JPH0819887A - Method and device for optical machining - Google Patents

Abstract

PURPOSE:To obtain SQUID of good characteristic by changing intensity distribution of laser beam at the laser beam irradiating part on a object to be machined to form recessed part of various shape on a substrate. CONSTITUTION:On an optical path of the laser beam emitted from a laser beam source 1, an object 5 to be machined, which is placed in sequence of a mask 3, lens 4 and object 5 to be machined, is placed as inclined to the optical axis of laser beam at the prescribed angle. The inclined angle alpha is about 110 deg.. By irradiating with laser beam under this condition, a beam intensity of a laser beam irradiating part 6 is the strongest at one end A of the irradiating part 6 and is gradually weakened toward other end side B. The recessed part 7 formed at this time has a step at one place and slope shape from the step part to the other end. In this case, an angle made by a substrate filmed face part 8 and stepped face 9 is about 70 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to SQUID (Supercond
The present invention relates to an optical processing method and apparatus for forming recesses having various cross-sectional shapes on a substrate or the like used when manufacturing ucting-Quantum-Interference-Devices).

[0002]

2. Description of the Related Art A conventional metal or intermetallic compound superconductor has a very limited field of use because it uses expensive liquid helium as a refrigerant. However, since 1986, Y-Ba-Cu
Since complex oxides such as —O type and Bi—Ca—Sr—Cu—O type that can use inexpensive liquid nitrogen as a refrigerant have been found, their applications have been studied in various fields.
By the way, SQUID, which is useful for magnetic measurement and the like, is known as an element utilizing the superconducting phenomenon. This SQUID
Is composed of an extremely thin insulator or a normal conductor sandwiched between superconductors. What sandwiches an insulator is called SIS junction, and what sandwiches a normal conductor is called SNS junction.
When the SQUID is formed of an oxide superconductor, it is usually
SNS junction is used. This SNS junction is formed by depositing an oxide superconductor thin film on a substrate having a recess 7 as shown in FIG.
12 is formed to have a thickness of several hundreds of nm, and the SNS junction is formed by the oxide superconductor thin film 13 having normal conductivity at the step portion of the recess 7.

The recess of the substrate has a depth of about 0.2 μm,
Such a shallow recess can be instantly formed by irradiating a laser beam. As shown in FIG. 6A, the optical processing apparatus for forming the concave portion comprises a laser light source 1 and a mask 3, a lens 4, and a workpiece 5 which are sequentially arranged on an optical axis 2 thereof. . Here, the optical axis means an axis parallel to the traveling direction of the laser light emitted from the laser light source. Conventionally, the laser beam emitted from the light source 1 has been applied to the laser beam application section 6 (see FIG. 6C) on the workpiece 5 with uniform intensity. The etching rate when a laser beam is used is uniquely determined by the energy density of the laser beam as shown in FIG. Therefore, as shown in FIG. 6B, the laser beam irradiation unit 6 irradiated with a uniform intensity is provided with the recess 7 having two steps. Although a wet etching method or the like can be applied to form the concave portion on the substrate, the optical processing method is by far superior in terms of formation speed.

[0004]

Problems to be Solved by the Invention The SN shown in FIG.
The Josephson element having the S junction had a lot of noise and had a large variation in Ic and the like. As a result of investigating the cause, it was found that there were two steps in the shape of the SNS joint, that is, in the recess forming the normal conductor. Therefore, a recess having a step formed only on one side and a gentle slope toward the other side has been proposed. However, the recess having such a shape could not be formed by the conventional optical processing method. An object of the present invention is to provide an optical processing method for forming concave portions of various shapes on a substrate, particularly a concave portion having one step, and an apparatus therefor.

[0005]

According to a first aspect of the present invention, there is provided a method of irradiating a laser beam to form a recess in a workpiece, wherein the intensity distribution of the laser beam at the laser beam irradiation portion on the workpiece is changed. It is a characteristic optical processing method.

