JP3330655B2 - Manufacturing method of microlens / microlens array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a microlens / microlens array. The microlens / microlens array manufactured by the method of the present invention can be used for a collimating lens of a semiconductor laser, a condensing lens for a light receiving section of a CCD, and a condensing lens array for a liquid crystal shutter array in a liquid crystal television.

[0002]

2. Description of the Related Art The use of microlenses and microlens arrays is intended for the purpose of enhancing light coupling with minute electronic elements such as CCDs and liquid crystal shutter arrays.

As a practical method of forming a microlens or a microlens array, a conventional method has been to form a photosensitive resin layer on a transparent substrate, and to form the photosensitive resin layer on the size of a microlens or a microlens. After patterning according to the size and arrangement of the microlenses constituting the lens array, the photosensitive resin is melted by heating, and the convex lens surface is formed by the surface tension of the melted resin.

Since the microlens or microlens array formed by such a method is made of resin, an electronic element such as a transistor is monolithically formed on a substrate on which the microlens or microlens array is formed. There was a problem that it was difficult.

That is, when an electronic element is formed on a substrate on which a microlens or a microlens array is formed, the resin constituting the microlens and the like is thermally destroyed during a high-temperature heat treatment accompanying the formation of the electronic element. is there.

Conversely, when an electronic element is first formed on a substrate to form a microlens or a microlens array, the electronic element is heated by the heat generated by melting the resin that forms the microlens or the microlens array. Are susceptible to adverse effects.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a novel method of manufacturing a microlens / microlens array which can be formed on the same substrate as an electronic element such as a transistor. With the goal.

[0008]

According to the first aspect of the present invention, there is provided a method of manufacturing a microlens, which is a method of "forming a microlens on a transparent quartz glass substrate", and is constituted as follows.

[0010] N atoms or C
A "penetration layer" of atoms is formed, and a silicon layer is formed to a predetermined thickness on the penetration layer. Next, the silicon layer or the silicon layer and the interstitial layer are removed except for the “shaped portion corresponding to the size of the microlens to be formed”. The removal of the silicon layer or the silicon layer and the interstitial layer can be performed by photolithography and etching. This removal process is hereinafter referred to as “patterning”. Next, the silicon layer is melted and solidified at a predetermined temperature lower than the melting temperature of the quartz glass substrate to form "small peaks of silicon having a smooth convex surface". Finally, an oxidation process is performed to convert the silicon that forms the minute peaks into a “transparent oxide”.

The method of manufacturing a microlens array according to claim 2 is a method of "forming a microlens array on a transparent quartz glass substrate", and is constituted as follows.

On the surface of a quartz glass substrate, N atoms or C
An intrusion layer for atoms is formed, and a silicon layer is formed on the intrusion layer to a predetermined thickness. Next, patterning is performed to remove the silicon layer or the silicon layer and the interstitial layer except for the shape arrangement portion corresponding to the size and arrangement of the microlenses to be formed as the microlens array.
Next, by melting and solidifying the silicon layer at a predetermined temperature lower than the melting temperature of the quartz glass substrate, an "array of silicon micro-peaks having a smooth convex surface" is formed. Finally, an oxidizing process is performed to convert the silicon constituting each minute crest into a transparent oxide.

In the manufacturing method according to the first and second aspects, the N-atom penetration layer is formed by “filming SiO ₂ by a thermal decomposition CVD method using SiH ₄ and N ₂ O as raw materials”. can be (claim 3), entering layer C atoms can be formed by "by ion implantation method with the CH ₄ source gas, the ion implantation into quartz glass substrate" (claim 4).

These claims 1 or 2 or 3 or 4
In the manufacturing method described above, “a protective layer is formed on the surface of a silicon layer or a minute mountain of silicon or an oxide”
(Claim 5). That is, the “formation of the protective film”
A silicon layer is formed on the intrusion layer, and may be performed after patterning, may be performed after melting and solidifying silicon, or may be performed after oxidation treatment.

A microlens can be manufactured by the manufacturing method according to the first, third, fourth, or fifth aspect, and a microlens array can be manufactured by the manufacturing method according to the second, third, fourth, or fifth aspect. Of course, the specific arrangement of the two-dimensional array may be appropriately determined regardless of whether the microlens array in the microlens array is a one-dimensional array or a two-dimensional array.

The "transparent quartz glass substrate" forming the microlens or microlens array may be a natural quartz glass plate or a synthetic quartz glass plate, and is formed by a sol-gel method. May be used. The size and thickness of the quartz glass substrate are determined according to the use and strength of the microlens or microlens array.

