JP2000001732A - Mo-W MATERIAL FOR WIRING FORMATION, Mo-W TARGET FOR WIRING FORMATION AND ITS PRODUCTION, AND Mo-W WIRING THIN FILM AND LIQUID CRYSTAL DISPLAY DEVICE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for wiring formation, having low resistivity and capable of tapering and having high resistance to etchant, such as interlayer insulator and ITO, a target for wiring formation, and a wiring thin film. SOLUTION: The material for wiring formation is composed of an Mo-W material having a composition consisting of 25-45 atomic % tungsten and the balance molybdenum with inevitable impurities, when it is taken for one body. The target for wiring formation is composed of the Mo-W material having a composition consisting of 25-45 atomic % tungsten and the balance molybdenum with inevitable impurities and prepared, e.g. by integrally compounding tungsten and molybdenum by a powder metallurgy method, a melting method, etc. The wiring film can be formed by using this Mo-W target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Mo-
W material, Mo-W target for forming wiring and method for manufacturing the same,
And a Mo-W wiring thin film and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, amorphous silicon (hereinafter referred to as "a-S
An active matrix type liquid crystal display device using a thin film transistor (hereinafter, referred to as “TFT”) formed using a film as a switching element is drawing attention. This is achieved by forming a TFT array using an a-Si film that can be formed at a low temperature on an inexpensive glass substrate, thereby providing a large-area, high-definition, high-quality and inexpensive panel display, that is, a flat-panel television. This is because there is a possibility that this can be achieved.

However, when a large-area display is constructed, the total length of the address wiring necessarily increases drastically, so that the resistance of the address wiring increases. With the increase in the resistance of the address wiring, the delay of the gate pulse applied to the switch element becomes remarkable, causing a problem that the control of the liquid crystal becomes difficult. For this reason, it is necessary to avoid delay of the gate pulse while maintaining at least parameters such as the wiring width.

As one means for avoiding the delay of the gate pulse, it is conceivable to form an address wiring using a wiring material having a lower resistivity. At present, Mo-Ta alloy films are often used as address wiring materials. However, since the resistivity of this alloy film is as large as about 40 Ω · cm, the realization of a large-area display is realized by using Mo-T
It is considered difficult with the resistivity of the a alloy film. In particular, for a high-definition direct-view display having about 1000 address wires, a wiring material having a resistivity of about 20 μΩ · cm or less is required.

[0005] The above-mentioned new wiring material is required to have not only low resistivity but also the following characteristics in addition to the low resistivity. For example, it is necessary to improve the step coverage of the interlayer insulating film formed on the address wiring and to increase the insulation between the wiring formed on the interlayer insulating film and the address wiring, so that the tapering process is possible. Is required.

That is, it is desired to realize a highly reliable liquid crystal display device in which the delay of the gate pulse is suppressed and the insulating property is ensured by forming the address wiring by using a wiring material having a low resistance. Such a demand is not limited to a large-area display, but a liquid crystal display device in which wiring and wiring intervals are narrowed in order to achieve high definition of the display,
Alternatively, a similar demand has been made in a liquid crystal display device or the like in which the wiring ratio is reduced and the aperture ratio is improved.

[0007] The conventional liquid crystal display device also has other problems as described below. Here, FIG. 5 is a sectional view of a TFT (switching element) and a storage capacitor portion used in the liquid crystal display device.

[0008] As shown in FIG.
The gate electrode 2, the address wiring, and the Cs line 9 are simultaneously formed by sputtering a Ta alloy. An a-Si active layer 4 is deposited via the gate insulating film 3 formed thereon. On both ends of the active layer 4, n ⁺ a-Si layers 5a and 5b are deposited. Then, an ITO pixel electrode 8 is formed via the gate insulating film 3. Next, an Al source electrode 6a having a connection portion on the n ⁺ a-Si layer 5a, a drain electrode 6b having a connection portion on a part of the n ⁺ a-Si layer 5b and the pixel electrode 8,
And data wiring are formed at the same time.

[0009] In the conventional TFT shown in FIG.
Since the pixel electrode and the data wiring exist in the same layer without interposing an insulating film, a short circuit may occur and a point defect may occur. In order to avoid this point defect, a structure in which an interlayer insulating film is formed after wiring of a source electrode, a drain electrode, and a data wiring, and a pixel electrode is formed thereon has been studied as an improvement.

In order to realize such a structure, (1) the data wiring and the like must have excellent resistance to HF as an etchant for an interlayer insulating film and ITO etchant for a pixel electrode. (2) By improving the step coverage of the interlayer insulating film,
In order to increase the insulation between the data wiring and the pixel electrode, the data wiring can be tapered. Etc. are required.

[0011]

However, a wiring material satisfying the above-mentioned requirements has not been found so far, so that it is difficult to realize the above-mentioned structure and improve the reliability of the liquid crystal display device. Was. In particular, in the development of large-area displays, it is important to reduce the incidence of point defects, and the development of such a highly reliable liquid crystal display device is desired. Therefore, wiring materials that satisfy the above requirements,
Further, development of a target for wiring formation is desired.

On the other hand, in the case of an Al-based or Ta-based alloy, a step of removing the surface oxide film is necessary because an oxide film is formed on the surface to increase the contact resistance with the upper metal wiring. Further, a barrier metal is required to prevent the reaction between ITO and Al, and there is a disadvantage that the number of manufacturing steps increases.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such problems, and an object of the present invention is to provide a wiring forming material, a wiring forming target, and a wiring thin film which have a low resistance and can be tapered. It is another object of the present invention to provide a wiring forming material, a wiring forming target, and a wiring thin film having low resistance and high resistance to an etchant such as an interlayer insulating film or ITO. It is another object of the present invention to provide a method of manufacturing a target for forming a wiring which enables the above-described target for forming a wiring to be manufactured with good reproducibility.

