JP2006339666A - Sputtering target for forming aluminum-alloy film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target useful for forming an aluminum-alloy film, in which the aluminum-alloy film can make direct contact with a transparent electrode, and a barrier metal can be eliminated. <P>SOLUTION: The sputtering target for forming the aluminum-alloy film includes 0.1-6 atomic% X<SB>1</SB>(X<SB>1</SB>= at least one kind of Ag, Zn, Cu and Ni) and 0.1-6 atomic% X<SB>2</SB>(X<SB>2</SB>=Nd) as the alloy components. Those contents satisfy a relationship of formula (I): 0.7≤0.5×CX<SB>1</SB>+CX<SB>2</SB>≤4.5. Where, in the formula (I), the CX<SB>1</SB>represents the content (atomic%) of Ag, Zn, Cu and Ni in the aluminum-alloy, and the CX<SB>2</SB>represents the content (atomic%) of Nd in the aluminum-alloy, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a sputtering target for forming an aluminum alloy film, and includes, for example, a pixel electrode and an aluminum alloy film used in active and passive matrix flat panel displays such as semiconductors and liquid crystal displays, reflective films, optical components, and the like. The present invention relates to a sputtering target used for forming the aluminum alloy film when manufacturing a novel display device or the like.

For example, an active matrix type liquid crystal display device uses a thin film transistor (TFT) as a switching element, a TFT array substrate having pixel electrodes and wiring portions such as scanning lines and signal lines, and a predetermined distance from the TFT array substrate. And a counter substrate having a common electrode disposed opposite to each other and a liquid crystal layer filled between the TFT array substrate and the counter substrate. As the pixel electrode, an indium tin oxide (ITO) film in which indium oxide (In ₂ O ₃ ) contains about 10% by mass of tin oxide (SnO) is used.

  In addition, the signal line of the wiring portion electrically connected to the pixel electrode is made of Mo, Cr, Ti, W as a barrier metal so that the pixel electrode is not in direct contact with pure aluminum or an aluminum alloy such as Al-Nd. However, recently, attempts have been made to omit these refractory metals and directly connect the pixel electrodes to the signal lines.

  For example, according to Patent Document 1, if a pixel electrode made of an ITO film in which about 10% by mass of zinc oxide is contained in indium oxide is used, direct contact with a signal line becomes possible.

Patent Document 2 discloses a method of performing surface treatment on the drain electrode by plasma treatment or ion implantation. Patent Document 3 discloses N, O, Si, and the like as the first layer gate, source, and drain electrodes. A method of forming a laminated film in which a second phase containing impurities such as C is laminated is disclosed. If these methods are employed, contact resistance with a pixel electrode can be reduced even when the above-described refractory metal is omitted. It has been shown that it can be maintained at a low level.
Japanese Patent Laid-Open No. 11-337976 JP-A-11-283934 JP-A-11-284195

  The reason why the barrier metal is interposed in the above-described conventional technology is that when the pixel electrode is directly contacted with the aluminum or aluminum alloy wiring constituting the signal line, the contact resistance is increased and the display quality of the screen is decreased. This is because aluminum is very easy to oxidize, and the surface is easily oxidized in the atmosphere. Also, since the pixel electrode is a metal oxide, aluminum is oxidized by oxygen generated during film formation and oxygen added during film formation. This is because an aluminum oxide layer is formed on the surface. When the insulating layer is formed at the contact interface between the signal line and the pixel electrode in this way, the contact resistance between the signal line and the pixel electrode increases, and the display quality of the screen decreases.

  On the other hand, barrier metal originally has the effect of preventing the surface oxidation of the aluminum alloy and improving the contact between the aluminum alloy film and the pixel electrode. To obtain a conventional structure in which the barrier metal is interposed at the contact interface. Since the barrier metal formation process is indispensable, in addition to the film formation sputtering apparatus required for forming the gate electrode, the source electrode, and the drain electrode, an additional film formation chamber for forming the barrier metal must be provided. Don't be. However, as the cost of liquid crystal panels and the like by mass production advances, the increase in manufacturing cost and the decrease in productivity due to the formation of barrier metal cannot be neglected.

  For these reasons, recently, electrode materials and manufacturing processes that can eliminate the barrier metal have been demanded. In response to such a request, in the above-mentioned Patent Document 2, a step for surface treatment is weighted by one step. On the other hand, in Patent Document 3, a gate electrode, a source electrode, or a drain electrode can be continuously formed in the same film formation chamber, but an increase in the number of steps is unavoidable. In addition, due to the difference in thermal expansion coefficient between the film that contains impurities and the film that does not, the film frequently peels off from the wall of the chamber during continuous use. There must be. Furthermore, in Patent Document 1, since the most popular indium tin oxide (ITO) film must be changed to an indium zinc oxide (IZO) film, the material cost is high.

  Furthermore, in order to maintain the display quality of the display device, the electrode material is required to have a low electrical resistance and a high level of heat resistance. For example, the characteristics required when used as a source or drain electrode material of an amorphous TFT, which is one of the elements of a display device, are an electrical resistivity of 8 μΩ · cm or less (preferably 5 μΩ · cm or less), and a heat resistant temperature is 300-350 ° C. The characteristics required for use as a gate electrode material are an electrical resistivity of 8 μΩ · cm or less and a heat resistant temperature of 400 to 450 ° C. Since the source / drain electrodes always pass a current for reading / writing the pixel, it is desirable to suppress the electric resistivity and reduce the power consumption of the display device. Moreover, it is necessary to reduce the time constant determined by the product of the resistance and the regulation capacity so that the display quality can be maintained even when the display panel is enlarged. Further, the required heat resistance varies depending on the structure of the display device, and depends on the film formation temperature of the insulating film used in the post-process after electrode formation, the film formation of the semiconductor layer, and the heat treatment temperature.

  The present invention has been made by paying attention to the above-described circumstances, and the object thereof is to enable the omission of the barrier metal as described above, for example, and to simplify the pixel electrode without increasing the number of processes, and to make the pixel electrode. Another object of the present invention is to provide a sputtering target for forming an aluminum alloy film that can be brought into direct and reliable contact.

  The sputtering target of the present invention is used for manufacturing a display device. The display device includes a thin film transistor disposed on a glass substrate, a pixel electrode formed by a transparent electrode, and the thin film transistor and the pixel electrode electrically. The aluminum alloy film and the pixel electrode are directly connected without a refractory metal, and a part or all of the alloy components constituting the aluminum alloy film are precipitated. Or it exists as a concentrated layer.

  The aluminum alloy film preferably contains 0.1 to 6 atomic% of at least one selected from the group consisting of Au, Ag, Zn, Cu, Ni, Sr, Sm, Ge, and Bi as an alloy component. Those containing at least Ni are preferable.

As the constituent material of the pixel electrode, indium tin oxide or indium zinc oxide is suitable, and the aluminum alloy film has a part or all of the alloy components dissolved in a non-equilibrium state as a precipitate or a concentrated layer. It is preferable that it exists and has an electrical resistivity of 8 μΩ · cm or less. At the contact interface between the aluminum alloy film and the pixel electrode, the number of conductive precipitates made of the second phase exceeds 0.13 per 100 μm ^{2 on the} assumption that the size of the conductive precipitate of the second phase exceeds 0.01 μm. It is preferable that it exists or exceeds 0.5% by area ratio.

  The aluminum alloy film may further contain at least one selected from the group consisting of Nd, Fe, and Co in the range of 0.1 to 6 atomic% as another alloy component.

Among the above-mentioned aluminum alloy films, X ₁ (at least one of X ₁ = Ag, Zn, Cu, Ni) and X ₂ (X ₂ = Nd) are included as the alloy components, and their contents Satisfying the following formula (I):
0.7 ≦ 0.5 × CX ₁ + CX ₂ ≦ 4.5 (I)
[Wherein, CX ₁ represents the content (atomic%) of Ag, Zn, Cu, Ni in the aluminum alloy, and CX ₂ represents the content (atomic%) of Nd in the aluminum alloy].

Alternatively, as an alloy component, X ₁ (at least one of X ₁ = Ag, Zn, Cu, Ni) and X ₃ (X ₃ = at least one of Fe, Co) are included, and the content thereof is represented by the following formula: It satisfies the relationship (II).
1 ≦ CX ₁ + CX ₃ ≦ 6 (II)
[Wherein CX ₁ represents the content (atomic%) of Ag, Zn, Cu, and Ni in the aluminum alloy, and CX ₃ represents the content (atomic%) of Fe and Co in the aluminum alloy, respectively).

