JP2005064337A - Array substrate, liquid crystal display device, and method for manufacturing array substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which a gate electrode can be thinned and reduced in resistance. <P>SOLUTION: The liquid crystal display device includes a gate insulating film 15 formed on a glass substrate 3 containing a plurality of island-like polysilicon films 71. The liquid crystal display device further includes a first metal layer 72 deposited on the gate insulating film 15 and patterned to provide a gate electrode 16 on the gate insulating film 15 opposed to a polysilicon layer 11 of parts becoming thin film transistors 4, 5. The liquid crystal display device also includes a second metal layer 73 deposited on the gate insulating film 15 including the gate electrode 16. A wiring part 17 is laminated on the gate electrode 16 of the thin film transistors 4, 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an array substrate including a switching element, a liquid crystal display device, and a method for manufacturing the array substrate.

  In recent years, liquid crystal display devices are not only simple driver circuits such as an X driver circuit and a Y driver circuit, but also external circuits such as DAC (Digital-to-Analog Converter) circuits that have been mounted with TAB (Tape Automated Bonding). A system liquid crystal in which a circuit is built on one main surface of a glass substrate as a translucent substrate, a memory function such as SRAM or DRAM, a photosensor, and the like are commercialized.

  For this reason, this type of liquid crystal display device requires a thin film transistor as a high-performance switching element, and also requires low power consumption and high aperture ratio. In order to improve the performance and the aperture ratio of this liquid crystal display device, it is necessary to make the gate wiring and signal wiring as the first metal layer thinner, reducing the power consumption (H common inversion drive) and the DA converter. In order to incorporate such a circuit, it is necessary to lower the flat band voltage (Vfb) of the MOS capacitor.

  If these gate wirings and signal wirings are thinned, the wiring resistance of these gate wirings or signal wirings is increased, resulting in an increase in power consumption and a reduction in circuit power supply margin. Therefore, a low resistance wiring material is required. is there. Here, the thinning means that a conventional wiring width of 3 μm or more and 5 μm or less is reduced to 0.5 μm or more and 2 μm or less.

  In the case where a polycrystalline semiconductor layer is used for the MOS capacitor, an impurity such as phosphorus (P) or boron (B) is implanted into the polycrystalline semiconductor layer in order to lower the flat band voltage of the MOS capacitor. A method of forming a p-type or a p-type is employed.

  As a specific method for manufacturing an array substrate for a liquid crystal display device, after forming an amorphous semiconductor layer on a glass substrate, the amorphous semiconductor layer is laser beam annealed to form a polycrystalline semiconductor layer and then patterned. . Thereafter, a gate insulating film is formed on the glass substrate including the polycrystalline semiconductor layer.

At this time, if the pixel auxiliary capacitance is not increased to a certain extent, the pixel auxiliary capacitance cannot be retained. Therefore, the thickness of the gate insulating film is preferably as thin as possible. Therefore, the gate insulating film is formed on the polycrystalline semiconductor layer, and the gate electrode layer is formed on the gate insulating film. Therefore, before forming the gate electrode, the resist is patterned and doped with an n-type dopant (PH ₃ ) and implanted to form an n ⁺ region of an n-ch thin film transistor (TFT), a pixel capacitance, a circuit Each is formed with a capacitor portion which is a capacitor region.

Further, after forming a gate electrode on the gate insulating film including each of the n ⁺ region, the pixel capacitor, and the capacitor portion of the circuit portion, the gate electrode for p-ch thin film transistor (TFT) is patterned. Then, a p-type dopant (B ₂ H ₅ ) is implanted as an impurity to form ap ⁺ region of the p-ch thin film transistor.

Next, after patterning the gate electrode on the n-ch thin film transistor side, each of the n-ch thin film transistor and the p-ch thin film transistor is annealed, and then the n ⁺ region of the n-ch thin film transistor and the p ^{+ of the} p-ch thin film transistor. Activate each of the regions. Next, an interlayer insulating film is formed on the gate insulating film including the gate electrodes of these n-ch and p-ch thin film transistors.

Further, in the interlayer insulating film, after forming a contact hole communicating with the p ⁺ region of the n-ch TFT of n ⁺ region and p-ch TFT, a conductive layer is formed on the interlayer insulating film including the contact holes . Thereafter, by patterning the conductive layer, constituting the formation of the electrically connected the source and drain electrodes were in the p ⁺ region of the n-ch TFT of n ⁺ region and p-ch TFT is known ( For example, see Patent Document 1.)

  In this liquid crystal display device, an alloy containing molybdenum (Mo) such as molybdenum-tungsten (MoW) or molybdenum-tantalum (MoTa) is used as a gate wiring. In addition, the gate electrode of the liquid crystal display device is also integrally formed with a single gate wiring line, pixel capacitor wiring, and circuit capacitor wiring.

Here, the molybdenum alloy has been used for the gate electrode as a material that has heat resistance and can be sufficiently removed from thermal annealing which is thermal activation of about 500 ° C. to 600 ° C. However, since the sheet resistance of a 300 nm-thickness molybdenum alloy is as high as 0.5 Ω / cm ² , the resistance increases when the wire is thinned, and thus the gate electrode cannot be miniaturized.

