JP2003017702A - Flat-panel display device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive circuit unit which can be improved in performance by controlling the growth direction of crystal grains, where a plurality of conduction directions of carriers reside in the drive circuit unit because of high integration. SOLUTION: After an amorphous silicon film is formed, the amorphous silicon film is patterned in a display unit so as to align its lengthwise direction in a certain direction, and the amorphous silicon film is patterned in a drive circuit unit so as to align its lengthwise direction with a plurality of directions for high integration. After patterning is carried out the patterned amorphous silicon films are irradiated with a laser beam in a certain direction so as to turn to poly-crystal silicon films. By this setup, crystal grains are grown in the direction vertical to the lengthwise directions of the poly-crystal silicon films, so that a device can be improved in performance without impeding the conduction of carriers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display device and a manufacturing method thereof, and more particularly to a drive integrated flat panel display device having a display section and a driving circuit section formed on the same insulating substrate and a manufacturing method thereof.

[0002]

2. Description of the Related Art In an active matrix flat panel display device, the voltage applied to the liquid crystal of each pixel is controlled by a thin film semiconductor element connected to the pixel. Hydrogenated amorphous silicon has been used as the semiconductor layer of the thin film semiconductor device. However, in recent years, polycrystalline silicon has come to be used as a higher performance thin film semiconductor element.

By using polycrystalline silicon, it becomes possible to integrally form the drive circuit portion of the flat display device or a part thereof on the same insulating substrate as the display portion. Furthermore, the concept of system-on-glass can be developed.

For example, the input / output function as the drive circuit section in the flat display device has not been formed on the insulating substrate on which the display section is formed so far. Normally, for these input / output functions, an LSI chip having a crystalline silicon substrate is connected via TAB (Tape Aided Bonding) or the like. The concept of system-on-glass is to form a drive circuit section that performs input / output functions and the like on the same insulating substrate as the display section. As described above, by integrating the display unit and the drive circuit unit associated therewith, the cost can be reduced. More importantly, it is possible to develop the possibility of a new device of small size, light weight, and thin shape that integrates various functions. By using the integrated type, the T that connects the LSI chip and the drive circuit unit as in the past has been connected.
Since AB is not required, a smaller, lighter and thinner device is possible.

By the way, in the drive-integrated device, a polycrystalline silicon film is formed on an insulating substrate as an active layer of a thin film semiconductor element. Polycrystalline silicon is composed of crystal grains that are crystal parts and crystal grain boundaries that exist between the crystal grains.

The crystal grain boundary is a region where the crystallinity is greatly disturbed and contains many defects. Regarding electrical conductivity,
Although the carriers can easily pass through the crystal grains, they are scattered at the grain boundaries or trapped in the defect level,
Difficult to pass. Therefore, polycrystalline silicon has higher electric conductivity in the crystal grains than the amorphous substance, but lower electric conductivity in the crystal grain boundaries than in the amorphous substance.

Therefore, when a polycrystalline silicon film is used as an active layer of a thin film semiconductor device, control of crystal grain boundaries is an important issue. The characteristics of the semiconductor device largely depend on the crystal grain boundaries existing in the channel layer in the active layer.

A conventional flat panel display using a polycrystalline silicon film will be described with reference to the drawings. In an active matrix flat panel display device using a polycrystalline silicon film, a display section and a drive circuit section for driving pixels in the display section are formed on the same substrate through the same manufacturing process.

As shown in FIG. 7, a flat panel display device 10 is provided.
1, a display unit 102 in which pixels are arranged in a matrix on the same insulating substrate, a Y drive circuit unit 104 that supplies an image signal to the pixels in the display unit 102, and a thin film semiconductor element provided for each pixel. An X drive circuit unit 103 for controlling a gate bus line connected to the gate is created. In the display section 102, as shown in FIG. 8, a thin film semiconductor element T for controlling the pixel potential for each pixel.
r are arranged in a matrix. Thin film semiconductor device T
In r, the gate is connected to the gate bus lines X1, X2, ..., On / off is controlled, and the source is the image signal line Y.
, Y2, ..., And the drain is connected to the pixel capacitor LC via the pixel electrode.

By the way, in the flat panel display device using amorphous silicon for the active layer of the thin film semiconductor element Tr, the drive circuit is realized by an LSI chip without being integrated. In a flat panel display device using polycrystalline silicon as an active layer, a driving circuit is integrated, but in this case, a thin film semiconductor element formed in the driving circuit portion is required to have high driving ability.

