JP2000275668A - Laser annealing device, liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve throughput, when carrying out crystallization of a semiconductor film by a laser and to improve a process margin in a process for producing a liquid crystal display device which is integrated with peripheral circuits. SOLUTION: This process includes a stage for forming a first semiconductor film, having first field effect mobility by a fixed phase growth method on direct deposition method on a substrate 1 having a display region 2a, a first peripheral circuit region 3a and a second peripheral circuit region 4a, a stage for changing the semiconductor film to the second semiconductor film, having second electric field effect mobility by irradiating the first semiconductor film on the first peripheral circuit region 3a with a first linear or two-dimensional laser beam at a first energy density, and a stage for changing the first semiconductor film to a third semiconductor film, having the third electric field effect mobility by irradiating the first semiconductor film on the second peripheral circuit region with a second linear or two-dimensional laser beam at a second energy density which is different from the first energy density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, a method of manufacturing the same, and a laser annealing device, and more particularly, to a liquid crystal display device having a built-in peripheral circuit and having a thin film transistor as a switching element, and a semiconductor of the liquid crystal display device. And a method for producing the same.

[0002]

2. Description of the Related Art A liquid crystal display device has a thin film transistor (T).
An active matrix drive type using FT (thin film transistor) has become mainstream. Recently, a peripheral circuit for driving a TFT in an image area formed on a liquid crystal display substrate has been commercialized, and a TFT is used as a transistor for the peripheral circuit.

In order to form a semiconductor film constituting these TFTs, a technique for growing crystalline silicon at a low temperature in consideration of the heat resistance of the substrate is indispensable. Techniques for crystallizing an amorphous silicon film include a laser crystallization technique, a solid phase growth technique (SPC technique), and a direct crystal growth technique, and these techniques will be described below. Note that crystalline silicon is a concept that includes both polycrystalline silicon and microcrystalline silicon.

(1) Laser crystallization technology At present, the most practical low temperature crystallization method is an excimer laser crystallization method. The excimer laser crystallization method uses, for example, an amorphous silicon film on a glass substrate by PECVD.
After being formed at a low temperature by the
This is a technique in which hydrogen in the amorphous silicon film is removed by a heat treatment at about 500 ° C., and then the silicon film is crystallized by irradiating the amorphous silicon film with an excimer laser. At the time of excimer laser irradiation, a method is employed in which either the laser beam or the glass substrate is scanned to crystallize the entire amorphous silicon film.

[0005] The amorphous silicon film on the substrate is sometimes called a "silicon starting film". The greatest advantage of crystallization by excimer laser is that high-quality crystalline silicon can be formed and high-quality TFTs can be formed without damaging the glass substrate by heat.

[0006] Such a crystalline silicon film can be applied to the formation of a TFT of a peripheral circuit requiring high field-effect mobility. Since the clock frequency of the data drive circuit in the peripheral circuit is several MHz, a TFT used for the data drive circuit has a field effect mobility of 50 cm ² / Vs or more and an appropriate threshold value for CMOS operation. Voltage is required.

(2) Solid phase growth technique (SPC technique) Solid phase growth is a method of crystallizing a silicon starting film by annealing it under heating conditions of, for example, about 600 ° C. for several tens of hours. However, according to solid-phase growth, it is difficult to obtain good crystals as compared with the laser crystallization technique, so that the transistor characteristics of a TFT having a crystalline silicon film subjected to solid-phase growth are not good.

For example, since the field effect mobility of a TFT formed using a crystalline silicon film solid-phase grown at 600 ° C. is 20 to 50 cm ² / Vs, a data driving circuit is formed on such a crystalline silicon film. Is not appropriate from a performance point of view. (3) Technique for forming crystalline silicon directly As a method for forming a crystalline silicon film, a technique for forming a polycrystalline silicon thin film (as-deposited p-Si) directly on a glass substrate by PECVD or sputtering. There is.

However, the field-effect mobility of such a polycrystalline silicon thin film is lower than the field-effect mobility of crystalline silicon formed by the solid phase growth method, so that it has not been put to practical use as a peripheral drive circuit. . In view of the above technical background, a laser crystallization technique is most preferable as a crystallization method of crystalline silicon for forming a peripheral circuit on a glass substrate.

[0010]

By the way, in a liquid crystal display device incorporating a typical dot-sequential driving peripheral circuit,
TFT with a field effect mobility of 20 cm ² / Vs or more in the pixel area
Is required, a gate drive circuit requires a TFT of about 30 cm ² / Vs or more, and a data drive circuit requires about 50 cm ² / Vs.
The field effect mobility according to the type of circuit is required, such as the requirement of a TFT of cm ² / Vs or more.

In the actual crystallization process, crystallization is performed in consideration of the TFT used in the data driver circuit, which is the highest specification in the substrate, without taking these factors into account. And the manufacturing process margin is reduced. The manufacturing process of matching the TFT characteristics of another circuit to the TFT characteristics of such a data driver circuit is based on the idea of crystallizing the entire surface of a silicon starting film by a laser crystallization technique or a solid phase growth technique.

However, when the display area and the peripheral circuit area are formed on a single substrate, the area occupied by the peripheral circuit area 102 on the substrate 101 is very small as shown in FIG. small. For example, in the case of a 5 μm design rule, the data driving circuit can be accommodated in an area of 5 mm or less in the case of a point-sequential driving method and within 10 mm in the case of a line-sequential driving method.

The diagonal line is 12.1 inches (1 inch).
Taking the area ratio between the peripheral circuit region 102 and the display region 103 as an example of a panel of type 2), the display region 103
The ratio of the area occupied 4400Mm ² of the peripheral circuit region 102 for the area occupied 45632Mm ² of about 9.6%. However, when the laser crystallization technique is adopted, as shown in FIG.
Generally, a laser is applied to the entire surface of the silicon film 104 on the substrate 101. The laser irradiation time is calculated, for example, as follows.