  In order to reduce the resistance of the gate electrode, it is considered that an aluminum alloy having a lower resistance than that of a molybdenum alloy, such as aluminum (Al) or aluminum-copper (AlCu), which has versatility, may be used. However, in this aluminum alloy, the temperature at the time of thermal activation, which is a subsequent process, is high, so that there is a possibility that the wiring is likely to be short-circuited or that the reliability deteriorates due to resistance degradation or disconnection due to electromigration. Therefore, it is difficult from the point of process to reduce the resistance of the gate electrode.

Further, when aluminum-neodymium (AlNd) is used, there is no problem in reliability or the like even if annealing is performed at a temperature of 500 ° C. or less, but there is a problem in processing accuracy and productivity. That is, when this aluminum-neodymium is thinned to 2 μm or less, variation in the width of the gate electrode of the thin film transistor becomes large because it is difficult to control variation in line width by wet etching. For this reason, the transistor characteristics of the thin film transistor cause variations, and the thin film transistor is processed by dry etching capable of controlling this variation.
JP 2002-359252 A (page 7-10, FIGS. 8-9)

However, when the gate electrode of the liquid crystal display device is aluminum-neodymium and this gate electrode is dry-etched, a large amount of etching products such as aluminum chloride (AlCl ₂ ) adhere to the inner wall surface of the chamber of the dry-etching device. Therefore, it is not easy to improve productivity. For this reason, it is difficult to use aluminum-neodymium as a gate electrode from the viewpoint of processing in a product that requires thinning of the gate electrode. Therefore, there is a problem that it is not easy to make the gate electrode thin and reduce the resistance.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an array substrate, a liquid crystal display device, and a method for manufacturing the array substrate that can reduce the thickness and resistance of the first conductive layer.

  The present invention provides a translucent substrate, a plurality of polycrystalline semiconductor layers provided on one main surface of the translucent substrate, and a main surface of the translucent substrate including the plurality of polycrystalline semiconductor layers. A gate insulating film provided; a first conductive layer provided via the gate insulating film so as to face any one of the plurality of polycrystalline semiconductor layers; and one main surface of the first conductive layer A wiring portion electrically connected to the first conductive layer, and any one of the plurality of polycrystalline semiconductor layers, and the polycrystalline semiconductor layer And a second conductive layer provided with a capacitor wiring portion for forming a capacitor between them.

  Then, a gate insulating film is provided on one main surface of the light transmitting substrate including a plurality of polycrystalline semiconductor layers provided on one main surface of the light transmitting substrate. Further, a first conductive layer is provided opposite to any one of the plurality of polycrystalline semiconductor layers with the gate insulating film interposed therebetween. Thereafter, a wiring portion of the second conductive layer is provided on one main surface of the first conductive layer, the wiring portion is electrically connected to the first conductive layer, and a plurality of layers are provided via the gate insulating film. A capacitor wiring portion of a second conductive layer that forms a capacitor through the polycrystalline semiconductor layer is provided opposite to any other of the polycrystalline semiconductor layers. As a result, the first conductive layer can be thinned and the resistance can be reduced.

  According to the present invention, the gate wiring can be thinned and the resistance can be reduced while minimizing the number of processes, so that the liquid crystal display device can have high definition, a high aperture ratio, and low power consumption. It is possible to form a liquid crystal display device having a thin film transistor incorporating the mounted drive circuit.

  The configuration of the first embodiment of the liquid crystal display device of the present invention will be described below with reference to FIGS.

  1 to 10, reference numeral 1 denotes a liquid crystal display device 1 as a flat display device. This liquid crystal display device 1 is a thin film transistor type liquid crystal display device and includes an array substrate 2 having a substantially rectangular flat plate shape. The array substrate 2 has a glass substrate 3 which is a light-transmitting substrate as a substantially transparent rectangular flat plate-like insulating substrate. On the surface which is one main surface of the glass substrate 3, an undercoat layer (not shown) composed of a silicon nitride film, a silicon oxide film or the like is laminated and formed.

  On the undercoat layer, a plurality of n-channel (n-ch) thin film transistors (TFTs) 4 which are n-type switching elements for liquid crystal display are formed in a matrix. Furthermore, a plurality of p-channel (p-ch) type thin film transistors 5 and a plurality of pixel auxiliary capacitors 6 which are p-type switching elements for liquid crystal display are formed in a matrix on the undercoat layer. Has been.

Here, each of these thin film transistors 4 and 5 is arranged as one pixel component. Further, each of these thin film transistors 4 and 5 includes a polysilicon layer 11 as a polycrystalline semiconductor layer formed on the undercoat layer. The polysilicon layer 11 is made of polysilicon formed by laser annealing of amorphous silicon as an amorphous semiconductor. The polysilicon layer 11 has a channel region 12 as an active layer provided at the center of the polysilicon layer 11. On both sides of the channel region 12, a source region 13 and a drain region 14 that are n ⁺ regions or P ⁺ regions are provided to face each other.

