KR20070057596A - Etching solution and etching method - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to form a laminated film by only one etching while preventing overhang formation of an upper layer from a laminated film comprising a first layer made of an aluminum alloy and a second layer made of a molybdenum-niobium alloy thereon. By etching both layers simultaneously, a fine wiring shape is formed with satisfactory precision.

The present invention is an etching solution for etching a laminated film comprising an aluminum alloy layer formed on a substrate and a molybdenum-niobium alloy layer formed on the substrate and having a niobium content of 2 to 19 wt%, comprising a mixture containing phosphoric acid, nitric acid and organic acid. An etching solution comprising an aqueous solution of an acid and a method for etching with the etching solution. In the etching solution, it is preferable that the phosphoric acid concentration Np is 50 to 75% by weight, the nitric acid concentration Nn is 2 to 15% by weight, and the acid component concentration defined by Np + (98/63) Nn is 55 to 85% by weight. .

Description

Etching solution and etching method {ETCHANT AND METHOD OF ETCHING}

TECHNICAL FIELD This invention relates to the etching liquid for patterning a metal thin film by a wet etching method, and the method of etching with the etching liquid. More specifically, the present invention relates to an etching solution and an etching method for etching a laminated film having an aluminum alloy layer and a molybdenum-niobium alloy layer.

In recent years, the precision of microfabrication of the electrode and gate wiring material used for semiconductor devices, such as a semiconductor element and a liquid crystal display element, is highly requested | required. In addition, the use of metal materials with smaller resistance has been proposed. Examples of metal materials having low resistance include aluminum and aluminum alloys, and the use of these materials is greatly increased.

As a processing technique for forming such a metal thin film into a pattern of a microstructure such as wiring, a wet type of patterning the metal thin film by etching with chemicals using a photoresist pattern formed on the surface of the metal thin film by photolithography as a mask. There are etching methods and dry etching methods such as ion etching and plasma etching.

Among them, the wet etching method is economically advantageous because the etching apparatus uses a chemical agent which is cheaper and relatively inexpensive than the dry etching method. And a large area substrate can be etched uniformly with high productivity per unit time. For this reason, a wet etching method is often used as a method for producing a thin film pattern.

During the process for forming such wiring, in a heat treatment process such as substrate heating in a film forming process in a semiconductor device manufacturing process, aluminum and aluminum alloy are hillock (blisterlike projections that occur on the aluminum surface during heat treatment). Water) may occur. If hillock occurs, it becomes difficult to deposit an insulating film on the aluminum wiring. That is, even if the insulating layer is formed on the aluminum wiring having the hillock on the surface, the hillock penetrates the insulating layer, resulting in poor insulation. The other portion of Hillock contacts the other conductive thin film layer and shorts the circuit.

In addition, when aluminum or an aluminum alloy is used as the wiring material, and the wiring is directly in contact with ITO (indium oxide-tin oxide alloy), which is a transparent electrode, a deteriorated layer is formed on the surface of the aluminum or aluminum alloy in contact with ITO. As a result, the contact resistance of a contact part may become large.

In order to prevent the hillock generation and the formation of the deterioration layer, a laminated wiring including an aluminum or aluminum alloy layer and other metal layers such as molybdenum, molybdenum alloy layers, and chromium layers, which are high melting point metals, has been proposed (for example, For example, see JP-A-9-127555, JP-A-10-256561, JP-A-2000-133635, JP-A-2001-77098, JP-A-2001-31l954).

When wet etching a laminated film comprising an aluminum alloy layer and a molybdenum alloy layer stacked thereon as described above, due to the combination of metals, it is necessary to sequentially etch each layer constituting the laminated film with, for example, two different etching solutions. As a result, productivity becomes very low. In addition, even if an etchant that can etch all the layers constituting the laminated film is used at the same time, a cell reaction occurs due to contact between different metal layers, resulting in a faster etching rate than in the case of single layer etching. It is known that behavior appears (see, for example, SID CONFERENCE RECORD OF THE 1994 INTERNATIONAL DISPLAY RESEARCH CONFERENCE).