In the present invention, an excimer laser having a large output is applied to the laser beam. Substrates mainly used for SQUID and the like can be cited as examples of the workpiece to be processed in the present invention. Examples of this type of substrate include MgO, SrTiO ₃ , LaAlO ₃ , and ZrO.
_2. There are single crystal substrates such as perovskite structure materials. Besides the single crystal substrate, for example, a polycrystalline Si substrate having an appropriate buffer layer formed on the film forming surface can be used. When the substrate as described above is used, the (100) plane is used as the film formation surface in order to orient the oxide superconductor in the c-axis.

The invention according to claim 2 is the optical processing method according to claim 1, wherein the intensity distribution of the laser beam of the laser beam irradiating part is changed so as to gradually weaken from one end to the other end. According to this invention, a step is formed at one end, and a concave portion having a gentle slope is formed toward the other end. The angle θ between the film-forming surface of the substrate and the step surface (see FIG.
(See (b)) is a wide range from 90 degrees to about 10 degrees.

The invention of claim 3 relates to claim 1 and claim 2.
Is a device for carrying out the method of the invention, the structure of which is a laser light source, and an optical processing device in which a mask, a lens, and a workpiece are sequentially arranged on the optical axis thereof, in which a laser beam of a laser beam irradiation unit on the workpiece is The optical processing apparatus is provided with a mechanism for changing the intensity distribution.

According to a fourth aspect of the present invention, the mechanism for changing the intensity distribution of the laser beam of the laser beam irradiating portion on the workpiece can hold the workpiece such that the laser beam irradiating portion on the workpiece can be inclined with respect to the optical axis. An optical processing device characterized by being a container. In this invention, by adjusting the inclination angle α with respect to the optical axis of the laser beam irradiation portion on the workpiece, the angle θ formed by the film-forming surface and the step surface is changed from an angle of more than 90 degrees to an angle of less than 10 degrees. Can be formed arbitrarily. Usually, it is changed in the range of 10 to 70 degrees, or 20 to 60 degrees. A holder that can be tilted only in one axis direction is used as the workpiece holder.

According to a fifth aspect of the present invention, in the mechanism for changing the intensity distribution of the laser beam at the laser beam irradiating portion on the workpiece, the opening end face of the opening through which the laser beam passes locally projects or is recessed in the optical axis direction. It is an optical processing device characterized by the above. In the present invention, the mask includes, for example,
A mask in which an opening is provided in a stainless plate and this mask is locally deformed, or a depth of the opening (d in FIG. 3A), that is, a mask in which the thickness of the inner peripheral surface is locally changed is applied. .

According to a sixth aspect of the present invention, there is provided an optical processing apparatus, wherein the mechanism for changing the intensity distribution of the laser beam at the laser beam irradiating portion on the workpiece is a filter. In the present invention, a stainless wire mesh, a color filter or the like is used as the filter. The filter can be arranged at any position that can locally block the light beam in the radial direction. For example, it is provided so as to overlap with one surface of the mask so as to cover a part of one side of the mask opening.

[0012]

According to the invention of claim 1, in the method of irradiating a laser beam to form a recess in a workpiece, since the intensity distribution of the laser beam in the laser beam irradiation portion on the workpiece is changed, the recess having one step is formed. It is possible to form recesses having various shapes such as. By changing the intensity distribution of the laser beam of the laser beam irradiation unit so as to gradually weaken from one end to the other end, a step is formed at one end and a concave portion having a gentle slope can be formed toward the other end.

