JP2001156296A - Method of driving active matrix display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of driving an active matrix display device well. SOLUTION: Thin film transistors adjacent to each other are improved in uniformity of threshold voltage to display excellent characteristics as an analog circuit. By this setup, a method of driving an active matrix display device well can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam irradiation process (so-called laser annealing method) in a semiconductor device manufacturing process. In particular, the present invention provides a semiconductor material comprising a part or all of an amorphous component, or
By irradiating a laser beam to a substantially intrinsic polycrystalline semiconductor material, and further to a semiconductor material that is damaged by ion irradiation, ion implantation, ion doping, or the like, and has significantly impaired crystallinity, The present invention relates to a method for improving the crystallinity of a material or recovering the crystallinity.

[0002]

2. Description of the Related Art In recent years, active research has been made on lowering the temperature of semiconductor device processes. The main reason is that
This is because a semiconductor element has to be formed on an insulating substrate such as glass. In addition, there is a demand accompanying miniaturization of elements and multilayering of elements. In a semiconductor process, the crystallization of an amorphous component or an amorphous semiconductor material contained in a semiconductor material, or the crystallinity of a semiconductor material that was originally crystalline but has been reduced in crystallinity due to irradiation with ions. In some cases, it is necessary to recover the crystallinity or to improve the crystallinity, although the crystallinity may be required.
Conventionally, thermal annealing has been used for such a purpose. When silicon is used as a semiconductor material,
By performing annealing at a temperature of 600 ° C. to 1100 ° C. for 0.1 to 48 hours or more, amorphous crystallization, recovery of crystallinity, improvement of crystallinity, and the like have been performed.

In general, the higher the temperature, the shorter the processing time may be. However, at a temperature of about 600 ° C., a long time processing is required. Therefore, from the viewpoint of lowering the temperature of the process, it has been necessary to replace the step conventionally performed by thermal annealing with another means. Laser light irradiation technology is attracting attention as the ultimate low-temperature process. In other words, laser light can be applied only to a required portion with high energy equivalent to thermal annealing, and it is not necessary to expose the entire substrate to a high temperature. Regarding the irradiation of laser light, roughly two methods have been proposed.

The first method uses a continuous wave laser such as an argon ion laser, and irradiates a semiconductor material with a spot beam. This is a method in which a semiconductor material is crystallized by melting and then solidifying slowly due to a difference in energy distribution inside the beam and movement of the beam. Second
Is a method in which a semiconductor material is crystallized by irradiating a semiconductor material with a high-energy laser pulse using a pulsed laser such as an excimer laser to instantaneously melt and solidify the semiconductor material.

[0005]

The problem with the first method is that it takes a long time to process. This is because the maximum energy of the continuous wave laser is limited, and the beam spot size is at most mm. On the other hand, in the second method, the maximum energy of the laser was very large, and therefore, mass productivity could be further improved by using a large spot of several cm ² or more.

However, in the case of irradiating a pulse laser, even if energy uniformity within a one-shot pulse beam can be achieved by improving the optical system, variation in element characteristics due to overlapping pulses is improved. It was difficult. In particular, when the element is located exactly at the end of the laser beam, the characteristics of the element (especially MO
The threshold voltage of the S transistor varied considerably. Regarding semiconductor devices, the variation in threshold voltage is quite acceptable in a digital circuit, but the variation in threshold voltage of an adjacent transistor is required to be 0.02 V or less in an analog circuit. Was.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem. In order to eliminate the variation due to the overlapping of the laser beams, it is ideal to perform the laser beam irradiation with a large beam that can irradiate the entire circuit at once, but it is practically impossible. Thus, in the present invention, by dividing the substrate into a relatively narrow region where the laser beam does not overlap and a relatively wide region where the laser beam overlaps,
As a whole, sufficient characteristics should be obtained.

In the present invention, the circuit on the substrate is divided into a circuit region centered on an analog circuit and a circuit region having a thin analog element. The circuit area is larger than the circuit area described above, so that the laser light can be applied to the entire circuit area centering on the analog circuit without substantially moving the laser light. Then, in a circuit area centered on the analog circuit, the laser light is irradiated substantially without moving the laser. That is, in the circuit area centering on the analog circuit,
The overlap of the laser beams is substantially eliminated.

