JPH11142889A - Active matrix substrate and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the generation of the defect caused by the short circuit in a display region by dividing the driving circuit into plural regions, alternatively arranging the regions while sandwitching a pixel region and pulling out the wirings for the anodizing of gate electrodes from the places where no driving circuit exists. SOLUTION: The signal side driving circuit of the driving circuit is divided into plural regions DAR1 to DAR3 and the regions DAR1 to DAR3 are alternatively arranged while sandwitching the display region. Moreover, a scanning line side driving circuit is divided into plural regions SAR1 to SAR3 and are alternatively arranged while sandwitching the display region. In this case, the gate electrode of the display region is the Ta, which is formed by the process that is same as the process of making the scanning lines. The electrode is electrically connected to a terminal AXC on a glass substrate through a wiring AXL on which the Ta is formed with the same process. The wiring AXL used for anodizing is formed to the opposite side with respect to the region, in which the scanning line side driving circuit, or the region in which no scanning line side driving circuit is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device using an active matrix substrate and the like. The configuration and the manufacturing method of the present invention are not limited to the active matrix type liquid crystal display device, and the present invention can be applied to fields such as a line sensor or a flat sensor in which a drive circuit is formed on an insulating substrate, or a liquid crystal shutter. It is.

[0002]

2. Description of the Related Art In recent years, among flat-panel image display devices, research on an active matrix type liquid crystal display device has been particularly advanced, and an image quality equal to or higher than that of a cathode-ray tube type image display device has been obtained. In order to achieve high-definition image quality and reduce manufacturing costs, research on configuring a thin film transistor driving circuit on the same insulating substrate as a pixel has been actively conducted. C-
In order to form a MOS driving circuit, a thin film transistor having high mobility needs to be manufactured on an insulating substrate. As shown in JP-A-58-4180, a thin film transistor having high mobility can be manufactured by crystallizing an active silicon layer of a thin film transistor by a solid phase growth method or a laser irradiation method. In particular, in the method in which a silicon layer is crystallized by laser irradiation, an excellent thin film transistor can be manufactured with the substrate kept at room temperature; therefore, a driver circuit can be formed over an inexpensive glass substrate having a low strain point.

[0003] As a method of manufacturing a silicon thin film by irradiating a laser beam with a laser beam, a silicon thin film having a large grain size of grain or having few dangling bonds is disclosed in Japanese Patent Application Laid-Open No. 61-78119. A method of recrystallizing only the portion once and then performing solid phase growth by heat treatment to increase the crystal grain size and improve the characteristics by uniforming the grain size.
As shown in JP-A-31108, a frame-shaped insulating film having low thermal conductivity is formed under a semiconductor thin film to be crystallized, and irradiation with a laser beam causes crystallization of the polycrystalline silicon film inside the frame to be centered. From now on, we are studying a method to improve crystallinity and improve the characteristics by forming an element in that part. Alternatively, as shown in JP-A-3-30433, the non-uniformity of the crystallinity caused by the edge portion of the laser beam can be reduced by irradiating the laser beam with a semiconductor to be first crystallized and an edge portion of an uncrystallized portion. On the substrate side of the film, via an insulating film that transmits ultraviolet light, the melting point is lower than this insulating film,
Attempts have been made to obtain a uniform semiconductor thin film with improved crystallinity by irradiating a laser beam by using a method of forming a film having a higher absorption coefficient with respect to ultraviolet light than a crystallized semiconductor thin film.

[0004]

However, it is difficult to uniformly crystallize the silicon layer over the entire substrate by laser beam irradiation. When a silicon thin film formed by PECVD or low pressure chemical vapor deposition is crystallized with an excimer laser beam, even if the laser beam is irradiated with a laser beam whose energy intensity is made uniform by an optical system, the portion crystallized by the first laser beam In addition, there is a problem that the microcrystalline particles generated at the edge of the boundary portion where the laser beam is not irradiated remain even after the laser beam is shifted and irradiated.

