JPH11168215A - Active matrix substrate and its manufacturing method and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the mobility of an active matrix substrate and the withstand voltage property of a retained capacity by providing SiO2 cap layers with different film thicknesses at one or both of each formation region of a thin-film transistor or the retained capacity. SOLUTION: A retained capacity is formed at each pixel region by the overlapped part between a first electrode layer being made of a silicon film that is formed between the same layers as the source and drain regions of a thin-film transistor(TFT) and a second electrode layer that is made of an extended part projecting from a scanning line in -Y direction. The retained capacity side is formed by a semiconductor film that is formed simultaneously with a semiconductor film for constituting the source, channel, and drain regions of the TFT. An SiO2 cap layer 45 is formed following the semiconductor film deposition process, and further the SiO2 cap layer 45 is left only at a formation region TA of the TFT or a formation region CA of the retained capacity or is left by differentiating thick thicknesses at both formation regions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an active matrix substrate using a thin film transistor (hereinafter, referred to as TFT), a method of manufacturing the same, and a liquid crystal display device. More specifically, the present invention relates to a technique for manufacturing each element with optimal characteristics in an active matrix substrate of a type including a pixel TFT and a storage capacitor in a pixel region.

[0002]

2. Description of the Related Art In an active matrix substrate of a liquid crystal display device, as shown in FIG. 1, a plurality of scanning lines 4 extending in the X direction and a Y direction intersecting the scanning lines 4 are provided. The pixel region 5 is defined by the plurality of data lines 3, and each pixel region 5 includes a TFT 10 connected to the data line 3 and the scanning line 4, a liquid crystal capacitor 6 connected to the TFT 10, and a storage capacitor 50. As shown in FIG. 2, the storage capacitor 50 is formed with the aid of the manufacturing process of the TFT 10, and a semiconductor region formed between the same layers as the active layer of the TFT 10 is used as a first electrode layer 51, and the gate electrode 1 is formed.
5 (scanning line 4) and the second electrode layer formed between the same layers.
An electrode layer 55 is provided, and between the first electrode layer 51 and the second electrode layer 55, a dielectric film 54 formed between the same layers as the gate insulating film 14 is provided.

In the active matrix substrate 2 configured as described above, as shown in FIG. 2, of the silicon film 30 formed in each pixel region 5, a corner portion of the pixel region 5 in FIG. Used to form.
On the other hand, after extending in the + X direction from the region where the TFT 10 is formed in the silicon film 30, the silicon film 30 bends along the extension portion 40 that extends perpendicularly to the −Y direction from the scanning line 4 and extends in the + Y direction. Later, the TFT 10 in the adjacent pixel region 5 extends in the + X direction toward the adjacent pixel region.
Of the storage capacitor 50 is used as the first electrode layer 51 of the storage capacitor 50.

In the active matrix substrate 2 configured as described above, it is desired that the TFT 10 be manufactured by a low-temperature process so that a glass substrate can be used as the substrate. However, a silicon film necessary for forming a channel region or the like of the TFT 10 can be formed by a low-temperature process as long as it is an amorphous silicon film, but has a drawback of low mobility.

Therefore, a laser melt crystallization method of irradiating a laser beam onto the amorphous silicon film 30 formed on the substrate to melt-crystallize the silicon film 30 has been studied, and this method has a long irradiation area in the Y direction, for example. The amorphous silicon film 30 is irradiated with a laser beam line beam LB, and is scanned in the + X direction to crystallize the entire silicon film 30. Here, the energy intensity of the laser beam is set to a level sufficient for amorphous silicon to be transferred to polycrystalline silicon. The higher the intensity, the higher the crystallinity of the silicon film 30 and the higher the mobility of the TFT 1.
0 can be produced. However, if the energy intensity is too high, the silicon film 30 is microcrystallized. Therefore, it is general to set the energy intensity slightly lower than that of the silicon film 30 microcrystallized.

On the other hand, the silicon film 30 for forming the first electrode layer 51 of the storage capacitor 50 is also irradiated with laser light at the same intensity as the silicon film 30 for forming the TFT 10, and is transferred to polycrystalline silicon. .

[0007]

However, as in the prior art, in order to manufacture a TFT 10 having a high mobility, the silicon film 30 is irradiated with a laser beam at a high intensity just before microcrystallization occurs. In addition, there is a problem that the withstand voltage is reduced in the storage capacitor 50 and the reliability of the liquid crystal display device is reduced. It is considered that the reason for this is that, as the silicon film 30 is irradiated with a laser beam with higher intensity, the surface of the silicon film 30 becomes rougher, which lowers the withstand voltage.

Therefore, an object of the present invention is to form a storage capacitor with the aid of a TFT manufacturing process.
After forming a silicon oxide film (SiO ₂ film) having a different film thickness on only one or both of the FT and the storage capacitor, by irradiating with energy light under optimum conditions, a TFT having high mobility and a high withstand voltage can be obtained. An object of the present invention is to provide an active matrix substrate on which a storage capacitor can be formed, a liquid crystal display device using the same, and a method for manufacturing the same.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, and a plurality of scanning lines and data lines. In an active matrix substrate having a plurality of thin film transistors to be connected and a storage capacitor, source / drain regions of the plurality of thin film transistors and a first electrode of the storage capacitor are formed of the same semiconductor layer, A first cap layer made of a silicon oxide film is disposed on the source / drain region of the thin film transistor. In the manufacturing method,
FT source / drain region and first of the storage capacitor
After forming a semiconductor film to form an electrode and forming a first cap layer on the source / drain region, when irradiating the semiconductor film with energy light, the source / drain region By setting the thickness of the formed SiO ₂ cap layer so as to exhibit the effect as a heat absorbing layer, the source / drain region where the TFT is to be formed has a high crystallinity when irradiated with energy light of the same intensity. Energy light slightly weaker than the threshold value at which microcrystallization occurs to obtain the property is applied, and the first electrode on which the storage capacitor is to be formed has a threshold value at which crystallization occurs more than the threshold value at which microcrystallization occurs. It is possible to irradiate energy light that is unlikely to cause surface roughness.

