JP2010114226A - Al alloy film for display device, display device, and sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device, capable of directly contacting an Al alloy film with a transparent pixel electrode in a wiring structure of a thin-film transistor substrate used in a display device and equipped with an Al alloy film developed for improving the corrosiveness relative to an amine-based stripper which is used in the production process of a thin-film transistor. <P>SOLUTION: This Al alloy film contains 0.2 to 2.0 atom% of Ge, at least one type of element selected from among an element group X (Ag, In, Sn, Ni, Co, Cu), and 0.02 to 1 atom% of at least one type of element selected from among an element group Q that consists of rare earth elements and high-boiling point metals (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf), in which the number of deposits having a particle diameter of more than 100 nm is one or less per 10<SP>-6</SP>cm<SP>2</SP>. A display device equipped with the Al alloy film is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an Al alloy film for a display device, a display device, and a sputtering target.

  A liquid crystal display device used in various fields ranging from a small mobile phone to a large television exceeding 30 inches uses a thin film transistor (hereinafter referred to as “TFT”) as a switching element, and a transparent pixel electrode. A TFT substrate having a wiring portion such as a gate wiring and a source-drain wiring, a semiconductor layer such as amorphous silicon (a-Si) or polycrystalline silicon (p-Si), and a predetermined distance from the TFT substrate. And a counter substrate provided with a common electrode, and a liquid crystal layer filled between the TFT substrate and the counter substrate.

  In a TFT substrate, wiring materials such as gate wiring and source-drain wiring are made of Al alloy such as pure Al or Al-Nd (hereinafter, these are collectively referred to) because they have low electrical resistance and are easy to process finely. Are sometimes used as Al-based alloys). In a conventional TFT substrate, a barrier metal layer made of a refractory metal such as Mo, Cr, Ti, or W is usually provided between the Al-based alloy wiring and the transparent pixel electrode. As described above, the reason why the Al-based alloy wiring is connected via the barrier metal layer is to ensure heat resistance and electrical conductivity when the Al-based alloy wiring is directly connected to the transparent pixel electrode.

  However, in order to form a wiring having a laminated structure having a barrier metal layer, it is necessary to form a laminated structure by vapor-depositing the wiring in a plurality of times using a cluster tool type sputtering apparatus or the like. As the cost of the liquid crystal display is reduced along with the mass production, an increase in manufacturing cost and a decrease in productivity due to the formation of the barrier metal layer cannot be neglected. Furthermore, due to the structure in which dissimilar metals are laminated, there is a problem that it is difficult to form a good tapered shape during wiring patterning due to an etching rate difference or a potential difference.

  Therefore, electrode materials and manufacturing methods that can omit the formation of the barrier metal layer and can directly connect the Al-based alloy wiring to the transparent pixel electrode have been proposed. For example, the applicant of the present application discloses a direct contact technique that enables the omission of the barrier metal layer, simplifies the process without increasing the number of processes, and connects the Al-based alloy wiring directly and securely to the transparent pixel electrode. (Patent Documents 1 to 4). Specifically, these technologies show that electrical conductivity at the interface between the transparent conductive film such as ITO and IZO and the aluminum alloy film is ensured through the precipitate derived from the alloy element dispersed in the Al alloy film. Has been.

Patent Document 5 discloses that an aluminum alloy thin film containing carbon contains at least one element selected from nickel, cobalt, and iron in an amount of 0.5 to 7.0 at%, so that the electrode has the same degree as that of an ITO film. It has been shown that an aluminum alloy thin film having a potential, low specific resistance and excellent heat resistance can be realized without diffusion of silicon.
JP 2006-261636 A JP 2007-142356 A JP 2007-186777 A JP 2008-124499 A JP 2003-89864 A

  As shown in Patent Documents 1 to 4 above, by adding an alloy element to pure Al, electrical conductivity characteristics (ITO direct contact property) between the transparent conductive film / Al alloy film can be ensured, etc. Various functions that were not present are added.

  However, when the barrier metal layer is omitted as shown in the cited documents 1 to 4, the Al alloy film is also required to have better corrosion resistance. In particular, the TFT substrate manufacturing process passes through a plurality of wet processes. However, when a metal nobler than Al is added, a problem of galvanic corrosion appears and corrosion resistance deteriorates. For example, in a cleaning process for removing a photoresist (resin) formed in a photolithography process, water washing is continuously performed using an organic stripping solution containing amines. However, when amines and water are mixed, an alkaline solution is formed, which causes a problem that Al is corroded in a short time. By the way, Al alloy has received the thermal history by passing through a CVD process before passing through a peeling cleaning process. In the course of this thermal history, alloy components form precipitates in the Al matrix. However, since there is a large potential difference between this precipitate and Al, alkaline corrosion proceeds due to the galvanic corrosion at the moment when the amines contained in the stripping solution come into contact with water, and Al which is electrochemically base is formed. When ionized and eluted, pit-shaped pitting corrosion (black spots, black dot-shaped etching marks) may be formed. This black dot-shaped etching mark does not adversely affect the conduction characteristics of the ITO film / Al alloy film interface, but it may be judged as defective in the inspection process during the TFT substrate manufacturing process, resulting in a decrease in yield. There is a risk of lowering.

