JP2020181985A - Display device - Google Patents

Abstract

To provide an LTPS TFT and an oxide semiconductor TFT on the same substrate.SOLUTION: A display device includes a substrate including a display area where a pixel is formed. The pixel includes a first TFT including an oxide semiconductor 109. An oxide film 110 that is an insulator is formed on the oxide semiconductor 109. A gate electrode 111 is formed on the oxide film 110. To a drain of the first TFT, a first electrode 115 is connected through a first through-hole formed in the oxide film 110. To a source of the first TFT, a second electrode 116 is connected through a second through-hole formed in the oxide film 110.SELECTED DRAWING: Figure 8

Description

The present invention relates to a display device, and relates to a display device using a hybrid structure using both a TFT using Poly-Si and a TFT using an oxide semiconductor.

In a liquid crystal display device, a TFT substrate in which pixels having pixel electrodes and thin film transistors (TFTs) are formed in a matrix and an opposing substrate are arranged facing the TFT substrate, and the liquid crystal is sandwiched between the TFT substrate and the opposing substrate. It has a structure of. Then, the image is formed by controlling the light transmittance of the liquid crystal molecules for each pixel. On the other hand, the organic EL display device forms a color image by arranging a self-luminous organic EL layer and a TFT on each pixel. Since the organic EL display device does not require a backlight, it is advantageous for thinning.

LTPS (Low Temperature Poly-Si) has high mobility and is therefore suitable as a TFT for a drive circuit. On the other hand, oxide semiconductors have a high OFF resistance, and when this is used for TFTs, the OFF current can be reduced.

Patent Document 1 and Patent Document 2 are examples of TFTs using oxide semiconductors. Patent Document 1 describes a configuration in which a metal oxide is formed on an oxide semiconductor constituting a channel and used as a gate insulating film. Patent Document 2 describes that a metal oxide or a semiconductor layer is used as a sacrificial layer for channel etching in a bottom type TFT using an oxide semiconductor.

Japanese Unexamined Patent Publication No. 2013-175718 Japanese Unexamined Patent Publication No. 2011-54812

The TFT used for pixel switching needs to have a small leakage current. A TFT made of an oxide semiconductor can reduce the leakage current. Hereinafter, oxide semiconductors that are optically transparent and non-crystalline are referred to as TAOS (Transient Amorphous Oxide Semiconductor). TAOS includes IGZO (Indium Galium Zinc Oxide), ITZO (Indium Tin Zinc Oxide), ZnON (Zinc Oxide Nitride), IGO (Indium Galium Oxide), and the like. However, since TAOS has low carrier mobility, it may be difficult to form a drive circuit built in the display device with a TFT using TAOS. Hereinafter, TAOS will also be used in the meaning of TFT using TAOS.

On the other hand, since the TFT formed by LTPS has a high mobility, the drive circuit can be formed by the TFT using LTPS. Hereinafter, LTPS will also be used in the meaning of TFT using LTPS. However, when LTPS is used as a switching TFT in a pixel, since LTPS has a large leakage current, two LTPS are usually used in series.

Therefore, it is rational to use TAOS as the pixel switching element in the display region and LTPS for the TFT of the peripheral drive circuit. However, since LTPS and TAOS have different material properties, there is a problem in forming them on the same substrate. That is, when forming a source electrode and a drain electrode on LTPS, it is necessary to wash LTPS with hydrofluoric acid (HF) in order to remove surface oxides, but TAOS is dissolved by hydrofluoric acid (HF). The same process cannot be used.

An object of the present invention is to make it possible to form a TFT by LTPS and a TFT by TAOS on the same substrate by solving such a problem.

The present invention overcomes the above problems, and specific means are as follows.

(1) A display device including a substrate having a display region on which pixels are formed, wherein the pixels include a first TFT using an oxide semiconductor, and oxidation which is an insulator on the oxide semiconductor. A film is formed, a gate electrode is formed on the oxide film, and a first electrode is connected to the drain of the first TFT via a first through hole formed in the oxide film. A display device characterized in that a second electrode is connected to the source of the first TFT via a second through hole formed in the oxide film.