In this case, for example, a line beam of laser light whose irradiation area extends in the Y direction is used as energy light for irradiating the semiconductor film, and the line beam is scanned in the X direction.

After the source / drain region of the TFT and the semiconductor film constituting the first electrode of the storage capacitor are irradiated with energy light, the source / drain region of the TFT is exposed to energy light.
Without removing the SiO ₂ cap layer on the drain region,
It can be used as a gate insulating film.

The SiO ₂ cap layer may be removed by etching after irradiation with energy light, and a new gate insulating film may be formed.

On the other hand, the active matrix substrate of the present invention comprises a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, a plurality of thin film transistors connected to the plurality of scanning lines and the data lines, In an active matrix substrate having a storage capacitor, a source / drain region of each of the plurality of thin film transistors and a first of the storage capacitor are provided.
The electrode is formed of the same semiconductor layer as the first layer.
A second cap layer made of a silicon oxide film is disposed on the electrode. According to such a configuration, in the manufacturing process, the thickness of the SiO ₂ cap layer formed on the first electrode of the storage capacitor is set so as to exhibit an effect as a filter layer, and irradiation with energy light having the same intensity is performed. Then, the source / drain regions where the TFTs are to be formed are irradiated with energy light slightly weaker than a threshold value at which microcrystallization occurs to obtain high crystallinity, and are crystallized. Can be crystallized by irradiating with energy light that is less likely to cause surface roughness closer to the threshold at which crystallization occurs than the threshold at which microcrystallization occurs.

In this case, for example, a line beam of laser light whose irradiation area extends in the direction in which the data line extends is used as the energy light for irradiating the semiconductor film, and this line beam is moved in the direction in which the scanning line extends. Scan.

After irradiating the source / drain region of the TFT and the semiconductor film constituting the first electrode of the storage capacitor with energy light, the SiO ₂ cap layer on the storage capacitor region is not removed, and It can be used as a capacitor dielectric film.

On the other hand, the SiO ₂ cap layer may be removed by etching after the irradiation of energy light, and a dielectric film of a storage capacitor may be newly formed.

Further, the present invention provides a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, a plurality of thin film transistors connected to the plurality of scanning lines and the data lines, and a storage capacitor. A source / drain region of the thin film transistor and a first electrode of the storage capacitor are formed of the same semiconductor layer, and a first cap made of a silicon oxide film is provided on the source / drain region. A second cap layer made of a silicon oxide film is formed on the first electrode, and the first cap layer is thinner than the second cap layer.

In the manufacturing process of the active matrix substrate having such a structure, a semiconductor film to form a source / drain region of the TFT and a first electrode of the storage capacitor is formed, and a first cap layer and a second cap layer are formed. After forming the cap layer, the method has a step of irradiating the semiconductor film with energy light, so that the thickness of the first cap layer exhibits an effect as a heat absorbing layer in the source / drain regions. When the second cap layer is irradiated with energy light of the same intensity by setting the thickness of the first cap layer to be smaller than the thickness of the second cap layer so as to exhibit the effect as a filter layer, The source / drain region of the TFT is irradiated with energy light slightly weaker than a threshold value at which microcrystallization occurs to obtain high crystallinity, and is crystallized. The the first electrode to be formed can be surface hail is hardly causes energy light close to the threshold of occurrence of crystallization than the threshold of occurrence of micro-crystallization is crystallized by irradiation.

In this case, for example, a line beam of laser light whose irradiation area extends in the direction in which the data line extends is used as the energy light for irradiating the semiconductor film, and this line beam is applied in the direction in which the scanning line extends. Scan.

After irradiating the source / drain region of the TFT and the semiconductor film constituting the first electrode of the storage capacitor with energy light, the SiO ₂ cap layer is not removed, and the gate insulating film and the storage layer are not removed. It can be used as a capacitor dielectric film.

On the other hand, the SiO ₂ cap layer may be removed by etching after irradiation with energy light, and a gate insulating film and a dielectric film of a storage capacitor may be newly formed.

As described above, according to the present invention, in any of the above embodiments, the SiO ₂ cap layer which functions as a heat absorbing layer or a filter layer is provided in the TFT forming region and the storage capacitor forming region. Therefore, when irradiating the semiconductor film with energy light, although the intensity of the energy light is constantly constant, the formation region of the TFT (source / drain region) and the formation region of the storage capacitor (the Each of the two electrodes (one electrode) is irradiated with light having an optimum energy intensity. That is, a semiconductor film for forming a TFT is irradiated with energy light slightly weaker than a threshold value at which microcrystallization occurs, thereby maximizing the crystallinity of the semiconductor film, thereby increasing the mobility of the TFT. Can be manufactured. On the other hand, the semiconductor film for forming the first electrode of the storage capacitor is irradiated with energy light closer to the threshold at which crystallization occurs than at the threshold at which microcrystallization occurs, and the crystallinity of the semiconductor film is slightly suppressed. By preventing the surface from being roughened, a storage capacitor having a high withstand voltage can be manufactured.

