JPH11199400A - Crystal substrate etching method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When a quartz substrate is etched with an etching solution containing hydrofluoric acid as a main component, a long etching time is required to make the etched sectional shape close to vertical. SOLUTION: All or a part of a part to be dissolved in an etching solution is irradiated with a laser in advance to form an altered layer. Thereafter, the substrate is immersed in an etching solution to perform etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to etching of a quartz substrate when elements using quartz such as vibrators and sensors are formed by wet etching of the quartz substrate.

[0002]

2. Description of the Related Art As a conventional technique, laser irradiation before etching has not been performed. This step will be described with reference to FIG. FIG. 6 is a view showing a conventional process, and shows a cross section of a quartz substrate to be etched.

In FIG. 6A, a corrosion-resistant film 2 that is not dissolved in an etching solution is formed on both surfaces of a quartz substrate 1. The corrosion-resistant film 2 is generally composed of a two-layer metal film, for which chromium or titanium is used for the base and gold or the like is used for the upper layer. A photosensitive photoresist material 3 is applied thereon as shown in FIG. Next, as shown in FIG. 6C, a desired photoresist pattern 4 is formed by exposure and development. Then, the corrosion resistant film 2 is etched as shown in FIG. 6D, and the quartz substrate 1 is etched as shown in FIG. Here, as an etching solution used for etching, an ammonium bifluoride solution, a mixed solution of ammonium fluoride solution and hydrofluoric acid, or the like is used. By removing the photoresist pattern 4 and the corrosion-resistant film 2 after the etching, FIG.
As shown in (f), a quartz substrate having a desired shape can be obtained. As described above, laser irradiation before etching was not performed as in the present invention.

[0004]

In the above prior art, the etched cross section of the quartz substrate is not completely vertical, and a portion of the quartz crystal element such as a vibrator or a sensor which is desired to have a perpendicular cross section is not necessarily vertical. If any, etching was performed for a long time to make the cross section as vertical as possible. Therefore, there was a problem that etching had to be performed for a long time. Further, in order to perform etching for a long time, FIG.
In (c), the size of the photoresist pattern 4 must be made large in accordance with the etching time, and there is a problem that the degree of freedom in design is lost. Here, the reason why the cross section does not become vertical is that when the crystal substrate is wet-etched, there is always a direction in which a projection is generated in the cross section due to the anisotropy of the crystal of the crystal. This is as described in FIG. 6 on page 208 of the December 1990 issue of Monthly Semiconductor World.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method of etching a quartz substrate in which an etched cross section is made vertical. Provided is a method for etching a quartz substrate that does not require etching and does not lose design flexibility.

[0006]

A method of etching a quartz substrate according to the present invention is characterized in that all or a part of a portion to be dissolved in an etching solution is irradiated with a laser beam in advance, and then immersed in the etching solution for etching. .

[0007] Alternatively, the etching is temporarily stopped during the etching, all or a part of the portion to be dissolved in the etching solution is irradiated with a laser, and the etching is further performed using an etching solution to dissolve the quartz substrate. Laser irradiation is repeated.

Alternatively, all or a part of a portion to be dissolved in an etching solution is irradiated with a laser, and etching is performed using an etching solution for dissolving a quartz substrate, or the above-described laser irradiation and etching are repeated. I do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred example of the method for etching a quartz substrate according to the present invention will be described in detail.

Embodiment 1 In Embodiment 1, an outline of a method for etching a quartz substrate according to the present invention will be described.

FIG. 1 is a process chart showing an outline of the present invention. In FIG. 1, the quartz substrate 1 is shown in a direction viewed from a cross section.

FIG. 1A shows a state in which a pattern 5 of a corrosion-resistant film and a pattern 4 of a photoresist have already been formed on the quartz substrate 1. Here, the photoresist pattern 4 is not necessary when etching the quartz substrate 1 in the future, and may or may not be present. FIG. 1 shows a certain state. Then, in the conventional example, the quartz substrate 1 is etched, but in the present invention, laser irradiation is performed as shown in FIG. In this figure, the laser beam 6 is schematically shown. The part irradiated with the laser beam 6 is all or a part of the part to be dissolved in the etching solution. This will be described later. In the embodiment shown in FIG. 1, the irradiation of the laser beam is set to a part of a portion to be dissolved in the etching solution.

When the laser beam 6 is irradiated, thermal energy is transmitted from the surface of the crystal to the inside of the crystal substrate 1 by the energy of the laser beam 6. When the heat energy becomes higher than a certain value, a phase transition of the crystal of the quartz substrate 1 or the like is caused, and the altered layer 7 is formed. The required number of the deteriorated layers 7 are formed in necessary portions.

FIG. 1C shows that the altered layer 7 is formed on the back side of the quartz substrate by the laser beam 7.

