KR20060039447A - Etching solution for titanium-containing layer and method for etching titanium-containing layer - Google Patents

Abstract

A titanium-containing layer which is formed on a silicon substrate or a silicate glass substrate and mainly contains one or more substances selected from the group consisting of titanium, titanium oxides, titanium nitrides and titanium oxynitrides is selectively etched at a high etching rate without eroding the substrate. Disclosed is an etching solution for etching a titanium-containing layer which is formed on a silicon substrate or a silicate glass substrate and mainly contains one or more substances selected from the group consisting of titanium, titanium oxides, titanium nitrides and titanium oxynitrides. This etching solution contains a silicofluoric acid. Also disclosed is a method for etching a titanium-containing layer formed on a silicon substrate or a silicate glass substrate using such an etching solution. The silicofluoric acid is a substance produced through a reaction between a hydrofluoric acid and silicon or a silicon oxide. While the silicofluoric acid is inactive against silicon or silicate glasses, it exhibits sufficient etching performance for titanium, titanium oxides, titanium nitrides and titanium oxynitrides. Consequently, the etching solution shows sufficient selectivity in etching of a titanium-containing layer formed on a silicon substrate or a silicate glass substrate.

Description

Etching Solution For Titanium-Containing Layer And Method For Etching Titanium-Containing Layer}

The present invention relates to a substrate and a metal wiring material when the metal wiring material is provided on a silicon wafer or a glass substrate during the production of an etching solution for a titanium-containing layer and an etching method of the titanium-containing layer using the etching solution, in particular in the manufacture of semiconductor devices, liquid crystal displays, and IC cards. Titanium-containing layer etching solution suitable for etching a titanium-containing layer mainly composed of one, two or more selected from the group of titanium, titanium oxide, titanium nitride and titanium oxynitride as an undercoat formed for improving adhesion The etching method of a titanium containing layer using the etching liquid for titanium containing layers is related.

Titanium is a metal that is easily passivated, and an oxide film is formed on the surface even if it is left in the air. For example, when a metal is placed on a titanium undercoat, when the titanium film is exposed to air or not, the adhesion to the upper metal tends to be different at the time of etching. It is known to be oxidized and become a strong oxide film. Such a titanium film is not normally dissolved when oxidative is strong. Therefore, in order to etch titanium or titanium oxide, it is possible to use harsh conditions by strong acids based on hot concentrated phosphoric acid, hot concentrated sulfuric acid, and hot concentrated hydrochloric acid, or a hydrofluoric acid / acetic acid mixture liquid, hydrofluoric acid / hydrogen peroxide mixture, or fluoride. It is known to use a mixed solution based on hydrofluoric acid such as an ammonium / hydrofluoric acid mixed solution.

However, in the case of etching a titanium layer or a titanium oxide layer formed on a silicon substrate or a glass substrate, when a hydrofluoric acid-based etching solution is used, the etching solution also invades the silicon substrate or the glass substrate, and only the titanium layer or the titanium oxide layer is selected. It is difficult to etch.

In order to solve this problem, it is also considered to express selectivity of titanium or a titanium oxide etching by lowering the concentration of hydrofluoric acid in the etching solution. In this case, however, the desired etching rate cannot be obtained. In addition, when etching liquids based on phosphoric acid, sulfuric acid, hydrochloric acid or the like other than hydrofluoric acid are used, a desired etching rate is difficult to be obtained unless conditions are extremely harsh. As such, there is no practical method yet for etching the titanium layer and / or the titanium oxide layer on the silicon substrate or the glass substrate.

As the undercoat layer on the silicon substrate or the glass substrate, not only a titanium layer or a titanium oxide layer, but also a titanium nitride layer or a titanium oxynitride layer may be used. The titanium nitride layer or the titanium oxynitride layer is a film that is harder than the titanium layer or the titanium oxide layer, and the etching of the titanium nitride layer or the titanium oxynitride layer cannot be practically etched unless the conditions are more severe than those of the titanium layer or the titanium oxide layer. . Moreover, it is difficult to express the etching performance which shows selectivity with respect to a silicon substrate and a glass substrate, and the practical method is not yet provided.

On the other hand, in manufacturing a semiconductor device, a liquid crystal display device, an IC card, etc., when providing a metal wiring material on a silicon wafer or a glass substrate, adhesiveness with a board | substrate, a metal wiring material, etc. is very important. Therefore, when the pattern which consists of a metal wiring material with bad adhesiveness with a board | substrate is formed on a board | substrate, the undercoat metal layer is formed in order to improve the adhesiveness of a board | substrate and a metal wiring material. As the metal material of the lower metal layer, it is necessary to select a metal having excellent adhesion to the substrate. However, the metal material having excellent adhesion to the substrate is limited depending on the material of the substrate, and examples thereof include Al, Cr, and Ti. In addition, Mo, W, Ta, etc. are mentioned as an adhesive force next to these. Of these metals, Al has a problem of occurrence of hillock, and Cr has a problem of toxicity.

Mo, W, and Ta are metals that are stabilized by forming an oxide film in air such as Ti. However, Mo has poor corrosion resistance and is often used in alloying than when used alone. W is likewise used in the form of alloying Ti to W, rather than Ti-W. Since Ta can only be etched with hydrofluoric acid and aqua regia, there is a problem in workability and many unsuitable aspects.

As a result, as a base metal, Ti is expected to be highly resistant to corrosion and to have a large electrical resistance (difficult to conduct electricity). However, as described above, the Ti layer on the silicon substrate or the glass substrate is difficult to selectively etch. At the same time, when the noble metal material, which is a metal wiring material, is laminated, electric corrosion is likely to occur, and there is also a molding problem. For this reason, Cr is a mainstream metal as a base metal of a metal wiring material conventionally, and there are few uses examples of Ti. However, in the future, it is desired to use Ti as a substitute for the underlying metal of Cr by solving the above-mentioned problem of Ti because of the toxicity problem of Cr.

As a treatment method of the undercoat layer using Ti metal, the use of a treatment agent containing urea and hydrofluoric acid is exemplified as a roughening surface treatment agent for the pretreatment of the surface of the titanium layer before the platinum plating treatment (Japanese Patent Application Laid-Open No. 08 -218185 publication). This treatment agent exhibits the effect by using together with iodine, and this technique is a technique regarding roughening, and does not concern the etching technique which removes a titanium layer completely. Moreover, the use of hydrofluoric acid is illustrated to remove the film which consists of (Ni, Co, Fe) CrAl (Ti) from a board | substrate (refer Unexamined-Japanese-Patent No. 2002-53985). The substrate used here is composed of a superalloy or a polymer, and there is no mention of selective etching of the titanium layer on the silicon substrate or the glass substrate.