On the other hand, an attempt has been made to provide a special optical system between a laser beam oscillation source and a silicon layer as a sample to make the energy distribution of the beam uniform.
The energy of the laser beam emitted from the laser oscillator is spatially Gaussian distributed. The energy distribution of this laser beam is spatially uniformed by an optical system such as a fly-eye lens as shown in FIG. However, the result of the improvement of the beam intensity distribution by this special optical system is that the beam is not uniform over the entire beam, and the non-uniformity still remains at the edge of the beam and the trapezoidal shape as shown in FIG. Energy distribution. FIG.
Assuming that the silicon thin film is melted by the irradiation energy from E ₂ to E ₁ to form a polycrystalline silicon thin film having a large grain size,
At an energy intensity from E ₃ to E ₂ that is insufficient to melt the silicon thin film, the silicon thin film irradiated with the laser beam becomes a microcrystalline silicon thin film. That is, from Xb to Xc
, And in the irradiation region between Xd and Xe, a microcrystalline silicon thin film is formed. Then the microcrystalline silicon layer, even when irradiated with an energy (E ₁ from E ₂₎ required to form a silicon layer having a large particles remain microcrystalline state. Therefore, in the conventional method of irradiating a pulsed laser beam so as to generate an overlapping portion, as shown in FIG. 12, a region of a microcrystalline silicon layer is generated between the polycrystalline silicon thin films CPS, A silicon thin film having an area larger than the beam cannot be uniformly converted into polycrystalline silicon. Thus, in pulsed laser irradiation,
It has been extremely difficult to obtain a crystalline silicon thin film having uniform properties over a large area larger than the beam.

JP-A-3-30433 attempts to make a silicon thin film uniform by laser irradiation by forming a thin film having a large absorption coefficient of ultraviolet light in a lattice shape.
In this method, the arrangement of the silicon layer of the thin film transistor forming the drive circuit is restricted, and the arrangement of the pixel transistors of the liquid crystal display is restricted in a lattice shape.
There is a drawback that a delta arrangement type active matrix substrate having better image display cannot be provided. Further, Japanese Unexamined Patent Publication No.
The method of No. 30433 has a disadvantage that a uniform silicon thin film for a drive circuit cannot be formed by laser irradiation. In JP-A-64-45162, a drive circuit formed by XeCl pulse laser irradiation is incorporated in an active matrix substrate. However, the electric circuit of a thin film transistor is formed by microcrystallization of a silicon thin film caused by an edge portion of a pulse laser beam. As for the variation in characteristics, no countermeasure was taken at all, so that there was a disadvantage that a high-performance peripheral circuit could not be built.

Further, the active matrix substrate has a problem of a short circuit between a signal line and a scanning line caused by dust or the like.

The present invention has been made in view of the above problems, and provides an active matrix substrate structure on an inexpensive glass substrate free from defects due to short-circuiting of a display region of an active matrix type liquid crystal display device, and a method of manufacturing the same.

Further, the present invention has been made in view of the above problems, and provides a structure of an active matrix substrate which prevents defects due to poor contact between source / drain electrodes of a thin film transistor and provides a good display, and a method of manufacturing the same.

[0010]

According to the present invention, there is provided an active matrix substrate, wherein a pixel region and a drive circuit are formed on the same substrate, wherein the thin film transistor in the pixel region is formed of a metal thin film; A gate electrode having an anodic oxide film formed on the surface thereof; and a silicon electrode disposed under the gate electrode with an insulating film interposed therebetween and doped with impurities while the anodic oxide film is formed on the gate electrode. A thin film and the drive circuit is divided into a plurality of regions, and is alternately arranged with the pixel region interposed therebetween. Wiring for anodic oxidation of the gate electrode is arranged in the drive circuit. It is characterized in that it is constructed so as to be drawn from a place where it is not.

In a method for manufacturing an active matrix substrate in which a pixel region and a drive circuit are formed on the same substrate, a step of forming a silicon thin film of a thin film transistor in the pixel region on the substrate; Forming a gate electrode made of a metal thin film via an insulating film, and anodizing the metal thin film of the gate electrode using a wiring drawn from a place where the drive circuit region is not formed, and forming the gate electrode on the gate electrode. Depositing and forming an anodic oxide film, and implanting impurities into the silicon thin film in a state where the anodic oxide film is formed on the gate electrode.
Forming a drain region.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of an active matrix substrate having a built-in peripheral driving circuit according to the present invention.

