JPH09260684A - Manufacture of liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the characteristic of a TFT at its boundary part gradually, by performing scanning of an energy beam a plurality of times, overlapping an end part irradiated region at each adjoining time, and performing the scanning, so that the boundaries between the overlapping regions and non- overlapping regions may be nonlinear. SOLUTION: At the time of linear energy beam irradiation for the n-th line, an optical system is moved by a step of 0.5mm per one shot in a range of ±2mm against a vibration center at random in the direction of Y-axis. The optical system from a first mirror 23 to an image forming lens 26 is moved in the direction of Y-axis by 96mm, and scanning for the (n+1)-th line is performed. And the optical system is moved by a step of 0.5mm per one shot at random, in the direction of Y-axis in a range of the maximum width 2mm. The overlapping region of the n-th line and the (n+1)-th line of the energy beam is in a random shape, and it is possible to change the characteristic (especially the threshold characteristic) of a TFT in the boundary part between the overlapping region and the non-overlapping region gradually.

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, and more particularly to a scanning method for irradiating amorphous silicon with a linear energy beam by scanning it a plurality of times to polycrystallize it.

[0002]

2. Description of the Related Art As a method of manufacturing a thin film transistor of a liquid crystal display device, a method of forming a source / drain region by reducing the resistance by partially polycrystallizing an amorphous silicon layer has been developed. To polycrystallize this amorphous silicon, a method of irradiating with an energy beam, melting and recrystallizing is adopted.

Regarding the method of irradiating this energy beam,
Japanese Patent Laid-Open No. 61-187222 discloses a method of converting an energy beam into a linear shape and irradiating it. Further, Japanese Patent Application Laid-Open No. 2-78217 discloses a method of keeping the overlapping region constant when scanning and irradiating the linear energy beam a plurality of times.

However, when the overlapping area is provided as described above, the overlapping area naturally has a larger irradiation amount of the energy beam than the other areas, and the characteristics of the thin film transistor, particularly the threshold characteristics change subtly. As a result, display unevenness appears in the image. As shown in FIG. 5, particularly when the overlapping area is always kept constant as described above, there is a problem that the display unevenness appears in a straight line and is visually very emphasized.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a liquid crystal display device in which display unevenness is not visually noticeable by giving a characteristic to a method of irradiating a linear beam beam. The purpose is to do.

[0006]

The present invention is directed to irradiating and scanning a linear beam on an amorphous silicon layer to convert the amorphous silicon layer into a polycrystalline silicon layer and irradiating a linear energy beam on the amorphous silicon layer. In the method of manufacturing a liquid crystal display device, the scanning is performed a plurality of times by shifting the position so as to cover the entire region converted into the polycrystalline silicon layer. The scanning is performed by overlapping the edge irradiation areas of each adjacent number of times of scanning,
This is a method for manufacturing a liquid crystal display device in which scanning is performed so that the boundary between the overlapping area and the non-overlapping area becomes non-linear.

According to the present invention, since the boundary between the overlapping region and the non-overlapping region of the energy beam is made non-linear, the display unevenness caused by the difference in the characteristics of the individual TFTs due to the energy beam irradiation amount can be visually recognized. Can be hardened.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 10 shows the structure of a liquid crystal display device. Array substrate 102 in which thin film transistor (TFT) 101 and pixel electrode 4 are formed on insulating substrate 1, and other insulating substrate 1
03, a color filter 104 and a counter substrate 106 on which a counter electrode 105 is formed are arranged so as to face each other with a spacer 107 and a seal 108 material interposed therebetween, and a liquid crystal 109 is sealed in this gap. Further, polarizing plates 110 and 111 are attached to the outer surfaces of the array substrate 102 and the counter substrate 106.

FIG. 1 shows a T used in an embodiment of the present invention.
1 shows the structure of FT101. First, a pixel electrode 4 made of indium tin oxide (ITO) is formed on an insulating substrate 1 made of glass. Then, a source electrode 5 and a drain electrode 6 made of a molybdenum-tungsten (MoW) alloy are formed. The drain electrode 6 has IT in the lower layer.
An O film is laid and has a two-layer structure. In addition, the source electrode 5 is IT which is an extension of the pixel electrode 4 in the lower layer.
O film is laid.

