JPH01241503A - Microlens and production thereof - Google Patents

Abstract

PURPOSE:To obtain a desired lens face shape by using light of the wavelength band which is hardly energy-absorbed in gaseous materials and executing laser CVD while stepwise or continuously changing the mixing ratios of SiH4, NO and NH3 in the gaseous raw materials. CONSTITUTION:The gaseous mixture composed of the SiH4, NO and NH3 is used as the gaseous materials and the light of the wavelength and which is hardly energy-absorbed in the gaseous materials among the radiation light rays of a CO2 laser is used as an energy source. The laser CVD is executed while the mixing ratios of the SiH4, NO and NH3 in the gaseous materials are stepwise or continuously changed to form the material film which has a gauss distribution-like profile and has desired etching rates in the respective parts of the film by the stepwise or continuous change of the film compsn. This material film is etched. The microlens having the desired surface shape is thereby obtd.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a microlens and a method for manufacturing the same.

(Prior art) A technology in which a substrate is irradiated with light, the energy distribution on the substrate is controlled by a predetermined program, a material film with a desired thickness distribution is formed by CVD, and this FF film is used as a lens. has been proposed (for example, Japanese Patent Laid-Open No. 62-260104).

As is well known, laser light has an intensity distribution that follows a Gaussian distribution, so by irradiating a substrate with the laser light, a material film having a profile that follows a Gaussian distribution can be formed. Although the vicinity of the maximum thickness of this material film can be used as a lens surface, it is thought that a lens with a desired surface shape can be formed by processing the lens surface by etching.

However, processing the lens surface by etching is not always easy, and a major problem in manufacturing microlenses by laser CVD is how to obtain a desired lens surface shape.

(Objective) The present invention was made in view of the above-mentioned circumstances, and aims to provide a novel microlens and a method for manufacturing the same.

(composition) The following describes the characteristics of the present invention. The invention of claim 1 has the following features.

A mixed gas of 5iH4, NO, and NH3 is used as the material gas, and as an energy source, light in a wavelength range of the CO□ laser radiation light whose energy is difficult to be absorbed by the material gas is used.

Laser CVD is performed while changing the mixture ratio of sjH<, NO, and NHs in the material gas stepwise or continuously.1, the film has a Gaussian distribution profile and the composition of the film changes stepwise or continuously. As a result, a material film is formed in which each part of the film has a desired elastin gray 1-.

In changing the mixing ratio, the mixing ratio of NH3 can be 0.

This material film is etched to obtain a microlens with a desired surface shape.

The invention of claim 2 has the following features.

A mixed gas of SjL+NO, NHi is used as the material gas, and of the emitted light of the CO□ laser as the energy source,
Light in a wavelength band whose energy is difficult to be absorbed by the material gas is used.

Laser CVD is performed while irradiating pulses with the above light, and by controlling the pulse irradiation, S
An iON material film is formed as a microlens.

The invention according to claim 3 is a microlens itself manufactured by the method according to claim 1 or 2 above.

Both claims 1 and 2 use, as an energy source, light in a wavelength range in which the energy is not easily absorbed by the material gas, out of the light emitted by the CO2 laser, and this has the following technical meaning. In other words, when laser CVD is performed by irradiating light whose energy is easily absorbed by the material gas, spike-like film growth occurs in the formed material film, which may be a drawback in terms of optical performance as a microlens. However, the spike-like film growth can be prevented by using, as an energy source, light in a wavelength range in which the energy is not easily absorbed by the material gas, out of the light emitted by the CO□ laser.

(Example) Hereinafter, a specific example will be described with reference to the drawings.

FIG. 1(A) schematically shows an apparatus for performing laser CVD. Code 1 is CO2 laser, code 2
3 is a Zn5e plate, 4 is a mirror, 5 is a Zn5e condenser lens, 6 is a Zn5e window, 7 is a chamber, 8 is a vacuum gauge, and 9 is a He-Ne laser that is a light source for guide light. 10 is a quartz substrate, 11 is a rotary pump, and 12 is a grating.

Embodiment of the invention according to claim 1 As a material gas, a gas introduction pipe 9 is introduced into the chamber 7.
First, a mixture of SiH4 and NO at a mixing ratio (partial pressure ratio) of 1:50 was introduced and sealed at a total pressure of 153 Torr. Of the laser light emitted by CO□Laser 1, P(20) is the light in the wavelength band whose energy is difficult to be absorbed by the material gas.
was selected using the grating 12, and vertically irradiated onto the quartz substrate 10 in the form of a spot using the Zn5e condenser lens 5. The Zn5e condenser lens 5 has f: 100+u+, and the thickness of the quartz substrate IO is about 380ILm.
The distance between the quartz substrate 5 and the Zn5e window 6 is about 4 cm, and the quartz substrate 10 is placed at a position of about #11 cm in front of the focal position of the Zn5e condenser lens 5.

