JPH04133032A - Tft panel - Google Patents

Abstract

PURPOSE:To prevent short circuit between the gate electrode of a thin film transistor and a drain electrode by forming a guard electrode on the outside of a scanning wiring so that it may be opposed to a drain electrode and forming the semiconductor layer of a thin film transistor at a part except a part corresponding to the guard electrode. CONSTITUTION:The guard electrode 33 for protecting a transistor is formed to project on the outside of the scanning wiring 22. Then, the tip of the guard electrode 33 is opposed to a guard electrode counter part 34 which is formed to project at one side edge part of the drain electrode 30. The semiconductor layer 28 of the thin film transistor 25 is formed only at the thin film transistor part opposed to the gate electrode 26 except the part corresponding to the guard electrode 33, and the guard electrode 33 is opposed to the guard electrode counter part 34 only through a gate insulating film 27. Thus, the breakdown of the gate insulating film caused by static electricity occurs in the guard electrode part earlier than in the thin film transistor, thereby protecting the thin film transistor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a TFT panel used in a TFT active matrix type liquid crystal display element.

[Conventional technology]

TFT panels used in TFT active matrix liquid crystal display elements are made of glass or the like on a transparent substrate.
a scanning wiring and a data wiring perpendicular to the scanning wiring;
A thin film transistor (T P
T) and a pixel electrode connected to the source electrode of this thin film transistor.

FIGS. 11 and 12 show conventional TFT panels. Note that this TFT panel has thin film transistors of an inverted stagger type.

This TFT panel has a transparent substrate 1 made of glass or the like, a large number of scanning lines 2, a large number of data lines 3 perpendicular to the scanning lines 2, and a large number of pixel electrodes made of a transparent conductive film such as ITO. 4 and a large number of thin film transistors 5 for selecting each pixel electrode 4, two thin film transistors 5 are provided for each pixel electrode 4, and both thin film transistors 5, 5 are formed. It is arranged along the scanning wiring 2.

Both of the thin film transistors 5.5 each include a gate electrode 6 formed on the scanning line 2 extending outward from the scanning line 2, a gate insulating film 7 formed on the gate electrode 6, and a gate insulating film 7 formed on the gate electrode 6. A semiconductor layer 8 is formed on top of the semiconductor layer 8 to face the gate electrode 6, and a source electrode 9 and a drain electrode 10 are formed on both sides of the semiconductor layer 8.
The pixel electrode 4 is connected to the source electrode 9 of both thin film transistors 5, 5. Further, the drain electrodes 10 of both thin film transistors 5, 5 are used as a common electrode, and this drain electrode 10 is connected to the data line 3. Note that 11 is a blocking insulating film formed on the channel region of the semiconductor layer 8.

Further, the gate insulating film 7 is formed of transparent 5iN (silicon nitride), and this gate insulating film 7 is formed almost over the entire surface of the substrate 1. The scanning line 2 is covered with a gate insulating film 7 except for its terminal portion, and the data line 3 and the pixel electrode 4 are covered with the gate insulating film 7.
is formed on top of.

Note that the scanning wiring 2 and the gate electrode 6 are made of Cr.
It is made of hard metal such as (chromium), Ta (tantalum), Mo (molybdenum), etc. Further, the semiconductor layer 8 of both thin film transistors 5, 5 is made of a-3t (amorphous silicon), and the source electrode 9 is made of n''-a
-Si (amorphous silicon doped with n-type impurities) is an n-type semiconductor. The drain electrode 10 is a two-layer structure in which an n-type semiconductor layer 10a made of the same n''-a-5i material as the source electrode 9 is used as a lower electrode in contact with the semiconductor layer 8, and a metal electrode 10b connected to the data wiring 3 is formed on top of the n-type semiconductor layer 10a. The metal electrode 10 and the data wiring 3 are made of a metal such as Cr that has good ohmic contact with the n-type semiconductor layer 10a.

The TFT active matrix liquid crystal display element is assembled by bonding the TFT panel and a transparent substrate on which a counter electrode is formed via a frame-shaped sealing material, and sealing liquid crystal therebetween.

By the way, in the above TFT panel, if the scanning line 2 and the data line 3 are short-circuited at their crossing opposing parts,
All the thin film transistors 5 connected to the short-circuited scanning line 2 and data line 3 become inoperable, and voltage cannot be applied to the pixel electrode 4 selected by each thin film transistor 5, resulting in a display defect in the liquid crystal display element. .

