JPH03217803A - Micro optical element forming method and forming apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Second Industrial Fields] The present invention relates to a method and apparatus for forming a microscopic optical element using space-selective thin film formation by laser abrasion.

3. Prior art] A conventional method for forming micro-optical elements is to place a substrate inside a CVD cell in which a material gas is kept at a predetermined pressure, and to irradiate the surface of the substrate with a laser beam. The thermal energy from irradiation causes a decomposition reaction of the material gas,
Means are used that allow thin films to be formed locally in the irradiated area of the substrate.

In addition, as material gases, silane gas such as SiH4 and N
When using a mixed system of laughing gas such as O and N2, S + O
A dielectric thin film of N, St 02, etc. can be obtained.

The growth rate of the thin film varies depending on the surface temperature of the irradiated substrate, and the film thickness distribution is formed by laser light irradiation.

Since the center of this film conforms to a spherical surface, it can be used to fabricate microlenses, and the film can also be used in BHF.
The present inventors have confirmed that wet enoching with buffered hydrofluoric acid (buffered hydrofluoric acid) expands the area that conforms to the spherical surface, making it possible to widen the effective diameter of the lens.

Furthermore, we are also considering fabricating a thin film waveguide by growing a film by moving the laser irradiation position in a line using a similar gas system.

The inventors of the present invention have conducted various studies regarding the formation of dielectric thin films by laser CVD, and are attempting to develop microscopic optical elements such as microlenses and waveguides using this technique.

In particular, a laser beam has excellent directivity, can be easily focused by a lens, etc., and has a significantly higher energy density than other energy sources.

Therefore, thin film growth with high spatial selectivity can be performed without a mask by the laser CVD method using a laser as an energy source.

When manufacturing microlenses using this method, C
While material gas is supplied into the VD cell under a predetermined pressure, the substrate installed in the C to 7D cells is
The laser is focused and irradiated vertically.

When the temperature of the substrate rises due to this laser irradiation, Q
The energy causes the material gas near the substrate surface to decompose and react, and a film grows on the substrate surface. The TEMoo mode laser beam has a Gaunian-like intensity distribution, and therefore, a symmetrical temperature distribution with a peak at the center of the irradiation beam is formed on the surface of the irradiated substrate.

On the other hand, the growth rate of the film varies depending on the supplied energy, in other words, depending on the temperature of the substrate surface. We found that membranes can be grown with good spatial selectivity.

Then, it was confirmed that the shape of the film with such a curvature distribution has a part that can be adapted as a spherical surface, and since this part has a light-concentrating effect, attention was paid to the possibility of using the dielectric thin film as a microlens. has been done.

[Problem to be solved by the invention]

The following technical issues exist when stably manufacturing microlenses having desired optical performance using the laser CVD method.

In other words, when using the laser CVD method, the shape and quality of the film depend on the laser energy density, oscillation mode, output stability,
It varies depending on factors such as the mixture ratio of material gases and total pressure.

Generally, in optical elements, refractive index accuracy is required to be on the order of 10-3.
Stability is extremely high. Furthermore, the aforementioned factors are intertwined with each other, and it is difficult to treat each factor as an independent parameter.

Further, a microlens manufactured by laser CVD has a refractive index distribution in the r direction.

Therefore, it is necessary to optimize the distribution in terms of both design and manufacturing.

Furthermore, regarding the lens shape, the spherical conforming part of the film obtained during TEMoo mote beam condensing irradiation is 15% of the total film thickness.
It remains at about %. In order to expand the spherical compatible region of this film, shape correction by etching using, for example, no-no-phar-do-hydrochloric acid is required as a secondary process.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for forming a micro-optical element by forming a novel spatially selective thin film having controllability of film shape and film quality.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for forming a micro optical element by irradiating a laser beam onto a target placed in a vacuum cell to evaporate the molecules/atoms constituting the target 7). A thin film is formed by laser ablation, in which molecules and atoms are deposited on the surface of the evaporation substrate through a mask, and a point source spot is formed on the target surface, which is irradiated through an optical system that focuses the laser light. The method is characterized in that a mask having an opening of a predetermined size is movably disposed between the point source spout and the deposition substrate.

Further, in the method for forming a micro-optical element according to claim 1, the incident angle of the laser beam incident on the target surface is set to 45 degrees, the target 7} and the vapor deposition substrate are arranged in parallel, and the Kuge/deposition substrate is arranged in parallel. The mask is disposed between the target and the deposition substrate so that the center of the mask opening coincides with the normal line of the target surface passing through the irradiation center position of the target.

