JP3580104B2 - Active matrix substrate, method of manufacturing the same, and liquid crystal display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an active matrix substrate using a thin film transistor (hereinafter, referred to as TFT), a method for 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]
[Prior art]
In the active matrix substrate of the liquid crystal display device, as shown in FIG. 1, a plurality of scanning lines 4 extending in the X direction and a plurality of data lines 3 extending in the Y direction intersecting the scanning lines 4. A pixel region 5 is defined by each pixel region 5, 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 help 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 15 (scan The electrode layer formed between the same layers as the line 4) is referred to as a second electrode layer 55, and between the first electrode layer 51 and the second electrode layer 55 is formed between the same layer as the gate insulating film 14. Dielectric film 54.
[0003]
In the active matrix substrate 2 configured as described above, as shown in FIG. 2, the TFT 10 is formed at the corner of the pixel region 5 in the silicon film 30 formed in each pixel region 5 as viewed in the drawing. Used for 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 extended portion 40 that extends perpendicularly to the −Y direction from the scanning line 4 and extends in the + Y direction. Later, a portion extending in the + X direction toward the adjacent pixel region and overlapping in the X direction with the formation region of the TFT 10 in the adjacent pixel region 5 is used as the first electrode layer 51 of the storage capacitor 50.
[0004]
In the active matrix substrate 2 configured as described above, it is desired to manufacture the TFT 10 by a low-temperature process so that a glass substrate can be used as the substrate. However, although a silicon film required to form a channel region or the like of the TFT 10 can be formed by a low-temperature process if it is an amorphous silicon film, it has a drawback of low mobility.
[0005]
Therefore, a laser melt crystallization method of irradiating the amorphous silicon film 30 formed on the substrate with a laser beam to perform melt crystallization has been studied. In this method, for example, a laser beam having a long irradiation region in the Y direction is used. The amorphous silicon film 30 is irradiated with the 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 10. Can be manufactured. However, if the energy intensity is too high, the silicon film 30 will be microcrystallized. Therefore, it is general to set the energy intensity slightly lower than that at which the silicon film 30 is microcrystallized.
[0006]
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 that of the silicon film 30 for forming the TFT 10, and is transferred to polycrystalline silicon.
[0007]
[Problems to be solved by the invention]
However, if the silicon film 30 is irradiated with laser light at a high intensity just before micro-crystallization occurs for the purpose of manufacturing the TFT 10 having high mobility as in the conventional case, the withstand voltage of the storage capacitor 50 decreases. This causes a problem that the reliability of the liquid crystal display device is reduced. It is considered that the reason is that the more the laser beam is irradiated to the silicon film 30 at a higher intensity, the more the surface of the silicon film 30 is roughened, which lowers the withstand voltage.
[0008]
In view of the above, an object of the present invention is to form a storage capacitor while assisting a manufacturing process of a TFT, and to form a silicon oxide film (SiO 2) having a different film thickness on only one or both of the TFT and the storage capacitor.₂An active matrix substrate capable of forming a TFT with high mobility and a storage capacitor with high withstand voltage by irradiating energy light under optimum conditions after forming the film, a liquid crystal display device using the same, and the active matrix substrate. It is to provide a manufacturing method.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a method of manufacturing a semiconductor device, comprising the steps of: forming a first semiconductor film to be a source / drain region of a thin film transistor; and forming a second semiconductor film to be a first electrode of a storage capacitor. On the first semiconductor filmHas a thickness that works as a heat absorbing layerForming a first insulating film;By irradiating the first insulating film and the second semiconductor film with energy light having the same intensity, the first semiconductor film isVia the first insulating filmHigher energy density than the energy lightthe lightLet it enterCrystallizationAndThe second semiconductor filmIs theEnergy lightLet it enterCrystallizing step.
[0010]
In this case, for example,The first semiconductor film and the second semiconductor filmIrradiation area as energy light to irradiateIn the direction in which the scanning lines extend or the data lines extendUsing the extended laser beam line beam,SaidLine beamThe direction in which the data line extends or the scanning line extendsScan in the direction.
[0011]
Further, each of the first semiconductor film and the second semiconductor filmAfter irradiating energy light toThe first insulating film may function as a gate insulating film.
