JP2006243767A - Liquid crystal electrooptical apparatus and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal electrooptical apparatus having satisfactory display characteristics. <P>SOLUTION: The liquid crystal electrooptical apparatus has a glass substrate, a thin-film transistor formed on the glass substrate, a flattening film formed on the thin-film transistor, a pixel electrode consisting of a transparent conductive film formed on the flattening film, a liquid crystal layer having nematic liquid crystal formed by using a die casting method on the pixel electrode, a counter electrode composed of the transparent conductive film on the liquid crystal layer, and a translucent resin on the counter electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an active display device, and more particularly to an active electro-optical device, a television set, and a wall-mounted television set, in which a clear gradation level can be set.

The liquid crystal composition has different dielectric constants in the horizontal and vertical directions with respect to the molecular axis due to its material properties, so it can be easily aligned horizontally or vertically with respect to an external electric field. Can be. The liquid crystal electro-optical device performs ON / OFF display by controlling the amount of transmitted light or the amount of dispersion using the anisotropy of the dielectric constant.

FIG. 2 shows the electro-optical characteristics of the nematic liquid crystal. When the applied voltage is Va (A point 101), the amount of transmitted light is almost 0%, Vb (B point 102) is about 30%, Vc (C point 103) is about 80%, Vd ( In the case of D point 104), it becomes about 100%. In other words, if only the points A and D are used, black and white two-tone display can be performed, and if the rising portion of the electro-optical characteristics such as points B and C is used, intermediate gray-scale display can be performed. As specific voltages confirmed by the present inventors, Va = 2.0V, Vb = 2.18V, Vc = 2.3V, Vd = 2.5V
Met.

Conventionally, in the case of gradation display of a liquid crystal electro-optical device using a TFT, gradation display is performed by adjusting the voltage in an analog manner by changing the gate applied voltage of the TFT or the applied voltage between the source and the drain.

A more detailed explanation will be given regarding the gradation display method of the liquid crystal electro-optical device using TFT. Conventionally, an n-channel thin film transistor used in a liquid crystal electro-optical device is shown in FIG.
It has the voltage-current characteristics as shown in The voltage-current characteristics shown in FIG. 3 are the characteristics 201 of the n-channel thin film transistor using amorphous silicon and the n-type using polysilicon.
This is a characteristic 202 of the channel thin film transistor.

By controlling the voltage applied to the gate electrode in an analog manner, the drain current can be controlled, and as a result, the resistance value between the source and the drain is changed. As a result, the magnitude of the electric field applied to the series-connected liquid crystal can be arbitrarily changed by the resistance division. As a result, gradation display is possible. On the contrary, there is a method in which the gate electrode is connected to the scanning signal line and the voltage between the source and drain is changed to arbitrarily control the electric field value itself applied to the liquid crystal.

In either method, there is no difference in the analog gradation display method that greatly depends on the characteristics of the TFT. However, it is difficult to make all of a large number of TFT elements having a matrix configuration so as to have uniform characteristics. In particular, the fine adjustment of the intermediate voltage required for gradation display is extremely difficult with the current technology. What is needed is the current situation. As can be seen from the electro-optical characteristics of the nematic liquid crystal shown in FIG. 2, all the values between 0.32V between the dark state boundary value of 2.08V and the bright state boundary value of 2.40V are obtained. Tone display must be performed. If 16 gradations are assumed, control at an average interval of 0.02 V is required.

If the liquid crystal is completely turned on / off, such as point A 101 and point D 104 shown in FIG. 2, the voltage difference can be 0.5 V or more.
It is worth reducing the variation in the in-plane characteristics. Using a plurality of writing frames, for example, 6 frames out of 10 frames are turned ON (2.5 V) and the remaining 4 frames are turned OFF (2.
0V), the average writing voltage becomes 2.3V, and intermediate gradation display is possible.

However, in this case, since a plurality of frames are used, there is a risk that a display of 30 Hz or less that can be visually confirmed by human eyes may occur, and depending on conditions, it may cause display defects such as flicker. . As a method for preventing this, speeding up of the driving frequency has been proposed, but the data transfer speed of the driver IC is limited to about 20 MHz, which is difficult.

Therefore, the present invention proposes means for supplying a clear gradation display level to the liquid crystal by performing digital gradation display instead of the conventional analog gradation display, and in that case, Rather than the method of gradation display by simply increasing the drive frequency as proposed in the past, the digital gradation without changing the frame frequency by making the data transfer frequency and gradation display frequency independent. It is characterized by displaying.

According to the present invention, in an active matrix liquid crystal display device, gradation display of a display device using a display driving method having a display timing related to a unit time t for writing to an arbitrary pixel and a time F for writing one screen is described above. Without changing the time F, the signal during the writing time of the time t is time-divided, whereby the average value of the electric field applied to the liquid crystal of the pixel at the time t is changed according to the division ratio, and the gradation is changed. It is characterized by enabling display.

In the case of the conventional display device, the electric field applied to the pixel electrode is determined by the strength of the electric field of the signal line in the data direction, thereby determining the transmittance of the liquid crystal.

In the present invention, such analog gradation control is not performed, but a signal during a writing time of a unit time t written to an arbitrary pixel is time-divided, and gradations corresponding to the number of divisions can be displayed. . At that time, the electric field change in the writing time becomes an average value in the non-writing time, and clear gradation display is possible.

