JPH10207397A - Manufacture of active matrix display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To average dispersion in a threshold value voltage of a thin film transistor of an analog buffer by making a width of irradiation of a laser light source for laser crystallization wider than an interval between source followers and integer times of the interval between the source followers. SOLUTION: A data holding control signal is connected to plural parallel connected source followers. As a method of parallel connection of source followers, the follower only once receiving laser irradiation and the follower twice receiving it are combined to be connected. Then, two kinds of source followers with threshold value voltages different from each other are manufactured alternately or at every plural pieces for the advance direction of laser light. Then, the width L of the irradiation of the laser light is made the integer times (L=3d) of the width d of the source follower. By making the length of the overlapped part of the irradiation area of the laser light the integer times of the width of the source follower, the source followers with different irradiation amounts are manufactured regularly arranging them for the moving direction of the laser light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an active matrix type display device comprising thin film transistors, and more particularly to a drive circuit for an active matrix type display device having a source follower as an analog buffer and having a small variation in its characteristics. Circuit.

[0002]

2. Description of the Related Art In an active matrix type display device, pixels are arranged at each intersection of a matrix, and all pixels are provided with switching elements, and image information is turned on / off by switching elements. What is controlled. As a display medium of such a display device, a liquid crystal, a plasma, an object or a state capable of electrically changing optical characteristics (reflectance, refractive index, transmittance, emission intensity, and the like) are used. In the present invention, a three-terminal element, that is, a field-effect transistor having a gate, a source, and a drain is used as the switching element.

In the description of the present invention, a row in a matrix refers to a row in which a signal line (gate line) arranged in parallel to the row is connected to a gate electrode of a transistor in the row. Means that a signal line (source line) arranged in parallel to the column is connected to a source (or drain) electrode of a transistor in the column. Further, a circuit that drives the gate line is called a gate drive circuit, and a circuit that drives the source line is called a source drive circuit. In the gate drive circuit, a shift register of the number of gate lines in the vertical direction is serially connected in one column in order to generate a signal of vertical scanning timing of the active matrix type display device. Thus, the thin film transistor in the active matrix display device is switched by the gate drive circuit.

In the source drive circuit, in order to display the horizontal image data of the image data displayed by the active matrix display device, shift registers having the number of source lines in the horizontal direction are connected in series in one column. The analog switch is turned on / off by a latch pulse synchronized with the horizontal scanning signal. In this manner, the source drive circuit allows a current to flow through the thin film transistor in the active matrix display device to control the orientation of the liquid crystal cell.
FIG. 9 is a schematic diagram of a conventional active matrix display device. There are two types of manufacturing processes for polycrystalline silicon thin film transistors, a high temperature process and a low temperature process. In the case of a high-temperature process, polycrystalline silicon is formed on an insulating film on a quartz substrate, and a thermally oxidized SiO ₂ film is formed on a gate insulating film. Thereafter, a gate electrode is formed, N ions or P ions are implanted, source / drain electrodes are formed, and a polycrystalline silicon thin film transistor is manufactured.

In the low-temperature process, there are two types of silicon crystallization methods, a solid phase growth method and a laser annealing method. First, the solid phase growth method uses amorphous silicon on an insulating film on a glass substrate. By applying a heat treatment to the film at 600 ° C. for 20 hours, a polycrystalline silicon film can be obtained,
Second, in the laser annealing method, a polycrystalline silicon film can be obtained by irradiating the amorphous silicon on the surface of the glass substrate with a laser and heat-treating only the film surface at a high temperature. Generally, crystallization is achieved using either or both of these methods. Then, an SiO ₂ film is formed on the gate insulating film by a plasma CVD method. Thereafter, a gate electrode is formed, N ions or P ions are implanted, source / drain electrodes are formed, and a polycrystalline silicon thin film transistor is manufactured.

The source line drive circuit is a circuit for vertically scanning image data on an active matrix panel of an active matrix type display device, and comprises a shift register, an analog switch formed of a thin film transistor, and a capacitor. And an analog buffer formed of thin film transistors.