(2) The wall of the through hole formed in the oxide film has a first taper θ1 on the side opposite to the oxide semiconductor and a second taper θ2 on the oxide semiconductor side, and θ1. The display device according to (1), wherein the display device is> θ2.

(3) The display device according to (1), wherein the oxide film is AlOx.

It is a top view of the liquid crystal display device. FIG. 1 is a sectional view taken along the line AA of FIG. It is sectional drawing which shows the 1st manufacturing process of this invention. It is sectional drawing which shows the 2nd manufacturing process of this invention. It is sectional drawing which shows the 3rd manufacturing process of this invention. It is sectional drawing which shows the 4th manufacturing process of this invention. It is sectional drawing which shows the 5th manufacturing process of this invention. It is sectional drawing which shows the feature of this invention. It is a plan view of the sacrificial layer. It is sectional drawing which shows the shape of the through hole of a sacrificial layer. It is sectional drawing which shows the detailed shape of the through hole of a sacrificial layer. It is sectional drawing which shows the process of two-step etching. It is sectional drawing which shows the problem in the case of etching only with hydrofluoric acid. It is a table which shows the specification of the sample of AlOx. It is a figure which shows the bond energy of an Al atom. It is a figure which shows the bond energy of an oxygen atom. It is sectional drawing which shows the structure of the TFT of Example 2. FIG. It is a top view of the sacrificial layer in Example 2. FIG. It is sectional drawing which shows the structure of the TFT of Example 3. FIG. It is sectional drawing of the liquid crystal display device. It is a top view of the organic EL display device. FIG. 19 is a cross-sectional view taken along the line BB of FIG. It is sectional drawing of the organic EL display device.

Hereinafter, the contents of the present invention will be described in detail with reference to Examples.

FIG. 1 is a plan view of a liquid crystal display device to which the present invention is applied. FIG. 2 is a cross-sectional view taken along the line AA of FIG. In FIGS. 1 and 2, the TFT substrate 100 and the opposing substrate 200 are formed so as to face each other, and a liquid crystal is sandwiched between the TFT substrate 100 and the opposing substrate 200. A lower polarizing plate 130 is attached below the TFT substrate 100, and an upper polarizing plate 230 is attached above the opposing substrate 200. The combination of the TFT substrate 100, the opposing substrate 200, the lower polarizing plate 130, and the upper polarizing plate 230 is called a liquid crystal display panel 500.

The TFT substrate 100 is formed larger than the facing substrate 200, and the portion where the TFT substrate 100 is one is the terminal portion 150, and is a flexible wiring board for supplying signals and power to the liquid crystal display device from the outside. 160 is connected. Since the liquid crystal display panel 500 does not emit light by itself, a backlight 400 is arranged on the back surface.

As shown in FIG. 1, the liquid crystal display device can be divided into a display area 10 and a peripheral area 20. A large number of pixels are formed in a matrix in the display area, and each pixel has a switching TFT. A drive circuit for driving a scanning line, a video signal line, or the like is formed in the peripheral region.

Since the TFT used for the pixel needs to have a small leakage current, TAOS needs to be used, and the TFT used for the peripheral drive circuit needs to have a high mobility, so it is rational to use LTPS. In the LTPS step, when the LTPS is connected to the drain electrode or the source electrode, hydrofluoric acid (HF) is formed to form a through hole in the insulating film covering the LTPS and to remove the surface oxide of the LTPS in the through hole. ) Need to be cleaned.

However, when the same process is applied to a TFT using TAOS, TAOS dissolves in hydrofluoric acid (HF) and the TFT cannot be formed. Therefore, in order to form a TFT by LTPS and a TFT by TAOS on the same substrate, this problem must be solved. FIG. 8 shows a configuration of the present invention that solves this problem, and FIGS. 3 to 7 are processes for realizing the configuration of FIG.

In FIG. 3, a first base film 101 and a second base film 102 are formed on a TFT substrate 100 made of glass, and a—Si (amorphous Si) 1031 is formed on the first base film 101 and the second base film 102. The first base film 101 is formed of, for example, silicon nitride SiNx, and the second base film 102 is formed of silicon oxide SiOx. The first base film 101 and the second base film 102 prevent impurities contained in the glass from contaminating the semiconductor layer. a-Si1031 is formed on the second base film 102 to a thickness of about 50 nm. The first base film 101, the second base film 102, and a-Si1031 are continuously formed by CVD.