If there is a difference in the etching rate between the dissimilar metal layers, an undercutting (lower metal layer is etched faster than the upper metal layer, so that the upper metal layer protrudes) occurs in the lower metal layer or a side etching (the upper metal layer is lower) May be etched faster than the metal layer). According to this inadequate etching method, since the shape of the laminated film after etching does not become tapered in the portion where undercutting occurs, the coating of the gate insulating film (for example, SiN _x ) at the protrusion is insufficient, resulting in poor insulation resistance or the like. There is a problem. In addition, when side etching of the upper metal layer occurs, there is a problem that the exposed area of the lower metal layer increases.

The present invention has been accomplished in view of such circumstances. An object of the present invention is satisfactory by etching a laminated film comprising a low-resistance aluminum alloy layer and a molybdenum alloy layer formed thereon in one etching operation to form a forward tapered side surface while preventing undercutting and side etching. It is to provide an etching solution and an etching method capable of forming a fine wiring shape with precision.

The etching solution of the present invention is an etching solution for etching a laminated film comprising an aluminum alloy layer formed on a substrate and a molybdenum-niobium alloy layer having a niobium content of 2 to 19% by weight, including phosphoric acid, nitric acid, and organic acid. It is an etching liquid containing the aqueous solution of mixed acid to make.

The etching method of the present invention is a method for etching a laminated film comprising an aluminum alloy layer formed on a substrate and a molybdenum-niobium alloy layer having a niobium content of 2 to 19% by weight with an etching solution, wherein the etching solution comprises It is an etching liquid and the ratio ((etching rate of molybdenum-niobium alloy layer) / (etching rate of aluminum alloy layer)] of the molybdenum-niobium alloy layer with respect to the etching rate of an aluminum alloy layer is in the range of 0.7-1.3. It is an etching method characterized by the above-mentioned.

The present inventors earnestly researched to solve the above problem. As a result, it was found that by using an etching solution containing phosphoric acid, nitric acid, and an organic acid, the laminated film as described above can be etched so that a forward tapered side is formed by one etching. Thus, the present invention has been completed.

According to the investigation of the inventors, the nitric acid in the etching solution of the present invention weakens the adhesion between the upper layer containing the molybdenum-niob alloy and the edge of the photoresist resin layer below the upper layer, and the etching solution to the interface therebetween. It has been shown to function to promote the penetration of. That is, by appropriately increasing the side etching rate of the molybdenum-niobium alloy layer in contact with the photoresist resin layer, the etching proceeds so that the etching rate of the molybdenum-niobium alloy layer is increased and a forward tapered side is formed. Since the etching rate of the molybdenum-niobium alloy layer is larger than the etching rate of the aluminum alloy layer, the laminated film can be etched with satisfactory precision so as to have a forward tapered shape in one etching operation.

In the etching solution of the present invention, when the phosphoric acid concentration Np is 50 to 75 wt%, the nitric acid concentration Nn is 2 to 15 wt%, and the acid component concentration defined by Np + (98/63) Nn is 55 to 85 wt% The function can be further improved.

In the laminated film to be etched, the ratio t _M / t _A of the thickness t _M of the second layer (molybdenum-niob alloy layer) to the thickness t _A of the first layer (aluminum alloy layer) is from 1 / 1O to l / 1. Is preferably.

In the present invention, the etching rate of the molybdenum-niobium alloy layer is preferably in the range of ± 30% of the etching rate of the aluminum alloy layer under the alloy layer.

(A), (b) and (c) of FIG. 1 show examples of cross-sectional shapes of wirings formed by etching.

Here, reference numerals 1 and 3 denote molybdenum-niobium alloy layers, respectively, and reference numeral 2 denote aluminum alloy layers.

Hereinafter, the preferable form of the etching liquid and etching method of this invention is demonstrated in detail.

The etching liquid of this invention is for etching the laminated | multilayer film containing an aluminum alloy layer and the molybdenum-niobium alloy layer formed on it.

