JPH08248442A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain low resistance, high chemical resistance in the succeeding processes and to obtain good adhesion property on a glass substrate which requires low temp. treatment by forming a conductive layer with addition of specified metal and a nitride layer of a second metal to constitute a wiring layer. CONSTITUTION: At least the wiring layer consists of a metal layer essentially comprising at least one kind of first metal selected from Cu, Al, Ag, Au, Pt with addition of at least one kind of second metal selected from Ti, Zr, Hf, Al, Ta, Si, B, and a second metal nitride layer which covers the surface of the metal layer. Namely, for example, the gate electrode wire 17a consists of a Cu-Zr alloy conductive layer 20a and a ZrN nitride layer 21a which covers the conductive layer 20a. The ZrN layer 21a is also formed between the conductive layer 20a and a substrate 12. Similarly, the storage capacitor line 19 consists of a Cu-Zr alloy conductive layer 20b and a ZrN insulating layer 21b which covers the conductive layer 20b. Further, the address line is patterned at one time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a wiring layer and an electrode layer arranged on a substrate.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device provided with a thin film transistor (TFT) using an amorphous silicon (a-Si) film as a switching element is formed at a low temperature by using an inexpensive amorphous glass substrate. A-
By forming a TFT array using a Si film, a large-area, high-definition, high-quality and inexpensive panel display (flat type television) can be realized.

By the way, in order to increase the definition and area of this type of active matrix type liquid crystal display device and to increase the aperture ratio of the pixel, it is connected to the data line connected to the source and drain of the TFT and the gate of the TFT. It is indispensable to thin, thin, and lengthen the electrode wiring such as the address line.

Moreover, in order to eliminate the waveform distortion of the pulse signal, the wiring resistance must be sufficiently low,
The resistivity of the wiring material must be low. Moreover, for example, when a gate line is formed on a glass substrate and an inverse stagger type TFT structure in which an insulating film or an a-Si film is stacked on the glass line to form a TFT, a gate electrode that becomes a gate of the address line or TFT The wire is also required to be a material that can withstand chemical treatments such as etching used in subsequent processes.

Conventionally, various metal films such as Ta, Ti, and Cr, and alloy films containing these elements have been used as address line and gate electrode wiring materials that satisfy such elements. In order to achieve high definition, a material having lower resistance and good workability and excellent resistance in various chemical treatment steps is desired.

The resistivity of the wiring is 640 ×, which is 12 inches or less.
205 μΩ for 480 pixel graphic array
15 μΩcm or less is required for a 1028 × 768 pixel graphic array of cm or less and 15 inches or less, and 10 μΩcm or less for a large graphic array of 1280 × 1028 pixels of 20 inches or less. Therefore, metals such as Al and Cu can be considered as wiring materials having a lower resistance. However, when the address lines and the storage capacitance lines are formed of Al and Cu, for example, IT in a post process is used.
Since there is no resistance to the etching solution for O, Al, SiOx, and SiNx, there is a problem such as disconnection. For this reason, as shown in FIG. 4, a wiring in which the surface of the Al wiring film 2 on the substrate 1 is covered with a Ta and Cr layer 3 having good acid resistance is used. When such wiring is used, a metal film is formed. 1 step each for patterning and etching
There is a problem that the cost increases as the number of times increases. Also,
Wiring in which the surface of Al is anodized and protected is also used, but the flexibility of the wiring pattern is limited, such as the need to short the wiring to anodize Al, and the contact of the wiring during anodization. Since a mask such as a resist is required to prevent the oxidation of the portion, there is a problem that the mask process is increased and the cost is increased.

Further, in the case of a stagger type TFT structure in which source and drain electrode wirings such as data lines are provided on the substrate surface, similar characteristics are required for the source and drain electrode materials, and the same characteristics are obtained. The problem also exists in the case of a liquid crystal display element that is not driven by TFT.