Then, a-Si1031 is irradiated with an excimer laser to convert a-Si into Poly-Si103. FIG. 4 is a cross-sectional view showing a state in which the semiconductor layer 103 converted to Poly-Si 103 is patterned. Hereinafter, this Poly-Si will be referred to as LTPS (Low Temperature Poly-Si) 103.

The gate insulating film 104 is formed by covering the LTPS 103. The gate insulating film 104 is SiOx formed by CVD using TEOS (tetraethoxysilane) as a raw material. The gate electrode 105 is formed on the gate insulating film 104. The gate electrode 105 is formed of an Al alloy, Mo, W, a laminated film thereof, or the like.

In FIGS. 5 to 8, TFTs using TAOS are shown on the right side of each figure, and a light-shielding film 106 is formed at the same time as the gate electrode 105 in the region where the TAOS TFT is formed. The TAOS is planned to be formed in the display area, but since the display area is exposed to the light from the backlight, it is necessary to prevent the photocurrent from flowing through the TAOS. When the LTPS TFT is used in the display area, it is desirable to form a light-shielding film under the first base film 101. The metal constituting the gate electrode 105 and the light-shielding film 106 is formed by sputtering, and then patterned by photolithography.

After that, as shown in FIG. 6, the first interlayer insulating film 107 is formed of SiNx so as to cover the gate electrode 105 and the light-shielding film 106, and the second interlayer insulating film 108 is formed of SiOx on the first interlayer insulating film 107. The first interlayer insulating film 107 and the second interlayer insulating film 108 are for insulating the TAOS layer 109 from the gate electrode 105 or the light-shielding film 106, but also act as a base film for the TAOS layer 109.

The TAOS layer 109 is formed on the second interlayer insulating film 108, and the sacrificial layer 110 is formed on the TAOS layer 109 with, for example, aluminum oxide AlOx. Then, as shown in FIG. 7, the TAOS layer 109 and the sacrificial layer 110 are patterned. TAOS109 is formed, for example, by IGZO, ITZO, IGO, etc., or an alloy thereof. The thickness of TAOS109 is, for example, 10 nm to 100 nm.

The sacrificial layer 110 is preferably an oxide, particularly AlOx, and the thickness is preferably 5 nm to 50 nm. If the film thickness of the sacrificial layer 110 is too small, it will not be a continuous film, and hydrofluoric acid may permeate into TAOS 109. On the other hand, if the film thickness of the sacrificial layer 110 is thick, it takes time to form the sacrificial layer 110. In addition, the TFT is easily depleted.

On the other hand, the etching rate of AlOx used as the sacrificial layer 110 varies greatly depending on the film quality. Therefore, in order to determine an appropriate film thickness of the sacrificial layer 110, it is necessary to determine it in relation to the etching rate. Since the cleaning of LTPS103 with hydrofluoric acid takes 30 seconds or less, Table 1 shows the film thickness of the sacrificial layer required for 30 seconds as a guide.

Table 1 evaluates the etching rate of 0.5% diluted hydrofluoric acid used for cleaning the through hole 113 of LTPS 103. As shown in Table 1, the film thickness of the sacrificial layer 110 is about 5 nm to 50 nm, which is appropriate in consideration of the film formation rate of the sacrificial layer, resistance to the etching solution, and the like. The sacrificial layer 110 may be formed by dividing it into several layers. By using a multilayer film, film defects due to foreign substances can be suppressed.

Patterning of the sacrificial layer 110 and TAOS 109 is performed by Cl-based dry etching or wet etching using oxalic acid, a developing solution, or the like. Since the sacrificial layer 110 and TAOS 109 are patterned at the same time, it is better to avoid an etching solution in which only TAOS 109 has an extremely fast etching rate.

Then, as shown in FIG. 8, a gate electrode 111 for the TAOS TFT is formed on the sacrificial layer 110. The gate electrode 111 is formed by the same manufacturing method as the gate electrode 105. That is, the metal to be the gate electrode 111 is formed into a film by sputtering, and then patterned. In the configuration of FIG. 8, the sacrificial layer 110 made of AlOx constitutes the gate insulating film.