A driving circuit is formed by a thin film transistor on the same substrate as the display area around the display area of the image in which the pixel transistors are arranged. As shown in FIG. 1, the signal-side drive circuit of the drive circuit is DAR1, DAR
2, DAR3 and a plurality of areas, which are alternately arranged with the display area interposed therebetween. In addition, the scanning line side driving circuit,
It is divided into a plurality of SAR1, SAR2, and SAR3 as necessary, and is arranged alternately with the display area interposed.
The length in the long side direction of each region changes depending on the beam area of the pulse laser beam for crystallizing the silicon thin film of the thin film transistor constituting the driving circuit and the capability of the thin film transistor.

For an active silicon thin film of a thin film transistor, a polycrystalline silicon thin film having a thickness of 25 nm formed by a low pressure chemical vapor deposition method has a FWHM of 308 nm of 50 nm.
When recrystallizing by irradiation with an XeCl excimer laser of ns, the energy intensity of the laser beam is 250 to
About 500 mJ / cm ² is required. The energy of one pulse of the excimer laser beam is 500 immediately before the sample.
mJ, and the length of the short side of the drive circuit is 2 mm, the length of the long side of each of the divided drive circuits is 50 mm to 100 mm. In a rectangular display area having a long side of 300 mm and a short side of 225 mm, an active matrix type liquid crystal display having a signal side driving circuit on a long side and a scanning side driving circuit on a short side. In the case of a body, the signal side drive circuit on the long side can be divided into three, and the scan side drive circuit on the short side can be divided into three. The size of each region of the signal line side driving circuit divided into three is 2 mm × 100 mm, and the size of each region of the scanning line side driving circuit divided into three is 2 mm × 100 mm.
It may be 75 mm. As shown in FIG. 1, the number of regions into which the drive circuit is divided and the area of each region are not limited to the above example. The shape of each area of the divided drive circuit does not have to be rectangular. Further, each divided region of the signal line side driving circuit does not have to have the same area. The scanning line side driving circuit can be divided and arranged in the same manner as the above described method of dividing the signal line side driving circuit.

FIG. 2 shows a specific configuration example of the drive circuit divided as described above.

FIG. 2 shows an example of the configuration of a substrate of an active matrix type liquid crystal display body by a dot sequential driving method, in which a scanning line side driving circuit is divided into three and a signal line side driving circuit is divided into three. Is shown. In FIG. 2, DDC1, DD
C2 and DDC3 are signal line side drive circuits, respectively. Although the video signal lines are shown by three lines V1, V2 and V3, the number of video signal lines may increase or decrease as necessary. In this example, in order to transmit a video signal to the pixel transistors in a dot-sequential manner, each signal line is switched by an analog switch ASW by a signal line side driving circuit to form a pixel transistor in a display area PARIA of a liquid crystal display. The data of the video signal is transmitted through the data line DL.

Further, SDC1, SDC2 and SDC3
Indicates a scanning line side driving circuit. B1, B
2 and B3 are the divided scanning line side driving circuits SD
It is a buffer circuit connected to each of C1, SDC2 and SDC3. The signal from the buffer circuit is the scanning line S
It is transmitted to the pixel transistor through L. Signal line DL
A thin film transistor for driving a pixel is formed at the intersection of the scan line SL and the scan line SL.

DDC1, DDC2, DDC3, SDC
The shift registers formed in the regions 1, 1, SDC2, and SDC3 are periodically arranged in a plane. For example, the edge of the laser beam is located between the closest thin film transistors formed in the regions DDC1 and DDC2. There is a distance of 5 mm to 50 mm so that the influence of is not affected.

According to the above-described embodiment, an active matrix substrate having a built-in peripheral driving circuit having excellent electrical characteristics can be formed by crystallization of a silicon thin film using a pulse laser. FIG. 2 shows an example of a dot-sequential type driving circuit, but the present invention can be applied to a method of manufacturing an active matrix substrate with a built-in driving circuit by another method or a line-sequential driving method.