The etchant of the present invention comprises a mixed acid aqueous solution containing phosphoric acid, nitric acid and organic acid, preferably a phosphoric acid concentration Np of 50 to 75% by weight, a nitric acid concentration Nn of 2 to 15% by weight, and Np + (98/63 The acid component concentration defined by) Nn is 55-85 weight%.

If the phosphoric acid content is too large, the etching rate of the entire laminated film is increased, but the etching layer of the aluminum alloy layer is larger than that of the molybdenum-niobium alloy layer. Accordingly, undercutting proceeds, and the molybdenum-niobium alloy layer protrudes to form an overhang. On the other hand, if the phosphoric acid content is too small, the etching rate becomes too small, which is not practical. Therefore, it is preferable to keep the phosphoric acid content within the above range.

Nitric acid acts as an acid for dissolution while contributing to the oxidation of metals as an oxidant. The nitric acid content in the etching solution of the present invention affects the etching characteristics similarly to the phosphoric acid content. Specifically, if the nitric acid content is too large, the etching rate of the entire laminated film is increased, but the etching layer of the aluminum alloy layer is larger than the etching layer of the molybdenum-niobium alloy layer. Thus, undercutting proceeds, and the molybdenum-niobium alloy layer protrudes to form an overhang. In addition, there is a possibility that the photoresist resin layer is damaged. On the other hand, if the nitric acid content is too small, there is a possibility that the etching rate becomes very small. Therefore, it is preferable to make nitric acid content into the said range.

When the etchant of the present invention contains acetic acid or alkylsulfonic acid, the etching function can be further improved.

When acetic acid is contained, the affinity of the etching liquid with respect to a hydrophobic photoresist resin layer improves. That is, the etching solution can be easily penetrated to the details of the fine wiring structure finely patterned mainly by the photoresist resin existing on the substrate surface. As a result, uniform etching becomes possible.

In this case, the acetic acid content can be appropriately determined according to the required etching area ratio, that is, the ratio of the area of the etched metal (exposed metal surface) present on the substrate to the area covered with the photoresist resin layer. Generally the acetic acid content is 1 to 30% by weight, preferably 2 to 20% by weight.

If the acetic acid content is too small, the effect may be insufficient, and the affinity for the photoresist resin layer formed on the substrate surface may be impaired and uniform etching may not be performed. Conversely, even when the acetic acid content is too large, such a high content is economically disadvantageous because not only the photoresist resin layer can be damaged, but also no improvement in the effect of compensating for the content increase is obtained.

The use of alkylsulfonic acid instead of acetic acid yields the following advantages. Odor peculiar to acetic acid is removed, and affinity to the photoresist resin layer is improved. Moreover, since alkylsulfonic acid is difficult to volatilize unlike acetic acid, the effect of etching composition and property change in an etching process can be suppressed and a more stable etching can be performed simultaneously. Sulfonic acid can be used with acetic acid. The sulfonic acid may be a salt, examples of which are potassium salts, ammonium salts and the like.

As the alkyl sulfonic acid used in the present invention, methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid, isopropanesulfonic acid and n-butanesulfonic acid are preferable. Among them, ethanesulfonic acid and methanesulfonic acid are preferable.

The content of alkylsulfonic acid in the etching solution of the present invention can be appropriately selected and determined according to the etching area ratio. The content of alkylsulfonic acid is generally from 0.5 to 20% by weight, preferably from 1 to 10% by weight.

As in the case of acetic acid described above, if the content of alkylsulfonic acid is too small, the effect is insufficient, and the affinity for the photoresist resin layer formed on the substrate surface may be impaired, thereby making it impossible to perform uniform etching. Conversely, even if the content of alkylsulfonic acid is too large, such a high content is economically disadvantageous because not only the photoresist resin layer can be damaged, but also no improvement in the effect of compensating for the content increase is obtained.

In the present invention, the phosphoric acid concentration Np is preferably 50 to 75% by weight, the nitric acid concentration Nn is preferably 2 to 15% by weight, and the acid component concentration defined as Np + (98/63) Nn is 55 to 85% by weight. In particular, 60-80 weight% is preferable.

