JP2851280B2 - Micro lens and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microlens and a method for manufacturing the same.

(Prior art) A technique of irradiating a substrate with light, controlling an energy distribution on the substrate by a predetermined program, forming a material film having a desired film thickness distribution by CVD, and using the material film as a lens. It has been proposed (for example, JP-A-62-260104).

As is well known, a laser beam has an intensity distribution according to a Gaussian distribution, so that a material film having a profile according to a Gaussian distribution can be formed by irradiating the substrate with the laser beam. This material film can be used in the vicinity of its maximum thickness as a lens surface, but it is considered that a lens having a desired surface shape can be formed by performing lens surface processing by etching.

However, lens surface processing by etching is not always easy, and in microlens production by laser CVD, how to obtain a desired lens surface shape has been a major problem.

(Purpose) The present invention has been made in view of the above circumstances, and has as its object to provide a novel microlens and a method of manufacturing the same.

(Configuration) Hereinafter, the present invention will be described.

 The invention of claim 1 has the following features.

As a material gas, a mixed gas of SiH ₄ , NO, and NH ₃ is used, and as an energy source, light in a wavelength band in which energy is not easily absorbed by the material gas, out of the emitted light of the CO ₂ laser.

Laser CVD is performed while changing the mixture ratio of SiH ₄ , NO, and NH ₃ in the material gas stepwise or continuously, and has a Gaussian profile, and the film composition changes stepwise or continuously. As a result, a material film in which each part of the film has a desired etching rate is formed. In the change of the mixing ratio, the mixing ratio of NH ₃ can be zero.

This material film is etched to obtain a micro lens having a desired surface shape.

 The invention of claim 2 has the following features.

As a material gas, a mixed gas of SiH ₄ , NO, and NH ₃ is used, and as an energy source, light in a wavelength band in which energy is not easily absorbed by the material gas, out of the emitted light of the CO ₂ laser.

Laser CVD is performed while irradiating the light with a pulse, and by controlling the pulse irradiation, a Si having a desired profile is obtained.
The ON material film is formed as a microlens.

Specifically, the pulse irradiation is controlled by controlling the pulse irradiation period and the irradiation time.

A third aspect of the present invention is a microlens itself manufactured by the method of the first or second aspect.

Both of the first and _second aspects use, as an energy source, light in a wavelength band in which energy is hardly absorbed by a material gas, among radiation light of a CO ₂ laser, and this has the following technical meaning.
That is, when laser CVD is performed by irradiating the material gas with light that is easily absorbed in energy, spike-like film growth occurs in the formed material film, which may be a defect in optical performance as a microlens. However, the spike-like film growth can be prevented by using, as an energy source, light in a wavelength band in which energy is hardly absorbed by the material gas out of the emitted light of the CO ₂ laser.

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

FIG. 1A is an explanatory view showing an apparatus for performing laser CVD. Reference numeral 1 denotes a CO ₂ laser, reference numeral 2 denotes a He-Ne laser as a light source for guide light, and reference numeral 3 denotes ZnSe.
Plate, reference numeral 4 is a mirror, reference numeral 5 is a ZnSe condenser lens, reference numeral 6
Is a ZnSe window, 7 is a chamber, 8 is a vacuum gauge,
Reference numeral 9 denotes a gas inlet tube, reference numeral 10 denotes a quartz substrate, reference numeral 11 denotes a rotary pump, and reference numeral 12 denotes a grating.

First, as a material gas, first, a mixture of SiH ₄ and NO at a mixing ratio (partial pressure ratio) of 1:50 is introduced into a chamber 7 by a gas introduction pipe 9 and sealed at a total pressure of 153 Torr. Was. Grating of P (20) as light in the wavelength band where energy is hardly absorbed by the material gas in the emitted laser light of the CO ₂ laser 1
Is selected by a ZnSe condensing lens 5 on a quartz substrate.
10 was vertically irradiated in a spot form. The ZnSe condenser lens 5 is f = 100 mm, the thickness of the quartz substrate 10 is about 380 μm, the distance between the quartz substrate 5 and the ZnSe window 6 is about 4 cm, and the quartz substrate 10 is the ZnSe condenser lens 5. It is placed at a position of about 1 cm in front of the focal position.

The laser beam irradiation was performed for 2 minutes at a power of 1.7 w. Subsequently, NH ₃ gas was additionally introduced into the chamber 7 and S 3
The partial pressure ratio of iH ₄ : NO: NH ₃ was adjusted to 1:50:15, the total pressure was set to 203 Torr, and laser light was irradiated for 4 minutes in the same manner as described above.
Further, NH ₃ gas is additionally introduced into the chamber 7 and SiH ₄ : N
The partial pressure ratio of O: NH ₃ was adjusted to 1:50:50, the total pressure was set to 303 Torr, and laser light was irradiated for 4 minutes in the same manner as described above.

