JPH06333912A - Hydrofluoric acid etchant - Google Patents

Abstract

PURPOSE:To obtain a hydrofluoric acid liquid chemical composition which can reduce the haze of glass resulting from the rugged surface of the glass and does not lower the etching rate of a thin film composed of SiOx, SiNx, etc., by mixing a specific amount of B in the etchant. CONSTITUTION:The etchant contains B by 0.2-20 at. wt.%. It is preferable that the etchant contains HF and NH4F by 0.1-65 and 0.1-60wt.%, respectively. It is also preferable, in addition, that the etchant contains at least acetic acid, nitric acid, or surface-active agent by 1-60%. It is especially preferable that the etchant contains acetic acid by 1-50%. For example, B2O3 is added as a B component to an etchant prepared by mixing 19-BHF (prepared by mixing 50% HF with 40% NH4F at a mixing ratio of 1:9) available on the market with 100% reagent acetic acid at a volumetric mixing ratio of 4:1. In such a case, the relations between the adding amount of B and the surface roughness Ra of aluminoborosilicate alkali-free glass after dipping and between the adding amount and the etching rate of an SiNx thin film become those shown in the figure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an etching process using a hydrofluoric acid-based chemical solution for manufacturing various displays.
The present invention relates to a chemical composition that reduces the haze generated in glass at that time.

[0002]

2. Description of the Related Art In recent years, an increasing number of liquid crystal displays have devices such as thin film transistors directly formed on a glass substrate. In this device manufacturing process, the glass substrate is often exposed to an etchant containing hydrofluoric acid because it etches a thin film of SiO _x , SiN _x, or the like.

When glass is exposed to a hydrofluoric acid type chemical solution, a sparingly soluble reaction product is generated on the surface, which acts as a masking material to cause etching unevenness, and 0.01 μm on the glass surface even after the reaction product is removed. Unevenness with a height of ~ 1 μm remains, producing a haze pattern. This haze pattern appears as unevenness on the screen when used as a display, and there is a problem that it cannot be used.

There are two approaches to prevent such haze. One is to make the composition of the glass durable, and the other is to make the composition of the etchant less damaging to the glass.

Considering the composition of the glass as a composition having durability against a hydrofluoric acid type chemical solution, particularly a buffered hydrofluoric acid containing ammonium fluoride as a buffer, a large amount of B ₂ O ₃ is contained. It is preferably glass. But B ₂
Since the glass containing a large amount of O ₃ has a low strain point, it has a problem in heat resistance such that it is easily deformed by heat treatment performed in a device manufacturing process and has large thermal shrinkage. The glass containing a large amount of B ₂ O ₃ is vigorously volatilized during production of B ₂ O ₃ is, there is a manufacturing problem such as causing striae.

Considering the composition of the etchant that causes less damage to the glass, a composition having a low concentration of hydrofluoric acid is desirable. However, with an etchant having a low concentration of hydrofluoric acid, there is a problem that the etching rate of a thin film of SiO _x , SiN _x or the like, which is intended for etching, becomes slow, and productivity deteriorates.

[0007] As described above, B haze does not occur in ₂ O ₃ content is sufficiently high glass composition, haze occurs on the entire surface in the glass opposite to the B ₂ O ₃ content is less composition, frosted become that way. However, when the content of B ₂ O ₃ is a composition between the two, the surface state of the glass before immersion in the etching solution affects the haze strength after immersion and drying.

The etching solution is used to reduce the surface tension.
Often, acetic acid or nitric acid or a surfactant is added as disclosed in JP-A-58-55323 and JP-A-58-55324. When such an additive is added, the haze after immersion may be deteriorated, which may cause a problem.

[0009]

The object of the present invention is to reduce the haze of irregularities generated on the glass surface by dipping in an etching solution, and to not lower the etching rate of thin films such as SiO _x and SiN _x. , To provide a composition of a hydrofluoric acid-based drug solution.

[0010]

The present invention provides a hydrofluoric acid-based etching solution containing 0.2 to 20% of B in atomic weight%. The etching liquid of the present invention preferably contains 0.1 to 65% of HF in weight% (hereinafter simply referred to as%), and further preferably contains 0.1 to 60% of NH ₄ F. It is also preferable to contain at least one selected from the group of acetic acid, nitric acid and a surface active agent.
It is particularly preferable that the content is up to 50%.