In addition, surfactants and the like can be added to the etching solution of the present invention in order to reduce the surface tension of the etching solution or to reduce the contact angle with the substrate surface to improve wettability to the substrate surface and to enable uniform etching. have.

The fine particles present in the etching solution of the present invention can inhibit uniform etching as the pattern becomes finer. Therefore, it is preferable to remove such microparticles beforehand to such an extent that the number of microparticles | fine-particles whose particle diameter is 0.5 micrometer or more becomes 1, OOO or less per mL. Particulates present in the etchant can be removed by filtering the etchant with a precision filter. The filtration can be carried out in a one-pass operation, but a circulation system is preferred in view of particulate removal efficiency. As a precision filter, what has a pore diameter of 0.2 micrometer or less can be used. As the material of the filter, so-called fluorine resin materials such as high density polyethylene and polytetrafluoroethylene may be used.

The etching liquid of this invention is an etching liquid especially suitable for the etching of the laminated film containing the 1st layer which consists of aluminum alloys, and the 2nd layer which consists of molybdenum-niobium alloys on it.

In this laminated film, the ratio (second layer thickness / first layer thickness) of the thickness of the second layer to the thickness of the first layer is not particularly limited. However, the ratio of the layer thickness is preferably 1/10 to 1/1 because the effect of the present invention described above is remarkable when etching the laminated film having the ratio of the layer thickness within this range.

A laminated film comprising a first layer made of an aluminum alloy and a second layer made of a molybdenum-niobium alloy thereon is used, for example, as a wiring and a gate electrode formed on the surface of a substrate for a liquid crystal display device.

As the material of the first layer of the laminated film, an alloy of aluminum with neodymium or copper is suitable. In particular, an aluminum-copper alloy having a copper content of 0.05 to 3% by weight, or an aluminum-neodymium alloy having a neodymium content of 1.5 to 15% by weight is suitable. The first layer may be a layer mainly composed of an aluminum alloy, and impurities such as other elements may be present. Examples of such impurities are sulfur, magnesium, sodium, potassium and the like. However, it is preferable that such impurities are as few as possible. Specifically, the content of these impurities is preferably 200 ppm or less, respectively. In particular, since sodium and potassium can greatly affect the characteristics of the semiconductor device, the content of sodium and potassium is preferably 20 ppm or less, respectively.

As the material of the second layer, a molybdenum-niobium alloy having a niobium content of 2 to 9% by weight, in particular 3 to 15% by weight is suitable.

This laminated film is generally formed on an insulating substrate such as glass. In addition, a lower layer may be formed between the substrate such as glass and the first layer to increase the adhesion of the laminated film to the substrate. As the material of this lower layer, a molybdenum-niobium alloy is suitable, and a molybdenum-niobium alloy having a niobium content of 2 to 19% by weight, particularly 3 to 15% by weight is suitable.

The thickness t _A of the first layer containing the aluminum alloy is preferably about 50 to 500 nm, and the thickness t _M of the second layer which is the upper layer containing the molybdenum-niobium alloy is preferably about 10 to 10 nm. In particular, t _M / t _A is preferably 0.01 to 1, particularly 0.2 to 0.8.

This laminated film is manufactured by a well-known method.

The etching method using the etching solution of the present invention can be carried out using various apparatuses and devices for wet etching.

In order to bring the etching solution into contact with the laminated film to be etched, a method of spraying the etching solution in the vertical direction of the surface (spray method) or the method of dipping the substrate in the etching solution (immersion method) can be used. .

In particular, in the spray method, in consideration of the properties (especially viscosity) of the etching solution, the distance between the substrate to be etched and the spray nozzle and the spraying pressure are adjusted so that the amount of etching solution supplied to the substrate surface and the inertia of the etching solution applied to the substrate surface are controlled. It is important to determine the power.