For this reason, in the above TFT panel, as shown in FIG.
The gate insulating film 7 and the auxiliary insulating film 12 reliably insulate the scanning line 2 and data line 3 from each other. Note that the auxiliary insulating film 12 is the same insulating film as the blocking insulating film 11 of the thin film transistor 5, for example, S
It is formed of an iN film.

[Problem to be solved by the invention]

However, the conventional TFT panel described above has a problem in that the scanning line 2 and the data line 3 are short-circuited at the thin film transistor 5 portion.

This is mainly due to the effect of static electricity, and if a charged object (such as a human finger) with static electricity touches the terminal part of the data wiring 3 or scanning wiring 2 while handling the TFT panel, the gate of the thin film transistor 5 A large potential difference occurs between the electrode 6 and the drain electrode 10, and dielectric breakdown occurs in the gate insulating film 7 at this portion, causing the gate electrode 6 and the drain electrode 10 to
There will be a short circuit. Note that this short circuit between the gate electrode 6 and the drain electrode 10 due to electrostatic discharge is most likely caused by the data wiring 3 of the two thin film transistors 5, 5.
This occurs in the transistor closer to the . If a short circuit occurs in the thin film transistor 5 in this way, the scanning line 2 and the data line 3 will be shorted at the thin film transistor 5 portion.

For this reason, in the conventional TFT panel, out of the two thin film transistors 5.5, the short-circuited thin film transistor 5.
The gate electrode 6 is cut along the cutting line a shown by the two-dot chain line in FIG.
The thin film transistor 5 is separated from the scanning line 2 by cutting along the line 2, and the short circuit between the scanning line 2 and the data line 3 is eliminated.

Note that short circuits in the thin film transistor 5 are checked by visually inspecting each thin film transistor in the pixel column in which a display defect occurred one by one using a microscope in a display test after assembling the liquid crystal display element. The cutting at 6 is performed by a laser.

If a short circuit occurs in the thin film transistor 5 in this way, this thin film transistor will be wasted.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to protect a thin film transistor from static electricity and reliably prevent a short circuit between the gate electrode and drain electrode of the thin film transistor. T that can be done
Our goal is to provide FT panels.

[Means to solve the problem]

The present invention provides, on a substrate, a scanning wiring, a data wiring perpendicular to the scanning wiring, a thin film transistor having a gate electrode connected to the scanning wiring and a drain electrode connected to the data wiring, and a thin film transistor connected to the source electrode of the thin film transistor. In a TFT panel formed with a pixel electrode,
A drain electrode of the thin film transistor is formed to extend outside the data wiring, a gate electrode of the thin film transistor is formed to face a part of the drain electrode, and the scanning wiring is formed on at least one side of the thin film transistor. Alternatively, a guard electrode for protecting the transistor is provided extending outside the drain electrode, and the guard electrode is opposed to the train electrode or the scanning wiring via the gate insulating film of the thin film transistor, and the semiconductor of the thin film transistor is The present invention is characterized in that the layer is formed except for a portion corresponding to the guard electrode.

[Effect]

That is, in the present invention, a guard electrode is provided on at least one side of a thin film transistor and is formed to protrude outside the scanning wiring or the drain electrode, and this guard electrode is connected to the drain electrode or the scanning wiring through the gate insulating film of the thin film transistor. The thin film transistor is protected from static electricity by facing the gate electrode.If the semiconductor layer of the thin film transistor is formed excluding the part corresponding to the gate electrode as described above, the thin film transistor part will be protected from static electricity. , a gate insulating film and a semiconductor layer are interposed between the gate electrode and the drain electrode, whereas a gate insulating film and a semiconductor layer are interposed between the guard electrode and the drain electrode or scanning wiring that faces the guard electrode. Since there is only an insulating film and no semiconductor layer, the dielectric breakdown voltage between the guard electrode and the opposing drain electrode or scanning wiring is equal to the dielectric breakdown voltage between the gate electrode and drain electrode of the thin film transistor part. This is lower than the withstand voltage, and therefore dielectric breakdown of the gate insulating film due to static electricity occurs in the guard electrode portion before the thin film transistor portion. When the gate insulating film breaks down at this guard electrode part, the scanning line and the drain electrode are short-circuited at this part, and static electricity flows through this short-circuited part, causing dielectric breakdown in the gate insulating film at the thin-film transistor part. Since static electricity that would otherwise cause the thin film transistor to be damaged does not act, it is possible to reliably prevent a short circuit between the gate electrode and the drain electrode of the thin film transistor. Furthermore, if the gate insulating film breaks down at the guard electrode portion and shorts between the scanning wiring and the drain electrode as described above, the data wiring and the scanning wiring to which the drain electrode is connected will be shorted. A short circuit with the wiring can be eliminated by cutting the guard electrode.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 10.

