JPH04192530A - Manufacture of thin film transistor and liquid crystal display panel - Google Patents

Abstract

PURPOSE:To prevent the concentration of electric field and the generation of leakage current by forming an action semiconductor which constitutes a channel region of a thin film transistor and an impurity diffusion layer which has a concentration gradient all over the interface between a source electrode and a drain electrode. CONSTITUTION:Two layer films which cover an active semiconductor layer 15 and a gate insulation film 105, are formed on each gap on a processing board where each thin film transistor device is formed thereon. A gate electrode 14 and a protection film 106 are further formed thereon, thereby forming each thin film transistor device. The two layer films for the semiconductor layer 15 and the insulation film 105 are formed based on a CVD process. As the temperature of the substrate at that time is around 250 deg.C, the phosphorous (P) deposited on the surface of a titanium (Ti) film 100 is diffused into the semiconductor layer 15, for example, an alpha-Si layer during the CVD processing, keeping a concentration gradient, thereby forming an impurity diffusion layer 104. The concentration of electric field will be eliminated by forming the impurity diffusion layer 104 all over the interface between the semiconductor layer 15 which constitutes the channel region of the thin film transistor, a source electrode 101, and a drain electrode 102 so that the generation of mark current may be prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a thin film transistor and a liquid crystal display panel, the leakage current between the source and drain electrodes of the thin film transistor used in an active matrix substrate and an active semiconductor layer is reduced, and the thin film transistor and the active matrix using the same are In order to improve the quality and reliability of type liquid crystal display panels, we have developed a process of forming source and drain electrodes made of titanium on a substrate with a gap between them that will serve as a channel region, and A method of manufacturing a thin film transistor including at least a step of forming an impurity layer on the surface and side surfaces of an electrode, and a step of laminating an active semiconductor layer, a gate insulating film, and a gate electrode on the source electrode and the drain electrode including the gap. Configure the manufacturing method. Further, an active matrix type liquid crystal display panel is constructed using an active matrix substrate (1) on which thin film transistors manufactured by this manufacturing method are arranged.

[Industrial application field]

The present invention relates to a method for manufacturing a thin film transistor and a liquid crystal display panel, particularly to an improvement in an active matrix type liquid crystal display panel using the same.

In recent years, with the improvement and spread of liquid crystal display devices, there has been a strong demand for larger capacity and color display devices. In particular, active matrix liquid crystal display devices that use thin film transistors as switching elements are expected to have a wide range of needs due to their excellent performance and quality. It is being

[Conventional technology]

FIG. 3 is a perspective view showing the appearance of an active matrix liquid crystal display panel.

In the figure, l is an active matrix substrate and a transparent substrate 11
A thin film transistor element array is formed thereon, and each element is provided with a transparent pixel electrode corresponding to a display pixel. Reference numerals 40 and 50 denote a gate lotus line and a drain lotus line to which the gate electrode and drain electrode of each thin film transistor element are connected, and an alignment film 1 is disposed thereon.
2 is provided. On the other hand, 2 is a common electrode substrate on which a transparent solid electrode 21 and an alignment film 22 are laminated on a transparent substrate 20 . Both substrates are sealed with a sealing material (not shown) between the substrates with a spacer (not shown) in between so that a narrow space is formed with the alignment film surface in the middle, and the liquid crystal 3 is injected into the space and sealed. In this way, an active matrix type liquid crystal display panel is constructed. Although this figure shows a case for black and white display, if a color filter is added to this, a color liquid crystal display panel can be constructed.

FIG. 4 is a diagram showing an example of the structure of a thin film transistor.
This is a conceptually enlarged view of a part of the thin film transistor element group of the active matrix substrate l described in the figure.

In the figure, IO is a thin film transistor, and gate pass line 4
Gate electrode 14 overhanging from 0. For example, Af, T
An active semiconductor layer 15. For example, an amorphous silicon film (α-3i film) is formed, and a drain electrode connected to the drain pass line 50 from both sides thereof, for example,
A thin film transistor is configured by providing a source electrode connected to a transparent pixel electrode 19 made of ITO (In203-3n02).

Since its operating mechanism is well known, its explanation will be omitted.

Note that in this figure, the gate electrode 14 is arranged on the top layer.

A so-called top gate stacker type example has been illustrated and explained.

On the contrary, the gate electrode 14 is arranged at the bottom layer. The so-called bottom gate stacker type is currently widely used for practical purposes because it provides relatively stable characteristics.

However, since the structure of the bottom gate stagger type is complicated and the manufacturing process is difficult, there is a strong need for improvements in the manufacturing method of thin film transistors with the top gate stagger type structure.

FIG. 5 is a diagram showing an example of a conventional thin film transistor manufacturing method, and is an example of a top gate stagger type structure.

Step (1): Transparent substrate IL For example, a transparent electrode film 190 is placed on a glass substrate. For example, ITO (In2O
3-3nO□) film and contact layer 110. For example, n4α-3i films are sequentially formed.