The above laser light irradiation was performed for 2 minutes at a power of 1.7W. Subsequently, N'As gas was additionally introduced into the chamber 7, and the partial pressure ratio of 5iH-:NO:NHx was adjusted to 1:50:1.
1 in 5! IM was performed, and the laser beam was irradiated for 4 minutes in the same manner as above at a total pressure of 203 Torr. Furthermore, NH3 gas is additionally introduced into the chamber 7, and SiH<:No:
The partial pressure ratio of Ni+3 was adjusted to 1:50:50, and the total pressure was 30
Laser light was irradiated at 3 Torr for 4 minutes in the same manner as above.

As a result, a material film having a profile as shown by the solid line in FIG. 2 was formed. When this material film was subjected to B)-IF etching for 8 minutes, the profile of the material film became as shown by the solid line in FIG. In the figure, the broken line is a spherical surface with the curvature of the maximum film thickness, and after etching,
The portion of the material film that conformed to the spherical surface reached 44% of the film thickness. Therefore, the material film thus obtained can be used as a good spherical microlens.

Here, the operation of the invention according to claim 1 will be explained in relation to the above embodiment.

In FIG. 2, the solid line represents the profile of the material film after deposition, and the broken line represents the profile of a spherical surface with curvature at the maximum thickness portion of the material film. The area where the profile of the material film itself matches the profile of the spherical surface shown by the broken line is relatively narrow, so etching the material film is necessary to obtain a good spherical lens. In order to obtain the profile, the shaded area in Figure 2 must be etched away. Looking at the part to be removed by etching, it becomes larger from the central part of the material aS (the part with the largest film thickness) toward the base of the material film. Therefore, the material film itself can simply be etched at a constant etching rate. However, in order to obtain the desired spherical shape, etching must be performed such that the etching rate increases from the center of the material FF film toward the base.

In this way, when removing a part of the material film by etching to obtain a desired lens surface shape, the etching rate of each part of the material film is distributed in advance so as to be convenient for etching. This is the essence of the invention, and to achieve this, the composition of the material film is changed stepwise or continuously.

In the case of the above embodiment, the material film formed on the quartz substrate 10 by laser CVD has a 3M structure due to its composition. That is, the layer formed directly on the substrate IO has a composition of SiO□, the layer formed thereon is a zero-rich SiON layer, and the top layer is N
It is a rich SiON layer.

The density in the obtained material film is higher as the energy applied per unit time is greater. Since the light intensity distribution of the laser beam follows a Gaussian distribution, this means that in the obtained material film, the density is high in the thick center part, and the density is low towards the base. It means becoming.

Now, the etching rate by BHF in a material film depends on the density and composition of the material film, and the lower the density, the higher the
The richer the etching, the higher the etching rate. Therefore, when considering the etching rate of the material film with the three-layer structure of the above example from this perspective, the density is high in the central part of the material film, and the surface layer is N-rich. The etching rate is low from a certain point, but as the density decreases toward the base of the film, the etching rate of the N-rich surface layer becomes high, and as this surface layer is further etched, the O-rich layer below it becomes higher. Since the SiON layer is easily etched, the overall etching rate is high. After all, the etching rate of the material film in the above example gradually increases from the center toward the base, and therefore, the portion of the film removed by etching is small in the center, but increases as it goes toward the base. Since it becomes larger, the part that fits the spherical surface can be easily enlarged by etching.

Note that although the above embodiment deals with the case where the lens surface shape is spherical, even when the lens surface shape is aspherical, a corresponding etching rate distribution can be realized by adjusting the material film composition. Changes in the composition of material films.

The present invention is not limited to the three-layer structure as in the above embodiment.

It may have a two-layer structure or a structure of four or more layers, and the composition may be changed continuously in the film thickness direction instead of being changed stepwise.

Embodiment of the invention according to claim 2 As shown in FIG. 1(B), the apparatus described in FIG. 1(A) is further equipped with a chopper 13, and a laser beam is intermittently irradiated into the chamber. It is now possible to block the

A material gas is introduced into the chamber 7 through the gas introduction pipe 9.
A mixture of SiH, No, and NH at a mixing ratio (partial pressure ratio) of 1:5:30 was introduced and sealed at a total pressure of 29xlO''Pa. Of the laser light emitted by CO2 laser 1.

P(20) was selected by the grating 12 as light in a wavelength band whose energy is difficult to be absorbed by the material gas, and was vertically irradiated onto the quartz substrate 10 in the form of a spot with a diameter of about 1111 using the Zn5e condenser lens 5. Zn5e
The condenser lens 5 has f=100m11, the thickness of the quartz substrate lO is about 380 μm, and the quartz substrate 5 and Zn5e
The distance to the window 6 was approximately 5c+s.

