JPH04196132A - Display device manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a liquid crystal display, and particularly to a method for manufacturing a display device suitable for, for example, manufacturing an active matrix type liquid crystal display.

[Prior Art] Active matrix type liquid crystal displays have been known in which display is performed by turning on and off pixel electrodes using thin film transistors formed in each pixel.

As disclosed in Japanese Unexamined Patent Publication No. 1-241862, as shown in FIG.
1, there is a silicon film 305 for forming a pixel electrode, a thin film transistor TPT formed of a silicon film, which is integrated with the silicon film for forming the pixel electrode, and a gate bus for turning the pixel electrode 305 on and off. It is composed of a line 305 in which the line and gate electrode are integrated, and a source bus line. The transistor has a gate electrode formed integrally with the gate pass line, a gate insulating film 306 which is a nitride film, a gate insulating film 307 which is a silicon dioxide film, and a pulsed laser beam applied to intrinsic (type 1) hydrogenated amorphous silicon. - Silicon film 303 crystallized by beam irradiation, L I M P I D (
Laser Induced Melting ofP
redeposited Impurity Dopi
The source region 304 and the drain region 305 are formed by an impurity doping method called .ng) method. Source region 304 and drain region 305
is formed in a self-aligned manner with respect to the gate electrode 308 by LIMPID. In this case, the source region is connected to the source pass line, and the drain region and the pixel electrode are integrally formed with a thin silicon film.

Conventionally, as thin film transistors for driving pixel transistors, 5ID90 Tnt'l Sympo, T
ech, Digest pp307-310 has a cobranar structure as shown in FIG. In this thin film transistor, a silicon thin film 402 is formed on a quartz substrate 401 by a method of decomposing monosilane gas by glow discharge or a low pressure chemical vapor deposition method, and a goo 1 insulating film 403 is formed on the silicon thin film. 2. A gate electrode 404 integrated with the gate line using a silicon thin film doped with impurities.
In order to form a source region and a drain region, impurities are ion-implanted through the insulating film in a self-aligned manner using the gate electrode as a mask, and a thermal process is performed to activate the impurities. Resistor source region 40
5 and drain region v1.406, a window for wiring was further formed, and a source electrode 407 and a drain electrode 408 were formed.

[Problems to be Solved by the Invention] In the thin film transistor in the conventional active matrix liquid crystal display shown in FIG. Since a method of introducing and activating impurities into the silicon film is used, the gate insulating films 306 and 307 had to be removed by etching in a self-aligned manner with respect to the gate electrode. For this reason,
Since interfaces are formed between the gate insulating film 306 and the interlayer insulating film 308 and between the gate insulating film 307 and the interlayer insulating film 308, leakage current is likely to occur at this interface when a voltage is applied to the gate electrode. Become. That is, the structure of the thin film transistor shown in FIG. 3 has a drawback that the gate breakdown voltage is extremely low.

In the thin film transistor in the conventional active matrix liquid crystal display shown in FIG. 4, the gate electrode and gate pass line are formed of a polycrystalline silicon film or an amorphous silicon film doped with impurities. In active matrix liquid crystal displays, parasitic capacitance Vgs occurs due to the overlap between the source region and gate electrode of the pixel thin film transistor, and the drain region and A major problem is the parasitic capacitance Vds caused by overlapping gate electrodes. In the conventional example, the parasitic capacitance Vg
In order to prevent the generation of s and Vds, the source region and the train region are formed in a self-aligned manner with respect to the gate electrode 204 by ion implantation.

However, since the gate electrode and gate pass line are formed from a silicon layer doped with impurities, as the screen size of the liquid crystal display increases, the gate pass line becomes longer and the resistance of the gate pass line increases. The gate write time is long, and thin film transistors in pixels that are far away from the gate drive circuit along the gate pass line have the disadvantage that not enough data is manually applied to the pixel electrodes, resulting in pixel unevenness. there were.

The purpose of the present invention is to solve the above-mentioned drawbacks all at once.
By forming the source and drain regions of thin film transistors in a self-aligned manner with respect to the gate electrode, which is a metal thin film, using a method with high gate breakdown voltage, pixel unevenness and point defects due to the generation of parasitic capacitance are eliminated. ,
A method for manufacturing a display device with high image quality in which pixel unevenness in the direction of the gate pass line caused by signal delay on the gate pass line is eliminated by using the gate pass line and the electrodes, which are metal thin films with low resistivity. It is about providing.