  The aluminum alloy film containing Ni as an alloy component preferably has a Ni concentrated layer having a Ni content of 10 atomic% or less in a thickness region of 1 to 10 nm from the surface of the film. These aluminum alloy films effectively function as reflective films or tab connection electrodes in display devices.

  The display device can also be applied to a passive matrix display device that does not include a thin film transistor.

  The manufacturing method disclosed in the present specification is positioned as a useful method for manufacturing the display device, and the structure thereof is obtained after an aluminum alloy film containing the above alloy components is formed on a glass substrate. By heat-treating at a temperature of 150 to 400 ° C., one or all of the alloy elements contained in the aluminum alloy film are included in the contact interface between the aluminum alloy film containing aluminum as a main phase and the pixel electrode. The gist is that a conductive precipitate composed of the second phase is formed.

  In carrying out this method, by partially diffusing part or all of the alloy components solid-dissolved in the aluminum alloy film in a non-equilibrium state and the alloy components of the pixel electrode, the aluminum alloy film and the pixel electrode An intermetallic compound can be formed at the contact interface. A sputtering method is employed as a preferred method for forming the aluminum alloy film. Then, after forming an insulating film on the aluminum alloy film and performing contact hole etching on the insulating film, the aluminum alloy wiring is subsequently light etched from 1 to 200 nm, more preferably from 3 to 100 nm from the aluminum alloy surface. If a part or all of precipitates or intermetallic compounds of the alloy components dissolved in a non-equilibrium state in the aluminum alloy film are partially exposed, the contact resistance with the pixel electrode formed thereon is reduced. Since it can reduce further, it is preferable.

  The light etching can be performed by dry etching using a gas that can etch the aluminum alloy film, or wet etching using a chemical that can etch the aluminum alloy film, and as a chemical used in the light etching process. It is preferable to use a photoresist stripping solution used for patterning.

The sputtering target of the present invention is a useful target for forming an aluminum alloy film as described above, and X ₁ (at least one of X ₁ = Ag, Zn, Cu, Ni) is 0 as an alloy component. 0.1-6 atom% and X ₂ (X ₂ = Nd) 0.1-6 atom%, and their content satisfies the relationship of the following formula (I),
0.7 ≦ 0.5 × CX ₁ + CX ₂ ≦ 4.5 (I)
[Wherein, CX ₁ represents the content (atomic%) of Ag, Zn, Cu, Ni in the aluminum alloy, and CX ₂ represents the content (atomic%) of Nd in the aluminum alloy].

Alternatively, X ₁ (at least one of X ₁ = Ag, Zn, Cu, Ni) is 0.1 to 6 atomic% as an alloy component, and X ₃ (at least one of X ₃ = Fe, Co) is 0. 1 to 6 atomic% is included, and the content thereof is characterized by satisfying the relationship of the following formula (II).
1 ≦ CX ₁ + CX ₃ ≦ 6 (II)
[Wherein CX ₁ represents the content (atomic%) of Ag, Zn, Cu, and Ni in the aluminum alloy, and CX ₃ represents the content (atomic%) of Fe and Co in the aluminum alloy, respectively).

  According to the present invention, an aluminum alloy film and a pixel electrode can be directly contacted, and the manufacturing process and cost are greatly reduced by omitting a barrier metal, so that an inexpensive and high-performance display device and display device array are provided. A sputtering target useful for manufacturing a substrate can be provided.

  When the sputtering rig target of the present invention is used, an element that has a relatively low electrical conductivity as an oxide, such as a precious metal that is not easily oxidized such as Au or Ag, or Zn, Cu, Ni, Sr, Ge, Sm in aluminum. Further, by adding a trace amount of an element having a low solid solubility limit in aluminum such as Bi to aluminum or an aluminum alloy, the contact between the aluminum alloy film and the pixel electrode can be prevented without deteriorating the conductivity of the wiring material itself. A region with low electrical resistance is formed partially or entirely on the interface, thereby greatly reducing the contact resistance between the aluminum alloy film and the pixel electrode, and maintaining the display quality of the liquid crystal display at a high level, while maintaining the number of processes. And manufacturing costs can be greatly reduced. Furthermore, the heat resistance can be significantly improved by adding at least one selected from Nd, Fe, and Co.

  Hereinafter, embodiments of a display device and a display device array substrate using the sputtering target of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the illustrated examples. The present invention can be implemented with appropriate modifications within a range that can be adapted to the purpose described above and below, and these are all included in the technical scope of the present invention.

  The sputtering of the present invention also applies to a reflective electrode such as a passive matrix drive display device that does not include a thin film transistor, a reflective liquid crystal display device, and a TAB (tab) connection electrode used for signal input / output to the outside. Although an aluminum alloy film using a target can be similarly applied, these embodiments are omitted.

  FIG. 1 is a schematic cross-sectional enlarged explanatory view of a liquid crystal panel structure mounted on a liquid crystal display device.

  The liquid crystal panel of FIG. 1 is disposed between a TFT array substrate 1, a counter substrate 2 disposed to face the TFT array substrate 1, and between the TFT array substrate 1 and the counter substrate 2, and serves as a light modulation layer. A functioning liquid crystal layer 3 is provided. The TFT array substrate 1 includes a thin film transistor (TFT) 4 disposed on an insulating glass substrate 1a, a pixel electrode 5, and a wiring portion 6 including scanning lines and signal lines.

  The counter substrate 2 includes a common electrode 7 formed on the entire surface of the TFT array substrate 1, a color filter 8 disposed at a position facing the pixel electrode 5, a thin film transistor (TFT) 4 on the TFT array substrate 1 and a wiring portion. 6 is formed of a light shielding film 9 disposed at a position facing 6.

  Further, polarizing plates 10 and 10 are disposed on the outer surface side of the insulating substrate constituting the TFT array substrate 1 and the counter substrate 2, and the liquid crystal molecules contained in the liquid crystal layer 3 are placed on the counter substrate 2 in a predetermined manner. An alignment film 11 for aligning in the direction is provided.

  In the liquid crystal panel having such a structure, the alignment direction of the liquid crystal molecules in the liquid crystal layer 3 is controlled by the electric field formed between the counter electrode 2 and the pixel electrode 5, and the liquid crystal panel between the TFT array substrate 1 and the counter substrate 2 is controlled. The light passing through the liquid crystal layer 3 is modulated, whereby the amount of light transmitted through the counter substrate 2 is controlled to display an image.

  The TFT array is driven by a driver circuit 13 and a control circuit 14 by a TAB tape 12 drawn out of the TFT array.

  In the figure, 15 is a spacer, 16 is a sealing material, 17 is a protective film, 18 is a diffusion plate, 19 is a prism sheet, 20 is a light guide plate, 21 is a reflector, 22 is a backlight, 23 is a holding frame, and 24 is a print. Each of the substrates is shown and will be described later.

  FIG. 2 is a schematic cross-sectional explanatory view illustrating the structure of the thin film transistor portion according to the first embodiment applied to the array substrate employed in the present invention. As shown in FIG. 2, a scanning line 25 is formed of an aluminum alloy film on the glass substrate 1a, and a part of the scanning line 25 functions as a gate electrode 26 for controlling on / off of the thin film transistor. A signal line is formed of an aluminum alloy film so as to cross the scanning line 25 with the gate insulating film 27 interposed therebetween, and a part of the signal line functions as a source electrode 28 of the thin film transistor.

In the pixel region on the gate insulating film 27, for example, a pixel electrode 5 formed of an ITO film in which Sn 2 is contained in In ₂ O ₃ is disposed. A drain electrode 29 of a thin film transistor formed of an aluminum alloy film using the sputtering target of the present invention is in direct contact with and electrically connected to the pixel electrode 5.

  When a gate voltage is supplied to the TFT array substrate 1 via the scanning line 25 to the gate electrode 26, the thin film transistor is turned on, and the driving voltage supplied to the signal line in advance from the source electrode 28 to the pixel via the drain electrode 29. Supplied to the electrode 5. When a predetermined level of drive voltage is supplied to the pixel electrode 5, a potential difference is generated between the pixel electrode 5 and the counter electrode 2 as described with reference to FIG. 1, and the liquid crystal molecules contained in the liquid crystal layer 3 are aligned to perform light modulation. Is called.

  Next, a method for manufacturing the TFT array substrate 2 shown in FIG. 2 will be briefly described. Here, an example of the thin film transistor formed as the switching element is an amorphous silicon TFT using hydrogen amorphous silicon as a semiconductor layer.

  An outline of the manufacturing process of the TFT array substrate 1 according to the first embodiment will be described with reference to FIGS.