[0014]

In order to achieve the above object, the present inventors systematically conducted experiments and studies on various metals and alloys as wiring materials in a display device such as a liquid crystal display device. As a result, an alloy film of molybdenum (Mo) and tungsten (W) having a limited composition range has a lower resistivity and a lower workability than a film composed of Mo or W alone. It was found for the first time that it was good, and the present invention was accomplished.

That is, the Mo-W material for forming a wiring according to the present invention is characterized in that when viewed as a single body, it is composed of 25 to 45% of tungsten in atomic percent, the balance being molybdenum and unavoidable impurities.

The Mo-W target for forming a wiring according to the present invention is characterized in that, when viewed as a single body, the Mo-W target is composed of 25 to 45% of tungsten by atomic percent, the balance being molybdenum and unavoidable impurities. Mo for forming wiring of the present invention
-W target is tungsten, especially in atomic percent
25-45%, Mo-W material consisting of molybdenum and unavoidable impurities, the relative density of the Mo-W material is 98% or more, the average grain size of crystal grains is 200μm or less, and the Vickers hardness is Hv 350 or less. It is characterized by:

The Mo-W wiring thin film of the present invention is formed by using the above-described Mo-W target for forming a wiring of the present invention, and has a tungsten content of 25 to 45% in atomic percent.
The balance consists of molybdenum and unavoidable impurities.

The method of manufacturing the Mo-W target for forming a wiring according to the present invention is as follows.
A step of molding a mixed powder adjusted to be composed of the remaining molybdenum and unavoidable impurities; a step of sintering the molded body obtained in the molding step in an inert atmosphere; and a step of sintering the sintered body obtained in the sintering step. And hot working.

[0019]

Embodiments of the present invention will be described below.

The Mo-W material for forming a wiring according to the present invention has a tungsten content of 25 to 4 atomic percent when viewed integrally.
5%, with the balance being molybdenum and unavoidable impurities. Here, the wiring forming M of the present invention is used.
Specific examples of the o-W material include: (A) a composite material / integration (for example, alloying) of a Mo material and a W material such that the composition ratio of W is in the range of 25 to 45% in atomic percent. ) For example, a sintered body by a powder metallurgy method, an ingot by a melting method, and the like. (B) The Mo material and the W material are arranged such that the W ratio is in the range of 25 to 45% in atomic percent when viewed as one. Etc. are exemplified.

When the ratio of W in the above Mo—W material is less than 25% in atomic percent, the resistance increases and
Resistance to an etchant such as an interlayer insulating film or ITO is reduced. On the other hand, if the ratio of W exceeds 45% in atomic percent, the resistance similarly increases, and the sputtering rate when a wiring thin film is formed by, for example, a sputtering method decreases.
In other words, the Mo—W material having a W ratio of 25 to 45% in atomic percent has low resistance, excellent etchant resistance, and a practically good sputtering rate. Further, the Mo—W material having the above composition ratio has an advantage that tapering can be performed when, for example, a thin film is formed. As described above, in order to obtain a good sputter rate and excellent etchant resistance, the ratio of W is set in the range of 25 to 45% in atomic percent in the present invention.

The Mo-W material for forming a wiring according to the present invention comprises:
In order to improve the characteristics of the obtained wiring, it is preferable to reduce the amount of impurity elements contained therein as much as possible (M
The same applies to the o-W target and the Mo-W wiring thin film). For example, oxygen as an impurity is preferably 500 ppm or less, more preferably 200 ppm or less, and desirably 100 pp.
m, preferably 50 ppm or less. this is,
If there is too much oxygen, there are generally many vacancies (pores),
This is to cause a decrease in density. Due to this decrease in density,
Particle generation increases. In order to reduce the amount of oxygen, reduction of the powder with hydrogen, improvement of sinterability, and the like are employed.

The Mo—W wiring thin film of the present invention is made of a Mo—W alloy having the above composition ratio. The reason for defining the composition ratio of W, the preferable composition range, and the like are as described above. An address wiring of a liquid crystal display device or the like made of such a Mo-W wiring thin film acts as a low resistance component to a gate pulse. Therefore, the gate pulse transmitted through the address wiring hardly receives a delay effect due to the resistance of the address wiring. Therefore, a gate pulse without delay is given to a switching element for driving a liquid crystal or the like.

Further, since the Mo-W wiring thin film of the present invention can be tapered, the step coverage of the interlayer insulating film formed on the address wiring composed of the wiring thin film is improved. Therefore, a high withstand voltage is obtained between the wiring formed on the interlayer insulating film and the address wiring. The Mo-W wiring thin film of the present invention further has excellent resistance to an etchant such as an interlayer insulating film or ITO. Therefore,
The insulation between the data wiring and the pixel electrode can be improved. Thus, a highly reliable liquid crystal display device can be realized even when the display area is enlarged.

The Mo-W wiring thin film of the present invention is not limited to a liquid crystal display device having a large area, but a liquid crystal display device in which wirings and wiring intervals are narrowed in accordance with high definition of a display, or a wiring width is reduced. This is also effective for a liquid crystal display device having a small aperture to improve the aperture ratio. The Mo-W wiring thin film of the present invention makes it possible to satisfactorily reduce the wiring width and the wiring interval. Further, the Mo-W wiring thin film of the present invention is effective not only for wiring of a liquid crystal display, but also for wiring of a plasma display, a solid display, a flat display using a field emission cold cathode, and the like. .

The Mo-W wiring thin film of the present invention has an additional advantage that an oxide film formed on its surface has a small resistance. Therefore, without performing the oxide film removal processing,
A good contact can be formed with the upper metal wiring or the like. As a result, the manufacturing cost can be reduced. Therefore, the liquid crystal display device manufactured using the Mo-W wiring thin film of the present invention is different from the conventional liquid crystal display device in that an oxide film is formed on the surface of the gate electrode, the address wiring, and the Cs line. It becomes possible to configure.

