JP3629716B2 - Wiring film manufacturing method, liquid crystal display device manufacturing method, and semiconductor device manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a wiring film, and more particularly to a liquid crystal display device having a nonlinear resistance element using an anodized film, a liquid crystal display device having a thin film transistor using an anodized film, and an anodized film. The present invention relates to a method for manufacturing an electronic element such as a semiconductor device.
[0002]
[Prior art]
An anodic oxidation method as one of methods for forming an oxide film on a metal surface is widely used because a uniform film is deposited in a substrate with a high throughput. For example, it is a technique that has been used for a long time in the production of capacitors for electrolytic capacitors and the plating of aluminum films. Recently, it has been used in the field of micro devices such as a semiconductor capacitor, a part of a gate insulating film of a thin film transistor (TFT), and an insulating film of a non-linear resistance element such as an MIM type non-linear element. 2. Description of the Related Art An active matrix liquid crystal display panel using a thin film transistor or a non-linear resistance element as an active element for driving a liquid crystal is used in various places as a display that is small, light, consumes less power, and can display a beautiful color.
[0003]
An active matrix type liquid crystal display device has a liquid crystal filled between a substrate on one side on which a non-linear element is provided for each pixel region to form a matrix array and a substrate on the other side on which a color filter is formed, The liquid crystal alignment state for each pixel region is controlled to display predetermined information. As a switching element, a three-terminal element such as a thin film transistor or a two-terminal element such as a nonlinear resistance element is used. In order to meet the demand for an increase in screen size and cost for a liquid crystal display element, a two-terminal nonlinear resistance element is used. The method used is advantageous because the manufacturing process is short. In addition, when a non-linear resistance element is used, a scanning line can be provided on one side of the substrate on which the matrix array is formed, and a signal line can be provided on the other side of the substrate. There is also an advantage that a crossover short circuit between the scanning line and the signal line is not generated.
[0004]
In an active matrix type liquid crystal display panel using such a non-linear resistance element, as shown in FIG. 3 which is an equivalent circuit of the liquid crystal display panel, each scanning line 31 and each signal line 32 in each pixel region 3. A non-linear resistance element 1 (indicated by the symbol of a varistor in the figure) and a liquid crystal display element 2 (indicated by a symbol of a capacitor in the figure) are connected in series between the scanning line 31 and the signal line 32. The display operation is controlled by switching the liquid crystal display element 2 between a display state and a non-display state or an intermediate state thereof based on the signal applied to.
[0005]
As shown in FIG. 4A, in the nonlinear resistance element 1, the voltage VNL applied to the first metal film and the second metal film of the nonlinear resistance element and the current INL flowing between the two metal films Has a non-linear relationship. Assuming that the threshold voltage of the non-linear resistance element 1 is Vth, the threshold voltage of the liquid crystal display element 2 is Vb, and the potential for the display state is (Vb + ΔV), as shown in FIG. By setting the potential difference V (voltage applied to the unit pixel) between the scanning line 31 and the signal line 32 in the predetermined pixel region 3 to (Vb + Vth), the liquid crystal display element 2 can be in a non-display state. By setting the potential difference V between the scanning line 31 and the signal line 32 to (Vb + Vth + ΔV), the liquid crystal display element 2 can be brought into a display state. On the other hand, in the non-selection period, the potential V applied to the unit pixel is set so as to be substantially close to the potential remaining in the liquid crystal display element 2, and if the difference is equal to or less than the threshold voltage Vth of the nonlinear resistance element, Within the non-selection period, the non-linear resistance element 1 is always in the cut-off state, and the state determined in the selection period is maintained as it is.
[0006]
As described above, it is possible to obtain an ideal non-linear resistance element 1 in which the capacity of the non-linear resistance element is sufficiently small and the non-linearity of the voltage-current characteristic is sufficiently high, and the resistance of the wiring that gives a signal to the non-linear resistance element can be sufficiently low. This is the most basic operation example.
[0007]
A general structure as described in Japanese Patent Laid-Open No. 52-149090 will be described with reference to FIG. 2A which is a plan view of a nonlinear resistance element and FIG. 2B which is a cross-sectional view of AA ′. The non-linear resistance element 1 is formed on the surface side of the transparent substrate 11 and has a first metal film 12 mainly composed of Ta atoms, which is conductively connected to the scanning circuit side via the scanning line 31, and a metal oxide on the surface side thereof. The film 13 includes a second metal film 14 made of Cr formed on the surface side and conductively connected to the pixel electrode 15. The metal oxide film 13 is formed by anodic oxidation of the first metal film 12 so that the film thickness is uniform on the surface of the Ta film and there is no pinhole.