  On the undercoat layer including each of the channel region 12, the source region 13, and the drain region 14, a gate insulating film 15 that is an insulating silicon oxide film is laminated and formed. Further, on the gate insulating film 15 facing the channel region 12, a gate electrode 16 composed of a first metal layer 72 composed of an alloy containing molybdenum (Mo), that is, molybdenum-tungsten (MoW). Are stacked to form a film. Here, the gate electrodes 16 are opposed to the channel regions 12 of the thin film transistors 4 and 5 through the gate insulating film 15, and have a width dimension substantially equal to the width dimension of the channel region 12.

  Further, a wiring portion 17 as a gate wiring composed of the second metal layer 73 is laminated on the gate electrodes 16. Each of the wiring portions 17 is an inter-gate electrode wiring that is electrically connected to each gate electrode 16 and has a width dimension equal to the width dimension of each gate electrode 16. Here, these wiring portions 17 are made of a material having a resistance value smaller than that of the gate electrode 16.

  On the other hand, on the undercoat layer continuous with the thin film transistors 4 and 5, a pixel auxiliary capacitor 6 made of polysilicon is laminated and formed. The pixel auxiliary capacitor 6 is provided adjacent to the p-channel type thin film transistor 5, and is provided on the opposite side of the n-channel type thin film transistor 4 through the thin film transistor 5.

  Further, the pixel auxiliary capacitor 6 is arranged in the same plane as the thin film transistors 4 and 5 on the glass substrate 3. The pixel auxiliary capacitor 6 includes a capacitor portion 22 made of polysilicon. The capacitor 22 is made of polysilicon formed by laser annealing of amorphous silicon as an amorphous semiconductor. The capacitor 22 is formed in the same process as the polysilicon layer 11 of the thin film transistors 4 and 5 and is laminated on the undercoat layer.

  On the undercoat layer including the capacitor portion 22, a gate insulating film 15 is laminated and formed. On the gate insulating film 15 facing the capacitor portion 22, a capacitor wiring portion 23 composed of a second metal layer 73 that is the same layer as the wiring portion 17 of each thin film transistor 4, 5 is laminated and formed. ing. The capacitor wiring portion 23 is provided on one side in the width direction of the capacitor portion 22 on the p-channel type thin film transistor 5 side. In other words, the capacitor wiring portion 23 is provided at a position closer to the p-channel type thin film transistor 5 side than the central portion in the width direction of the capacitor portion 22.

  Further, each of these capacitance wiring portions 23 forms a capacitance between these capacitance wiring portions 23 via the gate insulating film 15 between the capacitance wiring portions 23 and the capacitance portions 22. Here, these capacitor wiring portions 23 are formed by the same process and the same material as the wiring portions 17 of the thin film transistors 4 and 5. Therefore, these capacitance wiring parts 23 have a resistance value smaller than the resistance value of the wiring part 17 of each thin film transistor 4, 5.

  Further, an interlayer insulating film 31 that is an insulating silicon oxide film is laminated on the gate insulating film 15 including the capacitor wiring portion 23 and the wiring portions 17 of the thin film transistors 4 and 5. Yes. The interlayer insulating film 31 and the gate insulating film 15 have a plurality of contact holes 32, 33, 34, 35, and 36 as conductive portions penetrating the interlayer insulating film 31 and the gate insulating film 15, respectively. Is provided.

  Here, each of the contact holes 32 and 33 is provided on the source region 13 and the drain region 14 of the thin film transistor 4 on both sides of the gate electrode 16 of the n-channel thin film transistor 4. The contact hole 32 is opened to communicate with the source region 13 of the n-channel type thin film transistor 4, and the contact hole 33 is opened to communicate with the drain region 14 of the n-channel type thin film transistor 4.

  Each of the contact holes 34 and 35 is provided on the source region 13 and the drain region 14 of the thin film transistor 5 on both sides of the gate electrode 16 of the p-channel type thin film transistor 5. The contact hole 34 is opened to communicate with the source region 13 of the p-channel type thin film transistor 5, and the contact hole 35 is opened to communicate with the drain region 14 of the p-channel type thin film transistor 5. The contact hole 36 is opened to communicate with the capacitor portion 22 of the pixel auxiliary capacitor 6.

  In the contact hole 32 communicating with the source region 13 of the n-channel type thin film transistor 4, a source electrode 41 which is a signal line as a conductive layer is laminated and provided. The source electrode 41 is electrically connected to the source region 13 of the n-channel type thin film transistor 4 through the contact hole 32 to be conductive. In addition, in the contact hole 33 communicating with the drain region 14 of the n-channel type thin film transistor 4, a drain electrode 42 which is a signal line as a conductive layer is provided by being laminated. The drain electrode 42 is electrically connected to the drain region 14 of the n-channel type thin film transistor 4 through the contact hole 33 to be conductive.

  Further, in the contact hole 34 communicating with the source region 13 of the p-channel type thin film transistor 5, a source electrode 43 which is a signal line as a conductive layer is provided by being laminated. The source electrode 43 is electrically connected to the source region 13 of the p-channel type thin film transistor 5 through the contact hole 34 to be conductive. In addition, a drain electrode 44 that is a signal line as a conductive layer is provided in the contact hole 35 that communicates with the drain region 14 of the p-channel type thin film transistor 5. The drain electrode 44 is electrically connected to the drain region 14 of the p-channel type thin film transistor 5 through the contact hole 33 to be conductive. Further, a lead-out electrode 45 as a gate lead-out wiring, which is a conductive layer, is laminated and provided in the contact hole 36 communicating with the capacitor portion 22 of the pixel auxiliary capacitor 6.