[0008]

In order to reduce the resistance of the above wiring, low resistance wiring materials such as Ag, Au and Pt in addition to the above Al and Cu are conceivable. However, Al and Cu are very resistant to acid.
Alkali resistance is weak, and even if it is covered with an oxide film such as SiO, various chemical treatments in the subsequent steps may cause disconnection due to corrosion of the wiring material by chemicals through pinholes or the like of the insulating film. Further, Cu, Ag, Au, and Pt have weak adhesion of the coating film to the substrate and are easily peeled off. Also, Au and Pt are Si
When an insulating film such as O or SiN is formed on the insulating film, there is a problem that the insulating film is easily peeled off due to poor adhesion.

The present invention copes with such a situation and has a low resistance and a wiring material having resistance to various chemical treatments in a later step, and an easy construction, good adherence to a substrate, and high reliability. An object is to provide a liquid crystal display device having a wiring layer and an electrode layer.

[0010]

According to the present invention, a pair of substrates, a liquid crystal layer sandwiched between the substrates, an electrode formed on the surface of the substrate on the liquid crystal layer side, and the electrode are electrically connected. A liquid crystal display device comprising: a wiring layer connected to and disposed on the surface of the substrate, wherein at least the wiring layer is mainly composed of at least one first metal selected from Cu, Al, Ag, Au, and Pt. , Ti, Zr, Hf, A
at least one second selected from l, Ta, Si and B
A liquid crystal display device comprising a metal layer formed by adding the above metal and a nitride layer of the second metal, which covers the surface of the metal layer.

[0011]

The wiring material of the present invention has good acid resistance to Al, Au, Cu, Pt, Ag, etc., which is a low resistivity wiring material.
By adding Ti, Zr, Hf, Al, etc., which easily react with, and forming TiN, ZrN, HfN having good corrosion resistance and strong adhesion on the surface, a wiring material having low resistance and good corrosion resistance and adhesion can be realized.

According to the present invention, Al, Au, Cu, Pt
By forming a high chemical resistance layer on the surface of an alloy mainly containing these metals, it is possible to provide a wiring material having low resistance and excellent chemical resistance treatment characteristics. By using these metal wirings as address lines, a large-area, high-definition, high-quality liquid crystal display (liquid crystal display device) with few defects can be realized.

The wiring material of the present invention is a wiring material having a low resistance and a low resistivity as a wiring structure satisfying various chemical treatment characteristics in the post-process. The first wiring material is made of Al, Au, Cu, Pt, Ag. Ti, which has good acid resistance and easily reacts with nitrogen,
A conductive layer made of an alloy of Al, Au, Cu, Pt, Ag and a second metal by adding an easily nitriding metal such as Zr, Hf and Al and performing heat treatment in a nitriding gas such as NH ₃ and methylhydrazine. On the surface of TiN, ZrN, HfN, AlN
And so on. Nitride such as TiN has strong acid resistance and strong adhesion to the substrate so that it is not corroded by an etchant to cause wire breakage, and the inside is Cu and Al with low resistance, so overall low resistance and good corrosion resistance Wiring material can be realized. Further, since Al, Au, Cu, Pt, Ag, and the like inside are also added with Ti, Zr, and Hf having good corrosion resistance and heat resistance, it is possible to prevent internal etching even if the nitride on the surface is broken. it can.

Further, the wiring material according to the present invention will be described in detail. Al, Cu, Au, A on the glass substrate respectively
Alloy films obtained by adding 1 to 10 at% (atomic%) of Ti, Zr, and Hf to g and Al were formed by a sputtering apparatus. The electric resistance of each film after film formation or after annealing is 10 μΩcm or less, which is a sufficiently low value as a low-resistance wiring material, compared to about 45 μΩcm of Mo-Ta which has been conventionally used. Got

These alloy films were formed by using a phosphoric acid-based Al etching solution and dilute HF and ITO etchants (HCl, HNO ₃ , H).
_It was immersed in a mixed solution of ₂ O) for etching. Ti, Z
It has been found that there is no problem in acid resistance if an acid resistant metal such as r or Hf is added at 1 at% or more. The resistivity is Ti,
It increases with the addition amount of Zr and Hf, and if it is 10% or less, the increase in resistivity is three times or less and it can be used as an address line of a large-sized high-definition TFT switching type liquid crystal display device, but 5 at% is preferably used. The lower the resistivity.