[0008]
There are the following three proposals for manufacturing such a nonlinear resistance element. The first is to form three layers constituting the non-linear resistance element by continuous sputtering. Japanese Patent Laid-Open No. 60-30188, the second is to form an insulating film in FIG. 2 before depositing the second metal film of the non-linear resistance element. Japanese Patent Laid-Open No. 63-48528, No. 3, which dry-etches 13 chemically etches the surface of the first metal film before anodizing the first metal film of the nonlinear resistance element and depositing the insulating film. Japanese Patent Application Laid-Open No. 3-46633 that performs etching.
[0009]
[Problems to be solved by the invention]
However, in the conventional liquid crystal display panel using the non-linear resistance element 1, the non-uniformity of voltage-current characteristics of the non-linear resistance element is large within the substrate or between the wafers. There was a problem. As shown in Japanese Patent Application Laid-Open Nos. 58-92087 and 59-86092, it is possible to eliminate the unevenness by devising a panel driving method, but the circuit becomes complicated and the panel cost increases. The merit of the liquid crystal panel will be diminished if the weight is increased.
[0010]
Conventionally, the following three proposals have been made as methods for preventing variations in the voltage-current characteristics of nonlinear resistance elements within and between substrates.
[0011]
In the first method (Japanese Patent Laid-Open No. 60-30188), when the pixel electrode is formed by the conventional process, the first metal film 71 and the pixel electrode 74 are short-circuited as shown in FIG. A matrix array cannot be constructed. Therefore, it is necessary to form a film having a resistance higher by two digits or more than that of the insulator 72 on the side surface of the element at a low temperature. However, the manufacturing process becomes longer and the cost merit of manufacturing the non-linear resistance element is impaired. The contact resistance between the film 73 and the pixel electrode 74 becomes unstable, resulting in variations in element characteristics.
[0012]
In the second method (Japanese Patent Laid-Open No. 63-48528), the dry etching step and the deposition of the second metal film are continuously performed as described in the patent (the lower right lines 3 to 15 of publication p167). However, according to the experiment conducted by the applicant, the variation was slightly improved, but a current value variation of about 0.5 digits was observed when 10 V was applied. Further, the problem that the current density decreases when the element size is reduced has not been improved.
[0013]
The third method (Japanese Patent Laid-Open No. 3-46633) was insufficient in reducing the variation in voltage-current characteristics by chemical etching in the study conducted by the applicant.
[0014]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a high-quality wiring film that is free from defects and free from defects in a simple process.
[0015]
It is another object of the present invention to provide a method for manufacturing a liquid crystal display device having a non-linear resistance element with high quality and high manufacturing yield without complicating the manufacturing process.
[0016]
It is another object of the present invention to provide a method for manufacturing a liquid crystal display device having a thin film transistor having a high quality and a high manufacturing yield without complicating the manufacturing process.
[0017]
It is another object of the present invention to provide a method for manufacturing a semiconductor device with high quality and high manufacturing yield without complicating the manufacturing process.
[0018]
[Means for Solving the Problems]
[0019]
In the method for manufacturing a liquid crystal display device of the present invention, in the method for manufacturing a liquid crystal display device including a nonlinear resistance element having a metal layer and an anodic oxide film of the metal layer, the surface layer containing impurities in the metal layer is subjected to an electropolishing treatment. And a step of anodizing the metal layer after the electropolishing treatment.
[0020]
According to such a method for manufacturing a liquid crystal display device, since impurities in the anodic oxide film are reduced, variations in voltage-current characteristics in the non-linear resistance elements can be eliminated, and differences in current density due to differences in element sizes can be eliminated. In addition, a liquid crystal display device having a good contrast and a uniform in-plane display state can be manufactured with a simple process and a high yield. In the liquid crystal display device of the present invention, for example, a first insulating substrate and a second insulating substrate are opposed to each other through a liquid crystal layer, and a first signal electrode and a first signal electrode are disposed on the first insulating substrate. It is possible to use a non-linear resistance element and a pixel electrode which are arranged and a second signal electrode is arranged on the second insulating substrate.
[0021]
Further, a step of forming a tantalum oxide film on the substrate and forming the metal layer on the tantalum oxide film may be provided.
[0022]
Such manufacturing methodAccording to the above, when the TaOx film is deposited, the adhesion between the Ta film and the substrate is improved, and even if the substrate is etched slightly, the Ta film is not peeled off. Further, since the impurity element contained in the substrate can be prevented from diffusing to the surface of the Ta film, an anodic oxide film having no variation in electrical characteristics can be formed.
