JP2628072B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active matrix substrate for a display using an MIS (metal-insulator-semiconductor) transistor array.

(Prior Art) FIG. 5 shows a circuit diagram of one cell of a display panel using a conventional active matrix. In the figure, a scanning line 65 is connected to a gate of a thin film transistor (TFT) 52, and when the TFT 52 is turned on, a signal of a signal line 61 is changed to a charge storage capacitor 53, an intersection of the signal line 61 and the scanning line 65. Are stored as electric charges in the charge holding capacitance 55 provided in the first and second and the charge holding capacitance 56 provided in the intersection of the signal line 61 and the GND line. The signal from the signal line 61 is held by the capacitors 53, 55, and 56 until the data is written again, and simultaneously drives the liquid crystal 54. Here, Vc is a common electrode signal.

FIG. 6 is a plan view showing the structure of one cell of a conventional active matrix substrate, and FIG. 7 is a CD of FIG.
It is a line sectional view. The structures of the TFT 52 and the charge storage capacitor 53 are described in JP-A-62-148929.

The TFT 52 has an inverted staggered structure in which a gate electrode 8 is formed on a substrate 1, a gate insulating film 74 is formed on the entire surface, and a semiconductor layer 63 which is an active region of the transistor 52 is further formed. The pixel electrode 64 is arranged above the common electrode 9 formed on the substrate 1 with an insulating film 74 interposed therebetween.

In the manufacturing process of this conventional structure, photo etching for forming the gate electrode 8 and the common electrode 9, photo etching for forming the semiconductor layer 63, and photo etching for forming the pixel electrode 64 and the signal line 61 are performed. The TFT 52 and the charge storage capacitor 53 are formed by etching and photo etching three times in total.

When this substrate is actually used as an active matrix substrate, a contact hole is formed in the insulating film 74 to electrically connect the gate electrode 8 and the common electrode 9 formed under the insulating film 74 to external wiring. Must be opened, requiring a total of four photo-etching steps.

(Problems to be Solved by the Invention) In the above-mentioned conventional technology, the manufacturing process is complicated due to many photo-etching processes, and this has been a major obstacle in improving the yield.

An object of the present invention is to provide a semiconductor device capable of solving the above-mentioned problems, reducing the number of photo-etching steps, and improving the yield, and a method for manufacturing the same.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention relates to a semiconductor device including a thin film semiconductor element and a capacitor portion arranged close to each other on a main surface of an insulating substrate. Forming a transparent conductive film on the main surface of the conductive substrate,
The transparent conductive film is patterned to form a signal line of the thin film semiconductor element and a common electrode of the capacitor portion, and then, on the surface of the insulating substrate, the signal line, and the lower electrode, a semiconductor thin film, an insulating film, And a conductive film are laminated, and thereafter, the semiconductor thin film, the insulating film, and the conductive film are etched into the same shape to form the thin film semiconductor element and the transparent electrode capacitor.

(Operation) According to such a configuration, the photo-etching step
Etching for forming the signal line of the thin film semiconductor element and the common electrode of the capacitor portion and etching for forming the semiconductor thin film, the insulating film, and the conductive film in the same shape are performed twice.

Further, according to the above configuration, since the gate electrode of the thin film semiconductor element and the common electrode of the capacitor portion are exposed on the surface, a photo-etching step for opening through holes for connecting these to external wiring is provided. Can be omitted, the production yield can be improved, and the production cost can be reduced.

Example An example of the present invention will be described below with reference to the drawings.

FIG. 3 is a plan view showing a structure of one TFT constituting an active matrix substrate to which the present invention is applied, and FIG. 2 is a circuit diagram thereof. The same reference numerals as those described above denote the same or equivalent parts. .

In FIG. 2, the basic operation of the circuit, for example, the method of writing data, the method of retaining charges, and the like are the same as those of the prior art described with reference to FIG.

 FIG. 1 is a cross-sectional view taken along line AB in FIG.

In the figure, a signal line 61 is provided on the surface of a transparent insulating substrate 1.
The pixel electrode 64 is formed of a transparent conductive film.

Further, the semiconductor film 4 serving as a TFT channel and the holding of electric charges are respectively provided in a region in contact with the surface of the transparent insulating substrate 1 and covering a part of the signal line 61 and the pixel electrode 64, and in the surface of the pixel electrode 64. A semiconductor film 5 serving as a capacitor is formed.

Further, on the surfaces of the semiconductor film 4 and the semiconductor film 5, a gate insulating film 6 of a TFT and an insulating film 7 serving as a charge storage capacitor are formed in the same shape as the semiconductor film 4 and the semiconductor film 5, respectively. .