  First, an aluminum alloy thin film having a film thickness of, for example, about 200 nm is formed on the glass substrate 1a by a method such as sputtering, and the gate electrode 26 and the scanning line 25 are formed by patterning the aluminum alloy thin film (FIG. 3). At this time, it is preferable to etch the periphery of the aluminum alloy thin film in a taper shape of about 30 to 40 degrees so that the coverage of the gate insulating film 27 described later is improved. Next, as shown in FIG. 4, a gate insulating film 27 is formed of, for example, a silicon oxide film (SiOx) having a film thickness of about 300 nm by a method such as plasma CVD, and further, for example, a hydrogenated amorphous film having a film thickness of about 50 nm. A silicon film (a-Si: H) and a silicon nitride film (SiNx) having a thickness of about 300 nm are formed.

Subsequently, as shown in FIG. 5, the silicon nitride film (SiNx) is patterned by backside exposure using the gate electrode 26 as a mask to form a channel protective film. Further, an n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si: H) having a thickness of, for example, about 50 nm doped with phosphorus is formed thereon, and then, as shown in FIG. a-Si: H) and n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si: H) are patterned.

Then, an aluminum alloy film having a thickness of, for example, about 300 nm is formed thereon, and is patterned as shown in FIG. 7, so that the source electrode 28 integrated with the signal line and the drain electrode 29 in contact with the pixel electrode 5 are formed. Form. Further, the n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si: H) on the channel protection film (SiNx) is removed using the source electrode 28 and the drain electrode 29 as a mask.

  Then, as shown in FIG. 8, an interlayer insulating film is formed by forming a silicon nitride film 30 with a film thickness of about 300 nm, for example, using a plasma CVD apparatus or the like. The film formation at this time is performed at about 300 ° C., for example. Then, after a photoresist layer 31 is formed on the silicon nitride film 30, the silicon nitride film 30 is patterned, and contact holes 32 are formed in the silicon nitride film 30 by, for example, dry etching. At this time, even after the etching of the silicon nitride film 30 is completed, overetching of about 10% of the time required for etching the silicon nitride is further added. By this treatment, the surface of the aluminum alloy is also etched by about several tens of nm.

  Further, as shown in FIG. 9, after undergoing an ashing process using, for example, oxygen plasma, the photoresist layer 31 is stripped using, for example, an amine-based stripping solution. Finally, as shown in FIG. When the ITO electrode film is formed and the pixel electrode 5 is formed by patterning, the TFT array substrate is completed.

  In the TFT array substrate formed by such a manufacturing process, the pixel electrode 5 and, for example, the drain electrode 29 formed of an aluminum alloy are in direct contact. The aluminum alloy used in the present invention can also be used as a reflective electrode or a tab connection electrode of a reflective liquid crystal.

  When carrying out the above manufacturing method, for example, as an aluminum alloy film material constituting the drain electrode 29, at least one selected from the group consisting of Au, Ag, Zn, Cu, Ni, Sr, Sm, Ge, Bi is alloyed. When a sputtering target made of an aluminum alloy containing 0.1 to 6 atomic% as a component is used, the contact interface between the aluminum alloy film constituting the drain electrode 29 and the pixel electrode 5 according to the formation conditions of the drain electrode 29 In addition, for example, three types of interfaces are formed as shown in the enlarged sectional conceptual views of FIGS.

  Incidentally, if the amount of the alloy component contained in the aluminum alloy film is less than 0.1 atomic%, the amount of the concentrated layer, precipitates, and intermetallic compound formed at the contact interface with the pixel electrode is insufficient. The effect of reducing the contact resistance at the level intended by the invention is difficult to obtain. Conversely, if it is excessively contained in excess of 6 atomic%, the electrical resistance of the aluminum alloy film is increased and the response speed of the pixel is lowered, resulting in a reduction in power consumption. Increases and the quality of the display deteriorates, making it unusable for practical use. Therefore, in consideration of these advantages and disadvantages, the content of the alloy component is suppressed to 0.1 atomic% or more, more preferably 0.2 atomic% or more, and 6 atomic% or less, more preferably 5 atomic% or less. Is desired.

  In FIG. 11, the conductive precipitate containing the above-mentioned solid solution element is formed at the contact interface between the aluminum alloy film and the pixel electrode 5, and most of the contact current flows through the precipitate, whereby the aluminum alloy and the pixel are connected. It is the figure which showed notionally the state in which the electrode is electrically conducting. In such a state, for example, the heat history during the formation of the insulating film as described below or the heat treatment before the contact hole etching after the formation of the wiring film is performed, and a conductive precipitate containing a solid solution element is formed at the aluminum grain boundary. Can be obtained by:

  That is, a thermal history is added at the time of forming the insulating film, or after the formation of the wiring film and before the contact hole etching, preferably by heat treatment at 150 to 400 ° C. for 15 minutes or more to recrystallize the solid solution element. Or an intermetallic compound of a solid solution element containing aluminum is formed at the aluminum grain boundary.

  Next, in the contact hole etching process of the insulating film, an over-etching time is added so that about 1 to 200 nm, more preferably about 3 to 100 nm is etched from the surface of the aluminum alloy film, and light etching is performed on the surface of the aluminum alloy film. Apply. As the same effect, in the photoresist stripping process after the contact hole etching process of the insulating film, an amine stripping solution having a light etching effect on aluminum is used, and a solid solution element precipitate or metal is deposited on the surface of the aluminum alloy film. It is also possible to expose part of the intermetallic compound. At this time, even if an insulating film is formed on the surface of the aluminum alloy, the exposed portion hardly forms an oxide film as compared with aluminum due to the characteristics of the solid solution element. Forms a conductive oxide. In addition, since the exposed portion has low electric resistance, electricity easily flows, and even when the aluminum alloy film formed by the sputtering target of the present invention is directly connected to the pixel electrode 5, the contact resistance can be kept low.

  The type of stripping solution used here is not particularly limited, but preferably contains about 5 to 70% by mass, more preferably about 25 to 70% by mass of monoethanolamine as a main component. This stripping solution is a stripping solution generally used for the purpose of removing altered films and polymer films remaining after etching various metal materials, and has a high effect of removing contaminants. Therefore, a sufficiently low contact resistance value can be secured by using such a stripping solution for cleaning.

  In addition, an amine-based stripping solution such as hydroxylamine, and a stripping solution containing about 5 to 25% by weight of water in addition to the amine-based main component also has an excellent light etching effect, and has a thin aluminum Any oxide can be removed. However, this type of stripping solution is expensive, and the etching rate with respect to the aluminum alloy is fast, so that it is somewhat difficult to control.

  FIG. 12 shows a conceptual diagram in which a Ni concentrated layer is formed on the surface of the aluminum alloy at the pixel electrode interface as a structure capable of further reducing contact resistance in an aluminum alloy film using a sputtering target containing Ni. The thickness of the Ni enriched layer is preferably 1 to 10 nm, the Ni concentration is not less than the concentration of the aluminum alloy inside the thin film, and the Ni content inside the aluminum alloy film is not more than 8 atomic% (that is, the Ni content inside the aluminum alloy film is In the case of 2 atomic%, it is 10 atomic% or less). For example, it was confirmed by cross-sectional TEM observation and EDX composition analysis that an Ni-enriched layer having a thickness of 4 nm and a Ni concentration of 8.7 atomic% was present at the interface of the Al-2 atomic% Ni alloy film.

  Further, when Cr is added to Fe and heat treatment is performed, Cr is concentrated on the surface to form a concentrated layer, and an Fe alloy resistant to corrosion can be obtained.

  Similarly, in Ni-containing aluminum alloys, Ni exceeding the solid solubility limit (0.77%) of Ni in the aluminum alloy is precipitated at the aluminum grain boundary by heat treatment, etc., and partly diffuses and concentrates on the aluminum surface to concentrate Ni. It is believed that a layer is formed. Alternatively, during the contact hole etching process, the halogen compound of Ni is difficult to volatilize due to its low vapor pressure and remains on the surface of the aluminum alloy, so that it appears to have a higher concentration than the Ni concentration of the bulk aluminum alloy. Is also possible. This is because the overetching time (that is, the etching time added to stabilize the contact resistance with respect to the time required to etch the contact hole by the film thickness) is 2 even under the contact hole etching conditions. When it is doubled, the Ni concentration increases from 5 atomic% to 8.7 atomic%, and thus it is considered that there is a correlation.