[0029]
The metal layer may contain an element selected from the group consisting of aluminum, zinc, zirconium, and hafnium.
[0030]
Such manufacturing methodAccording to this, the metal layer can be anodized.
[0033]
The metal layer may contain titanium or niobium.
[0034]
Such manufacturing methodAccording to this, the metal layer can be anodized.
[0035]
Also take this formLiquid crystal displayIn this manufacturing method, it is preferable to perform the electropolishing treatment using a solution containing hydrofluoric acid.
[0036]
TakeLiquid crystal displayAccording to this manufacturing method, the metal layer can be subjected to electropolishing treatment, and the surface of the metal layer can be finished to a mirror surface.
[0037]
The method for manufacturing a wiring film of the present invention is a method for manufacturing a wiring film in which a metal layer is anodized, the step of removing a surface layer containing impurities in the metal layer by electropolishing, and the step after the electropolishing And anodizing the metal layer.
[0038]
According to such a method for manufacturing a wiring film, since the metal layer surface is subjected to an electropolishing treatment in advance when forming the anodic oxide film on the metal layer surface, impurities in the anodic oxide film are reduced, resulting in fewer defects and quality variations. A high-quality wiring film without any problems can be provided.
[0039]
Further, in the method for manufacturing a liquid crystal display device of the present invention, in the method for manufacturing a liquid crystal display device comprising a thin film transistor having a gate electrode and an anodic oxide film of the gate electrode, the gate electrodeRemove surface layer containing impurities in electrolytic polishing processProcess,After the electrolytic polishing processAnd anodizing the gate electrode.
[0040]
According to such a method for manufacturing a liquid crystal display device, the purity of the gate insulating film can be increased, so that the insulation is improved, and thus the switching characteristics of the thin film transistor itself are also improved, the variation is reduced, the line defects are reduced, and The display also has high image quality and pixel unevenness is reduced. That is, it is possible to simultaneously improve the yield and improve the image quality of the liquid crystal display device. In the liquid crystal display device of the present invention, for example, the signal lines and the scanning lines are arranged in a matrix on the first insulating substrate, and the thin film transistor is formed in the vicinity of the intersection of the signal lines and the scanning lines. The signal line and the scanning line are connected to the pixel electrode through the thin film transistor, and the first insulating substrate is disposed opposite to the second insulating substrate through the liquid crystal layer. Can do.
[0041]
Further, in the method for manufacturing a semiconductor device of the present invention, in the method for manufacturing a semiconductor device including a capacitor element including a metal film and an anodic oxide film of the metal film, the metal filmThe surface layer containing impurities in the surface by electropolishingProcess,After the electrolytic polishing processAnd anodizing the metal film.
[0042]
According to this method for manufacturing a semiconductor device, it is possible to reduce the variation in insulating properties, and thus allow for a design margin, so that miniaturization can be promoted. Accordingly, the number of wafers to be taken per wafer is increased, and the yield can be improved.
Further, the metal layer, the metal film, or the gate electrode may contain tantalum.
According to such a manufacturing method, when a film containing Ta atoms is used, the control of anodic oxidation is good and the processing becomes simple. The voltage-current characteristics of the nonlinear resistance element can also be improved.
Moreover, in the manufacturing method which takes this form, it is preferable to perform the said electropolishing process using the solution containing a hydrofluoric acid or hydrochloric acid.
According to this manufacturing method, an electrolytic polishing process can be performed. At this time, for example, by making the electrolytic polishing electrolytic solution into a solution containing hydrochloric acid, damage to the substrate can be eliminated and a glass substrate can be used. Furthermore, it is not necessary to use the underlying tantalum oxide film, and the manufacturing process can be simplified. For example, the electrolytic solution used for the electropolishing treatment is preferably an aqueous solution containing 0.2 to 10% hydrofluoric acid and 20 to 40% hydrochloric acid. For example, as another preferred example, the electrolytic solution used for the electrolytic polishing treatment is an aqueous solution containing 0.5 to 7% hydrofluoric acid and 32-38% hydrochloric acid, and the electrolytic polishing treatment is performed at an applied voltage of 40 to 60 V. , Current density 0.1-0.2A / cm 2 It is desirable to be performed at. Furthermore, for example, as another preferred example, the electrolytic solution used for the electropolishing treatment is desirably a 5 to 20% hydrofluoric acid aqueous solution.