  In Patent Documents 1 to 4, attention is not paid to the control of the precipitate shape so as to suppress the occurrence of the pit-like pitting corrosion, and as a result, the yield in the inspection process is reliably ensured. It does not have the recognition to increase.

  The present invention has been made paying attention to such a situation, and the object thereof is to ensure a low contact resistance when the barrier metal layer is omitted and directly connected to the transparent pixel electrode as in the prior art. It is an object of the present invention to provide an Al alloy film for a display device that exhibits high resistance to a stripping solution used in the manufacturing process of the display device and can also have excellent heat resistance.

The Al alloy film of the present invention that can achieve the above object is an Al alloy film that is directly connected to a transparent conductive film (transparent pixel electrode) on a substrate of a display device, and the Al alloy film comprises Ge. 0.2 to 2.0 atomic% and at least one element selected from element group X (Ag, In, Sn, Ni, Co, Cu), and a rare earth element and a refractory metal group (Ti, Precipitates containing 0.02 to 1 atomic% of at least one element selected from the element group Q consisting of Ta, V, Nb, Mo, W, Cr, Zr, and Hf) and having a particle size exceeding 100 nm Is less than 1 per 10 ⁻⁶ cm ² .

  Of the element group X, at least one selected from the group consisting of Ni, Co and Cu is preferably contained in an amount of 0.02 to 0.5 atomic%, and Ag is 0.1 to 0.3. It is preferable to contain 6 atomic%. In addition, In and / or Sn is preferably contained in an amount of 0.02 to 0.5 atomic%.

Furthermore, it is preferable that the content of the element of the element group X satisfies the following formula (1).
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]

  The present invention also includes a display device in which the Al alloy film is used in a thin film transistor.

  Further, the present invention includes Ge in an amount of 0.2 to 2.0 atomic% and at least one element selected from element group X (Ag, In, Sn, Ni, Co, Cu), and a rare earth element. And 0.02-1 atomic% of at least one element selected from the element group Q consisting of the refractory metal group (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf), with the balance being Also included are sputtering targets characterized by Al and inevitable impurities. Of the element group X, at least one element selected from the group consisting of Ni, Co and Cu is 0.02 to 0.5 atomic%, Ag is 0.1 to 0.6 atomic%, and In And / or Sn is preferably contained in an amount of 0.02 to 0.5 atomic%.

The element content of the element group X in the target preferably satisfies the following formula (1).
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]

  According to the present invention, an Al alloy film can be directly connected to a transparent pixel electrode (transparent conductive film, oxide conductive film) without interposing a barrier metal layer, and excellent in corrosion resistance (stripping solution resistance). An Al alloy film for a display device can be provided. Furthermore, an Al alloy film for a display device that also has excellent heat resistance can be provided. If the Al alloy film of the present invention is applied to a display device, the barrier metal layer can be omitted. Therefore, if the Al alloy film of the present invention is used, a display device with excellent productivity, low cost and high performance can be obtained.

  The present inventors have used a chemical solution used in the manufacturing process of a display device on the assumption that the contact resistance can be sufficiently reduced even when the barrier metal layer is omitted and directly connected to the transparent pixel electrode (transparent conductive film). Diligent research to realize an Al alloy film with excellent resistance to (stripping solution) (corrosion resistance) and suppressed black spots (black dot-like etching marks) to the extent that they are not judged as defective in the inspection process during the TFT substrate manufacturing process. Went.

  As a result, in order to realize a low contact resistance when the barrier metal layer is omitted and directly connected to the transparent pixel electrode, a prescribed amount of Ge and element group X (Ag, In, Sn, Ni, Co, Cu) It is effective to contain at least one element selected from the group (group X element), and the amount of the alloying elements is appropriately controlled or the elements are appropriately combined and combined and the film forming conditions are controlled. By doing so, it was found that if the precipitate is finely dispersed, the black spots generated around the precipitate can be made fine and controlled to a size that cannot be visually recognized.

Specifically, when the particle size [(major axis + minor axis) / 2] of each precipitate is observed with respect to the precipitates, one precipitate having a particle size exceeding 100 nm per 10 ⁻⁶ cm ^2. It was found that if it was as follows, it was not judged as defective in the inspection process during the TFT substrate manufacturing process. The particle size of the largest precipitate among the precipitates is preferably 100 nm or less, more preferably 90 nm or less, and still more preferably 80 nm or less.

In addition, the density (the number per 10 ^<-6 > cm ^{< 2} >) of the precipitate in which the said particle size exceeds 100 nm was measured by the method shown in the Example mentioned later.

  The component composition and recommended manufacturing conditions for refining the precipitate as described above on the premise of realizing low contact resistance will be described in detail below.