Further, a gate electrode 8 and a common electrode 9 are formed on the surfaces of the insulating film 6 and the insulating film 7, respectively, in the same shape as the gate insulating film 6 and the insulating film 7, respectively.

Further, a transparent counter substrate 11 is provided on a portion facing the transparent insulating substrate 1, and a counter electrode 10 is formed on the surface thereof.

In this embodiment having such a configuration, the common electrode 9 and the pixel electrode 64 form the charge storage capacitor (C _STG ) 53 shown in FIG.

FIG. 4 is a sectional view showing a manufacturing process of the active matrix cell shown in FIG. 1, and the same reference numerals as those in FIG. 1 represent the same or equivalent parts. As the transparent substrate 1, glass or insulating high-melting glass such as Pyrex or Corning is used. When using another transparent substrate having a small insulating property, a transparent insulating film such as a SiO ₂ film is deposited on the surface of the substrate 1 by a CVD method, a sputtering method, or the like.

First, an impurity-doped Si film 420, which is a transparent conductive film, is formed on the transparent substrate 1 by a low-pressure CVD method, a plasma CVD method, or the like (FIG. 1A).

Next, the Si film 420 is photo-etched into a required shape to form the signal line 61 and the pixel electrode 64 [FIG.
At this time, the Si film 420 serving as a transparent conductive film is deposited with a thickness of 300 nm or less so as to transmit light. Instead of directly attaching the Si film to the substrate 1, as is conventionally done, a metal film such as gold or aluminum is formed on the transparent substrate 1 to a thickness of about 50 nm or less to transmit light. Thinly,
Further, a film having a Schottky junction in which a Si film doped with impurities is formed with a thickness of 300 nm or less on the surface may be formed. In addition, ITO (Indium Tin Oxi
d) Alternatively, a multilayer film such as a semiconductor thin film in which a transparent conductive film such as tin oxide is doped with an impurity may be used.

Next, a semiconductor film (eg, Si) 430 to be a channel layer is formed by a CVD method such as a plasma CVD method or a low pressure CVD method, a sputtering method, or the like. Further, on the semiconductor film 430, an insulating film (SiO ₂ film, SiN
Film, Ta ₂ O ₃ film, etc.) 440 to CV by plasma CVD method or normal pressure CVD method
It is formed by a D method or a sputtering method. here,
The insulating film 440 may be formed by oxidizing the surface of the semiconductor film 430 in an O ₂ plasma atmosphere or the like. Also, the insulating film 44
0 may be a multilayer film in which an insulating film such as a Ta ₂ O ₃ film is laminated on a semiconductor oxide film.

Thereafter, on the insulating film 440, a conductive film (Al, Cr, doped Si, ITO, SnO ₂ film, etc.) 450 serving as a gate electrode and a scanning line is further deposited [FIG.

Thereafter, the conductive film 450 is masked into a required shape using a resist, and if the conductive film 450 is an Al film, it is wet-etched with an appropriate chemical such as a mixed solution of NaDH and HNO ₃ / HF if the conductive film 450 is a Si film. Then, a gate electrode 8 and a common electrode 9 of the charge storage capacitor are formed. Further, the insulating film 440 is wet-etched in a self-aligned manner using the gate electrode 8 and the common electrode 9 as a mask to form the gate insulating film 6 and the dielectric 7 having the charge storage capacitor. At this time, if the insulating film 440 is a SiO ₂ film, HF is used as an etchant. Further, the semiconductor film is self-aligned using the gate insulating film 6 and the dielectric 7 as a mask.
The channel layer 4 and the semiconductor layer 5 are formed by etching 430. At this time, if the semiconductor film is a Si film, a mixed solution of HNO ₃ / HF is used as an etchant.

Here, the semiconductor film 430 used in this process is not particularly limited as long as it is an intrinsic semiconductor such as amorphous silicon or polycrystalline silicon.
Polycrystalline silicon films that have been laser annealed after deposition by the VD method are particularly good.

Further, in the present embodiment, the applied technology described below can be applied.

(1) A light-shielding film is provided on at least one of the upper and lower sides of the transistor portion or a projection region of the transistor on the counter substrate in order to hold off-state current of the transistor portion.

(2) In order to prevent a leak current flowing on the surface of the active matrix substrate, after forming the transistor and the charge storage capacitor, an insulating film is deposited thereon.