As for the data transfer rate on the information signal side, for example, in the case of a liquid crystal electro-optical device having a 1920 × 400 dot configuration, a clock frequency of 5.76 MHz is required for 8-bit parallel transfer.
In addition, when the conventional multi-frame method is used, if 10 frames are used, 5 is simply used.
A clock frequency of 7.6 MHz is required. However, in the case of the present invention, since the clock frequency for gradation display is taken independently, when an IC having a driving capability of 8 MHz at the maximum is used, it is possible to display up to about 166 gradations. If a 12.3 MHz drive IC is used, the 256 gray scale display, which is said to be necessary for visual use, will be possible, and it will be a significant advantage over conventional analog and multi-frame digital gray scale displays. Sex occurs. Further detailed description will be given below with examples.

The present invention is characterized in that digital gradation display is performed using two independent drive frequencies, compared to the conventional analog gradation display. For example, 640
When assuming a liquid crystal electro-optical device having a pixel number of × 400 dots, a total of 256,00
It is extremely difficult to fabricate the characteristics of all 0 TFTs without variation. In reality, considering the mass productivity and the yield, 16 gradation display is considered to be the limit. In order to clarify the voltage level, the reference voltage value is input from the controller as a signal instead of the analog value, and the voltage applied to the TFT is controlled by controlling the timing of connecting the reference signal to the TFT with a digital value. The feature of the present invention is that the method of covering the characteristic variation of the TFT is controlled by controlling the above, and therefore clear digital gradation display is possible.

In addition, by using two types of drive frequencies, clear digital gradation display is possible without changing the number of frames for screen rewriting. The occurrence of flicker associated with a decrease in the number of frames can be avoided.

When digital gradation display according to the present invention is performed, it is difficult to be affected by variations in characteristics of TFT elements, and therefore, up to about 64 gradations is possible. In color display, a variety of 262,144 colors and subtle colors are displayed. Has been realized. When projecting software such as TV images,
For example, even the “rock” of the same color has a slightly different hue due to its fine depressions. When a display close to natural colors is to be performed, it is difficult to use 4096 colors with 16 gradations. The gradation display according to the present invention makes it possible to add these minute color tone changes.

Example 1 (Image Display Device / Television) In this example, a wall-mounted television is manufactured using a liquid crystal display device having a circuit configuration as shown in FIG. In addition, the TFT at that time is polycrystalline silicon using laser annealing, and is a stagger type.

An arrangement configuration of actual electrodes and the like corresponding to this circuit configuration is shown in FIG. In order to simplify the explanation, only the portion corresponding to 2 × 2 (or less) is shown. The actual drive signal waveform is shown in FIG. In order to simplify the description, the description will be given with the signal waveform in the case of a 2 × 2 matrix configuration.

First, a method for manufacturing a liquid crystal panel used in this embodiment will be described with reference to FIGS. FIG.
), A blocking layer 51 using a magnetron RF (high frequency) sputtering method on a glass 50 that can withstand a heat treatment of less expensive 700 ° C. or less, such as about 600 ° C., such as quartz glass.
The silicon oxide film is made to a thickness of 1000 to 3000 mm. Process conditions are oxygen 1
The atmosphere was 00%, the film forming temperature was 15 ° C., the output was 400 to 800 W, and the pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 cm / min.

A silicon film was formed thereon by plasma CVD. The film formation temperature is 250.
In this embodiment, the temperature was set to 320 ° C., and monosilane (SiH ₄ ) was used. Not only monosilane (SiH ₄ ) but also disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) may be used. These were introduced at a pressure of 3 Pa in the PCVD apparatus, and a high frequency power of 13.56 MHz was applied to form a film. At this time, 0.02 to 0.10 W / cm ² is appropriate as the high frequency power, and 0.055 W / cm ² was used in this example. The flow rate of monosilane (SiH ₄ ) is 20 SCCM,
The film formation speed at that time was about 120 cm / min. NTFT threshold voltage (V
In order to control th), boron may be added during film formation at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ using diborane. Further, not only the plasma CVD method but also a sputtering method and a low pressure CVD method may be used for forming a silicon layer which becomes a channel region of the TFT, and the method will be briefly described below.

When the sputtering method is used, the back pressure before sputtering is set to 1 × 10 ⁻⁵ Pa or less, the target is single crystal silicon, and the atmosphere is mixed with 20 to 80% hydrogen in argon. For example, 20% argon and 80% hydrogen. The film forming temperature is 150 ° C., the frequency is 13.56 MHz,
The sputtering output was 400 to 800 W, and the pressure was 0.5 Pa.

When formed by a vacuum gas phase method, 450 to 550 ° C., which is 100 to 200 ° C. lower than the crystallization temperature.
For example, disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) was supplied to a CVD apparatus at 530 ° C. to form a film. The pressure in the reactor was 30 to 300 Pa. Deposition rate is 50-250mm
/ Minutes.

The film formed by these methods preferably has oxygen of 5 × 10 ²¹ cm ⁻³ or less. In order to promote crystallization, the oxygen concentration is 7 × 10 ¹⁹ cm ⁻³ or less, preferably 1 × 10 ¹⁹ cm.
^-3 or less is desirable, but if it is too small, the leakage current in the off state is increased by the backlight, so this concentration was selected. If this oxygen concentration is high, it is difficult to crystallize, the laser annealing temperature must be high, or the laser annealing time must be lengthened. Hydrogen was 4 × 10 ²⁰ cm ⁻³ , and compared with silicon 4 × 10 ²² cm ⁻³ , it was 1 atomic%.