[0012]
After irradiating each of the first semiconductor film and the second semiconductor film with energy light, and after removing the first insulating film by etching,A gate insulating film may be formed.
[0013]
On the other hand, in the active matrix substrate of the present invention, in the manufacturing method, a step of forming a first semiconductor film serving as a source / drain region of a thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor; On the semiconductor filmHas a thickness that works as a filter layerForming a second insulating film;Irradiating the first semiconductor film and the second insulating film with energy light having the same intensity;The first semiconductor filmIs theEnergy lightLet it enterCrystallizationAnd the second semiconductor film hasVia the second insulating filmSaidThan energy lightLow energy densitythe lightLet it enterCrystallizing step.
[0014]
In this case, for example,The first semiconductor film and the second semiconductor filmIrradiated area as energy light to be irradiatedIn the direction in which the scanning lines extend or the data lines extendUsing the extended laser beam line beam,SaidLine beamThe direction in which the data line extends or the scanning line extendsScan in the direction.
[0015]
Further, for each of the first semiconductor film and the second semiconductor film,After irradiating energy lightThe second insulating film can also function as a dielectric film of the storage capacitor.
[0016]
After irradiating each of the first semiconductor film and the second semiconductor film with energy light, and after removing the second insulating film by etching,A dielectric film for the storage capacitor may be formed.
[0017]
Further, the present invention provides an active device including 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. In the matrix substrate, 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 insulating film serving as a gate insulating film is formed on the source / drain region. A second insulating film serving as a dielectric film is formed on the first electrode, the first insulating film is thinner than the second insulating film, and the source / drain region and the second One electrode is crystallized by laser irradiation through the first insulating film and the second insulating film, respectively.The source / drain region has higher crystallinity than the first electrodeIt is characterized by the following. In the manufacturing method, a first semiconductor film serving as a source / drain region of a thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor are formed, and a first insulating film is formed on the first semiconductor film. A second insulating film thicker than the first insulating film is formed on the second semiconductor film, and the first insulating film and the second insulating film are formed.Irradiate the same intensity energy light toThe first semiconductor filmEnergy light incident on the first semiconductor film is weaker than a threshold value that causes microcrystallization of the first semiconductor film;The second semiconductor filmThe incident energy light is energy light closer to a threshold value for causing crystallization than a threshold value for causing microcrystallization of the second semiconductor film.The first semiconductor film and the second semiconductor film are crystallized.
[0018]
Further, the method of manufacturing an active matrix substrate of the present application includes a step of forming a first semiconductor film serving as a source / drain region of a thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor; Forming a first insulating film, and forming a second insulating film thicker than the first insulating film on the second semiconductor film;Irradiating the first insulating film and the second insulating film with energy light of the same intensity,Via the first insulating filmHigh energy densitythe lightLet it enterCrystallizationAnd the second semiconductorVia the second insulating filmFirstFor semiconductor filmLet inThan lightLow energy densitythe lightLet it enterAnd a step of crystallization.
[0019]
In this case, for example,The first semiconductor film and the second semiconductor filmIrradiated area as energy light to be irradiatedIn the direction in which the scanning lines extend or the data lines extendUsing the extended laser beam line beam,SaidLine beamThe direction in which the data line extends or the scanning line extendsScan in the direction.
[0020]
In addition, each of the first semiconductor film and the second semiconductor filmAfter irradiating energy lightThe first insulating film may be a gate insulating film, and the second insulating film may function as a dielectric film of the storage capacitor.
[0021]
Further, after irradiating each of the first semiconductor film and the second semiconductor film with energy light, after removing the first insulating film or the second insulating film by etching, the gate insulating film or theA dielectric film for the storage capacitor may be formed.
[0022]
As described above, according to the present invention, in any of the above-described embodiments, the SiO region which functions as a heat absorbing layer or functions as a filter layer is formed in the TFT formation region and the storage capacitor formation region.₂Since the cap layer is provided, when the semiconductor film is irradiated with energy light, although the intensity of the energy light is constantly constant, the area where the TFT is formed (source / drain region) and the capacity of the storage capacitor are maintained. Light having an optimum energy intensity is applied to each of the formation regions (first electrodes). 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.