The distance between the substrate surface and the spray nozzle (the shortest distance between the tip of the spray nozzle and the substrate surface) is preferably 50 to 1,000 mm. When this distance is less than 50 mm or more than 1, OO mm, the adjustment of the spray pressure becomes difficult.

The spray pressure is preferably 0.01 to 0.3 MPa, more preferably 0.02 to 0.2 MPa, particularly preferably 0.04 to 0.15 MPa. In the present invention, "spray pressure" refers to the pressure applied to supply the etching liquid to the spray nozzle. By spraying the etching liquid onto the substrate at this spraying pressure, an appropriate force is applied to the substrate surface, and the surface can be etched uniformly.

The etching liquid spray form (spray nozzle shape) is not particularly limited, and examples thereof include a fan type and a cone type. It is preferable to arrange the required number of spray nozzles along the width direction of the substrate and along the moving direction of the substrate so that the etching liquid hits the entire surface of the substrate uniformly and to shake the nozzle during spraying. The substrate itself can be reciprocated while spraying the etchant.

In the etching method of the present invention, the temperature of the etching liquid may be appropriately selected from general etching temperatures (20 to 60 ° C). In view of the balance between the etching rate improvement and the etching control, etching is particularly preferable at 30 to 50 ° C.

In order to monitor the progress of etching in the etching method of the present invention, any desired monitoring means can be used. For example, the etching state of a portion (substrate outer periphery) which is not covered with a photoresist resin layer formed on the surface of a light transmissive substrate (hereinafter also referred to simply as "substrate") or a portion located in the contour of the photoresist pattern The method of monitoring can be used by continuously measuring the change of permeation and detecting an etching amount. Therefore, the progress of etching can be monitored.

That is, at the point when melting of the metal thin film layer in the portion without the photoresist resin layer (substrate outer periphery) formed on the substrate surface or in the portion located in the outline of the photoresist pattern ends, the light transmission changes rapidly. Therefore, this change can be used to detect the end point of etching. In the present invention, the time required from the start of etching until the end point detection in which the "transmission changes rapidly" is called just etching time. This endpoint can be determined, for example, by visually determining when the metal of the portion to be etched is completely dissolved by etching so that the substrate is exposed. Or 0.1% of the amount of light transmitted through the substrate (the amount of transmitted light in the absence of any state on the substrate) by using an actinometric (transmitted light) automatic detection device or the like, and the amount of transmitted light through the substrate The time point exceeding can be determined as the end point.

Since metal residues may exist on the surface of the substrate at the end point detection time, it is preferable to perform overetching after just etching in the etching method of the present invention.

In the etching method of the present invention, after end point detection, it is preferable to continuously perform overetching under the same etching conditions before etching is completed. The time for such overetching is preferably adjusted to 25% to 300% of the just etching time, in particular 50% to 150%.

If the overetch time is too short, etch residue may remain. In the case where the overetching time is very long, the side etching may cause the fine pattern of the laminated film wiring or the like to be excessively etched to have a reduced line width, thereby making the apparatus inoperable.

In general, in the case of wet etching, the components of the etching solution are consumed or evaporated for etching the metal constituting the laminated film. In particular, in the case of wet etching, the etching liquid component is attached to the substrate and taken out of the etching system together with the substrate. Therefore, since the quantity of each component of etching liquid decreases, etching liquid composition changes. In addition, the concentration of metal ions (main element is an element different from aluminum constituting the laminated film) increases.

In particular, in the wet etching method by the spray method which is often used in view of productivity, the acid concentration tends to be relatively high as the volatile component decreases due to evaporation.

In order to perform etching more efficiently by the etching method using the etching liquid of this invention, each low boiling point component of the quantity corresponded to the quantity of the low boiling point component which evaporates in an etching process, and the etching liquid attached to the board | substrate during the etching process was taken out. As described above, it is preferable to continuously or intermittently supplement the component discharged out of the etching system to the etching system. Therefore, stable etching can be performed.