Since the source line has a large load capacity, the analog memory cannot directly drive the thin film transistor in the active matrix type display device, so that an analog buffer is required. In the analog buffer, a thin film transistor is formed by a source follower, and as shown in FIG.
One thin film transistor is independently arranged and manufactured at a constant interval with respect to the wiring of the control signal for holding data in the book. FIG. 6A is an example of an N-channel type, but a P-channel type or both may be used as shown in FIG. 6B.

[0008]

The analog buffer constituting the source line driving circuit of the conventional active matrix type display device has the following problems. The analog buffer is formed by connecting thin film transistors independently by a source follower. As described above, when the laser annealing method is used as one of the crystallization means, there is no large-diameter laser device capable of processing a large substrate by batch irradiation. During crystallization, as shown in FIG.
A silicon laser light source having a band-like width L is irradiated on the silicon horizontally in the X-axis direction. When the laser light source is moved at a constant interval in the X-axis direction for irradiation, an overlapped portion of the laser processing is generated. Since the width L of the irradiation band of the laser light source does not always coincide with the distance d of the source follower shown in FIG. 7B, the amount of laser light irradiated differs depending on the location of silicon during the laser crystallization step.

For this reason, the thin film transistors manufactured from silicon have variations in location and characteristics, and as shown in FIG. 8, the threshold voltage V _{th of the} thin film transistors varies within a certain range with respect to a change in the value of the X axis. V _thH to V
It changes with _thL . The threshold voltage V _th decreases where lasers overlap, and increases where lasers do not overlap.
As a result, the output voltage of the source follower also varies in height, and the variation directly becomes the variation in the applied voltage to the liquid crystal element.

FIG. 11 shows the characteristics of the transmittance and the applied voltage of a normally white liquid crystal display device. Thus, the variation of the applied voltage applied to the liquid crystal element results in the variation of the transmittance by the width ΔV _th .

As described above, the output voltage of the source line driving circuit differs depending on the location, which causes display unevenness of the pixels of the active matrix display device.

[0012]

In order to solve the above problems, the present invention provides the following means. Conventionally, one analog buffer is arranged for a data holding control signal for one data line. In the present invention, however, a plurality of source followers in which data holding control signals are connected in parallel are provided. It is characterized by being connected. Further, as a method of connecting the source followers in parallel, a connection is made by combining a combination of receiving laser irradiation only once and a connection receiving laser irradiation twice. The irradiation width L of the laser light source for laser crystallization is wider than the distance d between the source followers and is set to an integer n times (3 or more) the distance d between the source followers. Note that the setting of the irradiation width L of the laser light source may be set with some margin. That is, L + ΔL may be set to allow a margin for alignment.

Further, the number of source followers connected in parallel is two or more and (n-1) or less. By combining those having different irradiation times, variation in the threshold voltage of the thin film transistor can be reduced. Here, the interval between the source followers and the width of the laser irradiation have been described. However, since the interval between the pixels and the interval between the source followers are generally equal, the above-described interval between the source followers can be rephrased as the interval between the pixels.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a circuit diagram of a first embodiment of the present invention, in which two source followers are connected in parallel with each other in parallel with the traveling direction of laser light. The distance between the source followers is d, and the irradiation width of the laser beam is L = 3d. The source follower matrix is defined as (l,
m), the source follower (p, q) and the source follower (p + q) in the rectangle indicated by the leftmost dotted line first.
1, q), source follower (p + 2, q), source follower (p, q + 1), source follower (p + 1, q +
1) and the source follower (p + 2, q + 1) are irradiated with laser light. Here, the source follower (p, q) and the source follower (p + 1, q) are irradiated once with laser light.

Next, the laser beam moves rightward, and the source follower (p + 2, q), the source follower (p + 3, q), and the source follower (p + 4,
q), source follower (p + 2, q + 1), source follower (p + 3, q + 1), and source follower (p + 2
4, q + 1). Further, the laser light moves to the right, and the source follower (p
+4, q), source follower (p + 5, q), source follower (p + 6, q), source follower (p + 4, q +
1) Irradiates the source follower (p + 5, q + 1) and the source follower (p + 6, q + 1).

When such irradiation is performed, the source follower (p, q) and the source follower (p, q) in the hatched area
q + 1), source follower (p + 2, q), source follower (p + 2, q + 1), source follower (p + 4,
q), source follower (p + 4, q + 1), source follower (p + 6, q), and source follower (p + 6, q
In the case of +1), since the laser light is irradiated twice, the threshold voltage becomes V _thL as shown in FIG.