FIG. 1 is a plan view of a portion of the TFT panel, and FIGS. 2 and 3 are enlarged sectional views taken along lines AA and BB in FIG. 1. Note that the TFT panel of this example has thin film transistors of an inverted stagger type.

This TFT panel has many scanning lines 22, many data lines 23 perpendicular to the scanning lines 22, and many pixel electrodes made of a transparent conductive film such as ITO on a transparent substrate 21 made of glass or the like. 24 and a large number of thin film transistors 25 for selecting each pixel electrode 24,
One thin film transistor 25 is provided for each pixel electrode 24.

Each of the thin film transistors 25 is connected to the scanning wiring 2.
2, a gate electrode 26 extending outward from the gate electrode 26, and a gate insulating film 2 formed on the gate electrode 26.
7 and the gate electrode 26 on this gate insulating film 27.
The semiconductor layer 28 is formed to face the semiconductor layer 28, and the source electrode 29 and the drain electrode 30 are formed on both sides of the semiconductor layer 28.
The pixel electrode 24 is connected to the pixel electrode 24 .

Further, the drain electrode 30 is located outside the data wiring 23.
The thin film transistor 25 is formed to extend parallel to the scanning line 22, and the thin film transistor 25 has a gate electrode 26 and a semiconductor layer 2.
8 are formed at the center of the drain electrode 30 by forming them opposite to the center of the drain electrode 30. Note that 31 is a blocking insulating film made of SiN formed on the channel region of the semiconductor layer 28.

Further, the semiconductor layer 28 of the thin film transistor 25 is a-3t
The source electrode 29 is made of an n-type semiconductor made of n''-a-Si.Furthermore, the portion of the drain electrode 30 facing the gate electrode 26 is made of the same n''-a-Si as the source electrode 29. n-type semiconductor layer 30 made of a-3t
It is a two-layer electrode in which a is a lower layer electrode in contact with the semiconductor layer 28, and a metal electrode 30a connected to the data wiring 23 is formed thereon, and the other part of the drain electrode 30 is a single layer of only the metal electrode 30b. It is considered an electrode. The metal electrode 30a and the data wiring 23 are made of a metal such as Cr that has good ohmic contact with the n-type semiconductor layer 30a.

Further, the gate insulating film 27 is made of transparent SiN, and the gate insulating film 27 is formed on almost the entire surface of the substrate 21. The scanning line 22 is covered with a gate insulating film 27 except for its terminal portion, and the data line 23 and the pixel electrode 24 are covered with the gate insulating film 27.
is formed on top of. Further, on the gate insulating film 27, auxiliary insulating films 32 are formed to be located at the crossing and opposing parts of the scanning wiring 22 and the data wiring 23, and between the scanning wiring 22 and the data wiring 23, , are insulated by the gate insulating film 27 and the auxiliary insulating film 32. Note that the auxiliary insulating film 32 is the thin film transistor 25
The blocking insulating film 31 is made of the same insulating film (SiN).

Reference numeral 33 denotes a pair of transistor protection guard electrodes provided on both sides of the thin film transistor 25, and both guard electrodes 33 are formed to extend outside the scanning line 22.

This guard electrode 33 is formed to have a width sufficiently smaller than the width of the gate electrode 26. Then, one guard electrode 3
3 is formed corresponding to the base end side of the drain electrode 30 extending from the data line 23 in parallel with the scanning line 22, that is, corresponding to a part of the area between the gate electrode 26 and the data line 23. , the other guard electrode 33 is formed to correspond to the tip of the drain electrode 30, and the tips of both guard electrodes 33 are opposite to the guard electrode formed overhanging one side edge of the drain electrode 30. It faces the section 34. This guard electrode opposing portion 34 is connected to the drain electrode 30
Similarly to the portion other than the portion facing the gate electrode, the metal electrode 30b
It is said to be a single-layer electrode. Further, the semiconductor layer 28 of the thin film transistor 25 is formed only in the thin film transistor portion facing the gate electrode 26, except for the portion corresponding to the guard electrode 33. Therefore, the guard electrode 33 is formed only in the gate insulating film 27. The guard electrode facing portion 34 of the drain electrode 30 is opposed to the guard electrode facing portion 34 of the drain electrode 30 via.