[0023]
In the present invention, in any of the above embodiments, the second electrode is formed in the same layer as the gate electrode, and a part of the previous gate line or a capacitor line arranged in parallel with the gate line. Some of them are used.
[0024]
Here, when a line beam is used, it is preferable that the scanning pitch is narrower than the width dimension of the line beam in the scanning direction, and the line beam is irradiated while overlapping the same region.
[0025]
The active matrix substrate thus configured has a high mobility and a high withstand voltage, and thus has a high holding capacity. Therefore, when a liquid crystal display device is manufactured using the active matrix substrate, display quality is high. The effect of high reliability is also obtained.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Before describing the embodiments of the present invention, a basic configuration of an active matrix substrate common to the embodiments and a basic process of forming a TFT and a storage capacitor at the same time will be described.
[0027]
[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.
[0028]
In FIG. 1, a liquid crystal display device 1 has pixels formed on an active matrix substrate 2 by a plurality of scanning lines 4 extending in an X direction and data lines 3 extending in a Y direction orthogonal to these scanning lines 4. It has a region 5, in which a liquid crystal capacitor 6 of a liquid crystal cell to which an image signal is inputted 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.
[0029]
The data driver unit 7 and the scan driver unit 8 include a CMOS circuit configured by N-type TFTs n1 and n2 and P-type TFTs p1 and p2, as exemplified by a two-stage inverter in FIG. It is formed with 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 p1 and p2 have the same basic structure, and are basically manufactured in the same process. The storage capacitor 50 is manufactured by using the manufacturing process of the TFT 10 as much as possible, as will be described in detail later.
[0030]
The active matrix substrate 2 includes only the active matrix unit 9 formed on the substrate, the one configured with the data driver unit 7 on the same substrate as the active matrix unit 9, and the scanning on the same substrate as the active matrix unit 9. There is a configuration in which the driver unit 8 is configured, and a configuration in which both the data driver unit 7 and the scanning driver unit 8 are configured on the same substrate as the active matrix unit 9. Further, even in the case of the active matrix substrate 2 with a built-in driver, the shift register 71, the level shifter 72, the video line 73, the analog switch 74, and the like included in the data driver unit 7 are all formed on the active matrix substrate 2. There are a driver built-in type and a partial driver built-in type in which a part of them is formed on the active matrix substrate 2, and the present invention can be applied to both types.
[0031]
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) and a scanning line are shown. The data lines and the pixel electrodes are omitted to make the formation region of 4 easy to understand.
[0032]
2, in the active matrix substrate 2 of the present embodiment, a plurality of scanning lines 4 extending in the X direction and a plurality of data lines extending in the Y direction orthogonal to the scanning lines 4 (not shown). In each of the pixel regions 5 partitioned by the TFTs, a TFT 10 connected to the data line and the scanning line 4 and a pixel electrode (not shown) connected to the TFT 10 are formed.
[0033]
Each pixel region 5 includes 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 an extended portion extending from the scanning line 4 in the −Y direction. The storage capacitor 50 is formed by an overlapping portion with the second electrode layer 55 made of 40.
[0034]
FIG. 3 is a cross-sectional view schematically illustrating the TFT 10 and the storage capacitor 50 formed in the pixel region 5 of the active matrix substrate 2.
[0035]
In these figures, in any pixel region 5, the TFT 10 is connected to the data line 3 on the substrate 20 via the contact hole 17 of the interlayer insulating film 16 and the source region 11 and the pixel electrode 19. Drain region 12 electrically connected through contact hole 18 of interlayer insulating film 16, channel region 13 for forming a channel between drain region 12 and source region 11, and gate insulation with respect to channel region 13. It is composed of gate electrodes 15 facing each other via the film 14. The gate electrode 15 is configured as a part of the scanning line 4. In addition, on the front side of the substrate 20, SiO 2₂A base protective film 21 made of a film is formed.
[0036]
On the storage capacitor 50 side, a semiconductor film 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 on the surface thereof, a dielectric film 54 formed simultaneously with the gate insulating film 14 on the surface side thereof and located on the same layer as the insulating film, and a gate electrode 15 and a scanning line 4 on the surface side. And the second electrode layer 55 located between the same layers as these electrodes and wirings.