According to the present invention, in any of the above embodiments, the second electrode is formed in the same layer as the gate electrode, and is disposed in parallel with a part of the preceding gate line or the gate line. Any one of the capacitance lines is used.

Here, when a line beam is used,
It is preferable that the scanning pitch is narrower than the width of the line beam in the scanning direction, and the line beam is irradiated while overlapping the same region.

The active matrix substrate thus configured has a high mobility and a high withstand voltage, and has a high holding capacity. Therefore, when a liquid crystal display device is manufactured using the same, the display quality is low. The effect of high reliability and high reliability can be obtained.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing each embodiment of the present invention, a basic structure of an active matrix substrate common to each embodiment and a basic structure in which a TFT and a storage capacitor are formed simultaneously. The steps will be described.

[Basic Configuration of Active Matrix Substrate]
FIG. 1A is an explanatory diagram schematically illustrating a configuration of an active matrix substrate of a liquid crystal display device.

In FIG. 1, the liquid crystal display device 1 is formed on an active matrix substrate 2 by a plurality of scanning lines 4 extending in the X direction and data lines 3 extending in the Y direction orthogonal to these scanning lines 4. A liquid crystal capacitor 6 of a liquid crystal cell to which an image signal is input via a pixel TFT 10 is formed. A data driver unit 7 including a shift register 71, a level shifter 72, a video line 73, and an analog switch 74 is configured for the data line 3, and a scan driver including a shift register 81 and a level shifter 82 is configured for the scanning line 4. The unit 8 is configured. In the pixel region 5, a storage capacitor 50 is formed between the preceding scanning line 4 or a capacitance line (not shown) arranged in parallel with the scanning line 4. This storage capacitor 50 is for improving the storage characteristics of the liquid crystal capacitor 6.

In the data driver section 7 and the scan driver section 8, as shown in FIG.
A CMOS circuit or the like constituted by N-type TFTs n1 and n2 and P-type TFTs p1 and p2 is formed at high density. However, the TFT 10 of the active matrix section 9
And the TFTs n1 and n2 of the data driver section 7 and the P-type TFTs.
FTp1 and p2 have the same basic structure and are basically manufactured in the same process. In addition, the storage capacity 50
Although the details will be described later, the TFT 10 is manufactured using the manufacturing process of the TFT 10 as much as possible.

The active matrix substrate 2 includes only the active matrix section 9 on the substrate, the same substrate on which the data driver section 7 is formed on the same substrate as the active matrix section 9, and the same substrate on which the active matrix section 9 is formed. The one on which the scanning driver unit 8 is configured,
In some cases, both the data driver section 7 and the scanning driver section 8 are formed on the same substrate as the active matrix section 9. Further, even if the active matrix substrate 2 has a built-in driver, the shift register 71, the level shifter 72, the video line 7
3. a complete driver built-in type in which all of the analog switches 74 and the like are configured on the active matrix substrate 2,
Although there is a partial driver built-in type in which a part of them is formed on the active matrix substrate 2, the present invention can be applied to any of them.

FIG. 2 is an enlarged plan view showing a part of the active matrix portion where the pixel region 5 is formed in the active matrix substrate 2 of the present embodiment. In this figure, a silicon film 30 (semiconductor film) is shown. In addition, in order to make the formation region of the scanning line 4 easy to understand, the data line and the pixel electrode are omitted.

In FIG. 2, the active matrix substrate 2 of the present embodiment has a plurality of scanning lines 4 extending in the X direction.
Each pixel region 5 partitioned by a plurality of data lines (not shown) extending in the Y direction orthogonal to the scanning lines 4 has a TF connected to the data lines and the scanning lines 4.
T10 and a pixel electrode (not shown) connected to the TFT 10 are formed.

In each pixel region 5, a first electrode layer 51 made of a silicon film formed between the same layers as the source region 11 and the drain region 12 of the TFT 10 and the scanning line 4 project in the -Y direction. The second consisting of the extension part 40
The storage capacitor 50 is formed by the overlapping portion with the electrode layer 55.

FIG. 3 shows the TFT 10 and the storage capacitor 5 formed in the pixel region 5 of the active matrix substrate 2.
FIG.

In these figures, any pixel region 5
However, the TFT 10 has the data line 3 on the substrate 20.
, A drain region 12 electrically connected to a pixel electrode 19 through a contact hole 18 in the interlayer insulating film 16, and a drain region 12. A channel region 13 for forming a channel between the semiconductor device and the source region 11, and a gate electrode 15 facing the channel region 13 via a gate insulating film 14. The gate electrode 15 is configured as a part of the scanning line 4. Note that a base protective film 21 made of a SiO ₂ film is formed on the front surface side of the substrate 20.

On the storage capacitor 50 side, a semiconductor film which is formed simultaneously with the semiconductor films constituting the active layers (the source region 11, the channel region 13, and the drain region 12) of the TFT 10 is formed. A first electrode layer 51 located between the same layers, and a gate insulating film 1
4 and a dielectric film 54 located at the same layer as the insulating film, and a gate electrode 15 and a scanning line 4 formed at the same time on the surface side between the dielectric layer 54 and the same layer as these electrodes and wiring. The located second electrode layer 55 is formed.