Thus, Ti, Zr, and Hf are contained at 1 at%
By leaving the above, the acid resistance to the ITO etchant became sufficiently strong, and the defects of disconnection became almost zero.

Further, in the liquid crystal display device, the nitriding temperature must be 450 ° C. or lower because a substrate having low heat resistance such as glass is used. For this purpose, when N ₂ gas is used, the reaction temperature is about 800 ° C., which is too high. On the other hand, the heat treatment temperature could be lowered to 450 ° C. or lower by using NH ₃ , methylhydrazine or the like. Ti, Zr, H
f is the enthalpy of formation of nitride ΔHf is −8 for TiN
0.8 kcal / mol, ZrN is -87.2, HfN
Is as small as −89.3, so it is possible to lower the temperature.

The enthalpy of formation of AlN is -74.8 k.
Although it is a little larger than cal / mol, it can be used in practice.
Further, the nitriding temperature could be lowered to 300 ° C. or lower by decomposing NH ₃ and methylhydrazine in plasma.

Further, by forming an alloy with a metal having a low melting point and a low resistance such as Cu, Ag and Al, the formation temperature of TiN, ZrN and AlN can be lowered. The addition amount of each of Cu, Ag, and Al was 1 to 10 at%, which was better than the nitriding temperature and the resistivity.

The heat treatment conditions may be appropriately selected depending on the combination of metals, and may be selected between 250 and 450 ° C. As a result, the amount of Zr, Ti, and Hf inside can be controlled, and if the amount of Zr, Ti, and Hf is controlled within the range of 1 to 5%, wiring with low resistance, good corrosion resistance, and good adhesion can be realized. 1 to 10 at% or less is preferable for a graphic array (VGA), and 1 to 5 at% for a larger VGA, 1080 × 102.
8-pixel super extended graphic array (S
For XGA), 0.5 to 3 at% is preferable from the viewpoint of resistivity.

Methylhydrazine (CH
₃ NHNH ₂ ) as well as hydrazine (NH ₂ N
H ₂ ), ethylaniline (C ₂ H ₅ NHC ₂ H ₅ ), N
Other gas such as H ₃ may be used. Further, the ZrN formation temperature could be lowered to 250 to 300 ° C. by decomposing NH ₃ or methylhydrazine gas in plasma and performing heat treatment. By nitriding from the vapor phase in this way, a nitride film is also formed on the substrate interface, so that the acid resistance at the substrate interface portion is improved and the adhesive force is also improved. Therefore, the acid resistance was better than that in the case where only the surface was nitrided by plasma or ion implantation, and the yield was improved.

In the above, the amounts of Ti, Zr and Hf are set to 5
If it is increased to 10 at%, it can be used because the acid resistance and adhesion are sufficiently good without nitriding the surface, but the resistivity is high, so the surface is nitrided and the amount of Ti, Zr, and Hf inside is reduced. It is more suitable for large-scale high-definition to lower the resistivity.

As the metal for nitriding, it is better that the enthalpy of formation ΔHf of the nitride is smaller, and it is −60 kcal / m.
ol or less is preferable, Al (-74.8), Ti (-8)
0.8), Zr (-87.2), Hf (-89.3) and Ta, Si, B, Sc, Th (-93.5), and other than Ti, Zr, Hf, and Al described above. Ta, Si, B can be used.

The nitriding can be performed without increasing the number of steps by forming it before depositing the gate insulating film and heating the substrate of the film forming apparatus, and the cost does not increase.

