JP2001076872A - Manufacture of electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provided an EL display device and an electronic device therewith at lower manufacturing costs. SOLUTION: A manufacture of an active matrix EL display device comprises a step of forming an EL material for a picture element portion 111 in an application process using a dispenser 116. Herein, a discharge port of a nozzle 118 is linearly formed to improve the throughput. The dispenser 116 is used for simplifying the forming process of an EL layer to produce a decrease in manufacturing cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent (EL) device formed by forming a semiconductor device (a device using a semiconductor, typically a transistor) on a substrate surface.
The present invention relates to an electro-optical device represented by a display device and an electronic device (electronic device) having the electro-optical device as a display. In particular, it relates to a method for producing them.

[0002]

2. Description of the Related Art In recent years, a technique for forming a thin film transistor (hereinafter, referred to as a TFT) on a substrate has been greatly advanced, and application development to an active matrix display device has been promoted. In particular, a TFT using a polysilicon film has higher field-effect mobility than a TFT using a conventional amorphous silicon film, and thus can operate at high speed. Therefore, the control of the pixel, which has been conventionally performed by the drive circuit outside the substrate, can be performed by the drive circuit formed on the same substrate as the pixel.

Such an active matrix type display device has various advantages such as reduction in manufacturing cost, downsizing of the display device, increase in yield, and reduction in throughput by forming various circuits and elements on the same substrate. Is gaining attention.

An active matrix type EL display device is
A switching element formed of a TFT is provided for each pixel, and a driving element for controlling current is operated by the switching element to emit light from the EL layer (light emitting layer). For example, there are EL display devices described in U.S. Pat. No. 5,684,365 (JP-A-8-234683) and JP-A-10-189252.

Various methods have been proposed for forming the EL layer. For example, vacuum deposition, sputtering,
Spin coating, roll coating, casting, LB
Method, ion plating method, dipping method, ink jet method, and the like.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the manufacturing cost of an EL layer and to provide an inexpensive EL display device. Another object is to reduce the product cost of an electronic device (electronic device) having the display as a display.

[0007]

In order to achieve the above object, the present invention is characterized in that an EL layer (especially a light emitting layer) is formed by a coating step (coating method) using a dispenser. Here, the present invention will be described with reference to FIG.

FIG. 1A shows a part of a dispenser used in the present invention. In FIG. 1, reference numeral 110 denotes a substrate, and a pixel portion 111, a data side (source side) driving circuit 112, and a gate side driving circuit 1
Reference numeral 13 is formed by a thin film transistor (hereinafter, referred to as TFT). Note that the present invention can also be implemented when a transistor is formed on a silicon substrate surface.

Reference numeral 114 denotes a mixture of an EL material and a solvent (hereinafter, referred to as an EL product), and 115 denotes an EL product 1
14 is the coated surface. Note that the EL material here is a fluorescent organic compound and refers to an organic compound generally called a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, or an electron injection layer.

As shown in FIG. 1A, by forming the discharge port of the dispenser into a linear shape, a coated surface as indicated by 115 is obtained. Then, by moving the dispenser in the direction of the arrow on the pixel portion 111, the application surface 115 moves in the direction of the arrow. At this time, it is desirable that the length in the longitudinal direction of the application surface is a length that can cover the entire pixel portion by one movement.

Although the case where the ejection port is linear is described here, it may be dot-like (dot-like). Needless to say, it is faster to apply the EL material on the entire surface in the form of a line, but in the case of applying for each pixel (in the case of applying in the form of dots), the ejection openings are formed in the form of dots. Must be. The disadvantage of dot-like application is that the throughput is lower than that of the linear shape.
This is effective when forming an L layer (for example, when EL layers corresponding to RGB are separately formed).

FIG. 1B is a side view of the application step shown in FIG. 1A. The tip (nozzle) 118 attached to the syringe 117 of the dispenser 116 is E
It serves as a discharge port for the L formation 114. And this nozzle 1
18 will move in the direction of the arrow.

FIG. 1C is an enlarged view of a region (coated surface) indicated by 119 in FIG. 1B. The pixel portion 111 provided on the substrate 110 includes a plurality of TFTs 120 and pixel electrodes 121. An inert gas such as nitrogen is blown into the syringe 117 from the inside, and the EL forming material 114 is discharged from the nozzle 118 by the pressure. At this time,
A sensor using light reflection may be attached to the vicinity of the tip of the syringe 117 so that the distance between the application surface and the tip of the nozzle is always kept constant.

The EL product 114 discharged from the nozzle 118 is applied linearly so as to cover the pixel electrode 121. After applying the EL product 114, the solvent contained in the EL product 114 is vaporized by heat treatment in a vacuum to leave the EL material. Thus, an EL material is formed. For this reason, the solvent is the glass transition temperature (T
It is necessary to use one that evaporates at a lower temperature than g). Further, the thickness of the EL layer finally formed is determined by the viscosity of the EL formed product. In this case, the viscosity can be adjusted by selecting the solvent, but the viscosity is 10 to 50 cp.
(Preferably 20 to 30 cp).

Further, if there are many impurities that can be crystal nuclei in the EL product 114, there is a high possibility that the EL material is crystallized when the solvent is vaporized. If crystallized, the luminous efficiency decreases, which is not preferable.
It is preferable that impurities are not contained in the L forming material 114.

In order to reduce impurities, it is necessary to use E
It is important to clean the environment when purifying the L material or mixing the solvent and the EL material as much as possible. However, when the EL material is applied by a dispenser as shown in FIG. It is preferable to pay attention to the atmosphere. Specifically, it is desirable that the above-mentioned EL forming product application step be performed by a dispenser installed in a clean booth filled with an inert gas such as nitrogen.

Here, the active matrix type E
Although the description is made by taking the L display device as an example, the present invention can also be applied to a passive matrix type (simple matrix type) EL display device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of a pixel portion of the EL display device according to the present invention, and FIG.
FIG. 3B is a top view, and FIG. 3B is a circuit configuration thereof. Actually, a plurality of pixels are arranged in a matrix to form a pixel portion (image display portion). Note that FIG. 2A is a cross-sectional view taken along a line AA ′ in FIG. 2 and 3
, A common reference numeral is used, so it is better to refer to both drawings as appropriate. Although two pixels are shown in the top view of FIG. 3, both have the same structure.

In FIG. 2, reference numeral 11 denotes a substrate, and 12 denotes an insulating film serving as a base (hereinafter, referred to as a base film). As the substrate 11, a glass substrate, a glass ceramic substrate, a quartz substrate, a silicon substrate, a ceramic substrate, a metal substrate, or a plastic substrate (including a plastic film) can be used.

The base film 12 is particularly effective when a substrate containing mobile ions or a substrate having conductivity is used, but may not be provided on a quartz substrate. As the base film 12, an insulating film containing silicon (silicon) may be used. Note that in this specification, the “insulating film containing silicon” specifically includes silicon, oxygen, or nitrogen at a predetermined ratio, such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film (indicated by SiOxNy). Refers to an insulating film.

Dispersing the heat generated by the TFT by providing the base film 12 with a heat radiation effect is also effective in preventing the deterioration of the TFT or the EL element. All known materials can be used to provide a heat radiation effect.

Here, two TFTs are formed in a pixel. 201 is a TF functioning as a switching element
T (hereinafter referred to as switching TFT), 202 is E
The TFT functions as a current control element for controlling the amount of current flowing to the L element (hereinafter, referred to as a current control TFT), and both are formed of n-channel TFTs.

The field effect mobility of an n-channel TFT is p
Because it is larger than the field effect mobility of the channel type TFT,
The operating speed is fast and a large current is easy to flow. Further, even when the same amount of current flows, the TFT size can be made smaller in the n-channel TFT. Therefore, it is preferable to use the n-channel type TFT as the current control TFT because the effective area of the display portion is increased.

The p-channel type TFT has the advantage that hot carrier injection hardly causes a problem and the off-current value is low. Examples of using it as a switching TFT and an example of using it as a current control TFT have already been reported. However, in the present invention, the problem of hot carrier injection and the problem of the off-current value are solved even in the n-channel TFT by adopting a structure in which the position of the LDD region is changed, and all the TFTs in all the pixels are replaced by the n-channel TFT. Another feature is that the TFT is used.

However, in the present invention, it is not necessary to limit the switching TFT and the current control TFT to n-channel TFTs, and it is possible to use p-channel TFTs for both or any one of them.

The switching TFT 201 includes a source region 13, a drain region 14, LDD regions 15a to 15d,
High concentration impurity region 16 and channel forming regions 17a, 1
Active layer including 7b, gate insulating film 18, gate electrode 19
a, 19b, a first interlayer insulating film 20, a source wiring 21, and a drain wiring 22.

Further, as shown in FIG.
A and 19b have a double gate structure electrically connected by a gate wiring 211 formed of another material (a material having a lower resistance than the gate electrodes 19a and 19b). Of course, not only a double gate structure but also a so-called multi-gate structure (a structure including an active layer having two or more channel forming regions connected in series) such as a triple gate structure may be used. The multi-gate structure is extremely effective in reducing the off-state current value. In the present invention, a switching element with a low off-state current value is realized by using a multi-gate structure for the pixel switching element 201.

