JPH10206605A - Microlens array and forming method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens array having little substantially invalid region between the mutual microlenses. SOLUTION: A transmissible film 26 is spread along the surface of an on-chip microlens 22, and an on-chip microlens array 23 is made up by a plurality of on-chip microlenses 22 that are arrayed in correspondence with respective image elements. Thus, the diameter of the on-chip microlens 22 is substantially large as much as the thickness of the transmissible film 26, so that the substantially invalid region between the mutual on-chip microlenses 22 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlens array used for a solid-state imaging device and the like, and a method for forming the same.

[0002]

2. Description of the Related Art FIG. 2 shows a solid-state imaging device to which a conventional example of the present invention is applied. The solid-state imaging device, a sensor (not shown) or the transfer unit and SiO ₂ film 12 as a gate insulating film on the surface of the Si substrate 11 (not shown) and the like are formed is formed, SiO ₂ film A transfer electrode is formed of the polycrystalline Si film 13 on the substrate 12.

[0003] The polycrystalline Si film 13 is made of S as an interlayer insulating film.
iO ₂ is covered with a film 14, SiO ₂ film 12 is covered with the SiO ₂ film 15 as a passivation film. On the SiO ₂ film 15, an Al film 16 as a light shielding film
Is formed, and a light receiving opening 16a is formed in a portion of the Al film 16 above the sensor. Then, a planarizing film 17 is formed on the Al film 16 and the SiO ₂ film 15.
Are formed.

A color filter 21 and an on-chip microlens 22 are sequentially formed on the flattening film 17, and an on-chip microlens array is formed by a plurality of on-chip microlenses 22 arranged corresponding to each pixel. 23 are configured. Therefore, in such a solid-state imaging device, since the light 24 is collected by the on-chip microlens 22, the sensitivity is higher than that of the structure in which the on-chip microlens array 23 is not provided.

FIG. 3 shows a conventional method of forming the on-chip microlens array 23 shown in FIG. In this conventional example, as shown in FIG. 3A, a photosensitive material layer 25 of the on-chip microlens 22, specifically, a photoresist is applied on the color filter 21, and The material layer 25 is patterned into a corresponding pattern by photolithography.

Next, as shown in FIG. 3B, the material layer 25 is reflowed by heat treatment to form an on-chip microlens 22 having a curved surface by the surface tension of the material layer 25, and then the on-chip microlens 22 is formed. Baking. When the material layer 25 is reflowed, the material layer 25 slides due to the compatibility between the material layer 25 and the color filter 21, and the distance between the on-chip microlenses 22 is reduced.
It becomes narrower than the interval between five.

[0007]

The above-mentioned slippage of the material layer 25 at the time of reflow causes the interval between the on-chip microlenses 22 to be narrower than the processing limit of the photolithography, and the invalidity between the on-chip microlenses 22 is reduced. This has the advantage that the area can be narrowed and the sensitivity of the solid-state imaging device can be increased.

However, if the material layer 25 slides too much during reflow, there is no space between the on-chip microlenses 22, and adjacent on-chip microlenses 22 are short-circuited as shown in FIG. 2 (c). At the short-circuited portion, an optimum lens shape cannot be obtained, and the light-collecting efficiency is reduced. Therefore, image quality unevenness and image defects occur in a solid-state imaging device having a plurality of pixels.

In particular, as the size and density of the solid-state image sensor increase, it becomes difficult to control the distance between the on-chip microlenses 22, and in the above-described conventional example, the sensitivity of the solid-state image sensor and the like is increased. It is difficult to form the on-chip microlens array 23 with a high yield.

[0010]

The microlens array according to the present invention is characterized in that a plurality of microlenses having a light-transmitting film extending along the surface are arranged.

In the microlens array according to the present invention, it is preferable that the light transmitting film is a SiON film.

In the microlens array according to the present invention, it is preferable that the refractive index of the light transmitting film is lower than the refractive index of the microlens.

In the microlens array according to the present invention, the light transmitting film may be a SiO ₂ film.

The method of forming a microlens array according to the present invention comprises the steps of processing a material layer of the microlens into a pattern corresponding to a plurality of microlenses in an array state, and reflowing the processed material layer. Forming a plurality of microlenses, and forming a light-transmitting film extending along the surfaces of the plurality of microlenses.

In the method of forming a microlens array according to the present invention, the light transmitting film can be formed by applying an organic film.

In the method of forming a microlens array according to the present invention, the light-transmitting film can be formed by depositing an inorganic film by a plasma CVD method.

In the microlens array according to the present invention, since the light transmitting film extends along the surface of the micro lens, the diameter of the micro lens is substantially large by the thickness of the light transmitting film. There is little substantial invalid area between them.

If the light transmitting film is a SiON film, Si
By adjusting the ratio of O and N in the ON film, the refractive index of the SiON film can be easily controlled. Therefore, even if the desired focal position cannot be obtained only by the microlens, the refractive index of the SiON film can be reduced. The focus position can be controlled by controlling the rate.

If the refractive index of the light transmitting film is lower than the refractive index of the microlens, the amount of light reflected by the microlens is small and the amount of light transmitted through the microlens is large.

In the method of forming a microlens array according to the present invention, since the light-transmitting film extending along the surface of the microlens is formed, the diameter of the microlens is substantially increased by the thickness of the light-transmitting film. be able to.