Disclosure of the Invention

Problems to be Solved by the Invention

The present invention has been accomplished to solve the above problems, the object of which is one or two or more selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate The present invention provides an etching solution for a titanium containing layer which can selectively etch a titanium containing layer to be used without eroding a substrate at a high etching rate, and a method of etching a titanium containing layer using the titanium containing layer etching solution.

The present inventors have made intensive studies to solve the above problems, the rule of hydrofluoric acid (H ₂ SiF ₆₎ an etching solution containing as a main component is for the titanium material, but did not extend to the etching rate of the hydrofluoric acid of the same concentration of the etching solution, For example, it has been found that the etching rate is significantly faster than that of conventional etching solutions of phosphoric acid, sulfuric acid, and hydrochloric acid, and is effective for selective etching of titanium. That is, hydrofluoric acid is a substance produced by the reaction of hydrofluoric acid with silicon or silicon oxide, and is inert to silicon or silicate glass, but has sufficient etching performance against titanium, and titanium on silicon substrate or silicate glass substrate. It has sufficient selectivity with respect to the etching of.

Means to solve the problem

The present invention has been accomplished based on the above-mentioned findings, and the etchant for titanium-containing layer of the present invention is one selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate. Or it is an etching liquid which etches the titanium containing layer which has 2 or more types as a main component, and contains hydrofluoric acid.

Moreover, the etching liquid for titanium containing layers of this invention is an etching liquid which etches the titanium containing layer which has a titanium nitride and / or a titanium oxynitride as a main component, and contains hydrofluoric acid and an oxidizing agent.

In the etching method of the titanium-containing layer of the present invention, a titanium-containing layer containing one or two or more selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate with an etching solution. It is a method of etching and the etching liquid for titanium containing layers mentioned above is used as etching liquid.

To practice the invention  Best embodiment for

Embodiment of this invention is described. First, the etching liquid for titanium containing layers is demonstrated. In addition, the etching liquid of this invention makes a titanium containing layer which has 1 type (s) or 2 or more types selected from the group which consists of a titanium, a titanium oxide, a titanium nitride, and a titan oxynitride as an etching target. Here, "main component" points out that content in a layer is 50-100 weight%. Such titanium-containing layers include a titanium layer, a titanium oxide layer, a mixed layer of titanium and titanium oxide, a titanium nitride layer, a mixed layer of titanium oxide and titanium nitride, a mixed layer of titanium and titanium nitride, and titanium oxynitride. In the following, for convenience of description, titanium, titanium oxide, titanium nitride, titanium oxynitride or such a mixture constituting the titanium-containing layer may be referred to collectively as simply 'titanium'.

Hydrofluoric acid used as an active ingredient of etching liquid is generally manufactured according to following Reaction Formula.

6 HF + Si0 ₂ → 2H ₂ 0 + H ₂ SiF ₆ (One)

6 HF + Si → 2H ₂ + H ₂ SiF ₆ (2)

Then, etching is performed by dissolving titanium in the hydrofluoric acid aqueous solution according to the following reaction formula.

Ti + 0 ₂ → Ti0 ₂ (3)

Ti0 ₂ + 2 H ₂ SiF ₆ → Ti (SiF ₆ ) ₂ + 2 H ₂ 0 (4)

In Schemes (1) and (2), hydrofluoric acid reacts reversibly with Si and Si0 ₂ . When an excessive amount of Si and Si0 ₂ is used in the hydrofluoric acid solution, HF is completely consumed, and hydrofluoric acid is dissolved in water to function as a strong acid. That is, H ₂ SiF ₆ dissociates in the form of H ⁺ and SiF ₆ ^{2 −} in water, and in this respect, it is completely different from dissociation of F ⁻ ions in BHF (hydrofluoric acid / ammonium fluoride aqueous solution).

However, the hydrofluoric acid aqueous solution varies depending on the concentration thereof, but when the temperature is raised to 60 ° C or higher, hydrofluoric acid itself is decomposed to generate HF (hydrofluoric acid gas) and SiF ₄ (silicon fluoride gas). And SiF ₄ reacts rapidly with water to produce SiO ₂ , and SiO ₂ precipitates in aqueous solution. For this reason, hydrofluoric acid aqueous solution cannot be used in too harsh conditions such as high concentration conditions or high temperature conditions, but except for too harsh conditions, the action of the hydrofluoric acid differs from hydrofluoric acid by SiF ₆ ^{2 -} ions. It can exhibit an etching function.

On the other hand, titanium has a dissolving region by ionization in a reducing atmosphere region in the presence of an acid. Oxygen in the air can be sufficiently used as the oxygen source of the reaction formula (3), but the etching rate of titanium can be controlled by appropriate addition of nitric acid or hydrogen peroxide as the oxidizing agent.

As shown in Schemes (3) and (4), titanium becomes an oxide once, and thereafter dissolves in the presence of an acid. Although it can be clearly seen from the reaction scheme, in the etching, since it is always dissolved through the form of an oxide, not only the titanium monolith but also the monolithic titanium oxide can be dissolved in hydrofluoric acid, and etching is possible. Titanium oxide as the titanium oxide to the lower call from titanium dioxide, titanium black as a white (Ti _x O _{2X -1} = _x is an integer of 1 or more) compounds, can be etched by the etching solution of the present invention.

From Schemes (1), (2), (3) and (4), hydrofluoric acid is inert to a silicon substrate or a silicic acid-based glass substrate, but since it shows activity for titanium, selective etching of titanium can be performed. .

As mentioned above, the etching liquid for titanium containing layers of this invention may contain an oxidizing agent, and an etching rate can be adjusted with an oxidizing agent. As this oxidant, nitric acid or hydrogen peroxide is preferable.

In particular, since titanium nitride and titanium oxynitride are harder than titanium or titanium oxide, combined use of an oxidizing agent is usually preferred. That is, titanium nitride and titanate nitride release nitrogen by the action of an oxidizing agent, titanium oxide is produced as an intermediate, and the titanium oxide is dissolved in hydrofluoric acid and etching is performed. Therefore, titanium nitride and titanium oxynitride can also be etched by the etching solution of the present invention in the same manner as in the case of titanium oxide.