To form polycrystalline silicon, a solid phase growth method is used in which amorphous silicon is first deposited on a substrate and grown using light energy or heat energy of a laser or the like. However, no matter what method is used, no regularity is found in the crystal grain shape. This is because the crystal nuclei 112 are randomly generated during the crystal formation process of the amorphous silicon film 111 as shown in the vertical cross-sectional view of FIG.
It is thought that it is because it grows in a random direction as shown in. Therefore, when the generation of crystal nuclei is not controlled, the crystal grains in the display section 102, the X drive circuit section 103, and the Y drive circuit section 104 are respectively indicated by arrows A1, A2, and A3 as shown in FIG. As shown, all of them grow in random directions.

The characteristic of the carrier conduction mechanism in polycrystalline silicon is that the carriers conduct the crystal grains in the crystal region and the crystal grain boundaries containing many defects.
Conduction in grains is explained by the same mechanism that is normally considered in crystals. However, carriers are scattered and captured at the crystal grain boundaries, which hinders conduction. Therefore, it is necessary to control the crystal grain boundaries in order to produce a thin film semiconductor device having a high driving ability.

Thus, in consideration of the carrier conduction mechanism in polycrystalline silicon, in order to improve the driving ability of the thin film semiconductor element, the crystal grains should be grown largely along the conduction direction of the carriers of the thin film semiconductor element. Alternatively, it is considered effective to form crystal grain boundaries in accordance with the conduction direction of carriers. That is, in the MOS type thin film semiconductor element, since the crystal grains of polycrystalline silicon are grown long along the direction connecting the source region and the drain region, the carrier scattering probability at the crystal grain boundaries can be reduced. It is considered that it becomes possible to improve the driving ability.

As a control method of grain boundaries, Sequential Lateral Solidification (Sequential Lateral
Solidification) method has been proposed. This technique
At the time of forming the polycrystalline silicon, a photomask is placed between the laser light source and the surface of the irradiation film, and laser light is irradiated so as to project the photomask. By irradiating in this manner, the film is melted in the region irradiated with the laser beam, and the melting is not caused in the non-irradiated region.

As a result, as shown in the vertical sectional view of FIG. 10, crystal nuclei 132 are generated at the boundary between the laser-irradiated region and the non-irradiated region of the amorphous silicon film 131, and the crystal is formed. Parallel to the substrate surface, that is, arrow B
Grows in the direction indicated by. By controlling the generation of crystal nuclei in this manner, crystal grains can be grown along the scan direction of the mask.

As shown in FIG. 11, the above-described method of controlling grain boundaries using a laser beam is used to drive and integrate the flat panel display device 12.
1 is applied to the display unit 122 and the X drive circuit unit 12
3 and the Y-driving circuit portion 124 have the same major axis direction of the particle diameters as indicated by arrows B1, B2, and B3. By controlling the major axis direction of the crystal grains by using such a method, the performance of the thin film semiconductor element in the drive circuit units 123 and 124 has been conventionally improved.

However, in the conventional device shown in FIG. 11, in order to improve the performance of the thin film semiconductor element in the drive circuit sections 123 and 124, the major axis direction of the crystal grains is the carrier conduction direction of the thin film semiconductor element in the display section 122. It could only be fulfilled when

Generally, in the drive circuit units 123 and 124,
It requires more elements than the display unit 122. But,
In the flat panel display device, it is necessary to make the areas of the drive circuit units 123 and 124 as small as possible. This is to realize a larger display section 122 from an insulating substrate having the same size.

In order to reduce the area of the drive circuit sections 123 and 124, it is necessary to improve the density of the thin film semiconductor elements in the drive circuit sections 123 and 124. As one of the methods, it is necessary to devise the carrier conduction direction of the thin film semiconductor elements in the drive circuit units 123 and 124 so as to increase the degree of integration. Therefore, the drive circuit units 123, 1
Regarding the carrier conduction direction of the thin film semiconductor device in 24, at least two directions existed instead of one direction.

However, in the conventional drive-integrated flat panel display device, the crystal grains of the polycrystalline silicon film of the thin film semiconductor element are grown in random directions as shown in FIG. 7 or as shown in FIG. It was growing in one direction. In such a device, the carrier conduction direction of the thin film semiconductor elements in the drive circuit portions 123 and 124 and the crystal grain growth direction do not coincide with each other, so that the circuit cannot be improved in performance and integrated. Therefore, conventionally, it was not possible to realize a flat display device in which a high-performance drive circuit unit is integrally mounted with a display unit.