Next, on the insulating substrate 1, an n-type polycrystalline semiconductor layer 7 connected to the source electrode 5 and the drain electrode 6, and
An active layer 7a made of amorphous silicon is formed between the n-type polycrystalline semiconductor layers 7. Then, a gate insulating film 8 made of silicon nitride (SiNx) is formed on the semiconductor layer 7, and a gate electrode 11 made of an aluminum (Al) layer and a molybdenum (Mo) layer 10 is further formed thereon. A protective film 13 made of silicon nitride is coated on the uppermost part.

The TFT 101 configured as described above
The manufacturing process of is described in detail below with reference to FIGS. First, on the insulating substrate 1 made of glass,
ITO film 2 and MoW alloy film 3 by sputtering method
And are sequentially laminated to form a film. Next, the ITO film 2 and the MoW alloy film 3 are patterned by photolithography to form the pixel electrode 4, the drain line, the source electrode 5, and the drain electrode 6 (FIG. 2A). At this time, the pixel electrode 4 is covered with the MoW alloy film 3, but the MoW alloy film 3 is removed later.

Next, as shown in FIG. 2B, the thickness 1000
Angstrom amorphous silicon layer 7a, thickness 40
A silicon nitride film 8 having a thickness of 00 angstrom is sequentially formed by plasma CVD, and an Al film 9 and Mo 10 are further formed by sputtering. After that, the Mo film 10, the Al film 9 and the Si film are formed by photolithography.
The Nx film 8 is etched with the same pattern to form an Al film 9
And a gate electrode 11 composed of two layers of Mo film 10 and Si
A gate insulating film 8 made of an Nx film is formed. At this time,
The amorphous silicon layer 7a is not etched. In order to prevent excessive etching of the amorphous silicon layer 7a, a film of silicon oxide (SiOx) or the like may be formed on the amorphous silicon layer 7a. After that, the amorphous silicon layer 7 is formed using the gate electrode 11 as a mask.
Phosphorus (P) was added to a at a accelerating voltage of 60 kV and a dose amount of 3 × 10 ¹⁵ / cm ² by a non-mass separation type ion implantation apparatus, and a part of the amorphous silicon layer 7 a was made into an n-type amorphous layer. Then, the amorphous silicon layer 7a is irradiated with an energy beam having an energy density of 150 mJ / cm ² by using XeCl excimer laser device having a wavelength of 308 nm.
The amorphous silicon layer 7a containing P is used as an n-type polycrystalline silicon layer 7, and the n-type polycrystalline silicon layer 7 is etched by photolithography to form source / drain contact regions (FIG. 2C). ).

Next, the entire surface of the structure thus formed is covered with, for example, SiNx by a plasma CVD method to form a protective film 13. Then, the protective film 13 on the peripheral electrodes and the pixel electrodes is removed by etching by photolithography. Further, since the MoW alloy film 3 remains on the pixel electrode 4 made of ITO at this point, the MoW alloy film 3 is removed by etching.

Thus, as shown in FIG. 1, the source electrode 5, the drain electrode 6, the pixel electrode 4, the polycrystalline semiconductor layer 7,
T composed of the gate insulating film 8, the gate electrode 9 and the protective film 13
The array substrate 102 of the liquid crystal display device having FT can be obtained.

In contrast to the array substrate 102, the insulating substrate 1
The counter substrate 106 having the color filter 104 and the counter electrode 105 formed thereon is bonded to the spacer 03 via the spacer 107 and the sealant 108, and the liquid crystal 109 is sealed therein. Further, polarizing plates 110 and 111 are attached to the outer surfaces of the array substrate 102 and the counter substrate 106 to obtain a liquid crystal display device.

Next, the linear energy beam irradiation for polycrystallizing the above-mentioned amorphous silicon will be described in detail. FIG. 3 shows the appearance of the excimer laser annealing apparatus used in this example. This excimer laser annealing apparatus has an optical system that forms a linear energy beam.