Next, an embodiment of a specific method for manufacturing an active matrix substrate having a driving circuit having the above-described structure will be described with reference to FIGS.

As shown in FIG. 3, a polycrystalline silicon thin film PLS is deposited on a GLS on a glass substrate having a low strain temperature. This polycrystalline silicon thin film was formed with a thickness of 25 nm at a temperature of 600 ° C. by a low pressure CVD method. The size of the crystal grains of the polycrystalline silicon thin film was about 5 nm. DAR1, DAR2, D in FIG. 1 which is a region where the drive circuit of the polycrystalline silicon thin film PLS is formed
The polycrystalline silicon thin film PLS was recrystallized by irradiating a laser beam LSR to the areas AR3, SAR1, SAR2, and SAR3, thereby forming a recrystallized silicon thin film CPS as shown in FIG. In this embodiment, the laser is applied to the portion where the drive circuit is formed without irradiating the active matrix area with the laser beam. The DCA shown in FIG.
Represents an active matrix area. As described above, when the silicon layer is irradiated with an energy beam having a trapezoidal spatial energy distribution, the silicon layer irradiated with the edge portion of the laser beam has a microcrystalline silicon thin film M
This produces CS.

Therefore, the laser beam is large enough to include the respective regions constituting the driving circuit, and furthermore, the laser beam is formed so that the edge of the laser beam exists between the divided driving circuit regions. Adjust the position and irradiate the laser. If the thickness of the polycrystalline silicon thin film PLS is 25 to 50 nm, the region where microcrystalline silicon is generated due to the edge of the laser beam is 100 μm.
Since the distance is about 500 μm, the interval between adjacent divided drive circuits is preferably 500 μm or more. This interval may extend to several tens of mm as long as there is no problem in the design of the drive circuit. The laser beam is irradiated so that the edge of the laser beam exists between the region DCA of the driving circuit and the pixel region PARIA. By this method, the glass substrate GL
The polycrystalline silicon thin film PLS on S is partially crystallized.

The conditions for irradiating the polycrystalline silicon thin film with a laser are, for example, 300 mJ / cm in the case of a XeCl excimer laser in which the energy intensity distribution is uniformly adjusted.
A laser beam of intensity ² is applied in vacuum.

If the length of DAR1, DAR2 and DAR3 in the scanning line direction is 10 cm and the length in the signal line direction is 2 mm, the energy of the pulse immediately before the sample is 60
It may be 0 mJ. Laser oscillator output is 1 per pulse
If J, shape the laser beam to the above size with a special optical system, adjust the transmittance of the optical system to the sample with an attenuator, etc., and set it to 0.6. The recrystallization of the silicon thin film in the region where If the areas of the SAR1, SAR2, and SAR3 regions are different from those of the DAR1, DAR2, and DAR3, laser irradiation may be performed by adjusting the optical system so as to have a required shape and transmittance. When the maximum output energy per pulse of the laser oscillator cannot be freely changed, the area to be divided into the drive circuits requiring laser irradiation and the number of drive circuit divisions must be adjusted according to the display area of the liquid crystal display. I just need.

When the active matrix substrate of the present invention is applied to display an NTSC television, the number of scanning lines is 525, so that the scanning line driving circuit only needs to have an operating frequency of 31.5 kHz. . Such a drive circuit can also be constituted by a thin film transistor using a polycrystalline silicon thin film formed by a low pressure CVD method without irradiating a laser beam. Therefore, irradiation of the laser beam to the silicon thin film forming the thin film transistor of the scan line driver circuit may be performed as needed.

