JPH07124775A - Microfabrication method - Google Patents

Abstract

PURPOSE:To form a deeper groove and a hole, and to form the groove and the hole with a high aspect ratio in the microfabrication of the groove, the hole, etc., by using a laser beam. CONSTITUTION:An object 1 to be worked, is immersed in silver mirror reaction solution 4, and a laser beam 2 is perpendicularly made incident on the working surface 1a of the object 1 to be worked. The silver mirror reaction solution 4 is prepared by adding formic acid to silver nitrate solution added with excessive ammonia. A silver reflection film 5 is formed in a part where a temperature is locally increased, that is, in the parts of a groove and near the groove by irradiating with a laser beam. The reflectance of the laser beam on the side wall of the groove becomes large, etching in the lateral direction of the side wall is suppressed, the laser beam is propagated to the tip part of the groove by multipath reflection on the side wall, and is converged at its tip part. Consequently, the energy of the laser beam at the tip part of the groove is improved, and the formation of a deeper groove is possible. This is equivalent to a high aspect ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microfabrication technique for grooves, holes, etc., by making the grooves or holes extremely deep and by preventing lateral etching as much as possible.
The present invention relates to a method for realizing high aspect ratio processing.

[0002]

2. Description of the Related Art Conventionally, a method for finely processing a ceramic substrate using a YAG laser has been known. In this method, the melt is prevented from adhering to the processed surface by irradiating a laser while the work is immersed in a KOH aqueous solution or pure water. By using this method, the side surface of the groove can be made extremely smooth.

[0003]

However, even if this method is used, the intensity distribution of the laser beam has a Gaussian distribution. Therefore, when the laser beam is scanned only once, the groove has the largest center axis. It becomes deep and the peripheral part becomes shallow. That is, the groove has a substantially semicircular cross-sectional shape. When this scanning is repeated several times to perform multiple scanning, the cross-sectional shape of the groove becomes V-shaped. Also, no matter how the number of scans is increased, the depth of the groove is
It saturates at a certain value proportional to the intensity of the laser beam, and the groove cannot be formed deeper than that.

The inventors considered the cause as follows. In the fine processing using laser light, the laser light advances while reflecting on the side wall of the groove, reaches the tip of the groove, and the laser light is absorbed by the tip to perform the processing. When the groove becomes deeper, the number of times the laser light is reflected by the side wall increases, and the energy attenuated by the side wall increases. As a result, the energy of the laser light at the tip of the groove does not increase. It seems to be.

Therefore, in order to form a deep groove, the output value must be relatively increased, and the groove width inevitably increases. Therefore, an increase in laser output becomes a problem when performing finer and deeper processing or processing with a high aspect ratio.

The present invention has been made to solve the above problems, and its object is to form deeper grooves and holes and to increase the aspect ratio in fine processing of grooves and holes using a laser. That is, it is possible to form grooves and holes.

[0007]

According to a first aspect of the present invention, by irradiating a predetermined portion of a material to be processed with a laser beam,
In a fine processing method for forming a groove, a hole, etc., a laser beam is irradiated to form a groove, a hole, etc. while forming a reflective film for reflecting the laser beam on the side wall of the groove formed by the irradiation of the laser beam. It is characterized by performing.

The second to sixth aspects are characterized in that the object to be processed is processed by immersing it in a silver mirror reaction solution. Claim 2
Is a method of immersing a workpiece in a silver mirror reaction solution for processing, thereby performing processing with a laser beam while forming a reflective film on the side walls of grooves and holes. A third aspect of the invention is characterized in that the silver mirror reaction solution is a solution that causes a silver mirror reaction when heated. Therefore, the reflective film is formed only on the processed portion of the workpiece which is heated by being irradiated with the laser beam of the groove or hole. A fifth aspect of the present invention is characterized in that the silver mirror reaction solution which reacts at the time of heating is a silver nitrate solution to which ammonia is excessively added, and an aldehyde which requires heating for the silver mirror reaction is added. Formic acid is used as the aldehyde in the silver mirror reaction solution that reacts when heated. In addition, claim 4 specifies the components of a silver mirror reaction solution that undergoes a silver mirror reaction when heated or not heated, and is a solution in which an aldehyde is added to a silver nitrate solution in which excess ammonia is added. To do.

According to a seventh aspect of the present invention, when the work piece is made of metal, the reflection film is formed by electroplating by immersing the work piece in a plating solution. Is formed by a thin film forming method such as sputtering or vacuum deposition.

[0010]

In the case of processing by the above method, a reflective film is formed on the side walls of the groove or hole after processing. Therefore, the laser beam is sufficiently reflected by the side wall of the groove or the like to reduce the energy loss, the laser beam propagates to the tip of the groove without being attenuated, and the energy converges on the tip. Therefore, extremely deep grooves and holes can be formed, and the lateral processing speed of the side wall becomes extremely low. That is, processing with a high aspect ratio becomes possible.

[0011]

EXAMPLES The present invention will be described below based on specific examples. First Embodiment FIG. 1 is a configuration diagram of an apparatus for implementing the method of the present invention, and FIG. 2 is a sectional view showing details of a processed portion. A ceramic workpiece 1 is immersed in a silver mirror reaction solution 4.
The laser beam 2 is condensed by the lens 3 and is vertically incident on the processing surface 1 a of the workpiece 1. The silver mirror reaction solution 4 is obtained by adding aldehydes to a silver nitrate solution containing excess ammonia water. The mixing ratio of these is 6-
It can be used in the range of 8 wt%, silver nitrate solution 64-84 wt%, and aldehydes 8-30 wt%.