The Mo-W target for forming a wiring according to the present invention enables a Mo-W wiring thin film having the above-mentioned characteristics to be formed with good reproducibility by a thin film forming method such as a sputtering method. The present invention utilizes the Mo-W material for wiring formation of the present invention. The Mo-W target for wiring formation is adjusted so as to be composed of 25 to 45% by atomic percent of tungsten, the balance being molybdenum and unavoidable impurities when viewed as a single unit for the same reason as the Mo-W material for wiring formation described above. Have been. The reason for defining the composition ratio of W, the preferable composition range, and the like are as described above.

However, since the composition of the Mo—W wiring thin film changes variously depending on the conditions for forming the wiring thin film, for example, various conditions such as the atmosphere during sputtering and the applied voltage,
Although not unequivocally determined, a good Mo-W wiring thin film can be obtained within the above-described composition range of W.

The Mo-W target for forming a wiring of the present invention can adopt various forms. As a specific form, a form similar to the above-described Mo-W material ((A)
And (B)) are exemplified. In particular, since the sputtering efficiency is different between Mo and W, in order to reduce the variation in composition between the target and the obtained wiring thin film and obtain a uniform film composition, the composite / integrated target according to the form (A) For example, an alloy target is suitable.

The Mo-W alloy target as described above can be manufactured according to the manufacturing method and manufacturing conditions, for example, the powder particle size, molding condition, sintering condition, machining condition, A material having various densities, structures, and the like can be obtained depending on the melting casting conditions and the like in the melting method.
Furthermore, the density, texture, etc. of the target affect the characteristics of the obtained wiring thin film. Therefore, in order to prevent the generation of particles at the time of sputtering and to improve the characteristics of the Mo-W wiring thin film, it is preferable that the Mo-W target be dense and have a fine metal structure. The particles cause disconnection or short circuit of the wiring. Specifically, the relative density is 98% or more, and the average grain size of the crystal grains is 200%.
It is preferably less than μm.

Since the above-mentioned Mo-W target is a polycrystal in which crystal grains having different crystal orientations are aggregated, the sputtering rate differs depending on the crystal orientation of the crystal grains. Therefore,
As the crystal grains are larger, the sputtered surface becomes more uneven, and a step occurs between the crystal grains. For this reason, sputtered particles are likely to adhere to the steps and crystal planes and deposit. In particular, sputter particles from an oblique direction are unstablely deposited at the center and the end of the target. Such unstablely deposited sputtered particles (or an adhered film due to the sputtered particles) peel off or fall off during sputtering, causing particles to be generated. Furthermore, a splash due to abnormal discharge occurs at a large step portion, and particles are generated.

When the crystal grains in the Mo-W target are refined, the generation of particles as described above can be suppressed. Therefore, the average grain size of the crystal grains is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. Here, the grain size of the crystal grain referred to in the present invention refers to the value of “(major axis + minor axis) / 2” of the crystal grain when an arbitrary polished surface in the sputter surface direction is observed at a cross section of 100 times magnification. Things. The average grain size of the crystal grains is an average value of the crystal grains present in the polished surface measured in 30 or more visual fields.

Further, when pores exist in the Mo-W target, sputtered particles sputtered out by Ar ions that have entered the pores during sputtering accumulate on the edges of the pores to form projections. This protrusion causes abnormal discharge,
Generate particles. When the Mo-W target is densified, generation of the above particles can be suppressed. Therefore, the relative density of the Mo-W target is 9
It is preferably at least 8%, more preferably at least 99%, and still more preferably at least 100%.

Further, the residual processing distortion of the Mo-W target also affects the generation of particles. If a large processing strain remains in the target, the sputter rate varies locally due to the influence of the residual strain. Due to this difference in sputter rate, many steps are generated on the sputter surface, and the amount of generated particles increases. The processing strain can be eliminated by the heat treatment, and can be determined by the hardness that decreases as the processing strain decreases. Therefore, M
The Vickers hardness of the OW target is preferably Hv 350 or less, more preferably Hv 300 or less, and further preferably Hv 250 or less.

The specific structure of the Mo-W target described above depends on the manufacturing method and manufacturing conditions, etc., depending on the manufacturing method, manufacturing conditions, etc., the structure of a uniform solid solution phase of Mo and W, and the presence of Mo and / or W in the solid solution phase of Mo and W. Various structures can be obtained, such as a structure existing in a single phase and a structure in which a solid solution phase of Mo and / or W exists in a single phase of Mo and / or W. Therefore, they can be variously selected depending on the desired characteristics. In particular, since it is preferable that Mo and W are uniformly distributed in the target, the structure of the Mo-W target is Mo and W.
It is preferable to obtain a uniform solid solution phase.

More specifically, the Mo-W target for forming a wiring according to the present invention is, for example, (a) manufactured by a powder metallurgy method using a mixed powder containing Mo powder and W powder in a predetermined composition ratio. Target. (b) A target manufactured by a dissolution method so that Mo and W have a predetermined composition ratio. (c) A target in which a target piece made of Mo and unavoidable impurities and a target piece made of W and unavoidable impurities are divided for each metal and arranged in a complex manner. The composition ratio of Mo and W is adjusted by the area ratio of both. And the like. Target (a) and target (b)
Is a specific example of the above-described embodiment (A). target
(c) is a specific example of the above-described embodiment (B).

An example of a method for manufacturing the target (a) will be described below. First, Mo powder and W powder are mixed in a ball mill to produce a uniform mixed powder. At this time, nylon or ceramics can be applied to the material of the ball, but by setting the material of the inner wall of the ball mill or the ball to be used to Mo or W, the amount of impurities mixed into the target can be reduced. .