On the other hand, a source follower (p + 1, q), a source follower (p + 1, q + 1) and a source follower (p + 3, q) and a source follower (p +
3, q + 1), the source follower (p + 5, q), and the source follower (p + 5, q + 1) each have 1 laser beam.
Since the irradiation is performed only once, the threshold voltage becomes V _thH as shown in FIG.

As described above, two types of source followers having different threshold voltages are produced alternately in the traveling direction of the laser beam or for each of a plurality of them.

In general, in the laser crystallization step, the laser beam is irradiated so as to overlap with the previous irradiation region so that there is no region not irradiated with the laser beam.

Therefore, in this embodiment, the width L of the laser beam irradiation is set to an integral multiple (L = 3d) of the width d of the source follower, or an approximate integral multiple. In this manner, by setting the length of the overlapping portion of the laser light irradiation area to be an integral multiple (d) of the width d of the source follower, the source followers having different laser light irradiation amounts can be moved with respect to the moving direction of the laser beam. And can be arranged regularly.

In the circuit arrangement shown in FIG. 1, the source follower (p, q) and the source follower (p + 1, q), the source follower (p + 2, q) and the source follower (p +
3, q), source follower (p + 4, q) and source follower (p + 5, q), source follower (p + 1, q +
1) and source follower (p + 2, q + 1), source follower (p + 3, q + 1) and source follower (p + 4, q
+1), the source follower (p + 5, q + 1) and the source follower (p + 6, q + 1) are connected in parallel.

When the laser beam irradiation as described above is performed in the state of such connection, the threshold voltage becomes V
state that the source follower of the source follower and V _thH of _thL are connected in parallel one by one each is obtained. With such a configuration, the characteristics of the entire source follower are averaged, and variations in characteristics caused by laser irradiation can be reduced.

FIG. 2 is a circuit diagram of a second embodiment of the present invention, in which three followers are connected in parallel in the traveling direction of laser light. In this example, the interval between the source followers is d, and the irradiation width of the laser beam is L = 4d.
First, the laser light is irradiated with a source follower (p, q) and a source follower (p + 1,
q), source follower (p + 2, q), source follower (p + 3, q), source follower (p, q + 1), source follower (p + 1, q + 1), source follower (p +
2, q + 1), source follower (p + 3, q + 1), source follower (p, q + 2), source follower (p +
1, q + 2), source followers (p + 2, q + 2), and source followers (p + 3, q + 2).

Here, the source follower (p, q), source follower (p, q + 1), source follower (p, q +
In 2), the laser light is irradiated in the laser light irradiation one step before, so that the three source followers are irradiated with the laser light for the second time.

Next, the laser beam moves one step, and the laser beam is irradiated. Then, the source follower (p + 3,
q), source follower (p + 4, q), source follower (p + 5, q), source follower (p + 6, q), source follower (p + 3, q + 1), source follower (p + 4
4, q + 1), source follower (p + 5, q + 1), source follower (p + 6, q + 1), source follower (p
+3, q + 2), source follower (p + 4, q + 2),
The source follower (p + 5, q + 2) and the source follower (p + 6, q + 2) are irradiated with laser light.

Thus, the source follower (p + 3,
q), the source follower (p + 3, q + 1), and the source follower (p + 3, q + 2) are irradiated with the second laser light.

Then, the next stage of laser light irradiation is performed, so that the source follower (p + 6, q), the source follower (p + 6, q + 1), the source follower (p + 6
6, q + 2) is irradiated with the second laser light.

In the source follower that has been subjected to the second laser light irradiation, the threshold voltage is V _thL as shown in FIG.
become.

On the other hand, a source follower (p + 1, q), a source follower (p + 2, q), a source follower (p + 1, q + 1), which has not been subjected to one laser beam irradiation,
Source follower (p + 2, q + 1), source follower (p + 1, q + 2), source follower (p + 2, q +)
2), source follower (p + 4, q), source follower (p + 5, q), source follower (p + 4, q + 1),
Source follower (p + 5, q + 1), source follower (p + 4, q + 2), source follower (p + 5, q +
In 2), the threshold voltage becomes V _thH as shown in FIG.

