the short-preparative incidence upon 50V applied for these samples between Gate electrode 2 and the source over the source electrode 7 It was measured. As a result, the number of defects was zero in each case.

Therefore, when the current value during the anodic oxidation for forming the first insulating film 3 is larger than 1 mA / cm ^{2 for} the first layer 3a and 1 mA / cm ² or less for the second layer 3b, the withstand voltage is reduced. It can be seen that a layer having a property and a layer having a hydrofluoric acid resistance can be formed.

A method for manufacturing a thin film transistor device according to a fourth embodiment of the present invention will be described. That is, similarly to Example 2, an Al: Ta film was formed on a glass substrate to a thickness of 300 nm.
Formed, to form a Gate electrode as the first electrode 2 by photolithography and etching. As shown in Table 4, the first layer 3a and the second layer 3b of the Al ₂ O ₃ film of the first insulating film 3 were formed under various anodic oxidation conditions, in particular, the temperature, ie, the bath temperature of the electrolytic solution and the HF resistance. Focusing on the relationship, each 100
It was formed to a thickness of nm. The anodic oxidation conditions at this time were as follows: a non-aqueous solution of ammonium adipate and a current density of 1 mA.
/ Cm ² . Others are the same as the first embodiment, and the film quality evaluation is the same as the second embodiment.

[0043]

[Table 4]

Referring to Table 4, the first layer 3a and the second layer 3
b is 20 ° C. as the temperature of the first layer / the temperature of the first layer.
Good results were obtained with four types: / 50 ° C, 20 ° C / 60 ° C, 30 ° C / 50 ° C, and 30 ° C / 60 ° C.

Further to prepare a thin film transistor element similar to the four multilayer structure as in Example 1, the short-preparative incidence upon 50V applied for these samples between Gate electrode 2 and the source over the source electrode 7 It was measured. As a result, the number of defects was zero in each case.

Therefore, the temperature at the time of anodic oxidation for forming the first insulating film 3 is 30 ° C. or lower for the first layer 3a and 50 ° C. or higher for the second layer 3b. It can be seen that a layer having hydrofluoric acid resistance can be formed.

A method for manufacturing a thin film transistor device according to a fifth embodiment of the present invention will be described. That is, similarly to Example 2, an Al: Ta film was formed on a glass substrate to a thickness of 300 nm.
Then, a gate electrode was formed as the first electrode 2 by photolithography and etching. As shown in Table 5, the first layer 3a and the second layer 3b of the Al ₂ O ₃ film of the first insulating film 3 were formed under various anodic oxidation conditions, in particular, the types of additives of the electrolytic solution and the HF resistance. Focusing on the relationship , each 100nm
It was formed in thickness. The anodic oxidation was performed at a temperature of 30 ° C. and a current density of 1 mA / cm ² using a non-aqueous solution of ammonium adipate. Others are the same as the first embodiment, and the film quality evaluation is the same as the second embodiment.

[0048]

[Table 5]

Referring to Table 5, the first layer 3a and the second layer 3
The composition of b is, as an additive of the first layer / an additive of the second layer,
None / HF, NH ₄ F / None, NH ₄ F / NH ₄ F, N
Good results were obtained with four types of H ₄ F / HF.

[0050] In addition to a thin film transistor element similar to the four multilayer structure as in Example 1, the short-preparative incidence upon 50V applied for these samples between Gate electrode 2 and the source over the source electrode 7 It was measured. As a result, the number of defects was zero in each case.

Therefore, by containing fluorine in the electrolytic solution at the time of anodic oxidation when forming at least one layer of the first insulating film 3, it is possible to form a layer having pressure resistance and a layer having resistance to hydrofluoric acid. Recognize.

When the first electrode 2 has a single-layer and laminated structure of a thin film containing Al or Ta as a main component,
Can easily be formed.

[0053]

According to the thin film transistor element of the first aspect, the first insulating film formed by anodic oxidation on the first electrode is formed as two or more layers including an insulating layer and a layer having resistance to hydrofluoric acid. In addition, the first insulating film is etched through the defective portion and the like during the BHF etching at the time of forming the channel stopper due to the defective portion of the second insulating film and the like, so that it is possible to prevent the generation of the low withstand voltage portion. Since the acidity and the withstand voltage can be simultaneously improved, there is an effect that a short circuit between the gate electrode and the source electrode can be prevented.