If the laser oscillation frequency is set to 200 Hz and the laser overlap rate is set to 95%, the short side length becomes 500 to 6
In order to process one silicon film on a substrate having a size of 50 mm, the number of laser pulse shots of 10,000 to 13000 is required, and it takes 50 to 60 seconds. As the number of pulse shots increases, the gas consumption for laser emission increases, and the life of the laser device is shortened. Further, as the processing time becomes longer, the throughput decreases. In recent years, the size of a glass substrate has tended to increase, and in the case of irradiating a large substrate such as the fourth stage production line while scanning with a laser, further processing time and material cost are further added.

Further, according to the laser crystal method of the scanning method, as shown in FIG.
And non-uniformity of crystallinity due to two kinds of fluctuations, ie, sudden fluctuations b due to instability of laser energy. When the non-uniformity of the crystallinity occurs, the TFT characteristics of the image display are deteriorated. Particularly, the problem is the image deterioration caused by the irregularity of the TFT characteristics in the pixel region. The biggest problem with liquid crystal display panels.

A display pattern appearing in a liquid crystal display image due to uneven TFT characteristics is called a "scan pattern" because it appears along the laser scanning direction. On the other hand, JP-A-5-203977 discloses that a polycrystalline silicon film is formed on a substrate, and after patterning the polycrystalline silicon film, a data line peripheral driving circuit is set to a beam diameter of 200 μm
It is described that annealing is performed with a laser of a certain degree. However, annealing the polycrystalline silicon pattern with a point spot laser after patterning the polycrystalline silicon film firstly requires a long time and lowers the throughput, and secondly, irradiates the polycrystalline silicon pattern with laser irradiation. A margin for alignment is required, and it becomes impossible to cope with miniaturization of the TFT.

An object of the present invention is to provide a method of manufacturing a liquid crystal display device which can improve the throughput when crystallization of a semiconductor film by a laser and can improve a process margin.

[0018]

Means for Solving the Problems (1) The above-mentioned problems are:
As illustrated in FIG. 2 to FIG. 5 and FIG. 9, the first peripheral circuit region 3a and the second peripheral circuit region 4a are formed on the substrate 1 by the solid phase growth method or the direct film forming method. Forming a first semiconductor film 10 having a field-effect mobility of: and applying a linear or two-dimensional first laser beam to the first semiconductor film 10 on the first peripheral circuit region 3a at a first energy. Irradiating at a density to change to a second semiconductor film 10c having a second field effect mobility, and applying a linear or two-dimensional second laser to the first semiconductor film 10 on the second peripheral circuit region 4a. Irradiating light with a second energy density different from the first energy density to change the third semiconductor film 10b having a third field-effect mobility into a third semiconductor film 10b. Solved by.

In the above-described method for manufacturing a liquid crystal display device, the first energy density is higher than the second energy density, and the first field-effect mobility is higher than the third field-effect mobility. It is characterized by the following. In the above-described method for manufacturing a liquid crystal display device, the third mobility of the third semiconductor film 10c may be different from that of the first semiconductor film 10c.
Is larger than the first mobility and smaller than the second mobility of the second semiconductor film 10b. In this case, data driving circuits 31 and 32 are formed on the second semiconductor film 10c on the first peripheral circuit region 3a, and the data driving circuits 31 and 32 are formed on the third semiconductor film 10b on the second peripheral circuit region 4a. May be formed with a gate drive circuit 38.

In the above-described method for manufacturing a liquid crystal display device, the irradiation of the first laser light is performed by relatively scanning the first laser light and the substrate in a first direction. The irradiation of the two laser beams is performed by relatively scanning the second laser beam and the substrate 1 in a second direction. In this case, the first direction and the second direction may be different. Further, after the irradiation of the first laser beam is completed, the first direction and the second direction may be made the same by rotating the substrate 1 by 90 degrees.

In the above-described method for manufacturing a liquid crystal display device, a thin film transistor having a first on-current is formed on the first semiconductor film 10, and the second semiconductor film 10
c, forming a second thin film transistor having a second on-state current larger than the first on-state current;
Forming a third thin film transistor having a third on-current larger than the first on-current and smaller than the second on-current in the semiconductor film 10b.

In the above-described method for manufacturing a liquid crystal display device, when the first laser light or the second laser light is irradiated, the first peripheral circuit area is formed by using light-shielding masks 28 and 29. 3a or the second peripheral circuit area 4a is selected. in this case,
A plurality of light-shielding masks 28 and 29 may be used.

In the above-described method for manufacturing a liquid crystal display device, the first or second laser beam is emitted from the first or second laser beam.
Of the peripheral circuit regions 3a and 4a. (2) The above-described problem is caused by the pixel region 2a having the first thin film transistors 35 and 36 composed of the first semiconductor layer 10a having the field effect mobility of 10 to 30 cm ² / Vs, and the periphery of the pixel region 2a. A liquid crystal comprising: a block line sequential driving type peripheral driving circuits 31 and 32 each having a second thin film transistor including a second semiconductor layer 10b having a field effect mobility of 30 cm ² / Vs or more. Solved by the display device.

In the liquid crystal display device, an external driver LSI 41 is connected to the peripheral driving circuits 31 and 32. In this case, it is preferable that the number of bits of the external driver LSI 41 be 300 bits or more. In the above-described liquid crystal display device, a writing time of the peripheral driving circuits 31 and 32 to the pixel region is 1 microsecond or more. (3) As illustrated in FIG.
cassette 71 for accommodating a-70e, substrate mounting table 74 for mounting substrate 60, laser light irradiating means 72 and 73 for irradiating laser light toward substrate 60, and light shielding mask in cassette 71 Laser annealing comprising a mechanism for selecting one of 70a to 70e and transporting it between the laser beam irradiation means 72 and 73 and the substrate mounting table 74, and a mechanism for heating or moving the substrate mounting table 74. Settle by device.