Further, the scanning wiring 22, the gate electrode 26, and the guard electrode 33 are made of the same metal film, and these wirings and electrodes 22, 26.33 are made of a low melting point metal made of Ti-containing Ag, which is made by adding Ti to Afi. It is formed. The reason why the wiring and the electrodes 22, 26, 33 are made of a low melting point metal is that the guard electrode 33 can be easily cut when the scanning wiring 22 and the drain electrode 30 are short-circuited at the guard electrode 33 portion. This is to do so. Furthermore, the reason why Ti-containing Ag is used as the low melting point metal is to prevent defects from occurring in the gate insulating film 27 that is formed after the wiring and electrodes 22, 26, 33 are formed.

In other words, A and Q are generally known as low melting point metals, but while this AI (pure A11) has excellent conductivity and a low melting point, when a film of this Al is heat-treated at several hundred degrees, the film Because the surface becomes rough and protrusions called hillocks occur, the wiring and electrodes 22, 26, 33 are made of aluminum.
1, when the gate insulating film 27 is formed next, protrusions called hillocks will occur on the surfaces of the wirings and electrodes 22, 26, 33, and the gate insulating film 27 will be formed due to the influence of these hillocks. defects will occur. but,
As in this embodiment, the wiring and electrodes 22°, 26.
33 is made of Ti-gold-containing Aj7, the wiring and electrodes 22, 26, 33 can be formed at the time of forming the gate insulating film 27.
Hillocks do not form on the surface of the
The occurrence of defects in the gate insulating film 27 due to the hillocks can be eliminated.

The above TFT panel can be manufactured by the following manufacturing method.

4 to 9 are manufacturing process diagrams of the above TFT panel. In each figure, (a) shows a cross section taken along line A-A in FIG. 1, and (b) shows a cross-section taken along line B-- A cross section taken along line B is shown.

[Step 1] First, as shown in FIG. 4, a TI-containing 1
A scanning wiring 22, a gate electrode 26, and a guard electrode 33 are formed. These wirings and electrodes 22, 26.
33 is formed by forming a Tj-containing All film on the substrate 21 using an evaporation device or a sputtering device, and patterning this Ti gold-containing A, Q film by a photoetching method.

In addition, the above-mentioned Ti gold-containing AI! The film formation temperature is 100-20
It is 0°C.

[Step 2] Next, as shown in FIG. 5, a gate insulating film 27 made of SIN and a
A semiconductor layer 28 made of -St is successively formed using a plasma CVD apparatus, and a blocking insulating film 31 is further formed on the semiconductor layer 28. This blocking insulating film 31 is formed by forming an SIN film using a plasma CVD apparatus following the formation of the gate insulating film 27 and the semiconductor layer 28, and patterning this SIN film using a photoetching method. Note that the auxiliary insulating film 32 shown in FIG.
This blocking insulating film 31 is formed simultaneously with the formation of the blocking insulating film 31 described above.

In this case, the Ti content of the Ti-containing Al film that is the scanning wiring 22, the gate electrode 26, and the guard electrode 33 is adjusted to a certain level depending on the film formation temperature of the gate insulating film 27, the semiconductor layer 28, and the blocking insulating film 31. If the amount is exceeded, the surfaces of the scanning wiring 22, the gate electrode 26, and the guard electrode 33 made of T1-containing Aj7 will be roughened and hillocks will occur during the formation of the gate insulating film 27, semiconductor layer 28, and blocking insulating film 31. There's nothing to do.

That is, FIG. 10 shows the relationship between the Ti content of the T1-containing A11 film and the heat treatment temperature at which hillocks occur in this Ti-containing Al film. For example, when the Ti content is 2.2w,
t% of T1-containing AI! Hillocks do not occur in the film when heat-treated at temperatures below 270° C., but hillocks occur when heat-treated at temperatures exceeding this temperature. Moreover, the Ti content is 4.
In an Al film containing 2 wt% Ti, hillocks do not occur when heat treated at temperatures below 370° C., but hillocks occur when heat treated at temperatures exceeding this temperature. Note that in Figure 1+, the shaded area indicates an uncertain range in which it is difficult to determine whether there is a hillock or not. In this way, the presence or absence of hillocks after heat treatment of a Ti-containing Ag film depends on the Ti content of the Tf-containing Ag film and the heat treatment temperature (the deposition temperature of the gate insulating film 27, semiconductor layer 28, and blocking insulating film 31). Determined by

On the other hand, to explain the film forming temperature when forming the gate insulating film 27, the semiconductor layer 28, and the blocking insulating film 31 using a plasma CVD apparatus, the semiconductor layer 28 has a temperature of about 2
At a film formation temperature of 50°C, the power density of RF discharge is 40~5.
The film is formed under control at 0°mW/cm'. The reason for forming the semiconductor layer 28 at such a film forming temperature is hydrogenated a-8i (a-
81+H) is because when the film is formed at a high temperature, the amount of hydrogen decreases and the semiconductor characteristics deteriorate.