[0021]

As described above, when polycrystalline silicon is used in the active layer of a thin film semiconductor device, when the crystal nuclei are randomly generated and the crystal grains are grown in a random direction, or in all unidirectional directions. In the case where the crystal grains were grown, the high performance and highly integrated drive circuit section could not be mounted integrally with the display section. It is considered that this is because the carrier conduction direction is limited to one direction in the display portion, while the carrier travels in a plurality of directions in the drive circuit portion.

In view of the above circumstances, the present invention has an integrated drive type flat display capable of forming a high performance thin film semiconductor element in a drive circuit section in which carriers are conducted in at least two directions in order to achieve high integration. An object is to provide an apparatus and a manufacturing method thereof.

[0023]

A flat panel display device according to the present invention is a device in which a display section and a drive circuit section for driving the display section are formed on the same insulating substrate. Polycrystalline silicon is used for the active layer of each thin film semiconductor element included in the drive circuit section, and the polycrystalline silicon of the polycrystalline silicon in the display section is arranged in the major axis direction of the crystal grains of the polycrystalline silicon in the drive circuit section. At least one direction different from the major axis direction of the crystal grain is included.

Here, in all of the thin film semiconductor elements formed in the display section, the major axis directions of the active layers are substantially the same, and the thin film semiconductor elements formed in the drive circuit section are You may comprise so that there exist at least 2 types of major axis direction of an active layer.

A method of manufacturing a flat panel display device according to the present invention is a method of manufacturing a device in which a display section and a drive circuit section for driving the display section are formed on the same insulating substrate. The step of depositing the amorphous silicon film and the longitudinal direction of the amorphous silicon film in the display section are substantially the same, and the longitudinal direction of the amorphous silicon film in the display section in the drive circuit section is substantially the same. Patterning the amorphous silicon film so as to have at least one longitudinal direction different from the direction, and irradiating the patterned amorphous silicon film in the display unit and the drive circuit unit with light energy. And crystallization.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The method of manufacturing the flat panel display device according to the present embodiment includes the steps shown in FIG.

First, in step S10, an amorphous silicon film is formed on an insulating substrate such as a glass substrate.

At step S12, the amorphous silicon film is patterned. This patterning is performed so that the shape of the active layer of each thin film semiconductor element can be obtained in the display section and the drive circuit section on the insulating substrate. In the display unit, an active layer is provided for each of the pixels arranged in a matrix, and the active layers are arranged so that their longitudinal directions face the same direction. On the other hand, in order to achieve high integration in the driving circuit unit, the active layer is arranged such that the longitudinal direction of the active layer is not only in the same direction as the display unit but also in at least one different direction.

In step S14, an excimer laser annealing (hereinafter referred to as ELA) process is performed on the patterned amorphous silicon film. Here, the laser light irradiation is performed on the film surface of the amorphous silicon along one direction. As a result, crystal grains grow in each active layer in a direction orthogonal to the longitudinal direction due to a phenomenon described later.

FIG. 2 shows the orientation of the thin film semiconductor element T1 in the display section 2 of the flat panel display device 1 according to this embodiment, that is, the carrier conduction direction between the source region and the drain region.
The carrier conduction direction in the thin film semiconductor elements T2 to T5 in the X drive circuit unit 3 and the Y drive circuit unit 4 and the long axis direction of the crystal grains in the display unit 2, the X drive circuit unit 3, and the Y drive circuit unit 4 are indicated by arrows. It is shown by C and D1 to D4.

In the display section 4, the pixels are regularly arranged in a matrix as described above. Therefore, the thin film semiconductor elements arranged for each pixel are arranged such that the source region and the drain region are located in the same direction C, that is, the carriers are conducted in the same direction.

In the display section 4, crystal grains are grown in the source / drain direction so that the long axis of the polycrystalline silicon coincides with the carrier conduction direction in order to enhance the driving ability of the thin film semiconductor element. Therefore, the crystal grains of polycrystalline silicon in the display unit 2 are all grown in the same direction as shown in FIG.

On the other hand, in the X drive circuit section 3 and the Y drive circuit section 4, the longitudinal directions of the active layers are arranged so as to be oriented in arbitrary directions D1 to D4.

As described above, in the present embodiment, in the display section 2, the crystal grains of the polycrystalline silicon film as the active layer in the thin film semiconductor element have the major axis direction in one direction, and the drive circuit sections 3 and 4 are crystallized. The grains include those whose major axis directions do not match those in the display unit 2. By providing such a configuration, the performance of the element in the display unit 2, that is, the ability to control the pixel potential is improved, the performance of the element in the drive circuit units 3 and 4, that is, the drive ability is improved, and high integration is achieved. Can be realized at the same time.