In the laser annealing apparatus, the laser light irradiating means may be structured to irradiate the linear or two-dimensional laser light toward the substrate. In addition,
The figures and reference numerals described above are cited for facilitating the understanding of the invention, and the invention is not limited thereto. Next, the operation of the present invention will be described.

According to the present invention, the field effect mobilities of a plurality of regions of the semiconductor device are changed by irradiating the semiconductor layer with linear or two-dimensional laser light. Thereby, regions having different crystallinities are selectively formed on the same substrate, and the characteristics of the pixel TFT and the peripheral circuit TFT are optimized.
In addition, the throughput is improved as compared with the case where a spot laser is used.

Further, since the semiconductor film in the pixel region is not irradiated with the laser light, a scan pattern due to a crystal change due to the laser irradiation does not appear. By using a semiconductor film formed on the substrate as a low mobility region and using a high mobility crystallization laser annealing around the periphery, the laser light irradiation area is greatly reduced, and the number of laser pulses and the number of laser pulses are short. A laser crystal can be efficiently realized in the irradiation time. In addition, since all the peripheral circuits are not irradiated with a laser beam having an intensity higher than necessary, an element having stable characteristics is formed on the semiconductor film irradiated with the laser.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 2A is a plan view showing an arrangement relationship between a peripheral circuit area, a display area, and a terminal area of a substrate used in a first embodiment of the present invention. The peripheral circuit area includes first and second data-side drive circuit areas along two long sides of the glass substrate 1 and first and second scan (gate) -side drive areas along two short sides. It is divided into four drive areas.

In FIG. 2A, a rectangular glass substrate 1
Is about 40 in the data bus line extending direction (Y direction in the figure).
0 mm, about 5 in the gate bus line extension direction (X direction in the figure)
It has a rectangular planar shape of 00 mm, and 11.
The first to fourth display panel areas 1a to 1d of type 3 are divided vertically and horizontally, and the boundary between these areas 1a to 1d is about 2 mm in width.
Cutting margin is secured. Each display panel area 1
In a to 1d, display areas 2a to 2d, data-side peripheral circuit areas 3a to 3h, scan-side peripheral circuit areas 4a to 4h, and terminal areas 5a to 5d are defined.

Each of the display areas 2a (2b, 2c, 2
d) is a rectangle of, for example, 246 mm x 185 mm, and on both sides in the Y direction, as shown in FIG. 2B, the first and second data side peripheral circuit areas within a range of 5 mm or less in width. 3a and 3b (3c to 3h) are arranged, and further, X
On both sides in the direction, the first and second scanning side peripheral circuit areas 4a and 4b (4c to 4h) are arranged within a range of 5 mm or less in width. Also, the first scanning side peripheral circuits 4a (4c, 4e, 4
g), a terminal forming region 5a (5b to 5b) having a width of about 3 mm
d) is arranged.

Next, a process of forming a thin film transistor (TFT) on the glass substrate 1 will be described with reference to FIGS. First, as shown in FIG. 3A, a film thickness of 300 to 1000 Å, preferably 45
A 0 ° crystalline silicon film 10 is formed by a solid phase growth method or a direct growth method. When a crystalline silicon film is formed by a solid phase growth method, an amorphous silicon film 10 is formed by a CVD method using silane (SiH4) gas, and then the amorphous silicon film is formed at a temperature of about 600 ° C. This is a method of heating and crystallizing to form a polycrystalline silicon film.

The crystalline silicon film 1 is formed by a direct growth method.
When the value is set to 0, the microcrystalline crystalline silicon film 10 is formed by a plasma CVD method using silane gas, and then the crystalline silicon film 10 is heated at, for example, 450 ° C. to remove hydrogen therein. The field effect mobility of the crystalline silicon film 10 formed by such a method is 20 to
30 cm ² / Vs.

Next, a part of the crystalline silicon film 10 is crystallized by using a two-system optical laser crystallization apparatus as shown in FIG. In FIG. 6, a point-like laser beam output from one excimer laser oscillator 21 is divided into two systems by an optical switch 22. The point-like laser light whose orbit has been changed to the first system by the optical switch 22 is input to the first linear converter 24 via the mirror 23. First
The linear converter 24 converts a point-like laser beam into a linear laser beam that is long in the X direction, and outputs the laser beam with a uniform energy distribution.

The point-like laser light whose trajectory has been changed to the second system by the optical switch 22 is transmitted through the mirror 25 to the second laser light.
Is input to the linear converter 26. Second linear converter 26
Converts a point-like laser beam into a linear laser beam that is long in the Y direction and outputs the laser beam with a uniform energy distribution. The first linear converter 24 has an energy intensity density E ₁ of about 320 to
A 360 mJ / cm ² vertical linear laser beam is output. The laser irradiation output from the first linear converter 24 has a pulse oscillation frequency of 200 Hz.

The second linear converter 26 outputs a vertical linear laser beam having an energy intensity density E ₂ of about 280 to 320 mJ / cm ² . That is, the energy density E1 of the _first linear laser beam is adjusted to be higher than the energy density E2 of the _second linear laser beam.
The laser irradiation output from the second linear converter has a pulse oscillation frequency of 200 Hz.

It should be noted that the laser crystallization apparatus uses the glass substrate 1
Has a mounting table 27 for scanning in the X direction or the Y direction and a heater (not shown) for heating the glass substrate 1. When irradiating the glass substrate 1 with the first linear laser beam, as shown in FIG. 7, the first linear laser beam shields the area other than the first and second data side peripheral circuit areas 3a to 3h. One light shielding mask 28 is used. Further, when irradiating the glass substrate 1 with the second linear laser beam, as shown in FIG. 8, the first and second scanning side peripheral circuit regions 4a to 4
The second light-shielding mask 29 that shields the area other than h is used.