As a result, a material film having a profile shown by a solid line in FIG. 2 was formed. When this material film was subjected to BHF etching for 8 minutes, the profile of the material film was 3rd.
The result is as shown by the solid line in the figure. In the figure, the broken line is the spherical surface having the curvature of the maximum film thickness portion. After etching, the portion of the material film which conforms to the above 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 of claim 1 will be described in relation to the above embodiment.

In FIG. 2, the solid line is the profile of the material film after film formation.
The broken line shows the profile of the spherical surface having the curvature of the maximum thickness portion of the material film. The region where the profile of the substance itself coincides with the spherical profile shown by the dashed line is relatively narrow, and therefore, it is necessary to etch the material film to obtain a good spherical lens. In order to obtain (1), the hatched portions in FIG. 2 must be removed by etching. Looking at the portion to be removed by etching, the portion of the material film becomes larger from the central portion (the portion having the largest thickness) toward the foot of the material film. Therefore, the material film itself is simply etched at a constant etching rate. However, a desired spherical shape cannot be obtained. In order to obtain a desired spherical shape, the etching must be performed such that the etching rate increases from the center of the material film toward the foot.

Thus, in order to obtain a desired lens surface shape by removing a part of the material film by etching, the etching rate of each part of the material film is previously distributed so as to be convenient for etching. The essence of the invention,
In order to realize 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 three-layer structure due to its composition. That is, the layer formed directly on the substrate 10 has a composition of SiO ₂ , the layer formed thereon is an O-rich SiON layer, and the uppermost layer is an N-rich SiON layer.
Layer.

The density in the obtained material film is higher as the energy applied per unit time is higher. Since the light intensity distribution of the laser beam follows the Gaussian distribution, this indicates that in the obtained material film, the density increases as the thickness of the central part increases, and the density decreases toward the foot. Means things.

The etching rate of a material film by BHF depends on the density and composition of the material film.
The richer, the higher the etching rate. Considering the etching rate of the material film having the three-layer structure in the above embodiment from this viewpoint, the etching rate is low at the center portion of the material film and is low because the surface layer is N-rich. However, since the density decreases toward the bottom of the film, the etching rate of the N-rich SiON layer on the surface layer increases, and when this surface layer is further etched, the O-rich SiON layer thereunder is easily etched. Therefore, the etching rate is increased as a whole. As a result, the etching rate of the material film of the above embodiment gradually increases from the central portion toward the foot, so that the film portion removed by etching is small at the central portion, but as it goes toward the foot. Since it becomes large, the portion that fits the spherical surface can be easily enlarged by etching.

In the above embodiment, the lens surface shape is a spherical surface. However, even when the lens surface shape is an aspherical surface, an etching rate distribution corresponding thereto can be realized by adjusting the material film composition. The composition change of the material film is not limited to the case of the three-layer structure as in the above embodiment, but may be a two-layer structure or a configuration of four or more layers. The direction may be changed continuously.

As shown in FIG. 1 (B), a chopper 13 is further provided in the apparatus described with reference to FIG. 1 (A) to intermittently irradiate a laser beam for irradiating the inside of the chamber. So that it can be shut off.

A mixture of SiH ₄ , NO, and NH ₃ at a mixing ratio (partial pressure ratio) of 1: 5: 30 was introduced as a material gas into the chamber 7 by a gas introduction pipe 9 and sealed at a total pressure of 29 × 10 ³ Pa. Of the radiation laser light of the CO ₂ laser 1, P (20) is selected by the grating 12 as light in a wavelength band in which energy is hardly absorbed by the above material gas, and the P (20) is applied to the quartz substrate 10 by the ZnSe condenser lens 5 to have a diameter of about Irradiation was performed vertically in a 1 mm spot. The ZnSe condensing lens 5 was f = 100 mm, the thickness of the quartz substrate 10 was about 380 μm, and the distance between the quartz substrate 5 and the ZnSe window 6 was about 5 cm.

Laser output was set to 2 watts and laser CVD was performed while pulse irradiation was performed by the chopper 13. Pulse irradiation is 1
The irradiation was performed periodically for 10 minutes at a rate of 1 second irradiation for 8 seconds. As a result, Si having a profile as shown by the solid line in FIG.
An ON material film was formed. In this material film, the spherical portion at the center is 33% of the film thickness.