The active layer is formed of a semiconductor film having a crystal structure. That is, a single crystal semiconductor film, a polycrystalline semiconductor film, or a microcrystalline semiconductor film may be used. Further, the gate insulating film 18 may be formed using an insulating film containing silicon. As the gate electrode, the source wiring, or the drain wiring, any conductive film can be used.

Further, in the switching TFT 201, the LDD regions 15a to 15d
Are provided so as not to overlap with the gate electrodes 19a and 19b through the gate electrode. Such a structure is very effective in reducing the off-current value.

It is more preferable to provide an offset region (a region formed of a semiconductor layer having the same composition as the channel forming region and to which no gate voltage is applied) between the channel forming region and the LDD region in order to reduce the off-current value. . In the case of a multi-gate structure including two or more gate electrodes, a high-concentration impurity region provided between channel formation regions is effective in reducing an off-current value.

As described above, a TFT having a multi-gate structure
Is used as the switching element 201 of the pixel, a switching element with sufficiently low off-state current can be realized. Therefore, Japanese Patent Application Laid-Open No. 10-189252
The gate voltage of the current controlling TFT can be maintained for a sufficient time (between selection and the next selection) without providing a capacitor as shown in FIG.

That is, it is possible to eliminate the capacitor which has conventionally been a factor of reducing the effective light emitting area,
It is possible to increase the effective light emitting area. This means that the image quality of the EL display device can be made bright.

Next, the current controlling TFT 202 includes an active layer including the source region 31, the drain region 32, the LDD region 33 and the channel forming region 34, the gate insulating film 18, the gate electrode 35, the first interlayer insulating film 20, It is formed to have a wiring 36 and a drain wiring 37. The gate electrode 35 has a single gate structure, but may have a multi-gate structure.

As shown in FIGS. 3A and 3B, the drain of the switching TFT is connected to the current control TF.
It is connected to the gate of T. Specifically, T for current control
The gate electrode 35 of the FT 202 is the switching TFT 2
01 is electrically connected to a drain region 14 via a drain wiring (also referred to as a connection wiring) 22. Also,
Source wiring 36 is connected to current supply line 212.

The current controlling TFT 202 is an EL element 203
Is an element for controlling the amount of current injected into the
Considering the deterioration of the L element, it is not preferable to flow too much current. Therefore, it is preferable to design the channel length (L) to be longer so that an excessive current does not flow through the current controlling TFT 202. Desirably, it is 0.5 to 2 μA (preferably 1 to 1.5 μA) per pixel.

In view of the above, as shown in FIG. 9, the channel length of the switching TFT is set to L1 (where
1 = L1a + L1b), when the channel width is W1, the channel length of the current controlling TFT is L2, and the channel width is W2, W1 is 0.1 to 5 μm (typically 0.5 to 2 μm).
m), W2 is 0.5 to 10 μm (typically 2 to 5 μm)
It is preferred that L1 is 0.2 to 18 μm
(Typically 2 to 15 μm), and L2 is preferably 1 to 50 μm (typically 10 to 30 μm). However, the present invention is not limited to the above numerical values.

By setting these numerical ranges, VGA
From the EL display device having the number of pixels of the class (640 × 480), the number of pixels of the HDTV class (1920 × 108)
0 or 1280 × 1024) can cover all standards.

The length (width) of the LDD region formed in the switching TFT 201 is 0.5 to 3.5 μm.
Typically, the thickness may be 2.0 to 2.5 μm.

In the EL display device shown in FIG. 2, the LDD region 33 is provided between the drain region 32 and the channel forming region 34 in the current controlling TFT 202.
Further, the LDD region 33 is characterized in that the LDD region 33 has a region overlapping the gate electrode 35 with the gate insulating film 18 interposed therebetween and a region not overlapping.

The current controlling TFT 202 is connected to the EL element 20.
At the same time as supplying a current for causing the light emitting device 4 to emit light, the supplied amount is controlled to enable gradation display. Therefore, it is necessary to take measures against deterioration by hot carrier injection so that the deterioration does not occur even when a current flows. When displaying black, the current control TFT 202 is turned off. However, in this case, if the off-current value is high, a clear black display cannot be performed, which causes a decrease in contrast and the like. Therefore, it is necessary to suppress the off-current value.

With respect to deterioration due to hot carrier injection, it is known that a structure in which an LDD region overlaps a gate electrode is very effective. However,
If the entire LDD region is overlapped with the gate electrode, the off-current value increases. Therefore, the present applicant has developed a new structure in which an LDD region that does not overlap the gate electrode is provided in series, thereby taking measures against hot carriers and off-current values. And solve at the same time.

At this time, the length of the LDD region overlapping the gate electrode is 0.1 to 3 μm (preferably 0.3 to 1.5 μm).
m). If the length is too long, the parasitic capacitance is increased, and if it is too short, the effect of preventing hot carriers is weakened. The length of the LDD region that does not overlap with the gate electrode is 1.0 to 3.5 μm (preferably 1.5 to 3.5 μm).
2.0 μm). If it is too long, a sufficient current cannot be supplied, and if it is too short, the effect of reducing the off-current value becomes weak.

In the above structure, the gate electrode and the LD
Since a parasitic capacitance is formed in a region where the D region overlaps, it is preferable not to provide the parasitic capacitance between the source region 31 and the channel formation region 34. Since the current control TFT always has the same flowing direction of carriers (here, electrons), it is sufficient to provide an LDD region only on the drain region side.

However, the driving voltage (voltage applied between the source region and the drain region) of the current controlling TFT 202 is 1
When the voltage is lower than 0 V, hot carrier injection hardly causes a problem, so that the LDD region 33 can be omitted. In this case, the active layer includes a source region 31, a drain region 32, and a channel forming region.

From the viewpoint of increasing the amount of current that can flow, the thickness of the active layer (particularly, the channel formation region) of the current controlling TFT 202 is increased (preferably 50).
To 100 nm, more preferably 60 to 80 nm). Conversely, in the case of the switching TFT 201, from the viewpoint of reducing the off-current value, the thickness of the active layer (particularly, the channel formation region) is reduced (preferably 20 to 50 nm, more preferably 25 to 40 n).
m) is also effective.

Next, reference numeral 41 denotes a first passivation film having a thickness of 10 nm to 1 μm (preferably 200 to 50 μm).
0 nm). As a material, an insulating film containing silicon (in particular, a silicon nitride oxide film or a silicon nitride film is preferable) can be used. The passivation film 41 has a role of protecting the formed TFT from an alkali metal or moisture. The EL layer finally provided above the TFT contains an alkali metal such as sodium. That is, the first passivation film 41 also functions as a protective layer that does not allow these alkali metals (mobile ions) to enter the TFT side.

It is also effective to make the first passivation film 41 have a heat radiation effect to prevent the EL layer from being thermally degraded. However, since the EL display device having the structure of FIG. 2 emits light toward the substrate 11, the first passivation film 41 needs to have translucency. In the case where an organic material is used for the EL layer, it is preferable that an insulating film from which oxygen is easily released be not used because the EL layer is deteriorated by bonding with oxygen.

[0048] Prevents the penetration of alkali metals, and furthermore has a heat dissipation effect
B (boron), C (charcoal)
Element) or at least one element selected from N (nitrogen)
And Al (aluminum), Si (silicon), P (phosphorus)
Insulating film containing at least one element selected from
I can do it. For example, aluminum nitride (AlxNy)
Representative nitrides of aluminum, silicon carbide (SixC
y), silicon carbide and silicon nitride (SixN
y), boron nitride (BxN)
y), a boron nitride represented by boron nitride (Bx
Py phosphide represented by Py) can be used.
Noh. Also, substitute for aluminum oxide (AlxOy)
The expressed aluminum oxide has excellent translucency and thermal conductivity
The rate is 20Wm^-1K ^-1Is one of the preferred materials
You. These materials not only have the above effects, but also
There is also the effect of preventing. Note that, in the light-transmitting material,
x and y are arbitrary integers.

The above compound may be combined with another element. For example, by adding nitrogen to aluminum oxide, aluminum nitride oxide represented by AlNxOy can be used. This material not only has a heat dissipation effect, but also has an effect of preventing intrusion of moisture, alkali metal and the like. In the above aluminum nitride oxide, x, y
Is any integer.

Further, the materials described in JP-A-62-90260 can be used. That is, Si, A
an insulating film containing l, N, O, and M (where M is at least one of rare earth elements, preferably Ce (cerium), Yb
(Ytterbium), Sm (samarium), Er (erbium), Y (yttrium), La (lanthanum), G
d (gadolinium), Dy (dysprosium), Nd
(At least one element selected from (neodymium)). These materials have not only a heat dissipation effect, but also an effect of preventing intrusion of moisture, alkali metal and the like.