Furthermore, the present invention provides a micro optical element forming apparatus that includes a laser light source, a condensing optical system that condenses the beam emitted from the laser light source, and a light guide window that can guide the condensed beam by the condensing optical system. It consists of a vacuum cell equipped with an exhaust system that exhausts residual gas inside, a leak valve that can adjust the internal pressure, a target support rotation movement mechanism that can support the target, and a deposition substrate support mechanism that can support the deposition substrate. ,
The target 7} support rotation movement mechanism is arranged so that the incident angle of the condensed beam on the irradiation surface is 45 degrees,
The evaporation substrate support mechanism is arranged such that the evaporation substrate is parallel to the target irradiation surface, and is equipped with a evaporation substrate position adjustment mechanism that can adjust the distance between the evaporation substrate and the target. The structure is characterized in that the center of the opening of the mask to be placed is placed on the normal line of the target surface passing through the center of incidence of the target surface.

[For production]

According to the configuration of the present invention, molecules and atoms (hereinafter referred to as particles) constituting the target spread out in a conical shape from a point source spot on the target surface and head toward the deposition substrate. In this case, the shape of the deposited film on the deposition substrate can be controlled by controlling the position of a mask with an opening of a predetermined size placed between the point source spot on the target surface and the deposition substrate. Furthermore, due to the arrangement of the Kuge 71- and the deposition substrate, a deposited thin film with good symmetry can be formed and the deposition rate can be increased, making it suitable for use as a microlens.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a configuration in which the method for forming a micro optical element of the present invention can be carried out.

A laser beam from a laser light source 1 such as a CO2 laser or an exhaust laser is directed to a target 5 placed in a vacuum cell 3 via a condensing element 2 made of a Zn Se lens or the like.
A focused beam of light is irradiated towards the target.

Inside the vacuum cell 3, an exhaust system 9 consisting of a rotary pump, a diffusion pump, etc. is connected, and a leak valve 10 is also connected, so that the pressure inside the vacuum cell 3 can be finely adjusted.

The pressure inside the vacuum cell 3 is monitored by a vacuum gauge 11,
A light guide window 4 is formed for guiding a laser beam into the vacuum cell 3.

The target 5 placed in the vacuum cell 3 is supported by a support rotation mechanism 6 such that the laser beam from the laser light source 1 is incident on the target 5 at an incident angle of 45 degrees. By rotating the support rotation movement mechanism 6 for the target 7}, a new target surface can be moved to the laser beam irradiation position while maintaining an angle of 45 degrees between the laser beam and the irradiation surface of the target 5.

A vapor deposition substrate 7 is placed on the vapor deposition substrate support mechanism 12 parallel to the laser irradiation surface of the target 5 at a predetermined interval, and the laser irradiation surface of the target 5 and the vapor deposition surface of the vapor deposition substrate 7 are A mask 8 is placed between them. The size of the opening of the mask 8 is determined depending on the evaporation area on the evaporation substrate 7. Further, the distance between the target 5 and the deposition substrate 7 can also be adjusted.

In the configuration of the present invention as described above, the laser beam emitted from the laser light source 1 is directed by the condensing element 2 through the light guide window 4 to the target 5 in the vacuum cell 3 at an incident angle of 45 degrees. Irradiate with.

By irradiating the laser beam, the constituent molecules and
The atoms are ablated and scattered into the vacuum atmosphere inside the vacuum cell 3. By irradiating the laser beam, the surface of the target 5 is gradually scraped and the scattering direction changes, but due to the rotation of the target support rotation movement mechanism 6, a new surface of the target 5 is always irradiated with the laser beam.
The scattering direction of the constituent molecules/atoms of the target 5 is kept constant.

Since the distribution of the scattering direction of the constituent molecules/atoms from the surface of the target 5 follows the cosine law, by irradiating the target 5 with a laser beam at an incident angle of 45 degrees, the distribution in the direction perpendicular to the surface of the target 5 can be The amount of scattered constituent molecules/atoms becomes maximum (see Figure 4).

Therefore, the mask 8 is placed on the normal line to the surface of the target 5, passing through the irradiation position A of the target 5. This arrangement maximizes the effect of depositing constituent molecules and atoms onto the vapor deposition surface of the vapor deposition substrate 7 located parallel to the target 5.

Also, for the size of the opening of the mask 8, the Yuichi get 5
By sufficiently reducing the size of the source of constituent molecules/atoms, which is the irradiation position A, and localizing the source, the size and shape of the deposition on the vapor deposition base 7 can be controlled using the mask 8. Furthermore, by adjusting the distance between the deposition substrate 7 and the target 5, the size and shape of the deposition on the deposition substrate 7 can be controlled.

The constituent molecules and atoms scattered from the target material 5 collide with the residual gas in the vacuum cell 3 in the process of reaching the deposition substrate 7, and the probability of collision in this case is lower as the residual gas is smaller. Therefore, the probability of collision can be changed by adjusting the pressure within the vacuum cell 3 by controlling the leak valve 10.