If the polishing ability is insufficient, a very small amount of hydrofluoric acid that does not damage the substrate may be added to the electrolytic solution. The hydrofluoric acid also has a role of mirror finishing the surface of the metal layer.
Moreover, in the manufacturing method which takes the form of this invention, it is preferable to perform the said electropolishing process using the electrolyte solution containing the solution selected from the group which consists of phosphoric acid, perchloric acid, and nitric acid.
According to this manufacturing method, when this electrolytic solution is used, the surface layer containing impurities is electropolished. Perchloric acid-based solutions and nitric acid-based solutions have the advantage that the throughput of the process is improved due to the high polishing speed. On the other hand, the phosphoric acid solution has an advantage that the controllability of the electrolytic polishing is good, although the electrolytic polishing rate is somewhat slower than the above-described solution. Further, when priority is given to controllability, for example, the electrolytic solution used for the electrolytic polishing treatment is an aqueous solution containing phosphoric acid, and the electrolytic polishing treatment is applied with an applied voltage of 10 to 80 V and a current density of 0.01 to 0.5 A / cm. 2 Is preferably carried out.
Further, in the manufacturing method according to the embodiment of the present invention, a step of removing the layer containing the impurities by electrolytic polishing treatment;
The anodizing step;
It is preferable to perform pure water cleaning during the period.
[0043]
Here, the principle of the above-described effect will be described.
[0044]
As a cause of variations in the voltage-current characteristics, the applicant investigated the manufacturing process of the non-linear resistance element, and found that the cause was related to the amount of impurity elements contained in the metal oxide film constituting the non-linear resistance element. confirmed.
[0045]
A film containing tantalum (Ta) atoms is used as the first metal film of the nonlinear resistance element that also serves as the wiring film. When patterning the tantalum (Ta) film, a resist is used. At this time, as shown in FIG. 5, the surface of the Ta film is included in carbon (C), hydrogen (H) and etching gas contained in the resist. A layer 51 having a thickness of several nanometers reacted with fluorine (F) to be produced. The amount of carbon and hydrogen at this time varies considerably within the substrate and between wafers. That is, since the amount of impurities contained in the insulating film deposited by anodizing the Ta film that has reacted with carbon, hydrogen, or fluorine is different, the voltage-current characteristics of the nonlinear resistance element vary. Furthermore, since the insulating film containing these impurities has different nonlinear characteristics, the current density flowing through the element changes if the element size is different.
[0046]
The wiring film made of Ta film and its anodic oxide film are used for the gate electrode and gate insulating film of the thin film transistor, respectively. However, if the amount of carbon and hydrogen contained in the oxide film is large, dielectric breakdown tends to occur, and point defects And will induce line defects. The same applies to the case of use in an LSI capacitor or the like. The same applies not only to the Ta film but also to other metal films.
[0047]
The fact that impurities on the metal surface serving as the wiring film are contained in the anodic oxide film is explained from the mechanism of oxide film formation. FIG. 5B shows a process in which an anodic oxide film is grown on the wiring film shown in FIG. 5A. FIG. 5B shows the anodic oxidation indicated by a dotted line when oxygen ions are supplied from the surface of the wiring film. A film 53 grows. In this growth process, the oxygen ions in the solution move to the interface between the oxide film and the metal film and react with the metal to grow the oxide film, and the metal ions move to the surface of the oxide film. As shown in FIG. 5B, all of the layer 51 containing impurities on the surface of the wiring film is taken into the anodic oxide film.
[0048]
In order to prevent impurities in the surface layer of the wiring film from being removed together with the components of the wiring film in order to prevent impurities from being contained in the anodic oxide film in the wiring film used by anodizing the exposed portion on the substrate, Electropolishing is performed before anodization. By doing so, an oxide film having a constant composition in the depth direction is deposited, and variations in devices using the oxide film are reduced.
[0049]
In view of the stability of the oxide film, a film containing tantalum atoms is often used for the wiring film. However, the electrolyte solution at this time has a surface layer containing impurities without damaging the wiring film when a liquid containing hydrochloric acid is used. Can be removed.
