JP3985620B2 - Etching method - Google Patents

Description

【００４８】
表１から次のことが明らかである。即ち、比較例の従来の技術ではオーバーエッチングをしないようにエッチングを行うと、残渣発生の箇所が増加してしまうのに対し、実施例の本発明のエッチング方法によれば、必要以上のオーバーエッチングとならないエッチング時間でも、充分に残渣の発生を抑制することができ、サイドエッチングによるエッチングの不均一が生じないという効果に優れる。
【００４９】
特に、実施例１及び実施例５の結果から、エッチング液における酢酸濃度を１５〜３５重量％の範囲内（表１においては２５．４重量％）とすることにより、エッチング液中の銀イオンが少量であっても、優れた効果を奏することが判る。
【００５０】
【発明の効果】
以上詳述した通り、本発明のエッチング方法によれば、必要以上のエッチング（オーバーエッチング）を行うことなく、銀又は銀合金残渣の発生を抑制することができ、このため、サイドエッチングによる不均一エッチングを防止することができる。従って、本発明によれば、高精度な銀又は銀合金薄膜の微細加工を短時間に、寸法精度良く、均一且つ安定して行うことが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device such as, a liquid crystal display device, it relates to a suitable etching methods from fine processing of the silver or silver alloy wiring, such as an IC card.
[0002]
[Prior art]
In recent years, with respect to electrode wiring materials used as semiconductor and liquid crystal display devices, there is an increasing demand for finer processing accuracy . In addition, the use of silver and silver alloys as metals having high light reflectivity and low resistance is increasing.
[0003]
Silver and silver alloys have higher reflectivity than aluminum and aluminum alloys, and are widely used as reflective electrode wiring materials for semiconductor devices, liquid crystal display devices, solar cells, and the like. In order to form an electrode wiring made of silver or a silver alloy, it is necessary to process the silver or the silver alloy into a predetermined pattern shape. As a processing technique for forming this pattern, there are a wet etching method using chemicals and a dry etching method such as ion etching and plasma etching.
[0004]
The wet etching method is economically advantageous because it does not require an expensive apparatus as compared with the dry etching method and can be performed using an inexpensive chemical. The wet etching method is also suitable for a three-dimensional structure because it has a feature that it is hardly influenced by the surface shape of a metal material to be etched. Further, the wet etching method is widely used because it has an advantage that silver or a silver alloy compound can be easily recovered from an etching waste liquid.
[0005]
Conventionally, as an etching solution for silver or a silver alloy, generally, an iron nitrate aqueous solution, a solution containing iodine and an iodine compound, a solution containing hydrogen peroxide and ammonia, a solution containing nitric acid, and the like are known. Among these etching solutions, a solution containing nitric acid is preferably used because it reacts well with silver or a silver alloy, has a high etching rate, and is excellent in handleability.
[0006]
These etching solutions are also used for etching fine electrode wiring patterns made of silver or silver alloys for semiconductor devices and liquid crystal display devices formed by photolithography.
[0007]
At this time, it has been proposed to contain hydrochloric acid or a surfactant in the etching solution in order to remove silver or silver alloy residues that are difficult to dissolve in the etching solution and prevent re-adhesion to the substrate (Japanese Patent Laid-Open 9-208267 etc.).
[0008]
Conventionally, liquid crystal display substrates and the like are generally manufactured by the following process. That is, first, a silver or silver alloy thin film layer having a predetermined thickness is formed on the surface of a glass substrate by sputtering or the like, and then a resist resin layer for forming a fine electrode pattern or wiring is formed by a photolithography technique. . Then, after removing the silver or silver alloy thin film layer between these electrode patterns and wirings by wet etching or the like, the resist layer is removed.
[0009]
In the etching process for removing the finely patterned silver or silver alloy thin film layer formed by this photolithography technique, it is usually uniform so that no etching residue (etching unevenness) occurs in the exposed portion of the silver or silver alloy to be etched. In addition, the etching is required to be controlled so that the side surface of the silver or silver alloy layer covered with the resist resin layer is not excessively etched (side etching).