Next, the mixed powder is filled in a carbon mold or the like and sintered. Hot pressing in a vacuum can be applied to sintering. In addition, in order to improve sinterability and to densify, a combination of isostatic pressing such as cold isostatic pressing (CIP) and sintering in a reducing atmosphere such as a hydrogen atmosphere is applied. Is also good. Further, it is effective to subject the sintered body obtained by these methods to hot working such as HIP processing, forging, and rolling to further densify the target material. Hot press, heating temperature 1973K or more, surface pressure 20M
It is preferable to carry out the reaction at Pa or higher, and more preferable conditions are a heating temperature of 2073 K or higher and a surface pressure of 30 MPa or higher. Similarly, sintering after pressure molding is 1973K or more, more preferably
Preferably, the temperature is 2073K or higher. Preferred conditions for the HIP treatment are a heating temperature of 1773K or more and a pressure of 150MPa or more, more preferably a heating temperature of 2073K or more and a pressure of 180MPa.
That is all. This is because if the heating temperature and the surface pressure are too low, sintering does not easily proceed, and it is difficult to obtain a target material composed of a high-density sintered body.

The target material obtained by the powder metallurgy method described above is subjected to machining such as grinding to form a target material having a predetermined shape.
An oW target.

As the target (b), a sintered body composed of, for example, Mo, W and unavoidable impurities is produced by powder metallurgy, and then an ingot is produced by a melting method such as electron beam melting. Then, after performing hot working such as forging or rolling as necessary, machining such as grinding is performed to obtain a Mo-W target having a predetermined shape.

As described above, the Mo-W target for forming a wiring according to the present invention preferably satisfies the above-mentioned conditions regarding the density and the structure in order to prevent generation of particles during sputtering. For this reason,
In particular, it is preferable to apply a manufacturing method combining powder metallurgy and hot working. By subjecting the sintered body obtained by the powder metallurgy method to hot working, it is possible to maintain a fine crystal grain size and increase the density of the target material. For example, when the relative density is 98% or more and the average grain size of the crystal grains is 200 μm
The following Mo-W target is obtained. In the target material produced by the melting method, the crystal grain size tends to be coarse,
There is a possibility that the mechanical strength is reduced, cracks occur during hot working, and the like.

The sintered body subjected to the hot working described above preferably has a relative density of 90% or more. If the relative density of the sintered body is too low, the target material may not be finally densified even if hot working is performed. The sintered body subjected to hot working is preferably a sintered body of a press-formed body by CIP or the like. According to the hot press, Mo or W may react with the carbon mold at a high temperature at which densification is possible.

As described above, the wiring-forming Mo-W of the present invention is used.
A preferred method of manufacturing the target is a method in which a predetermined composition ratio (W:
Molding mixed powder adjusted to 25-45at%) (especially CIP
Etc.), a step of sintering the molded body in a reducing atmosphere such as a hydrogen atmosphere, and a step of hot working the sintered body. Further, it is preferable that the target material after hot working is subjected to a strain removing heat treatment in order to remove residual working strain.

The specific conditions of the above-described target manufacturing method are as follows. Density as described above,
In order to obtain a Mo-W target having a metal structure and hardness, the processing temperature during sintering in a reducing atmosphere such as a hydrogen atmosphere, the processing temperature and processing rate during hot working, and the subsequent heat treatment temperature are important. Factors.

First, the sintering temperature in a reducing atmosphere such as a hydrogen atmosphere affects the density of the target material. Therefore, the sintering temperature is preferably set to 2173K or more. If the sintering temperature is lower than 2173K, it becomes difficult to increase the relative density to 98% or more even after hot rolling. As for the sintering time, the density increases as the time becomes longer, but if the time is too long, the productivity is reduced. Therefore, about 5 to 30 hours is appropriate. A more preferred treatment temperature is 2272K or more, and further more preferably 2473K or more. Further, a more preferable sintering time is about 10 to 25 hours.

The processing temperature at the time of hot working is an important factor for preventing cracking at the time of working and stably manufacturing. In particular, pure tungsten tends to become brittle rapidly below 1473 K, and the processing temperature must be raised as the W content increases. Therefore, the processing temperature is preferably set to 1673K or higher, more preferably 1873K or higher. The processing time is 2 to 8 in consideration of the heat uniformity of the sintered body.
It is preferable to set the time to about time. Furthermore, when hot working is performed by hot rolling, it is preferable that the rolling reduction be 50% or more in order to make the relative density of the target 98% or more. Further, the rolling reduction is more preferably 60% or more, and further preferably 70% or more. here,
The rolling ratio (%) in the present invention is the ratio of the thickness of the sintered body before rolling to the thickness after rolling (working), and is expressed as ((thickness of sintered body before rolling−rolling (working)). Thickness after) / thickness of sintered body before rolling) × 100.

The heat treatment for removing strain performed after hot rolling is 1473-
It is preferably carried out at a temperature in the range of 1923K. If the heat treatment temperature is lower than 1473K, the residual strain may not be sufficiently removed. On the other hand, if the heat treatment temperature is higher than 1923K, pores may be generated in the material and particles may be generated. It is preferable to set the strain relief heat treatment temperature in the range of 1673 to 1823K.

The above-mentioned target (a) and target
(b) is preferably manufactured integrally to prevent the generation of particles during the formation of the thin film, but a plurality of targets having the same composition may be used in combination for the purpose of increasing the size of the target. In this case, the multiple targets are fixed by brazing to a backing plate or the like,
In particular, in order to prevent generation of particles from the edge portion, it is preferable that the targets be bonded by diffusion. As a method of diffusion bonding, a direct bonding method and
Various methods such as a method of bonding with o and / or W interposed and a method of bonding with a Mo and / or W plating layer interposed at the bonding portion are adopted.

Next, an example of a method for manufacturing the target (c) will be described. First, a Mo target piece and a W target piece are manufactured by a melting method such as a powder metallurgy method or an electron beam melting method. The obtained ingot is subjected to machining if necessary. By dividing each metal and arranging it in a complex manner, a Mo-W target having a predetermined shape is obtained. The composition ratio of Mo and W is adjusted by the area ratio of the two so that a predetermined composition ratio is obtained.