In this embodiment, as the silver mirror reaction solution 4, a silver mirror reaction solution in which the reaction proceeds in a heated state was used. This solution can be realized by using formic acid or the like as the aldehyde. The ratio of formic acid is preferably 8-10wt%.

By using a silver mirror reaction solution in which a silver mirror reaction occurs only in a heated state, as shown in FIGS. 1 and 2, a portion where the temperature is locally increased by irradiation with a laser beam, that is, a groove and The silver reflection film 5 is formed in the vicinity of the groove. As a result, the reflectance of the laser beam on the side wall 10a of the groove 10 increases, and etching in the lateral direction of the side wall is suppressed.

Then, the laser beam propagates to the tip portion of the groove by the multiple reflection on the side wall and is converged on the tip portion because the reflectance on the sidewall is improved. Therefore, the energy of the laser beam at the tip of the groove is improved, and a deeper groove can be formed. This means that the energy of the laser beam propagating in the optical axis direction at the tip portion of the groove is much larger than the energy of the laser beam propagating perpendicularly to the side wall. As a result, a deep groove can be formed and a groove having an extremely high aspect ratio can be processed.

In this apparatus, the processing residue generated in the groove 10 at the time of processing is removed by exciting the ultrasonic vibrator 6, so that the deep groove and the groove having a high aspect ratio are formed. Is possible. However, when the laser beam is being irradiated, the liquid surface is wavy, so the ultrasonic transducer 6 is not excited at the same time as the laser beam is being irradiated.

After the processing, the silver reflection film 5 is sublimated and scattered by a thermal process by irradiating a laser beam having a sufficiently weak intensity in the atmosphere or pure water to remove the silver reflection film 5. Is possible.

Second Example In this example, a silver mirror reaction solution in which the silver mirror reaction proceeds at room temperature was used. As the aldehyde, benzaldehyde, valeric acid, aldehyde, etc. can be used. The mixing ratio of them is preferably about 1/2 of the specified concentration of the silver nitrate solution. In this case, since a silver mirror reaction occurs at room temperature, a silver reflection film is formed on the entire surface of the workpiece 1 including the side walls of the groove being processed.

Since the formation of the reflection film on the side wall of the groove being processed is similar to that of the first embodiment, the same effect as that described in the first embodiment can be obtained.

Third Embodiment In this embodiment, the reflection film is formed by electroplating. Similar to silver (98%) for lasers with wavelengths in the infrared region
Other metals that have a reflectivity include gold and copper. When the object to be processed is a metal having conductivity, electroplating can be used to form the reflective film on the sidewall of the groove. A copper nitrate solution can be used as this plating solution, and by immersing the positive electrode of the copper plate in the copper nitrate solution and using the work piece as the negative electrode, a constant potential difference is applied between the two electrodes from the external power source, so that the surface of the work piece is processed. Copper can be deposited. This electroplating is performed simultaneously with the laser beam irradiation. This makes it possible to form a copper reflection film on the side wall of the groove to be processed. Also in this case, the same effect as that of the first embodiment can be obtained.

Fourth Embodiment In this embodiment, the reflection film was formed by sputtering gold.
First, the work piece is dipped in KOH or pure water and irradiated with a laser beam to slightly form a groove. Next, take out this work piece, sputter gold near the groove,
A reflective film is formed. Next, the workpiece is dipped in KOH or pure water and irradiated with a laser beam to form a groove. Repeat this operation. As a result, when a new groove is formed at a deep position, a gold vapor deposition process is performed next, and a reflective film is also formed on the new groove.
Therefore, like the first embodiment, the groove can be processed in the state where the reflective film is formed on the side wall of the groove, and the same effect as that of the first embodiment can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus that realizes an embodiment method of the present invention.

FIG. 2 is a sectional view showing a detailed structure of a groove processed by the method of the embodiment.

[Explanation of symbols]

 1 ... Workpiece 2 ... Laser beam 3 ... Lens 4 ... Silver mirror reaction solution 5 ... Reflective film 6 ... Ultrasonic transducer 10 ... Groove 10a ... Side wall

Claims (8)

[Claims] 1. A microfabrication method for forming a groove, a hole or the like by irradiating a predetermined portion of a material to be processed with a laser beam, wherein the laser beam is reflected on a side wall of the groove formed by the irradiation of the laser beam. While forming a reflective film to
A fine processing method comprising irradiating the laser beam to process grooves, holes and the like. 2. The microfabrication method according to claim 1, wherein the reflective film is formed by processing the material to be processed in a state of being immersed in a silver mirror reaction solution. 3. The microfabrication method according to claim 2, wherein the reflective film is processed by immersing the material to be processed in a silver mirror reaction solution in which a silver mirror reaction occurs during heating, and irradiating with the laser beam. It is characterized in that it is formed only on the processed portion of the processing material heated by. 4. The fine processing method according to claim 2, wherein the silver mirror reaction solution is a solution of aldehydes added to a silver nitrate solution containing excess ammonia. 5. The microfabrication method according to claim 3, wherein the silver mirror reaction solution is a solution in which an aldehyde that requires heating for the silver mirror reaction is added to a silver nitrate solution in which excess ammonia is added. Characterize. 6. The fine processing method according to claim 5, wherein the aldehyde is formic acid. 7. The microfabrication method according to claim 1, wherein when the workpiece is a metal, the reflection film is formed by immersing the workpiece in a plating solution and performing electroplating. It is characterized by being formed. 8. The microfabrication method according to claim 1, wherein the reflective film is formed by a thin film forming method such as sputtering or vacuum deposition.