[Failure to solve the problem]

In manufacturing a thin film transistor, the present invention includes a step of forming a silicon film on an insulating substrate, a step of patterning the silicon film, a step of forming a gate insulating film on the silicon film, and a step of forming a gate insulating film on the insulating film. A step of forming a thin film, a step of patterning the metal film to form a gate electrode, a step of implanting impurities into the silicon film through the insulating film, and applying an energy beam to the silicon film into which the impurities have been implanted. A method of manufacturing a display device is characterized in that the method includes the step of forming a source region and a drain region of the thin film transistor by irradiating the impurities with the impurities.

[For A] According to the above-mentioned means, without removing the goo 1 insulating film,
Since the source region and drain electrode are formed, it is possible to form a thin film transistor with a high gate withstand voltage, resulting in image quality with fewer defects. Because of this configuration, a good gate signal can be supplied from the drive circuit to the pixel transistor, so that a display device with uniform and good image quality without unevenness can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. This embodiment is an example in which the present invention is applied to the manufacture of an active matrix type liquid crystal display.

1(a) to 1(e) show a method for manufacturing an active matrix type liquid crystal display according to an embodiment of the present invention in the order of steps, and FIG. 2 shows the completed state. Note that FIGS. 1(a) to 1(d) are cross-sectional views taken along the line xx in FIG. 2.

In this embodiment, as shown in FIG. 1A, first, a transparent glass substrate 101 that has been pre-washed is coated with a film having a thickness of, for example, 1.5 mm at a substrate temperature of, for example, 300° C. by, for example, plasma CVD. A nitride film SiN of OO0 and an insulating film of 102 are formed. The glass substrate 10 is formed by the nitride film.
It is possible to prevent contamination from 1.

Next, the insulating film 102 is covered over the entire surface by, for example, low pressure chemical vapor deposition at a substrate temperature of 600° C.
For example, a polycrystalline silicon film having a thickness of about 250 nm is formed. A thin film transistor, which will be described later, is produced by etching the polycrystalline silicon thin film.

An island-like pattern 103 is formed to become a source region, a drain region, and an active region. Next, for example, by APCVD method, the substrate temperature is increased to 3 to cover the island-shaped silicon film.
The insulating film 104 made of silicon dioxide film was heated to 1500°C at 00°C.
Form people. Next, a metal thin film, for example, a 4000 aluminum metal thin film, is deposited to cover the insulating film 104 by, for example, the sppack method. The aluminum metal thin film is patterned into a predetermined shape by etching to form a gate electrode 105 and a gate pass line 113 as shown in FIG.

Next, as shown in FIG. 1B, for example, phosphorus is ion-implanted at an acceleration voltage of, for example, 120 KeV to reach the polycrystalline silicon thin film through the insulating film 104 at a concentration of, for example, 3×10” cm −2 . Impurities are doped at a high density to form ion-implanted silicon layers 108 and 109 as shown in FIG.
09 serve as a source region and a drain region, respectively. At this time, the active region of the thin film transistor T is not doped with the impurity due to the shielding effect of the gate electrode.

Next, an energy beam 110 is irradiated to activate the impurity ions implanted into the silicon thin film. The energy beam for activating this impurity is, for example, XeC
] There is an excimer laser, and the irradiation conditions are, for example, the substrate temperature is room temperature, the pulse width is 50 nsec, and the energy density is 300 mJ/crn'. Since this energy beam activation can be performed substantially at room temperature, alkali-free glass with a low melting point can be used for the substrate. Further, under the above excimer laser irradiation conditions, the resistance of the aluminum metal thin film of the gate electrode does not change, but energy is transmitted only to the source and drain regions and impurities are activated. Furthermore, since a high temperature of 300° C. or higher is not required for impurity activation, hydrogen is not desorbed from the silicon thin film in the active region in this step. Due to this activation, the resistivity of the source region and the drain region becomes 10<-2> to 10<-3 >[Omega].cm, and a resistance that is sufficient for driving a thin film transistor is obtained.

Next, an interlayer insulating film 111 is formed by, for example, atmospheric pressure chemical vapor deposition at a substrate temperature of 300° C., and a silicon dioxide film 50 is formed so as to cover the gate electrode and gate pass line 113.
Formed by 00 people.