Using the above laser crystallization apparatus,
First, the first and second data-side drive regions 3 of the glass substrate 1
The direction of the glass substrate 1 is adjusted so that the long sides of a to 3h are parallel to the longitudinal direction of the first linear laser beam. Then, with the first linear converter 24 fixed, the first and second data-side peripheral circuits of the first to fourth panel regions 2a to 2d are scanned while scanning the glass substrate 1 in the Y direction. Crystal silicon film 1 existing in regions 3a-3h
0 is irradiated with a linear laser beam. In this case, the laser beam overlap rate is set to 90 to 95% (that is, 10 to 20 pulse overlap), and the substrate heating temperature is set to a room temperature (20 ° C.) to 4%.
Set within the range of 00 ° C.

The irradiation of the laser beam is specifically as follows. That is, as shown in FIG. 9, the crystalline silicon film 10 in the first data-side driving regions 3a and 3c of the first and second display panel regions 1a and 1b on the glass substrate 1 respectively.
Is irradiated with a linear laser beam. Subsequently, when the linear laser beam scans over the two display areas 2a and 2b,
The irradiation of the linear laser beam is shielded by a light shielding mask 28 disposed above the glass substrate 1. In a region where the linear laser beam is blocked by the light shielding mask 28, the scanning speed of the glass substrate 1 is increased.

Further, the first and second display panel areas 1
a, 1b each of the second data-side drive regions 3b, 3b
d is irradiated with a linear laser beam on the crystalline silicon film 10 existing in the third and fourth display panel regions 1c and 1c.
A linear laser beam is applied to the crystalline silicon film 10 existing in each of the first data-side drive regions 3e and 3g.

Third and fourth display panel areas 1c, 1d
When scanning over the respective display areas 2c and 2d,
Irradiation of the linear laser beam is blocked by the light-shielding mask 28 disposed above the glass substrate 1. Also in this case, the scanning speed of the glass substrate 1 is increased in a region where the linear laser beam is shielded by the light shielding mask 28.

Subsequently, the third and fourth display panel areas 1
c, 1d second data-side drive regions 3f, 3
The linear laser beam is applied to the crystalline silicon film 10 existing in the area h. By the irradiation of the linear laser beam as described above, portions of the crystalline silicon film 10 existing in the respective data-side driving regions 3a to 3h of the first to fourth display panels 1a to 1d become polycrystalline, and the mobility thereof is increased. Is 50cm ² / Vs
That is all.

FIG. 3 is a sectional view showing the laser irradiation of the crystalline silicon film 10 in the data side driving regions 3a to 3h.
(b). Thereafter, the optical switch 21 changes the trajectory of the laser beam from the first optical system to the second optical system. Next, while the second linear converter 26 is fixed, the glass substrate 1 is scanned in the X direction, and the first and second display-side areas of the first to fourth display panel areas 1a to 1d are respectively scanned. Crystal silicon film 1 existing in circuit regions 3a-3h
Irradiation is performed while scanning a linear laser beam at zero. In this case, the overlap ratio of the linear laser beam is 90 to 95%,
That is, 10 to 20 pulses overlap. Further, the substrate heating temperature at the time of laser irradiation is set in a range from room temperature of about 20 ° C. to 400 ° C.

In this case, as shown in FIG. 10, the first scanning side peripheral circuit areas 4a and 4e and the second scanning side peripheral circuit area 4b of the first and third display panel areas 1a and 1c, respectively. , 4f are sequentially irradiated with a linear laser beam E2,
Further, the linear laser beam E2 is applied to the first scanning side peripheral circuit areas 4c and 4g and the second scanning side peripheral circuit areas 4d and 4h of the second and fourth display panel areas 1b and 1d, respectively.
Are sequentially irradiated. When the linear laser beam E2 passes through each of the display areas 2a to 2d, the second light shielding mask 2
By 9, the irradiation of the crystalline silicon film 10 with the linear laser beam is cut off, and the scanning speed of the glass substrate 1 is increased to improve the throughput.

As a result, the field-effect mobility of the crystalline silicon film 10 corresponding to the data-side drive regions 4a and 4e of the first to fourth display panel regions 1a to 1d becomes 30 cm ² / Vs or more. Become. FIG. 3C is a cross-sectional view of laser irradiation of the crystalline silicon film 10 in the scanning side driving regions 4a to 4h.

In the above-described laser device, two data-side peripheral circuit regions of the crystalline silicon film 10 are simultaneously irradiated with the linear laser beam E 1, and two scan-side peripheral circuits of the crystalline silicon film 10 are further irradiated. Although the structure in which the regions are irradiated with the linear laser beam at the same time is adopted, the linear laser beams E1 and E2 are separately provided for each of the display panel regions 1a to 1d.
May be adopted. Although two laser scanning systems are provided in the above-described laser irradiation apparatus, one laser scanning system may be used. When one laser scanning system is used, FIG.
A substrate rotating mechanism is attached to the substrate mounting table 27 shown in (1). After the laser irradiation of the data side peripheral circuit area is completed, the substrate mounting table 27 is rotated by 90 degrees, and in that state, the laser of the scanning side peripheral circuit area is irradiated. To Further, the light shielding masks 28 and 29 do not have to be used at the time of laser beam irradiation. In this case, the linear converter 2 is placed on the display areas 2a to 2d.
When the positions 4 and 26 are located, the output of the laser light source 21 is stopped.

Incidentally, the irradiation energy of the excimer laser
-The relationship between density and mobility is as shown in Fig. 11, for example.
Linear laser beam applied to the inspection-side peripheral circuit areas 4a to 4h
Energy density of 280-300mJ / cm^TwoIn the range
Is easy to control the mobility and contributes to the improvement of the yield.
Each display panel irradiated with a linear laser beam as described above
In the display areas 1a to 1d, the connection of the display areas 2a to 2d is performed.
Mobility of the crystalline silicon film 10 is 20 to 30 cm^Two/ Vs, data
Of the crystalline silicon film 10 in the side peripheral circuit regions 3a to 3h
The degree is 50-100cm^Two/ Vs, scanning side peripheral circuit area 4a-4
h. The mobility of the crystalline silicon film 10 is 30 to 50 cm.^Two/ Vs and
Become.