In this case, in the etching method of the present invention, etching is performed such that the phosphoric acid content is 50 to 75% by weight, the nitric acid content is 2 to 15% by weight, and the acid component concentration (Np + (98/63) Nn) is 55 to 85% by weight. After replenishing the etchant with the etchant component consumed or taken out of the etchant, the etching is preferably continued.

In the etching method of the present invention, any preferable method can be used for replenishment of the etching liquid components. An example is the following method.

For example, the method which decided the etching liquid replenishment composition, the quantity, and replenishment time previously can be used. That is, the composition of the low boiling point components (eg, acetic acid and water) evaporating in the etching process can be specified when the etching solution composition and the etching solution temperature are kept constant. This is because vapor-liquid equilibrium is maintained when the composition of the initial etching liquid (original etching liquid) and the temperature of the etching liquid are fixed. The amount (evaporation rate) of the etching liquid to evaporate depends on the degree of discharge of the etching system (the amount of gas emitted from the etching system) and the like. As a result, by considering these factors, it is possible to determine in advance the change in the composition of the etching solution after the start of etching, and based on this, the composition composition, the amount of replenishment, and the replenishment timing can be determined.

When the etching conditions (etching composition, etching solution temperature, etc.) are constant, the composition and amount of the etching solution evaporated during the etching process can be calculated from the concentration change of the etching solution per unit time measured by a conventional concentration analyzer. Therefore, it is possible to determine the replenishment composition, the replenishment amount to be added and replenishment timing from these calculated values.

In addition, a method of supplementing the etching system components continuously or intermittently based on the analysis results while using the existing concentration analyzer to continuously and intermittently monitor the etching liquid composition in the etching process can be used.

In consideration of the replenishment amount of each component thus calculated, the etching liquid component is replenished continuously or intermittently so that the amount of the component is within the above range. Therefore, continuous etching can be performed. The additionally supplied etchant component may be supplemented individually or as a mixture.

In addition, since part of the etching liquid adheres to the etched substrate and is taken out of the etching system together with the substrate, the amount of etching liquid present in the etching system decreases as the etching process proceeds. When the amount of the etchant is significantly reduced, for example, in a spray wet etching, cavitation or the like may occur in the etchant supply pump, and it may be difficult to continuously perform stable wet etching. Moreover, when the amount of etching liquid is so reduced, for example, the etching liquid heater or the like provided in the etching liquid tank may be exposed at the liquid level, resulting in insufficient control of the etching liquid temperature. Therefore, it is preferable to appropriately supplement the etching liquid (original etching liquid) to maintain the amount of etching liquid in the etching system at a level within a certain range.

Specifically, this replenishment can be made in the following manner. The weight change per board | substrate before and after an etching is determined, or the density | concentration of the acid which entered the rinsing process performed after an etching process is determined. The number of substrates to be etched and the amount of etching solution taken out of the etching system are calculated in advance from the weight change or the acid concentration. What is necessary is just to make this amount the replenishment amount of etching liquid quantity (original etching liquid).

In this way, by adjusting the concentration of each component and the metal ion in the etching solution, the etching solution can be regenerated and used. Therefore, this method is also advantageous in terms of profitability.

According to the above-described etching method of the present invention, for example, a laminated film including an aluminum alloy layer and a molybdenum-niob layer can be etched stably and uniformly with satisfactory precision in one etching operation, thereby obtaining the desired wiring shape without overhang. .

In the etching method of the present invention, the ratio of the etching rate of the molybdenum-niobium alloy layer to the etching rate of the aluminum alloy layer is [(etching rate of molybdenum-niob alloy layer) / (etching rate of aluminum alloy layer)]. It is preferable to exist in the range of 7-1.3, especially 0.8-1.2.

In the present invention, the optimum range of the etchant composition varies depending on the film to be etched. Therefore, it is preferable to change the composition of the etching solution according to the niobium content of the molybdenum-niob alloy layer to be etched and the like so that the ratio of the etching rate is in the range of 0.7 to 1.3, more preferably 0.8 to 1.2. Those skilled in the art can determine the optimum composition range without undue experimentation.