According to the method for manufacturing a thin film transistor element of claim 2, the method for manufacturing a thin film transistor element according to claim 1, wherein the organic solvent of the electrolytic solution at the time of anodic oxidation for forming the first insulating film includes one layer contains 30% water 10%, by the second layer comprising 90% water 60%, absolutely
Since the edge layer and the layer having hydrofluoric acid resistance are formed, a thin film transistor element without a short circuit between the gate electrode and the source electrode can be formed, so that the yield can be improved.

According to a third aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the current value at the time of anodic oxidation for forming the first insulating film is as follows. From the value exceeding 1 mA / cm ² to 10
mA / cm ² , the second layer is 0.1 mA / cm ² to 1 mA
/ Cm ² to form an insulating layer and a layer having resistance to hydrofluoric acid.

According to a fourth aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the temperature of the first layer is set to 20 times during anodic oxidation. C to 30 C and the second layer is 5
By setting the temperature to 0 ° C. to 60 ° C. , an insulating layer and a layer having resistance to hydrofluoric acid are formed.

According to a fifth aspect of the present invention, there is provided the method of manufacturing a thin film transistor element according to the first aspect, wherein the electrolytic solution during the anodic oxidation for forming at least one of the first insulating films is used. Since it contains fluorine, it has the same effect as the second aspect.

According to the method of manufacturing a thin film transistor of claim 6, in claim 2, claim 3, claim 4, or claim 5, the first electrode is formed of a thin film containing Al or Ta as a main component. In addition to the effects of claim 2, claim 3, claim 4, or claim 5, the formation of the first insulating film can be facilitated regardless of whether the first electrode is a single layer or a stacked layer.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a conventional thin film transistor element .

FIG. 2 is a partial cross-sectional view showing a manufacturing process of the thin film transistor element .

FIG. 3 is a thin film transistor element according to the first embodiment of the present invention;
It is a fragmentary sectional view showing a manufacturing process of a child .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 1st electrode 3 1st insulating film 3a 1st layer 3b 2nd layer 4 2nd insulating film 5 Semiconductor layer 6 Channel stopper layer 7 2nd electrode

──────────────────────────────────────────────────続 き Continuing on the front page (72) Tatsuhiko Tamura 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-264774 (JP, A) JP-A-63-166236 (JP, A) JP-A-4-356926 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/786 H01L 21/336 G02F 1/1368 H01L 21/316 H01L 21/32 H01L 21/473

Claims (6)

(57) [Claims] And 1. A first electrode formed on an insulating substrate was formed by anodic oxidation on the surface of the first electrode insulation
Two or more first insulating films including an edge layer and a layer having hydrofluoric acid resistance, a second insulating film formed on the first insulating film by means other than the anodic oxidation, A semiconductor layer including a channel stopper layer formed on the insulating film of
And a second electrode formed on the semiconductor layer. 2. The method for manufacturing a thin film transistor element according to claim 1, wherein the first layer contains 20 % to 30% of water as an organic solvent of an electrolytic solution at the time of anodic oxidation for forming the first insulating film.
The second layer contains 60% to 80 % water,
A method for manufacturing a thin film transistor element, comprising forming an insulating layer and a layer having resistance to hydrofluoric acid. 3. The method for manufacturing a thin film transistor device according to claim 1, wherein a current value during anodic oxidation for forming the first insulating film is set to 1 from a value exceeding 1 mA / cm ² for the first layer.
0 mA / cm ² , the second layer is 0.1 mA / cm ² to 1 m
A method for manufacturing a thin film transistor element, wherein an insulating layer and a layer having resistance to hydrofluoric acid are formed at A / cm ² . 4. The method for manufacturing a thin film transistor element according to claim 1, wherein the temperature during the anodic oxidation for forming the first insulating film is 20 ° C. to 30 ° C. for the first layer and 50 ° C. for the second layer.
Forming an insulating layer and a layer having resistance to hydrofluoric acid at a temperature of from 60 ° C. to 60 ° C. 5. The method for manufacturing a thin film transistor element according to claim 1, wherein the electrolytic solution at the time of anodic oxidation when forming at least one of the first insulating films contains fluorine. Production method. 6. The method according to claim 2, wherein the first electrode is a thin film containing Al or Ta as a main component.