[Basic Configuration of Manufacturing Method of Active Matrix Substrate 2] With reference to FIG. 4, basic steps of a manufacturing method of the TFT 10 and the storage capacitor 50 will be described.

(Base Protective Film Forming Step) In FIG. 4A, first, a surface of a substrate 20 made of a 300 mm square non-alkali glass plate or the like is formed on the surface of the substrate 20 by ECR-PECVD.
Under a temperature condition of 50 ° C. to 300 ° C., a 200 nm-thick SiO ₂ film to be the underlying protective film 21 is formed. SiO
_{The two} films can also be formed by the APCVD method. In this case, the temperature of the substrate 20 is set in the range of 250 ° C. to 450 ° C., and monosilane and oxygen are used as source gases.
An iO ₂ film is formed.

(Semiconductor Film Deposition Step) Next, the underlying protective film 2
50 n of intrinsic silicon film 30 (semiconductor film)
about m. In this example, the amorphous silicon film 30 is deposited at a deposition temperature of 425 ° C. using a high-vacuum LPCVD apparatus while flowing disilane as a source gas at 200 SCCM. In forming the silicon film 30, a PECVD method or a sputtering method may be used.
Can be set in the range up to.

[0040] In the present invention performs the formation of the SiO ₂ cap layer 45 subsequent to the semiconductor film deposition steps, further the SiO ₂ cap layer 45 only in the formation area CA of the forming area TA or storage capacitor 50 of the TFT 10, Alternatively, it is necessary to perform patterning in order to leave a difference in the film thickness in both the formation regions. This detailed description will be described later for each embodiment.

(Annealing Step by Laser Melt Crystallization) Next, as shown in FIG. 4B, the amorphous silicon film 30 is irradiated with laser light directly or via a SiO ₂ cap layer (not shown). Is performed to modify the amorphous silicon film 30 into polycrystalline silicon. In this example, for example, an excimer laser (wavelength: 248 nm) of krypton / fluorine (KrF) is irradiated. In this step, the laser irradiation is performed to bring the substrate 20 to room temperature (25
C.), in a vacuum atmosphere or an inert gas atmosphere, and further in the air.

In performing the annealing step,
In the above example, the entire surface of the silicon film 30 formed on the substrate 20 was irradiated with the laser light.
The laser irradiation may be selectively performed only on the region A where the capacitor A and the storage capacitor 50 are formed to shorten the laser annealing time.

(Silicon film patterning step)
As shown in FIG. 4C, the silicon film 30 that has been subjected to the annealing process is patterned by using a photolithography technique, and an island-shaped silicon film is formed in the formation region TA of the TFT 10 and the formation region CA of the storage capacitor 50. 30 are formed. The annealing step may be performed after the silicon film 30 and the SiO ₂ cap layer 45 are collectively patterned.

(Step of Forming Gate Insulating Film) Next, FIG.
As shown in (D), 25 by ECR-PECVD method.
Under a temperature condition of 0 ° C. to 300 ° C., a gate oxide film 14 made of a SiO ₂ film and a dielectric film 54 are formed on the silicon film 30.

(Step of Forming First Electrode Layer 51 of Storage Capacitor 50) Next, the silicon film 30 on the side of the formation area TA of the TFT 10 is covered with a resist mask 33, and in this state, the silicon film 30 of the formation area CA of the storage capacitor 50 is covered. A high-concentration impurity is introduced into the film 30 to make it conductive, thereby forming a first electrode layer 51.

(Gate Electrode Forming Step) Next, a tantalum thin film having a thickness of 600 nm is formed on the surface side of the gate oxide film 14 by a sputtering method, and as shown in FIG.
It is patterned using a photolithography technique to form a gate electrode 15 and a second electrode layer 55.
In this example, when forming a tantalum thin film, the substrate temperature is set to 1
The temperature was set to 80 ° C., and 6.7 nitrogen gas was used as a sputtering gas.
% Argon gas is used. The tantalum thin film thus formed has an α-structure crystal structure and low specific resistance.

(Implantation Step of Impurity) Next, using a bucket type mass non-separation type ion implantation apparatus (ion doping apparatus), impurity ions are implanted into the silicon film 30 on the formation region TA side of the TFT 10 using the gate electrode 15 as a mask. Type. When an N-channel TFT is formed, phosphine or the like diluted with hydrogen gas to a concentration of 5% is used as a source gas. As a result, the gate electrode 15
A source region 11 and a drain region 12 are formed in a self-aligned manner. At this time, the silicon film 30
Of these, the portion where the impurity ions are not implanted becomes the channel region 13.

When a P-channel TFT is formed, diborane or the like diluted with hydrogen gas to a concentration of 5% is used as a source gas.

(Step of Forming Interlayer Insulating Film) Next, FIG.
(F) As shown in FIG.
Under a temperature condition of 00 ° C., an SiO ₂ film having a thickness of 50 nm as the interlayer insulating film 16 is formed. The source gases at this time are TEOS and oxygen. Substrate temperature is 250 ° C
３００300 ° C.

(Activation Step) Next, heat treatment is performed at 300 ° C. for 1 hour in an argon gas atmosphere containing 3% of hydrogen to activate the implanted phosphorus ions and to modify the interlayer insulating film 16. .

