JPH0794744A - Mis transistor - Google Patents

Abstract

PURPOSE:To increase ON characteristics and prevent leakage current from occurring at OFF without enlarging an occupied area, by dividing a channel layer formed between a source region and a drain region into a plurality of areas along its channel width. CONSTITUTION:A source electrode 405 and a drain electrode 404 formed on both sides of a gate electrode 402, respectively, in parallel thereto, are connected via a through hole provided respectively in a silicon nitride film 405 to a source region and a drain region formed in a semiconductor layer 401. An MIS transistor formed in this manner is formed by being split into a plurality of areas along a channel width as a channel layer formed between the source region and the drain region forms a groove 410 in the semiconductor layer 401. Consequently, there is an increase in the number of sides in each channel layer corresponding to its channel length, thus increasing an ON current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIS transistor, and more particularly to improvement of a MIS transistor incorporated in a drive circuit of a liquid crystal display substrate.

[0002]

2. Description of the Related Art For example, an active matrix type liquid crystal display substrate is used by connecting a vertical scanning circuit and a video signal driving circuit to its terminals.

Several switching elements are incorporated in each of the vertical scanning circuit and the video signal driving circuit. These switching elements have a SMIS structure thin film transistor (TFT) whose semiconductor layer is a polycrystalline silicon film. ).

[0004]

However, it is desired that the thin film transistors incorporated in the vertical scanning circuit and the video signal driving circuit can be driven at high speed.

This is because high-speed driving of each of the above circuits is required as the liquid crystal display section becomes finer.

Particularly, the thin film transistor of the video signal drive circuit is required to have sufficient ON / OFF characteristics for writing the signal voltage to each pixel during the selected writing time.

For this reason, it is known that the thin film transistor has a large channel width. However, even though the area occupied by the thin film transistor is large, such an effect cannot be expected, and the leakage current at the time of OFF is reduced. The problem of increasing numbers came to be pointed out.

Therefore, the present invention has been made under such circumstances, and the object of the present invention is to improve the ON characteristics without increasing the occupied area, and further, the leakage at the time of OFF. An object of the present invention is to provide a MIS transistor that can prevent the generation of current.

[0009]

In order to achieve such an object, the present invention basically provides a direction in which each region is connected between a source region and a drain region formed on the surface of a semiconductor substrate. In a MIS transistor in which a gate electrode for forming a channel layer whose side is a channel length and whose side is a channel width in a direction intersecting the side is formed with an insulating film interposed between the channel layer and the channel width. It is characterized by being divided into a plurality along the.

[0010]

In the MIS transistor having the above structure, the channel layer formed between the source region and the drain region is divided into a plurality of parts along the channel width.

By doing so, the number of sides corresponding to the channel length in each channel layer increases, and the ON current increases.

That is, O in the MIS transistor
It was found that the N current concentrates on the side portion corresponding to the channel length of the channel layer, and it is preferable to increase the number of side portions corresponding to the channel length as described above, rather than increasing the channel width. Proved to be effective.

This means that a plurality of channel layers can be formed without increasing the occupied area of the MIS transistor, and the occupied area of the channel layer is inevitably reduced, so that the leak current at the time of OFF also occurs. It will be possible to make it smaller.

[0014]

The invention, further objects of the invention and further features of the invention will be apparent from the following description with reference to the drawings.

<< Active Matrix Liquid Crystal Display Device >>
An embodiment in which the present invention is applied to an active matrix type color liquid crystal display device will be described below. In the drawings described below, components having the same function are designated by the same reference numeral, and repeated description thereof will be omitted.

<< Outline of Matrix Unit >> FIG. 2 is a plan view showing one pixel and its periphery of an active matrix type color liquid crystal display device to which the present invention is applied, and FIG.
-3 is a view showing a section taken along a cutting line, and FIG.
It is sectional drawing in a cutting line.

As shown in FIG. 2, each pixel has two adjacent scanning signal lines (gate signal lines or horizontal signal lines) GL.
And an adjacent two video signal lines (drain signal line or vertical signal line) DL are intersected with each other (in a region surrounded by four signal lines). Each pixel includes a thin film transistor TFT, a transparent pixel electrode ITO1 and a storage capacitor element Cadd. The scanning signal lines GL extend in the left-right direction in the figure, and a plurality of scanning signal lines GL are arranged in the vertical direction. Video signal line DL
Extend in the up-down direction and are arranged in the left-right direction.

As shown in FIG. 3, a thin film transistor TFT and a transparent pixel electrode ITO1 are formed on the lower transparent glass substrate SUB1 side with respect to the liquid crystal layer LC, and a color filter FIL and a light-shielding film are provided on the upper transparent glass substrate SUB2 side. A black matrix pattern BM is formed. Silicon oxide films SIO formed by dipping or the like are provided on both surfaces of the transparent glass substrates SUB1 and SUB2.

On the inner surface (liquid crystal LC side) of the upper transparent glass substrate SUB2, a light shielding film BM and a color filter FI are provided.
L, protective film PSV2, common transparent pixel electrode ITO2 (CO
M) and the upper alignment film ORI2 are sequentially stacked.

<< Outline of Matrix Periphery >> FIG. 5 is a plan view of a main part around a matrix (AR) of a display panel PNL including upper and lower glass substrates SUB1 and SUB2, and FIG. 7 is a diagram showing an enlarged plane near the seal portion SL corresponding to the upper left corner of the panel in FIGS. 5 and 6. Further, FIG. 8 is a diagram showing a cross section taken along a cutting line 8a-8a in FIG. 7 on the left side and a cross section near the external connection terminal DTM to which the video signal drive circuit is to be connected on the right side with the cross section of FIG. 3 as the center. is there. Similarly, FIG. 9 is a diagram showing a cross section near the external connection terminal GTM to which the scanning circuit is to be connected on the left side and a cross section near the seal portion where there is no external connection terminal on the right side.