In FIG. 3, an excimer laser oscillation source 21 having an oscillation wavelength of 308 nm was used as the laser oscillation source.
The energy beam 22 oscillated from the excimer laser oscillation source 21 is reflected by the first mirror 23 to change its course, and then the optical system 24 including a homogenizer.
And the course is changed by being reflected by the second mirror 25.

Then, the energy beam is formed by the imaging lens 2
On the substrate 28 placed on the stage table 27 by 6,
It is imaged as a linear beam 29. This stage stand 27
Can be moved in the X-axis direction, and the first mirror of the one-way optical system to the imaging lens 26 can be integrally moved in the Y-axis direction. That is, the scanning direction is the X-axis direction and the direction perpendicular to the scanning direction is the Y-axis direction.

FIG. 4A shows the X of the linear energy beam intensity.
FIG. 4B shows a cross-sectional profile in the Y-axis direction of the linear energy beam intensity, and both cross-sectional profiles show a top flat trapezoidal profile. The length of the energy density uniform portion in the X-axis direction (width direction) of the linear energy beam is 0.4.
mm, and the length of the energy density uniform part in the Y-axis direction (longitudinal direction) is 100 mm. However, the end of each axis has a hem, so that 10% to 9% of the maximum value of energy intensity
Between 0%, a skirt of about 0.05 mm in the X-axis direction and about 1 mm in the Y-axis direction is drawn.

From the first mirror 23 to the imaging lens 26
The optical system up to is moved in synchronization with the oscillation of the energy beam. The oscillation frequency of the energy beam is 100 Hz, and the stage table 29 is 0.1 mm for one pulse irradiation of the linear energy beam so that the overlap amount of the linear energy beam in the X-axis direction is 75%.
Move in the X-axis direction. That is, since the width of the linear energy beam in the X-axis direction is 0.4 mm, four shots of energy beam irradiation are performed at one location.

Here, in this embodiment, in order to prevent the overlapping region with the (n + 1) th column from being linear, the optical system is moved to the Y-axis during the scanning of the linear energy beam irradiation of the nth column. Randomly moving in a direction within a range of ± 2 mm with respect to the center of vibration in steps of 0.5 mm per shot.

Next, after scanning the nth row linear energy beam, the optical system from the first mirror 23 to the imaging lens 26 is moved in the Y-axis direction by 96 mm, and then the (n + 1) th.
Scan the columns. Then, as in the case of the irradiation of the n-th row, the optical system is randomly set in the Y-axis direction within the range of the maximum width of 2 mm.
The shot is moved and scanned in steps of 0.5 mm.
FIG. 5 schematically shows such a scanning state of the nth row and the n + 1th row of the linear energy beam.

FIG. 7 shows 0.1 mm in the X-axis direction when the linear energy beams in the nth and (n + 1) th columns, which are scanned while vibrating in the direction perpendicular to the scanning direction, are superposed.
It is a figure showing the number of shots in the area of 0.5 mm in the Y-axis direction, the number of times of individual shots and the number of times of superposition. From FIG.
It can be seen that the number of shots in the overlapping region of the linear energy beams in the nth column and the (n + 1) th column is gradually changing.

FIG. 6A is a diagram showing an overlapping region of the nth column and the (n + 1) th column of the linear energy beam, and FIG. 6B is a linear energy of the nth column and the (n + 1) th column vibrating in the Y-axis direction. It is a figure which shows the shape of the edge part of a beam. 6A and 6B
As is clear from the above, the overlapping regions of the nth column and the (n + 1) th column of the linear energy beam have a random shape, and by doing so, at the boundary between the overlapping region and the non-overlapping region, Since the characteristics of the TFT (in particular, the threshold characteristics) gradually change, it is difficult to visually recognize the display unevenness resulting from this, and an image with a good appearance can be obtained.

In the present embodiment, both the nth column and the (n + 1) th column are moved in the Y axis direction at random while scanning in the X axis direction. For example, the nth column is randomly moved to the (n + 1) th column.
The column may be scanned linearly, or the nth column may be randomly scanned and the (n + 1) th column may be scanned in the same manner as the nth column. The shape of the boundary between the nth column and the (n + 1) th column can be a periodic function curve.