For comparison, the result of continuously irradiating the laser at an output of 1.5 w for 10 minutes has a profile as shown by the broken line in FIG. In the profile of this broken line, the spherical-fit portion is 15% of the film thickness, and the fit portion is narrower than that of the above embodiment,
In order to use as a spherical lens, lens surface processing by etching is required, but in the case of the embodiment, the formed material film itself can be used as a micro lens.

Here, the operation of the second aspect of the invention will be described in relation to the above embodiment.

As is well known, film formation by laser CVD is performed as follows. When the substrate is irradiated with laser light, the substrate absorbs the energy of the laser light and the temperature rises. When the temperature of the substrate exceeds the threshold value of the reaction temperature of the material gas due to the temperature rise, a reaction occurs on the substrate surface, and the compound is deposited on the substrate to form a film. Since the reaction and the deposition occur more actively as the substrate temperature increases, the thickness of the formed material film increases as the substrate temperature increases. Since the laser beam has a Gaussian distribution type intensity distribution, the temperature of the substrate irradiated with the laser beam also becomes a Gaussian distribution type, and thus the obtained material film also has a Gaussian distribution type profile. However, when the laser beam is continuously irradiated, the temperature of the substrate gradually increases even in the area around the irradiated area due to heat conduction, and the compound is deposited around the irradiated area. Is a so-called thick profile with a broader skirt with respect to the intensity distribution of the laser beam in the irradiated portion, and the portion that fits the spherical surface becomes narrower.

However, when the laser beam is pulse-irradiated as in the second aspect of the present invention, since there is a dissipation of heat in the substrate between the irradiations, it is effective to increase the substrate temperature around the irradiated portion. The reaction in this part
As a result of suppressing the deposition, it is possible to form a material film having a “thinner” profile (solid line in FIG. 4) as compared with the case of continuous irradiation (the profile indicated by the broken line in FIG. 4) as in the embodiment. And the portion that fits the spherical surface becomes larger.

Of course, the “thinness” of the profile of the deposited material film
By controlling the pulse irradiation period, irradiation time, and the like, the control can be performed so as to conform well to the desired lens surface depending on whether the lens surface is spherical or aspherical.

(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, each of them has a lens surface shape that is well suited to a desired lens surface shape, in other words, has a wide area compatible with the desired lens surface shape. Microlenses can be easily manufactured. Further, the lens according to claim 3 is easy to manufacture and is bright. Since the composition of the microlens manufactured by the method of claim 1 has a change in the lens itself, the lens function by the refractive index distribution can be used in addition to the lens function by the lens surface shape. 3. The method according to claim 2, wherein the material gas is Si.
The mixing ratio of H ₄ , NO, and NH ₃ is set so that SiH ₄ : NO: NH ₃ =
About 1: 5: 30 is preferable.

[Brief description of the drawings]

FIG. 1 (A) is a diagram schematically showing only an essential part of an example of an apparatus for carrying out the invention of claim 1, and FIG. 1 (B) is an example of an apparatus for carrying out the invention of claim 2. FIGS. 2 and 3 schematically show only a main part, and FIGS.
FIG. 4 is a diagram for explaining the embodiment of claim 2. 1 ...... CO ₂ lasers, 7 ...... chamber 10 ...... quartz substrate, 13 ...... Chopper

Claims (3)

(57) [Claims] 1. A method for manufacturing a microlens by laser CVD, wherein a mixed gas of SiH ₄ , NO, and NH ₃ is used as a material gas, and the material gas is used as an energy source in the emission light of a CO ₂ laser. Laser CVD is performed using light in a wavelength band that is difficult to absorb energy, while gradually or continuously changing the mixing ratio of SiH ₄ , NO, and NH ₃ in the material gas, and has a Gaussian profile, and The film composition changes stepwise or continuously so that each part of the film forms a material film having a desired etching rate, and the material film is etched to obtain a microlens having a desired surface shape. A method of manufacturing a microlens. 2. A method for manufacturing a microlens by laser CVD, wherein a mixed gas of SiH ₄ , NO, and NH ₃ is used as a material gas, and the material gas is used as an energy source in the emission light of a CO ₂ laser. Using light in a wavelength band that is difficult to absorb energy, performing laser CVD while irradiating the above light with a pulse, and controlling the period and irradiation time of the above pulse irradiation to convert a SiON material film with a desired profile into a microlens A method for producing a microlens, characterized in that it is formed as a microlens. 3. A microlens manufactured by the method according to claim 1.