Next, as shown in FIG. 4A, the crystalline silicon film 10 is patterned by a photolithography method to form display regions 2a to 2d and a data side peripheral circuit region 3a.
3h and the scanning-side peripheral circuit regions 4a to 4h, the crystalline silicon film 10 is left in the region where the TFT is to be formed. Here, the crystalline silicon film 10 patterned in the display regions 2a to 2d is defined as a first silicon pattern 10a, and the crystalline silicon film 10 patterned in the data side peripheral circuit regions 3a to 3h is defined as a second silicon pattern 10b. The crystalline silicon film 10 patterned in the scanning-side peripheral circuit regions 4a to 4h is used as a third silicon pattern 10c.

Subsequently, the first to third silicon patterns 1
0a to 10c and silicon oxide (Si) on the glass substrate 1.
O ₂ ) The film 11 is formed from 1000 to 120
It is formed to a thickness of 0 °. The silicon oxide film 11 is made of silane (S
It is grown using iH ₄ ) gas and oxygen nitride (N ₂ O) gas. This silicon oxide film 11 functions as a gate insulating film on the first to third silicon patterns 10a to 10c.

Subsequently, as shown in FIG. 4B, gate electrodes 12a to 12c are formed on the respective channel regions of the first to third silicon patterns 10a to 10c via the silicon oxide film 11. At the same time, a gate bus line (not shown) and other wiring are formed on the silicon oxide film 11. Thereafter, impurities are introduced into each of the silicon patterns 10a to 10c by using the gate electrodes 12a to 12c as a mask, thereby forming the gate electrodes 12a to 1c of the first to third silicon patterns 10a to 10c.
Impurity diffusion layers 13a to 13f serving as source / drain are formed in regions on both sides of 2c. Gate electrodes 12a-12
Aluminum is used as a constituent material of c.

Subsequently, a first interlayer insulating film 14 of 4000 nm thick silicon nitride is formed on the gate electrodes 12a to 12c, the silicon oxide film 11, and the like. next,
As shown in FIG. 4C, the first interlayer insulating film 14 and the silicon oxide film 11 are patterned to form each impurity diffusion layer 13.
Source / drain contact holes 15a to 15f are formed on a to 13f, and second and third gate electrodes 12b and 12c of data-side peripheral circuit regions 3a to 3h and scan-side peripheral circuit regions 4a to 4h. The gate contact holes 16b and 16c are formed thereon.

Subsequently, as shown in FIG. 5A, the data side peripheral circuit areas 3a to 3h and the scan side peripheral circuit areas 4a to 4h
h, source / drain electrodes 17c to 17f connected to the impurity diffusion layers 13c to 13f through the contact holes 15c to 15f are formed on the first interlayer insulating film 14, and the gate electrode 12b is formed through the contact holes 16b and 16c. , 12c connected to the first interlayer insulating film 14 are formed. In the display regions 2a to 2d, the source extraction electrode 17 connected to the impurity diffusion layer 13a serving as a source is provided.
a is formed on the first interlayer insulating film 14, and a drain bus line 17b connected to the impurity diffusion layer 13b serving as a drain is formed on the first interlayer insulating film 14.

Next, as shown in FIG. 5B, an insulating material such as acrylic or polyimide is applied on the source lead electrode 17a, the drain bus line 17b, the first interlayer insulating film 14, and the like. Is heated at 300 ° C. to solidify. The insulating material is used as the second interlayer insulating film 19.
After that, the second protective insulating film 19 is patterned by photolithography to form a via hole 19 a for a pixel electrode on the source extraction electrode 19.

Next, as shown in FIG. 5C, a pixel electrode 20 is formed on the second interlayer insulating film 19. 2 in pixels
As a constituent material of No. 0, indium tin oxide (ITO) is used when the liquid crystal display device is a transmissive type, and aluminum is used when the liquid crystal display device is a reflective type. Furthermore, the terminal regions 5a to 5a shown in FIG.
After forming a terminal (not shown) on 5c, the glass substrate 1 is divided into first to fourth display panel regions 1a to 1d,
Obtain four display panels. These display panels are opposed to a counter substrate with a liquid crystal (not shown) interposed therebetween.

The display areas 2a to 2a are formed by the above steps.
d, three types of TFTs having different characteristics are formed in the data-side peripheral circuit regions 3a to 3h and the scan-side peripheral circuits 4a to 4h, respectively. The on / off characteristics of the TFTs after the hydrogenation heat treatment were examined. It became like 12. Hydrogenation is important for sufficiently improving TFT off characteristics.

The first TFTs in the display areas 2a to 2d are:
As shown by the broken line in FIG. 12, the off current (leak current) was the smallest and the on current was the smallest. In the second TFTs in the data-side peripheral circuit regions 3a to 3h, both the off-state current and the on-state current are largest as shown by the solid line in FIG. Third TFT in scanning side peripheral circuits 4a to 4h
As shown by the dashed line in FIG. 12, the off-state current and the on-state current were intermediate values as compared with the first TFT and the second TFT.

It is preferable that the first TFTs in the display regions 2a to 2d have a small off-current, and that the second TFTs in the data side peripheral circuit regions 3a to 3h have a large field-effect mobility from the viewpoint of high-speed operation. Is preferred. The magnitude of the on-state current is caused by the magnitude of the field-effect mobility, and the first TF
The mobility increases in the order of T, the third TFT, and the second TFT.

Incidentally, the SXG provided with the above-described TFT
The circuit configuration of the display panel A is as shown in FIG. FIG.
3, the data side peripheral drive circuit 3a (3b to 3h)
Is formed with a shift register circuit 31 and a buffer circuit 32 having a ten-stage configuration. Further, a gate drive circuit 33 for driving 1024 gate lines (scan lines) in the display areas 2a to 2d is formed in the scan side peripheral drive circuit area.