In addition, the oxygen concentration is set to 7 × 10 ¹⁹ cm in order to promote crystallization to the source and drain.
⁻³ or less, preferably 1 × 10 ¹⁹ cm ⁻³ or less, and oxygen is added only to the channel formation region of the TFT constituting the pixel so as to be 5 × 10 ^{20 to} 5 × 10 ²¹ cm ⁻³ by ion implantation. May be.

By the above method, an amorphous silicon film 52 was formed to a thickness of 500 to 5000 mm, in this example, 1000 mm.

Thereafter, as shown in FIG. 6B, the photoresist 53 is removed from the source
A pattern in which only the drain region was opened was formed. A silicon film to be an n-type active layer was formed thereon by plasma CVD. The film formation temperature was 250 ° C. to 350 ° C., and in this example, 320 ° C., and monosilane (SiH ₄ ) and monosilane-based phosphine (PH ₃ ) 3% concentration were used. These were introduced into the PCVD apparatus at a pressure of 5 Pa, and a high frequency power of 13.56 MHz was applied to form a film. At this time, high frequency power, 0.05~0.20W / cm ² are suitable, in the present embodiment, a 0.120W / cm ^2. The specific conductivity of the n-type silicon layer obtained by this method was about 2 × 10 ⁻¹ [Ωcm ⁻¹ ]. The film thickness is 50
I was ecstatic.

On the other hand, as shown in FIG. 6C, a pattern was formed by opening only the source / drain regions of the photoresist 54 using the mask P2. On top of that, the plasma CVD method is used
A silicon film to be the active layer of the mold was produced. The film forming temperature was 250 ° C. to 350 ° C., and in this example, 320 ° C., and monosilane (SiH ₄ ) and monosilane-based diborane (B ₂ H ₆ ) having a concentration of 2% were used. These were introduced into the PCVD apparatus at a pressure of 4 Pa, and a high frequency power of 13.56 MHz was applied to form a film. At this time, high frequency power, 0.05~0.20W / cm ² are suitable, in the present embodiment, a 0.080W / cm ^2. The specific conductivity of the p-type silicon layer completed by this method was about 1 × 10 ⁻¹ [Ωcm ⁻¹ ]. The film thickness was 50 mm.

Thereafter, the source / drain regions 55, 56 and 57, 58 were formed by using a lift-off method. Thereafter, an N-channel thin film transistor island region 63 and a P-channel thin film transistor island region 64 were formed using the mask (P3) 62. (
(Fig. 6 (D))

Thereafter, the source / drain / channel region was laser-annealed using a XeCl excimer laser, and at the same time, the active layer was laser-doped. The laser energy at this time is such that the threshold energy is 130 mJ / cm ² and the entire film thickness melts.
0 mJ / cm ² is required. However, when energy of 220 mJ / cm ² or more is irradiated from the beginning, hydrogen contained in the film is suddenly released, so that the film is broken. For this reason, it is necessary to melt after first expelling hydrogen with low energy. In this embodiment, after performing the purging of the hydrogen in the first 150 mJ / cm ^2, crystallization was performed at 230 mJ / cm ^2.

By annealing, the silicon film moves from an amorphous structure to a highly ordered state, and a part thereof exhibits a crystalline state. In particular, a region having a relatively high order in the state after the film formation of silicon tends to be crystallized into a crystalline state. However, since silicon is bonded to each other by silicon existing between these regions, the silicons are pulled together. When measured by laser Raman spectroscopy, a peak shifted to a lower frequency side than the peak 522 cm ⁻¹ of single crystal silicon is observed.
The apparent particle size is 50 to 500 mm when calculated from the half-value width, but in reality, there are a large number of regions with high crystallinity and a cluster structure. It was possible to form a film having a structure with bonding (anchoring).

As a result, the film exhibits a state that may be said to be substantially free of grain boundary (hereinafter referred to as GB). Since the carriers can easily move to each other through the anchored portions between the clusters, the carrier mobility is higher than that of polycrystalline silicon in which a so-called GB is clearly present. That is, electron mobility (μe) = 15 to 300 cm ² / VSec and hole mobility (μe) = 5 to 100 cm ² / VSec were obtained.

On this, a silicon oxide film was formed as a gate insulating film to a thickness of 500 to 2000 mm, for example, 1000 mm. This was performed under the same conditions as the production of the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix sodium ions.

Thereafter, a silicon film in which phosphorus enters a concentration of 1 to 5 × 10 ²¹ cm ^{−3 on} the upper side or a multilayer of this silicon film and molybdenum (Mo), tungsten (W), MoSi ₂ or WSi ₂ thereon. A film was formed. This was patterned with a fourth photomask 69 to obtain FIG. 6 (E). Gate electrodes 66 and 67 were formed, for example, a channel length of 7 μm, and as a gate electrode, Lind-silicon was formed with a thickness of 0.2 μm, and molybdenum was formed thereon with a thickness of 0.3 μm.

In addition, when aluminum (Al) is used as a gate electrode material, the surface is anodized after patterning with a fourth photomask 69, so that the self-line method can be applied. Since the drain contact hole can be formed at a position closer to the gate, the characteristics of the TFT can be further improved by reducing the mobility and the threshold voltage.