  On the other hand, on the interlayer insulating film 31 including the source electrodes 41 and 43 and the drain electrodes 42 and 44 of the thin film transistors 4 and 5 and the extraction electrode 45 of the pixel auxiliary capacitor 6, the thin film transistors 4 and 5 and the pixel auxiliary capacitor 6 are provided. A protective film 51 is laminated and formed so as to cover each of the above. The protective film 51 is provided with a contact hole 52 opened as a conducting portion that penetrates the protective film 51. The contact hose 52 is open to communicate with the extraction electrode 45 of the pixel auxiliary capacitor 6.

  A pixel electrode 53 is laminated and formed on the protective film 51 including the contact hole 52. The pixel electrode 53 is electrically connected to the extraction electrode 45 through the contact hole 52 and is conductive. That is, the pixel electrode 53 is electrically connected to the capacitor portion 22 of the pixel auxiliary capacitor 6 through the extraction electrode 45. The pixel electrode 53 is controlled by one of the thin film transistors 4 and 5. Further, an alignment film 54 is laminated on the protective film 51 including the pixel electrode 53.

  On the other hand, an opposing substrate 61 having a rectangular flat plate shape is disposed facing the array substrate 2. The counter substrate 61 includes a glass substrate 62 that is a translucent substrate as a substantially transparent rectangular flat plate-like insulating substrate. A counter electrode 63 is provided on one main surface of the glass substrate 62 facing the array substrate 2. An alignment film 64 is laminated on the counter electrode 63. A liquid crystal 65 is inserted between the alignment film 64 of the counter substrate 61 and the alignment film 54 of the array substrate 2 and sealed.

  Next, a method for manufacturing the array substrate according to the first embodiment will be described.

  First, an amorphous silicon film as an amorphous silicon which is an amorphous semiconductor having a film thickness of 50 nm is formed on the glass substrate 3 by a CVD (Chemical Vapor Deposition) method. Thereafter, the amorphous silicon film on the glass substrate 3 is irradiated with an excimer laser beam and crystallized by laser annealing to form a polysilicon film 71 as a polycrystalline semiconductor layer. At this time, it is desirable that the thickness of the polysilicon film 71 be in the range of 40 nm to 80 nm.

Next, diborane (B ₂ H ₅ ) is doped into the polysilicon film 71 and implanted into an island shape by a photolithography process. At this time, the boron concentration implanted into the polysilicon film 71 is set to 1E16 or more and 17 or less / cm ³ . Note that by injecting boron into the polysilicon film 71, the threshold voltages of the thin film transistors 4 and 5 can be controlled.

  Further, a gate insulating film 15 having a thickness of 100 nm is formed on the glass substrate 3 including each island-like polysilicon film 71 by PE (Plasma Enhanced) -CVD.

Next, as shown in FIG. 2, a 300-nm-thick molybdenum-tungsten alloy (MoW) is formed on the gate insulating film 15 to be the gate electrodes 16 of the thin film transistors 4 and 5, and the first conductive layer is formed. A first metal layer 72 is formed. At this time, the sheet resistance of the first metal layer 72 was 0.5 Ω / cm ² . The first metal layer 72 may be molybdenum-tantalum (MoTa) in addition to molybdenum-tungsten (MoW).

  Thereafter, the first metal layer 72 is patterned by a photolithography process on a resist (not shown) except for the portions to be the source region 13 and the drain region 14 on both sides of the gate electrode 16 of the p-channel type thin film transistor 5. Plasma etching is performed on both sides of the polysilicon layer 11 of the thin film transistor 5 with a mixed gas containing fluorine and oxygen. At this time, the wiring width of the p-channel type gate electrode 16 is set to 1.0 μm or more and 2.0 μm or less.

  Then, after this plasma etching, the resist on the gate insulating film 15 is stripped with an organic alkaline solution.

In this state, as shown in FIG. 3, the first metal layer 72 remaining after the plasma etching is used as a mask to form a p-type dopant in a portion to become the source region 13 and the drain region 14 of the p-channel thin film transistor 5. Some diborane (B ₂ H ₅ ) is doped and implanted. Here, the doping of diborane is to lower the resistance value of the polysilicon layer 11 and make ohmic contact with the metal. The diborane is implanted into the polysilicon layer 11 with an acceleration voltage of 50 keV and a dose of 1E15 cm ⁻¹ .

  Next, a resist (not shown) is patterned on each of the portion of the first metal layer 72 which becomes the gate electrode 16 of the n-channel type thin film transistor 4 and the portion of the first metal layer 72 which becomes the p-channel type thin film transistor 5 in the photolithography process. Plasma etching is performed on a portion to be the source region 13 and the drain region 14 and a portion to be the pixel auxiliary capacitor 6 of the channel type thin film transistor 4 with a mixed gas containing fluorine and oxygen. At this time, the wiring width of the gate electrode 16 of the n-channel thin film transistor 4 is also set to 1.0 μm or more and 2.0 μm or less.