(Wiring Step) Next, contact holes 17 and 18 are formed in the interlayer insulating film 16. Thereafter, as shown in FIG. 2 through the contact holes 17 and 18,
The TFT 10 is formed by electrically connecting the source electrode (data line 3) to the source region 11 and electrically connecting the drain electrode (pixel electrode 19) to the drain region 12.

The above manufacturing method is an example of manufacturing the TFT 10 in a self-aligned structure.
The present invention can also be applied to a case where 10 is manufactured with an LDD structure or an offset gate structure. Although a description of the structure and the manufacturing method in this case is omitted, a low concentration source / drain region is formed in a portion of the source / drain region facing the end of the gate electrode 15 using a resist mask or a sidewall. (LDD region) or an offset region is formed.

[Energy intensity and film quality at the time of laser irradiation] Before describing the embodiment of the present invention, the basic amorphous silicon film 30 is irradiated in the annealing step described with reference to FIG. The relationship between the energy density (energy intensity) of the laser beam and the film quality after laser irradiation will be described with reference to FIGS.

In any of the embodiments of the present invention, as described later, an amorphous silicon film is polycrystallized by a laser melting crystallization method. In this laser melting crystallization method, as shown in FIG. As E is increased, the silicon film is melt-solidified and polycrystallized at Ec or more indicated by “▲” and the dashed line L1. Here, as the energy density E increases, the polycrystallization progresses. However, when the energy density E is “□” and E is indicated by a dotted line L2.
If it exceeds a, the silicon film will be microcrystallized, and the mobility will decrease. When the thickness of the silicon film is small, even if the energy density E does not exceed Ea, when the energy density E exceeds "E" and Eb indicated by the two-dot chain line L3, the film returns to the amorphous silicon film. . In addition,
When the energy density E exceeds Ed shown by “□” and the solid line L4, the silicon film is evaporated.

Further, the crystallinity of the silicon film when the energy density E of the pulsed laser light is changed is indicated by “○” and a solid line L13 in FIG. Since the vertical axis in FIG. 6 is the half width of the Raman peak, the smaller the value, the higher the crystallinity. As can be seen from a comparison of these results, in the laser melting crystallization, the crystallinity can be enhanced by setting the maximum value of the energy density E to a value considerably close to the upper limit value Ea. The reason why the half-width of the Raman peak jumps slightly above the upper limit Ea is that the silicon film is microcrystallized.

Similarly, the roughness of the silicon film surface when the energy density E is changed is indicated by “で” and a solid line L23 in FIG. Here, the vertical axis in FIG. 7 is the difference between the maximum value and the minimum value on the average plane in the measurement area, and the larger the value, the more rough the surface. As can be seen by comparing these results, as the energy density increases, the surface of the silicon film becomes rougher. Then, when microcrystallization occurs, the surface roughness is reduced, but the silicon film is completely melted once, and during that time, partly evaporated silicon adversely affects the optical components of the annealing apparatus.

Here, T is converted from the amorphous silicon film.
In order to form the FT 10 and the storage capacitor 50 (see FIGS. 3 and 4), even if the surface of the silicon film 30 is roughened, the TFT 10 has as high a crystallinity as possible and has a high mobility. I want to get a degree. On the other hand, the storage capacity 5
In the case of 0, it is desired to obtain a high withstand voltage by suppressing the surface roughness even if the crystallinity is somewhat low. However, in the layout shown in FIG.
Since the formation area CA overlaps in both the X direction and the Y direction, the energy intensity at the time of laser beam irradiation cannot be changed for each area. By changing the layout, the area T where the TFT 10 is formed is changed.
If it is assumed that the area A and the formation area CA of the storage capacitor 50 do not overlap in both the X direction and the Y direction, the output of the laser oscillator is changed according to each area, or the output is kept constant, and an attenuator (attenuator) is used. Needs to be changed. The pixel pitch of the TFT is about 50 μm, while the feed pitch of the laser beam LB is 10 μm.
It is about μm, and even if any one of the laser oscillator and the attenuator is modulated, it is necessary to perform it in about five shots, which is difficult.

Therefore, in the present invention, as will be described below, the formation area TA of the TFT 10 and the storage capacitor 50 are explained.
In one or both of the formation regions CA having different film thicknesses.
By providing the SiO ₂ cap layer 45 and controlling the intensity of the laser beam reaching each region, the laser beam can be irradiated with the optimum energy intensity for each region.

[Embodiment 1] FIG.
(A) After forming the base protective film 21 on the surface of the substrate 20 and forming the semiconductor film 30, the cap layer 4 is further formed.
5 to become SiO ₂ film is a cross-sectional view of forming a.

In forming the SiO ₂ cap layer 45, the temperature is set at 250 ° C. or lower by ECR-PECVD.
An SiO ₂ film is formed at a temperature of 300 ° C. SiO ₂ film in this case, can also be formed by APCVD method, in which case, the SiO ₂ film is formed the temperature of the substrate 20 in a state set in a range of up to 450 ° C. from 250 ° C., monosilane and oxygen as material gas I do.

Depending on the thickness of the SiO ₂ film, the effective intensity of the laser beam irradiated in the annealing step by the next laser melt crystallization method differs, and the obtained polycrystalline silicon film has different crystallinity. It is necessary to set the film thickness.