(3) A drive circuit for an active matrix, that is, a shift register, a sample hold circuit, and a scanning circuit are formed on an active matrix substrate.

Note that in the above embodiment, only the conductive film 450 serving as a common electrode of the TFT gate electrode and the charge storage capacitor is etched using a mask, and the insulating film and the semiconductor film formed thereunder are self-aligned. Although it has been described that the etching is performed sequentially, this is for preventing sand etching.

Therefore, if etching is performed using appropriate means such as dry etching or ion milling in which side etching hardly occurs, all the films may be etched using the mask. Also in this case, it is necessary to select a reactive gas according to the material of the film to be etched.

In the above-described embodiment, the substrate 1 is described as being a transparent substrate. However, if the active matrix substrate is used for a reflective liquid crystal display device,
Instead of a transparent substrate, a Si substrate or the like having a mirror-like surface may be used.

(Effects of the Invention) As is clear from the above description, according to the present invention, the manufacturing process can be simplified by reducing the number of photo-etching steps, so that the yield can be improved and the manufacturing cost can be reduced. Can also be reduced.

[Brief description of the drawings]

1 is a sectional view of an active matrix type liquid crystal display device to which the present invention is applied, FIG. 2 is a circuit diagram of one cell of an active matrix substrate, FIG. 3 is a plan view of FIG. 1, and FIG. FIG. 5 is a cross-sectional view showing a manufacturing process of the invention, FIG. 5 is a circuit diagram of a conventional active matrix substrate, FIG. 6 is a plan view of one cell of the conventional active matrix substrate, and FIG. It is sectional drawing in the D line. 1 ... Transparent substrate, 4 ... Semiconductor film, 8 ... Gate electrode, 9 ... Common electrode, 61 ... Signal line, 64 ... Pixel electrode

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Etsuko Kimura 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Hiroshi Kaneko 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research, Ltd. In-house (56) References JP-A-61-183622 (JP, A) JP-A-58-21863 (JP, A)

Claims (5)

(57) [Claims] 1. A pair of insulative substrates and a transparent insulative substrate which are disposed opposite to each other to seal liquid crystal, a transparent pixel electrode formed in a matrix on a main surface of the insulative substrate, and each of the transparent pixel electrodes A plurality of signal lines formed at the same time as the transparent pixel electrodes in each of the gaps in the column direction, a plurality of scanning lines formed in each of the gaps in the row direction between the transparent pixel electrodes, In each gap between the scanning lines, a plurality of common electrode lines formed simultaneously with the scanning lines, such that a part thereof faces the transparent pixel electrode, at an intersection of each of the scanning lines and each of the signal lines. Each formed,
One of the source / drain regions is connected to a signal line, the other is connected to a transparent pixel electrode, and the gate electrode is a plurality of thin film semiconductor elements connected to a scanning line; and a projection region of the scanning line and the common electrode line. An insulating film and a semiconductor film laminated at least between the scanning line and the signal line and between the common electrode line and the transparent pixel electrode; the common electrode line, the insulating film, the semiconductor film, and A liquid crystal display device wherein the transparent pixel electrodes are laminated to form a transparent electrode capacitor. 2. The liquid crystal display device according to claim 1, wherein a transparent insulating film is provided on a main surface of said insulating substrate. 3. The liquid crystal display device according to claim 1, wherein said insulating substrate is transparent. 4. A method for manufacturing a liquid crystal display device according to claim 1, wherein a transparent conductive film is formed on a main surface of an insulating substrate, and then the transparent conductive film is patterned to form the signal. Simultaneously forming a line and a transparent pixel electrode; forming a semiconductor thin film on the surface of the insulating substrate, the signal line and the transparent pixel electrode; forming an insulating film on the surface of the semiconductor thin film; Forming a conductive film on the surface of the film; and etching the semiconductor thin film, the insulating film, and the conductive film into the same shape to form the thin film semiconductor element and the transparent electrode capacitor. A method for manufacturing a liquid crystal display device. 5. The step of etching the semiconductor thin film, the insulating film and the conductive film to have the same shape, the step of patterning the conductive film and simultaneously forming the scanning line and the common electrode line, Patterning the insulating film in a self-aligned manner using the electrode lines as a mask to form a gate insulating film of the thin-film semiconductor element and a first dielectric film of the transparent electrode capacitor; and A step of patterning the semiconductor thin film in a self-aligned manner using a dielectric film as a mask to form an active region of the thin film semiconductor element and a second dielectric film of the transparent electrode capacitor. 5. The method for manufacturing a liquid crystal display device according to claim 4.