Further, the SiN film that becomes the gate insulating film 27 is heated at a temperature of 250° C.
The film is formed at a film forming temperature in the range of 370°C.

However, when forming a SiN film at a low film forming temperature within the above temperature range, the power density of the RF discharge is lowered. This is because when forming a SiN film at a low film forming temperature, the power density of the RF discharge is set high (then SiN is deposited in a dispersed state (sprayed with water on the flat plate surface) in the initial stage of film formation. This is because the degree of growth of the SiN film becomes uneven due to the influence, and defects such as pinholes and weak spots occur in the deposited SiN film.In the past, SiN films were deposited at low temperatures. In this case, it is necessary to lower the power density of the RF discharge.If the power density of the RF discharge is lowered in this way, the SiN film will grow slowly from the initial stage of film formation, which will prevent pinholes, weak spots, etc. It is possible to obtain a defect-free SiN film with sufficient dielectric breakdown voltage.In addition, when forming a SiN film at a high film forming temperature, R
The power density of the F discharge may be high, and if the film forming temperature is high, the formed SiN film will be free of defects such as pinholes and weak spots and will have a dense film quality. For example, when the SiN film deposition temperature is approximately 250°C to 270°C, the power density of the RF discharge is 60 to 100 mW/c.
It is sufficient to control the film-forming temperature to about 350°C to 350°C.
If the temperature is 70℃, the power density of RF discharge should be 120~
It may be controlled to 130rnW/cm2.

The blocking insulating film 31 is used to prevent the surface of the semiconductor layer 28 from being etched and damaged during patterning of the source and drain electrodes 29 and 30.
Although such dielectric breakdown voltage is not required, in this embodiment, the 5iNJII, which becomes the blocking insulating film 31, is also formed under the same film forming conditions as the SiN film, which becomes the gate insulating film 27.

Since there is a relationship as shown in FIG. 10 between the Ti content of the T1-containing All film and the heat treatment temperature at which hillocks occur in this Ti-containing AN film, for example, the gate insulating film 2
7 and the blocking insulating film 31 are formed at a film formation temperature of 250 to 270°C (the film formation temperature of the semiconductor layer 28 is approximately 250°C), the scanning wiring 22, the gate electrode 26, and the guard electrode 33 are formed using a Ti-containing film. Ti amount is 2.2wt% or more
When forming the gate insulating film 27 and the blocking insulating film 31 with gold-containing AI at a film forming temperature of 250 to 270°C, the scanning wiring 22, the gate electrode 26, and the guard electrode 33 are formed with a Ti content of 4. .2wt% or more TI content A
If the scanning wiring 22, the gate electrode 26, and the guard electrode 33 are formed with Tf-containing Ap having such a Ti content, the gate insulating film 27, the semiconductor layer 28, and the blocking insulating film 31 can be formed easily. Hillocks sometimes occur on the surfaces of these wirings and electrodes 22, 26, 33, and defects do not occur in the gate insulating film 27 formed thereon.

[Step 3] After forming the gate insulating film 27, the semiconductor layer 28, and the blocking insulating film 31 as described above, as shown in FIG. 6, a source electrode 29 and a drain electrode are formed on the semiconductor layer 28. An n-type semiconductor layer 30a, which is a lower layer electrode 3o, is formed at the same time.

The second source electrode 29 and the n-type semiconductor layer 30a are formed by forming an n"-a-5i layer using a plasma CVD apparatus, and forming the n"-a-5i layer using a plasma CVD apparatus.
The -a-3i layer is formed by patterning by photoetching.

Note that the n''-a-5t layer is the semiconductor layer 28
- Same film formation conditions as the 3t layer (film formation temperature, approx. 250℃, RF
The film is formed at a discharge power density of 40 to 50 mW/'c12).