Here, an example is shown in which a region shown by a dotted line in the drawing is irradiated once with a laser beam, and the laser beam is irradiated so as to partially overlap the region. However, a single location may be irradiated with laser light a plurality of times. However, the number of times must be determined.

As shown in FIG. 2, the source follower (p,
q), source followers (p + 1, q) and source followers (p + 2, q), source followers (p + 3, q), source followers (p + 4, q), and source followers (p + 5, p + 5)
q), source follower (p + 1, q + 1), source follower (p + 2, q + 1) and source follower (p + 3, q
+1), source follower (p + 4, q + 1), source follower (p + 5, q + 1) and source follower (p + 6,
q + 1), source follower (p + 2, q + 2), source follower (p + 3, q + 2) and source follower (p +
4, q + 2), three source followers are connected in parallel, so that one source follower that has been twice irradiated with laser and two source followers that have been once irradiated with laser are connected in parallel. Can be connected. With such a configuration, the characteristics of all sets of source followers can be made uniform, and variations in characteristics caused by laser irradiation can be suppressed.

FIG. 3 is a circuit diagram of a third embodiment of the present invention.
This is an example in which two units are connected in parallel by skipping every other unit. In this embodiment, similarly to the second embodiment shown in FIG. 2, the distance between the source followers is d, and the width L of the laser beam irradiation is L = 4.
As d, the laser light is irradiated so that the irradiation areas overlap by the width d.

First, the source follower (p, q) and the source follower (p, q + 1) are irradiated with laser light. Then, the laser beam is applied to the source follower (p,
q), source follower (p + 1, q), source follower (p + 2, q), source follower (p + 3, q), source follower (p, q + 1), source follower (p + 1, q)
q + 1), the source follower (p + 2, q + 1), and the source follower (p + 3, q + 1).

Next, the laser light moves, and the source follower (p + 3, q), the source follower (p + 4, q), the source follower (p + 5, q), and the source follower (p + 6, p + 6)
q), source follower (p + 3, q + 1), source follower (p + 4, q + 1), source follower (p + 5, q
+1), the source follower (p + 6, q + 1) is irradiated with laser light.

Next, the laser light moves, and the source follower (p + 6, q) and the source follower (p + 6, q + 1)
Is irradiated with laser light.

Here, the source follower (p, q), the source follower (p, q + 1), the source follower (p + 3,
q), source follower (p + 3, q + 1), source follower (p + 6, q), source follower (p + 6, q +
In 1), since the laser light is irradiated twice, the threshold voltage becomes V _thL as shown in FIG.

On the other hand, the source follower (p + 1, q), the source follower (p + 2, q), the source follower (p + 2, q)
1, q + 1), source follower (p + 2, q + 1), source follower (p + 4, q), source follower (p +
5, q), the source follower (p + 4, q + 1), and the source follower (p + 5, q + 1) are not irradiated with the laser light once, so that the threshold voltage is V as shown in FIG.
It becomes _thH .

As shown in FIG. 3, the source follower (p, q) and the source follower (p + 2, q), the source follower (p + 1, q) and the source follower (p + 3,
q), source follower (p + 4, q) and source follower (p + 6, q), source follower (p, q + 1) and source follower (p + 2, q + 1), source follower (p +
1, q + 1) and source follower (p + 3, q + 1), source follower (p + 4, q + 1) and source follower (p
+6, q + 1), by connecting two source followers in parallel every other source, any one of the two source followers receives laser irradiation twice in all parallel circuits, It is possible to realize a combination in which the other one receives laser irradiation once. The equivalent circuit of the configuration shown in FIG. 3 is the same as the configuration shown in FIG. 1, and the same effect as in the arrangement shown in FIG.
Can also be obtained when the configuration shown in FIG.

FIG. 4 is a circuit diagram of a fourth embodiment of the present invention, in which two source followers are obliquely connected in parallel to the traveling direction of the laser. As in the first embodiment shown in FIG. 1, the laser beam is irradiated with the source follower interval being d and the irradiation width L of the laser beam being L = 3d.

Therefore, the source follower (p, q), the source follower (p, q + 1), the source follower (p + 2,
q), source follower (p + 2, q + 1), source follower (p + 4, q), source follower (p + 4, q +
1), the source follower (p + 6, q), and the source follower (p + 6, q + 1) are irradiated with laser light twice, so that the threshold voltage is V as shown in FIG.
It becomes _thL .