  Then, after this plasma etching, the resist on the gate insulating film 15 is stripped with an organic alkaline solution.

Thereafter, as shown in FIG. 4, resist 70 is applied to each of a portion of the first metal layer 72 that becomes the gate electrode 16 of the n-channel type thin film transistor 4 and a portion that becomes the p-channel type thin film transistor 5 in the photolithography process. Is patterned, and the source region 13 and the drain region 14 of the n-channel type thin film transistor 4 and the polysilicon layer 11 serving as the capacitor portion 22 of the pixel auxiliary capacitor 6 are doped with phosphine (PH ₃ ) as an n-type dopant. inject. The phosphine is implanted into the polysilicon layer 11 with an acceleration voltage of 70 keV and a dose of 1E15 cm ⁻¹ .

Here, when the n-channel type thin film transistor 4 has an LDD (Lightly Doped Drain) structure, the first metal layer 72 in the portion that becomes the gate electrode 16 of the n-channel type thin film transistor 4 is etched again. After reducing the width dimension, the n ⁻ region can also be formed by lightly doping the n-type dopant.

  At this time, since the first metal layer 72 to be the gate electrode 16 of the n-channel type thin film transistor 4 can be used as the same mask, both the high doping and the low doping can be performed. The transistor characteristics (Ion characteristics) of the channel type thin film transistor 4 can be improved.

Thereafter, the source region 13 and the drain region 14 of each of the n-channel thin film transistor 4 and the p-channel thin film transistor 5 and the capacitor portion 22 of the pixel auxiliary capacitor 6 are thermally annealed at a temperature of 400 ° C. or more and 500 ° C. or less. By processing, the source region 13, the drain region 14, and the capacitor portion 22 are activated. At this time, the sheet resistance of the source region 13 and the drain region 14 which are p ⁺ regions of the p-channel type thin film transistor 5 is 3 kΩ / cm ^2, and the source region 13 and the drain which are n ⁺ regions of the n-channel type thin film transistor 4 are used. The sheet resistance of each region 14 was ² kΩ / cm ² .

  Next, as shown in FIG. 5, on the gate insulating film 15 including the gate electrode 16 of each thin film transistor 4, 5, the wiring portion 17 connecting the gate electrodes 16 of the thin film transistors 4, 5 and the capacitor wiring of the pixel auxiliary capacitor 6 A second metal layer 73, which is a second conductive layer to be the portion 23, is formed with a low resistance material film, and the second metal layer 73 is formed directly on the gate insulating film 15.

At this time, as the second metal layer 73, a laminated film having a three-layer structure in which the thicknesses of titanium (Ti) / aluminum-copper (AlCu) / titanium (Ti) are 50 nm / 300 nm / 75 nm from the lower layer. It was. Further, the sheet resistance of the second metal layer 73 was 0.12 Ω / cm ² . As the second metal layer 73, a five-layer structure of titanium (Ti) / titanium nitride (TiN) / aluminum-copper (AlCu) / titanium (Ti) / titanium nitride (TiN), or aluminum ( A structure changed to Al), aluminum-neodymium (AlNd) / molybdenum (Mo), or the like may be used.

  Thereafter, as shown in FIG. 6, the second metal layer 73 is patterned so as to become a wiring portion 17 and a capacitance wiring portion 23 that connect the gate electrodes 16 of the first metal layer 72 by a photolithography process. At this time, if the second metal layer 73 contains aluminum (Al) or aluminum-copper (AlCu), dry etching with a metal chlorine-based gas is performed. When the second metal layer 73 contains aluminum-neodymium (AlNd), wet etching is performed.

  Next, as shown in FIG. 7, a 600 nm-thickness silicon oxide film is formed on the gate insulating film 15 including the wiring portion 17 and the capacitor wiring portion 23 by PE-CVD to form an interlayer insulating film 31. Form.

  Subsequently, as shown in FIG. 8, in the photolithography process, contact holes 32, 33, which communicate with the source region 13 and the drain region 14 of each thin film transistor 4, 5 and the capacitor portion 22 of the pixel auxiliary capacitor 6, respectively. Each of 34, 35, and 36 is formed.

  Thereafter, on the interlayer insulating film 31 including each of the contact holes 32, 33, 34, 35, and 36, as a conductive layer 74 to be a signal line wiring, for example, molybdenum (Mo) having a film thickness of 50 nm and a film thickness of 500 nm. A laminated film of aluminum (Al) is formed by sputtering.

  Subsequently, as shown in FIG. 9, the conductive layer 74 is etched by a photolithography process to form source electrodes 41 and 43, drain electrodes 42 and 44, and an extraction electrode 45. At this time, when the conductive layer 74 is formed of a metal such as aluminum (Al) or aluminum-copper (AlCu), it is patterned by etching with chlorine gas.

  Further, as shown in FIG. 10, silicon nitride having a thickness of 500 nm is formed on the entire surface of the interlayer insulating film 31 including the source electrodes 41 and 43, the drain electrodes 42 and 44, and the extraction electrode 45 by PE-CVD. A protective film 51 is formed by forming a film.

