JPH03292773A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To make the interface of an insulating thin film clean and to restrain the interface level of the thin film so as to enable a thin film transistor to be lowered in power consumption and to operate at a high speed by a method wherein an insulating film is formed and then irradiated with ozone. CONSTITUTION:A semiconductor thin film layer highly doped with impurities is laminated on all the surface of an insulating substrate 101 and patterned into a source region and a drain region 102. Then, an intrinsic semiconductor layer 103 with no impurity is laminated through the thermal decomposition of silane or the like apd patterned. In succession, an insulating film 104 serving as a gate insulating film is laminated on the whole surface. The insulating film 104 is subjected to an ozone irradiation treatment, then a conductor thin film layer serving as a gate electrode is formed through a sputtering method and etched into a gate electrode 105 by removing the disused part of the conductor thin film, an interlaminar insulating film 106 is laminated thereon, the insulating thin film 104 and the interlaminar insulating film 106 on a region where a source and a drain electrode are built are removed to provide a contact hole 107, and a source electrode 108 and a drain electrode 109 are provided there.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for manufacturing a thin film transistor.

[Prior Art] FIG. 3 shows an example of a conventional manufacturing method for forming a thin film transistor on an insulating substrate.

First, a semiconductor thin film layer 302 doped with high-temperature impurities is formed on a transparent insulating substrate 301 as a source/drain region, and after patterning, an intrinsic semiconductor layer 303 containing no impurities is laminated and patterned as an active region. ,
After that, a gate insulating film 304, a gate electrode 305, and an interlayer insulating film 306 are laminated, and after opening a contact hole 307, a source electrode terminal 308 and a drain electrode terminal 309 are formed.
is formed to complete the thin film transistor.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, as a method for forming an insulating film, atmospheric pressure CVD method, low pressure CVD method, plasma CVD method is used.
However, in the above methods, it is important to keep the interface of the formed insulating film clean, so the interface state is large. Therefore, it has been difficult to form a thin film transistor with excellent operating characteristics.

The present invention solves the problems of conventional thin film transistors, and its purpose is to provide a thin film transistor that can achieve lower power consumption and higher speed, and a method for manufacturing the same.

[Means for Solving the Problems] The method for manufacturing a thin film transistor of the present invention includes a semiconductor layer doped with high-temperature impurities as a source/drain electrode on an insulating substrate, and an intrinsic semiconductor layer as an active region. A method for manufacturing a thin film transistor having a structure in which a gate insulating film and a gate electrode are sequentially laminated, the method comprising: irradiating the gate insulating film of the thin film transistor with ozone.

[Function] According to the above method of the present invention, by performing ozone irradiation treatment after forming the insulating film, the interface between the insulating thin film and the underlying thin film can be cleaned, and by suppressing the interface state, the It is possible to construct thin film transistors that can reduce power consumption and increase speed.

[Example code] FIG. 1 is a diagram showing an embodiment of the present invention in the order of steps.

First, as shown in FIG. 1(a), a semiconductor thin film layer doped with high concentration impurities is laminated over the entire surface of an insulating substrate 101.
The source and drain regions 102 are patterned. To form a semiconductor thin film layer to which high-temperature impurities are added, a low-pressure CVD method using direct phosphine or a mixed gas of disilane and silane, an ion implantation method, or the like is used.

Next, an intrinsic semiconductor layer 103 containing no impurities is laminated to a thickness of about 250 Å by thermal decomposition of silane or the like, and patterned. This state is shown in Figure 1(b). Silane decomposes at temperatures above 300°C, but ideally around 600°C. Next, about 1,500 people coated the entire surface with an insulating thin film 104 that will become the gate insulating film. 1(c). The insulating thin film is made of a silicon dioxide film, a silicon nitride film, etc., using a normal pressure CVD method, a low pressure CVD method, or a Blaze 7 film.
It is formed and used by a CVD method, an ECR Blaze 7CVD method, a photo-CVD method, or a combination thereof.

Next, after performing ozone irradiation treatment, a conductive thin film layer that will become the gate electrode is formed by sputtering or the like, and then etched except for the part that will become the gate electrode 105, as shown in FIG.
d). A metal such as aluminum or chromium or a polycrystalline silicon film is used for the gate electrode. Next, an interlayer insulating film 106 is laminated, and then the insulating thin film 104 and the interlayer insulating film 1 in the portions where source/drain electrodes are to be formed are laminated.
06 is removed, a contact hole 107 is formed, and a source electrode 108 and a drain electrode 109 are formed in the contact hole 107, as shown in FIG. 1(e). In addition to an insulating film formed by the same method as the insulating thin film 104, an organic film such as polyimide may be used for the interlayer insulating film 106.

FIG. 2 shows the gate voltage-source current characteristics of a thin film transistor manufactured in an example of the present invention.

The solid line A indicates that ozone irradiation was not performed before forming the insulating film, and the broken line B indicates that ozone irradiation was performed after forming the insulating film. From FIG. 2, it can be seen that the characteristics of the thin film transistor are improved by ozone irradiation before and after forming the insulating film.

This is because the interface level between the gate insulating film and the intrinsic semiconductor layer that does not contain impurities, which is the active region, can be suppressed by irradiating ozone after forming the gate insulating film.

Through the manufacturing process described above, the resulting thin film transistor has a cleaner interface than conventional thin film transistors, and therefore has smaller interface states, making it possible to reduce power consumption and increase speed. .

[Effects of the Invention] According to the method for manufacturing a thin film transistor of the present invention described above, by irradiating ozone after forming an insulating film, the interface of the insulating thin film can be cleaned, and the interface state can be suppressed. This makes it possible to provide thin film transistors with lower power consumption and higher speed. Since the manufacturing process of such thin film transistors does not involve high-temperature processes of 600°C or higher, they are very effective for applications such as drive circuits for each pixel of liquid crystal display devices that use glass substrates as insulating substrates. .

[Brief explanation of the drawing]

FIGS. 1'(a) to 1(e) are sectional views of a thin film transistor according to an embodiment of the present invention at each manufacturing process. Figure 2 shows the case where ozone irradiation is applied after the insulating film is formed.
A comparison diagram comparing the characteristics of thin film transistors when no treatment is applied. FIG. 3 is a cross-sectional view of a conventional thin film transistor. 101.301... Insulating substrate 102.302... Source/drain region 103.3
03... Intrinsic semiconductor layer 104.304... Gate insulating film 105.305... Gate electrode 106.306... Interlayer insulating film 107.307... Contact hole 108.308
...Source electrode 109.309...Drain electrode or higher

Claims (1)

[Scope of claims] A semiconductor layer doped with high concentration impurities as source/drain electrodes on an insulating substrate and an intrinsic semiconductor layer as an active region, and a gate insulating film and a gate electrode are sequentially laminated. A method for manufacturing a thin film transistor having a structure comprising: irradiating a gate insulating film of the thin film transistor with ozone.