For example, with respect to the molybdenum-niobium alloy layer having a niobium content of 5% by weight, shown in the examples described later, the phosphoric acid concentration Np is 50 to 75% by weight, the nitric acid concentration Nn is 2 to 5% by weight, and Np + (98 / The etching liquid whose acid component density | concentration defined by 63) Nn is 55-85 weight%, and an acetic acid concentration is 3-10 weight% is preferable. Instead of acetic acid, alkylsulfonic acid can be used at a concentration of 1.5 to 8% by weight.

<Example>

Hereinafter, the present invention will be described in more detail with reference to Examples and Reference Examples, but the present invention is not limited to the following Examples without departing from the gist of the present invention.

Example  1 to 7 and Reference Example  1 to 6

A molybdenum-niobium alloy layer (niobium content 5% by weight) (3) having a thickness of 50 nm was formed on the glass substrate by sputtering. On this layer, AlCu (aluminum-copper alloy; copper content 5% by weight) having a thickness of 300 nm was formed as an aluminum alloy layer 2 by sputtering using argon gas. Then, the molybdenum-niobium alloy layer 1 having the same composition as above and having a thickness of 50 nm was continuously formed. In this way, MoNb / AlCu / MoNb laminated films were formed as shown in Figs. 1A, 1B, and 3C.

A positive photoresist resin layer (thickness: about 1.5 mu m) was further formed thereon by spin coating, and the layer was processed by photolithography to form a fine wiring pattern. The line width of this resist pattern was about 5 micrometers.

This substrate was cut into pieces having a width of about 10 mm and a length of 50 mm, and the pieces were used as samples for etching test.

On the other hand, only the molybdenum-niobium alloy layer having the same thickness as described above was formed on the glass substrate, and the photoresist layer was formed in the same manner. The cut piece of this coated substrate was used as a sample for etching test of molybdenum-niobium monolayer film.

Phosphoric acid (85% by weight aqueous solution), nitric acid (70% by weight aqueous solution), acetic acid (glacial acetic acid) and pure water were selectively mixed with methanesulfonic acid so as to have the composition of Table 1, thereby preparing an etching solution. Each etchant was filtered with a precision filter. 200 g of etching liquid was put into the 200 ml beaker, respectively. The temperature of these etching liquids was adjusted to 40 degreeC. The said etching test sample was immersed in the said etching liquid, and the sample was etched moving up, down, left, and right.

The time from the start of etching to the end point was regarded as the etching time. The end point was determined by visually determining the point at which the metal on the substrate located at the portion to be etched is completely dissolved and the substrate is exposed (transparent).

The etching rate was calculated at this etching time and the layer thickness home.

The etching rate of the molybdenum-niobium layer can be obtained by dividing the thickness of this layer by the etching time of a single layer made of an alloy.

The etching rate of the aluminum alloy layer in the laminated film can be obtained by the following method. The etching time of the molybdenum-niobium single layer film is subtracted from the etching time of the entire laminated film, and the etching time of only the aluminum alloy layer is obtained. Next, the etching rate of only the aluminum alloy layer is obtained by dividing the thickness of the aluminum alloy layer by this etching time.

Table 1 shows the ratio ((etching rate of molybdenum-niobium alloy layer) / (etching rate of aluminum alloy layer)) of the etching rate and the etching rate of each layer thus obtained.

The surface state of the substrate after etching was examined by the following method, and the results are shown in Table 1.

[1] states of resist

The state (swelling, cracking, etc.) of the photoresist resin layer was observed with the laser microscope (VK-8500, Keyence Corp. make), and the following references | standards evaluated.

○ = no change

× = defects such as swelling and cracking

[2] wiring shapes

Using the scanning electron microscope (SEM) or focused ion beam (FIB) (FB-2000A and C-4100, manufactured by Hitachi Ltd.), the state of the overhang (protrusion length L) of FIG. 1 (c) and the residue around the electrode The state was examined and the shape was evaluated based on the following criteria.