Subsequently, in the photolithography process, the protective film 51 is etched, and a contact hole 52 that is electrically connected to the extraction electrode 45 of the pixel auxiliary capacitor 6 is formed in the protective film 51. At this time, this etching was plasma etching using tetrafluoromethane (CF ₄ ) gas and oxygen gas.

  Thereafter, a transparent conductive film is formed on the protective film 51 including the contact hole 52 by sputtering to form a pixel electrode 53, and then a photolithography process and an etching process are performed to form the pixel electrode 53 into a pixel shape. Pattern. At this time, oxalic acid (HOOC-COOH) is used for etching the pixel electrode 53.

Here, as in the prior art, when the gate electrodes of the n-channel thin film transistor and the p-channel thin film transistor are formed in two layers to connect the wiring portion which is a low resistance metal, the step of forming the second metal layer In addition to the film forming process, the photolithographic process, and the etching process, a photolithographic process, an n ⁺ doping process, and a resist stripping process are added as a process for forming the capacitor portion, which increases the number of processes and deteriorates productivity.

In particular, when an attempt is made to form a pixel auxiliary capacitor with a capacitor portion made of polysilicon, a gate insulating film, and a gate electrode, phosphine is used as an n-type dopant in the polysilicon layer that becomes the capacitor portion before the gate electrode is formed. It was necessary to dope (PH ₃ ) before implantation.

Therefore, as in the first embodiment, the pixel auxiliary capacitor 6 is composed of the capacitor portion 22 made of polysilicon, the gate insulating film 15, and the second metal layer 73 which is a low resistance wiring. As the configured capacitor wiring portion 23, n ⁺ doping necessary for the formation of the capacitor portion 22 of the pixel auxiliary capacitor 6 is performed in the same process simultaneously with the formation of the source region 13 and the drain region 14 of the n-channel type thin film transistor 4. .

As a result, it is possible to eliminate the capacity forming process, that is, the photolithography process, the n ⁺ doping process, and the resist stripping process, which are conventionally required. Therefore, since the gate electrode 16 can be made thin and low in resistance while minimizing the number of processes, the liquid crystal display device 1 can have high definition, high aperture ratio and low power consumption, and at the same time, a memory circuit, It is possible to form the liquid crystal display device 1 incorporating the drive circuit that has been TAB-mounted.

  Each of the n-channel thin film transistor 4 and the p-channel thin film transistor 5 has a two-layer structure of a gate electrode 16 and a wiring portion 17. As a result, a heat-resistant material is used for the gate electrode 16 that must be formed before thermal activation, and a low-resistance material is used for a portion where the wiring length of the capacitor wiring portion 23 of the pixel auxiliary capacitor 6 is long. A second metal layer 73 is formed after thermal activation. For this reason, the wiring resistance of the gate electrode 16 of each of these thin film transistors 4 and 5 can be miniaturized and lowered.

  Therefore, the gate electrodes 16 of the thin film transistors 4 and 5 are formed in two layers and the structure of the pixel auxiliary capacitor 6 is changed, so that the increase in the number of steps of the array substrate 2 is minimized and the thin film transistors 4 and 5 are formed. The resistance of the gate electrode 16 can be reduced.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  The liquid crystal display device 1 shown in FIGS. 11 to 19 is basically the same as the liquid crystal display device 1 shown in FIGS. 1 to 10 except that the first interlayer is formed on the gate insulating film 15 including the gate electrode 16. After the formation of the insulating film 81, contact holes 82 and 83 are formed in the first interlayer insulating film 81 as conductive portions communicating with the gate electrodes 16, and then the first holes including the contact holes 82 and 83 are formed. A second metal layer 73 is formed on the interlayer insulating film 81.

  In other words, the liquid crystal display device 1 is formed by dividing the interlayer insulating film 31 into two layers of the first interlayer insulating film 81 and the second interlayer insulating film 84, and the first interlayer insulating film 81. And a second interlayer insulating film 84 is formed with a second metal layer 73. In other words, in the liquid crystal display device 1, after the first metal layer 72 is formed, the second metal layer 73 is formed via the first interlayer insulating film 81.

  The first interlayer insulating film 81 is laminated and formed on the gate insulating film 15 including each gate electrode 16. The first interlayer insulating film 81 on each gate electrode 16 is provided with contact holes 82 and 83 penetrating the first interlayer insulating film 81 in a direction perpendicular to the surface direction. Yes. These contact holes 82 and 83 have a width dimension equal to the width dimension of each gate electrode 16. In the contact holes 82 and 83, the wiring portion 17 is formed. Each of these wiring portions 17 is electrically connected to each gate electrode 16.

  Further, a second interlayer insulating film 84 is laminated and formed on the first interlayer insulating film 81 including the wiring portion 17 and the capacitor wiring portion 23. Then, the second interlayer insulating film 84, the first interlayer insulating film 81, and the gate insulating film 15 are respectively connected to the second interlayer insulating film 84, the first interlayer insulating film 81, and the gate insulating film 15. A plurality of contact holes 32, 33, 34, 35, 36 penetrating in the up-down direction, which is a vertical direction perpendicular to the surface direction, are opened.

  Next, a method for manufacturing the array substrate according to the second embodiment will be described.

  The process until the gate electrode 16 is formed on the gate insulating film 15 is the same as the process shown in FIGS. 2 to 4 of the first embodiment.