  First, in the present invention, as described above, Ge is contained in an amount of 0.2 to 2.0 atomic%, and at least one element selected from element group X (Ag, In, Sn, Ni, Co, Cu) ( X group element). Thus, by including Ge as an alloy component in the Al alloy film together with the group X element, finer precipitates can be formed more easily than before, and black spots can be suppressed. In addition, it seems that most of the contact current flows between the Al alloy film and the transparent pixel electrode (for example, ITO film) through the Ge-containing precipitate, so that the contact resistance can be kept low.

  In order to sufficiently exhibit the above effect, Ge is contained in an amount of 0.2 atomic% or more (preferably 0.3 atomic% or more). On the other hand, when the amount of Ge is too large, the electrical resistance of the Al alloy film itself increases. In addition, the corrosion resistance also decreases. Therefore, the amount of Ge is suppressed to 2.0 atomic% or less. Preferably it is 1.0 atomic% or less, More preferably, it is 0.4 atomic% or less.

  About said X group element, since content required for an effect expression changes with kinds of element, it is preferable to make it contain as follows. That is, in the case where at least one element selected from the group consisting of Ni, Co and Cu is included in the element group X, 0.02 to 0.5 atomic% may be included. If these elements are too small, it is difficult to sufficiently reduce the contact resistance. Therefore, at least one element selected from the group consisting of Ni, Co and Cu is preferably 0.02 atomic% or more, more preferably 0.03 atomic% or more. On the other hand, if the content of Ni, Co, and Cu is excessive, the electrical resistance increases, so that the total amount is preferably suppressed to 0.5 atomic% or less. More preferably, it is 0.35 atomic% or less.

  When Ni is contained alone as the X group element, the Ni content is more preferably 0.2 atomic% or less, and further preferably 0.15 atomic% or less. When Co is contained alone as the X group element, the Co content is more preferably 0.2 atomic% or less, and further preferably 0.15 atomic% or less.

  When Ag is included in the element group X, it may be included in an amount of 0.1 to 0.6 atomic%. From the viewpoint of sufficiently reducing the contact resistance, the Ag content is preferably 0.1 atomic% or more, and more preferably 0.2 atomic% or more. On the other hand, if the amount of Ag is excessive, the electrical resistance of the film itself is likely to increase. Therefore, it is preferably suppressed to 0.6 atomic% or less, more preferably 0.5 atomic% or less, still more preferably 0.3 atomic% or less. It is.

  Further, in the case of containing In and / or Sn in the element group X, 0.02 to 0.5 atomic% may be included. From the viewpoint of sufficiently reducing the contact resistance, it is preferable to contain 0.02 atomic% or more of In and / or Sn, and more preferably 0.05 atomic% or more. On the other hand, when In and / or Sn is excessively contained, the electrical resistance of the film itself is easily increased and the adhesion between the Al alloy film and the base is lowered.

  In addition, when In is contained alone as the X group element, the In amount is more preferably 0.2 atomic% or less, and still more preferably 0.15 atomic% or less. In addition, when Sn is contained alone as the X group element, the Sn content is more preferably 0.2 atomic% or less, and still more preferably 0.15 atomic% or less.

  In the case of a combination of Ni and Ag or a combination of Co and Ag in which the group X elements are phase-separated, each element diffuses independently to form a precipitate, so that each additive element does not coarsen the precipitate independently ( It is desirable to keep it within the range of addition of only one element. That is, the amount of Ni is preferably 0.2 atomic percent or less, and more preferably 0.15 atomic percent or less. The Ag content is preferably 0.5 atomic percent or less, and more preferably 0.3 atomic percent or less. Further, the Co content is preferably 0.2 atomic% or less, and more preferably 0.15 atomic% or less.

On the other hand, when the X group elements are in a solid solution or a combination forming a compound (a combination other than the above Ni and Ag and Co and Ag), the precipitate species and form change depending on the type of the X element. It is desirable to combine within the following concentration range. That is, it is preferable that the content of the element in the element group X satisfies the following formula (1). The left side in the following formula (1) is more preferably 2 atomic% or less, still more preferably 1 atomic% or less.
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]

  In addition to the X group element, at least one element selected from an element group Q consisting of a rare earth element and a refractory metal group (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf). Element (Q group element). By containing the Q group element, the resistance to the resist stripping solution used in the manufacturing process can be sufficiently increased. In addition, a silicon nitride film (protective film) is subsequently formed on the substrate on which the Al alloy film is formed by a CVD method or the like. At this time, the high temperature heat applied to the Al alloy film causes a gap between the substrate and the substrate. It is presumed that a difference in thermal expansion occurs and hillocks (cove-like projections) are formed. However, the inclusion of the rare earth elements and refractory metals can suppress the formation of hillocks and can improve the heat resistance.

  In order to sufficiently exhibit the above effects, it is preferable that the Q group element is contained in an amount of 0.02 atomic% or more (preferably 0.03 atomic% or more. However, if the Q group element is excessively contained, the X group element is contained. As in the case of elements, the electrical resistance of the Al alloy film itself is likely to increase, so the content of the Q group element is set to 1 atomic% or less (preferably 0.7 atomic% or less).