  As a preferable condition for obtaining the above contact state by selecting Bi as an alloy component, for example, an insulating film (SiNx) is formed on an aluminum alloy thin film containing about 0.1 to 6 atomic% of Bi. Then, Bi is deposited on the aluminum grain boundary by heat treatment at 150 to 400 ° C., more preferably 200 to 350 ° C. for about 15 minutes to 1 hour. Then, the ITO / Al-Bi alloy film is formed by overetching about 10% of the etching time required for etching the insulating film by dry etching at the time of contact hole formation, and further light etching the surface using an amine-based stripping solution. Bi precipitates may be generated at the interface. At this time, the size and number of Bi precipitates can be adjusted by the amount of Bi added, the temperature and time of heat treatment, the amount of overetching, and the like.

  In FIG. 13, a solid solution element and an element (In, Sn, etc.) constituting the pixel electrode 5 are interdiffused, and an interdiffusion layer of the solid solution element and In or Sn is formed at the interface between the aluminum alloy film and the pixel electrode 5. The conceptual diagram from which electrical continuity is taken by forming is shown. That is, when Sm is selected as the solid solution element, a contact state as shown in the illustrated example can be obtained depending on the film forming conditions.

  Specific conditions for obtaining the contact state as described above by selecting Sm as an alloy component include, for example, forming an insulating film (SiNx) on an aluminum alloy thin film containing about 0.1 to 6 atomic% of Sm. After film formation, Sm is precipitated at the aluminum grain boundaries by heat treatment at 150 to 400 ° C., more preferably 200 to 350 ° C. for about 15 minutes to 1 hour. Then, by etching about 10% of the etching time required for etching the insulating film by dry etching at the time of contact hole formation, and further light-etching the surface using an amine-based stripping solution, the ITO / Al-Sm alloy film A diffusion layer of Sm and In and Sn in ITO may be formed at the interface. The thickness of the diffusion layer is preferably in the range of 5 to 50 nm, and this thickness may be adjusted depending on the amount of Sm added, the temperature and time of heat treatment, the amount of overetching, and the like.

  In the examples shown in FIGS. 12 and 13, since it is difficult to form an insulating layer at the interface between the aluminum alloy film and the pixel electrode, both are directly connected, and a reliable connection with lower resistance is realized. The

  If a flat display device including a TFT array substrate formed in this way is used as, for example, a liquid crystal display device, the contact resistance between the pixel electrode and the connection wiring portion can be minimized. The adverse effect on the display quality of the screen can be suppressed as much as possible.

  Next, the structure of another thin film transistor applied to the array substrate will be described.

  FIG. 14 is an enlarged cross-sectional explanatory view schematically showing the structure of another thin film transistor applied to the array substrate. In this example, a thin film transistor having a top gate structure is applied.

  As shown in FIG. 14, a scanning line is formed on the glass substrate 1a by an aluminum alloy thin film formed using the sputtering target of the present invention, and a part of the scanning line controls on / off of the thin film transistor. It functions as the gate electrode 26. Further, a signal line is formed of an aluminum alloy so as to cross the scanning line through an interlayer insulating film (SiOx), and a part of the signal line functions as a source electrode 28 of the thin film transistor.

In the pixel region on the interlayer insulating film (SiOx), for example, a pixel electrode 5 formed of an ITO film containing SnO in In ₂ O ₃ is disposed, and also a drain electrode of a thin film transistor formed of an aluminum alloy 29 functions as a connection electrode portion electrically connected to the pixel electrode 5. That is, the drain electrode 29 of the thin film transistor formed of an aluminum alloy using the sputtering target of the present invention is in direct contact with and electrically connected to the pixel electrode 5.

  Accordingly, when the gate voltage is supplied to the TFT array substrate via the scanning line to the gate electrode 26 as in the example of FIG. 2, the thin film transistor is turned on, and the driving voltage supplied in advance to the signal line is applied to the source electrode. When a predetermined level of driving voltage is supplied from the pixel 28 to the pixel electrode 5 via the drain electrode 29, a potential difference is generated between the counter electrode 10 and the liquid crystal layer 3 as described with reference to FIG. The liquid crystal molecules contained in the liquid crystal align and perform light modulation.

  Next, a manufacturing method of the TFT array substrate shown in FIG. 14 will be described. The thin film transistor provided in the array substrate according to the second embodiment has a top gate structure using a polysilicon film (poly-Si) as a semiconductor layer. FIGS. 15 to 21 illustrate TFTs according to the second embodiment. It is the figure which showed the manufacturing process of the array board | substrate schematically.

First, a silicon nitride film (SiNx) with a film thickness of about 50 nm, a silicon oxide film (SiOx) with a film thickness of about 100 nm, and a film are formed on the glass substrate 1a by, for example, plasma CVD at a substrate temperature of about 300 ° C. A hydrogenated amorphous silicon film (a-Si: H) having a thickness of, for example, about 50 nm is formed, and heat treatment and laser annealing are performed in order to convert the hydrogenated amorphous silicon film (a-Si: H) into polysilicon. The heat treatment is performed by, for example, an atmosphere heat treatment at about 470 ° C. for about 1 hour, and after dehydrogenation treatment, the laser is irradiated with, for example, an excimer laser annealing apparatus under a condition of energy of about 230 mJ / cm ² , for example. The film (a-Si: H) is irradiated to obtain, for example, a polysilicon film (poly-Si) having a thickness of about 0.3 μm (FIG. 15).

  Thereafter, as shown in FIG. 16, the polysilicon film (poly-Si) is patterned by plasma etching or the like. Next, as shown in FIG. 17, a silicon oxide film (SiOx) is formed to a thickness of, for example, about 100 nm to form a gate insulating film 27. On the obtained gate insulating film 27, an aluminum alloy film that becomes the gate electrode 26 integrated with the scanning line is formed with a film thickness of, for example, about 200 nm using the sputtering target of the present invention, and then a method such as plasma etching is used. By patterning, the gate electrode 26 integrated with the scanning line is formed.

Subsequently, as shown in FIG. 18, a mask is formed with a photoresist 31, and, for example, phosphorus is doped with about 1 × 10 ¹⁵ pieces / cm ^{2 at} about 50 KeV by an ion implantation apparatus or the like, and a polysilicon film (poly-Si) is formed. An n ⁺ type polysilicon film (n ⁺ poly-Si) is formed on a part of the photoresist 31, and then the photoresist 31 is peeled off and diffused by heat treatment at about 500 ° C., for example.

Subsequently, as shown in FIG. 19, a silicon oxide film (SiOx) is formed, for example, with a film thickness of about 500 nm and a substrate temperature of about 300 ° C. by using a plasma CVD apparatus or the like, and then an interlayer insulating film is formed. After patterning the photoresist, the interlayer insulating film (SiOx) and the silicon oxide film of the gate insulating film 27 are dry-etched, contact holes are formed, and an aluminum alloy film is formed to a thickness of, for example, about 450 nm by sputtering. By patterning, the source electrode 28 and the drain electrode 29 integrated with the signal line are formed. As a result, the source electrode 28 and the drain electrode 29 are contacted with the n ⁺ type polysilicon film (n ⁺ poly-Si) through the contact holes, respectively.

  After that, as shown in FIG. 20, a silicon nitride film (SiNx) is formed at a film thickness of, eg, about 500 nm and a substrate temperature of about 300 ° C. by using a plasma CVD apparatus or the like to form an interlayer insulating film. Then, after a photoresist layer 31 is formed thereon, a silicon nitride film (SiNx) is patterned, and after contact holes 32 are formed in the silicon nitride film (SiNx), for example, by dry etching, further etching of silicon nitride is performed. Over etching of about 10% of the time required is added. By this treatment, the surface of the aluminum alloy is also etched by about several tens of nm.

  Then, as shown in FIG. 21, after performing an ashing process using, for example, oxygen plasma, and stripping the photoresist using an amine-based stripping solution as described above, an ITO film having a thickness of about 100 nm is formed by sputtering, for example. The pixel electrode 5 is formed by patterning by wet etching. In this process, the drain electrode 29 is in direct contact with the pixel electrode 5.

  Thereafter, in order to stabilize the characteristics of the transistor, for example, annealing is performed at about 350 ° C. for about 1 hour, thereby completing a polysilicon TFT array substrate.

  According to the TFT array substrate according to the second embodiment described above and the liquid crystal display device including the TFT array substrate, the same effects as those of the first embodiment described above can be obtained. Similarly to the first embodiment, in the second embodiment, the aluminum alloy film formed using the sputtering target of the present invention can also be used as a reflective electrode of a reflective liquid crystal.

The material of the pixel electrode 5 is preferably indium tin oxide or indium zinc oxide, and the aluminum alloy film is formed by depositing a part or all of the alloy components solid-dissolved in a non-equilibrium state between the metal and the metal. It is preferably formed as a compound or a concentrated layer, and the electrical resistivity is preferably adjusted to 8 μΩ · cm or less, more preferably 5 μΩ · cm or less. The precipitates or intermetallic compounds present at the contact interface between the aluminum alloy film and the pixel electrode can be present in a number exceeding 0.13 per 100 μm ² assuming that the major axis exceeds 0.01 μm. It is preferable because the contact resistance can be significantly reduced.