By controlling the probability of collision between the constituent molecules/atoms that fly away and the residual gas in the vacuum cell 3, the number of constituent molecules/atoms that can reach the vapor deposition substrate 7 changes, and the number of constituent molecules/atoms that can reach the vapor deposition substrate 7 changes.
Shape of the deposit above. The size changes.

According to experiments, when the degree of vacuum in the vacuum cell 3 is high, there is little residual gas in the vacuum cell 3, and a flat film as shown in FIG. 3 is deposited; When the temperature is low, the number of collisions between the constituent molecules/atoms and the residual gas in the vacuum cell increases, and a bell-shaped film as shown in FIG. 2 is deposited.

During the film deposition process, the shape of the film can be controlled at any time in the deposition direction by appropriately changing the internal pressure of the vacuum cell 3.

A desired film shape can be obtained by each of the above methods.

The case where a microlens is manufactured as a prototype using the micro optical element forming apparatus of the present invention shown in FIG. 1 will be explained.

A quartz target with a thickness of 1 mm was used as the target 5, and after the quartz target was ultrasonically cleaned with methanol, N2
It was dried and installed in the target support rotation movement mechanism 6.

As the laser light source 1, a CO2 laser is used. The laser emission beam is transmitted through a Zn Se lens (f=2[)0
+++m), and the quartz target 5 is condensed and irradiated via the Zn Se light guide window 4. The distance between the Zn Se lens 2 and the Zn Se light guide window 4 is adjusted using the defocusing mechanism of the 2n Se lens 2 so that the distance is 10Q'+nm.

The target support rotation movement mechanism 6 is arranged so that the quartz target 5 faces at 45 degrees with respect to the beam incidence direction, and has a rotation function so that the beam can always be incident on a new surface of the quartz target 5. .

A quartz plate with a thickness of 380 μm was used as the vapor deposition base 7.
A mask 8 made of a copper wire with a thickness of 25 μm and a diameter of 260 μm was placed between the quartz target 5 and the quartz evaporation substrate 7, parallel to the quartz target 5 and spaced apart from each other by 10 mm. In this case, the mask is placed at a position 500 μm from the quartz deposition substrate 7.

The vacuum cell 3 is equipped with a rotary pump 9 as an exhaust system. It is equipped with a leak valve lO for pressure adjustment and a vacuum gauge 11.

In this state, the pressure inside the vacuum cell 3 is evacuated to 6 x 10-3 Torr by the rotary pump 9, and the pressure inside the vacuum cell 3 is evacuated to 6 x 10-3 Torr by the pressure adjustment leak valve 10.
The pressure was maintained at Torr.

With the above conditions set, the laser beam power 1 5
The quartz target 5 was irradiated with W for 10 minutes.

In this case, on the surface of the quartz vapor-deposited substrate 7, as shown in FIG.
A lenticular deposit with a film thickness distribution was obtained. The dotted line in Figure 2 has a radius of curvature of 3. It is a spherical surface with 6 m+n, and 35% of the total film thickness is suitable as a lens.

The shape of the obtained microlens was 7.9 μm in thickness and 350 μm in full width at half maximum.

When the distance between the quartz target 5 and the quartz deposition substrate 7 is made closer, the deposition rate increases and a lens-shaped deposit with a sharp curvature is obtained.

Since the target is supported by a target support rotation movement mechanism equipped with a rotation function, a new target surface is constantly irradiated with the laser, which causes particles to fly away due to roughness of the target surface due to ablation. Changes in the distribution pattern can be prevented, and the state of film deposition is stable.

The microlens according to the present invention allows easy control of curvature distribution. In addition, the film formed on the evaporation substrate by particles deposited on the target by flying particles has the same refractive index as the target material, and therefore, the refractive index of the microlens can be determined by selecting the target material. The mixing ratio of the material gas in the CVD process is 1. If the laser energy is controlled, etc.
A stable refractive index can be obtained.

Furthermore, a case will be described in which a pilot waveguide is manufactured as a prototype using the micro-optical element forming apparatus of the present invention shown in FIG.

In this case, sapphire is used as the target material,
A slit-shaped mask with a width of 250 μm was used as the mask.
The mask was placed so as to be in substantially close contact with the same 380 μm quartz vapor deposited substrate 7 as described above.

The distance between the quartz target 5 and the quartz deposition substrate 7 was set to 10 mm as in the previous case, and the pressure inside the vacuum cell 3 was maintained at 4 × 10-' Torr.
Buko.

Under these conditions, the power of the laser beam is -15w.
By irradiating the quartz target 5 for 10 minutes, a leading waveform having the shape shown in FIG. 3 was obtained. The shape of this leading wavepath is 260 μm in width and 8.9×10−2 μm in height.
Met.

In this case, due to the difference in linear expansion coefficient between the quartz vapor-deposited substrate and the target 5 made of sapphire, especially when the film is thickened,
Cracks may also occur.