[0010]
[Problems to be solved by the invention]
However, in the conventional wet etching technique, silver or silver is particularly used in a portion where vertical and horizontal lines to be etched intersect, that is, in a narrow portion surrounded by silver or a silver alloy and a resist resin layer. There has been a problem that an etching residue of the alloy is easily generated. In the past, in order to solve this problem, etching was performed until this residue disappeared. However, in this method, etching required to obtain a desired etching amount according to the wiring width of silver or a silver alloy is performed. Etching is performed over time (ie, overetching). In this case, generation of a residue can be prevented by this over-etching, but naturally the side etching of the silver or silver alloy thin film layer proceeds and the etching becomes non-uniform (that is, the side etching amount increases). ) Was an unavoidable problem.
[0011]
The present invention solves the above-mentioned conventional problems, suppresses the generation of etching residues of silver or silver alloy in wet etching of a silver or silver alloy thin film layer, suppresses the generation of side etching due to overetching, and achieves a uniform and to provide an etching how that can be etched stably.
[0012]
[Means for Solving the Problems]
The etching method of the present invention is a method of etching with an etchant of silver or silver alloy thin layer present on the substrate surface, the silver ion concentration 0.005 wt% of the etchant, etching bath or the etching solution supplying device was filled in, the etching liquid, a Rue etching process is brought into contact with the substrate surface having a silver or silver alloy thin layer, controls the silver ion concentration in the etchant always be 0.005 wt% It is characterized by doing.
[0014]
In general, the metal ions to be etched in the etching solution is present, dissolved acid components (e.g. phosphoric acid, acetic acid, etc.) in the etching solution or an oxidizing agent component (e.g., nitric acid) is consumed, the etching rate decreases It is well known that such phenomena occur. Therefore, conventionally, metal ions or the like to be etched are naturally not present in the etching solution (etching new solution) used at the start of etching. In addition, the used etching solution is usually discarded because it is difficult to remove metal ions.
[0015]
The present inventors have made intensive studies to solve the problems definitive in etching how the silver or silver alloy described above, in the etching of silver or silver alloy, previously silver ions a certain amount, specifically, Etching is preferably performed by filling an etching bath or etching solution supply apparatus with 0.005 to 1% by weight of a new etching solution and bringing the etching solution into contact with the substrate surface having a silver or silver alloy thin film layer. Etching is always performed at a silver ion concentration of 0.005 to 1 wt% in the liquid, thereby suppressing the generation of silver or silver alloy residues in the etched portion, thereby preventing the occurrence of excessive side etching due to overetching. The inventors have found that uniform etching can be performed stably, and have completed the present invention.
[0016]
The etching method of the present invention is particularly effective in etching for forming reflective electrode wirings such as semiconductor devices, liquid crystal display devices, and solar cells. That is, most of the substrate surface is covered with a resist resin layer or the like, and exhibits an effect in etching that etches a silver or silver alloy part of a fine region exposed on the surface, without performing overetching more than necessary, It is possible to perform uniform etching while suppressing side etching without leaving a residue in the fine region.
[0017]
In the present invention, that is to the silver ion concentration in the etching solution constantly 0.005 wt%, specifically, the silver ion concentration to 0.005 wt% of etching the new chemical, Filling the etching tank or the etching solution supply apparatus, and in addition to bringing the etching solution into contact with the substrate surface having the silver or silver alloy thin film layer at the start of etching, for example, while the substrate is immersed in the etching solution The etching solution having a silver ion concentration of 0.005 to 1% by weight is always brought into contact with the silver or silver alloy thin film layer to be etched by maintaining the silver concentration of the immersion liquid in the etching solution at 0.005 to 1% by weight. to table it to be.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the etching how the present invention in detail.
[0019]
In the etching method of the present invention, is controlled so that the silver ion concentration in the etching solution is always 0.005 (50 wt ppm) to 1% by weight. The silver ion concentration in the etching solution is preferably 0.02% by weight (200 ppm by weight) or more, and the upper limit thereof is preferably 0.5% by weight (5000 ppm by weight) or less.