On the other hand, in a circuit region where analog elements are thin, laser light is irradiated by scanning with laser light. As a result, laser beams overlap in this region. For example, in a liquid crystal display (monolithic liquid crystal display) in which an active matrix circuit and a peripheral circuit (driver circuit) for driving the active matrix circuit are formed on the same substrate, a circuit region centering on an analog circuit is defined as an active circuit. Driver circuit for driving the matrix,
Above all, it is a source driver (column driver) circuit that outputs an analog signal. On the other hand, a circuit region having a thin analog element is an active matrix circuit or a gate driver (scan driver) circuit.

In order to carry out the present invention, it is necessary to adjust the shape of the laser beam to such a circuit, or to adjust the shape of the circuit to the laser beam. It is desirable that Further, for example, since the column driver and the scan driver of the liquid crystal display are formed substantially orthogonally, the direction of the laser beam may be changed, or the direction of the substrate may be changed by approximately 1/4 turn to perform these processes. (More generally, (n / 2 + ／) (where n is a natural number) rotation).

[0011]

By performing the above processing, in the analog circuit area, no overlap can be made, and only the in-plane uniformity of the laser beam is controlled. As a result, by sufficiently improving the in-plane uniformity of the laser beam,
An element having uniform characteristics can be formed. On the other hand, in a circuit region where analog elements are thin, variations in characteristics due to the overlap of laser beams are inevitable, but in the first place, in such a circuit, a slight variation is allowed, so there is no substantial problem. .

As described above, according to the present invention, as a whole circuit formed on the substrate, the adverse effect due to the overlap of the laser beams can be eliminated, and the characteristics of the whole circuit can be improved. In the present invention, the shape of the object to be irradiated with the laser may be a film shape having no pattern or a device having a substantially completed device shape. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0013]

Embodiment 1 FIG. 4 shows a conceptual diagram of a laser annealing apparatus used in this embodiment. The laser light is oscillated by an oscillator 42, amplified by an amplifier 43 via total reflection mirrors 45 and 46, and further amplified by total reflection mirrors 47 and 4.
8, the light is introduced into the optical system 44. The laser beam up to that time has a rectangular shape of about 30 × 90 mm ² , but the optical system 64 has a length of 100 to 300 m.
m, processed into an elongated beam with a width of 10 to 30 mm. The energy of the laser beam passing through this optical system is up to 30J
/ Shot.

The optical path inside the optical system 44 is shown in FIG. The laser light incident on the optical system 44 passes through a cylindrical concave lens A, a cylindrical convex lens B, a horizontal fly-eye lens C, and a vertical fly-eye lens D. By passing through these fly-eye lenses C and D, the laser light changes from the Gaussian distribution type to the rectangular distribution. Further, the light passes through the cylindrical convex lenses E and F, passes through the mirror G (mirror 59 in FIG. 5), is focused by the cylindrical lens H, and is irradiated on the sample.

In this embodiment, the distances X ₁ and X ₂ in FIG. 5 are fixed, and the distance X ₃ between the virtual focus I (which is caused by the difference in the curved surface of the fly-eye lens) and the mirror G. , And the distances X ₄ and X ₅ were adjusted to adjust the magnification M and the focal length F. That is, there is a relationship between these, M = (X ₃ + X ₄ ) / X ₅ and 1 / F = 1 / (X ₃ + X ₄ ) + 1 / X ₅ . In this embodiment, the total length of the optical path X ₆
Was about 1.3 m.

By using a beam processed into such an elongated beam, the laser processing ability has been dramatically improved. That is, the strip-shaped beam exits the optical system 44 and is then irradiated onto the sample 51 via the total reflection mirror 49. However, since the width of the beam is substantially equal to or longer than the width of the sample, the beam is eventually turned on. The sample need only be moved in one direction. Accordingly, the sample stage and the driving device 50 have a simple structure and are easy to maintain. Further, the operation of alignment (alignment) when setting the sample is also easy. In the present invention, it is only necessary to have a function of rotating the sample in addition to the movement in one direction.