  The rare earth element referred to here is an element obtained by adding Sc (scandium) and Y (yttrium) to a lanthanoid element (a total of 15 elements from La of atomic number 57 to Lu of atomic number 71 in the periodic table). Means group. Among the Q group elements, for example, use of La, Nd, Y, Gd, Ce, Dy, Ti, and Ta is more preferable, and La and Nd are particularly preferable. Of these, one or more can be used in any combination.

  The Al alloy film is desirably formed by a sputtering method using a sputtering target (hereinafter also referred to as “target”). This is because a thin film having excellent in-plane uniformity of components and film thickness can be easily formed as compared with a thin film formed by ion plating, electron beam vapor deposition or vacuum vapor deposition.

  Further, in order to form the Al alloy film by the sputtering method, as the target, 0.2 to 2.0 atomic% of Ge, and element group X (Ag, In, Sn, Ni, Co, Cu) And at least one element selected from an element group Q comprising a rare earth element and a refractory metal group (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf). If the Al alloy sputtering target having the same composition as that of the desired Al alloy film is used, containing 0.02-1 to 1 atomic% of the seed element and the balance being Al and inevitable impurities, the composition is not shifted. An Al alloy film having a desired component / composition can be formed.

As an element of the element group X in the sputtering target,
(A) at least one element selected from the group consisting of Ni, Co and Cu is 0.02 to 0.5 atomic%;
(B) Ag is 0.1 to 0.6 atomic%,
(C) In and / or Sn is preferably contained in an amount of 0.02 to 0.5 atomic%.

The element content in the element group X preferably satisfies the following formula (1) as necessary.
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]

  The shape of the target includes those processed into an arbitrary shape (such as a square plate shape, a circular plate shape, or a donut plate shape) according to the shape or structure of the sputtering apparatus.

  As a method for producing the above target, a method of producing an ingot made of an Al-based alloy by a melt casting method, a powder sintering method, or a spray forming method, or a preform made of an Al-based alloy (the final dense body is prepared) Examples thereof include a method obtained by producing an intermediate before being obtained) and then densifying the preform by a densification means.

In order to suppress precipitation of coarse precipitates in the Al alloy film so that the number of precipitates having a particle size exceeding 100 nm is 1 or less per 10 ⁻⁶ cm ² , during the film formation, The residual oxygen partial pressure is adjusted to be 1 × 10 ⁻⁸ Torr or more (more preferably 2 × 10 ⁻⁸ Torr or more) by controlling the ultimate vacuum of Is preferably finely dispersed.

  The present invention also includes a display device characterized in that the Al alloy film is used in a thin film transistor. As an aspect of the display device, the Al alloy film includes a source electrode and / or a drain electrode of a thin film transistor and a signal. It is used for the wire, and the drain electrode is directly connected to the transparent conductive film.

  The transparent conductive film of the present invention is preferably an indium tin oxide (ITO) film or an indium zinc oxide (IZO) film.

  Hereinafter, a preferred embodiment of a display device according to the present invention will be described with reference to the drawings. Hereinafter, a liquid crystal display device (for example, FIG. 1, which will be described in detail later) provided with an amorphous silicon TFT substrate or a polysilicon TFT substrate will be described as a representative example, but the present invention is not limited to this.

(Embodiment 1)
An embodiment of an amorphous silicon TFT substrate will be described in detail with reference to FIG.

  FIG. 2 is an enlarged view of a main part A of FIG. 1 (an example of the display device according to the present invention), and illustrates a preferred embodiment of the TFT substrate (bottom gate type) of the display device according to the present invention. It is a schematic cross-sectional explanatory drawing.

  In the present embodiment, Al alloy films are used as the source-drain electrode / signal line (34) and the gate electrode / scanning line (25, 26). In the conventional TFT substrate, a barrier metal layer is formed on the scanning line 25, the gate electrode 26, and the signal line 34 (the source electrode 28 and the drain electrode 29), respectively. In the TFT substrate of this embodiment, these barrier metal layers can be omitted.

  That is, according to the present embodiment, the Al alloy film used for the drain electrode 29 of the TFT can be directly connected to the transparent pixel electrode 5 without interposing the barrier metal layer. In such an embodiment, too. As a result, good TFT characteristics comparable to or higher than those of conventional TFT substrates can be realized.

  Next, an example of a method for manufacturing the amorphous silicon TFT substrate according to the present invention shown in FIG. 2 will be described with reference to FIGS. The thin film transistor is an amorphous silicon TFT using hydrogenated amorphous silicon as a semiconductor layer. 3 to 10 are denoted by the same reference numerals as those in FIG.

  First, an Al alloy film having a thickness of about 200 nm is laminated on a glass substrate (transparent substrate) 1a using a sputtering method. The film forming temperature of sputtering was 150 ° C. By patterning this Al alloy film, the gate electrode 26 and the scanning line 25 are formed (see FIG. 3). At this time, in FIG. 4 to be described later, the periphery of the Al alloy film constituting the gate electrode 26 and the scanning line 25 is etched to a taper of about 30 ° to 40 ° so that the coverage of the gate insulating film 27 is improved. It is good to leave.