FIG. 9 shows a base protective film 21 having a thickness of 5
The substrate 20 in which the thickness of the SiO ₂ cap layer 45 is 0 to 150 nm on the intrinsic silicon film 30 having a thickness of 0 nm
FIG. 6 shows the relationship between the energy density and the film quality after laser irradiation when laser light irradiation is performed while changing the energy density of laser light.

Here, the SiO ₂ cap layer 45 is made of TF
A description will be given of a cross-sectional view in the case where patterning is performed by using a photolithography technique in order to leave only on the formation region TA of T10 and remove the other portions, with reference to FIG.

In FIG. 9, the energy density, which is the threshold at which crystallization occurs as indicated by “▲” and the solid line L5, is S
By forming the iO ₂ cap layer 45 to serve as a heat absorbing layer and having a thickness of less than 70 nm, the value is lower than when the SiO ₂ cap layer 45 is not formed. This excimer laser wavelength (here KrF: wavelength 248 nm) for reflectance to is the smaller of the SiO ₂ film as compared with the silicon film, by forming the SiO ₂ cap layer 45, the laser beam is silicon This is because it is easy to enter the film. Originally, the SiO ₂ film should not absorb the wavelength of the incident laser light,
Although it should not change for the effect of reducing the reflectance by increasing the thickness of the SiO ₂ film, in fact, progress of as crystallization shown in FIG. 9 depends largely on the thickness of the SiO ₂ film. This is because the sum of the silicon film and the SiO ₂ film is as thin as half or less of the wavelength of the incident laser light, so that the degree of penetration of the laser light wave into the silicon film varies depending on the thickness of the SiO ₂ film, and light absorption This is because the amount changes. Accordingly, the energy density, which is the threshold for microcrystallization, indicated by "□" and the solid line L6, and the energy density, which is the threshold for ablation indicated by "△" and the solid line L7, are also low. Especially SiO ₂
The effective condition of the film thickness is 50 nm.

Then, the thickness of the SiO ₂ cap layer 45 formed on the formation region TA of the TFT 10 is set to 50 nm, and the laser light is applied so that the amorphous silicon film 30 in the formation region TA of the TFT 10 has high crystallinity. By setting the energy density to ETA1 which is slightly lower than the energy density which is a threshold value at which microcrystallization occurs, a TFT 10 having high mobility can be manufactured.

On the other hand, in the area where the SiO ₂ cap layer 45 is not provided, the energy density of the laser beam in which ECA1 = ETA1 is closer to the threshold at which crystallization occurs than the energy density at which microcrystallization occurs. ,
Although the crystallinity is suppressed, the storage capacitor 50 having high withstand voltage can be manufactured by preventing the surface from being roughened. Therefore, the active matrix substrate 2 according to the present embodiment
Since the liquid crystal display device 1 is manufactured by using the TFT 10 having high mobility and the storage capacitor 50 having high withstand voltage, the display quality is high and the reliability is high. .

After going through such a process, the TFT
The SiO ₂ cap layer 45 left on the formation region TA of the substrate 10 can be used as a part of the gate insulating film, or by a wet process before forming the gate insulating film in the next step. The gate insulating film may be removed by etching and a new gate insulating film may be formed.

[Embodiment 2] Similarly, FIG. 8A shows that after forming a base protective film 21 and a semiconductor film 30 on the surface of the substrate 20 shown in FIG. 45 is a cross-sectional view in which a SiO ₂ film having a thickness of 45 is formed.
The method of forming the SiO ₂ film is the same as that of the first embodiment, and thus the description is omitted.

FIG. 8B is a cross-sectional view showing a case where patterning is performed using photolithography to leave the SiO ₂ cap layer 45 only on the formation area CA of the storage capacitor 50 and to remove other portions. -2) will be described.

In FIG. 9, the energy density, which is the threshold at which crystallization occurs as indicated by “▲” and the solid line L5, is Si
70 nm serving as an O ₂ cap layer 45 as a filter layer
With the above-described formation, the temperature increases as compared with the case where the SiO ₂ cap layer 45 is not formed. This is SiO ₂
When the thickness of the film is 70 nm or more, the penetration of the wavelength of the incident laser light (here, KrF: the wavelength is 248 nm) into the silicon film is significantly reduced, and as a result, light absorption is reduced. is there. Therefore, by forming the SiO ₂ cap layer 45, a larger amount of laser light is required for crystallization, and the melting of the silicon film is suppressed. Accordingly, the energy density, which is the threshold for microcrystallization, indicated by “□” and solid line L6, and the energy density, which is the threshold for ablation indicated by “Δ” and solid line L7, also increase.

Therefore, the thickness of the SiO ₂ cap layer 45 formed on the formation area CA of the storage capacitor 50 is set to 110 n.
On the other hand, in order to obtain high crystallinity in the amorphous silicon film 30 in the formation area TA of the TFT 10, the energy density of the laser beam is slightly lower than the energy density which is the threshold value at which microcrystallization occurs.
By setting to 2, the TFT 10 with high mobility can be manufactured.

In this case, in the formation area CA of the storage capacitor 50 where the SiO ₂ cap layer 45 is located, this ECA
The energy density of the laser light of 2 = ETA2 is closer to the threshold at which crystallization occurs than the energy density at which microcrystallization occurs, and the crystallinity is suppressed.
By preventing the surface from being roughened, the storage capacitor 50 with high withstand voltage can be manufactured. Therefore, the active matrix substrate 2 according to the present embodiment includes the TFT 10 having a high mobility.
And the storage capacitor 50 having a high withstand voltage, so that when the liquid crystal display device 1 is manufactured using the same, the display quality is high and the reliability is high.