  In carrying out the above production method, a part or all of the alloy components (particularly Sm) solid-dissolved in the aluminum alloy film in a non-equilibrium state and the alloy components of the pixel electrode are preferably 15 to 150 ° C. at 15 ° C. If interdiffusion is performed by heat treatment for more than an minute, an intermetallic compound can be easily formed at the contact interface between the aluminum alloy film and the pixel electrode. Moreover, when forming the said aluminum alloy film, the sputtering target of this invention is used.

  Then, after forming an insulating film on the aluminum alloy film and performing contact hole etching on the insulating film, the aluminum alloy film is subsequently light-etched 1 to 200 nm, more preferably 3 to 100 nm from the surface, If a part or all of precipitates or intermetallic compounds of the alloy components dissolved in a non-equilibrium state in the aluminum alloy film are partially exposed, the contact resistance with the pixel electrode formed thereon is further increased. This is preferable because it can be further reduced.

  The light etching can be performed by dry etching using a gas that can etch the aluminum alloy film, or wet etching using a chemical that can etch the aluminum alloy film, and as a chemical used in the light etching process. It is preferable to use a photoresist stripping solution used for patterning.

  The TFT array substrate thus obtained is used to complete a liquid crystal display device as a flat display device as shown in FIG.

  That is, for example, polyimide is applied to the surface of the TFT array substrate 1 completed as described above, and after drying, a rubbing process is performed to form an alignment film.

  On the other hand, the counter substrate 2 first forms a light shielding film 9 on a glass substrate by patterning, for example, chromium in a matrix pattern. Then, resin red, green, and blue color filters 8 are formed in the gaps between the light shielding films 9. A counter electrode is formed by disposing a transparent conductive film such as ITO as the common electrode 7 on the light shielding film 9 and the color filter 8. Then, for example, polyimide is applied to the uppermost layer of the counter electrode, and after drying, a rubbing process is performed to form the alignment film 11.

  Then, the surfaces of the array substrate 1 and the counter substrate 2 on which the alignment film 11 is formed are arranged so as to face each other, and the two substrates are bonded together with a sealing material 16 made of resin, excluding the liquid crystal sealing port. At this time, the gap between the two substrates is kept substantially constant between the two substrates through a spacer 15 or the like.

  By placing the empty cell thus obtained in a vacuum and gradually returning it to atmospheric pressure with the sealing port immersed in liquid crystal, a liquid crystal material containing liquid crystal molecules is injected into the empty cell to form a liquid crystal layer, Seal the sealing port. Finally, polarizing plates 10 are attached to both sides of the cell to complete the liquid crystal panel.

  Further, as shown in FIG. 1, a driver circuit for driving the liquid crystal display device is electrically connected to the liquid crystal panel and disposed on the side portion or the back surface portion of the liquid crystal panel. Then, the liquid crystal panel is held by a frame including an opening that defines a display surface of the liquid crystal panel, a backlight 22, a light guide plate 20, and a holding frame 23 that form a surface light source, thereby completing the liquid crystal display device.

  Next, Table 1 shows the results of measuring the contact resistance between the pixel electrode 5 and the aluminum alloy film formed using the sputtering target of the present invention when directly contacting the pixel electrode 5 on the array substrate.

The measurement experiment was as follows.
1) Configuration of pixel electrode: Indium tin oxide (ITO) in which 10% by mass of tin oxide is added to indium oxide, or indium zinc oxide (IZO) in which 10% by mass of zinc oxide is added to indium oxide. 200nm,
2) Composition of aluminum alloy film: Alloy component content is as shown in Table 1.
3) Heat treatment conditions: After forming an insulating film (SiNx) having a thickness of 300 nm, heat treatment at 300 ° C. for 1 hour in vacuum,
4) Light etching: After the above insulating film (SiNx) is dry-etched using fluorine-based plasma, each aluminum wiring material is subsequently etched by about 10 nm, and further stripping solution (“Peeling solution 106” manufactured by Tokyo Ohka Co., Ltd.). ) And about 15 nm in total (5% of the film thickness) are etched together with the surface contamination layer.
5) Contact resistance measurement method:
A Kelvin pattern as shown in FIG. 22 is prepared and measured at four terminals [a method of passing a current through ITO (or IZO) -Al alloy and measuring a voltage drop between ITO (or IZO) -Al alloy at another terminal] I do. That is, by passing the current I between I _{1 and} I ₂ in FIG. 22 and monitoring the voltage V between V _{1 and} V ₂ , the contact resistance R of the contact portion C is reduced to [R = (V ₂ −V ₁ ). / I ₂ ]. The method for producing the pattern was as follows.

  Moreover, the measurement of the additive element in the aluminum alloy formed using the said sputtering target was performed by the ICP emission analysis (inductively coupled plasma emission analysis) method.

Instead of a glass substrate, a silicon wafer with a 400 nm thick oxide film (SiO ₂ thermal oxide film) formed on the surface is used to insulate the substrate from the surface, and an Al alloy 300 nm is formed by sputtering and patterned. After that, an insulating film (SiNx) having a thickness of 300 nm is formed by a CVD method. Thereafter, the heat treatment is carried out for 1 hour in a vacuum film forming chamber as it is, and then taken out. Thereafter, a contact hole of 80 μm □ is patterned by photolithography, and the contact hole is formed by etching with fluorine-based plasma. At this time, in addition to the etching time of the insulating film, 10% overetching is performed in terms of time. By this treatment, the surface layer of the aluminum alloy film is removed with a thickness of about 10 nm (3.3% of the film thickness).

  Thereafter, oxygen plasma ashing and resist stripping with a stripping solution are performed. As the stripping solution, “Peeling solution 106” manufactured by Tokyo Ohka Kogyo Co., Ltd. is used, and cleaning is performed at 100 ° C. for 10 minutes. At this time, contamination such as fluoride, oxide and carbon formed on the surface layer of the aluminum alloy is removed (approximately several nm in thickness). Then, ITO (or IZO) is deposited to 200 nm by sputtering and patterned.

Next, for measurement of contact resistance, a 4-terminal manual prober and a semiconductor parameter analyzer “HP4156A” (manufactured by Hewlett-Packard) were used. In this measurement, the pure resistance value of the ITO (or IZO) / Al alloy joint portion represented by R (contact resistance) = [I ₂ / (V ₂ −V ₁ )] and excluding the influence of the wiring resistance. Can be measured.

For each sample, the size and number of intermetallic compounds present in the ITO (or IZO) / Al alloy joint of the contact hole were examined by scanning mapping electron microscope observation and secondary mapping of the composition by Auger spectroscopy. In the case of Al—Ag, it was confirmed that an intermetallic compound having a size of about 0.3 μm was present at a density of 1/100 μm ² or more. Similarly, in the case of Al—Zn, when the size and number of intermetallic compounds present in the ITO (or IZO) / Al alloy joint of the contact hole were examined, both of them were between metal with a size of about 0.3 μm. It was confirmed that the compound was present at a density of 3/100 μm ² or more.

  In the case of using a sputtering target in which Nd, Fe, and Co are added to the aluminum alloy, the crystal grain size of the structure becomes fine, so that the size of the intermetallic compound is generally reduced. For example, since the size of the intermetallic compound existing in the ITO / Al alloy joint is difficult to observe by TEM at the ITO / Al alloy joint interface, the structure in the thin film of the aluminum alloy formed using the sputtering target is planar TEM. As a result, an intermetallic compound having a major axis of 0.05 μm was observed for Al—Ni and a major axis of 0.02 to 0.04 μm was observed for Al—Ni—Nd. The size of the intermetallic compound at the interface is considered to be the same.

As is apparent from Table 1, when a pure aluminum alloy film is directly contacted with the ITO film, the contact resistance is 1.5 × 10 ⁵ Ω, which is a typical aluminum alloy film directly with the ITO film. When an Al—Nd alloy is contacted, the contact resistance is 8.4 × 10 ⁴ Ω. Further, as a conventional structure, the contact resistance when Mo is arranged as a barrier metal between the ITO film and the Al—Nd wiring is 7.4 × 10 ¹ Ω.