  Next, as shown in FIG. 4, a gate insulating film 27 is formed of a silicon oxide film (SiOx) having a thickness of about 300 nm by using a method such as plasma CVD. The film formation temperature of the plasma CVD method was about 350 ° C. Subsequently, a hydrogenated amorphous silicon film (a-Si-H) having a thickness of about 50 nm and a silicon nitride film (SiNx having a thickness of about 300 nm are formed on the gate insulating film 27 by using a method such as plasma CVD. ).

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) 56 having a thickness of about 50 nm doped with phosphorus is formed thereon, and then, as shown in FIG. The silicon film (a-Si-H) 55 and the n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si-H) 56 are patterned.

Next, a barrier metal layer (Mo film) 53 having a thickness of about 50 nm and an Al alloy film having a thickness of about 300 nm are sequentially stacked thereon using a sputtering method. The film forming temperature of sputtering was 150 ° C. When the Al alloy film is formed, the ultimate vacuum at the time of evacuation is controlled and the residual oxygen partial pressure is adjusted to be 1 × 10 ⁻⁸ Torr or more, so that the origin of precipitate nuclei in the Al alloy is obtained. Is finely dispersed. Next, by patterning as shown in FIG. 7, the source electrode 28 integrated with the signal line and the drain electrode 29 that is in direct contact with the transparent pixel electrode 5 are formed. Furthermore, using the source electrode 28 and the drain electrode 29 as a mask, the n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si—H) 56 on the channel protective film (SiNx) is removed by dry etching.

  Next, as shown in FIG. 8, a silicon nitride film 30 having a thickness of about 300 nm is formed by using, for example, a plasma CVD apparatus, and a protective film is formed. The film formation temperature at this time is about 250 ° C., for example. Next, after forming a photoresist 31 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 the same time, a contact hole (not shown) is formed in a portion corresponding to the connection with TAB on the gate electrode at the panel end.

  Next, after an ashing process using, for example, oxygen plasma, as shown in FIG. 9, the photoresist 31 is stripped using, for example, an amine-based stripping solution. Finally, within the range of storage time (about 8 hours), for example, as shown in FIG. 10, an ITO film having a thickness of, for example, about 40 nm is formed and patterned by wet etching to form the transparent pixel electrode 5 To do. At the same time, when the ITO film is patterned for bonding to the TAB at the connection portion of the gate electrode at the edge of the panel, the TFT substrate 1 is completed.

  In the TFT substrate thus manufactured, the drain electrode 29 and the transparent pixel electrode 5 are directly connected.

  In the above description, an ITO film is used as the transparent pixel electrode 5, but an IZO film may be used. Further, polysilicon may be used as the active semiconductor layer instead of amorphous silicon (see Embodiment 2 described later).

  Using the TFT substrate thus obtained, for example, the liquid crystal display device shown in FIG. 1 is completed by the method described below.

  First, for example, polyimide is applied to the surface of the TFT substrate 1 manufactured as described above and dried, and then a rubbing process is performed to form an alignment film.

  On the other hand, the counter substrate 2 forms the light shielding film 9 on the glass substrate by patterning, for example, chromium (Cr) in a matrix. Next, resin-made 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 an ITO film 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.

  Next, the TFT substrate 1 and the surface of the counter substrate 2 on which the alignment film 11 is formed are arranged so as to oppose each other, and the TFT substrate 1 is opposed to the TFT substrate 1 by a sealing material 16 made of resin, excluding the liquid crystal sealing port. The 22 substrates are bonded together. At this time, a gap between the two substrates is kept substantially constant by interposing a spacer 15 between the TFT substrate 1 and the counter substrate 2.

  The empty cell thus obtained is placed in a vacuum, and the liquid crystal layer containing the liquid crystal molecules is injected into the empty cell by gradually returning it to atmospheric pressure with the sealing port immersed in the liquid crystal. Form and seal the sealing port. Finally, polarizing plates 10 are attached to both sides of the empty cell to complete the liquid crystal display.

  Next, as shown in FIG. 1, the driver circuit 13 for driving the liquid crystal display device is electrically connected to the liquid crystal display, and is arranged on the side portion or the back surface portion of the liquid crystal display. Then, the liquid crystal display is held by the holding frame 23 including the opening serving as the display surface of the liquid crystal display, the backlight 22 serving as the surface light source, the light guide plate 20, and the holding frame 23, thereby completing the liquid crystal display device.

(Embodiment 2)
An embodiment of a polysilicon TFT substrate will be described in detail with reference to FIG.

  FIG. 11 is a schematic cross-sectional explanatory view illustrating a preferred embodiment of a top gate type TFT substrate according to the present invention.

This embodiment is mainly different from Embodiment 1 described above in that polysilicon is used instead of amorphous silicon as an active semiconductor layer and that a top gate type TFT substrate is used instead of a bottom gate type. Yes. Specifically, in the polysilicon TFT substrate of the present embodiment shown in FIG. 11, the active semiconductor film is a polysilicon film not doped with phosphorus (poly-Si) and a polysilicon film into which phosphorus or arsenic is ion-implanted. It differs from the amorphous silicon TFT substrate shown in FIG. 2 described above in that it is formed of (n ⁺ poly-Si). Further, the signal line is formed so as to intersect the scanning line through an interlayer insulating film (SiOx).

