JP2979737B2 - Dry etching method - Google Patents

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 from one main surface of a glass substrate, for example, for manufacturing a micromechanical component.

[0002]

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

[0003]

However, the glass substrate 1
In a method of forming a concave portion or a through hole by general machining, it is possible to form a concave portion 2 or a through hole 3 having a side wall perpendicular to the main surface 11 of the substrate. Therefore, it takes a very long time to process a large amount. In addition, there is a problem that microcracks and processing distortion remain on the processing surface of the concave portion or the through-hole, and the microcrack is broken when used as a micromechanical component.

On the other hand, wet etching using a hydrofluoric acid solution or the like is an isotropic etching, and therefore, FIG.
As shown in (31), a recess or a through hole having a side wall perpendicular to the main surface 11 of the glass substrate 1 cannot be formed. Further, since a resist is used as a mask, a large etching selectivity cannot be obtained, and it is difficult to form a deep concave portion or a through hole. Furthermore, as described in, for example, "Super LSI Process Data Handbook" published by Science Forum, the etch rate is very small at about 150 .mu.m / min, so that there is a disadvantage that the processing time is long and the productivity is poor.

Accordingly, 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 high accuracy, and to provide several hundred recesses or through-holes. It is an object of the present invention to provide a dry etching method capable of forming holes at once with good uniformity.

[0006]

In order to achieve the above object, the present invention provides a dry etching apparatus of the anodic bonding type, in which a mask having a window is applied to wet etching of one principal surface of a glass substrate to be processed. In a dry etching method of processing a glass substrate from a window of a mask using a mask, a mask is formed of aluminum, and a distance between parallel plate electrodes is 30.
Sulfur hexafluoride gas at a flow rate of 6 to 150 ccm and oxygen gas at a flow rate of 1 to 50 ccm were simultaneously introduced into the reaction chamber of the apparatus under the conditions of ~ 70 mm and an etching pressure of 25 to 50 Pa, and the electrode area was set between both electrodes. To be applied with a high frequency power of 0.3 to 0.6 W / cm ² . It is effective that the flow rate of the oxygen gas is 20 to 50% of the flow rate of the sulfur hexafluoride gas. In addition, a concave portion or a through hole can be formed in the glass substrate by this method.

[0007]

The dry etching reaction mechanism of the present invention is considered as follows. First, SF ₆ gas is dissociated in plasma, and F radicals are generated. Next, F radicals adhere to the surface of the glass substrate exposed at the window of the mask,
Reacts with Si atoms present in the glass SiF ₄ is produced, the SiF ₄ is boiling point for very low -130.4 ° C. at 10 Torr, and is exhausted volatilized spontaneously. On the other hand, O ₂
The gas also dissociates in the plasma at the same time, generating O radicals. These O radicals are formed by F radicals on the surface of the workpiece and Si radicals.
It is used to instantaneously generate an intermediate oxide, SiO, when reacting with atoms, and this SiO reacts with F radicals.
SiF ₄ is formed and volatilizes. 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 when etching is performed with a mixed gas of _two gases, it becomes larger.

The side wall of the concave portion formed by etching from the window of the mask is temporarily oxidized by O radicals or the like 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 a concave portion having a predetermined depth is formed or penetrates the glass substrate. However, in the etching reaction, the bottom of the recess is oxidized simultaneously with the sidewall of the recess, but ions dissociated from the reactive gas molecules, which are considered to be present in a small amount in the plasma, 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 only the bottom surface of the concave portion is etched. As a result, the parallel plate electrode spacing 30 to 70 m
m, applied high frequency power of 0.3 to 0.6 W / cm ² _, etching pressure of 25 to 50 Pa, flow rate of sulfur hexafluoride gas of 6 to 150 ccm, and flow rate of oxygen gas of 1 to 50 ccm. It is presumed that a concave portion or a through hole perpendicular to the surface is formed.

