JP3390889B2 - Manufacturing method of optical aperture - 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 an optical aperture, and more particularly to a method for manufacturing an optical aperture having a fine three-dimensional structure for controlling the incident angle of light on an optical sensor with high accuracy.

[0002]

2. Description of the Related Art Conventionally, various types of photosensors having an array of light-receiving elements, such as a solid-state image sensor, are controlled to control the angle of incidence of light to prevent intrusion of light or stray light outside the field of view and to improve sensitivity. The optical aperture of was adopted.

In recent years, in order to improve the precision of such an optical aperture, it has been proposed to use a single crystal semiconductor wafer as a base material of the optical aperture and to apply a fine processing technique in the semiconductor field for its processing. FIG. 5 is a diagram illustrating a manufacturing process of an optical aperture using such a single crystal semiconductor wafer.

First, a pattern corresponding to an array-shaped slit 3 for forming an optical aperture is formed on one main surface of a first silicon semiconductor wafer 2 having a (110) surface as a main surface. The photoresist 4 is provided, and using the photoresist 4 as a mask, etching is performed to a predetermined depth by wet anisotropic etching using, for example, a KOH aqueous solution to form the array-shaped slits 3. The drawing shows three array-shaped slits.

Next, as shown in FIG. 5 (b), isotropic etching is performed with the peripheral portion protected from the opposite main surface to form a large concave portion 5 having the peripheral portion as a wall to form an array slit. The slit substrate 1 is formed by controlling the height of the slit substrate 3.

Next, as shown in FIG. 5 (c), the second silicon semiconductor wafer 6 having the (110) plane as the main surface is anisotropically etched.
The slit groove substrate 8 which penetrates the wafer and has the stripe-shaped grooves 7 corresponding to the array-shaped slits 3 is aligned with the slit substrate 1, and the slit substrate 1 is bonded and fixed with an adhesive 9 such as an epoxy resin and then diced. And divide it into individual array slits.

FIG. 5 (d) is a perspective view of the optical aperture provided with the array-shaped slits 3 manufactured in this manner, and the width w in the figure is shown.
Corresponds to the width w in FIG. 5 (c). Further, the individual slits forming the arrayed slit correspond to the respective light receiving elements of the optical sensor, and a highly accurate optical aperture can be obtained as compared with the conventional slit using a metal plate.

[0008]

However, in the above-mentioned conventional method for manufacturing an optical aperture, when forming a large recess for controlling the height of the slit by isotropic etching, a large recess is formed in the silicon semiconductor wafer. There is a problem that the depth of the concave portion does not become a uniform depth over the front surface of the wafer, and therefore the height of the slit is not always uniform.

Further, since the central portion of the slit substrate is much thinner than the peripheral portion and the mechanical strength is weakened, distortion and bending occur during handling during alignment with the stripe groove substrate, and There was also a problem that handling was difficult.

Therefore, it is an object of the present invention to control the height of the slit of an optical aperture provided with an array of slits with high accuracy and to facilitate wafer handling in the manufacturing process.

[0011]

The present invention is applicable to a slit substrate (1 in FIG. 1) provided with an array slit (3 in FIG. 1) and the array slit in a method for manufacturing an optical aperture. Forming a composite substrate by adhering the stripe groove substrate (7 in FIG. 1) provided with the stripe groove substrate (8 in FIG. 1) in alignment with each other, and for grinding the stripe groove substrate side of the composite substrate. The method is characterized by including a step of adhering to a support substrate (11 in FIG. 1) and a step of controlling the thickness of the slit substrate by grinding the slit substrate side of this composite substrate.

Further, the present invention is characterized in that a semiconductor wafer having an epitaxial layer or a diffusion layer provided on the surface as a slit substrate is used, and the etching depth of the slit is controlled by the thickness of the epitaxial layer or the diffusion layer. And

The present invention is also characterized in that the array-shaped slits provided on the slit substrate are formed by wet anisotropic etching.

The present invention uses an epoxy resin as an adhesive in the step of forming a composite substrate, and
The epoxy resin is filled in the bottom of the array-shaped slits.

Further, the present invention is characterized in that anodic bonding is used in the step of forming the composite substrate.

Further, the present invention is characterized in that, in the step of adhering the composite substrate to the supporting substrate, wax is used as an adhesive, and the wax is filled also in the stripe grooves and the array-shaped slits.