[0020]
If the silver ion concentration in the etching solution is too low, an etching residue may be generated in the etched portion. Conversely, if the silver ion concentration is too high, the amount of side etching may increase, and a large amount of expensive silver will be used, which is not economical.
[0021]
The above-mentioned etching solution having a silver ion concentration can be prepared, for example, by adding a predetermined amount of silver or a silver compound to a commonly used etching solution for silver or a silver alloy. As a method for adding silver or a silver compound, a method in which silver or a silver compound is directly added and dissolved in an etching solution, a silver solution in which silver or a silver compound is dissolved in an acid constituting the etching solution, or a silver compound is used. Examples thereof include a method of adding an aqueous silver solution dissolved in water to the etching solution.
[0022]
Examples of silver used as the silver ion source include pure silver. Examples of the silver compound include inorganic compounds such as silver nitrate, silver nitrite, silver phosphate, silver hexafluorophosphate, silver tetrafluoroborate, silver sulfate, silver chlorate, silver perchlorate, and silver iodate. Examples thereof include silver salts of acids, silver bromide, silver chloride, silver oxide, and silver sulfide. Examples of the organic compound include silver salts of organic acids such as silver acetate, silver benzoate, silver thiocyanate, silver p-toluenesulfonate, silver trifluoroacetate, and silver trifluoromethanesulfonate, and silver cyanide. Is mentioned.
[0023]
These silver or silver compounds are preferably dissolved uniformly in the etching solution and present as silver ions in the etching solution. For this reason, what is used as the silver ion source may be appropriately selected depending on the solubility in the etching solution. In addition, a silver ion source may be used individually by 1 type, and may use 2 or more types together. As the silver ion source, pure silver powder having a purity of 99% or more and silver sand are particularly preferable.
[0024]
What is necessary is just to select suitably the other composition of the etching liquid used with the etching method of this invention. Among them, an etching solution containing nitric acid, an etching solution containing nitric acid and acetic acid, particularly an etching solution containing phosphoric acid, nitric acid and acetic acid is preferable.
[0025]
In this case, the nitric acid concentration in the etching solution is usually 0.1% by weight or more, preferably 0.25% by weight or more, and usually 15% by weight or less, preferably 10% by weight or less. If the nitric acid concentration is too high, for example, the resist resin layer may be damaged. Conversely, if the nitric acid concentration is too low, the etching rate may be reduced.
[0026]
The phosphoric acid concentration in the etching solution is usually 10% by weight or more, preferably 20% by weight or more, and usually 80% by weight or less, preferably 70% by weight or less. If the phosphoric acid concentration is too high, the viscosity of the solution will increase. For example, when such an etching solution is used in a single wafer etching apparatus, the etching solution is sprayed from the etching solution supply device filled with the etching solution onto the substrate to be etched. There is a risk of hindering discharge. Conversely, if the phosphoric acid concentration is too low, it will cause a significant decrease in the etching rate.
[0027]
The concentration of acetic acid in the etching solution is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 15% by weight or more, and usually 50% by weight or less, especially 40% by weight or less. It is preferably 35% by weight or less. When the acetic acid concentration is too high, the composition change due to evaporation of acetic acid becomes remarkable, and the liquid life is shortened. On the other hand, if the acetic acid concentration is too low, the wettability with respect to the resist resin layer is lowered and etching defects are likely to occur.
[0028]
In the etching method of the present invention, in particular, when a resist resin layer or the like is provided on the majority of the substrate surface, and when etching the linear silver or silver alloy portion of the fine region exposed on the surface, the concentration of acetic acid in the etching solution It is preferable to keep the content at 1% by weight or more. As a result, the wettability to the resist resin layer can be improved, the etching solution can be easily penetrated into the fine details of the wiring structure, and silver or a silver alloy can be formed in the fine region without overetching more than necessary. No residue is left, and therefore, side etching can be suppressed and uniform etching can be performed.