The characteristics of the obtained thin film are influenced by the structure of each target piece and the like. For this reason, the powder particle size of each powder in the powder metallurgy method, molding conditions, sintering conditions, machining conditions, melt casting conditions in the melting method, and the like are appropriately selected. As described above, by changing various manufacturing conditions, various structures, crystal structures, and the like of the obtained target can be obtained. It is preferable that the structure, density, and the like of each target piece have values according to the above-described alloy target.

In the target (c), since a plurality of target pieces are arranged in a complex manner, it is preferable that the target pieces are diffusion-bonded so as to prevent generation of particles particularly from an edge portion. As a method of the diffusion bonding, a direct bonding method, Mo and / or W
Bonding method, or a method of bonding with a Mo and / or W plating layer at the bonding portion,
Various methods can be employed.

[0052]

Next, specific examples of the present invention will be described.

Example 1 Mo powder having an average particle size of 10 μm and W powder having an average particle size of 10 μm
After blending so as to have various atomic percentages, the mixture was put into a ball mill whose inner wall was covered with Mo, and mixed for 48 hours using nylon balls to obtain a plurality of uniform mixed powders. After filling each mixed powder into a carbon mold, sintering was performed by vacuum hot pressing under the conditions of heating temperature of 2073K, heating time of 5 hours, and surface pressure of 30MPa to obtain sintered bodies with a density of 97%, respectively. Was. After that, each obtained sintered body is machined for cutting and grinding, diameter 250mm, thickness 8mm
Mo-W targets having the various compositions described above.

These Mo—W targets were bonded to an oxygen-free copper backing plate with an In-based brazing material, and then attached to a sputtering apparatus. Using such a sputtering apparatus, the distance between the glass substrate as a film forming substrate and the target was set to 70 mm, and after heating the glass substrate, the input power was 1 kW with a DC power supply, and the Ar pressure was 0.5 Pa.
Sputtering was performed under the following conditions to form Mo-W alloy films.

The resistivity of each of the obtained Mo—W alloy films was measured. The results are shown in FIG. 1 as a relationship with the W content.
As is clear from FIG. 1, the Mo—W wiring thin film of the present invention (W content = 25 to 45 at%) has a resistivity significantly lower than 40 μΩ · cm, and has a Mo film and a W film. It has a lower resistivity than a single film of the material.

Next, an example in which a wiring thin film formed using the above Mo-W target is applied to a liquid crystal display device will be described. FIG. 5 is a cross-sectional view showing an example of a TFT (switching element) and a storage capacitor portion used in the liquid crystal display device. The configuration and process of the TFT and the storage capacitor will be described.

On the glass substrate 11, the above-described M
The gate electrode (control electrode) 2, the address line, and the Cs line 9 are formed simultaneously by sputtering 300 nm using an ow target. Next, the oxide film 3 is formed to a thickness of 350 nm by plasma CVD.
After the formation, the a-Si active layer 4 is continuously formed so as to have a thickness of 300 nm and the n ⁺ a-Si layers 5a and 5b are formed so as to have a thickness of 50 nm, thereby forming an a-Si island portion. Next, the pixel electrode 8 is formed by sputtering ITO to a thickness of 120 nm. Next, the SiO _x
Is etched with dilute HF to form a contact hole. Then, a predetermined wiring metal such as Al is sputtered, and the source electrode (first electrode) 6 is wet-etched.
a, a drain electrode (second electrode) 6b and a data wiring are simultaneously formed. At this time, a surface oxidation treatment was required before sputtering of Al or the like.

Here, since the Mo—W wiring thin film of the present invention formed using the Mo—W target of the present invention has a low resistivity, the address wiring formed by using the thin film has a low resistance. . As a result, a gate pulse was not delayed due to wiring resistance, and a gate pulse having no delay in a predetermined switching element was obtained. In addition, the Mo of the present invention
Since the -W wiring thin film can be tapered, the step coverage of the interlayer insulating film formed on the address wiring formed using this alloy film is improved, and a high withstand voltage can be ensured. . Therefore, for example, even when the display area is enlarged, a highly reliable liquid crystal display device can be realized. Here, Table 1 shows the relationship between the composition ratio of the Mo-W target and the taper angle.

[0059]

[Table 1] The taper angle was measured by observing the cross section of the thin film with a SEM and measuring the angle with the glass substrate. As is clear from Table 1, the taper angle increases as the ratio of W increases, and it can be seen that the taper processing is good within the composition range of the present invention.

Next, in order to measure the chemical resistance of the Mo—W alloy films having the various compositions described above, an etchant of ITO as a pixel electrode material and a BH as an etchant of an interlayer insulating film were used.
The etching rates (nm / min) of the etchants of F and Al were measured. The result is shown in FIG.

As is clear from FIG. 2, the etching rate of the Mo—W alloy film is 8 nm / min or less for the etchant of ITO, and 3 to 4 for the etchant of Al.
It was 0 nm / min or less, and was not etched at all by BHF which is an etchant for the interlayer insulating film. W is 50a
In the case of t% or more, no etching is performed. Therefore, even when a pinhole is generated in the interlayer insulating film, the wiring under the interlayer insulating film such as the gate electrode and the data line is not corroded by the above-described etchants.
Therefore, there is an advantage that the degree of freedom of the structure design / process design above the interlayer insulating film can be increased.

FIG. 3 shows the results of measuring the stress (dyn / cm ² ) of the Mo—W alloys having the various compositions described above. As is clear from FIG. 3, since the stress greatly changes depending on the composition ratio, it is possible to reduce the stress by adjusting the composition ratio.

FIG. 4 shows the measurement results of the sputtering rate (nm / min) when a Mo—W alloy film was obtained by sputtering using a Mo—W target. This sputter rate is measured by the following method.

First, the Mo after sputtering was applied to the film thickness measurement points at the four corners of the glass substrate toward the center of the substrate and at the four center sides toward the opposing sides.
-Marking with oil-based ink for the purpose of reducing the adhesion of the W alloy film. Then, sputtering is performed to remove Mo-
After forming the W alloy film, an adhesive tape is attached to a portion marked with oil-based ink, and the Mo-W alloy film on the oil-based ink is peeled off when the tape is peeled off. Then, only the oil-based ink is wiped with an organic solvent or the like to obtain a glass substrate surface. The step between the part where the Mo-W alloy film was peeled off and the other part where the Mo-W alloy film was not peeled off was measured at the same position from the edge to the center using a step difference measuring device. The obtained film thickness was compared as a sputter rate (nm / min).