[0017]

The thickness of the slit substrate, that is, the height of the slit is controlled by grinding the surface of the slit substrate on the side where the arrayed slits are not provided. An array-shaped slit composed of the slits is obtained.

Further, by using a semiconductor wafer having an epitaxial layer or a diffusion layer on the surface as the slit substrate, the slit depth can be stabilized by utilizing the difference in etching rate between the substrate and the epitaxial layer or the diffusion layer. You can control it well.

By using wet anisotropic etching when forming the array-shaped slits, highly accurate slits can be formed with high productivity.

Further, when the composite substrate is formed, the mechanical strength of the slits is enhanced by filling the bottom of the array-shaped slits with an epoxy resin as an adhesive agent, and the slits can be prevented from being damaged during the grinding process. Furthermore, by using anodic bonding in the step of forming the composite substrate, bonding at room temperature becomes possible.

Further, in the step of adhering the composite substrate to the supporting substrate, the mechanical strength of the slits and stripe grooves is improved by using wax as an adhesive and filling the inside of the stripe grooves and the array-shaped slits with wax. Since it is reinforced, damage to the slits and stripe grooves in the grinding process can be prevented.

[0022]

1 and 2 are views for explaining a manufacturing process of an optical aperture provided with a slit of a one-dimensional array which is an embodiment of the present invention. First, see FIG. 1A. An epitaxial layer 10 was provided on the surface (110).
Array-shaped slits 3 for forming an optical aperture on one main surface of the first silicon semiconductor wafer 2 whose main surface is the main surface
A photoresist 4 having a pattern corresponding to
Using this photoresist 4 as a mask, etching is performed to a predetermined depth by anisotropic etching using, for example, a KOH aqueous solution to form array-shaped slits 3,
The slit substrate 1 is configured. In this case, by providing a difference in the etching rate between the semiconductor wafer body and the epitaxial layer 10 provided on the surface thereof by providing a difference in the concentration of impurities, the array-shaped slits 3 having a predetermined depth are formed.
Can be stably formed. The drawing shows three array-shaped slits.

Next, as shown in FIG. 1B, the second silicon semiconductor wafer 6 also having the (110) plane as the main surface is anisotropically etched to obtain
A stripe groove substrate 7 is formed by penetrating the wafer and forming stripe grooves 7 corresponding to the array slits 3. Of course, either the slit substrate 1 or the stripe groove substrate 8 may be formed first.

Next, referring to FIG. 1 (c), the slit substrate 1 and the stripe groove substrate 8 are aligned, and an epoxy resin is used so that the surface of the slit substrate 1 on which the array-shaped slits 3 are provided is bonded. Adhesive 9 is used to form a composite substrate. At this time, the epoxy resin is also filled in the bottom of the array-shaped slits 3 according to the thickness of the epoxy resin 9.

Next, referring to FIG. 1 (d), the surface of the composite substrate on the side of the stripe groove substrate 8 is placed on a supporting substrate 11 for grinding made of a glass substrate or the like and the wax 1
Glue with 2. At this time, wax is intentionally filled also in the stripe-shaped grooves 7 of the stripe groove substrate 8 and the array-shaped slits 3 of the slit substrate 1.

2E, the surface of the composite substrate on the side not fixed to the grinding support substrate, that is, the slit substrate 1 is ground until the array-shaped slits 3 are sufficiently exposed. Grind while measuring the height. In this case, the bottom of the array-shaped slits is filled with epoxy resin, and the interior of the array-shaped slits and stripe grooves is also filled with wax, so that the mechanical strength of the slits is increased, and By controlling the thickness, only the epoxy resin filled area is ground, and the slit is not damaged during grinding.

Next, referring to FIG. 2 (f), after the composite substrate ground by melting the wax 12 is separated from the grinding support substrate 11, the separated composite substrate is washed by an organic solvent to be attached. Remove residual wax.

Finally, as shown in FIG. 2G, the composite substrate is diced to divide it into individual chips to complete the optical aperture. The structure itself of the optical aperture obtained here is the same as the structure shown in FIG.

Although the array-shaped slits are one-dimensional array-shaped slits in the above embodiment, they may be two-dimensional array-shaped slits as shown in FIG. 3 depending on the purpose. The slit substrate 1 having the elongated array slits 14 and the stripe groove substrate 8 having the elongated stripe grooves 7 are aligned so that the array slits and the stripe grooves are orthogonal to each other, and the epoxy resin 9 is formed. It is formed by grinding and then bonding. The figure shows the optical aperture after dicing.