It is also possible to use a carbon film containing at least a diamond thin film or an amorphous carbon film (especially one having characteristics close to diamond, called diamond-like carbon or the like). These have extremely high thermal conductivity and are extremely effective as heat dissipation layers. However, when the film thickness increases, the film becomes brownish and the transmittance decreases, and thus it is preferable to use the film as thin as possible (preferably 5 to 100 nm).

Since the purpose of the first passivation film 41 is to protect the TFT from alkali metals and moisture, the effect of the first passivation film 41 must not be impaired. Therefore, a thin film made of the material having the above-described heat radiation effect can be used alone. However, these thin films and an insulating film (typically, a silicon nitride film (SixNy) or a nitrided Silicon film (SiOxN
It is effective to stack y)). Note that in the above silicon nitride film or silicon nitride oxide film, x and y are arbitrary integers.

On the first passivation film 41, a second interlayer insulating film (which may be referred to as a flattening film) 44 is formed so as to cover each TFT, and a step formed by the TFT is flattened. . As the second interlayer insulating film 44, an organic resin film is preferable, and polyimide, polyamide, acrylic,
BCB (benzocyclobutene) or the like is preferably used. Of course, if sufficient planarization is possible, an inorganic film may be used.

It is very important that the step caused by the TFT is flattened by the second interlayer insulating film 44. Since an EL layer formed later is extremely thin, poor light emission may be caused by the presence of a step. Therefore, it is desirable that the EL layer be flattened before forming the pixel electrode so that the EL layer can be formed as flat as possible.

Reference numeral 45 denotes a second passivation film, which plays an important role in blocking an alkali metal diffused from the EL element. The thickness may be 5 nm to 1 μm (typically 20 to 300 nm). As the second passivation film 45, an insulating film that can prevent permeation of alkali metal is used. As the material, the material used for the first passivation film 41 can be used.

The second passivation film 45 also functions as a heat dissipation layer that functions to release heat generated in the EL element and prevent heat from being accumulated in the EL element. Further, when the second interlayer insulating film 44 is an organic resin film, it is weak to heat, so that the heat generated in the EL element does not adversely affect the second interlayer insulating film 44.

As described above, it is effective to flatten the TFT with an organic resin film in manufacturing an EL display device. However, there is no conventional structure in which the deterioration of the organic resin film due to heat generated in the EL element is taken into consideration. . One of the features of the present invention is that the point is solved by providing the second passivation film 45.

Further, the second passivation film 45 functions as a protective layer for preventing the alkali metal in the EL layer from diffusing to the TFT side while preventing the deterioration due to the above-mentioned heat. It also functions as a protective layer for preventing moisture and oxygen from entering from the TFT side.

Reference numeral 46 denotes a pixel electrode (anode of an EL element) made of a transparent conductive film.
5, second interlayer insulating film 44 and first passivation film 4
After a contact hole (opening) is formed in the TFT 1, the opening is formed so as to be connected to the drain wiring 37 of the current controlling TFT 202.

Next, an EL layer (strictly speaking, an E layer in contact with the pixel electrode) is used.
The L layer 47 is formed by a coating process using a dispenser. The EL layer 47 is used in a single layer or a laminated structure, but is often used in a laminated structure. However, in the case of laminating, it is desirable to combine the coating method and the vapor phase method (particularly, preferably the vapor deposition method). In the application method, since a solvent and an EL material are mixed and applied, if there is an organic material on the base, there is a possibility that the organic material may be dissolved again.

Accordingly, a layer of the EL layer 47 that directly touches the pixel electrode is formed by a coating process using a dispenser.
After that, it is preferable to form by a gas phase method. Of course, all the layers can be formed with a dispenser as long as it can be applied using a solvent in which the EL material of the lower layer does not dissolve. The layers directly touching the pixel electrode include a hole injection layer,
Although there may be a hole transport layer or a light emitting layer, the present invention can be used in forming either layer.

In the present invention, since a coating process using a dispenser is used as a method for forming the EL layer, it is preferable to use a polymer material as the EL material. Representative polymer-based materials include polyparaphenylenevinylene (PPV), polyvinylcarbazole (PVK),
A polymer material such as polyfluorene is used.

In order to form a hole injection layer, a hole transport layer, or a light emitting layer made of a polymer material by a coating process using a dispenser, a polymer precursor is applied and heated in a vacuum. With this, it is converted into an EL material made of a polymer material. Then, the EL required by vapor deposition or the like
Materials are stacked to form a stacked EL layer.

Specifically, for the hole transport layer, it is preferable to use polytetrahydrothiophenylphenylene, which is a polymer precursor, and to convert it to polyphenylenevinylene by heating. The film thickness is 30 to 100 nm (preferably 4
(0 to 80 nm). Also, as the light emitting layer,
Preferably, cyanopolyphenylenevinylene is used for the red light emitting layer, polyphenylenevinylene is used for the green light emitting layer, and polyphenylenevinylene or polyalkylphenylene is used for the blue light emitting layer. The film thickness is 30 to 150 nm (preferably 40 to
100 nm).

Further, a pixel electrode and an EL formed thereon are formed.
It is also effective to provide copper phthalocyanine as a buffer layer between the material.

However, the above example is an example of the organic EL material that can be used as the EL material of the present invention, and it is not necessary to limit to this. In the present invention, an EL layer is formed by applying a mixture of an EL material and a solvent with a dispenser and vaporizing and removing the solvent. Accordingly, any combination of EL materials may be used as long as the combination does not exceed the glass transition temperature of the EL layer when the solvent is vaporized.

Typically, an organic solvent such as chloroform, dichloromethane, γ-butyl lactone, butyl cellosolve or NMP (N-methyl-2-pyrrolidone) may be used as a solvent, or water may be used. Also,
It is also effective to add an additive for increasing the viscosity of the EL product.

When the EL layer 47 is formed, it is preferable that the processing atmosphere be a dry atmosphere with a minimum amount of moisture and be performed in an inert gas. Since the EL layer is easily deteriorated by the presence of moisture and oxygen, it is necessary to eliminate such factors as much as possible when forming the EL layer. For example, a dry nitrogen atmosphere or a dry argon atmosphere is preferable. For this purpose, it is desirable to install the dispenser in a clean booth filled with an inert gas and perform the coating process in that atmosphere.

After the EL layer 47 is formed as described above, a cathode 48 and a protection electrode 49 are formed next. The cathode 48 and the protection electrode 49 may be formed by a vacuum evaporation method. Further, by forming the cathode 48 and the protection electrode 49 continuously without exposing them to the atmosphere, the deterioration of the EL layer 47 can be further suppressed. In this specification, a light emitting element formed of a pixel electrode (anode), an EL layer, and a cathode is referred to as E.
It is called an L element.

As the cathode 48, a material containing magnesium (Mg), lithium (Li) or calcium (Ca) having a small work function is used. Preferably MgAg
(Material in which Mg and Ag are mixed at Mg: Ag = 10: 1)
May be used. In addition, MgAgAl electrode,
A LiAl electrode and a LiFAl electrode are mentioned. The protection electrode 49 is an electrode provided to protect the cathode 48 from external moisture and the like, and is made of aluminum (A).
l) or a material containing silver (Ag) is used. The protection electrode 48 also has a heat radiation effect.

It is desirable that the EL layer 47 and the cathode 48 are continuously formed in a dried inert atmosphere without being released to the atmosphere. This is because when an organic material is used for the EL layer, it is very weak to moisture, so that it does not absorb moisture when exposed to the atmosphere. Further, it is more preferable to continuously form not only the EL layer 47 and the cathode 48 but also the protective electrode 49 thereon.

The structure shown in FIG. 2 is an example in the case of using a monochromatic light emitting method for forming one type of EL element corresponding to any of RGB. Although only one pixel is shown in FIG. 2, a plurality of pixels having the same structure are arranged in a matrix in the pixel portion. A known material may be used for the EL layer corresponding to any of RGB.

In addition to the above method, a white light emitting EL
A method in which a device and a color filter are combined, an EL device emitting blue or blue-green light and a phosphor (fluorescent color conversion layer: CC
M), and a method in which a transparent electrode is used as a cathode (counter electrode) and an EL element corresponding to RGB is overlapped to perform color display. Of course, it is also possible to perform monochrome display by forming a white light emitting EL layer as a single layer.

A third passivation film 50 has a thickness of 10 nm to 1 μm (preferably 200 to 50 μm).
0 nm). The purpose of providing the third passivation film 50 is mainly to protect the EL layer 47 from moisture, but may have a heat radiation effect similarly to the second passivation film 45. Therefore, the same material as the first passivation film 41 can be used as a forming material. However, in the case where an organic material is used for the EL layer 47, it is preferable that an insulating film from which oxygen is easily released be not used since the EL layer 47 may be deteriorated by bonding with oxygen.

Further, since the EL layer is weak to heat as described above, it is desirable to form the film at a temperature as low as possible (preferably in a temperature range from room temperature to 120 ° C.). Therefore, it can be said that a plasma CVD method, a sputtering method, a vacuum evaporation method, an ion plating method, or a solution coating method (spin coating method) is a preferable film forming method.