Further, the etching solution for titanium-containing layers of the present invention is alcohols, glycols, organic acids and surfactants, preferably alcohols having 4 or less carbon atoms, glycols having 4 or less carbon atoms, organic acids having 4 or less carbon atoms, and anionic surfactants. And at least one selected from the group consisting of nonionic surfactants. By containing these, the surface tension of an etching liquid can be reduced and the etching property of a micro part can be improved, and the functionality, such as preventing the side etching mentioned later, can be obtained.

Hereinafter, the etching liquid for titanium containing layers of this invention is demonstrated in detail. The etching liquid for titanium containing layers of this invention is a liquid containing hydrofluoric acid, and is generally a hydrofluoric acid aqueous solution. When the hydrofluoric acid concentration in this hydrofluoric acid aqueous solution is in the range of 0.1-40 weight%, it is known that hydrofluoric acid concentration has a linear functional relationship with respect to the etching rate of titanium. And even if the hydrofluoric acid concentration of the hydrofluoric acid aqueous solution exceeds 20 weight%, there will be no problem, but if the hydrofluoric acid concentration exceeds 50 weight%, the etching liquid for titanium containing layers will become unstable by decomposition | disassembly of hydrofluoric acid, etc. . In addition, the hydrofluoric acid aqueous solution can be easily purchased in the form of an aqueous solution of 40% by weight or less. Therefore, the concentration of hydrofluoric acid in the hydrofluoric acid aqueous solution is usually in the range of 0.1 to 50% by weight, preferably 1 to 40% by weight, more preferably 1 to 20% by weight. In addition, when the hydrofluoric acid concentration is less than 0.1% by weight, a sufficient etching rate cannot be obtained.

As described above, except for the case where the titanium nitride or the titanium oxynitride is etched, an oxidizing agent may be added to the etching liquid for the titanium containing layer in order to adjust the etching rate. The oxidant concentration in the etchant for titanium containing layer varies depending on the kind of oxidant to be used. For example, when nitric acid is used as an oxidizing agent, the nitric acid concentration in the etching liquid for titanium containing layers is 20 weight% or less normally, Preferably it is 10 weight% or less. When hydrogen peroxide is used, the hydrogen peroxide concentration in the titanium-containing layer etching solution is usually 10% by weight or less, preferably 5% by weight or less, and more preferably 3% by weight or less. When adding an oxidizing agent, the lower limit of the concentration is not particularly limited, but is usually 0.1% by weight. If less than 0.1% by weight, the effect of improving the etching rate is not exhibited. In addition, in this invention, sufficient etching rate can be obtained in many cases, without adding an oxidizing agent. If the oxidant concentration is too high, a solid oxide film layer is formed on the surface of titanium, and dissolution of the formed oxide film takes time, and as a result, there is a risk of impairing the function of the functional agent described later. Therefore, when using an oxidizing agent, it is preferable to use it at low concentration.

On the other hand, when etching titanium nitride or titanium oxynitride, since it is necessary to convert nitride or oxynitride into an oxide, it is preferable to use an oxidizing agent. For example, when nitric acid is used as the oxidizing agent, the lower limit of nitric acid concentration in the titanium-containing layer etching solution is usually 10% by weight, preferably 20% by weight, and the upper limit is usually 50% by weight, preferably 40% by weight. . In the case of using hydrogen peroxide, the lower limit of the hydrogen peroxide concentration in the titanium-containing layer etching solution is usually 5% by weight, preferably 10% by weight, and the upper limit is usually 20% by weight, preferably 15% by weight.

In general, the basic component of the etching solution is a mixture of a complex or a functional agent having a function of dissolving a metal oxide or an acid and an oxidizing agent for oxidizing the metal and a surface tension of the etching solution having to introduce the liquid into the fine portion. Suitable. The functional agent to be added is usually selected from the group consisting of organic acids, alcohols, glycols, and surfactants of organic carboxylic acids. When the strength of the oxidizing agent in the etching solution is strong, the functional agent is deteriorated or degraded by the oxidizing agent, and in many cases, its function is lost. Generally, there is little choice of functional agent.

Therefore, in many cases, only organic acids corresponding to oxidation products can be used as the functional agent. However, as described above, in the case of etching titanium or titanium oxide by the etching solution for titanium-containing layer of the present invention using hydrofluoric acid, since an oxidizing agent is almost unnecessary or a small amount of oxidizing agent is required, There is no particular limitation as long as it is soluble in hydrofluoric acid aqueous solution, has a function of lowering the surface tension or contact angle of the etching solution, and exhibits a function of infiltrating the hydrophilic etching solution into the gap between the hydrophobic resist patterns of the microfabrication process. For example, there are water-soluble compounds such as alcohols, glycols, organic acids, and surfactants.

However, as the titanium nitride and / or titanium oxynitride etching solution, as described above, since a predetermined amount of oxidizing agent is used, there are organic acids as functional agents, specifically, acetic acid, methanesulfonic acid, oxalic acid and the like can be used.

The alcohols as the functional agent added to the titanium-containing layer etching solution of the present invention usually have 4 or less carbon atoms, preferably 1 to 4 carbon atoms, and examples thereof include methanol, ethanol, and propanol. The glycols are usually glycols having 4 or less carbon atoms, preferably 2 to 4 carbon atoms, and examples thereof include ethylene glycol, diethylene glycol, propylene glycol, propanediol, butanediol, glycerin, and water-soluble glycol ethers thereof. Can be mentioned. In addition, the acids are usually an organic carboxylic acid having 4 or less carbon atoms, preferably 1 to 4 carbon atoms. For example, monobasic acids include formic acid, acetic acid, propionic acid, butyric acid, and the like, oxalic acid, malonic acid and citric acid. , Succinic acid, glutaric acid, malic acid, and the like.

Anionic surfactant and nonionic surfactant are preferable as surfactant, For example, dodecylbenzene sulfonic acid is mentioned as anionic surfactant, and polyoxyethylene glycol ether is mentioned as a nonionic surfactant. The upper limit of the density | concentration in the etching liquid for titanium containing layers of these surfactant is 500 weight ppm normally, Preferably it is 200 weight ppm, and the lower limit is 10 weight ppm normally. When the concentration of the surfactant is too high, it is not preferable because it causes foaming, and when the concentration of the surfactant is less than 10 ppm by weight, the effect as a functional agent is not expressed. Such a functional agent may be used individually by 1 type, and may be added in 2 or more types of mixtures.