Further, in the above embodiment, the epitaxial layer is used for stable etching when forming the array-shaped slits, but this may be replaced with a uniform diffusion layer. . That is, it suffices if a layer having a different etching rate from the semiconductor wafer body is provided on the surface.

Further, in the above embodiment, the epoxy resin is used when forming the composite substrate, but a polyimide resin may be used or anodic bonding may be used.

Referring to FIG. 4, this anodic bonding is performed by the slit substrate 1 and the stripe groove substrate 8
To have a low melting point glass thin film 1 having a low viscosity even at a low temperature on the bonding surface of one substrate, for example, the slit substrate 1.
3 is formed to a thickness of 1 to 5 μm by RF sputtering, and then a voltage is applied between both substrates to perform bonding, which enables bonding at room temperature.

Further, in the above-mentioned embodiment, the wet anisotropic etching is used for forming the array-shaped slits with emphasis on the productivity, but when higher accuracy is required, the productivity is increased. Alternatively, dry anisotropic etching may be used at the expense of.

Further, in the above embodiment, wax is used for fixing to the grinding substrate, but it is not limited to wax, other adhesives may be used, and further, the slit substrate and the stripe may be used. The same silicon semiconductor is used as the groove substrate, but like GaAs
Of course, other semiconductors such as III-V compound semiconductors may be used, and the slit substrate and the stripe groove substrate may be made of different semiconductors.

[0035]

According to the present invention, by using the grinding technique, the height of the fine array-shaped slits can be easily controlled with high accuracy, the uniformity thereof can be improved, and in the manufacturing process. Wafer handling is facilitated, and damage to slits in wafer handling can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a manufacturing process up to the middle of an optical aperture having a slit in a one-dimensional array according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the manufacturing process of FIG. 1 and subsequent figures for an optical aperture provided with a slit in a one-dimensional array, which is an embodiment of the present invention.

FIG. 3 is a diagram illustrating a manufacturing process of an optical aperture having slits of a two-dimensional array which is another embodiment of the present invention.

FIG. 4 is a diagram illustrating an anodic bonding method when forming the composite substrate of the present invention.

FIG. 5 is a diagram illustrating a manufacturing process of a conventional optical aperture having slits in the shape of a one-dimensional array.

[Explanation of symbols]

1 slit board 2 First silicon semiconductor wafer 3 array-shaped slits 4 photoresist 5 recess 6 Second silicon semiconductor wafer 7 stripe groove 8 stripe groove substrate 9 Epoxy resin 10 Epitaxial layer 11 Grinding support substrate 12 wax 13 Low melting point glass thin film 14 long and narrow slits

Claims (7)

(57) [Claims] 1. A step of forming a composite substrate by adhering a slit substrate provided with array-shaped slits and a stripe groove substrate provided with stripe grooves corresponding to the array-shaped slits in alignment with each other, Bonding the striped groove substrate side of the composite substrate to a supporting substrate for grinding,
And a grinding step of grinding the slit substrate side of the composite substrate to control the thickness of the slit substrate. 2. A semiconductor wafer having an epitaxial layer or a diffusion layer on the surface thereof is used as the slit substrate, and the etching depth of the slit is controlled by the thickness of the epitaxial layer or the diffusion layer. Item 2. A method of manufacturing an optical aperture according to item 1. 3. The method of manufacturing an optical aperture according to claim 2, wherein the array-shaped slits provided on the slit substrate are formed by wet anisotropic etching. 4. In the step of forming the composite substrate,
4. The method of manufacturing an optical aperture according to claim 1, wherein an epoxy resin is used as an adhesive and the bottom of the array-shaped slit is also filled with the epoxy resin. 5. In the step of forming the composite substrate,
The method of manufacturing an optical aperture according to claim 1, wherein anodic bonding is used. 6. A wax is used as an adhesive in the step of adhering the composite substrate to the supporting substrate, and
6. The method of manufacturing an optical aperture according to claim 1, wherein the wax is also filled in the stripe grooves and the array-shaped slits. 7. The composite substrate is divided into individual array slits by removing the composite substrate from the support substrate and dicing after the grinding step. The method for manufacturing an optical aperture according to any one of items.