Next, the quartz substrate 1 is etched as shown in FIG. Hydrogen fluoride water or the like that dissolves the quartz substrate 1 is used as an etchant. At this time, the altered layer 7 dissolves much faster than the quartz substrate 1. Therefore, it is possible to make the etching time very short.

If etching is performed for a necessary time and the photoresist pattern 4 and the corrosion-resistant film pattern 5 are removed, the result is as shown in FIG. 1E, and a desired crystal shape is obtained.

(Embodiment 2) FIG. 2 is a sectional view showing a laser irradiation position according to an embodiment of the present invention. The position where the altered layer is formed will be described using this.

FIG. 2A shows a case where the altered layer 7 is formed by laser irradiation on all of the portions to be dissolved in the etching solution. In this case, it is important to control the laser irradiation apparatus in order to perform laser irradiation to the vicinity of the photoresist pattern 4 and the corrosion-resistant film pattern 5 to form the altered layer 7.

In FIG. 2B, similarly to FIG. 2A, the deteriorated layer 7 is formed by irradiating the laser to the vicinity of the pattern 4 of the photoresist and the pattern 5 of the anti-corrosion film. The altered layer 7 is not formed on all the portions to be irradiated by laser irradiation. This is because when a quartz substrate 1 called a quartz Z plate is used, a projection is formed in the + X-axis direction, so that the altered layer 7 is formed only in the vicinity of the + X-axis direction of the quartz substrate 1 remaining after etching. The dissolution rate of this portion in the etching solution is increased, and the protrusion in the + X-axis direction is reduced. The vicinity of the pattern 4 of the photoresist on the -X side and the pattern 5 of the anti-corrosion film are etched almost straight due to the anisotropy of the quartz crystal, so that there is no need to perform laser irradiation. Even when a substrate having a cutout angle other than the Z plate is used, laser irradiation may be performed in the vicinity of a portion where the cross section is desired to be vertical.

FIG. 2C shows a photoresist pattern 4.
And an altered layer 7 formed apart from the pattern 5 of the corrosion resistant film. It is difficult to irradiate a laser to the vicinity of the photoresist pattern 4 and the corrosion-resistant film pattern 5, and the purpose is to prevent heat by the laser from affecting the corrosion-resistant film pattern 5 and the photoresist pattern 4. is there.

FIG. 2D is almost the same as FIG. 2C, but the size of the altered layer 7 in the depth direction is shorter. This is effective when the thickness of the quartz substrate 1 is large.

Here, the reason why the use of the method for etching a quartz substrate of the present invention speeds up the etching will be described with reference to FIG.

FIG. 3 is a view showing a cross-sectional shape after etching when the Z-plate quartz substrate 1 is used as a photoresist pattern 4 and a corrosion-resistant film pattern 5 as a mask.
When the quartz substrate 1 is etched, +
A projection occurs in the X-axis direction. In FIG. 3, the projections 8 generated in the + X-axis direction in the case of the conventional method are indicated by broken lines, and are generated in the + X-axis direction of the etched shape after forming the altered layer 7 of FIG. The protrusions 9 are shown by solid lines at the same time. Here, the etching time in the case of the conventional method and the etching time in the case of the method of the present invention are the same.

In the case of the conventional method, the projection 9 generated in the + X direction is large, and it is necessary to perform further etching to reduce the projection. On the other hand, + in the case of the method of the present invention
The protrusion that occurs in the X direction is very small. This is because the anisotropy of quartz disappears in the altered layer generated by laser irradiation, and the etching rate becomes extremely high.

(Embodiment 3) An example in which an embodiment of the present invention is applied to a tuning fork type vibrator will be described with reference to FIG.

FIG. 4 is a front view of a quartz substrate showing a portion where laser irradiation is performed. Here, it is assumed that a tuning-fork type vibrator is formed using a Z-plate quartz substrate 1. For simplicity, the case where one tuning fork vibrator is formed on the quartz substrate 1 is shown.

On the quartz substrate 1, a tuning fork-shaped pattern 10 of a corrosion-resistant film and a photoresist has already been formed. That is, the process shown in FIG. 1A has already been completed.

What is important in manufacturing a tuning-fork type vibrator is that the characteristics of the vibrator are improved when the cross-sectional shapes of the tip portion of the tuning fork and the fork portion of the tuning fork are closer to vertical.
Therefore, in the third embodiment, laser irradiation is performed so that the cross section of the tuning fork tip portion and the tuning fork portion is perpendicular to each other. The laser irradiation is not performed here because the cross-sectional shape of the root portion of the tuning fork hardly affects the characteristics of the vibrator. However, in the case of a tuning fork type gyro sensor or the like, the cross-sectional shape of the root portion of the tuning fork may be important. In this case, this embodiment may be applied.