In the present invention, the first main body of the wiring layer
When Al is used as the metal of No. 3, if Al is selected as the second metal that is an easily nitrided metal, the result is that the first and second metals have the same Al. However, the structure in which the Al wiring is covered with AlN makes it possible to obtain a wiring layer having good chemical resistance and adherence and an electrode layer formed at the same time while maintaining a desired low resistivity.

When the first metal is Cu or Al, which has low acid resistance, the second metal group includes easily nitriding metals such as Ti, Zr, and Hf having a strong nitriding property and Au, Pd, Cr, Ge, Ag, and Sm. Acid resistant metals such as rare earths, which have strong acid resistance and are less nitriding than easily nitriding metals, are added together.
It is also possible to increase the process margin by completely reacting the easily nitriding metal having strong nitriding property such as Zr and Hf on the surface and leaving the acid resistant metal having strong acid resistance inside. Since the resistivity of the alloy changes depending on the amount of the added metal, when adding only the easily nitrided metal, the amount of the added metal remaining inside may change due to the degree of nitriding of the easily nitrided metal, and the resistivity may vary. It is possible to prevent and increase the manufacturing margin.

Further, as a method of selecting the easily nitriding metal and the acid resistant metal, two kinds of metals having a strong nitriding property such as Ti, Zr, Hf, Sc and Si are selected, and the same group of metals such as Zr is selected. Of these, the metal having the highest nitriding property may be nitrided, and a metal having a slightly weaker nitriding property such as Ti may be selected as the metal for improving the acid resistance.

The wiring material in the present invention is not limited to the reverse stagger type TFT, but may be an etching stopper / reverse stagger type, back channel / reverse stagger type, or stagger type TFT. Further, it may be used not only as a gate line but also as a signal line or the like. Further, the semiconductor film of the TFT is not limited to the a-Si film, and may be a polysilicon film without any problem.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 to FIG.
This is applied to an active matrix type liquid crystal display device using FT switching. As shown in FIG. 1, a liquid crystal display device 10 includes a glass observation-side substrate 11 having an ITO (indium tin oxide) film transparent common electrode 13 formed on one surface, and an ITO film transparent pixel on one surface. The counter substrate 12 on which the electrodes 14 are formed is arranged with the surfaces on the electrode sides facing each other.

The substrates 11 and 12 are arranged with a gap of several μm therebetween with a substrate gap agent and the peripheral edges are sealed. The liquid crystal layer 15 is filled in this gap and sandwiched by the substrates.

The counter substrate 12 having the pixel electrodes 14 is called a matrix substrate, and is a substrate equivalent to the circuit shown in FIG.
Pixel electrode 14 and TFT switching element 16 in the next surface arrangement
An address line (gate line) 17, a data line 18, and a storage capacitance line 19 are arranged.

That is, n address lines 17 extending in the row direction of the screen display and m data lines 18 extending in the column direction are arranged in a matrix, and the storage capacitors are arranged in parallel with each address line. The line 19 is arranged.

T is a unit of the area surrounded by the address line and the data line.
The FT switching element 16 and the pixel electrode 14 are formed,
The TFT 16 is electrically connected to the address line 17 and the data line 18 at the intersection of the area units. That is, the drain electrode of the TFT is the data line 18, and the source electrode of the TFT is the pixel electrode 1.
4, the gate electrode is connected to the address line 17. In the figure, reference numeral 15a denotes a liquid crystal layer portion in a unit of area, that is, a liquid crystal layer portion sandwiched between the pixel electrode 14 and the common electrode 13 in a unit of region, and forms one pixel each.

FIG. 2 is an enlarged sectional view showing the arrangement of the TFT switching element 16 on the glass substrate 12, the gate electrode line 17a integrally extended from the address line, and the storage capacitance line 19, and the gate electrode line 17a is Conductive layer 20a made of an alloy of Cu and Zr and ZrN nitride layer 21 covering the conductive layer 20a
a. The ZrN layer 21a includes the conductive layer 20a and the substrate 12
Also intervenes in between.