On the other hand, the source follower (p + 1, q), the source follower (p + 1, q + 1), the source follower (p
+3, q), source follower (p + 3, q + 1), source follower (p + 5, q), source follower (p + 5,
q + 1) is irradiated with laser light only once, so that the threshold voltage becomes V _thH as shown in FIG.

As shown in FIG. 4, the source follower (p,
q) and source follower (p + 1, q + 1), source follower (p + 1, q) and source follower (p + 2, q +
1), source follower (p + 2, q) and source follower (p + 3, q + 1), source follower (p + 3, q) and source follower (p + 4, q + 1), source follower (p + 4, q) and source follower (p + 5, q + 1) ,
Source follower (p + 5, q) and source follower (p + 5)
6, q + 1) are connected in parallel, these parallel circuits have a different connection pattern from the parallel circuit of the first embodiment shown in FIG. 1, but are equivalent in terms of circuit, and the same effect can be obtained. it can.

FIG. 5 is a circuit diagram of a fifth embodiment of the present invention, in which three source followers are obliquely connected in parallel. In this embodiment, similar to the second embodiment shown in FIG.
Let d be the distance between the source followers and the width L of the laser beam irradiation
Is set to L = 4d, and the laser light is irradiated so that the irradiation area overlaps by the width d.

Accordingly, the source follower (p, q), the source follower (p, q + 1), and the source follower (p, q +
2), source follower (p + 3, q), source follower (p + 3, q + 1), source follower (p + 3, q +)
2), source follower (p + 6, q), source follower (p + 6, q + 1), source follower (p + 6, q +)
In 2), since the laser light is irradiated twice, the threshold voltage becomes V _thL as shown in FIG.

On the other hand, the source follower (p + 1, q), the source follower (p + 2, q), the source follower (p + 2, q)
1, q + 1), source follower (p + 2, q + 1), source follower (p + 1, q + 2), source follower (p
+2, q + 2), source follower (p + 4, q), source follower (p + 5, q), source follower (p + 4,
q + 1), source follower (p + 5, q + 1), source follower (p + 4, q + 2), source follower (p +
5, q + 2) is irradiated with laser light only once, so that the threshold voltage becomes V _thH as shown in FIG.

As shown in FIG. 5, the source follower (p, q), the source follower (p + 1, q + 1), the source follower (p + 2, q + 2), and the source follower (p +
1, q), source follower (p + 2, q + 1), source follower (p + 3, q + 2), source follower (p +
2, q), source follower (p + 3, q + 1), source follower (p + 4, q + 2), source follower (p +
3, q), source follower (p + 4, q + 1), source follower (p + 5, q + 2), source follower (p +
4, q), the source follower (p + 5, q + 1) and the source follower (p + 6, q + 2), when these three source followers are connected in parallel, these circuits are the same as in the second embodiment shown in FIG. One of the three source followers receives laser irradiation twice and the other two follow
It can be a combination of receiving laser irradiation twice. Then, the same effect as in the second embodiment can be obtained.

Hereinafter, a manufacturing process of an example of a source follower formed using a thin film transistor will be described with reference to FIG.
Explanation will be made using 0. Here, a complementary inverter circuit is taken as an example.

First, a glass substrate (a low alkali glass such as Corning 7059 or quartz glass is used)
A silicon oxide film having a thickness of 1000 to 3000 ° was formed thereon as a base oxide film. As a method for forming this oxide film, a sputtering method in an oxygen atmosphere was used. However, in order to further improve mass productivity, a film in which TEOS is decomposed and deposited by a plasma CVD method may be used.

Thereafter, an amorphous silicon film is deposited in a thickness of 300 to 5000 °, preferably 500 to 1000 ° by a plasma CVD method or an LPCVD method.
The crystals were left to crystallize in a reducing atmosphere at 4 ° C. for 4 to 48 hours. After this step, it is performed by laser irradiation,
Further, the degree of crystallization was increased. The laser light source is 3
Those that emit light having a wavelength of 08 nm or 248 nm were used. Then, the silicon film crystallized in this manner was patterned to form island regions 1 and 2. Further, a silicon oxide film 3 having a thickness of 700 to 1500 ° was formed thereon by sputtering.