On the other hand, if the beam is nearly square, it is impossible to cover the entire surface of the substrate by itself, and the sample must be moved two-dimensionally in the vertical and horizontal directions. . However, in that case, the driving device of the stage becomes complicated, and it is difficult to perform positioning in two dimensions. In particular, when the alignment is performed manually, time loss in the process is large and productivity is reduced. These devices need to be fixed on a stable base 41 such as an anti-vibration table.

The above-mentioned laser device may be constituted independently, or may be constituted by another device, for example, a plasma CV.
It may be a multi-chamber combined with a D film forming apparatus, an ion implantation apparatus (or an ion doping apparatus), a thermal annealing apparatus, and other semiconductor manufacturing apparatuses. In this embodiment, an active matrix type liquid crystal display device (AMLC
In D), a so-called monolithic AMLCD in which peripheral circuits for driving an active matrix circuit are formed on the same substrate will be described.

In such an apparatus, as shown in FIG. 1A, an area 14 of an active matrix circuit, a column driver 13 and a scan driver 12 are provided on the edge of the substrate 11. I have. Actually, at this laser irradiation stage, as is clear from the above process, there is only a uniform film on the substrate, but for simplicity, the position where the circuit is formed is shown. . Column driver 13 is also scan driver 1
2 also has a shift register, but since the column driver outputs an analog signal, an amplifier (buffer circuit) for that is included. Such an A
The outline of the manufacturing process of the thin film transistor among the elements used in the MLCD was as follows.

[1] Formation of a base silicon oxide film and an amorphous silicon film on a glass substrate, and / or application of a crystallization accelerator (eg, nickel acetate, etc.) on the amorphous silicon film [2] Crystallization of amorphous silicon film by solid phase growth (example of solid phase growth conditions: 550 ° C., 8 hours in nitrogen atmosphere) [3] Laser treatment of crystallized silicon film (to improve crystallinity) [4] Formation of island-shaped silicon region by etching of silicon film [5] Formation of gate insulating film (silicon oxide) [6] Formation of gate electrode [7] Injection of impurity element (phosphorus, boron, etc.) Source /
Drain formation [8] Activation of implanted impurities by laser irradiation [9] Interlayer insulation formation [10] Source / drain electrode formation

In this embodiment and the following embodiments 2 and 3, the above-mentioned process relates to the laser light irradiation of [3] performed for the purpose of further improving the crystallinity of the polycrystalline silicon film.

FIG. 1 shows a laser processing step of this embodiment. In the present embodiment, the laser beam 15 has a size sufficient to irradiate the entire column driver 13, and is, for example, a rectangle having a width of 10 mm and a length of 300 mm. First, FIG.
As shown in (B), the substrate was moved so that the laser light was irradiated on the column driver. At this stage, the substrate is not irradiated with laser light. Thereafter, the laser beam was irradiated without substantially moving the laser beam and the substrate. Laser light irradiation was performed in the air, and the substrate temperature was 200 ° C. As a laser, a KrF excimer laser (wavelength: 248 nm) was used. The oscillation frequency of the laser is 10 Hz and the energy density of the laser light is 30
0 mJ / cm ² , and the pulse of the laser beam was 10 shots. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (FIG. 1 (B))

After that, the position to be irradiated with the laser beam was shifted downward, and the substrate was moved to a position where the active matrix region 14 and the upper end of the scan driver 12 hit the laser beam 15. (FIG. 1 (C)) Then, the substrate was moved while being irradiated with a laser beam. For example, the oscillation frequency of the laser was 10 Hz, the energy density of the laser light was 300 mJ / cm 2, and the scanning speed of the laser light was 10 mm / s. As a result, the laser beam 15 shifts by 1 mm. Since the width of the beam is 10 mm, about 10 shots of laser light are irradiated at one location. (Fig. 1 (D))

As described above, the laser was scanned to the lower end of the substrate, and the scan driver 12 and the active matrix area 14 were irradiated with laser light. (FIG. 1 (E)) In this embodiment, the laser beam did not overlap in the column driver 13. As a result, the threshold voltage of the thin film transistor in the column driver became very small, and was typically 0.01 V or less in the adjacent thin film transistor and 0.05 V or less in the column driver. Other characteristics were similar.
On the other hand, a laser beam overlapped between the scan driver 12 and the active matrix area 14. Therefore, for example, the variation of the threshold voltage of the thin film transistor in the scan driver 12 was about 0.1 V for the adjacent one, and was about the same in the plane. The same applies to the active matrix region 14. However, this degree of variation did not hinder the operation of each circuit.