Similarly, the storage capacitance line 19 is composed of a conductive layer 20b made of an alloy of Cu and Zr and a ZrN insulating layer 21b covering the conductive layer 20b. Although not shown in FIG. 2, the address line 17 is also patterned at the same time.

The insulating film 22 is deposited on the substrate on which the electrode layer 17a and the wiring layers 17 and 19 are formed, the (a-Si) layer 16a is formed in the TFT region on the upper surface thereof, and the drain electrode layer 16b is further formed. And the source electrode layer 16c is formed. On the other hand, in the pixel area on the storage capacitance line 19, the IT
The pixel electrode 14 made of O is formed, and the source electrode layer 16
It is electrically connected to c. The drain electrode layer 16b is shown in FIG.
Although not shown, it is electrically connected to the data line.

A method of manufacturing the address line 17, the gate electrode line 17a and the storage capacitance line 19 having this structure will be further described.

First, Cu and Zr were simultaneously sputtered on the glass substrate 12, and Zr was 10 at% (atomic%) CuZr.
An alloy film is deposited at 3000 A (angstrom) and etched with a phosphoric acid solution to form a CuZr alloy layer pattern of an address line 17 having a line width of 20 μm, a gate electrode line 17a having a line width of 12 μm and a storage capacitor line 19 having a line width of 35 μm. Formed.

Next, 400 in a methylhydrazine atmosphere.
Heat treatment at ℃, nitriding Zr in the pattern, ZrN on the surface
And nitrided layers 21a and 21b were formed. That is, by this heat treatment, Zr of the CuZr alloy layer diffuses to the surface and is nitrided to form the ZrN nitride layers 21a and 21b, and the CuZr in the inside is
The density of Zr in the r conductive layers 20a and 20b is reduced to 2 at
%Became. The nitride layers 21a and 21b are the conductive layer and the substrate 12
Also formed in between. The thickness of the nitride layer on the surface of the conductive layer is 100.
It was 0A.

Next, the plasma CVD method is used as the insulating film 22 to form 3000A of SiOx 22a and 500A of SiNx.
22b are stacked, and further undoped (a-Si) 16a
1000A, stopper SiNx16d 2000A
Deposited. After etching the stopper SiNx, n
⁺ (A-Si) 16e was deposited at 500 A. Mo 5
After depositing 00A, patterning was performed to form a-Si islands. After forming the ITO pixel electrode 14, a contact hole was opened. Thereafter, a Mo layer serving as the drain electrode layer 16b and the source electrode layer 16c was deposited to 500 A and an Al layer was deposited to 0.5 μm, and then the drain electrode 16b and the source electrode 16c were formed by an Al etching solution.
A data line pattern is formed at the same time when the aluminum Al layer of 0.5 μm is formed, and the data line 18 is formed of Al.

Next, the n ⁺ (a-Si) 16e was etched by CDE, then a protective film of SiNx was formed, and an opening was provided in the contact portion to complete the TFT array.

In the liquid crystal driving matrix substrate 12 thus constructed, the resistivity of the Mo-Ta alloy or the like which has been conventionally used as the address line is about 30 to 45 μΩcm, which is less than 10 μΩcm and 1/3 to 1/4. A smaller value is obtained, and the aperture ratio can be expanded because the width of the address line can be made smaller than in the past, and the wiring length can be increased in response to large area, high definition, and high image quality liquid crystal displays. Can also handle. Also, due to the nitriding of the surface, ITO, A
Since the resistance to the 1, l, SiOx, and SiNx etching solutions is also improved, defects due to disconnection are dramatically reduced as compared with the case where Al, Cu, or an alloy thereof is used for the gate line.