[0037]
[Basic Configuration of Manufacturing Method of Active Matrix Substrate 2]
With reference to FIG. 4, basic steps of a method for manufacturing the TFT 10 and the storage capacitor 50 will be described.
[0038]
(Base protective film forming step)
In FIG. 4A, first, the thickness of the base protective film 21 is formed on the surface of a substrate 20 such as a 300 mm square alkali-free glass plate under a temperature condition of 250 ° C. to 300 ° C. by ECR-PECVD. 200nm SiO₂Form a film. SiO₂The film 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 a source gas.₂Form a film.
[0039]
(Semiconductor film deposition process)
Next, an intrinsic silicon film 30 (semiconductor film) is deposited on the surface of the underlying protective film 21 to a thickness of about 50 nm. 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. According to these methods, the film formation temperature can be set in a range from room temperature to 350 ° C.
[0040]
In the present invention, following this semiconductor film deposition step, SiO 2₂The cap layer 45 is formed, and the SiO 2₂In order to leave the cap layer 45 only in the formation region TA of the TFT 10 or the formation region CA of the storage capacitor 50, or to leave a difference in film thickness between both formation regions, it is necessary to perform patterning. This detailed description will be described later for each embodiment.
[0041]
(Annealing process by laser melting crystallization method)
Next, as shown in FIG. 4B, laser light is directly applied to the amorphous silicon film 30 or SiO₂Irradiation is performed via a cap layer (not shown) to transform 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 at a room temperature (25 ° C.) of the substrate 20 in a vacuum atmosphere, an inert gas atmosphere, and further in the air.
[0042]
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. However, only the formation area TA of the TFT 10 and the formation area CA of the storage capacitor 50 were selectively applied. Laser irradiation may be performed to shorten the laser annealing time.
[0043]
(Silicon film patterning process)
Next, as shown in FIG. 4C, the silicon film 30 that has been subjected to the annealing step is patterned by using a photolithography technique, so that an island shape is formed in the formation area TA of the TFT 10 and the formation area CA of the storage capacitor 50. Are formed, respectively. In addition, the above-mentioned annealing step is performed by₂The patterning may be performed after the cap layer 45 is collectively patterned.
[0044]
(Step of forming gate insulating film)
Next, as shown in FIG. 4D, SiO 2 is applied to the silicon film 30 by the ECR-PECVD method under a temperature condition of 250 ° C. to 300 ° C.₂The gate oxide film 14 and the dielectric film 54 are formed.
[0045]
(Step of forming first electrode layer 51 of storage capacitor 50)
Next, the silicon film 30 on the side of the formation region TA of the TFT 10 is covered with a resist mask 33. In this state, a high concentration impurity is introduced into the silicon film 30 of the formation region CA of the storage capacitor 50 to make it conductive. , The first electrode layer 51.
[0046]
(Gate electrode formation 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 thereafter, as shown in FIG. And a second electrode layer 55 is formed. In this example, when forming a tantalum thin film, the substrate temperature is set to 180 ° C., and an argon gas containing 6.7% of a nitrogen gas is used as a sputtering gas. The tantalum thin film thus formed has an α-structure crystal structure and low specific resistance.
[0047]
(Impurity introduction step)
Next, 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 by using a bucket type mass non-separation type ion implantation apparatus (ion doping apparatus). In the case of forming an N-channel TFT, phosphine or the like diluted with hydrogen gas to have a concentration of 5% is used as a source gas. As a result, the source region 11 and the drain region 12 are formed in a self-aligned manner with respect to the gate electrode 15. At this time, the portion of the silicon film 30 where the impurity ions have not been implanted becomes the channel region 13.
[0048]
In the case of forming a P-channel TFT, diborane or the like diluted with hydrogen gas to a concentration of 5% is used as a source gas.
[0049]
(Step of forming interlayer insulating film)
Next, as shown in FIG. 4F, a 50-nm thick SiO 2 film as the interlayer insulating film 16 is formed by PECVD under a temperature condition of 250 ° C. to 300 ° C.₂Form a film. The source gas at this time is TEOS and oxygen. The substrate temperature is between 250C and 300C.