In this way, a C / TFT can be produced without applying temperature in all steps to 400 ° C. or higher. Therefore, it is not necessary to use an expensive substrate such as quartz as the substrate material, and it can be said that this process is extremely suitable for the large-screen liquid crystal display device of the present invention.

In FIG. 6F, the interlayer insulator 68 is formed as a silicon oxide film by the sputtering method described above. The silicon oxide film may be formed by LPCVD, photo CVD, or atmospheric pressure CVD. For example, it is formed to a thickness of 0.2 to 0.6 μm, and then the fifth photomask 7
An electrode window 79 was formed using 0. After that, all the aluminum is further reduced to 0
. A thickness of 3 μm is formed by sputtering, and a lead 74 is formed using a sixth photomask 76.
After forming the contact 73, the interlayer insulator 80 was again formed as a silicon oxide film by the sputtering method described above. The silicon oxide film is formed by LPCVD, photo-CVD,
An atmospheric pressure CVD method may be used. Thereafter, patterning was performed using a seventh photomask 81. Thereafter, aluminum was formed on the whole by sputtering to a thickness of 0.3 μm, and a lead 83 and a contact 84 were produced using an eighth photomask 82. (Fig. 6 (G))

The surface was coated and formed with an organic resin 85 for planarization, for example, a light-transmitting polyimide resin, and electrode drilling was performed again with the ninth photomask 86. Further, ITO (Indium Tin Oxide) was formed to a thickness of 0.1 μm on all of these by sputtering, and a pixel electrode 88 was formed using a tenth photomask 87. This ITO was deposited at room temperature to 150 ° C., and 200 to 40
Achieved with 0 ° C oxygen or atmospheric anneal. (Fig. 6 (H))

As the electrical characteristics of the obtained TFT, the mobility of NTFT is 80 (cm ² / Vs), and Vth is 5.
The mobility of 0 (V), PTFT was 30 (cm ² / Vs), and Vth was 5.5 (V). One substrate for a liquid crystal electro-optical device manufactured according to such a method could be obtained.

A method for manufacturing the other substrate is shown in FIGS. A polyimide resin in which a black pigment is mixed with polyimide is formed over a glass substrate 900 to a thickness of 1 μm by using a spin coating method, and a black stripe 901 is formed using the first photomask 11. Thereafter, a polyimide resin mixed with a red pigment is formed into a thickness of 1 μm using a spin coating method, and the second photomask 12 is formed.
The red filter 902 was produced using Similarly, the green filter 903 using the third photomask 13 and the blue filter 904 using the fourth photomask 14 are used.
Was made. During these production, each filter was baked in nitrogen at 350 ° C. for 60 minutes. Thereafter, the leveling layer 905 was produced using transparent polyimide, also using the spin coat method.

Thereafter, ITO (indium tin oxide) was formed to a thickness of 0.1 μm on all of these by sputtering, and a common electrode 906 was formed using the fifth photomask 15. This ITO
Was formed at room temperature to 150 ° C., and was accomplished by oxygen at 200 to 300 ° C. or annealing in the atmosphere to obtain a second substrate.

A polyimide precursor was printed on the substrate using an offset method, and baked at 350 ° C. for 1 hour in a non-oxidizing atmosphere such as nitrogen. Thereafter, a known rubbing method was used to modify the polyimide surface, and at least initially, means for aligning liquid crystal molecules in a certain direction was provided.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. TAB-shaped drive IC and common signal on the lead on the board,
A PCB having a potential wiring was connected, a polarizing plate was attached on the outside, and a transmissive liquid crystal electro-optical device was obtained.

FIG. 8 is a schematic structural diagram of the electro-optical device according to this embodiment. The liquid crystal panel 1000 obtained in the above process was installed in combination with the rear illumination device 1001 in which three cold cathode tubes were arranged. Thereafter, a tuner 1002 for receiving television radio waves was connected to complete the electro-optical device. Compared to the conventional CRT type electro-optical device, the device has a planar shape and can be installed on a wall or the like.

Next, a peripheral circuit of the liquid crystal electro-optical device for completing the present invention will be described with reference to FIG. Information signal side wirings 350 and 351 connected to the matrix circuit of the liquid crystal electro-optical device
The drive circuit 352 is connected to this. The drive circuit 352 includes two parts when divided by the drive frequency system. One is a data latch circuit system 353 similar to that of the conventional driving system, which is mainly composed of a basic clock φH355 for sequentially transferring data 356, and 1-bit to 12-bit parallel processing is performed. The other one is a component according to the present invention, which includes a clock CLK357, a magnitude comparator circuit 358, and a panel driving buffer 360 corresponding to the division ratio necessary for gradation display. A pulse corresponding to the gradation display data sent from the data latch circuit system 353 is generated by the counter 359.

The features of the present invention are just these portions, and by using two types of drive frequencies, clear digital gradation display is possible without changing the number of frames for screen rewriting. is there. The occurrence of flicker associated with a decrease in the number of frames can be avoided.