An inorganic passivation film 112 is formed by covering the TAOS 109, the sacrificial layer 110, and the gate electrode 111. After that, as shown in FIG. 8, a through hole 113 for forming a drain electrode and a source electrode in the TFT by LTPS 103 is provided with an inorganic passivation film 112, a second interlayer insulating film 108, a first interlayer insulating film 107, and a gate insulating film. It is formed through 104. Further, through holes 114 for forming the drain electrode and the source electrode in the TFT formed by TAOS 109 are formed in the inorganic passivation film 112 and the sacrificial layer. The formation of the through holes 113 and the through holes 114 is performed simultaneously by dry etching.

Dry etching is performed using CF-based (CF4) or CHF-based (CHF3) gas. The etching rate of dry etching is, for example, 70 nm / min for SiOx and 6 nm / min for AlOx, and AlOx is extremely smaller than SiOx. Therefore, while the through hole 113 on the LTPS side performs dry etching of four layers, the through hole 114 on the TAOS side only etches two layers, but AlOx remains on the through hole 114 side and is sacrificed. The role as the layer 110 can be maintained.

In FIG. 8, the through hole 113 on the LTPS 103 side is hydrofluoric acid-cleaned, and at the same time, the through hole 114 on the TAOS 109 side is also hydrofluoric acid-cleaned. In the present invention, since AlOx is present in the through hole 114 on the TAOS109 side, hydrofluoric acid does not come into contact with the TAOS109, so that the TFT on the TAOS109 side is prevented from being destroyed.

The etching rate with 5% hydrofluoric acid is AlOx: 4 to 14 nm / min, IGZO: 6000 nm or more / min, ITZO: 480 nm / min, Poly-IGO: 0 nm / min. Poly-IGO is hardly etched, which is the value in the case of bulk crystals. In the thin film state, there is a risk that hydrofluoric acid permeates from the grain boundaries and destroys TAOS109.

FIG. 9 is a plan view of the sacrificial layer 110. Through holes 114 are formed on both sides of the sacrificial layer 110, and drain electrodes 115 and source electrodes 116 are formed on the through holes 114, respectively. The through holes 114 for forming the drain electrode 115 and the source electrode 116 are formed inside by Δx and Δy from the end of the sacrificial layer 110. This is to prevent hydrofluoric acid from entering from around the sacrificial layer 110 and dissolving the TAOS layer 109 when etching with hydrofluoric acid.

The cross-sectional shape of the region shown by A in FIG. 8, that is, the through hole 112 formed in the sacrificial layer 110 is important. FIG. 10 is a cross-sectional view of the through hole 114 of the sacrificial layer 110 corresponding to the region A of FIG. As shown in FIG. 10, the taper of the through hole 114 has two stages. The taper angle of the through hole 114 of the sacrificial layer 110 is larger on the surface side of the sacrificial layer 110 than on the TAOS 109 side. FIG. 11 is an enlarged view of a portion B of FIG. 10, and is a cross-sectional view showing a definition of a taper angle. In FIG. 11, the taper angle θ1 on the surface side of the sacrificial layer 110 of the through hole is larger than the taper angle θ2 on the TAOS 109 side.

This is the result of etching the through hole 112 in two steps. This situation is shown in FIG. In FIG. 12, the figure on the left side shows the state after hydrofluoric acid cleaning. This corresponds to the first stage etching. Then, as shown in the figure on the right side of FIG. 12, the second stage etching is performed with an aqueous solution of TMAH (tetramethylammonium).

TMAH is generally used as a developing solution. The etching rate of AlOx by TMAH is as small as 7 nm / min. Further, even if the overetching time is slightly longer, the decrease in TAOS109 can be suppressed to a very small value. Two-step etching can be enabled by appropriately setting the thickness of the sacrificial layer 110 of AlOx. The etching solution in the second stage may be not only TMAH but also an etching solution having an etching rate slower than that of hydrofluoric acid with respect to AlOx.

On the other hand, when the sacrificial layer 110 is etched only with hydrofluoric acid, the difference in etching rate between the sacrificial layer 110 and the TAOS 109 is large, so that the eaves of the sacrificial layer 110 are formed in the through holes as shown in FIG. Such a shape causes poor contact at the drain or source, and reduces the reliability of the TAOS TFT.