The portion 11 to be processed by the laser is formed along the + X direction of the tip of the tuning fork. In the −X direction, since the cross section is naturally vertical, it is not necessary to irradiate a laser in particular, but it may be performed when the etching rate is to be increased.

Further, a projection is liable to be formed on the cross section also at the cross section of the tuning fork, and the projection is irradiated with a laser because the projection has a bad influence on the vibrator characteristics.

Regarding the depth direction of laser irradiation,
1 (a) to 1 (c), or may be a part as shown in FIG. 1 (d).

Although the laser irradiation position has been described above, the laser irradiation position is not limited to only the position where the projection is formed as long as the position where the etching speed of the quartz crystal is to be increased is irradiated. However, laser irradiation is effective for reducing projections by etching in a short time.

(Embodiment 4) FIG. 5 shows that the etching is temporarily stopped during the etching, all or a part of the portion to be dissolved in the etching solution is irradiated with a laser, and the etching is performed using an etching solution to dissolve the quartz substrate. It is sectional drawing of the crystal which shows a process.

FIG. 5A shows a state in which the pattern 5 of the corrosion resistant film and the pattern 4 of the photoresist have already been formed on the quartz substrate 1. Here, the photoresist pattern 4 is not necessary when etching the quartz substrate 1 in the future, and may or may not be present.

FIG. 5B shows a shape in a state where the etching is temporarily stopped during the etching.

FIG. 5 (c) shows that the altered layer 7 is formed by irradiating a laser to the portion to be dissolved in the etching solution in FIG. 5 (b).

FIG. 5D shows a state in which the altered layer 7 is also formed on the opposite side of the surface where the altered layer 7 is formed in FIG. 5C. In FIG. 5C, if the deteriorated layer 7 can be formed from the front and back of the quartz substrate 1 by irradiating a laser from one side of the quartz crystal in the same manner, this step is not essential.

FIG. 5E shows a state in which etching is further performed after FIG.

As described above, the present invention can be applied to a thick quartz substrate by alternately performing etching and laser irradiation. Further, the conditions for forming the altered layer by laser irradiation are relaxed, and the layer can be formed with good control.

In the fourth embodiment, the procedure in which etching is performed halfway, laser irradiation is performed, and further etching is performed. However, these steps are combined to perform various combinations such as intermediate etching, laser irradiation, intermediate etching, laser irradiation, and etching. It is possible.
Alternatively, laser irradiation may be performed first, and a combination such as etching, laser irradiation, and etching may be performed.

[0041]

According to the present invention, the etching section of the quartz substrate can be made vertical by short-time etching without performing long-time etching. In addition, since the cross section can be made vertical by short-time etching, the degree of freedom in design is increased.

Further, since the etched cross section can be made vertical, there is an effect that characteristics are improved in a vibrator using quartz, other sensors, and the like.

[Brief description of the drawings]

FIG. 1 is a process chart showing an outline of an embodiment of the present invention.

FIG. 2 is a sectional view showing a laser irradiation position according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a quartz substrate after etching using a conventional technique and a cross-sectional view of a quartz substrate using one embodiment of the present invention.

FIG. 4 is a front view of a quartz substrate showing a portion where laser irradiation according to one embodiment of the present invention is performed.

FIG. 5 is a cross-sectional view of a quartz substrate showing a step of one embodiment of the present invention.

FIG. 6 is a cross-sectional view of a quartz substrate showing a process using a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Quartz substrate 2 Corrosion-resistant film 3 Photoresist 4 Photoresist pattern 5 Corrosion-resistant film pattern 6 Laser light 7 Altered layer 8 Protrusion generated in + X direction in the conventional method 9 In + X direction in the method of the present invention Produced protrusions 10 Corrosion resistant film and tuning fork pattern of photoresist 11 Portion processed by laser

Claims (3)

[Claims] In the case where a quartz crystal is etched into a desired shape using an etching solution that dissolves a quartz substrate,
A method for etching a quartz substrate, comprising irradiating all or a part of a portion to be dissolved in an etching solution with a laser beam in advance, and thereafter immersing the portion in an etching solution to perform etching. 2. When etching a quartz substrate into a desired shape using an etching solution that dissolves the quartz substrate, the etching is temporarily stopped during the etching, and a laser is applied to all or a part of the portion dissolved in the etching solution. A method of etching a quartz substrate, which comprises irradiating and further etching using an etchant that dissolves the quartz substrate, or repeating the above etching and laser irradiation. 3. In the case where a quartz substrate is etched into a desired shape using an etching solution that dissolves the quartz substrate, a laser is applied to all or a part of a portion to be dissolved in the etching solution, and the quartz substrate is further dissolved. A method for etching a quartz substrate, wherein etching is performed using an etchant, or the above-described laser irradiation and etching are repeated.