(Example 2) As in Example 1, 10
at% Zr was added. Since Au has better acid resistance than Cu, it is not necessary to leave Zr inside, so that the time was lengthened at 430 ° C. to sufficiently nitride Zr. The amount of Zr in the inside was at% or less than that of Cu because the melting point of 0.5 R was low. As a result, the resistivity could be sufficiently lowered to 3 μΩcm or less.

(Embodiment 3) Al in the same manner as in Embodiment 1
at% Zr was added. Since Al has a lower melting point than Cu, it could be nitrided at 300 to 350 ° C., which is lower than Cu. The internal Zr amount was 2 at%. This gives a resistivity of 10
It was μΩcm or less.

(Embodiment 4) As in Embodiment 1, Cu is added to 10
At% Zr and 3 at% Ti were added. When nitrided at 400 ° C., since Zr is easily nitrided, almost all is nitrided on the surface, and 2.5 at% of Ti remains inside.
The amount of Ti inside could be controlled better than that of Resistivity is 10μ
It was as low as Ωcm or less.

(Embodiment 5) As in Embodiment 1, Cu is added to 10
At% Hf and 3 at% Ta were added. When nitrided at 400 ° C, Hf is easier to nitride than Zr and Ta is T
Since nitriding is more difficult than i, almost all of Hf is nitrided on the surface, and Ta of 3 at% remains inside, so that the amount of Ta inside can be controlled better than in Example 4. Resistivity is 10μ
It was as low as Ωcm or less.

(Example 6) As in Example 1, 1a was added to Au.
t% Ti was added. Sufficiently nitriding at 430 ° C., nitriding Ti almost entirely on the surface, and 1 at% Ti, which is almost the same as the initial addition amount, remained inside, and the amount of Ti in the inside could be controlled better than in Example 5. . Resistivity is 3μΩc
It was as low as m or less.

(Example 7) As in Example 1, nitriding was performed with Al0 methylhydrazine at 300 to 350 ° C. Since Al was used, the nitriding temperature could be lowered sufficiently. The surface was nitrided and the inside was Al. Resistivity is 3μΩ because Al is used
It could be sufficiently lowered to a value equal to or less than cm and almost equal to Al.

[0050]

As described above, the wiring material according to the present invention has a low resistance and a high chemical resistance property in the post-process, and it can be applied to a glass substrate requiring a low temperature treatment. Good wearability. Therefore, when it is used for signal wiring of various electronic components, it greatly contributes to good performance.
Further, when it is used for forming a signal wiring of a liquid crystal device or an electrode of a driving semiconductor element to be mounted, a low resistance address line or the like can be realized. Further, this wiring layer can be obtained only by heat treatment without increasing patterning or etching in the liquid crystal display device manufacturing process, and exhibits excellent characteristics as a low resistance wiring layer even after the subsequent heat treatment structure or etching process.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal display element of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged main part of the embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of an active matrix type liquid crystal display element according to an embodiment of the present invention.

FIG. 4 is a sectional view showing an element structure of a conventional active matrix type substrate.

[Explanation of symbols]

 11 ... Observation-side substrate 12 ... Counter substrate 13 ... Transparent common electrode 14 ... Transparent pixel electrode 15 ... Liquid crystal layer 16 ... TFT switching element 17 ... Address line 17a ... Gate electrode line 18 ... Data line 19 ... Storage capacitance line 20a, 20b ... Conductive layers 21a, 20b ... Nitriding layer

Claims (1)

[Claims] 1. A pair of substrates, a liquid crystal layer sandwiched between the substrates, an electrode formed on the surface of the substrate on the liquid crystal layer side, and an electrode electrically connected to the electrode and arranged on the surface of the substrate. In a liquid crystal display device including a wiring layer provided, at least the wiring layer includes Cu, Al, Ag, Au,
A conductive layer mainly composed of at least one first metal selected from Pt and added with at least one second metal selected from Ti, Zr, Hf, Al, Ta, Si and B; A liquid crystal display device, comprising: the second metal nitride layer covering the surface of the conductive layer.