FIG. 14 is a table showing the film quality and characteristics of AlOx used as the sacrificial layer 110. Samples A, B, and C have different AlOx composition ratios, that is, O / Al. Then, for these three types of AlOx, the evaluation of the chemical bond state of Al and O, the refractive index, and the film stress is shown in a table. Samples A and B have slightly higher water content in AlOx than sample C.

In FIG. 14, the characteristic point of AlOx is that the film stress of AlOx changes from the compressive stress to the tensile stress with only a slight change in the composition ratio. On the other hand, the higher the density of the film, the higher the refractive index. Therefore, it can be said that sample C is a dense film.

Moisture affects the density of the film. 15 and 16 are the measurement results by XPS (X-ray photoelectron Spectroscopy) for each sample. In FIGS. 15 and 16, the horizontal axis represents the binding energy and the vertical axis represents the number of electrons emitted at each energy.

FIG. 15 shows the binding energy of an Al atom with oxygen measured for an electron in the 2p orbital of the Al atom. In this regard, as shown in FIG. 15, the three samples show almost the same characteristics.

FIG. 16 is a measurement of electrons in the 1s orbit at O. The O-Al bond and the O-H bond are almost the same for the three samples, but the strength of the binding energy derived from water shown by the O-adsorbed water is smaller in the sample C than in the samples A and B. This indicates that there is little water in AlOx.

From the experimental results, it was found that the sample C, which has a low water content and a high refractive index, exhibits stable characteristics as the sacrificial layer 110. Correspondingly, the refractive index of AlOx used as the sacrificial layer 110 is preferably 1.58 to 1.65. As shown in FIG. 14, the film stress of AlOx changes greatly depending on the slight difference in the composition ratio of Al and O or the amount of water. This property can also be used to adjust the membrane stress.

Table 2 is an example of the combination of TAOS 109 and the sacrificial layer 110. TAOS109 can be formed not only of a single layer but also of a plurality of layers. Further, although AlOx is used for the sacrificial layer 110, film defects due to foreign matter can be reduced by forming this AlOx also with a plurality of layers.

In Table 2, orientation is synonymous with crystallinity, but since both TAOS109 and the sacrificial layer 110 are thin films, crystals do not grow in the film thickness direction, but crystals grow only in the plane direction. To describe this, we use the term orientation.

As described above, according to the present invention, even when the through hole 113 on the LTPS103 side is hydrofluoric acid-cleaned, the TFT is not destroyed in the through hole 114 on the TAOS109 side. The TFT by TAOS109 can be formed on the same substrate. Therefore, it is possible to realize a display device having high image quality and high reliability.

FIG. 17 is a cross-sectional view showing a second embodiment of the present invention. The difference between FIG. 17 and FIG. 8 of the first embodiment is that the sacrificial layer 110 also covers the side surface of the TAOS 109. As a result, even if hydrofluoric acid may invade toward the side surface of TAOS 109, the side surface of TAOS 109 is protected by the sacrificial layer 110, so that the influence on TAOS 109 can be avoided.

As a result, as shown in FIG. 18, the diameter of the through hole 114 in which the drain electrode 115 and the source electrode 116 are formed can be made larger than the diameter yy of the sacrificial layer. That is, the channel width of the TFT can be increased and the ON current can be increased.

By adopting the configuration shown in FIG. 17 for the TAOS 109 and the sacrificial layer 110, the number of steps can be increased, but the degree of freedom of the process can be increased. Alternatively, the process can be increased. Further, since the channel width can be increased, the size of the TFT can be reduced by that amount, and the pixel density can be increased accordingly.

FIG. 19 is a cross-sectional view showing a third embodiment of the present invention. The difference between FIG. 19 and FIG. 8 of Example 1 is that a gate insulating film 117 made of SiOx is added to the sacrificial layer 110 as the gate insulating film of the TFT made of TAOS 109. By adding the gate insulating film 117 made of SiOx, the degree of freedom in the film thickness of the sacrificial layer 110 formed of AlOx can be increased. That is, the film thickness and film quality of the sacrificial layer 110 can be determined by focusing only on the threshold of the TAOS TFT and the etching characteristics as the sacrificial layer, not on the insulating characteristics.