[0016]

The method of manufacturing a microlens according to the present invention will be described with reference to FIG. FIG. 1A shows a state in which an N or C intrusion layer 12 is formed on the surface side of a transparent quartz glass substrate 10 and a silicon layer 14 is further formed thereon to a predetermined thickness. . The intrusion layer 12 may be formed as a separate layer on the surface of the quartz glass substrate 10 as in the case of the invention described in claim 3, or may be formed on the surface of quartz glass as in the invention described in claim 4. The atoms may be ion-implanted on the side to form a surface layer of the quartz glass substrate 10. The method by ion implantation is also applicable to the case of forming a penetrating layer of N atoms.

The N atoms or C atoms in the intrusion layer 12 must exist as a layer at least on the surface on which the silicon layer 14 is formed. In other words, the N atoms or C atoms may be present at the interface of the intrusion layer 12 with the silicon layer 14 with a thickness of one atomic layer or more, and exist over the entire area of the intrusion layer 12 in the thickness direction. It may be. The concentration of interstitial atoms in the interstitial layer 12 is limited by the amount of nitrogen in Si ₃ N ₄ when the interstitial atoms are N atoms, and is limited by the amount of carbon in SiC when the interstitial atoms are C atoms. The concentration is optimized as described above according to the microlens production conditions. When the invading atoms are present over the entire area of the invading layer 12 in the thickness direction, the density of N atoms and C atoms may be optimized at the interface with the silicon layer 14.
The concentration may be changed inside the intrusion layer 12. In any case, it is necessary for the silicon layer 14 to contact the layer of N atoms or C atoms on the surface of the interstitial layer 12.

The method for forming the intrusion layer 12 is described in claim 3.
In addition to the method described in No. 4, a known gas phase method such as CVD, vacuum deposition, or sputtering, a thermal diffusion method, or the like can be used.

The silicon layer 14 is to be a substantial part of the microlens and is formed to a "predetermined thickness". As a method for forming the silicon layer 14, various methods such as a vapor phase method such as CVD and a coating method for coating powdered silicon are possible.
The structure of the silicon layer 14 may be crystalline or amorphous, but the higher the density, the better. The thickness of the silicon layer 14 is “predetermined thickness” as described above, and this thickness is determined according to the focal length of the microlens to be formed. The general range of the predetermined thickness is 5000 to 100 μm.
It is.

FIG. 1B shows a state in which the silicon layer 14 and the intrusion layer 12 are removed except for a shape portion corresponding to the size of the microlens to be formed, that is, patterning is performed according to the microlens to be formed. This shows the state of the operation. This patterning may be performed by removing only the silicon layer 14 as shown in FIG.
As shown in 2), the size of the interstitial layer 12 left on the quartz glass substrate 10 is
May be slightly larger than the size of. Patterning can be performed by ordinary photolithography and etching as described above. The shape of the patterned silicon layer 14 is generally circular, but may be polygonal.

FIG. 1C shows a state in which the silicon layer 14 is melted by heating after patterning and then solidified. Heating can be performed by various methods such as heating in a furnace, light heating by laser light or lamp light, particle heating by an electron beam, and the like. There is no particular limitation as long as solidification can be achieved. The melting point of silicon is approximately 1412 degrees Celsius.

The silicon melted by heating becomes liquid, and its free surface becomes a shape close to a spherical surface due to the action of surface tension. This is because the size of the silicon layer left by patterning is extremely small, so that the action of surface tension acts strongly on the entire free surface, and the surface has a substantially uniform curvature.

When the silicon is melted and solidified in this manner, a minute peak 14 ′ of silicon is formed on the intrusion layer 12. In this state, the solidified silicon is opaque.
Therefore, the silicon is then oxidized by an oxidation treatment (a normal silicon oxidation process performed in a semiconductor manufacturing process or an oxidation method of light heating in an oxygen atmosphere) to convert the silicon into a transparent oxide: SiO ₂ . This oxidation process, small mountain 14 of silicon 'is transparent oxide: is converted by SiO ₂ on the microlenses 16 (FIG. 1 (D)).

Through this conversion process, the height d ₁ of the minute peak 14 ′ of the silicon before the oxidation treatment is determined by the micro lens 1.
6 Height: increased to d _2. The size of d ₂ is approximately 1.5 times the size of d _1.

It is to be noted that the higher the oxidation temperature, the higher the oxidation speed, which is advantageous in manufacturing. However, when the oxidation temperature is close to the melting point of silicon, the surface shape changes due to the softening of the silicon, which leads to deterioration of the performance of the microlens. Therefore, it is necessary to set the oxidation temperature to an appropriate temperature.