  Then, as shown in FIG. 12, a first interlayer insulating film 81 is formed by forming a 50 nm-thick silicon oxide film on the gate insulating film 15 including each gate electrode 16 by PE-CVD. . At this time, the film thickness of the first interlayer insulating film 81 is determined so that the capacitance in the pixel auxiliary capacitor 6 is larger than the value of the product specification.

  Next, as shown in FIG. 13, contact holes 82 and 83 for bonding to the gate electrodes 16 are formed in the first interlayer insulating film 81 by a photolithography process.

  Thereafter, as shown in FIG. 14, on the first interlayer insulating film 81 including the contact holes 82 and 83, the wiring portion 17 connecting the gate electrodes 16 and the capacitor wiring portion 23 of the pixel auxiliary capacitor 6 are formed. After forming the second metal layer 73 with a low resistance material film, as shown in FIG. 15, an etching process is performed after a photolithography process. Here, the photolithography process and the etching process are the same as those in the first embodiment.

  Further, as shown in FIG. 16, a second interlayer insulating film 84 is formed by forming a 600 nm-thickness silicon oxide on the first interlayer insulating film 81 including each wiring portion 17 and the capacitor wiring portion 23. To do.

  Thereafter, as shown in FIG. 17, a plurality of contact holes 32, 33, 34, 35 penetrating through the second interlayer insulating film 84, the first interlayer insulating film 81, and the gate insulating film 15 in the photolithography process. , 36.

  Further, as shown in FIG. 18, after forming a conductive layer 74 to be a signal line wiring on the second interlayer insulating film 84 including each of these contact holes 32, 33, 34, 35, 36, The conductive layer 74 is etched by a photolithography process to form source electrodes 41 and 43, drain electrodes 42 and 44, and an extraction electrode 45.

  Next, as shown in FIG. 19, a silicon nitride film is formed on the entire surface of the interlayer insulating film 31 including the source electrodes 41 and 43, the drain electrodes 42 and 44, and the extraction electrode 45 by PE-CVD. A protective film 51 is formed.

  Thereafter, in the photolithography process, the protective film 51 is etched to form the contact hole 52, and then the pixel electrode 53 is formed on the protective film 51 including the contact hole 52.

  As described above, according to the second embodiment, since the interlayer insulating film 31 has the two-layer structure of the first interlayer insulating film 81 and the second interlayer insulating film 84, the first embodiment described above. Compared to the above, the number of steps for forming the contact holes 82 and 83 is increased. However, since the gate electrode 16 of the first metal layer 72 is protected by the first interlayer insulating film 81 when the second metal layer 73 is etched, it is not necessary to use high selectivity etching. Etching of the second metal layer 73 is facilitated.

  Further, when the gate electrode 16 of the first metal layer 72 is etched, the gate insulating film 15 is over-etched by about 30 nm. Therefore, when the high-performance thin film transistors 4 and 5 are formed by the gate electrode 16 and the gate insulating film 15, if the gate insulating film 15 is thin, the film of the gate insulating film 15 in the portion serving as the pixel auxiliary capacitor 6. The thickness becomes thin.

  Further, when the polysilicon film 71 is formed by laser annealing, there is a possibility that protrusions are formed on the surface of the polysilicon film 71. Accordingly, when the thickness of the gate insulating film 15 in the portion serving as the capacitor portion 22 of the pixel auxiliary capacitor 6 is thin, the capacitor formed from the polysilicon film 71 and the capacitor formed from the second metal layer 73. There is a risk that the capacitance portion 22 and the capacitance wiring portion 23 may leak without being sufficiently insulated from the wiring portion 23. As a result, the liquid crystal display device 1 may have a point defect, which may reduce the yield.

  Therefore, in the second embodiment, productivity can be improved particularly in the case of the liquid crystal display device 1 in which the gate insulating film 15 is thin (for example, 90 nm or less).

  In each of the above embodiments, the capacitance between the capacitance portion 22 and the capacitance wiring portion 23 of the pixel auxiliary capacitance 6 can be a circuit portion capacitance for driving the liquid crystal display device 1.

  The first metal layer 72 can also be made of an alloy containing molybdenum (Mo), that is, either molybdenum-tungsten (MoW) or molybdenum-tantalum (MoTa).

  Further, as the second metal layer 73, an alloy containing aluminum (Al), that is, at least one of aluminum (Al) and aluminum-copper (AlCu), molybdenum (Mo), titanium (Ti) and A laminated film with at least one of titanium nitride (TiN) can also be used.