Step (2): A gap 107, which will become a channel region, is formed in required portions of the transparent electrode film 190 and the contact layer 110 of the processing substrate using a known photolithography technique.

Step (3): An active semiconductor layer 15. is formed on each gap 107 of the processed substrate. For example, the α-3i film and the gate insulating film 105. For example, forming a SiN film, and
Gate electrode 14 as shown thereon. For example, T
i-electrode and protective film 106. For example, a 5tNz film is formed, and elements are separated using a known photolithography technique to form each thin film transistor element. Further, at this time, the active matrix substrate 1 is manufactured in such a way that the contact layer 110 is removed and the pixel electrode 19 is formed in a portion where the transparent electrode film 190 is exposed.

Note that instead of the transparent electrode film 190, a metal film, for example,
In some cases, a Ti film is formed as the source and drain electrodes.

[Problem that the invention sought to solve]

However, in the above conventional thin film transistor having a top gate staggered structure, the source electrode 101 and the drain electrode 102 (in FIG. 5, both transparent electrode films 19
There is a steep slope between the contact layer 110 and the active semiconductor layer 15 on top of the transparent electrode film 190 and the active semiconductor layer 15 (consisting of 0), and between the transparent electrode film 190 and the active semiconductor layer 15 on the side surface (portion indicated by A). It forms a contact junction (abrupt junction), and leakage current is likely to occur due to electric field concentration at the side surface (portion indicated by A). There were serious problems such as deterioration of device quality and reliability, and a solution was needed.

[Means to solve the problem]

The above-mentioned problem involves a step of forming a source electrode 101 and a drain electrode 102 made of a titanium film 100 on a substrate 11 with a gap 107 therebetween, which will become a channel region;
forming an impurity layer 103 on the surface and side surfaces of the source electrode 101 and the drain electrode 102, and forming an active semiconductor layer 15 and a gate insulating film 105 on the source electrode O1 and the drain electrode 102 including the gap 107;
This problem can be solved by a thin film transistor manufacturing method including at least the steps of: and a step of laminating the gate electrode 14. Note that the source electrode 101 and the drain electrode 102 may be configured to be composed of a two-layer film including a transparent conductive film 190 and a titanium film 100 laminated thereon.

Further, as a specific liquid crystal display panel, either one of the source electrode 101 and the drain electrode 102 is extended and widened, and the titanium film 10 in the region that becomes the pixel is
A thin film transistor to be used as an active matrix substrate is manufactured by oxidizing 0 to form a transparent and conductive pixel electrode 19, and further, an active matrix type liquid crystal display is manufactured using the active matrix substrate I thus formed. The problem can be solved by creating panels.

[Effect]

According to the present invention, since the impurity diffusion layer 104 having a concentration gradient is formed at all the interfaces between the active semiconductor layer 15 constituting the channel region of the thin film transistor 10 and the source electrode 101 and the drain electrode 102, the impurity diffusion layer 104 has an appropriate gradient. It acts as an energy barrier with , preventing electric field concentration and preventing leakage current from occurring. Furthermore, the pixel electrode 19
Since all the wiring portions except for the wiring portions are made of metal, for example, Ti, the wiring resistance can also be kept low.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, and shows an outline of the main steps in the order of the steps.

Step (1): Transparent substrate 11. For example, a titanium (Ti) film 100 with a thickness of 80 to 1100 nm is placed on a glass substrate.
of.

For example, it is formed by a sputtering method.

Step (2): A cap 107 that will become a channel region is formed at a required portion of the titanium (Ti) film 100 of the processing substrate using a known photolithography technique.

Step (3) An impurity layer 103 is deposited on the surface and end surfaces of the titanium (Ti) film 100 of the second treated substrate. For example, by heating the above-mentioned treated substrate to 250°C, for example, 0.5°C.
% of PH3 (gas pressure: 40 Pa), high frequency discharge is performed to deposit an impurity layer 103 made of a thin layer of phosphorus (P) on the surface of the titanium (Ti) film 100.

Step (4): An active semiconductor layer 15 is formed on each cap of the treated substrate. For example, a 15 nm thick α-3i film and a gate insulating film 105. For example, 5I with a thickness of 200 nm
A two-layer film of NK and 5ift with a thickness of 1100 nm is formed.

Further, as shown above, a gate electrode 14°, for example, a Ti electrode with a thickness of 80 nm and a protective film I06. For example, a SiNx film with a thickness of 50 nm is formed, and thin film transistor elements are formed using known photolithography techniques. Note that the active semiconductor layer 15°, for example, α-
3i film and Kate insulating film 105. For example, 5tNx/
The two-layer film of StO□ was formed using the CVD method.
Since the substrate temperature at that time is about 250°C, the phosphorus (P) deposited on the surface of the titanium (Ti) film 10O is CvD.
During processing the active semiconductor layer 15. For example, the impurity diffuses into the α-3i layer with a concentration gradient and forms the impurity diffusion layer 104.
form.