The additional effect of such a functional agent is demonstrated below. Titanium is not suitable for wiring materials because of its large electrical resistance. However, titanium is often used as a base metal material of a metal wiring member having poor adhesion to a substrate because of its high adhesion to a silicon substrate or a silicic acid-based glass substrate. And the laminated structure which formed the wiring pattern which consists of other metal materials on the titanium undercoat layer is used. In such a case, after forming a metal layer as a wiring material on the board | substrate through the titanium layer as an undercoat layer, providing a resist pattern on it again, and etching the wiring material (henceforth "upper metal"), The titanium layer (hereinafter referred to as "lower Ti") is etched.

Pt, Au, Ag, Cu, Pd, etc. are mentioned as a wiring metal material which peels, without obtaining sufficient adhesiveness, when formed directly on a silicon substrate or a silicic acid-type glass substrate. However, after the upper metal coated with the resist pattern is etched with another etching solution and the lower Ti is exposed, the lower metal can be etched as the mask pattern with the upper metal by the etching solution for the titanium-containing layer of the present invention.

In this case, in the stacking system of metals in which the upper metal and the lower Ti are different, the etching liquid contacts both metals at the same time, so that the etching rate is accelerated in the metal having a lower oxidation potential (higher ionization tendency) than in the case of a single layer metal film. The phenomenon occurs. For example, when the upper metal is Au, the ionization potential of Au is +1.6 V, whereas the ionization potential of the Ti sublayer is -1.6V, and the potential difference between Ti and Au is 3.2V. As described above, the greater the potential difference is, the more polarized at the time of etching, the higher the oxidation potential becomes the cathode, and the metal is transferred in the form of anodic oxidation even if the oxidation potential is low. Since Ti has a large potential difference with respect to Au, it is easy to accelerate the etching rate. Therefore, the lower Ti under the upper Au undergoes side etching as a metal mask, and in the case of lamination, the side etching speed is usually increased by 50 to 100 times with respect to the film thickness. do. For example, during the etching of the lower Ti having a thickness of 0.1 mu m, there is a possibility that a 5 to 10 mu m side etching (transverse gap etching) phenomenon occurs.

The above-mentioned functional agent also has the effect of preventing such a problem. That is, in the etching liquid for titanium containing layers of this invention, when the functional agent concentration is raised in the range which can dissolve hydrofluoric acid, moisture concentration will become comparatively low. However, when the moisture concentration is lowered, the overvoltage at which hydrogen gas is generated becomes high, and as a result, electron transfer between the laminated metals is less likely to occur, resulting in less appearance of electroplating and suppressed side etching. Therefore, it is important to be able to regulate the water concentration in selecting the functional agent, and it is important to consider the solubility in the titanium salt produced by dissolving titanium in hydrofluoric acid.

In addition, when the resist pattern is formed, the resist may be dissolved in the functional agent. Therefore, when a resist exists, the addition of alcohols as the functional agent may be restricted. However, the resist pattern is necessary for etching the upper metal of the above-described laminated structure, but is not necessarily required when the lower Ti is etched because the upper metal acts as a metal mask. Therefore, if the resist may be removed together with the etching of titanium, an alcohol-based functional agent can also be used.

In this manner, the use of the functional agent produces effects such as reduction of the surface tension of the etching solution and prevention of side etching. Although functional agent concentrations other than surfactant in the etching liquid for titanium containing layers of this invention differ also by the kind and required performance of the functional agent to be used, it is 5 to 90 weight% normally, Preferably it is the range of 40 to 80 weight%.

The etching liquid for titanium containing layers of this invention contains hydrofluoric acid and the said oxidizing agent and / or functional agent as needed, Preferably the remainder consists of water substantially. The particles in the etching liquid are preferably removed because the uniform etching may be inhibited as the pattern size on the substrate becomes finer. Specifically, the number of fine particles having a particle size of 0.5 µm or more is usually 1000 pieces / ml or less. Particle removal of the etchant is possible by, for example, filtering the prepared etchant through a precision filter. In this case, although the filtration system may be a one-pass system, a circulation type is more preferable from a removal efficiency of microparticles | fine-particles.

Hereinafter, although the preferable composition of the etching liquid for titanium containing layers of this invention is shown for every etching object, the etching liquid for titanium containing layers of this invention does not have any restriction | limiting in the following composition.

<Etching solution for titanium and titanium oxide>

Hydrofluoric acid: usually 0.1 to 40% by weight,

Oxidizing agent: usually 20% by weight or less, preferably 10% by weight or less,

Functional agent: usually 90% by weight or less, preferably 80% by weight or less,

<Etching solution for titanium nitride and titanium oxynitride>

Hydrofluoric acid: usually 0.1 to 40% by weight,

Oxidizing agent: usually 10 to 50% by weight, preferably 20 to 40% by weight,

Functional agent: in the case of acetic acid or methanesulfonic acid, usually 30% by weight or less, preferably 20% by weight or less,

The etching method of the titanium containing layer of this invention uses the etching liquid for titanium containing layers, Comprising: The titanium containing layer on a silicon substrate or a silicic acid-based glass substrate is etched. That is, the etching method of the titanium containing layer of this invention is carried out on the titanium containing layer on a board | substrate. Particularly suitable for etching of the titanium containing layer on a substrate on which a pattern of at least one of metals other than titanium, preferably platinum, gold, silver, copper and palladium is formed, leaving a metal pattern on the titanium containing layer, Only the titanium-containing layer exposed between the metal patterns can be etched away efficiently without eroding.

In this case, the etching temperature is not particularly limited, and room temperature is easy to use, but if the temperature is raised, the reaction activity of titanium and the etching solution is increased. However, when the temperature is raised to a high temperature exceeding 60 ° C., as described above, hydrofluoric acid causes decomposition. For this reason, the upper limit of an etching temperature is 60 degreeC normally, Preferably it is 50 degreeC. Since the pressure at the time of etching does not affect especially etching performance, it is normal pressure.