[0021] Any For this panel In the manufacture of, if small size divided from simultaneously processing a plurality fraction of the device in one glass substrate for increased throughput, manufacturing facilities if large size shared In each type of product, a standardized glass substrate is processed, and then the size is reduced to a size suitable for each product. In each case, the glass is cut after going through one step. 5 to 7 show an example of the latter case. In both of FIGS. 5 and 6, the upper and lower substrates SUB1 and SUB are shown.
2 shows the state after cutting, and FIG. 7 shows the state before cutting. LN is the edge of both substrates before cutting, and CT1 and CT2 are the substrate SU.
The positions where B1 and SUB2 should be cut are shown. In either case, in the completed state, the external connection terminal groups Tg, Td (subscripts omitted)
Are present (on the upper and lower sides and the left side in the figure), the size of the upper substrate SUB2 is such that the lower substrate SUB2 is exposed.
It is restricted to the inside of 1. The terminal groups Tg and Td are a tape carrier package TC in which a scanning circuit connection terminal GTM, a video signal circuit connection terminal DTM, and their lead-out wiring portions, which will be described later, are mounted on an integrated circuit chip CHI.
A plurality of Ps (FIGS. 18 and 19) are collectively named. The lead wiring from the matrix portion of each group to the external connection terminal portion is inclined toward both ends. This is due to the arrangement pitch of the package TCP and the connection terminal pitch of each package TCP on the display panel PN.
This is for matching the L terminals DTM and GTM.

A liquid crystal LC is provided between the transparent glass substrates SUB1 and SUB2 along the edge thereof except for the liquid crystal sealing port INJ.
A seal pattern SL is formed so as to seal the. The sealing material is made of epoxy resin, for example. The common transparent pixel electrode ITO2 on the upper transparent glass substrate SUB2 side is connected to at least one of the lead wirings INT formed on the lower transparent glass substrate SUB1 side by the silver paste material AGP at four corners of the panel in this embodiment. ing. The lead wiring INT is formed in the same manufacturing process as a gate terminal GTM and a drain terminal DTM described later.

The orientation films ORI1 and ORI2, the transparent pixel electrode ITO1 and the common transparent pixel electrode ITO2, and their respective layers are formed inside the seal pattern SL. Polarizing plate P
OL1 and POL2 are lower transparent glass substrates SUB, respectively.
1. Formed on the outer surface of the upper transparent glass substrate SUB2. The liquid crystal LC is enclosed in a region partitioned by a seal pattern SL between a lower alignment film ORI1 and an upper alignment film ORI2 that set the orientation of liquid crystal molecules. The lower alignment film ORI1 is a protective film P on the lower transparent glass substrate SUB1 side.
It is formed on top of SV1.

In this liquid crystal display device, various layers are separately stacked on the lower transparent glass substrate SUB1 side and the upper transparent glass substrate SUB2 side, and the seal pattern SL is provided on the substrate SUB2.
Formed on the side, the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2 are overlapped, the liquid crystal LC is injected from the opening INJ of the sealing material SL, and the injection port INJ is sealed with epoxy resin or the like to form the upper and lower substrates. It is assembled by cutting.

<< Thin Film Transistor TFT >> Next, referring to FIG.
Returning to FIG. 3, the configuration on the TFT substrate SUB1 side will be described in detail.

The thin film transistor TFT has a gate electrode G
When a positive bias is applied to T, the channel resistance between the source and the drain decreases, and when the bias is zero, the channel resistance increases.

A plurality of (two) thin film transistors TFT1 and TFT2 are redundantly provided in each pixel. Each of the thin film transistors TFT1 and TFT2 has substantially the same size (channel length and channel width are the same), and has a gate electrode GT, a gate insulating film GI, and an i-type (intrinsic,
intrinsic, conductivity type determination impurities are not doped)
It has an i-type semiconductor layer AS made of amorphous silicon (Si), a pair of source electrodes SD1 and a drain electrode SD2. It should be understood that the source and drain are originally determined by the bias polarity between them, and the polarity is inverted during operation in the circuit of this liquid crystal display device, so it should be understood that the source and drain are switched during operation. However, in the following description, for convenience, one is fixed as the source and the other is fixed as the drain.

<< Gate Electrode GT >> The gate electrode GT is formed in a shape protruding vertically from the scanning signal line GL (branched into a T shape). The gate electrode GT projects so as to extend beyond the respective active regions of the thin film transistors TFT1 and TFT2. Thin film transistor TFT
The gate electrodes GT of the TFT 1 and the TFT 2 are integrally formed (as a common gate electrode) and are formed continuously with the scanning signal line GL. In this example, the gate electrode GT is formed of the single-layer second conductive film g2. An aluminum (Al) film formed by sputtering, for example, is used as the second conductive film g2, and an Al anodic oxide film AOF is provided thereon.

The gate electrode GT is formed larger than the i-type semiconductor layer AS so as to completely cover the i-type semiconductor layer AS (when viewed from below), and is devised so that the i-type semiconductor layer AS is not exposed to external light or backlight light. .

<< Scanning Signal Line GL >> The scanning signal line GL is the second
It is composed of a conductive film g2. The second conductive film g2 of the scanning signal line GL is formed in the same manufacturing process as the second conductive film g2 of the gate electrode GT, and is integrally formed. Also, an Al anodic oxide film AOF is provided on the scanning signal line GL.

<< Insulating Film GI >> The insulating film GI is used as a gate insulating film for applying an electric field to the semiconductor layer AS in the thin film transistors TFT1 and TFT2 together with the gate electrode GT. The insulating film GI is formed on the gate electrode GT and the scanning signal line GL. As the insulating film GI, for example, a silicon nitride film formed by plasma CVD is selected and is formed to a thickness of 1200 to 2700Å (in this embodiment, about 2000Å). As shown in FIG. 7, the gate insulating film GI is formed so as to surround the entire matrix portion AR, and the peripheral portion is removed so as to expose the external connection terminals DTM and GTM. The insulating film GI is a scanning signal line G
It also contributes to the electrical insulation between L and the video signal line DL.

<< i-type semiconductor layer AS >> i-type semiconductor layer AS
In this example, each of the thin film transistors TFT1 and TFT2 is formed as an independent island, and is made of amorphous silicon and has a thickness of 200 to 2200Å (2 in this example.
The film thickness is about 000Å). The layer d0 is a phosphorus (P) -doped N (+)-type amorphous silicon semiconductor layer for ohmic contact, the i-type semiconductor layer AS exists on the lower side, and the conductive layer d2 (d3) exists on the upper side. It is left only where you do.