The micro lens 16 thus formed has a function of condensing light as a positive lens as shown in FIG.

Here, the function of the intrusion layer 12 will be described. FIG.
Angle in (C): θ indicates “contact angle”. As is well known, the contact angle is determined by the magnitude relationship between the surface energy of the liquid and the surface energy of the solid surface in contact with the liquid. The surface energy of molten liquid silicon, that is, the surface tension, is extremely large,
When the silicon layer 14 is formed directly on the quartz glass substrate 10 and is melted and solidified, the contact angle of the formed silicon hills is large and the surface has a strong curvature.
If it is further oxidized to make it transparent, the radius of curvature of the surface of the formed “microlens-like” becomes extremely small with the increase in the height of the minute peaks due to the oxidizing process,
It cannot be used practically as a micro lens.

The intrusion layer 12 suppresses the "increase of the contact angle" when the silicon layer 14 is melted, and prevents the curvature of the surface of the minute mountain of silicon from becoming excessively large. The curvature of the surface of the “micro silicon ridge” formed by melting and solidifying the silicon layer 14 is the same as that of the patterned silicon layer 1.
4 and determined by the surface tension of the molten silicon. In the microlens manufacturing method of the present invention, the fact that the silicon layer is formed to “predetermined thickness” means that an appropriate curvature is set according to the microlens to be formed in anticipation of an increase in curvature accompanying the oxidation treatment. This means that the silicon is formed to a thickness necessary for forming minute hills of silicon.

The surface tension of the molten silicon changes depending on the temperature of the silicon, and the higher the temperature, the lower the surface tension. By utilizing this fact, the curvature of the microlens surface can be adjusted by controlling the melting temperature of silicon.

If the temperature of the melted silicon is sufficiently raised and the surface tension of the silicon is sufficiently lowered, the silicon layer is formed directly on the quartz glass substrate, and the microlenses are formed by melting / solidification and oxidation. It seems that this is possible, but if the temperature of the molten silicon is raised to such an extent that it is possible, the quartz glass as the substrate will be melted. Therefore, the intrusion layer 12 is absolutely necessary.

The method for manufacturing a microlens according to claim 1 has been described. It is apparent that a microlens array can be formed in the same manner as described above by performing patterning according to the microlens array in the patterning step in this method.

When a protective layer is formed on the surface of a microlens or a microlens array as in the manufacturing method of the fifth aspect, the material of the protective layer is SiO ₂ , Si _3.
Silicon compounds such as N ₄ and SiON are preferable, and a gas phase method such as CVD is preferable as the formation method.

[0033]

EXAMPLES Two specific examples will be given below.

Example 1 The transparent quartz glass substrate 10 shown in FIG.
A 5 μm synthetic quartz glass plate was used. An intrusion layer of N atoms was formed as an intrusion layer 12 on the surface of the quartz glass substrate. That is, the flow rate of SiO ₄ is 20 sccm (0 degree Celsius,
The flow rate of N ₂ O is 100
At a flow rate of 0 sccm, a penetration temperature of 750 ° C. and a deposition pressure of 2.0 Torr were used to form the penetration layer 12 as a SiO ₂ film to a thickness of 5000 ° by a thermal decomposition CVD method. N atoms generated by the decomposition of the source gas N ₂ O enter the SiO ₂ film to form a nitrogen intrusion layer.

A silicon layer 14 was formed on the intrusion layer 12 as a polycrystalline silicon film by a thermal decomposition CVD method using SiH ₄ as a raw material. The flow rate of SiH ₄ is 200 sccm,
The deposition temperature is 630 degrees Celsius and the deposition pressure is 0.09 Torr
r, the film thickness is 2.5 μm. As a result of X-ray diffraction measurement, the polycrystalline silicon film was a single (110) oriented film having a grain size of about 500 °.

After patterning by photolithography and etching on the substrate so that the intrusion layer 12 and the silicon layer 14 remain in a “circular shape having a diameter of 220 μm”, the silicon film is heated in an electric furnace. Melt 14
It solidified to form minute silicon peaks 14 '.

The heating is carried out in a nitrogen atmosphere at atmospheric pressure, and the temperature is raised at a rate of 100 ° C./min from room temperature to 1200 ° C.
0.5 degrees C / m from 1200 degrees Celsius to 1415 degrees Celsius
in. The time kept in the molten state was 2 minutes, and cooling was naturally cooled in the furnace. As a result, the formed fine hills of silicon have a diameter of 200 μm and a height of the top of 3.2 μm.
μm.