As the etching method, any conventional method may be used, and in general, a batch deposition method or a spray method may be mentioned. In addition, the etching method does not particularly affect the etching performance. It is a preferable aspect to stir etching liquid during an etching process, and it is also a preferable aspect to rock the process board | substrate in etching liquid.

The thickness of the titanium-containing layer on the silicon substrate or the silicic acid-based glass substrate to be etched by the present invention is not particularly limited, but the thickness of the titanium-containing layer as the undercoat metal layer is usually about 0.05 to 0.2 µm. Moreover, the thickness of the metal wiring material layer on such a titanium also containing layer is about 0.05-0.5 micrometer normally.

Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

Example 1

A test piece was prepared by cutting a thermal oxide film having a thickness of 0.08 μm on an 8B silicon wafer to a size of 1 cm × 5 cm. Separately, the titanium oxide film was cut to the same size so as to have a thickness of 0.1 μm by sputtering on an 8B silicon wafer having the thermal oxidation film having a thickness of 0.08 μm to prepare a titanium specimen for etching rate measurement. Although the titanium specimen was observed by SEM, the titanium layer was in close contact with the silicon thermal oxide film and was not mechanically peeled off, and was completely identical to the adhesion of the chromium layer.

After preparing such specimens, 50 ml of 15% by weight aqueous hydrofluoric acid solution containing no other additives were added to two beakers for 100 ml each by stirring with a stirrer and fixed to a constant temperature at 50 ° C. Titanium specimens and silicon specimens were suspended so that the specimens were immersed in aqueous hydrofluoric acid solution. As for the titanium specimen, the etching rate was visually measured by measuring the time until the titanium film disappeared from the naked eye. On the other hand, since it is impossible to measure visually about a silicon specimen, it measured by the optical interference film thickness meter, and the etching rate was calculated | required from the inclination which calculated the film thickness decrease. Table 1 shows the measurement results of the etching rate of titanium and the etching rate of silicon oxide.

Comparative Example 1 :

In Example 1, the etching rates of titanium and silicon oxide were measured in the same manner as in Example 1, except that 80 wt% concentrated sulfuric acid aqueous solution was used instead of the aqueous hydrofluoric acid solution as the etching solution. The results are shown in Table 1.

Comparative Example 2 :

In Example 1, the etching rates of titanium and silicon oxide were measured in the same manner as in Example 1, except that 35 wt% concentrated hydrochloric acid aqueous solution was used instead of the aqueous hydrofluoric acid solution as the etching solution. The results are shown in Table 1.

Comparative Example 3 :

In Example 1, it carried out similarly to Example 1 except having used the beaker made from Teflon (trademark), and using the aqueous 1 weight% hydrofluoric acid solution instead of the aqueous hydrofluoric acid solution as an etching solution, and carrying out oxidation with titanium. Each etching rate of silicon was measured. The results are shown in Table 1.

Etching solution Etching rate (nm / min) Etching liquid component Water concentration (% by weight) (calculated) Temperature (℃)  titanium  Silicon oxide Kinds Concentration (% by weight) Example 1 Hydrofluoric acid 15 85 50 3500 13 Comparative Example 1 Sulfuric acid 80 20 50 264 One Comparative Example 2 Hydrochloric acid 35 65 50 160 One Comparative Example 3 Hydrofluoric acid One 99 50 2500 160

From Table 1, it can be seen that by using the etching solution for the titanium containing layer containing hydrofluoric acid, the titanium layer is selectively etched with almost no erosion of the silicon substrate, and the etching rate is also very fast.

Example 2 :

A thermal oxide film was formed on the 8B silicon wafer to a thickness of 0.08 μm, and titanium was deposited thereon so as to have a thickness of 0.10 μm by the sputter, and the titanium surface of the sputter was kept in contact with air, and then gold was deposited thereon. The film was laminated with a sputter so as to have a thickness of 0.5 µm. On this laminated film, the resist film was formed again, and the patterned specimen was prepared. In other words, a laminated specimen 1 composed of a silicon substrate / silicon oxide layer / titanium layer / gold layer / pattern resist layer was prepared.

In the 100 ml beaker, the gold layer should first be etched, and 50 ml of an aqueous solution of 3% by weight of iodine and 9% by weight of potassium iodide was added as a gold etching solution, stirred with a stirrer, and the temperature was fixed at 25 ° C. (1) was hung to immerse and fixed. It was etched visually until the gold of the resist gap disappeared, and the gold part of the resist gap was etched away. At that time, it was confirmed that the titanium layer was not etched at all by the etching solution with the naked eye, but the titanium layer was not etched even from the thickness measurement in the SEM photograph of the surface cut in the longitudinal direction with respect to the laminated film. Confirmed. After the gold was removed, the laminated test piece (1) (called the test piece (2)) was used, and then 50 ml of a 20 wt% aqueous solution of hydrofluoric acid containing no other additives was added to a 100 ml beaker and stirred with a stirrer. During the fixation to be constant at ° C, the specimen 2 was suspended and fixed so that the specimen was immersed in the aqueous solution, and the titanium layer portion was etched. While the titanium film of the resist gap disappeared with the naked eye and the lower oxide film layer (colored) could be confirmed, etching was stopped, SEM photograph of the surface cut | disconnected longitudinally with respect to the laminated film was observed, and the following calculation values were computed.

That is, even though the gold layer is a metal mask, it is confirmed that the lateral side etching of the titanium layer is underway, the etching rate in the film thickness direction of the titanium layer is determined, and the etching rate in the film thickness direction is determined. The ratio of the side etch rate with respect to was calculated | required as the side / film thickness etching ratio. The results are shown in Table 2. At that time, although it confirmed also in Example 1, only the titanium layer was eroded-etched by the thickness test | inspection, and since the temperature was reduced compared with Example 1, it was confirmed that none was erosion of the silicon oxide film layer.

Example 3 :

In Example 2, etching was carried out in the same manner as in Example 2, except that 20 wt% hydrofluoric acid, 55 wt% propylene glycol, and 25 wt% water were used as the etching solution for the titanium layer. The etching rate in the film thickness direction and the side / film thickness etching ratio were determined. The results are shown in Table 2.

Example 4 :

In Example 2, etching was carried out in the same manner as in Example 2, except that 10 wt% hydrofluoric acid, 77 wt% propylene glycol, and 13 wt% water were used as the etching solution for the titanium layer. The etching rate in the film thickness direction and the side / film thickness etching ratio were determined. The results are shown in Table 2.