Embodiment 2 FIG. 2 shows a laser processing step of this embodiment. Also in this embodiment, the laser beam 25
Is a size sufficient to irradiate the entire column driver 23, and is, for example, a rectangle having a width of 10 mm and a length of 200 mm. First, as shown in FIG. 2B, the substrate was moved so that a laser beam was applied to the column driver. At this stage, the substrate is not irradiated with laser light. afterwards,
With virtually no movement of the laser beam and substrate,
Irradiated with laser light. Laser light irradiation was performed in the air, and the substrate temperature was 200 ° C. K as a laser
An rF excimer laser (wavelength 248 nm) was used.
The oscillation frequency of the laser was 10 Hz, the energy density of the laser light was 300 mJ / cm ² , and the pulse of the laser light was 10 shots. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (Figure 2
(B))

After that, the position to be irradiated with the laser beam was shifted downward, and the substrate was moved to a position where the upper end of the active matrix area 24 hit the laser beam 25. In this case, unlike the first embodiment, the scan driver 22 is not irradiated with the laser beam at this time. (FIG. 2 (C)) Then, the substrate was moved while irradiating a laser beam. For example, the oscillation frequency of the laser was 10 Hz, the energy density of the laser light was 250 mJ / cm ² , and the scanning speed of the laser light was 10 mm / s. As a result, the laser beam 25 is shifted by 1 mm. Since the width of the beam is 10 mm, about 10 shots of laser light are irradiated at one location. (FIG. 2 (D))

Thus, the laser was scanned to the lower end of the substrate, and the active matrix area 24 was irradiated with the laser beam. (FIG. 2 (E)) Thereafter, the substrate was rotated 1/4 turn. In FIG. 2F, a dotted square 26 is the position of the first substrate. (Figure 2
(F) Then, as shown in FIG. 2G, the substrate was moved so that the scan driver 22 was irradiated with laser light. At this stage, the laser beam is not irradiated to the substrate. . Thereafter, the scan driver 22 was irradiated with laser light without substantially moving the laser beam and the substrate. Laser oscillation frequency is 10H
z, the energy density of the laser beam is 300 mJ / cm ²
The pulse of the laser beam was 10 shots. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (Fig. 2 (G))

In this embodiment, not only the column driver 23 but also the scan driver 22 did not have laser beam overlap. In the present embodiment, the driver circuit irradiates a laser beam of 300 mJ / cm ² , whereas the active matrix circuit irradiates a laser beam of 250 mJ / cm ^2.
A laser beam of J / cm ² was irradiated. This is to obtain a thin film transistor having a small leakage current (a leakage current when a reverse bias voltage is applied to a gate; also referred to as an off current) in an active matrix circuit. On the other hand, driver circuits require high-speed operation of thin film transistors, so the energy of laser light is increased,
Get high mobility.

Embodiment 3 FIG. 3 shows a laser processing step of this embodiment. In the present embodiment, unlike the first and second embodiments, the present invention relates to a monolithic liquid crystal display having driver circuits on the upper, lower, left, and right sides of the substrate.
Such a display activating step (“[8] Activation of implanted impurities by laser irradiation” in Example 1)
Corresponding to).

FIG. 6 shows an outline of the whole process of the substrate to be processed according to the present embodiment. First, a substrate (Corning 7059, 300 mm × 200 mm) 101 is formed as a base oxide film 102 with a thickness of 1000 to 5000
A silicon oxide film of 2000 mm was formed. 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, TEOS may be formed by decomposition and deposition by plasma CVD. Also,
The silicon oxide film thus formed may be annealed at 400 to 650 ° C.