Each of the pixel cells 34 in the display areas 2a to 2d is connected in parallel with a parasitic capacitance 37 of liquid crystal and an auxiliary capacitance Cs sandwiched between the pixel electrode 20 and a counter electrode (not shown). In addition, the capacitances 37, Cs and the data bus line DB are connected to the two first TFTs 35, 3
6 are connected in series. Those first TFTs 35
The gate electrodes 5 and 36 are connected to the scanning-side peripheral circuit area 4a (3
b to 3h) are connected to a gate bus line GB connected to the gate drive circuit 38 formed in (b) to (h).

Further, 3840 (RGB) data for each of 1280 gate bus lines (horizontal lines) GB is divided into first to tenth blocks. The ten block signal lines BL _{1 to} BL ₁₀ drawn from the shift register circuit 31 extend to the first to tenth blocks via the buffer circuit 32, and in each block, one block signal line BL ₁ (BL _{2 to} BL ₁₀ ) are 384 CMOSs
Type TFT (analog switch) 40.

38 of each of the first to tenth blocks
The display area 2a (2b
To 2d) are connected one-to-one. Also, 384 CMOs in each block
The S-type TFT40 is common signal line line D ₁ to D ₃₈₄ of 384 the number of bits extending from an external driver LSI41 more than 300 bits are connected in a one-to-one.

Note that in FIG.
The reference signal SP indicates a horizontal synchronization signal. As shown in FIG.
The circuit thus implemented complies with the drive timing chart shown in FIG.
And writing time to the pixel area is 1 micron.
Seconds or more. That is, it is turned on by the gate scanning signal.
In one horizontal line GB, the first to tenth blocks
The analog switch 40 in the block to the block signal line BL.₁
~ BL _TenWrite in block order through Its analog
The switch 40 is turned on / off by the buffer circuit 32.
It is controlled by a block control signal. Also, shift
The block signal line BL selected by the register circuit 31
_nCommon signal line D connected to (1 ≦ n ≦ 10)₁~ D
₃₈₄The display signal is sent via the.

In the block sequential method, the writing time is 1.4 μs, which is longer than the writing time in the dot sequential method. Therefore, the mobility of the TFTs 355 and 36 in the pixel cell 34 is 10 cm ² / Vs or more. If you can, you can write in principle. s
Since the mobility of the pixel TFT using the pc crystallization technique is 20 to 30 cm ² / Vs as described above, the pixel TFT has no problem in characteristics at all. Of course, if the mobility is 10 cm ² / Vs or more, polycrystalline silicon or microcrystalline silicon formed by a sputtering method, a PECVD method, an ECR method, or the like is used for the pixel T.
It may be used as a silicon film (active layer) of FT, and these methods do not require a manufacturing process such as solid phase growth.

If the writing time is designed to be sufficiently long, the driving frequency of not only the pixel TFT but also the data driving circuit can be reduced. For example, if the number of bits in one block (or the number of bits of the external driver LSI) is set to 300 bits or more, the operating frequency of the peripheral circuit (particularly, the shift register unit) can be significantly reduced. Therefore, a low mobility SPC crystallized film can be used for part or all of the peripheral circuit.

The shift register circuit 31 in the data side peripheral circuit area has a D-type flop flop circuit 42 having a buffer 41 as shown in FIG. The buffer circuit 32 in the data-side peripheral circuit region has a configuration in which CMOS transistors 43 as shown in FIG.
It has a p output terminal and an n output terminal connected to the S and n-type MOS, respectively. Further, the gate drive circuit 38 has a circuit configuration as shown in FIG.
4, a shift register unit 45, a multiplexer unit 46, and an output buffer unit 47.

The transistors shown in FIGS. 15 to 17 are TFTs whose mobility has been adjusted by the above-described method.
Is used. (Second Embodiment) A laser light irradiation method using a plurality of light-shielding masks at the time of laser light irradiation for crystallization of silicon will be described.

FIGS. 18A to 18C are plan views showing a light-shielding mask used for crystallization by irradiating a laser beam to an amorphous silicon film on a glass substrate. FIG. 18 (a)
A first light-shielding mask 52 having a first laser light transmission port 51 in a portion corresponding to the display region of the amorphous silicon film. FIG. 18B shows a second light shielding mask 54 having a plurality of rectangular second laser light transmitting windows 53 formed at portions corresponding to outside the four sides of the display area. FIG.
8 (c) is a third light-shielding mask 56 having a rectangular third laser light transmitting window 55 formed at a portion corresponding to the outside of the four corners of the display area.

The first to third light shielding masks 52, 54, 56
Has a structure in which first to third laser light transmission windows 51, 53, and 55 are formed in a metal film such as molybdenum formed on quartz glass, or a structure in which a first to third laser light is formed in a metal plate such as molybdenum. It has a structure in which transmission windows 51, 53 and 55 are formed. When the linear laser light and the glass substrate are relatively scanned by sequentially exchanging the first to third light-shielding masks 52, 54, and 56, as shown in FIG. Are formed with three types of regions 62 to 64 having different field-effect mobilities.

For example, when the first light shielding mask 52 is used, the mobility of the amorphous silicon film 61 is 10 cm ² / Vs
The first linear laser light having the energy density as described above is irradiated. When the second light shielding mask 54 is used, the mobility of the amorphous silicon film 61 is 30 to 50 cm.
^{A second} linear laser beam having an energy density of ² / Vs is applied. Further, when the third light-shielding mask 56 is used, a second linear laser beam having an energy density at which the mobility of the amorphous silicon film 61 becomes 50 cm ² / Vs or more is applied.

According to this, the region 62 of the crystalline silicon film 61 irradiated with the linear laser beam using the first light-shielding mask 52 becomes a low-speed operation region. Region 63 irradiated with linear laser light
Is a medium-speed operation region, and a region 64 irradiated with linear laser light using the third light-shielding mask 54 is a high-speed operation region.

The pixel TFT is formed in the low-speed operation area, the peripheral circuit is formed in the medium-speed operation area, and the CPU, the interface circuit, the memory element and the like are formed in the high-speed operation area. CP on liquid crystal display panel
An apparatus in which a sheet type computer such as U is formed is called a system on panel.

