JPH056874A - Dry etching method - Google Patents

Abstract

PURPOSE:To solve the following problems: to form a recessed part or a through hole in a glass substrate by means of a machining operation is not suitable for a working operation in large quantities and a strain is left on the substrate; and to form the recessed part or the through hole by a wet etching operation cannot form a sidewall perpendicular to the main face of the substrate and its working speed is slow. CONSTITUTION:A parallel-plate dry etching apparatus according to an anode coupling system is used; a mixed gas which is composed of SF6 and O2 is used as a reaction gas; an interelectrode interval, an etching pressure, a gas flow rate and impressed high-frequency electric power are limited to proper ranges. Thereby, many recessed parts 2 or many through holes which are provided with sidewalls perpendicular to a substrate main face 11 can be formed in a glass substrate 1 at a large processing speed and uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for forming a recess or a through hole having a side wall perpendicular to a main surface of a glass substrate for manufacturing a micromechanical component, for example.

[0002]

2. Description of the Related Art There are two conventional processing methods for forming a recess or a through hole from a main surface of a glass substrate: general mechanical processing and wet etching using a hydrofluoric acid solution or the like. The machining method is performed by directly processing from one main surface 11 side of the glass substrate 1 as shown in FIGS. 3 (a) and 4 (a), and then forming the recess 2 as shown in FIG. 3 (b). This is a method of forming the through hole 3 as shown in (b). On the other hand, in the wet etching method, as shown in FIGS. 5 (a) and 6 (a), a mask 41 made of photoresist or the like is adhered to one main surface 11 of the glass substrate 1 and the surface 11 is exposed with a hydrofluoric acid solution. Etching from the portion to recess 21 as shown in FIG. 5 (b) to FIG. 6 (b)
The through hole 31 as shown in is formed.

[0003]

However, the glass substrate 1
In the method of forming the recesses or through holes by general machining, the recesses 2 or through holes 3 having side walls perpendicular to the main surface 11 of the substrate can be formed, but the processed parts are processed one by one. Therefore, it takes a very long time to process a large amount. Further, there is a problem that microcracks and processing strains remain on the processed surface of the recess or the through hole, and cracks occur when used as a micromechanical component.

On the other hand, wet etching using a hydrofluoric acid solution or the like is isotropic etching, and therefore, it is not shown in FIG.
As shown in No. 31, it is impossible to form a recess or a through hole having a side wall perpendicular to the main surface 11 of the glass substrate 1. Further, since a resist is used as a mask, a large etching selectivity cannot be obtained, and it is difficult to form deep recesses or through holes. Further, as described in, for example, "VLSI Process Data Handbook" published by Science Forum, since the etching rate is very small, about 150Å / min, it has a drawback of long processing time and poor productivity.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and to form a recess or through hole having a side wall perpendicular to one main surface in a glass substrate at high speed and with high accuracy, and also to provide hundreds of recesses or through holes. It is an object of the present invention to provide a dry etching method capable of forming holes with good uniformity at one time.

[0006]

In order to achieve the above object, the present invention provides a dry etching apparatus of an anodic bonding type in which a mask having a window is applied to wet etching of one main surface of a glass substrate to be processed. In a dry etching method in which a glass substrate is processed through a window of a mask using, the mask is made of aluminum and the parallel plate electrode spacing is 30
Under the conditions of ~ 70mm and etching pressure of 25 ~ 50Pa, a flow rate of 6 ~ 150ccm of sulfur hexafluoride gas and a flow rate of 1 ~ 50ccm of oxygen gas are simultaneously introduced into the reaction chamber of the equipment, and the electrode area is between both electrodes. The high frequency power of 0.3 to 0.6 W / cm ² is applied. It is effective that the flow rate of oxygen gas is 20 to 50% of the flow rate of sulfur hexafluoride gas. Further, it is possible to form a recess or a through hole in the glass substrate by this method.

[0007]

The mechanism of the dry etching reaction of the present invention is considered as follows. First, SF ₆ gas is dissociated in plasma to generate F radicals. Next, F radicals adhere to the glass substrate surface exposed in the window of the mask,
SiF ₄ is produced by reacting with Si atoms present in the glass, and this SiF ₄ has a boiling point of -130.4 ° C. at 10 Torr, which is so low that it volatilizes spontaneously and is exhausted. On the other hand, O ₂
The gas also dissociates in the plasma at the same time, and O radicals are generated. The O radicals are the F radicals and Si on the surface of the processed part.
It is used to instantly generate intermediate oxide SiO when reacting with atoms. By reacting this SiO with F radical
SiF ₄ is formed and volatilized. Therefore, it is considered that the O radical plays a large role in the progress of the etching reaction. The reason is that, from the etching speed when etching was performed with SF ₆ gas alone, SF ₆ gas and O
_This is because there is a fact that the etching becomes larger when etching is performed with a mixed gas of _two gases.