Thereafter, aluminum having a thickness of 1000 to 3 μm (1 wt% of Si or 0.1 to 0.3 wt.
% Of Sc (scandium) film was formed by an electron beam evaporation method or a sputtering method. Then, a photoresist (for example, OFPR800 /
30 cp) by spin coating. In addition,
Before forming the photoresist, a thickness of 1
When an aluminum oxide film of 100 to 1000 ° is formed on the surface, the adhesion to the photoresist is improved, and the leakage of current from the photoresist is suppressed. This was effective in forming the oxide only on the side surfaces. Thereafter, the photoresist and the aluminum film were patterned and etched together with the aluminum film to form gate electrodes 4 and 5 and mask films 6 and 7. (FIG. 10a)

Further, this is anodized by passing an electric current in an electrolytic solution to have a thickness of 3000 to 6000 °, for example, a thickness of 5 mm.
An anodic oxide of 000 ° was formed. Anodizing is 3-2
It may be performed by using 0% citric acid or an acidic aqueous solution of oxalic acid, phosphoric acid, chromic acid, sulfuric acid or the like, and applying a constant current of 10 to 30 V to the gate electrode. In this embodiment,
The voltage was set to 10 V in an oxalic acid solution (30 ° C.)
Anodized for 40 minutes. The thickness of the anodic oxide was controlled by the anodic oxidation time. (FIG. 10b)

Next, the mask was removed, and a current was again applied to the gate electrode in the electrolytic solution. In this embodiment,
An ethylene glycol solution containing 3 to 10% tartaric acid, boric acid, and nitric acid was used. A better oxide film was obtained when the temperature of the solution was lower than room temperature around 10 ° C. For this reason, the barrier type anodic oxide 10 is provided on the upper and side surfaces of the gate electrode.
11 was formed. The thickness of the anodic oxides 10 and 11 is proportional to the applied voltage.
A 0 ° anodic oxide was formed. Anodic oxides 10, 11
Was determined by the magnitude of the required offset. To obtain an anodic oxide with a thickness of 3000 mm or more, 2
Although it is necessary to apply a high voltage of 50 V or more, it is preferable to set the thickness to 3000 ° or less because it adversely affects the characteristics of the thin film transistor. In this example, the applied voltage was increased to 80 to 150 V, and the voltage was selected according to the required thickness of the anodic oxide films 10 and 11.

It should be noted that although barrier-type anodic oxidation is a later step, barrier-type anodic oxide is not formed outside the porous anodic oxide, but barrier-type anodic oxidation is performed. The objects 10 and 11 are to be formed between the porous anodic oxides 8 and 9 and the gate electrodes 4 and 5. And
Dry etching method (or wet etching method)
The insulating film 3 was thus etched. This etching depth is arbitrary, and etching may be performed until the underlying active layer is exposed, or may be stopped during the etching. However, from the viewpoint of mass productivity, yield, and uniformity, it is desirable to perform etching up to the active layer. At this time, the insulating films 12 and 13 having the original thickness are left on the insulating films (gate insulating films) below the regions covered with the anodic oxides 8 and 9 and the gate electrodes 4 and 5. . (FIG. 10c)

Thereafter, the anodic oxides 8 and 9 were removed. As the etchant, a phosphoric acid-based solution, for example, a mixed acid of phosphoric acid, acetic acid, and nitric acid is preferable. At this time, in the phosphoric acid-based etchant, the etching rate of the porous anodic oxide is at least 10 times the etching rate of the barrier anodic oxide. Therefore, barrier-type anodic oxides 10, 1
Sample No. 1 was substantially not etched by the phosphoric acid-based etchant, so that the inner gate electrode could be protected.