After that, an amorphous silicon film is formed in a thickness of 300 to 500 by plasma CVD or LPCVD.
0 °, preferably 400-1000 °, for example 500
Å Deposit and put it in a reducing atmosphere at 550-600 ° C for 8
It was left to crystallize for 24 hours. In that case, crystallization may be promoted by adding a trace amount of a metal element such as nickel which promotes crystallization. This step may be performed by laser irradiation. Then, the silicon film crystallized in this manner was etched to form the island-shaped region 103. Further, a thickness of 700 to 1500.
Of silicon oxide film 104 was formed.

After that, an aluminum (containing 1 wt% Si or 0.1 to 0.3 wt% Sc (scandium)) film having a thickness of 1000 to 3 μm, for example, 5000 ° is formed by sputtering. By etching, a gate electrode 105 and a gate wiring 106 were formed. (FIG. 6 (A))

Then, the gate electrode 105 and the gate electrode 106 are anodic oxidized by passing a current in an electrolytic solution to have a thickness of 5 mm.
Anodized oxide 1 having a thickness of 00 to 2500 °, for example, 2000 °
07 and 108 were formed. The electrolytic solution used was prepared by diluting L-tartaric acid with ethylene glycol at a concentration of 5%, and adjusting the pH to 7.0 ± 0.2 using ammonia. The substrate 101 is immersed in the solution, the + side of the constant current source is connected to the gate wiring on the substrate, the platinum electrode is connected to the-side, and a voltage is applied at a constant current of 20 mA, and 150 V is applied.
Oxidation was continued until was reached. Further, the oxidation was continued at a constant voltage of 150 V until the voltage became 0.1 mA or less. As a result, an aluminum oxide film having a thickness of 2000 mm was obtained.

Thereafter, the island is formed by ion doping.
A gate electrode portion (that is, a gate electrode portion)
Self-alignment using the electrode and the anodic oxide film around it as a mask
As shown in FIG. 6B, an impurity (here, phosphorus) is implanted.
Thus, the low concentration impurity region (LDD) 109 was formed.
Dose amount is 1 × 10¹³~ 5 × 10¹⁴Atom / cm²,
The acceleration voltage is 10 to 90 kV, for example, the dose is 5 ×
10¹³Atom / cm ², And the acceleration voltage was 80 kV.
(FIG. 6 (B))

Then, a silicon oxide film 110 was deposited by a plasma CVD method. Here, the source gas is TEO
S and oxygen, or monosilane and nitrous oxide were used.
The optimum value of the thickness of the silicon oxide film 110 varies depending on the height of the gate electrode and the wiring. For example, as in this embodiment, the height of the gate electrode / wiring is about 60 including the anodic oxide film.
In the case of 00Å, 1/3 to 2 times that of 2000Å
1.2 μm is preferable, and here, it was 6000 °.
In this film forming process, it is required that both the uniformity of the film thickness in the flat portion and the step coverage be good. As a result, the thickness of the silicon oxide film on the side surface of the gate electrode / wiring is increased by the amount indicated by the dotted line in FIG. (FIG. 6 (C))

Next, this silicon oxide film 1 is subjected to anisotropic dry etching by a known RIE method.
08 was performed. This etching is completed when the etching reaches the gate insulating film 105. Regarding the end point of such etching, for example,
The etching rate of the gate insulating film 105 can be controlled by making it smaller than that of the silicon oxide film 110. Through the above steps, substantially triangular insulators (sidewalls) 111 and 112 remain on the side surfaces of the gate electrode and wiring.

Thereafter, phosphorus was introduced again by the ion doping method. The dose in this case is shown in FIG.
Is preferably 1 to 3 digits larger than the dose in the step. In this embodiment, the dose is set to 2 × 10 ¹⁵ atoms / cm ^{2, which} is 40 times the dose of the first phosphorus doping. Acceleration voltage is 80k
V. As a result, a region (source / drain) 114 into which a high concentration of phosphorus was introduced was formed, and a low concentration region (LDD) 113 was left below the sidewall. (FIG. 6 (D))

Further, a KrF excimer laser (wavelength: 248 nm, pulse width: 20 nsec) was irradiated to activate the doped impurities. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² .
(FIG. 6E)