In FIG. 3, crystal grains of polycrystalline silicon are grown in the same direction C in the display section 2, and a plurality of desired directions D1 to D4 are formed in the pixel drive circuit sections 3 and 4 in the same step.
I will show how to grow.

As shown in FIG. 3A, the insulating substrate 2
1 as an initial film of polycrystalline silicon, for example, PEC
The amorphous silicon film 22 is deposited by the VD method.

As shown in FIG. 3B, the amorphous silicon film 22 is patterned into a desired shape, that is, an active layer shape. The active layer has a relation of a <b, where a is a dimension in the direction of carrier conduction between the source and drain and b is a dimension orthogonal to this direction, and the direction having the dimension b is the longitudinal direction. Therefore, in the display unit 2, all of the active layers are patterned so that the longitudinal directions thereof are the same, and in the drive circuit units 3 and 4, the longitudinal direction of each active layer is an arbitrary direction as shown in FIG. To be patterned.

After this, as shown in FIGS. 3B and 4, crystallization is performed by irradiating, for example, an excimer laser beam as the laser beam 43 so as to scan in one direction shown by an arrow E. . As a result, the amorphous silicon film 22 becomes a crystallized polycrystalline silicon film. The length of the crystal grains of the obtained polycrystalline silicon film in the major axis direction is about half the patterning width a.

In order to realize the above-mentioned crystal growth, it is necessary to optimize the values of the patterning width a and the film thickness t according to the irradiation energy of the laser light 23 and the conditions of the substrate 21. For example, an insulating substrate 21 based on silicon oxide is used, and the intensity of the excimer laser is 200 to 2000 mJ /
When the cm ² and the initial film thickness t are 30 nm to 200 nm, the patterning width a is preferably in the range of a <20 μm. Further, the width of the laser light 43 needs to be larger than the width a of the amorphous silicon film 22.

In the plan view of FIG. 4, an amorphous silicon film to be an active layer of the thin film semiconductor element in the drive circuit portions 3 and 4 is
The crystalline state of the polycrystalline silicon films 31, 41 and 51 obtained by scanning the laser light along the one direction E is shown. In each polycrystalline silicon film 31, 41, 51, the width a
The grain boundaries 32, 42 and 52 are formed in the central portion of about half of the above so as to run along the longitudinal direction, and the crystal grain of width 1/2 * a grows in the direction orthogonal to the longitudinal direction.

The reason why the crystal grains grow in this way is considered as follows. When the amorphous silicon film formed on the insulating substrate is irradiated with the laser beam, only the amorphous silicon film has a high temperature. In the amorphous silicon film, heat escapes in the direction of easy release, so that the heat is radiated not in the longitudinal direction but in the direction of ½ * a from almost the center of the width a. Crystal grains having a length of 1/2 * a grow along this heat radiation direction.

FIG. 5 shows the surface of the polycrystalline silicon film 61 thus obtained. As described above, the crystal grain boundary 62 exists along the longitudinal direction at approximately the center. The presence of the crystal grain boundaries 62 makes it easier for scattering and trapping to occur at carriers when carriers are conducted between the source and drain located at both ends in the lateral direction. However, since all the elements have one crystal grain boundary in the central portion similarly, reproducibility is improved, and elements having equivalent characteristics can be uniformly formed.

As described above, according to the present embodiment, the amorphous silicon film is first formed, and the integration degree is improved in the drive circuit section so that the longitudinal direction is located in the same direction in the display section. Therefore, patterning is performed so that the longitudinal direction is located in an arbitrary direction, and laser light is irradiated along one direction to crystallize to obtain a polycrystalline silicon film. As a result, regardless of the scanning direction of the laser beam, in each polycrystalline silicon film, crystal grains grow along the carrier conduction direction from approximately the center to a length of about half the width a, so that the carrier conductivity is excellent. It is possible to produce the device with good reproducibility. As a result, high performance and high integration of the elements can be realized at the same time in the drive circuit section.

FIG. 6A shows an active layer 71 made of the polycrystalline silicon film obtained by the above embodiment and a gate electrode 73. This shows a structure of an element having a single gate structure. A crystal grain boundary 72 is formed along the longitudinal direction at a central position of about half the width of the active layer 71, and the crystal grain boundary 72 is located on the crystal grain boundary 72. The gate electrode 73 is arranged so that

FIG. 6B shows the structure of an element having a double gate structure. A crystal grain boundary 82 is formed along the longitudinal direction in about half the width of the active layer 81, and two gate electrodes 83 and 84 are arranged between the crystal grain boundaries 82.
The gate electrodes may be arranged in any manner, but, for example, when the design rule regarding the gate electrodes is large, the structure shown in FIG.
A single gate structure may be used as shown in FIG. 6A and a double gate structure may be used as shown in FIG. 6B when the design rule is reduced.