[0050]
(Activation process)
Next, heat treatment is performed at 300 ° C. for one hour in an argon gas atmosphere containing 3% of hydrogen to activate the implanted phosphorus ions and to modify the interlayer insulating film 16.
[0051]
(Wiring process)
Next, contact holes 17 and 18 are formed in the interlayer insulating film 16. Thereafter, the source electrode (data line 3) is electrically connected to the source region 11 through the contact holes 17 and 18, and the drain electrode (pixel electrode 19) is electrically connected to the drain region 12 as shown in FIG. To form a TFT 10.
[0052]
Although the above-described manufacturing method is an example in which the TFT 10 is manufactured with a self-aligned structure, the present invention can be applied to a case where the TFT 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 by using a resist mask or a sidewall. (LDD region) or an offset region is formed.
[0053]
[Energy intensity and film quality during laser irradiation]
Before describing the embodiment of the present invention, in the annealing step described with reference to FIG. 4C, the energy density (energy intensity) of the laser light applied to the basic amorphous silicon film 30 and the laser light The relationship with the film quality after irradiation will be described with reference to FIGS.
[0054]
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. Then, the silicon film is melted and solidified at a temperature equal to or higher than Ec indicated by “」 ”and the alternate long and short dash line L1, and polycrystallized. Here, as the energy density E increases, the polycrystallization progresses. However, when the energy density E exceeds Ea indicated by “□” and the dotted line L2, the silicon film is microcrystallized, and the mobility is reduced. . 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. . When the energy density E exceeds “□” and Ed shown by the solid line L4, the silicon film evaporates.
[0055]
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 by comparing these results, in laser melting crystallization, the crystallinity can be enhanced by setting the maximum value of the energy density E to a value that is quite 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 microcrystallization occurs in the silicon film.
[0056]
Similarly, the roughness of the silicon film surface when the energy density E is changed is indicated by “○” 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, part of the evaporated silicon adversely affects the optical components of the annealing apparatus.
[0057]
Here, in order to form the TFT 10 and the storage capacitor 50 (see FIGS. 3 and 4) from the amorphous silicon film, the TFT 10 has a high crystallinity even if the surface of the silicon film 30 is roughened. Want to get as high a mobility as possible. On the other hand, in the case of the storage capacitor 50, it is desirable to suppress surface roughness and obtain a high withstand voltage even if the crystallinity is somewhat low. However, in the layout shown in FIG. 2, the formation area TA of the TFT 10 and the formation area CA of the storage capacitor 50 overlap in both the X direction and the Y direction. The strength cannot be changed. If the layout is changed so that the formation area TA of the TFT 10 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 in accordance with each area. It is necessary to change the attenuator while keeping the output constant. The pixel pitch of the TFT is about 50 μm, while the feed pitch of the laser beam LB is about 10 μm. Even if any of the laser oscillator and the attenuator is modulated, it is necessary to perform the modulation in about 5 shots, which is difficult.
[0058]
Therefore, in the present invention, as will be described below, one or both of the formation region TA of the TFT 10 and the formation region CA of the storage capacitor 50 have different thicknesses of SiO 2.₂By providing the 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.
[0059]
[Embodiment 1]
FIG. 8A shows that after forming the base protective film 21 and the semiconductor film 30 on the surface of the substrate 20 shown in FIG.₂It is sectional drawing in which the film was formed.
[0060]
This SiO₂In forming the cap layer 45, the ECR-PECVD method is used to form SiO 2 under a temperature condition of 250 ° C. to 300 ° C.₂Form a film. SiO in this case₂The film 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 a source gas.₂Form a film.
[0061]
This SiO₂Depending on the thickness of the film, the effective intensity of the laser light irradiated in the annealing step by the next laser melt crystallization method varies, and the crystallinity of the obtained polycrystalline silicon film differs, so it is necessary to set an appropriate film thickness There is.
