JPH0385529A - Thin film semiconductor display device - 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 [Field of Industrial Application] The present invention relates to a thin film semiconductor device, and particularly to a thin film semiconductor display device using liquid crystal or the like.

[Conventional technology]

In recent years, flat displays using liquid crystals have been progressing in two ways: increasing screen size and incorporating pixel drive circuits into display substrates.

In order to increase the screen size, we use TPT with an inverted staggered structure made of amorphous silicon (a-8i).
The TPT with this structure, which is used to realize a 14-inch diagonal display, has a small leakage current and has good charge retention characteristics for applying an electric field to the liquid crystal, making it easy to increase the screen size. However, the carrier mobility is about 0,
34/Vs, the current drive capability is small, and it is difficult to assemble a circuit using this TPT. Japanese Patent Application Laid-Open No. 83025/1983 is related to the above technology. on the other hand.

Regarding the built-in peripheral drive circuit, polycrystalline silicon (p-
8i) is used. A TPT with this structure has a carrier mobility of about 30 ci/V8 or more, a large current driving ability, and can form a circuit to incorporate a peripheral circuit for pixel movement on the display substrate. Therefore, the number of terminals taken out from the display can be reduced, and the cost for the external LSI can be reduced.

However, T of the coplanar structure using p-8i
Since PT has a large leakage current, it does not have sufficient charge retention ability and has the disadvantage that it is difficult to increase the size of one screen.

[Problem to be solved by the invention]

The above conventional technology uses the same type of TPT structure from the viewpoint of not complicating the process,
It is difficult to keep up with the two trends of larger displays and built-in peripheral circuits, and there has been a problem in that large-screen displays cannot incorporate peripheral circuits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure that allows a liquid crystal display to have a larger screen and to incorporate peripheral circuits into the display substrate at the same time.

[Means to solve the problem]

In order to achieve the above object, the present invention provides that the pixel portion of the display is made of staggered TFT or metal-insulator-metal (metal-insulator-metal).
The device is constructed of switching elements having an MIM) structure, and the peripheral circuit portion is constructed of TPTs having a coplanar structure.

[Effect]

The invention works as follows. As shown in FIG. 1(b), the TPT has a staggered structure.

Since the channel region and the source and drain regions are separated in the thickness direction of the film by the high-resistance film itself, the current value is generally small, and this TPT is used in the pixel part of the display shown in Figure 1(a). For example, it has a large charge retention capacity that satisfies the leakage current specification of approximately 3 x 10" A or less, allowing for larger displays. TPT with an inverted stagger structure has a small current of approximately 0.3 cm2/Vs. Although it only has carrier mobility, the carrier mobility of TPT in the pixel part is 0.2 cm2/V s
The above requirements are met. This low carrier mobility is not a problem because the leakage current image retention ability is important for increasing the size of the display.On the other hand, as shown in Figure 1(c), TPT with a coplanar structure Because of the structure in which the channel, source, and drain are in contact with each other on one plane, the carrier mobility is as high as approximately 40 d/Vs, and the current drive capability is also large in order to meet the carrier mobility specification of approximately 30 cm2/Vs or more. , Figure 1 (a
) It is possible to configure the pixel driving circuit shown in FIG. A TPT with a coplanar structure has a large leakage current of about 10-"A, but the current drive is too large to configure a zero pixel drive circuit that satisfies the TPT leakage current specification of about 2X10-11A or less in the peripheral circuit. Since performance is important, this large leakage current is not a problem.

As shown in Figure 2, a switching element with a metal-insulator-metal (MIM) structure allows current to flow only when a high electric field is applied between metals, and the off-state current is small. Similar to structural TPT, it is possible to configure the pixel section of a large screen display, and if the peripheral circuit section is configured with a TPT with a coplanar structure as shown in Figure 3, a large display with built-in peripheral circuits can be realized. .