As described above, the second passivation film 45
Is sufficient to suppress the deterioration of the EL element. However, more preferably, the EL element is formed of a two-layer insulating film sandwiching the EL element such as a second passivation film 45 and a third passivation film 50. Surrounded by a film, the intrusion of moisture and oxygen into the EL layer is prevented, the diffusion of alkali metal from the EL layer is prevented, and the accumulation of heat in the EL layer is prevented. As a result, deterioration of the EL layer is further suppressed, and a highly reliable EL display device can be obtained.

The EL display device of the present invention has a pixel portion composed of pixels having a structure as shown in FIG. 1, and TFTs having different structures according to functions are arranged in the pixels. With this, the switching TFT with sufficiently low off current value
In addition, a current controlling TFT resistant to hot carrier injection can be formed in the same pixel, and an EL display device having high reliability and capable of displaying a good image (high operating performance) can be obtained.

Although a multi-gate TFT is used as a switching TFT in the pixel structure of FIG. 1, it is not necessary to limit the configuration such as the arrangement of the LDD regions to the configuration of FIG.

The present invention having the above configuration will be described in more detail with reference to the following embodiments.

[Embodiment 1] FIG. 4 shows an embodiment of the present invention.
This will be described with reference to FIG. Here, a method for simultaneously manufacturing TFTs of a pixel portion and a driving circuit portion provided therearound is described. However, for the sake of simplicity, a CMOS circuit, which is a basic circuit, is illustrated for the drive circuit.

First, as shown in FIG. 4A, a base film 301 is formed on a glass substrate 300 to a thickness of 300 nm. In this embodiment, a silicon nitride oxide film is stacked and used as the base film 301. At this time, the nitrogen concentration in contact with the glass substrate 300 is preferably set to 10 to 25 wt%.

It is effective to provide an insulating film made of the same material as the first passivation film 41 shown in FIG. 2 as a part of the base film 301. Current control TFT
Since a large current flows, heat is easily generated, and it is effective to provide an insulating film having a heat radiation effect as close as possible.

Next, an amorphous silicon film (not shown) having a thickness of 50 nm is formed on the base film 301 by a known film forming method. Note that the present invention is not limited to an amorphous silicon film, and may be any semiconductor film including an amorphous structure (including a microcrystalline semiconductor film). Further, a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used. The film thickness is 2
The thickness may be 0 to 100 nm.

Then, the amorphous silicon film is crystallized by a known technique, and a crystalline silicon film (also called a polycrystalline silicon film or a polysilicon film) 302 is formed. Known crystallization methods include a thermal crystallization method using an electric furnace, a laser annealing crystallization method using laser light, and a lamp annealing crystallization method using infrared light. In this embodiment, X
Crystallization is performed using excimer laser light using eCl gas.

In this embodiment, a pulse oscillation type excimer laser beam processed into a linear shape is used, but a rectangular shape may be used, or a continuous oscillation type argon laser beam or a continuous oscillation type excimer laser beam may be used. You can also.

In this embodiment, a crystalline silicon film is used as an active layer of a TFT, but an amorphous silicon film can be used. However, in order to reduce the area of the current controlling TFT as much as possible and to increase the aperture ratio of the pixel, it is more advantageous to use a crystalline silicon film through which a current can easily flow.

It is effective to form the active layer of the switching TFT for which the off current needs to be reduced with an amorphous silicon film and the active layer of the current controlling TFT with a crystalline silicon film. Since the amorphous silicon film has a low carrier mobility, it is difficult for an electric current to flow and an off current is hard to flow. That is, the advantages of both an amorphous silicon film through which a current is hard to flow and a crystalline silicon film through which a current easily flows can be utilized.

Next, as shown in FIG. 4B, a protective film 303 made of a silicon oxide film is
It is formed to a thickness of nm. This thickness is 100-200 nm
(Preferably 130 to 170 nm). Further, any other insulating film containing silicon may be used.
The protective film 303 is provided to prevent the crystalline silicon film from being directly exposed to plasma when adding impurities and to enable fine concentration control.

Then, a resist mask 304 is formed thereon.
a and 304b are formed, and an impurity element imparting n-type (hereinafter, referred to as an n-type impurity element) is added via the protective film 303. Note that the n-type impurity element is typically 15
Elements belonging to the group, typically phosphorus or arsenic, can be used. In this embodiment, phosphine (PH ₃ )
Is added at a concentration of 1 × 10 ¹⁸ atoms / cm ³ using a plasma doping method in which plasma is excited without mass separation. Of course, an ion implantation method for performing mass separation may be used.

In the n-type impurity regions 305 and 306 formed in this step, the n-type impurity element contains 2 × 10 ^{16 to} 5 × 10 ^16.
× 10 ¹⁹ atoms / cm ³ (typically 5 × 10 ^{17 to} 5 × 10
^The dose is adjusted so as to be contained at a concentration of ¹⁸ atoms / cm ³ ).

Next, as shown in FIG.
03 is removed, and the added element belonging to Group 15 is activated. As the activating means, a known technique may be used. In this embodiment, the activating means is activated by excimer laser light irradiation.
Needless to say, a pulse oscillation type or a continuous oscillation type may be used, and it is not necessary to limit to an excimer laser beam. However, since the purpose is to activate the added impurity element, it is preferable that the irradiation be performed with energy that does not melt the crystalline silicon film. Note that laser light irradiation may be performed with the protective film 303 attached.

When activating the impurity element by the laser beam, activation by heat treatment may be used in combination. When activation by heat treatment is performed, heat treatment at about 450 to 550 ° C. may be performed in consideration of the heat resistance of the substrate.

By this step, n-type impurity regions 305, 3
A boundary portion (junction portion) between the end portion 06 and the region around the n-type impurity regions 305 and 306 to which the n-type impurity element is not added becomes clear. This is later explained by TF
When T is completed, it means that the LDD region and the channel forming region can form a very good junction.

Next, as shown in FIG. 4D, unnecessary portions of the crystalline silicon film are removed, and an island-shaped semiconductor film (hereinafter, referred to as an island-shaped semiconductor film) is formed.
307 to 310 are formed.

Next, as shown in FIG.
A gate insulating film 311 is formed to cover the layers 07 to 310.
As the gate insulating film 311, an insulating film containing silicon with a thickness of 10 to 200 nm, preferably 50 to 150 nm may be used. This may have a single-layer structure or a laminated structure. In this embodiment, a 110-nm-thick silicon nitride oxide film is used.

Next, a conductive film having a thickness of 200 to 400 nm is formed and patterned to form gate electrodes 312 to 316. Note that in this embodiment, the gate electrode and a wiring for wiring (hereinafter, referred to as a gate wiring) electrically connected to the gate electrode are formed using different materials. Specifically, a material having lower resistance than the gate electrode is used for the gate wiring. This is because a material that can be finely processed is used for the gate electrode, and a material that does not allow fine processing and has low wiring resistance is used for the gate wiring. Of course, the gate electrode and the gate wiring may be formed of the same material.

The gate electrode may be formed of a single-layer conductive film, but is preferably formed as a two-layer or three-layer film as required. As a material for the gate electrode, any known conductive film can be used. However, a material that can be finely processed as described above, specifically, a material that can be patterned into a line width of 2 μm or less is preferable.

Typically, tantalum (Ta), titanium (Ti), molybdenum (Mo), tungsten (W),
A film made of an element selected from chromium (Cr) and silicon (Si), a nitride film of the above element (typically, a tantalum nitride film, a tungsten nitride film, a titanium nitride film), or an alloy combining the above elements Membrane (typically Mo-W
Alloy, a Mo—Ta alloy), or a silicide film of the above element (typically, a tungsten silicide film or a titanium silicide film) can be used. Of course, they may be used as a single layer or stacked.

In this embodiment, a 50 nm thick tungsten nitride (WN) film and a 350 nm thick tungsten (W)
A laminated film composed of a film is used. This may be formed by a sputtering method. When an inert gas such as Xe or Ne is added as a sputtering gas, the film can be prevented from peeling due to stress.

At this time, the gate electrodes 313 and 316 are formed so as to overlap a part of the n-type impurity regions 305 and 306 with the gate insulating film 311 interposed therebetween. This overlapping portion later becomes an LDD region overlapping with the gate electrode.

Next, as shown in FIG. 5A, an n-type impurity element (phosphorus in this embodiment) is added in a self-aligned manner using the gate electrodes 312 to 316 as a mask. The n-type impurity regions 3 are formed in the impurity regions 317 to 323 thus formed.
1/2, 1/10 of 05, 306 (typically 1/3 to
Adjust so that phosphorus is added at a concentration of 1/4). Specifically, a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms / cm ³ (typically, 3 × 10 ^{17 to} 3 × 10 ¹⁸ atoms / cm ³ ) is preferable.