The laser beam applied to the amorphous silicon film 61 may be a linear laser beam as in the first embodiment or a two-dimensional laser beam. As shown in FIG. 20, a laser crystallization apparatus using a plurality of light-shielding masks and a two-dimensional laser beam includes a laser beam emission source 72 on a side of a mask storage cassette mechanism 71 for storing a plurality of light-shielding masks 70a to 70e. It has a structure including a two-dimensional laser converter 73 and an XY scan type substrate mounting table 74. Light shielding masks 53, 54, 56
Is performed by a mask moving mechanism (not shown).

In the peripheral circuit area shown in the first embodiment, linear laser light is applied to the data-side peripheral circuit area 3a and the scanning-side peripheral circuit area 4a, and FIGS. The two types of light-shielding masks 28 and 29 shown in FIG. However, when a two-dimensional laser beam is used, laser light transmitting windows 57a to 57d are provided at portions corresponding to the data side peripheral circuit regions 3a and 3b and the scanning side peripheral circuit regions 4a and 4b as shown in FIG. A light shielding mask 57 may be used.

The laser irradiation apparatus according to the present embodiment is not applied only to laser crystallization.
The present invention can also be applied to the case where a doping gas containing an impurity element such as PH ₃ or B ₂ H ₆ is introduced. (Other Embodiments) Laser transmission window 5 shown in FIG.
Alternatively, a plurality of light-shielding masks 58a to 58h may be used in which the light-shielding substrates 1 to 55 are collectively formed on one light-shielding substrate and divided into a plurality of light-shielding masks as shown in FIG. In this case, the light-shielding masks 58a to 58h having the laser transmission windows 51a to 51h, 53, and 55 are arranged at positions adjacent above the glass substrate, and the alignment is performed using a stepper or the like.

Further, the shape of the laser transmission window formed in the light shielding mask may be the pattern shape of the active layer used for the TFT. In this case, the amorphous silicon film other than the region irradiated with the laser beam through the laser transmission window may be removed from the glass substrate using a mixed solution of hydrofluoric acid, nitric acid, and acetic acid. In the first embodiment, laser light is applied to the entire data-side peripheral circuit regions 3a and 3b and the scan-side peripheral circuit regions 4a and 4b of the crystalline silicon film 10. However, as shown in FIGS. 23A and 23B, the data side peripheral circuit areas 3a and 3b and the scan side peripheral circuit areas 4a and 4b
May be used as light-shielding masks 81 and 82 having laser transmission windows 81a and 82a, each of which is divided into a plurality of block regions, whereby a high-speed operation region 83 and a medium-speed operation region 84 as shown in FIG. Formed in 10.

[0075]

As described above, according to the present invention, the field effect mobility of a plurality of regions of the semiconductor device is changed by irradiating the semiconductor layer with linear or two-dimensional laser light. Regions having different crystallinities are selectively formed on the same substrate to optimize the characteristics of the pixel TFT and the peripheral circuit TFT, and the through-put can be improved as compared with the case where a spot laser is used.

Further, since the semiconductor film in the pixel region is not irradiated with the laser beam, it is possible to prevent the occurrence of a scan pattern due to a crystal change due to the laser irradiation. By using a semiconductor film formed on the substrate as a low mobility region and using a high mobility crystallization laser annealing around the periphery, the laser light irradiation area is greatly reduced, and the number of laser pulses and the number of laser pulses are short. A laser crystal can be efficiently realized in the irradiation time.

Furthermore, since all the peripheral circuits are not irradiated with a laser beam having an intensity higher than necessary, an element having stable characteristics can be formed on the semiconductor film irradiated with the laser beam.

[Brief description of the drawings]

1 (a) is a plan view showing a functional region on a substrate, FIG. 1 (b) is a plan view showing a conventional laser light irradiation state, and FIG. 1 (c) is a laser irradiation state. FIG. 4 is a diagram showing the crystallinity of a semiconductor film in a pixel region that has been set.

FIGS. 2A and 2B are plan views showing positions of a pixel region, a peripheral circuit region, and a terminal region on a substrate used for manufacturing the liquid crystal display device according to the first embodiment of the present invention. .

FIGS. 3A to 3C are cross-sectional views illustrating a process for forming a thin film transistor according to the first embodiment of the present invention (part 1);
It is.

FIGS. 4A to 4C are cross-sectional views illustrating a process for forming a thin film transistor according to the first embodiment of the present invention (part 2);
It is.

FIGS. 5A to 5C are cross-sectional views illustrating steps of forming a thin film transistor according to the first embodiment of the present invention (part 3).
It is.

FIG. 6 is a configuration diagram showing a laser irradiation device used for manufacturing the liquid crystal display device according to the first embodiment of the present invention.

FIG. 7 is a plan view showing a first light-shielding mask used for manufacturing the liquid crystal display device according to the first embodiment of the present invention.

FIG. 8 is a plan view showing a second light-shielding mask used for manufacturing the liquid crystal display device according to the first embodiment of the present invention.

FIG. 9 is a plan view (part 1) showing laser irradiation used for manufacturing the liquid crystal display device according to the first embodiment of the present invention and an irradiation area thereof.

FIG. 10 is a plan view (part 2) showing laser irradiation used for manufacturing the liquid crystal display device according to the first embodiment of the present invention and an irradiation area thereof.

FIG. 11 is a diagram showing the relationship between the energy density of a laser beam and the mobility of a semiconductor layer of a laser irradiation device used for manufacturing the liquid crystal display device according to the first embodiment of the present invention.

FIG. 12 is a voltage-current characteristic diagram of a plurality of thin film transistors formed in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 13 is a circuit configuration diagram of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 14 is an operation timing chart of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 15 is a circuit diagram of a D-type flip-flop of a shift register circuit included in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 16 is a circuit diagram of a CMOS buffer included in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 17 is a circuit diagram of a gate driver included in the liquid crystal display device according to the first embodiment of the present invention.