Next, the reason for limiting the composition range of each component as described above will be described. When B is 0.2% or less, haze generated on the glass surface is not sufficiently improved, and when it is 20% or more, etching power is lost, which is not preferable. HF
If it is less than 0.1% by weight, the etching power is weak, and if it is more than 65%, the etching power is too strong to control etching. When NH ₄ F is 60% or more, it is not sufficiently dissolved in water, which is not preferable. Any one of acetic acid, nitric acid and a surfactant added to reduce the surface tension of the etching solution is 0.
If it is less than 1%, the effect of the additive is not sufficient, and if it exceeds 60%, it hinders etching, which is not preferable. The most effective haze improvement appears when the acetic acid content is 1 to 50%.

In the present invention, B may be present as B in the above-mentioned amount, and the sources thereof are B ₂ O ₃ , H ₃ BO ₃ and HBF ₄
Any form such as Usually, B ₂ O ₃ can be preferably used.

[0013]

It is considered that when the etching solution of the present invention is used, easily soluble complex ions are generated in water containing B, and crystals that cause unevenness on the surface are not generated.

[0014]

Example As a base hydrofluoric acid-based etching solution, commercially available 19BHF (50% HF and 40% NH ₄ F mixed 1: 9) and 100% reagent acetic acid were mixed at a volume ratio of 4 at room temperature. A mixture of 1: 1 was used. The immersion of the glass in the etching solution was performed at room temperature for 5 minutes using aluminoborosilicate-based alkali-free glass whose surface was mirror-polished. After the immersion, the glass plate was washed and dried, and the degree of haze remaining on the glass was measured. The degree of haze was evaluated as a surface roughness Ra with a stylus type surface roughness meter. Apart from the above glass immersion test, the etching rate of the SiN _x thin film was also measured.

The measurement was carried out by applying an acid resistant resin to a part of the SiNx thin film prepared by the vapor phase method on a Si wafer and immersing it in an etching solution at room temperature for 5 minutes as in the glass immersion test. After washing the acid resistant resin with an organic solvent, the step difference was measured with a stylus type surface roughness meter, and the etching rate was measured as an average of 5 minutes.

FIG. 1 and Table 1 show the amount of B added, Ra (degree of haze), and etching of SiN _x thin film when B ₂ O ₃ was added as a B component to the above hydrofluoric acid-based etching solution. Show the rate relationship.

[0017]

[Table 1]

From the figure, in 19BHF containing no B, Ra
While the haze is large at 150, the surface roughness with addition of B, that is, the haze generated on the glass surface decreases, and the addition of 1.13 atomic weight% gives 22 Å, which is the same as the surface roughness of the glass before immersion, and haze is completely You can see that it no longer occurs.

The etching rate of the SiN _x thin film slightly increased with the addition of B, but the surface roughness of the glass was 1.13 ~.
In the range of addition of 2.26 atomic weight%, an etching rate similar to that of no addition is secured.

The liquid composition in this example is 2.63 of B.
The reason why the SiN _x etching rate decreased with the addition of wt% was that HF was replaced by HBF ₄ which has a weak etching power by the following formula: 8HF + B ₂ O ₃ → 2HBF ₄ + 3H ₂ O. It seems that the haze problem has been solved.

[0021]

The composition of the hydrofluoric acid type chemical solution according to the present invention is suitable for the purpose of reducing the haze generated on the glass surface. Further, by properly selecting the liquid composition, especially the amount of B, a predetermined etching rate can be secured.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of B added, the surface roughness, and the etching rate of SiN _x .

Claims (5)

[Claims] 1. A hydrofluoric acid-based etching solution containing 0.2 to 20% of B in atomic weight%. 2. The hydrofluoric acid-based etching solution according to claim 1, which contains 0.1 to 65% by weight of HF. 3. A hydrofluoric acid-based etching solution according to claim 1, which contains 0.1 to 60% by weight of NH ₄ F. 4. The hydrofluoric acid-based etching solution according to claim 1, which contains 0.1 to 60% by weight of at least one selected from the group consisting of acetic acid, nitric acid and a surface active agent. 5. The hydrofluoric acid-based etching solution according to claim 4, which contains acetic acid in an amount of 1 to 50% by weight.