Next, as shown in FIG. 5, the polycrystalline silicon thin film CPS is patterned into an island shape by lithography. Furthermore, E using SiH ₄ and O ₂ as a source gas
A gate insulating film GIS made of a silicon oxide thin film having a thickness of 150 nm is formed by CR-CVD so as to cover the island-shaped silicon thin film CPS. Further, the island-shaped silicon thin film CP covered with the gate insulating film GIS
A gate electrode GEL is formed so as to partially overlap S. The material of the gate electrode GEL is a Ta metal thin film having a thickness of 350 nm formed by a sputtering method. The gate electrode GEL is formed by patterning by lithography. The gate electrodes GEL of the signal line side driving circuit and the scanning line side driving circuit are formed in an island shape. On the other hand, as shown in FIG. 6, the gate electrode in the display region is Ta formed in the same step as the scanning line, and further connected to the terminal AXC on the glass substrate via the wiring AXL formed in Ta in the same step. ing.

As shown in the circuit diagram of FIG. 7, since the scanning line side driving circuit has a high density CMOS formed by thin film transistors, the scanning line side driving circuit is connected to the anodic oxidation wiring AXL. It is difficult to form a scanning line SL across it. Therefore, the wiring AXL for anodizing is preferably formed on the side opposite to the region where the scanning line side driving circuit is formed or in the region where the scanning line side driving circuit is not formed.

Next, as shown in FIG.
The surface of L is oxidized by an anodic oxidation method to form a tantalum oxide thin film. The substrate on which the gate electrode GEL was formed was immersed in a citric acid electrolyte solution having a weight concentration of 0.01%, and a terminal AXL was formed.
Through the gate electrode GEL and the gate line GL
A DC voltage of 20 V is applied for 2 hours. By this method, a tantalum oxide thin film AXI having a thickness of 200 nm is formed on the surface of the gate electrode GEL.

When the process up to FIG. 10 described later is completed, the wiring AXL is cut off the substrate along the line CTL shown in FIG. 6 and removed.

Next, as shown in FIG. 9, impurities are ion-implanted into the island-shaped polycrystalline silicon thin film in a self-aligned manner with respect to the gate electrode to form a source region and a drain region. In order to form the driving circuit with a C-MOS circuit, impurities are appropriately implanted using a material having a blocking ability against ion implantation as a mask. For example, using a resist as an appropriate mask, only a 3 × 10 ¹⁵ cm ⁻² p-type impurity such as boron ions is used for the configuration of a p-type thin film transistor, and 3 × 10 ¹⁵ cm ⁻² is used for an n-type thin film transistor. For example, phosphorus ions are implanted only into an n-type impurity of × 10 ¹⁵ cm ⁻² . The driver circuit may be formed using an n-type thin film transistor or a p-type thin film transistor. In FIG. 9, PSD is a region into which a p-type impurity is implanted, and NSD is a region into which an n-type impurity is implanted. Next, a laser beam is irradiated to activate impurities in the source region and the drain region. The laser irradiation may be performed by using an XeCl excimer laser having a wavelength of 308 nm and an energy of 350 mJ / cm ² on the substrate surface in the atmosphere at a FMWH of 50 ns.
Next, in order to reduce dangling bonds existing in the active region of the thin film transistor, ECR-
Hydrogen particles are injected by the CVD method.

Next, as shown in FIG. 10, an interlayer insulating film MIS is formed by depositing a silicon oxide film to form a source region, a drain region, and a through hole reaching the gate electrode.

Next, an ITO thin film is formed by sputtering, and a pixel electrode DEL is formed by lithography. Further, an Al thin film containing silicon atoms and copper atoms is formed by a sputtering method, and the signal line SL and a wiring MS required for a driving circuit are formed by patterning.
Form D. Further, a passivation film PAL is formed of a silicon nitride film to protect the thin film transistor from an external environment.

In the above embodiment, the polysilicon PLS
Although the crystallization by laser irradiation is performed before patterning the polycrystalline silicon, the laser irradiation may be performed after the polycrystalline silicon thin film is patterned into an island shape. Subsequent manufacturing steps of the active matrix substrate are the same as those shown in FIG.

In the above embodiment, an example of a self-alignment type is shown. However, the present invention can be applied to the manufacture of an active matrix substrate using a non-self-alignment type thin film transistor.

In the above embodiment, a method of manufacturing an active matrix substrate in which a drive circuit is constituted by a silicon thin film obtained by crystallizing a polycrystalline silicon thin film with a laser beam has been described. The invention is applicable. In the above example, the thin film transistor for driving the pixel electrode in the display region is n-type, but may be p-type depending on the purpose. Further, the pixel electrode is driven by both n-type and p-type thin film transistors. May be.