After such a process, the SiO ₂ cap layer 45 left on the formation area CA of the storage capacitor 50 can be used as a part of the dielectric film of the storage capacitor. However, before forming the gate insulating film in the next step, it may be removed by etching by a wet process, and a gate insulating film may be formed again and used as a dielectric film of the storage capacitor.

[Other Embodiments] As described above, the SiO ₂ cap layer 45 can be left not only in one of the formation area TA of the TFT 10 or the formation area CA of the storage capacitor 50 but also in both of them. It is. FIG. 8 (B-
As shown in 3), Si is adjusted to the formation area CA of the storage capacitor 50 requiring a thicker SiO ₂ cap layer.
After an O ₂ film is formed to a thickness of 75 nm, TF is
T10 SiO ₂ film on the formation region TA of the processing up to 50nm. Therefore, in FIG.
In order to obtain high crystallinity in the amorphous silicon film 30, the energy density of the laser beam is set to ETA3 which is slightly lower than the energy density which is a threshold value at which microcrystallization occurs.
10 can be manufactured.

On the other hand, in the formation area CA where the storage capacitor 50 is formed, the energy density of the laser light of ECA3 = ETA3 is closer to the threshold at which crystallization occurs than the energy density at which microcrystallization occurs. Although the resistance is suppressed, the storage capacitor 50 having high withstand voltage can be manufactured by preventing the surface from being roughened. Therefore,
Since the active matrix substrate 2 according to the present embodiment includes the TFT 10 having high mobility and the storage capacitor 50 having high withstand voltage, when the liquid crystal display device 1 is manufactured using the TFT, the display quality is low. High and reliable.

After passing through such a process, the TFT
The SiO ₂ cap layer 45 left over the formation region TA of the storage capacitor 10 and the formation region CA of the storage capacitor 50 can be used as a gate insulating film or a part of a dielectric film of the storage capacitor. Before forming the gate insulating film in the next step, the gate insulating film may be removed by etching by a wet process, and a gate insulating film may be formed again and used as a gate insulating film or a dielectric film of a storage capacitor.

Further, the semiconductor film to be irradiated with energy light is not limited to an amorphous silicon film, and the present invention is applied to irradiate energy light to a crystallized silicon film to recrystallize the crystallized silicon film, thereby improving its crystallinity. May be. The present invention may be applied to a case where lamp light for rapid heat treatment is used as well as laser light as energy light.

[0078]

As described above, in the active matrix substrate according to the present invention, the TFT is provided in each pixel region.
By providing an SiO ₂ cap layer having a different thickness in one or both of the formation region of the storage capacitor and the formation region of the storage capacitor, and controlling the laser beam reaching each region, the laser with the optimum energy intensity is provided for each region. Light can be irradiated. That is, a semiconductor film for forming a TFT is irradiated with light having an energy intensity slightly lower than a threshold value at which microcrystallization occurs, thereby maximizing the crystallinity of the semiconductor film, thereby achieving high mobility. TFTs can be manufactured. On the other hand, the semiconductor film for forming the first electrode of the storage capacitor is irradiated with light having an energy intensity closer to the threshold at which crystallization occurs than the threshold at which microcrystallization occurs, and the crystallinity of the semiconductor film is slightly increased. By preventing the surface from being roughened by suppressing it, a storage capacitor having a high withstand voltage can be manufactured.

[Brief description of the drawings]

FIG. 1A is an explanatory diagram schematically showing an active matrix substrate of a liquid crystal display device, and FIG. 1B is an explanatory diagram of a CMOS circuit used for a driving circuit thereof.

FIG. 2 is an enlarged plan view of a pixel region on an active matrix substrate of the liquid crystal display device, schematically showing a positional relationship between a TFT and a storage capacitor.

FIG. 3 is a cross-sectional view of a TFT and a storage capacitor formed in a pixel region of an active matrix substrate.

FIG. 4 is a process sectional view illustrating the method of manufacturing the TFT and the storage capacitor illustrated in FIG. 3;

FIG. 5 is an explanatory diagram showing a relationship between an energy density in laser melting crystallization and a change occurring in a silicon film.

FIG. 6 is a graph showing the relationship between energy density and crystallinity in laser melting crystallization.

FIG. 7 is a graph showing the relationship between energy density and surface roughness in laser melting crystallization.

8A is a sectional view showing a step of the method for manufacturing the TFT and the storage capacitor shown in FIG. 3 according to the present invention, and FIG.
Is a process sectional view according to Embodiment 1 of the present invention, (B-
2) is a process sectional view according to Embodiment 2 of the present invention, (B)
-3) is a process sectional view according to another embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a relationship between an energy density in laser melting crystallization and a change occurring in a silicon film when a SiO ₂ cap layer is provided.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Active matrix substrate 3 Data line 4 Scan line 4A Capacitance line 5 Pixel region 6 Liquid crystal capacitor 9 Active matrix part 10 TFT 11 Source region 12 Drain region 13 Channel region 14 Gate insulating film 15 Gate electrode 30 Silicon film (semiconductor) Film) 45 SiO ₂ cap layer 50 storage capacitor 51 first electrode layer 54 dielectric film 55 second electrode layer TA TFT formation region CA storage capacitance formation region LB line beam (laser light)