[0050]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
[0051]
FIG. 1 is a diagram showing a method of manufacturing a wiring film. (A) is a figure which shows the method of electropolishing, (b) is a figure which shows the manufacturing method of an anodic oxide film. As shown in FIG. 1A, the wiring film 12 patterned into a predetermined shape is used as an anode, and voltage is applied between the cathode 10 and electrolytic polishing treatment is performed. Thereafter, the substrate 11 is washed with pure water and then drained, and immersed in an anodizable electrolyte as shown in FIG. 1B to deposit an anodic oxide film 13 on the surface of the wiring film 12. The wiring film portion 51 containing the resist and the etching gas shown in FIG. 5 is removed in the electrolytic polishing process, and the oxide film 13 having no variation in electrical characteristics is produced. Here, in order to enhance the etching effect on the surface of the wiring film by electropolishing, it is desirable to form the anodic oxide film as soon as possible after electropolishing so that component elements in the atmosphere do not adhere to the surface layer. If possible, it is more desirable to form an anodized film immediately after electrolytic polishing.
[0052]
The electrolytic solution and electrolytic conditions for electrolytic polishing will be described. Since the present invention is intended for a wiring film that is used after anodization after electrolytic polishing, the materials for the wiring film include aluminum (Al), tantalum (Ta), titanium (Ti), and zinc that can be anodized. Examples thereof include (Zn), niobium (Nb), zirconium (Zr), hafnium (Hf), and compounds containing the above metals.
[0053]
[Example 1]
First, a case will be described in which the wiring film is made of an element mainly composed of Al, Zn, Zr, and Hf. The manufacturing method is the same as the method shown in FIG. The electrolyte contained impurities when using a phosphoric acid-based solution composed of H3PO4, H2SO4 and H2CrO4, a perchloric acid-based solution composed of HClO4 and (CH3CO) 2O, a nitric acid-based solution composed of HNO3, H3PO4 and CH3COOH, and an aqueous solution thereof. The surface layer of the wiring film is electrolytically polished. Perchloric acid-based solutions and nitric acid-based solutions have the advantage that the throughput of the process is improved due to the high polishing speed. On the other hand, the phosphoric acid solution has an advantage that the controllability of the electrolytic polishing is good, although the electrolytic polishing rate is somewhat slower than the above-described solution. Since the polishing time is several minutes, if controllability is given priority, the substrate and the wiring film are not damaged if the phosphoric acid aqueous solution is applied under the conditions of an applied voltage of 10 to 80 V and a current density of 0.01 to 0.5 A / cm 2. The exposed part can be polished. In order to increase the polishing rate under these conditions, the temperature of the electrolytic solution should be 40 to 50 ° C. The conditions at this time are applied voltage 20 to 50 V, current density 0.05 to 0.2 A / What is necessary is just to make it cm2. At this time, the smoothness of the wiring film surface is improved.
[0054]
[Example 2]
Second, the case where the wiring film is composed of an element mainly composed of Ta will be described. When the wiring film is Ta, the manufacturing method is the same as that shown in FIG. The Ta film has an oxide film deposition rate faster than the etching rate in most acid and alkali aqueous solutions, so the electrolytic solution is limited to a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution.
[0055]
When using a hydrofluoric acid aqueous solution, polishing with an aqueous solution having a concentration of about 20% at an applied voltage of 30 to 60 V and a current density of 0.01 to 0.5 A / cm 2, polishing at a rate of 1 to 5 nm / min. The surface is also mirror finished. If priority is given to the smoothness of the surface, the concentration of hydrofluoric acid may be about 5%, and the number of treatments under the above polishing conditions for 2 to 3 minutes may be increased. When the substrate is etched with hydrofluoric acid such as glass, if the etching rate is high, the substrate will be roughened, and the wiring film may be peeled off or the surface may be bumpy due to this effect. Accordingly, it is necessary to adjust the concentration so as not to adversely affect the wiring film. For example, a concentration of 5% or less is desirable for general plate glass, and a concentration of 1 to 10% is desirable for Corning 7059. At this time, the polishing speed is lowered, so that the time may be lengthened or the number of short-time treatments may be increased under the above-described electrolytic polishing conditions.
[0056]
When using a hydrochloric acid-based aqueous solution, polishing with an aqueous solution having a concentration of about 50% at an applied voltage of 40 to 80 V and a current density of 0.01 to 0.5 A / cm 2, at a rate of 0.3 to 3 nm / min. Polished. When it is necessary to increase the polishing speed, the applied voltage may be 70 to 80 V and the current density may be 0.2 to 0.3 A / cm 2. In order to improve the smoothness of the surface, the applied voltage 40 to 60 V, The current density may be 0.01 to 0.2 A / cm2. However, when the impurity contained in the impurity layer on the surface is heavy metal, it becomes difficult to be polished. In this case, the polishing ability is improved by adding a small amount of 3% or less hydrofluoric acid to the electrolytic solution.