Sources and drains were formed by implanting N-type or P-type impurity ions accelerated by this structure into the active layer. First, while the thin film transistor region on the left side was covered with the mask 14, phosphor ions were irradiated at a relatively low speed (typically, an acceleration voltage of 5 to 30 kV) by an ion doping method. In this embodiment,
The accelerating voltage is 20 kV, phosphine (PH ₃ ) is 9 as doping gas, and the dose is 5 × 10 ^{14 to} 5
× 10 ¹⁵ cm ^-2 . In this step, since phosphorus ions cannot pass through the insulating film 13, phosphorus ions were implanted only into the exposed regions of the active layer to form the drain 15 and the source 16 of the N-channel thin film transistor. (FIG. 10d)

Next, a relatively high speed (typically, an acceleration voltage of 60 to 120
kV) of phosphorus ions. In this embodiment, the acceleration voltage is 90 kV, and the dose is 1 × 10 ^{13 to} 5 × 10 ¹⁴ c.
m ^-2 . In this step, the phosphorus ions penetrate the insulating film 13 and reach the region thereunder. However, since the dose is small, low-concentration N-type regions 17 and 18 are formed.
(FIG. 10e)

After the phosphorus ion doping is completed, the mask 14 is removed. This time, the N channel type thin film transistor is masked. Similarly, the source 19, the drain 20 and the low concentration P type Regions 21 and 22 were formed. Then, irradiation with a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) was performed to activate the impurity ions introduced into the active layer.

Finally, a silicon oxide film is formed as an interlayer insulator 23 on the entire surface by the CVD method so as to have a thickness of 3000 to 6000Å.
Formed. Then, contact holes were formed in the source and drain of the thin film transistor, and aluminum wiring and electrodes 24, 25, and 26 were formed. 200 to 400
Hydrogen annealing was performed at ℃. Thus, a complementary inverter circuit using a thin film transistor was completed.
(FIG. 10f) In the above description, the inverter circuit has been described, but the same applies to other circuits. Although a coplanar thin film transistor has been described here, the present invention can be applied not only to a coplanar thin film transistor but also to another type of thin film transistor such as an inverted staggered thin film transistor.

[0059]

According to the present invention, for example, in the laser crystallization step, even if the threshold voltage _Vth of the source follower constituting the analog buffer varies, the source follower is connected in parallel. Of the threshold voltage of the thin film transistor can be averaged.

Further, a plurality of source followers constituting the analog buffer are arranged in parallel, and the laser light is irradiated so as to overlap a predetermined number of the source followers, thereby suppressing variations in the characteristics of the analog buffer. be able to.

Specifically, the laser irradiation width is set to n times (n ≦ n) the interval between the source followers arranged according to a predetermined rule.
By setting 3) and making the laser beams overlap at some of the source followers, the characteristics of the analog buffer can be averaged. That is, a combination of source followers having different numbers of laser beam irradiations can be the same in a plurality of analog buffers, so that variations in characteristics of the analog buffers can be averaged.

By using such an analog buffer, for example, a liquid crystal display device having no display variation can be realized.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of an analog buffer of an embodiment in an active matrix display device according to the present invention.

FIG. 2 is a circuit diagram of an analog buffer of an embodiment in an active matrix display device according to the present invention.

FIG. 3 is a circuit diagram of an analog buffer of an embodiment in the active matrix display device according to the present invention.

FIG. 4 is a circuit diagram of an analog buffer of an embodiment in an active matrix display device according to the present invention.

FIG. 5 is a circuit diagram of an analog buffer of an embodiment in an active matrix display device according to the present invention.

FIG. 6 shows a circuit diagram of an analog buffer in a conventional active matrix display device.

FIG. 7 shows a schematic view of laser irradiation in a conventional analog buffer manufacturing process.

FIG. 8 shows a relationship between a laser light source position x and a threshold voltage _Vth of a thin film transistor when a thin film transistor used for a conventional analog buffer is manufactured.

FIG. 9 is a schematic view of a conventional active matrix display device.

FIG. 10 shows a method of manufacturing a complementary inverter circuit.

FIG. 11 is a diagram showing a relationship between an applied voltage and a transmittance in a conventional normally white liquid crystal element.