FIGS. 18A to 18C are plan views of a light-shielding mask used for manufacturing a liquid crystal display device according to a second embodiment of the present invention.

FIG. 19 is a plan view showing a crystallinity improvement region by laser light irradiation using the light-shielding mask shown in FIG. 18;

FIG. 20 is a configuration diagram showing a laser beam irradiation device used in a second embodiment of the present invention.

FIG. 21 is a perspective view showing a state in which crystallization of a semiconductor film is improved by irradiation with a two-dimensional laser beam used in an embodiment of the present invention.

FIG. 22 is a plan view showing a plurality of light shielding masks used in the embodiment of the present invention.

FIGS. 23A and 23B are plan views showing an example of a light-shielding mask used when irradiating a part of a peripheral circuit of the liquid crystal display device of the embodiment of the present invention with laser.

FIG. 24 is a plan view showing a laser irradiation region on the semiconductor film irradiated using the light shielding mask shown in FIG. 23;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 1a-1d ... Display panel area, 2a-
2d: display area, 3a to 3h: data side peripheral circuit area,
4a to 4h: scanning-side peripheral circuit area; 10: crystalline silicon film; 11: silicon oxide film; 12a to 12c: gate electrode; 14: first interlayer insulating film; 15a to 15f: contact holes; 16b, 16c: contacts Hall, 17
a: Source extraction electrode, 17b: Drain bus line,
17c to 17f: source / drain electrodes, 18a, 18
b: gate wiring, 21: laser light source, 22: optical switch, 23, 25: mirror, 24, 26: linear converter, 2
7: substrate mounting table, 28, 29: light shielding mask, 31: shift register circuit, 32: buffer circuit, 34: pixel cell, 35, 36 ... TFT, 37: liquid crystal, 38: gate drive circuit, 41: external driver LSI, 70a to 70e
.., Light shielding mask, 71, cassette, 72, laser beam emission source, 73, two-dimensional laser converter.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 21/336 H01L 29/78 627G F term (Reference) 2H092 GA59 JA25 JA29 JA38 JA42 JA44 JB13 JB23 JB32 JB33 JB38 JB51 JB57 JB63 JB69 KA04 KA07 KB14 MA05 MA07 MA14 MA15 MA16 MA18 MA19 MA20 MA27 MA30 MA35 MA37 MA41 NA25 NA27 5F052 AA02 AA11 BA02 BA07 BA18 BB07 CA10 DA01 DA02 DB01 HA01 JA01 5F110 AA01 AA30 BB02 NN02 GG02 NN02 GG02 NN02 PP03 PP05 PP06 PP10 PP29 QQ21

Claims (14)

[Claims] A first semiconductor film having a first field-effect mobility is formed on a substrate having a display region, a first peripheral circuit region, and a second peripheral circuit region by a solid phase growth method or a direct film formation method. Forming; and irradiating the first semiconductor film on the first peripheral circuit region with a linear or two-dimensional first laser beam at a first energy density to have a second field-effect mobility. Converting the first semiconductor film on the second peripheral circuit region to a linear or two-dimensional second laser beam at a second energy density different from the first energy density. Changing to a third semiconductor film having a field-effect mobility of 3. 2. The method according to claim 1, wherein the first energy density is higher than the second energy density, and the first field-effect mobility is higher than the third field-effect mobility. The manufacturing method of the liquid crystal display device according to the above. 3. The third mobility of the third semiconductor film is higher than the first mobility of the first semiconductor film and higher than the second mobility of the second semiconductor film. 2. The method according to claim 1, wherein the liquid crystal display device is also small. 4. A data driving circuit is formed in the second semiconductor film on the first peripheral circuit region, and a gate driving circuit is formed in the third semiconductor film on the second peripheral circuit region. The method according to claim 3, wherein the liquid crystal display device is formed. 5. The irradiation of the first laser light is performed by relatively scanning the first laser light and the substrate in a first direction, and the irradiation of the second laser light is performed by the second laser light. The method according to claim 1, wherein the method is performed by relatively scanning a second laser beam and the substrate in a second direction. 6. The method according to claim 5, wherein the first direction is different from the second direction. 7. The method according to claim 5, wherein after the irradiation of the first laser beam is completed, the first direction and the second direction are made the same by rotating the substrate by 90 degrees. 3. The method for manufacturing a liquid crystal display device according to 1. 8. A thin film transistor having a first on-state current is formed on the first semiconductor film, and a second on-state current is larger than the first on-state current on the second semiconductor film. A second thin film transistor is formed; and a third thin film transistor having a third on-current larger than the first on-current and smaller than the second on-current is formed on the third semiconductor film. A method for manufacturing a liquid crystal display device, further comprising a step. 9. When irradiating the first laser light or the second laser light, by using a light shielding mask,
2. The method according to claim 1, wherein the first peripheral circuit region or the second peripheral circuit region is selected. 10. The method according to claim 9, wherein a plurality of the light-shielding masks are used. 11. The method according to claim 1, wherein the first or second laser beam is applied to a part of the first or second peripheral circuit region. . 12. A cassette for accommodating a plurality of light-shielding masks, a substrate mounting table for mounting a substrate, a laser light irradiating means for irradiating a laser beam toward the substrate, and selecting the light-shielding mask in the cassette. And a mechanism for transporting the substrate between the laser beam irradiating means and the substrate mounting table, and a mechanism for heating or moving the substrate mounting table. 13. The laser annealing apparatus according to claim 12, wherein said laser light irradiating means has a structure for irradiating said substrate with said linear or two-dimensional laser light. A pixel region having a first thin film transistor composed of 14. The first semiconductor layer of a field-effect mobility of 10 to 30 cm ² / Vs, in the vicinity of the pixel area, 30 cm ² / Vs or more field A liquid crystal display device comprising: a block line sequential driving type peripheral driving circuit having a second thin film transistor including a second semiconductor layer having an effective mobility.