The i-type semiconductor layer AS is also provided between both the intersections (crossover portions) of the scanning signal lines GL and the video signal lines DL. The i-type semiconductor layer AS at the intersection reduces the short circuit between the scanning signal line GL and the video signal line DL at the intersection.

<< Transparent Pixel Electrode ITO1 >> Transparent Pixel Electrode I
TO1 constitutes one of the pixel electrodes of the liquid crystal display section.

The transparent pixel electrode ITO1 is the source electrode SD1 of the thin film transistor TFT1 and the thin film transistor T.
It is connected to both source electrodes SD1 of FT2. Therefore, even if a defect occurs in one of the thin film transistors TFT1 and TFT2, if the defect causes a side effect, an appropriate portion is cut by laser light or the like, and if not, the other thin film transistor operates normally. You can leave it alone because it does. The transparent pixel electrode ITO1 is composed of the first conductive film d1.
Is a transparent conductive film (Indium-Tin) formed by sputtering.
-Oxide ITO: Nesa film), 1000-200
With a thickness of 0Å (in this embodiment, a film thickness of about 1400Å)
It is formed.

<< Source Electrode SD1, Drain Electrode SD
2 >> Each of the source electrode SD1 and the drain electrode SD2 is composed of a second conductive film d2 in contact with the N (+) type semiconductor layer d0 and a third conductive film d3 formed thereon.

The second conductive film d2 is a chromium (Cr) film formed by sputtering and is formed to a thickness of 500 to 1000 Å (in this embodiment, about 600 Å). If the Cr film is formed thicker, the stress increases.
It is formed within a range not exceeding the film thickness of 0Å. Cr film is N
It is used for the purpose of improving adhesion to the (+) type semiconductor layer d0 and preventing Al of the third conductive film d3 from diffusing into the N (+) type semiconductor layer d0 (so-called barrier layer). Second
As the conductive film d2, in addition to the Cr film, refractory metal (Mo, T
i, Ta, W) film, refractory metal silicide (MoS
An i ₂ , TiSi ₂ , TaSi ₂ , WSi ₂ ) film may be used.

The third conductive film d3 is formed by sputtering Al to a thickness of 3000 to 5000Å (400 in this embodiment).
0 Å) formed. The Al film has less stress than the Cr film and can be formed to have a large film thickness, and the source electrode SD1, the drain electrode SD2 and the video signal line DL can be formed.
Of the gate electrode GT and the i-type semiconductor layer AS are ensured (step coverage is improved).

After patterning the second conductive film d2 and the third conductive film d3 with the same mask pattern, an N (+) type film is formed by using the same mask or by using the second conductive film d2 and the third conductive film d3 as a mask. The semiconductor layer d0 is removed. That is,
The N (+) type semiconductor layer d0 remaining on the i type semiconductor layer AS
The portions other than the second conductive film d2 and the third conductive film d3 are removed by self-alignment. At this time, the N (+) type semiconductor layer d
Since 0 is etched so that the entire thickness thereof is removed, the surface portion of the i-type semiconductor layer AS is also slightly etched, but the degree may be controlled by the etching time.

<Video Signal Line DL> The video signal line DL is composed of a second conductive film d2 and a third conductive film d3 in the same layer as the source electrode SD1 and the drain electrode SD2.

<< Protective Film PSV1 >> Thin Film Transistor TF
A protective film PSV1 is provided on the T and the transparent pixel electrode ITO1. The protective film PSV1 is formed mainly for protecting the thin film transistor TFT from moisture and the like,
Use one with high transparency and good moisture resistance. The protective film PSV1 is formed of, for example, a silicon oxide film or a silicon nitride film formed by a plasma CVD apparatus, and has a thickness of 1 μm.
It is formed with a film thickness of about m.

As shown in FIG. 7, the protective film PSV1 is formed so as to surround the entire matrix portion AR, the peripheral portion is removed so as to expose the external connection terminals DTM and GTM, and the common electrode of the upper substrate side SUB2. COM to the lower substrate SUB
Silver paste A on the lead wire INT for connecting the external connection terminal 1
The part connected by GP is also removed. Protective film PSV1
Regarding the thickness relationship between the gate insulating film GI and the gate insulating film GI, the former is made thicker in consideration of the protection effect, and the latter is made thin in the transconductance gm of the transistor. Therefore, as shown in FIG.
The protective film PSV1 having a high protective effect is formed so as to be larger than the gate insulating film GI so as to protect the peripheral portion over as wide a range as possible.

<< Light-shielding film BM >> Upper transparent glass substrate SUB
On the second side, external light or backlight is exposed to the i-type semiconductor layer A.
A light shielding film BM is provided so as not to enter S. Figure 2
The closed polygonal contour line of the light-shielding film BM shown in (3) indicates an opening inside which the light-shielding film BM is not formed. The light-shielding film BM is formed of, for example, an aluminum film or a chromium film having a high light-shielding property, and in this embodiment, the chromium film is formed by sputtering to a thickness of about 1300Å.

Therefore, the thin film transistors TFT1 and TF
The i-type semiconductor layer AS of T2 is sandwiched by the upper and lower light-shielding films BM and the large gate electrode GT,
External natural light or backlight does not hit. The light-shielding film BM is formed in a lattice shape around each pixel (so-called black matrix), and the effective display area of one pixel is partitioned by this lattice. Therefore, the outline of each pixel is the light-shielding film BM.
Improves clarity and contrast. That is, the light blocking film BM has two functions of blocking the i-type semiconductor layer AS and serving as a black matrix.

The edge portion (lower right portion in FIG. 2) on the root side of the transparent pixel electrode ITO1 in the rubbing direction is also shielded from light by the light-shielding film BM. Therefore, even if a domain occurs in the above-mentioned portion, the domain cannot be seen. The display characteristics do not deteriorate.

As shown in FIG. 6, the light-shielding film BM is also formed in a frame shape in the peripheral portion, and its pattern is formed continuously with the pattern of the matrix portion shown in FIG. There is. As shown in FIGS. 6 to 9, the light-shielding film BM in the peripheral portion is extended to the outside of the seal portion SL to prevent leak light such as reflected light caused by a mounting machine such as a personal computer from entering the matrix portion. . On the other hand, the light-shielding film BM is retained inside about 0.3 to 1.0 mm from the edge of the substrate SUB2, and is formed so as to avoid the cut region of the substrate SUB2.

<< Color Filter FIL >> The color filter FIL is formed in a stripe shape by repeating red, green and blue at positions facing the pixels. The color filter FIL is formed to have a large size so as to cover all of the transparent pixel electrode ITO1, and the light shielding film BM overlaps with the edge portions of the color filter FIL and the transparent pixel electrode ITO1.
It is formed inside the peripheral portion of TO1.

The color filter FIL can be formed as follows. First, a dyeing base material such as an acrylic resin is formed on the surface of the upper transparent glass substrate SUB2, and the dyeing base material other than the red filter forming region is removed by a photolithography technique. After that, the dyed substrate is dyed with a red dye and a fixing process is performed to form a red filter R. Next, the green filter G and the blue filter B are sequentially formed by performing the same process.

<< Protective Film PSV2 >> The protective film PSV2 is provided to prevent the dye of the color filter FIL from leaking to the liquid crystal LC. The protective film PSV2 is formed of a transparent resin material such as acrylic resin or epoxy resin.

<< Common Transparent Pixel Electrode ITO2 >> The common transparent pixel electrode ITO2 faces the transparent pixel electrode ITO1 provided for each pixel on the lower transparent glass substrate SUB1 side, and the optical state of the liquid crystal LC is the pixel electrode ITO1. And the common transparent pixel electrode ITO2 change in response to a potential difference (electric field). A common voltage Vcom is applied to the common transparent pixel electrode ITO2. In this embodiment, the common voltage Vcom is the minimum level drive voltage Vdmin and the maximum level drive voltage V applied to the video signal line DL.
Although it is set to an intermediate DC potential with respect to dmax, an AC voltage may be applied if it is desired to reduce the power supply voltage of the integrated circuit used in the video signal drive circuit to about half. For the planar shape of the common transparent pixel electrode ITO2, see FIGS. 6 and 7.

<< Structure of Storage Capacitance Element Cadd >> The transparent pixel electrode ITO1 is formed so as to overlap the adjacent scanning signal line GL at the end opposite to the end connected to the thin film transistor TFT. In this superposition, as is clear from FIG. 4, the transparent pixel electrode ITO1 is used as one electrode PL2 and the adjacent scanning signal line GL is used as the other electrode PL.
A holding capacitance element (electrostatic capacitance element) Cadd which is 1 is configured. The dielectric film of the storage capacitor Cadd is an insulating film G used as a gate insulating film of the thin film transistor TFT.
I and the anodic oxide film AOF.

The storage capacitor element Cadd is formed in the portion where the width of the second conductive film g2 of the scanning signal line GL is widened. The second conductive film g2 at the portion intersecting the video signal line DL is thinned in order to reduce the probability of short circuit with the video signal line DL.

Even if the transparent pixel electrode ITO1 is broken at the step portion of the electrode PL1 of the storage capacitor Cadd, the second conductive film d2 and the third conductive film d2 formed so as to cross the step.
The defect is compensated by the island region formed of the conductive film d3.

<< Gate Terminal Section >> FIG. 10 is a diagram showing a connection structure from the scanning signal line GL of the display matrix to its external connection terminal GTM. (A) is a plane and (B) is B of (A). -B shows a cross section taken along the line B. It should be noted that the figure corresponds to the lower part of FIG. 7, and the diagonal wiring portions are shown in a straight line for convenience.

AO is a mask pattern for photographic processing, in other words, a photoresist pattern for selective anodic oxidation. Therefore, this photoresist is removed after anodization,
The pattern AO shown in the figure does not remain as a finished product, but since the oxide film AOF is selectively formed on the gate line GL as shown in the cross-sectional view, its locus remains. In the plan view, with respect to the photoresist boundary line AO, the left side is a region covered with the resist and not anodized, and the right side is a region exposed from the resist and anodized. Anodized A
The oxide Al ₂ O ₃ film AOF is formed on the surface of the L layer g2, and the volume of the conductive portion therebelow is reduced. Of course, the anodic oxidation is performed by setting an appropriate time and voltage so that the conductive portion remains. The mask pattern AO does not intersect with the scanning line GL by a single straight line, but is bent in a crank shape and intersects.

In the figure, the AL layer g2 is hatched for easy understanding, but the region which is not anodized is patterned in a comb shape. This is because whiskers are generated on the surface when the width of the Al layer is wide. Therefore, by narrowing the width of each one and arranging a plurality of them in parallel, whiskers can be prevented and wire breakage can be prevented. The aim is to minimize the probability of and the sacrifice of conductivity. Therefore, in this example, the portion corresponding to the base of the comb is also displaced along the mask AO.

The gate terminal GTM has a Cr layer g1 which has a good adhesiveness to the silicon oxide SIO layer and has a higher electric contact resistance than Al or the like.
Further, the surface thereof is protected and is composed of a transparent conductive layer d1 of the same level (same layer, simultaneously formed) as the pixel electrode ITO1.
In addition, the conductive layers d2 and d3 formed on the gate insulating film GI and on the side surfaces thereof have their regions so that the conductive layers g2 and g1 are not etched together due to pinholes or the like during the etching of the conductive layers d3 and d2. It remains as a result of being covered with photoresist. In addition, the ITO layer d1 which extends over the gate insulating film GI and extends rightward is one in which the same measures are taken more thoroughly.

In the plan view, the gate insulating film GI is formed on the right side of the boundary line and the protective film PSV1 is formed on the right side of the boundary line, and the terminal portion GTM located at the left end.
Are exposed from them to allow electrical contact with external circuitry. In the figure, only one pair of the gate line GL and the gate terminal is shown, but in reality, a plurality of such pairs are arranged vertically as shown in FIG. 7 to form the terminal group Tg (FIGS. 6 and 7). In the manufacturing process, the left end of the gate terminal is extended beyond the cutting region CT1 of the substrate to form the wiring SH.
shorted by g. Such a short-circuit line SHg in the manufacturing process is useful for supplying power during anodization and preventing electrostatic breakdown during rubbing of the alignment film ORI1.

<< Drain Terminal DTM >> FIG. 11 is a diagram showing the connection from the video signal line DL to the external connection terminal DTM, (A) shows the plane, and (B) shows B of (A).
-B shows a cross section taken along the line B. 7 corresponds to the vicinity of the upper right of FIG. 7, and although the orientation of the drawing is changed for convenience, the right end direction corresponds to the upper end (or lower end) of the substrate SUB1.

TSTd is an inspection terminal, which is not connected to an external circuit, but is wider than the wiring portion so that a probe needle or the like can come into contact therewith. Similarly, the drain terminal D
The width of the TM is also wider than that of the wiring portion so that the TM can be connected to an external circuit. The inspection terminals TSTd and the external connection drain terminals DTM are alternately arranged in a zigzag pattern in the vertical direction, and the inspection terminals TSTd terminate without reaching the end portion of the substrate SUB1 as shown in the figure, but the drain terminal DTM.
7 further extend beyond the cutting line CT1 of the substrate SUB1 to form a terminal group Td (subscripts omitted) as shown in FIG. 7, all of which are interconnected to each other to prevent electrostatic breakdown during the manufacturing process.
Shorted by Hd. The drain connection terminal is connected to the opposite side of the matrix of the video signal lines DL in which the inspection terminals TSTd are present, and conversely the inspection terminal is placed on the opposite side of the matrix of the video signal lines DL in which the drain connection terminals DTM are present. Are connected.

The drain connection terminal DTM has the Cr layer g1 and the ITO layer d1 for the same reason as the above-mentioned gate terminal GTM.
Is formed of two layers, and is connected to the video signal line DL at a portion where the gate insulating film GI is removed. The semiconductor layer AS formed on the end portion of the gate insulating film GI is for etching the edge of the gate insulating film GI in a tapered shape. The protective film PSV1 is, of course, removed on the terminal DTM to connect to an external circuit. AO is the anodizing mask described above, and its boundary line is formed so as to largely surround the entire matrix. In the figure, the left side of the boundary line is covered with the mask, but the layer g2 is covered in the part not covered in this figure. This pattern is not directly relevant as it does not exist.

The lead wiring from the matrix portion to the drain terminal portion DTM is, as shown in FIG. 8C, a video signal line DL immediately above the layers d1 and g1 at the same level as the drain terminal portion DTM. Although the layers d2 and d3 of the same level are laminated part way up to the middle of the seal pattern SL, this minimizes the probability of disconnection and facilitates electrical contact.
The purpose is to protect the l layer d3 as much as possible with the protective film PSV1 and the seal pattern SL.

<< Equivalent Circuit of Entire Display Device >> FIG. 12 shows a connection diagram of an equivalent circuit of the display matrix portion and its peripheral circuits.
Although the figure is a circuit diagram, it is drawn corresponding to the actual geometrical arrangement. AR is a matrix array in which a plurality of pixels are two-dimensionally arranged.

In the figure, X means a video signal line DL, and subscripts G, B and R are added corresponding to green, blue and red pixels, respectively. Y represents the scanning signal line GL, and subscripts 1, 2, 3, ..., End are added according to the order of scanning timing.

The video signal lines X (subscripts omitted) are alternately connected to the upper (or odd) video signal drive circuit He and the lower (or even) video signal drive circuit Ho.

The scanning signal line Y (subscript omitted) is connected to the vertical scanning circuit V.

The SUP is a TFT liquid crystal display device which displays information for a CRT (cathode ray tube) from a power supply circuit or a host (upper processing unit) for obtaining a plurality of divided and stabilized voltage sources from one voltage source. It is a circuit including a circuit for exchanging information for use.

<< Function of Storage Capacitance Element Cadd >> The storage capacity element Cadd functions to reduce the influence of the gate potential change ΔVg on the midpoint potential (pixel electrode potential) Vlc when the thin film transistor TFT switches. This situation is expressed by the following equation.

ΔVlc = {Cgs / (Cgs + Cadd + Cpix)} × ΔVg where Cgs is the gate electrode G of the thin film transistor TFT
Parasitic capacitance formed between T and source electrode SD1, C
pix is a capacitance formed between the transparent pixel electrode ITO1 (PIX) and the common transparent pixel electrode ITO2 (COM), ΔV
lc represents a change amount of the pixel electrode potential due to ΔVg. This variation ΔVlc causes a direct current component applied to the liquid crystal LC, but the value can be reduced as the holding capacitance Cadd is increased. Further, the storage capacitor element Cadd also has the function of prolonging the discharge time, and thus the thin film transistor TFT
Accumulates video information for a long time after is turned off. The reduction of the direct current component applied to the liquid crystal LC improves the life of the liquid crystal LC,
It is possible to reduce so-called burn-in in which the previous image remains when the liquid crystal display screen is switched.

As described above, since the gate electrode GT is made large so as to completely cover the i-type semiconductor layer AS, the overlap area with the source electrode SD1 and the drain electrode SD2 is increased, so that the parasitic capacitance Cgs is increased. The reverse effect is that the midpoint potential Vlc is easily affected by the gate (scanning) signal Vg. However, this demerit can be eliminated by providing the storage capacitor element Cadd.

The storage capacitance of the storage capacitance element Cadd is 4 to 8 times (4.C
pix <Cadd <8 · Cpix), 8 to 3 for parasitic capacitance Cgs
Set to a value about twice (8 · Cgs <Cadd <32 · Cgs).

The scanning signal line GL (Y ₀ ) in the first stage, which is used only as the storage capacitor electrode line, is the common transparent pixel electrode ITO2.
Set to the same potential as (Vcom). In the example of FIG. 7, the scanning signal line at the first stage is short-circuited to the common electrode COM through the terminal GT0, the lead wire INT, the terminal DT0 and the external wiring. Alternatively, the storage capacitor electrode line Y ₀ in the first stage is the scanning signal line Ye in the last stage.
It may be connected to nd, connected to a DC potential point (AC ground point) other than Vcom, or connected to receive one extra scanning pulse Y ₀ from the vertical scanning circuit V.

<< Manufacturing Method >> Next, a manufacturing method of the substrate SUB1 side of the above-described liquid crystal display device will be described with reference to FIGS.
Will be described with reference to. In the figure, the letters in the center are abbreviations of process names, the left side shows the pixel portion shown in FIG. 3, and the right side shows the processing flow as seen in the sectional shape near the gate terminal shown in FIG. Except for the step D, steps A to I are divided corresponding to each photographic process, and all the cross-sectional views of each process show the stage after the photo process is finished and the photoresist is removed. In this description, the photographic processing means a series of operations from the application of the photoresist to the selective exposure using the mask to the development thereof, and the repetitive description will be omitted. A description will be given below according to the divided steps.

Step A, FIG. 13 After forming a silicon oxide film SIO on both surfaces of a lower transparent glass substrate SUB1 made of 7059 glass (trade name) by dipping, baking is performed at 500 ° C. for 60 minutes. The film thickness is 1100Å on the lower transparent glass substrate SUB1.
The first conductive film g1 made of chromium is provided by sputtering, and after the photographic processing, the first conductive film g1 is selectively etched with a cerium ammonium nitrate solution as an etching solution. Thereby, the gate terminal GTM, the drain terminal DTM, the anodized bus line SHg connecting the gate terminal GTM, the bus line SHd shorting the drain terminal DTM, and the anodized pad (not shown) connected to the anodized bus line SHg. To form.

Step B, FIG. 13 Al-Pd, Al-Si, Al-S having a film thickness of 2800Å
The second conductive film g2 made of i-Ti, Al-Si-Cu, or the like
Are provided by sputtering. After the photographic processing, the second conductive film g2 is selectively etched with a mixed acid solution of phosphoric acid, nitric acid and glacial acetic acid.

Step C, FIG. 13 After photographic processing (after forming the above-mentioned anodic oxidation mask AO), 3
Substrate SUB1 is immersed in an anodizing solution consisting of a solution prepared by diluting 1% of tartaric acid with ammonia to pH 6.25 ± 0.05 with ethylene glycol solution, and the formation current density is 0.5 mA / cm. ² so as to adjust (constant current Kasei). Next, anodic oxidation is performed until the formation voltage 125 V required to obtain a predetermined Al ₂ O ₃ film thickness is reached. After that, it is desirable to hold this state for several tens of minutes (constant voltage formation). This is important for obtaining a uniform Al ₂ O ₃ film. Thereby, the conductive film g2 is anodized,
An anodic oxide film AOF having a film thickness of 1800Å is formed on scanning signal line GL, gate electrode GT and electrode PL1.

Step D, FIG. 14 Ammonia gas, silane gas, and nitrogen gas are introduced into the plasma CVD apparatus to form a nitrided Si film having a film thickness of 2000 Å, and silane gas and hydrogen gas are introduced into the plasma CVD apparatus. After forming an i-type amorphous Si film having a thickness of 2000Å, hydrogen gas and phosphine gas are introduced into the plasma CVD apparatus to form an N (+)-type amorphous Si film having a film thickness of 300Å.

Step E, FIG. 14 After photo processing, SF ₆ and CC are used as dry etching gas.
Use l ₄ N (+) type amorphous Si film, i-type amorphous Si
The island of the i-type semiconductor layer AS is formed by selectively etching the film.

Step F, FIG. 14 After the photographic process, SF ₆ is used as a dry etching gas to selectively etch the Si nitride film.

Step G, FIG. 15 A first conductive film d1 made of an ITO film having a film thickness of 1400Å is provided by sputtering. After the photographic processing, the first conductive film d1 is selectively etched with a mixed acid solution of hydrochloric acid and nitric acid as an etching solution, whereby the uppermost layers of the gate terminal GTM and the drain terminal DTM and the transparent pixel electrode ITO1.
To form.

Step H, FIG. 15: A second conductive film d2 made of Cr and having a film thickness of 600 Å is provided by sputtering.
Pd, Al-Si, Al-Si-Ti, Al-Si-C
A third conductive film d3 made of u or the like is provided by sputtering. After the photographic processing, the third conductive film d3 is etched with the same liquid as the process B, and the second conductive film d2 is etched with the same liquid as the process A to form the video signal line DL, the source electrode SD1, and the drain electrode SD2. To do. Next, by introducing CCl ₄ and SF ₆ into the dry etching apparatus, N (+) type amorphous S
By etching the i film, the N (+) type semiconductor layer d0 between the source and the drain is selectively removed.

Step I, FIG. 15 Ammonia gas, silane gas, and nitrogen gas are introduced into the plasma CVD apparatus to form a Si nitride film having a thickness of 1 μm. After the photo processing, the protective film PSV1 is formed by selectively etching the Si nitride film by a photo-etching technique using SF ₆ as a dry etching gas.

<< Overall Structure of Liquid Crystal Display Module >> FIG.
[Fig. 3] is an exploded perspective view showing each component of the liquid crystal display module MDL.

SHD is a frame-shaped shield case (metal frame) made of a metal plate, LCW display window, PNL is a liquid crystal display panel, SPB is a light diffusion plate, MFR is an intermediate frame, BL is a backlight, and BLS is a backlight. The support and the LCA are the lower case, and the modules MDL are assembled by stacking the respective members in a vertical arrangement relationship as shown in the figure.

The module MDL is a shield case SH.
The whole is fixed by the claw CL and the hook FK provided on D.

The intermediate frame MFR is formed in a frame shape so as to have an opening corresponding to the display window LCW, and the frame portion has a diffusion plate SPB, a backlight support BLS, and various circuit components in accordance with the shapes and thicknesses thereof. There are irregularities and openings for heat dissipation.

The lower case LCA also serves as a reflector for backlight light, and a reflection mountain RM is formed corresponding to the fluorescent tube BL so as to reflect light efficiently.

<< Display Panel PNL and Drive Circuit Board PCB
1 >> FIG. 17 is a top view showing a state in which the video signal drive circuits He and Ho and the vertical scanning circuit V are connected to the display panel PNL shown in FIG.

CHI is a driving IC chip for driving the display panel PNL (the lower three are driving ICs on the vertical scanning circuit side)
Chips, 6 each on the left and right are drive I on the video signal drive circuit side
C chip). TCP is a tape carrier package in which a driving IC chip CHI is mounted by a tape automated bonding method (TAB), as will be described later with reference to FIGS. 18 and 19, and PCB1 is a drive in which the TCP, the capacitor CDS and the like are mounted. It is divided into three parts on the circuit board. FGP is a frame ground pad,
A spring-like fragment FG provided by cutting into the shield case SHD is soldered. FC is a flat cable that electrically connects the lower drive circuit board PCB1 and the left drive circuit board PCB1, and the lower drive circuit board PCB1 and the right drive circuit board PCB1. As the flat cable FC, as shown in the figure, a plurality of lead wires (phosphor bronze material plated with Sn) sandwiched between a striped polyethylene layer and a polyvinyl alcohol layer are used.

<< Video Signal Drive Circuit >> FIG. 18 is a schematic circuit diagram of the drive IC chip CHI which constitutes the video signal drive circuit.

In the figure, in order to extend the life of the liquid crystal, the video signal applied to the liquid crystal display panel PNL is converted into alternating current, and V (1), V (2), V (3), V ( E
The wirings 10a, 10b, 10c to which the voltage of E) is applied,
There is 10d. Here, V (1) is positive, V (2) is negative,
V (3) is positive and V (EE) is negative.

The wirings 10a, 10b, 10c,
From 10d, the above voltages V (1), V (2), V
(3), V (EE) is output transistor 20a, 20
It is adapted to be inputted to one of video signal input terminals of a liquid crystal display substrate (not shown) via b, 20c and 20d.

Output transistors 20a, 20b, 20
c and 20d are MIS transistors, and the control voltage is applied to the respective gate electrodes of the output from the shift register 30 through the decoders 40a, 40b, 40c and 40d.

Note that the above-described structure has the same structure in the portion connected to the other video signal input terminal of the liquid crystal display substrate.

<< Output Transistor >> FIG. 1 is a configuration diagram showing one of the output transistors 20a, 20b, 20c, and 20d. FIG. 1A is a plan view and FIG. It is sectional drawing in the aa line.

In each drawing, there is a quartz substrate 400, and a semiconductor layer 401 made of polysilicon is formed on the main surface of the quartz substrate 400. This semiconductor layer 401
The pattern is substantially rectangular, and the grooves 410 are formed in parallel along the longitudinal direction. The groove 410 is formed by exposing the main surface of the quartz substrate 400, and its long side is formed parallel to the short side of the semiconductor layer 401.

Then, on the main surface of the quartz substrate 400,
A silicon nitride film 405 serving as a gate insulating film is formed so as to cover the semiconductor layer 401 and the groove 410 formed in the semiconductor layer 401.

Further, a gate electrode 402 made of a polysilicon layer is formed on the surface of the silicon nitride film 405, and the gate electrode 402 is positioned so as to straddle each of the trenches 410. After forming the polysilicon layer forming the gate electrode 402,
For example, by doping an n-type impurity, the polysilicon layer is made conductive, and a source region and a drain region are formed in the semiconductor layer 401.

Further, on both sides of the gate electrode 402,
A source electrode 405 and a drain electrode 404, which are positioned parallel to the gate electrode 402, are formed. The source electrode 405 and the drain electrode 404 are respectively formed in the source region through through holes provided in the silicon nitride film 405. , And to the drain region.

In the MIS transistor configured as in this example, the channel layer formed between the source region and the drain region is formed along the channel width by forming the groove 410 in the semiconductor layer 401. It will be divided into a plurality of parts.

By doing so, the number of sides corresponding to the channel length in each channel layer increases, and the ON current increases.

That is, O in the MIS transistor
It was found that the N current concentrates on the side portion corresponding to the channel length of the channel layer, and it is preferable to increase the number of side portions corresponding to the channel length as described above, rather than increasing the channel width. Proved to be effective.

This means that a plurality of channel layers can be formed without increasing the occupied area of the MIS transistor, and the occupied area of the channel layer is inevitably reduced, so that the leak current at the time of OFF also occurs. It will be possible to make it smaller.

FIG. 22 is a graph in which the characteristics of the above-mentioned MIS transistor are experimentally examined. The horizontal axis of the graph shows the gate voltage, and the vertical axis shows the drain current. In the figure, the characteristic A is the MIS transistor of this embodiment, and the characteristic B is the conventional MIS transistor.

In each case, the channel length L is 6 μm,
In the case of this embodiment, the channel width is divided (10 divisions).
While each channel width is 3 μm, the conventional channel width is 50 μm as an undivided one.

<< TCP Connection Structure >> FIG. 18 shows a sectional structure of a tape carrier package TCP in which an integrated circuit chip CHI, which constitutes the scanning signal driving circuit V and the video signal driving circuits He and Ho, is mounted on a flexible wiring substrate. FIG. 19 is a cross-sectional view of essential parts showing a state in which it is connected to the liquid crystal display panel, in this example, the video signal circuit terminal DTM.

In the figure, TTB is an input terminal / wiring portion of the integrated circuit CHI, and TTM is an output terminal / wiring portion of the integrated circuit CHI, which is made of, for example, Cu and has inner ends (commonly called inner leads). ) Is the integrated circuit C
The HI bonding pad PAD is connected by a so-called face-down bonding method. Terminals TTB, T
Outer end portions (commonly called outer leads) of TM correspond to the input and output of the semiconductor integrated circuit chip CHI,
CRT / TFT conversion circuit / power supply circuit S by soldering, etc.
A liquid crystal display panel P is formed on the UP by an anisotropic conductive film ACF.
Connected to NL. The package TCP has a protective film PS whose front end exposes the connection terminal DTM on the panel PNL side.
Since it is connected to the panel so as to cover V1, and therefore the external connection terminal DTM (GTM) is covered by at least one of the protective film PSV1 and the package TCP, it is strong against electric contact.

BF1 is a base film made of polyimide or the like, and SRS is a solder resist film for masking the solder so that it will not stick to an unnecessary place during soldering. The gap between the upper and lower glass substrates outside the seal pattern SL is protected by an epoxy resin EPX or the like after cleaning, and a silicone resin SIL is further filled between the package TCP and the upper substrate SUB2 for multiple protection.

<< Drive Circuit Board PCB2 >> Intermediate Frame M
As shown in FIG. 31, the drive circuit board PCB2 of the liquid crystal display unit LCD which is held / stored in the FR is L-shaped, and has electronic parts such as ICs, capacitors and resistors mounted thereon. This drive circuit board PCB2 is provided with a power supply circuit for obtaining a plurality of divided and stabilized voltage sources from one voltage source, and information for a CRT (cathode ray tube) from a host (upper processing unit). A circuit SUP including a circuit for converting into information for a TFT liquid crystal display device is mounted. CJ is a connector connecting portion to which a connector (not shown) connected to the outside is connected. The drive circuit board PCB2 and the inverter circuit board PCB3 are electrically connected by a backlight cable through a connector hole provided in the intermediate frame MFR.

Drive circuit board PCB1 and drive circuit board PC
B2 is electrically connected by a foldable flat cable FC. When assembled, drive circuit board PCB
2 is stacked on the back side of the drive circuit board PCB1 by bending the flat cable FC by 180 ° and fitted into a predetermined recess of the intermediate frame MFR.

In the above-mentioned embodiment, the semiconductor layer is divided into a plurality along the channel width, but the invention is not limited to this, and the gate electrode is divided into a plurality along the channel width. It goes without saying that it is good. In short, it suffices that the channel layer be divided into a plurality along the channel width.

Further, although the above-described embodiment has been described with respect to the MIS transistor applied to the video signal drive circuit, the present invention is not limited to this and may be applied to the vertical scanning circuit. Further, a thin film transistor TFT built in the liquid crystal display panel PNL
It goes without saying that it can also be applied to.

Although the MIS transistor applied to the liquid crystal display device has been described in the above-mentioned embodiments, the invention is not necessarily limited to the one applied to the liquid crystal display device.

[0114]

As is apparent from the above description,
According to the MIS transistor of the present invention, it is possible to improve the ON characteristics and prevent the generation of a leak current at the time of OFF without increasing the occupied area.

[Brief description of drawings]

1A and 1B are configuration diagrams showing an embodiment of a MIS transistor according to the present invention, FIG. 1A is a plan view, and FIG. 1B is a cross section taken along line bb of FIG. It is a figure.

FIG. 2 is a main-portion plan view showing one pixel and its periphery of a liquid crystal display portion of an active matrix type color liquid crystal display device to which the present invention is applied.

FIG. 3 is a cross-sectional view showing one pixel and its periphery taken along the section line 3-3 in FIG.

FIG. 4 is a cross-sectional view of the additional capacitance Cadd taken along the line 4-4 in FIG.

FIG. 5 is a plan view for explaining the configuration of the matrix peripheral portion of the display panel.

FIG. 6 is a panel plan view for slightly exaggerating the peripheral portion of FIG. 5 to explain it more specifically.

FIG. 7 is an enlarged plan view of a corner portion of a display panel including electrical connection portions of upper and lower substrates.

FIG. 8 is a cross-sectional view showing the vicinity of a panel angle and the vicinity of a video signal terminal portion on both sides, with the pixel portion of the matrix at the center.

FIG. 9 is a cross-sectional view showing a scan signal terminal on the left side and a panel edge portion without an external connection terminal on the right side.

FIG. 10 is a plan view and a cross-sectional view showing the vicinity of a connecting portion between a gate terminal GTM and a gate wiring GL.

FIG. 11 is a plan view and a cross-sectional view showing the vicinity of a connection portion between a drain terminal DTM and a video signal line DL.

FIG. 12 is a circuit diagram including a matrix portion and its periphery of an active matrix type color liquid crystal display device.

FIG. 13 is a flowchart of a cross-sectional view of a pixel portion and a gate terminal portion showing a manufacturing process of steps A to C on the substrate SUB1 side.

FIG. 14 is a flow chart of a cross-sectional view of a pixel portion and a gate terminal portion showing a manufacturing process of processes D to F on the side of the substrate SUB1.

FIG. 15 is a flow chart of a cross-sectional view of a pixel portion and a gate terminal portion showing manufacturing steps of steps GI on the side of the substrate SUB1.

FIG. 16 is an exploded perspective view of a liquid crystal display module.

FIG. 17 is a top view showing a state in which a peripheral drive circuit is mounted on a liquid crystal display panel.

FIG. 18 is a circuit diagram in the drive IC chip.

FIG. 19 is a graph showing the effect of the present invention.

FIG. 20 is a diagram showing a cross-sectional structure of a tape carrier package TCP in which an integrated circuit chip CHI forming a drive circuit is mounted on a flexible wiring board.

FIG. 21 is a main-portion cross-sectional view showing a state where the tape carrier package TCP is connected to the video signal circuit terminal DTM of the liquid crystal display panel PNL.

FIG. 22: Peripheral drive circuit board PCB1 (top surface visible)
It is a top view which shows the connection state of power supply circuit circuit board PCB2 (a lower surface is visible).

[Explanation of symbols]

SUB ... Transparent glass substrate, GL ... Scan signal line, DL ... Video signal line GI ... Insulating film, GT ... Gate electrode, AS ... i-type semiconductor layer SD ... Source or drain electrode, PSV ... Protective film, BM ... Light-shielding film LC ... Liquid crystal, TFT ... Thin film transistor, ITO ... Transparent pixel electrode g, d ... Conductive film, Cadd ... Storage capacitor element, AOF ... Anodized film AO ... Anodized mask, GTM ... Gate terminal, DTM ...
Drain terminal SHD ... Shield case, PNL ... Liquid crystal display panel, S
PB ... Light diffusion plate, MFR ... Intermediate frame, BL ... Backlight, BLS ... Backlight support, LCA ... Lower case, RM ... Backlight light reflection mountain (abbreviated above).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeo Shimomura, 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd. (72) Hirofumi Koshi 3300, Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Device Business (72) Inventor Hiroko Hayada 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division

Claims (1)

[Claims] 1. A channel layer is formed between a source region and a drain region formed on a surface of a semiconductor substrate and has a channel length on a side connecting the regions and a channel width on a side intersecting the side. A MIS transistor in which a gate electrode for forming is formed via an insulating film, wherein the channel layer is divided into a plurality along the channel width.