1 is an explanatory cross-sectional view showing a first embodiment of a liquid crystal display device of the present invention. It is explanatory sectional drawing which shows the state which formed the 1st conductive layer on the translucent board | substrate of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which doped the part used as the source region and drain region of the p channel type thin-film transistor of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which doped the part used as the source region of the n channel type thin-film transistor of a liquid crystal display device same as the above, and the part used as the capacity | capacitance part of an auxiliary capacity | capacitance. It is explanatory sectional drawing which shows the state which formed the 2nd metal layer on the gate insulating film containing the gate electrode of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which patterned the 2nd conductive layer of the liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which provided the interlayer insulation film on the gate insulation film containing the wiring part and capacitive wiring part of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the contact hole in the interlayer insulation film of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which patterned the conductive layer formed on the interlayer insulation film containing the contact hole of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the protective film on the interlayer insulation film containing a source electrode, a drain electrode, and an extraction electrode of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the liquid crystal display device of the 2nd Embodiment of this invention. It is explanatory sectional drawing which shows the state which formed the 1st interlayer insulation film on the gate insulation film containing the gate electrode of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the contact hole in the 1st interlayer insulation film of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the 2nd metal layer on the 1st interlayer insulation film containing the contact hole of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which patterned the 2nd metal layer of the liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which provided the 2nd interlayer insulation film on the gate insulating film containing the wiring part and capacitive wiring part of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the contact hole in the 2nd interlayer insulation film of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which patterned the conductive layer formed on the 2nd interlayer insulation film containing the contact hole of a liquid crystal display device same as the above. It is explanatory sectional drawing which shows the state which formed the protective film on the 2nd interlayer insulation film containing the source electrode of the same liquid crystal display device, a drain electrode, and an extraction electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Array substrate 3 Glass substrate as translucent substrate 4 N channel type thin film transistor as n type switching element 5 P channel type thin film transistor as p type switching element 6 Pixel auxiliary capacity as auxiliary capacity
13 Source area
14 Drain region
15 Gate insulation film
16 Gate electrode
17 Wiring section
22 Capacity section
23 Capacitance wiring section
61 Counter substrate
65 LCD
71 Polysilicon film as polycrystalline semiconductor layer
72 First metal layer as first conductive layer
73 Second metal layer as second conductive layer
81 First interlayer insulating film as an interlayer insulating film
82,83 Contact hole as conducting part

Claims (9)

A translucent substrate;
A plurality of polycrystalline semiconductor layers provided on one main surface of the translucent substrate;
A gate insulating film provided on one main surface of the translucent substrate including the plurality of polycrystalline semiconductor layers;
A first conductive layer provided via the gate insulating film so as to face any one of the plurality of polycrystalline semiconductor layers;
The gate insulating film is provided on one main surface of the first conductive layer so as to oppose any one of the wiring portion electrically connected to the first conductive layer and the plurality of polycrystalline semiconductor layers. An array substrate comprising: a second conductive layer provided with a capacitance wiring portion provided between the polycrystalline semiconductor layer and a capacitance wiring portion. The array substrate according to claim 1, wherein the second conductive layer has a resistance value smaller than that of the first conductive layer. The first conductive layer is an alloy containing molybdenum (Mo),
The array substrate according to claim 1, wherein the second conductive layer is an alloy containing aluminum (Al). The first conductive layer is made of either molybdenum-tungsten (MoW) or molybdenum-tantalum (MoTa),
The second conductive layer is composed of a laminated film of at least one of aluminum (Al) and aluminum-copper (AlCu) and at least one of molybdenum (Mo), titanium (Ti), and titanium nitride (TiN). The array substrate according to any one of claims 1 to 3, wherein the array substrate is formed. The array substrate according to any one of claims 1 to 4, wherein the polycrystalline semiconductor layer facing the capacitor wiring portion is doped with either a p-type dopant or an n-type dopant. An array substrate according to any one of claims 1 to 5;
A counter substrate provided opposite to the array substrate;
A liquid crystal display device comprising: the counter substrate; and a liquid crystal interposed between the array substrates. A plurality of polycrystalline semiconductor layers are provided on one main surface of the translucent substrate,
A gate insulating film is provided on one main surface of the translucent substrate including the plurality of polycrystalline semiconductor layers,
A first conductive layer is provided on one main surface of the gate insulating film,
Patterning the first conductive layer to form a pair of gate electrodes facing one of the plurality of polycrystalline semiconductor layers;
Using either one of the pair of gate electrodes as a mask, the polycrystalline semiconductor layer facing the gate electrode is doped to form a source region and a drain region of the p-type switching element,
Using any one of the pair of gate electrodes as a mask, each of the polycrystalline semiconductor layer facing the gate electrode and the polycrystalline semiconductor layer not provided facing the gate electrode are doped, forming a source region and a drain region of the n-type switching element, and a capacitance portion of the auxiliary capacitance;
Forming a second conductive layer on one main surface of the gate insulating film including the pair of gate electrodes;
The second conductive layer is patterned so that the pair of wiring portions facing the pair of gate electrodes and the auxiliary capacitor facing the polycrystalline semiconductor layer where the pair of gate electrodes are not provided facing each other. A method of manufacturing an array substrate, comprising forming each of the auxiliary capacitor section and the auxiliary capacitor section. The method for manufacturing an array substrate according to claim 7, wherein the second conductive layer is directly formed on one main surface of the gate insulating film including a plurality of gate electrodes. Forming an interlayer insulating film on one main surface of the gate insulating film including a plurality of gate electrodes;
Forming a plurality of conductive portions communicating with the plurality of gate electrodes in the interlayer insulating film;
8. A second conductive layer is formed on the interlayer insulating film including the plurality of conductive portions, and the second conductive layer is electrically connected to the plurality of gate electrodes. Manufacturing method of array substrate.

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