[0057]
As described above, when the wiring film is an element mainly composed of Ta, a hydrofluoric acid aqueous solution is preferable if the substrate is not etched. When the substrate is attacked by hydrofluoric acid, a hydrochloric acid-based aqueous solution may be used. When the polishing ability is insufficient, a very small amount of hydrofluoric acid that does not attack the substrate may be added to the electrolytic solution. The electrolytic solution at this time is an aqueous solution of 0.2 to 10% hydrofluoric acid and 20 to 40% hydrochloric acid, and the electrolysis conditions are an applied voltage of 20 to 80 V and a current density of 0.02 to 0.3 A / cm2, preferably hydrofluoric acid. What is necessary is just to make an applied voltage 40-60V and current density 0.1-0.2 A / cm <2> with the aqueous solution of 0.5-7% and hydrochloric acid 32-38%. The amount of hydrofluoric acid added at this time is preferably as small as possible so that the impurity-containing layer 51 shown in FIG. 5 is removed. In other words, if the concentration of hydrofluoric acid is reduced and hydrochloric acid is added, the polishing ability can be reduced without damaging the substrate.
[0058]
If a tantalum oxide (TaOx) film that is not affected by hydrofluoric acid is deposited between the wiring film and the substrate even when the substrate is affected by hydrofluoric acid, a hydrochloric acid aqueous solution containing 20% or less hydrofluoric acid Can be used. Even when an aqueous solution of 0.5 to 7% hydrofluoric acid and 32 to 38% hydrochloric acid is used, the TaOX film is preferably deposited. When the TaOX film is deposited, the adhesion between the Ta film and the substrate is improved, and even if the substrate is slightly etched, the Ta film is not peeled off. Further, since the impurity element contained in the substrate can be prevented from diffusing to the surface of the Ta film, an anodic oxide film having no variation in electrical characteristics can be formed.
[0059]
The Ta film can change the film quality of the anodic oxide film depending on the type of chemical conversion solution, and any impurities can be removed without damaging the substrate by the electrolytic polishing process. Therefore, the Ta film can be used as a wiring film with an oxide film on the surface. Provides the best process integrity.
[0060]
Example 3
Third, the case where the wiring film is an element mainly composed of Ti and Nb will be described. The electrolytic solution is a hydrofluoric acid aqueous solution, which is an aqueous solution having a concentration of about 20%, and if polished at 30 to 60 V and 0.01 to 0.5 A / cm 2, it is polished at a rate of 1 to 5 nm / min, and the surface is also mirrored Finished.
[0061]
Next, an application example to a device using a wiring film with an anodized film will be described.
[0062]
Example 4
FIG. 2 is a diagram showing a nonlinear resistance element. The method for forming the metal layer and the conductive layer integrally formed with the wiring film is the same as that shown in FIG.
[0063]
First, in the case where a wiring film with an anodic oxide film on the surface is used as a scanning line and a non-linear resistance element is formed by a part of the anodic oxide film to have a liquid crystal switching function, the pixels arranged in a matrix array This will be described with reference to FIG. 2A which is a plan view and FIG. 2B which is a cross-sectional view of AA ′ across the element. In this case, the wiring film 12 also serves as the first metal film, and a material mainly composed of Ta having a film thickness of 100 to 500 nm is used from the voltage-current characteristics, and the surface of the first metal film is anodized. Then, a metal oxide film 13 made of TaOX having a thickness of 30 to 80 nm is deposited, and a second metal film 14 made of Cr having a thickness of 50 to 200 nm is deposited so as to cross a part of the metal oxide film 13. The intersection of the metal films is a non-linear resistance element. Here, the second metal film may also be used as the pixel electrode 15 made of an ITO film. Although the first metal film is described as a scanning line here, the first metal film can be connected to a signal supply circuit as a signal line. In this case, a scanning signal is supplied to the electrode arranged on the counter substrate side.
[0064]
If no treatment is performed after patterning the first metal film before depositing the anodic oxide film, a current of about one digit is applied when a voltage of 10 V is applied to the element in the same substrate or between the substrates as shown in FIG. The value is different. (The relationship between voltage and current is in the shaded area.) FIG. 6 shows voltage-current characteristics of a non-linear resistance element having an element size of 4 μm square and an insulating film thickness of 60 nm. Further, as shown in FIG. 3, since the non-linear resistance element is connected in series with the liquid crystal, the capacity of the non-linear resistance element 1 is made as small as possible with respect to the liquid crystal display element 2 in order to prevent the outflow of charges during the holding period of the liquid crystal. Therefore, it is desirable to make the element size of the nonlinear resistance element as small as possible. However, when the element size is reduced in the conventional manufacturing method, the current density is reduced. For example, when the element size is changed from 4 μm square to 2 μm square, the current density is reduced by an order of magnitude when the second metal film material is chromium (Cr).