[0009]

1 (a) and 1 (b) show an outline of a method for forming a concave portion in a glass substrate according to an embodiment of the present invention. The same reference numerals as in FIGS. 3 to 6 denote the same parts. Is attached. For example, an aluminum thin film having a thickness of 1 μm is formed on one main surface 11 of a glass substrate 1 having a thickness of 500 μm by a vacuum evaporation method, and is patterned using phosphoric nitric acid as an etching solution to form a glass as shown in FIG. An aluminum mask 4 exposing the substrate surface 11 at the portion to be processed was formed. Next, Japanese Unexamined Patent Publication
Using a dry etching apparatus of anodic bonding method disclosed in -280,324 JP, SF ₆ gas flow rate 35ccm and flow
A mixed gas of 15 ccm of O ₂ gas was introduced, the pressure in the reaction chamber was maintained at 30 Pa, and a high frequency power of 0.45 W / cm ² with respect to the electrode area was supplied to parallel plate electrodes facing each other up and down at 50 mm intervals. Upon application, a plasma was generated. As a result, a physicochemical reaction occurs between radicals and reaction gas ions present in the plasma and the exposed glass.
As shown in (b), a concave portion 2 having a side wall perpendicular to the main surface 11 of 500 μm square and depth of 300 μm was formed at an etching rate of 3000 ° / min.

FIGS. 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 portions common to FIG. 1 are denoted by the same reference numerals. . Again,
After forming an aluminum mask 4 as shown in FIG. 2A in the same manner as in the embodiment shown in FIG. 1, dry etching is performed under the same conditions so that the depth as shown in FIG. A through hole 3 having a side wall perpendicular to the main surface 11 of 500 μm was formed.

Further, the interval between the parallel plate electrodes is 30 to 70 mm, the etching pressure is 25 to 50 Pa, the flow rate of SF ₆ gas is ₆ to 150 ccm, and the flow rate of O ₂ gas is 1 to 50 ccm.
In the range of ccm, and the applied high-frequency power density is 0.3 to 0.6 W
1 or FIG.
It has been found that a recess or a through hole as shown in FIG. The mixing ratio of the O ₂ gas to the SF ₆ gas was suitably from 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. A recess having a thickness of 300 μm or a through-hole having a depth of 500 μm could be formed by dry etching. Further, since the processing speed is very high, the processing time is short, and since a large number of concave portions or through holes can be formed simultaneously and uniformly in the glass substrate, extremely high productivity is secured. Furthermore, in the case of the method according to the present invention, the main component of the etching reaction is radicals in the plasma, and the applied power is very small, so that microcracks do not remain on the processed surface of the glass substrate and the residual strain is extremely low. There is also the advantage of being small.

[Brief description of the drawings]

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

FIG. 2 is a 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 sectional view showing a method of forming a concave portion in 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 sectional view showing a method of forming a concave portion on a glass substrate by conventional wet etching in the order of (a) and (b).

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate 11 substrate main surface 2 concave portion 3 through hole 4 aluminum mask

Claims (4)

(57) [Claims] In a dry etching method, a mask having a window is attached on one main surface of a glass substrate to be processed, and the glass substrate is processed from a window of the mask using an anodic bonding type dry etching apparatus. Is formed in aluminum, under the condition that the distance between the parallel plate electrodes is 30 to 70 mm and the etching pressure is 25 to 50 Pa, the sulfur hexafluoride gas having a flow rate of 6 to 150 ccm and the oxygen gas having a flow rate of 1 to 50 ccm are introduced into the reaction chamber of the apparatus. Gas is introduced at the same time, and 0.3 ~
A dry etching method in which a high frequency power of 0.6 W / cm ² is applied. 2. The method according to claim 1, wherein the flow rate of the oxygen gas is less than the flow rate of the sulfur hexafluoride gas.
2. The dry etching method according to claim 1, wherein the content is 20 to 50%. 3. The dry etching method according to claim 1, wherein a concave portion 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.