[Explanation of symbols]

 1, 2 island-shaped region (active layer) 3 silicon oxide film (gate insulating film) 4, 5 gate electrode 6, 7 mask film 8, 9 anodic oxide 10, 11 barrier type anodic oxide 12, 13 insulating film 14 Mask 15 Drain 16 Source 17, 18 Low-concentration N-type region 19 Source 20 Drain 20, 21 P-type region 23 Interlayer insulator 24, 25, 26 Electrode

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[Procedure amendment]

[Submission date] February 2, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] work of an active matrix display device
Manufacturing method

Claims (14)

[Claims] 1. A source line drive that includes at least an active matrix circuit composed of thin film transistors arranged in a matrix and a plurality of analog buffers arranged with a width d in a first direction, and supplies a signal to the active matrix circuit. A method for manufacturing an active matrix display device having a circuit, wherein a step of forming a semiconductor film above the substrate; Irradiating the semiconductor film with laser light while scanning in a direction, and forming at least the active matrix circuit and the analog buffer using a semiconductor film crystallized by the laser light, The width of the overlapping portion of the laser light irradiation area in the first direction is an integral multiple of the width d. Method of manufacturing an active matrix display device according to claim. 2. The active matrix display device according to claim 1, wherein each of the analog buffers includes a plurality of source followers arranged in the first direction and connected in parallel with each other. Method. 3. An active matrix circuit composed of thin film transistors arranged in a matrix and at least a plurality of buffer circuits arranged with a width d in a first direction, and a source line drive for supplying a signal to the active matrix circuit A method of manufacturing an active matrix display device having a circuit, a step of forming a semiconductor film above a substrate; and a step of irradiating the semiconductor film with a laser beam extending in a direction perpendicular to the first direction. Scanning the laser beam in a direction perpendicular to the first direction; and forming at least the active matrix circuit and the buffer circuit using a semiconductor film crystallized by the laser beam. A width of the overlapping portion of the laser light irradiation area in the first direction is larger than the width d. A method for manufacturing an active matrix display device, which is characterized by the following. 4. The manufacturing method of an active matrix display device according to claim 3, wherein each of the buffer circuits includes a plurality of source followers arranged in the first direction and connected in parallel with each other. Method. 5. The method for manufacturing an active matrix display device according to claim 1, wherein the laser light is pulsed laser light. 6. A drive circuit comprising: a plurality of active matrix elements; a plurality of buffer circuits connected to a plurality of signal lines; Forming a semiconductor film above a substrate; irradiating the semiconductor film with a laser beam to crystallize the semiconductor film; and the crystallized semiconductor film. Forming the active matrix element and the buffer circuit using an active matrix element as an active layer. Each of the buffer circuits is connected in parallel corresponding to at least one of the plurality of signal lines. A method for manufacturing an active matrix display device comprising the first and second element circuits described above. 7. The buffer circuit according to claim 6, wherein the buffer circuit is arranged above the substrate in a first direction, and an overlapping area of the laser light irradiation area is a second direction orthogonal to the first direction. A method for manufacturing an active matrix type display device, characterized in that the display device is elongated. 8. The active matrix display device according to claim 6, wherein in one of the plurality of buffer circuits, a first element circuit has an electrical characteristic different from that of the second element circuit. Method of manufacturing. 9. A semiconductor device comprising: a plurality of active matrix elements; and a plurality of buffer circuits connected to a plurality of signal lines extending in a first direction, and supplies a signal to the active matrix element via the plurality of signal lines. At least one
A method for manufacturing an active matrix display device having two driving circuits, wherein: a step of forming a semiconductor film above a substrate; a step of irradiating the semiconductor film with laser light to crystallize the semiconductor film; Forming the active matrix element and the buffer circuit by using the formed semiconductor film as an active layer, wherein each of the buffer circuits comprises at least a first and a second element circuit; One of the element circuits of one of the plurality of buffer circuits is arranged along the first direction on the same line as one of the element circuits of the other one of the plurality of buffer circuits. A method for manufacturing an active matrix display device, characterized in that: 10. The method for manufacturing an active matrix display device according to claim 9, wherein the buffer circuits are arranged in a second direction orthogonal to the first direction. 11. The active device according to claim 10, wherein an overlapping portion of the irradiation area of the laser light extends long in the first direction, and the laser light is scanned in the second direction. Matrix display device. 12. The method for manufacturing an active matrix display device according to claim 6, wherein the driving circuit is a source driving circuit for supplying a video signal to the matrix element. 13. The method according to claim 6, wherein the first
And a method for manufacturing an active matrix display device, wherein the second element circuit is a follower circuit. 14. The method according to claim 6, wherein the first
And a second element circuit is a source follower circuit, the method for manufacturing an active matrix display device.