[Step 4] Next, as shown in FIG. 7, the semiconductor layer 28 is patterned into the outer shape of the thin film transistor 25 by photoetching, and the portions of the semiconductor layer 2 corresponding to the guard electrodes 33 are patterned.
Remove 8.

[Step 5] Next, as shown in FIG. 8, on the gate insulating film 27,
The pixel electrode 24 is formed with its negative edge portion overlapping the two Sos electrodes. The pixel electrode 24 is formed by forming a transparent conductive film such as an ITO film using a vapor deposition device or a sputtering device, and patterning the transparent conductive film using a photoetching method. In addition, the film-forming temperature of the said transparent conductive film is 100-200 degreeC.

[Step 6] Next, as shown in FIG.
The data wiring 23 and the metal electrode 30b, which is the upper layer electrode of the drain electrode 30, are formed on the upper layer a, thereby completing the TFT panel. The data wiring 23 and the metal electrode 30b are formed by forming a metal film such as Cr using a vapor deposition device or a sputtering device, and patterning the metal film using a photoetching method. Note that the deposition temperature of the metal film is 1
00-200°C.

That is, in the TFT panel of the above embodiment, the drain electrode 30 of the thin film transistor 25 is formed to extend outside the data wiring 23, and the gate electrode 26 of the thin film transistor 25 is formed to face the center of the drain electrode 30. At the same time, guard electrodes 33 for protecting the transistor are formed on both sides of the thin film transistor 25 so as to extend to the outside of the scanning wiring 22 , and the guard electrodes 33 are connected to the drain electrode 30 through the gate insulating film 27 of the thin film transistor 25 .
, and the semiconductor layer 28 of the thin film transistor 25 is placed opposite the guard electrode opposing portion 34 of the guard electrode 33 .
It was formed by excluding the part corresponding to .

According to the TFT panel of this embodiment, guard electrodes 33 are provided on both sides of the thin film transistor 25 and extend outward from the scanning wiring 22, and the guard electrodes 33 are connected to the drain electrode 30 through only the gate insulating film 27. Because they are opposed to each other, dielectric breakdown of the gate insulating film 27 due to static electricity occurs in the guard electrode 33 portion before the thin film transistor 25 portion.

This is because the semiconductor layer 28 of the thin film transistor 25 is formed excluding the portion corresponding to the guard electrode 33. If this is done, the thin film transistor 25
In the section 5, a gate insulating film 27 and one conductor layer 28 are interposed between the gate electrode 26 and the drain electrode 30, whereas the guard electrode 30 and the drain electrode 30 with the guard electrode facing each other are interposed between the gate electrode 26 and the drain electrode 30. There is a gate insulating film 2 between
Since the semiconductor layer 28 is not present in the semiconductor layer 28, the dielectric breakdown voltage between the guard electrode 33 and the opposing drain electrode 30 is equal to that between the gate electrode 26 and the drain electrode 30 of the thin film transistor 25 portion. It is weaker than the dielectric breakdown voltage of . In the above embodiment, the part of the drain electrode 30 facing the gate electrode is a two-layer electrode consisting of the n-type semiconductor layer 30a in contact with the semiconductor layer 28 and the metal electrode 30b connected to the data wiring 23, and the other part is the metal electrode. Since only the single layer electrode 30b is used, the dielectric breakdown voltage between the guard electrode 33 and the drain electrode 30 can be further weakened. Therefore, dielectric breakdown of the gate insulating film 27 due to static electricity occurs in the guard electrode 33 portion before the thin film transistor 25 portion.

In most cases, this dielectric breakdown of the guard electrode 33 portion occurs in one of the guard electrode 33 portions on both sides of the thin film transistor 25.

That is, for example, if a charged object carrying static electricity touches the data wiring 23 and static electricity flows from the data wiring 23 to the drain electrode 30, the potential of the drain electrode 30 will be Therefore, in this case, the guard electrode 33 on the data wiring 23 side
Dielectric breakdown occurs in some parts. This is also the case when a charged object touches the terminal portion of the scanning wiring 22. In this case as well, the static electricity flowing through the scanning wiring 22 tends to flow from a point close to the data wiring 23 to the data wiring 23. Wiring 23
The dielectric breakdown occurs in the guard electrode 33 portion on the side. Further, for example, if a charged object is brought close to the data wiring 23, the data wiring 23
3 is inductively charged, the charge induced in the drain electrode 30 by the inductive charging of the data line 23 concentrates on the tip of the drain electrode 30. In this case, the guard electrode 33 on the tip side of the drain electrode 30 Dielectric breakdown occurs in some parts.