As is apparent from FIG. 4, the sputter rate is good when the ratio of W is low. In consideration of such a sputter rate and the etchant resistance as shown in FIG. 2, in the present invention, the ratio of W is in the range of 25 to 45 at%.

The above-described embodiment is an example of the present invention, and the thickness of each layer and the film forming method can be changed as appropriate. Even in such a case, the same effect as in the present embodiment can be obtained. The TFT has another structure, for example, a TFT having a structure in which a stopper of an insulating film is provided on a channel.
Etc. can also be used. The storage capacitor portion may have a structure formed in a wiring in the same layer as the gate electrode and a wiring in the same layer as the data wiring.

Example 2 Mo powder having an average particle diameter of 10 μm and W powder having an average particle diameter of 10 μm were
After blending so that the atomic% of W is in the range of 25-45%,
The resulting mixture was put into a ball mill whose inner wall was covered with Mo, and mixed for 30 hours using nylon balls to obtain a uniform mixed powder. The obtained mixed powder is filled in a molding die, and pressure
Wet-CIP molding was performed under the condition of 200 MPa. The obtained molded body was sintered in a hydrogen atmosphere under the conditions of 2073K × 10 hours to obtain a sintered body having a density of 90%. Thereafter, the obtained sintered body was subjected to machining processing such as cutting and grinding to obtain Mo-W targets having various compositions with a diameter of 250 mm and a thickness of 8 mm.
This Mo-W target was bonded to an oxygen-free copper packing plate with an In-based brazing material, and attached to a sputtering apparatus.

FIG. 6 is a sectional view of a TFT and a storage capacitor used in a liquid crystal display device different from that of the first embodiment.
The configuration and process of the TFT and the storage capacitor will be described.

On the glass substrate 11, a predetermined wiring metal such as Mo—Ta is sputtered to a thickness of 300 nm to form the gate electrode 1.
2. Address lines and Cs lines 19 are formed simultaneously. Next, an oxide film or a nitride film 13 is formed by plasma CVD.
After the formation of 50 nm, the a-Si layer 14 is continuously formed to have a thickness of 300 nm and the n ⁺ a-Si layers 15 a and 15 b are continuously formed to have a thickness of 50 nm.
An island-shaped portion i is formed. Next, the contact hole is
After forming by etching with F, the surface oxide film is removed.

After sputtering using the Mo-W target of the present invention, the source electrode 16a, the drain electrode 16b, and the data wiring are simultaneously formed by wet etching. Next, after forming the oxide film 17 to a thickness of 300 nm, etching using an HF-based solution (for example, an etching rate of about 10 nm / min) or dry etching using a gas such as CF ₄ (for example, an etching rate of about 3 to 10
A contact hole is formed on the drain electrode 16b at a speed of 120 nm / min.
To form

The Mo-W wiring thin film formed using the above-described Mo-W target of the present invention has excellent chemical resistance as described in the first embodiment. A data wiring made of a Mo-W wiring thin film having such excellent chemical resistance is an alkali etchant (pH 7 to 13) containing an oxidizing agent having a higher redox potential than an etchant used for etching a Mo film or a W film. By using, it was possible to perform tapering without deteriorating the resist.

Therefore, in the pixel array formed in this way, the data wiring is tapered, so that the stop coverage of the interlayer insulating film formed thereon is good, and a high withstand voltage can be secured. Further, since the drain electrode 16b has excellent chemical resistance, it is possible to form a contact hole with HF on the drain electrode 16b, and it is also possible to process the pixel electrode with a mixed solution of chlorine and nitric acid. there were. Further, the M of the present invention
It has been found that when wiring is formed using an oW wiring thin film, unlike Al, hillocks do not occur and no reaction with ITO occurs, so that a barrier metal is unnecessary.

As shown in the first embodiment, the Mo—W wiring thin film of the present invention has an advantage that it has basically low resistance, and further, the stress largely changes depending on the composition ratio of the Mo—W alloy. Therefore, the stress can be reduced.

The above-described embodiment is an example of the present invention, and the thickness of each layer and the film forming method can be changed as appropriate. Even in such a case, the same effect as in the present embodiment can be obtained. The TFT has another structure, for example, a TFT having a structure in which a stopper of an insulating film is provided on a channel.
Etc. can also be used. The storage capacitor portion may have a structure formed in a wiring in the same layer as the gate electrode and a wiring in the same layer as the data wiring.

Example 3 Mo powder having an average particle diameter of 10 μm and W powder having an average particle diameter of 10 μm were
After blending so that the atomic% of W is in the range of 25-45%,
The mixture was charged into a ball mill whose inner wall was covered with Mo, and mixed for 24 hours using nylon balls to obtain a uniform mixed powder. The obtained mixed powder was filled in a molding die, and pressure 20
Wet-CIP processing and molding were performed under 0 MPa conditions. The obtained compact was sintered in a hydrogen atmosphere under the conditions of 2073K for 8 hours,
A sintered body with a density of 90% was obtained. In addition, 2073
HIP treatment at 180MPa for 4 hours at K, density 98
% Sintered body was obtained. After that, the obtained sintered body is machined for cutting and grinding, and is 180 mm long, 180 mm wide and 6 mm thick.
mm target piece. The target pieces obtained in this way are combined in three pieces in the vertical direction and two pieces in the horizontal direction, and the Mo
A -W target was used. This Mo-W target was bonded to an oxygen-free copper backing plate with an In-based brazing material, and attached to a sputtering apparatus.