Etching solution Etch Rate of Titanium Layer * Metal species on the titanium layer Etch solution component concentration (% by weight) Water concentration (% by weight) (calculated value)  Temperature (℃) Film thickness direction (nm / min) Side / film thickness etching ratio Hydrofluoric acid Propylene glycol Example 2 20 0 80 25 240 17 gold Example 3 20 55 25 25 100 18 gold Example 4 10 77 13 25 46 3 gold

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As can be seen from Table 2, when a gold layer was formed on the titanium layer, the gold layer was etched, and then the titanium layer was etched with an aqueous solution of hydrofluoric acid, about 17 times the thickness etching proceeded ( Example 2 and 3) and by adjusting the compounding of the functional agent, the side etching with respect to the thickness of this titanium layer could be suppressed up to 3 times (Example 4). In addition, the gold layer was not etched with hydrofluoric acid.

Example 5 :

A titanium nitride layer was formed in the same manner as in Example 1 except that a titanium nitride layer was formed instead of the titanium layer, and an aqueous solution of 15% by weight hydrofluoric acid and 23% by weight nitric acid was used as the etching solution. The etching rate of each silicon oxide was measured. The results are shown in Table 3 below.

Etching solution Etching rate (nm / min) Etch solution component concentration (% by weight)  Water concentration (% by weight) (calculated)  Temperature (℃)   Titanium nitride   Silicon oxide Hydrofluoric acid nitric acid Example 5 15 23 62 50 34 13

From Table 3, it can be seen that, according to the etching solution of the present invention, the etching rate ratio between titanium nitride and silicon oxide is not different from that of Example 1, but it is remarkable and selective etching of the titanium nitride layer is also possible.

Examples 6 and 7 :

In Examples 2 and 4, except that a silver layer was formed on the titanium layer instead of the gold layer, and 44% by weight of phosphoric acid, 5% by weight of nitric acid, and 30% by weight of acetic acid were used as the silver etching solution instead of the gold etching solution. The titanium layer was etched in exactly the same manner as in Example 2 (Example 6) and Example 4 (Example 7), and the etching rate and the thickness / film thickness etching in the film thickness direction of the titanium layer were similarly performed. The ratio was obtained. The results are shown in Table 4 below.

Etching liquid Etch Rate of Titanium Layer *   Metal species on the titanium layer Etch solution component concentration (% by weight)  Water concentration (% by weight) (calculated value)  Temperature (℃)  Film thickness direction (nm / min)  Side / film thickness etching ratio Hydrofluoric acid Propylene glycol Example 6 20 0 80 25 130 6 silver Example 7 10 77 13 25 38 2 silver

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As is clearly shown in Table 4, since dissimilarity occurs between dissimilar metals of silver and titanium in the same manner as in the case of the gold layer of Example 2, it was confirmed that side etching proceeded, but a large amount of propylene glycol was contained in the etching solution. By adding, it was possible to suppress side etching. In addition, the silver layer was not etched in hydrofluoric acid without an oxidizing agent.

Examples 8 and 9 :

In Examples 2 and 4, except that the copper layer was formed on the titanium layer instead of the gold layer, and instead of the gold etching solution, an aqueous solution containing 3% by weight of ammonium oxalate and 0.5% by weight of hydrogen peroxide was used as the copper etching solution. The titanium layer was etched in exactly the same manner as in Example 2 (Example 8) and Example 4 (Example 9). Similarly, the etching rate and the side / film thickness etching ratio of the titanium layer in the film thickness direction were determined. . The results are shown in Table 5 below.

Etching liquid Etch Rate of Titanium Layer *   Metal species on the titanium layer Etch solution component concentration (% by weight)  Water concentration (% by weight) (calculated value)  Temperature (℃)  Film thickness direction (nm / min)  Side / film thickness etching ratio Hydrofluoric acid Propylene glycol Example 8 20 0 80 25 130 4 Copper Example 9 10 77 13 25 36 One Copper

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As clearly shown in Table 5, since dissociation occurs between dissimilar metals between copper and titanium in the same manner as in the case of the gold layer of Example 2, it is confirmed that side etching proceeds, but a large amount of propylene glycol is contained in the etching solution. By adding, it was possible to suppress side etching. In addition, the copper layer was not etched in hydrofluoric acid without an oxidizing agent.

Examples 10 and 11 :

Example 2 and 4 WHEREIN: Except forming a platinum layer on a titanium layer instead of a gold layer, and using the aqua regia solution of 5 weight% nitric acid and 10 weight% hydrochloric acid as a platinum etching liquid instead of a gold etching liquid, respectively. (Example 10) and Example 4 (Example 11) were carried out in exactly the same manner, and the titanium layer was etched. Similarly, the etching rate and the side / film thickness etching ratio of the titanium layer in the film thickness direction were determined. The results are shown in Table 6 below.

Etching liquid Etch Rate of Titanium Layer *   Metal species on the titanium layer Etch solution component concentration (% by weight)  Water concentration (% by weight) (calculated value)  Temperature (℃)  Film thickness direction (nm / min)  Side / film thickness etching ratio Hydrofluoric acid Propylene glycol Example 10 20 0 80 25 220 11 platinum Example 11 10 77 13 25 42 3 platinum

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As is apparent from Table 6, since dissimilar metals between platinum and titanium were formed in the same manner as in the case of the gold layer of Example 2, it was confirmed that side etching proceeded, but a large amount of propylene glycol was contained in the etching solution. By adding, it was possible to suppress side etching. In addition, the platinum layer was not etched in hydrofluoric acid without an oxidizing agent.

Examples 12 and 13 :

In Examples 2 and 4, except that a palladium (Pd) layer was formed on the titanium layer instead of the gold layer, and 5% by weight of nitric acid and 10% by weight of hydrochloric acid were used as the palladium etching solution instead of the gold etching solution. The titanium layer was etched in exactly the same manner as in Example 2 (Example 12) and Example 4 (Example 13), and the etching rate and the thickness / film thickness etching ratio in the film thickness direction of the titanium layer were similarly applied. Was obtained. The results are shown in Table 7 below.