[0062]
FIG. 9 shows that an underlying protective film 21 having a thickness of 50 nm is formed on an intrinsic silicon film 30 having a thickness of 50 nm.₂The relationship between the energy density and the film quality after laser irradiation when the laser light irradiation is performed on the substrate 20 in which the thickness of the cap layer 45 is 0 to 150 nm is changed.
[0063]
Here, SiO₂A 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 the cap layer 45 only on the formation region TA of the TFT 10 and remove the other portions, with reference to FIG. 8B-1.
[0064]
In FIG. 9, the energy density, which is the threshold at which crystallization occurs as indicated by “▲” and the solid line L5, is SiO 2₂By forming the cap layer 45 of less than 70 nm acting as a heat absorbing layer,₂This is lower than the case where the cap layer 45 is not formed. This is because the reflectivity for the wavelength of the excimer laser (here, KrF: the wavelength is 248 nm) is higher than that of the silicon film.₂Because the film is smaller, SiO₂This is because the formation of the cap layer 45 makes it easier for laser light to enter the silicon film. Originally SiO₂Since the film should not absorb the wavelength of the incident laser light,₂Although the effect of reducing the reflectance should not change even if the film is made thicker, the progress of crystallization is actually SiO 2 as shown in FIG.₂It largely depends on the thickness of the film. This is silicon film and SiO₂Since the sum of both films is as thin as less than half of the wavelength of the incident laser light, SiO₂This is because the degree of penetration of the laser light wave into the silicon film varies depending on the thickness of the film, and the amount of light absorbed changes. In accordance with this, the energy density which is the threshold value at which microcrystallization occurs as indicated by “□” and the solid line L6 and the energy density which is the threshold value at which ablation occurs as indicated by “Δ” and the solid line L7 are also reduced. Especially SiO₂An effective condition for the film thickness is 50 nm.
[0065]
Therefore, the SiO formed on the formation area TA of the TFT 10₂When the thickness of the cap layer 45 is set to 50 nm, the energy density of the laser beam is set to a value slightly smaller than the energy density which is a threshold value at which microcrystallization occurs so that the amorphous silicon film 30 in the formation area TA of the TFT 10 has high crystallinity. By setting the ETA 1 below, the TFT 10 with high mobility can be manufactured.
[0066]
On the other hand, SiO₂In the area where the cap layer 45 is not provided, the energy density of the laser light of ECA1 = ETA1 is closer to the threshold at which crystallization occurs than the energy density at which microcrystallization occurs, and the crystallinity is suppressed. However, by preventing the surface from being roughened, the storage capacitor 50 having a high withstand voltage can be manufactured. Therefore, 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 10, the display is performed. High quality and high reliability.
[0067]
Further, after such a process, the SiO 10 left on the formation area TA of the TFT 10 is formed.₂The cap layer 45 can be used as a part of the gate insulating film, or it can be removed by etching by a wet process before forming the gate insulating film in the next step, and the gate insulating film can be formed again. I do not care.
[0068]
[Embodiment 2]
Similarly, FIG. 8A shows the SiO 2 that becomes the cap layer 45 after the base protective film 21 is formed on the surface of the substrate 20 shown in FIG.₂FIG. 3 is a cross-sectional view in which a film is formed;₂The method for forming the film is the same as that in the first embodiment, and will not be described.
[0069]
Here, SiO₂FIG. 8B-2 is a cross-sectional view of a case where patterning is performed using photolithography to leave the cap layer 45 only on the formation region CA of the storage capacitor 50 and remove the other portions.
[0070]
In FIG. 9, the energy density, which is the threshold at which crystallization occurs as indicated by “▲” and the solid line L5, is SiO 2₂By forming the cap layer 45 having a thickness of 70 nm or more that functions as a filter layer,₂It rises compared to the case where the cap layer 45 is not formed. This is SiO₂If 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, SiO₂By forming the 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 the solid line L6, and the energy density, which is the threshold for ablation, indicated by “Δ” and the solid line L7, also increase.
[0071]
Therefore, the SiO formed on the formation area CA of the storage capacitor 50₂While the thickness of the cap layer 45 is set to 110 nm, the energy density of the laser light is set to a threshold value at which microcrystallization occurs so that high crystallinity can be obtained in the amorphous silicon film 30 in the formation area TA of the TFT 10. By setting ETA2 slightly lower than the above, TFT 10 having high mobility can be manufactured.