When the gate insulating film 27 breaks down at this guard electrode 33 portion, the scanning wiring 22 and the drain electrode 30 are short-circuited at this portion, and static electricity or induced charges are transferred from the data wiring 23 to the scanning wiring 22 through this short-circuited portion. To,
Alternatively, since the static electricity flows from the scanning line 22 to the data line 23, static electricity that would cause dielectric breakdown in the gate insulating film 27 does not act on the thin film transistor 25 portion.

According to the TFT panel, the thin film transistor 25 can be protected from static electricity, and the thin film transistor 25 can be protected from static electricity.
A short circuit between the gate electrode 26 and the drain electrode 30 can be reliably prevented.

Furthermore, if dielectric breakdown occurs in the guard electrode 33 portion as described above and the scanning wiring 22 and the drain electrode 30 are short-circuited, the data wiring 23 and the scanning wiring 22 to which the drain electrode 30 is connected will be short-circuited. A short circuit between the data wiring 23 and the scanning wiring 22 is caused by the guard electrode 33 at the short circuit location.
Laser cut along the cutting line shown in Figure 1, or
Alternatively, this problem can be solved by melting and cutting the guard electrode 33 by applying current. Note that the scanning wiring 2
2 and the data wiring 33 can be checked by performing a display test after assembling the liquid crystal display element. Furthermore, since the guard electrode 33 is made of a low melting point metal (Ti gold-containing A, ll) and its width is small, the guard electrode 33 can be easily cut by laser cutting or melt cutting. I can do it.

Note that when cutting the guard electrode 33 with a laser, the short-circuit location may be visually determined using a microscope and only the guard electrode 33 at this short-circuit location may be cut; however, all the guard electrodes along the short-circuited scanning wiring 22 may be cut. 33, there is no need to visually determine the short circuit location. In addition, when cutting the guard electrode 33 by melting, it is sufficient to simply flow a large current between the scan wiring 22 and the data wiring 33 that are short-circuited, and since this current flows through the guard electrode 33 at the short-circuit location, 3
3 is heated by Joule heat and melted and cut. In this case, if the guard electrode 33 portion is anodized to increase its resistance value, the guard electrode 33 can be melted and cut more easily.

Further, in the above embodiment, the guard electrode 33 is connected to the gate insulating film 27 of the scanning wiring 22 and the drain electrode 30.
Since it is formed on the scanning wiring 22 below the scanning wiring 22,
If the gate electrode 26 and the guard electrode 33 are formed of Al1, which is generally known as a low melting point metal, the surfaces of the scanning wiring 22, the gate electrode 26, and the guard electrode 33 will be Hillocks occur in the gate insulating film 27 due to the influence of these hillocks, but as in the above embodiment, the scanning wiring 22
And the gate electrode 26 and the guard electrode 33 are made of Ti to Ap.
If the gate insulating film 27 is formed using T1-containing Al, no hillocks will be generated on the surfaces of the scanning wiring 22, gate electrode 26, and guard electrode 33. Gate insulating film 2 by hillock
7 defects can be eliminated.

In the above embodiment, the guard electrodes 33 are provided on both sides of the thin film transistor 25, but the guard electrodes 33 may be provided on only one side of the thin film transistor 25. Further, the guard electrode 33 may be extended to a point below the side edge of the drain electrode 30 by increasing its projecting length.
does not necessarily have to protrude from the drain electrode 30.

Further, in the above embodiment, the guard electrode 33 is formed on the scanning line 22 under the gate insulating film 27, but this guard electrode 33 is formed on the drain electrode 33 on the gate insulating film 27.
In that case, the guard electrode and the metal electrode 30 of the drain electrode 30 on which the guard electrode is formed
b may be formed of a low melting point metal. In this case, since the data wiring 23, the drain electrode 30, and the guard electrode are formed after the gate insulating film 27 is formed, these wirings and electrodes may be formed of A and Q that do not contain T1. Further, when the guard electrode 33 is cut by laser cutting, the guard electrode 33 and the scanning wiring forming the guard electrode may be formed of metal such as Cr, Ta, Mo, or the like.