Etching liquid Etch Rate of Titanium Layer *  Metal species on the titanium layer Etch solution component concentration (% by weight)  Water concentration (% by weight) (calculated value)  Temperature (℃)  Film thickness direction (nm / min)  Side / film thickness etching ratio Hydrofluoric acid Propylene glycol Example 12 20 0 80 25 200 9 Pd Example 13 10 77 13 25 40 2 Pd

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As clearly shown in Table 7, since dissimilar metals between the palladium and titanium were also carried out in the same manner as in the case of the gold layer of Example 2, it was confirmed that side etching proceeded, but a large amount of propylene glycol was contained in the etching solution. By adding, it was possible to suppress side etching. In addition, the palladium layer was not etched in hydrofluoric acid without oxidizing agent.

Example 14

Titanium was formed into a film by the sputter | spatter to make thickness 0.10 micrometer with a sputter | spatter for liquid crystal, and it patterned by apply | coating a positive novolak-type resist on it, irradiating an ultraviolet-ray, and removing the labyrinth part (soluble part) with alkali agent, Postbaking heat treatment was performed at 130 ° C. in the presence of air. As a result, a titanium oxide layer was formed on the surface of the titanium portion exposed from the opening of the cured film of the resist.

As the test piece, the etching rate of titanium oxide and the etching rate of the silicic acid-based glass were measured in the same manner as in Example 1, except that the test piece in which the titanium oxide layer was formed in this way and the test piece of the silicic acid-based glass were used. The results are shown in Table 8 below.

Etching solution Etching rate (nm / min) Etching liquid component  Water concentration (% by weight) (calculated)  Temperature (℃)   Titanium nitride   Silicate glass  Kinds  Concentration (% by weight) Example 14 Hydrofluoric acid 15 85 50 3200 30

As clearly shown in Table 8, although the etching rate of titanium oxide was slightly slower than the etching rate of titanium in Example 1, it was etched at a sufficient etching rate. On the other hand, the silicate-based glass was hardly etched, and was equivalent to the etching performance of the silicon oxide film on the silicon wafer. Therefore, in the titanium oxide layer, the etching rate is slightly lowered and the etching rate of the glass layer is increased, but a sufficient etching rate difference can be obtained between the glass layer and the titanium oxide layer, and the selectivity of the etching solution with respect to titanium oxide can also be confirmed. there was.

Example 15

In Example 2, etching was carried out in the same manner as in Example 2, except that 20 wt% hydrofluoric acid and 10 wt% acetic acid were used as the etching solution of titanium, and the etching rate and the thickness in the film thickness direction of the titanium layer were measured. The film thickness etching ratio was obtained. The results are shown in Table 9 below.

Etching liquid Etch Rate of Titanium Layer * Metal species on the titanium layer Etch solution component concentration (% by weight) Water concentration (% by weight) (calculated value) Temperature (℃) Film thickness direction (nm / min) Side / film thickness etching ratio Hydrofluoric acid Acetic acid Example 15 20 10 70 25 600 7 gold

Note: In any case, the etching rate of silicon oxide is 0 nm / minute.

As is apparent from Table 9, the etching rate of titanium increased by using an etching solution containing acetic acid, while the side etching tended to decrease. This increase in etching rate is thought to be due to the effect of improving wettability and acid strength by acetic acid, but there is no detailed theoretical explanation. Moreover, there was no change in etching property, such as a silicon oxide.

Example 16 :

The etching was carried out in the same manner as in Example 15, except that 20 wt% hydrofluoric acid and 10 wt% acetic acid were used as the etching solution of titanium, and the etching rate and the thickness / film thickness ratio in the film thickness direction of the titanium layer. Was obtained. The results are shown in Table 10 below. Further, in a substrate in which gold has already been removed from the substrate (silicon substrate / silicon oxide layer / gold layer / pattern resist layer) and the titanium portion has been removed by the etching method of the embodiment, the silicon oxide film is exposed in the gap portion of the resist pattern remaining film. In the portion, by using a Nano-Spec non-contact type optical interference film thickness measuring device (L-6100 manufactured by Nanometrics) based on the original reference film thickness of the silicon oxide powder, by measuring the film thickness after the measurement treatment The erosion fraction of the silicon oxide portion was calculated, and the etching rate of the silicon oxide was measured from the value. The results are written together in Table 10.

Example 17

In Example 15, etching was carried out in the same manner except that 20 wt% hydrofluoric acid and 3 wt% hydrogen peroxide were used as the etching solution of titanium, and the etching rate and the thickness / film thickness ratio of the titanium layer were measured. Was obtained. The results are shown in Table 10 below. Further, in a substrate in which gold has already been removed from the substrate (silicon substrate / silicon oxide layer / gold layer / pattern resist layer) and the titanium portion has been removed by the embodiment method, a portion where the silicon oxide film is exposed in the gap portion of the resist pattern remaining film. The eroded powder of the silicon oxide portion was measured by measuring the film thickness after the measurement treatment based on the original reference film thickness of the silicon oxide powder using a nano-spec non-contact optical interference film thickness measuring device (L-6100 manufactured by Nanometrics). It calculated and measured the etching rate of a silicon oxide from the value. The results are written together in Table 10.

Etching solution Etching Speed (nm / min)   Side / film thickness etching ratio Etching liquid component  Water concentration (% by weight) (calculated)   Temperature (℃) Hydrofluoric acid concentration (% by weight) Oxidant   titanium  Silicon oxide  Kinds  Concentration (% by weight) Example 16 20 nitric acid 10 70 25 600 2 7 Example 17 20 Hydrogen peroxide 3 77 25 200 2 13

From Table 10, in Example 16 using nitric acid, the etching rate of titanium increased and there was a tendency that side etching decreased. One of these effects is thought to increase the etching rate due to the wettability improvement effect and nitric acid improvement effect by nitric acid, but there is no detailed theoretical explanation. The etching property of silicon oxide and the like was not changed at the addition of this nitric acid concentration and at low temperature conditions.

In addition, in Example 17, the etching rate of titanium tended to be low, and the side etching tended to be suppressed. Titanium ash is known to form an oxide film on the surface and to form a passivation under conditions of high oxidizing agent. As shown in Example 14, since the etching rate decreases when an oxide film is formed on the surface, the decrease in the etching rate is removed by acid. It is thought to be due to the interaction between the effect and the forming effect of the oxide film.