[0072]
In this case, SiO₂In the formation area CA of the storage capacitor 50 where the cap layer 45 is located, the energy density of the laser light of ECA2 = ETA2 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 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 10, the display is performed. High quality and high reliability.
[0073]
Further, after passing through such a process, the SiO 2 left over the formation area CA of the storage capacitor 50 is formed.₂The cap layer 45 can be used as a part of the dielectric film of the storage capacitor. Before the formation of the gate insulating film in the next step, the cap layer 45 is removed by etching using a wet process to form the gate insulating film again. Alternatively, it may be used as a dielectric film of a storage capacitor.
[0074]
[Other embodiments]
As described above, only one of the formation area TA of the TFT 10 and the formation area CA of the storage capacitor 50 is made of SiO.₂Instead of leaving the cap layer 45, it is also possible to leave it on both. As shown in FIG. 8B-3, the thicker SiO₂SiO according to the formation area CA of the storage capacitor 50 requiring the cap layer thickness₂After a film is formed to a thickness of 75 nm, SiO 2 is formed on the formation region TA of the TFT 10 by etching.₂Process the film to 50 nm. Therefore, in FIG. 9, the energy density of the laser beam is set to be slightly lower than the energy density which is the threshold value at which microcrystallization occurs so that high crystallinity can be obtained in the amorphous silicon film 30 in the formation region TA of the FT 10. By doing so, a TFT 10 having a high mobility can be manufactured.
[0075]
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, and the crystallinity is suppressed. However, by preventing the surface from being roughened, the storage capacitor 50 having a high withstand voltage can be manufactured. Therefore, 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 10, the display is performed. High quality and high reliability.
[0076]
After such a process, the SiO 2 remaining on the formation area TA of the TFT 10 and the formation area CA of the storage capacitor 50 is formed.₂The cap layer 45 can be used as a part of a gate insulating film or a dielectric film of a storage capacitor. Before the formation of the gate insulating film in the next step, the cap layer 45 is removed by etching by a wet process, and the gate layer is renewed. An insulating film may be formed and used as a gate insulating film or a dielectric film of a storage capacitor.
[0077]
Furthermore, the semiconductor film for irradiating the energy light is not limited to the amorphous silicon film, and the present invention may be applied to increase the crystallinity by irradiating the crystallized silicon film with the energy light for recrystallization. Good. The present invention may be applied to a case where a lamp light for rapid heat treatment is used as well as a laser light as the energy light.
[0078]
【The invention's effect】
As described above, in the active matrix substrate according to the present invention, in each pixel region, one or both of the TFT formation region and the storage capacitor formation region have different thicknesses of SiO 2.₂By providing the cap layer and controlling the laser light reaching each region, it is possible to irradiate the laser light with the optimum energy intensity for each region. 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 value at which crystallization occurs than the threshold value at which microcrystallization occurs, thereby slightly reducing the crystallinity of the semiconductor film. 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 a 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 a relationship between energy density and surface roughness in laser melting crystallization.
8A is a process sectional view showing a method for manufacturing the TFT and the storage capacitor shown in FIG. 3 according to the present invention, FIG. 8B is a process sectional view according to Embodiment 1 of the present invention, (B-2) is a process cross-sectional view according to Embodiment 2 of the present invention, and (B-3) is a process cross-sectional view according to another embodiment of the present invention.
FIG. 9: SiO₂FIG. 4 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 cap layer is provided.
[Explanation of symbols]
1 Liquid crystal display device
2 Active matrix substrate
3 Data line
4 scan lines
4A capacity line
5 pixel area
6 liquid crystal capacity
9 Active matrix section
10 TFT
11 Source area
12 Drain region
13 Channel area
14 Gate insulating film
15 Gate electrode
30 Silicon film (semiconductor film)
45 SiO₂Cap layer
50 holding capacity
51 1st electrode layer
54 Dielectric film
55 second electrode layer
TA TFT formation area
CA storage capacitor formation area
LB line beam (laser light)

Claims (12)

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 an active matrix substrate including a storage capacitor.