  Also in this embodiment, the barrier metal layer formed on the source electrode 28 and the drain electrode 29 can be omitted.

  Next, an example of a method for manufacturing the polysilicon TFT substrate according to the present invention shown in FIG. 11 will be described with reference to FIGS. The thin film transistor is a polysilicon TFT using a polysilicon film (poly-Si) as a semiconductor layer. 12 to 18, the same reference numerals as those in FIG. 11 are given.

First, a silicon nitride film (SiNx) having a thickness of about 50 nm, a silicon oxide film (SiOx) having a thickness of about 100 nm, and a thickness are formed on the glass substrate 1a by a plasma CVD method or the like, for example. A hydrogenated amorphous silicon film (a-Si-H) of about 50 nm is formed. Next, in order to convert the hydrogenated amorphous silicon film (a-Si-H) into polysilicon, heat treatment (about 1 hour at about 470 ° C.) and laser annealing are performed. After the dehydrogenation treatment, the hydrogenated amorphous silicon film (a-Si-H) is irradiated with a laser having an energy of about 230 mJ / cm ² using, for example, an excimer laser annealing apparatus, so that the thickness is about 0. A polysilicon film (poly-Si) of about 3 μm is obtained (FIG. 12).

  Next, as shown in FIG. 13, the polysilicon film (poly-Si) is patterned by plasma etching or the like. Next, as shown in FIG. 14, a silicon oxide film (SiOx) having a thickness of about 100 nm is formed, and a gate insulating film 27 is formed. An Al alloy film with a thickness of about 200 nm and a barrier metal layer (Mo thin film) 52 with a thickness of about 50 nm are stacked on the gate insulating film 27 by sputtering or the like, and then patterned by a method such as plasma etching. Thereby, the gate electrode 26 integral with the scanning line is formed.

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

Next, as shown in FIG. 16, a silicon oxide film (SiOx) having a thickness of about 500 nm is formed at a substrate temperature of about 250 ° C. using a plasma CVD apparatus, for example, and an interlayer insulating film is formed. The interlayer insulating film (SiOx) and the silicon oxide film of the gate insulating film 27 are dry-etched using a mask patterned with photoresist to form contact holes. A barrier metal layer (Mo film) 53 having a thickness of about 50 nm and an Al alloy film having a thickness of about 450 nm are formed by sputtering and then patterned to form a source electrode 28 and a drain electrode 29 that are integral with the signal line. To do. When the Al alloy film is formed, the ultimate vacuum at the time of evacuation is controlled and the residual oxygen partial pressure is adjusted to be 1 × 10 ⁻⁸ Torr or more, so that the origin of precipitate nuclei in the Al alloy is obtained. Is finely dispersed. The source electrode 28 and the drain electrode 29 are in contact with an n ⁺ type polysilicon film (n ⁺ poly-Si) through contact holes, respectively.

  Next, as shown in FIG. 17, a silicon nitride film (SiNx) having a thickness of about 500 nm is formed at a substrate temperature of about 250 ° C. by a plasma CVD apparatus or the like to form an interlayer insulating film. After a photoresist 31 is formed on the interlayer insulating film, the silicon nitride film (SiNx) is patterned, and contact holes 32 are formed in the silicon nitride film (SiNx) by dry etching, for example.

  Next, as shown in FIG. 18, after an ashing process using, for example, oxygen plasma, the photoresist is stripped using an amine-based stripping solution in the same manner as in the first embodiment, and then an ITO film is formed. Then, the transparent pixel electrode 5 is formed by patterning by wet etching.

  In the polysilicon TFT substrate thus manufactured, the drain electrode 29 is directly connected to the transparent pixel electrode 5.

  Next, in order to stabilize the characteristics of the transistor, for example, annealing is performed at about 250 ° C. for about 1 hour to complete a polysilicon TFT array substrate.

  According to the TFT substrate according to the second embodiment and the liquid crystal display device including the TFT substrate, the same effects as those of the TFT substrate according to the first embodiment described above can be obtained.

  Using the TFT array substrate thus obtained, for example, the liquid crystal display device shown in FIG. 1 is completed in the same manner as the TFT substrate of Embodiment 1 described above.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

An Al alloy film (film thickness = 300 nm) having various alloy compositions shown in Table 1 and Table 2 was formed under the following conditions by DC magnetron sputtering using a load lock type sputtering apparatus CS-200 manufactured by ULVAC. Filmed.
・ Substrate: Glass substrate after cleaning (Corning Eagle 2000)
・ DC power: total 500W
-Substrate temperature: 25 ° C (room temperature)
・ Atmospheric gas: Ar
Ar gas pressure: 2 mTorr

At the time of film formation, by controlling the ultimate vacuum at the time of evacuation and adjusting the residual oxygen partial pressure to be 1 × 10 ⁻⁸ Torr or more, the origin of precipitate nuclei is made fine within the Al alloy. Dispersed. The Al alloy films having various alloy compositions described above were formed by using a plurality of various binary component targets composed of Al and alloy elements, which are different in the kind of alloy elements.