Example 18

A thermal oxide film was formed on the 8B silicon wafer to a thickness of 0.08 mu m, a titanium layer was formed by a sputter to a thickness of 0.1 mu m, and a positive novolac-based resist was applied on the titanium layer to form various intervals. After the various patterns provided in various ways were patterned by ultraviolet irradiation, the labyrinth light part (soluble part) was removed with an alkali chemicals, and then post-baked at 130 degreeC in presence of air. The substrate was cut into strips as specimens. In this embodiment, the other dissimilar metal laminate film is not formed, but is a laminated structure of Si substrate / silicon oxide / titanium / resist.

As an etching solution of titanium, when a 20 wt% aqueous solution of hydrofluoric acid (base solution) is used, if the wiring interval is narrow, the resist is hydrophobic and the solution is hydrophilic, so that the wettability is poor, and the original etching performance cannot be exhibited, and the apparent etching Slowed down As a result, in the case of narrow wirings, the etching process was performed in the same manner as in Example 1 except that an etching solution in which 10 wt% of n-propanol was added to a 20 wt% aqueous hydrofluoric acid solution was used as the etching solution so that the etching solution could penetrate. In the same manner as in Example 1, the etching rates of titanium and silicon oxide were measured. The results are shown in Table 11 below.

Moreover, when 13 weight% or more of n-propanol is added, it is also confirmed that a resist melts and peels. In this Example, it was confirmed that the etching liquid smoothly enters even at intervals of 15 µm or less, reaching almost the same performance level as the basic liquid. Moreover, when nitric acid or hydrogen peroxide as an oxidant coexisted in this etching liquid, it was also confirmed that n-propanol deteriorates, and since this oxidizing agent was not used in this etching liquid, etching liquid was stable.

Example 19 :

In Example 18, the etching solution was carried out in the same manner as in the etching solution except that an aqueous solution containing 200 ppm by weight of dodecylbenzenesulfonic acid (DBS) as anionic surfactant was added to the 20 wt% aqueous hydrofluoric acid solution instead of n-propanol. It etched and similarly measured the etching speed of titanium and a silicon oxide. The results are shown in Table 11 below.

Moreover, when DBS added 500 weight ppm or more, foaming was severe and foaming was slightly suppressed by 200 weight ppm addition. In this Example, it was confirmed that the etching liquid smoothly enters even at intervals of 15 µm or less, reaching almost the same performance level as the basic liquid. Moreover, when nitric acid or hydrogen peroxide as an oxidant coexisted in this etching liquid, it was also confirmed that DBS oxidizes and loses effect over time. There was no problem because these etching liquids did not add these oxidants.

Example 20

In Example 19, as an etching solution of titanium, an aqueous solution obtained by adding 200 ppm by weight of nonionic surfactant polyoxyethylene glycol alkyl ether (POEG) to 20% by weight aqueous solution of hydrofluoric acid instead of anionic surfactant DBS was used. The etching process was carried out in the same manner except for the above, and the etching rates of titanium and silicon oxide were measured in the same manner. The results are shown in Table 11 below.

Moreover, when POEG added 500 weight ppm or more, foaming was severe and foaming was suppressed slightly by addition of 200 weight ppm. In this Example, it was confirmed that the etching liquid smoothly enters even at intervals of 15 µm or less, reaching almost the same performance level as the basic liquid. Moreover, when nitric acid or hydrogen peroxide as an oxidant coexisted in this etching liquid, it was also confirmed that POEG is oxidized and loses effect over time, and since there was no problem in these etching liquids, since these oxidizing agents were not added.

Etching liquid Etch Rate ((nm / min Etching liquid component  Water concentration (% by weight) (calculated)  Temperature (℃) Hydrofluoric acid concentration (% by weight)  n-propanol (% by weight) Surfactant (wt ppm)  titanium  Silicon oxide  DBS  POGE Example 18 20 10 0 0 60 50 3000 0 Example 19 20 0 200 0 79.98 50 3200 0 Example 20 20 0 0 200 79.98 50 3100 0

According to the present invention, a fast etching rate is selectively performed on a titanium-containing layer including one or two or more selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate In order to form a pattern of platinum, gold, silver, copper, palladium, etc., which are poor in adhesion to a silicon substrate or a silicic acid-based glass substrate, the titanium layer, the titanium oxide layer, the titanium nitride layer, Alternatively, even when the titanium oxynitride layer is applied, the titanium base coating layer can be easily etched. Therefore, according to the present invention, titanium, titanium oxide, titanium nitride, or titanium oxynitride can be applied as the underlying metal as a substitute for the conventional chromium underlying metal, and its industrial value is very high.

According to the present invention, the titanium containing layer on the silicon substrate or the silicic acid-based glass substrate can be selectively etched without eroding the substrate at a high etching rate.

Claims (11)

An etching solution for etching a titanium-containing layer composed mainly of one, two or more selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate, containing hydrofluoric acid The etching liquid for titanium containing layers characterized by the above-mentioned. The etching liquid for titanium containing layers of Claim 1 in which an etching liquid contains an oxidizing agent. The etchant for titanium-containing layer according to claim 1, wherein the titanium-containing layer contains titanium nitride and / or titanium oxynitride as a main component, and the etching solution contains an oxidizing agent. The etching liquid for titanium containing layers of Claim 2 or 3 whose oxidizing agent is nitric acid or hydrogen peroxide. The etchant for titanium-containing layer according to any one of claims 1 to 4, wherein the etching solution contains at least one member selected from the group consisting of alcohols, glycols, organic acids, and surfactants. The etchant for titanium-containing layers according to claim 5, wherein the alcohols, glycols, and organic acids have 1 to 4 carbon atoms. The etching liquid for titanium containing layers of Claim 5 whose surfactant is an anionic surfactant and / or nonionic surfactant. An etching solution for etching a titanium-containing layer containing, as a main component, one or two or more selected from the group consisting of titanium, titanium oxide, titanium nitride and titanium oxynitride formed on a silicon substrate or a silicic acid-based glass substrate, using an etching solution. An etching method for a titanium-containing layer is used as the etching liquid for titanium-containing layer according to any one of claims 1 to 7. The method of etching a titanium-containing layer according to claim 8, wherein a pattern made of a metal other than titanium is formed on the titanium-containing layer formed on the substrate. 10. The method of etching a titanium-containing layer according to claim 9, wherein the metal other than titanium is at least one selected from the group consisting of platinum, gold, silver, copper and palladium. The method for etching a titanium-containing layer according to any one of claims 8 to 10, wherein the titanium oxide is titanium dioxide or lower titanium oxide.