The operation waveforms of the C / TFT according to this example are shown in FIGS. FIG. 10 shows this C /
It is an oscilloscope photograph which shows the input signal waveform to TFT and the output signal waveform from C / TFT. From FIG. 10 (A) to FIG. 11 (B), the drive frequency of the input signal is 5 KHz, 50 KHz.
, 500 KHz, and further increased to 1 MHz. As apparent from FIG. 11B, the output signal waveform was not so much even at 1 MHz, and a sufficiently practical output signal could be obtained.
Therefore, the gradation display number can be calculated by dividing the drive frequency by the duty number and the frame number. In this case, a gradation display number of 42 obtained by dividing 1 MHz by 400 and 60 is obtained, and 42 gradation display is possible. ing.

When analog gradation display is performed, 16 gradation display is the limit due to variations in TFT characteristics. However, when digital gradation display according to the present invention is performed, it is difficult to be affected by variations in the characteristics of TFT elements, so that it is possible to display up to 42 gradations.
There are a variety of 088 colors, and subtle colors can be displayed.

Example 2 (View Finder) In this example, a video camera view finder using a liquid crystal electro-optical device having a diagonal of 1 inch was manufactured and the present invention was carried out.

In this example, the first substrate was provided using the same process as that of “Example 1” with a configuration of 387 × 128 pixels. In addition, using a method similar to that of “Example 1” on an insulating substrate,
A color filter and a transparent conductive film ITO were deposited in a thickness of 1000 mm to form a second substrate.

On the substrate, a polyimide precursor is printed using an offset method, and a non-oxidizing atmosphere,
For example, firing was performed at 350 ° C. for 1 hour in nitrogen. Thereafter, a known rubbing method was used to modify the polyimide surface, and at least in the initial stage, means for aligning liquid crystal molecules in a certain direction was provided to form first and second substrates.

Thereafter, the nematic liquid crystal composition was sandwiched between the first substrate and the second substrate, and the periphery was fixed with an epoxy adhesive. Since the pitch of the leads on the substrate is as fine as 46 μm, the connection was made using the COG method. In this embodiment, a method is adopted in which gold bumps provided on an IC chip are connected with an epoxy-based silver palladium resin, and the IC chip and the substrate are buried and fixed with an epoxy-modified acrylic resin for the purpose of fixing and sealing. Using. Thereafter, a polarizing plate was attached to the outside to obtain a transmissive liquid crystal display device.

Since the TFT according to this example has a channel length of 5 μm, the drive frequency can be increased to about 2 MHz. Therefore, it is possible to display up to 260 gradations, approximately 256 gradations, obtained by dividing 2 MHz by 128 and 60. For example, 384 × 128 dots 49,152
When a normal analog gradation display is performed on a liquid crystal electro-optical device in which a set of TFTs is made into a 50 mm square (36 multi-sided from a 300 mm square substrate), the characteristic variation of the amorphous TFT is about ± 10%. Because of the existence, 16 gradation display was the limit. However, when digital gradation display according to the present invention is performed, it is difficult to be affected by variations in characteristics of TFT elements, and therefore, it is possible to display 256 gradations or more, and color display has a variety of 16,777,216 colors. Subtle color display has been realized.

Example 3 (Projection-type image display device)
In this embodiment, a projection type image display apparatus as shown in FIG.

In this embodiment, the projection unit for the projection type image display device is assembled using three liquid crystal electro-optical devices 1300. Each of them has a configuration of 640 × 480 dots, and 307,200 pixels were manufactured in a diagonal of 4 inches. The size per pixel is 127μm
It was a corner.

As a configuration of the projection type image display device, the liquid crystal electro-optical device 1300 is divided and installed for three primary colors of red, green, and blue, and a red filter 1301, a green filter 1302, a blue filter 1303, and a reflection The plate 1304 includes a 150 W metal halide light source 1307 and a focusing optical system 1308.

The substrate of the liquid crystal electro-optical device used in the electro-optical device of this example was a substrate having a matrix circuit having a C / TFT configuration. An element using a high mobility TFT by a low temperature process was formed to constitute a projection type liquid crystal electro-optical device. A method for manufacturing a liquid crystal display device used in this embodiment will be described with reference to FIGS. In FIG. 13A, a silicon oxide film as a blocking layer 602 is formed on a glass 601 that can withstand a heat treatment of less than 700 ° C., for example, about 600 ° C. such as quartz glass, using a magnetron RF (high frequency) sputtering method. 1000
Fabricate to a thickness of ~ 3000 mm. Process conditions are 100% oxygen atmosphere, film forming temperature 15 ° C.
The output was 400 to 800 W and the pressure was 0.5 Pa. The film formation rate using quartz or single crystal silicon for the target was 30 to 100 cm / min.

A silicon film was formed thereon by LPCVD (low pressure vapor phase) method, sputtering method or plasma CVD method. When formed by the reduced pressure gas phase method, it is 100 to 200 ° C. lower than the crystallization temperature 4
Disilane (Si ₂ H ₆ ) or trisilane (Si ₃ H ₈ ) is converted to CV at 50 to 550 ° C., for example, 530 ° C.
The film was supplied to the D apparatus. The pressure in the reactor was 30 to 300 Pa. The deposition rate is 5
It was 0 to 250 kg / min. Boron may be added during film formation at a concentration of 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ using diborane in order to control the threshold voltage (Vth) of PTFT and NTFT to be approximately the same. .

When the sputtering method is used, the back pressure before sputtering is set to 1 × 10 ⁻⁵ Pa or less, the target is single crystal silicon, and the atmosphere is mixed with 20 to 80% hydrogen in argon. For example, 20% argon and 80% hydrogen. The film forming temperature is 150 ° C., the frequency is 13.56 MHz,
The sputtering output was 400 to 800 W, and the pressure was 0.5 Pa.