FIG. 7 is a sectional view of a TFT and a storage capacitor used in a liquid crystal display device different from those of the first and second embodiments. In the liquid crystal display device of this embodiment, similarly to the first embodiment, the above-described Mo-W
Sputtering 300nm using target, gate electrode 2
2. Address lines and Cs lines 29a are formed simultaneously. Next, similarly to the second embodiment, after sputtering using the Mo-W target of the present invention, the source electrode 26a, the drain electrode 26b, and the data wiring are simultaneously formed by wet etching.

The liquid crystal display device of the third embodiment is similar to that of the second embodiment.
In place of the back channel cut type TFT that etches the channel portion applied in the above, a TFT having a structure in which an insulating film stopper is provided on the channel is used.
The storage capacitor portion is formed by wiring in the same layer as the gate electrode and in the same layer as the data wiring.

That is, on the glass substrate 21, the M
Sputtering using an oW target, the gate electrode 2
2. Address lines and Cs lines 29a are formed simultaneously. Next, the interlayer insulating film 23, the a-Si layer 24, the channel protective layer 3
0, n ⁺ a-Si layers 25a and 25b are continuously formed. Then, sputtering is performed using a Mo-W target, and the source electrode 26a, the drain electrode 26b, the data wiring and the Cs
The line 29b is formed at the same time. Then, after forming the oxide film 27, a contact hole is formed on the drain electrode 26b, and the pixel electrode 28 is formed.

According to the third embodiment, both the effects of the first embodiment and the effects of the second embodiment can be obtained.

Here, the present invention is not limited to the embodiment described above, and the semiconductor is not limited to a-Si, but may be p-Si,
It may be formed using CdSe or the like. The insulating film on the data wiring is not limited to the oxide film, but may be a nitride film. further,
In the wiring thin film of the present invention, instead of adopting a one-layer structure as in the above embodiment, Mo-W having a different composition is used.
It may be formed as a laminated film of two or more layers made of an alloy. Oxidation resistance may be improved by laminating Ta, TaN or the like on the wiring thin film of the present invention. Further, Al, Cu or the like may be laminated below the wiring thin film of the present invention to lower the resistance.

Example 4 A mixed powder obtained by mixing Mo powder having an average particle diameter of 4.5 μm and W powder having an average particle diameter of 3.6 μm at a predetermined ratio was filled in a molding rubber mold, and then a pressure of 200 MPa was applied. A molded article was prepared by addition by CIP. Next, the obtained molded body was sintered under various conditions in a hydrogen atmosphere. The sintering conditions are as shown in Table 2. Further, these sintered bodies were heated in a hydrogen atmosphere to perform hot rolling of the cloth. The rolling conditions are as shown in Table 2. These rolled materials were heat-treated under the conditions shown in Table 2 and then machined to obtain Mo-W targets each having a diameter of 250 mm and a thickness of 8 mm.
Thus, each of the Mo-W targets No. 1 to No. 18 shown in Table 2 was obtained.

The reference examples (No19 to No26) in Table 2 are as follows:
Example 4 except that the hydrogen sintering conditions, the rolling conditions, and the heat treatment conditions were out of the preferred ranges of the present invention.
This is a Mo-W target produced in the same manner as in the above.

[0083]

[Table 2] The relative density, the average grain size of the crystal grains, and the Vickers hardness of each Mo-W target according to Example 4 and the reference example described above were measured. Table 3 shows the results. Furthermore, each Mo
The -W target was mounted on a DC magnetron sputtering apparatus, and a Mo-W alloy film (thickness = 30 nm) was formed by sputtering on the surface of a 6-inch Si wafer. Obtained Mo-W
The number of particles of 0.3 μm or more present in the alloy film was examined. The measurement result of the number of particles is based on Mo- after removing 5 mm from the edge of the 6-inch Si wafer.
5 is a measurement result of the number of particles in a W alloy film. Table 3 also shows the results.

[0084]

[Table 3] As is clear from Table 3, each of the Mo—W targets according to Example 4 had a relative density of 98% or more and a Vickers hardness of Hv 350 or less. And it turned out that the number of generated particles can be significantly reduced by forming a film using such a Mo-W target.

Further, the Mo- of sample No. 11 in Example 4 was used.
FIG. 8 shows an optical microscope photograph (magnification: 100 ×) showing the metal structure of the W target in an enlarged scale, and an optical microscope photograph (magnification: 100) showing the metal structure of the Mo—W target of sample No. 15 in an enlarged manner.
9) is shown in FIG. In addition, M of sample No. 25 in Reference Example
FIG. 10 shows an optical microscope photograph (magnification: 100 times) showing the metal structure of the oW target in an enlarged manner.

FIG. 8 shows a metal structure from which distortion has been removed. On the other hand, FIG. 10 shows a state where the strain is not sufficiently removed because the temperature of the strain removing heat treatment is low. FIG. 9 shows a state where distortion has been removed and recrystallization has occurred. As shown in FIG. 9, since the strain is completely removed by recrystallization, the M
It is suitable as an oW target.

FIG. 8 shows a state in which the distortion has been removed. However, the distortion is not as complete as in FIG. 9 and a slight distortion remains. . Therefore, it is preferable to recrystallize. However, if the temperature of the strain-relieving heat treatment is too high, some pores are generated in the crystal. Therefore, it is preferable to set a temperature at which no pores are generated.

Further, when the liquid crystal display devices shown in the above-described Embodiments 1, 2 and 3 were produced using the Mo-W target according to Embodiment 4, similar good results were obtained. Was done. Furthermore, since the Mo-W wiring thin film formed using the Mo-W target according to Example 4 has a significantly small number of particles, it was possible to further improve the electrical characteristics of the address wiring and the data wiring. .

The present invention is not limited to the configuration and the manufacturing method of each of the above-described embodiments, and the Mo—W material and the Mo—W target of the present invention are used to form the wiring thin film of the present invention. The present invention can be applied to any device that uses the device or uses the Mo-W wiring thin film of the present invention. For example, the present invention is effective not only for wiring of a liquid crystal display device, but also for wiring of a plasma display device, a solid-state display device, a flat display device using a field emission cold cathode, and the like.