The above-described embodiment is an example and does not limit the present invention. Further, the present invention can be widely applied to a liquid crystal display device, a flat display device using an organic EL element, and the like, in which a display portion and a drive circuit portion are formed on the same insulating substrate. is there.

[0048]

As described above, by patterning an amorphous silicon film and then irradiating it with laser light to crystallize the amorphous silicon film, at least one of the polycrystalline silicon crystal grains in the major axis direction in the display portion is aligned. It is possible to obtain a flat display device in which crystal grains of polycrystalline silicon of a drive circuit section are grown in different directions, which improves the driving ability of each thin film semiconductor element of the display section and the drive circuit section, and at the same time High integration of the circuit unit can be realized.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method of manufacturing a flat panel display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing directions of crystal grains of an active layer of a thin film semiconductor element of a display section and a drive circuit section in the flat display device.

FIG. 3 is an explanatory view showing a method of performing heat treatment on the active layer of the thin film semiconductor element of the display section in the flat display device.

FIG. 4 is an explanatory view showing that light energy is applied after patterning the active layer of the thin film semiconductor element of the display section in the flat panel display device.

5 is a plan view showing crystal grains of an active layer that has been heat-treated by the method shown in FIG.

FIG. 6 is a plan view showing a configuration of a thin film semiconductor element in the flat panel display device.

FIG. 7 is a plan view showing a configuration of a conventional flat panel display device.

FIG. 8 is a perspective view showing a circuit configuration of a display unit in the flat panel display device.

FIG. 9 is a vertical cross-sectional view showing growth of crystal grains of a thin film semiconductor element in a display section of the flat panel display device.

FIG. 10 is a vertical cross-sectional view showing the growth of crystal grains in the active layer of the thin film semiconductor element of the display section in the flat panel display device.

FIG. 11 is a plan view showing the configuration of another conventional flat panel display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Flat display device 2 Display part 3, 4 Drive circuit part 21 Insulating substrate 22 Amorphous silicon film 23 Laser beam 24, 32, 42, 52, 62, 72, 82 Crystal grain boundary 31, 41, 51, 61, 71 , 81 polycrystalline silicon films 73, 83, 84 gate electrodes T1 to T5 thin film semiconductor element

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/20 H01L 29/78 612B 21/336 618Z 627G F term (reference) 2H092 GA59 JA24 JA40 JB22 JB31 JB61 KA04 KA05 MA13 MA28 MA30 NA21 NA27 NA29 5C094 AA15 BA03 CA19 FB14 5F052 AA02 BA01 BA04 BB07 DA02 DB03 EA15 FA22 JA01 5F110 AA01 AA04 BB02 CC01 DD02 EE28 GG02 GG13 GG45 PP03 PP05 PP06 PP24 5G435 AA18 EE33 HEE37 HKK

Claims (3)

[Claims] 1. A flat display device in which a display section and a drive circuit section for driving the display section are formed on the same insulating substrate, wherein the display section and the drive circuit section each include a thin film semiconductor element. Polycrystalline silicon is used for the active layer, and the major axis direction of the polycrystalline silicon crystal grains in the drive circuit section is at least one of the major axis direction of the polycrystalline silicon crystal grains in the display section. A flat-panel display device characterized by including different directions. 2. The long-axis directions of the active layers of all the thin-film semiconductor elements formed in the display section are substantially the same, and the thin-film semiconductor elements formed in the driving circuit section are the active layers. 2. The flat panel display device according to claim 1, wherein there are at least two types of layers in the major axis direction. 3. A method of manufacturing a flat panel display device, wherein a display part and a drive circuit part for driving the display part are formed on the same insulating substrate, wherein an amorphous silicon film is deposited on the insulating substrate. And in the display unit, all the longitudinal directions of the amorphous silicon film are substantially the same, and in the drive circuit unit, at least one different longitudinal direction from the longitudinal direction of the amorphous silicon film in the display unit is used. Patterning each of the amorphous silicon films to have a direction, and irradiating the patterned amorphous silicon films in the display unit and the driving circuit unit with light energy to crystallize the amorphous silicon films. A method of manufacturing a flat panel display device, comprising: