JPH095788A - Matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a matrix type liquid crystal display device having a contact hole shape which is excellent uniformity in the reproducibility and coverage of working shapes and is sufficient in the reliability of the contact between layers at the time of etching the contact holes. CONSTITUTION: The contact holes of the matrix type liquid crystal display device having a layer structure consisting of an insulating layer and a conductive layers having conductive electrode patterns in a lower layer and upper layer are formed to a tapered shape, i.e., are so formed that the angle θ formed by the side wall surfaces and the base of the holes attains <=75 deg.. When the surface shape of the contact holes is rectangular, the contact holes are formed to a shape so that the ratio X of the long side and short side satisfies 1<X<=2. Further, the contact holes may be so formed that the plane shape is made into a polygonal shape to avoid the formation of right-angled corners in these holes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device, and more particularly to a matrix type liquid crystal display device having a thin film transistor on a transparent substrate.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device having a thin film transistor, electrical insulation between layers (layers, hereinafter, simply referred to as layers) of conductive layers having conductive electrode patterns of upper and lower layers with an insulating layer in between. Contact (hereinafter,
It is known that a square shape is an ideal shape as a plane shape of a contact hole for making a contact), but it is not always possible to form a square pattern due to the restriction of the pattern layout.

In such a case, JP-A-61-166
It is known that a plurality of squares are arranged at equal intervals as disclosed in Japanese Patent Publication No. 048 (see FIG. 4).

[0004]

When a contact hole having the above-described shape is processed and provided, dry etching is generally performed by using a pattern formed by using a resist as an etching mask. With this method, when the vicinity of the resolution limit of the exposure apparatus is used, for example, the square resist pattern is actually circular due to the light sneak, and the skirt of the resist occurs in the depth direction. Scum easily occurs.
Therefore, when a pattern of a plurality of squares arranged as shown in FIG. 4 is formed, the reproducibility and stability of the formed resist pattern are insufficient and reliable contact cannot be obtained. A characteristic problem such as a malfunction of the obtained thin film transistor occurs.

Further, the plan shape of the contact hole is shown in FIG.
In the case of a rectangular pattern as shown in FIGS. 6A and 6B, in the profile of the cross section of the hole formed by dry etching, the shape of the profile in the long side direction and the profile in the short side direction Therefore, the uniformity that the coverage is evenly applied to any surface and any corner of the contact hole during the film formation in the next step (hereinafter, simply referred to as “uniformity of coverage”) becomes insufficient, and Since the disconnection occurs to cause the disconnection, there is a possibility of causing a serious failure in guaranteeing the reliability of the contact between layers.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a liquid crystal display device having improved coverage of contact holes and excellent reproducibility of a resist pattern in manufacturing and uniformity of coverage. To do.

[0007]

According to the present invention, there is provided:
Regarding the shape of a rectangular contact hole when forming a matrix type liquid crystal display device in order to solve such a problem, a maximum contact area is ensured in a plane, and the cross-sectional profile shape is set to a short side and a long side. By defining the vertical and horizontal composition ratios that can secure the processing uniformity that is almost the same, a stable laminated structure with reliable contact in the contact hole portion and good coverage uniformity can be formed.

Further, by forming the contact hole so that a right-angled corner does not occur in the contact hole, that is, the plane shape of the contact hole is polygonal, the cross-sectional profile of the contact hole is made uniform. As a result, it is possible to form a stable laminated structure in which the contact in the contact hole portion is surely secured and the coverage is uniform.

Therefore, the matrix type liquid crystal display device of the present invention comprises a thin film transistor on an insulating substrate, and a layered structure composed of an insulating layer and a conductive layer having a conductive electrode pattern on the lower layer and the upper layer across the insulating layer. A matrix type liquid crystal display device comprising: a liquid crystal display device, wherein a contact hole for making contact between layers of the layer structure is formed in a taper shape, and a sectional shape of the hole is a side wall surface of the hole. And the bottom surface of the hole forms an angle of 75 degrees or less.

The contact hole has a rectangular planar shape, and at least the long side of the rectangle is used for pattern formation by a photolithography process using a photosensitive resin and an etching process. When the resolution limit length of the exposure apparatus is 1.25 times or more, it is preferable that the ratio X of the long side and the short side of the rectangle satisfies 1 <X ≦ 2.

The ratio X of the long side to the short side of the rectangle is 1 <X
If ≦ 2 is not satisfied, the contact hole is
It is preferable that the hole is formed so that the planar shape thereof is polygonal.

It is preferable that the contact hole is formed so that the planar shape of the hole is polygonal.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings.

Example 1 FIG. 1 is an explanatory plan view showing an example according to the present invention. When an additional capacitance type structure is adopted as a structure including an auxiliary capacitance, an electrode forming an auxiliary capacitance and a front stage are shown. FIG. 6 shows a plan view of a device having a contact hole formed in an insulating film for making contact with the gate line of FIG. 2A is a sectional view taken along the line AA of FIG.
(B) is a BB line sectional view of FIG.

Here, Cr, Mo, Ta, ITO or the like formed by a sputtering method can be used for the auxiliary capacitance electrode formed in the lower layer. The film thickness is in the range of 50 to 200 nm and is formed to an appropriate film thickness. Also, as the insulating film, CVD
A silicon nitride film or a silicon oxide film formed by the method can be used. Further, for the gate wiring formed in the upper layer, a metal such as Cr, Al or Ta formed by the sputtering method is used. The film thickness is formed in the range of 100 to 500 nm.

Next, a contact hole is formed by dry etching using a pattern formed using a resist as an etching mask. The method of forming the contact hole in a tapered shape by dry etching is performed in the same manner as normal dry etching, as described below. A normal novolac-based positive resist is used as the mask resist. The baking after development is preferably performed on a hot plate at a temperature of about 150 ° C. for a time of about 3 minutes. The standard condition for dry etching is CF by RIE method.
Pressure of 7.5 with ₄ / O ₂ (80/40 SCCM) gas
Pa, RF power is 1.5 kW.

Next, the method of measuring the angle between the side wall surface and the bottom surface of the contact hole and the reason for defining the range of the angle will be described. The method of measuring the angle is to measure the cross-sectional profile shape with a cross-sectional SEM (scanning electron).
Measurement is performed using a scanning electron microscope. Here, the angle θ formed between the side wall surface and the bottom surface is, for example, from the bottom surface of the insulating layer in the portion where the insulating layer 12 is in contact with the auxiliary capacitance electrode pattern 2 in FIG. 2A toward the side wall surface of the contact hole. The measured angle θ is referred to. The preferable angle between the side wall surface and the bottom surface of the contact hole is set to 75 degrees or less for the following reason. That is, when the angle exceeds 75 degrees, the side wall surface is in a vertical direction, and such a cross-sectional shape causes poor coverage during film formation of the upper conductive layer, which causes a contact failure. This is because, when various angles were changed and experimentally examined, it was found that when the angle was set to 75 degrees or less, the contact failure did not occur and a product could be stably manufactured. Although the lower limit of the angle is not particularly limited, an angle of, for example, 60 degrees or less is not preferable because the thickness of the insulating layer around the contact hole becomes thin, and thus is actually 75 degrees or less. 7 due to manufacturing variations
It is carried out in a range up to an angle slightly smaller than 5 degrees.

Of the coverage of the sputtered metal film covering the contact hole formed as described above, the coverage of the bottom or edge of the contact hole (the edge of the hole entrance), etc. Since there is no cracking and no partial disconnection occurs, the contact between layers is good.

Embodiment 2 FIG. 3A is a plan view of a contact portion of a conventional example, and FIG.
3B is an explanatory plan view showing another example of the embodiment of the contact portion to which the present invention is applied in the same configuration as FIG. In this embodiment, the contact hole has a rectangular planar shape, and both the long side length and the short side length of the rectangle, or the long side length is a photolithography plate using a photosensitive resin. It is applied when the resolution limit length of the exposure apparatus used for forming a pattern by the process and the etching process is 1.25 times or more. Both the length of the long side and the length of the short side of the rectangle, or the length of the long side is 1.25 times the resolution limit length of the exposure apparatus or more is the length of the long side and the short side. As a result of experimentally checking various lengths, when the length is 1.25 times or more, when there is a large difference in length between the long side and the short side of the rectangular pattern (the long side and the short side It is based on the finding that the reproducibility and stability of the contact hole shape obtained when the ratio X does not satisfy 1 <X ≦ 2) becomes poor.

In the case of the pattern size shown in FIG. 3A, in the case of having a square which is said to be most advantageous as the planar shape of the contact, both of the side lengths x and y are obtained. For example, assuming 4 μm (z is 6 μm and w is 4 μm), the total area of the ^two square contacts is 32 μm ² , but if the present invention is applied, FIG.
As shown in Fig. 4, the length x of the long side is 6 µm and the length y of the short side is 4 µm (z is 4 µm) to secure 48 µm ² as the total area of the ^two rectangular contacts. A device having necessary and sufficient characteristics can be formed without deteriorating the characteristics required as a contact such as uniformity.

Here, the cross-sectional profile on the long side and the cross-sectional profile on the short side can be processed into substantially the same shape,
As a range in which the uniformity of coverage can be achieved in a good state on both the long side, the ratio X of the long side of the rectangle to the short side is 1 <X ≦ 2.
And

Example 3 Next, as a modification of Example 2, which is an example in which the ratio X of the long side to the short side of the rectangle does not satisfy 1 <X ≦ 2, a rectangular contact hole is used. A contact hole formed so that a right-angled corner does not occur, that is, the contact hole has a polygonal planar shape will be described. Here, in the method of forming such a planar shape to be a polygon, a polygonal pattern is formed as a mask pattern, and the resist is exposed and developed using the mask to transfer it onto the substrate. By doing. By forming the contact holes so that the planar shape of the contact holes is polygonal, corners at right angles do not occur in the contact holes, and the maximum contact area can be secured in plan view.

When a contact hole having a polygonal planar shape in which a right-angled corner does not occur is formed in the contact hole regardless of the ratio of the long side to the short side of the rectangle, the sectional profile of the hole is tapered. As a result, the uniformity of coverage can be obtained and a sufficient contact area can be secured.

[0024]

As described above, in the liquid crystal display device of the present invention, the maximum contact area can be secured in the plane, and the contact hole having the good cross-sectional profile uniformity can be formed. The results show that the contact resistance and uniformity of coverage are equal to or better than those of conventional products. Therefore, as a ripple effect thereof, there is also an effect that the degree of freedom in design can be increased because the shape that can be adopted can be widened without being restricted by making the contact shape square.

[Brief description of drawings]

FIG. 1 is an explanatory plan view of an embodiment of the present invention.

2A is a sectional view taken along line AA of FIG. 1 showing an embodiment of the present invention, and FIG. 2B is a sectional view taken along line BB of FIG. 1 showing an embodiment of the present invention.

FIG. 3A is a plan explanatory view of a contact portion of a conventional example,
FIG. 3B is a plan explanatory view of a contact portion to which the present invention is applied in the same configuration as that of FIG.

FIG. 4 is a plan view of a contact portion according to a conventional example.

FIG. 5 is a plan explanatory view of a contact portion according to another conventional example.

6A is a sectional view taken along the line AA of FIG. 5 showing a conventional example,
(B) is a BB line sectional view of FIG. 5 showing a conventional example.

[Explanation of symbols]

 1 Contact Hole Pattern 2 Auxiliary Capacitance Electrode Pattern 3 Gate Electrode Pattern 10 Lower Conductive Electrode Pattern 11 Upper Conductive Electrode Pattern 12 Insulating Layer

Claims (4)

[Claims] 1. A matrix type liquid crystal display device comprising: a thin film transistor on an insulating substrate; and a layer structure comprising an insulating layer and a conductive layer having a conductive electrode pattern as a lower layer and an upper layer sandwiching the insulating layer. In the liquid crystal display device, a contact hole for making contact between layers of the layer structure is formed in a tapered shape, and a sectional shape of the hole is an angle formed between a side wall surface of the hole and a bottom surface of the hole. Is formed to be less than or equal to 75 degrees, a matrix type liquid crystal display device. 2. When the contact hole has a rectangular planar shape, and at least the long side length of the rectangle is patterned by a photolithography process using a photosensitive resin and an etching process. When the resolution limit length of the exposure apparatus used for the above is 1.25 times or more, the ratio X of the long side to the short side of the rectangle is 1 <X ≦ 2.
The matrix type liquid crystal display device according to claim 1, which satisfies the above condition. 3. The ratio X of the long side to the short side of the rectangle is 1 <
3. The matrix type liquid crystal display device according to claim 2, wherein the contact hole is formed such that the planar shape of the hole is polygonal when X ≦ 2 is not satisfied. 4. The contact hole is formed such that the planar shape of the hole is polygonal.
The matrix type liquid crystal display device described.