Further, in the above embodiment, the part of the drain electrode 30 facing the gate electrode is a two-layer electrode consisting of the n-type semiconductor layer 30a in contact with the semiconductor layer 28 and the metal electrode 30b connected to the data wiring 23, and the other part, that is, the guard electrode 33 Although the part corresponding to the metal electrode 30b is a single layer electrode, the part corresponding to the guard electrode 33 of the drain electrode 30 is as follows.
It may be a two-layer electrode consisting of an n-type semiconductor layer 30a and a metal electrode 30b, similar to the gate electrode opposing part, and even in that case,
Since the semiconductor layer 28 is not present in the guard electrode 33 portion, dielectric breakdown of the gate insulating film due to static electricity can occur in the guard electrode portion before the thin film transistor.

Further, in the above embodiment, one thin film transistor 25 is provided for one pixel electrode 24, but a plurality of thin film transistors 25 (for example, two) may be provided for each pixel electrode 24. In that case, guard electrodes 33 may be provided on both sides of the plurality of thin film transistors.

The present invention is not limited to TFT panels in which the thin film transistors 25 are of an inverted stagger type, but can also be applied to TFT panels in which thin film transistors are of an inverted stagger type, stagger type, or coplanar type. A guard electrode is formed on at least one side to extend outside the scanning wiring or drain electrode, and this guard electrode is opposed to the drain electrode or scanning wiring with the gate insulating film and semiconductor layer interposed therebetween. The portion facing the gate electrode may be a two-layer electrode consisting of an n-type semiconductor layer in contact with the semiconductor layer and a metal electrode connected to the data wiring, and the other portion may be a single-layer electrode consisting of only the metal electrode.

〔Effect of the invention〕

According to the present invention, a guard electrode is formed on at least one side of a thin film transistor so as to extend outside the scanning wiring or the drain electrode, and the guard electrode is connected to the drain electrode or the scanning wiring through the gate insulating film and the semiconductor layer. and facing the semiconductor layer of the thin film transistor,
Since the gate insulating film is formed excluding the part corresponding to the guard electrode, dielectric breakdown of the gate insulating film due to static electricity occurs in the guard electrode part before the thin film transistor, and dielectric breakdown occurs in the gate insulating film in the thin film transistor part. Since such static electricity does not act, the thin film transistor can be protected from static electricity and a short circuit between the gate electrode and drain electrode of the thin film transistor can be reliably prevented. Also,
As mentioned above, if the gate insulating film breaks down at the guard electrode part and the scanning wiring and the drain electrode are short-circuited, the data wiring and the scanning wiring to which the drain electrode is connected will be short-circuited. The short circuit can be eliminated by cutting the guard electrode.

[Brief explanation of drawings]

Figures 1 to 10 show an embodiment of the present invention.
Figure 1 is a plan view of a portion of the TFT panel, Figures 2 and 3 are enlarged sectional views taken along lines A-A and B-B in Figure 1, and Figures 4 to 9 are views of the TFT panel. The manufacturing process diagram, FIG. 10, is a diagram showing the relationship between the T1 content of the T1-containing A11 film and the heat treatment temperature at which hillocks occur in the TI-containing AII film. FIG. 11 is a plan view of a portion of a conventional TFT panel, and FIG. 12 is an enlarged sectional view taken along the Z-Z line in FIG. 11. 21... Substrate, 22... Scanning wiring, 23... Data wiring, 24... Pixel electrode, 25... Thin film transistor, 26... Gate electrode, 27... Gate insulating film, 28... ... Semiconductor layer, 29... Source electrode (n-type semiconductor layer), 30... Drain electrode, 30a... N-type semiconductor layer, 30b... Metal electrode, 31... Blocking insulating film, 32 ... Auxiliary insulating film, 33... Guard electrode, 34... Guard electrode opposing part. Applicant: Casio Computer Co., Ltd. 94 Figure 116 Figure 1!7J! 1 lN9N Fig. 11

Claims (1)

[Claims] A scanning wiring, a data wiring perpendicular to the scanning wiring, a thin film transistor having a gate electrode connected to the scanning wiring and a drain electrode connected to the data wiring, and a pixel electrode connected to the source electrode of the thin film transistor are provided on the substrate. In the formed TFT panel, the drain electrode of the thin film transistor is formed to extend outside the data wiring, the gate electrode of the thin film transistor is formed to face a part of the drain electrode, and at least one of the thin film transistors is A guard electrode for protecting a transistor is provided on a side thereof and is formed to protrude outside the scanning wiring or the drain electrode, and the guard electrode is opposed to the drain electrode or the scanning wiring with a gate insulating film of the thin film transistor interposed therebetween; A TFT panel characterized in that the semiconductor layer of the thin film transistor is formed excluding a portion corresponding to the guard electrode.