[0065]
After patterning the first metal film, the metal oxide film 13 is deposited by anodic oxidation after being processed under the above-described electrolytic polishing conditions for the wiring film containing Ta as a main component. The difference in current density depending on the element size was within the range of error in element size due to variations in patterning dimensions. Specifically, the variation in the current value when a voltage of 10 V was applied to the non-linear resistance element was 0.1 digit or less, and the current density was the same regardless of the element size. The electrolytic polishing conditions for the wiring film at this time are preferably a hydrochloric acid-based electrolyte because the substrate is glass. In this case, since the polishing ability is slightly small, a non-linear resistance element with small variation in characteristics is produced when a hydrochloric acid aqueous solution containing hydrofluoric acid that does not etch the substrate is used. Specifically, electrolytic polishing may be performed with a room temperature aqueous solution of hydrofluoric acid 0.5 to 7% and hydrochloric acid 32 to 38% under conditions of an applied voltage of 40 to 60 V and a current density of 0.1 to 0.2 A / cm 2. .
[0066]
Example 5
Next, a case where a wiring film with an anodic oxide film on the surface layer is used as a scanning line, a gate insulating film of a thin film transistor is formed by a part of the anodic oxide film, and a liquid crystal switching function is provided will be described. FIG. 8 is a view showing a thin film transistor according to a twenty-second aspect. FIG. 8A is a top view of one pixel constituting the matrix array, and FIG. 8B is a cross-sectional view of the line segment AA ′. 81 is a substrate, 82 is a scanning line made of a metal film, and an exposed portion thereof is covered with an anodic oxide film 83 of the metal film, and a silicon nitride film 84 constitutes a gate insulating film. 85 is an active layer made of intrinsic silicon, 86 is an electrode of a transistor, 87 is a signal line, and 88 is a pixel electrode. In the case of a thin film transistor, if the insulating property of the gate insulating film made of the anodic oxide film 83 is lowered, the scanning line and the signal line are likely to be short-circuited, so that a line defect is generated and the yield is lowered. Further, when the gate insulating film is thickened to prevent line defects, the switching characteristics of the transistor are deteriorated and a beautiful display image cannot be obtained. Further, the impurities in the gate oxide film cause variations in the electrical characteristics of the transistor, thereby causing unevenness in the display image. That is, when the purity of the gate insulating film is deteriorated, the product yield is lowered and it is difficult to improve the image quality of the liquid crystal display element. Therefore, it is necessary to reduce the variation in insulating properties of the anodic oxide film by performing an electrolytic polishing process before depositing the anodic oxide film 83.
[0067]
Example 6
Finally, a case where a part of the oxide film formed on the wiring film surface layer deposited on the silicon substrate is used for the capacitor will be described. FIG. 9 is a view showing a semiconductor device according to claim 25, FIG. 9A is an equivalent circuit diagram of one element of a DRAM, and FIG. 9B is a sectional view of the element. 91 is a word line, 92 is a bit line, 93 is a switching transistor, and 94 is a region. The capacitor insulating film is formed of an anodic oxide film 96 of a metal film 95. When the same voltage is applied to the capacitor 94, if the current value differs by an order of magnitude, it is necessary to increase the design margin, so that miniaturization is difficult and the yield is also reduced. Therefore, also in this case, if the electropolishing treatment is performed before the anodic oxidation, the variation in insulating properties can be reduced.
[0068]
【The invention's effect】
In the method for manufacturing a wiring film according to the present invention, an electrolytic polishing process is performed before depositing an oxide film in a wiring film with an anodic oxide film, so that impurities in the anodic oxide film are reduced in a simple process. It is possible to provide a high quality wiring film with few defects and no quality variation. As a result, in the non-linear resistance element, the thin film transistor, and the capacitor on the semiconductor, it is possible to provide a wiring film that eliminates variations and has a high yield.
[0069]
In addition, the method for manufacturing a liquid crystal display device of the present invention eliminates variations in voltage-current characteristics in a liquid crystal display device having nonlinear resistance elements, and can also eliminate differences in current density due to differences in element sizes. A liquid crystal display device using such a non-linear resistance element can be manufactured with a high yield by a simple process with good contrast and uniformity within the surface.