On the other hand, the contact resistance of the Al—Au alloy is 7.6 × 10 ¹ Ω, the contact resistance of the Al—Ag alloy is 5.7 × 10 ¹ Ω, the contact resistance of the Al—Zn alloy is 9.3 × 10 ¹ Ω, The contact resistance of Al—Cu alloy is 2.3 × 10 ² Ω, the contact resistance of Al—Ni alloy is 1.7 × 10 ¹ Ω, the contact resistance of Al—Sr alloy is 2.3 × 10 ¹ Ω, Al— The contact resistance of the Sm alloy is 8.6 × 10 ¹ Ω, the contact resistance of the Al—Ge alloy is 2.3 × 10 ¹ Ω, and the contact resistance of the Al—Bi alloy is 9.2 × 10 ¹ Ω. This was almost the same as when Mo which is a conventional structure was used as a barrier metal.

  Table 1 also shows the results of using an IZO film containing Zn, which has an ionization potential as high as aluminum and excellent reduction resistance, as the pixel electrode.

The IZO film is a transparent film in which about 10% by mass of ZnO is added to In ₂ O _3. In this case, the contact resistance is further reduced, and is a fraction of that of the ITO film. There are two possible reasons for this.

  First, since the electrical potential (work function) of IZO is higher than that of ITO, an extremely thin insulating layer is temporarily formed at the interface between the aluminum alloy wiring and the pixel electrode, and an MIM structure (Metal made of metal-insulating film-pixel electrode). -Insulator-Metal), even if the thickness of the insulation film is the same, the pixel electrode with a high work function looks thinner than the apparent thickness of the insulation film at the interface when a potential difference is applied, and the tunneling current component This is thought to increase.

  In addition, Zn in IZO has a higher ionization potential than Sn in ITO and has a property that it is difficult to be reduced to aluminum, so that it is difficult to form an insulator at the interface between the aluminum alloy and the pixel electrode. It is done.

  The contact region between the pixel electrode and the contact wiring portion used in the above measurement was 80 × 80 μm square.

  Table 3 also shows the contact resistance with ITO when the addition amount of the solid solution element is changed, the wiring resistance after 300 ° C. × 1 hour heat treatment, and 300 ° C. × 1 hour of the binary alloy. The data regarding the area ratio of the precipitate when the plane TEM observation of the alloy film was performed after heat processing was shown. The main conductive precipitates observed at this time are also shown. The contact resistance was evaluated by making an evaluation element in the same manner as in Table 1. In addition, a composition is content of the solid solution element contained in an aluminum alloy. In planar TEM observation, the alloy wiring portion was sliced parallel to the surface, and the state of the internal structure of the alloy was observed. As the content of the solid solution element increases, the contact resistance of ITO decreases and the resistance increases. The area ratio of the deposit is correlated with the composition, and the contact resistance and the area ratio of the deposit are in an inversely proportional relationship.

  The area ratio of the precipitate is a value obtained by identifying the precipitate appearing in the field of view of 0.3 μm × 0.3 μm square at a magnification of 500,000 by plane TEM observation by EDX and calculating the ratio to the Al phase by calculation. . According to this, in any aluminum alloy, the contact resistance becomes 200Ω when the area ratio is around 0.5%, and when it exceeds 0.5%, it becomes 200Ω or less. If the current component flowing through the precipitate is the main current component, it can be said that the area ratio mainly determines the contact resistance, although it depends on the electrical resistivity of the precipitate.

  Furthermore, the composition of the precipitates is determined for the main precipitates observed from the results of quantification by composition analysis using EDX and the X-ray diffraction results for a plurality of precipitates observed using the same planar TEM observation sample. It was.

For example, the Ni-containing aluminum alloy used as the sputtering target includes at least one selected from the group consisting of Al ₃ Ni, Al ₃ Ni ₂ , AlNi, and AlNi ₃ , and the Ag-containing aluminum alloy is The conductive precipitate contains at least one selected from the group consisting of Ag, Al ₂ Ag, and AlAg, and the Zn-containing aluminum alloy contains at least one selected from AlZn, Zn, ZnO, and the Cu-containing aluminum alloy. The contained aluminum alloy contains at least one selected from AlCu, Cu, CuO, and Cu ₂ O as the conductive precipitate.

  On the other hand, Table 4 below shows that when the content of the Al-Ag alloy is fixed at 2 atomic%, the over-etching amount is changed and the etching depth from the surface layer of the Al-Ag alloy is changed in the range of 0 to 50 mm. In this case, the bottom surface of the contact hole, that is, the outermost surface of the contact portion of the Al-Ag alloy is observed at a magnification of 60,000 by surface SEM observation, and the major axis of 0.3 μm or more appearing in the field of view of 1.5 μm × 1.5 μm The value obtained by calculation of the number of precipitates appearing on the bottom surface of the contact hole of 10 μm × 10 μm from the number of precipitates and the contact resistance with ITO at that time are shown. This is because the Al—Ag alloy can count almost all the number of precipitates. At this time, the number was counted by secondary mapping using an observed image, EDX, and Auger.

  As the etching depth increases and the number of precipitates required by surface SEM observation increases, the contact resistance decreases. As the etching depth increases, conductive precipitates gradually grow on the Al-Ag alloy surface. This is considered to indicate that the contact area between the conductive precipitate and the ITO film formed in the subsequent process increases and the contact resistance decreases. Then, from the point where the etching depth exceeds 30 nm, the number of precipitates determined by observing the surface with SEM converges, and at the same time, the contact resistance converges to a constant value.

  Next, when the solid solution elements are Ag and Zn in the structure shown in FIG. 11, the contact resistance of each alloy shown in Table 1 above and the solid solution element precipitates or the metal between the solid solution elements including aluminum. The relationship with the density of the compound is the value shown in Table 2. In this table, the number of precipitates required when the contact resistance is assumed to be 200Ω is approximated by calculation. On the other hand, the values in this table are calculated results when the contact resistance value is 200Ω, but in the example, the contact resistance of Al-3.8% Ag is 58Ω and the contact resistance of Al-2.4% Zn is 93Ω. ing.

  When it is assumed that all the precipitates are circular with a diameter of 0.03 μm, the number of precipitates is estimated from the contact resistance values of the examples by calculation. As shown in Tables 5 and 6, the number of precipitates is Al. -3.8 atomic% Ag is 45 (10 μm □), and Al-2.4 atomic% Zn is 110 (10 μm □).

  In addition, when it is assumed that the precipitates in Al-Ag are circular with a diameter of 0.3 μm actually observed with a flat TEM or a scanning electron microscope, the number is 0.5 (10 μm □). . In the case of Al-Ag, although the addition amount was different, the order was almost the same as the number of precipitates counted experimentally shown in Table 4. Incidentally, in the case of IZO, it is considered that there is an effect of preventing contact oxidation of Al due to high reduction resistance of Zn. Therefore, formation of a high resistance layer in a portion other than the precipitate is suppressed, and the precipitate It can be considered that the current increment in other parts contributed.

  Next, an example of a ternary system is shown.

In the same manner as in the case of the binary system, the contact resistance value with ITO through a contact hole of 80 μm × 80 μm was measured. The contact resistance of the Al—Ag—Nd film is 1.3 × 10 ² Ω, the contact resistance of the Al—Zn—Nd film is 4.3 × 10 ² Ω, and the contact resistance of the Al—Ni—Nd film is 1.7 ×. Each contact resistance value of 10 ² Ω is a slightly higher value as compared with the case where Mo is used for the barrier metal having the conventional structure, but it is a level with no problem. The other Au, Ge, Sr, Sm, and Bi were also in the range of 1.0 × 10 ^{2 to} 5.0 × 10 ³ Ω which was almost equivalent.

  On the other hand, there is a correlation between the composition of the aluminum alloy film, contact resistance, electrical conductivity, and heat resistance. For example, when the X content of Al-X-Nd (X = Ni) is increased, the contact resistance is decreased, but the electrical resistance is increased, and the heat resistance is improved [see FIGS. 24A and 24B]. Further, when the Nd content is increased, the heat resistance is improved, but the electrical resistivity and the contact resistance are increased [see FIGS. 25A and 25B]. These tendencies are the same for any X. The required contact resistance varies depending on the structure of the display device and the manufacturer, and varies from 150Ω to 5 kΩ for an 80 μm square contact hole. Since electrical characteristics and heat resistance are in a trade-off relationship, the required specifications can be met by adjusting the composition.

Further, when X is Ni in an Al—X—Nd alloy, similarly to Nd, Ni is pinned to the grain boundary of Al, and there is an effect of suppressing migration of Al when heat is applied. For example, as shown in FIG. 26, “0.7> 0.5 CX ₁ + CNd” [where CX ₁ is the Ni content (atomic%) in the aluminum alloy, and CNd is the Nd content in the aluminum alloy ( In the region of “Atom%”], heat resistance is insufficient in heat treatment at 300 ° C., and hillocks are generated. On the other hand, in the region of “0.5CX ₁ + CNd> 4.5”, the electrical resistivity of the wiring exceeds 8 μΩ · cm, so that it cannot be put to practical use. From this, the optimum range is “0.7 <0.5 CX ₁ + CNd <4.5”.