Step (5): For example, the source electrode 1 of the treated substrate
The titanium film 100 in the area that will become the extended and widened pixel of the titanium (Ti) film constituting 01 is oxidized, for example, by high-frequency discharge in an oxygen atmosphere at a gas pressure of 150 Pa, to make it transparent and conductive. A pixel electrode 19 was formed by forming a titanium oxide film. As a result, the thin film transistor of the present invention connected to the pixel electrode 19 is manufactured.

In the above embodiment, the thin film transistor IO and the pixel electrode 19
Although one set has been illustrated and explained, if these are arranged and formed in a matrix, an active matrix substrate l according to the present invention is constructed, and if a liquid crystal display panel is constructed using this active matrix substrate, an active matrix according to the present invention is formed. A liquid crystal display panel of this type is manufactured, and a high-quality, highly reliable liquid crystal display device is realized. Figure 2 shows another embodiment of the present invention, and the main steps are outlined in the order of the steps. This is what is illustrated.

Note that the same reference numerals are given to the same parts as those explained in the above countries, and the explanation of the same parts will be omitted.

In this embodiment, a transparent substrate 11. For example, a transparent conductive film 190. For example, thickness 80-11
After forming a 00n ITO (Inz03-3nO2) film by sputtering, for example, a film with a thickness of 80 to 1100n is formed.
A titanium (Ti) film 100 is similarly formed by the sputtering method, and thereafter the thin film transistor of the present invention is formed according to the steps of the embodiment described in detail in FIG. 1 above. In this embodiment, the wiring portion including the pixel electrode 19 is entirely composed of a metal film, for example, a Ti film and a transparent electrode film 190, so compared to the case of the single-layer Ti film of the previous embodiment, mainly the passthrough is achieved. This has the advantage of greatly reducing line wiring resistance.

Note that the above-mentioned embodiments are merely examples, and as long as the purpose of the present invention is met, the parts used, their combinations, the configuration of each part, the treatment process, etc. may be appropriately selected and used. It goes without saying that the present invention may be implemented in the following manner.

〔Effect of the invention〕

As explained above, according to the present invention, the impurity diffusion layer 104 with a concentration gradient is formed at all the interfaces between the active semiconductor layer I5, which constitutes the channel region of the thin film transistor 10, and the source electrode 101 and the drain electrode 102. Therefore, it becomes an energy barrier with an appropriate slope, preventing electric field concentration and preventing leakage current from occurring. Furthermore, since all the wiring parts except the pixel electrode 19 are made of metal, for example, Ti, the wiring resistance can be kept low. It greatly contributes to improving sexual performance.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing another embodiment of the invention, Fig. 3 is a perspective view showing the external appearance of an active matrix type liquid crystal display panel, and Fig. 4 is a diagram showing an embodiment of the present invention. 5 is a diagram showing an example of the structure of a thin film transistor, and FIG. 5 is a diagram showing an example of a conventional method for manufacturing a thin film transistor. In the figure, ■ is an active matrix substrate, 2 is a common electrode substrate, 3 is a liquid crystal, IO is a thin film transistor, 11 is a substrate, 14 is a gate electrode, 15 is an active semiconductor layer, 19 is a pixel electrode, 100 is a titanium film, 101 is a 102 is a source electrode, 102 is a drain electrode, 103 is an impurity layer, 104 is an impurity diffusion layer, 105 is a gate insulating film, and 106 is a protective film. 10: Usui II-, Ushiji Matarigi 418 month 7 points one point Hi Jiri I begging ceremony 1T [Ko condolence 1
Fig. 2 Fig. 7 Gutative matrix liquid display panel n Appearance needle view Fig. 3 An example of the present invention/) gun n Tora brother 1 Fig. 7 Fig. 4 figure

Claims (4)

[Claims] (1) A step of forming a source electrode (101) and a drain electrode (102) made of a titanium film (100) on a substrate (11) with a gap (107) therebetween that will become a channel region; ), forming an impurity layer (103) on the surface and side surfaces of the drain electrode (102), and forming the source electrode (101) including the gap (107).
) and the drain electrode (102), an active semiconductor layer (
15), gate insulating film (105), and gate electrode (14)
1. A method for manufacturing a thin film transistor, comprising at least a step of laminating and forming a thin film transistor. (2) The source electrode (101) and the drain electrode (
2. The method of manufacturing a thin film transistor according to claim 1, wherein 102) comprises a two-layer film of a transparent conductive film (190) and a titanium film (100) laminated thereon. (3) The source electrode (101) and the drain electrode (
102) is extended and widened, and the titanium film (100) in the area that will become a pixel is oxidized to form a transparent and conductive pixel electrode (19), which is used as an active matrix substrate. A method for manufacturing a thin film transistor according to claim 1 or 2, characterized in that: (4) In a liquid crystal display panel in which a liquid crystal (3) is sealed in a liquid crystal sealed space formed between an active matrix substrate (1) and a common electrode substrate (2), the active matrix substrate (1) An active matrix liquid crystal display panel characterized in that the thin film transistor (10) and the pixel electrode (19) are formed by the method according to claim (3).