Then, the side wall of the recess formed by the etching through the window of the mask is temporarily oxidized by O radicals existing in the plasma, and the etching proceeds while the side wall is protected by the temporary oxide at this time. . This state is maintained until the glass substrate is formed with a recess having a predetermined depth or penetrates. However, in the etching reaction, not only the sidewall of the recess but also the bottom of the recess are oxidized, but the ions dissociated from the reaction gas molecules, which are considered to be present in the plasma in a trace amount, are accelerated toward the bottom of the recess by the electric field in the plasma and collide. The oxide film formed on the bottom surface is removed by the impact, so that the instantaneous oxide film on the bottom surface does not play a protective role, and etching of only the bottom surface of the recess proceeds. As a result, the distance between parallel plate electrodes is 30 to 70 m.
m, applied high-frequency power 0.3 to 0.6 W / cm ² _, etching pressure 25 to 50 Pa, sulfur hexafluoride gas flow rate 6 to 150 ccm, oxygen gas flow rate 1 to 50 ccm. It is presumed that a recess or through hole perpendicular to the surface is formed.

[0009]

1 (a) and 1 (b) show an outline of a method for forming a recess in a glass substrate according to an embodiment of the present invention, in which parts common to those in FIGS. It is attached. For example, an aluminum thin film with a thickness of 1 μm is formed on one main surface 11 of a glass substrate 1 with a thickness of 500 μm by a vacuum deposition method, and phosphoric nitric acid is used as an etching solution for patterning to form a glass as shown in FIG. 1 (a). An aluminum mask 4 was formed to expose the substrate surface 11 at the processed portion. Next, JP-A-2
Using the anodic coupled dry etching device described in -280324, SF ₆ gas with a flow rate of 35 ccm and a flow rate of 35 ccm
A mixed gas of 15 ccm of O ₂ gas was flown in, the pressure in the reaction chamber was maintained at 30 Pa, and high frequency power of 0.45 W / cm ² was applied to the parallel plate electrodes facing each other at intervals of 50 mm. A voltage was applied to generate plasma. As a result, a physicochemical reaction occurs between the exposed glass and the radicals or reaction gas ions present in the plasma, and
As shown in (b), a recess 2 having a side wall of 500 μm square and a depth of 300 μm and perpendicular to the main surface 11 was formed at an etch rate of 3000 Å / min.

2 (a) and 2 (b) show an outline of a method of forming a through hole in a glass substrate according to another embodiment of the present invention, and the same parts as those in FIG. 1 are designated by the same reference numerals. . Also in this case,
Similar to the embodiment shown in FIG. 1, after the aluminum mask 4 is formed as shown in FIG. 2 (a), dry etching is performed under the same conditions to obtain the depth shown in FIG. 2 (b). A through hole 3 having a side wall perpendicular to the main surface 11 of 500 μm was formed.

Further, the distance between the parallel plate electrodes is in the range of 30 to 70 mm, the etching pressure is in the range of 25 to 50 Pa, the flow rate of SF ₆ gas is in the range of ₆ to 150 ccm, and the flow rate of O ₂ gas is 1 to 50.
In the range of ccm, the applied high frequency power density is 0.3-0.6W
1 and FIG.
It was found that the recessed portion or the through hole as shown in FIG. A suitable mixing ratio of O ₂ gas to SF ₆ gas was 20 to 50%.

[0012]

According to the present invention, by using an aluminum mask and limiting various conditions to an appropriate range, a glass substrate has a side wall perpendicular to the main surface of the substrate which cannot be formed by the wet etching method, for example, It was possible to form a 300 μm deep recess or a 500 μm deep through hole by dry etching. Further, since the processing speed is very high, the processing time is short, and a large number of recesses or through holes can be uniformly formed in the glass substrate at the same time, so that extremely high productivity is secured. Further, in the case of the method according to the present invention, the main component of the etching reaction is the radicals in the plasma, and since the applied power is very small, microcracks do not remain on the processed surface of the glass substrate and residual strain is very small. There is also the advantage of being small.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of forming a recess on a glass substrate according to an embodiment of the present invention in the order of (a) and (b).

FIG. 2 is a cross-sectional view showing a method of forming a through hole in a glass substrate according to another embodiment of the present invention in the order of (a) and (b).

FIG. 3 is a cross-sectional view showing a method of forming a recess on a glass substrate by conventional machining in the order of (a) and (b).

FIG. 4 is a sectional view showing a method of forming a through hole in a glass substrate by conventional machining in the order of (a) and (b).

FIG. 5 is a cross-sectional view showing a method of forming a recess in a glass substrate by conventional wet etching in the order of (a) and (b).

FIG. 6 is a sectional view showing a method of forming a through hole in a glass substrate by conventional wet etching in the order of (a) and (b).

[Explanation of symbols]

1 glass substrate 11 Substrate main surface 2 recess 3 through holes 4 Aluminum mask

Claims (4)

[Claims] 1. A dry etching method of depositing a mask having a window on one main surface of a glass substrate to be processed, and processing the glass substrate from the window of the mask by using a dry etching apparatus of an anodic bonding method. Is made of aluminum, and the parallel plate electrode spacing is 30 to 70 mm and the etching pressure is 25 to 50 Pa. In the reaction chamber of the apparatus, a flow rate of 6 to 150 ccm of sulfur hexafluoride gas and a flow rate of 1 to 50 ccm of oxygen are provided. Gas is introduced at the same time, and the area between the electrodes is 0.3-
A dry etching method in which a high frequency power of 0.6 W / cm ² is applied. 2. The flow rate of oxygen gas is the same as that of sulfur hexafluoride gas.
The dry etching method according to claim 1, which is 20 to 50%. 3. The dry etching method according to claim 1, wherein a recess is formed in the glass substrate. 4. The dry etching method according to claim 1, wherein a through hole is formed in the glass substrate.