For this reason, when processing the material layer of the microlens into a pattern corresponding to the plurality of microlenses in the arrangement state, it is possible to secure a large space between the patterns. Also, adjusting the thickness of the light-transmitting film can more accurately control the distance between the microlenses than adjusting the reflow of the material layer, so that the effective area between the microlenses is reduced. can do.

If the light transmitting film is formed by applying an organic film or depositing an inorganic film by plasma CVD, the light transmitting film can be formed at a temperature lower than the reflow temperature of the material layer of the microlens. In addition, the light transmitting film can be formed without deforming the formed microlens.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to an on-chip microlens array of a solid-state imaging device and a method for forming the same will be described below with reference to FIG.
As shown in FIGS. 1A and 1B, also in this embodiment, until the material layer 25 is reflowed by heat treatment to form the on-chip microlens 22 having a curved surface due to the surface tension of the material layer 25, FIG. The steps substantially the same as those of the conventional method shown in FIG.

However, in the present embodiment, it is not necessary to optimize the interval between the on-chip microlenses 22 only by reflow by heat treatment, so that there is a sufficient margin for a short circuit between adjacent on-chip microlenses 22. Thus, it is sufficient that a relatively wide interval of about 0.6 to 1 μm can be obtained.

Next, as shown in FIG. 1C, the same organic film as the material layer 25 which is a photoresist, or the material layer 2 is used.
The light-transmitting film 26, which is an organic film having a refractive index equal to or less than the refractive index of the material layer 25 even if the organic film is
Spin-coat to the following thickness. At the time of coating, the thickness of the light transmitting film 26 is adjusted by adjusting the rotation speed of the coating machine, the viscosity of the organic film, and the like, so that the light transmitting film 26 is spread thinly along the surface of the on-chip microlens 22. I do.

As a result, as shown in FIG. 1C, the diameter of the on-chip micro lens 22 is substantially increased by the thickness of the light transmitting film 26, and
There is less substantial ineffective area between each other.

Even when the light-collecting state of the on-chip microlens 22 is changed by the light-transmitting film 26, the change of the focal position by the light-transmitting film 26 is estimated in advance, and the material layers in both the vertical direction and the horizontal direction are estimated. 25 on-chip micro lens 2
2 can be optimized.

In the above embodiment, the light transmitting film 26 is formed by applying an organic film. However, the SiO ₂ film or the S ₂ film is formed by a high-density plasma CVD method at a temperature of 180 ° C. or less.
An inorganic film such as an iON film may be formed.

In particular, the SiON film is made of a material gas of Si
The conditions of H ₄ , N ₂ O and NH ₃ are appropriately selected, and
By adjusting the ratio of O and N in the N film, this S
The refractive index of the iON film can be easily controlled. Therefore, even when the desired focal position cannot be obtained only by the on-chip micro lens 22, the sensitivity of the solid-state imaging device can be increased by controlling the refractive index of the SiON film and controlling the focal position.

In the above embodiments, the invention of the present application is applied to an on-chip microlens array of a solid-state imaging device and a method of forming the same. For example, the present invention is applied to an on-chip microlens array of a liquid crystal display device and a method of forming the same. By applying the invention of the present application, the image quality of a liquid crystal display element can be improved.

[0031]

According to the microlens array of the present invention, since the effective area between the microlenses is small, the sensitivity of the solid-state imaging device can be improved.

If the light-transmitting film is a SiON film, the focal position can be controlled by controlling the refractive index of the SiON film even when a desired focal position cannot be obtained only by the microlens. In addition, the sensitivity and the like of the solid-state imaging device can be further increased.

If the refractive index of the light transmitting film is lower than the refractive index of the microlens, the amount of light reflected by the microlens is small and the amount of light transmitted through the microlens is large. Can be even higher.

In the method of forming a microlens array according to the present invention, when processing a material layer of a microlens into a pattern corresponding to a plurality of microlenses in an arrayed state, it is possible to secure a large space between the patterns. Therefore, a short circuit between adjacent microlenses can be suppressed, and a microlens array can be formed with a high yield.

Further, since a substantially ineffective area between the microlenses can be reduced, a microlens array capable of improving the sensitivity and the like of the solid-state imaging device can be formed.

If the light transmitting film is formed by applying an organic film or depositing an inorganic film by a plasma CVD method, the light transmitting film can be formed without deforming the formed micro lens. Arrays can be formed with higher yields.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a forming method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a side sectional view of a solid-state imaging device to which a conventional example of the present invention is applied.

FIG. 3 is a side sectional view showing a forming method according to a conventional example in the order of steps.

[Explanation of symbols]

22 On-chip micro lens 23 On-chip micro lens array 25 Material layer 26 Light transmitting film

Claims (7)

[Claims] 1. A microlens array, wherein a plurality of microlenses having a light-transmitting film extending along the surface are arranged. 2. The microlens array according to claim 1, wherein said light transmitting film is a SiON film. 3. The microlens array according to claim 1, wherein a refractive index of said light transmitting film is lower than a refractive index of said microlens. 4. The microlens array according to claim 3, wherein said light transmitting film is a SiO ₂ film. 5. A step of processing the material layer of the microlens into a pattern corresponding to a plurality of microlenses in an array state, and a step of reflowing the processed material layer to form the plurality of microlenses. And forming a light-transmitting film extending along the surfaces of the plurality of microlenses. 6. The method for forming a microlens array according to claim 5, wherein the light transmitting film is formed by applying an organic film. 7. The method according to claim 5, wherein the light transmitting film is formed by depositing an inorganic film by a plasma CVD method.