  The content of each alloy element in the various Al alloy films used in the examples was determined by ICP emission analysis (inductively coupled plasma emission analysis).

  Next, a heat treatment (heating at 330 ° C. for 30 minutes in a nitrogen flow) simulating a heat history applied when the TFT substrate was formed was applied to the sample after film formation to deposit precipitates.

The precipitates thus deposited were observed with a reflection SEM (scanning electron microscope), and as shown in the photograph described later, individual precipitates (acceleration voltage 1 keV (near the surface)) confirmed as white spots were seen. The particle size of the precipitate was calculated as (major axis + minor axis) / 2. Further, the particle size of the maximum precipitate and the density of the precipitates having a particle size exceeding 100 nm (the number of precipitates having a particle size exceeding 100 nm present in 10 ⁻⁶ cm ² ) were obtained as follows. That is, the number of precipitates having a particle size of more than 100 nm observed in a 125 μm × 100 μm field of view was obtained using SEM and converted to the number per 10 ⁻⁶ cm ² .

And it evaluated as follows. That is, the number of black spots (black spot-like etching traces) observed in a 10 μm square contact hole is preferably less than one, and the black spots (black spot-like etching traces) are around large precipitates having a particle size exceeding 100 nm. For this reason, it is desirable that the density of large precipitates having a particle size exceeding 100 nm is low. From such a viewpoint, the size of the precipitate obtained by the SEM observation was evaluated as follows.
-The thing whose particle size of a largest precipitate is less than 100 nm, or a precipitate with a particle size exceeding 100 nm is 1 or less per 10 < ^-6 > cm < ² > is set as (circle).
- the particle size of the largest precipitates precipitates 100~120nm a and particle size exceeds 100nm is to those ¹⁰ -6 cm ² per one than 2 or less △.
-The case where the particle size of the largest precipitate is more than 120 nm or the number of the precipitates having a particle size exceeding 100 nm is more than ² per 10 ⁻⁶ cm ² is ^defined as x.

  Subsequently, the immersion test in the aqueous solution of the amine-based resist stripping solution was performed by the following process, simulating the cleaning process of the photoresist stripping solution. That is, after immersing in an amine stripping solution adjusted to pH 10.5 (liquid temperature 25 ° C.) for 1 minute and then immersing the aqueous amine resist stripping solution in pH 9.5 (liquid temperature 25 ° C.) for 5 minutes. Then, running water washing was performed for 30 seconds. Using the sample thus obtained, optical microscope observation (magnification 1000 times) was carried out, and the precipitates of one field of view (the size of one field of view is approximately 130 μm × 100 μm) that was judged as an average field by observing the whole It was observed whether the presence or absence of surrounding etching marks (black dot-shaped etching marks) could be confirmed.

And
・ Those with 1 or less visible black spots
・ If the number of visible black spots is more than 1 and less than 2
-The density of visible black spots is more than 2 ×
It was evaluated.

  These results are shown in Tables 1 and 2.

  From the results shown in Tables 1 and 2, the following can be understood. First, the Al alloy film containing the prescribed amounts of Ge, X group element, and Q group element and formed by the recommended method suppresses coarse precipitates. As a result, even when exposed to an amine-based stripping solution aqueous solution, black spots It was found that a good Al alloy film surface could be realized.

On the other hand, the Al alloy film was not formed by the recommended method (that is, the ultimate vacuum at the time of vacuum evacuation at the time of film formation was controlled, and the residual oxygen partial pressure was not set to 1 × 10 ⁻⁸ Torr or more. In this case, precipitate nuclei could not be finely dispersed in the Al alloy, and coarse precipitates were deposited. As a result, black spots were visually recognized when exposed to an aqueous amine stripping solution.

  As an example of observing the precipitate, for reference, No. 20, no. 19 and no. 8 reflection SEM observation photographs are shown in FIGS. In these photographs, No. which does not satisfy the prescribed component composition. In FIG. 20 (FIG. 19), the precipitates observed as white spots are coarse. On the other hand, No. 1 satisfying the prescribed component composition and having an Al alloy film formed under the recommended conditions. In FIG. 19 (FIG. 20), the precipitate is fine. Also, No. containing Ni as an alloying element. 8 (FIG. 21) It can be seen that the precipitates are finer than 19.

  No. above. 20, no. 19 and no. 8 is also shown in FIGS. 22 to 24, respectively. From these photographs, no. In FIG. 20 (FIG. 22), it can be seen that the black spot-like corrosion marks are considerably conspicuous. On the other hand, no. 19 (FIG. 23), almost no black spot-like corrosion marks are seen. It can be seen that there is almost nothing for 8 (FIG. 24).