According to a third aspect of the present invention, in a laser beam source and an optical processing apparatus in which a mask, a lens, and a workpiece are sequentially arranged on the optical axis thereof, the intensity distribution of the laser beam at the laser beam irradiation portion on the workpiece is changed. It is a device equipped with a mechanism for making it. Therefore, it is possible to form concave portions of various shapes, such as a concave portion having one step, on the laser beam irradiation portion on the workpiece. The mechanism for changing the intensity distribution of the laser beam of the laser beam irradiation unit is a workpiece holder that tilts the workpiece with respect to the optical axis, and the opening end face of the opening through which the laser beam passes locally protrudes or dimples in the optical axis direction. The mask is a mask, a filter for locally blocking the light flux, or a filter for weakening the intensity. These mechanisms can be easily realized by partially modifying the existing optical processing device.

[0014]

【Example】

(Embodiment 1) FIG. 1 is an explanatory view of essential parts showing a first embodiment of the present invention. As shown in FIG. 1A, a mask 3, a lens 4, and a workpiece 5 are sequentially arranged on an optical axis 2 of a laser beam emitted from a laser light source 1. The workpiece 5 is arranged so as to be inclined at a predetermined angle with respect to the optical axis 2 of the laser beam. The inclination angle α is 110 degrees. When the laser beam is irradiated in this state, the light intensity of the laser beam irradiation unit 6 becomes one end A of the irradiation unit 6 as shown in FIG.
Is the strongest, and gradually weakens toward the other end B side. As shown in FIG. 1B, the recess 7 formed at this time has one step and has a gentle slope shape from the bottom of the step toward the other end. In this case, the substrate film-forming surface 8 and the step surface 9
The angle θ formed by is 70 degrees.

(Embodiment 2) FIG. 2 is an explanatory view of essential parts showing a second embodiment of the present invention. As shown in FIG. 2A, the mask 3, the lens 4, and the workpiece 5 are sequentially arranged on the optical axis 2 of the laser beam emitted from the laser light source 1.
One end side of the mask 3 is bent toward the laser light source 1 side, and as a result, the opening end face of the opening 10 through which the laser beam passes is locally depressed toward the laser light source 1 side. As shown in FIG. 2B, the recess 7 formed at this time has one step and has a gentle slope shape from the bottom of the step to the other end. In this case, the angle θ between the substrate film forming surface 8 and the step surface 9 is 90 degrees.

(Embodiment 3) FIG. 3 is an explanatory view of essential parts showing a third embodiment of the present invention. As shown in FIG. 3A, the mask 3, the lens 4, and the workpiece 5 are sequentially arranged on the optical axis 2 of the laser beam emitted from the laser light source 1.
Depth d of the opening 10 through which the laser beam of the mask 3 passes
Is gradually increased from one side edge to the other side edge. The shape of the recess formed at this time is the same as that of the second embodiment, as shown in FIG.

(Embodiment 4) FIG. 4 is an explanatory view of the essential parts of a fourth embodiment of the present invention. As shown in FIG. 4A, the mask 3, the lens 4, and the workpiece 5 are sequentially arranged on the optical axis 2 of the laser beam emitted from the laser light source 1.
Two filters 11a and 11b are arranged on one surface of the mask 3 so as to cover a part of the opening 10 on the lower side in the drawing. Filter 11a has filter 11b with opening 10
It is arranged so as to cover a part of the range that covers. In this way, the two filters 11 arranged at different heights are
This is because the slope of the recess is formed more gently. Figure 5
[Fig. 4] is a front view of the filter and mask of Fig. 4B seen from the laser light source side. The filters 11a and 11b are arranged so as to partially block the lower side of the opening 10 of the mask 3 in the figure. In this embodiment, the filter is located in front of the mask 3 (on the left side in FIG. 4A) and is installed at a distance of 100 μm or more from the mask. For this reason, the image is deviated from the focus position, and the image is not formed on the processed surface by the filter. The filter may be installed behind the mask 3. The shape of the recess formed at this time is the same as that of the second embodiment, as shown in FIG.