Next, as shown in FIG. 5B, resist masks 324a to 324d are formed so as to cover the gate electrodes and the like, and an n-type impurity element (phosphorus in this embodiment) is added to increase the concentration. The impurity regions 325 to 331 containing phosphorus are formed. Also in this case, the ion doping method using phosphine (PH ₃ ) is performed, and the phosphorus concentration in this region is 1 × 10 ²⁰ to 1
× 10 ²¹ atoms / cm ³ (typically 2 × 10 ^{20 to} 5 × 10
Adjust so as to be ²⁰ atoms / cm ³ ).

In this step, a source region or a drain region of the n-channel TFT is formed. In the switching TFT, a part of the n-type impurity regions 320 to 322 formed in the step of FIG. The remaining regions correspond to the LDD regions 15a to 15d of the switching TFT in FIG.

Next, as shown in FIG. 5C, the resist masks 324a to 324d are removed, and a new resist mask 332 is formed. Then, a p-type impurity element (boron in this embodiment) is added to form impurity regions 333 and 334 containing boron at a high concentration. Here, diborane (B
3 × 10 ²⁰ to 3 × by ion doping using ₂ H ₆ )
10 ²¹ atoms / cm ³ (typically 5 × 10 ²⁰ to 1 × 10 ²¹ a
toms / cm ³ ) Add boron to a concentration.

Note that phosphorus is already added to the impurity regions 333 and 334 at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms / cm ³ , and the boron added here is at least three times as large as that. It is added at a concentration. Therefore, the n-type impurity region formed in advance is completely inverted to P-type and functions as a P-type impurity region.

Next, after removing the resist mask 332, the n-type or p-type impurity element added at each concentration is activated. As the activation means, a furnace annealing method, a laser annealing method, or a lamp annealing method can be used. In this embodiment, heat treatment is performed in an electric furnace at 550 ° C. for 4 hours in a nitrogen atmosphere.

At this time, it is important to eliminate oxygen in the atmosphere as much as possible. This is because the presence of even a small amount of oxygen oxidizes the exposed surface of the gate electrode, causing an increase in resistance and making it difficult to obtain an ohmic contact later. Therefore, the oxygen concentration in the processing atmosphere in the activation step is 1 ppm or less, preferably 0.1 ppm or less.
pm or less.

Next, when the activation step is completed,
A thick gate wiring 335 is formed. As a material of the gate wiring 335, a metal film containing aluminum (Al) or copper (Cu) as a main component (of which composition occupies 50 to 100%) may be used. The arrangement is such that the gate electrode 3 of the switching TFT is arranged like the gate wiring 211 in FIG.
14 and 315 (corresponding to the gate electrodes 19a and 19b in FIG. 3A) are formed so as to be electrically connected. (FIG. 5
(D))

With such a structure, the wiring resistance of the gate wiring can be extremely reduced, so that an image display region (pixel portion) having a large area can be formed. That is, the pixel structure of the present embodiment is extremely effective in realizing an EL display device having a screen size of 10 inches or more (more preferably 30 inches or more) diagonally.

Next, as shown in FIG. 6A, a first interlayer insulating film 336 is formed. As the first interlayer insulating film 336, an insulating film containing silicon may be used as a single layer or a stacked film obtained by combining them. The film thickness is 400 n
m to 1.5 μm. In this embodiment, 200n
A structure in which a silicon oxide film having a thickness of 800 nm is stacked over a silicon nitride oxide film having a thickness of m is provided.

Further, in an atmosphere containing 3 to 100% of hydrogen, a heat treatment is performed at 300 to 450 ° C. for 1 to 12 hours to perform a hydrogenation treatment. This step is a step of terminating dangling bonds of the semiconductor film with thermally excited hydrogen.
As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.

The hydrogenation treatment is performed for the first interlayer insulating film 336.
May be inserted during formation. That is, a hydrogenation treatment may be performed as described above after a 200-nm-thick silicon nitride oxide film is formed, and then a remaining 800-nm-thick silicon oxide film may be formed.

Next, a contact hole is formed in the first interlayer insulating film 336, and source wirings 337 to 340 are formed.
Drain wirings 341 to 343 are formed. In this embodiment, this electrode is a three-layer laminated film in which a titanium film is formed to a thickness of 100 nm, an aluminum film containing titanium is formed to a thickness of 300 nm, and a titanium film is formed to a thickness of 150 nm. Of course, other conductive films may be used.

Next, 50 to 500 nm (typically 20 to 500 nm)
The first passivation film 34 with a thickness of
4 is formed. In this embodiment, the first passivation film 3
A silicon nitride oxide film having a thickness of 300 nm is used as 44. This may be replaced by a silicon nitride film. Of course, it is possible to use the same material as the first passivation film 41 in FIG.

Note that, prior to the formation of the silicon nitride oxide film, H
_2. It is effective to perform a plasma treatment using a gas containing hydrogen such as NH ₃ . Hydrogen excited by this pretreatment is supplied to the first interlayer insulating film 336, and by performing a heat treatment, the film quality of the first passivation film 344 is improved. At the same time, the hydrogen added to the first interlayer insulating film 336 diffuses to the lower layer side, so that the active layer can be effectively hydrogenated.

Next, as shown in FIG. 6B, a second interlayer insulating film 347 made of an organic resin is formed. As the organic resin, polyimide, polyamide, acrylic, BCB (benzocyclobutene), or the like can be used. In particular, since the second interlayer insulating film 347 has a strong meaning of flattening, acrylic having excellent flatness is preferable. In this embodiment, the TFT
The acrylic film is formed to a thickness that can sufficiently flatten the step formed by the above. The thickness is preferably 1 to 5 μm (more preferably 2 to 4 μm).

Next, 100n is formed on the second interlayer insulating film 347.
An m-thick second passivation film 348 is formed. In this embodiment, since an insulating film containing Si, Al, N, O, and La is used, diffusion of an alkali metal from an EL layer provided thereon can be prevented. At the same time, moisture is prevented from penetrating into the EL layer, and heat generated in the EL layer is dispersed, whereby deterioration of the EL layer and deterioration of the flattening film (second interlayer insulating film) due to heat can be suppressed. .

Then, the second passivation film 348,
Second interlayer insulating film 347 and first passivation film 34
4, a contact hole reaching the drain wiring 343 is formed, and a pixel electrode 349 is formed. In this embodiment, an indium tin oxide (ITO) film is formed to a thickness of 110 nm and patterned to form a pixel electrode. This pixel electrode 349 becomes the anode of the EL element. Note that as other materials, an indium-titanium oxide film or a film in which zinc oxide is mixed with ITO can be used.

In this embodiment, the pixel electrode 349 is electrically connected to the drain region 331 of the current controlling TFT via the drain wiring 343. This structure has the following advantages.

Since the pixel electrode 349 comes into direct contact with an organic material such as an EL layer (light emitting layer) and a charge transporting layer,
There is a possibility that mobile ions contained in the L layer and the like diffuse in the pixel electrode. That is, in the structure of this embodiment, the pixel electrode 349 is not directly connected to the drain region 331 which is a part of the active layer, but the relay of the drain wiring 343 can prevent the penetration of mobile ions into the active layer. .

Next, as shown in FIG. 6C, the EL layer 3
50 is formed by the coating process using the dispenser described with reference to FIG.
The Ag electrode 351 and the protection electrode 352 are formed without being exposed to the atmosphere. At this time, it is preferable that heat treatment be performed on the pixel electrode 349 before forming the EL layer 350 and the cathode 351 to completely remove moisture. In addition,
In this embodiment, a MgAg electrode is used as the cathode of the EL element, but another known material may be used.

Note that the EL layer 350

The materials described in the section of the present invention can be used. In this embodiment, the hole transport layer (Hole transportin
g layer) and a light-emitting layer (Emitting layer) are used as the EL layer, but any of a hole injection layer, an electron injection layer, and an electron transport layer may be provided. Various examples of such combinations have already been reported, and any of these configurations may be used.

In this embodiment, a polymer precursor, polytetrahydrothiophenylphenylene, is formed by a printing method as a hole transporting layer, and is heated to polyphenylenevinylene. The light emitting layer is formed by vapor deposition of a 30% to 40% molecular dispersion of PBD of a 1,3,4-oxadiazole derivative in polyvinyl carbazole, and about 1% of coumarin 6 is used as a green light emitting center. Has been added.

Although the protection layer 352 can protect the EL layer 350 from moisture and oxygen, it is more preferable to provide the third passivation film 353. In this embodiment, a silicon nitride film having a thickness of 300 nm is provided as the third passivation film 353. This third passivation film may be formed continuously after the protection electrode 352 without being exposed to the atmosphere. Of course, as the third passivation film 353, the third passivation film 5 of FIG.
The same material as 0 can be used.

Further, the protection electrode 352 is formed of the MgAg electrode 35.
A metal film mainly provided with aluminum and provided to prevent the oxidation of 1 is typical. Of course, other materials may be used. In addition, since the EL layer 350 and the MgAg electrode 351 are extremely weak to moisture, it is desirable to form the protection electrode 352 up to the protection electrode 352 continuously without opening to the atmosphere to protect the EL layer from the outside air.