[0029]
When the etching solution used in the present invention contains phosphoric acid, nitric acid, acetic acid and silver ions , this etching solution usually contains water. This water concentration is usually 5% by weight or more, preferably 7.5% by weight or more, and usually 50% by weight or less, preferably 40% by weight or less.
[0030]
The component ratio of the etching solution is appropriately determined depending on the required etching rate and etching area ratio (ratio of the silver or silver alloy to be etched and the area masked by the resist resin layer).
[0031]
In the etching solution used in the present invention , an additive such as a surfactant may be added. In this case, as the surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a nonionic surfactant can be used, and the surfactant concentration in the etching solution is usually 0.00. It is preferably 001 to 1% by weight, particularly 0.005 to 0.1% by weight.
[0032]
By the way, the fine particles present in the etching solution may inhibit uniform etching as the pattern size is reduced. Therefore, the fine particles having a particle diameter of 0.5 μm or more in the etching solution are 1000 particles / ml or less. It is preferable to remove in advance. Removal of fine particles in the etching solution can be performed by filtering the etching solution using a precision filter. The filtration method may be a one-pass method, but a circulation method is more preferable from the viewpoint of the removal efficiency of fine particles.
[0033]
The pore size of the precision filter used for removing fine particles is preferably 0.2 μm or less. The filter material may be a fluororesin material such as high-density polyethylene or polytetrafluoroethylene.
[0034]
Etching how the present invention, such as a liquid crystal display device substrate, is suitable for the production of a liquid crystal display device substrate having a silver or silver alloy thin layer on the substrate surface, according to the present invention, these substrates fine Patterns such as electrode wirings can be etched uniformly with high accuracy.
[0035]
In the present invention, the silver or silver alloy thin film layer generally refers to a layer having a thickness of about 1 μm or less, preferably about 0.5 μm or less. The thickness of the silver or silver alloy thin film layer is usually 0.1 μm or more.
[0036]
In the etching method of the present invention, a new etching solution having a silver ion concentration of 0.005 to 1% by weight is filled in an etching tank or an etching solution supply device, and the etching solution is added to the silver or silver alloy thin film at the start of etching. Contact the substrate surface with the layer. A method for bringing the substrate surface into contact with the etching solution is arbitrary. For example, a new etching solution filled in the etching solution supply device is sprayed from the vertical direction onto the surface of the substrate through a spray nozzle or the like (spray method), or an etching bath is filled with the new etching solution. A general method such as a method of immersing the substrate in the liquid (immersion method) can be used, and the operating conditions are not particularly limited.
[0037]
For example, in the case of the spray method, the distance between the substrate to be etched and the spray nozzle and the spray pressure are adjusted based on the liquidity (especially viscosity) of the etching solution, and the amount of the etching solution applied to the substrate surface, What is necessary is just to determine a striking pressure. In general, the distance between the substrate surface and the spray nozzle is 50 to 150 mm, and the spray pressure of the etching solution is 0.01 to 0.5 MPa, preferably 0.05 to 0.2 MPa.
[0038]
What is necessary is just to select suitably the temperature of the etching liquid at the time of etching by the etching method of this invention from the general etching temperature range, ie, 20-50 degreeC. In particular, in the present invention, it is preferably performed in a low temperature range of a general etching temperature range, and is preferably performed at 20 to 40 ° C, more preferably 25 to 35 ° C, and particularly preferably 25 to 30 ° C.
[0039]
In the etching method of the present invention, the silver ion concentration of the etching solution used is 0.005 to 1% by weight. However, the etching of the silver or silver alloy layer increases the silver ion concentration in the etching solution. Therefore, when the etching solution is repeatedly used, the silver ion concentration in the etching solution may increase excessively. Therefore, in such a case, for example, the silver ion concentration in the etching solution is measured, and if necessary, a part of the etching solution is extracted so that the silver ion concentration does not become higher than the appropriate range of the present invention, The silver ion concentration may be adjusted by adding a new etching solution (containing no silver ions). At this time, it is more preferable to adjust the concentration by adding other components (phosphoric acid, nitric acid, acetic acid, etc.) in consideration of the concentration.