[0090]

As is clear from the above description, the Mo-W material for forming a wiring according to the present invention has a low resistance, can be tapered, and has excellent etchant resistance. It is very effective as a material for forming address wirings and data wirings. Since the Mo-W wiring thin film of the present invention uses the Mo-W material (Mo-W alloy) as described above, it greatly contributes to the improvement of operation characteristics and reliability of a liquid crystal display device and the like. In addition, the Mo for forming a wiring according to the present invention.
The -W target enables the Mo-W wiring thin film as described above to be formed favorably and with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the resistivity of a Mo—W alloy and the W content.

FIG. 2 is a diagram showing a relationship between an etching rate and a W content for each etchant of the Mo—W alloy.

FIG. 3 is a diagram showing the relationship between the stress of the Mo—W alloy and the W content.

FIG. 4 is a diagram showing the relationship between the W content and the sputtering rate when a Mo—W alloy film is obtained by sputtering using a Mo—W target.

FIG. 5 is a cross-sectional view of a TFT and a storage capacitor used in a liquid crystal display device.

FIG. 6 is a sectional view of a TFT and a storage capacitor portion used in another liquid crystal display device.

FIG. 7 is a cross-sectional view of a TFT and a storage capacitor portion used in another liquid crystal display device.

FIG. 8 is an enlarged micrograph showing a metal structure of a Mo—W target formed in one example of the present invention.

FIG. 9 is an enlarged micrograph showing a metal structure of a Mo—W target formed in another example of the present invention.

FIG. 10 is an enlarged micrograph showing a metal structure of a Mo—W target formed as a reference example.

[Explanation of symbols]

 1, 11, 21 ... glass substrate 2, 12, 22 ... gate electrode 3 ... oxide film 4, 14, 24 ... a-Si layer 6a, 16a, 26a ... source electrode 6b, 16b, 26b ... Drain electrode 8, 18, 28 ... Pixel electrode 9, 19, 29a ... Cs line 13 ... Oxide film or nitride film 23 ... Interlayer insulating film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Ikeda 2-3-20- 711, Tarumachi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Michio Sato 488-7-1-1, Sugata-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture 205 (72) Inventor Toshihiro Maki 3-8-15-P 2-101 Konan-ku, Yokohama, Kanagawa

Claims (23)

[Claims] 1. A wiring-forming Mo-W comprising 25 to 45% of tungsten in atomic percent and the balance of molybdenum and unavoidable impurities when viewed as a unit.
Wood. 2. The Mo-W material for wiring according to claim 1, wherein the average grain size of the crystal grains is 200 μm or less. 3. The Mo-W material for wiring formation according to claim 1, wherein the Vickers hardness is Hv 350 or less. 4. The Mo-W material for forming a wiring according to claim 1, wherein the amount of oxygen in the Mo-W material is 500 ppm or less. 5. A Mo-W for forming a wiring, comprising 25 to 45% of tungsten in atomic percent and the balance of molybdenum and unavoidable impurities when viewed as a unit.
target. 6. The Mo-W target for wiring formation according to claim 5, wherein the tungsten and molybdenum are combined and integrated. 7. The Mo-W target for wiring formation according to claim 5, wherein the tungsten and molybdenum are alloyed. 8. The Mo-W target for wiring formation according to claim 5, wherein the Mo-W target is formed of a sintered body by a powder metallurgy method. 9. The wiring forming Mo-W target according to claim 5, wherein the Mo-W target is formed of a processed material obtained by hot working a sintered body by a powder metallurgy method. Mo-W target. 10. The Mo-W target for wiring according to claim 5, wherein the Mo-W target has a metal structure composed of a uniform solid solution phase of molybdenum and tungsten. -W target. 11. The Mo-W target for wiring formation according to claim 5, wherein the Mo-W target has a relative density of 98% or more. 12. The Mo-W target according to claim 5, wherein the Mo-W target has an average crystal grain size of 200 μm.
A Mo-W target for forming a wiring, characterized in that: 13. The Mo-W target according to claim 5, wherein the Mo-W target has an average crystal grain size of 100 μm.
A Mo-W target for forming a wiring, characterized in that: 14. The Mo-W target for wiring formation according to claim 6, wherein the Mo-W target has a Vickers hardness of Hv 350 or less. 15. The Mo-W target for wiring formation according to claim 6, wherein the Mo-W target has a Vickers hardness of Hv 300 or less. 16. The Mo-W target for wiring formation according to claim 6, wherein the Mo-W target has a Vickers hardness of Hv 250 or less. 17. The Mo-W target for wiring formation according to claim 5, wherein the amount of oxygen in the Mo-W target is 500 ppm or less. 18. A Mo-W material comprising 25 to 45% of tungsten in atomic percent, the balance being molybdenum and unavoidable impurities, when viewed as a single body.
The material has a relative density of 98% or more and an average crystal grain size of 200 μm
Hereinafter, a Mo-W target for wiring formation, having a Vickers hardness of 350 or less Hv. 19. An atomic percent of tungsten 25-4.
5%, a step of molding a mixed powder adjusted to be composed of molybdenum and unavoidable impurities, a step of sintering the compact obtained in the compacting step in a reducing atmosphere, and a step of sintering the compact in a reducing atmosphere. Hot-working the obtained sintered body. A method for producing a Mo-W target for forming a wiring, comprising: 20. The Mo-W for forming a wiring according to claim 19.
A method of manufacturing a target for forming a wiring, further comprising a step of performing a strain removing heat treatment on the work material obtained in the hot working step. 21. A Mo-W wiring thin film formed by using the Mo-W target according to claim 5. 22. A liquid crystal display device comprising the Mo-W wiring thin film according to claim 21 for at least a part of wiring. 23. The liquid crystal display device according to claim 22, wherein the Mo-W wiring thin film is used as at least one of a gate electrode, an address line, and a Cs line.