Laser CVD was performed with a laser output of 2 W and pulse irradiation using a chopper 13. Pulse irradiation was carried out periodically for 10 minutes at intervals of 1 second of irradiation for 18 seconds. As a result, a SiON material film having a profile as shown by the solid line in FIG. 4 was formed. In this material film, the spherical conforming portion at the center is 33% of the film thickness.

For comparison, laser irradiation was performed continuously for 10 minutes at an output of 1.5 W, resulting in a profile as shown by the broken line in FIG. 4. In the profile shown by this broken line, the spherical compatible part is 15% of the film thickness, and the compatible part is narrower than that of the above example, and in order to use it as a single spherical lens, lens surface processing by etching is required. The formed material film itself can be used as a microlens.

Here, the operation of the invention of claim 2 will be explained in relation to the above embodiment.

As is well known, film formation by laser CVD is performed as follows. When a substrate is irradiated with laser light, the substrate absorbs the energy of the laser light and its temperature increases. This temperature rise causes the temperature of the substrate to exceed the reaction temperature of the material gas! −
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A reaction occurs on the substrate surface, and a compound is deposited on the substrate to form a film. Since reactions and their deposition occur more actively as the substrate temperature increases, the thickness of the deposited material film becomes thicker where the substrate temperature is higher. Since laser light has a Gaussian intensity distribution, the temperature of the substrate irradiated with the laser light also has a Gaussian distribution.

Therefore, the profile of the resulting material film also has a Gaussian distribution. However, when the laser beam is continuously irradiated, the temperature of the substrate gradually increases in the area around the irradiated area due to heat conduction, and However, since compound deposition occurs, the profile of the material film actually obtained has a wide base with respect to the intensity distribution of the laser beam in the irradiated area, so that it does not match the spherical surface. The part becomes narrower.

However, when irradiating pulsed laser light as in the invention of claim 2, heat is dissipated in the substrate between irradiations, so it is effective to increase the temperature of the substrate around the irradiated area. As a result, reaction and deposition in this area are suppressed.

As in the example, it is possible to form a material film with a thinner profile (solid line in Figure 4) than in the case of continuous irradiation (profile in broken line in Figure 4), and the area that matches the spherical surface is becomes larger.

Of course, the "thinness" of the profile of the deposited material film can be controlled by controlling the pulse irradiation cycle, irradiation time, etc.
Depending on whether the desired lens surface is spherical or aspherical, it can be controlled to suit the desired lens surface well.

(Effects) As described above, according to the present invention, a novel microlens and a method for manufacturing the same can be provided.

Since the manufacturing methods of claims 1 and 2 are configured as described above, both have a lens surface shape that is well adapted to the desired lens surface shape, in other words, has a lens surface shape that has a wide range of compatibility with the desired lens surface shape. Microlenses can be easily manufactured. Furthermore, the microlens produced by the method of claim 1 has a compositional change within the lens itself, so in addition to the lens action due to the lens surface shape, the lens of claim 3 is easy to manufacture and bright. Lens effects based on refractive index distribution can also be utilized. In the manufacturing method of claim 2, the material gas 5IH
4, No., N1 (the mixing ratio of 3 is SiH
4:NO:NH3=about 1:5:30 is preferable.

[Brief explanation of the drawing]

FIG. 1(A) is a diagram schematically showing only the essential parts of an example of an apparatus for carrying out the invention of claim 1, and FIG.
FIGS. 2 and 3 are diagrams for explaining an embodiment of claim 1, and FIG. 4 is a diagram for explaining an embodiment of claim 2. FIG. 3 is a diagram for explaining an example. 1, CO□ laser, 790. Chamber, 10.
,, Ishiju l Figure (A) (B) Z 4

Claims (1)

[Claims] 1. A method for manufacturing a microlens by laser CVD, which uses a mixed gas of SiH_4, NO, and NH_3 as a material gas, and uses the above material gas as an energy source out of the emitted light of a CO_2 laser. Laser CVD is performed using light in a wavelength band where energy is difficult to be absorbed, while changing the mixing ratio of SiH_4, NO, and NH_3 in the material gas stepwise or continuously.
A material film having a Gaussian distribution profile and a desired etching rate in each part of the film is formed by changing the composition of the film stepwise or continuously, and this material film is etched. A method for manufacturing a microlens, characterized by obtaining a microlens with a desired surface shape. 2. A method for manufacturing microlenses by laser CVD, using a mixed gas of SiH_4, NO, and NH_3 as the material gas, and using a wavelength range of the emitted light of the CO_2 laser as the energy source, in which energy is difficult to be absorbed by the material gas. Using the light of
A method for manufacturing a microlens, comprising forming an iON material film as a microlens. 3. A microlens manufactured by the method according to claim 1 or 2.