Overhang status (length):

X: L is 60 nm or more

○: L is less than 60 nm

Prior to the inspection of the wiring shape, the photoresist resin layer formed on the substrate surface was dissolved and removed with acetone. Another example of the wiring shape is shown in FIGS. 1A and 1B. Fig. 1A is an example of the most preferable shape, and Fig. Lb shows an example of the shape in which the molybdenum-niob alloy layer is overetched.

From Table 1 it is clear that: That is, in Reference Examples 1 and 5, the ratio of the etching rate of the molybdenum-niobium alloy layer to the etching rate of the aluminum-copper alloy serving as the intermediate layer is larger than 1.3, and the shape after etching is large in the side etching amount of the molybdenum-niobium alloy layer. Therefore, it became (b) of FIG.

In Reference Examples 2, 3, 4 and 6, the ratio of the etching rate of the molybdenum-niobium alloy layer to the etching rate of the aluminum-copper alloy serving as the intermediate layer is less than 0.7, and the shape after etching is molybdenum-niobium alloy layer (2) It became (c) of FIG. 1 because of the slow etching. For this reason, the wiring shape in each of Reference Examples 1-6 was determined as x.

In contrast, in Examples 1-7, all the evaluation results including cross-sectional shape evaluation were satisfactory.

While the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit thereof.

The contents of Japanese Patent Application (Application No. 2003-312852), filed on September 4, 2003, are incorporated herein by reference.

According to the etching solution and the etching method of the present invention, the laminated film including the aluminum alloy layer and the molybdenum alloy layer formed thereon can be etched to be a forward tapered side by only one etching to form a fine wiring shape with satisfactory precision. have.

Therefore, according to the present invention, the wiring material including the low resistance laminated film having excellent electrical characteristics can be etched stably and uniformly with satisfactory precision, and a highly reliable wiring can be formed at low cost. Therefore, a highly reliable liquid crystal display device or the like can be provided at low cost.

Claims (9)

An etching solution for etching a laminated film comprising an aluminum alloy layer formed on a substrate and a molybdenum-niobium alloy layer formed on the substrate and having a niobium content of 2 to 19 wt%, An etching solution comprising an aqueous solution of a mixed acid containing phosphoric acid, nitric acid and organic acid. The method of claim 1, Phosphoric acid concentration Np is 50 to 75% by weight, Nitric acid concentration Nn is 2 to 15% by weight, Etching liquid characterized by the acid component concentration defined by Np + (98/63) Nn being 55-85 weight%. The etchant according to claim 1 or 2, wherein the organic acid is acetic acid or alkylsulfonic acid. The etching liquid according to claim 1 or 2, wherein the organic acid is acetic acid and its concentration is 1 to 30% by weight. The etching liquid according to claim 1 or 2, wherein the organic acid is methanesulfonic acid and / or ethanesulfonic acid, and its concentration is 0.5 to 20% by weight. A method of etching a laminated film comprising an aluminum alloy layer formed on a substrate and a molybdenum-niobium alloy layer formed thereon with a niobium content of 2 to 19% by weight, comprising: The etchant is the etchant of any one of claims 1 to 5, The ratio of the etching rate of the molybdenum-niobium alloy layer to the etching rate of the aluminum alloy layer [(etching rate of molybdenum-niobium alloy layer) / (etching rate of aluminum alloy layer)] is in the range of 0.7 to 1.3. Etching method. The etching method according to claim 6, wherein the laminated film further has a lower layer interposed between the aluminum alloy layer and the substrate, and the lower layer comprises a molybdenum-niobium alloy having a niobium content of 2 to 19 wt%. The etching method according to claim 6 or 7, wherein the aluminum alloy is an aluminum-copper alloy having a copper content of 0.05 to 3% by weight or an aluminum-neodymium alloy having a neodymium content of 1.5 to 15% by weight. . The ratio t _M / t _A of the thickness t _M of the upper molybdenum-niobium alloy layer to the thickness t _A of the lower aluminum alloy layer is Ol to 1 according to any one of claims 6 to 8. Etching method.

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