[0037]

As described above, according to the present invention, the gate electrode of the thin film transistor in the pixel region is formed of a metal thin film, and the anodized metal oxide film surrounds the gate electrode. Since the offset region is formed between the drain region and the channel region immediately below the gate electrode, the leakage current between the source and drain when the gate voltage is off is extremely small.
When this active matrix substrate is applied to a liquid crystal display, it is possible to obtain a display having a high aperture ratio, a large contrast ratio, and little flicker and color unevenness.

Another advantage is that the anodized wiring of the gate electrode can be configured without any problem due to the existence of the drive circuit.

Further, since two insulating thin films of a tantalum oxide thin film formed by anodic oxidation and a silicon oxide thin film exist between the scanning line and the signal line, a short circuit between the signal line and the scanning line is extremely small. There are advantages. As a result, it is possible to manufacture an active matrix substrate having good display characteristics without defects.

According to the above-mentioned method, a drive circuit built-in type having a display region with high definition and uniform display characteristics and capable of driving a thin film transistor in this display region with excellent electric characteristics and uniform driving capability. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view of an active matrix substrate with a built-in drive circuit of the present invention.

FIG. 2 is a circuit diagram of a drive circuit built-in type active matrix substrate of the present invention.

FIG. 3 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 4 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 5 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 6 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 7 is a schematic diagram of a drive circuit.

FIG. 8 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 9 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 10 is a process chart of a method for manufacturing an active matrix substrate of the present invention.

FIG. 11 is an energy distribution diagram of a laser beam.

FIG. 12 is a diagram of a conventional laser beam irradiation method.

[Explanation of symbols]

DAR1, DAR2, DAR3 ... signal line side drive circuit area SAR1, SAR2, SAR3 ... scan line side drive circuit area DDC1, DDC2, DDC3 ... signal line side drive circuit SDC1, SDC2, SDC3 ... scan line side drive circuit B1, B2, B3: Buffer circuit PARIA: Display area of active matrix substrate DL: Signal line SL: Scanning line ASW: Analog switch V1, V2, V3: Video signal GLS: Glass substrate PLS: Polycrystalline silicon thin film LSR: Laser irradiation CPS: Recrystallization Polycrystalline silicon MCS… Microcrystalline silicon DCA… Drive circuit area GIS… Gate insulating film GEL… Gate electrode AXL… Anodic oxidation wiring AXC… Anodic oxidation terminal CTL… Glass substrate cutting line CNT… Connection terminal PIXEL… Pixel and pixel Transis AXI ... tantalum oxide thin film PSD ... p-type source and
Drain region NSD ... n-type source
Drain region MIS: interlayer insulating film DEL: pixel electrode MSD: metal wiring PAL: passivation film

Claims (2)

[Claims] 1. An active matrix substrate in which a pixel region and a drive circuit are formed on the same substrate, wherein the thin film transistor in the pixel region is formed of a metal thin film, and an anodic oxide film is formed on the surface thereof. A gate electrode, disposed under the gate electrode via an insulating film,
A silicon thin film into which an impurity is implanted in a state where an anodic oxide film is formed on the gate electrode, wherein the drive circuit is divided into a plurality of regions and arranged alternately with the pixel region interposed therebetween. An active matrix substrate, wherein a wiring for anodic oxidation of the gate electrode is drawn out from a place where the driving circuit is not arranged. 2. A method of manufacturing an active matrix substrate in which a pixel region and a drive circuit are formed on the same substrate, comprising: forming a silicon thin film of a thin film transistor in the pixel region on the substrate; Forming a gate electrode made of a metal thin film via an insulating film, and anodizing the metal thin film of the gate electrode using a wiring drawn from a place where the drive circuit region is not formed, and forming the gate electrode on the gate electrode. Depositing an anodic oxide film, and forming source / drain regions by injecting impurities into the silicon thin film with the anodic oxide film deposited on the gate electrode. Of manufacturing an active matrix substrate.