FIG. 20 is a cross-sectional view showing a case where the TFT by TAOS described in Examples 1 to 3 is applied to the display region. In FIG. 20, the TFT array layer 120 is formed on the TFT substrate 100. The TFT array layer 120 has a layer structure of the TAOS TFT shown in FIG. 8 or FIG. 19, and an organic passivation film is formed on the layer structure of the TAOS TFT.

FIG. 20 shows a case of an IPS type liquid crystal display device, in which a common electrode 121 is formed in a plane on the TFT array layer 120. A capacitive insulating film 122 is formed so as to cover the common electrode 121, and a pixel electrode 123 is formed on the capacitive insulating film 122. The pixel electrode 123 has a comb-like shape or a striped shape. An alignment film 124 for initially aligning the liquid crystal molecules 301 is formed so as to cover the pixel electrode 123.

When a video signal is applied between the pixel electrode 123 and the common electrode 121, electric lines of force are generated as shown by the arrows, and the liquid crystal molecules 301 are rotated to control the transmittance of the liquid crystal layer 300 to control the image. To form.

In FIG. 20, the opposing substrate 200 is arranged with the liquid crystal layer 300 interposed therebetween. A color filter 201 and a black matrix 202 are formed on the facing substrate 200. An overcoat film 203 is formed over the color filter 201 and the black matrix 202, and an alignment film 204 for initially orienting the liquid crystal molecules 301 is formed on the overcoat film 203.

When a video signal is written to the pixel electrode 123 in the liquid crystal display device, the voltage is held for one frame by the holding capacitance formed by the pixel electrode 123, the common electrode 121, and the capacitive insulating film 122. At this time, if the leakage current of the TFT is large, the voltage of the pixel electrode 123 changes, flicker or the like occurs, and a good image cannot be formed. By using the TAOS TFT of the present invention, it is possible to realize a liquid crystal display device having a small leakage current and a good image.

The combination of the LTPS TFT and the TAOS TFT described in Examples 1 to 3 can also be applied to an organic EL display device. FIG. 21 is a plan view of the organic EL display device 2. In FIG. 21, a display area 10 and a peripheral circuit area 20 are formed. An organic EL drive TFT and a switching TFT are formed in the display region 10. As the switching TFT, a TAOS TFT having a small leakage current is suitable. Peripheral drive circuits are formed by TFTs, but LTPS TFTs are mainly used.

In FIG. 21, an antireflection polarizing plate 220 is attached so as to cover the display area 10. Since a reflective electrode is formed on the organic EL display device, a polarizing plate 220 is used to suppress reflection of external light. A terminal portion 150 is formed in a portion other than the display area 20, and a flexible wiring board 160 for supplying a power supply or a signal to the organic EL display device is connected to the terminal portion 150.

FIG. 22 is a cross-sectional view taken along the line BB of FIG. In FIG. 22, a display element layer 210 including an organic EL layer is formed on the TFT substrate 100. The display element layer 210 is formed corresponding to the display region 10 of FIG. Since the organic EL material is decomposed by water, the protective layer 215 is formed of SiNx or the like so as to cover the display element layer 210 in order to prevent the invasion of water from the outside. A polarizing plate 220 is attached on the protective layer 215. Further, a terminal portion 150 is formed in a portion other than the display element layer 215, and the flexible wiring board 160 is connected to the terminal portion 150.

FIG. 23 is a cross-sectional view of a display area of the organic EL display device. In FIG. 23, the TFT array layer 120 is formed on the TFT substrate 100. The TFT array layer 120 includes the layer structure of the TAOS TFT shown in FIG. 8 or FIG. 19, and an organic passivation film is formed on the layer structure of the TAOS TFT.

In FIG. 23, the reflection electrode 211 is formed of an Al alloy or the like on the TFT array layer 120, and the lower electrode 212 as a cathode is formed of an ITO or the like on the reflection electrode 211. An organic EL layer 213 is formed on the lower electrode 212. The organic EL layer 213 is formed of, for example, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and the like. An upper electrode 214 as an anode is formed on the organic EL layer 213. The upper electrode 214 is formed of a transparent conductive film such as IZO (Indium Zinc Oxide) or ITO (Indium Tin Oxide), or may be formed of a thin film of a metal such as silver. A protective film 215 is formed of SiNx or the like so as to cover the upper electrode 214, and a polarizing plate 220 for preventing reflection is adhered to the protective film 215 by an adhesive material 216.