[0040]
In the present invention, the spent etching solution can be recycled and used by adjusting the silver ion concentration and the concentration of other components in the etching solution as described above. Then, the generation of etching residues and excessive side etching can be suppressed without performing overetching more than necessary, and uniform and stable etching can be performed.
[0041]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[0042]
Examples 1-10, Comparative Examples 1-3
A silver layer (thickness 0.2 μm) was formed as a metal thin film layer on the glass substrate by sputtering, and a positive photoresist layer (thickness 1.2 μm) was spin-coated thereon. The photoresist line having a width of 5 μm was removed every 70 μm in the vertical direction and the photoresist line having a width of 5 μm was removed every 200 μm in the horizontal direction by photolithography.
[0043]
A substrate cut into a width of about 10 mm and a length of about 50 mm was used as a sample for etching test.
[0044]
An etching solution was prepared by mixing phosphoric acid (85 wt%), nitric acid (70 wt%), acetic acid (glacial acetic acid), silver (99% silver powder), and pure water so as to have the composition shown in Table 1. 200 g of each etching solution was put into a 200 cc beaker, and the temperature was adjusted to 30 ° C. The etching test sample was immersed in this, and the etching was performed for 60 seconds without causing over-etching while moving the sample vertically and horizontally. Next, the sample was taken out, washed with ultrapure water (manufactured by Nippon Millipore: MilliQSP) for 1 minute, and then air-dried using clean air.
[0045]
The state of the substrate surface after etching was observed by using a laser microscope (manufactured by Keyence Co., Ltd .: VK-8500) and observing the etched portion having a width of 5 μm where silver should be etched at about 1000 times. The observation was performed at 200 randomly selected locations, and the portion where there was no silver residue in the etched portion was regarded as acceptable, and the evaluation was made based on the acceptable ratio (acceptance rate). The results are shown in Table 1.
[0046]
In addition, the increase in the silver ion concentration in the etching solution after completion of the etching was extremely small, and in all the examples and comparative examples, the increase was about 2 wtppm.
[0047]
[Table 1]

[0048]
From Table 1, the following is clear. That is, when etching is performed so as not to over-etching in the conventional art of the comparative example, whereas locations remaining渣発students increases, according to the e etching method of the present invention embodiments, excessive over Even in an etching time when etching is not performed, generation of a residue can be sufficiently suppressed, and the effect of non-uniform etching due to side etching is excellent.
[0049]
In particular, from the results of Example 1 and Example 5, when the acetic acid concentration in the etching solution is within the range of 15 to 35% by weight (25.4% by weight in Table 1), the silver ions in the etching solution are reduced. It can be seen that even a small amount has an excellent effect.
[0050]
【The invention's effect】
As described above in detail, according to the etching how the present invention, without undue etching (over-etching), it is possible to suppress the occurrence of the silver or silver alloy residues and therefore, not due to side etching Uniform etching can be prevented. Therefore, according to the present invention, it is possible to carry out fine processing of a highly accurate silver or silver alloy thin film in a short time with high dimensional accuracy, uniformly and stably.

Claims (5)

In a method of etching a silver or silver alloy thin film layer present on a substrate surface with an etching solution, an etching solution having a silver ion concentration of 0.005 to 1% by weight is filled in an etching tank or an etching solution supply device, and the etching solution An etching method for contacting a substrate surface having a silver or silver alloy thin film layer,
An etching method comprising controlling the concentration of silver ions in an etching solution to be always 0.005 to 1% by weight.   The etching method according to claim 1, wherein the etching solution contains phosphoric acid, nitric acid, and acetic acid.   The etching method according to claim 2, wherein the acetic acid concentration is 1% by weight or more.   4. The etching method according to claim 2, wherein the phosphoric acid concentration in the etching solution is 10 to 80% by weight and the nitric acid concentration is 0.1 to 15% by weight. The etching method according to any one of claims 1 to 4 , wherein the etching solution temperature is 35 ° C or lower.