When a silicon film is formed by plasma CVD, the temperature is, for example, 300 ° C., and monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used. 12. These are introduced into the PCVD apparatus.
A film was formed by applying a high frequency power of 56 MHz.

The film formed by these methods preferably has oxygen of 5 × 10 ²¹ cm ⁻³ or less. If the oxygen concentration is high, it is difficult to crystallize, the thermal annealing temperature must be increased, or the thermal annealing time must be increased. On the other hand, if the amount is too small, the leakage current in the off state increases due to the backlight. Therefore, the range is 4 × 10 ¹⁹ to 4 × 10 ²¹ cm ⁻³ . Hydrogen is
It was 4 × 10 ²⁰ cm ⁻³ , and compared with silicon 4 × 10 ²² cm ⁻³ , it was 1 atomic%.

By the above method, the silicon film in an amorphous state is 500 to 5000 mm, for example 1500
After producing the thickness of the ridge, it was maintained at a temperature of 450 to 700 ° C. for 12 to 70 hours in a non-oxide atmosphere, for example, at a temperature of 600 ° C. in a hydrogen atmosphere. Since an amorphous silicon oxide film is formed on the surface of the substrate under the silicon film, the specific nucleus does not exist in this heat treatment, and the whole is annealed uniformly. That is, at the time of film formation, it has an amorphous structure, and hydrogen is merely mixed.

By annealing, the silicon film shifts from an amorphous structure to a highly ordered state, and a part thereof exhibits a crystalline state. In particular, a region having a relatively high order in the state after silicon film formation is particularly crystallized and tends to be in a crystalline state. However, since silicon is bonded to each other by silicon existing between these regions, the silicons are pulled together. When measured by laser Raman spectroscopy, a peak shifted to a lower frequency side than the peak 522 cm ⁻¹ of single crystal silicon is observed. The apparent grain size is calculated from the half-value width, which is 50 to 500 mm, which is like a microcrystal, but in reality, there are many regions with high crystallinity and have a cluster structure. Was able to form a semi-amorphous film 603 in which silicon was bonded to each other (anchoring).

As a result, the coating film exhibits a state that it may be said that there is substantially no grain boundary (hereinafter referred to as GB). Since the carriers can easily move to each other through the anchored portions between the clusters, the carrier mobility is higher than that of polycrystalline silicon in which GB is clearly present. That is, hole mobility (μh) = 10 to ²⁰⁰ cm ² / VSec and electron mobility (μe) = 15 to 300 cm ² / VSec are obtained.

On the other hand, when the film is polycrystallized by high temperature annealing at 900 to 1200 ° C. instead of annealing at the medium temperature as described above, impurities in the film are segregated by solid phase growth from the nucleus, and GB
Contains a large amount of impurities such as oxygen, carbon, and nitrogen, and the mobility in the crystal is large, but it creates a barrier in the GB and inhibits the movement of carriers there. As a result, 10cm ² /
The reality is that mobility of more than Vsec cannot be obtained easily. That is, in this embodiment, a silicon semiconductor having a semi-amorphous or semi-crystal structure is used for such reasons.

On top of this, a silicon oxide film 604 is used as a gate insulating film, 500 to 2000 mm, for example 1000
It was formed in the thickness of the ridge. This was performed under the same conditions as the production of the silicon oxide film as the blocking layer. During the film formation, a small amount of fluorine may be added to fix sodium ions.

Thereafter, a silicon film in which phosphorus enters a concentration of 1 to 5 × 10 ²¹ cm ^{−3 on} the upper side or a multilayer of this silicon film and molybdenum (Mo), tungsten (W), MoSi ₂ or WSi ₂ thereon. Membrane 605
Formed. This was patterned with the first photomask (P1) to obtain FIG. 13 (B). In this example, the channel length was 10 μm, and molybdenum was formed to a thickness of 0.3 μm as the gate electrode. At that time, overetching 600 of about 3 μm of the metal of the gate electrode was performed.
Thereafter, a positive photoresist 607 was applied to the entire substrate.

The resist 608 can be obtained by performing exposure and development from the back surface of the substrate using a photomask (P2). Thereafter, an n layer was deposited by sputtering. Thereafter, the resist 608 is lifted off to obtain FIG.

Similarly, after applying a positive photoresist 610 to the entire substrate, a photomask (P3)
The resist 610 can be obtained by performing exposure and development from the back surface of the substrate using. Thereafter, a p-layer was deposited by sputtering. Thereafter, the resist 610 is lifted off to obtain FIG.

Next, heating annealing was performed again at 600 ° C. for 10 to 50 hours. Sources 612, 614
The impurities in the drains 613 and 615 were activated to produce N ⁺ or P ⁺ . Also,
Channel formation regions 618 and 619 are formed as semi-amorphous semiconductors under the gate electrodes 616 and 617.

In this way, a C / TFT can be made without applying temperature in all the steps to 700 ° C. or higher even though it is a self-alignment method. Therefore, it is not necessary to use an expensive substrate such as quartz as the substrate material, and this process is extremely suitable for the large-pixel liquid crystal display device of the present invention. In this embodiment, the thermal annealing was performed twice in FIGS. 13 (A) and 13 (E). However, the annealing of FIG. 13A may be omitted depending on the required characteristics, and both may be combined with the annealing of FIG. 13E to shorten the manufacturing time.