Various TFTs such as driving TFTs and switching TFTs are formed in the TFT array layer. However, since the LTPS TFT and the TAOS TFT can be formed by a common process by using the present invention, various types of the LTPS TFT and the TAOS TFT can be formed. Since the combination of the above can be used, it is possible to realize an organic EL display device having excellent image quality and capable of reducing power consumption.

In the above description, the TAOS TFT is used for the display area and the LTPS TFT is used for the peripheral drive circuit. However, depending on the product specifications, the TAOS TFT may be added to the peripheral circuit or the LTPS TFT may be used for the display area. A TFT may be added.

1 ... Liquid crystal display device, 2 ... Organic EL display device, 10 ... Display area, 20 ... Peripheral circuit area, 100 ... TFT substrate, 101 ... First base film, 101 ... Second base film, 103 ... LTPS semiconductor layer, 104 … Gate insulating film, 105… gate electrode, 106… light-shielding film, 107… first interlayer insulating film, 108… second interlayer insulating film, 109… TAOS layer, 110… sacrificial layer, 111… gate electrode, 112… inorganic passivation Film, 113 ... through hole, 114 ... through hole, 115 ... drain electrode, 116 ... source electrode, 117 ... gate insulating film, 120 ... TFT array layer, 121 ... common electrode, 122 ... capacitive insulating film, 123 ... pixel electrode, 124 ... Alignment film, 130 ... Lower polarizing plate, 140 ... Through hole, 150 ... Terminal part, 160 ... Flexible wiring board, 200 ... Opposite board, 201 ... Color filter, 202 ... Black matrix, 203 ... Overcoat film, 210 ... Display element layer, 211 ... Reflective electrode, 212 ... Lower electrode, 213 ... Organic EL layer, 214 ... Upper electrode, 215 ... Protective layer, 216 ... Adhesive material, 220 ... Antireflection polarizing plate, 230 ... Upper polarizing plate, 300 ... Liquid crystal layer, 301 ... Liquid crystal molecule, 400 ... Backlight, 500 ... Liquid crystal display panel, 1031 ... a-Si

Claims (12)

A display device including a substrate having a display area in which pixels are formed.
The pixel includes a first TFT using an oxide semiconductor.
An oxide film which is an insulator is formed on the oxide semiconductor, and a gate electrode is formed on the oxide film.
A first electrode is connected to the drain of the first TFT via a first through hole formed in the oxide film.
A second electrode is connected to the source of the first TFT via a second through hole formed in the oxide film.
The substrate comprises a second TFT by LTPS in the display area.
A display device characterized in that a metal layer is formed in the same layer as the gate electrode of the second TFT and in the lower layer of the first TFT. The display device according to claim 1, wherein both the first TFT and the second TFT are top-gate TFTs. The display device according to claim 1, wherein the substrate has a drive circuit, and the drive circuit further includes a TFT by the LTPS. The display device according to claim 1, wherein the first through hole and the second through hole are formed in the oxide film when viewed in a plane. The wall of the first through hole or the wall of the second through hole formed in the oxide film has a first taper θ1 on the side opposite to the oxide semiconductor and is on the oxide semiconductor side. The display device according to claim 1 to 4, wherein the display device has a second taper θ2 and θ1> θ2. The display device according to any one of claims 1 to 5, wherein the oxide film is AlOx. The display device according to claim 6, wherein the refractive index of AlOx is 1.58 to 1.65. The display device according to any one of claims 1 to 7, wherein the oxide film is composed of a plurality of layers of AlOx. The display device according to any one of claims 1 to 8, wherein the oxide semiconductor is IGZO, ITZO, IGO or a combination thereof. The display device according to any one of claims 1 to 9, wherein an insulating film is formed between the gate electrode and the oxide film. The display device according to any one of claims 1 to 10, wherein the display device is a liquid crystal display device. The display device according to any one of claims 1 to 10, wherein the display device is an organic EL display device.

Images