The source / drain region of the thin film transistor and the first electrode of the storage capacitor are formed of the same semiconductor layer,
A first insulating film serving as a gate insulating film is formed on the source / drain region; a second insulating film serving as a dielectric film is formed on the first electrode; Is thinner than the second insulating film, and the source / drain region and the first electrode are crystallized by laser irradiation via the first insulating film and the second insulating film, respectively , so that the source / drain The active matrix substrate, wherein the region has higher crystallinity than the first electrode . 2. The active matrix substrate according to claim 1, wherein a 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. . 2. The device 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 capacitor line arranged in parallel with the gate line. Active matrix substrate characterized by: A liquid crystal display device using the active matrix substrate according to claim 1. In a method for manufacturing an active matrix substrate,
Forming a first semiconductor film serving as a source / drain region of the thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor;
Forming a first insulating film on the first semiconductor film and forming a second insulating film thicker than the first insulating film on the second semiconductor film;
By irradiating the first insulating film and the second insulating film with energy light having the same intensity, the energy light incident on the first semiconductor film is weaker than a threshold value for causing microcrystallization of the first semiconductor film. Energy light incident on the second semiconductor film as energy light, the energy light being closer to a threshold value for causing crystallization than a threshold value for causing microcrystallization of the second semiconductor film. And a method of manufacturing an active matrix substrate, wherein the second semiconductor film is crystallized. In a method for manufacturing an active matrix substrate,
  Forming a first semiconductor film serving as a source / drain region of the thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor;
  Forming a first insulating film having a thickness acting as a heat absorbing layer on the first semiconductor film;
  The first insulating film and the second semiconductor film are irradiated with energy light having the same intensity, and light having an energy density higher than that of the energy light is incident on the first semiconductor film via the first insulating film. Crystallizing, and irradiating the energy light to the second semiconductor film to crystallize;
  A method for manufacturing an active matrix substrate, comprising: In a method for manufacturing an active matrix substrate,
  Forming a first semiconductor film serving as a source / drain region of the thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor;
  Forming a second insulating film having a thickness acting as a filter layer on the second semiconductor film;
  The first semiconductor film and the second insulating film are irradiated with energy light having the same intensity, the energy light is incident on the first semiconductor film, and the first semiconductor film is crystallized. Crystallizing by irradiating light having a lower energy density than the energy light through the film;
  A method for manufacturing an active matrix substrate, comprising: In a method for manufacturing an active matrix substrate,
  Forming a first semiconductor film serving as a source / drain region of the thin film transistor and a second semiconductor film serving as a first electrode of a storage capacitor;
  Forming a first insulating film on the first semiconductor film, and forming a second insulating film thicker than the first insulating film on the second semiconductor film;
  The first insulating film and the second insulating film are irradiated with energy light having the same intensity, and light having a high energy density is incident on the first semiconductor via the first insulating film to be crystallized. (2) crystallizing the semiconductor by injecting light having a lower energy density than light incident on the first semiconductor film via the second insulating film;
  A method for manufacturing an active matrix substrate, comprising: In any one of claims 5 to 8,
  As the energy light for irradiating the first semiconductor film and the second semiconductor film, a line beam of laser light whose irradiation region extends in a direction in which a scanning line extends or a direction in which a data line extends, is used as the energy beam. A method of manufacturing an active matrix substrate, wherein scanning is performed in a direction in which a data line or a scanning line extends. 10. The active matrix according to claim 9, wherein a scanning pitch of the line beam is narrower than a width dimension of the line beam in a scanning direction, and the line beam is irradiated while overlapping the same region. Substrate manufacturing method. In any one of claims 5 to 8,
  After irradiating each of the first semiconductor film and the second semiconductor film with energy light, the first insulating film serves as a gate insulating film, and the second insulating film functions as a dielectric film of the storage capacitor. A method of manufacturing an active matrix substrate. In any one of claims 5 to 8,
  After irradiating each of the first semiconductor film and the second semiconductor film with energy light, and removing the first insulating film or the second insulating film by etching, the dielectric of the gate insulating film or the storage capacitor is removed. A method for manufacturing an active matrix substrate, comprising a step of forming a body film.

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