Using the above-mentioned four types of optical processing equipment, 12 mm square,
A recess having one step was formed on a 0.5 mm thick MgO (100) substrate. A KrF excimer laser with a wavelength of 248 nm was used as the laser light source. A thin film of YBa ₂ Cu ₃ O _x was oriented on the C axis by sputtering to form a 300 nm-thick film on each substrate in which the concave portions were formed. The obtained film-formed body was processed into SQUID, and the magnetic flux resolution and magnetic field resolution in direct current conduction were measured. For comparison, a conventional optical processing device was used to form a MgO (100) recess having two steps.
A substrate is prepared, and YBa is formed on the substrate under the same conditions as described above.
The same measurement was performed on the SQUID processed thin film of ₂ Cu ₃ O _x (comparative example product). The results are shown in Table 1.

[0019]

[Table 1]

As is clear from Table 1, all of Examples 1 to 4 were excellent in magnetic flux resolution and magnetic field resolution. On the other hand, the comparative example product was poor in magnetic flux resolution and magnetic field resolution. This is because the conventional optical processing apparatus was used to form the concave portion in the substrate, and two steps were formed in the concave portion, which deteriorated the characteristics of the SQUID junction.

The case has been described above in which the MgO substrate for SQUID is provided with a single step and a recess having a gentle slope toward the other end. However, the present invention is applicable to other types of substrates such as strontium titanate. However, the same effect can be obtained by applying it to the case of forming a recess of another shape.

[0022]

As described above, according to the present invention,
It is possible to form recesses of various shapes, such as a recess having one step, and it is possible to obtain a remarkable effect when applied to the manufacture of a SQUID substrate and the like.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part showing a first embodiment of the present invention.

FIG. 2 is an explanatory view of a main part showing a second embodiment of the present invention.

FIG. 3 is an explanatory view of main parts showing a third embodiment of the present invention.

FIG. 4 is an explanatory view of a main part showing a fourth embodiment of the present invention.

5 is a front view of the filter and mask of FIG. 4B as viewed from the laser light source side.

FIG. 6 is an explanatory view of a main part of a conventional optical processing device.

FIG. 7 is a plan view showing an aspect of SQUID.

FIG. 8 is a relationship diagram between an energy density and an etching rate in optical processing using a laser beam.

[Explanation of symbols]

 1 ... Laser light source 2 ... Optical axis of laser beam 3 ... Mask 4 ... Lens 5 ... Workpiece 6 ... Laser beam irradiation area 7 ... Substrate recess 8 ... Substrate film formation surface 9 ... Recess Step surface 10 …… Aperture for passing laser beam of mask 11 …… Filter 12 …… Oxide superconductor thin film 13 …… Oxide superconductor thin film in recess

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 39/24 ZAA F

Claims (6)

[Claims] 1. A method of forming a recess in a workpiece by irradiating a laser beam, wherein the intensity distribution of the laser beam at the laser beam irradiation portion on the workpiece is changed. 2. The optical processing method according to claim 1, wherein the intensity distribution of the laser beam at the laser beam irradiation section is changed so as to gradually weaken from one end to the other end. 3. A laser light source, and an optical processing apparatus in which a mask, a lens, and a workpiece are sequentially arranged on the optical axis thereof, and a mechanism for changing the intensity distribution of the laser beam of a laser beam irradiation section on the workpiece is provided. An optical processing device characterized in that 4. The mechanism for changing the intensity distribution of the laser beam of the laser beam irradiation section on the workpiece is a workpiece holder capable of inclining the laser beam irradiation section on the workpiece with respect to the optical axis. The optical processing device according to claim 3, which is characterized in that. 5. A mechanism for changing the intensity distribution of a laser beam at a laser beam irradiating portion on a workpiece is characterized in that an opening end face of an opening through which the laser beam passes is locally projected or recessed in the optical axis direction. The optical processing device according to claim 3. 6. The optical processing apparatus according to claim 3, wherein the mechanism for changing the intensity distribution of the laser beam at the laser beam irradiation section on the workpiece is a filter.