In FIG. 13F, an interlayer insulator 620 was formed as a silicon oxide film by the sputtering method described above. The silicon oxide film may be formed by LPCVD, photo CVD, or atmospheric pressure CVD. For example, it is formed to a thickness of 0.2 to 0.6 μm, and then a photomask (P4
) To form an electrode window 621. Further, as shown in FIG. 13F, aluminum is formed on the entire surface by sputtering, and a lead 622 and a contact 623 are formed using a photomask (P5), and then the surface is planarized with an organic resin 624. For example, translucent polyimide resin was applied and formed, and electrode drilling was performed again with a photomask (P6) as shown in FIG.

An ITO (indium tin oxide film) was formed by sputtering in order to connect the output end of the electrode of one pixel of the liquid crystal device as a transparent electrode. Photomask (P7)
To form an electrode 625. This ITO is deposited at room temperature to 150 ° C.
Achieved by oxygen at 200-400 ° C. or annealing in the atmosphere. Like this,
NTFT 626, PTFT 627, and transparent conductive film electrode 625 were formed on the same glass substrate 601. The mobility of the obtained NTFT 626 is 120 (cm ² / Vs), Vth
Is 5.0 (V), mobility of electrical characteristics of PTFT 627 is 50 (cm ² / Vs), and Vth is 5.
3 (V). (Fig. 13 (G))

FIG. 14 shows an outline of the structure. A mixture of fumaric acid polymer resin and nematic liquid crystal dissolved in xylene as a common solvent in a ratio of 65:35 was formed on the substrate 1500 to a thickness of 10 μm by using a die-cast method. Thereafter, the solvent was removed in a nitrogen atmosphere at 120 ° C. for 180 minutes to form a liquid crystal dispersion layer 1501. In this case, if the pressure is slightly reduced from the atmospheric pressure,
It was found that the tact time can be shortened.

Thereafter, ITO (indium tin oxide film) is formed by sputtering, and the counter electrode 1
502 was obtained. The ITO was formed at room temperature to 150 ° C. Thereafter, a translucent silicon resin was applied in a thickness of 30 μm using a printing method and baked at 100 ° C. for 30 minutes to obtain a liquid crystal electro-optical device.

The functional configuration of the driving IC used in this example is the same as that of “Example 1”. 640x48
When a normal analog gradation display is performed on a liquid crystal electro-optical device in which 307,200 sets of TFTs of 0 dots are formed in a 300 mm square, there is about ± 10% variation in TFT characteristics. The key display was the limit. The TFT according to this embodiment has a driving frequency of 2.5 MHz.
Since it was possible to increase to z, the number of gradation display was 2.5 MHz with 480 scanning lines and 6
It was possible to display up to 86 shades of 0 frames. Therefore, when digital gradation display according to the present embodiment is performed, it is difficult to be affected by variations in characteristics of TFT elements, and therefore, it is possible to display up to 64 gradations. In color display, there are a wide variety of 262,144 colors. Display of various colors.

When projecting software such as TV images, for example, even the “rock” of the same color has a slightly different hue due to the amount of light falling on the minute depressions. When a display close to natural colors is to be displayed, it is difficult to express with 16 gradations, which is not suitable for expressing these subtle depressions. The gradation display according to the present invention makes it possible to add these minute color tone changes.

This liquid crystal electro-optical device can be used not only for the front type projection television shown in FIG. 12, but also for the rear type projection television.

"Example 4" (portable computer)
In this embodiment, a portable computer electro-optical device using a reflective liquid crystal dispersion display device as shown in FIG.

As the first substrate used in this example, a substrate prepared in the same process as “Example 1” was used. A nematic liquid crystal in which 15% of a fumaric acid polymer resin and a black pigment is mixed on the substrate is 65:
A mixture of 35 dissolved in xylene, which is a common solvent, was added to a 10
A liquid crystal dispersion layer was formed by removing the solvent for 180 minutes at 120 ° C. in a nitrogen atmosphere.

Here, because of the use of black pigments, flat displays, which were difficult with dispersive liquid crystal display, can display black when light is scattered (when no electric field is applied) and white when transmitted (when an electric field is applied). It is possible to display characters written on paper.

Further, as an opposite structure, it is possible to express white when scattering without expressing black pigment and express black when transmitting. However, in this case, the back side shown below needs to be black. This also makes it possible to display characters written on paper.

Thereafter, ITO (indium tin oxide film) was formed by sputtering to obtain a counter electrode. The ITO was formed at room temperature to 150 ° C. Thereafter, using a printing method, a white silicon resin was applied to a thickness of 55 μm and baked at 100 ° C. for 90 minutes to obtain a liquid crystal electro-optical device.

2 shows a driving waveform according to the present invention. The electro-optical characteristics of nematic liquid crystal are shown. The electrical characteristics of TFTs made of polysilicon and amorphous silicon are shown. The matrix circuit by a present Example is shown. The planar structure of the element by a present Example is shown. A process for manufacturing a TFT according to this example will be described. A manufacturing process of a counter substrate according to this example will be described. The structure of the liquid crystal display device (television) by a present Example is shown. 1 shows a system configuration of a drive circuit according to the present embodiment. The photograph which shows the waveform of the oscilloscope of the characteristic of TFT by a present Example. The photograph which shows the waveform of the oscilloscope of the characteristic of TFT by a present Example. 1 shows a structure of a projection-type liquid crystal electro-optical device according to the present embodiment. A process for manufacturing a TFT according to this example will be described. 1 is a cross-sectional view of a liquid crystal electro-optical device according to the present embodiment. The structure of the portable computer by a present Example is shown.