Note that the total thickness of the EL layer 350 is 1
0 to 400 nm (typically 60 to 160 nm, preferably 100 to 120 nm), and the thickness of the MgAg electrode 351 is 80 to 200 nm (typically 100 to 150 nm).
It is good.

Thus, an active matrix type EL display device having a structure as shown in FIG. 6C is completed. By the way, the active matrix EL display device of the present embodiment has a TF having an optimal structure not only for the pixel portion but also for the drive circuit portion.
By arranging T, very high reliability can be exhibited and operating characteristics can be improved.

First, a TFT having a structure in which hot carrier injection is reduced so as not to lower the operation speed as much as possible,
N-channel type TFT of CMOS circuit forming drive circuit
Used as 205. Note that the drive circuit here includes a shift register, a buffer, a level shifter, a sampling circuit (a sample and hold circuit), and the like. When digital driving is performed, a signal conversion circuit such as a D / A converter may be included.

In the case of this embodiment, as shown in FIG. 6C, the active layer of the n-channel TFT 205 includes a source region 355, a drain region 356, an LDD region 357, and a channel forming region 358, and the LDD region 357 Overlaps the gate electrode 313 with the gate insulating film 311 interposed therebetween.

The reason why the LDD region is formed only on the drain region side is to prevent the operating speed from being lowered.
Further, the n-channel TFT 205 does not need to care much about the off-current value, and it is better to emphasize the operation speed. Therefore, it is desirable that the LDD region 357 be completely overlapped with the gate electrode and the resistance component be reduced as much as possible. That is, it is better to eliminate the so-called offset.

Also, a p-channel type TFT of a CMOS circuit
In 206, since the deterioration due to hot carrier injection is hardly noticeable, an LDD region need not be particularly provided. Of course, it is also possible to provide an LDD region similarly to the n-channel type TFT 205 and take measures against hot carriers.

Note that among the driving circuits, the sampling circuit is a little special as compared with other circuits, and a large current flows in both directions in the channel forming region. That is, the roles of the source region and the drain region are switched. In addition, it is necessary to keep the off-current value as low as possible, and in that sense, it is desirable to arrange a TFT having a function approximately between the switching TFT and the current control TFT.

Therefore, it is desirable to arrange the TFT having the structure as shown in FIG. 10 as the n-channel TFT forming the sampling circuit. As shown in FIG.
Part of the regions 901 a and 901 b overlap with the gate electrode 903 with the gate insulating film 902 interposed therebetween. This effect is as described in the description of the current control TFT 202, and is different in that a sampling circuit is provided so as to sandwich the channel formation region 904.

In fact, when completed up to FIG. 6C, a protective film (laminate film, ultraviolet curable resin film, etc.) with high airtightness and low degassing so as not to be further exposed to the outside air, or a ceramic sealing can is used. It is preferable to package (enclose) with a housing material such as. At this time, the interior of the housing material is made to have an inert atmosphere, or a hygroscopic material (for example, barium oxide)
Is arranged, the reliability (lifetime) of the EL layer is improved.

When the airtightness is enhanced by processing such as packaging, a connector (flexible printed circuit: FPC) for connecting terminals routed from elements or circuits formed on the substrate to external signal terminals. To complete the product. Such an EL display device that can be shipped is referred to as an EL module in this specification.

Here, the configuration of the active matrix type EL display device of this embodiment will be described with reference to the perspective view of FIG.
The active matrix EL display device of this embodiment includes a pixel portion 602, a gate driver circuit 603, and a source driver circuit 604 formed on a glass substrate 601. The switching TFT 605 of the pixel portion is an n-channel TFT, and is arranged at an intersection of a gate wiring 606 connected to the gate driver circuit 603 and a source wiring 607 connected to the source driver circuit 604. The drain of the switching TFT 605 is connected to the gate of the current control TFT 608.

Further, the source side of the current control TFT 608 is connected to the current supply line 609 and the current control TFT 6
The EL element 610 is connected to the drain 08.

An FPC 61 serving as an external input / output terminal
1 includes input / output wirings (connection wirings) 612 and 613 for transmitting signals to the drive circuit, and input / output wirings 614 connected to the current supply line 609.

FIG. 8 shows an example of a circuit configuration of the EL display device shown in FIG. The EL display device according to this embodiment includes a source-side drive circuit 701 and a gate-side drive circuit (A) 70.
7, a gate side driver circuit (B) 711, and a pixel portion 706. In this specification, a drive circuit is a generic term including a source-side processing circuit and a gate-side drive circuit.

The source side driving circuit 701 includes a shift register 702, a level shifter 703, a buffer 704, and a sampling circuit (sample and hold circuit) 705. The gate side driver circuit (A) 707 includes a shift register 708, a level shifter 709, a buffer 7
10 is provided. The gate side driver circuit (B) 711 has the same configuration.

Here, the shift registers 702 and 708 have a drive voltage of 5 to 16 V (typically 10 V), and are n-channel TFTs used in a CMOS circuit forming the circuit.
Is suitable for the structure shown by 205 in FIG.

The level shifters 703 and 709 and the buffers 704 and 710 are similar to the shift registers in FIG.
A CMOS circuit including the n-channel TFT 205 shown in FIG. The gate wiring has a double gate structure,
The use of a multi-gate structure such as a triple gate structure is effective in improving the reliability of each circuit.

Since the source and drain regions of the sampling circuit 705 are inverted and the off-current value needs to be reduced, a CMOS circuit including the n-channel TFT 208 shown in FIG. 10 is suitable.

In the pixel portion 706, pixels having the structure shown in FIG. 2 are arranged.

The above structure can be easily realized by manufacturing a TFT according to the manufacturing steps shown in FIGS. In this embodiment, only the configuration of the pixel portion and the driving circuit is shown. However, according to the manufacturing process of this embodiment, other components such as a signal dividing circuit, a D / A converter circuit,
It is considered that a logic circuit other than a drive circuit such as an operational amplifier circuit and a gamma correction circuit can be formed over the same substrate, and that a memory portion, a microprocessor, and the like can be formed.

Further, an EL module of this embodiment including a housing material will be described with reference to FIGS. 11 (A) and 11 (B). The reference numerals used in FIGS. 7 and 8 will be referred to as needed.

Substrate (including base film below TFT) 170
0, a pixel portion 1701, a source side driver circuit 1702,
A gate side drive circuit 1703 is formed. Various wirings from each drive circuit are input / output wirings 612 to 61
4 to the FPC 611 to be connected to an external device.

At this time, the housing material 170 is formed so as to surround at least the pixel portion, preferably the driving circuit and the pixel portion.
4 is provided. Note that the housing member 1704 is connected to the pixel portion 17.
01 is a shape or a sheet shape having a concave portion whose inner dimension (depth) is larger than the outer dimension (height) of the substrate 1700, and is fixed to the substrate 1700 by the adhesive 1705 so as to form a closed space together with the substrate 1700. Is done. At this time, the EL element is completely sealed in the closed space, and is completely shut off from the outside air. Note that a plurality of housing members 1704 may be provided.

The material of the housing member 1704 is preferably an insulating material such as glass or polymer. For example, amorphous glass (borosilicate glass, quartz, etc.), crystallized glass,
Examples include ceramic glass, organic resins (acrylic resin, styrene resin, polycarbonate resin, epoxy resin, etc.) and silicone resins. Further, ceramics may be used. If the adhesive 1705 is an insulating substance, a metal material such as a stainless steel alloy can be used.

Further, as the material of the adhesive 1705, an adhesive such as an epoxy resin or an acrylate resin can be used. Further, a thermosetting resin or a photocurable resin can be used as the adhesive. However, it is necessary that the material does not transmit oxygen and moisture as much as possible.

Further, a gap 1706 between the housing material and the substrate 1700 is formed by an inert gas (argon, helium,
Nitrogen or the like). Further, not only gas but also an inert liquid (liquid fluorinated carbon represented by perfluoroalkane or the like) can be used. As the inert liquid, a material as used in JP-A-8-78159 may be used.

It is also effective to provide a desiccant in the gap 1706. As a desiccant, JP-A-9-1480
No. 66 can be used. Typically, barium oxide may be used.

Further, as shown in FIG. 11B, a plurality of pixels having individually isolated EL elements are provided in the pixel portion, and all of them have the protective electrode 1707 as a common electrode. In this embodiment, it is preferable that the EL layer, the cathode (MgAg electrode), and the protection electrode are formed continuously without opening to the atmosphere. However, the EL layer and the cathode are formed using the same mask material, and only the protection electrode is separately formed. 11B, the structure shown in FIG. 11B can be realized.

At this time, the EL layer and the cathode need only be provided in the pixel portion, and need not be provided on the driving circuit. Of course, there is no problem even if it is provided on the drive circuit.
Considering that the layer contains an alkali metal, it is preferable not to provide the layer.