Finally, as an interlayer insulator 115 on the entire surface,
A silicon oxide film was formed to a thickness of 5000 ° by the CVD method. Then, contact holes are formed in the source / drain of the TFT, and the aluminum wiring / electrode 11 of the second layer is formed.
6, 117 were formed. The thickness of the aluminum wiring was 4000 to 6000 °, almost the same as the gate electrode and wiring. Through the above steps, a TFT having an N-channel LDD was completed. To activate the impurity region,
Further, hydrogen annealing may be performed at 200 to 400 ° C. In the second-layer wiring 117, the step at the portion over the gate wiring 106 is moderated by the presence of the sidewall 112, so that the thickness of the second-layer wiring is almost the same as that of the gate electrode / wiring. Nevertheless, almost no break was observed. (FIG. 6 (F))

The following is a step of activating doping impurities by laser irradiation in FIG. 6E among the above steps. Next, an outline of the configuration of a substrate to be processed in this embodiment will be described. FIG. 7 shows an outline of a cross section of the substrate processed in this embodiment. A peripheral driving circuit area and a pixel circuit area are provided on the substrate, and the peripheral driving circuit is formed by NMOS and PMOS TFTs.
The pixel circuit is constituted by a PMOS TFT.
Note that a pixel electrode is provided in the TFT of the pixel circuit. (FIG. 7)

FIG. 3 shows a state in which the substrate to be processed in this embodiment is viewed from above. As apparent from FIG. 6E, no interlayer insulator, second-layer wiring, and the like are formed in the steps described below. As shown in FIG.
The scan drivers 32 and 33, the column drivers 34 and 35, and the active matrix circuit 36 are formed thereon. Also in this embodiment, the laser beam 37 has a size enough to irradiate the entire column drivers 34 and 35, for example, a width of 10 mm and a length of 300 m.
m is a rectangle.

First, as shown in FIG. 3B, the substrate was moved so that the scan driver 32 was irradiated with laser light. At this stage, the substrate is not irradiated with laser light. Thereafter, the laser beam was irradiated without substantially moving the laser beam and the substrate. Laser light irradiation was performed in the air, and the substrate temperature was 200 ° C. KrF excimer laser (wavelength 248n)
m) was used. The oscillation frequency of the laser was 10 Hz, the energy density of the laser light was 300 mJ / cm ² , and the pulse of the laser light was 10 shots. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (FIG. 3 (B))

Thereafter, the substrate is moved, and the scan driver 33 is set to be irradiated with laser light.
Laser irradiation was performed without moving the substrate and the laser beam. In this case also, 1
A laser beam of 0 shot was irradiated. When the required number of shots of laser light were irradiated, the laser light irradiation was stopped.
(FIG. 3 (C)) Thereafter, the substrate was rotated 1/4. In FIG. 3D, a dotted square 38 is the position of the first substrate. (FIG. 3
(D))

Thereafter, as shown in FIG. 3E, the substrate was moved so that the column driver 34 was irradiated with a laser beam. Then, the laser beam was irradiated without substantially moving the laser beam and the substrate. The irradiation conditions at this time were the same as above, and the pulse of the laser beam was 10
Shot. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (FIG. 3
(E))

Next, the position to be irradiated with the laser beam was shifted downward, and the substrate was moved to a position where the upper end of the active matrix area 36 (and the scan drivers 32 and 33) hit the laser beam 37. Then, the substrate was moved while irradiating a laser beam. For example, the oscillation frequency of the laser is 10 Hz, the energy density of the laser light is 250 mJ / cm ² , and the scanning speed of the laser light is 1
0 mm / s. As a result, the laser beam 25 becomes 1
mm. Beam width is 10mm
Therefore, about 10 shots of laser light are irradiated at one location. (FIG. 3 (F))