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Cr2 is vapor-deposited on the glass substrate 1 on the diagonal 300-, and patterned for electrodes and wiring of the inverted staggered pixel structure TPT by a photo process. Thereafter, a nitride film 3 and an a-Si film (i-layer) 4 are formed by plasma CVD. a
-s is is cut into islands by a photo process, and then only the peripheral circuit portion is annealed using an excimer laser with a wavelength of 3.8 mm to polycrystallize it. Thereafter, a-Si films (n middle layer) 5 and 6 are formed by plasma CVD. After forming source and drain regions by a photo process, an oxide film 7 is formed by atmospheric pressure CVD. Patterning for the gate insulating film of the peripheral circuit section coplanar structure TPT is performed by a photo process. Next, after depositing Cr8 for signal wiring, patterning is performed in a photo process. Next, mainly the peripheral circuit section T
After depositing Ag3 for PT wiring, patterning is performed in a photo process. Next, ITOIO, which is a transparent electrode, is deposited and patterned in a photo process. Finally, the display is completed by sealing liquid crystal between the color filter and another glass substrate equipped with a polarizing plate.The 0-line display has a diagonal of 10 inches, and both the number of scanning lines and signal lines. 1200
It's a book. The peripheral circuit section includes multiplexers, inverters, level switches, and matrix switches. FIG. 1(a) shows the display substrate obtained in this manner. Here, in addition to the one pixel portion 16, peripheral circuits such as a scanning circuit 17 and a signal circuit 18 are constructed on one substrate. I can see what's going on.

As a result of the above, the mobility of TPT used in the pixel portion is 0.
, 2 (cd/Vs) or more, preferably 0.3
(d/Vs), l,, threshold voltage 8 (V) or less, leakage current 3X10-1! (A) Below, on-current lXl0'(A
) or more, the mobility of TPT used as a peripheral circuit is 30 (cm2/V s ) or more, and the threshold voltage is 8 (v
) or less, leakage current 2 x 10-1' (A) or less, preferably 1 x 10-11 (A) or less, on-current I
10'(A) or more, a high performance display device can be constructed.

〔Effect of the invention〕

According to the present invention, it is possible to increase the screen size of a liquid crystal display and to incorporate a pixel driving peripheral circuit into a display substrate.

[Brief explanation of drawings]

FIG. 1 is a plan view of a liquid crystal display according to an embodiment of the present invention, and a cross-sectional view showing a TPT structure, and FIG. FIG. 1(b) shows an inverted staggered structure TPT in the pixel section, FIG. 1(Q) shows a coplanar structure TPT in the peripheral circuit section, and FIG. 2 shows a cross-sectional structure of an MIM in the pixel section according to another embodiment of the present invention. FIG. 3 shows a cross-sectional structure of a conventional coplanar structure TPT. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Cr electrode, 3... Insulating film, 4
... Channel region, 5... Source, 6... Drain, 7... Gate insulating film, 8... Cr wiring, 9...
・Afl wiring, 10...transparent electrode (ITO), 11=
4'a, 12-Tazoa, 13...insulating film, 14-
...Cr, 15...passivation film, 16...pixel section, 17...scanning side circuit, 18...Fig. 1(a) Fig. 1(b) Fig. fig.

Claims (1)

[Claims] 1. In a display device having an insulating substrate and a semiconductor layer formed on the substrate, a pixel portion is formed of a thin film transistor with a staggered structure or a switching element with a metal-insulator-metal (MIM) structure. , a thin film semiconductor display device characterized in that a peripheral circuit section is composed of thin film transistors having a coplanar structure. 2. A thin film semiconductor display device characterized in that the pixel portion is composed of staggered thin film transistors made of amorphous silicon, and the peripheral circuit portion is composed of coplanar thin film transistors made of polycrystalline silicon. 3. In a display device having an insulating substrate and a semiconductor layer formed on the substrate, the leakage current of the thin film transistor in the pixel portion is made smaller than the leakage current of the thin film transistor in the peripheral circuit, and the carrier mobility of the latter is made smaller than that of the former. A thin film semiconductor display device characterized by having a carrier mobility greater than that of a carrier. 4. An insulating substrate provided with a pixel part and a peripheral circuit part is provided, the leakage current of the thin film transistor used in the pixel part is 3×10^-^1^2 A or less, and the mobility of the thin film transistor used in the peripheral circuit part is 30 cm. A thin film semiconductor display device characterized by having a voltage of ^2/Vs or more.