Next, predetermined portions of the gate insulating film [04 and interlayer insulating film 11] are removed to form contact holes reaching the source and drain regions, and then a transparent conductive film, such as an ITO film, is deposited by sputtering. Then, this ITO
The film is etched and patterned into a predetermined shape to form the pixel electrode 112. Next, aluminum is deposited on the interlayer insulating film by sputtering, and the aluminum film is etched and patterned into a predetermined shape to form a source electrode 114 and a source pass line 115 communicating with the source region. Next, an insulating film, for example, a nitride film 11, is formed to cover the goo 1-electrode, the source line, and the pixel electrode.
The insulating film 116 deposited on the substrate 6 prevents contamination from the external environment.

Next, the polycrystalline silicon layer 107 in the active region and the insulating film 1
In order to improve the characteristics of the interface with 04 and the grain boundaries of silicon microcrystals constituting the polycrystalline silicon layer in the active region, for example, 3
Annealing is performed at a temperature of 00°C. After this, after forming a liquid crystal alignment film on the entire surface,
After going through the liquid crystal encapsulation process, the desired liquid crystal display is completed.

This thin film transistor T allows high-speed switching of the gate pass line. moreover,
Silicon N 1 in a self-aligned manner with respect to the gate electrode 105
．． 03 is doped with impurities, source region 1
08 and the drain region lO9 can be formed in a self-aligned manner with respect to the gate electrode 105. As a result, the response speed of the thin film transistor T becomes faster, and the parasitic capacitance Vgs between the gate electrode and the source region and the parasitic capacitance Vds between the gate electrode and the drain region are eliminated.
You can obtain high-quality images without unevenness.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications are possible based on the technical idea of the present invention.

For example, MO or Ta, which is a metal with a higher melting point, can be used as the gate electrode. Further, the metal thin film constituting the gate electrode and gate line is not limited to one layer, and may have a two-layer structure, for example, a chromium thin film and an aluminum thin film having a lower resistivity.

Although the present invention has been described in the case where it is applied to the manufacture of an active matrix type liquid crystal display, the present invention can be applied to the manufacture of active matrix type display devices other than liquid crystal displays. for example,
Interlayer insulating film 1 on pixel electrode 115 in the above embodiment
If 16 is removed and, for example, an electrochromic (EC) material is used instead of liquid crystal as the display material, an active matrix type electrochromic display can be manufactured. Note that a two-dimensional sensor can also be manufactured by using an optical sensor material instead of liquid crystal.

Effect of the Invention 1 As explained above, according to the present invention, the constituent material of the gate electrode is a metal with low resistivity, and the source region and the drain region are formed in self-alignment with the gate electrode. Therefore, the signal from the gate pass line from the drive circuit reaches the thin film transistor of the pixel very quickly. Therefore, in a large screen, for example, a 20-inch diagonal NTC3 type liquid crystal display, the pixel m, in the direction of the gate pass line, It is possible to obtain a good display image quality without any distortion.

Furthermore, even in a television display system in which the number of scanning lines and the amount of information are greater than the NTSC system, good image quality can be obtained with an active matrix liquid crystal display. Furthermore, since the gate breakdown voltage is high, there are no defects due to poor gate breakdown voltage, and high quality images can be obtained.

[Brief explanation of the drawing]

Section 1 (a) to FIG. 1 (e) are cross-sectional views for explaining the manufacturing method of an active matrix type liquid crystal display according to an embodiment of the present invention in the order of steps, and FIG.
Perspective views showing completed states of the liquid crystal displays manufactured by the methods shown in a, ) to FIG. Perspective view, Figure 4 is 5
ID90Int'l Sympo,,Tech,Dig
est pp307-310 is a sectional view showing an example of an active matrix type liquid crystal display according to the invention. 101...Glass substrate 102...Insulating film 103...Polycrystalline silicon thin film 104...Gate insulating film 105...Gate electrode 106...Ion implantation 107...Activation region 108 of thin film transistor...
Source region 109... Drain region 110... Energy beam] 11... Interlayer insulating film 112... Pixel electrode 113 Gate pass line 114... Source electrode 115... Source pass line 116... Passivation film People Seiko Epson Corporation

Claims (1)

[Claims] In manufacturing a thin film transistor, a step of forming a silicon film on an insulating substrate, a step of irradiating the silicon film with an energy beam, a step of patterning the silicon film, and a step of forming a gate on the silicon film. a step of forming an insulating film, a step of forming a metal thin film on the insulating film, a step of patterning the metal thin film to form a gate electrode, and a step of implanting impurities into the silicon film through the insulating film. and irradiating the impurity-implanted silicon film with an energy beam to activate the impurity, thereby forming a source region and a drain region of the thin film transistor. .