In the above example, the linear energy beam is oscillated by moving the optical system in the Y-axis direction, but it is also possible to move the stage. further,
In the above example, by moving the optical system or the stage in the Y-axis direction, the overlapping region of the linear energy beams of the nth column and the (n + 1) th column is made non-linear, but as shown in FIG. A light modulation element array 40 in which a plurality of light modulation elements 30 are arranged along the linear energy beam 29 is arranged under the imaging lens 26, and light at a position corresponding to the end of the linear energy beam is arranged. The refractive index or the transmittance of the modulation element 30 may be changed.

(Embodiment 2) Next, a TFT having a structure different from that of Embodiment 1 will be described as an example. FIG. 11 shows T of this embodiment.
The structure of FT201 is shown. Insulating substrate 20 made of glass
2 has a polycrystalline silicon layer 203 formed thereon, and this polycrystalline silicon layer 203 has a channel region 203a and a source region 203b so as to sandwich the channel region 203a.
And a drain region 203c. A gate insulating film 204 is formed so as to cover the other crystalline silicon layer 203. Further, a gate electrode 205 is patterned and formed on the gate insulating film 204.
An interlayer insulating film 206 is formed so as to cover 5. The source electrode 207 and the source region 203b are connected to each other and the drain region 203c and the drain electrode 208 are connected to each other through a contact hole formed in the interlayer insulating film 206. The pixel electrode 20 is formed on the source electrode 207.
9 is connected.

Next, a method of manufacturing the TFT 201 will be described below. First, an amorphous silicon layer having a thickness of about 800 Å is formed on the insulating substrate 202 made of glass by the plasma CVD method. Subsequently, this amorphous silicon layer is irradiated with a linear energy beam while scanning to form a polycrystalline silicon layer 203. The energy density at this time is set to about 300 to 500 mJ / cm ² . Then, as in the first embodiment, irradiation is performed so that the overlapping region of a plurality of scans becomes non-linear. The polycrystalline silicon layer 203 thus formed is patterned into an island shape.

Next, a SiOx film is formed as a gate insulating film 204 so as to cover the polycrystalline silicon layer 203, and a MoW alloy is deposited by a sputtering method. The deposited MoW alloy is patterned to form the gate electrode 205. Next, using this gate electrode 205 as a mask, the polycrystalline silicon layer 20
Ion doping is performed on the regions to be the source region 203b and the drain region 203c. Next, SiOx is formed as an interlayer insulating film 206 so as to cover the gate electrode 205. Further, in this state, the doped ions are activated, and then the polycrystalline silicon layer 203 is hydrogenated. Then, contact holes are formed in the interlayer insulating film 206 on the source region 203b and the drain region 203c, and the source electrode 207 and the drain electrode 208 made of Al or the like are formed as the source region 203b and the drain region 2, respectively.
It is formed so as to be connected to 03c.

In the first and second embodiments described above, the TF of the pixel area is
Although the present invention is applied to the manufacture of T, the present invention can be applied to peripheral drive circuits, that is, the X driver and the Y driver shown in FIG. In this case, the scanning direction of the linear energy beam is set parallel to the extending direction of the X driver so that the X driver does not cross the overlapping region of the linear energy beams of the nth column and the (n + 1) th column. It is preferable to remove the overlap region of the beam from the X driver.

[0031]

According to the present invention, when forming a TFT,
When a linear energy beam is scanned a plurality of times, non-linearly irradiating the overlapped area makes it difficult to visually perceive the display unevenness caused by the difference in the characteristics of individual TFTs depending on the energy beam irradiation amount. As a result, a good image can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thin film transistor of a liquid crystal display device in an example of the present invention.

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

FIG. 3 is an external view of an excimer laser annealing apparatus used in an example of the present invention.

FIG. 4 is a graph showing the relationship between the irradiation width and the energy intensity in the X-axis direction and the Y-axis direction of the linear energy beam used in the example of the present invention.