The protection electrode 1707 is connected to the input / output wiring 1709 in a region indicated by 1708.
The input / output wiring 1709 is a wiring for applying a predetermined voltage (ground potential, specifically, 0 V in this embodiment) to the protection electrode 1707, and is connected to the FPC 611 via the conductive paste material 1710.

Here, a manufacturing process for realizing the contact structure in the region 1708 will be described with reference to FIGS.

First, according to the steps of this embodiment, FIG.
Get the state of. At this time, the first interlayer insulating film 336 and the gate insulating film 311 are removed at the end of the substrate (the region indicated by 1708 in FIG. 11B), and the input / output wiring 1709 is formed thereon. Needless to say, it is formed simultaneously with the source wiring and the drain wiring in FIG. (FIG. 12
(A))

Next, when etching the second passivation film 348, the second interlayer insulating film 347, and the first passivation film 344 in FIG. 6B, the region indicated by 1801 is removed, and the opening 1802 is formed. To form (FIG. 12 (B))

In this state, a process of forming an EL element (a process of forming a pixel electrode, an EL layer, and a cathode) is performed in the pixel portion.
At this time, in a region shown in FIG. 12B, an EL element is not formed using a mask material. Then, after forming the cathode 351, the protective electrode 3 is formed using another mask material.
52 is formed. Thus, the protection electrode 352 and the input / output wiring 1709 are electrically connected. Further, a third passivation film 353 is provided to obtain a state shown in FIG.

Through the above steps, 1708 in FIG.
The contact structure in the region indicated by is realized. The input / output wiring 1709 has a gap between the housing material 1704 and the substrate 1700 (however, the adhesive 1705 is filled with the adhesive 1705. That is, the adhesive 1705 needs to have a thickness enough to flatten the step of the input / output wiring. FPC through
611. Here, the input / output wiring 170
9, the other output wirings 612 to 614 also pass under the housing material 1704 in the same manner.
11 is connected.

[Embodiment 2] In this embodiment, an example in which the pixel configuration is different from the configuration shown in FIG.
Shown in

In this embodiment, the two pixels shown in FIG. 3B are arranged symmetrically with respect to the current supply line 212. That is, as shown in FIG. 13, by sharing the current supply line 212 between two adjacent pixels, the number of required wirings can be reduced. Note that the TFT structure and the like arranged in the pixel may be unchanged.

With such a configuration, it is possible to manufacture a higher definition pixel portion, and the quality of an image is improved.

The structure of this embodiment can be easily realized according to the manufacturing process of Embodiment 1. For the TFT structure and the like, the description of Embodiment 1 and FIGS.

[Embodiment 3] In this embodiment, the case of forming a pixel portion having a structure different from that of FIG. 2 will be described with reference to FIG. The first embodiment may be followed up to the step of forming the second interlayer insulating film 44. The switching TFT 201 and the current control TF covered with the second interlayer insulating film 44
T202 has the same structure as that of FIG.

In the case of this embodiment, after contact holes are formed in the second passivation film 45, the second interlayer insulating film 44, and the first passivation film 41, the pixel electrode 51 is formed, and then the cathode 52 and the EL layer 53 are formed. To form In this embodiment, after forming the cathode 52 by a vacuum evaporation method,
The EL layer 53 is formed by a coating process using the dispenser shown in FIG. 1 while maintaining the dried inert atmosphere.

In this embodiment, as the pixel electrode 51, 150
An aluminum alloy film (an aluminum film containing 1 wt% titanium) having a thickness of nm is provided. Note that any material may be used as the material of the pixel electrode as long as it is a metal material, but a material having high reflectance is preferable. A 120 nm thick MgAg electrode is used as the cathode 52, and the EL layer 53 has a thickness of 70 nm.

In this example, polyvinyl carbazole was added with 1,3,4-oxadiazole derivative PBD from 30 to
40% molecular dispersion, about 1 coumarin 6 as emission center
% Is used as an EL material, which is mixed with chloroform to produce an EL product. Then, the EL product is applied by a coating process using a dispenser and baked to obtain a green light emitting layer having a thickness of 50 nm.
Then, a TPD having a thickness of 70 nm is formed thereon by an evaporation method to obtain an EL layer 53.

Next, a transparent conductive film (ITO in this embodiment)
The anode 54 made of a film is formed to a thickness of 110 nm. Thus, the EL element 209 is formed. If the third passivation film 55 is formed using the material described in the first embodiment, a pixel having a structure as shown in FIG. 14 is completed.

In the case of the structure of this embodiment, green light generated in each pixel is emitted to the side opposite to the substrate on which the TFT is formed. Therefore, almost the entire area within the pixel, that is, the TFT
Can be used as an effective light emitting region. As a result, the effective light emitting area of the pixel is significantly improved, and the brightness and contrast ratio (brightness / darkness ratio) of the image are improved.

The structure of this embodiment can be freely combined with any of the structures of Embodiments 1 and 2.

[Embodiment 4] In the first to third embodiments, the case of a top gate type TFT has been described.
It is not limited to the structure, so the bottom gate type T
The present invention may be implemented by using an FT (typically, an inverted staggered TFT). Further, the inverted staggered TFT may be formed by any means.

Since the inverted staggered TFT has a structure in which the number of steps is easily reduced as compared with the top gate type TFT, it is very advantageous in reducing the manufacturing cost which is an object of the present invention. The configuration of the present embodiment can be freely combined with any of the configurations of the second and third embodiments.

Fifth Embodiment In the structure of FIG. 6C or FIG. 2 of the first embodiment, as a base film provided between the active layer and the substrate, a high heat radiation effect is obtained as in the case of the second passivation film 45. It is effective to use materials. In particular, the current control TFT is likely to generate heat due to the flow of current for a long time, which may cause deterioration due to self-heating. In such a case, the thermal deterioration of the TFT can be prevented by the heat radiation effect of the base film as in this embodiment.

Of course, the effect of preventing mobile ions and the like diffused from the substrate is also important. Therefore, similarly to the first passivation film 41, a stack of a compound containing Si, Al, N, O, M and an insulating film containing silicon is used. It is also preferred to use a structure.

The structure of this embodiment can be freely combined with any of the structures of the first to fourth embodiments.

[Embodiment 6] In the case of the pixel structure shown in Embodiment 3, since the light emitted from the EL layer is radiated to the side opposite to the substrate, the insulating film or the like existing between the substrate and the pixel electrode There is no need to worry about transmittance. That is, a material having a somewhat low transmittance can be used.

Therefore, it is advantageous to use a carbon film called a diamond thin film or an amorphous carbon film as the base film 12, the first passivation film 41 or the second passivation film 45. That is, since there is no need to worry about a decrease in transmittance, the film thickness can be set to be as large as 100 to 500 nm, and the heat radiation effect can be further enhanced.

In the case where the above-mentioned carbon film is used as the third passivation film 50, it is preferable that the film thickness is set to about 5 to 100 nm, since a decrease in transmittance should be avoided.

In this embodiment, the base film 12, the first passivation film 41, and the second passivation film 4 are also used.
Regardless of whether a carbon film is used for the fifth or third passivation film 50, it is effective to use the carbon film laminated with another insulating film.

This embodiment is particularly effective when the pixel structure shown in Embodiment 3 is used.
Any combination of 2, 4, or 5 can be freely combined.

[Embodiment 7] In the present invention, the switching TFT has a multi-gate structure in the pixel of the EL display device, thereby reducing the off-current value of the switching TFT and eliminating the necessity of a storage capacitor. This is a device for effectively utilizing the area occupied by the storage capacitor as a light emitting region.

However, even if the storage capacitor cannot be completely eliminated, the effect of increasing the effective light emitting area can be obtained only by reducing the occupied area. That is, the switching TF
By making T a multi-gate structure, it is sufficient to reduce the off-current value and reduce the area occupied by the storage capacitor.

In this case, as shown in FIG. 15, the current control TF is connected to the drain of the switching TFT 201.
The storage capacitor 1401 may be formed in parallel with the gate of T202.

The structure of this embodiment can be freely combined with any of the structures of Embodiments 1 to 6. That is, only the storage capacitor is provided in the pixel, and TF
It does not limit the material of the T structure or the EL layer.

[Eighth Embodiment] In the first embodiment, laser crystallization is used as a means for forming the crystalline silicon film 302. In this embodiment, a case where a different crystallization means is used will be described.

In this embodiment, after forming the amorphous silicon film, crystallization is performed by using the technique described in Japanese Patent Application Laid-Open No. Hei 7-130652. The technique described in this publication is a technique for obtaining a crystalline silicon film having high crystallinity by using an element such as nickel as a catalyst for promoting (promoting) crystallization.

After the crystallization step is completed, a step of removing the catalyst used for crystallization may be performed. In that case, JP-A-10-270363 or JP-A-8-3
The catalyst may be gettered by the technique described in No. 30602.

Also, Japanese Patent Application No. Hei 11-076 filed by the present applicant.
TFT using the technology described in the application specification No. 967
May be formed.

As described above, the manufacturing process shown in Embodiment 1 is one embodiment, and if the structure shown in FIG. 2 or FIG. There is no problem with using it.