Next, when an oxidation treatment was performed at an oxidation temperature of 1000 degrees Celsius in an oxygen atmosphere saturated with water vapor, the microlens formed of transparent SiO ₂ had a diameter of 205 μm and a height of 5 μm. At 0.0 μm, the surface was substantially spherical and had a focal length of approximately 2 mm.

Example 2 As a transparent quartz glass substrate, a quartz glass plate having a thickness of 1.0 mm formed by polishing from fused quartz was used. C atoms are implanted into the surface of the quartz glass substrate by ion implantation using CH ₄ as a source gas (acceleration voltage of C ions: 1).
50 KV, implantation amount: 1 × 10 ¹⁵ / cm) to form an invasion layer as a C ion implantation layer.

A silicon layer is formed on this intrusion layer in the same manner as in the first embodiment, and patterning is performed according to the size and arrangement of the microlenses constituting the microlens array. Melting and solidification of
By the oxidation treatment, as shown in FIG. 2B, microlenses M1, M2,. . . M
i,. . Mj. . . Obtained a microlens array regularly arranged.

As shown in FIG. 2A, on the back side of the quartz glass substrate 100 on which the microlens array Mi is formed.
A liquid crystal shutter array was formed as shown in FIG. FIG.
In (A), reference numeral 100A indicates an intrusion layer formed by implantation of C ions.

On the back surface of the quartz glass substrate 100, the pixel electrodes 9 corresponding to the respective micro lenses Mi on the front side in a 1: 1 ratio.
06i and a thin film transistor 905i for driving the same are formed, and a liquid crystal 907 is sealed between the common electrode 908 and the pixel electrode and the substrate surface on which the thin film transistor is formed. Since each microlens and pixel electrode are formed on the same substrate in a one-to-one correspondence, light can be efficiently coupled to each shutter.

When forming a pixel electrode and a thin film transistor, the microlens is also heated with the heat treatment, but the temperature of the heat treatment is about 600 to 700 degrees.
Since the silicon oxide constituting the microlens is not softened or melted, the microlens is not affected by the heat treatment.

[0044]

As described above, according to the present invention, a novel method of manufacturing a microlens / microlens array can be provided. Since the microlens / microlens array manufactured by the method of the present invention is configured as described above, it can be formed on a quartz glass substrate as a substrate together with electronic elements such as transistors.

[Brief description of the drawings]

FIG. 1 is a view for explaining a microlens manufacturing method of the present invention.

FIG. 2 is a diagram for explaining a second embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transparent quartz glass substrate 12 Penetration layer by C atom or N atom 14 Silicon layer 14 'Micro-peak made of silicon 16 Micro lens

Claims (5)

(57) [Claims] 1. A method for forming a microlens on a transparent quartz glass substrate, comprising: forming an intrusion layer of N atoms or C atoms on the surface of the quartz glass substrate; After removing the silicon layer or the silicon layer and the intrusion layer except for a portion corresponding to the size of the microlens to be formed, a predetermined temperature lower than the melting temperature of the quartz glass substrate Then, the silicon layer is melted and solidified to form minute peaks of silicon having a smooth convex surface, and then oxidation treatment is performed to convert the silicon constituting the minute peaks into a transparent oxide. A method of manufacturing a microlens. 2. A method for forming a microlens array on a transparent quartz glass substrate, comprising forming an N or C intrusion layer on the surface of the quartz glass substrate, and forming a silicon layer on the intrusion layer. After removing the silicon layer or the silicon layer and the interstitial layer except for a shape arrangement portion corresponding to the size and arrangement of the microlens to be formed as a microlens array, a quartz glass substrate is formed. The silicon layer is melted and solidified at a predetermined temperature lower than the melting temperature of the silicon to form an array arrangement of minute peaks of silicon having a smooth convex surface. A method for manufacturing a microlens array, comprising converting silicon constituting a peak into a transparent oxide. 3. The method according to claim 1, wherein the N-atom penetration layer is formed by depositing SiO ₂ by a thermal decomposition CVD method using SiH ₄ and N ₂ O as raw materials. A method for manufacturing a microlens or a microlens array. 4. The method according to claim 1, wherein the C-atom penetration layer is formed by ion implantation into a quartz glass substrate by an ion implantation method using CH ₄ as a source gas. To manufacture a microlens or a microlens array. 5. The microlens or microlens array according to claim 1, wherein a protective layer is formed on the surface of the silicon layer or the minute hills of silicon or the oxide. Manufacturing method.