Explanation of symbols

50 ... Glass substrate 51 ... Blocking layer 66 ... NTFT gate electrode 67 ... PTFT gate electrode 88 ... Pixel electrode

Claims (24)

A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode formed on the planarization film;
A liquid crystal layer having a nematic liquid crystal on the pixel electrode;
A counter electrode on the liquid crystal layer;
A liquid crystal electro-optical device having a light-transmitting resin on the counter electrode. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode made of a transparent conductive film formed on the planarizing film;
A liquid crystal layer having a nematic liquid crystal on the pixel electrode;
A counter electrode made of a transparent conductive film on the liquid crystal layer;
A liquid crystal electro-optical device having a light-transmitting resin on the counter electrode. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode formed on the planarization film;
A liquid crystal layer having a nematic liquid crystal formed on the pixel electrode using a die-cast method;
A counter electrode on the liquid crystal layer;
A liquid crystal electro-optical device having a light-transmitting resin on the counter electrode. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode made of a transparent conductive film formed on the planarizing film;
A liquid crystal layer having a nematic liquid crystal formed on the pixel electrode using a die-cast method;
A counter electrode made of a transparent conductive film on the liquid crystal layer;
A liquid crystal electro-optical device having a light-transmitting resin on the counter electrode. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode formed on the planarization film;
A liquid crystal layer having a nematic liquid crystal on the pixel electrode;
A counter electrode on the liquid crystal layer;
And a translucent resin formed on the counter electrode by a printing method. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode made of a transparent conductive film formed on the planarizing film;
A liquid crystal layer having a nematic liquid crystal on the pixel electrode;
A counter electrode made of a transparent conductive film on the liquid crystal layer;
And a translucent resin formed on the counter electrode by a printing method. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode formed on the planarization film;
A liquid crystal layer having a nematic liquid crystal formed on the pixel electrode using a die-cast method;
A counter electrode on the liquid crystal layer;
And a translucent resin formed on the counter electrode by a printing method. A glass substrate;
A thin film transistor formed on the glass substrate;
A planarization film formed on the thin film transistor;
A pixel electrode made of a transparent conductive film formed on the planarizing film;
A liquid crystal layer having a nematic liquid crystal formed on the pixel electrode using a die-cast method;
A counter electrode made of a transparent conductive film on the liquid crystal layer;
And a translucent resin formed on the counter electrode by a printing method. 9. The liquid crystal electro-optical device according to claim 1, wherein the planarizing film is made of an organic resin. 10. The liquid crystal electro-optical device according to claim 1, wherein the translucent resin is a translucent silicon resin. 11. The liquid crystal electro-optical device according to claim 1, wherein the liquid crystal layer is formed using a mixture of a polymer resin and a nematic liquid crystal. 12. The liquid crystal electro-optical device according to claim 1, wherein the liquid crystal electro-optical device is a front or rear projection television. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode;
Forming a counter electrode on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, comprising forming a light-transmitting resin on the counter electrode. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode made of a transparent conductive film on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode;
Forming a counter electrode made of a transparent conductive film on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, comprising forming a light-transmitting resin over the counter electrode. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode using a die-cast method;
Forming a counter electrode on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, comprising forming a light-transmitting resin on the counter electrode. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode made of a transparent conductive film on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode using a die-cast method;
Forming a counter electrode made of a transparent conductive film on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, comprising forming a light-transmitting resin over the counter electrode. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode;
Forming a counter electrode on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, wherein a translucent resin is formed on the counter electrode by a printing method. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode made of a transparent conductive film on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode;
Forming a counter electrode made of a transparent conductive film on the liquid crystal layer;
A method of manufacturing a liquid crystal electro-optical device, wherein a translucent resin is formed on the counter electrode by a printing method. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode using a die-cast method;
Forming a counter electrode on the liquid crystal layer;
A method for manufacturing a liquid crystal electro-optical device, wherein a translucent resin is formed on the counter electrode by a printing method. A thin film transistor is formed on a glass substrate,
Forming a planarization film on the thin film transistor;
Forming a pixel electrode made of a transparent conductive film on the planarizing film;
Forming a liquid crystal layer having a nematic liquid crystal on the pixel electrode using a die-cast method;
Forming a counter electrode made of a transparent conductive film on the liquid crystal layer;
A method of manufacturing a liquid crystal electro-optical device, wherein a translucent resin is formed on the counter electrode by a printing method. 21. The method for manufacturing a liquid crystal electro-optical device according to claim 13, wherein the planarizing film is made of an organic resin. The method for manufacturing a liquid crystal electro-optical device according to claim 13, wherein the light-transmitting resin is a light-transmitting silicon resin. 23. The method for manufacturing a liquid crystal electro-optical device according to claim 13, wherein the liquid crystal layer is formed using a mixture of a polymer resin and a nematic liquid crystal. 24. The method of manufacturing a liquid crystal electro-optical device according to claim 13, wherein the liquid crystal electro-optical device is a front-type or rear-type projection television.

Images