However, as a deposition substrate, quartz (the coefficient of linear expansion of quartz is 5.
5 x 10-'/t) instead of Pyrex (the coefficient of linear expansion of Pyrex is 3.25
By selecting the target material, sapphire (the coefficient of linear expansion of sapphire is 7.7×10-6/℃
), it is possible to reduce the difference in coefficient of linear expansion with respect to ), thereby making it possible to avoid the occurrence of cracks as described above.

In this case, the difference in refractive index between the vapor deposition substrate portion and the leading waveguide portion is also sufficient since the refractive index of Pyrex is 1.474 and the refractive index of sapphire is 1.769. Note that the refractive index of quartz is 1. 4 5 8. Each of the above refractive indices indicates a refractive index for a wavelength of 589.3 nm.

The guide waveguide according to the present invention has better stability of refractive index than an optical waveguide manufactured by the laser CVD method.

In addition, in the laser CVD method, the laser irradiation position on the substrate is moved in a line shape and the film is deposited in the shape of a waveguide.
Due to fluctuations in laser output, the film quality in each laser irradiation area became non-uniform, and the moving speed of the laser irradiation position was slow, requiring a long time to fabricate. However, in the case of the present invention, the slit can be formed. By using such a mask shape, a uniform film can be simultaneously deposited along the length of the slit, and manufacturing efficiency can be increased.

Although quartz and Pyrex have been described as vapor deposition substrates, it is natural to use materials having similar properties to quartz and Pyrex.

〔effect〕

According to the configuration of the present invention, a laser beam is concentratedly irradiated onto the target, and by changing the position of the mask, the particles from the particle source consisting of a point source are scattered in a conical area through the opening of the mask and deposited. The shape of the film deposited on the substrate can be controlled, and by changing the degree of vacuum in the vacuum cell, the residual gas concentration can be controlled, and the shape of the film deposited on the deposition substrate can be controlled. Furthermore, due to the relationship between the Yuichi get and the deposition substrate, the density distribution of particles from the particle source is scattered according to the cosine law, obtaining a film shape with good symmetry with respect to the mask shape and improving the deposition rate. This symmetry is suitable when the deposited thin film is used as a lens.

Furthermore, by using the apparatus of the present invention, microlenses and guiding waveguides can be manufactured efficiently.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of the present invention, FIG. 2 is a cross-sectional view of a microlens manufactured using the configuration of the present invention, and FIG. 3 is a cross-sectional view of an optical waveguide manufactured using the configuration of the present invention. , FIG. 4 is an explanatory diagram showing the relationship between the target 7} irradiated with the laser beam and the particles scattered from the target. DESCRIPTION OF SYMBOLS 1... Laser light source, 2... Condensing element, 3... Vacuum cellobe 4... Light guiding window part, 5-Target, 6... Target support rotation movement mechanism, 7... Evaporation substrate, Death: Mask, 9: Rotary pump, 10: Leak hull for pressure adjustment, 11: Vacuum gauge, 12: Vapor deposition substrate support mechanism.

Claims (3)

[Claims] (1) By laser ablation, molecules and atoms constituting the target are evaporated by irradiating a target placed in a vacuum cell with laser light, and these molecules and atoms are deposited on the surface of the deposition substrate via a mask. A thin film is formed, a point source spot is formed on the target surface irradiated through an optical system that focuses the laser beam, and an aperture of a predetermined size is provided between the point source spot of the target and the deposition substrate. A method for forming a micro optical element, characterized in that a mask is movably arranged. (2) Set the incident angle of the laser beam incident on the target surface to 4
5 degrees, and place the target and the deposition substrate parallel to each other so that the center of the mask opening matches the normal to the target surface passing through the irradiation center position of the target. The method for forming a micro optical element according to claim 1, characterized in that a mask is arranged. (3) A laser light source, a condensing optical system that condenses the emitted beam from the laser light source, a light guide window that can guide the condensed beam from the condensing optical system, and an exhaust system that exhausts residual gas inside. A vacuum cell includes a leak valve capable of adjusting internal pressure, a target support rotation movement mechanism capable of supporting a target, and a vapor deposition substrate support mechanism capable of supporting a vapor deposition substrate, and the target support rotation movement mechanism is configured to focus light. The beam is arranged so that the angle of incidence on the target irradiation surface is 45 degrees, and the evaporation substrate support mechanism is arranged so that the evaporation substrate is parallel to the target irradiation surface, and the distance between the evaporation substrate and the target is The method is characterized in that it is equipped with a deposition substrate position adjustment mechanism that can adjust the position of the deposition substrate, and is configured such that the aperture center of a mask placed between the deposition substrate and the target is placed on the normal line of the target surface passing through the center of incidence of the target surface. Micro optical element forming device.