  Similarly, even when the same 3A group yttrium (Y) is contained, as shown in FIG. 27, substantially the same electrical characteristics and heat resistance as in the case of Nd can be obtained.

Similarly, in the composition of Al—Ni—Fe, as shown in FIG. 28, “1> CX ₁ + CX ₃ ” [where CX ₁ is the Ni content (atomic%) in the aluminum alloy, and CX ₃ is in the aluminum alloy. In the range of [representing Fe content (atomic%)], hillocks were generated due to insufficient heat resistance during heat treatment at 300 ° C. On the other hand, in the region of “CX ₁ + CX ₃ > 6”, the electrical resistivity of the wiring exceeds 8 μΩ · cm, so that it cannot be put to practical use. Therefore, the optimum range is “1 <CX + CX ₃ <6”.

By the way, Co and Fe may be considered to have almost the same effect as the same transition metal. In the case of Al—Ni—Co, the same characteristics as those of Al—Ni—Fe are obtained as shown in FIG. Here, the heat resistance means the highest temperature that does not deteriorate the morphology of the aluminum alloy surface due to the generation of hillocks and voids when heat treatment is performed. In the figure, a hillock density generated when heat treatment at 300 ° C. was cleared to 3 × 10 ⁸ m ⁻² or less was accepted.

  Similarly, the case of Al—X—Nd, Fe, Co alloy with X = Ag is shown in FIGS. 30, 31, 32, and 33, and the case of Al—X—Nd, Fe, Co alloy with X = Zn is shown. 34, 35, 36, and 37. Furthermore, FIGS. 38, 39, 40, and 41 show the case where Al = X—Nd, Fe, Co alloy and X = Cu. Even when any alloy element is added, almost the same result is obtained.

  In the present invention, when electrical conduction is established between the pixel electrode and the aluminum alloy film formed using the sputtering target of the present invention through precipitates of solid solution elements or intermetallic compounds, that is, the pixel electrode and aluminum in each aluminum alloy. At the interface of the alloy film, aluminum that is easy to oxidize except the precipitated portion of the solid solution element is in contact with the pixel electrode, and when a high resistance aluminum oxide exists on the surface, the contact resistance is a solid solution element with low resistance. This is considered to be determined by the electrical resistivity of the precipitate or intermetallic compound. Assuming that all are electrically connected by a single precipitate of a solid solution element, the surface area and density of the precipitate necessary to satisfy a desired contact resistance can be defined by calculation.

Now, it is assumed that the contact resistance required when the contact size is 80 × 80 μm square is 200Ω or less. When the solid solution element is zinc, the electrical resistivity of zinc is 5.92 μΩ · cm, and it is assumed that a single precipitate of zinc having a major axis of 0.03 μm is deposited in a plane on the interface between the pixel electrode and the aluminum alloy. 3287 or more precipitates are required. That is, a density of 51.4 / 100 μm ² or more is required. Further, when the solid solution element is silver, the resistivity of silver is 1.5 μΩ · cm, and it is assumed that a single precipitate of silver having a major axis of 0.03 μm is planarly deposited on the interface between the pixel electrode and the aluminum alloy. 833 or more precipitates are required. That is, a density of 12.9 / 100 μm ² or more is required.

Assuming that the major axis of the precipitate is 0.3 μm, which is the same as the actually measured value, as shown in Table 7, in the case of Al—Ag, 8.3 or more precipitates in an 80 × 80 μm square, and in the case of Al—Zn, 32. Nine or more precipitates are required. That is, the density is 0.13 / 100 μm ² and 0.51 / 100 μm ² or more.

On the other hand, in the case of Al—Ni, the major axis of the structure is 0.05 μm. In this case, assuming that the electrical resistivity of Ni is 6.84 μΩ · cm and the electrical resistivity of the precipitate is substantially the same, the calculation is roughly In the case of an 80 × 80 μm square and a major axis of 0.05 μm, 1345 pieces are necessary. That is, 21 pieces / 100 μm ² .

Furthermore, when one kind selected from Nd, Fe, and Co is added to this Ni-containing aluminum alloy, the structure becomes finer. For example, in the case of Al—Ni—Y, the major axis of the structure becomes 0.01 to 0.03 μm. . In this case, assuming that the electrical resistivity of Ni and the electrical resistivity of the precipitate are substantially the same, 3740 are required when the major axis is 80 × 80 μm square and the major axis is 0.03 μm. That is, 58 pieces / 100 μm ² . Also, if all was the major diameter 0.01μm will 526 pieces / 100 [mu] m ^2.

Alternatively, in the case of Al—Ni—Nd, the major axis of the tissue is 0.02 to 0.04 μm. In this case, in the case of 80 × 80 μm ² squares and a major axis of 0.04 μm, approximately 2104 are necessary, that is, 33/100 μm ² . Also, if all becomes long diameter 0.02 [mu] m, the 132 pieces / 100 [mu] m ^2.

To summarize the above, in order to clear the required contact resistance of 200 Ω using Ag having the lowest single electrical resistivity, the density of 0.13 / 100 μm ² or more is required as a precipitate having a major axis of 0.3 μm. Required. Further, when Al—Ni—Y having the smallest precipitate is used, a density of 526/100 μm ² is required as a precipitate having a major axis of 0.01 μm. In the case of the Al-Ag alloy, when the precipitate has a major axis of 0.01 μm, the density of the precipitate is 115/100 μm ² .

  However, the above value assumes that the electrical resistivity of the precipitate is equal to that of the additive element alone. In some cases, the intermetallic compound containing the element and aluminum has a significantly large change in electrical resistivity as compared with the elemental element. In that case, the area ratio calculated from the size and the number of precipitates may be different from the area ratio derived by TEM observation on the actual contact surface. This is considered to be due to the fact that when the contact resistance of 200Ω is realized, the number of precipitates increases in accordance with the ratio of the electrical resistivity of the precipitate and the additive element alone.

  However, in the case of an alloy system that makes an intermetallic compound, it is thought that it exists in the form of an intermetallic compound and mixed in large and small, but the calculation results of contact resistance when using zinc and silver are experimental results It was almost the same order.

As described above, when the aluminum alloy according to the present invention is used, the contact resistance is about 1/10 ⁴ as compared with the case where the pure aluminum wiring is directly contacted with the ITO film.

  Note that when the substrate temperature at the time of sputtering the transparent electrode is increased, the contact resistance decreases. For example, in the case of ITO, the contact resistance is halved when the substrate temperature is 50 ° C. or higher. More preferably, when the crystallinity of ITO is improved by heating the substrate at 100 ° C. or higher, the contact resistance is reduced to about 1/5.

  Even when the film is formed at a substrate temperature of room temperature, if the ITO is polycrystallized by applying a heat treatment at 150 ° C. or higher for about 30 minutes after the film formation, the contact resistance is halved. Usually, since it is difficult to etch polycrystalline ITO, the ITO film is formed at room temperature, and after etching after pattern formation, it is polycrystallized by heat treatment to reduce the electrical resistivity of the ITO.

  For this reason, in order to reduce the contact resistance, the substrate temperature during film formation of the transparent electrode should be 50 ° C. or higher, more preferably 100 ° C. or higher. After the film formation, it is desirable to apply a heat treatment at 150 ° C. or higher for 30 minutes or longer. The same effect can be obtained when the transparent electrode is IZO. However, since the crystallization of IZO does not proceed in this temperature range, the contact resistance is hardly lowered.

  As described above, when the liquid crystal display device was prototyped in the above embodiment using the sputtering target of the present invention, both the production yield and display quality were at the same level as when the ITO film and the barrier metal were combined. Therefore, in this liquid crystal display device, it is possible to obtain the same performance as a conventional liquid crystal display device without disposing a barrier metal.

  Therefore, the barrier metal can be omitted and the manufacturing process can be simplified, so that the manufacturing cost can be greatly reduced.

  That is, instead of the conventional pure aluminum, aluminum alloy, or Mo-W film, an aluminum alloy formed by using a sputtering target containing a specific element as described above is used as an electrode material, so that Direct contact is possible, the manufacturing process is simplified, and the manufacturing cost can be greatly reduced.