FIG. 1 is an enlarged schematic cross-sectional explanatory view showing a configuration of a typical liquid crystal display to which an amorphous silicon TFT substrate is applied. FIG. 2 is a schematic cross-sectional explanatory view showing the configuration of the TFT substrate according to the first embodiment of the present invention. FIG. 3 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 4 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 5 is an explanatory diagram showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 6 is an explanatory view showing an example of the manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 7 is an explanatory diagram showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 8 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 9 is an explanatory diagram showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 10 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 2 in order. FIG. 11 is a schematic cross-sectional explanatory view showing a configuration of a TFT substrate according to the second embodiment of the present invention. FIG. 12 is an explanatory diagram showing an example of a manufacturing process of the TFT substrate shown in FIG. 11 in order. FIG. 13 is an explanatory view showing, in order, an example of a manufacturing process of the TFT substrate shown in FIG. FIG. 14 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 11 in order. FIG. 15 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 11 in order. FIG. 16 is an explanatory view showing an example of a manufacturing process of the TFT substrate shown in FIG. 11 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the TFT substrate shown in FIG. 11 in order. FIG. 18 is an explanatory view showing, in order, an example of the manufacturing process of the TFT substrate shown in FIG. FIG. 19 is a SEM observation photograph of an Al-0.2 atomic% Ni-0.35 atomic% La alloy film. FIG. 20 is an SEM observation photograph of an Al-0.5 atomic% Ge-0.02 atomic% Sn-0.2 atomic% La alloy film. FIG. 21 is a SEM observation photograph of an Al-0.5 atomic% Ge-0.1 atomic% Ni-0.2 atomic% La alloy film. FIG. 22 is an optical microscopic photograph of an Al-0.2 atomic% Ni-0.35 atomic% La alloy film. FIG. 23 is an optical microscopic photograph of Al-0.5 atomic% Ge-0.02 atomic% Sn-0.2 atomic% La. FIG. 24 is an optical microscope observation photograph of an Al-0.5 atomic% Ge-0.1 atomic% Ni-0.2 atomic% La alloy film.

Explanation of symbols

1 TFT substrate 2 Counter substrate 3 Liquid crystal layer 4 Thin film transistor (TFT)
5 Transparent pixel electrode (transparent conductive film)
6 Wiring section 7 Common electrode 8 Color filter 9 Light shielding film 10 Polarizing plate 11 Alignment film 12 TAB tape 13 Driver circuit 14 Control circuit 15 Spacer 16 Sealing material 17 Protective film 18 Diffuser 19 Prism sheet 20 Light guide plate 21 Reflector 22 Backlight 23 holding frame 24 printed circuit board 25 scanning 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 33 Amorphous silicon channel film (active semiconductor film)
34 Signal lines 52 and 53 Barrier metal layer 55 Non-doped hydrogenated amorphous silicon film (a-Si-H)
56 n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si-H)

Claims (11)

An Al alloy film directly connected to the transparent conductive film on the substrate of the display device,
The Al alloy film contains 0.2 to 2.0 atomic% of Ge and at least one element selected from element group X (Ag, In, Sn, Ni, Co, Cu), and a rare earth element And 0.02-1 atomic% of at least one element selected from the element group Q consisting of the refractory metal group (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf), and
An Al alloy film for a display device, wherein the number of precipitates having a particle size exceeding 100 nm is 1 or less per 10 ⁻⁶ cm ² .   2. The Al alloy film for a display device according to claim 1, comprising 0.02 to 0.5 atomic% of at least one element selected from the group consisting of Ni, Co, and Cu in the element group X. 3.   The Al alloy film for a display device according to claim 1, wherein the element group X contains 0.1 to 0.6 atomic percent of Ag.   The Al alloy film for a display device according to any one of claims 1 to 3, comprising 0.02 to 0.5 atomic% of In and / or Sn in the element group X. The Al alloy film for a display device according to any one of claims 1 to 4, wherein an element content of the element group X satisfies the following formula (1).
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]   6. A display device, wherein the Al alloy film for a display device according to claim 1 is used for a thin film transistor.   It contains at least one element selected from 0.2 to 2.0 atomic% Ge and element group X (Ag, In, Sn, Ni, Co, Cu), and includes a rare earth element and a refractory metal group ( (Ti, Ta, V, Nb, Mo, W, Cr, Zr, Hf) containing at least one element selected from element group Q consisting of 0.02 to 1 atomic%, with the balance being Al and inevitable impurities A sputtering target characterized by that.   The sputtering target according to claim 7, comprising 0.02 to 0.5 atomic% of at least one element selected from the group consisting of Ni, Co, and Cu in the element group X.   The sputtering target according to claim 7 or 8 which contains 0.1-0.6 atomic% of Ag among said element group X.   The sputtering target according to any one of claims 7 to 9, comprising 0.02 to 0.5 atomic% of In and / or Sn in the element group X. The sputtering target according to any one of claims 7 to 10, wherein an element content of the element group X satisfies the following formula (1).
2Ag + 10 (In + Sn + Ni + Co + Cu) ≦ 5 (1)
[In the formula (1), Ag, In, Sn, Ni, Co, Cu indicate the content of each element contained in the Al alloy film (unit: atomic%)]