Claims (15)

[Claims] 1. An active matrix substrate having a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, a plurality of thin film transistors connected to the plurality of scanning lines and the data lines, and a storage capacitor. Wherein the source / drain regions of the plurality of thin film transistors and the first electrode of the storage capacitor are formed of the same semiconductor layer, and a first silicon oxide film is formed on the source / drain regions of the thin film transistor. An active matrix substrate having a cap layer disposed thereon. 2. An active matrix substrate having a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, a plurality of thin film transistors connected to the plurality of scanning lines and the data lines, and a storage capacitor. The source / drain regions of the plurality of thin film transistors and the first electrode of the storage capacitor are formed of the same semiconductor layer, and a second cap layer made of a silicon oxide film is formed on the first electrode. An active matrix substrate, which is arranged. 3. An active matrix substrate having a plurality of scanning lines, a plurality of data lines intersecting the plurality of scanning lines, a plurality of thin film transistors connected to the plurality of scanning lines and the data lines, and a storage capacitor. Wherein the source / drain region of the thin film transistor and the first electrode of the storage capacitor are formed of the same semiconductor layer, and a first cap layer made of a silicon oxide film is formed on the source / drain region An active matrix substrate, wherein a second cap layer made of a silicon oxide film is formed on the first electrode, and the first cap layer is thinner than the second cap layer. 4. The storage capacitor according to claim 1, wherein the second electrode of the storage capacitor is formed in the same layer as a gate electrode of the thin film transistor, and the second electrode is a part of a previous gate line. An active matrix substrate, comprising: 5. The storage capacitor according to claim 1, wherein the second electrode of the storage capacitor is formed in the same layer as a gate electrode of the thin film transistor, and the second electrode is arranged in parallel with the gate line. An active matrix substrate, which is a part of a capacitance line. 6. A liquid crystal display device using the active matrix substrate according to claim 1. 7. The method of manufacturing an active matrix substrate according to claim 1, further comprising: forming a semiconductor film serving as the source / drain region of the thin film transistor and the first electrode of the storage capacitor; After forming the first cap layer, irradiating the semiconductor film with energy light, and setting the thickness of the first gap layer so as to exhibit an effect as a heat absorbing layer. Irradiating the source / drain region and the first electrode with the energy light, the source / drain region is irradiated with an energy light slightly weaker than a threshold at which microcrystallization occurs, and crystallized; The first electrode is crystallized by irradiating energy light closer to the threshold at which crystallization occurs than the threshold at which microcrystallization occurs. Method for manufacturing an active matrix substrate. 8. The method of manufacturing an active matrix substrate according to claim 2, wherein a semiconductor film serving as the first electrode of the source / drain region of the thin film transistor and the storage capacitor is formed, and the semiconductor film is formed on the first electrode. Irradiating the semiconductor film with energy light after forming the second cap layer; setting the thickness of the second gap layer to exhibit an effect as a filter layer; Light source
By irradiating the drain region and the first electrode,
The source / drain regions are crystallized by irradiation with energy light slightly weaker than a threshold value at which microcrystallization occurs, and the first electrode has a threshold value at which crystallization occurs at a level lower than the threshold value at which microcrystallization occurs. A method for producing an active matrix substrate, wherein the active matrix substrate is irradiated with energy light and crystallized. 9. The method for manufacturing an active matrix substrate according to claim 3, wherein a semiconductor film serving as the source / drain region and the first electrode of the thin film transistor is formed.
After the first cap layer is formed on the drain region, the second gap layer is formed on the first electrode layer, and the first cap layer is formed thinner than the second cap layer. And irradiating the semiconductor film to be the first electrode with energy light having the same intensity to crystallize the semiconductor film. 10. The method of manufacturing an active matrix substrate according to claim 9, wherein said energy light having the same intensity is an energy light weaker than a threshold value at which said source / drain region undergoes microcrystallization. 11. The semiconductor device according to claim 9, wherein the energy light having the same intensity is crystallized by energy light closer to a threshold at which crystallization takes place than a threshold at which the semiconductor film in the storage capacitor region undergoes microcrystallization. A method for manufacturing an active matrix substrate. 12. The method according to claim 7, 8 or 9, wherein
As an energy light for irradiating the semiconductor film, an irradiation region uses a line beam of laser light extending in a direction in which a scanning line or a data line extends, and a direction in which a data line extends the line beam or A method for manufacturing an active matrix substrate, wherein scanning is performed in a direction in which scanning lines extend. 13. The method according to claim 12, wherein a scanning pitch of the line beam is narrower than a width of the line beam in a scanning direction, and the line beam is irradiated while overlapping the same region. A method for manufacturing an active matrix substrate. 14. The method of manufacturing an active matrix substrate according to claim 1, wherein energy light is applied to a source / drain region of the thin film transistor and a semiconductor film to form a first electrode of the storage capacitor. After the irradiation, the first cap layer made of the silicon oxide film is used as a gate insulating film, and
The method for manufacturing an active matrix substrate, wherein the gap layer functions as a dielectric film of the storage capacitor. 15. The method for manufacturing an active matrix substrate according to claim 1, wherein the source / drain region of the thin film transistor and the semiconductor film serving as the first electrode are irradiated with energy light. Forming a gate insulating film or a dielectric film of the storage capacitor after removing the first or second cap layer made of the silicon oxide film by etching.