In this manner, the laser was scanned to the lower end of the active matrix circuit 36 and the active matrix area 36 was irradiated with laser light. When irradiation to the lower end of the active matrix is completed,
Laser irradiation was stopped. Then, as shown in FIG. 3G, the substrate was moved so that the laser light was irradiated on the column driver 35. Then, the column driver 3 is moved without substantially moving the laser beam and the substrate.
5 was irradiated with a laser beam. The oscillation frequency of the laser is 1
0Hz, energy density of laser beam is 300mJ / c
m ² , the laser light pulse was 10 shots. When the required number of shots of laser light irradiation were completed, the laser light irradiation was stopped. (Fig. 3 (G))

In this embodiment, the column drivers 34, 3
In No. 5, the laser beams did not overlap at all. On the other hand, in the scan driver, the laser beams did not overlap in the laser beam irradiation process shown in FIGS. 3B and 3C, but did occur during the laser irradiation of the active matrix circuit. However, the scan driver is substantially less susceptible to variations in characteristics than the column driver, and has a substantial effect because the energy of laser light irradiation on the active matrix circuit is smaller than the energy of the first laser irradiation. There was no effect.

[0048]

According to the laser irradiation technique of the present invention,
The characteristics of the semiconductor circuit as a whole could be improved while maintaining mass productivity. The present invention can be used for all laser processing processes used for semiconductor device processes. In particular, when a TFT is taken as a semiconductor device, the first and second embodiments are used in order to improve the uniformity of the threshold voltage of the TFT. When used in the step of irradiating the polycrystalline silicon film with a laser as described in the above section, the effect is great. In addition, in order to improve the field-effect mobility of the TFT or the uniformity of the on-current, the present invention may be used in the step of activating the source / drain impurity elements in addition to the above steps as in the third embodiment. It is effective. Thus, the present invention is considered to be industrially useful.

[Brief description of the drawings]

FIG. 1 shows a laser processing method according to an embodiment. (See Example 1)

FIG. 2 shows a laser processing method according to an example. (See Example 2)

FIG. 3 shows a laser processing method according to an example. (See Example 3)

FIG. 4 shows a conceptual diagram of a laser annealing apparatus used in the examples.

FIG. 5 shows a conceptual diagram of an optical system of a laser annealing apparatus used in the example.

FIG. 6 shows an outline of a manufacturing process of a TFT element of an example. (See Example 3)

FIG. 7 shows a cross section of a TFT circuit. (Example 3
reference)

[Explanation of symbols]

11, 21, 31 Substrate 12, 22, 32, 33 Scan driver 13, 23, 34, 35 Column driver 14, 24, 36 Active matrix circuit area 15, 25, 37 Laser beam spot (linear laser beam) 26 , 38 show the position of the substrate before rotation.

Claims (6)

[Claims] 1. A method for driving an active matrix display device having a source driver circuit, a gate driver circuit, and an active matrix circuit, wherein the active matrix circuit is driven by the source driver circuit and the gate driver circuit. The gate driver circuit and the active matrix circuit each have a plurality of TFTs, and a difference between threshold voltages of adjacent TFTs among the plurality of TFTs of the source driver circuit is 0.01 V or less. A method for driving a matrix display device. 2. The method according to claim 1, wherein the plurality of Ts of the source driver circuit are provided.
2. The driving method of an active matrix display device according to claim 1, wherein the variation of the threshold voltage of the FT is 0.05 V or less. 3. A method for driving an active matrix display device having a source driver circuit, a gate driver circuit, and an active matrix circuit, wherein the active matrix circuit is driven by the source driver circuit and the gate driver circuit, A driving method for an active matrix display device, wherein each of the gate driver circuit and the active matrix circuit has a plurality of TFTs, and a variation in threshold voltage of the plurality of TFTs of the source driver circuit is 0.05 V or less. 4. The TFT included in the source driver circuit
4. The driving method of an active matrix display device according to claim 1, wherein the variation of the threshold voltage is smaller than the variation of the threshold voltage of the TFT included in the active matrix circuit. 5. The TFT included in the source driver circuit
5. The driving method of an active matrix display device according to claim 1, wherein the variation of the threshold voltage is smaller than the variation of the threshold voltage of the TFT included in the gate driver circuit. 6. The T of the active matrix circuit
6. The driving method of an active matrix display device according to claim 1, wherein a variation in a threshold voltage of the FT is 0.1 V or less.