FIG. 5 is a diagram schematically showing a scanning state of the n-th column and the (n + 1) -th column in the embodiment of the present invention.

FIG. 6 is an enlarged view showing an overlapping region of linear energy beam irradiation on the n-th column and the (n + 1) -th column in the embodiment of the present invention.

FIG. 7 is a diagram showing the number of shots when the linear energy beams of the n-th column and the (n + 1) th column are overlapped in the embodiment of the present invention, the individual number of times and the number of times of superimposition.

FIG. 8 is a diagram schematically showing a liquid crystal display device including a peripheral drive circuit in an example of the present invention.

FIG. 9 is a view showing another device for making the overlapping region of the linear energy beam non-linear, which is applied to the present invention.

FIG. 10 is a cross-sectional view of a liquid crystal display device in an example of the present invention.

FIG. 11 is a sectional view of a thin film transistor according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 202 ... Insulating substrate 4, 209 ... Pixel electrode 5, 207 ... Source electrode 6, 208 ... Drain electrode 7, 203 ... Semiconductor layer 7a ... Active layer 8, 204 ... Gate insulating film 11, 205 ... Gate electrode 13 ... Protect Film 21 ... Laser oscillation source 26 ... Imaging lens 27 ... Stage base 28 ... Substrate 29 ... Linear beam

Claims (10)

[Claims] 1. A step of forming an amorphous silicon layer on a substrate, irradiating and scanning a linear beam on the amorphous silicon layer to convert the amorphous silicon layer into a polycrystalline silicon layer, Irradiation with the linear energy beam and scanning are performed a plurality of times by shifting the position so as to cover the entire region converted into the polycrystalline silicon layer, and a step of forming an array substrate, A method of manufacturing a liquid crystal display device comprising a step of bonding the array substrate and a counter substrate together and enclosing a liquid crystal in a gap between the array substrate and the counter substrate, wherein the energy beam is a plurality of times of adjacent linear energy beam scans. A method of manufacturing a liquid crystal display device, wherein scanning is performed by overlapping edge irradiation areas, and scanning is performed so that a boundary between an overlapping area and a non-overlapping area becomes non-linear. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein the scanning of the linear energy beam is performed while vibrating in a direction perpendicular to the scanning direction. 3. The n-th scan and the n + scan among the plurality of scans
2. The method of manufacturing a liquid crystal display device according to claim 1, wherein at least one of the first scanning is performed while oscillating while oscillating perpendicularly to the scanning direction. 4. The method of manufacturing a liquid crystal display device according to claim 1, wherein the linear energy beam scans in a fixed direction, and the substrate is vibrated in a direction perpendicular to the scanning direction. 5. The substrate on which the linear energy beam is irradiated has an X drive circuit portion substantially parallel to the major axis direction and a Y drive circuit portion substantially parallel to the minor axis direction at a peripheral portion of the substrate, The method of manufacturing a liquid crystal display device according to claim 1, wherein the scanning direction of the linear energy beam is substantially parallel to at least one of the drive circuit units. 6. The method for manufacturing a liquid crystal display device according to claim 5, wherein at least one of the drive circuit portions is irradiated with the linear energy beam by only one scanning. 7. The method of manufacturing a liquid crystal display device according to claim 5, wherein the scanning direction of the linear energy beam is substantially parallel to the X drive circuit section. 8. The shape of the boundary between the overlapping region and the non-overlapping region is approximate to a periodic function curve.
The manufacturing method of the liquid crystal display device according to the above. 9. The method of manufacturing a liquid crystal display device according to claim 1, wherein the linear energy beam is an excimer laser beam. 10. The optical path of the linear energy beam comprises:
Arranging a light modulation element array composed of a plurality of light modulation elements capable of changing the refractive index or the transmittance, and changing the refractive index or the transmittance of the light modulation element at the position corresponding to the end of the linear energy beam. The method for manufacturing a liquid crystal display device according to claim 1, wherein the boundary between the overlapping region and the non-overlapping region is made non-linear by the above method.