[0070]
In the liquid crystal display device manufacturing method of the present invention, the purity of the gate insulating film can be increased in the liquid crystal display device having a thin film transistor, so that the insulation is improved, the switching characteristics are improved, and the variation is reduced. In a liquid crystal display device using such a thin film transistor, line defects are reduced, image quality is improved, and pixel unevenness is reduced. That is, it is possible to simultaneously improve the yield and improve the image quality of the liquid crystal display device.
[0071]
In addition, since the semiconductor device manufacturing method of the present invention can reduce the variation in insulation in the capacitor on the semiconductor substrate, the design margin can be increased and miniaturization can be promoted. Accordingly, the number of wafers taken per wafer is increased and the yield can be increased.
[Brief description of the drawings]
FIG. 1A is a diagram showing a method of electrolytic polishing.
(B) The figure which shows the manufacturing method of an anodic oxide film.
FIG. 2A is a top view of a matrix array using the nonlinear resistance element of the present invention.
(B) Sectional drawing of the nonlinear resistive element of this surface.
FIG. 3 is an equivalent circuit diagram of an active matrix liquid crystal display device.
FIG. 4A is a diagram showing a relationship between an applied voltage and a current value of a conventional nonlinear resistance element.
(B) The figure which shows the relationship between the voltage applied to the unit pixel of a liquid crystal display element, and brightness.
FIG. 5 is a view showing a film quality of a first metal film of a nonlinear resistance element.
FIG. 6 is a graph showing variations in voltage-current characteristics of nonlinear resistance elements.
FIG. 7 is a cross-sectional view of a conventional nonlinear resistance element.
FIG. 8A is a top view of a matrix array using the thin film transistor of the present invention.
(B) A cross-sectional view of a thin film transistor on the front surface.
FIG. 9A is an equivalent circuit diagram of a DRAM element.
(B) A cross-sectional view of a DRAM device.
[Explanation of symbols]
1 Nonlinear resistance element
2 Liquid crystal display elements
3 pixel area
10 Cathode
11, 81 Transparent substrate
11a TaOX film
12, 71 First metal film
13, 72, 83, 96 Metal oxide film
14, 73 Second metal film
15,74,88 pixel electrode
31, 82 scan lines
32,87 signal line
51 First metal film containing impurities
53 Anodized film
75 Insulating film
84 Gate oxide film
85 Active layer
86 n-type semiconductor layer
91 word lines
92 bit lines
93 Switching transistor
94 Capacitor
95 Metal film

Claims (8)

In a method of manufacturing a liquid crystal display device comprising a non-linear resistance element having a metal layer formed on a substrate and an anodic oxide film of the metal layer,
  Removing the surface layer containing impurities in the metal layer by electrolytic polishing;
  Anodizing the metal layer after the electropolishing treatment;
A method for manufacturing a liquid crystal display device, comprising: In a manufacturing method of a liquid crystal display device comprising a thin film transistor having a gate electrode and an anodic oxide film of the gate electrode,
  Removing a surface layer containing impurities in the gate electrode by electrolytic polishing;
  Anodizing the gate electrode after the electropolishing treatment;
A method for manufacturing a liquid crystal display device, comprising: In either claim 1 or claim 2,
  The method for manufacturing a liquid crystal display device, wherein the metal layer or the gate electrode contains tantalum, and the electrolytic polishing treatment uses a solution containing hydrofluoric acid or hydrochloric acid. In a method of manufacturing a semiconductor device comprising a capacitor element including a metal film and an anodic oxide film of the metal film,
  Removing the surface layer containing impurities in the metal film by electrolytic polishing;
  And a step of anodizing the metal film after the electropolishing treatment. In the method of manufacturing a wiring film in which the metal layer is anodized,
  Removing the surface layer containing impurities in the metal layer by electrolytic polishing;
And a step of anodizing the metal layer after the electropolishing treatment. In claim 5,
  The method for producing a wiring film, wherein the metal layer contains tantalum, and a solution containing hydrofluoric acid or hydrochloric acid is used for the electropolishing treatment. In claim 5,
The metal layer includes an element selected from the group consisting of aluminum, zinc, zirconium, and hafnium,
  A method of manufacturing a wiring film, wherein the electrolytic polishing treatment is performed using an electrolytic solution containing a solution selected from the group consisting of phosphoric acid, perchloric acid, and nitric acid. In claim 5,
  Removing the surface layer containing impurities in the metal layer by electrolytic polishing;
  Anodizing the metal layer;
A method for producing a wiring film, wherein pure water cleaning is performed in between.

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