  Further, in the same manner as in the experimental method shown in Table 1, after silicon nitride (SiNx) was formed on an Al-2 atomic% Ag alloy (film thickness: 300 nm), heat treatment was performed at 300 ° C. for 1 hour to obtain an 80 μm square. After the contact hole was patterned by photolithography, dry etching was performed using fluorine-based plasma. At this time, the etching depth for the aluminum alloy was changed by adjusting the time for overetching following the etching of the silicon nitride (SiNx) film. Thereafter, ashing and cleaning with “stripping solution 106” were performed to form an ITO film. The etching depth of the aluminum alloy surface was measured by cross-sectional observation with a scanning electron microscope and a transmission electron microscope.

  FIG. 23 shows the relationship between the etching depth of the aluminum alloy surface and the contact resistance. As is clear from this figure, when the aluminum alloy surface is etched even slightly, the contact resistance decreases rapidly. I understand. This is presumably because the precipitate of the solid solution element or the intermetallic compound was exposed on the surface of the aluminum alloy by the etching and could be electrically connected to the pixel electrode.

  Experimentally, it was confirmed that a contact resistance of about 56Ω was obtained even at an etching depth of about 5 nm from the aluminum alloy surface. It is considered that the etching depth necessary for making such a low resistance contact depends on the size and distribution of the structure of precipitates or intermetallic compounds, the thickness of the surface oxide layer of the aluminum alloy, and the like. According to Auger electron spectroscopy, it was confirmed that precipitates containing Ag as a main component were exposed on the surface of the aluminum alloy. Further, there is no insulating layer such as an oxide layer on the surface of the precipitate.

  The observed sample has already been etched by 5 nm from the surface of the aluminum alloy, and if it is possible to expose the precipitate or the intermetallic compound to the surface of the aluminum alloy, it is considered that the electrical connection with the pixel electrode is possible as it is. At least the surface contamination layer needs to be etched. In addition, since the thickness of the oxide layer on the surface of the oxidized aluminum alloy is about 3 to 5 nm, in such a case, in order to remove the oxide layer and expose the aluminum alloy surface, at least about 3 nm or more is required. Etching depth is required.

  On the other hand, if the etching depth is too deep, the film thickness as the wiring becomes thin, which causes problems such as an increase in electrical resistance and a decrease in reliability. For example, the film thickness of the source / drain electrode used in this example is 300 nm, and the etching depth for securing the direct contact between the aluminum alloy formed using the sputtering target of the present invention and the pixel electrode is preferably It is determined to be in the range of 1 to 200 nm, more preferably 3 to 100 nm.

  It is desirable to reduce impurities contained in the sputtering target of the present invention, which is an aluminum alloy wiring material, as much as possible. For example, oxygen and carbon cause the film to become cloudy and increase the electrical resistivity of the wiring. Therefore, the concentration of these impurities contained in the wiring material is the quantitative value of the composition analysis by XPS analysis when the electrical resistivity is to be 5 μΩ · cm level or less, the oxygen content is 7 atomic% or less, and the carbon content is 0. It should be suppressed to 4 atomic percent or less, more preferably 0.2 atomic percent or less.

For example, when the impurity is carbon, a carbon compound such as Al ₄ C ₃ or NiC, which has a stoichiometric composition, is ceramic and inherently has electrical insulation, and the electrical resistivity of the wiring itself depends on the amount added. Is expected to increase. Further, the precipitate appearing at the Al grain boundary by the heat treatment becomes an intermetallic compound containing the carbon compound. When the current path between the ITO and the wiring material passes through the precipitate, which is the main part of the present invention, the contact resistance is considered to be higher than that of the precipitate containing no carbon. For this reason, it is preferable that the contact resistance with ITO does not contain carbon in the Al alloy wiring material.

Further, when a wiring material containing carbon is formed by sputtering, a carbon compound such as an aluminum carbide compound adheres to the chamber of the sputtering apparatus and is contaminated, so that frequent maintenance of the apparatus is required. Will also occur. The same is true when the impurity is oxygen, and since electrical insulating alumina (Al ₂ O ₃ ) is generated, the electrical resistivity of the wiring increases. In order to prevent this, it is desirable to prevent contamination from entering in the manufacturing process, and take measures such as increasing the ultimate vacuum pressure of the apparatus during sputtering to about 5 × 10 ⁻⁶ or less. .

FIG. 1 is a schematic cross-sectional enlarged explanatory view illustrating the configuration of a liquid crystal panel substrate to which a display device array substrate using a sputtering target of the present invention is applied and a liquid crystal display device. FIG. 2 is a schematic cross-sectional explanatory view illustrating the structure of a thin film transistor applied to the display device array substrate according to the first embodiment. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is a cross-sectional schematic diagram which illustrates the structure of the contact interface of an aluminum alloy film and a pixel electrode in the array substrate for display devices obtained in the example of the present invention. It is a conceptual diagram of the contact hole which formed the precipitate or the intermetallic compound, and also formed Ni concentration layer in the interface. It is a cross-sectional schematic diagram which illustrates further another structure of the contact interface of the aluminum alloy wiring and the pixel electrode in the array substrate for display devices obtained in the example of the present invention. FIG. 6 is a schematic cross-sectional explanatory view illustrating the structure of a thin film transistor applied to a display device array substrate according to a second example of the invention. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 14 later on in order. FIG. 22 is a diagram showing a Kelvin pattern used for measurement of contact resistance between an aluminum alloy film formed using the sputtering target of the present invention and a pixel electrode. It is a graph which shows the relationship between the etching depth of the aluminum alloy film surface obtained by experiment, and contact resistance. (A) is a graph which shows the influence which X content of Al-X-Nd (X = Ni) has on an electrical property, (B) is a graph which similarly shows the influence which X content has on heat resistance. (A) is a graph showing the effect of the Nd content of Al-X-Nd (X = Ni) on the electrical characteristics, and (B) is a graph showing the effect of the Nd content on the heat resistance. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ni and Nd of Al-Ni-Nd. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ni and Y of Al-Ni-Y. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ni and Fe of Al-Ni-Fe. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ni and Co of Al-Ni-Co. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ag and Nd of Al-Ag-Nd. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ag and Y of Al-Ag-Y. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ag and Fe of Al-Ag-Fe. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Ag-Co of Al-Ag-Co. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Zn and Nd of Al-Zn-Nd. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Zn and Y of Al-Zn-Y. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Zn-Fe of Al-Zn-Fe. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Al-Zn-Co Zn and Co. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Cu and Nd of Al-Cu-Nd. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Cu and Y of Al-Cu-Y. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Cu and Fe of Al-Cu-Fe. It is a figure which shows the composition range which can ensure the electrical resistivity of 8 microhm * cm, and the heat resistance of 300 degreeC or more with respect to the composition of Cu and Co of Al-Cu-Co.

Explanation of symbols

1 TFT array substrate 2 Counter electrode 3 Liquid crystal layer 4 Thin film transistor (TFT)
DESCRIPTION OF SYMBOLS 5 Pixel electrode 6 Wiring part 7 Common electrode 8 Color filter 9 Light-shielding film 10 Polarizing plate 11 Orientation film 12 TAB tape 13 Driver circuit 14 Control circuit 15 Spacer 16 Sealing material 17 Protection film 18 Diffusing plate 19 Prism sheet 20 Light guide plate 21 Reflecting plate 22 Backlight 23 Holding frame 24 Printed circuit board 25 Scan line 26 Gate electrode 27 Gate insulating film 28 Source electrode 29 Drain electrode 30 Protective film (silicon nitride film)
31 Photoresist 32 Contact hole

Claims (2)

A sputtering target for forming an aluminum alloy film, wherein X ₁ (at least one of X ₁ = Ag, Zn, Cu, and Ni) is 0.1 to 6 atomic% and X ₂ (X ₂ = Nd) is contained in an amount of 0.1 to 6 atomic%, and the content thereof satisfies the relationship of the following formula (I).
0.7 ≦ 0.5 × CX ₁ + CX ₂ ≦ 4.5 (I)
[Wherein, CX ₁ represents the content (atomic%) of Ag, Zn, Cu, Ni in the aluminum alloy, and CX ₂ represents the content (atomic%) of Nd in the aluminum alloy.] A sputtering target for forming an aluminum alloy film, wherein X ₁ (X ₁ = at least one of Ag, Zn, Cu, Ni) is 0.1 to 6 atomic% as an alloy component, and X ₃ (X ₃ = At least one of Fe and Co) is contained in an amount of 0.1 to 6 atomic%, and the content thereof satisfies the relationship of the following formula (II).
1 ≦ CX ₁ + CX ₃ ≦ 6 (II)
[Wherein, CX ₁ represents the content (atomic%) of Ag, Zn, Cu, Ni in the aluminum alloy, and CX ₃ represents the content (atomic%) of Fe, Co in the aluminum alloy, respectively]