The structure of this embodiment can be freely combined with any of the structures of Embodiments 1 to 7.

[Embodiment 9] In driving the EL display device of the present invention, an analog drive using an analog signal as an image signal or a digital drive using a digital signal can be performed.

When analog driving is performed, an analog signal is sent to the source wiring of the switching TFT, and the analog signal including the gradation information becomes the gate voltage of the current controlling TFT. Then, a current flowing through the EL element is controlled by the current control TFT, and the emission intensity of the EL element is controlled to perform gradation display. Note that in the case of performing analog driving, the current control TFT is preferably operated in a saturation region.

On the other hand, when digital driving is performed, gradation display called time-division driving is performed, unlike analog gradation display. That is, by adjusting the length of the light emission time, the color gradation is visually changed. When digital driving is performed, the current control TFT is preferably operated in a linear region.

Since the EL element has a much higher response speed than the liquid crystal element, it can be driven at a high speed. Therefore, it can be said that the element is suitable for time division driving in which one frame is divided into a plurality of subframes and gradation display is performed.

As described above, since the present invention is a technology relating to the element structure, any driving method may be used.

[Embodiment 10] In Embodiment 1, it is preferable to use an organic EL material for the EL layer. However, the present invention can be implemented by using an inorganic EL material. However, since a current inorganic EL material has a very high driving voltage, a TFT having a withstand voltage characteristic capable of withstanding such a driving voltage must be used in performing analog driving.

Alternatively, if an inorganic EL material having a further lower driving voltage is developed in the future, it can be applied to the present invention.

The structure of this embodiment can be freely combined with any of the structures of the first to ninth embodiments.

[Embodiment 11] An active matrix EL display device (EL module) formed by carrying out the present invention is of a self-luminous type, and therefore has better visibility in a bright place than a liquid crystal display device. I have. Therefore, direct-view EL
It is widely used as a display (refers to a display incorporating an EL module).

One of the advantages of the EL display over the liquid crystal display is the wide viewing angle. Therefore, to watch TV broadcasts on a large screen, the diagonal 3
The EL display of the present invention may be used as a display (display monitor) of 0 inches or more (typically, 40 inches or more).

In addition to being used as an EL display (a personal computer monitor, a TV broadcast receiving monitor, an advertisement display monitor, etc.), it can be used as a display for various electronic devices.

[0203] Examples of such electronic devices include a video camera, a digital camera, a goggle type display (head mounted display), a car navigation system, a personal computer, a portable information terminal (mobile computer, mobile phone or electronic book, etc.), and a recording medium. Equipped image reproducing device (specifically, compact disc (CD),
Plays a recording medium such as a laser disk (registered trademark) (LD) or a digital versatile disk (DVD),
Device having a display capable of displaying the image). FIG. 16 shows examples of these electronic devices.

FIG. 16A shows a personal computer, which includes a main body 2001, a housing 2002, a display portion 2003,
And a keyboard 2004. The present invention can be used for the display portion 2003.

FIG. 16B shows a video camera, which includes a main body 2101, a display portion 2102, an audio input portion 2103, operation switches 2104, a battery 2105, and an image receiving portion 210.
6 inclusive. The present invention can be used for the display portion 2102.

FIG. 16C shows a part (right side) of a head-mounted EL display, which includes a main body 2201, a signal cable 2202, a fixed head band 2203, a display monitor 2204, an optical system 2205, and a display device 2206. including. The present invention can be used for the display device 2206.

FIG. 16D shows an image reproducing apparatus (specifically, a DVD reproducing apparatus) provided with a recording medium.
1, a recording medium (CD, LD, DVD, etc.) 2302,
An operation switch 2303, a display unit (a) 2304, and a display unit (b) 2305 are included. The display device (a) mainly displays image information, and the display device (b) mainly displays character information. The present invention can be used for these display portions (a) and (b). Note that the present invention can be applied to a CD playback device, a game machine, and the like as an image playback device provided with a recording medium.

FIG. 16E shows a portable computer, which includes a main body 2401, a camera section 2402, an image receiving section 2403, operation switches 2404, and a display section 2405. The present invention can be used for the display portion 2405.

FIG. 16F shows an EL display.
A housing 2501, a support 2502, a display portion 2503, and the like are included. The present invention can be used for the display portion 2503. E
Since the L display has a wide viewing angle, it is advantageous when the screen is enlarged as compared with the liquid crystal display.
This is advantageous in displays larger than inches (especially, 30 inches or more on a diagonal).

If the emission luminance of the EL material becomes higher in the future, it becomes possible to enlarge and project the light containing the output image information with a lens or the like and use it for a front-type or rear-type projector.

As described above, the applicable range of the present invention is extremely wide, and can be applied to electronic devices in various fields. Further, the electronic device of this embodiment can be realized by freely combining Embodiments 1 to 10.

[0212]

According to the present invention, the EL layer can be formed very inexpensively. Therefore, manufacturing cost for manufacturing the EL display device is reduced.

Further, by providing an insulating film between the EL layer and the TFT that can prevent the transmission of the alkali metal, it is possible to prevent the alkali metal from diffusing from the EL layer and adversely affecting the TFT characteristics. As a result, the operation performance and reliability of the EL display device can be significantly improved.

Further, by using an inexpensive EL display device as a display, the manufacturing cost of the electronic device can be reduced. In addition, by using an EL display device with improved operation performance and reliability, it is possible to produce a durable (highly reliable) applied product (electronic device) with good image quality.

[Brief description of the drawings]

FIG. 1 is a view for explaining an application step using a dispenser of the present invention.

FIG. 2 is a diagram illustrating a cross-sectional structure of a pixel portion of an EL display device of the present invention.

FIG. 3 is a diagram showing a top structure and a configuration of a pixel portion of an EL display device of the present invention.

FIG. 4 is a diagram showing a manufacturing process of the active matrix EL display device of Example 1.

FIG. 5 is a diagram showing a manufacturing process of the active matrix EL display device of Example 1.

FIG. 6 is a diagram showing a manufacturing process of the active matrix EL display device of Example 1.

FIG. 7 is a diagram illustrating an appearance of the EL module according to the first embodiment.

FIG. 8 is a diagram illustrating a circuit block configuration of the EL display device according to the first embodiment.

FIG. 9 is an enlarged view of a pixel portion of an EL display device of the present invention.

FIG. 10 is a diagram showing an element structure of a sampling circuit of the EL display device according to the first embodiment.

FIG. 11 is a top view and a cross-sectional view of the EL module according to the first embodiment.

FIG. 12 is a diagram showing a manufacturing process of the contact structure of the first embodiment.

FIG. 13 is a diagram illustrating a configuration of a pixel portion of an EL display device according to a second embodiment.

FIG. 14 is a diagram illustrating a cross-sectional structure of a pixel portion of an EL display device according to a third embodiment.

FIG. 15 is a diagram illustrating a circuit block configuration according to a seventh embodiment.

FIG. 16 is a diagram showing a specific example of the electronic device of the eleventh embodiment.

Claims (10)

[Claims] 1. A method for manufacturing an electro-optical device, comprising applying an EL product using a dispenser. 2. A method for manufacturing an electro-optical device, comprising applying an EL product linearly using a dispenser. 3. A step of forming a plurality of semiconductor elements on a substrate surface; a step of forming a plurality of pixel electrodes connected to each of the plurality of semiconductor elements; and an EL product on the plurality of pixel electrodes A method of manufacturing an electro-optical device, comprising: applying an EL material to the electro-optical device using a dispenser. 4. A step of forming a plurality of semiconductor elements on a substrate surface; a step of forming a plurality of pixel electrodes connected to each of the plurality of semiconductor elements; and an EL formation on the plurality of pixel electrodes And applying a heat treatment to the EL product after the EL product is applied using a dispenser. A method for manufacturing an electro-optical device, comprising: 5. A step of forming a plurality of semiconductor elements on a substrate surface; a step of forming a plurality of pixel electrodes connected to each of the plurality of semiconductor elements; Forming an EL material; and forming a second EL material on the first EL material by a vapor phase method, wherein the first EL material is formed by dispersing an EL product using a dispenser. A method for manufacturing an electro-optical device, wherein the method is formed by applying a liquid. 6. A step of forming a plurality of semiconductor elements on a substrate surface; a step of forming a plurality of pixel electrodes connected to each of the plurality of semiconductor elements; Forming an EL material, and forming a second EL material on the first EL material by a vapor phase method, wherein the first EL material is formed by applying an EL product. , Said E
A method for manufacturing an electro-optical device, characterized by being formed by subjecting an L-formed product to a heat treatment. 7. The method for manufacturing an electro-optical device according to claim 1, wherein the EL product is a mixture of an EL material and a solvent. 8. The method according to claim 7, wherein the EL material is an organic compound. 9. An electro-optical device according to claim 1, wherein the EL product is applied by a dispenser in a clean booth filled with an inert gas. Method. 10. The method for manufacturing an electro-optical device according to claim 3, wherein the EL product is applied linearly.